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water discharge limits to address Objective 3 of the

CWA: ‘The discharge of toxic pollutants in toxic

amounts is prohibited’. The narrative limits are fully

enforceable. Waste water dischargers must therefore

comply with both local narrative and numerical

limits.

0013 Specific numerical limits are actual physical

concentration limits and represent the water quality

criteria that most waste water treatment plants were

designed to meet. Currently all 50 US states and

US territories have established water quality criteria.

Specific numerical limits are developed by each

state according to the following criteria: the water

body-designated use and the water quality criteria

necessary to protect that designated use. All US

surface waters have been categorized by water

body or segment of water body according to specific

designated beneficial uses. These designated benefi-

cial uses for each water body are established locally

by each state and revised at least every 3 years

through periodic reviews. Examples of designated

beneficial use classifications include public water

supplies, propagation of fish and wildlife, recre-

ational purposes, agricultural, industrial, and navi-

gation.

0014 The exact categories incorporated by each state

may differ; however, the basic principles outlined in

the CWA for support and propagation of aquatic life

and recreation in and on the water are conserved by

all states. States often set specific standards for spe-

cific uses or establish standards to protect individual

species, for example. Special standards are also

established for outstanding national resource waters

(ONRWs). These are ecologically unique waters with

standards set to protect the highest potential water

quality.

0015 The water quality criteria for protecting the desig-

nated beneficial use for each water body are also

established at the state level. The EPA has published

criteria recommendations in the Quality Criteria for

Water 1986 (called the Gold Book), consisting of

scientific information on the effects of specific pollu-

tants on aquatic life or human health. These criteria

are used by state regulatory agencies to establish

enforceable local discharge limits.

The NPDES Permit

0016 The monitoring and enforcement tool of states

and EPA is the NPDES permit. All food-processing

industries that discharge waste water directly to

surface waters in the USA must have an NPDES

permit. To address indirect discharges from industries

to POTWs, the EPA, through CWA authority, estab-

lished the National Pretreatment Program as a

component of the NPDES Permitting Program. The

National Pretreatment Program requires industrial

and commercial dischargers to treat or control

pollutants in their waste water prior to discharge to

POTWs. Indirect dischargers (to a POTW) must meet

specific pretreatment criteria under the authority of

the POTW’s NPDES permit to insure compliance by

the permit holder. Violations of NPDES or pretreat-

ment permit parameters could result in an adminis-

trative order (AO), financial penalties, or revocation

of the permit, resulting in a cease discharge order and

closing the facility. The 5-year NPDES permits con-

tain region and site-specific effluent limits as well as

specific effluent monitoring and reporting require-

ments. The specific numerical limits enforced by the

NPDES permit are categorized as conventional par-

ameters and toxicity limits. These toxicity limits are

based on whole effluent toxicity testing with aquatic

organisms monitoring endpoints such as survival,

growth, and reproduction.

Conventional Parameters

0017Conventional parameters are those pollutants that

were initially targeted under the CWA for reduction.

These parameters include the following:

0018biochemical oxygen demand (BOD)

0019chemical oxygen demand (COD)

0020oil and grease (O&G)

0021total organic carbon (TOC) and total oxygen

demand (TOD)

0022suspended solids (SS) and volatile solids (VS)

0023total dissolved solids (TDS)

0024nitrogen forms

0025phosphorus

0026pH, alkalinity, and acidity

0027heavy metals

0028specific organic compunds

Although effluent limits on these parameters have

reduced the threat of food-processing industry efflu-

ents to human health and the environment, more

stringent controls are necessary to achieve the goals

of the CWA.

Priority Pollutants

0029In 1987 the CWA was amended to require states to

adopt statewide numeric water quality criteria for

toxic pollutants (Section 303(c)(2)(B) of the CWA).

If numerical criteria were not available, the states

were required to adopt criteria based on biological

monitoring or assessment methods. A ‘hit list’ of

regulated toxic compounds has been established over

a period of years; these compounds are generally

referred to as priority pollutants.

EFFLUENTS FROM FOOD PROCESSING/Disposal of Waste Water 1987

The Role of Toxicity Testing in Water

Quality Evaluation

0030 The EPA issued a national policy directive in 1984

entitled Development of Water Quality-Based Permit

Limitations for Toxic Pollutants: National Policy.

The EPA policy established control of toxic dis-

charges through the NPDES permit system. Many

food-processing NPDES dischargers are now being

required to monitor for whole effluent toxicity

(WET) to determine if their waste stream is toxic

under specific low-flow conditions.

0031 A discharge that repeatedly fails the toxicity test

may receive a compliance letter from the state or the

EPA which requires the discharger to perform a tox-

icity reduction evaluation to bring the effluent into

compliance. The EPA policy states that biological

testing of effluents is an important aspect of the

water quality-based approach for controlling toxic

pollutants. Effluent toxicity data, in conjunction

with other data, can be used to establish control

priorities, assess compliance with state water quality

standards, and set permit limitations to achieve those

standards.

