EPA 440/l-74/031_a Development Document for Proposed Effluent Limitations Guidelines and New Source Performance Standards for the RENDERER Segment of the MEAT PRODUCTS Point Source Category p \ UJ a UNITED STATES ENVIRONMENTAL PROTECTION AGENCY AlUST 1974 ------- DEVELOPMENT DOCUMENT for PROPOSED EFFLUENT LIMITATIONS GUIDELINES and NEW SOURCE PERFORMANCE STANDARDS for the RENDERER SEGMENT OF THE MEAT PRODUCTS POINT SOURCE CATEGORY Russell E. Train Administrator James L. Agee Assistant Administrator for Water and Hazardous Materials Allen Cywin Director, Effluent Guidelines Division Jeffery D. Denit Project Officer August, 1974 Effluent Guidelines Division Office of Water and Hazardous Materials U. S. Environmental Protection Agency Washington, D. C. 20460 ------- ABSTRACT This document presents the findings of an extensive study of the independent rendering industry by the Environmental Protection Agency for the purpose of developing effluent limitations guidelines, Federal standards of performance, and pretreatment standards for the industry, to implement Sections 304(b) and 306 of the Federal Water Pollution Control Act Amendments of 1972 (the "Act") . The rendering plants included in the study were those plants specifically processing animal by-products at an independent plant (i.e., a plant located, operated and managed separately from meat slaughtering and packing plants). Plants processing fish by-products and rendering operations carried out as an adjunct to meat packing plants were not included. Effluent limitations guidelines are set forth for the degree of effluent reduction attainable through the application of the "Best Practicable Control Technology Currently Available," and the "Best Available Technology Economically Achievable," which must be achieved by existing point sources by July 1, 1977, and July 1, 1983, respectively. The "Standards of Performance for New Sources" set forth the degree of effluent reduction which is achievable through the application of the best available demonstrated control technology, processes, operating methods, or other alternatives. The proposed regulations require the best secondary treatment technology currently available for discharge into navigable water bodies by July 1, 1977, and for new source performance standards. This technology is represented by anaerobic plus aerobic lagoons, or their equivalent. The recommendation for July 1, 1983 is for the best secondary treatment and in-plant control, as represented by in-plant containment and separate treatment or recycle of high strength waste waters, and a final sand filter added to the 1977 technology. When suitable land is available, land disposal with no discharge may be a more economical option, particularly for small plants. Supportive data and rationale for development of the proposed effluent limitations guidelines and standards of performance are contained in this report. ------- CONTENTS Section I. CONCLUSIONS 1 II. RECOMMENDATIONS 3 III. INTRODUCTION 5 Purpose and Authority 5 Summary of Methods Used for Development of the Effluent Limitations Guidelines and Standards of Performance 6 General Description of the Industry 7 Process Description 12 Inedible Rendering 13 Batch System 13 Continuous Systems 18 Edible Rendering -\Q Cooker Uses and Process Variations 23 Vapor Condensing 24 Grease and Tallow Recovery 25 Solids Processing 26 Odor Control 26 Waste Water Sources 27 Materials Recovery 28 Hide Curing 29 IV. INDUSTRY CATEGORIZATION 31 Categorization 31 Rationale for Categorization 31 Waste Water Characteristics and Treatability 31 Raw Materials 34 Manufacturing Processes 35 m ------- CONTENTS (Continued) Section Processing Equipment 36 Size, Age, and Location of Production Facilities 40 V. WATER USE AND WASTE CHARACTERIZATION 43 Waste Water Characteristics 43 Raw Waste Characteristics 43 Discussion of Raw Wastes 44 Sources of Waste Water 48 Raw Materials Receiving 50 Vapor Condensing 50 Spills and Plant and Truck Cleanup 52 Odor Control 54 Hide Control 54 Miscellaneous Sources 56 VI. SELECTION OF POLLUTANT PARAMETERS 57 Selected Parameters 57 Rationale for Selection of Identified Parameters 57 5-Day Biochemical Oxygen Demand 57 Chemical Oxygen Demand 60 Suspended Solids 60 Total Dissolved Solids 62 Total Volatile Solids 63 Grease 63 Ammonia Nitrogen 64 Kjeldahl Nitrogen 65 Nitrates and Nitrites 66 Phosphorus 66 Chloride 67 Fecal Coliforms 68 PH 69 Temperature 70 VII. CONTROL AND TREATMENT TECHNOLOGY 73 Summary 73 In-Plant Control Techniques 73 Condensables 75 Control of High Strength Liquid Wastes 75 Truck and Barrel Washings 75 Odor Control 76 Plant Cleanup and Spills 7g IV ------- CONTENTS (Continued) Section £§2® VII. CONTROL AND TREATMENT TECHNOLOGY (Continued) In-Plant Primary Treatment 76 Flow Equalization 76 Screens 77 Catch Basins 78 Dissolved Air Flotation 79 Waste Water Treatment Systems 84 Anaerobic Processes 84 Aerated Lagoons 88 Aerobic Lagoons 88 Activated Sludge 90 Rotating Biological Contactor 93 Performance of Various Secondary Treatment Systems 94 Tertiary and Advanced Treatment 96 Chemical Precipitation 96 Sand Filter 98 Microscreen-Microstrainer 101 Nitrification-Denitrification 103 Ammonia Stripping 106 Spray/Flood Irrigation 107 Ion Exchange 110 VIII. COST, ENERGY AND NONWATER QUALITY ASPECTS 115 Summary 115 "Typical" Plant 124 Waste Treatment Systems 125 Treatment and Control Costs 127 In-Plant Control Costs 127 Investment Costs Assumptions ]27 Annual Cost Assumptions 131 Energy Requirements 132 Nonwater Pollution by Waste Treatment Systems 133 Solid Wastes 133 Air Pollution 134 Noise 134 ------- CONTENTS (Continued) Section IX. EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF THE BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY AVAILABLE—EFFLUENT LIMITATIONS GUIDELINES 137 Introduction I O / Effluent Reduction Attainable Through the Application of Best Pollution Control Technology Currently Available 138 Identification of Best Pollution Control Technology Currently Available 140 Rationale for the selection of Best Practicable Control Technology Currently Available 142 Size, Age, Processes Employed, and Location of Facilities 142 Data Presentation 143 Engineering Aspects of Control Technique Applications 144 Nonwater Quality Environmental Impact 145 X. EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF THE BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE—EFFLUENT LIMITATIONS GUIDELINES 147 Introduction 147 Effluent Reduction Attainable Through Application of the Best Available Technology Economically Achievable 148 Identification of the Best Available Technology Economically Achievable 150 Rationale for Selection of the Best Available Technology Economically Achievable 154 Size, Age, Processes Employed, and Location of Facilities 154 Data Presentation 154 Engineering Aspects of Control Technique Applications 156 Process Changes 156 Nonwater Quality Impact 156 ------- CONTENTS (Continued) Section XI. NEW SOURCE PERFORMANCE STANDARDS 159 Introduction 159 EFFLUENT REDUCTION ATTAINABLE FOR NEW SOURCES 159 Identification of New Source Control Technology 160 Technology Rationale for Section of New Source Performance Standards 162 Pretreatment Requirements 162 XII. ACKNOWLEDGMENTS 165 XIII. REFERENCES 167 XIV. GLOSSARY 171 Vll ------- FIGURES Number 1 Distribution of Rendering Plants by State 11 2 General Flowsheet of Operations of a Typical Inedible Rendering Plant 15 3 Batch Cooker Rendering Process 17 4 Continuous Rendering - Duke Process 20 5 Continuous Rendering - Anderson Carver-Greenfield Process 22 6 Manufacturing Processes of a Rendering Plant 32 7 Average and Range of BOD5 by Raw Material Type 35 8 Average and Range of BOD5 Data by Cooker Type 37 9 Average and Range of BOD 5 Data by Condenser Type 33 10 Average and Range of BOD5 Values for Three Size Groups of Plants and for All Plants Studied 41 11 Typical Rendering Process and Waste Water Flow Arrangement 49 12 Suggested Waste Reduction Program for Rendering Plants 74 13 Dissolved Air Flotation 80 14 Process Alternatives for Dissolved Air Flotation 83 15 Anaerobic Contact Process 87 16 Activated Sludge Process 91 17 Chemical Precipitation 98 18 Sand Filter System 99 19 Microscreen/Microstrainer 102 20 Nitrification/Denitrification 104 21 Ammonia Stripping 10g ix ------- FIGURES (Continued) Number Page 22 Spray/Flood Irrigation System 109 23 Ion Exchange 109 24 Waste Treatment Cost Effectiveness 130 ------- TABLES Number 1 Inedible Tallow and Greases: Use, By-Products, 1960-1970 9 2 Statistics by Employment Size of Establishment, 1967 12 3 Raw Material and Product Yields for Inedible Rendering by Type of Animal 14 4 Product Yields for Inedible Rendering by Type of Raw Material 14 5 Raw Waste Water Data on Rendering Plants by Equipment Type 39 6 Summary of the Plant and Raw Waste Water Characteristics for the Rendering Industry 45 7 Waste Water Flow and Raw Material Data on Off-Site Rendering Plants 46 8 Correlation Coefficients of Raw Waste Load Parameters from the Field Sampling Results 47 9 Summary of Concentrations of Undiluted Condensed Cooking Vapors 5] 10 Summary of Waste Loads of Undiluted Condensed Cooking Vapors 53 11 Waste Load Characteristics for Hide Curing at a Rendering Plant Versus Those for a Tannery 55 12 Measured Waste Strengths of Tank Water and Blood Water 55 13 Performance of Various Secondary Treatment Systems 95 13A Profile of Typical Plants by Size ]]5 14 Likely Capital Expenditures by Plant Size to Meet Limitations with Condenser Recirculation as Needed ng 15 Estimated Waste Treatment Costs for Renderers with High Waste Water Volume -]20 ISA Total Annual and Operating Costs for Renderer with High Waste Water Volume ------- TABLES (Continued) Number 15B Annual and Operating Costs Per Unit Weight of Raw Material l41 16 Comparison of Most Likely and Maximum Investment with Condenser Recirculation 122 17 Total Annual and Operating Costs for a Rendering Plant to Meet the Indicated Performance '" 18 Annual and Operating Costs Per Unit Weight of Raw Material for a Rendering Plant to Meet Indicated Performance 122 19 "Typical" Plant Parameters for Each Plant Size 124 20 Waste Treatment Systems, Their Use and Effectiveness 126 21 Estimates of In-Plant Control Equipment Cost 128 22 Recommended Effluent Limitation Guidelines for July 1, 1977 139 23 Effluent Limitations Adjustment Factors for Hide Curing 24 Raw and Final Effluent Information for Ten Off-Site Rendering Plants 141 25 Recommended Effluent Limitation Guidelines for July 1, 1983 149 26 Effluent Limitation Adjustment Factors for Hide Curing 149 27 Raw and Final Effluent Information for Ten Off-Site Rendering Plants 151-152 28 Investment and Operating Costs for New Source Performance Standards 160 29 Conversion Table 180 ------- SECTION I CONCLUSIONS The study presented herein is a part of an overall investigation of the meat processing (no slaughtering of animals accomplished in the plants) and rendering (accomplished independent of slaughterhouses, packinghouses and poultry processors) industry segments of the meat products point source category. Because of evidence developed early in the investigation, it became apparent that meat processing operations differed materially from rendering operations as to raw materials, processes, products and other factors. As a result, an initial categorization which split the two industry segments was utilized to facilitate a thorough analysis with a separate study report for each, with the rendering industry segment presented herein. A conclusion of this study is that the rendering industry con- stitutes a single category. Unless otherwise specifically designated, all subsequent discussions of the rendering industry, or references to the rendering industry, deal with the independent rendering operation or plants not included as a part of livestock or poultry slaughtering, packing or processing. The primary criterion for the establishment of the category was the 5-day biochemical oxygen demand (BOD5) in the total plant raw waste water. Other criteria were plant size and type of processing equipment used in the plant. Information relating to other pollutants and the effects of such parameters as age and location of plants, type of raw material, production processes, and treatability of wastes all lent support to the categorization decision. The wastes from rendering plants are amenable to biological treatment processes, and no materials harmful to municipal waste treatment processes were found. The 1977 discharge limits for BOD5, suspended solids, and grease, representing the average of the best treatment systems in the rendering industry, are currently being met by a number of plants included in the survey. Several of the plants meeting the limits discharge waste water to receiving waters, while a number of other plants, particularly small plants, meet the limits by irrigating or ponding waste waters. These limits, plus a fecal coliform limit, are recommended for 1977. The same limits plus limitations on ammonia are recommended for new sources. The limits for ammonia and phosphorus are recommended for new sources. The nutrient limits for new sources represent limits being met by the majority of plants with the best treatment systems. It is estimated that there will be about $2.1 million ------- in capital costs required to achieve the 1977 limits by the industry. For 1983, effluent limits were determined as the best achievable in the industry for BOD5, suspended solids, ammonia, and phosphorus. It is estimated that the cost to achieve the 1983 limits by the industry will be $8.9 million. The 1977 cost for the industry represents about 7 percent, and the 1983 cost approximately 30 percent of the $30 million spent by the industry in 1972 on new capital expenditures. It is also concluded that, where suitable and adequate land is available, land disposal is a more economical option for meeting discharge limits, particularly for small plants. ------- SECTION II RECOMMENDATIONS Limitations recommendations for discharge to navigable waters by rendering plants for July 1, 1977 are based on the characteristics of well operated secondary treatment plants being used by the industry. The limitations are for 5-day biochemical oxygen demand (BOD5) , suspended solids, grease, and fecal coliform. These limitations are 0.15 kg BOD5/kkg raw material (RM); 0.17 kg SS/kkg RM; 0.10 kg grease/kkg RM; and 400 counts fecal coliform/100 ml. Adjustments in the BOD5 and SS limitations are provided for plants curing hides. Recommended New Sources Standards include the 1977 limitations plus limitations on ammonia (NH3J, nitrites and nitrates (NO2~ NO3) , and total phosphorus (TP). The additional limitations are also based on the performance characteristics of well operated secondary treatment plants. These additional limitations are: 0.17 kg NH3 as N/kkg RM; and 0.05 kg TP/kkg RM. Limitations recommended for the industry for 1983 are considerably more stringent and are based upon the performance characteristics of the best operated secondary treatment systems being used to treat rendering waste waters. These limitations include the same pollutant parameters as included in the new source standards plus a limitation on the total Kjeldahl nitrogen (TKN) and on pH range. The 1983 limitations are: 0.07 kg BOD5/kkg RM; 0.10 kg SS/kkg RM; 0.05 kg grease/kkg RM; 0.02 kg NH3 as N/kkg RM; 0.05 kg TP/kkg RM; a pH range of 6.0 to 9.0; and a fecal coliform count of 400/100 ml. Again, adjustments in the BOD5 and SS limitations are provided for plants curing hides; however, these adjustments are smaller than those for the 1977 limitations. ------- SECTION III INTRODUCTION PURPOSE AND AUTHORITY Section 301(b) of the Federal Water Pollution Control Act Amendments of 1972 (the Act) requires the achievement by not later than July 1, 1977, of effluent limitations for point sources, other than publicly owned treatment works, which are based on the application of the best practicable control technology currently available as defined by the Administrator pursuant to Section 304 (b) of the Act. Section 301(b) also requires the achievement by not later than July 1, 1983, of effluent limitations for point sources, other than publicly owned treatment works, which are based on the application of the best available technology economically achievable which will result in reasonable further progress toward the national goal of eliminating the discharge of all pollutants, as determined in accordance with regulations issued by the Administrator pursuant to Section 304(b) of the Act. Section 306 of the Act requires the achievement by new sources of a Federal standard of performance providing for the control of the discharge of pollutants which reflects the greatest degree of effluent reduction which the Administrator determines to be achievable through the application of the best available demonstrated control technology, processes, operating methods, or other alternatives, including, where practicable, a standard permitting no discharge of pollutants. Section 304(b) of the Act requires the Administrator to publish regulations providing guidelines for effluent limitations setting forth the degree of effluent reduction attainable through the application of the best practicable control technology currently available and the degree of effluent reduction attainable through the application of the best control measures and practices achievable including treatment techniques, process and procedure innovations, operation methods and other alternatives. The regulations proposed herein set forth effluent limitations guidelines pursuant to Section 304(b) of the Act for the independent renderers sutcategory of the meat products point source category designated in Section 306. Section 306 of the Act requires the Administrator, within one year after a category of sources is included in a list published pursuant to Section 306 (b) (1) (A) of the Act, to propose regulations establishing Federal standards of performance for new sources within such categories. The Administrator published in the Federal Register of January 16, 1973 (38 F.R. 1624) a list of 27 source categories. Publication of the list constituted announcement of the Administrator's intention of establishing the off-site rendering plants engaged in the manufacture of animal ------- and marine fats and oils source category, which was included in the list published January 16, 1973. SUMMARY OF METHODS USED FOR DEVELOPMENT OF THE EFFLUENT LIMITATIONS GUIDELINES AND STANDARDS OF PERFORMANCE The effluent limitations guidelines and standards of performance proposed herein were developed in the following manner. The point source category was first studied for the purpose of determining whether separate limitations and standards are appropriate for different segments within a point source category. This analysis included a determination of whether dif- ferences in raw material used, product produced, manufacturing process employed, equipment, age, size, waste water constituents, and other factors require development of separate effluent limitations and standards for different segments of the point source category. The raw waste characteristics for each segment were then identified. This included an analysis of (1) the source and volume of water used in the process employed and the source of waste and waste waters in the plant; and (2) the constituents (including thermal) of all waste waters including toxic constituents and other constituents which result in taste, odor, and color in water or aquatic organisms. The constituents of waste waters which should be subject to effluent limitations guidelines and standards of performance were identified (see Section VI). The result of this analysis was that there was no reason for separate limitations and standards for different segments of the industry. The full range of control and treatment technologies existing within the point source category was identified. This included identification of each distinct control and treatment technology, including an identification in terms of the amount of constituents (including thermal) and the chemical, physical, and biological characteristics of pollutants, and of the effluent level resulting from the application of each of the treatment and control technologies. The problems, limitations and reliability of each treatment and control technology and the required implementation time was also identified. In addition, the nonwater-quality environmental impact, such as the effects of the application of such technologies upon other pollution problems, including air, solid waste, noise and radiation were also identified. The energy requirements of each of the control and treatment technologies were identified as well as the cost of the application of such technologies. The information, as outlined above, was then evaluated in order to determine what levels of technology constituted the "best practicable control technology currently available," "best available technology economically achievable," and the "best available demonstrated control technology, processes, operating methods, or other alternatives." In identifying such technologies, various factors were considered. These included the total cost of application of technology in relation to the ------- effluent equipment and facilities involved, the process employed, the engineering aspects of the application of various types of control techniques, process changes, nonwater-quality environmental impact (including energy requirements) and other factors. The data for identification and analysis were derived from a number of sources. These sources included Refuse Act Permit Program data; EPA research information; data and information from North Star files and reports; a voluntary questionnaire issued through the National Renderers Association (NRA); qualified technical consultants; and on-site visits and interviews at several exemplary rendering plants in various areas of the United States. Questionnaires provided information on 49 plants; 12 of these were also included in the field sampling survey. Two other plants that did not submit questionnaires were also sampled. Thus, the total number of plants included in this study was 51, or about 11 percent of the off-site rendering industry. All references used in developing the guidelines for effluent limitations and standards of performance for new sources reported herein are included in Section XIII of this document. GENERAL DESCRIPTION OF THE INDUSTRY The off-site rendering industry falls within industry No. 2077, Animal and Marine Fats and Oils.1 SIC 2077 includes; "Establishments primarily engaged in manufacturing animal oils, including fish oil and other marine animal oils and fish and animal meal; and those rendering inedible grease and tallow from animal fat, bones, and meat scraps. Establishments primarily engaged in manufacturing lard and edible tallow and stearin are classified in Group 201; those refining marine animal oils for medicinal purposes in Industry 2833; and those manufacturing fatty acids in Industry 2899. "Fish liver oils, crude Oil, neat's-foot Fish meal Oils, animal* Fish oil and fish oil Oils, fish and marine animal: herring, meal menhaden, whale (refined), sardine Meat meal and tankage* Rendering plants, grease and tallow* Neat's-foot oil Stearin, animal: Inedible" Oil and meal, fish *The off-site rendering industry covered in this report includes only meat-meal and tankage; oils, animal; and rendering plants, grease and tallow. Rendering is a process to convert animal by-products into fats, oils, and proteinaceous solids. Heat is used to melt the fats out of tissue, to coagulate cell proteins and to evaporate the raw material moisture. Rendering is universally used in the production of proteinaceous meals from animal blood, feathers, bones, fat tissue, meat scraps, inedible animal carcasses, and animal offal. The rendering industry consists of off-site or 7 ------- independent Tenderers and on-site or captive renderers. The independent renderers reprocess discarded animal materials such as fats, bones, hides, feathers, blood, and offal into saleable by-products, almost all of which are inedible for human consumption, and "dead stock" (whole animals that die by accident or through natural causes). Captive rendering operations, on the other hand, are usually conducted as an adjunct to meat packing or poultry processing operations and are housed in a separate building on the same premises. consequently, captive renderers produce almost all of the edible lard and tallows made from animal fats in addition to producing inedible by-products. Two usual process differences between rendering edible or inedible materials are the composition and freshness of the materials, and, second, the process used. Edible rendering requires fresh (inspected) fats and usually is conducted by a wet or low temperature process. These processes do not evaporate raw material moisture during cooking, and therefore require an additional step to separate water from the edible products. Inedible rendering is accomplished exclusively by dry rendering where the raw material is cooked with no addition of steam or water. Rendering of animal by-product materials is one of the original recycling industries; it began as an industry over 150 years ago. During the past two decades the production of inedible tallow and grease (the major products of rendering plants) has increased from 2.3 billion pounds, worth $150 million in early 1950, to an estimated 5.4 billion pounds, worth $430 million for 1971-72.2 This increase is largely caused by an expansion in livestock and poultry production. The increase resulting from increased plant efficiency is negligible. The United States is the world's leading producer, consumer, and exporter of tallow and grease. Since the early 1950's, the United States has accounted for 55 to 60 percent of the world's tallow and grease output. The export market has been the largest single outlet for inedible tallow and grease, consuming about 50 percent of the domestic output. Table 1 lists the various markets for inedible tallows and greases and shows the current use of tallow and grease in both soap and fatty acid manufacturing to be about one-half of that for animal feeds. It also shows that between 1960 and 1970 there was a slight decrease in their use for soap manufacturing, which is more than offset by a 2.5 times increase in their use for animal feeds. Off-site renderers send out trucks daily on regular routes to collect discarded fat and bone trimmings, meat scraps, bone and offal, blood, feathers, and entire animal carcasses from a variety of sources: butcher shops, supermarkets, restaurants, poultry processors, slaughterhouses, and meat packing plants, farmers and ranchers. Each day the rendering industry, including both on-site and independent plants, processes more than 80 million pounds of animal fat and bone materials, in addition to dead stock, that would otherwise have to be suitably disposed of to prevent its becoming a national public health problem.3 ------- Table 1. Inedible Tallow and Greases: Use, By-Products, 1960-1970^ Year Beginning October 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970* Soap 732 702 688 660 690 649 665 631 637 601 615 Animal Feeds Fatty Acids 443 732 774 861 714 855 972 990 1061 1093 1140 351 402 433 478 530 575 547 576 585 610 568 Lubricants and Similar Oils Million Pounds 70 79 78 91 102 107 98 89 98 97 89 Other Exports 151 177 151 230 203 208 283 291 289 320 214 1769 1710 1738 2338 2155 1962 2214 2212 2009 2051 2591 Total 3516 3802 3862 4658 4394 4356 4779 4789 4679 4772 5217 *Preliminary data; based on census reports, ------- The independent renderer pays for the raw material he collects and he manufactures usable products, such as tallow for soap^and for derivatives for the chemical industry, and meal and inedible grease for animal and poultry feed. Because of the perishable nature of the raw material collected, renderers must process the material without delay. This normally restricts the collection area to a 150-mile radius around the plant. However, if the renderer is only picking up restaurant grease, which is more stable, it is possible that he may travel greater distances. Off-site renderers are located in both urban and rural areas. The urban renderer normally has more modern equipment, shorter routes for pick-up of raw materials, a better grade of raw materials, and high production rates that enable his operation to run more efficiently. The urban renderer usually has access to municipal sewer and has the option of either providing his own treatment system or buying into the municipal plant. The country renderer, on the other hand, normally has older equipment, longer routes, picks up dead stock, and has a lower capacity system. The location of the rural renderer does not permit him to tie into a sewer facility and, therefore, he normally has his own waste treatment facilities. Figure 1 provides a general idea of the distribution of all rendering plants throughout the country; it includes both edible and inedible rendering plants, on-site as well as independent. Also, fish rendering plants are included in the state totals. Judging from Figure 1, the number of rendering facilities is greatest in the central states. However, the National Renderers Association indicated that production from facilities along the Atlantic seaboard equals that from facilities located between the Appalachian Mountains and the Rockies. Data from the 1967 Census of Manufactures* is summarized in Table 2. These data provide some information regarding the size of existing rendering plants. However, since the data reflect only 69 percent of the industry, the distribution of plant sizes should be considered only approximate. Plants range in size from small operations employing one to four men with annual sales of about $100,000 to large operations employing over 100 men with sales from $5 to $10 million. An average plant could be characterized as employing 23 men and having annual sales of approximately $1 million. Judging from our recent observations of the industry, it would appear that these figures are no longer correct, since many companies have consolidated their plants and installed more modern gear with larger capacities. However, because we measured size not by products, but rather by amount of raw material handled, it is difficult to make an exact comparison. In any event, based on the assumption that the average size plant is as found in this study—a plant handling 59,000 kg (130,000 pounds) per day of raw material—and based on average yield values and on current market prices, the average plant would have annual sales of about $1.5 million. 10 ------- Figure 1. Distribution of Rendering Plants by State2 ------- As of 1968 -there were 770 firms operating in 850 facilities engaged in the rendering of inedible animal matter.2 Of this number, some 460 were operated by independent renderers (off- site) , 330 were controlled by the meat packing and poultry industries (on-site), and the remainder were owned by a variety of concerns. It is estimated that some 275, or about 83 percent, of the plants controlled by the meat industry are also involved in edible rendering. The industry estimates that the number of independent Table 2. Statistics by Employment Size of Establishment, 1967^ Establishment With an Average of: 1 to 4 employees 5 to 9 employees 10 to 19 employees 20 to 49 employees 50 to 99 employees 100 to 249 employees TOTALS Number of Establishments 132 103 127 157 51 18 588 Number of Employees 300 700 1800 4800 3500 2600 13,700 Value of Shipments (millions of dollars) 12.0 27.9 62.2 207.1 117.1 131.0 557.9* *Total value of shipments from all sources. renderers is now 450 or less, and they expect an additional 50 plants, primarily small, to close because of the economic impact on capital investment caused by enforcement of new air and water pollution standards.5 This conclusion is based on the argument that, because tallow and protein meal products from rendering plants must compete on the open commodity market, pollution control costs can not be passed off to the consumer as is done in the other industries where prices are raised to absorb these costs. PROCESS DESCRIPTION A general flow sheet of the processes of a typical inedible, independent rendering plant is shown in Figure 2. (A general flow sheet for edible rendering would be similar.) The bulk material (offal, bones, and trimmings) collected by independent renderers is normally dumped into a pit from which it is conveyed 12 ------- to a grinder. Liquid wastes collected on the bottom of the pits are usually sewered, although in a few cases the liquid, if not an excessive amount, is pumped on top of the materials being conveyed to the grinder or the cooker. In the case of poultry offal, it is not always necessary to grind the raw material before cooking unless it contains a large number of whole birds. Feathers, if they are not mixed with poultry offal, are dumped directly on a floor to allow excess liquid to drain off. Off- site rendering plants normally process feathers separately from poultry offal. Oils are poured into receiving tanks and from there go directly to cookers. The process of rendering consists of two essential steps. First, the raw material is heated or cooked to melt the tallow or grease and permit the phases to separate and, in the dry inedible process, to evaporate the moisture. Also, the animal fibrous tissues are conditioned. The second step is a separation of tallow or grease from the solid proteinaceous material. Proper conditioning of the fibrous tissue is important to accomplish the second step efficiently. In edible rendering little, if any, of the raw material moisture is evaporated; the cooking is normally conducted at a lower temperature (49°to 82°C, or 120° to 180°F) to improve the quality of the grease and tallow. However, since this is done almost exclusively by on-site renderers, it will not be discussed in great detail in this report. The product yields and process control of the cookers are very dependent on the nature of the raw materials., For example, the moisture content of raw materials ranges from 20 percent moisture for beef fats to 87 percent moisture for blood. Tables 3 and 4 give the percentage of yield of a number of common materials processed by independent rendering plants. The percentage of moisture, of course, can be calculated by subtracting the total percentage of yield of fat and solids from 100 percent. Additional information on the amount and type of animal by- products processed for various animal sources and on product yields can be found in reference 6 which is also the source of the information presented in Tables 3 and 4. INEDIBLE RENDERING Batch System Note: Throughout the discussion of production methods and concepts which follows, the use of trade names is included as necessary to facilitate the explanations presented and understanding by the reader. Use of such trade names, however, should in no way be construed as a product endorsement or recommendation by the U. S. Environmental Protection Agency. Batch rendering, a dry process, is a cooking and moisture- evaporation operation performed in a horizontal steam jacketed cylindrical "cooker" equipped with an agitator. It is referred 13 ------- Table 3. Raw Material and Product Yields for Inedible Rendering by Type of Animal By-Products from Animals Steers Cows Calves Sheep Hogs Broilers (offal & feathers) Offal and Bone per Head, kg (lb) 41-45 (90-100) 50-57 (110-125) 6.8-9.1 (15-20) 3.6-4.5 (8-10) 4.5-6.8 (10-15) 0.45 (1) Tallow and Grease, Percent 15-20 10-20 8-12 25-35 15-20 4 Cracklings at 10-15% Fat, Percent 30-35 20-30 20-25 20-25 18-25 26 Table 4. Product Yields for Inedible Rendering by Type of Raw Material6 By-Products from Materials Shop fat and bones Dead cattle Dead cows Dead hogs Dead sheeu Poultry offal (broiler) Poultry feathers Blood Tallow and Grease , Percent 37 12 8-10 30 22 14 — — Cracklings at 10-15% Fat, Percent 25 25 23 25-30 25 4 12 (meal) 12-14 (meal) 14 ------- PROCESSES WASTE WATER DRYING RAW MATERIAL RECOVERY CRUSHING AND GRINDING COOKING AND MOISTURE REMOVAL LIQUID -SOLID SEPARATION LIQUID I MEAL GRINDING j AND SCREENING BLENDING SOLIDS MEAL STORAGE SHIPPING HIDE CURING GREASE CLARIFYING GREASE STORAGE SHIPPING ODOR CONTROL VAPOR CONDENSING __ _.J PLANT AND TRUCK WASHING 1 MATERIAL RECOVERY SYSTEM T SANITARY FACILITIES TREATMENT SYSTEM •WASTE WATER FLOW •*- PRODUCT AND MATERIAL FLOW Figure 2. General Flowsheet of Operations for a Typical Inedible Rendering Plant 15 ------- to as a dry rendering process because the raw material is cooked with no addition of steam or water and because the moisture in the material is removed from the cooker by evaporation. It. is a batch process because it follows the repetitive cycle of charging with raw material, cooking under controlled conditions, and finally discharging of the material. A typical modern batch rendering process is illustrated schematically in Figure 3. Although only one cooker is shown, the usual installation will have from three to ten cookers. Before charging the dry batch cookers, the raw material is usually reduced in size by crushers (sometimes called grinders, prebreakers, or hoggers) to a size of one to two inches to provide for efficient cooking. Cooking normally requires 1.5 to 2.5 hours, but may run as long as 3.5 to 4 hours. The cookers are charged with raw material by either a screw conveyor or by blowing the material in under pressure from a "blow tank." The raw materials used are quite variable, depending on the source, and adjustments in cooking time, temperature, and speed of agitation are usually required to properly process the material. For example, shop fat and bone from butcher shops may yield 37 percent tallow and have an initial moisture content of only 40 percent; dead beef cattle, when processed, may yield only 12 percent tallow and have an initial moisture content of 63 percent. Then again, poultry feathers, which yield no grease, and may have an initial moisture content of 75 percent, require cooking under pressure (about 3.7 atmospheres or 40 psig) for 30- 45 minutes in a batch cooker for hydrolysis, prior to cooking under normal or atmospheric pressure for an additional 30-40 minutes to reduce the rroisture content to 40-50 percent. Finally, the feathers are dried in a rotary or ring dryer to reduce the moisture content to 5 percent. The general practice in determining the end point of the cooking operation is by previously established cook cycles and by periodic withdrawal of samples by the operator to determine the consistency by touch of the cooked material. A less frequently used method is to measure the moisture content of the material with an electrical conductivity device, but this approach has not been generally successful; it is ineffective when cooking blood or a variety of other materials. Temperature is used to follow the progress of the cooking. The temperature of the material being processed remains substantially constant until the moisture level has dropped to 5 to . 