EPA 440/l-74/031_a
Development Document for
Proposed Effluent Limitations Guidelines
and New Source Performance Standards
for the
RENDERER
Segment of the
MEAT PRODUCTS
Point Source Category
p
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UJ
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
AlUST 1974
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DEVELOPMENT DOCUMENT
for
PROPOSED EFFLUENT LIMITATIONS GUIDELINES
and
NEW SOURCE PERFORMANCE STANDARDS
for the
RENDERER
SEGMENT OF THE
MEAT PRODUCTS POINT SOURCE CATEGORY
Russell E. Train
Administrator
James L. Agee
Assistant Administrator for Water and
Hazardous Materials
Allen Cywin
Director, Effluent Guidelines Division
Jeffery D. Denit
Project Officer
August, 1974
Effluent Guidelines Division
Office of Water and Hazardous Materials
U. S. Environmental Protection Agency
Washington, D. C. 20460
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ABSTRACT
This document presents the findings of an extensive study of the
independent rendering industry by the Environmental Protection
Agency for the purpose of developing effluent limitations
guidelines, Federal standards of performance, and pretreatment
standards for the industry, to implement Sections 304(b) and 306
of the Federal Water Pollution Control Act Amendments of 1972
(the "Act") .
The rendering plants included in the study were those plants
specifically processing animal by-products at an independent
plant (i.e., a plant located, operated and managed separately
from meat slaughtering and packing plants). Plants processing
fish by-products and rendering operations carried out as an
adjunct to meat packing plants were not included. Effluent
limitations guidelines are set forth for the degree of effluent
reduction attainable through the application of the "Best
Practicable Control Technology Currently Available," and the
"Best Available Technology Economically Achievable," which must
be achieved by existing point sources by July 1, 1977, and July
1, 1983, respectively. The "Standards of Performance for New
Sources" set forth the degree of effluent reduction which is
achievable through the application of the best available
demonstrated control technology, processes, operating methods, or
other alternatives. The proposed regulations require the best
secondary treatment technology currently available for discharge
into navigable water bodies by July 1, 1977, and for new source
performance standards. This technology is represented by
anaerobic plus aerobic lagoons, or their equivalent. The
recommendation for July 1, 1983 is for the best secondary
treatment and in-plant control, as represented by in-plant
containment and separate treatment or recycle of high strength
waste waters, and a final sand filter added to the 1977
technology. When suitable land is available, land disposal with
no discharge may be a more economical option, particularly for
small plants.
Supportive data and rationale for development of the proposed
effluent limitations guidelines and standards of performance are
contained in this report.
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CONTENTS
Section
I. CONCLUSIONS 1
II. RECOMMENDATIONS 3
III. INTRODUCTION 5
Purpose and Authority 5
Summary of Methods Used for Development of the
Effluent Limitations Guidelines and Standards of
Performance 6
General Description of the Industry 7
Process Description 12
Inedible Rendering 13
Batch System 13
Continuous Systems 18
Edible Rendering -\Q
Cooker Uses and Process Variations 23
Vapor Condensing 24
Grease and Tallow Recovery 25
Solids Processing 26
Odor Control 26
Waste Water Sources 27
Materials Recovery 28
Hide Curing 29
IV. INDUSTRY CATEGORIZATION 31
Categorization 31
Rationale for Categorization 31
Waste Water Characteristics and
Treatability 31
Raw Materials 34
Manufacturing Processes 35
m
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CONTENTS (Continued)
Section
Processing Equipment 36
Size, Age, and Location of Production
Facilities 40
V. WATER USE AND WASTE CHARACTERIZATION 43
Waste Water Characteristics 43
Raw Waste Characteristics 43
Discussion of Raw Wastes 44
Sources of Waste Water 48
Raw Materials Receiving 50
Vapor Condensing 50
Spills and Plant and Truck Cleanup 52
Odor Control 54
Hide Control 54
Miscellaneous Sources 56
VI. SELECTION OF POLLUTANT PARAMETERS 57
Selected Parameters 57
Rationale for Selection of Identified Parameters 57
5-Day Biochemical Oxygen Demand 57
Chemical Oxygen Demand 60
Suspended Solids 60
Total Dissolved Solids 62
Total Volatile Solids 63
Grease 63
Ammonia Nitrogen 64
Kjeldahl Nitrogen 65
Nitrates and Nitrites 66
Phosphorus 66
Chloride 67
Fecal Coliforms 68
PH 69
Temperature 70
VII. CONTROL AND TREATMENT TECHNOLOGY 73
Summary 73
In-Plant Control Techniques 73
Condensables 75
Control of High Strength Liquid Wastes 75
Truck and Barrel Washings 75
Odor Control 76
Plant Cleanup and Spills 7g
IV
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CONTENTS (Continued)
Section £§2®
VII. CONTROL AND TREATMENT TECHNOLOGY (Continued)
In-Plant Primary Treatment 76
Flow Equalization 76
Screens 77
Catch Basins 78
Dissolved Air Flotation 79
Waste Water Treatment Systems 84
Anaerobic Processes 84
Aerated Lagoons 88
Aerobic Lagoons 88
Activated Sludge 90
Rotating Biological Contactor 93
Performance of Various Secondary Treatment
Systems 94
Tertiary and Advanced Treatment 96
Chemical Precipitation 96
Sand Filter 98
Microscreen-Microstrainer 101
Nitrification-Denitrification 103
Ammonia Stripping 106
Spray/Flood Irrigation 107
Ion Exchange 110
VIII. COST, ENERGY AND NONWATER QUALITY ASPECTS 115
Summary 115
"Typical" Plant 124
Waste Treatment Systems 125
Treatment and Control Costs 127
In-Plant Control Costs 127
Investment Costs Assumptions ]27
Annual Cost Assumptions 131
Energy Requirements 132
Nonwater Pollution by Waste Treatment Systems 133
Solid Wastes 133
Air Pollution 134
Noise 134
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CONTENTS (Continued)
Section
IX. EFFLUENT REDUCTION ATTAINABLE THROUGH THE
APPLICATION OF THE BEST PRACTICABLE CONTROL
TECHNOLOGY CURRENTLY AVAILABLE—EFFLUENT
LIMITATIONS GUIDELINES 137
Introduction
I O /
Effluent Reduction Attainable Through the
Application of Best Pollution Control
Technology Currently Available 138
Identification of Best Pollution Control
Technology Currently Available 140
Rationale for the selection of Best Practicable
Control Technology Currently Available 142
Size, Age, Processes Employed, and
Location of Facilities 142
Data Presentation 143
Engineering Aspects of Control Technique
Applications 144
Nonwater Quality Environmental Impact 145
X. EFFLUENT REDUCTION ATTAINABLE THROUGH THE
APPLICATION OF THE BEST AVAILABLE TECHNOLOGY
ECONOMICALLY ACHIEVABLE—EFFLUENT LIMITATIONS
GUIDELINES 147
Introduction 147
Effluent Reduction Attainable Through Application
of the Best Available Technology Economically
Achievable 148
Identification of the Best Available Technology
Economically Achievable 150
Rationale for Selection of the Best Available
Technology Economically Achievable 154
Size, Age, Processes Employed, and
Location of Facilities 154
Data Presentation 154
Engineering Aspects of Control Technique
Applications 156
Process Changes 156
Nonwater Quality Impact 156
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CONTENTS (Continued)
Section
XI. NEW SOURCE PERFORMANCE STANDARDS 159
Introduction 159
EFFLUENT REDUCTION ATTAINABLE FOR NEW SOURCES 159
Identification of New Source Control
Technology 160
Technology Rationale for Section of
New Source Performance Standards 162
Pretreatment Requirements 162
XII. ACKNOWLEDGMENTS 165
XIII. REFERENCES 167
XIV. GLOSSARY 171
Vll
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FIGURES
Number
1 Distribution of Rendering Plants by State 11
2 General Flowsheet of Operations of a Typical
Inedible Rendering Plant 15
3 Batch Cooker Rendering Process 17
4 Continuous Rendering - Duke Process 20
5 Continuous Rendering - Anderson Carver-Greenfield
Process 22
6 Manufacturing Processes of a Rendering Plant 32
7 Average and Range of BOD5 by Raw Material Type 35
8 Average and Range of BOD5 Data by Cooker Type 37
9 Average and Range of BOD 5 Data by Condenser Type 33
10 Average and Range of BOD5 Values for Three Size
Groups of Plants and for All Plants Studied 41
11 Typical Rendering Process and Waste Water Flow
Arrangement 49
12 Suggested Waste Reduction
Program for Rendering Plants 74
13 Dissolved Air Flotation 80
14 Process Alternatives for Dissolved Air Flotation 83
15 Anaerobic Contact Process 87
16 Activated Sludge Process 91
17 Chemical Precipitation 98
18 Sand Filter System 99
19 Microscreen/Microstrainer 102
20 Nitrification/Denitrification 104
21 Ammonia Stripping 10g
ix
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FIGURES (Continued)
Number Page
22 Spray/Flood Irrigation System 109
23 Ion Exchange 109
24 Waste Treatment Cost Effectiveness 130
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TABLES
Number
1 Inedible Tallow and Greases: Use, By-Products,
1960-1970 9
2 Statistics by Employment Size of Establishment,
1967 12
3 Raw Material and Product Yields for Inedible
Rendering by Type of Animal 14
4 Product Yields for Inedible Rendering by Type of
Raw Material 14
5 Raw Waste Water Data on Rendering Plants
by Equipment Type 39
6 Summary of the Plant and Raw Waste Water
Characteristics for the Rendering Industry 45
7 Waste Water Flow and Raw Material Data on Off-Site
Rendering Plants 46
8 Correlation Coefficients of Raw Waste Load
Parameters from the Field Sampling Results 47
9 Summary of Concentrations of Undiluted Condensed
Cooking Vapors 5]
10 Summary of Waste Loads of Undiluted Condensed
Cooking Vapors 53
11 Waste Load Characteristics for Hide Curing at a
Rendering Plant Versus Those for a Tannery 55
12 Measured Waste Strengths of Tank Water and Blood
Water 55
13 Performance of Various Secondary Treatment Systems 95
13A Profile of Typical Plants by Size ]]5
14 Likely Capital Expenditures by Plant Size to Meet
Limitations with Condenser Recirculation as Needed ng
15 Estimated Waste Treatment Costs for Renderers
with High Waste Water Volume -]20
ISA Total Annual and Operating Costs for Renderer
with High Waste Water Volume
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TABLES (Continued)
Number
15B Annual and Operating Costs Per Unit Weight of Raw
Material l41
16 Comparison of Most Likely and Maximum Investment
with Condenser Recirculation 122
17 Total Annual and Operating Costs for a Rendering
Plant to Meet the Indicated Performance '"
18 Annual and Operating Costs Per Unit Weight of Raw
Material for a Rendering Plant to Meet Indicated
Performance 122
19 "Typical" Plant Parameters for Each Plant Size 124
20 Waste Treatment Systems, Their Use and
Effectiveness 126
21 Estimates of In-Plant Control Equipment Cost 128
22 Recommended Effluent Limitation Guidelines for
July 1, 1977 139
23 Effluent Limitations Adjustment Factors for Hide
Curing
24 Raw and Final Effluent Information for Ten
Off-Site Rendering Plants 141
25 Recommended Effluent Limitation Guidelines for
July 1, 1983 149
26 Effluent Limitation Adjustment Factors for Hide
Curing 149
27 Raw and Final Effluent Information for Ten
Off-Site Rendering Plants 151-152
28 Investment and Operating Costs for New Source
Performance Standards 160
29 Conversion Table 180
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SECTION I
CONCLUSIONS
The study presented herein is a part of an overall investigation
of the meat processing (no slaughtering of animals accomplished
in the plants) and rendering (accomplished independent of
slaughterhouses, packinghouses and poultry processors) industry
segments of the meat products point source category.
Because of evidence developed early in the investigation, it
became apparent that meat processing operations differed
materially from rendering operations as to raw materials,
processes, products and other factors. As a result, an initial
categorization which split the two industry segments was utilized
to facilitate a thorough analysis with a separate study report
for each, with the rendering industry segment presented herein.
A conclusion of this study is that the rendering industry con-
stitutes a single category. Unless otherwise specifically
designated, all subsequent discussions of the rendering industry,
or references to the rendering industry, deal with the
independent rendering operation or plants not included as a part
of livestock or poultry slaughtering, packing or processing.
The primary criterion for the establishment of the category was
the 5-day biochemical oxygen demand (BOD5) in the total plant raw
waste water. Other criteria were plant size and type of
processing equipment used in the plant. Information relating to
other pollutants and the effects of such parameters as age and
location of plants, type of raw material, production processes,
and treatability of wastes all lent support to the categorization
decision.
The wastes from rendering plants are amenable to biological
treatment processes, and no materials harmful to municipal waste
treatment processes were found.
The 1977 discharge limits for BOD5, suspended solids, and grease,
representing the average of the best treatment systems in the
rendering industry, are currently being met by a number of plants
included in the survey. Several of the plants meeting the limits
discharge waste water to receiving waters, while a number of
other plants, particularly small plants, meet the limits by
irrigating or ponding waste waters. These limits, plus a fecal
coliform limit, are recommended for 1977. The same limits plus
limitations on ammonia are recommended for new sources. The
limits for ammonia and phosphorus are recommended for new
sources. The nutrient limits for new sources represent limits
being met by the majority of plants with the best treatment
systems. It is estimated that there will be about $2.1 million
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in capital costs required to achieve the 1977 limits by the
industry.
For 1983, effluent limits were determined as the best achievable
in the industry for BOD5, suspended solids, ammonia, and
phosphorus.
It is estimated that the cost to achieve the 1983 limits by the
industry will be $8.9 million. The 1977 cost for the industry
represents about 7 percent, and the 1983 cost approximately 30
percent of the $30 million spent by the industry in 1972 on new
capital expenditures.
It is also concluded that, where suitable and adequate land is
available, land disposal is a more economical option for meeting
discharge limits, particularly for small plants.
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SECTION II
RECOMMENDATIONS
Limitations recommendations for discharge to navigable waters by
rendering plants for July 1, 1977 are based on the
characteristics of well operated secondary treatment plants being
used by the industry. The limitations are for 5-day biochemical
oxygen demand (BOD5) , suspended solids, grease, and fecal
coliform. These limitations are 0.15 kg BOD5/kkg raw material
(RM); 0.17 kg SS/kkg RM; 0.10 kg grease/kkg RM; and 400 counts
fecal coliform/100 ml. Adjustments in the BOD5 and SS
limitations are provided for plants curing hides.
Recommended New Sources Standards include the 1977 limitations
plus limitations on ammonia (NH3J, nitrites and nitrates (NO2~
NO3) , and total phosphorus (TP). The additional limitations are
also based on the performance characteristics of well operated
secondary treatment plants. These additional limitations are:
0.17 kg NH3 as N/kkg RM; and 0.05 kg TP/kkg RM.
Limitations recommended for the industry for 1983 are
considerably more stringent and are based upon the performance
characteristics of the best operated secondary treatment systems
being used to treat rendering waste waters. These limitations
include the same pollutant parameters as included in the new
source standards plus a limitation on the total Kjeldahl nitrogen
(TKN) and on pH range. The 1983 limitations are: 0.07 kg
BOD5/kkg RM; 0.10 kg SS/kkg RM; 0.05 kg grease/kkg RM; 0.02 kg
NH3 as N/kkg RM; 0.05 kg TP/kkg RM; a pH range of 6.0 to 9.0; and
a fecal coliform count of 400/100 ml. Again, adjustments in the
BOD5 and SS limitations are provided for plants curing hides;
however, these adjustments are smaller than those for the 1977
limitations.
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SECTION III
INTRODUCTION
PURPOSE AND AUTHORITY
Section 301(b) of the Federal Water Pollution Control Act
Amendments of 1972 (the Act) requires the achievement by not
later than July 1, 1977, of effluent limitations for point
sources, other than publicly owned treatment works, which are
based on the application of the best practicable control
technology currently available as defined by the Administrator
pursuant to Section 304 (b) of the Act. Section 301(b) also
requires the achievement by not later than July 1, 1983, of
effluent limitations for point sources, other than publicly owned
treatment works, which are based on the application of the best
available technology economically achievable which will result in
reasonable further progress toward the national goal of
eliminating the discharge of all pollutants, as determined in
accordance with regulations issued by the Administrator pursuant
to Section 304(b) of the Act. Section 306 of the Act requires
the achievement by new sources of a Federal standard of
performance providing for the control of the discharge of
pollutants which reflects the greatest degree of effluent
reduction which the Administrator determines to be achievable
through the application of the best available demonstrated
control technology, processes, operating methods, or other
alternatives, including, where practicable, a standard permitting
no discharge of pollutants.
Section 304(b) of the Act requires the Administrator to publish
regulations providing guidelines for effluent limitations setting
forth the degree of effluent reduction attainable through the
application of the best practicable control technology currently
available and the degree of effluent reduction attainable through
the application of the best control measures and practices
achievable including treatment techniques, process and procedure
innovations, operation methods and other alternatives. The
regulations proposed herein set forth effluent limitations
guidelines pursuant to Section 304(b) of the Act for the
independent renderers sutcategory of the meat products point
source category designated in Section 306.
Section 306 of the Act requires the Administrator, within one
year after a category of sources is included in a list published
pursuant to Section 306 (b) (1) (A) of the Act, to propose
regulations establishing Federal standards of performance for new
sources within such categories. The Administrator published in
the Federal Register of January 16, 1973 (38 F.R. 1624) a list of
27 source categories. Publication of the list constituted
announcement of the Administrator's intention of establishing the
off-site rendering plants engaged in the manufacture of animal
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and marine fats and oils source category, which was included in
the list published January 16, 1973.
SUMMARY OF METHODS USED FOR DEVELOPMENT OF THE EFFLUENT
LIMITATIONS GUIDELINES AND STANDARDS OF PERFORMANCE
The effluent limitations guidelines and standards of performance
proposed herein were developed in the following manner. The
point source category was first studied for the purpose of
determining whether separate limitations and standards are
appropriate for different segments within a point source
category. This analysis included a determination of whether dif-
ferences in raw material used, product produced, manufacturing
process employed, equipment, age, size, waste water constituents,
and other factors require development of separate effluent
limitations and standards for different segments of the point
source category. The raw waste characteristics for each segment
were then identified. This included an analysis of (1) the
source and volume of water used in the process employed and the
source of waste and waste waters in the plant; and (2) the
constituents (including thermal) of all waste waters including
toxic constituents and other constituents which result in taste,
odor, and color in water or aquatic organisms. The constituents
of waste waters which should be subject to effluent limitations
guidelines and standards of performance were identified (see
Section VI). The result of this analysis was that there was no
reason for separate limitations and standards for different
segments of the industry.
The full range of control and treatment technologies existing
within the point source category was identified. This included
identification of each distinct control and treatment technology,
including an identification in terms of the amount of
constituents (including thermal) and the chemical, physical, and
biological characteristics of pollutants, and of the effluent
level resulting from the application of each of the treatment and
control technologies. The problems, limitations and reliability
of each treatment and control technology and the required
implementation time was also identified. In addition, the
nonwater-quality environmental impact, such as the effects of the
application of such technologies upon other pollution problems,
including air, solid waste, noise and radiation were also
identified. The energy requirements of each of the control and
treatment technologies were identified as well as the cost of the
application of such technologies.
The information, as outlined above, was then evaluated in order
to determine what levels of technology constituted the "best
practicable control technology currently available," "best
available technology economically achievable," and the "best
available demonstrated control technology, processes, operating
methods, or other alternatives." In identifying such
technologies, various factors were considered. These included
the total cost of application of technology in relation to the
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effluent equipment and facilities involved, the process employed,
the engineering aspects of the application of various types of
control techniques, process changes, nonwater-quality
environmental impact (including energy requirements) and other
factors. The data for identification and analysis were derived
from a number of sources. These sources included Refuse Act
Permit Program data; EPA research information; data and
information from North Star files and reports; a voluntary
questionnaire issued through the National Renderers Association
(NRA); qualified technical consultants; and on-site visits and
interviews at several exemplary rendering plants in various areas
of the United States. Questionnaires provided information on 49
plants; 12 of these were also included in the field sampling
survey. Two other plants that did not submit questionnaires were
also sampled. Thus, the total number of plants included in this
study was 51, or about 11 percent of the off-site rendering
industry. All references used in developing the guidelines for
effluent limitations and standards of performance for new sources
reported herein are included in Section XIII of this document.
GENERAL DESCRIPTION OF THE INDUSTRY
The off-site rendering industry falls within industry No. 2077,
Animal and Marine Fats and Oils.1 SIC 2077 includes;
"Establishments primarily engaged in manufacturing animal
oils, including fish oil and other marine animal oils and
fish and animal meal; and those rendering inedible grease and
tallow from animal fat, bones, and meat scraps.
Establishments primarily engaged in manufacturing lard and
edible tallow and stearin are classified in Group 201; those
refining marine animal oils for medicinal purposes in
Industry 2833; and those manufacturing fatty acids in
Industry 2899.
"Fish liver oils, crude Oil, neat's-foot
Fish meal Oils, animal*
Fish oil and fish oil Oils, fish and marine animal: herring,
meal menhaden, whale (refined), sardine
Meat meal and tankage* Rendering plants, grease and tallow*
Neat's-foot oil Stearin, animal: Inedible"
Oil and meal, fish
*The off-site rendering industry covered in this report includes
only meat-meal and tankage; oils, animal; and rendering plants,
grease and tallow.
Rendering is a process to convert animal by-products into fats,
oils, and proteinaceous solids. Heat is used to melt the fats
out of tissue, to coagulate cell proteins and to evaporate the
raw material moisture. Rendering is universally used in the
production of proteinaceous meals from animal blood, feathers,
bones, fat tissue, meat scraps, inedible animal carcasses, and
animal offal. The rendering industry consists of off-site or
7
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independent Tenderers and on-site or captive renderers. The
independent renderers reprocess discarded animal materials such
as fats, bones, hides, feathers, blood, and offal into saleable
by-products, almost all of which are inedible for human
consumption, and "dead stock" (whole animals that die by accident
or through natural causes). Captive rendering operations, on the
other hand, are usually conducted as an adjunct to meat packing
or poultry processing operations and are housed in a separate
building on the same premises. consequently, captive renderers
produce almost all of the edible lard and tallows made from
animal fats in addition to producing inedible by-products. Two
usual process differences between rendering edible or inedible
materials are the composition and freshness of the materials,
and, second, the process used. Edible rendering requires fresh
(inspected) fats and usually is conducted by a wet or low
temperature process. These processes do not evaporate raw
material moisture during cooking, and therefore require an
additional step to separate water from the edible products.
Inedible rendering is accomplished exclusively by dry rendering
where the raw material is cooked with no addition of steam or
water.
Rendering of animal by-product materials is one of the original
recycling industries; it began as an industry over 150 years ago.
During the past two decades the production of inedible tallow and
grease (the major products of rendering plants) has increased
from 2.3 billion pounds, worth $150 million in early 1950, to an
estimated 5.4 billion pounds, worth $430 million for 1971-72.2
This increase is largely caused by an expansion in livestock and
poultry production. The increase resulting from increased plant
efficiency is negligible.
The United States is the world's leading producer, consumer, and
exporter of tallow and grease. Since the early 1950's, the
United States has accounted for 55 to 60 percent of the world's
tallow and grease output. The export market has been the largest
single outlet for inedible tallow and grease, consuming about 50
percent of the domestic output. Table 1 lists the various
markets for inedible tallows and greases and shows the current
use of tallow and grease in both soap and fatty acid
manufacturing to be about one-half of that for animal feeds. It
also shows that between 1960 and 1970 there was a slight decrease
in their use for soap manufacturing, which is more than offset by
a 2.5 times increase in their use for animal feeds.
Off-site renderers send out trucks daily on regular routes to
collect discarded fat and bone trimmings, meat scraps, bone and
offal, blood, feathers, and entire animal carcasses from a
variety of sources: butcher shops, supermarkets, restaurants,
poultry processors, slaughterhouses, and meat packing plants,
farmers and ranchers. Each day the rendering industry, including
both on-site and independent plants, processes more than 80
million pounds of animal fat and bone materials, in addition to
dead stock, that would otherwise have to be suitably disposed of
to prevent its becoming a national public health problem.3
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Table 1. Inedible Tallow and Greases: Use, By-Products, 1960-1970^
Year
Beginning
October
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970*
Soap
732
702
688
660
690
649
665
631
637
601
615
Animal
Feeds
Fatty
Acids
443
732
774
861
714
855
972
990
1061
1093
1140
351
402
433
478
530
575
547
576
585
610
568
Lubricants
and Similar
Oils
Million Pounds
70
79
78
91
102
107
98
89
98
97
89
Other
Exports
151
177
151
230
203
208
283
291
289
320
214
1769
1710
1738
2338
2155
1962
2214
2212
2009
2051
2591
Total
3516
3802
3862
4658
4394
4356
4779
4789
4679
4772
5217
*Preliminary data; based on census reports,
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The independent renderer pays for the raw material he collects
and he manufactures usable products, such as tallow for soap^and
for derivatives for the chemical industry, and meal and inedible
grease for animal and poultry feed. Because of the perishable
nature of the raw material collected, renderers must process the
material without delay. This normally restricts the collection
area to a 150-mile radius around the plant. However, if the
renderer is only picking up restaurant grease, which is more
stable, it is possible that he may travel greater distances.
Off-site renderers are located in both urban and rural areas.
The urban renderer normally has more modern equipment, shorter
routes for pick-up of raw materials, a better grade of raw
materials, and high production rates that enable his operation to
run more efficiently. The urban renderer usually has access to
municipal sewer and has the option of either providing his own
treatment system or buying into the municipal plant. The country
renderer, on the other hand, normally has older equipment, longer
routes, picks up dead stock, and has a lower capacity system.
The location of the rural renderer does not permit him to tie
into a sewer facility and, therefore, he normally has his own
waste treatment facilities.
Figure 1 provides a general idea of the distribution of all
rendering plants throughout the country; it includes both edible
and inedible rendering plants, on-site as well as independent.
Also, fish rendering plants are included in the state totals.
Judging from Figure 1, the number of rendering facilities is
greatest in the central states. However, the National Renderers
Association indicated that production from facilities along the
Atlantic seaboard equals that from facilities located between the
Appalachian Mountains and the Rockies.
Data from the 1967 Census of Manufactures* is summarized in Table
2. These data provide some information regarding the size of
existing rendering plants. However, since the data reflect only
69 percent of the industry, the distribution of plant sizes
should be considered only approximate. Plants range in size from
small operations employing one to four men with annual sales of
about $100,000 to large operations employing over 100 men with
sales from $5 to $10 million. An average plant could be
characterized as employing 23 men and having annual sales of
approximately $1 million. Judging from our recent observations
of the industry, it would appear that these figures are no longer
correct, since many companies have consolidated their plants and
installed more modern gear with larger capacities. However,
because we measured size not by products, but rather by amount of
raw material handled, it is difficult to make an exact
comparison. In any event, based on the assumption that the
average size plant is as found in this study—a plant handling
59,000 kg (130,000 pounds) per day of raw material—and based on
average yield values and on current market prices, the average
plant would have annual sales of about $1.5 million.
10
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Figure
1. Distribution of Rendering Plants by State2
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As of 1968 -there were 770 firms operating in 850 facilities
engaged in the rendering of inedible animal matter.2 Of this
number, some 460 were operated by independent renderers (off-
site) , 330 were controlled by the meat packing and poultry
industries (on-site), and the remainder were owned by a variety
of concerns. It is estimated that some 275, or about 83 percent,
of the plants controlled by the meat industry are also involved
in edible rendering. The industry estimates that the number of
independent
Table 2. Statistics by Employment Size of Establishment, 1967^
Establishment
With an Average
of:
1 to 4 employees
5 to 9 employees
10 to 19 employees
20 to 49 employees
50 to 99 employees
100 to 249 employees
TOTALS
Number of
Establishments
132
103
127
157
51
18
588
Number of
Employees
300
700
1800
4800
3500
2600
13,700
Value of
Shipments
(millions of
dollars)
12.0
27.9
62.2
207.1
117.1
131.0
557.9*
*Total value of shipments from all sources.
renderers is now 450 or less, and they expect an additional 50
plants, primarily small, to close because of the economic impact
on capital investment caused by enforcement of new air and water
pollution standards.5 This conclusion is based on the argument
that, because tallow and protein meal products from rendering
plants must compete on the open commodity market, pollution
control costs can not be passed off to the consumer as is done in
the other industries where prices are raised to absorb these
costs.
PROCESS DESCRIPTION
A general flow sheet of the processes of a typical inedible,
independent rendering plant is shown in Figure 2. (A general
flow sheet for edible rendering would be similar.) The bulk
material (offal, bones, and trimmings) collected by independent
renderers is normally dumped into a pit from which it is conveyed
12
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to a grinder. Liquid wastes collected on the bottom of the pits
are usually sewered, although in a few cases the liquid, if not
an excessive amount, is pumped on top of the materials being
conveyed to the grinder or the cooker. In the case of poultry
offal, it is not always necessary to grind the raw material
before cooking unless it contains a large number of whole birds.
Feathers, if they are not mixed with poultry offal, are dumped
directly on a floor to allow excess liquid to drain off. Off-
site rendering plants normally process feathers separately from
poultry offal. Oils are poured into receiving tanks and from
there go directly to cookers.
The process of rendering consists of two essential steps. First,
the raw material is heated or cooked to melt the tallow or grease
and permit the phases to separate and, in the dry inedible
process, to evaporate the moisture. Also, the animal fibrous
tissues are conditioned. The second step is a separation of
tallow or grease from the solid proteinaceous material. Proper
conditioning of the fibrous tissue is important to accomplish the
second step efficiently. In edible rendering little, if any, of
the raw material moisture is evaporated; the cooking is normally
conducted at a lower temperature (49°to 82°C, or 120° to 180°F)
to improve the quality of the grease and tallow. However, since
this is done almost exclusively by on-site renderers, it will not
be discussed in great detail in this report.
The product yields and process control of the cookers are very
dependent on the nature of the raw materials., For example, the
moisture content of raw materials ranges from 20 percent moisture
for beef fats to 87 percent moisture for blood. Tables 3 and 4
give the percentage of yield of a number of common materials
processed by independent rendering plants. The percentage of
moisture, of course, can be calculated by subtracting the total
percentage of yield of fat and solids from 100 percent.
Additional information on the amount and type of animal by-
products processed for various animal sources and on product
yields can be found in reference 6 which is also the source of
the information presented in Tables 3 and 4.
INEDIBLE RENDERING
Batch System
Note: Throughout the discussion of production methods
and concepts which follows, the use of trade names is
included as necessary to facilitate the explanations
presented and understanding by the reader. Use of such
trade names, however, should in no way be construed as
a product endorsement or recommendation by the U. S.
Environmental Protection Agency.
Batch rendering, a dry process, is a cooking and moisture-
evaporation operation performed in a horizontal steam jacketed
cylindrical "cooker" equipped with an agitator. It is referred
13
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Table 3. Raw Material and Product Yields for Inedible Rendering by Type of Animal
By-Products from Animals
Steers
Cows
Calves
Sheep
Hogs
Broilers (offal & feathers)
Offal and Bone
per Head,
kg (lb)
41-45 (90-100)
50-57 (110-125)
6.8-9.1 (15-20)
3.6-4.5 (8-10)
4.5-6.8 (10-15)
0.45 (1)
Tallow and
Grease,
Percent
15-20
10-20
8-12
25-35
15-20
4
Cracklings
at 10-15% Fat,
Percent
30-35
20-30
20-25
20-25
18-25
26
Table 4.
Product Yields for Inedible Rendering by Type of
Raw Material6
By-Products from
Materials
Shop fat and bones
Dead cattle
Dead cows
Dead hogs
Dead sheeu
Poultry offal (broiler)
Poultry feathers
Blood
Tallow and
Grease ,
Percent
37
12
8-10
30
22
14
—
—
Cracklings
at 10-15% Fat,
Percent
25
25
23
25-30
25
4
12 (meal)
12-14 (meal)
14
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PROCESSES
WASTE WATER
DRYING
RAW MATERIAL
RECOVERY
CRUSHING AND
GRINDING
COOKING
AND MOISTURE
REMOVAL
LIQUID -SOLID
SEPARATION
LIQUID
I MEAL GRINDING
j AND SCREENING
BLENDING
SOLIDS
MEAL
STORAGE
SHIPPING
HIDE
CURING
GREASE
CLARIFYING
GREASE
STORAGE
SHIPPING
ODOR
CONTROL
VAPOR
CONDENSING
__ _.J
PLANT AND
TRUCK WASHING
1
MATERIAL
RECOVERY
SYSTEM
T
SANITARY
FACILITIES
TREATMENT
SYSTEM
•WASTE WATER FLOW
•*- PRODUCT AND MATERIAL FLOW
Figure 2. General Flowsheet of Operations for a Typical Inedible Rendering Plant
15
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to as a dry rendering process because the raw material is cooked
with no addition of steam or water and because the moisture in
the material is removed from the cooker by evaporation. It. is a
batch process because it follows the repetitive cycle of charging
with raw material, cooking under controlled conditions, and
finally discharging of the material. A typical modern batch
rendering process is illustrated schematically in Figure 3.
Although only one cooker is shown, the usual installation will
have from three to ten cookers.
Before charging the dry batch cookers, the raw material is
usually reduced in size by crushers (sometimes called grinders,
prebreakers, or hoggers) to a size of one to two inches to
provide for efficient cooking. Cooking normally requires 1.5 to
2.5 hours, but may run as long as 3.5 to 4 hours. The cookers
are charged with raw material by either a screw conveyor or by
blowing the material in under pressure from a "blow tank." The
raw materials used are quite variable, depending on the source,
and adjustments in cooking time, temperature, and speed of
agitation are usually required to properly process the material.
For example, shop fat and bone from butcher shops may yield 37
percent tallow and have an initial moisture content of only 40
percent; dead beef cattle, when processed, may yield only 12
percent tallow and have an initial moisture content of 63
percent. Then again, poultry feathers, which yield no grease,
and may have an initial moisture content of 75 percent, require
cooking under pressure (about 3.7 atmospheres or 40 psig) for 30-
45 minutes in a batch cooker for hydrolysis, prior to cooking
under normal or atmospheric pressure for an additional 30-40
minutes to reduce the rroisture content to 40-50 percent.
Finally, the feathers are dried in a rotary or ring dryer to
reduce the moisture content to 5 percent.
The general practice in determining the end point of the cooking
operation is by previously established cook cycles and by
periodic withdrawal of samples by the operator to determine the
consistency by touch of the cooked material. A less frequently
used method is to measure the moisture content of the material
with an electrical conductivity device, but this approach has not
been generally successful; it is ineffective when cooking blood
or a variety of other materials. Temperature is used to follow
the progress of the cooking. The temperature of the material
being processed remains substantially constant until the moisture
level has dropped to 5 to . 10 percent. At this point the
temperature begins to rise rather rapidly and the cooking process
should then be stopped to prevent product degradation and odor
problems. Throughout the cook, the jacket stream pressure
usually is maintained constant, between 2.7 and 6.1 atmospheres
(25 and 75 psig), although a few use a pressure as great as 7.8
atmospheres (100 psig) or a temperature of 170°C (334°F).
The cooked material is discharged from the batch cooker into a
percolation pan and let stand until all free-draining fat has run
off. The solids are then conveyed to a press (usually screw
16
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Dead Stock Carcasses
I
Shop Fat
and Bone
RAW MATERIAL RECEIVING
ENTRAPMENT SEPARATOR
Exhaust Vapor
CRUSHER
Steam - 25-75 PS I •
•u
-r~i
(fir"!
II
COOKER
V fl
II /
Jacket Condensate —/
PRECOAT
LEAF FILTER
CENTRIFUGE
Solids to Screw Press
PERCOLATOR
— DRAIN PAN
Figure 3. Batch Cooker Rendering Process
-------
press) to further reduce the fat content. Finally, the solids
are conveyed to grinding and screening operations.
Prior to ten years ago, essentially all inedible rendering at
independent rendering plants was conducted using the dry batch
cookers. In recent years, however, a number of plants have
replaced batch cookers with continuous systems because these
systems offer inherent advantages: improved product quality
control; better confinement of odor and fat aerosol particles
within the equipment, thereby requiring less cleanup; less space;
and less labor for operation and maintenance. Also, continuous
systems permit increased throughput and occasionally result in
consolidation of two or more plants. It is currently estimated,
however, that 75 to 80 percent of the plants still use dry batch
cookers. The percentage of batch cookers is expected to continue
to decrease in the near future for economical reasons, but it is
very doubtful that it will ever be entirely replaced by
continuous systems. This is because most small plants could not
afford continuous sytems and because some materials such as
feathers and fclood are better handled in a dry batch system.