Future Developments in Water Quality

Standards

0032 While a major reauthorization of the CWA did not

take place in the late 1990s, focused changes on spe-

cific issues occurred. The Clean Water Action Plan

(CWAP) was released in 1998 and is a broad compre-

hensive program that emphasizes a watershed

management approach to water pollution control,

strengthened existing and proposed new water qual-

ity standards (WQS) for water bodies, and imple-

mented nonpoint source (NPS) controls for water

discharges. The USEPA has a commitment to the

CWAP objectives of restoring and protecting water

resources on a watershed basis and maintaining

a partnership with the States in achieving water

resource goals.

0033 In the coming year(s), EPA will continue to imple-

ment the Total Maximum Daily Load (TMDL) Pro-

gram, as well as other watershed based water quality

initiatives. The States are required to develop lists of

impaired waters. These are waters that do not meet

water quality standards, even after point sources of

pollution (i.e. NPDES dischargers) have installed the

minimum required levels of pollution control equip-

ment. A TMDL specifies the maximum amount of a

pollutant that a waterbody can receive and still meet

water quality standards, and allocates pollutant load-

ings among point and nonpoint pollutant sources.

The draft rule has elicited much interest and debate

from the regulated community and the states due to

the probability that the rule will call for increasingly

stringent effluent limits on point dischargers, resulting

in capital expenditures for larger and more sophisti-

cated waste water treatment plants. Even indirect

dischargers to a POTW will be affected as their dis-

charge limits may be lowered to relieve the burden on

POTWs.

0034The water quality standards also contain antide-

gradation policies which are designed to protect

improvements in water quality and existing high-

quality waters. This would require new or expanding

dischargers to obtain an offset of 1.5 times their

proposed discharge before beginning to discharge.

These proposed offset requirements are in addition

to current Clean Water Act provisions requiring dis-

charge limits to protect water quality standards.

Water quality standards will ultimately play an

important role in the decision making process for

food manufacturers as to where to build new facilities

or relocate for consolidation.

0035Future pollution control strategies can be summar-

ized in two words: waste minimization. With the

1984 congressional amendments to the Resource

Conservation Recovery Act (RCRA), also known

as the Hazardous and Solid Waste Amendments

(HSWAs), the national waste management priority

was shifted from treatment and disposal to waste

reduction and recycling. The EPA defines waste mini-

mization as the changes that can be made to reduce or

recycle waste material that would otherwise have to

be treated and disposed. While this effort initially

focused on hazardous waste generation and disposal,

the effort was soon applied to waste sources in

general and waste water treatment.

0036Waste water reclamation and reuse was a major

focus of waste minimization programs and can

also provide an alternative water supply. The

potential uses for recycled waste water include pro-

cess water, wash water, rinse water and dilution

water. It is evident that waste minimization practices

provide opportunities for water conservation and

water resources management as well as pollution

control.

0037Prior to appropriate recycling or reuse, the waste

water effluent must meet certain criteria for its

intended use. As previously discussed, the conven-

tional parameters may often be limiting factors in the

water quality necessary for an intended use. Waters

high in suspended or dissolved solids, for example,

may not be suitable for reuse without additional

treatment to remove solids. The list of regulated

toxic compounds complicates the issue further as

food-processing establishments use more effective

sanitizing and cleaning agents to meet other

1988 EFFLUENTS FROM FOOD PROCESSING/Disposal of Waste Water

regulatory requirements. (See Cleaning Procedures in

the Factory: Overall Approach; Sanitization.)

0038 Agricultural reuse of waste water has economic

advantages. Considerable benefits are realized by

agricultural growers using reclaimed effluent as a

water source, including a more dependable water

supply and reduced water pumping and fertilization

costs. Additional treatment by carbon filtration, dis-

infection, and reverse osmosis may be required for

subsequent potable water use. Groundwater recharge

with reclaimed waste water is practised in many

areas. Zero discharge processes are being designed

in many modern food processing facilities, utilizing

water reuse and recycling to meet other water needs.

Membrane technologies such as microfiltration,

ultrafiltration, and reverse osmosis, are used for

rinse water recycling and other effluent treatment.

(See Water Supplies: Water Treatment.)

0039 Most industries are resistant to change. As long as

waste water treatment and disposal are economically

viable and water is readily available, waste minimiza-

tion will not be integrated into standard plant prac-

tice. The EPA is promoting waste minimization by

applying increasingly more stringent discharge limits

on all industrial and municipal dischargers. In add-

ition to conventional parameters, the EPA has begun

to emphasize whole-ecosystem impact of pollutant

discharges.

0040 New water quality standards will reflect this em-

phasis. Three main areas of emphasis for future water

quality standards will be sediment toxicity, bioassess-

ment, and ecological risk assessment. Of these three

main areas, sediment toxicity and bioassessment

standards continue to be defined. Evaluating Stand-

ardized and validated sediment toxicity test methods

now exist allowing monitoring of sediment quality.

