SETOV United States Environmental Protection Agency Industrial Environmental Research Laboratory Cincinnati OH 45268 Research and Development EPA-600/S2-81-112 Aug. 1981 Project Summary Protein Recovery from Beef Packing Effluent John C. Ward, Walter Adams, and H. Chr. Isaksen The wastewater from a large beef packing plant, containing 3000 mg/l BOD5 and 2,500 mg/l of suspended solids was treated in a physiochemical process that recovers protein. This process removed 58% of the total nitrogen, 80% of the oxygen demand and suspended solids, and 94% of the fat, oil and grease. The discharge of BODS was reduced to less than 3 pounds per head of beef slaughtered. For every pound of BOD5 entering the wastewater treatment plant, 0.77 pounds of product was recovered with a composition of 38% protein, 11% grease and oil, 27% inorganic solids, and 24% other solids (dry weight basis). About 2 pounds of protein were recovered per head. Total cost was $3 per 1,000 gallons (44% capital costs). A price of 420 per pound of protein would pay all costs. The figures given above were observed in a full scale plant and should not change significantly with different size waste- water treatment plants. This waste- water treatment process can be used as a pretreatment process for beef packing effluent prior to discharge to a sewage treatment plant. Seven different beef packing waste- water treatment processes including other methods of protein recovery are discussed and compared in the full report. This Project Summary was devel- oped by EPA's Industrial Environ- mental Research Laboratory, Cincin- nati, OH, to announce key findings of the research project that is fully docu- mented in a separate report of the same title (see Project Report ordering information at back). Introduction Beef packing effluents pose a consid- erable challenge to wastewater treat- ment technology. Several water quality parameters are listed below in Table 1 along with their average concentrations in domestic wastewater and the average concentrations observed in the effluent from this beef packing plant. Clearly the oxygen demand of beef packing effluent is 20 to 30 times that of domestic wastewater, so that at least 95% removal would be necessary to reduce the oxygen demand of beef packing effluent to that of untreated domestic wastewater. In addition, the quantity of suspended solids is over 10 times that of domestic wastewater. As a final complication, beef packing plants are not usually operated continuously, so that conventional biological waste- water treatment techniques leave a great deal to be desired. This lack of continuous operation indicates the desirability of a physio- chemical wastewater treatment process. In addition, it would be highly desirable if some cost recovery were possible from the sale of the relatively large quantities of sludge that can be expected. The Alwatech process is a physio- chemical wastewater treatment process that also recovers protein (from the beef packing effluent) which can be sold to partially recover the cost of wastewater treatment. The process uses sulfuric acid, H2S04, for pH reduction, calcium lignosulfonate for protein precipitation. ------- Table 1 Comparison of Beef Packing and Domestic Wastewaters Average Concentration, mg/l Water Quality Parameter COD 5-Day, 20°C BOD Suspended Solids in domestic wastewater 150 140 235 in beef packing effluent 4,610 2.940 2,460 and calcium hydroxide, Ca(OH)2, for both effluent and sludge neutralization. This report gives the results of a full scale evaluation of the Alwatech process installed at a large beef packing plant in the United States. While the Alwatech process is not necessarily limited to treatment of and protein recovery from beef packing effluents, this report is based on beef packing effluent treat- ment and protein recovery. Other efflu- ents treated by the Alwatech process include those from poultry and pig abattoirs. Unit Waste Production Table 2 shows the unit waste produc- tion rates for 6 different waste products. From this table, it is clear that the quantities of the last 3 wastes listed are minor when compared to the quantities of the first 3 wastes listed. Because the average live weight of beef killed at this plant is 1,040±15 pounds, the quantity of waste produced per 1000 pounds live weight killed is close to the quantity produced per head of beef. About 350 gallons of wastewater are produced per head. Brief Description of the System