Continuous Systems
Continuous rendering systems, as mentioned above, have replaced
some batch systems. A continuous system has the ability to
provide an uninterrupted flow of material and to produce a
product of more constant quality- In addition, the residence
time in some continuous systems is much less than in batch
systems, ranging between 30 and 60 minutes; as a result of less
exposure to heat, product quality is improved. An inherent
disadvantage of the continuous system is that when a component
breaks down, the entire plant is shut down. Hence, it is
important that a thorough preventive maintenance program be
rigidly followed to keep the plant in operation.
Unlike batch systems, the manufacturers of continuous systems do
not use the same basic design. Currently there are at least
three major manufacturers of continuous systems being used by
independent renderers. These three companies are the Duke
continuous system, manufactured by the Dupps Company; the
Anderson C-G (Carver-Greenfield) system, manufactured by
Anderson-Ibec; and the Strata-Flow System manufactured by
Albright-Nell Co.
Duke Rendering System
The Duke System was designed to provide a method of cooking
similar to that of batch systems except that it operates
continuously. This system is illustrated in Figure 4. The
cooker, called the Equacooker, is a horizontal steam-jacketed
cylindrical vessel equipped with a rotating shaft to which are
attached paddles that lift the material and move it horizontally
through the cooker. Steam-heated coils are also attached to the
18
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shaft to provide increased heat transfer. The Equacooker con-
tains three separate compartments which are fitted with baffles
to restrict and control the flow of materials through the cooker.
The feed rate to the Equacooker is controlled by adjusting the
speed of the variable speed drive for the twin screw feeder; this
establishes the production rate for the system. The discharge
rate for the Equacooker is controlled by the speed at which the
control wheel rotates (see Figure 4). The control wheel contains
buckets similar to those used in a bucket elevator that pick up
the cooked material from the Equacooker and discharge it to the
Dranor. Next to the control wheel is located a site glass column
which visually shows the operating level in the cooker. A
photoelectric cell unit is provided to shut off the twin screw
feeder when the upper level limit is reached.
The Drainor performs the same function as a perculator pan in the
batch cooker process. It essentially is an enclosed screw
conveyor that contains a section of perforated troughs allowing
the free melted fat to drain through as the solids are conveyed
to the Pressor or screw press for additional separation of
tallow. The Pressor is similar to any other screw press used
along with a batch cooker to reduce the grease level of the
crackling.
A central control panel consolidates the process controls for the
Duke system. The control panel houses a temperature recorder,
steam pressure indicators, equipment speed settings, motor load
gages, and stop and start buttons, allowing one person to operate
the Equacooker part of the Duke system.
C-G (Carver-Greenfield) Continuous System
The C-G continuous process is of a considerably different design
than the Duke system. Figure 5 is a schematic diagram of a one-
stage evaporator C-G system. In the C-G system, the partially
ground raw material is fed continuously by a triple screw feeder
at a controlled rate to a fluidizing tank. Fat recycled through
the C-G system at 104°C (220°F) suspends the material and carries
it to a disintegrater for further size reduction—the final range
is from about one inch to 1/4-inch pieces. This slurry is then
pumped to an evaporator. The evaporator can be a single or
double-stage unit, and is held under vacuum. The vacuum, which
facilitates moisture removal, allows the C-G system to operate at
a lower temperature than some other systems. The evaporator
system is basically a vertical shell-and-tube heat exchanger
connected to a vacuum system. The slurry of solids and fat flows
by gravity through the tubes of the heat exchanger (evaporator),
while steam is injected into the shell. The water vapor is then
separated from the slurry in the vapor chamber, which is under a
vacuum of 660 to 710 mm (26 to 28 inches) of mercury. Water
vapor then passes through a shell and tube condenser connected to
a steam-ejection vacuum system. The condensed vapors are removed
from the condenser through a barometric leg, which helps maintain
19
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VAPOR CONTROLLER
RAW
MATERIAL
BIN
MAGNET
TWIN SCREW
FEEDER
-a
ENTRAINMENT
SEPARATOR
Vapor Inlet
Air
Inlets
Pump
c
PU4
Condensing Tubes
Water Spray Nozzles
Blower
NON-
Condensables
INCIN-
ERATOR
i i
I 0
Condensate to Sewer
p pin nip a
CONTROL Vent
WHEEL
Fat
Drainer
Steam to Coils
EQUACOOKER
D
TUT1
D!D n!
D D
T
CENTRIFUGE
I I
I Solids I
FAT
STORAGE
VARI-SPEED
Vent
Steam to Jacket
Blower
Meal Cake to Grinding
Press Fat
Figure k. Continuous Cooker - Duke Process
-------
the vacuum in the system. In the case of a two-stage evaporator
system, the vapor evaporated from the second stage serves as a
heating medium for the first stage. Two-stage evaporators
provide steam economy, and are especially useful for raw
materials with a high moisture content. The dried slurry of fat
and cracklings is then pumped from the evaporator to a centrifuge
which separates the solids from the liquid. Part of the fat is
removed from the system at this point, while the remainder is
recycled back to the fluidizing tank. The solids discharged from
the centrifuge are screw conveyed to expellers (screw presses)
that reduce the fat content of the solids from about 26 percent
by weight to 6 to 10 percent.
A central control panel allows one operator to control the entire
cooking process. Level indicators and controls are provided to
stabilize the flow through the fluidizing and other process tanks
and also for the vacuum chamber. Evaporator vacuum and
temperature are also monitored. Equipment speed settings, motor
current readings and start/stop push buttons are also located on
this panel.
Strata-Flow Continuous System
The third system, ANCO-Hormel Strata-Flow continuous system,
manufactured by the Albright-Nell Company, is basically a series
of batch cookers stacked one above the other. Normally five or
six stages are provided in series. Each cooker stage is vented
to a common manifold that is connected to a condenser for
removing vapors.
The crushed raw material from the prebreaker is blown
continuously to the first stage cooker. This eliminates screw
conveying and pumping of the raw material. The cooked material
discharges from the last stage to a percolation pan called an
Autoperc. A drag conveyor located in this pan continuously
removes material after the free run fat has drained off.
EDIBLE RENDERING
Edible rendering is estimated to be conducted by less than two
percent of the independent renderers.7 However, these plants do
both edible and inedible rendering, and probably less than one
percent of the raw material handled by independent renderers is
used for edible rendering.
Edible rendering of inspected fats can be conducted by either a
wet or a low-temperature process. The wet process is conducted
in a vertical tank with injection of live steam under a pressure
of about 3.7 atmospheres (40 psig) and a large volume of "tank
water," which should be evaporated. The quality of the lard and
tallow thus produced is quite low. For this reason, this once
common process is rarely used any more and no independent
rendering plants surveyed in this study use the wet rendering
21
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Water
rv>
ro
EVAPORATOR
•+ DISINTEGRATOR
PREBREAKER
AFTER
CONDENSER
CENTRIFUGE
VAPOR
CHAMBER
FLUIDIZING
TANK
Expeller
Vent
Vent
Discharge
Pump
Fluidizing pump
Recirculation Pump
Expeller Cake
to Grinding
Recycle Fat at 200" Fahrenheit
Recycle Pump
Expeller Fat
To Fat Storage
lire 5 . Corxtituj-ou-s Cookeir "by Carrie.!? — Careen, field Process
-------
process. Low-temperature rendering of fats is the most commonly
used method for edible rendering. Fats, after being finely
pulverized in a grinder, are placed in a melter and heated to a
temperature of 49° to 82°C (120° to 180°F) . When the cooking
temperature is maintained at or below 49°C (120°F), the
cracklings or solids may also be used as an edible product.
Cooking at these low temperatures does not evaporate the raw
material moisture. Hence, after the fat has separated from the
solids and water in the melter, the cooked material is desludged
by screening or centrifuging. The water phase is also separated
during desludging. The remaining water entrained in the hot fat
is then removed in a second centrifuge. The separated water,
called tank water, can be further evaporated to a thick material
known as stick, which can be used as tankage for inedible
rendering.
The general practice in either wet or low temperature edible
rendering is to directly sewer the tank water. However, this is
a poor practice from a pollutional standpoint because tank water
can have a BOD5 of anywhere from 30,000 to 45,000 mg/18 and a
grease value as high as 20,000 to 60,000 mg/1. If, instead, the
tank water is evaporated and the stick used for tankage, the
water waste load from wet-or low-temperature rendering would be
similar to that from a dry process.
COOKER USES AND PROCESS VARIATIONS
The type of inedible cooker chosen—batch or continuous—is in
some instances very dependent upon the material handled and, of
course, on the size of the plant. Poultry feathers and hog hair,
for example, are handled in most plants in batch systems. This
is because these materials must first be cooked under pressure of
about 4.4 atmospheres (50 psig) to hydrolize the proteinaceous
material (primarily keratin) to usable protein before being
cooked and dried in the same way as other materials are in a
batch system. A continuous processing system is now available
for materials that require hydrolysis, such as feathers, in which
the material passes through a hydrolyzer and then into a cooker.
Blood is another material normally handled in batch cookers.
However, in some cases, the final drying and conditioning of
blood, feathers, and hog hair is carried out in a ring or rotary
dryer. This method of drying following batch cooking permits a
higher production rate for a plant with a given number of batch
cookers. This is because of poor heat transfer during the later
stages of drying in batch cookers as the material passes through
a "glue stage." In a few cases, blood is processed by steam
sparging, which coagulates the albumin; then the albumin and
fibrin are separated from the blood water by screening and are
processed in a batch cooker or ring dryer. The blood water,
which can have a BOD5 up to 16,000 mg/1, is usually sewered.
The ring dryer system, as the name implies, is in the shape of a
flattened ring or race track, positioned vertically. The
23
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material to be dried is first pulverized and then blown into the
ring where it is conveyed around the ring by furnace gases of
314° to 425°C (600° to 800°F). Centrifugal force, recirculation
rates, and control dampers permit the material to recirculate
until the particles of the material become light enough because
of drying to escape along with the exhaust gases. A cyclone
separates the material from the exhaust gases, which are conveyed
away by an exhaust fan. This exhaust fan is necessary to ensure
a slight negative pressure in the ring dryer and thus to prevent
material from leaking out of the dryer. The high temperature of
the furnace gases can cause scorching of the proteinaceous
material, resulting in strong odors. Consequently, the exhaust
gases are frequently ducted through a spray scrubber.
Rotary (air) dryers are also used to further dry blood, feather
and hoghair meals. The dryer is a horizontal cylindrical vessel
equipped with longitudinal steam tubes. The material cascades
through the dryer as it rotates. Rotary dryers create less of an
odor problem than ring dryers because of the lower temperatures
involved and the lower volumes of air required for drying.
VAPOR CONDENSING
Cooking vapors from dry batch processes and also from evaporating
tank water are condensed by one of three methods: barometric
leg, air condenser, and shell-and-tube heat exchanger. Prior to
five or ten years ago, all vapors were condensed with the use of
a barometric leg.
In a barometric leg, the cooking vapors are contacted with
condensing waters and together flow gravimetrically out through a
standpipe. A barometric leg condenser is basically a water-
powered ejector located on top of a standpipe. As the high
velocity water passes through the ejector, it creates a vacuum on
the downstream side. The vacuum draws the cooking vapors into
the high velocity water where the vapors are cooled and
condensed. The vacuum is usually very slight for batch cookers,
whereas for several continuous systems using barometric leg
condensers the vacuum may be quite high, thus requiring a long
standpipe. The standpipe serves two purposes. First, it
provides a confined space for contact between the vapor
condensing water. Second, it acts as a reverse water trap. This
prevents condensed vapors and cooling waters from being
accidentally sucked back into a sealed cooker as it cools. To
ensure against back-up even under a nearly perfect vacuum, the
standpipe should be slightly over 10 meters (33 feet) high. This
is because a one-atmosphere vacuum can lift water to a height of
only about 10 meters. In general, it was observed that very few
barometric leg condensers used in the industry are near 33 feet
in height. However, a few plants with barometric legs protect
against back-up by installing an air check valve in the
standpipe. Hence, before a vacuum can lift water to the top of
the standpipe, the air valve will open and reduce the vacuum.
24
-------
Air condensers and shell-and—tube heat exchangers are rapidly
replacing the barometric leg for condensing water vapors.
Probably the major reason for this is that air condensers and
shell-and-tube heat exchangers do not dilute the waste waters.
Barometric legs, on the other hand, highly dilute the waste
waters resulting from the condensing of vapors. Usually a
barometric leg is used on each batch cooker, and each requires 57
to 151 liters (15 to 40 gallons) per minute of water for
condensing. In plants that are continuing to use barometric
legs, the trend is to recycle treated or partially treated water
through the barometric leg.
Air condensers force ambient air across a bank of externally
finned tubes. A typical unit has a horizontal section containing
finned tubes, a steel supporting structure with plenum chambers
and fan ring, axial-flow fan, drive assembly, and miscellaneous
accessories such as louvers, fan guards, and temperature-operated
fan speed controls.
Shell-and-tube heat exchangers are basically cylindrical vessels
containing a bundle of parallel tubes. The tubes are enclosed in
such a manner that they isolate the liquid inside the tubes from
the liquid surrounding the tubes. Normal flow arrangement is to
have the condensate inside the tubes. The cooling water is
recirculated through a cooling tower to dissipate the heat
collected in condensing the cooking vapors. Water is
continuously added to the cooling water to make up for that lost
by evaporation.
GREASE AND TALLOW RECOVERY
Grease and tallow recovery is normally accomplished in two steps.
The first step is draining in percolation or drain pans just
after the material is dumped or removed from cookers. For batch
systems, the material may be allowed to drain for up to two
hours. This normally reduces the fat content of the solids to 25
percent. The second step in fat reduction involves the pressing
of solids to reduce the residual tallow content to 6 to 10
percent. The usual practice is to use a screw press to allow for
continuous throughput, although some small or old plants may
still use hydraulic batch-operated presses. The screw press
consists of a cylindrical barrel of metal bars that are spaced
with narrow openings between to allow the fat to be squeezed
through by the action of a rotating screw. Hence, the pressure
within the screw press is maintained by friction and the fat
present in the solids provides a lubricating effect. It is
important that overpressing of the tallow from the solids be
avoided; otherwise overheating and scorching can result in
producing smoke and strong odors. Frequently, the smoke
generated by screw presses is drawn through an odor control
system that uses either wet scrubbing or incineration.
In possibly one percent of the plants, the second step in grease
and tallow reduction involves solvent extraction. In this
25
-------
process a solvent such as hexane is used to remove the excess
grease. Heat is then required to separate the solvent from the
grease and to remove it from the solids. The solvent is
recovered for recycle. This process reduces the tallow and
grease content of the solids to one percent or less. The
increased income derived from the additional fat recovered by
solvent extraction, however, is usually too small to encourage
widespread use of solvent recovery.
Tallow and grease recovered in the two steps of drainage and
pressing are normally combined and then further clarified. This
usually involves screening, centrifuging, or filtering, or
combinations thereof. Solids recovered from clarification are
returned to the cracklings prior to the second step of tallow and
grease recovery. The tallow and grease are then pumped into
storage tanks and held for later shipment.
SOLIDS PROCESSING
The solid proteinaceous material discharged from the screw press,
known as cracklings, is normally screened and ground with a
hammer mill to produce a meat and bone meal product that passes
through a 10- to 12-mesh screen. The finely divided solids are
usually stored in bulk handling systems for later shipment.
Occasionally this material is blended with another, such as blood
or feather meal, to ensure a high level of crude protein.
Frequently, the blood and/or feather meal are bagged prior to
shipment, although this operation is normally a relatively small
one.
ODOR CONTROL
Odor control is practiced in nearly all rendering plants today.
Although rendering odors are not necessarily harmful to health,
they may be very offensive to people because of their distinct
nature and the complexity of the odor compounds present. A
recent study9 identified a number of odorous compounds present in
rendering plant emissions. The important categories of compounds
identified were sulfides, amines, aldehydes, ketones, alcohols,
and organic acids. The major methods of odor control basically
involve using scrubbers with or without chemical oxidant
solutions (the most commonly used chemical is sodium
hypochlorite) , and incinerators. Condensers and temperature
control of cooking vapors involve rendering plant operations
which should be adequately controlled to minimize odors.
Excellent discussions of the control of odors from inedible
rendering plants can be found in references 2 and 10.
The primary sources of odor are from the cooking and pressing
operations because, in both cases, the material is heated to
temperatures of 105°C (220°F) or higher. Of course, aged or
deteriorated raw materials will appreciably increase the
intensity of odors from these operations. Furthermore, if the
26
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raw materials are not particularly fresh, it may be necessary to
control this odor source by covering screw conveyors and venting
them to the odor control system.
The condenser plays a very important part in controlling odors
from cookers. One of the best ways of controlling any odors from
the cookers is to ensure that the final temperature of the
condensed cooking vapors is below 52°C (125°F), or preferably
below 38°C (100°F). In addition, the noncondensable vapors from
the cooker, which give high-intensity odors, can be controlled by
venting directly to the boiler used for generating the plant
steam. This is feasible only under certain circumstances. If
the odorous stream is used as primary combustion air, the
necessary precautions must be taken to remove solid and fat
aerosol particles before passing this air through the boiler and
controls. Also, the boiler must be equipped with suitable burner
controls to ensure that the minimum firing rate is sufficient to
incinerate the maximum volume of effluent gas passing through the
boiler firebox, regardless of the steam requirements. Press
odors are treated by venting these vapors through a scrubber or
incinerator. The intensity of the smoke and odor from the
presses is occasionally high enough that the scrubbing water
cannot be recycled.
Using water without chemicals in a scrubber usually does not
permit high recirculation rates, and thus requires large water
use; the effect is that the waste waters from the plant are
diluted. When chemicals such as sodium hypochlorite are used, it
is normal to recycle up to 95 percent of the scrubber waters;
this minimizes chemical and waste water treatment costs. Wasting
five percent of chemical scrub water should not affect either the
volume of the waste water or its treatability to any noticeable
degree.
Direct-fired incineration units could be used anywhere in place
of the scrubber, although they are normally used only for low-
volume high intensity odors. However, in recent months, the use
of incinerators has been reduced drastically because of the
difficulty in obtaining the necessary fuel. Even before there
was difficulty in obtaining fuels, scrubbers were believed to be
the most economical method of odor control.9
WASTE WATER SOURCES
Waste waters from the rendering of raw materials contain the
condensate or moisture evaporated from the raw materials and wash
water from cleaning the plant and the raw materials pickup
trucks. In some cases, the waste water contains additional
condenser water and liquid drainage from the raw materials. The
strength of these waste waters, which contain organic materials
including soluble and insoluble protein, grease, suspended
solids, and inorganic materials, can be greatly increased as a
result of run-down and poorly maintained equipment. Also, poor
housekeeping practices can result in accidental spills of raw and
27
-------
finished materials into the waste waters and the foaming over of
material from the cookers.
Trucks and barrels used for picking up raw materials are
carefully washed after each use. The amount of water used for
this is probably insignificant, although these operations can
contribute significantly to the waste load, particularly to the
grease load. Barrel washing, however, is not as common a
practice as it once was in rendering plants, since most barrels
are emptied at the pick-up site and are not brought to the plant.
Barrels are primarily used to transport restaurant grease.
Washdown in inedible rendering plants is not nearly as intensive
as it is in meat processing and packing plants. In fact,
washdown usually occurs at the end of a day's operation when
rendering has been completed. Normally only the areas for
receiving, grinding and cooking of raw materials and the product
separating and grinding areas are washed down. The other areas
of the plant are generally dry cleaned. Washdown does occur
within the plant, however, whenever there is an accidental spill.
Washdown of accidental spills without prior dry cleanup obviously
adds significantly to the waste load from inedible rendering
plants. The most common accidental spills observed, that were
entirely cleaned up by washdown, were of tallow and grease.
Fortunately, a properly operated materials recovery system
(primary or in-plant treatment) can recover a large portion of
these materials for recirculation to the cookers.
MATERIALS RECOVERY
Materials recovery from the waste water streams (primary or in-
plant treatment) is conducted in essentially all rendering
plants. The most common materials recovery system used by
independent renderers is a catch basin or skimming device.
Basically, this device is a large rectangular tank in the
effluent stream to allow grease and oil to float to the surface
and solids to settle to the bottom, thus separating them from the
waste water. Grease and oil that float to the surface in catch
basins are normally removed manually once or twice a day and
blended in with the raw materials for recycling, or are processed
separately. With automatic skimming devices, the materials may
be collected for recycle once or twice a day or they may be
continuously recycled using screw conveyor systems. Solids
collected from catch basins are less frequently recycled;
however, it is becoming more common practice today to
occasionally pump out solids and recycle them through the
rendering equipment.
Some rendering plants (15 out of 49 plants included in the
survey) have air flotation systems in place of catch basins or
skimming devices. However, these systems are normally not
operated under optimum conditions for either materials recovery
or waste water treatment. Optimum conditions might require flow
equalization, pH control, temperature control, and the addition
28
-------
of chemical flocculating agents. The temperature of rendering
plant waste waters is often somewhere between 70° and 85°C (125°
and 150°F), which is too high for effective grease removal by air
flotation systems or by other gravity separation methods. At
these temperatures, grease is too soluble in water for the
required phase separation. Further, chemicals are not normally
added to the air flotation system because the resulting sludge
collected would be very high in water (85 to 95 percent) and,
consequently, this excess water would add considerably to the
heat load if recycled through the cookers. The addition of
chemicals could also change the nature of the grease and thus
lower its market value. One solution to this is to have two
materials recovery systems in series, where the second one is an
air flotation device to which chemicals have been added.
HIDE CURING (ANCILLARY OPERATION)
Hide curing occurs in a number of rendering plants, essentially
as a separate operation from rendering. In many cases,
slaughterhouses and packinghouses from which the renderers
collect their material are either too small to handle hide curing
or do not have the necessary equipment. Consequently, for the
renderer to obtain these sources as users of his "services," he
must also pick up the hides along with his raw materials. In
addition, many rendering plants handling a large number of dead
animals will find it economically favorable to remove the hides
from dead carcasses for curing.
The older method of curing hides was to dry pack hides in salt.
However, in recent years the trend has been to replace this
operation with brine curing in raceways Or brine vats.
Essentially, the hide curing is a dehydration process, and in the
brine-wring process there results a net overflow of approximately
two to three gallons cf brine cure for each hide handled. These
wastes are nearly saturated with salt and also contain other
dissolved solids plus blood, tissue, and fats and oils. The
overall contribution of this waste load to that from the
rendering plant is usually relatively small. However, a high
salt load can cause probleirs in the treatment of the waste waters
and in some cases may make it very difficult for a plant to
obtain a final chloride content that would meet some state and
local regulations. A possible solution to this problem might be
to blend the curing effluent with the raw material as it enters a
dry cooker.
29
-------
SECTION IV
INDUSTRY CATEGORIZATION
CATEGORIZATION
In developing effluent limitations guidelines and standards of
performance for the independent rendering industry, a judgment
was made as to whether limitations and standards are appropriate
for different segments (subcategories) within the industry. To
identify any such subcategories, the following factors were
considered:
o Waste water characteristics and treatability
o Raw materials
o Manufacturing processes (operations)
o Processing equipment
o Size, age, and location of production facilities.
After considering all of these factors, no justification could be
found for dividing the industry into subcategories. Hence,
independent rendering constitutes only one subcategory, and the
effluent limitations and standards of performance recommended in
this report are intended to apply to all independent rendering
plants except those processing fish by-products.
An independent rendering plant is one that collects animal by-
products such as bone, offal, fat, and dead animals from such
sources as slaughterhouses, processing plants, butcher shops,
restaurants, feed lots, and ranches, and processes them into
products such as fats, oils, and solid proteinaceous meal. The
products may be either edible or inedible. Plants processing
fish by-products are not included in this study. In addition,
rendering plants that are an adjunct to meat and poultry
operations and are located on the same premises are not included
in the category of independent renderers. An independent
rendering plant may also cure hides as an ancillary operation.
The manufacturing processes in an independent rendering plant are
shown in Figure 6.
RATIONALE FOR CATEGORIZATION
Waste Water Characteristics and Treatability
Basic processes in independent rendering plants are essentially
the same, although such factors as equipment type, raw materials,
and size and age of the plant may differ. Hence, it was possible
to consider division of the industry on the basis of these
factors which might group plants with similar raw waste water
characteristics. The waste water characteristic used in
31
-------
BASIC PROCESSES
ANCILLARY PROCESS
RAW MATERIAL
RECEIVING
CRUSHING AND
GRINDING
COOKING AND
DRYING
PRODUCT
SEPARATION
MEAL GRINDING
AND SCREENING
GREASE
CLARIFYING
BLENDING
STORAGE
STORAGE
SHIPPING
SHIPPING
HIDECU(RING
Figure 6. Manufacturing Processes of a Rendering.Plant
32
-------
attempting to categorize (subdivide) the industry was the 5-day
biochemical oxygen demand (BOD5) in units per 1000 units raw
material (RM) handled or processed: kg BOD5/kkg RM (Ib BOD5/1000
Ib RM) . BOD5 provides the best measure of plant operation and
treatment effectiveness among the parameters studied, and more
data are available than for all ether waste parameters.
Suspended solids, grease, and COD data serve to substantiate the
conclusions developed from using BOD5 in characterizing both the
industry and the raw waste (Section V). The raw waste was
evaluated and is herein discussed as that waste water discharged
subsequent to materials recovery operations—catch basins,
skimming tanks, etc.
The major plant waste load is organic and biodegradable: BOD5,
which is a measure of biodegradability, is the best measure of
the load entering the waste stream from the plant. Furthermore,
because secondary waste treatment is a biological process, BOD5
also provides a useful measure of the treatability of the waste
and the effectiveness of the treatment process. Chemical oxygen
demand (COD) measures total organic content and some inorganic
content. COD is a good indicator of change, but does not relate
directly to biodegradation, and thus does not indicate the demand
on a biological treatment process or on a stream.
A number of additional parameters were also considered for use in
categorization besides BOD5, suspended solids, grease and COD.
Among these were nitrites and nitrates, Kjeldahl nitrogen,
ammonia, total dissolved solids, total volatile solids, and
phosphorus. In each case, data were insufficient to justify
categorizing on the basis of the specified parameters; on the
other hand, the data on these parameters helped to verify the
judgments based on BOD5.
Judging from secondary waste treatment effectiveness and final
effluent limits, waste waters from all plants contain the same
constituents and are amenable to the same kinds of biological
treatment concepts. Geographical location, and hence climate,
affects the treatability of the waste to some degree. All
biological activity slows at lower temperatures; hence,
biological waste treatment systems do not perform as well in the
winter months in northern areas as they do when the weather is
warm. Climate has occasionally influenced the kind of secondary
waste treatment used. However, the ultimate treatability of the
waste or the treatment effectiveness can be maintained at the
highest levels by not discharging during the coldest months of
the year. The time period for no discharge will vary with
location, but should never exceed six months. This is the same
practice that is used by plants that dispose of their waste water
by irrigation.
In the following parts of this section, the factors that were
considered in categorizing the industry for the basis of raw
waste water characteristics are examined.
33
-------
Raw Materials
No clear relationship of direct statistical dependence between
kind of raw material and raw BOD5 waste load could be found by
statistical (multiple regression) analysis. As a result, a clear
independent relationship was disclosed that all types of raw
materials may be expected to result in similar BOD5 discharges.
In addition, the range (low and high) and average of BOD5 waste
water values for plants processing greater than 50 percent
poultry by-products could not be differentiated from those plants
processing less than 50 percent poultry by-products or from those
for the total industry. This is illustrated by bar graphs in
Figure 7. Hence, the type of raw materials processed is not a
meaningful factor for categorization.
Animal by-products were classified for the multiple regression
analysis as:
o Packinghouse (slaughterhouse) materials which are
primarily animal offal
o Shop fat and bones
o Grease
o Blood
o Dead animals
o Poultry offal
o Feathers and hair
The multiple regression analysis correlated the percent of raw
material in each of these classes with the raw BOD5 load for each
set of data. A total of 45 sets of data were included in the
analysis, representing information on 29 independent renderers.
There were several sets of information, up to three, for a number
of these plants. The sources of this information were voluntary
questionnaires distributed by the National Renderers Association,
supplementary data supplied by the companies such as reports from
consulting firms, and the results of our field sampling survey.
Some questionnaire data represent the average of data over a
period of several months; other data represent grab or composite
values over short periods such as a day or two. The result of
the regression analysis is best indicated by the multiple
correlation coefficient. This turned out to be 0.39. The square
of this number, or 0.16, is a measure of the predictability of
the change in BOD5 load caused by a change in raw materials. In
other words, 16 percent of a BOD5 load change could be accounted
for by a change in raw materials. For the dependence between
animal by-products and BOD5 load to be
significant, the square of the multiple correlation coefficient
should be greater than 0.5. The lack of dependence between BOD5
load and raw materials is somewhat surprising since the raw
34
-------
CO
en
CC
LD
Q
O
m
6.00
5.00
4.00
3.00
2.00
1.00
(29)
(25)
-MAXIMUM
(4)
-AVERAGE
-MINIMUM
TOTAL
INDUSTRY
< 50%
POULTRY
BY-PRODUCTS
2 50%
POULTRY
BY-PRODUCTS
Figure 7. Average and Range of BOD5^ Data by Raw Material Type
-------
materials in each of the classes have different initial moisture
contents and product yields of solids and of tallow and grease.
But then a simple regression analysis between BOD5 load and waste
water flow, both expressed in units per 1000 units of raw
material processed, also did not reveal a correlation. The
correlation coefficient for this analysis was -0.027.
Manufacturing Processes
The manufacturing processes in independent rendering were shown
in Figure 6. Those processes considered as basic—raw materials
receiving, crushing and grinding, cooking and drying, product
separation, meal grinding and blending, grease clarifying, and
storage and shipping—are conducted in most plants. In a few
cases, such as plants processing poultry byproducts (offal and
feathers mixed together), the only product is meal, and no grease
is separated and clarified. These plants may have more complex
meal grinding and screening processes. The net result, based on
field survey results, was that the basic manufacturing processes
were found to further reiterate the single subcategory conclusion
first discovered when analyzing raw materials.
The ancillary manufacturing process (hide curing), however, can
contribute additional waste to the plants' raw effluent when the
waste load is only based upon the amount of raw material used for
the basic manufacturing processes, as it is in this report. But
to create a separate category for independent rendering plants
that cure hides would not result in a separate set of fixed
effluent standards. This is because the additional waste load
caused by hide curing is dependent on the relative amounts of raw
materials processed in the basic and ancillary manufacturing
processes.
The best way of accounting for the additional raw waste load
caused by hide curing, therefore, is by the use of an adjustment
factor. The adjustment factor for hide curing is presented in
detail in Sections IX and X. In summary, then, the manufacturing
processes, basic and ancillary, were not considered meaningful
factors for categorization.
Processing Equipment
The processing equipment considered as factors for categorization
were the type of cookers—batch versus continuous—and the type
of condensers used for condensing cooking vapors—barometric leg,
shell-and-tube, and air condensers. Other types of equipment
such as grinders, presses, etc., were not considered because the
basic operating principles were generally quite similar for each
type of equipment, regardless of the manufacturer, and because
the contribution to the waste water load from the use of this
equipment was not significant.
36
-------
6.00
(29)
5.00
4.00
to
cc
o>
if)
Q
O
00
3.00
2.00
1.00
(17)
-MAXIMUM
(5)
(4)
-AVERAGE
-MINIMUM
TOTAL
INDUSTRY
BATCH
SYSTEMS
DUKE
SYSTEMS
C-G
SYSTEMS
Figure 8. Average and Range of BOD5_ Data by Cooker Type
-------
6.00
(29)
5.00
4.00
to
oo
cc
en
^
if)
Q
O
00
3.00
2.00
1.00 —
(5)
(6)
-MAXIMUM
(14)
-AVERAGE
-MINIMUM
TOTAL
INDUSTRY
BAROMETRIC
CONDENSER
SHELL & TUBE
CONDENSER
AIR-COOLED
CONDENSER
-------
Table 5. Raw Waste Data on Rendering Plants by Equipment Type
Parameter
BOD5
kg/kkg RM
(lb/1000 Ib RM)
SS
kg/kkg RM
(lb/1000 Ib RM)
Grease
kg/kkg RM
(lb/1000 Ib RM)
Equipment
Type*
Total
Batch
Duke
C-G
Baro
S & T
Air
Total
Batch
Duke
C-G
Baro
S & T
Air
Total
Batch
Duke
C-G
Baro
S & T
Air
Number of
Observations
29
17
4
5
6
14
6
26
14
4
5
3
14
5
16
9
2
5
2
9
4
Average
Value
2.15
2.31
1.92
1.56
2.10
1.78
2.42
1.13
1.06
1.54
0.97
1.79
0.98
0.56
0.72
0.44
1.66
0.90
2.09
0.55
0.41
Standard
Deviation
1.34
1.34
0.99
1.97
1.39
0.95
2.00
1.39
0.91
2.44
1.87
2.20
1.44
0.65
1.14
0.48
1.82
1.83
2.96
0.96
0.43
High
Value
5.83
5.83
3.15
4.83
4.83
3.64
5.83
5.18
3.33
5.18
4.32
4.32
5.18
1.45
4.18
0.92
2.94
4.18
4.18
2.94
1.07
Low
Value
0.10
0.72
1.07
0.10
1.20
0.10
0.72
0.03
0.03
0.05
0.06
0.39
0.05
0.03
0.00
0.00
0.37
0.04
0.00
0.04
0.04
*Values listed as:
• Total represents the summary of combined data, regardless of equipment type.
• Batch, Duke, or C-G summarizes the results of the data from plants with
batch, Duke and Carver-Greenfield cookers, respectively. See Section III
for a discussion of these cookers.
• Baro, S & T, or Air summarizes the results of plants with barometric leg,
shell and tube, or air condensers.
39
-------
Table 5 summarizes the raw waste data on independent rendering
plants using various kinds of cookers and condensers for BOD5,
suspended solids, grease, flow, and amount of raw materials
handled. The data for the total industry are included in Table 5
for comparative purposes. Figures 8 and 9 graphically illustrate
the average and range of the BOD5 data from Table 5 for the
various cookers and condensers, respectively. These data show
that there are no distinct raw waste water load differences when
the data are grouped by the types of cookers and condensers used.
Thus, it was concluded that the factor of process equipment
proved consistent with findings regarding manufacturing process
and substantially supported reasoning to designate a single
category for the rendering industry.
Size, Age, and Location of Production Facilities
Size, age, and location are not meaningful factors for developing
subcategories. Size as a factor was evaluated by a simple
regression analysis between raw BOD5 waste load and the amount of
raw material processed per day using the data collected in this
study. This analysis revealed no discernible relationship
between BOD5 waste load and size, as measured by the daily amount
of raw materials processed. This is indicated by the value of
the correlation coefficient, which was 0.062. It is necessary
that a correlation coefficient value greater than 0.5 exist to
establish a meaningful correlation. The same data were also
separated into three data groups based on amount of raw material
used. The data groups represented approximately equal numbers of
plants. Analysis of the data in each of the groups showed no
correlation of plant size with BOD5 waste load. Figure 10 shows
the average and range values of BOD5 for the three size groups
and for all the plants included in the study (indicated in Figure
10 by total).
Age is often reflected by the type of processing equipment used.
Plants over ten years old were originally equipped with batch
cookers and barometric leg condensers. However, in recent years
some older plants have replaced batch systems with continuous
systems and barometric leg condensers with air or shell-and-tube
condensers. Newer plants use both batch and continuous systems
and also use shell-and-tube and air condensers more frequently
than barometric legs. Therefore, the major difference, from a
raw waste load standpoint between old and new plants is the type
of processing equipment. Since processing equipment served to
indicate a single discrete category, the close correlation
between age of facilities and equipment means that age helps to
reiterate this conclusion.
Examination of the raw waste water characteristics relative to
plant location reveals no apparent relationship or pattern. The
type of animal by-products processes is soiretimes influenced by
location, but as mentioned previously, the type of raw material
processed had no discernible effect on raw waste.
