04874

SPINOFF ON

F R U I T A N D V E G E T A B L E W A T E R A N D

WASTEWATER MANAGEMENT

ROY E. CARAWAN

JAMES V. CHAMBERS ROBERT R. ZALL

PROJECT SUPERVISOR

ROGER H. WILKOWSKE

EXTENSION SPECIAL REPORT No. AM-18E

JANUARY, 1979

PREPARED BY:

EXTENSION SPECIALISTS AT:

NORTH CAROLINA STATE UNIVERSITY

CORNELL UNIVERSITY

PURDUE UNIVERSITY

WITH THE SUPPORT OF THE

SCIENCE AND EDUCATION

ADMINISTRATION-EXTENSION

USDA - WASHINGTON, D.C.

WATER AND WASTEWATER MANAGEMENTIn Food Processing Plants - An

Educational ProgramThe objective of this program is

to increase the knowledge of foodscientists, food processors,engineers, scientists, wastemanagement specialists andother practitioners in the con-cepts and principles neededto properly control water use andproduct waste in food processingfacilities. The materials aredesigned for individuals concerned with management of foodplants, with pretreatment of foodprocessing wastewaters, withtreatment of food processingwastewaters and with the utiliza-tion or disposal of food plantresiduals. The modules in thisprogram incorporate knowledgefrom food science and tech-nology, food processing, sanitaryand environmental engineering,agronomy, soil science, agricul-tural engineering, economics andlaw.

The program consists of some15 modules. Introductory mate-rial is presented in the CoreManual to introduce the program.Technical specifics are providedin 7 technical spinoffs. The appli-cation of water and wastemanagement in specific foodplants is related in 7 commoditySpinoff Manuals.

Published by

THE NORTH CAROLINA AGRICULTURAL EXTENSION SERVICE

North Carolina State University at Raleigh, North Carolina Agricultural and Technical State University at Greensboro, and the U. S.Department of Agriculture, Cooperating. State University Station, Raleigh, N. C., T. C. Blalock, Director. Distributed in furtheranceof the Acts of Congress of May 8 and June 30, 1914. The North Carolina Agricultural Extension Service offers its programs to alleligible persons regardless of race, color, or national origin, and is an equal opportunity employer.

F&V SPNOFF/PREFACE

PREFACE

Purpose: The main purpose of this FRUIT AND VEGETABLE WATER AND

WASTEWATER MANAGEMENT SPINOFF is to be a primary reference

document to aid the extension specialist in assisting fruit

and vegetable processors in meeting water pollution

requirements. This document is intended as a guide, in that

it attempts to provide broad coverage, but cannot be totally

comprehensive on all topics. Instead, it gives general

information on a wide scale, and then directs the reader to

additional specific data and bibliographic information.

By presenting the fundamentals of water and waste management

for fruit and vegetable processing, this booklet will enable

the extension specialist to help fruit and vegetable pro-

cessors develop effective water and waste control programs.

Such programs can enable these processors to better meet

current water pollution control regulations and prepare for

future, more stringent regulations. Thus, this guide can be

a tool to help extension specialists and food processors

alleviate present misunderstandings and avoid future pro-

blems. In addition, this guide can aid in bringing together

representatives from the food industry and regulatory

agencies-to coordinate their mutual interest in reducing

water pollution.

Audience: This guide should be valuable not only to extension

specialists for which it was prepared, but also for food

processors and regulatory officials charged with the review

and approval of wastewater discharge from food plants not

only to surface waters but also to municipal wastewater

treatment systems.

F&V SPNOFF/PREFACE

Scope: The subject of this guide is the management and control of

water use and waste discharge in fruit and vegetable

processing, with emphasis on necessary legal, sanitary,

environmental and energy factors. In preparing this guide,

the committee has attempted to maintain a uniformity of

recommendations and suggestions, despite the variety of

processing plants and the disparity of requirements for

pollution control throughout the country.

Limitations: No written material dealing with pollution control regula-

tions can remain current and up-to-date with our rapidly

changing regulations. Therefore, the reader is advised to

check on current laws and local regulations before consider-

ation of any pollution control project. The vast differ-

ences and complexities that exist in fruit and vegetable

processing do not allow for a detailed information that

would be applicable to any plant without modification.

Disclaimer: The mention of manufacturers, trade names or commercial

products is for illustration purposes and does not imply

their recommendation or their endorsement for use by the

Agricultural Extension Service.

Learning Objectives:

1. Recognition of unit operations and, plant practices that

can or do contribute to pollution.

2. Understanding of the key elements in a water and waste

control program for a fruit and vegetable processing

plant.

3. Identification of the key federal, state and local

pollution laws and regulations that affect fruit and

vegetable processors.

4. Appreciation of the possible role of an extension

specialist in assisting processors to meet water

pollution control regulations.

ii

F&V SPNOFF/SUMMARY

SUMMARY

The important factors for extension specialists to consider in

developing programs to assist the fruit and vegetable industries in

meeting water pollution requirements are presented. This document

includes the following: (1) role an extension specialist can play in

plant pollution problems, (2) components of an effective water and wastecontrol program in fruit and vegetable processing, (3) methods for

monitoring and analyzing fruit and vegetable wastewaters, (4) terminology

and concepts of pretreatment and treatment of fruit and vegetable waste-

waters, and (5) notes for developing an effective extension program forfruit and vegetable processing plants.

Each fruit and vegetable plant has numerous operations that use waterand discharge skins, juices, bits of flesh or rejects which can contribute

to pollution and specific examples are reviewed for selected plants. The

possible ways these operations can be modified or employee practices

changed to reduce water use and waste are identified and discussed. The

role of management in processing water and waste control is explained.

Various practices to reduce pollution after the institution of

inplant water and waste management procedures are presented. Thesepractices include pretreatment, by-product recovery and/or treatment. The

most important aspects of each of these are reviewed.

The opportunities for wastewater discharge from a fruit and vegetable

processing plant are recognized as either discharge to a municipal systemor discharge directly to a stream, estuary or the ocean. The importantfactors to consider in municipal discharge of fruit and vegetable pro-

cessing wastes are identified as sewer use ordinances, user charges and

pretreatment. State, federal and local regulations for pretreatment arereviewed. State and local requirements for discharge limitations to meetNPDES permits or water quality criteria are listed and discussed.

Parameters of importance for fruit and vegetable processors for

municipal or direct discharge are identified as BOD5, TSS, pH and

flow. The importance of proper sampling and analytical techniques are

explained.

iii

1

F&V SPNOFF/LAND DISPOSAL

I N T R O D U C T I O N

Fruit and Vegetable Industries

The fruit and vegetable industries are as varied as the name implies

- this industry processes in a number of ways the great variety of fruit

and vegetables grown in the United States. The categories of processing

include canning, freezing, dehydrating, and pickling and brining. The 1972

Census of Manufacturers indicates there are over 3000 establishments in

this SIC Code classification including 2032, 2033, 2034, 2035, 2037 and

2038.

The Census also tabulated statistics showing that over 300,000

employees are employed by this industry. The annual payroll in 1972

amounted to about $1.5 billion.

The value of products produced by this group of industries in 1972 was

over $15 billion. The industries have plants all over the United States,

but California has the heaviest concentration of production of fruit and

vegetable products.

Water

Water in its pure state is a simple molecule consisting of two

hydrogen atoms attached to a single atom of oxygen. The greatest quantity

of water on this planet is in the oceans which contain 97.13% of the

supply. The largest supply for human consumption exists as ground or

subsurface waters with an 0.612% of the supply. Only a relatively small

portion of the supply exists as surface water in lakes (0.009%) or streams

(0.0001%). Most water pollution laws are designed to protect the water in

the streams, although newer legislation looks at the total water supply.

Legislation

Congress, on October 18, 1972, established PL 92-500, the Federal

Water Pollution Control Act Amendments of 1972. This law was passed to

create a successful mechanism to control water pollution. Authority was

granted to the United States Environmental Protection Agency (EPA) to

establish a permit system including pollutant discharge limitations to help

abate water pollution. In fact, the law, establishes a national goal to

2 F&V SPNOFF/LAND DISPOSAL

The limitations for industries were required to be established in

three parts. First a set of effluent limitations reflecting the

application of the "best practicable control technology currently

available" (BPT) to be achieved by July 1, 1977. Second, limitations to be

achieved by July 1, 1983 reflecting the application of the "best available

technology economically achieveable" (BAT). Also, a set of effluent

limitations were to be established for all new sources based on the "best

available demonstrated technology." Subsequently, Congress in 1977, passed

the Clean Water Act and EPA was required to replace BAT standards with

"best conventional pollutant control technology" (BCT).

To assure that the effluent limitations and water quality standards

would be met, PL, 92-500 established the National Pollutant Discharge

Elimination System (NPDES). Although the program was developed by and is

the responsibility of EPA, the various states have in most cases assumed

the responsibility for the NPDES program.

eliminate pollutant discharges into navigable waters by 1985.

Industrial facilities that discharge to municipal systems were also

affected by PL 92-500. User charges and industrial cost recovery (ICR)

were required of those industries in municipalities that receive federal

funds. Also, effluent limitations were established for publicly owned

treatment works (POTWS). These increased standards require more costly

treatment processes and these costs are passed on to the users, including

industrial discharges.

F&V SPNOFF/PROC PLANT SCHEMES

T Y P I C A L F R U I T A N D V E G E T A B L EPROCESSING PLANT SCHEMES

INTRODUCTION

This chapter presents some flow diagrams and process descriptions of

a few different fruit and vegetable commodities. These flow charts will

give you a basic idea of the steps involved in processing fruit and vege-

tables. Including flow charts for every fruit and vegetable commodity is

beyond the scope of this chapter. The charts and accompanying texts were

taken from a publication by Soderquist.

GREEN BEANS

As shown in Figure 1, the green bean canning process involves an ini-

tial washing followed by grading, snipping of the ends, cutting, blanching,

canning and retorting. The physical layout of a green bean processing plant

analyzed in the Soderquist study is presented in Figure 2. The major con-

tributors to the total pollutant load were found to be the washing, grading,

and blanching processes.

CHERRIES

The Soderquist study investigated the processing of two different vari-

eties of sweet cherries; Royal Anne and Lambert. The processing layout

appears in Figure 3. A comparison of Figures 4 and 5 reveals that the pro-

cessing methods for both varieties are similar.

PEARS

The plant layout for processing Bartlett pears appears in Figure 6.

The pollutional effects of two different types of mechanical peeling systems

were compared: the older Ewald peelers, and the more modern contour peelers.

The Ewald peelers peel the fruit by slicing over a pre-set contour, while

the more modern contour model follows the individual contour of each pear,

abrading the peel and thereby increasing the yield of saleable product by as

much as 10%. The study noted that the more modern peeler was decidedly in-

ferior to the Ewald peelers in terms of waste management.

5


6F&V SPNOFF/PROC PLANT SCHEMES

8


Figure 6. Physical configuration of pear processing.


Figure 7 depicts the pear canning process. After grading, the pears

are peeled and then flumed in a sodium chloride brine (which retards the

browning reaction on the peeled surface) to a fresh water rinsing tank for

removal of excess brine solution. After rinsing, the pears are conveyed to

trimming tables where blemishes are removed. After trimming, any severely

disfigured pears are directed from the main process line to the "chopping"

area where they are processed for incorporation into secondary products.

CORN

TWO corn processing plants were studied; both plants produced frozen

whole kernel corn and frozen corn-on-the-cob. The flow diagram depicting

the parallel corn processing lines in one plant appears in Figure 8. In

this figure, solid waste generation is indicated by the heavier arrows and

generation of liquid or waterborne wastes is indicated by the lighter arrows.

About 85% (by weight) of the total production from this plant was packed as

cut corn. Fifteen percent of the total input remained on the cob.

As indicated in Figure 8 the first major unit operation in the process

was the air blower. The blower was used to remove the loose material which

was received at the plant along with the raw product. The waste material

from this operation was collected dry and used as silage. No liquid wastes

were generated at this point.

The second major unit operation was the mechanical husker. Here the

husks were removed and again the solid wastes were collected and used for

silage. No liquid wastes were generated here either.

The third major unit operation involved in the corn process was the

de-silker, or "silker." Two types of silkers were in use at the time of the

study. One consisted of a large tumbler into which water was sprayed from

the inside. The second silker was of the roller type. In this type, the

corn passed over a set of hard rubber rollers while it was being sprayed

from above. Both types of silkers reused water which had been used in a

subsequent unit process; generally the water from the cooling operation was

reused in the silkers.

The steps described above were common to the cut corn process and on-

the-cob process. From this point on, it was necessary to consider separ-

ately the cut corn and corn-on-the-cob lines. After the silk was removed,

the corn was sorted. As mentioned before, about 85% (by weight) of the in-

coming raw product was shunted to the cut corn line. The yield for cut corn

10


Figure 7. Bartlett pear canning process diagram.

11


Figure 8. On-the-cob and whole-kernel corn processing flow schematic.


was about 30% by weight.

Referring again to Figure 8, in the corn cutting operation the kernels

were mechanically removed and the cobs collected as solid waste. Practically

no liquid waste was generated in the cutting operation during processing, but

considerable amounts of highly contaminated liquid wastes were generated

during the clean-up operation in the proximity of the cutter.

After being cut, the corn was blanched in a conventional steam blancher.

The only liquid waste generated at this point was the condensate. Following

blanching, the corn was sent to flotation washers. These washers removed un-

wanted material by encouraging it to float to the surface. The overflow from

the tank carried the waste solids away.

After washing, the corn was transported by vacuum lines to large hoppers,

and from there, flumed to the freezing tunnel where it was dewatered, frozen,

and packaged.

The corn-on-the-cob was processed in a separate line after de-silking.

Following sorting it was steam blanched. After blanching, the cobs were

passed beneath a series of overhead sprays for cooling. Some of the corn at

this point was cut into uniform lengths and subjected to a second cooling

process before passing to carbon dioxide coolers. The cob ends resulting

from this trimming operation were collected as solid waste and used for si-

lage. The remainder of the corn, as indicated in Figure 8, passed directly

to the carbon dioxide coolers.

B L A C K B E R R I E S

The Soderquist study observed one blackberry freezing plant in detail.

The flow diagram for the blackberry freezing process in that plant is shown

in Figure 9.

The berries arrived from the field in plastic crates or trays, each

tray holding about 15 pounds. After the berries were dumped from the crates,

the crates were washed as shown in Figure 9. After the crates were emptied,

the blackberries were passed through an air blower if the debris level in

the incoming product was sufficient to warrant using the blower. If the

berries were adequately clean and free of debris upon arrival at the plant,

the blower was not used. The blower normally had to be used when the berries

had been mechanically harvested. Conversely, it was normally not used when

the berries had been manually picked.

The next unit operation in the process was the washing step where the

13


Figure 9. Blackberry freezing process schematic.


berries were subjected to a wash by overhead sprays. This washing constituted

the only point in the process where the product actually came into contact with

water. Consequently, most of the plant waste load was generated at this

point. After washing, the berries were inspected, sorted, and conveyed

mechanically to the freezing tunnel. The conveyor belt was continuously

cleaned using a small water spray.

SUMMARY

The flow charts in this chapter are by no means meant to represent a

complete picture of all operations involved in processing various fruit and

vegetable products. As you might imagine, processing schemes for many dif-

ferent commodities have some unit operations in common. There are on the

other hand, of course, many unit operations which are strictly commodity-

specific.

The flow diagrams and texts offered here represent a small sampling of

the many and varied processing schemes that are associated with equally as

many different fruit and vegetable commodities. Their value is in intro-

ducing you to some general processing layouts which comprise the processing

of fruits and vegetables.

References

1) Soderquist, M. R. Characterization of Fruit and Vegetable Processing

Wastewaters. Water Resources Research Institute, Oregon State University.

1975.

15

F&V SPNOFF/WW CHARACTERIZATION

W A S T E W A T E R C H A R A C T E R I Z A T I O N

I N T H E F R U I T A N D V E G E T A B L E

P R O C E S S I N G I N D U S T R I E S

Introduction

Whenever food, in any form, is handled, processed, packaged and

stored, there will always be an inherent generation of wastewater. The

quantity of this processing wastewater that is generated and its general

quality (i.e., pollutant strength, nature of constituents), has both

economic and environmental consequences with respect to its treatability

and disposal.

The economics of the wastewater lie in the amount of product loss from

the processing operations and the cost of treating this waste material.

The cost for product loss is self evident, however, the cost for treating

the wastewater lies in its specific characteristics. Two significant

characteristics which dictate the cost for treatment are the daily volume

of discharge and the relative strength of the wastewater. Other

characteristics become important as system operations are affected and

specific discharge limits are identified (i.e., suspended solids).

The environmental consequences i n not adequately removing the

pollutants from the waste stream can have serious ecological ramifications.

For example, if inadequately treated wastewater were to be discharged to a

stream or river, an eutrophic condition would develop within the aquatic

environment due to the discharge of biodegradable, oxygen consuming

compounds. If this condition were sustained for a sufficient amount of

time, the ecological balance of the receiving stream, river or lake (i.e.,

aquatic microflora, plants and animals) would be upset. Continual

depletion of the oxygen in these water systems would also result in the

development of obnoxious odors and unsightly scenes.

This chapter will deal with those industries who utilize the processes

of the canned and preserved fruits and vegetables industry to extend the

shelf life of raw commodities through the use of various preservation

methods including canning, freezing, dehydrating, and brining. Fruit and

vegetable preservation generally includes the following unit operations:

cleaning and sorting, peeling, sizing, stabilizing and processing.

16


Fruit and vegetable processing plants are major water users and waste

generators. Raw foods must be rendered clean and wholesome and food

processing plants must be sanitary at all times.

For the most part these wastes have been shown to be biodegradable,

although salt is not generally removed during the treatment of olive

storage and processing brines, cherry brines, and sauerkraut brines.

According to Standard Industrial Classifications of the fruit and

vegetable industries, the following industrial categories and subcategories

have been assigned: Note - the subcategories listed here are tentative

(1978).

The apple, citrus and potato processing segment of the industry has

been subcategorized as follows:

Subcategory Designation

Apple Juice A

Apple Products B

Citrus Products C

Frozen Potato Products D

Dehydrated Potato Products E

The above subcategorization does not include caustic peeled and

dehydrated apple products, and pectin and pharmaceuticals derived from

citrus products. The remaining part of the industry has been tentatively

subcategoried, but is still subject to change. The tentative subcate-

gorization is as follows:

Added ingredients Dried fruits, prunes, figsApricots Dry beans, cannedAsparagus Ethnic vegetables, Chinese &Baby foods MexicanBeets Grape pressingBroccoli Grape juiceBrussels sprouts Jams, jellies and preservesCranberries, Blueberries Lima beansCarrots Mayonnaise and salad dressingsCauliflower MushroomsCherries, sweet & sour OlivesCherries, brined Onions (canned)Corn PeachesCorn chips PearsCranberries PeasDehydrated onions & garlic Pickles, fresh packDehydrated vegetables Pickles, process pack

17


PimentosPineapplesPlumsPotato chipsPrune juicePumpkin and squashRaisinsSauerkraut, cuttingSauerkraut, canningSnap beans (green & wax)

SoupsSpinach/leafy greensStrawberriesSweet potatoesTomatoes, peeledTomato productsTomato - starch cheese, cannedspecialtiesWhite potatoes, whole

Process Description

In general, all subcategories have similar process operations as

follows.

Field to Plant

The crop is harvested, separated from "trash" (stems, leaves),

sorted, transported, and received at the plant. No wastewaters are

generated.

Washing and Rinsing

Prior to processing the fruits and vegetables are washed and rinsed

by means of flumes, soak tanks, water sprays, flotation chambers, or any

combination of these methods. Great quantities of water are used.

Detergents and ultrasonic techniques are also being tested for increased

cleaning efficiency.

Sorting (Grading)

The commodity is sorted and graded by mechanical, optical, manual or

hydraulic means. Density graders employing brine of controlled density are

used to separate mature from over mature produce. Weed seeds, chaff, and

stones may be separated by density and in froth separators.

Stemming, Snipping, Trimming

Steeming, snipping, and trimming are accomplished by a variety of

mechanical means. No wastewaters are generated.

18


In-Plant Transport

Various means have been adapted for conveying fruit or vegetable

products at unloading docks into and through the processing plant. These

include fluming, elevating, vibrating, screw conveying, air propulsion,

negative air conveying, hydraulic flow, and jet or air blasting. Water, in

one way or another, has been extensively used in conveying products within

plants because it has been economical in such use and because it serves not

only as conveyance but also for washing and cooling.

It has been traditional to consider water an economical means to

transport fruits and vegetables within a plant and to assume there was some

sanitary significance to such use, not only for the product, but also for

the equipment. A significant disadvantage, however, may be leaching of

solubles from the product, such as sugars and acids from cut fruit; and

sugars and starch from cut corn, beets, and carrots. Alternative systems

to decrease such losses from water have been investigated, such as

osmotically equivalent fluid systems.

Peeling

Many fruits and vegetables are peeled for processing. This serves

the multiple purpose of removing residual soil, pesticide residues, coarse,

fuzzy, or tough peeling with unpleasant appearance, mouth feel, or diges-

tive properties.

Peeling is accomplished mechanically by cutting or abrasion; thermally

by puffing and loosening the peel-by application of steam, hot water, hot

oil flame, or blasts of heated air; or chemically, principally using

caustic soda (with optional surfactants) to soften the cortex so it may be

removed by mechanical scrubbers or high-pressure water sprays.

Pitting, Coring, Slicing and Dicing

Pitting, coring, slicing and dicing are accomplished by a variety of

mechanical techniques depending upon commodity used and end product

desired. No wastewaters are generated.

Pureeing and Juicing

Widely varied techniques are used for pressing and separating fluid

from fruits and vegetables. Equipment includes reamers and a wide variety

of crusher-presses, either batch or continuous in operation.

19


The oxygen and other gases (nitrogen, carbon dioxide) present in

freshly pressed or extracted fruit and vegetable juices may be effectively

removed by deaeration under vacuum. The liquids to be deaerated are pumped

into an evacuated chamber either as a spray or as a thin film. Modern

deaerators operate at a vacuum of 29 inches or above. Deaeration properly

carried out not only improves color and flavor retention, but reduces

foaming during filling and also reduces separation of suspended solids.