10 percent. At this point the temperature begins to rise rather rapidly and the cooking process should then be stopped to prevent product degradation and odor problems. Throughout the cook, the jacket stream pressure usually is maintained constant, between 2.7 and 6.1 atmospheres (25 and 75 psig), although a few use a pressure as great as 7.8 atmospheres (100 psig) or a temperature of 170°C (334°F). The cooked material is discharged from the batch cooker into a percolation pan and let stand until all free-draining fat has run off. The solids are then conveyed to a press (usually screw 16 ------- Dead Stock Carcasses I Shop Fat and Bone RAW MATERIAL RECEIVING ENTRAPMENT SEPARATOR Exhaust Vapor CRUSHER Steam - 25-75 PS I • •u -r~i (fir"! II COOKER V fl II / Jacket Condensate —/ PRECOAT LEAF FILTER CENTRIFUGE Solids to Screw Press PERCOLATOR — DRAIN PAN Figure 3. Batch Cooker Rendering Process ------- press) to further reduce the fat content. Finally, the solids are conveyed to grinding and screening operations. Prior to ten years ago, essentially all inedible rendering at independent rendering plants was conducted using the dry batch cookers. In recent years, however, a number of plants have replaced batch cookers with continuous systems because these systems offer inherent advantages: improved product quality control; better confinement of odor and fat aerosol particles within the equipment, thereby requiring less cleanup; less space; and less labor for operation and maintenance. Also, continuous systems permit increased throughput and occasionally result in consolidation of two or more plants. It is currently estimated, however, that 75 to 80 percent of the plants still use dry batch cookers. The percentage of batch cookers is expected to continue to decrease in the near future for economical reasons, but it is very doubtful that it will ever be entirely replaced by continuous systems. This is because most small plants could not afford continuous sytems and because some materials such as feathers and fclood are better handled in a dry batch system. Continuous Systems Continuous rendering systems, as mentioned above, have replaced some batch systems. A continuous system has the ability to provide an uninterrupted flow of material and to produce a product of more constant quality- In addition, the residence time in some continuous systems is much less than in batch systems, ranging between 30 and 60 minutes; as a result of less exposure to heat, product quality is improved. An inherent disadvantage of the continuous system is that when a component breaks down, the entire plant is shut down. Hence, it is important that a thorough preventive maintenance program be rigidly followed to keep the plant in operation. Unlike batch systems, the manufacturers of continuous systems do not use the same basic design. Currently there are at least three major manufacturers of continuous systems being used by independent renderers. These three companies are the Duke continuous system, manufactured by the Dupps Company; the Anderson C-G (Carver-Greenfield) system, manufactured by Anderson-Ibec; and the Strata-Flow System manufactured by Albright-Nell Co. Duke Rendering System The Duke System was designed to provide a method of cooking similar to that of batch systems except that it operates continuously. This system is illustrated in Figure 4. The cooker, called the Equacooker, is a horizontal steam-jacketed cylindrical vessel equipped with a rotating shaft to which are attached paddles that lift the material and move it horizontally through the cooker. Steam-heated coils are also attached to the 18 ------- shaft to provide increased heat transfer. The Equacooker con- tains three separate compartments which are fitted with baffles to restrict and control the flow of materials through the cooker. The feed rate to the Equacooker is controlled by adjusting the speed of the variable speed drive for the twin screw feeder; this establishes the production rate for the system. The discharge rate for the Equacooker is controlled by the speed at which the control wheel rotates (see Figure 4). The control wheel contains buckets similar to those used in a bucket elevator that pick up the cooked material from the Equacooker and discharge it to the Dranor. Next to the control wheel is located a site glass column which visually shows the operating level in the cooker. A photoelectric cell unit is provided to shut off the twin screw feeder when the upper level limit is reached. The Drainor performs the same function as a perculator pan in the batch cooker process. It essentially is an enclosed screw conveyor that contains a section of perforated troughs allowing the free melted fat to drain through as the solids are conveyed to the Pressor or screw press for additional separation of tallow. The Pressor is similar to any other screw press used along with a batch cooker to reduce the grease level of the crackling. A central control panel consolidates the process controls for the Duke system. The control panel houses a temperature recorder, steam pressure indicators, equipment speed settings, motor load gages, and stop and start buttons, allowing one person to operate the Equacooker part of the Duke system. C-G (Carver-Greenfield) Continuous System The C-G continuous process is of a considerably different design than the Duke system. Figure 5 is a schematic diagram of a one- stage evaporator C-G system. In the C-G system, the partially ground raw material is fed continuously by a triple screw feeder at a controlled rate to a fluidizing tank. Fat recycled through the C-G system at 104°C (220°F) suspends the material and carries it to a disintegrater for further size reduction—the final range is from about one inch to 1/4-inch pieces. This slurry is then pumped to an evaporator. The evaporator can be a single or double-stage unit, and is held under vacuum. The vacuum, which facilitates moisture removal, allows the C-G system to operate at a lower temperature than some other systems. The evaporator system is basically a vertical shell-and-tube heat exchanger connected to a vacuum system. The slurry of solids and fat flows by gravity through the tubes of the heat exchanger (evaporator), while steam is injected into the shell. The water vapor is then separated from the slurry in the vapor chamber, which is under a vacuum of 660 to 710 mm (26 to 28 inches) of mercury. Water vapor then passes through a shell and tube condenser connected to a steam-ejection vacuum system. The condensed vapors are removed from the condenser through a barometric leg, which helps maintain 19 ------- VAPOR CONTROLLER RAW MATERIAL BIN MAGNET TWIN SCREW FEEDER -a ENTRAINMENT SEPARATOR Vapor Inlet Air Inlets Pump c PU4 Condensing Tubes Water Spray Nozzles Blower NON- Condensables INCIN- ERATOR i i I 0 Condensate to Sewer p pin nip a CONTROL Vent WHEEL Fat Drainer Steam to Coils EQUACOOKER D TUT1 D!D n! D D T CENTRIFUGE I I I Solids I FAT STORAGE VARI-SPEED Vent Steam to Jacket Blower Meal Cake to Grinding Press Fat Figure k. Continuous Cooker - Duke Process ------- the vacuum in the system. In the case of a two-stage evaporator system, the vapor evaporated from the second stage serves as a heating medium for the first stage. Two-stage evaporators provide steam economy, and are especially useful for raw materials with a high moisture content. The dried slurry of fat and cracklings is then pumped from the evaporator to a centrifuge which separates the solids from the liquid. Part of the fat is removed from the system at this point, while the remainder is recycled back to the fluidizing tank. The solids discharged from the centrifuge are screw conveyed to expellers (screw presses) that reduce the fat content of the solids from about 26 percent by weight to 6 to 10 percent. A central control panel allows one operator to control the entire cooking process. Level indicators and controls are provided to stabilize the flow through the fluidizing and other process tanks and also for the vacuum chamber. Evaporator vacuum and temperature are also monitored. Equipment speed settings, motor current readings and start/stop push buttons are also located on this panel. Strata-Flow Continuous System The third system, ANCO-Hormel Strata-Flow continuous system, manufactured by the Albright-Nell Company, is basically a series of batch cookers stacked one above the other. Normally five or six stages are provided in series. Each cooker stage is vented to a common manifold that is connected to a condenser for removing vapors. The crushed raw material from the prebreaker is blown continuously to the first stage cooker. This eliminates screw conveying and pumping of the raw material. The cooked material discharges from the last stage to a percolation pan called an Autoperc. A drag conveyor located in this pan continuously removes material after the free run fat has drained off. EDIBLE RENDERING Edible rendering is estimated to be conducted by less than two percent of the independent renderers.7 However, these plants do both edible and inedible rendering, and probably less than one percent of the raw material handled by independent renderers is used for edible rendering. Edible rendering of inspected fats can be conducted by either a wet or a low-temperature process. The wet process is conducted in a vertical tank with injection of live steam under a pressure of about 3.7 atmospheres (40 psig) and a large volume of "tank water," which should be evaporated. The quality of the lard and tallow thus produced is quite low. For this reason, this once common process is rarely used any more and no independent rendering plants surveyed in this study use the wet rendering 21 ------- Water rv> ro EVAPORATOR •+ DISINTEGRATOR PREBREAKER AFTER CONDENSER CENTRIFUGE VAPOR CHAMBER FLUIDIZING TANK Expeller Vent Vent Discharge Pump Fluidizing pump Recirculation Pump Expeller Cake to Grinding Recycle Fat at 200" Fahrenheit Recycle Pump Expeller Fat To Fat Storage lire 5 . Corxtituj-ou-s Cookeir "by Carrie.!? — Careen, field Process ------- process. Low-temperature rendering of fats is the most commonly used method for edible rendering. Fats, after being finely pulverized in a grinder, are placed in a melter and heated to a temperature of 49° to 82°C (120° to 180°F) . When the cooking temperature is maintained at or below 49°C (120°F), the cracklings or solids may also be used as an edible product. Cooking at these low temperatures does not evaporate the raw material moisture. Hence, after the fat has separated from the solids and water in the melter, the cooked material is desludged by screening or centrifuging. The water phase is also separated during desludging. The remaining water entrained in the hot fat is then removed in a second centrifuge. The separated water, called tank water, can be further evaporated to a thick material known as stick, which can be used as tankage for inedible rendering. The general practice in either wet or low temperature edible rendering is to directly sewer the tank water. However, this is a poor practice from a pollutional standpoint because tank water can have a BOD5 of anywhere from 30,000 to 45,000 mg/18 and a grease value as high as 20,000 to 60,000 mg/1. If, instead, the tank water is evaporated and the stick used for tankage, the water waste load from wet-or low-temperature rendering would be similar to that from a dry process. COOKER USES AND PROCESS VARIATIONS The type of inedible cooker chosen—batch or continuous—is in some instances very dependent upon the material handled and, of course, on the size of the plant. Poultry feathers and hog hair, for example, are handled in most plants in batch systems. This is because these materials must first be cooked under pressure of about 4.4 atmospheres (50 psig) to hydrolize the proteinaceous material (primarily keratin) to usable protein before being cooked and dried in the same way as other materials are in a batch system. A continuous processing system is now available for materials that require hydrolysis, such as feathers, in which the material passes through a hydrolyzer and then into a cooker. Blood is another material normally handled in batch cookers. However, in some cases, the final drying and conditioning of blood, feathers, and hog hair is carried out in a ring or rotary dryer. This method of drying following batch cooking permits a higher production rate for a plant with a given number of batch cookers. This is because of poor heat transfer during the later stages of drying in batch cookers as the material passes through a "glue stage." In a few cases, blood is processed by steam sparging, which coagulates the albumin; then the albumin and fibrin are separated from the blood water by screening and are processed in a batch cooker or ring dryer. The blood water, which can have a BOD5 up to 16,000 mg/1, is usually sewered. The ring dryer system, as the name implies, is in the shape of a flattened ring or race track, positioned vertically. The 23 ------- material to be dried is first pulverized and then blown into the ring where it is conveyed around the ring by furnace gases of 314° to 425°C (600° to 800°F). Centrifugal force, recirculation rates, and control dampers permit the material to recirculate until the particles of the material become light enough because of drying to escape along with the exhaust gases. A cyclone separates the material from the exhaust gases, which are conveyed away by an exhaust fan. This exhaust fan is necessary to ensure a slight negative pressure in the ring dryer and thus to prevent material from leaking out of the dryer. The high temperature of the furnace gases can cause scorching of the proteinaceous material, resulting in strong odors. Consequently, the exhaust gases are frequently ducted through a spray scrubber. Rotary (air) dryers are also used to further dry blood, feather and hoghair meals. The dryer is a horizontal cylindrical vessel equipped with longitudinal steam tubes. The material cascades through the dryer as it rotates. Rotary dryers create less of an odor problem than ring dryers because of the lower temperatures involved and the lower volumes of air required for drying. VAPOR CONDENSING Cooking vapors from dry batch processes and also from evaporating tank water are condensed by one of three methods: barometric leg, air condenser, and shell-and-tube heat exchanger. Prior to five or ten years ago, all vapors were condensed with the use of a barometric leg. In a barometric leg, the cooking vapors are contacted with condensing waters and together flow gravimetrically out through a standpipe. A barometric leg condenser is basically a water- powered ejector located on top of a standpipe. As the high velocity water passes through the ejector, it creates a vacuum on the downstream side. The vacuum draws the cooking vapors into the high velocity water where the vapors are cooled and condensed. The vacuum is usually very slight for batch cookers, whereas for several continuous systems using barometric leg condensers the vacuum may be quite high, thus requiring a long standpipe. The standpipe serves two purposes. First, it provides a confined space for contact between the vapor condensing water. Second, it acts as a reverse water trap. This prevents condensed vapors and cooling waters from being accidentally sucked back into a sealed cooker as it cools. To ensure against back-up even under a nearly perfect vacuum, the standpipe should be slightly over 10 meters (33 feet) high. This is because a one-atmosphere vacuum can lift water to a height of only about 10 meters. In general, it was observed that very few barometric leg condensers used in the industry are near 33 feet in height. However, a few plants with barometric legs protect against back-up by installing an air check valve in the standpipe. Hence, before a vacuum can lift water to the top of the standpipe, the air valve will open and reduce the vacuum. 24 ------- Air condensers and shell-and—tube heat exchangers are rapidly replacing the barometric leg for condensing water vapors. Probably the major reason for this is that air condensers and shell-and-tube heat exchangers do not dilute the waste waters. Barometric legs, on the other hand, highly dilute the waste waters resulting from the condensing of vapors. Usually a barometric leg is used on each batch cooker, and each requires 57 to 151 liters (15 to 40 gallons) per minute of water for condensing. In plants that are continuing to use barometric legs, the trend is to recycle treated or partially treated water through the barometric leg. Air condensers force ambient air across a bank of externally finned tubes. A typical unit has a horizontal section containing finned tubes, a steel supporting structure with plenum chambers and fan ring, axial-flow fan, drive assembly, and miscellaneous accessories such as louvers, fan guards, and temperature-operated fan speed controls. Shell-and-tube heat exchangers are basically cylindrical vessels containing a bundle of parallel tubes. The tubes are enclosed in such a manner that they isolate the liquid inside the tubes from the liquid surrounding the tubes. Normal flow arrangement is to have the condensate inside the tubes. The cooling water is recirculated through a cooling tower to dissipate the heat collected in condensing the cooking vapors. Water is continuously added to the cooling water to make up for that lost by evaporation. GREASE AND TALLOW RECOVERY Grease and tallow recovery is normally accomplished in two steps. The first step is draining in percolation or drain pans just after the material is dumped or removed from cookers. For batch systems, the material may be allowed to drain for up to two hours. This normally reduces the fat content of the solids to 25 percent. The second step in fat reduction involves the pressing of solids to reduce the residual tallow content to 6 to 10 percent. The usual practice is to use a screw press to allow for continuous throughput, although some small or old plants may still use hydraulic batch-operated presses. The screw press consists of a cylindrical barrel of metal bars that are spaced with narrow openings between to allow the fat to be squeezed through by the action of a rotating screw. Hence, the pressure within the screw press is maintained by friction and the fat present in the solids provides a lubricating effect. It is important that overpressing of the tallow from the solids be avoided; otherwise overheating and scorching can result in producing smoke and strong odors. Frequently, the smoke generated by screw presses is drawn through an odor control system that uses either wet scrubbing or incineration. In possibly one percent of the plants, the second step in grease and tallow reduction involves solvent extraction. In this 25 ------- process a solvent such as hexane is used to remove the excess grease. Heat is then required to separate the solvent from the grease and to remove it from the solids. The solvent is recovered for recycle. This process reduces the tallow and grease content of the solids to one percent or less. The increased income derived from the additional fat recovered by solvent extraction, however, is usually too small to encourage widespread use of solvent recovery. Tallow and grease recovered in the two steps of drainage and pressing are normally combined and then further clarified. This usually involves screening, centrifuging, or filtering, or combinations thereof. Solids recovered from clarification are returned to the cracklings prior to the second step of tallow and grease recovery. The tallow and grease are then pumped into storage tanks and held for later shipment. SOLIDS PROCESSING The solid proteinaceous material discharged from the screw press, known as cracklings, is normally screened and ground with a hammer mill to produce a meat and bone meal product that passes through a 10- to 12-mesh screen. The finely divided solids are usually stored in bulk handling systems for later shipment. Occasionally this material is blended with another, such as blood or feather meal, to ensure a high level of crude protein. Frequently, the blood and/or feather meal are bagged prior to shipment, although this operation is normally a relatively small one. ODOR CONTROL Odor control is practiced in nearly all rendering plants today. Although rendering odors are not necessarily harmful to health, they may be very offensive to people because of their distinct nature and the complexity of the odor compounds present. A recent study9 identified a number of odorous compounds present in rendering plant emissions. The important categories of compounds identified were sulfides, amines, aldehydes, ketones, alcohols, and organic acids. The major methods of odor control basically involve using scrubbers with or without chemical oxidant solutions (the most commonly used chemical is sodium hypochlorite) , and incinerators. Condensers and temperature control of cooking vapors involve rendering plant operations which should be adequately controlled to minimize odors. Excellent discussions of the control of odors from inedible rendering plants can be found in references 2 and 10. The primary sources of odor are from the cooking and pressing operations because, in both cases, the material is heated to temperatures of 105°C (220°F) or higher. Of course, aged or deteriorated raw materials will appreciably increase the intensity of odors from these operations. Furthermore, if the 26 ------- raw materials are not particularly fresh, it may be necessary to control this odor source by covering screw conveyors and venting them to the odor control system. The condenser plays a very important part in controlling odors from cookers. One of the best ways of controlling any odors from the cookers is to ensure that the final temperature of the condensed cooking vapors is below 52°C (125°F), or preferably below 38°C (100°F). In addition, the noncondensable vapors from the cooker, which give high-intensity odors, can be controlled by venting directly to the boiler used for generating the plant steam. This is feasible only under certain circumstances. If the odorous stream is used as primary combustion air, the necessary precautions must be taken to remove solid and fat aerosol particles before passing this air through the boiler and controls. Also, the boiler must be equipped with suitable burner controls to ensure that the minimum firing rate is sufficient to incinerate the maximum volume of effluent gas passing through the boiler firebox, regardless of the steam requirements. Press odors are treated by venting these vapors through a scrubber or incinerator. The intensity of the smoke and odor from the presses is occasionally high enough that the scrubbing water cannot be recycled. Using water without chemicals in a scrubber usually does not permit high recirculation rates, and thus requires large water use; the effect is that the waste waters from the plant are diluted. When chemicals such as sodium hypochlorite are used, it is normal to recycle up to 95 percent of the scrubber waters; this minimizes chemical and waste water treatment costs. Wasting five percent of chemical scrub water should not affect either the volume of the waste water or its treatability to any noticeable degree. Direct-fired incineration units could be used anywhere in place of the scrubber, although they are normally used only for low- volume high intensity odors. However, in recent months, the use of incinerators has been reduced drastically because of the difficulty in obtaining the necessary fuel. Even before there was difficulty in obtaining fuels, scrubbers were believed to be the most economical method of odor control.9 WASTE WATER SOURCES Waste waters from the rendering of raw materials contain the condensate or moisture evaporated from the raw materials and wash water from cleaning the plant and the raw materials pickup trucks. In some cases, the waste water contains additional condenser water and liquid drainage from the raw materials. The strength of these waste waters, which contain organic materials including soluble and insoluble protein, grease, suspended solids, and inorganic materials, can be greatly increased as a result of run-down and poorly maintained equipment. Also, poor housekeeping practices can result in accidental spills of raw and 27 ------- finished materials into the waste waters and the foaming over of material from the cookers. Trucks and barrels used for picking up raw materials are carefully washed after each use. The amount of water used for this is probably insignificant, although these operations can contribute significantly to the waste load, particularly to the grease load. Barrel washing, however, is not as common a practice as it once was in rendering plants, since most barrels are emptied at the pick-up site and are not brought to the plant. Barrels are primarily used to transport restaurant grease. Washdown in inedible rendering plants is not nearly as intensive as it is in meat processing and packing plants. In fact, washdown usually occurs at the end of a day's operation when rendering has been completed. Normally only the areas for receiving, grinding and cooking of raw materials and the product separating and grinding areas are washed down. The other areas of the plant are generally dry cleaned. Washdown does occur within the plant, however, whenever there is an accidental spill. Washdown of accidental spills without prior dry cleanup obviously adds significantly to the waste load from inedible rendering plants. The most common accidental spills observed, that were entirely cleaned up by washdown, were of tallow and grease. Fortunately, a properly operated materials recovery system (primary or in-plant treatment) can recover a large portion of these materials for recirculation to the cookers. MATERIALS RECOVERY Materials recovery from the waste water streams (primary or in- plant treatment) is conducted in essentially all rendering plants. The most common materials recovery system used by independent renderers is a catch basin or skimming device. Basically, this device is a large rectangular tank in the effluent stream to allow grease and oil to float to the surface and solids to settle to the bottom, thus separating them from the waste water. Grease and oil that float to the surface in catch basins are normally removed manually once or twice a day and blended in with the raw materials for recycling, or are processed separately. With automatic skimming devices, the materials may be collected for recycle once or twice a day or they may be continuously recycled using screw conveyor systems. Solids collected from catch basins are less frequently recycled; however, it is becoming more common practice today to occasionally pump out solids and recycle them through the rendering equipment. Some rendering plants (15 out of 49 plants included in the survey) have air flotation systems in place of catch basins or skimming devices. However, these systems are normally not operated under optimum conditions for either materials recovery or waste water treatment. Optimum conditions might require flow equalization, pH control, temperature control, and the addition 28 ------- of chemical flocculating agents. The temperature of rendering plant waste waters is often somewhere between 70° and 85°C (125° and 150°F), which is too high for effective grease removal by air flotation systems or by other gravity separation methods. At these temperatures, grease is too soluble in water for the required phase separation. Further, chemicals are not normally added to the air flotation system because the resulting sludge collected would be very high in water (85 to 95 percent) and, consequently, this excess water would add considerably to the heat load if recycled through the cookers. The addition of chemicals could also change the nature of the grease and thus lower its market value. One solution to this is to have two materials recovery systems in series, where the second one is an air flotation device to which chemicals have been added. HIDE CURING (ANCILLARY OPERATION) Hide curing occurs in a number of rendering plants, essentially as a separate operation from rendering. In many cases, slaughterhouses and packinghouses from which the renderers collect their material are either too small to handle hide curing or do not have the necessary equipment. Consequently, for the renderer to obtain these sources as users of his "services," he must also pick up the hides along with his raw materials. In addition, many rendering plants handling a large number of dead animals will find it economically favorable to remove the hides from dead carcasses for curing. The older method of curing hides was to dry pack hides in salt. However, in recent years the trend has been to replace this operation with brine curing in raceways Or brine vats. Essentially, the hide curing is a dehydration process, and in the brine-wring process there results a net overflow of approximately two to three gallons cf brine cure for each hide handled. These wastes are nearly saturated with salt and also contain other dissolved solids plus blood, tissue, and fats and oils. The overall contribution of this waste load to that from the rendering plant is usually relatively small. However, a high salt load can cause probleirs in the treatment of the waste waters and in some cases may make it very difficult for a plant to obtain a final chloride content that would meet some state and local regulations. A possible solution to this problem might be to blend the curing effluent with the raw material as it enters a dry cooker. 29 ------- SECTION IV INDUSTRY CATEGORIZATION CATEGORIZATION In developing effluent limitations guidelines and standards of performance for the independent rendering industry, a judgment was made as to whether limitations and standards are appropriate for different segments (subcategories) within the industry. To identify any such subcategories, the following factors were considered: o Waste water characteristics and treatability o Raw materials o Manufacturing processes (operations) o Processing equipment o Size, age, and location of production facilities. After considering all of these factors, no justification could be found for dividing the industry into subcategories. Hence, independent rendering constitutes only one subcategory, and the effluent limitations and standards of performance recommended in this report are intended to apply to all independent rendering plants except those processing fish by-products. An independent rendering plant is one that collects animal by- products such as bone, offal, fat, and dead animals from such sources as slaughterhouses, processing plants, butcher shops, restaurants, feed lots, and ranches, and processes them into products such as fats, oils, and solid proteinaceous meal. The products may be either edible or inedible. Plants processing fish by-products are not included in this study. In addition, rendering plants that are an adjunct to meat and poultry operations and are located on the same premises are not included in the category of independent renderers. An independent rendering plant may also cure hides as an ancillary operation. The manufacturing processes in an independent rendering plant are shown in Figure 6. RATIONALE FOR CATEGORIZATION Waste Water Characteristics and Treatability Basic processes in independent rendering plants are essentially the same, although such factors as equipment type, raw materials, and size and age of the plant may differ. Hence, it was possible to consider division of the industry on the basis of these factors which might group plants with similar raw waste water characteristics. The waste water characteristic used in 31 ------- BASIC PROCESSES ANCILLARY PROCESS RAW MATERIAL RECEIVING CRUSHING AND GRINDING COOKING AND DRYING PRODUCT SEPARATION MEAL GRINDING AND SCREENING GREASE CLARIFYING BLENDING STORAGE STORAGE SHIPPING SHIPPING HIDECU(RING Figure 6. Manufacturing Processes of a Rendering.Plant 32 ------- attempting to categorize (subdivide) the industry was the 5-day biochemical oxygen demand (BOD5) in units per 1000 units raw material (RM) handled or processed: kg BOD5/kkg RM (Ib BOD5/1000 Ib RM) . BOD5 provides the best measure of plant operation and treatment effectiveness among the parameters studied, and more data are available than for all ether waste parameters. Suspended solids, grease, and COD data serve to substantiate the conclusions developed from using BOD5 in characterizing both the industry and the raw waste (Section V). The raw waste was evaluated and is herein discussed as that waste water discharged subsequent to materials recovery operations—catch basins, skimming tanks, etc. The major plant waste load is organic and biodegradable: BOD5, which is a measure of biodegradability, is the best measure of the load entering the waste stream from the plant. Furthermore, because secondary waste treatment is a biological process, BOD5 also provides a useful measure of the treatability of the waste and the effectiveness of the treatment process. Chemical oxygen demand (COD) measures total organic content and some inorganic content. COD is a good indicator of change, but does not relate directly to biodegradation, and thus does not indicate the demand on a biological treatment process or on a stream. A number of additional parameters were also considered for use in categorization besides BOD5, suspended solids, grease and COD. Among these were nitrites and nitrates, Kjeldahl nitrogen, ammonia, total dissolved solids, total volatile solids, and phosphorus. In each case, data were insufficient to justify categorizing on the basis of the specified parameters; on the other hand, the data on these parameters helped to verify the judgments based on BOD5. Judging from secondary waste treatment effectiveness and final effluent limits, waste waters from all plants contain the same constituents and are amenable to the same kinds of biological treatment concepts. Geographical location, and hence climate, affects the treatability of the waste to some degree. All biological activity slows at lower temperatures; hence, biological waste treatment systems do not perform as well in the winter months in northern areas as they do when the weather is warm. Climate has occasionally influenced the kind of secondary waste treatment used. However, the ultimate treatability of the waste or the treatment effectiveness can be maintained at the highest levels by not discharging during the coldest months of the year. The time period for no discharge will vary with location, but should never exceed six months. This is the same practice that is used by plants that dispose of their waste water by irrigation. In the following parts of this section, the factors that were considered in categorizing the industry for the basis of raw waste water characteristics are examined. 33 ------- Raw Materials No clear relationship of direct statistical dependence between kind of raw material and raw BOD5 waste load could be found by statistical (multiple regression) analysis. As a result, a clear independent relationship was disclosed that all types of raw materials may be expected to result in similar BOD5 discharges. In addition, the range (low and high) and average of BOD5 waste water values for plants processing greater than 50 percent poultry by-products could not be differentiated from those plants processing less than 50 percent poultry by-products or from those for the total industry. This is illustrated by bar graphs in Figure 7. Hence, the type of raw materials processed is not a meaningful factor for categorization. Animal by-products were classified for the multiple regression analysis as: o Packinghouse (slaughterhouse) materials which are primarily animal offal o Shop fat and bones o Grease o Blood o Dead animals o Poultry offal o Feathers and hair The multiple regression analysis correlated the percent of raw material in each of these classes with the raw BOD5 load for each set of data. A total of 45 sets of data were included in the analysis, representing information on 29 independent renderers. There were several sets of information, up to three, for a number of these plants. The sources of this information were voluntary questionnaires distributed by the National Renderers Association, supplementary data supplied by the companies such as reports from consulting firms, and the results of our field sampling survey. Some questionnaire data represent the average of data over a period of several months; other data represent grab or composite values over short periods such as a day or two. The result of the regression analysis is best indicated by the multiple correlation coefficient. This turned out to be 0.39. The square of this number, or 0.16, is a measure of the predictability of the change in BOD5 load caused by a change in raw materials. In other words, 16 percent of a BOD5 load change could be accounted for by a change in raw materials. For the dependence between animal by-products and BOD5 load to be significant, the square of the multiple correlation coefficient should be greater than 0.5. The lack of dependence between BOD5 load and raw materials is somewhat surprising since the raw 34 ------- CO en CC LD Q O m 6.00 5.00 4.00 3.00 2.00 1.00 (29) (25) -MAXIMUM (4) -AVERAGE -MINIMUM TOTAL INDUSTRY < 50% POULTRY BY-PRODUCTS 2 50% POULTRY BY-PRODUCTS Figure 7. Average and Range of BOD5^ Data by Raw Material Type ------- materials in each of the classes have different initial moisture contents and product yields of solids and of tallow and grease. But then a simple regression analysis between BOD5 load and waste water flow, both expressed in units per 1000 units of raw material processed, also did not reveal a correlation. The correlation coefficient for this analysis was -0.027. Manufacturing Processes The manufacturing processes in independent rendering were shown in Figure 6. Those processes considered as basic—raw materials receiving, crushing and grinding, cooking and drying, product separation, meal grinding and blending, grease clarifying, and storage and shipping—are conducted in most plants. In a few cases, such as plants processing poultry byproducts (offal and feathers mixed together), the only product is meal, and no grease is separated and clarified. These plants may have more complex meal grinding and screening processes. The net result, based on field survey results, was that the basic manufacturing processes were found to further reiterate the single subcategory conclusion first discovered when analyzing raw materials. The ancillary manufacturing process (hide curing), however, can contribute additional waste to the plants' raw effluent when the waste load is only based upon the amount of raw material used for the basic manufacturing processes, as it is in this report. But to create a separate category for independent rendering plants that cure hides would not result in a separate set of fixed effluent standards. This is because the additional waste load caused by hide curing is dependent on the relative amounts of raw materials processed in the basic and ancillary manufacturing processes. The best way of accounting for the additional raw waste load caused by hide curing, therefore, is by the use of an adjustment factor. The adjustment factor for hide curing is presented in detail in Sections IX and X. In summary, then, the manufacturing processes, basic and ancillary, were not considered meaningful factors for categorization. Processing Equipment The processing equipment considered as factors for categorization were the type of cookers—batch versus continuous—and the type of condensers used for condensing cooking vapors—barometric leg, shell-and-tube, and air condensers. Other types of equipment such as grinders, presses, etc., were not considered because the basic operating principles were generally quite similar for each type of equipment, regardless of the manufacturer, and because the contribution to the waste water load from the use of this equipment was not significant. 36 ------- 6.00 (29) 5.00 4.00 to cc o> if) Q O 00 3.00 2.00 1.00 (17) -MAXIMUM (5) (4) -AVERAGE -MINIMUM TOTAL INDUSTRY BATCH SYSTEMS DUKE SYSTEMS C-G SYSTEMS Figure 8. Average and Range of BOD5_ Data by Cooker Type ------- 6.00 (29) 5.00 4.00 to oo cc en ^ if) Q O 00 3.00 2.00 1.00 — (5) (6) -MAXIMUM (14) -AVERAGE -MINIMUM TOTAL INDUSTRY BAROMETRIC CONDENSER SHELL & TUBE CONDENSER AIR-COOLED CONDENSER ------- Table 5. Raw Waste Data on Rendering Plants by Equipment Type Parameter BOD5 kg/kkg RM (lb/1000 Ib RM) SS kg/kkg RM (lb/1000 Ib RM) Grease kg/kkg RM (lb/1000 Ib RM) Equipment Type* Total Batch Duke C-G Baro S & T Air Total Batch Duke C-G Baro S & T Air Total Batch Duke C-G Baro S & T Air Number of Observations 29 17 4 5 6 14 6 26 14 4 5 3 14 5 16 9 2 5 2 9 4 Average Value 2.15 2.31 1.92 1.56 2.10 1.78 2.42 1.13 1.06 1.54 0.97 1.79 0.98 0.56 0.72 0.44 1.66 0.90 2.09 0.55 0.41 Standard Deviation 1.34 1.34 0.99 1.97 1.39 0.95 2.00 1.39 0.91 2.44 1.87 2.20 1.44 0.65 1.14 0.48 1.82 1.83 2.96 0.96 0.43 High Value 5.83 5.83 3.15 4.83 4.83 3.64 5.83 5.18 3.33 5.18 4.32 4.32 5.18 1.45 4.18 0.92 2.94 4.18 4.18 2.94 1.07 Low Value 0.10 0.72 1.07 0.10 1.20 0.10 0.72 0.03 0.03 0.05 0.06 0.39 0.05 0.03 0.00 0.00 0.37 0.04 0.00 0.04 0.04 *Values listed as: • Total represents the summary of combined data, regardless of equipment type. • Batch, Duke, or C-G summarizes the results of the data from plants with batch, Duke and Carver-Greenfield cookers, respectively. See Section III for a discussion of these cookers. • Baro, S & T, or Air summarizes the results of plants with barometric leg, shell and tube, or air condensers. 39 ------- Table 5 summarizes the raw waste data on independent rendering plants using various kinds of cookers and condensers for BOD5, suspended solids, grease, flow, and amount of raw materials handled. The data for the total industry are included in Table 5 for comparative purposes. Figures 8 and 9 graphically illustrate the average and range of the BOD5 data from Table 5 for the various cookers and condensers, respectively. These data show that there are no distinct raw waste water load differences when the data are grouped by the types of cookers and condensers used. Thus, it was concluded that the factor of process equipment proved consistent with findings regarding manufacturing process and substantially supported reasoning to designate a single category for the rendering industry. Size, Age, and Location of Production Facilities Size, age, and location are not meaningful factors for developing subcategories. Size as a factor was evaluated by a simple regression analysis between raw BOD5 waste load and the amount of raw material processed per day using the data collected in this study. This analysis revealed no discernible relationship between BOD5 waste load and size, as measured by the daily amount of raw materials processed. This is indicated by the value of the correlation coefficient, which was 0.062. It is necessary that a correlation coefficient value greater than 0.5 exist to establish a meaningful correlation. The same data were also separated into three data groups based on amount of raw material used. The data groups represented approximately equal numbers of plants. Analysis of the data in each of the groups showed no correlation of plant size with BOD5 waste load. Figure 10 shows the average and range values of BOD5 for the three size groups and for all the plants included in the study (indicated in Figure 10 by total). Age is often reflected by the type of processing equipment used. Plants over ten years old were originally equipped with batch cookers and barometric leg condensers. However, in recent years some older plants have replaced batch systems with continuous systems and barometric leg condensers with air or shell-and-tube condensers. Newer plants use both batch and continuous systems and also use shell-and-tube and air condensers more frequently than barometric legs. Therefore, the major difference, from a raw waste load standpoint between old and new plants is the type of processing equipment. Since processing equipment served to indicate a single discrete category, the close correlation between age of facilities and equipment means that age helps to reiterate this conclusion. Examination of the raw waste water characteristics relative to plant location reveals no apparent relationship or pattern. The type of animal by-products processes is soiretimes influenced by location, but as mentioned previously, the type of raw material processed had no discernible effect on raw waste. 