cvEPA United States Environmental Protection Agency Risk Reduction Engineering Laboratory Cincinnati OH 45268 Research and Development EPA/600/S-92/019 May 1992 ENVIRONMENTAL RESEARCH BRIEF Waste Minimization Assessment for a Manufacturer of Metal-Plated Display Racks Gwen 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 waste but who lack the expertise to do so. Waste Minimization Assessment Centers (WMACs) were established at selected universities and proce- dures were adapted from the EPA Wasfe Minimization Opportu- nity Assessment Manual (EPA/625/7-88/003, July 1988). The WMAC team at the University of Tennessee performed an assessment at a plant manufacturing metal-plated display racks. Steel wire, tubing, and sheets undergo machining operations, and the resulting parts are then nickel and brass-plated, nickel- plated, zinc-plated, nickel and chrome-plated, or painted. The various finished parts are assembled into display racks. The team's report, detailing findings and recommendations, indi- cated that the majority of waste was generated by the plating lines and that the greatest waste reduction would result from utilizing a Zero Discharge Recovery system in the nickel-plating baths. 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 available from the authors. Introduction The amount of waste generated by industrial plants has be- come an increasingly costly problem for manufacturers and an additional stress on the environment. One solution to the prob- lem of 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 waste but who lack the in-house expertise to do so. Under agreement with EPA's Risk Reduction Engineering Laboratory, the Science Center has es- tablished three WMACs. This assessment was done by engi- neering faculty and students at the University of Tennessee's (Knoxville) WMAC. The assessment teams have considerable direct experience with process operations in manufacturing plants and also have the knowledge and skills needed to minimize 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 an- nual sales not exceeding $50 million, employ no more than 500 persons, and lack in-house 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 proce- dures outlined in the EPA Waste Minimization Opportunity As- sessment Manual (EPA/625/7-88/003, July 1988). The WMAC staff locates the sources of 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 supporting tech- nological and economic information is developed. Finally, a confidential report that details the WMAC's findings and recom- ------- mandations (Including cost savings, implementation costs, and payback times) is prepared for each client. Plant Background This plant manufactures metal-plated display racks. The plant's 200 employees process approximately ten million Ibs of metal annually and operate the plant 4,160 hr/yr. Manufacturing Process Raw materials for the display racks include steel wire, tubing, and sheets; nickel, zinc, and brass plating anodes; cleaning agents and plating solution chemicals; and powder and liquid paints. Approximately 40% of the finished products are nickel and brass-plated, 26% are nickel-plated, 24% are zinc-plated, and 10% are nickel and chrome-plated. The steel wire, tubing, and sheets undergo stamping, bending, forming, shaping, welding, and riveting. The parts to be plated are then sent through one of the three following plating lines. Other parts are sent to the paint line, which is also described here. Barrel Plating Line Smalt fabricated parts are cleaned prior to plating to remove residual oils and grease by using either a vibrating cleaning unit or a rotating abrasive tub. The vibrating tub cleans parts by Vibrating them In a chemical solution. Spent cleaning solution and rinse water are sent to the plant's wastewater treatment facility. In the other method, the parts and abrasive pellets are placed in small rotating tubs for cleaning. Spent abrasive is disposed of In a landfill. The cleaned parts are placed in hollow barrels which are at- tached to an overhead conveyor system. The barrels, which have holes along the length of their surfaces, are slowly rotated while being submerged for a specified amount of time in the various tanks of the plating line. Each batch of parts to be plated undergoes specific steps in the line. All of the pieces pass through most of the same prepara- tory stages, while later stages in the line are reserved for one type of plated part only. Spent solutions from all tanks except the plating baths are dumped to the plant's wastewater treat- ment facility. Plated