Environmental Protection Technology Series
LIBBY, McNeill & LIBBY
FOOD TECH. RES. LIBRARY
CHICAGO, ILLINOIS
MINIMIZATION OF WATER USE IN LEAFY
VEGETABLE WASHERS
Industrial Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
EPA-600/2-77-135
July 1977
MINIMIZATION OF WATER USE
IN LEAFY VEGETABLE WASHERS
by
Malcolm E. Wright
Agricultural Engineering Department
and
Robert C. Hoehn
Civil Engineering Department
Virginia Polytechnic Institute and State University
Blacksburg, Virginia 24061
Grant No. S-802958
Project Officer
Harold W. Thompson
Industrial Pollution Control Division
Industrial Environmental Research Laboratory
Corvallis, Oregon 97330
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO A5268
DISCLAIMER
This report has been reviewed by the Industrial Environmental Research
Laboratory, Cincinnati, U.S. Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily reflect
the views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
11
FOREWORD
When energy and material resources are extracted, processed, converted,
and used, the related pollutional impacts on our environment and even our
health often require that new and increasingly more efficient pollution control
methods be used. The Industrial Environmental Research Laboratory - Cincinnati
(lERL-Ci) assists in developing and demonstrating new and improved methodo-
logies that will meet these needs both efficiently and economically.
This report covers the construction and evaluation of an improved
leafy greens vegetable washing system. This system consisted of two series
drum immersion washers, each with associated settling tanks and moving belt
screens. Wash water was used in a counter-current flow regime. Results
obtained when comparing the prototype process to current commercial washing
systems were encouraging. Significant reductions in wash water requirements
and wastewater generation were reported; as was an increase in cleaning
efficiency.
It appears that this process modification will become a building block
in the development of economically achievable waste management systems for
the leafy greens processing industry. As a result this report should be of
interest to processors of leafy greens, designers of processing facilities,
equipment manufacturers and environmental regulatory agencies.
Further information on this project can be obtained by contacting the
Food and Wood Products Branch of lERL-Ci.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
111
ABSTRACT
This project was undertaken to construct and test an improved leafy
greens washing system employing water recirculation, to characterize the
quality of the wash water and waste stream, and to make comparisons to con-
ventional washers. The prototype system produced a cleaner product while
reducing water requirements and consolidating waste loads.
The prototype system consisted of two drum immersion washers in series,
each with associated settling tanks, filters, and water recirculation systems.
Construction was similar to conventional washers but with modifications to
improve removal of floating trash and increase hydraulic agitation of
product. Fresh water input was limited to that required to replace water
carried off by the product plus a small, overflow, effluent stream from the
system.
The prototype was tested in a commercial processing plant during the
fall and spring harvesting seasons, 1975-76. Sixty-seven metric tons of
collards, spinach, and turnip greens were processed through the prototype
in 52 hours of actual operating time. Conventional washers were monitored
for 27 hours (38 tons) for comparison. Insect and bacteria counts, COD,
TSS , VSS , and several other water and product parameters were measured at
predetermined times and locations. Data were obtained to predict expected
waste loads from the products processed.
Economic considerations indicate that the annual fixed costs of owning
the prototype system would be approximately $600 per year more than the costs
of owning a conventional system, of comparable capacity. Operating costs,
however, were $100/day less for the prototype than for the conventional
system in an example problem using conditions similar to those at the test
site. These results would, of course, vary considerably depending on local
utility rates and other operating costs.
This report was submitted in fulfillment of Grant No. S802958 by the
Virginia Polytechnic Institute and State University under the partial
sponsorship of the Environmental Protection Agency. This report covers the
period from May 1, 1974 to January 31, 1977, and work was completed as of
January 31, 1977.
IV
CONTENTS
Foreword iil
Abstract iv
Figures vi
Tables ix
Abbreviations xi
Acknowledgment xii
1. Introduction 1
2. Conclusions 3
3. Recommendations 5
4. Prototype Washer System 7
Washer design 7
Water flow Instrumentation 15
Installation and modifications 19
5. Procedures 22
Overview 22
Specific procedures 27
6. Results and Discussion 34
Operating parameters 34
Product quality parameters 48
Water quality parameters 52
Summary of waste production from washers 62
Economic comparisons 66
References 70
Appendices 72
A. Operating parameters data 72
B. Product quality data 80
C. Water quality data 84
FIGURES
Number Page
1 Diagram of washing system showing water and product flow
patterns, sampling sites, and water flow meter locations ... 8
2 Overhead view of washing system adjacent to Exmore plant.
Rotary sand tumbler and conveyor into plant are at right
and foreground 9
3 Diagram of prototype washer 10
4 Paddle wheel showing expanded metal covering and spoked end
construction. Elevated nozzle banks are shown in fore-
ground 12
5 Exit conveyor of washer number 2 13
6 View of washer side drains in operation 14
7 Moving belt screen in operation 16
8 Moving belt screen and trash collector. Compressed air hose
for removing trash from belt is shown in foreground 17
9 Prototype settling tank 18
10 HS flume meter number 4 with water level recorder 20
11 HS flume meter number 5 with water level recorder 21
12 Schematic showing water and product sampling sites for
comparative study of new vs. conventional leafy greens
washing systems at Exmore Foods, Exmore, Va 24
13 Water flow rates vs. operating time, trial 1, Fall, 1975,
when processing collards with prototype system. Refer to
Figure 1 for meter locations 37
14 Water flow rates vs. operating time, trial 1, Spring,
19 76, when processing spinach with prototype system.
Refer to Figure 1 for meter locations 37
VI
Number Page
15 Water overflow rates from conventional washers vs.
operating time, trial 1, Spring, 1976, when processing
spinach on the east line 37
16 Product flow rate vs. operating time, trial 2, Fall, 1975,
when processing collards with the prototype system .... 41
17 Accumulated product input vs. operating time, trial 2,
Fall, 1975, when processing collards with the prototype
system 41
18 Summation percentages vs. particle size for grit
accumulated in the prototype system sub-unit 1; trial
5, Fall, 1975, when processing spinach 47
19 Summation percentages vs. particle size for grit
accumulated in the prototype system sub-unit 2; trial
5, Fall, 1975, when processing spinach 47
20 Summation percentages vs. particle size for grit
samples taken from conventional Washer 1, East Line,
trial 2, Spring, 1976 when processing spinach A7
21 Grit (inorganic solids) on spinach vs. accumulated product
at three sites in prototype system, trial 1, Spring;
unwashed product (Site 1) , product exiting first washer
(Site 3) , product exiting second washer (Site 4) 51
22 Grit (inorganic solids) on spinach vs. accumulated product
at three sites in conventional system, trial 1, Spring;
unwashed product (Site 7) , product exiting first washer
(Site 8) , product exiting second washer (Site 10) .... 51
23 Grit (inorganic solids) on turnip greens vs. accumulated
product at three sites in prototype system, trial 6,
Spring; unwashed product (Site 1) , product exiting first
washer (Site 3) , product exiting second washer (Site 4) . 51
24 Grit (inorganic solids) on turnip greens vs. accumulated
product at three sites in conventional system, trial 6,
Spring; unwashed product (Site 12) , product exiting first
washer (Site 14) , product exiting second washer (Site 15) . 51
25 Total bacterial plate counts per gram of spinach at three
sampling points, trial 1, Spring; prototype system.
Before washing (Site 1) , exiting the first washer
(Site 3) , exiting the second washer (Site 4) 53
Vll
Number Page
26 Total bacterial plate counts per gram of turnip greens at
three sampling points, trial 6, Spring; prototype system.
Before washing (Site 1) , exiting the first washer (Site 3) ,
exiting the second washer (Site 4) 53
27 Total bacterial plate counts per gram of spinach at three
sampling points, trial 1, Spring; conventional system.
Before washing (Site 7) , exiting the first washer (Site 9) ,
exiting the second washer (Site 10) 53
28 Total bacterial plate counts per gram of turnip greens of
three sampling points, trial 6, Spring; conventional system.
Before washing (Site 12) , exiting the first washer (Site 14) ,
exiting the second washer (Site 15) 53
29 Bacterial populations and chlorine residual in wash water at
Site 1 of prototype, trial 2, Fall, when processing
collards 56
30 Bacterial populations and chlorine residual in wash water
at Site 4 of prototype, trial 2, Fall, when processing
collards 56
31 Total suspended solids vs. accumulated product input at all
six sampling sites, trial 4, Fall, when processing collards
with prototype system 58
32 Chemical oxygen demand vs. accumulated product at all six
sampling sites, trial 4, Spring, when processing turnip
greens with prototype system 58
33 Total suspended solids vs. accumulated product at all four
sampling sites, trial 1, Spring, spinach processed with
conventional washer 58
34 Chemical oxygen demand vs. accumulated product at all
four sites, trial 6, Spring, turnip greens processed
with conventional system 58
35 Five-day biochemical oxygen demand vs. color, trial 2,
Fall, when processing collards with prototype system .... 61
36 Five-day biochemical oxygen demand vs. color, trial 3,
Fall, when processing collards with prototype system .... 61
37 Five-day biochemical oxygen demand vs. color, trial 4,
Fall, when processing collards with prototype system .... 61
Vlll
TABLES
Number Page
1 Summary of Information for Trials of Prototype Washer System
During the Fall Season of 1975 25
2 Summary of Information for Trials of Prototype and Conventional
Washing System During the Spring Season of 1976 26
3 Average Water Use Date for Prototype Leafy Vegetable Washing
System During Fall Trials, 1975 35
4 Average Water Use Data for Prototype Leafy Vegetable Washing
System During Spring Trials, 1976 36
5 Average Water Use Data for Conventional Leafy Vegetable
Washers During Spring Trials, 1976 39
6 Product Data for Prototype Leafy Vegetable Washing System
During Fall Trials, 1975 42
7 Product Data for Prototype Leafy Vegetable Washing System
During Spring Trials, 1976 43
8 Product Data for Conventional Leafy Vegetable Washers During
Spring Trials, 1976 44
9 Dry Weight of Grit from Various Units of the Prototype Leafy
Vegetable Washer at End of Each Trial 46
10 Accumulation of Floating Trash from Settling Tank Moving Belt
Screens for Prototype System During Fall and Spring Trials • • 49
11 Comparisons of Bacterial Population Densities (Total Plate Counts)
for Product Leaving to Product Entering a Two-Washer System
and for Water Leaving the Second Washer to Water Entering the
First During Greens - Washing Trials 54
12 Magnitude of Average Changes in Total Plate Counts From Beginning
to End of Trials at all Sampling Sites Recorded 57
13 Concentration of Phosdrin in Water of First Washer of Prototype
System , Spring Trials 60
XX
Number Page
14 Waste Loads Discharged with Water from Prototype System During
Fall Trials, 1975 63
15 Waste Loads Discharged with Water from Prototype System During
Spring Trials, 1976 64
16 Waste Loads Discharged with Water from Conventional Washers
During Spring Trials, 1976 65
17 Waste Stream Characteristics From Prototype and Conventional
Systems 57
ABBREVIATIONS
BOD — biochemical oxygen demand
BODc — five-day biochemical oxygen demand
BOD„-. — twenty-day biochemical oxygen demand
COD — chemical oxygen demand
TS — total solids
TSS — total suspended solids
VSS — volatile suspended solids
SS — suspended solids
0„ — oxygen
metric ton — 1000 kilograms
PVC — polyvinylchloride
XI
ACKNOWLEDGMENTS
The most generous cooperation of the personnel of Exmore Foods, Exmore,
Virginia is gratefully acknowledged. The open-handed willingness to allow
the use of plant space, utilities, and personnel time in the conduct of this
project was exemplary, indicating a far-sightedness that transcends immediate
gain. The results of this work will carry much additional weight by virtue
of the tests being performed in a practical, working environment.
Principals to be cited include Mr. Caspar Battaglia, President of Exmore
Foods, for his suggestion that his plant be used for the test site and his
continued interest throughout the project; Mr. Charles Floyd, Plant Manager,
for his cooperation in day-to-day arrangements; Mr. Stoakely Pearson, Plant
Engineer, for the skill, care, and energy exerted in getting the equipment
installed and making certain necessary modifications; and Mrs. Lucille Floyd,
Mr. Woodrow Brawley, and Mr. James Morrison for allowing the unrestrained
use of their laboratory. Many others should be cited, particularly the
foremen and workers on the processing lines. Their patience, humor, and
apparent pride in being associated with the project were a source of inspira-
tion, especially during trying moments.
Special recognition is extended to the graduate students associated
with the project, particularly Bill Robinson, Paige Geering, and Jim Coleman.
Several others also made significant contributions. The kind and amount
of work that they were subjected to and the inconveniences of the travel
imposed were uncoimnon compared to usual graduate studies. Their response
and enthusiasm were also uncommon — well above the ordinary requirements
implied by the receipt of stipends and degrees.
Xll
SECTION 1
INTRODUCTION
A 1971 estimate by the National Canners Associations indicated that the
1838 fruit and vegetable canning and freezing plants in the U. S. used 99
billion gallons of water and discharged 96 billion gallons of wastewater (14).
Approximately 626 million pounds of leafy greens and broccoli were processed
in 80 plants during that same year (6) (21) requiring an estimated 2.5 billion
gallons of process water. Even though greens processing represents only a
small percentage of the fruit and vegetable industry output, research in
areas related to it can have general applicability in many instances.
Two major concerns of leafy greens processors are water use management
and initial cleaning of freshly harvested product. Concerns in water
management, particularly those related to effluents, have assumed added
importance in recent years relative to the new emphases on environmental
protection. Major problems have arisen in handling effluents from the lack
of knowledge of waste stream characteristics. Design information on waste-
water parameters for treating combined flows from fruit and vegetable
processing is sketchy at best. Flow and concentrations of waste stream
constituents from unit operations within plants are even less available.
A limited amount of information is available on combined waste stream
loadings from leafy vegetable processing in reports by Mercer (12) ,
Ramseier (16), Frey (8) (9), the NCA (14) and SCS Engineers (18). Carter (4),
Bough (2), Frey and SCS Engineers have reported on certain unit operations.
The data available, however, are still inadequate for proper design of in-
plant or out-of-plant waste stream management. The parameters reported vary
from study to study and might include any of the following: BOD, COD, TS,
TSS, VSS, dissolved 0„, pH, alkalinity, or bacterial counts. Methods of
reporting each parameter may also vary. For instance, COD may variously be
given in terms of miligrams/liter of wastewater, pounds per ton of product
processed or even pounds per 1000 cases of canned product. Other important
information, such as flow rates of product and water, is often omitted or
crudely estimated. Total water consumption has been reported to range from 3.2
to 5.4 gal/lb of greens processed. Estimates of total water consumption re-
quired for initial washing range from 68 to 88 percent. Obviously, the major
volume of the total wastewater comes from this source. While the inconsisten-
cies cited above do not necessarily invalidate reported results, they do limit
their usefulness and/or credibility.
Virtually no information is available on the relative effectiveness of
different devices used in the initial cleaning of various greens. Typical
equipment used prior to blanching is described by Carter, Bough, Frey and
Lopez (11). This usually includes, in order, a dry tumbler for removal of
loose soil and small particles, hand inspection and picking belts, and from
one to four wet washers.
The present study was initiated to address the two major problems of
producing cleaner product in the initial processing of leafy greens and to
characterize the waste streams from these processes. An experimental, two-
washer, prototype system incorporating the principle of water recirculation
was constructed and tested during two harvesting seasons at a commercial,
frozen-vegetable processing plant. Design of the washers was based on
modifications of conventional washers developed by Frey to increase their
effectiveness. High recirculation rates within the system provided hydraulic
agitation to supplement the mechanical agitation. Input water was limited
to that required for makeup plus one small waste stream from the system.
Water and product quality and flow rates were monitored at several points in
the prototype during the fall of 1975 to determine washing effectiveness and
characterize internal and external water flows. A similar testing program,
conducted during the spring of 1976, included tests on conventional washers
for comparison purposes.
SECTION 2
CONCLUSIONS
The experimental prototype leafy-greens washing system was more
effective, though not dramatically so, in removing grit and insects from
product than the conventional washers. It also showed a potential for
better control of bacteria counts on product prior to blanching. The final
rinse, with fresh chlorinated water, appeared to be quite effective for grit
removal and bacteria control. There was no apparent increase in grit or
insects on product as washing proceeded with recirculated water. A soap-
like foam accumulated on the water surfaces of the prototype that may have
had a significant effect on product cleaning.
Differences in water use between the two systems to obtain cleaning
was dramatic, the prototype using only about 1/5 the amount of water used by
the conventional washers. Waste water discharge from the prototype was
approximately 1/12 that of the conventional washers. The average amount of
water carried out on product from the prototype was 2.2 £/kg (0.26 gal/lb)
A fresh water input rate to the system of 3.5 Ji/kg (0.42 gal/lb) is a
recommended minimum.
The amount of each type of waste constituent (TSS, VSS, COD) discharged
with the water from the prototype system per unit of product processed was
less than that from the conventional washers though the concentrations were
higher. For example, the average discharges, from each system respectively,
while processing turnip greens were: TSS - 0.26 and 1.54, VSS - 0.04 and
0.26, COD - 0.16 and 2.31 kg per metric ton of product. Some of this differ-
ence, particularly for the non-volatile solids, was due to accumulations in
the washers and settling tanks of the prototype that could be disposed of
separately from the waste stream. VSS and COD production in the prototype
was less than in the conventional washers, probably due to lower osmotic
gradients between the recirculated water and the vegetables. Average con-
centrations in the discharge from the prototype and conventional washers,
respectively, while processing turnip greens were: TSS - 273 and 85, VSS -
37 and 14, COD - 135 and 128 mg/Jl of waste stream.
Approximately 75 percent of the cleaning took place in the first washer-
settling tank sub-system of the prototype. Given steady inputs of product
and water similar to the average conditions of this study (1278 kg/hr and 72
X-/min), the waste strength parameters in the washers and settling tanks will
stabilize at some maximum value after approximately 5 hours of operation.
This maximum value will be affected, of course, by the average "dirtiness"
of the vegetables.
Waste production varies greatly between different varieties of vege-
tables and between different cuttings of the same vegetable. All para-
meters — organic, inorganic, insects and bacteria — are affected by age at
harvest, growing conditions, method of harvest, etc. Of the three varieties
tested, spinach consistently produced the most TSS per unit of product and
could be used as a model for design information for this waste parameter.
Other results, however, do not indicate that any of the three products
tested - collards, spinach or turnip greens — could be used as a general
model for VSS and COD emissions. Wash waters were generally neutral in all
trials indicating that pH would not be a problem in treatment of effluents.
The mechanical performance of the prototype washer was very satisfactory
though it could be improved as outlined in the recommendations section.
Of particular note are the product discharge conveyor belts and moving belt
screens for the recirculated water. The discharge belts were made of plastic
and appear to be a very effective and inexpensive substitute for stainless
steel. The screen belts, also of a monofilament plastic, provided a
relatively simple, inexpensive means of separating small leaf fragments and
even insects from the wash water.
Processors of frozen vegetables use large quantities of water to cool
blanched product prior to packaging. After the cooling water is separated
from the product it is usually used in the raw product washers. Assuming that
alternate means of economically cooling product (by chilled air, for example)
can be found, then freezers, as well as canners, of leafy-vegetables would
find considerable advantage in implementing low-water-ase washing systems.
Recycling wash water in the initial processing of leafy vegetables is a
viable means of consolidating wastes, reducing the amount of effluent and
reducing the amount of total water required. Increased hydraulic agitation
of product by high internal flow rates in the system coupled with a final
rinse of controlled chlorine content can improve vegetable cleaning compared
to conventional washers. These findings are significant in terms of
environmental protection, resource conservation, and food quality. They
indicate that the final efforts needed to encourage implementation by the
food industry should be taken.