In the concentration of solutions by evaporation, the liquid to be

concentrated continuously flows across a heat exchange surface which

separates it from the heating medium. There are various types of

evaporators, including: open kettles, shell-and-tube heat exchangers,

flash evaporators, rising and falling film evaporators, plate type

evaporators, thin-film centrifugal evaporators, vapor separators, vacuum

evaporators and heat pump evaporators. The process involves heating the

product to evaporation and separating the vapors from the residual liquid.

Size Reduction

A wide range of size reduction equipment is required to produce

different types of particulated solids. Selection of a machine which can

most economically product desired results is affected by physical charac-

teristics of the material and by the required particle size and shape.

Blanching

Blanching (scalding or parboiling) of vegetables for canning,

freezing, or dehydration is done for one or more reasons: removal of air

from tissues; removal of solubles which may affect clarity of brine or

liquor; fixation of pigments; inactivation of enzymes; protection of

flavor; leaching of undesirable flavors or components such as sugars;

shrinking of tissues; raising of temperature; and destruction of microor-

ganisms.

Blanching is accomplished by putting the products in contact with water

or steam. In almost all cases for preparation of vegetables to be frozen,

it is imperative that the blancher processes be terminated quickly.

Consequently, some type of cooling treatment is used. Typically, if the

product has been water blanched, the vegetable is passed over a dewatering

20


screen and cooled either by cold water flumes or cold water sprays.

Product to be canned is usually not cooled after blanching.

The pollution loads from blanching are a significant portion of the

total pollution load in the effluent stream during the processing of

certain vegetables.

Canning

The sanitary codes of most states require that cans be washed before

being filled. There are usually three steps in the can cleaning operation.

First, the cans travel a short distance in the inverted position; second,

they are flushed with a relatively large volume of water under high

pressure; and third, they travel another short distance in the inverted

position for the purpose of draining excess water. This is usually

accomplished mechanically.

The commodity is then filled into the can by hand, semiautomatic

machines, or fully automatic machines, depending on the product involved.

In some products, there is a mixture of product and brine or syrup. In

other cases, brine or syrup is added hot or cold as top-off liquid. When

the top-off is cold, it is necessary to exhaust the headspace gases to

achieve a vacuum and maintain product quality.

Exhausting in order to create a vacuum, is usually accomplished by one

of the three methods:

1. Thermal exhaust or hot filling. The contents of the container are

heated to a temperature of 160o to 18OoF, prior to closing the

container. Contraction of the contents of the container after sealing

produces a vacuum.

2. Mechanical. A portion of the air in the container headspace is pumped

out by a gas pump.

3. Steam displacement. Steam is injected into the headspace to replace

the air, and sealed. A vacuum is produced when the steam condenses.

Drying or Dehydration

Continuous belt dryers are the most commonly used method for dehy-

dration. They are usually long and multi-staged with baffled chambers

which blow heated and sometimes desiccated air from over and under the

bed-depth of the raw slices. Residence time in this type of dryer is

21


usually ten to twenty hours, resulting in a product that has a finished

moisture content of no greater than 4.25 percent of onions or 6.0 percent

for garlic.

Post-Drying Operations

After dehydration the dried slices are usually screened, milled,

aspirated, separated, and ground in various mechanical combinations to

achieve the final desired piece size.

Mixing and Cooking

Certain commodities utilize additional ingredients in the manu-

facture of the finished products. For example, many frozen vegetables are

prepared with butter, cheese, cream sauce, sugar, starch and tomato sauce

added. Equipment washouts and spills add an incremental waste load to the

total plant waste production.

Freezing

Freezing is accomplished in a tunnel freezer. The frozen commodity

is then inspected, sorted and sized prior to packing. The only waste loads

generated from this operation are from the clean-up operations and from

cooling water.

Clean-Up

Clean-up operations vary widely from plant to plant and from product

to product. Normally the plant and equipment is cleaned at the end of the

shift, usually by washing down the equipment and floors with water. In

some plants it is desirable to maintain a continuous cleaning policy so

that end-of-shift clean-up is minimized.

Clean-up begins with a dry collection of wastes followed by a

washdown. The washdown may be done with either water alone or with water

mixed with detergent. Water is applied through either high-volume,

low-pressure hoses or low-volume, high-pressure hoses.

In some operations, such as the mayonnaise processing operation, clean

water is used to flush out the entire system at the end of the shift to

remove any residues which might harbor bacteriological growth. The water

used in clean-up operations generally flows through drains directly into

the wastewater system.

22


Wastewater Characterization

Characteristics

Major wastewater characteristics of concern to the fruit and

vegetable industries are the wide ranges of wastewater volume and organic

strength generated. The wastewater characteristics depend upon the

particular commodity being processed, the particular operation employed,

and daily and seasonal variations. Treatment facilities must be designed

to handle large volumes intermittently. Citrus wastes are highly

putrescible and contain pectic substances which interfere with the

settling of suspended solids.

Pollutant parameters of significance to the fruit and vegetable

processing wastewaters are biochemical oxygen demand (BOD) and total sus-

pended solids (TSS). These parameters dictate the level of waste treatment

required and define the limitations of the permit to discharge to a tri-

butary stream (NPDES) or a municipal sewer (Sewer Use Ordinance). These

parameters can be defined by monitoring the plant's processing flow.

Sampling

Of equal importance is the problem of obtaining a truly representa-

tive sample of the stream of effluent. The samples may be required not

only for the 24 hr effluent loads, but to determine the peak load

concentrations, the duration of peak loads and the occurrence of variation

throughout the day. Assuming that a sample can be taken from the effluent

drain which will be representative of the liquid in the weir or flume,

there are a number of different ways of obtaining a 24 hr composite.

(a) A time-proportional method, which involves taking a sample at a

set time interval, e.g., every 1 min, or every 30 min; the greater the

frequency of sampling, the more representative will be the sample;

(b) A volume proportional method, in which a small sample is taken

from the drain after a known volume, e.g., 1000 1, has passed through the

flow measuring device;

(c) A flow proportional method, in which a sample is taken from the

drain at a particular time but proportional to the flow passing the

particular device at the time the sample is taken; and

(d) A combination method, in which the sample is taken proportional to

both time and volume.

23


Obtaining good results will depend upon certain details. Among these are

the following:

(a) Insuring that the sample taken is truly representative of the

wastestream.

(b) Using proper sampling techniques.

(c) Protecting the samples until they are analyzed.

The first of these requirements, obtaining a sample which is truly

representative of the wastestream, may be the source of significant errors.

This is especially apparent in the case of "grab" or non-composited

samples. It must be remembered that waste flows can vary widely both in

magnitude and composition over a 24-hour period. Also, composition can

vary within a given stream at any single time due to a partial settling of

suspended solids or the floating of light materials. Because of the lower

velocities next to the walls of the flow channel, materials will tend to

deposit in these areas. Samples should therefore be taken from the

wastestream where the flow is well mixed. Since suitable points for

sampling in sewer systems are limited, numerous ideal locations are not

usual.

The usual method for accounting for variations in flow and waste

constituents and minimizing the analytical effort is by compositing the

samples. Basically, sufficient samples should be taken so that, when mixed

together (before analysis), the results which are obtained will be similar

to taking a sample from a completely-mixed tank which had collected all the

flow from the stream in question. Greater accuracy is obtained if the

amount of sample in the composite is taken in proportion to the flow. In

general, the greater the frequency of samples taken for the composite, the

more accurate the results.

Obtaining a representative sample should be of major concern in a

monitoring program. A thorough analysis of the waste flows in the plant

must be made and a responsible staff member should be assigned to insure

that the samples taken are representative. As a general rule, closer

attention must be given to waste sampling than in the sampling of a

manufacturing process stream.

In many process operations, the wastes are pumped from sumps within

the plant before the liquid goes into settling tanks. Where a liquid is

being pumped through a pipe, flow monitoring and sampling are often

24


simplified, for in most cases the variations in pumping rate are minor

and can either be calculated from the pump curves, or by calibrating pumps.

Sampling under these systems involves using time-operated solenoid valves

which open for a brief interval every minute or so. The timers should be

attached to the pump motors so that samples are taken only when the

effluent is being pumped.

Once the samples have been obtained, analysis procedures should be

initiated as soon as practical. Table 1 summarizes the recommended storage

procedure for specific analysis.

Process Waste Point Sources

Figure 10 presents a simplified process flow diagram for both a

fruit and vegetable process line. Major wastewater generation occurs

during the washing steps and at plant clean-up as noted by the heavy

arrows. Because of the variation in wastewater characteristics found

throughout the fruit and vegetable industries, an attempt has been made to

group the commodity oriented industry according to BOD strength of the

wastewater. Table 2 gives the raw waste characteristics for this

industry.

The table has been grouped by the following formula:

Group I - Commodities with BOD less than 500 mg/lGroup II - Commodities with BOD between 500-1000 mg/l

Group III - Commodities with BOD between 1000-2000 mg/lGroup IV - Commodities with BOD between 2000-3000 mg/lGroup V - Commodities with BOD between 3000-5000 mg/l

Group VI - Commodities with BOD greater than 5000 mg/l

Loading Factors and Their Estimates

It is a well established fact that a given volume or quantity of

production will have a direct effect on the level of waste generated.

Tables 3, 4 and 5 present data gathered by the U. S. and Canadian federal

environmental protection agencies as a result of plant surveys conducted

for the fruit and vegetable industry.

In the use of these tables, one can only develop a gross estimate of

the loading factors for a given commodity operation. It should be empha-

sized that these tables should not be used as a substitute for an actual

plant survey of sufficient duration to establish the loading factors based

on actual production.

25


Table 1. Recommended Storage Procedure.

26


Figure 10. Food Plant process flow diagram (Fruit and Vegetables).

28


29


NOTE; * The BOD5 loadings for small and large fruit/vegetable processing

plants are low because the commodity mix indicates

that tomatoes comprise of the bulk of the processing, and the

average unit BOD5 loadings for tomatoes is comparitively lower

at 4.7 kg/t.

31


References

CH2M Hill, Corvallis, Oregon. 1976. Wastewater Treatment - Pollution

Abatement in the Fruit and Vegetable Industry. Prepared for Food

Processors Institute and Sponsored by Office of Technology Transfer,

Environmental Protection Agency.

EPA. 1976. Wastewater and Its Treatment. Published by EPA, Construction

Grants Programs. Environmental Protection Agency Technical Transfer

Series (EPA-43-9-76-017c), Vol. III, Appendix 8.

Mulyk, P. A. and A. Lamb. 1977. Inventory of the Fruit and Vegetable

Processing Industry in Canada - A report for Environment Canada,

Environmental Protection Service, Ottawa, Ontario, Canada.

32

CONTROL OF WATER AND WASTEWATERIN FRUIT AND VEGETABLE PROCESSING

F&V SPNOFF/CONTROL OF WATER & WW

I N T R O D U C T I O N

Water is an absolute necessity in most fruit and vegetable process ing

operations, and by practicing its conservation and reuse, the amount of liq-

uid waste from these operations can be reduced. Until recently, little con-

sideration has been given to water reuse because it was cheap and relatively

abundant; reuse was considered hazardous because of bacterial contamination.

This chapter is divided into three major parts. The first portion pre-

sents some basic concepts related to controlling water and wastewater. The

second section presents some case studies which examine various water and

wastewater control methods that have been applied to the processing of sev-

eral different fruit and vegetable commodities. The third section explores

reuse and recycling methods in more detail, and presents some commodity-

specific information on by-product recovery and use.

CONTROL OF WATER AND WASTEWATER - SOME CONCEPTS

The type of waste management system suitable for a food processing oper-

ation will depend upon:

the characteristics of the waste

the location of the processing plant

the degree of waste treatment required

available points of discharge for the treated liquid wastesand for the collected solid wastes.

As with almost all industrial waste situations, a unique waste management

solution may exist for each operation.

One of the first and best approaches to devising a fruit or vegetable

processing waste management system is to investigate the opportunities for

in-field and in-plant modifications. Let's Took at some of these in-plant

and in-field techniques that help decrease wastewater strength and reduce

water use. These techniques include:

Using harvesting equipment that allows more of the stems,leaves and culled material to remain in the field.

Washing and/or partially processing the crop in the fieldto allow return of any residue to the land,

Separation of low and high strength waste streams

Installation of low-volume high-pressure clean-up systems

Dry in-plant transport of products

Two

plant:

1)

2)

Countercurrent reuse of wash/flume/cooling waters

Dry handling of solid wastes

Dry caustic peeling

Change-over from water to steam blanching (where possible)

Air cooling after blanching

An active and progressive waste management program.

major streams contribute wastewater flows in a food processing

Water used in processing the product

Water used for cooling.


Using air blowers and water-filled flotation tanks to re-move debris from the crop.

Modifying peeling and pitting operations to use less waterand waste less of the raw product.

Recovering and reusing process water through the plant.

Separating waste process streams at their sources for po-tential by-product use.

Separate waste treatment and disposal of wastes withdiffering characteristics.

A nationwide study of the preserved fruits and vegetables processing

industry was conducted in 1974.About 500 processing plants were visited in

the course of this study. Certain unit processes and/or technologies were

readily identified as having an impact on reducing raw waste loads. Some of

these were:

Water conservation is practical in today's plants and can be practiced by

the use of low-volume high-pressure sprays for plant clean-up, elimination

of excess overflow from water supply tanks , use of automatic shut-off valves

on water lines, and use of mechanical conveyors to replace the old style of

water-gobbling flumes. Reusing cooling water in counter-flow schemes to

wash the incoming raw fruits or vegetables is an example of a separation and

reuse technique.

Another water conservation method is the closed loop system for certain

processing units, such as a hydrostatic cooker-cooler used for canned pro-

ducts. The water is reused continuously; fresh makeup water is added only

to offset the minor losses from evaporation. Closed loop systems not only

34F&V SPNOFF/CONTROL OF WATER & WW

conserve water but also reclaim heat and can result in significant economic

savings.

Eliminating water in certain unit operations in turn eliminates atten-

dant problems of treating the wastewaters which were generated by those

operations. Wherever possible, food should be handled by either a mechani-

cal belt or pneumatic dry conveying systems. If possible, an air system in-

stead of a water system should be used for cooling the products. Studies

comparing hot air blanching of vegetables with conventional hot water blan-

ching showed that both the product and environmental quality were improved

by using air. Blanching is used to deactivate enzymes and produces a very

strong liquid waste when the hot water technique is used. In a pea proces-

sing operation, for example, this small volume of wastewater is estimated to

be responsible for 50% of the plant's entire BOD wasteload; for corn, the

estimate is 60%; and for beets with peelings, 80%. Preliminary results have

shown a reduced pollution load, while simultaneously providing a product

quality improvement in terms of nutrient, vitamin and mineral content.

Segregating wastes within a plant can be important in optimizing the

least-cost approach to waste treatment. For example in a typical brewery,

3% of the flow contains 59% of the plant's BOD load. It is usually less ex-

pensive to treat this small flow separately than to mix it with the entire

plant waste flow, and then attempt to treat this much larger volume.

Other modifications to food processing operations for waste product

separation become apparent when a mass balance is conducted at a plant and

when by-product utilization opportunities are available. The development of

dry caustic potato and fruit peeling methods has reduced both the volume and

strength of wastes from these operations. A waste survey of a food process-

ing facility, including a water balance and mass balances of product, BOD,

solids, and nutrients can reveal other opportunities for in-plant waste man-

agement modifications.

It has been determined that by controlling the pH of fruit fluming

waters using additions of citric acid, it is possible to reduce the flume

water volume without risk of increasing the size of the bacterial population,

thereby avoiding contamination. A pH of 4.0 will maintain optimum conditions

with cut fruit such as peaches. This technique not only reduces the total

volume of water required and therefore the amount of wastewater discharged,

but also increases the product yield by decreasing the loss of solids from

sugar and acids which would otherwise have leached from the fruit. Conse-

quently, there is a reduction in the total pounds of organic pollutants


appearing in the wastewater. Still another advantage offered by this process

is the improved flavor and color of the canned fruit due to better retention

of soluble solids.

Many factors determine the final effectiveness of proper water use. For

example, tomatoes spray-washed on a roller belt where they are turned over

are almost twice as clean as the same tomatoes washed on a belt of wire mesh

construction. Also, warm water is about 40% more effective in removing con-

taminants than the same volume of cold water.

The last major source of liquid wastes is the washing of equipment,

utensils and cookers, as well as washing of floors and food preparation areas.

The wastewater from clean-up periods is likely to contain a large concentra-

tion of caustic, thus increasing the pH above the level experienced during

processing.

Use of waste monitoring equipment such as temperature recorders, conduc-

tivity measurements, flow measurement devices, and turbidity measurements can

be used toconduct mass balances at a processing plant, and to pinpoint po-

tential improvements in processing operations. Such waste production indices

can be used to measure the performance of both management and production wor-

kers. By using these techniques, waste handling costs can be reduced, water

conservation and reuse can be enhanced, and savings of raw materials may

result.

Proper management of processing wastes requires consideration of indi-

vidual operations from harvest through waste disposal as integrated subunits

of the total process. Every effort should be made to eliminate wastes and

to avoid bringing wastes from the harvesting fields into the processing plant.

Where possible, preprocessing should be done directly in the field to permit

the return of organic materials to the land,

Remember that in water reuse schemes, a delicate balance exists between

water conservation and sanitation. There is no straightforward or simple

formula to obtain the least water use. Each case and each process scheme has

to be evaluated in terms of the equipment used in order to arrive at a satis-

factory procedure for maintaining product quality while reducing wastage and

water use.

SOME CASE STUDIES

The previous section outlined some concepts and the general techniques

which can put those concepts into practice. This section presents various


methods for controlling water and wastewater in commodity-specific processes.

CARROT PROCESSING MODIFICATIONS

WASH WATER RFCYCLING

Washing soil from root vegetables requires a lot of water. One large

fresh carrot supplier in California used about 4,000 gal/min of wash water

in the course of processing 500 T carrots/day the year round. Because of

short supplies of water and expensive waste disposal, wash water recycling

became attractive. The continuous water recycling system is described below

and depicted in Figure 11.

Two settling ponds, each 60' by 150', serve as surge reservoirs. From

here, water is pumped for use in fluming the carrots. The flume water is

used for flushing the carrots from the trucks. This flushing removes 90% of

the field soil. Carrots go through a brush washer, and then through sorting

stations, where small sizes and misshapen carrots are removed as culls. The

desired sizes are hydrocooled, then sent through a second brush washer, Po-

table water is sprayed over the carrots in the final section.

Part of the flume water is pumped through a patented, cylindrical, sol-

ids-liquid separator. Here, water enters an annular space at the top; flow

velocities decrease as solids are spun inward through orifices toward the

center, rather than outward as in conventional cone-shaped cyclone separators.

The cleaned water exits at the top; solids settle to the bottom where they

are continuously flushed out and returned to the settling pond. Trash is

screened out through a stationary curved screen separator before entering

the four centrifugal separators. Flow through the four separators is 2OO-300

gpm total.

Water in the hydrocoolers and in the final sprays is chlorinated at 100

ppm. Chlorination of these flows, which cycle through the ponds, keeps the

reservoirs, flumes, and equipment free of bacterial, fungal or algal growth.

RESULTS ACHIEVED

The low-cost self-installed recycling system just described, effectively

recycles all wash and flume water, excepting a small amount sprayed during

final rinse, and the water carried out with the product. The system requires

no extra energy except that for handling a pressure drop of about 8 psi to

pump the water through the centrifugal separators, Separators remove 98% of

37


Figure 11. Carrot wash water recycling system.

38

F&V SPNOFF/CONTROL OF WATER & WWthe soil particles sized 44 microns (325 screen size) or larger. The best

result of all is that there is no waste to treat.

IN-PLANT CHANGES RESCUE CARROT PROCESSOR

Plant "A" processes frozen carrots. The plant operates on a typical

schedule of 5 days per week, 10 to 11 months each year. Normal production

is set for two shifts per day with additional clean-up time as needed.

Average throughput is about 8 raw tons per hour.

Figure 12 shows the typical flow diagram that plant A followed before

any process modifications were made. Carrots were delivered in bins either

directly from the fields or from a sorting shed. They were washed, trimmed,

conventionally lye peeled and diced or sliced. Blanching was accomplished

in a water blancher; post blanch cooling was also accomplished using water.

Water use was high, approaching a daily average consumption of 1.5 mgd; BOD

levels were correspondingly high, averaging about 2,400 mg/l.

This plant, landlocked by city growth, was already paying a surcharge

for its effluent disposal to the municipal waste treatment system. The city

recognized that expanded treatment facilities were needed to accommodate in-

dustrial users. So, the city proposed tentative revisions in its surcharge

system which if adopted, would cause monthly rates to approach $4,000.

At this point, plant A's managers decided to institute changes in the

form of capital investments. When designing the plant modifications, the

engineers considered each waste contributing process within the processing

scheme. Figure 13 shows the results of these efforts; Table 6 records the

benefits gained.

CARROT WASHING

Water used to wash the incoming carrots had previously been combined

with the main plant effluent stream. However, observation and testing of

this stream indicated that its chief components were sand and dirt, some

field debris, and occasional carrot particles. Because of the plant's lo-

cation, it was decided that this stream should be isolated from the streams

with higher waste concentrations and discharged separately under an NPDES

permit. A double screening system was installed (not shown on diagram) to

remove various solid particles from the waste stream. This not only lower-

ed the suspended and settleable solids but also, in part, contributed to re-

ducing the BOD discharge. Freezer defrost water was also diverted to merge

39


Figure 12. Original flow, carrot processor "A".

40


Figure 13. Modified flow, carrot processor "A".

41


Table 6. Carrot Process "A". Parameter Differences

1 0.35 MGD discharqed under NPDES permit, 0.25 MGD to city

42

F&V SPNOFF/CONTROL OF WATER & WWwith this stream. The effect of this separation should not be underestimated.

These two components are responsible for about 60% of the total plant flow -

about 350,000 gallons per day. The alternative discharge of this large water

volume to a municipal waste treatment system would have been extremely expen-

sive.

PEELING

The peeling process was identified as the main source of BOD and SS gen-

eration. The water required for peel removal was a substantial percentage of

the plant's total effluent. A new lye peeler (ferris wheel type) was pur-

chased and installed.