40 ------- in D O m 6.00 — 5.00 — 4.00 3.00 2.00 1.00 (29) TOTAL INDUSTRY (10) (8) -MAXIMUM -AVERAGE -MINIMUM (11) <45,000 kg (<100,000 Ib) 45,000-114,000 kg (100,000-250,000 Ib) '114,000 kg >250,000 Ib) Plant Size: kg (Ib) of Raw Material Figure 10. Average and Range of BODs Values for Three Size Groups of Plants and for All Plants Studied (Total) ------- SECTION V WATER USE AND WASTE CHARACTERIZATION WASTE WATER CHARACTERISTICS Water is used in the rendering industry for condensing cooking vapors, plant cleanup, truck and barrel washing, odor control, and for boiler makeup water. The principal operations and processes in rendering plants where waste water originates are: o Raw material receiving o Condensing cooker vapors o Plant cleanup o Truck and barrel washing Waste waters from rendering plants contain organic matter (including grease), suspended solids, and inorganic materials such as phosphates, nitrates, nitrites, and salt. These materials enter the waste stream as blood, meat and fatty tissue, body fluids, hair, dirt, manure, hide curing solutions, tallow and grease, and meal products (such as meat, bone, blood, feathers, hair and poultry meal), and caustic or alkaline detergents. Raw Waste Characteristics The raw waste load characteristics from the rendering industry discussed in the following paragraphs include the effects of the materials recovery process (considered the primary waste treatment system such as catch basins and skimming tanks). The parameters used to characterize the raw effluent were the flow, BOD5, suspended solids (SS), grease, COD, total volatile solids (TVS), total dissolved solids (TDS), Kjeldahl nitrogen, ammonia, nitrates, nitrites, chlorides, and phosphorus. As discussed in Section IV, BOD5 is considered to be the best available measure of the waste load. The parameter used to characterize the size of the operations was the amount of raw materials processed. All values of waste parameters are expressed as kg/kkg of raw materials (RM), which has the same numerical value when expressed in lb/1000 Ib RM. Amount of raw materials processed is expressed in units of kkg RM. Table 6 summarizes the plant and raw waste water characteristics for the single category of independent rendering plants. The summary includes averages, standard deviations, ranges (high and low values), and number of observations (plants). 43 ------- The data used to compute the values presented in Table 6 were obtained through questionnaires distributed to their members by the National Renderers Association (NRA), through supplementary data submitted by the companies (such as laboratory analysis reports and consulting engineers' reports) , and through data obtained from the field sampling survey conducted by North Star. Questionnaires provided information on 49 plants; 12 of these were also included in the field sampling survey. Two other plants that did not submit questionnaires were also sampled. Thus, the total number of plants included in this study was 51, or about 11 percent of the industry. Note, however, that data were not available for all plants for all pertinent parameters; thus, the number of observations used to develop averages or other characteristics may not conform to the sample total even for such parameters as waste water flow or pounds of raw materials processed. The data in Table 6 for flow, raw materials, BOD5, suspended solids, and grease are primarily based on questionnaire data; data on the other variables were largely based on supplementary and field sampling information. Note also that while the sampling data generally verified questionnaire information, a number of atypical conditions esixted for four or five plants during the field visits which clearly caused unusual results for raw waste loads. The conditions included spills from cookers, emergency use of old equipment, and malfunctions of certain in-plant controls. Thus, the general waste load characteristics (for BOD5, TSS) were derived from submissions by the industry itself. Discussion of Raw Wastes The data in Table 6 cover a waste water flow of 467 to 80,936 1/kkg RM (56 to 9708 gal./lOOO Ib RM); a BOD5 waste load range of 0.10 to 5.83 kg BOD5/kkg RM (0.10 to 5.83 Ib BOD5/1000 Ib RM) ; and a production range of 3.6 to 390 kkg RM/day (8000 to 860,000 Ib RM/day) . Variations in waste water flow per unit of raw material are largely attributable to the type of condensers used for condensing the cooking vapors and, to a lesser extent, on the initial moisture content of the raw material (see Section III) . Table 7 shows that the average waste water flow for plants using barometric leg condensers is much higher, by at least a factor of 2, than for those using either shell-and-tube or air condensers. The range and standard deviation in the flow values are large, however, for all three types of condensers, which undoubtedly is partially caused by the type of raw materials processed. The volume of water used for cleanup can be a significant portion of the flow per unit of RM; typically it amounts to 30 percent of the total flow. A regression analysis of the field sampling data revealed that the raw BOD5 waste load correlates very well with grease and COD waste loads. Raw BOD5 waste load also correlates with total volatile solids (TVS), total dissolved solids (TDS), and total 44 ------- Table 6. Summary of Raw Waste Characteristics for Rendering Industry Parameter* Flow, 1/kkg RM (gal. /1000 Ib RM) Raw Material, kkg/day (1000 Ib/day) BOD , kg/kkg RM SS, kg/kkg RM Grease, kg/kkg RM COD, kg/kkg RM Total Volatile Solids, kg/kkg RM Total Dissolved Solids, kg/kkg RM Total Kjeldahl Nitrogen, kg/kkg RM Ammonia, kg/kkg RM Nitrate, kg/kkg RM Nitrite, kg/kkg RM Chloride, kg/kkg RM Total Phosphorus, kg/kkg RM Number of Observations 47 48 29 26 18 16 18 17 17 16 14 13 14 17 Average Value 3261 (403) 94 (206) 2.15 1.13 0.72 8.04 3.34 3.47 0.476 0.299 0.008 0.003 0.793 0.044 Standard Deviation — 94 (206) 1.34 1.39 1.14 8.32 3.09 3.05 0.313 0.196 0.016 0.011 0.767 0.064 High 20,000 (2400) 390 (860) 5.83 5.18 4.18 37.03 13.12 11.67 1.200 0.740 0.060 0.040 2.56 0.280 Low 467 (56) 3.6 (8) 0.10 0.03 0.00 1.59 0.04 0.01 0.120 0.080 0.0001 0.00002 0.080 0.003 *kg/kkg RM = lb/1000 Ib RM 45 ------- Table 7. Waste Water Flow and Raw Material Data Summary as Shown Parameter Flow, 1000 liters (1000 gal.) Raw Material , kkg/day (1000 Ib/day) Equipment Type* Total Batch Duke C-G Baro S & T Air Total Batch Duke C-G Baro S & T Air Number of Observations 51 35 6 6 15 21 9 48 34 5 5 14 19 9 Average Value 326(86) 314(83) 276(73) 110(29) 443(117) 185(49) 64(17) 94(206) 60(132) 195(430) 128(282) 37(82) 132(291) 62(137) Standard Deviation 643(170) 708(187) 166(44) 42(11) 764(202) 174(46) 38(10) 94(206) 80(176) 90(198) 61(135) 44(98) 89(195) 37(82) High Value 3028(800) 3028(800) 488(129) 170(45) 2952(780) 628(166) 121(32) 390(860) 390(860) 318(700) 204(450) 182(400) 318(700) 114(250 Low Value 3.8(1) 3.8(1) 64(17) 68(18) 7.6(2) 7.6(2) 19(5) 3.6(8) 3.6(8) 68(150) 61(135) 5.4(12) 11(25) 11(25) ^Values listed as: o Total summary of all data, regardless of equipment type. o Batch, Duke, or C-G: Summary of the information on plants having these cookers, respectively. o Baro, S & T, or Air: Summary of the information on plants having barometric leg, shell-and-tube, and air condensers, respectively. 46 ------- Kjeldahl nitrogen (TKN). This means that an increase (decrease) in one of these waste load parameters will account for a certain predictable increase (decrease) in one of the other parameters. In fact, the square of the correlation coefficient (called the coefficient of determination) is a measure of the predictability. Consequently, the high degree of correlation between BOD5 and grease waste load implies that much of the variation in BOD5 waste load is caused by variations in the grease load. The correlation coefficients from these analyses are presented in Table 8. Table 8. Correlation Coefficients of Several Raw Waste Load Parameters with EOD5 from the Field Sampling Results Parameter Grease COD Total Volatile Solids Total Dis- solved Solids Kjeldahl Nitrogen Correlation .Coefficient 0. 905 0.933 0. 789 0.796 0.580 The basic manufacturing processes in independent rendering (see Section IV) should have no influence on the raw waste load, because they are universal. However, some processing equipment, such as cookers and condensers, dc differ significantly in operating principles. However, a comparison of data for batch versus Duke and C-G continuous cookers and for the three types of condensers—barometric leg, shell-and-tube, and air—revealed no discernible difference in raw BOD5_ waste load. These data were presented in Section IV and Figures 8 and 9, along with a further discussion. Incidentally, it was previously mentioned and illustrated with the data from Table 7 that barometric leg condensers use far more water per unit of raw material processed. Obviously, the amount of water used for condensing does not affect the raw waste load per unit of RM processed. In fact, a regression analysis for raw BOD5 waste load and waste water flow oer unit of RM processed revealed no correlation. The correlation coefficient for this analysis was -0.027. Earlier studies on meat packing plants8 and poultry slaughterhouses 11 revealed a strong positive relationship between raw waste load and water use. 47 ------- The effect of plant size (amount of raw materials processed per day) on waste load as measured by BOD5 was assessed by a multiple regression analysis. This analysis showed no discernable relationship between BOD5 per unit of RM processed and plant size. The correlation coefficient was 0.062 and the square of this coefficient, which is the coefficient of determination, is only 0.0038. Plant size does, however, appear to be related to the type of cooker and condenser used. Table 7 shows that the average amount of raw material processed is smaller for plants using batch cookers and barometric leg condensers than for plants using continuous cookers (Duke and C-G) and shell-and-tube air condensers. Plants with batch cookers and barometric leg condensers frequently are older plants—built more than ten years ago. Plant age, although apparently related to both size and equipment type, is not related to waste load. Size and age were factors considered in categorizing the industry and were discussed in more detail in Section IV. Sources of Waste Water The most typical process and waste water flow arrangement used by the independent rendering industry is shown schematically in Figure 11. Hide curing is shown in this figure (even though the majority of the plants do not handle hides) because it can represent a significant portion of the total raw waste load. Some plants, rather than using the sequence of manufacturing processing illustrated in Figure 11, use slight variations of it. A plant processing poultry by-products, for example, will usually have two complete processing operations on the same premises. One operation is for poultry offal and dead birds, which will be very similar to the arrangement shown in Figure 11; the other operation will be for the feathers and blood. The feather and blood operation will not include the liquid-solid separation process nor any of the grease processes. Other rendering plants may not have blending and bagging processes if, for example, they do not handle blood or feather meal and their meat and bone is consistently of a high crude protein level. Still others may not have a size-reduction process; these include plants that handle grease only, or a high percent of poultry offal. Plants that have large grease operations probably vary more from the process flow arrangement of Figure 11 than do any other plants. In these operations, there is receiving, cooking (or heating), separation of the water and solids from the grease, storage and shipping. Yet these operations still have the same characteristic waste loads as the other rendering plants. In addition, there are very few plants with large grease operations, and most of these usually have a separate operation schematically similar to that of Figure 11 for processing of fats and other raw materials. Figure 11 also shows the major sources of waste water as indicated by the dashed line. The sources include auxiliary operations in addition to manufacturing processes. The auxiliary 48 ------- MANUFACTURING PROCESSES WASTE WATER FLOW RAW MATERIAL RECEIVING SIZE REDUCTION COOKING AND DRYING VAPOR CONDENSING LIQUID - SOLID SEPARATION r ODOR CONTROL MEAL MILLING AND SCREENING BLENDING AND BAGGING r SPILLS I PLANT AND TRUCK CLEAN UP 1 GREASE AND SOLIDS RECYCLED TO COOKING & DRYING MATERIALS RECOVERY r: RAW WASTE SANITARY FACILITIES ,FRESH WATER -*- PRODUCT AND MATERIAL FLOW •*- WASTE WATER FLOW Figure 11. Typical Rendering Process and Waste Water Flow Arrangement 49 ------- operations are odor control, spills, and plant and truck cleanup; the manufacturing processes are receiving, vapor condensing from cooking and drying, and hide curing. These sources this section. Total plant waste loads including the effects of materials recovery were presented in Table 6 and discussed previously in this section. Raw Materials Receiving Liquid drainage from raw materials receiving areas can contribute significantly to the total raw waste load. Frequently throughout the processing period large amounts of raw materials accumulate in receiving areas (either in bins or on floors) allowing strong liquors to drain off and enter sewers. This is especially true of plants processing poultry feathers because of the manner in which feathers, offal and blood are sometimes handled at their source (poultry slaughterhouses). As a result, the feathers or combined feathers and offal often contain much blood and excess water. At one such plant that was sampled, this drainage amounted to roughly 20 percent of the original raw material weight and had an average BOD5 value of 12,500 mg/1. This BOD5 loss amounted to 2.5 kg BOD5/kkg RM (2.5 lb/1000 Ib RM) and 43 percent of the total plant raw BOD5 waste load. In another plant that had a dual operation for poultry offal and for feathers and blood, the loss caused by drainage from the feather operation was calculated from field sampling information; it was about 1.4 kg BOD5/kkg RM, or about 39 percent of the waste load prior to materials recovery processes. In these examples, the waste load caused by drainage of liquors from raw materials is obviously very significant. A partial remedy for these losses, which was practiced in a plant included in the field survey, is to isolate, steam sparge, and screen these waste waters. Vapor Condensing Condensate from the cooking and drying process typically contributes atout 30 percent of the total raw BOD5 waste load. The field sampling condensables was from 0.049 to 1.53 kg BOD5/kkg RM (0.049 to 1.53 Ib BOD5/1000 Ib RM), with an average value of 0.73 kg/kkg RM. A summary of concentrations and waste loads of undiluted condensed cooking vapors is presented in Tables 9 and 10, respectively. of course, being undiluted means the vapors were condensed in a closed system: air or shell-and- tube condensers. A number of factors, such as rate of cooking, speed of agitation, cooker overloading, foaming, lack of traps, etc., are probably responsible for much of the variation in values. Raw materials could also have a direct effect on the values, although no discernible difference between raw materials and total plant raw waste load was revealed by a multiple regression analysis, as discussed in Section IV. 50 ------- Table 9. Concentrations of Undiluted Condensed Cooking Vapors Parameter BOD5 COD Total Volatile Solids Total Dissolved Solids Total Phosphorus Chlorides Total Kjeldahl Nitrogen Nitrate Nitrite Grease Suspended Solids mg/1 Number of Observations 11 10 10 7 7 7 7 7 7 7 10 Average Value 1723 2207 185 201 6.3 196 493 263 0.11 109 60.9 Standard Deviation 1165 1383 169 143 6.3 212 317 238 0.08 76 94.3 Low Value 80 192 15 59 2.45 13 36 14 0.01 63 11 High Value 3950 4212 579 413 20.4 593 1005 750 0.02 271 327 51 ------- The pH of the condensables averaged 8.7 for 11 observations with a standard deviation of 1.12 and with low and high values of 6.8 and 9.7, respectively. Incidentally, the number of observations for the waste parameters in these tables is frequently less for the waste load values than for the concentration values. This is because some of the data were lacking to permit the calculation of the waste load; e.g., the amount of raw material processed was not always known. The use of barometric leg condensers will dilute the condensables and thus lower the concentrations from those listed in Table 9. In many cases, treated waste waters are recycled through barometric legs for condensing cooking vapors and to allow a high water throughput to lower the barometric leg effluent temperature to at least 38°C (10C°F) for odor control. This practice may increase the actual waste load slightly; however, an analysis of the data by type of condenser (see Section IV) did not reveal any distinct differences in waste loads caused by type of condenser. Spills and Plant and Truck Cleanup Washdown (cleanup) of the plant, trucks, and spills can contribute significantly to the total plant raw waste load. In one plant that was sampled, the waste waters from cleanup were isolated from the condensables. Analysis of this source revealed that cleanup in this plant added 16.2 kg BOD5/kkg (Ib BOD5/1000 Ib) RM to the raw waste load, an extraordinarily high value. The reasons for this high value were that the plant used a constant flow of hot water throughout the entire production period; it constantly cleaned up spills from worn, leaking equipment, and frequently shut off the automatic skimmer of the materials recovery systems, resulting in large amounts of grease carry- over. The large amounts of hot water helped maintain the cleanup effluent temperature above 52°C (125°F), thus preventing efficient grease separation. Needless to say, the plant was clean. In another plant, the BOD5 and suspended solids load just from cleanup were 43 and 50 percent of the total, respectively. It was observed on the field survey studies that spills caused by equipment breakdown occurred frequently and that leaks from worn equipment were not uncommon. This does not mean that spills cannot be prevented or limited; however, the common practice when equipment breaks down is to open it and dump materials directly on the floor. This allows free draining grease and liquors to enter the sewers. Also, after the bulk of the solids have been shoveled up, the remainder is washed off. More effort could be made to contain materials when equipment breaks down and to better maintain equipment by use of regularly scheduled maintenance programs on equipment during down-time. 52 ------- Table 10. Waste Loads for Undiluted Condensed Cooking Vapors Parameter BOD COD Total Volatile Solids Total Dissolved Solids Total Phosphorus Chloride Total Kjeldahl Nitrogen Nitrate Nitrite Grease Suspended Solids kg/kkg KM or lb/1000 Ib BM Number of Observations 10 7 7 6 6 6 6 6 6 7 9 Average Value 0.73 1.10 0.086 0.21 0.0021 0.056 0.17 0.081 0.0018 0.14 0.018 Standard Deviation 0.50 0.75 0.093 0.25 0.00015 0.078 0.12 0.067 0.0038 0.25 0.017 High Value 1.53 2.23 0.31 0.73 0.0043 0.21 0.35 0.16 0.0096 0.70 0.056 Low Value 0.049 0.12 0.0032 0.0013 0.00081 0.0046 0.022 0.0086 0.000008 0.015 0.0058 53 ------- Odor Control Air scrubbers are common in the rendering industry for odor control. The relative volume of water used, however, varies greatly, although the waste load caused by scrubbing is insignificant. The reason for the variation in water flow is that scrubbers for plant air and other low-aerosol-containing emissions (smoke and grease particulates) can tolerate recycling of up to 95 percent of the scrubbing waters. However, air heavily laden with odorous aerosols is usually scrubbed with fresh water to prevent grease buildup and clogging of the equipment. For example, one dual operation (one batch operation and one continuous operation) plant contained a total of nine scrubbers. Although some scrubbers did use partial recycle of scrubbing water, the volume of scrubbing waters was about 75 percent of the total plant effluent volume. Typically, plants will have only two or three scrubbers: one for total plant air, one for the presses, and possibly one for the ring or rotary dryers. Most of the scrubbing waters then are recycled, and the relative waste water volume from scrubbing is small. For example, one plant that was sampled had two scrubbers—one for plant air and one for a dryer—and the volume of waste water from the scrubbers amounted to only six percent of the total effluent volume. Hide Curing Hide curing is conducted in a number of independent rendering plants. The waste water from this operation is high in strength but relatively low in volume, particularly when the curing solution is only dumped a few times each year. Data from previous studies°2,8 indicate that about 7.7 liters (2 gallons) is the waste water overflow volume for brine curing each cattle hide. The waste load for just curing hides at an independent rendering plant is, however, considerably less than the waste load for curing at a packing plant. This is because curing of hides at a packing plant includes a number of additional operations. These are washing, demanuring, and defleshing. In addition, the time differential between hide removal and hide delivery at a rendering plant allows for much of the blood and other fluids to seep from the hides. This time differential ranges from several hours to a few days. Also, hides and accompanying flesh removed from dead animals at a rendering plant do not appear to contain anywhere near the amount of blood and fluid that a hide removed at a packing plant from an animal killed just moments earlier contains. Data from the recent study of packing plants8 states that the average waste load for handling and curing hides of a packinghouse is 1.5 kg BOD5/kkg LWK (live weight killed). Since the average LWK for beef is about 454 kg (1000 pounds), this can be equivalently expressed as 0.68 kg BOD5/hide. On the other hand, a study of tannery effluents0* lists the waste load for just hide curing at a tannery as 3.9 kg BOD5/kkg hides (3.9 lb/1000 Ib). Using an average hide weight of 32 kg (70 pounds), 54 ------- Table 11. Waste Load Characteristics for Hide Curing at an Off-Site Rendering Plant Versus Those for a Tannery 12 Table 12. Measured Waste Strengths of Tank Water and Blood Water en en Parameter BOD COD Total Volatile Solids Suspended Solids Kjeldahl Nitrogen Ammonia Nitrate Nitrite Total Phosphorus Total Dis- solved Solids Chloride Grease kg /hide Rendering Plant 0.11 0.21 0.17 0.064 0.014 0.0013 4.4 x 10~5 4.1 x 10~6 0.0021 2.9 1.26 0.0011 T annery 0.12 0.24 0.08 0.32 Parameter BOD5 COD Total Volatile Solids Total Dissolved Solids Total Phosphorus Chloride Total Kjeldahl Nitrogen Ammonia Nitrate Nitrite Grease Suspended Solids mg/1 Tank Water 31,390 49,152 36,739 54,791 1,350 8,638 2,187 81 3.43 0.35 9,901 6,647 Blood Water 18,950 27,200 17,516 315 3,498 1,813 ------- this value can be expressed as 0.12 kg (0.26 Ib) BOD5 per hide. This latter example should also typify the waste load for hide curing at an independent rendering plant. In fact, analysis of only the hide curing effluent at one independent rendering plant yielded a BOD5 waste load of 0.11 kg (0.24 Ib) per hide. The results of this analysis are summarized in Table 11. For comparison, the value recalculated from reference 12, assuming 32 kg/hide (70 pounds), is also included. Miscellaneous Sources Sewered tankwater and blood water are major sources of waste load. The sources of tank water are grease processing, and wet and low-temperature rendering; the source of blood water is from processing blood by steam sparging and then separating the blood water from the coagulated blood by screening. Fortunately, not many independent rendering plants have the processes that generate these sources of waste. Also, some plants that do generate tankwater eliminate it as a waste source by evaporating it down to stick, which is used for tankage in dry inedible rendering. As mentioned in Section III, the BOD5 and grease concentrations of tankwater can be as high as 30,000 to 45,000 mg/1 and 20,000 to 60,000 mg/1, respectively. Table 12 shows the measured waste strengths of tankwater from a grease operation and of blood water from steam sparging and screening of blood. The waste load resulting from the sewering of the tankwater was 9.4 kg BOD5/kkg (9.4 Ib BOD5/1000 Ib) grease before primary treatment (materials recovery process). However, much of this waste load was removed by primary treatment, since the amount of grease processed was about 63 percent of the total plant RM and since the total plant waste load was only 2.2 kg BOD5/kkg (2.2 lb/1000 Ib) RM. Likewise, the sewering of blood water added 16.3 kg BOD5/kkg blood before primary treatment. Judging from the values of the total plant raw waste load and the waste loads of the other sources, it would appear that the primary treatment recovered very little, if any, of the waste load from the sewering of blood water; this is as expected. It should be pointed out, however, that the blood screening process was not very efficient and that a pilot study at that plant revealed that an improved screening process would significantly lower the load from sewering blood water. 56 ------- SECTION VI SELECTION OF POLLUTANT PARAMETERS SELECTED PARAMETERS Based on a review of the Corps of Engineers1 Permit Applications from the independent renderers, previous studies on similar waste waters such as from the meat packing plants, industry data, questionnaire data, and data obtained from sampling plant waste waters during this study, the following chemical, physical, and biological constituents constitute pollutants as defined in the Act. BOD5 (5-day, 20°C biochemical oxygen demand) COD (chemical oxygen demand) Total suspended solids (TSS) Total dissolved solids (TDS) Total volatile solids (TVS) Oil and grease Ammonia nitrogen Kjeldahl nitrogen Nitrates and nitrites Phosphorus Chloride Bacteriological counts (total and fecal coliform) pH, acidity, alkalinity Temperature On the basis of all evidence reviewed, there do not exist any purely hazardous pollutants (such as heavy metals or pesticides) in the waste discharge from the independent rendering plants. While all of the above parameters are in present renderer plant waste water, the amount and reliability of available data, costs for treatment or control, and availability of technology were factors which resulted in limitations only for the primary parameters BOD5, TSS, Oil and grease, fecal coliforms, ammonia, phosphorus and pH. RATIONALE FOR SELECTION OF IDENTIFIED PARAMETERS 5-Day Biochemical Oxygen Demand (BOD5) This parameter is an important measure of the oxygen consumed by microorganisms in the aerobic decomposition of the wastes at 20°C over a five-day period. More simply, it is an indirect measure of the biodegradability of the organic pollutants in the waste. BOD5 can be related to the depletion of oxygen in the receiving stream or to the requirements for the waste treatment. Values of BOD5 range from 100 to 9000 mg/1 in the raw waste, although typical values range from 1000 to 5000 mg/1. Low BOD5 values in the raw waste are frequently the result of the dilutional effects of using a barometric condenser; high values due to a combination 57 ------- of factors, such as undiluted condenser waters, frequent spills, and a relatively large amount of drainage of high strength liquids from the raw material. If the BOD5 of the final effluent of a rendering plant into a receiving body is too high, it will reduce the dissolved oxygen level in that stream to below a level that will sustain most fish life; i.e., below about 4 mg/1. Many states currently restrict the BOD5 effluents to below 20 mg/1 if the stream is small in comparison with the flow of the effluent. A limitation of 200 to 300 mg/1 of BOD5 is often applied for discharge to a municipal sewer, and surcharge rates often apply if the BOD5 is above the designated limit. BOD5 is included in the effluent limitations recommended because its discharge to a stream is harmful to aquatic life since it depletes the oxygen supply. A 20-day biochemical oxygen demand (BOD20), sometimes called "ultimate" BOD, is usually a better measure of the waste load than BOD5. However, the test for BOD20 requires 20 days to run, so it is an impractical measure for most purposes. Biochemical oxygen demand (BOD) is a measure of the oxygen consuming capabilities of organic matter. The BOD does not in itself cause direct harm to a water system, but it does exert an indirect effect by depressing the oxygen content of the water. Sewage and other organic effluents during their processes of decomposition exert a BOD, which can have a catastrophic effect on the ecosystem by depleting the oxygen supply. Conditions are reached frequently where all of the oxygen is used and the continuing decay process causes the production of noxious gases such as hydrogen sulfide and methane. Water with a high BOD indicates the presence of decomposing organic matter and subsequent high bacterial counts that degrade its quality and potential uses. Dissolved oxygen (DO) is a water quality constituent that, in appropriate concentrations, is essential not only to keep organisms living but also to sustain species reproduction, vigor, and the development of populations. Organisms undergo stress at reduced DO concentrations that make them less competitive and able to sustain their species within the aquatic environment. For example, reduced DO concentrations have been shown to interfere with fish population through delayed hatching of eggs, reduced size and vigor of embryos, production of deformities in young, interference with food digestion, acceleration of blood clotting, decreased tolerance to certain toxicants, reduced food efficiency and growth rate, and reduced maximum sustained swimming speed. Fish food organisms are likewise affected adversely in conditions with suppressed DO. Since all aerobic aquatic organisms need a certain amount of oxygen, the consequences of total lack of dissolved oxygen due to a high BOD can kill all inhabitants of the affected area. If a high BOD is present, the quality of the water is usually visually degraded by the presence of decomposing materials and 58 ------- algae blooms due to the uptake of degraded materials that form the foodstuffs of'the algal populations. 59 ------- Chemical Oxygen Demand (COD) COD is yet. another measure of oxygen demand. It measures the amount of organic (and some inorganic) pollutants under a carefully controlled direct chemical oxidation by a dichromate- sulfuric acid reagent. COD is a much more rapid measure of oxygen demand than BOD5, and is potentially very useful. However, it does not have the same significance, and at the present time cannot be substituted for BOD5, because COD:BOD5 ratios vary with the types of wastes. The COD measures more than only those materials that will readily biodegrade in a stream and hence deplete the stream's dissolved oxygen supply. COD provides a rapid determination of the waste strength. Its measurement will indicate a serious plant or treatment malfunction long before the BOD5 can be run. A given plant or waste treatment system usually has a relatively narrow range of COD:BOD5 ratios, if the waste characteristics are fairly constant, so experience permits a judgment to be made concerning plant operation from COD values. In the rendering industry, COD ranges from about 1.5 to 6 times the BOD5 in both the raw and treated wastes, with typical ratios between 1.5 and 3.0. Although the nature of the impact of COD on receiving waters is the same as for BOD5, BOD_5 was chosen for inclusion in the effluent limitations rather than COD because of the industry's frequent use and familiarity with BOD5. Total Suspended Solids (TSS) This parameter measures the suspended material that can be removed from the waste waters by laboratory filtration, but does not include coarse or floating matter that can be screened or settled out readily. Suspended solids are a visual and easily determined measure of pollution and also a measure of the material that may settle in tranquil or slowmoving streams. A high level of suspended solids is an indication of high BOD5. Generally, suspended solids range from one-third to three-fourths of the BOD5 values in the raw waste. Suspended solids are also a measure of the effectiveness of solids removal systems such as clarifiers and fine screens. Suspended solids frequently become a limiting factor in waste treatment when the BOD5 is less than about 20 mg/1. In fact, in highly treated waste, suspended solids usually have a higher value than the BOD5, and in this case, it may be easier to lower the BOD5 even further, perhaps to 5 to 10 mg/1, by filtering out the suspended solids. Suspended solids in the treated waste waters of rendering plants correlate well with BOD5, COD, and total volatile solids. The same is not true, however, for the raw wastes. Suspended solids in receiving waters act as adsorption surface for ionic nutrients, and as a substrate for bacterial population, thus resulting in high BOD5 values. Suspended solids also 60 ------- inhibit light penetration and thereby reduce the primary productivity of algae (photosynthesis). Because of the strong impact suspended solids can have on receiving waters, suspended solids were included in the effluent limitations recommended in this report. Suspended solids include both organic and inorganic materials. The inorganic components include sand, silt, and clay. The organic fraction includes such materials as grease, oil, tar, animal and vegetable fats, various fibers, sawdust, hair, and various materials from sewers. These solids may settle out rapidly and bottom deposits are often a mixture of both organic and inorganic solids. They adversely affect fisheries by covering the bottom of the stream or lake with a blanket of material that destroys the fish-food bottom fauna or the spawning ground of fish. Deposits containing organic materials may deplete bottom oxygen supplies and produce hydrogen sulfide, carbon dioxide, methane, and other noxious gases. In raw water sources for domestic use, state and regional agencies generally specify that suspended solids in streams shall not be present in sufficient concentration to be objectionable or to interfere with normal treatment processes. Suspended solids in water may interfere with many industrial processes, and cause foaming in boilers, or encrustations on equipment exposed to water, especially as the temperature rises. Suspended solids are undesirable in water for textile industries; paper and pulp; beverages; dairy products; laundries; dyeing; photography; cooling systems, and power plants. Suspended particles also serve as a transport mechanism for pesticides and other substances which are readily sorbed into or onto clay particles. Solids may be suspended in water for a time, and then settle to the bed of the stream or lake. These settleable solids discharged with man's wastes may be inert, slowly biodegradable materials, or rapidly decomposable substances. While in suspension, they increase the turbidity of the water, reduce light penetration and impair the photosynthetic activity of aquatic plants. Solids in suspension are aesthetically displeasing. When they settle to form sludge deposits on the stream or lake bed, they are often much more damaging to the life in water, and they retain the capacity to displease the senses. Solids, when transformed to sludge deposits, may do a variety of damaging things, including blanketing the stream or lake bed and thereby destroying the living spaces for those benthic organisms that would otherwise occupy the habitat. When of an organic and therefore decomposable nature, solids use a portion or all of the dissolved oxygen available in the area. Organic materials also serve as a seemingly inexhaustible food source for sludgeworms and associated organisms. 61 ------- Turbidity is principally a measure of the light absorbing properties of suspended solids. It is frequently used as a substitute method of quickly estimating the total suspended solids when the concentration is relatively low. Total Dissolved Solids (TDS) The total dissolved solids in the waste waters of most independent rendering plants contain both organic and inorganic matter. A large source of organic dissolved solids is blood. Inorganic salts can be a major part of the dissolved solids if hide curing is conducted at the plant. The amount of dissolved solids will also vary to a large extent with the type of in-plant operations and the housekeeping practices. Dissolved solids are of the same order of magnitude and correlate well with the total volatile solids in both the raw and treated waste waters, implying that, in general, most of the dissolved solids are volatile. The inorganic dissolved solids are particularly important because they are relatively unaffected by biological treatment processess. Therefore, unless removed, they will accumulate within the water system on total recycle or reuse, or build up to high levels with partial recycle or reuse of the waste water. Dissolved solids affect the ionic nature of receiving waters and are usually the nutrients for bacteria and protozoans. Thus, they increase the eutrophication rate of the receiving body of water. Total dissolved solids were not included in the effluent limitations recommended in this report because the organic portion would be limited by BOD5 limitations and the nutrient portion by the nitrogen and phosphorus limitations. In natural waters the dissolved solids consist mainly of carbonates, chlorides, sulfates, phosphates, and possibly nitrates of calcium, magnesium, sodium, and potassium, with traces of iron, manganese and other substances. Many communities in the United States and in other countries use water supplies containing 2000 to 4000 mg/1 of dissolved salts, when no better water is available. Such waters are not palatable, may not quench thirst, and may have a laxative action on new users. Waters containing more than 4000 mg/1 of total salts are generally considered unfit for human use, although in hot climates such higher salt concentrations can be tolerated whereas they could not in temperate climates. Waters containing 5000 mg/1 or more are reported to be bitter and act as bladder and intestinal irritants. It is generally agreed that the salt concentration of good, palatable water should not exceed 500 mg/1. Limiting concentrations of dissolved solids for fresh-water fish may range from 5,000 to 10,000 mg/1, according to species and prior acclimatization. Some fish are adapted to living in more saline waters, and a few species of fresh-water forms have been found in natural waters with a salt concentration of 15,000 to 62 ------- 20,000 mg/1. Fish can slowly become acclimatized to higher salinities, but fish in waters of low salinity cannot survive sudden exposure to high salinities, such as those resulting from discharges of oil-well brines. Dissolved solids may influence the toxicity of heavy metals and organic compounds to fish and other aquatic life, primarily because of the antagonistic effect of hardness on metals. Waters with total dissolved solids over 500 mg/1 have decreasing utility as irrigation water. At 5,000 mg/1 water has little or no value for irrigation. Dissolved solids in industrial waters can cause foaming in boilers and cause interference with cleanness, color, or taste of many finished products. High contents of dissolved solids also tend to accelerate corrosion. Specific conductance is a measure of the capacity of water to convey an electric current. This property is related to the total concentration of ionized substances in water and water temperature. This property is frequently used as a substitute method of quickly estimating the dissolved solids concentration. Total Volatile Solids (TVS) Total volatile solids is a rough measure of the amount of organic matter in the waste water. Actually it is the amount of combustible material in both the total dissolved solids and total suspended solids. Total volatile solids in the raw waste waters of rendering plants correlates quite well with total dissolved solids and COD, and fairly well with BOD5, SS, and grease; total volatile solids in the final waste waters correlates well with total dissolved solids and BOD5, and fairly well with SS, grease, and COD, in the final waste waters. Because of these correlations and because total volatile solids is a relatively easy parameter to determine, it could be used as a rapid method to determine a serious plant or treatment system malfunction. Volatile solids in receiving waters are food for microorganisms, and thus create increased eutrophicaticn. Effluent limitations for total volatile solids were not established because TVS will be limited by limitations on other pollutant parameters such as BOD5 and suspended solids. Oil and Grease Grease, also called oil and grease, or hexane solubles, is a major pollutant in the raw waste stream of rendering plants. The source of grease is primarily from spillages of processed tallow and grease and cleanup of equipment, floors, barrels, and trucks. Grease forms unsightly films on the water, interferes with aquatic life, clogs sewers, disturbs biological processes in sewage treatment plants, and can also become a fire hazard. It is also a food source for microorganisms which may be pathogenic. 