United States Environmental Protection Agency Risk Reduction Engineering Laboratory Cincinnati, OH 45268 Research and Development EPA/600/SR-92/188 October 1992 Project Summary An Automated Aqueous Rotary Washer for the Metal Finishing Industry Arun R. Gavaskar, Robert F. Olfenbuttel, Jody A. Jones, and Tad C. Fox Product quality, waste reduction, and economic issues involved in the use of an automated aqueous rotary washer in the metal finishing industry were evaluated in this study. The automated washer can be used for most metal parts that would or- dinarily be cleaned by vapor degreasing, hand-aqueous washing, or alkaline tum- bling. The automated washer had good potential to reduce waste, was economi- cally viable, produced good product qual- ity, and also avoided the vapor degreaser's use of perch loroethylene. When compared with hand-aqueous washing and alkaline tumbling, the automated washer used less chemicals. The payback period was about 7 years. This Project Summary was developed by EPA's Risk Reduction Engineering Laboratory, Cincinnati, OH, to announce key findings of the research project that is fully documented in a separate report of the same title (see Project Report ordering information at back). Introduction The Pollution Prevention Act of 1990 es- tablishes pollution prevention as a "national objective." The Act notes that there are sig- nificant opportunities for industry to reduce or prevent pollution at the source through cost- effective changes in production, operation, and raw materials use. Source reduction is fundamentally different from and more desir- able than waste management and pollution control. Source reduction is defined in the law to mean any practice that reduces the amount of a hazardous substance, pollutant, or con- taminant entering a wastestream or other- wise released into the environment before recycling, treatment, or disposal. The objective of the U.S. Environmental Protection Agency's (EPA) Waste Reduction Innovative Technology Evaluation (WRITE) Program is to evaluate, in a typical workplace environment, examples of prototype or com- mercial technologies that have potential for pollution prevention. This particular evaluation was a cooperative effort among EPA's Risk Reduction Engineering Laboratory, Connecti- cut Hazardous Waste Management Service, and Quality Rolling and Deburring (QRD) Company. The study evaluated an automated aqueous washer for cleaning small metal parts in the metal finishing industry. The goal of the study was to provide information to potential users of this technology. The objectives were to evaluate (1) the product quality resulting from new automated washer versus each of three older processes, (2) the pollution pre- vention potential of the new technology, and (3) the economic attributes of the new tech- nology. One of the major steps in metal finishing is cleaning metal parts to remove oil and grease, dirt, and metal chips. Cleaning may involve washing with a detergent or degreasing with a solvent. Before installing the automated aqueous washer, QRD (the site for this study) routed metal cleaning jobs through one of three cleaning processes: vapor degreasing, alkaline tumbling, or hand-aqueous washing. The cleaning process chosen is based on the type of metal part and the suitability of the cleaning process. Product Quality Evaluation The product quality evaluation was based on (a) an examination of the cleaned metal Printed on Recycled Paper ------- parts from some of QRD's normally sched- uled cleaning jobs, (b) an examination of cleaned test panels inserted along with the metal parts in the cleaning jobs, and (c) a water break test conducted on the cleaned test panels from the alkaline tumbler and automated washer. Three cleaning jobs (each containing sev- eral thousand small metal parts) were selected from the several that QRD receives every day. Job A consisted of steel caplets that were suitable for cleaning on the vapor de- greaser. Job B consisted of aluminum rivets that were suitable for cleaning on the hand- aqueous washer. Job C consisted of steel cylinders that were suitable for cleaning on the alkaline tumbler. Job C involved cleaning as well as electroplating (nickel plating). Each job was split into halves. Half was cleaned by the automated washer, and the other half was cleaned by one of the older processes. This experimental design provided a one-to-one comparison between the auto- mated washer and each of the three older processes. After each cleaning run, a predetermined number (150) of randomly selected, cleaned parts were examined for product quality. Visual examination revealed no noticeable contami- nation on any of the parts for all three jobs nor on the cleaned test panels. The water- break test indicated that the parts destined for electroplating had been cleaned well. The results of these examinations, therefore, show that the