&EPA United States Environmental Protection Agency Risk Reduction Engineering Laboratory Cincinnati OH 45268 Research and Development EPA/600/S-92/011 May 1992 ENVIRONMENTAL RESEARCH BRIEF Waste Minimization Assessment for a Manufacturer Producing Galvanized Steel Parts 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 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 Minimi- zation Opportunity Assessment Manual (EPM625/7-88/QQ3, July J1988). The WMAC team at Colorado State University per- formed an assessment at a plant producing galvanized steel parts-approximately 10,000 tons/yr. The major process opera- tions are degreasing and rinsing, acid pickling and rinsing, prefluxing, and galvanizing. All these operations, except galva- nizing, result in the formation of waste streams requiring off-site disposal. Bottom dross from the galvanizing kettle and zinc oxide skimmed from the surface of the molten zinc are sold as usable products. The team's report, detailing findings and rec- ommendations, indicated that most waste was generated in acid pickling and rinsing and that the greatest savings could be obtained by continuous air agitation to extend the life of the .pickling acid and rinse by enabling more complete removal of dissolved iron when those solutions are treated. 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. 'University City Science Center, Philadelphia, PA 19104. 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 who lack the in-house 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 manu- facturing 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 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. ------- This assessment was done by engineering faculty and students at Colorado State University's (Fort Collins) WMAC. 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- sassmant Manual (EPA/625/7-88/003, 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 produces galvanized steel (reinforcing strips, pipes, ducts, angle iron, and prefabricated parts). The plant operates 4,420 hr/yrto galvanize about 10,000 tons of steel products. Manufacturing Process The plant produces galvanized steel products. The raw materi- als In addition to the steel include zinc ingots, alkaline phos- phate cleaner, 10% hydrochloric acid for pickling, and zinc ammonium chloride for prefluxing the steel. The following steps are involved in galvanizing the steel: • The steel parts are carried through an alkaline phosphate degreasing cleaner solution followed . by a water rinse. • Acid pickling is done in 10% to 4% hydrochloric acid followed by a water rinse. • The steel is prefluxed by immersion in a 30% zinc ammonium chloride solution. • Galvanizing is done by immersion in molten zinc. Existing Waste Minimization Practices The plant uses degreasing rinse water as make-up for water lost 'by evaporation from the degreasing tank. This practice eliminates the need to dispose of contaminated degreasing rinse water and reduces the consumption of caustic in the degreasing tank. 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 WMAC team recommended for the plant. The type of waste, the minimization opportunity, the possible waste reduction and as- sociated savings, and the implementation cost along with the payback time are given in the table. The quantities of hazard- ous 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 a long payback time as indicated below. They were brought to the plants's attention for future reference, however, since these approaches to waste reduction may in- crease in attractiveness with changing plant conditions. Use dry descaling by an airless grit blast cleaner instead of acid pickling to descale reinforcing strips for galvanizing. A solid waste of scale and spent grit would be generated instead of spent pickling acid and rinse. Because the scale would contain a small amount of hazardous chromium, disposal would be costly. Pilot tests were suggested to determine the life of the grit, necessary for eco- nomic evaluation. Install an electrodialysis system, a wastewater treatment system and an ion exchange unit to reduce the amount of acid pickling wastes gener- ated. Operating costs, including disposal of large amounts of chromium-containing sludge, would be high with a long payback period. Rinsing efficiency could be improved by dipping the steel into the rinse tanks twice. However, the improvement from dipping twice could not be quan- tified. 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 Sources of Waste Annual Quantity Generated Annual Waste Management Cost Degreaser and rinse tank sludge Spent pickling acid (4% HCL) and rinse water Spent preflux solution (zinc ammonium chloride) Preflux tank sludge Sludge from caustic degreasing 20,200 gal and rinsing of steel to be galvanized is dried in drums and disposed of as landfill. Spent acid solution (from pickling 105,400 gal the steel for galvanizing) and spent rinse water each contain about 10% dissolved iron. They are combined with spent preflux solution and disposed of as hazardous waste. Prefluxing of the steel prior to galvanizing 19,300 gal results in spent preflux-solution containing about 20% zinc ammodium chloride. It is combined with spent pickling acid and rinse water for disposal as hazardous waste. Iron dissolved in spent preflux solution is 2,400 gal removed by precipitation as ferric hydroxide. The resulting non-hazrardous sludge is separated by decanting, dried and disposed of as landfill. $500 66,435 12,165 60 Table 2. Summary of Recommended Waste Minimization Opportunities Waste Generated Minimization Opportunity Annual Waste Reduction Net Annual Quantity Percent Savings Implementation Payback Cost Years Spent preflux solution and preflux tank sludge Spent preflux solution Spent pickling acid Spent pickling acid and spentpreflux solution Provide continuous air 25,325 gal 62 $24,550 agitation and filtration of , the preflux solution for complete removal of contained iron as ferric hydroxide on addition of hydrogen peroxide. Removal of iron will extend the life of the preflux solution and - * the pickling rinse water which is discarded when the preflux solution is discarded. Provide air agitation of the 5,510 gal 29 4,370 acid pickling rinse tank preceding the preflux tank. This agitation will reduce dissolved iron drag-out into j the preflux solution, extending its life. Provide continuous filtration 19,300 gal 22 10,700 of the pickling acid solution to remove solid contaminants and extend its life. Increase drainage time — — . • 990 above the pickling and preflux tanks from 1 to 15 seconds to reduce drag-out and extend reagent life. (A reduction in the rate of generating spent solutions is expected but could not be quantified.) $16,000 0.7 3,820 0.9 25,040 2.3 •fru.S. GOVERNMENT PRINTING OFFICE: IWZ - «W>80/40Z«6 ------- Teb)a2. Summary of Recommended Waste Minimization Opportunities (concluded) Waste Generated Degreasing rinse sludge Minimization Opportunity Parts for re-cleaning after Annual Waste Reduction Quantity Percent 7,580 gal 75 Net Annual Savings 190 Implementation Cost 0 Payback Years 0 pickling are rinsed in the degreasing rinse before pickling again. Drag-out from the pickling tank reacts with alkaline compounds in the degreasing rinse to form sludge. Use the pickling rinse, which is not alkaline, instead of the degreasing rinse to avoid forming sludge. 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 Penaity for Private Use $300 EPA/600/S-92/011 ------- |