The conventional high-pressure water lye peel removal system was replaced

with a Magnuscrubber. The resulting peel waste slurry was pumped directly to

a holding tank. Ultimately this waste fraction is disposed of in sanitary

landfill.

In addition to 'the water use and BOD reductions expected, the equipment

modifications just described were responsible for improving finished product

recoveries for both sliced and diced carrots, These increased yields were a

direct result of the new peel removal system. Plant personnel also noticed a

reduction in caustic soda consumption.

DRY SOLIDS HANDLING

The engineers working on process modifications recognized that every

attempt should be made to stop the introduction of solid wastes into the eff-

luent stream. The original plant flow allowed for trimmings and solid waste

to be flushed into gutters, followed by final screening before discharge to

the city sewer system. This allowed for additional leaching of soluble sol-

ids and was, in part, responsible for the plant's high BOD. To overcome this

problem, a separate series of dry solids conveyors were installed to trans-

port trimming table and other wastes directly to outside bins. Plant mana-

gers also made a concerted effort to instruct plant employees on proper

methods of handling solid waste.

BLANCHING

As shown in Figure 12, this plant had used a hot water blancher for years.

Water blanchers, however, have been shown to be major sources of water pollu-

tion. Leaching solids, continuous spillage and overflow, all contribute


heavily to a plant's BOD and SS loads. The waste stream from the water blan-

cher was not only concentrated, but was of substantial volume. So, the old

water blancher was removed and a steam blancher was installed. Now the only

effluent from this unit process is a highly concentrated l-2 gpm condensate.

The effect on total BOD and SS load has been considerably lessened, yet the

desirable product quality characteristics have been retained.

COOLING

Similarly, post blanch hydrocooling, necessary to prepare carrots for

freezing and to optimize freezer efficiencies, was found to contribute to the

plant's effluent load. The conventional hydrocooling system was replaced

with an ambient air cooler. Working on a fluidized bed principle, the pro-

duct leaves the blancher and is blown and vibrated over perforated screens

by the action of air jets blowing through and upward to contact the product.

The action of the air and the mechanical vibrations of the screen move the

product across the screen during which time the required cooling gradient is

achieved. Using air eliminates almost all water contact after blanching ex-

cept for one or two fine water sprays between the blancher and cooler. Water

use at this stage was estimated at no more than 2 gal/min.

CAPITAL INVESTMENT

The plant estimated that their total expenditures for all the improve-

ments and modifications amounted to about $90,000. Although no attempt was

made to calculate paybacks on investment capital, it can be seen in Table 6

that savings accrued due to reduced discharged volume and pounds of pollu-

tants sent to the city waste treatment system accounts for about $42,000 per

year. If one were to add a monetary value to the increased yeilds obtained,

the investment would become even more attractive. The changes just described

were documented in a study by LaConde and Schmidt (1976).

DRY CAUSTIC PEELING

Of the unit operations in the processing of fruits and vegetables which

use water and generate waste, the most notable for magnitude of water use and

waste generation is the peeling operation. Whether product peeling is by

water, steam, caustic, or a combination of these, the operation has always

generated a liquid waste troublesome because of its volume, organic load, and


pH value. For example, approximately 40 percent of the BOD from peach can-

ning comes from the peeling operation.

In recent years interest in dry peeling of fruits and vegetables has

increased because of the impact that this process has on reducing water pol-

lution. As a result of this interest, equipment manufacturers have explored

developing machinery for such peeling processes. This section will present

the waste and water reduction results that have been achieved by using such

processes.

TOMATOES AND PEACHES

Tomatoes, clingstone peaches and potatoes are the principal “target"

commodities at which dry caustic peeling efforts have been aimed. The peel-

ing machine is basically designed to gently remove the peel from soft fruits

and vegetables without using water, and to collect the peel waste residue so

that it does not enter the plant's wastewater effluent. This is done by col-

lection, haulage, and separate disposal of concentrated peeling wastes.

To gently wipe away peel softened by caustic, the machine uses very thin

soft rubber discs. These rubber discs are placed on rotating cylindrical

rolls arranged in a circular revolving cage containing a feed screen through

the center. The fruit moves parallel to the roll axis and perpendicular to

the surfaces of the roll discs. The soft, moving disc surfaces provide gen-

tle, thorough scrubbing much like wiping the fruit with the palms of the

hands. The feed rate is accurately controlled by the central screw conveyor.

A final rinse to remove the last traces of peel and caustic is the only fresh

water used. During an EPA demonstration grant with the Del Monte Corp.,

water use in the peeling operation was reduced from 850 gal water/ton peaches

to 90 gal water/ton peaches by using the dry peeling process.

In conventional peeling, the peel is pre-softened by contact with di-

lute sodium hydroxide and then removed from the peach using large volumes of

fresh potable water that comprise high-pressure sprays. Water from this

peeling operation therefore contains essentially all of the removed peel.

Dry caustic peeling in which mechanical rubbing is used to remove the

softened peel was originally developed for the potato processing industry;

however, peeling softer fruit such as peaches required the development of

the new process just described.

Peeling is the largest single source of waste from fruit processing,

accounting for as much as 10 percent of the total wastewater flow and 40

percent of the total biochemical oxygen demand.


The dry caustic peeling process also allows for collection of the peel

as a pumpable slurry. This slurry may have potential value as an animal

supplement or in reclaiming marginal farm land, Because the peel is not

carried in the wastewater flow, the total organic and suspended solids load-

ing of the wastewater from the peeling process is reduced by about 60 percent.

Peach quality was judged to be equal to that of conventionally peeled peaches.

The most striking result of the commercial tests of the dry caustic

peeler is the 90 percent reduction in water use as compared to the convention-

al caustic peeler. Significant pollution parameters can be reduced by approx-

imately 60 percent. Table 7 illustrates the average wastewater volumes and

pollution loadings for each process, based on 24-hour composite samples taken

on each of the 21 days of the demonstration period.

Table 8 sununarizes the characteristics of the peach peel solid wastes.

The relatively high pH of the slurry and the low pH of the rinse water indi-

cate that most of the caustic is removed with the peel.

A commercial dry caustic peeler has also been operated successfully on

freestone peaches. There is additional economic incentive for use on free-

stone (as opposed to clingstone) peaches, since the mechanical action of the

wiper effectively removes bruises and decreases the higher cost of hand in-

spection associated with freestone peaches.

After having tested dry caustic peeling on peaches, Magnuson Engineers,

Inc. decided to try the process on tomatoes. They established that a dry

caustic peeling machine they designed would also very effectively peel caus-

tically-treated tomatoes.

Tomatoes peel very differently from peaches. Much stronger caustic sol-

utions are required and caustic-compatible wetting agents must be used.

While the tomato surface beneath the skin is attacked by the caustic, the

skin itself remains intact and dislodges as sheets of tissue. Other types

of tomato peelers have difficulty in thoroughly removing this peel tissue

because it tends to transfer from tomato to tomato, or from tomato to equip-

ment and back to another tomato. Water sprays are generally used to try to

flush away these skins and hand labor is required to finish the skin removal.

The dry caustic peeler that has been used on peeling tomatoes removes

substantially 100% of the peel at capacities of 8 to 10 tons per hour with-

out using any wash water. This method has eliminated nearly all of the hand

labor required to remove the peel. About one gal/min of "lubrication"

water is used in the machine.

46


Table 7. Comparison of the Average Liquid Effluent from the Del Monte Dry

Caustic Demonstration Project with Conventional Caustic Peeling


BOD REDUCTION

In both the tomato and peach peeling operations, the dry caustic peeler

collects and delivers a full strength, essentially undiluted peel waste sludge.

Since the peel waste is a major source of BOD, it is highly desirable to keep

this peel waste out of a plant's wastewater. Smith (1976) cited a 1974 study

that discovered that peel wastes accounted for 60% of the total plant BOD

load in a peach cannery and 35% of the total BOD load in a tomato cannery.

The plants comprising that study were generally typified by California pro-

cessing methods. Food processors now recognize that removing BOD loads from

wastewater is very expensive, both in terms of the plant investment for waste-

water treatment facilities and the facilities' operating costs. It is now

widely acknowledged that preventing wastes from entering the plant effluent

is an excellent method for precluding wastewater treatment costs. This is

especially true in seasonal operations where expensive wastewater treatment

facilities would be used for only two or three months per year.

INCREASED PRODUCT RECOVERY

Smith (1976) also noted that a California tomato processor who was using

four dry peeling machines reported an increased product recovery of 2.5 cases

per ton. This product recovery was attributed to the reduction in product

losses made possible by the dry peeling units. The same processor also no-

ticed a 44.7% reduction in the amount of caustic consumption as a result of

installing the dry peelers. Such savings were possible because the mechani-

cal wiping action of the-rubber discs can do an effective job while exposing

the tomatoes to less caustic. This product savings of course, means less

product loss in the spent caustic solution. Similarly, since water washing

is not used during peel removal, the loss of tomato solids which in conven-

tional peelers are normally carried away by the wastewater, is eliminated.

SOME BY-PRODUCT POSSIBILITIES

Now that the mechanics of dry caustic peeling have been proven, much

attention is being focused on the handling and disposal of peel waste sludge.

So far, this sludge has been disposed of by spreading on land; sometimes it

has been spread on pasture land where cattle are feeding.

As this sludge material becomes available in greater quantities, possi-

ble uses for it will arise. Brandy manufacture is one possible outlet.

Tomato peel waste offers promise for use as a by-product. The peel


waste has a higher solids content than pureed whole tomatoes, because it is

made up entirely of material from the outer cell walls of the tomatoes. This

material is the most highly colored portion of the tomato, so it is very high

in desirable red pigment. Of course, the material contains caustic (NaOH),

but this can be neutralized with hydrochloric acid (HCl) and converted to

common table salt (NaCl) and water. Salt is usually added to tomato products

anyway, so it's very likely that the tomato peel fraction can be processed

into high quality tomato products for human consumption.

LEAFY-GREENS WASH WATER RECYCLE

Industries that process leafy vegetables use large volumes of water,

mainly during four unit operations:

washing

blanching

cooling

transporting product.

Three types of washers are most commonly used in commercial operations: im-

mersion, spray-belt, and rotary-spray. Estimates of wash water requirements

per unit weight of product range from 50% of the total water requirement of

3 to 5 gal/lb necessary for complete processing, to 73% of a total 1.1 to

1.5 gal/lb cited elsewhere for complete processing requirements.

One obvious way to conserve water in a greens-washing operation is to

modify the system in some way to-permit recycling of the wash water itself.

Of course the chief concern is that the recycled water be of good enough

quality throughout the period of use to insure against degradation of the

product quality beyond acceptable limits.

To learn more about effects of water recycling on product quality, two

full-scale, immersion-type washers that would permit wash water recycling

during greens-washing operations, were designed and evaluated in a study

whose description follows.

The washers' performances were monitored during five trials, four when

collard greens were being processed and one when spinach was being processed.

THE PROCESS DESCRIPTION

Two washers were designed to wash 4,000 lbs of product per hour. The

bottoms were comprised of three sections, each V-shaped to facilitate the


collection and removal of grit when the washers were drained, The maximum

depth in each washing tank was 3 ft., and the nominal capacity of each was

688 gallons. Water from each washer was recycled through separate settling

tanks whose nominal capacities were 718 gallons.

Both washers were identical and were operated in series. Each was

equipped at the input end with three banks of sprayers (4 nozzles each); one

bank placed at water level and two above the incoming product. One of the

overhead banks of sprayers was later taken out of service in order to main-

tain high pressure on the nozzles while reducing the overall recirculation

rate from 200 gpm (757 l/min) to about 125 gpm (473 l/min). This change was

necessary because it was discovered that the washer drain system and the re-

turn sump-pump could not handle the larger flow.

As product entered, it was spread out and vigorously agitated by the

sprayers, and pushed toward the first of three center-mounted, paddle wheels

covered with flattened expanded metal. The three revolving paddle-wheel

drums propelled the product through the washer, alternately submerging and

releasing it. Insects and leaf fragments floated to the surface inside each

drum while the product was submerged, while water, forcefully dispensed

through a stationary bank of three spray nozzles (positioned inside each

drum), prevented leaves from becoming entangled in the expanded metal cover-

ing and provided additional cleaning. An exit conveyor - - made of an open-

mesh, plastic belting with flights every 2 ft - - carried product out of each

washer.

Water and floating trash that collected inside the rotating drums flowed

out of the washers through surface side-drains into a trough leading to a box

containing a submersible sump-pump. This pump forced water into the settling

tanks through a moving-belt filter made of polyester screen that trapped

trash and carried it to a collection box. Streams of compressed air at the

end of the conveyor were directed upward through the belt across its width to

force trash into the collection box. The nominal capacity of each settling

tank was 718 gal, and provided a detention time of about 7 min for grit to

settle when the recirculation rate was 100 gpm.

Fresh, chlorinated water was added to the system at only one point: the

second settling tank. The overflow was carried through an H-flume into the

first settling tank. The volume in excess of that required to make up for

losses in each washer, caused by carry-over on the product, was discharged as

waste from the first settling tank through a second H-flume. Flow meters

were installed to allow monitoring of fresh-water input and recirculation


rates, which could be controlled by opening or closing gate valves through

each washer-settling tank system. The H-flumes were equipped with continu-

ous stage recorders and were calibrated so that depth of flow through the

flumes could be converted to volume flow rates.

The researchers concluded that the experimental washing system, as a

whole, performed well during the four trials using collards and the one

using spinach. While the quality of the water as it was recycled through

the washers did deteriorate as more and more greens were processed, cleaning

of the greens while they passed through the system was always evident. Re-

duction of bacterial population densities on the greens were observed in all

five trials, probably because chlorine residuals were maintained at high

levels and because of a detergent action in the wash water induced by dis-

solved organic compounds leached from the vegetables.

Conclusions from this study were:

1) Most of the actual cleaning of product occurred in thefirst washer and settling basin; an average of 71% oforganic and inorganic wastewater constituents were pre-sent in the-first washer and settling basin.

2) The settling tanks were effective in removing smallparticles such as silt and fine sand. In one trial whensufficient grit for analysis was recovered, 63 percentof the total was found in settling tank No. 1. WasherNo. 1 collected the most of the fine and medium sand (12percent of the total weight of grit collected). Differ-ences in total suspended solids concentrations in thewash water from the head to the back of a settling tankdid not accurately reflect the actual solids removalthat occurred.

3) There were distinct differences in final wash water qual-ity when different cuttings of collards were processed,the differences most probably being a function of pro-duct maturity.

4) The water-usage rate in the experimental system, was, onthe average, 15.6 gal/min (59.0 l/min), which is 77 per-cent less than that used by the conventional commercialwashers. Water use per unit product was an average ofonly 0.56 gal/lb (4.66 l/kg) compared to an estimatedusage of 1.5-2.5 gal/lb (12.5-20.8 l/kg) by conventionalequipment.

5) The average chemical concentrations of the wash waterbeing discharged from the system at the end of the tri-als were high, both in organic and inorganic suspendedsolids. When collards were washed, the organic suspen-ded solids were concentrated at 110 mg/l while the in-organic suspended solids were at concentrations of 61mg/l. When spinach was washed, organic suspended solidsconcentrations rose to 632 mg/l, and inorganic suspended


solids concentrations occurred at concentrations of 57mg/l. The magnitudes of the solids concentrations pro-bably reflect the fact that there was considerable turbu-lence in the settling tanks because of the high recircu-lation rates within the system, and because the lighterparticulates (clay and small leaf fragments, e.g,) didnot settle well.

6) The average concentrations of COD and BOD5 in waste waterbeing discharged from the system at the end of the trialswere similar to those in weak municipal sewage. Whencollards were processed, COD values averaged 356 mg/l andBOD values average 80 mg/l. When spinach was washed, CODvalues averaged 211 mg/l while BOD values averaged 46 mg/l.

7) Concentrations of both organic and inorganic compounds inwash water were much lower than those reported in anotherstudy, as were the waste loads generated per unit weightof product processed. The best agreement of data betweenthe two studies was for total suspended solids. The otherstudy's values for organic waste loads (COD and BOD, lb/ton) were from 5 to 6 times higher than those calculatedin this study.

8) Recirculation of wash water in immersion-type, leafy-greenwashing systems is a promising modification of existingprocessing methods for reducing water consumption and con-centrating waste loads so that they can be more easilytreated.

INDIVIDUAL QUICK BLANCHING (IQB)

Preparing vegetables for preservation by canning, freezing, or dehydra-

tion results in large volumes of high-strength organic waste streams. For

the purpose of reducing total plant effluent and BOD, attention has been

focused on the blanching operation. Blanching serves several purposes in-

cluding:

removing tissue gasses

inactivating or activating enzymes

reducing microbial load

cleaning the product

wilting the tissue to facilitate packing.

These objectives are accomplished by heating the vegetables in either hot

water or steam. Both hot water and steam blanching produce liquid wastes

high in BOD, and both result in loss of water soluble nutrients, A report

based on a study of two Wisconsin canning plants stated that a 90% reduction

in blancher effluent volume would reduce total plant waste flow by 10 to 20%,


and would reduce total plant BOD production by 20 to 50%. In an effort to

approach these reductions, a study was made to design a blanching process

which would produce a wastewater flow of 10% of that from a commercial hot

water blancher. The project resulted in a new concept of heating foods and

the application to blanching was demonstrated. The process, individual

quick blanch (IQB), was used as a precanning process, and the results of

that study are presented here.

EQUIPMENT DESCRIPTION

The IQB unit used in the study consisted of two insulated chests, one

heated by direct steam and the other heated indirectly. The IQB's capacity

was about 300 lbs/hr. The product, taken from the process line just prior

to entering the conventional pipe blancher, was distributed in a single layer

on a mesh belt moving through the steam chamber. The residence time in the

chamber allowed the mass average temperature of the product to reach desir-

able blanching temperatures. The product was then transferred to a much slow-

er moving belt traveling through the second chamber. The product remained

there until blanching was accomplished. The product was then hand-packed

into 303 x 407 cans to a given fill weight, brine and hot water were added,

and the cans were sealed. Then the cans were inserted into the plant's con-

veying line to go through the continuous retort process.

Previous investigations by other researchers with the IQB unit showed

that the reduction in waste flow from blanching was enhanced by slightly dry-

ing the product prior to steaming. So, some of the experiments in this study

were conducted on the product which was dried by a 5 to 20% weight reduction

in an alternating upflow-downflow hot (160-180°F) air dryer.

The effluent from the IQB blancher was collected and analyzed for BOD,

total solids, suspended solids, total and soluble phosphorus, total organic-

nitrogen, ammonia-nitrogen, nitrate-nitrogen, and pH.

CONCLUSIONS OF THE IQB STUDY

The results of this study indicate that IQB can be used successfully for

blanching vegetables prior to their canning. The IQB process results in re-

duction of blancher effluent by 68 to 99% while maintaining product quality.

Specific results include:

1) Peas: Blancher effluent was reduced at least 68% in theIQB process compared to pipe-blanching. Excessive dryingof the peas resulted in skin breakage with resultingcloudy brine and loss of product quality.


2) Corn: IQB reduced blancher effluent between 77 and 99%.There was no product quality loss except under high tem-perature pre-drying conditions where the product wasdarker in color than the control.

3) Green Beans: An 86 to 95% reduction in blancher effluentwas obtained using IQB. Product quality was comparableto pipe-blanched canned product except when pre-dried.With pre-drying, sloughing was evident.

4) Lima Beans: Reductions up to 99% were accomplished inthe blanching operation using IQB. With drying, the lossof skins seemed to impair product quality.

HEAT-COOL SEQUENCE FOR TOMATO PEEL REMOVAL

A new process for commercial tomato peeling uses only heat and water,

both of which can be recycled. Conventional peeling processes use large

amounts of heated caustic (lye). Caustic is expensive and requires large

amounts of energy for its production.

The new process involves heating tomatoes with steam at about 315oC,

then cooling them in a water bath or spray. Each step lasts about 10 sec-

onds, and the heat-cool sequence is usually conducted three times for a total

of 60 seconds. Peels can then be removed mechanically.

TOMATO PROCESSING

Tchobanoglous et al. (1976) studied the effects of some in-cannery pro-

cess modifications on reducing water use and waste at Hickmott Foods, Inc.,

a small independent tomato cannery. The nature and results of their in-plant

water pollution control efforts are summarized here.

Hickmott Foods, Inc. cans tomatoes in an 80-day operating season during

the months of July through October. Except for a week or two at the beginning

and end of the season, canning is a continuous, 'round-the-clock operation.

To meet waste discharge requirements, the plant undertook a program of waste-

water management to clean up its wastewater discharge to the San Joaquin River.

Significant reductions in the wastewater flow rate and strength have been

accomplished by modifying various operations within the cannery production

area. These changes and their impact are discussed in this following section.

WASTEWATER FLOW REDUCTION

The two principal components of the wastewater produced during the 1973


and 1974 tomato canning seasons were the process water and the water from the

evaporators and retorts (see Table 9). Water used in the production process

is derived primarily from the municipal water supply; the water used to cool

the evaporators and retorts is filtered San Joaquin River water.

Several steps were taken between 1973 and 1974 to reduce the quantity of

water used by the cannery and to reduce the wastewater flow rates. The cool-

ing water was analyzed and found to be suitable for direct discharge to the

river (COD less than 50 mg/l) after cooling. Eliminating the cooling water

from the waste stream reduced the flow requiring treatment from 3.1 million

gal/day to 1.14 million gal/day, while cannery production increased 20%.

The installation of four dry peel removal machines reduced the total

water needed for peeling from 306 to 124 gal/min. The quantity of peel sludge

produced dropped from 150 to 25 gal/min while cannery production increased 20%.

This reduced volume of peeling sludge made it possible to isolate this mater-*ial and process separately.

All low pressure-high volume washdown hoses were removed and a high pres-

sure hose system with nozzles that shut off upon release was installed. This

change resulted in a washdown flow reduction of at least 80 gal/min (see Table

9). As low pressure hoses were usually left to run on the floor, the reduc-

tion was probably somewhat larger. Some employees objected to the use of the

high pressure spray as it was harder to control, but they eventually became

accustomed to using these nozzles. No degradation in the quality of the pro-

duct or plant sanitation was observed.