Because sediment often serves as a reservoir or depot

for toxicant accumulation, monitoring the surface

water itself only provides a partial picture of potential

ecological hazard. Further, toxicity characterization

procedures have been developed for sediments

allowing suspect toxicants to be determined in solid-

phase samples analogous to procedures developed

previously for effluents or surface waters.

0041 Emphasis on whole-ecosystem monitoring and

watershed management has prompted the use of

ecological bioassessment. The most widely utilized

bioassessment practice includes biological surveys

which monitor community structure, biological

diversity, and the presence or absence of pollution

tolerant/sensitive species. Various trophic levels

ranging from benthic invertebrates to fish may be

included in these surveys.

0042 An emerging trend in ecological water quality moni-

toring within a given watershed is the establishment

of site-specific water quality standards. Although the

site-specific water quality monitoring approach has

been used primarily with metals to date, the concept

may eventually be broadly applicable to a large

number of chemicals. This approach essentially com-

pares the toxicity of a specific metal (i.e., Cu, Zn, Pb,

Ni, etc.) to traditional biomonitoring test organisms

in the laboratory prepared synthetic culture water

to?the toxicity of the same metal in the receiving

stream. Because many toxicity mitigating and exacer-

bating factors exist in nature which cannot be

accounted for in the laboratory, this approach pro-

vides a reasonable approach for determining the po-

tential bioavailability (toxic fraction) of the toxicant

in a specific environment. Since no two ecosystems

or watersheds are identical, this approach has merit

in identifying criteria for each specific ecoregion.

In essence, this approach combines the use of labora-

tory biomonitoring testing with the in situ toxicity

monitoring.

0043Several areas have emerged recently in ecological

risk assessment. First, the use of sentinel species to

provide a general indicator of ecosystem health has

become more widely noted within the last several

years. One of the best recent examples of the use of a

sentinel species in monitoring ecosystem health, is the

identification of deformed amphibians in several dif-

ferent locations in North America. Amphibians repre-

sent a sensitive class of animals which have raised

‘environmental flags’ in regions where deformed spe-

cimens have been identified. Not only are amphibians

indicators of general ecosystem health, but are also

potential indicators of risk to the human population.

Obviously, the gap between ecological risk suggested

by an adverse response in a sentinel species and po-

tential human risk must be bridged.

0044Although the significance between the presence of

endocrine disrupting chemicals (EDC) and their

impact in the environment is still being addressed,

the second area of intense focus in ecological risk

assessment is the identification and monitoring of

EDC. Passage in 1996 of the Food Quality Protection

Act (FQPA) and Amendments to the Safe Drinking

Water Act (SDWA) reflected these concerns and

required EPA to develop a screening program using

appropriately validated test systems and other scien-

tifically relevant information to determine whether

certain substances may have an effect in humans

that is similar to an effect produced by naturally

occurring estrogen or other such endocrine effects.

0045Specifically, EPA was required to develop a

screening program by August 1998; to implement

the program by August 1999; and to report to Con-

gress on the program’s progress by August 2000. In

1996, EPA formed the Endocrine Disruptor Screening

EFFLUENTS FROM FOOD PROCESSING/Disposal of Waste Water 1989

and Testing Advisory Committee (EDSTAC), charging

the Committee to provide advice on how to design a

screening and testing program for EDCs. This report

contains the findings of the Committee, and is organ-

ized into sections discussing the EDSTAC recommen-

dations on: a Conceptual Framework; Priority Setting;

Screening and Testing; and Communications and

Outreach. As a result, the EDSTAC recommended

that EPA’s Endocrine Disruptor Screening and Testing

Program (EDSTP) should address both human and

ecological (wildlife) effects; examine effects on estro-

gen, androgen, and thyroid hormone-related pro-

cesses; evaluate endocrine disrupting properties of

both chemical substances and common mixtures.

The Committee determined that a tiered approach

would be most effective in utilizing reasonably avail-

able resources to detect endocrine disrupting chem-

icals and quantify their effects. The core elements of

the approach include initial sorting, priority setting,

Tier 1 Screening (T1S), and Tier 2 Testing (T2T).

EDSTAC recommended that T1S include three in

vitro assays, three in vivo mammalian assays, and

two in vivo nonmammalian assays. Specifically, these

assays included:

In Vitro

1.0046 Estrogen receptor (ER) binding/transcriptional

activation assay,

0047 Androgen receptor (AR) binding/transcriptional

activation assay, and

0048 Steroidogenesis assay with minced testis

In Vivo

1.0049 Rodent 3-day uterotrophic assay (subcutaneous),

0050 Rodent 20-day pubertal female assay with

thyroid,

0051 Rodent 5–7-day hershberger assay, and

0052 Frog metamorphosis assay and fish gonadotropic

assay

EDSTAC recommended that the T2T battery include

a mammalian two-generation reproductive toxicity

study, or a less comprehensive test in accordance

with the guidelines outlined above, and tests address-

ing four additional taxonomic groups, including

amphibians, fish, and invertebrates as follows:

Mammalian Tests

1.0053 Two-generation mammalian reproductive toxicity

study; or

0054 A less comprehensive test:

0055 Alternative mammalian reproductive test or

0056 One-generation test

Multigeneration Tests in Other Taxa

1. 0057Avian reproduction (with bobwhite quail and

mallard),

0058Fish life cycle (fathead minnow),

0059Mysid life cycle (Americamysis), and

0060Amphibian development and reproduction

(Xenopus)

See also: Cleaning Procedures in the Factory: Overall

Approach; Legislation: International Standards; Plant

Design: Basic Principles; Designing for Hygienic

Operation; Sanitization; Water Supplies: Water

Treatment

Further Reading

American Society for Testing and Materials (1993) Stand-

ard Guide for Conducting Sediment Toxicity Tests with

Freshwater Invertebrates, E1383–93. Philadelphia, PA:

ASTM.

