ia 4,100,000 1,630,000
But the mere counting of the number of bacteria furnishes
_ little information of the character of an effluent, as is shown by
the following observations :
1. Meade Bolton and others have proved that some organisms
commonly occurring in water, such as M. agquatilis and
B. erythrosporus, can multiply enormously even in sterilized
_ distilled water free from almost every particle of organic matter.
2. The nitrifying organisms will live in the absence of all
organic matter, and will not grow in the ordinary culture media; -
hence would be entirely omitted in the ordinary counting. |
3. During the purification carbonic acid is produced in con-
siderable quantity. This gas is inimical to a large number of
; bacteria.
es
i alee
OTHER ORGANISMS WHICH AFFECT PURIFICATION.
I Besides bacteria in sewage, there are generally found many
_ organisms of a higher grade. Water-worms, such as Anguillula
_ and Nais, are stopped or killed in efficient purification ; in fact,
one of the causes that calls for an anaerobic stage is that these
animals require oxygen, and perish rapidly under the air-free
_ conditions. At the same time, their preliminary agency in
consuming and breaking down organic débris is almost cer-
tainly of value. Though bacteria are the chief workers in the
_ purification of rivers, it must be borne in mind that fish, rats,
and birds act as scavengers, and that the larger flora of the
river also plays an important part. Letts remarks on the
absorption of nitrogen into the tissues of animals or plants
_ which feed on the sewage: ‘‘ The bacteria beds at ‘Belfast and
78 SEWAGE AND ITS PURIFICATION
elsewhere swarm with minute insects (Podura aquatica), which,
escaping in myriads, often form a thick layer like soot on the
surface of the effluent. In thus escaping these animals carry
with them some of the nitrogenous constituents of the sewage
which they have devoured, but as yet there has been no
estimate of the quantity so removed. There are also species of
worms always present in the bacteria beds in considerable
numbers, which no doubt also feed on the sewage.”’!
Infusoria and other minute animals assist in the work of
purification by acting as scavengers; their presence in vigorous
activity is a proof of good aeration. Amoebz require scarcely
any oxygen; I have even found them in small numbers in
the sediment of the Exeter septic tank, which is practically
anaerobic. They also must act usefully in attacking nitro-
genous matter.
Algze and water-plants assist in the purification of an effluent —
by the nascent oxygen which they disengage from their green
parts. They. can also absorb by their roots and white parts
ammonia and putrescent nitrogenous matter; they require, of —
course, clearing out at intervals to prevent the decayed portions
from reversing the process. J. Kénig? has found that the ©
higher water-plants, Elodea canadensis (Anacharis), Potamogeton,
Myriophyllum, and Ceratophyllum, take up the. nitrogen they
require from organic substances in the water, such as asparagin
or albumose, but not urea; and that the same is probably true
for Salvinia and Azolla. All these plants, together with Lemna |
minor and L. polyrhiza, assimilate carbon from organic carbon
compounds when the water is free from CQ,.
Much trouble is sometimes caused by the clogging of —
conduits and pipes by growths of Beggiatoa, Cladothrix,
Crenothrix, and other filamentous organisms allied to fungi,
and producing earthy, sulphuretted, and other odours. These
organisms are undesirable, and an indication of faults in the
management of the process.
Beggiatoa (Fig. 13), however, although it has been called
the ‘‘sewage fungus,’’ seems, according to Wuinogradsky
(p. 73), to have really oxidizing functions. It lives in water —
containing sulphuretted hydrogen, such as sulphur springs, as
well as in sewage.
Crenothrix (Fig. 14), Pylobolus, and fresh-water sponges, are —
1 British Association Report, Glasgow, Igol, p. 601.
2 Zeits. f. Untersuch. Nahr, u. Genussmittel, 1900, vi., 377.
.
)
2 |
2 |
|
|
i
|
|
» |
: PLATEZY,
Fic, 15.—Lrpromitus LactrEus, SHOWING CONSTRICTION AND
NUCLEUS.
Fic. 16,—Lrptomitus Lactreus, sHOWING BRANCHING,
on oe enn
BACTERIA OCCURRING IN SEWAGE 79
more common in continuous than in intermittent filtration.
Crenothrix only grows rapidly when the dissolved oxygen is
low and when certain metals are present, and is favoured by
the presence of much organic matter and of carbonic acid and
the absence of light. Jackson’ distinguishes three species:
(1) The common C. Kiihniana, red or reddish brown, pre-
cipitating ferric hydrate; (2) C. (formerly Leptothrix) ochracea,
white or yellowish, precipitating alumina; and (3) C. manga-
nifera, dark brown or black, precipitating manganese.
—_
Fic, 13.—BEGGIATOA ALBA,
Showing attached, free, curved, and
spiral forms. (a) Chain of spores;
(0) free spores (motile) ; (c) portion
under a higher power, showing trans-
verse and longitudinal division; (d)
Fic, 14,—CRENOTHRIX KUHNIANA,
x 600, )
(a) Arthrospores; (b) single seg-
ments ; (c) common sheath surround-
ing the separate spores,
filaments breaking up (the small dark
circles are granules of sulphur highly
refracting) ; (e) free motile segment
with terminal flagella,
Among the species that have been identified as constituting
_ masses of “sewage fungus” are: Leptomitus lacteus (Sapro-
legniz), soft, gelatinous, white, rusty, or black masses of long-
branching filaments, constricted at intervals, each segment
_ having a refractile nucleus. Spherotilus natans, allied to the
~ leptothrix forms of bacteria, and possibly identical with
_ Beggiatoa. It is more gelatinous than Leptomitus; like it,
forms long wavy masses, usually whitish, but, according to
1 Fournal of the Society of Chemical Industry, 1902, p. O81.
80 SEWAGE AND ITS PURIFICATION
Boyce, indicates much greater pollution (he states that it is
favoured by warmth and the presence of H,S, but requires
oxygen for its development, therefore will not grow in crude
sewage, but may cause blocking of aerobic contact beds).
Carchesium lachmanni, a protozoon allied to Vorticella, found in
great masses under similar conditions to those of the Sphzro-
tilus. The occurrence of these organisms is described by
Boyce in the Second Report of the Royal Commission on
Sewage, 1902, p. 104, by whose kind permission I reproduce
the figures in Plates V. and VI.
ORGANISMS CAUSING ODOURS.
I have found in some cases that foreshore odours have been
attributed to the entrance of effluents when they’ have been
really caused by ordinary marine and fluviatile life. Thus ina
harbour scum which I recently examined the odour was very
powerful, being described as strongly earthy, weedy, and some-
what fishy, and was undoubtedly due to the organisms.
Among those specially mentioned as causing unpleasant odours
which were identified were the diatoms Melosira, Tabellaria,
Diatoma, Meridion, with Volvox, Oscillaria, Ulothrix, Beg-
giatoa, and Spongilla. Similar occurrences were described by
Sir E. Frankland in his report on the alleged pollution of Loch
Long and Loch Goil in 1889, and he was of opinion they were
not due to contamination by sewage.
A green frondose seaweed, Ulva lactuca or latissima, ‘‘ sea-
lettuce,’ widely distributed on the coast, is sometimes washed
ashore, and forms banks of a strongly fishy odour, which in
decaying emit a putrid gas. As this evil is acute in Belfast
Lough, Professor Letts has subjected the plant to examination.
The mean results of analysis of the dried substance were, in
per cents: C, 35°15; H, 5°27; N, 6:25; O, 37°96; ash, 15°37,
containing S, 3°21, and Fe, 2°20; and the proximate analysis
showed in per cents: Chlorophyll, fats, etc., 17; albuminoids
or proteids, 33; cellulose, 50. No carbohydrate beyond cellu-
lose was identified. In fermentation the weed at first evolves
about equal volumes of CO, and H, while fatty acids are
produced, chiefly propionic, with butyric and probably acetic.
1 “ Absorption of Ammonia from Water by Algze,” Report of British Associa-
tion, 1900, p. 935; ‘‘ Ulva latissima and its Relation to the Pollution of Sea-water
by Sewage,” Letts and Hawthorne, Proceedings of the Royal Society of Edinburgh,
March 4, 1901 ; Report of Commission on Sewage, vol ii., 1902, p. 469 ; Second
Report on the Scheme of Sewage Purification for Belfast, by Dr. Letts, 1904.
on i
PAsATE V4.
Fic. 17.—SPHAEROTILUS NATANS.
Fic, 18.—CARCHESIUM LACHMANNI.
i
BACTERIA OCCURRING IN SEWAGE 81
Later, sulphides are formed, probably by the reduction of the
sulphates in the sea water, and the seaweed blackens from the
formation of ferrous sulphide, which disengages sulphuretted
hydrogen by the action of the fatty acids. Two species of
bacteria seem specially concerned.
Letts and others consider the occurrence of this alga im
quantity to be associated with sewage pollution—first, on
account of its nitrogen being in excess of that recorded in any
other seaweed; secondly, because by cultivation experiments
it was found that its power of absorbing nitrogen was remark-
ably high (thus in one experiment it absorbed in seventeen
hours the whole of the free ammonia from a polluted sea water
containing 0°05 part per 100,000; nitrates were also rapidly
absorbed, but not albuminoid matters; the plant remained
healthy); thirdly, it grows most abundantly where sewage is
discharged. He remarks that, “‘ while thus acting as scavenger,
it may itself give rise to a very extensive nuisance,” and that
in this case biological effluents rich in nitrates and non-putre-
factive also supply the nitrogen for the growth of the Ulva
and other plants.
Many varying odours occur on shores unpolluted by sewage,
and can arise from either animal or vegetable sources. In
_ some parts the deposits of birds evolve an ammoniacal and
pungent odour. The smell of seaweeds is frequently strong
even in the fresh state, and when thrown up on shore and
decaying they may be very offensive. Dead marine animals
are often drifted in quantities into hollows in the coast ; and
large numbers of jelly-fish (medusz), shells, and crabs frequently
_ putrefy on the sands, and sea-anemones on the rocks. Littoral
flowering plants when growing profusely, as in salt marshes,
sometimes produce very distinct odours, which may be strong
and unpleasant in addition to the smell from masses of decaying
vegetation. In this latter connection it must be remembered
that brine of the strength of sea water has no antiseptic power.
Besides the above occasional causes of local nuisance, there
are a number of vegetable and animal microscopic organisms
| which in their growth develop odours of various kinds, while
any of the species, when unusually abundant, can after their
death render wide areas of water offensively putrid. Apart
from these peculiarities, large groups of ‘“ macroscopic ”” life,
including diatoms, the smaller alge, the infusoria, and minute
crustaceans, act harmlessly as scavengers in waters which may
6
82 SEWAGE AND ITS PURIFICATION
contain only small quantities of vegetable matter. But the
difficulties from the smells that they produce have often arisen
in lakes and reservoirs in different parts of the world. Odours
produced by the living forms have proved to be due in many
cases to the secretion of compounds analogous to the essential
oils, which have been actually extracted by ether or gasolene ;
the oil globules may be seen in many species under the micro-
scope, and the effect on the water increases when the organisms
divide or disintegrate, especially in the autumn.
Crenothrix Kiihniana or polyspora was first observed in 1852 in
the drains from a cultivated field in Silesia, and was described
by Ktihn. It is capable of very rapid multiplication and of
fouling large quantities of water, which must, however, contain
a certain quantity of ferrous iron. Thresh mentions that a few
years ago a number of wells in Essex developed smells in the
autumn, which he traced to species of Crenothrix; most of
them were free from suspicion of sewage pollution, although
the odour was strongly suggestive of sewage. A similar result,
with a reddish colour and turbidity, occurred in the reservoirs
at Cheltenham in 1896 from a variety of C. polyspora. This or
allied species have been connected with an unpleasant odour
and appearance in many subsoil waters, but Dr. Garrett has
found that the organism has no effect on health. The luxuriant
growth of C. Kuiihniana at the Berlin waterworks in 1878
proved so troublesome that fresh filter-beds were constructed.
It developed to a thickness of some feet in the streams supplying
the reservoirs, although the organic matter dissolved in the
water was small. Nine years later Rotterdam was similarly
affected, and United States records contain numerous examples.
In 1891 a strong foetor was communicated to the water-supply
of Bolton, Lancashire, by a copious growth of Conferva
bombycina in the reservoirs, and the same occurred in another
Lancashire town in 1898. Treatment with minute quantities
of copper sulphate has been found to be successful; I have
also noticed that the presence of a very small quantity of ©
available chlorine inhibits many of these growths.
The following organisms have been specially offensive at
various times :
Cyanophycee. Anabaena, a bluish-green or brownish fila-
mentous alga, family Nostocacee, accompanied by an odour
described as like ‘‘ horse-dung” in England, ‘ pig-pen” in
America. It is remarkable that in A. civcinalis, according to
=
i he ee ee eT 8 ee Se a hoe ee
= eS
BACTERIA OCCURRING IN SEWAGE > 83
Jackson and Ellms,! the dry substance contains 9°66 per cent.
of nitrogen, a higher percentage than that found by Letts in
Ulva latissima (6°18 per cent.), and much higher than is
recorded for others of the larger alge (1°3 to 4°6). The “ pig-
_ pen” odour is attributed to “the breaking down of highly
organized compounds of sulphur and phosphorus, and to the
presence of the high percentage of nitrogen.” Analysis of the
gas evolved during decomposition gave in volumes per cent. :
hydrogen 82°4, CH, 0°8, N 12°4, CO, 1°5, O 2°9; the oxygen
and a portion of the nitrogen probably represented residual air,
and a large quantity of the CO, produced remained dissolved
in the water surrounding the plant. Oscillaria, Nostoc, and
Lyngbya (the latter with “‘a peculiar suffocating odour’’)
_ belong to the same family, and have a similar effect. I have
found the two former and Anabzna in some English water-
supplies, notably in June, 1905, in a portion of a Surrey supply
of high organic and bacterial purity. LLyngbya was present in
the Cheltenham reservoir. Celosphearium is mentioned in the
Brooklyn Board of Health reports as having caused smells,
and as being one of the worst of its class. Many of the Chloro-
phyce@, or green microscopic algz, impart strong fishy or sea-
- weed odours. Volvox, formerly classed among the protozoa, is
conspicuous in its fishy smell; I found this organism in the
_ harbour water at Chichester, and there are records of its effect
on English public water-supplies.
_ “Aromatic” is the general term applied to the volatile pro-
ducts of the Diatomaceag, and in foreshore muds I have noticed
that a peculiar aromatic smell was associated with large
numbers of these organisms. But many of them are much
_ more unpleasant, and I discovered several of the odorous forms
| at Chichester in Igor (see Chap. XIII.). Asterionella causes a
disagreeable fishy smell. Like other green organisms, it grows
/ most luxuriantly in ground water exposed to the light. In the
States it has occasioned great inconvenience; in 1896 the
reservoir supplying Brooklyn contained 25,000 to 30,000 per c.c.
I have found it in a few English drinking-waters, as also
Synedra, which is credited with a disagreeable “ grassy ”’ smell.
! _ Whipple records an instance of a large mass of water being
rendered offensive by the breaking up by a storm of a thick
marginal growth of Melostra varians.
1 “ Odours and Tastes of Surface Waters,”’ United States Technology Quarterly,
x., December, 1897.
6—2
84 SEWAGE AND ITS PURIFICATION
Among aquatic animal forms that have caused serious
nuisance in their growth are the protozoa Uroglena and Synura,
the former fishy and oily, the latter the origin of the so-called
‘* cucumber” smell at Boston,.U.S.A., in 1881 and 1892; other
protozoa are Bursaria gastris (strong seaweed smell), Crypto-
monas (sweetish), Mallomonas (fishy). Fresh-water sponges and
Bryozoa have also given trouble, mainly in their decay.
Whipple gives a classification of organisms and odours."
Of 1,404 waters examined in Massachusetts, only 275 were
inodorous; the smell of I00 was reported as offensive, g2 dis-
agreeable, 458 vegetable or sweetish, 202 grassy, 84 mouldy,
47 fishy, and 146 aromatic.
In an investigation as to the origin of the smell in Chichester
Harbour in 1go1, that of the scum was undoubtedly due to
diatoms. The mud contained an abundance of confervoid
algze and of diatoms belonging to species known to be objection-
able in this sense, and the very marked odours noticed in the
samples I collected at different points were certainly produced
by these organisms, which, as we have seen, grow independently
of sewage, and some of them preferably in clean waters.
Diatoms flourish best in shallows with a muddy bottom, and
the periods of stagnation and aeration characteristic of such
mud-banks are distinctly favourable to these kinds of life.
The Cladothrix so frequently noticed in mud samples is a
fungoid organism, often present in large numbers both in fresh
and brackish waters, whether running or stagnant, and in its
growth it generates a mouldy smell, which was well marked in
many of these specimens.
The city sewage in the above case had been precipitated by
aluminoferric and lime, settled in tanks, then passed over land
into a tidal basin, and stored till the state of the tide admitted
of its discharge into the creek. It contained oniy 3 to 7 parts
per 100,000 of suspended matter, and the smells and deposition
in the harbour seemed to be derived from other sources.
SURVIVAL OF PATHOGENIC ORGANISMS.
This important point was raised at the Exeter Local Govern-
ment Board Inquiry, referring to the pathogenicity of the
product after anaerobic treatment, since it has been suggested
a oe
a >
that, whilst cultivating the bacteria necessary for the destruc-
tion of the organic matter in sewage, the pathogenic organisms
1 “ Microscopy of Drinking-Water,” p. 125.
BACTERIA OCCURRING IN SEWAGE 85
_ present in the crude sewage will not only survive, but may
; possibly multiply, and so cause the effluent to be dangerous to
health. It is important, however, to remember that the
_ bacterial processes are not novel, but are identical with those
which obtain in Nature, so that effluents from sewage farms are
strictly comparable with filtrates obtained after either a ‘‘ coarse
bed” or a tank treatment.
} It must be recollected that hitherto little attention has been
_ paid to the study of land effluents from this point of view, and
until sewaye-farm drainage waters have been investigated in a
similar manner to those derived from continuous well-aerated
filters, no detinite conclusion on this point can be formed.
It seems to be accepted that the treatment of sewage on
land, though formerly urged to be more satisfactory from the
bacteriological point of view than its treatment in bacterial
_ beds, would not seem to by any means entirely remove the
_ danger arising from the discharge of effluents into potable
' rivers. Experiments on the subcutaneous inoculation with
_ crude sewage and with effluents for the Royal Commission
show that ‘‘ the pathogenic qualities of most effluents point to
the improbability of sewage being so modified by treatment on
land or by artificial processes as to be other than a liquid
potentially dangerous to human beings. The absence of any
pathogenic result when sewage is rendered germ-free by filtra-
tion, on the other hand, tends to show that the chemical
products of the vital activity of the bacteria in sewage are not
of a markedly poisonous nature.” |
Although with any new scheme it is difficult to obtain direct
evidence as to its ultimate effect upon a river water which is
_ subsequently to be used as a drinking supply, one must recollect
that under existing circumstances the removal of all kinds of
bacteria from the river water is attempted by those who desire
' to use such water for drinking purposes, so that, even assuming
that bacterial systems tend to increase the bacteria in the
river, they do not make any new departure necessitating a
reconsideration of our methods of water purification. Even if
an anaerobic treatment alone resulted in an effluent which
_ possessed toxic properties disastrous to a small river, it must
be recollected that no process is at present suggested which
does not involve a full and efficient aerating filtration as a final
method of purification, and it is the pathogenicity of such
|
| filtrates upon which information is wanted. Satisfactory
|
86 SEWAGE AND ITS PURIFICATION
evidence on most of the systems is now available, from which,
I think, we are justified in concluding that, even if towns on a
river like the Thames adopted bacterial schemes, the patho-
genicity of the London water-supply would not be adversely
affected. That the health of fish is not injured appears from
the fact that, with intermittent fine-bed filters following coarse-
bed or chemical treatment, as at Leeds and London, they have
lived in the filtrate. |
At Exeter the tank effluent, the filtrate, and the river water
were examined before and after admixture. Broth inoculated
with these fluids and incubated for forty-eight hours had no
effect upon rabbits or guinea-pigs when 2 c.c. was injected
subcutaneously. Incubated for eleven days, the tank effluent,
and the water at Belle Isle contaminated with the untreated
town sewage, were found to be morbific, but the filtrate and the
water at Salmon Pool Weir, some little distance below the
town, contained so little morbific material of any kind that
even with this severe test both kinds of animals remained alive
and perfectly well. Dr. Woodhead in his report concludes
“that none of the organisms found in the tank effluent are
themselves capable, in the quantities present or in which they
can grow even in broth, of setting up any morbid changes.”
With regard to typhoid fever, Lawes and Andrews showed
that some liquefying organisms have a germicidal effect upon
typhoid bacilli, so that their sojourn in a septic tank, or their
arrest in an anaerobic upward filter, with such organisms
diminishes instead of increases their chances of survival.
Dr. Pickard, of Exeter, has proved this fact again experi-
mentally by introducing an emulsion of the typhoid bacilli into .
a septic tank, when he found that, instead of increasing, they
rapidly diminished, until after fourteen days less than I per
cent. of the number introduced were surviving. The same
investigation also proved that filtration was even more efficient
in removing typhoid bacilli, as he found that filtration, as con-
ducted at Exeter, removed about go per cent. of typhoid
bacilli from sewage inoculated with this organism, and that
subsequent filtration of tank effluent containing no typhoid
through the same filter yielded filtrates containing only about
1 per cent. of the bacilli introduced in the first filtration, show-
ing that the environment was unsuitable for their development
if their absence from the first filtrate was due only to a straining
action.
BACTERIA OCCURRING IN SEWAGE 87
Dr. Houston, with the Ducat filter, has shown that with
sewage containing 1,200,000 B. coli per c.c. a filtrate is obtained
which contained no colonies resembling the organism in this
quantity; and that sewage containing between 1,000 to
10,000 spores of B. enteritidis sborogenes per c.c. contained after
filtration less than 10 per c.c., whilst the aerobic bacteria
_ causing liquefaction of gelatine were likewise reduced from
22 to less than I per unit. :
Professor Boyce found that B. coli diminishes in the septic
_ tank, the liquid being inimical to it, and therefore to the other
more delicate pathogenic bacteria. In one series of experi-
ments the average number of coli per c.c. was—crude sewage,
5,0II; open septic tank, 2,130; Cameron closed tank, 2,099.
In another series the average was—crude sewage, 45,600 ;
_ septic tank, 3,433 ; keeping the liquor for two days, the number
had gone down to 2,025.!
On p. 74 a table is given showing the maximum and
minimum numbers of coli organisms and spores of B. enteritidis
sporogenes obtained recently at the Guildford Sewage Works;
it will be seen that coli organisms are in each effluent reduced
as the purification of the sewage proceeds, the total reduction
amounting to over 99°9 per cent. of those present in the original
crude sewage. As would be expected, the anaerobic B. entert-
tidis does not show any reduction during the septic tank
treatment, but finally the spores are reduced to one-tenth the
original numbers.
Before this evidence of the comparatively innocuous character
of the filtrates from bacterial systems was available, I pointed
out that subsequent chemical treatment could be used for
sterilizing the filtrate if necessary. Such reagents as may be
conveniently employed may be called “ finishers,’ as when
employed the resulting purified sewage is satisfactory both from
the chemical and bacterial points of view. Chlorine is one of
such reagents, and the late Dr. Kanthack established the fact
that with 1 grain of free chlorine to 4 gallons of the tank
effluent or to 5 of filtrate, with a contact of about five minutes,
the number of bacteria can be reduced from any number (even
millions) that may be present to ten to fifty per cubic centimetre,
and that no pathogenic organisms were found in any of the
numerous samples of Maidenhead sewage finished in this way.
I found at the same inquiry that on adding 1°77 parts of avail-
! Royal Commission on Sewage, Second Report, 1902, p. II.
88 SEWAGE AND ITS PURIFICATION
able chlorine per I00,000, although about half the amount
immediately combines with any organic matter present, if the
aerating filter has not worked efficiently, the micro-organisms
by contact with the remainder are gradually killed, so that
plate cultivations of such sewage taken after fourteen minutes
showed no growth with three and a half days’ incubation.
Later, in 1904, an experimental plant was installed at the
Guildford Sewage Works for treating the sewage at its various
stages of purification with an electrolytic chlorine solution, in
order to determine the amounts of available chlorine required
to deodorize and sterilize the various effluents. It was found
that chlorine had very little precipitating or coagulating effect,
the only visible change being a slight bleaching, the deposited
sludge becoming dense and more amenable to treatment. The
destruction of odours was complete and very rapid, provided
the addition of available chlorine was equivalent to the imme-
diate oxygen-consumed figure of the effluent. Absolute
sterilization was not found to be practicable ; in a cubic centi-
metre of sewage spores are present which will resist several
minutes’ steaming, and the quantity of available chlorine
required to destroy these would of itself be objectionable,
irrespective of the high cost. But it was found that the addi-
tion of available chlorine in excess of that immediately taken
up by the organic matter, as indicated by an oxygen-consumed
determination, rapidly destroyed the vast majority of organisms,
so that after a few hours’ contact the bacteriological condition
of the effluent was almost comparable with standards for
potable waters.
In Chapter VIII. further details will be found.
In the report of the London County Council, October, 1899,
Dr. Houston specially studied the possibility of the survival of
pathogenic organisms after passage through bacterial filter beds,
and from his investigation of the intermittent filters under
experiment, he summarizes his opinion as follows:
“‘ It is to be noted, in the first place, that the biological treatment
of sewage is conducted wnder control; secondly, that the process
always gradually secures the destruction of the pabulum on which
bacteria feed, and hence leads to their death; thirdly, that the
balance of evidence points to the probability that some, at all events,
of the pathogenic organisms are crowded out in the struggle for
existence in a nutritive medium containing a mixed bacterial flora,
their vitality being weakened or destroyed by the enzymes of the
saprophytic species; fourthly, that while it is true that bacteria
produce poisonous substances in their growth, it also is true that
6 a he Li a on ee en ee ea ee - e
nearer a A
—EE “ —
SOT eS Peer
——
“ag See eee
me
CO oe
BACTERIA OCCURRING IN SEWAGE 89
their chemical poisons are toxic in proportion to the dose, and,
moreover, are highly unstable, and readily break down into their
elementary and innocuous constituents; and, lastly, that in some
cases it may not be necessary to attempt to complete purification
of the sewage, the solution of the suspended matters and partial
destruction of the putrescible matter in solution being all that is
urgently called for, as, for example, where the effluent is of rela-
tively small bulk and is turned into a stream, the water of which is
not used for domestic purposes (as is the case in the Lower Thames),
or else when the effluent is to be subsequently treated by land
irrigation.”
He does not imply that such organisms as the typhoid bacillus
or the cholera vibrio would necessarily lose their vitality, or even
suffer a diminution in virulence, under the conditions prevailing
in a biological filter. In the absence of actual experiments
with the particular sewage in question, he is not prepared to
say more than that he believes that if these germs did gain
access to the sewage they would suffer diminution in numbers, ~
primarily in the sewers, and secondarily in the coke-beds.
Dr. Houston, early in 1898, isolated from Thames mud four
organisms, named by him B. typhosus simulans a, b, c, d, which
differed from the true typhoid organism in failing to sediment
with typhoid serum and in possessing a less number of flagella.
They might, therefore, possibly be degenerate varieties of active
typhosus caused by prolonged existence in sewage-polluted
water. Horrocks! studied the behaviour of the B. typhosus in
sewage, and concludes that the bacillus will usually be found
alive after sixty days’ immersion in sewage freed from other living
organisms. The power of sedimentation will be unchanged,
but the colonies may present a dark, granular, crumpled appear-
ance, and the bacillus will show diminished resistance to
carbolic acid. In unsterilized sewage he failed to obtain any
evidence of their survival after fourteen days, and inferred that
the life of the bacillus is much shorter in unsterilized than in
sterile sewage.
Among the organisms which can be easily identified as
directly derived from sewage, and which are either themselves
pathogenic or are associated with organisms causing disease,
| the B. enteritidis sporogenes of Klein (Fig. 8, Plate II.) and
B. coli communis are the most important.
At Crossness, in the crude sewage and the effluents from the
1 Fournal of the Sanitary Institute, xx., part iv., 1899. See also “ Enteric
_ Fever and Sewage Disposal in Foreign Countries,” by Major Aldridge (¥ournal
at of Hygiene, July, 1902, p. 360).
go SEWAGE AND ITS PURIFICATION
4-foot bed, the spores of B. enteritidis varied from 10 to I,000
perc.c. In the effluents from the 6-foot coke-bed and from the
laboratory vessel they varied from 10 to 100 per c.c.; but
there may have been more spores present, as the minimum
amount of liquid added to the milk-tubes was o’or c.c.
Houston continues :
“Judging the results as a whole, it cannot be said that the
biological processes at work in the coke-beds produced any significant
alteration in the number of spores of this pathogenic anaerobe.
This is the less to be regretted, since the effluents are discharged
into a large tidal river below locks, the water of which is not used
for drinking purposes. Still, it is to be thought of that the cultures
of B. enteritidis sporogenes are extremely virulent, and that Dr. Klein’s
results seem to prove that this anaerobe may be causally related to
acute diarrhcea. Atall events, it is highly important from a practical
as well as from a scientific point of view to continue these observa-
tions on the number of spores of B. enteritidis in crude sewage and in
the effluents from the coke-beds.” (This was done in 1899,' and it
was noted that, although the number of these spores was frequently
less in effluents than in the sewage, it was still between 100 and
1,000 per C.C.)
On the other hand, in a preliminary Report to the Royal
Commission, Professor Boyce, from experiments with this
organism, concludes as follows:
‘‘ Filtration has a marked effect in keeping back this bacillus,
especially when combined with precipitation. It was not found in
the filter effluent from the septic tank at Manchester, nor in the
pure filter effluent at Chorley or Oldham. It was, however, obtained
in the former by filtering a quantity through a porcelain filter, and
subsequently scraping the surface. The addition of lime and copperas
does not appear to have much effect on this bacillus.”
In concluding, Dr. Houston adds :
‘‘ Judging the experiments as a whole, it cannot be said that the
biological processes at work in the coke-beds effected any marked
alteration in the number of B.colz. It must not, however, be too
lightly considered that this implies that the effluent was necessarily
of an offensive and putrescible character. B. col: and other putre-
factive bacteria no doubt work in the direction of purifying the
sewage, and their presence in the effluent might only mean that the
purification had not been carried sufficiently far to allow of a
decrease in their numbers, owing to the incomplete reduction of
the organic matters on which they feed, and which allow of their
continued multiplication. Yet, when this has been said, it must
also be admitted that the passage of an aerobic non-spore-forming
1 London County Council Report, Jaly, 1900.
BACTERIA OCCURRING IN SEWAGE gI
bacillus typical of excremental matters through the coke-beds in
practically unaltered numbers is not a desirable state of things.
It is true that B. coli is not pathogenic in the ordinary meaning
of the word, but its presence in the effluents implies the possible
presence of other bacteria—it might be of a dangerous sort. Still,
on the whole it may be said that the balance of evidence points to
pathogenic aerobic bacteria being liable to be crowded out in the
struggle for existence in a nutrient fluid containing a mixed bacterial
flora and one rich in saprophytic micro-organisms. Lastly, it must
be remembered that the effluent is discharged into a large tidal river
at a point far below the lowest ‘intake’ of water for waterworks
purposes. Moreover, the Thames before it reaches the outfalls of
the sewage works is already grossly polluted with excremental
matters.”’
A subsequent report! of July, 1900, confirms most of these
conclusions, but points out that the effluents from the experi-
mental beds at Barking and Crossness cannot be reasonably
assumed to be more safe in their possible relation to disease
_ than diluted raw sewage. This must, however, be regarded
as only applicable to beds worked in the way described. The
chemical results taken generally show that nitrification was
never pushed to a satisfactory point, and the main object of the
- whole inquiry in London has been to produce, a an effluent suit-
able to discharge into tidal waters.
I examined the effluents from the Scott-Moncrieff filters at
_ Caterham with a view to ascertaining whether the sewage
_ organisms survived the oxidizing influence to which they were
subjected in their passage through the nitrifying trays, and
_ found that the number of organisms capable of growing on
_ carbolized gelatine surface plates, amongst which the B. colt
communis is found, was reduced from 2,180,000 per c.c. to
_ 100,000 in the filtrate from filter C, to 50,000 in that from D,
and 80,000 in the filtrate from F, so that, whilst the least
_ efficient of the filters removed 95 per cent. of these organisms,
the filter D removed 98°5 per cent.
Although the addition of o*ooor c.c. of the tank effluent to a
broth tube and incubation at blood heat for four days produced
indol, the same dilution of the filtrate from D gave no turbidity
or indol, whilst the filtrates from C and F, although producing
_ turbidity, also failed to give any indol reaction.
A disappearance of spores of B. enteritidis also occurred, and
may be best seen from the following table, where + indicates the
presence of such spores, and —their absence.
1 Royal Commission on Sewage, vol. iii., 1904, pp. 95, 96.
g2 SEWAGE AND ITS PURIFICATION
| Tank Effluent. : Filtrates.
| ee me
COL :- C16, ree + + _ +
OOO! C.C. af | + + _ =
O°002 C.C. odst\ + + _ +
O'OOOI C.Cc. : — - - —
The nitric nitrogen and the ammoniacal nitrogen present in
the filtrates when the bacterial samples were collected are
shown in the following table:
Tank Effluent. | Filtrates.
: tre eer
Nitric nitrogen tak st Nil. 5°48 11°6 10°96
Ammoniacal nitrogen a8 ‘2°73 4°56 2°05 3°28
It may therefore be concluded that the greater the aeration
and nitrification, theless is the possibility of the survival of
pathogenic organisms.
Johnson and Whipple have shown! that the colon bacillus is
taken up by fish, and multiplies rapidly in their intestinal tract,
whereas fish caught in an unpolluted water failed to reveal the
presence of this organism. It would seem possible, therefore,
that fish, having taken up the colon bacillus from a polluted
water, might migrate to a water of comparative purity, where
they would naturally discharge the greatly increased number of —
these organisms. If the colon bacillus can be thus easily
transferred from one water to another, the transportation of the
typhoid bacillus may be considered quite as likely. This may
explain the phenomenon frequently noted where B. coli com-
munis is found in comparatively large numbers in waters
apparently open to but remote chances of feecal contamination.
In the subcutaneous injection of guinea-pigs (Royal Commis-
sion, Second Report, 1902, p. 57) Dr. Houston found that crude
sewage always produced a local reaction, and not uncommonly ~
death. Street washings, storm water, overflow liquid from —
sewage works, and, in general, bad effluents, were apt to be
pathogenic. Good effluents could be injected in relatively —
large amounts without producing a fatal result. His opinion ©
1 American Public Health Association, Fournal of Infectious Diseases, Chicago,
March 19, 1904.
i ed ee ee es ee) =
-
Shien oie
ee
ne a lh eg
{
BACTERIA OCCURRING IN SEWAGE 93
that land effluents are usually less pathogenic than those from
bacteria beds is very inadequately supported by his one fatal
result on injection of an effluent from a single bacterial process
(Report, p. 49). In the only other case quoted, from a different
bacterial process, the animal, recovered. Crude sewages and
effluents, which had been heated to roo° C. for one hour, or
passed through a Pasteur filter, did not produce any injurious
effect, even in large doses. It would follow that the ptomaines,
which have sometimes been suggested as a danger of bacterial
processes, are not of significance.
In the same Report, Dr. MacConkey (“ Longevity of
_ B. typhosus in Sewage and Sewage Effluents,”’ zbzd., p. 62) sums
up his results as follows:
“We know that typhoid bacilli must find their way into the
sewage from the excreta of persons suffering from typhoid, but they
cannot be in large numbers, and in the various samples of crude
_ sewage which we have examined we have not found any. Therefore
it may be concluded that, allowing that these bacilli do reach
biological beds or septic tanks, they are present in such small
numbers, and the conditions are so adverse to their existence, that
they will not survive the treatment. But if from any cause they
arrived at the beds or tanks in such numbers as the B. coli, then
certainly they might appear in the effluent just as the B. coli does.
But as in the case of the latter bacillus, so also in the case of the
_B. typhosus, there is no tendency to multiplication in the effluent.”
From some sewages and effluents Dr. Houston records his
isolation of B. pseudo-tuberculosis and B. pyocyaneus, ‘‘ both
highly pathogenic to lower animals, and also related to morbid
_ processes occurring in the human subject” (zbid., p. 58). He
has discovered B. anthracis at Yeovil in sewage and some
effluents connected with hide factories (ibid., p. 31). In crude
_ sewage he finds B. coli and allied forms are apt to be at least
| 100,000, spores of B. enteritidis sporogenes at least 100, and
streptococci at least I,000 per c.c. (p. 25). He urges the im-
| portance of a streptococcus test (further explained at p. 144 of
_the Report), and remarks (p. 29) that, although both bacteria-bed
and land processes can yield effluents seemingly non-putrescible,
these are not to be thought of as safe in the case of drinking-
_ streams. Chemical standards are always essential. A bacterial
| standard is required for drinking-streams, and is of more im-
portance than the chemical one; for non-drinking streams it is
useful as an adjunct to the chemical standard (cbid., p. 29).
The effect of subsequent filtration on a biological effluent was
Investigated by the Commission, and it was_concluded that
94 SEWAGE AND ITS PURIFICATION
‘‘when an effluent containing upon an average 800,000 bacteria —
per c.c. is passed through a depth of 4 feet of soil at a slow —
rate (150,000 to 400,000 gallons per acre per twenty-four hours) —
there is a very great reduction in the total numbers and in the s
B. colt.”
When the effluent was inoculated at intervals with cultures
of B. typhosus or of B. anthracis, tests for these organisms in the
filtrate were negative. B. pyocyaneus, similarly added, was
observed to die out in the filter.
CHAPTER V
CHEMICAL CHANGES PRODUCED BY BACTERIA
Hydrolysis and oxidation—Nature and order of the reactions—
Symbiosis and antagonism—Enzymes—Classes of transforma-
tions—Utilization of gases produced—Sources of energy—
Nitrosification, nitrification, and denitrification.
SomE thirty-five years ago trials of upward filtration (Chap. XI.)
in the place of chemical precipitation gave such satisfactory
results that it is difficult to understand why chemical treatment
_ was almost universally adopted. In slow upward filtration of
sewage the arrested suspended matter slowly disappears just in
the same way as when the solids, after being removed by strain-
ing or by chemical precipitation, subsequently disappear when
_ buried in the soil.. Similar changes take place in mud-banks in
estuaries, below the surface of the water, and the conversion of
organic matter of vegetable or animal origin at the bottom of a
_ stagnant pool into harmless gases is of the same nature. Such
_ transformations formerly almost escaped attention, yet are as
_ important as those which take place in the presence of light
and air. In nearly all cases of destruction of organic matter
_ preliminary disintegration takes place before the final oxidation
of the elements. Solid organic matter capable of undergoing
change can only be oxidized by air directly on its surface,
| whereas in a rotten apple or cheese changes take place beneath
the surface, which pave the way for oxidation. Similarly,
organic matter in solution seldom oxidizes directly to its final
oxidation products, but passes through intermediate conditions
until the complex organic forms are resolved into others of
more simple structure, and these are subsequently burnt up to
the stable oxidized compounds—water and carbonic acid.
The older terms for these phenomena—“ decay,’ ‘‘ putre-
faction,” ‘‘eremacausis”!— did not sufficiently differentiate
1 From 7péua, quietly ; xadovs, burning.
95
96 SEWAGE AND ITS PURIFICATION
between them and the combustion which follows so closely.
‘“‘ Bacteriolysis’’ refers to the principal living agents of the
changes. ‘‘ Hydrolysis” signifies a chemical breaking down by
combination with the hydrogen and oxygen of molecules of
water. Other cases, in which the decomposition takes place
without any absorption of water, are grouped under the general
term ‘‘ fermentation.’’ Sometimes oxidation is simulated, since
the organic matter is partly converted into oxidized compounds;
but the oxygen is not derived from the air, being that which was
originally present in the organic matter or in the water taking
part in the reaction. As an example, albumin contains the
elements C, H, N, and O in the ratio represented by the
empirical formula C,H,,N,O;. An anaerobic change, due to
hydrolysis, could be expressed thus :
4C,H,,N,0,+ 14H,O =4N, + 19CH,+13CO, + 2H,.
Such an ideal change would result in the production of all the
gases which are commonly met with in these decompositions,
and leave no- soluble organic matter for oxidation. Non-nitro-
genous substances like cellulose and woody fibre can similarly
break down into starch, sugar, etc., and then, in presence of
yeast, into carbonic acid and alcohol. In most natural anaerobic
' changes of this character it is found, however, that there are
residual compounds containing nitrogen, of a humus-like char-
acter, which are very stable, and resist chemical action.’ In
peaty soils they exist in appreciable quantity. Adeney has
noticed their formation in ‘his experiments, and in the Exeter
septic tank the dark suspended matter is of allied nature. That
it does slowly disintegrate is shown from the experiments at
Harpenden, where crops have grown on unmanured land for
long periods under such conditions that it is difficult to ascribe
any other source for their nitrogen. Humus slowly undergoes
oxidation to CO, and nitrate.
I was one of the first to point out that when changes are
brought about by organisms which are facultative anaerobes, —
the breaking down of gelatine to albumoses, ammonia, pep-
tones, etc.,” is not accompanied by any absorption of oxygen
or the formation of any oxidized products, and it is, moreover,
obvious that in the natural process of digestion solid foods,
1 See Chap. XI. ; also the author’s paper on “ Humus and the So-called Irre-
ducible Residue in Bacterial Treatment of Sewage” (British Association, I901; —
Chemical News, vol. |xxxiv., p. 149).
2 See also Selitrenny, Monatsch., x., 908.
PR mee
CHEMICAL CHANGES 97
} both nitrogenous and non-nitrogenous, are digested in the
_ stomach and intestines before the products are absorbed by the
_ blood, and so rendered useful by oxidation.
_ The amount of oxygen required to render inoffensive the
| _ substances occurring in sewage depends on the species of the
: bacteria which are acting, as they determine whether the result
_ should be a complete burning to CO,, H,O, and N, or a partial
_ decomposition to equally harmless compounds like NH, and
_ collidine, and peptones.?
1 Elastin, with anaerobic organisms, evolves CO,, H, CHy,,
and N, whilst the sulphur remains in solution as mercaptan,
and is not evolved as H,S.2_ Grass similarly evolves CO, and
| N under the action of B. subtilis and other organisms. B. my-
_coides also acts upon the carbohydrates in grass, ferments
_ glucose to inactive lactic acid, and hydrolyses cane-sugar,
' maltose, and glycogen? Pakes and Jollyman‘ describe an
"apparatus for examining the gas generated by bacteria, and
have specially investigated B. pyocyaneus and B. coli communis,
which produce CO, and H, or N if nitrate be present.
| The gases found in the septic tank at Exeter are as follows:
Per Cent, By Volume,
COe i: al SL sO IS On 06
os ¢ Gineee kta’ is sine O23 iw 24°4
EE eee ia seen eee he 36°4
oe chedaaiugegae of ae at 38°6
100°O 100°0
According to Wood and Wilcox, similar gases are produced
in the manufacture of leather by Bacterium furfuris, which does
“not attack cellulose, but only starch and nitrogenous matter.
_A sample of the gas contained in per cents.: CO, and traces of
ey 25, 25°2; O, 2°51; H, 46°7; N, 26°0; while formic, acetic,
_ butyric, and lactic acids were produced: these in sewage would
“combine with ammonia. Much of the CO, dissolves in the
| water, as does also the ammonia formed, whilst the hydrogen,
i from its easy diffusibility, escapes from the tank more rapidly
_ than the heavier gases. As to H,S, see p. 114.
1 Emmerlich, Ber., 1897, xxx., p. 1863.
2 Zoja, Zeit. Physiol. Chem., 1897, xxiii., 236.
3 Emmerlich, Ber., 1897, xxx., p. 1896.
4 Fournal of the Chemical Society, 1901, pp. 322, 459.
5
_CH,. There are a number of intermediate products ; thus, |
H Streptococcus longus liquefies fibrin to ammonia, methylamine, |
_ trimethylamine, tyrosine, leucine, fatty acids, succinic acid, |
98 SEWAGE AND ITS PURIFICATION
The further important change necessary for the complete
destruction of the organic matter involves the essential that
free or available oxygen, either from the air or oxidized com-
pounds, shall be present. The following table shows the weight
required to oxidize some typical organic compounds completely
to their final stable products:
Si Percentage Composition. Cd eat amide 25 Bra
Substance. Empirical
Formula.
CO:, H2O, | COo,NHs3,
C. H. N. 0. tod N. aad HO.
Albumin ... C,H,3N,03? | 53°4| 7°r | 15°8 | 23°7 1°754 1°48
Gelatine .. Bs —_ 50 | 66 | 15°3 | 251 1°61 1°33
Starch, cellulose,
and woody fibre! C,H,)0; 44 | 62 | — | 40% 1184 1°'184
Ammonium amido-
acetate (ammo-
nium salt of gly-
cocine) ... «| CyHgN,O, 261 | 8°76 | 30°43) 34°78} 1'043 0°53
Urea CH,N,O 20 | 67 |46°7 | 2°66) 0°803 —
Fatty acids require a higher amount of oxygen. Thus, a
molecule of stearic acid, C;,H.,,0,=284, requires 832 of O, or
nearly three times its weight. But most of these are insoluble,
and none of them are putrescent or dangerous.
The action which takes place in filter-beds and in rivers,
as well as beneath the surface of sewage farms, is sometimes
referred simply to “ nitrification”’; but since organic carbon is
oxidized along with the nitrogen in these processes, the more
general term “ oxidation”? should be employed as indicative of
both the carbon and nitrogen purification.
The experiments of the Massachusetts Board of Health and
of the London County Council at Barking have been directed —
almost entirely to the second and final stages in sewage treat-
ment. The Barking t-acre filter-bed only dealt with sewage
which had been chemically precipitated. It is also important
to recollect that the anaerobic or hydrolytic change takes place
very rapidly under favourable conditions, and that it is not
——
unusual to find, especially in towns in which the sewers are
old and tortuous, a crude sewage in which the preliminary dis- —
any
integrating changes have taken place to a very considerable —
extent.
Anaerobic fermentation is called by the Germans true putre-
sao
faction (Faulniss), while aerobic is termed mouldering (Verwe-—
CHEMICAL CHANGES 99
t sung). It seems sufficient to recognise the first as a hydrolytic
_ and the second as an oxidation change.
Calculating from the discharges (p. 54), an average sewage
from a water-closet town with a water-supply of, say,
_ 25 gallons per head should, when fresh, contain about 10 parts
_ of organic nitrogen per 100,000; yet in most cases the sewage
_ of a town contains only from 1 to 2 parts of organic nitrogen,
and frequently less than this amount. The difference must be
_ due to the very rapid breaking up of the organic matter by the
anaerobic changes described, and is accompanied by a corre-
sponding increase in the ammonia from mere traces_up to
8 parts per 100,000, and a loss from the evolution of free
_ nitrogen gas and possibly oxides of nitrogen.
When fecal and other solid matters are first discharged, the
earliest changes must be aerobic, because of the free oxygen
dissolved in the water and contained in the air. The effect is
mainly the same as the /ast stage—i.e., the organisms acting in a
normal manner upon those simpler constituents like ammonia,
already present in small quantities, into which the process
itself afterwards resolves the main ingredients of the sewage.
| } Nitrates in small quantities are consequently often observed in
| ‘moderately fresh discharges.
| As soon as the free O has been exhausted, these oxidation
if
|
| changes come to an end, and the bacteria which require air in
‘part disappear and in part remain quiescent, to resume their
functions at a later stage. On the other hand, the anaerobic
i organisms will commence to multiply, the nitrate will be
reduced to nitrite, and this to nitrogen, according to reactions
| we shall explain later, and the liquefaction and hydrolysis
| ehanges will proceed. This is the usual condition When the’
of the treatment proper commences.
In the second stage aeration is to be encouraged, so that the
| Miproduced with the help of some of the facultative anaerobes.
| In the third stage, with provision of a still larger quantity
_ products.
| 4 We may summarize the order of the changes as follows:
| sewage arrives at the works, and the first, or anaerobic, stage
Ma
Bacrobic bacteria may act and ammonia and carbonic acid be
_ of oxygen, the nitrifying group will get rid of the remaining
100 SEWAGE AND ITS PURIFICATION
Substances dealt with. Characteristic Products,
Initial.
Transient aerobic changes | Urea, ammonia, and
by the oxygen of the easily decomposable
water - supply, rapidly matters,
passing to—
First Stage.
Anaerobic liquefaction and| Albuminous matters, | Soluble nitrogenous com-
preparation by hydro- Cellulose and fibre, pounds. Phenol de-
lysis. Fats, 5 - rivatives. Gases. Am-
monia,
Qo
Second Stage.
Semi-anaerobic breaking | Amido - compounds. Ammonia, Nitrites,
down of the intermediate Fatty acids, Dis- Gases,
dissolved bodies, solved residues, Phe-
nolic bodies,
Third Stage.
Complete aeration: oxida- | Ammonia and carbon- | CO,, H,O, and nitrate.
tion and nitrification, aceous residues,
In ordinary bacteria beds these reactions are often reversed
and confused, according to the periods of filling or rest, which
allow the different bacteria to act in the same filter. Although
it is practically impossible to confine the bacterial action to
one species, by seeding or otherwise, in view of the immensely
varied character of the organisms that are present—nor would
such a proceeding be advantageous—yet the best conditions are ©
attained when a sewage plant is so arranged as to afford separate
areas favourable to groups of organisms which work similarly.
This principle will be further discussed in Chapter XI. We
have seen that the disappearance of pathogenic bacteria in
cultivation beds, through the crowding out of these special
forms by the more numerous harmless varieties which thrive —
at ordinary temperatures, is also an important part of natural
purification.
SYMBIOSIS AND ANTAGONISM.
Organisms growing together either antagonize each other’s
development or, more rarely, encourage it, or even are necessary
to one another. The former is ‘‘ antagonism,” the latter |
‘‘symbiosis.”” In mixed cultures certain species develop
rapidly, to be supplanted later by those of slower growth, and
the more vigorous organisms are not always the most useful.
Some species prevent the growth of others by (1) exhausting
CHEMICAL CHANGES IOI
their special food, or (2) by excreting products which are
injurious; the latter is true antagonism. ‘Thus Freudenreich
found that B. pyogenes fetidus (p. 72) prevented the growth of
the cholera spirillum, that Micrococcus roseus similarly inhibited
M. tetragenus, whilst B. pyocyaneus, phosphorescens, and prodigio-
sus caused a change in broth which prevented the growth of
other species. Garré demonstrated antagonism by making
streak cultures of various bacteria on gelatine plates, in parallel
or intersecting lines! Lewek inoculated gelatine or agar with
_ equal numbers of different varieties, adjusted by counting and
appropriate dilution.? K. B. Lehmann draws the practical
inference that in counting bacteria very dense plates should be
avoided.
Symbiosis is the condition when two or more kinds of
bacteria act together and effect decompositions which neither
of them could do separately. Each may live independently,
but they thrive better and more continuously in company than
alone, and are said to be synergetic. Lehmann states that some
organisms ordinarily anaerobic can thrive on the admission of
_ air if certain aerobes be also present, which is one reason
accounting for the presence of anaerobes in oxidizing beds or
filters.
_ The cause of symbiosis is generally found in each of the
_ organisms taking one part in a sequence of chemical actions.’
_ Thus, Omeliansky, by pure cultivations, explained some results
_ that Adeney and others had previously noticed. When three
_ organisms, B. racemosus, nitrosomonas, and nitrobacter, are added
to bouillon, the first bacillus produces ammonia from the
_ organic nitrogen, the second converts it into nitrite, and the
_ third the nitrite into nitrate. The first change requires no
_ oxygen, the second requires some oxygen, and the final change
_ astill greater quantity. With a culture of the first two, nitrite
and no nitrate was produced. Witha mixture of B. racemosus
_ and nitrobacter, ammonia was the only product, as the absence
_ of the nitrite-forming organism prevented the conversion of the
ammonia into food for the nitrifying organism. A mixture of
_ the two last species failed to determine the decomposition of
the original culture medium even after ten months. Otto
Kiinnemann‘ found that Burri and Stutzer’s B. denitrificans I.
1 Corresp. fiir Schweizer Aertze, 1897.
2 Centr. f. Bakt., vii., 107. 3 Kossowicz, Woch. f. Brau., 1906, xxiii., 262.
4 Landw, Versuchs Stat., 1898, 65.
102 SEWAGE AND ITS PURIFICATION
is effective only in symbiosis with B. coli: the latter supplies it
with its necessary ammoniacal food. B. coli! reduces nitrate
to nitrite, which in turn is denitrified by the organism I.
ENZYMES.
A great number of changes, most of them hydrolytic, are
accomplished by the large class of organic substances termed
“enzymes,” which, though not living, are products of animal
and vegetable life. They have been defined by Lehmann and
Neumann as ‘‘chemical bodies, which in minimum amounts
and without being used up are able to separate large amounts
of complicated organic molecules into simpler, smaller, more
soluble and diffusible molecules.” The definition is not quite
accurate, as the milk ferment, for instance, actually coagulates
casein, or renders it insoluble, but it gives an idea of the
immense power that these enzymes possess, and the economy
of their use as distinguished from ordinary chemical or
mechanical means. Many of them are products of bacteria or
other fungi, and are powerful agents in resolving action, as a
bacillus is not only able to act in its immediate neighbourhood,
but also at a considerable distance, through the soluble ferments
it forms and disengages.
The enzymes are soluble nitrogenous bodies, which can be
precipitated and rendered inert by strong alcohol, mercuric
chloride, and by boiling. They can be separated from bacteria
by filtration, when the enzymes pass through, while the
bacteria are retained. Other distinctions from the organisms
which produce them are:
1. Enzymes can often work at a greater range of temperature ;
that is, are less susceptible to heat and cold than the living
bacteria. Therefore it is possible to find temperatures which
will inhibit, if not kill, bacteria without affecting enzymes.
2. Antiseptics, like chloroform, thymol, etc., which kill or
inhibit bacteria, do not prevent enzymes from acting. Thus
1 Weissenberg, Archiv. f. Hygiene, 1897, xxx., 3.
? Brunton and Macfadyen (Proceedings of the Royal Society, 1890, xlvi., 542),
working on the liquefaction of gelatine by a variety of micro-organisms, found
that a temperature of 100° C, destroyed both the bacteria and the power of :
liquefaction, while a temperature of 50° destroyed neither. Between 60° and 75°
the organisms were destroyed, but not the liquefying action, showing that it was
due to an enzyme secreted by the bacteria. They succeeded in isolating this
enzyme, and demonstrated its peptonizing effect apart from the bacteria which
produced it. It was hindered by acidity, and favoured by alkalinity. Adiastatic
enzyme was also identified. These bacteria evinced adaptiveness to the media —
in which they grew, and could digest animal fibre and carbohydrates, but not fats.
|
Salkowski! inoculated fibrin with putrefactive bacteria and
kept it in chloroform water. It remained sterile for an un-
limited time, but nevertheless underwent solution with the
_usual products, due to an enzyme secreted by the bacteria at
first. Hoppe-Seyler describes several fermentations which are
initiated by bacteria, but continue after the destruction of the
organisms by ether.?
Dr. Armstrong? proposes the terms zymosis for fermenta-
tion by living organisms, and enzymosis for change by enzymes
_ or unorganized ferments. The former class of changes would
_ be intracellular, or within the cell, under the immediate action
_ of the protoplasm ;‘ the latter class would be external or extra-
cellular. By such means bacteria are able to produce effects
_ which are quite out of proportion to their size or numbers. As
_an example of intracellular action, Wroblewski® states that
_ with Buchner’s yeast-extract filtration through a Berkefeld or
_ sandstone filter diminishes, and through a Chamberland filter
entirely removes, the fermenting power; this shows that in
_ fermentation by yeast cells the zymase remains in the cells and
does not diffuse into the sugar solution. If the cells are
_ collected on a sandstone filter, fermentation in the sugar
_ solution ceases; Wroblewski is therefore of the opinion that
_ the sugar solution passes into the cells and is there fermented.
_ Alcohol and carbonic acid, accordingly, are true excreta of the
| yeast cells.
iF Enzymes are formed not only by bacteria, but by moulds,.
_ Jarger fungi, and also by plants and animals, but have not as
yet been prepared artificially. Free oxygen is not necessary
for their production. The mode of action is still imperfectly
1 understood; probably they act like some inorganic bodies by
forming unstable compounds with portions of the organic
molecule, which then break up, leaving the substance
_ hydrolysed, and freeing the enzyme to act again. As they
are of such value, it will be useful to give a list of the more
_ important ; many of them, or their analogues, must occur in
“sewage, since the changes they produce are present. We may
divide them into groups.
1 Zeit. Phys. Chem., 1899, xxvii., 305. 2 Pfliger’s Archiv, xii., 1.
3 Transactions of the Chemical Society, June, 1890, p. 528.
__ + Martinus Beyerinck uses the term ‘‘katabolic” for changes brought about by
the direct action of living protoplasm, having proved that dead bacteria have no
effect on certain compounds which are decomposable by enzymes (Proc. K. Akad.
_ Wetensch., Amsterdam, 1900, ii., 495).
> Fourn, Prakt. Chemie., 1901, ii., 64, p. I.
6 Godlewski, Bull. Acad. Sci. Cracow, 1901, 227.
CHEMICAL CHANGES 103
it
104 SEWAGE AND ITS PURIFICATION
1. Enzymes which break up Albuminous Bodies:.—The ordinary
digestive ferments, pepsin, pancreatin, etc., are of this class.
Bodies identical or similar are secreted by many bacteria, and
Lehmann believes that the body which liquefies gelatine in
cultivations is the same as trypsin from the pancreas. They
form albumoses, then peptones. Papain is an example of a
vegetable enzyme which hydrolyses nitrogenous matter. I
found that the enzyme! produced by B. fluorescens liquefaciens,
when separated from the organism by a Pasteur filter, is
capable of causing liquefaction of gelatine. Boyce has con-
firmed this observation, and has observed that B. enteritidis
sporogenes forms a similar enzyme.
2. Enzymes which attack Carbohydrates. — Diastase, which
dissolves starch, forming dextrine and sugar,? is a type of a
class of amylases, comprising glucase, granulase, maltase, and —
dextrinase, described as having slightly different functions. ~
Invertase and lactase alter the sugars. Zymase (Buchner), from
yeast and some other fungi, converts sugar into alcohol and
CO,. Cytase, which dissolves cellulose, we shall describe later. —
3. Enzymes which decompose Fats.—Lipase and others will
also be further described. | 4
4. Special Actions are very numerous, and will be sepaintell
alluded to.
Enzyme changes are arrested when the vineditibie reach a
certain amount, and the existence of points of equilibrium
between a direct and inverse change has been proved by Hill,*
in the case of the conversion of maltose into glucose by maltase.
With a 4o per cent. solution he shows that equilibrium is —
reached when 84 per cent. of sugar is maltose and 16 per cent. —
glucose.
Maltose — Glucose
84 per cent. paar 16 per cent, f 19 4° Pet cent. solutions. -
In weaker solutions the equilibrium point for maltose
increases, so that in a 2 per cent. sugar solution it is almost |
completely converted. In a solution so dilute as a sewage the ©
influence of the products might hardly be felt, so that the
enzyme changes would proceed to completion. Still, the q
1 Rideal and Orchard, Analyst, Oct, 1897; Fermi., Centr. Bakt., 1906, 176.
* A, R. Ling shows that diastase can directly dissolve raw starch granules —
(British Association Report, 1903; Chemical News, October 2, 1903). .
3 Beyerinck, Bied. Centr,, 1896, xxv., 753. 4
4 Journal of the Chemical Society, August, 1898. See also Kastle and Loevenhart,
American Chemical Journal, xxiv., No, 6, and Chemical News, March 8, 1gol,
pp. 113, 127. Further observations by Hill and others show that reversibility is #
general (ibid., April 24, 1903). Slator, Proc. Chem. Soc., Jan. 4, 1906. “
CHEMICAL CHANGES 105
j
} action is more energetic when the products are removed as
The fermentations occurring in the first or hydrolytic part of
i the process may be chemically classified as follows:
I. Solution and decomposition of albuminous bodies.
2. Fermentation of urea. :
| 3. Fermentation of the amido-compounds formed from the
i albuminous bodies.
: 4. The formation of organic acids and fermentation of their
f
salts. . |
5. Cellulose or methane changes.
6. Fermentation of carbohydrates.
7. Decomposition of fats.
_ 8. The formation of small quantities of sulphur compounds,
_ like H,S, mercaptan, etc. This, from the odour of the pro-
4 ducts, often attracts the most attention.
_ These, as a rule, are brought about in sewage by bacteria,
rather than by moulds and yeasts, which, as Andreasch showed,
_ may be distinctly prejudicial to normal bacterial action.
1. Hydrolysis of Albuminous Bodies is caused by a large
-number of organisms, and the first action is parallel to
ordinary digestion—that is, the so-called peptonization, or con-
version into a soluble form. The peptones are then split up,
| amido-acids are formed, together with a number of substances
| of the aromatic group.
L. Geret and Martin Hahn? describe proteolytic enzymes
existing in yeast and also in such bacteria as Sarcina rosea,
B. tuberculosis, and B. typhosus, and state that they not only
decompose and dissolve the albumin already present, but also
_ attack additional quantities of albumin from other sources.
_ Biltz and Kréhnke,? Fowler and Andern,! have shown that
some of the sewage solids are not dialysable, so that part of
_ the organic nitrogen causing opalescence in the liquid is in the
- colloidal state. Johnston,® working with Jones and Travis,
| suggests that surfaces determine the separation of this colloidal
- matter from solution, so that a mechanical or physical change
_ ? The conditions are further worked out by E. Frankland Armstrong (Pro- |
_ ceedings of the Royal Society, 1904, \xxiii., 500-542); also, as to the hindrance of
_ fermentation by chemically indifferent substances, see H. Braeuning, Zeit. Phys.
_ Chem., 1904, xliv., 70.
_ # Berichte, 1899, xxxi., 2335; also Emmerlich and Liw, Zeits. f. Hyg., 1899, I.
_ ® Berichte d. Chem. Gesell., xxxvii., 1745.
-* ahaa of the Society of Chemical Industry, xxiv., 483.
_ § Fournal of the Royal Sanitary Institute, 1906. t
106 SEWAGE AND ITS PURIFICATION
may accompany a hydrolytic change due to bacterial activity.
He recognises that, as shown by Sonstadt,! crystalloids as
well as colloids are separated from solutions by surfaces, but
insists on the importance of the natural tendency of colloids
to flocculation, especially in contact with surfaces, as aiding
and determining bacterial decomposition of albuminoids.
2. The Fermentation of Urea.—In the ordinary hydrolysis
by B. urea and M. uree—CO(NH,),+ H,O=CO, +2NH,;—the
CO, and NH, combine to form carbonate of ammonium, which
dissolves; therefore none is evolved as gas, and no oxygen is
required beyond that derived from the water, even for the
bacteria, since these are facultatively anaerobic. M. uree, for
example, grows equally well in oxygen and hydrogen, and we
know that urine putrefies in closed bottles. Miquel found that —
several water bacteria readily converted urea into ammonium
carbonate, and that M. uree was constantly present in the
atmosphere.