Cooling water discharge was reduced by 200 gal/min by reusing the retort

cooling water for can washing. Besides reducing the amount of water to be

cooled before discharge to the river, the amount of river water that required

filtering and chlorination for use in the can washing system was also reduced.

ORGANIC WASTE REDUCTION

The quantity of raw tomato constituents present in the process waste-

water was reduced from the 1973 to 1974 season by modifications in the peel-

ing operation and floor waste management.

Dry Peeling. The installation of four dry peel removal machines and mod-

ifications in the operation of the caustic peelers resulted in a reduction

in caustic chemical use and in the quantity of waste generated that required

treatment. This was accomplished with no deterioration in product quality.

Dry caustic peeling, using rotating rubber discs to mechanically rub peel from


Table 9. Daily Water Usage During 1974 Canning Season and PercentReduction Data Over 1973 Canning Seasonal


tomatoes dipped in sodium hydroxide, replaced the conventional water rinse

peeling operation. Effective peeling was obtained with this method while

reducing the concentration of caustic in the peelers. Through a combination

of reducing the peeler speed (resulting in more tomatoes per bucket but a

longer contact time with the caustic per tomato) and using mechanical peel-

ing, it was possible to use a caustic solution of 7 to 10% in 1974 as op-

posed to an 18 to 20% solution in 1973. This operation change resulted in

a reduction in caustic use (6.9 lbs/ton in 1974 as opposed to 11.7 lbs/ton

previously) and reduced other chemical requirements for neutralization of

the resulting wastewater. As discussed later, reducing the pH value of the

caustic sludge can also make the possibility of product recovery more prac-

ticable.

Dry caustic mechanical peeling requires about 80 gallons of potable

water per ton of tomatoes as opposed to 720 gal/ton using conventional meth-

ods. The 80 gal/ton which amounted to 24 gal/min of caustic sludge produced

in the operation is a small enough volume so that it can be disposed of in a

land spreading operation. Eliminating this sludge from the waste stream re-

duced the BOD load on the water pollution control plant by 46%.

Floor Waste Management. Because tomatoes are, for the most part, a water

soluble fruit, the longer they remain on the cannery floor or in a wastewater

conveyance facility, the greater the amounts of tomato solids and juices con-

tributing to the soluble COD and BOD of the wastewater. If processing wastes

are picked up in solid form they can be fed to livestock or at least disposed

of as solid wastes. Manual collection of large solid tomato parts was stress-

ed during the 1974 season. Gratings covering all floor drains were also bol-

ted down. Reliable solid waste per ton of data were not available for the

1973 season but it was estimated that considerably more solid waste was used

for cattle feed during the 1974 season. This is waste that does not reach

the treatment facility as fine suspended matter or soluble organics.

FUTURE IMPROVEMENTS THAT WILL LEAD TO REDUCE WATER USE

Because Hickmott Foods no longer processes sweet potatoes and asparagus,

daily water use could be reduced further by shortening the lengths of belts

on which peeled tomato products must travel. This change would eliminate

about 50 gal/min of water now used for belt lubrication. In turn, this would

reduce the peak water use in the cannery to between 750 and 800 gal/min.

This quantity is considered to be the minimum water use possible for maintain-

ing sanitary conditions. Heightened concern by the U.S. Department of Agri-


culture over the issue of machine mold may ultimately result in increased per

ton water use by Hickmott Foods.

IN-PLANT WATER RECYCLE WITH OFF-LINE MUD REMOVAL

With the advent of mechanical harvesting of tomatoes, tomato processors

noted an increase in the soil accumulations within fluming systems. Most of

the soil accumulated in the initial flumes or bin dumps. Flow velocities

within the bin dumps were insufficient to scour settled soil solids from the

base. The resulting accumulation of soil in the bin dump eventually impaired

product flow and required processing downtime to remove.

There are two widely practiced procedures for alleviating the accumula-

tion of soil in the bin dump. The first is to employ a high overflow rate

from the bin dump, this overflow discharging to the plant's sewer system.

The second procedure involves processing downtime to drain off excess liquids

and to hand shovel the accumulated soil into an adjacent receptacle.

Several-adverse impacts result from the current procedure for handling

bin dump mud. In the case of the high overflow rates, the excess water used

adds to the hydraulic surcharge to the sewer system from this seasonal indus-

try. The high soil loadings discharged to municipal treatment systems result

in operation and maintenance problems. As a consequence of the necessity for

periodically shutting down the bin dump to remove accumulated soil, the time

requirements for processing a given tonnage of tomatoes are extended, resul-

ting in reduction of the plant's productivity. This, in turn, results in

further excess water use through the down-time period and for the additional

required clean-up and washdown.

During the 1974 processing season, a study by Wilson, et al. (1976) was

undertaken to evaluate alternative water recycle system configurations. Bin

dump model studies were then undertaken in the spring of 1975 to develop de-

sign data on an efficient system for intercepting soil solids in the bin dump

and transporting them to a solids removal system without interfering with

product flow.

The objective of the '75 season tomato water recycle project

monstrate a water recycle system which when used in conjunction w

was to de-

ith a normal

bin dump operation, would significantly reduce the adverse impacts associated.

with current practices. An essentially closed loop recycle system was employ-

ed. The recycled water was used to maintain adequate scouring velocities

within the bin dump without detrimentally affecting product flow. A solids


removal system was constructed within the closed loop to remove the settleable

solids and thereby prevent their accumulation within the bin dump. This recy-

cle system was expected to eliminate excessive water use related to high bin

dump overflow rates, as well as those rates related to clean-up down-time and

extended operational period for processing a given tonnage of tomatoes.

The researchers investigated four modes of operation aimed at minimizing

wastewater-related costs. These modes comprised the following:

conventional cleaning, without water recycle

conventional cleaning with water recycle

disc cleaner with water recycle

disc cleaner with recycle and chemical coagulation-flocculation.

Water consumption and total solids balances were made on each mode. The con-

clusions of the study are discussed below.

CONCLUSIONS

Not surprisingly, the daily average tonnage of tomatoes processed increas-

ed substantially with disc cleaning and water recycle, as compared with the

conventional system. An increase of 26% in the tonnage of tomatoes processed

was realized with the disc cleaner combined with water recycle and chemical

flocculation. These increases in the daily tonnage of tomatoes processed may

be primarily due to the virtual elimination of solids accumulation in the

dump tank with consequent impaired product flow. No incident of temporary

shutdown of shift operation for dump tank clean-up was encountered during the

modes of operation with water recycle.

With respect to the water consumption, the following findings were estab-

lished in this study:

1) The majority of daily water usage was operational (48-61%),followed by clean-up (31-44%) and filling (6-8%). Therewere no significant variations in percentage usage in thevarious modes of operations. In all modes of operation,approximately 7% was filling; approximately 55% operation-al; and approximately 39% clean-up.

2) A 26% decrease in the average total daily water use wasrealized when disc cleaner, combined with water recycle andchemical flocculation relative to the conventional system,was applied.

3) A decrease in the average unit water consumption rate rel-ative to counter-current flow conventional cleaning, occur-ed when water recycle measures were applied. A 41%


decrease in average unit water consumption rate was real-ized when the disc cleaner, with water recycle and chemicalflocculation (164 gal/ton), was applied relative to theconventional system (278 gal/ton).

With respect to the total solids balances, the following conclusions

were drawn:

1)

2)

3)

With the water recycle measures implemented, the soil sol-ids removed from the dump tank per tonnage of tomatoesprocessed were significantly reduced; the soil solids lostto the sewer per tonnage of tomatoes processed were reducedsubstantially.

The estimated soil solids incoming to the plant per unitweight of tomatoes processed ranged from 10 to 20 lbs/ton,and averaged 13 lbs soil solids per ton of tomatoes pro-cessed. The total soil loaded was estimated from the sumof soil solids which were collected from the dump tank,lost to the sewer, and removed from the sludge thickener.It appeared that the amount of soil reaching the plantvaried considerably, depending on the type of soil inwhich the tomatoes were grown, the moisture content ofthe soil in which the tomatoes were harvested, and themethod of tomato harvesting.

Efficient clarification of the thickener overflow re-quired surface loading rates of less than 1,000 gpd/ft2.Approximately one-half of the gravity settleable soilsolids overflowed from the thickener at surface loadingrates of 2,000 gpd/ft2.

Using performance parameter values found in this study, it was demon-

strated that installation and operation of an in-plant water recycle system

with off-line mud removal, would result in about a 50% savings in the total

annual wastewater-related costs. For the 35 tons tomatoes/hr plant evaluated

in this study, annual savings would amount to about $47,000.

1)

2)

3)

4)

5)

6)

7)

8)

9)

10)

11)

12)

13)


References

Liptak, B. G. Food Processing Wastes. Environmental Engineer's Handbook.

Volume I - Water Pollution. 1974.

Loehr, R. C. Agricultural Waste Management, Problems, Processes, Approa-

ches. 1974.

LaConde, K. V. and C. J. Schmidt. In-Plant Control Technology for the

Fruits and Vegetables Processing Industry. Proceedings Seventh National

Symposium on Food Processing Wastes. EPA-600/2-76-304. December, 1976.

Robe, K., associate editor. Low-cost, total recycling of wash water.

Food Processing. December, 1977.

Dry Caustic Peeling of Clingstone Peaches, Capsule Report. U.S. Environ-

mental Protection Agency Industrial Demonstration Grant with Del Monte

Corporation. EPA Technology Transfer.

Smith, T. J. Dry Peeling of Tomatoes and Peaches. Proceedings of the

Sixth National Symposium on Food Processing Wastes. EPA-600/2-76-224.

December, 1976.

Hoehn, R. C. et al. Changes in Organic and Inorganic Constituents of

Wash Water Upon Recycle in a Prototype Leafy-Greens Washer. Proceedings

of the Seventh National Symposium on Food Processing Wastes. EPA/600-2-

76-304. December, 1976.

Heat-cool sequence for tomato peel removal. Picks and Packs. Technical

Notes for the California Fruit and Vegetable Processing Industry. Coop-

erative Extension, University of California. March, 1978.

Tchobanoglous, G. Wastewater-Management at Hickmott Foods, Inc. Pro-

ceedings of the Sixth National Symposium on Food Processing Wastes.

EPA-600/2-76-224. December, 1976.

Wilson, G. E. et al. Tomato Flume Water Recycle with Off-Line Mud Re-

moval. Proceedings of the Seventh National Symposium on Food Processing

Wastes. EPA-600/2-76-304. December, 1976.

Liquid Wastes from Canning and Freezing Fruits and Vegetables. U.S.

Environmental Protection Agency Water Pollution Control Research Series.

12060 EDK 08/71. August, 1971.

Mercer, W. A. Conservation and Recycling of Water and Other Materials.

Food Industry Week Conference. Proceedings Waste Management and Pollution

Control. 1971.

Kamm, R. et al. Evaluating New Business Opportunities from Food Wastes.

Food Technology, June, 1977.

61

F&V SPNOFF/RECYCLING & REUSE OF FD PROC WW

R E C Y C L I N G A N D R E U S E O F P R O C E S S I N G

W A S T E W A T E R S

Sources of Potable Water

Water can be obtained from two sources, surface reservoirs or

streams, and underground reservoirs or streams. These sources can be tapped

by a municipality or by a private party. If a food processor's water comes

from a municipal supply system, the water's quality is the responsibility

of the municipality. But, a food processor who supplies his own potable

water comes directly under the provisions of the Safe Drinking Water Act.

Food processing plants must use water that is of potable quality.

Potable water must also be used for cleaning all equipment which contacts

the foods. Water must meet Federally established quality standards in

order to be classified as potable. However, the standards set by any given

state may be even more strict than the Federal standards. For this reason,

a food processor must know exactly what qualities the state expects of a

processing plant's water supply. Please turn to Chapter 5 of the Core

Manual entitled By-products, Reuse and Recycling for more information on

this topic. However, in some cases, it is possible to have multiple-use or

reuse of water as discussed in the following.

Introduction to Recycling and Reuse

This section explores several aspects of recycling and reusing food

processing wastewaters. It is meant to give you an overview of the factors

affecting wastewater reuse and recycling.

Keep the following basic concept in mind with regard to reusing

wastewater. Reusing wastewater basically involves collecting the effluent

from one or more unit processes, and then using that effluent as the

influent for other unit processes. The key to wastewater reuse lies in

matching the effluent from one unit process with the influent requirements

of another unit process. The "matchmaker" must be careful to take into

account the effluent's quantity and quality when examining the source

requirements of prospective processes.

62


Legal Aspects of Water Reuse

Water rights and related laws are under nationwide review. Scien-

tists, economists and lawyers are evaluating current and future use of out

water resources; constitutional rights as well as individual state laws may

be involved before the present systems of water regulations can be applied

to multiple-use water.

Reusing water is not a new concept. Published data estimate that 60

percent of the population presently reuses water. The intake water supply

pipe of one city is often downstream from the discharge sewage pipe of

another metropolis, and coastal municipalities have no choice but to com-

mingle supply and wastewaters when tidal conditions return the sewage

effluents into the water supply storage reservoir. The use of interstate

streams is not only subjected to the laws of each user state but is also

under regulations and control by federal authorities.

Two basic systems of water law in the United States include riparian

and appropriation. Generally, those areas with abundant water supplies use

the common-law doctrine of riparian rights. Areas sparse in water re-

sources found the first users and statutory prior appropriation doctrine

more suitable. Unfortunately, there are also some states that use combina-

tions of both systems with regional special interpretations.

Pollution abatement programs have generally classified state waters

according to use and thus have established standards of quality in accor-

dance with these objectives. It seems only prudent that the processor

should consult the stream classifications and standards that govern water

purity in the state within which wastewater is to be reused.

Public Health Aspects of Wastewater Reclamation

Decision to reuse renovated wastewater for human consumption or in

processes that normally require potable water (i.e., food processing), must

be equated with potential health risk and hazards. The U.S. Public Health

Service in a policy statement believes that renovated wastewater is not

suitable for drinking water when other sources are available.

Reclamation Methods

Water is absolutely necessary in food processing, and by practicing

conservation, reuse and recycling, the amount of liquid waste and conse-

63


quently the pollution load from food processing operations can be reduced.

Reduction of water use through reuse of the same water can pay significant

dividends in improving a waste disposal situation. Water reuse is bene-

ficial because water is no longer a free commodity; it costs money to

procure water; it costs money to pump water; and it costs money to dispose

of water.

Food processing waters cannot be reused indiscriminately. Their

recirculation in contact with food products must allow satisfactory product

and plant sanitation. To offer more specific guidance in the use of

reclaimed waters, NCA offered the following recommendations:

o The water should be free of microorganisms of public healthsignificance.

o The water should contain no chemicals in concentrations toxic orotherwise harmful to man, and no chemical content of the watershould impose the possibility of chemical adulteration of the finalproduct.

o The water should be free of any materials or compounds which couldimpart discoloration, off-flavor, or off-odor to the product, orotherwise adversely affect its quality.

o The appearance and content of the water should be acceptable froman aesthetic viewpoint.

As an example of the possibilities for water reuse, a survey was

made in a tomato and vegetable packing plant. The effect of water reuse

was measured in terms of the percent reduction in water use per ton of

product processed. With no water reuse in can cooling, product washing, or

other operations, water use totaled 3,340 gal/ton of product. When product

wash waters were recirculated, water use was reduced by 16%. Recirculation

of can cooling water added a 22% reduction. In the case of vegetable pro-

cessing these water reuses allowed a total water use reduction of 38%. When

tomatoes were being processed, reuse of the excess water from the

evaporative condenser system to wash product allowed a total overall

reduction of 45% in water use/ton of product.

Water is best saved by reducing its rate of consumption. Industries

that routinely monitor their water usage and their waste effluent flows

have been able to reduce the in-house uses of water by as much as 50%.

Unfortunately, some water managers consider renovated wastewater to be

acceptable only as a last resort alternative. Such attitudes obscure the

64


real importance of wastewater as being potentially the most economical

choice available as a source of water.

Wastewater treatment and renovation can exist in varied forms. Direct

reuse occurs in canneries when counterflow untreated streams are used

stepwise. Clean water is piped into the cooking areas where, following

use, it flows to blanching operations. Having fulfilled its service here,

it discharges to water-conveying canals and finally to incoming washing

troughs where it removes filed detritus from fruits and vegetables.

Spent water handling can be simplified by segregating wastes into

appropriate categories. The commingling of fluids into common sewers

complicates reuse and reclamation programs. The first task in reusing

wastewater is to establish the objectives. A water demand inventory should

be taken to determine usage amounts with quality levels of purity.

Subtotals of departmental (industrial plant sections) use should add to the

total documented need required for the site.

The dairy industry (Fig. 14) collects salvaged condensed milk vapors

from vacuum pan evaporators and uses them for boiler water feed and for

plant cleaning wash water. Inline turbidity meters monitor the salvaged

condensate and divert contaminated milk and water vapors to the sewer in

case of a malfunction.

Salvageable Food Fractions

Food wastes found in water can consist of particulate matter, dis-

solved solids and fats - either as an emulsion or in a free-floating state.

Both the food and the water quality have an influence on deciding whether

or not the salvaged fractions gathered from wastewater are suitable for

human or animal consumption. If wastes are channeled into sewer lines,

these materials become a treatment burden, at some cost to a waste treat-

ment system. Obviously, processes that reclaim human food-grade materials

must meet sanitary standards. By-products for animal foods are continu-

ously being upgraded; thus, it may be prudent to furnish reasonable

duplication in nonhuman food production of those techniques used in human

food processing.

Food as particulate matter is often separated from liquids by settl-

ing, screening, skimming, or centrifuging. Automated continuous processes

suitable for cleaning in place are most attractive (as contrasted with

65


Fig. 14. Recovery of milk vapors in powdered milk production. The milk

evaporator functions much like steam generaged in boiler. Because the

vacuum pan is subjected to a high vacuum through the air ejector system,

milk boils at low temperature that rarely climb higher than 15OoF. Milk

vapors change back to water, which collects against the cold condenser

tubes. Vacuum increases linearly to maximum with lowest temperature thus

vapors flow from A to B to C. Malfunctioning milk evaporators tend to

foam, carrying over milk solids; hence, an inline turbidity meter

safeguards the condensate purity for the salvaged water reuse.

66


batch methods) for both short-term and long-term goals. Careful planning

with well-defined objectives is required to create resources from wastes.

Toward the end of this text you will find a section entitled "By-Product

Recovery Use." This section outlines some commodity-specific recovery

schemes.

Recovery of Chemicals

While cleaning chemicals in waste matter often cause toxicity and poor

performance of the biological treating processes, they also represent a BOD

demand. For example, surfactants or common acid detergents produce 0.65 lb

BOD5/lb of substance. Table 10 shows the BOD demand of selected substances,

cleaners and sanitizers.

Liquid detergents, sanitizers and other analogous products can be

handled in bulk in a series of vessels. These materials may then be piped

to reservoirs that can store and feed the cleaning solutions. Clean-in-

place (C.I.P.) circuits can be designed to reuse fluids that are circulated

by pumping through pipelines, bulk tanks, storage reservoirs and other

media. Final uses of captured liquids include floor cleaning or use as the

fluidizing liquid in sludge pumping.

Heat Recovery

Flow measurements are also necessary because the temperature alone is

not adequate to reflect the magnitude of potential heat recovery. Waste-

waters should be grouped according to purity and temperature, and the

hot-test water should be without dilution to avoid heat dissipation. Steam

condensate is returned to the boiler by deaerators because the water is

soft as well as hot.

Sometimes a water demand may be satisfied by preferential water make-

up, where the idea is to use all the salvage water first with fresh water

supplied only when the other sources are exhausted.

Water Reuse

Water reuse may be adopted with economical advantage when:

o there is insufficient water available locally to maintainan open circuit system all year 'round.

o valuable by-product materials can be economically recovered fromthe treatment processes.

67


68


o treatment cost of recycling water is less than the initialcost of water, plus the cost incurred in discharging theeffluent into the sewer.

o cost of treating the effluent to a required standard issuch that, for a little extra investment, the water qualitycan be made suitable for recycling.

The practice of water reuse can be divided into sequential reuse,

recirculation without treatment and recirculation with treatment.

Sequential reuse is the practice of using a given water stream for two or

more processes or operations before final treatment and disposal, i.e., to

use the effluent of one process as the input to another. Recirculation is

the practice of recycling the water within a unit process or group of

processes. A combination of these practices will probably be required for

an optimum reuse scheme.

Table 11 indicates some of the cannery operations in which water may

be reused indiscriminately. Its recirculation in contact with food

products must allow for satisfactory plant and product sanitation.

In an effort to optimize industrial water use and wastewater manage-

ment, emphasis is now being given to decreasing the quantities of water

used and the contaminants introduced during use. Alternatives available

for volume and pollutant reduction include water conservation, good

housekeeping, waste stream segregation, process modification and water

reuse.

Historically, little consideration was given to water reuse because of

its abundance in nature and because it was considered to be hazardous due

to bacterial contamination. Contamination potential shows that, in washing

fruit, unless 40% of the water is exchanged each hour, the growth rate of

bacteriological organisms becomes extremely high. In order to overcome

this, other means of control, such as chlorination, must be used. When

chlorination is discontinued, the bacterial count more than doubles. As

soon as chlorination is resumed, the bacterial counts are again brought

under control.

Water conservation can be achieved through counterflow reuse systems.

Figure 15 outlines a counterflow system for reuse of water in a pea

cannery. At the upper right, fresh water is used for the final product wash

before the peas are canned, and from this point the water is reused and

carried back in successive stages for each preceding washing and fluming

69F&V SPNOFF/WATER USE & REUSE

70


Fig. 15. Four-stage counterflow system for reuse of water in a pea cannery.

Key: A. First use of water; B. Second use of water; C. Third use

of water; D. Fourth use of water; E. Concentrated chlorine

water.

71


operation. As the water flows countercurrent to the product, the washing

and fluming water can become more contaminated; therefore, it is extremely

important (Fig. 15) to add chlorine in order to maintain satisfactory

sanitation. At each stage, sufficient chlorine should be added to satisfy

completely the chlorine demand of the organic matter in the water. With

this arrangement, satisfactory bacteriological conditions should exist in

each phase of the washing and fluming program.