Carawan RE (1989) Environmental Issues facing Food

Processors in the 1990s. Proceedings of the 1989 Food

Processing Waste Conference, pp. 217–237. Atlanta,

USA: Georgia Technical Research Institute.

Driscoll TP (1990) Waste Minimization and Product

Recovery in the Crabmeat Processing Industry. Proceed-

ings of the 1990 Food Industry Environmental Confer-

ence, pp. 362–266. Atlanta, GA USA: Georgia Technical

Research Institute.

Fort DJ and Stover EL (1997) Development of short-term,

whole embryo assays to evaluate detrimental effects on

amphibian limb development and metamorphosis using

X. laevis. In: Dwyer FJ, Doane TR and Hinman ML

(eds) pp. 376–390. Environmental Toxicology and Risk

Assessment: Modeling and Risk Assessment, vol. 6,

ASTM STP 1317, Philadelphia, PA: American Society

for Testing and Materials.

Fort DJ and Stover EL (1997) Significance of experimental

design in evaluating ecological hazards of sediments/

soils to amphibian species. In: Dwyer FJ, Doane TR

and Hinman ML (eds) Environmental Toxicology and

Risk Assessment: Modeling and Risk Assessment, pp.

427–442. vol. 6, ASTM STP 1317, Philadelphia, PA:

American Society for Testing and Materials.

Kendall RL and Asaday GH (1989) Environmental Regula-

tions Pertaining to Land Application Systems in the

United States, pp. 1–14. Proceedings of the 1989 Food

Processing Waste Conference. Georgia, Atlanta, USA:

Georgia Technical Research Institute.

London Environmental Protection Agency (1999) Introduc-

tion to the National Pretreatment Program. EPA-833-B-

98-002.

Lounsbury J (1988) A Federal Perspective on Waste Mini-

mization. Proceedings of the 1988 Food Processing

Waste Conference, Section 10, pp. 1–6. Georgia,

Atlanta, USA: Georgia Technical Research Institute.

1990 EFFLUENTS FROM FOOD PROCESSING/Disposal of Waste Water

Richardson SS (1989) Waste Audit – a Self Help Ap-

proach to Waste Reduction. Proceedings of the 1989

Food Processing Waste Conference, pp. 48–62. Georgia,

Atlanta, USA: Georgia Technical Research Institute.

Richardson SS (1990) Waste Reduction in Food Processing.

A People Management Issue. Proceedings of the 1990

Food Industry Environmental Conference, pp. 82–89.

Georgia, Atlanta, USA: Georgia Technical Research

Institute.

Composition and Analysis

M Tarbox, Technology Centre, Kingston Seymour,

Clevedon, UK

This article is reproduced from Encyclopaedia of Food Science,

Introduction

0001 Effluents from food industries show great variability

in flow and composition, are substantially organic

and biodegradable, and tend to become acidic or

start decomposing if their treatment is not immediate.

The food industries considered in the present article

are:

0002 meat and poultry

0003 dairy (processing of milk and milk products)

0004 breweries and distilleries

0005 fruit and vegetable processing, fruit juices

0006 sugar beet

0007 miscellaneous: egg processing, contact drying of

foods, edible oil refining, prepared meals and

foods, fish farming; cider, perry and alcoholic

beverages

Meat and Poultry

0008 Slaughtering and processing operations release

mostly organic materials and the pollutants are

classified by their potential effects on receiving

water rather than as specific chemical compounds.

0009 Meat and poultry effluents are characterized by

high and variable 5-day biochemical oxygen demand

(BOD

), which are influenced by blood content. Im-

proved blood collection is the most effective way of

reducing BOD load. Wide differences in discharge

volumes and strengths exist. Beef abattoirs produce

1.6–10.2 kg BOD per head and 0.4–3.4 m

per head,

whilst poultry processors range over 13–45 kg

BOD per 1000 birds and 20–32 m

per 1000 birds.

Table 1 shows potential pollution loads from modern

slaughterhouses.

0010Suspended solids (SS) are both organic and

inorganic. Fats, oils, and greases (FOG) float on the

surface of water and produce high BOD values.

0011Nitrogen results from breakdown of proteinaceous

materials into amino acids and ammonia.