63 ------- The loading of grease in the raw waste load varies widely, from less than 0.1 to about 15 kg/kkg RM. The average raw waste loading of grease is about 0.7 kg/kkg RM, which corresponds to an average concentration of about 1660 mg/1. Grease may be harmful to municipal treatment facilities and to trickling filters. Grease correlates well with BOD5 and COD in the raw wastes, but not in the treated wastes. Because grease appears to constitute a major portion of the waste load from rendering plants, effluent limitations were established for it. Oil and grease exhibit an oxygen demand. Oil emulsions may adhere to the gills of fish or coat and destroy algae or other plankton. Deposition of oil in the bottom sediments can serve to exhibit normal benthic growths, thus interrupting the aquatic food chain. Soluble and emulsified material ingested by fish may taint the flavor of the fish flesh. Water soluble components may exert toxic action on fish. Floating oil may reduce the re- aeration of the water surface and in conjunction with emulsified oil may interfere with photosynthesis. Water insoluble components damage the plumage and costs of water animals and fowls. Oil and grease in water can result in the formation of objectionable surface slicks preventing the full aesthetic enjoyment of the water. Oil spills can damage the surface of boats and can destroy the aesthetic characteristics of beaches and shorelines. Ammonia Nitrogen Ammonia nitrogen in the raw waste is just one of many forms of nitrogen in a waste stream. Anaerobic decomposition of protein, which contains organic nitrogen, leads to the formation of ammonia. Thus, anaerobic lagoons or digesters produce high levels of ammonia. Also, septic (anaerobic) conditions within the plant in traps, basins, etc., may lead to ammonia in the waste water. Another source of ammonia can be liquid drainage from raw materials containing manure, and also from proteinaceous matter such as blood that has been "aged." Ammonia is oxidized by bacteria in a process called "nitrification" to nitrites and nitrates. This may occur in an aerobic treatment process and in a stream. Thus, ammonia will deplete the oxygen supply in a stream; its oxidation products are recognized nutrients for aquatic growth. Also, free ammonia in a stream is known to be harmful to fish. Typical concentrations in the raw waste range from 25 to 300 mg/1; however, after treatment in an anaerobic system, the concentrations of ammonia can reach 100 to 500 mg/1. Ammonia is limited in drinking water to 0.05 to 0.1 mg/l.°3 In some cases a stream standard is less than 2 mg/1. Effluent limitations for new sources and the 1983 limits were established for ammonia because of the strong impact it can have on receiving waters. 64 ------- Ammonia is a common product, of the decomposition of organic matter. Dead and decaying animals and plants along with human and animal body wastes account for much of the ammonia entering the aquatic ecosystem. Ammonia exists in its non-ionized form only at higher pH levels and is the most toxic in this state. The lower the pH, the more ionized ammonia is formed and its toxicity decreases. Ammonia, in the presence of dissolved oxygen, is converted to nitrate (NO3) by nitrifying bacteria. Nitrite (NO2), which is an intermediate product between ammonia and nitrate, sometimes occurs in quantity when depressed oxygen conditions permit. Ammonia can exist in several other chemical combinations including ammonium chloride and other salts. Nitrates are considered to be among the poisonous ingredients of mineralized waters, with potassium nitrate being more poisonous than sodium nitrate. Excess nitrates cause irritation of the mucous linings of the gastrointestinal tract and the bladder; the symptoms are diarrhea and diuresis, and drinking one liter of water containing 500 mg/1 of nitrate can cause such symptoms. Infant methemoglobinemia, a disease characterized by certain specific blood changes and cyanosis, may be caused by high nitrate concentrations in the water used for preparing feeding formulae. While it is still impossible to state precise concentration limits, it has been widely recommended that water containing more than 10 mg/1 of nitrate nitrogen (NO3-N) should not be used for infants. Nitrates are also harmful in fermentation processes and can cause disagreeable tastes in beer. In most natural water the pH range is such that ammonium ions (NH4+) predominate. In alkaline waters, however, high concentrations of un-ionized ammonia in undissociated ammonium hydroxide increase the toxicity of ammonia solutions. In streams polluted with sewage, up to one half of the nitrogen in the sewage may be in the form of free ammonia, and sewage may carry up to 35 mg/1 of total nitrogen. It has been shown that at a level of 1.0 mg/1 un-ionized ammonia, the ability of hemoglobin to combine with oxygen is impaired and fish may suffocate. Evidence indicates that ammonia exerts a considerable toxic effect on all aquatic life within a range of less than 1.0 mg/1 to 25 mg/1, depending on the pH and dissolved oxygen level present. Ammonia can add to the problem of eutrophication by supplying nitrogen through its breakdown products. Some lakes in warmer climates, and others that are aging quickly are sometimes limited by the nitrogen available. Any increase will speed up the plant growth and decay process. Kjeldahl Nitrogen This parameter measures the amount of ammonia and organic nitrogen; when used in conjunction with the ammonia nitrogen, the organic nitrogen can be determined by the difference. Under septic conditions, organic nitrogen decomposes to form ammonia. Kjeldahl nitrogen is a good indicator of the crude protein in the 65 ------- effluent and, hence, of the value of proteinaceous material being lost in the waste water. The protein content is usually taken as 6.25 times the organic nitrogen. The sources of Kjeldahl nitrogen are basically the same as for ammonia nitrogen, above. The raw waste loading of Kjeldahl nitrogen is extremely variable and is highly affected by blood losses from raw material drainage and blood and feather operations, and by liquid entrainment in the cooking vapors. Typical raw loadings range from 0.12 to 1.20 kg/kkg (0.12 to 1.20 lb/1000 Ib) raw material; concentrations range from about 60 to 800 mg/1, with the lower values usually caused by the dilutional effects of barometric leg condensers. Typical raw waste concentrations of Kjeldahl nitrogen are between 50 and 100 mg/1. Kjeldahl nitrogen has not been a common parameter for regulation and is a much more useful parameter for raw waste than for final effluent. Even so, effluent limitations for 1983 were established for Kjeldahl nitrogen because, in addition to ammonia which has a strong environmental impact on receiving waters, it can be a major source of organic material, which is food for microorganisms in receiving waters. Nitrates and Nitrites Nitrates and nitrites, normally reported as N, are the result of oxidation of ammonia and of organic nitrogen. Nitrates as N should not exceed 20 mg/1 in water supplies.04 They are essential nutrients for algae and other aquatic plant life. For these reasons, effluent limitations for new sources and for the 1983 limits were established for nitrites-nitrates as N. Nitrites ranged from a trace to 0.040 kg/kkg RM in the raw wastes and from a trace to 0.08 kg/kkg EM in the treated wastes; nitrates ranged from a trace to 0.06 kg/kkg RM in the raw and from a trace to 0.012 kg/kkg RM in the treated wastes. Concentrations of nitrites varied from 0.02 to 26 mg/1 in the raw and from O.OU to 1.2 mg/1 in the final; nitrate concentrations varied from 0.02 to 13 mg/1 in the raw and from 0.02 to 3.25 mg/1 in the treated waste. Again, low values are primarily caused by the dilutional effects of barometric leg condensers. Nitrates and nitrites are important measurements, along with Kjeldahl nitrogen, in that they allow for the calculation of a nitrogen balance on the treatment system. In fact, the field sampling data verified that when there was a substantial nitrogen reduction by the treatment system, it was accompanied by good BOD5, SS, and grease reductions. Phosphorus Phosphorus, commonly reported as P, is a nutrient for aquatic plant life and can therefore cause an increased eutrophication rate in water courses. The threshold concentration of phosphorus in receiving bodies that can lead to eutrophication is about 0.01 ma/1. The primary sources of phosphorus in raw waste from 66 ------- rendering are bone meal, detergents, and boiler water additives. The total phosphorus in the raw effluent ranges from about 0.007 to 0.28 kg/kkg RM (0.007 to 0.28 lb/1000 Ib RM), or a typical concentration range of 3 to 50 mg/1 as P. Effluent limitations were established for phosphorus for new source performance standards and for the 1983 limits because of its effect on eutrophication rates. During the past 30 years, a formidable case has developed for the belief that increasing standing crops of aquatic plant growths, which often interfere with water uses and are nuisances to man, frequently are caused by increasing supplies of phosphorus. Such phenomena are associated with a condition of accelerated eutrophication or aging of waters. It is generally recognized that phosphorus is not the sole cause of eutrophication, but there is evidence to substantiate that it is frequently the key element in all of the elements required by fresh water plants and is generally present in the least amount relative to need. Therefore, an increase in phosphorus allows use of other, already present, nutrients for plant growths. Phosphorus is usually described, for these reasons, as a "limiting factor." When a plant population is stimulated in production and attains a nuisance status, a large number of associated liabilities are immediately apparent. Dense populations of pond weeds make swimming dangerous. Boating and water skiing and sometimes fishing may be eliminated because of the mass of vegetation that serves as a physical impediment to such activities. Plant populations have been associated with stunted fish populations and with poor fishing. Plant nuisances emit vile stenches, impart tastes and odors to water supplies, reduce the efficiency of industrial and municipal water treatment, impair aesthetic beauty, reduce or restrict resort trade, lower waterfront property values, cause skin rashes to man during water contact, and serve as a desired substrate and breeding ground for flies. Phosphorus in the elemental form is particularly toxic, and subject to bioaccumulation in much the same way as mercury. Colloidal elemental phosphorus will poison marine fish (causing skin tissue breakdown and discoloration). Also, phosphorus is capable of being concentrated and will accumulate in organs and soft tissues. Experiments have shown that marine fish will concentrate phosphorus from water containing as little as 1 ug/1. Chlorides Chlorides in concentrations of the order of 5000 mg/1 can be harmful to people and other animal life. High chloride concentrations in waters can be troublesome for certain industrial uses and for reuse or recycling of water. The major sources of chlorides from rendering plants are the salt from animal tissues, hide curing operations, and blood. The concentrations in raw waste are extremely variable from plant to 67 ------- plant, and are normally much higher for plants treating hides or sewering blood waters (e.g., drainage from poultry feathers) than they are for other plants. The amount in the waste water is an indicator that these processes are being operated. For example, chloride concentrations from liquid drainage of cured hides were measured at 80,000 mg/1 as Cl; from drainage of bloody waters from poultry offal, at 691 mg/1 as Cl; and from sewered blood waters from a blood operation, at 3500 mg/1 as Cl. The range of chloride loadings in raw waste effluents is from 0.08 to greater than 2.56 kg/kkg RM (2.56 lb/1000 Ib RM). Chloride loadings are unaffected by biological treatment systems used by the industry today, and once in the waste waters they are very costly to remove. While high chloride concentrations in biological treatment systems and receiving waters can upset the metabolic rate of organisms, effluent concentrations are probably too low to have a serious impact. Fecal Coliforms The coliform bacterial contamination (total and fecal) of raw waste is substantially reduced (by a factor of 100 to 200) in the larger waste treatment systems used in the industry, such as anaerobic lagoons followed by several aerobic lagoons. Chlorination will reduce coliform counts to less than 400 per 100 ml for total, and to less than 100 per 100 ml for fecal. Data indicate that the total coliform of the raw waste from rendering plants is in the 0.65- to 500-million per 100 ml range with a median value of about 7 million per 100 ml; for fecal coliform, the range is 0.05- to 75-million per 100 ml, with a median value of about 0.7 million per 100 ml. Typically, states require that the total coliform count not exceed 50-200 MPN (most probable number) per 100 ml for waste waters discharged into receiving waters. Hence, most final effluents require chlorination to meet state standards. When waters contain 200 counts of fecal coliform per 100 ml, it is assumed that pathogenic enterobacteriacea, which can cause intestinal infections, are present. Consequently, effluent limitations were established for fecal coliforms. Fecal coliforms are used as an indicator since they have originated from the intestinal tract of warm blooded animals. Their presence in water indicates the potential presence of pathogenic bacteria and viruses. The presence of coliforms, more specifically fecal coliforms, in water is indicative of fecal pollution. In general, the presence of fecal coliform organisms indicates recent and possibly dangerous fecal contamination. When the fecal coliform count exceeds 2,000 per 100 ml there is a high correlation with increased numbers of both pathogenic viruses and bacteria. Many microorganisms, pathogenic to humans and animals, may be carried in surface water, particularly that derived from effluent sources which find their way into surface water from municipal and industrial wastes. The diseases associated with bacteria 68 ------- include bacillary and amoebic dysentery, Salmonella gastroenteritis, typhoid and paratyphoid fevers, leptospirosis, cholera, vibriosis and infectious hepatitis. Recent studies have emphasized the value of fecal coliform density in assessing the occurrence of Salmonella, a common bacterial pathogen in surface water. Field studies involving irrigation water, field crops and soils indicate that when the fecal ccliform density in stream waters exceeded 1,000 per 100 ml, the occurrence of Salmonella was 53.5 percent. pH, Acidity, Alkalinity pH is of relatively minor importance, although waters with pH outside the 6.0 to 9.0 range can affect the survival of most organisms, particularly invertebrates. The usual pH for raw waste falls between 6.0 and 9.0; although the pH of the condensables tends to be higher (7.2 to 9.6). This pH range is close enough to neutrality that it does not significantly affect treatment effectiveness or effluent quality. However, some adjustment may be required, particularly if pH adjustment has been used to lower the pH for protein precipitation, or if the pH has been raised for ammonia stripping. The pH of the waste water then should be returned to its normal range before discharge. The effect of chemical additions for pH adjustment should be taken into consideration, as new pollutants could result. Acidity and alkalinity are reciprocal terms. Acidity is produced by substances that yield hydrogen ions upon hydrolysis and alkalinity is produced by substances that yield hydroxyl ions. The terms "total acidity" and "total alkalinity" are often used to express the buffering capacity of a solution. Acidity in natural waters is caused by carbon dioxide, mineral acids, weakly dissociated acids, and the salts of strong acids and weak bases. Alkalinity is caused by strong bases and the salts of strong alkalies and weak acids. The term pH is a logarithmic expression of the concentration of hydrogen ions. At a pH of 7, the hydrogen and hydroxyl ion concentrations are essentially equal and the water is neutral. Lower pH values indicate acidity while higher values indicate alkalinity. The relationship between pH and acidity or alkalinity is not necessarily linear or direct. Waters with a pH below 6.0 are corrosive to water works structures, distribution lines, and household plumbing fixtures and can thus add such constituents to drinking water as iron, copper, zinc, cadmium and lead. The hydrogen ion concentration can affect the "taste" of the water. At a low pH water tastes "sour." The bactericidal effect of chlorine is weakened as the pH increases, and it is advantageous to keep the pH close to 7. This is very significant for providing safe drinking water. Extremes of pH or rapid pH changes can exert stress conditions or kill aquatic life outright. Dead fish, associated algal blooms, 69 ------- and foul stenches are aesthetic liabilities of any waterway. Even moderate changes from "acceptable" criteria limits of pH are deleterious to some species. The relative toxicity to aquatic life of many materials is increased by changes in the water pH. Metalocyanide complexes can increase a thousandfold in toxicity with a drop of 1.5 pH units. The availability of many nutrient substances varies with the alkalinity and acidity. Ammonia is more lethal with a higher pH. The lacrimal fluid of the human eye has a pH of approximately 7.0 and a deviation of 0.1 pH unit from the norm may result in eye irritation for the swimmer. Appreciable irritation will cause severe pain. Temperature Because of the long detention time at ambient temperatures associated with typically large biological treatment systems used for treating renderer plant waste water, the temperature of the treated effluent from most rendering plants will be virtually the same as the temperature of the receiving body of water. Therefore, temperature effluent limitations were not established. Temperatures of the raw waste waters are, however, between 29° and 66°C (85° and 150°F), with a typical value of about 52°C (125°F); temperatures, of course, run higher during summer months than winter months. The major source of high temperature waters is the condensed cooking vapors. These high temperatures, along with the high strength wastes are an asset for biological treatment of the wastes, maintaining high growth rates of microorganisms required for good treatment. However, if the temperature of the raw wastes is too high—-greater than 52°C, the raw wastes may create a strong odor problem. Raw waste temperatures below 38°C (100°F) rarely cause odor problems. Temperature is one of the most important and influential water quality characteristics. Temperature determines those species that may be present; it activates the hatching of young, regulates their activity, and stimulates or suppresses their growth and development; it attracts, and may kill when the water becomes too hot or becomes chilled too suddenly. Colder water generally suppresses development. Warmer water generally accelerates activity and may be a primary cause of aquatic plant nuisances when other environmental factors are suitable. Temperature is a prime regulator of natural processes within the water environment. It governs physiological functions in organisms and, acting directly or indirectly in combination with other water quality constituents, it affects aquatic life with each change. These effects include cheirical reaction rates, enzymatic functions, molecular movements, and molecular exchanges between membranes within and between the physiological systems and the organs of an animal. Chemical reaction rates vary with temperature and generally increase as the temperature is increased. The solubility of gases in water varies with temperature. Dissolved oxygen is 70 ------- decreased by the decay or decomposition of dissolved organic substances and the decay rate increases as the temperature of the water increases reaching a maximum at about 30°C (86°F) . The temperature of stream water, even during summer, is below the optimum for pollution-associated bacteria. Increasing the water temperature increases the bacterial multiplication rate when the environment is favorable and the food supply is abundant. Reproduction cycles may be changed significantly by increased temperature because this function takes place under restricted temperature ranges. Spawning may not occur at all because temperatures are too high. Thus, a fish population may exist in a heated area only by continued immigration. Disregarding the decreased reproductive potential, water temperatures need not reach lethal levels to decimate a species. Temperatures that favor competitors, predators, parasites, and disease can destroy a species at levels far below those that are lethal. Fish food organisms are altered severely when temperatures approach or exceed 90°F. Predominant algal species change, primary production is decreased, and bottom associated organisms may be depleted or altered drastically in numbers and distribution. Increased water temperatures may cause aquatic plant nuisances when other environmental factors are favorable. Synergistic actions of pollutants are more severe at higher water temperatures. Given amounts of domestic sewage, refinery wastes, oils, tars, insecticides, detergents, and fertilizers more rapidly deplete oxygen in water at higher temperatures, and the respective toxicities are likewise increased. When water temperatures increase, the predominant algal species may change from diatoms to green algae, and finally at high temperatures to blue-green algae, because of species temperature preferentials. Blue-green algae can cause serious odor problems. The number and distribution of benthic organisms decreases as water temperatures increase above 90°F, which is close to the tolerance limit for the population. This could seriously affect certain fish that depend on benthic organisms as a food source. The cost of fish being attracted to heated water in winter months may be considerable, due to fish mortalities that may result when the fish return to the cooler water. Rising temperatures stimulate the decomposition of sludge, formation of sludge gas, multiplication of saprophytic bacteria and fungi (particularly in the presence of organic wastes), and the consumption of oxygen by putrefactive processes, thus affecting the esthetic value of a water course. In general, marine water temperatures do not change as rapidly or range as widely as those of freshwaters. Marine and estuarine fishes, therefore, are less tolerant of temperature variation. Although this limited tolerance is greater in estuarine than in open water marine species, temperature changes are more important to those fishes in estuaries and bays than to those in open 71 ------- marine areas, because of the nursery and replenishment functions of the estuary that can be adversely affected by extreme temperature changes. 72 ------- SECTION VII CONTROL AND TREATMENT TECHNOLOGY SUMMARY The waste load discharged from the independent rendering industry to receiving streams can be reduced to desired levels, including no discharge of pollutants, by conscientious water management, in-plant waste controls, process revisions, and by the use of a primary, secondary and tertiary waste water treatment. Figure 12 is a schematic of a suggested waste reduction program for the independent rendering industry to achieve a high quality effluent. This section describes many of the techniques and technologies that are available or that are being developed to achieve the various levels of waste reduction. In-plant control techniques and waste water management suggestions are described first. Waste treatment technology normally used as a primary treatment is then described. In the case of the offsite rendering industry, this "primary" treatment is a materials recovery process, and is considered as part of the in-plant system, although many of these systems have been improved to reduce pollution levels. The effluent frcm primary treatment is considered the "raw waste." Secondary treatment systems are used in the treatment of the raw waste. Each treatment process is described, and the specific advantages and disadvantages of each system, and the effectiveness on the specific waste water contaminants found in rendering waste are discussed. The tertiary and advanced treatment systems that are applicable to the waste from typical rendering plants are described in the last part of this section. Some of these advanced treatment systems have not been used on full scale for rendering plant wastes; therefore, the development status, reliability, and potential problems are discussed in greater detail than for the primary and secondary treatment systems that are in widespread use. IN-PLANT CONTROL TECHNIQUES The waste load from an independent rendering plant is composed of a waste water stream containing the various pollutants described in Section VI. The cost and effectiveness of treatment of the waste stream will vary with the quantity of water and the waste load. As indicated in Section V, the pollutant waste flow increases with plant size, and is higher for plants using barometric leg condensers. In-plant control techniques will reduce both water use and waste load. The former will be reduced by minimizing the entry of raw materials into the waste water stream, and the latter by cleanup procedures and frequency and by the type of condensing system used. 73 ------- Figure 12. Suggested Waste Reduction Program for Rendering Plants Waste Reduction Techniques Waste Reduction Effect Point of Application Plant Operations Partial Tertiary Treat. Irrigation Evaporation Reirto va1 of fine Sus. So'ids. Salt, 'hosphorus, V.'tnonia (as if c essary) r 9?.5% BOD \/ ------- The in-plant control techniques described below have been used in offsite rendering plants or are technically feasible. Condensables Condensables typically are high in BOD5, phosphorus, suspended solids, dissolved solids, TKN, ammonia, nitrates and grease (see Table 9). However, a number of plants are able to minimize the strength of Condensables in several ways. These include: o Avoid overloading cookers; o Provide and maintain traps in the vapor lines; o Control the speed of agitation; o Provide by-pass valves for controlling pressure bleed-down on cookers used for hydrolyzing raw material; o Control cooking rate. The volume of Condensables is dependent upon the type of raw material being processed and on the type of condenser used. From the standpoint of waste treatment, Condensables should not be diluted with fresh water. Treated waters should be used for operating barometric leg condensers. Control of High Strength Liquid Wastes Liquid drainage from raw materials can contribute significantly to the total raw waste load. These sources can be controlled or eliminated by containing them and then mixing the drainage with the raw materials as they enter a cooker, screening, or steam sparging and screening. Containing drainage may require plugging drains in the raw materials receiving area and in wet wells below receiving bins. Blood water and tank water, both of which are high-strength wastes (see Section V), can be eliminated by evaporating to stick and using as tankage for dry inedible rendering. Whole blood drying processes do not generate any blood water and should be considered as an alternative method to steam sparging and screening, followed by evaporation of blood water. Hide curing waste waters are of high strength (see Section V) and can be a significant part of the total raw waste load. This source can be eliminated by blending the hide curing wastes in relatively small amounts with raw materials being charged to cookers. Truck and Barrel Washings Solids, including grease, should be scraped or squeegeed from the trucks and barrels prior to washdown. Truck washings should be screened. 75 ------- Odor Control Although odor control by scrubbing does not contribute significantly to the raw waste load, it can add significantly to the waste water volume. This large contribution to the waste water volume can be avoided by using chemicals and recycling scrubbing water or by reusing treated water. Plant Cleanup and Spills Cleanup of the plant and spills should include dry cleanup by squeegeeing or scraping prior to washdown. Plant cleanup is usually required only once daily. Accidental spills and leaky equipment can, however, necessitate more frequent plant cleanup. Thus, considerable effort should be expended to avoid spills and to prevent leaks. A regularly scheduled maintenance program will minimize leaks; it will minimize the spills caused by equipment failure. IN-PLANT PRIMARY TREATMENT Flow Equalization Equalization facilities consist of a holding tank and pumping equipment designed to reduce the fluctuations of waste water flow through materials recovery systems. They can be economically advantageous, whether the industry is treating its own wastes or discharging into a city sewer after some pretreatment. The equalizing tank should have sufficient capacity to provide for uniform flow to treatment facilities throughout a 24-hour day. The tank is characterized by a varying flow into the tank and a constant flow out. The major advantages of equalization are that treatment systems can be smaller since they can be designed for the 24-hour average rather than the peak flows, and many secondary waste treatment systems operate much better when not subjected to shock loads or variations in feed rate. Many plants do not require any special tanks to achieve flow equalization because of the manner in which they are operated. For example, plants with large continuous systems or a number of batch systems (10 to 20) with staggered cooking cycles that operate most of the day are inherently achieving a near-constant flow of waste water. Screens Since so much of the pollutant matter for some sources of rendering plant wastes is originally solid (meat and fat particles), interception of the waste material by various types of screens is a natural first step. To assure the best performance on a plant waste water stream, flow equalization may be needed preceding screening equipment. 76 ------- Unfortunately, when the pollutant materials enter the sewage stream, they are subjected to turbulence, pumping, and mechanical screening, and they break down and release soluble BOD^ into the stream, along with colloidal, suspended, and greasy solids. Waste treatment—that is, the removal cf soluble, colloidal and suspended organic matter—is expensive. It is usually far simpler and less expensive to keep the solids out of the sewer. Static, vibrating, and rotary screens are the primary types used for this step in the in-plant primary treatment. Whenever possible, pilotscale studies are warranted before selecting a screen, unless specific operating data are available for the specific use intended, in the same solids concentration range, and under the same operating conditions. Static Screens The primary function of a static screen is to remove "free" or transporting fluids. This can be accomplished in several ways, and in most older concepts, only gravity drainage is involved. A concavely curved screen design using high velocity pressure feeding was developed and patented in the 1950's for mineral classification and has been adapted to other uses in the process industries. This design employs bar interference to the slurry which knives off thin layers of the flow over the curved surface.is Beginning in 1969, United States and foreign patents were allowed on a three-slope static screen made of specially coined curved wires. This concept used the Coanda or wall attachment phenomenon to withdraw the fluid from the under layer of a slurry which is stratified by controlled velocity over the screen. This method of operation has been found to be highly effective in handling slurries containing fatty or sticky fibrous suspended matter.1S Vibrating Screens The effectiveness of a vibrating screen depends on a rapid motion. Vibrating screens operate between 99 rpm and 1800 rpm; the motion can be either circular or straight line, varying from 0.08 to 1.27 cm (1/32 to 1/2 inch) total travel. The speed and motion are selected by the screen manufacturer for the particular application. Of prime importance in the selection of a proper vibrating screen is the application of the proper cloth. The capacities on liquid vibrating screens are based on the percent of open area of the cloth. The cloth is selected with the proper combination of strength of wire and percent of open area. If the waste solids to be handled are heavy and abrasive, wire of a greater thickness and diameter should be used to assure long life. However, if the material is light or sticky in nature, the durability of the 77 ------- screening surface may be the least consideration. In such a case, a light wire may be desired to provide an increased percent of open area. Rotary Screens One type of barrel or rotary screen, driven by external rollers, receives the waste water at one open end and discharges the solids at the other open end. The screen is inclined toward the exit end to facilitate movement of solids. The liquid passes outward through the screen (usually stainless steel screen cloth or perforated metal) to a receiver and then to the sewer. To prevent clogging, the screen is usually sprayed continuously by a line of external spray nozzles. Another rotary screen commonly used in various industries, such as the meat industry, is driven by an external pinion gear. The raw waste water is fed into the interior of the screen, below the longitudinal axis, and solids are removed in a trough and screw conveyor mounted lengthwise at the axis (center line) of the barrel. The liquid exits outward through the screen into a tank under the screen. The screen is partially submerged in the liquid in the tank. The screen is usually 40 x 40 mesh, with 0.4 mm (1/64 inch) openings. Perforated lift paddles mounted lengthwise on the inside surface of the screen assist in lifting the solids to the conveyor trough. This type is also generally sprayed externally to reduce blinding. Grease clogging can be reduced by coating the wire cloth with teflon. Solids removal up to 82 percent is reported.15 Applications A broad range of applications exists for screens as the first stage of in-plant waste water treatment. These include both the plant waste water and waste water discharged from individual sources, especially streams with high solids content such as raw material drainage. Catch Basins The catch basin for the separation of grease and solids from independent rendering waste waters was originally developed to recover marketable grease. Since the primary objective was grease recovery, all improvements were centered on skimming. Many catch basins were not equipped with automatic bottom sludge removal equipment. These basins could often be completely drained to the sewer and were "sludged out" weekly or at frequencies such that septic conditions would not cause the sludge to rise. Rising sludge was undesirable because it could affect the color and reduce the market value of the grease. In the past twenty years, with waste treatment gradually becoming an added economic incentive, catch basin design has been improved in the solids removal area as well. In fact, the low market 78 ------- value of inedible grease and tallow has reduced concern about quality of the skimmings, and now the concern is shifting toward overall effluent quality improvement. Gravity grease recovery systems will remove 20 to 30 percent of the BOD5, 40 to 50 percent of the suspended solids, and 50 to 60 percent of the grease (hexane solubles).15 The majority of the gravity grease recovery basins (catch basins) are rectangular. Flow rate is the most important criterion for design; 30 to 40 minutes detention time at one-hour peak flow is a common design sizing factor.15 The use of an equalizing tank ahead of the catch basin obviously minimizes the size requirement for the basin. A shallow basin—up to 1.8 meters (6 feet)—is preferred. A "skimmer" skims the grease and scum off the top into collecting troughs. A scraper moves the sludge at the bottom into a submerged hopper from which it can be pumped or carries it up and deposits it into a hopper. Both skimmings and sludge can be recycled as a raw material for rendering. Two identical catch basins, with a common wall, are desirable so operation can continue if one is down for maintenance or repair. Both concrete and steel tanks are used. Concrete tanks have the inherent advantages of lower overall maintenance and more permanence of structure. However, some plants prefer to be able to modify their operation for future expansion or alterations or even relocation. All-steel tanks have the advantage of being semipcrtable, more easily field- erected, and more easily modified than concrete tanks. The all- steel tanks, however, require additional maintenance as a result of wear from abrasion and corrosion. A tank using all-steel walls and a concrete bottom is probably the best compromise between the all-steel tank and the all- concrete tank. The advantages are the same as for steel; however, the all-steel tank requires a footing underneath the supporting members, whereas the concrete bottom forms the floor and supporting footings for the steelwall tank. Dissolved Air Flotation This system is, by definition, a primary treatment system; thus, the effluent from a dissolved air flotation system is considered raw waste. This system is normally used to remove fine suspended solids and is particularly effective on grease in the waste waters from independent rendering plants. It is a relatively recent technology in the rendering industry; therefore, it is not in widespread use, although increasing numbers of plants are installing these systems. Dissolved air flotation appears to be the single most effective device currently available for a plant to use to reduce the 79 ------- Compressed Air Feed OD O Effluent Totol Pressurizotion Process Float V Sludge Figure 13. Dissolved Air Flotation ------- pollutant waste load in its raw waste water stream. It is expected that the use of dissolved air flotation will become more common in the industry, especially as a step in achieving the 1983 standards. Technical Description Air flotation systems are used to remove any suspended material from waste water with a specific gravity close to that of water. The dissolved air system generates a supersaturated solution of waste water and air by pressurizing waste water and introducing compressed air, then mixing the two in a detention tank. This "supersaturated" waste water flows to a large flotation tank where the pressure is released, thereby generating numerous small air bubbles which effect the flotation of the suspended organic material by one of three mechanisms: 1) adhesion of the air bubbles to the particles of matter; 2) trapping of the air bubbles in the floe structures of suspended material as the bubbles rise; and 3) adsorption of the air bubbles as the floe structure is formed from the suspended organic matter.16 In most cases, bottom sludge removal facilities are also provided. There are three process alternatives that differ by the proportion of the waste water stream that is pressurized and into which the compressed air is mixed. In the total pressurization process, Figure 13, the entire waste water stream is raised to full pressure for compressed air injection. In partial pressurization, Figure 14, only a part of the waste water stream is raised to the pressure of the compressed air for subsequent mixing. Alternative A of Figure 14 shows a sidestream of influent entering the detention tank, thus reducing the pumping required in the system shown in Figure 13. In the recycle pressurization process, Alternative B of Figure 14, treated effluent from the flotation tank is recycled and pressurized for mixing with the compressed air and then, at the point of pressure release, is mixed with the influent waste water. Operating costs may vary slightly, but performance should be essentially equal among the alternatives. Improved performance of the air flotation system is achieved by coagulation of the suspended matter prior to treatment. This is done by pH adjustment or the addition cf coagulant chemicals, or both. Aluminum sulfate, iron sulfate, lime, and polyelectrolytes are used as coagulants at varying concentrations up to 300 to 400 mg/1 in the raw waste. These chemicals are essentially totally removed in the dissolved air unit, thereby adding little or no load to the downstream waste treatment systems. However, the resulting float and sludge may become a less desirable raw material for recycling through the rendering process as a result of chemical coagulation addition. Che -..Gal precipitation is also discussed later, particularly in regard to phosphorus removal, under tertiary treatment; phosphorus can also be removed at this primary (inplant) treatment stage. A slow paddle mix will 81 ------- improve coagulation. It has been suggested that the pro+^inaceous matter in rendering plant waste could be removed by reducing the pH of the waste water to the isoelectric point of about 3«5«lf> The proteinaceous material would be coagulated at that point and readily removed as float from the top of the dissolved air unit. This is not being done commercially in the rendering industry in the United States at the present time. Similarly, the Alwatec process has been developed by a company in Oslo, Norway, using a lignosulfonic acid precipitation and dissolved air flotation to recover a high protein product that is valuable as a feed.16 Nearly instantaneous protein precipitation and hence, nitrogen removal, is achieved when a high protein- containing effluent ia acidified to a pH between 3 and 4 with a high molecular weight lignosulfonic acid. BOD5 reduction is reported to range from 60 to 95 percent. The effluent must be neutralized before further treatment by the addition of milk of lime or some other inexpensive alkali. This process is being evaluated on meat packing waste in one plant in the United States at the present time.18 One of the manufacturers of dissolved air flotation equipment indicated a 60 percent suspended solids removal and 80 to 90 percent grease removal without the addition of chemicals. With the addition of 300 to 400 mg/1 of inorganic coagulants and a slow mix to coagulate the organic matter, the manufacturer says that 90 percent or more of the suspended solids and more than 90 ercent of the grease can be removed.19 Total nitrogen reduction >:^-: "sn 35 and 70 percent was found in dissolved air units surveyed in the meat packing industry-8 North Star's staff observed the operation of several dissolved air units during the verification sampling program and plant visits of the rendering and meat packing industries. One meat packing plant that was visited controlled the feed rate and pH of the waste water and achieved 90 to 95 percent removal of solids and grease. other plants had relatively good operating success, but some did not achieve the results that should have been attainable. It appeared that they did not fully understand the process chemistry and were using erroneous operating procedures. Problems and Reliability The reliability of the dissolved air flotation process and of the equipment seems to be well established, although it is relatively new technology for the rendering industry. As indicated above, it appears that the use of the dissolved air system is not fully exploited by some of the companies who have installed it for waste water treatment. The potential reliability of the dissolved air process can be realized by proper installation and operation. The feed rate and process conditions must be maintained at the proper levels at all times to assure this reliability. This fact does not seem to be fully understood or of sufficient concern to some companies, and thus full benefit is frequently not achieved. 