Water Conservation

There may be several operations in a food processing plant where water

is wasted continuously, thus causing an overload to subsequent collection

and treatment systems. Consideration should be given to steps that can be

taken within a plant to conserve water, thus enabling the liquid waste

disposal system to operate more efficiently and thereby reduce water

pollution. As an example of water conservation methods the steps possible

in a food processing plant include 1) using automatic shutoff valves on all

water hoses to prevent waste when hoses are not in use (a running hose can

discharge up to 300 to 400 gallons of water/hour), 2) using low-volume,

high-pressure nozzles rather than low-pressure sprays for cleanup,

3) avoiding unnecessary water overflow from equipment, especially when not

in use, and providing automatic fresh water makeup valves, 4) avoiding

using water to transport the product or solid waste when the material can

be moved effectively by dry conveyors, and 5) reducing cooling water flow

to the minimum to accomplish product cooling.

Recently, it was determined that by controlling the pH of fruit

fluming waters by the addition of citric acid, it was possible to reduce

the water use without an increase in bacterial numbers. A pH of 4 will

maintain optimum conditions with cut fruit, such as peaches. The system

not only reduces the total volume of water required and therefore the

amount of wastewater discharged, but also increased the product yield as a

result of decreasing the loss of solids from leaching of sugar and acids.

Consequently, there is a reduction in the total pounds of organic pollu-

tants in the wastewater. Another advantage is improved flavor and color of

the canned fruit because of better retention and soluble solids.

Another water conservation method is using the closed loop systems on

certain processing units, such as a hydrostatic cooker-cooler for canned

72


product. The water is reused continuously, fresh makeup water being added

only to offset the minor losses from evaporation. Closed loop systems notonly conserve water but also reclaim much heat and can result in signifi-

cant economic savings.

It is not possible to describe all the concepts and ramifications

inherent in various food processing industries to reduce water and waste

loads while at the same time maintaining product quality. Many factors

determine the final effectiveness of proper water use. For example,

tomatoes spray-washed on a roller belt where they are turned are almosttwice as clean as the same tomatoes washed on a belt of wire mesh construc-

tion. Also, warm water is approximately 40 percent more effective inremoving contaminants than the same volume of cold water.

A delicate balance exists between water conservation and sanitation.there is no straightforward or simple formula to obtain the least water

use. Each case and each food process has to be evaluated with the

equipment used in order to arrive at a satisfactory procedure involvingwater use, chlorination and other factors, such as detergents.

Elimination of Water Use

Eliminating water in certain unit operations in turn eliminates

attendant problems of treating the wastewaters, which were generated by

those operations. Wherever possible, food should be handled by either a

mechanical belt or pneumatic dry conveying system. If possible, the foodshould be cooled by an air system rather than by a water cooling system.

Recent studies by the National Canners Association in comparing hot air

blanching of vegetables with conventional hot water blanching show thatboth product and environmental quality were improved by using air. Blanch-ing, used to deactivate enzymes, produces a very strong liquid waste. For

a pea processing operation, this small volume of wastewater is estimated tobe responsible for 50% of the entire wasteload BOD; for corn, 60%, and for

beets with peelings, 80%. Preliminary results show a reduced pollutionload, while at the same time providing a product quality improvement in

terms of nutrients, vitamins and mineral content.

Waste Stream Segregation

Waste segregation involves the separation of waste streams according

to their wastewater load. Noncontaminated streams offer the possibility of

73


being discharged directly to receiving bodies of water, whereas contaminat-

ed waste streams have to be treated.

As a general rule, all plants should be provided with three water

discharge systems, namely 1) storm and cooling water, 2) sanitary waste,

and 3) industrial waste.

The stormwater system should receive all surface and storm runoff.

This system can also be used for discharging uncontaminated waters, such as

cooling waters, that require no treatment prior to discharge. Although it

is desirable to keep uncontaminated wastewater out of the treatment plant,

the cost of installing separate collection systems for small, isolated

streams may be so high that by-passing the treatment plant becomes uneco-

nomical.

The sanitary system should collect the wastewaters from all washrooms

and shower rooms. For most industrial plants it is desirable to send these

wastes to a municipal plant for treatment, rather than to treat them

individually.

Process Modification

One alternative available for eliminating or reducing the wastes

created during processing involves the modification or elimination of the

step or steps which are producing the wastes. For example, since the

peeling process is one of the greatest sources of wastes in most fruit and

vegetable processing plants, efforts have been directed toward modifying

the peeling process so that the peel waste can be removed without using

excessive amounts of water. One recent process modification, is the "dry"

caustic peeling process for potatoes. In conventional steam or hot lye

peeling processes, potato peels may contribute up to 80 percent of the

total plant wastewater BOD. The new dry caustic vegetable peeling method

collects peels and caustic as a dry and semidry residue, thus preventing

their entrance into plant wastewaters. Dry caustic peeling is discussed in

more detail in Chapter 4.

A Summary

Reuse of wastewater is the utilization of a process waste stream one

or more times before it leaves plant boundaries. This can be accomplished

by piping the wastewater from one unit to another, by treating or diluting

74


effluents before reuse in other units, or by combining a few or all efflu-

ents, treating them and reusing the water.

Incentives for water reuse involves the possibilities of reduction of

wastewater treatment costs and raw water costs. Although lower waste

treatment costs currently provide the major savings from reuse, in some

areas the supply of acceptable raw water is decreasing, the price is

rising, and reduced raw water usage may provide a significant incentive in

the future. The typical plant considering reuse seldom plans to completely

eliminate wastewater discharges since this would usually require very

extensive modifications. The important standard for economic reuse is that

an unused makeup process water can be replaced by a lower-quality water

without harming the process. So, reuse schemes should always be considered

in planning for pollution abatement.

Ultimate requirements for water pollution control may be completely

closed systems from which no discharges are permitted, and use of fresh

water is only required as makeup for evaporation losses. Closed water

systems as the final goal of pollution research has long been an ideal.

Even though total reuse may not be legally required, it may be a viable

alternative to meeting stringent discharge regulations.

Possible steps for proceeding toward an intermediate or total reuse

system are:

o Determine the effluent qualities and quantities andmakeup requirements for plant units. A waste streamsurvey is a must for such an analysis.

o Study the lowest-cost treatments needed for variouseffluents to reach the required qualities of secondaryusers. Trends have been toward treatment of combinedwaste streams. Segregation of waste streams may offerbetter reuse possibilities.

o Reduce wastewater volumes by increased maintenance andequipment modifications can reduce flows significantly.

o Study the effects of reuse on existing treatment equipmentbecause water reuse generally results in a lower volume,more concentrated waste stream.

Commitment to total reuse requires an economic justification

covering the expected future costs of fresh water and ultimate waste

disposal. In some areas of the world, the cost of fresh water is rising

75


and the cost for ultimate disposal may gradually decrease as technology

improves. The key to inexpensive reuse is volume reduction. The total-

reuse will be able to economically treat only a small waste stream for

total removal of contaminants.

The decision of whether to implement total reuse will be set by a

comparison of costs of raw water and water treatments with and without

discharges. These include: water supply; treatment required before use of

fresh water; waste treatment required before discharge; treatment required

for use of reused water; plant modification to accept lower quality or

higher temperature reused water; extra piping and control valving; loss of

flexibility due to integrated water system.

A total reuse plan should begin at the individual process units, since

it will affect their operation. In certain cases it may even be more

economical to modify a process so that it requires little or no water. The

economics of total reuse will vary from plant to plant.

References

1) Mercer, W. A. 1971. Conservation and Recycling of Water and Other

Materials. Food Industry Week Conference. Proceedings Waste

Management and Pollution Control.

2) Liptak, B. G. 1974. Environmental Engineer's Handbook. Volume I -

Water Pollution.

3) Morresi, A. C., et al. 1978. Cooling Water and Boiler Possibilities

for Wastewater Reuse. Industrial Wastes, March/April.

76

F&V SPNOFF/BY-PRODUCT RECOV & USE

BY-PRODUCT RECOVERY AND USE

Introduction

Food processing plants inherently tend to generate significant

quantities of waste material. Frequently, the waste is believed to have

potential nutritional or industrial value, thereby representing a possible

basis for a new business opportunity. But turning these beliefs into new

business is often a complex technical and economic problem. Extracting the

critical business and engineering parameters for decision making requires

an analysis of the economic, technological, and marketing factors involved,

as well as an ability to resolve problems arising from these factors.

This section presents some recovery schemes by fruit and vegetable

processors to transform hitherto waste products into useful by-products.

This idea of recovering by-products from waste has been "catching on"

throughout the food processing industry, but many of these recovery schemes

have not been published. The examples that follow are not meant to

represent a full-scale review of the state-of-the-art.

SCP From Potatoes

A northern Maine potato processor is helping develop a new process

of single cell protein (SCP) production as a part of the answer to meeting

stricter wastewater discharge standards. These plants reclaim starch from

the cutter deck in potato processing. Wash water solids, after sand-filter

screening and dewatering, go to the "tate meal" dryer for drying and

subsequent sale as animal feed. Up to 16% of such solids are added to

normal silage to provide the same amino acid level as other conventiona

protein sources.

This system is said to be best applicable to wet food processing

operations, where high concentrates of soluble solids with a corresponding

high level of biological oxygen demand (BOD) are present. Estimated

protein output is one pound of protein for every 2 pounds of dissolved

solids converted to SCP yeast. The higher the BOD, the greater the

expected production.

77


Size of treatment system is another consideration. Where a land

disposal operation takes many acres, and even a settling pond, with primary

and secondary treatment plants taking nearly as many acres as do

conventional activated sludge water treatment systems, the SCP system fills

the corner of a warehouse, taking up little more space (about 2,000 sq ft)

than the processing equipment that comprises the unit, less than one

hundredth the space occupied by any of the more traditional systems.

Scrap Potato to Molasses

At one Ore-Ida Foods vegetable processing plant a study revealed

that converting scrap potato to molasses would raise the value of those

wastes by a factor of seven; converting to alcohol would increase the value

by a factor of thirteen. However, both options were rejected in favor of

simpler sugar production and starch recovery because of a smaller capital

investment and a-more stable market.

Peel Sludge to Puree

A California tomato processor attempted to recover caustically-

removed tomato peels as an edible by-product. The processing plant was

losing about 120 tons of tomato constituents per day in the form of caustic

peeling sludge. A test run was conducted to investigate the feasibility of

recovering the tomato peeling sludge, after acidifying it, as products.

The flow scheme used is shown in Figure 16. The quality of the puree made

from a 1:1 blend of acidified caustic peeling sludge and fresh crushed

tomatoes was judged to be good by the NCA with respect to both flavor and

appearance. The quantities of acid required to lower the pH value of the

caustic juice were kept to a minimum by operating the peelers at 8%

caustic. Further studies are being conducted to establish whether this

method can be accepted cannery practice. If this peel recovery scheme can

be proven to be safe, the tomato processor would be able to recover and

additional 4 tons/hr of usable tomato material, reduce the plant waste loss

from 16% to 6%, and cut the volume of sludge that must be hauled for

disposal by one-half.

78


Figure 16. Flowsheet for proposed recovery of waste peeling sludge.

79


BTU's From Olive Pits

Every weekday at Lindsay Olive Growers plant, Lindsay, CA, about 27

tons of pits pour from the ripe olive-pitting machines. This continues

seven or eight months a year. Disposal was an expense, whether hauled to

the county disposal site, or to nearby orchards for use as roadbed

material.

The Lindsay plant ran tests and found that the pits, although half

water, yielded nearly 400 BTU of heat per wet pound. This potential heat

could supply part of the 450,000 lb of steam per day needed in the

two-shift plant operation. After considering all the possibilities, and in

view of fuel shortages in the future, the president of Lindsay Olive

Growers and the Board of Directors gave the go-ahead to use the pits as

boiler fuel.

A furnace in use for burning wet sawdust was studied and adapted to

Lindsay needs. The diagram and caption show the details of the fluidized-

bed unit. Briefly, wet pits fall through a swirling-flame, vapor-removal

section into a fluidized bed of sand heated to 1,400°F. A gas flame heats

the sand at start-up; after two to three hours, the pits themselves furnish

the 1,400oF heat, and the burners shut off.

The fluidized-bed furnace started up in January, 1977 with minimum

mechanical difficulties. It is capable of burning a wide assortment of

agricultural wastes, such as peach and apricot pits, and almond shells from

nearby plants.

Pits furnish about 25% of the steam used by the plant. The cost of

hauling and disposing of pits is eliminated. There is no soot produced at

the high burning temperatures and no air pollution

Payout on the installation through savings of

is difficult to determine because of the rapidly r

but the unit is expected to make a good profit.

problem.

fuel and haulage costs

ising cost of fuel oil,

80


References

Dry Caustic Peeling of Clingstone Peaches. Capsule Report. U.S. Environ-

mental Protection Agency Industrail Demonstration Grant with Del Monte

Corporation. EPA Technology Transfer.

Forwalter, J., Associate Editor. 1978. Turns 3000 ppm food processing

waste into by-product, cuts sewage charges. Sanitation and

Maintenance. Food Processing, May.

Heat-cool sequence for tomato peel removal. 1978. Picks and Packs.

Technical Notes for the California Fruit and Vegetable Processing

Industry. Cooperative Extension, University of California, March.

Hoehn, R. C. et al. 1976. Changes in Organic and Inorganic Constituents

of Wash Water Upon Recycle in a Prototype Leafy-Greens Washer.

Proceedings of the Seventh National Symposium on Food Processing

Wastes. EPA/600-2-76-304, December.

Kamm, R. et al. 1977.. Evaluating New Business Opportunities from Food

Wastes. Food Technology, June.

LaConde, K. V. and C. J. Schmidt. 1976. In-Plant Control Technology for

the Fruits and Vegetables Processing Industry. Proceedings Seventh

National Symposium on Food Processing Wastes. EPA-600/2-76-304,

December.

Liptak, B. G. 1974. Food Processing Wastes. Environmental Engineer's

Handbook. Volume I - Water Pollution.

Liquid Wastes from Canning and Freezing Fruits and Vegetables. 1971. U.

S. Environmental Protection Agency Water Pollution Control Research

Series. 12060 EDK 08/71, August.

Loehr, R. C. 1974. Agricultural Waste Management Problems, Processes,

Approaches.

Mercer, W. A. 1971. Conservation and Recycling of Water and Other

Materials. Food Industry Week Conference. Proceedings Waste

Management and Pollution Control.

Morresi, A. C. et al. 1978. Cooling Water and Boiler Possibilities for

Wastewater Reuse. Industrial Wastes, March/April.

Pratt, M., Editor. 1977. Food Processing Plant Wastes: The Economics of

Recovery. AE Update., Agricultural Engineering, December.

81


Robe, K., Associate Editor. 1977. Low-cost, total recycling of wash water.

Food Processing, December.

Robe, K., Assistant Editor. 1977. Lindsay turns wet olive pits into

profit, uses wastes to furnish 25% of plant steam requirements. Food

Processing, May.

Smith, T. J. 1976. Dry Peeling of Tomatoes and Peaches. Proceedings of

the Sixth National Symposium on Food Processing Wastes.

EPA-600/2-76-224, December.

Tchobanoglous, G. 1976. Wastewater Management at Hickmott Foods, Inc.

Proceedings of the Sixth National Symposium on Food Processing Wastes.

EPA-600/2-76-224, December.

Wilson, E. G. et al. 1976. Tomato Flume Water Recycle with Off-Line Mud

Removal. Proceedings of the Seventh National Symposium on Food

Processing Wastes. EPA-600/2-76-304, December.

82

F&V SPNOFF/WW TREATMENT

W A S T E W A T E R T R E A T M E N T

Pretreatment

The pretreatment of food processing wastewaters is commonly

associated with discharges to a municipal waste treatment system. The

degree of pretreatment required of the food processor is determined by the

specified discharge limitations defined in the municipal sewer use

ordinance. These limitations focus on wastewater characteristics which

have, historically, caused either a hazardous condition for the waste

treatment plant operators or have been responsible for detrimental

influences on the waste treatment system's operation and waste removal

efficiences.

Another factor which has identified pretreatment as a necessity when

discharging to a municipal waste treatment facility is the Federal Water

Pollution Control Act. of 1972 which requires that before any grant is

approved to a municipality for facility expansion or improvement, the EPA

must be assured that provisions are made to prevent the municipal system

from receiving pollutants that would inhibit the operation of the municipal

treatment works, or that would pass through the system untreated.

Therefore, if the municipality receives a federal grant, the food processor

may be required to provide some form of pretreatment if the waste being

discharged, "as is", to the municipality is judged detrimental to the

system and modifications are indicated. However, EPA has noted that fruit

and vegetable processing wastes are amenable to municipal treatment.

Discharging of fruit and vegetable process wastewaters to a municipal

sewer system and the possibility of requiring a pretreatment system are

quite probable realities for the fruit and vegetable processing industries.

Screening is one form of pretreatment often required by municipal sewer use

ordinances. Other forms of pretreatment required by these ordinances could

be flow equalization, neutralization, and soil removal. In addition to

meeting the municipal ordinance requirements, pretreatment may help to

reduce sewer use costs and accommodate production increases without

exceeding discharge limitations (i.e., suspended solids).

83


Alternatives

It is an obvious economic fact that before any food processor

undertakes the task of building a pretreatment facility for discharge to a

municipal sewer, pays a municipal charge for wastewater treatment, or

builds a complete treatment plant for discharge to a receiving stream that

he must initiate in-plant waste saving practices, along with water

recycling and reuse measures. Another consideration is the restrictions

that are placed on the food processing wastewater discharge. Principal

limitations focus on substances that may be toxic, cannot be adequately

treated or stabilized, or materials which cause obstruction to flow in the

sewers. While toxic substances are not commonly associated with fruit and

vegetable type process waste streams, certain wastes are present that are

not amenable to treatment and can cause obstruction and maintenance

requirements. These troublesome wastes include those that contribute large

quantities of suspended solids or alkalinity to the waste treatment

facility. Thus, some form of isolation and pretreatment of the waste

stream becomes necessary prior to discharge to this facility.

The third consideration the food processor must address is to the

strength and volume of his processing wastewater. These parameters are

influenced by the fluctuation in production volumes and production facility

expansion programs. As these activities take place, increasing waste loads

can occur which could, and frequently do, reduce the ability of the

municipal's waste treatment system to adequately treat the added waste.

Should this happen with regularity, then the food processor may be faced

with a problem of pretreatment or supporting a municipal waste treatment

plant modification or expansion program. In either case, careful economic

considerations will need to be reviewed. Since the food processor knows

what his sewer costs are, he can calculate the cost of the added sewage

treatment load and determine whether the projected cost could better be

handled by pretreatment or financially supporting a municipal expansion

program.

Cost Considerations

Inherent in modification or expansion of a municipal's waste treat-

ment facility is the federal requirement (if federal grant money is used)

that should these activities include treatment capacity for industrial

wastewaters, then some form of industrial cost recovery system must be

84


established. Much of this cost recovery activity is accomplished through

the use of a surcharge system keyed to specific wastewater parameters.

Common parameters used are BOD strengths, suspended solids and the fats,

oils and grease category.

Surcharge systems vary, and no one can predict whether pretreatment

can be justified economically until costs are evaluated. A surcharge

system should be based upon an evaluation, by the city's consulting

engineer, of the cost of the elements of the municipal treatment plant

necessary to accomodate the flow, remove the suspended matter, and treat

the other ingredients of the industrial wastewater to the required levels

all on a unit basis (cost per pound of constituent).

Many surcharge systems start with a flow base rate and apply multi-

pliers for concentrations of any or all such ingredients as BOD, suspended

solids, and grease. As an example, the flow base rate charged to all sewer

users may be 50 percent of the water bill, including flow from private

water supplies. Then, taking BOD as an example, assume that 250 mg/l

been established as a bottom base for surcharges. Then a multiplier

be applied for BOD between 250 and 500 mg/l, and a higher multiplier

between 500 and 1,000 mg/l. Another set of multipliers might be appl

for suspended solids, another for grease, others for other factors.

multipliers are then added together to establish a single multiplier

applied to the flow base charge to arrive at the total bill.

has

might

ied

These

to be

An example of the cost formulation as developed by the Federal EPA and

used as a general guideline is as follows:

Ci=voVi+boBi+soSi

where Ci = charge to industrial users, dollars per year

V O = average unit cost of transport and treatment chargeable tovolume, per gallon

bo = average unit cost of treatment, chargeable to BOD, dollarsper pound

s o = average unit cost of treatment (including sludge treatment)chargeable to suspended solids, dollars per pound

V i= volume of wastewater from industrial users, gallons per year

B i= weight of BOD from industrial users, pounds per year

Si = weight of suspended solids from industrial users, pounds peryear

85


Note: The principle applies equally well with additional termse.g., chlorine feed rates) or fewer terms (e.g., voVi only).

The terms bo and so may include charges (surcharges) for concentratedwastes above an established minimum based on normal load criteria.

Inasmuch as it is an objective of the guidelines to encourage the

initiation and use of user charges, this general method of allocation is

both preferable and acceptable.

Since this guideline was published before enactment of the act, it

serves only as an indication of possible procedures. No guidelines

pursuant to the act have been developed at this time. However, the

decision to provide extensive pretreatment for discharge to a municipal

sewer system or to separate and treat the plant's wastewater should be

based upon a thorough, after-tax analysis of the costs involved.

Evaluating Needs

After the plant has been surveyed completely, and all possible waste

conservation and water reuse systems have been identified, the necessary

pretreatment system must be designed and the cost estimated. Those parts

of the treatment attributable to flow (such as grease basins and dissolved

air flotation) should be totaled and reduced to a cost per 1,000 gallons.

Similar breakouts in cost per pound can be carried out for grease,

suspended solids, and BOD.

Then each major in-plant expense for waste conservation and water

recycle and reuse can be evaluated, based on the estimated reduction in

flow, BOD, suspended solids, and grease. From such data, priorities can be

established for each in-plant waste-conservation measure suggested in the

survey.

Pretreatment Processes: Pretreatment can cover a broad range of

wastewater processing elements, including flow equalization, screening,

gravity separation of solids and floatables, dissolved air flotation,

chemical treatment as an adjunct to gravity separation or flotation, and

biological treatment such as aerated lagoons or some other form of

biological treatment.