0012Bacterial counts are high and include a small

percentage of pathogens. Positive results for fecal

coliforms simply indicate the possible presence of

intestinal pathogens. Coliform counts are in excess

of 2 10

per 100 ml, which is comparable to crude

sewage. Hygiene regulations in food factories show

increasing concern to avoid salmonella infection. The

risk of animal diseases, for example, anthrax and

helminthic infection in some parts of the world, is

an important consideration. (See Food Poisoning:

Economic Implications; Parasites: Occurrence and

Detection; Zoonoses.)

Dairy Processing

0013Milk, a major food commodity, is used for market

milk (whole or skimmed, cream), butter, cheeses, an-

hydrous milk for use in icecreams and frozen desserts,

and many other products.

0014Most (90%) of the pollution load in wastes is

derived from dilutions of milk or milk products, but

especially from cleaning and rinsing of residues in

equipment. They are mainly organic, but large

quantities of water are used for cooling or in the

condensers of evaporators. Hygiene requirements

and continuing trends for improved standards result

in extensive use of cleaning compounds and biocides.

(See Cleaning Procedures in the Factory: Overall

Approach.)

0015The high strengths of dairy fluids emphasize

the need to prevent wastage and spillage. The organic

strengths of these materials are assessed by BOD

and chemical oxygen demand (COD). Whole milk

(BOD 100 000 mg l

1

) is about 250 times stronger

tbl0001Table 1 Water volume and pollution per kilogram of carcass

Water volume (m

)

perkg of carcass

Cattle 4.81 Pigs 6.11 Poultry 8.11

Pollution

COD

32.327.321.0

BOD

13.213.29.3

FOG 5.2

Total N 1.6 1.6

SS 11.8 9.3 4.5

Note that tripe and offal processing contributes more than 50% of the total

chemical oxygen demand (COD) pollution.

BOD

, 5-day biochemical oxygen demand; FOG, fats, oils, and greases.

Data from Degre8mont Water Treatment Handbook, 6th edn, vol. 1, 1991.

Paris: Lavoisier.

EFFLUENTS FROM FOOD PROCESSING/Composition and Analysis 1991

than domestic sewage. The major contributors to the

BOD of milk are 4.8% lactose, 3.6% milk fat, 3.5%

protein, and lactic acid. BOD is the generally

accepted parameter for determining the pollution po-

tential, and is the normal basic design parameter for

effluent and sewage treatment plants, despite well-

documented disadvantages of the test, e.g., a 5-day

test with poor reproducibility ( + 20%). The COD

test is relatively simple, cheap, gives better reproduci-

bility ( + 5%), is quick (2.5 h), and is used by many

dairy plants as a monitor of the effluent strength.

Characteristics of Dairy Wastes

0016 Dairy effluents differ in composition from domestic

sewage, often having higher BOD values (up to 2500

mg l

1

), and higher carbon:nitrogen ratios (11:1

compared to 3:1 for sewage). Wide ranges in BOD

and COD are possible, but typical BOD averages are

2500 mg l

1

and for COD 4000 mg l

1

, with BOD:-

COD ratios 0.45–0.67.

0017 The use of BOD coefficients assists in controlling

processing plants. A BOD coefficient of 1.0 kg BOD

per m

milk is equivalent to 1% of all the milk solids

received, representing loss of the milk and product

value and additional costs for effluent treatment.

Wastage may represent 0.5–6.0% of the milk

received, but an efficient plant has low coefficients

(0.5 kg BOD per m

milk received; 0.5 m

water

per m

milk received).

0018 Milk fat losses give high BOD values which can be

quantified in the standard FOG test using non-

aqueous solvent extraction.

0019 Eighty-five percent of the SS in dairy wastes is

organic and noted for poor settlability. The values

typically range from 400 to 2000 mg l

1

0020 The pH value of dairy food waste water is most

influenced by either acidic or alkali cleaning com-

pounds. Variations throughout the working day

typically range from pH 2 to 11, with daily averages

being 4.4–9.4. Temperatures can show wide short-

term variations from 11 to 72



0021 Data from the International Dairy Federation for

a number of countries show waste volumes of 0.5–

37 m

per m

milk, indicating for high values the

presence of cooling and evaporator waters, even

stormwater.

0022 Dairy processing plants show wide fluctuations in

rates of flow, strength, and temperature, which are

compounded by daily and seasonal fluctuations. In

some countries, dairy plants are shut in wintertime.

Quantity and strength of wastes are not related to

plant size or degree of automation as the main factor

is the control of waste (milk). Dairy wastes are free

of toxic compounds, other than those that may be

introduced by the use of cleaning chemicals and bac-

tericidal compounds.

0023Whey from casein and cheese-making is a major

source of pollution (BOD 34 000 mg l

1

; COD 75 000

mg l

1

). Although whey is often considered a waste

product, whey processing methods are utilizing this

material for food and animal feeds.

0024Membrane technology in the dairy and other food

industries uses reverse osmosis modules in a range of

configurations. Spiral-wound modules are well suited

for waste water applications, including whey concen-

tration. (See Membrane Techniques: Applications of

Reverse Osmosis; Principles of Ultrafiltration.)