The intial cost of the prototype system developed in this study was
estimated at $16,000 compared to $12,000 for a conventional system of
equivalent capacity. Annual fixed costs of ownership were $2208 and $1656,
respectively, for a difference of $552 per year. Assuming a product mix of
3/4 spinach and 1/4 turnip greens, operating conditions similar to those in
this study, and using local labor and utility costs, the daily operating
cost for the prototype was $158 and for the conventional washers $251 an
advantage of $93 per day for the prototype. The difference in annual fixed
costs, in this example then, were recovered in approximately six days of
operation. If this is considered representative, then the economics of
owning and operating the two systems strongly favor the low-water-use
prototype washing system.
SECTION 3
RECOMMENDATIONS
The prototype, leafy- vegetable washing system is effective in cleaning
leafy vegetables while using a minimum amount of water. No changes in its
functional design are considered to be necessary at this time. This does
not imply, however, that the effectiveness of the system could not be
improved by study of additional components or techniques in operation. The
relative effectiveness of the new system compared to similar conventional
washers does seem to warrant its adoption by the food processing industry
as soon as possible.
The present prototype has some limitations, unrelated to function,
that need improvement prior to considering it for commercial use over an
extended period. As now constructed, it requires too much space and is
too complicated. These problems, however, can easily be overcome by a
redesign that will not affect system performance and might possibly improve
it. For example, overflow water from each washer is now collected in a
sump and pumped over a moving-belt screen prior to discharge to a settling
tank. From the settling tank it is returned to the washer via a high pressure
spray system. The washer system could be greatly simplified by locating the
settling tanks and moving-belt screens underneath the washers where they could
receive the overflow by gravity. This would eliminate the sump pumps, reduce
the floor space required and would probably increase the effectiveness of the
settling tanks by equalizing the flow to them.
The redesign of the system should include construction of a second
prototype, some limited laboratory testing to verify certain operating
characteristics, and development of a complete set of plans and specifi-
cations. These plans could than be made available to interested food
processors and equipment manufacturers. The food processing industry as
a whole is very large and includes several giant corporations. Most food
processing plants, however, tend to operate in an autonomous fashion, draw-
ing little more than administrative support from their parent companies.
Research and development of needed machinery are pursued rather haphazardly,
usually on a "cut and try" basis. In order for a new system to achieve
maximum and speedy acceptance by this industry, information on it should
be presented in the most usable form. A processor given a complete set of
plans and specifications for an apparatus is more likely to build it in
his own shop or have it built than one who has to worry about design detail.
After the second prototype is built it should be installed in a commer-
cial processing plant, somewhere in the U. S. , and used under normal operat-
ing conditions for an extended period of two to three years. This would
provide a reference demonstration for other processors and allow for refine-
ments in design and operating technique.
Leafy vegetables go directly from the blancher to the cans in a canning
process. In frozen food plants, however, they must be cooled before being
packaged. This is usually done by fluming the product in large volumes of
fresh, cool water. The water from this cooling process, or a portion of it,
is then used in the washers after the cooled product is dewatered. Because the
cooling water is usually in excess of that required by the washers little
economic or environmental advantage would be gained by using low-water-use
washers in vegetable freezing plants without using alternate means of product
cooling. Some devices, such as air coolers, are available, but it appears
that further studies in this area of vegetable processing are warranted.
A comprehensive review of literature on both combined- and unit-
operation's effluents from fruit and vegetable processing should be
initiated before this literature becomes voluminous. This review should
be conducted with the object of accumulating known data in condensed form
and "normalizing" it to a standard form of presentation. A corollary
effort to this review would be the publication of guidelines for future
studies to indicate what data should be taken and how it should be
expressed. The review and guidelines should be developed with the view
of providing designers of processing equipment and waste treatment facil-
ities with the most useable data.
SECTION 4
PROTOTYPE WASHER SYSTEM
WASHER DESIGN
Lopez (11) described the three most common types of leafy vegetable
washers as the 1) immersion, 2) rotary spray, and 3) spray belt. Of these
the immersion (sometimes called immersion drum, drum, paddle wheel or
dunker washer) is the most popular. Frey (8) (9) , in response to industry
concerns for cleaner product, made several modifications to a conventional
immersion washer and demonstrated their effectiveness for removing insects
and grit from spinach. He also measured BOD, COD, TS, SS and VSS of the
waste stream. The water-use rate in this washer was approximately one gal/
lb of product, well below the industry average. The low levels of the waste
strength parameters indicated the feasibility of developing a washer proto-
type system incorporating the principle of water recirculation.
General Design of Washing System
A full scale prototype of an immersion washing and water recirculating
system was constructed incorporating several of Frey's modifications to a
conventional washer. It consisted of two, modified, leafy-vegetable immer-
sion washers in series and their respective settling tanks and moving-belt
screens for cleaning the water in the recirculation process. Figure 1 shows
the arrangement of the system, as well as product- and water-flow patterns.
Fresh makeup water was introduced into settling tank number 2 during trials
in the fall of 1975. This arrangement was changed to apply the makeup water
as a final spray on the product leaving washer number 2 during the spring
trials of 1976. Excess water from settling tank number 2 overflowed into
settling tank number 1. This was the only hydraulic link between the two
washing units. Excess water in settling tank 1 flowed to waste. Figure
2 is an overhead view of the washing system as it was installed.
Description of a Washing Unit
Each washer and settling tank was constructed of 11 gage, type 304,
stainless steel sheets, with a 2 x 2 x 1/4 inch angle-iron frame around the
top. The washer was designed to wash approximately 4,000 pounds of product
per hour based on similar conventional washers at a local processing plant.
Each washer was 4 feet wide and 16 feet long with three "V" shaped sections
forming the bottom of the tank (Figure 3) . This configuration aided in the
removal of grit when the tank was drained. The tank was three feet deep at
the deepest point, 1 foot-10 inches at the shallowest point, and held 688
gallons of water when filled to the working depth of 2 feet, 7 inches.
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patterns, sampling sites and water flow meter locations.
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Water was introduced from the settling tanks into the washer at several
locations. There were three banks of nozzles at the input end of the tank,
one located at the water level and two positioned above the incoming pro-
duct (Figure 3). Each bank consisted of four, brass, Flat-Jet No. 1/2
P35100 nozzles, manufactured by Spraying Systems Company. They were mounted
on 1-1/4- inch PVC pipe with split-eyelet connectors. Spraying Systems No.
8370A. These sprayers spread the incoming product, began the agitation
process to remove grit and trash, and propelled the product toward the first
agitation drum. The entire spraying system was designed for 200 gallons per
minute (gpm) at a pressure of 35 pounds per square inch (psi) .
Three agitation drums, or paddle wheels, on each washer served to
agitate the product by alternately submerging and releasing it to remove
grit and trash. They were driven with No. 60 roller chain at 11 revolutions
per minute (rpm) by a 1-horsepower (hp) , 3-phase electric motor coupled to
a Winsmith >D00T right angle, 60:1, speed reducer. The drums were 1 foot
11-3/4 inches in diameter and were covered with 16 gage, 3/4-inch mesh,
flattened expanded stainless steel metal that allowed insects and leaf
fragments to float to the surface inside the drum while the product was
submerged (Figure 4). They each had four, 4-inch fins around their perimeter.
A stationary bank of three, flat-fan, brass Vee Jet No. H 1/2 U80100 nozzles,
manufactured by Spraying Systems Company was positioned inside each drum.
The nozzles were mounted with split-eyelet connectors on a 1-1/4 inch, PVC
pipe. This pipe was inserted through a hollow hub of the drum which located
the bank along the axis of the drum and thus allowed it to remain stationary
while the drum rotated. The nozzle bank was oriented so that the spray would
strike the drum covering at the water surface where the product was released.
This served to clean the drums during operation by preventing leaves from
becoming entangled in the expanded metal covering. In addition the spray
from these nozzles was another water input to the washer and an aid in the
agitation process. The drums propelled the product through the washer and on-
to an exit conveyor (Figures 3, 5). This conveyor was constructed of an open-
mesh belting made of plastic sections (manufactured by Intralox, Inc.). It
had flights every 24 inches and was driven with No. 60 roller chain by a
1/4-hp, single-phase, gear motor at a speed of 33 feet per minute (f pm) .
The conveyor was inclined 30° from the horizontal.
The agitation drums had a spoked construction on one end (Figure 4) to
allow water and trash collected inside the drum to flow out through side
drains cut in the washer tank. The side drains were 4 1/2 inch diameter semi-
circles with their bottom edges located 5 inches below the top of the washer
(at the working depth of the water). Skimmers made of
3-inch diameter stainless steel tubing with lengthwise slots 4 feet long by
2 inches wide were installed directly behind each drum. They were positioned
to allow the product to flow beneath them before surfacing after it had been
submerged by the paddle wheels. Their purpose was to skim floating trash
from the water surface before it could recontaminate the product.
Water and trash from the skimmers and side drains (Figure 6) were
collected in a sump box, 2 feet by 2 feet by 1 foot 4 inches. A sump pump
(2-hp, 230 volt, single phase, Kenco No. 34N2 submersible), with a capacity
11
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Figure 6. View of washer side drains in operation.
14
of 14,000 gallons per hour at 15 feet of head, was used to pump trash and
water from the sump box to a moving-belt screen that was mounted on top of
the settling tank. This pump was controlled by a Kenco Series 112-C12
Liquid Level Control.
A gate valve was used to regulate the flow from the sump pump through
a 3-inch, PVC pipe to the filter. The moving-belt screen was a conveyor (5
feet long by 1 foot wide) inclined at an angle of 16° from the horizontal
to prevent water from flowing off the exit end. The belt was made of
No. 410 Monofilament Polyester Screen manufactured by the Globe Albany
Company and had a permeability of 600 cubic feet per minute (cfm) per
square foot under a 1/4-inch head (Figure 7) . The belt was chain-driven
at 47 fpm by a 1/4 hp electric gear motor. Trash was carried away on the
belt while the water flowed through it. A 3/4-inch galvanized pipe, which
had forty-eight 1/16-inch holes spaced 1/4- inch apart along its length,
was positioned under the exit end of the moving-belt screen. Compressed air
was directed through this pipe and against the belt to remove the trash. This
trash was collected in boxes placed at the end of the moving-belt screen
(Figure 8) .
Water flowed through the moving-belt screen and into a settling tank
where grit could settle out. The tank was 8-feet long by 4-feet wide with a
4-foot-6 inch maximum depth and a 3-foot minimum depth. Figure 9 shows the
settling tank construction as well as the direction of water flow through it.
The baffles prevented floating material from getting to the pump. The tank
held approximately 700 gallons of water and had an overflow rate of 2.81 gpm/
ft^ based on an assumed particle size of 50 microns and a particle density of
2.65 g/cc [Metcalf and Eddy (13)].
An Aurora Model 344 centrifugal pump, with a 3-inch inlet and a 2 1/2-
inch outlet, was used to pump the water from the settling tank to the washer
spray nozzles. The pump capacity was 200 gpm against 35 psi. It was driven
by a 3-phase, 1800 rpm, 7-1/2 hp, electric motor with a V-belt drive.
A gate valve was used to regulate the flow from the settling tank
through a 2-1/2-inch PVC pipe to the washer tank. The flow was divided at
the washer and carried to the nozzle banks by 1-1/4-inch PVC pipe.
Motor starters for the 10 electric motors in the system were assembled
on a control panel, making it possible for one person to control the entire
washing system from one location.
WATER FLOW INSTRUMENTATION
Five meters were installed in the washing system to monitor fresh
water input, recirculation rates, and overflow rates (Figure 1). Meters
and 2 measured the recirculation rates within washing units 1 and 2,
respectively. The meters used were Badger Model MLFT, 3- inch totalizing
propeller meters with a normal operating range of 35 to 200 gpm.
15
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A. Water input
B. Water outlet to pump
C. Baffles
D. Direction of flow
E. Port for draining tank
Figure 9: Prototype settling tank
18
Flow meter 3 measured the flow of fresh makeup water into the system.
A 1-1/2-inch Badger Model SC-ER totalizing, disc-type meter, with a normal
operating range between 5 and 80 gpm, was used to monitor this flow which
was regulated by a gate valve. The makeup water was piped directly into
the second settling tank from the meter during the test trials made in the
fall of 1975. During the spring trials of 1976, the makeup water was intro-
duced as a spray through five nozzles (Spraying Systems Co. Flat-Jet No. 1/2
P35100) onto the exit belt of washer 2 to provide a final product rinse.
This was the only modification made to the experimental prototype between
the two seasons.
The overflow from settling tank 2 to settling tank 1 was measured by
meter number 4. This meter was an 0.8-foot deep, Plexiglas, HS flume con-
structed according to specifications in the Field Manual for Research in
Agricultural Hydrology (10). A Friez FW-2, water stage recorder was used
to continuously monitor the depth of water in the flume (Figure 10) . For
details of the construction and calibration of Plexiglas HS flumes, see
Robinson and Wright (17) .
Meter number 5 measured the water flow from settling tank No. 1 to the
drain. An 0.8-foot, HS flume and Friez recorder were also used to monitor
this flow (Figure 11).
INSTALLATION AND MODIFICATIONS
The washing system was built in the Agricultural Engineering Department
Laboratory on the campus of Virginia Polytechnic Institute and State Univer-
sity (VPI&SU) . It was determined to be operational and then disassembled and
transported to the Exmore Foods, Inc., plant in Exmore, Virginia. The
washing apparatus was reassembled adjacent to the Exmore plant for testing
at that site (Figure 2) . Leafy greens were conveyed out of the plant to the
washers after having passed over a series of dry inspection belts. After
passing through the experimental washers, the product was carried back into
the plant and allowed to pass through the plant's conventional washers. A
reversible- feed belt was used to carry the product from the dry inspection
belts directly into the conventional washers when the experimental washers
were not in use.
Initial testing of the washer system with turnip greens revealed that
the skimmers did not function as anticipated. The product did not pass
under the skimmers, but collected on top of them. A skimmer had been used
successfully by Frey (8) , but with a considerably lower product flow rate.
The skimmers were removed and their drains sealed off. The remaining side
drains, located at the ends of jthe paddle wheels, were not large enough to
carry off the flow introduced by the nozzle banks, so two modifications
were made to overcome this problem. Larger rectangular side-drains (4 inches
high by 7 inches wide) were cut at these locations with the bottom of each
drain 2 inches below the designed water surface level of the washer. In
addition, the bank of nozzles closest to the first drum was sealed off.
This latter modification was made in order to maintain high nozzle pressure
while reducing the water recirculation rate.
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SECTION 5
PROCEDURES
OVERVIEW
Construction of the prototype leafy green's washer was completed on
June 20, 1975, and attempts were made to purchase leafy vegetables in bulk
quantities for laboratory tests. Very dry weather in the local area, how-
ever, had shortened the spring harvest season considerably. Packers, who
would normally have excess leafy greens, were importing product from other
regions to meet their obligations. Hence, testing was postponed until the
fall season of 1975. Arrangements were made in the interim to test the
prototype on site at the Exmore Foods Plant in Exmore, Virginia.
Testing the washer in a commercial food plant had several advantages.
Tests were more realistic because the experimental equipment was subjected
to the same conditions under which conventional washers operate. The minimum
material needed for a reasonable test was estimated to be 25 tons. Arranging
for delivery of this amount of material to the laboratory without spoilage,
devising means to correctly meter it into the washers and disposing of it as
waste after testing would have been a formidable task. Pre-washing treatments
of product, such as dry tumbling and hand inspection, could also be performed
more easily in-plant than in the laboratory. A final advantage was that the
experimental equipment could be tested in comparison with conventional
washers. These comparison tests were subsequently arranged for the spring
season of 1976 under an extension of the original project.
Several difficulties were encountered as a result of working under
commercial conditions. Principal among these was the distance to the test
site, 350 miles. Each trip to collect data required a minimum of three
days, two for travel and one for tests. A large volume of samples was
taken during each trial, and it required special packing to avoid deteriora-
tion during transport from the plant back to the laboratory at Virginia
Tech. For each trial, a considerable number of small instruments and a
variety of glassware had to be transported to the plant and set up in a
temporary lab on the processing floor to supplement the company's laboratory
facilities. Finally, there was considerable difficulty in arranging travel
schedules to coincide with the plant's processing schedule, which was very
unpredictable. Decisions to process a certain vegetable, dependent on
weather and several other factors, were often made only a few hours in
advance of actual processing. Decisions to terminate processing were often
more precipitous, usually depending on some factor that affected quality.
22
Additional difficulties, if they can be called that, included the fact
that the investigators had no control over the rate at which product was
processed, its initial condition before washing, or down time during trials.
Even input water flow rates fluctuated somewhat due to changes in operating
pressures in the plant's water system. Developing equipment and procedures
to control all of these variables in a laboratory experiment would, of
course, have added a degree of precision to the results, plus considerable
time and expense in obtaining them. This added precision, however, would
not have offset the insight gained from working under more realistic
conditions.
Prototype Installation, Plant Layout and Conventional Washers
The prototype washer system was installed adjacent to the Exmore Foods
Plant in Exmore, Virginia during the week of August 4, 1975 as described in
Section 4. Exmore Foods has two leafy vegetable processing lines, an east
line and a west line. The prototype was located so that it could operate in
series with the conventional washers of the west line or, when not in use,
could be bypassed (Figure 12) .
The east and west conventional processing lines had two paddle wheel
washers each in series (Figure 12) followed by a combined paddle wheel
washer/pre-blancher, and then a blancher. The washers were three and one-
half feet wide, approximately eighteen feet long, and three feet deep at the
deepest point. There were four paddle wheels in each washer for propelling
the product through the washer. Product from the blancher was cooled and
transported in a cooling flume fed by fresh water. Dewatering and recircula-
tion of the cooling flume water provided all the input water for the washers
on the west line. The water input was at the head of each washer through a
perforated pipe. The dewatering of the cooling flume water on the east line
provided only a portion of the input water. The majority of this water was
fresh, piped into the bottom of the washers. All the overflow from the
washers was wasted to an open channel floor drain.
Overflow from the conventional washers was measured with HS flumes and
water stage recorders like those used in the prototype system. An attempt
was made to measure input water, which was under pressure, with propeller-
type totalizing water meters. These meters soon became inoperative because
some large, vegetable particles were being pumped from the dewaterers to the
washers. However, an accurate estimate of the input water, it was reasoned,
could be made by measuring the amounts of effluent water from each unit and
using the data in water carried off by the product available from the proto-
type trials.
Summary of Trials
Tables 1 and 2 summarize the trials that were made during the fall and
spring processing seasons. A total of 35,200 kilograms of product was
processed through the prototype in 27 hours of actual operation during the
fall and 31,500 kilograms in 24.4 hours during the spring. A total of
16,500 kilograms was processed in 11.7 hours through the east conventional
line and 21,200 kilograms in 15.3 hours through the west conventional line
23
®
End of Packaging Line
To Blancher
^ End of K<
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To Blancher A
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East Line
West Line
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Outside Wall of Plant
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Figure 12: Schematic showing water and product sampling sites for
comparative study of new vs. conventional leafy greens
washing systems at Exmore Foods, Exmore, Va. Circled
numbers refer to water and/or product sampling sites.
