vvEPA United States Environmental Protection Agency Risk Reduction Engineering Laboratory Cincinnati OH 45268 Research and Development EPA/60Q/S-92/021 May 1992 ENVIRONMENTAL RESEARCH BRIEF Waste Minimization Assessment for a Manufacturer of Sheet Metal Cabinets and Precision Metal Parts Gweh P. Looby and F. William Kirsch* 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 who lack the expertise to do so. Waste Minimization Assess- ment Centers (WMACs) were established at selected universi- ties, and procedures were adapted from the EPA Waste Mini- mization Opportunity Assessment Manual (EPA/625/7-88/003, July 1988). The WMAC team at Colorado State, University performed an assessment for a plant that manufactures sheet metal cabinets and precision metal parts. To make the cabi- nets, sheet metal is cut to size, bent, welded, and polished. The metal parts are then surface treated and painted. The machined parts are produced from bar stock which is cut, drilled, milled, and ground as needed. The team's report, de- tailing findings and recommendations, indicated that the most waste was generated by the chromate conversion and iron phosphate coating processes that prepare the parts for paint- ing. The plant could achieve the greatest cost savings by replacing solvent-based painting with powder-based painting. 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 a separate report of the same title, which is available from the authors. Introduction The amount of hazardous waste generated by industrial plants has become an increasingly costly problem for manufacturers *Universfty City Science Center, Philadelphia, PA 19104. 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 who lack the in-house expertise to do so. Under agreement with EPA's Risk Reduction Engineering Laboratory, the Sci- ence Center has established three WMACs. This assessment was done by engineering faculty and students at Colorado State University's (Fort Collins) WMAC. The assessment teams 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 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 lack in-house expertise in waste minimiza- tion. 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 proce- ' oĢ6 Printed on Recycled Paper ------- durss outlined in the EPA Waste Minimization Opportunity Assessment Afam/a/(EPA/825/7-88/003, July 1988). The WMAC 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. Fi- nally, 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 This plant manufactures sheet metal cabinets and precision metal parts. Approximately 1.15 million parts are produced annually by 140 employees who operate the plant 2,210 hr/yr. Manufacturing Process Sheet Metal Parts Sheets of aluminum and steel are cut to the proper size and shape. Holes are punched into the metal that is then bent as needed. Some pieces are welded together. Rough edges and surfaces are polished with power sanders and buffers. Metal scrap is shipped to a scrap metal dealer for recycling. Spent cutting fluid and waste hydraulic oil are combined and shipped offsite for recycle or incineration. Before painting, metal parts are surface treated to improve paint bonding and provide corrosion protection. Aluminum parts receive a chromate conversion coating while steel parts re- ceive an iron phosphate coating. Aluminum parts are first dipped in a caustic cleaning solution that is followed by a continuous-flow tap-water rinse. A third tank contains a desmut solution and is followed by another continuous-flow tap-wafer rinse tank. A fifth tank contains the chromic acid-based chromate conversion solution. A sixth tank is a continuous-flow tap-water rinse and a final tank is a heated dead rinse of tap water. The caustic cleaner, desmut, and first rinse tanks are dumped monthly; the chromic acid tank is dumped every three to four years; and the remaining solutions are dumped every five months. In addition, sludge accumu- lates in the caustic cleaner tank and is disposed of monthly. In iron phosphate coating of steel parts, the first stage involves a caustic cleaning tank followed by a continuous-flow tap-water rinse. A third tank contains the iron phosphating solution and is followed by another continuous-flow tap-water rinse. A final tank contains a deoxidizing solution. All of these baths are dumped and replenished on a monthly basis. Combined waste- waters from the iron phosphate and chromate conversion lines drain to an overflow tank and are then drained to the sewer as Industrial wastewater. Typically, pretreatment before discharge is not required because the wastewater meets discharge limits set by the publicly owned treatment works (POTW). Sludge accumulates in the caustic cleaner and iron phosphate tanks and is disposed of monthly. Solvent-based paint is applied to metal parts in dry paint booths. Waste paint that is generated when the paint mixture becomes too thick to be used is shipped to a hazardous waste treatment, storage, and disposal facility (TSDF). Spent paint thinner is also shipped offsite. Painted parts are dried and cured in ovens. The plant uses powder-based paint coatings on a small portion of parts. The type of paint used is dictated by customer requirements. Machined Parts Bar stock is cut, drilled, milled, and ground as needed. Fin- ished parts are assembled (if required) and shipped to custom- ers. Metal scrap is shipped to a scrap metal dealer for recycle. Spent cutting fluid and waste hydraulic oil are combined with similar waste from the manufacture of sheet metal parts and shipped offsite for recycle or incineration. Existing Waste Management Practices This plant has taken the following steps to manage and mini- mize its wastes: Scrap metal is segregated onsite and sold to a recycler. All reagent tanks in the phosphating and chromating lines are located in a large pit with a central drain to contain spills. Drain boards are used between surface treatment tanks to reduce drag-out. Reagent solutions in the surface treatment lines are agi- tated with air to increase the effectiveness of the reagents. Dry paint booths are used for painting to avoid generating aqueous paint-laden wastes that are generated in wet paint booths. A small powder coating unit is used for painting some products in order to avoid using solvent-based paints. Tank dumps are coordinated to achieve neutralization so that the sewered effluent meets POTW requirements. Waste Minimization Opportunities The type of waste currently generated by the plant, the waste management method used, the quantity of the waste, and the annual management costs are given in Table 1. Table 2 shows the opportunities for waste minimization that the WMAC team recommended for the plant. The present practice, the recommended action, and the waste reduction and associ- ated savings are also given in Table 2. 