parts are then sent to other areas of the plant for assembly. Zinc Plating Line Larger-sized metal pieces are manually hung on racks attached to an overhead conveyor system which is used to dip parts in the 22 tanks of the line. All spent tank solutions are piped to the plant's wastewater treatment facility. Plated parts are trans- ferred to the assembly areas of the plant. Frame Plating Line The frame plating line is used to plate nickel, nickel and chrome, and nickel and brass onto large display rack frames. Parts are hung on racks as In the zinc-plating line; some tanks in this line are bypassed depending on which type of plating is required. Spent tank solutions are sent to the plant's wastewater treat- ment facility. Finished parts are transferred to the assembly areas of the plant. Paint Line ; Miscellaneous metal pieces which do not require plating are sent to the three-stage washer and paint I areas. The parts are hung on a small conveyer system which transports them through an enclosed washer line containing three different solution-filled tanks. Spent solutions are dumped directly to the municipal sewer. . i After cleaning and drying, parts are painted using electrostatic powder coating or liquid dip painting. Overspray powder is collected and reused. Drag-out from dip painting is collected on cardboard or plastic sheets which are disposed of in a landfill. After drying, the painted parts are transferred to the assembly areas of the plant. : Existing Waste Minimization Practices i • The plant operates an electrostatic powder paint system to reduce the amount of paint wastes it generates. i • Water-based, nonhazardous liquid paints are used. • Filtering systems recover zinc and nickel from spent plating solutions. ' Cyanide-laden brass plating water is stored in a holding tank and used as rinse water in several of the plating line stages. i All wastewater is treated onstte before release to the municipal sewer. ; A natural gas-fired dryer is used to reduce the volume of sludge resulting from the filter press operation. Waste Minimization Opportunities The type of waste currently generated by; the plant, the source of the waste, the quantity of the waste, jand the annual treat- ment and disposal costs are given in Table 1. Table 2 shows the opportunities for waste, minimization that the WMAC team recommended for the plant. Jhe type of waste, the minimization opportunity, the possible waste reduction and as- sociated savings, and the implementatioh cost along with the payback time are given in the table. Thfe quantities of 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 the economic sayings of the minimiza- tion opportunity, in most cases, results from the need for less raw material and from reduced present and future costs associ- ated with 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 independently and do not reflect duplication of savings that would result when the oppor- tunities are implemented in a package. ------- This research brief summarizes a part of the work done under , tal Protection Agency. The EPA Project Officer was Emma Lou Cooperative Agreement No. CR-814903 by the University City George. Science Center under the sponsorship of the U.S. Environmen- Table 1. Summary of Current Waste Generation Waste Stream Barrel Plating Line Waste Management Method Treated onsite and sewered Annual Quantity Generated 208,000 gal Annual Waste Management Cost $2,290 Contaminated wash and rinse water from cleaning process Spent abrasive from cleaning process Contaminated plating, wash, and rinse water Zinc-Plating Line Contaminated plating, wash, and rinse water Frame Plating Line Contaminated plating, wash, and rinse water Paint Line Contaminated wash and rinse water Paint overspray on cardboard and plastic sheets • . Boiler Condensate Wastewater Treatment Waste solids Offsite landfill Treated onsite and sewered Treated onsite and sewered Treated onsite and sewered Sewered Offisite landfill Treated onsite and sewered Offsite landfill 6,000 Ib 817,860 gal 1,201,080 gal 1,067,260 gal 153,360 gal 110 gal 262,000 gal 4,180 gal 2,290 18,860 18,860 24,150 2,290 2,290 940 59,050 Table 2. Summary of Recommended Waste Minimization Opportunities Present Practice Proposed Action Waste Reduction and Associated Savings Contaminated plating, wash, and rinse water from the barrel, zinc and frame plating lines and contaminated wash and rinse water from the paint line are treated onsite and sewered. As the nickel plating baths in the barrel and frame plating lines become contaminated, they