United States Environmental Protection Agency Risk Reduction Engineering Laboratory Cincinnati, OH 45268 Research and Development EPA/600/S2-91/054 Dec. 1991 EPA Project Summary Waste Minimization Opportunity Assessment: Scott Air Force Base A waste minimization opportunity as- sessment (WMOA) was made of three selected processes at Scott Air Force Base (AFB), IL: nondestructive Inspec- tion (NDI) of C-9 medical aircraft wheel hubs; painting/paint removal/parts cleaning operations of all aerospace ground equipment at the base; and the manufacture of printed circuit boards. One WM option applicable to NDI in- spection of wheel hubs Involved modi- fying tanks holding the emulsifier and developer. The primary contaminant (the penetrant from the first tank) floats on the surface of the second and third tanks because of Its low density. The life of these second and third baths could be extended by Installing a drain valve on the side of a tank and remov- ing the floating penetrant from these tanks every 6 mo. Other options for other processes are given together with their cost savings and payback peri- ods. 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 U.S. Environmental Protection Agency (EPA) has developed a system- atic approach to identify, evaluate, and implement options to reduce or eliminate hazardous waste. The approach is pre- sented in a report entitled, "Waste Minimi- zation Opportunity Assessment Manual" (EPA/625/7-88/003). To encourage use of this manual, EPA is conducting a series of assessment projects; the report sum- marized here describes the application of the waste minimization assessment pro- cedures to selected processes at Scott AFB, IL. This facility volunteered to par- ticipate in the project and provided techni- cal support during the study. The assessment was conducted for the EPA's Risk Reduction Engineering Labo- ratory under the purview of the Waste Reduction Evaluations at Federal Sites (WREAFS) Program of EPA's Pollution Prevention Research Branch. The proce- dure described in the EPA Manual pro- vides detailed worksheets and a process/ option evaluation method for use in indus- trial settings. Scott AFB is located near Belleville, IL. About 3,000 civilians and 5,000 military personnel either work or live there. The base is part of the Military Airlift Com- mand (MAC) and operates and maintains a fleet of C-9 medical aircraft. Twelve C- 9's are outfitted, flown, and maintained in a ready condition by base staff. Procedure Waste minimization (WM) is a policy specifically mandated by the U.S. Con- gress in the 1984 Hazardous and Solid Waste Amendments to the Resource Con- servation and Recovery Act (RCRA). The WM assessment procedure used during this project is an acceptable approach for meeting one part of the WM program re- quired by the law for hazardous waste generators. The systematic WM assessment proce- dure can be used by a facility's own em- ployees to identify WM opportunities. As a structured program, it provides intermedi- ate milestones and a step-by-step proce- dure to (1) understand the facility's pro- cesses and wastes, (2) identify options for reducing waste, and (3) determine if the options are technically and economically feasible to justify implementation. This procedure consists of four major steps: (1) planning and organization—or- ganization and goal setting; (2) assess- ment—careful review of a facility's opera- tions and wastestreams and identification and screening of potential options to mini- mize waste; (3) feasibility analysis—evalu- ation of the technical and economic feasi- bility of the options selected and the sub- Printed on Recycled Paper ------- sequent ranking of options and (4) imple- mentation—procurement, installation, implementation, and evaluation. The WM opportunity assessment manual contains a set of 19 worksheets designed to facili- tate the WM assessment procedure. Discussions with base environmental staff and EPA personnel resulted in a focus on three areas of investigation: • nondestructive inspection (NDI) of C-9 wheel hubs, • painting/paint removal/parts clean- ing, and * printed circuit board manufacture. This project completed the first three steps of the procedure for NDI and the first two steps for the other selected areas at Scott AFB. The fourth step, implemen- tation, is at the discretion of the host facil- ity. The following describes each of the three selected processes, the wastes gen- erated, and the current status of MAC actions to reduce the volume and/or toxic- 'rty of wastes generated. Nondestructive Inspection (NDI) As part of the preventative maintenance practices on the C-9's, two test methods are used at the AFB to inspect landing wheels for signs of fatigue such as cracks or other discontinuities that penetrate to the surface. An eddy-current method is used to inspect the bead seat area, and a liquid penetrant inspection method is used to check all other areas. The eddy-current method places an electric current in prox- imity to a conductive test specimen (such as the aluminum wheel) and measures impedance changes due to discontinuities. Eddy-current, unlike liquid .penetrant in- spection, does not generate wastestreams. The liquid penetrant process at Scott AFB begins by immersing aluminum wheel halves into the penetrant tank long enough for the penetrant to permeate into discontinuities