»EPA United Stales Environmental Protection Agency Risk Reduction Engineering Laboratory Cincinnati, OH 45268 Research and Development EPA/600/M-91/046 Oct. 1991 ENVIRONMENTAL RESEARCH BRIEF Waste Minimization Assessment for a Manufacturer of Speed Reduction Equipment F. William Kirsch and J. Clifford Maginn* Abstract The U.S. Environmental Protection Agency (EPA) has funded a pilot project to assist small- and medium-size manufacturers who want to minimize their generation of hazardous waste but lack the expertise to do so. Waste Minimization Assessment Centers (WMACs) were established at selected universities and procedures were adapted from the EPA Waste Minimiza- tion Opportunity Assessment Manual (EPA/625/7-88/003 July 1988). The WMAC team at Colorado State University per- formed an assessment at a plant manufacturing speed reduc- tion equipment - approximately 110,000 speed reduction units/ yr. Plant operations include machining and assembling parts for worm gear shafts and other shafts, worm gear bodies hubs and housings, bearings and seals. Keyed and threaded shafts are case-hardened, ground with athread grinder, and deburred. Component parts are washed with an aqueous cleaner before assembly, and finished assemblies are spray painted with solvent-based paints and lacquer thinner. Spent cutting fluid and sludge, including turnings, and spent wash water are shipped offsite for disposal. Spent hydraulic oil and nonaqueous cutting fluid are shipped to a recycler. Waste paint and spent lacquer thinner are shipped offsite for incineration. The team's report, detailing findings and recommendations, indicated that most waste consists of spent aqueous cutting fluid, and that the •University City Science Center. Philadelphia, PA 19104. greatest savings could be obtained by ultrafiltration and recycle of spent wash water. This Research Brief was developed by the principal investiga- tors and EPA's Risk Reduction Engineering Laboratory, Cincin- nati, OH, to announce key findings of an ongoing research project that is fully documented in aseparate report of the same title available from the authors. Introduction The amount of hazardous waste generated by industrial plants has become an increasingly costly problem for manufacturers and an additional stress on the environment. One solution to the problem of hazardous waste is to reduce or eliminate the waste at its source. University City Science Center (Philadelphia, PA) has begun a pilot project to assist small- and medium-size manufacturers who want to minimize their formation of hazardous waste but lack the inhouse expertise to do so. Under agreement with EPA's Risk Reduction Engineering Laboratory, the Science Center has established three WMACs. This assessment was done by engineering faculty and students at Colorado State University's (FortCollins) WMAC. The assessmentteams have considerable direct experience with process operations in manufacturing plants and also have the knowledge and skills needed to minimize hazardous waste generation. The waste minimization assessments are done for small- and medium-size manufacturers at no out-of-pocket cost to the {g/y Printed on Recycled Paper ------- client. To qualify for the assessment, each client must fall within Standard Industrial Classification Code 20-39. have gross annual sales not exceeding $50 million, employ no more than 500 persons, and lackinhouse expertise in waste minimization. The potential benefits of the pilot project include minimization of the amount of waste generated by manufacturers, reduced waste treatment and disposal costs for participating plants, valuable experience for graduate and undergraduate students who participate in the program, and a cleaner environment without more regulations and higher costs for manufacturers. Methodology of Assessments The waste minimization assessments require several site visits to each client served. In general, the WMACs follow the procedures outlined in the EPA Waste Minimization Opportu- nity Assessment Manual (EPA/625/7-88/003, July 1988). The WM AC staff locates the sources of hazardous waste in the plant and Identifies the current disposal or treatment methods and their associated costs. They then identify and analyze a variety of ways to reduce or eliminate the waste. Specific measures to achieve that goal are recommended and the essential support- ing technological and economic information is developed. Finally, a confidential report that details the WMAC's findings and recommendations (including cost savings, implementation costs, and payback times) is prepared for each client. Plant Background The plant produces speed-reduction equipment. The plant operates 7,480 hr/yr to produce approximately 110,000 speed reduction units. Manufacturing Process The plant machines and assembles parts for worm gear shafts and other shafts, worm gear bodies, hubs and housings, bearings and seals. (The term "worm gear" refers to a compo- nent part of speed reduction units.) Except for bearings, motors and cast housings, all speed reduction unit parts are made in the plant. Raw materials include steel and bronze bar stock, aluminum and iron castings, cutting fluids, paint and lacquer thinner. The following operations are involved in making the speed reduction units: • Worm gear shafts are machined from bar stock. Key slots are cut, and a thread mill cuts worm gear threads in the shafts. After case-hardening in a gas-fired carburizing furnace, the shafts are ground with a thread grinder and deburred in a tumbler with ceramic chips and an aqueous slurry of aluminum oxide. • Worm gear bodies, made of a bronze alloy, are machined on a numerically controlled machine and pressed on the hubs. • Spent cutting fluid and sludge containing metal turnings are shipped for offs'rte disposal. Spent hydraulic oil and nonaqueous cutting fluid are shipped to a waste oil recy- cler. • Most component parts are washed with a water soluble cleaner before assembly. Spent wash water and mop water from cleanup around machinery are shipped offs'rte for disposal. • Many of the finished assemblies are spray painted using solvent-based paints and lacquerthinner. Waste paint and spent lacquerthinner are shipped offs'rte for incineration in a cement plant. Spent paint-booth air-filter elements are discarded with conventional trash. Existing Waste Management Practices • Metal scraps and chips are segregated and sold to a scrap