DEVELOPMENT DOCUMENT
for
EFFLUENT LIMITATIONS GUIDELINES
and
NEW SOURCE PERFORMANCE STANDARDS
for the
RENDERER
SEGMENT OF THE
UCTS AND RENDERING PROCESSING POINT SOURCE CATEGORY
Russell E. Train
Administrator
James L. Agee
Assistant Administrator for Water and
Hazardous Materials
Allen Cywln
rector, Effluent Guidelines Division
Jeffery D. Denlt
Project Officer
January, 1975
Effluent Guidelines Division
Office of Water and Hazardous Materials
U. S, Environmental Protection Agency
Washington, D. C.
For Mle by lh» Supedatendiat of X>o«ttB»ati, U.S. QOT«rom«at Printing Offle*. WaiWistton, 0.C. 30402 - Pi*» W.70
-------
-------
DEVELOPMENT DOCUMENT
for
EFFLUENT LIMITATIONS GUIDELINES
and
NEW SOURCE PERFORMANCE STANDARDS
for the
RENDERER
SEGMENT OF THE
MEAT PRODUCTS AND RENDERING PROCESSING 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
January, 1975
Effluent Guidelines Division
Office of Water and Hazardous Materials
U. S. Environmental Protection Agency
Washington, D. C. 20460
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $2.70
-------
-------
ABSTRACT
This document presents the findings of an extensive study of the
renderer segment of the meat products industry by the
Environmental Protection Agency (EPA) for the purpose of
developing effluent limitations guidelines, standards of
performance for new sources, and pretreatment standards for the
industry, to implement Sections 301, 304(b), 306 and 307(b) and
(c) 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 or poultry 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 regulations are based upon efficient
biological treatment for existing sources to discharge into
navigable water bodies by July 1, 1977, and for new source per-
formance standards. This technology is represented by anaerobic
plus aerobic lagoons, or their equivalent. The recommendation
for July 1, 1983, is for biological treatment and in-plant
control, as represented by in-plant containment and separate
treatment or recycle of high strength waste waters, and an
advanced waste water treatment process (i.e., nitrification
and/or filtration) added to the 1977 technology. When suitable
land is available, land disposal with no discharge may be a more
economical option, particularly for plants in rural locations.
Supportive data and rationale for development of the effluent
limitations guidelines and standards of performance are contained
in this report.
in.
-------
-------
CONTENTS
Section
I. CONCLUSIONS
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 9
Process Description 11
Inedible Rendering 13
Batch System 13
Continuous Systems 17
Edible Rendering 21
Cooker Uses and Process Variations 23
Vapor Condensing 25
Grease and Tallow Recovery 26
Solids Processing 27
Odor Control 27
Waste Water Sources 28
Materials Recovery 29
Hide Curing 30
IV. INDUSTRY CATEGORIZATION 31
Categorization 31
Rationale for categorization 31
Waste Water Characteristics and
Treatability 31
Raw Materials 34
Manufacturing Processes 36
-------
CONTENTS (Continued)
Section
Processing Equipment and Methods 36
Size, Age, and Location of Production
Facilities 40
V. WATER USE AND WASTE CHARACTERIZATION 45
Waste Water Characteristics 45
Raw Waste Characteristics 45
Discussion of Raw Wastes 46
Sources of Waste Water 50
Raw Materials Receiving 51
Vapor condensing 51
Spills and Plant and Truck Cleanup 53
Odor Control 56
Hide Curing 56
Miscellaneous Sources 59
VI. SELECTION OF POLLUTANT PARAMETERS 61
Selected Parameters 61
Rationale for Selection of Identified Parameters 61
5-Day Biochemical Oxygen Demand 61
Chemical Oxygen Demand 63
Total Suspended Solids 63
Total Dissolved Solids 65
Total Volatile Solids 66
Oil and Grease 66
Ammonia Nitrogen 67
Kjeldahl Nitrogen 68
Nitrates and Nitrites 68
Phosphorus 69
Chloride 70
Fecal coliforms 71
pH, Acidity, and Alkalinity 71
Temperature 72
VII. CONTROL AND TREATMENT TECHNOLOGY 75
Summary 75
In-Plant Control Techniques 75
Condensables 77
control of High-Strength Liquid Wastes 77
Truck and Barrel Washings 77
Odor Control 78
Plant Cleanup and Spills 78
vi
-------
CONTENTS (Continued)
Section
In-Plant Primary Treatment 78
Flow Equalization 78
Screens 78
Catch Basins 80
Dissolved Air Flotation 81
Waste Water Treatment Systems 86
Anaerobic Processes 86
Aerated Lagoons 90
Aerobic Lagoons 90
Activated Sludge 92
Extended Aeration 94
Rotating Biological Contactor 95
Performance of Various Biological Treatment
Systems 96
Advanced Waste Water Treatment 99
Chemical Precipitation 99
Sand Filter 100
Microscreen Microstrainer 106
Nitrogen control 108
Nitrification 108
Nitrification/Denitrification 111
Ammonia Stripping 114
Disinfection 116
Breakpoint Chlorination 117
Spray/Flood Irrigation 118
Ion Exchange 121
VIII. COST, ENERGY, AND NONWATER QUALITY ASPECTS 125
Summary 125
"Typical" Plant 135
Waste Treatment Systems 136
Treatment and control Costs 138
In-Plant Control Costs 138
Investment Costs Assumptions 138
Annual Cost Assumptions 142
Energy Requirements 143
Nonwater Pollution From waste Treatment Systems 143
Solid Wastes
Air Pollution
Noise .,
-------
-------
CONTENTS (Continued)
Section
In-Plant Primary Treatment 78
Flow Equalization 78
Screens 78
Catch Basins 80
Dissolved Air Flotation 81
Waste Water Treatment Systems
86
Anaerobic Processes 86
Aerated Lagoons 90
Aerobic Lagoons 90
Activated Sludge 92
Extended Aeration 94
Rotating Biological Contactor 95
Performance of Various Biological Treatment
Systems 96
Advanced Waste Water Treatment 99
Chemical Precipitation 99
Sand Filter 100
Microscreen Microstrainer 106
Nitrogen Control 108
Nitrification 108
Nitrification/Denitrification 111
Ammonia Stripping 114
Disinfection 116
Breakpoint Chlorination 117
Spray/Flood Irrigation 118
Ion Exchange 121
VIII. COST, ENERGY, AND NONWATER QUALITY ASPECTS 125
Summary 125
"Typical" Plant 135
Waste Treatment Systems 136
Treatment and control Costs 138
In-Plant Control Costs 138
Investment Costs Assumptions 138
Annual Cost Assumptions 142
Energy Requirements 143
Nonwater Pollution From Waste Treatment Systems 143
Solid Wastes -,4^
Air Pollution 14^
Noise ., Mb
-------
CONTENTS (Continued)
Section Page
IX. EFFLUENT REDUCTION ATTAINABLE THROUGH THE
APPLICATION OF THE BEST PRACTICABLE CONTROL
TECHNOLOGY CURRENTLY AVAILABLE—EFFLUENT
LIMITATIONS GUIDELINES 147
Introduction 147
Effluent Reduction Attainable Through the
Application of Best Pollution Control
Technology currently Available 148
Identification of Best Pollution Control
Technology Currently Available 150
Rationale for the Selection of Best Practicable
Control Technology Currently Available 151
Size, Age, Processes Employed, and
Location of Facilities 151
Total Cost of Application in Relation to
Effluent Reduction Benefits 151
Data presentation 152
Engineering Aspects of Control Technique
Applications 154
Nonwater Quality Environmental Impact 155
X. EFFLUENT REDUCTION ATTAINABLE THROUGH THE
APPLICATION OF THE BEST AVAILABLE TECHNOLOGY
ECONOMICALLY ACHIEVABLE—EFFLUENT LIMITATIONS
GUIDELINES 157
Introduction 157
Effluent Reduction Attainable Through Application
of the Best Available Technology Economically
Achievable 159
Identification of the Best Available Technology
Economically Achievable 160
Rationale for Selection of the Best Available
Technology Economically Achievable 162
Size, Age, Processes Employed, and
Location of Facilities 162
Data Presentation 162
Engineering Aspects of Control Technique
Applications 166
Process Changes 166
Nonwater Quality Impact 167
Vlll
-------
CONTENTS (Continued)
Section
XI. NEW SOURCE PERFORMANCE STANDARDS 169
Introduction 169
Effluent Reduction Attainable For New Sources 169
Identification of New source Control
Technology 170
Technology Rationale for Section of
New Source Performance Standards 172
Pretreatment Requirements 172
XII. ACKNOWLEDGMENTS 175
XIII. REFERENCES 177
XIV. GLOSSARY 185
IX
-------
-------
FIGURES
Number
1 Distribution of Rendering Plants by State 12
2 General Flowsheet of operations of a Typical
Inedible Rendering Plant 18
3 Batch cooker Rendering Process 20
4 Continuous Rendering: Duke Process 22
5 continuous Rendering: Anderson Carver-Greenfield
process 24
6 Manufacturing Processes of a Rendering Plant 32
7 Average and Range of BODji by Raw Material Type 35
8 Average and Range of BOD5 Data by Cooker Type 37
9 Average and Range of BOD5 Data by Condenser Type 38
10 Average and Range of BOD5 Values for Three Size
Groups of Plants and for All Plants Studied 41
10A Scatter Diagram of Raw Wasteload Versus Size 42
11 Typical Rendering Process and Waste Water Flow
Arrangement 52
12 Suggested Waste Reduction
Program for Rendering Plants 76
13 Dissolved Air Flotation 82
m process Alternatives for Dissolved Air Flotation 84
15 Anaerobic contact Process 88
16 Activated Sludge Process 93
17 chemical Precipitation 104
18 Sand Filter System 105
19 Microscreen/Microstrainer 107
20 Nitrification/Denitrification 112
21 Ammonia Stripping 119
-------
FIGURES (Continued)
Number
22 Spray/Flood Irrigation System
23 Ion Exchange
2U Waste Treatment Cost Effectiveness
X1T
-------
TABLES
Number
1 Inedible Tallow and Greases: Use, By-Products,
1960-1970 8
2 Statistics by Employment Size of Establishment,
1967 14
3 Raw Material and Product Yields for Inedible
Rendering by Type of Animal '*
ft Product Yields for Inedible Rendering by Type of
Raw Material 16
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 47
7 Waste Water Flow and Raw Material Data on Independent
Rendering Plants 48
8 Correlation Coefficients of Raw Waste Load
Parameters From the Field Sampling Results 49
8A Observed Housekeeping and Operating Procedures
Adversely Affecting Raw Waste Control and
Treatment Plant Performance 54
9 Summary of Concentrations of Undiluted Condensed
Cooking Vapors 55
10 Summary of Waste Loads of Undiluted Condensed
Cooking Vapors 57
11 Waste Load Characteristics for Hide Curing at a
Rendering Plant Versus Those for a Tannery 58
12 Measured Waste strengths of Tank Water and Blood
Water 58
13 Performance of Various Biological Treatment Systems 97
13A Effluent Quality From Conventional Filtration
of Various Biologically Treated Waste Waters 103
13B Performance of Microstrainers in Advanced
Treatment of Biologically Treated Waste Waters 107
13C Selected Results for Nitrogen Control in
Effluents 110
xiii
-------
TABLES (Continued)
Number Pa9e
13D Profile of Typical Plants by Size 126
14 Likely Capital Expenditures by Plant Size to Meet
Limitations With Condenser Recirculation 128
15 Estimated waste Treatment Costs for Renderers
With High Waste Water Volume 130
ISA Total Annual and Operating Costs for Renderer
With High waste Water Volume 130
15B Annual and Operating Costs Per Unit Weight of Raw
Material 131
16 Comparison of Most Likely and Maximum Investment
With condenser Recirculation 133
17 Total Annual and Operating Costs for a Rendering
Plant to Meet the Indicated Performance 134
18 Annual and Operating Costs Per Unit Weight of Raw
Material for a Rendering Plant to Meet Indicated
Performance 133
19 "Typical" Plant Parameters for Each Plant Size 135
20 Waste Treatment Systems, Their Use and
Effectiveness 137
21 Estimates of In-Plant Control Equipment Cost 139
22 Recommended Effluent Limitations for
July lr 1977 149
23 Effluent Limitations Adjustment Factors for Hide
Curing 149
24 Raw and Final Effluent Information for Ten
Independent Rendering Plants 153
25 Recommended Effluent Limitations for
July 1, 1983 158
26 Effluent Limitations Adjustment Factors for.Hide
Curing 158
27 Raw and Final Effluent Information for Ten
Independent Rendering Plants 163
28 Investment and Operating Costs for New Source
Performance Standards 170
29 Conversion Table 174
xiv
-------
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 and rendering processing 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.
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.
A conclusion of this study is that the rendering industry con-
stitutes a single subcategory. Using BOD5 as the basis for the
analysis, the variables of raw material, processing methods,
plant age and size, water use, and treatability of wastes were
analyzed and found to demonstrate this conclusion.
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
irrigation or impoundment of waste waters. These limits, plus
limits on pH and fecal coliforms can be met by 1977. The same
limits plus limitations on ammonia can be met by new sources.
The ammonia standard for new sources coincides with the
performance already achieved by plants with the best treatment
systems. It is estimated that there will be about $2.6 million
in capital costs required to achieve the 1977 limits by the
industry.
For 1983, effluent limits were determined on the basis of best
available technology economically achievable in the industry for
-------
BOD5, suspended solids, ammonia, oil and grease, pH, and fecal
coliforms.
It is estimated that the cost to achieve the 1983 limits by the
industry will be $6.75 million. The 1977 cost for the industry
represents about 8 percent, and the 1983 cost approximately 22
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
the effluent limitations.
-------
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 biological treatment plants
being used by the industry. The limitations are for 5-day
biochemical oxygen demand (BOD5) , total suspended solids, oil and
grease, and fecal coliform. These limitations are 0.17 kg
BOD5/kkg raw material (RM); 0.21 kg TSS/kkg RM; 0.10 kg
grease/kkg RM; and UOO counts fecal coliform/100 ml. Adjustments
in the BOD5 and TSS limitations are provided for plants curing
hides. In all cases, pH is established at a range of 6.0 to 9.0.