3. The Disposal of Amido-Compounds derived from Albu- —
minous Bodies.—It will be seen from the table (p. 98) that
either nitrogen or ammonia can be produced by bacterial —
action. That both transformations occur is proved by the ©
composition of the gases from a closed tank, and also by the —
liberation of H and CO, in anaerobic cultures.?
Every 8 parts by weight of oxygen absorbed from water —
would involve the liberation of an equivalent, or I part by
weight of hydrogen, so that the weights, if increased by one-
eighth, give the weight of water taking part in the hydrolysis.
Both the transformations given in the last two columns of the —
table on p. 98 occur in sewage purification. The first or more ~
complete change is one in which the gases evolved are entirely
without odour, but the N, being in the free state, is lost. In
the second or less complete anaerobic change the gas will have ~
an ammoniacal odour, and would be offensive if allowed to —
escape into the air. The effluent also will contain combined
N in the form of NH, and compound ammonias, and make it —
absolutely necessary to insure that adequate nitrification should
follow. In this case the final effluent theoretically contains all —
1 Fournal of the Chemical Society, 1xxxix., 339.
2 Hugouneng and Doyon found that under these conditions B. coli communis
generated H and CO, (the gas bubbles), B. tetani also H and CQO,, B. typhosus
N and CO, (Aun. Chim. Phys. 1898, vii., 45). According to Pennington and Kisel, |
B. coli evolved in per cents, 62 to 70 H, 23 to 34 CO,, I to 4 methane (not formed
when O excluded), and I to 5 N (fournal of the American Chemical Society, 1900, |
xxii., 556). See also Pakes and Jollyman (loc, cit.).
'
r
|
ie
the original organic N in the form of nitrate, which is available
for plant nutrition. As compared to the voluminous “ sludge”
of chemical or mechanical treatment, anaerobic liquefaction
leaves only the small quantity of humus residue already
alluded to.
| The amido-acids formed in liquefaction break up into fatty
or aromatic acids and ammonia. Since many of them are very
stable bodies, the decomposition is slow. Following the general
rule, being products of bacterial action, they hinder the activity
of the bacteria themselves, furnishing an additional argument
for the constant removal of the products by a continuous as
_ opposed to an intermittent system. Examples are:
CHEMICAL CHANGES 107
Name. Constitution. Formula. Products.
Glycocine ...; Amido-acetic acid CH,(NH,)COOH | Ammonia and acetic
a.
Leucine... Amido-isocaproic {cook Ammonia ang iso-
_ Tyrosine ... ae Agere CHINEEICOGET a Viabeeie:
“Aspartic ...| Amido-succinic | {CHINHJCOOH | "acid, then succinic.
: Asparagin ...|_ Amido-succinamic CHINE )CGOH Tous \oubetncceme
—— © [eget | Ammonia and prob
a
7
ag
_ Tyrosine has been said to be strongly antiseptic, but its
_ quantity in feces is small, and it is largely diluted in the
sewage. It breaks up into indol, skatol, phenol, and acids
Telated to benzoic. Spirillum rugula and the B. coprogenes
group develop a strong fecal odour, probably owing to this
_feaction. In the Exeter and Ashtead hydrolysed effluents I
only found leucine unchanged; acetic, butyric, and caproic
_ acids were, however, isolated, and traces of succinic as well as
_indol and skatol.
_ The development of these more or less antiseptic substances
‘in the intestines probably accounts for the excreta not being
further liquefied in the body, although large numbers of the
_ hecessary organisms are present. On emerging, however, and
_ undergoing dilution the bacteria at once become active.
a SEWAGE AND ITS PURIFICATION
The basic amines are of two classes :
(1) Non-volatile crystalline compounds known as ptomaines
and leucomaines. They are poisonous, but that they are
destroyed in the subsequent aerobic treatment is shown by the
fact that the final effluents are not poisonous to fish.
(2) Volatile bases or substituted ammonias, usually of strong’
odours and alkaline. These, in the ordinary method of analysis
by distillation, are partly put down as “ free ammonia,’’ which
includes not only the ammonia existing as carbonate, but also
that combined with the organic acids as salts, as well as such
compound ammonias as react with Nessler test. Many years
ago Young pointed out that in the usual mode of distillation
a great deal of volatile nitrogenous matter escaped which was
not recorded by Nessler test. The Wanklyn determination
also gives an “albuminoid ammonia” which is far short of the
fixed organic nitrogenous matter, probably accounting for such
low figures as 0°34 (with 13°8 of chlorine) and 0°24 (with I0°3
of chlorine) for raw sewages in the recent Manchester and other
reports. The Kjeldahl process can be made to give the whole ~
of the ammoniacal and organic nitrogen.
In a septic tank effluent I lately found by fractionation of —
the hydrochlorides, in parts per 100,000: actual ammonia, 3°48;
monomethylamine (CH,NH,), 0°844; trimethylamine, traces; q
the original having given 4°6 parts of “‘ free ammonia” and (by
Kjeldahl) 1°98 parts of fixed organic nitrogen, with a chlorine
content of 6°2.
Trimethylamine has a fishy smell, which is very marked —
in some sewages. B. uree@, B. prodigiosus, and B. fluorescens —
putridus: develop this compound during putrefaction. Amy- —
lamine and others are also found. The chief importance of —
the group lies in—(r1) their volatility and odours; (2) their
removing carbon as well as nitrogen; (3) the toxic nature ©
of some, by which they hinder the subsequent nitrification. —
These points would indicate that :—
(a) The preliminary liquefaction should be conducted in a ;
closed chamber:
(b) The amines must be removed by a nitrous or other
oxidation in the second part of the process, before reaching —
the nitric organisms.
4. The Formation of Organic Acids and Fermentation of their
Salts. —In the resolution of complex organic molecules a
number of organic acids are set free, and combine with any
CHEMICAL CHANGES
109g
| 4 bases present, their salts being afterwards further broken down
by such fermentations as are given in the annexed table.!
TABLE OF FERMENTATION OF ORGANIC ACIDS.
(For simplicity, the sodium salts ave taken, though the lime salts are vathey move
fermentable. )
Salt Fermented.
mentations., )
B. lactis aerogenes (O.
Emmerling).
» Cause of Fermentation. Products.
4 Formate “ Bacteria from sewage | Acid sodium carbonate, NaHCO,, car-
if slime,” bonic acid and hydrogen,
ie.
Acetate “ Bacteria from sewage | NaHCO, CO,, and methane, CH,.
ii slime.”
a
Lactate “ Thin bacillus” (Fitz).| 1. Propionic acid, and as by-products
| i (Undergoes ‘Other species of acetic and succinic acids and alcohol.
four different; bacteria; short aero- | 2. Propionic and valeric acid.
_ fermenta- bic butyric bacteria” | 3. Butyric and propionic acid.
_ tions.) (Fitz). 4. Butyric acid and hydrogen.
_ Malate __... | Bacterianotdescribed. | 1. Chief product, propionic acid; by-
_ (Different fer- | ‘‘ Thin bacilli.” product, acetic aci
>
Chief product, succinic acid; by-
product, acetic acid.
3. Butyric acid and hydrogen,
4. Lactic acid and CQ,.
Va Tartrate
Different species of
bacteria.
1. Chief product, propionic acid; by-
product, acetic acid.
2. Butyric acid.
3. Chief product, an acetate; by- ~pro-
ducts, alcohol, butyric and succinic
acids,
’
ty
Citrate
‘“* Small, thin bacilli.”
Acetic acid in large quantities, with
small quantities of alcohol and suc-
cinic acid.
|
|
a Bp yeersto ne
Micrococci; medium-
sized bacilli.
1, An acetate, with small quantities of
succinic acid and alcohol.
2 Formicacid, with some methyl alcohol
and acetic acid.
= <= —- ee Sanaa 5 an
eae Trt ee
Dicarbonate of the base.
Under active microbic fermentation all eventually pass into
CO, and H, or CH, The CO, is partly free and partly as
Acetic acid is generally the penulti-
mate product, therefore the common production of methane.
1 Herfeldt, Centr. f. Bakt. , February, 1895 ; Fournal of the Society of Chemical
ee vaustry, May, 1895.
IIO SEWAGE AND ITS PURIFICATION
Any amides of the acids are hydrolysed, with liberation of
ammonia.
Hoyer! has shown that acetic acid bacteria can live in
absence of air, and then reduce colouring matters such as:
indigotin, methylene blue, and litmus, with liberation of CO,.
They can obtain their nitrogen from peptone, asparagin,
nitrites, and ammonium salts, and their carbon from acetates,
lactates, and sugar. This shows that aerobic and anaerobic
species are by no means rigidly separated; very few are
obligatory in either sense. |
Fungi and most vegetables secrete ferments, called by
Bertrand ‘‘ oxydases,” which are capable of acting on phenol
and the aromatic compounds in the second stage. W. H.
Perkin states that pyridine, benzene, and naphthalene deriva-
tives disappear in the contact beds at Manchester.
Rapid oxidation of organic acids in presence of traces of
ferrous salts, which always exist in sewage, seems to take place
without the agency of bacteria.”
5. Solution of Cellulose and Fibrous Matters.—Mitscherlich in
1850 proved that cellulose was dissolved by fermentation ; and
Van Tieghem,? in 1870, describes the most active organism as
B. amylobacter, anaerobic, and derived principally from the
intestines of animals. It is always found in putrefying infu-
sions, and hydrolyses sugars and starch as well as cellulose,
yielding butyric acid and hydrogen, whence its later name of
B. butyricus. ‘Tappeiner* fermented cotton-wool and paper
pulp in a weak nitrogenous solution, and obtained CO, and
methane in neutral, and CO, and H in alkaline solution.
Hoppe-Seyler® in 1886, finding only traces of residue, con-
cluded that at first a soluble carbohydrate was formed by the ©
action of water, and then split up into COs and CH,:
C,H,,0,; + H,O =C,H,,0,-
C,H,,0,=3CO,+3CH,.
If more water took part, less CH, and more H would be ©
obtained. Horace Brown® found that a cellulose-dissolving —
enzyme in the digestive tract of herbivora was secreted by the ©
food plants themselves, and came into activity under favour- —
1 Chem. Centralblatt, 1899, i., 854.
2 Fenton and Jones, Chemical Society’s Transactions, January, 1900, 69.
3 Zeit. Phys. Chem., vi., 287, and De Bary’s Lectures.
4 Zeits. f. Biol., xxiv., 105. 5 Zeits. f. Biol., X., 401.
6 ¥ournal of the Chemical Society, 1892, 1xi., 352.
4
= eg
ee a ce eRe en ne
Fi erthgecs
able conditions. ‘‘ Rot-steep,” or retting of flax, and skele-
tonizing of leaves, are processes of similar character.
Von Senus, in 1890, proved the fermentation of fibre to be
anaerobic, that it was occasioned by a symbiosis, or concurrent
action of B. amylobacter with other organisms, and that gaseous
products of the above character finally remained. He isolated
an enzyme which dissolves fibre, and also a group of the
resolving bacteria from mud, stomach contents, and decaying
vegetable matter. Brown and Morris’ have also isolated from
fungi a similar or identical ferment called ‘‘ cytase,” quickly
dissolving celluloses. Vignal found it in B. mesentericus vulgatus.
It is well known how rapidly Merulius lachrymans, or “‘ dry rot,”
_ softens the fibre of hard wood.
In laboratory experiments with different kinds of cellulose,
paper, cotton-wool, etc., in water inoculated with sewage
organisms, I have observed gradual liquefaction with the pro-
duction of inflammable gases. Omeliansky believes that
_ B. amylobacter is not a separate species, but includes a number
of forms that act as butyric ferments, and that none of them
separately dissolve pure cellulose to any marked extent. Swedish
paper in a solution containing chalk, magnesium, and ammo-
nium sulphates and potassium phosphate, inoculated with Neva
_mud, fermented actively, and both it and the chalk dissolved.
_ By Winogradsky’s elective cultures he isolated the chief bacillus
causing the change, which he describes.
| The changes occurring in silos and in manure heaps may be
| noticed as examples of the anaerobic breaking down of cellulose
| and fibrous matters. Macfadyen and Blaxall show that these
|| results are due to an extensive group of thermophilic bacteria,
| 1’ which are widely distributed in Nature, and especially in sewage
|| and in ensilage. The majority reduce nitrates and decompose
| _proteid matter, but, in addition, they possess the important
|| property of decomposing cellulose into probably CO, and marsh
| * gas. Swedish filter-paper in ten to fourteen days was com-
| pletely disintegrated by these organisms. Omeliansky describes
| a B. fermentationts cellulose, yielding 70 per cent. of fatty acids,
chiefly acetic and butyric, and 30 per cent. of gases(CO, and H).!
| _ His subsequent work differentiates two organisms, which occur
CHEMICAL CHANGES III
1 Transactions of the Chemical Society, 1890, p. 497.
2 Annals of Botany, vii. 120 ; also see J. G. Green, Phil. Trans., 1887, clxxviii.,
57; Marshall Ward, Annals of Botany, 1888, ii., 319; Reinitzer, Zeit, Phys.
Chem., 1897, xxiii. 175 ; Biedermann and Moritz, Pfliiger’s Archiv, 1898, lxiii., 219.
3 Comptes vendus, cxxi., 653.
4 Arch. Sci. Biol. St. Petersburg, 1899, vii., 411.
I12 SEWAGE AND ITS PURIFICATION
very widely, and do not grow on ordinary media, but can be
isolated by the method of accumulation.1 One species evolves
hydrogen, 3°22 grammes of cellulose yielding o‘014 gramme of ©
hydrogen, 0°9722 gramme of CO,, and 2°24 grammes of fatty
acid (1 part butyric and 1°7 parts acetic). The second evolves
CH,, 2°03 grammes of cellulose yielding 0°14 gramme of CH,,
0°87 gramme of CO,, and 1°02 grammes of fatty acids (1 part
butyric and g parts acetic). Both grow best at 35° to 40° C.
This explains the presence of H and CH, in the septic tank in
different proportions.
Vasculose (Fremy), constituting the harder parts of plants, is
also slowly disintegrated by organisms.
The smaller remains of vegetable matter which pass down
sinks occasion considerable nuisance when an attempt is made
to remove them by screens, or on the top of a coarse filter.
They act objectionably in three ways:
1. They set up acid fermentation and corrode iron.
2. A large proportion of domestic vegetable débris (cabbage, —
etc.) contains sulphur compounds, and evolves on decomposition
very offensive odours.
3. They form a pulp which blocks the strainers.
Under anaerobic conditions in a closed space they rapidly —
rot away and disappear, their pectose first dissolving and then q
their cellulose, while the ammonia takes up the acids.
Cellulose can also be brought into solution by the action of
denitrifying, non-sporulating bacteria with restricted access of —
air.2 The presence of considerable quantities of soluble organic
matter prevents the nitrification process, but cellulose is without
influence if the aeration be good. The conjoint action of nitri- —
fication and denitrification processes must play an important
part in the destruction of cellulose in the self-purification of
waters and soils and the biological purification of effluents. —
Cellulose is also decomposed by aerobic, non-sporulating —
bacteria, of which a brown pigment bacterium (B. ferrugineus) ~
is the most important. This bacterium is particularly active
in symbiosis with a yellow micrococcus, which by itself is
inactive. In nutritive solutions, in which the cellulose is
decomposed by the aerobic bacteria of mud or garden soil,
spirilla cultures are always formed abundantly. The property
of attacking cellulose is a general one among the fungi, and is
1 Journal of the Chemical Society, abstract, 1902, 468,
2 C, van Iterson, Centr. Bakt. Par., xi., 689; Chem, Cenir., 1904, i., 1388.
CHEMICAL CHANGES II3
__ due to the enzyme, “cellulase” or cytase. One of the causes
of the formation of humus colouring matters is the production
_of pigments from cellulose by the action of bacteria and fungi,
such as the “ Bismarck-brown ”’ cladothrix found in dust-heaps.
Anaerobically, in absence of nitrates, CO; and hydrogen or
methane, together with acetic and butyric acids, are formed ;
whilst in presence of a nitrate the cellulose is decomposed by
denitrifying bacteria, with formation of nitrogen, COs, and
water.
_ 6. Fermentation of Other Carbohydrates. — Starch, different
‘sugars, and gummy substances undoubtedly enter into sewage,
_but their hydrolysis is so rapid that very little trace of them
‘is found after a short period. The ferments in human feces
allied to diastase and invertase were investigated in 1887-1888
| by O. Loew,! Pavy,? and R. von Jaksch,? and later by
-MacConkey*‘ and others. Those fermentations, such as the
alcoholic, which are usually occasioned by higher fungi like
yeasts and moulds, do not present themselves distinctly,
although the B. coli communis is capable of fermenting sugars
and producing lactic acid, alcohol, and a volatile acid. The
changes are either lactic, from B. acidi lactici, or butyric, from
Clostridium butyricum. or B. butyricus (both anaerobic), and
give, besides the respective acids, carbonic acid, hydrogen, and
water.
it 7. Decomposition of Fats.—Soapsuds and greasy matters
}| Occasion considerable trouble in the mechanical treatment of
| a At Bradford fhe refuse of wool-scouring has been the
|| chief difficulty for years, and has led to several special pro-
esses (see later, Chap. XIV.).
In a bacterial tank the grease is first emulsified by the
ammonia. There are several bacteria that attack fats in
|| presence of nitrogenous substances,° breaking them up into the
) simpler acids of the fatty series, like acetic and butyric, which
/|in their turn are finally resolved, as on p. 109. Mucor mucedo,a
; common mould, resolves glycerides into their constituent parts,
| and at the same time produces a secondary change, giving
| bodies of an aldehydic character,® which would be subsequently
) oxidized. Many other moulds also act on fats, notably the
| iT ! Pfliiger’s Archiv, , xxvii., 203.
| ? Maly’s Jahresb., xiv., 294. 3 Zeit. phys. Chem., xii., 116,
) * Fournal of Hygiene, 1905, v., 333-
: ; pomarues, Zeits, Hyg., xvii. 441.
_ .Fat-consuming Organisms,’’ K6nig, etc. (Analyst, January, 1902, p. 10) ;
also Hanns and Stocky (ibid., 1901, p, 1 5).
1} 8
II4 SEWAGE AND ITS PURIFICATION
ordinary green Penicillium glaucum, which Hanriot found to
contain lipase! besides emulsin and other ferments. Moulds
are not commonly present in the anaerobic stage, but occur in
the second or limited aeration. Ritthausen and Baumann ~ |
found that a great destruction of fat occurred by the action of |
moulds and bacteria in a substance containing proteids as well. — |
The substance they experimented on was rape-cake.2 The
glycerine also ferments. R. Sazerac discovered a bacterium
which has the power of rapidly oxidizing glycerine.® ;
8. The Sulphur Fermentation. — Sims Woodhead found —
Bacterium sulphureum in the Exeter tank. It liquefies gelatine, — :
casein, and other albuminoids, and produces sulphuretted —
hydrogen. Several observers did not, however, find H,S in
the tank gases. I have found that a mercaptan (methyl hydro- ~ :
sulphide) and other ethereal compounds are undoubtedly present
.
:
|
:
in small quantities. They are very soluble and easily oxidized. —
The sulphur fermentations seem to have many stages. —
Zelinski obtained from Black Sea ooze an organism which he
named Bacterium hydrosulphureum ponticum: it reduced sul- .
phates to sulphides, and evolved H,S. He cultivated it in
a special medium containing I per cent. ammonium tartrate,
one to 2 per cent. glucose, 0°5 to I per cent. sodium thio-
sulphate, o’r per cent. potassium phosphate, and a trace of
calcium chloride.* Letts, using this solution, succeeded in
cultivating a similar organism from the foreshore mud of
Belfast Lough.® Martinus Beyerinck® groups in a new genus
Aerobacter—bacteria derived from air, buf facultatively anaerobic,
which cause fermentations, giving H, CO,, and lactic acid,
and also form sulphuretted hydrogen from proteids and from—
sulphur compounds other than sulphates. They are detected
by the blackening of white lead diffused in the cultures. They
reduce nitrates to nitrites, but the presence of the former
prevents fermentation and gas formation. In air they may act
as oxidizers, except the aerobacter known as B. colt communis.
‘The nauseous odours of putrefaction are not due to sulphides.
The reduction of sulphates is due to Spirillum desulphuricans.””
Saltet isolated a B. desulphuricans which reduces sulphates tom
sulphites, but produces no H,S.
1 See Kastle and Loevenhart, American Chemical fournal, xxiv., No. 6. ?
2 Landw, Versuchs. Stat., xlvii., 386, 1896. :
3 Bull. Soc. Chim. de Paris, [3], xxix., No. 16, 1903. \!
4 Proceedings of the Russian Physical and Chemical Society, xxv., [5], 1893. 3
5 Proceedings of the Royal Society of Edinburgh, March 4, 1901. &
6 Arch, Nederland Sci. nat., 1900, [2], iv., I.
)
a ann ne lind
Lo
| ,
ig
ih
CHEMICAL CHANGES 115
Most of the sulphur, however, enters into combination with
the iron present in the sewage, forming insoluble ferrous sul-
phide, and giving a black colour to the suspended matter.
When the black matter is treated with acids, sulphuretted
hydrogen is evolved and the substance becomes brownish, just
as when strong acid effluents from factories are discharged into
ditches or on to the black mud-banks of neglected rivers a
liberation of H,S occurs. In the tank, however, the ferrous
sulphide is protected by the ammonia; on reaching the oxida-
tion stage it is converted into a basic ferric sulphate, forming
an ochreous coating on the materials, which considerably assists
_ in the transfer of oxygen and absorption of organic matter.
At Melbourne a large proportion of sulphuretted hydrogen is
produced during the passage of the sewage through the 23 miles
of pipes from the pumping-station. Being protected from light
and air during transit, a septic action is set up, and much local
; complaint arose as to escaping smell. Sulphur has been burnt
and the SO, forced into the sewage, with the result that com-
_ plaints ceased; but directly the process is stopped the smell
returns. A remedy has been found in ventilation.!
A proportion of the bacteria escape from the septic tank or
_ other anaerobic chamber, but a large number remain entangled
_ in a zooglwa mass either at the top or bottom of an unobstructed
tank, or as a layer on the surface of the flints or other filling
material.
With the exception of not requiring extraneous heat, the
first stage of anaerobic resolution of organic substances is
analogous to the decomposition of coal in gas retorts, the chief
| products, free hydrogen and methane (CH,) being identical ; in
| fact, the latter has been called ‘‘ marsh gas,” from its being pro-
| duced in stagnant pools, where hydrolytic changes occur beneath
the surface. As disengaged from closed tanks, the gas is found
| to burn with a blue flame, like that of an ordinary atmospheric
| burner, giving great heat, which can either be utilized under
boilers or, by means of incandescent mantles, be applied to the
| lighting of the works. At Exeter a gas-lamp of the usual street
| pattern is fed from the gases of the septic tank (see Fig. 26).
Even from open tanks gas can be collected. At Manchester
| -a small gasometer, about 4 feet in diameter, was floated on the
surface of one of the tanks, and from the spherical head of this
1 Thwaite’s Report to Melbourne Board of Works, rgo1. p. 55.
8—2
116 SEWAGE AND ITS PURIFICATION
receiver a pipe conveyed the gas to the attendant’s hut, where
it was used efficiently for light in an incandescent burner, or
for heat in a small gas-stove. The volume generated is tested
by this gasometer, and it is stated that about a cubic foot is
produced in twenty-four hours for every square foot of surface,
and that it is equal in heating power to good coal-gas' (see
further, Chap. XI.).
The residual gaseous energy that is available in this way can ©
be approximately calculated from the consideration that the —
organic matter removed from the sewage and converted into ~
gas in the tank is, for the most part, not oxidized or burnt
therein. The oxygen-consumed figure of the raw sewage, with
its suspended matter, less the oxygen-consumed figure of the
tank effluent, gives a measure of the combustibility of the gases
produced. For example:
PARTS PER 100,000.
OXYGEN-CONSUMED FIGURES,
_Raw Sewage. | Tank Effluent. Difference,
Exeter es Py 6°56 4°32 2°24
Caterham ... tp 14°97 9°25 5°72
Yeovil EN a 7°43 6°11 1°32
It is easy to understand, bearing in mind ordinary burning,
how, in oxidation changes, energy is obtained for the continuance
of the reaction. In hydrolytic changes the source of energy is
not so clear, but it is certain that there occurs a distinct evolu-
tion of heat, small in amount, and almost imperceptible in the
bulk of water, but sufficient to continue the reaction, which is
therefore exothermic, or containing within itself the conditions —
of its own propagation.” Thus in the case of urea—
Heats of formation +77°5 +684 +97°6 2x(+20°4)
es — , Som |
145°9 138'4
but the 2NH,; and CO, neutralize one another, resulting in a
further evolution of about 20 units.
1 Waiter, June 16, 1902. 2 Cf. Berthelot, Comptes rendus, lix., 901, 1864.
;
‘
|
:
$
-
CHEMICAL CHANGES 117
Hence 145*9 must be absorbed, while 158°4 must be evolved,
_ giving a balance of 12° 12°4 units evolved.
[The units are kilogramme-centigrade, and the Sdbetinnees
_ are taken in gramme-molecules. ]
Cellulose.
C,H,,O,+H,O = 3C0,+3CH,
Heat of formation 246 68 29I 49°5
_— _—_—_———————’
Heat absorbed, 314. Heat evolved, 340°5.
Evolution of heat, 26°5 units.
_ The heat of formation of cellulose is calculated thus:
- Complete combustion of 6C and 10H to CO, and water :
6C + 5H, +O in excess = 6CO, + 5H,O
6x97 5x 68"4
924 units.
Combustion of cellulose (C,H,,O,) gives 678 units (Stohmann).
924 — 678 = 246.
Albumin.
Berthelot and André! state that 1 gramme of albumin dried
at 100° C. gives 5,691 calories (gramme-centigrade units).
Hence C,H,,N.0, = 185 of albumin give 185 x 5,691=
| . 1,052,835 =1,053 kilogramme units.
We must first calculate from this the heat of formation of
| albumin:
(8C + 13H+2N +30) burnt =8CO,+6H,O+N,+H
8x97 6x68
776+ 408 =1,184.
Hence heat of formation = 1,184 - 1,053 =131 units.”
Now, assuming a complete hydrolytic change :
4C,H,,N,0,+ 14H,O=4N,+ 19CH,+13CO,+4H
Thermally 4x 131 14x68 Igx16°5 13x97
5244952 314°5+1,261
1,476 absorbed. 1575°5 evolved,
Giving a balance of 1,576 — 1,476 = 100 units evolved.
1 Chemical Society Abstracts, 1890, p. 937
2 I have left out one hydrogen atom in 1 this calculation, because in the enzyme
_ reaction one hydrogen per molecule of albumin is set free.
118 SEWAGE AND ITS PURIFICATION
It is curious that the percentage of the heat evolved in the
products is in each case nearly the same:
en oa Heat evolved, Per Cent.
Urea... a +e 158°4 12°4 8
Cellulose... na 340 | 26°5 8
Albumin... pie 1,575 100 7
These enzyme reactions follow the ordinary chemical law of
going in the direction of an evolution of heat. They occur
at atmospheric temperature, and it has been pointed out by
Van t’Hoff that the lower the temperature the more nearly will
Berthelot’s law of maximum work be obeyed.
THE SECOND STAGE, OR SEMI-AEROBIC BREAKING-DOWN
OF THE INTERMEDIATE DISSOLVED BODIEs,
is not generally distinguished sufficiently from the first, nor
allowed adequate time to develop. It occurs in the upper layers
of bacterial filters, as requiring little oxygen, and results —
generally in the production of mttrites, the conditions being ~
favourable to the growth of B. nitrosomonas. In this stage the ©
amido-compounds, fatty acids, and dissolved residues of hydro-
lysis undergo a further resolution.
Nitrosification, or the production of nitrites, and secondarily
of nitrogen and its lower oxides, by partial oxidation, should
normally occur in the second stage of bacterial purification.
Wherever we find a final filter acting badly, either from deficient
aeration or other cause, the fault is at once indicated by the
appearance of a high proportion of nitrites, as nitrostfication is
not nearly so delicate a process or so difficult to initiate or
control as nitrification, or the production of nitrates, which it
would naturally precede. For example, P. F. Richter isolated
a coccus of medium size, which in twenty minutes produced a —
very intense nitrite reaction in fresh urine, and in addition ©
reduced nitrate to nitrite—a retrograde change which I have ©
already remarked as common to many bacteria, and character- —
istic of crude attempts to introduce nitrification before the —
sewage is properly hydrolysed and prepared. Nitrosification —
proceeds most rapidly in the presence of diffused light and of
ga aT ®
a
—s
ape SE ES Ds AS
1
CHEMICAL CHANGES 119
a moderate amount of air. In many processes the purification
_ goes no farther, when nitrification is not subsequently active.
The nitrosification change in the second stage gets rid of the
transition products—ammonia, amido-acids, and the amides—
by double decomposition into water, or hydroxy-compounds
(which are afterwards broken up by fermentation) and nitrogen
gas. As simple instances we have:
NH,+ HNO, = 2H,O+N,
(NH,)CH,COOH+HNO, = (OH)CH,COOH+H,0+N,
Amido-acetic acid. Glycolic acid.
(NH,)C,H,+ HNO, = C,H,0OH+H,0+N,
Ethylamine. Alcohol,
In the process, which takes place especially in the resting-
full period of filters, nitrogen, and sometimes secondarily CO,,
_ are evolved, but scarcely any hydrogen or methane. It is there-
_ fore accompanied by a great loss of nitrogen, a smaller loss of
_ carbon, and a removal of odour.
Grimbert! has shown that B. coli communis and B. typhosus
do not disengage gas in 1 per cent. solution of peptone plus
_ I per cent. potassium nitrate, but the gas is produced when the
_ peptone is replaced by meat extract, which contains simpler
- amido-compounds. The volume of nitrogen evolved is always
about double the amount which the nitrate destroyed could-
possibly produce, proving that the gas is derived from the
secondary reaction between amido-substances and the nitrous
_acid produced by denitrification. The bacilli develop very well
‘in a medium containing 1 per cent. of nitrites, and disengage
an equal or even larger quantity of nitrogen than in the same
medium containing 1 per cent. of nitrates. He believes that
_ this is the explanation of the loss of nitrogen in the soil.
| __ Nitrous compounds also serve as carriers of oxygen from the
air tothe organic matter in a way similar to their well-known
| action in vitriol chambers. Miintz? found that the calcium
| } nitrite in sterilized soil, when CO, was passed over it, gave off
nitrous acid rapidly, but on exposure to air, or on passing CO,
Bh Jatgely diluted with air, it was quickly oxidized to nitrate. The
_ following are examples from my own experience of the changes
| in filter effluents (parts per 100,000) :
1 Annales de I’ Institut Pasteur, January, 1899.
: Comptes rendus, 1891, CXii., 1142.
120 SEWAGE AND ITS PURIFICATION
Original N as | After Twelve | Original N as | After Twelve
Number. Nitrate. Days. Nitrite. | Days.
VI. I‘OI I°'l5 About or 0°48
VIL. 0°59 0°62 About 0°05 | 0°67
VIII. 0°70 0°77 About 0°05 | 0°55
i
Another filter effluent illustrates a usual rule—that while
nitrosification is active. nitrification is almost stationary ; but
when the nitrites begin to decline the nitrates rapidly rise:
November Io. November 18. December 2.
Nitrous N... ah 0°03 0°74 trace
Nitric N -... — 1°49 1°51 2°58
In a septic tank effluent on November ro the nitrate was
0'030, the nitrite none; on December 2 the nitrate was 0°060,
the nitrite excessive; the nitrite had obviously been formed
from ammonia, and not by reduction of nitrate. An instance
of the transfer of oxygen by means of the oxidized nitrogen
compounds, resulting in a reduction of the organic carbon,
without a corresponding decrease in the amount of total
nitrogen, was given by my analyses of the Caterham effluents
in 1899, when kept for a short time in stoppered bottles partially
full.
No. 1. No. 2. No. 3. No. 4. | No. 5.
Samples. |
Jan.26| Feb. 1 | Jan. 27| Feb. 1| Jan. 28) Feb. 1| Jan. x0 Feb. 1 ee 31| Feb. 1
Ammoniacal N ... | 12°15 |11°g | 12°56 |12"r | 12°35 | 11°54 |21'4 |20°6 | 23°8
Organic N --. | 0°618] O'412) 0°823) 1°03 | 0°618) o-41 | 1°23 | 1°44 | O°82
Nitrous N ++» | O°148| 0°074) I°924|. 1°702| 1°184] 1°40 | 0°407/ O°4I | O'59 | 0°666
Nitric N ... | 7°68 | gto | 4°14 | 4°36 | 5°60 | 6°46 |10°3 | 10°64 | 6°46] 5°52
Total nitrogen 20°596] 21°386| 19°447| 19°192| 19°752| 19°81 | 33°337| 33°09 | 31°67
Oxidized nitrogen | 7°828) 9°74 | 6:064| 6062, 6°784| 7°86 |10°707| 11°05 | 7°05
Percentage of
nitrification ... | 38°0 |45°5 | 310 |32°0 | 34°5 |39°6 |32°0 |33°4 |22°3 |19°5
oxygen consumed | 3°32/ 2°24 | 6°27 | 4°43) 4°19 | 3°47 | 4°85 | 2°78 | 4°52
hlorine ... > | 8s — |19°75| —-~ |2I°5 — |2215| — | 24°35
Percentage of re-
duction in the
oxygen consumed) — | 32°5 — |30°0 on 1X70 — 43 sy
The chief change seems to have been a transfer of the oxygen
of the air by means of the nitrous acid to the carbonaceous
matter. The nitrifying and nitrosifying changes appear to
have gone on continuously, the nitric being reduced to nitrous
FC a i hy AMIS confirms and extends these
| fesults, early observed by Jordan and Richards.
1 Ann, Chim. Phys, , 1898, vii., 45.
2 Fournal of the Royal Agricultural Society, 1897, II1., viii., 577.
3 Chemical Society’s Transactions, 1888, 391.
4 Bied. Central., 1900, xxiv., 273.
® Centr. Bakt. Par., 1901, ii., 781.
128 SEWAGE AND ITS PURIFICATION
Another form of denitrification is the reduction of mitrate to
nitrite. Meusel’ first showed in 1875 that well-water con-
taining nitrates on standing soon developed a reaction for
nitrites—a change that was prevented by sterilization or by
certain antiseptics—and Wagner of Darmstadt first elucidated
the importance of the reaction. According to Abelous a
soluble ferment exists in both animal and vegetable organisms
which is able to convert nitrates into nitrites.”
Percy Frankland*® gives the following list of thirty-two
species that he examined:
1. Reducing Nitrate to Nitrite.-—B. vamosus, violaceus, verm-
cularis, liquidus, cereus, pestifer, plicatus, prodigiosus, chlorinus,
citreus* (strongly). B. nubilus, aurescens, fluorescens, aureus, pro-
fusus (slightly). Mucrococcus carnicolor, rosaceus (very slight).
2. Not Reducing Nitrate to Nitrite-—B. viscosus, arborescens,
aurantiacus, subtilis,’ aquatilis, levis, polymorphus ; Sarcina auran-—
tiaca, lutea, liquefaciens ; Streptococcus liquefaciens ; Micrococcus
gigas, albus, candicans, chryseus.
He concluded that the chemical behaviour of these organisms —
was the same, whether air was present or excluded, and that —
none of them could either produce ammonia from nitrate or
oxidize ammonia to nitric acid. t
R. Warington® states that his results in cultivation did not _
bear out the general opinion that wheat straw promoted
denitrification. Probably this is explained by the observation
of Matz and Wagner,’ connected with what we have said
about humus, that as ‘‘ humification”’ proceeds the power of —
destroying nitrates diminishes. W. Kruger and Schneidewind —
attribute the action of straw to the pentosans present, while
sugars, glycerol, citrates, malates, etc., also promote the
activity of denitrifying organisms, as well as excess of moisture
ae |
1 Berichte, vili., 1215.
2 Comptes rendus Soc. Biol., 1903, lv., 1080. .
8 Loc. cit., 372. See also on the same subject: Hatton, Chemical Society's
Transactions, 1881, 266 et seg. Gayon and Dupetit, Berichte, 1882, xv., 2736; 1883,
xvi., 221 (anaerobic organisms.) Déhérain and Maquenne, Berichte, 1882, xv.,
3081 (B. butyricus). R. Warington, and Munro, Chemical Society’s Tvansactions,
1886, 632 (organisms generally). Heraeus, Zeits. f. Hyg., 1886, 193 (pure
cultivations). Also Clark and Gage, Eng. News, N.Y., 1905, p. 27; Techn.
Quarterly, xviii., 1905, p. 5; J. Amer. Chem. Soc., xvii., 327, 1905.
4 To these must be added Proteus mirabilis and vulgaris, B. mycoides, megaterium,
and acidi lactici, which powerfully reduce nitrates to nitrites, and sometimes even
to ammonia, and are frequent in sewage,
5 Houston states that several varieties of B. subtilis occur in sewage (Second
Report of the London County Council, 1899).
8 Journal of the Royal Agricultural Society, 1897, III., viii., 577.
7 Landw. Versuchs Stat., 1897, xlviii., 247.
i
CHEMICAL CHANGES 129
: (as in sewage) and a high temperature.! Th. Pfeiffer? showed
| that denitrification did not generally take place in the absence
‘of particles of straw, feeces, or vegetable tissue which act
as food to the denitrifying organisms, and considered their
chief food substance to be xylane, or wood-gum (C,H,O,),
isomeric with cellulose, but soluble in alkalies, therefore re-
moved by the first alkaline fermentation. This is an additional
fact, explaining why the sewage should be properly fermented
‘before entering the final nitrifying filters (see further, the
‘London results, Chapter IX.).
q Denitrifying bacteria are of three classes: (1) Those which
‘destroy nitrites, but not nitrates—namely, Bacterium denitri-
ficans I. of Burri and Stutzer. (2) Those destroying nitrates,
but not nitrites—B. pyocyaneus and Bacterium denttrificans V.
(and also many of those already quoted from Percy Frankland).
(3) Other denitrifying bacteria which destroy both nitrites
and nitrates. From Adeney’s and other researches, the last
e not common, though among them sometimes appear B.
fluorescens liquefaciens,® B. pyocyaneus, and Vibrio demittrificans.*
‘hey rapidly produce N, and perhaps N oxides, in presence of
| much CO,, but are antagonized by abundant aeration. Jensen
| describes six others.°
| Houston, in the London County Council Report, 1899,
records: B. Coli Communis.—In twenty-four hours at 37° C.,
‘teduction of nitrates to nitrites well marked (broth, 5 per
| cent.; potassium nitrate, o°I per cent.; water, 94°9 per cent.).
>. Mesentericus.—Sewage variety E.: Great reduction of nitrates
0 nitrites in twenty-four hours at 37° C. Sewage variety I.:
No reduction of nitrates (showing the value of the nitrite test for
| diagnosis). He also gives B. frondosus fusiformis as negative,
| B membraneus patulus and B. capillareus as active, in formation
| of nitrites from nitrates.
Ie aN large mbar of organisms found in sewage exert a distinct
| Binence in bringing about nitrification, besides the species
) Specially described as “nitrifying,” since many which grow
| a and break up sewage material have the power of
) 1} Landw. Jahrb, 1899, 217. Dr. Hugo Weissenberg has also some elaborate
| indies on ‘ ‘ Denitrification,” in the Archiv f. Hygiene, 1897, xxx., 3.
2 Deut. Landw. Presse, 1897, 911; also J. Stocklasa, Bied. Centr., 1899, xXxXvii.,
{ 797: Stutzer and Hartleb, ibid., 1900, Xxix., 126; Jensen, Centr. Bakt., iv., 401.
_ ° Hygien. Rundsch., 1899., ix. , 538; Chem. ‘Centr. 1900, i., 52.
4 Bied. Centr., 1899, XXV., 854.
(35 Centr, f. Bakt., 1898, iv., 401.
ih
130 SEWAGE AND ITS PURIFICATION
inducing or commencing this process if sufficient oxygen be
present. Those mentioned on p. 68 had been separated by
plate cultivation in gelatine; therefore the ordinary nitrifying
organism, which will not grow in gelatine, could not have been
concerned.
The Massachusetts Report of 1890, p. 788, states that ‘‘an
effluent from a sewage filter, where nitrification is complete, con-
taining 2 per cent. of the total organic matter of the sewage,
will not serve as food for bacteria, because it has been worked
over already by bacteria in the filter, nearly everything
available having been removed.’’ This is true of most species,
but we have seen that denitrifying organisms in presence of
nitrates can freely attack this residual organic matter, and that
after partial nitrification in a filter the action of these bacteria,
which absolutely require a certain amount of organic food,
converts it into carbonic acid and harmless gases, taking the
requisite oxygen from the nitrates dissolved in the water. I
refer later to the CO, evolved in the “ resting empty ”’ stage of
intermittent filtration.
The weight of dissolved oxygen in well-aerated river water |
being approximately I part per 100,000, the oxygen-consumed —
figure in a sewage or effluent indicates the minimum quantity —
of such water required to destroy the organic matter by means
of the free dissolved oxygen alone. In raw sewages this may
amount to as much as 20 volumes. In the raw sewages
yielding the effluents referred to in the table on p. 131, the
oxygen-consumed figure was as follows in parts per 100,000:
Exeter, 6°56. Sutton, 2°94. Caterham, 14°97.
The ‘“‘available oxygen” is that present as nitrate or nitrite,
and the amount of carbonaceous matter requiring destruction
is measured by the ordinary figure of ‘‘oxygen consumed” as
determined by permanganate, since after four hours’ heating
with permanganate no dangerous matter can be left. The
table shows that the available oxygen as nitrates and nitrites _
is in good effluents quite sufficient to deal with the organic —
matter, even without help from the oxygen dissolved in river
water. A large number of the published analyses of effluents —
are vitiated by the fact that the samples have not been analysed —
until some days after collection, frequently at the end of a —
long transit by rail or other conveyance, during which the
agitation and inevitable contact with air will have considerably
,
*]
L
CHEMICAL CHANGES 131
altered the composition in a favourable sense. It is therefore
desirable, wherever possible, to analyse an effluent within a
very brief time from its collection, and the more important
determinations should be made on the spot within a few
minutes of the discharge. Although this is undoubtedly the
only fair procedure, such analyses are not, of course, comparable
with those carried out under the usual conditions, which give
an apparently higher quality to the effluent, but they demon-
strate the existence of the rapid and. beneficial improvement
in some effluents which I consider, with Adeney, one of the
main criteria of safety.
TypicAL EXAMPLES OF THE OxyGEN RELATIONS.
Parts per 100,000.
S§ 5 a ee S
gf/e ¢ igo Of |) & (ReocbhBvoals
Bl 8s | £ ES] os |] 2 ioe. 6 eoh| ad
= | #0] # [59] 62) & [sR l|Csse| seg
me [Aw Bee) ae 8 Oe] os Ea! 92
aj sz] 4a [8a] 89) 8 |o528| 228s | #3
Oo re) “<3 | ® lwe-|Seaels
Zz a = 0 ® | Os Sea] G
$4) Oo |ot [68s v
ou 30 > en o
| Be cates sewage farm
. osha 1896 ++ [0°75 | 2°r4 |heavy) — | 2°14 | 1°79) 1°2 foe) 48°7
oydon sewage farm
uent, 1895 0°88 | 2°51 |jheavy) — | 2°51 | 1°29) I°9 0°O 63'0
River Brent, polluted, : ;
1896 .. oo | o'o | faint | — | oo | 2°32) o'o 2°32 | ovo
_ Precipitation and coke- trace
breeze filter, Dibdin,
- 1894 0°202|} 0°577, — | — | o° 1°04) 0° 0°46 | —-
_ Tank effluents: ca fons i
Exeter, 1896 ++» |O°O4I| O*°II7| trace; — | O'II7| 4°32) 0'027| 4°2 I‘o
Ashtead, 1898 ... 0°12 | 0°343| 0'0 (0'0 | 0°343) 9°84) 0°035 9°5 I‘o
| z Eaterbam, slong 0°70 | o'o | trace} — | — | 9°25! o’o 9°25 |trace
oarse utton, 1899 0°73 | 2°09 | 0°186.0°316; 2°41 | 1°46 1°6 oho) 27°0
_ Filtrates (final effluent) ; i ; ,
averages :
Exeter, 1897 s+» |0°848) 2°44 | 0°565.0°970| 3°41 |0°966 3°53 | O'0 33°0
Ashtead, 1898 ... |6°44 |18°4 | 0°03 lo °051/18'45 |0°609 30°0 0°O 916
Caterham, 1899... g'0 [25°74 | o '346/0" *59 |26°33 | 2°71| 9°7 0'o 62°0
Sutton, 1899 —....._—- (3°33. | 9°51 | oF es 184 9°69 cee | ee ohio) 82°0
\
Q—2
CHAPTER VI
IRRIGATION AND SEWAGE FARMS
Broad irrigation—Soils—Application of lime or ashes—Trenching—
Organisms in soils—Suitable crops—Transpiration of water—
Statistics of sewage farms—Systems of distribution—Ridge and -
furrow — Catchwater — Intermittent irrigation with under-
drainage—Merthyr Tydvil—Calculation of dilution by subsoil
water—Irrigation with previous treatment—Areas required—
General aspect of land treatment.
EARTH-disposal is the main factor in the three forms of
irrigation :
A. Broad Irrigation, defined by the Royal Commission on
Metropolitan Sewage Discharge, 1884, as “ the distribution of
sewage over a large surface of ordinary agricultural land, having
in view a maximum growth of vegetation (consistent with due
purification) for the amount of sewage supplied.”
_ B. Irrigation with Copious Underdrainage, similarly defined
under the head of “ Filtration ” as ‘‘the concentration of sewage,
at short intervals, on an area of specially-chosen porcus ground,
as small as will absorb and cleanse it, not excluding vegetation,
but making the produce of secondary importance. The inter-
mittency of application is a sime qué non even in suitably con-
stituted soils, wherever complete success is aimed at.”
c. Mixed Systems, including Previous Sedimentation or Chemical
Preparation.—These, which may be called shortly the broad,
the intermittent, and the mixed systems of irrigation, are
‘“sewage farm” schemes, and are jointly saddled with the
following difficulties :
(1) The unsuitability of the only land often attainable.
(2) Local opposition, and the very high prices generally
demanded for the area.
(3) The failure, under these conditions, of making the sale of
the produce remunerative.
A. Broad Irrigation. This, the oldest method, demands a very
large extent of land (approaching 1 acre per 100 of population),
132
‘ ib * 5
IRRIGATION AND SEWAGE FARMS 133
since it chiefly depends on the surface for purification, and
especially on the nitrifying organisms, which, as requiring air, —
do not work well in the depth, and disappear altogether at a
certain distance below the surface. R. Warington tested for
them in the heavy soil at Rothamsted by their power of
nitrifying weak urine. Thirty-eight out of thirty-nine samples
down to 3 feet were active; at 5. feet half were inert, and below
6 feet the organisms seemed to be absent. The action extended
for only 18 inches in clay, but to a greater depth in sand, and,
besides the scanty aeration, the deficiency of phosphates in the
lower layers adversely affected nitrification. Soil which rapidly
nitrified when in a moist, aerated condition became a vigorous
denitrifying medium when water-iogged.
Very near the surface aerobic organisms greatly pre-
dominate; deeper down the anaerobes increase until we come
to a layer in which practically only anaerobic bacteria . are
found, while deeper still there may be no organisms.!
For these reasons sewage is preferably made to pass obliquely,
by digging deep trenches at the lower end of the farm, and the
feeders are made to follow the contour of the ground. When,
owing to geological structure, the liquid. can rise again as
springs, the absence of the first nitration may be concealed by
a second process occurring in the ascent to the surface. On
areas at a distance from habitations, with a porous soil (espe-
cially under rice cultivation, as in India), broad irrigation has
been successful, ditches and intercepting drains being provided,
and all wells on the sewage area, or within a radius likely to be
affected, being closed.
The action of soil on sewage consists of (1) mechanical
straining ; (2) mordant or ‘‘ adsorptive”’ effect, chiefly possessed
__ by the hydrous silicates of clay, which, if it be made sufficiently
porous, takes up soluble matters, but soon becomes saturated ;
(3) biological changes. While it was originally held that the
“cleansing power’ of a soil was determined solely by its
physical condition, porosity, freedom from clogging and water
retention, it has since been proved that chemical composition
and bacterial efficiency have a high influence. Sir E. Frank-
land, in 1870, comparing the soil of the Barking sewage farm,
in which nitrification was absent or very slow, with a loam
from Dursley, in Gloucestershire, which showed his highest
efficiency (purifying sewage at the rate of nearly 100,000 gallons
' Sims Woodhead, Baltimore Sewerage Commission, 1899, p. 105.
134 SEWAGE AND ITS PURIFICATION
per acre per day), notes that the latter contained 8°I per cent.
.of carbonate of lime, the former under 2 per cent.; and we
now know that the lime is favourable to the nitrifying organism.
Effluents which have been chemically treated with lime may
acquire sufficient alkaline base to favour the growth of the
nitrifying organisms, even when the soil or the filter-bed is
originally devoid of such base. In the case of a sewage farm
in Surrey, where the soil, a ferruginous sandstone, is very
deficient in lime, I found that the calcium carbonate increased
through the treatment of the land with sewage, and the quality
of the effluent also improved :
x II. III.
Land before | After 18 months,| After 18 months,
Treatment. Field I. Field II.
Moisture... a : 10°96 13°56 | 14°20
Mineral matter os 80°34 82°76 81°04
Organic Ki ve 8°70 3°68 4°76
10000 100°00 “10000 ©
Lime.. a 0'224 0°54 1°23
Equal to CaCO, a 0°40 096 2°20
Organic nitrogen ea 0064 0°193 0'230
I have obtained the following results in an inquiry in which q
alternative sites were available for a sewage farm :
A. B. C.
Percentage of water ... Sen, OFF5.4 1°OO stam
Parts of nitric nitrogen produced per
100,000 parts of soil in five days on
dilute urine ... asi see ... O'168 0°504 0°36
Showing that the dryest of the soils was the most active
bacteriologically.
Both a mechanical and chemical analysis of samples of soil
is necessary in the selection of proposed sites. The most un-
suitable conditions are stiff tenacious clays, peaty or boggy
ground, and coarse gravel with hard conglomerated layers. In
India, where the temperature is higher, all bacterial change,
including nitrification, occurs more rapidly, the growth con-
tinues for a longer time in the year, and the sewage is generally
less voluminous than in England'; hence a less area per person
1 A. E. Silk instances a sewage at Calcutta which consisted of fecal matter
and urine mixed with only 3 gallons of water per head,
IRRIGATION AND SEWAGE FARMS 135
is found requisite; thus, Jones! recommends at least 1 acre of
good soil for 500 persons at 15 gallons per head. Professor
Robinson gives the average of English sewage farms as 149
people to each acre irrigated with 38 gallons of sewage per
head per day, and this is frequently too limited an amount of
land.
Madras in 1gor daily disposed of some 4,000,000 gallons
of its sewage on farms in various parts, and eventually
the whole 15,000,000 gallons are to be dealt with on a farm
with sandy soil near the sea, where indefinite extension is
possible. Nothing but successive crops of Harriali grass were
grown on the farms by the contractor, who paid an annual rent
of 50,000 rupees. In the transit for three to six miles a con-
siderable amount of nitrification occurs in the sewage. Sydney
and Melbourne, and some other places in Australia, have yor
sewage farms on areas of sandy soil.
At Berlin, on a sand subsoil, 1 to 2} tons of ‘‘ waste lime”’ per
acre have been spread with benefit over fields previously
drenched with sewage. For clay, ashes from the town refuse
are dug or ploughed in. Deep steam-sloughing, and even sub-
soiling to turn in the sludge, are at intervals necessary, since
crude sewage discharged direct on land rapidly coats it with a
felted layer of black decomposing matter, which hinders the
access of oxygen, chokes the plants, and soon creates a nuisance.
Dr. Divers describes the cultivation of rice in Japan by
surface irrigation on clay land. The sewage as collected is
placed in large tanks in the fields, covered over with a loose
roof of straw, where it is allowed to ferment for some time, till
all the urea is converted into ammonia. The liquid passes over
terraces from field to field till it reaches the watercourse in the
valley. Dr. Kellner ascertained that the crops were good; the
liquid flowing over the soil gave up much of the mineral con-
stituents, nitrates were formed and absorbed, and the effluent
was very satisfactory.
In broad irrigation there is always a risk that a portion of
the raw sewage may escape wholly unpurified. On clayey
soils the liquid passes almost entirely over the surface, and this,
if a sufficient distance be given, has been found, as above, to
effect a great purification, with, however, generally a nuisance.
Mere deep trenching of heavy soils, laying pipe drains, and
filling up with ballast, etc., yields an almost unoxidized and
‘* Manual of Hygiene,’’ 1896, p. 484.
136 SEWAGE AND ITS PURIFICATION
very impure effluent; the same occurs from the production of
cracks in clay by drying, or from the fissures so common in
chalk formations. At Beverley, in Yorkshire, the top layer of
clay had become extensively cracked in the summer, allowing ©
raw irrigation sewage to reach the chalk beneath, whence it
travelled through fissures about half a mile to a deep well that
was a portion of the water-supply of Beverley.’ The reports to
the Royal Commission on Sewage” give examples of under-
drained farms with shallow surface soil over clay, where “ the
sewage partly finds its way into the drains through cracks”; in |
one case the effluent contained pieces of straw up to 4 inch
long, which had reached it through these cracks, and the
effluents were generally of very bad quality.
Stretford Sewage Farm (Mersey and Irwell watershed) reports
that the drains should be laid in parallel lines, not in herring-
bone fashion. ‘Trouble has been encountered from worms and —
rats causing holes, which allow sewage to run straight to the
drains.
“In dealing with an infected worm area, we pump the very
strongest sewage we can from the bottom of the tank, and on some
occasions, previous to dosing the land with strong sewage, have
sunk down to the drains and temporarily blocked them up, and have
thus been so far successful in killing them that the land has again
continued to produce as good an effluent as before. The worms do ©
not die in their holes, but come to the surface. They have caused
an imperfect effluent even when the drains have been as much as
44 feet in depth.”
Dr. Houston has counted the number of bacteria and spores
present in twenty-one different soils) Among them he finds:
Organisms per
Gramme of Soil.
1. Sandy soil near the sea.. ‘se 8,000
2. Suburban garden soil, not recently manured ae 518,000 ©
3. Dark garden soil, manured six months previous ... 795,000
4. Light-coloured soil, not recently manured or “a
disturbed.. 1,051,000
5. Black loamy soil, occasionally having farmyard |
manure ... is 1,084,000
6. Rich heavy clay, periodically manured .. in 2,531,000
7. No. 3 above, after recent manuring ... 3,308,000
8. Garden soil treated with human feces and urine
for six months previous de . 26,780,000
g. Sewage field, from a trench along which sewage
had been running a short time before w+. 115,000,000
’ See p. 9, also a report to the War Office by Davies and Tyndale in 1902.
2 Vol. iv., part ii., 1904, pp. 243-249.
,
B. coli and its allies are not discoverable, or are present in
small numbers only, in virgin soils, such as those from unculti-
vated uplands... Dr. W. G. Savage obtained similar results
from a number of mountain samples, and concluded that if
present in ordinary hillside soils the coli has been derived from
animal excreta.”
Dr. Sidney Martin has proved that B. typhosus in virgin soils
attenuates and after a short time disappears, but in those which
contain large quantities of organic matter, particularly from
sewage, it will multiply even through extremes of heat and cold
(from 37° to 3° C.), and under conditions of dryness, and will
_ survive for at least 450 days alone, or 50 days in presence of
other bacteria.
Although no injury to health has been directly attributed to
sewage farms, the possibility of the survival, or even the multi-
plication, of pathogenic organisms on such farms must be taken
into account when the drainage waters pass into or near
drinking-water supplies. (See further p. 193 et seq.)
IRRIGATION AND SEWAGE FARMS 137
SUITABLE CROPS.
Unless proper cultivation is adopted on sewage farms, the
soil is given up to a profuse growth of weeds, which have to ‘be
removed and the soil broken up to keep it porous, without any
return for the labour. The conditions are different from those
of ordinary agriculture, inasmuch as, although the liquid un-
_doubtedly contains the elements of plant food, they are supplied
too continuously and in too great dilution with water, while
the volume is usually greatest at a season when it is absolutely
injurious to crops. Therefore for successful cultivation the
plants must only receive the sewage as they want it, the
remainder being treated by other methods. It is also neces-
sary that the plants should be of such a character as can be
grown on a ridge, so as to prevent the liquid at any time
flooding their growing tops. The difficulties are obviously
lessened under the “separate system” of sewerage, in which
surface and storm water are excluded (see Fourth Report of
Royal Commission on Sewage, 1904, part iv., p. 5).
Déhérain® has determined the quantity of water exhaled in
one hour by certain growing leaves exposed to the sun:
1 Report of the Medical Officer of the Local Government Board, 1899-1900,
Pp. 510.
* Fournal of Hygiene, July, 1902, p. 331. 3 Chimie Agricole, p. 281.
138 SEWAGE AND ITS PURIFICATION
Plant Temperature of Weight of Water transpired by
; the Air. 100 Parts of Leaves,
I. Il, Ill.
Colza ... 25°C Eginia I'5 se)
Colza ... 36° Ea'9 1] —- a=
19° 74°2 718 os
Wheat i 28° 88-2 | a he Sal
Rye ... r? 36° Io0'0 = gto QQ
Therefore in one hour a young leaf of a cereal can evolve about
its own weight of water. Hellnegel and Wollny found that
the transpiration of water varies from 233 to g12 pounds for
every I pound of plant tissue formed, according to the leaf
surface and length of growth, being greatest in clovers and
grasses, and least in roots and potatoes. Lawes estimated that
250 to 300 parts of water are evaporated for every 1 part of
dry solids elaborated. by the plant. The transpiration of
Graminez (grasses and cereals) is greater than other plants;
hence they are indicated as absorbing a larger quantity of
sewage. At the Berlin sewage farms the proportion grown is,
in acres, cereals 3,000, grass (rye grass and Timothy) 2,000,
root crops 1,000, oil seeds (colza, etc.) 250, with rotation.
Italian rye grass, according to Rawlinson and Read’s report
to the Local Government Board in 1876, “absorbs the largest —
volume of sewage, occupies the soil so as to choke down weeds,
comes early into the market, bears five to seven cuttings in the ©
year, and produces 30 to 50 tons of wholesome grass per
acre.” It generally exhausts itself in about three years, when
it is ploughed up and replaced by root crops (usually mangolds)
or cabbages (Beddington), with a return afterwards to rye
grass. Mangolds yield a heavy but rather watery crop. Wheat
and oats are stated to run to straw rather than to grain.
Leguminous plants, which are capable of taking up nitrogen
from the air, are not adapted for an object which aims at re-
ducing the organic nitrogen. The Royal Agricultural Society’s
Report on the Bedford Sewage Farm mentions one plant,
“prickly comfrey,” useful for horse fodder, ‘‘ which it seems
impossible to damage by sewage, as it was completely flooded
for three weeks in succession, with benefit, and yielded three
crops in a year.”’ Celery also flourishes, and sunflowers have
been successful. Generally the plants that are found to suit
a
IRRIGATION AND SEWAGE FARMS 139
best are those that are commonly grown in the neared
hood.
At Berlin, before reaching the grass plots, the sludge is
| | removed by catch-pits, as a coating of sludge interferes with
| |the growth. For cereals and seeds unstrained sewage is only
_ applied while the crops are underground, so that it does not
_ come in direct contact with the plant, but roots and_ grass are
| irrigated all the year round. The farms have an area one and
| a half times that of the city, and lie about six to ten miles
| distant. The surface is divided into level beds 150 to 200 feet
| square, separated by distributing embankments and ditches,
‘y with underdrains 4 to 6 feet deep and 16 to 30 feet apart,
|} according to the nature of the ground. The effluents, which
)) are clear and without odour, are collected by main channels
and carried to the nearest watercourse. The sewage is admitted
to the carriers from the forcing mains through checking
chambers, made of woven willow and posts driven into the
sand; thence it passes through wooden sluices to the beds.
Average amount dealt with: 6 to 73 million gallons per acre ~
per annum, or I acre to 750 people. The best paying crop is
Tye grass, of which six to seven crops are raised each year;
turnips, beet, cabbage, and other water-absorbing plants are
raised in larger quantities. The farms are said to yield a
small profit over the working expenses, excluding the cost of
pumping.
At Brighouse, Yorkshire, it was reported in 1903 that the
sewage, treated with 18 grains per gallon of lime and sedimented,
gives good crops of rye grass and mangolds, and that cabbages
make an excellent crop providing no stagnant water is allowed
to remain about the plants. The sludge is used freely, and is
found to bea good manure on the lands at present not irrigated,
and is taken by farmers. The provision for land and works was
unusually liberal, and had cost £100,000.
Details of a number of sewage farms are given in the Fourth
Report of the Royal Commission on Sewage, 1904.
\ Analyses of drainage from land receiving raw and chemically
| treated sewage show that nitrification takes place more rapidly
with the latter, as the felting of the solids on the surface
prevents air from passing into the soil for oxidation when
untreated sewage is passed directly on the land.’
1 For an interesting example vide Ashton, ‘‘ Treatment of Wigan Sewage,’’
. Transactions of the Institute of Sanitary Engineers, November, 1899; see also
Pp. 147 and 159.
140 SEWAGE AND ITS PURIFICATION
Osier beds are often planted, and act partly as strainers;
watercress and many aquatic plants have been found useful.
With careful management the sale of produce from a sewage
farm may be made to yield a small balance over working
expenses, but not sufficient to repay the capital, which is
estimated to be about five times that required for an ordinary
farm. There is a better prospect where a large area of vacant
seashore is available, as in the case of Dantzig, where a daily
sewage flow of over 3} million gallons (in 1894) was disposed
of by irrigation on ‘‘dune sand.” The liquid sank rapidly,
leaving the suspended matter on the surface and in the pores
of the soil. The land, originally let at 4$d. per acre, was sub-
sequently leased to a contractor for thirty years at £1 11s. 6d.
per acre, and the scheme is said to have been in every way
successful. The depth of humus or vegetable soil was increased
by the continued irrigation of about 5,500 gallons per acre per
day, and the effluent would have satisfied the coqnienaa of
- our Rivers Pollution Commissioners. !
In America, especially in Massachusetts, where there is
sufficient area of sandy soil, the sewage is successfully treated
by intermittent filtration at the rate of 50 to go thousand
gallons per day. Ina great number of localities the treatment
is screening, sedimentation, and filtration through land which
is prepared by removing the loam and levelling. The land is
ploughed and harrowed, and planted with corn or other crops
every spring.
Some statistics of sewage farms are given on p.141. The first
series was published in 1896; the Berlin figures are dated 1890;
and the subsequent ones are of 1900, from the Fourth Report
of the Royal Commission on Sewage, 1904, vol. iv., part i., p. 7.