24
TABLE 1. SUMMARY OF INFORMATION FOR TRIALS OF PROTOTYPE WASHER SYSTEM
DURING THE FALL SEASON OF 1975
Trial
Date
Product
Total Operating
Time (hrs)
Total
of Pi
*
Fresh Weight
roduct Washed
(kg)
1
10/24/75
Collards
3.80
**
4418
2
11/4/75
Collards
5.78
9975
3
11/20/75
Collards
6.68
8866
A
12/1/75
Collards
6.68
7945
5
12/15/75
Spinach
4.05
3989
**
Fresh weight through washer system obtained from weight of product
packaged adjusted by determinations of relative moisture contents
of incoming and packaged product. These figures approximate raw
product entering first washer.
Product samples for moisture content analysis were damaged in
transport to laboratory. Estimate was made from data from other
collard trials.
25
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26
during the spring. The amounts of product quoted here (and in the last
columns of Tables 1 and 2) are fresh (i.e. raw) weights as delivered into
the first washer from the dry inspection belts. Each trial consisted of a
complete or partial eight or nine hour shift. Down time and breaks were
substracted from total time.
The company packaged five different varieties of leafy greens during
the fall season, the largest volume of which was collards. Consequently,
travel schedules of the investigators coincided with collard processing
four out of five trials. The leaves of this variety tended to be large,
very mature, relatively clean, and easy to wash. Spinach was processed
during the fifth trial. It was not as clean as the collards, and the
leaves tended to be small and immature.
Initial plans for the spring season included dual trials with the
prototype on the west line running simultaneously with the conventional
east line. Unfortunately, there were only a few days early in the season
when both lines were processing the same product, and travel to the plant
could not be arranged at those times. As a best alternative, the prototype
system was tested during the day shift (8:00 a.m. to 5:00 p.m.), and data
were taken on one of the conventional lines the same night for the first
half of the night shift (6:30 p.m. to 11:00 p.m.). Clean-up and sample
preparation were usually complete by 12:30 a.m. Material processed during
a given day usually came from the same field, so comparisons between the
prototype and conventional lines could be made. Taking data on the con-
ventional washers for complete shifts was not necessary because the water
was not recirculated and, thence, effluent characteristics and product
quality parameters were not time dependent. Four trials were made in this
manner.
Data were taken on conventional lines alone during trials 2 and 3. The
west line, where the prototype was located, was not operated on the day of
trial 2. Plant operations were precipitously curtailed on the day of trial
3 by a deterioration in the quality of locally grown product. Only one
large truck load of spinach, purchased in a neighboring state, was processed.
Consequently, a decision was made to take data on the conventional washers
of the west line because data for spinach washing with the prototype were
already available. Quality of the spinach processed in the spring varied
consider ablly — from prime (trial 3) to overly mature (trials 1 and 2) and
from very clean (trial 3) to very dirty because of sprinkler irrigation in
the field (trial 2). The variation in quality of turnip greens, although
great, was much less than spinach. Those in trial 4 were average in quality
and cleanliness, in trial 5 overly mature and clean, and in trial 6 good
quality and dirty.
SPECIFIC PROCEDURES
The following sections outline, in order, (1) water and product sampling
sites, (2) typical procedures that were followed for a trial during the fall
season, (3) modifications of those procedures for the spring trials and
(4) analytical procedures.
27
Sampling Sites
Water and product sampling sites were selected so that the effect of
each major component of the system could be evaluated for each parameter
measured. Product samples were taken on the feed conveyor to the first
washer, the exit conveyor for the first washer and the exit conveyor for
the second washer in each case (product sampling sites 1, 2, 3, Figure 1
for the prototype; sites 7, 8, 10, for the east conventional line and 12,
13, 15 for the west conventional line, Figure 12). Packaged product samples
were taken at the end of the respective line in each trial (sites 11, 16,
Figure 12) .
Water sampling sites for the prototype are depicted in Figure 1. Sites 1
and 3 were the spray nozzles at the head end of washers 1 and 2, respectively,
sites 2 and 4 the sump boxes that collected the total flow from each washer,
and sites 5 and 6 the input ends of the settling tanks. Hence, for example,
difference in samples between sites 1 and 2 measured the effect of washer 1,
between sites 2 and 6 the effect of the sump pump and filter belt, and between
sites 6 and 1 the effect of the settling tank. Similarly, water samples from
the conventional line were taken at entrance end of each washer and from the
overflow at the exit end of each washer. (Sites 7, 8, 9, 10, 12, 13, 14, 15,
Figure 12) .
Typical Day - Fall Trials
The sequence of events for each trial, of course, varied,
outlines a typical work day during the trials.
The following
Time
Event
1) Night prior to trial
a) Laboratory set up on location.
b) Water quality instruments and flow
meters calibrated.
c) BOD dilution water prepared and aerated.
d) Prototype washers and settling tanks
rinsed and filled.
2) Morning of trial, before
processing
a) Washer and instruments turned on.
b) Flow rates set on meters 1, 2, and 3.
(See Figure 1).
c) Recorders started on meters 4 and 5.
d) Sodium sulfite prepared to neutralize
chlorine in BOD and bacteriological
samples.
28
Time
3) Beginning of trial
4) After 15 minutes
operation
Event
a) Start-up time recorded.
a) Grab samples of product taken for moist-
ure content, bacterial counts and insect
counts.
5) After each hour of
operating time (exclusive
of breaks and dovmtime) .
b) Grab samples of water taken for biochemical
oxygen demand (BOD) , chemical oxygen demand
(COD), color, turbidity, chlorine residual,
total suspended solids (TSS) , volatile
suspended solids (VSS) , conductivity and
pH.
c) Grab samples of water collected in sterile
bottles for total plate counts and con-
form counts (repeated at middle and end
of trial) .
a) Same as 4, a and b.
b) Number of packages of product processed
recorded.
c) Flow meters 1, 2 and 3 checked with stop
watch.
6) Between samplings
a) Chlorine residual determined-
fa) bod's set up and placed in a low
temperature. Precision Model 815
incubator.
c) Conductivity, color, turbidity, and pH
determined.
d) Samples for TSS and VSS filtered, cruci-
bles and filters prepared for shipment
to Virginia Polytechnic Institute and
State University laboratory in Blacksburg,
Virginia.
e) Remaining water preserved with acid for
return to Blacksburg for COD determin-
ation.
f) Water samples for bacteriological
analysis plated and incubated at 35°C.
g) Product samples weighed and frozen in
plastic bags.
29
Time Event
7) After trial a) Trash collected and weighed.
b) Tanks drained.
c) Grit collected.
8) Day after trial a) Product samples packed in ice.
b) BOD bottles placed in cartons to
maintain approximate temperature of
20°C during transport.
c) Bateriological samples with sufficient
growth were counted. Others were packed
for transport.
d) Samples and equipment transported to
Blacksburg.
9) Week following trial (in a) Moisture contents, grit particle sizes,
V.P.I. & S.U. laboratory) COD's, TSS, VSS , BOD^'s, BOD„q's, insect
counts and bacterial counts determined.
b) Preparations made for next trial.
Variations Between Spring and Fall Trials
Procedures for the spring trials were essentially the same as those for
the fall with the following exceptions:
(1) Product samples were taken for grit analysis in addition to samples
taken for moisture content, bacterial counts, and insect counts. Samples for
grit analysis were taken at two-hour intervals of operating time rather than
every hour. Product samples for grit analyses were hand washed and the wash
water filtered between sampling periods for later determination of suspended
solids.
(2) Water samples were taken for analyses of COD, TSS, VSS, chlorine
residual, pH, and pesticides both spring and fall, but BOD, color, turbidity,
and conductivity were not measured in the spring trials. Samples for
pesticide analysis were taken twice during each trial, mid-way and end, at
the outlet of the first washer of the prototype only (site 2, Figure 1).
During the fall trials water samples were taken at the input end of each
settling tank (sites 5 and 6, Figure 1) by dipping the container into the
surface of the water. Some rapidly settling solids may have been lost by
this technique. In the spring trials these samples were taken by holding
the container directly under the moving screen belt to catch the water before
it entered the settling tank.
30
(3) Water and product sampling for the conventional washers were
essentially the same as those for the prototype except for sampling
associated with the settling tanks. An attempt was made to get a quanti-
tative analysis of grit accumulated in the conventional washers, but this
could not be accomplished without interfering with company personnel in
their clean-up procedures. One set of soil samples, however, was obtained
for particle size analysis.
Analytical Procedures
Following is a brief summary of the procedures used in analyzing samples
for each type of data taken during the investigation.
Water Flow Rates —
Totalizing water meters on the prototype were read at the beginning of
each trial and hourly thereafter to obtain flow rates as a function of time.
Depth of water flow through the HS flumes was continuously recorded on strip
chart recorders. Flow rates, as they varied with time, were later calculated
using these recordings and the calibration curve of flow vs. depth that had
been developed for the flumes (17).
Product Flow Rates - -
Product samples for moisture content determination were taken from input
conveyors, weighed, sealed in plastic bags and frozen for transport. Sample
packages of product from the end of the processing line were taken simul-
taneously and frozen for transport. At the lab, these samples were dried at
105°C for 24 hours in a forced convective oven, and moisture contents were
calculated on a wet basis. The relative moisture contents of input and
output product and the package counts of output product were then used to
calculate the rate of fresh product input to the washers. This was a
better measure of input product than total field weight because considerable
material was lost from the dry tumbler and the dry inspection belts ahead of
the washers and very little was removed by subsequent inspections between
the blanchers and packaging.
Grit Accumulation - -
The washers and settling tanks of the prototype were drained after
each trial and the volume of grit on the bottom of each tank was measured.
Some grit was inevitably lost while the tanks were draining. An attempt to
recover this loss was made by filtering the water as it flowed from the
tank. These filters were effective in trapping the larger sand particles,
but allowed some of the smaller silt and clay particles (those particles
with a diameter of less than 50 microns) to be lost. Grit loss in the
washer tanks was minimized by draining the tank through the port farthest
from the incoming product, where the grit accumulation was lowest. At the
end of trial 5 in the fall, a submersible sump pump was used to empty the
two settling tanks. This technique was used to empty the washers and
settling tanks in the spring trials.
31
After the volume of grit had been determined, samples were taken from
each of the three bottom sections of the washers and from the settling
tanks. At the laboratory, they were dried in a forced convective oven at
lOS^C for 24 hours. A soil particle size analysis was then performed
using standard hydrometer methods (5) for particles in the range below
50 microns and standard sieve analysis (3) for larger particles.
Trash Accumulation - -
The trash collectors for the prototype were emptied at the end of each
trial and their contents weighed. Samples from each moving-belt screen were
taken, weighed, and frozen for transport to the laboratory. There, they were
dried by the same procedure as used for the product, and moisture contents
were calculated. These figures were compared with those for the incoming
product to determine the weight of trash collected when corrected to the
moisture content of the incoming product.
Water Sample Analyses - -
Following is a summary of methods used in analyzing water samples taken
during the trials.
Chlorine residual — The total chlorine residual was determined
amperometrically as described in Standard Methods for the Examination of
Water and Waste Water (Sec. 114B) (19) with a Fischer-Porter amperometric
titrator.
pH — The pH was determined as described in Standard Methods (Sec. 144A)
(19) with a Corning Model F pH Meter in the fall, with a Fisher Accumet Model
230 in the spring.
BOD;. — The BOD_ was determined as described in Standard Methods (Sec.
219) (19) . Sodium sulfite was added stoichiometrically to neutralize
the chlorine residual, which, if not treated, could kill the microorganisms
present in the sample. Experiments were conducted to determine the difference
between BOD_ of a seeded and unseeded sample. No difference was detected, so
the samples were not seeded.
Color — True color was determined by filtering a portion of water
sample through a Reeve Angei glass- fiber filter and determining the optical
density on a Klett-Summerson Photometer, using a #42 (blue) filter.
Turbidity — Turbidity was determined by measuring the optical density
of a small portion of water sample with a Klett-Summerson Photometer, using
a #42 (blue) filter.
Solids — Total suspended and volatile suspended solids were determined
according to Standard Methods (Sec. 148B and 244D, respectively) (19).
COD — Water samples for COD were acid-fixed (ph 'v 2.0) for preservation
until analyzed. Determinations were made in the laboratory as described in
Standard Methods (Sec. 220) (19).
32
Bacterial counts — The total plate count was determined according to
Standard Methods (Sec. 660) (19) except during trials 3, 4 and 5 during the
fall and trials 1, 2 and 3 during the spring when the streak-plate technique
was used instead of the pour-plate technique.
In addition to total plate counts, a non-specific coliform count was
made in the fall trials using desoxycholase agar, a selective medium for
conforms. The pour-plate technique was used during trials 1 and 2 and
the streak-plate technique was used during trials 3, 4 and 5. All colonies
growing on the media were counted.
Pesticide Analyses — Pesticide analyses were made on water samples
taken from the first washer in the prototype during the spring trials. The
samples were examined only for organophosphorus pesticides, as they were the
only ones applied to the crops during the growing season. Phosdrin was the
principal one in use at the time of the study. Methods of analyses were
EPA-approved (Federal Register 38, No. 85, Part II, Nov. 28, 1973), gas
chromatrographic analyses of solvent extracts of the samples. These were
conducted in the Department of Biochemistry Pesticide Analysis laboratory.
Product Sample Analyses —
Following is a summary of methods used in analyzing product samples
during the trials.
Bacterial counts — The method used for determining the total plate
count of the product was that used by technicians at Exmore Foods. Eleven
grams of product were placed in a bottle containing ninety milliliters of
sterile dilution water. From this bottle, a series of dilutions was made
and plated out on Total Plate Count agar. The test proceeded as described
in Standard Methods (Sec. 660) (19). Coliforms were determined on several
occasions (but not routinely) by plating aliquots of the water on desoxycho-
late agar.
Insect counts — Insect counts on product samples were made using the
gasoline extraction method described by Townsend et al. (20).
Grit on product — A simple hand washing test was devised to determine
the amount of grit on the product at each product sampling site. Duplicate,
1000-gram samples of product from each site were agitated 1-2 minutes by
hand in containers with 15 liters of water. Product was separated from the
water with a large-mesh screen and an aliquot of 500 ml. from each water
sample was filtered for solids determination.
33
SECTION 6
RESULTS AND DISCUSSION
OPERATING PARAMETERS
The following is concerned with those quantities measured during the
trials that could be considered operating parameters, i.e., those things
that were either under the control of or required action by personnel
operating the systems. They include water and product flow rates for both
the prototype and conventional systems, and grit and trash accumulations
in the prototype system.
Water Flow Rates
Tables 3 and 4 summarize the water flow rates used in the prototype
during the fall and spring trials, respectively. Figures 13 and 14 are
examples of the water flows in the prototype for the fall and spring trials.
Meters 1 and 2 in each graph represent the recirculation rates for washers 1
and 2, respectively. Meter 3 is the input of fresh water to the system;
meter 4, the flow from settling tank 2 to settling tank 1; and meter 5, the
overflow to waste from settling tank 1 (refer to Figure 1). All tables and
graphs relate only to water flows during actual processing time. Meters 1, 2,
and 3 were totalizing meters and the graphs were plotted from readings taken
at timed intervals. Meters 4 and 5 were open channel HS flumes with water
level strip chart recorders. Data for the graphs was taken from the strip
charts at 15 minute intervals. Graphs for the spring trials were plotted by
hand (Figures 13, A-1 through A-4) . Graphs for the spring trials were taken
from computer plots (Figures 14, A-5 through A-12) .
Recirculation rates in the washers varied somewhat but were generally
maintained near 404 S,/min (107 gal/min). A recirculation rate of 530 Jl/min
(140 gal/min) in washer 1 was tried for a few hours in one trial (trial 5,
fall. Figure A-4) , but it was discovered that the control system on the
sump pump did not react fast enough to handle this flow.
Fresh water to the system was introduced into the second settling tank
during the fall trials (meter 3, Figure 1). No attempt was purposely made
to vary this flow, maintained as near the average of 66.8 Ji/min (17.7 gal/
min) as fluctuations in the plant water pressure would permit. Fresh water
was introduced as a final rinse spray on the produce discharge belt of
washer 2 during the spring trials. In trials 4, 5, and 6 (Figures A-5, A-6 ,
A-7) this rate was increased with each trial [52.9, 71.3, 94.8 fc/min (respec-
tively, 14.0, 18.8, 25.0 gal/min)]. During the fall trials, the input
water was turned off during periods of down time. This technique was tried
34
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Figure 13: Water flow rates vs. operating tlae, trial ] ,■ Fall,
1975, when processing collards with prototype
syscen. Refer to Figure 1 for meter locations.
Kigurp 14: U.iter flow r.ntt-s v^. o|>crt.it 1 iig tine, trial I. •^priiiR,
1476, wlien processing spinanrli '.Itli protntypo Rvstctn.
Refer to Figure I for meter loi.iiion^.
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OPERATING TIME (hrs.)
Figure 15. Water owerflc« rates Iron conventional washers
operating time, trial 1. spring, 1976, when
processing spinach on the east line.
37
during trial 1 of the spring trials, but the amount of water carried off
by the product was such that there were periods of time after breaks when
the overflow to waste and the overflow between settling tanks was reduced
to zero (Figure 14) . In trial 4 (Figure A-5) the input was left partially
open during breaks. Again, however, there were periods of no overflow to
waste. This was due to water carried off by the product plus the low rate
of fresh water input (52.9 Jl/min) . On subsequent trials the fresh water was
left on during breaks which ultimately had the effect of reducing the con-
centration of the waste components used as measures of water quality.
Differences between the flow rates at meters 3 and 5 represent the water
being carried from the system on the product. Differences between meters
4 and 5 represent water carried from washer 1 into washer 2 by the product,
and differences between meters 3 and 4 represent additional wetting of the
product in washer 2. As expected, the amount of additional wetting of the
product in washer 2 was relatively slight in trials 1 and 2 during the fall
(Figures 13 and A-1) . However, this trend was not observed in the remainder
of the fall and spring trials. This additional wetting may have been
influenced by a number of factors including the age and variety of product.
A particularly interesting phenomenon was the build-up of a soap-like foam
on the surface of the water in the settling tanks and washers. It resulted,
no doubt, from the surfactant action of organic matter leached from the greens.
Table 5 is a summary of the water flow data for the conventional washers,
and Figure 15 is an example graph (trial 1, spring). Graphs of the flows in
other trials are included in Figures A-8 through A-12 , Appendix A.
The flow rate of water to the conventional washers was left entirely to
the judgement of the line foreman during each shift. More or less water was
used in each washer based on his judgement and experience. The graphs show
considerable variations in flow that did not always appear to be related to
initial product quality or product flow rate. One mechanical influence on
the east line (trials 1 and 2, Figures 15 and A-8) was the inefficiency of
the cooling flume dewaterer, requiring that most of the input water to
these washers be fresh. Consequently, water use on this line tended to be
minimized, especially in washer 2. Conversely, the dewaterer on the west
line (trials 4 through 6, Figures A-9 through A-12) worked well, and all of
the input to these washers was recirculated product cooling water, used
unstintingly. In most, but not all, cases more water was used in the first
conventional washer in a line than in the second. It seems obvious that
some means of cooling blanched product other than with large quantities of
fresh water would be necessary in order for a company to take maximum
advantage of a water-conserving washing system.
Several other observations can be made from the water flow data. 1)
Though the number of trials for each product are few, there is an indication
that different varieties of greens tend to carry away different amounts of
water from a washing process. Average values, in order, are: collards -
1.79 Jl/kg (0.22 gal/lb), turnip greens - 2.40 Jl/kg (0.29 gal/lb), and
spinach - 2.78 A/kg (0.33 gal/lb). These figures, on a relative basis, are
consistent with expectations based on qualitative evaluations of leaf sur-
faces; i.e., collards have a waxy, smooth surface compared to spinach.