Recommended New Sources Standards include the 1977 limitations
plus limitations on ammonia (NH3[). The additional limitations
are also based on the performance characteristics of well-
operated biological treatment plants. The new source standard
for ammonia is recommended at 0.17 kg/kkg RM.
Limitations recommended for the industry for 1983 are more
stringent and are based upon the performance characteristics of
the best operated biological treatment systems being used to
treat rendering waste waters. These limitations include the same
pollutant parameters as included in the new source standards.
The 1983 limitations are: 0,07 kg BOD5/kkg RM; 0.10 kg TSS/kkg
RM; 0.05 kg grease/kkg RM; and 0.02 kg NH3 as N/kkg RM. Again,
there is established a pH range of 6.0 to 9.0 and a fecal
coliform count of 400/100 ml. Also, adjustments in the BOD5 and
TSS limitations are provided for plants curing hides; however,
these adjustments are smaller than those for the 1977
limitations.
The limitations summarized above are applicable as an average of
daily values for any period of 30 consecutive days. Recommended
daily maximum limitations are based on a variability factor of
2.0; or daily limitations are recommended as 2.0 times the
average for 30 consecutive days.
-------
-------
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 subcategory of the meat products point
source category designated in Section 306.
Section 306 of the Act requires the Administrator, within 1 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,
under Section 306, standards of performance based upon best
available demonstrated technology applicable to new sources of
-------
the rendering segment of the meat products and rendering
processing point source category, which was included in the list
published January 16, 1973.
Section 307 (c) of the Act requires the Administrator to
promulgate pretreatment standards for new sources at the same
time that standards of performance for new sources are
promulgated pursuant to Section 306. Similarly, Section 307(b)
requires the establishment of pretreatment standards for
pollutants introduced into publicly owned treatment works. The
regulations set forth pretreatment standards for new sources and
existing sources pursuant to Sections 307(b) and (c) of the Act
for the renderer segment of the meat products and rendering
processing point source category.
SUMMARY OF METHODS USED FOR DEVELOPMENT OF THE EFFLUENT
LIMITATIONS GUIDELINES AND STANDARDS OF PERFORMANCE
The effluent limitations guidelines and standards of performance
set forth 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.11 In identifying such
technologies, various factors were considered. These included
the total cost of application of technology in relation to the
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 and were included in the "questionnaire" data base.
Thus, the total number of plants included in this study was 51,
or about 11 percent of the rendering industry. All principal
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.
The reviews and analyses of data described above were performed
using accepted methodology. The "questionnaire" data base (51
total plants) served as the principal source of information for
all analyses. Field verification sampling data was used
principally in support of the derivation of effluent limitations.
Subjective information (plant practices, processes, equipment,
etc.) gained from the site visits was also used to complement
industry submissions. Because of the apparently representative
nature of the industry questionnaire information, these data were
used for analyses to categorize and characterize the industry
processes, waste water discharges, and operating conditions. The
analyses involved both rigorous mathematical procedures (using
computer statistical methods) and subjective judgments and
observations using experience from site visits, consultant
comments, information from trade publications, and similar
sources as more fully described in Sections IV and V. Similarly,
cost information was developed on the basis of data supplied by
plants in the industry with supporting information as developed
for other segments of the meat products industry.
The effluent limitations and standards of performance were
derived from available data on the actual performance of existing
-------
plants. Limitations for 1977 (BPCTCA) were derived as the
average of the performance for the best plants. (Some data were
excluded due to plant malfunctions, etc., as noted in section
IX.) The same procedure was used to establish new source
performance standards (NSPS); limitations for 1983 were derived
on the basis of the very best performance achieved by plants in
the industry (between 3 and 5 plants depending upon the
availability of data for all limited parameters).
Table 1. Inedible Tallow and Greases: Use, By-Products, 1960-19701*
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
tLllion 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.
-------
GENERAL DESCRIPTION OF THE INDUSTRY
The rendering industry falls within Industry No. 2077, Animal and
Marine Fats and Oils.* 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 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
independent Tenderers and on-site or captive Tenderers. The
independent Tenderers 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 tallow 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.U 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.
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
The independent Tenderer 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
Tenderer is only picking up restaurant grease, which is more
stable, it is possible that he may travel greater distances.
Renderers are located in both urban and rural areas. The urban
Tenderer normally has more modern equipment, shorter routes for
pickup 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
sewers 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.
10
-------
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 persons with annual sales
of about $100,000 to large operations employing over 100 persons
with sales from $5 to $10 million. An average plant could be
characterized as employing 23 people 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 size was measured not in terms of 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.
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 Tenderers (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 renderers is now around 350.
PROCESS DESCRIPTION
A general flowsheet of the processes of a typical inedible
rendering plant is shown in Figure 2. (A general flowsheet for
edible rendering would be similar.) The bulk material (offal,
bones, and trimmings) collected by renderers is normally dumped
into a pit from which it is conveyed 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
11
-------
Figure 1. Distribution of Rendering Plants by State'
-------
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. 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 U
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
to as a dry rendering process because the raw material is cooked
with no addition of steam or water and because the moisture in
13
-------
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
-------
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 1.0 to 2.0 inches to
provide for efficient cooking. Cooking normally reguires 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
to 45 minutes in a batch cooker for hydrolysis, prior to cooking
under normal or atmospheric pressure for an additional 30 to 40
minutes to reduce the moisture content to 40 to 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 steam 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 left standing until all free-draining fat has
run off. The solids are then conveyed to a press (usually screw
press) to further reduce the fat content. Finally, the solids
are conveyed to grinding and screening operations.
15
-------
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 sheep
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)
16
-------
Prior to 10 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 economic 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 blood 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-lbec; 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 <*. 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
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.
17
-------
PROCESSES
WASTE WATER
RAW MATERIAL
RECOVERY
CRUSHING AND
GRINDING
ODOR
CONTROL
1—I
COOKING
AND MOISTURE
REMOVAL
p— >|
1
MATERIAL
RECOVERY
SYSTEM
T
1
TREATMENT
SYSTEM
•»- WASTE WATER FLOW
•*- PRODUCT AND MATERIAL FLOW
Figure 2. General Flowsheet of Operations for a Typical Inedible Rendering Plant
18
-------
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 U.) 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 Drainor. 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 percolator 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 disintegrator for further size reduction—the final range
is from about 1.0 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
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
19
-------
ro
O
Dead Stock Carcasses and Bone
ENTRAINMENT SEPARATOR
RAW MATERIAL RECEIVING
Exhaust vapor
Screw Press Vent
SCREW PRESS
Steam - 25-75 PSI
PERCOLATOR
— DRAIN PAN
Jacket Condensate
Screw Fat Press
PRECOAT
LEAF FILTER
CENTR FUGE
Solids to Screw Press
Figure 3. Batch Cooker Rendering Process
-------
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 Tenderers.7 However, these plants do
both edible and inedible rendering, and probably less than 1.0
percent of the raw material handled by independent Tenderers 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 (UO 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
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
21
-------
VAPOR CONTROLLER
Condensing Tubes
Blower
Water Spray Nozzles
INCIN-
ERATOR
RAW
MATERIAL
BIN
Blower
^T) NON-
Condensate to Sewer
CENTRIFUGE
CRUDE TALLOW
TANK
\\S\S yt VARI-SPEED
Steam to Coils
EQUACOOKER
Steam to Jacket
Meal Cake to Grinding
Press Fat
Figure 4. Continuous Cooker - Duke Process
-------
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
waste water 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
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
23
-------
RAW
MATERIAL
BIN
Water
MAGNET
DISINTEGRATOR
PREBREAKER
1vent_^JJ
[Over Y
I8'"
FLUIDIZING
TANK
I 140°F
&—
Fluidizing pump
EVAPORATOR
Condensate
Recycle Fat at 200° Fahrenheit
Expeller Fat
FAT
RECYCLE
TANK
Recycle Pump
Expeller Cake
to Grinding
To Fat Storage
Figure 5. Continuous Cooker by Carrier - Greenfield Process
-------
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 ejectcr, 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 backup even under a nearly perfect vacuum, the
standpipe should be slightly over 10 meters (33 feet) high. This
is because a 1.0-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 backup 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.
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.
25
-------
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 2.0
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 1.0 percent of the plants, the second step in grease
and tallow reduction involves solvent extraction. In this
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
26
-------
grease content of the solids to 1.0 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
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.
27
-------
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
5.0 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 obtairiing 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 rundown and poorly maintained equipment. Also, poor
housekeeping practices can result in accidental spills of raw and
finished materials into the waste waters and the foaming over of
material from the cookers. A detailed discussion of the waste
water characteristics, sources, and contributing factors is
presented in Section V.
28
-------
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 pickup 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 drycleaned, 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
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
29
-------
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-curing process there results a net overflow of
approximately 2.0 to 3.0 gallons of 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 problems 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.
30
-------
SECTION IV
INDUSTRY CATEGORIZATION
CATEGORIZATION
In developing effluent limitations guidelines and standards of
performance for the 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 Final products 4
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 subdividing the industry. Hence, the industry as a
whole constitutes a single 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 which are evaluated as
part of the studies of the Seafood Processing point source
category.
As described above, the typical plant representative of the
subcategory 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 subcategory
of 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 eguipment type, raw materials,
size, and age of the plant may differ. Hence, it was possible to
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
HIDE CURING
Figure 6. Manufacturing Processes of a Rendering Plant
32
-------
consider division of the industry on the basis of those factors
which might group plants with similar raw waste water
characteristics. The waste water characteristic used in analyses
of possible subcategorization of 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 BOD5/1°°0
Ib RM). BOD5 provides the best measure of plant operation and
treatment effectiveness among the parameters studied, and more
data are available than for any other waste parameters.
Suspended solids, grease, and COD data substantiate the
conclusions developed from using BODJ5 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 BODJ5.
Waste Waters from all plants contain the same general
constituents and are amenable to treatment by a variety of
biological treatment concepts. Geographical location, and hence
climate, does not affect the treatability of the waste. Climate
may influence the selection or design of biological waste
treatment concepts employed. However, the ultimate treatability
of the waste is not affected by the biological process used if
treatment effectiveness can be sustained at the highest levels by
adhering to sound principles of design and operation as outlined
in Section VII- Judging from biological 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
33
-------
treatability of the waste or the treatment effectiveness can be
maintained at the highest levels by using a variety of
alternatives including not discharging during the coldest months
of the year. The time period for no discharge will vary with
location, but should never exceed 6 months. This is the same
practice that is used by plants that dispose of their waste water
by irrigation.
Raw Materials
The type and nature of raw materials processed is meaningful in
substantiating a single subcategory. 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.
For the purposes of conducting a rigorous analysis of possible
effects due to this factor, raw materials (as waste animal by-
products) were classified as follows:
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.
Multiple regression analysis techniques described in Section III
were used to correlate the percent of raw material in each of
these classes with the raw BODji load for each set of data.
Information from questionnaires and other data sources for 29
independent Tenderers was sufficiently complete with flow, BOD5,
and raw material data to permit this analysis. Some of this data
represented the average of data over a period of several months;
other data represented grab or composite values over short
periods such as one or two days. The result of the regression
analysis is best indicated by the multiple correlation co-
efficient. This coefficient was found 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 explained with reasonable
-------
6.00
5.00
4.00
cc
Jsi
in
Q
O
CO
3.00
2.00
1.00
(29)
-MAXIMUM
(4)
-MINIMUM
TOTAL
INDUSTRY
<50%
POULTRY
BY-PRODUCTS
>50%
POULTRY
BY-PRODUCTS
Figure 7. Average and Range of BOD5. Data by Raw Material Type
-------
certainty as a basis for subcategorization, the square of the
multiple correlation coefficient should be greater than 0.5.
That is, it could be predicted that at least half of the changes
or differences in raw BOD5 were attributable to raw material
characteristics. The lack of dependence between BOD5 load and
raw materials is somewhat surprising since the raw 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.
Final Products
The final products are generally the same for all plants. The
factor was found to be closely related to overall manufacturing
processes and equipment thus supporting subcategorization based
on these factors as described below.
Manufacturing Processes
The manufacturing processes in 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. Coupled with the analysis of processing
equipment and methods described below, the basic manufacturing
processes were found to be consistent throughout the industry
thus substantiating the single subcategory conclusion first
discovered when analyzing raw materials.
The ancillary manufacturing process (hide curing) is not
practiced by all plants, but the process can contribute
additional waste to the 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 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 most equitable method of accounting for the additional raw
waste load caused by hide curing, therefore, was found to be the
use of an adjustment factor. The adjustment factor for hide
curing is presented in detail in Sections IX and X.
Processing Equipment and Methods
36
-------
6.00
(29)
5.00
4.00
a:
1A
Q
O
CO
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
-------
se
BOD5 kg/kkg RM
H-
e
CD
^O
o
Hi
Cd
O
|g
o
o
3
o
o
o
o
CO
b
o
o
01
b
o
en
b
o
co-t
m 3)
to
oi
O m
O'
mco
"2
mC
3J ED
0>
mO
20
m m
JJU
(D
m
O
>
X
-------
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 EM)
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:
o "Total'7 is a summary of all data, regardless of equipment type
and included four plants using more than one type of cooker or
condenser.
o Batch, Duke, or C-G: Summary of the information on plants using
one type of these cookers, respectively.
o Baro, S & T, or Air: Summary of the information on plants using
one of the following types of condensers: barometric leg, shell-
and-tube, and air condensers, respectively.
39
-------
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
there was no significant difference in the contribution to the
waste water load from different equipment designs within a given
equipment type (e.g., all batch cookers or all continuous
cookers) .
Table 5 summarizes the raw waste data on 51 rendering plants (<*9
from questionnaires, 2 from field survey) comparing various kinds
of cookers and condensers with resultant raw waste BOD5,
suspended solids, grease, flow, and amount of raw materials
handled. Figures 8 and 9 graphically illustrate the conclusion
to group the industry into single segment because of close
similarities in waste load regardless of processes or equipment
employed. 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
designation of 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 BOD^ 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 was indicated by the value of
the correlation coefficient, 0.062, showing a very low degree of
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).