In each of the latter cases only a fraction of the irrigable area
(one-sixth to one-half) is sewaged at one time, in order to allow
the remaining land a resting period.
1 Proceedings of the Institute of Civil Engineers, vol. xliv.
IRRIGATION AND SEWAGE FARMS I4I
—
! Area Sewage. Inhabitants
Place. Population. | irrigated. Subsoil. Gallons per | per Acre
Acres. 24 Hours. irrigated.
Aldershot 12,000 8 | Loamy sand 389,000 I,500
Banbury 12,700 155 sb 450,000 82
Bedford... e 25,400 130 | Loamandgravel | 1,000,000 193
Burton-on-Trent 46,400 430 Gravel 5,000 108
Cheltenham 49,000 360 — 1,000,000 136
Crewe ... 35,000 257 | Stiff clay I, 378,000 136
Croydon 114,000 565 ve 4,500,000 201
Bisby (West) .. 40,400 207 ee I,100,000 195
Doncaster 23,600 ate Light gravel 500,000 85
Leamington 27,000 350 tate 770,000 77
Norwich 106,000 309 pa 4,500,000 343
Oxford ... 50,000 335 | Sand and clay I, 300,000 149
Reading sé 65,000 350 om 1,500,000 185
Tunbridge Wells 30,000 310 ree 800,000 96
Warwick Se 12,000 265 | Clay gravel 750,000 42
Wigan ... 59,000 420 eS and sandy | 1,250,000 140
i. oam
‘Wimbledon 25,000 73 Clay and some 600,000 342
Va gravel
rexham 12,000 84 | Drift gravel 400,000 143
| Berlin:
_ Osdorf 198
Draikenbee 1,600,000 | 11,000 | Sand 30,000,000 165
_ Malchow 122
Aldershot Camp 20,000 120'5 | Sand 1,000,000 166
Camb ridge 50,000 74 |Sandy loam | 2,250,000 675
overlying gravel
Beddington and sand
(Croydon) 100,000 420 |Gravelly loam | 4,000,000 238
~ over gravel and
| South Norwood sand
_ ~ (Croydon) 21,000 152 |Aclay soil rest- | 600,000 138
| ae ing on London
Ba 4 clay
: Leicester 197,000 | 1,350 | Stiff clayey soil .| 7,250,000 146
Bia overlying dense
hg . clay
Nottingham 258,584 651 |Lightsandyloam| 7,000,000 397
ye and gravel over-
44 lying gravel and
i sand
Ap
ah
m, SYSTEMS OF DISTRIBUTION.
oy
1. Ridge and Furrow.—Flat and heavy soils are laid in ridges
| 40 feet apart, sloping 20 feet on either side, at an incline of
Iin 50 to 1 in 150, to furrows in the centre. From a trans-
verse main carrier at the upper end the sewage passes into
istributing channels on the ridges, whence it flows in a uniform
layer down the slopes, any not absorbed running from the furrows
into a lower plot. The distributing channels (with the ridges)
| have a longitudinal slope of x in 600 to 1 in 300. The main
' Carriers must be lined ; the channels may be dug in the soil.
142 SEWAGE AND ITS PURIFICATION
In places where the soil is sufficiently porous the land is laid
out in a different way, the sewage being fed along the furrows
with the vegetation on the ridges, and the underdrains between,
so that the liquid reaches the roots from underneath, the excess
passing laterally to the drains. This method seems to be recog-
nised as the best for avoiding water-logging, ‘‘ sewage sickening,”
and other evils of sewage-farming by broad irrigation. It must
be remembered that the reliance is here on the filtering qualities
of the soil, the plants playing a subordinate part in utilizing —
the nitrogen of the soil afterwards (Fig. 19). ;
At Paris a portion of the city sewage is treated in this way
at Gennevilliers and Achéres. At the former the soil is sand
=f, =
< * S
eng : , , i Sewage Y a
= ee
3 Z, a
VYWis ph Yj
Fic, 19.—SECTION SHOWING UNDERDRAINS IN IRRIGATION.
mixed with clay, and the crops are various, but chiefly vege-
tables, with also fruit-trees, flowers, and some meadow land.
The irrigation is managed by flooding at intervals, the vege-
tables growing on ridges as described above. Part is worked
by private lessees and part by the State, and the results seem:
to have been satisfactory until lately, when, owing to the
increase of population and greater volume of sewage, com-
plaints have been made to the municipality of flooding and
nuisance. For a number of years experiments have been con-
ducted at Gennevilliers and Achéres to ascertain the amount
of sewage that may be applied to land without injuring the
crops. It is stated that 144,000 cubic metres per hectare
(13,000,000 gallons per acre) annually may be turned on a field
of lucerne and 170,000 (15,000,000 per acre) on meadow land.
These figures are far in excess of anything hitherto accomplished
in regular daily work.
Bechmann states that the experiments at the model garden
of Genevilliers show that from 80,000 to 130,000 cubic metres
of sewage per hectare (7,000,000 to I1,500,000 gallons per acre)
annually can be applied without prejudice to the success of the
IRRIGATION AND SEWAGE FARMS 143
crops or the purification of the sewage. The lowest of these
figures is equal to 20,000 gallons per acre per twenty-four hours ;
the Berlin farms (see table) only take 2,730. It must be
remembered that in cases where such large quantities are sup-
plied frequently after a time the land becomes “sick,” and
great nuisance has been occasioned.
During 1900 the Gennevilliers farm of goo hectares received
54,223,020 cubic metres of sewage, equal to about 14,500 gallons
per acre per twenty-four hours. On a report of M. Launay,
_ who is known as an advocate of the tout a l’égout system, it has
| been decided to experiment with the English bacterial methods
| on the Paris sewage, which is organically stronger than the
average met with in England. At the same time it is con-
templated to extend the irrigation area. ‘‘ Intensive irrigation ”
has been tried with rather satisfactory results at Gennevilliers,
and later at Achéres. Instead of supplying the land with the
amount of water requisite for culture, the amount was increased
ten and twelve times, accompanied with successive ploughings
whenever the superficial soil became caked with an impermeable
layer of mud. Not only did the soil retain its filtering proper-
ties, but also all the decomposing substances were completely
absorbed and assimilated without the aid of any vegetation.
_ At Milan the sewers join in a canal, the Vettabia, which dis-
charges into about 4,000 acres of land arranged in terraces, the
final effluent falling into the river about ten miles below the
city. The proportion of sewage applied is calculated as that of
forty persons per acre of land.
At Dantzig, Breslau, and other places on the Continent,
sewage farms are also at work, but almost invariably on light
soil.
2. Catchwatey.—On irregular ground an upper main carrier
is made I to 2 feet wide and 6 to ro inches deep. The sewage
overflows from it at any point by temporarily damming, and,
after spreading over the ground, the excess collects in a lower
catchwater gutter made to the contour of the land, from which
it is dammed and released on the same principle. This method
requires much control.
Growing plants, especially of certain species, are capable to
acertain extent of absorbing and using as food the organic and
ammoniacal constituents of raw sewage, and, by means of
the numerous enzymes they secrete, are able to dissolve and
utilize organic suspended matter. But vegetation ordinarily
144 SEWAGE AND ITS PURIFICATION
absorbs most of its carbon from the air and its nitrogen from
nitrates, and requires its food to be well prepared before it is
assimilated. Excess of ammonia acts very unfavourably.
S. Cloetz found that 10 parts of ammonia in 100,000 (a strength
not uncommon in sewage) was injurious. Déhérain showed
that ammonium salts were prejudicial, and that soils which had
received a dose of them wn peu forte remained sterile for several
years.
In the ditches conveying sewage that used to be so common,
and even in the open drains from cottages, it is noticed that the
channel remains black and barren till the sludgy solids have
had time to deposit or become fermented, and the soil to
reassert its action, when the liquid clears and loses its odour,
and a copious growth of vegetation arises. Therefore, in
cottage gardens and allotments the sewage is not applied to
the ground till it has been dissolved and fermented in pits or
cesspools. Such a process, when scattered over a neighbour-
hood, is sure to create a nuisance, but carefully managed and
conducted collectively in special large areas it has proved to be
fairly successful, as shown by the late Dr. Poore.?
The main faults of irrigation with raw sewage are therefore— —
(a) Choking and felting of the surface by organic slime.
a a ne
(b) A surplus of unprepared organic matter and of ammonia
over the wants of the plants.
(c) In consequence of the above, a deficiency of oxygen and
of healthy action in the body of the soil.
(d) Great inconstancy owing to season, temperature, and
cultivation.
The faults (0) and (c) are avoided to a certain extent by the
second system—that of
B. Intermittent irrigation with copious underdrainage, which is
really using the land as a partially-regulated bacterial tank and
filter.. If properly arranged, the drains act also as aerators, so
that the soil is more thoroughly supplied with oxygen, allowing
nitrification to proceed more actively and to greater depths.
At Merthyr Tydvil in 1871 “‘ 20 acres of a porous soil, drained
from 5 to 7 feet deep, were arranged by Mr. Bailey Denton in
four series of beds; and over each series in succession the
drainage water from 50,000 inhabitants, more than one-third
of whom were connected with the sewers, was poured for six
1 Chimie Agricole, 1892.
2 «The Earth in Relation to Contagia,’’ 1902.
—_——
IRRIGATION AND SEWAGE FARMS 145
hours at a time,” by the ridge and furrow system, with intervals
of eighteen hours per day for rest and aeration, crops of cabbages
being grown. The works were suggested by the experiments
of Sir E. Frankland in the laboratory of the Royal Commission.
‘It is reported that the crops at Merthyr were healthy and
luxuriant, and were valued in 1872 at £42 to £45 per acre, also
that no nuisance had arisen. From Frankland’s analyses of the
effluents in 1871-1872 I have calculated the following averages,
adding also his “‘ proposed standards of purity ”:
@ | SuspENDED
———
x | 3, |e | Z | af Kis Soups.
| 23d a3 on aids ales gv
%, gs bh A & NHs3. Ax ° 5 Cl ait é
an Za 5 EI pa
{ = o)
Proposed standards .. we | — |2%0 jo3 | — | — | — | — | 3%] 10
Sewage after liming ... vs | 52°0|2°44 '0°g |2°7 |o°017/3°18 | 5°98 |11°8 |21°6
‘Filtrate... ae Ase eee | 33°2 |O°F4 0°03 0°063|0°273 /0°348) 2°74 |trace/trace
Subsoil water ... at .. | 19°4 |0°106,0°011/0'004|0°061|0°075|0°9 | — | —
a
\
In the use of land by any system there is always a variable
dilution with rain and subsoil water, so that the improvement
effected by soil, as indicated by the quality of sewage and
effluent, would appear to be greater than it is, unless we take
| this feature into account. Frankland’ applies the formula
i
A+C
bet S's
“in which a, 0, and c represent the amount of chlorine in
100,000 parts of sewage, subsoil water, and effluent respectively,
and x the required volume of the subsoil water which has thus
become commingled with each volume of the original sewage.”
In this case he finds that each gallon of the sewage had
become mixed with from I'g to 2°2 gallons of subsoil water,
) and probably also with some rain, as the mean dissolved solids
of the sewage and subsoil water are about the same as those in
a effluent, while the chlorine in the effluent is less than half
that in the sewage. But even with this allowance the result
justifies Frankland’s statement that ‘‘ the effluent water on all
Occasions was purified to an extent much beyond that required
by the standards of pollution suggested by us as those below
which refuse liquids should not be permitted to enter rivers.”
| The analyses are of further interest at the present time, as we
1 “ Experimental Researches,” p. 763.
IO
Se
————
_ ae
146 SEWAGE AND ITS PURIFICATION
can see from them that—(1) The reduction of the total N by
about 75 per cent. (making allowance for dilution) is not
accounted for by the somewhat meagre production of nitrate
and nitrite. (2) Since the sewage “ gradually sank into the soil
as it flowed,” this improvement can only be partially due
to volatilization of free ammonia, of which soils, as is known,
are very retentive. (3) The organic nitrogen may at first have
been largely absorbed by the soil; but as the analyses extended
over nearly a year and a half, and. the later ones showed the
same changes, this mechanical absorptive active is of minor
importance. The explanation is rather to be found in the
life of the soil bacteria, acting by the process of denitrification,
in which free nitrogen and lower oxides of nitrogen are
generated from both ammonia and organic matter, and evolved
as gas. In fact, the whole process, instead of being, as it was
then considered, partly mechanical and partly chemical, was
in its essence bacterial. But as this sewage was admittedly
weak, Frankland over-estimated the efficiency of the method
when he stated that “the application of the sewage of more
than 1,000 persons to an acre of land is consistent with the
growth of crops and a superabundant purification of the effluent —
water,” and that ‘‘ the sewage of a much larger number could ©
be effectually purified on an acre if the growth of crops
were given up.” The Local Government Board, on the
other hand, prescribed “for intermittent filtration without pre-
cipitation, through sandy gravel, r acre for every I00 to 300
persons.”
c. Irrigation with Filtration or Precipitation. — From the
faults and difficulties we have mentioned, it is rare for any
sewage system to depend on the land solely. Even in the
Merthyr Tydvil trials the raw sewage was previously treated
with lime, and ‘‘a roughing filter’ of gravel, coke, broken
ballast, or some other suitable material, is almost universally
used, and often by itself effects considerable bacterial improve-
ment in proportion to the time the liquid remains in contact,
although its functions are primarily to strain off the solids.
At Leicester, fair success was attained! by broad irrigation
on clay land after clarifying by coarse banks of clinker, ¢ to
2 inch size, from the refuse destructor.
1 Society of Engineers, December, 1898.
i
IRRIGATION AND SEWAGE FARMS 147
| Later a bacterial scheme was introduced, and in Igoo
Mr. Mawbey issued his report on the experiments. These
-_ were of limited scope and open to some objections, but under
local conditions it was considered that the best results were
obtained by passing the raw sewage through (1) a “closed
detritus tank,” (2) ‘‘ clarifying bacteria beds, single contact, and
_ three fillings a day,” followed by one application to old pasture.
__ The system has been adopted by the Corporation.1
It is cbvious that the solids are an integral part of sewage,
and that their removal, entirely or in part, by any system
_of straining, settlement, precipitation, or filtration, results in
the production of a “sludge,” which has to be separately
treated; also that precipitation, if the effluent is afterwards
| to be applied to crops, must not involve such use of chemicals
as may be injurious to the vegetation. Iron and aluminium
salts, such as alumino-ferric, followed by lime, give a much-
_ purified effluent which has proved to be innocent in agriculture,
although both this and simple sedimentation or filtration
_ remove from the liquid some of the constituents which, when
_ properly fermented, are capable of assimilation by plants, and
also, along with the suspended solids, many of the bacteria
which affect these changes.
The areas that have been officially demanded in England
for the purification of sewage according to the process adopted
are as follows; a much less amount has been often used suc-
cessfully with proper management and care, but local conditions
_may even demand larger quantities:
raion
See.
PET Pee
POPULATION PER ACRE OF LAND.
1. Irrigation without precipitation—
. | Stiff clay ys ... Tacre for every 25 persons
ey Loamy gravel ... * ¢ ty 100 persons
2. Intermittent filtration without precipitation—
Sandy gravel ... 1 acre for every 100 to 300 persons
3. Irrigation and precipitation—
pale “ee ... I acre for every 200 persons
Loamy gravel ... pay iN us 400 persons
4. Intermittent filtration and precipitation—
Sandy gravel ... I acre for every 500 to 600 persons
1 See further Mr. Mawbey’s paper, Congress of the Royal Institute of Public
eth, Exeter, 1902.
I0o—2Z2
—
148 SEWAGE AND ITS PURIFICATION
5. Precipitation and filtration through specially-prepared
filters, followed by irrigation—z acre for every 2,000
persons.
The Local Government Board have required, in the con- —
struction of special filtration areas, that provision shall be made
for— |
1. A rainfall and sewage calculated at three times the dry-
weather flow.
2. Above three times and up to six times to be treated on a
further special area of storm-water filters, and not until the
flow is above six times may it be discharged into a stream or
on to prepared land without passing through the filters or other
method of treatment.
3. The capacity of the filters to be taken at one-third for the ©
fluid and two-thirds for the filtering material.
4. A cycle of eight hours for filling, emptying, and rest for
aeration.
In any system of sewage-farming the difficulties of controlling —
the drainage area, so as to provide for the varying amounts and ©
qualities of the sewage, will always exist. Ifthe land be suffi-
ciently porous and well drained to prevent its being water-
logged, and to allow the free passage of the effluent during wet
seasons, in dry weather it will permit it to run through too —
rapidly, and the effluent will not be purified. A denser soil”
adapted for ordinary weather will be entirely clogged by unusual —
rains, and therefore unsuited for any broad irrigation scheme, — |
unless a very large area is available.
Another obstacle is the distance to be traversed before reach-
ing a suitable site. Thus at Wigan the sewage had to be
conveyed to the farm for 7} miles through a 27-inch cast-iron
main costing £50,000, with three siphons; it took ten hours in —
transit, and on arrival was more or less charged with
sulphuretted hydrogen and other foul gases.2. I have drawn
| attention® to a further disadvantage of land treatment—the
_ risk of polluting the subsoil water. The present Royal Com-
mission on Sewage‘ state that these effluents contain large
numbers of organisms, ‘‘ many of which appear to be of in-
testinal derivation, and some of which are of a kind liable, ©
under certain circumstances, to give rise to disease”’’;® they
1 See a paper by S. Krawkow, $. Landw., 1900, xlviii., 209, on “‘ The Move- |
ment of Aqueous Fluids in Soils,”
2 Institute of Sanitary Engineers, November 16, 1899.
3 Engineering Conference, Institute of Civil Engineers, 1903, Section VI.
4 Interim Report, 1901, p. Io. ° 5 Tbid,, vol. iv., part i., section 9.
i
IRRIGATION AND SEWAGE FARMS 149
_ also find that the effluents from land possess a bacterial flora
- characteristic of sewage, and that the microbes characteristic
of soil are relatively absent.
The chief objections to land filtration have been summarized
as follows: :
i. Generally the worst part of the sewage—the acer is
not dealt with at all.
| _2.. As crops are usually grown, their cultivation is often con-
_ sidered, by those left in charge, as more important than the |
_ purification of the sewage, and so the latter is not fully treated |
_ except where irrigation is of advantage to the crops.
__ 3. Unless the land receives very careful attention, a bad
_ result is generally produced from even the best farm, and it is
difficult for anyone but a highly-trained man to keep the works
_ under proper control.
4. There are many possibilities whereby land which has been
laid out carefully may fail, even with careful working, such as
the cracking of the land, admitting crude sewage into the
drains without filtration.
5. Land of sufficient quantity or quality, and at a reasonable
) _ price, is often unattainable.
The strongest argument for sewage farms and irrigation must
| always be the restoration to the land of the matter taken away
_ from it, without which there must be a continual impoverish-
ment. This aspect of the question was brought into prominent
notice by Sir W. Crookes.!_ I point out in later chapters how,
4 under graduated bacterial purification, an effluent containing
practically all the nitrogen, phosphates, and other mineral
_ constituents, is obtained in a condition suitable to be returned
_ to the soil without loss, and available for plant life.
iF Insistence on final land treatment is now decidedly a mistake,
_ as where a proper process is used no further purification will
be necessary; indeed, in many instances an originally good
_ effluent suffers deterioration by subsequent passage through
i land, and as the sewage in passing through the filters falls 6 to
8 feet, the expense of pumping may have to be added. At
_ Newcastle-under-Lyme in September, 1go1, the Local Govern-
ment Board sanctioned a loan for a scheme of disposal by —
bacterial treatment, and consented, for the first time, to waive
| their usual requirements with respect to land treatment for the
filtered effluent, having regard to the limited area and unsuit-
\) able nature of the land available.
1 British Association Reports, 18098.
i
_
a pe
CHAPTER VII
SUBSIDENCE AND CHEMICAL PRECIPITATION
Screens—Settling tanks—Roughing filters—Clarification—Lime—
Aluminium sulphate—Ferric sulphate— Ferrous sulphate—
Alumino-ferric—Sludge: its composition, volume, and disposal.
Mechanical separation, used as an adjunct to many processes,
deals with suspended solids, inorganic or organic:
(1) Grit and detritus, small stones and sand, carried down
largely by sewers of steep gradient, or in periods of storm,
under the combined system, will be always present, but even
under a separate system, intended to take only excretory and
household waste, cannot be entirely avoided. They are
removed by settlement without nuisance, since any entangled
organic matter rapidly disintegrates, as in gravel soil. They
collect in the street gullies, in sumps in the line of the sewers,
and the remainder in grit chambers at the sewage works.
Processes using mixing machinery require careful removal of
hard matters.
(2) Organic residues—vegetable, feeces, paper, fibres, wood—
in great part float, owing to lightness, or to gases generated by
fermentation. Their inclusion or exclusion constitutes a main
difference, as we shall see further, between some modern
methods of ultimate treatment ; and the question as to whether
a sewage is dealt with strained, settled, or absolutely raw is a
matter of very great importance.
Screening is often used to prevent the clogging of filters. The
screens are either cleared at intervals by hand labour or con-
tinuously by automatic contrivances, one of the most effective
being a revolving wire drum, rotated by a paddle wheel moved
by the current of sewage (Fig. 20). At Leeds the solids thus
removed, and requiring separate treatment, were estimated to
be thirty barrow-loads, or, say, 2 or 3 tons daily, mainly con-
sisting of feces, paper, and vegetable residues. The screens
150
SUBSIDENCE I5I
should be in duplicate, and some have been made with sharp
edges to cut up the organic matter.
Grease, which is often a great difficulty, may be intercepted
by grease-traps, or it may be broken up into an emulsion with
lime or other materials for subsequent treatment. The
Fic, 20.—RoTary SCREEN FOR CRUDE SEWAGE AT SOUTHALL SEWAGE Works, ISLEWORTH.
methods used at Bradford and other towns will be described in
Chapter XIV. Grease from ordinary soap-suds does not seem
to admit of profitable extraction, as the fat is so much con-
taminated.
The amount of suspended matter in sewage is greatly
influenced by its history before arrival at the works. Where
the sewers are long and have a varying gradient, much deposi-
152 SEWAGE AND ITS PURIFICATION
tion and dissolving may occur. Pumping causes some of the
organic matter in suspension to disintegrate, and thus renders
it more easily soluble. Agitation with pulverization of the
organic solids has been the subject of many patents.
At Manchester up to 1897 the heavy insoluble matter brought
down with the sewage (sometimes as much as 300 tons after a
flood) was deposited in the precipitation tanks, from which it had
to be removed by manual labour at considerable cost. Catch-
pits were then interposed “ to intercept large solids which might
cause damage to the machinery,” with movable coarse screens
balanced by weights so that they could be raised for cleaning.
Finer screens, with mechanical rakes, were fixed at the outlet.
London sewage is screened through iron gratings, and in
1897 it was stated that the weight of the screenings was
between 80 and 100 tons per week. A destructor furnace
built close by was used for destruction of the refuse. Screening
is also mentioned at Friern Barnet, Oldham, Swinton (‘strainer
with cleaning rakes attached”’), Glasgow (“ wrought-iron grid
to catch heavy and floating matter’’), Accrington (‘‘ screening
chamber where detritus is deposited, with wrought-iron grid to
prevent floating and large substances from passing into the
precipitation tanks. A revolving fork arrangement cleans the
screen by lifting the deposited material to the surface.
The chamber has also a hopper-dredger for removing the
detritus that accumulates at the bottom’’), Kingston (“ Native
Guano process’’), Launceston (‘‘ferrozone and polarite”); in
fact, all places and systems except those with a preliminary
hydrolysing tank find it necessary to separate the coarser organic
matters mechanically.
At Melbourne, Victoria, the city sewage is pumped into
‘ straining-cages,”’ and the material caught in them is subjected
to steam at 292° F. (45 pounds pressure), ‘‘ which should
effectually render the material innoxious.”” The dry result is
destroyed in a furnace, as of no manurial value. In 18gg-1g00
it amounted to g61 tons, or 141 tons after drying.!
- Roughing Filters.— In Colonel Waring’s, used in the first stage
of his system in the United States, a 10-inch suction - pump
delivered the solids and liquids on to a shallow bed of broken
stone, divided by a vertical partition; when one side became
choked the other was used. From this it passed into “‘strainers”’
' Report by W. Thwaites, Chief Engineer to Melbourne Board of Works,
April, IgoI.
SUBSIDENCE | 153
of stones, pebbles, and coarse gravel. Although it is claimed
that the ‘‘ function of the strainers is merely mechanical sedi-
- mentation,” they also perform a bacterial office, as can be
| judged from his report. All materials used—stones, broken
| bricks, coal, ballast, or large coke —exert at first simply a
- mechanical action, but after a time develop coatings of organ-
isms which greatly extend their effect. The Massachusetts
Report stated that ‘‘with the gravels and sands, from the
coarsest to the finest, we find that nitrification takes place in
all, when the quantity of sewage is adapted to their ability, and
the surface is not allowed to become clogged by organic matter
to the exclusion of air.”
SUBSIDENCE AND MECHANICAL CLARIFICATION.
_ After any method of straining, sewage remains turbid from a
large quantity of suspended matter, which, as shown in the
second chapter (p. 28), contains about one-third of the organic
nitrogen and half the carbonaceous matter of the sewage.
| Settling basins were once almost the only means of clearing a
| strained sewage, the deposit being at intervals cleaned out and
| thrown on land, or even into the nearest ditch or watercourse.
The deposition was sometimes supplemented by adding clay,
ashes, slag, shale, peat, or charcoal, so that these in settling
down should entangle the solid impurities. But except with
_ weak liquids the result was not good, as the fermentation kept
_ the organic matter in suspension, and a nuisance was also
occasional.
_ P.F. Frankland’s experiments in 1885 on clarification with
chalk, animal charcoal, coke, spongy iron, china clay, brick
dust, plaster of Paris, oxide of manganese, etc., with special
reference to the removal of organisms, showed that although
“suspended matters were at first carried down, they rose again
_ subsequently, and the organisms, particularly those which were
motile, multiplied in the liquid.!' Kriiger, in 1889, confirmed
these conclusions.” Therefore, at a time when it was sought to
remove all micro-organisms from sewage, mechanical clarifica-
tion was proved to be unsatisfactory, and it had little or no
effect on organic matter in solution.
_ Moreover, any such system results in the formation of
1 Proceedings of the Royal Society, 1885; Proceedings of the Institute of Civil
_ Engineers, 1886.
* Zeits. f. Hygiene, vii., 86.
in
154 SEWAGE AND ITS PURIFICATION
“sludge,” which is the greater in amount as the straining
medium is finer, and is also increased by the precipitant. A
great difficulty in dealing with sludge is that its bulk is swelled
by its containing g2 to 98 per cent. of water. If it be tried to
obtain it in a denser condition by longer deposition, obnoxious
gases are certain to be produced. Spreading it over the soil to
dry, and finally digging or ploughing in, is in some places
possible, but for filling up low-lying land? it is unsuited through
its density, wetness, and unsanitary character.
In 1886 the adoption of destructor furnaces at Southampton
and Ealing led to experiments at Leyton and Cardiff, founded
on the hope that sludge could be burned remuneratively and
without offence with the aid of a certain amount of coal to
dry the cake, the ammonia evolved being collected, and the
volatile matters passed through the fire. The net cost of
incineration was not to exceed sixpence per ton, the coke pro-
duced paying for the coal and working expenses. But in all
the numerous attempts at utilization of sludge either as manure
or by chemically extracting some of its constituents, it was
found that the agricultural value was disappointing, while in
combustion processes the cost of machinery and fuel absorbed
all the profits.
The object now being merely to reduce the bulk and avoid ~
nuisance, sludge was compressed in filter-presses of various
constructions to a cake containing 25 to 50 per cent. of water,
with usually an addition of lime or other substance to facilitate
pressing. The cost was still great, and the product nearly
worthless. The following are analyses of two examples:
| Native Guano Com- | Pressed Sludge Cake, |
pany’s Sludge Manure, Crossness, 1886.
Crossness, 1872.
Water... i as " 26°45 58°06
Organic matter... a2 3 16°16 16°69
Alkaline salts a is ae 0°36 1°76
Carbonate of lime and magnesia__.... 2°62 7°94
Phosphoric acid... re a 0°48 0°66
Alumina and oxide of iron ... Sas 15°42 4°36
Insoluble silicious matter ... test 38°51 8°08
Free lime... Seb st ae 2 2°45
100°00 100°00
Total nitrogen in the organic matter
calculated as ammonia .., one 0°93 1°06
' L, Flower and others, Royal Commission on Metropolitan Sewage, 1875. _
CHEMICAL PRECIPITATION 155
CHEMICAL CLARIFICATION OR PRECIPITATION.
Lime, since the success of Clark’s process for treating waters,
has been very widely used for sewage, either alone or as an
accompaniment to other precipitants.1 The Rivers Pollution
Commission of 1868 made their first experiments on the precipi-
tation of sewage with milk of lime alone, and pronounced it to
be a failure, as, although the liquid was rendered clear, it was
not sterilized, was rendered alkaline, ammonia was developed,
and the whole rapidly became foul. Where Local Boards
have used lime and sedimentation alone before discharge into
rivers, a prosecution for nuisance has almost invariably
followed.
At Birmingham, for example, systematic sewerage of the
borough was commenced in 1852, liquids and solids being dis-
charged direct into the river Tame. In 1858 tanks were con-
structed, and various methods of purification by precipitation,
sedimentation, and filtration tried. Treatment with about
I2 grains per gallon of lime, with subsequent sedimentation,
was adopted in 1872 and continued till t900. The sludge was
collected in three large tanks of a total capacity of 440,400 cubic
feet, with sixteen smaller tanks of 729,000 cubic feet capacity.
The effluent and sludge were both treated separately on land,
the area of which increased from a few acres round the tanks
in 1870 to 2,800 acres in 1902.”
The results of the lime treatment led to a series of legal pro-
ceedings and an injunction, on account of the great pollution
of the Tame. In some cases 4 grain per gallon of chloride
of lime added with the lime used for precipitation was said to
have beneficial results and to prevent the growth of fungus,
total cost being stated at eightpence per head of population
per annum. But the precipitant rendered the effluent alkaline,
and its discharge into rivers gave rise to nuisance, and was
destructive to fish. Afterwards a bacterial process was adopted,
and septic tank effluent is being treated on land with success.
* Clark’s patent, 1841. In 1846 Higgs patented the use of lime for sewage,
which seems to have been the earliest chemical method adopted on a large scale.
_H. Stothert introduced the alumina process in 1852, and the use of salts of iron,
first known as Dover's process, was brought out in 1851. For further historical
details, see Baldwin Latham’s address to the Association of Managers of Sewage
’ Disposal Works, April 15, 1905.
? O'Shaughnessy on Birmingham Sewage, F¥ournal of the Society of Chemical
Industry, May 31, 1902, p. 665.
156 SEWAGE AND ITS PURIFICATION
The land is laid out in various ways, partly as intermittent
filters, and the greater part in broad irrigation.’
Whatever be the cheapness of lime, therefore, it has not been
found to be successful alone, but as an adjunct to other pro-
cesses it is frequently of great use, and may be absolutely
necessary in some cases where the sewage is strongly acid from
trade effluents.
A good quality of lime is slaked, and then ground with a
portion of the sewage or other water to an even cream. The
quantity to be added must be regulated by the content of actual
free lime; this should be determined at intervals by diluting a
measured sample (5 c.c.) of the well-mixed cream with recently
boiled distilled water to 250 c.c. in a stoppered flask, well
agitating, allowing to settle, withdrawing an aliquot portion of
the clear liquid with a pipette, and testing the alkalinity by 7
hydrochloric acid and phenolphthalein. Quicklime sometimes
contains large quantities of impurities, and in all forms it loses
strength by absorption of carbonic acid if exposed to air;
therefore bins, vats, or tanks for storage require to be carefully
covered. The usual dose of lime, when used alone, has been
one ton to each million gallons, or 15°68 grains per gallon. The
following conditions must be observed :
1. Sufficient must be used, in the case of acid or trade
effluents, for neutralization and precipitation.
2. In ordinary cases enough must be added to combine with
the free carbonic acid and half of that combined as bicarbonate,
as in ordinary water softening ; the precipitated carbonate of
lime carries down much organic matter.
3. A slight excess is generally needed to precipitate organic
acids and colouring matters of a humous character.
4. Best results are obtained when the lime is in solution; if
only suspended it is less active as a chemical precipitant, while
all the insoluble impurities are added to the sludge.
5. The effluent must not be rendered more than faintly alka-
line, and determinations of the alkalinity of raw sewage and
effluent must be made.
6. The amount used will vary according | to the quality of the
sewage and of the lime.
Dibdin has drawn attention to the solvent action of lime on
many of the suspended matters in sewage, so that ‘‘the addition
of an excessive quantity of lime, while affording a rapid settle-
1 Report of the Royal Commission on Sewage, 1902, vol. li., p. 536.
CHEMICAL PRECIPITATION 157
- ment of the sludge, and a more or less clear effluent, dissolves
a by no means inconsiderable quantity of the offensive matters
previously in suspension, and this is apt to render the last state
of the liquid worse than the first. The well-known offensive
_ character of the liquids from sludge-presses when lime has been
used is an example of its solvent action.”
If other water than sewage is used for making up the lime
mixtures, the corresponding dilution of the effluent must be
remembered in judging of its quality.
When lime is used in conjunction with salts like sulphates of
alumina and iron, there will be no free lime left if the molecular
proportions are observed, thus:
Al,(SO,),+ 3Ca(OH), = Al,(OH), + 3CaSO,.
FeSO, + Ca(OH), = Fe(OH), + CaSQj.
Fe,(SO,), + 3Ca(OH), = Fe,(OH), + 3CaSQ,.
Only sulphate of lime will be left in the liquid, increasing its
permanent hardness, and sometimes affording a measure of the
sewage when discharged into rivers (p. 40).
Alumina or Iron Clarification.—The use of aluminium and
iron salts as clarifiers and deodorizers has long been known. It
depends on several actions, namely :
I. Forming in neutral solutions insoluble compounds (called
_ generally “lakes”’), with colouring matters and other dissolved
substances.
2. Antiseptic power of the metallic salts themselves, and also,
in commercial specimens, of the excess of acid, generally sul-
phuric, with which they are mixed. The latter, when they are
used conjointly with lime, or when the acid is neutralized by
the ammonia or other alkalies of sewage, will, of course, not
count as an antiseptic.
3. In an alkaline solution the gelatinous precipitate of
hydroxides entangles and carries down suspended matters, in-
cluding organisms. The latter, however, rapidly rediffuse in
the liquid, as with mechanical agents, so that the precipitate
must be quickly separated. This separation by deposition and
filtration, with subsequent sludge-press, adds a great difficulty
and expense to the method.
4. Aluminium and iron salts neutralize ammonia and basic
compounds; iron salts also destroy sulphuretted hydrogen,
giving a black sulphide, FeS (plus free sulphur in the case
of ferric), eventually oxidized to red-brown ferric sulphate,
158 SEWAGE AND ITS PURIFICATION
Fe,(SO,)3, forming an ochreous deposit which acts as a further
purifier. This red deposit often occurs from iron naturally
present, and shows generally that the liquid has been so far
oxidized.
Aluminium Sulphate is made from bauxite or clay, by treat-
ment with sulphuric acid. As sold, it often contains excess of
the acid, and samples should always be tested, as the more
neutral it is the better. Freedom from iron is not requisite
for this purpose ; in fact, ‘‘Spence’s Alumino-ferric”’ is a mixture
of the crude sulphates of iron and alumina, made in blocks
which slowly dissolve. The amount of iron is generally small.
At Glasgow 5 grains per gallon of alumino-ferric were used with
7 grains of lime, or 24 grains (or more) of sulphate of alumina
with 5 grains (or more) of lime, resulting in a production of
over a million gallons of wet sludge from 200 million gallons
daily flow of sewage.
Alum, the double sulphate of aluminium and potash, or
ammonium, has the advantage of a definite composition, so
that an exact quantity can be used, but is precluded by its
cost, and also by its leaving behind the alkaline sulphates.
In local purifications on the small scale it has often been of
use.
Ivon Salts— When chemical precipitation was prevalent —
there was much controversy as to whether ferrous or ferric
salts should be used. The former were cheaper, in the form of
ferrous sulphate or ‘green copperas,” but had the disadvantage
of being veducing. Copperas with lime was largely used for
London sewage. The precipitate of ferrous hydroxide, Fe(OH),,
absorbed oxygen from the air, and to a certain extent commu-
nicated it to the organic matter, acting as a carrier.
Ferric Salts not only possess a higher power of clarification,
but also act as direct oxidizers. A solution of ferric sulphate
has: been used in several systems of purification, and the small
quantity present in ‘‘alumino-ferric”’ may consequently be ad-
vantageous. Ferric chloride with lime was formerly employed,
especially at Northampton. The presence of arsenic in it
was commented on by Letheby, Hofmann, and Frankland.
‘* Clarine’”’ was a basic ferric chloride. ‘‘ Ferrozone,” at one
time much used as a precipitant, is a mixture of ferrous, ferric,
and some aluminium salt, with a less quantity of calcium and
magnesium sulphates.
An important difference between the behaviour of ferrous
’
CHEMICAL PRECIPITATION 159
and ferric salts as precipitants is not only that the former act
as reducers, diminishing the amount of free oxygen available,
but that ferrous oxide is soluble in alkaline liquors, while ferric
oxide is almost entirely precipitated, so that a liquid treated
with ferric or per-salts of iron after filtration or deposition may
contain no iron, whereas one from ferrous or proto-salts, such
as copperas, retains iron dissolved in the ferrous state, and
on exposure to the air gradually oxidizes and gives rusty
deposits. 7
When iron salts have been added to sewage, I have observed
that a residue of the metal was always left in solution, with
ferrous salts from the solvent action of alkalies already men-
tioned, with ferric compounds from the well-known fact that
organic matter prevents their precipitation by alkalies. After
a time, if not thoroughly aerated, a black deposit of sulphide
of iron is liable to form, and is often seen on sides of channels.
Aluminium salts have not these disadvantages. The presence
of any of these chemicals in more than traces is injurious to
fish and hinders nitrification.
In the Massachusetts experiments on the effect of different
amounts of chemicals in removing micro-organisms it was
found better to add the metallic salts first, and then an equiva-
lent amount of lime afterwards. Ferric sulphate gave the best
_ results as to removal of organisms and organic matter, .cop-
peras or alum acting about equally in the second place. In
cost, their table gives the preference to copperas (ferrous sul-
phate) and lime.
At the London County Council’s Works, Mr. Dibdin adopted
I grain of copperas and 4 grains of lime to 1 gallon sewage,
after a long series of experiments with various amounts of
different precipitants.1_ His conclusions are that the following
rules should, as far as practicable, be observed: (1) The sewage
should be diluted as little as possible ; (2) agitation after mixing
should be avoided; (3) unless absolutely necessary, no pumping
should take place before precipitation, the reason apparently
being that the entanglement of air with the precipitate prevents
settling. He also infers that with lime iron is superior to
alumina and also cheaper, and that a large increase in the
quantity of chemicals yields no advantage.
At York in 1896 the sewage was chemically treated with
1 His results were given in detail in the second edition of the present work,
p- 141.
160 SEWAGE AND ITS PURIFICATION
alumino-ferric and lime, in proportions adjusted to the volume
and to some extent to the strength, and averaging about 5 grains
of each per gallon. During this period! the average results in
parts per 100,000 are given as: Oxygen consumed—sewage,
4°92; effluent, 1°58. Albuminoid ammonia—sewage, 0°469;
effluent, o°r11. But beyond its organic impurity, the effluent
was made too alkaline by the lime, and complaints arose as to
its action on fish in the river; therefore during 1897 alumino-
ferric alone was used, and the average results are recorded as
follows: Oxygen absorbed—sewage, 7°95; effluent, 2°36.
Albuminoid—sewage, 1°21 ; effluent, 0°266. As the results were
so unsatisfactory, biological treatment was commenced in 1899. ~
It is reported that during fifty-six days of the first working of —
an open septic tank and continuous filter the sludge was only ©
one-ninth of that produced by the former chemical precipita- —
tion, and the effluent was of good quality.
At Kingston-on-Thames the “ A B C” process has been for
some time in operation. This method is of early date; the
letters originally signified alum, blood, and clay as precipitants,
but it is now stated that the three principal ones are sulphate
of alumina, clay, and carbon, and that 50 grains “‘of materials
including sulphate of alumina” are used per. gallon of sewage,
with a purification measured by albuminoid ammonia of 83 per |
cent. An essential feature is the production by sludge-pressing
and drying of a manure called ‘“‘ Native Guano,” offered at
£3 10s. perton. Sir Alexander Binnie reported to the Corpora-
tion of Kingston in 1903 that the process was very expensive
and not protected by patent, nor, probably, patentable. The —
effluent, under proper working, was clear and bright, but —
appeared in the conduits and near the river outfall to cause the
growth of considerable quantities of sewage fungus. The
sludge . produced was. comparatively free from odour, and
amounted, at 90 per cent. moisture, to 27 tons per million
gallons of sewage. Pressed, dried, and ground, it gave about
2,000 tons per annum of manure.
Metallophilic organisms—a convenient term I would suggest
for vegetable and animal species whose growth is encouraged ~
by the presence of small quantities of metals in solution,
especially iron, aluminium, and manganese, which they secrete
in their tissues or as an incrustation (see Chapter IV., p. 79)—
1 “Sewage Disposal, York,’ A. Creer, City Engineer and Surveyor, Public
Health Engineer, May 21, 1904.
ee ee OS Dee YA a *
CHEMICAL PRECIPIIATION: ... 161
have often caused inconvenience by developing luxuriantly in
effluents from treatment by metallic precipitants, or from
various chemical trades. In October, 1902, I examined the
growths at Kingston in the channels and on the top of the
continuous filter. In different parts of the latter there were
gelatinous grayish-white flocculi, and reddish and nearly black
slimy coatings. These consisted of Spherotilus natans (p. 79),
Crenothrix ochracea, and abundance of a cyanophycaceous alga,
probably Szrosiphon. The growths in the channel were of
similar character. The flakes of both kinds stained with log-
wood a deep purple, like an iron-alumina reaction. Iron and
aluminium were found in solution in the effluents in larger
amounts than usual, and sometimes one and sometimes the
other predominated. :
The real strength of all precipitants must be periodically
ascertained by analysis. Where they do not deteriorate on
keeping, a large weighed quantity can be dissolved in a definite
volume of water or effluent, stored in covered tanks, and drawn
off by suitable measuring arrangements in proportion to the
flow and strength of the sewage. The whole process must be
quantitative, and it is hardly necessary to warn against the
practice of turning so many hundredweights of crude chemical
into a tank of raw sewage, stirring roughly, and taking little
notice of imperfect solution or admixture. Many inventions
have had for object the automatic supply of precipitants to
sewage according to the flow,’ but the fault of these appliances
has been that the sewage varies so much in composition that
| the chemicals will be sometimes in excess and sometimes in
deficiency.
For separating the clarified liquid from the precipitate, either
siphoning, a floating arm drawing off from cocks at different
levels, or letting out the sludge at the bottom, is applied, with
a large number of patented modifications.
Settling tanks may be constructed on the intermittent system,
in which the liquid is allowed to rest quiescent for a certain
number of hours, and the clear portion is then decanted. A
more usual method is continuous sedimentation, when the whole
runs very slowly through a tank of sufficient depth to allow the
_ solids to gravitate, while the clear solution overflows from the
top. Santo Crimp stated that the minimum size of the tanks
‘should be such as to hold two hours’ sewage flow during the
1 See Colonel Moore’s “ Sanitary Engineering,” 1898, p. 443.
Il
162 SEWAGE AND ITS PURIFICATION
period of maximum discharge, and this quantity may be roughly
estimated at one-seventh of the whole day’s flow.
In cases in which it is proposed to adapt tanks constructed
for chemical precipitation to the settling of sewage prior to
bacterial treatment their size must be augmented sufficiently to
allow time for the solution of the organic solids. Such tanks
are originally too large to act as grit chambers, and too small if
sludge is to be dissolved. |
The relation between occasional flushes and the steady
ordinary flow will vary with locality, and has to be specially
determined by gauging at intervals. A fairly constant average
from day to day will be found, with irregular interferences from
storms. On the combined system of sewerage these render
necessary the large surplus capacity given in the Local Govern-
ment Board regulations ; but even on the separate system they
temporarily increase the volume.
Forms of Settling Tanks.—These at first were simply earth or
clay-lined reservoirs with flat bottoms, from which the settled
liquid was drawn by siphon-pipes at a little distance from the
bottom, the soakage into the porous sides allowing great foul-
ness. ‘Then iron tanks were constructed, with flat bottoms,
and outlet pipes placed generally at too lowa level, the removal
of the sludge at intervals requiring emptying and drawing off
with considerable labour. A further improvement was to make
the tank rectangular, four times as long as broad, with its lower
surface inclined 1 in 80 to I in 100 towards the inlet end.
Transverse walls, coming near to the surface, divided the tank,
so as to allow the sewage to deposit and flow over them, while
“scum plates ’’ dipped from above, and intercepted any floating
matters. At the base of the transverse walls there were open-
ings allowing the sludge to gravitate, or be carefully swept
down, to a sump at the lowest point at the inlet end. At the
other end, the clarified liquid was drawn by a valve or a
floating arm. Santo Crimp gave as examples of the capacity
of settling tanks: Coventry, 42 per cent. of the day’s flow;
Birmingham and Burnley, 56; Leicester, 40; Wimbledon, 80
(designed for a large increase in population). In Germany it is
claimed that the best results are obtained from long, narrow
and shallow tanks.
The quantity of sludge made is stated to average ? ton per
day per 1,000 inhabitants, and the cost of filter-pressing to vary
from ts. 10d. to 2s. 6d. per ton of sludge cake produced. The
CHEMICAL PRECIPITATION 163
essed out water must be taken back to the tanks for re-
reatment. :
The Dortmund Tank is eects and yer with the lower
yart conical, and with a vertical cylinder fixed in the middle.
) ; The strained sewage, after treatment with lime and aluminium
i phate, passes downwards through the central cylinder, and
s then distributed horizontally by specially constructed arms.
if Phe sludge deposited in the cone is withdrawn by suction-
: mps through a 6-inch pipe opening’ near the bottom, at
a uniform rate of 15 feet per hour. This tank had its origin
n the Rockner-Rothe process, and was first used at Dortmund
1 Germany, subsequently at the Chicago Exhibition, and at
Al freton and Ilkeston in England. The deposition in conical
vessels has been long known in laboratories as a means of
concentrating precipitates. The idea aimed at in the Dort-
mund is timing the deposition with the withdrawal of clear
‘iquor. The fault of conical, as distinguished from cylindrical
\ essels, is that the former allow deposition on their sides,
the greater in proportion to their low angle. Hence the
orking is sometimes deficient, ‘the sides of the cone being
ated with filth, which decomposes, making the effluent very
atisfactory.”
L At Essen (Racknat-Rothe principle) shallower tanks are
d opted with pneumatic raising.
fe oshan’s Tank has the advantage of compactness, by means
) a radial arrangement with two concentric circles, the middle
e being divided into two, the outer space into eight compart-
ne snts, the whole arrangement being conical, so that the inner
| © divisions are deepest, and the shallower outside ones
mcircle them. The sewage passes into the centre and over-
Hows gradually through the other compartments, with deposi-
| Onin each. Arrangements are made by which the sediment
can be withdrawn from the bottom of each chamber, or passed
nt © the centre divisions and siphoned out collectively." A
ectangular form is also included. This system is said to have
, rked satisfactorily in twenty-five places, amongst which is
tibshalf, Derbyshire.
| | he Ives’ Tank (patent 16,724 of 1894) is also circular, and
|
|
f
|
cludes arrangements for aeration and, as a preliminary, a
cel itrifugal reducer of coarser solids, with a “chemical cage”
4 8
a 1 For details see Moore’s “ Sanitary Engineering,” p, 452.
II—2
q a .
ae
13
164 SEWAGE AND ITS PURIFICATION
for regulating the supply of precipitant. The details, including
a ‘‘flocculent flue,” are very elaborate.’
The sludge or precipitate left after either subsidence or filtra-
tion putrifies very rapidly in warm weather, therefore requires
rapid removal from filters or tanks. It was formerly intended
to disinfect it at great cost. It is of very varying composition,
and is disposed of at the present time by many processes,
namely :
I. Drying in open air on specially-prepared beds.
2. Running on to land a few inches thick, and then ploughing
or digging in.
3. Running into deep valleys.
4. Transport to sea in specially-constructed barges.
5- Mechanical pressing and disposal to farmers, or tipping.
6. Drying mechanically, pressing, and using as a basis for
fertilizers.
7. Centrifugal drying.
The centrifugal drying-machine and the filter-press were
first introduced about 1855 at Leicester Sewage Works under
Wickstead.
The Ashton-Booth sludge-remover now in course of installa-
tion at Bolton claims to take the place of the old methods of —
manual labour. This remover is propelled by pressure from
the inflowing sewage, can be worked by two men, and takes
fifteen minutes to clean a tank 4oo feet long. It is applicable
to any tank having a flat bottom, and claims to effect economy
)
)
)
)
in tank construction, owing to the absence of channels and |
underground sludge-pipes.
Pressed sludge from the London sewage at Crossness averaeay
according to Dibdin’s analysis—
Water i Tr ets 162 16. 58308
Organic matter (he ie Se 61 tay, oO OO
Inorganic or ash ih are PUR” yg
100°00
Saline ammonia Ay ae ‘. 0°035
Organic nitrogen _... a sae 0°87
The composition of the: mineral matter was affected by the —
treatment with lime and ferrous sulphate, being—
1 For details see Moore’s “ Sanitary Engineering,” p. 453.
CHEMICAL PRECIPITATION 165
Calcium carbonate ... ie Lis 7°94
Calcium hydrate (‘ free lime’’) ys 2°45
Silica (sandy matter) sui Lis 8:08
Ferric oxide sae ae As 0°97
Alumina (from clay) ... a oat 3°39
_ Phosphoric acid a sip a 0°66
Magnesia ... on bah eR gO
the total amount of wet sludge being 30 tons per million
gallons. |
With regard to the effluent, Mr. Dibdin estimates that the
organic matter put into the Thames estuary in the course of
twelve months is equal to only 5 grain per ton of water, “ but
as the organic matter probably does not last in any form longer
than a week, there would be at no time more than, on an
average, <1, grain per ton of water.”
At Wimbledon in 1893 8'2 tons of pressed sludge cake were
obtained per million gallons sewage, the average for a number
of towns where filter-presses are used being 9°28 tons per
million gallons. In pressing sludge, lime is generally added to
_make the substance more manageable; as much as 2 per cent.
is often used. The result, as we have indicated, is a dissolving
of the organic matters and an extra foulness of the pressed
liquid, besides the additional bulk. At Ealing, Bolton, and
some other places, the sludge has been mixed with town ashes
and burnt in a refuse destructor. James Ashton reports that
sludge cake cannot produce a clinker, but when burned either
falls to dust and is blown over the grate into the flues, or falls
out on breaking the hard clinker obtained from the ashpit
refuse. At Birmingham the sludge was mixed with the general
refuse and offered as manure.
Although free lime tends to inhibit the multiplication of
micro-organisms, we have already noticed that large quantities
of it, added either to the raw sewage or mixed with the sludge
to assist consolidation, increase the amount of organic matter
in the effluent or in the sludge-press water, so that these
liquids, after their alkalinity has been diminished by dilution
_ or absorption of carbonic acid from the air, readily putrefy.
Sludge includes the greater proportion of the organisms of
the original sewage, and when fresh may contain, according
to Professor Boyce, 150 millions per c.c., but on standing the
1 Fournal of Preventive Medicine, July, 1905 ; see also Royal Commission on
Sewage, vol. iii., 1904, pp. 47, 75, etc., as to the volume of the Thames and of the
_ sludge discharged.
166 SEWAGE AND ITS PURIFICATION
number slowly diminishes, reaching go millions after twenty-
four hours, and falling to 7 millions. in three months. With
regard to sludge cake, the further addition of lime, together
with abstraction of water by the presses, renders the mass
almost sterile at first, but when exposed to the weather and to
dust a ripening process takes place on the development of
bacterial life. ir
Bradford, Yorkshire, has met with great difficulty on account
of the large quantity of grease, mainly wool-fat, amounting
sometimes to 20 per cent. of the dry solids, preventing the
squeezing out of more than 25 per cent. of water. The usual
percentage of water in the wet sludge of other towns is
go per cent., the increase from go to 98 per cent. at Brad-
ford making a vast difference in the total bulk. Thus, wet
sludge
with go per cent. water = 9 vols. H,O to 1 of solids;
9» 95 ” re) = 19 ” 9 I 9
” 98 ” ” = 49 9 ? I ”
Therefore, 100 tons with go per cent. water become 200 tons
with 95, and 500 tons with 98 per cent., so that the watery
character of the Bradford sludge caused its volume to be
increased five times. Being so thin and greasy, it was difficult -
to press, and after being pressed in the most improved —
machines it left fully 75 per cent. of water in the cake.
Sludge cake can be brought to 50 per cent. water by pressing,
and to 12 per cent. by air-drying. As the value, either as
manure or fuel, is inversely proportional to the amount of —
water present, it follows that in all cases air-drying should be
used before disposal. In the table (p. 167) the monetary value
of air-dried sewage sludges is given, while their calorific value
is roughly proportional to the organic matter. Since the latter
is largely nitrogenous in character, its value as fuel is much ©
lower than that of coal, and, of course, the remaining water
associated with it must be evaporated before any energy is
available. Santo Crimp estimated that in an efficient chemical
process 10 cwt. per head per year of wet sludge with go per
cent. water was obtained, equal to 2 cwt. of dried sludge with
50 per cent. moisture. _
The following are analyses of air-dried sludges as given by
Professor Robinson :
167
CHEMICAL PRECIPITATION
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‘(aalud-uly) ADaNIg AOVMAS AO SASAIVNY
CHAPTER VIII
STERILIZATION BY HEAT, CHEMICALS, AND ELECTRICITY
Removing odour—Metallic salts—Action of manganates and per-
manganates—Oxynite process—Chlorine and hypochlorites—
Bleaching powder — Hermite — Electrozone — Oxychloride—
Acids—Bergé—Ozone—Liernur process—Disposal of refuse—
Destructors.
In the foregoing methods for the mechanical separation of the
solids and the production of a clear effluent chemicals were
sometimes employed, but almost solely with a view to clarifica-
tion. The Rivers Pollution Commission and a large number
of legal actions led to attempts at “‘ disinfection” of the raw
material or its products by processes aimed at removing or
preventing smells or destroying the bacteria, at a time when
all organisms were held to be dangerous. Odour and appear-
ance were often the only things considered. In these earlier
attempts at disinfection on a practical scale disinfectants like
mercuric chloride and carbolic acid were soon seen to be too
costly when used in effective strength.
It was therefore found that the complete sterilization of
crude sewage was impracticable on a large scale. Later, when
it became acknowledged that the attempt was in general on
the wrong lines, and that biological change was, on the whole,
the most economical and efficient means of purification, and
should be encouraged and not inhibited, the bacterial flora of
an effluent which was inoffensive to sight and smell and con-
formed to certain chemical standards excited little attention.
This attitude was generally right, as I have frequently con-
tended that it is no part of a sewage scheme to convert sewage
into drinking-water, and that where the water of a river must
be used for drinking, it is always necessary to purify it by
efficient filtration or by other means. In Chapter 1V. I have
already reviewed the question of the survival of pathogenic
168
q
ie
| 2
a
b
STERILIZATION 169
organisms in bacterial sewage treatment. Filtration has a marked
effect in keeping back B. enteritidis sporogenes (see p. 91), and
the number of B. coli is diminished during the stay in a septic
tank. A septic tank liquid is inimical to B. coli and to other
more delicate pathogenic bacteria. Experiments of my own
at Caterham proved that nitrifying filters removed 98°5 per
cent. of the coli organisms, and all or nearly all of the enteri-
tidis. Fuller states that in America sewage filtered inter-
mittently through sand contains only about 1 per cent. of the
bacteria present in the raw liquid.1. So that we were justified
in concluding that effluents from an efficient bacterial treatment
were, with the limitations I have above indicated, perfectly
safe to discharge into rivers, and that the greater the aeration
and nitrification, the less the possibility of survival of patho-
genic organisms.
Judged from a bacterial standard, and sometimes from a
chemical one, there is not a river whose waters are safe to
_ drink without purification, and my contention many years ago
that a good effluent frequently improved a river has been recog-
nised as true, and is conceded in the report of the Royal
Commission.” Therefore there does not seem to be much
advantage in insisting, in the language of the Commission,
on the ‘fundamental difference between the discharge of
effluents into drinking-water and non-drinking-water streams.”
In most cases it is only practicable, in the majority it is alone
necessary, and in all cases it should be compulsory, to carry
the purification of sewage to a stage when, in my words at the
time mentioned, “‘ such factors as time, light, volume of oxygen,
and various life in the river, will be more than sufficient to deal
with the effluent,” leaving, in the instance of ‘‘ drinking-water
streams,” the removal of the reduced number of bacteria to.
the water companies, with, as I have indicated elsewhere,?
a final line of defence in domestic sterilization.
The suggestion that local authorities should in general be
further hampered by increasing their existing burdens in
_ treating sewage, so as to produce effluents equal to drinking-
water, is obviously absurd and unjust. The means by which
sterilization of effluents can be effected when necessary will be
presently described.
* Transactions of the American Society of Civil Engineers, vol. liv., part E,
1905.
® Vol. iv., part i., 1904, p. 105.
® Rideal, Cantor Lectures, Society of Arts, 1902, p. 27; also ¥ournal of the
Society of Arts, December 17, 1897, p. 86.
170 SEWAGE AND ITS PURIFICATION
Much sewage is still, however, locally discharged without
any treatment, or with only screening or a rough sedimenta-
tion. The Rivers Pollution Act, 1876, restrains such a practice
as regards “‘rivers, streams, canals, lakes, and watercourses,
other than watercourses at the passing of the Act mainly used
as sewers and emptying direct into the sea or tidal waters”
(section 20). Under the provisions of this Act, and the supple-
mentary one of 1893, damages have been obtained and injunc-
tions granted. But the working, on the whole, has not been
satisfactory, and the Royal Commission on Sewage observes :
‘“*At an early stage of our investigation we were struck by the
fact that in many parts of England the pollution of rivers goes
on unchecked, notwithstanding the fact that the Rivers Pollu-
tion Prevention Act has been on the statute book for over a
quarter of a century, and in our Interim Report we deemed it
necessary to state that the protection of our rivers is a matter
of such grave concern as to demand the creation of a supreme
rivers authority.”” They give, further, an outline of the powers
and duties of such a central authority and of proposed River
Boards. |
In certain estuaries the polluted water is carried up and
down by the tide, and is only slowly cleared out to sea; and
yet tidal waters, as will be seen by the quotation we have given
from the Rivers Pollution Act, are exempted from its operation ;
as a consequence raw sewage continues to be discharged from
a large number of sea-coast towns. Recent cases at Ems-
worth and Southend have, however, shown that pollution of
oyster beds, if proved to be due to such discharge, is actionable
at common law.
The risks to health, especially from the contamination of
fisheries and shell-fish layings, claimed early scientific attention.
In India it has been held from ancient times that: uncooked
shell-fish are a cause of bowel affections and even of cholera.
In 1880 Sir C. Cameron pointed to the possible relation of
typhoid in Dublin to the consumption of specifically polluted
oysters. Sir R. Thorne Thorne, in the Local Government
Board Report for 1894, expressed his conviction that the dis-
tribution of shell-fish from certain centres had been concerned
in the diffusion of cholera over a somewhat wide area in Eng-
land. In the same year Dr. Newsholme commenced his
investigations as to the connection of typhoid at Brighton with
1 Third Report, 1903, p. 26. 3
STERILIZATION ! I71
sewage-polluted shell-fish, and afterwards proved that the per-
centage of cases due to this cause was in 1894, 1895, 1896, and
1897, 38°2, 33°9, 31°8, and 30°7 respectively,' and that at least
one-third of these cases are due to mussels.2. Dr. Nash in 1900
obtained clear evidence that a severe outbreak of typhoid fever
at Southend was originated by infected cockles.2 These had
been obtained from a sewage-polluted creek in another district ;
had been scraped up with an ample amount of mud attached,
then washed on a sieve in the creek water, and partially cooked
by being plunged into an open copper containing very hot
water. In a few minutes, when the shells opened, the cockles
were removed, the shells separated by sifting, and the fish either
sold at once or pickled in brine for transport.
The important points are that the usual cleansing is delusive,
and the parboiling commonly practised is no protection.
Dr. Thresh, in an experiment with these cockles, washed them
twice with pure water, and then plunged them into boiling
water. At the end, living sewage bacteria were present in the
liquid draining from them, a result confirmatory of conclusions
previously arrived at by Dr. Klein, working with oysters,
cockles, and mussels, and with typhoid and cholera organisms,
who, moreover, found that the organisms remained even when
the infected water had been replaced for three days by clean
sea water, and that they actually increased in numbers within
the bodies of the shell-fish.t Dr. Nash also remarks® that
inquiries should not be limited to the eating of shell-fish, but
should extend to the handling of such from suspicious sources,
since germs can easily be carried from the hands to the mouth.
The proofs of the connection between polluted shell-fish and
_ typhoid are clear and numerous, and have been summed up by
Newsholme,® and also in the Fourth Report of the Royal Com-
mission on Sewage, vol. i., p. xv. In the careful surveys of the
gathering-grounds of England and Wales in 1894 and 1895,
and of Ireland in 1903, conducted for the Local Government
Board, it became evident that a number of them were liable to
invasion by recent sewage. Its discharge into tidal waters
came into wide public notice in 1903, in connection with serious
1 Fournal of the Royal Sanitary Institute, vol. xvii., part iv., January, 1897.
2 [bid., vol. xxv., part iii., October, 1904.
® Ibid., vol. xxiii., part iv., January, 1903.
_ 4 Report of Medical Officer to Local Government Board, 1900-1901, p. 567.
5 Public Health, August, 1902.
8 Fournal of the Royal Sanitary Institute, October, 1904, p. 454.
172 SEWAGE AND ITS PURIFICATION
illness following mayoral banquets at Winchester and South-
ampton, which illness was traced to Emsworth oysters.
Legislation had been widely demanded for the prohibition of
the laying down of shell fish in sewage-polluted water or other
dangerous localities, and the protection of those laid down in
hitherto unpolluted places. The whole subject was therefore
dealt with as urgent by the Royal Commission in their Fourth
Report, 1904. They concluded that (vol. i., p. xi), “ generally
speaking, it may be said that the Statute Law does not prohibit
the discharge of polluting liquids into tidal waters.’’ From the
mass of evidence collected, they gave official confirmation to
facts of which others, including myself, had long been aware—
that sewage from towns and tidal rivers on the coast is usually
discharged in an unpurified condition, that injuries to health ~
and to fisheries may be thereby caused, and that some altera-
tion of the law was necessary. In many layings of oysters the
sewage can reach them in a very short time after its discharge,
and organisms of intestinal origin can be taken up by the shell-
fish and remain alive in them for several days, and can produce
diseases (ibid., p. xv).