82 ------- Compressed Air , [Retention f V Tank I Recycle Pressurizotion Process (Alternative B) CO CO 1 1 Feed from , Primary i fa > Treatment j i ^(Retention ] 1 Flotation Tank 1 1 • >v c S C L ' rioai V Sludge Treated Effluent Compressed Air Partial Pressurization Process (Alternative A) Figure 14. Process Alternatives for Dissolved Air Flotation ------- The sludge and float taken from the dissolved air system can both be recycled through the rendering process. The addition of polyelectrolyte chemicals was reported to create some problems for sludge dewatering and for subsequent use as a raw material for rendering. The mechanical equipment involved in the dissolved air flotation system is fairly simple, requiring standard maintenance attention for such things as pumps and mechanical drives. WASTE WATER TREATMENT SYSTEMS The secondary treatment methods commonly used for the treatment of rendering plant wastes after in-plant primary treatment (solids removal) are the following biological systems: anaerobic process, aerobic lagoons, and variations of the activated sludge process. Several of these systems are capable of providing up to 97 percent BOD5 reductions and 95 percent suspended solids reduction, as observed primarily in the meat packing industry. Combinations of these systems can achieve reductions up to 99 percent in BOD5 and grease, and up to 97 percent in suspended solids for rendering plant waste water. Based on operating data from a pilot-plant system on packing plant wastes, the rotating biological contactor also shows potential as a secondary treatment system. The selection of a secondary biological system for treatment of rendering plant wastes depends upon a number of important system characteristics. Some of these are waste water volume, waste load concentration, equipment used, pollutant reduction effectiveness required, reliability, consistency, and resulting secondary pollution problems (e.g., sludge disposal and odor control). The characteristics and performance of each of the above-mentioned secondary treatment systems, and also for common combinations of them, are described below. Capital and operating costs are discussed in Section VIII. Anaerobic Processes Elevated temperatures (29° to 35°C, or 85° to 95°F) and high concentrations of carbohydrates, fats, proteins, and nutrients in some independent rendering-plant wastes make these wastes well suited to anaerobic treatment. Anaerobic or facultative microorganisms, which function in the absence of dissolved oxygen, break down the organic wastes to intermediates such as organic acids and alcohols. Methane bacteria then convert the intermediates primarily to carbon dioxide and methane. Unfortunately, much of the organic nitrogen present in the influent is converted to ammonia nitrogen. Also, if sulfur compounds are present (such as from high-sulfate raw water—50 to 100 mg/1 sulfate), hydrogen sulfide will be generated. Acid conditions are undesirable because methane formation is suppressed and noxious odors develop. Anaerobic processes are economical because they provide high overall removal of BOD5 and suspended solids with no power cost (other than pumping) and with 84 ------- low land requirements. Two types of anaerobic processes are used: anaerobic lagoons and anaerobic contact systems. Anaerobic Lagoons Anaerobic lagoons are widely used in the rendering industry as the first step in secondary treatment or as pretreatment prior to discharge to a municipal system. Reductions of up to 97 percent in BOD5 and up to 95 percent in suspended solids can be achieved with the lagoons; 85 percent reduction is common. Occasionally two anaerobic lagoons are used in parallel and sometimes in series. These lagoons are relatively deep (3 to 5 meters, or about 10 to 17 feet), low surface area systems with typical waste loadings of 240 to 320 kg BOD5/1000 cubic meters (15 to 20 Ib BOD5/1000 cubic feet) and detention times of five to ten days. A thick scum layer of grease may accumulate on the surface of the lagoon to retard heat loss, to ensure anaerobic conditions, and hopefully to retain obnoxious odors. Low pH and wind can adversely affect the scum layer. Paunch manure and straw may be added to this scum layer but this would increase the nutrient levels. Plastic covers of nylon-reinforced Hypalon, polyvinyl chloride, and styrofoam have been used on occasion by other industries in place of the scum layer; in fact, some states require this. Properly installed covers provide a convenient means for odor control and collection of the by-product methane gas. THe waste water flow inlet should be located near, but not on, the bottom of the lagoon. In some installations, sludge is recycled to ensure adequate anaerobic seed for the influent. The outlet from the lagoon should be located to prevent short circuiting of the flow and carry-over of the scum layer. For best operation, the pH should be between 7.0 and 8.5. At lower pH, methane-forming bacteria will not survive and the acid formers will take over to produce very noxious odors. At a high pH (above 8.5), acid-forming bacteria will be suppressed and lower the lagoon efficiency. Advantages/-Pi sadyant ages. Advantages of an anaerobic lagoon system are initial lew cost, ease of operation, and the ability to handle large grease loads and shock waste loads, and yet continue to provide a consistent quality effluent.20 Disadvantages of an anaerobic lagocn are the hydrogen sulfide generated from sulfate-containing waters and the typically high ammonia concentrations in the effluent of 100 mg/1 or more. If acid conditions develop, severe odor problems result. Incidentally, if the gases evolved are contained, it is possible to use iron filings to remove sulfides. 85 ------- ^BfiiiS^tionjE^,. Anaerobic lagoons used as the first stage in secondary treatment are usually followed by aerobic lagoons. Placing a small, mechanically aerated lagoon between the anaerobic and aerobic lagoons is becoming popular. A number of meat packing plants are currently installing extended aeration units following the anaerobic lagoons to obtain nitrification. Anaerobic lagoons are not permitted in some states or areas where the ground water is high or the soil conditions are adverse (e.g., too porous) , or because of odor problems. Anaerobic Contact Systems Anaerobic contact systems require far more equipment for operation than do anaerobic lagoons, and consequently were not found to be used by the rendering industry. However, their use by some meat packing plants has demonstrated their applicability to rendering plant waste waters because of the similarity in waste characteristics. The equipment, as illustrated in Figure 15, consists of equalization tanks, digesters with mixing equipment, air or vacuum gas stripping units, and sedimentation tanks (clarifiers) . Overall reduction of 90 to 97 percent in BOD5 and suspended solids is achievable. Equalized waste water flow is introduced into a mixed digester where anaerobic decomposition takes place at a temperature of 33° to 35°C (90° to 95°F) . BOD5 loading into the digester is between 2.4 and 3.2 kg/cubic meter (0.15 and 0.20 Ib/cubic foot) and the detention time is between three and twelve hours. After gas stripping, the digester effluent is clarified and sludge is recycled at a rate of about one-third the raw waste influent rate. Sludge is removed from the system at the rate of about 2 percent of the raw waste volume. Advantages-Pi sadyantages^ Advantages of the anaerobic contact system are high organic waste load reduction in a relatively short time; production and collection of methane gas that can be used to maintain a high temperature in the digester and also to provide auxiliary heat and power; good effluent stability to grease and waste load shocks; and application in areas where anaerobic lagoons cannot be used. Disadvantages of anaerobic contactors are higher initial cost and maintenance costs and potential odor emissions from the clarifiers. Anaerobic contact systems are restricted to use as the first stage of secondary treatment and can be followed by the same systems as follow anaerobic lagoons. 86 ------- oo —I Plant Effluent Equalizing Tank A w Sludge Recycle U/vA- HeatersV/ V^y Anaerobic Digesters Gas Stripping Units Sedimentation Tanks Effluent Figure 15. Anaerobic Contact Process ------- Aerated Lagoons Aerated lagoons have been used successfully for many years in a small number of installations treating meat packing and rendering plant wastes. However, with the tightening of effluent limitations, and because aerated lagoons can provide the additional treatment, the number of installations is increasing. Aerated lagoons use either fixed mechanical turbine-type aerators, floating propeller-type aerators, or a diffused air system for supplying oxygen to the waste water. The lagoons usually are 2.4 to 4.6 meters (8 to 15 feet) deep, and have a detention time of two to ten days. BOD5 reductions range from 40 to 60 percent, with little or no reduction in suspended solids. Because of this, aerated lagoons approach conditions similar to extended aeration without sludge recycle (see below). Advantages-Di sadvantages Advantages of this system are that it can rapidly add dissolved oxygen (DO) to convert anaerobic effluent to an aerobic state; provide additional BOD5 reduction; and it requires a relatively small amount of land. Disadvantages include the power requirements and the fact that the aerated lagoon, in itself, usually does not reduce BOD5 and suspended solids adequately to be used as the final stage in a high performance secondary system. Applications Aerated lagoons are usually the first or second stages of secondary treatment, and must be followed by aerobic (shallow) lagoons to reduce suspended solids and to provide the required final treatment. Aerobic Lagoons Aerobic lagoons (stabilization lagoons or oxidation ponds) are large surface area, shallow lagoons, usually 1 to 2.3 meters (3 to 8 feet) deep, loaded at a BOD5 rate of 20 to 50 pounds per acre. Detention times vary from about one month to six or seven months; thus, aerobic lagoons require large areas of land. Aerobic lagoons serve three main functions in waste reduction: o Allow solids to settle out; o Equalize and control flow; o Permit stabilization of organic matter by aerobic and facultative microorganisms and also by algae. ------- Actually, if the pond is quite deep, 1.8 to 2.4 meters.(6 to 8 feet), the waste water near the bottom may be void of dissolved oxygen and anaerobic organisms may be present. Therefore, settled solids can be decomposed into inert and soluble organic matter by aerobic, anaerobic, or facultative organisms, depending upon the lagoon conditions. The soluble organic matter is also decomposed by microorganisms. It is essential to maintain aerobic conditions in at least the upper six to twelve inches in shallow lagoons, since aerobic microorganisms cause the most complete removal of organic matter. Wind action assists in carrying the upper layer of liquid (aerated by air-water interface and photosynthesis) down into the deeper portions. The anaerobic decomposition generally occurring in the bottom converts solids to liquid organics, which can become nutrients for the aerobic organisms in the upper zone. Algae growth is common in aerobic lagoons; this currently is a drawback when aerobic lagoons are used for final treatment because the algae appear as suspended solids and contribute BOD5. Algae added to receiving waters are thus considered a pollutant. Algae in the effluent may be reduced by drawing off the lagoon effluent at least 30 cm (about 14 inches) below the surface, where concentrations are usually lower. Algae in the lagoon, however, play an important role in stabilization. They use CO2, sulfates, nitrates, phosphates, water and sunlight to synthesize their own organic cellular matter and give off oxygen. The oxygen may then be used by other microorganisms for their metabolic processes. However, when algae die they release their organic matter in the lagoon, causing a secondary loading. Ammonia disappears without the appearance of an equivalent amount of nitrite and nitrate in aerobic lagoons as evidenced by the results of our field sampling survey. From this, and the fact that aerobic lagoons tend to become anaerobic near the bottom, it appears that considerable denitrification can occur. Ice and snow cover in winter reduces the overall effectiveness of aerobic lagoons by reducing algae activity, preventing mixing, and preventing reaeration by wind action and diffusion. This cover, if present for an extended period, can result in anaerobic conditions. When there is no ice and snow cover on large aerobic lagoons, high winds can develop a strong wave action that can damage dikes. Riprap, segmented lagcons, and finger dikes are used to prevent wave damage. Finger dikes, when arranged appropriately, also prevent short circuiting of the waste water through the lagoon. Rodent and weed control, and dike maintenance are all essential for good operation of the lagoons. Advantages-Di sadvantages Advantages of aerobic lagoons are that they reduce the suspended solids and colloidal matter, and oxidize the organic matter of the influent to the lagoon; they also permit flow control and waste water storage. Disadvantages are reduced effectiveness 89 ------- during winter months that may require no discharge for periods of three months or more, the large land requirements, the algae growth problem leading to higher suspended solids, and odor problems for a short time in spring, after the ice melts and before the lagoon becomes aerobic again. Applications Aerobic lagoons usually are the last stage in secondary treatment and frequently follow anaerobic or anaerobic-plus-aerated lagoons. Large aerobic lagoons allow plants to store waste waters for discharge during periods of high flow in the receiving body of water or to store for irrigation purposes during the summer. These lagoons are particularly popular in rural areas where land is available and relatively inexpensive. Activated Sludge The conventional activated sludge process is schematically shown in Figure 16. In this process recycled biologically active sludge or floe is mixed in aerated tanks or basins with waste water. The microorganisms in the floe adsorb organic matter from the wastes and convert it by oxidation-enzyme systems to such stable products as carbon dioxide, water, and sometimes nitrates and sulfates. The time required for digestion depends on the type of waste and its concentration, but the average time is six hours. The floe, which is a mixture of microorganisms (bacteria, protozoa, and filamentous types)„ food, and slime material, can assimilate organic matter rapidly when properly activated; hence, the name activated sludge. From the aeration tank, the mixed sludge and waste water, in which little nitrification has taken place, are discharged to a sedimentation tank. Here the sludge settles out, producing a clear effluent, low in BOD5 and a biologically active sludge. A portion of the settled sludge, normally about 20 percent, is recycled to serve as an inoculum and to maintain a high mixed liquor suspended solids content. Excess sludge is removed (wasted) from the system, to thickeners and anaerobic digestion, to chemical treatment and dewatering by filtration or centrifugation or to land disposal where it is used as fertilizer and soil conditioner to aid secondary crop growth. This conventional activated sludge process can reduce BOD5 and suspended solids up to 95 percent. However, it cannot readily handle shock loads and widely varying flows and therefore might require upstream flow equalization. Various modifications of the activated sludge process have been developed, such as the tapered aeration, step aeration, contact stabilization, and extended aeration. Of these, extended aeration processes are most frequently being used for treatment of meat processing, meat packing and rendering wastes. 90 ------- Raw Waste Primary Sedimentation Secondary Sedimentation Aeration Tank |_Return_ Activated Sludge Effluent Waste Sludge Waste I Sludge^ Figure 16. Activated Sludge Process ------- Extended Aeration The extended aeration process is similar to the conventional activated sludge process, except that the mixture of activated sludge and raw materials is maintained in the aeration chamber for longer periods of time. The usual detention time in extended aeration ranges from one to three days, rather than six hours as in the conventional process. During this prolonged contact between the sludge and raw waste, there is ample time for the organic matter to be adsorbed by the sludge and also for the organisms to metabolize the organic matter which they have adsorbed. This allows for a much greater removal of organic matter. In addition, the organisms undergo a considerable amount of endogenous respiration, and therefore oxidize much of the organic matter which has been built up into the protoplasm of the organism. Hence, in addition to high organic removals from the waste waters, up to 75 percent of the organic matter of the microorganisms is decomposed into stable products and consequently less sludge will have to be handled. In extended aeration, as in the conventional activated sludge process, it is necessary to have a final sedimentation tank. Some of the solids resulting from extended aeration are rather finely divided and therefore settle slowly, requiring a longer period of settling. The long detention time in the extended aeration tank makes it possible for nitrification to occur. In nitrification under aerobic conditions, ammonia is converted to nitrites and nitrates by specific groups of nitrifying bacteria. For this to occur, it is necessary to have sludge detention times in excess of ten days. 20 This can be accomplished by regulating the amounts of recycled and wasted sludge. Oxygen-enriched gas could be used in place of air in the aeration tanks to improve overall performance. This would require that the aeration tank be partitioned and covered, and that the air compressor and dispersion system be replaced by a rotating sparger system. When cocurrent, staged flow and recirculation of gas back through the liquor are employed, between 90 and 95 percent oxygen use is claimed. Although this modification of extended aeration has not been used in treating rendering plant wastes, it is being used successfully for treating other wastes. Adyantages~Disadvantages._ The advantages of the extended aeration process are that it is immune to shock loading and flow fluctuations because the incoming raw waste load is diluted by the liquid in the system to a much greater extent than in the conventional activated sludge. Also, because of the long detention time, high BOD5 reductions can be obtained. Other advantages of the system are the elimination of sludge digestion equipment and the capability to produce a nitrified effluent. Disadvantages are that it is difficult to remove most of the suspended solids from the mixed liquor discharged from the aeration tank; large volume tanks or basins are required to 92 ------- accommodate the long detention times; and operating costs for aeration are high. Applications^ Because of the nitrification process, extended aeration systems are being used by some industries following anaerobic processes or lagoons to produce low BOD5 and low ammonia-nitrogen effluents. They are also being used as the first stage of secondary treatment, followed by polishing lagoons. Rotating Biological Contactor Process Description The rotating biological contactor (RBC) consists of a series of closely spaced flat parallel disks which are rotated while partially immersed in waste waters being treated. A biological growth covering the surface of the disk adsorbs dissolved organic matter present in the waste water. As the biomass on the disk builds up, excess slime is sloughed off periodically and is settled out in sedimentation tanks. The rotation of the disk carries a thin film of waste water into the air where it absorbs the oxygen necessary for the aerobic biological activity of the biomass. The disk rotation also promotes thorough mixing and contact between the biomass and the waste waters. In many ways the RBC system is a compact version of a trickling filter. In the trickling filter, the waste waters flow over the media and thus over the microbial flora; in the RBC system, the flora is passed through the waste water. The system can be staged to enhance overall waste load reduction. Organisms on the disks selectively develop in each stage and are thus particularly adapted to the composition of the waste in that stage. The first stages might be used for removal of dissolved organic matter, while the latter stages might be adapted to nitrification of ammonia. Development Status The RBC system was developed independently in Europe and the United States about 1955 for the treatment of domestic waste; it found application only in Europe, where there are an estimated 1000 domestic installations.20 However, the use of the RBC for the treatment of meat plant waste is being evaluated at the present time. The only operating information available on its use on meat packing waste is from a pilotscale system; no information appears to be available on its use for treating rendering plant wastes. The pilot-plant studies were conducted with a four-stage REC system with four-foot diameter disks. The system was treating a portion of the effluent from the Austin, Minnesota, anaerobic contact plant used to treat meat packing waste. These results showed a BOD5 removal in excess of 50 percent, with loadings less than 0.037 kg BOD5 per unit area on an average BOD5 influent concentration of approximately 25 mg/1.2i 93 ------- Data from Autotrol Corporation, one of the suppliers of RBC systems, revealed ammonia removal of greater than 90 percent by nitrification in a multistage unit.21 Four to eight stages of disks with maximum hydraulic loadings of 61 liters per day per square meter (1.5 gallons per day per square foot) of disk area are considered normal for ammonia removal. A large installation was recently completed at the Iowa Beef Processors plant in Dakota City, Nebraska, for the further treatment of the effluent from an anaerobic lagoon.22 No data are available on this installation, which has been plagued with mechanical problems. Advantages-Disadvantages The major advantages of the RBC system are its relatively low first cost; the ability to stage to obtain dissolved organic matter reduction with the potential for removal of ammonia by nitrification; and its good resistance to hydraulic shock loads. Disadvantages are that the system should be housed, if located in cold climates, to maintain high removal efficiencies and to control odors. Although this system has demonstrated its durability and reliability when used on domestic wastes in Europe, it has not yet been proved on rendering plant wastes. Uses Rotating biological contactors could be used for the entire aerobic secondary system. The number of stages required depend on the desired degree of treatment and the influent strength. Typical applications of the rotating biological contactor, however, may be for polishing the effluent from anaerobic processes, and as pretreatment prior to discharging wastes to a municipal system. A BOD5 reduction of 98 percent is reportedly achievable with a four-stage RBC.20 Performance of Various Secondary Treatment Systems Table 13 shows BOD5, suspended solids (SS) , and grease removal efficiencies for various biological treatment systems on rendering plant and meat packing plant waste waters. Exemplary values each represent results from an actual treatment system, except for the data on the anaerobic plus aerobic lagoon system under treatment on meat packing waste waters, which includes two plants. The number of systems used to calculate average values is shown in Table 13. It is apparent that the anaerobic plus aerobic lagoon system is the one most commonly used by meat packing and rendering plants. The estimated reduction of BOD5 for meat packing waste waters shown for the anaerobic lagoon plus rotating biological contactor 94 ------- Table 13. Performance of Various Secondary Treatment Systems CO +J C CO rH PL. M n •H (-1 0) T3 C (1) P3 Secondary Treatment System (number of systems used to determine averages) Anaerobic + Aerobic Lagoon (4) Activated Sludge (2) Aerated + Aerobic Lagoon (2) Anaerobic + Aerobic Lagoon (22) Anaerobic + Aerated + Aerobic Lagoon (3) Anaerobic Contact Process + Aerobic Lagoon (1) co CO .u C nJ PM w c •H ^1 O cd fi . M-t 4-1 0) 0) S Extended Aeration + Aerobic Lagoon (1) Anaerobic Lagoon + Rotating Biological Contactor Anaerobic Lagoon + Extended Aeration + Aerobic Lagoon Anaerobic Lagoon + Trickling Filter (1) 2-Stage Trickling Filter (1) Aerated + Aerobic Lagoon (1) Anaerobic Contact (1) Water Wasteload Reduction, Percent Ave BOD 5 97.7 93.7 96.9 95.4 98.3 98.5 96.0 98. 5e 98e 97.5 95.5 99.4 96.9 rage V< SS 97.3 86.1 88.2 93.5 93.3 96.0 86.0 — 93e 94.0 95.0 94.5 97.1 alues Grease 89.2 92.2 77.5 95.3 98.5 99.0 98.0 98e 96.0 98.0 — 95.8 Exem BOD 5 99.0 96.6 97.7 98.9 99.5 96.0 99.4 96.9 Diary \ SS 99.9 97.1 93.8 96.6 97.5 86.0 94.5 97.1 ralues Grease 99.4 99.4 78.8 98.9 99.2 98.0 95.8 e = estimated 95 ------- is based on preliminary pilot-plant results. The values shown for the anaerobic-lagoon plus extended aeration system are based on estimates of their combined effectiveness that are below the value calculated by using the average removal efficiency for the two components of the system, individually. For example, if the BOD5 reduction for the anaerobic lagoon and the extended aeration were each 90 percent, the calculated efficiency of the two systems combined would be 99 percent. The data of Table 13 show that, for rendering plants, the anaerobic plus aerobic lagoons are the most effective system of those studied for BOD5, SS, and grease removal. Furthermore, the anaerobic plus aerobic lagoon system appears, by percent reductions, to be more effective en rendering than on meat packing waste waters. This conclusion could be the result of an insufficient number of observations; however, it most likely is because the rendering waste loadings in the treatment system were frequently low. In fact, the BOD5 waste loadings to this type of system for three of the rendering plants were 12.8; 125, and 35.3 kg BOD5/1000 cubic meters (15 to 20 Ib BOD5/1000 cubic feet). All of the secondary treatment systems listed in Table 13 are capable of treating typical rendering plant waste waters to a degree sufficient to meet the 1977 standards recommended in Section IX. These systems, equipped with a sand filter or its equivalent, are also capable of producing a final effluent that would meet the 1983 standards recommended in Section X. In fact, the data presented in Section X show that at least three of these systems alone—anaerobic plus aerobic lagoon, activated sludge, or aerated plus aerobic lagoon--are already producing rendering plant effluent that meets the majority of pollutant parameter limitations for 1983. TERTIARY AND ADVANCED TREATMENT Chemical Precipitation Phosphorus is an excellent nutrient for algae and thus can promote heavy algae blooms. As such, it cannot be discharged into receiving streams, and its concentration should not be allowed to build up in a recycle water stream. However, the presence of phosphorus is particularly useful in spray or flood irrigation systems as a nutrient for plant growth. The effectiveness of chemical precipitation for removing phosphorus. Figure 17, has been verified in full scale during the North star verification sampling program of the meat packing industry.a One packing plant operates a dissolved air flotation system as a chemical precipitation unit and achieves 95 percent phosphorus removal, to a concentration of less than 1 mg/1. Chemical precipitation can be used for primary (in-plant) treatment to remove BOD5, suspended solids, and grease, as discussed earlier in conjunction with dissolved air flotation. 96 ------- Also, it can be used as a final treatment following biological treatment to remove suspended solids in addition to phosphorus. Technical Description Phosphorus occurs in waste water streams from rendering plants primarily as phosphate salts. Phosphates can be precipitated with trivalent iron and trivalent aluminum salts. It can also be rapidly precipitated by the addition of lime; however, the rate of removal is controlled by the agglomeration of the precipitated colloids and by the settling rate of the agglomerate.16 Laboratory investigation and experience with in-plant operations have substantially confirmed that phosphate removal is dependent on pH and that this removal tends to be limited by the solubility behavior of the three phosphate salts—calcium, aluminum, and iron. The optimum pH for the iron and aluminum precipitation occurs in the 4 to 6 range, whereas the calcium precipitation occurs on the alkaline side at pH values above 9.5. Since the removal of phosphorus is a two-step process involving precipitation and then agglomeration, and both are sensitive to pH, controlling the pH level takes on added significance. If a chemical other than lime is used in the precipitation-coagulation process, two levels of pH are required. Precipitation occurs on the acid side and coagulation is best carried out on the alkaline side. The precipitate is removed by sedimentation or by dissolved air flotation.16 Polyelectrolytes are polymers that can be used as primary coagulants, flocculation aids, filter aids, or for sludge conditions. Phosphorus removal may be enhanced by the use of such polyelectrolytes by producing a better floe than might occur without such chemical addition.23 The chemically precipitated sludge contains grease and organic matter in addition to the phosphorus, if the system is used in primary treatment. If it is used as a post-secondary treatment, the sludge volume will be less and it will contain primarily phosphorus salts. The sludge from either treatment can be landfilled. Development Status This process is well established and understood, technically. However, its use on rendering plant waste waters, normally as a primary waste treatment system, is very limited and is not expected to gain widespread acceptance. This is because most rendering plants do not have high phosphorus levels in their total waste waters and have other effective primary treatment processes for BOD5, S3, and grease removal. 97 ------- Problems and Reliability As indicted above, the reliability of this process is well established; however, it is a chemical process and as such requires the appropriate control and operating procedures. The problems that can be encountered in operating this process are frequently the result of a lack of understanding or inadequate equipment. Sludge disposal is not expected to be a problem, although the use of polyelectrolytes and their effect on the dewatering properties of the sludge are open to some question at the present time. In addition, the use of the recovered sludge as a raw material for rendering may be less desirable as a result of chemical addition. Sand Filter A slow sand filter is a specially prepared bed of sand or other mineral fines on which doses of waste water are intermittently applied and from which effluent is removed by an under-drainage system (Figure 18); it removes solids from the waste water stream. BOD5 removal occurs primarily as a function of the degree of solids removal, although some biological action occurs in the top inch or two of sand. Effluent from the sand filter is of a high quality, with BOD5 and suspended solids concentrations of less than 10 mg/1.24 Although the performance of a sand filter is well known and documented, it is not in common use be- cause it is not needed to reach current waste water standards. A rapid sand filter may operate under pressure in a closed vessel or may be built in open concrete tanks. It is primarily a water treatment device and thus would be used as tertiary treatment, following secondary Float Primary or Qopnnflnrv ^> Treatment Effluent pH Ajustment N s> Chemical Addition \ j> / ^ Air Flotation System Partial - — - • ^> lemury Treated Effluent V Sludge Figure 17. Chemical Precipitation Schematic treatment. Mixed media filters are special versions of rapid sand filters that permit deeper bed-penetration by gradation of particle sizes in the bed. Up-flow filters are also special cases of rapid filters. 98 ------- Figure 18. Sand Filter System Primary or Secondary Effluent IO Chlorination, Optional for Odor Control ^L. Effluent Surface nr Back Clean Wash to Regenerate ------- Technical Description The slow sand filter removes solids primarily at the surface of the filter. The rapid sand filter is operated to allow a deeper penetration of suspended solids into the sand bed and thereby achieve solids removal through a greater cross section of the bed. The rate of filtration of the rapid filter is up to 100 times that of the slow filter. Thus, the rapid filter requires substantially less area than the slow filter; however, the cycle time averages about 2U hours in comparison with cycles of up to 30 to 60 days for a slow filter.25 The larger area required for the latter means a higher first cost. For small plants, the slow sand filter can be used as secondary treatment. In larger sizes, the labor in maintaining and cleaning the surface may mitigate its use. The rapid sand filter, on the other hand, can be used following secondary treatment. However, it would tend to clog quickly and require frequent backwashing, resulting in a high water use, if used as secondary treatment. This wash water would also need treatment if the rapid sand filter were used in secondary treatment with only conventional solids removal upstream in the plant. The rapid filters operate essentially unattended with pressure loss controls and piping installed for automatic backwashing. They are contained in concrete structures or in steel tanks.23 Cleanup of the rapid sand filter requires backwashing of the bed of sand with a greater quantity of water than used for the slow sand filter. Backwashing is an effective cleanup procedure and the only constraint is to irinimize the wash water required in cleanup, since this must be disposed of in some appropriate manner other than discharging it to a stream. Development Status The slow sand filter has been in use for 50 years and more. It has been particularly well suited to small cities and isolated treatment systems serving hotels, motels, hospitals, etc., where treatment of low flow is required and land and sand are available. Treatment in these applications has been of sanitary- or municipal-type raw waste. The Ohio Environmental Protection Administration is a strong advocate of slow sand filters as a secondary treatment for small meat plants, following some form of settling or solids removal. As of early 1973, 16 sand filters had been installed and eight were proposed and expected to be installed in Ohio. All 24 of these installations were on waste from meat plants.26 The land requirements for a slow sand filter are not particularly significant in relation to those required for lagooning purposes in secondary treatment processes. However, the quality and quantity of sand is important and may be a constraint in the use of sand filters in some local situations. It should also be recognized that this process requires hand labor for raking the crust that develops on the surface. TOO ------- Frequency of raking may be weekly or monthly, depending upon the quality of pretreatment and the gradation of the sand. Problems and Reliability The reliability of the slow sand filter seems to be well established in its long-term use as a municipal waste treatment system. When the sand filter is operated intermittently there should be little danger of operating mishap with resultant discharge of untreated effluent or poor quality effluent. The need for bed cleaning becomes evident with the reduction in quality of the effluent or in the increased cycle time, both of which are subject to monitoring and control. Operation in cold climates is possible as long as the appropriate adjustment in the surface of the bed has been made to prevent blanking off the bed by freezing water. Chlorination, both before and after sand filtering, particularly in the use of rapid filters, may be desirable to minimize or eliminate potential odor problems and slimes that may cause clogging. The rapid sand filter has been used extensively in water treatement plants and in municipal sewage treatment for tertiary treatment; thus, its use in tertiary treatment of secondary treated effluents from rendering plants appears to be a practical method of reducing BOD5 and suspended solids to levels below those expected from conventional secondary treatment. Microscreen-Microstrainer A microstrainer is a filtering device that uses a fine mesh screen on a partially submerged rotating drum to remove suspended solids and thereby reduce the BOD5 associated with those solids. Figure 19. The microstrainer is used as a tertiary treatment following the removal of most of the solids from the waste water stream, and suspended solids and BOD5 have been reduced to 3 to 5 mg/1 in applications on municipal waste.16 There are no reports of their use in the tertiary treatment of rendering plant wastes. Technical Description The microstrainer is a filtration device in which a stainless steel microfabric is used as the filtering medium. The steel wire cloth is mounted on the periphery of a drum which is rotated partially submerged in the waste water. Backwash immediately follows the deposition of solids en the fabric, and in one installation, this is followed by ultraviolet light exposure to inhibit microbiological growth.16 The backwash water containing the solids amounts to about 3 percent of the waste water stream and must be disposed of by recycling to the biological treatment system.27 The drum is rotated at a minimum of 0.7 and up to a maximum of 4.3 revolutions per minute.16 The concentration and 101 ------- percentage removal performance for micros-trainers on suspended solids and BOD5 appear to be approximately the same as for sand •F-i 1 +- o-t-c: . filters. Development Status while there is general information available on the performance of microstrainers and on tests involving the use of them, there appears to be only one recorded installation of a microstrainer in use on municipal waste; the requirements for effluent quality have not necessitated such installation. The economic comparisons between sand filters and microstrainers are inconclusive; the mechanical equipment required for the microstrainer may be a greater factor than the land requirement for the sand filter at the present time. Secondary Treatment Effluent Backwash to Clear Screen/Strainer Tertiary Treated Effluent Figure 19. Microscreen/Microstrainer 102 ------- Problems and Reliability The test performance of the microstrainer fairly well establishes the reliability of the device and its ability to remove suspended solids and associated BOD5. Operating and maintenance problems have not been reported; this is probably because, in large part, of the limited use of the device in full-scale applications. As a mechanical filtration device requiring a drive system, it would have normal maintenance requirements associated with that kind of mechanical equipment. As a device based on microopenings in a fabric, it would be particularly intolerant to any degree of grease loading. Nitrification-Denitrification This two-step process of nitrification and denitrification, Figure 20, is a system to remove the nitrogen which appears as ammonia in treated rendering plant waste waters, and it is of primary importance for removal of the ammonia generated in anaerobic secondary treatment systems. Ammonia removal is becoming more important because of stream standards being set at levels as low as 1 to 2 