The scatter diagram of raw BOD5 wasteload versus plant size
(Figure 10A) shows that the raw wasteload is not a function of
the plant size. That is, several plants of the same size will
have different wasteloads depending on plant practices. This is
further substantiated by the results of a regression analysis of
the wasteload and plant size data in that the linear model
obtained from the analysis is not statistically significant.
Age is often reflected by the type of processing equipment used.
Plants over ten years old were originally equipped with batch
40
-------
6.00
5.00
4.00
3.00
2.00
1.00
(29)
(10)
(8)
MAXIMUM
-AVERAGE
-MINIMUM
(11)
TOTAL
INDUSTRY
<45,000 kg
dOO.OOO lb)
45,000-114,000 kg
(100,000-250,000 16)
>114,000 kg
[>250,000 lb)
Plant Size: kg (lb) of Raw Material
Figure 10. Average and Range of BOD5 Values for Three Size Groups of Plants
and for All Plants Studied (Total)
-------
Figure 10A - Scatter Diagram of Raw Wasteload Versus Plant Size
6.00 r
5.00
4.00
KKg RM
3.00
2.00
1.00
ort o
-------
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 subcategory, 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 revealed no apparent relationship or pattern.
Variations in raw waste load were observed to be as large or
larger during a given month as they were between different months
for a specific location. The same pattern also existed when
comparing data for plants in different locations. This "pattern
of randomness" for location is to be expected, however, and is in
agreement with similar results encountered in other segments of
the meat industry. As discussed in section V, it is such factors
as materials recovery practices, production spills, clean-up
practices, and disposition of condensates which most clearly
affect raw waste for any specific plant. The type of animal by-
products being processed is sometimes influenced by location
(e.g. more poultry in southern areas, more livestock in midwest) ,
but as mentioned previously, the type of raw material processed
had no discernible effect on raw waste.
43
-------
-------
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, skimming tanks, and air
flotation) .
The parameters used to characterize the raw effluent were the
flow, BOD5, suspended solids (TSS), grease, COD, total volatile
solids (TVS), total dissolved solids (TDS), Kjeldahl nitrogen,
ammonia, nitrates, nitrites, chlorides, and phosphorus. As
discussed in Section IV, BOD,5 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 independent rendering plants- The summary includes averages,
standard deviations, ranges (high and low values), and number of
observations (plants).
45
-------
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 engineers1 reports) , and through data
obtained from the field sampling survey. 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. 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.
While the sampling data generally verified questionnaire
information, a number of presumably atypical conditions existed
for four or five plants during the field visits which clearly
caused unusual results for raw waste loads. As summarized in
Table 8A, the conditions included spills from cookers, emergency
use of old equipment, and malfunctions of certain in-plant
controls. Wherever helpful for the purposes of industry and
process descriptions, however, the data or circumstances
reflecting these conditions are included to provide as much
thoroughness as possible in the presentation. 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 20,000
1/kkg RM (56 to 2400 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 she11-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.
-------
Table 6. Summary of Raw Waste Characteristics for Rendering Industry3
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
47b
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
a. All raw waste data is for effluent following in-plant materials
recovery (catch basins, skimmers etc.)-
b. Excludes one plant reporting water use at nearly 10,000 gal/1000
Ib RM.
47
-------
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:
a "Total" is a summary of all data, regardless of equipment type
and included four plants using more than one type of cooker or
condenser.
o Batch, Duke, or C-G: Summary of the information on plants using
one type of these cookers, respectively.
o Baro, S & T, or Air: Summary of the information on plants using
one of the following types of condensers: barometric leg, shell-
and-tube, and air condensers, respectively.
48
-------
A regression analysis of the field sampling data revealed that
the raw BOD5 waste load correlates very well with oil and grease
and COD waste loads. Raw BOD5 waste load also correlates with
total volatile solids (TVS), total dissolved solids (TDS), and
total 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 oil and grease waste load implies that much of
the variation in BOD5 waste load is caused by variations in the
oil and grease load. The correlation coefficients from these
analyses are presented in Table 8.
Table 8. correlation coefficients of Several
Raw waste Load Parameters with BOD5.
from the Field Sampling Results
Correlation
Parameter Coefficient
Oil and 0.905
Grease
COD 0.933
Total Volatile 0.789
Solids
Total Dis- 0.796
solved Solids
Kjeldahl 0.580
Nitrogen
The basic manufacturing processes in independent rendering (See
Section IV) should have no influence on the raw waste loadr
because they are universal. However, some processing equipment,
such as cookers and condensers, do 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. As was previously mentioned and further illustrated
with the data from Table 7, it may be oberved that water use
rates per unit of raw material associated with barometric
condensers are higher than for other condensers. At the same
time, 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 per unit of
RM processed revealed no correlation. The correlation
49
-------
coefficient for this analysis was -0.027, Earlier studies on
meat packing plants8 and poultry slaughterhouses11 revealed a
strong positive relationship between raw waste load and water
use.
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 discernible
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 exact 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
50
-------
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
operations are odor control, spills, and plant and truck cleanup;
the manufacturing processes are receiving, vapor condensing from
cooking and drying, and hide curing. Total plant waste loads
including the effects of materials recovery were presented in
Table 6 and discussed 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 BQD5, 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 about 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.f 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
51
-------
MANUFACTURING PROCESSES
WASTE WATER FLOW
LIQUID - SOLID
SEPARATION
MEAL MILLING
AND SCREENING
ODOR
CONTROL
SPILLS
PLANT AND TRUCK
CLEAN UP
GREASE AND SOLIDS
RECYCLED TO
COOKING & DRYING
SANITARY
FACILITIES
.FRESH WATER
-»- PRODUCT AND MATERIAL FLOW
-*- WASTE WATER FLOW
Figure 11. Typical Rendering Process and Waste Water Flow Arrangement
52
-------
and total plant raw waste load was revealed by a multiple
regression analysis, as discussed in Section IV.
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 (100°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 downtime. (See Table 8A)
53
-------
Table 8A
Observed Housekeeping and
Operating Procedures Adversely
Affecting Raw Waste Control and
Treatment Plant Performance I/
- Barrel washing and standpipe water discharge with
water temperature in excess of 130°F.
- Excessive hot water cleanup without preliminary
dry cleanup.
- Improper operation of materials recovery systems
leading to grease spills into aerated lagoons.
- Spill from cookers and dump of entire cooker
contents to sewer.
- Severe treatment plant overload due to plant
production overload.
- Pumping non-contaminated, non-process water into
treatment facilities.
- Drainage or discharge of detrimental chemical
substances to treatment facilities.
]_/ Developed from information compiled during field survey, September
to November, 1973.
54
-------
Table 9. Concentrations of Undiluted Condensed Cooking Vapors
Parameter
BOD
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
55
-------
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 6.0 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 studies12,8 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 plants* 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 45U kg (1000 pounds) , this can
be equivalently expressed as 0.68 kg BOD5/hide. On the other
hand, a study of tannery effluents 12 lists the waste load for
56
-------
Table 10. Waste Loads for Undiluted Condensed Cooking Vapors
Parameter
EOD5
COD
Total
Volatile
Solids
Total
Dissolved
Solids
Total
Phosphorus
Chloride
Total
Kjeldahl
Nitrogen
Nitrate
Nitrite
Grease
Suspended
Solids
kg/kkg EM or lb/1000 Ib EM
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
57
-------
Table 11. Waste Load Characteristics for Hide Curing at an
Independent Rendering Plant Versus Those for a Tannery
12
Table 12. Measured Waste Strengths of Tank Water
and Blood Water
Ln
CO
Parameter
BOD5
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
Tannery
0.12
0.24
0.08
0.32
Parameter
BOD
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
-------
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),
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 tank water 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 tank water 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 tank water from a
grease operation and of blood water from steam sparging and
screening of blood. The waste load resulting from the sewering
of the tank water 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.
59
-------
-------
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, and alkalinity
Temperature
On the basis of all evidence reviewed, there do not exist any
extremely 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
Tenderer 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, 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.
BOD£ 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 are due to a
61
-------
combination 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 BOD^ 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 BOD£ is often applied for discharge to a municipal
sewer, and surcharge rates often apply if the BOD5 is above the
designated limit. BOD55 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 (BOD2J)) , sometimes called
"ultimate" BOD, is usually a better measure of the waste load
than BOD5. However, the test for BOD^O 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. 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 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
62
-------
algae blooms due to the uptake of degraded materials that form
the foodstuffs of the algal populations.
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 BOD£, 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, BOD5 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.
Suspended solids are a visual and easily determined measure of
pollution and also a measure of the material that may settle in
tranquil or slow-moving streams. A high level of suspended
solids is an indication of high BOD5. Generally, suspended
solids range from 1/3 to 3/U 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 BODJS, COD, and
total volatile solids. The same is not true, however, for the
raw wastes.
Suspended solids also may inhibit light penetration and thereby
reduce the primary productivity of algae (photosynthesis).
63
-------
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 man1s 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.
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.
64
-------
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. 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 may 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 substantially limited by BOD5
limitations and the nutrient portion by the ammonia nitrogen
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 tag/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 UOOO 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
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
65
-------
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. 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.
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
Oil and grease, or grease, 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. 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 PM, which
corresponds to an average concentration of about 1660 mg/1.
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
prohibit 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 coats of water animals and
fowl, oil and grease in water can result in the formation of
objectionable surface slicks preventing the full 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/1.1* 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.
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 nitrification is
not complete. Ammonia can exist in several other chemical
combinations including ammonium chloride and other salts.
67
-------
In most natural water the pH range is such that ammonium ions
(NH4+) predominate. In alkaline waters, however, high
concentrations of un-ionized ammonia 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. Because of the significance of ammonia as
a pollutant and as an important parameter in the effluent from
rendering plants, limitations have been established for 1983 and
for new sources.
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
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. 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. Moreover, control of ammonia
leads to substantial reductions of Kjeldahl nitrogen.
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 10 mg/1 in water supplies.1* They are
essential nutrients for algae and other aquatic plant life.
Nitrites ranged from a trace to O.OUO kg/kkg RM in the raw wastes
and from a trace to 0.08 kg/kkg RM in the treated wastes;
68
-------
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 0.0** 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. Low values are primarily caused by the
dilutional effects of barometric leg condensers.
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.
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. The field sampling
data verified that when there was a substantial nitrogen
reduction by the treatment system, it was accompanied by good
BODJ5, TSS, and oil 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
mg/1. The primary sources of phosphorus in raw waste from
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. Final effluent
concentrations of phosphorus are usually even lower and
limitations have not been established for this parameter.
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. Phosphorus is not the sole
cause of eutrophication, but there is evidence to substantiate
that it is frequently the key element required by fresh water
plants and is generally present in the least amount relative to
69
-------
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 may 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
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. 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 KM (2.56
lb/1000 Ib FM). 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.
70
-------
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 warmblooded 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
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 coliform density in
stream waters exceeded 1,000 per 100 ml, the occurrence of
Salmonella was 53,5 percent.
pH, Acidity, and 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
71
-------
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 pR
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,
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
72
-------
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 chemical 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
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.
73
-------
Figure 12. Suggested Waste Reduction Program for Rendering Plants
Waste Reduction
Techniques
Waste Reduction
Effect
Point of
Application
BOD, Sus
Solids,
Grease
Removal
to 98.5%
BOD
Removal of
Fine Sus.
Solids, Salt,
Phosphorus,
Ammonia (as
necessary)
to 99.5%
BOD.
Post
Secondary
Treatment
-------
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 bypass valves for controlling pressure bleed-down
on cookers used for hydrolyzing raw material; and
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 recycled for
use in 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.
77
-------
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 chemically conditioned and
recycled 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 2U-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 2U-hour average
rather than the peak flows, and many biological 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.
78
-------
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 of 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, pilot-scale 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 water as it flows over the
curved surface.15
Beginning in 1969, United States and foreign patents were allowed
on a three-slope static screen made of specially curved wires.
This concept used the Canada or wall attachment phenomenon to
withdraw the fluid from the underlayer 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.15
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
screening surface may be the least consideration. In such a
79
-------
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 UO mesh, with O.U
mm (1/6U 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.*'
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
value of inedible grease and tallow has reduced concern about
80
-------
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, ^0 to 50
percent of the suspended solids, and 50 to 60 percent of the
grease (hexane solubles).*5
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 semiportable, 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.
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
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 limitations.
81
-------
Compressed
Air
Feed
Total Pressurizotion
Process
Treated
Effluent
Float
Sludge
Figure 13. Dissolved Air Flotation
-------
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
"supersaturated11 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.1* 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 1U, only a part of the waste
water stream is raised to the pressure of the compressed air for
subsequent mixing. Alternative A of Figure 1U 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 1ft,
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 of 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* Chemical precipitation is also
discussed later, particularly in regard to phosphorus removal,
under tertiary treatment; phosphorus can also be removed at this
primary (in-plant) treatment stage. A slow paddle mix will
improve coagulation. It has been suggested that the
proteinaceous matter in rendering plant waste could be removed by
reducing the pH of the waste water to the isoelectric point of
about 3.5.16 The proteinaceous material would be coagulated at
that point and readily removed as float from the top of the
83
-------
Compressed
Air
Recycle Pressurizotion
Process
(Alternative B)
(Retention
Tank
n
00
1
Feed from .
Primary ... >
Treatment i
1 Treated
Flotation
Tank
• 7 C.IIIUCIII
1 C|«rt*
i ^(Retention}
Tank
Sludge
Compressed
Air
Partial Pressurization
Process
(Alternative A)
Figure 14. Process Alternatives for Dissolved Air Flotation
-------
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.1* Nearly instantaneous protein precipitation
and hence, nitrogen removal, is achieved when a high protein-
containing effluent is 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 or
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 UOO 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
percent of the grease can be removed.19 Total nitrogen reduction
between 35 and 70 percent was found in dissolved air units
surveyed in the meat packing industry.8
The operation of several dissolved air units has been observed
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.
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
85
-------
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, aerated and aerobic lagoons, and variations of the
activated sludge process. Several of these systems individually
are capable of providing up to 97 percent BOD5. reductions and 95
percent suspended solids reduction, as observed primarily in the
meat packing industry.8 Combinations of these systems can
achieve reductions up to 99 percent in BOD£ and grease, and up to
97 percent in suspended solids for rendering plant waste water.
Based on operating data from pilot-plant systems for packing
plant wastes and sludge supernatant, the rotating biological
contactor also shows potential.