In the evidence it was urged! that every endeavour should be
made by local authorities to prevent typhoid bacilli or other
pathogenic organisms from gaining access to sewage, by
sterilization of the excreta of patients. It was admitted, how-
ever, that in the large discharge of typhoid bacilli in the urine
during prolonged convalescence there would be almost in-
surmountable difficulty.
We gather, therefore, from the Royal Commission’s Report
that sterilization of effluents is necessary—
1. Where shell-fish or vegetables commonly eaten raw are
liable to be infected, provided it is necessary for them to lie in
such situations.
2. Where disease organisms are discharged in large numbers,
as in the instance mentioned above, and in fever hospitals.?
3. Where the effluent is discharged into streams from which
water is subsequently taken without proper purification.
In their Third Report the Royal Commissioners had stated,
‘* We are continuing the investigations referred to in our Interim
Report (1901), for the purpose of ascertaining whether it is
practicable to destroy those micro-organisms which are com-
mon to sewage effluents, and which may be dangerous if the
1 Vol, ii., 1904, p. 100. 2 Interim Report, vol. ii., p. 538.
STERILIZATION 173
effluent flows into a river from which water for drinking is
obtained, and we are generally considering what measures may
be desirable to lessen dangers so arising” (p. 29). It was
hoped that the Commission would have followed by informa-
tion as to processes of destroying micro-organisms or steriliza-
tion of effluents on the large scale, but although evidence on
the subject was given before them by Drs. Klein, Thresh,
myself, and others, and one of their references was as to what
remedies were practical and available for injuries caused by
sewage, sterilization finds no further mention in their conclu-
sions. The nearest approach is in their Fourth Report, vol. i.,
p. 20, under ‘‘ Remedies Suggested,” where the proposal that
all sewage should be purified is met by two objections: non-
necessity, and non-efficiency.
Non-necessity, because there are ‘‘ many cases where shell-fish
are not concerned . . .. and to require purification in all cases
would lead to the waste of large sums of money.”
Non-efficiency, because they consider that no treatment at
present in use can be relied on as safe.
They seem to have ignored the point that sterilization of a
partially purified effluent when necessary was possible, and had
been achieved in several places without ruinous expense. And
yet the keynote to this idea had been struck shortly before in
the Report of the Local Government Board for Ireland, 1903,
p. 7, in the phrase, ‘“‘ Short, however, of the sterilization of
sewage effluents discharging in the immediate vicinity of shell-
fish beds, no other form of treatment at present in use is likely
to be effectual in destroying or removing, although it may
succeed in reducing, the number of pathogenic germs.”
Owing to the foul condition of rivers near or within large
towns, vigorous attempts have been made to disinfect them
with chemicals, or to add the latter to the sewage, with the
object of removing or neutralizing free ammonia, compound
ammonias, and sulphuretted hydrogen, and so to render the
liquids almost inodorous for the time, and to hinder further
decomposition of the organic matters. Any acid or acid salt
would neutralize the ammonia; many metallic solutions would
absorb sulphuretted hydrogen, and also precipitate much of the
organic matter, and a clear effluent without much odour and
almost colourless would be obtained. But several difficulties
occur :—
1. It is a mistake to suppose that the odorous ingredients
174 SEWAGE AND ITS PURIFICATION
of sewage are all basic like ammonia, or readily combine with
chemical reagents. Acids and many other chemicals, when
added to. urine, feces, or vegetable refuse, develop a very
unpleasant odour, which may be often noticed in the vicinity
of works where organic matters are treated. Substances like
indol and skatol, from feces, are very weak bases, and readily
escape in the vapour even from acid solutions.
In distilling sewages or contaminated waters for ammonia
and albuminoid, the distillate will be found to have a peculiar
nauseous, somewhat aromatic odour, which is so constant that
in waters it points strongly to sewage admixture. When in
considerable quantities, the compound causing the smell
collects as a greasy white scum on the top of the distillate.
On account of its ready volatility, and its not combining with
reagents, it is very difficult to separate, but from large volumes
of sewage I have obtained it as a white neutral crystalline
substance. In small quantities, it floats like a grease on the
surface of water: from its odour and general occurrence, though
in minute amount, it would seem to be an important cause of
the residual sewage odour when ammonia, etc., have been
removed.
The volatile oil giving the chief odour to urine has also been
isolated: it is neutral and does not readily combine; the same
would be the case with essential oils from vegetables, hydro-
carbons like naphthalene from gas-tar, etc. Among acid
compounds, phenylacetic acid, which I have isolated from
effluents, has a strong odour. Ethereal salts, like mercaptan,
may also be mentioned among the many substances which
may render chemical deodorization inefficient.
2. Chemicals, in the quantities that were applied, did not
kill the organisms of putrefaction, and only to a slight extent
reduced the organic matters in solution, therefore the effluent
soon resumed a condition of turbidity and foulness. Some
chemicals render the liquid acid, others unduly alkaline—both
objectionable features. We have already spoken of the increase
of the sludge by precipitants ; while the difficulty of sterilizing
it is well known.
Where expense is a secondary factor, as, for instance, in
some of the effluents from hospitals, metallic salts are of
service, notably those of copper, on account of their combining
with sulphur and ammonia, and their marked germicidal pro-
perties. The easy removal by lime and sand filtration, with
STERILIZATION 175
| ‘subsequent recovery of the copper from the material, induced
| -Kroncke! to adopt cuprous chloride; others—e.g., the’ French
authorities in combating the cholera in 1892—used the cheaper
cupric: sulphate. Mr. Shrapnell Smith, of Liverpool, stated at
the Leeds Sanitary Congress, 1897, that he was using salts of
‘copper, and drawing air through the filter-beds by fans. More
tecently sulphate of copper has been somewhat extensively
used in America and India for the removal of alge and the
bacterial contamination of rivers and reservoirs, but owing to
_the expense this method is only of very limited application.
_ In 19042 I confirmed the results obtained by Dr. Moore,?
and found that copper chloride could be substituted for the
sulphate, and that the quantities required were so small as to
cause little apprehension as to injury to fish.
The efficiency of different copper compounds depends on
the percentage of copper present in the salt; for instance,‘
I in 8,500 of copper sulphate, or I in 13,500 of copper chloride,
killed B. coli in three hours; I in 7,000° of sulphate, or I in
10,000 of chloride, killed Siaploilonoceis pyogenes aureus in two
hours. |
_ Hence it appears that these salts might be useful in steri-
Hizing oyster or watercress beds without danger.
Even plates of metallic copper® in ordinary water give off
enough of the metal in a so-called colloidal state to make the
liquid toxic to many alge and bacteria, and I am trying the
effect on sewage filtrates of passing them through copper gauze
to reduce the number of pathogenic organisms, with a view to
| meine watercress beds and oyster layings.
Bassett Smith® experimented with B. typhosus, coli, enteritidis,
B. dysenteri@ (Flexner), Micrococcus melitensis (the organism of
) Mediterranean fever), and with ordinary water organisms, com-
| paring the effect of copper with that of iron, zinc, lead, and tin.
His copper sulphate solutions were of 1 in 1,000, r in 10,000, and
I in 100,000 strength, and he observed that in all the dilutions
) with distilled water B. typhosus was killed in under one hour;
| but in tap water the highest dilution required twenty- -four hours ;
| I in 10,000 required twelve hours. With B. coli in distilled or
| a water the highest dilution was insufficient to kill in twenty-
_ 1 Fourn. f. Gasbeleucht, xxxvi., 513.
2 Fournal of the Royal ‘Sanitary Institute, vol. xxv.
° Bulletin, Department of Agriculture, Washington, 1903.
4 See also Green, Zeits. f. Hygiene, 1893, p. 495.
5. For details I must refer to my paper, mentioned above,
6 F¥ournal of Preventive Medicine, July, 1904.
176 SEWAGE AND ITS PURIFICATION
four hours, but 1 in 1,000 was fatal under that time. JB. enteri-
tidis was very similar. With B. dysenterie and M. melitensis
fifteen hours was effective. ;
A ferrous sulphate solution was also tried in comparison. One
in 100,000 was ineffective ; I in 10,000 was fatal to B. typhosus
under seven hours, and to B. enteritidis under forty-eight hours;
1 in 1,000 killed B. coli in less than twenty-four hours. He
therefore finds ferrous sulphate almost as effective as copper
sulphate, but it has the disadvantage of rendering the water
yellow and turbid.
He confirmed the germicidal power of bright copper surfaces.
B. typhosus in a copper vessel was still living at twelve hours, but
was dead at twenty-four. With ordinary tap-water organisms,
the number being 1,020 per c.c. at first, only 8 per c.c. were
left after twenty-four hours ; the main decrease occurred in the
first hour, and the liquefying bacteria decreased from sixteen to
two in three hours, and to none in twenty hours. No copper
was found in solution.
He concluded that clean iron was nearly equal to copper,
and zinc had almost the same effect; but as the metals must
be bright, iron soon loses its value by rusting, and zinc also
becomes oxidized. Strips of ordinary zinc foil up to forty-eight _
hours had not sterilized any of the organisms. Iron coated
with zinc, or galvanized iron, should give good results.
An attempt to sterilize urine containing pathogenic organisms,
by keeping it in a copper vessel, was not successful after twenty-
four hours’ contact, and it was considered that this was due to
the action of the urine on the metal.
Lead, tin, and a control glass vessel showed practically no
effect. The conclusions of the paper are that in tanks for the
storage of water, iron, copper, and zinc as galvanized iron
show only a slight difference in bactericidal power, and that |
“zinc, or iron, coated with zinc, though less rapid in action |
than copper, yet after twenty-four to forty-eight hours appears _
to free the water from typhoid organisms.”
It is possible to thoroughly deodorize sewage by permanganate
and sulphuric acid (giving ozonized oxygen), either before or after
the removal of the suspended matters by precipitation.’ Sodium
manganate, as a cheaper salt, was used for the London sewage
from 1884 to 1887 by introducing it into sewers at different
1 See Report of Commission of 1882, on the effects of the discharge of the
sewage of London into the Thames, vol. xi., p. 142.
STERILIZATION 177
points; being strongly alkaline, it disengaged ammonia, which
was neutralized by acid treatment at the outfall.
The amount of oxygen liberated from manganates and per-
manganates depends upon the way they are applied. The
maximum, when permanganate with sulphuric acid acts on
organic matter, is 5 atoms, thus:
K,Mn,O, + 3H,SO,=K,SO, + 2MnSO,+3H,0+50.
If the acid be insufficient, a brown precipitate of hydrated
peroxide falls, and only 3 atoms of oxygen are liberated :
K,Mn,O, + H,SO, + 3H,O = K,SO, + 2Mn(OH), + 30.
Manganate spontaneously gives up I atom of oxygen with great
readiness:
Na,MnO,+3H,O = 2NaOH + Mn(OH), +0.
With a dilute acid, even carbonic, in excess, it yields per-
manganate and hydrated peroxide :
3Na,MnO, + 2H,SO, = Na,Mn,O, + Mn(OH), + 2NaSO, ;
the permanganate further changing as shown above.
Processes for recovery of the manganese or iron oxides from
the pressed sludge have not been commercially successful.
Manganates and permanganates are rapidly destroyed by
harmless organic matter and other substances, so that there is
often no remainder left for bactericidal action. They were
_ formerly much used in street watering-carts, and an experiment
of my own may be illustrative.!
The Westminster Vestry had for some time at permanganate
in their water-carts in the proportion of 2 ounces to 400 gallons,
Or I in 32,000, the 400 gallons covering about 600 square yards
ona dry and 3,000 square yards on a wet day. The reasons
given for discontinuing it are interesting: (1) That it was com-
plained of as damaging the asphalt; (2) that it was more costly
than other disinfectants ; (3) that being without odour the rate-
payers had no belief that a place had been disinfected; (4) that
it attacked the iron tanks and fittings ; (5) that children collected
the pink liquid in various utensils, and sometimes drank it.
To test the bacterial efficiency of a I in 5,000 solution, at the
_ Yate per yard mentioned above, I watered two plots of asphalt
roadway in Victoria Street, under ordinary day conditions of
horse droppings, etc., (a) with ordinary water, and the other
1 Sanitary Record, July 27, 1900.
12
178 SEWAGE AND ITS PURIFICATION
(b) with the permanganate I in 5,000. The liquid running off
was collected and bacterially examined. The rapid destruction
of the permanganate was again noted.
The permanganated sample was almost free from odour, and
on keeping for three days smelt much less foul than the other.
The cultivation experiments showed the following results :
Colonies per c.c.
Gelatine plates at 22°C. ... aoss AM) 1,930,000
” ” ” tee tee (d) 85,000
Agar plates at 37°5° C.... ... (@) O00! C.c. gave numerous
colonies, and plate was
too clouded in twenty
hours for counting.
9 9 ‘i Ps ... (bd) oro1 c.c. gave a similar
result.
Carbolized gelatine plates at 22° C. (a) 122;200
” ” » r (2) 4,830
Although the permanganate has exercised considerable in-
fluence, destroying about 96 per cent. of the bacteria, the result
cannot be considered sterilization, and it will be noticed that
its effect upon those growing at blood heat and on carbolized
gelatine, which include those of the “‘ coli” group, was similar
to that on those growing on the ordinary gelatine plate. I
did not specially test in these experiments as to the survival —
of spores of B. enteritidis sporogenes, but from previous work
with this organism I believe it to be extremely resistant
to permanganate. (See also p. 186, use of chlorine for this
purpose.) |
An important point in this treatment is that lower oxides of
manganese are always left in the sludge. Any metal having
two oxides which easily pass one into the other may act as a
carrier of oxygen from the air to organic matter, as is the case
with iron. Manganese has a still higher range of activity,
hence its oxygen compounds have long been used as destructors
of organic matter. The native mineral pyrolusite, MnO,, has
been used in the granular state in filters, or added in very fine
powder to sewage; but beyond mechanical action it gives no
oxygen, and remains practically unchanged. A better result
occurs when it is mixed with carbonaceous matters and heated
in closed retorts, so as to reduce it to a lower state of oxidation.
On exposure to air and water a film of flocculent hydrated
peroxide is formed, which readily parts with oxygen to organic
matter in solution, reabsorbing oxygen from the air when the
STERILIZATION 179
_ water has drained away. Such a material has high oxidizing
_ powers, the expense being the main objection.
___ Bertrand,' in his investigation of oxydases (p. 110), pointed out
the invariable presence of traces of manganese, and suggests
__ that the oxydases are compounds of manganese in which the
acid radicle is of a proteid character, and of sufficient activity
| Hf to keep the metal in solution, whilst the manganese is the real
carrier of oxygen. Antoine Villiers? and Achille Livache?
confirm this view of the agency of very small quantities of
| _manganese in transferring oxygen from one compound to
_ another, and it seems probable that the traces of manganese
_ in coke, clinker, and other materials of filter-beds may be help-
_ ful to oxidizing action by supplying this element to oxidizing
_ enzymes. In the natural oxidations that occur in ferruginous
_ waters, the action of enzymes has also been asserted.
_ Adeney, in 1894,‘ observed that the sludge from sewage that
_had been treated with manganate of soda slowly evolved
carbonic acid and nitrogen gas. This oxidation of the organic
: matter was clearly traced by him to the available oxygen of the
i hydrated peroxide of manganese in the precipitate, as he found
_ that the peroxide became completely converted into manganous
carbonate, MnCO,. The process is exactly parallel to denitrifi-
|| cation (p. 125), and is similarly dependent on organisms, as
_McWeeney® found that in sterilized media the reduction of
peroxide to carbonate did not occur. In his ‘“‘ Oxynite”
rocess the sewage first deposited nearly go per cent. of the
| olid matters ‘‘unmixed with precipitating chemicals,’ and
| then was precipitated by manganate of soda and sulphate of
alumina; this sludge underwent the spontaneous oxidation
| described above, and admits of the recovery of the manganese.°
The effluent was mixed with nitrate of soda to supply more
oxygen.
| Chlorine and Chlorine Compounds as conveyers of oxygen have
een often used. Chlorine by itself may act in different ways.
When concentrated it can combine directly with organic
‘matters or replace the hydrogen in them, precipitating all
albuminous substances’ and rendering them imputrescible,
1 Comptes Rendus, 1896, cxxiii., 493; and 1897, cxxiv., 1355.
2 Tbid., 1349. 3 [bid., 1520.
rk: Proceedings of the Royal Dublin Society, Viii., 247.
\ Transactions of the Royal Dublin Society, August, 1897.
® See also Wilson, Patent 1725, 1891.
7 Rideal and Stewart, Analyst, 1897, p. 228.
pO ae:
180 SEWAGE AND ITS PURIFICATION
besides killing all life. In localized situations, therefore,
chlorine and its compounds are effectively used for dealing
with special nuisances. The offensive gases of putrefaction
are decomposed, sulphuretted hydrogen being resolved into
sulphur and hydrochloric acid—
H,S+Cl,=2HCl+$
phosphuretted hydrogen being also decomposed, while ammonia _
and compound ammonias give a corresponding chloride and
nitrogen—
8NH, + 3Cl,=6NH,CI+N,,
hence the copious white fumes frequently noticed when a
chlorine mixture is thrown into a dung - pit. With more
chlorine intensely acrid vapours, which attack the eyes and ©
lungs, due to chlorides of nitrogen and chloropicrin, C(NO,.)Cls, —
are produced. In dealing with cesspools, ashbins, or privies
this becomes strongly prominent in chlorine disinfection. —
Chlorine acts as an oxidizing agent by decomposition of
water— g
H,0+Cl,=2HC1+0,
the nascent oxygen so liberated being far more energetic than
atmospheric oxygen, and acting directly on organic substances. —
A cheap source of chlorine is chloride of lime or bleaching
powder, CaCl,O, which, on dissolving in water, breaks up into
calcium chloride, CaCl,, and calcium hypochlorite, Ca(ClO)o;
the latter only is available for chlorinating or oxidizing. The _
commercial dry powder contains as a rule about one-third of
its weight of active or ‘“‘available” chlorine.t. When mixed
1 “ Available chlorine” means that portion of the whole chlorine which
liberates oxygen on reaction with water. Hydrochloric acid and most chlorides
liberate none. Free chlorine, for every molecule Cl,, or 71 parts by weight,
free Latom, weighing 16 parts, of oxygen :
Cl, +H,O=2HC1+0 ;
that is, the weight of chlorine used is about 44 times the oxygen obtained. 3
Hypochlorous acid and hypochlorites can break up directly into hydrochloric
acid or chlorides and oxygen : .
HCIO=HCl+0O
Ca(CIO),—CaCl, +20%
NaClO=NaCl+.0.
Hence gure hypochlorous acid, or a pure hypochlorite, would give 1 atom of
oxygen for 1 of chlorine, or double the amount yielded by free chlorine.
Commercially, however, the hypochlorite is always obfained mixed with an
equivalent amount of the inert chloride, as in the formation of solutions of chloride
of lime and chlorinated soda :
2NaOH + Cl,=NaCl+NaClO+H,0. = VY
2Ca(OH), + 2Cl, = CaCl, + Ca(ClO),+2H,0.
Therefore, apart from the question of difference of activity, the total amount o 7 i
chlorine present in these chlorinated products bears the same relation to the —
STERILIZATION 181
_ with ordinary water containing carbonic acid, the latter decom-
_ poses the hypochlorite, setting free hypochlorous acid—
Ca(Cl0), + CO, + H,O = CaCO, + 2HCIO.
Hypochlorous acid can either combine with organic matter
_ directly, forming innocuous compounds, or can furnish hydro-
_ chloric acid and nascent oxygen.
_ “Chloros” is a solution of sodium hypochlorite NaClO,
_ containing to per cent. of available chlorine. It has recently
been used by the Metropolitan Water Board for sterilizing the
' effluents from the Hertford Sewage Works, as the outfall is
not far from the intake of the Lea water-supply to London.
_ Allusion has already been made to the use of chloride of lime
/ at Birmingham (p. 155) in small quantity along with slaked
|” lime; as the latter absorbs the carbonic acid, the action of the
| hypochlorite is extremely slow. Chloride of lime was used
| before 1884, and again in 1887, for the river Thames during
_ the hot weather, but it was shown that “unless large and
| continuous doses were kept up,” the foulness of the stream
ie was not controlled. Hofmann and Frankland found in 1859
_ that it required 400 pounds of chloride of lime to deodorize a
| million gallons of London sewage, the effluent remaining in-
_ offensive for three days. On the river Brent in 1896, when
_ complaints were made of the effluvium, chloride of lime was
_ scattered on each bank during the warm weather. Its use in
_ dustbins, gulleys, streets, and urinals is well known. Louis
_ Parkes,’ speaking of the insanitary condition of wood pave-
_ ments during dry weather where horse-droppings are frequent,
| recommends that “‘ wood-paved streets should be watered from
_ carts containing a weak antiseptic and deodorant solution,
| which will inhibit the growth of the putrefactive microbes on
| the wood surface. Probably the best would be a weak chlcrine
| solution, say r part of chlorine in 10,000 to 20,000 parts of
| water... being volatile, it leaves no residue on the road.’’
| But free chlorine, even in this dilution, would attack the iron
_ fittings of the carts and the grids of the sewers, and be itself
removed as basic ferric chloride, A I per cent. solution of
| oxygen yielded as it does in solutions of the free element. In the manufactured
| products lime or soda is always present in excess for the sake of stability ; but
__ all of them deteriorate when stored, especially in presence of light. The available
_ chlorine requires to be frequently controlled by analyses. In “ chloride of lime”
_ itis expected to be 33 to 34 per cent. ; in “chloros” solution it is regulated to.
| IO per cent.
|? British Medical Fournal, December 9g, 1899.
182 SEWAGE AND ITS PURIFICATION
bleaching powder (I : 300 available chlorine) was used by Sims
Woodhead for sterilizing the Maidstone water-supply during
the 1897 typhoid epidemic. Schumacher, working at the
Hamburg Hygienic Institute, has also recently conducted a
long series of experiments which demonstrate the disinfectant
value of chloride of lime and its applicability for sewage treat-
ment.’
Although powerful disinfectants, chlorine and the hypochlo-
rites have several disadvantages :
1. Their own odour, and the persistent odours they create
and leave behind, lead often to their use irregularly, or in in-
effective quantities.
2. The action on metals, wood, leather, and caoutchouc.
Lead even is corroded, so that in water-closets with leaden
siphons the pipe would be eaten through rapidly. Free
chlorine, or acidified chlorine mixtures, exert rapid action on
iron, cutting the fittings generally just at the level of the liquid,
and even, owing to evolved gas or spray, corroding the metal
some distance above. The hypochlorites, being alkaline, are
much less destructive, as shown by the fact that iron tanks are
largely used to store strong “ bleach liquor” in factories.
3. Their immediate destruction by amido-compounds like -
urea or by ammonium salts, with loss of nitrogen, so that the ©
chlorine may be entirely used up in dealing with inodorous
and inoffensive matters, unless a large excess be employed.
One reaction between chlorine and ammonia has already been
given (p. 180). The complete decomposition would be—
2NH,+3Cl,=N,+6HCL.
With hypochlorous acid :
2NH,+3HCIO=N,+3HC1+3H,0O.
Urea and hypochlorous acid:
CO(NH,), + 3HCIO=N, + 3HC1+CO,+2H,0.
Urea and a solution of bleaching powder react thus:
3Ca(Cl1O), + 2CO(N H,), = 2N, + 2CO, + 3CaCl, + 4H,O.
Soap and domestic slop waters rapidly exhaust chlorine
liquors, while paper, fibre, etc., absorb chlorine readily.
Although deodorization, and still more sterilization, can only
occur when the agent is in excess, an effluent containing free
chlorine or its oxides would not be allowed to be discharged
1 Public Health Engineer, March and April, 1906.
STERILIZATION 183
into main rivers. Care and certain precautions have, there-
fore, to be adopted. The presence of excess of chlorine, or its
oxides, is tested for by adding a solution of iodide of potassium
and starch, which is turned blue.
The soluble hypochlorites are alkaline; when acidified they
give off chlorine or hypochlorous acid in vapour, so that the
walls of sewers and culverts can be thoroughly disinfected in
special cases, as in the drains from hospitals. On the other
hand, the action of unacidified hypochlorites is very slow,
especially on organic colouring matters as derived from trade
effluents. In the Manchester report of 1898 a portion of the
Swinton sewage is thus described :
“Raw Sewage.—Pink colour ; slight purple suspended matter;
smells of bleach liquor ; neutral to litmus.”
“Tank Effivent.—Slight pink colour; brown precipitate of
ferric hydroxide”; lime and copperas had been added (see
p- 159); “‘ smells of bleach; neutral.”
There was an excess of chlorine compounds, since “on the
addition of acid, chlorine was liberated equivalent to 0°08 grain
per gallon of oxygen” (o°II4 part per 100,000). The incu-
bator tests given show aslight, but distinct, effect of the chlorine
in the bleach, indicated by the “ three minutes oxygen absorp-
tion ”’:
Grains per Gallon. ei EK Putrescibility.
Raw sewage, high level, as described
__ above... stb ioe hig aa batere) 2°15 Slight after 5 days.
; Raw sewage, low level, no bleach ... 0°68 1°86 Quite putrid after
f 4 days.
Tank effluent, as above, from the
_ two mixed ... ve side aes 0°88 | 1°31 Putrid after 4 days.
Sterilization of septic tank effluents has been successfully
effected by chlorinated lime in some experiments carried out by
the Indian Government on the Hooghly River. This investi-
gation showed that 5 grains per gallon of bleaching powder,
equal to less than 2 grains of available chlorine, rendered the
fluid virtually sterile, and that a tank effluent from 2,000 people
could be rendered inodorous and sterile at from Rs. 10 to 14 per
month. ‘The time of contact to complete the action was found
to be about one hour, as little or no improvement was noticed
when plates were taken after a longer period. At the Tittagurh
“installation, near Calcutta, this treatment was applied to latrines,
184 SEWAGE AND ITS PURIFICATION
and was proved to be cheaper than sand filtration (3 feet thick
and at the rate of 4 gallon per square foot), combined with
the application of copper sulphate, which was suggested as an
alternative method for dealing with the problem.
ELECTROLYTIC PROCESSES.
About 1859 Charles Watt first introduced electrolysed solu-
tions of the chlorides of alkalies or alkaline earths as bleaching
liquids. They contained chlorides and hypochlorites, but
apparently were more active than a solution prepared by pass-
ing chlorine into an alkali. Magnesium chloride was said to be
preferable.
The Webster process allowed ordinary sewage to flow through
channels between iron electrodes, so that the chlorides were
electrolysed, the chlorine and oxygen liberated at the positive
pole deodorizing the sewage, while the iron salts formed assisted
in the purification. Later aluminium plates were substituted
for iron, and the aluminium hydrate generated acted as the
precipitant. A fault in practice was that a great part of the
sewage passed between the plates nearly or quite unaltered.
Hermite electrolysed sea water, and either added it to sewage
or used the liquid for flushing latrines and sewers. Piton’s
report on the trials at Nice illustrates a point now well estab-
lished, that an attempt to disinfect hinders or prevents the
natural bacteria from breaking down organic débris, in his
remark that ‘‘the Hermite solution, diluted to a strength of
about 0°25 gramme of chlorine per litre, does sterilize the fecal
matter in the sewers, but that, in spite of the rapid absorption
of chlorine, the disintegration of paper and fecal matter is no
more rapid than when ordinary water is employed.” The
system was tried at Worthing in 1894, and later at Ipswich,
and was fully examined by many authorities.*
The Lancet Commission (1894) found that in Hermite’s
electrolysis of sea water the sodium chloride was not decom-
posed, only acting as a conductor; but that the magnesium
chloride was converted into hypochlorite, which then deposited
magnesic hydrate, and left free hypochlorous acid in solution—
Mg(C10), +2H,O = Mg(OH), + 2HCI1O.
The Hermite fluid agreed in properties with a solution of hypo-
chlorous acid, made by passing carbonic acid through a bleach-
1 For further details of chlorine disinfection, see Rideal’s “ Disinfection and
Disinfectants,” 1903, pp. 77-98.
q
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STERILIZATION 185
ing powder solution of the same strength in available chlorine,
except that in the bacterial tests the two, for some unexplained
reason, were not found to act exactly alike.
The standard strength of Hermite solution was 0°5 gramme
of available chlorine per litre. When dilute it rapidly dete-
riorated, but this defect has now been overcome.
More recently Dr. Alexander, at Poplar, has installed a plant at
_ the municipal electricity works, and now uses the Hermite fluid
for all disinfectant purposes in the district, including street
watering.
About 1895 Woolf introduced in America, for water purifica-
tion, a liquid similar to ‘‘ Hermite,’ called ‘‘ Electrozone,”’
obtained by electrolysing brine containing 2 or 3 per cent. NaCl,
or sea water. In 1897 a plant was erected for supplying the
liquid to the sewage of Maidenhead, England (after previous
precipitation with ‘‘ferrozone” and _ filtration through
_‘polarite”’), 1 part being added to from 400 to 600 of
effluent. In an examination of the process in 1898, with Pro-
fessors Robinson and Kanthack, I found that the solution had
the properties of sodium hypochlorite, with chloride, the
available chlorine being 0°355 per cent., or practically deci-
normal; and that although the treated sewage gave at the out-
fall a blue reaction with potassium iodide and starch, showing
excess of the reagent, the amount of organic matter was hardly
reduced. On the other hand, the bacterial examinations
proved that the germicidal action was very marked, so that
“an effluent nearly colourless, free from odour, and containing
very few bacteria,’”’ was left. The electrozone process has been
discontinued at Maidenhead, but it was subsequently employed
(July, 1899) at Havana, Cuba, for streets, sewage, and harbour,
reports stating that it kept the city practically free from yellow
fever, and that the cost of generating was 50 cents per 1,000
__ gallons.*
' Lately I have had a further opportunity of investigating the
application of oxy-compounds of chlorine to sewage treatment
_at the Guildford Sewage Works.” The electrolytic chlorine
used in these tests were generated from brine in a special
form of electrolyser owned by the ‘‘ Oxychloride”? Company,
which claims certain economic advantages over the earlier types
of apparatus.
1 Electricity, New York, November 1, 1899.
2 Fournal of the Royal Sanitary Institute, vol. xxvi., No. 7, 1905.
186 SEWAGE AND ITS PURIFICATION
Raw sewages from this and other places, and effluents from
septic tanks, primary, secondary, and tertiary filters, were
treated with the solution under varying conditions to ascertain
its efficiency as regards (1) putrefactive organisms, and (2)
sewage organisms comparable in origin and vitality with those
which cause typhoid fever and cholera. The tests were also
directed to secure such freedom of the effluent from suspended
solid material as would prevent the formation of mud banks,
and from organic matter in solution, as to render it impossible
for it to become putrid when subsequently mixed with water.
My experiments indicated that the germicidal value of the elec-
trolytic solution, containing chlorine oxides and other com-
pounds, was greater than that of the equivalent of free chlorine
liberated chemically. I have, however, always stated the strength
of the addition in parts of available chlorine (av. Cl, as ordinarily
measured by arsenious acid), added to 100,000 parts of sewage
or effluent. The actual volume used would depend upon its
strength: at Guildford the machine gave a solution containing
o°2 to o°5 per cent. of available chlorine. By daily bacterial
and chemical analyses I was enabled to establish at Guildford,
in reference to the amount of reagent required, an easy practical
guide that may be applied to other places. There was a very
nearly constant relation between the five minutes’ oxygen-
consumed figure, representing the amount of the agent that
would be at once taken up by the organic matter, and the
quantity of the oxychloride that was needed, so that there
should be an excess capable of killing the bacteria. The five
minutes’ oxygen multiplied by 1°7 gave the amount of available
chlorine required in parts per 100,000, and the strength of the
solution. being determined, the proportion to be added is easily
calculated.
Raw Sewages.—The following is a type of the results :
The untreated sewage had a very foul odour: it gave, in parts
per 100,000, Cl in chlorides 18°6, oxygen consumed in five
minutes 4°14, in two and a half hours 18°8, free and saline
ammonia 7°2, albuminoid 2°4, B. coli 1,000,000 per c.c. The
addition of 3 parts of available chlorine per 100,000 reduced
the coli to less than 1 per c.c., and spores of B. enteritidis
sporogenes to less than to per c.c., after four and a quarter
hours’ contact. With 5 to 7 parts of av. Cl, negative results”
were obtained for both these organisms with 5 c.c. after four
and a quarter hours’ contact. The total number of organisms
STERILIZATION 187
_ was reduced by 3 parts of av. Cl from several millions to 50,000,
by 5 parts to 20, and by 7 parts to Io, per c.c.
Incubation tests by dilution with 9 volumes of river water
and keeping at 20° C.: 3 parts av. Cl, very slightly foul after
three days; 5 and 7 parts av. Cl, inoffensive after four days’
incubation.
In another case 3°7 parts per 100,000 of av. Cl added to raw
sewage reduced the coli from over 1,000,000 per c.c., so that
none were found in I c.c.; the enteritidis spores from over
1,000 to less than 10; and the total organisms from 23,200,000
to 540 per C.c. |
Experience showed that considerably smaller quantities of
the solution could be used with sewages of average strength,
and within limits a longer period of treatment allows of reduc-
tion in the amount of available chlorine. Taking the raw
sewage as it entered the works, it was found practicable to
treat it direct with an electrolysed salt solution in place of
chemical precipitants in settling tanks. Much less sludge was
produced than by ordinary chemical treatment, and neither
sludge nor effluent readily decomposed. The expense of
chemicals, power for the mixers, and labour in slaking lime
and in other operations, must thus be balanced against the
cost of the sterilizing solution. The effluent from the latter
was fit for discharging direct on to land, and the final effluent
from the underdrains was suitable for passing into any body
of water. The sludge when spread upon land remained sweet
as compared with that from ordinary chemical treatment.
It was further found that nearly a constant proportion, about
60 per cent., of the available chlorine was taken up almost
immediately, while about 40 per cent. remained and declined
more gradually, pointing distinctly to the chlorine existing in
the reagent in two forms—one which acts at once on readily
putrescible matter, the other remaining to attack bacteria and
resistant organic substances.
Septic Tank E ffluents.—It was found better in most cases to
deal with the sewage after it had undergone a preliminary septic
treatment, since thereby it was carried a stage further in its
Tesolution. But the most important reason was that vegetable
masses (and, still more, solid excreta) are, as is well known, very
difficult to sterilize by any means, because there is little pene-
__ tration; and the difficulty is encountered in the disinfection of
the stools of fever patients. A fault of the Hermite process as
188 SEWAGE AND ITS PURIFICATION
tried at Worthing was that it failed to sterilize the interior of
solid faeces, and the trials at Nice showed, as I have already
mentioned, that an attempt to disinfect hinders or prevents the
natural bacteria from breaking down organic débris, therefore
the disinfectant should be applied after the breaking down. In
the septic tank the suspended substances are reduced to a much
finer state of division, and the bacteria are thus more readily
attacked. I found, somewhat unexpectedly, that ammonia did
not react with oxychloride in the dilutions employed in treat-
ment, so that the solution was not destroyed or wasted by the
ammonia produced in the tank. Urea also did not interfere
with the first action of oxychloride, but tends to remove any
trace of the reagent remaining after the process.
The simple treatment of raw sewage by means of a septic
tank and then addition of the solution would be sufficient for a
large number of cases where the organic purity was of less
importance than the removal of pathogenic organisms, as in
localities close to shellfish gathering - grounds or watercress
beds. For both of these, and particularly for vegetables, com-
plete organic purification might be a disadvantage, as depriving
them of food. In places where open septic tanks had been
objected to on account of suggested nuisance, closed tanks
could be adopted of a rather smaller size than usual, the solution
being added ina covered carrier with baffle plates as the effluent
passed out, with a certainty of removing all objectionable
odours. If existing tanks are divided by a party wall into
two unequal chambers; in the first of say twenty hours’ dry-
weather capacity, the anaerobic preparation could go on as at
present ; while in the second, of say four hours’ capacity, the
chlorine solution would be added in sufficient quantity to cause
the remaining suspended solids to subside in a more or less
sterilized condition, and the effluent to be free from smell and
objectionable organisms. The cost and space required for
primary, secondary, and tertiary beds would in this way be
saved. I believe that the method, in the case of seaside towns
and those discharging into estuaries, would greatly contribute
to local healthy conditions, and would insure the absence of
unsightly sewage matter on the shores.
In the septic tank effluents at Guildford the total organisms
were 2,500,000 to 4,500,000, the coli 100,000 to 1,000,000, and
the spores of B. enteritidis sporogenes 10 to 1,000, per c.c. After
the addition of available chlorine (regulated by the five minutes’
2
STERILIZATION 189
oxygen consumed) from 2°5 to 4°4 parts per 100,000, and a
contact of from one to four hours (Experiments 12 to 59), the
coli and the enteritidis spores were absent from I c.c., and
in most cases from 5 c.c. The total organisms were very
greatly reduced : they were not regularly counted, as of less
importance, but on four occasions they have been lowered
from the many millions originally present to 20, IIo, I40,
and 600 per c.c. Even the last number is below that usual
in rivers.
The anaerobic organisms were found to have been reduced
from an average of 2,500,000 per c.c. in the untreated septic
effluent; to 200 after one and a half hours’ contact with the
chlorine solution, and 150 per c.c. after three hours.
Incubation tests, by mixing with 3 parts of the river water,
showed that the untreated effluents had a smell at first, which
progressively increased, while the dissolved oxygen rapidly
disappeared ; but the mixture with treated effluent kept sweet,
and the dissolved oxygen did not sensibly decrease in twenty-
four hours, and did not fall below 3 c.c. per litre in the closed
vessel for three or four days.
A feature common to all oxidation treatments, the rapid dis-
appearance of the reagent at the first onset, suggested that
there might be an advantage in adding the solution in suc-
cessive portions. This modification takes a longer time, and is
apt to leave a residue of available chlorine, requiring a storage
of 8 to 18 hours for its disappearance. Where such storage is
possible it tends to a complete sterilization of the liquid.
By estimating the dissolved oxygen in mixtures of 3 parts
river water to 1 of septic effluent, I proved that with
untreated effluents after 19 hours the oxygen had entirely
disappeared ; while with the treated, after an initial fall, it rose,
so that after 3 days it was higher than at first, and almost
equal to the river water. It remained throughout well above
the quantity essential to fish life. This proportion of effluent
is larger than in practice would be discharged into river waters.
The result may be due to the destruction of the putrefactive
bacteria by this treatment, leaving the oxidizing organisms pre-
dominant, so that the river does not foul. Two or three days,
the time of the incubation tests, brings the whole liquid down
to the sea.
Primary, Secondary, and Tertiary Contact-Beds.—In a large
number of experiments I found that, as in the different stages
1gO SEWAGE AND ITS PURIFICATION
the organic matter decreased, the amount of available chlorine
consumed was correspondingly lessened, and the proportion of
1 to 1°7 between five minutes’ oxygen and available chlorine
still remained a guide.
The primary effluent at Guildford required 2 parts of av. Cl
per 100,000 to reduce the coli from 100,000 per c.c. to less than
I per 5 c.c. after 40 minutes’ contact, and the B. enteritidis
spores from 20 per c.c. to mil in 5 c.c. after 2 hours’ contact.
After being kept for 4 days, the untreated had a strong sewage
odour, the treated remained odourless.
In the secondary effluent, with 1°06 parts av. Cl, coli was
reduced from 1,000,000 per c.c. to none per 5 c.c.; B. enteritidis
spores from 100 to 1,000 per c.c. to none in 5 c.c.; and the total
organisms from 1,000,000 to 40 per c.c. Incubation 48 hours:
untreated, sewage smell; treated, inodorous.
In the tertiary effluent the small amount of 0°25 part of
av. Cl reduced the coli from over 10,000 per c.c. to mil in 5 c.c.
in I hour, and the B. enteritidis spores to less than 1 per c.c.
in 44 hours. o0°5 part av. Cl reduced the coli from over 10,000
per c.c. to less than I per 5 cc. in 30 minutes, and the
B. enteritidis spores to less than 1 per 5 cc. in four and a
half hours. The incubation tests gave after 4 days a distinct
odour in the untreated, none in the treated. Decided chemical
improvement was shown, and the treatment caused an increase
of free, with a decrease in albuminoid, ammonia, showing a
breaking down of the organic matter.
The effect of treating infected drinking-water was tried. A
tap water contained go organisms per c.c., and coli was present
in4c.c. After treatment with 0075 part of available chlorine
(Exp. 54), the total organisms were reduced in 5 hours to
I4 per c.c., and coli was then absent from 20 c.c. Another
portion was mixed with s$5 of its volume of tertiary effluent,
and o°08 part of available chlorine added (Exp. 58). The
infected tap water had contained 100 coli per c.c., but after one
hour’s action of the oxychloride there were none present in
20 c.c., and this condition remained through a channel more
than 100 feet long. The water after standing did not retain
any taste or smell of the treatment, and the chloride as
measured by chlorine was only increased by 1°75 to 2 parts
per 100,000, which is obviously of no significance. The tap
water at this time contained more total organisms and more
coli than remained in the sewage after the chlorine treatment,
SaaS
STERILIZATION 1gI
so that the extraordinary result was realized of obtaining at the
sewage works an effluent which had a greater bacterial purity
than the town water-supply.
The general conclusion was that, with a good effluent, sterility
can be insured by the addition of about 5 parts per 100,000 of
available chlorine. If removal of coli and enteritidis only is
aimed at, one-tenth of this amount (=0°5 part), or sometimes
even less, is sufficient, as would be the case in a discharge near
shell-fish gathering-grounds, into watercress beds, or into rivers
that are used as a source of supply by water companies.
Absolute Sterility—Even the tertiary effluent contained some
thousands of spores per c.c., of which forty to fifty are capable
of resisting the temperature of boiling water for several
minutes; therefore I soon found that absolute sterility was
not practical, not merely on account of the cost of the large
quantity of disinfectant required, but also because the residual
disinfectant would be inadmissible in an effluent. For this
Teason it became necessary to discover what the _highly-
resistant organisms were, and particularly whether they could
be injurious. I found that they were constant in character
throughout the sewages and effluents, and consisted of a group
of bacteria of the hay-bacillus type, non-pathogenic, not pro-
ducing smell, and of great assistance towards the resolution of
organic matter. Absolute sterility, therefore, is not required,
and, if attained, would not be maintained.
When chlorine or its oxy-compounds are used as sterilizers,
the cost of their production becomes important. It is obvious
that the economy of a process will be determined by the
quantity of ‘‘available chlorine” produced in a continuous
process for a given expenditure of electrical energy, or, in
other words, the cost of electrolytic chlorine per kilo, in com-
parison with chloride of lime, hypochlorous acid, and free
chlorine obtained chemically.1
In the Digby process, which I have recently had occasion to
critically examine, the costs are reduced to a minimum by
insuring a greater percentage of free chlorine being produced
from a given quantity of salt. This is attained by enclosing
| the electrodes in asbestos diaphragms, which prevent the salt
solution from passing with the liberated ions from the cell. In
1 As to cost of chlorine electrolytic plant, see Hiussermann, Dingler’s Polyt.
| Fourn., 1895, 296, p. 189; Schoop, Zeits. f. Electrochemie, 1895, ii. [10], 209 ;
| Electrical Review, 1898, April 29.
192 SEWAGE AND ITS PURIFICATION
this way the amount of salt required to yield a given amount
of available chlorine is considerably reduced.
The higher oxides of chlorine have been employed for dis-
infection and destruction of organic matter, but expense has
‘militated against their use on a large scale for sewage. The —
Bergé process prepares peroxide of chlorine thus: ;
3KCl0, + 2H,SO, = KCIO, + 2KHSO, + Cl,0,. i
The gas is passed into water, and this solution allowed to mix |
with the polluted effluent. Organic matter is quickly oxidized —
by the gas, so that the liquid shows after treatment less organic ©
matter and an increase in the chlorides formed by the reaction ©
of the oxide on the carbonates in solution. The quantity ©
required to produce sterility in drinking-waters or effluents prac-
tically free from organic matter, by contact for at least fifteen
minutes, is given at I gramme of potassium chlorate per cubic
metre of water. JB. coli and typhosus in Seine water were killed
in three hours’ contact by 0°24 part of Cl,O, per 100,000, and
even when the amount does not exceed 0°08 (or say I part per
million) considerable reduction in the number of bacteria is
assured. The solution used contains o’013 per cent. of per-
oxide, and is added to the effluent or water to be purified
in the proportion of about I per cent.
In Germany Wiederhold used chlorate and hydrochloric acid
during the cholera epidemic. The expense, offensive odours,
and danger of explosion, caused their discontinuance.
Sterilization by Actds.—The large majority of bacteria,
especially the pathogenic forms, have a preference for neutral
or slightly alkaline solutions, and it has long been known thea
in culture liquids they refuse to grow, and die, even with small
amounts of acid. Koch first noticed the fact with regard to
the cholera organism, Kitasato showed that it was killed by
dilute sulphuric or hydrochloric acid in a few hours, and
A. Stutzer found that 0°05 per cent. of sulphuric acid was fatal
in fifteen minutes, 0°02 per cent. in twenty-four hours. Ivanoff,
with 0°04 to 0°08 per cent. sulphuric acid, destroyed cholera
organisms in Berlin and Potsdam sewage. In the Liernur
process, and in that of Beck and Henkel’s of Igor, sewage is
sterilized by sulphuric acid. The successful use of acids in
disinfection is very old, and was limited by inconveniences,
which, however, would not affect their employment for liquids _
in the very dilute state shown above to be effective. Stronger ; |
4
.
i
STERILIZATION 193
solutions of mineral acids have long been used in medicine,
and have probably owed a great part of their efficiency to their
action against bacteria. Organic acids also possess this
property, as in the example of the ancient employment of
vinegar, and there is a great probability that the almost
universal practice of using vinegar or lemon juice with salads,
shellfish, or other foods, has been a piece of natural selection
founded on experience of the danger of intestinal or parasitic
diseases originating from such sources. I may quote an experi-
_ ment of my own. I added B. coli to a good table vinegar
_ (5°3 per cent. acetic strength), and to the same diluted to twice
and to ten and fifty times its volume with distilled water. In
the weaker two liquids the bacillus was alive after forty minutes,
_ in the half strength it was killed in fifteen minutes, and in the
_ undiluted vinegar in five minutes.
Vegetable acids are, of course, too expensive for treating
effluents, but cheap mineral acids, like sulphuric, are practicable
_ and efficient in cases of serious infection. I have found? that
_ 0°072 per cent. of sulphuric acid is effective against typhoid
_ organisms in fifteen minutes; Kitasato practically agrees, as he
_ finds 0°08 fatal. In sterilizing with acids an additional quantity
_must be added to balance the alkalinity of the liquid: in
sewage this ranges usually between o°2 and 60 parts per
_ 100,000, and 4 grammes of sulphuric acid per gallon is sufficient
for causing the death of the typhoid bacillus in the usual
drainage from an isolation hospital or other infected area.
The free acidity is soon neutralized when such liquid becomes
mixed with ordinary sewage. B. enteritidis is killed by the
_Teagent, and Sp. cholere succumbs with great rapidity. It
l also kills intestinal worms and their ova. These observations
_ suggest that it should be added to the water in which vegetables
_ are washed, especially those which are to be eaten as salads;
in tropical countries these are habitually fertilized with fresh
manure, which may be often infected. For many purposes,
instead of the corrosive sulphuric acid, I have succeeded in
_ using bisulphate of soda, which is portable and not dangerous,’
and is added in the proportion of 15 grains per pint, equal to
_ O°I7 per cent.
I do not know that disease has been conclusively traced to
_ vegetables which have been grown in connection with sewage
a
_ 1 Parkes and Rideal, Epidemiological Society, 1901 ; Lancet, January 26, 1901.
2 Galli Valerio, Bull. Soc. Vaudoise des Sciences Naturelles, 1902, No. 143.
’ Parkes and Rideal, Joc. cit.
13
194 SEWAGE AND ITS PURIFICATION
or effluents; in fact, English experience with the land plants
grown on sewage farms has pronounced them to be safe.
Wurtz and Bourges! grew cress, radishes, and lettuce in earth
watered with various pathogenic cultures, and found the bacilli
on the stalks of the plant at a height of even a foot above the
ground. Potatoes infected with anthrax and planted were
allowed to grow: the bacillus was recovered from the stalks as
long as ror days afterwards. It is noted that out-of-door con-
ditions, such as the cleansing effect of rain, and the bactericidal
action of sunlight, are different from those in the laboratory.
But in heavy storms mud may be splashed to a great distance,
and so contaminate the leaves or fruit. A French Commission
was appointed in 1902 on the subject of possible dangers from
raw vegetables and fruit grown on sewage farms, and recom-
mended to the Comité d’Hygiéne Publique that vegetables and
fruit intended to be consumed in the raw state should not be
allowed upon land fed with sewage.
Many attempts have been made to use ozone, either in admix-
ture with air, to be passed through or over the sewage, or to be
generated electrolytically in the sewage itself. Hagen (1881)
ozonized air by the silent discharge, passed it through sewage,
then ozonized it again, absorbing the carbonic acid by lime, so
making the process continuous. Marmier and Abraham? have >
used ozone for sterilizing the water-supply at Lille, and state
that it removes nitrates and organic matter, and all germs except
B. subtilis. The cost of the plant is given at £500 for sterilizing
5,000 cubic metres per day.
THERMAL METHODS.
To raise the entire volume of sewage to a heat sufficient to
sterilize it would be obviously impossible in practice; in addition,
besides the odours evolved, it would leave a liquid which, on
fresh inoculation with microbes from air, water, or earth, would
become as foul as before.
The Liernur process is a combination of conservancy, pneu-
matic removal, and disinfection. At Amsterdam in 1871 a trial
was made on a small quarter of 15,000 inhabitants for the
conveying of the fecal matter and closet water, excluding the
household slops. The system was applied at Leyden, Riga,
and other places, and afterwards carried out more completely
1 Archives de Médecine Expérimentale, July, 1901.
2 Comptes Rendus, 1899, cxxviii., 1024 ; Revue ad’ Hygiene, 1899, 321, 540.
ft
STERILIZATION 195
at Trouville, in France, where about half of the 1,800 houses
were connected up and worked at the company’s expense at an
average annual charge of 16s. per house. The method is based
on the separation of ‘‘excrementitious ” and ‘‘ non-excremen-
_titious’’ matters. The latter, including rain, storm, and surface
water and industrial effluents, are conveyed by separate con-
duits, “utilizing as much as possible the existing sewers of
towns.” It is said that these liquids ‘‘ in consideration of their
pathogenic inoffensiveness can be safely delivered into the
nearest watercourse, after being clarified, if necessary.” It
must be remarked that, as we have shown in the first chapter,
road and field drainage is by no means inoffensive, that indus-
trial effluents are frequently putrescent, and that the droppings
_ of animals are often highly pathogenic.
The ‘‘ polluted liquids, including fecal matter, sink slops,
soapy and dirty water,” pass through iron pipes into closed
iron underground receptacles, thence by 4-inch pipes to “ dis-
trict reservoirs,”’ communicating by pipes of 10 to 30 inches
internal diameter with the central pumping station. A slight
vacuum is continually maintained, and at intervals the whole
system is exhausted by sections into a main reservoir. In the
original description the excreta, with as little admixture of
water as possible, were heated with 1 to 2 per cent. sulphuric
acid, like a Kjeldahl process on a large scale, until the whole
was reduced to a brown syrup, containing nearly all the original
nitrogen as ammonium sulphate. This was either distilled with
lime and the ammonia utilized, or dried up with ashes and sold
as manure, containing, however, usually an excess of acid. The
cost in Holland was said to amount to 4s. 1od. per head per
annum. In this system—(1) Sewers can be laid at a uniform
depth, just sufficient to protect them from frost, and at 2 or 3 feet
in such countries as India. (2) No flushing is required, which
is important in places where water is scarce. (3) No gratings
or ventilating columns are needed, as the air pumps remove all
gases, and the ordinary manholes are also not required. (4) As
the system depends on working of a vacuum, any leak will be
at once detected, and percolation of the subsoil will be pre-
_ vented. (5) There is no dependence on fall, therefore it can be
used on land of any contour.
At Trouville! the sewage was stored in a large covered brick
tank for about a week (thereby undergoing septic change), then
_ 1 Report of Surveyor to Tendring Rural District Council, Essex, July, 1899.
I3—2
196 SEWAGE AND ITS PURIFICATION
mixed with “the necessary quantity of sulphuric acid for the
purpose of fixing the ammonia,” heated in tubular boilers to
120° C., evaporated till semi-solid, and reduced in a rotary
chamber to a dry powder, which is said to be worth £7 to £8
per ton. J.A. Jones, sanitary engineer of Madras, has reported
in favour of the use of the system in India. It has been in use
at Stansted, Essex, since Igo02.
In large towns evaporation would be impossible; as an
alternative, a bacterial treatment was proposed, with sterilization
of the sludge by acid and heat and reduction to manure. The ~
process used at Cassel, Germany, for treatment of sludge by
sulphuric acid, combined with the extraction of grease, is —
described later,in Chapter XIV. See also English patent 21,856
of rgot.
TOWN REFUSE.
The solid matters included under the general name of “dust,”
as removed by carts, have of late years been destroyed by heat
in place of the former insanitary methods of shoots, sorting —
yards, and ‘“‘made ground,” especially since a chance has
appeared of utilizing the energy derived from the burning.
The methods of disposal have included : i
1. Carting and Tipping on Waste Land.—Street dust is recom-
mended as manure by Strabo, Pliny, and Columella, and was
highly valued during the Middle Ages: its use is still continued —
in many places where there is plenty of land.* By-laws in ~
London and other localities enact that no land on which refuse |
has been deposited can be built on until it has remained —
untouched for at least seven years. Organic matter in such ©
made ground disappears very slowly. At Leicester? some heaps —
of refuse after one year retained 30 per cent. of organic matter,
and after nine years 27 per cent. Hering records a case which
indicated that garbage can remain in a decomposing condition
for hundreds of years, as evidenced by some excavations in the |
city of Rome.* We may conclude that ‘‘ made ground ” of this
kind remains unhealthy until it has been purified by frequent
ploughing and planting. An attempt has lately been made to
1 For analyses, and an advocacy of the practice, see Casali, Staz. Sper. Ital
agray., 1898, xx¥i., 377.
2 Leicester Meeting of Cleansing Superintendents, 1899.
3 Transactions of the American Public Health Association, xx., 196; also see a
paper by Dr, Savage on ‘‘ The Self-purification of ‘Made Soil,’’’ givingchemical ©
and bacteriological analyses; Fournal of the Royal Sanitary Institute, vol. xxiv., |
P- 442, 1903.
STERILIZATION | 197
lighten the clay land, and reclaim the bogs, of Essex by plough-
ing in street sweepings from the City of London.
2. Barging from Wharves and Carrying out to Sea.—Much
_ nuisance is occasioned, both at the wharves and along the
coast: solid refuse in this respect is much worse than strained
_ sewage. ;
3. Sorting with a view to utilization—now less practised than
formerly. When the system was usual in London, for street
_ sweepings, of which some 2,000,000 tons are picked up annually,
_ each public authority required a large space for sorting, sifting,
and draining. Some thousands of tons were sent into the
_ country as manure; but the nearest farms are a long way from
_ London, and manuring is done during the season of the year
_when the amount of street sweepings is the lightest, therefore
_ an allowance of about 2s. per ton had to be made to the farmer
to pay the carriage. Even then all tins and glasses had to be
_ sorted out and barged away at a cost of about 4s. per ton.
_ London will produce on a wet day about a hundred times more
_ sloppy street sweepings than on a dry one. Before this could
_ be loaded into railway trucks it had to be drained for some
long time upon the depots, then to be picked up and carted
to the railway sidings at considerable expense. There was,
| therefore, always a large stock of decomposing vegetable matter
on hand, and in many depots a mass of slop on the one side,
_and perhaps forty women screening house refuse on the other.
| It is said that the town refuse of Paris, which is sys-
| tematically collected and carefully sorted by chiffoniers, is worth
| £2,000 per annum. Sardine and other tins are made into toys
-and parts of tinware, while bottles, rags, etc., are more care-
_ fully utilized than in English dustyards.1 At Chelsea, for some
years, an attempt was made to work up the débris by machine-
1 sorting with graded sieves, using the fine ash for cement, or
mixed with the stones, bricks, and clinker as concrete; the
breeze and cinders, with the assistance of a little coal, were
. burnt as fuel for the boilers by which the machines were driven
} and the works electrically lighted, while a special feature was
_ the manufacture on the spot of a coarse brown paper from the
| paper and wood fragments. The thermal value of the breeze
1 For details of a similar mode of collection at Leicester, and the prices
realized, see Allen’s paper, Fournal of the Sanitary Institute, vol. xxv., April, 1904.
In New York and Boston dry refuse, other than ashes, is sorted as it passes over
a moving platform, and only the worthless residue is burnt (Hering, Report of the
American Public Health Association, vol. xxii., p- 105).
198 SEWAGE AND ITS PURIFICATION
and ashes sifted out was found to be one-seventh that of coal.
The work, however, was discontinued, as the disinfection or
sterilization of the various products added considerably to the
expense.
The Bury (Lancashire) Corporation, following the example of
a few other towns, recently arranged for the distribution to
shops and offices in the town of large bags, into which is placed
the waste paper of the establishment, the full bags being
collected periodically, and exchanged for empty ones. During
the four months in which this system has been in operation
there has been collected paper which realized, when sold, —
about £30.1
4. Reduction, so called, applies more particularly to certain
portions of the refuse and to certain kinds, and effects utilization
by extraction of grease by steam or naphtha, the residue being
ground and dried for fertilizer stock. In the United States in
1902, according to a report of the American Public Health
Association, vol. xxix., ‘‘ reduction ” plant was in use in nineteen
cities, and was worked by private companies under contract,
the Arnold process being the most frequent. It was concluded
in this report that (1) economically the two systems, reduction
and cremation, are fairly well balanced, but the former gives
rise to a nuisance, whereas the latter can be conducted without —
it; (2) experience shows that the English and German system
of burning the ashes and garbage together in cellular in-
cinerators, with sloping grate bars for-preliminary drying, and
forced draught, is cheaper and more satisfactory than the
American (single large chamber and horizontal grate) ; (3) the
disposal of garbage in water or on waste land is strongly
condemned.
5. Burning—Although this is the most perfect means of
sterilization, the difficulties have been:
(a) The large and varying proportion of water, which often
renders the material incombustible without being dried; the
nuisance occasioned during drying in air; and the cost of the
fuel for drying artificially.
(b) The low combustibility of the material, even after desic-
cation, requiring assistance by coal, special furnaces, and much
labour.
(c) The offensive nature of the gases evolved during the
burning.
1 Public Health, September, 1905.
a
STERILIZATION 199
(d) The loss of manurial matter as nitrogen and carbonic
acid.
(e) The low value of the products, ash and clinker, and the
expense of their removal.
The accumulations could be greatly reduced, and their
character made more tractable, if every householder would
follow the advice repeatedly given to burn all his vegetable
refuse in the kitchen fire, and throw little besides clean ashes
in the dustbin, also by the regulations enforced on the Con-
‘tinent and in many places in England against littering the
streets.
Town refuse may be roughly divided into that derived from
streets, from houses, and from trades, the latter, according to the
Public Health. Act, having to be separately paid for. House
refuse is known to be of most miscellaneous character, both in
regard to organic and inorganic constituents. In London the
“fairly combustible matter’ in the refuse is said to be 64 per
cent., in Edinburgh 26 per cent. The average total weight for
London in 1895 was stated to be ‘‘ about 1 ton per annum for
every four inhabitants, or 1,250,000 tons for the whole area.”
The old style of house dustbin was as insanitary as the collec-
tion by dustmen was formerly dirty and careless. Many types
of portable covered metallic bins, with daily collection, are in
use both in London and the provinces.
After the failure to profitably utilize the nitrogenous matters
of refuse as manure, its carbonaceous constituents were still
available by burning as sources of heat, after drying. Modern
dust destructors, therefore, dating from 1876, generally include
some arrangement for steam raising and electric light, with a
view to saving to some extent the cost of destruction. But the
_ aspect with relation to health must always be the first con-
sideration.
Modern dust destructors must fulfil the following conditions :
1. A temperature not lower than 1,300° F.: in good forms
_ 1,600° to 1,800° is reached, and with forced draught by a steam
jet or fans up to 2,000° F. can be in many cases attained by
the burning of the refuse itself. The earlier forms were of low
temperature type, reaching only 750° to 1,000° F. in the main
flue or combustion chamber. This was not sufficient to deal
with the effluvia, the destruction was often imperfect, and the
resulting clinker, instead of being hard, was soft, friable, and
sometimes even putrescible ; indeed, it was not uncommon for
200 SEWAGE AND ITS PURIFICATION
this imperfectly-burned clinker to take fire again after being
removed.
2. A supply of sufficient oxygen to maintain steady combus-
tion without over-cooling the gases produced.
3. A suitable site. If this can be central to the district, it
will greatly save cost of cartage, etc., and facilitate disposal.
Refuse properly cremated, with a high chimney, creates no
nuisance, even in populous neighbourhoods. The prevailing
winds should be studied, with regard to the carriage of the gases.
4. Carriage to the works without offence. Improved covered
carts are now constructed. The supply should be as regular as
can be managed.
5. Where used for steam-raising, the boilers must be so
placed as not to cool down too much the evolved gases.
Street sweepings, which furnish a large portion of the matter
to be treated in a dust destructor, vary very much in com-
position. .
The following analyses are recorded :
y Washington City.
pid god Trenton, *
Su vuasaens .| New Jersey. :
: Maximum. Minimum.
Moisture ... 38°89 — — —
Ash . ; vis 37°67 — — —
Organic matter ... 22°44 os 35°50 10°20
Total nitrogen ... unt 0°48 0°18 1°18 O'17
Ammoniacal nitrogen ... 0°004 — — —
Phosphoric anhydride ... 0°45 0°30 0°16 o'IO
Potash, K,O .. ia 0°37 o*Ig 0°50 0°08
Lime, CaO dbs vik 1°89 =e esti ie
Magnesia, MgO... id 0°35 a — —
With regard to the fuel value of dry refuse, authorities agree
that it is about one-seventh to one-ninth that of coal. The
best conditions, both as to prevention of smoke and fume, and
the concentration of heat for utilization, being a slow, steady
combustion, quick-burning materials do not prove to have any
advantage. It is in the drying stage that the main risk of
nuisance occurs; in many old processes it has simply amounted
to a distillation in which strongly odorous substances have
escaped with the water vapour. Therefore the aim has been
(1) to raise the drying gases toas high a temperature as possible;
(2) to subject the evolved vapours to a secondary cremation by
passing through ignited material.
STERILIZATION 201
I must refer to special treatises for details of modern dust
destructors. The different types have been adapted in different
places to local requirements, and portable destructors are made
for thinly-populated places, camps, etc. In Midland towns,
_where privy middens still exist, their contents have been suc-
cessfully passed through the destructors along with the ordinary
dust.
