United States Environmental Protection Agency Research and Development Risk Reduction Engineering Laboratory Cincinnati, OH 45268 EPA/600/S-92/030 Sept. 1992 ENVIRONMENTAL RESEARCH BRIEF Waste Minimization Assessment for a Manufacturer of Finished Metal Components Harry W. Edwards and Michael F. Kostrzewa* 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 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 Waste Minimization Oppor- tunity Assessment Manual (EPA/625/7-88/003, July 1988). The WMAC team at Colorado State University performed an as- sessment at a plant manufacturing finished metal components — approximately 260,000 sq ft/yr. Customer-specified coatings and surface treatments are applied to prefabricated aluminum and stainless steel parts. Aluminum parts may be finished by hard-coat or soft-coat anodizing, and chromate conversioq coating. Stainless steel parts are finished by surface passivation. Parts are also processed for surface inspection using a fluo- rescent dye and ultraviolet light. The team's report, detailing findings and recommendations, indicated that most waste was generated in the aluminum anodizing process, and that the greatest savings could be obtained by using hot deionized water instead of nickel acetate solution to seal pores in the aluminum oxide coating applied by anodizing. This Research Brief was developed by the principal investiga- tors and EPA's Risk Reduction Engineering Laboratory, Cin- cinnati, OH, to announce key findings of an ongoing research project that is fully documented in a separate report of the same title available from University City Science Center. Introduction The amount of waste generated by industrial plants has be- come an increasingly costly problem for manufacturers and an ' Colorado State University, Department of Mechanical Engineering " University City Science Center, Philadelphia, PA additional stress on the environment. One solution to the problem 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 hazardous waste but who 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 (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 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 $75 million, employ no more than 500 persons, and lack inhouse 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 pro- cedures outlined in the EPA Waste Minimization Opportunity Assessment Manual (EPA/625/7-88/003, July 1988). The Printed on Recycled Paper ------- WMAC staff locate the sources of waste in the plant and identify 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 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 is a metal-finishing job shop that applies coatings and surface treatments to prefabricated metal parts. The plant operates 2,448 hr/yr to produce approximately 280,000 sq ft of finished metal parts. Manufacturing Process This plant does hard-coat and soft-coat anodizing, chromate conversion coating, and surface inspection of aluminum parts. Processing of stainless steel parts involves surface passivation surface inspection, or both. The raw materials used include aluminum cleaner, NaOH aluminum etch, nitric/hydrofluoric (HF) acid deoxidizer, sulfuric acid, dyes, nickel acetate, sodium dichromate, chromate conversion coatings, nitric acid, hy- drofluoric acid, oil-base penetrant, developer, water washable penetrant, and hydrophilic emulsifier. The following steps are carried out in the surface finishinq operations: • The aluminum anodizing line involves alkaline cleaning and etching, acidic deoxidizing to remove smut left after etching, anodizing in an electrolytic solution of sulfuric acid, dyeing, and sealing the aluminum oxide layer with aqueous nickel acetate. • Chromate conversion coating of aluminum involves alka- line cleaning and etching, acidic deoxidizing, clear or gold- colored chromate conversion coating, and rinsing in deion- ized water. • For stainless steel passivation, parts are degreased, etched, and immersed in a passivating acid solution. • For surface inspection, parts are first degreased and etched A fluorescent dye is then applied and the surface is illumi- nated with ultraviolet light to reveal surface flaws. An abbreviated process flow diagram is shown in Figure 1. Existing Waste Management Practices • Two-stage and three-stage counterftow rinses in the anod- izing and chromate conversion lines reduce water con- sumption and waste generation. • Process solutions are made up with deionized water to reduce sludge formation. • Drain boards are used between solution tanks to reduce dragout. • Spent etching solution is used for adjusting the Ph of spent rinse water. 