40
-------
in
D
O
m
6.00 —
5.00 —
4.00
3.00
2.00
1.00
(29)
TOTAL
INDUSTRY
(10)
(8)
-MAXIMUM
-AVERAGE
-MINIMUM
(11)
<45,000 kg
(<100,000 Ib)
45,000-114,000 kg
(100,000-250,000 Ib)
'114,000 kg
>250,000 Ib)
Plant Size: kg (Ib) of Raw Material
Figure 10. Average and Range of BODs Values for Three Size Groups of Plants
and for All Plants Studied (Total)
-------
SECTION V
WATER USE AND WASTE CHARACTERIZATION
WASTE WATER CHARACTERISTICS
Water is used in the rendering industry for condensing cooking
vapors, plant cleanup, truck and barrel washing, odor control,
and for boiler makeup water. The principal operations and
processes in rendering plants where waste water originates are:
o Raw material receiving
o Condensing cooker vapors
o Plant cleanup
o Truck and barrel washing
Waste waters from rendering plants contain organic matter
(including grease), suspended solids, and inorganic materials
such as phosphates, nitrates, nitrites, and salt. These
materials enter the waste stream as blood, meat and fatty tissue,
body fluids, hair, dirt, manure, hide curing solutions, tallow
and grease, and meal products (such as meat, bone, blood,
feathers, hair and poultry meal), and caustic or alkaline
detergents.
Raw Waste Characteristics
The raw waste load characteristics from the rendering industry
discussed in the following paragraphs include the effects of the
materials recovery process (considered the primary waste
treatment system such as catch basins and skimming tanks).
The parameters used to characterize the raw effluent were the
flow, BOD5, suspended solids (SS), grease, COD, total volatile
solids (TVS), total dissolved solids (TDS), Kjeldahl nitrogen,
ammonia, nitrates, nitrites, chlorides, and phosphorus. As
discussed in Section IV, BOD5 is considered to be the best
available measure of the waste load. The parameter used to
characterize the size of the operations was the amount of raw
materials processed. All values of waste parameters are
expressed as kg/kkg of raw materials (RM), which has the same
numerical value when expressed in lb/1000 Ib RM. Amount of raw
materials processed is expressed in units of kkg RM.
Table 6 summarizes the plant and raw waste water characteristics
for the single category of independent rendering plants. The
summary includes averages, standard deviations, ranges (high and
low values), and number of observations (plants).
43
-------
The data used to compute the values presented in Table 6 were
obtained through questionnaires distributed to their members by
the National Renderers Association (NRA), through supplementary
data submitted by the companies (such as laboratory analysis
reports and consulting engineers' reports) , and through data
obtained from the field sampling survey conducted by North Star.
Questionnaires provided information on 49 plants; 12 of these
were also included in the field sampling survey. Two other
plants that did not submit questionnaires were also sampled.
Thus, the total number of plants included in this study was 51,
or about 11 percent of the industry. Note, however, that data
were not available for all plants for all pertinent parameters;
thus, the number of observations used to develop averages or
other characteristics may not conform to the sample total even
for such parameters as waste water flow or pounds of raw
materials processed. The data in Table 6 for flow, raw
materials, BOD5, suspended solids, and grease are primarily based
on questionnaire data; data on the other variables were largely
based on supplementary and field sampling information. Note also
that while the sampling data generally verified questionnaire
information, a number of atypical conditions esixted for four or
five plants during the field visits which clearly caused unusual
results for raw waste loads. The conditions included spills from
cookers, emergency use of old equipment, and malfunctions of
certain in-plant controls. Thus, the general waste load
characteristics (for BOD5, TSS) were derived from submissions by
the industry itself.
Discussion of Raw Wastes
The data in Table 6 cover a waste water flow of 467 to 80,936
1/kkg RM (56 to 9708 gal./lOOO Ib RM); a BOD5 waste load range of
0.10 to 5.83 kg BOD5/kkg RM (0.10 to 5.83 Ib BOD5/1000 Ib RM) ;
and a production range of 3.6 to 390 kkg RM/day (8000 to 860,000
Ib RM/day) .
Variations in waste water flow per unit of raw material are
largely attributable to the type of condensers used for
condensing the cooking vapors and, to a lesser extent, on the
initial moisture content of the raw material (see Section III) .
Table 7 shows that the average waste water flow for plants using
barometric leg condensers is much higher, by at least a factor of
2, than for those using either shell-and-tube or air condensers.
The range and standard deviation in the flow values are large,
however, for all three types of condensers, which undoubtedly is
partially caused by the type of raw materials processed. The
volume of water used for cleanup can be a significant portion of
the flow per unit of RM; typically it amounts to 30 percent of
the total flow.
A regression analysis of the field sampling data revealed that
the raw BOD5 waste load correlates very well with grease and COD
waste loads. Raw BOD5 waste load also correlates with total
volatile solids (TVS), total dissolved solids (TDS), and total
44
-------
Table 6. Summary of Raw Waste Characteristics for Rendering Industry
Parameter*
Flow, 1/kkg RM
(gal. /1000 Ib RM)
Raw Material, kkg/day
(1000 Ib/day)
BOD , kg/kkg RM
SS, kg/kkg RM
Grease, kg/kkg RM
COD, kg/kkg RM
Total Volatile
Solids, kg/kkg RM
Total Dissolved
Solids, kg/kkg RM
Total Kjeldahl
Nitrogen, kg/kkg RM
Ammonia, kg/kkg RM
Nitrate, kg/kkg RM
Nitrite, kg/kkg RM
Chloride, kg/kkg RM
Total Phosphorus,
kg/kkg RM
Number of
Observations
47
48
29
26
18
16
18
17
17
16
14
13
14
17
Average
Value
3261
(403)
94
(206)
2.15
1.13
0.72
8.04
3.34
3.47
0.476
0.299
0.008
0.003
0.793
0.044
Standard
Deviation
—
94
(206)
1.34
1.39
1.14
8.32
3.09
3.05
0.313
0.196
0.016
0.011
0.767
0.064
High
20,000
(2400)
390
(860)
5.83
5.18
4.18
37.03
13.12
11.67
1.200
0.740
0.060
0.040
2.56
0.280
Low
467
(56)
3.6
(8)
0.10
0.03
0.00
1.59
0.04
0.01
0.120
0.080
0.0001
0.00002
0.080
0.003
*kg/kkg RM = lb/1000 Ib RM
45
-------
Table 7. Waste Water Flow and Raw Material Data Summary as Shown
Parameter
Flow,
1000 liters
(1000 gal.)
Raw Material ,
kkg/day
(1000 Ib/day)
Equipment
Type*
Total
Batch
Duke
C-G
Baro
S & T
Air
Total
Batch
Duke
C-G
Baro
S & T
Air
Number of
Observations
51
35
6
6
15
21
9
48
34
5
5
14
19
9
Average
Value
326(86)
314(83)
276(73)
110(29)
443(117)
185(49)
64(17)
94(206)
60(132)
195(430)
128(282)
37(82)
132(291)
62(137)
Standard
Deviation
643(170)
708(187)
166(44)
42(11)
764(202)
174(46)
38(10)
94(206)
80(176)
90(198)
61(135)
44(98)
89(195)
37(82)
High
Value
3028(800)
3028(800)
488(129)
170(45)
2952(780)
628(166)
121(32)
390(860)
390(860)
318(700)
204(450)
182(400)
318(700)
114(250
Low
Value
3.8(1)
3.8(1)
64(17)
68(18)
7.6(2)
7.6(2)
19(5)
3.6(8)
3.6(8)
68(150)
61(135)
5.4(12)
11(25)
11(25)
^Values listed as:
o Total summary of all data, regardless of equipment type.
o Batch, Duke, or C-G: Summary of the information on plants having
these cookers, respectively.
o Baro, S & T, or Air: Summary of the information on plants having
barometric leg, shell-and-tube, and air condensers, respectively.
46
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Kjeldahl nitrogen (TKN). This means that an increase (decrease)
in one of these waste load parameters will account for a certain
predictable increase (decrease) in one of the other parameters.
In fact, the square of the correlation coefficient (called the
coefficient of determination) is a measure of the predictability.
Consequently, the high degree of correlation between BOD5 and
grease waste load implies that much of the variation in BOD5
waste load is caused by variations in the grease load. The
correlation coefficients from these analyses are presented in
Table 8.
Table 8. Correlation Coefficients of Several
Raw Waste Load Parameters with EOD5
from the Field Sampling Results
Parameter
Grease
COD
Total Volatile
Solids
Total Dis-
solved Solids
Kjeldahl
Nitrogen
Correlation
.Coefficient
0. 905
0.933
0. 789
0.796
0.580
The basic manufacturing processes in independent rendering (see
Section IV) should have no influence on the raw waste load,
because they are universal. However, some processing equipment,
such as cookers and condensers, dc differ significantly in
operating principles. However, a comparison of data for batch
versus Duke and C-G continuous cookers and for the three types of
condensers—barometric leg, shell-and-tube, and air—revealed no
discernible difference in raw BOD5_ waste load. These data were
presented in Section IV and Figures 8 and 9, along with a further
discussion. Incidentally, it was previously mentioned and
illustrated with the data from Table 7 that barometric leg
condensers use far more water per unit of raw material processed.
Obviously, the amount of water used for condensing does not
affect the raw waste load per unit of RM processed. In fact, a
regression analysis for raw BOD5 waste load and waste water flow
oer unit of RM processed revealed no correlation. The
correlation coefficient for this analysis was -0.027. Earlier
studies on meat packing plants8 and poultry slaughterhouses 11
revealed a strong positive relationship between raw waste load
and water use.
47
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The effect of plant size (amount of raw materials processed per
day) on waste load as measured by BOD5 was assessed by a multiple
regression analysis. This analysis showed no discernable
relationship between BOD5 per unit of RM processed and plant
size. The correlation coefficient was 0.062 and the square of
this coefficient, which is the coefficient of determination, is
only 0.0038.
Plant size does, however, appear to be related to the type of
cooker and condenser used. Table 7 shows that the average amount
of raw material processed is smaller for plants using batch
cookers and barometric leg condensers than for plants using
continuous cookers (Duke and C-G) and shell-and-tube air
condensers. Plants with batch cookers and barometric leg
condensers frequently are older plants—built more than ten years
ago. Plant age, although apparently related to both size and
equipment type, is not related to waste load. Size and age were
factors considered in categorizing the industry and were
discussed in more detail in Section IV.
Sources of Waste Water
The most typical process and waste water flow arrangement used by
the independent rendering industry is shown schematically in
Figure 11. Hide curing is shown in this figure (even though the
majority of the plants do not handle hides) because it can
represent a significant portion of the total raw waste load.
Some plants, rather than using the sequence of manufacturing
processing illustrated in Figure 11, use slight variations of it.
A plant processing poultry by-products, for example, will usually
have two complete processing operations on the same premises.
One operation is for poultry offal and dead birds, which will be
very similar to the arrangement shown in Figure 11; the other
operation will be for the feathers and blood. The feather and
blood operation will not include the liquid-solid separation
process nor any of the grease processes. Other rendering plants
may not have blending and bagging processes if, for example, they
do not handle blood or feather meal and their meat and bone is
consistently of a high crude protein level. Still others may not
have a size-reduction process; these include plants that handle
grease only, or a high percent of poultry offal. Plants that
have large grease operations probably vary more from the process
flow arrangement of Figure 11 than do any other plants. In these
operations, there is receiving, cooking (or heating), separation
of the water and solids from the grease, storage and shipping.
Yet these operations still have the same characteristic waste
loads as the other rendering plants. In addition, there are very
few plants with large grease operations, and most of these
usually have a separate operation schematically similar to that
of Figure 11 for processing of fats and other raw materials.
Figure 11 also shows the major sources of waste water as
indicated by the dashed line. The sources include auxiliary
operations in addition to manufacturing processes. The auxiliary
48
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MANUFACTURING PROCESSES
WASTE WATER FLOW
RAW MATERIAL
RECEIVING
SIZE
REDUCTION
COOKING AND
DRYING
VAPOR
CONDENSING
LIQUID - SOLID
SEPARATION
r
ODOR
CONTROL
MEAL MILLING
AND SCREENING
BLENDING
AND BAGGING
r
SPILLS
I
PLANT AND TRUCK
CLEAN UP
1
GREASE AND SOLIDS
RECYCLED TO
COOKING & DRYING
MATERIALS
RECOVERY
r:
RAW WASTE
SANITARY
FACILITIES
,FRESH WATER
-*- PRODUCT AND MATERIAL FLOW
•*- WASTE WATER FLOW
Figure 11. Typical Rendering Process and Waste Water Flow Arrangement
49
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operations are odor control, spills, and plant and truck cleanup;
the manufacturing processes are receiving, vapor condensing from
cooking and drying, and hide curing. These sources this section.
Total plant waste loads including the effects of materials
recovery were presented in Table 6 and discussed previously in
this section.
Raw Materials Receiving
Liquid drainage from raw materials receiving areas can contribute
significantly to the total raw waste load. Frequently throughout
the processing period large amounts of raw materials accumulate
in receiving areas (either in bins or on floors) allowing strong
liquors to drain off and enter sewers. This is especially true
of plants processing poultry feathers because of the manner in
which feathers, offal and blood are sometimes handled at their
source (poultry slaughterhouses). As a result, the feathers or
combined feathers and offal often contain much blood and excess
water. At one such plant that was sampled, this drainage
amounted to roughly 20 percent of the original raw material
weight and had an average BOD5 value of 12,500 mg/1. This BOD5
loss amounted to 2.5 kg BOD5/kkg RM (2.5 lb/1000 Ib RM) and 43
percent of the total plant raw BOD5 waste load. In another plant
that had a dual operation for poultry offal and for feathers and
blood, the loss caused by drainage from the feather operation was
calculated from field sampling information; it was about 1.4 kg
BOD5/kkg RM, or about 39 percent of the waste load prior to
materials recovery processes. In these examples, the waste load
caused by drainage of liquors from raw materials is obviously
very significant. A partial remedy for these losses, which was
practiced in a plant included in the field survey, is to isolate,
steam sparge, and screen these waste waters.
Vapor Condensing
Condensate from the cooking and drying process typically
contributes atout 30 percent of the total raw BOD5 waste load.
The field sampling condensables was from 0.049 to 1.53 kg
BOD5/kkg RM (0.049 to 1.53 Ib BOD5/1000 Ib RM), with an average
value of 0.73 kg/kkg RM. A summary of concentrations and waste
loads of undiluted condensed cooking vapors is presented in
Tables 9 and 10, respectively. of course, being undiluted means
the vapors were condensed in a closed system: air or shell-and-
tube condensers. A number of factors, such as rate of cooking,
speed
of agitation, cooker overloading, foaming, lack of traps, etc.,
are probably responsible for much of the variation in values.
Raw materials could also have a direct effect on the values,
although no discernible difference between raw materials and
total plant raw waste load was revealed by a multiple regression
analysis, as discussed in Section IV.
50
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Table 9. Concentrations of Undiluted Condensed Cooking Vapors
Parameter
BOD5
COD
Total
Volatile
Solids
Total
Dissolved
Solids
Total
Phosphorus
Chlorides
Total
Kjeldahl
Nitrogen
Nitrate
Nitrite
Grease
Suspended
Solids
mg/1
Number of
Observations
11
10
10
7
7
7
7
7
7
7
10
Average
Value
1723
2207
185
201
6.3
196
493
263
0.11
109
60.9
Standard
Deviation
1165
1383
169
143
6.3
212
317
238
0.08
76
94.3
Low
Value
80
192
15
59
2.45
13
36
14
0.01
63
11
High
Value
3950
4212
579
413
20.4
593
1005
750
0.02
271
327
51
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The pH of the condensables averaged 8.7 for 11 observations with
a standard deviation of 1.12 and with low and high values of 6.8
and 9.7, respectively. Incidentally, the number of observations
for the waste parameters in these tables is frequently less for
the waste load values than for the concentration values. This is
because some of the data were lacking to permit the calculation
of the waste load; e.g., the amount of raw material processed was
not always known.
The use of barometric leg condensers will dilute the condensables
and thus lower the concentrations from those listed in Table 9.
In many
cases, treated waste waters are recycled through barometric legs
for condensing cooking vapors and to allow a high water
throughput to lower the barometric leg effluent temperature to at
least 38°C (10C°F) for odor control. This practice may increase
the actual waste load slightly; however, an analysis of the data
by type of condenser (see Section IV) did not reveal any distinct
differences in waste loads caused by type of condenser.
Spills and Plant and Truck Cleanup
Washdown (cleanup) of the plant, trucks, and spills can
contribute significantly to the total plant raw waste load. In
one plant that was sampled, the waste waters from cleanup were
isolated from the condensables. Analysis of this source revealed
that cleanup in this plant added 16.2 kg BOD5/kkg (Ib BOD5/1000
Ib) RM to the raw waste load, an extraordinarily high value. The
reasons for this high value were that the plant used a constant
flow of hot water throughout the entire production period; it
constantly cleaned up spills from worn, leaking equipment, and
frequently shut off the automatic skimmer of the materials
recovery systems, resulting in large amounts of grease carry-
over. The large amounts of hot water helped maintain the cleanup
effluent temperature above 52°C (125°F), thus preventing
efficient grease separation. Needless to say, the plant was
clean. In another plant, the BOD5 and suspended solids load just
from cleanup were 43 and 50 percent of the total, respectively.
It was observed on the field survey studies that spills caused by
equipment breakdown occurred frequently and that leaks from worn
equipment were not uncommon. This does not mean that spills
cannot be prevented or limited; however, the common practice when
equipment breaks down is to open it and dump materials directly
on the floor. This allows free draining grease and liquors to
enter the sewers. Also, after the bulk of the solids have been
shoveled up, the remainder is washed off. More effort could be
made to contain materials when equipment breaks down and to
better maintain equipment by use of regularly scheduled
maintenance programs on equipment during down-time.
52
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Table 10. Waste Loads for Undiluted Condensed Cooking Vapors
Parameter
BOD
COD
Total
Volatile
Solids
Total
Dissolved
Solids
Total
Phosphorus
Chloride
Total
Kjeldahl
Nitrogen
Nitrate
Nitrite
Grease
Suspended
Solids
kg/kkg KM or lb/1000 Ib BM
Number of
Observations
10
7
7
6
6
6
6
6
6
7
9
Average
Value
0.73
1.10
0.086
0.21
0.0021
0.056
0.17
0.081
0.0018
0.14
0.018
Standard
Deviation
0.50
0.75
0.093
0.25
0.00015
0.078
0.12
0.067
0.0038
0.25
0.017
High
Value
1.53
2.23
0.31
0.73
0.0043
0.21
0.35
0.16
0.0096
0.70
0.056
Low
Value
0.049
0.12
0.0032
0.0013
0.00081
0.0046
0.022
0.0086
0.000008
0.015
0.0058
53
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Odor Control
Air scrubbers are common in the rendering industry for odor
control. The relative volume of water used, however, varies
greatly, although the waste load caused by scrubbing is
insignificant. The reason for the variation in water flow is
that scrubbers for plant air and other low-aerosol-containing
emissions (smoke and grease particulates) can tolerate recycling
of up to 95 percent of the scrubbing waters. However, air
heavily laden with odorous aerosols is usually scrubbed with
fresh water to prevent grease buildup and clogging of the
equipment. For example, one dual operation (one batch operation
and one continuous operation) plant contained a total of nine
scrubbers. Although some scrubbers did use partial recycle of
scrubbing water, the volume of scrubbing waters was about 75
percent of the total plant effluent volume. Typically, plants
will have only two or three scrubbers: one for total plant air,
one for the presses, and possibly one for the ring or rotary
dryers. Most of the scrubbing waters then are recycled, and the
relative waste water volume from scrubbing is small. For
example, one plant that was sampled had two scrubbers—one for
plant air and one for a dryer—and the volume of waste water from
the scrubbers amounted to only six percent of the total effluent
volume.
Hide Curing
Hide curing is conducted in a number of independent rendering
plants. The waste water from this operation is high in strength
but relatively low in volume, particularly when the curing
solution is only dumped a few times each year. Data from
previous studies°2,8 indicate that about 7.7 liters (2 gallons)
is the waste water overflow volume for brine curing each cattle
hide.
The waste load for just curing hides at an independent rendering
plant is, however, considerably less than the waste load for
curing at a packing plant. This is because curing of hides at a
packing plant includes a number of additional operations. These
are washing, demanuring, and defleshing. In addition, the time
differential between hide removal and hide delivery at a
rendering plant allows for much of the blood and other fluids to
seep from the hides. This time differential ranges from several
hours to a few days. Also, hides and accompanying flesh removed
from dead animals at a rendering plant do not appear to contain
anywhere near the amount of blood and fluid that a hide removed
at a packing plant from an animal killed just moments earlier
contains.
Data from the recent study of packing plants8 states that the
average waste load for handling and curing hides of a
packinghouse is 1.5 kg BOD5/kkg LWK (live weight killed). Since
the average LWK for beef is about 454 kg (1000 pounds), this can
be equivalently expressed as 0.68 kg BOD5/hide. On the other
hand, a study of tannery effluents0* lists the waste load for
just hide curing at a tannery as 3.9 kg BOD5/kkg hides (3.9
lb/1000 Ib). Using an average hide weight of 32 kg (70 pounds),
54
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Table 11. Waste Load Characteristics for Hide Curing at an
Off-Site Rendering Plant Versus Those for a Tannery
12
Table 12. Measured Waste Strengths of Tank Water
and Blood Water
en
en
Parameter
BOD
COD
Total Volatile
Solids
Suspended
Solids
Kjeldahl
Nitrogen
Ammonia
Nitrate
Nitrite
Total
Phosphorus
Total Dis-
solved Solids
Chloride
Grease
kg /hide
Rendering
Plant
0.11
0.21
0.17
0.064
0.014
0.0013
4.4 x 10~5
4.1 x 10~6
0.0021
2.9
1.26
0.0011
T annery
0.12
0.24
0.08
0.32
Parameter
BOD5
COD
Total Volatile
Solids
Total Dissolved
Solids
Total
Phosphorus
Chloride
Total Kjeldahl
Nitrogen
Ammonia
Nitrate
Nitrite
Grease
Suspended
Solids
mg/1
Tank Water
31,390
49,152
36,739
54,791
1,350
8,638
2,187
81
3.43
0.35
9,901
6,647
Blood
Water
18,950
27,200
17,516
315
3,498
1,813
-------
this value can be expressed as 0.12 kg (0.26 Ib) BOD5 per hide.
This latter example should also typify the waste load for hide
curing at an independent rendering plant. In fact, analysis of
only the hide curing effluent at one independent rendering plant
yielded a BOD5 waste load of 0.11 kg (0.24 Ib) per hide. The
results of this analysis are summarized in Table 11. For
comparison, the value recalculated from reference 12, assuming 32
kg/hide (70 pounds), is also included.
Miscellaneous Sources
Sewered tankwater and blood water are major sources of waste
load. The sources of tank water are grease processing, and wet
and low-temperature rendering; the source of blood water is from
processing blood by steam sparging and then separating the blood
water from the coagulated blood by screening. Fortunately, not
many independent rendering plants have the processes that
generate these sources of waste. Also, some plants that do
generate tankwater eliminate it as a waste source by evaporating
it down to stick, which is used for tankage in dry inedible
rendering. As mentioned in Section III, the BOD5 and grease
concentrations of tankwater can be as high as 30,000 to 45,000
mg/1 and 20,000 to 60,000 mg/1, respectively.
Table 12 shows the measured waste strengths of tankwater from a
grease operation and of blood water from steam sparging and
screening of blood. The waste load resulting from the sewering
of the tankwater was 9.4 kg BOD5/kkg (9.4 Ib BOD5/1000 Ib) grease
before primary treatment (materials recovery process). However,
much of this waste load was removed by primary treatment, since
the amount of grease processed was about 63 percent of the total
plant RM and since the total plant waste load was only 2.2 kg
BOD5/kkg (2.2 lb/1000 Ib) RM. Likewise, the sewering of blood
water added 16.3 kg BOD5/kkg blood before primary treatment.
Judging from the values of the total plant raw waste load and the
waste loads of the other sources, it would appear that the
primary treatment recovered very little, if any, of the waste
load from the sewering of blood water; this is as expected. It
should be pointed out, however, that the blood screening process
was not very efficient and that a pilot study at that plant
revealed that an improved screening process would significantly
lower the load from sewering blood water.
56
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SECTION VI
SELECTION OF POLLUTANT PARAMETERS
SELECTED PARAMETERS
Based on a review of the Corps of Engineers1 Permit Applications
from the independent renderers, previous studies on similar waste
waters such as from the meat packing plants, industry data,
questionnaire data, and data obtained from sampling plant waste
waters during this study, the following chemical, physical, and
biological constituents constitute pollutants as defined in the
Act.
BOD5 (5-day, 20°C biochemical oxygen demand)
COD (chemical oxygen demand)
Total suspended solids (TSS)
Total dissolved solids (TDS)
Total volatile solids (TVS)
Oil and grease
Ammonia nitrogen
Kjeldahl nitrogen
Nitrates and nitrites
Phosphorus
Chloride
Bacteriological counts (total and fecal coliform)
pH, acidity, alkalinity
Temperature
On the basis of all evidence reviewed, there do not exist any
purely hazardous pollutants (such as heavy metals or pesticides)
in the waste discharge from the independent rendering plants.
While all of the above parameters are in present renderer plant
waste water, the amount and reliability of available data, costs
for treatment or control, and availability of technology were
factors which resulted in limitations only for the primary
parameters BOD5, TSS, Oil and grease, fecal coliforms, ammonia,
phosphorus and pH.
RATIONALE FOR SELECTION OF IDENTIFIED PARAMETERS
5-Day Biochemical Oxygen Demand (BOD5)
This parameter is an important measure of the oxygen consumed by
microorganisms in the aerobic decomposition of the wastes at 20°C
over a five-day period. More simply, it is an indirect measure
of the biodegradability of the organic pollutants in the waste.
BOD5 can be related to the depletion of oxygen in the receiving
stream or to the requirements for the waste treatment. Values of
BOD5 range from 100 to 9000 mg/1 in the raw waste, although
typical values range from 1000 to 5000 mg/1. Low BOD5 values in
the raw waste are frequently the result of the dilutional effects
of using a barometric condenser; high values due to a combination
57
-------
of factors, such as undiluted condenser waters, frequent spills,
and a relatively large amount of drainage of high strength
liquids from the raw material.
If the BOD5 of the final effluent of a rendering plant into a
receiving body is too high, it will reduce the dissolved oxygen
level in that stream to below a level that will sustain most fish
life; i.e., below about 4 mg/1. Many states currently restrict
the BOD5 effluents to below 20 mg/1 if the stream is small in
comparison with the flow of the effluent. A limitation of 200 to
300 mg/1 of BOD5 is often applied for discharge to a municipal
sewer, and surcharge rates often apply if the BOD5 is above the
designated limit. BOD5 is included in the effluent limitations
recommended because its discharge to a stream is harmful to
aquatic life since it depletes the oxygen supply.
A 20-day biochemical oxygen demand (BOD20), sometimes called
"ultimate" BOD, is usually a better measure of the waste load
than BOD5. However, the test for BOD20 requires 20 days to run,
so it is an impractical measure for most purposes.
Biochemical oxygen demand (BOD) is a measure of the oxygen
consuming capabilities of organic matter. The BOD does not in
itself cause direct harm to a water system, but it does exert an
indirect effect by depressing the oxygen content of the water.
Sewage and other organic effluents during their processes of
decomposition exert a BOD, which can have a catastrophic effect
on the ecosystem by depleting the oxygen supply. Conditions are
reached frequently where all of the oxygen is used and the
continuing decay process causes the production of noxious gases
such as hydrogen sulfide and methane. Water with a high BOD
indicates the presence of decomposing organic matter and
subsequent high bacterial counts that degrade its quality and
potential uses.
Dissolved oxygen (DO) is a water quality constituent that, in
appropriate concentrations, is essential not only to keep
organisms living but also to sustain species reproduction, vigor,
and the development of populations. Organisms undergo stress at
reduced DO concentrations that make them less competitive and
able to sustain their species within the aquatic environment.
For example, reduced DO concentrations have been shown to
interfere with fish population through delayed hatching of eggs,
reduced size and vigor of embryos, production of deformities in
young, interference with food digestion, acceleration of blood
clotting, decreased tolerance to certain toxicants, reduced food
efficiency and growth rate, and reduced maximum sustained
swimming speed. Fish food organisms are likewise affected
adversely in conditions with suppressed DO. Since all aerobic
aquatic organisms need a certain amount of oxygen, the
consequences of total lack of dissolved oxygen due to a high BOD
can kill all inhabitants of the affected area.
If a high BOD is present, the quality of the water is usually
visually degraded by the presence of decomposing materials and
58
-------
algae blooms due to the uptake of degraded materials that form
the foodstuffs of'the algal populations.
59
-------
Chemical Oxygen Demand (COD)
COD is yet. another measure of oxygen demand. It measures the
amount of organic (and some inorganic) pollutants under a
carefully controlled direct chemical oxidation by a dichromate-
sulfuric acid reagent. COD is a much more rapid measure of
oxygen demand than BOD5, and is potentially very useful.
However, it does not have the same significance, and at the
present time cannot be substituted for BOD5, because COD:BOD5
ratios vary with the types of wastes. The COD measures more than
only those materials that will readily biodegrade in a stream and
hence deplete the stream's dissolved oxygen supply.
COD provides a rapid determination of the waste strength. Its
measurement will indicate a serious plant or treatment
malfunction long before the BOD5 can be run. A given plant or
waste treatment system usually has a relatively narrow range of
COD:BOD5 ratios, if the waste characteristics are fairly
constant, so experience permits a judgment to be made concerning
plant operation from COD values. In the rendering industry, COD
ranges from about 1.5 to 6 times the BOD5 in both the raw and
treated wastes, with typical ratios between 1.5 and 3.0.
Although the nature of the impact of COD on receiving waters is
the same as for BOD5, BOD_5 was chosen for inclusion in the
effluent limitations rather than COD because of the industry's
frequent use and familiarity with BOD5.
Total Suspended Solids (TSS)
This parameter measures the suspended material that can be
removed from the waste waters by laboratory filtration, but does
not include coarse or floating matter that can be screened or
settled out readily. Suspended solids are a visual and easily
determined measure of pollution and also a measure of the
material that may settle in tranquil or slowmoving streams. A
high level of suspended solids is an indication of high BOD5.
Generally, suspended solids range from one-third to three-fourths
of the BOD5 values in the raw waste. Suspended solids are also a
measure of the effectiveness of solids removal systems such as
clarifiers and fine screens.
Suspended solids frequently become a limiting factor in waste
treatment when the BOD5 is less than about 20 mg/1. In fact, in
highly treated waste, suspended solids usually have a higher
value than the BOD5, and in this case, it may be easier to lower
the BOD5 even further, perhaps to 5 to 10 mg/1, by filtering out
the suspended solids. Suspended solids in the treated waste
waters of rendering plants correlate well with BOD5, COD, and
total volatile solids. The same is not true, however, for the
raw wastes.
Suspended solids in receiving waters act as adsorption surface
for ionic nutrients, and as a substrate for bacterial population,
thus resulting in high BOD5 values. Suspended solids also
60
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inhibit light penetration and thereby reduce the primary
productivity of algae (photosynthesis). Because of the strong
impact suspended solids can have on receiving waters, suspended
solids were included in the effluent limitations recommended in
this report.
Suspended solids include both organic and inorganic materials.
The inorganic components include sand, silt, and clay. The
organic fraction includes such materials as grease, oil, tar,
animal and vegetable fats, various fibers, sawdust, hair, and
various materials from sewers. These solids may settle out
rapidly and bottom deposits are often a mixture of both organic
and inorganic solids. They adversely affect fisheries by
covering the bottom of the stream or lake with a blanket of
material that destroys the fish-food bottom fauna or the spawning
ground of fish. Deposits containing organic materials may
deplete bottom oxygen supplies and produce hydrogen sulfide,
carbon dioxide, methane, and other noxious gases.
In raw water sources for domestic use, state and regional
agencies generally specify that suspended solids in streams shall
not be present in sufficient concentration to be objectionable or
to interfere with normal treatment processes. Suspended solids
in water may interfere with many industrial processes, and cause
foaming in boilers, or encrustations on equipment exposed to
water, especially as the temperature rises. Suspended solids are
undesirable in water for textile industries; paper and pulp;
beverages; dairy products; laundries; dyeing; photography;
cooling systems, and power plants. Suspended particles also
serve as a transport mechanism for pesticides and other
substances which are readily sorbed into or onto clay particles.
Solids may be suspended in water for a time, and then settle to
the bed of the stream or lake. These settleable solids
discharged with man's wastes may be inert, slowly biodegradable
materials, or rapidly decomposable substances. While in
suspension, they increase the turbidity of the water, reduce
light penetration and impair the photosynthetic activity of
aquatic plants.
Solids in suspension are aesthetically displeasing. When they
settle to form sludge deposits on the stream or lake bed, they
are often much more damaging to the life in water, and they
retain the capacity to displease the senses. Solids, when
transformed to sludge deposits, may do a variety of damaging
things, including blanketing the stream or lake bed and thereby
destroying the living spaces for those benthic organisms that
would otherwise occupy the habitat. When of an organic and
therefore decomposable nature, solids use a portion or all of the
dissolved oxygen available in the area. Organic materials also
serve as a seemingly inexhaustible food source for sludgeworms
and associated organisms.
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Turbidity is principally a measure of the light absorbing
properties of suspended solids. It is frequently used as a
substitute method of quickly estimating the total suspended
solids when the concentration is relatively low.
Total Dissolved Solids (TDS)
The total dissolved solids in the waste waters of most
independent rendering plants contain both organic and inorganic
matter. A large source of organic dissolved solids is blood.
Inorganic salts can be a major part of the dissolved solids if
hide curing is conducted at the plant. The amount of dissolved
solids will also vary to a large extent with the type of in-plant
operations and the housekeeping practices. Dissolved solids are
of the same order of magnitude and correlate well with the total
volatile solids in both the raw and treated waste waters,
implying that, in general, most of the dissolved solids are
volatile. The inorganic dissolved solids are particularly
important because they are relatively unaffected by biological
treatment processess. Therefore, unless removed, they will
accumulate within the water system on total recycle or reuse, or
build up to high levels with partial recycle or reuse of the
waste water.
Dissolved solids affect the ionic nature of receiving waters and
are usually the nutrients for bacteria and protozoans. Thus,
they increase the eutrophication rate of the receiving body of
water. Total dissolved solids were not included in the effluent
limitations recommended in this report because the organic
portion would be limited by BOD5 limitations and the nutrient
portion by the nitrogen and phosphorus limitations.
In natural waters the dissolved solids consist mainly of
carbonates, chlorides, sulfates, phosphates, and possibly
nitrates of calcium, magnesium, sodium, and potassium, with
traces of iron, manganese and other substances.
Many communities in the United States and in other countries use
water supplies containing 2000 to 4000 mg/1 of dissolved salts,
when no better water is available. Such waters are not
palatable, may not quench thirst, and may have a laxative action
on new users. Waters containing more than 4000 mg/1 of total
salts are generally considered unfit for human use, although in
hot climates such higher salt concentrations can be tolerated
whereas they could not in temperate climates. Waters containing
5000 mg/1 or more are reported to be bitter and act as bladder
and intestinal irritants. It is generally agreed that the salt
concentration of good, palatable water should not exceed 500
mg/1.
Limiting concentrations of dissolved solids for fresh-water fish
may range from 5,000 to 10,000 mg/1, according to species and
prior acclimatization. Some fish are adapted to living in more
saline waters, and a few species of fresh-water forms have been
found in natural waters with a salt concentration of 15,000 to
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20,000 mg/1. Fish can slowly become acclimatized to higher
salinities, but fish in waters of low salinity cannot survive
sudden exposure to high salinities, such as those resulting from
discharges of oil-well brines. Dissolved solids may influence
the toxicity of heavy metals and organic compounds to fish and
other aquatic life, primarily because of the antagonistic effect
of hardness on metals.
Waters with total dissolved solids over 500 mg/1 have decreasing
utility as irrigation water. At 5,000 mg/1 water has little or
no value for irrigation.
Dissolved solids in industrial waters can cause foaming in
boilers and cause interference with cleanness, color, or taste of
many finished products. High contents of dissolved solids also
tend to accelerate corrosion.
Specific conductance is a measure of the capacity of water to
convey an electric current. This property is related to the
total concentration of ionized substances in water and water
temperature. This property is frequently used as a substitute
method of quickly estimating the dissolved solids concentration.
Total Volatile Solids (TVS)
Total volatile solids is a rough measure of the amount of organic
matter in the waste water. Actually it is the amount of
combustible material in both the total dissolved solids and total
suspended solids. Total volatile solids in the raw waste waters
of rendering plants correlates quite well with total dissolved
solids and COD, and fairly well with BOD5, SS, and grease; total
volatile solids in the final waste waters correlates well with
total dissolved solids and BOD5, and fairly well with SS, grease,
and COD, in the final waste waters. Because of these
correlations and because total volatile solids is a relatively
easy parameter to determine, it could be used as a rapid method
to determine a serious plant or treatment system malfunction.