The selection of a 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
ancillary pollution problems (e.g., sludge disposal and odor
control). The characteristics and performance of each of the
above-mentioned biological treatment systems, and also for common
combinations of them, are described below. Capital and operating
costs are discussed in Section VIII.
Anaerobic Processes
The combination of normally warm raw waste water (20° to 35°C, or
65° to 95°F) and the high concentrations of readily digested
organic nutrients associated with 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. Much of the organic nitrogen (protein
materials) present in the influent is converted to ammonia
nitrogen. Also, if sulfur compounds are present (such as from
high-sulfate raw water—100 to 200 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 BODjS and suspended solids with low power
cost and with low land requirements. Two types of anaerobic
processes are used in this industry segment or in other meat
products industry segments: anaerobic lagoons and anaerobic
contact systems.
86
-------
Anaerobic Lagoons
Anaerobic lagoons are widely used in the rendering industry as
the first step in biological 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 be allowed to
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 are sometimes added to help maintain the
physical structure of the scum layer.
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 carryover 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-Disadvantages. Advantages of an anaerobic lagoon
system are initial low 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 lagoon 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. If the
gases evolved are contained, it is possible to use iron filings
to remove sulfides and methane gas could serve as a fuel source.
Applications. Anaerobic lagoons used as the first stage in
biological treatment are usually followed by aerobic lagoons or
other aerobic treatment process. Placing a small, mechanically
aerated lagoon between the anaerobic and aerobic lagoons is
becoming popular. Anaerobic lagoons are not permitted in some
87
-------
Equalizing Tank
00
CO
Plant
Effluent
I \
\f
Sludge Recycle
L/vA
HeatersV V~x
Anaerobic
Digestors
Gas
Stripping
Units
Sedimentation
Tanks
-> Effluent
Figure 15. Anaerobic Contact Process
-------
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 more equipment for operation
than do anaerobic lagoons. These systems are not known to be in
use 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.a and 3.2 kg/cubic meter~{0.15 and 0.20 Ib/cubic foot) and the
detention time is between 3.0 to 12.0 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-Disadvantages- 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.
Applications. Anaerobic contact systems are restricted to use as
the first stage of biological treatment and can be followed by
the same systems as follow anaerobic lagoons.
89
-------
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 from several hours up 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-Disadvantages
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 biological
treatment system.
Applications
Aerated lagoons are usually the first or second stages of
secondary treatment, and must be followed by a solids separation
unit such as 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; and
90
-------
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.U 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 mi croorganisms. 11 i s essential to maintain
aerobic conditions in at least the upper 6.0 to 12,0 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) 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.
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, maintenance cleaning of
the lagoon, installation of a "polishing" clarifier, or
combination of these actions. 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.
When algae die they either settle out or become part of the
overall food supply (substrate) for other microorganisms.
It has been frequently observed that ammonia is reduced without
the appearance of an equivalent amount of nitrite and nitrate in
aerobic lagoons as evidenced by the results of field sampling
surveys at various meat products treatment facilities. From
this, and the fact that aerobic lagoons tend to become anaerobic
near the bottom, it appears that considerable nitrification and
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. If necessary, it has been shown that the adverse
effects of this condition can be substantially overcome by
supplemental aeration using submerged aerators or by the use of
effluent storage.74,79 When there is no ice and snow cover on
large aerobic lagoons, high winds can develop a wave action that
can damage dikes. Riprap, segmented lagoons, 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.
91
-------
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
during winter months that may require supplemental aeration,
increased design capacity, possible requirements to include
provisions for no discharge for periods of three months or more.
In addition, there are relatively large land requirements, the
potential 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 biological
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, or nitrogen gas (denitrification). The time
required for digestion depends on the type of waste and its
concentration, but the average time is 6.0 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 BODji, and a settled 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 a
fertilizer and soil conditioner to aid secondary crop growth.
92
-------
Primary
Sedimentation
Secondary
Sedimentation
Raw
Waste
Aeration Tank
[^Return Activated _Sludge
Effluent
Waste
Sludge
I
I
Waste I
Sludge^
Figure 16. Activated Sludge Process
-------
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.
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. 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 nitrifying bacteria. For this to occur, it is necessary to
have sludge detention times in excess of ten days.2® This can be
accomplished by regulating the amounts of recycled and wasted
sludge. Oxygen-enriched gas may be substituted for 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 countercurrent, staged flow and
recirculation of gas back through the liquor are employed,
between 90 and 95 percent oxygen use is claimed. Although this
modification has not been used in treating rendering plant
wastes, it is being used successfully for treating other wastes.
The concept of nitrification and the treatment systems involved
are discussed later in greater detail under the heading "Nitrogen
Control.«
94
-------
es^ One advantage 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 attained. 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 soli ds from the mixed liquor di scharg ed from the
aeration tank; large volume tanks or basins are required to
accommodate the long detention times; and operating costs for
aeration are high.
Applications- Because of the high efficiency in reduction of
organic waste load and the additional benefit of the
nitrification process, extended aeration systems are being used
by some meat products plants in lieu of, or in conjunction with,
anaerobic processes or lagoons to produce low BOD5 and low
ammonia-nitrogen effluents. They are also being used as the
first stage of biological 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
95
-------
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 pilot scale 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 RBC 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 BODS influent concentration of approximately 25
mg/1.21
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 with final ammonia
concentrations as low as 2.0 mg/1 or less.55
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 achieve dissolved organic
matter reduction with the potential for removal of ammonia by
nitrification; and its 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
and on several industrial wastes in the United States, it has not
yet been proved on rendering plant wastes.
Uses
Rotating biological contactors could be used as a substitute for
the entire aerobic 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, nitrification of effluents, 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.2°
Performance of Various Biological Treatment Systems
96
-------
Table 13. Performance of Various Biological Treatment Systems
Plants
w
c
•H
I ,
Rendei
Secondary Treatment System
(number of systems used
to determine averages)
Anaerobic -V 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
c
cfl
(^
w
e
•H
O
CO
P->
•u
CO
QJ
2
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
BOB5
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
alues
Grease
99.4
99-4
78.8
98.9
99.2
98- d
—
95.8
e = estimated
97
-------
Table 13 shows BOD£, 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 an
average for 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
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 BODS, SS, and grease removal. Furthermore, the
anaerobic plus aerobic lagoon system appears, by percent
reductions, to be more effective on 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 to the treatment system are
generally lower in absolute amounts than in the more complex
operations at meat packing plants. 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 lb
BOD5/1000 cubic feet). All of the treatment systems listed in
Table 13 are capable of treating typical rendering plant waste
waters to a degree sufficient to meet the 1977 limitations
recommended in Section IX. 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.
98
-------
ADVANCED WASTE WATER 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
verification sampling program of the meat packing industry.8 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.
Also, it can be used as a final treatment following biological
treatment to remove suspended solids in addition to phosphorus.
Technical De scription
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.*6
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.*6
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
99
-------
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, SS, and grease removal.
Problems, and Reliability
As indicated 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 recovere6 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. A variety of filters can be used to remove the solids in
a treated waste water: intermittent sand filters, slow sand
filters, rapid sand filters, and mixed media filters. BOD5
removal occurs primarily as a function of the degree of solids
removal. The effluent from the sand filter is of a high quality.
A summary of available information indicates that effluent
suspended solids concentrations of less than 10 mg/1 can be met.
Although the performance of a sand filter is well known and
documented, it is not in common use in the meat products industry
because use of refinements of this type has not been needed to
reach current waste water standards.
100
-------
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 for final 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.
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 sand filter. Thus, the rapid sand filter
requires substantially less area than the slow sand filter;
however, the cycle time averages about 24 hours in comparison
with cycles of up to 30 to 60 days for a slow sand filter.23 The
larger area required for the latter means a higher initial cost.
For small plants, the slow sand filter can be used as tertiary
treatment. The rapid sand filter can be more generally applied
following secondary treatment for all plant sizes. If a rapid
sand filter were used as secondary treatment it would tend to
clog quickly and require frequent backwashing, resulting in a
high water use. This wash water would also need treatment prior
to discharge particularly if the rapid sand filter were used in
secondary treatment applications with only conventional solids
removal upstream in the plant. Thus, its use is generally
confined to applications for "polishing" final effluents.
The rapid sand filters operate essentially unattended with
pressure loss controls an<3 piping installed for automatic
backwashing. They are contained in concrete structures or in
steel tanks.
In a rapid sand filter, as much as 80 percent of the head loss
can occur in the upper few inches of the filter. One approach to
increase the effective filter depth is the use of more than one
media in the filter. Other filter media have included coarse
coal, heavy garnet or ilmenite media, and sand. There is no one
mixed media design which will be optimum for all waste water
filtration problems. As an example, "removal of small quantities
of high-strength biological floe often found in activated sludge
effluents may be satisfactorily achieved by a good dual media
design. With a weaker floe strength or with an increase in
applied solids loading, the benefits of the mixed, tri-media bed
become more pronounced."23
Although a mixed media filter can tolerate higher suspended
solids loadings than can other filtration processes, it still has
an upper limit of applied suspended solids at which economically
long runs can be maintained. With activated sludge effluent
101
-------
suspended solids loadings of up to 120 mg/1, filter runs of 15 to
24 hours at 5 gpm/ft have been maintained when operating to a
terminal head loss of 15 feet of water.23
The effluent quality produced by plain filtration of biological
effluents is essentially independent of filter rate within the
range of 5-15 gpm/ft primarily due to the high strength of the
biological floe. The following quality of filter effluents are
presented as general guides to the suspended solids concentration
which might be achieved when filtering a secondary effluent of
reasonable quality, without chemical coagulation: high rate
trickling filter, 10-20 mg/1; two stage trickling filter, 6-15
mg/1; contact stabilization; 6-15 mg/1; conventional activated
sludge plant, 3-10 mg/1; activated sludge plant with a load
factor less than 0.15, 1-5 mg/1.
Development Status
The slow sand filter has been in use for more than 50 years. 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 in lieu
of biological treatment for small meat plants. 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.31 The land requirements for a
slow sand filter are not particularly significant in relation to
those required for lagooning purposes in biological 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. Frequency of raking may be weekly or monthly,
depending upon the quality of pretreatment and the gradation of
the sand. Rapid sand filters have received most attention as the
principal method to treat water supplies. More recently,
applications as an advanced waste treatment mode for municipal
and joint municipal-industrial waste water facilities have proven
successful. Multi-media filters were developed for general use
in the mid 1960's and these filters also have been used for
potable water treatment and final treatment of waste water since
that time. A summary of results using filtration on a variety of
treated effluents is given in Table 13A.
Problems and Reliability
The reliability of all principal types of filters seems to be
well established in its long-term use as a principal component of
water treatment systems. When the sand filter is operated
intermittently there should be little danger of operating mishap
with resultant discharge of untreated effluent or poor quality
102
-------
Table ISA. Effluent Quality from Conventional
Filtration of Various Biologically Treated Wastewaters*
Influent
Source
Activated Sludge
Activated Sludge
Extended
Aeration plus
settling
Trickling
Filter
Activated Sludge
with Clarifier
Contact
Stabilization
(raw waste
includes
cannery)
Miscellaneous
Filter
Type
Gravity
mixed media
multi -media
pressure,
multi-media
Gravity,
Sand
multi-media
mixed -media
sand
(slow and
rapid)
Filter Influent (mg/1) Filter Effluent
BOD TSS BOD
15-20 10-25 4-10
11-50 28-126 3-8
7-36 30-2180 1-4
15-130 8-75 2-74
18
(AVE)
2-4
10-50 15-75 2-6
(ma/1)
TSS
2-5
1-17
1-20
1-27
2.4
(AVE)
2-8
3-10
Reference
67
67
67
60,62
61
65
59,61
0
Trickling
Filter with
Nitrification
sand
9-28
3-7
54
*See also, performance data in references 23, 24, 62, 63, and 66.
-------
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
precautionary measures are taken to prevent "blanking off" of the
bed by freezing water.
With larger sized slow sand filters, the labor in maintaining and
cleaning the surface should receive adequate consideration.
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 minimize the washwater required in
cleanup, since this must be disposed of in some appropriate
manner other than discharging it to a stream, 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 also been receiving more extensive
application in municipal sewage treatment for tertiary treatment;
thus, its use in tertiary treatment of secondary treated
effluents from any type of meat or rendering processing plants
appears to be a practical method of reducing BOD5 and suspended
solids to levels below those expected from conventional secondary
treatment.
Float
or
Secondary ^
Treatment
Effluent
PH
Ajustment
*>
Chemical
Addition
N
Air
Flotation
System
Partial
^"Tertinrw
Treated
Effluent
V
Sludge
Figure 17. Chemical Precipitation Schematic
104
-------
Figure 18. Sand Filter System
Primary or
Secondary
Treatment
Effluent
Chlorination,
Optional -
for Odor Control
ss
to Regenerate
Treated
Effluent
-------
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 BOD£ associated with those solids.
Figure 19. The microstrainer is used as 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.*5 70 One poultry
processing plant using microscreens as tertiary treatment
consistantly achieves a BOD5 in the effluent of less than 15 mg/1
and frequently below 5 mg/1- The effluent quality obtained by
the microstrainer at the poultry processing plant is consistent
with data reported by other situations in which microstrainers
have been used to remove solids from secondary effluents. The
percent removal of suspended solids by a microstrainer are
related to the size of the aperture of the screen. Fifty to 60
percent removals can be anticipated with a 23 micron strainer and
$0-50 percent removals with a 35 micron strainer. The
microstrainer effluent quality from a number of studies indicated
suspended solids concentrations of 6 to 8 mg/1 when activated
sludge effluent was tested, and 15 to ttO mg/1
filter effluent was treated.**
when a trickling
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 on the fabric, and in one
installation, this is followed by ultra-violet light exposure to
inhibit microbiological growth. 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 U.3 revolutions per minute. The concentration and
percentage removal performance for microstrainers on suspended
solids and BOD5 appear to be approximately the same as for sand
filters.