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. ft 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, several additional measures were consid- ered. These measures were not analyzed completely because of insufficient data, implementation difficulty, or a projected lengthy payback. Since one or more of these approaches to waste reduction may, however, increase in attractiveness with changing conditions in the plant, they were brought to the plant's attention for future consideration. Install filtration units for the iron phosphating and caustic cleaner solutions to increase solution lifetime. Use deionized water to make-up and maintain the caustic cleaner and iron phosphating solutions, thereby reducing sludge formation. Substitute nonchromate conversion coating for the chro- mate conversion coating currently used on aluminum parts. Increase drainage times over the tanks in the iron phosphating and chromate conversion lines in order to reduce drag-out. Segregate waste oil from the spent cutting fluid and re- cycle ft. Improve segregation of scrap metal before recycling. Implement a preventive maintenance program for the ma- chine shop to reduce the quantities of spent cutting fluid and waste oil. 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. Table 1. Summary of Current Waste Generation Waste Generated Waste Management Method Annual Quantity Generated (gal) Annual Waste Management Cost ($) Machining ' Scrap metal Cutting fluid/hydraulic oil Chromate Conversion Coating Spent caustic cleaner Caustic cleaner sludge Caustic cleaner rinse water Spent desmut solution Desmut rinse water Spent chromating solution Chromating rinse water Heated dead rinse Iron Phosphate Coating Spent caustic cleaner Caustic cleaner sludge Caustic cleaner rinse water Spent iron phosphate solution Iron phosphate sludge Phosphating rinse water Spent deoxidizer solution Painting Waste paint and paint sludge Spent paint thinner Shipped to scrap dealer for recycle Off site recycle or incineration Sewered as industrial wastewater Conventional disposal in landfill Sewered as industrial wastewater Sewered as industrial wastewater Sewered as industrial wastewater Sewered as industrial wastewater Sewered as industrial wastewater Sewered as industrial wastewater Sewered as industrial wastewater Conventional disposal in landfill Sewered as industrial wastewater Sewered as industrial wastewater Conventional disposal in landfill Sewered as industrial wastewater Sewered as industrial wastewater Offsite recycle or incineration Offsite recycle or incineration N/A 1,320 14,400 60 359,160 14,400 345,260 300 345,260 2,880 33,600 60 378,360 33,600 60 378,360 33,600 1,430 1,320 N/A 5,780 20 0 660 20 640 0 640 0 60 0 700 60 0 1,160 60 61,370 11,330 A U.S. GOVERNMENT PRINTING OFFICE: 199Z - 648-080/40265 ------- Summary of Waste Minimization Opportunities Recommended Present Practice Proposed Action Savings Solvent-based paints are used to coat tho majority of this plant's products. Wasta paint, paint sktdgo, and spent thinner are disposed of off site. A solvent recovery unit In tfte plant currently Is not operational because of o/7 and water leaks. Cutting fluid currently is used until It becomes malodorous or until Us viscosity and lubricity are unacceptable. Average fluid Sfoiimo is about three months. Rinso water rates set by operators exceed flow rates required by the rinses in the chromate conversion and phosphating lines. Replace solvent-based painting with powder-based painting for a portion of the plant's products. Cost savings will result from reduced disposal costs and reduced raw material costs. Installation of a batch spray booth for powder coating will be required. Replace solvent-based painting with water-based painting fora portion of the plant's products (a separate portion from previous WMO). Cost savings will result from reduced disposal costs and reduced raw material costs. Requires the purchase of new paint application equipment and may require increased curing times. Overhaul the solvent recovery unit to permit reuse of spent paint thinner. Cost savings will result from reduced disposal costs and reduced purchases of thinner. Institute a program to recycle the cutting fluid onsite. Fluid should be filtered periodically to remove metal chips and particulate matter, thereby extending the life of the cutting fluid. In addition, the spent cutting fluid can be treated with acid to reduce the volume of wastes that must be shipped offsite. The addition of acid will cause a phase separation; the aqueous phase can be neutralized and sewered and the organic phase should be disposed of offsite. Install a flow reducer and flow meter in the water supply line upstream of the rinses in the chromate conversion ' andiron phosphating lines, thus reduc- ing the quantity of water purchased and sewered. Waste reduction = 72 gal/yr (waste paint and paint sludge) + 66 gal/yr (spent thinner) Waste management cost savings = $740/yr Net raw material cost savings = $14,230/yr Total cost savings = $14,970/yr Implementation cost = $20,600 Simple payback = 1.4 yr Waste reduction = 72 gal/yr (waste paint and paint sludge) + 66 gal/yr (spent thinner) Waste management cost savings = $740/yr New raw material cost savings = $10,930/yr Total cost savings = $11,670/yr Implementation cost = $2,500 Simple payback = 0.2 yr Waste reduction = 660 gal/yr Waste management cost savings = $3,890/yr Raw material cost savings = $1,780/yr Operating cost of recovery unit = $430/yr Net cost savings = $5,240/yr Implementation cost = $2,500 Simple payback = 2.1 yr Waste reduction = 425 gal/yr Waste management cost savings = $2,920/yr Raw material cost savings = $570/yr Operating cost of filtration unit = $370/yr Total cost savings = $3,120/yr Implementation cost = $7,050 Simple payback = 2.3 yr Waste reduction = 331,500 gal/yr Waste management cost savings = $100/yr Raw material cost savings = $510/yr Total cost savings - $610/yr Implementation cost = $100 Simple payback = 0.2 yr 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/S-92/001 ------- |