three old processes and the auto- mated process resulted in good product quality, although certain delicate parts still need vapor degreasing and some parts that are diffucult to clean need hand-aqueous washing. Pollution Prevention Potential Pollution prevention was measured in terms of waste volume reduction (Table 1) and pollutant reduction (Table 2). The total waste volume generated by the automated washer is much bwer than either the alkaline tumbler or hand-aqueous washer. This indicates that the automated washer needs fewer resources to process wastes downstream. Note that the processing energy require- ment of the automated washer is higher than the energy requirement of any of the three older processes. The moderately higher pro- cessing energy requirement of the automated washer should, however, be weighed against the potentially higher energy requirements of the older processes in such other areas as waste treatment. Secondary pollution resulting from energy consumption was not a part of this evaluation. Although the waste volume generated by the vapor degreaser is bwer than that of the automated washer, it is much more hazardous. Table 1. Comparison of Annual Waste Volume from the Cleaning Processes Wastestrearn Vapor Degreasing a Wastewater in separator Still bottom sludge Air emissions Alkaline Tumbling fr Wastewater Hand-Aqueous Washingc Wastewater Volume Generated Per Year Wastestream Volume Generated Per Year (gal) 200 1,440 see Table 2 1,010,880 296,400 Automated Washing' Wastewater 143,000 Oily Liquid 962 Automated Washing" Wastewater 85,800 Oily Liquid 577 Automated Washingc Wastewater 57,200 Oily Liquid 385 3 Based on 5,200 bbl/yr run on automated washer instead of vapor degreaser. " Based on 3.120 bbl/yr run on automated washer instead of alkaline tumbler. c Based on 2 080 bbl/yr run on automated washer instead of hand-aqueous washer. Perchloroethylene, used in vapor degreasing, is a hazardous chlorinated solvent on the EPA's Toxics Release Inventory. Perchloro- ethylene is also one of the 17 prbrity pollutants targeted in the EPA Administrator's 33/50 Program for 50% reduction in releases by 1995. It is used in degreasing because it has a high boiling point and is therefore suitable for removing high melt waxes and for clean- ing light-gauge metal parts. Perchloroethylene can be a health prob- lem, with inhalation and skin as the main entry routes. Occupational Safety and Health Administration exposure limits are 100 ppm (8-hr time weighted analysis), 200 ppm (ac- ceptable ceiling concentration), and 300 ppm (acceptable maximum peak). Vapor inhalation can cause eye irritation (at 400 ppm), respi- ratory irritation (at 600 ppm), or anesthesia (200 ppm for 8 hr) according to the Metals Finishing Guidebook and Directory (1988). Prolonged or repeated skin exposure can cause dermatitis. Spent perchloroethylene is listed under Resource Conservation and Recovery Act (RCRA) as a hazardous waste (EPA hazard- ous waste number F001). Other commonly used degreasing solvents are methylene chloride, 1,1,1-trichloroethane, and trichforo- ethylene, all of which are hazardous. The use of the automated washer reduces the use of these solvents. The automated washer generates a wastewater containing surfactants, which are a much lower hazard both in terms of occu- pational safety and the environment. Surfac- tants are not RCRA hazardous wastes. They can, however, cause environmental problems. Phosphate detergents are the main cause of increased algal growth (eutrophication) in Table 2. Pollutants Generated by Cleaning Processes Pollutant Vapor Degreasing 3 Perchloroethylene Perchloroethylene Perchloroe thylene Alkaline Tumbling" Anionic surfactant Hand-Aqueous Washing Non-ionic surfactant Medium Sludge Water Air Amount Generated Per Year (Ib) 45 negligible 6,145 Pollutant Automated Washing * Anionic surfactant Non-ionic surfactant Amount Generated Per Year Medium (Ib) Water 2 Water 22 Water Water 43 105 Automated Washing" Anionic surfactant Water 1 Non-ionic surfactant Water 13 Automated Washingc Anionic surfactant Water 1 Non-ionic surfactant Water 9 3 Based on 5,200 bbl/yr run on automated washer instead of vapor degreaser. " Based on 3,120 bbl/yr run on automated washer instead of alkaline tumbler. c Based on 2,080 bbl/yr run on automated washer instead of hand-aqueous washer. ------- face waters where they are discharged, cause waters to have an obnoxious odor and taste, have a detrimental effect on fish because of the high biochemical oxygen demand (BOD) they create, and become a nuisance for rec- reational activities. Hence, nonphosphate de- tergents are increasingly being used. Different surfactants vary widely in terms of aquatic toxicity and ease of biodegradation. Surfactants accumulate within aquatic organ- isms and impair their functions. When com- pared with alkaline tumbling or hand-aqueous washing, the automated washer