mg/1. Removal of ammonia is virtually complete, with the nitrogen gas as the end product. Technical Description The large quantities of organic matter in raw waste from rendering plants is frequently and effectively treated in anaerobic lagoons. Much of the nitrogen in the organic matter, present mainly as protein, is converted to ammonia in anaerobic systems or in localized anaerobic environments. The following sets of equations indicate the nitrification of the ammonia to nitrites and nitrates, followed by the subsequent denitrification to nitrogen and nitrous oxide.28 The responsible organisms are also indicated. Nitrification does not occur to any great extent until most of the carbonaceous material has been removed from the waste water stream. The ammonia nitrification is carried out by aerating the effluent sufficiently to assure the conversion of all the nitrogen in the raw effluent to the nitrite-nitrate forms prior to the aerobic denitrification step. The denitrification step, converting nitrates to nitrogen and nitrogen oxides, takes place in the absence of oxygen. It is thought to proceed too slowly without the addition of a biodegradable carbon source such as sugar, ethyl alcohol, acetic acid, or methanol. Methanol is the least expensive and performs satisfactorily. Investigators working on this process have found that a 30-percent excess of methanol over the stoichiometric amount is required.23,29 In current waste treatment practice using anaerobic and aerobic lagoons, ammonia nitrogen that disappears in the aerobic system 103 ------- Partial Secondary Treatment Effluent \ Aeration System Anaerobic Pond Aeration Cell Carbon Source, e.g. Methanol Figure 20. Nitrification/Denitrification Partial Tertiary ^ Treated Effluent Nitrification: NH3 + 02 TO2 + HsO (Nitrosotnonas) 2N0 2NO- (Nitrobacter) Denitrification (using methanol as carbon source) 6H + 6N03 5CH3OH 5C0 13 Small amounts of N20 and NO are also formed (Facultative heterotrophs) ------- does not show up to a large extent as nitrites and nitrates. Ammonia stripping is not likely to account for the loss. It appears that denitrification must actually be occurring in the bottom reaches of the aerobic lagoons, where anaerobic conditions are probably approached (see data presented in Section X). Presuming total conversion of the ammonia to nitrites or nitrates, there will be virtually no nitrogen remaining in the effluent from the denitrification process. Nitrogen removal can be maintained at about 90 percent over the range of operating temperatures; the rate increases with temperature to an optimum value at approximately 30°C for most aerobic waste systems. Temperature increases beyond 30° result in a decrease in the rate for the mesophilic organisms.28 The waste water is routed to a second aeration basin following denitrificaticn, where the nitrogen and nitrogen oxide are readily stripped from the waste stream as gases. The sludge from each stage is settled and recycled to preserve the organisms required for each step in the process. Development Status The specific nitrification-denitrification process described herein has only been carried out at the bench- and pilot-^scale levels. Gulp and Gulp23 suggest that the "practicality of consistently maintaining the necessary biological reactions and the related economics must be demonstrated on a plant-scale before the potential of the process can be accurately evaluated." A pilot model of a three-stage system using this process was reportedly developed at the Cincinnati Water Research Laboratory of the EPA and is being built at Manassas, Virginia.30 This work is also reported to be experimental. Thus, it can be concluded that this process is, as of now, unproven. However, as mentioned above, observations of treatment lagoons for rendering plants indicates that the suggested reactions are occurring in present systems. Also, Halvorson31 reported that Pasveer is achieving success in denitrification by carefully controlling the reaction rate in an oxidation ditch, so that dissolved oxygen levels drop to near zero just before the water is reaerated by the next rotor. Problems and Reliability In view of the experimental status of this process, it would be premature to speculate on the reliability or problems incumbent in a fullscale operation. It would appear that there would be no exceptional maintenance or residual pollution problems associated with this process in view of the mechanisms suggested for its implementation at this time. 105 ------- Ammonia Stripping Ammonia stripping is a modification of the simple aeration process for removing gases in water. Figure 21. Following pH adjustment, the waste water is fed to a packed tower and allowed to flow down through the tower with a countercurrent air stream introduced at the bottom of the tower flowing upward to strip the ammonia. Ammonia-nitrogen removals of up to 98 percent and down to concentrations of less than 1 mg/1 have been achieved in experimental ammonia stripping towers.23 Technical Description The pH of the waste water from a secondary treatment system is adjusted to between 11 and 12 and the waste water is fed to a packed or cooling tower type of stripping tower. As pH is shifted to above 9, the ammonia is present as a soluble gas in the waste water stream, rather than as the ammonium ion.2' Ammonia-nitrogen removal of 90 percent was achieved with countercurrent air flows between 1.8 and 2.2 cubic meters per liter (250 and 300 cubic feet per gallon) of waste water in an experimental tower with hydraulic loadings between 100 and 125 liters per minute per square meter (2.5 and 3 gallons per minute per square foot). The best performance was achieved with an air rate of 5.9 cubic meters per liter (800 cubic feet per gallon) and a hydraulic loading of 33 liters per minute per square meter (0.8 gallons per minute per square foot) and the ammonia concentration was reduced to less than one part per million at 98 percent removal. The high percentage removal of ammonia-nitrogen is achieved only at a substantial cost in terms of air requirements and stripping tower cross-sectional area.23 Development Status The ammonia stripping process is a well-established industrial practice in the petroleum refinery industry. The only significant difference between the petroleum refinery application and that on rendering waste would be the comparatively small size of stripping tower required for the rendering plants, compared to the refinery. The air stripping of ammonia from secondary effluent is reported primarily on an experimental basis in equipment that is 1.8 meters (6 feet) in diameter with a packing depth of up to 7.3 meters (24 feet). Two large-scale installa- tions of ammonia stripping of lime-treated waste water are reported at South Tahoe, California, and Windhoek, South Africa.°6,23 The South Tahoe ammonia stripper was rated at 14.2 M liters per day (3.75 MGD) and was essentially constructed as a cooling tower structure, rather than as a cylindrical steel tower which might be used in smaller sized plants. Thus, although there is no reported use of ammonia stripping on rendering plant waste, the technology is well established and implementation, when standards require it, would be possible without great difficulty. Problems and Reliability 106 ------- The reliability of this process has been established by petroleum refinery use cf the process over many years. Although the source of the ammonia may be different and there may be other contaminants in the water stream, this should not affect the established reliability of this process. The experience of other users of the process will have identified potential problems, and, presumably, the solutions for these problems will have been found. The maintenance requirements would be only those normally associated with the mechanical equipment involved in pumping the waste water to the top of the tower where the feed is introduced to the tower, and in maintaining the air blowers. The tower fill would undoubtedly be designed for the kind of service involved in treating a waste water stream that has some potential for fouling. Spray/Flood Irrigation A no-discharge level for rendering waste water can be and is being achieved by the use of spray or flood irrigation of relatively flat land, surrounded by dikes to prevent runoff. A cover crop of grass or other vegetation is maintained on the land. Specific plant situations may preclude the installation of irrigation systems; however, where they are feasible, the economics can be very favorable and serious consideration should be given to them. Technical Description Wastes are disposed of in spray or flood irrigation systems by distribution through piping and spray nozzles over relatively flat terrain or by the pumping and disposal through the ridge and furrow irrigation systems which allow a certain level of flooding on a given plot of land, Figure 22. Pretreatment for removal of solids is advisable to prevent plugging of the spray nozzles, or deposition in the furrows of a ridgeand-furrow system, or collection of solids on the surface, which may cause odor problems or clog the soil. Therefore, the BOD5 will usually have already been reduced in preliminary treatment (primary plus some degree of secondary treatment) upstream from the distribution system. In flood irrigation, the waste loading in the effluent would be limited by the waste loading tolerance of the particular crop being grown on the land, or it may be limited by the soil conditions or potential for vermin or odor problems. Waste water distributed in either manner percolates through the soil and the organic matter in the waste undergoes a biological degradation. The liquid in the waste stream is either stored in the soil or leached to a groundwater aquifer and discharged into the groundwater. Approximately ten percent of the waste flow will be lost by evapotranspiration (the loss caused by evaporation to the atmosphere through the leaves of plants).28 Spray runoff irrigation is an alternative technique which has been tested on the waste from a small meat packer32 and on 107 ------- cannery waste.28 With this technique, about 50 percent of the waste water applied to the soil is allowed to run off as a discharge rather than no dischare, as discussed here. The runoff or discharge from this type of irrigation system is of higher quality than the waste water as applied, with BOD5 removal of about 80 percent; total organic carbon and ammonia nitrogen system is of higher quality than the waste water as applied, with BOD5 removal of about 80 percent; total organic carbon and ammonia nitrogen are about 85 percent reduced, and phosphorus is about 65 percent reduced.32 The following factors will affect the ability of a particular land area to absorb waste water: 1) character of the soil, 2) stratification of the soil profile, 3) depth to groundwater, 4) initial moisture content, and 5) terrain and groundcover.28 The potentially greatest concern in the use of irrigation as a disposal system is the total dissolved solids content and particularly the salt content of the waste water. A maximum salt content of 0.15 percent is suggested by Eckenfelder.28 Some plants or some locations may require treatment in an ion exchange system upstream from the irrigation system to reduce the dissolved solids and the salt content to acceptable levels for continuing application of the waste water on land. However, the average plant should have no problem with salt, since the average salt content of rendering waste waters is about a factor of six less than the limit of 0.15 percent suggested by Eckenfelder. An application rate of up to 330 liters per minute per hectare (35 gallons per minute per acre) has been suggested in determining the quantity of land required for various waste water flows. This amounts to almost 5 cm (2 inches) of moisture per day, and is relatively low in comparison with application rates reported by Eckenfelder for various spray irrigation systems.28 However, solids vary widely in their percolation properties and experimental irrigation of a small area is recommended before a complete system is built. In this report land requirements were based on 2.5 cm (one inch) applied per operating day for six months of the year with lagoon storage for six-months' accumulation of waste water. Waste water application rates currently used by rendering plants with spray irrigation systems are less than 4.0 cm (1.6 inches) water per two weeks for a six-month irrigation period. If rendering plant waste waters were being used as the sole nitrogen source for corn growth, the waste waters would probably have to contain 250 to 500 mg/1 nitrogen. For lower nitrogen concentrations, the corn crop would probably be damaged by flooding or by heavy overwatering before the corn received sufficient nitrogen from the waste waters. This is based on the assumptions that one bushel of ccrn requires 454 gm (1 pound) of nitrogen; that the yield is 120 bushels of corn per acre, and that the corn would require from 25 to 75 cm (10 to 30 inches) of water per season.3* This water rate amounts to 3.1 to 9.5 cm (1.2 to 3.7 inches) of water per two weeks, over a four-month 108 ------- Secondary Treatment Effluent PH Adjustment Treated Effluent Figure 21. Ammonia Stripping Primary, Secondary or Partial Tertiary Treatment Effluent X. Holding Basin N^ ^"^ Pumping System \ ^~ Application Site V Grass or Hay Crop Figure 22. Spray/Flood Irrigation System Partial Tertiary Treatment Effluent Tertiary -> Treated Effluent Ion Exchange Column(s) Backwash 8 Regenerant System Figure 23. Ion Exchange 109 ------- season- Thus^ treated waste water from rendering is a small enough volume so it can be used as a supplementary nutrient source for corn rather than a sole resource of nutrients. Data were not discovered for any cases in which waste water treated only by primary systems was used for irrigation. The economic benefit from spray irrigation is estimated on the basis of raising two crops of grass or hay per season with a yield of 13.4 metric tons of dry matter per hectare (six tons per acre) and values at $22 per metric ton ($20 per ton). These figures are reportedly conservative in terms of the number of crops and the price to be expected from a grass or hay crop. The supply and demand sensitivity as well as transportation problems for moving the crop to a consumer all mitigate against any more optimistic estimate of economic benefits.33 Cold climate uses of spray irrigation may be subject to more constraints ad have greater land requirements than plants operating in more temperate climates. However, a meat packer in Illinois reportedly operated an irrigation system successfully. Eckenfelder also reports that the wastes have been successfully disposed of by spray irrigation from a number of other industries.28 Rendering plants located in cold climates or short growing areas should consider two crops for spray irrigation. One could be a secondary crop such as corn and the other a grass crop. The grass crop could tolerate heavier volume loadings without runoff and erosion, and also would extend the irrigation season from early spring to possibly late November. Corn, although a more valuable crop, tolerates irrigation in cold climate areas only during the summer months. North Star found in its survey of the rendering industry that the plants located in the arid regions of the Southwest were most inclinded to use spray or flood irrigation systems. Problems and Reliability The long-term reliability of spray cr flood irrigation systems is a function of the ability of the soil to continue to accept the waste, and thus reliability remains somewhat open to question. Problems in maintenance are primarily in the control of the dissolved solids level and salinity content of the waste water stream and also in climatic limitations that may exist or develop. Many soils may be improved by spray irrigation. Ion Exchange Ion exchange, as a tertiary waste treatment, is used as a deionization process in which specific ionic species are removed from the waste water stream, Figure 23. Ion exchange would be used to remove salt (sodium chloride) from waters. Ion exchange resin systems have been developed to remove specific ionic species, to achieve maximum regeneration operating efficiency, and to achieve a desired effluent quality. In treating rendering 110 ------- waste, the desired effluent quality would be a waste water with a salt concentration of less than 300 mg/1. Ion exchange systems are available that will remove up to 90 percent of the salt in a water stream.*6 They can also be used to remove nitrogen. Technical Description The deionization of water by means of ion exchange resin involves the use of both cation and anion exchange resins in sequence or in combination to remove an electrolyte such as salt. The normal practice in deionization of water has been to make the first pass through a strong acid column, cation exchange resin, in which the first reaction shown in the equations occurs. Effluent from the first column is passed to a second column of anion exchange resin to remove the acid formed in the first step, as indicated in the second reaction. As indicated in the two reactions, the sodium chloride ions have been removed as ionic species. A great variety of ion exchange resins have been developed over the years for specific deionization objectives for various water quality conditions. Waste water treatment with ion exchange resins has been investigated and attempted for over 40 years; however, recent process developments in the treatment of secondary effluent have been particularly successful in achieving high quality effluent at reasonable capital and operating costs. One such process is a modification of the Rohm and Haas, Desal process.16 In this process a weak base ion exchange resin is converted to the bicarbonate form and the secondary effluent is treated by the resin to remove the inorganic salts. After this step, the process includes a flocculation/aeration and precipitation step to remove organic matter; however, this should be unnecessary if a sand filter or comparable system is used upstream of the. ion exchange unit. The effluent from the first ion exchange column is further treated by a weak cation resin to reduce the final dissolved salt content to approximately 5 mg/1. The anion resin in this process is regenerated with aqueous ammonia, and the cation resin with an aqueous sulfuric acid. The resins did not appear to be susceptible to fouling by the organic constitutents of the secondary effluent used in this experiment. Other types of resins are available for ammonia, nitrate, or phosphate removal as well as for color bodies, COD and fine suspended matter. Removal of these various constitutents can range from 75 percent to 97 percent, depending on the constituent.2 3 The cycle time on the ion exchange unit will be a function of the time required to block or to take up the ion exchange sites available in the resin contained in the system. Blockage occurs when the resin is fouled by suspended matter and other contaminants. The ion exchange system is ideally located at the 111 ------- end of the waste water processing scheme, thus having the highest quality effluent available as a feedwater. To achieve a recycleable water quality, it may be assumed that less than 500 mg/1 of total dissolved solids would have to be achieved. Of the total dissolved solids, 300 mg/1 of salt are assumed to be acceptable. To achieve this final effluent quality, some portion or all of the waste water stream would be subjected to ion exchange treatment. The residual pollution will be that resulting from regeneration of the ion exchange bed. The resin systems, as indicated earlier, can be tailored to specific ion removal and efficient use of regneration chemicals, thus minimizing liquid wastes from the regeneration step. Development Status Ion exchange as a unit operation is well established and commonly used in a wide range of applications in water treatment and water deionization. Water softening for boiler feed treatment and domestic and commercial use is probably the most widespread use of ion exchange in water treatment. Deionization of water by ion exchange is used to remove carbon dioxide; metal salts such as chlorides, sulfates, nitrates, and phosphates; silica; and alkalinity. Specific resin applications such as in waste water treatment have not been widespread up to the present time, since there has not been a need for such a level of treatment. However, process development and experimental work have shown the capability of ion exchange systems to achieve the water quality that may be required for irrigation and closed-loop water recycle systems. Part of the economic success of an ion exchange system in treating rendering plant waste will probably depend on a high quality effluent being available as a feed material. This again, can be provided by an upstream treatment system such as sand filtration to remove a maximum of the particularly bothersome suspended organic material. However, the effect of a low quality feed would be primarily economic because of shorter cycle times, rather than a reduction in the overall effectiveness of the ion exchange system in removing a specific ionic species such as salt. Problems and Reliability The application of the technology in waste treatment has not been tested and therefore the reliability in that application has yet to be established. The problems associated with ion exchange operations would primarily center on the quality of the feed to the ion exchange system and its effect on the cycle time. The operation and control of the deionization-regeneration cycle can be totally automated, which would seem to be the desired approach. Regeneration solution is used periodically to restore the ion exchange resin to its original state for continued use. This solution must be disposed of following its use and that may 112 ------- require special handling or treatment. The relatively small quantity of regenerant solution will facilitate its proper disposal by users of this system. 113 ------- SECTION VIII COST, ENERGY AND NONWATER QUALITY ASPECTS SUMMARY The waste water from rendering plants is amenable to treatment in secondary and tertiary waste treatment systems to achieve low levels of pollutants in the final effluent. In-plant controls, product recovery operations, and strict water management practices can be highly effective in reducing the waste load and waste water flow from any rendering plant. The water management practices will reduce the requisite size of secondary and tertiary treatment systems and improve their waste reduction effectiveness s. For purposes of estimating treatment costs, the rendering industry can be divided into small, medium, and large size plants. The plant size is based on the weight of raw material processed per day. This division of the industry does not imply the need to categorize the industry according to size; the primary categorization criterion—raw waste load—does not vary with size. Total investment costs and unit operating costs for waste treatment, on the other hand, will vary with plant size. Costs that represent the industry situation could not be determined on the basis of one "typical" plant size, with the wide range of production and waste water flow for plants in the industry. Therefore, the three rendering plant sizes that are relatively closely grouped in production and waste water flow are used to describe the waste treatment economics for the entire rendering industry and for plants within the industry. Waste water treatment investment cost is primarily a function of waste water flow rate. Cost per unit of production for waste treatment will vary with total investment cost and the production rate. Therefore, the rendering industry treatment costs have been estimated on the basis of "typical" plants for each size. A "typical" plant is a hypothetical plant with an average production rate and the indicated waste water flow rate as shown in Table 13A. The average BOD5 raw waste load is the same for each plant size, as indicated by the single industry category, described in Section IV. The additional capital expenditures required of a "typical" plant in each size group to upgrade or install a waste water treatment system to achieve the indicated performance are indicated in Table 14. Table 15 shows comparative costs as related to expanding the hydraulic capacity of existing treatment facilities if barometric condenser recirculation is not practiced. The estimated total investment cost to the industry is also reported for the proposed 1977 and 1983 limitations. 115 ------- Table 13A. Profile of Typical Plants by Size Small Medium Large Rendering Plant Size Ran kg /day <45,000 45,000 - 113,500 >113,500 ges Ib/day <100,000 100,000 - 250,000 >250,000 Average Raw Materials Processed kg /day 16,800 76,300 240,600 Ib/day 37,000 168,000 530,000 Average Waste Water Flow Rate liters /day 20,000 91,000 288,000 gal /day 5,300 24,000 76,000 cr> ------- The estimate of the cost of achieving the proposed 1977 limitations is based on the following assumptions, which reflect the data collected on the industry in the North Star survey questionnaire: o 80 percent of the small plants with treatment systems will need to install pumps and piping to recirculate waste water to the barometric condensers; or expand lagoon capacity if recirculation of barometric condenser water is not practiced. o 50 percent of all plants with treatment systems will need to add an anaerobic lagcon or the equivalent. o 50 percent of all plants with treatment systems will need to install chlorination. The rendering industry waste treatment practices are assumed to be as reflected in questionnaire data for 49 plants. The data reveals a 50-50 split between municipal discharge and those that treat or control their own waste waters. The latter group is itself split about 50-50. Thus, of the approximately 450 plants encompassed by this study, 225 are municipal discharges, 112 achieve no discharge of pollutants, and 113 treat waste waters and discharge to streams. A further discussion of the relevance of this distribution is presented below under the heading, "Waste Treatment Systems" between no discharge and treatment with discharge. The 1983 limitations will require the following additions to the existing treatment systems, over and above the additions for 1977: o 90 percent of all plants with treatment systems must add sand filters, or the equivalent; o 50 percent of all plants with treatment systems will have to make capital improvements in their primary treatment facilities; o 12 percent of all plants with treatment systems will have to eliminate direct blood drainage to the sewer and recover it in their product streams; o 20 percent of all plants with treatment systems will have to install ammonia stripping equipment or nitrification-denitrification systems. The costs for irrigation and for ponding are included in Table 14 to indicate the economic advantages of both approaches. Both techniques produce no discharge, which is the ultimate goal of the legislation, and free a plant from waste water discharge regulations. The no-discharge options are particularly advantageous to the small renderers. 117 ------- The investment costs for new point sources of waste water effluent are cost estimates of treatment systems presently in use in the industry based on the average flow for the plant size, as indicated in Table 14. The basis of the cost estimates for a plant to achieve the proposed limitations involved various additions to existing facilities, thus the investment cost for a given plant could vary from a minimum to a maximum cost. A "most likely" investment cost was computed for each plant size based on the cost of the combination of treatment-system additions with the highest probability of occurrence. The most likely and maximum costs are presented in Table 16. All operating and total annual costs include the "most likely" investment cost rather than the minimum or maximum cost. Tables 15, ISA, and 15B are also presented to provide an indication of the approximate cost of waste treatment for plants with waste water volume per unit of raw material processed equivalent to the average batch process renderer without the use of water conservation or recirculation systems (3300 liters/1000 kgs or 400 gal/1000 Ib RM). Investment costs would be higher for such a plant. Operating costs would increase in comparison with the low waste water volume plant by 18 to 75 percent depending on plant size and annual costs would increase by 12 to 125 percent. The medium size plants would experience the largest increase in the per unit annual cost for 1977 of 0.030/lb RM and small plants would incur the largest increase in annual cost for 1983 of 0.28iZ/lb RM, again in comparison with the plant using only 143 gal/1000 Ib RM. The additions to plant operating cost and total annual cost, in total dollars and in dollars per unit of raw material processed, for the indicated type or level of waste treatment performance are listed in Table 17 and 18. The additional costs for the 1977 limitations include the payroll and burden (at 50 percent of payroll) for the equivalent of one-half man. This assumed cost of manpower for the treatment system accounts for between 70 and 82 percent of the annual operating cost and between 45 and 60 percent of the total annual cost. This allocation of manpower cost would be highly discretionary within each rendering plant. Therefore, the reported operating and total annual costs are very conservative estimates of expected real plant experience, the estimates probably are higher than what will actually occur. The maximum annual costs per unit weight of raw material occur in the small plants. The 1977 limitations would add 0.350/kg (0.160/lb) to the annual operating cost of an average small plant, and the 1983 limitations would add 0.840/kg (0.380/lb). In comparison with the operating margin of a rendering plant, these are significant additions to their costs. The costs for irrigation or ponding are at least a factor of six less than the cost for other treatment methods for small plants. The additional cost for the medium or large rendering plant to meet 118 ------- Table 14. Likely Capital Expenditures by Plant Size to Limitations Shown with Condenser Recirculation as Needed Small Plant Medium Plant Large Plant Total Rendering Industry 1977 Limitation (?) 26,500 27,000 52,000 2,100,000 1983 Limitation ($) 53,000 85,000 119,000 8,900,000 New Source Standard ($) 38,000 78,000 133,000 __ Irrigation System Only** ($) 5,000 14,000 37,000 ^^ Percolator & Evaporation Pond ($) 14,000 32,000 62,000 — _ ------- the 1983 limitations is no greater than matter which treatment system is used. 0.2fZ/kg (0.10/lb) , no The total rendering industry spent approximately $30 million in 1972 on new capital expenditures. This estimate is based on a projection of the capital expenditures reported for 1958 through 1967 in the 1967 Census of Manufactures.4 The total industry waste treatment expenditures reported in Tables 14 and 15 of $2.1 to $4.2 million for 1977 limitations and $8.9 million for the 1983 limitations, amounting to about 10 percent and 30 percent of the $30 million estimate, respectively. The waste treatment expenditures can be programmed over a number of years, thus the requisite investment appears reasonable and achievable. The small rendering plant is put in the most difficult financial position, however, this can be minimized by the use of irrigation or ponding. The electrical energy consumption in waste water treatment by the rendering industry amounts to less than 2 percent of their current total use of electrical energy, and less than 0.1 of one percent of their total (heat plus electrical) energy consumption. Thus, in absolute terms and comparatively speaking, waste treatment energy use is of little consequence. With the implementation of these standards, land becomes the primary waste sink instead of air and water. The waste to be disposed on land from rendering plants can improve soils with nutrients and soil conditioners contained in the waste. Odor problems can be avoided or eliminated in all treatment systems. Table 15. Estimated Waste Treatment Investment Costs for Renderers with High Waste Water Volume (3300 liters/1000 kgs RM or 400 Gals/1000 Ibs KM) Plant Size Small Medium Large 1977 Limitations 20,700 47,600 94,000 1983 Limitations 135,000 208,000 293,000 Irrigation System, Only 13,100 34,000 90,000 120 ------- Table 15A. Total Annual and Operating Costs for a Rendering Plant with High Waste Water Volume to Meet the Indicated Performance, $/Year Plant Size. Small Medium Large Cost Annual Operating Annual Operating Annual Operating 1977 Limitations 16,600 12,400 24,400 14,900 36,800 18,000 1983 Limitations 61,100 30,000 87,700 36,600 121,900 44,500 Irrigation System, Only 6,200 4,000 9,800 4,200 16,300 2,000 Table 15B. Annual and Operating Costs Per Unit Weight of Raw Material for a Rendering Plant with High Waste Water Volume to Meet Indicated Performance Plant Size Small Medium Large Cost Annual Operating Annual Operating Annual Operating 1977 Limitations C/kg 0.39 0.30 0.13 0.08 0.06 0.03 C/lb 0.18 0.13 0.06 0.035 0.03 0.014 1983 Limitations C/kg 1.45 0.71 0.46 0.19 0.20 0.07 C/lb 0.66 0.32 0.21 0.09 0.09 0.03 121 ------- Table 16. Comparison of Most Likely and Maximum Investment, with Condenser Recirculation, By Plant Size Performance 1977 Limitations 1983 Limitations Small Plant Most Likely Cost ($) 26,500 53,000 Maximum Cost ($) 26,500 100,000 Medium Plant Most Likely Cost ($) 27,000 85,000 Maximum Cost ($) 42,000 160,000 Large Plant Most Likely Cost ($) 52,000 119,000 Maximum Cost ($) 52,000 221,000 Table 18. Annual And Operating Costs Per Unit Weight of Raw Material for a Rendering Plant to Meet Indicated Performance Plant Small Medium Large Cost Annual Cost Operating Cost Annual Cost Operating Cost Annual Cost Operating Cost 1977 Limitation C/kg 0.35 0.24 0.07 0.04 0.03 0.02 /lb 0.16 0.11 0.03 0.02 0.014 0.01 1983 Limitation 0/kg 0.84 0.53 0.2 0.13 0.09 0.04 C/lb 0.38 0.24 0.1 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 0.02 122 ------- Table 17. Total Annual and Operating Costs for a Rendering Plant to Meet the Indicated Performance, $/Year Plant Size Small Medium Large Cost Annual Cost Operating Cost Annual Cost Operating Cost Annual Cost Operating Cost 1977 Limitation 16,500 11,900 16,200 12,200 21,600 14,000 1983 Limitation 40,300 25,100 48,200 27,300 62,600 31,300 New Source Standard 20,500 14 , 700 30,600 18,800 44,100 24,100 Irrigation System 1,500 500 3,500 700 7,600 230 Ponding 2,700 750 6,100 1,600 11,800 3,100 ------- "TYPICAL" PLANT The waste treatment systems applicable to waste water from the rendering industry can be used effectively by all plants in the industry. Irrigation or ponding with no discharge is most widely used by small plants, and is usually the most attractive treatment option for small plants. A hypothetical "typical" plant was determined for each plant size as the basis for estimating investment cost and total annual and Operating costs for the application of each waste treatment system for each plant size. The costs were estimated, and in addition, effluent reduction, energy requirements, and nonwater quality aspects of the treatment systems were determined. The waste treatment systems are applied on the basis of the "typical" plants described in Table 19 for each plant size. Table 19. "Typical" Plant Parameters for each Plant Size Plant Parameter Average Raw Material Processed, kg/day, (Ibs/day) Standard Deviation of Average R. M. Processed kg/day, (Ibs/day) Total Waste Water Volume, liters/day (gals/day) Waste Water Vol- ume per unit of R. M. Processed liter /1000 kgs , (gals/1000 Ib RM) Average Value of Plant Parameter by Plant Size Small 16,800 (37,000) 9,100 (20,000) 20,000 (5,300) 1,191 (143) Medium 76,300 (168,000) 26,300 (58,000) 91,000 (24,000) 1,191 (143) Large 240,000 (530,000) 74,900 (165,000) 288,000 (76,000) 1,191 (143) The small rendering plant generally has a lower production limit of about 4500 to 6800 kg (10,000 to 15,000 Ib) of raw material processed per day. This estimate is based on the industry sample data and involves the use of one batch cooker operating on two batches per day. This level of operation would be at the low end of economic viability. The North Star sample included one plant that processed about 3600 kg (8000 Ib) per day of only dead 124 ------- animals. This type of raw material enabled the plant to operate at that production level, however, it was unique in the sample. The waste water volume is primarily based on the average normalized water volume for all of the continuous process plants in the sample, 1191 liters/kkg RM (143 gal./lOOO Ib RM). This means that all plants with barometric condensers and waste treatment will have to recirculate condenser water from the waste treatment system and thus avoid this large consumption of fresh water and reduce the total waste water volume. Costs have been included for such revision of barometric condenser water supply systems, as indicated previously. At the same time, however, the "typical" batch plant was also analyzed regarding costs for treatment without condenser recirculation for both the purely (lagoon) treatment mode and the option of irrigation, in each case with respect to the 1977 limitations. WASTE TREATMENT SYSTEMS The waste treatment systems included in this report as appropriate for use on rendering plant waste water streams can be used, subject to specific operating constraints or limitations as described later, by most plants in the industry. The use of some treatment systems may be precluded by physical or economic impracticability for some plants. The waste treatment systems, their use, and the minimum effluent reduction associated with each are listed in Table 20. The dissolved air flotation system can be used upstream of any secondary treatment system. The use of chemicals should increase the quantity of grease removed from the waste water stream, but may reduce the value of the grease because of chemical contaminants. The secondary treatment systems are generally land intensive because of the long retention time required in natural biological processes. Mechanically assisted systems have reduced the land requirements but increased the energy consumption and cost of equipment to achieve comparable levels of waste reduction. Some of the tertiary systems are interchangeable. Any of them can be used at the end of any of the secondary treatment systems to achieve a required effluent quality. Chlorination is included if a disinfection treatment is required. A final clarifier has been included in costing out all biological treatment systems that generate a substantial sludge volume; e.g., extended aeration and activated sludge. The clarifier is needed to reduce the solids content of the final effluent. The most feasible system to achieve no discharge at this time is flood or spray irrigation or ponding. Closing the loop to a total water recycle or reuse system is technically feasible, but far too costly for consideration. The irrigation option does require large plots of accessible land—roughly 2.0 125 ------- Table 20 Waste Treatment Systems, Their Use and Effectiveness Treatment System Use Effluent Reduction Dissolved air flotation (DAF) DAF with pH control and flocculants added Anaerobic + aerobic lagoons Anaerobic contact process Activated sludge Extended aeration Anaerobic lagoons + rotating biological contactor Chlorination Sand filter Microstrainer Ammonia stripping Chemical precipitation Spray irrigation Flood irrigation Ponding and evaporation Nitrification and Denitrification Primary treatment or by-product recovery Primary treatment or by-product recovery Secondary treatment Secondary treatment Secondary treatment Secondary treatment Secondary treatment Finish and disinfection Tertiary treatment & secondary treatment Tertiary treatment Tertiary treatment Tertiary treatment No discharge No discharge No discharge Tertiary treatment Grease, 60% removal, to 100 to 200 mg/1 BOD5, 30% removal SS, 30% removal Grease, 95-99% removal BOD5, 90% removal SS, 98% removal BODS, 95% removal BOD5, 90-95% removal BOD5, 90-95% removal BOD5, 95% removal BOD5, 90-95% removal BOD5, to 5-10 mg/1 SS, to 3-8 mg/1 BOD5, to 10-20 mg/1 SS, to 10-15 mg/1 90-95% removal Phosphorus, 85-95% removal, to 0.5 mg/1 or less Total Total Total N, 85% removal 126 ------- hectares/mi11ion liters (0.2 acres/thousand gallons) of waste water per day and limited concentrations of dissolved solids. More detailed descriptions of each treatment system and its effectiveness are presented in Section VII—Control and Treatment Technology. Of the 49 plants responding to the study questionnaire, about one-half reported having either their own waste water treatment system or no discharge; the others indicated discharging their waste to a municipal treatment system. Twelve plants reported on-site secondary treatment with lagoon systems or other combinations of secondary treatment processes. Twelve plants also reported treatment systems with no discharge. Chlorination is used by five plants, according to the data. The North Star sample of rendering plants provided the following waste water treatment information and industry sources believe these data conform to overall industry practice: Discharge to Secondary Treatment No Municipal System With Discharge Discharge Small Plants 7 48 Medium Plants 7 53 Large Plants 9 31 TOTALS 23 12 12 TREATMENT AND CONTROL COSTS In-Plant Control Costs The purchase and installation cost of in-plant control equipment is primarily a function of each specific plant situation. Building layout and construction design will largely dictate what can be done, how, and at what cost in regard to in-plant waste control techniques. In-plant control equipment costs were not included in the total investment cost estimates. Rough approximations of the range of costs for the in-plant controls requiring capital equipment are listed in Table 21. These cost ranges are based somewhat on plant size variation, but are primarily based on the expected cost that might be incurred by any rendering plant, depending on the plant layout, age, type of construction, etc. Investment Costs Assumptions The waste treatment system costs are based on the average plant production capacity and waste water flow listed previously for a 127 ------- Table 21. Estimates of In-Plant Control Costs Plant Area ro oo Raw Materials Storage Cookers Air Scrubbing Hide Curing Materials Recovery Item Steam sparge and screen for high blood contain- ing waters. By-pass controls on vapor lines from cookers Recycle system for scrubber water Pipe curing waste waters to cookers Flow equalization tank Equipment Cost Range $10,000-$15,000 $100-$300 per cooker $10,000-$20,000 $1,000-$3,000 $2,000-$5,000 ------- "typical," but hypothetical, plant of each size. Investment costs for specific waste treatment systems are primarily dependent on the waste water volume. The total waste water flow for each plant size will vary up to 100 percent or more of the average total flow for that size. This variability coupled with that in cost estimating suggests that the waste treatment investment costs for a specific plant may be only within an accuracy of + 50 to 100 percent. The investment cost data were collected from data included on questionnaires from rendering plants, the literature, personal plant visits, equipment manufacturers, engineering contractors, and consultants. The costs are "ball-park"-type estimates, implying an accuracy of + 20 to 25 percent. Rarely is it minus. All costs are reported in August 1971 dollars. Percentage factors were added to the treatment system equipment cost for design and engineering (10 percent) and for contingencies and omissions (15 percent). Land costs were estimated to be $2470 per hectare ($1000 per acre) . The irrigation system costs are based on application and storage assumptions to take into consideration geographic and climatic variables throughout the country. These assumptions are as follows: o Application rate is one inch of waste water applied per operating day during six months per year. o Storage capacity for six months accumulation of waste water in a lagoon 1.2 m (4 feet) deep plus land for roads, dikes, etc. o Irrigation equipment includes pumps, piping and distribution system, dikes to prevent all runoff at a reference cost of $70,000 for 21 hectares (52 acres) . The chlorine costs are based on chlorinating the waste water to 8 mg/1. The assumed cost of 180 per kg (80 per Ib) for chlorine results in a cost of 0.10 per 1000 liters (0.40 per 10CO gal.) of waste water chlorinated. In addition to the variation in plant water flows and BOD5 loadings and the inherent inaccuracy in cost estimating, one additional factor further limits the probability of obtaining precise cost estimates for specific waste treatment systems. This factor was reported by a number of informed sources who indicated that municipal treatment systems will cost up to 50 percent more than comparable industrial installations. The literature usually makes no distinction between municipal and industrial installation in reporting investment costs. 