Breweries and Maltings

0025Brewing is carried out in most parts of the world.

Malting is less widespread in its locations but is a

precursor to brewing since malt is essential to the

fermentation process.

0026Malting of barley is the first stage of brewing and

whisky distilling, producing steep liquor which is a

strong, deeply colored, readily putrescible liquid,

prone to excessive frothing. The waste has high

BOD, low SS, and lacks nitrogen and phosphorus.

The COD:BOD ratio is generally less than 2, with

COD up to 4300 mg l

1

and BOD up to 2300 mg l

1

Brewing

0027In the brewing process, malt and other grains undergo

enzymatic changes when insoluble compounds

(starches) and high-molecular-weight protein com-

pounds are converted to soluble sugars. After a

cooking stage with hops, fermentation using yeast

produces alcohol. Yeast is recoverable for reuse or

use as food supplements and the draught beer is put

into casks. Other beers such as lager, keg, canned, and

bottled are aged in a secondary fermentation stage.

0028Large volumes of strong effluent are produced

from most of the processing stages, but they are

generally less polluting than maltings liquors.

0029Historically, spoilt beer was discharged into sewers

as a requirement by HM Customs and Excise before

allowing duty paid to be reclaimed. This practice

continues under strictly controlled procedures.

0030Brewery wastes comprise 2.4–9.0 m

waste water

per m

beer and 2.3–17.5 kg BOD per m

beer with

typical BOD 775–1622 mg l

1

and COD 1220–2944

mg l

1

and a BOD:COD ratio of 0.67.

Distilleries

0031In the UK, barley and maize are the main carbohy-

drates for the production of whisky, gin, and vodka.

1992 EFFLUENTS FROM FOOD PROCESSING/Composition and Analysis

0032 The initial processes are similar to brewing.

A starch substrate is converted by enzymes into

sugars and then fermented. Conversion is unneces-

sary when using molasses or cane juice. Processes

are optimized to maximize the alcohol yield and

exhaust the fermentable sugars. BOD of spent mash

from cereals averages 12 000–34 000 mg l

1

, with

pH 3.5–4.0.

0033 Spent mash contains large amounts of organic

acids and is liable to rapid anaerobic fermentation

because of the high BOD and COD concentrations,

producing hydrogen sulfide.

0034 Effluents contain yeast and nonfermentable mater-

ials and comprise mainly washing, steaming, cleaning,

and cooling waters, with overall average BOD values

between 400 and 1600 mg l

1

(and up to 10 000 mg l

1

if there is no byproduct recovery).

0035 Waste water and pollution load for a cereal distil-

lery are 0.29 m

waste water per tonne cereal and

3.4 kg BOD per tonne cereal, respectively, assuming

the stillage is used as cattle feed.

Fruit- and Vegetable-Processing

Industries

0036 Waste waters from these industries are mainly

organic; much of the material is dissolved and highly

reactive with bacteria. Special difficulties may arise

owing to their high immediate oxygen demand, sea-

sonal load variations, large variations in strength and

volume, low pH, lack of nutrients, and the influence

of product changes.

0037 Carbohydrates, as simple sugars, such as mono-

and disaccharides, promote acidification.

0038 Waste water pH variations are a common

problem at fruit and vegetable plants. In many

potato-processing plants, most of the pollution load

is from caustic or lye peeling, producing high pH

values, when starch becomes swollen, partly hydro-

lyzed and gelatinized in the process and traces of soil

are rendered colloidal. Lye peeling of potatoes may

create effluent with pH value exceeding 11, BOD

2000 mg l

1

, and COD 3000 mg l

1

. Modern plants

use alternative ‘dry lye’ methods of peeling which give

lower-strength effluents.

0039 Washing and peeling operations for fruit and vege-

table canning and freezing produce 15–30 m

per

tonne of raw product and 8–38 kg COD per tonne

of raw product. Blanching creates approximately

5–10 m

of waste water per tonne of raw product.

0040 Factories packing fruit and vegetables produce

waste waters characterized by soil and plant residues,

detergent cleaning compounds, bactericides, storage

waxing compounds, and citrus-processing com-

pounds.

Fruit Juices

0041Effluents are characterized by low pH due to high

organic acid content, an imbalance of nutrients

dueto low nitrogen and phosphorus, and considerable

fluctuations in volume and loads, with the bulk of the

pollution load dissolved and not readily settlable.

0042Typical waste water from apple processing is

waste water volume 1.2 m

1

, BOD 1.4 kg t

1

COD 2.0 kg t

1

, pH 5.5, BOD 2880 mg l

1

and

COD 6374 mg l

1

Sugar Beet Mills

0043Effluent from sugar beet processing comprises surplus

transport water and wash waters. The concentration

of organic matter increases from the start of the

beet harvesting campaign and reaches a plateau

after 1–2 months. Excess transport water, stored in

large ponds, may be slightly sugary, containing or-

ganic matter such as root hairs, and with a BOD

increasing to 3000 mg l

1

or more by the end of a

campaign.