Evaluated The plant wastewaters, excluding those from the stock pens and con- densers, are sent to an existing clarif ier which was modified to also balance flow volumes. The pH of the effluent from this clarifier is reduced with H2S04 to between 2 and 3. Calcium lignosulfonate is added to the wastewater in quantities that are directly proportional to the COD concentration. Following this protein precipitation step, the resulting floe containing protein, fat, and suspended material is separated in two dissolved air flotation tanks. Following this separation, the pH of the liquid effluent is raised to about 4 with Ca(OH)2 and then mixed with other wastewater streams that are not treated by this process. The pH of the resulting mixture is about 7 and consequently is suitable for additional treatment by biological wastewater treatment processes. The sludge is also neutralized with Ca(OH)2 to an initial pH of 9.1 which eventually drops to a pH of 7.6. The sludge is dewatered in a centrifuge, dried and sold. Table 2. Unit Waste Production Waste Produced Conclusions For a beef packing effluent with an initial BODS averaging 3,000 mg/l, the Alwatech process is capable of removing over 80% of the oxygen demand, about 86% of the suspended solids, and 94% of the fat, oil, and grease. Average removals of 41 % of the ammonia N and 63% of the organic N were observed. The solids concentration of the sludge produced by this flotation process aver- ages about 9%. The optimum calcium lignosulfonate dose is about 5% of the influent COD concentration although additional work may later show that this dose can be reduced somewhat. While the optimum pH range varies from about 2 to less than 3, for incoming COD concentrations greater than about 1,800 mg/l, it is less Ib 10*lbLWK* 5-day, 20°C BOD Total suspended solids Grease and oil Organic nitrogen Ammonia nitrogen Phosphate 6.51 5.44 1.26 0.28 0.18 0.04 •lb/103 Ib live weight killed Scope of This Project The major water quality parameters used to measure the effectiveness of this process are (listed in order of decreasing concentration): COD BOD5 Total suspended solids Total volatile solids Volatile suspended solids Grease and oil Organic nitrogen Ammonia nitrogen Phosphate The data summarized in this report cover a period of 8 months of operation. Because both the BOD5 and suspended solids loadings were 50% greater than the values used in the initial design, a certain amount of additional research and development work was necessary during this 8 month period. Near the end of the 8 month data logging interval, 2 perf orma nee tests of 2 weeks each were conducted. The results obtained during these 2 trial periods may be a better indication of the capabilities of this process than the averages observed during the 8 month duration of the data collection summarized in this report. expensive to use pH values nearer 2 because lower calcium lignosulfonate doses can be used. While chemical costs increase as the influent COD con- centration increases, the rate of increase is less at oH values near 2. While the centrifuge efficiency was about 94% for water, it was only 52% for total solids, 66% for protein and 21 % for oil and grease. When the centrifuge reject solution is recirculated back to the plant influent, the incoming COD is increased 32%, the influent suspended solids are increased 29%, and the influent grease and oil is increased 36% to 52%. Total observed operating costs were 470 per head or $1.68 per 1,000 gallons of wastewater treated. About 2 pounds of protein were recovered per head, so this protein would have to sell for 23.50 per pound in order to cover all operating costs. However, operating costs could be reduced to 400 per head by using less calcium lignosulfonate. Calcium lignosulfonate accounted for 39% of the total operating costs followed by 25% for labor, 15% for hlsSO^ 10% for Ca(OH)2, 9% for energy (1979), and 2% t for repairs. ------- Biological activity in the clarifier balancing tank preceding the Alwatech plant had an influence on oxygen demand and nitrogen removal efficien- cies. This biological activity is believed due to the paunch and gut contents, relatively long detention time (1.5-2 hours), and high effluent temperatures (100° to 125°F). However, the detention time cannot be reduced below 1.5 hours as fat skimming and bottom sludge removal would both suffer. The discharge of 5-day, 20°C BOD from this beef packing plant has been reduced to less