Wherever possible, the combination of a destructor plant for
town refuse with the sewage disposal works has great advan-
tages for the following reasons: (1) The power derived from
the burning of the refuse, though not so great as has sometimes
been hoped, is available for the pumps and machinery of the
sewage works. In this way a scheme that would be preferred
but for the cost of pumping is frequently rendered practicable.
(2) Larger organic débris screened from the sewage can be
- burned in the destructor. (3) The clinker from a properly-
worked destructor can be used in paving construction, and as
a material for filter-beds. (4) A site chosen as suitable for
sewage works will also be suitable for a destructor, and the
management of the two require similar precautions as to public
health. The apparent difficulty of carriage of the town refuse
to the works has not been insuperable. As in towns the ratio
of the volume of the sewage to that of the solid refuse is more
_ or less constant, it follows that when the steam-raising efficiency:
of a given type of destructor is known, the height to which the
town sewage can be lifted by power derived from the destructor
is fixed.
CHAPTER IX
BACTERIAL PURIFICATION
History of the idea and of early experiments—Mueller’s process
—Mouras’ automatic scavenger—Massachusetts—London—
Sutton—Oswestry—Leeds—Triple filtration or contact.
It had been proved early in the nineteenth century that natural
destruction of organic matter was due to living organisms, and
that these were the actual cause of decay and putrefactive
change ;! but the powerful advocacy of Liebig and his school of
the so-called ‘‘ Catalytic” theory delayed the general acceptance
of the “ germ theory” for more than thirty years. ‘‘ Catalysis ”
meant that some organic substances, in the act of undergoing
decomposition, possessed the power of causing the alteration
and decay of other organic substances in contact with them,
and this mechanical, as distinct from a biological, explanation
survived until Pasteur re-proved that fermentation and putre-
faction did not take place in the absence of living organisms.
He divided them into aerobic, or thriving in presence of oxygen,
and anaerobic, or growing without it, and their life-history and
character were elaborated by a number of observers. The
purifying action of soil was still regarded as partly mechanical
straining and partly chemical oxidation, and the necessity of
the co-operation of life in the processes was hardly taken into
account, more especially as in the important action of nitrifica-
tion no causal organism had been then discovered. The Berlin
Sewerage Commission, however, reported in 1872 that sewage
matter was converted into nitrates, not by a simply molecular
process, but by organisms present in natural sewage and soil,
and many observers demonstrated in various ways how the
purification of sewage was accomplished by bacterial action.
1 On the history of the subject see J. T. Wood, Fournal of the Society of Chemical
Industry, February 15, 1906, p. 109; Sims Woodhead, ‘‘ Bacteria and their
Products,” p. 49.
202
BACTERIAL PURIFICATION 203
Among them Hatton investigated! the conditions under which
oxygen was absorbed and CO, and H produced by bacteria ;
he also examined the effect of adding nitre to putrescent
organic liquids, and concluded that “‘ during the reduction of
nitrates by sewage CO, is generated in the liquid, and perhaps
free N given off, while O is absorbed.”
Sorby, in 1883, remarked on the very large proportion of the
detritus of feces which was lost in the river Thames, owing to
the action of larger organisms. Dupré, in a report to the Local
Government Board in 1884 on his experiments on aeration,
stated that ‘‘the consumption of oxygen from the dissolved
air of a natural water is due to the presence of growing
organisms, and that in the complete absence of such organisms
little or no oxygen would be thus consumed.”? Notwith-
standing this knowledge, the Royal Commission of 1882-1884,
after deciding against the discharge of crude sewage into any
portion of the Thames, prescribed ‘‘ some process of deposition
or precipitation, the solid matters to be applied to the raising
of low-lying ground, or to be burnt, or dug into land, or carried
away to sea.” The latter course was chosen as the only one
available for London. In 1896 Dupré proposed “ to cultivate
the low organisms on a larger scale, and to discharge them
with the effluent into the river, as the power these lower
organisms had wasremarkable”; and at the Sanitary Congress,
Bolton, in 1887, he said, ‘‘ Whatever scheme may be adopted,
except destruction of the sewage material by fire, the agents
to which the ultimate destruction of sewage is due are living
organisms (not necessarily micro-organisms), either vegetable
or animal. Our treatment should be such as to avoid the
killing of these organisms, or even hampering them in their
actions, but rather to do everything to favour them in their
beneficial work.”
Meanwhile, Emich in Germany was experimenting on the
changes which occurred in water and sewage on exposure to
and after agitation with air; also the behaviour of sterilized
* Chemical Society's Fournal, May, 1881, ‘‘ Action of Bacteria on Gases,” and
** Reduction of Nitrates by Sewage.”
* The Second Report of the Royal Commission on Sewage, 1902, p. 9, shows that
when sewage is sterilized either by chemicals or heat its oxidation, either by
filter or aeration, is almost prevented. The average percentage purification
obtained in the experiments was—with sterile filters, 1 5; with normal filters, 42.
The average nitrification was—nitrous nitrogen, sterile trace; normal, 0°o17 ;
nitric nitrogen, sterile, 0-027; normal, 0°452.
204 SEWAGE AND ITS PURIFICATION
water, and the influence of ozone and hydrogen peroxide. His
investigations were published in 1885, and show that
“When left standing, and after agitation with air, the self-purifica-
tion only took place if the water had not been sterilized through
boiling, and had not been protected against the entrance of germs
during the period of observation. If, however, sterilized water was
afterwards fully exposed to the air, or if it was afterwards infected
with ordinary water, the same changes took place in it as in non-
sterilized water exposed to air, viz., the quantity of potassium per-
manganate required for the oxidation of the organic matter, and the
amount of ammonia, decreased with the formation of nitrous and
nitric acid. A direct oxidation through the oxygen of the air did not
take place, and even one brought about by ozone and hydrogen
dioxide plays only an unimportant part compared with that played
by the biological process,”’
All this had main reference to oxidation, which, as we have
seen in earlier chapters, is only a later part of the cycle of
changes in the course of purification. The first hydrolytic, or
dissolving, stage had been conducted from very early times in
a leaky and objectionable way in the old cesspools, which, how-
ever, when well managed and under favourable conditions, were
quite capable of giving a good result. I have mentioned in
Chapter I. an example in 1858.
About 1865 Dr. Alexander Mueller had come to the following
conclusions :”
“The contents of sewage are chiefly of organic origin, and in
consequence of this, an active process of decomposition takes place
in sewage, through which the organic matters are gradually dissolved
into mineral matters, or, in short, are mineralized, and thus become
fit to serve as food for plants. To the superficial observer this pro-
cess appears to be a chemical self-reduction; in reality, however,
it is chiefly a process of digestion, in which the various—mostly
microscopically small—animal and vegetable organisms utilize the
organically fixed power for their life purposes. . . . The decomposi-
tion of sewage in its various stages is characterized by the appear-
ance of enormous numbers of spirilla, then of vibrios (swarming
spores), and, finally, of moulds. At this stage commences the re-
formation of organic substance, with the appearance of the
chlorophyll-holding protococcus, etc.”
Mueller recognised the importance of a preliminary change,
and later patented a process (German patent 9,792 of 1878)
for utilizing the micro-organic life in sewage in its purification,
which was actually in operation at one time to purify the
1 Monatshefte, vi., 77; Chem, Centralblatt, 1885, 333.
2 Landwirthschaftliche Versuch-stationen, xvi., 273.
BACTERIAL PURIFICATION 205
effluent of some works for the manufacture of sugar from
beetroot.1
_About the same time the ‘‘ Mouras Automatic Scavenger ”’
was inaugurated in France. According to the Cosmos les
Mondes, December, 1881; January, 1882; ‘‘ this mysterious
contrivance, which has been used for twenty years, consists
of a closed vault with a water seal, which rapidly transforms
all the excrementitious matter which it receives into a homo-
geneous fluid, only slightly turbid, and holding all the solid
matters in suspension in the form of scarcely-visible filaments.
The vault is self-emptying and continuous in its working, and
the escaping liquid, while it contains all the organic and
inorganic elements of the feces, is almost devoid of smell,
and can be received into watering-carts for horticultural
_ purposes, or may pass away into the sewer for use in irriga-
tion.” As to the theory of the action, it is said, “ May not
the unseen agents be those vibrions or anaerobies which,
according to Pasteur... only manifest their activity in vessels
from which air is excluded ?”
Observations with a glass model showed that “ feecal matters
introduced on August 29 were entirely dissolved on Sep-
tember 16, while even kitchen refuse, onion peelings, etc.,
which at first floated on the surface, descended after a time
and awaited decomposition. Everything capable of being
dissolved acted in a similar way, and even paper wholly
disappeared.” |
“The principle on which M. Mouras bases the action of his
machine is that the animal dejecta contain within themselves
all the principles of fermentation or of dissolution necessary and
sufficient to liquefy them, and to render them useful in their
return to the soil, and without appreciable loss.”
A later article of January, 1883, by the Abbé Moigno gives
formule for the dimensions of the tank, estimating its super-
ficial area as preferably y5 metre, or about I square foot per
person. (The Exeter tank, I may remark in passing, works out
to about 0°6 square foot per person.) The article also specifies
that ‘‘ for the complete solution of the floating solid matter a
period of thirty days should be allowed,” and calculates that
this gives—
I+2+3+4...... + 304,
30
1 Roechling, Fournal of the Society of Arts, January 7, 1898; .Travis, Tvans-
actions of the Civil and Mechanical Engineers’ Society, 1906, gives extracts from this
specification..
206 SEWAGE AND ITS PURIFICATION
as the total average amount of suspended matter present in the
tank at any instant when M is the weight of suspended organic
matter present in the volume of sewage dealt with per day.
The size of the tank required is, therefore, not so large as to be
impossible with ordinary sewages, but the fact that the effluent
from such a tank was not sufficiently purified without further
nitrification prevented the ‘‘ Automatic Scavenger ”’ from being
more generally adopted.
About 1880 E. S. Philbrick, of Boston, Mass., constructed in
a number of places in America sewage plants comprising “‘a
tank or tight cesspool in which the solid particles of the sewage
may become macerated and finely divided by fermentation
before entering the distribution pipes.”! It was noticed that
the scum and deposit increased rapidly at first, and then
practically remained constant. In one case after four years
it was found that the surface accumulation was very small
(about 1 foot), and the bottom deposit less, showing that septic
action was going on, though it was then imperfectly known.
These tanks had the submerged inlet and outlet; they were
circular, but in other respects were very similar to the Exeter
septic tank. Glover in 1882 took out patents in America for
liquefying tanks followed by aerating filters.’
At the time of the Royal Commission of 1882, owing to the
failure of most sewage farms to yield satisfactory results, pre-
cipitation and attempted disinfection or sterilization, as de-
scribed in the preceding chapters, were elaborately carried out.
In January, 1887, Mr. Dibdin observed at the Institution of
Civil Engineers that.
*« One object claimed for the use of an excessive quantity of lime,
and also for some other substances, is that they destroy the living
organized bodies, such as bacteria, etc., which give rise to the
phenomena known as putrefaction.... As the very essence of
sewage purification is the ultimate destruction, or resolution into
other combinations, of the undesirable matters, it is evident that an
antiseptic process is the very reverse of the object to be aimed at... .
Very alkaline effluents, such as those produced by the use of lime in
excessive quantities are very liable to putrefy instead of becoming
purified by oxidizing organisms.”
Meanwhile, bacteriology had been advanced by a large
number of researches in various countries, at first directed
1 Engineering Record, New York, May Io, 1883, p. 530.
2 For further details see Metcalf’s ‘‘ Antecedents of the Septic Tank,” Tvans-
actions of the American Society of Civil Engineers, xlvi., No. 909, 1901.
4
BACTERIAL PURIFICATION 207
mainly to the special organisms of disease, but gradually
developing a knowledge of the larger class that are not patho-
genic, but effect ordinary changes in organic matter.
In November, 1887, the Massachusetts State Board of
Health commenced their experiments on the purification of
water and sewage by chemical precipitation and by filter-beds,
and in the two first volumes of their reports, extending to 1890,
details are worked out of different filtering media, size of grains,
thickness of strata, influence of time, temperature, and methods
of procedure, the results of about 4,000 analyses of raw sewages
and effluents being tabulated. At first they aimed at the
removal or destruction of bacteria by straining and chemical
means, without practical success; later they studied inter-
mittent filtration with the actual assistance of aerobic organisms.
All that was found necessary to completely destroy dead organic
matter was to provide conditions favourable to the action of
bacteria, giving suitable material on which the organisms
would be retained, surrounding them at certain intervals with
air, and providing periods of rest. They selected as suitable,
sand from 4 to 5 feet in depth, under-drained, allowing the
sewage to flow on the sand only six hours out of each twenty-
four.
On this principle at Worcester, Mass., sixteen filtration beds
of about I acre each were constructed of coarse sand from which
all pockets of clay and quick-sand had been removed. They
are separated by dikes, tamped with clay, and drained by 10-inch
pipes with open joints, 6 feet deep and 50 feet apart. The feed
is by split pipes laid on the beds.
This intermittent sand filtration is capable of purifying per
acre about 100,000 gallons of domestic sewage in each twenty-
four hours, so far as to remove any danger of subsequent
putrefaction ; with 20,000 to 30,000 gallons per day, the pro-
duct is chemically and bacterially exceptional.!
On this aerobic plan, if a filter-bed were overworked, it
rapidly choked, and putrefaction occurred in the interior owing
to a deficiency of aeration, so that it was necessary to have
‘very slow motion of very thin films of liquid over the surface
of particles having spaces between them sufficient to allow air
to be continually in contact,’ a condition, however, which did
not prevent the sand filters from becoming over-burdened, and
1 «Purification of Sewage by Bacterial Methods,” L. Kinnicut, September,
1900 (Fournal of the New England Water-works Association, xv., 2).
208 SEWAGE AND ITS PURIFICATION
also greatly limited the amount of sewage treated. Moreover,
the “thin film” oxidation of Massachusetts requires large
filtering areas with great labour to keep them in order—there-
fore is exceedingly costly when applied to sewage—it is also
attended with certain dangers from ‘‘ channelling ” of the beds
by careless or too rapid working, or by frost, whereby it arises
that the effluent escapes almost unpurified. In the Massa-
chusetts Report of 1890,! the process is compared to a com-
bustion, and was found to be most rapid in the summer
months. It must be remembered that sewage in America is
usually weaker and of greater volume than it is in Europe, on
account of the more abundant supply of water.’
In Ohio State there were in 1903 eleven plants for inter-
mittent sand filtration without any previous treatment.
R. W. Platt reports in 1905 that the best of these, at Mans-
field Reformatory, treated 70,000 gallons per diem (from only
700 persons) on seven beds of crushed sandstone, I°r acres
total area. There was considerable trouble in winter, and
the results were poor, owing to frost, even when the surface
was ploughed with deep or with shallow furrows. Sand treat-
ment alone is inadequate over most of this great region, and
preliminary processes have had to be adopted.’ Barbour finds
that in the Middle West U.S. sand filters usually cost from
£400 to £500 per acre per foot in depth. Ten years’ experi-
ence in Massachusetts‘ proves that their cost averages 43 cents
per capita per annum, divided about equally between capital
charges at 5 per cent. and maintenance. Over the glacial
drift area, where porous sand and gravel are available at low
cost, intermittent sand filters are used with a measure of suc-
cess, and when operating at low rates require little attention.
The maximum rate in practical design is that possible at the
time of lowest temperature. About double the area necessary
for summer is required for maintenance of filters in New
England after some years’ use. It issuggested that mechanical
filters could be used as “ finishers.”
The work of the Massachusetts State Board still left un-
1 Mills, pp. 578, 586.
2 The daily consumption of water per head in New York is 92 U.S. gallons;
in New Jersey, 92 gallons ; in Philadelphia, 143 ; in Los Angeles, California, 200 ;
in Alleghany, Pennsylvania, as much as 247 gallons. (Ten U.S. gallons=7
imperial.)—Mason. See also p. 16. .
3 See Ohio Sanitary Bulletin, ix., 177; Eighteenth Annual Report of the Ohio State
Board of Health; Transactions of the American Society of Civil Engineers, liv., E,
1905.
+ Report of State Board for 1903.
BACTERIAL PURIFICATION 209
settled—(x) how the sewage of cities could be purified by
bacteria where large tracts of sandy soil did not occur; (2) how
_ the large amount of suspended matter, like paper, wool waste,
and the other various forms of cellulose not easily acted upon
by bacteria, could be prevented from forming a layer over, and
clogging up the sand; (3) whether sewage containing large
__ amounts of manufacturing waste, especially free acid and iron
salts, could be treated bacterially. The Massachusetts inter-
mittent filtration could treat with permanent success not more
than. 100,000 gallons per day per acre, much too limited a
volume for towns and cities which. would be obliged to con-
struct beds with sand not im situ. This point was quickly
perceived in England, where such sand is not of common
occurrence, and the bacterial sewage work in England started
with the problem: -Can the amount of land required by the
intermittent filtration method be so reduced that the construc-
tion of artificial bacteria beds will be a practical possibility ??
The sewage of Lawrence City, in the Massachusetts in-
vestigation, had been run on the filters without any previous
purification, or even settlement. On the other hand, the
sewage of London had been previously treated with 1 grain per
gallon of ferrous sulphate and 4 grains of lime, the precipitated
sludge being then conveyed in boats to be discharged at the
mouth of the Thames. It was hoped that the clarified liquid
could be discharged into the river direct without creating
nuisance. But it still contained about 7 grains per gallon of
‘suspended solids, and was by no means free from odour. The
Royal Commissioners of 1884 had decided that the liquid
could not be discharged at the outfalls as a permanent measure,
and required further purification by application to land.
_ In 1866 an experiment with London sewage as applied to
land had already been made at Barking. The Metropolis
Sewage Company obtained a concession to treat the sewage of
North London, amounting to about 2,000 tons in nine or ten
hours, on 5 or 6 acres of grass land on a light gravelly soil.
The experiment was not a success, either culturally or with
regard to the cleansing of the effluent. But with the
200,000,000 gallons daily of London sewage, it was recognised
that the requisite area of suitable land is entirely unattainable.
1 Fuller has calculated the average composition and volume per capita of the
sewage of several English cities from published records, 1898 to 1902.—Technology
) Quarterly, June, 1903. Also see R. Commission on Sewage, vol. iii,, 1902.
3 14
Re
210 SEWAGE AND ITS PURIFICATION
An extension of chemical treatment and precipitation having
proved to be inadequate as well as costly, the Main Drainage
Committee of the County Council in 1891 authorized a series
of experiments at Barking outfall, on the lines of the Massa-
chusetts researches. From preliminary trials with small filters,
coke breeze appeared the most suitable material, although burnt
ballast nearly equalled it in purifying efficiency. Sand and
gravel effected a greater clarification, but the removal of dis-
solved organic matter, as measured by the reduction in the
oxygen consumed, given by Mr. Dibdin’s report was consider-
ably less than with the coarser materials, while there seemed a )
tendency for this effluent to become putrid, owing to deficient
aeration from the closeness of texture, and the filter required
frequent scraping and renewals. The average rate of working,
including periods of rest, was 411,000 gallons per acre, or )
250 gallons per square yard in twenty-four hours. For eight _
hours a day the effluent ran continuously, the filters being kept
full; the filter was then emptied, and allowed to rest for :
sixteen hours. Mr. Dibdin’s figures were:
Clarification, as measured by the units of depth required to
obscure a standard mark: Burnt ballast, 1; coke breeze, 1;
pea ballast, 13; sand, 24.
Reduction of Organic Matter (oxygen-consumed): Burnt
ballast, 43°3 per cent.; sand 46°6; pea ballast, 52°3; coke
breeze, 62°2.
The report adds significantly, ‘‘ The number of organisms in
the tank effluent before filtration, and in the filtrates, was
found to vary very considerably, those in the filtrate being —
generally present in larger numbers; but it soon became appa- —
rent... that the presence of a large number of organisms
was evidence of the activity of the process of splitting up the
organic compounds in the sewage matters passing through the
filters. Hereit is clear that the main purification was bacterial,
and only the beginning of a further resolving change to be
carried on in the river. It would undoubtedly have been an
advantage if the biological process so initiated could have been
allowed to develop a further stage in the filter, but the pre-
scribed object of the experiments was ‘the attainment of the
highest rate of speed consistent with such purification as
would remove the obvious objectionable characters such as
odour, colour, and liability to putrefaction.’ ”
At this time, the importance of the surface contact action as
¥
BACTERIAL PURIFICATION 211
distinguished from the bacterial changes in the chemical con-
_ stitution was to some extent lost sight of, and it has required
subsequent writers to accentuate the proposition that the cata-
lytic theory of Liebig was true in the sense that the reduction
of the organic matter from a sewage in a contact-bed was
primarily due to absorption, and that this mechanical removal
of organic matter was determined by the bacterial surfaces in
the bed independent of their vital activity.!
In the further experiments with a 1-acre coke-breeze filter at
_ Barking it was found, as at Massachusetts, that continuous
running resulted in clogging and a foul effluent, and that it was
best to commence with small quantities of liquid, the filter
(3 feet of coke breeze and 3 inches of gravel) being at first
merely filled and emptied twice a day, with a view to producing
an active bacterial bed. The following are averages computed
_ from the daily analyses :
AVERAGE ANALYSES FROM I-ACRE FILTER (D1BDIN),
Parts per 100,000,
Ylame Oxygen Albuminoid Nitro
i : POgen: as P t.
Fite per Day. | Four Hours. | Ammonia, Nitrates. | Purification
; a ard. oong
Gallons. | Effluent.) Filtrate.| Effluent.} Filtrate.| Effluent.| Filtrate. EYiiCe
"April 7 to © }
|) June g, 1804 J | 500000 5°85 | 1°23 | 0°593 | 0°138 | 0-182 | 07340 | 79°3
Neo. 9, e854 f | 601000) 5:28 | 1-42 | 0°565 | 0°158 | 0°032 | 0-200 | 79°6
. eri 20, 1805 Peery SO | FAS | O'St4 | O40 | O'204 | EO | 7844
he ae 1,000,000! 6°62 | O’9QI _ — deat hh 80°7
The highest efficiency reached was 83 per cent. purification,
with 1,000,000 gallons daily and a shorter time of rest. The
filter was finally worked on the system considered to be the
best at Barking, Exeter, and Sutton—namely, alternate filling,
resting full, and emptying, with a periodical entire rest empty
| for complete aeration. At Barking the filling occupied two
hours, the standing full one hour, the emptying five hours, so
that three cycles of eight hours were completed each day.
% See, further, Dunbar, Vierteljahrsschf. Med. u. offentl. Sanitélswesen, 3 Folge,
Kattein u. Jubbert, Gesundheits-Ing, 1903; Jones and Travis, Proc. L.C.E.,
Joos -1906 ; Fermi, Z. Spirit. ind,, 1906, xxix., 221.
14—2
212 SEWAGE AND ITS PURIFICATION
From 10 p.m. on Saturday till 6 a.m. on Monday the filter
rested empty, making a period of thirty-two hours each week.
This weekly rest involves the storage of the crude effluent in
reservoirs for the corresponding period—a practice which has
many objections. At Exeter, where the flow through the
septic tank is continuous, and no reservoirs are employed, the
cycles are continued by means of the automatic gear throughout
the entire week; but if a filter shows signs of exhaustion, which
occurs at long intervals, or rarely through accident, it is thrown
out of use for one or two weeks till recuperated.
The t1-acre filter is still in use. After five years’ working it
was reported to be free from clogging, and not impaired in
working capacity. It will be noticed that the filtering material
is only 3 feet deep, and that it is used for treating an effluent
from precipitation by lime and copperas.. In 1897-98 new coke- ~
beds were constructed at the northern and southern outfalls
for dealing with raw screened sewage, and were made of greater
depths—6, 9, 4, 12, and 13 feet. In a report of the London
County Council giving the results of the working of these
beds up to August 9, 1898, Dr. Clowes and Dr. Houston show
that they have been continuing the experiments on the lines —
of Mr. Dibdin, with special reference to the following
points : Se 3
“‘(a) The effect of using the coke in fragments about the size
of a walnut. | a
“‘(b) The effect of increasing the depth of the layer of coke
beyond the usual limit. 4
‘“‘(c) The extent to which the raw sewage underwent purifi-
cation by the treatment.
“‘(d) The practicability of maintaining the constant ”’ (mean-
ing, clearly, regular intermittent, not continuous) ‘‘ passage of —
raw sewage through the same coke-bed without deterioration,
either in the bed or in the effluent.
“‘(e) The amount of sewage which could be treated daily by
a superficial unit of the coke-bed.
““(f) The extent:to which the effluent underwent further —
improvement by its passage through a second similar coke-bed. —
“(g) The suitability of the effluent for maintaining the life —
of fish. |
‘“‘(h) The effect of the treatment on the number and nature
of the bacteria which were present in the raw sewage.” g
The report shows that the size of coke is of importance:
BACTERIAL PURIFICATION 213
‘The use of ordinary gas coke, in pieces about the size of walnuts,
seems to be attended with the following advantages, as compared with
the use of smaller coke. ‘The larger coke enables the bed to hold a
larger volume of sewage. The beds now in use had an original
capacity for sewage which was nearly equal to the volume of the
coke which they contained, in place of only 20 or 30 per cent. of that
volume, as is shown by beds containing smaller coke. The use of
the larger coke also allows the bed to be more rapidly filled and
emptied, and to be more completely emptied and aerated.”
The increase of depth of the beds beyond 5 feet, as I had
_ predicted in my Cantor Lectures, has not been attended by
higher efficiency. The report states that “ coke-beds similar
in character, but differing in depth, have been found to give
practically identical purifying effects ... with a 4-feet and
a 6-feet bed. A bed 13 feet in depth ... has given a purifi-
_ cation approximately equal to that effected by the 4-foot bed.’’
_ The depth is always of great importance, both as to fall, volume,
oe
and cost. In the intermittent system the bed is really used at
intervals as a storage tank, so that in this sense greater depth
means higher capacity. |
in the report of July 28, 1900 (p. 59), Dr. Houston says:
«‘ It must be admitted that the 13-feet coke-bed at Crossness yielded
very unsatisfactory results from the bacteriological point of view.
Thus, although the effluents usually contained fewer bacteria and
less of B. coli and spores of B. enteritidis than the crude sewage, the
reduction was not well marked, and, indeed, was immaterial from
the epidemiological point of view, considering the actwal number still
remaining. For, as has been already pointed out, the effluents
_ usually contained more than 1,000,000 microbes, more than 100,000
B. coli, and at least 100, but less than 1,000 spores, of B. enteritidis
spovogenes per C.C.”’
An important point is that the capacity of the 4-foot bed had
_ during ten months been reduced from 50 to 33 per cent. of the
whole volume of the bed, ‘‘ mainly due to fragments of straw
_and chaff, apparently derived from horse-dung, and to woody
fibre, derived from the wear of the wood pavements. ... The
original capacity is not restored in any degree by prolonged
aeration, which proves that the deposit on the coke surface was
not organic matter of animal origin; but it has been found that
the vegetable tissue, which seems to be the main cause of the
difference in capacity, can be in great measure separated from
the raw sewage by a brief period of sedimentation before the
sewage is allowed to flow into the coke-bed.”! It should be
1 Compare Waring’s and Lowcock’s experiments,
214 SEWAGE AND ITS PURIFICATION
noted that it is earlier stated in the report that ‘‘ the sewage
had been roughly screened before reaching the coke-beds, and
was free from larger matter usually described as ‘ filth,’ and
from coarse sand and heavy mineral road detritus .. .,’’ so
that, as I have always insisted, the additional sedimentation
would mean a further evasion of complete bacterial treatment,
and a production of a further amount of supplementary sludge.
A strong confirmation of the suggested origin of the loss of
capacity is found in the remark that “‘ the ash in the coke has
been reduced in amount by about 25 per cent. during its ex-
posure to sewage in the coke-beds,” cellulose being nearly
ashless.
These results confirm the view which has been frequently
urged—namely, that these non-animal substances cannot be
successfully destroyed without anaerobic action (see Chapter V.),
by which they are dissolved with production of gas. They are
the great difficulty in all processes where the first or hydrolytic
change is not properly specialized. The degree to which the
nitrogenous matter is dealt with cannot be traced from the
report, as only the ‘‘ oxygen-absorbed”’ figures are given, and
it is obvious that if the non-nitrogenous matter is arrested by
the tilter-bed, the improvement in the effluent as measured by
the oxygen-consumed figure must in part be attributed to this
cause, at the expense of clogging or diminution of capacity.
I have already remarked that the first stage requires no
oxygen, and is actually hindered by it, the second requires
~ some, while the third demands a very large and rapid supply.
In place of providing three separate areas in which these con-
ditions are carefully and continuously observed, as we should
in the culture of plants which required different amounts of
water, heat, or manures, it is attempted to alternate them in
two receptacles by causing the air in each to be cut off and
supplied intermittently, and the sewage to be either stagnant,
or run in and out with a rush, with the result that the bacteria
are periodically disturbed, and neither class of organisms can
work under their normal vital conditions. My own analyses
and those of others have proved that under the intermittent
system, first adopted from the laboratory experiments of Sir E.
Frankland in 1870, the effluents, although the average results
show a great improvement, yet manifest such fluctuations in
character, tending to be periodic, as show that the quiet and
regular working of the bacteria suffers avoidable interruption
BACTERIAL PURIFICATION 215
and interference. A small significant fact is that the discharge
from the fine beds at Sutton and Exeter, and I believe in other
places, is always, at the first rush, turbid and of inferior quality,
as a consequence of disturbance. Dr. Clowes also in the
above report remarks on the occasional turbidity of the effluent,
“apparently due in ordinary flow mainly to the presence of
bacteria.”
The want of provision of a separate area for the first stage is
often concealed by the fact that where the sewers are old, or of
great capacity or length, or when the sewage has been stored
for sedimentation, the first, or even a part of the second, stage
may have actually been passed through before arrival at the
works, so that the liquid may be quite amenable to the third
stage of strong aeration, such as is supplied by Lowcock’s,
Waring’s, and Ducat’s systems.
A remark in the above report is: ‘‘ Fish die at once when
they are placed in the present effluent produced by chemical
precipitation, probably because there is a serious deficiency of
dissolved oxygen in the liquid... .”! Various fish ‘‘ have
lived for months in the first effluent from the coke-beds, and
would apparently live and thrive in this liquid for an indefinite
period.”
In a supplementary report by Drs. Clowes and Houston
(October 26, 1899), the former finds that the cellulose deposit
on the coke containing ‘‘some fine coke particles and sand
grains, cotton and woollen fibres, and diatoms, but consisting
largely of chaff, straw, and woody fibre,’ caused a diminution
of capacity of about 1 per cent. per week in the 13-foot bed, but
that this was reduced to 0°64 per cent. per week by previously
sedimenting the sewage in a partitioned wooden trough. The
sediment was inoffensive, and contained 52 to 70 per cent. of
combustible matter. Dr. Houston found 1,800,000 bacteria
per gramme of deposit, not accounting, however, for its amount,
as ‘‘this number of typhoid bacilli, for example, weigh only
0°0000147 gramme.” The character of the bacteria differ some-
what from those in crude sewage. There were more B. enteritidis
and fewer coli. Proteus-like germs were abundant, with B. pro-
digiosus, arborescens, and an allied form. From colour tests and
inoculations he concluded the probable presence of tubercle
bacilli; in only one case, however, was a fatal effect produced
on animals.
1 See Chapter XIII., and also p. 57.
7
216 SEWAGE AND ITS PURIFICATION
In 1894, following the success at Barking, experiments on |
the same principle were started at Sutton, Surrey. The filters
were of different materials, but again showed coke breeze to be
the best, with burnt ballast as a good second, the latter being
very simply constructed by digging out the clay to form a pit
about 3 feet deep, and filling it up with the same clay after
burning, the cost of a filter of this kind, having an area of
rather more than one-tenth of an acre being given as less than
£100, including all charges. It will be remembered that the
cost of the Barking 1-acre coke-filter was stated as £2,000.
The Sutton sewage (500,000 gallons) was at that time treated
with g grains of lime and 2 grains of ferrous sulphate per gallon,
and the settled liquid passed on to land. Thesoil, London clay,
acting unsatisfactorily, in 1895-96, on the advice of Mr. Dibdin,
two ‘fine-grain bacteria filters’? were constructed for the
treatment of the precipitated effluent. The sludge from the
precipitation was pressed into cake at a cost of £7 per week,
but there was no demand for the product, and ‘‘the nuisance
which is inseparably connected with the process was highly
offensive.”
In November, 1896, chemical precipitation was definitely
abandoned, but an important feature of mechanical aid was ~
still retained, since the. raw sewage was ‘‘ screened from grosser ~
solids”? by a revolving wire drum (p. 151). From 2 to 3 tons
of solid matter per 1,000,000 gallons of sewage thus escape
bacterial action.!
From the screen the liquid passed on to the top of pits filled
with coarse burnt ballast called variously ‘“‘ bacteria tanks’’ or
“coarse filters,” analogous to the “ roughing filters” of former __
systems, but differing from them in the intention not only to
remove solid matter, but to alter it bacterially. The effluent,
though greatly improved, was liable to secondary putrefaction,
therefore it was distributed by channels over fine beds of coke
breeze, whence it issued at intervals as a liquid usually clear
and deprived of offensive character.
The coarse beds were constructed by filling the chemical pre-
cipitation tanks with burnt clay ballast 34 feet deep, the bottom
having a 6-inch main drain with screw-down outlet valve, and |
3-inch branch drains 6 feet apart. The bed is charged to
1 Thudichum, Society of Engineers, December 5, 1898. In 1899 the rotary
screen was abandoned in favour of a detritus tank, which has now, in its turn,
been converted into a septic tank by trapping both inlet and outlet.
eT gaa
BACTERIAL PURIFICATION 217
within 6 inches from the surface, and the sewage remains in
contact for two hours, after which the valve is opened and the
liquid flows on to the fine bed, in which it is similarly treated.
The coarse-grain filters are charged three times daily, with an
interval of not less than two hours’ rest after being emptied.
_ The filling and emptying are controlled by Adams’ siphons
(Chapter XII.). An additional rest, of about one week in six,
is given to each bed.
After three months’ working, Mr. Dibdin was able to give a
satisfactory report. The oxygen consumed by the organic
_ matter was reduced by the tank 66 per cent., and by the filter-
beds 86°5 per cent. The solids in suspension were reduced by
_ the tank g5 per cent., and by the filter g9°6 per cent., while the
filtrate was practically clear, had no objectionable odour, and
_ did not putrefy on keeping. The process has continued to the
present time with satisfactory results, except when the filters ©
were overtaxed, “‘some of them,’’ as Mr. Dibdin reports, “ having
_ been purposely worked up to a rate of nearly 3,000,000 gallons
; per acre per day, with the result that the bacterial action was
_ evidently checked, as shown by the decrease in the production
of nitrates, and an increase in the quantity of organic con-
_ stituents in the effluent. As the result of careful watching,
_ however, no permanent harm was done, as the filters were
_ immediately restored to their usual condition, when they pro-
ceeded to give good results.”
Here, again, we gather that when there is reliance on pre-
sumably aerobic filters and organisms for combined liquefaction
and nitration, indiscriminately, in the same receptacles, the
_ result is apt to be variable, and to depend on “ careful watch-
ing,” an inference that is borne out by Mr. Dibdin’s analyses
during 1896 and 1897.
SUTTON SYSTEM.
Parts per 100,000.
| Oxygen bs Albu- Residue on
Cl. absorbed) N as Nas | Free p, nungid 'Suspended Micro-filter.
in Four | Nitrites.| Nitrates.| N H;. “NH "| Matter. , Millimetres
Hours. | per Litre.
ie |
_ Crude sewage en 12°8, 6°49 || o'o21| None |12°53\1'13 | 85°76 3,000
_ Tank effluent .. |12°8) 3°96 | 0-301) 0°751 | 3°850°60 | "1 213
aa
_ Filtrate from coke |
breeze... Fok. 12°8
|
|
I°Ig | 0°087' I'99 | 1°25/0°316! 1°35 23
218 SEWAGE AND ITS PURIFICATION
The average results in his table (p. 217) I have calculated,
for the purpose of comparison, to a uniform chlorine content
of 12°84 parts, the average given for the Sutton crude sewage.
These figures show the following percentages of purification :
Oxyge Albuminoid | Suspended
| abearaed Free NH¢. NH3. | Matter.
By the ‘‘ bacterial tank” | 53 69 47 | 94
By the coke filter a | 29 21 | 25 | 4°4
Total purification Ot 82 go | 72 98°4
|
It will be observed that the chief purification occurs in the
‘“‘ bacterial tank,” and that a large proportion of it consists in
the removal of the suspended solids.
Fic. 21.—ConTACT, OR ‘‘ DIBDIN”’ FILTERS ON DUAL SYSTEM AT SUTTON.
During the two hours of resting full, a mixture of organisms,
of which I believe a great proportion are anaerobic, as indicated
by the large production of nitrites, are liquefying the sludge.
It was estimated that in the three tanks 80 tons of dry matter
had been thus reduced from November, 1896, to December, 1897.
During the period of resting empty, the aerobic bacteria. are —
supposed to be at work, although, according to Mr. Dibdin, no
air enters except that drawn in while emptying out the liquid.
The subsequent coke-breeze filter is intended, under the same
conditions, to be entirely aerobic and nitrifying. The Second
Report of the Royal Commission on Sewage, 1902, No. 2,
‘Fr
BACTERIAL PURIFICATION 219
p- 22, says that ‘‘the destruction of solid organic matter takes
place most advantageously during the period of rest. The
sludge of a manufacturing town is more resistant than domestic
sludge.” I pointed out in 1896 that as the organisms pro-
ducing nitrates require much oxygen (p. 121), and we know
they do not thrive in a water-logged soil, their action is almost
entirely confined to the periods of emptying and resting empty.
The prevalent fault of these fine or secondary beds on the
Sutton system is the deficiency of aeration, resulting in a
generally low nitrification, shown also by the presence of
nitrites. Thus at Exeter in 1896 I found that the discharge
from the Dibdin filters contained ordinarily only 2°7 to 3 c.c.
of oxygen per litre, or less than half saturated, with about
_ I part per 100,000 of nitrogen as nitrates, whereas in a filter
which had rested for some time the nitric nitrogen in the first
|| discharge was 2 parts per 100,000. The Leeds report, 1900,
_ mentions that large quantities of nitrates were produced in the
resting periods. In one instance where the filtrate had deterio-
rated and the nitric nitrogen was o'16 part, after a rest of
eighteen days it advanced to 3'4 part per 100,000, and the
capacity at the same time increased 21 per cent. (see also
Chap. XI.). It will be noticed, further, that the Sutton sewage
has already. been broken down to a very considerable extent, as
shown by the 12°53 parts of free ammonia, and only 1°13 parts
of albuminoid.
The total cost of the farm when formerly worked on the
chemical precipitation and broad irrigation system was for the
year ending March 31, 1895, £15 11s. 11d. per 1,000,000 gallons
(taking into account the amount earned by the farm and sale of
sludge, which was {117 7s.) ; in 1899 it was £3 Igs. with the
biological system.
In June, 1899, I made an examination of the Sutton results
for the Local Government Board. The samples of screened
sewage, coarse and fine bed effluents were so collected as to
represent the working of one pair of beds on one day, the
average samples being obtained by taking equal volumes at
intervals of five minutes throughout the whole period of filling
or discharge. Gauging of coarse bed, 6,600 gallons; fine bed,
4,369 gallons. The volume sampled. was, therefore, approxi-
mately 19,800 gallons of screened sewage, of which 13,107
gallons were subsequently passed through the fine bed. The
flow through the coarse bed (3355 feet=201% square yards)
Va
220 SEWAGE AND ITS PURIFICATION
was 102 gallons per square yard per day, while the fine filter
(83°3 square yards) dealt with the coarse filtrate at the rate of
157 gallons per square yard per day, or approximately, for the
double filtration, 10 acres for 3,000,000 gallons of screened
sewage. 3
At that time the distribution of the liquid over the beds was
of the simplest type, causing an irregularity of contact between
the material and the liquid which was revealed in the analysis.
The suspended solids in passing the coarse bed fell from 61
to 18, the difference of 43 being retained. Their resolution, as
I have pointed out, is mainly an anaerobic process, actually
antagonistic to the oxidizing and nitrifying changes which are
intended to occur in the fine bed. It is proved, however, by
the increase of combined nitrogen in solution from 3°4 to 4°I
parts, that the fine bed had in this case to supplement the
coarse bed in dissolving nitrogenous solids.
The general lowness of the free and albuminoid ammonias
with high organic nitrogens is probably explained by the fact
that the effluents were analysed in such a fresh state that the
nitrogen was mainly present as urea, since this compound does
not readily yield its nitrogen by distillation with alkali or per-
manganate, but is completely changed into ammonia by the
Kjeldahl process, hence would appear as organic N. It is well
known that before urea can be nitrified it must be hydrolysed
into ammonia: the first stage should be effected in the coarse
bed, the second in the fine.
On the other hand, during the thirteen hours of rest and —
aeration that had elapsed before the first samples were taken,
the coarse bed had temporarily assumed a nitrifying function,
as shown by the very considerable amounts of nitric nitrogen
found, with a lower quantity of nitrite, and only a slight re-
duction of the oxygen consumed. Later in the day, when the
rest periods are shorter, all this nitrate disappears, with a heavy
fall in the total nitrogen, and a considerable lessening of the
oxygen consumed. There is little doubt that this is explained
by a Gayon and Dupetit reaction, by which nitrates and organic
nitrogenous matter decompose one another, the oxygen of the
nitrate burning up the carbon, and nitrogen or oxides of nitro-
gen being evolved as gas. Possibly the disturbance occasioned
by the formation of this gas accounts for the extraordinary
variations in individual samples, and for the high suspended
matter occasionally met with.
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222 SEWAGE AND ITS PURIFICATION
In this case we have actually a reversal for a time of the
functions of the two beds, and a violation of the law that “‘ the
bacterial changes should be carried out with regularity and in
natural sequence.”
A great divergency was noticed in the successive individual
samples, taken at fifteen minutes’ interval, and can be ac-
counted for by the interference of the filling material with the
free mixing of the sewage, so that zones and channels are
formed through which the liquid flows at varying rates. The
effluent issuing at successive intervals of time comes from
different layers and parts of the beds, and really represents
sewages of different hours or even days, as proved by the
individual chlorine figures.
There is a considerable loss of nitrogen in contact-beds
(see pp. 118 and 126 in Chapter V.). Letts and Lorrain
Smith investigated this at Belfast,' and their chief results
are:
1. They confirmed previous observations that a main cause,
reaction between nitrates, nitrites, ammonia, and organic
matter with production of free nitrogen and CO,, was due to
vital processes of organisms and not to enzymic or chemical
action, and that the common B. coli was one of the species
taking part in the change.”
2. Green algz sometimes flourished on the bacteria beds,
and absorbed large quantities of ammonia and nitrates; their
tissues contained a larger proportion of nitrogen, and less
mineral matter, than when they were growing in ordinary
waters.? [Compare the vigorous growth of grass and weeds
that generally forms, if allowed, on inland filter-beds. In
America, sand filtration beds have been regularly planted and
cropped. |
3. In the brick beds at Belfast, “‘12 to 20 per cent. of the
nitrogen disappearing can be recovered as free N dissolved in
the effluents,’’ and a further portion escapes as nitrogen gas or
oxides of nitrogen.
4. An uncertain amount passes into the tissues of animalcule,
worms and insects (see Chapter IV., p. 77). The bacterial
jelly, or zoogloea, encrusting the filtering material also contains
much nitrogen.
Phelps and Farrell have demonstrated experimentally the
1 Belfast City Reports, r901 and 1904; Chem. News, No. 2184, 1901.
2 See Pakes and Jollyman’s Papers, Tvans. Chem. Soc., 1901, pp. 322, 386, 459.
$ Belfast Report, 1904, p. 46.
BACTERIAL PURIFICATION 223
chemical and mechanical actions in contact-beds,! and give
curves of the changes agreeing with the explanations I have
given. They emphasize the importance of adsorption” by the
zoogloeal jelly, on which Dunbar and Thumm lay so much stress,
but the phenomenon is common to all kinds of bacterial filters.
They found the loss of nitrogen in contact-beds to be 29 to
50 per cent. (Clark found 38 to 50 per cent.) ; in continuous or
trickling filters it was only 1 to 6 per cent. (see Chapter X., p. 270.)
In 1903, the Sutton U.D.C. Surveyor, Mr. Chambers Smith,
reported that ‘‘the net cost for the year of treating the sewage,
including pumping, was £775, equivalent to a cost of £4 Is. 73d.
per 1,000,000 gallons, or 11:07d. per head of population, whilst
_ the charge on the rates amounted to 13d. only, a figure which
compares very favourably with the cost of similar work in other
districts. The land on which the sewage disposal works are
- situated is stiff clay, but a portion has been rendered suitable
for sewage farming by ploughing domestic ashes into it. About
8 acres are given up to the production of peppermint, one of
the most profitable crops which can be grown on a sewage
_ farm, and from this source alone £178 15s. was realized in the
_ year 1902-1903.”
At Oswestry, in 1898,® material for beds on the Sutton system
_ was obtained by screening from an old refuse tip, in which
“everything excepting hard carbonaceous matter had dis-
| appeared,” the coarser portions being used for the primary
| beds, 44 feet deep, and the intermediate portions for the
_ secondary filters, 4 feet deep. The total cost of the screened
refuse was about Is. 3d. per cubic yard. The crude sewage
was previously clarified by subsidence in a large settling tank
in two sections, used alternately. About half the sludge
_ settled in these tanks, and was removed weekly, mixed with the
|| dust screened out of the town refuse, and sold as manure.
The Surveyor writes in 1906 that three primary beds have
| since been filled in the same way, but that the refuse of latter
| years contains a much less proportion of large cinders and is
not the best material. The beds have lost a great deal in
capacity, chiefly through insufficient settling-tank accommoda-
_! Research Laboratory, Mass. Inst. of Technology ; see fourn. of Infect. Diseases,
_ Chicago, 1905.
? The property by which certain substances, notably colloids, remove dissolved
material from solution.
% Population, 10,000; dry-weather sewage, 300,000 gallons per day; water-
_ supply, 20 gallons per head; ‘‘total cost of works, £1,800; annual working
expenses, about £80,”
224 SEWAGE AND ITS PURIFICATION
tion, causing clogging and the close consolidation of rather
small material. Present settling-tank capacity 58,000 gallons;
average dry-weather flow 350,000 gallons per day. The new
scheme provides open sedimentation tanks holding slightly
more than a day’s flow, with additional beds for storm water.
‘Leeds, with the Sutton method in 1898, experienced much
difficulty owing to “sludging-up”’ of the beds, but by increasing
the periods of rest, and by the introduction of finer screens, —
which remove a greater portion of the suspended solids (sludge)
to be otherwise dealt with, better results were for a time
obtained. The increase of capacity gained by a long rest was
rapidly lost on renewal of working ; thus the capacity regained —
by a rest of thirty-eight days fell again in a fortnight from
56,500 to 45,800 gallons. Probably the long aeration had
destroyed or enfeebled the anaerobes, and the liquefaction was
therefore suspended until an anaerobic state was restored. The
drying up of the spongy matter during lengthened rests accounts
to a great extent for the increase of capacity. Another cause
of diminution of capacity in rough beds of clinker was found
to be that the material had sunk and become consolidated, in
consequence of the alternate filling and emptying, and the
slight rise and settlement at each turn of the work. This is
liable to occur with all materials in intermittent filtration.
After three years, in 1900, the decrease in capacity in contact-
beds was still so serious that ‘‘ they could not be regarded as
suitable for Leeds sewage without preliminary treatment.”
Besides the disintegration and settlement of the coke and
clinker, there was an accumulation of sediment in the interstices,
much of it irreducible, and therefore unaffected by the periods
of rest. If the beds must still be used, ‘‘ the problem would be
(1) to find material of sufficiently even size not liable to degra-
dation ; (2) to reduce, as far as possible, the solid matter put on
to the rough beds; and (3) to exclude and treat separately all
iron liquors.”
** Sutton,” or ‘‘ Dibdin,” beds were adopted at a large number
of places. At Manchester experimental filter-beds on the same
principle were named ‘‘ double contact-beds.”’
As it became gradually evident that the two beds, coarse and
fine, even with preliminary screening or sedimentation, were not
exactly adapted to the three processes of bacterial change that
we have mentioned, a third bed, or “‘ triple treatment,” was in
many places adopted. In the Manchester inquiry of 1899 it
:j
BACTERIAL PURIFICATION 225
. was stated that if the ‘‘ double contact ”’ did not suffice, they
_ would employ a “third contact.” This triple treatment was
_ adopted at the Hampton Sewage Works in the beginning of
_ 1899, and also at Lincoln and elsewhere.
_ In America it is recognised that intermittent filtration is
much more expensive than was formerly anticipated. The
filters constructed in New England a few years ago are one by
one becoming clogged and inoperative except at very low rates,
and it is now evident that they necessitate heavy maintenance
charges.
15.
CHAPTER X
BACTERIAL PURIFICATION (continued)
Capacity of filters—Nature and size of materials—Gases in filters— _
Depth .of beds— Aerating processes— Lowcock— Waring —
Ducat— Artificial warming—‘“ Thermal aerobic ”—Continuous
filtration—Salford—Stoddart’s filter.
TuHE regulations of the Local Government Board as to filters
originally provided that each set of filters—z.e., both coarse and
fine—must be of sufficient capacity to contain the normal dry-
weather flow for twenty-four hours. Coarse-grain beds can
hold 25 per cent. sewage, and fine beds 334 per cent. This
means, taking an eight-hour cycle, that the beds will be large
enough to deal with three times the dry-weather flow—ze.,
I volume normal, 2 volumes storm water.
As to material, its size and mode of arrangement have been
shown to be more important than its kind, and it has been
unfortunate that the Board have not during the past few years
allowed considerations of material and distribution to modify
their insistence on a fixed filter capacity.
Coke breeze from its porosity exposing a larger surface was
recommended by the Barking experiments and has been
generally adopted, but it is somewhat expensive when required
in large quantities, therefore in many localities local material,
when properly screened and graded, can be employed.
The Massachusetts Reports, 1898-99, comparing filter-beds
of ashes and cinders with those of sand and gravel, state that —
the former have great advantage as regards rapidity and not
becoming clogged, that they are equal or even better in the —
colour and chemical character of the effluent, though the
percentage of bacteria removed is less.
In 1897 fine coal was used as a medium for the filtration of ©
chemically precipitated effluents, at Wolverhampton, Lichfield, ~
and other places. The sewage of the former town is heavily —
226
BACTERIAL PURIFICATION 227
polluted with chemicals, that of Lichfield contains a large
amount of brewery refuse. I cannot see how the action of coal
is different from that of other media, though Dr. Bostock Hill
contended that effluents from coal filters show a greater loss of
organic carbon as compared to organic nitrogen than in filters
made of other materials, and that this is a characteristic property
of coal, but Mr. Garfield, now of Bradford, to whom the sugges-
tion is due, has not adopted this material for his present works.
Dr. Fowler, in his report of the Davyhulme experiments in
1897, confirms the results of previous observers that coal and
burnt clay filters, when worked continuously, rapidly become
clogged, and that improved results are obtained with intervals
for rest and aeration. He also considers coal to be superior to
burnt clay.
The table in my last edition of the comparative nitrifica-
tion effected by different filters, ranks the Garfield filter as
lower than other forms, but, as already mentioned, this result
is more likely due to the difference in the mode of working and
aeration of the filter than to the material.
Partly for the sake of cheapness, and also because it was
expected that coke would in time disintegrate, the use of more
compact materials has been suggested. Broken slate’ or shale
has been much used in the North, and Thudichum even made
laboratory experiments with pounded glass, and found a certain
amount of efficiency. Burnt ballast, clinker, cinder, slag,
polarite and iron sand have their advocates. Non-porous
materials might be expected to have a lower capacity, but it is
mainly on the surfaces, and not in the interior of the masses,
_ that the bacterial action occurs. At Exeter, Mr. Cameron
expresses a general preference for clinker: at Southampton and
other places assorted clinkers from the dust destructors are
used. But coke, if available, seems the best material for nitri-
_ fication, and has shown no noticeable disintegration in nine
years. Burnt ballast must be carefully made, as many kinds
_ crumble and block up the filter. Road granite, crockery, and
_ old iron and tins are stated to have given satisfactory results,
and broken saggers from pottery kilns have been successfully
_ used at Hanley in 1903, and in other places in the Midlands.
_ Durability of “ Ballast.’ If clay be thoroughly burnt, its
_ 1} InNov., 1898, rough state filters were proposed at Festiniog, and in March,
1899, Chambers Smith reported to the Sutton Council his trials of various
_ Materials. See San. Record, Aug. 9, 1906.
15—2
L
228 SEWAGE AND ITS PURIFICATION
durability is unquestioned, as shown in brick. But when treated
in the cheaper way employed for roads and railway embank-
ments—that of piling the clay in alternate layers with small
coal and refuse, firing in places and allowing to burn slowly
till the mass has the usual brick-red colour—the burning
is apt to be irregular and insufficient, so that much of the
material on wetting becomes soft and crumbly. Burnt ballast
appears to be almost unknown in America, since the Massa-
chusetts Board did not include it in their investigations of
materials, and Rudolph Hering alludes to it in September,
1g00,' as “a material made out of clay which is used in
England because they have very little sand.” He says it is
not permanent, but crumbles, and adds that unless very hard,
coke behaves in the same way, observing that it is a question
for calculation whether it is cheaper to get a more expensive
permanent material, such as gravel or quartz sand, which will
last longer, though it may not purify so much sewage at first,
or to occasionally renew the material.
Burnt ballast seems to have been first tried for this purpose
by Dibdin at Barking in 1891 (see p. 210), and was used after-
wards at Sutton and elsewhere for coarse primary beds (the
fine secondary ones being generally coke breeze, p. 216). At
Dorking and some other places besides Sutton, it has since
been found faulty, and has been replaced by clinker or other
material. That it is capable, if well made, of considerable
permanence is shown by an examination of a coarse bed at
Harrow, after two and a halt years’ working. Washed samples
from different depths were ‘‘ clean and red, and apparently as
hard as when it was laid down.” In the washings, however,
“the heavy particles consisted almost entirely of small sharp
particles of ballast ’’-—such would occur with any material,
whatever its hardness, that had not been thoroughly washed at
first—with ‘“‘ not more than the slightest suspicion of ballast-
mud.” The material lost on washing 4°44 per cent. of its
weight, made up of ballast dust and sand 1°14, raw clay 2°60,
organic matter o’7 per cent. The capacity of the beds was
considerably less than at first, but this was due, not to dis-
integration of the ballast, but to clay that had come in from
the top. At Belfast broken brick is used for the coarse beds.?
At Friern Barnet Sewage Works, Middlesex, it was found that
1 F. New England W. Works Assoc., xv. 2. The meaning is not given in
Webster’s large dictionary, 1890, nor in Nuttall.
2 City Surveyor’s Report, 1900.
BACTERIAL PURIFICATION 229
burnt ballast works better than clinker. The contact beds in
this case are 4 feet 6 inches deep, and the flow of sewage
400,000 gallons per day. The amount of nitrate in the effluent
_ has been as high as 5°2 parts per 100,000."
In some places where the beds have been made by the simple
method mentioned in p. 216, care has not been taken that the
work was sound, and earth and clay from the sides have washed
into the filter.
From the enormous waste heaps in the neighbourhood of
various collieries and iron works, Wake and Hollis, Darlington,
separated by special machinery tap cinder, coke breeze, clinker,
broken bricks, and ‘‘ carbonaceous iron sand”’; the latter was
proposed by them as a suitable and cheap material for bacteria
beds.” Its content of iron oxides, with a trace of manganese,
suggested the action of these substances as carriers of oxygen
to the organic matter (p.179). But, as in coke, which also
contains iron, and often manganese, and in many patented
materials prepared by ignition, the density and insolubility
make chemical action very slight, and quite subordinate to the
use as strainers and bacterial surfaces.
Dibdin and Thudichum compared “carbonaceous iron sand”’
with other materials in some experiments on triple filtration of
crude sewage. In each set the size of the grain was :—
First bed, passed by 3-inch mesh and rejected by +-inch.
Second ,, 3 4-inch _,, ee a 24-inch.
Third. .,; ‘a 23-inch ,, se * yz-inch.
After five weeks’ running with two fillings per day, the
effluents were analysed. The composition of the crude sewage,
calculated to parts per 100,000, is given as: Free NH; 13°53,
Albumd. 0°740, Oxygen consumed 9'14. The effect in reduction
of these figures, or “percentage of purification,” the water
capacity at this stage, and the nitrogen oxidized, is shown in
the annexed table. From it we may gather the following
conclusions :—
1. The iron sand shows in this case a slight superiority over
the coke breeze alone, but, in the words of the report, “‘ it was
practically identical in work effected with the other materials,
and there was no specific advantage in the use of any one
1 Sanitary Record, April 20, 1905, p. 333.
2 An analysis by W. F. K. Stock gives—moisture 6°75, FeO 30°41, Fe,O, 10°33,
carbon 7°53, rough sand 16°70,
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BACTERIAL PURIFICATION 231
material more than another, so far as the chemical results were.
concerned. . . . Observations were made as to the bacteria in
the respective effluents, but no specific advantage seemed to be
shown by any one material in this respect.”
As in the Massachusetts, Barking, and Berlin experiments,
the sacrifice of capacity and of output on substituting a less
porous material, like sand, was not accompanied, in the case of
sewage, by an equivalent advantage in purification.
2. That no nitrate or nitrite was produced in any case in the
first beds is a strong indication that they were acting hydro-
lytically and anaerobically, their function being that of an
“open septic tank.”
3. The double filtration, or result of the second bed, cannot
be exactly followed, as the nitrites are not separately given, but
it corresponds mainly with the second stage of partial oxidation.
4. In the triple contact, the coke breeze has shown a higher
power of nitrification, as noticed by other observers, owing,
undoubtedly, to its greater porosity.
It is also important to note that these filters prove that the
organic carbon is more easily oxidized than the organic nitrogen,
and confirm the criticism on the use of coal (p. 227).
To study the influence on nitrification, in October, 1899, I
examined six tray filters after running about three months with
a hydrolysed sewage. D, E, and F, had an area of Ioo square
feet each; A, B, and C, were one-third the area, and had
become much clogged. D was most freely exposed to the air.
The filtrates gave on successive days the averages in parts per
100,000 on p. 232.
Denitrification with loss of nitrogen is here shown by those
filters which are not in proper order. The superiority of a
graded filter (F) is also evident, while coal has exhibited the
peculiarity that has been noticed in other cases, of encouraging
the production of nitrites. Filter F shows the extraordinary
nitration of a strong sewage, resulting in an excellent effluent ;
in these cases a gain of total nitrogen, presumably from the air,
has often been observed.! The great variation produced by the
ventilation and aeration of similar filters is also seen in com-
paring B, D, and E.
With reference to porous materials the conclusions of the
Manchester Report? agree with previous experience in finding—
1 Some species of bacilli can assimilate free N, as in the agricultural prepara-
tion ‘‘ nitragin.”
2 Baldwin Latham, P. Frankland, and W. H. Perkin, October, 1899.
232
SEWAGE AND ITS PURIFICATION
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BACTERIAL PURIFICATION 233
if “1. That the initial capacity of a contact bed is practically
_ uninfluenced by the grade of material with which it is filled.!
_ “2. That there is a rapid decrease in capacity during the
earlier period of working [before the resolving bacteria become
| established and active].’’ (See also ante, p. 224.)
_ After noticing the increase of capacity during a period of rest,
the report concludes that coarse cinders, 3 inches to 1 inch,
_ permit too free access of sludge to the body of the filter and
even into the drains, while ‘‘if the material is too fine the
_ beds soon become quite impervious to sewage.’’ With bed C,
_ % to 4 inch, followed by D, 4 to } inch, they obained better
‘results, but their final opinion is that the most suitable material
_ for bacterial beds consists of clinkers passing through 14-inch
'| mesh and rejected by }-inch.
| It was concluded that “contact beds, after a comparatively
“short space of time, acquire a practically constant capacity,”
| “usually found to be about 33 per cent. ; that suspended matter
| ‘must be removed as far as possible by sedimentation, and that
‘any not so removed should be retained on the surface of the
} bed ; that the surface must be raked or forked over about once
month ; and that periodical intervals of rest must be allowed.
_ At Sutton Mansergh reported that in three years the water-
content of the coarse filters had diminished from 32 to 19 per
|| cent., while the fine filters had not sensibly lost capacity. At
| tamburg, with single contact without previous sedimentation,
| Dunbar and Thumm found that with one filling per day, after
700 fillings the original capacity of 33 per cent. had fallen to
0 per cent., and with two fillings an original 40 per cent. had
fallen to 14. Resting, forking, flushing, and altering the direc-
| on of supply, did not prevent the clogging, and the only
‘remedy was removal of the material and washing against
\\screens, by which about ro per cent. of the medium was lost.
| The London County Council investigated in 1899 the effect
J of “double treatment ”—that is, by an extra coke bed. Their
| “single treatment’’ meant two coke beds, the first correspond-
jing to an anaerobic tank, and about 4 feet deep; the second of
6 feet thickness, called the “‘ primary bed, for the first stage of
) . ouble treatment”’; while the third, also 6 feet, was called the
‘commonly named triple treatment. The coke in all was of
1 This is only the case within certain limits. See p. 226.
234 SEWAGE AND ITS PURIFICATION
secondary beds were matured, or inoculated, by frequently
charging with crude sewage for about three months to seed
them with bacteria.
The aeration of the 6 and 15 foot beds was tested by sinking
vertical pipes into the bed and aspirating the gas. The amounts
are given as follows :—
Six-foot Depth. Thirteen-foot Depth.
Number of Number of
Hours since | ofGyvucrin | ofGarboe | Hours since | frgcreee | Cotbonic Acid
P hea sigs ys Air. Acid in Air. | 4 Sewage. in Air. in Air.
oe 19°8 0*4 22 18°4 I°4
22 9°8 5°8 - 26°75 14°0 3°8
24°5 btohe) 6'0 50°75 14°8 3°0
37 17°8 2°O 51°25 15°3
40°5 16°8 2°4 70°O 14°7 08
|
Later experiments (report of October 26, 1899) agree with
the above, and in a third report (July, 1900) the average ¢
almost daily analyses of the air in a ‘‘ primary ” coke bed abou
10 feet deep showed after ‘‘resting empty” periods of twenty- —
one hours, oxygen 10°3 and CO, 5°7 per cent.; after five hours’ ©
rest, oxygen 8°0, CO, 5°7: air containing normally 21 per ce
of oxygen and 0°04 per cent. of CQ,. A
At Lawrence, Mass., in 1899, a cinder filter which had beco
clogged and was resting, had air drawn through it constan
for two months except at certain intervals, at a rate s
cient to change the air-contents every three hours. |
gas in the filter gave in averages per cent.: (a) aspirator work-
ing continuously: CO, 0°25, O 20; (6) aspirator shut off for
some hours: CO, 1°3 to 2°6, O less than ro. The oe
are irregular, but show that a reduction of the free oxygel
occurs from the 21 per cent. normally present in air. Th
carbonic acid produced usually corresponds to an ccuivall
diminution of the organic carbon. A point to notice is t
besides the CO, in the gases an additional quantity, propor
tional to the vapour tension, is retained dissolved by the liqui
remaining in the coke. Several observers have proved th
inhibiting action of carbonic acid on bacteria, especially those
which are oxidizing, therefore it is important when the third or
oxidizing stage is reached that the carbonic acid should be
removed by free circulation of air as soon as formed, or the
i
BACTERIAL PURIFICATION 235
failure of nitrification noticed in so many of these filters will
follow.