0044The total water requirement for processing a tonne

of beet is approximately 9–19 m

, and concentrated

effluents have BOD values 4000–5000 mg l

1

. Efflu-

ent volumes using water recirculation are estimated

to be 1.2 m

per tonne of beet, 2–3 kg COD per tonne

and 200–600 kg SS per tonne. COD values are

approximately 1.5 times the BOD value.

Miscellaneous Waste Waters

Egg Processing

0045High BOD (up to 10 000 mg l

1

) and SS owing to

product loss and cleaning processes.

Contact Drying of Foods

0046Evaporation equipment for milk can be used for gum

arabic, flavorings, and caramel. The main effect

occurs when a product is changed, requiring exten-

sive cleaning out and giving high CODs and, for

caramel, high color.

Edible Oil Refining

0047Sources of waste include leaks and cleaning oper-

ations, although refining processes transfer impurities

into water, and there is oil–water emulsion. In

modern refineries, oil production, refining, and wash-

ing stages generate 56–86 kg COD per tonne. Re-

finery wastes show values of BOD 500–6700 mg l

1

SS 540–5850 mg l

1

, and FOG 300–4200 mg l

1

BOD and SS values are directly proportional to

FOG concentration.

EFFLUENTS FROM FOOD PROCESSING/Composition and Analysis 1993

Prepared Meals and Foods

0048 Factories producing prepared meals may do little

processing of raw materials since meat portions are

prepared elsewhere, and vegetables are also generally

preprocessed. Waste waters result from plant and

equipment cleaning, continuously as product mix

changes or as spillages occur. Vegetable rinsing and

blanching, frying, cooking, and cooling water are

other sources.

0049 BOD generation ranges from 9 to 34 kg per

1000 kg of production with waste water concentra-

tions of 600–4000 mg l

1

0050 Waste from frozen bakery products results from

cleaning of equipment and product loss. The major

ingredients (flour, eggs, butter, and sugar) are high in

BOD, SS, and fat; waste water strength is 2100–

4300 mg l

1

, equating to 23 BOD kg per 1000 kg of

product.

0051 Manufacture of salad dressings, mayonnaise, mus-

tard, and sauces produces high-strength waste waters

derived from equipment cleaning, but volumes are

relatively small. Typically BOD values are 2700 mg

1

, but overall waste generation is as low as 8 kg

per 1000 kg product with waste-water volume

0.3 m

per 1000 kg product.

0052 Canneries for soups and baby foods use a variety of

vegetables, meat, starch, and fruit ingredients and

process raw vegetables on site. Waste-water sources

are similar for fruit- and vegetable-processing indus-

tries. Wastes vary greatly in volume and strength;

typical waste generation is 12 kg per 1000 kg raw

product, with BOD value of 560 mg l

1

0053 Factories making jams, preserves, and jellies pro-

duce wastes from cleaning equipment and cooking

vessels and are strong owing to dissolved organic

materials. Examples are 3–7 kg BOD per 1000 kg fini-

shed product with BOD strength 1100–3600 mg l

1

0054 Confectionery production and bakeries generate

high CODs due to sugars and cream, particularly

associated with cleaning of utensils and equipment.

Pollution loads can be considerably reduced by ‘good

housekeeping’ techniques of brushing and collecting

dry materials spilled on floors rather than hosing into

drainage channels. A modern bakery using dry

cleaning methods and silicone grease may have negli-

gible effluent.

0055 In summary, the prepared foods industries generate

typical food-processing wastes with high COD

and BOD concentrations, and organic suspended

solids. The wastes are comparatively low in nutrients

(phosphorus and nitrogen). FOG concentrations

are significant where there is frying. Waste volumes

and loads vary greatly and the following have

been reported for a variety of prepared-food

manufacturers: BOD 310–3200 mg l

1

; COD 560–

7000 mg l

1

; SS 200–3700 mg l

1

; total P 4–

22 mg l

1

;N13–76 mg l

1

; FOG 82–2000 mg l

1

;

with volumes 2.4–85 m

per 1000 kg and waste

loads 5–26 kg BOD per 1000 kg, 9–53 kg COD per

1000 kg of production, and 1–21 kg SS per 1000 kg of

production.