Development
While applications of microscreens for filtration are more recent
than conventional filters, there is general information available
on the performance of microstrainers and on tests involving the
use of them. In addition to its use on poultry processing waste,
there has been a substantial increase in full-scale applications
at municipal facilities. As with conventional filters, the
requirements for effluent quality imposed by State and Federal
regulatory agencies have not necessitated such installations in
the past. The economic comparisons between sand filters and
106
-------
Table 13B. Performance of Microstrainers
in Advanced Treatment of Biologically Treated Wastewater
Influent (mg/1)
Effluent (mg/1)
Reference
BOD
15-20
10-30
-
15-25
TSS
20-25
10-40
6-54
15-30
BOD
3-5
3-8
-
4-5
TSS
6-3
3-10
2-14
3-7
23
70
67*
poultry pi
*Data from 22 municipal installations including several with
wasteload contributions from unidentified industrial sources.
Secondary
Trorttmf*nt "b
Effluent
Micro-
Screen
N
f
Ba<
(C
s»
:kwash
Clear
to
Screen/Strainer
Tertiary
Effluent
Figure 19. Microscreen/Microstrainer
107
-------
microstrainers are inconclusive; the mechanical equipment
required for the microstrainer may be a more relevant factor than
the space requirement for the sand filter at the present time.
Table 13B provides a brief summary of the general performance
achieved by microstrainers on biologically treated waste water.
Problems and Reliability
The reported performances 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 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 substantial degree of grease loading.
NITROGEN CONTROL
Nitrification
Nitrification is the biological conversion of nitrogen in organic
or inorganic compounds from a more reduced to a more oxidized
state. In the field of water pollution control, nitrification
usually is referred to as the process in which ammonium ions
(NH4) are oxidized to nitrite and nitrate sequentially. When
aeration systems are used to treat an industrial waste water,
some nitrification and ammonia stripping can be expected to occur
naturally and thus reduce the quantity of ammonia requiring
further removal. This "incidental" treatment has been observed
for treated effluents from several types of meat products plants
where concentrations of about 10 to 50 mg/1 of ammonia have been
found while partially treated wastes have concentrations of 100
mg/1 or more. Ammonia removal is becoming more important since
it is recommended that the concentration of un-ionized ammonia
(NH3) in surface water be no greater than 0.02 mg/1 at any time
or place to assure protection of some aquatic organisms. Because
ammonia may be indicative of pollution, it is recommended that
ammonia nitrogen in public water supply sources not exceed 1.5
mg/1.39
Technical Description
Nitrification can be used to reduce the ammonia concentration of
waste waters. Figure 20 indicates a schematic of the
nitrification process. The equations following the figure
indicate the nitrification sequence and organisms involved.
108
-------
Adequate process design and operating control are necessary for
consistent results. Factors that affect the nitrification
process include concentration of nitrifying organisms,
temperature, pH, dissolved oxygen concentration, and the
concentration of any inhibiting compounds,*o The nitrifying
organisms of significance in waste management are autotrophic
with Nitrosomonas and Nitrobacter being the major bacterial
genera that are involved. Nitrifying bacteria are ubiquitous in
the soil although they may not be part of untreated wastes.
Nitrifying organisms are aerobic and adequate dissolved oxygen
(DO) in the aeration system is necessary. DO concentrations
should be above 1 to 2 mg/1 to assure consistent nitrification.
Nitrification is affected by the temperature of the system.
Available information provides conflicting data on the
performance of nitrification systems at low temperatures.
Although detailed studies are lacking, it should be possible to
achieve nitrification at low temperatures and compensate for
slower nitrifying organism growth rates by maintaining a longer
solids detention time and hence larger nitrifying active mass in
the system.*1
The optimum pH for nitrification of municipal sewage has been
indicated to be between 7.5 and 8.5. Nitrification can proceed
at low pH levels, but at less than optimum rates. During
nitrification, hydrogen ions are produced and the pH decreases,
the magnitude of the decrease being related to the buffer
capacity, of the system. A decrease in pH is a practical measure
of the onset of nitrification.
High concentr art ions of un-ionized ammonia (NH3) and un-ionized
nitrous acid (H NO2) can inhibit nitrification. These compounds
can be in the influent waste water or can be generated as part of
the nitrification process. The concentrations of un-ionized
ammonia and nitrous acid that are inhibitory and operational
approaches to avoid such inhibition have been documented. Using
these approaches it should be possible to operate nitrification
systems that produce consistent results even with waste waters
having high nitrogen concentrations.
pe ve IQ pme n t S t a tug
While research on nitrification has been conducted for a
number of years, most pilot and full-scale studies have been
initiated since 1970. Even though there has been a relatively
short time frame of evaluation, nitrification is already a very
readily described process for which treatment system designs can
be implemented. Most of the applications have been on municipal
effluents, but concentrations of ammonia in these effluents
ranged between 20 mg/1 and 800 mg/1. Ammonia concentrations in
biologically treated effluents from various types of meat and
poultry packing and processing plants have been found to range
between 10 mg/1 and 200 mg/1, or more, and thus fall within the
limits of the nitrification investigations cited below in Table
13C. Like any other "tertiary" level of treatment, nitrification
109
-------
Table 13C. Selected Results for Nitrogen
Control in Effluents
Nitrogen Control-'
Parameter(s) Effluent
Mode
Extended aeration(N)
Clarification(DN)
Denitrification Tower
Nitrification
Single Stage (DN)
Submerged Filter(N)
Rotating Disc(N)
Trickling Filter Tower(N)
Aerated sludge and
anaerobic reactor(DN)
Breakpoint(N)
chlorination
Activated Sludge(N)
Measured Concentration (mg/1)
Total Kjeldahl
Nitrogen
Total Nitrogen
Ammonia
Ammonia
Total Nitrogen
Ammonia
Ammonia
Ammonia
Ammon i a
nitrates
Ammon i a
Ammonia
0.5-10.0
5.0
0.8-1.2
1 .7 June-
1 .9 January
3.8-5.9
0.3-1.2
1.6-2.5
1.2-1.9
0.0-1.5
0.0
1.0
0.0-2.7
Reference
57
44
44
44
44
56
55b/
54£/
50
68
69
i/Note (N) refers to nitrification system and {DN) refers to nitrification-
denitrification
k/Influent ammonia concentrations range of 450-800 mg/1
£/Range of data for 18 month period; test site in Michigan with seasonal
data collected for approximately two weeks each season.
-------
requires more operational attention than has generally been given
to simple biological treatment, but the applicability of the
process to all types of meat product effluents appears very
reasonable.
Problems and Reliability
As discussed above, emphasis on nitrification as a treatment
process has been relatively recent. Except for incidental
ammonia removal facilities, nitrification processes have not been
specifically applied in this industry. Water temperature,
particularly below 10°C, is an apparent constraint for which an
increase in sludge age or solids retention time (via sludge
recycle) may compensate. Maintenance of adequate dissolved
oxygen levels is also important since nitrification activity
effectively ceases at DO levels below 1.0 mg/1. The process is
relatively delicate and requires attentive operation.
Nitrificatjon/Denitrification
This two-step process of nitrification and denitrification.
Figure 20, is of primary importance for removal of the residual
ammonia and nitrites-nitrates in secondary treatment systems.
Removal of the above soluble nitrogen forms can be virtually
complete, with the nitrogen gas as the end product. This process
differs from ammonia stripping and nitrification in that the
latter processes convert or remove only the ammonia content of a
waste water. Table 13C shows a summary of results in removing
both ammonia and other nitrogen from waste waters.
Technical Description
As described in an earlier section, nitrification is carried out
under controlled process conditions by aerating the waste water
sufficiently to assure the conversion of the nitrogen in the
waste water to the nitrite-nitrate forms. The denitrification
process reduces the oxidized nitrogen compounds (nitrites and
nitrates) to nitrogen gas and nitrogen oxides thereby reducing
the nitrogen content of the waste water as the gases escape from
the liquid.
Denitrification takes place in the absence of dissolved oxygen.
Additional important factors affecting denitrification include
carbon source and temperature. Denitrification is brought about
by heterotrophic
111
-------
Secondary
Treatment
Effluent
Aeration
System
^ Anaerobic ^ Aeration ^ Tertiary
!
~ Pond ^ Cell ' Treated
Effluent
Carbon
Source,
e.g. Methanol
Figure 20. Nitrification/Denitrification
Nitrification:
NH + 02
N02" +
(Nitrosomonas)
0
2HO.
(Nitrobacter)
Denitrification (using methanol as carbon source)
6H
6N03 + 5CH3OH
5C0
13
Small amounts of N20 and MO are also formed
(Facultative heterotrophs)
-------
facultative bacteria. Generally, high denitrification rates
require 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
Denitrification does not take place until the dissolved oxygen
concentration of the waste water is near or at zero. The
organisms responsible for denitrification are ubiquitous and can
adapt to pH levels within the range of about 6.0 to 9.0. AS with
any biochemical process, denitrification exhibits a temperature
dependency although within the range of 20°C to 30°C, little
effect has been observed. Denitrification activity decreased
when the temperature decreased to 10°C. Denitrification can be
operated at low temperatures by designing systems with long
solids retention times (SRT). For denitrification systems, an
SRT of at least 3 to U days at 20°C and 30°C and 8 days at 10°C
has been recommended. Nitrate reduction efficiency in
denitrification can be controlled by adjusting the SRT of the
process to assure adequate numbers of denitrifying organisms and
adequate denitrification rates as environmental conditions
change.
In a sequential nitrification-denitrification process (Figure
20) , the waste water from the denitrification step may be sent to
a second aeration basin following denitrification, where the
nitrogen gases are stripped from the waste stream. The sludge
from each stage is settled and recycled to preserve the organisms
required for each step in the process. The processes of
nitrification and denitrification can occur simultaneously in
aeration systems in which both aerobic and anaerobic portions
occur.
Development Status
Although, nitrification-denitrification has not been applied to
rendering processing waste waters as yet, the process has been
evaluated in a number of bench and pilot scale studies on a
variety of wastes.*o *2 Anaerobic processes evaluated as part of
the denitrification sequence have included anaerobic ponds, an
anaerobic activated sludge system, and anaerobic filters.
Efficient nitrogen removals from agricultural subsurface drainage
water were accomplished with an anaerobic filter. In Germany,
the successful elimination of nitrogen from sewage and digester
supernatant was achieved by first nitrifying the wastes and then
denitrifying in a separate vessel. Two and three sludge systems
have been shown to be feasible for the nitrification-
denitrification process.** A pilot model of a three-stage system
using this process was developed at the Cincinnati water Research
Laboratory of the EPA and is being built at Manassas, Virginia.
Observations of treatment lagoons indicate that the suggested
reactions are occurring in present systems. Also, Halvorson
reported that Pasveer achieved success in denitrification by
113
-------
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.26 31 Denitrification of
animal wastes has been evaluated and shown to be feasible.*2
Depending upon how a biological system such as an oxidation ditch
is operated, the nitrogen total loss can range from 30 to about
90 percent.*3
Problems and Reliability
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. For some of
the newer concepts, i.e., denitrification by fluidized bed
reactors, operational difficulties due to biological matting of
the carbon filter bed have been encountered in bench scale tests.
Completely mixed reactors with methanol addition appear to be
favored from the standpoints of operational control and long term
reliability in nitrogen removal. However, a final aeration
chamber may be required to offset increases in effluent BOD due
to methanol leakage from the denitrification reactor. As with
nitrification, sludge return has also been shown to assist system
stability in the denitrification mode.**
Ammonia Stripping1
Ammonia stripping is a physical process and amounts to 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.
Technical Description
Because of the chemistry of ammonia, the pH of the waste water
from a secondary treatment system should be adjusted to between
11 and 12 and the waste water fed to a packed or cooling tower
type of stripping tower. *° As pH is shifted to above 9, the
ammonia
114
-------
is present as a soluble gas in the waste water stream, rather
than as the ammonium ion. Ammonia-nitrogen removal of 90 percent
has been achieved on a municipal effluent 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); 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-
2® y.elO]2nient_ Status
The ammonia stripping process (using both steam and air as the
stripping medium) has been practiced on "sour water" in the
petroleum refinery industry.*6 Differences between the petroleum
refinery application and that on rendering or meat processing
waste would be the comparatively small size of stripping tower
and higher pH required for the meat plants, compared to the
refinery. The air stripping of ammonia from secondary effluent
is reported primarily on a pilot plant basis using various
equipment.*8 Two large-scale installations of ammonia stripping
of lime-treated waste water are reported at south Tahoe,
California, and Windhoek, South Africa. The South Tahoe ammonia
stripper was rated at 1U.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 or meat processing plant waste, the technology is
established and implementation, when standards require it, would
be a possible alternative particularly for well stabilized
secondary effluents.
Problems and Reliability
The reliability of this process has been found reasonable in
petroleum refinery and pilot plant applications of 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. Among the maintenance requirements would be 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. Problems with temperature and tower scaling are
115
-------
also documented. Recent advances in possible anti-scale
chemicals appear promising.** It has also been observed that
efficiency losses due to low temperature can be at least
partially overcome by breakpoint chlorination, by housing the
stripping tower, or heating the water or air with waste steam.
The most recent advance in the process includes an ammonia
recovery step and preliminary results indicate that most problems
with stripping towers have been overcome.*i
DISINFECTION
The disinfection of domestic and industrial waste water is
usually achieved through chlorination. While not discussed in
detail herein, another disinfection process, ozonation, has
received some attention for several years and may become more
popular in the future as costs (compared with chlorination)
become competitive and there is somewhat more widespread use.23
Chlorine, when added to waste waters, forms various compounds
including HOCl, OCC1, and chloramines. The germicidal effect is
believed due to the reaction of the chlorine compounds achieved
with essential enzymes of the bacterial cell, thereby stopping
the metabolic process. Among the conditions affecting germicidal
effectiveness are pH, temperature, contact time, and chlorine
concentration. Residual pH affects germicidal power through its
relation to the formation of HOCl which is many times more
effective than OCCl and chloramines.
Chlorine is used principally to disinfect treated effluent prior
to its discharge into surface waters. To be effective, chlorine
requires a contact time of not less than fifteen minutes at
maximum flow rates at which time there should remain a residual
of not less than 0.2 to 1.0 mg/1. Under these conditions,
chlorination of effluent from secondary treatment will generally
result in more than a 99.9 percent reduction in the coliform
content of the effluent. The range of chlorine dosage generally
required for disinfection varies from 3 to 30 mg/1 depending upon
the quality of the effluent.