38
TABLE 5. AVERAGE WATER USE DATA FOR CONVENTIONAL LEAFY
VEGETABLE WASHERS DURING SPRING TRIALS. 1976
Trial ^ ^
XT Date
No.
Product
and
Line
Input tot
Two
Washers
il/min)
Output From
Two
Washers
(Jl/min)
Input
Water/
Productf
(^/kg)
Water*
Carried Out
On Productf
()l/kg)
1 4/22/76
Spinach(E)
380.3
328.3
20.3
2.78
2 5/12/76
Spinach(E)
179.0
107.2
6.9
2.78
3 5/21/76
Spinach (W)
341.5
266.3
12.6
2.78
4 6/4/76
Turnip
Greens (W)
461.1
405.9
20.0
2.40
5 6/10/76
Turnip
Greens (W)
455.9
396.6
18.4
2.40
6 6/11/76
Turnip
Greens (W)
438.6
393.0
23.1
2.40
Averages
376
(99 gal /rain)
316
(84 gal/min) (2
16.9
.02 gal/lb)
* Estimated from average values determined in prototype trials.
t Calculated from output data and estimated values of water carried out
on product.
(E) = East conventional line.
(W) = West conventional line.
+ Fresh (raw) product entering first washer from dry inspection belts
(Figure 12) .
39
2) The water input to two conventional washers averaged 5.2 times that of the
prototype system, the water output or waste stream 12.7 times that of the
prototype. 3) Average fresh water input for the conventional washers was
16.9 Ji/kg (2.02 gal/lb) vs. 3.43 J!,/kg (0.41 gal/lb) for the prototype, a
ratio of 5:1.
Product Flow Rates
Several different sizes of packages were used at the Exmore plant.
Retail packages for collards and turnip greens were 283 g nominal net weight
(10 oz) and those for spinach were 340 g (12 oz) . In some cases diced
turnip roots were included with the greens (8 oz of greens, 2 oz of roots).
The weight of roots was accounted for when analyzing the moisture content of
samples, and only the greens processed are reported here. These packages
were counted with an electronic counter located immediately following the
packaging machine. Some product was packed in 6.8 kg (15 lb) trays for
institutional packs and some on open trays in lots of 181 kg (400 lb) for
bulk freezing and storage. The number of these units was recorded as they
were put into the freezer.
Figures 16 and 17 are examples of the instantaneous flow rate and cumu-
lative flow of fresh product into the washers versus operating time. Figures
A-13 through A- 30 depict flows during other trials. Initially, it was
assumed that the flow of material through the system would be rather uniform.
Consequently, only the total product processed was recorded during trial 1
in the fall. During this trial it became obvious that input to the system
was very erratic. Inputs to the prototype system ranged from 456 to 2251
kg/hr (1105 to 4963 Ibs/hr) ; for the conventional washers 459 to 3330 kg/hr
(1012 to 7341 Ib/hr) . These wide fluctuations in input rates undoubtedly
affected the quality of the product. An obvious means of improving washing
quality, and perhaps increasing the average processing rate, would be to
devise a means of metering the product more evenly into the washers.
Tables 6, 7, and 8 are summaries of the product data. The average rate
of fresh product input into the washers for all trials was 1324 kg/hr (2918
Ib/hr) , and the average rate of output from processing was 1808 kg/hr (3985
Ib/hr) , for an output/input ratio of 1.37. A limited number of tests during
the fall trails indicated that very little water was absorbed in the washing
process. It is assumed, therefore, that most of the water absorption took
place during blanching. The average input/output ratios for the three
varieties tested were: spinach - 1.54, collards - 1.34, and turnip greens -
1.25, indicating the relative abilities of each vegetable to absorb moisture
during processing. The range of absorption within each variety, however, was
considerable indicating that other factors — such as initial leaf condition
(turgid or wilted), age, size, etc. — would have effects. Particularly note-
worthy is the fact that variation in moisture content of the fresh product
(8.8%) was much greater than that of the packaged product (3.2%). Plant
records indicate that overall ratios for packaged product to product deliver-
ed from the field are approximately 0.75 for turnip greens, 0.90 for collards
and 0.95 for spinach. These ratios include wastage such as the losses on the
dry inspection belts and the gains due to water absorption. They vary con-
siderably both within seasons and from year to year.
40
3 4
OPERATING TIME (HRS 1
Figure 16:
Product flow rate vs. operating time, trial 2, Fall, 19*5, wlien processing
collards with the prototvpe systeo. Fresli product into first washer.
2
8
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OPERATING TIME (HRS )
Aiiumiilati'd proilutt input v.. upt-r/it Inji tlni.>, TrI.il .',
^'^11, 197S, wlicn procciiKlng L-ollArils with the prototvpe
sv;tP"- Fresh product into llrnt wjbIut.
41
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44
Grit Accumulation
Removing accumulated grit from the washers is one of the clean-up tasks
required at the end of a shift, or sooner if necessary. Mechanical or
hydraulic means for continuous removal could have been incorporated into the
experimental system at considerable expense. An expedient, but workable,
alternative used in the operation of the conventional washers was to open
the first drain valve on the first washer for a few seconds as necessary to
"flush out" excess grit, because most grit tends to settle out immediately
beneath the fresh product input. This technique was not often required,
although it did increase the effort needed in clean-up when used.
The amount of grit on incoming product varies greatly depending on the
particular type green being processed. Spinach is usually the "dirtiest"
because the convolutions in the leaf surfaces tend to trap soil particles
and because it grows close to the ground. Collards, on the other hand, have
smooth, waxy surfaces and grow erect. Turnips greens are intermediate in
these characteristics. Other factors include soil splashing from recent
rains or sprinkler irrigation, age of the leaves (older leaves tend to be
larger, smoother and cleaner) , and the cutting (first cuttings are made
closer to the ground than subsequent ones) .
Table 9 summarizes the measurements of accumulated grit in the trials of
the prototype washer. The collards processed during the fall trials 1
through 4 were very clean, leaving very little grit in the system. During
these trials, several techniques were tried to capture or collect the grit
as the water flowed out of the drains. In trial 5 (spinach) a measurable
amount of grit accumulated in the system, and it was scooped out of each
tank after the tank had been drained over the top with a sump pump. This
technique was used in the spring trials with the prototype and required
approximately an hour's work for each clean-up plus considerable agility on
the part of the clean-up crew.
The majority of the grit collection took place in the first washer (38%
avg.) and in the first settling tank (43% avg.). Only 4 percent was collected
in the second washer and 15 percent in the second settling tank. Although
the figures for the maximum amount in each trial vary between washer 1 and
settling tank 1, the amount accumulated in washer 2 was always the lowest
for all four units. In only one case (trial 6, spring) did settling tank 2
collect more grit than settling tank 1. These figures strongly indicate
that the majority of grit removal took place in the first washer sub-system.
The washers each had three drains, located at the apex of the V-shaped
bottom sections (Figure 3) . Approximately 60 percent of the grit collected
in each of the washers settled in the first V-section, 26 percent in the
second and 13 percent in the third. Figures 18 and 19 show the summation
percentages of the particle size analyses for grit from the various units of
the prototype system for trial 5 in the fall. Figures A-31 through A-34,
Appendix A, depict these results for the spring trials. These analyses
indicate: (1) that most of the larger particles (>100 y) settle out in the
washers, (2) that the settling tanks were removing some particulate matter
smaller than the design diameter of 50 y, and (3) there was little or no
45
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46
s<:>viN33a:-td NiUitTiwns
47
variation in the particle size distribution of grit from spinach, collards or
turnip greens. These analyses should be useful for designers developing
similar equipment for product grown on sandy and sandy-loam soils. For
other soils, particle-size analyses would have to be developed.
The effectiveness of grit removal in the settling tanks could probably
be improved by using a lower recirculation rate. Necessary hydraulic agita-
tion could be provided by increasing the pressure on the spray nozzles in
the washers. The surges in flow to the settling tanks produced by the sump
pumps probably reduced effectiveness of the tanks. This problem could be
eliminated by locating the settling tanks beneath the washers so that they
would receive the overflow by gravity.
The amount of time required to remove acciamulated grit, and the con-
figuration of the conventional washers made it impossible to measure the grit
collected in them during the trials. Only in trial 2 (spring) was the amount
of grit on incoming product significantly different from that processed
during the prototype runs. Accumulated grit had to be shoveled out of the
first conventional washer during the lunch break — approximately 1700 kg.
Visual observation of the conventional washers in the other trials indicated
that the amount collected was of the same order of magnitude as that collected
in the prototype washers. Again, most of this accumulation was in the front
section of the first washer. Only limited amounts accumulated in the second
washer. Samples for particle size analysis were taken during trial 2 (Figure
20) . Because the accumulated soil had reached a level within a few inches
of the water level in the washer where smaller particles could be deposited
it is assumed that these results are representative of the total soil brought
in on the product. If true then, 86 percent of the grit to be removed from
the product was in the size range above 100 microns.
Trash Accumulation
Two operational characteristics can be derived from the trash collection
data for the prototype system. They are: (1) the amount of waste product
that would have to be disposed of and (2) the amount expected to be lost
during washing. Table 10 summarizes these data and indicates that neither
of the above would be a major concern. The data for equivalent weight of
fresh product lost to trash was determined by adjusting the wet weight of
the trash to the average moisture content of the incoming product during
each trial.
The trash generated by the prototype consisted primarily of leaf
particles. This type of material from the conventional washer flowed
directly into the waste stream and had to be removed by vibrating screens
before the plant effluent was released to treatment facilities.
PRODUCT QUALITY PARAMETERS
The product quality parameters measured were insect counts, bacterial
contamination and grit on the leaves. Of these, only insect and bacterial
48
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49
counts were made during the fall trials. The hand washing test for grit
analysis was not devised until the start of the spring trials.
Insect Counts
Insect infestation of product was extremely low during the fall trials
and not very severe during the spring trials. Though fortunate for Exmore
Foods, this s'.tuation did not allow for a very rigorous test of the proto-
type for removing insects. Insect counts for trial 5 (fall) and trials
1-6 (spring) are included in Tables B-1 through B-7 in Appendix B. A total
of only 10 insects were found on all the product samples taken during trials
1 through 4 in the fall with no more than 2 in any one sample.
Significant insect populations on the product appeared only during
trial 2 (spring) when the prototype was not in operation. In this trial
the two conventional washers removed 63% of the insects (aphids) from the
spinach, and for all trials averaged 62%. Whether or not this could be
considered representative is not known.
Several bits of evidence indicate that the prototype was effective in
removing insects. First, the data show that it was consistent in lowering
insect counts as the product was washed. Second, there was no evidence of
build-up of insects or insect fragments on the product as time proceeded.
This is significant in view of the fact that the wash water was being
recirculated. Finally, counts on the trash collected from the washers
during the fall averaged 124 whole insects and 81 fragments per 100 grams
even though incoming product averaged only 4 whole and 1 fragment per 100
grams of sample taken. Over all trials the prototype removed 70% of all
insects.
Grit on Product
Figures 21 through 24 depict some of the results of the hand washing
tests of product samples for grit analysis in the spring trials. Complete
data are included in Tables B-8 through B-13, Appendix B. The amount of
grit on entering product varied greatly. The amount on product leaving the
first washer varied less than initial readings and that leaving the second
washer even less. In all four trials where both the prototype and conventional
systems were operated the prototype removed a greater percentage of the grit -
averages of 73 percent and 69 percent respectively.
Spinach harbored more grit than turnip greens. In trial 1 the prototype
removed 80% of the grit and the conventional washers 73%. The conventional
washers averaged 70% removal in trials 1, 2 and 3 (spinach). The maximum
amount of grit observed on incoming spinach was 22,000 mg per lOOOg product,
10 times greater than the maximum observation for turnip greens, 2070 mg per
lOOOg of product. In trials 4, 5, and 6 (turnip greens) the prototype aver-
aged 64 percent removal and the conventional washers 59 percent. Removal
percentages for turnip greens appeared to be lower in general than those for
spinach. This probably relates more to the amount of grit on product than
any other factor in these trials. Given several varieties of greens of "equal
dirtiness" spinach would undoubtedly be the most difficult to clean.
50
6 O
10
ACCUMULATED PRODUCT INPUT. KG X 10
ACCUMULATED PRODUCT INPUT, KG X 10
Figure 21: Crlt {inorganic solids) on splnacli vs. accumulated
product at three sttes in prototvpe svstcm. Trial I,
Spring; unwaslied product (Site 1) , product ex i ting
first washer (Site 3), product exiling second washer
(Site i>).
figure 22 : (^r i r ( ln»i ftani r snl i,K) .-ii •^piiiAi '> vs. a(-t'ur>ti>lat< ■!
product al tliroc sites in cnveni ional syiic:-, Tri^
I , Spring; unwashed product (Sin- 7) , product pxit i
firsE wASher (Site 8), product exiting s^ecoiiJ wa^-io
(Site 10).
leo
O 13 5
O 9 0
7 8
ACCUMULATED PRODUCT INPUT, KG X 10^
) 12 3 4
ACCUMULATED PRODUCT INPUT, KG X 10
Figure 23: Crit (inorganic solids) on turnip greens vs.
accumulated product at three bltos in prototype
svstem. Trial 6, Spring; unwashed product (Site 1),
product exiting first washer (Site i) , product
exiting second washer (Site 4).
' rlt (iiiurganic solid^^) on turnip greens vs.
accumulated produn .it three sites in ccnveniicna]
svstein, Trul h. Spring; unwashed product (9,itc 12),
product cxiiiiiji (irst w.isl.er (Site 14). product
exiting secoiid washer (Sltr 15).
51
The greater percentage removal of grit by the prototype over the conven-
tional system may be attributed to the increased hydraulic agitation and
the final fresh water rinse. However there was a decrease in the percent
of grit removal with time in three of four trials, probably due to the use
of recirculated water. Grit removal in the conventional washers varied
randomly with time.
Bacteria Counts
Bacterial counts for both product and water samples are not as complete
as originally planned for a variety of reasons — including considerable
variation in the amount of bacteria on input product, problems in transporting
samples under controlled conditions and, in general, the rather primitive
laboratory facilities on site. The data, however, are sufficient for certain
inferences.
Bacteria counts on product samples are included in Tables B-14 through
B-23, Appendix B. Table 11 is a summary of the principal effects on product
and water bacteria. Over all trials, the prototype and the conventional
systems each reduced the bacterial counts on product 74 percent of the time.
Of special significance, however, are the prototype trials in the spring —
1, 4, 5, 6. Unfortunately, a spreader- type organism present in the water
overgrew the plates in trial 4, obscuring the colonies. In the other three
trials, however, there was a very consistent and obvious lowering of bacterial
counts (100% of the time) as the product passed through the system. Undoubt-
edly the addition of fresh chlorinated water as a final rinse on the product
in these trials had an influence here.
Factors other than chlorine in the wash water appear to be operating
in the reduction of bacteria on product. It may be that something from the
product itself, which accumulates in the water, has a bacteriacidal action.
Again, the results of the spring trials with the prototype showed a consistent
reduction in counts in the first washer which received no fresh water (Figures
25 and 26) . Counts for the conventional washers did not exhibit this
consistency (Figures 27 and 28). Two other observations can be made
from the data on bacteria counts. 1) There does not seem to be a clear
relationship, if any at all, between counts in the wash water (data presented
below) and on the product. 2) Though not obvious, it appears that higher
initial bacteria counts may be expected on spinach than on collards or turnip
greens. There are many uncontrolled influences here, however.
WATER QUALITY PARAMETERS
A total of 10 different water quality parameters were measured during the
trials. In the fall these included bacteria counts (including total colif orms) ,
chlorine residual, BOD , BOD , COD, TSS, VSS, turbidity, color and pH. In
the spring bacteria counts, chlorine residual, COD, TSS, VSS and pesticide
analyses were made.
52
2 50
150
50 ■
I
Ni^i [^ Ka
I
8
01
SITE , I 3 4
TIME .25H0UR
li
i
ill
I
4H0UR
7 HOUR
4 HOUR
65 HOUR
Figure 25: Total bacterial place counts per gram of spinach at
three saiapling points, Trial 1, Spring; prototype system.
Ik-fore washing (Site 1). exitinR the first washer
(Site 3), exiting the second washer (Site it).
Figure 26: Total hacterial plato count'i per Rr.im <>( turnip Krrfns
at three sampling points. Trial h, spi ihr; protntvpc
system. Before washing (Site 1). exiting the (irsr
washer (Site 3). exiting the second wa-^her (Site 4).
a: 150-
(00
**00
.1.
!
II
4 HOUR
TIME 25 HOUR 1 HOUR 4 HOUR
Figure 27: Toial bacterial plate counts per gram of spinach
at three sampling points. Trial 1, Spring; convention
svscem. Before uasliing (Site 7). exiting the fir^^t
washer (Site 9), exiting the second washer (Site 10).
Figure 28: r..tal hacterial plate counts per gram of turnip greens
of three sampling points. Trial 6, Spring; conventional
svstcm. Before washing (Sltr J2), exiting the first
w.ishcr (Site 14), exiting the second washer (Site 15).
53
TABLE 11. COMPARISONS OF BACTERIAL POPULATION DENSITIES (TOTAL PLATE COUNTS)
FOR PRODUCT LEAVING TO PRODUCT ENTERING A TWO-WASHER SYSTEM AND
FOR WATER LEAVING THE SECOND WASHER TO WATER ENTERING THE FIRST
DURING GREENS - WASHING TRIALS.
Trial
Product
Water
Product
Total Chli
Drine,
***
mg/L
A*
B**
A*
B**
Beginning
End
Average
Fall trials, prototyp
e washer
1
Collards
3/3
0.15
-
-
2.16
0.65
1.10
2
Collards
3/3
0.02
1/4
2.17
2.58
0.0
1.39
3
Collards
3/3
0.23
3/4
0.46
0.4
2.03
1.35
A
Collards
2/2
0.09
6/8
0.64
1.16
2.30
2.06
5
Spinach
2/3
0.98
3/5
0.50
1.30
1.50
1.52
Spring
trials, p
irototype washe
r^
1
Spinach
3/3
0.11
3/3
0.72
1.30
0.57
0.61
5
Turnip
Greens
2/3
0.73
3/3
0.33
1.79
0.68
1.02
6
Turnip
Greens
2/2
0.28
3/3
0.07
1.32
0.62
0.91
Spring
trials, conven
tional washers
1
Spinach
2/3
2.57
2/2
0.59
1.23
1.15
1.07
2
Spinach
-
-
2/3
0.04
0.28
0
0.47
3
Spinach
1/3
1.49
3/3
0.03
0.23
0
0.08
A
Turnip
Greens
1/2
1.15
4/5
6.26
0.55
0
0.18
5
I'tirnlp
Creens
1/3
L.22
3/5
0. J8
1.56
0
0.52
6
Turnip
Greens
1/3
0.92
3/5
0.85
0.54
0
0.18
*
A = ratio of number of observations during a trial that the bacterial count
was lowered (input of first washer to output of second washer) to total
number of observations.
**
B = ratio of average bacteria counts during trial, output of second washer
to input of first.
***
" Residuals measured amperometrically and represent concentrations at the
back of the second washer at the beginning and end of each trial, nnd
the average for the entire trial. (3 to 8 observations per trial).