Before any pretreatment is considered, an adequate survey should be

made, including flow measurement, composite sampling, and chemical

analysis, to determine the extent of the problem and the possibilities for

pretreatment. Analyses may include BOD, suspended solids, suspended

86


volatile solids, settleable solids, pH, temperature and FOG. A permanent

flow-measuring and composite-sampling arrangement are warranted if sampling

is done regularly to determine municipal surcharges.

Most common pretreament practices will include flow equalization,

neutralization and the separation of floatables and settleable solids. In

some instances lime and alum, ferric chloride, or a selected polymer may be

added to enhance separation. Paddle flocculation may follow alum and lime

or ferric chloride additions to assist in coagulation of the suspended

solids. Separation may be accomplished by gravity or by air flotation.

Screening, which could include vibrating, rotary or static type screens,

may precede the separation process and may also be used to concentrate the

separated floatables and settled solids. These various systems will be

discussed under separate headings.

Flow equalization and neutralization are important in reducing

hydraulic loading and correcting pH deficiencies if needed in the waste

stream. Equalization and neutralization facilities consist of a holding

tank, aeration capability for mixing, and, pumping equipment designed to

reduce the fluctuations of waste streams as well as a means to adjust pH.

These facilities can be economically advantageous whether the industry is

treating its own wastes or discharging into a city sewer after some

pretreatment. The equalizing and neutralization tank will store wastewater

for recycle or reuse, or to feed the flow uniformly to treatment facilities

throughout the 24-hour day. The tank is characterized by a varying flow

into the tank and a constant flow out. Lagoons may serve as equalizing

tanks or the tank may be a simple steel or concrete tank, often without a

cover.

Removal of floatables and suspended matter will provide a satisfactory

means of reducing BOD concentrations. Frequently this degree of treatment

will reduce the waste load sufficiently to comply with municipal sewer use

ordinance limitations. If additional BOD removal is required, a study of

biological processes for pretreatment may be instituted, possibly in pilot

scale. Several biological treatment systems have been successfully adapted

to the treatment of food processing wastes. These include the lagoon

arrangement, activated sludge, and land application.

87


Treatment Alternatives to Meet Regulations

In the treatment of fruit and vegetable processing wastewaters one

should be cognizant that these wastewaters often contain high concentra-

tions of organics and suspended solids. These wastes are amenable to

municipal waste treatment processes but when treated separately possess

inherent treatment problems. In most cases the processing wastes are

nutrient deficient, often lacking sufficient nitrogen and phosphorus

compounds essential to support adequate biological activity. Table 12

presents a summary of BOD/Nitrogen/Phosphorus ratio relationships

associated with common fruit and vegetable commodity wastewaters. For

adequate biological activity to proceed without limitation, the

BOD/Nitrogen/Phosphorus ratio should be at least 100/5/l, respectively,

expressed in mg/l units. Thus an examination of Table 12 reveals that

nutrient supplements are needed for nitrogen and phosphorus. Common

wastewater fortification practices utilize anhydrous ammonia and phosphoric

acid as N and P sources, respectively, with NaOH used to standardize the pH

of the pretreated raw wastewater stream.

In addition, the unit processes employed in commodity production may

produce an acid or alkaline effluent stream, resulting in fluctuations in

the pH of the final effluent. Therefore, some form of neutralization is

needed to correct the pH of these waste streams to the compatible pH range

(6-9).

Treatment alternatives have been briefly mentioned in the pretreatment

section of this chapter. If additional information is required for the

treatment alternatives mentioned, the reader is encouraged to refer to the

supplemental reference material provided in this manual series entitled

"Wastewater Treatment of Food Processing Effluents". Basically, the

treatment processes involve screening, sedimentation or dissolved air

flotation.

Perhaps the most commonly used process is screening. Screening may

employ vibrating screens, static screens or a rotary screen. In

pretreating specialty food processing waste streams, the vibrating and

rotary screens are the most frequently used. These screening systems are

used in a flow away (water in forward flow and passes through with solids

constantly removed from screen) mode of operation and can vary widely both

88


Table 12. Available Nutrients Fruit & Vegetable Wastewaters.

89


in mechanical action and in mesh size. Mesh sizes can range from 0.5 inch

in a static screen to 200 mesh in high-speed circular vibratory polishing

screens. Screening systems may be used in combination (i.e., prescreen-

polish screen) to achieve the desired solids removal efficiency.

Sedimentation is another process form

wastewater influent. Sizing of the detent

quiescent state for the raw wastewater are

Temperature variation of the wastewater is

because of the development of heat convect

used to remove solids from the

on vessel and providing a

important design considerations.

another important consideration

on currents and the potential

interference with marginal settling particles. Grease removal is also

accomplished with this unit process through removal of the surface scum.

A more complete treatment of the fruit and vegetable processing

wastewaters can be achieved through biological assimilation. Frequently

used systems, after suspended solids removal, are: treatment in an anaero-

bic lagoon followed by an aeration lagoon and stabilization-polishing pond;

activated sludge system; aerated lagoon followed by a stabilization-

polishing pond; trickling filters, utilizing plastic media, and rotating

biological contractors; with land application used as an effluent polishing

technique.

Treatment of Fruit and Vegetable Processing Wastewaters

A number of waste treatment systems are available for treating fruit

and vegetable processing waste streams. These systems are summarized in

Table 13 which defines the unit process, its order of use in the waste

treatment sequence and the expected waste reduction performances by these

unit processes.

Anaerobic Lagoons

Anaerobic lagoons may be used as a primary biological process in

order to reduce the organic and solids loadings on aerobic biological

processes which may be more expensive to operate. The lagoons are usually

2.4 to 6.1 meters deep with 3:l side slopes. In most cases, the detention

time is between 5-25 days and the lagoons are designed for high surface

loadings, 34 to 112 g,BOD5/day/m2.

90


Table 13. Food Industry Wastewater Treatment Practices.

91


The operation depends on the activity of anaerobic bacteria which

degrade organic materials in the absence of oxygen to form organic acids,

methane, ammonia, hydrogen sulphide and carbon dioxide. The reaction is

relatively slow, with an optimum temperature of approximately 33 to 35oC.

However, there are a number of advantages:

1. Low initial cost.

2. Ease of operation.

3. No energy consumption.

4. Ability to handle shock loads.

5. Low operation costs.

6. Small land area requirement.

Odors may occur periodically but this problem can be minimized by good

management. In some cases plastic covers of nylon, reinforced hypalon,

polyvinyl chloride or Styrofoam are utilized to retain heat and odorous

gases in the pond.

Anaerobic lagoons are particularly suitable for treating the high

strength biodegradable wastes characteristic of the fruit and vegetable

processing industry. Anaerobic ponds have achieved 85% removal of BOD5and suspended solids. Typical values for BOD5 removal are given in

Table 14.

The ponds must be designed with sufficient sludge storage capacity

such that sludge removal is required only infrequently. Treatability

studies are recommended to assess sludge accumulation rates for design

purposes.

The anaerobic process can be enhanced by the construction of enclosed,

well mixed reaction systems. The systems consist of flow equalization

tanks, anaerobic contact tanks (0.12 to 0.5 days' detention time), air or

vacuum gas stripping units, and a clarifier with sludge recirculation

pumps. Loadings of 2.4 to 3.2 kg BOD5/day/m3 have been used with a waste

recycle rate equal to 30% of the average daily flow to achieve BOD5 and

suspended solids removals of 90 to 97%. Methane gas produced in the

process can be collected and burned. The capital and operating costs are

high but the units are suitable for installations where odor emissions

cannot be tolerated and where insufficient land is available for the

installation of anaerobic ponds.

92


Table 14. BOD5 Loadings and Removal Efficiencies - Anaerobic Lagoons.

93


Aerobic Lagoons

Aerobic lagoons or stabilization ponds are the most common

biological treatment system used in the U.S. fruit and vegetable industry.

The type of lagoons used are seasonal retention ponds, aerobic

stabilization ponds, and aerated lagoons. All these processes depend on

the action of aerobic bacteria on the soluble organics contained in the

waste streams.

The organic carbon is converted to carbon dioxide and bacterial cells.

Algal growth is stimulated by incident sunlight which penetrates to a depth

of 1 to 1.5 meters. Photosynthesis results in the production of excess

oxygen which is available to the aerobic bacteria; additional oxygen is

provided by mass transfer at the air/water interface.

Aerobic stabilization ponds are 0.18-0.9 m deep to optimize algal

activity and are usually saturated with dissolved oxygen throughout the

depth during daylight hours. The ponds are designed to provide a detention

time of 2 to 2O days, with surface loadings of 5.5 to 22 g BOD5/day/m2.

The ponds are usually multiple cell units operated in series to

eliminate the possibility of short circuiting and to permit sedimentation

of dead algae and bacterial cells. The ponds are constructed with inlet

and outlet structures located in positions to minimize short circuiting due

to wind induced currents; the dimensions and geometry are designed to

maximize mixing. These systems can achieve 80 to 95% removal of BOD5and approximately 80% removal of suspended solids, with most of the

effluent solids discharged-as algae cells.

During winter periods the degree of treatment decreases markedly as

the temperature decreases and ice cover eliminates algal growth. In

regions where ice cover occurs, the lagoons may be equipped with variable

depth overflow structures in order that processing waste flows can be

stored during the winter. An alternative method is to provide long

retention storage ponds; the wastes can then be treated aerobically during

the spring prior to discharge.

Aerobic stabilization ponds are utilized where land is readily avail-

able. In regions where soils are permeable, it is often necessary to use

plastic, asphaltic, or clay liners to prevent contamination of adjacent

groundwater.

94


Typical BOD5 removal efficiencies for fruit and vegetable wastes

are given in Table 15.

Facultative Ponds

Facultative ponds are usually 0.9 to 1.8 meters deep. The processes

involved in aerobic stabilization ponds occur in the upper layers of

facultative ponds. Anaerobic bacteria operate at depths greater than one

meter and are important in the degradation of organic compounds contained in

the suspended solids which settle to the bottom of the ponds. Seasonal

retention ponds belong to this category.

Detention times for facultative ponds range from 7 to 30 days at

surface loadings of 2.2 to 5.6 g BOD5/m2. Considerably higher organic

loadings and longer retention times are utilized in seasonal holding ponds

which are generally deeper than two meters.

Holding pond systems can generally produce an effluent of acceptable

quality for discharge to receiving streams (BOD5 and suspended solids

concentrations less than 30 mg/l and 70 mg/l, respectively). They are

particularly suitable for use in conjunction with other forms of treatment

such as spray irrigation, or as flow equalization basins prior to the

disposal of wastes to municipal sewage treatment works. The quality of

effluent from holding ponds treating various commodities is provided in

Table 16.

Aerated Lagoons

Where sufficient land is not available for seasonal retention or

aerobic lagoons, efficient biological treatment can be achieved by the use

of aerated lagoons. Air is applied to these ponds by fixed or floating

mechanical aerators or by compressors through air diffusers located on the

bottom of the pond. The ponds are between 2.4 and 4.6 meters deep, with 2

to 10 days retention time and achieve 55 to 90% reduction in BOD5.

There are two types of aerated lagoons in common use:

1. Completely mixed (all solids are kept in suspension and only

aerobic oxidation takes place).

2. Facultative-aerated lagoon (the contents of the pond only

partially mixed and suspended solids settle to depths where

anaerobic decomposition occurs).

95


Table 15. BOD5 Loadings and Removal Efficiencies - Stabilization Ponds.

96


Table 16. Effluent Quality - Holding Lagoons.

97


Loading rates for aerated lagoons vary considerably and are determined by

rigorous laboratory or pilot scale testing carried out on the raw waste.Specific BOD removal rates for given commodities in an aerated lagoon

under completely mixed conditions are given in Table 17. Aerated lagoons

achieve good BOD5 removal. Levels of suspended solids in the effluent

are usually high and therefore aerated lagoons are usually followed by

quiescent settling to reduce the concentration of solids.

Trickling Filters

Trickling filters, utilizing plastic media in columns 4.5 to 6.0

meters high, have been used in the treatment of high strength fruit and

vegetable wastes (3000 to 4000 mg/l BOD5). High liquid recirculation

rates and forced air circulation are used to achieve BOD5 removals up

to 90%.

Wastewater is distributed by rotating arms at constant rates onto the

top surface of packed columns of plastic media. A biological film is

formed on the media and cellular material periodically sloughs-off when the

thickness becomes sufficiently great that oxygen transfer cannot occur

throughout its depth and anerobic conditions develop. Underdrains located

beneath the column transport the effluent to settling tanks where the dense

sludge is separated from the liquid effluent. A portion of the effluent is

recirculated to seed the process with biological cells and to promote

consisten sloughing.

General design criteria for trickling filters are as follows:

roughing filters may be loaded at rates of 4.8 kg BOD5/day/m3 filter media

and achieve BOD5 reductions of 40-50%; high rate filters achieve BOD5reductions of 40-70% at organic loadings of 0.4 to 4.8 kg BOD5/day/m/3

standard rate filters are loaded at 0.08 to 0.4 kg BOD5/day/m3 and achieve

BOD5 removals greater than 70%. Both high rate and roughing filters

are normally followed by additional treatment. In general they are used to

reduce the loading on subsequent treatment processes because of cost and

ease of operation. Limited data shown in Table 18 are principally from

pilot plant operations.

Activated Sludge

In an activated sludge treatment system, an acclimatized, mixed,

biological growth of microorganisms (sludge) is contacted with organic

98


Table 17. BOD5 Removal Rate Constants and Efficiencies - Aerated Lagoons.

NOTE: Fraction of BOD5 removed = (1 - kt)-'

99


Table 18. BOD5 Loadings and Removal Efficiencies - Trickling Filters.

100


material in the wastewater in the presence of excess dissolved oxygen and

nutrients (nitrogen and phosphorus). The microorganisms convert the

soluble organic compounds to carbon dioxide and cellular material. Oxygen

is obtained from applied air which also maintains adequate mixing. The

effluent is settled to separate biological solids and a portion of the

sludge is recycled; the excess is wasted for further treatment such as

dewatering.

Activated sludge systems utilized in the fruit and vegetable industry

are the extended aeration types: that is, they combine long aeration times

with low applied organic loadings. The detention times are three to ten

days. The suspended solids concentrations are maintained at high values to

facilitate treatment of the high strength wastes.

It is usually necessary to provide nutrient addition, pH control and

flow equalization prior to the activated sludge process, to ensure optimum

operation. BOD5 and suspended solids removals in the range of 95-98%

have been achieved, using similar processes for many fruit and vegetable

wastes. However, pilot or laboratory scale studies are required to

determine organic loadings, oxygen requirements, sludge yields, sludge

settling rates, etc. for these high strength wastes.

The following information required for the design of activated sludge

systems can be obtained from bench or pilot scale experiments:

1. BOD5 removal rate data.

2. Oxygen requirements for the degradation of organic material

and the degradation of dead cellular material (endogenous

respiration).

3. Sludge yield, determined from the conversion of soluble

organics to cellular material and the influx of inorganic

solids in the raw waste.

4. Solid/liquid separation rate; the final clarifier would be

designed to achieve rapid sedimentation of solids which

would be recycled or further treated. A maximum surface

settling rate of 16.5 m3/day/m2 has been suggested

for fruit and vegetable waste.

Activated sludge systems used in the fruit and vegetable processing

industry may be batch ("fill and draw") or continuous flow. The activated

sludge reactors and clarifiers are often lined earthen basins rather than

concrete or steel tanks, the former involving lower construction costs.

101


These systems are more difficult to operate than lagoon systems or

trickling filters but can consistently produce a specified effluent

quality. They are particularly suited for use in locations where there is

limited land available. However, operational power costs and operation and

maintenance costs are relatively high.

Typical design criteria and operating conditions for activated sludge

systems treating fruit and vegetable wastes are as follows:

- activated sludge concentration 2,000 - 4,000 mg/l

- organic loading 0.1 to 0.5 kg BOD5/kg microbial solids,

- aeration time 16 - 48 hours, dependent on organic loading and

sludge age requirements,

- depth 3.0 - 6.1 meters (2.1 m minimum),

- return sludge rate 25 - 100% of plant inflow rate.

Rotating Biological Contactors

The use of rotating biological contactors is relatively new in North

America but has been utilized in Europe for a number of waste treatment

applications. BOD5 reductions up to 90% have been achieved with multi-

stage units on citrus and apple processing wastes.

Rotating contactors consist of closely spaced flat parallel disks

mounted on horizontal shafts which rotate at 1 to 6 rpm perpendicular to

the direction of waste flow. The disks are partially submerged in the

wastes and a biological film consisting of a mixed population of bacteria,

fungi and protozoans develops on the surface of the disks. The biological

film is alternately contacted with the waste and with the atmosphere for

oxygen exchange. The rotational motion maintains solids in suspension and

entrains air in the liquid effluent. As the biological growth increases, a

portion of it separates from the disks and is settled in a clarifier.

The organic loading required for 90% BOD5 removal is specific to

the waste being treated. A high degree of treatment is possible since the

contactors are designed to provide plug flow and the bacterial growth

changes with distance along the contactor. The contactors may be used

subsequent to roughing treatment such as anaerobic or aerated lagoons; a

number of contactors in series may be used without roughing treatment.

Biological contactors can cope with fluctuating loadings and can

provide consistently good quality effluent. They are relatively simple to

102


operate, require little maintenance and consume relatively little energy.

At the present time, economic consideration of high capital cost detract

from their widespread use.

References

CH2M Hill, Corvallis, Oregon. 1976. Wastewater Treatment - PollutionAbatement in the Fruit and Vegetable Industry. Prepared for Food

Processors Institute and Sponsored by Office of Technology Transfer,

Environmental Protection Agency.Dornbush, J. N., D. A. Rollag and W. J. Trygotad. 1976. Investigation of

an anaerobic-aerobic lagoon system treating potato processing wastes.

IN Proceedings of the Sixth National Symposium on Food Processing

Wastes. EPA - 600/2-76-224, p. 3, December.Hemphill, B. W. and R. G. Dunnahoe. 1977. Improved Biological Treatment

of Food Processing Wastes with Two-Stage ABF Process. IN Proceedings

Eighth National Symposium on Food Processing Wastes.EPA-600/2-77-184, p. 235, August.

Mulyk, P. A. and A. Lamb. 1977. Inventory of the Fruit and Vegetable

Processing Industry in Canada - A report for Environmental Canada,

Environmental Protection Service, Ottawa, Ontario, Canada.

Mulyk, P. A. and A. Lamb, of Stanley Associates Engineering Ltd. 1977.Review of Treatment Technology in the Fruit and Vegetable Processing

Industry in Canada. Economic and Technical Review Report EPS

3-WP-77-5, Water Pollution Control Directorate.Steffen, A. J. 1973. In-Process Modifications and Pretreatment -

Upgrading Meat Packing Facilities to Reduce Pollution, #l. EPA

Technology Transfer Seminar Publication, October.Steffen, A. J. 1973. Pretreatment of Poultry Processing Wastes -

Up-grading Poultry-Processing Facilities to Reduce Pollution. #2. EPA

Technology Transfer Seminar Publication (EPA - 625/3-73-OOl), July.Stephenson, J. P. and P.H.M. Guo. 1977. State-of-the-Art Review of

Processes for Treatment and Reuse of Potato Wastes. Economic and

Technical Review Report EPS 3-WP-77-7, Water Pollution Control

Directorate.

103


L A N D D I S P O S A L

Introduction

Food processing wastewaters have been applied to the land through

engineered systems for more than 25 years. Major interest began in the

late 1940's with the objective being primarily waste disposal. Since

then, a wide variety of food processing wastewaters has been applied to

the land. Many of the earlier installations were loaded on the basis of

successful experience elsewhere, without regard for differing soil and

drainage characteristics. As a result of this oversight, many systems

failed and land treatment systems began to acquire a poor public image.

Today's PL 92-500 "zero discharge" goals, however, coupled with improved

understanding of the capabilities and limitations of soil systems have

renewed the interest in using land application.

A 1964 survey resulted in the identification of 844 systems applying

food processing wastewater to the land. Pennsylvania had the most systems

(143) followed by Wisconsin (141) and California (131). In 1972 as a

result of surveys and studies by the American Public Works Association

(APWA) and Metcalf & Eddy, Inc., data on more than 84 operating systems

were collected. These reports serve as the basis for much of the

information presented here.

This information is not meant to stand alone as the final work on the

subject of land applied fruit and vegetable processing wastes. Its

purpose is to provide a commodity-specific perspective of the suitability

of land application systems for the fruit and vegetable processing

industry.

Wastewater Quality and Pretreatment Requirements

Wastewater Characteristics

The characteristics of food processing wastewaters that must be

considered with regard to land treatment include BOD and COD, suspended

solids (SS), total fixed dissolved solids, nitrogen, pH, temperature, heavy

metals, and the Sodium Adsorption Ratio (SAR). These characteristics vary

widely among food processing wastes applied to the land.

104


BOD and COD. The ratio of BOD to COD is a measure of a

wastewater's biodegradability. Most food processing wastewaters are

readily degradable and exhibit a high BOD to COD ratio. Most soils are

highly efficient biological treatment systems. So, liquid loading rates

for land treatment operations are usually governed by the water holding

capacity of the soil rather than by the organic loading rate. This

operational independence from BOD loading can be a distinct advantage of

land treatment systems over conventional systems in treating high-strength

wastewaters. There are limits, of course, to the organic loading that can

be placed on the land without stressing the soil system. The effects of

organic overloads on the soil include damage to or killing of vegetation,

severe clogging of the soil surface, and leaching of undegraded organics

into the groundwater. Defining the limiting organic loading rate for a

system must be done on an individual site-specific basis. However,

rule-of-thumb rates have been developed based on experience. A maximum BOD

rate of 200 lb/acre/day has been suggested as a safe loading rate for pulp

and paper wastewaters. A somewhat higher rate can normally be used with

food processing wastewaters containing a higher percentage of sugars rather

than starchy or fibrous material. Substantially higher loading rates

(greater than 600 lb/acre/day) have been used on a short-term seasonal

basis for infiltration-percolation systems. For overland flow systems,

organic loadings in the range of 40 to 100 lb/acre/day have been used

successfully.