129 ------- Figure 24. Waste Treatment Cost Effectiveness CO CD QQ ^ i/iJ.vJ — 99 — \— QR g 98 — LU CJ CC LU Q_ Qf- _M — yo z o o 90 - D Q LU CC Q 80 - **t. O LU 70 — H 00 | 60 — ^> cc 50 - LU ^ 40 - » § 30 - cc Q_ 0. < 20 — TO _ .! i c 91,000 I/day . (24,000 GPD)7 I ,- I ^ 1 1 I ) 20 40 1 | 1 1 SECONDARY ! TREATMENT , 1 ' n /_ 288,000 I/day (76,000 GPD) I nrtinAAi-ix/ -rn i- A TRfli-M-r 60 80 100 120 140 160 180 200 220 240 260 280 300 ------- Cost effectiveness data are presented in Figure 24, as investment cost required to achieve the indicated BOD5 removal with the typical lagoon waste treatment system at two levels of waste water flow. The low flow is the average for the medium size rendering plant and the high flow is the average for the large plants. The raw waste reduction is based on the construction of waste treatment systems with the incremental waste reduction achieved by adding treatment components to the system as indicated below (a catch basin is assumed to be standard practice, and the raw waste is that discharged from the catch basin). Treatment Component Total Raw Waste Reduction, % Catch Basin 0 + Improved Primary Treatment 15 + Anaerobic and Aerobic Lagoons 95 + Aerated Lagoon 98 + Sand Filter 99+ Annual Cost Assumptions The components of total annual cost are capital cost, depreciation, operating and maintenance costs, and energy and power costs. The cost of capital is estimated to be ten percent of the investment cost for the rendering industry—the same as in the meat packing industry. This cost should be a weighted average of the cost of equity and of debt financing throughout the industry. Neither individual companies nor industry associations have a known figure for this cost. Presuming that target and realized return-on-investment (ROI) or return-on- assets (ROA) figures incorporate some estimate of capital cost plus an acceptable profit or return, industry and corporate reports were used as a guide in selecting the ten percent figure for the meat packing industry. One sample of companies reported earnings at 7.1 percent of total assets for 1971 ;35 a recent business periodical reported earnings at 10.1 percent of invested capital,36 and meat packing industry sources report corporate target ROI and ROA figures at 12 to 15 percent for new ventures. The ten percent figure is probably high, and thus tends to contribute to a high estimate of total annual cost. Operating cost includes all the components of total annual cost except capital cost and depreciation. The depreciation component of annual cost was estimated on a straight-line tasis over the following lifetimes, with no salvage value: Land costs — not depreciated Land intensive treatment systems; e.g., lagoons -- 25 years 131 ------- All other treatment systems — 10 years. The operating and maintenance costs for the 1983 system include the cost of one man-year at $4.20/hour plus 50 percent for burden, supervision, etc. One-half man-year was used for the annual cost for the 1977 limitations plus the 50 percent burden, etc. General and maintenance supplies, taxes, insurance, and miscellaneous operating costs were estimated as 5 percent of the total investment cost per year. Specific chemical-use costs were added when such materials were consumed in the waste treatment system. By-product income, relative to waste treatment, was credited only in the irrigation system for 13,400 kg of dry matter (hay or grass) per hectare at $22/100 kg (6 tons/acre at $20/ton) and two crops per year.37 ENERGY REQUIREMENTS The electrical energy consumption by the rendering industry—SIC 2077, including marine fats and oils—was reported for 1967 (then under SIC 2094) to be 362 million KWH and total heat and power energy consumption at the equivalent of 8108 KWH.* The rendering industry consumes relatively small quantities of electrical energy but large quantities of fuel. The waste treatment systems require power primarily for pumping and aeration. The aeration horsepower is a function of the waste load and that for pumping depends on waste water flow rate. Total power consumption to achieve the 1977 limitations is estimated to be 7 million KWH per year for the rendering industry. This amounts to about 2 percent of electrical energy consumption, and roughly 0.1 percent of the total (heat and electrical) energy consumption of the industry reported for 1967. The same approximate percentage would apply to current power consumption. The additional power needed to achieve 1983 limitations amounts to about 4 percent and 0.2 percent of electrical and the total energy, respectively, and does not appear to raise serious power supply or cost questions for the industry. However, widespread use of chlorine as a disinfectant may pose some energy problems in the future, or, conversely, the future supply of chlorine may be seriously affected by the developing energy situation. Waste treatment systems impose no significant addition to the thermal energy requirements of plants. Waste water can be reused in cooling and condensing service. These heated waste waters improve the effectiveness of anaerobic ponds, which are best maintained at about 90°F. Improved thermal efficiencies are also achieved within a plant when waste water is reused in this manner. Waste water treatment costs and effectiveness can be improved by the use of energy and power conservation practices and techniques in plant operations. Reduced water use therefore reduces the 132 ------- pumping costs and heating costs, the last of which can be further reduced by water reuse as suggested above. NONWATER POLLUTION BY WASTE TREATMENT SYSTEMS Solid Wastes Solid wastes are the most significant nonwater pollutants associated with the waste treatment systems applicable to the rendering industry. Screening devices of various design and operating principles are used primarily for removal of large- scale solids from waste water. These solids have economic value as inedible rendering raw material and can be returned to the feed end of a plant. The organic and inorganic solids material separated from the waste water stream, including chemicals added to aid solids separation, is called sludge. Typically, it contains 95 to 98 percent water before dewatering or drying. Both primary and secondary treatment systems generate some quantities of sludge; the quantity will vary by the type of system and is roughly estimated as shown below. Tr ea tm en t_ Sy_s tern Dissolved air flotation Anaerobic lagoon Aerobic and aerated lagoons Activated sludge Extended aeration Anaerobic contact process Rotating biological contactor Sludge Volume as Percent of Raw Wastewater TVolume Up to 10% Sludge accumulation in these lagoons is usually not sufficient to require removal. 10 - 15% 5 - 10% Approximately 2% Unknown The raw sludge can be concentrated, digested, dewatered, dried, incinerated, land-filled on-site, or spread in sludge holding ponds. The sludge from any of the treatment systems, except air flotation with polyelectrolyte chemicals added, is amenable to any of these sludge handling processes. The sludge from air flotation with chemicals has proven difficult to dewater in a couple of plants. A dewatered sludge is an acceptable land fill material. Sludge from secondary treatment systems is normally ponded by plants on their own land or dewatered or digested sufficiently for hauling and depositing in public land fills. The final dried sludge material can be safely 133 ------- used as an effective soil builder. Prevention of water runoff is a critical factor in plant-site sludge holding ponds. Costs of typical sludge handling techniques for each secondary treatment system generating sufficient quantities of sludge to require handling equipment are included in the costs for these systems. Air Pollution Odors are the only significant air pollution problem associated with waste treatment in the rendering industry. Malodorous conditions usually occur in anaerobic waste treatment processes or localized anaerobic environments within aerobic systems. However, it is generally agreed that anaerobic ponds will not create serious odor problems unless the process water has a sulfate content; then it most assuredly will. Sulfate waters are definitely a localized condition varying even from well to well within a specific plant. In a northern climate, the change in weather in the spring may be accompanied by a period of increased odor problems. The anaerobic pond odor potential is somewhat unpredictable as evidenced by a few plants without sulfate waters that have odor problems. In these cases a cover and collector of the off-gas from the pond controls odor. The off-gas is burned in a flare. The other potential odor generators in waste water treatment are leaking tanks and process equipment items used in the anaerobic contact process that normally generate methane. However, with the process confined to a specific piece of equipment it is relatively easy to confine and control odors by collecting and burning the off-gases. The high heating value of these gases makes it worthwhile and a frequent practice to recover the heat for use in the waste treatment process. Odors have been generated by some air flotation systems which are normally housed in a building, thus localizing, but intensifying the problem. Minimizing the unnecessary holdup of any skimmings or grease-containing solids has been suggested as a remedy. Odors can best be controlled by elimination at the source, rather than resorting to treatment for odor control, which remains largely unproven at this time. Noise The only material increase in noise within a rendering plant caused by waste treatment is that caused by the installation of an air flotation system or aerated lagoons with air blowers. Large pumps and an air compressor are part of an air flotation system. The industry frequently houses such a system in a low- cost building; thus, the substantial noise generated by an air flotation system is confined and perhaps amplified by installation practices. All air compressors, air blowers, and 134 ------- 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. 135 ------- SECTION IX EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF THE BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY AVAILABLE—EFFLUENT LIMITATIONS GUIDELINES INTRODUCTION The effluent limitations which must be achieved July 1, 1977, are to specify the degree of effluent reduction attainable through the application of the Best Practicable Control Technology Currently Available. This technology is generally based upon the average of the best existing performance by plants of various sizes, ages, and unit processes within the industrial category and/or subcategory. This average was not based upon a broad range of plants within the independent rendering industry, but based upon performance levels achieved by exemplary plants. Consideration was also given to: o The total cost of application of technology in relation to the effluent reduction benefits to be achieved from such application; o The size and age of equipment and facilities involved; o The processes employed; o The engineering aspects of the application of various types of control techniques; o Process changes; o Nonwater quality environmental impact (including energy requirements). Also, Best Practicable Control Technology Currently Available emphasizes treatment facilities at the end of a manufacturing process, but includes the control technologies within the process itself when the latter are considered to be normal practice within an industry. A further consideration is the degree of economic and engineering reliability which must be established for the technology to be "currently available." As a result of demonstration projects, pilot plants and general use, there must exist a high degree of confidence in the engineering and economic practicability of the technology at the time of start of construction of installation of the control facilities. 137 ------- EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF BEST POLLUTION CONTROL TECHNOLOGY CURRENTLY AVAILABLE Based on the informatior contained in Sections III through VIII of chis report, a determination has been made that the quality of effluent attainable through the application of the Best Pollution Control Technology Currently Available is as listed in Table 22. Of the ten plants with materials recovery systems and secondary treatment systems for which information on effluent quality was available^ two are meeting these standards. An additional four of the plants come close to meeting these standards. Hide curing at an independent rendering plant requires an adjustment in the limitation for BOD5, and SS (Table 23). An adjustment does not become significant, however, unless the number of hides handled is quite large. For example, an average size plant, as found in this study, is one handling 94,000 kg (206,000 pounds) RM (raw materials) per day, and also curing 100 hides, and would have the following adjustment factors (AF): AF (BOD5) = 8_x_100 = 0.0085 kg/kkg RM (lb/1000 Ib RM) 94,000 AF (TSS) = ll_x_100 = 0.012 kg/kkg RM (lb/1000 Ib RM) 94,000 From Table 22 and the above correction, the effluent limitations for this pollutant would be 0.15 + 0.0085, and 0.17 + 0.012 or 0.182 kg/kkg (lb/1000 Ib) RM (a 5 and 7 percent increase) for BOD5 and SS, respectively. An adjustment for grease was not included because there was no correlation between the raw and final waste loads for grease. For instance, for the six plants meeting the grease limit (of the nine plants for which final effluent data on grease were available) only two of the six plants had raw grease loads less than the industry average (which was 0.72 kg/kkg RM) . The other four plants had raw grease loads that were 1.5, 1.6, 4.3, and 7.6 times greater than the average value of 0.72. Yet, five of the six plants had final grease concentrations that '-'ere within a range of 2 to 23 mg/1; the sixth had a final grer.ss concentration of 54 mg/1. It thus appears that the treatment system used, can reduce grease in the final effluent to relatively low values, independent of the grease in the raw waste. 138 ------- Table 22. Recommended Effluent Limitation Guidelines for July 1, 1977 Effluent Parameter Effluent Limitation BOD 5 Suspended solids (SS) Grease Fecal coliform 0.15 kg/kkg RM (lb/1000 Ib KM) 0.2Q kg/kkg RM (lb/1000 Ib RM) 0.10 kg/kkg RM (lb/1000 Ib RM) 400 counts/100 ml Table 23. Effluent Limitations Adjustment Factors for Hide Curing Effluent Parameter (kg/kkg RM or lb/1000 Ib RM) BOD5 8.0 x (no. of hides) _ j-7.6 x (no. of hides) ( kg of RM) ~ (Ib of RM) ... ,-_, 11 x (no. of hides) 24.2 x (no. of hides) Suspended solxds (SS) = ( kg of RM) = (Ib of RM) 139 ------- IDENTIFICATION OF BEST POLLUTION CONTROL TECENOLOGY CURRENTLY AVAILABLE Best Pollution Control Technology Currently Available for the independent rendering industry involves biological waste treatment following a materials recovery process for grease and solids. To assure that treatment will successfully achieve the limits specified, certain in-plant practices should be followed: 1. Materials recovery system—catch basins, skimming tanks, air flotation, etc.—should provide for at least a 30- minute detention time of the waste water. 2. Reuse of treated waters for operating barometric leg condensers rather than fresh water. This minimizes net waste water volume; for a given size of treatment system, it permits a longer effective residence time. 3. Removal of grease and solids from the materials recovery system on a continuous or regularly scheduled basis to permit optimum performance. 4. Provide adequate cooling of condensables to ensure that the temperature of the waste water in the materials recovery system does not exceed 52°C (125°F). This allows for improved grease recovery. 5. Scrape, shovel, or pick up by other means as much as possible of material spills before washing the floors with hot water. 6. Minimize drainage from materials receiving areas. This may require the pumping of the liquid drainage back onto the raw materials as it is conveyed from the area. 7. Repair equipment leaks as soon as possible. 8. Provide for regularly scheduled equipment maintenance programs. 9. Avoid over-filling cookers. 10. Provide and maintain traps in the cooking vapor lines to prevent overflow to the condensers. This is particularly important when the cookers are used to hydrolyze materials. 11. Contain materials when equipment failure occurs and while equipment is being repaired. 12. Steam sparge and screen liquid drainage from high water- and blood-containing materials, such as poultry feathers on which blood has been dumped. 13. Plug sewers and provide supervision when unloading or transferring raw blood. Blood has a BOD5 of between 140 ------- Table 24. Raw and Final Effluent Information for Ten Rendering Plants Plant Number —' 1 2 3 4 5 6 7 8 9 10 Flow, 1000 liters (1000 gal.) 454 (120 57 U5) 132 (35) 45 (12) 3028 (800) 102 (27) 2120 (560) 106 (28) 625 (165) 19 (5) RM/Day , kkg (1000 Ib) 170 (374) 9 (20) 86 (190) 68 (150) 390 (860) 32 (70) 300 (660) 75 (165) 265 (583) 26 (57) BOD Load, kg /kkg RM* Raw 1.77 0.79 16.22 2.66 4.51 1.28 5.86 6.93 3.64 3.50 Final 0.06 0.04 0.16 0.06 0.18 0.27 0.86 0.09 0.34 0.07 SS Load, kg /kkg RM* Raw 2.81 6.96 6.69 1.45 2.42 0.65 3.50 2.77 0.80 — Final 0.08 0.21 0.006 0.09 0.42 0.30 4.4 0.14 0.20 — Grease Load, kg /kkg RM* Raw 0.04 1.050 5.45 1.070 0.920 — 1.340 3.120 1.150 0.63 Final 0.006 0.10 0.035 0.150 0.220 — 0.300 0.028 0.038 0.040 Final Fecal Coliform** (Counts/100 ml) — 3,600 70,000 50 99 (Cl) — 270,000 99 100 (Cl) 4,700 *kg/kkg RM = lb/1000 Ib RM **(C1) indicates chlorination of final effluent. 17 For plant number 3, high raw wastes due to malfunction in grease/ solids recovery system, and final SS value not used due to atypical final settling. Plant number 7 was not used to derive limits due to apparent severe malfunction in normally satisfactory treatment facility. ------- 150,000 and 200,000 mg/1.8 J 14. Provide by-pass controls for controlling pressure reduc- :* tion rates of cookers after hydrolysis. Cooker agitation '' may have to be stopped also, during cooker pressure bleed-'! down to prevent, or minimize materials carry-over. 15. Minimize water use for scrubbers by recycling and reuse. 16. Evaporate tank water to stick and use as tankage in dry :i inedible rendering. ' 17. Do not add uncontaminated water to the contaminated water l to be treated. ; 18. By-pass the materials recovery process with low grease- bearing waste waters. The above practices can readily produce a raw waste load below that cited as average in Section V. With an average waste load, use of the following secondary biological treatment systems i should produce an effluent that meets the recommended effluent limitations: 1. Anaerobic lagoon + aerobic (shallow) lagoons 2. Activated sludge + aerobic (shallow) lagoons 3. Aerated lagoons -t- aerobic (shallow) lagoons. Plants with a higher-than-average raw waste load or an undersize treatment system may require a solids removal stage or chlorination as the final treatment process. Furthermore, a plant located in a cold climate area may need sufficient holding capacity in the aerobic lagoons because it cannot discharge for periods of three to six months. RATIONALE FOR THE SELECTION OF BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY AVAILABLE The rationale used in developing the effluent limitations presented in Table 24 was based upon the actual performances of ten plants having what was considered to be complete secondary treatment and for which sufficient information was available. A complete secondary treatment system would include any properly sized system mentioned in the preceding paragraph. Size, Age, Processes Employed, and Location of Facilities The ten plants used for developing the effluent limitations cover operations using different processes, equipment, raw materials, and are of different size, age, and location of facilities. Data presented in Section IV showed that these factors did not have a distinct influence on the raw waste characteristics from 142 ------- independent rendering plants. Furthermore, the final effluent data from these ten plants reveal that the raw waste loads can be readily reduced by secondary treatment to a similar level regardless of in-plant operations, raw materials used, and size, age, and location of facilities. Data Presentation Table 24 presents the data for the ten plants. Included in Table 24 are the plant size (kkg or 1000 Ib RM/day), effluent flow,raw and final waste loads for BOD5, SS, and grease, and fecal coliform counts in the final treated effluent. Data for four of the plants represent information obtained as a result of our field sarrpling survey; data for the other six plants were obtained primarily from questionnaire information and of these, data for three plants were verified by the results of the field survey. Data for plant number 7 were included, although it was evident from visiting the plant and the results shown that the treatment system at this plant was not functioning properly; the effluent data were not used in determining the effluent limits. Similarly, the test results for SS for plant number 3 were found to be inconsistent and were not used for calculating the effluent limits. The BOD5 effluent limitation of 0.15 kg/kgg RM is basically the average value of the BOD5 data for all but plant number 7. The data of Table 24 show that five of the ten plants easily meet this limitation, while plants 3 and 5 come very close. It should be noted that the raw BOD5 waste loads for the five plants meeting the effluent range from 0.79 to 6.93 kg BOD5/kkg (lb/1000 Ib) RM and that the raw value for plant 3, whose final value comes close to the limitation, is 16.2 kg/kkg RM. In fact, the average raw BOD5 value for the five plants meeting the limitation is 3.13 kg BOD5/kkg (lb/1000 Ib) RM. The average of all plants stuided was 2.15 kg BOD5/kkg RM; thus even plants with higher raw BOD5 waste loads than these industry averages can meet the BOD5 effluent limitation. The suspended solids (SS) effluent limitation value of 0.17 kg SS/kkg RM is close to the average of all the values except for that of plant 7. The values for four plants meet the effluent limitation for suspended solids. Also, the raw SS values for these four plants range from 1.45 to 6.69 kg SS/kkg (lb/1000 Ib) RM with an average value of 3.43 kg SS/kkg (lb/1000 Ib RM). The overall average for all plants studied is 1.13 kg SS/kkg (lb/1000 Ib) RM. The grease effluent limitation value of 0.10 kg grease/kkg RM is very nearly the average grease value for the nine values shown. There are six plants that meet the effluent limitation. These six plants have raw waste values ranging from 0.04 to 5.45 kg grease/kkg (lb/1000 Ib) RM, with an average value of 2.30. This average raw grease value for plants meeting the guidelines is 143 ------- over three times as great as the average for grease for all plants included in the study, which is 0.72. Based on the average raw waste load values for the ten plants, with biological treatment systems, these plants must achieve the following percent reduction to meet the effluent limitation: 96.8 for BOD5, 94.5 for SS, and 95.2 for grease. If, however, the reductions are based on the average raw waste values for all plants included in the study, the following percentages are obtained: 93.0 for BOD5, 85.0 for suspended solids, and 86.1 for grease. Although from four to seven of the plants used in developing the effluent limitations meet at least one of the three effluent limitations, only two plants are known to meet all three: BOD5, SS, and grease. Another four plants meet the limitations for two of the parameters and come very close to meeting the third. The fecal coliform effluent limitation of 400 counts/100 ml is a typical value being used for a number of industries. Data from Table 24 show that four plants can meet this value, and that two of those are doing so without chlorination. These two plants not needing chlorination have large anaerobic lagoons plus aerobic lagoons for secondary treatment. The fecal coliform counts given in Table 24 were obtained using the membrane filter procedure. This method and the multiple-tube technique which results in a MPN (most probable number) value, yield comparable results. The BOD5 and SS effluent limitation adjustment factors for hide curing shown in Table 23 were developed using the data from Table 11 and the average BOD5 and SS reduction required to meet the limitations. These reductions are 93 and 85 percent for BOD5 and SS, respectively; the values produce adjustment factors of 0.008 kg (0.0176 Ib) BOD5/hide and 0.011 kg (0.0242 Ib) SS/hide. As discussed earlier, no adjustment was developed for grease. Engineering Aspects of Control Technique Applications The specified level of control technology, primary plus biological treatment, is practicable because it is currently being practiced by plants representing a wide range of plant sizes and types. However, if additional treatment is needed, such as sand beds or mixed media filter beds this technology is practical as evidenced by its use by other industries8 and municipalities. Process Changes Significant in-plant changes will not be needed by the vast majority of plants to meet the limitations specified. Many plants will have to improve plant cleanup and housekeeping practices, both responsive to good plant management control. This can best be achieved by ir.iniirdzing spills, containing materials upon equipment breakdown, and using dry cleaning prior 144 ------- to washdown. Some plants may find it necessary to pretreat truck and raw materials drainage, blood water, and tank water before mixing them with other waste waters prior to entering the materials recovery system. Some plants may also find it necessary to use improved gravity separation systems, such as air flotation with chemical precipitation. Additional cooling of the waste water before grease recovery may be required in some cases. Nonwater Quality Environmental Impact \ The major impact when the option of an activated sludge type of system or, possibly, chemical precipitation in the materials recovery system is used to achieve the limitations will be disposal of the sludge. Nearby land for sludge disposal may be necessary; in some cases a sludge digester (stabilizer) may offer a solution. Properly operated activated sludge-type systems should permit well conditioned sludge to be placed in small nearby soil plots for drying without great difficulty. It was concluded that the odor emitted periodically from anaerobic lagoons is not a major impact as it can be with the meat packing industry.8 Also, there are no new kinds of impact introduced by the application of the best current technology. 145 ------- SECTION X EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF THE BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE— EFFLUENT LIMITATIONS GUIDELINES INTRODUCTION The effluent limitations which must be achieved no later than July 1, 1983, are not based on an average of the best performance within an industrial category, but are determined by identifying the very best control and treatment technology employed by a specific point source within the industrial category or subcategory, or by one industry where it is readily transferable to another. A specific finding must be made as to the availability of control measures and practices to eliminate the discharge of pollutants, taking into account the cost of such elimination. Consideration was also given to: o The age of the equipment and facilities involved; o The process employed; o The engineering aspects of the application of various types of control techniques; o Process changes; o The cost of achieving the effluent reduction resulting from application of the technology; o Nonwater quality environmental impact (including energy requirements) . Also, Best Available Technology Economically Achievable emphasizes in-process controls as well as control or additional treatment techniques employed at the end of the production process. This level of technology considers those plant processes and control technologies which, at the pilot-plant, semi-works, and other levels, have demonstrated both technological performances and economic viability at a level sufficient to reasonably justify investing in such facilities. It is the highest degree of control technology that has been achieved or has been demonstrated to be capable of being designed for plant-scale operation up to and including "no discharge" of pollutants. Although economic factors are considered in this development, the costs of this level of control are intended to be the top-of-the- line of current technology, subject to limitations imposed by economic and engineering feasibility. However, there may be some technical risk with respect to performance and with respect to 147 ------- certainty of costs. Therefore, some industrially sponsored development work may be needed prior tc its application. EFFLUENT REDUCTION ATTAINABLE THROUGH APPLICATION OF THE BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE Based on the information contained in this section and in Sections III through VII of this report, a determination has been made that the quality of effluent attainable through the application of the Best Available Technology Economically Achievable is as listed in Table 25. The technology to achieve these goals is generally available, although it may not have been applied as yet to an independent rendering plant or on a full scale. Hide curing at an independent rendering plant requires an adjustment in the limitations for BOD5 and SS. These adjustments are listed in Table 26. An adjustment does not become significant, however, unless the number of hides handled by a plant is quite large. For example, an average size plant as found in this study, is one handling 94,000 kg (206,000 pounds) raw material (RM) per day, and that also cures 100 hides would have the following adjustment factors (AF): AF(BOD5) = 3...6_x_100 = 0.0038 kg/kkg RM (lb/1000 Ib RM) 94,000 AF (TSS) = 6.._2_x_100 = 0.0066 kg/kkg RM (lb/1000 Ib RM) 94,000 The effluent limitations for this plant would therefore be 0.074 and 0.107 kg/kkg RM (lb/1000 Ib RM) for BOD5 and SS, respectively (a 5.7 and 7 percent increase). An adjustment for grease was not included because there was no correlation between the raw and final grease values. For example, the six plants that had the lowest final grease loads (which ranged between about 0.006 and 0.10 kg grease/kkg RM) out of the nine plants for which final effluent data on grease were available, had raw grease loads ranging from 0.04 to 5.450 kg/kgg (lb/1000 Ib) RM, with an average for the six raw values of 1.91 kg/kkg (lb/1000 Ib) RM. Also, only two of the six plants had raw grease loads less than the industry average (which was 0.72); the other four plants had raw grease loads that were 1.5, 1.6, 4.3 and 7.6 times the average. It thus appears that the treatment system used can reduce grease in the final effluent to relatively low values, independent of the raw grease load. It should also be pointed out that an independent renderer should consider land disposal, and hence no discharge, for 1983. Where suitable land is available, evaporation or irrigation is an option that not only is recommended from the discharge viewpoint, but also will usually be more economical than the system 148 ------- Table 25. Recommended Effluent Limitation Guidelines for July 1, 1983 Effluent Parameter Effluent Limitation* BOD5 Suspended solids (SS) Grease Ammonia as N Total phosphorus as P pH Fecal coliform 0.07 kg/kkg RM 0.10 kg/kkg RM 0.05 kg/kkg RM 0.02 kg/kkg RM 0.05 kg/kkg RM 6.0 - 9.0 400 counts/100 ml *kg/kkg RM = lb/1000 lb RM Table 26. Effluent Limitation Adjustment Factors for Hide Curing Effluent Parameter BOD5 Suspended Solids (SS) Adjustment Factor kg/kkg RM 3.6 x (no. of hides) (kg of RM) 6.2 x (no. of hides) (kg of RM) lb/1000 lb RM 7.9 x (no. of hides) ( lb of RM) 13 . 6 x (no . of hides) (lb of RM) 149 ------- otherwise required. In fact, out of the 48 independent rendering plants included in this study for which discharge information was available, 24 did not discharge to a municipal treatment system, and 12 of them had no discharge. IDENTIFICATION OF THE BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE The Best Available Technology Economically Achievable includes that listed under the Best Practicable Control Technology Currently Available (Section IX) , and a sand filter or equivalent following secondary treatment. In addition, some plants may require improved pretreatment, such as dissolved air flotation with pH control and chemical flocculation, and an ammonia stripping or nitrification-denitrification sequence. In-plant controls and modifications may also be required to achieve the specified levels. These include the following: 1. Materials recovery systems—catch basins, skimming tanks, air flotation, etc.—should provide for at least a 30- minute detention time of the waste water. 2. Reuse of treated waters for operating barometric leg condensers rather than fresh water. This minimizes net waste water volumes; for a given size of treatment system it permits a longer effective residence time. 3. Removal of grease and solids from the materials recovery system on a continuous or regularly scheduled basis to permit optirruin performance. 4. Provide adequate cooling of condensables to ensure that the temperature of the waste water in the materials recovery system does not exceed 52°C (125°F). A tempera- ture below 38°C (100°F) is even better. This allows for improved grease recovery and, incidentally, minimizes odor problems. 5. Scrape, shovel, or pick up by other means as much as possible of material spilled before washing the floors with hot water. 6. Minimize drainage from materials receiving areas. This may require the pumping of the liquid drainage back onto the raw materials as it is conveyed from the area to the first processing step. 7. Repair equipment leaks as soon as possible. 8. Provide for regularly scheduled equipment maintenance programs. 9. Avoid over-filling cookers. 150 ------- Table 27. Raw and Final Effluent Information for Ten Rendering Plants Table 27A. Flow, RM/Day, Final Fecal Coliform, and BOD5, SS, and Grease Waste Loads Plant Number ^J 1 2 3 4 5 6 7 8 9 10 Flow 1000 liters (1000 gal.) 454 C120) 57 (15) 132 (35) 45 (12) 3028 (800) 102 (27) 2120 (560) 106 (28) 625 (165) 19 (5) RM/Day kkg (1000 Ib) 170 (374) 9 (20) 86 (190) 68 (150) 390 (860) 32 (70) 300 (660) 75 (165) 265 (583) 26 (57) BOD5 Load, kg /kkg KM* Raw 1.77 0.79 16.22 2.66 4.51 1.28 5.86 6.93 3.64 3.50 Final 0.06 0.04 0.16 0.06 0.18 0.27 0.86 0.09 0.34 0.07 SS Load, kg /kkg RM* Raw 2.81 6.96 6.69 1.45 2.42 0.65 3.50 2.77 0.80 — Final 0.08 0.21 0.006 0.09 0.42 0.30 4.4 0.14 0.20 — Grease Load, kg/kkg RM* Raw 0.04 1.050 5.45 1.070 0.920 — 1.340 3.120 1.150 0.63 Final 0.006 0.10 0.035 0.150 0.220 — 0.300 0.028 0.038 0.040 Final Fecal Coliform** (Counts/100 ml) 3,600 70,000 50 99 (Cl) — 270,000 99 100 (Cl) 4,700 en *kg/kkg RM = pounds/1000 pounds RM **(C1) indicates chlorination of final effluent. I/ For plant number 3, high raw wastes due to malfunction in grease/ solids recovery system, and final SS value not used due to atypical final settling. Plant number 7 was not used to derive limits due to apparent severe malfunction in normally satisfactory treatment facility. ------- Table 27. Raw and Final Effluent Information for Ten Rendering Plants (Continued) Table 27B. TKN, NH3, N02, N03 and TP Waste Loads Plant Number 1 2 3 4 5 6* 7 8 9 10 Total Kjeldahl Nitrogen Load as N kg/kkg RM Raw 0.49 0.38 0.94 0.38 0.44 — 1.2 0.33 0.82 0.23 Final 0.03 0.02 0.27 0.034 0.30 — 1.92 0.35 0.32 0.08 Ammonia Load as N kg/kkg RM Raw 0.26 0.17 0.08 0.19 0.30 — 0.66 0.14 0.29 0.18 Final 0.001 0.005 0.26 0.0086 0.16 — 0.53 0.11 0.11 0.044 Nitrite Load as N kg/kkg RM Raw 0.04 0.0001 0.0003 0.00002 0.0004 — 0.00036 0.00007 0.00079 0.0013 Final 0.001 0.008 0.00015 0.00005 0.0002 — 0.00036 0.00009 0.0013 0.00004 Nitrate Load as N kg/kkg RM Raw 0.06 0.0001 0.0014 0.0015 0.0001 — 0.012 0.0015 0.018 0.0075 Final 0.0004 0.001 0.0024 0.00068 0.0001 — 0.012 0.0018 0.0077 0.001 Total Phosphorus Load as P kg/kkg RM Raw 0.01 0.013 0.08 0.031 0.062 — 0.28 0.04 0.04 0,023 Final 0.029 0.001 0.046 0.014 0.08 — 0.26 0.029 0.024 0.013 en *Nutrient values for this Part A of this table for plant are missing because the plant was not sampled. The values shown in this plant were obtained from the questionnaire. ------- 10. Provide and maintain traps in the cooking vapor lines to prevent overflow to the condensers. This is particularly important when the cookers are used to hydrolyze materials. 11. Contain materials when equipment failure occurs and while equipment is being repaired. 12. Steam sparge and screen liquid drainage from high water- and blood-containing materials such as poultry feathers on which blood has been dumped. 13. Plug sewers and provide supervision when unloading or transferring raw blood. Blood has a BOD5 of between 150,000 and 200,000 mg/1.8 14. Provide by-pass controls for controlling pressure reduc- tion rates of cookers after hydrolysis. Cooker agitation may have to be stopped also, during cooker pressure bleed- down to prevent or minimize material carry-over. 15. Minimize water use for scrubbers by recycling and reuse. 16. Evaporate tank water to "stick" and use as tankage in dry inedible rendering. 17. Do not add uncontaminated water to the contaminated water to be treated. 18. By-pass the materials recovery process with low grease- bearing waste waters. 19. Provide for flow equalization (constant flow with time) through the materials recovery system. 20. Eliminate hide curing waste waters by mixing small volumes with large volumes of raw materials being fed to cookers. If suitable land is available, land disposal is the best technology; it is no discharge. However, secondary treatment may still be required before disposal of waste waters to soil, although the degree of treatment need not be the same as that required to meet the 1977 limitations (Section IX). Any of the systems mentioned in Section IX are suitable. Currently a number of independent rendering plants are achieving no discharge via land irrigation, ponding, and discharge to septic tanks followed by sub-soil drainage (drain fields or large cesspools). some plants use two of the above technologies to achieve no discharge. For example, evaporation and ponding may be used for disposal of wash water and drainage from raw materials receiving areas, and septic tanks followed by drain fields for disposal of condensables. This method of disposal of condensables also helps to contain the associated odor problem. 