54
Bacteria Counts and Chlorine Residual
Total plate count data are recorded in tables C-1 through C-10, Appendix
C. These counts ranged over 5 orders of magnitude during the fall trials and
4 orders of magnitude in the spring. The relative counts for water where the
product entered compared to those where it was discharged in the prototype
system exhibited some consistency as shown in the first two columns of Table
11. The bacteria count was lower for the output of the second washer compared
to the input of the first washer in 20 of 22 observations. The opposite was
true in the conventional washers where the output counts were lower only for
6 of 14 observations. These last results seem to indicate that the last water
the product is exposed to does not necessarily have a direct effect on the
product bacteria counts which were consistently lowered by the conventional
washers .
The response to chlorine was not always consistent either as indicated
in Figures 29 and 30. Total chlorine was measured and recorded each time a
water sample was taken. Chlorine input to the fresh water in the plant was
manually regulated and varied considerably. A high value of 3.8 mg/£ was re-
corded in the fall trials and a high of 1.79 mg/Jl in the spring. Concentra-
tions usually but not always decreased toward the end of the trials (Table 11) ,
often falling to zero. This correlates with the fact that 73 percent of the
counts on water samples taken at the end of the trials (all sites) were
greater than those taken at the beginning. Fewer (54 percent) of the product
samples at those times showed higher counts , and the magnitude of these
changes was not as great as for the water samples.
The data in Table 12 re-enforce the lack of correlation between bacteria
in water and on product. There appeared to be a consistent increase in
bacteria counts in the water in both systems as time proceeded. The build-up
in the conventional system may indicate a trend to higher levels because
these trials were usually shorter than those with the prototype. The
differences in counts on the product for the fall and spring prototype trials
may be attributed to the generally higher levels of chlorine in the water
during the fall. Warmer weather in the spring may have also been a factor.
The differences between the build-up of counts on product for the prototype
and conventional washers in the spring may merely be the influence of exposing
the product to more chlorine treated water in the conventional washers.
In summary the influences on bacteria counts, both product and water, are not
clear. A system similar to the prototype using a final product rinse with
closely controlled chlorine content would appear, however, to have an
advantage over conventional washers in bacteria control.
55
1/3W '3Nia01H3 TViOi
( nw a3d jOix S3iNonoo)
INnOO 3iVld "IViOi. 30 DOT
1/ ow ' a^iHOHHO nviOi
— 3
( nw y3d jOIX S31N0103)
iNnoD 3ivnd nwiOi 30 ooi
56
TABLE 12. MAGNITUDE OF AVERAGE CHANGES IN TOTAL PLATE COUNTS FROM BEGINNING
TO END OF TRIALS AT ALL SAMPLING SITES RECORDED.
Trials Water* Product**
Prototype (Fall) +169.0 -110.3
Prototype (Spring) +78.3 + 41.7
Conventional +356.0 - 4.6
_
Colonies X 10 per milliliter
Colonies X 10 per gram
Tables C-11 through C-15, Appendix C record data from the fall trials
on total conforms in the wash water. These organisms indicate the presence
of fecal material on the incoming product. Their effect on final product,
however, is not known.
TSS, VSS, COD and BOD
Figures 31 and 32 are two examples of water quality parameters at
strategic points and times during the fall and spring trials of the prototype.
In both cases the waste strength parameter is plotted vs. accumulated fresh
product input to the washers during the trial. All parameters in all trials
tended to follow similar patterns. Data on all trials are contained in
Tables C-16 through C-57, Appendix C.
The six sites in the figures represent sampling locations (refer to
Figures 1 or 12) and differences between adjacent sites in the flow pattern
represent the effect of a certain component of the system on the quality of
the wash water. Values at site 2 minus those at site 1, for instance,
represent the amount of a waste component added to the wash water in washer 1;
similarly for sites 3 and 4 in washer 2. Sites 2 and 6 bracket the effects
of the sump pump and moving-screen belts in sub-system 1; sites 4 and 5 in
sub-system 2. Sites 6 and 1 bracket the effects of the settling tank in the
first sub-system; sites 5 and 3 in the second. Site 1 also represents the
overflow to waste for the entire system.
The most obvious fact from these graphs is the considerable difference
in waste strength in the first sub-system (sites 1, 2, and 6) compared to the
second (sites 3, 4, 5). Approximately 75 percent of the product cleaning
took place in the first washer and settling tank based on analysis of grit
accumulated in the bottom of the tanks and remaining in the water at the end
of each trial. These graphs also indicate the general effectiveness of the
moving-belt screens and settling tanks. The effectiveness of the settling
tanks, as noted earlier, could be improved by lowering the recirculation
rate and eliminating the surges in flow caused by the intermittant operation
of the sump pumps. Also, the settling tanks apparently performed better in
57
250
225
.200
cn
Q
_i
o
CO
Q
UJ
Q
■z.
Ld
Q.
(/5
3
If)
_l
O
175
150
125
100
0123456789
ACCUMULATED PRODUCT INPUT, kgxIO^
Figure 31: I'Hal 5;uspended solids vs. accumulated product input
at .ill six sampling !;ltes. Trial '<, Fall, uhen process!
cul lards with prototype system.
200
100
Figure 32
ACCUMULATED PRODUCT INPUT, KG X 10
il.rimcal oxygon drmand vs. acriimu lai cd |>roilucl at nil six
-i-impilnR «;Iti.s. Trial U , ■Spring, when prcccssing lurnJp
greens with prototvpc sv^lem.
J 200
'0 1 2 3 'i
ACCUMULATED PRODUCT INPUT, KG X
o SI rE I-'
o SITE n
• SITE I^
■ SITE 1^
ACCUMULATED PRODUCT INPUT, KG X 10^
Figure 33. Total suspended ';olld<; vi . accumulated prod
at all four sampling siti--;. Trial 1, Spring
spinach processed with conventional washer.
Figure ^u. Cliemical oxygen demand vs. arcumulated product at
all four sites. Trial b. Spring, turnip greens
processed with conventional system.
58
the fall trials than the data indicates due to the method of taking samples
at sites 5 and 6 (input ends of the tanks). In the fall trials, water samples
were taken at these points by dipping the container into the surface of the
water. Some rapidly settling solids may have been missed by this technique.
In the spring trials, these samples were taken by holding the container under
the moving-screen belts to catch the samples before the water entered the
tanks .
Ideally, a waste strength parameter in any one of the washers or settling
tanks in a recirculating system should increase by some relationship such as:
X = A(l - e'^"^)
where :
X = concentration of the particular parameter at any time, t.
q = total material processed to time, t.
A and B = constants.
In other words, given constant inputs - i.e., constant rate of material
input of constant "dirtiness" and a constant fresh water input rate — the
waste strength parameter should approach the asymptotic value A with time.
Material input rates, the amount of soil on the vegetables, and even the
range in volatiles produced varied too much to be able to make precise
predictions of concentrations. In general, however, it appears that the
water quality parameters in the prototype system, operated as in these trials,
could be expected to stablize in approximately 5 hours. Leaving the fresh
water on during breaks in processing would, of course, tend to dilute the
waste strength parameters, (note dip in values of TSS for first sub-system
in Figure 31) . Very low fresh water input rates as in trial 4 in the spring
(Figure 32) would tend to increase the time until stability is reached.
Accumulations of dissolved organics may also have the effect of lowering the
emission rates of COD and BOD. The decrease in osmotic gradients between
the product and the wash water could reduce the leaching of these materials
as washing proceeds with recirculated water.
Twenty-day BOD values were taken on some of the water samples during the
fall trials. These are tabulated in Tables C-54 through C-57, Appendix C.
Figures 33 and 34 show examples of water quality parameters vs.
accumulated product for the sampling sites on the conventional washers. The
waste strength parameters are again plotted vs. accumulated fresh product in-
put to the washers. Generally the concentrations in the first washer (sites
7 and 8 or 12 and 13) were higher than those in the second (sites 9 and 10
or 14 and 15). This was not always consistent, strongly affected by the
amount of water used in each washer. Waste strength also varied considerably
from beginning to end of the trials and inconsistently with the amount of
product processed. This inconsistency was the result of, not only variations
in incoming product quality, but also in water flow rates.
59
pH was measured and recorded every time water samples were taken.
The range in the fall trials was 6.5 to 7.6 and in the spring trials 7.6
to 8.5. These ranges do not indicate any problems for waste treatment due
to pH.
Color, Turbidity and Conductivity
Readings on color, turbidity and conductivity were taken and recorded
during the fall trials with the prototype. These parameters generally
followed the trends of the other waste strength parameters. These measurer
ments are easy to make and any or all of them may provide simple means for
controlling the operation of recirculating systems in the future. For
example, Figures 35, 36 and 37 present simple regressions for BOD vs.
color for trials 2, 3, and 4 (fall) with collards. Further study on
these general relationships for each commodity appears warranted.
Pesticides
Water samples for pesticide analysis were taken midway and at the end of
each trial of the prototype at the overflow of washer 1 (site 2) during the
spring trials. These samples were analyzed for Phosdrin, the insecticide
used by Exmore Foods. The results are listed in Table 13 below.
TABLE 13. CONCENTRATION OF PHOSDRIN IN WATER OF FIRST WASHER OF PROTOTYPE
SYSTEM, SPRING TRIALS
Trial
Water/Product
ii-/kR
Hours of Operation
Concentration
ppb*
2.18
3
5
1.45
0.81
3.99
0.17
4.22
7
4
non-detectable
Trace
(< 0.01)
6.5
non-detectable
Parts per billion.
Samples from Trial 1, the first of the four trials with the prototype
in the spring became overheated in transit, began to decompose anerobically,
and consequently could not be analyzed. Samples from the other trials indicate
that 1) concentrations of pesticide were very low, 2) they tended to decrease
with time rather than build up in the recirculated water and 3) they tended
to decrease with increased water/product ratios.
60
MO
•
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130
/
120
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R=0 9l
110
/
100
■ • /
.
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80
70
60
• /
50
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40
30
" "/. "
20
- • /
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'■III
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100
-
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80
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70
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-
. /
/ R=095
50
-
/
40
-
/•
30
,
• /
20
, /
<;••
10
50 100 ISO 200 250 300
COLOR IN KLETT UNITS
20 30 40 50 60 70
COLOR IN KLETT UNITS
Figure J5. FjvL-Jav biochemical oxvgcn dcmnn.l «<; . color. Trial 2,
Fall, ulien processing collards with prototype svsten.
Figure ^h. Flvc-riay hiochenical oxvgcn demand v
when processing collards with protol
.■lor. Trial 3. Fall.
120
-
/
110
-
/
KDO
-
• •
/.
90
-
•.■
' Y= I43X+ 836
80
-
,
/.
R= 0 77
70
-
• •
/
60
-
•
/
50
-
••/
40
■
/ .
.
30
_
/
"
20
/
10
r :
10 20 30 40 50 60 70 80 90
COLOR IN KLETT UNITS
Figure 37. Five-day bloi hemlcal oxvgcn demand vs. color. Trial U. Fall,
when processing collards with prototype system.
61
SUMMARY OF WASTE PRODUCTION FROM WASHERS
Waste is carried from the washers by the water in three different
ways: 1) with the effluent during processing , 2) with the water carried out
of the system on the product and 3) with the water dumped from the washers
(and settling tanks for the prototype) at the end of a processing shift.
Tables 14, 15 and 16 show the amounts of each waste parameter measured in
these trials per metric ton of product processed. Concentrations for each
time period multiplied by average water flow during the period were summed
for an entire trial to obtain the total waste leaving in the effluent.
Similarly, the concentrations in the last washer multiplied by average
product flow and amount of water leaving per unit of product were also
summed. The amounts of waste in the washers and settling tanks at the end
of processing was determined by multiplying the final concentrations by the
volume of the tanks in which they were measured.
Tables 15 and 16 (spring trials) show the amounts of waste leaving the
washers by each route. The percentages in each case varied considerably.
The waste leaving the prototype (Table 15) on the product may be slightly
less than estimated here because of the final rinse on the discharge belt of
the second washer. One consistency to be noted for the three trials when
turnip greens were processed (4, 5, 6) is that the percentage of waste
removed by the system overflow increased very rapidly as the amount of fresh
water input increased.
There are at least three things that affect total waste production and
waste stream concentrations. They are: 1) the variety of vegetable being
processed, 2) the amount of water per unit of product processed, and 3)
the condition of the vegetables. Potter (15) shows that collards are high in
nutritive value — 7.5 vs. 4.3 grams of carbohydrates and 40 vs. 26 calories
per 100 grams compared to spinach. This implies that there should be con-
siderable difference in VSS and COD production from different varieties.
On the other hand. Bough (2) found that spinach produced significantly
higher waste loads during washing when compared to collards, turnip greens,
mustard and kale. The results of this study however, do not indicate that
any one of the three products tested could be used as a model for maximum
VSS and COD emission. Emission rates for TSS were consistently higher for
spinach. The combination of savoy leaf surfaces and low growth profile
undoubtedly increases grit accumulation compared to other leafy vegetables.
The amount of water used to wash a unit of product appears to have con-
siderable influence on waste production. VSS and COD mass emission rates
were consistently lower for the prototype than for the conventional system.
There are at least four possible reasons for this: 1) The concentrations
of these waste components in the recirculated water of the prototype were
considerably higher than those in the conventional washer. The more dilute
and larger amounts of water used in the conventional washers may have
affected the surface of the leaves and induced more leaching of organics,
a possibility noted by EPA (7) . 2) The water used in the conventional washers
was, for the most part, taken from the product cooling flumes and did contain
some soluble material. 3) A significant amount of these components may have
left the system with the leaf fragments separated out by the moving belt
62
TABLE 14. WASTE LOADS DISCHARGED WITH WATER* FROM PROTOTYPE SYSTEM
DURING FALL TRIALS, 1975
Trial
Product
Waste Stream/
Product
(Ji/kg)
Waste Load, kg/metric ton+
TSS VSS COD BOD^
1
2
4
5
Collards
Collards
Collards
Spinach
1.97
0.69
1.30
1.55
0.38
0.19
0.92
0.25
0.27
0.21
0.77
0.16
0.43
0.24
0.88
0.22
2.44
0.21
0.91
0.17
(15.0)**
Sum of wastes carried out overflow of system during trials, plus waste
in water carried out on product, plus waste in water remaining in system
at end of processing.
**
Grit collected from bottom of washers and settling tanks at end of trial.
Amount of grit from this source was negligible in other trials.
Waste loads given in kg/metric ton of fresh (raw) product entering washing
system. See Table 6 for factors to convert these readings to field weight
or packaged weight.
63
TABLE 15. WASTE LOADS DISCHARGED WITH WATER FROM PROTOTYPE SYSTEM DURING
SPRING TRIALS, 1976
Trial
Product
Waste stream/
Product Waste*
Jl/kg Source
Waste Load, kg/metric ton"*" and
percent of total
TSS
VSS
COD
Spinach
1.38
Turnip
Greens
Turnip
Greens
Turnip
Greens
0.16
1.35
1.68
A
B
C
TOTAL
D
A
B
C
TOTAL
D
A
B
C
TOTAL
D
A
B
C
TOTAL
D
0.65(25.4%)
0.97(38.2%)
0.93(36.4%)
2.54(100%)
5.30
0.43(38.1%)
0.06( 4.9%)
0.64(57.0%)
1.13(100%)
2.10
0.19(32.5%)
0.20(34.2%)
0.20(33.3%)
0.59(100%)
1.10
0.06( 6.9%)
0.53(65.6%)
0.22(27.5%)
0.81(100%)
2.90
0.11(26.6%)
0.15(38.0%)
0.14(35.4%)
0.40(100%)
0.07(44.8%)
O.OK 6.9%)
0.07(48.3%)
0.15(100%)
0.04(38.1%)
0.03(28.6%)
0.04(33.3%)
0.11(100%)
O.OK 8.3%)
0.08(66.7%)
0.03(25.0%)
0.12(100%)
0.37(32.4%)
0.39(34.7%)
0.37(32.9%)
1.13(100%)
0.20(35.2%)
0.02( 3.6%)
0.34(61.2%)
0.56(100%)
0.13(27.7%)
0.15(31.9%)
0.19(40.4%)
0.47(100%)
0.04( 8.2%)
0.32(64.3%)
0.13(27.5%)
0.49(100%)
A - Carried out with water on product.
B - Discharged from settling tank #1.
C - Remaining in water in system at end of processing.
TOTAL - Total of wastes from water in system
D - Total grit collected in the bottom of the washers and settling tanks
at the end of each trial.
+ - Waste loads given in kg/metric ton of fresh (raw) product entering
washing system. See Table 7 for factors to convert these readings
to field weight or packaged weight.
64
TABLE 16. WASTE LOADS DISCHARGED WITH WATER FROM CONVENTIONAL WASHERS DURING
SPRING TRIALS, 1976
Trial
Product
Spinach
Spinach
Spinach
Turnip
Greens
Turnip
Greens
Turnip
Greens
Waste stream/
Product Waste*
Jl/kg Source
Waste Load, kg/metric ton"*" and per-
cent of total
17.5
4.1
9.8
17.6
16.0
20.7
TSS
A 1.74(12.2%)
B 12.10(85.1%)
C 0.39( 2.7%)
TOTAL 14.23(100%)
A 4.30(46.5%)
B 4.52(48.9%)
C 0.43( 4.6%)
TOTAL 9.25(100%)
A 0.81(16.8%)
B 3.55(74.2%)
C 0.43( 9.0%)
TOTAL 4.79(100%)
A 0.24( 9.3%)
B 2.26(87.4%)
C 0.09( 3.3%)
TOTAL 2.59(100%)
A 0.12( 8.1%)
B 1.24(87.3%)
C 0.07( 4.6%)
TOTAL 1.43(100%)
A 0.21(14.6%)
B 1.14(79.2%)
C 0.09( 6.2%)
TOTAL 1.44(100%)
VSS
0.04(10.4%)
0.29(85.1%)
0.02( 4.5%)
0.35(100%)
0.03(13.0%)
0.19(82.6%)
0.01( 4.4%)
0.23(100%)
COD
0.22(13.0%) 0.39( 8.7%)
1.37(82.5%) 3.93(87.1%)
0.07( 4.5%) 0.19( 4.2%)
1.66(100%) 4.51(100%)
0.40(42.0%) 0.65(46.8%)
0.51(54.3%) 0.65(46.8%)
0.04( 3.7%) 0.09( 6.4%)
0.95(100%) 1.37(100%)
0.15(17.2%) 0.56(15.9%)
0.62(73.4%) 2.59(74.1%)
0.08( 9.5%) 0.35(10.0%)
0.85(100%) 3.50(100%)
0.04(10.3%) 0.45(13.5%)
0.29(85.3%) 2.74(81.9%)
0.02( 4.4%) 0.15( 4.6%)
0.35(100%) 3.34(100%)
0.49(15.1%)
2.57(79.3%)
0.18( 5.6%)
3.24(100%)
0.42(18.9%)
1.62(73.6%)
0.16( 7.5%)
2.20(100%)
A - Carried out with water on product.
B - Discharged from washers 1 and 2
C - Remaining in water in system at end of processing.
TOTAL - Total of wastes from water in system. Grit remaining in bottom of
washers at end of each trial could not be collected without inter-
f erring with plant operations.
+ - Waste loads given in kg/metric ton of fresh (raw) product entering wash-
ing system. See Table 8 for factors to convert these readings to field
weight or packaged weight.
65
screens. 4) Some of these components may have settled out with the finer
soil particles in the prototype settling tanks. Soil samples taken from
these tanks were observed to be high in organic matter.
The amount of grit removed by the water from the conventional system
(TSS minus VSS) appears to be greater than that for the prototype system.
No direct comparisons, however, can be made because the grit collected in the
bottom of the conventional washers could not be measured in these trials.
