United States Environmental Protection Agency Risk Reduction Engineering Laboratory Cincinnati OH 45268 Research and Development EPA/600/S2-91/067 Feb. 1992 Project Summary Evaluation of Five Waste Minimization Technologies at the General Dynamics Pomona Division Plant Lisa M. Brown and Robert Ludwig Eight waste reduction technologies encompassing five industrial process areas at the General Dynamics Pomona Division (GDPD) were technically and economically evaluated under the Cali- fornia/U.S. Environmental Protection Agency (EPA) Waste Reduction Innova- tive Technology Evaluation (WRITE) Pro- gram. Evaluations were made through site visits and followup discussions with GDPD staff and equipment suppliers. The technologies included (1) com- puterized printed circuit board plating; (2) sulfuric acid anodizing; (3) robotic paint facility operations with (a) propor- tional paint mixing, (b) water-based sol- vent replacement, (c) electrostatic paint spraying, and (d) solvent distillation; (4) bead-blast paint stripping; and (5) Freon' recovery. Overall, there was a decrease in haz- ardous waste generation and an in- crease in productivity or reuse of recycled materials. In most cases, the technologies could be easily transferred to other industries except for the pro- hibitive costs of the computerized cir- cuit board and some processes within the robotic paint operation. The payback period estimates ranged from less than a year for the Freon recovery still to 67 yr for the sulfuric acid anodizing sys- tem. Difficulties in estimating payback periods resulted mainly from the un- ' Mention of trade names or commercial products does not constitute endorsement or recommendation for use. availability of company-sensitive infor- mation. This Project Summary was devel- oped by EPA's Risk Reduction Engi- neering Laboratory, Cincinnati, OH, and California's Department of Toxic Sub- stances Control, Sacramento, CA, 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 This study, performed under the Cali- fornia/EPA WRITE Program, was a coop- erative effort among EPA's Risk Reduction Engineering Laboratory (RREL), the Cali- fornia Department of Toxic Substances Control (DTSC), and GDPD whose waste minimization processes are the subject of this report. GDPD builds various tactical defense weapons, primarily air defense missiles and gun systems. In 1984 General Dy- namics established a corporate environ- mental program with individual division responsibility for hazardous waste reduc- tion, including reductions in the use of toxic substances. As a result of implementing this corpo- rate policy, several waste reduction pro- cess modifications have been instituted at the Pomona Division. GDPD has reported a reduction of 97% in the annual discharge of hazardous (about 10,600 tons), liquid, and solid wastes and 95% in volatile or- ganic contaminant (VOC) emissions (about Vv Printed on Recycled Paper ------- 17.5 tons) through a combination of waste reduction and treaitment technologies. Of the 14 waste minimization technolo- gies recently employed at GDPD, only 5 process areas encompassing 8 technolo- gies were evaluated: (1) computerized printed circuit board plating; (2) sulfuric acid anodizing; (3) robotic paint facility with (a) proportional paint mixing, (b) water- based solvent replacement, (c) electrostatic paint spraying, and (d) solvent distillation; (4) bead-blast paint stripping; and (5) Freon recovery. Technologies The 14 waste minimization technolo- gies employed at GDPD were screened for technology applicability, source reduction potential, extent of process modification, and cost-effectiveness. The Worth Assess- ment Model that was used was developed by EPA specifically for the WRITE Pro- gram. As a result of applying the model, the five process areas encompassing the eight individual technologies were chosen for further analysis. Technical and economic evaluations were conducted during site visits, and the additional information required was ob- tained through subsequent followup con- versations with GDPD staff and system suppliers. As economic objectives were centered around return on capital, internal rate of return, and payback periods, which are considered company sensitive infor- mation, a simple payback for each process was calculated. Technology Descriptions and Evaluations Printed Circuit Board Plating System Chemcut Corporation installed a new computerized printed circuit board plating system at GDPD in July 1988, at a cost of $4,100,000. This new plating system com- pletely eliminated rinse tanks from the pro- cess by use of a unique spray-rinse configuration contained in a transporter hoist system that passes over the plating bath tanks. This computerized hoist sys- tem allows the circuit boards to be rinsed for only a short time after being immersed in a process solution. The rinse water dis- charge from this new process is less than 10 gpm versus 60 gpm from the old pro- cess. This reduction in wastewater dis- charge allowed for a corresponding reduction in the size of the metal recovery system. The use of a spray rinse versus a dip rinse can also be a major design factor if water