4 In the Exeter experiments I sunk ‘‘ compo”’ tubes to different
Lie evels in filter No. 2, 5 feet deep, which had been in constant
ork for several days, and aspirated the gas for analysis two or
| three hours after the last discharge. The results were :—
Air Tube 1, Tube 2, Tube 3,
5 18 Inches. 36 Inches. 54 Inches.
H): Per cent, of CO, by volume _.. 0°04 0°375 0°98 0°75
| Relation to volume in air Bae I‘o 9°4 24°4
| Assuming the air in each empty filter to contain I per cent.
| of CO,, it follows that the volume of carbonic acid removed as
| ge s is also 1 per cent. of the volume of sewage dealt with in the
i filters. The weight of organic carbon destroyed in this way is
therefore about 50 pounds per 1,000,000 gallons, or 0°5 part per
| b 00,000, without reckoning the dissolved CO, in the interstitial
| a
_ The interference of this carbonic acid in deep filters seems to
}/ account, even more than the insufficient time during which the
be ds had been working, for the fact that the purification re-
‘ported by Dr. Clowes, even by his ‘‘ secondary ”’ (really triple)
treatment, is not equal to what has been attained elsewhere.
| He states that ‘‘ the purification effected by a single treatment
i f the raw sewage in the coke beds amounts to a complete
‘emoval of the suspended matters, and to a further removal of
a least 51°3 per cent. of the dissolved putrescible oxidizable
‘matter. The primary 6-foot coke bed actually removed on the
a erage 49°9 per cent. of dissolved impurity, and a second
'process has effected thus far an additional purification of about
I9°3 per cent., giving a total average of purification of the
¢ avified vaw sewage amounting to about 692 per cent.”’ With
| this deeper filter nearly 70 acres of filter 12 feet deep would be
‘required.
Mr. Dibdin states? that slate or tiles laid in layers and
‘separated by spaces of 2 to 4 inches give a coarse bed effluent
} from which the solids have practically been removed, and at
| the same time a working capacity equal to double that of the
Lap? F. of Preventive Medicine, July, 1905; F. Soc. Chem, Ind., May 15, 1906; also
, somerville, Public Health, September, 1904.
236 SEWAGE AND ITS PURIFICATION
ordinary coarse bed. The cost of slate beds is from 6s. to Ios.
per square yard. Cost per “‘ efficiency yard” 3s. to 5s. A bed
at Devizes has been working eighteen months, with an abnor-
mally heavy sewage, unscreened and unsettled, followed by
a fine bed. Although the raw sewage frequently contains
200 grains of suspended matter per gallon, and the fillings are
two or three times daily, the capacity has never been reduced
below 50 per cent.; then by opening the valve to full bore it
was flushed to 64 per cent. More thorough flushing increased
it to the original capacity, 82 per cent. of the cubic content.
Thus he finds no necessity for removing or renewal of contact
material, while the size of the beds need be only half that —
of coke coarse beds. The deposit on the slates contained
3,000,000,000 bacteria per c.c.
The Ames-Crosta Co. make a special form of tiles for floors
of filters, which are easily set, and allow free and uniform
passage of liquid and air.
In the northern: portion of the United States, where the
severe winter weather interferes seriously with most of the
distributing devices, experience at Madison, Wisconsin, and
other places has shown that success may follow the application
of sewage to filters by means of lines of perforated tile pipes
laid close together, and covered to protect them from frost.
We revert to the processes depending mainly on strong
aeration, of which the chief are Lowcock’s, Waring’s, and
Ducat’s. In Chapter V., p. 121, we have given a table of the
volumes of air required to oxidize the mitrogen of organic
matter: a further quantity would be demanded by the car-
bonaceous matters, measured approximately by the ‘“ oxygen-
consumed’”’ figure. It has been shown how in an effluent that
has properly passed through all the stages, the residual organic
carbon can be disposed of by the nitrates, in presence of the
appropriate organism; but that for an imperfectly hydrolysed
effluent, and still more for a raw sewage, a large volume of air
is required, and the action is apt to be slow, irregular, and
incomplete. This is well seen from experiments! in which
Dr. Fowler exposed a chemically precipitated effluent (lime and
copperas) to the air in thin layers, protected from dust, for
various periods and under different conditions. In no case
was sufficient oxidation effected in twenty-four hours to render
the effluent subsequently non-putrefactive. Even after seventy-
1 Manchester City Surveyor’s Report for 1897.
GR
+ ingles
BACTERIAL PURIFICATION
two hours’ exposure pu-
trefaction took place on
afterwards incubating.1
In 1892 investigations
were begun at Lawrence,
Mass., with the artificial
aeration of coarse gravel
filters to which sewage at
relatively high rates was
applied, with a view of
purifying it partly so that
final purification could
take place rapidly in a
second filter of sand,
cinders, or coke. Air was
drawn through either up-
wards or downwards, but
in all cases these filters
clogged in a manner which
indicated that this artificial
aeration, while beneficial
toa certain degree,was not
helpful in proportion to its
cost.
Mr. Lowcock, at Mal-
vern, in 1892, forced in air
at a mean pressure of
4% inches of water. He
used* a pressure varying
from 3°4 to 6 inches, but
bearing no relation to the
volume of liquid which
flowed continuously
_ through the bed. At Mal-
vern the filter was made
of sand and gravel (Fig. 22),
and later, at Wolverhamp-
ton, of sand and coke
breeze. The sewage had
been screencd and chemically
' See also Chapter V., p. 122.
COKE BREEZE
——
PASE .
ares ss
SAND AND GRAVEL
Saud
Course Jav/ecte
Dine Gravel & Dolomite Chippings %
Coarse Gravel
“
ELS Iavferakea Qin Piper
Sana a4 Co fee 1 ;
i Perforertied Avr Rpes
* Proc, Inst. C.E., 1893.
Fine Idnreexe
Chippirgs %
a
.7
=
oo
ae)
—
—
_
»
a
)
—
—
iw)
Gravee 72
bd -
’ »
7 =
a |
pan vs
» a
~
c >
8 oe
to) -
CS
9 + 9 '
237
SECTION OF Lowcock’s AERATED BACTERIAL FILTERS AT MALVERN AND WOLVERHAMPTON,
Fic, 22,
238 SEWAGE AND ITS PURIFICATION
precipitated and sedimented before entering the filters. ‘‘ The
quantity applied when the most satisfactory results were
obtained was at the rate of 263,780 gallons per acre per day, so
that at this rate the area required per 1,000,000 gallons of
effluent of the same impurity as that experimented upon would
be 3°8 acres. The dry-weather flow of the sewage experimented
upon is 16 gallons per head per day of the population, so that
the quantity treated at the most efficient rate is equal to that
from 16,486 persons per acre.”’
The results are stated in October, 1895, as follows in parts
per 100,000 :—
October 8, 1855 ae): ee Sa
Free ammonia .. ate 4°00 I*20 70
Albuminoid ammonia ... 0°35 0°07 80
Oxygen consumed sak ae 1°70 0°40 77
Nitrogen as nitrites and nitrates traces 2°68 —-
Chlorine ... ‘ 20°00 24°00 —
‘‘ Calculated on the sewage, the results of the whole treat-
ment, tank and filter, would be a reduction of considerably over
go per cent. The Wolverhampton sewage is a most difficult
one to deal with, as it contains a large quantity of manufac-
turers’ and acid waste.”’
In the Lowcock filters constructed at Tipton in 1896 the
sewage had also been: preliminarily treated’ with lime and
alumino-ferric in precipitating tanks. The filters were 33 feet
deep, with a bottom of coarse coke, a body of coke breeze, and
a top layer of fine broken limestone and sand. The outlets of
the filters were open, and air was forced in at a pressure of
4 inch of water, the rate of flow of the effluent being 240 gallons
per square yard per day.
A purification of the tank effluent of 75°7 per cent. calculated
on the organic ammonia, and 68°5 per cent. on the oxygen
absorbed, was obtained.!
On this filter Mr. Mansergh, in his report to the Baltimore
Sewage Commission, 1899, remarks:
‘It would seem that the supply of air into the filter enables the
bacteria to increase their activity, but the recent practice of resting
the filter for twelve hours each day tends to show that natural aeration
is necessary to the smooth working of the system. The original
1 See further Lowcock’s paper in Proc. Inst. Civ. Engineers, vol. cxv.
oe
- 9 om
BACTERIAL PURIFICATION 239
idea that the mechanical forcing of air into the filtering material
would enable the tank effluent to be applied continuously has been
modified by the adoption of the half-day intermittent working, and
this result tends to support the Dibdin process of alternate fillings.”
Waring’s System.—In 1894 a portion of the sewage of New-
port, R.I., was treated by this method of forced aeration, which
differs from Lowcock’s mainly in the separate treatment of the
sludge by means of “aerators.” The “combined” sewage of
this city became frequently mixed with sea water, the effect
being an increase of the suspended solids by precipitation of
soap and other matters, a result that has been noted in tidal
reaches, and has contributed to the formation of mud banks
and deposits. The lime and magnesia in ordinary waters do
not seem to secure the removal of all the higher fatty acids, as
a greasy scum is seen frequently in sewers. I have found the
soda salts of oleic and other fatty acids in solution in sewage,
especially that of towns with a soft-water supply, owing prob-
ably to the influence of the ammonia formed. These soluble
soaps are decomposed and precipitated by the high amount of
calcium and magnesium salts existing in salt water, so that the
sewage of Newport contained unusual amounts of soap curds.
The sewage, after passing through a grit chamber, was
pumped alternately through either side of a divided tank con-
taining a shallow bed of broken stone to arrest the coarser
solids. ‘‘ The impurities in the section thrown out of use dis-
appeared rapidly in its interval of rest.” The liquid next passed
slowly through four straining tanks filled with stones and
gravel, whose function was said to be “‘mere mechanical
sedimentation.’”’ As soon as these became clogged a plug was
drawn, and the sludge emptied into a separate ‘‘ aerating tank,”
filled with stones and gravel, where air was driven constantly
through the mass, and as soon as active bacterial action had
set in, the sludge was rapidly dissolved. Air was also forced
through the straining tank till it was again in condition for use.
This complex system is another instance of continuous working,
assisted by forced aeration for long periods in the hope that in
a given tank capacity a larger volume of sewage could be treated.
The action here is apparently entirely aerobic, and unaccom-
panied by previous hydrolysis, except what would have happened
in the sewers.
Several alterations have been made in the details, and instal-
lations have been constructed at Willow Grove Park, Philadel-
240 SEWAGE AND ITS PURIFICATION
phia, at East Cleveland, Ohio, and at other places in the States.
The roughing filters are masonry tanks filled to a depth of
2} feet with Bessemer slag ‘‘ about egg-coal size.” The total
area of the strainers (four down-flow and two up-flow beds) is
3,630 square feet, designed to receive 150,000 gallons of sewage
per day. The aerators are 6,248 square feet, and the rate of
application to them is 1,000,000 gallons per day of strained
sewage, or 661,000 gallons per day on the total area. The
bottom of the aerators is a false floor of half-round drain-pipes
through which the air is forced. Nineteen other installations
were also designed, but little is now heard of the method.
At East Cleveland Dr. A. Smith reported ‘‘a reduction in
the ammonias of 98°8 per cent., in the bacteria of gg per cent.,
by double filtration through slag and coke, with aeration under
light pressure by a blower.”
Ducat Filter.—Colonel Ducat constructed an aerating filter
with walls of 3-inch drain-pipes set nearly horizontally in
Portland cement, the inner ends being 3 inches lower than the
outer, to prevent the sewage running out. The free exposure
to air causes considerable cooling, rendering necessary a special
provision by larger pipes for hot-water heating in winter to
prevent freezing. It was first tried on crude sewage in 1808 at
Hendon, but a large quantity of ammonia was carried off by
the air without being ‘nitrified, and sludge collected in the
sewer before treatment. Satisfactory continuous working was
based on an ample provision of oxygen. The bed was coarse-
grained above and fine below, and the action was intended to
be exclusively aerobic, as atmospheric oxygen in excess was
brought in contact with the contents at once without giving
any period of anaerobic incubation, as in a part of the Waring
process. I have already observed that in towns with long and
old sewers, or where storage is practised, the liquids may have
already received sufficient hydrolytic resolution to be quite pre-
pared for such strong aeration. This is illustrated by an
analysis furnished by Dr. Houston :—
Oxygen Free | Albuminoid | Oxidized
absorbed. Ammonia. | Ammonia. Nitrogen.
Sewage, October 14, 1898 aii 14°72 8°7 | 316 --
Filter effluent, ditto vis ces 0°78 0°3 0'094 0°477
= eee
“ ere ate a" Pas
be pee ie 4 :
WZ ee 77 lee
aa —— 2
“LD MEN IM AN NRE ponperiesiepaaies
OMG Ch Bin, oa ‘é E feds 2 o- Vy Sarees
CNY N , Oo —
| 7 [a
3 ao WR ISN
Wert Oe ae
AT, TTR
A, Sewage inlet; B, C, Grit chamber and Sump; D, Cultivation tank; E,
grating ; F, G, underspace; H, Outlets to channel J; K, L, valves; M, N,
Tippers; P, Nitrifying trays; Q, exit.
Fic, 29.—ASHTEAD CULTIVATION BED AND ZONAL TRAY FILTERS,
By using a series of smaller, separate areas, and passing the
effluent continuously and progressively through them, with
ample opportunity for the access of the air where it is required,
BACTERIAL PURIFICATION 269
the organisms gradually chose their own conditions, and allied
groups gather together at different levels as coatings on the
filtering material. The advantage of separating the organisms
appeared early from a remark of Jordan and Richards, in the
Massachusetts Report of 1890 (1i., 877), that ‘‘in the filter-
tanks at the Lawrence Experiment Station, speedy nitrification
was always coincident with a marked decline in the numbers of
bacteria. The more complete the nitrification, the fewer were
the bacteria in the effluent.” In the latter sections the nitrify-
ing organisms should be almost alone, and therefore able to
exert their full activity. In this way Moncrieff secured a much
higher nitrification than was obtained by the other processes.
This he has accomplished by spreading the “‘ tank effluent ”’
by tipping troughs or distributors over the uppermost of a series
of “nitrifying trays.” (See Fig. 29.) . In experiments at Ash-
tead with a domestic sewage, nine perforated trays, each having
an effective area of I square foot and containing 7 inches of coke
broken to 1 inch in diameter, were supported vertically over
one another at about three inches apart. It required only from
eight to ten minutes for the liquid to pass through all the trays.
In 1898, after the apparatus had been running continuously for
three months at a flow equal to one million gallons per acre
per 24 hours, I collected on two occasions samples from the
different trays and examined them separately.
The results of these analyses of the tank effluent and final
filtrate from the ninth tray are given in the table :—
PARTS PER 100,000.
I II | III
° 9 ° | 9 oO | 9
Chlorine ‘es | 9°0 7°5 6°3 64 5°5 5°5
Ammonia tok bes II‘5 0°25 4°25 0°755 4°0 0°42
Albuminoid ammonia... I'5 0°60 2°93 0°475 1°472 0°107
Nitric nitrogen... tds O12 fe hze) none 5°98 none 4°34
Nitrous nitrogen aie none | slight | none 0'06 none 0°034
trace
Total unoxidised N ... 12°35 0°60 6°60 I‘I2 5°35 0'148
Organic N tas he 2°05 0°394 3°10 0'50 2°06 O'113
Total nitrogen ... ‘ee 12°47 2°60 6°60 7°16 5°35 4°522
Oxygen consumed ... 9°84 0°589 9°05 0°608 7°52 0°632
270 SEWAGE AND ITS PURIFICATION
PERCENTAGE PURIFICATION.
ai org. Ill. - Average.
(1) Oxygen consumed bie tes 94 93°3 91°6 93
(2) Oxidation of nitrogen ae 93°7 84°3 96°7 g1°6
The intermediate stages of the first sample are expressed in
the curve (Fig. 30), in which the horizontal figures indicate the
trays and the vertical ones the parts of nitrogen. We notice
that :—
ee ee ee wae --
Total Nees Ths Pee eee
=
iS)
1h
14
Total,
Inorganic N NITROGEN| LosT| IN
YN
MX KK
iC NITROGEN
3
4
1
ae
Total Oxidize
Witrous Nitrogen, : 1 2 3 4 5 6 7 3 9
©
Fic, 30.—CHANGES OF NITROGEN IN OxIDIzING TRAYS.
BACTERIAL PURIFICATION 271
1. The nitrate has developed with extraordinary rapidity.
2. The formation of nitrite is much less marked; it rapidly
reaches a maximum and then declines.
3. The free ammonia has been almost completely oxidized ;
at the same time it was noticed that the original yellowish
colour, black suspended matter and sewage odour had dis-
appeared.’
The following figures give the oxygen relations which I found
for the first and last trays :—
PARTS PER 100,000.
| Dissolved ,Oxygen consumed
| Oxygen, c.c. per by Organic Available Oxygen.
| Litre. Matter.
January 28: |
Original vr — 9°54 minus 9°54
Last tray — 0°39 plus 20°!
February 8: |
Original ne ts hens oO 9'05 minus 9°05
Last tray ‘ Hy a 6°34 0°44 plus 12°99
| |
The organic matter therefore had been very rapidly reduced,
and the effluent was in a state of active natural purification by
means of its available oxygen. When allowed to stand, the
oxygen of the nitrate is utilized for the burning up of organic
matter, provided the latter has been properly fermented as in this
case, and the effluent can be finally purified by a denitrifying
bed.
In the trays described above the quantity of available oxygen
is obviously far greater than would be supplied by any process
of mere aeration, hence such an effluent can be easily ‘“ finished ”’
by a fine filter without fouling the latter, or can be beneficially
applied to a small area of land, or mixed with a river of moderate
volume not only without pollution, but possibly with an actual
benefit to the stream.
The principle of dividing the bacteria into separate zones,
where each class can naturally choose its own habitat and work
successively to others, is paralleled by the rotation of crops. Of
the antagonism and symbiosis of bacteria we have already
spoken in Chapter V.
1 It is stated that ‘‘ by transposing the trays so as to upset the natural survival
of organisms in the sequence, the whole process was arrested, a high-coloured
and inferior effluent being the result, and one or two days were required to
re-establish the conditions that had been disturbed.”
272 SEWAGE AND ITS PURIFICATION
Sims Woodhead proved that in coke-breeze upward filters at
Claybury, in the deeper parts of the filters anaerobic organisms
were more numerous, with high ammonia; while near the sur-
face aerobic organisms prevailed and nitrates were predominant.
From other experiments he recognised ‘“‘ that there was a sharp
line of distinction between the work done by the anaerobe, and
that by the aerobe, and that the two processes should be kept
as separate as possible.” In these filters, natural working had
established separate zones for the two operations, but being too
close in one apparatus, they were liable to vary and intrude on
one another, and a smell was sometimes present.
Installations on Scott-Moncrieff’s principle have been work-
ing in many places in South Africa, where frost does not present
any difficulty by retarding the work of the organisms. In cold
countries a slight protection seems to be sufficient. At Cater-
ham Barracks, England, works were constructed for the War
Office, in 1898, to deal on the Moncrieff system with about
16,000 gallons daily of an exceptionally strong sewage.
In 1899, I collected and examined samples representing two
cycles of 24 hours, when the filter was producing effluent at an
average rate of 340,000 gallons per acre. The average results
were :—
Raw Sewage. Tank Effluent. | Finished Effluent.
Chlorine ... roe ces ii 15‘I 14°8 13°3
Oconsumed ... oh he 14°97 9°25 2°71
Nitrous nitrogen cu es trace trace 0°346
Nitric nitrogen .., af pls — —— 9'0
Organic nitrogen a ma 4°0 yy 0°67
Ammoniacal nitrogen ... ais 13‘2 14°9 50
Total nitrogen ... a Fe 17'2 17°6 15°02
The percentage purification was :—
Caneicks Organic Nitrogen.
Raw sewage to tank effluent Ki Lie “es 40 32°5
r ,, to finished effluent ... re se 82 33
Subsequently on my suggestion two denitrifying tanks were
placed after the nitrifying filter. These tanks receive the over-
flow from the hydrolytic tank, together with the nitrated
effluent, and in this way the oxidizing filters can work to their
Crepe pa. Sen OE wrt
TODO OE OE
SH Sye a bs aed
am a ee eee
SO PREIS TE
BACTERIAL PURIFICATION 273.
best advantage, the purification of the effluent being completed
by denitrification of the mixed liquids.
THE MANCHESTER EXPERIMENTS.
The disposal of the sewage of 564,000 inhabitants, with much
manufacturing refuse, has been a difficult problem, which has been
carefully investigated. Formerly it was treated at Davyhulme
on the London plan of screening, adding milk of lime, then
ferrous sulphate, sedimentation, and discharge of the clarified or
filtered liquid into the Ship Canal, while the sludge was stored
in two tanks, holding 1,000 tons each, thence flowing at intervals
into a sludge steamer which carried it to sea. Pollution of the
Canal led to interference from the Mersey and Irwell Joint
Committee, and to the necessity of the adoption of some other
system. The Manchester Corporation in 1898 instructed
Baldwin Latham, Percy Frankland, and W. H. Perkin, to
examine into the merits of various processes, following a report
of the Rivers Committee :—
1. ‘ That filtration by land is altogether impracticable, as no
land obtainable in the district is suitable for such process,” as
proved by the experiments which, at great cost, had been made
upon 25 acres of land at the works. Visits to the works of
other authorities had shown that ‘‘in all cases the land filtra-
tion is ineffective, and is, in many cases, to be superseded by
artificial methods of filtration. The imposition of conditions
by the Local Government Board, making the purchase of large
areas of land compulsory, should be removed.” }
2. ‘‘ That no practicable system of precipitation by chemicals
alone has been laid before them which will meet the require-
ments of the Mersey and Irwell Joint Committee.” [The
experiments had been very elaborate, and are detailed in the
City Reports of 1897 and of previous years. |
3. They agreed that the method nearest to natural action and
“most reasonably practicable and reasonable for adoption ”’
was the biological filter or bacteria bed, such as had been seen
in operation at various places.
The land available at Davyhulme for all disposal purposes is
1653 acres, and the three experts soon concluded that this area
was ample for the necessary works to purify the sewage includ-
ing storm-water—the works existing at the time occupied
273 acres. They pronounced adversely on the alternative pro-
posals of treatment of a tank effluent on land, and the Culvert
18
274 SEWAGE AND ITS PURIFICATION
scheme for conveyance of the present effluent through a tunnel
to the tidal part of the Mersey.
The experimental plant of 1899 consisted of three independent
sections.
I. Five ‘‘ Bacteria Beds,” with sloping sides,* filled with 3 ft.
of clinker of the following sizes:.A, 3 in. to I in.; B, I in. to
tin.; C, # in. to} in.; D and E (extra bed), 4 in. to 4 in.
Distribution by perforated wooden troughs, collection by drain
pipes below. Area of A to Dj, acre. A and B were started
with settled sewage in September, 1898, run on at first once,
then twice, and finally three times a day. A month later raw
sewage, screened through a grid, was applied at a rate of four fill-
ings per day, each cycle including: filling = hour, resting full
2 hours, emptying ? hour, resting empty 24 hours. After a
week the surface of bed A showed signs of clogging, so settled
sewage was again used. Subsequently the time of filling A was
shortened + hour, and of emptying to 3 hour, to give a longer
period of rest, and also because it was thought that by “‘ rush-
ing’? sewage on to the filter a larger amount of air would be
entangled with it. The result would belong to the partially
aerobic class, but with as much as possible avoidance of suspended
solids. Samples were taken at short intervals and mixed for
analyses. Beds C and D were first used together, being filled
twice a day wth settled sewage, with }-hour filling and two hours
contact. As A was too coarse, it was changed to #” to }” mesh.
II. Septic Tank System.—Concrete tank 40 x 12 ft., with
arched roof g ft. high, and air-tight manholes; rest of construc-
tion as at Exeter. Six filter-beds with vertical concrete walls;
total area I96 sq. yds., and depth 4 ft., containing from the
bottom upwards—1 ft. clinker between 3 in. and I in. mesh:
2 ft. g in. clinker between ? in. and } in. mesh: 3 in. residue
from above, passing at 4 in. mesh.
Raw unscreened sewage was passed through, but not so
regularly as at Exeter.
III. Two Roscoe Filters, first used in December, 1895, were
12 ft. 6 in. by 18 ft., or 25 sq. yds., with 3 ft. of rough clinker,
graded coke or cinders, and a covering of 1 ft. of clean gravel.
They were worked like the bacteria beds, but with chemically
precipitated effluent.
1 Sloping sides obviously give greater surface and aeration at a sacrifice of
capacity which can be calculated from the angle of inclination of the sides,
Hence the adoption of this shape, lately recommended, would largely increase
area, and would only be justified by increased efficiency, on which further experi-
ments are needed,
BACTERIAL PURIFICATION 275
It became evident that the main difficulties with contact beds
were due to their being used chiefly as simple strainers, and
that a previous preparation of the sewage was necessary.
Except with the septic tank, this had taken the form of screen-
ing, sedimentation, or precipitation.
The enquiry included a comparison between a closed and an
open septictank. For the latter one of the large precipitation
tanks at Davyhulme was used, raw sewage being allowed to flow
over the end sill in a very thin stream, passing through the tank
almost continuously at a rate of 1,700,000 gallons per 24 hours.
Similar phenomena to those at Exeter are described, the liquid
becoming covered with a scum which excluded the air, while
‘‘up to the present time the only notable quantity of sludge
which can be perceived. . . . is immediately beneath the inlet
penstocks. ... An enormous quantity of the sludge which
would otherwise accumulate has been destroyed in this way.”
The effluents from both closed and open tanks are shown to
be closely similar.!
With reference to the question of closed or open septic tanks,
I may remark that some of the advantages of the former are
that the gases can be utilized and all smell avoided, that the
temperature is more even, and interference from frost or wind
is prevented.2, At the same time it was found at Manchester
that the outfall sewage was 10° F. warmer than the temperature
of the air.
The deposit from this open septic tank in April, rgoo, con-
tained organic matter 5°24, inorganic 6°78, water 87°98 per cent. ;
or in the solids, 57 per cent. inorganic matter and 43 per cent.
organic. The sludge of the chemical precipitating tank was
much more prone to putrefactive decomposition than that of
the septic tank.
It was agreed that in the management of contact beds :—
! In an enquiry at Yeovil, in March, rgo0o, the balance of opinion was that in
the case of a strong sewage a closed tank is necessary. Open septic tanks are
now often called ‘‘scum tanks.’’ Drs. Kenwood and Butler state (Sanitary
Institute, April. 1901) that in the Willesden and Finchley scum tank the sludge
maintains a fairly uniform bulk, and certainly does not accumulate sufficiently to
require removal for many months, and that at Acton after a year’s working the
deposit averages only a few inches with a spongy scum 8 to 10 inches deep. The
albuminoid ammonia is reduced 4o per cent., the sludge contains 78 per cent. of
non-volatile matter, while the scum contains 39 per cent. The deposited sludge
can be removed with little offence, and at Finchley has been spread over small
areas of land, with no offence, even in the immediate neighbourhood.
2 Mr. Barbour states that at Saratoga, in the winter of 1903-4, the scum froze
to a depth of 4 in, under the concrete groined roof covered with 18 in. of soil ;
‘‘ what would have happened if the tanks had been uncovered is a question worth
considering.’’—Tyrans. Am. Soc. C.E., LIV., part E, 1905,
18—2
276 SEWAGE AND ITS PURIFICATION
1. The suspended matter must be previously removed by
sedimentation ;
2. If any passes over it must be retained as far as possible on
the surface of the bed ; '
3. The surface of the bed must be raked over from time to
time.
4. Periodical intervals of rest must be allowed.
Professor Boyce found in 1900: in the effluent from the first
contact bed 331,700 bacteria and 1,420 coli per c.c.; from final
(second) contact 115,100 bacteria and 329 coli. The Ship
Canal contained some 6,000 coli per c.c. above the sewage
outfall.
The closed tank and single contact gave an effluent which
‘‘ senerally resisted putrefaction in the incubator test, in conse-
quence of its containing a comparatively high proportion of
nitrate.” The effluent from the open tank was passed through
the beds C and D, and by the “ double contact ” a better result
was naturally obtained. ‘‘ With four fillings per day, every
sample was non-putrescible, and well within the limit of im-
purity.” In other instances where the Mersey and Irwell Joint
Committee’s standard (1 grn. per gal. of O absorbed in four
hours, and o'r grain albuminoid NH;) was infringed, it was
shown to be due to trade refuse, ‘“‘ which, being non-putrescible,
does not cause nuisance in the Ship Canal.” ‘The object of
purification is primarily the production. of an effluent free from
putrescibility, and not one in which the chemical ingredients
are below some necessarily more or less arbitrary standard.”
(See Chapter III., p. 56; Chapter V., p. 130.)
The report confirmed previous observations by Adeney (Proc.
R. Soc. Dublin, September, 1895), myself (J. San. Inst., vol. xviii.,
part i., 1896), Fowler (summer of 1896), Scott-Moncrieff (patent
4994 of 1898), and others, as to the utility of mixing a nitrated
effluent from a “second contact” bed with that from a first,
whereby a liquid was obtained which satisfied the incubator
test, so that “ only one-fifth of the filter acreage need be at a
low level,’ and the area of the second contact beds could be
considerably reduced. I had also before suggested the intro-
duction of a portion of the nitrated effluent into the septic tank
itself, as the denitrification change which takes place on mixing
is due to the reaction between the nitrates and the organic
matter, and could be induced earlier in the process as soon as
the organic matter is in a soluble reacting condition, while it is
a
a a ee ee
SAPS are
Se See ee
BACTERIAL PURIFICATION 277
more economically conducted in a tank which is continuously
full, than in a filter bed constructed for aeration. Nitrification
is usually most energetic in liquids in which the organic matters,
especially carbohydrates,!: are a minimum, and therefore a
denitrification change effected during the anaerobic preliminary
stage, by reducing the oxygen-consumed figure to a greater
extent than would be the case if the change were only due to
hydrolysis, yields an effluent which contains its nitrogen in the
most available form for the changes of which nitrification is the
final result. Thus, for example, a hydrolysed effluent with, say
an oxygen-consumed figure of 3, and unoxidized nitrogen
10 parts, on passing through the filters often yields not more
than 3 parts of nitric N; if, however, a portion of this liquid be
returned to the tank, it will so reduce the O consumed figures,
as to allow the nitrification to approximate to the theoretical
amount. ,
The Report of the experts finally recommended that the
sewage be submitted to an efficient process of screening (or to
roughing tanks), then passed through open tanks with sub-
merged walls and floating scum-boards, and afterwards over
60 acres of double-contact beds 3°33 ft. deep, with four fillings
per 24 hours. As the dry-weather flow was 30 million gallons,
the filters dealt with half a million gallons per acre, allowing
one day per week rest. The open tanks were to hold 15 million
gallons, and would therefore change their fluid contents in dry
weather every twelve hours.’
As to storm-water it. was found that there was even a
greater amount of oxidizable matter in the first flush than in
ordinary sewage. They advise that the storm-flow should be
dealt with in the same system, and the excess, after passing
through roughing tanks, should be taken to specially-prepared
bacteria beds of at least 25 acres area. No decrease in efficiency
was noticed after the storm had passed.’
The Local Government Board decided that a larger area of
land must be purchased, “‘ over or through which the sewage
after it had left the bacteria beds should pass,” also (Oct. 4,
1899) ‘‘that not less than g2 acres of filter beds shall be pro-
vided for the treatment of sewage by double contact; and that
the filter beds be worked in cycles with the usual provisions as
1 R. Warington, ¥. Chem. Soc., May, 1900.
2 Report Manchester Rivers Committee, Jan. 22, 1900.
3 A critical analysis of the Manchester experiments, by Boyce and McGowan,
is given in the 2nd Report of the R. Sewage Commission, 1902.
278 SEWAGE AND ITS PURIFICATION
to storm-water’’ (Chapter VI., p. 148). These requirements
were unnecessarily onerous, and in a later report of Dec.,
1899, the experts confirm their estimate of 60 acres, and state
that by “‘ preliminary septic sedimentation ” they have obtained
an improved effluent, also that they work most successfully with
6 hour cycles 6 days per week, but that the exact length of the
cycle must vary according to the nature of the sewage. Con-
tinuous incubation experiments showed that the effluent im-
proved the water of the Ship Canal, that by subsequent land
filtration the effluent was actually deteriorated, and that there-
fore the land clauses were superfluous. The engineer reported
(Sept., 1900) that the experts’ scheme would cost £337,000,
the culvert plan £350,000. The L.G.B. consented to a modi-
fication as follows: (a) 46 acres of primary filters at Davy-
hulme; (b) 46 acres of secondary beds at Carrington (which
involved the purchase of 213 more acres of land), the primary
effluent being conveyed to the secondary beds by means of a
culvert ; (c) special storm-filters at Davyhulme for the treat-
ment of excess storm-water (say 63,000,000 gallons per diem) at
arate not exceeding 500 gallons per square yard per diem. Cost
£487,000, finally accepted by the Manchester Council.
Chemical treatment was entirely discontinued in Aug., 1904,
and the works now deal by bacterial methcds with the whole
sewage, averaging 30 to 35 million gals. per day, or 52-62 gals.
per head: daily water supply 29 gals. per head, rainfall 26-34 in.
The sewage passes through screens and catch-pits with sub-
merged walls, scum boards and outlet sills, into open septic
tanks, and then on to the half-acre bacteria beds; or in exces-
sive rains it flows, after simple sedimentation, on to the 26°8
acres of storm beds. The latter beds sometimes require forking
over to a depth of 4 or 5 inches. By opening each of the valves
in turn for a short time, as much as 200 tons of sludge contain-
ing 877 of water can be removed from a septic tank without
running off the top water. In 1904 and 1905 the sludge removed
averaged per million gals. of sewage 83 tons containing 857/
water, as distinguished from over 18 tons per million, contain-
ing 887 water, during the former chemical treatment. The
suspended matter passing away from the bacteria beds has
somewhat increased, averaging 5 parts per 100,000, and
secondary beds are being constructed.’ |
1 For further details see the annual reports of the Rivers Department, City of
Manchester,
» s
Sih ts te
a.
—
BACTERIAL PURIFICATION 279
The plant and working at Manchester still admit of improve-
ment. The sewage is a difficult one to deal with, but is not
worse than that of other centres which have met with better
success. The resolution of solids in the septic tank, estimated
as from 25 to 30/, is lower than at other places owing,
as is implied in the reports,’ to the irregularity and frequent
disturbance in operating. The mode of distribution on the
beds by radiating troughs on the surface is not a good one, and
as to the unsuccessful trials with sprinklers, the report of 1903
itself says (p. 29) ‘it is difficult to draw trustworthy conclu-
sions from comparative experiments made in this manner.”
At Birmingham, since the abandonment of the lime process
(ante, p. 155) in 1900, the plant has been used for a modified
septic treatment. In 1go02 out of 244 million gals. of sewage
per day only 3 million gals. were domestic, the remainder being ©
chiefly trade effluents, into which sulphuric, hydrochloric and
nitric acids and salts of heavy metals had passed. It was
noticed that the nitrates disappeared in the sewage in hot
weather. The flow is received into three large tanks, each
divided into three parts by submerged walls rising to within
2 ft. of the surface. The first chamber retains the heavier
detritus, the other two arrest the bulk of the residual suspended
matter,and are used alternately and cleaned out once a fortnight.
The sewage passes on to 16 smaller septic tanks, where it stays
8 hours, and finally is distributed over land at an average rate
of 15,000 gallons per acre per day. It is reported that ‘‘ an
enormous quantity of gas escapes from the septic tank, result-
ing in a loss of about 8 per cent. of the solid matter which
enters these tanks,” that the suspended solids are very much
altered in quality, and that the sulphides developed precipitate
most of the heavy metals in solution. The effluent ‘‘is not
merely harmless, but has considerable manurial properties ; for
in grass land irrigated by it the path of the water may be traced
by the increased vigour of the herbage.’? An important point
is that ‘“‘the enormous fall in liquid sludge’’— from 281,000
cub. yds. for 20,000,000 gallons daily dry-weather flow in 1896,
to 128,000 cub. yds. for 21,500,000 gallons in 1g01—“‘ is largely
due to the cessation of the use of lime and adoption of septic
treatment.’”’ With regard to organic improvement the analyses
given show that the arrangement of the tanks should be different.
1 Manchester Rivers Department, 1903, p. 20; 1904, p. 17.
2 F. Soc. Chem, Industry, May 31, 1902.
280 SEWAGE AND ITS PURIFICATION
The septic tank is too small, and the ‘‘roughing tank” too
large.’
At Sheffield (population about 400,000, average dry-weather
sewage 17°3 million gals. per day, water supply per head 21°89
gals.; hence the sewage contains much surface water), the local
Act of 1900 allowed a scheme without land treatment, to
include open septic tanks, 11 million gals. capacity, 32 acres
of coarse-bed filters, 33 acres of fine-bed filters, and a small
area of storm filters. Following the satisfactory results from
continuous filters at Leeds, the Sheffield Council began experi-
ments on their use instead of double contact, as the Leeds
experiments showed that it would be possible to replace the
65 acres of double contact beds by about 17 acres for continuous
filters.
At Leeds? the first open septic tank had an area of 6,000
sq. ft. and a capacity of 250,000 gallons, or 24 hours’ flow,
which proved to be the best rate of transit. The advantages
found were: ‘‘(1) The production ofa practically uniform effluent
from sewage of such varying composition as that of Leeds:
(2) the digestion of part of the solids in suspension, amounting
at Leeds to 40 per cent.: (3) the anaerobic putrefaction which
takes place facilitates subsequent filtration, rendering the filtrate
less liable to secondary putrefaction.”” As at Manchester, the
results with open and closed tanks were practically identical,
the scum itself soon giving a cheap roof and preserving the heat,
which averaged only 0°8° F. less in the open than in the closed.
It was recommended that the tanks should be in series, the
first being in duplicate so as to be emptied from time to time.
The gas produced did not occasion nuisance.
Continuous filtration of septic effluent over very coarse matertal,*
spreading the liquid like rain over coke of not less than 1} in.
diameter, well aerated at the bottom and sides, gave, in so short
a time as the 15 minutes required to pass through the bed, better
results than double contact, if the solids in suspension which
pass through are afterwards settled. These solids are largely
mineral, non-putrescible, subside easily, and the drying does not
give rise to evil odours, while it would seem that their coming
through ensures the permanence of the beds. It was found
practicable, for long periods, to work continuous beds 1o ft.
1 Vide the author’s remarks in the discussion of the above report, ibid., p, 669.
2 City Report, 1900.
3 See evidence R. Comm, on Sewage, vol. ii., 1902, questions 7258 and 8232.
4 Chapter X , p. 246
PA ak ee ae a et
ee
BIST LS PI E ES
ne
‘BACTERIAL PURIFICATION 281
deep at the rate of 200 gals. per square yard, or 1 million gals.
per acre per day for septic effluent, with over go/ purification
after settlement, the beds being occasionally washed out by
storm-water.
American experience has been that, working with preliminary
septic treatment, contact filters are able to produce a non-putres-
cible effluent at rates several times as great as intermittent sand
filters, and sprinkling filters can produce corresponding results
even with much higher rates. The latter give a better oppor-
tunity for oxidation, and the films deposited on the filtering |
material become detached from time to time and pass off with
the effluent. Contact filters are generally more expensive in
working than the sprinkler type with settling basins: the
effluent from the latter contains only from 3 to 5/ of the
bacteria in the crude sewage, and in most cases requires no
further treatment before discharge.
CHAPTER XII
DISTRIBUTION AND DISTRIBUTORS
Intermittent — Continuous — Stationary Sprayers— Moving Distri-
butors—Tippers—Testing Apparatus.
CHOICE of methods in great part depends on the character of
the site, as in many places the sewage has to be raised by
pumps, lifts, or ejectors, and the problem becomes an engineering
one. A really anaerobic treatment in the first stage, like
Cameron’s or Moncrieff’s, requires no fall, the sewage simply
flowing in below and flowing out above. With terraced beds
fed from the top, the fall to be provided includes the sum of the
depths of the beds and of the distributing apparatus: increasing
the depth of material may economize surface area, but adds to
the expense of raising. |
Ordinarily, the sewage, owing to its fluctuations, has to be
controlled by penstocks and valves at the entrance and exit. A
restraint at the entrance involves storage. ‘‘ Holding up” is
temporarily closing the outlet valve so that the filter fills with
fluid. In the Lowcock filter and others, the entrance is con-
trolled and the outlet always open. Variation in flow occasions
great difficulty where the admission is direct to bacteria beds,
but in septic tanks of sufficient capacity the irregularity is ‘not
felt. In any case, the flow of sewage can be regulated by means
of “‘ modules.” .The first module, introduced in Piedmont, for
the purpose of giving a uniform discharge of water out of a
main channel or canal, was a chamber commanded by a sluice,
and with a square orifice of suitable size below. The sluice was
opened till the flowing water remained at a fixed level in the
chamber.
Such a module, though giving for the purpose a sufficiently
uniform flow, would not adjust itself except within narrow
limits. A great number of self-acting modules were used on
the Indian canals, especially one devised by Lunt Jarrols. In
the Piedmont form a free fall is a necessity, but with self-adjust-
ing modules this is not required, those at Barrhead (Fig. 58,
282
DISTRIBUTION AND DISTRIBUTORS 283
Chap. XIII.) working with a difference of level of about an inch.
The arrangement consists of a module chamber having a circular
opening in the bottom ; through this opening is a body, conoidal
in shape, attached to a float. Asa head of liquid falls, so do the
float and cone, making the opening larger, and vice versd.
. DISTRIBUTORS.
A. In the intermittent or ‘‘ holding up” system the sewage has
to be applied at intervals to a number of beds. The chief auto-
matic apparatus for this purpose are the following :
FLAN
Fic, 32.—PLAN OF INTERMITTENT SUPPLY BY ADAMS’ SYPHON.
I. Adams’ Syphon (Adams’ Hydraulics Limited, York), also
| adapted to the continuous systems. In the intermittent form
_ (Figs. 31, 32) A is the inlet, B a scum or resolving tank, Ca
syphon feeding the first bed, coupled by air pipes with the
domes E and F. The sluice supplying the second bed is closed
while the first is filling from the feed C through the distributor G.
The feed apparatus is a plain trap-like casting through which
liquid passes freely from the source of supply to the bed to be
TE RIED
Sa a ———
a pe TS
284 SEWAGE AND ITS PURIFICATION
filled, until the air contained in its attached dome E is transferred
by the pressure of liquid around it, as the bed fills, through a
trapped air-pipe to the interior of the feed, creating an air-
lock, and blocking the further passage of liquid so that the
latter rises to a higher level in the source of supply until the
inlet sluice to the next bed is reached. Where an automatic
discharge is also used (Figs. 33, 34), the liquid contents of the
first bed will in the meantime have been discharged through
syphon M, and the overdraw pipe K attached. A tap L delivers
ioe fi helto
z= “4 7
a POL
ote,
~
PLAN
FIG, 34.—PLAN,
liquid to the syphon chamber, and the time occupied in the
filling of this chamber will be that for which the sewage is held
up on the bed in contact with the filtering material. The fact
that the feed and discharge apparatus are quite distinct, enables
users to fix any desired time of contact. The second bed thus
fills and its liquid in turn displaces air from dome R (Fig. 34) ;
thus air is transferred to the feed C, its added bulk forcing the
water seal, freeing the confined air, and again bringing on the
supply to the first bed. At N isa pipe dotted, through which
any accumulation in tank B may be drawn off by valve O.
As applied to continuous filters, the feed C discharging to
—
RS PI I a = = ie,
fT ILO
DISTRIBUTION AND DISTRIBUTORS 285
filter No. 1 gradually fills a receptacle into which dome E dips.
The taps supplying the inlet and outlet may be set so that the
receptacle fills in any given time, when, as in Fig. 31, the air
will be transferred to the feed C, causing an air lock which will
divert the sewage to the next feed or bed. ‘‘ With this apparatus
any desired area may be flooded for a given time, sewage being
sent to one area or bed after the other, regardless of the numbers
used or volumes dealt with, automatically and without move-
ment.”
II. Ridgway Automatic Distributor (Mather and Platt, Man-
chester). Screened or sedimented sewage is received into a
syphon chamber built to hold a given number of gallons
according to the average volume to be treated. When full, the
syphon discharges this amount into the ‘‘ Distributing Chamber.”
At the same time, a hollow cylindrical float, which has been
previously raised by the filling of the syphon chamber, descends
to the bottom, and by a pawl and rachet wheel causes a
horizontal shaft to revolve, and, by means of cams, to open or
close in succession a series of valves communicating with
different beds [patent 12287 of 1gor].
At Hale, near Manchester, Dr. Garstang reported in 1899
that this distributor was passing 72,000 gallons per day on to
180 sq. yds. of single contact beds (2 million gals. per acre per
diem), during a period of 10 months. He gives the following
average analyses:
PARTS PER 100,000. Per cent. Puri-
raid? 16 cata
O consumed. Free NH3. ANE :
Crude sewage (screened) 50 2°184 0°668 a
Effluent from bed ‘as I‘o 0'841 O°215 80
Final land effluent ss 0°43 0°668 0°126 92
It appears from the report that the effluent remains at the
bottom of the bed for two hours before being expelled by the
next succeeding charge. This involves an increase in the
capacity of the bed, and renders denitrification changes possible.
III. Cameron's Automatic Alternating Gear at Exeter has
been already mentioned (Chap. IX.). At Barrhead six of the
eight filters are in use at once, one being filled at a time. As
soon as a filter is full, the flow of tank effluent is automatically
286 SEWAGE AND ITS PURIFICATION
diverted to the next filter, and after a certain time, the contents
of the full filter are discharged by lines of drain pipe into a
‘stoneware main collector running into the discharge valve box.
Both the admission and discharge valves are suspended by valve
rods from a lever, which is pivoted on a bearing between the
admission valve chamber and the discharge well. At one end
of this lever is a counterweight, so adjusted as to hold the
admission valve open and the discharge valve down on its seat.
The gearing used later, while similar to that at Barrhead,
embodies several improvements, chiefly stated as follows:
1. The discharge well and admission valve chamber are
made in cast-iron and mounted on a bed plate of the same
material so as to be entirely independent of the walls.
2. The mechanical details of the gear have been greatly
sim plified.
3. Before each filter is filled, the tank effluent is held back |
for a period of from one to two hours, the quantity so
accumulated filling the filters in a much shorter time than if
it had been allowed to flow continuously.
This obviates Mansergh’s criticism of the automatic gear,
that the decreased flow in the night fills one filter so slowly
that the corresponding one in the resting-full stage remains
charged so long as to seriously interfere with its aerobic action.
The machinery works without loss of head, so that its employ-
ment does not increase the fall which the filters would require
if used without gear.
At Lake Forest, Illinois, and Wauwatosa, Wisconsin, the
apparatus used for dosing the sand filters consists of a float
which lifts a cannon ball in one of a set of hollow wooden columns
arranged in series; at a certain height the ball rolls through a
trough from one column to the next, its passage striking a catch
which opens an air-valve attached to one of a series of bell
syphons discharging in rotation on the sand filters.
Various forms of automatic gears are given in English patents
2647 of 1900; 5834, 10346 and 11368 of 1901; 9247 of Igoz.
We have seen that in the intermittent or holding-up system
the main work is done almost anaerobically in ‘‘ resting full,”’
and aerobically in “resting empty.” The filling drives out
carbonic acid and other gases formed by decomposition, the
emptying renews the air in the filter bed. The first and last
stages of the cycle can be shortened so as to leave more time
for the fermentations, but (1) the entrance must not be so rapid
Rk a ee le ee ea ial . 3
rN 9 aE eT CT TE a eee Oar oe
. E
05 Re Tae errs
DISTRIBUTION AND DISTRIBUTORS 287
as to disturb the filter, (2) for proper aeration the bed should be
run out completely after each discharge, (3) the opening of the
discharge valve should be gradual, so as to prevent any initial
rush of effluent, such as I have frequently found to render the
first runnings from these filters turbid and inferior.
B. In the Continuous System, it is of extreme importance
that the liquids should be'distributed uniformly over the material.
The cost of so doing. is only a small fraction of the total cost
of the material of a bed, and by attention to distribution the
amount of material required for dealing efficiently with a given
sewage may be reduced considerably.
The problem of spreading a liquid issuing from a narrow
channel evenly over a broad area is not a simple one. In
upward filtration it is easy; the liquid rising from the bottom
naturally distributes itself throughout the filter. But when
the introduction occurs from the top, there are considerable
mechanical difficulties. Where sand filtration is used, it is
chiefly necessary to protect the sand from disturbance by a
coarser heavy layer of flint or stones, to run the liquid on the
top, and trust to the evenness of the fine layer for equal dis-
tribution. The deficiency of aeration, and blocking of the beds,
are faults of this method when applied to sewage (see
Chapter IX.).
With aerating filters of open material, flushing the liquids,
however rapidly, from penstocks at the sides or in the middle,
leads to the formation of channels, and only a local use of the
filtering mass; therefore many arrangements for spreading the
fluid more equally have been devised. Networks of split pipes
or iron or wooden troughs are not satisfactory. Perforated
- pipes occasion trouble, through blocking by solid matters, there-
fore the ends have to be made with openings, so that the tubes
can be brushed through at intervals: the corrosion of the iron
by the chlorides and nitrates in the liquid also blocks up the
holes. In some cases the tubes have been made of gun-metal,
but this also is liable to corrosion, particularly along the lines
where it may have been joined or soldered. These difficulties,
however, have not prevented many of these contrivances from
being made to work well.
I. Stationary Sprayers.
(a) Mr. Stoddart, of Bristol, introduced a distributor depend-
ing on the dropping of the sewage from vertical points and not
288 SEWAGE AND ITS PURIFICATION
from holes. It consisted of a number of gutters arranged at
right angles to the supply channel, provided with a series of
points on their under surface, from which the overflowing
sewage or tank effluent fell in a series
of fine drops.
It is said to work with only three
inches of head, and to be unaffected by
accidents such as a discharge of sludge
4 ). or continued frost. Suspended matter
4 ¢ settling in the troughs of the distributor
3} is removed by a brush from time to
4 5 time.
: A later form of the Stoddart Con-
4} tinuous Sewage Filter is made in one
a 4 ¢ piece of corrugated iron sheeting fixed
ws 4) just clear of the surface of the filter bed
| J; and filled with septic effluent from
= jj transverse fixed troughs. The edges of
= ax 4; the corrugation are notched every few
= HN be eessnes 4) inches, and as the hollows fill up they
mi : Mee Syi8 3 / overflow through the notches and the
8 m tase sis j | sewage falls from points attached to
3 OSiscseen 4; the under surfaces of the hollows. In
is seeniee j ) this way, if the corrugated sheeting is
e Iyoseete 4; kept absolutely true and horizontal, a
= rages > 3) good and uniform distribution can be
- 41; effected. The difficulty is to keep the
4} ridges absolutely true and level and to
|; prevent inequalities due to changes of
4 | temperature, sinking of the supports,
4 { or displacement due to high winds.
The improvements are intended to
reduce these difficulties (Figs. 35 to 37).
Fig. 36 shows the triangular projections
on which the corrugated sheeting is sup-
ported (the inner surfaces only of the
ridges are carried), and Fig. 35 the
sheeting in position. The distributors
are constructed in sections of 2 sq. yds
each, so that any desired area can be built up. Mr. Stoddart
prefers to limit beds to 500 square yards. The cost of the
apparatus averages I5s. per section. An advantage peculiar
OGIO ART yen, 2h
DISTRIBUTION AND DISTRIBUTORS 289
to this type is that in the event of accident a section can be
removed for repair, but the whole bed is not thrown out of
action as in the case of a moving distributor. The Stoddart
apparatus seems to be working well ina number of small tn-
stallations, but owing to the extended exposed surface of the
septic sewage on the corrugated sheeting, precautions have
frequently to be taken to prevent smell or nuisance arising,
so that the filter bed is frequently covered over.
Fic. 37.—TROUGH SHEETING.
The following are types of upward jet sprayers. Obviously
this system of sewage fountains is not to be recommended in
exposed situations in the neighbourhood of dwellings where a
fine spray can be blown about to some distance, both on account
of aerial nuisance and the possibility of the distribution of
pathogenic organisms.
(b) Spraying: Nozzles at Salford Sewage Works. The
general arrangements have been described in Chap. X. The
_ nozzles are fixed on the gridiron of pipes, and work with a
head of 3 or 4 feet, but there is commonly sufficient pressure to
cause the liquid to spout out to a height of 5 to 8 ft., and it then
falls like rain on the surface of the filter. The delivery is about
19
290 SEWAGE AND ITS PURIFICATION .
500 gals. per sq. yd., to be increased when necessary to 1,000 gals.
The total dry weather flow to be treated in this way will be
8 million gals.
The nozzles used in the earlier experiments were in*the form
of a jet playing against a disc or cone, “‘ but these only threw a
ring of water, not an area.’ Afterwards the ‘‘ Simplex Sprayer ”’
(Gjers and Harrison’s patent) was employed: it has two impinging
jets like the fishtail gas burner, and throws a “‘ very even spray
over an oval area, and so suits our spacing of 5 to 10 ft.”* The
later used type is more complicated, and “throws an even
Fic. 38.—‘' AcME’’ FIxED SpRays,
circular area of spray”: it has six holes in the base disc,
bored obliquely like a Bie so as to set the water sant as
it passes out.
(c) ‘* Acme” Fixed Sprays (Ames- Beaks eotkars Engineer-
ing Co., Ltd.).. The jets are screwed into vertical Tee pieces
forming connectors in horizontal pipes run 4 or 5 inches below
the surface of the filter bed. The jets are spaced about 7 ft. 6 in.
apart on the pipes, and the pipe runs themselves are at’7 ft. 6 in.
centres. Head recommended 1 ft. 6 in. minimum and 3 ft. |
maximum, giving a contracting spray from 4 ft. 6 in. radius to
the jet centre. Rate of discharge estimated at 2} gallons per
minute per jet or about 735 gallons per square yard per 24 hours-
The supply to the submerged pipes is regulated by an automatic.
1 Letter from Mr, Corbett, Borough Engineer, May 29, 1906.
~
‘SHUOM HZOVMAS VAY ANV AWV], WVHONIWAIG LIV NOILAGIYISIG 31ZZON—‘6E ‘or a
—— Soe
ee
2 ee ct gente test
292 SEWAGE AND ITS PURIFICATION
valve which opens and closes in such a way that as the pressure
at the orifice of the jet slightly increases, the filter bed is covered
from the centre of each jet gradually until the maximum radius
of 4 ft. 6 in. is obtained, and then the pressure falls off and the jet
gradually dies away. The pipe lengths are fitted with cleaning
caps, and an emptying pipe for use in frosty weather (see
Fig. 38).
(d) Ham and Baker’s Nozzle Distributor and its application
at Birmingham are shown in Figs. 39 and 40. Their Revolving
Sprinkler is represented later in Fig. 50. 7
(e) Columbus, Ohio. Hering and Fuller kindly give me the
following details of the proposed arrangements for the 10 acres
[Fic. 40.—HaM AND BakeEr’s NozzLE As USED AT BIRMINGHAM,
of filter beds. Each bed, 2} acres in area, is estimated to yield
two million gallons per acre per 24 hrs., dealing with septic tank
effluent only, with an average period of flow through the tank
of about 83 hours. The rows of sprinklers are to be worked
from 6-in. underground mains, the nozzles being 15 ft. 4 ins.
and the mains 13 ft. 3 ins. apart. Each nozzle will be mounted
on a 3-in. cast-iron rising branch from the 6-in. supply main.
After extended experiments the type of nozzle chosen was of
brass, having a single orifice ;°, in. diam. with rounded edges,
above which an inverted cone is held by two thin arms, the
axes of the cone and orifice coinciding. The jet of liquid
impinges against the cone and is transformed into a thin sheet
which spreads out radially and then breaks into a mass of drops,
which fall on the area included between two concentric circles.
For each nozzle to discharge 13°5 gals. per minute, a head of
5 ft. is required. In operating it is intended to vary the head
ee eee
a
AIOE ERIE NTE FH
DISTRIBUTION AND DISTRIBUTORS 293
so as to cover as much of the surface as possible. From a
minimum of 2 ft. 9 in., with a discharge of 10 gals. per min.,
to a maximum head of 5 ft. and a discharge of 13°5 gals., it is
expected that 777% of the area will be covered in a satisfactory
manner. The two arms which hold the inverted cone on the
nozzle will be ground down to sharp edges in a vertical radial
plane; ‘‘in consequence the sheet of liquid after passing heels
up so that trouble from these obstructions is eliminated.”
Figs. 41, 42 show the nozzle and its arrangement on the
Fic, 41.—SPRINKLER NozzLe, CoLumBus, OHIO.
Surface of Filte tT Sprinkler Nozzle —_~
Effluent Conduit //
Fic. 42.—SECTION oF BED, CoLumMBus, OHIO.
filter bed. For flushing and other purposes a 10-in. water main
has been run to the works, and to maintain “an uniform dis-
tribution at the nozzles and to keep the consequential losses
low in the main collectors it has been necessary to use depositing
velocities.”
A similar nozzle distribution is a part of the works authorized
for the city of Baltimore, Md., and a description and drawings
of the whole scheme, and of a testing plant, with several valuable
comments, are given in the Report of the Advisory Engineers
(Hering, Gray, and Stearns), May 31, 1906.
294 SEWAGE AND ITS PURIFICATION
II. Moving Distributors.
In Nos. 1 to 5,7 and 8 of the following, the principle is that of
‘‘ Barker’s Mill”; or of the still more ancient “ AZolipile”’ (des-
cribed by Hero of Alexandria about 200 B.c.)—rotary motion
produced by the recoil from jets of fluid issuing from holes on
one side of suspended and balanced tubes.
1. Candy - Caink ‘self-propelled revolving sprinkler and
aerator’’ (International Purification Syndicate). This form
was installed at Reigate, Southampton, and Southwold, where
the sewage, after passing a catch-pit, or after a first anaerobic
treatment, was distributed by the sprinkler over aerobic beds.
Mr. Caink seems to have been the first person to introduce
revolving sprinklers into sewage treatment.
2. Candy - Whittaker Sprinklers (Patent Automatic Sewage
Distributors, Ltd.). In the smaller sizes the arms are attached to
a revolving cylinder suspended from an overhead ball-bearing
attached to a fixed central column. The sewage enters the
cylinder through ports in the column, and then flows into the
- perforated arms. The patent joint between the moving cylinder |
and the fixed standard is formed with a trap of mercury, so as
to be water-tight and almost frictionless. Variations in water
pressure are guarded against by a check ring. Oscillation of ©
the distributor arms in a vertical direction is guarded against
by a ball-bearing in combination with the mercury seal, and
precautions are taken to render the bearings as moisture-proof
as possible. Variations in flow are dealt with by the usual
device, by means of which two additional perforated arms come
into action as soon as the level of the liquor in the cylinder is
sufficient. For large sprinklers the weight, which may be as
much as 2 or 3 tons, is carried by means of a circular buoy
floating in a small tank of water in the centre of the bed. This
method is said to require only a fourth of the power (as com-
pared with ball-bearing distributors) to set it revolving. There
are two of these buoyant distributors of 120 ft. diameter at
Harrogate and Birmingham, and six of 200 ft. diameter are in
course of construction for Worcester. Non-buoyant distributors
of 80 ft. diameter are at work at Redhill, Wednesbury, and
elsewhere, and smaller ones of 8 ft. diameter and upwards are
‘made. The average price may be taken as 20s. for each foot
diameter of bed, exclusive of an automatic flusher, which is
usually supplied (see Fig. 43).
eet OEM lt DS ert, |
—--
Se
gs be a
POP SS i Sr Ora
.
o dicsikuseinieadaaadinn
DISTRIBUTION AND DISTRIBUTORS 295
3. Mather and Platt, Ld., Manchester, supply a Patent
Revolving Spreader driven by the head of sewage through a
turbine at the centre of the bed (Fig. 44). The arms are open
troughs, perforated along the bottom of one side of each.
This arrangement is easier to clean than perforated tubes.
The Spreader is hung from a cast-iron standard, and in the
larger sizes it is found desirable to steady the outer end of each
arm by guide wheels running on a circular rail track. Trough
arms are more affected by wind than tubes, but with outer rails
a motor can be added for driving during high winds. It is
(OU). > EA
PA ryont NX
an a 4
4
‘Ma
77S
Fic, 43.—CANDY-WHITTAKER DISTRIBUTOR AT BEDFORD.
always desirable to work this form of distributor with automatic
flushing gear.
- 4. Adams’ Hydraulics, Ltd., Vite make several forms of
revolving Distributors. The ‘“Cresset”’ differs from others
mainly in the air-lock water-seal between the fixed standard
and the revolving body, to which the spray arms are connected
{see Fig. 45). A fixed tank has an inner division in which the
revolving body rotates, and an outer division which when filled
with water develops an air-lock between it and the revolving
body, and thus prevents the escape of the sewage between
those two portions. The whole weight is carried by a cross-
head on the top of the central column. At Derby there are
.18 ‘‘ Cressets,’”’ each roo ft. diam., at Birmingham one 120 ft., |
at Hurlford five of 40 ft., and smaller sizes are made down to
io ft. diam. Exclusive of supply pipes, valves, or flushing
296 SEWAGE AND ITS PURIFICATION
gear, carriage, and erection, the cost is as follows: 25 ft. diam.,
£35; 50 ft., £55; 100 ft., £100; and so on in proportion.
‘* The least head required is that which would cause the sewage
to gravitate to a point 6” above the centre of the surface of the
filter bed, but it is advisable to allow not less than g” for a
constant uniform supply.” If the supply is variable, the head
must be greater in proportion. The maximum head is not
stated, but apparently there is a limit beyond which there may
be an overflow of sewage from the central air-lock. The
apparatus is intended to work with an automatic flushing tank
when the rate of distribution falls below a certain quantity per
SVM eer ay es
eS
Fic. 44.—PAaTENT REVOLVING SPREADER, IN CONJUNCTION WITH A PATENT
AUTOMATIC MEASURING VALVE, FOR EITHER CONTINUOUS OR INTER-
MITTENT FEEDING (MATHER AND PLATT).
sq. yd., and under these conditions it is said to distribute as
much as 100 gals. per sq. yd. per 24 hrs. The effect of wind
pressure is naturally much the same as on other types of the
Barker's Mill, and if this be taken into account at least 12” of
head would be required to drive it against an ordinary wind.