The prototype showed a consistent advantage over the conventional washers in
reducing the amount of grit on product samples that were hand washed as
described earlier. Assuming that this is a correct representation of the
relative effectiveness of the two systems, then the prototype has the added
advantage of consolidating more of the wastes in its washers and particularly
in the settling tanks for disposal separate from washer effluents.
Emission rates of the various waste components are also strongly
influenced by the conditions of incoming product within a variety. This
condition is influenced by many things including maturity of plants, growing
conditions, whether wilted or turgid, rain or irrigation prior to harvest, etc.
These effects are demonstrated by the data for each variety presented in
Tables 14, 15, 16 and in Table 17 (described below). Even if these data were
"normalized" to constant amounts of water per unit of product processed there
would still be considerable differences in TSS, VSS and COD per kg of product
within each variety.
Table 17 is a summary of average waste stream size and average waste
component concentrations for each of the trials, fall and spring. These data
do not reflect the changing concentration of waste components in the prototype
system with time. They should, however, be useful in planning for design
of a waste treatment system that uses either conventional or recirculating
washers.
Overall average operating conditions for the prototype washing system
during these trials included a product input rate of 1278 kg/hr and fresh
water input of 72 X,/min. Under these conditions 2.20 Jl/kg left the system
with the product, 1.18 left via the waste stream and the waste concentrations
(TSS, VSS, COD) in the various units of the system could be expected to
stabilize in approximately five hours of continuous operation. The number
of trials run were insufficient to indicate whether or not these were
"optimum" conditions. Nevertheless, they appear to be "good" or minimum
conditions for producing suitably clean product. For all product flow
rates a minimum fresh water input of 3.5 Jl/kg (0.42 gal /lb) is recommended.
ECONOMIC COMPARISONS
The following is an example problem to demonstrate the comparative
economics of owning and operating a two-washer prototype system vs. a two-
washer conventional system of equal output. Many variables will, of course,
affect this type of comparison. The basis here is an assumed "reasonable"
set of operating and economic conditions.
66
TABLE 17. WASTE STREAM CHARACTERISTICS FROM PROTOTYPE AND CONVENTIONAL
SYSTEMS
Product
Average Waste
Stream ±
«,/min
Avg.
Waste Cone.
.*, mg/Ji
Trial
TSS
VSS
COD
BOD
1-F*-P+
Collards
38.2
80.8
30.6
137.6
46.8
2-F-P
Collards
20.0
91.7
68.6
264.1
62.6
3-F-P
Collards
18.9
158.0
95.0
346.3
62.5
4-F-P
Collards
25.8
121.4
65.9
127.7
57.0
5-F-P
Spinach
25.5
516.8
45.6
144.0
42.3
1-S-P
Spinach
29.5
818.5
126.9
331.1
4-S-P
Turnip
Greens
3.9
414.5
48.0
191.7
5-S-P
Turnip
Greens
24.1
194.4
28.0
131.7
— — —
6-S-P
Turnip
Greens
37.7
230.0
35.6
139.9
1-S-C
Spinach
328.3
1157.1
103.1
216.2
2-S-C
Spinach
107.2
3618.0
168.9
255.1
3-S-C
Spinach
266.3
336.7
60.1
228.9
4-S-C
Turnip
Greens
405.9
129.3
17.2
156.2
5-S-C
Turnip
Greens
396.3
70.6
16.4
147.8
6-S-C
Turnip
Greens
393.0
54.9
9.1
78.6
F = fall trial, S = spring trial
P = prototype, C = conventional
± = Values are averages for the single waste stream from the prototype
system and are weighted averages for the total waste flow from the
two conventional washers.
67
Annual Fixed Costs
The assumptions here are: 1) The two conventional washers will cost
$12,000 ($6,000 each. Estimate from A. K. Robins Co., Baltimore, Md.) and
the prototype will cost $16,000. The prototype cost is based on an estimate
of 1.33 times that of the conventional washers and assumes that it will be
constructed to include the simplifications cited in the recommendations
(section 3 of this report). 2) Useful life of the equipment is 12 years and
salvage value at the end of usefulness will be 10% of initial cost. Straight
line depreciation will be used. 3) Interest on investment will be equal to
8% of the average value of the equipment over its useful life, per year; and
4) cummulative over ownership costs (taxes, housing, insurance) are equal to
2% of the initial cost per year. The following annual costs are derived
using these assumptions.
Item
Depreciation
Interest on investment
Taxes, housing, insurance
Totals
Washer
Line
Conventional
Prototype
$ 900
$1200
516
688
240
320
$1656
$2208
Yearly difference: $2208 - 1656 = $552.00
Operating Costs
Operating costs and variables are taken from local information
(Blacksburg, Va.) and conditions comparable to those reported in this study.
Only the waste stream from the washers is considered in computing sewer
charges. Assumptions include:
Item
Hours of operation
Man-hours labor/day
Labor cost, $/hr
Product throughput, Ib/hr
Input water rate, gal/min
Water for filling system, gal.
Waste stream, gal/min
Waste production, into waste
stream, lbs/ton of product,
(Assumes that 3/4 of the product
processed is spinach, 1/4 turnip
greens) :
TSS
VSS
COD
Washer
Line
Conventional
P]
rototype
16
16
18
20
3.5
3.5
3000
3000
100
20
1500
3000
85
6.5
11.53
1.49
5.14
3.16
0.48
1.33
68
Power to operate washers, kw
Electricity costs, c/kwh
Fresh water cost, $/1000 gal
Sewer charge for water, $/1000 gal
High strength surcharge rates, <?/lb
TSS above 200 mg/«,
COD above 120 mg/ I
Repairs and maintenance,
(0.02% of initial cost/hr.) $/hr.
3.0
3.4
0.5
1.0
10
7
2.40
14.6
3.4
0.5
1.0
10
7
3.20
Using the above assumptions the following daily operating costs were calcu-
lated:
Item
Washer Line
Conventional Prototype
Electric Power
$ 1.62
$ 7.96
Water (including two flll-ups/
day)
49.50
12.60
Sewer Charges
84.60
12.24
Sewer Surcharges
14.03
4.38
Repairs
28.40
51.20
Labor
63.00
70.00
TOTAL
$251.15
$158.38
Daily difference $251.15-158.38 =$92.77
Under the assumed conditions for this problem, then, the average
annual difference in owning the two types of systems could be recovered in
slightly less than 6 days of operating time.
69
REFERENCES
1. Agricultural Research Service, 1963. "Composition of Foods." Agriculture
Handbook No. 8, USDA, Washington, D. C.
2. Bough, W. A. 1973. "Composition and Waste Load of Unit Effluents from
a Commercial Leafy Greens Canning Operation." Journal of Milk and Food
Technology, Vol. 36, No. 11, pp. 544-553.
3. Buckman, H. 0., and N. C. Brady. 1969. The Nature and Properties of
Soils, 7th Edition, The MacMillan Co., Printed in U.S.A.
4. Carter, L. W. 1970. "A Study of Water Conservation and Reuse at the
Stillwell Canning Co. in Stillwell, Oklahoma." Report prepared for
the Ozarks Regional Commission.
5. Day, P. R. 1965. "Hydrometer Method of Particle-Size Analysis."
Methods of Soil Analysis, Part 1, Amer. Soc. Agron., Madison, Wis.
6. Directory of the Canning, Freezing and Preserving Industries. 1971.
E. E. Judge, and Sons Publishers. Westminister, Maryland.
7. E.P.A. 1976. "Final Effluent Guidelines and Standards for Phase II
of the Canned and Preserved Fruits and Vegetables Processing Industry
Point Source Category." Federal Register. Chapter I. Subchapter N,
Part 407.
8. Frey, B. C. 1973. "Modification of a Leafy Vegetable Immersion Washer."
Unpublished Master's Thesis, Virginia Polytechnic Institute and State
University.
9. Frey, B. C, M. E. Wright, and R. C. Hoehn. 1974. "Modification of a
Leafy Vegetable Immersion Washer." Transactions of the A.S.A.E.,
Vol. 17, No. 6, pp. 1057, 1058, 1059 and 1063, St. Joseph, Mich.
10. Holtan, H. N., N. E. Minshall, and L. L. Harrold. 1962. Field Manual
for Research in Agricultural Hydrology. Agricultural Research Service.
Agricultural Handbook No. 224, Washington, D. C.
11. Lopez, A. 1969. A Complete Course in Canning, 9th Edition. The Canning
Trade, Baltimore, Maryland.
12. Mercer, W. H. 1956. "Canner Foods." Industrial Waste Water Control.
Edited by C. F. Guinham, Academic Press, New York, n. Y., pp. 65-71.
70
13. Metcalf & Eddy, Inc. 1972. Wastewater Engineering. McGraw-Hill Book
Co., New York, N. Y.
14. National Canners Association. 1971. "Liquid Wastes from Canning and
Freezing Fruits and Vegetables." Water Pollution Control Research
Series, 12060 EDK-08/71. U.S. Government Printing Office, Washington,
D. C.
15. Potter, N. N. 1968. "Food and Waste." Food Science, The AVI Publishing
Co., Inc., Westport, Conn., pp. 471-587.
16. Ramseier, R. E. 1942. "The Evaluation of Industrial Wastes in the East
Bay." California Sewage Works Journal, XIV, No. 1, pp. 26-37.
17. Robinson, W. H. , Jr., and M. E. Wright. "A Note on Plexiglass H S
Flumes." Water Resources Research. In press.
18. S.C.S. Engineers. 1971. Industrial Waste Study on Canned and Frozen
Vegetables, Interim Report, Contract No. 68-01-0021 for the U.S.
E.P.A. , Long Beach, California.
19. Standard Methods for the Examination of Water and Wastewater. 1971.
Edited by AWWA, APHA, and WPCF, 13th Edition.
20. Townsend, C. T., I. I. Somers, F. C. Lamb, and N. A. Olsen. 1956.
A Laboratory Manual for the Canning Industry, 2nd Edition, National
Canners Association Research Laboratories, Washington, D. C.
21. U.S. Department of Agriculture. 1971. Agricultural Statistics.
Government Printing Office, Washington, D. C.
71
APPENDIX A
460
440
420
•METER I
METER 2
METER 5
o -METER 2
METERS
OPERATING TIME (HRS.)
Plpire A-1: Water flow racee vs. operating tine, trial 2, Pall. 1975.
whan prooeaslog collardi with prototype waahcr.
OPERATINO TIME (HRS)
Figure A-2: Hater flow races ve. operating tlac. trial 3, Pall, 1975,
when processing collards with prototype waaher.
400
1
380
360
en
1
340
b.
80
a:
60
40
20
^i— METER 3
_i_
2 3 4 5 6 7
OPERATING TIME (HRS)
Figure A-3: Uater flow race* vs. operating clBc, irlal it, Fail, 1975,
when proceaalog collards with prototype ayaceiii.
560
540
520
500
480
^
^
460
^
*<
e
440
3
420
i
400
fH
K
i
380
■METER 2
METER I
METER 5
0 12 3 4 5
OPERATWG TIME (HRS.)
Figure *-«; Hater flow rates vs. operating clac, trial 5. Pall.
1875. when proceaaing aplnach wlch prototype ayetea.
72
^^^
OPERATING TIME (hrs.)
Figure A-5: Water flow rates vs. operatlnR time. Trial i. Spring,
1*176, when processing turnifi (treens with prototypp
systes.
Figure A-6: Untct flr>w rates ■
OHtRATINC TIME (hrs.)
oper.irloR time. Tri.il 5. Sprinc,
when processing turnip greens with prototype washer.
HETF.R 3
METER <•
METER 5
3 4 S 6
OrERATINC TIME (hrs.)
TOTAL
WASIIKR 1
WASHi.k 2
Figure A-7i Water flow rale* vs. oporatlng tlin'. Trial 6, SprlnR. 1976.
when processing turnip grecn.« with prototype washer.
OPERATINC TlHV (hrs.)
Water overflow ralefi from conventional washers vs.
operating time. Trial 2. Spring. 1975, when processing
spinach on the cast line.
73
500
-
1 1 I 1 1
1 r
400
-
■
300
^
-r
»-.
■
200
•
, — i
i-i
■
100
— 1
1 1 — .. i 1 1
Ed 200
-I \ r
OPERATING TIHF (hrs.)
Figure A-9: Water overflow rates from conventional washers vs.
operating time. Trial 3, Spring. 1976, wlien processing
spinach on the west line.
(TEKATINC TI^U (hrs.)
Klgiirc A-tO: Wnter over fltiw rotes from c<invrnt Ioii.tI w^iHhcr>i vs.
oiiomtinR linu-. Trl.il '4, Spring, iy7f». when proc.-;slnR
turnip greens on west line.
, WASllEH 1
^WASHER 1
500
-
■ T-
T ■ "t
_ 100
E
*
—
^^ TOTAL
■
-
a 100
•
^ WASHTH 1
2
s
K 200
,
^
5
100
^ WASHER 2
1 1 1
1 1
OPERATING TIME (hrs.)
Figure A-II. Water overflow rates from convent lon^il washers vs. operating
time. Trial 5. Spring. 1976, when processing turnip greens
on west line.
ni'EKATIHr. TUU (hr.s)
Figure A-U: Uator overflow rates- from tonvont f on.il washers vs.
operating time. Trial fi. Spring, l')76, when procctJ
turnip greens on west line.
74
■
(D
sx^
'
3
"x^
■ I
< ^\
111 x,
i 1 i 1 \
i
i
UJ
o
o
o
o
o
o
o
o
o
o
o
o
OX) indNi ionaoad oaivinwroDv
S-
JM/fin '3iva Monj ionooMd
(aH/ox) 31VH AMTij ionootw
75
■9 «
(^H/>:i) 2vn noii i^aaond
(tiH/OX) 31VU MOId lOnOOHd
< ^ ">
(9)1) indNi ionooHd 03i.vnnwnD3v
-J a
-« o
3 — .
OX) indNi ionooHd aaxvnnwnoov
76
S 9000
s
a 75O0
u
g 6000
^
^
y^
/ ^
.
/ */^^ •
PROTOTYPE
,
y/\^^ *
CONTONTIONU.
(East Line)
r X t • 1 •
OPERATING TIME (hrs)
Figure A-20: Accunulited product input vs. operating tine, Trl«l 1,
Spring, 1976, when processing spinach.
3000
2 700
\ .
21i0O
/ .
5 2100
/
A /
ju leoo
/\ /\ /
g 1500
e!
/ N,^,--*. / \ / ■
y 1200
\y \ / ■
a.
900
\ / ■
60O
V
300
1 1 1 L.. ....
"ll'KRATINr. rJMK (lir<)
Figure A-21; Product flow ratr vs.
1 1 1 r
12000
/■
« 10500
/ -
£ 9000
y^-^ .
H
y
= 7500
1
y
o bOOO
s
.J
/"
•
1 4500
,
<
300O
y'
-
1500
■ y^
G
Z3
o u
6000
•
4500
y
3000
^y
1500
^ 1 1 > • 1 • I 1
operating tiw. Trial 2. Spring.
0 12 3 4 5 6 7 8
OPERATING TIME (hrs.)
Figure A-22: Accumulated product Input vs. operating tine. Trial 2,
Spring, 1976, when processing spinach with the conventional
washers . east line.
1976 when procesRlng spinach with the conventional washi-rs.
east line.
3 ft 5
OPERATING TIME (hrs)
Figure A-21; iToJuct flow rate vs. onerntlng tftne. Trial 3, Spring,
1976, when processing spinach with the conventional
washers, west line.
OPERATlNt; TIME (hrs)
Figure A-2A: Accumulated product Input vs. opi-rotlng time. Trial 3,
Spring 1976, when processing spinach with conventional
washers, west line.
77
2100
\
j:
IHOI)
^^~^^
.
3
___/^
\ A
2
1300
^
^^\
.
•
i
1200
•
V .
\
•
a.
900
,
\^^
,
600
^
• — rRtTOTYPE
300
* — CiiNVENTIONAL
(Went line)
1 1 . I
•
0 12 3 4 5 6 7 8
OPERATING TIME (hrs.)
Figure A-25: Product flow rate vs. operating time. Trial 4, Spring
1976, when processing turnip greens.
KOOU
/■)(HI
^
B
ftOUO
/^
c
o
4 500
-
y^
\
3000
• PHOTOTYPE
1500
— * CONVfNTIONAL
(W.St llnel
OPJRATIKC TIMK (hrs)
Figure A-26i Accumulated product input vs. operating tine. Trial k.
Spring. 1976, when processing turnip greens.
moo
.
T "T I 1 r-
^
1500
/
p>^
■
<
1200
- / /
\. y
■
1
900
w^^
6
o
s
a.
600
• /
—■ • mOTOTVPE
■
r
1 .
(Wfst line)
1 1 I i ,
3 4 5 6
OPERATING TIME (hrs)
Figure A-27: Product flow rate vs. operating time. Trial 5. Spring,
1976. when processing turnip greens.
J 7500
■ T 1 1 1 r-
•^
A. 60U0
.
y^
S 4500
y /^
■
ACCUMULATED
X y^ *
IMiMirrvfK
/ y^ --*-
i:nKVF.NTio;i.M.
(kost line)
3 u 5
Orr-RATINC TIME (lirs)
rigurc A-28; Accumulated product Input vs. oper.iting time. Trial 5,
Spring, 1976, when processing turnip greens.
-• — I'RinOTYPE
A COHVKNTlONAI.
(WcHC line)
90U0
•
1 1 T- - T r
7500
-
y
■
6000
■
y^
■
4500
/O
■
300»
^ — • PKOTUTYPE
■
^""^ 1 I
* — Cl'NVENTlOKAl
OPKRATINC TIME (hrs)
A-30: Ai'cuiTiulatcd priKJuct Input vs. oprrjttng tlmo. Trial 6,
RprlnR, 1976, vlien proces<;lng turnip greens.
OPERATING Tl^ff Oirs)
Figure A-29: Product flow rate va. operating time. Trial 6, Spring,
1976, wh«n proceaalng turnip greens.
78
S3JVJ.N33H-I.1 NOIlVWWnS
S'JDVJ.H33HHd NOIlVHHnS
N o e
snoviNHnan.! Noiiviwns
SHtJVlN^DUtH.r NOllVHHnS
79
APPENDIX B
TABU B-1.
TOrrU. IKSECIS ON PRODUCT SAMPLES OP SPIHACH GREENS.
TRIAL S, PALL, DECEHBCR IS, 1975
Hours of Operation
Sice
1.0 2.0 3.0 t.O
12
0
10
100 graa saaples, replicated values.
9
10
TABLE B-2. TOTAL INSECTS ON- SAMPLES* OF SPINAOI CREEHS,
TRIAL 1, SPRING, APRIL 22. 19?t.
Houra
0
f Operation
Sice
.2S
1
2
3
« 5
6
7
1
0
-
-
0
2 1
0
0
3
0
-
-
0
0 1
0
0
k
0
-
-
1
0 1
0
0
100 graa saaplea
TABLE B-3. TOTAL INSECTS AND FRAOIENT COUNTS ON PRODUCT SAMPLES OF SPINACH GKEEHS, TRIAL 2. SPRING,
MAY 12. 1976
Houra ot Operation
Ina. Frag? Ins. FraR. Ins. Frag. Ina. Frag. Ins. Frag. Ins. Frag. Ins. Frag.
71" K" 91 23
'lOO gran sanples Average of Two VaLues Fragments Inaeccs
TABLE B-4. TOTAL INSECTS AND FRAGMENT COUNTS ON PRODUCT SAMPLES* OF SPINACH GREENS. TRIAL 3. SPRING.