Volatile solids in receiving waters are food for microorganisms,
and thus create increased eutrophicaticn. Effluent limitations
for total volatile solids were not established because TVS will
be limited by limitations on other pollutant parameters such as
BOD5 and suspended solids.
Oil and Grease
Grease, also called oil and grease, or hexane solubles, is a
major pollutant in the raw waste stream of rendering plants. The
source of grease is primarily from spillages of processed tallow
and grease and cleanup of equipment, floors, barrels, and trucks.
Grease forms unsightly films on the water, interferes with
aquatic life, clogs sewers, disturbs biological processes in
sewage treatment plants, and can also become a fire hazard. It
is also a food source for microorganisms which may be pathogenic.
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The loading of grease in the raw waste load varies widely, from
less than 0.1 to about 15 kg/kkg RM. The average raw waste
loading of grease is about 0.7 kg/kkg RM, which corresponds to an
average concentration of about 1660 mg/1. Grease may be harmful
to municipal treatment facilities and to trickling filters.
Grease correlates well with BOD5 and COD in the raw wastes, but
not in the treated wastes. Because grease appears to constitute
a major portion of the waste load from rendering plants, effluent
limitations were established for it.
Oil and grease exhibit an oxygen demand. Oil emulsions may
adhere to the gills of fish or coat and destroy algae or other
plankton. Deposition of oil in the bottom sediments can serve to
exhibit normal benthic growths, thus interrupting the aquatic
food chain. Soluble and emulsified material ingested by fish may
taint the flavor of the fish flesh. Water soluble components may
exert toxic action on fish. Floating oil may reduce the re-
aeration of the water surface and in conjunction with emulsified
oil may interfere with photosynthesis. Water insoluble
components damage the plumage and costs of water animals and
fowls. Oil and grease in water can result in the formation of
objectionable surface slicks preventing the full aesthetic
enjoyment of the water. Oil spills can damage the surface of
boats and can destroy the aesthetic characteristics of beaches
and shorelines.
Ammonia Nitrogen
Ammonia nitrogen in the raw waste is just one of many forms of
nitrogen in a waste stream. Anaerobic decomposition of protein,
which contains organic nitrogen, leads to the formation of
ammonia. Thus, anaerobic lagoons or digesters produce high
levels of ammonia. Also, septic (anaerobic) conditions within
the plant in traps, basins, etc., may lead to ammonia in the
waste water. Another source of ammonia can be liquid drainage
from raw materials containing manure, and also from proteinaceous
matter such as blood that has been "aged."
Ammonia is oxidized by bacteria in a process called
"nitrification" to nitrites and nitrates. This may occur in an
aerobic treatment process and in a stream. Thus, ammonia will
deplete the oxygen supply in a stream; its oxidation products are
recognized nutrients for aquatic growth. Also, free ammonia in a
stream is known to be harmful to fish.
Typical concentrations in the raw waste range from 25 to 300
mg/1; however, after treatment in an anaerobic system, the
concentrations of ammonia can reach 100 to 500 mg/1. Ammonia is
limited in drinking water to 0.05 to 0.1 mg/l.°3 In some cases a
stream standard is less than 2 mg/1. Effluent limitations for
new sources and the 1983 limits were established for ammonia
because of the strong impact it can have on receiving waters.
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Ammonia is a common product, of the decomposition of organic
matter. Dead and decaying animals and plants along with human
and animal body wastes account for much of the ammonia entering
the aquatic ecosystem. Ammonia exists in its non-ionized form
only at higher pH levels and is the most toxic in this state.
The lower the pH, the more ionized ammonia is formed and its
toxicity decreases. Ammonia, in the presence of dissolved
oxygen, is converted to nitrate (NO3) by nitrifying bacteria.
Nitrite (NO2), which is an intermediate product between ammonia
and nitrate, sometimes occurs in quantity when depressed oxygen
conditions permit. Ammonia can exist in several other chemical
combinations including ammonium chloride and other salts.
Nitrates are considered to be among the poisonous ingredients of
mineralized waters, with potassium nitrate being more poisonous
than sodium nitrate. Excess nitrates cause irritation of the
mucous linings of the gastrointestinal tract and the bladder; the
symptoms are diarrhea and diuresis, and drinking one liter of
water containing 500 mg/1 of nitrate can cause such symptoms.
Infant methemoglobinemia, a disease characterized by certain
specific blood changes and cyanosis, may be caused by high
nitrate concentrations in the water used for preparing feeding
formulae. While it is still impossible to state precise
concentration limits, it has been widely recommended that water
containing more than 10 mg/1 of nitrate nitrogen (NO3-N) should
not be used for infants. Nitrates are also harmful in
fermentation processes and can cause disagreeable tastes in beer.
In most natural water the pH range is such that ammonium ions
(NH4+) predominate. In alkaline waters, however, high
concentrations of un-ionized ammonia in undissociated ammonium
hydroxide increase the toxicity of ammonia solutions. In streams
polluted with sewage, up to one half of the nitrogen in the
sewage may be in the form of free ammonia, and sewage may carry
up to 35 mg/1 of total nitrogen. It has been shown that at a
level of 1.0 mg/1 un-ionized ammonia, the ability of hemoglobin
to combine with oxygen is impaired and fish may suffocate.
Evidence indicates that ammonia exerts a considerable toxic
effect on all aquatic life within a range of less than 1.0 mg/1
to 25 mg/1, depending on the pH and dissolved oxygen level
present.
Ammonia can add to the problem of eutrophication by supplying
nitrogen through its breakdown products. Some lakes in warmer
climates, and others that are aging quickly are sometimes limited
by the nitrogen available. Any increase will speed up the plant
growth and decay process.
Kjeldahl Nitrogen
This parameter measures the amount of ammonia and organic
nitrogen; when used in conjunction with the ammonia nitrogen, the
organic nitrogen can be determined by the difference. Under
septic conditions, organic nitrogen decomposes to form ammonia.
Kjeldahl nitrogen is a good indicator of the crude protein in the
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effluent and, hence, of the value of proteinaceous material being
lost in the waste water. The protein content is usually taken as
6.25 times the organic nitrogen. The sources of Kjeldahl
nitrogen are basically the same as for ammonia nitrogen, above.
The raw waste loading of Kjeldahl nitrogen is extremely variable
and is highly affected by blood losses from raw material drainage
and blood and feather operations, and by liquid entrainment in
the cooking vapors. Typical raw loadings range from 0.12 to 1.20
kg/kkg (0.12 to 1.20 lb/1000 Ib) raw material; concentrations
range from about 60 to 800 mg/1, with the lower values usually
caused by the dilutional effects of barometric leg condensers.
Typical raw waste concentrations of Kjeldahl nitrogen are between
50 and 100 mg/1. Kjeldahl nitrogen has not been a common
parameter for regulation and is a much more useful parameter for
raw waste than for final effluent. Even so, effluent limitations
for 1983 were established for Kjeldahl nitrogen because, in
addition to ammonia which has a strong environmental impact on
receiving waters, it can be a major source of organic material,
which is food for microorganisms in receiving waters.
Nitrates and Nitrites
Nitrates and nitrites, normally reported as N, are the result of
oxidation of ammonia and of organic nitrogen. Nitrates as N
should not exceed 20 mg/1 in water supplies.04 They are
essential nutrients for algae and other aquatic plant life. For
these reasons, effluent limitations for new sources and for the
1983 limits were established for nitrites-nitrates as N.
Nitrites ranged from a trace to 0.040 kg/kkg RM in the raw wastes
and from a trace to 0.08 kg/kkg EM in the treated wastes;
nitrates ranged from a trace to 0.06 kg/kkg RM in the raw and
from a trace to 0.012 kg/kkg RM in the treated wastes.
Concentrations of nitrites varied from 0.02 to 26 mg/1 in the raw
and from O.OU to 1.2 mg/1 in the final; nitrate concentrations
varied from 0.02 to 13 mg/1 in the raw and from 0.02 to 3.25 mg/1
in the treated waste. Again, low values are primarily caused by
the dilutional effects of barometric leg condensers.
Nitrates and nitrites are important measurements, along with
Kjeldahl nitrogen, in that they allow for the calculation of a
nitrogen balance on the treatment system. In fact, the field
sampling data verified that when there was a substantial nitrogen
reduction by the treatment system, it was accompanied by good
BOD5, SS, and grease reductions.
Phosphorus
Phosphorus, commonly reported as P, is a nutrient for aquatic
plant life and can therefore cause an increased eutrophication
rate in water courses. The threshold concentration of phosphorus
in receiving bodies that can lead to eutrophication is about 0.01
ma/1. The primary sources of phosphorus in raw waste from
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rendering are bone meal, detergents, and boiler water additives.
The total phosphorus in the raw effluent ranges from about 0.007
to 0.28 kg/kkg RM (0.007 to 0.28 lb/1000 Ib RM), or a typical
concentration range of 3 to 50 mg/1 as P. Effluent limitations
were established for phosphorus for new source performance
standards and for the 1983 limits because of its effect on
eutrophication rates.
During the past 30 years, a formidable case has developed for the
belief that increasing standing crops of aquatic plant growths,
which often interfere with water uses and are nuisances to man,
frequently are caused by increasing supplies of phosphorus. Such
phenomena are associated with a condition of accelerated
eutrophication or aging of waters. It is generally recognized
that phosphorus is not the sole cause of eutrophication, but
there is evidence to substantiate that it is frequently the key
element in all of the elements required by fresh water plants and
is generally present in the least amount relative to need.
Therefore, an increase in phosphorus allows use of other, already
present, nutrients for plant growths. Phosphorus is usually
described, for these reasons, as a "limiting factor."
When a plant population is stimulated in production and attains a
nuisance status, a large number of associated liabilities are
immediately apparent. Dense populations of pond weeds make
swimming dangerous. Boating and water skiing and sometimes
fishing may be eliminated because of the mass of vegetation that
serves as a physical impediment to such activities. Plant
populations have been associated with stunted fish populations
and with poor fishing. Plant nuisances emit vile stenches,
impart tastes and odors to water supplies, reduce the efficiency
of industrial and municipal water treatment, impair aesthetic
beauty, reduce or restrict resort trade, lower waterfront
property values, cause skin rashes to man during water contact,
and serve as a desired substrate and breeding ground for flies.
Phosphorus in the elemental form is particularly toxic, and
subject to bioaccumulation in much the same way as mercury.
Colloidal elemental phosphorus will poison marine fish (causing
skin tissue breakdown and discoloration). Also, phosphorus is
capable of being concentrated and will accumulate in organs and
soft tissues. Experiments have shown that marine fish will
concentrate phosphorus from water containing as little as 1 ug/1.
Chlorides
Chlorides in concentrations of the order of 5000 mg/1 can be
harmful to people and other animal life. High chloride
concentrations in waters can be troublesome for certain
industrial uses and for reuse or recycling of water. The major
sources of chlorides from rendering plants are the salt from
animal tissues, hide curing operations, and blood. The
concentrations in raw waste are extremely variable from plant to
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plant, and are normally much higher for plants treating hides or
sewering blood waters (e.g., drainage from poultry feathers) than
they are for other plants. The amount in the waste water is an
indicator that these processes are being operated. For example,
chloride concentrations from liquid drainage of cured hides were
measured at 80,000 mg/1 as Cl; from drainage of bloody waters
from poultry offal, at 691 mg/1 as Cl; and from sewered blood
waters from a blood operation, at 3500 mg/1 as Cl. The range of
chloride loadings in raw waste effluents is from 0.08 to greater
than 2.56 kg/kkg RM (2.56 lb/1000 Ib RM). Chloride loadings are
unaffected by biological treatment systems used by the industry
today, and once in the waste waters they are very costly to
remove. While high chloride concentrations in biological
treatment systems and receiving waters can upset the metabolic
rate of organisms, effluent concentrations are probably too low
to have a serious impact.
Fecal Coliforms
The coliform bacterial contamination (total and fecal) of raw
waste is substantially reduced (by a factor of 100 to 200) in the
larger waste treatment systems used in the industry, such as
anaerobic lagoons followed by several aerobic lagoons.
Chlorination will reduce coliform counts to less than 400 per 100
ml for total, and to less than 100 per 100 ml for fecal. Data
indicate that the total coliform of the raw waste from rendering
plants is in the 0.65- to 500-million per 100 ml range with a
median value of about 7 million per 100 ml; for fecal coliform,
the range is 0.05- to 75-million per 100 ml, with a median value
of about 0.7 million per 100 ml. Typically, states require that
the total coliform count not exceed 50-200 MPN (most probable
number) per 100 ml for waste waters discharged into receiving
waters. Hence, most final effluents require chlorination to meet
state standards. When waters contain 200 counts of fecal
coliform per 100 ml, it is assumed that pathogenic
enterobacteriacea, which can cause intestinal infections, are
present. Consequently, effluent limitations were established for
fecal coliforms.
Fecal coliforms are used as an indicator since they have
originated from the intestinal tract of warm blooded animals.
Their presence in water indicates the potential presence of
pathogenic bacteria and viruses.
The presence of coliforms, more specifically fecal coliforms, in
water is indicative of fecal pollution. In general, the presence
of fecal coliform organisms indicates recent and possibly
dangerous fecal contamination. When the fecal coliform count
exceeds 2,000 per 100 ml there is a high correlation with
increased numbers of both pathogenic viruses and bacteria.
Many microorganisms, pathogenic to humans and animals, may be
carried in surface water, particularly that derived from effluent
sources which find their way into surface water from municipal
and industrial wastes. The diseases associated with bacteria
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include bacillary and amoebic dysentery, Salmonella
gastroenteritis, typhoid and paratyphoid fevers, leptospirosis,
cholera, vibriosis and infectious hepatitis. Recent studies have
emphasized the value of fecal coliform density in assessing the
occurrence of Salmonella, a common bacterial pathogen in surface
water. Field studies involving irrigation water, field crops and
soils indicate that when the fecal ccliform density in stream
waters exceeded 1,000 per 100 ml, the occurrence of Salmonella
was 53.5 percent.
pH, Acidity, Alkalinity
pH is of relatively minor importance, although waters with pH
outside the 6.0 to 9.0 range can affect the survival of most
organisms, particularly invertebrates. The usual pH for raw
waste falls between 6.0 and 9.0; although the pH of the
condensables tends to be higher (7.2 to 9.6). This pH range is
close enough to neutrality that it does not significantly affect
treatment effectiveness or effluent quality. However, some
adjustment may be required, particularly if pH adjustment has
been used to lower the pH for protein precipitation, or if the pH
has been raised for ammonia stripping. The pH of the waste water
then should be returned to its normal range before discharge.
The effect of chemical additions for pH adjustment should be
taken into consideration, as new pollutants could result.
Acidity and alkalinity are reciprocal terms. Acidity is produced
by substances that yield hydrogen ions upon hydrolysis and
alkalinity is produced by substances that yield hydroxyl ions.
The terms "total acidity" and "total alkalinity" are often used
to express the buffering capacity of a solution. Acidity in
natural waters is caused by carbon dioxide, mineral acids, weakly
dissociated acids, and the salts of strong acids and weak bases.
Alkalinity is caused by strong bases and the salts of strong
alkalies and weak acids.
The term pH is a logarithmic expression of the concentration of
hydrogen ions. At a pH of 7, the hydrogen and hydroxyl ion
concentrations are essentially equal and the water is neutral.
Lower pH values indicate acidity while higher values indicate
alkalinity. The relationship between pH and acidity or
alkalinity is not necessarily linear or direct.
Waters with a pH below 6.0 are corrosive to water works
structures, distribution lines, and household plumbing fixtures
and can thus add such constituents to drinking water as iron,
copper, zinc, cadmium and lead. The hydrogen ion concentration
can affect the "taste" of the water. At a low pH water tastes
"sour." The bactericidal effect of chlorine is weakened as the pH
increases, and it is advantageous to keep the pH close to 7.
This is very significant for providing safe drinking water.
Extremes of pH or rapid pH changes can exert stress conditions or
kill aquatic life outright. Dead fish, associated algal blooms,
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and foul stenches are aesthetic liabilities of any waterway.
Even moderate changes from "acceptable" criteria limits of pH are
deleterious to some species. The relative toxicity to aquatic
life of many materials is increased by changes in the water pH.
Metalocyanide complexes can increase a thousandfold in toxicity
with a drop of 1.5 pH units. The availability of many nutrient
substances varies with the alkalinity and acidity. Ammonia is
more lethal with a higher pH.
The lacrimal fluid of the human eye has a pH of approximately 7.0
and a deviation of 0.1 pH unit from the norm may result in eye
irritation for the swimmer. Appreciable irritation will cause
severe pain.
Temperature
Because of the long detention time at ambient temperatures
associated with typically large biological treatment systems used
for treating renderer plant waste water, the temperature of the
treated effluent from most rendering plants will be virtually the
same as the temperature of the receiving body of water.
Therefore, temperature effluent limitations were not established.
Temperatures of the raw waste waters are, however, between 29°
and 66°C (85° and 150°F), with a typical value of about 52°C
(125°F); temperatures, of course, run higher during summer months
than winter months. The major source of high temperature waters
is the condensed cooking vapors. These high temperatures, along
with the high strength wastes are an asset for biological
treatment of the wastes, maintaining high growth rates of
microorganisms required for good treatment. However, if the
temperature of the raw wastes is too high—-greater than 52°C, the
raw wastes may create a strong odor problem. Raw waste
temperatures below 38°C (100°F) rarely cause odor problems.
Temperature is one of the most important and influential water
quality characteristics. Temperature determines those species
that may be present; it activates the hatching of young,
regulates their activity, and stimulates or suppresses their
growth and development; it attracts, and may kill when the water
becomes too hot or becomes chilled too suddenly. Colder water
generally suppresses development. Warmer water generally
accelerates activity and may be a primary cause of aquatic plant
nuisances when other environmental factors are suitable.
Temperature is a prime regulator of natural processes within the
water environment. It governs physiological functions in
organisms and, acting directly or indirectly in combination with
other water quality constituents, it affects aquatic life with
each change. These effects include cheirical reaction rates,
enzymatic functions, molecular movements, and molecular exchanges
between membranes within and between the physiological systems
and the organs of an animal.
Chemical reaction rates vary with temperature and generally
increase as the temperature is increased. The solubility of
gases in water varies with temperature. Dissolved oxygen is
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decreased by the decay or decomposition of dissolved organic
substances and the decay rate increases as the temperature of the
water increases reaching a maximum at about 30°C (86°F) . The
temperature of stream water, even during summer, is below the
optimum for pollution-associated bacteria. Increasing the water
temperature increases the bacterial multiplication rate when the
environment is favorable and the food supply is abundant.
Reproduction cycles may be changed significantly by increased
temperature because this function takes place under restricted
temperature ranges. Spawning may not occur at all because
temperatures are too high. Thus, a fish population may exist in
a heated area only by continued immigration. Disregarding the
decreased reproductive potential, water temperatures need not
reach lethal levels to decimate a species. Temperatures that
favor competitors, predators, parasites, and disease can destroy
a species at levels far below those that are lethal.
Fish food organisms are altered severely when temperatures
approach or exceed 90°F. Predominant algal species change,
primary production is decreased, and bottom associated organisms
may be depleted or altered drastically in numbers and
distribution. Increased water temperatures may cause aquatic
plant nuisances when other environmental factors are favorable.
Synergistic actions of pollutants are more severe at higher water
temperatures. Given amounts of domestic sewage, refinery wastes,
oils, tars, insecticides, detergents, and fertilizers more
rapidly deplete oxygen in water at higher temperatures, and the
respective toxicities are likewise increased.
When water temperatures increase, the predominant algal species
may change from diatoms to green algae, and finally at high
temperatures to blue-green algae, because of species temperature
preferentials. Blue-green algae can cause serious odor problems.
The number and distribution of benthic organisms decreases as
water temperatures increase above 90°F, which is close to the
tolerance limit for the population. This could seriously affect
certain fish that depend on benthic organisms as a food source.
The cost of fish being attracted to heated water in winter months
may be considerable, due to fish mortalities that may result when
the fish return to the cooler water.
Rising temperatures stimulate the decomposition of sludge,
formation of sludge gas, multiplication of saprophytic bacteria
and fungi (particularly in the presence of organic wastes), and
the consumption of oxygen by putrefactive processes, thus
affecting the esthetic value of a water course.
In general, marine water temperatures do not change as rapidly or
range as widely as those of freshwaters. Marine and estuarine
fishes, therefore, are less tolerant of temperature variation.
Although this limited tolerance is greater in estuarine than in
open water marine species, temperature changes are more important
to those fishes in estuaries and bays than to those in open
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marine areas, because of the nursery and replenishment functions
of the estuary that can be adversely affected by extreme
temperature changes.
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SECTION VII
CONTROL AND TREATMENT TECHNOLOGY
SUMMARY
The waste load discharged from the independent rendering industry
to receiving streams can be reduced to desired levels, including
no discharge of pollutants, by conscientious water management,
in-plant waste controls, process revisions, and by the use of a
primary, secondary and tertiary waste water treatment. Figure 12
is a schematic of a suggested waste reduction program for the
independent rendering industry to achieve a high quality
effluent.
This section describes many of the techniques and technologies
that are available or that are being developed to achieve the
various levels of waste reduction. In-plant control techniques
and waste water management suggestions are described first.
Waste treatment technology normally used as a primary treatment
is then described. In the case of the offsite rendering
industry, this "primary" treatment is a materials recovery
process, and is considered as part of the in-plant system,
although many of these systems have been improved to reduce
pollution levels. The effluent frcm primary treatment is
considered the "raw waste." Secondary treatment systems are used
in the treatment of the raw waste.
Each treatment process is described, and the specific advantages
and disadvantages of each system, and the effectiveness on the
specific waste water contaminants found in rendering waste are
discussed. The tertiary and advanced treatment systems that are
applicable to the waste from typical rendering plants are
described in the last part of this section. Some of these
advanced treatment systems have not been used on full scale for
rendering plant wastes; therefore, the development status,
reliability, and potential problems are discussed in greater
detail than for the primary and secondary treatment systems that
are in widespread use.
IN-PLANT CONTROL TECHNIQUES
The waste load from an independent rendering plant is composed of
a waste water stream containing the various pollutants described
in Section VI. The cost and effectiveness of treatment of the
waste stream will vary with the quantity of water and the waste
load. As indicated in Section V, the pollutant waste flow
increases with plant size, and is higher for plants using
barometric leg condensers. In-plant control techniques will
reduce both water use and waste load. The former will be reduced
by minimizing the entry of raw materials into the waste water
stream, and the latter by cleanup procedures and frequency and by
the type of condensing system used.
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Figure 12. Suggested Waste Reduction Program for Rendering Plants
Waste Reduction
Techniques
Waste Reduction
Effect
Point of
Application
Plant
Operations
Partial
Tertiary
Treat.
Irrigation
Evaporation
Reirto va1 of
fine Sus.
So'ids. Salt,
'hosphorus,
V.'tnonia (as
if c essary)
r 9?.5%
BOD
\/
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The in-plant control techniques described below have been used in
offsite rendering plants or are technically feasible.
Condensables
Condensables typically are high in BOD5, phosphorus, suspended
solids, dissolved solids, TKN, ammonia, nitrates and grease (see
Table 9). However, a number of plants are able to minimize the
strength of Condensables in several ways. These include:
o Avoid overloading cookers;
o Provide and maintain traps in the vapor lines;
o Control the speed of agitation;
o Provide by-pass valves for controlling pressure bleed-down
on cookers used for hydrolyzing raw material;
o Control cooking rate.
The volume of Condensables is dependent upon the type of raw
material being processed and on the type of condenser used. From
the standpoint of waste treatment, Condensables should not be
diluted with fresh water. Treated waters should be used for
operating barometric leg condensers.
Control of High Strength Liquid Wastes
Liquid drainage from raw materials can contribute significantly
to the total raw waste load. These sources can be controlled or
eliminated by containing them and then mixing the drainage with
the raw materials as they enter a cooker, screening, or steam
sparging and screening. Containing drainage may require plugging
drains in the raw materials receiving area and in wet wells below
receiving bins.
Blood water and tank water, both of which are high-strength
wastes (see Section V), can be eliminated by evaporating to stick
and using as tankage for dry inedible rendering. Whole blood
drying processes do not generate any blood water and should be
considered as an alternative method to steam sparging and
screening, followed by evaporation of blood water.
Hide curing waste waters are of high strength (see Section V) and
can be a significant part of the total raw waste load. This
source can be eliminated by blending the hide curing wastes in
relatively small amounts with raw materials being charged to
cookers.
Truck and Barrel Washings
Solids, including grease, should be scraped or squeegeed from the
trucks and barrels prior to washdown. Truck washings should be
screened.
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Odor Control
Although odor control by scrubbing does not contribute
significantly to the raw waste load, it can add significantly to
the waste water volume. This large contribution to the waste
water volume can be avoided by using chemicals and recycling
scrubbing water or by reusing treated water.
Plant Cleanup and Spills
Cleanup of the plant and spills should include dry cleanup by
squeegeeing or scraping prior to washdown. Plant cleanup is
usually required only once daily. Accidental spills and leaky
equipment can, however, necessitate more frequent plant cleanup.
Thus, considerable effort should be expended to avoid spills and
to prevent leaks. A regularly scheduled maintenance program will
minimize leaks; it will minimize the spills caused by equipment
failure.
IN-PLANT PRIMARY TREATMENT
Flow Equalization
Equalization facilities consist of a holding tank and pumping
equipment designed to reduce the fluctuations of waste water flow
through materials recovery systems. They can be economically
advantageous, whether the industry is treating its own wastes or
discharging into a city sewer after some pretreatment. The
equalizing tank should have sufficient capacity to provide for
uniform flow to treatment facilities throughout a 24-hour day.
The tank is characterized by a varying flow into the tank and a
constant flow out.
The major advantages of equalization are that treatment systems
can be smaller since they can be designed for the 24-hour average
rather than the peak flows, and many secondary waste treatment
systems operate much better when not subjected to shock loads or
variations in feed rate.
Many plants do not require any special tanks to achieve flow
equalization because of the manner in which they are operated.
For example, plants with large continuous systems or a number of
batch systems (10 to 20) with staggered cooking cycles that
operate most of the day are inherently achieving a near-constant
flow of waste water.
Screens
Since so much of the pollutant matter for some sources of
rendering plant wastes is originally solid (meat and fat
particles), interception of the waste material by various types
of screens is a natural first step. To assure the best
performance on a plant waste water stream, flow equalization may
be needed preceding screening equipment.
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Unfortunately, when the pollutant materials enter the sewage
stream, they are subjected to turbulence, pumping, and mechanical
screening, and they break down and release soluble BOD^ into the
stream, along with colloidal, suspended, and greasy solids.
Waste treatment—that is, the removal cf soluble, colloidal and
suspended organic matter—is expensive. It is usually far
simpler and less expensive to keep the solids out of the sewer.
Static, vibrating, and rotary screens are the primary types used
for this step in the in-plant primary treatment. Whenever
possible, pilotscale studies are warranted before selecting a
screen, unless specific operating data are available for the
specific use intended, in the same solids concentration range,
and under the same operating conditions.
Static Screens
The primary function of a static screen is to remove "free" or
transporting fluids. This can be accomplished in several ways,
and in most older concepts, only gravity drainage is involved. A
concavely curved screen design using high velocity pressure
feeding was developed and patented in the 1950's for mineral
classification and has been adapted to other uses in the process
industries. This design employs bar interference to the slurry
which knives off thin layers of the flow over the curved
surface.is
Beginning in 1969, United States and foreign patents were allowed
on a three-slope static screen made of specially coined curved
wires. This concept used the Coanda or wall attachment
phenomenon to withdraw the fluid from the under layer of a slurry
which is stratified by controlled velocity over the screen. This
method of operation has been found to be highly effective in
handling slurries containing fatty or sticky fibrous suspended
matter.1S
Vibrating Screens
The effectiveness of a vibrating screen depends on a rapid
motion. Vibrating screens operate between 99 rpm and 1800 rpm;
the motion can be either circular or straight line, varying from
0.08 to 1.27 cm (1/32 to 1/2 inch) total travel. The speed and
motion are selected by the screen manufacturer for the particular
application.
Of prime importance in the selection of a proper vibrating screen
is the application of the proper cloth. The capacities on liquid
vibrating screens are based on the percent of open area of the
cloth. The cloth is selected with the proper combination of
strength of wire and percent of open area. If the waste solids
to be handled are heavy and abrasive, wire of a greater thickness
and diameter should be used to assure long life. However, if the
material is light or sticky in nature, the durability of the
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screening surface may be the least consideration. In such a
case, a light wire may be desired to provide an increased percent
of open area.
Rotary Screens
One type of barrel or rotary screen, driven by external rollers,
receives the waste water at one open end and discharges the
solids at the other open end. The screen is inclined toward the
exit end to facilitate movement of solids. The liquid passes
outward through the screen (usually stainless steel screen cloth
or perforated metal) to a receiver and then to the sewer. To
prevent clogging, the screen is usually sprayed continuously by a
line of external spray nozzles.
Another rotary screen commonly used in various industries, such
as the meat industry, is driven by an external pinion gear. The
raw waste water is fed into the interior of the screen, below the
longitudinal axis, and solids are removed in a trough and screw
conveyor mounted lengthwise at the axis (center line) of the
barrel. The liquid exits outward through the screen into a tank
under the screen. The screen is partially submerged in the
liquid in the tank. The screen is usually 40 x 40 mesh, with 0.4
mm (1/64 inch) openings. Perforated lift paddles mounted
lengthwise on the inside surface of the screen assist in lifting
the solids to the conveyor trough. This type is also generally
sprayed externally to reduce blinding. Grease clogging can be
reduced by coating the wire cloth with teflon. Solids removal up
to 82 percent is reported.15
Applications
A broad range of applications exists for screens as the first
stage of in-plant waste water treatment. These include both the
plant waste water and waste water discharged from individual
sources, especially streams with high solids content such as raw
material drainage.
Catch Basins
The catch basin for the separation of grease and solids from
independent rendering waste waters was originally developed to
recover marketable grease. Since the primary objective was
grease recovery, all improvements were centered on skimming.
Many catch basins were not equipped with automatic bottom sludge
removal equipment. These basins could often be completely
drained to the sewer and were "sludged out" weekly or at
frequencies such that septic conditions would not cause the
sludge to rise. Rising sludge was undesirable because it could
affect the color and reduce the market value of the grease.
In the past twenty years, with waste treatment gradually becoming
an added economic incentive, catch basin design has been improved
in the solids removal area as well. In fact, the low market
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value of inedible grease and tallow has reduced concern about
quality of the skimmings, and now the concern is shifting toward
overall effluent quality improvement. Gravity grease recovery
systems will remove 20 to 30 percent of the BOD5, 40 to 50
percent of the suspended solids, and 50 to 60 percent of the
grease (hexane solubles).15
The majority of the gravity grease recovery basins (catch basins)
are rectangular. Flow rate is the most important criterion for
design; 30 to 40 minutes detention time at one-hour peak flow is
a common design sizing factor.15 The use of an equalizing tank
ahead of the catch basin obviously minimizes the size requirement
for the basin. A shallow basin—up to 1.8 meters (6 feet)—is
preferred.
A "skimmer" skims the grease and scum off the top into collecting
troughs. A scraper moves the sludge at the bottom into a
submerged hopper from which it can be pumped or carries it up and
deposits it into a hopper. Both skimmings and sludge can be
recycled as a raw material for rendering.
Two identical catch basins, with a common wall, are desirable so
operation can continue if one is down for maintenance or repair.
Both concrete and steel tanks are used.
Concrete tanks have the inherent advantages of lower overall
maintenance and more permanence of structure. However, some
plants prefer to be able to modify their operation for future
expansion or alterations or even relocation. All-steel tanks
have the advantage of being semipcrtable, more easily field-
erected, and more easily modified than concrete tanks. The all-
steel tanks, however, require additional maintenance as a result
of wear from abrasion and corrosion.
A tank using all-steel walls and a concrete bottom is probably
the best compromise between the all-steel tank and the all-
concrete tank. The advantages are the same as for steel;
however, the all-steel tank requires a footing underneath the
supporting members, whereas the concrete bottom forms the floor
and supporting footings for the steelwall tank.
Dissolved Air Flotation
This system is, by definition, a primary treatment system; thus,
the effluent from a dissolved air flotation system is considered
raw waste. This system is normally used to remove fine suspended
solids and is particularly effective on grease in the waste
waters from independent rendering plants. It is a relatively
recent technology in the rendering industry; therefore, it is not
in widespread use, although increasing numbers of plants are
installing these systems.
Dissolved air flotation appears to be the single most effective
device currently available for a plant to use to reduce the
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Compressed
Air
Feed
OD
O
Effluent
Totol Pressurizotion
Process
Float
V
Sludge
Figure 13. Dissolved Air Flotation
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pollutant waste load in its raw waste water stream. It is
expected that the use of dissolved air flotation will become more
common in the industry, especially as a step in achieving the
1983 standards.
Technical Description
Air flotation systems are used to remove any suspended material
from waste water with a specific gravity close to that of water.
The dissolved air system generates a supersaturated solution of
waste water and air by pressurizing waste water and introducing
compressed air, then mixing the two in a detention tank. This
"supersaturated" waste water flows to a large flotation tank
where the pressure is released, thereby generating numerous small
air bubbles which effect the flotation of the suspended organic
material by one of three mechanisms: 1) adhesion of the air
bubbles to the particles of matter; 2) trapping of the air
bubbles in the floe structures of suspended material as the
bubbles rise; and 3) adsorption of the air bubbles as the floe
structure is formed from the suspended organic matter.16 In most
cases, bottom sludge removal facilities are also provided.
There are three process alternatives that differ by the
proportion of the waste water stream that is pressurized and into
which the compressed air is mixed. In the total pressurization
process, Figure 13, the entire waste water stream is raised to
full pressure for compressed air injection.
In partial pressurization, Figure 14, only a part of the waste
water stream is raised to the pressure of the compressed air for
subsequent mixing. Alternative A of Figure 14 shows a sidestream
of influent entering the detention tank, thus reducing the
pumping required in the system shown in Figure 13. In the
recycle pressurization process, Alternative B of Figure 14,
treated effluent from the flotation tank is recycled and
pressurized for mixing with the compressed air and then, at the
point of pressure release, is mixed with the influent waste
water. Operating costs may vary slightly, but performance should
be essentially equal among the alternatives.
Improved performance of the air flotation system is achieved by
coagulation of the suspended matter prior to treatment. This is
done by pH adjustment or the addition cf coagulant chemicals, or
both. Aluminum sulfate, iron sulfate, lime, and polyelectrolytes
are used as coagulants at varying concentrations up to 300 to 400
mg/1 in the raw waste. These chemicals are essentially totally
removed in the dissolved air unit, thereby adding little or no
load to the downstream waste treatment systems. However, the
resulting float and sludge may become a less desirable raw
material for recycling through the rendering process as a result
of chemical coagulation addition. Che -..Gal precipitation is also
discussed later, particularly in regard to phosphorus removal,
under tertiary treatment; phosphorus can also be removed at this
primary (inplant) treatment stage. A slow paddle mix will
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improve coagulation. It has been suggested that the
pro+^inaceous matter in rendering plant waste could be removed by
reducing the pH of the waste water to the isoelectric point of
about 3«5«lf> The proteinaceous material would be coagulated at
that point and readily removed as float from the top of the
dissolved air unit. This is not being done commercially in the
rendering industry in the United States at the present time.
Similarly, the Alwatec process has been developed by a company in
Oslo, Norway, using a lignosulfonic acid precipitation and
dissolved air flotation to recover a high protein product that is
valuable as a feed.16 Nearly instantaneous protein precipitation
and hence, nitrogen removal, is achieved when a high protein-
containing effluent ia acidified to a pH between 3 and 4 with a
high molecular weight lignosulfonic acid. BOD5 reduction is
reported to range from 60 to 95 percent. The effluent must be
neutralized before further treatment by the addition of milk of
lime or some other inexpensive alkali. This process is being
evaluated on meat packing waste in one plant in the United States
at the present time.18
One of the manufacturers of dissolved air flotation equipment
indicated a 60 percent suspended solids removal and 80 to 90
percent grease removal without the addition of chemicals. With
the addition of 300 to 400 mg/1 of inorganic coagulants and a
slow mix to coagulate the organic matter, the manufacturer says
that 90 percent or more of the suspended solids and more than 90
ercent of the grease can be removed.19 Total nitrogen reduction
>:^-: "sn 35 and 70 percent was found in dissolved air units
surveyed in the meat packing industry-8
North Star's staff observed the operation of several dissolved
air units during the verification sampling program and plant
visits of the rendering and meat packing industries. One meat
packing plant that was visited controlled the feed rate and pH of
the waste water and achieved 90 to 95 percent removal of solids
and grease. other plants had relatively good operating success,
but some did not achieve the results that should have been
attainable. It appeared that they did not fully understand the
process chemistry and were using erroneous operating procedures.