Messrs. Adams are now constructing distributors to be driven:
by power, which appears to indicate that for the larger sizes, at:
all events, automatic distributors cannot be entirely relied on.
In one of the latest forms the arms are fitted with two rows of.
spray holes, the lower for the minimum, and the upper for the:
maximum discharge. In this case the minimum and maximum
‘"NOLXOgG LV NOLAdINIsIg ,, LassaUD,,-—"Sh ‘oI
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ae
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2098 SEWAGE AND ITS PURIFICATION
heads are expected to be 7” and 15”. Suitable vanes may be
attached to the ends of the arms, and controlled by a master
vane, so that the wind pressure may be utilized to help the pro-
pelling arrangements during times of storm.
5. Jennings’ Patent Automatic Sprinkler claims among
special features that the arms are jointless, and carried on
protected ball-bearings, and that the loss of head in the
Distributor itself is negligible. The centre tank T (Fig. 46) is
fixed, and the arms alone rotate, their weight being carried on
the moving vertical shaft S, which runs on ball-bearings.
An overdraw syphon O supplies each arm from the central
tank. The syphon is kept full by water traps at the inlet and 3
outlet ends, but it has to be filled in the first place by means
of a pump. The perforations in the arms are arranged with
25 MO Eiee, ban Hy Pal oa
thee ae
pace
——
—
=
Fic. 46.—JENNINGS’ PATENT Avromaric SPRINKLER FOR SEWAGE AND WATER FILTRATION
the object of distributing equally over each sq. yd. of filtering
area. The feed supply F to the central tank T, through the
underground pipe A, is regulated by an automatic syphon D,
governed according to the volume of sewage by a syphon valve
and ball float. The head is kept constant by a weir. When
the flow increases two additional arms come into operation as
in some other forms; in this way it is said that the maximum -
flow may be four times as great as the minimum. The pattern
shown is adapted for filters up to 50 ft. diam.; above this size
a fixed central column is used. It is not explained how the
central bearing would be affected if one arm of the distributor
became filled before the other, and consequently threw the
distributor out of balance. Jennings’ sprinklers, 80 ft. diam.,
are in operation at the sewage works, Cole Hall, Yardley,
and Kenilworth, and smaller ones of ro to 40 ft. at St. Leonards,
RR aati ap
SET ng
better: pe
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300
SEWAGE AND ITS PURIFICATION
Windsor, Eastwood, and Greasley Sewage Works, and else-
where.
Prices: 25 ft. diam., £25 to £31; 50 ft., £50 to £56;
100 ft., £100 to £122; delivery and erection, £5 to £10 extra.
A,
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LAN lepplde ded dscete ie bitetedetetietleletet ee,
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each yard of the bed gets just the same dose at equal intervals -
of time. The loss of head is practically negligible, being only
CHEE
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The head required is stated
as from 21” to 9’, with a flushing
tank, and 15” to g” in contin-
uous working, with a maximum
distribution of 1,000 gals. per
sq. yd. per 24 hours, and the
minimum 150 gals. Below
150 gals. an automatic flush-
ing tank is found essential, and
is usually provided for higher
rates. Jennings’ gauging ap-
paratus is on the float principle,
graduated over a weir.
6. Scott - Moncrieff Distri-
butor, made by Manlove Alliott,
Ltd., for large filter beds, is in-
tended to be driven by power.
In this form the distribution can
be effected over the entire bed
with mathematical accuracy,
while all passages or openings
are of such a size that they are
readily accessible and can be
easily cleansed. Variations in
flow are dealt with automatic-
ally without alterations to the
distributor itself. The limits of
distribution range from 50 gals.
per sq. yd. per 24 hrs. up to
2,000 gals. or more. The rate
does not control the speed of
revolution as in most other dis-
tributors, since the driving motor
works quite independently of
the sewage, and consequently
that which is absorbed by the pipe connections from the external
carrier to the centre of the bed. The apparatus is of a heavier
ee ae ee ee eee
ae a a TR Pe ne
Sree NE COTA TET ENT rey: 4
-~
3a AL ge TPES REEL OI
DISTRIBUTION AND DISTRIBUTORS 301
and more massive description than other makes, and con-
sequently the first cost is also greater, but there appears to be
no doubt that, owing to the equality of distribution, a greater
average rate of flow can be allowed, and a higher class effluent
secured. The makers con-
tend that the combined
cost of filter bed and dis-
tributor to produce a given
standard of effluent from
a given volume of sewage
is less if this distributor be
used than with any other.
Two forms of the dis-
tributor are given in
Figs. 47, 48, the latter
representing an _ equally
efficient, but less costly,
form than the former.
The sewage flows from a
central standpipe along
a main trough to the ex-
tremity of the rotating
arm. Alongside the main
trough (which is supported
by lattice work) runs a
small subsidiary trough,
which is subdivided into
compartments. Each
compartment is connected
with the main trough by
a port-hole, the size of
which varies with the dis-
tance of the section from
the centre of the filter
bed. The sewage over-
flows from the subsidiary
Fic. 49.—'‘' SIMPLEX” SPREADER,
troughs on to the filter bed. The subsidiary troughs are each
fitted with adjustable weirs, and drip points coming close to the
_ surface of the bed. The first cost per square yard of area
covered has been found to lie between that of the Barker’s
Mill type of distributor and the fixed type of distributor. The
sizes made are for } acre beds and upwards.
302 SEWAGE AND ITS PURIFICATION
—
7. Simplex Spreader (Ames-Crosta Sanitary Engineering
Co.). A central pillar supports a weatherproof cap running on
ball-bearings and supporting the arms. Oscillation is prevented
ee ee ae ae ee
duct ‘Wh ‘<
—, —_—e
—ss eve
Fic, 50.—REVOLVING SPRINKLER AT ABBOTS LANGLEY, NEAR WATFORD.
by adjustable guide rollers fixed on the underside of the bucket,
which revolves with the arms (Fig. 49). The guide rollers run
on a machined surface on the central pillar. The joint between
PTC a er rn") Fy
qq 88
DISTRIBUTION AND DISTRIBUTORS 303
the central rotating bucket and the fixed central pillar is made
by means of two anti-friction rings and a resilient washer of
rubber or corrugated copper. Arrangements are made for an
easy inspection of the bearings. The least head desirable is stated
to be 4”, and to give three times the dry weather flow a head of
28” would be required, unless extra arms are placed at slightly
higher levels on the central bucket. _ For intermittent working
an automatic flushing tank is recommended.
8. Ham and Baker’s Revolving Sprinkler at Abbots Langley,
near Watford, is illustrated in Fig. 50.
The Fiddian Automatic Distributor (Birch, Killon and Co.)
consists of one or more elongated water wheels 9” to 18”
diameter, which roll bodily over the surface of a filter on
Fic. 51.—SECTION OF FIDDIAN WATER WHEEL.
circular rail tracks about a central pivot. Each rolling drum
has a pipe connecting it to a supply of tank effluent, which falls
into the buckets of the wheel.. The water-wheel buckets are
divided transversely into sections, each section being supplied
from a separate opening in the feed-tube (Fig. 51). The
openings are fitted with adjustable weirs of a width propor-
tional to their distance from the centre of the filter bed. . It is
claimed by this system that equal distribution can be obtained
without the sewage passing through any restricted areas, or
any power other than the head of the sewage itself being
utilized. Filters up to 20 ft. diameter have the rolling drum
supported on one roller track in addition to the central stand-
pipe. A second rolling track is provided when the filter is
between 20 and 30 ft. in diameter. A balancing arm or second
rolling drum is required when the bed exceeds 30 ft. diameter,
304 SEWAGE AND ITS PURIFICATION
and is less than 54 ft. diameter. Above 54 ft. diameter a third
rolling drum is introduced together with an intermediate track,
which is usually carried upon cast-iron columns. This system
is suitable for beds up to 120 ft. diameter. The interval
between the application of each dose to the filter bed surface is
from 3 to 6 minutes, thus giving the bed time for aeration.
The standard sizes actually erected so far are on filters from
g ft. (Wolverley, Loughborough) to 100 ft. diameter. Various
sizes are in use at Ford House, Shrivenham, Alvechurch,
Atherstone, Walsall, Sileby, and a distributor for 100 ft. bed
(of clinker, 0°18 acre, to purify 250,000 gals. per day) has been
Fic, 52.—FIDDIAN REVOLVING DISTRIBUTOR AT ENFIELD,
erected at Enfield (Fig. 52). Prices quoted are: 25 ft. diam.,
£50; 50 ft., £106; roo ft., £225; not including the iron tracks.
It is stated that only 18” of head is required between the sill of
the Septic Tank and the top of the filtering medium, not only
for driving the distributor, but also to overcome pipe friction
and clearance’ underneath the rolling drum. The flow of
sewage may vary within wide limits: the makers state that
the test at Tividale shows that the Distributor can work with
50 gals. per sq. yd. per diem, and according to Dr. Reid the
mean fluctuations over or under the mean delivery per yard of
filter only amounted to 107%. No flushing tank or automatic
valves are required.
The Septic Tank Company, Ltd., have a “turbine ring”
revolving distributor with graduated trough arms. The sewage
a
DISTRIBUTION AND DISTRIBUTORS 305
entering the central chamber drives the turbine ring attached
to the open-trough revolving arms, from one edge of which the
sewage overflows on to the bed through slots graduated in size
according to the distance from the centre, with the object of
attaining equality of distribution. The troughs have corrugated
pendent rims like Stoddart’s on their under sides. The quantity
of sewage delivered is restricted by regulators or equilibrium-
intermitting valves, such as are used by the Company for land
irrigation. ‘The distributors are offered in sizes from 15 ft. to
too ft. diam.
“ Travelling distributors” is the trade term for those which ©
Fic, 53.—TRAVELLING DISTRIBUTOR FOR RECTANGULAR BEDs AT
WEDNESBOURY.
pass backwards and forwards over a rectangular bed (Fig. 53).
They are not of such general application as revolving sprinklers,
and are more affected by wind resistance. They can be driven
by the recoil from jets, the liquid being automatically made to
issue alternately from each side, or can be actuated by other
available means, such as by wires worked by a small water-
wheel, with reversing arrangements. They are sometimes
supported by floats placed in the feed channel. Hartley’s
(patent 29,203 of 1904) has a travelling syphon, and is worked
by wire ropes actuated by independent power.
III. Distributors with Tippers.
The Ashtead tippers have already been described (Fig. 29):
in the later form at Caterham and other places they were
double V-shaped trays mounted on trunnions and automatically
20
306
SEWAGE AND ITS PURIFICATION
discharging on alternate sides when the liquid reaches a level
which upsets their equilibrium.
‘MOLAGINLSIG: SMANAVY AO NVIG—'bS ‘OI
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7
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TIPPER
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-——_« wvanraaa \_{ Tf
Farrer Automatic
Distributor (Figs. 54,
55, 56) is mainly suit-
able for smaller instal-
lations; the largest at
present is on a bed 32
by 20 ft. Septic effluent
is discharged into a
tipper which supplies
distributing channels on
the’ beds, whence it
flows along troughs per-
forated on the lower
sides; these being made
with a concave bottom,
_ clear themselves readily.
The maximum head re-
quired is stated to be
14’ for small installa-
tions, increasing for
larger ones on account
of the section of the
tipper varying with the
greater volume. Con-
verging shoes under-
neath the tipper cause
equal quantities of
sewage to pass along
each distributing
channel.
Continuous and _ in-
termittent filtration,
apart from the differ-
ences between the re-
sults obtained, present
a contrast both in the
mechanical arrangements and in the bacterial process itself.
In the case of contact beds, except when they are used in
series, there is no differentiation of the organisms in relation to
DISTRIBUTION AND DISTRIBUTORS 307
the food supply, because, although the conditions are changed
from being purely anaerobic to those more or less favourable to
€ Feet,
EFFLUENT »»—>
Poot
. = \
\
. \
z N
; = N
5 5 N
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: : \ :
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ais fo eae HNy ee a)
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oo BY eg
INGET -?-—
aerobic action, these are conducted in such a way as to provide
neither condition continuously, and the results. obtained have
already been dealt with and explained in previous chapters.
20—2
308 SEWAGE AND ITS PURIFICATION
When an apparatus is designed from the point of view of
overcoming these objections, it is obvious that the methods of
bringing about the contact between the sewage and the bacterial
surfaces must be radically different.
In the filtration of hydrolysed effluents, whenever there is
a continual dripping upon a particular spot, growth is liable to
occur of a filamentous character allied to Crenothrix, but it
has been found that if a sufficient time is allowed to elapse
between the discharges of liquid on the upper surfaces, this
filamentous clogging is generally avoided. In a Whittaker bed
at Leeds in May, 1899, a falling off in the results was due to
the surface being covered by an abundant gelatinous growth of
Pylobolus, which prevented aeration and appeared to be pro-
Fic. 56.—DIsTRIBUTING CHANNEL, SHOWING FLANGE AT END.
moted by the heating of the liquid. As the growth did not
penetrate more than a few inches, the surface was removed and
replaced by a foot of very coarse coke, which proved effectual.
Mr. Dibdin states that some streaming filters were objection-
able on account of their smell, and at Carshalton relief had been
found by covering the beds with peat moss carried on wire
network.
Continuous filter beds are frequently constructed for aeration
purposes with lower layers of very coarse material, but it is
found better to build them with a perforated base or “‘ aerating
floor,” arched or supported by girders, leaving an air space at
the base of the bed (see Chap. X.).
Scott-Moncrieff's Sewage Testing Apparatus (Fig. 57) has been
in operation at Staines, Keighley, and elsewhere. It consists of
a box about 8 ft. high, 3 ft. wide, and 1 foot broad, filled to a
depth of exactly 6 ft. with the filtering material to be tested,
3 re
DISTRIBUTION AND DISTRIBUTORS 309
gauged to any required size. The sewage to be tested is dis-
tributed on the top by a tipper working at a measured rate.
The filter effluent can be drawn off at any one of six levels. By
means of a water tank and syphon arrangement the amount
of air which is supplied to the filter bed can be measured.
Mr. Moncrieff claims that the apparatus is capable of deter-
mining the depth of the filter required to produce the necessary
Fic. 57.—Scott-MoONCRIEFF SEWAGE TESTING APPARATUS.
standard of purity in the effluent, the quantity of air necessary
for the life processes of the organisms, the proper rate of flow
per unit of filter bed surface in order to obtain the best results,
and the best period of rest between every discharge. The
apparatus is likely to be of great use in competent hands pro-
vided that due allowances are made for the smallness of the
quantity of sewage it is possible to experiment with on an area
of only three square feet, and for this, provision has been made
by an ingenious device for gauging the liquid without having
any small orifices. It is maintained that one square foot of
filter bed is as good a unit as any other for estimating surface
distribution, and as the testing machine is six feet in depth it is
of full size in this particular.
CHAPTER XIll
SEWAGE OUTFALLS AND DISCHARGE
Rainfall and storm-water—Separate and combined systems—Storm
overflows—Position of outfalls—Objections and legal remedies
—Foreshore smells—Unsightliness— Mud banks—Fish— Water
supplies—Contamination of shellfish and watercress.
THE general principles guiding final discharge have been
explained in previous chapters (see especially pp. 14, 55-60,
130 and 172), but it has been shown that there must be some
elasticity according to local circumstances, and that at present
many anomalies have arisen. In manufacturing districts
streams still exist which are ‘‘inky black sewers,’ and at one
point a community may have been at great expense to turn out
a good effluent, while, a few miles above, a large town is dis-
charging millions of gallons of a foul liquid daily. An early
suggested remedy was “‘a sliding scale,’ enforcing that each -
effluent should be, say 20 per cent. better than the stream:
“the effect would be that the towns on the upper part would be
turning in something better than the stream, and the towns
below would have to comply.” If there were sufficient space
between the towns for natural purification in the river, the
latter would remain in good condition throughout its course.
The present Royal Commission on Sewage find that ‘‘ in many
parts of England the pollution of rivers goes on unchecked,”
and recommend the creation of a supreme rivers authority, with
Rivers Boards having control also of estuaries and foreshores,!
and such an organization has been long necessary. In most
other countries a special administration of the kind has been
for many years in operation.
RAINFALL AND STORM-WATER.
Provision for these is essential in all systems of sewage dis-
posal. A rainfall of or to o’2 inch in an hour increases the out-
1 Third Report, 1903, p. 26 et seq.
310
> oe PROTOS OOP a ee *
SEWAGE OUTFALLS AND DISCHARGE _ 311
flow of a sewer to five or more times its volume, but there is no
exact relation between the rainfall as ordinarily recorded and
the increment of flow at the outlet, the size, length, and in-
clination of the sewer greatly influencing the result. At Exeter
five-eighths of the ordinary rainfall is estimated to find its way
into the sewers. Mr. Silcock! estimated from gaugings at King’s
Lynn that ‘‘ the ordinary dry-weather flow of sewage per acre
of a purely urban district, with an average population of seventy-
five persons per acre, consuming 20 gallons of water per head
per day, is 20 cubic feet (125 gallons) per hour. A rainfall of
+ inch in 25 hours, or approximately $5 inch per hour, will
amount to the same discharge as the dry-weather flow per acre,
assuming that the streets are paved, and that only 50 per cent.
of the actual rainfall finds its way into the sewers. In other
words, a rainfall of +35 inch per hour will double the ordinary
dry-weather flow. Now a rainfall at the rate of + inch per hour
is a common occurrence, which would mean multiplying the
ordinary sewage flow by 25, and short storms at the rate of
4 inch per hour are not infrequent when the ordinary sewage
flow is augmented 50 times. ... Fora town with a population of
100,000, if the whole of the sewage and rainfall had to be taken to
the purification works, the ordinary maximum sewage flow at 20
gallons per head would be at the rate of 4,000,000 gallons per 24
hours, and if the sewage were treated on bacterial intermittent
filters, 4 acres of filters would be required, but to deal with a
rainfall of 4 inch per hour would require I00 acres of filters, and
if the sewage had to be pumped it would require 25 engines
and pumps each capable of dealing with a dry-weather flow to
cope with the combined rainfall and sewage. It is therefore
evident that the whole of the rainfall cannot be taken to the
purification works, and that after a certain degree of dilution has
been reached, the storm-water must be discharged into the
streams.”
Both the quality and quantity of the local sewage have to be
considered in choosing a sewerage scheme. The effect of rain
must not be considered as simple dilution, since the rain-water
carries the washings of the surfaces over which it has travelled.
Where the rock, or a clay-bed, is near the surface, the showers
will run off almost unchanged. From manured or peaty land
there will be an addition of brown humous liquids which are
particularly difficult to decolorize. See also pp. 6 and 27, and
1 Leeds Sanitary Congress, 1897.
312 SEWAGE AND ITS PURIFICATION
the Manchester observations in Chap. XI. I have repeatedly
observed storm-water to be even more impure than the ordinary
sewage; a sample I analysed in 1905 contained in parts per
100,000, free ammonia 1°61, albuminoid *40, oxygen consumed
6'o1, chlorine 5°*4, nitrogen as nitrates and nitrites ‘197;
whereas the sewage gave generally better results, and the land
effluent from the same works yielded an average of ‘6 free
ammonia, ‘12 albuminoid, 053 oxygen consumed, and °57 of
oxidized nitrogen. The Royal Commission on Sewage also
found,! that storm-water was almost invariably impure, both
chemically and biologically, that street washings were all
impure biologically, even when they contained only a small
quantity of organic matter, and that the liquid might even be
very impure after long continued rain ; and remarked that “the
practical advantages of the separate system may be great, and
doubtless storm overflows are necessary, but the fact that storm
liquids may be so impure, both chemically and bacteriologically,
is a point of considerable importance.”’
For the safety of the sewers and the avoidance of flooding of
basements, it is always necessary to construct storm overflows.
Without these in a sewage farm scheme the ground is liable to
become waterlogged, and in a filtration process the excess of
water by its volume and velocity tends to derange the purifica-
tion plant, hence it is usually allowed to escape from the sewers
by special outlets when above a certain amount, carrying with
it a mixture of the unpurified sewage. The combined system
also involves the construction and maintenance of sewers very
much larger than the volume of the regular flow, in order to
provide for occasional contingencies. This greater capacity
presents inducements to the disposal of grosser refuse which
would not be tolerated in a smaller sewer, and often it is im-
possible—except at rare intervals—to properly flush the entire
surface of these large channels.
The ‘‘ separate system,” in which the sewage proper is kept
apart from rainfall and storm-water, has conduits of such size
only as to preclude the possibility of the sewage becoming stag-
nant therein, the size being governed by the bore of the water
main, since if a given diameter of pipe supplies all the water
needed, a little above the same diameter should be sufficient for
an exit. Mr. Silcock proposes that the rainfall sewers of a
separate system should be provided with leaping weirs dis-
' 1904 Report, vol. iv., part i., p, 105.
FEELS LAL EI OS Oe
SEWAGE OUTFALLS AND DISCHARGE | 313
charging into the sewage sewers to separate the foul street
washings from the later discharges of heavy rainfalls.
Storm-water passing rapidly off the land carries with it
disease germs, as is shown by the repeated occurrence of epi-
demics when a sudden storm succeeds a period of drought.
But the liquid is ordinarily supplied with abundance of the
liquefying and oxidizing bacteria, which if it be allowed to
subside in auxiliary reservoirs will effect its purification rapidly,
aided by the oxygen derived from the air, and by the nitrites
and nitrates that rain-water always contains. The sand, chalk,
or especially the clay, may be a long time in subsiding, but
when deposited will leave the water comparatively pure, and
fit for flushing sewers, watering roads, or for supplying the
deficiency in rivers during dry seasons.
Whatever system be adopted the raw storm-water of populous
districts should never be allowed to pass in large volumes at the
beginning of a storm directly into a stream. . The general con-
sensus of opinion is that if the first foul storm-water be treated
as ordinary sewage, the subsequent rain-flow becomes so dilute
that it can be discharged, with only a slight treatment, into a
river. The Manchester experts placed a limit of time of two
hours after the commencement of the storm. Many towns adopt
a volume limit. Thus, Mr. A. M. Fowler, at. Stockport, made
provision for an escape after eight times the dry-weather flow ;
other places in Lancashire and Yorkshire allow 6 or even 5 to I.
By the Leicester Extension Act, 1891, the overflow culvert came
into action when the rainfall increased the dry-weather flow of
35 gallons per head to 60 gallons, but in this case the overflow
passes into the river Soar, which has a flow during dry weather
of only about 6 or 7 million gallons per day, so that the storm-
water is actually useful for flushing the river bed.
I have found from analyses—
1. That, after the first flush, the chlorine content varies with
the rainfall. |
2. That with low chlorine and high rainfall, higher nitrifica-
tion is obtained.
3. That, as might be expected, the later diluted sewage
comes within the usual standards of permissible impurity,
therefore could not, under them, be excluded from streams.
As I remarked at the Manchester Congress of the Royal
Sanitary Institute,' purification to a bacterial standard of the
1 Journ, R, San. Inst, vol. xxiii., part iv., 1903, p. 617.
314 SEWAGE AND ITS PURIFICATION
120 million gallons daily of Manchester sewage would involve
works similar to waterworks as an adjunct to the sewage works,
but six times the size of the waterworks already existing.
With contact beds, Mr. Dibdin considered “it was not a
question of whether they had more or less water, it was the
amount of the organic.matter that was put on the bed, and if
that was not materially increased it mattered not how much
storm-water was put upon it. They had been able (at Sutton)
to put three or four times the quantity of storm-water on to a
bed than the volume of sewage they had put previously.” As
a matter of fact, an occasional flush of storm-water through a
bacterial system is advantageous, as it removes some of the
products, and so stimulates the bacteria to fresh activity.
The present regulations of the Local Government Board
have been already given (p. 148), and several towns have now
provided special storm-filters of sufficient extent to allow a rate
of filtration of 500 gallons per square yard per diem for the
balance of three times the dry weather flow in excess of that
required to be fully treated. Lloyd-Davies! has described in
detail the design of the storm-water overflow chambers at
Birmingham, and discusses the various discharge formule
which have been suggested by Santo Crimp (the one preferred),
Burkli-Ziegler, McMath, Kuichling, and others.
A. J. Martin? remarks on the wide difference between the —
dry-weather sewages of different towns, so that if a hard and
fast relation of volumes be prescribed as above, ‘the diluted
sewage which one public body may discharge without treat-
ment will be considerably stronger than that which another
authority will be called upon to purify.” |
The Local Government Board insists that fixed weirs shall
be used, which will only come into operation when the sewage,
as mentioned above, has been diluted with five times its volume
of storm-water, that is, when a certain rate of flow in the sewer
is reached. But Martin proves that the amount of dilution
secured by a fixed weir is variable, and will at times be con-
siderably less than the works are intended to secure.
Among the advantages of the bacterial processes involving a
large anaerobic preliminary chamber, is the ease with which
the works can be adapted for dealing with storm-water. In
such systems provision is made for the subsidence of solids, as
well as for their liquefaction, as a tank constructed to hold the
1 Proc. 1.C.E., 1905-6. 2 J. San. Inst., xx., 4, p. 624.
2 pig igi PRIS ON, LE en STE om
SEWAGE OUTFALLS AND DISCHARGE 315
dry weather flow of a sewage for 24 hours would admit of six
times the. dry-weather flow passing through such tank by
reducing the time of stay from 24 hours to 4 hours. The rate
of flow under such conditions would still be so slow as to ensure
the retention in the tank of nearly all the suspended solids, and
these would therefore accumulate during stormy weather to be
_
(IMMEDIATE) |
ee ae
- STORM OVERFLOW”
(DEFERRED) —t*~”
Fic. 58.—STORM OVERFLOWS AT BARRHEAD,
digested by the tank at leisure during the dry-weather periods.
A curious anomaly arises out of these considerations. If the
time of sojourn in the tank is reduced owing to the rate of flow
through the tank being increased, the liquid products of hydro-
lysis usually contributed to the effluent from the stay in the |
tank will not exist in the effluent water to the same extent. In
other words, the effluent from such a tank during a storm will
be purer than from the tank in dry weather proportionately to
the rate of flow, even after due allowance has been made for
dilution, provided only the rate be not so high as to bring
316 SEWAGE AND ITS PURIFICATION
untreated suspended matter to the outlet. Mr. Martin shows
that at the Barrhead Works the velocity of flow in the tanks
with three times the volume of the dry-weather flow passing
through them only amounts to 1% in. per minute. With six
times the dry weather flow, therefore, the velocity does not
exceed 3? in. per minute, which is so slowa rate as to be power-
less to disturb solid matter in the tank. Martin’s arrangement
of weir and regulated flow by modules is shown in Fig. 58.
In bacterial treatment, whether by tanks, filters, or land, it is
known that the resolving organisms are most active, especially
in the final or oxidizing stage, when the liquid is of moderate
strength, since undue concentration retards the growths, while
too rapid a flow is liable to wash them away. Chemical pro-
cesses of precipitation or sterilization on the other hand find
concentration an advantage, so much so that some of them, as
for instance the Liernur process, require the aid of evaporation.
It is clear, therefore, that in both cases heavy dilution is to be
avoided, if possible, for other reasons than that it increases the
size of the works. Modern practice suggests the importance
of making the sewers watertight, and of disposing separately of
subsoil water, which is usually innocent of contamination.
The conclusions, therefore, are :— |
1. Subsoil and deep drainage water can as a rule be separately
pumped and discharged, if the sewers are properly constructed.
The relief that may result to a system of sewage treatment has
been shown in a recent instance at Rathmines, Dublin, where
the normal sewage of 2} million gallons per day is swelled to
6 millions by subsoil drainage. A similar observation has been
made in other towns. :
2. Road washings are dangerous, and especially under the
separate system should be sterilized im situ by sprinkling the
surface with effective disinfectants.
3. Storm water should be impounded and stored or other-
wise treated, and must never be allowed to pass in large
volumes directly into a stream. The larger the volume of
liquid the more dilute it will generally be, and prpportonately
so much less of a disinfectant will be required.
POSITION OF OUTFALLS.
This is not always a matter of choice, and is affected by
questions of cost and engineering. Among the varieties of
final discharge are :—
SEWAGE OUTFALLS AND DISCHARGE 317
(a) Sewers and drains opening directly into the nearest body of
water. This primitive method is still common, although it is
not even excusable in remote districts, as it is now known that
small and simple installations with tank and filters can be easily
constructed and work well. .
(b) Tunnels or pipe lines to convey the sewage to a long distance.
The Manchester ‘‘ Culvert Scheme” of 1899 proposed to convey
the effluent to the tidal river Mersey at Randall’s sluices, by a
circular tunnel 63 ft. diam., with a fall of 1 in 2,100, and a
full discharging capacity of about 67,000,000 gallons a day.
The scheme was not adopted, as considerable nuisance was
anticipated. Eventually a tunnel-syphon 5 ft. diam., carrying
bacteria-bed effluent under the river Mersey, with a shaft at each
end, was constructed. On the further side of the river the tunnel
communicates with a supply channel 13 feet wide, following
the contour of the high land, from which the effluent radiates
over the land in subsidiary carriers 18 inches wide, with disc
valves on the upper ends in the carrier wall, so that any length
can be opened or shut at will. The main drain lies midway
between these carriers, communicating with an open channel
delivering into the Ship Canal at a point over a tumbling bay,
placed sufficiently far back from the canal bank to minimise
any current prejudicial to navigation. |
In Chap. I., p. 19, I have already discussed sewage discharge
into the sea. Letts and his colleagues have studied the effect
of the admixture of sewage with a body of sea water,! and
conclude that (1) the first effect is chiefly absorption of O and
production of almost the equivalent amount of CO,; (2) com-
parisons between the ‘‘oxygen-consumed”’ test and the O
actually absorbed as determined by analyses of the dissolved
gases prove that ‘‘a more energetic oxidation is induced by
micro-organisms and free oxygen than by the nascent oxygen
of the permanganate solution’; (3) the nitrifying organism
can grow in sea water, but a large quantity of free ammonia
remains for a long time unnitrified; (4) under no circumstances
is a nuisance likely to arise from sea water contaminated by
sewage up to I per cent.; but the changes in the nitrogenous
constituents as measured by the free and albuminoid ammonia
and the nitrates are very slow. (See further Chap. I., p. 19.)
Purvis and Coleman in a series of experiments just published?
1 Proc. R. Dublin Soc., July 27, 1900.
2 F. AR. San, Inst., xxvili., No. 8, 1906, p. 433.
318 SEWAGE AND ITS PURIFICATION
have not obtained any nitrification in mixtures of sea-water
with one per cent. of sewage, although there was a rapid
breaking down of organic matter with formation of ammonia
and odorous compounds. By trials with the marine salts
separately and together they found that they had an inhibitive
effect on oxidizing changes. Their conclusions are strongly
against sewage being discharged untreated.
The principal objections to sewage outfalls that appear in
most official enquiries are:—(1) Smells; (2) Unsightliness and
inconyenience through turbidity of the water or floating débris,
formation of mud banks, and unpleasant deposits on the shores ;
(3) Destruction of fish, and sometimes of aquatic vegetation ;
(4) Contamination of water supplies drawn from rivers and
lakes; and in special cases, (5) Pollution of shell-fish or of
watercress beds.
As a result of the enquiries it has been frequently found that
the faults were not entirely due to crude sewage, and only
exceptionally to purified effluents. Taking the above points in
detail :— |
(1) Smells. Many sewage- and water-bacteria effect lique-
faction without creating any offence. On the other hand we
have described at p. 81 a number of natural causes of objec-
tionable odours unconnected with sewage.
(2) Faults above mentioned that are occasioned by suspended
solids. Screening and roughing tilters prevent the more glaring
evils, and in many cases this is all that is done, but it is rightly
made an essential of satisfactory treatment that the effluent
should contain very little suspended matter. As an example of
pollution, 26 miles of the river Severn were examined for the
Royal Commission on Sewage.! This stretch receives the
untreated sewage of Shrewsbury (pop. 28,396, dry weather flow
about 900,000 gallons, mixing with about 100 volumes of river
water), besides less amounts from other sources. Chemically
the river shows a marked recovery from its Shrewsbury pollu-
tion within some 20 miles from the town, and it still further
recovers as it proceeds, in spite of some additional contamina-
tions.” Hence it is fair to infer that with a good effluent there
would not have been any injury. But the results of discharging
sewage entirely untreated were found to be:
(a) The bed of the river consists of putrefying sludge, and
the velocity of the stream is always tending to spread the
1 Reports, vol. ii., 1902, pp. 93-133. 2 Ibid., p. 132.
SEWAGE OUTFALLS AND DISCHARGE 319
deposit to a great distance down, and to shift it from place to
place.
(b) Although on emerging tious the sewers the solids are for
the most part well broken down, yet a very considerable amount
of the lighter feeces, various débris, and pieces of disintegrated
paper float for a long distance down the stream, and disfigure
the banks. In the little bays where these accumulate, the mud
is blacker than elsewhere, and the willows have strained out a
considerable quantity of the floating material ; offensive decom-
positions occur; the water usually presents a scum ; the bacteria
are more numerous and B. colt more abundant. The course
taken by floating matters was traced by throwing large numbers
of coloured corks into the river. Some of them were followed
for 8 miles, where the observation stopped, and were seen even
6 months after they had been thrown in, showing how long
solids may remain, even in a rapid river.
Mud banks can obviously form independently of the solids of
sewage, which in many cases amount to only a small portion of
their volume, or to merely a film on their surface. Besides the
presence of coal dust or soot, they often acquire a dark colour
from the production of black sulphide of iron, as described on
p- 115. Quantities of shrimps, mussels, and marine or fluviatile
organisms are usually found on them, which shows that they
are not poisonous to such life.
(3) Destruction of fish and sometimes of aquatic vegetation.—The
two are connected, as the water plants not only themselves
serve for food for certain fishes, but also harbour the lower
forms of animal and vegetable life which help to support fish.
In the Severn, where the deposit is at all abundant, there is no
growth of aquatic plants, and “‘the absence of a clean bottom,
supporting weeds, will most probably act injuriously on fish.’’!
“The absorption of oxygen and the evolution of not only
CO;, but of other gases such as H,S, must act injuriously on
fish life. Indeed, Kénig and Haselhoff have shown that carp
and tench are injuriously affected by 8 milligrammes of HS,
per litre.’
That greater care is necessary in securing the cleanliness of
shores and estuaries has been for some time obvious, from the
1 Reports, vol. ii., 1902, p. 97.
2 Ibid., p, 106. Further authorities on this subject are Nitsche and Tharaud,
Weigelt, J. Konig, Hoppe-Seyler, Duncan, Saare and Schab (Verunreinigung der
Gewasser, vols. i. and ii., by Dr. Kénig), US. Fish Commission, 1880, Bulletin,
vol. v. See also evidence given before R. Sew. Commission, Interim Report,
vol, li., 1902, especially pp. 485-496.
320 SEWAGE AND ITS PURIFICATION
nuisances that have been occasioned in many localities by the
presence of foul matter on foreshores and on the banks of tidal
rivers. Experience as to the dangers to health has already
been given (ante, pp. 170, 172), but apart from this aspect, it is
not to the advantage of any local body to be continually in
danger of a fine, and large law costs, now that the liability has
been proved in the Courts, in spite of the almost complete
exemption that was granted to tidal waters by the Rivers’
Pollution Act of 1876.
At present in England there exists no authority with powers
to prohibit the laying down of shellfish in sewage-polluted
water or other dangerous localities, and to ensure the protection
of unpolluted layings, storage ponds, fattening beds, and other
places where shellfish are laid or stored, against contamination
by sewage. The Royal Commission recognise the deficiency,
and outline an administrative change to comprise a Central
Water Authority with Rivers Boards exercising jurisdiction
over separate water sheds, including shores, as an extension of
the Rivers Pollution Act of 1876, the new authority to be well
equipped for carrying on the necessary scientific work as part
of regular duties. (Fourth Report, 1904, vol. 1., p. xxv).
This remedy is practically the same as they have already
suggested in the third report for inland towns, and does not,
after all, give any immediate answer to any particular offending
locality. Until legislation is passed and the new controlling
authorities have had years of experience, it will still be difficult
in many cases to decide how much or how little treatment is
required. :
In the case of Rivers Boards having tidal waters under their
jurisdiction, the Commissioners think that the Fisheries
Committee should be empowered to appoint representatives
thereon, and this would transfer to the new board the powers
of the Salmon Conservators and other similar bodies.
The improvement on our coasts that would ensue if good
bacterial effluents only were discharged can readily be
appreciated.
The law with reference to the pollution of tidal waters is
thus at the present time in a more hopeless condition than that
of non-tidal waters. Thus, for example, the Section 17 of the
Public Health Act of 1875, under which, in the past, many
injunctions have been obtained for prohibiting the discharge of
noxious matter into streams, watercourses, canals, ponds, or
SEWAGE OUTFALLS AND DISCHARGE _ 321
lakes, has usually been held not to apply to tidal waters; and
similarly the provisions of the Rivers Pollution Prevention Act
of 1876 can only be operative after the Local Government
Board have made a local enquiry, and declared that for the
purposes of the Act the estuary or tidal portions of a river shall
be deemed a part of the river on sanitary grounds. :
The Salmon Fishery Acts are also equally unsatisfactory,
and the Royal Commission on Salmon Fisheries in 1902 has
pointed out serious defects in the existing Acts.
On the other hand, we may note that under the common
law, when injury to others has been proved, a local authority
may be restrained from discharging sewage into tidal waters.
The case of Lord Gifford against the Corporation of Chichester
in 1gor is illustrative, and after this decision several oyster
fisheries and owners of fishing rights in tidal waters have taken
steps in a similar way to enforce the purification of sewage
discharged into tidal waters by local authorities, when such
sewage has been detrimental to their trades. In the above
case the evidence was partly bacteriological, and the action
was won largely on the fact, which was undisputed, that “coli’”’
“organisms were found in the mud of the estuary below the
outfall, but the present works, approved by the Local Govern-
ment Board to meet the injunction, will no more stop the
passage of coli into the estuary than bacteriological treatment
of London sewage would sterilize the Thames.
Although the extent of illness attributable to the consump-
tion of contaminated shellfish is difficult to gauge, the present
Sewage Commission find the evil sufficiently great to demand a
remedy, and thus save the expenses and uncertainty of these
actions. In 1899 a Government Bill was introduced, but not
passed, for the protection of public health against dangers
arising from the consumption of unwholesome oysters. The
interests of the industry, which is estimated to have a capital
value of from six to eight million pounds sterling, still remain
sufficiently great to warrant serious consideration, as the oyster
scares have, from time to time, brought about severe disturbance
to the trade. |
The remedies suggested are threefold: (1) Purification of
sewage; (2) seizure and destruction of unwholesome fish
exposed for sale; (3) the creation of a competent authority to
deal with tidal waters.
With regard to the first, the Commissioners recognise that
21
322 SEWAGE AND ITS PURIFICATION
there are difficulties in the way of the sterilization of sewage
effluents, but these I have dealt with in Chapter VIII. It
would appear that as, failing such sterilization, all sewage
outfalls must necessarily more or less contaminate shellfish,
watercress, or drinking-water below, either the sewage outfall
must be removed, or nothing in the contaminated area should
be offered for internal consumption without purification.
A bacteriological examination associated with topographical
evidence may even be misleading, as there are no doubt many cases
daily in which temporary pollution of a fishery or oyster laying
may take place by, say, feecal discharge from closets on board a
ship, and there is little evidence at present as to distance, time,
dilution, tides, and other factors which determine the possibility
of infection of shellfish by estuary waters.
In a report by Dr. Houston to the Commission,! a careful
investigation of over 1,000 oysters, from various layings through-
out the country, shows that nearly all contained B. coli communis
or closely allied organisms. It cannot be too widely known
that the Commission are clearly of the opinion that the mere
presence of B. coli microbes in an oyster does not justify its
condemnation.
With regard to foreign shellfish, the Commissioners are
satisfied that in the interests of public health some safeguards
are necessary in connection with their importation and sale. A
suggestion was made that all consignments of foreign shellfish
should be required to be relaid for some period, in approved
waters, before being sold to the public. The Commissioners
doubt if such a requirement could be justified in the case of all
foreign shellfish. For the present, they think that it would be
a sufficient precaution to require a guarantee on the part of
each Government concerned that all oysters, or other shellfish,
imported into this country for human consumption had been
procured from localities where they were not liable to be
contaminated by sewage or other objectionable filth.
Watercress, being at times almost immersed, may become
coated with polluted lime-crusts and not be easily cleaned by
washing. The London County Council’s report of February 7,
1905, on watercress beds supplying London, concludes that,
‘“‘ having in view the extent to which careful washing eliminates
impurity, it may be assumed that there is under existing cir-
1 Fourth Report, 1904, vol. iii.
———— Sl el hl
ee ee ae
ee en
SEWAGE OUTFALLS AND DISCHARGE 323
cumstances no material risk in consuming the watercress supplied
from the majority” of these beds. Objection is taken on
topographical, chemical, and bacteriological grounds to certain
beds where there was actual gross pollution, “‘and effort should
be made to prevent the consumption of watercress from these
beds in their present condition.”
The annual consumption of watercress in London is about
1,500 tons, and the 120 beds examined, with areas from less
than } to 40 acres, comprise all those within 50 miles known to
supply the London market. In most cases the waters were
examined by the chemist, who gives his own classification
according to the albuminoid ammonia as follows :—
Group. No. of Samples. Nitrogenous Organic Matter.
A 53 About the same as the filtered (Thames-
derived) London supply.
B 47 About the same as in the Thames at Hampton
and Sunbury above the intakes.
C 22 | Large in quantity.
D 7 Very large in quantity.
Thirteen of the waters were submitted to the bacteriologist,
and those containing coli in 1 cc. or less are condemned. It
will be seen that our Guildford chlorine-treated effluents would
have easily passed this test (pp. 189, 190). The two worst
samples were effluents from sewage farms, and contained
10,000 coli-like microbes per c.c., and enteritidis spores in ‘I c.c.
Dr. Houston concludes that “‘no ordinary amount of wash-
ing could be relied on to rid cress grown in polluted waters of
all undesirable microbes.” It was of great moment to ascertain
whether pathogenic organisms could exist and multiply in the
interior of plants, and this was partially studied by analogy
with B. coli. The results on the whole were against the
hypothesis, as Sir Shirley Murphy notices in his summing up,
although Dr. Houston lends some probability to the idea that
the leaf and stalk of cress ‘‘ may foster undesirable organisms.”
Even if it were true that pathogenic infection of the interior of
living plants were occasionally possible, I believe that in the
acid washings I have described at p. 193, the acid, being more
diffusible than the bacteria, would reach them in sufficient
quantity to destroy them, and then be removed in the subsequent
washing with water. A point in favour of the success of cleansing
is that the B. typhosus is actively motile, and therefore would
2I—2
324 SEWAGE AND ITS PURIFICATION
probably be removed more easily than B. coli. The subject
demands further investigation.
I have already pointed out that, in the contamination of
shellfish gathering-grounds and watercress beds, sewage and
sewage effluents are not always in fault, and that some of the
other occasional polluting matters, being more recent, are more
dangerous in character. The L.C.C. Watercress Report, just
noticed, specifies beds polluted by cattle, by house drainage,
by trade effluents, adjacent farms and stables, and “ occasional
deposit of human excreta near the intake.”” In my inspection
of the Medway fisheries I found that no adequate sanitary
provision was made for the men engaged in the industries, and,
_as I should surmise in other fisheries, local contamination may
arise from this cause. Evidence before the Royal Commission
on Sewage as to another locality stated that ‘‘a large number
of barges after unloading refuse pump out the offensive and
highly polluted bilge water into the creek,” and the oysters in
the neighbourhood are found to be infected although there is
no discharge of sewage in the vicinity.
In an analogous case within my own experience, oysters
from a laying far from any source of sewage pollution had been
condemned independently by Dr. Klein and by myself, and it
appeared that some other form of contamination must be
present. On an inspection I found in a creek joining the
channel a heap of about 5,000 tons of town refuse which had
been discharged partly below high-water mark, and was drain-
ing into the creek, and another screened heap about half the
size near by. Other objectionable cargoes were also being
unloaded on the banks. In a case that has just occurred
where crabs were condemned, and were reported to be ‘‘ swarm-
ing with organisms which would cause serious illness,” it was
suggested that they had been contaminated by the flooding of
a barge while being brought to London.
If the damage, on the other hand, is clearly traced to the
sewage, the remedy lies at law. The sequel to the Emsworth
outbreak of typhoid has been an action! by the owner of the
beds for an injunction to. restrain the District Council from
placing or maintaining their sewage outfalls in the neighbourhood
of his oyster beds, and from delivering sewage on the said
foreshore so as to contaminate the same, and to render the
oysters liable to be infected and unsafe for food, with damages
1 Foster v. The Warblington Urban District Council, Dec. to Jan., 1905.
SEWAGE OUTFALLS AND DISCHARGE 325
to the business. The judge allowed the claim that these were
private oyster beds, and disallowed the defence of prescriptive
right to discharge of sewage, chiefly on the ground ‘that the
Sea Fisheries Act, 1868, made it criminal to discharge sewage
so as to contaminate private oyster beds, and there could be
no prescriptive right to commit a criminal act. Further, no
one can acquire by prescription a right to pollute a public
fishery. He would not, however, grant an injunction on the
grounds stated in the analogous case of Harrington v. Derby,
in Dec., 1904, when similarly there was judgment for the
plaintiff with damages. At Southend also the owners of the
oyster beds were successful on their appeal.
The law, therefore, as defined by these recent instances, is
that a corporation may continue the pollution and be fined at
intervals to an indefinite amount when injury is proved. This
liability is further foreshadowed by a well-known case lately
decided in which a large dairy company had to pay heavy
damages, upheld by the Court of Appeal, on account of a death
assigned to the presence of typhoid germs in milk supplied by
them (see later, p. 326). It seems obvious that the same
might apply to a pollution of water, and to a public authority.
It is clear that public interest in the prevention of disease, as
well as economy and the avoidance of trouble, indicate the
sterilization of effluents as a general course.
At places of holiday resort where large numbers of people
consume shellfish that they have gathered on the shore,
enteric fever often results. These shellfish are not owned by
anyone, and the site cannot be registered. Therefore no sewage
should be allowed to be discharged in an unpurified state,
otherwise it would be almost impossible to compel authorities
to exercise supervision over the whole foreshore.
On the gathering - grounds for the Glasgow market,
Dr. Chalmers! found that the regular trade gatherers of shell-
fish are in the habit of rejecting those lying on the surface and
regarded by them as “sick,” and of only collecting those which
have embedded themselves in the sand, and therefore have been
to a great extent protected from the sewage. These regular
collectors were quite aware of the danger attached to certain
contaminated areas, and mussels were not taken from places
near sewer outfalls. Visitors, however, were not so careful,
with the result that there had been a number of cases of typhoid
1 Report of Med. Off. of Health, Glasgow, 1905.
326 SEWAGE AND ITS PURIFICATION
associated with the collection and consumption of shellfish by
excursionists, but there was little evidence throwing suspicion
on the market supply. Dr. Chalmers finds that the information
is not at present sufficient to define the distance from outfalls
that would render shellfish safe to gather: it would be much
influenced by tides and currents.
But there are large cities, such as London and Manchester,
whose sewage is of such immense volume that the cost of
sterilization may be beyond present possibility. It seems that
the difficulty must here be solved as a financial question,
namely (in the words of Rudolph Hering, speaking of similar
cases in America, notably New York and Baltimore), ‘“‘ whether
the city is to purify its sewage, or whether the oysters that
may be polluted by the same will have to be grown elsewhere,’
like other cultivation industries that have to be moved in the
extension of cities. Dr. Buchanan has shown? that shellfish
collected one or two miles from a sewer outfall were free from
contamination. But the Royal Commission had before them
evidence that many established beds could not be moved
without great loss, nor suitable sites found elsewhere.
The Duty of the Vendor.—The decision in a High Court of
Justice appeal, Frost v. Aylesbury Dairy Co., Feb. 24, 1905
(the case I have alluded to above), laid it down as common law
that on the sale of an article for a specific purpose (in this case .
for consumption as an article of food), there was a warranty
implied by the vendor that it was reasonably fit for the purpose,
and there was no exception as to latent undiscoverable defects.
It is only very recently that the communication of disease
has been considered as a ground for recovering damages. Even
if the giving of a warranty be avoided by putting up a notice,
liability for negligence or want of care will still remain. It
seems, therefore, that an action for damages could be laid by
the customer against the vendor, and that the latter could
recover from the polluters of his beds; but this is an expensive
and dilatory process. One of the safeguards for vendors is the
inspection of supplies. In London the power exists, through
the Fishmongers’ Company, of prohibiting the importation of
polluted fish to the metropolitan markets. I may notice, in
passing, that sprats, whitebait, and smelts, as they are eaten
uncleaned, and the cooking is often not sufficient to ensure
1 Trans. Amer. Soc. C.E., vol. liv., part E, 1905.
2 Journ, R. San. Inst., vol, xxv., part lii., 1904, p. 466.
SEWAGE OUTFALLS AND DISCHARGE 327
sterilization, require bacteriological attention, and that in the
examination for coli and enteritidis it is not the presence, but
the frequency or number of these organisms that is of most
import.
Taken together, the precautions that lie in the hands of the
trader, and finally in those of the consumer, are the following :—
1. Selection and maintenance of clean beds—That good shell-
fish can be raised under such circumstances is proved by the
Report of the Local Government Board for Ireland, 1904, and
by evidence before the Royal Commission on Sewage, vol. ii.,
1904, showing that many of the best brands come from localities
free from dangerous pollution. With regard to watercress, the
London County Council Report, already referred to, shows that
cress of the best quality can be grown under conditions to
which, from a public health point of view, no exception can be
taken (p. 7), and that the best beds were, generally speaking,
found ona bottom of hard clean gravel: such beds are regularly
cleansed, and in some cases a light dressing of lime is used at
each cleansing in order to mene organisms deemed to be
injurious (p. 6). |
2. Relaying of shellfish in purer water.—Although in common
use, and recommended by a large number of witnesses before
the Royal Commissioners, the purifying value of this practice
was defined in the Report as ‘‘at present uncertain.” Referring
to the work of Herdman, Boyce, and Klein, it was said! that
“judged from these experiments it would seem that polluted
oysters placed in approved waters might free themselves from
dangerous organisms in the course of a comparatively short
period [ten days to a month were mentioned], but as regards
cockles and mussels, relaying might be less effective.”
3. Sterilizing objectionable organisms in the beds themselves.—
Better precede by cleansing as far as possible. How chlorine,
acids, or copper can then be used I. have indicated: the first
would probably be the cheapest, and at the seaside electrolysed
sea-water would readily be attainable (Chapter VIII.).
It is customary to lay the oysters required for market in pits
at high-water mark, so that they shall be readily available for
transport. In these pits it is easy to add a sterilizing agent and
keep for a period of, as it were, quarantine, and to inspect them
as to objectionable organisms being killed. This would be
cheaper than attempting to sterilize the whole of the estuary or
1 R. Comm. on Sewage, Fourth Report, vol. i., p. 40.
328 SEWAGE AND ITS PURIFICATION
sewage discharging therein, or even to ensure the non-coli
environment of the oyster beds themselves. Such sterilization
is on the principle I have always advocated—that it should be
as near the consumer as possible, and should be confined to the
thing consumed. Actual details have to be worked out for the
particular industry. The similar removal and temporary storage
apart of the watercress required for market seems possible. It
is conceivable that sterilizing, with chlorine or other agent, the
beds where shellfish spat or young watercress is present might
have an injurious effect on the young growth, therefore that
treating the adult product would be preferable.
4. Sterilizing by Cooking.—Where this can be done thoroughly
it is effective, and the Commission found that cockles and
mussels can be so thoroughly boiled as to bring about the
destruction of pathogenic organisms without rendering the
mollusc itself uneatable. An incidence of typhoid at Glasgow
in 1903 was due to raw cockles; those who had eaten cooked
mussels and clams escaped injury.!. The heating is very often
imperfectly done: thus a number of enteric cases in South
London two years ago were due to cockles which were stated
to have been boiled for three minutes, but this had not sterilized
the interior. I have also quoted earlier an instance at Southend
(p. 171). When, as is frequently the practice, cockles are put
into the boiler in a bag, the centre portions may easily fail to
reach the temperature, a little above 60° C., necessary to
sterilize B. typhosus; hence it is better to put them in loose or
on a grating, and stir at first. The adoption of precautions
without injury to the trade is exemplified in Dr. Nash’s report
to the Borough of Southend for 1904, in which he states that
the shellfish are now drawn from purer sources, and that
nearly every seller in the town subjects them to the action of
live steam under pressure for four or five minutes, the result
being that not a single case of typhoid due to cockles occurred
during the year.’
5. Sterilization by the Consumer, the last line of defence.—I
have suggested how this has been done instinctively, with a
measure of success, in the usual consumption of vinegar with
these foods, and have indicated how it may be more certainly
1 Fourn, R. San. Inst., vol. xxv., part iii., 1904, p. 467.
2 Local vigilance is, however, maintained, and I notice that at Southend on
Nov. 8, 1904, a fisherman was fined for selling mussels unfit for food. Dr. Klein
stated that 80 per cent. of these mussels contained a very large quantity of
sewage organisms, and the water from the spots at which ey were taken was
polluted.— Public Health, Jan., 1905, p. 266.
SEWAGE OUTFALLS AND DISCHARGE — 329
accomplished by washing with weak chlorine or acids.
Obviously, the vendor is not thereby absolved from his
attention to the quality of his goods, nor the local authority
from the duty of obviating pollution where it is dangerous.
We must remember that most articles of the kind we are
discussing are habitually washed at least twice, by the retailer
and by the private purchaser, before consumption, and that
sterilization of dangerous organisms at the same time would
scarcely add appreciably to the trouble or cost.
The danger that has been so much urged of admitting
effluents to drinking-water streams, and a great deal of the
expense of sterilizing effluents and water-supplies, would be
minimized if the consumer also sterilized the small quantity of
water used for drinking (estimated at about a gallon per head
per day) in a way that I have for some years advocated."
During the passage to houses through pipes there is a
constant risk of contamination from the liability of the pipes,
even under pressure, to suck in polluting matter from the soil,
so that it has been frequently demonstrated that the supply to
houses is often much inferior to the filtered waters in the
reservoirs and mains. Here again a final line of defence is
necessary. I pointed out that as sterilization, so far as concerns
dangerous organisms, is essential for safety, much of the expense
might be saved by making the treatment at the works less costly,
since it was superfluous to purify water required for a large
number of domestic uses, for flushing the streets, or for sanitary
purposes. It became a question whether we should aim at the
whole public supply being purified up to the maximum standard
of a good drinking-water, with a great extension of stringency
as regards discharging effluents, or whether we should be content
with a somewhat less purified water for the general supply, and
sterilize separately in each house, under some conditions of
municipal control, such portions as should be required for food
purposes. Of the three methods I have described for rendering
the fluid germ-free, the chemical one, by ozone or chlorine for
| instance, could be employed at the works, while the heat-
sterilizer, or Pasteur filter, could be put into the consumer’s
house by the municipality or by a water company—preferably
by the former—as an integral part of the ordinary water fittings,
and the duty of keeping it cleansed and in order secured by
official inspection.
* Cantor Lectures, Fourn. Soc. of Arts, Aug. 1, 1902, p. 749; also Fourn. R. San.
Inst., vol. xxii., part iv., p. 565.
CHAPTER XIV
AGRICULTURAL VALUE OF BACTERIAL EFFLUENTS—
TRADE EFFLUENTS
Conservation of the valuable constituents of sewage—Economic
value of nitrated effluents—Trade effluents—Classification—
Chemical and mechanical treatment—Recovery of products—
Wool grease—Relation to the bacterial process—Recommenda-
tions of the Royal Commission.
*
THE earlier attempts to utilize sewage and its sludge for agri-
cultural purposes have been discussed in Chapter VI. Sludge
in its various forms has never been of great value, and the
analyses show that it is not rich in plant food, especially when
large quantities of lime have had to be added in order to make
it into a marketable cake. Sewage effluents, on the other hand,
contain all the soluble constituents of the original sewage, and —
after oxidation the nitrogen in the form of nitrates is easily and
quickly assimilated by plants. Maerker,’ from agricultural
experiments in Germany, considered 100 parts of nitrogen, as
albumen, equal to 90, as ammonia, and 60, as nitrate, so that
for economic utilization the organic nitrogen should be nitrated
as far as possible ; and denitrification changes, as already seen,
must also be avoided in order to prevent loss. Sir William
Crookes estimated that in the sewage and drainage of towns
we ‘‘hurry down to the sea fixed nitrogen to the value of
£16,000,000 per annum.’”
Estimates of the agricultural value of human excreta. Annual
value per adult 6s. 6d. to 20s. (various authorities). 1 lb. human
excreta=15 lb. horse dung or 6 lb. cow dung (Macaire and
Marcet). Mechi ranks the droppings of a sheep at the same
value as the total excreta of one human adult. Voelcker
reckons the yearly excreta of an adult as equal to 75 lb. of
1 Kew Bulletin, 1899, No. 144.
2 «©The Wheat Problem,’’ Murray, London, 1899.
339
ee SS, rl lr
AGRICULTURAL VALUE OF EFFLUENTS 331
Peruvian guano. Tidy tabulates the components of urine and
feeces as follows! :—
_ Puospuoric Acip. |
| gr he {ee aed: SOR ies | Potash at Estimated Value
Shed. Soluble at puamable 3d. per lb. per Ton.
| . é
4d. per Ib. aig 8 |
Constituents per Ton.
lbs. lbs. | lbs. lhs. fe a
Urine in natural state... 23°94 2°94 £4— 3°34 0 15 IO
Fzeces in natural state ... | 35°45 — | 26°62 9°46 2 ee
Mixed excreta of a popu- | |
lation ... ae ee 23°13 2°79 | 1°93 3°83 015 8
1.000 tons of London | |
crude sewage .., beh | \ SEO ST ol OF OL | 24°20 50°65 oo If
The Royal Commission of 1858-1865 concluded after ex-
haustive experiments that sludge contained only one-eighth of
the value of the sewage from an agricultural point of view, and
thus encouraged the principle of sewage farms, with direct
application to the land. The chief causes of failure were (1) the
very large volume of sewage that had to be continuously dealt
with, (2) its property of fouling or clogging, (3) the relatively
small amount of important manurial ingredients like phos-
phates, potash, and nitrogen it contained in proportion to the
quantity of water, (4) the unsuitable form in which the organic
nitrogen existed. The last difficulty suggested that if the liquid
was properly prepared or matured by a fermentation process
analogous to that by which a farmer “‘ripens”’ manure, this
nitrogen might be more readily utilized by plants. Mr. Davies?
held out great hopes in this direction, while Mr. Daniel Pidgeon®
dealing with the bacterial purification of sewage, showed
forcibly the practical value of highly nitrified effluents for all
kinds of cultivation.
Scott-Moncrieff* pointed out that a 907% nitrification of the
total nitrogen in ordinary sewage would, based on the cost of
nitrate of soda, amount to £14,000,000 per annum on the whole
sewage of the United Kingdom, a saving which nearly recovers
the waste mentioned by Sir W. Crookes. These highly
nitrated effluents also contain plant-food in nearly ideal pro-
1 Fournal of the Society of Arts, Oct. 8,1886. See also ‘‘ Collection and Utiliza-
tion of Excreta,’’ James Ashton, Inst. San. Engineers, Wolverhampton Meeting,
1903.
2 Fourn, R. Agric. Soc., Oct., 1899. 3 [bid,
4 Southampton Sanitary Congress, 1899; J. San. Inst., vol. xx., part iv.
332 SEWAGE AND ITS PURIFICATION
portions, according to the standard solution adopted by Nobbe,
which contained in parts per 100,000 :—
Lame <7. aS oe Chlorine ... age
I
Magnesia ay ise ee Oxide ofiron ... _0°5
Potash . mihi: | eo Nitrogen ... 8:2
Phosphoric acid seit
By experiments on plants I have found these effluents to give
great fertility. While some plants (Leguminosz) can assimi-
late free nitrogen, others organic compounds, and still others
nitrogen in the form of ammonia, nitrates appear to be the
form in which nitrogen is taken up with the greatest readiness
by most plants. The change of sewage into a fertilizing effluent
is favoured bya higher temperature. In India a report of 1g01
states that at Bombay, Poona and Calcutta septic tanks and
bacteria beds produced an effluent that gave much better crops
than the poudrette manure and irrigation with canal water
previously employed, and that at the Matunga Asylum farm,
Bombay, irrigation with the septic tank effluent alone gave a
gross profit of over £60 per acre per annum.
As regards the mineral constituents of different sewage
effluents not much information is recorded. An average
sample of the final flow from the Sutton beds showed :—
PARTS PER 100,000.
Fixed mineral matter ... ie es wet edie: 3.
Volatile and organic matter ie ah ie aa ao
Actual sodium chloride.. 15°77
Soda in other forms (sulphate, “carbonate, etc.), “calculated
as Na,O ; pea Avs ty vad Xa Oe
Total soda as Na,O ay re _ ve sony GOT
Total potash as K,O ... sae ee 4 sae ee
Phosphate as P,O, dni fost t Eh nh dah “fk ist =. OTRO
Nitrogen as nitrate ‘all re Aes $3 Ba 5:
Total nitrogen Bes -# os ate Zens reg
100 parts of total solids would correspond to—
Total N 4°25 : K,O 3°48: P,O; 0°32
Mineral matters 77°93 : Organic 22°07
Probably coke in the filters absorbs much of the phosphorus
as phosphate of iron, and accounts for the small amount of
phosphoricacid. Polarite and other highly ferruginous mixtures
would have a still greater effect. Disused filtering materials
must consequently contain a large proportion of phosphate.
The difficulty of utilizing any of the valuable constituents of
sewage resulting from their extreme dilution, prevents evapora-
tion, distillation, or any of the ordinary chemical methods
AGRICULTURAL VALUE OF EFFLUENTS 333
from being economical. The free ammonia present would be a
marketable article if it could be cheaply extracted. In 1882-
1883, Dupré suggested its separation by blowing air through
the liquid and absorbing the ammonia in acid, the aeration at
the same time improving the sewage and reducing the nuisance
at discharge. He states with reference to London, that the
sewage contains 3 to 4 grains of ammonia per gallon, equal to
31 tons of ammonia in 140 million gallons—one day’s discharge,
giving 120 tons of sulphate of ammonia, worth from £14 to £20
per ton, or a total value per annum of about £400,000. ‘“ By
blowing air into the sewage much of the ammonia would be
expelled, and if only a fraction of it were recovered, the expense
of aeration would be covered.”’
It does not seem that this idea has been attempted on a large
scale. It would include, in common with other artificial
methods that we have seen, a continuous mechanical expense,
hence natural nitrification is more economical. See also p. 194.
Besides the plants mentioned in Chap. VI. as being grown
on sewage farms, the Sutton Urban District Council have
found peppermint a lucrative crop and one very suited to
irrigation with a bacterial effluent. The oil can be easily
distilled on the works with waste steam. The yield from the
2% acres cultivated at Sutton in 1898 was 614 lbs. sold as first-
class oil at 24s. 3d. per lb., realizing £75. The amounts and
acreage since then are reported as: 1902, 8 acres, £235; 1903,
64a., £179; 1905, 6a., £145. Similar successes have been
recorded in connection with one or two other sewage works.