HAY 21. 1976
Hours of Operation
Ins. Frag.
Ins. Frag.
Ins. Frag.
100 graa saaplas
80
lA lO
d
sg
I I
I r I
o o
o o
o o o o
o o o
I
m
i
u
ee
8
I
9
M
S
05,
G2
S ■
O -^
K -4
w
s
8
000
000
o o
81
TABLE B-9. MILLIGRAMS OF GRIT TtR KILOGRAM OF PRODUCT KOR TRIAL 2.
TABLL B-IO. MILLIGRAMS OF GRIT PER KUAXIRAM OF PRODUCT FOR TRIAL 3,
SfRINC. WASHING OF SPINACH GREENS, MAY 21. 1976
SPRING, yASHI
INC OF SPINACH CKEENS, HAT IZ
—
'
Hnurs of Operation
SlEC
.25
Hours
n_f
Dpctilt
Ion
3 5
7
2
7
9
10
6255
1845
1275
22275 4245
6525 1920
3765 1215
3510
1920
1080
12
U
IS
1740
1230
660
1890
1230
900
TABLE 8-11. HILLICRAMS OF CRIT PFR KILOGRAM OF PRODUCT FOR TRIAL 4,
SPRING. WASUmC OF TURNIP GREENS. JimL 4. 1976
TABLE 8-12. MILLIGRAMS OF CRIT PER KILOCRAM OF PRODUCT FOR TRIAL 5,
SPRING, WASHING OF TURMIP GREENS, JUNE 10. 1976
Hours of Operation
1
3
4
12
14
15
.25
2070
1080
673
835
613
375
1560
855
765
11B5
750
630
1530
1035
660
750
285
270
690
675
480
Hours of Operation
Site
.25
2
4
6.5
1
1005
945
1230
615
3
300
352
1410
451
4
195
300
345
242
12
615
1)95
1005
-
14
300
720
570
-
15
345
510
465
-
TABLE B-13. MILLIGRAMS OF CRIT PER KILOGRAM OF PRODUCT FOR TRIAL 6,
SPRING, WASHING OF TURNIP GREENS. JUNE 11, 1976
TOTAL PLATE COUNT (COLONIES XIO PER GRAM) ON PRODUCT FROM
PROTOTYPE FOR TRIAL 2, FALL, WASHING OF COLLARD GREENS,
NOVEMBER 4, 1975
1
3
i
12
U
13
.25
1080
343
ISO
1125
675
435
Hours of Operation
Hours of Operation
1740
840
330
750
630
433
915
660
375
1935
945
510
840
840
480
1.7
4.1
6.0
7.3
3.5
1.7
11.6
54.5
2.7
5.3
11.2
8.3
Each value is average of two reading:
TABLE B-15. TOTAL PLATE COUNT (COLONIES XIO PER CRAM) ON PRODUCT FROM
PROTOTYPE FOR TRIAL 3. FALL. WASHING OF COLLARD GREENS,
NOVEMBER 20, 1975
682.0
509.0
2S0.O
Hours of Operation
1227.0
473.0
163.0
350.0
109.0
1418.0'
7
359.0
682.0
80.0
TABLE B-16. TOTAL PLATE COUNT (COLONIES XIO"' PER GR,SM1 ON PRODUCT FROM
PROTOTYPE FOR TRIAL 4, FALL, WASHING OF COLLARD GREENS,
DECEMBER I, 1975
Hours of Operation
0.25
160. 0
180.0
80.0
'' 140.0 290.0 420.0 150.0 430.0 630.0 180.0
20.0 - 100. 0 350.0 30.0 4.0 120.0
520.0 40.0 100. 0 650.0 50.0 1.0
70.0
'single value, other values are average of two readings.
Cram positive rods.
Single vaiuL., other values are aver.igc of two readings.
82
TABLE B-U. TOTU, PLATE COUNT (COLONIES Xio' PER CRAM) ON PRODUCT FROM
PROTOTYPE FOR TRIAL 5, FALL. WASHING OF SPINACH GREENS.
DECEMBER 15. 1975
TABLE B-I8. TOTAL PLATE COUNT (COLONIES XIO PER CRAM) FOR PRODUCT FROM
PROTOTYPE AND CONVENTIONAL SYSTEMS FOR TRIAL 1. SPRING.
WASHING OF SPINACH CRLENS. APRIL 22. 19 ?6
Site
3
1
!
1
Sit
1
600
o'
2090
0'
210
0'
820
0=
170
0-=
3
710
o'
100
0^
230
o'
-
140
0*
i
255
o'
150
0'
1090
0'
110
0"^
300
0'
10
Average
of
two values.
Average
of
three
values
Average
of
four
or
more values
Hours of Operation
.25
164.0
14.7
6.0
155.0
27.3
96.4
245.0
222.0
52.7
31.6
218.0
14.2
7
265.0
182.0
104.0
TABLE B-19. TOTAL PLATE COUNT (COLONIES XIO PER GRAM) FOR PRODUCT FROM TABLE B-20. T(7TAL PLATE COUNT (COLONIES XIO PER GRAM) KOR PRODUCT FROM
CONVENTIONAL SYSTEM FOR TRIAL 2. SPRING, WASHING OF SPINACH CONVENTIONAL SYSTEM FOR TRIAL 3. SPRING. WASHING OF SPINACH
GREENS. HAY 12. 1976 GREENS. MAY 21. 1976
Hours of Operation
Hours of Operation
9
10
35.5
2.1
1.6
95.5
1.2
0.9
0.6
0.4
2.9
12
14
IS
3.3"
0.2^
0.3
4.1"
2.6
0.7
136.0'
1.8"
2.0'
Average o( two values.
TABLE B-21. TOTAL PLATE COUNT (COLONIES XIO PER CRAM) FOR PRODUCT FROM
CONVENTIONAL SYSTEM FOR TRIAL 4. SPRING, WASHING OF TURNIP
GREENS, JUNE 4, 1976
TABLE B-22. TOTAL PLATE COUNT (COLONIES XIO PER CR.\H) FOR PRODUCT FROM
PROTOIYI'L AND CONVI.NTIONAL SYSTLHS FOR TRIAL 5, SPRING.
WASHING OF TURNIP GREENS. JUNE 10, 1976
12
It
IS
.25
4.1
0.7
1S7.0
Hours of Operation
Hours of Operation
4.6
4.3
1.7
5.6
S.6
3.0
2.1
2.«
5.5
Site
3.5 1
2.3 3
1.5 4
12
14
0.2
-
-
-
0.1
-
-
-
0.1
-
-
-
2.6
3.7
61.8
10.1
1.2
0.5
0.8
11.9
2.8
0.5
19.5
4.8
0.4
0.3
0.2
2.9
3.1
3.8
I.l
0.1
0.2
TABLE B-23. TOTAL PLATE COUNt' (COLONIES XIO PER GRAM) FOR PRODUCT FROM
PROTOTYPE AND CONVENTIONAL SYSTEMS FOR TRIAL 6. SPRING,
WASHING OF TURNIP GREENS. JUNE 11, 1976
Hours
of
Operation
Site
.25
1
2
3
4
6
1
2.32
-
-
-
0.9
10.7
3
0.7
-
-
-
0.6
O.i
i
0.3
-
-
-
0.4
0.3
12
20.5
2.3
15.7
8.1
1.4
-
14
0.4
9.1
2.8
1.7
1.9
-
IS
1. 5
29.3
2.4
6.2
1.6
-
Average of two values.
83
APPENDIX C
TABLE C-l. TOTAL rL*Tt COUNT (COLONIES'' X 10 PER HH.Llt.lTEII) IN WASH
WATER FROM PROTOTYPE FOR TRIAL 1. FALL, WASHING OF COLLARO
CREEBS, OCTOIIER 24. 1975 ^_^
Hourit of QpTntlon
1
ua.o
0.2
0.2
U.6
13.3
10.2
10.2
IS.O
33.0
6.0
O.S
s.s
232.0
>30.0''
3.3
3.9
110.0
710.0
Slca
1
TOTAL PUTE COUNT (COLONlt.s X 10"^ PKR MILI.I LITER) IN WASH
WATER FROM PROTOTYPE FOR TRIAL i. FALL, WASHING OF COLLARD
GREENS. NOVEMJER 4, H;-;
.0.25 .
15. t*^
24.7"=
U.O'
14.0"=
13.7'
le.o'
Houra of Operation
)_
345.0''
561.0^
2.7"
7.6'
3.2^
1573.0"
4
1177.5'
1065.0'
9.2'>
3.8"
12.7"
1270.0*'
Average of two values. ""Average of ihrce
'aluea. Average of four values
Average of nore Chan one value. Insufficient dilutions before placing.
TABLE C-4.
TOTAL PLATE COUNT (COLONIES X lo' PER MILLILITER) IN WASH
WATER FROM PROTOTVPt FOR TRIAL 6. FALL WASHING OF COLLARD
GREENS. DECEMBER 1. n;s ^^
TABLE C-3. TOTAL PLATE COUNT (COLONIES X 10 PER MILLILITER) IN WASH
WATER FROM PROTOTYPE FOR TRIAL 3, FALL, WASHING OF COLLARD
GREENS, NOVEMBER 20, 1975
Hours of Operaclon
Hours of Operacloo
U.O
0.1
100.0
18.0
100.0
32.0
All values replicated. Colonies were 991 Bacillus subtllls.
TABLE C-5. TOTAL PLATE COUNT (COLONIES X 10 PER MILLILITER) IN WASH
WATER FROM PROTOTYPE FOR TRIAL 5. FALL, WASHING OF SPINACH
(3f£ENS. DECEMBER 15. 1975 ,
36. 0"
18.0*
0.2=
0.2
16.1
Average of two values.
3
3.9
7. a"
9.2'
9.4"
2.8'
2.9»
6.6'
14.0
Hours of Operation
TABLE C-6. TOTAL PLATE COUNT (COLONIES X 10 PER MILLILITER) IS PROTOTYPE
AND CONVENTIONAL WASH WATER. TRIAL 1, SPRING, WASHING OF
SPINACH GREENS. APRIL 21. 1976
.3.0"
>3.0'
2.7
0.04'
0.04
>3.0"
Hours of Operation
8.4"
13.9'
5.8»
24.9'
3.0'
16.5*
15.5-
10.1'
3.2'
4.9'
5.0°
12.9°
0.3
-
90.0
-
25.4
0.2
-
7.0
-
5.3
12.0
14.6
-
700.0
-
3.6
4.4
-
1860.0
-
'Average of cwo values. "insuf f icienc dilutions before plating.
TABLE C-7. TOTAL PLATE COUNT (COLONIES X 10 PER MILLILITER) IN WASH
WATER OF CONVENTIONAL SYSTEM FOR TRIAL 3, SPRING, WASHING
OF SPINACH GREENS, MAY 21. 1976
Hours of Operation
TABLE C-a. TOTAL PLATE COUNT (COLONIES X lo' Pl.R MILLILIIFR) IN rROTOTYPE
AND CONVENTIONAL WATER FOR TRIAL 4. SPRING. WASHING OF TURNIP
1 »
Hours of Ope
ration
site
.25
2
3
5.5
1
>30.0'
-
200.0
30.0'
2
>30.0'
-
450.0
300.0"
4
.30.0'
-
390.0
600.0
13
>30.0*
63.0
-
38.0
15
>30.(V'
85.0
31.0
'Avetags of two values.
'insufficient Dilution.
84
TABLE t-9. TtTTAI, riATf. CdUMT (rjlUWlfS I 10 ' ri« Mll.l.l I.ITKI) III MCOTOTTPE TAIIJ C-IO. TOTAl. PUTT. CUUfT (■.'OURIIES X lo' PKt NIIXILITa) l« PMITOnn
AHD COHVarriOIIAL UATLII ro« THIAl. S. SPKlHi;. MASIIIIir. or TUWIP AND COUVDtTlOIIAL yATtH ITMI TilAL (.. SPHtHC ■AUIIB 0» Tvnir
CHEEKS, JWE 10. 1976 - i»p»ir
Hour* of OpTatlon
9.2
-
26.0
24.0
».7
-
2*.0
3S.0
2.S
-
1.2
40.0
13
3S.0
220.0
55.0
-
15
ti.O
300.0
39.0
-
Houra
ot Oxra
lion
"" ...
.2>
2
4
6
1
M.S
-
25.0
2).0
2
IM.O
-
SJ.i
11.0
A
-
-
?.5
6.0
IJ
A9.0
290.0
160. 0
-
IS
70.0
IJO.O
260.0
"
TABU C-U. TOTAL roLlKOIlM COUNT (COLONIES X lo' PE« MlLLlLlTt«) IN WASH
HATER rHOII PHOTOTYPE ro« TRIAL 1. FALL. HASH INC OF COLLA«D
CBEEMS. OCTOBER 24, 1975
1.00
0.32
Hour« of Operation
>3.ao
0.02
0
M.O
TABU C-12. TOTAL COLIPORH COUNT (COLONIES I lo' PU MILLILITER) IH HASH
HATER rtM PROTOniE FOR TRIAL 2, PALI.. HASIIIHC OF COLLARS
(jREtMS. MOWER 4. 1975
0.25
0.01
O.JI»
O.Jl"
7.n»
Hwifa of Operation
IS.M
11.7S»
39.00
90.00
6.15'
1.00
5.10"
'insufficient dilution before plating.
Avvrage of two vaiuon.
of tlirrc v.iltics.
TABLE C-n. TOTAL CoHFOWl COUNT (COLONIES X 10 Pt« MlLLlLlTtR) IN HASH
HATER mOM PROTOTYPE FOR TRIAL 3, FALL, HASHING OF COLLARD
CKEENS, NOVEMBER 20. 1975
Houra ot Operation
14.00-
o.os
4.00
22.00
^Average of three values.
TABU C-15. TOTAL COLIFORM COUNT (COLONIES X 10 PER MILLILITER) IN HASH
HATER FROM PROTOTYPE FOR TRIAL 5. FALL. HASHINC OF SPINACH
CREENS, DECEMBER 15, 1975
Hours of Operation
3
>ip.oo
>i0.oo''
>io.oo''
1.20
2.»0»
14.00
21.60"
"Average of tvo values. Insufficient dilutions before plating.
TABU C-14. TOTAL OOLIFURM COUNT (COLnMlfS X 10 PER MILLILITER) lU HASH
HATER FROM PROTOTYPE FOR TRIAL i. FALL. HASHING OF COLLARD
CRKBiS_L DECQBER 1. 1975
Hours of Operation
33(...l"
174.0''
1.."
2.0"
134.0
39. 0'
w.r
29.0*
Average of two values. Aver.-icc of (our vjlues. ''Average of five values.
TABU C-10. ANALYTICAI. CCMCKNTR.U10NS (•f/c) OP TOTAL SUSI'KHDED SOLIDS,
TRIAL 1. FALL. HASHING OF COLLARD (a£EMS. OCTOBER 24. 1975
Houra of ilpcratlon
10"
M
»"
2
r'
2
79*
132
9'
4
12"
64
10»'
120
17"
2
10
112
91
100-
4i"
12
»■•
us"
109"
152"
20
14
40
124
Average of two valu«s.
85
T*BLE C-17.
ANALYTICAJ. CONCtNTRATlONS (he/D UF TOTAL SUSPENDED SOLIDS.
TRIAL 2. FALL. UASHINC OF COLLARD CRKENS. NOVEMBER 4. 1975
Hours of Operation
Sice
0.25 12 3 4 5 6
TABLE C-18. ANALYTICAL CONCENTRATIliNS (mc/O UP TOTAL SUSPENDKD SOLIDS,
2»'
32
20
10
!••
25
58"
92
92»
119
220'
120"
128
155*
180»
24
29«
22
64
44»
36
58
72
12
44^
60
76
134"
116
145"
210»
*
-I
Sii i — " "^
jy_j — iji J
Hours of
Operation
Site
1
3
5
7
52-
26'
Average of two voiues.
240
68
156
225
Average of two values.
TABLE C-19. ANALYTICAL CONCENTRATIONS (»g/t) OF TOTAL SUSPENDED SOLIDS,
TRIAL 4, FALL, WASHING OF COLLARD GREENS, DECEMBER 1, 1975
Hours of Operation
16'
7
10
10
58
,62
69'
68=
94
15
22
10
37'
18
31
63"
96
TABLE C-20. AHALYTICAL CONCENTRATIONS* (mg/t) OF TOTAL SUSPENDED SOLIDS,
TRIAL 5, FALL. WASHING OF SPINACH GREENS. DECEMBER 15, 1975
Hours of Operation
184
166
148'
200
230"
184
214"
232"
33
47
42
44
41
56"
46"
36"
48
60
48
20
211"
196
184"
200
6
0
1
2
3
4
39
384
720
752
689
32
491
802
902
632
16
112
199
224
227
29
137
217
274
280
18
121
207
274
274
41
456
766
902
712
Average of two values.
Average of two values in each case.
TABLE C-21 AHALYTICAL CONCENTRATIONS (mg/l) OF TOTAL SUSPENDED SOLIDS.
TRIAL 1. SPRING. WASHING OF SPINACH GREENS. APRIL 22. 1976
3
4
5
6
7
8
9
10
69
78
80
347
1321
1277
449
445
Hours of Operation
637
1069
98
100
112
960
2188
2175
1219
1156"
1057
1537
351
371
361
1485
1252"
1145"
849'
680"
3
1213
1673
514
559
543
1680
199
265
544
471
913
533
475
158
480
910
295
239
366
379
797
1130
337
369
358
1101
750
690
277
333
289
827
938
1280
318
397
320
1104
TABLE C-22. ANALYTICAL CONCENTRATIONS (mg/!) OF TOTAL SUSPENDED SOLIDS,
TRIAL 2. SPRING, WASHING OF SPINACH GREEHS, MAT 12, 1976
Hours of Operation
Site 2 3 4 5 6 7 T^J
9
10
2596"
6830"
1354
1047"
46S"
953"
950
2464"
8306"
1386
996"
455"
1022"
929
I760"
3:eo"
24:4'
1U7 7''
515"
951"
1026
1612"
3716"
2195"
1041"
4 36"
851"
985
Average of two values.
TABLE C-23. ANALYTICAL CONCENTRATIONS (me/n OF TOTAL SUSPENDED SOLIDS.
TRIAL 3. SPRING, WASHING OF SPINACH GREENS. MAY 21. 197&
Hours of Operation
Average of cwo values.
12
162
343
469"
523
446'
13
158
423
304"
490
419'
14
128
356
321
446"
376"
15
121
311
280
449"
416'
Average of two values.
86
TABLE C-24. A1IA1.YTICAL COKCENTRATIOIl (mg/t) OF TOTAL SUSPENDED SOLIDS,
TABLE C-25. ANALYTICAL C0NCEN1 RATIONS (tnR/O OK TOTAL SUSPENDED SOLIDS.
TRIAL 5. SPmNC, UASHIWC OF TURNIP CREENS. JUNE 10, 1976
Hours of
Operation
Site
Hours
of Operation
Site
0.25
I
2
3
4
5.5
578*
0.25
1
2
3
4 _
274
5
6.5
1
lis
367
399
440*
588*
1
66
166
153
410°
158
132
t
324*
530"
4 76°
608*
635*
2
94*
210
200
5)0*
33)
187
155
3
67
221
212-'
275°
32b*
3
27
75
40
160
149
101
68
4
117
200
258"
280'
329*
4
27
85
40
16S
110
69
72
S
103
2 38
230°
316*
339*
5
23
77
90
120
15«
65
157
«
123
49»'
494*
603°
635*
6
87
152
229
4 71°
)24
184
154
12
S3
230
119
81
-
12
31
82
133
94
88
-
-
13
62
227
166
125
-
13
39
76
148
106
89
-
-
14
S3
185
115
79
-
14
21
52
76
74
54
-
-
15
54
164
119
72
15
26
40
79
59
48
~
~
Average of two values.