Problems and Reliability
The reliability of the dissolved air flotation process and of the
equipment seems to be well established, although it is relatively
new technology for the rendering industry. As indicated above,
it appears that the use of the dissolved air system is not fully
exploited by some of the companies who have installed it for
waste water treatment. The potential reliability of the
dissolved air process can be realized by proper installation and
operation. The feed rate and process conditions must be
maintained at the proper levels at all times to assure this
reliability. This fact does not seem to be fully understood or
of sufficient concern to some companies, and thus full benefit is
frequently not achieved.
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Compressed
Air
, [Retention
f V Tank
I
Recycle Pressurizotion
Process
(Alternative B)
CO
CO
1
1
Feed from ,
Primary i fa >
Treatment j
i ^(Retention ] 1
Flotation
Tank
1 1
• >v c
S C
L ' rioai
V
Sludge
Treated
Effluent
Compressed
Air
Partial Pressurization
Process
(Alternative A)
Figure 14. Process Alternatives for Dissolved Air Flotation
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The sludge and float taken from the dissolved air system can both
be recycled through the rendering process. The addition of
polyelectrolyte chemicals was reported to create some problems
for sludge dewatering and for subsequent use as a raw material
for rendering. The mechanical equipment involved in the
dissolved air flotation system is fairly simple, requiring
standard maintenance attention for such things as pumps and
mechanical drives.
WASTE WATER TREATMENT SYSTEMS
The secondary treatment methods commonly used for the treatment
of rendering plant wastes after in-plant primary treatment
(solids removal) are the following biological systems: anaerobic
process, aerobic lagoons, and variations of the activated sludge
process. Several of these systems are capable of providing up to
97 percent BOD5 reductions and 95 percent suspended solids
reduction, as observed primarily in the meat packing industry.
Combinations of these systems can achieve reductions up to 99
percent in BOD5 and grease, and up to 97 percent in suspended
solids for rendering plant waste water. Based on operating data
from a pilot-plant system on packing plant wastes, the rotating
biological contactor also shows potential as a secondary
treatment system.
The selection of a secondary biological system for treatment of
rendering plant wastes depends upon a number of important system
characteristics. Some of these are waste water volume, waste
load concentration, equipment used, pollutant reduction
effectiveness required, reliability, consistency, and resulting
secondary pollution problems (e.g., sludge disposal and odor
control). The characteristics and performance of each of the
above-mentioned secondary treatment systems, and also for common
combinations of them, are described below. Capital and operating
costs are discussed in Section VIII.
Anaerobic Processes
Elevated temperatures (29° to 35°C, or 85° to 95°F) and high
concentrations of carbohydrates, fats, proteins, and nutrients in
some independent rendering-plant wastes make these wastes well
suited to anaerobic treatment. Anaerobic or facultative
microorganisms, which function in the absence of dissolved
oxygen, break down the organic wastes to intermediates such as
organic acids and alcohols. Methane bacteria then convert the
intermediates primarily to carbon dioxide and methane.
Unfortunately, much of the organic nitrogen present in the
influent is converted to ammonia nitrogen. Also, if sulfur
compounds are present (such as from high-sulfate raw water—50 to
100 mg/1 sulfate), hydrogen sulfide will be generated. Acid
conditions are undesirable because methane formation is
suppressed and noxious odors develop. Anaerobic processes are
economical because they provide high overall removal of BOD5 and
suspended solids with no power cost (other than pumping) and with
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low land requirements. Two types of anaerobic processes are
used: anaerobic lagoons and anaerobic contact systems.
Anaerobic Lagoons
Anaerobic lagoons are widely used in the rendering industry as
the first step in secondary treatment or as pretreatment prior to
discharge to a municipal system. Reductions of up to 97 percent
in BOD5 and up to 95 percent in suspended solids can be achieved
with the lagoons; 85 percent reduction is common. Occasionally
two anaerobic lagoons are used in parallel and sometimes in
series. These lagoons are relatively deep (3 to 5 meters, or
about 10 to 17 feet), low surface area systems with typical waste
loadings of 240 to 320 kg BOD5/1000 cubic meters (15 to 20 Ib
BOD5/1000 cubic feet) and detention times of five to ten days. A
thick scum layer of grease may accumulate on the surface of the
lagoon to retard heat loss, to ensure anaerobic conditions, and
hopefully to retain obnoxious odors. Low pH and wind can
adversely affect the scum layer. Paunch manure and straw may be
added to this scum layer but this would increase the nutrient
levels.
Plastic covers of nylon-reinforced Hypalon, polyvinyl chloride,
and styrofoam have been used on occasion by other industries in
place of the scum layer; in fact, some states require this.
Properly installed covers provide a convenient means for odor
control and collection of the by-product methane gas.
THe waste water flow inlet should be located near, but not on,
the bottom of the lagoon. In some installations, sludge is
recycled to ensure adequate anaerobic seed for the influent. The
outlet from the lagoon should be located to prevent short
circuiting of the flow and carry-over of the scum layer.
For best operation, the pH should be between 7.0 and 8.5. At
lower pH, methane-forming bacteria will not survive and the acid
formers will take over to produce very noxious odors. At a high
pH (above 8.5), acid-forming bacteria will be suppressed and
lower the lagoon efficiency.
Advantages/-Pi sadyant ages. Advantages of an anaerobic lagoon
system are initial lew cost, ease of operation, and the ability
to handle large grease loads and shock waste loads, and yet
continue to provide a consistent quality effluent.20
Disadvantages of an anaerobic lagocn are the hydrogen sulfide
generated from sulfate-containing waters and the typically high
ammonia concentrations in the effluent of 100 mg/1 or more. If
acid conditions develop, severe odor problems result.
Incidentally, if the gases evolved are contained, it is possible
to use iron filings to remove sulfides.
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^BfiiiS^tionjE^,. Anaerobic lagoons used as the first stage in
secondary treatment are usually followed by aerobic lagoons.
Placing a small, mechanically aerated lagoon between the
anaerobic and aerobic lagoons is becoming popular. A number of
meat packing plants are currently installing extended aeration
units following the anaerobic lagoons to obtain nitrification.
Anaerobic lagoons are not permitted in some states or areas where
the ground water is high or the soil conditions are adverse
(e.g., too porous) , or because of odor problems.
Anaerobic Contact Systems
Anaerobic contact systems require far more equipment for
operation than do anaerobic lagoons, and consequently were not
found to be used by the rendering industry. However, their use
by some meat packing plants has demonstrated their applicability
to rendering plant waste waters because of the similarity in
waste characteristics. The equipment, as illustrated in Figure
15, consists of equalization tanks, digesters with mixing
equipment, air or vacuum gas stripping units, and sedimentation
tanks (clarifiers) . Overall reduction of 90 to 97 percent in
BOD5 and suspended solids is achievable.
Equalized waste water flow is introduced into a mixed digester
where anaerobic decomposition takes place at a temperature of 33°
to 35°C (90° to 95°F) . BOD5 loading into the digester is between
2.4 and 3.2 kg/cubic meter (0.15 and 0.20 Ib/cubic foot) and the
detention time is between three and twelve hours. After gas
stripping, the digester effluent is clarified and sludge is
recycled at a rate of about one-third the raw waste influent
rate. Sludge is removed from the system at the rate of about 2
percent of the raw waste volume.
Advantages-Pi sadyantages^ Advantages of the anaerobic contact
system are high organic waste load reduction in a relatively
short time; production and collection of methane gas that can be
used to maintain a high temperature in the digester and also to
provide auxiliary heat and power; good effluent stability to
grease and waste load shocks; and application in areas where
anaerobic lagoons cannot be used. Disadvantages of anaerobic
contactors are higher initial cost and maintenance costs and
potential odor emissions from the clarifiers.
Anaerobic contact systems are restricted to use as
the first stage of secondary treatment and can be followed by the
same systems as follow anaerobic lagoons.
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oo
—I
Plant
Effluent
Equalizing Tank
A
w
Sludge Recycle
U/vA-
HeatersV/ V^y
Anaerobic
Digesters
Gas
Stripping
Units
Sedimentation
Tanks
Effluent
Figure 15. Anaerobic Contact Process
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Aerated Lagoons
Aerated lagoons have been used successfully for many years in a
small number of installations treating meat packing and rendering
plant wastes. However, with the tightening of effluent
limitations, and because aerated lagoons can provide the
additional treatment, the number of installations is increasing.
Aerated lagoons use either fixed mechanical turbine-type
aerators, floating propeller-type aerators, or a diffused air
system for supplying oxygen to the waste water. The lagoons
usually are 2.4 to 4.6 meters (8 to 15 feet) deep, and have a
detention time of two to ten days. BOD5 reductions range from 40
to 60 percent, with little or no reduction in suspended solids.
Because of this, aerated lagoons approach conditions similar to
extended aeration without sludge recycle (see below).
Advantages-Di sadvantages
Advantages of this system are that it can rapidly add dissolved
oxygen (DO) to convert anaerobic effluent to an aerobic state;
provide additional BOD5 reduction; and it requires a relatively
small amount of land. Disadvantages include the power
requirements and the fact that the aerated lagoon, in itself,
usually does not reduce BOD5 and suspended solids adequately to
be used as the final stage in a high performance secondary
system.
Applications
Aerated lagoons are usually the first or second stages of
secondary treatment, and must be followed by aerobic (shallow)
lagoons to reduce suspended solids and to provide the required
final treatment.
Aerobic Lagoons
Aerobic lagoons (stabilization lagoons or oxidation ponds) are
large surface area, shallow lagoons, usually 1 to 2.3 meters (3
to 8 feet) deep, loaded at a BOD5 rate of 20 to 50 pounds per
acre. Detention times vary from about one month to six or seven
months; thus, aerobic lagoons require large areas of land.
Aerobic lagoons serve three main functions in waste reduction:
o Allow solids to settle out;
o Equalize and control flow;
o Permit stabilization of organic matter by aerobic and
facultative microorganisms and also by algae.
-------
Actually, if the pond is quite deep, 1.8 to 2.4 meters.(6 to 8
feet), the waste water near the bottom may be void of dissolved
oxygen and anaerobic organisms may be present. Therefore,
settled solids can be decomposed into inert and soluble organic
matter by aerobic, anaerobic, or facultative organisms, depending
upon the lagoon conditions. The soluble organic matter is also
decomposed by microorganisms. It is essential to maintain
aerobic conditions in at least the upper six to twelve inches in
shallow lagoons, since aerobic microorganisms cause the most
complete removal of organic matter. Wind action assists in
carrying the upper layer of liquid (aerated by air-water
interface and photosynthesis) down into the deeper portions. The
anaerobic decomposition generally occurring in the bottom
converts solids to liquid organics, which can become nutrients
for the aerobic organisms in the upper zone.
Algae growth is common in aerobic lagoons; this currently is a
drawback when aerobic lagoons are used for final treatment
because the algae appear as suspended solids and contribute BOD5.
Algae added to receiving waters are thus considered a pollutant.
Algae in the effluent may be reduced by drawing off the lagoon
effluent at least 30 cm (about 14 inches) below the surface,
where concentrations are usually lower. Algae in the lagoon,
however, play an important role in stabilization. They use CO2,
sulfates, nitrates, phosphates, water and sunlight to synthesize
their own organic cellular matter and give off oxygen. The
oxygen may then be used by other microorganisms for their
metabolic processes. However, when algae die they release their
organic matter in the lagoon, causing a secondary loading.
Ammonia disappears without the appearance of an equivalent amount
of nitrite and nitrate in aerobic lagoons as evidenced by the
results of our field sampling survey. From this, and the fact
that aerobic lagoons tend to become anaerobic near the bottom, it
appears that considerable denitrification can occur.
Ice and snow cover in winter reduces the overall effectiveness of
aerobic lagoons by reducing algae activity, preventing mixing,
and preventing reaeration by wind action and diffusion. This
cover, if present for an extended period, can result in anaerobic
conditions. When there is no ice and snow cover on large aerobic
lagoons, high winds can develop a strong wave action that can
damage dikes. Riprap, segmented lagcons, and finger dikes are
used to prevent wave damage. Finger dikes, when arranged
appropriately, also prevent short circuiting of the waste water
through the lagoon. Rodent and weed control, and dike
maintenance are all essential for good operation of the lagoons.
Advantages-Di sadvantages
Advantages of aerobic lagoons are that they reduce the suspended
solids and colloidal matter, and oxidize the organic matter of
the influent to the lagoon; they also permit flow control and
waste water storage. Disadvantages are reduced effectiveness
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during winter months that may require no discharge for periods of
three months or more, the large land requirements, the algae
growth problem leading to higher suspended solids, and odor
problems for a short time in spring, after the ice melts and
before the lagoon becomes aerobic again.
Applications
Aerobic lagoons usually are the last stage in secondary treatment
and frequently follow anaerobic or anaerobic-plus-aerated
lagoons. Large aerobic lagoons allow plants to store waste
waters for discharge during periods of high flow in the receiving
body of water or to store for irrigation purposes during the
summer. These lagoons are particularly popular in rural areas
where land is available and relatively inexpensive.
Activated Sludge
The conventional activated sludge process is schematically shown
in Figure 16. In this process recycled biologically active
sludge or floe is mixed in aerated tanks or basins with waste
water. The microorganisms in the floe adsorb organic matter from
the wastes and convert it by oxidation-enzyme systems to such
stable products as carbon dioxide, water, and sometimes nitrates
and sulfates. The time required for digestion depends on the
type of waste and its concentration, but the average time is six
hours. The floe, which is a mixture of microorganisms (bacteria,
protozoa, and filamentous types)„ food, and slime material, can
assimilate organic matter rapidly when properly activated; hence,
the name activated sludge.
From the aeration tank, the mixed sludge and waste water, in
which little nitrification has taken place, are discharged to a
sedimentation tank. Here the sludge settles out, producing a
clear effluent, low in BOD5 and a biologically active sludge. A
portion of the settled sludge, normally about 20 percent, is
recycled to serve as an inoculum and to maintain a high mixed
liquor suspended solids content. Excess sludge is removed
(wasted) from the system, to thickeners and anaerobic digestion,
to chemical treatment and dewatering by filtration or
centrifugation or to land disposal where it is used as fertilizer
and soil conditioner to aid secondary crop growth.
This conventional activated sludge process can reduce BOD5 and
suspended solids up to 95 percent. However, it cannot readily
handle shock loads and widely varying flows and therefore might
require upstream flow equalization.
Various modifications of the activated sludge process have been
developed, such as the tapered aeration, step aeration, contact
stabilization, and extended aeration. Of these, extended
aeration processes are most frequently being used for treatment
of meat processing, meat packing and rendering wastes.
90
-------
Raw
Waste
Primary
Sedimentation
Secondary
Sedimentation
Aeration Tank
|_Return_ Activated Sludge
Effluent
Waste
Sludge
Waste I
Sludge^
Figure 16. Activated Sludge Process
-------
Extended Aeration
The extended aeration process is similar to the conventional
activated sludge process, except that the mixture of activated
sludge and raw materials is maintained in the aeration chamber
for longer periods of time. The usual detention time in extended
aeration ranges from one to three days, rather than six hours as
in the conventional process. During this prolonged contact
between the sludge and raw waste, there is ample time for the
organic matter to be adsorbed by the sludge and also for the
organisms to metabolize the organic matter which they have
adsorbed. This allows for a much greater removal of organic
matter. In addition, the organisms undergo a considerable amount
of endogenous respiration, and therefore oxidize much of the
organic matter which has been built up into the protoplasm of the
organism. Hence, in addition to high organic removals from the
waste waters, up to 75 percent of the organic matter of the
microorganisms is decomposed into stable products and
consequently less sludge will have to be handled.
In extended aeration, as in the conventional activated sludge
process, it is necessary to have a final sedimentation tank.
Some of the solids resulting from extended aeration are rather
finely divided and therefore settle slowly, requiring a longer
period of settling.
The long detention time in the extended aeration tank makes it
possible for nitrification to occur. In nitrification under
aerobic conditions, ammonia is converted to nitrites and nitrates
by specific groups of nitrifying bacteria. For this to occur, it
is necessary to have sludge detention times in excess of ten
days. 20 This can be accomplished by regulating the amounts of
recycled and wasted sludge. Oxygen-enriched gas could be used in
place of air in the aeration tanks to improve overall
performance. This would require that the aeration tank be
partitioned and covered, and that the air compressor and
dispersion system be replaced by a rotating sparger system. When
cocurrent, staged flow and recirculation of gas back through the
liquor are employed, between 90 and 95 percent oxygen use is
claimed. Although this modification of extended aeration has not
been used in treating rendering plant wastes, it is being used
successfully for treating other wastes.
Adyantages~Disadvantages._ The advantages of the extended
aeration process are that it is immune to shock loading and flow
fluctuations because the incoming raw waste load is diluted by
the liquid in the system to a much greater extent than in the
conventional activated sludge. Also, because of the long
detention time, high BOD5 reductions can be obtained. Other
advantages of the system are the elimination of sludge digestion
equipment and the capability to produce a nitrified effluent.
Disadvantages are that it is difficult to remove most of the
suspended solids from the mixed liquor discharged from the
aeration tank; large volume tanks or basins are required to
92
-------
accommodate the long detention times; and operating costs for
aeration are high.
Applications^ Because of the nitrification process, extended
aeration systems are being used by some industries following
anaerobic processes or lagoons to produce low BOD5 and low
ammonia-nitrogen effluents. They are also being used as the
first stage of secondary treatment, followed by polishing
lagoons.
Rotating Biological Contactor
Process Description
The rotating biological contactor (RBC) consists of a series of
closely spaced flat parallel disks which are rotated while
partially immersed in waste waters being treated. A biological
growth covering the surface of the disk adsorbs dissolved organic
matter present in the waste water. As the biomass on the disk
builds up, excess slime is sloughed off periodically and is
settled out in sedimentation tanks. The rotation of the disk
carries a thin film of waste water into the air where it absorbs
the oxygen necessary for the aerobic biological activity of the
biomass. The disk rotation also promotes thorough mixing and
contact between the biomass and the waste waters. In many ways
the RBC system is a compact version of a trickling filter. In
the trickling filter, the waste waters flow over the media and
thus over the microbial flora; in the RBC system, the flora is
passed through the waste water.
The system can be staged to enhance overall waste load reduction.
Organisms on the disks selectively develop in each stage and are
thus particularly adapted to the composition of the waste in that
stage. The first stages might be used for removal of dissolved
organic matter, while the latter stages might be adapted to
nitrification of ammonia.
Development Status
The RBC system was developed independently in Europe and the
United States about 1955 for the treatment of domestic waste; it
found application only in Europe, where there are an estimated
1000 domestic installations.20 However, the use of the RBC for
the treatment of meat plant waste is being evaluated at the
present time. The only operating information available on its
use on meat packing waste is from a pilotscale system; no
information appears to be available on its use for treating
rendering plant wastes. The pilot-plant studies were conducted
with a four-stage REC system with four-foot diameter disks. The
system was treating a portion of the effluent from the Austin,
Minnesota, anaerobic contact plant used to treat meat packing
waste. These results showed a BOD5 removal in excess of 50
percent, with loadings less than 0.037 kg BOD5 per unit area on
an average BOD5 influent concentration of approximately 25
mg/1.2i
93
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Data from Autotrol Corporation, one of the suppliers of RBC
systems, revealed ammonia removal of greater than 90 percent by
nitrification in a multistage unit.21 Four to eight stages of
disks with maximum hydraulic loadings of 61 liters per day per
square meter (1.5 gallons per day per square foot) of disk area
are considered normal for ammonia removal.
A large installation was recently completed at the Iowa Beef
Processors plant in Dakota City, Nebraska, for the further
treatment of the effluent from an anaerobic lagoon.22 No data
are available on this installation, which has been plagued with
mechanical problems.
Advantages-Disadvantages
The major advantages of the RBC system are its relatively low
first cost; the ability to stage to obtain dissolved organic
matter reduction with the potential for removal of ammonia by
nitrification; and its good resistance to hydraulic shock loads.
Disadvantages are that the system should be housed, if located in
cold climates, to maintain high removal efficiencies and to
control odors. Although this system has demonstrated its
durability and reliability when used on domestic wastes in
Europe, it has not yet been proved on rendering plant wastes.
Uses
Rotating biological contactors could be used for the entire
aerobic secondary system. The number of stages required depend
on the desired degree of treatment and the influent strength.
Typical applications of the rotating biological contactor,
however, may be for polishing the effluent from anaerobic
processes, and as pretreatment prior to discharging wastes to a
municipal system. A BOD5 reduction of 98 percent is reportedly
achievable with a four-stage RBC.20
Performance of Various Secondary Treatment Systems
Table 13 shows BOD5, suspended solids (SS) , and grease removal
efficiencies for various biological treatment systems on
rendering plant and meat packing plant waste waters. Exemplary
values each represent results from an actual treatment system,
except for the data on the anaerobic plus aerobic lagoon system
under treatment on meat packing waste waters, which includes two
plants.
The number of systems used to calculate average values is shown
in Table 13. It is apparent that the anaerobic plus aerobic
lagoon system is the one most commonly used by meat packing and
rendering plants.
The estimated reduction of BOD5 for meat packing waste waters
shown for the anaerobic lagoon plus rotating biological contactor
94
-------
Table 13. Performance of Various Secondary Treatment Systems
CO
+J
C
CO
rH
PL.
M
n
•H
(-1
0)
T3
C
(1)
P3
Secondary Treatment System
(number of systems used
to determine averages)
Anaerobic + Aerobic
Lagoon (4)
Activated Sludge (2)
Aerated + Aerobic
Lagoon (2)
Anaerobic + Aerobic
Lagoon (22)
Anaerobic + Aerated +
Aerobic Lagoon (3)
Anaerobic Contact Process +
Aerobic Lagoon (1)
co
CO
.u
C
nJ
PM
w
c
•H
^1
O
cd
fi .
M-t
4-1
0)
0)
S
Extended Aeration +
Aerobic Lagoon (1)
Anaerobic Lagoon + Rotating
Biological Contactor
Anaerobic Lagoon + Extended
Aeration + Aerobic Lagoon
Anaerobic Lagoon +
Trickling Filter (1)
2-Stage Trickling Filter (1)
Aerated + Aerobic
Lagoon (1)
Anaerobic Contact (1)
Water Wasteload Reduction, Percent
Ave
BOD 5
97.7
93.7
96.9
95.4
98.3
98.5
96.0
98. 5e
98e
97.5
95.5
99.4
96.9
rage V<
SS
97.3
86.1
88.2
93.5
93.3
96.0
86.0
—
93e
94.0
95.0
94.5
97.1
alues
Grease
89.2
92.2
77.5
95.3
98.5
99.0
98.0
98e
96.0
98.0
—
95.8
Exem
BOD 5
99.0
96.6
97.7
98.9
99.5
96.0
99.4
96.9
Diary \
SS
99.9
97.1
93.8
96.6
97.5
86.0
94.5
97.1
ralues
Grease
99.4
99.4
78.8
98.9
99.2
98.0
95.8
e = estimated
95
-------
is based on preliminary pilot-plant results. The values shown
for the anaerobic-lagoon plus extended aeration system are based
on estimates of their combined effectiveness that are below the
value calculated by using the average removal efficiency for the
two components of the system, individually. For example, if the
BOD5 reduction for the anaerobic lagoon and the extended aeration
were each 90 percent, the calculated efficiency of the two
systems combined would be 99 percent.
The data of Table 13 show that, for rendering plants, the
anaerobic plus aerobic lagoons are the most effective system of
those studied for BOD5, SS, and grease removal. Furthermore, the
anaerobic plus aerobic lagoon system appears, by percent
reductions, to be more effective en rendering than on meat
packing waste waters. This conclusion could be the result of an
insufficient number of observations; however, it most likely is
because the rendering waste loadings in the treatment system were
frequently low. In fact, the BOD5 waste loadings to this type of
system for three of the rendering plants were 12.8; 125, and 35.3
kg BOD5/1000 cubic meters (15 to 20 Ib BOD5/1000 cubic feet).
All of the secondary treatment systems listed in Table 13 are
capable of treating typical rendering plant waste waters to a
degree sufficient to meet the 1977 standards recommended in
Section IX. These systems, equipped with a sand filter or its
equivalent, are also capable of producing a final effluent that
would meet the 1983 standards recommended in Section X. In fact,
the data presented in Section X show that at least three of these
systems alone—anaerobic plus aerobic lagoon, activated sludge,
or aerated plus aerobic lagoon--are already producing rendering
plant effluent that meets the majority of pollutant parameter
limitations for 1983.
TERTIARY AND ADVANCED TREATMENT
Chemical Precipitation
Phosphorus is an excellent nutrient for algae and thus can
promote heavy algae blooms. As such, it cannot be discharged
into receiving streams, and its concentration should not be
allowed to build up in a recycle water stream. However, the
presence of phosphorus is particularly useful in spray or flood
irrigation systems as a nutrient for plant growth.
The effectiveness of chemical precipitation for removing
phosphorus. Figure 17, has been verified in full scale during the
North star verification sampling program of the meat packing
industry.a One packing plant operates a dissolved air flotation
system as a chemical precipitation unit and achieves 95 percent
phosphorus removal, to a concentration of less than 1 mg/1.
Chemical precipitation can be used for primary (in-plant)
treatment to remove BOD5, suspended solids, and grease, as
discussed earlier in conjunction with dissolved air flotation.
96
-------
Also, it can be used as a final treatment following biological
treatment to remove suspended solids in addition to phosphorus.
Technical Description
Phosphorus occurs in waste water streams from rendering plants
primarily as phosphate salts. Phosphates can be precipitated
with trivalent iron and trivalent aluminum salts. It can also be
rapidly precipitated by the addition of lime; however, the rate
of removal is controlled by the agglomeration of the precipitated
colloids and by the settling rate of the agglomerate.16
Laboratory investigation and experience with in-plant operations
have substantially confirmed that phosphate removal is dependent
on pH and that this removal tends to be limited by the solubility
behavior of the three phosphate salts—calcium, aluminum, and
iron. The optimum pH for the iron and aluminum precipitation
occurs in the 4 to 6 range, whereas the calcium precipitation
occurs on the alkaline side at pH values above 9.5.
Since the removal of phosphorus is a two-step process involving
precipitation and then agglomeration, and both are sensitive to
pH, controlling the pH level takes on added significance. If a
chemical other than lime is used in the precipitation-coagulation
process, two levels of pH are required. Precipitation occurs on
the acid side and coagulation is best carried out on the alkaline
side. The precipitate is removed by sedimentation or by
dissolved air flotation.16
Polyelectrolytes are polymers that can be used as primary
coagulants, flocculation aids, filter aids, or for sludge
conditions. Phosphorus removal may be enhanced by the use of
such polyelectrolytes by producing a better floe than might occur
without such chemical addition.23
The chemically precipitated sludge contains grease and organic
matter in addition to the phosphorus, if the system is used in
primary treatment. If it is used as a post-secondary treatment,
the sludge volume will be less and it will contain primarily
phosphorus salts. The sludge from either treatment can be
landfilled.
Development Status
This process is well established and understood, technically.
However, its use on rendering plant waste waters, normally as a
primary waste treatment system, is very limited and is not
expected to gain widespread acceptance. This is because most
rendering plants do not have high phosphorus levels in their
total waste waters and have other effective primary treatment
processes for BOD5, S3, and grease removal.
97
-------
Problems and Reliability As indicted above, the reliability of
this process is well established; however, it is a chemical
process and as such requires the appropriate control and
operating procedures. The problems that can be encountered in
operating this process are frequently the result of a lack of
understanding or inadequate equipment. Sludge disposal is not
expected to be a problem, although the use of polyelectrolytes
and their effect on the dewatering properties of the sludge are
open to some question at the present time. In addition, the use
of the recovered sludge as a raw material for rendering may be
less desirable as a result of chemical addition.
Sand Filter
A slow sand filter is a specially prepared bed of sand or other
mineral fines on which doses of waste water are intermittently
applied and from which effluent is removed by an under-drainage
system (Figure 18); it removes solids from the waste water
stream. BOD5 removal occurs primarily as a function of the
degree of solids removal, although some biological action occurs
in the top inch or two of sand. Effluent from the sand filter is
of a high quality, with BOD5 and suspended solids concentrations
of less than 10 mg/1.24 Although the performance of a sand
filter is well known and documented, it is not in common use be-
cause it is not needed to reach current waste water standards.
A rapid sand filter may operate under pressure in a closed vessel
or may be built in open concrete tanks. It is primarily a water
treatment device and thus would be used as tertiary treatment,
following secondary
Float
Primary
or
Qopnnflnrv ^>
Treatment
Effluent
pH
Ajustment
N
s>
Chemical
Addition
\
j>
/
^
Air
Flotation
System
Partial
- — - • ^> lemury
Treated
Effluent
V
Sludge
Figure 17. Chemical Precipitation Schematic
treatment. Mixed media filters are special versions of rapid
sand filters that permit deeper bed-penetration by gradation of
particle sizes in the bed. Up-flow filters are also special
cases of rapid filters.
98
-------
Figure 18. Sand Filter System
Primary or
Secondary
Effluent
IO
Chlorination,
Optional
for Odor Control
^L.
Effluent
Surface nr Back
Clean Wash
to Regenerate
-------
Technical Description
The slow sand filter removes solids primarily at the surface of
the filter. The rapid sand filter is operated to allow a deeper
penetration of suspended solids into the sand bed and thereby
achieve solids removal through a greater cross section of the
bed. The rate of filtration of the rapid filter is up to 100
times that of the slow filter. Thus, the rapid filter requires
substantially less area than the slow filter; however, the cycle
time averages about 2U hours in comparison with cycles of up to
30 to 60 days for a slow filter.25 The larger area required for
the latter means a higher first cost. For small plants, the slow
sand filter can be used as secondary treatment. In larger sizes,
the labor in maintaining and cleaning the surface may mitigate
its use. The rapid sand filter, on the other hand, can be used
following secondary treatment. However, it would tend to clog
quickly and require frequent backwashing, resulting in a high
water use, if used as secondary treatment. This wash water would
also need treatment if the rapid sand filter were used in
secondary treatment with only conventional solids removal
upstream in the plant.
The rapid filters operate essentially unattended with pressure
loss controls and piping installed for automatic backwashing.
They are contained in concrete structures or in steel tanks.23
Cleanup of the rapid sand filter requires backwashing of the bed
of sand with a greater quantity of water than used for the slow
sand filter. Backwashing is an effective cleanup procedure and
the only constraint is to irinimize the wash water required in
cleanup, since this must be disposed of in some appropriate
manner other than discharging it to a stream.
Development Status
The slow sand filter has been in use for 50 years and more. It
has been particularly well suited to small cities and isolated
treatment systems serving hotels, motels, hospitals, etc., where
treatment of low flow is required and land and sand are
available. Treatment in these applications has been of sanitary-
or municipal-type raw waste. The Ohio Environmental Protection
Administration is a strong advocate of slow sand filters as a
secondary treatment for small meat plants, following some form of
settling or solids removal. As of early 1973, 16 sand filters
had been installed and eight were proposed and expected to be
installed in Ohio. All 24 of these installations were on waste
from meat plants.26 The land requirements for a slow sand filter
are not particularly significant in relation to those required
for lagooning purposes in secondary treatment processes.
However, the quality and quantity of sand is important and may be
a constraint in the use of sand filters in some local situations.
It should also be recognized that this process requires hand
labor for raking the crust that develops on the surface.
TOO
-------
Frequency of raking may be weekly or monthly, depending upon the
quality of pretreatment and the gradation of the sand.
Problems and Reliability
The reliability of the slow sand filter seems to be well
established in its long-term use as a municipal waste treatment
system. When the sand filter is operated intermittently there
should be little danger of operating mishap with resultant
discharge of untreated effluent or poor quality effluent. The
need for bed cleaning becomes evident with the reduction in
quality of the effluent or in the increased cycle time, both of
which are subject to monitoring and control. Operation in cold
climates is possible as long as the appropriate adjustment in the
surface of the bed has been made to prevent blanking off the bed
by freezing water.
Chlorination, both before and after sand filtering, particularly
in the use of rapid filters, may be desirable to minimize or
eliminate potential odor problems and slimes that may cause
clogging.
The rapid sand filter has been used extensively in water
treatement plants and in municipal sewage treatment for tertiary
treatment; thus, its use in tertiary treatment of secondary
treated effluents from rendering plants appears to be a practical
method of reducing BOD5 and suspended solids to levels below
those expected from conventional secondary treatment.
Microscreen-Microstrainer
A microstrainer is a filtering device that uses a fine mesh
screen on a partially submerged rotating drum to remove suspended
solids and thereby reduce the BOD5 associated with those solids.
Figure 19. The microstrainer is used as a tertiary treatment
following the removal of most of the solids from the waste water
stream, and suspended solids and BOD5 have been reduced to 3 to 5
mg/1 in applications on municipal waste.16 There are no reports
of their use in the tertiary treatment of rendering plant wastes.
Technical Description
The microstrainer is a filtration device in which a stainless
steel microfabric is used as the filtering medium. The steel
wire cloth is mounted on the periphery of a drum which is rotated
partially submerged in the waste water. Backwash immediately
follows the deposition of solids en the fabric, and in one
installation, this is followed by ultraviolet light exposure to
inhibit microbiological growth.16 The backwash water containing
the solids amounts to about 3 percent of the waste water stream
and must be disposed of by recycling to the biological treatment
system.27 The drum is rotated at a minimum of 0.7 and up to a
maximum of 4.3 revolutions per minute.16 The concentration and
101
-------
percentage removal performance for micros-trainers on suspended
solids and BOD5 appear to be approximately the same as for sand
•F-i 1 +- o-t-c: .
filters.
Development Status
while there is general information available on the performance
of microstrainers and on tests involving the use of them, there
appears to be only one recorded installation of a microstrainer
in use on municipal waste; the requirements for effluent quality
have not
necessitated such installation. The economic comparisons between
sand filters and microstrainers are inconclusive; the mechanical
equipment required for the microstrainer may be a greater factor
than the land requirement for the sand filter at the present
time.
Secondary
Treatment
Effluent
Backwash to
Clear Screen/Strainer
Tertiary
Treated
Effluent
Figure 19. Microscreen/Microstrainer
102
-------
Problems and Reliability
The test performance of the microstrainer fairly well establishes
the reliability of the device and its ability to remove suspended
solids and associated BOD5. Operating and maintenance problems
have not been reported; this is probably because, in large part,
of the limited use of the device in full-scale applications. As
a mechanical filtration device requiring a drive system, it would
have normal maintenance requirements associated with that kind of
mechanical equipment. As a device based on microopenings in a
fabric, it would be particularly intolerant to any degree of
grease loading.
Nitrification-Denitrification
This two-step process of nitrification and denitrification,
Figure 20, is a system to remove the nitrogen which appears as
ammonia in treated rendering plant waste waters, and it is of
primary importance for removal of the ammonia generated in
anaerobic secondary treatment systems. Ammonia removal is
becoming more important because of stream standards being set at
levels as low as 1 to 2 mg/1. Removal of ammonia is virtually
complete, with the nitrogen gas as the end product.
Technical Description
The large quantities of organic matter in raw waste from
rendering plants is frequently and effectively treated in
anaerobic lagoons. Much of the nitrogen in the organic matter,
present mainly as protein, is converted to ammonia in anaerobic
systems or in localized anaerobic environments. The following
sets of equations indicate the nitrification of the ammonia to
nitrites and nitrates, followed by the subsequent denitrification
to nitrogen and nitrous oxide.28 The responsible organisms are
also indicated.
Nitrification does not occur to any great extent until most of
the carbonaceous material has been removed from the waste water
stream. The ammonia nitrification is carried out by aerating the
effluent sufficiently to assure the conversion of all the
nitrogen in the raw effluent to the nitrite-nitrate forms prior
to the aerobic denitrification step.
The denitrification step, converting nitrates to nitrogen and
nitrogen oxides, takes place in the absence of oxygen. It is
thought to proceed too slowly without the addition of a
biodegradable carbon source such as sugar, ethyl alcohol, acetic
acid, or methanol. Methanol is the least expensive and performs
satisfactorily. Investigators working on this process have found
that a 30-percent excess of methanol over the stoichiometric
amount is required.23,29
In current waste treatment practice using anaerobic and aerobic
lagoons, ammonia nitrogen that disappears in the aerobic system
103
-------
Partial
Secondary
Treatment
Effluent
\
Aeration
System
Anaerobic
Pond
Aeration
Cell
Carbon
Source,
e.g. Methanol
Figure 20. Nitrification/Denitrification
Partial
Tertiary
^ Treated
Effluent
Nitrification:
NH3 + 02
TO2 + HsO (Nitrosotnonas)
2N0
2NO-
(Nitrobacter)
Denitrification (using methanol as carbon source)
6H
+
6N03
5CH3OH
5C0
13
Small amounts of N20 and NO are also formed
(Facultative heterotrophs)
-------
does not show up to a large extent as nitrites and nitrates.