BOD can be reduced by the use of chlorine. Approximately two
mg/1 of BOD is satisfied by each mg/1 of chlorine absorbed up to
the point at which orthotolidine residual is produced. Chlorine
alone can reduce BOD by as much as 15 to 35 percent.
An important potential use for chlorine is to kill algae prior to
algae removal operations performed on lagoon effluent. Dead
algae are much easier to remove by flotation, sedimentation, and
filtration than are live algae, according to experience with
removal of algae from domestic waste water lagoon effluents.
Chlorination of algae laden lagoon effluents requires high
dosages of chlorine (up to 25 mg/1) because chloramines are
formed. Chloramines are not as effective a killing agent as the
other chlorine compound forms in water.
116
-------
Chlorine is also effective in the oxidation of hydrogen sulfide
and is used for odor control. It may be applied whenever there
is a decomposition odor problem. In general, control will result
from the application of four to six mg/1 and without the
production of a residual.
Chlorine is available as liquified chlorine, in powdered form,
and in solutions. Liquified chlorine in 68 kg (150 pound) and
970 kg (1 ton) cylinders is generally used for all but the
smallest facilities. Chlorination facilities include
chlorinators, chlorine handling and storage, mixing, and
detention facilities for effluent. Since chlorine is a hazardous
substance, special safety precautions in storage and handling are
required.
Chlorination is utilized for final waste water disinfection at
several meat products plants in the U.S., in each case on a
secondary effluent prior to direct discharge to surface waters.
Breakpoint Chlorination
When waste water containing ammonia is treated with chlorine, a
chemical reaction toward the formation of chloramines is
observed. Further Chlorination to the "breakpoint" (free
chlorine residuals predominate) converts the chloramines to
nitrogen gas which is lost to the atmosphere*
Technical Description
A detailed discussion of the chemistry of breakpoint Chlorination
is readily found in numerous textbooks and references on
disinfection.*0 7t In summary, chlorine is added (as a gas or
liquid) to waste waters containing ammonia in amounts sufficient
to cause the release of nitrogen gas. For each part of ammonia,
about nine parts of chlorine are required to drive the chemical
reactions from monochloramines through to nitrogen gas. At
proper chlorine feed rates, a contact time of 30 minutes or less
is necessary.
Development Status
Breakpoint Chlorination is a well understood and well documented
technology. Applications have centered on tertiary treatment of
secondary municipal wastes, although the concept has been found
to be useful as a "polishing" mode in conjunction with ammonia
stripping. It appears from the literature that the process
offers a possible alternative for ammonia control of ammonia
concentrations similar to those encountered in municipal
secondary effluents.
2£2b1ems_and_ Relia bility
Under low pH (less than 6.0) conditions, Chlorination of ammonia
may produce nitrogen trichloride which is highly odorous. The
removal of ammonia is not adversely affected if it becomes
117
-------
necessary to add a base (sodium hydroxide) to overcome acid
conditions. Under field conditions described in the literature,
the natural alkalinity of the waste water being treated proved to
be sufficient to preclude depression of pH below 6,0. The
process operates equally well in the temperature range of 5°C to
UO°C; more chlorine may be needed at lower temperatures. Process
efficiencies consistently range between 95 and 99 percent and the
process is easily adapted to complete automation which helps
assure quality and operational control. Excessive use of
chlorine can result in substantial relative increases in
dissolved solids (choride salts) in effluents.
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 landr 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 ridge-and-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 prior 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. Approximately 10.0
percent of the waste flow will be lost by evapotranspiration (the
loss caused by evaporation to the atmosphere through the leaves
of plants) .2S
Spray runoff irrigation is an alternative technique which has
been tested on the waste from a small meat packer3* and on
cannery waste.2» 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 discharge. The runoff or discharge from
118
-------
Secondary
Treatment
Effluent
PH
Adjustment
Treated
Effluent
Primary,
Secondary
or
Partial
Tertiary
Treatment
Effluent
Figure 21. Ammonia Stripping
— s
Holding
Basin
N
Pumping
System
"s
Application
Site
V
Grass or
Hay Crop
Figure 22. Spray/Flood Irrigation System
Partial
Tertiary
Treatment
Effluent
Backwash
Regenerant
system
Tertiary
> Treated
Effluent
Figure 23. Ion Exchange
119
-------
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 are about 85 percent
reduced, and phosphorus is reduced about 65 percent.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, t»j
initial moisture content, and 5) terrain and ground cover,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 has been suggested.28 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 this suggested limit.
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 for various spray irrigation systems.*o 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 U.O 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
cpncentrations, 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 corn requires U5U gm (1 pound) of
nitrogen; that the yield is 120 bushels of corn per acre, and
that the corn would require from 25 to 7t5 cm (10 to 30 inches) of
water per season.34 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
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.U metric tons qf dry matter per hectare (six tons per
acre) and values'at $22 per metric ton ($20 per ton). These
120
-------
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."
Cold climate uses of spray irrigation may be subject to more
constraints and have greater land requirements than plants
operating in more temperate climates. 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
inclined to use spray or flood irrigation systems.
Problems and Reliability
The long term reliability of spray or 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
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.*• 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.
121
-------
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 UO 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.** 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 constituents
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.23
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
end of the waste water processing scheme, thus having the highest
quality effluent available as a feedwater.
To achieve a recyclable 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 regeneration chemicals, thus
minimizing liquid wastes from the regeneration step.
122
-------
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
require special handling or treatment. The relatively small
quantity of regenerant solution will facilitate its proper
disposal by users of this system.
123
-------
-------
SECTION VIII
COST, ENERGY, AND NONWATER QUALITY ASPECTS
SUMMARY
The waste water from rendering plants is amenable to treatment in
biological and advanced 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
effectivenesss.
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 13D.
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.
125
-------
Table 13D. Profile of Typical Plants by Size
Small
Medium
Large
Rendering Plant Size
Ran
kg /day
<33,800
33,800- 113,500
>113,500
ges
Ib/day
<75,000
75,000 - 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
lit era /day
37,700
91,000
288,000
gal /day
10,000
24,000
76,000
-------
The estimate of the cost of achieving the proposed 1977
limitations is based on the following assumptions and criteria,
which reflect the data collected on the industry in the study
survey, and additional information developed in the course of
this study.
o Because an analysis of economic impact revealed that
small rendering plants would be subject to closure with
the imposition of costs to achieve the 1977 limitations,
cost estimates for these plants (processing 75,000
pounds of raw material per day or less) is included for
information purposes only.
o There are about 76 medium and large plants with a direct
discharge to streams.
o For purposes of total industry cost estimates all medium
and large plants with a direct discharge were assumed to
need to improve treatment by expanding aerobic lagoons
or comparable cost alternatives such as adding aerated
lagoons.
o 50 percent of all medium and large plants with a direct
discharge will need to install chlorination.
o All plants currently have installed primary treatment
(materials recovery in the form of a catch basin or
mechanical skimmer/settler) and a single lagoon system
of 30 days holding capacity.
o On the basis of water use rates, the medium and large
plants are distributed as approximately 85 percent
achieving low water use rates (typically about 150
gallons per 1000 pounds of raw material) and 15 percent
at high rates (averaging about UOO gallons per 1000
pounds of raw material) .
The rendering industry waste treatment practices are estimated to
conform closely to survey data supplied by the industry and
specific questionnaire data for (*9 plants. The data reveals a 15
to 55 split between plants with a municipal discharge and those
that treat or control their own waste waters. Thus, of the
approximately 350 plants encompassed by this study, slightly less
than half are municipal discharges, about 15 percent achieve no
discharge of pollutants, and over 150 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."
Using the same assumed distribution of medium and large plants by
water use rate, the 1983 limitations are estimated to require the
following additions to the existing treatment systems,
incremental to the additions for 1977:
o 15 percent of all plants with a direct discharge
127
-------
Table 14. Likely Capital Expenditures by Plant Size to Meet Limitations
Shown For Plants with Condenser Recirculation
Small Plant
Medium Plant
Large Plant
Total
Rendering
Indus try
1977
Limitation
($)
26,500
27,000
52,000
2,000,000*
1983
Limitation
($)
53,000
63,000
119,000
6,750,000
New Source
Standard
($)
38,000
78,000
133,000
Irrigation
System Only**
(?)
5,000
14,000
37,000
Percolator &
Evaporation Pond
($)
14,000
32,000
62,000
l-o
CO
*Approximately 85% of medium and large plants have flows (150 gal/1000 Ib RM)
reflecting recirculation
-------
(i.e., those at high rates of water use) must add
sand filters, or the equivalent;
o 50 percent of all plants with a direct discharge will
have to make capital improvements in their primary
treatment facilities;
o 12 percent of all plants with a direct discharge will
have to eliminate direct blood drainage to the sewer
and recover it in their product streams; and
o 95 percent of all plants with a direct discharge will
have to install ammonia control (nitrification) systems.
The costs for irrigation and for ponding are included in Table 14
to indicate the economic advantages of both approaches. The no-
discharge options are particularly advantageous to those plants
with relatively low effluent volumes.
The investment costs for new point sources are derived from cost
estimates of treatment systems presently in use in the industry
based on the average flow for the plant size, as indicated in
Table Itt.
The cost estimates for a plant to achieve the recommended
limitations are predicated upon additions to existing facilities
which are presently installed at most plants discharging directly
to streams. The investment cost for a given plant will vary
depending upon the extent to which investments have already been
made in pollution control equipment. 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 are
based on 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 UOO gal/1000 lb 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 0.032/lb RM and small plants
would incur the largest increase in annual cost for 1983 of
0.28^/lb RMf again in comparison with the plant using only 1U3
gal/1000 lb 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
129
-------
Table 15. Estimated Waste Treatment Investment Costs for
Renderers with High Waste Water Volume
(3300 liters/1000 kgs KM or 400 Gals/1000 Ibs EM)*
Plant
Size
Small
Medium
Large
•
1977
Limitations
20,700
47,600
94,000
1983
Limitations
135,000
202,000
337,000
Irrigation
System, Only
13,100
34,000
90,000
* Approximately 15% of medium and large plants are at this flowrate
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
86,200
36,300
132,900
46,700
Irrigation
System, Only
6,200
4,000
9,800
4,200
16,300
2,000
130
-------
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
-------
are listed in Tables 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-year. This assumed
cost of manpower for the treatment system accounts for between 70
and 82 percent of the annual operating cost and between U5 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 0.35£/kg
(0.16^/lb) to the annual operating cost of an average small
plant, and the 1983 limitations would add 0.84*/kg (0.382/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
the 1983 limitations is no greater than 0.20/kg (0.1£/lb), no
matter which treatment system is used.
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 Manufacturers and generally verified
by more recent comments supplied by industry.* The total
industry waste treatment expenditures reported in Tables 1U and
15 of $2.6 million for 1977 limitations and $6.75 million for the
1983 limitations, amounting to about 8.0 percent and 22 percent
of the $30 million estimate, respectively. The waste treatment
expenditures can be programed over a number of years, thus the
requisite investment appears reasonable and achievable. The
small rendering plant is put in the most difficult financial
position, however, this can be minimized by the use of irrigation
or ponding.
The electrical energy consumption in waste water treatment by the
rendering industry amounts to less than 2 percent of their
current total use of electrical energy, and less than 0.1 of one
percent of their total (heat plus electrical) energy consumption.
Thus, in absolute terms and comparatively speaking, waste
treatment energy use is of little consequence.
With the implementation of these standards, land becomes the
primary waste sink instead of air and water. The waste to be
disposed on land from rendering plants can improve soils with
nutrients and soil conditioners contained in the waste. Odor
problems can be avoided or eliminated in all treatment systems.
132
-------
Table 16. Comparison of Most Likely and Maximum Investment, with Condenser
Recirculation, By Plant Size
Performance
1977 Limitations
1983 Limitations
Small Plant
Most
Likely
Cost
($)
26,500
53,000
Maximum
Cost
($)
26,500
100,000
Medium Plant
Most
Likely
Cost
($)
27,000
63,000
Maximum
Cost
($)
47,600
202,000
Large Plant
Most
Likely
Cost
($)
52,000
119,000
Maximum
Cost
($)
94,000
337,000
Table 18, Annual And Operating Costs Per Unit Weight
of Raw Material for a Rendering Plant with
Condenser Recirculation to Meet Indicated
Performance
Plant
Small
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
C/lb
0.16
0.11
0.03
0.02
0.014
0.01
1983
Limitation
C/kg
0.84
0.53
0.20
0.13
0.09
0.04
C/lb
0.38
0.24
0.10
0.06
0.04
0.02
New
Source
Standards
c/kg
0.42
0.31
0.13
0.09
0.07
0.04
c/lb
0.19
0.14
0.06
0.04
0.03
0.02
133
-------
Table 17. Total Annual and Operating Costs for a Rendering
Plant with Condenser Recirculation 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
42,700
26,200
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
UJ
-------
"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 guality aspects of
the treatment systems were determined.
The waste treatment systems are applied on the basis of
"typical" plants described in Table 19 for each plant size.
the
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)
37,700
(10,000)
2,240
(268)
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 sample included one plant that
processed about 3600 kg (8000 Ib) per day of only dead animals.
135
-------
This type of raw material enabled the plant to operate at that
production level, however, it was unique in the sample.
Individual, "typical" plant costs have been derived on the basis
of production characteristics so that equal emphasis is given to
each plant type. Thus, costs for plants with low rates of water
use (characteristic of plants with continous cookers and
condenser recirculation) and with high rates of water use
(characteristic of plants with batch cookers and little or no
condenser recirculation) have been derived for achieving both the
1977 and the 1983 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 biological 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
since disinfection treatment is probably necessary for at least
half of the plants. 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
hectares/million 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
136
-------
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
EOD5, 90% removal
SS, 98% removal
BOD5, 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
137
-------
effectiveness are presented in Section VII—Control and Treatment
Technology.
Of the 19 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. A summary of the
distribution of the type of treatment or control used by plants
in the study survey is as follows:
Discharge to Secondary Treatment No
Municipal System With Discharge
Small plants 7 US
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. Approximations of the range of costs for the
in-plant controls requiring capital equipment are listed in Table
21 and are incorporated into investment cost estimates for
meeting 1983 limitations. 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
"typical," but hypothetical, plant of each size. Investment
costs for specific waste treatment systems are primarily
dependent on the waste water volume.