153 ------- RATIONALE FOR SELECTION OF THE BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE The rationale used in developing the 1983 effluent limitations presented in Table 25 was based upon the performances of ten waste treatment systems and information contained in Sections III through VII. The ten treatment systems were considered to be complete secondary treatment systems. In addition, chlorination was being used by two of the ten plants. Size, Age, Processes Employed, and Location of Facilities The ten plants used for developing the effluent limitations cover operations using different processes, equipment, raw materials, and are of different sizes, ages, and locations of facilities. Data presented in Section IV showed that these factors do not have a distinct influence on the raw waste characteristics from independent rendering plants. The final effluent data from these ten plants reveal that the raw waste loads can be substantially reduced by secondary treatment to a similar level regardless of in-plant operations, raw materials used, and size, age, and location of facilities. The levels to which secondary treatment can reduce the raw waste loads will be sufficient to allow the effluent from secondary treatment to meet effluent limitations for a number of the pollutants for 1983; however, tertiary treatment will be needed to ensure that others will consistently meet 1983 standards. Plants located in cold climates may need sufficient holding capacity in the secondary treatment system because they cannot discharge during the coldest months of the year. This is true not only for plants that discharge their treated waste waters to navigable streams, but also for plants that irrigate. Data Presentation Table 27 presents the data for the ten plants. Included in Table 27A are the plant size (kkg or 1000 Ib RM/day), effluent flow, raw and final waste loads for BOD5, SS, and grease, and fecal coliform counts in the final treated effluent. Table 27B includes raw and final waste load data for total Kjeldahl nitrogen (TKN) , ammonia (NH3) , nitrates (NO3) , nitrites (N02) , and total phosphorus (TP) . Data for four of the plants in Table 27A represent information obtained as a result of our field sampling survey; data for the other six plants listed were obtained primarily from questionnaire information, and of these, data for three plants were verified by the results of the field survey. The data included in Table 27B were all obtained from the results of the field sairpling survey. Data for plant number 7 were included, although it was evident from visiting the plant and from the results shown in the table that the treatment system at this plant was not functioning properly. 154 ------- The BOD5 effluent limitation of 0.07 kg/kgg RM (0.07 lb/1000 Ib RM) is a value being met by four of the ten plants (see Table 27A) . TWO of the four plants meeting this limit have raw waste BOD5 loads greater than the industry average of 2.15 kg BODS/kkg RM. Thus, it appears that a well operated and properly sized secondary treatment system can produce an effluent with a BOD5 load that will meet the 1983 limitation. Using the average flow value for the industry, which is 4977 liters/kkg RM (597 gal./lOOO Ib RM), the BOD5 effluent limit value of 0.07 kg/kkg RM corresponds to a final effluent concentration of 4.4 mg/1. A BOD5 concentration this low usually means that the majority of the BOD5 remaining is contained in the suspended solids. In fact, this is supported by the results of a correlation analysis between final BOD5 and suspended solids waste loads that showed a high correlation between the two—the correlation coefficient was 0.87 (a coefficient of 1 would be a perfect correlation). Consequently, to ensure that the final effluent will meet the 1983 BOD5 limit during all periods of discharge will require the use of a sand filter or its equivalent to reduce the remaining SS and thus the EOD5. The suspended solids (SS) effluent limitation value of 0.10 kg/kkg RM (0.10 lb/1000 Ib RM) is currently being met by three of the nine plants with secondary treatment for which there are data. These three plants all have raw SS loads greater than the industry average, which is 1.13 kg/kkg RM, as shown in Table 6. As mentioned in the above paragraph, a sand filter or its equivalent will be required to remove SS and hence to lower the BOD5. This should therefore permit all plants to meet the SS limitation value. The SS limit, using the average flow value for the industry of 4977 1/kkg (597 gal./lOOO Ib) RM corresponds to a final concentration for SS of 20 mg/1. This concentration was also considered to be about the practical limit for SS removal via a sand filter (see Section VII). The grease limit of 0.05 kg/kkg RM (0.05 lb/1000 Ib RM) was chosen because five of nine plants for which grease data were available (see Table 27A) met this limit. This limit should not be difficult to achieve via secondary treatment; four of the five plants meeting the limit had raw grease loads considerably greater than the industry average of 0.72 kg grease/kkg RM. Incidentally, this limit corresponds to a concentration of 10 mg/1 when the water use equals the industry average of 4977 1/kkg RM (597 gal./lOOO Ib RM). The ammonia limit of 0.02 kg NH3 as N/kkg RM (0.02 lb/1000 Ib RM) is being met by three plants that are showing substantial reduction in Total Kjeldahl Nitrogen. The reason for this is that the TKN value, which is the sum of the organic and ammonia nitrogen, is largely caused by ammonia in the final effluent, as can be seen in Table 27B. Thus, the same steps that are being used to reduce the TKN value will also help to reduce the ammonia value. Of course, the best approach to this problem is to eliminate or reduce the sources, one of which is blood. 155 ------- The pH limits of from 6.0 to 9.0 are not expected to require any special control since all plants for which there were data have effluents with pH in this range. The fecal coliform effluent limitation of 400 counts/100 ml is the same as for the 1977 limits. Data from Table 27A show that four plants can meet this value, and that two of those are doing so without chlorination. The two plants not needing chlorination have large anaerobic lagoons plus aerobic lagoons for secondary treatment. The fecal ccliform counts given in Table 27A were obtained using the membrane filter procedure. This method and the multiple-tube technique which results in a MPN (most probable number) value, yield comparable results. Engineering Aspects of Control Technique Applications The specified level cf control technology, primary, plus secondary, plus tertiary (which will include at least a sand filter or its equivalent if it is needed), is practicable; a number of plants without tertiary treatment are currently meeting the limits for the individual waste parameters as previously mentioned. In fact, one plant is currently meeting all waste parameter limits, and several others are meeting the majority. Tertiary treatment is required, however, to permit all plants to meet the limits for all pollutants. The specified tertiary treatment is practicable because it is currently being used by other industries. Plants located in cold climates will have to have sufficient capacity in the treatment systems because they cannot discharge for periods of about three months. This, too, should be no major engineering problem since a number of plants in this industry as well as others are currently doing this.8 Process Changes Most plants will have to make in-plant changes to meet the 1983 limitations, particularly to meet the TKN and ammonia limitations. This will involve improved plant cleanup and housekeeping practices, both responsive to good plant management control. This will include minimizing spills, containing materials upon equipment breakdown, using dry cleaning prior to washdown, and additional cooling of the waste waters before the materials recovery system. Still, some plants may find it necessary to control drainage from trucks and raw materials, blood waters, tank water, and hide-curing waste waters. Specific suggestions on controlling these sources of waste water were made earlier in this section. Some plants may also find it necessary to improve the materials recovery system or replace it with an improved system such as air flotation with chemical precipitation. Nonwater Quality Impact The major impact will occur when the land disposal option is chosen. There is a potential long-term effect on the soil from 156 ------- irrigation of rendering plant waste water and on ground waters. To date, impacts have been generally obviated by careful water application management and by biological treatment prior to disposal. Otherwise, the effects will essentially be those described in Section IX, where it was concluded that no new kinds of impacts would be introduced. 157 ------- SECTION XI NEW SOURCE PERFORMANCE STANDARDS INTRODUCTION The effluent limitations that must be achieved by new sources are termed New Source Performance Standards. The New Source Performance Standards apply to any source for which construction starts after the publication of the proposed regulations for the Standards. The Standards are determined by adding to the consideration underlying the identification of the Best Practicable Control Technology Currently Available, a determina- tion of what higher levels of pollution control are available through the use of improved production processes and/or treatment techniques. Thus, in addition to considering the best in-plant and end-of-process control technology. New Source Performance Standards are based on an analysis of how the level of effluent may be reduced by changing the production process itself. Alternative processes, operating methods cr other alternatives are considered. However, the end result of the analysis is to identify effluent standards which reflect levels of control achievable through the use of improved production processes (as well as control technology), rather than prescribing a particular type of process or technology which must be employed. A further determination is made as to whether a standard permitting no discharge of pollutants is practicable. Consideration was also given to: o Operating methods; o Batch, as opposed to continuous, operations; c Process employed; o Plant size; o Recovery of pollutants as by-products. EFFLUENT REDUCTION ATTAINABLE FOR NEW SOURCES The effluent limitations for new sources are the same as those for the Best Practicable Control Technology Currently Available for the pollutants BOD5, SS, grease, and fecal coliform (see Section IX). In addition to these pollutant parameters, the following additional limits on nutrients are required for new sources: 159 ------- Effluent Parameter Ammonia as N Effluent Limitation kg/kkg (lb/1000 Ib) RM 0.17 These limitations are readily achievable in newly constructed plants since a number of existing well operated plants are meeting them. (For the actual data, see Section X.) However, the guidelines for the Best Available Technology Economically Achievable should be kept in mind; it may be a practical approach to design a plant which approaches the 1983 guidelines. Consideration should also be given to land disposal, which is no discharge; in many cases this will be the most attractive and economical option, particularly for small rendering plants. Table 28 shows the estimated costs for new sources to achieve the new source performance standards. Table 28. Investment and Operating Costs for New Source Performance Standards Plant Size Small Medium Large Waste Water Treatment System Costs Investment Cost $ 38,000 78,000 133,000 Annual Cost Total $/yr 20,500 30,600 44,100 C/kg (C/lb) 0.42 (0.19) 0.13 (0.06) 0.07 (0.03) Operating Cost Total $/yr 14,700 18,800 24,100 C/kg (C/lb) 0.31 (0.14) 0.09 (0.04) 0.04 (0.02) Identification of New Source Control Technology The control technology is the same as that identified as the Best Practicable Control Technology Currently Available (see Section IX). However, certain steps that will be necessary to meet the 1983 guidelines should be considered and, where possible, incorporated. These include: o Segregation of drainage from trucks and raw materials, hide curing waste, blood water, and tank water from other waste waters for special treatment. This special treatment may be to eliminate these wastes by adding them to the raw material as it enters a cooker or by evaporating them down to a point where they can be used as tankage for dry inedible rendering. Another special treatment method would be to steam sparge and 160 ------- screen some wastes before combining them with other waste waters. Of course, the formal methods are the best for lowering the raw waste load and particularly the TKN and ammonia loads. o Materials recovery systems—catch basins, skimming tanks, air flotation, etc.—should provide for at least a 30- minute detention time of the waste water. o Reuse of treated waters for operating barometric leg condensers rather than fresh water. This minimizes net waste water volumes for a given size of treatment system and permits a longer effective residence time. o Removal of grease and solids from the materials recovery system on a continuous or regularly scheduled basis to permit optimum performance. o Provide adequate cooling of condensables to ensure that the temperature of the waste water in the materials recovery system does not exceed 52°C (125°F). A tempera- ture below 38°C (100°F) is even better. This allows for improved grease recovery, and minimizes odor problems. o Scrape, shovel or pick up by other means as much as possible of material spills before washing the floors with hot water. o Repair equipment leaks as soon as possible. o Provide for regularly scheduled equipment maintenance programs. o Avoid over-filling cookers. o Provide and maintain traps in the cooking vapor lines to prevent overflow to the condensers. This is particularly important when the cookers are used to hydrolyze materials. o Contain materials when equipment failure occurs and while equipment is being repaired. o Plug sewers and provide supervision when unloading or transferring raw blood. o Provide by-pass controls for controlling pressure reduction rates of cookers after hydrolysis. Cooker agitation may have to be stopped also, during cooker pressure bleed-down to prevent or minimize material carry-over. o Minimize water use for scrubbers by recycling and reuse. o Do not add uncontaminated water to the contaminated 161 ------- water to be treated. o By-pass the materials recovery process with low grease- bearing waste waters. o Provide for flow equalization (constant flow with time) through the materials recovery system. In addition, the following end-of-process treatments should be considered. o Land disposal (irrigation, evaporation) wherever possible; this should be a prime consideration, especially for economic reasons. o Sand filter or equivalent for polishing the effluent from secondary treatment. Rationale for Selection of New Source Performance Standards The BOD5, SS, grease and fecal colifcrm limits are discussed in Section IX on the rationale for Best Practicable Control Technology Currently Available. The ammonia limit of 0.17 kg/kkg RM is the average ammonia value for the nine plants whose data are presented in Section X. Six of those nine plants meet this limit. Three are not meeting the limit because of poor practices: two are allowing too much blood to enter the sewer, and the third is adding nutrients to the lagoons to form a grease cover on the anaerobic lagoon. A total Kjeldahl nitrogen (TKN) limit was not established because the majority of the TKN in the effluent is ammonia (the rest, organic nitrogen) and restricting ammonia will restrict the TKN load in the effluent. Pretreatment Requirements No constituents of the effluent discharged from a plant within the offsite rendering industry have been found which would interfere with, pass through, or otherwise be incompatible with a well designed and operated publicly owned activated sludge or trickling filter waste water treatment plant. The effluent, however, should have passed through materials recovery (primary treatment) in the plant to remove settleable solids and a large portion of the grease. The concentration of pollutants acceptable to the treatment plant is dependent on the relative sizes of the treatment facility and the effluent volume from independent rendering plants, and must be established by the treatment facility. It is possible that grease remaining in the rendering effluent will cause difficulty in the treatment system; trickling filters appear to be particularly sensitive. A 162 ------- 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. 163 ------- SECTION XII ACKNOWLEDGMENTS The program was conducted under the overall supervision of Dr. E.E. Erickson. John Pilney was the Project Engineer; he was assisted by Messrs R.J. Reid and R.J. Parnow. Special assistance was provided by North Star staff members: Messrs R.H. Forester and A.J. Senechal. The contributions and advice of Mr. William H. Prokop of the National Renderers Association and of their plant operations committee and of Dr. H.O. Halvorson are gratefully acknowledged. Special thanks are due Mr. Jeffery D. Denit, Effluent Guidelines Division for his guidance in the direction of the program and for his invaluable help in carrying out all aspects of the research program. The cooperation of the independent rendering industry is greatly appreciated. The National Renderers Association and its members deserve special mention, as do several companies that provided information and cooperation in plant visits and on-site sampling programs. The help of Dr. Dwight Ballinger of EPA in Cincinnati in establishing sampling and testing procedures used for the field verification stuides was also appreciated. Many state and local agencies were also most helpful and much appreciated. 165 ------- SECTION XIII REFERENCES 1. standard Industrial Classification Manual, Executive Office of the President, Office of Management and Budget, U.S. Government Printing Office, Washington, 1972. 2. Dion, J.A., Osag, T.R., Bunyard, F.L., and Crane, G.B., Control of Odors from Inedible Rendering Plants: An Information Document, Environmental Protection Agency, Washington, 1973. 3. "Uniqueness of the Rendering Industry," National Renderers Association, unpublished, undated. 4. 1967 Census of Manufactures, Bureau of the Census, U.S. Department of Commerce, U.S. Government Printing Office, Washington, 1972. 5. Pollution Control Costs and Research Priorities in the Animal Slaughtering and Processing Industries, National Industrial Pollution Control Council, U.S. Government Printing Office, Washington, June 1973. 6. Protein Conversion Equipment, Chemetron Corporation, Chicago, 1973. 7. Personal communication. National Renderers Association. 8. Development Document for Proposed Effluent Limitations Guidelines and New Source Performance Standards for the Red Meat Processing Segment of the Meat Product and Rendering Processing Point Source Category, U.S. Environmental Protection Agency, Report No. 4UO/173/012, Washington, October 1973. 9. Doty, D.M., et al., Investigation of Odor Control in the Rendering Industry, by Fats and Proteins Research Foundation, Incorporated, for Environmental Protection Agency, Report No. PB- 213 386, National Technical Information Service, Springfield, Va., October 1972. 10. Prokop, William H., "The Rendering Industry and Ecology Control," National Renderers Association for presentation at the 2nd Annual International Food and Beverage F.I.D. Symposium, Montreal, June 1973. 11. Meat Industry Waste Management, Robert S. Kerr Water Research Center, Ada, Oklahoma, Environmental Protection Agency, June 1972. 12. Development Document for Effluent Limitations Guidelines and standards of Performance for the Leather Tanning and Finishing Industry, DRAFT, for the U.S. Environmental Protection Agency, June 1973. 167 ------- 13. Basics of Pollution Control, Gurnham & Associates, prepared for Environmental Protection Agency Technology Transfer Program, Kansas City, Mo., March 7-8, 1973, Chicago. 14. Public Health Service Drinking Water Standards, Revised, 1962, U.S. Department of Health, Education and Welfare, U.S. Public Health Service Publication No. 956, U.S. Government Printing Office, Washington, 1962. 15. Steffan, A.J., In-Plant Modifications to Reduce Pollution and Pretreatment of Meat Packing Wastewaters for Discharge to Municipal Systems, prepared for Environmental Protection Agency Technology Transfer Program, Kansas City, Mo., March 7-8, 1973. 16. Water Quality Improvement by Physical and Chemical Processes, Earnest F. Gloyna and W. Wesley Eckenfelder, Jr., Eds., University of Texas Press, Austin, 1970. 17. Rosen, G.D., "Profit from Effluent," Poultry Industry (April 1971) . 18. Personal communication, J. Hesler, Greyhound Corporation, 1973. 19. Telephone communication with M. Hartman, Infilco Division, Westinghouse, Richland, Virginia, May 1973. 20. Upgrading Meat Packing Facilities to Reduce Pollution: Waste Treatment Systems, Bell, Galyardt, Wells, prepared for Environmental Protection Agency Technology Transfer Program, Kansas City, Mo., March 7-8, 1973, Omaha. 21. Private communication from Geo. A. Hormel & Company, Austin, Minnesota, 1973. 22. Chittenden, Jimmie A., and Wells, W. James, Jr., "BOD Removal and Stabilization of Anaerobic Lagoon Effluent Using a Rotating Biological Contactor," presented at the 1970 Annual Conference, Water Pollution Control Federation, Boston. 23. Gulp, Russell L., and Gulp, Gordon L. , Advanced Wastewater Treatment, Van Nostrand Reinhold Company, New York, 1971. 24. Babbitt, Harold E., and Baumann, E. Robert, Sewerage and Sewage Treatment, Eighth Ed., John Wiley & Sons, Inc., London, 1967. 25. Fair, Gordon Maskew, Geyer, John Charles, and Okun, Daniel Alexander, Water and Wastewater Engineering: Volume 2. Water Purification and Wastewater Treatment and Disposal, John Wiley & Sons, Inc., New York, 1968. 26. Personal communication, H.O. Halvorson, 1973. 168 ------- 27. Fair, Gordon Maskew, Geyer, John Charles, and Okun, Daniel Alexander, Water and Wastewater Engineering: Volume 1. Water Supply and Wastewater Removal, John Wiley & Sons, Inc., New York, 1966. 28. Eckenfelder, W. Wesley, Jr., Industrial Water Pollution Control, McGraw-Hill Book Company, New York, 1966. 29. Eliassen, Rolf and Tchobanoglous, George, "Advanced Treatment Processes," Chemical Engineering (October 14, 1968). 30. Knowles, Chester L., Jr., "Improving Biological Processes," Chemical Engineering (October 14, 1968). 31. Personal communication, H.O. Halvorson, May 1973. 32. Witherow, Jack L. , Small Meat Packers Wastes Treatment Systems, Presented at 4th National Symposium on Food Processing Wastes, Syracuse, N.Y., March 26-28, 1973 33. Personal communication, C.E. Clapp, United States Department of Agriculture, Agricultural Research Service, University of Minnesota, Minneapolis, May 1973. 34. Personal communication with Lowell Hanson, Soil Science, Agricultural Extension Service, University of Minnesota, 1973. 35. Financial Facts About the Meat Packing Industry, 1971, American Meat Institute, Chicago, August 1972. 36. "Survey of Corporate Performance: First Quarter 1973," Business Week, p. 97 (May 12, 1973). 37. Mckinney, Ross E., Microbiology for Sanitary Engineers, McGrawHill Book Company, New York, 1962. 38. Frazier, W. C., Food Microbiology, 2nd Edition, McGraw-Hill Book Company, New York, 1967. 169 ------- SECTION XIV GLOSSARY "Act": The Federal Water Pollution Control Act Amendments of 1972. Activated Sludge Process: Aerated basin in which waste waters are mixed with recycled biologically active sludge for periods of about 6 hours. Aerated: The introduction and intimate contacting of air and a liquid by mechanical means such as stirring, spraying, or bubbling. Aerobic: Living or occurring only in the presence of dissolved or molecular oxygen. Algae: Major group of lower plants, single and multi-celled, usually aquatic and capable of synthesizing their foodstuff by photosynthesis. Ammonia Stripping: Ammonia removal from a liquid, usually by intimate contacting with an ammonia-free gas such as air. Anaerobic: Living or active only in the absence of free oxygen. Bacteria: Primitive plants, generally free of pigment, which reproduce by dividing in one, two, or three planes. They occur as single cells, chains, filaments, well-oriented groups, or amorphous masses. Biodegradable: The condition of a substance which indicates that the energy content of the substance can be lowered by the action of biological agents (bacteria) through chemical reactions that simplify the molecular structure of the substance. Biological Oxidation: The process whereby, through the activity of living organisms in an aerobic environment, organic matter is converted to more biologically stable matter. Biological Stabilization: Reduction in the net energy level of organic matter as a result of the metabolic activity or organisms, so that further biodegradation is very slow. Biological Treatment: Organic waste treatment in which bacteria and/or biochemical action are intensified under controlled conditions. Blood Water (serum): Liquid remaining after coagulation of the blood. Slowdown: A discharge of water from a system to prevent a build up of dissolved solids; e.g., in a boiler. 171 ------- BOD_5: A measure of the oxygen consumption by aerobic organisms over a five day test period at 20°C. It is an indirect measure of the concentration of biologically degradable material present in organic wastes contained in a water stream. Category and Subcategory: Divisions of a particular industry which possess different traits that affect raw waste water quality. Chemical Precipitation: A waste treatment process whereby substances dissolved in the waste water stream are rendered insoluble and form a solid phase that settles out or can be removed by flotation techniques. Clarification: Process of removing undissolved materials from a liquid, specifically, removal of solids either by settling or filtration. Clarifier: A settling basin for separating settleable solids from waste waters. cm: Centimeter. Coagulant: A material, which, when added to liquid wastes or water, creates a reaction which forms insoluble floe particles that absorb and precipitate colloidal and suspended solids. The floe particles can be removed by sedimentation. Among the most common chemical coagulants used in sewage treatment are ferric sulfate and alum. Coanda Phenomenon: Tendency of a flowing fluid to adhere to a curved surface. COD - Chemical Oxygen Demand: An indirect measure of the biochemical load imposed on the oxygen resource of a body of water when organic wastes are introduced into the water. A chemical test is used to determine COD of waste water. Condensables: Cooking vapors capable of being condensed. Condensate: The liquid produced by condensing rendering cooking vapors. Contamination: A general term signifying the introduction into water of microorganisms, chemical, organic, or inorganic wastes, or sewage, which renders the water unfit for its intended use. Cracklings: The crisp solid residue left after the fat has been separated from the fibrous tissue in rendering lard or tallow. Denitrification: The process involving the faculative conversion by anaerobic bacteri of nitrates into nitrogen and nitrogen oxides. 172 ------- Digestion: Though "anaerobic" digestion is used, the term digestion commonly refers to the anaerobic breakdown of organic matter in water solution or suspension into simpler or more biologically stable compounds or both. Organic matter may be decomposed to soluble organic acids or alcohols, and subsequently converted to such gases as methane and carbon dioxide. Complete destruction of organic solid materials by bacterial action alone is never accomplished. Dissolved Air Flotation: A process involving the compression of air and liquid, mixing to super-saturation, and releasing the pressure to generate large numbers of minute air bubbles. As the bubbles rise to the surface of the water, they carry with them small particles that they contact. The process is particularly effective for grease removal. Dissolved Oxygen: The oxygen dissolved in sewage, water, or other liquid, usually expressed as milligrams per liter or as percent of saturation. Dry Rendering: Cooking of inedible raw materials to remove all excess raw material moisture by externally applied heat. Edible: Products that can be used for human consumption. Effluent: Liquid which flows from a containing space or process unit. Equalization Tank: A means of liquid storage capacity in a continuous flow system, used to provide a uniform flow rate downstream in spite of fluctuating incoming flow rates. Eutrophication: Applies to lake or pond—becoming rich in dissovled nutrients, with seasonal oxygen deficiency. Evapotranspiration: Loss of water from the soil, both by evaporation and by transpiration from the plants growing thereon. Extended Aeration: A form of the activated sludge process except that the retention time of waste waters is one to three days. Facultative Bacteria: Bacteria which can exist and reproduce under either aerobic or anaerobic conditions. Facultative Decomposition: Decomposition of organic matter by facultative microorganisms. Fat: Refers to the rendering products of tallow and grease. Fatty Acid: A type of organic acid derived from fats. Filtration: The process of passing a liquid through a porous medium for the removal of suspended material by a physical straining action. 173 ------- Finger Dikes: Barriers or walls extending out into lagoonsin waste water treatment—to prevent or minimize the flow of incoming water directly to the outlet and thereby short circuiting the treatment process. Floe: A mass formed by the aggregation of a number of fine suspended particles. Flocculationt The process of forming larger flocculant masses from a large number of finer suspended particles. Grease: Fat that has a titre (or melting point) below 40°C. Grease is produced from poultry and hot fat. Hydrolyzing: The reaction involving the decomposition of organic materials by interaction with water in the presence of acids or alkalines. Hog hair and feathers for example, are hydrolyzed to a proteinaceous product that has some feed value. Inedible: Products that can not be used for humar consumption. Influent: A liquid which flows into a containing space or process unit. Ion Exchange: A reversible chemical reaction between a solid and a liquid by means of which ions may be interchanged between the two. It is in common use in water softening and water deionizing. Isoelectric point: The value of the pH of a solution at which the soluble protein becomes insoluble and precipitates out. kg: Kilogram or 1000 grams, metric unit of weight. kkg: 1000 kilograms. Kjeldahl nitrogen: A measure of the total amount of nitrogen in the ammonia and organic forms in waste water. KWH: Kilowatt-hours; a measure of total electrical energy consumption. Lagoon: An all-inclusive term commonly given to a water impoundment in which organic wastes are stored or stabilized or both. Low Temperature Rendering: A rendering process in which the cooking is conducted at a low temperature which does not evaporate the raw material moisture. Normally used to produce a high quality edible product such as lard. m: Meter; metric unit of length. Meal: A coarsely ground proteinaceous product of rendering made from such animal by-products as meat, bone, and feathers. 174 ------- mg/1: Milligrams per liter; approximately equals parts per million; a term used to indicate concentration of materials in water. MGD or MGPD: Million gallons per day. Microstrainer/Microscreen: A mechanical filter consisting of a cylindrical surface of metal filter fabric with openings of 20-60 micrometers in size. mm: Millimeter = 0.001 meter. Municipal Treatment: A city- or community-owned waste treatment plant for municipal and possible industrial waste treatment. New Source: Any building, structure, facility, or installation from which there is or may be a discharge of pollutants and whose construction is commenced after the publication of the proposed regulations. Nitrate, Nitrite: Chemical compounds that include the NO_3- (nitrate) and NO2- (nitrite) ions. They are composed of nitrogen and oxygen, are nutrients for growth of algae and other plant life, and contribute to eutrophication. Nitrification: The process of oxidizing ammonia by bacteria into nitrites and nitrates. No Discharge: No discharge of effluents to a water course. A system of land disposal with no run-off or total recycle of the waste water may be used to achieve it. Noncondensables: Cooking gases that can not be condensed and are usually very odorous. Nonwater Quality: Thermal, air, noise and all other environmental parameters except water. Offal: The parts of a butchered animal removed in eviscerating and trimming that may be used as edible products or in production of inedible by-products. Off-Gas: The gaseous products of a process that are collected for use or more typically vented directly, or through a flare, into the atmosphere. Organic Content: Synonymous with volatile solids except for small traces of some inorganic materials such as calcium carbonate which will lose weight at temperatures used in determining volatile solids. Oxidation Lagoon: Synonymous with aerobic or aerated lagoon. Oxidation Pond: Synonymous with aerobic lagoon. 175 ------- Packed Tower: Equipment used in rendering plants for odor control. A cylindrical column loaded with a packing material used to increase the contact area between scrubbing solution and odorous air. pH: A measure of the relative acidity or alkalinity of water. A pH of 7.0 indicates a neutral condition. A greater pH indicates alkalinity and a lower pH indicates acidity. A one unit change in pH indicates a ten fold change in concentration of hydrogen ion concentration. Point Source: Regarding waste water, a single plant with a waste water stream discharging into a receiving body of water. Polishing: Final treatment stage before discharge of effluent to a water course. Carried out in a shallow, aerobic lagoon or pond, mainly to remove fine suspended solids that settle very slowly. Some aerobic microbiological activity also occurs. Pollutant: A substance which taints, fouls, or otherwise renders impure or unclean the recipient system. Pollution: The presence of pollutants in a system sufficient to degrade the quality of the system. Polyelectrolyte Chemicals: High molecular weight substances which dissociate into ions when in solution; the ions either being bound to the molecular structure or free to diffuse throughout the solvent, depending on the sign of the ionic charge and the type of electrolyte. They are often used as flocculating agents in waste water treatment, particularly along with dissolved air flotation. Ponding: A waste treatment technique involving the actual holdup of all waste waters in a confined space. ppm: Parts per million, a measure of concentration usually expressed currently as mg/1. Prebreaker: A mechanical grinder used by rendering plants for size reduction of raw materials prior to cooking operations. Pretreatment: Waste water treatment located on the plant site and upstream from the discharge to a municipal treatment system. Primary waste treatment: In-plant by-product recovery and waste water treatment involving physical separation and recovery devices such as catch basins, screens, and dissolved air flotation. Raceway: Circular shaped vat containing brine, agitated by a paddle wheel and used for brine curing of hides. Raw Material Moisture: Refers to the water content of raw materials used in rendering. 176 ------- Raw Waste: The waste water effluent from the in-plant primary waste treatment system. Recycle: The return of a quantity of effluent from a specific unit or process to the feed stream of that same unit including the return of treated plant waste water for several plant uses. Rendering: Separation of fats and water from tissue by heat or physical energy. Return on Assets (ROA): A measure of potential or realized profit as a percent of the total assets (or fixed assets) used to generate the profit. Return on investment (ROI): A measure of potential or realized profit as a percentage of the investment required to generate the profit. Reuse: Referring to waste reuse. The subsequent use of water following an earlier use without restoring it to the original quality. Riprap: A foundation or sustaining wall, usually of stones and brush, so placed on an embankment or a lagoon to prevent erosion. RM: Referring to the raw material used in the rendering process. Rotating Biological Contactor: A waste treatment device involving closely spaced lightweight disks which are rotated through the waste water allowing aerobic microflora to accumulate on each disk and thereby achieving a reduction in the waste content. Sand Filter: A filter device incorporating a bed of sand that, depending on design, can be used in secondary or tertiary waste treatment. Screw Press: An extrusion device used to expel excess fat from proteinaceous solids after cooking. Scrubber: Used as an odor control device in the rendering industry. Operates by the contacting of numerous droplets of scrubbing solution with cdcrous air streams. Secondary Treatment: The waste treatment following primary in- plant treatment. Typically involving biological waste reduction systems. Sedimentation Tank: A tank or basin in which a liquid (water, sewage, liquid manure) containing settleable suspended solids is retained for a sufficient time so part of the suspended solids settle out by gravity. The time interval that the liquid is retained in the tank is called "detention period." In sewage treatment, the detention period is short enough to avoid putrefaction. 177 ------- Settling Tank: Synonymous with sedimentation tank. Sewage: Water after it has been fouled by various uses. From the standpoint of source it may be a combination of the liquid or water-carried wastes from residences, business buildings, and institutions, together with those from industrial and agricultural establishments, and with such groundwater, surface water, and storm water as may be present. Shock Load: A quantity of waste water or pollutant that greatly exceeds the normal discharged into a treatment system, usually occurring over a limited period of time. Skimmings: Fats and flotable solids recovered from waste waters for recycling by catch basins, skimming tanks and air flotation devices. Sludge: The accumulated settled sclids deposited from sewage or other wastes, raw or treated, in tanks or basins, and containing more or less water to form a semiliquid mass. Slurry: A solids-water mixture, with sufficient water content to impart fluid handling characteristics to the mixture. Stick or Stickwater: The concentrated (thick) liquid product from the evaporated tank water from wet rendering operations. It is added to solids and may be further dried for feed ingredients. Stoichiometric Amount: The amount of a substance involved in a specific chemical reaction, either as a reactant or as a reaction product. Surface Waters: The waters of the United States including the territorial seas. Suspended Solids (SS): Solids that either float on the surface of, or are in suspension, in water; and which are largely removable by laboratory filtering as in the analytical determinate cf SS content of waste water. Tallow: Fat that has a titre (melting point) of 40°C or higher. Tallow is produced from beef cattel and sheep fat. Tankage: Dried animal by-product residues used as feedstuff. Tankwater: The water phase resulting from rendering processes usually occurring in wet rendering. Tertiary Waste Treatment: Waste treatment systems used to treat secondary treatment effluent and typically using physical- chemical technologies to effect waste reduction. Synonymous with "advanced waste treatment." 178 ------- Total Dissolved Solids (TDS): The solids content of waste water that is soluble and is measured as total solids content minus the suspended solids. Wet Rendering: Cooking with water or live steam added to the material under pressure. This process produces tankwater. Zero Discharge: The discharge of no pollutants in the waste water stream of a plant that is discharging into a receiving body of water. 179 ------- TABLE 29 METRIC TABLE CONVERSION TABLE MULTIPLY (ENGLISH UNITS) by ENGLISH UNIT ABBREVIATION CONVERSION TO OBTAIN (METRIC UNITS) ABBREVIATION METRIC UNIT acre acre - feet British Thermal Unit British Thermal Unit/pound cubic feet/minute cubic feet/second cubic feet cubic feet cubic inches degree Fahrenheit feet gallon gallon/minute horsepower inches inches of mercury pounds million gallons/day mile pound/square inch (gauge) square feet square inches ton (short) yard ac 0.405 ac ft 1233.5 BTU 0.252 BTU/lb 0.555 cfm 0.028 cfs 1.7 cu ft 0.028 cu ft 28.32 cu in 16.39 °F 0.555(°F-32)* ft 0.3048 gal 3.785 gpm 0.0631 hp 0.7457 in 2.54 in Hg 0.03342 Ib 0.454 mgd 3,785 mi 1.609 psig (0.06805 psig +1 )* sq ft 0.0929 sq in 6.452 ton 0.907 yd 0.9144 ha hectares cu m cubic meters kg cal kilogram - calories kg cal/kg kilogram calories/kilogrc cu m/min cubic meters/minute cu m/min cubic meters/minute cu m cubic meters 1 liters cu cm cubic centimeters °C degree Centigrade m meters 1 liters I/sec liters/second kw killowatts cm centimeters atm atmospheres kg kilograms cu m/day cubic meters/day km kilometer atm atmospheres (absolute) sq m square meters sq cm square centimeters kkg metric ton (1000 kilograir m meter * Actual conversion, not a multiplier 180 ------- |