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 man- agement costs are given in Table 1. Table 2 shows the opportunities for waste minimization that the WMAC team recommended for the 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 independently and do not reflect duplication of savings that would result when the opportunities are implemented in a package. 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. Environmental Protection Agency. The EPA Project Officer was Emma Lou George. Aluminum Parts from Customers' Surface Inspection - Cleaning - Etching • Inspection Anodizing - Cleaning - Etching - Anodizing - Dyeing - Sealing Chromate Conversion Coating - Cleaning - Chromate Conversion Stainless Steel Parts from Customers Surface Inspection - Cleaning - Etching - Inspection Passivation - Cleaning - Passivation Finished Parts Shipped to Customers Figure 1. Abbreviated process flow diagram. ------- Table 1. Summary of Current Waste Generation Waste Generated Source of Waste Spent rinse water Spent anodizing solutions Spent chromate conversion coating solutions Spent passivation solutions Spent acidic etchant solution Spent penetrants Batch treatment sludge Annual Quantity Generated (gal) Annual Waste Management Cost Rinse waters from anodizing, chromate conversion 1,547,734 coating, and surface inspection are Ph adjusted and discarded as industrial wastewater. Aluminum cleaner, alkaline etch bath, acidic 5,000 deoxidizer solution, anodizing reagent solution, and dyeing and nickel acetate seal solutions are batch treated (Ph adjusted) and discarded with rinse water as industrial wastewater. Hexa valent chromate solutions are reduced with 641 sodium metabisulfite; then, with aluminum cleaner, alkaline etch bath, and acidic deoxidizer solution, are batch treated (Ph adjusted) and discarded with rinse water as industrial wastewater. Hexavalent chromium solutions are reduced with 125 sodium metabisulfite and, with nitric acid solutions, are batch treated (Ph adjusted) and discarded with rinse water as industrial wastewater. Spent acidic etchant from surface inspection is 40 batch treated to adjust Ph and precipitate dissolved metals then discarded as industrial wastewater. Spent dyes, developer, and emulsifier from surface 20 inspection are shipped as hazardous waste for use as cement kiln fuel. Sludge (metal hydroxides and trivalent chromium 150 compounds) from treatment of spent process solutions and rinse waters is disposed of as hazardous waste. $19,963 8,589 759 306 123 985 5,191 •fru.g. GOVERNMENT PUNTING OFFICE: MM - 55»4C7/M)Ma ------- Table 2. Summary of Recommended Waste Minimization Opportunities Waste Generated Minimization Opportunity Annual Waste Reduction Net Quantity (gal) Implementation Percent Annual Savings Costs Payback Years Spent nickel acetate seal solution Nickel hydroxide sludge from treatment of spent nickel acetate solution Spent anodizing solutions Spent reagent solutions from chromate conversion coating Anodizing and chromate conversion coating water rinses Alkaline etch water rinses Anodizing and chromate conversion coating water rinses Use hot deionized water instead of nickel acetate as a seal after anodizing. Use hot deionized water instead of nickel acetate as a seal after anodizing. Neutralize the spent solutions with 50% aqueous caustic instead of sodium hydroxide pellets. Use automated metering equipment to reduce raw material and labor costs. Allow increased drainage time above the chromate conversion coating line reagent baths. Increased solution life will result in waste reduction and cost savings. Eliminate the soft-coat anodizing rinse (use the hard-coat rinses for both treatments), and install timer switches to shut off all flowing rinses when not in use. Use spent acidic deoxidizer rinse water instead of tap water for the anodizing and chromate conversion coating alkaline etch rinses. Install flow reducers and flow meters on flowing water rinses in the anodizing and chromate conversion coating lines to avoid excessive use of rinse water. 2,275 104 100 100 1,292 651,346 259,820 144,015 20 42 17 10 $3,094 1,109 2,933 2,498 2,351 756 419 $ 1,020 0 1,140 2,081 260 1,210 0.3 0 0.4 0.9 0.3 2.9 United States Environmental Protection Agency Center for Environmental Research Information Cincinnati, OH 45268 Official Business Penalty for Private Use $300 BULK RATE POSTAGE & FEES PAID EPA PERMIT No. G-35 EPA/600/S-92/030 ------- |