Ammonia stripping is not likely to account for the loss. It
appears that denitrification must actually be occurring in the
bottom reaches of the aerobic lagoons, where anaerobic conditions
are probably approached (see data presented in Section X).
Presuming total conversion of the ammonia to nitrites or
nitrates, there will be virtually no nitrogen remaining in the
effluent from the denitrification process. Nitrogen removal can
be maintained at about 90 percent over the range of operating
temperatures; the rate increases with temperature to an optimum
value at approximately 30°C for most aerobic waste systems.
Temperature increases beyond 30° result in a decrease in the rate
for the mesophilic organisms.28
The waste water is routed to a second aeration basin following
denitrificaticn, where the nitrogen and nitrogen oxide are
readily stripped from the waste stream as gases. The sludge from
each stage is settled and recycled to preserve the organisms
required for each step in the process.
Development Status
The specific nitrification-denitrification process described
herein has only been carried out at the bench- and pilot-^scale
levels. Gulp and Gulp23 suggest that the "practicality of
consistently maintaining the necessary biological reactions and
the related economics must be demonstrated on a plant-scale
before the potential of the process can be accurately evaluated."
A pilot model of a three-stage system using this process was
reportedly developed at the Cincinnati Water Research Laboratory
of the EPA and is being built at Manassas, Virginia.30 This work
is also reported to be experimental. Thus, it can be concluded
that this process is, as of now, unproven. However, as mentioned
above, observations of treatment lagoons for rendering plants
indicates that the suggested reactions are occurring in present
systems. Also, Halvorson31 reported that Pasveer is achieving
success in denitrification by carefully controlling the reaction
rate in an oxidation ditch, so that dissolved oxygen levels drop
to near zero just before the water is reaerated by the next
rotor.
Problems and Reliability
In view of the experimental status of this process, it would be
premature to speculate on the reliability or problems incumbent
in a fullscale operation. It would appear that there would be no
exceptional maintenance or residual pollution problems associated
with this process in view of the mechanisms suggested for its
implementation at this time.
105
-------
Ammonia Stripping
Ammonia stripping is a modification of the simple aeration
process for removing gases in water. Figure 21. Following pH
adjustment, the waste water is fed to a packed tower and allowed
to flow down through the tower with a countercurrent air stream
introduced at the bottom of the tower flowing upward to strip the
ammonia. Ammonia-nitrogen removals of up to 98 percent and down
to concentrations of less than 1 mg/1 have been achieved in
experimental ammonia stripping towers.23
Technical Description
The pH of the waste water from a secondary treatment system is
adjusted to between 11 and 12 and the waste water is fed to a
packed or cooling tower type of stripping tower. As pH is
shifted to above 9, the ammonia is present as a soluble gas in
the waste water stream, rather than as the ammonium ion.2'
Ammonia-nitrogen removal of 90 percent was achieved with
countercurrent air flows between 1.8 and 2.2 cubic meters per
liter (250 and 300 cubic feet per gallon) of waste water in an
experimental tower with hydraulic loadings between 100 and 125
liters per minute per square meter (2.5 and 3 gallons per minute
per square foot). The best performance was achieved with an air
rate of 5.9 cubic meters per liter (800 cubic feet per gallon)
and a hydraulic loading of 33 liters per minute per square meter
(0.8 gallons per minute per square foot) and the ammonia
concentration was reduced to less than one part per million at 98
percent removal. The high percentage removal of ammonia-nitrogen
is achieved only at a substantial cost in terms of air
requirements and stripping tower cross-sectional area.23
Development Status
The ammonia stripping process is a well-established industrial
practice in the petroleum refinery industry. The only
significant difference between the petroleum refinery application
and that on rendering waste would be the comparatively small size
of stripping tower required for the rendering plants, compared to
the refinery. The air stripping of ammonia from secondary
effluent is reported primarily on an experimental basis in
equipment that is 1.8 meters (6 feet) in diameter with a packing
depth of up to 7.3 meters (24 feet). Two large-scale installa-
tions of ammonia stripping of lime-treated waste water are
reported at South Tahoe, California, and Windhoek, South
Africa.°6,23 The South Tahoe ammonia stripper was rated at 14.2
M liters per day (3.75 MGD) and was essentially constructed as a
cooling tower structure, rather than as a cylindrical steel tower
which might be used in smaller sized plants.
Thus, although there is no reported use of ammonia stripping on
rendering plant waste, the technology is well established and
implementation, when standards require it, would be possible
without great difficulty. Problems and Reliability
106
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The reliability of this process has been established by petroleum
refinery use cf the process over many years. Although the source
of the ammonia may be different and there may be other
contaminants in the water stream, this should not affect the
established reliability of this process. The experience of other
users of the process will have identified potential problems,
and, presumably, the solutions for these problems will have been
found. The maintenance requirements would be only those normally
associated with the mechanical equipment involved in pumping the
waste water to the top of the tower where the feed is introduced
to the tower, and in maintaining the air blowers. The tower fill
would undoubtedly be designed for the kind of service involved in
treating a waste water stream that has some potential for
fouling.
Spray/Flood Irrigation
A no-discharge level for rendering waste water can be and is
being achieved by the use of spray or flood irrigation of
relatively flat land, surrounded by dikes to prevent runoff. A
cover crop of grass or other vegetation is maintained on the
land. Specific plant situations may preclude the installation of
irrigation systems; however, where they are feasible, the
economics can be very favorable and serious consideration should
be given to them.
Technical Description
Wastes are disposed of in spray or flood irrigation systems by
distribution through piping and spray nozzles over relatively
flat terrain or by the pumping and disposal through the ridge and
furrow irrigation systems which allow a certain level of flooding
on a given plot of land, Figure 22. Pretreatment for removal of
solids is advisable to prevent plugging of the spray nozzles, or
deposition in the furrows of a ridgeand-furrow system, or
collection of solids on the surface, which may cause odor
problems or clog the soil. Therefore, the BOD5 will usually have
already been reduced in preliminary treatment (primary plus some
degree of secondary treatment) upstream from the distribution
system.
In flood irrigation, the waste loading in the effluent would be
limited by the waste loading tolerance of the particular crop
being grown on the land, or it may be limited by the soil
conditions or potential for vermin or odor problems.
Waste water distributed in either manner percolates through the
soil and the organic matter in the waste undergoes a biological
degradation. The liquid in the waste stream is either stored in
the soil or leached to a groundwater aquifer and discharged into
the groundwater. Approximately ten percent of the waste flow
will be lost by evapotranspiration (the loss caused by
evaporation to the atmosphere through the leaves of plants).28
Spray runoff irrigation is an alternative technique which has
been tested on the waste from a small meat packer32 and on
107
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cannery waste.28 With this technique, about 50 percent of the
waste water applied to the soil is allowed to run off as a
discharge rather than no dischare, as discussed here. The runoff
or discharge from this type of irrigation system is of higher
quality than the waste water as applied, with BOD5 removal of
about 80 percent; total organic carbon and ammonia nitrogen
system is of higher quality than the waste water as applied, with
BOD5 removal of about 80 percent; total organic carbon and
ammonia nitrogen are about 85 percent reduced, and phosphorus is
about 65 percent reduced.32
The following factors will affect the ability of a particular
land area to absorb waste water: 1) character of the soil, 2)
stratification of the soil profile, 3) depth to groundwater, 4)
initial moisture content, and 5) terrain and groundcover.28
The potentially greatest concern in the use of irrigation as a
disposal system is the total dissolved solids content and
particularly the salt content of the waste water. A maximum salt
content of 0.15 percent is suggested by Eckenfelder.28 Some
plants or some locations may require treatment in an ion exchange
system upstream from the irrigation system to reduce the
dissolved solids and the salt content to acceptable levels for
continuing application of the waste water on land. However, the
average plant should have no problem with salt, since the average
salt content of rendering waste waters is about a factor of six
less than the limit of 0.15 percent suggested by Eckenfelder.
An application rate of up to 330 liters per minute per hectare
(35 gallons per minute per acre) has been suggested in
determining the quantity of land required for various waste water
flows. This amounts to almost 5 cm (2 inches) of moisture per
day, and is relatively low in comparison with application rates
reported by Eckenfelder for various spray irrigation systems.28
However, solids vary widely in their percolation properties and
experimental irrigation of a small area is recommended before a
complete system is built. In this report land requirements were
based on 2.5 cm (one inch) applied per operating day for six
months of the year with lagoon storage for six-months'
accumulation of waste water.
Waste water application rates currently used by rendering plants
with spray irrigation systems are less than 4.0 cm (1.6 inches)
water per two weeks for a six-month irrigation period. If
rendering plant waste waters were being used as the sole nitrogen
source for corn growth, the waste waters would probably have to
contain 250 to 500 mg/1 nitrogen. For lower nitrogen
concentrations, the corn crop would probably be damaged by
flooding or by heavy overwatering before the corn received
sufficient nitrogen from the waste waters. This is based on the
assumptions that one bushel of ccrn requires 454 gm (1 pound) of
nitrogen; that the yield is 120 bushels of corn per acre, and
that the corn would require from 25 to 75 cm (10 to 30 inches) of
water per season.3* This water rate amounts to 3.1 to 9.5 cm
(1.2 to 3.7 inches) of water per two weeks, over a four-month
108
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Secondary
Treatment
Effluent
PH
Adjustment
Treated
Effluent
Figure 21. Ammonia Stripping
Primary,
Secondary
or
Partial
Tertiary
Treatment
Effluent
X.
Holding
Basin
N^
^"^
Pumping
System
\
^~
Application
Site
V
Grass or
Hay Crop
Figure 22. Spray/Flood Irrigation System
Partial
Tertiary
Treatment
Effluent
Tertiary
-> Treated
Effluent
Ion
Exchange
Column(s)
Backwash 8
Regenerant
System
Figure 23. Ion Exchange
109
-------
season- Thus^ treated waste water from rendering is a small
enough volume so it can be used as a supplementary nutrient
source for corn rather than a sole resource of nutrients. Data
were not discovered for any cases in which waste water treated
only by primary systems was used for irrigation.
The economic benefit from spray irrigation is estimated on the
basis of raising two crops of grass or hay per season with a
yield of 13.4 metric tons of dry matter per hectare (six tons per
acre) and values at $22 per metric ton ($20 per ton). These
figures are reportedly conservative in terms of the number of
crops and the price to be expected from a grass or hay crop. The
supply and demand sensitivity as well as transportation problems
for moving the crop to a consumer all mitigate against any more
optimistic estimate of economic benefits.33
Cold climate uses of spray irrigation may be subject to more
constraints ad have greater land requirements than plants
operating in more temperate climates. However, a meat packer in
Illinois reportedly operated an irrigation system successfully.
Eckenfelder also reports that the wastes have been successfully
disposed of by spray irrigation from a number of other
industries.28 Rendering plants located in cold climates or short
growing areas should consider two crops for spray irrigation.
One could be a secondary crop such as corn and the other a grass
crop. The grass crop could tolerate heavier volume loadings
without runoff and erosion, and also would extend the irrigation
season from early spring to possibly late November. Corn,
although a more valuable crop, tolerates irrigation in cold
climate areas only during the summer months.
North Star found in its survey of the rendering industry that the
plants located in the arid regions of the Southwest were most
inclinded to use spray or flood irrigation systems.
Problems and Reliability
The long-term reliability of spray cr flood irrigation systems is
a function of the ability of the soil to continue to accept the
waste, and thus reliability remains somewhat open to question.
Problems in maintenance are primarily in the control of the
dissolved solids level and salinity content of the waste water
stream and also in climatic limitations that may exist or
develop. Many soils may be improved by spray irrigation.
Ion Exchange
Ion exchange, as a tertiary waste treatment, is used as a
deionization process in which specific ionic species are removed
from the waste water stream, Figure 23. Ion exchange would be
used to remove salt (sodium chloride) from waters. Ion exchange
resin systems have been developed to remove specific ionic
species, to achieve maximum regeneration operating efficiency,
and to achieve a desired effluent quality. In treating rendering
110
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waste, the desired effluent quality would be a waste water with a
salt concentration of less than 300 mg/1. Ion exchange systems
are available that will remove up to 90 percent of the salt in a
water stream.*6 They can also be used to remove nitrogen.
Technical Description
The deionization of water by means of ion exchange resin involves
the use of both cation and anion exchange resins in sequence or
in combination to remove an electrolyte such as salt.
The normal practice in deionization of water has been to make the
first pass through a strong acid column, cation exchange resin,
in which the first reaction shown in the equations occurs.
Effluent from the first column is passed to a second column of
anion exchange resin to remove the acid formed in the first step,
as indicated in the second reaction. As indicated in the two
reactions, the sodium chloride ions have been removed as ionic
species. A great variety of ion exchange resins have been
developed over the years for specific deionization objectives for
various water quality conditions.
Waste water treatment with ion exchange resins has been
investigated and attempted for over 40 years; however, recent
process developments in the treatment of secondary effluent have
been particularly successful in achieving high quality effluent
at reasonable capital and operating costs. One such process is a
modification of the Rohm and Haas, Desal process.16 In this
process a weak base ion exchange resin is converted to the
bicarbonate form and the secondary effluent is treated by the
resin to remove the inorganic salts. After this step, the
process includes a flocculation/aeration and precipitation step
to remove organic matter; however, this should be unnecessary if
a sand filter or comparable system is used upstream of the. ion
exchange unit. The effluent from the first ion exchange column
is further treated by a weak cation resin to reduce the final
dissolved salt content to approximately 5 mg/1. The anion resin
in this process is regenerated with aqueous ammonia, and the
cation resin with an aqueous sulfuric acid. The resins did not
appear to be susceptible to fouling by the organic constitutents
of the secondary effluent used in this experiment.
Other types of resins are available for ammonia, nitrate, or
phosphate removal as well as for color bodies, COD and fine
suspended matter. Removal of these various constitutents can
range from 75 percent to 97 percent, depending on the
constituent.2 3
The cycle time on the ion exchange unit will be a function of the
time required to block or to take up the ion exchange sites
available in the resin contained in the system. Blockage occurs
when the resin is fouled by suspended matter and other
contaminants. The ion exchange system is ideally located at the
111
-------
end of the waste water processing scheme, thus having the highest
quality effluent available as a feedwater.
To achieve a recycleable water quality, it may be assumed that
less than 500 mg/1 of total dissolved solids would have to be
achieved. Of the total dissolved solids, 300 mg/1 of salt are
assumed to be acceptable. To achieve this final effluent
quality, some portion or all of the waste water stream would be
subjected to ion exchange treatment. The residual pollution will
be that resulting from regeneration of the ion exchange bed. The
resin systems, as indicated earlier, can be tailored to specific
ion removal and efficient use of regneration chemicals, thus
minimizing liquid wastes from the regeneration step.
Development Status
Ion exchange as a unit operation is well established and commonly
used in a wide range of applications in water treatment and water
deionization. Water softening for boiler feed treatment and
domestic and commercial use is probably the most widespread use
of ion exchange in water treatment. Deionization of water by ion
exchange is used to remove carbon dioxide; metal salts such as
chlorides, sulfates, nitrates, and phosphates; silica; and
alkalinity. Specific resin applications such as in waste water
treatment have not been widespread up to the present time, since
there has not been a need for such a level of treatment.
However, process development and experimental work have shown the
capability of ion exchange systems to achieve the water quality
that may be required for irrigation and closed-loop water recycle
systems.
Part of the economic success of an ion exchange system in
treating rendering plant waste will probably depend on a high
quality effluent being available as a feed material. This again,
can be provided by an upstream treatment system such as sand
filtration to remove a maximum of the particularly bothersome
suspended organic material. However, the effect of a low quality
feed would be primarily economic because of shorter cycle times,
rather than a reduction in the overall effectiveness of the ion
exchange system in removing a specific ionic species such as
salt.
Problems and Reliability
The application of the technology in waste treatment has not been
tested and therefore the reliability in that application has yet
to be established. The problems associated with ion exchange
operations would primarily center on the quality of the feed to
the ion exchange system and its effect on the cycle time. The
operation and control of the deionization-regeneration cycle can
be totally automated, which would seem to be the desired
approach. Regeneration solution is used periodically to restore
the ion exchange resin to its original state for continued use.
This solution must be disposed of following its use and that may
112
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require special handling or treatment. The relatively small
quantity of regenerant solution will facilitate its proper
disposal by users of this system.
113
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SECTION VIII
COST, ENERGY AND NONWATER QUALITY ASPECTS
SUMMARY
The waste water from rendering plants is amenable to treatment in
secondary and tertiary waste treatment systems to achieve low
levels of pollutants in the final effluent. In-plant controls,
product recovery operations, and strict water management
practices can be highly effective in reducing the waste load and
waste water flow from any rendering plant. The water management
practices will reduce the requisite size of secondary and
tertiary treatment systems and improve their waste reduction
effectiveness s.
For purposes of estimating treatment costs, the rendering
industry can be divided into small, medium, and large size
plants. The plant size is based on the weight of raw material
processed per day. This division of the industry does not imply
the need to categorize the industry according to size; the
primary categorization criterion—raw waste load—does not vary
with size. Total investment costs and unit operating costs for
waste treatment, on the other hand, will vary with plant size.
Costs that represent the industry situation could not be
determined on the basis of one "typical" plant size, with the
wide range of production and waste water flow for plants in the
industry. Therefore, the three rendering plant sizes that are
relatively closely grouped in production and waste water flow are
used to describe the waste treatment economics for the entire
rendering industry and for plants within the industry.
Waste water treatment investment cost is primarily a function of
waste water flow rate. Cost per unit of production for waste
treatment will vary with total investment cost and the production
rate. Therefore, the rendering industry treatment costs have
been estimated on the basis of "typical" plants for each size. A
"typical" plant is a hypothetical plant with an average
production rate and the indicated waste water flow rate as shown
in Table 13A.
The average BOD5 raw waste load is the same for each plant size,
as indicated by the single industry category, described in
Section IV.
The additional capital expenditures required of a "typical" plant
in each size group to upgrade or install a waste water treatment
system to achieve the indicated performance are indicated in
Table 14. Table 15 shows comparative costs as related to
expanding the hydraulic capacity of existing treatment facilities
if barometric condenser recirculation is not practiced. The
estimated total investment cost to the industry is also reported
for the proposed 1977 and 1983 limitations.
115
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Table 13A. Profile of Typical Plants by Size
Small
Medium
Large
Rendering Plant Size
Ran
kg /day
<45,000
45,000 - 113,500
>113,500
ges
Ib/day
<100,000
100,000 - 250,000
>250,000
Average Raw
Materials Processed
kg /day
16,800
76,300
240,600
Ib/day
37,000
168,000
530,000
Average Waste
Water Flow Rate
liters /day
20,000
91,000
288,000
gal /day
5,300
24,000
76,000
cr>
-------
The estimate of the cost of achieving the proposed 1977
limitations is based on the following assumptions, which reflect
the data collected on the industry in the North Star survey
questionnaire:
o 80 percent of the small plants with treatment systems
will need to install pumps and piping to recirculate
waste water to the barometric condensers; or expand
lagoon capacity if recirculation of barometric
condenser water is not practiced.
o 50 percent of all plants with treatment systems will
need to add an anaerobic lagcon or the equivalent.
o 50 percent of all plants with treatment systems will
need to install chlorination.
The rendering industry waste treatment practices are assumed to
be as reflected in questionnaire data for 49 plants. The data
reveals a 50-50 split between municipal discharge and those that
treat or control their own waste waters. The latter group is
itself split about 50-50. Thus, of the approximately 450 plants
encompassed by this study, 225 are municipal discharges, 112
achieve no discharge of pollutants, and 113 treat waste waters
and discharge to streams. A further discussion of the relevance
of this distribution is presented below under the heading, "Waste
Treatment Systems" between no discharge and treatment with
discharge.
The 1983 limitations will require the following additions to the
existing treatment systems, over and above the additions for
1977:
o 90 percent of all plants with treatment systems must
add sand filters, or the equivalent;
o 50 percent of all plants with treatment systems will
have to make capital improvements in their primary
treatment facilities;
o 12 percent of all plants with treatment systems will
have to eliminate direct blood drainage to the sewer
and recover it in their product streams;
o 20 percent of all plants with treatment systems will
have to install ammonia stripping equipment or
nitrification-denitrification systems.
The costs for irrigation and for ponding are included in Table 14
to indicate the economic advantages of both approaches. Both
techniques produce no discharge, which is the ultimate goal of
the legislation, and free a plant from waste water discharge
regulations. The no-discharge options are particularly
advantageous to the small renderers.
117
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The investment costs for new point sources of waste water
effluent are cost estimates of treatment systems presently in use
in the industry based on the average flow for the plant size, as
indicated in Table 14.
The basis of the cost estimates for a plant to achieve the
proposed limitations involved various additions to existing
facilities, thus the investment cost for a given plant could vary
from a minimum to a maximum cost. A "most likely" investment
cost was computed for each plant size based on the cost of the
combination of treatment-system additions with the highest
probability of occurrence. The most likely and maximum costs are
presented in Table 16. All operating and total annual costs
include the "most likely" investment cost rather than the minimum
or maximum cost.
Tables 15, ISA, and 15B are also presented to provide an
indication of the approximate cost of waste treatment for plants
with waste water volume per unit of raw material processed
equivalent to the average batch process renderer without the use
of water conservation or recirculation systems (3300 liters/1000
kgs or 400 gal/1000 Ib RM). Investment costs would be higher for
such a plant. Operating costs would increase in comparison with
the low waste water volume plant by 18 to 75 percent depending on
plant size and annual costs would increase by 12 to 125 percent.
The medium size plants would experience the largest increase in
the per unit annual cost for 1977 of 0.030/lb RM and small plants
would incur the largest increase in annual cost for 1983 of
0.28iZ/lb RM, again in comparison with the plant using only 143
gal/1000 Ib RM.
The additions to plant operating cost and total annual cost, in
total dollars and in dollars per unit of raw material processed,
for the indicated type or level of waste treatment performance
are listed in Table 17 and 18. The additional costs for the 1977
limitations include the payroll and burden (at 50 percent of
payroll) for the equivalent of one-half man. This assumed cost
of manpower for the treatment system accounts for between 70 and
82 percent of the annual operating cost and between 45 and 60
percent of the total annual cost. This allocation of manpower
cost would be highly discretionary within each rendering plant.
Therefore, the reported operating and total annual costs are very
conservative estimates of expected real plant experience, the
estimates probably are higher than what will actually occur.
The maximum annual costs per unit weight of raw material occur in
the small plants. The 1977 limitations would add 0.350/kg
(0.160/lb) to the annual operating cost of an average small
plant, and the 1983 limitations would add 0.840/kg (0.380/lb).
In comparison with the operating margin of a rendering plant,
these are significant additions to their costs. The costs for
irrigation or ponding are at least a factor of six less than the
cost for other treatment methods for small plants. The
additional cost for the medium or large rendering plant to meet
118
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Table 14. Likely Capital Expenditures by Plant Size to Limitations Shown
with Condenser Recirculation as Needed
Small Plant
Medium Plant
Large Plant
Total
Rendering
Industry
1977
Limitation
(?)
26,500
27,000
52,000
2,100,000
1983
Limitation
($)
53,000
85,000
119,000
8,900,000
New Source
Standard
($)
38,000
78,000
133,000
__
Irrigation
System Only**
($)
5,000
14,000
37,000
^^
Percolator &
Evaporation Pond
($)
14,000
32,000
62,000
— _
-------
the 1983 limitations is no greater than
matter which treatment system is used.
0.2fZ/kg (0.10/lb) , no
The total rendering industry spent approximately $30 million in
1972 on new capital expenditures. This estimate is based on a
projection of the capital expenditures reported for 1958 through
1967 in the 1967 Census of Manufactures.4 The total industry
waste treatment expenditures reported in Tables 14 and 15 of $2.1
to $4.2 million for 1977 limitations and $8.9 million for the
1983 limitations, amounting to about 10 percent and 30 percent of
the $30 million estimate, respectively. The waste treatment
expenditures can be programmed over a number of years, thus the
requisite investment appears reasonable and achievable. The
small rendering plant is put in the most difficult financial
position, however, this can be minimized by the use of irrigation
or ponding.
The electrical energy consumption in waste water treatment by the
rendering industry amounts to less than 2 percent of their
current total use of electrical energy, and less than 0.1 of one
percent of their total (heat plus electrical) energy consumption.
Thus, in absolute terms and comparatively speaking, waste
treatment energy use is of little consequence.
With the implementation of these standards, land becomes the
primary waste sink instead of air and water. The waste to be
disposed on land from rendering plants can improve soils with
nutrients and soil conditioners contained in the waste. Odor
problems can be avoided or eliminated in all treatment systems.
Table 15. Estimated Waste Treatment Investment Costs for
Renderers with High Waste Water Volume
(3300 liters/1000 kgs RM or 400 Gals/1000 Ibs KM)
Plant
Size
Small
Medium
Large
1977
Limitations
20,700
47,600
94,000
1983
Limitations
135,000
208,000
293,000
Irrigation
System, Only
13,100
34,000
90,000
120
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Table 15A. Total Annual and Operating Costs for a Rendering
Plant with High Waste Water Volume to Meet the
Indicated Performance, $/Year
Plant
Size.
Small
Medium
Large
Cost
Annual
Operating
Annual
Operating
Annual
Operating
1977
Limitations
16,600
12,400
24,400
14,900
36,800
18,000
1983
Limitations
61,100
30,000
87,700
36,600
121,900
44,500
Irrigation
System, Only
6,200
4,000
9,800
4,200
16,300
2,000
Table 15B. Annual and Operating Costs Per Unit Weight of
Raw Material for a Rendering Plant with High
Waste Water Volume to Meet Indicated Performance
Plant
Size
Small
Medium
Large
Cost
Annual
Operating
Annual
Operating
Annual
Operating
1977 Limitations
C/kg
0.39
0.30
0.13
0.08
0.06
0.03
C/lb
0.18
0.13
0.06
0.035
0.03
0.014
1983 Limitations
C/kg
1.45
0.71
0.46
0.19
0.20
0.07
C/lb
0.66
0.32
0.21
0.09
0.09
0.03
121
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Table 16. Comparison of Most Likely and Maximum Investment, with Condenser
Recirculation, By Plant Size
Performance
1977 Limitations
1983 Limitations
Small Plant
Most
Likely
Cost
($)
26,500
53,000
Maximum
Cost
($)
26,500
100,000
Medium Plant
Most
Likely
Cost
($)
27,000
85,000
Maximum
Cost
($)
42,000
160,000
Large Plant
Most
Likely
Cost
($)
52,000
119,000
Maximum
Cost
($)
52,000
221,000
Table 18. Annual And Operating Costs Per Unit Weight
of Raw Material for a Rendering Plant to
Meet Indicated Performance
Plant
Small
Medium
Large
Cost
Annual
Cost
Operating
Cost
Annual
Cost
Operating
Cost
Annual
Cost
Operating
Cost
1977
Limitation
C/kg
0.35
0.24
0.07
0.04
0.03
0.02
-------
Table 17. Total Annual and Operating Costs for a Rendering
Plant to Meet the Indicated Performance, $/Year
Plant
Size
Small
Medium
Large
Cost
Annual
Cost
Operating
Cost
Annual
Cost
Operating
Cost
Annual
Cost
Operating
Cost
1977
Limitation
16,500
11,900
16,200
12,200
21,600
14,000
1983
Limitation
40,300
25,100
48,200
27,300
62,600
31,300
New Source
Standard
20,500
14 , 700
30,600
18,800
44,100
24,100
Irrigation
System
1,500
500
3,500
700
7,600
230
Ponding
2,700
750
6,100
1,600
11,800
3,100
-------
"TYPICAL" PLANT
The waste treatment systems applicable to waste water from the
rendering industry can be used effectively by all plants in the
industry. Irrigation or ponding with no discharge is most widely
used by small plants, and is usually the most attractive
treatment option for small plants. A hypothetical "typical"
plant was determined for each plant size as the basis for
estimating investment cost and total annual and Operating costs
for the application of each waste treatment system for each plant
size. The costs were estimated, and in addition, effluent
reduction, energy requirements, and nonwater quality aspects of
the treatment systems were determined.
The waste treatment systems are applied on the basis of the
"typical" plants described in Table 19 for each plant size.
Table 19. "Typical" Plant Parameters for each Plant Size
Plant Parameter
Average Raw Material
Processed, kg/day,
(Ibs/day)
Standard Deviation
of Average R. M.
Processed
kg/day, (Ibs/day)
Total Waste Water
Volume, liters/day
(gals/day)
Waste Water Vol-
ume per unit of R. M.
Processed
liter /1000 kgs ,
(gals/1000 Ib RM)
Average Value of Plant Parameter by Plant Size
Small
16,800
(37,000)
9,100
(20,000)
20,000
(5,300)
1,191
(143)
Medium
76,300
(168,000)
26,300
(58,000)
91,000
(24,000)
1,191
(143)
Large
240,000
(530,000)
74,900
(165,000)
288,000
(76,000)
1,191
(143)
The small rendering plant generally has a lower production limit
of about 4500 to 6800 kg (10,000 to 15,000 Ib) of raw material
processed per day. This estimate is based on the industry sample
data and involves the use of one batch cooker operating on two
batches per day. This level of operation would be at the low end
of economic viability. The North Star sample included one plant
that processed about 3600 kg (8000 Ib) per day of only dead
124
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animals. This type of raw material enabled the plant to operate
at that production level, however, it was unique in the sample.
The waste water volume is primarily based on the average
normalized water volume for all of the continuous process plants
in the sample, 1191 liters/kkg RM (143 gal./lOOO Ib RM). This
means that all plants with barometric condensers and waste
treatment will have to recirculate condenser water from the waste
treatment system and thus avoid this large consumption of fresh
water and reduce the total waste water volume. Costs have been
included for such revision of barometric condenser water supply
systems, as indicated previously. At the same time, however, the
"typical" batch plant was also analyzed regarding costs for
treatment without condenser recirculation for both the purely
(lagoon) treatment mode and the option of irrigation, in each
case with respect to the 1977 limitations.
WASTE TREATMENT SYSTEMS
The waste treatment systems included in this report as
appropriate for use on rendering plant waste water streams can be
used, subject to specific operating constraints or limitations as
described later, by most plants in the industry. The use of some
treatment systems may be precluded by physical or economic
impracticability for some plants.
The waste treatment systems, their use, and the minimum effluent
reduction associated with each are listed in Table 20.
The dissolved air flotation system can be used upstream of any
secondary treatment system. The use of chemicals should increase
the quantity of grease removed from the waste water stream, but
may reduce the value of the grease because of chemical
contaminants.
The secondary treatment systems are generally land intensive
because of the long retention time required in natural biological
processes. Mechanically assisted systems have reduced the land
requirements but increased the energy consumption and cost of
equipment to achieve comparable levels of waste reduction. Some
of the tertiary systems are interchangeable. Any of them can be
used at the end of any of the secondary treatment systems to
achieve a required effluent quality. Chlorination is included if
a disinfection treatment is required. A final clarifier has been
included in costing out all biological treatment systems that
generate a substantial sludge volume; e.g., extended aeration and
activated sludge. The clarifier is needed to reduce the solids
content of the final effluent.
The most feasible system to achieve no discharge at this time is
flood or spray irrigation or ponding. Closing the loop to a
total water recycle or reuse system is technically feasible, but
far too costly for consideration. The irrigation option does
require large plots of accessible land—roughly 2.0
125
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Table 20 Waste Treatment Systems, Their
Use and Effectiveness
Treatment System
Use
Effluent Reduction
Dissolved air
flotation (DAF)
DAF with pH control
and flocculants
added
Anaerobic + aerobic
lagoons
Anaerobic contact
process
Activated sludge
Extended aeration
Anaerobic lagoons +
rotating biological
contactor
Chlorination
Sand filter
Microstrainer
Ammonia stripping
Chemical
precipitation
Spray irrigation
Flood irrigation
Ponding and
evaporation
Nitrification and
Denitrification
Primary treatment or
by-product recovery
Primary treatment or
by-product recovery
Secondary treatment
Secondary treatment
Secondary treatment
Secondary treatment
Secondary treatment
Finish and
disinfection
Tertiary treatment &
secondary treatment
Tertiary treatment
Tertiary treatment
Tertiary treatment
No discharge
No discharge
No discharge
Tertiary treatment
Grease, 60% removal,
to 100 to 200 mg/1
BOD5, 30% removal
SS, 30% removal
Grease, 95-99% removal
BOD5, 90% removal
SS, 98% removal
BODS, 95% removal
BOD5, 90-95% removal
BOD5, 90-95% removal
BOD5, 95% removal
BOD5, 90-95% removal
BOD5, to 5-10 mg/1
SS, to 3-8 mg/1
BOD5, to 10-20 mg/1
SS, to 10-15 mg/1
90-95% removal
Phosphorus, 85-95%
removal, to 0.5 mg/1
or less
Total
Total
Total
N, 85% removal
126
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hectares/mi11ion liters (0.2 acres/thousand gallons) of waste
water per day and limited concentrations of dissolved solids.
More detailed descriptions of each treatment system and its
effectiveness are presented in Section VII—Control and Treatment
Technology.
Of the 49 plants responding to the study questionnaire, about
one-half reported having either their own waste water treatment
system or no discharge; the others indicated discharging their
waste to a municipal treatment system. Twelve plants reported
on-site secondary treatment with lagoon systems or other
combinations of secondary treatment processes. Twelve plants
also reported treatment systems with no discharge. Chlorination
is used by five plants, according to the data.
The North Star sample of rendering plants provided the following
waste water treatment information and industry sources believe
these data conform to overall industry practice:
Discharge to Secondary Treatment No
Municipal System With Discharge Discharge
Small Plants 7 48
Medium Plants 7 53
Large Plants 9 31
TOTALS 23 12 12
TREATMENT AND CONTROL COSTS
In-Plant Control Costs
The purchase and installation cost of in-plant control equipment
is primarily a function of each specific plant situation.
Building layout and construction design will largely dictate what
can be done, how, and at what cost in regard to in-plant waste
control techniques. In-plant control equipment costs were not
included in the total investment cost estimates. Rough
approximations of the range of costs for the in-plant controls
requiring capital equipment are listed in Table 21. These cost
ranges are based somewhat on plant size variation, but are
primarily based on the expected cost that might be incurred by
any rendering plant, depending on the plant layout, age, type of
construction, etc.
Investment Costs Assumptions
The waste treatment system costs are based on the average plant
production capacity and waste water flow listed previously for a
127
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Table 21. Estimates of In-Plant Control Costs
Plant Area
ro
oo
Raw Materials Storage
Cookers
Air Scrubbing
Hide Curing
Materials Recovery
Item
Steam sparge and screen
for high blood contain-
ing waters.
By-pass controls on
vapor lines from
cookers
Recycle system for
scrubber water
Pipe curing waste
waters to cookers
Flow equalization tank
Equipment Cost Range
$10,000-$15,000
$100-$300 per cooker
$10,000-$20,000
$1,000-$3,000
$2,000-$5,000
-------
"typical," but hypothetical, plant of each size. Investment
costs for specific waste treatment systems are primarily
dependent on the waste water volume.
The total waste water flow for each plant size will vary up to
100 percent or more of the average total flow for that size.
This variability coupled with that in cost estimating suggests
that the waste treatment investment costs for a specific plant
may be only within an accuracy of + 50 to 100 percent.
The investment cost data were collected from data included on
questionnaires from rendering plants, the literature, personal
plant visits, equipment manufacturers, engineering contractors,
and consultants. The costs are "ball-park"-type estimates,
implying an accuracy of + 20 to 25 percent. Rarely is it minus.
All costs are reported in August 1971 dollars. Percentage
factors were added to the treatment system equipment cost for
design and engineering (10 percent) and for contingencies and
omissions (15 percent). Land costs were estimated to be $2470
per hectare ($1000 per acre) .
The irrigation system costs are based on application and storage
assumptions to take into consideration geographic and climatic
variables throughout the country. These assumptions are as
follows:
o Application rate is one inch of waste water applied
per operating day during six months per year.
o Storage capacity for six months accumulation of
waste water in a lagoon 1.2 m (4 feet) deep plus
land for roads, dikes, etc.
o Irrigation equipment includes pumps, piping and
distribution system, dikes to prevent all runoff
at a reference cost of $70,000 for 21 hectares
(52 acres) .
The chlorine costs are based on chlorinating the waste water to 8
mg/1. The assumed cost of 180 per kg (80 per Ib) for chlorine
results in a cost of 0.10 per 1000 liters (0.40 per 10CO gal.) of
waste water chlorinated.