than 3 pounds per head. For every pound of 5-day, 20°C BOD entering the Alwatech plant, an average of 0.77 pounds of product was recovered with an average composition of 38% protein, 11% grease and oil, 27% fixed solids, and 24% other solids on a dry weight basis. Monthly Average Effluent Concentrations The monthly average effluent con- centrations were 806± 413 mg/l BOD, 46± 24 mg/l organic nitrogen, 41 ± 13 mg/l ammonia nitrogen, and 15 ± 11 ng/l phosphate where the first figure is the average (arithmetic mean) and the second figure is the arithmetic standard deviation. Both the grease and oil and the total suspended solids effluent concentrations were so variable (coef- ficient of variation >1) that they were better represented by a tog normal (geometric) frequency distribution. Accordingly, the suspended solids ef- fluent concentration geometric mean was 309 mg/l with a geometric mean standard deviation of 2.2. The grease and oil effluent concentration geometric mean was 40 mg/l with a geometric standard deviation of 4.8. Ammonia and Organic Nitrogen The ratio of the standard deviation/ mean for both the influent ammonia and organic nitrogen concentrations was the same (0.48). The total nitrogen concentration averaged 210 mg/l with a standard deviation of 74 mg/l giving a standard deviation/mean ratio of 0.35 which indicates that the total influent nitrogen concentration was less variable. The average removal of total nitrogen was 58% with a standard deviation of 21% giving a standard deviation/mean ratio of 0.36 which indicates that the % removal of total nitrogen was also less I variable. Total nitrogen = ammonia + organic nitrogen because it is assumed that nitrate plus nitrite nitrogen is negligible in comparison in this waste- water. On the average,41% of the influent ammonia nitrogen concentration of 82 mg/l was removed and 63% of the influent organic nitrogen concentration of 128 mg/l was removed. Consequently, the ammonia and organic nitrogen con- centrations in the effluent were both about 48 mg/l each so that the nitrogen effluent concentration was 95 mg/l. An equation developed during the course of a laboratory investigation of protein recovery using chitosan was modified so that the % removal of organic nitrogen could be predicted as a func- tion of temperature, pH, calcium ligno- sulfonate dose, and the COD concentra- tion in the wastewater influent. Com- parison of the % organic nitrogen re- movals calculated by this equation with the observed data gave a correlation coefficient of 0.84. Percent COD remov- al and % organic nitrogen removal are linearly related with a correlation coeffi- cient of 0.82. Phosphate and Fecal Coliforms The average rempval of phosphate was 49% which reduced the average influent concentration of 17 mg/l P to 9 mg/l P. A concentration of 6,600 fecal coliforms per 100 ml were observed in the effluent. Solids Bottom sludge from the air flotation tanks is 28% of the total wet sludge volume produced. Total dried sludge production averaged 5 pounds per 1,000 pounds live weight killed. The dried sludge was 38% protein, 27% inorganic solids, 11% grease and oil, and 24%other. The solids concentration of the dried sludge was 88% and there- fore the water concentration was 12%. The dried sludge is sold for use in animal feeds. Material Balances of Pollutants On the average, 27.5 gallons of wet sludge were produced per 1,000 gallons of wastewater treated. Ninety percent of the wet sludge becomes centrifuge reject solution and 10% becomes de- watered sludge. The concentrations of COD, grease and oil, and suspended solids in the centrifuge reject solution averaged 50,000 mg/l, 5,860 mg/l, and 21,000 mg/l, respectively. Consequently, pumping the centrifuge reject solution back into the plant influent increased the incoming COD 32%. Eighty-three percent of the incoming COD is removed, and of the amount removed, 62% winds up in the dewatered sludge and the remaining 38% leaves in the centrifuge reject solution. Based on separate disposal of the centrifuge reject solution, 81% of the suspended solids is removed, and of the amount removed, 64% winds up in the dewatered sludge and the remaining 36% leaves in the centrifuge reject solution. Consequently, pumping the centrifuge reject solution back into the plant influent would increase the influ- ent suspended solids 29%. Again based on separate disposal of the centrifuge reject solution, 94% of the grease and oil is removed, and