that are accessible from the surface. After the specified soak time, the parts are placed over a drip station that returns surface runoff back to the pen- etrant tank. The parts are then rinsed with water, then re-immersed in an emulsion solution for a specified time, removed and rinsed again to remove penetrant from the surface of the parts. Next, the parts are soaked in a developer that deposits a thin layer of solid material on the surface of the parts. Parts are placed above the de- veloper where surface runoff is returned to the developer tank. The parts are placed in a dryer at a specified temperature and time. After drying, parts are inspected un- der ultraviolet (UV) light. Cracks are indi- cated by fluorescent lines or spots. Parts can then be rejected or repaired as war- ranted. The three primary wastes generated by the liquid penetrant NDI process are the penetrant, emulsifier, and developer. The penetrant tank is periodically emptied and refilled to prevent contaminants from af- fecting process sensitivity. The need for a tank change is determined by comparing the sensitivity of two test specimens (metal plates with known flaws) when" one is dipped in the current batch of penetrant and the other into an unused portion. Waste penetrant is drummed and a waste handler incinerates it in a cement kiln. The Defense Reutilization and Marketing Office (DRMO) currently classifies the pen- etrant waste as a D001 (flammable) waste; however, the flash point is above the 140°F criteria established for D001 waste. A small amount of penetrant is lost to the sewage treatment plant when wheels are rinsed before being dipped in the emulsifier. The Scott AFB is considering an oil-water sepa- rator to recover the penetrant from this stream. The emulsifier tank solution eventually becomes contaminated with penetrant that was not completely rinsed off. The solu- tion batch is changed about every 6 mo (based on a standard operating proce- dure, SOP) and sent to the sewage treat- ment plant through a floor drain. Each batch size is approximately 100 gal. Al- though the waste is not hazardous, the manufacturer recommends disposing of the waste by incineration. A small amount of emulsifier is also discarded to the sew- age treatment plant with the post-emulsi- fier rinse water during each hub inspec- tion. Developer batches become contami- nated primarily with penetrant. Batches of approximately 100 gal are changed on about the same frequency as the emulsi- fier batches. Like the emulsifier, the de- veloper is sent to the sewage treatment plant through a floor drain. Unlike the emul- sifier though, the waste is hazardous ac- cording to the developer manufacturer. Be- cause of the levels of sodium chromate present, the batches meet the criteria for a D007 waste and should not be directed to the sanitary system. Palntlng/Palnt Removal/Parts Cleaning The paint shop handles all aerospace ground equipment (AGE) for Scott AFB. Paint booths are normally used during one 8 hr shift per day, but they can be oper- ated around-the-clock during peak times. Approximately 24 kits (each containing 1 gal of polyurethane paint) are used per year. About 90% of the paint used at the paint shop is polyurethane, and the re- mainder is various lacquers and varnishes. Parts to be painted are dry-sanded or dipped into a bath containing a multi-layer stripping solvent. This solvent is used un- til contaminated with paint sludge; it is then drummed and hauled offsite as a hazardous (F002) waste. This process is to be replaced by a plastic media blasting (PMB) method. The PMB equipment is located onsite and lacks only some minor fittings before it can be operated. Parts requiring a clean, grease-free sur- face for subsequent processing such as inspection or repainting are brought into the Cleaning Shop. Excess grease is wiped off and the parts are immersed in a bath of Safety Kleen 105* degreaser for at least 45 min. The part is then removed and manually scrubbed with a brush. Any re- maining solvent is rinsed off at a cleaning station. The AFB contracts with Safety Kleen, Inc., to remove the contaminated solvent and replace it with fresh solvent. Safety Kleen, Inc., then recycles the sol- vent and distributes it back to its custom- ers. The solvent is primarily mineral spirits and is classified as a D001 waste be- cause of its 105° F flash point tempera- ture. Parts such as aluminum alloy landing wheels are next dipped into a weak acid solution to remove oxidized metal from the surface in a process referred to as pickling. Since the metal now has a bare surface, the wheel is dipped into a solu- tion containing a corrosion inhibitor. The acid solution used for pickling and the solution of corrosion inhibitor do not gen- erate wastestreams because they are both replenished as needed. The wastes generated by painting are overspray solids, booth compound, booth wastewater, waste paint and thinner, and volatile organic compounds (VOCs). The current paint guns used in the Paint Shop typically transfer about 50% of the paint to . the.Jarget (when,,used properly). .The overspray contains solids that become entrained in the waterfall curtain. These solids accumulate as either floating scum or sludge. About 220 gal of sludge and scum are placed in 55-gal drums and hauled away each year. Booths are peri- odically coated with a protective