metal dealer for recycling. • For drilling and tapping operations the plant uses a lubri- cant with reduced emission of volatile organic compounds (VOCs). Nonhazardous waste oil is processed offs'rte by a recycler and blended into industrial boiler fuel. Solvent- based cleaners have been replaced by a nonhazardous aqueous cleaning solution. • Spent cutting fluid is occasionally filtered and re-used. • Dry booths are used for painting, eliminating the aqueous paint-laden wastes associated with wet paint booths. Waste Minimization Opportunities The type of waste currently generated by the plant, the source of the waste, the quantity of the waste, and the annual manage- ment costs are given in Table 1. Table 2 shows the opportunities for waste minimization that the WMACteam recommended forthe plant. The type of waste, the minimization opportunity, the possible waste reduction and associated savings, and the implementation cost along with the payback time are given in the table. The quantities of hazardous waste currently generated by the plant and possible waste reduction depend on the production level of the plant. All values should be considered in that context. It should be noted that, in most cases, the economic savings of the minimization opportunities result from the need for less raw material and from reduced present and future costs associated with hazardous waste treatment and disposal. Other savings not quantifiable by this study include a wide variety of possible future costs related to changing emissions standards, liability, and employee health. It should also be noted that the savings given for each opportunity reflect the savings achievable when implementing each waste minimization opportunity indepen- dently and do not reflect duplication of savings that would result when the opportunities are implemented in a package. Additional Recommendations In addition to the opportunities recommended and analyzed by the WMAC team, four additional measures were considered. These measures were not completely analyzed because of insufficient data or minimal savings as indicated below. They were brought to the plant's attention for future reference, however, since these approaches to waste reduction may increase in attractiveness with changing plant conditions. • Treat spent wash water and mop water containing sulf uric acid to separate organic and aqueous phases. The organ- ics would be shipped for offs'rte disposal, but the water phase could be sewered to a local industrial wastewater treatment facility. Because the plant does not have an industrial sewer connection.at this time, this measure was not recommended. Ultrafiltration was recommended in- stead, because it provides an aqueous phase suitable for discharge to the POTW sewer or re-use as mop water. • Install a tramp-oil separator and two outside atmospheric evaporators to reduce the quantity of wastewater shipped ------- offsite for disposal. Because expected savings are small, with a long payback period, this measure was not recom- mended. Replace two water-soluble cutting fluids now in use with a single standardized cutting fluid. Because the resulting waste reduction and savings resist quantification, this measure was not recommended. However, if the recom- mendation to recycle the cutting fluid is implemented, use of a single cutting fluid will reduce substantially the cost of equipment and operating costs. Table 1. Summary of Current Waste Generation • Install tramp-oil separators on the washers to allow recycle of the alkaline wash water. The extended life of the wash water would result in waste reduction, but the expected cost savings would be small in comparison to operating costs. This Research Brief summarizes a part of the work done under Cooperative Agreement No. CR-814903 by the University City Science Center under the sponsorship of the U.S. Environmen- tal Protection Agency. The EPA Project Officer was Emma Lou George. Waste Generated Spent cutting fluid Cutting fluid sludge Cutting fluid and rainwater Spend hydraulic oil and nonaqueous cutting oil Source of Waste Decanted from metal chips produced in machining operations. Shipped for offsite disposal. Metal chips sludge produced in machining operations. Shipped for offsite disposal. Runoff to pit drainage from metal chips collection bins. Drained from machinery when no longer effective. Shipped to a waste oil recyder. Annual Quantity Generated 61. 380 gal 650 gal 12,480 gal 3,000 gal Annual Waste Management Cost $19,640 330 . 300 Waste paint (sludge) and thinner Sludge formed as the paint becomes too thick and the thinner no longer useful for thinning or cleaning. Shipped for incineration in a cement plant. 2,150 gal 16,250 Spent air filter elements Paint booth ventilation air filtration. Conventional trash disposal. Spent wash water Spent mop water Spent aqueous cleaning solution from cleaning finished metal parts before assembly. Shipped for offsite disposal. Soapy mop water from cleanup around plant machinery. Shipped for offsite disposal. 1,200 gal 9,420 gal 380 3,000 Table 2. Summary of Recommended Waste Minimization Opportunities Waste Generated Minimization Opportunity Annual Waste Reduction Net Implementation Payback Quantity Percent Annual Savings Cost Years Paint waste from cleaning spray guns Spent aqueous cutting fluids Use waste-based paints instead of 2,150 gal solvent-based paints to eliminate solvent and thinner and produce only conventional, nonhazardous waste. Filter and recycle the aqueous 31,340 gal cutting fluids. Spent mop water from Install an ultrafiltration system to 9,420 gal cleanup around process spent wash water for use as machinery mop water. Excess treated water can be discharged to the POTW. Only the separated oil layer need be shipped for disposal. 100 51 13 $27,370' 17,430' 33,410' $13,750 22,400 35,100 0.5 1.3 1.1 Spent cutting fluid from chip collection bins Use a portable sump cleaner to remove accumulated cutting fluid from chip collection bins for filtration and recycle (as proposed above for recycle of spent cutting fluid). 12,480 gal 100 3,120' 'Includes savings on raw materials. •ArU.S. GOVERNMENT PRINTING OFFICE: 1991 - 548428/40074 ------- United States Environmental Protection Agency Center for Environmental Research Information Cincinnati OH 45268 BULK RATE POSTAGE & FEES PAID EPA PERMIT NO. G-35 Official Business Penalty for Private Use $300 EPA/600/M-91/046 ------- |