generates bwer amounts of these surfactant wastes. The results of the study indicate that mea- surable pollution prevention accrues from us- ing the automated washer instead of any of the three older cleaning processes. Economic Evaluation The economic evaluation of automated washing was based on (a) major operating costs of the automated washer compared with each of the three older cleaning pro- cesses and (b) an estimation of the return on investment (ROI) and payback period for the automated washer. The number of barrels of metal parts that were used in this estimate was based on the annual number of barrels processed through the automated washer. This total was divided into three parts based on the percentages of the parts run on the automated washer that could have gone to each of the three older processes. Of the 10,400 barrels run on the automated washer per year, 5,200 would have gone to vapor degreasing, 3,120 to alkaline tumbling, and 2,080 to hand-aqueous washing. Tables 3, 4, and 5 compare the operating costs of the older cleaning processes and those of the automated washer. The results of the economic calculations showed that, based on a capital requirement of $207,260, the payback period for QRD (where the ROI exceeds 15%) was about 7 yr. Reducing the amount of solvent used can also reduce pos- sible liability resulting from health claims or pollution fines, but these savings were not quantified by this study and were not in the economic calculations. Discussion and Conclusions The automated aqueous washer evaluated in this study is an example of a pollution prevention technology for the metal finishing industry. Source reduction is achieved by substituting an aqueous cleaning process for a solvent cleaning process (vapor degreasing). Source reduction is also achieved by reducing the amount of raw materials (cleaners or detergents) and process water used (alkaline tumbling and hand-aqueous washing). Auto- mated washing reduces the volume of wastewater that has to be treated (either on- srte or at the publicly owned treatment works) Table 3. Operating Costs of Vapor Degreasing and Automated Washing Cost Element Vapor Degreasing Cost • ($/Yr) Automated Washing Cost' ($/Yr) Labor(base rate) Energy Chemicals Water Onsite Waste Treatment Offsite Waste Disposal Total 13,866 2,943 1,795 0 Negligible 1,440 20,044 17,300 10,712 2,711 665 1,032 2,624 35,044 * Based on 2,080 bbl/yr. and discharged downstream. This is done without compromising the cleaned product quality, and no additional skill (above that required to operate the old processes) is re- quired to operate the automated washer. Parts cleaned in the automated washer can be either electroplated or sent out as finished products. One current limitation is that the automated washer cannot yet totally substitute for the three older processes. Certain delicate parts have to be sent through the vapor degreaser and some difficutt-to-clean parts have to be processed through the hand-aqueous washer. Most jobs that can be run on the older pro- cesses can, however, be routed through the automated washer. Thus the automated washer is a good technology for metal finish- ers who are considering an expansion in capacity. In summary, use of the automated washer results in good product quality, increased pollution prevention, and economic savings. An added incentive for using the automated aqueous process is its potential to reduce liability as a result of reducing solvent use. The full report was submitted in fulfillment of Contract No. 68-CO-0003 by Battelle un- der the sponsorship of the U.S. Environmen- tal Protection Agency. Table 4. Operating Costs of Alkaline Tumbling and Automated Washing Cost Element Alkaline Tumbling Costa ($/Yr) Labor 18,720 Energy 2,847 Chemicals 2,434 Water 4,700 Onsite Waste Treatment 7,299 Offsite Waste Disposal 0_ Total 36,000 3 Based on 3,120 bbl/yr. Automated Washing Cost3 ($/Yr) 10,380 6,427 1,626 399 619 1+57A 21,025 Table 5. Operating Costs of Hand-Aqueous Washing and Automated Washing Cost Element Labor Energy Chemicals Water Onsite Waste Treatment Offsite Waste Disposal Total Hand-Aqueous Washing Cost' ($/Yr) 16,640 3,256 33,134 1,213 2,140 Q 56,383 Automated Washing Cost' ($/Yr) 6,920 4,285 1,084 266 413 LQ50_ 14,018 ' Based on 2,080 bbl/yr. 'U.S. Government Printing Office: 1992— 64B-080/60134 ------- A.R. Gavaskar, R.F. Olfenbuttel, J.A. Jones, and T.C. Fox are with Batelle, Columbus, OH 43201 Lisa Brown is the EPA Project Officer (see below). The complete report, entitled "An Automated Aqueous Rotary Washer for the Metal Finishing Industry," (Order No. PB92-228469/AS; Cost: $19.00, 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 Officer can be contacted at: Risk Reduction Engineering Laboratory U.S. Environmental Protection Agency Cincinnati, OH 45268, NC 27711 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/SR-92/188 ------- |