'Average of two values.
TABLE C-26. ANALYTICAL CONCENTRATIONS ('S/t) OF TOTAL SUSPENDED SOLIDS, ANALYTICAL CONCENTRATIONS (mg/f) OF VOLATILL SUSPFJIDED SULIUS.
TRIAL 6. SPRING, WASHING OF TURNIP GREENS, JUNE U, 1976 TRIAL 1, FALL. MASHINC m COLLARD CHLENS . OCTUbF.R 24. 1975.
Hours of Operation
Hours of Operation
1
2
3
4
s'
6
12
13
14
IS
138
216
45
62
50
214*
41
37
22
23
204
290
68
91*
70
2 78
43
50
32
40
376-
461°
129°
141
139
476°
45
52
47
40
*Average of two values.
365-
4)0*
1)4
142
137
414
79
71
46
59
179
224
79
91
84
226
77
75
59
84
166
213
182
232
89
92
88
220
17"
36"
38
61'
44
46
50
70'
15'
13*
15*
14
2
4
18
34
12*
18
20*
34
28
3)"
53*
80
Average of two values.
TABLE C-28. ANAI.YTICAI. rONCrNTHATlON*; (hir/O OF VilJ.ATll.F: SnSPr.NIIKR SOLIDS.
TKIAL 2. FALL. HASIIINC UK COLLAKO GKEUNS. NOVEHBrB U. 1975.
Hogrs of Opcrntton
13"
20
7
27
36*
9
15*
32
39*
155
145"
Avor.ige o( twn valued
87
TABLE C-29. AHALYTICM, CCWCmTRATIONS (m»/0 OF VOLATILE SUSPWOFD SOLIDS, lABLF. C-IO. ANALYTICAl. CONCENTRATrwiS (ait/l) OF VOLATFIF SUSrF.HDtO SOLIDS.
TRIAL 3, FALL. UASHINr. OF COUMW r.»t.e>IS. HOVrFgH ZO, 1975 TBIAL «. FALL. WASIIIMC OF COLLAM) r«F.tNS . UFI FMI\F» I. 1975
Hours of Op«r«clon
Hours of Operation
46"
2»'
*Averase of two values
106
120
120
SO
108
150
17-
124
27*
17'
6
12
-
10
10
15
20
36'
36
70
7b
82*
114'
48
84'
lOO
94'
lOo'
8
24
27
32
20
33*
26
38'
37'
14'
21
27
36
44
-
TABLE C-31. ANALYTICAL CONCENTRATIONS (mg/t) OF VOLATILE SUSPENDED SOLIDS.
TRIAL 5. FALL. UASHINC OF SPINACH QUEENS. DECEMBER 15, 1975
Averaee of two values.
Hours of Operation
• TABLE C-32. ANALYTICAL CONCENTRATIONS (ag/t) OF VOLATILE SUSPENDED SOLIDS,
TRIAL 1, SPRING, WASHING OF SPINACH GREENS, APRIL 22. 1976.
52
1)
It
18
45
66
69
19
31
23
68
61
6i
17
2$
29
54
32
20
27
29
40
Houra of Operation
Single values, all others are average of two readings.
TABLE C-33. ANALYTICAL CONCENTRATIONS («g/l) OF VOLATILE SUSPENDED SOLIDS,
miAL 2. SPRING, UASHINC OF SPINACH GREENS, MAY 12. 1976
__^ Hours of Operation
Site
1
2
3
4
5
6
7
8
9
10
26
36
40
134
136
68
112
182
180
144
153
150
103
164
257
92
188
131
188
14
41
74
91
70
55
55
17
44
88
11
72
61
58
26
44
82
93
72
60
54
90
160
259
183
20o
156
163
241
123'
22
62
-
-
-
228
114'
25
54
-
-
-
144
106"
58
71
-
-
-
137'
7 7'
52
71
_
.
.
7
8
9
10
190'
306'
138
156'
55
81'
77
177'
521'
160
152'
65
84'
77
161'
2 78'
200'
165'
72
90'
85
145'
267'
184'
164'
70
86'
86
Average of two values.
TABLE C-35. ANALYTICAL CONCENTRATIONS (hk/D OF VOLATILt SUSPt.NDED SOLIDS,
TRIAL 4, SPRING. WASHINL OF TURNIP GREENS. JUNE 4, 1976
Hours of Operation
Average of two values.
TABLE C-34. ANALYTICAL CONCENTRATIONS (niB/t) OF VOLATILE SUSPENDED SOLIDS,
TRIAL 3, SPRING, MASHING OF SPINACH GREENS, KAY 21. 1976
12
13
It
IS
20
21
20
IS
Hours of Operation
60
67
67
62
64*
50"
57
55
95
8)
93*
85*
6
12
13
14
15
18
36'
10
19
15
34
12
12
32
28
51
15
20
21
17
45
6 3'^
29
30
35"
61^
38"
35'
34»
36'
18
15
1
15
20
13
42°
7l'
Average of two values.
Average ut two values.
88
TABLE C-3«.. ANALYTICAL CONCENTRATIONS (ruR/t) OF VOLATILE SUSPENDED SOLIDS, TABLE C-37. ANALYTICAL CONCENTRATIONS (cg/l) OF VOLATILE SUSPENDED SOLIDS,
TRIAL 5, SPRING. HASHING OF TURNIP GREENS, JUNE 10, 1976 TRIAL 6. SPRING, UASHINC OF TURNIP GREENS. JUNE 11, 1976
Niiura or Oncratlon
lie
0 ._25_
1
2
5
1
7
18
17
64''
26
2
12^
28
26
..a
30
1
A
8
-
12
4
8
12
-
13
5
1
11
11
12
6
6
14
34
j.a
28
12
11
20
21
-
13
15
15
19
-
14
13
25
21
-
15
12
17
20
-
. Jl^ur^. J^ Oi>e ration
llj.
0.25
.-.I
2
25
49
56"
39
73
102-^
9
17
2)'
14
21"
23
U
17
22
41"
85
64"
12
8
7
9
13
8
8
8
14
10
11
9
IS
9
10
8
28
29
2J
25
24
15
14
15
23
15
16
15
54"
26
25
25
Average of two values.
Average of two values.
TABLF. C-38.
ANALYTICAL CONCENTRATIONS (mg/1) OF ClltMICAL OXYCFN DEHAND,
TRIAL I, FALL. UASIIINC OF tOLLAW) CREtNS. OCTOBER 24. 1975
Hours of Operation
Sice
0.25 12 3 4
26
13
10
91
132
33
47
45
110
136
169
43
57
173
207
69
96
93
206
TABLE C-39.
ANALYTICAL CONCENTRATIONS (mg/I) OF CHFMtCAL OXXC.F.K DEMAND.
TRIAL 2. FALL. UASHINC OF COLLARD GREENS. NOVEMBER 4. 1975
Hours of Operation
Site
0.25 1 2 3 4 5 6
262
1
146
2
103
3
144
4
132
5
303
6
45
49
25
33
31
92
129
35
214
59
75
192
304
355
430
419
349
453
492
428
98
13]
172
103
121
123
209
219
117
148
201
212
155
194
414
557
Single value, all others are average of two values.
Average of tw
TABLE C-40. AN\LYTICAL CONCENTRATIONS (mp/f) OF CIIFHtCAl. OXYGEN DEMAND.
TRIAL 1, FALL, UASHINC OF C0LI.AKD GKtXNS, NOVEMBER 20, 1975
Hours of Operation
Site 1 3 5 7
149
93
378
186
409
458
194
Avpr.igc of two v,ilues in each rase
400
264
lABlE C-42. ANALVTICAI. CONCKNTRATIONs' (mg/l) OF ClltMlCAL OXYGIN DEMAND,
TRIAL 5, FALL. UASHINC OF SPIWACU GREENS, DECEMBER 15. 1975
Hours of Operation „
TABLE C-41. ANALYTICAL CONCENTRATIONS (mg/l) OF CHEMICAL O.XYGEN DEMAND,
TRIAL 4. FALL. HASHING OF COLLARD GREENS, DECEMBER 1, 1975
^ Hours of Operation
24
86
96
204
244
275
292
321
26
140
158
214
290
315
359
167
20
16
192
67
81
67
106
112
28
58
l,l<
89
108
no
111
210
24
40
66
91
87
1 17
127
127
29
42
218
220
2(.5
290
110
141
Average of two valuea in each case.
25
25
25
16
31
35
113
115
62
63
171
194
79
112
200
240
98
129
130
240
211
246
95
113
115
214
"Average of two values in each case.
89
TAIL! C-«3. ANAUTICAL CONCENTRATIONS (ii|M) OF CIICHICAL OXYOIN DUMND,
THIAL 1. aniNC. WASHIKC 07 SPIWACM CMENS. APML 22. H7t
TABLE C-«4. ANALYTICAL CONCEHTKATIUNS (m|/t) Or ClIIIHICAL OXYCLN DEHAND,
miAL 2. SrRINC. WAJHINC Of SUMACH GREENS. HAY 12. 197t
Houri ot Operation
Houf of Oporatlon
1
2
3
4
S
e
7
8
9
10
0.25
82*
89''
U»
63
109
lit
274
261'
117
in"
161"
194*
106
124
72'
318*
506
514
247
277"
313
354
76
136*
105
343*
271*
204
97*
96
433* 463*
579 765^
173
203*
183
563*
49
53
69
220
347*
229
641°
164*
168"
155
134
431-
538°
170*
185*
181
414*
388
509*
132
164*
145
492*
;
378
464
136
168*
152
492*
9
10
7
280*
557°
154°
2 79*
113-'
221°
210'
222
724
139
249
87
208
202
277*
386*
267*
247*
128
192*
205'
236
385
301
274*
111
149
190'
Average of two value* ,
TABLE C-45. ANALYTICAL CONCENTRATIONS (i»g/«) OF CHEMICAL OXYCtN DEHAND,
TRIAL 3. SPRING. WASHING OF SPINACH GREENS, MAY 21. 1976
Site
.25
1
3
»e nf
two valuea.
3.25
*Aver
12
80*
237
252*
309°
304°
TABLE
C-46.
ANALYTICAL
CONCENTRATIONS (lug/l) Ot
■ CHEMICAL
OXYGEN
DEMAND
13
14
85
82*
236
219
190*
213°
321
308°
349
TRIAL 4, SPRIHC^ WASHING
OF TURNIP
GREENS,
JUNE 4. 1976
a
375°
lloura of Operation
IS
71
222
186*
301
329
Slce
0.25
1
2
4
5.5
60
77*
141
152"
163
200*
269*
255
282*
288
316*
'Average ut
two val
UL'B.
43
N
102
149
204
45"
82"
108*
1S1°
159*
205*
TABLE C-47
. ANALYTICAL CONCENTRATION (og/t) OF CHEMICAL OXYGEN DEMAND,
TRIAL 5, SPRING. WASHING OF TURNIP CRtENS, JUNE 10. 19 76
47
94
114
157
208
u
13
87*
SO*
63
141"
141
145
190*
185°
188
256*
167°
283*
137*
125
306°
Hours of
Operatl
on
Site
0.25
1
2
3
4
5
6.5
-
1
32
78*
155°
216*
151*
155
135*
It
67"
192
263*
7n*
190*
-
2
28
102
157
220
178
149
153*
IS
61
194
259
190
-
3
4
5
6
19*
16
16°
44
45°
18
38*
98
106°
63
60*
149
122°
118
119°
243
72*
82
87°
169
61°
67
55°
145
67
63
159°
141
*Aveiag« of
two valuea.
12
65*
88°
199*
193°
186°
-
-
13
49*
69
200
184
180°
-
-
14
40*
133°
295*
225°
228°
-
-
13
41
92
235
222
204
_
_
Average of two valuai.
90
TABLE C-4H. ANALYTICAL CONCENTRATION (mg/t) OP CllfcHICAL OXYCbN DEHAHD,
TR I AL_ /jj_ SPRING, WASHIWti UF^ fURN IJJiW.MH , J UNE__Ujl J9±b
TABl.t C-69. ANAI.YTfCAL CtWCKNTRATIdNS (mg/O OV FIVK-I>AY HItK;tli:MH:AI.
nXYUKN nKHANI). TKIAl. I. VALL, WASItINC OF CUl.LAKU i:k>.KNS,
lltMirw of li|ifi(il Iti
2 3
li.i^u(j»_ iJ__up_»miii_op__
1
92 =
1B5'
194°
178'
114'
104"
112'
2
144
240
228'
200
US'
120
124
3
38'
68'
92
98'
61'
56'
65'
4
44
80
104
98'
66
57'
70
5
47 =
79'
122'
90'
66'
55'
72*
6
136
240
228
200
124
116'
130'
12
36'
64'
93'
89'
115'
-
-
13
36'
60
99'
74
115'
-
-
U
35'
86'
133'
112'
157'
-
-
15
32
76
92'
'>2
166'
Average of two values
Average of three values.
sit.
1
2
4
1
28
31
8I'
2
17
34'
89
3
9
8
20"
i
10
15'
36'
5
18"
10
36'
Average of two values.
TABLE C-51. ANALYTICAL CONCENTRATIONS (m%/l) OF F1VK-0AY BIOiHI.MlLAL
OXYCtN OEMAWD. TRIAL 3. FALL. WASHING OF COLLARD CRttNS,
NUVLMBER 20. 1975
TABLE C-50. ANALYTICAL CONCENTRATIONS (mg/l) OF FIVL-DAY BIOCHtHICAL
OXYGEN DEHAND, TRIAL 2, FALL. WASHING OF COLLARD GREENS
NOVEMBER ^. 1975
Hours of Operation
lliL
Hours ot
Operation
site
0.25
1
2
3
4
5
6
8
24'
44
62
95'
108
97
11
30
45
88
89'
134
103'
4
8
11'
24'
28
35
20'
3
5
12
25
18
35
59
4
6
8
21'
27'
47
46
10
21
50
87
114
98
91'
Average of two values, other values are average of three.
TABLE C-53. ANALYTICAL CONCENTRATIONS (mg/O OF FIVE-DAY BIOCHEMICAL
OXYGEN DEMAND, TRIAL 5. FALL, WASHING OF SPINACH GREENS.
___^ DECEMBER 15, 1975
Hours of Operation
Slf
e 1
2
3
4
1
30"
49''
44"
46"
30"
52'
57'
39*
5-
24*'
25"=
22*
i
»'
21'
Si"
22*
»•
22''
32'
19"
(
21*
^^
Si'
32"=
Average oC two values.
TABLE C-52. ANALYTICAL CONCENTRATIONS (ng/!) OF FIVE-DAY BIOCHEMICAL
OXYGEN DEMAND, TRIAL 4, FALL, WASHING OF COLLARD GREENS.
DLCLUBER 1. 1975
Hours u( Operatltin
27
50
60
31'
52"
71'
12'
14'
19'
14''
15'
22'
75
88'
76
91'
116'
97
22'
30'
35
30'
36'
39
39
42
38
99'
101'
24
Average of two v.tIucb. Average of three values. '^Average of four values.
"Average of two values. ''Average of three values. ^Average of four vdJues.
91
TAILE C-St. ANALVTICAL COCUITIUTIONS (ag/I) OF ZO-DAV BIOOIEmCAL OnCEM
DUIAMD, TlltAL 1, FALL, UASHIHC OF COLLARS CUENS, OCTOIER 2i,
H75
Houf of Optratton
tHe «.0
1 99
2 lOS
1 10
» 21
i M
« »]
lAlU C-55. AKALYTICAL COHCtHT HAT IONS (■«/') OF 20-DAV BIOCHEMICAL OXYGEN
DCHAND, T«UU. 2, FALL, UASHIHC OF COLLARD UREEHS, NOVEMBER 4,
1975
Uoura of Opgration
Average o( two v.ilu«-9.
TABLE C-S«. AHALVTICAL COMCENTRATIONS (•(/!) OF 20-DAV BIOCHEMICAL OXVCEN
DEHAMD TRIAL *■ FALL. WASIUHC OF COLURP (■.Rt:tJIS. DECEMBER 1. 197}
Houri of Opration
1 35"
2 12 S0°
3 It 10*
« - 13"
5 »"
6 0 J?*"
'Avaraga of two valuea. Avaragc of threr valuea. *^Avcrage of four values.
TABLE C-il. AHALVTICAL COHCRMTRATIONS (•«/>) OF 20-l>AY BIOOILMLCAL OXVCEN
DEHAHII. TRIAL 5. FALL. MASHING OF SPIHAOI CKtEHS. DFX . . IS. 1975
Houra of Oparatlon
1»*
3J'
41"
»»"
15*
37'
w-^
m"
12*
6*
2."
30'
17*
13*
30"
»3«
17*
12*
27*
«'
13*
31"
62"=
J7'
Awrat* **' '^'O valuua. Avcrat* ot thrae valuon. Avorngc uf four valuaa.
92
TECHNICAL REPORT DATA
(Please read Inuructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-77-135
3. RECIPIENT'S ACCESSIOI*NO.
4. TITLE AND SUBTITLE
5. REPORT DATE
July 1977 issuing date
Minimization of Water Use in Leafy Vegetable Washers
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Malcolm E. Wright
Robert C. Hoehn (Civil Engr. Dept. - VPI & SU)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Agricultural Engineering Department
Virginia Polytechnic Institute & State University
Blacksburg, VA 24061
10. PROGRAM ELEMENT NO.
1BB610
11. CONTRACT/GRANT NO.
S-802958
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Lab
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
- Cin.
OH
13. TYPE OF REPORT AND PERIOD COVERED
Final 5/1/74 - 1/31/77
14. SPONSORING AGENCY CODE
EPA/600/12
IS. SUPPLEMENTARY NOTES
16. ABSTRACT
This project was undertaken to construct and test an improved leafy greens washing
system employing water recirculation, to characterize the quality of the wash water
and waste stream and to make comparisons to conventional washers. The prototype
system produced a cleaner product while reducing water requirements and consolidating
waste loads. The prototype system consisted of two drum immersion washers in series,
each with associated moving belt screens, settling tanks and water recirculation
systems. Construction was similar to conventional washers but with modifications to
improve removal of floating trash and increase hydraulic agitation of product. The
prototype was tested in a commercial processing plant during the fall and spring
harvesting seasons, 1975-76. Sixty-seven metric tons of collards, spinach, and
turnip greens were processed through the prototype in 52 hours of actual operating
time. Conventional washers were monitored for 27 hours (38 tons) for comparison.
Insect and bacteria counts, COD, TSS, VSS, and several other water and product
parameters were measured at predetermined times and locations. Data were obtained
to predict expected waste loads from the products processed. Wastewater discharge
from the prototype was approximately 1/12 that of the conventional washers.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Food Processing, Circulation, Canneries,
Freezers, Water Quality
Leafy-vegetable process-
ing, Process modification
Washing systems. Water
reuse
13/B
IS. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
105
20. SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
93
,v U. S GOVERNMENT PRINTING OFFICE 1977-757-056/6'.99 Region No. 5-11
J
TX 601 .Un3
2^fC
United States. Environmental
Protection Agency.
Minimization of Water Use in
Leafy Vegetable Washers.
DATE I ISSUED TO
TX 601 .Un3
e.s/(^
United States. Environmental
Protection Agency.
Minimization of Water Use infers
Leafy Vegetable Washers.
*' */2 0e2
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