are emptied into dedicated filtering units which are used to recover a large portion of the paniculate nickel in the solutions. The filtering units are periodically cleaned by back- flushing with a weak acid solution. The acid solution, which contains contaminants, is sent to the plant's waste water treatment facility. Currently, a significant amount of nickel is discharged in the waste water sludge which, as a result, is classified as hazardous waste. Install a piping system to recycle treated waste water within the plant to reduce purchases of water. If necessary, improve the current methods of waste water filtering to provide sufficiently clean water. Estimated waste reduction = 3,114,290 gal/yr Raw material cost savings =$11,120/yr Operating cost = $3,840/yr Total cost savings = $7,280/yr Implementation cost = $56,380/yr Simple payback = 7.8 yr Modify the plating lines in question to incorporated the utilization of a Zero Discharge Recovery (ZDR) system. It is recommended that the sytem use reverse osmosis technology to recover plating bath solutions at plant-specific concentration levels. The system will operate in a closed-loop manner and therefore the amount of nickel dishcarged to the wastewater treatment facility will be reduced. A portion of the chemicals .required by the baths and by the water treatment facility will no longer be needed. Approximately the same amount of sludge will be generated, but it will be classified as nonhazardous. Estimated waste reduction = none Waste disposal cost savings = $24,460/yr Raw material cost savings = $6,250/yr Operating cost = $8,000/yr Total cost savings = $22,710/yr Implementation cost = $70,000 Simple Payback = 3.1 yr •fru.S. GOVERNMENT PRINTING OFFICE: 1992 - 648-080/40267 ------- Tebla 2, Summary of Recommended Waste Minimization Opportunities (concluded) Present Practice Proposed Action Waste Reduction ar\d Associated Savings Acid wash tanks, which are used in each of the plating lines for cleaning of metal parts, are dumped to the waste water treatment facilitiy as they become contaminated RJnstog in the plating lines is accomplished by dipping parts In rinse tanks. As a result, considerable drag-out and contamination occur. Spent water from the rinsing tanks is dumped to the onslta waste water treatment facility, treated, and released to the municipal sewer. Drag-out ki the three plating lines currently accounts for an estimated 10% loss in chemical solutions. Varotis tanks In the plating and paint lines are steam-heated, Condensate is not returned to boiler because of concerns about possible contamination; it Is sent to the waste water treatment facility. Recover and reuse the spent salt/ add solution from the contaminated wash tanks. It is estimated that 70% of the acid salt can be recovered using an evaporator and reused. Implementation of this recommendation will lead to a reduction in the amount of acid salt purchases. Wherever possible, modify the zinc and frame plating lines to utilize spray rinsing techniques instead of dipping in tanks. Install rinse devices above each plating and wash tank in the zinc and frame plat- ing lines to spray water on parts as they are removed from tanks. As a result, plating solutions will be returned to their tanks before drag-out occurs. Install individual heat exhangers to serve each heated wash tank and plating bath. The proposed units should transfer heat from the main steam line to smaller lines feeding each tank. Therefore, the steam will not come in contact with any process fluids and can be returned to the boiler. Estimated waste reduction = 42 gal/yr (waste solids) + 30,860 gal/yr water Waste management cost savings = $390/yr Rasw material cost savings =$7,700/yr Total cost savings = $B,090/yr Implementation cost = $29,440 Simple payback = 3.6yr Estimated waste reduction = 617,760 gal/yr Raw material cost savings = $2,200/yr Implementation cost = $16,900 Simple payback = 7.7yr Estimated waste reduction = none Raw material cost savings = $2,800/yr Implementation cost = $17,940 Simple payback = 6.4 yr Estimated waste reduction = 262,00 gal/yr Raw material cost savings = $940fyr Energy cost savings = $870/yr Boiler feedwater chemical cost savings = $3,SOO/yr ' Total cost savings = $S,310/yr Implementation cost = $33,700 Simple payback = 6.3 yr United States Environmental Protection Agency Center for Environmental Research Information Cincinnati, OH 45268 Printed on Recycled Paper BULK RATE POSTAGE & FEES PAID EPA PERMIT MO. G-35 Official Business Penalty for Private Use $300 EPA/600/S-92/019 ------- |