TRADE EFFLUENTS.
Where land or precipitation is solely relied on, trade effluents
are a source of great difficulty. For instance, in a town in the
north “‘ they had six times the ordinary flow of sewage, owing
to brewery refuse, complaints were very numerous, and they
had to reconstruct their sewers and get a farm of 500 acres, at
a cost of £250,000. Wherever they had a staple trade they
could not rigidly enforce the law, and they frequently had
water discharged into the sewers at 212° F.” The Belgian
Government are experimentally treating trade wastes at a
special station at Verviers.
The investigation of the sediment at the bottom of a stream
is of great importance. . An instructive case is cited by Marsson!
1 Mitteilungen aus der Koniglichen Priifungsanstalt, Berlin, Heft 2, pp. 28-31.
334 SEWAGE AND ITS PURIFICATION
of an effluent from a works producing nitro-naphthalene.
When diluted by cooling and condenser water, it was apparently
harmless to fish under the conditions at the point of discharge.
On investigation of the mud near the outfall, however, it was
found to have a strong smell of naphthalene products, and all
signs of the organic life, necessary for the gradual breaking
down of putrefactive matter, had disappeared. This effect was
discernable 400 metres below the outfall. In a recent case of
alleged contamination from a paper-mill I found a considerable
amount of gypsum, chalk and various pigments in the river
mud. In another instance, below a copper works, although
the water appeared to be free from dissolved copper, the metal
was present in the mud, and had an injurious effect on fish.
Especially in the North of England, processes for treatment
of factory waste-waters on the works themselves have been
greatly improved, and in a large number of cases made
remunerative by recovery of products. Mr. Tatton, inspector
of the Mersey and Irwell Board, classifies these liquors into
those from (1) print works, (2) dye works, (3) bleach works,
(4) waste bleach works, (5) paper-mills, (6) paper stainers,
(7) tanners and leather dressers, (8) fellmongers, (9g) woollen
trades, (10) silk trades, (11) coal slack washers, (12) soap-
makers, (13) stone polishers, (14) chemical manufacturers,
- (15) brewers, (16) unclassified! The discharges are mostly
dealt with, after screening, by precipitation with iron and lime,
and as mentioned in Chapter VII., a ferric salt is found to be
more effective than a ferrous salt (copperas).
Bleach, Dye, Finishing and Calico-printing Works.—The waste
liquors contain various dyes and mordants, soap, starch, soda
or acids, exhausted bleach, etc. They are generally screened
and settled, and in some works traverse a long channel in~- ©
which blocks of iron alum (ferric ammonium sulphate) are
suspended and gradually dissolve, precipitating most of the
colouring and other matters. Lime is added either before or
after the iron precipitation, in various amounts according to
quality of the liquids. After again settling in tanks, the liquid
is usually drawn off by floating outlets and passed through
shallow (13 to 34 ft.) graded filters of stones and clinkers
covered with 6 to 18 in. of fine ashes, which are renewed at
intervals. Owing to biological action and the formation of
1 Purification of Water after Use in Manufactories,’’ by R. A. Tatton,
M.1.C.E., Proc, Inst, Civ, Engineers, Jan. 9, 1900,
a
TRADE EFFLUENTS 335
films, the filters gain in purifying power by use as long as they
pass the effluent freely.
Logwood liquor is reported to present special difficulties and
to require separate precipitation, ‘‘though the product is at
present valueless, even for manure, as it generates fungus; it is
simply pressed and burnt.” Bichromate liquors in some cases
are pumped into the boilers for preventing scale: ‘‘no other
boiler composition has been found necessary, and the valves
have lasted better than previously.’’ It is usually more profit-
able to recover bichromate by precipitation.
The recovery of indigo is now profitably adopted, according
to Mr. Tatton, at all large works. In a Mersey print factory
about £1,200 a year was recovered on £4,000 worth of raw
material. Wash waters are precipitated with alumino-ferric
and soda (aluminium chloride partially saturated by sodium
carbonate is said to be better!), and the solids, with the vat
sediments, treated chemically to separate pure indigo
Considerable saving is effected in materials by the necessity
for preventing pollution of rivers. ‘‘ Formerly, if a mixing
was wrong it was sent down the drains into the river, now it
has to be taken to the tip and the error is detected.’”’ The
West Riding Rivers Board report, 1903, states that many
manufacturers found their purification works profitable. One
paper-maker found that his purification plant resulted in a
saving of £500 a year, while a colliery manager similarly
effected a saving of 300 tons of coal a fortnight, which formerly
went into the river.
One of the most polluting liquids is the water from the kiers
in which cloth, rags, esparto, and straw are boiled—a strongly
alkaline fluid which alone is difficult to treat. Judicious mixture
with acid liquors and precipitation are used, while at one works
carbonic acid is forced in to reduce the caustic alkalinity.
DISPOSAL OF GREASE.
The average amount of grease contained in the sewage of
various towns is given as, in parts per 100,000:—Ilkley rr,
Keighley 9°8, Harrogate 13, Huddersfield 15°2, Cassel 18,
Hemsworth 39°6, Bradford (Frizinghall) 45°3, Pudsey 46°8.2
Grease from wool is peculiarly intractable, owing to the
partial replacement of the glycerin of ordinary fats by choles-
1 J. Soc. Chem, Ind., May 31, 1902, p. 702.
° J. Garfield, Sanitary kecord, Feb. 2, 1905, p. 87.
336 SEWAGE AND ITS PURIFICATION
tevin, C,,H, (OH), a solid insoluble alcohol with a distinct
affinity for water, insoluble in alkalies and in acids except
concentrated sulphuric. The cholesterides show a remarkable
adhesion to water, not rising to the surface like ordinary fats,
but remaining suspended, so-as not to be separated by centri-
fugal machines without concentration. Ferric sulphate, with
lime, carries down the greater part, giving a sludge difficult to
press (p. 166), and containing about 25% of grease; moreover,
an inordinate amount of chemicals is required.
Wool-grease has a special commercial value, when purified,
as ‘‘lanoline ”’; it also contains considerable quantities of potash,
which pays for separation along with the alkali from the potash
or soft soaps used for scouring. Grease is now recovered at
some of the larger factories, and if smaller firms combined and
conveyed their suds by pipe sewers to one or more centres,
they could be dealt with collectively... This suggestion of
co-operative treatment applies to other trades, and economy
of neutralization might sometimes be effected by mixing alkalies
with acid waste.
At a flannel and dye works near Rochdale the following
treatment is pronounced to be very effective :—The liquid first
passes through a fine copper sieve to remove wool fibres: the
sieve is cleaned by a revolving brush, and the flocks of value
collected. It is then mixed by a water-wheel with milk of
lime, afterwards with a solution of ferric chloride 12 feet further
on, next passes through five settling tanks (arranged so that
any one of the first three can be thrown out for cleansing, and
each provided with scum-boards), on to two filters of fine
ashes, used alternately, thence into the streams.
The sludge is treated with sulphuric acid to break up lime
soaps, and pressed through cocoanut matting, the acid filtrate
being used again. The sludge cake is further pressed to
recover oil, various products from which are made and sold;
the refuse is burnt.
At a print works on the Mersey, soap liquor is treated with
lime and iron alum, pressed, the cake steamed with acid, the
grease separated, and the acid and alum from the press-filtrate
used again. The grease is stated to be worth at least 47 per
ton, but even at £4 Ios. it pays the whole of the expenses of
recovery, the quantity being 15 to 20 tons a year.
In a large number of woollen mills, simpler works have given
1 Borough Surveyor’s Report, Bradford, September, 1896.
TRADE EFFLUENTS 337
excellent results. They consist of ‘‘Sap-tanks” (in which the
water from the scouring processes, which contains most of the
grease, is treated with acid and the grease recovered), also
precipitation tanks and filter-beds.
Dr. Beckhold’s! report on the sewage sludge in the pre-
cipitation basins at Frankfort, Germany, states that (1) the
sludge contains an easily saponified mixture of fats and fatty
acids (27°8 per cent. of the latter being combined with bases),
the total fatty matters varying from 3 to 27 per cent.; (2) the
scum contains 80 per cent. of mixed fats; (3) the annual
amount of fat lost in the sewage is over 14 million pounds, or
about 8 lbs. per head; (4) the amount of sulphuric acid required
for complete decomposition is very large, 35 to 50% by weight ;
(5) the iron in the sludge is wholly in the ferrous state ; (6) the
fat collected in the basins is reduced in a few months by
bacteria to a small fraction of the original, more rapidly in the
dark and at summer temperature.
Several special processes are used in connection with wool.
See also p. 198.
I. Degreasing. Treatment with volatile solvents, such as
bisulphide of carbon, benzene, or light petroleum in an
apparatus similar to Leuner’s, used for degreasing bones; the
fat is thus extracted almost unaltered, and the solvent used
again. At present this method has not been found commer-
cially successful. The Delattre Process treats first with sulphuric
acid, then with steam and benzene: it is said that it can be
applied economically to wool-suds or to a very dense sludge.
The apparatus is an inclined cylinder, 4 ft. diam. and 200 ft.
long, in three horizontal sections. The wet sludge is pumped
in at the top, and in flowing down the incline, meets the
benzene or other volatile solvent pumped in from below,
mixture being attained by revolving paddles at short intervals.
The solvent charged with grease is separated and distilled, the
distillate being used again, and the residue of grease run into
barrels. The extracted sludge is steamed to recover remaining
solvent, and pressed hot, resulting in a dry cake, which can be
sold as manure. The method has been applied at the sewage
works, Roubaix, France, and was tried in 1900 on a ferric-
sulphate sludge sent from Bradford, but it was found that it
would be necessary to reduce the bulk to about one-fifth in the
process of precipitation. The grease was valued at £9 per ton.
1 Zeits. angew. Chemie, xxxvi., 849.
22
338 SEWAGE AND ITS PURIFICATION
II. The Ayrshire Process (Biggart & Co., Dalry), specially
applicable for certain classes of wool and potash soaps. The
sedimented suds are evaporated, and the grease which separates
is removed. The residue is calcined, and yields a crude car-
bonate of potash, which is either dissolved and used again for
scouring, or refined, when it sells at £16 ros. per ton. The
grease is boiled with sulphuric acid, and may be sold at about
£6 per ton, or purified further. The process is said to be
worked at a profit.
III. Kimmins and Craig’s patent (adopted by Holden and
Sons, Bradford, 1890) ; coagulating the liquor by chloride of
calcium to obtain a clarified neutral liquid.
IV. Ordinary or Sulphuric Acid Process. When the suds are
treated or ‘‘cracked”’ with sufficient acid to decompose the
soaps, the grease and fatty acids rise as a dark scum and are
collected and filtered, pressed hot, and sold as “ Yorkshire
Brown Grease.”’
V. Mechanical or ‘‘ Battage’’ Process of Motte & Co., Roubaix,
France. The suds are agitated by beaters, raising a froth
which carries to the surface the globules of insoluble fats, this
is skimmed off by travelling scrapers and heated to 60° C. with
one-thousandth of sulphuric acid to clarify and separate it.
The grease is strained through canvas bags, and the refuse is
sold as manure. The acidified effluent is precipitated by lime,
and is then said to be neutral and perfectly clear.
VI. Lagerie Process, Roubaix. In France and Belgium and
in a few cases in England (as at Alston Works, Bradford), the
potash and much of the organic matter is extracted by hot
water from the wool before scouring, and the liquor evaporated
and calcined as above.
VII. Vial process. This method has special mechanical
arrangements for efficient sedimentation. The sludge after
treatment with sulphuric acid and straining is passed into vats
containing agitators and scrapers, and dried by steam coils and
finally by superheated gases. The dry residue is extracted by
a solvent in a vessel provided with rotating screw mixers and
conveyors.
VIII. Spence process. The sewage is precipitated by quantities
of ferric sulphate and sulphuric acid ascertained by tests as to
alkalinity and impurity, the sludge further acidulated, heated,
pressed, dried, and extracted with a solvent.
IX. The Cassel Process, used at Cassel, Germany, is on similar
TRADE EFFLUENTS 339
principles. The screened sludge is acidified with sulphuric
acid, heated to roo° C. and pressed (the pressing requires
12 hours); dried by steam till the moisture is reduced to 15 per
cent., and afterwards extracted three times by benzene. 300 to
450 tons of liquid sludge, containing about go per cent. moisture,
are dealt with per week. From each charge of cake, some
800 kilos. of crude grease are obtained by the use of 1320
gallons of benzene (or petroleum spirit), 99 per cent. of which
is recovered by distillation. The dry extracted residue con-
tains 3 percent. of nitrogen, and fetches 30s. per ton as manure.
The crude grease is treated by vacuum distillation, at a cost of
7s. to Ios. per ton: 7 toms crude grease yield 1 ton of water,
5 tons of distillate (valued for soap and candle making at £19
per ton), 1 ton of tar, and a little gas, which is burned under
the boilers.?
X. The Smith-Leach Process, used at Bradford, consists in first
driving off about four-fifths of the water in a Yaryan multiple
evaporator, when the concentrated suds can be centrifuged into
(r) mud, (2) concentrated potash soap solution, and (3) crude
lanoline. At the Fieldhead Mills the potash soap is then
further concentrated, and finally burnt in a revolving cylindrical
incinerator to crude carbonate of potash, which is either sold,
or used again for washing wool. No effluent remains, and the
distilled water from the evaporator is utilized for wool-washing,
and from its softness effects a saving of 15 to 30/ in the
quantity of soap required. The trials show a considerable
profit, as the grease sells at nearly £20 per ton and the potash
at £23.
The Bradford sewage at the Frizinghall works is at present
passed through a detritus tank of 260,000 gallons capacity and
then treated by a modification of the Cassel process. The
press-cake contains so much grease as to be unsuitable for
manure. At Frizinghall a plant is being erected for extracting
the grease by distillation, as it has been found that in this way
practically all the grease can be extracted, and the cake left in
a dry powder containing all the nitrogen. About 25 tons of
sulphuric acid are required per day for 12,000,000 gallons of
sewage, and 300 tons of sludge are pressed per day, producing
60 tons of cake.
Paper Works. The process must vary with the materials
used. Caustic liquors from esparto or straw are evaporated
1 For details of cost, and analyses of products, see Garfield’s paper, loc. cit.
22—2
340 SEWAGE AND ITS PURIFICATION
and the soda-ash recovered by incineration. The wash waters
are economized by being used over and over again and finally
are precipitated and filtered as above. Wood-pulp works
introduce much less pollution: the whole of the pulp, which is
usually prepared abroad, is of value, and is kept back by a
variety of “save-alls”’ (revolving sieves of fine gauze), and
settling tanks.
At Chorley Paper Mill, Lancashire, it was decided in August,
1900, to try the effect of bacterial treatment on their waste,
with highly satisfactory results, the turbidity being removed
by the coagulating effect of the sewage. In almost all mills
where esparto grass is used, much difficulty is experienced in
obtaining a clear effluent, even after filtration through very
fine ashes. After admixture with sewage, however, and sprink-
ling, the final effluent contains much less suspended matter
than that from brewery waste.!
Tanners’ and Fellmongers’ Waste is generally admitted to the
sewers after deposition of the grosser solids. If precipitation
is practised, the tanks require to be cleaned out frequently in
warm weather, and suitable land or double filtration is resorted
to afterwards. |
Breweries. A large quantity of water is used for cooling ;
this does not require treatment. The washings of barrels, vats,
and tanks are precipitated and filtered, but in many breweries
they are discharged direct into the sewers. All these wastes
are preferably treated by bacterial methods.”
Sewage consisting Jargely of brewery waste was sieeullatly
intractable under the old methods of purification, and neither
chemical precipitation nor the most favourable land treatment
effected much improvement. At Burton-on-Trent (pop. 40,000,
sewage for 24 hours 5 to 6 million gallons) the sewage was first
precipitated, then filtered through 450 acres of land—less than
gO persons per acre—yet the farm had never been able to pro-
duce a good effluent.? But it has been found amenable to
bacterial treatment by septic tanks and filters that have been
properly managed and matured, and a successful instance is
given by Anson and Shenton‘ at Ash in Kent using a septic
tank and triple contact.
1 «* Bacterial Treatment of Trade Waste,” W. Naylor, p. 223.
2 J. Soc. Chem. Ind., June, 1got.
3 Dr. S. Barwise, Royal Commission on Sewage, vol. ii., 1902, p. 240. See also
Mr. Chatterton’s evidence, ibid., p. 354.
4 « Purification of Sewage and Brewery Refuse,” published by Davis, Epping,
1903.
TRADE EFFLUENTS 341
Hops in large quantities are particularly difficult to deal with,
and may be easily intercepted at the breweries.
At many places, as for example Dorchester, when brewery
refuse is present in the sewage in large quantities, a ‘‘ pig-pen ”’
odour is noticed at the septic tanks and sprinklers, and the
author has suggested in order to obviate this aerial nuisance, a
partial treatment with chlorine. When the works are far
removed from habitations, bacterial treatment of such sewage,
as shown by Dr. Barwise at Burton, and Dr. Maclean Wilson
in the West Riding of Yorkshire, can be accomplished without
any difficulty. |
The treatment of “‘ burnt ale,” or “ pot ale,” from distilleries
has received much attention in Scotland: it contains about
45 times as much total solids as ordinary sewage, and when
precipitated by lime it gave a manure worth about 70s. per ton,
but the liquor that was left was quite unfitted to be turned into
any stream without further purification. Evaporation, and
blowing into furnaces or smoke stacks in spray, have presented
difficulties owing to its stickiness and corrosive action on metals.
At Mortlach distillery, according to Dr. Cowie, it had been
treated successfully by tanks, coke beds, and coarse sand filters.!
But by themselves brewery and distillery wastes are treated
with difficulty on bacterial filters directly, owing to the forma-
tion of acids. The Hook Norton Brewery Company in 1900,
according to Naylor, impounded the strong liquor in a settling
tank for not less than 24 hours in contact with putrid sludge
from sewage, and when the putridity had once been established
throughout the liquid, sewage-sludge was no longer necessary.
The contents of this tank, which may be termed an “anti-
souring”’ rather than a septic tank, are pumped continually on
to a coal filter; the little suspended matter present after the
first filtration is intercepted by shallow sand filters, and the
effluent is clear, neutral, colourless, sweet, contains nitrates,
and about o’I part per 100,000 of albuminoid ammonia. The
diminution of dissolved oxygen after saturation is less than
30 per cent. Naylor states that a number of works in the
north of England now use a septic tank holding not less than
3 days’ flow, started by old sewage sludge, and fed with a
mixture of waste liquors with not less than 5/ of domestic
sewage. He finds that the species of bacteria so introduced
have the effect, partly by generating ammonia and so neutraliz-
1 J. R. San. Inst., 1g00.
342 SEWAGE AND ITS PURIFICATION
ing acids, and partly by competitive growth, of almost com-
pletely preventing souring of liquors containing starch or other
carbohydrates. The outflow from the tank is delivered by a
revolving sprinkler on a bed of furnace-ashes or coal, and after
passing through a small sand filter is as satisfactory as the one
last mentioned. The sewage has a coagulating effect in
removing turbidity from difficult liquors such as those from
esparto, china clay, etc.
Slack-washing, practised at some collieries for separating small
coal, gives a water which readily clears in settling tanks, and
can be used again and again. As to neglect of this precaution,
the Royal Commission on Salmon Fisheries, 1902, says of the
river Rhymney, that on account of the coal washing from
collieries the bed is in a filthy state and the beach is covered
with coal dust.
Chemical works give waste water of so various a character
that each case must be decided separately.
In a number of experiments on trade effluents, Meade-King'
found that the addition of salt water greatly helped the pre-
cipitation, either by iron alum, which he considers the most
useful precipitant, or by tannin (from oak bark, leaves or galls),
which is specially useful in gelatinous effluents like those from
print works, but is rather an expensive precipitant.
Gas Liquors. At Rotherham the waste water from sulphate
of ammonia plant occasioned trouble, as it has in other places
when not controlled. The suspended matter can very easily
be removed, but the purification of the liquid portion is quite
another thing. When much of this refuse is present in the
sewage, there is no process that can be adopted on a large scale
that will precipitate the cyanogen compounds. H. W. Crow-
ther (patent 11,964 of 1893) precipitates and recovers them by
cuprous oxide, which has been replaced by a solution of cupric
and ferrous sulphates followed by lime, but the process is hardly
applicable to sewage. Kershaw found at times as much as
110 parts NH,SCN per 100,000 in these liquors. This class of
refuse is present in the sewage of many towns, and if there is
any place where it is satisfactorily dealt with it is largely due
to the fact that its strength is greatly reduced by the volume
of sewage. In this condition it can be purified biologically to
a considerable extent. He further pointed out in his evidence
to the Commission, that very often sulphocyanides in filtrates,
1 Proc. Inst. Civ. Engineers, Jan. 9, 1900.
TRADE EFFLUENTS 3 343
etc., disappear on keeping, which indicates that the satis-
factory purification of sewage containing this class of refuse
is not beyond the range of possibility.
On the whole, the effect of trade liquors generally has been
greatly exaggerated. In the case of small settlements collected
round factories, the domestic products may be only in small
proportions, and the effluent must be treated specially by
chemical methods and not as a sewage proper. In large towns
these discharges are usually so largely diluted that they cannot
interfere with a bacterial process when rightly carried out.
It has been said that the antiseptic action of some chemicals
would arrest the bacterial changes. But by actual cultures it
has been shown that the amount of disinfectant required to
kill or even inhibit the organisms is far in excess of what can
be present in the mixed sewage. For example, at Yeovil,
where arsenic as sulpharsenite of calcium is derived from the
refuse of glove-making, I found that the maximum quantity of
orpiment, As,S,, that could enter the sewers per week, if the
whole amount escaped, was 2 cwt., equal in 120,000 gallons of
sewage daily to 3°9 parts of As,O; per 100,000, or *0039 per
cent., whereas Miquel observed that 0°6 per cent., or 600 parts
per 100,000 of As,O, was required to prevent bacterial growth,
and Frankland and Ward assert that it has little effect on
lower forms of life.
In December, 1899, I examined the waste liquors from two
of these factories, and found :—
Arsenic (As) parts per 100,000 ... i idk 1 686 9°45 -
Equal to arsenious acid As,O,... ; Kon IO 12°48
Total bacteria per c.c. Ra te ... 16,900 3,300
Rapidly liquefying ditto mB ¥? bai 7 100
Spores nhs ati oe. 100 1,000
Therefore, although arsenic in this quantity has an inhibitory
effect on some organisms, the liquid still contains a large
number, including those of a rapidly liquefying character, and
spores, so that the bacterial work would not be arrested, even
if the liquid reached the tanks undiluted with sewage or storm-
water. In comparative trials with the sewage alone, and mixed
with ;; of waste liquor, I found that both denitrifying and
nitrifying changes proceeded similarly with either. As a matter
of fact, the total volume of trade liquors in the Yeovil sewage
on any one day does not exceed one-fortieth of the estimated
dry-weather flow. ,
1 Kershaw, Association of Sewage Disposal Managers, 1905.
344 SEWAGE AND ITS PURIFICATION
Tannery liquors in the United States are said to contain
such a quantity of arsenic, even after sedimentation, as to
hinder bacterial treatment. The Massachusetts State Board
(Report, 1898) found that passing through a coke strainer com-
pletely removed the arsenic as ferric arsenate, and that by
afterwards filtering through beds of sand and gravel at the
same rate as ordinary town sewage, a satisfactory effluent,
fairly nitrified, could be obtained. The fats, retained by the
filter for a time, were destroyed by bacteria. A similar process
was used successfully with the waste liquor of paper mills.
With that from wool-scouring it was found impossible to filter
the heavy liquors, as they quickly clogged the surfaces of either
coke or sand. After neutralizing with sulphuric acid to remove
the fat, the liquid was mixed with 5 times its volume of city
sewage, when the bacterial action became very vigorous, finally
. high nitrification set in, and a sand filter gave a good result.
As an instance of an acid effluent, I found that a soap works
at Exeter was discharging 3-ton of acid liquor daily. Even if
this contained 1 per cent. of sulphuric acid, it would amount
on a million gallons of sewage to o°I part per 100,000. But
the crude sewage has sufficient alkalinity to neutralize more
than this amount of acid provided the latter be not supplied
in spurts as when poured direct on a filter. I have already
remarked on the beneficial mixing and ‘‘ smoothing ”’ effect of
the septic tank on the great fluctuations that occur at different
times in all varieties of sewage. I believe that the same natural
neutralization and precipitation would dispose of most metallic
admixtures such as iron salts, galvanizing pickle, etc.
With regard to tanning refuse, the antiseptic power of tannin
itself is very small, and, moreover, it does not pay to let much
of it escape. At Exeter I estimated the daily quantity from
the large tannery in that town as equivalent to that in six fluid
ounces of brewed tea per head of population, and it certainly
could have no influence.
Popp and Becker’ found that ‘‘ liquefying bacteria” were
killed by 0°5% of sulphuric acid or by 1% of sodium carbonate,
an acidity or alkalinity that would be higher than the ordinary
factory runnings, and would be brought down when mixed with
the whole of the sewage to an unimportant factor. As an
example I ascertained that at a certain paper mill 35 lbs. of
soda-ash were used daily: the maximum addition to the
1 Chem. Hyg. Inst., Frankfort, 1896.
LO,
TRADE EFFLUENTS 345
alkalinity of the whole daily sewage was 0°3 parts per 100,000
or ‘0003%.
Gas liquor and the effluents from timber works often contain
a large quantity of suspended tar, which clogs up filter beds
and presses, and fouls the catch-pits and sewers. Therefore
they must usually be excluded. A sample of refuse from a
timber yard which I examined in May, i899, contained, in
parts per I00,000 :—
Heavy petroleum Ay! se ate ss 1560
Pieces of wood, straw, leaves ti oy ae fake
Earthy matter and oxide of iron ... er i sie a
Solids in solution ~ aye an ik ¥-- 33
This is an example of discharges that are easily dealt with
by a catch-basin and straining, as the filtrate was nearly clear,
almost inodorous, neutral, and not injurious to bacteria. With-
out such treatment the floating tarry film might possibly some-
what hinder the activity of the upper bacterial layer of a septic
tank, but the aqueous liquid itself in its dilution would not be
likely to interfere either by its sulphides, cyanides, ammonia or
tar-acids, inasmuch as many bacteria generate and live in a
medium impregnated with ammonium sulphide, while cyanogen
compounds are far less poisonous to lower organisms than to
higher animals, and the strongest of the tar derivatives are not
bactericidal under 0°5%, or 500 parts per 100,000,—an impos-
sible amount to be present in the mixed sewage.
_ In exceptional cases, however, where intense acidity or other
strong admixture cannot be avoided, the use of lime and a
settling tank would become necessary: in this case a sludge
would be created which would ‘not be that of sewage.
Neutralization of acid sewage containing galvanizing pickle
by lime, and subsequent passage through contact beds, has
been found satisfactory at Bilston, Staffordshire.
Kinnicutt and Eddy examined the action of the septic tank
on the acid iron sewage of Worcester, Massachusetts, which
contained in parts per 100,000, FeSO, 15°77, Al.(SO,)3 0°44,
free H,SO, 10°32. They concluded that (1) about one-fourth
of the total solids was removed by passage through the tank ;
(2) about 21 per cent. of the soluble matter, and 25 per cent. of
the suspended matter, was removed, the former being greater,
and the latter much less, than the proportion usual with
sewages ; the result being due to the change of the soluble
sulphate of iron into insoluble sulphide of iron, a part of which
346 SEWAGE AND ITS PURIFICATION
is carried out of the tank in the effluent; (3) the action of
a septic tank removes a large amount of iron from an acid iron
sewage; (4) the reduction of organic matter, 26 per cent., is
much less than occurs with an alkaline domestic sewage ;
(5) the quantity of gas given off depends greatly on the amount
and character of the sludge at the bottom of the tanks, and on
the temperature, and is less in winter than in summer; (6) the
average volume of gas, 2°2 gallons per 100 gallons of sewage, is
probably less than would be obtained where the sludge contains
more organic matter: (7) its composition is CH,, N, COs, with
little, if any, hydrogen; (8) the amount of sludge changed into
soluble or gaseous substances, 28 per .cent., is probably less
than usual on account of the presence of so much ferrous
sulphide ; (9) the top crust or scum here contains much more
organic matter than the sludge; (10) the formation, non.-
formation, and disappearance of the crust appears to be an
incident, rather than a result, of bacterial action.1 Lime is
now added to this sewage. :
Effluents from oil, wool, and dye works at Trowbridge,
Wilts (Dibdin’s report of Sept., 1900), interfered little with
bacterial treatment, and not at all when diluted, with the
exception of bichromate liquors. None of the fourteen effluents
tried, when added singly or in mixture, in the proportion of
one per cent. to sewage I5 minutes before cultivation, had any
antiseptic effect, while with seven per cent. of the mixture the
influence was only slight.
Fibrous matters, such as those from wool manufacture, and
from horse-dung and wood-pavements, as mentioned in Dr.
Clowes’ L.C.C. Report of 1899, seriously interfere with the
action of the bacterial filters, but are easily dealt with by
hydrolysis in a septic tank.
In England,? at present, the relations between local authori-
ties and manufacturers in regard to the disposal of manufac-
turing effluents are contained in Section 21 of the Public Health
Act, 1875, which reads :—
‘““The owner or occupier of any premises within the district
of a local authority shall be entitled to cause his drains to empty
into the sewers of that authority, on condition of his giving such
notice as may be required by such authority.”
And in Section 7 of the Rivers Pollution Prevention Act, 1876:—
1 Third Annual Report of the Connecticut Sewerage Conimission, 1902.
2 Roy. Com., 3rd Report, 1903.
TRADE EFFLUENTS 347
‘“‘ Every sanitary or other local authority having sewers under
their control shall give facilities for enabling manufacturers
within their districts to carry the liquids proceeding from their
factories or manufacturing processes into such sewers.”’
But the efficiency of this section is practically neutralized by
the ensuing provisos :—
‘“‘ Provided that this section shall not extend to compel any
sanitary or other local authority to admit into their sewers any
liquid which would prejudicially affect such sewers or the dis-
posal by sale, application to land, or otherwise, of the sewage
matter conveyed along such sewers, or would from its tempera-
ture or otherwise be injurious from a sanitary point of
view.
‘* Provided also that no sanitary authority be required to give
such facilities as aforesaid, where the sewers of such authority
are only sufficient for the requirements of their district, nor
where such facilities would interfere with any order of any
court of competent jurisdiction respecting the sewage of such
authority.”’
Local Acts have in some cases accentuated these provisos,
and actions have been successful in prohibiting trade wastes
from gas-works and factories, when it was proved that such dis-
charges interfered with the treatment of the sewage at the out-
fall. Thus, at present, local authorities are not generally bound
to provide such sewers as may be necessary to carry off all the
trade effluents and liquid refuse coming from manufactories,
but only to provide for sewage in the ordinary sense of the term,
including “‘ water produced in the ordinary course of domestic
management,’’ and surface water.
The Commission reported as follows (3rd Report, p. xvil) :—
“ Purification of trade effluents by the local authority is, in
the great majority of cases, practicable; purification by the
manufacturer is in some cases difficult, if not impracticable, and
would generally be more costly than purification by the local
authority. Local authorities, as well as manufacturers, are of
opinion that there should be laid upon the local authority a dis-
tinct obligation to receive trade effluents. Further advantages
which would follow from such a change in the law would be
that the average standard of purification which would be reached
throughout the country would be higher than if each manufac-
turer separately attempted to purify his own effluent, and also
that the work of preventing the pollution of rivers would be
348 SEWAGE AND ITS PURIFICATION
greatly assisted, in that the number of purification works to be
kept under observation would be diminished.”
They find that it should be “the duty of the local authority
to provide such sewers as are necessary to carry trade effluents
as well as domestic sewage, and that the manufacturer should
be given the right, subject to the observance of certain safe-
guards, to discharge trade effluents into the sewers of the local
authority, if he wishes to do so. ... In each district it would
probably be desirable that the local authority should frame
regulations, which should be subject to confirmation by a
Central Authority. ... It appears from the evidence that
-manufacturers would much prefer to have standards to work to.”
This alteration in the law should involve “‘no charge on the
manufacturer, in those cases in which the regulations as to
preliminary treatment are complied with.” ... Where the
. effluent must not be discharged into the sewer because the
water is obtained from a stream and must therefore be returned
to it, the duty of purification will rest with the manufacturer,
‘but they do not consider that this will be a serious grievance,
as he obtains his water without charge, and this advantage may
be set against the cost of purification.”
With regard to Sludge Removal from Manufactories (3rd
Report, p. xxil), manufacturers are generally willing to adopt
reasonable means for the removal of solids from their effluents
before entering the sewers. But sedimentation, and still more
precipitation, involved the production of “ sludge,’’ which was
a cause of difficulty. The Salford Corporation undertake to
dispose of such sludge; and in London the sanitary authority
removes trade refuse at a reasonable cost.
They further urge the need of setting up a Central Authority as
a new department under the Local Government Board for—
(a) The settlement of differences between manufacturers and
local authorities ;
(b) The general protection of sources of water supply.
(c) The collection of facts, and the scientific investigation of
questions of general importance relating to the protection
of water.
The recommendation also includes the formation of Rivers
Boards throughout the country, each to have jurisdiction over
the whole of a watershed, and to be a first tribunal of appeal.
INDEX
A
ABC process, 160
Accrington, sewage treatment, 152, 242
Acetates, fermentation of, 109
Acidity of sewage, 32, 344
Acids organic, 109
bi Sterilization by, 192
Acreage of land required, 147
Acts, Rivers Pollution, 170
Adams’ Automatic Syphons, 283
Adeney’s limit of impurity, 58
Adsorption, 133, 223 ‘
Aeration figure, 50, 53
4s of water, 48, 189
ie processes, 122, 234, 236
ds stage, 121
Aerobacter, 114
Aerobic bacteria, 63, 72, TIO
Africa, South, sewage treatment in, 272
Agar-agar, 62
Agriculture, relation of sewage to, 137, 331
Algze, 78, 82
Alkalies in sewage, 41, 200, 332
Alkalinity, fixed and volatile, 28, 32, 124,
125, 206
Albuminoid (see Ammonia albuminoid)
Albuminous substances, decomposition of,
98, 105, 117
Alumina process, 157
Aluminium salts, precipitation by, 157, 335
Alumino-ferric, 84, 158, 335
Alum, 158
Alternating gear, 258, 283, 285
Ames tank, 266
America, discharge of ee into streams,
15, 18, 56
rat Massachusetts experiments, 46,
84, 159, 207, 209, 226, 269
FS sewage methods, 21, 140, 206-209,
225, 281
‘5 street sweepings, 198, 200
ae typhoid from cig aubach mud, 4
water-supply, 4, 84, 208
Kininoala, absorption, 173
0 albuminoid, meaning of, 57, 108,
238
- decompositions, 99, 251
"f effect on nitrification, 124
” ” plants, 330
a free and albuminoid, determina- |
tion of, 35, 45, 174
* recovery from sewage, 195, 333
Amido-compounds, changes of, 106
Amines, 108
Amcebee, 78
Anabeena, 82
‘Analysis, bacterial processes, 61
os chemical processes, 31-54
|
Anaerobic bacteria, 64, 72, 189
oe changes, 98, 112, 252
rf cultures, 64
be tanks (see Septic tanks)
Anguillula, 77
Antagonism of bacteria, 100
Antiseptic treatment (see Chemical)
Antiseptics, interference with bacterial
action, 66, 343
Area of land required, 147
Aromatic compounds, r10
Arsenical liquors, 343, 344
Ash of sewage, determination of, 33
Ashes, 10, 197
Ashtead experiments, 250, 269
Ashton-Booth sludge remover, 164
Asparagin and aspartic acid, 107
Australia, 115, 152
Automatic gear, 259, 283-287
scavenger, 205
Available chlorine, 180
si oxygen, 16, 130, 271
B
Bacillus amylobacter, 72, 75, 110
», anthracis, 93, 94
», aquatilis, 72, 128
», arborescens, 72, 215
», coli communis, 66, 72, 74, 89, 92,
97, 102, 129, 137, 1690, 175, 188,
193, 215
», denitrificans, Ior, 127, 129
», desulphuricans, 114
» enteritidis sporogenes, 73. 87, 88,
89, 104, 169, 175, 188, 193, 215
», erythrosporus, 77
,, fermentationis cellulosee, 111
,, fluorescens liquefaciens, 72, 104,
129
», mesentericus, 74, III, 129
»» Mycoides, 72, 97
», prodigiosus, 9, 101, 108, 215
», pseudo-tuberculosis, 93
” pyocyaneus, 73, 93, 97, IOl, 127,
129
», Subtilis, 73, 74, 97, I91, 194
», tuberculosis, 105, 215
», typhosus, 86, 89, 105, 137, 175
os urez, 73, 108
See also Chap. IV., p. 72, ete.
Bacteria as a test for pollution, 8
m3 beds, 75, 100, 210
» counting, 63, 77, ror
oe colonies of, 62
mf: cultivation media, 62, 66, 67
¥ in sludge, 165
», in soil, 136
a pathogenic, 84, 100
349
350 INDEX
Bacteria, spores of, 64, 74
as stages of action, 100, 272
Bacterial efficiency, testing, 68
samples, 61
Bacteriolysis, 96 (see also Hydrolysis and
Nitrification)
Bacterium sulphureum, 73
Ballast, 210, 227
Baltimore, 295
Barking filter, 98, 211
Barrhead installation, 262, 315
‘*Battage ” of grease, 338
Beggiatoa alba, 73, 78
Berlin sewage farms, 135, 139
», Sewerage Commission, 202
» street sweepings, 200
Belfast, 80, 222
Bergé process, 192
Bichromate liquors, 335
Birmingham, sewage disposal at, 155, 165
Bleach liquor, 183, 334.
Bleaching powder, 180, 183
Blood-heat organisms, ‘64
Bradford, sewage disposal at, 166
2s wool-scouring refuse, 336, 339
Brent, use of chloride of lime on, 181
Brewery waste, 341
Brighton, 170
Broad irrigation (see Irrigation)
Burning, disposal by, 1, 154, 198
Burton-on-Trent, 141
Bury, dust disposal, 198
By-laws, 8, 55, 347
Cc
Calcutta sewage, footnote, 134, 332
Cameron’s alternating gear, 259, 286
Candy-Caink sprinkler, 294
Capacity of beds, 213, 226, 233
Carbohydrates, decomposition of, 110, 113
Carbonaceous iron sand, 229
Carbonic acid in sewage and effluents, 51,
75
», in air of filters, 125, 234
Carchesium lachmanni, 80
Carriage of sewage and refuse by
carts, 6, 196
oR pneumatic tubes, 195
Me water, 4, 7, 13
Cassell process, 196
Catalytic theory of putrefaction, 202, 211
Catch-pits, 7, 345
Catchwater system, 143
Caterham works, 91, 252
Cellulose, 113, 215
hydrolysis of, 110, 117
Centrifugal method for solids, 34
Cesspits, 10
Cesspools, 2, 3, 8, 206
Chalk for earth closets, 11
,, asa filtering medium, 246
» infiltration through, 8, 136
Chemical precipitation, 155
nd sterilization, 168
Chemicals injurious to plants, 147
Chichester, 83, 84
Chloride of lime, 180, 183
Chlorine and its compounds as disinfectors,
87, 179-192
rs as measuring strength of sewage,
13, 35, 145
5 as a finisher, 87
as determination of, 34
Chlorine ratio to nitrogen, 58
x loss of, 125, 181, 189
Chloros, 181
Chlorates, 192
Cholera organisms, 192, 193
Cinders as filtering material, 234
Cladothrix, 78, 84
Clarification, 11, 153, 210
Clarine, 158
‘Claybury, bacterial treatment at, 272
Clay soils, 733, 136
Clinker as a filtering medium, 228
Closets, dry, 8
», arth, 11
» water, 12
Clostridium butyricum and foetidum, 73,
75, 113
Coal as a filtering medium, 226
Coarse filters, 227, 232, 240
Coke beds, 210, 212, 227
Cold, influence on purification, 242
Coli (see B. coli communis)
Collection of samples, Chapter II.
3 ms bacterial, 61
Colloids, 223
Colonies of bacteria, 62
Columbus, Ohio, investigations, 208, 264
Combined system of sewerage, 150, 162, 312
Combustion of excreta, 1
a sewage gases, 116, II7
i town refuse, 198
Commissions on sewage, 19, 34, 47, 55, 85,
168, I71, 202, 203, 347
Conservancy systems, 9, II
Contact beds, 189, 210
Continuous filtration, 280
Copperas, 158, 159
Copper salts for sewage treatment, 174
Corrosion of fittings, 182
Cosham’s tank, 163
Cost of purification, 168, 194
Counting bacteria, 63, 71
Cremation of effete matters, tT, 154, 198
Crenothrix, 78, 82, 161, 308
Cultivation tanks (see Septic tanks)
Culture media, 62, 67, 114
Cultures, anaerobic, 64
mA plate, 62
me stab and streak, 65
ae surface, 66, 72
Cytase, 104, 113
D
Dejecta, burning, 1
re covering by earth, 1, 2
-. quantities and manurial value, 40,
I
is removal by screening (see Screen-
ing
Delattre process for grease recovery, 337
Denitrification, 125, 231, 251
by soil, 133
Depth of filters, 213
Derbyshire County Council standards, 55
Destructors, 154, 199-201
Detritus, road, composition of, 6, 7, 200
», tanks, 23, 253
Detroit, water-borne typhoid of, 4
Diastase, 104, 113
Dibdin beds, 71, 75, 221
Dibdin’s experiments, 206, 217
», fish test, 56
Digby process, 191
INDEX
Dilution by subsoil water, 145, 311
» Calculation of, 35
» effects of, 14
», methods for bacteria, 61, 72
Discharge into rivers, 4, 14, 169, 310
me into the sea, 19, 20, 317
¥3 into tidal estuaries, 19, 170, 319
Disinfection of sewage and excreta (see
Sterilization)
ss by chlorine, 182
Distribution on beds, 283
over land, 141.
Distributors, 282-308
Dortmund tank, 163
Double treatment, 216, 231
Dover's process, 155
Drainage waters from farms, 5, 8, 149
Dry-rot, 111
Dublin, 20, 316
Ducat’s filter, 87, 236, 240
Dust collection, 6, 196
», destructors, 199, zor
», methods of disposal, 196
» use of screened for beds, 223
Dye-water, 334
E
Earth closets, 11
», committal to, 1, r1, 132
Electrolytic processes, 184
Electrozone, 185 cama ect
Energy produced by bacterial changes, 116
Enteric (see Typhoid)
Enteritidis bacillus (see B. enteritidis)
Enzymes, 102, 143
Essen tank, 163
Estuaries, 19, 170, 317
Excreta, burning, 1, 198
a chemical treatment, 187
ie nature of, 5, 40, 331
ek primitive disposal of, 1
oa removal in scavenging, 11
weights per day per person, 40, 54
Exeter sewage treatment at, 18, 86, 254
Exothermic change, 116
F
Facultative aerobes and anaerobes, 65, 72
Feeces, 5, 11, 40, 54, 99, 187, 331
Farm pollution, 5
Farms, sewage (see Sewage farms)
Farrer’s distributor, 306
Fats, decomposition of, 98, 113
», Yremoval of, 265
», utilization, 336
Fatty acids, 80, 98, 109, III, 337
Ferments and fermentations, Chap. V.
Ferric and ferrous salts, 157, 158, 176
Sees? sulphide (see Suiphuretted hydro-
gen
Ferrozone, 158
Fibre, resolution of, 110
Fiddian distributor, 304
Filter presses, 154
Filters, aerating, 240
», Capacity of, 226
»» contact, 243
»» continuous, 244
», distribution on (see Distributors)
», gases in, 125, 234
», Materials for, 227, 248
», Oxidizing, 206, 240
», roughing or straining, 28, 152
351
Filters, zonal, 75, 91, sts
Filtration areas, 147, 2
« through hats ee Chap. IV.
», upward, 249
Finishers, 87, 175, 194
Fish test for effluents, 56, 215
“8 as conveying coli, 92
iy: injury to, by sewage, 319, 334
Fisheries, contamination of, 170
Flies, infection by, 14
Float method of gauging, 20, 22
Flow, gauging the, 22, 23
» regulation of, 282, 311
», Variations of, 28, 312
Foreshores, 19, 80, 170, 318
Formulz : Mouras’ Scavenger, 205
a discharge of sewage, 16
es ratio of Cl to N, 58
os volume of subsoil water, 145 .
Ks V-notch, 23
a weirs, 22
France, pneumatic emptying of cesspools, 4
», pollution of river Seine near Paris, 4
», Roubaix method of extracting waste
wool fat, 337
», treatment of Paris sewage, 143
Frankfort sewage sludge, 337
Friern Barnet, 228
Frost, effect on purification, 208, 242, 265,
275
Fungi, 78, 103, IIo
Furnaces for refuse, 199
G
Garfield filter, 227
Gas in cesspools, 2
Gas from sewage, utilization of, 115, 259
Gas-liquor, 342, 345
Gases from refuse, 200
» produced by bacteria, 65, 97, 106,
Chap. V.
», from tanks, 97, 115, 259
Gauging, 22
Gayon and Dupetit reaction, 126, 220
Gelatine cultures, 62.
», hydrolysis, 98, ro2
Germany, sewage treatment in, 135, 139,
143, 196, 202, 204, 223, 337
Germ theory of putrefaction, 202 .
Germicidal action, Chap. VIII., 168
Glasgow, sewage treatment at, 152
Glover's tank, 206
Glycerine, fermentation of, 113, 114
Glycocine (amido-acetic acid), 107
Gooch crucible, 33
Goux-Thulasne method of disposal, 11
Grasses on sewage farms, 138
Gravel, 3, 7, II, 210
Grease, I13
,, traps, I5r
», (see Utilization)
Grit chambers, 28, 162, 261
,, and detritus, 150
Guildford investigations, 73, 87, 185
H
Hagen’s process, 194
Hampton, 224, 267
Hanging-drop cultivations, 69
Harriali grass, 135
Havana, sewage disinfection at, 185
Heat, evolved in bacterial changes, 116
», sterilization by, 195, 199
352
Heating of bacteria beds, 240, 242
Hendon, Ducat filter at, 240
Hermite solution, 184
Holding up, 283
Horfield, sewage treatment at, 247
Hospitals, discharges from, 172, 193
Household waste, 5
Humus, 96, 113, 123, 140
Hydrogen, anaerobic cultivations in, 64
im production of, 96, 97
pews? of organic matter, - 96, 99,
105, 250
Hydrolytic tank, 267
Hypochlorous acid and hypochlorites, 180
I
Impression preparations, 69
Incubation temperatures, 62, 64, 71
Incubator tests, 52
India, sewage disposal in, 134, 183, 195
Indigo solution for nitrates, 43
Indol, 91
Infiltration of soil, 2, 3, 8
Infusoria, 78
Inoculation of beds, 75
Intermittent filtration, 211
a irrigation, 144
ie subsidence, 161
Invertase, 104, I13
Ireland, 20, 80, 170, 173, 222
Iron, corrosion by chlorine, 182
,, Salts as precipitants, 158, 334
»» 9» ON sewage farms, 147
,, sand as a filtering medium, 229
Irrigation, Chap. VI., 132
intensive, 143
Irwell, pollution of, 4
Italian rye grass, Tt 38
Ive’s tank, 163
J
Japan, sewage treatment in, 135
Jelly, nutrient for bacterial cultures, 62
,», Silica, 67 .
K
Katabolic, 103, footnote
Killon’s automatic regulator, 303
Kingston-on-Thames, sewage treatment at,
152, 160, 161
Kjeldahl process, 45, 108
L
Lactic fermentation, 109, 113
Land filtration, Chapter VI., p. 132
,, Official requirements as to, 147, 149
restoring valuable matters to, 149, 330
», Of sewage farms, 134
Lanoline from waste wool fat, 336
Lawrence city, sewage treatment, 209
Leeds, sewage treatment at, 224, 280
Legal actions for nuisance, 321, 326
Leguminous plants, 332
Leicester, sewage treatment at, 146
Leptomitus lacteus, 79
Leucine, 107
Lichfield, sewage treatment at, 227
Liebig’s theory, 202.
Liernur process, 194
Lime, addition to sludge, 165
- 4, application of waste, 135
», asa purifier, 155, 206
», effect of in soils, 134
INDEX
Lime, effects of in waters, 157
», soaps, 28
Limestone in filters, 264
Lipase, 104, 114
Liquefaction of gelatine, 62, 104
Liquefying organisms, 62, 70
Liverpool, pollution of wells by cesspools, 3
Local Government Board, 8, 19, 147, 148,
277, 314, 321, 327, 348
‘London County Council experiments, 72,
74, 88, 98, 159, 210, 212, 322, 327
London sewage, 152, 209
Loss on ignition, 33
Lowcock’s filter, 236
M
MacConkey’s medium, 67
Madras sewage farms, 135
Maidenhead, sewage experiments, 87, 185
Maidstone, 8
Malvern, Lowcock’s filter at, 237
Manchester experiments, 54, 152, 183, 224,
273-279) 313, 317
Maltose, 104
Manganates, 177
Manganese, use of compounds of, 176-179
Manufacturing refuse and effluents, 32, 55,
261, 333-348
Manure, decompositions of, 128, 330
si from sewage, II, 152, 160, 330
5 treatment in farmyards, 5
be value of sewage as, 41, 331
Marsh gas (see Methane)
Massachusetts experiments (see America)
Materials for filters and bacteria beds, 227
9 size of, 229, 248
oi comparative efficiency, 227, 230
Media for bacterial cultivations, 62, 123
Mechanical separation of solids, 152 (see
Screening and Sedimentation)
Melbourne, 115, 152
Melosira and Meridion, 80
Mersey and Irwell Board, 39, 56, 273
Merthyr Tydvil sewage disposal, 144
Mercaptan, 105
Merulius lachrymans, I11
Metallic salts for sewage treatment, 174
», surfaces as sterilizers, 176
Metallophilic organisms, 160
Metals, action of chlorine.on, 182
Meters, 24°
Methane, 105, 109, 110
Methylamines, 108
Micrococci, 73
Micrococcus aquatilis, 77
He candicans, 75 —
e urez, 73
Microscopical examination of bacteria, 69
Mineral constituents of sewage, 40, 43, 332
Middens, 2, 10
Midden heaps, 2
Midden towns, 12
Milan, disposal of sewage at, 143
Mixing of sewage liquids, 272, 276
Modules for regulating flow, 282, 316
Moncrieff (see Scott-Moncrieff)
Motility of bacteria, 69
Moulds, 113
Moule’s earth closet system, II
Mouras’ Automatic Scavenger, 205, 249
Mudbanks, 4, 319
Mucor, 113
Mueller's process, 204
INDEX
N
Nais, 77
‘* Native Guano”’ process, 160
Nesslerizing, 35, 45
Night-soil, 10
Nitrates, 16, 17, 99, 100
», addition to effluents, 179, 276
», determination of, 43
ie in soil, 124
Nitrification, 58, 68, 77, 121, 202, 232, 251,
317
Nitrifying organisms, 66, 77
” trays, 65, 268
Nitrites, 16, 17, 49
;, determination of, 44
», aS Oxygen carriers, 119
Nitrogen, disappearance of, 99, 220
» dissolved, 50
oi forms of, 30, 59
& gain of, 231
= loss of, 58, 106, 119, 126, 222, 330
AR production of free, 119, 126
ye organic, 28, 59
= oxygen required to oxidize, 121
determination of, 45
pe ratios, 30, 59
: x restoration to the land, 33
Nitrobacter, 76, 101
Nitrosification, 68, 118
Nitrosomonas, 76, ror, 118
Nitrous oxide, production of, 126, 127
Nobbe’s solution for plant food, 332
Nuisance actions, 188, 341
Nutrient media for bacteria, 62, 123
O
Obligate aerobes and anaerobes, 64, 72
Odour, removing, 168. 174, 180, 181, 341
Odours from sewage, 80, 173, 318
», from organisms, 80, 82
Oldham sewage, 12
One-acre filter at Barking, 98, 211
Organic acids, 107, tog
Organisms, larger, effecting purification, 77
o6 causing odours, 80
‘9 methods of counting number of,
63
Oscillaria, 80, 83
Osier beds, 140
Oswestry, Sutton system at, 223
Outfalls, position of, 316
Overflows, storm-water, 315
Oxidation by manganese compounds, 179
“ ratios, 30
Oxidizing agents, 56, 177, 179, 192, 194
Oxychlorides, 185-190
Oxydases, 110
Oxygen, available, 16, 130° .
zi consumed or absorbed, determina-
tion of, 37
consumed process, criticism of, 37
m odifications
of, 39
Ee dissolved, 47, 48, 189
a liberated from manganates and
permanganates, 177
5 required for nitrification, 121
Oxynite process, 179
Oysters, 21, 170, 320-322
Ozone, 194
ly
Pail system, 10
Paper dissolved anaerobically, 110
353
Paris, disposal of dust, 197
», pollution of Seine at, 4
», treatment of sewage at, 143
Pasteur’s researches, 65, 202
Pasteur-Chamberland filter for sterilizing,
68, 70, 329
Pathogenic organisms, 75, 84, 100, 186,
215, 327
Pavements, 6, 181
Peat and peaty matters (see Humus)
Penicillium glaucum, 114
Peptones, 62
Permanganate alkaline, 36
” test, 37
Permanganates, use of, for sewage, 176
Peroxide of chlorine, 192
3 of manganese, 178
Per-salts of iron (see Ferric Salts)
Petri dish, 62, 63, 67
Phenol derivatives, too, 107, 110
», in cultivations, 67°
Phenylacetic acid, 174
Phosphates in sewage, 41, 200, 332
Pipe lines, 21, 148, 317
Plants, on sewage farms, 137, 194, 333
», Water, 78
Plate cultures, 62
Ploughing in, 135, 154
Pneumatic control (see Adams)
3 disposal of sewage, Liernur’s,
194
* emptying of cesspools, 3
Podura aquatica, 78
Polarite, 227, 322
Pollution of rivers (see Rivers)
Pollution of drinking water and wells, 3, 8,
Io
Population per acre of land, 147
Potassium in sewage, 41, 332
Precipitation before application to land, 146
o chemical, 155
Pressing sludge, 166
Primary beds, 216
Privies, 8
Proteus vulgaris and other species, 73, 74
Proto-salts of iron (see Ferrous)
Protozoa, 84
Ptomaines, 93, 108
Pumping sewage, 152, 201
Putrefaction, theories of, 95, 202
Pyrolusite, 178
Q
Quality of sewages, 28, 311
Quantities excreted daily, 40, 54, 331
Quantity of land required, 147
R
Rainfall, 6, 27, 148, 310
Rathmines, 20, 316
Recovery of grease, 335
ig of manganese, 179
ts of waste products (see Utilization)
‘*Reduction” of refuse, 198
Refuse, as filtering material, 223
», Classification of, 5, 199
», destruction and disposal, 196
» trade, 55, 199, 312, 335
Regulations (see Local Government Board
and By-laws)
se of Massachusetts Board, 7
Reversible reactions, 104
Retting of flax, 111
23
354
Ribble Joint Board, 55
Rideal’s formula for dilution of sewage, 16
Ridge and furrow irrigation, 137, 141 ~
Ridgway Automatic Distributor, 285
Rivers Board, 348
», disinfection of, 169, 173
», pollution of, 4, 14, 18, 41
»» Pollution Commissions, 19, 55, 168,
310, 320, 329
», purifying action of, 14, 18,130
», permissible admixture of sewage or
effluent, 15, 18, 169
Road detritus, 6, 28
Rochdale, 1o
Rockner-Rothe tank, 163
Roll cultures, 66
Root crops on sewage farms, 138
Roscoe filters, 274
Rotary screens for sewage, 150
Roubaix process of extracting waste wool
fat, 337, 338
Roughing filters, 152
Royal Commission reports, 34, 47, 85, 154,
I71, 172, 203, 320, 327, 347
Rye-grass in irrigation, 138
S
Salford sewage treatment, 244
Samples, method of collecting, 27
+ bacterial, 61
Sand filters, 207-209, 210, 263
Sandy soils, Chap. VI.
Sarcina, 1c5
Scavenging, 6
Scott-Moncrieff, 250, 268-272, 300, 309
Screening, 150, 214, 216
Scum, bacterial, 254, 264, 275
», harbour, 80
», Plates, 162, 263
», tanks, footnote, 275
Sea, discharge into, 19, 20, 170, 317
», lettuce, 80
», Water admixture, 317
- », electrolyzed, 184
,, weed, 80, 81
Secondary beds, 217, 221
Sedimentation (see Settling)
Separate system, 12, 137, 312
Septic fermentations, 100
», tank, antecedents of, 204, 250
os » effluents, 108, 187
», tanks, 253, 258-267
De », closed and open, 259, 275, 280
z », duration of stay in, 254, 261
Settling tanks, 161
Sewage, application to land, Chap. VI., 209
Bie classification of, 5, 11
re discharge into cesspools, 2
», Tivers, 4, 14, 56, 169
rs nF », the sea, 19,170, 217
re farms, suitable crops, 137
a farm effluents, 40, 145
a farms, pollution by, 9, 193
», flow of (see Gauging and Flow)
rr fungus, 78, 79
»» precipitation by chemicals, 155
rs strength of, 13, 161
Sewer gas, 2 (see also Gases)
Shake cultures, 65
Sheffield, sewage treatment at, 280
- Shellfish, 170, 327
Ship Canal, Manchester, 276, 317
Shores (see Foreshores)
” a)
INDEX
Silica jelly for nitrifying organisms, 67
Silicates for cultures, 123
Sirosiphon, 161
Slate in filters, 235
Slop closets, 13
Slop-water, 5, 12
Sludge, 55, 154, 164, 187, 255, 319, 337, 348
», cake, analyses of, 167
Smith-Leach process for recovering grease,
* 339
Soap-water, 6, 12, 27, 113
Soil, action of, on sewage, 93
» infiltration of, 2, 3, 8, 9
.y, Nitrification by, 124
,, Suitability for sewage farms, 134
Soils, organisms in, 136
Solids of sewage, determination of, 32
is te suspended, 12, 28, 33, 150
South Africa, 14, 29, 272
Spheerotilus natans, 79, 161
Spirilla, 72, 114
Spores, method of counting, 63 64
Sprinklers, 287-308
Stab cultures, 65
Staining bacteria, 70
Standards for effluents, 15, 55
Stages of purification, 100
Starch, hydrolysis of, 98, 113
Steam blown into filters, 242
Sterility, absolute, 191
Sterilization by chemicals, 168-194
“ filtration, 70, 329
re heat, 62, 70, 171
Storm-water, 5, 12, 312-315
Stoddart’s distributor, 288
i filters, 246
Straining for analysis, 29
‘4 sewage, 28, I50
Straw, influence on denitrification, 129
y, anaerobic solution, 112
», ‘presence in primary bacteria beds,
215
Street cleansing, 6
» gullies,7
»» sweepings, 200
», washings, 6
Streak cultures, 65
Streptococci, 75, 128
Streptothrix chromogena, footnote, 123
Sub-cultures, 68
Subsidence, 150
Subsoil water, 145, 316
Sugars, fermentation of, 113
Sulphates in sewage and waters, 40
Sulphide of iron, 115, 319
Sulphur compounds, 81, 97, I14
Sulphuretted hydrogen, 28, 114
Surface plate cultures, 66, 72
Survival of pathogenic organisms, 84, 186
Sutton, analyses of sewages and effluents,
216
», system, 217, 222
Sydney, N.S.W., 19, 21
Symbiosis and synergetic, 100, Io1, 112
Syphons, automatic, 283
T
Tanks, aerating, 239
», anaerobic (see Septic)
» Dortmund, 163
,, sedimentation (see Settling)
», septic, 187
», settling, 161, 162
INDEX
Tanks, straining, 152
Tanning liquors, 344
Temperatures of incubating cultures, 62, 64, |
71
of oxygen consumed test, 39
influence of, on bacterial ©
action, 242, 275
Tertiary beds, 190, 224
Thames Conservancy, 55
a river, 51, 181, 203
Thermophilic organisms, 63, III
Thermal methods, 194, 242
Thermal aerobic filter, 242
Tidal discharge, 19, 20, 21, 170, 317
Tiles in filters, 236
Tipping of dust, 196
Tipping troughs, 268, 305
Town refuse, 196-201
Trade refuse and effluents, 12, 36, 55, 333
Trays, nitrifying, 65, 2
Treble contact (see Triple contact)
Trimethylamine, 108
Triple contact, 224
Trowbridge, waste liquors at, 346
Tubercle bacilli (see B. tuberculosis)
Typhoid bacilli, (see B. typhosus)
Typhoid from sewage mud-banks, 5
vitality of the bacillus in soils, 14,
D 137
Tyrosine, 107
U
Ulva latissima, 80
Urea, 36, 98, 106, 116, 220
,, decomposition by chlorine, 182
Urine, 5, 11, 27, 331
», Chlorine in, 35
», daily amounts of, 40, 54
of animals, 12, 41
volatile oil from, 174
- Utilization of ammonia from sewage, 333
= effluents agriculturally, 330
gases from sewage, I15, 116,
259
Cait night soil, ro
sewage and sludge as manure,
154, 160, 164, 195, 341
sewage on land, 132
town refuse, 197
waste products, 335
Vv
V-notch for gauging, 23
pica control of sewage by (see Distribu-
tion
Variations in sewage, 27, 28
Vegetable débris and washings, 5, 11, 28,
112
Vegetables on sewage farms, 138
THE
355
Vegetation, aquatic, 78
Ri growth of, 144
* encouraged by effluents, 332
Venturi meter, 24, 26
Vinegar, 193
Volatile boaies from sewage, 174
_ Volume of sewage and storm-water (see
Gauging and Flow)
Volvox, 80
W
Wanklyn, albuminoid ammonia process,
6
Secs of solids and of sul-
phates, 40
Waring's system, 152, 236, 239
Warming, artificial, of bacteria beds, 241,
242
Waste, manufacturing (see Trade effluents)
Water carriage, 2, 7, 14
», Closets, 12
cress, 323
exhaled by plants, 138
logging of soils, 148
,, plants, 78
subsoil, dilution of sewage by, 145
», supplies, 35, 41
9 a in United States, 18
Webster process, 184
Weirs, aerating, 258
» gauging by, 22
», overflow, 312
Wells, pollution of, 3, 8, 10, 148
Whittaker - Bryant thermal - aerobic filter,
242
Whittaker sprinkler, 242, 294
Wimbledon, sewage at, 165
Wolverhampton, Lowcock filter at, 238
Woody fibre, solution of, 110
Wool fibre and scourings, 336, 338
Worcester, Mass., sewage, 207, 345
Worms in sewage farms, 136
ec. Weer, 77
”
X
‘*X” nitrogen, 46, 47
Xylane or wood-gum, 129
Y
Yeast, 65
Yeovil, 93, 343
York, sewage treatment at, 159, 265
Z
Zones of bacteria, 75, 268
Zooglzea, 115
Zymase, 104
Zymosis, 103
END
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