supply limitations must be consid- ered or if space is limited in locating the plating line. The new system employs copper spheres in anode baskets rather than the conventional anode bar-and-hook system that was used in the old plating system. This allows a 1-to-1 ratio of anode-to-cath- ode for a very even plating across the panel and through the holes. When the new production equipment was installed, Chemcut Corporation was required to provide a nonsludge-producing treatment system for all waste streams generated by the process. This resulted in a new copper-recovery system using short- bed ion exchange columns and electro- winning technologies. The system now produces salable scrap copper metal and eliminates a major waste stream to the conventional sludge-producing waste treat- ment system. The difference in the cost of labor and waste treatment between the newly in- stalled printed circuit board plating system and the original one resulted in a favorable net annual operating savings. The payback period for the new system was estimated to be 8.3 yr. Annual cost savings of $130,000 in waste treatment and disposal were determined from the recovery of cop- per from rinse water and process tank solutions, which had previously been treated and disposed of as a hazardous sludge. An annual cost savings for water use was estimated to be $10,000 based on a net overall decrease in rinse water discharges of 50 gpm. Sulfuric Acid Anodizing System In December 1988, GDPD replaced its 35-yr-old chromic acid aluminum anodiz- ing system with a new computerized sulfu- ric acid anodizing system—one that utilizes computerized hoists and on-demand rins- ing. The new system, supplied by NAPCO, Inc., enabled GDPD to eliminate a major source of chromium emissions. GDPD used chromic acid in the original aluminum anodizing process because of military contract specifications. Typically, when parts are either subject to stress or contain blind holes (e.g., trapped areas, recesses, porous castings) in which anod- izing solution could be entrapped, the much less corrosive chromic acid is used. Chro- mic acid is also used to detect fine surface flaws on finished parts. This process, in spite of its higher operating costs, is used by the aerospace industry, the military, and military contractors. General Dynamic's motivation for con- verting to a sulfuric acid anodizing sys- tem was that its original chromic acid system could not be modified cost-effec- tively to meet production requirements and maintain compliance with current and anticipated air and water regulatory re- quirements. General Dynamics had deter- mined that it was not possible to meet proposed air emission requirements (99.8% removal efficiency for chrome discharged to the atmosphere) with their original pro- cess. In addition, General Dynamics was committed to eliminating all wastewater discharges of chromium to ensure compli- ance with the California Safe Drinking Wa- ter and Toxic Enforcement Act of 1986 (Proposition 65), which prohibits an indus- try from discharging detectable levels of hazardous chemicals, including chromium, into any source of drinking water. Because GDPD's industrial wastewater discharges to a local publicly owned treatment works (POTW) which then uses the treated efflu- ent for groundwater recharge, there was a concern that the Pomona Division could not maintain compliance with the law while continuing to operate a chromic acid anod- izing process. In addition to chemical substitution to eliminate chromium releases, adding the automated hoists and the on-demand wa- ter bath rinse system helped reduce waste- water treatment requirements. The computerized automated hoists monitor the time intervals that parts are treated and then allowed to drain. When compared with manual immersion and parts draining, this system reduces treatment requirements by avoiding unnecessary drag-out of im- mersion fluids to downstream rinse tanks. Subsequently, the on-demand water rinse system helps reduce rinse water use and wastewater treatment requirements by re- ducing water consumption and by monitor- ing the conductivity of the rinse water in the tank. Unlike manually operated rinse tanks, which have constant overflows, the on-demand system adds water only when the conductivity of the tank exceeds a set value. By using this on-demand water pro- cess, rinse water requirements were re- duced from approximately 15 to 20 gpm to approximately 6 to 8 gpm. Spray rinsing is an alternative approach to on-demand im- mersion rinsing; however, in this case im- mersion rinsing was required to maintain coating performance with complex and vari- able parts configuration. This sulfuric acid anodizing system is capable of retrieving samples from several process baths, performing the required chemical analysis, calculating the amount of feed material needed, and activating a chemical feed system to provide the nec- essary amount of material needed. This system is also capable of continuously monitoring and automatically controlling ------- physical process parameters such as bath temperatures, rinse water quality, voltage, and current density. The advantages in- clude