Suspended Solids. Solids are generally the major source of

operational problems such as clogged sprinklers and clogged soil surface.

Pretreatment to remove solids will normally minimize these problems.

Nitrogen. Nitrogen in food processing wastewaters is normally

not of major concern because it is usually present in such concentrations

that it is almost completely removed by bacterial assimilation or crop

uptake. Notable exceptions are feed-lot, dairy, potato processing, and

meat packing wastes. The latter have been found to contribute a

significant nitrate load to groundwaters.

pH. Wastewaters that have a pH between 6.0 and 9.5 are generally

suitable for continuous application to most crops and soils. Wastewaters

with pH below 6.0 have been successfully applied to soils that have a large

105


buffering capacity. "Beware of applying caustic wastes before diluting or

neutralizing them.

Temperature. High temperature wastewaters from cooking

operations can sterilize the soil and prevent growth of cover vegetation.

Heavy Metals. The soil has a large capacity to adsorb heavy

metals. Once this capacity is exceeded, however, the metals may be

leached to the groundwater (under acid soil conditions) or inhibit plant

growth.

Salt Loading-Sodium Adsorption Ratio (SAR). The ratio of sodium

to other cations, primarily calcium and magnesium, can adversely affect

the permeability of soils, particularly clay soils. Wastewaters with a

SAR below 8 are considered safe for most soils. Sandy soils can tolerate

higher SAR values.

Pretreatment

Pretreatment is required in most cases to eliminate frequent

operating difficulties and avoid adverse effects on the terrain

environment.

Screening. Screening with rotary or vibration screens has been

almost universally employed as a form of pretreatment to separate coarse

solids from food processing wastewaters. Such solids can cause serious

problems with wastewater distribution, particularly with spray

applications. Fine screens at pump intakes or in-line screens in the

discharge piping have also been employed as an added precaution against

sprinkler nozzle clogging.

Lagooning. The use of lagoons or settling ponds prior to land

application of industrial wastewaters has been prevalent. Such lagoons

serve to remove silt and other suspended particles which may contribute to

clogging of the distribution system as well as hasten the clogging of soil

pore space. This form of pretreatment is normally used when applying

wastewaters to vegetated fields by flood irrigation techniques. This

practice does, however, tend to create noxious odors.

pH Adjustment. Industrial wastewaters with sustained flows

outside the pH range of 6 to 9.5 should be neutralized prior to land

application if the site is to be vegetated. Wastewaters with widely

fluctuating flows can be self-neutralizing if an equilization basin is

106


provided prior to land application. In other cases a continuous pH

control system may be necessary.

Cooling. For wastewaters below 150°F, application by sprinkling

normally provides sufficient cooling to protect vegetation and soil. Such

cooling may be enhanced by the use of sprinklers that produce small spray

droplets or that have large spray diameters. Wastewaters with tempera-

tures much above 150°F generally should be cooled prior to spraying if

vegetation is desired.

Nutrient Addition. Nutrient addition in the form of nitrogen or

phosphates may be necessary for nutrient deficient wastes unless the

fields are adequately fertilized.

Land Treatment Processes

Land application systems for treatment and disposal of food

processing wastes are normally categorized into three types of systems

based on differences in the interaction of the wastewater with vegetation

and soil. These three catagories are referred to as (1) irrigation, (2)

overland flow, and (3) infitration-percolation. Selection of the type of

system at a given site is primarily governed by the drainability of the

soil because it is this property that largely determines the allowable

liquid loading rate. Schematic diagrams indicating the major process

characteristics of each 'of the systems are shown in Figure 17. A summary

of the comparative characteristics of the three systems is presented in

Table 19.

Irrigation. Irrigation is considered to include those systems

where wastewater is applied to land by either spray or surface techniques

at normal agricultural irrigation rates or somewhat in excess of those

rates. Liquid loading rates generally range from about 0.1 in./day to 0.6

in./day. At these loading rates, land requirements range from about 60 to

370 acres/mgd of wastewater, plus a buffer zone.

Within the food processing industry the most common method of liquid

waste disposal on the land is spray irrigation. The availability of

suitable land, soil characteristics, cover crop, the wastewater, and

climatic conditions all affect this method of disposal. Some irrigation

l07


Figure 17. Land Application Approaches

108


Table 19. Comparative Characteristics of Land Treatment Systems

*l acre inch = 27,154 gallons

109


systems operate with little or no run-off and remove practically all of

the pollutional load (Table 20).

Loamy, well-drained soil is most suitable for irrigation systems,

particularly where crop production is a major goal of the operation.

However soil depth of 5 feet above groundwater is preferred to prevent

saturation of the root zone. Underdrain systems have been used

successfully to adapt to high groundwater or impervious subsoil

conditions.

The objective of most irrigation systems for food processing waste-

waters is to maximize hydraulic loadings rather than crop production. The

result is that most systems use a water tolerant perennial grass as a

cover crop. A few systems use higher valued crops, such as alfalfa or

corn, for cover vegetation, but these have only been successful when

standard irrigation practices have been followed.

Cover vegetation plays an important role in irrigation systems. This

is particularly true in spray application systems where the cover

vegetation prevents soil erosion and sealing of the soil surface due to

the battering action of water droplets. The root structure of cover

vegetation also aids in maintaining the infiltrative capacity of the

surface by expanding the soil and promoting dispersion of clogging

materials. Plants are also largely responsible for removal of nutrients

such as nitrogen and phosphorus. Removal of the organic materials in the

wastewater is accomplished primarily by microorganisms residing in the

soil.

A few systems employing surface application techniques, such as

border strip or ridge and furrow irrigation, do not use cover crops

because the wastewater is either toxic to plants or contains a high

suspended solids load that would be trapped by a cover crop at the head of

an irrigated strip.

Spray irrigation on slopes draining to lagoons appears to be very

successful and adaptable to soils which limit lateral movement of

underground water; 99% BOD reduction, total color removal, and 90% N and P

reduction may be expected.

In irrigation systems most of the applied wastewater is either

consumed through evapotranspiration or percolates through the soil to

become groundwater. Evaporative consumption generally is equal to or

111


greater than percolation. A portion of the applied wastewater may appear

as surface runoff. Failure to adequately control this runoff is a common

source of problems at existing systems..

These 1970 figures show the percentages of canners and freezers of

the listed products disposing of effluents by irrigation in the

continental U.S.:

Overland Flow

The overland flow technique is an adaptation of spray irrigation to

impermeable or poorly drained soils. The technique was pioneered in 1954

by the Campbell Soup Company at Napoleon, Ohio, and was studied in depth

at the Campbell installation at Paris, Texas. Until recent studies with

municipal wastewaters were performed, its application had been restricted

to the food processing industry. Overland flow differs from spray

irrigation primarily in that a substantial portion of the wastewater

applied is designed to run off and must be collected and discharged to

receiving waters, or in certain cases where wastewater is produced only

during part of the year, stored for deferred application. An overland

flow system therefore functions more as a land treatment system than a

land disposal system.

Wastewater is applied by sprinklers to the upper two-thirds of sloped

terraces that are 100 to 300 feet in length, [see Figure 17(b)]. A runoff

collection ditch or drain is provided at the bottom of each slope.

Treatment is accomplished by bacteria on the soil surface and within the

vegetative litter as the wastewater flows down the sloped, grass-covered

surface to the runoff collection drains. Ideally, the slopes should have a

grade of 2 to 4 percent to provide adequate treatment and prevent ponding

or erosion. The system may be used on naturally sloped lands (such as the

two Campbell Soup Company installations at Napoleon, Ohio, and Paris,

112


Texas) or it may be adapted to flat agricultural land by reshaping the

surface to provide the necessary slopes.

Higher liquid loading rates are possible with the overland flow

technique than with conventional spray irrigation. These rates may range

between 0.25 to 0.7 in./day, resulting in a land requirement of about 50

to 150 acres plus buffer zone for each mgd applied.

As mentioned previously, the system is especially suited to use with

slowly permeable soils such as clays or clay loams. With this type of

soil very little water percolates to the groundwater. Most of it appears

as surface runoff or is consumed by evapotranspiration.

A cover crop is essential with the overland flow system to provide

slope protection and media for the soil bacteria as well as to provide

nutrient removal by plant uptake. A water tolerant perennial grass such as

Reed canary grass or tall fescue has been found to be suitable to the high

liquid loading rates.

Infiltration-Percolation

Infiltration-Percolation systems are characterized by percolation of

most of the applied wastewater through the soil and eventually to the

groundwater. The method is restricted to use with rapidly permeable soils

such as sands and sandy loams. This type of system is normally thought to

be associated with recharge or spreading basins although in food

processing applications high-rate-spray systems have been used to provide

distribution of the wastewater. In actual practice there is not a

definite division between irrigation systems previously described and

high-rate spray infiltration-percolation systems, but rather a complete

spectrum of operations with liquid loading rates ranging from 0.1 in./day

to 12 in./day. For purposes of discussion, an average loading rate of 0.6

in./day is used as an arbitrary dividing point between the two types Of

systems. At this minimum loading rate, infiltration-percolation systems

would require about 60 acres plus a buffer zone for each mgd applied.

The use of recharge or spreading basins for treatment and disposal of

food processing wastewaters has been limited primarily due to the high

organic strength and high solids concentration of typical wastewaters.

These constituents clog the soil surface and make it difficult to maintain

consistently high soil infiltration rates.

113


Vegetation is essential in high-rate spray systems to protect the

infiltrative surface. For spreading basins, cover vegetation would

normally not be used for wastewaters containing a high solids concentration

because it would tend to entrap solids and prevent satisfactory

distribution in the basin.

In infiltration-percolation systems, plants play a relatively minor

role in terms of treatment of the applied wastewater. Physical,

chemical, and biological mechanisms operating within the soil are

responsible for treatment. The more permeable the soil, the further the

wastewater must travel through the soil to receive treatment. In very

sandy soils this minimum distance is considered to be approximately 15

feet.

Existing Land Treatment Systems

The design and management as well as common operating problems of

the different types of systems described above are discussed through

description of several selected existing operations.

Irrigation Systems

Under the category of irrigation the two basic techniques of

wastewater application employed are spray irrigation and surface

irrigation. Under spray irrigation, variations that have been observed

include solid set sprinklers, portable sprinklers, and tower spraying.

Surface techniques include border strip flood irrigation with or without

crops and ridge and furrow irrigation also with or without crops.

A selected list of spray irrigation systems handling a wide variety

of food processing wastewaters is presented in Table 20 along with the

major operating characteristics. A similar list for surface irrigation

systems is presented in Table 21. Typical systems employing each of the

various application techniques are described below.

Solid Set Sprinkler Irrigation. An example of solid set spraying

is the system of the Idaho Supreme Potato Company in Firth, Idaho. The

distribution system is buried with risers spaced on 80-foot squares

discharging at 80 to 100 psi. The spray fields are planted to a mixture of

Reed canary grass, meadow foxtail, and alta fescue with the yield of hay

115


being 5 tons/acre annually. Potato washing wastewater passes through

vacuum filters with the mud going to lagoons and the filtrate to the spray

fields where it is mixed with screened wastewater from the potato peeling

and cutting operations. The system is well managed with wastewater applied

in 12 hours followed by 8 to 9 days of resting in the summer. The system

continues to operate during the winter with ice mounds building up to

heights of 5 feet. The only change in operation is that spraying lasts for

24 hours followed by 16 to 18 days of resting.

Portable Sprinkler Irrigation. The spray system at Tri Valley

Growers tomato processing installation near Stockton, California, is a good

example of a portable sprinkler system. The spray field consists of 165

acres with 90 acres planted to water grass and 75 acres planted to Sudan

grass. The sprinkler system consists of 16-inch portable aluminum mains

and 4-inch portable laterals with sprinklers on a 60-foot grid. Although

the system is portable, it is operated as a solid set system without moving

the laterals prior to the end of the season. Pretreatment of the

wastewater consist of coarse screening, holding pond for equalization and

sedimentation, plus in-line screens in the discharge lines of the spray

system pumps.

Prior to the addition of the 75 acres to the spray fields in 1973,

approximately 3 mgd of tomato processing wastewater was applied to 90

acres with each of nine lo-acre sections receiving full flow for

approximately 3 hours at a time. The resulting average liquid loading

rate was in excess of 1.2 inches per day on a clay loam soil. This

application rate was far in excess of the infiltrative capacity of the

soil and the evapotranspiration demand of the cover crop. Therefore

approximately 30 percent of the applied water appeared as runoff. The

runoff was collected and channeled back to the pumping station for

recirculation over the system. Runoff was not discharged to local

receiving waters because of particularly stringent discharge requirements

of 15 mg/l BOD and 15 mg/l suspended solids. The recirculated runoff,

therefore, accumulated and was actually stored on the field surface and in

the drainage ditches. The flooded conditions that developed led to odor

and mosquito propagation problems. The crop was allowed to grow throughout

the season and became quite tall. This tall grass impeded drying of the

soil surface and produced sheltered habitat for mosquito breeding.

116


The flooded condition was partially relieved in 1973 by the addition

of 75 acres of spray field and regrading the existing 90 acres. The

resulting loading rate was 0.67 in./day. In addition, the cover crop was

harvested as part of the field management. Prior to harvesting, the field

was allowed to dry for a period of 7 days. The grass was mowed and removed

as green chop in one cutting during the 1973 season. For 1974, the

expected flow is 2 mgd as a result of the separation of cooling water and

the resulting application rate would be reduced to 0.45 in./day.

Tower Spray Irrigation. A unique spraying system has evolved at

the Stokely-Van Camp installation at Fairmount, Minnesota. In the early

1950's a portable solid-set system was used, but the labor required to move

the laterals proved too expensive. This system was replaced by a boom-type

center pivot irrigation rig which also was too demanding of labor for

maintenance. Finally, a fixed tower system was designed with fog nozzles

operating at high pressure. The system now operates successfully using

towers at 500-foot centers that are about 25 feet high.

Flood Irrigation. An example of flood irrigation is the Idaho

Fresh Pak system at Lewisville, Idaho. The land has been graded into

2.5-acre plots for border strip irrigation. Potato-peel wastewater passes

through a vacuum filter and the filtrate is pumped 4.5 miles to the site.

In the summer, grass is grown and harvested for hay. In the winter the

50°F wastewater melts the snow and ice and percolates into the soil. Some

odors exist and more land is being acquired by the company.

Ridge and Furrow Irrigation. This form of irrigation has been

replaced, for the most part, by spray irrigation. Whereas Schraufnagel

reported about 50 ridge and furrow systems in 1962, Sullivan reported only

one ridge and furrow system out of the 56 responding to the APWA

questionnaire. That system was the Green Giant Company installation at

Buhl, Idaho, where corn-processing wastewater is screened and used as

supplemental irrigation water for corn. Other systems reported in

existence by an APWA mail survey are five creameries in Wisconsin and three

food processing plants in Indiana.

Overland and Flow Systems. The overland flow systems described below

are examples of how the system may be adapted to different site conditions.

A list of existing systems with operating characteristics is presented in

Table 22.

117


Table 22 - Selected Overland Flow Systems

118


The Hunt-Wesson Foods cannery in Davis, California, employs the

overland flow technique to treat approximately 3.25 mgd of tomato pro-

cessing wastewater from July through September, plus smaller volumes of

wastewater from other products during the remainder of the year. The

system consists of a series of sloped terraces with collection ditches at

the toe of each slope. The terraces were constructed on a slope of 2.4

percent with a length of 175 feet. A considerable amount of earthwork was

required to form the slopes (over 300,000 cu yd) since the site was

originally flat agricultural land. The slopes were planted to a

combination of Reed canary grass, tall fescue, Italian rye grass, and

trefoil with the anticipation that Reed canary grass would eventually

dominate. The distribution system consists of a solid set sprinker system

with risers spaced at lOO-foot intervals and 65 feet from the top of each

slope.

Spraying is preceeded by coarse screening. The application of

wastewater is controlled automatically by clock timers that actuate

pneumatic valves in the field. During peak season, however, the spray

rotation is controlled manually.

Infiltration-Percolation Systems. Under the category of infiltra-

tion-percolation, two methods of wastewater application are employed.

These are spreading basins or percolation beds and high rate spraying.

Tri Valley Growers' Plant No. 2 near Modesto, California, is one of

the few processing plants where classical spreading basins are employed

for infiltration-percolation. A waste-flow of approximately 2.5 mgd is

generated from the processing of tomatoes, peaches, and pears with the

canning season normally extending from July through September. The

infiltration-percolation site consists of 70 acres of spreading basins and

20 acres of wine grapes. The grapes are irrigated with wastewater using

normal application rates with no adverse affects on grape quality. The

soil at the site is primarily sand and loamy sand.

The infiltration-percolation site is divided into one-acre basins.

Most of the basins receive wastewater from concrete-lined ditches equipped

with slide gates, while the remainder are served by a buried-pipe system

with flood valves. This pipe must be flushed with fresh water after each

application to prevent release of odors. The application schedule and

loading rates have been developed by trial and error, since each basin was

119


found to have a different percolation capacity. The differences are due

to hardpan layers in the subsoil. This situation is a good example of why

subsurface soil conditions should be determined as part of a site

investigation for infiltration-percolation systems. Applications range

from 50,000 to 500,000 gallons per acre depending on the basin. Each

application is followed by 7 to 10 days of resting. The applications are

regulated to achieve elimination of standing water within 24 hours of the

start of application. This avoids both odor and mosquito problems.

During the summer no cover crop is used on the basins. After each

application the basins are disked to allow the soil to aerate and maintain

its infiltrative capacity. As the season proceeds, the infiltrative

capacity drops somewhat due to clogging by solids in the wastewater.

Following the canning season, the basins are planted to oats which are

harvested in the following spring. The oats serve to take up some of the

nitrogen that was contained in the wastewater and held in the soil

structure, as well as to restore the infiltration capacity of the soil.

Costs

At present the availability of useful cost data on land treatment

systems is limited. The cost data presented herein are based primarily on

the APWA report and are supplemented with information on a few systems in

California.

Spray Irrigation

Costs for selected spray irrigation systems are given in Table 23.

Construction costs include costs for pumping stations, force mains, land

preparation, and distribution systems, except as noted, and depend on the

year constructed as well as many local conditions. Land costs have been

separated because of their variability and are presented in Table 24. In

addition to the cost of land when purchased, the estimated value of the

land in 1972 is included in Table 24. In all cases the value of the land

is at least as high as when it was purchased and in several cases land

values have appreciated substantially. The total capital cost is the sum

of the costs for land and construction plus easements, pretreatment

facilities, monitoring facilities, and administrative, engineering, and

120F&V SPNOFF/LAND DISPOSAL

Table 23. Construction and Operating Costs for Selected SprayIrrigation Systems

121


legal fees. In the case of the Libby operation at Liepsic, Ohio, the land

for spray irrigation is leased.

Operating costs are also given in Table 23. The annual budget was

divided by the total annual flow to obtain the cost in cents per thousand

gallons. The period of operation ranged from 4 months for the Green Giant

Company operation at Montgomery, Minnesota, to 12 months for the Gerber

operation at Fremont, Michigan.

Surface Irrigation

Costs for surface irrigation depend a great deal on the existing

topography. Consequently the cost-of preparing the land for irrigation

must be balanced against the purchase price of the land. For example, the

Libby's system at Gridley did not entail any land preparation costs because

the fields were leveled previously for irrigation. However, the land cost

was $1,400 per acre. On the other hand, for the California Canners and

Growers system at Thornton, costs for land preparation and the distribution

system totalled $450 per acre (total construction cost shown in Table 25).

Adding this to the land cost of $870 per acre yields a total of $1,320 per

acre at Thornton, as compared to the $1,400 per acre at Gridley. Of

course, many of the local conditions were different. However, the

combination of land cost and land preparation cost is an especially

important consideration for surface irrigation systems. Additional land

costs are given in Table 26.

The initial expenditure for a land application system is appreciably

lower than that for a biological wastewater treatment plant. The primary

investment of a land application system is the cost of land. In the

midwest region of the United States, except for major metropolitan areas,

land prices vary from $400 to $1,500 per acre. Equipment and installation

costs are as high as $1,000 per acre, the major equipment expense usually

being the piping. Four-inch aluminum pipe costs roughly $1.30 per foot,

and 6" spiral-wound steel pipe costs about $1.50 per foot, including

connections.

Operating costs include the cost of pumping, maintenance and

operation. If the semipermanent system is used, two men are capable of

properly operating the system. The permanent system requires only one

operator's attention.

122

F&V SPNOFF/LAND DISPOSAL OF F&V PROCESSING WASTEWATERS

Table 25 - Construction and Operating Costs for Selected

Surface Irrigations Systems

123


Overland Flow

Construction cost items for overland flow include earthwork,

pretreatment, transmission, distribution, and collection. Clearing of

land, grading of slopes, and planting is generally equal in cost to the

distribution system. The available costs for distribution systems and land

preparation for two operating systems are given in Table 27. The operating

costs shown are total costs not including the return from the sale of hay.

The return on the sale of hay is approximately 8 to 10 percent of the total

annual operating cost.

Infiltration-Percolation

For infiltration-percolation systems, the costs per gpd, as shown in

Table 28, are relatively low compared to spray irrigation. Similarly, the

operating costs are lower due also to the high-rate applications and low

land requirements. The only available land cost was $400 per acre in 1961

for the Hunt-Wesson system at Bridgeton, New Jersey.

Applicability and Potential of Land Application

It is apparent from the descriptions of the various existing

systems that land application can be adapted to a wide range of soil types

and site drainage conditions. One of the keys to a successful system is

to determine the site characteristics--soil type, soil drainage,

subsurface conditions, topography, and climatic conditions--and then adapt

the most suitable technique to them. Equally important to successful

operation is conscientious field management to avoid stressing or

overloading the system.

Of particular interest to the food processing industry is the ability

of land application techniques to meet "zero discharge" requirements at a

reasonable cost. As more food processing activity becomes centered in

rural areas the economic advantages of land application will become more

evident.

Land application, however, is not a panacea. Many uncertainties

still remain regarding long-term effects of wastewater on soils, plants,

and groundwater. Research in this regard is being carried on at several

124F&V SPNOFF/LAND DISPOSAL

Table 27 - Construction and Operating Costs for Overland Flow Systems

aDepends upon the period of operation.