Fish Farming

0056Fish farms continuously abstract high-quality river or

borehole water which is returned to the river contam-

inated by fish excreta and fish food residues. These

large volumes impose considerable pollution loads on

to rivers. Pollution is assessed by BOD, SS, and am-

monia concentrations and stringent standards apply

for Consents to Discharge. Consent is a legal docu-

ment setting out the terms under which an industrial

waste water may be discharged into a public sewer for

conveyance, treatment and disposal by a water com-

pany in England and Wales (or local authorities in

Scotland), or the terms under which the National

Rivers Authority (or River Purification Board in Scot-

land) will allow a water company, local authority,

domestic, or industrial effluent to be discharged into

a watercourse. Consent values for fish farms may be

absolute or differential, typically restricting the max-

imum increase in BOD, SS, and ammonia between

inlet and outlet water to 3 mg l

1

, 6 mg l

1

, and

0.4 mg l

1

, respectively. Similar restrictions on in-

creases apply to color (6 Hazen units), turbidity

(3 Formazin turbidity units), and use of chemicals

for controlling disease, e.g., Malachite Green

(0.1 mg l

1

), formaldehyde (1.0 mg l

1

), and phenolic

compounds (0.005 mg l

1

Cider, Perry, and Alcoholic Beverages

0057There is strong seasonal variation in effluent strength,

peaking in late autumn with processing of new

seasons’ apples and pears. Effluents are characterized

by low pH (a value of 5, sometimes offset where there

is caustic washing of bottles), low SS (200 mg l

1

soluble organic matter giving high BOD (1500–

3000 mg l

1

), and COD (2500–5000 mg l

1

) and neg-

ligible nutrients (N, P).

Analysis of Food Effluents

0058The definitive guidelines for analysis of waters and

effluents in the UK are the HMSO Blue Book series

entitled Methods for the Examination of Waters and

Associated Materials. First published in 1976, the

series consists of individual books giving the method-

ology for both manual and automatic techniques for a

specific parameter or groups of closely related para-

meters. Similar standard methods of analysis are used

1994 EFFLUENTS FROM FOOD PROCESSING/Composition and Analysis

in North America, Europe, and other developed

countries.

0059 The HMSO books are revised only occasionally

and there is a tendency for the specialist laboratories

to develop their own methods or new techniques and

check them against those in the Blue Book. Thus, in

1991, little or no information appears in the Blue

Book series on techniques such as capillary column

gas chromatography, solid-phase extraction, gas

chromatography mass spectrometry, plasma mass spe-

ctrometry, plasma emission, and automated discrete

analysis. (See Chromatography: Gas Chromatog-

raphy; Mass Spectrometry: Principles and Instrumen-

tation.)

0060 For routine work, the water companies generally

take two types of samples from industrial and food-

processing premises. First, spot samples are taken for

quality control and compliance with the limits speci-

fied in the Consent to Discharge. Second, water com-

panies take composite samples for charging purposes.

Where treatment works discharge to rivers, trade

wastes are charged on a volumetric and strength

basis, the strength being assessed by a comparison of

trade sample to domestic sewage using suspended

solids and settled COD values. (At coastal sites, if

there is no biological treatment, a strength factor

based on COD is omitted since charges relate to the

treatment given.)

0061 Laboratories frequently observe that trade samples

undergo a change in pH from the time of sampling to

analysis, by as much as one pH unit. This is particu-

larly noticeable with food wastes, although other

factors such as the time lapse and storage temperature

are influential.

0062 The COD test is performed on the supernatant of

the trade sample which has been settled for 1 h after

the pH has been adjusted to pH 7. As a guide, trade

samples are invariably stronger than they look. Some-

times settled CODs are higher than shaken values

(i.e., unsettled CODs), especially when floating fats

or greases are present.

0063 Treatment plants for both sewage and trade wastes

have biological capacity designed on a BOD basis.

The variability in strength of food wastes requires a

range of dilutions to be used to avoid all the oxygen

being consumed during the 5-day BOD incubation

period. A useful tip is to divide the shaken COD

value by 8, the figure being indicative of the dilution

factor to be used for the BOD test.

0064 If chlorine is in an effluent, this should be removed

before starting the BOD test. If the trade waste has a

high or low pH, this should be adjusted to neutrality

before starting the BOD test.

0065 As a general guide for food wastes, the BOD value

is approximately 50–75% of the COD value, and

abnormally low ratios could indicate, for example,

the presence of biocides.

0066The three most important routine analyses are

BOD, COD, and SS, details of which are given below.

0067BOD. The amount of dissolved oxygen consumed

by microbiological action when a sample is incu-

bated for 5 days at 20



C. Allyl thiourea is added

to the dilution water if it is desired to inhibit

nitrification in a sample containing nitrifying or-

ganisms, so as to obtain a value for carbonaceous

BOD.

0068COD. The amount of oxygen consumed in a

standard arbitrary manner with sulfuric acid and

potassium dichromate upon boiling for 2 h.

0069SS. The solids retained after filtration through a

glass-fiber filter paper (grade C, 70 mm in diam-

eter) followed by washing and drying at 105



0070In certain instances more specific analyses may be

required for analytes relevant to the particular food-

processing operation in question. For example, dis-

solved or suspended tin may be a significant pollutant

from canneries, or heavy-metal catalysts may be lost

from hydrogenation facilities. It should be noted that

in most of these cases significant pollution only arises

from poor manufacturing control, and in these situ-

ations pollution also represents an economic loss.

See also: Chromatography: Gas Chromatography;

Cleaning Procedures in the Factory: Overall Approach;

Food Poisoning: Economic Implications; Mass

Spectrometry: Principles and Instrumentation;

Membrane Techniques: Applications of Reverse

Osmosis; Principles of Ultrafiltration; Parasites:

Occurrence and Detection; Zoonoses