lowered labor costs, (i.e., fewer labo- ratory personnel and machine operators), improved worker health and safety, im- proved productivity, improved product qual- ity, lowered chemical usage, lowered production wastes, and minimized process waste. The capital cost of the new sulfuric acid anodizing system was $955,000 and in- cluded the computerized hoist and on-de- mand anodizing rinse systems. The operating and maintenance costs were lower for the new system when compared with those of the old chromic acid system because it is less energy intensive, it has a smaller plating interval, and wastewater treatment costs are less. Because sulfuric acid is much more conductive as an elec- trolyte, the anodizing process requires less power. The cost savings for electricity were estimated to be $10,900, based on an annual decrease in electrical consumption. The sulfuric acid process is also much faster than chromic acid, so less process time is needed for a given film thickness. The increased throughput potential results in lower operating costs. Wastewater treatment costs are less for the new system due to a decrease in metals removal requirements. The sulfuric acid process requires only aluminum re- duction and results in a nonhazardous sludge; the chromic acid system required aluminum and chromium reduction and the additional tanks and chemicals for treat- ment and settling. The disposal costs for the aluminum sludges generated from the sulfuric acid process are less than the hazardous chromium and aluminum sludge generated from the chromic acid process. The computerized hoists and on-de- mand spray rinse systems realize addi- tional cost savings. Both of these systems have reduced labor requirements; water consumption has been reduced from 20 to 8 gpm. The cost savings in reduced water consumption has been estimated to be $2,300 annually. GDPD also expects the computerized hoist system to lower costs associated with rejects and rework. Robotic Paint Facility The GDPD paint production operations facility was completed in December 1988 to replace manual mixing and hand spray- ing of metal parts in naval weapons sys- tems. It includes computer-controlled robots (a GRI OM 5000 Unit) that allow quick, automated precision painting. A propor- tional paint mixer was also added; this feeds preselected quantities of individual paint components directly to a paint spray nozzle thus eliminating batch makeup op- erations. Electrostatic spray guns and au- tomatic waste cleaning solvent collection systems were also introduced to allow for recycle and reuse of waste paint. Spray paint booths are also available for touch- ups. Stills are used for recycling paint clean- ing solvents. The painting facility uses both oil- and water-based paints. For oil-based paints, polyurethane thinner is used for paint thin- ning and equipment cleaning. A thinner containing isopropyl alcohol and xylene is used with water-based paint. Paint waste was reduced from 42 tons in 1987 to 31 tons in 1988 and was further reduced to 17 tons in 1989. About 1,000 gal of polyure- thane cleaning solvent per year is now being recycled through the paint shop sol- vent stills; this results in approximately 60 to 100 Ib of still bottoms per week or about 5,000 Ib/yr. The still bottoms and waste paint are sent offsite for incineration. Paint purchases decreased from 6,530 gal in 1988 to 5,230 in 1989; solvent pur- chases decreased from 2,500 gal in 1988 to 1,080 gal in 1989. These decreases are mainly due to changes in equipment and operating purchases in the paint shop but are also partially due to changes in inven- tory and a decrease in production rates. Only polyurethane solvent (for oil-based paints) is currently being recycled in the stills. When distilling the water-based paint solvent, which contains isopropyl alcohol and xylene, the recycled solvent separates into two layers, a water and a solvent layer. Even when the water is removed by draining, water contained within the sol- vent prevents the solvent from being re- used for thinning and cleaning. Potentially, the water can be removed by adding a water separator upstream and a molecular sieve downstream of the stills. The installation cost of the robotic paint- ing system was $1,400,000. The system included a parts conveyor, computer-con- trolled robots, electrostatic spray guns, pro- portional paint mixing, and cleaning solvent collection equipment. The disposal of 42 tons of waste in 1987 would have cost about $73,000 at the current disposal rates of $420 per drum, plus $7,000 per truck- load for transportation (80 drums). The disposal costs of 21 tons in 1989 would be about $36,000. The payback period from a waste disposal standpoint alone would be 40 yr. This substantially overstates the payback period, however, because the sav- ings in labor costs from painting and waste disposal and any decrease in rejects in parts were not included, as it was consid- ered company sensitive information. Payback for the solvent stills is only about 4 yr, but it would be less if all cleaning solvent were being recycled. Bead-Blast Paint Stripper The plastic bead-blast paint stripper at GDPD was