125


locations. Dr. Jay Smith of the USDA in Kimberly, Idaho, is conducting a

3-year study of land application of potato processing wastewaters in Idaho.

EPA has sponsored considerable research on overland flow.

The food processing industry has taken the lead in developing land

application as an economic alternative to conventional treatment method.

This is evidenced by the fact that over one-third of all the land

application systems in the United States serve the industry. Active

interest indicates that the industry will continue to be at the forefront

of future development.

References

Bogedain, F., A. Adamczyk, and T. J. Tofflemire. 1974. Land Disposal of

Wastewater in New York State. New York State Dept. of Environmental

Conservation.

Cole, L., B. Morris, and Wm. S. Stinson. 1977. Potato processor achieves

98+% BOD, 99+% suspended solids removal. Food Processing, Feb.

Crites, R. W., C. E. Pound, and R. G. Smith. 1974. Experience with land

treatment of food processing wastewater. Proceedings Fifth National

Symposium on Food Processing Wastes.

EPA. Municipal Wastewater Treatment Works Construction Grants Program.

references--Regulations, Guidance, Procedures.

Koo, R. C. J. 1976. Back to the Tree, citrus processing plants use

wastewater for irrigation. Water Research in Action. Vol. 1, No. 7.

Liptak, B. G. 1974. Environmental Engineer's Handbook. Vol. I and III.

National Canners Association. 1971. Liquid Wastes from Canning and

Freezing Fruits and Vegetables (12060 EDK 08/71).

126

F&V SPNOFF/DIRECT DISCH

DIRECT DISCHARGE

Introduction

Fruit and vegetable processing plants that discharge wastewaters

directly to streams, bays, sounds, rivers, creeks and/or estuaries must

have a permit for this discharge as required under the NPDES permit pro-

gram. In most cases, even small plants that have septic tanks for process

wastewaters must also have a state or local permit. Plants that use

non-discharge systems such as land disposal will also probably need a

permit. Permits for discharge or disposal are usually obtained from the

state environmental control agency.

Effluent Guidelines and Limitations

Introduction

In response to widespread public concern about the condition of the

Nation's waterways, Congress enacted the Federal Water Pollution Control

Act Amendments of 1972. The 1972 act built upon the experiences of earlier

water pollution control laws. The 1972 act brought dramatic changes.

What the 1972 law says, in essence, is that nobody - no city or town,

no industry, no government agency, no individual - has a right to pollute

our water. What was acceptable in the past - the free use of waterways as

a dumping ground for our wastes - is no longer permitted. From now on,

under the 1972 law, we must safeguard our waterways even if it means fun-

damental changes in the way we manufacture products, produce farm crops,

and carry on the economic life of our communities.

Congress declared that the objective of the 1972 law is "to restore

and maintain the chemical, physical, and biological integrity of the

Nation's waters."

- The law requires EPA to establish national "effluent limitations"

for industrial plants - including fruit and vegetable products plants. An

"effluent limitation" is simply the maximum amount of a pollutant that

anyone may discharge into a water body.

- By July 1, 1977, the law required existing industries to reduce

their pollutant discharges to the level attainable by using the "best

127


practicable" water pollution control technology (BPT). BPT was determined

by averaging the pollution control effectiveness achieved by the best

plants in the industry.

- By July 1, 1983, the law requires existing industries to reduce

their pollutant discharges still more - to the level attainable by using

the "best available" pollution control technology (BAT). BAT is based on

utilizing the best pollution control procedures economically achievable.

If it is technologically and economically feasible to do so, industries

must completely eliminate pollutant discharges by July 1, 1983.

- The law requires new fruit and vegetable plants to limit pollutant

discharges to the level attainable by meeting national "standards of

performance" established by EPA for new plants. A new plant must meet

these standards immediately, without waiting for 1977 or 1983. These new

plant standards may require greater reduction of pollutant discharges than

the 1977 and 1983 standards for existing plants. Where practicable, zero

discharge of pollutants can be required. However, for the fruit and

vegetable industry, the standards are equal to the most stringent 1983

standards, with allowance not granted for plant size.

- The law requires fruit and vegetable facilities that send their

wastes to municipal treatment plants - as almost half the do - to make sure

the wastes can be adequately treated by the municipal plant and will not

damage the municipal plant. In some industries, discharges to municipal

plants may thus have to be "pre-treated." That is, the portion of the

industrial waste that would not be adequately treated or would damage the

municipal plant must be removed from the waste before it enters the

municipal system. To date, the fruit and vegetable industry has not been

required by law to pretreat their wastewaters.

- The law does not tell any industry what technology it must use.

The law only requires industries to limit pollutant discharges to levels

prescribed by law.

- The law also says that if meeting the 1977 and 1983 requirements is

not good enough to achieve water quality standards, even tougher controls

may be imposed on dischargers.

- And while the law requires industries to meet the national dis-

charge standards set for 1977, 1983 and for new plants, the law also allows

a state or community to impose stricter requirements if it wishes. The

128


national standards are thus minimum requirements that all industries must

meet.

The key to applying the effluent limits to industries - including the

fruit and vegetable industry - is the national permit system created by the

1972 law. (The technical name is the "national pollutant discharge

elimination system," or NPDES.)

Under the 1972 law it is illegal for any industry to discharge any

pollutant into the Nation's waters without a permit from EPA or from a

State that has an EPA-approved permit program. Every industrial plant

that discharges pollutants to a waterway must therefore apply for a

permit.

When issued, the permit regulates what may be discharged and the

amount of each identified pollutant. It sets specific limits on the

effluent from each plant. It commits the discharger to comply with all

applicable national effluent limits and with any State or local

requirements that may be imposed. If the industrial plant cannot comply

immediately, the permit contains a compliance schedule - firm target dates

by which pollutant discharges will be reduced or eliminated as required.

The permit also requires dischargers to monitor their wastes and to report

the amount and nature of wastes put into waterways.

The permit, in essence, is a contract between a company and the

government.

This combination of national effluent standards and limits, applied to

specific sources of water pollution by individual permits with substantial

penalties for failure to comply, constitutes the first effective nationwide

system of water pollution control.

Now what does all this mean to the fruit and vegetable industry? How

does one determine the NPDES permit limitations for a plant discharge into

a receiving stream?

The U. S. Environmental Protection Agency prepared standards for fruit

and vegetable plants under the 1972 law. EPA did so, after considering

many factors: the nature of plant raw materials and wastes; manufacturing

processes; the availability and cost of pollution control systems; energy

requirements and costs; the age of size of plants in the industry; and the

environmental implications of controlling water pollution. (For instance,

129


we would gain nothing if, in controlling water pollution, we created a new

air or land pollution problem.)

The proposed regulations were issued by EPA in March, 1974 and October

1975. Then, they were sent to the industry and other interested organiza-

tions for review and comments. They were made public by publication in the

Federal Register. Comments were submitted by companies and industry

organizations, by State agencies, and by Federal agencies. EPA then

carefully analyzed the comments and made appropriate changes in the

standards. Then, EPA issued the final standards for the plants to follow

in order to meet the requirements of the 1972 law.

The standards are contained in an official government regulation

published in the Code of Federal Regulations. This regulation is supported

by a detailed technical document called the "Development Document for

Interim Final and Proposed Effluent Limitations Guidelines and New Source

Performance Standards for the Fruits, Vegetables and Specialties Segment of

the Canned and Preserved Fruits and Vegetables Point Source Category."

Subsequent regulations and amendments have been made over the last several

years.

In brief, here is what the regulation does:

- Sets limits on identified pollutants that can be legally discharged

by plants in the sub-categories of the fruit and vegetable products

industry.

- Zeroes in on the major fruit and vegetable industry pollutants, it

establishes maximum limitations for BOD and suspended solids that plants

can discharge during any one day, on an average over a thirty-day period,

and on an annual average based in terms of lbs pollutant that can be

discharged per 1000 lbs of raw material processed.

- Sets limits that can be met by using the "best practicable control

technology currently available" - the 1977 requirement.

- Sets more stringent limits that can be met by using the "best

available technology economically achievable" - the 1983 requirment (Table

29 for fruits and Table 30 for vegetables).

- Requires that the pH (acidity or alkalinity) of fruit and vegetable

plant discharges be within the range of 6.0 to 9.5.

- Establishes performance standards that new plants must meet without

waiting for 1977 or 1983. For the fruit and vegetable industry, the new

132


plant standard is the same as the 1983 (BAT) standard for existing plants

except that the limitations for the large plants are the new source

standards regardless of plant size. However, regulatory officials shall be

consulted for up-to-date information.

- Does not require zero discharge of any pollutant by a fruit and

vegetable plant. Zero discharge may be technically possible in the

industry, but the cost would be prohibitive for most if not all plants

the industry.

in

- Does not tell companies what technology to use to meet regulations.

The standards only require fruit and vegetable companies to limit pollutant

discharges to the levels required.

In 1978, EPA reviewed the BAT standards in light of Section 304 (b)(4)

of the Clean Water Act which established "best conventional pollutant

control technology" (BCT). BCT was intended to replace BAT. Congress

directed EPA to consider the:

. . . reasonableness of the relationship between thecosts of attaining a reduction in effluents and theeffluent reduction benefits derived, and thecomparison of the cost and level of reduction of suchpollutants from the discharge of publically ownedtreatment works to the cost and level of reduction ofsuch pollutants from a class or category of industrialsources

The fruit and vegetable processing industry was studied and

regulations were proposed in the August 23, 1978, Federal Register. The

results of these studies lead EPA to concluded that BAT regulations were

found to be established from insufficient data and they were recommended to

be suspended. Only the tomato and mushroom BAT regulations were found

acceptable for BCT.

Despite the voluminous amount of material available in regard to the

regulations, many fruit and vegetable processors will find they are facing

state regulations more stringent than the BPT, BAT or BCT standards.

When facing a permit situation, prompt contact with the proper regulatory

officials is recommended.

133

F&V SPNOFF/MUNC DISCH

M U N I C I P A L D I S C H A R G E

Introduction

PL 92-500 and PL 95-217 have some subtleties that will increase

costs for your fruit and vegetable plants discharging to municipal systems.

The requirements for industrial cost recovery, user charges and sewer use

ordinances will surely affect many plants. Probably almost 50% of the

fruit and vegetable plants now discharge to municipal systems. However,

with developing regulations and technologies, the future may find many more

plants discharging to municipal systems.

The sewer use ordinance as used is to refer to the "sewer ordinance"

defined as an instrument setting forth rules and regulations governing the

use of the public sewer system. In most cases, the industrial cost

recovery and surcharges (user charges) may be a part of this instrument.

Little can be reported about industrial cost recovery as few municipalities

have imposed the same and an 18 month moratorium has been imposed in PL

95-217. Surcharges will be treated as a section of the sewer use ordinance

although in reality some municipalities pass separate ordinances for user

charges.

Processors must ask themselves what is happening now and what will

happen in the near future. Although charges for industrial wastes began as

early as 1907, as late as 1969 only about 10% of United States municipali-

ties collected these charges. Most municipalities did not have a stringent

sewer use ordinance until after 1960. Most municipalities do not have one

in 1978 although state and federal pressure and encouragement will surely

force most municipalities to draft such an ordinance. Key questions that

must be asked by industrial dischargers is how they can get a reasonable

ordinance that gives both them and the city system protection -- them in

having sewage treatment, at a reasonable cost and the city in preventing

illegal or toxic discharges.

PL 92-500 and EPA require that municipalities institute industrial

cost recovery, a system of user charges and have a sewer use ordinance if

they obtain federal funds for water or wastewater facilities. However, one

must look carefully at exactly what is required. The initial requirements

were modified substantially by PL 95-217.

134


Industry should assist in the development of a "practical and sound

regulatory ordinance fitted to local conditions". Industry should want the

minimum number of restrictions that will protect the municipal system.

These restrictions should be technically sound and rigidly enforced.

Specific Requirements

Sewer use ordinances are largely a matter of local and state

jurisdiction. However, many individuals have been to a town council

meeting and been told that "EPA insists and requires a 28 page document".

There is a difference in what each EPA Regional Administrator requires.

There are seven specific requirements for a sewer use ordinance if Federal

monies are received. These include:

(1) 35.927-4

(2) 35.927-4

35.925-11

(3) 35.935-13

X. (1976 a.)

(4) 4.2.2

(1976 a.)

(5) x.

(1976 a.)

(6) Appendix B. (f)

(1976 a.)

(7) 35.905-6

3)

Prohibit new connections from inflow sources

into sanitary sewers.

Insure that new sewers and connections are

properly designed and constructed.

System of user charges paying proportionate

share of 0 + M.

User charge system must be incorporated.

Equitable system of cost recovery. Note - all

users pay user charge -- not just industrial

users.

Users shall be required to immediately notify

waste treatment plant of any unusual discharge

(flow or waste parameters).

Pretreatment of wastes that would otherwise be

detrimental.

User charges shall be reviewed annually to

assure 0 + M recovery.

Recovery from industrial users of the grant

amount allocable to the treatment of their

wastes.

Review of Proposed Sewer Use Ordinance

The best and perhaps the only time that industry can get input into

a sewer use ordinance is during the passage by the city council or the

135


sewer district board; i.e., the governing body. Normally public hearings

are held but everyone must be most observant for the hearing notice.

The study of a proposed sewer use ordinance requires time and

expertise. However, anyone can read and understand such an ordinance with

a little extra effort.

A description of some key parts of a sewer use ordinance can be found

in Table 31. Each word and sentence can have a real meaning. Industry

management should not only ask the engineer or utilities director to

explain what they meant to say but insist that the ordinance have language

that clearly states the same. For example, does "sample manhole" refer to

the manhole in the street or does it refer to a specially constructed box

with a wier, flow recorder, sampler and sample refrigerator that might cost

as much as $25,000. Specific problems seen in ordinances for fruit and

vegetable plants have included:

- Holding tanks or flow equilization being required - where are you

going to. put the tank?

- Control manhole or sampling facility costing more than $25,000.

- Limitations or prohibitions on BOD, FOG, etc. i.e., BOD less than

300 mg/l, FOG less than 25 mg/l.

- Surcharge for industrial users only with other contributing

commercial customers not charged equally.

Specific review points when considering a sewer use ordinance should

include the following:

- What's it going to cost as proposed - after enactment?

- Are there defacto or real limitations prohibiting your discharge?

- Who is the boss?

- Who handles complaints and reviews decisions?

- Will samples be representative and who pays for sampling and analysis?

- Are there unrealistic limitations - pH, FOG, BOD5?

- Did you review the ordinance before enactment?

- Can you obtain split samples?

- Can you object to unreasonable results? If so, how?

Normally the ordinance is passed by a public body. This is industry's

best chance of getting a receptive audience. They can more easily obtain

changes then than later. The procedures for obtaining changes are

presented in the "Municipal Discharge Spinoff".

136F&V SPNOFF/MUNC DISCH

Table 31. Some Key Parts to A Sewer Use Ordinance

Definitions

Resampling

Mock Bill

Appeal Procedure

Responsible Person

Representative Samples(wastewatercharacteristics)

Waiver (Special Agreement)

When in the event thatmetered water does notequal wastewater

Pretreatment

All key words should be included in thedefinitions. For instance: Doesrepresentative sample mean a grab sample, anaverage of 4 grab samples at 15 minuteintervals or a 24 hour, proportional compositesample?

Does the ordinance contain the specifics ofresampling if industry objects to a particularsample? What are the costs of the resampling?

A clause in a new ordinance can require thecity to sample for a period of 6-12 months toperfect their techniques while billing you on a"mock bill" which does not have to be paid. Ifthere are high charges, you have time toinstitute in-plant changes or pretreatment.

State law probably requires an appeal if anaction is considered unreasonable or injust.However, if a procedure and time schedule forappeal is not specified, an industry may findthemselves without water and sewer for anextended period while court action is followed.

The individual(s) responsible forinterpretation and enforcement should bespecified. Everyone should be aware of anyinterpretable decisions that might be made.

What method(s) is specified for sampling? Isthe sample proportional to flow? What is thefrequency of the samples? Does each sampleperiod give a set of characteristics or aresample periods averaged to determine wastewatercharacteristics?

Does the-ordinance have a special clauseallowing a contract or agreement betweenindustry and the municipality to allowotherwise prohibited flows or concentrations?Who okays such a pact ? Will you be able to getone approved?

There should be a clause allowing plant recordsor metering or engineering studies to establisha percentage of metered water which actuallyleaves in the sanitary sewer which is sampled.Thus a "fair" wastewater load can be estab-lished.

When, who and how is pretreatment or flowequilization required?

137

SEAFOOD SPNOFF/MUNC DISCH

Municipal

Muni

surcharge

compute wa

Charges

cipal charges for industrial plants include water, sewer,

(user charge) and industrial cost recovery. Most municipalities

ter and sewage charges as follows:

Water . . .

Sewer Charge . . .

Surcharge . . .

Industrial Cost

Recovery . . .

(Rules &

Reg. 35.905-6)

Surcharges

Based on water consumption metered into the plant.

Often on a declining block scale so that the cost/

unit decreases as you use more water. Note that

the bill is usually in hundreds of cubic feet

(1 cu. ft. = 7.48 gal.). Cost usually ranges from

$0.10 to $1.00 per 1000 gallons.

Based on computed water charge and usually

represents 10 to 200 % of the water bill. Normally

100% is the most common figure seen in the

Southeast.

Based most often on metered water consumption and a

parameter(s) measured in the wastewater. The most

common factor is BOD5 and usually charged at a

rate of $0.10 to $2.00 per pound for those pounds

in excess of normal sewage. Similarly, the

suspended solids (TSS) load is also used. A

hydraulic load charge is sometimes included and is

often used as a "demand charge" especially for

seasonal operations.

Recovery by the grantee from the industrial users

of a treatment works of the grant amount allocable

to the treatment of wastes from such users pursuant

to section 204 (b) of the Act and this subpart.

(Note that ICR is under review and there may be

some changes.)

Surcharges are often included in a sewer use ordinance. However,

they may be included in a separate ordinance.

Surcharges are usually passed because of local government's problems

such as: (1) Waste treatment costs are rising, (2) More treatment is being

138


required, (3) Loads are often increasing, (4) Property tax is already

overburdened, or (5) because the municipality has received federal funds

and is required to institute user charges.

Any food plant should keep careful records about their surcharge

bill. A plant should keep up with the following in respect to their

surcharge bills:

- For which characteristics are you paying

- Do these vary widely

- Does your flow vary widely

- How does your bill compare with similar plants

Careful attention should be paid to the method the city uses for calcu-

lating the surcharge. Careful attention should be directed toward the

sampling method, sample analysis procedures, flow measurement method and

the validity of the results. A surcharge calculation involves flow

measurement, sampling, sample preservation, sample analysis, laboratory

calculation, and surcharge calculation. An error in any of these will

cause an error in the surcharge bill. However, remember that errors can be

in the plant's favor.

Conclusions

The lack of details is explained in part by the procedure a sewer

use ordinance follows. As a normal rule, the person in charge of the waste

treatment works and planning presents an ordinance drafted by an

engineering firm for approval of the board or council. As the council

members feel incompetent to review and discuss the same, rapid passage is

the rule. Mr. Rankine, an attorney, noted that it is the most important

matter that a sewer regulating authority can pass.

The fruit and vegetable industry is affected because for health and

sanitation, much cleaning and washing results in large amounts of organic

wastes which equate to BOD5. Also, much of the raw material is wasted

in fruit and vegetable processing due to peeling and trimming.

The legal field of sewer use ordinance making is complex and ill

reported. Challenges are usually settled out of court and legal records and

precedents have not been established. The best defense a plant has to a

badly drafted sewer use ordinance is a good lawyer and a friend(s) on the

body responsible for voting on the same. Industries faced with bad ordi-

139


nances must rally their forces and present a united front. City managers

should consult industry when they draft sewer ordinances.

A pact with the city fathers allowing specific exemption for your

wastes is a realistic alternative if an ordinance is in existence with a

clause for such a pact. But, a fruit and vegetable processor should get

the best technical and legal advise before doing this.

In conclusion, your fruit and vegetable plants will probably face the

issues discussed herein within the next several years. It would be to your

benefit to be ready to assist them in these most serious negotiations. You

must tell them to be alert to any indication that a sewer use ordinance is

being developed or revised.

ACKNOWLEDGEMENTS

The development of this program and the preparation of themodules resulted from the collaboration of Drs. Roy E. Carawan, N.C.State University, James V. Chambers, Purdue University, Robert R. Zall,Cornell University and Roger H. Wilkowske, SEA-Extension, USDA.Financial support which supported the development of this project andthe modules was provided by the Science and Education Administration-Extension, U.S.D.A., Washington, D. C., and the Cooperative ExtensionServices of North Carolina, New York and Indiana.

STAFF AND PART-TIME PARTICIPANTS

An Advisory Committee made up of individuals from the foodprocessing industry, equipment manufacturers, regulatory agencies andthe legal profession assisted in the planning and development of thesematerials. The authors appreciate their advice and support.

Much of the information presented in these documents has beengleaned from the remarks, presentations and materials of others. Theircooperation and assistance is appreciated.

Ms. Torsten Sponenberg (Cornell University) provided support indeveloping several modules and chapters. The authors appreciate herinterest, enthusiasm and dedication.

Ms. Jackie Banks (Cornell University) provided many hours of typingand proof-reading needed to pull together the wide array of material inthe different documents. The authors appreciate her contributions.

Mr. V. K. (Vino) Chaudhary (Purdue University) provided support indeveloping the materials on pretreatment and treatment.

Ms. Cindy McNeill (N. C. State University) provided support in thepreparation of the final documents.

Mr. Paul Halberstadt (N. C. State University) provided support in thedevelopment of many of the modules. He also was the principal reviewerand editor for these materials. The authors acknowledge his contributionto this program.

Mrs. Gloria Braxton (N. C. State University) provided typing forseveral of the modules.

Mrs. Judy Fulp (N. C. State University) served as secretary for theproject. She is primarily responsible for typing the materials in the manymodules. The authors deeply appreciate her invaluable contribution.Only through her interest, dedication and hard work were the authors’notes turned into these documents.

Sets of the modules are available from:

Publications OfficeN. C. Agricultural Extension ServiceRicks HallN. C. State UniversityRaleigh, North Carolina 27650

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