In addition to the variation in plant water flows and BOD5
loadings and the inherent inaccuracy in cost estimating, one
additional factor further limits the probability of obtaining
precise cost estimates for specific waste treatment systems.
This factor was reported by a number of informed sources who
indicated that municipal treatment systems will cost up to 50
percent more than comparable industrial installations. The
literature usually makes no distinction between municipal and
industrial installation in reporting investment costs.
129
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Figure 24. Waste Treatment Cost Effectiveness
CO
CD
QQ ^
i/iJ.vJ —
99 —
\— QR
g 98 —
LU
CJ
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LU
Q_ Qf- _M
— yo
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o
o 90 -
D
Q
LU
CC
Q 80 -
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H
00
| 60 —
^>
cc 50 -
LU
^ 40 -
»
§ 30 -
cc
Q_
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< 20 —
TO _
.!
i
c
91,000 I/day .
(24,000 GPD)7
I
,- I
^ 1
1 I
) 20 40
1
|
1
1 SECONDARY
! TREATMENT
, 1
' n
/_ 288,000 I/day
(76,000 GPD)
I nrtinAAi-ix/ -rn i- A TRfli-M-r
60 80 100 120 140 160 180 200 220 240 260 280 300
-------
Cost effectiveness data are presented in Figure 24, as investment
cost required to achieve the indicated BOD5 removal with the
typical lagoon waste treatment system at two levels of waste
water flow. The low flow is the average for the medium size
rendering plant and the high flow is the average for the large
plants. The raw waste reduction is based on the construction of
waste treatment systems with the incremental waste reduction
achieved by adding treatment components to the system as
indicated below (a catch basin is assumed to be standard
practice, and the raw waste is that discharged from the catch
basin).
Treatment Component Total Raw Waste Reduction, %
Catch Basin 0
+ Improved Primary Treatment 15
+ Anaerobic and Aerobic Lagoons 95
+ Aerated Lagoon 98
+ Sand Filter 99+
Annual Cost Assumptions
The components of total annual cost are capital cost,
depreciation, operating and maintenance costs, and energy and
power costs. The cost of capital is estimated to be ten percent
of the investment cost for the rendering industry—the same as in
the meat packing industry. This cost should be a weighted
average of the cost of equity and of debt financing throughout
the industry. Neither individual companies nor industry
associations have a known figure for this cost. Presuming that
target and realized return-on-investment (ROI) or return-on-
assets (ROA) figures incorporate some estimate of capital cost
plus an acceptable profit or return, industry and corporate
reports were used as a guide in selecting the ten percent figure
for the meat packing industry. One sample of companies reported
earnings at 7.1 percent of total assets for 1971 ;35 a recent
business periodical reported earnings at 10.1 percent of invested
capital,36 and meat packing industry sources report corporate
target ROI and ROA figures at 12 to 15 percent for new ventures.
The ten percent figure is probably high, and thus tends to
contribute to a high estimate of total annual cost. Operating
cost includes all the components of total annual cost except
capital cost and depreciation.
The depreciation component of annual cost was estimated on a
straight-line tasis over the following lifetimes, with no salvage
value:
Land costs — not depreciated
Land intensive treatment systems; e.g., lagoons -- 25 years
131
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All other treatment systems — 10 years.
The operating and maintenance costs for the 1983 system include
the cost of one man-year at $4.20/hour plus 50 percent for
burden, supervision, etc. One-half man-year was used for the
annual cost for the 1977 limitations plus the 50 percent burden,
etc. General and maintenance supplies, taxes, insurance, and
miscellaneous operating costs were estimated as 5 percent of the
total investment cost per year. Specific chemical-use costs were
added when such materials were consumed in the waste treatment
system. By-product income, relative to waste treatment, was
credited only in the irrigation system for 13,400 kg of dry
matter (hay or grass) per hectare at $22/100 kg (6 tons/acre at
$20/ton) and two crops per year.37
ENERGY REQUIREMENTS
The electrical energy consumption by the rendering industry—SIC
2077, including marine fats and oils—was reported for 1967 (then
under SIC 2094) to be 362 million KWH and total heat and power
energy consumption at the equivalent of 8108 KWH.* The rendering
industry consumes relatively small quantities of electrical
energy but large quantities of fuel. The waste treatment systems
require power primarily for pumping and aeration. The aeration
horsepower is a function of the waste load and that for pumping
depends on waste water flow rate.
Total power consumption to achieve the 1977 limitations is
estimated to be 7 million KWH per year for the rendering
industry. This amounts to about 2 percent of electrical energy
consumption, and roughly 0.1 percent of the total (heat and
electrical) energy consumption of the industry reported for 1967.
The same approximate percentage would apply to current power
consumption. The additional power needed to achieve 1983
limitations amounts to about 4 percent and 0.2 percent of
electrical and the total energy, respectively, and does not
appear to raise serious power supply or cost questions for the
industry. However, widespread use of chlorine as a disinfectant
may pose some energy problems in the future, or, conversely, the
future supply of chlorine may be seriously affected by the
developing energy situation.
Waste treatment systems impose no significant addition to the
thermal energy requirements of plants. Waste water can be reused
in cooling and condensing service. These heated waste waters
improve the effectiveness of anaerobic ponds, which are best
maintained at about 90°F. Improved thermal efficiencies are also
achieved within a plant when waste water is reused in this
manner.
Waste water treatment costs and effectiveness can be improved by
the use of energy and power conservation practices and techniques
in plant operations. Reduced water use therefore reduces the
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pumping costs and heating costs, the last of which can be further
reduced by water reuse as suggested above.
NONWATER POLLUTION BY WASTE TREATMENT SYSTEMS
Solid Wastes
Solid wastes are the most significant nonwater pollutants
associated with the waste treatment systems applicable to the
rendering industry. Screening devices of various design and
operating principles are used primarily for removal of large-
scale solids from waste water. These solids have economic value
as inedible rendering raw material and can be returned to the
feed end of a plant.
The organic and inorganic solids material separated from the
waste water stream, including chemicals added to aid solids
separation, is called sludge. Typically, it contains 95 to 98
percent water before dewatering or drying. Both primary and
secondary treatment systems generate some quantities of sludge;
the quantity will vary by the type of system and is roughly
estimated as shown below.
Tr ea tm en t_ Sy_s tern
Dissolved air flotation
Anaerobic lagoon
Aerobic and aerated lagoons
Activated sludge
Extended aeration
Anaerobic contact process
Rotating biological contactor
Sludge Volume as Percent of
Raw Wastewater TVolume
Up to 10%
Sludge accumulation in
these lagoons is usually
not sufficient to require
removal.
10 - 15%
5 - 10%
Approximately 2%
Unknown
The raw sludge can be concentrated, digested, dewatered, dried,
incinerated, land-filled on-site, or spread in sludge holding
ponds. The sludge from any of the treatment systems, except air
flotation with polyelectrolyte chemicals added, is amenable to
any of these sludge handling processes.
The sludge from air flotation with chemicals has proven difficult
to dewater in a couple of plants. A dewatered sludge is an
acceptable land fill material. Sludge from secondary treatment
systems is normally ponded by plants on their own land or
dewatered or digested sufficiently for hauling and depositing in
public land fills. The final dried sludge material can be safely
133
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used as an effective soil builder. Prevention of water runoff is
a critical factor in plant-site sludge holding ponds. Costs of
typical sludge handling techniques for each secondary treatment
system generating sufficient quantities of sludge to require
handling equipment are included in the costs for these systems.
Air Pollution
Odors are the only significant air pollution problem associated
with waste treatment in the rendering industry. Malodorous
conditions usually occur in anaerobic waste treatment processes
or localized anaerobic environments within aerobic systems.
However, it is generally agreed that anaerobic ponds will not
create serious odor problems unless the process water has a
sulfate content; then it most assuredly will. Sulfate waters are
definitely a localized condition varying even from well to well
within a specific plant. In a northern climate, the change in
weather in the spring may be accompanied by a period of increased
odor problems.
The anaerobic pond odor potential is somewhat unpredictable as
evidenced by a few plants without sulfate waters that have odor
problems. In these cases a cover and collector of the off-gas
from the pond controls odor. The off-gas is burned in a flare.
The other potential odor generators in waste water treatment are
leaking tanks and process equipment items used in the anaerobic
contact process that normally generate methane. However, with
the process confined to a specific piece of equipment it is
relatively easy to confine and control odors by collecting and
burning the off-gases. The high heating value of these gases
makes it worthwhile and a frequent practice to recover the heat
for use in the waste treatment process.
Odors have been generated by some air flotation systems which are
normally housed in a building, thus localizing, but intensifying
the problem. Minimizing the unnecessary holdup of any skimmings
or grease-containing solids has been suggested as a remedy.
Odors can best be controlled by elimination at the source, rather
than resorting to treatment for odor control, which remains
largely unproven at this time.
Noise
The only material increase in noise within a rendering plant
caused by waste treatment is that caused by the installation of
an air flotation system or aerated lagoons with air blowers.
Large pumps and an air compressor are part of an air flotation
system. The industry frequently houses such a system in a low-
cost building; thus, the substantial noise generated by an air
flotation system is confined and perhaps amplified by
installation practices. All air compressors, air blowers, and
134
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large pumps in use on intensively aerated treatment systems, and
other treatment systems as well, may produce noise levels in
excess of the Occupational Safety and Health Administration
standards. The industry must consider these standards in solving
its waste pollution problems.
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SECTION IX
EFFLUENT REDUCTION ATTAINABLE THROUGH THE
APPLICATION OF THE BEST PRACTICABLE
CONTROL TECHNOLOGY CURRENTLY
AVAILABLE—EFFLUENT LIMITATIONS GUIDELINES
INTRODUCTION
The effluent limitations which must be achieved July 1, 1977, are
to specify the degree of effluent reduction attainable through
the application of the Best Practicable Control Technology
Currently Available. This technology is generally based upon the
average of the best existing performance by plants of various
sizes, ages, and unit processes within the industrial category
and/or subcategory. This average was not based upon a broad
range of plants within the independent rendering industry, but
based upon performance levels achieved by exemplary plants.
Consideration was also given to:
o The total cost of application of technology in relation
to the effluent reduction benefits to be achieved from
such application;
o The size and age of equipment and facilities involved;
o The processes employed;
o The engineering aspects of the application of various
types of control techniques;
o Process changes;
o Nonwater quality environmental impact (including energy
requirements).
Also, Best Practicable Control Technology Currently Available
emphasizes treatment facilities at the end of a manufacturing
process, but includes the control technologies within the process
itself when the latter are considered to be normal practice
within an industry.
A further consideration is the degree of economic and engineering
reliability which must be established for the technology to be
"currently available." As a result of demonstration projects,
pilot plants and general use, there must exist a high degree of
confidence in the engineering and economic practicability of the
technology at the time of start of construction of installation
of the control facilities.
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EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF
BEST POLLUTION CONTROL TECHNOLOGY CURRENTLY AVAILABLE
Based on the informatior contained in Sections III through VIII
of chis report, a determination has been made that the quality of
effluent attainable through the application of the Best Pollution
Control Technology Currently Available is as listed in Table 22.
Of the ten plants with materials recovery systems and secondary
treatment systems for which information on effluent quality was
available^ two are meeting these standards. An additional four
of the plants come close to meeting these standards.
Hide curing at an independent rendering plant requires an
adjustment in the limitation for BOD5, and SS (Table 23). An
adjustment does not become significant, however, unless the
number of hides handled is quite large.
For example, an average size plant, as found in this study, is
one handling 94,000 kg (206,000 pounds) RM (raw materials) per
day, and also curing 100 hides, and would have the following
adjustment factors (AF):
AF (BOD5) = 8_x_100 = 0.0085 kg/kkg RM (lb/1000 Ib RM)
94,000
AF (TSS) = ll_x_100 = 0.012 kg/kkg RM (lb/1000 Ib RM)
94,000
From Table 22 and the above correction, the effluent limitations
for this pollutant would be 0.15 + 0.0085, and 0.17 + 0.012 or
0.182 kg/kkg (lb/1000 Ib) RM (a 5 and 7 percent increase) for
BOD5 and SS, respectively. An adjustment for grease was not
included because there was no correlation between the raw and
final waste loads for grease. For instance, for the six plants
meeting the grease limit (of the nine plants for which final
effluent data on grease were available) only two of the six
plants had raw grease loads less than the industry average (which
was 0.72 kg/kkg RM) . The other four plants had raw grease loads
that were 1.5, 1.6, 4.3, and 7.6 times greater than the average
value of 0.72. Yet, five of the six plants had final grease
concentrations that '-'ere within a range of 2 to 23 mg/1; the
sixth had a final grer.ss concentration of 54 mg/1. It thus
appears that the treatment system used, can reduce grease in the
final effluent to relatively low values, independent of the
grease in the raw waste.
138
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Table 22. Recommended Effluent Limitation
Guidelines for July 1, 1977
Effluent Parameter
Effluent Limitation
BOD 5
Suspended solids (SS)
Grease
Fecal coliform
0.15 kg/kkg RM (lb/1000 Ib KM)
0.2Q kg/kkg RM (lb/1000 Ib RM)
0.10 kg/kkg RM (lb/1000 Ib RM)
400 counts/100 ml
Table 23. Effluent Limitations Adjustment
Factors for Hide Curing
Effluent Parameter (kg/kkg RM or lb/1000 Ib RM)
BOD5
8.0 x (no. of hides) _ j-7.6 x (no. of hides)
( kg of RM) ~ (Ib of RM)
... ,-_, 11 x (no. of hides) 24.2 x (no. of hides)
Suspended solxds (SS) = ( kg of RM) = (Ib of RM)
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IDENTIFICATION OF BEST POLLUTION CONTROL
TECENOLOGY CURRENTLY AVAILABLE
Best Pollution Control Technology Currently Available for the
independent rendering industry involves biological waste
treatment following a materials recovery process for grease and
solids. To assure that treatment will successfully achieve the
limits specified, certain in-plant practices should be followed:
1. Materials recovery system—catch basins, skimming tanks,
air flotation, etc.—should provide for at least a 30-
minute detention time of the waste water.
2. Reuse of treated waters for operating barometric leg
condensers rather than fresh water. This minimizes
net waste water volume; for a given size of treatment
system, it permits a longer effective residence time.
3. Removal of grease and solids from the materials recovery
system on a continuous or regularly scheduled basis to
permit optimum performance.
4. Provide adequate cooling of condensables to ensure that
the temperature of the waste water in the materials
recovery system does not exceed 52°C (125°F). This allows
for improved grease recovery.
5. Scrape, shovel, or pick up by other means as much as
possible of material spills before washing the floors with
hot water.
6. Minimize drainage from materials receiving areas. This
may require the pumping of the liquid drainage back onto
the raw materials as it is conveyed from the area.
7. Repair equipment leaks as soon as possible.
8. Provide for regularly scheduled equipment maintenance
programs.
9. Avoid over-filling cookers.
10. Provide and maintain traps in the cooking vapor lines
to prevent overflow to the condensers. This is particularly
important when the cookers are used to hydrolyze materials.
11. Contain materials when equipment failure occurs and while
equipment is being repaired.
12. Steam sparge and screen liquid drainage from high water-
and blood-containing materials, such as poultry feathers
on which blood has been dumped.
13. Plug sewers and provide supervision when unloading or
transferring raw blood. Blood has a BOD5 of between
140
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Table 24. Raw and Final Effluent Information for Ten Rendering Plants
Plant
Number —'
1
2
3
4
5
6
7
8
9
10
Flow,
1000 liters
(1000 gal.)
454 (120
57 U5)
132 (35)
45 (12)
3028 (800)
102 (27)
2120 (560)
106 (28)
625 (165)
19 (5)
RM/Day ,
kkg
(1000 Ib)
170 (374)
9 (20)
86 (190)
68 (150)
390 (860)
32 (70)
300 (660)
75 (165)
265 (583)
26 (57)
BOD Load,
kg /kkg RM*
Raw
1.77
0.79
16.22
2.66
4.51
1.28
5.86
6.93
3.64
3.50
Final
0.06
0.04
0.16
0.06
0.18
0.27
0.86
0.09
0.34
0.07
SS Load,
kg /kkg RM*
Raw
2.81
6.96
6.69
1.45
2.42
0.65
3.50
2.77
0.80
—
Final
0.08
0.21
0.006
0.09
0.42
0.30
4.4
0.14
0.20
—
Grease Load,
kg /kkg RM*
Raw
0.04
1.050
5.45
1.070
0.920
—
1.340
3.120
1.150
0.63
Final
0.006
0.10
0.035
0.150
0.220
—
0.300
0.028
0.038
0.040
Final Fecal
Coliform**
(Counts/100 ml)
—
3,600
70,000
50
99 (Cl)
—
270,000
99
100 (Cl)
4,700
*kg/kkg RM = lb/1000 Ib RM
**(C1) indicates chlorination of final effluent.
17 For plant number 3, high raw wastes due to malfunction in grease/
solids recovery system, and final SS value not used due to
atypical final settling. Plant number 7 was not used to derive
limits due to apparent severe malfunction in normally satisfactory
treatment facility.
-------
150,000 and 200,000 mg/1.8 J
14. Provide by-pass controls for controlling pressure reduc- :*
tion rates of cookers after hydrolysis. Cooker agitation ''
may have to be stopped also, during cooker pressure bleed-'!
down to prevent, or minimize materials carry-over.
15. Minimize water use for scrubbers by recycling and reuse.
16. Evaporate tank water to stick and use as tankage in dry :i
inedible rendering. '
17. Do not add uncontaminated water to the contaminated water l
to be treated. ;
18. By-pass the materials recovery process with low grease-
bearing waste waters.
The above practices can readily produce a raw waste load below
that cited as average in Section V. With an average waste load,
use of the following secondary biological treatment systems i
should produce an effluent that meets the recommended effluent
limitations:
1. Anaerobic lagoon + aerobic (shallow) lagoons
2. Activated sludge + aerobic (shallow) lagoons
3. Aerated lagoons -t- aerobic (shallow) lagoons.
Plants with a higher-than-average raw waste load or an undersize
treatment system may require a solids removal stage or
chlorination as the final treatment process. Furthermore, a
plant located in a cold climate area may need sufficient holding
capacity in the aerobic lagoons because it cannot discharge for
periods of three to six months.
RATIONALE FOR THE SELECTION OF BEST PRACTICABLE
CONTROL TECHNOLOGY CURRENTLY AVAILABLE
The rationale used in developing the effluent limitations
presented in Table 24 was based upon the actual performances of
ten plants having what was considered to be complete secondary
treatment and for which sufficient information was available. A
complete secondary treatment system would include any properly
sized system mentioned in the preceding paragraph.
Size, Age, Processes Employed, and Location of Facilities
The ten plants used for developing the effluent limitations cover
operations using different processes, equipment, raw materials,
and are of different size, age, and location of facilities. Data
presented in Section IV showed that these factors did not have a
distinct influence on the raw waste characteristics from
142
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independent rendering plants. Furthermore, the final effluent
data from these ten plants reveal that the raw waste loads can be
readily reduced by secondary treatment to a similar level
regardless of in-plant operations, raw materials used, and size,
age, and location of facilities.
Data Presentation
Table 24 presents the data for the ten plants. Included in Table
24 are the plant size (kkg or 1000 Ib RM/day), effluent flow,raw
and final waste loads for BOD5, SS, and grease, and fecal
coliform counts in the final treated effluent. Data for four of
the plants represent information obtained as a result of our
field sarrpling survey; data for the other six plants were
obtained primarily from questionnaire information and of these,
data for three plants were verified by the results of the field
survey. Data for plant number 7 were included, although it was
evident from visiting the plant and the results shown that the
treatment system at this plant was not functioning properly; the
effluent data were not used in determining the effluent limits.
Similarly, the test results for SS for plant number 3 were found
to be inconsistent and were not used for calculating the effluent
limits.
The BOD5 effluent limitation of 0.15 kg/kgg RM is basically the
average value of the BOD5 data for all but plant number 7. The
data of Table 24 show that five of the ten plants easily meet
this limitation, while plants 3 and 5 come very close. It should
be noted that the raw BOD5 waste loads for the five plants
meeting the effluent range from 0.79 to 6.93 kg BOD5/kkg (lb/1000
Ib) RM and that the raw value for plant 3, whose final value
comes close to the limitation, is 16.2 kg/kkg RM. In fact, the
average raw BOD5 value for the five plants meeting the limitation
is 3.13 kg BOD5/kkg (lb/1000 Ib) RM. The average of all plants
stuided was 2.15 kg BOD5/kkg RM; thus even plants with higher raw
BOD5 waste loads than these industry averages can meet the BOD5
effluent limitation.
The suspended solids (SS) effluent limitation value of 0.17 kg
SS/kkg RM is close to the average of all the values except for
that of plant 7. The values for four plants meet the effluent
limitation for suspended solids. Also, the raw SS values for
these four plants range from 1.45 to 6.69 kg SS/kkg (lb/1000 Ib)
RM with an average value of 3.43 kg SS/kkg (lb/1000 Ib RM). The
overall average for all plants studied is 1.13 kg SS/kkg (lb/1000
Ib) RM.
The grease effluent limitation value of 0.10 kg grease/kkg RM is
very nearly the average grease value for the nine values shown.
There are six plants that meet the effluent limitation. These
six plants have raw waste values ranging from 0.04 to 5.45 kg
grease/kkg (lb/1000 Ib) RM, with an average value of 2.30. This
average raw grease value for plants meeting the guidelines is
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over three times as great as the average for grease for all
plants included in the study, which is 0.72.
Based on the average raw waste load values for the ten plants,
with biological treatment systems, these plants must achieve the
following percent reduction to meet the effluent limitation:
96.8 for BOD5, 94.5 for SS, and 95.2 for grease. If, however,
the reductions are based on the average raw waste values for all
plants included in the study, the following percentages are
obtained: 93.0 for BOD5, 85.0 for suspended solids, and 86.1 for
grease.
Although from four to seven of the plants used in developing the
effluent limitations meet at least one of the three effluent
limitations, only two plants are known to meet all three: BOD5,
SS, and grease. Another four plants meet the limitations for two
of the parameters and come very close to meeting the third.
The fecal coliform effluent limitation of 400 counts/100 ml is a
typical value being used for a number of industries. Data from
Table 24 show that four plants can meet this value, and that two
of those are doing so without chlorination. These two plants not
needing chlorination have large anaerobic lagoons plus aerobic
lagoons for secondary treatment. The fecal coliform counts given
in Table 24 were obtained using the membrane filter procedure.
This method and the multiple-tube technique which results in a
MPN (most probable number) value, yield comparable results.
The BOD5 and SS effluent limitation adjustment factors for hide
curing shown in Table 23 were developed using the data from Table
11 and the average BOD5 and SS reduction required to meet the
limitations. These reductions are 93 and 85 percent for BOD5 and
SS, respectively; the values produce adjustment factors of 0.008
kg (0.0176 Ib) BOD5/hide and 0.011 kg (0.0242 Ib) SS/hide. As
discussed earlier, no adjustment was developed for grease.
Engineering Aspects of Control Technique Applications
The specified level of control technology, primary plus
biological treatment, is practicable because it is currently
being practiced by plants representing a wide range of plant
sizes and types. However, if additional treatment is needed,
such as sand beds or mixed media filter beds this technology is
practical as evidenced by its use by other industries8 and
municipalities.
Process Changes
Significant in-plant changes will not be needed by the vast
majority of plants to meet the limitations specified. Many
plants will have to improve plant cleanup and housekeeping
practices, both responsive to good plant management control.
This can best be achieved by ir.iniirdzing spills, containing
materials upon equipment breakdown, and using dry cleaning prior
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to washdown. Some plants may find it necessary to pretreat truck
and raw materials drainage, blood water, and tank water before
mixing them with other waste waters prior to entering the
materials recovery system. Some plants may also find it
necessary to use improved gravity separation systems, such as air
flotation with chemical precipitation. Additional cooling of the
waste water before grease recovery may be required in some cases.
Nonwater Quality Environmental Impact
\
The major impact when the option of an activated sludge type of
system or, possibly, chemical precipitation in the materials
recovery system is used to achieve the limitations will be
disposal of the sludge. Nearby land for sludge disposal may be
necessary; in some cases a sludge digester (stabilizer) may offer
a solution. Properly operated activated sludge-type systems
should permit well conditioned sludge to be placed in small
nearby soil plots for drying without great difficulty.
It was concluded that the odor emitted periodically from
anaerobic lagoons is not a major impact as it can be with the
meat packing industry.8 Also, there are no new kinds of impact
introduced by the application of the best current technology.
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SECTION X
EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF
THE BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE—
EFFLUENT LIMITATIONS GUIDELINES
INTRODUCTION
The effluent limitations which must be achieved no later than
July 1, 1983, are not based on an average of the best performance
within an industrial category, but are determined by identifying
the very best control and treatment technology employed by a
specific point source within the industrial category or
subcategory, or by one industry where it is readily transferable
to another. A specific finding must be made as to the
availability of control measures and practices to eliminate the
discharge of pollutants, taking into account the cost of such
elimination.
Consideration was also given to:
o The age of the equipment and facilities involved;
o The process employed;
o The engineering aspects of the application of various
types of control techniques;
o Process changes;
o The cost of achieving the effluent reduction resulting
from application of the technology;
o Nonwater quality environmental impact (including energy
requirements) .
Also, Best Available Technology Economically Achievable
emphasizes in-process controls as well as control or additional
treatment techniques employed at the end of the production
process.
This level of technology considers those plant processes and
control technologies which, at the pilot-plant, semi-works, and
other levels, have demonstrated both technological performances
and economic viability at a level sufficient to reasonably
justify investing in such facilities. It is the highest degree
of control technology that has been achieved or has been
demonstrated to be capable of being designed for plant-scale
operation up to and including "no discharge" of pollutants.
Although economic factors are considered in this development, the
costs of this level of control are intended to be the top-of-the-
line of current technology, subject to limitations imposed by
economic and engineering feasibility. However, there may be some
technical risk with respect to performance and with respect to
147
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certainty of costs. Therefore, some industrially sponsored
development work may be needed prior tc its application.
EFFLUENT REDUCTION ATTAINABLE THROUGH APPLICATION OF THE
BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE
Based on the information contained in this section and in
Sections III through VII of this report, a determination has been
made that the quality of effluent attainable through the
application of the Best Available Technology Economically
Achievable is as listed in Table 25. The technology to achieve
these goals is generally available, although it may not have been
applied as yet to an independent rendering plant or on a full
scale.
Hide curing at an independent rendering plant requires an
adjustment in the limitations for BOD5 and SS. These adjustments
are listed in Table 26. An adjustment does not become
significant, however, unless the number of hides handled by a
plant is quite large. For example, an average size plant as
found in this study, is one handling 94,000 kg (206,000 pounds)
raw material (RM) per day, and that also cures 100 hides would
have the following adjustment factors (AF):
AF(BOD5) = 3...6_x_100 = 0.0038 kg/kkg RM (lb/1000 Ib RM)
94,000
AF (TSS) = 6.._2_x_100 = 0.0066 kg/kkg RM (lb/1000 Ib RM)
94,000
The effluent limitations for this plant would therefore be 0.074
and 0.107 kg/kkg RM (lb/1000 Ib RM) for BOD5 and SS, respectively
(a 5.7 and 7 percent increase). An adjustment for grease was not
included because there was no correlation between the raw and
final grease values. For example, the six plants that had the
lowest final grease loads (which ranged between about 0.006 and
0.10 kg grease/kkg RM) out of the nine plants for which final
effluent data on grease were available, had raw grease loads
ranging from 0.04 to 5.450 kg/kgg (lb/1000 Ib) RM, with an
average for the six raw values of 1.91 kg/kkg (lb/1000 Ib) RM.
Also, only two of the six plants had raw grease loads less than
the industry average (which was 0.72); the other four plants had
raw grease loads that were 1.5, 1.6, 4.3 and 7.6 times the
average. It thus appears that the treatment system used can
reduce grease in the final effluent to relatively low values,
independent of the raw grease load.
It should also be pointed out that an independent renderer should
consider land disposal, and hence no discharge, for 1983. Where
suitable land is available, evaporation or irrigation is an
option that not only is recommended from the discharge viewpoint,
but also will usually be more economical than the system
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Table 25. Recommended Effluent Limitation
Guidelines for July 1, 1983
Effluent Parameter
Effluent Limitation*
BOD5
Suspended solids (SS)
Grease
Ammonia as N
Total phosphorus as P
pH
Fecal coliform
0.07 kg/kkg RM
0.10 kg/kkg RM
0.05 kg/kkg RM
0.02 kg/kkg RM
0.05 kg/kkg RM
6.0 - 9.0
400 counts/100 ml
*kg/kkg RM = lb/1000 lb RM
Table 26. Effluent Limitation Adjustment Factors
for Hide Curing
Effluent Parameter
BOD5
Suspended Solids (SS)
Adjustment Factor
kg/kkg RM
3.6 x (no. of hides)
(kg of RM)
6.2 x (no. of hides)
(kg of RM)
lb/1000 lb RM
7.9 x (no. of hides)
( lb of RM)
13 . 6 x (no . of hides)
(lb of RM)
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otherwise required. In fact, out of the 48 independent rendering
plants included in this study for which discharge information was
available, 24 did not discharge to a municipal treatment system,
and 12 of them had no discharge.
IDENTIFICATION OF THE BEST AVAILABLE TECHNOLOGY
ECONOMICALLY ACHIEVABLE
The Best Available Technology Economically Achievable includes
that listed under the Best Practicable Control Technology
Currently Available (Section IX) , and a sand filter or equivalent
following secondary treatment. In addition, some plants may
require improved pretreatment, such as dissolved air flotation
with pH control and chemical flocculation, and an ammonia
stripping or nitrification-denitrification sequence.
In-plant controls and modifications may also be required to
achieve the specified levels. These include the following:
1. Materials recovery systems—catch basins, skimming tanks,
air flotation, etc.—should provide for at least a 30-
minute detention time of the waste water.
2. Reuse of treated waters for operating barometric leg
condensers rather than fresh water. This minimizes
net waste water volumes; for a given size of treatment
system it permits a longer effective residence time.
3. Removal of grease and solids from the materials recovery
system on a continuous or regularly scheduled basis to
permit optirruin performance.
4. Provide adequate cooling of condensables to ensure that
the temperature of the waste water in the materials
recovery system does not exceed 52°C (125°F). A tempera-
ture below 38°C (100°F) is even better. This allows for
improved grease recovery and, incidentally, minimizes
odor problems.
5. Scrape, shovel, or pick up by other means as much as
possible of material spilled before washing the floors
with hot water.
6. Minimize drainage from materials receiving areas. This
may require the pumping of the liquid drainage back onto
the raw materials as it is conveyed from the area to the
first processing step.
7. Repair equipment leaks as soon as possible.
8. Provide for regularly scheduled equipment maintenance
programs.
9. Avoid over-filling cookers.
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Table 27. Raw and Final Effluent Information for Ten Rendering Plants
Table 27A. Flow, RM/Day, Final Fecal Coliform,
and BOD5, SS, and Grease Waste Loads
Plant
Number ^J
1
2
3
4
5
6
7
8
9
10
Flow
1000 liters
(1000 gal.)
454 C120)
57 (15)
132 (35)
45 (12)
3028 (800)
102 (27)
2120 (560)
106 (28)
625 (165)
19 (5)
RM/Day
kkg
(1000 Ib)
170 (374)
9 (20)
86 (190)
68 (150)
390 (860)
32 (70)
300 (660)
75 (165)
265 (583)
26 (57)
BOD5 Load,
kg /kkg KM*
Raw
1.77
0.79
16.22
2.66
4.51
1.28
5.86
6.93
3.64
3.50
Final
0.06
0.04
0.16
0.06
0.18
0.27
0.86
0.09
0.34
0.07
SS Load,
kg /kkg RM*
Raw
2.81
6.96
6.69
1.45
2.42
0.65
3.50
2.77
0.80
—
Final
0.08
0.21
0.006
0.09
0.42
0.30
4.4
0.14
0.20
—
Grease Load,
kg/kkg RM*
Raw
0.04
1.050
5.45
1.070
0.920
—
1.340
3.120
1.150
0.63
Final
0.006
0.10
0.035
0.150
0.220
—
0.300
0.028
0.038
0.040
Final Fecal
Coliform**
(Counts/100 ml)
3,600
70,000
50
99 (Cl)
—
270,000
99
100 (Cl)
4,700
en
*kg/kkg RM = pounds/1000 pounds RM
**(C1) indicates chlorination of final effluent.
I/ For plant number 3, high raw wastes due to malfunction in grease/
solids recovery system, and final SS value not used due to
atypical final settling. Plant number 7 was not used to derive
limits due to apparent severe malfunction in normally satisfactory
treatment facility.
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Table 27. Raw and Final Effluent Information for Ten Rendering Plants
(Continued)
Table 27B. TKN, NH3, N02, N03 and TP Waste Loads
Plant
Number
1
2
3
4
5
6*
7
8
9
10
Total
Kjeldahl
Nitrogen
Load as N
kg/kkg RM
Raw
0.49
0.38
0.94
0.38
0.44
—
1.2
0.33
0.82
0.23
Final
0.03
0.02
0.27
0.034
0.30
—
1.92
0.35
0.32
0.08
Ammonia
Load as N
kg/kkg RM
Raw
0.26
0.17
0.08
0.19
0.30
—
0.66
0.14
0.29
0.18
Final
0.001
0.005
0.26
0.0086
0.16
—
0.53
0.11
0.11
0.044
Nitrite
Load as N
kg/kkg RM
Raw
0.04
0.0001
0.0003
0.00002
0.0004
—
0.00036
0.00007
0.00079
0.0013
Final
0.001
0.008
0.00015
0.00005
0.0002
—
0.00036
0.00009
0.0013
0.00004
Nitrate
Load as N
kg/kkg RM
Raw
0.06
0.0001
0.0014
0.0015
0.0001
—
0.012
0.0015
0.018
0.0075
Final
0.0004
0.001
0.0024
0.00068
0.0001
—
0.012
0.0018
0.0077
0.001
Total
Phosphorus
Load as P
kg/kkg RM
Raw
0.01
0.013
0.08
0.031
0.062
—
0.28
0.04
0.04
0,023
Final
0.029
0.001
0.046
0.014
0.08
—
0.26
0.029
0.024
0.013
en
*Nutrient values for this
Part A of this table for
plant are missing because the plant was not sampled. The values shown in
this plant were obtained from the questionnaire.
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10. Provide and maintain traps in the cooking vapor lines to
prevent overflow to the condensers. This is particularly
important when the cookers are used to hydrolyze materials.
11. Contain materials when equipment failure occurs and while
equipment is being repaired.
12. Steam sparge and screen liquid drainage from high water-
and blood-containing materials such as poultry feathers
on which blood has been dumped.
13. Plug sewers and provide supervision when unloading or
transferring raw blood. Blood has a BOD5 of between
150,000 and 200,000 mg/1.8
14. Provide by-pass controls for controlling pressure reduc-
tion rates of cookers after hydrolysis. Cooker agitation
may have to be stopped also, during cooker pressure bleed-
down to prevent or minimize material carry-over.
15. Minimize water use for scrubbers by recycling and reuse.
16. Evaporate tank water to "stick" and use as tankage in
dry inedible rendering.
17. Do not add uncontaminated water to the contaminated water
to be treated.
18. By-pass the materials recovery process with low grease-
bearing waste waters.
19. Provide for flow equalization (constant flow with time)
through the materials recovery system.
20. Eliminate hide curing waste waters by mixing small volumes
with large volumes of raw materials being fed to cookers.
If suitable land is available, land disposal is the best
technology; it is no discharge. However, secondary treatment may
still be required before disposal of waste waters to soil,
although the degree of treatment need not be the same as that
required to meet the 1977 limitations (Section IX). Any of the
systems mentioned in Section IX are suitable.
Currently a number of independent rendering plants are achieving
no discharge via land irrigation, ponding, and discharge to
septic tanks followed by sub-soil drainage (drain fields or large
cesspools). some plants use two of the above technologies to
achieve no discharge. For example, evaporation and ponding may
be used for disposal of wash water and drainage from raw
materials receiving areas, and septic tanks followed by drain
fields for disposal of condensables. This method of disposal of
condensables also helps to contain the associated odor problem.
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RATIONALE FOR SELECTION OF THE BEST AVAILABLE
TECHNOLOGY ECONOMICALLY ACHIEVABLE
The rationale used in developing the 1983 effluent limitations
presented in Table 25 was based upon the performances of ten
waste treatment systems and information contained in Sections III
through VII. The ten treatment systems were considered to be
complete secondary treatment systems. In addition, chlorination
was being used by two of the ten plants.