installed in June 1988 to re- place methylene chloride stripping. Reus- able plastic beads or media are used in this mechanical stripping operation, which is similar to sand blasting. Paint is stripped from the hangers used to hold parts being painted in the paint shop and from parts having paint defects. The plastic bead-blasting booth is a Pauli and Griffin Pram Machine approxi- mately 3ftx3ftx3ft and uses size 20 to 30 mesh Poly Plus beads. The unit is used only on an as-needed basis, generally a few hours per week. The waste generated during the opera- tion of the plastic-bead blasting unit, which consists primarily of paint chips with a small amount of spent plastic beads, is sent offsite for incineration. Stripping by methylene chloride resulted in about 10,000 Ib/yr of toxic solvent contaminated with paint sludge, which was also sent offsite for incineration. The bead-blast paint strip- per was installed at a cost of $18,000. This system eliminated the disposal of the sol- vent. Both the methylene chloride and bead-blast waste are disposed of by incin- eration; the annual waste disposal costs are $10,000 for methylene chloride and $5,000 for bead-blast waste. The plastic bead-blast paint spripper provides a cost savings of $5,000/yr. The payback period from a waste disposal perspective is about 3.6 yr. This does not consider differences in operator time, maintenance require- ments, and stripping materials that will vary depending on parts being stripped, whether methylene chloride stripping is being done by spray-on or dip tank methods, operator skill, and recovery of stripping material. Freon Recovery Stills Three Freon recovery stills manufac- tured by Recyclene were installed in De- cember 1988 to collect and distill waste from solvent degreasing operations throughout GDPD at a cost of $240,000, plus $40,000 for add-on equipment to ad- dress operating problems. Recovered sol- vent is tested and reformulated under a quality assurance program to ensure that all the manufacturer's specifications are met before returning the solvent to material stores for reissue to production operations. Still bottoms are dried in the distillation process and sent offsite for incineration. Before installing these stills, a single Freon recovery still was installed in No- •&U.S. GOVERNMENT PRINTING OFFICE: 1992 - 648-080/40151 ------- vember 1985 to extend the life of Freon used in conveyorized cleaners. This ex- tended the solvent change out period to once per year and annually saved 35,000 Ib in Freon purchases. Tests of the Freon recovery stills in 1988 indicated that the distillation process was working but that the Freon being re- cycled was contaminated with water, which degraded the quality of the recovery prod- uct. The Pomona Division has installed separators to remove water and molecular sieves to further dry the Freon after distilla- tion. Although the additions to each still cost $13,000, plus installation, they allow the Freon recovery to be operated as planned to produce a quality recycled sol- vent. Reduction in Freon purchases through 1988 have primarily come through improved operating procedures such as extended change out times for Freon and reduced evaporative losses. A baseline of 421,000 Ib of Freon for 1988 was used to calculate the reduced Freon use that is attributable to the three Freon stills; it is assumed they were utilized at full capacity for the first time in 1989. The capital cost of the stills was $270,000 with annual operating costs considered negligible. The amount of Freon recycled or the amount of avoided pur- chases were 212,473 Ib, the cost of which, at $1.64/lb, was $348,456. The cost to incinerate 11,183 Ib of still bottoms was $8,000 with a cost savings from avoided Freon disposal equal to $148,583. The total savings were $489,039 with a payback period of 0.55 yr. This is a minimum payback number based on recycling all of the Freon that is not lost through evapora- tion and drag-out losses. Conclusions Under the EPA/California WRITE Pro- gram, five waste minimization technolo- gies were evaluated at the GDPD. The level of technology varied from a comput- erized printed circuit board system costing $4.1 million to a bead-blast paint stripper costing $10,000. The range of payback periods also varied—from a high of 67 yr for the sulfuric acid anodizing system to a low of 0.55 yr for the Freon recovery stills. The full report was submitted in fulfill- ment of Contract No. 68-03-3389 by PEI Associates, Inc., under the sponsorship of the U.S. Environmental Protection Agency. This Project Summary was prepared by Lisa M. Brown (also the EPA Project Officer, see below) of the Risk Reduction Engineering Laboratory, Cincinnati, OH 45268, and Robert Ludwig of the State of California Department of Toxic Substances Control, Sacramento, CA 94234-7320, based on the draft report by PEI Associates, Inc. The complete report, entitled "Evaluation of Five Waste Minimization Technologies at the General Dynamics Pomona Division Plant," (Order No. PB92-125756/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 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/S2-91/067 ------- |