138
-------
Table 21. Estimates of In-Plant Control Costs
Plant Area
u>
so
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
-------
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 parkw-type estimates,
implying an accuracy of +20 to 25 percent. Rarely is it minus.
All costs are reported in August 1973 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 1000 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.
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).
140
-------
Figure 24. Waste Treatment Cost Effectiveness
h-1
-P-
h-
z
UJ
o
QC
UJ
O.
z
o
§
o
HI
tr
o
o
UJ
w
i
cc
UJ
1-
X
O
ec
D-
CU
90.5 —
99 -
QK —
yo
90 ~
80 -
70 —
60 -
50 -
40 -
30 -
20 -
10 _
o
91,000 I/day
(24,000 GPD) 7
/
*.
I
!
i
i '
3 20 40
—i »™
1 SECONDARY
! TREATMENT
1
,_ J
1
* 7
Z 288,000 I/day
(76,000 GPD)
1 nninnAi-iw -rni- n -i-nflCMT
1 I 1 1 1 1 1 1 1 1 1 11
60 80 100 120 140 160 180 200 220 240 260 280 300
INVESTMENT COST (SlOOO's)
-------
Component Cumulative
BOD5 Removal
* 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 10.0 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 10.0 percent figure
for the meat packing industry. One sample of companies reported
earnings at 7.1 percent of total assets for 1971;" a recent
business periodical reported earnings at 10.1 percent of invested
capital,3* and meat packing industry sources report corporate
target ROI and ROA figures at 12 to 15 percent for new ventures.
The 10.0 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 basis over the following lifetimes, with no salvage
value:
Land costs — not depreciated
Land intensive treatment systems; e.g., lagoons — 25 years
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
142
-------
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 the horsepower 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
pumping costs and heating costs, the last of which can be further
reduced by water reuse as suggested above.
NONWATER POLLUTION FROM WASTE TREATMENT SYSTEMS
Solid Wastes
Solid wastes are the most significant nonwater pollutants
associated with the waste treatment systems applicable to the
143
-------
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.
21 £ atment Svstern
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 Waste Water Volume
Up to 10%
Sludge accumulation in
these lagoons is usually
not sufficient to require
removal.
10 to 15%
5 to 10%
Approximately 2%
Unknown
The raw sludge can be concentrated, digested, dewatered, dried,
incinerated, land-filled 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
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.
For those waste materials considered to be non-hazardous where
land disposal is the choice for disposal, practices similar to
proper sanitary landfill technology may be followed. The
principles set forth in the EPA1s Land Disposal of Solid Wastes
144
-------
Guidelines (CFR Title <*0, chapter 1; Part 241) may be used as
guidance for acceptable land disposal techniques.
For those waste materials considered to be hazardous, disposal
will require special precautions. In order to ensure long-term
protection of public health and the environment, special
preparation and pretreatment may be required prior to disposal.
If land disposal is to be practiced, these sites must not allow
movement of pollutants such as fluoride and radium-226 to either
ground or surface water. Sites should be selected that have
natural soil and geological conditions to prevent such
contamination orr if such conditions do not exist, artificial
means (e.g./ liners) must be provided to ensure long-term
protection of the environment from hazardous materials. Where
appropriate, the location of solid hazardous materials disposal
sites should be permanently recorded in the appropriate office of
the legal jurisdiction in which the site is located.
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.
145
-------
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; thusr the substantial noise generated by an air
f1otat ion sy stem i s confined and perhaps ampli fie d by
installation practices. All air compressors, air blowers, and
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.
146
-------
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 by July lr 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; and
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.
147
-------
EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF
BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY AVAILABLE
Based on the information contained in Sections III through VIII
of this report, a determination has been made that the quality of
effluent attainable through the application of the Best Practicable
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) = ll_x_100 = 0.0085 kg/kkg RM (lb/1000 Ib RM) ; and
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 were within a range of 2 to 23 mg/1; the
sixth had a final grease 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.
148
-------
Table 22. Recommended Effluent Limitations
for July 1, 1977*
Effluent Parameter
Effluent Limitation
BOD 5
Suspended solids (TSS)
Grease
PH
Fecal coliform
0.17 kg/kkg EM (lb/1000 Ib
0.21 kg/kkg RM (lb/1000 Ib RM)
0.10 kg/kkg RM (lb/1000 Ib RM)
6.0 - 9.0
400 counts/100 ml
^Applicable for any period of 30 consecutive days; daily
maximum is 2.0 times values except pH and coliforms
Table 23. Effluent Limitations Adjustment
Factors for Hide Curing
Effluent Parameter (kg/kkg RM or lb/1000 Ib RM)
BOD 5
Suspended solids (SS) =
8.0 x (no. of hides)
( kg of RM)
11 x (np_._ of hides)
(kg of RM )
17r ..6..x_ (no. of hides)
(Ib of RM)
24.2 x (no. of hides)
(Ib of RM)
149
-------
IDENTIFICATION OF BEST PRACTICABLE CONTROL
TECHNOLOGY CURRENTLY AVAILABLE
Best Practicable Control Technology Currently Available (BPCTCA)
for the independent rendering industry involves biological waste
treatment following a materials recovery process for grease and
solids. The following housekeeping activities will help prevent
slug loads to treatment systems and greatly assist overall waste
control programs:
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. Removal of grease and solids from the materials recovery
system on a continuous or regularly scheduled basis to
permit optimum performance.
3. Scrape, shovel, or pick up by other means, as much as
possible, material spills before washing the floors with
hot water.
4. Minimize drainage from materials receiving areas.
One possibility is to pump the liquid drainage back onto
the raw materials as it is conveyed from the area.
5. Repair equipment leaks as soon as possible.
6. Provide for regularly scheduled equipment maintenance
programs.
7. Avoid overfilling cookers.
8. Contain materials when equipment failure occurs and
while equipment is being repaired.
9. Try to prevent spills and provide supervision when
unloading or transfering raw blood.
10. Do not add uncontaminated water to the contaminated
water to be treated.
The following secondary biological treatment ' systems should
produce an effluent that meets the recommended effluent
limitations:
1. Anaerobic lagoon + aerobic (shallow) lagoons
2. Anaerobic + aerated + aerobic lagoons
3. Activated sludge
4. Aerated lagoons + aerobic (shallow) lagoons.
150
-------
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.
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
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.
Total cost of Application in Relation to Effluent
Reduction Benefits
Based on information contained in Section VIII of this report,
the total investment cost to the independent renderer industry to
implement the waste treatment to achieve the 1977 effluent
limitations is estimated to be $2.6 million. This expenditure
will be incurred only by the medium and large plants in the
industry with a discharge to navigable waters. It amounts to
about 20 percent of the estimated total capital expenditures made
in 1972 by this segment of the industry.
This capital expenditure is associated with a substantial
reduction in pollution discharged directly to navigable waters.
Using BOD£ as a basis for calculations, it is estimated that this
segment of large and medium size plants is discharging about 1.1
million Ibs of BOD5 to streams each year at present levels of
pollution control. Full implementation of the 1977 effluent
limitations for BOD£ by these plants is estimated to provide a
reduction of BOD5 to approximately one-half million Ibs per year.
The investment cost for the 1977 limitations per unit weight of
BODJ5 reduction amounts to $0.35 per year per Ib of BODji removed
when evaluated over the six year period during which the 1977
limitations are applicable.
The additional operating cost associated with achieving 1977
limitations varies from 1.4^/lb of raw material for a large
151
-------
rendering plant to 3.5^/lb for a medium size plant. The
estimated increase in total annual cost, which includes operating
costs, depreciation, and capital recovery amounts to 32/lb of raw
material for large plants and 6*/lb for medium size plants.
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 sampling 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 0.17 kg/kkg RM is basically the
average value of all available BOD5 data for all plants except
plant number 7. The data of Table 2** 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 waste load data from
field sampling for plant 3, whose final effluent comes close to
the limitation, was 16.2 kg/kkg RM. In fact, the average raw
3OD5 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 0.21 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
over three times as great as the average for grease for all
plants included in the study, which is 0.72.
152
-------
Table 24. Raw and Final Effluent Information for Ten Rendering Plants
Plant
Number =J
1
2
3
4
5
6
7
8
9
10
Flow,
1000 liters
(1000 gal.)
454 (120
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)
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 EM
**(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.
-------
Based on the average raw waste load values for the ten plants,
with biological treatment systems, these plants must achieve
about 94 to 95 percent efficiency to meet the effluent
limitation.
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 BOD5, SS, and
grease simultaneously. 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 resulting from the use of disinfection. 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 BOD£ 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.
For all of the above limitations, a variability factor was
derived for the relationship of the daily maximum to the average
of daily values for 30 consecutive days. This factor was found
to be 2.0; in other words, the daily maximum is 2.0 times the 30-
day average.
This factor was developed by a direct comparative analysis of all
available data regarding relationships of daily and monthly
effluent values. Because of similarities in treatment systems
and effluent quality, findings related to renderer plants were
verified by comparisons with data on slaughterhouses and
packinghouses for which a factor of 2.0 was also derived.
Finally, the daily maximum limitations themselves were compared
to field sampling results and other reported daily information as
a practical check on the validity of the factor.
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.
Process changes
154
-------
Significant in-plant changes will not be needed for any plant 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
minimizing spills, containing materials upon equipment breakdown,
and using dry cleaning prior to washdown. Some plants may find
it necessary to institute better control of 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 improve
gravity separation systems. 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 BPCTCA.
155
-------
-------
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, 1983r 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; and
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
157
-------
Table 25. Recommended Effluent Limitations
for July 1, 1983**
Effluent Parameter
Effluent Limitation*
BOD5
Suspended solids (TSS)
Grease
Ammonia as H
PH
Fecal coliform
0.07 kg/kkg RM
0.10 kg/kkg RM
0.05 kg/kkg RM
0.02 kg/kkg RM
6.0 - 9.0
400 counts/100 ml
**Applicable to any period of 30 consecutive days; daily
maximum is 2.0 times values except pH and coliforms
*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 KM)
13,6 x (no. of hides)
(lb of RM)
158
-------
certainty of costs. Therefore, some industrially sponsored
development work may be needed prior to 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) = S..6 x 100 = 0.0038 kg/kkg RM (lb/1000 Ib RM) ;
947000
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.
159
-------
but also will usually be more economical than most other types of
treatment or control systems.
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. Including, and in addition to, the
housekeeping principals described in section IX, these controls
are as follows:
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 optimum performance.
U. 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, 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 to the
first processing step.
7. Repair equipment leaks as soon as possible.
8. Provide for regularly scheduled equipment maintenance
programs.
9. Avoid overfilling cookers.
160
-------
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
tranfering raw blood. Blood has a BOD5 of between
150,000 and 200,000 mg/l.s
It. 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 subsoil 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.
161
-------
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, some type of tertiary treatment may
be needed to ensure that others will consistently meet 1983
standards.
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 (NO2),
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 sampling survey. Data for plant number
7 were included because the components of a satisfactory
treatment facility were in place, 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.
The BOD5 effluent limitation of 0.07 kg/kkg 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
162
-------
Table 27. Raw and Final Effluent Information for Ten Rendering Plants
Table 27A. Flow, RM/Day, Final Fecal Coliform,
and EOD, SS, and Grease Waste Loads
Plant
Number i>
1
2
3
4
5
6
7
8
9
10
Flow
1000 liters
(1000 gal.)
454 (120)
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/kke 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
—
Greas,* 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 = pounds/1000 pounds RM
A*(C1) indicates chlorination of final effluent.
_!/ 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.
-------
Table 27. Raw and Final Effluent Information for Ten Rendering Plants
(Continued)
Table 27B. TKN, NH-, 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 tf
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
*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.
-------
BOD5 loads greater than the industry average of 2.15 kg BOD5/kkg
RM. Thus, it appears that a well operated and properly sized
secondary treatment system can produce an effluent with a BOD£
load that will meet the 1983 limitation. The BOD5 effluent limit
value of 0.07 kg/kkg RM corresponds to a final effluent
concentration of 56 mg/1 for plants with low rates of water use
(150 gal/1000 Ibs RM) and about 21 mg/1 for plants with higher
rates of water use (UOO gal/1000 Ibs RM). A BOD5 concentration
as low as 21 mg/1 usually means that the majority of the BODJ5
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 from plants with
higher water use rates will meet the 1983 BOD5 limit during all
periods of discharge may require the use of a sand filter or its
equivalent to reduce the remaining SS and thus the BOD5.
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, corresponds to a final
concentration for SS of 80 mg/1 for plants with low rates of
water use and about 30 mg/1 for plants with higher water use
rates. This latter concentration is a readily achievable 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.
The ammonia limit of 0.02 kg NHl 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.
With respect to treatment itself, most plants should find it
advantageous to utilize nitrification processes for ammonia
control. Treatment concepts such as modifications of single cell
activated sludge or extended aeration systems would apply. In
165
-------
addition to the removal of ammonia, these systems include
clarification with sludge return and thus are likely to obviate
the need for final filtration to meet the BOD5 and TSS
limitations. In concentration units, the BOD5 and TSS
limitations are well within the range achieved by nitrification
systems.
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 100 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 coliform counts given in T^ble 27A were
obtained using the membrane filter procedure. This1 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 of control technology, primary, plus
secondary, plus tertiary (which will generally include at least
the addition of nitrification systems or its equivalent if it is
needed), is achievable; 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 in many other applications for
waste water treatment.
Process changes
Most plants will find it necessary to make in-plant improvements
to meet the 1983 limitations. This will not require any
substantial process changes per se^ rather, 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 drycleaning 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.
166
-------
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
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.
The electrical energy consumption attributable to the waste
treatment facilities required to achieve the 1983 effluent
limitations is estimated to be 15 million KWh per year for the
rendering industry. This is equivalent to about 0.2 percent of
the total energy, including heat and power, consumed by the
industry in 1967. it amounts to about 4 percent of the
electrical energy consumed in 1967* This increase in energy
consumption does not appear to raise serious supply or cost
problems for the Tenderers.
Otherwise, the effects will essentially be those described in
Section IX, where it was concluded that no new kinds of impacts
would be introduced.