Size, Age, Processes Employed, and Location of Facilities
The ten plants used for developing the effluent limitations cover
operations using different processes, equipment, raw materials,
and are of different sizes, ages, and locations of facilities.
Data presented in Section IV showed that these factors do not
have a distinct influence on the raw waste characteristics from
independent rendering plants.
The final effluent data from these ten plants reveal that the raw
waste loads can be substantially reduced by secondary treatment
to a similar level regardless of in-plant operations, raw
materials used, and size, age, and location of facilities. The
levels to which secondary treatment can reduce the raw waste
loads will be sufficient to allow the effluent from secondary
treatment to meet effluent limitations for a number of the
pollutants for 1983; however, tertiary treatment will be needed
to ensure that others will consistently meet 1983 standards.
Plants located in cold climates may need sufficient holding
capacity in the secondary treatment system because they cannot
discharge during the coldest months of the year. This is true
not only for plants that discharge their treated waste waters to
navigable streams, but also for plants that irrigate.
Data Presentation
Table 27 presents the data for the ten plants. Included in Table
27A are the plant size (kkg or 1000 Ib RM/day), effluent flow,
raw and final waste loads for BOD5, SS, and grease, and fecal
coliform counts in the final treated effluent. Table 27B
includes raw and final waste load data for total Kjeldahl
nitrogen (TKN) , ammonia (NH3) , nitrates (NO3) , nitrites (N02) ,
and total phosphorus (TP) . Data for four of the plants in Table
27A represent information obtained as a result of our field
sampling survey; data for the other six plants listed were
obtained primarily from questionnaire information, and of these,
data for three plants were verified by the results of the field
survey. The data included in Table 27B were all obtained from
the results of the field sairpling survey. Data for plant number
7 were included, although it was evident from visiting the plant
and from the results shown in the table that the treatment system
at this plant was not functioning properly.
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The BOD5 effluent limitation of 0.07 kg/kgg RM (0.07 lb/1000 Ib
RM) is a value being met by four of the ten plants (see Table
27A) . TWO of the four plants meeting this limit have raw waste
BOD5 loads greater than the industry average of 2.15 kg BODS/kkg
RM. Thus, it appears that a well operated and properly sized
secondary treatment system can produce an effluent with a BOD5
load that will meet the 1983 limitation. Using the average flow
value for the industry, which is 4977 liters/kkg RM (597
gal./lOOO Ib RM), the BOD5 effluent limit value of 0.07 kg/kkg RM
corresponds to a final effluent concentration of 4.4 mg/1. A BOD5
concentration this low usually means that the majority of the
BOD5 remaining is contained in the suspended solids. In fact,
this is supported by the results of a correlation analysis
between final BOD5 and suspended solids waste loads that showed a
high correlation between the two—the correlation coefficient was
0.87 (a coefficient of 1 would be a perfect correlation).
Consequently, to ensure that the final effluent will meet the
1983 BOD5 limit during all periods of discharge will require the
use of a sand filter or its equivalent to reduce the remaining SS
and thus the EOD5.
The suspended solids (SS) effluent limitation value of 0.10
kg/kkg RM (0.10 lb/1000 Ib RM) is currently being met by three of
the nine plants with secondary treatment for which there are
data. These three plants all have raw SS loads greater than the
industry average, which is 1.13 kg/kkg RM, as shown in Table 6.
As mentioned in the above paragraph, a sand filter or its
equivalent will be required to remove SS and hence to lower the
BOD5. This should therefore permit all plants to meet the SS
limitation value. The SS limit, using the average flow value for
the industry of 4977 1/kkg (597 gal./lOOO Ib) RM corresponds to a
final concentration for SS of 20 mg/1. This concentration was
also considered to be about the practical limit for SS removal
via a sand filter (see Section VII).
The grease limit of 0.05 kg/kkg RM (0.05 lb/1000 Ib RM) was
chosen because five of nine plants for which grease data were
available (see Table 27A) met this limit. This limit should not
be difficult to achieve via secondary treatment; four of the five
plants meeting the limit had raw grease loads considerably
greater than the industry average of 0.72 kg grease/kkg RM.
Incidentally, this limit corresponds to a concentration of 10
mg/1 when the water use equals the industry average of 4977 1/kkg
RM (597 gal./lOOO Ib RM).
The ammonia limit of 0.02 kg NH3 as N/kkg RM (0.02 lb/1000 Ib RM)
is being met by three plants that are showing substantial
reduction in Total Kjeldahl Nitrogen. The reason for this is
that the TKN value, which is the sum of the organic and ammonia
nitrogen, is largely caused by ammonia in the final effluent, as
can be seen in Table 27B. Thus, the same steps that are being
used to reduce the TKN value will also help to reduce the ammonia
value. Of course, the best approach to this problem is to
eliminate or reduce the sources, one of which is blood.
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The pH limits of from 6.0 to 9.0 are not expected to require any
special control since all plants for which there were data have
effluents with pH in this range.
The fecal coliform effluent limitation of 400 counts/100 ml is
the same as for the 1977 limits. Data from Table 27A show that
four plants can meet this value, and that two of those are doing
so without chlorination. The two plants not needing chlorination
have large anaerobic lagoons plus aerobic lagoons for secondary
treatment. The fecal ccliform counts given in Table 27A were
obtained using the membrane filter procedure. This method and
the multiple-tube technique which results in a MPN (most probable
number) value, yield comparable results.
Engineering Aspects of Control Technique Applications
The specified level cf control technology, primary, plus
secondary, plus tertiary (which will include at least a sand
filter or its equivalent if it is needed), is practicable; a
number of plants without tertiary treatment are currently meeting
the limits for the individual waste parameters as previously
mentioned. In fact, one plant is currently meeting all waste
parameter limits, and several others are meeting the majority.
Tertiary treatment is required, however, to permit all plants to
meet the limits for all pollutants. The specified tertiary
treatment is practicable because it is currently being used by
other industries. Plants located in cold climates will have to
have sufficient capacity in the treatment systems because they
cannot discharge for periods of about three months. This, too,
should be no major engineering problem since a number of plants
in this industry as well as others are currently doing this.8
Process Changes
Most plants will have to make in-plant changes to meet the 1983
limitations, particularly to meet the TKN and ammonia
limitations. This will involve improved plant cleanup and
housekeeping practices, both responsive to good plant management
control. This will include minimizing spills, containing
materials upon equipment breakdown, using dry cleaning prior to
washdown, and additional cooling of the waste waters before the
materials recovery system. Still, some plants may find it
necessary to control drainage from trucks and raw materials,
blood waters, tank water, and hide-curing waste waters. Specific
suggestions on controlling these sources of waste water were made
earlier in this section. Some plants may also find it necessary
to improve the materials recovery system or replace it with an
improved system such as air flotation with chemical
precipitation.
Nonwater Quality Impact
The major impact will occur when the land disposal option is
chosen. There is a potential long-term effect on the soil from
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irrigation of rendering plant waste water and on ground waters.
To date, impacts have been generally obviated by careful water
application management and by biological treatment prior to
disposal.
Otherwise, the effects will essentially be those described in
Section IX, where it was concluded that no new kinds of impacts
would be introduced.
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SECTION XI
NEW SOURCE PERFORMANCE STANDARDS
INTRODUCTION
The effluent limitations that must be achieved by new sources are
termed New Source Performance Standards. The New Source
Performance Standards apply to any source for which construction
starts after the publication of the proposed regulations for the
Standards. The Standards are determined by adding to the
consideration underlying the identification of the Best
Practicable Control Technology Currently Available, a determina-
tion of what higher levels of pollution control are available
through the use of improved production processes and/or treatment
techniques. Thus, in addition to considering the best in-plant
and end-of-process control technology. New Source Performance
Standards are based on an analysis of how the level of effluent
may be reduced by changing the production process itself.
Alternative processes, operating methods cr other alternatives
are considered. However, the end result of the analysis is to
identify effluent standards which reflect levels of control
achievable through the use of improved production processes (as
well as control technology), rather than prescribing a particular
type of process or technology which must be employed. A further
determination is made as to whether a standard permitting no
discharge of pollutants is practicable.
Consideration was also given to:
o Operating methods;
o Batch, as opposed to continuous, operations;
c Process employed;
o Plant size;
o Recovery of pollutants as by-products.
EFFLUENT REDUCTION ATTAINABLE
FOR NEW SOURCES
The effluent limitations for new sources are the same as those
for the Best Practicable Control Technology Currently Available
for the pollutants BOD5, SS, grease, and fecal coliform (see
Section IX). In addition to these pollutant parameters, the
following additional limits on nutrients are required for new
sources:
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Effluent Parameter
Ammonia as N
Effluent Limitation
kg/kkg (lb/1000 Ib) RM
0.17
These limitations are readily achievable in newly constructed
plants since a number of existing well operated plants are
meeting them. (For the actual data, see Section X.) However,
the guidelines for the Best Available Technology Economically
Achievable should be kept in mind; it may be a practical approach
to design a plant which approaches the 1983 guidelines.
Consideration should also be given to land disposal, which is no
discharge; in many cases this will be the most attractive and
economical option, particularly for small rendering plants.
Table 28 shows the estimated costs for new sources to achieve the
new source performance standards.
Table 28. Investment and Operating Costs
for New Source Performance Standards
Plant Size
Small
Medium
Large
Waste Water Treatment System Costs
Investment
Cost
$
38,000
78,000
133,000
Annual Cost
Total
$/yr
20,500
30,600
44,100
C/kg
(C/lb)
0.42
(0.19)
0.13
(0.06)
0.07
(0.03)
Operating Cost
Total
$/yr
14,700
18,800
24,100
C/kg
(C/lb)
0.31
(0.14)
0.09
(0.04)
0.04
(0.02)
Identification of New Source Control Technology
The control technology is the same as that identified as the Best
Practicable Control Technology Currently Available (see Section
IX). However, certain steps that will be necessary to meet the
1983 guidelines should be considered and, where possible,
incorporated. These include:
o Segregation of drainage from trucks and raw materials,
hide curing waste, blood water, and tank water from
other waste waters for special treatment. This special
treatment may be to eliminate these wastes by adding
them to the raw material as it enters a cooker or by
evaporating them down to a point where they can be
used as tankage for dry inedible rendering. Another
special treatment method would be to steam sparge and
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screen some wastes before combining them with other
waste waters. Of course, the formal methods are the
best for lowering the raw waste load and particularly
the TKN and ammonia loads.
o Materials recovery systems—catch basins, skimming tanks,
air flotation, etc.—should provide for at least a 30-
minute detention time of the waste water.
o Reuse of treated waters for operating barometric leg
condensers rather than fresh water. This minimizes
net waste water volumes for a given size of treatment
system and permits a longer effective residence time.
o Removal of grease and solids from the materials recovery
system on a continuous or regularly scheduled basis to
permit optimum performance.
o Provide adequate cooling of condensables to ensure that
the temperature of the waste water in the materials
recovery system does not exceed 52°C (125°F). A tempera-
ture below 38°C (100°F) is even better. This allows for
improved grease recovery, and minimizes odor problems.
o Scrape, shovel or pick up by other means as much as
possible of material spills before washing the floors
with hot water.
o Repair equipment leaks as soon as possible.
o Provide for regularly scheduled equipment maintenance
programs.
o Avoid over-filling cookers.
o Provide and maintain traps in the cooking vapor lines
to prevent overflow to the condensers. This is
particularly important when the cookers are used to
hydrolyze materials.
o Contain materials when equipment failure occurs and
while equipment is being repaired.
o Plug sewers and provide supervision when unloading or
transferring raw blood.
o Provide by-pass controls for controlling pressure
reduction rates of cookers after hydrolysis. Cooker
agitation may have to be stopped also, during cooker
pressure bleed-down to prevent or minimize material
carry-over.
o Minimize water use for scrubbers by recycling and reuse.
o Do not add uncontaminated water to the contaminated
161
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water to be treated.
o By-pass the materials recovery process with low grease-
bearing waste waters.
o Provide for flow equalization (constant flow with time)
through the materials recovery system.
In addition, the following end-of-process treatments should be
considered.
o Land disposal (irrigation, evaporation) wherever possible;
this should be a prime consideration, especially for
economic reasons.
o Sand filter or equivalent for polishing the effluent
from secondary treatment.
Rationale for Selection of New Source
Performance Standards
The BOD5, SS, grease and fecal colifcrm limits are discussed in
Section IX on the rationale for Best Practicable Control
Technology Currently Available.
The ammonia limit of 0.17 kg/kkg RM is the average ammonia value
for the nine plants whose data are presented in Section X. Six
of those nine plants meet this limit. Three are not meeting the
limit because of poor practices: two are allowing too much blood
to enter the sewer, and the third is adding nutrients to the
lagoons to form a grease cover on the anaerobic lagoon. A total
Kjeldahl nitrogen (TKN) limit was not established because the
majority of the TKN in the effluent is ammonia (the rest, organic
nitrogen) and restricting ammonia will restrict the TKN load in
the effluent.
Pretreatment Requirements
No constituents of the effluent discharged from a plant within
the offsite rendering industry have been found which would
interfere with, pass through, or otherwise be incompatible with a
well designed and operated publicly owned activated sludge or
trickling filter waste water treatment plant. The effluent,
however, should have passed through materials recovery (primary
treatment) in the plant to remove settleable solids and a large
portion of the grease. The concentration of pollutants
acceptable to the treatment plant is dependent on the relative
sizes of the treatment facility and the effluent volume from
independent rendering plants, and must be established by the
treatment facility. It is possible that grease remaining in the
rendering effluent will cause difficulty in the treatment system;
trickling filters appear to be particularly sensitive. A
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concentration of 100 mg/1 is often cited as a limit, and this may
require an effective air flotation system in addition to the
usual catch basins. If the waste strength in terms of BOD5 must
be further reduced, various components of secondary treatment
systems can be used such as anaerobic contact, aerated lagoons,
etc., as pretreatment.
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SECTION XII
ACKNOWLEDGMENTS
The program was conducted under the overall supervision of Dr.
E.E. Erickson. John Pilney was the Project Engineer; he was
assisted by Messrs R.J. Reid and R.J. Parnow. Special assistance
was provided by North Star staff members: Messrs R.H. Forester
and A.J. Senechal.
The contributions and advice of Mr. William H. Prokop of the
National Renderers Association and of their plant operations
committee and of Dr. H.O. Halvorson are gratefully acknowledged.
Special thanks are due Mr. Jeffery D. Denit, Effluent Guidelines
Division for his guidance in the direction of the program and for
his invaluable help in carrying out all aspects of the research
program.
The cooperation of the independent rendering industry is greatly
appreciated. The National Renderers Association and its members
deserve special mention, as do several companies that provided
information and cooperation in plant visits and on-site sampling
programs.
The help of Dr. Dwight Ballinger of EPA in Cincinnati in
establishing sampling and testing procedures used for the field
verification stuides was also appreciated.
Many state and local agencies were also most helpful and much
appreciated.
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SECTION XIII
REFERENCES
1. standard Industrial Classification Manual, Executive Office
of the President, Office of Management and Budget, U.S.
Government Printing Office, Washington, 1972.
2. Dion, J.A., Osag, T.R., Bunyard, F.L., and Crane, G.B.,
Control of Odors from Inedible Rendering Plants: An Information
Document, Environmental Protection Agency, Washington, 1973.
3. "Uniqueness of the Rendering Industry," National Renderers
Association, unpublished, undated.
4. 1967 Census of Manufactures, Bureau of the Census, U.S.
Department of Commerce, U.S. Government Printing Office,
Washington, 1972.
5. Pollution Control Costs and Research Priorities in the
Animal Slaughtering and Processing Industries, National
Industrial Pollution Control Council, U.S. Government Printing
Office, Washington, June 1973.
6. Protein Conversion Equipment, Chemetron Corporation,
Chicago, 1973.
7. Personal communication. National Renderers Association.
8. Development Document for Proposed Effluent Limitations
Guidelines and New Source Performance Standards for the Red Meat
Processing Segment of the Meat Product and Rendering Processing
Point Source Category, U.S. Environmental Protection Agency,
Report No. 4UO/173/012, Washington, October 1973.
9. Doty, D.M., et al., Investigation of Odor Control in the
Rendering Industry, by Fats and Proteins Research Foundation,
Incorporated, for Environmental Protection Agency, Report No. PB-
213 386, National Technical Information Service, Springfield,
Va., October 1972.
10. Prokop, William H., "The Rendering Industry and Ecology
Control," National Renderers Association for presentation at the
2nd Annual International Food and Beverage F.I.D. Symposium,
Montreal, June 1973.
11. Meat Industry Waste Management, Robert S. Kerr Water
Research Center, Ada, Oklahoma, Environmental Protection Agency,
June 1972.
12. Development Document for Effluent Limitations Guidelines
and standards of Performance for the Leather Tanning and
Finishing Industry, DRAFT, for the U.S. Environmental Protection
Agency, June 1973.
167
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13. Basics of Pollution Control, Gurnham & Associates, prepared
for Environmental Protection Agency Technology Transfer Program,
Kansas City, Mo., March 7-8, 1973, Chicago.
14. Public Health Service Drinking Water Standards, Revised,
1962, U.S. Department of Health, Education and Welfare, U.S.
Public Health Service Publication No. 956, U.S. Government
Printing Office, Washington, 1962.
15. Steffan, A.J., In-Plant Modifications to Reduce Pollution
and Pretreatment of Meat Packing Wastewaters for Discharge to
Municipal Systems, prepared for Environmental Protection Agency
Technology Transfer Program, Kansas City, Mo., March 7-8, 1973.
16. Water Quality Improvement by Physical and Chemical
Processes, Earnest F. Gloyna and W. Wesley Eckenfelder, Jr.,
Eds., University of Texas Press, Austin, 1970.
17. Rosen, G.D., "Profit from Effluent," Poultry Industry
(April 1971) .
18. Personal communication, J. Hesler, Greyhound Corporation,
1973.
19. Telephone communication with M. Hartman, Infilco Division,
Westinghouse, Richland, Virginia, May 1973.
20. Upgrading Meat Packing Facilities to Reduce Pollution:
Waste Treatment Systems, Bell, Galyardt, Wells, prepared for
Environmental Protection Agency Technology Transfer Program,
Kansas City, Mo., March 7-8, 1973, Omaha.
21. Private communication from Geo. A. Hormel & Company,
Austin, Minnesota, 1973.
22. Chittenden, Jimmie A., and Wells, W. James, Jr., "BOD
Removal and Stabilization of Anaerobic Lagoon Effluent Using a
Rotating Biological Contactor," presented at the 1970 Annual
Conference, Water Pollution Control Federation, Boston.
23. Gulp, Russell L., and Gulp, Gordon L. , Advanced Wastewater
Treatment, Van Nostrand Reinhold Company, New York, 1971.
24. Babbitt, Harold E., and Baumann, E. Robert, Sewerage and
Sewage Treatment, Eighth Ed., John Wiley & Sons, Inc., London,
1967.
25. Fair, Gordon Maskew, Geyer, John Charles, and Okun, Daniel
Alexander, Water and Wastewater Engineering: Volume 2. Water
Purification and Wastewater Treatment and Disposal, John Wiley &
Sons, Inc., New York, 1968.
26. Personal communication, H.O. Halvorson, 1973.
168
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27. Fair, Gordon Maskew, Geyer, John Charles, and Okun, Daniel
Alexander, Water and Wastewater Engineering: Volume 1. Water
Supply and Wastewater Removal, John Wiley & Sons, Inc., New York,
1966.
28. Eckenfelder, W. Wesley, Jr., Industrial Water Pollution
Control, McGraw-Hill Book Company, New York, 1966.
29. Eliassen, Rolf and Tchobanoglous, George, "Advanced
Treatment Processes," Chemical Engineering (October 14, 1968).
30. Knowles, Chester L., Jr., "Improving Biological Processes,"
Chemical Engineering (October 14, 1968).
31. Personal communication, H.O. Halvorson, May 1973.
32. Witherow, Jack L. , Small Meat Packers Wastes Treatment
Systems, Presented at 4th National Symposium on Food Processing
Wastes, Syracuse, N.Y., March 26-28, 1973
33. Personal communication, C.E. Clapp, United States
Department of Agriculture, Agricultural Research Service,
University of Minnesota, Minneapolis, May 1973.
34. Personal communication with Lowell Hanson, Soil Science,
Agricultural Extension Service, University of Minnesota, 1973.
35. Financial Facts About the Meat Packing Industry, 1971,
American Meat Institute, Chicago, August 1972.
36. "Survey of Corporate Performance: First Quarter 1973,"
Business Week, p. 97 (May 12, 1973).
37. Mckinney, Ross E., Microbiology for Sanitary Engineers,
McGrawHill Book Company, New York, 1962.
38. Frazier, W. C., Food Microbiology, 2nd Edition, McGraw-Hill
Book Company, New York, 1967.
169
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SECTION XIV
GLOSSARY
"Act": The Federal Water Pollution Control Act Amendments of
1972.
Activated Sludge Process: Aerated basin in which waste waters
are mixed with recycled biologically active sludge for periods of
about 6 hours.
Aerated: The introduction and intimate contacting of air and a
liquid by mechanical means such as stirring, spraying, or
bubbling.
Aerobic: Living or occurring only in the presence of dissolved
or molecular oxygen.
Algae: Major group of lower plants, single and multi-celled,
usually aquatic and capable of synthesizing their foodstuff by
photosynthesis.
Ammonia Stripping: Ammonia removal from a liquid, usually by
intimate contacting with an ammonia-free gas such as air.
Anaerobic: Living or active only in the absence of free oxygen.
Bacteria: Primitive plants, generally free of pigment, which
reproduce by dividing in one, two, or three planes. They occur
as single cells, chains, filaments, well-oriented groups, or
amorphous masses.
Biodegradable: The condition of a substance which indicates that
the energy content of the substance can be lowered by the action
of biological agents (bacteria) through chemical reactions that
simplify the molecular structure of the substance.
Biological Oxidation: The process whereby, through the activity
of living organisms in an aerobic environment, organic matter is
converted to more biologically stable matter.
Biological Stabilization: Reduction in the net energy level of
organic matter as a result of the metabolic activity or
organisms, so that further biodegradation is very slow.
Biological Treatment: Organic waste treatment in which bacteria
and/or biochemical action are intensified under controlled
conditions.
Blood Water (serum): Liquid remaining after coagulation of the
blood.
Slowdown: A discharge of water from a system to prevent a build
up of dissolved solids; e.g., in a boiler.
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BOD_5: A measure of the oxygen consumption by aerobic organisms
over a five day test period at 20°C. It is an indirect measure
of the concentration of biologically degradable material present
in organic wastes contained in a water stream.
Category and Subcategory: Divisions of a particular industry
which possess different traits that affect raw waste water
quality.
Chemical Precipitation: A waste treatment process whereby
substances dissolved in the waste water stream are rendered
insoluble and form a solid phase that settles out or can be
removed by flotation techniques.
Clarification: Process of removing undissolved materials from a
liquid, specifically, removal of solids either by settling or
filtration.
Clarifier: A settling basin for separating settleable solids
from waste waters.
cm: Centimeter.
Coagulant: A material, which, when added to liquid wastes or
water, creates a reaction which forms insoluble floe particles
that absorb and precipitate colloidal and suspended solids. The
floe particles can be removed by sedimentation. Among the most
common chemical coagulants used in sewage treatment are ferric
sulfate and alum.
Coanda Phenomenon: Tendency of a flowing fluid to adhere to a
curved surface.
COD - Chemical Oxygen Demand: An indirect measure of the
biochemical load imposed on the oxygen resource of a body of
water when organic wastes are introduced into the water. A
chemical test is used to determine COD of waste water.
Condensables: Cooking vapors capable of being condensed.
Condensate: The liquid produced by condensing rendering cooking
vapors.
Contamination: A general term signifying the introduction into
water of microorganisms, chemical, organic, or inorganic wastes,
or sewage, which renders the water unfit for its intended use.
Cracklings: The crisp solid residue left after the fat has been
separated from the fibrous tissue in rendering lard or tallow.
Denitrification: The process involving the faculative conversion
by anaerobic bacteri of nitrates into nitrogen and nitrogen
oxides.
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Digestion: Though "anaerobic" digestion is used, the term
digestion commonly refers to the anaerobic breakdown of organic
matter in water solution or suspension into simpler or more
biologically stable compounds or both. Organic matter may be
decomposed to soluble organic acids or alcohols, and subsequently
converted to such gases as methane and carbon dioxide. Complete
destruction of organic solid materials by bacterial action alone
is never accomplished.
Dissolved Air Flotation: A process involving the compression of
air and liquid, mixing to super-saturation, and releasing the
pressure to generate large numbers of minute air bubbles. As the
bubbles rise to the surface of the water, they carry with them
small particles that they contact. The process is particularly
effective for grease removal.
Dissolved Oxygen: The oxygen dissolved in sewage, water, or
other liquid, usually expressed as milligrams per liter or as
percent of saturation.
Dry Rendering: Cooking of inedible raw materials to remove all
excess raw material moisture by externally applied heat.
Edible: Products that can be used for human consumption.
Effluent: Liquid which flows from a containing space or process
unit.
Equalization Tank: A means of liquid storage capacity in a
continuous flow system, used to provide a uniform flow rate
downstream in spite of fluctuating incoming flow rates.
Eutrophication: Applies to lake or pond—becoming rich in
dissovled nutrients, with seasonal oxygen deficiency.
Evapotranspiration: Loss of water from the soil, both by
evaporation and by transpiration from the plants growing thereon.
Extended Aeration: A form of the activated sludge process except
that the retention time of waste waters is one to three days.
Facultative Bacteria: Bacteria which can exist and reproduce
under either aerobic or anaerobic conditions.
Facultative Decomposition: Decomposition of organic matter by
facultative microorganisms.
Fat: Refers to the rendering products of tallow and grease.
Fatty Acid: A type of organic acid derived from fats.
Filtration: The process of passing a liquid through a porous
medium for the removal of suspended material by a physical
straining action.
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Finger Dikes: Barriers or walls extending out into lagoonsin
waste water treatment—to prevent or minimize the flow of
incoming water directly to the outlet and thereby short
circuiting the treatment process.
Floe: A mass formed by the aggregation of a number of fine
suspended particles.
Flocculationt The process of forming larger flocculant masses
from a large number of finer suspended particles.
Grease: Fat that has a titre (or melting point) below 40°C.
Grease is produced from poultry and hot fat.
Hydrolyzing: The reaction involving the decomposition of organic
materials by interaction with water in the presence of acids or
alkalines. Hog hair and feathers for example, are hydrolyzed to
a proteinaceous product that has some feed value.
Inedible: Products that can not be used for humar consumption.
Influent: A liquid which flows into a containing space or
process unit.
Ion Exchange: A reversible chemical reaction between a solid and
a liquid by means of which ions may be interchanged between the
two. It is in common use in water softening and water
deionizing.
Isoelectric point: The value of the pH of a solution at which
the soluble protein becomes insoluble and precipitates out.
kg: Kilogram or 1000 grams, metric unit of weight.
kkg: 1000 kilograms.
Kjeldahl nitrogen: A measure of the total amount of nitrogen in
the ammonia and organic forms in waste water.
KWH: Kilowatt-hours; a measure of total electrical energy
consumption.
Lagoon: An all-inclusive term commonly given to a water
impoundment in which organic wastes are stored or stabilized or
both.
Low Temperature Rendering: A rendering process in which the
cooking is conducted at a low temperature which does not
evaporate the raw material moisture. Normally used to produce a
high quality edible product such as lard.
m: Meter; metric unit of length.
Meal: A coarsely ground proteinaceous product of rendering made
from such animal by-products as meat, bone, and feathers.
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mg/1: Milligrams per liter; approximately equals parts per
million; a term used to indicate concentration of materials in
water.
MGD or MGPD: Million gallons per day.
Microstrainer/Microscreen: A mechanical filter consisting of a
cylindrical surface of metal filter fabric with openings of 20-60
micrometers in size.
mm: Millimeter = 0.001 meter.
Municipal Treatment: A city- or community-owned waste treatment
plant for municipal and possible industrial waste treatment.
New Source: Any building, structure, facility, or installation
from which there is or may be a discharge of pollutants and whose
construction is commenced after the publication of the proposed
regulations.
Nitrate, Nitrite: Chemical compounds that include the NO_3-
(nitrate) and NO2- (nitrite) ions. They are composed of nitrogen
and oxygen, are nutrients for growth of algae and other plant
life, and contribute to eutrophication.
Nitrification: The process of oxidizing ammonia by bacteria into
nitrites and nitrates.
No Discharge: No discharge of effluents to a water course. A
system of land disposal with no run-off or total recycle of the
waste water may be used to achieve it.
Noncondensables: Cooking gases that can not be condensed and are
usually very odorous.
Nonwater Quality: Thermal, air, noise and all other
environmental parameters except water.
Offal: The parts of a butchered animal removed in eviscerating
and trimming that may be used as edible products or in production
of inedible by-products.
Off-Gas: The gaseous products of a process that are collected
for use or more typically vented directly, or through a flare,
into the atmosphere.
Organic Content: Synonymous with volatile solids except for
small traces of some inorganic materials such as calcium
carbonate which will lose weight at temperatures used in
determining volatile solids.
Oxidation Lagoon: Synonymous with aerobic or aerated lagoon.
Oxidation Pond: Synonymous with aerobic lagoon.
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Packed Tower: Equipment used in rendering plants for odor
control. A cylindrical column loaded with a packing material
used to increase the contact area between scrubbing solution and
odorous air.
pH: A measure of the relative acidity or alkalinity of water. A
pH of 7.0 indicates a neutral condition. A greater pH indicates
alkalinity and a lower pH indicates acidity. A one unit change
in pH indicates a ten fold change in concentration of hydrogen
ion concentration.
Point Source: Regarding waste water, a single plant with a waste
water stream discharging into a receiving body of water.
Polishing: Final treatment stage before discharge of effluent to
a water course. Carried out in a shallow, aerobic lagoon or
pond, mainly to remove fine suspended solids that settle very
slowly. Some aerobic microbiological activity also occurs.
Pollutant: A substance which taints, fouls, or otherwise renders
impure or unclean the recipient system.
Pollution: The presence of pollutants in a system sufficient to
degrade the quality of the system.
Polyelectrolyte Chemicals: High molecular weight substances
which dissociate into ions when in solution; the ions either
being bound to the molecular structure or free to diffuse
throughout the solvent, depending on the sign of the ionic charge
and the type of electrolyte. They are often used as flocculating
agents in waste water treatment, particularly along with
dissolved air flotation.
Ponding: A waste treatment technique involving the actual holdup
of all waste waters in a confined space.
ppm: Parts per million, a measure of concentration usually
expressed currently as mg/1.
Prebreaker: A mechanical grinder used by rendering plants for
size reduction of raw materials prior to cooking operations.
Pretreatment: Waste water treatment located on the plant site
and upstream from the discharge to a municipal treatment system.
Primary waste treatment: In-plant by-product recovery and waste
water treatment involving physical separation and recovery
devices such as catch basins, screens, and dissolved air
flotation.
Raceway: Circular shaped vat containing brine, agitated by a
paddle wheel and used for brine curing of hides.
Raw Material Moisture: Refers to the water content of raw
materials used in rendering.
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Raw Waste: The waste water effluent from the in-plant primary
waste treatment system.
Recycle: The return of a quantity of effluent from a specific
unit or process to the feed stream of that same unit including
the return of treated plant waste water for several plant uses.
Rendering: Separation of fats and water from tissue by heat or
physical energy.
Return on Assets (ROA): A measure of potential or realized
profit as a percent of the total assets (or fixed assets) used to
generate the profit.
Return on investment (ROI): A measure of potential or realized
profit as a percentage of the investment required to generate the
profit.
Reuse: Referring to waste reuse. The subsequent use of water
following an earlier use without restoring it to the original
quality.
Riprap: A foundation or sustaining wall, usually of stones and
brush, so placed on an embankment or a lagoon to prevent erosion.
RM: Referring to the raw material used in the rendering process.
Rotating Biological Contactor: A waste treatment device
involving closely spaced lightweight disks which are rotated
through the waste water allowing aerobic microflora to accumulate
on each disk and thereby achieving a reduction in the waste
content.
Sand Filter: A filter device incorporating a bed of sand that,
depending on design, can be used in secondary or tertiary waste
treatment.
Screw Press: An extrusion device used to expel excess fat from
proteinaceous solids after cooking.
Scrubber: Used as an odor control device in the rendering
industry. Operates by the contacting of numerous droplets of
scrubbing solution with cdcrous air streams.
Secondary Treatment: The waste treatment following primary in-
plant treatment. Typically involving biological waste reduction
systems.
Sedimentation Tank: A tank or basin in which a liquid (water,
sewage, liquid manure) containing settleable suspended solids is
retained for a sufficient time so part of the suspended solids
settle out by gravity. The time interval that the liquid is
retained in the tank is called "detention period." In sewage
treatment, the detention period is short enough to avoid
putrefaction.
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Settling Tank: Synonymous with sedimentation tank.
Sewage: Water after it has been fouled by various uses. From
the standpoint of source it may be a combination of the liquid or
water-carried wastes from residences, business buildings, and
institutions, together with those from industrial and
agricultural establishments, and with such groundwater, surface
water, and storm water as may be present.
Shock Load: A quantity of waste water or pollutant that greatly
exceeds the normal discharged into a treatment system, usually
occurring over a limited period of time.
Skimmings: Fats and flotable solids recovered from waste waters
for recycling by catch basins, skimming tanks and air flotation
devices.
Sludge: The accumulated settled sclids deposited from sewage or
other wastes, raw or treated, in tanks or basins, and containing
more or less water to form a semiliquid mass.
Slurry: A solids-water mixture, with sufficient water content to
impart fluid handling characteristics to the mixture.
Stick or Stickwater: The concentrated (thick) liquid product
from the evaporated tank water from wet rendering operations. It
is added to solids and may be further dried for feed ingredients.
Stoichiometric Amount: The amount of a substance involved in a
specific chemical reaction, either as a reactant or as a reaction
product.
Surface Waters: The waters of the United States including the
territorial seas.
Suspended Solids (SS): Solids that either float on the surface
of, or are in suspension, in water; and which are largely
removable by laboratory filtering as in the analytical
determinate cf SS content of waste water.
Tallow: Fat that has a titre (melting point) of 40°C or higher.
Tallow is produced from beef cattel and sheep fat.
Tankage: Dried animal by-product residues used as feedstuff.
Tankwater: The water phase resulting from rendering processes
usually occurring in wet rendering.
Tertiary Waste Treatment: Waste treatment systems used to treat
secondary treatment effluent and typically using physical-
chemical technologies to effect waste reduction. Synonymous with
"advanced waste treatment."
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Total Dissolved Solids (TDS): The solids content of waste water
that is soluble and is measured as total solids content minus the
suspended solids.
Wet Rendering: Cooking with water or live steam added to the
material under pressure. This process produces tankwater.
Zero Discharge: The discharge of no pollutants in the waste
water stream of a plant that is discharging into a receiving body
of water.
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TABLE 29
METRIC TABLE
CONVERSION TABLE
MULTIPLY (ENGLISH UNITS) by
ENGLISH UNIT ABBREVIATION CONVERSION
TO OBTAIN (METRIC UNITS)
ABBREVIATION METRIC UNIT
acre
acre - feet
British Thermal
Unit
British Thermal
Unit/pound
cubic feet/minute
cubic feet/second
cubic feet
cubic feet
cubic inches
degree Fahrenheit
feet
gallon
gallon/minute
horsepower
inches
inches of mercury
pounds
million gallons/day
mile
pound/square
inch (gauge)
square feet
square inches
ton (short)
yard
ac 0.405
ac ft 1233.5
BTU 0.252
BTU/lb 0.555
cfm 0.028
cfs 1.7
cu ft 0.028
cu ft 28.32
cu in 16.39
°F 0.555(°F-32)*
ft 0.3048
gal 3.785
gpm 0.0631
hp 0.7457
in 2.54
in Hg 0.03342
Ib 0.454
mgd 3,785
mi 1.609
psig (0.06805 psig +1 )*
sq ft 0.0929
sq in 6.452
ton 0.907
yd 0.9144
ha hectares
cu m cubic meters
kg cal kilogram - calories
kg cal/kg kilogram calories/kilogrc
cu m/min cubic meters/minute
cu m/min cubic meters/minute
cu m cubic meters
1 liters
cu cm cubic centimeters
°C degree Centigrade
m meters
1 liters
I/sec liters/second
kw killowatts
cm centimeters
atm atmospheres
kg kilograms
cu m/day cubic meters/day
km kilometer
atm atmospheres (absolute)
sq m square meters
sq cm square centimeters
kkg metric ton (1000 kilograir
m meter
* Actual conversion, not a multiplier
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