of the amount removed, 53% winds up in the dewatered sludge and the remaining 47% leaves in the centrifuge reject solution. The grease and oil concentra- tion in the dewatered sludge is about 6%. Recirculation of the centrifuge reject solution back to the plant influent would increase the influent grease and oil by roughly 44%. Filter Belts Initially it was attempted to dewater the wet sludge using filter belts, but these were found to perform unsatisfac- torily on the wet sludge produced, so they were replaced with a centrifuge. Economics Virtually all cost inputs to the process were measured including labor, cost of repairs and maintenance, energy, and chemicals. Operating costs were $1.68 per thousand gallons treated. The capital costs for an 800,000 gpd plant are an additional $1.32 per thousand gallons treated, so the total cost is $3.00 per 1,000 gallons treated. The capital costs (and consequently the total costs) include property taxes, interest recovery of principal, and insurance. These costs do not give any credit for the protein recovered and sold. About 2 pounds of protein are recovered per head. The average quantity of waste- water treated in the Alwatech plant was 276 gallons per head. Therefore the average cost of treating this wastewater was 830 per head, so that the protein recovered would have to sell for about 420 per pound of protein in order to recover all costs. The wastewater treatment plant ef- fluent pH averaged 3.7, but the waste- water discharged to the sewage treat 0 US GOVERNMENT PRINTING OFFICE: 1981-757-OU/7Z86 ------- ment plant averaged 7 because of the effect of mixing the plant effluent with other wastewater streams from the beef packing plant. If the Alwatech waste- water treatment plant effluent had been raised to pH 7, this would have resulted in a needless increase of 10% in total costs. Recommendations Means of reducing the operating cost of the Alwatech process should be investigated. While the pH should be near 2 for minimum operating cost, the calcium lignosulfonate dose need not exceed 5% of the influent COD concen- tration. The effect of doses less than 5% on COD removal, and especially protein recovery should be studied. The results of a detailed laboratory investigation of the use of chitosan are summarized. A similar study should be done for calcium lignosulfonate, be- cause of the potential for significant reduction in operating costs. In addition, it is virtually impossible in a full scale operation (such as the one described in this report) to evaluate the effect of various plant operating practices on the sludge produced. Where protein recovery and hence financial recovery is possible, it is essential to know the effect of changes in operating variables on sludge production and characteristics. Ways to increase the centrifuge ef- ficiency for total solids as well as protein need to be investigated. The low protein efficiency (66%) of the centrifuge pre- cludes separate treatment of the centri- fuge reject solution unless one is willing to accept a 34% loss of potentially recoverable protein. Before treatment by the Alwatech process, it may be desirable to have heavy solids and readily floatable grease removed by an efficient continuous screening system followed by a balanc- ing tank with a relatively short detention time (30 minutes) to even out rapid variations in flow and concentration. This might improve solids handling and sludge product quality. While additional investigation of this process has been recommended, the process is ready to be used in its present state of development. John C. Ward was attending Colorado State University. Fort Collins. CO 80523; Walter Adams is with Sterling Colorado Bgbt.Company, Sterling, CO 80751; andH. Chr. Isaksen is Process Department Head of Alwatech, Oslo, Norway. A Kenneth Dostal and Jack Witherow are the EPA Project Officers (see below). \ The complete report, entitled "Protein Recovery from Beef Packing Effluent," (Order No. PB 81-224 362; Cost: $15.50, subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 Telephone: 703-487-4650 The EPA Project Officers can be contacted at: Industrial Environmental Research Laboratory U.S. Environmental Protection Agency Cincinnati, OH 45268 United States Environmental Protection Agency Center for Environmental Research Information Cincinnati OH 45268 Postage and Fees Paid Environmental Protection Agency EPA 335 Official Business Penalty for Private Use $300 ------- |