167
-------
-------
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, or 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;
o process employed;
o Plant size; and
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:
169
-------
Effluent Parameter
Effluent Limitation
kq/kkq (Ib/lOOQ lb)"JM
Ammonia as
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 (assuming low
water use rates of 150 gallons/1000 pounds RM) 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
$
78,000
148,000
220,000
Annual Cost Operating
Total
$/yr
32,125
50,025
70,725
*/kg
tt/lb)
0.67
(0.31)
0.26
(0.12)
0.12
(0.05)
Total
$/yr
19,325
25,425
33,325
Cost
*/kg
U/lb)
0.40
(0.18)
0.13
(0.06)
0.06
(0.03)
*Note: Based upon a treatment system of catch basin with skimmer,
anaerobic-aerated-aerobic lagoons, ammonia control
(nitrification) and disinfection.
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 used 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
170
-------
special treatment method would be to steam sparge and
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 octor 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 overfilling 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
transfering 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.
171
-------
o Do not add uncontaminated water to the contaminated
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 coliform 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 were allowing too much
blood to enter the sewer, and the third was adding nutrients
(such as paunch manure) to the system to help sustain a natural
scum layer (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 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
172
-------
rendering effluent will cause difficulty in the treatment system;
trickling filters appear to be particularly sensitive. A
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.
173
-------
TABLE 29
METRIC TABLE
CONVERSION TABLE
MULTIPLY {ENGLISH UNITS) by TO OBTAIN (METRIC UNITS)
ENGLISH UNIT ABBREVIATION CONVERSION ABBREVIATION METRIC UNIT
acre ac
acre - feet ac ft
British Thermal
Unit - BTU
British Thermal
Unit/pound BTU/lb
cubic feet/minute cfm
cubic feet/second cfs
cubic feet cu ft
cubic feet cu ft
cubic inches cu in
degree Fahrenheit °F
feet ft
gallon gal
gallon/minute gpm
horsepower hp
inches in
inches of mercury in Hg
pounds Ib
million gallons/day mgd
mile mi
pound/square
inch (gauge) psig
square feet sq ft
square inches sq in
ton (short) ton
yard yd
* Actual conversion, not a multiplier
0.405
1233.5
0.252
0.555
0.028
1.7
0.028
28.32
16.39
0.555(°F-32)*
0.3048
3.785
0.0631
0.7457
2.54
0.03342
0.454
3,785
1.609
(0.06805 psig +1)*
0.0929
6.452
0.907
0.9144
ha
cu m
kg cal
kg cal/kg
cu m/min
cu m/min
cu m
1
cu cm
°C
m
1
I/ sec
kw
cm
atm
kg
cu m/day
km
atm
sq m
sq cm
kkg
m
hectares
cubic meters
kilogram - calories
kilogram calories/kilogram
cubic meters/minute
cubic meters/minute
cubic meters
1i ters
cubic centimeters
degree Centigrade
meters
1i ters
liters/second
killowatts
centimeters
atmospheres
kilograms
cubic meters/day
kilometer
atmospheres (absolute)
'square meters
square centimeters
metric ton (1000 kilograms)
meter
174
-------
SECTION XII
ACKNOWLEDGMENTS
The Environmental Protection Agency gratefully acknowledges the
assistance of the North Star Research and Development Institute
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 the member plants
operations committee and of Dr. H.O. Halvorson are gratefully
acknowledged.
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- •
Invaluable consultation and assistance was provided by Dr.
Raymond D. Loehr, Director, Environmental Studies Program,
Cornell University, and presently serving as Program Advisor,
Effluent Guidelines Division.
The Agency also wishes to acknowledge the overall supervision and
guidance provided by Mr. Allen Cywin, Director, Mr, Ernst P.
Hall, Deputy Director, and Mr. John Riley, Chief, Technical
Analysis and Information Branch of the Effluent Guidelines
Division. Special mention is also due Mr. Richard Stevenson of
the Economic Studies Division for his help in evaluations of
costs and economic impact.
The help of Dr, Dwight Ballinger of EPA in Cincinnati in
establishing sampling and testing procedures used for the field
verification studies was also appreciated.
Many State and local agencies were also most helpful and much
appreciated.
And special mention is due Mrs, Pearl Smith, Effluent Guidelines
Division, for her invaluable assistance in editing and compiling
the final document.
175
-------
-------
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.
-------
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 Waste Waters 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 Waste Water
Treatment, Van Nostrand Reinhold Company, New York, 1971.
21*. 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 Waste Water Engineering: Volume 2.
Water Purification and Waste Water Treatment and Disposal,
John Wiley & Sons, Inc., New York, 1968.
26, Personal communication, H.O. Halvorson, 1973.
178
-------
27. Fair, Gordon Maskew, Geyer, John Charles, and Okun, Daniel
Alexander, Water and Waste Water Engineering: Volume 1.
Water Supply and Waste Water Removal, John Wiley S 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, McGraw-
Hill Book company. New York, 1962.
38. Frazier, W. C., Food Microbiology, 2nd Edition, McGraw-Hill
Book Company, New York, 1967.
39. "Water Quality Criteria - 1972", National Academy
of Sciences and National Academy of Engineering for the
Environmental Protection Agency, Washington, D. C. 1972
(U. S. Govt. Printing Office Stock No. 5501-00520).
40. Loehr, Raymond C. Agricultural Waste Management,
Academic Press, New York, 1974.
41. Anthonisen, A.C., R. C. Loehr, et. al., "Inhibition of
Nitrification by Unionized Ammonia and Unionized Nitrous
Acid", presented at 47th Annual Conference, Water Pollution
Control Federation, October, 1974.
42. Development and Demonstration of Nutrient Removal.from
Animal Wastes EPA-R2-73-095 U. S. Environmental Protection
179
-------
Agency, January, 1973.
43. Prakasam, T.B.S. et al, "Approaches for the Control of
Nitrogen With an Oxidation Ditch", Proceedings 1974
Agricultural Waste Management conference, Cornell University,
Ithaca, New York, pp 421-435.
44. "Control of Nitrogen in Waste Water Effluents", U. S.
Environmental Protection Agency, ORD (NERC) Cincinnati,
Ohio, March 1974.
45. "ABF Nitrification System, 1974 Pilot Plant Study", Interim
Report, Neptune Microfloc, Inc. September, 1974.
46. Reeves, T.G., "Nitrogen Removal" a literature review",
JWPCF volume 44, No. 10 pp 1895-1908, October, 1972.
47. Gonzales, J. G. and R. L, Gulp, "New Developments in
Ammonia Stripping", Public Works p. 78, May, 1973.
48. O'Farrell, T. P. et. al., "Nitrogen removal by ammonia
stripping", JWPCF vol. 44, no. 8 pp 1527-1535, August, 1972.
49. "Nitrogen Removal from Waste Waters", Federal Water Quality
Administration, AWT Laboratory Cincinnati, Ohio May, 1970.
50. "Evaluation of Anaerobic Denitrification Processes" Journal
SED, American Society of Civil Engineers pp 108-111,
February, 1971.
51. McLaren, J. R. and G. J. Farguhar, "Factors Affecting Ammonia
Removal by Clinoptilolite" Jour. EED, American Society of
Civil Engineers, pp 429-446 August, 1973.
52. Johnson, W. K., "Process Kinetics for Denitrification", Jour.
SED, ASCE pp 623-634 August, 1972.
53. "How to Get Low Ammonia Effluent", Water and Sewage Works
p 92, August 1974.
54. Duddles, Glenn A., et.al., "Plastic Medium Trickling Filters
for Biological Nitrogen Control", JWPCF vol. 46 No. 5
pp 937-946, May 1974.
55. Lue-Hing, Cecil, et.al. "Nitrification of a High Ammonia
Content Sludge Supernatent by use of Rotating Discs",
presented at 29th Annual Purdue Industrial Waste Conference,
May 1974.
56. Haug, R. T. and Perry L. Mccarty, "Nitrification with the
Submerged Filter" presented at Annual Water Pollution Control
Federation Conference San Francisco, ca., October, 1971.
57. Sutton, Paul M., et.al., "Biological Nitrogen Removal - The
Efficacy of the Nitrification Step", presented at Annual
180
-------
Conference WPCF, Denver, Colorado, October 1974.
58. Lawrence, Alonzo W and C. G. Brown, "Biokinetic Approach to
Optimal Design and Control of Nitrifying Activated Sludge
Systems "presented at Annual Meeting New York Water Pollution
Control Association, New York, January 1973.
59, Baumann, R. E. and J. L. Cleasby, "Design of Filters for
Advanced Waste Treatment" Engineering Research Institute,
Iowa State University, Ames, Iowa, October, 1973.
60. Rice, G. A. and J. L. Cleasby, "Reported Efficiencies for
Direct Filtration of Plant Effluents", Iowa State University,
Ames, Iowa, March 197U.
61. Baumann, R. E., "Design of Filters for Advanced waste Water
Treatment", Engineering Research Institute, Iowa State
University Ames, Iowa, June 1973.
62. "Water and Pollution Control Technology Report" Neptune
Micro FLOC, Inc., Volume U, Number 1, September 1970.
63. Weddle, C. L., et.al., "Studies of Municipal Waste Water
Renovation for Industrial water" presented before Annual
Conference of the Water Pollution Control Federation,
October, 1971.
61. "Comprehensive Monthly Report", Dallas Water Utilities
Department, Water Reclamation Research center, July 1973.
65. University Area Joint Authority, operating report of
October 6, 1971, State College, Pa.
66. Metropolitan sewer District, operating report of October,
1971, Louisville, Kentucky.
67. "Upgrading Existing Waste Water Treatment Plants" U. S.
Environmental Protection Agency Technology Transfer
Process Design Manual, October 197U.
68. Beckman, W. J., et al, "Combined Carbon Oxidation -
Nitrification", Journal WPCF, p 1916-1931 volume U4,
October 1972.
69. Drews, R.J. L.C. and A.M. Greef, "Nitrogen Elimination
by Rapid Alternation of Aerobic/Anoxic conditions in
Orbal Activated Sludge Plants", Water. Research
Volume lf Pergaman Press, 1973.
70. Lynam, B.T. and V.W. Bacon, "Filtration and Microstraining
of Secondary Effluent", from Water Quality Improvement
by Physical and Chemical Processes University of Texas
Press, 1970.
71. Gulp, Gordon L., "Physical Chemical Techniques
181
-------
for Nitrogen Removal" prepared for EPA Technology
Transfer Seminar, March, 1974.
72. "Ammonia Removal from Agricultural Runoff and
Secondary Effluent by Selected Ion Exchange",
U. S. Department of the Interior, FWPCA,
Cincinnati, Ohio, March, 1969.
73. "Waste Water Filtration Design Considerations", U. S.
Environmental Protection Agency, Technology Transfer,
Washington, D. C., July 1974.
74. "Upgrading Existing Lagoons", U. S. Environmental
Protection Agency, NERC, Cincinnati, Ohio, October,
1973.
75. Reynolds, J. H., et. al., "Single and Multi-stage
Intermittent Sand Filtration to Upgrade Lagoon
Effluents" Utah State University, Logan, Utah,
November, 1974.
76. Middlebrooks, E. J., et. al., "Evaluation of Techniques
for Alage Removal from Waste Water Stabilization Ponds",
Utah Water Research Laboratory, Utah State University,
Logan, Utah January, 1974.
77. Clark, S. E., et. al., "Alaska Sewage Lagoons", Federal
Water Quality Administration, Alaska Water Laboratory,
College, Alaska, 1970.
78. "Lagoon Performance and the State of Lagoon Technology"
U. S. Environmental Protection Agency, Office of Research
and Monitoring, June, 1973.
79. "Supplementary Aeration of Lagoons in Rigorous Climate
Areas", U. S. Environmental Protection Agency,
October, 1971.
80. "Biological Waste Treatment in the Far North", Federal
Water Quality Administration, Alaska Water Laboratory,
June 1970.
81. Eckenfelder, W. W. and D. J. O'Connor, Biological
Waste Treatment. Pergamon Press, New York, 1961.
82. "The 1974 Environmental Wastes Control Manual"
Public Works, Ridgewood, New Jersey.
83. Stenquist, R. J., et.al., "Carbon Oxidation-
Nitrification in Synthetic Media Trickling Filters,"
JWPCF, Vol. 46 p 2327, October, 1974.
84. "Ammonia Removal in a Physical-Chemical Waste Water
Treatment Process," U.S. Environmental Protection
Agency, Report EPA-R2-72-123, Washington, D. C.
182
-------
November, 1972.
85. "Water Pollution Control in Cold Climates" Proceedings,
International Symposium, U. S. Environmental Protection
Agency, 1970 (U.S. GPO stock number 5501-0208).
86. "Development Document for Effluent Limitations and Standards
of Performance for New Sources for the Petroleum Refining
Point Source Category", U. S. Environmental Protection
Agency, Washington, D. C. April, 1974.
87. Beychok, M. R. Aqueous Wastes from Petroleum and
Petrochemical Plants^ John Wiley and Sons, New York, 1967.
183
-------
-------
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
photosynthe si s.
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 plants. 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
buildup of dissolved solids; e.g., in a boiler.
185
-------
BOD5: 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: Cent imet er.
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 facultative
conversion by anaerobic bacteria of nitrates into nitrogen and
nitrogen oxides.
186
-------
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
dissolved 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.
187
-------
Finger Dikes: Barriers or walls extending out into lagoons—in
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.
Flocculation: 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 UO°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 human 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.
188
-------
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 NO3-
(nitrate) and NO2~ (nitrite) ions. They are composed of riitrogen
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 runoff 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.
189
-------
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 tenfold 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
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.
190
-------
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 odorous 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.
191
-------
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 solids deposited from sewage or
other wastes, raw or treated, in tanks or basins, and containing
more or less water to form a semi-liquid 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 of SS content of waste water.
Tallow: Fat that has a titre (melting point) of t*0°C or higher.
Tallow is produced from beef cattle 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."
192
-------
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 tank water.
Zero Discharge: The discharge of no pollutants in the waste
water stream of a plant that is discharging into a receiving body
of water.
193 4U.S. GOVERNMENT PRINTING OFFICE: 1975 58Z-4Z1/259 1-3
-------
-------
-------
------- |