film called booth compound to prevent adhesion to the metal walls. This material eventually peels from the booth surfaces or is manu- ally peeled as it deteriorates. A new coat- ing is then applied, and the old compound is discarded in a sanitary landfill. The booth water is drained to the sewage treatment plant every 2 mo to remove the sludge. No water treatment chemicals are added to the booth water. Paint thinner is used to clean paint gun nozzles to prevent clog- * Mention of trade names or commercial products does not constitute endorsement or recommen- dation for use. ------- ging. The mixed thinner and paint, along with unused paint, are placed in 30-gaI drums for disposal by Safety Kleen, Inc. VOCs are released as the spray guns atomize the paint. The water curtain does not control the emissions of these VOCs to the atmosphere since they are not soluble in water. The amount of VOCs generated depends on the amount of paint used and the amount of volatiles in the paints used. Printed Circuit Board Manufacture Scott AFB maintains a laboratory-scale circuit board production capability. A small quantity of circuit boards are needed as replacement parts or special designs for electronic instrumentation. Large quantity 'orders for circuit boards are hot handled by the facility. The three principal wastes generated are electroless copper solution, sodium persulfate solution, and ammonium persulfate solution. Since the process is proprietary, the constituencies of the solu- tions were not made available. If the sodium persulfate and ammonium persulfate solutions are hazardous wastes, it would be because they are corrosive (D002). The electroless copper solution probably contains formaldehyde, a listed nonacute hazardous waste (U122). Results and Discussion The assessment team visited three ar- eas at Scott AFB; NDI, painting/paint re- moval/parts cleaning, and printed circuit board manufacture. NDI was of special interest to the EPA because of its wide- spread use in the military and by commer- cial airlines. The WM options identified during the detailed analysis of the NDI process (see Appendix A of the full re- port) are discussed below and summa- rized in Table 1. No detailed analyses were performed for the other areas be- cause Scott AFB had either past or neared the implementation phase for several op- tions. A brief discussion of painting/paint removal/parts cleaning and printed circuit board manufacture is included in this sec- tion to highlight the current status of Scott AFB's effort and to suggest further en- hancements. Since the exact composition of solutions used were proprietary infor- mation, many uncertainties remain regard- ing the circuit board operation. Nondestructive Inspection (NDI) Option One Scott AFB has tried to address the waste generated by NDI inspection in the past. A feasibility study was conducted at Scott AFB to determine if the eddy-current equip- ment could be modified to handle the com- plete inspection including areas other than the bead seat area. Scott AFB determined that modifying the equipment was cost prohibitive. Option Two The current operating procedure calls for the emulsifier and developer tanks to be completely emptied and cleaned about every 6 mo to remove contaminants and to adjust the fluid characteristics to origi- nal specifications. The primary contami- nant (the penetrant) floats on or near the surface because of its low density. Option two involves an inexpensive method of periodically skimming the top layer of fluid in these tanks. By skimming off the top layer and adding either fresh makeup emulsifier or developer to the respective tanks, contaminants floating at or near the surface can be removed and suspended contaminants can be diluted. To remove the fbating penetrant, a drain valve could be installed on the side of the tank. To ensure adequate contaminant re- moval, the assessment was based on draining off 25 gal or 25% from each tank every 6 mo and completely draining and cleaning them out every 2 yr. With this amount of makeup, contaminant buildup should be controlled. This method has minimal capital cost, little or no effect on operation of NDI equipment, and no addi- tional O&M costs. The option represents a payback period of about 3 mo. A QA/ QC test program equivalent to the one provided by the supplier is necessary to evaluate this option. The option is also flexible in that the makeup and clean-out schedule suggested in this report can be easily modified. The suggested schedule assumes removal of 8 in. of fluid to elimi- nate the contaminants at the surface. Se- lecting 25-gal increments simplifies refill- ing the developer tank (after refilling to the 100-gal level, one full bag of devel- oper mix is required). Option Three The NDI-system vendor reports that they rarely specify wet developer baths with new dye penetrant inspection systems. To eliminate the need for the wet chro- mate solution, new systems use a dry, nonhazardous (silica-based) developer. These dry systems apply developer to the parts by one of two methods: (1) a swirl cloud, which involves placing the part in a shallow tank above a bed of dry devel- oper and expanding the bed of developer with air, or (2) a dynamic cloud, which subjects the part to a fine spray of dry developer similar to a painting-type pro- cess. The dynamic cloud is generally pre- ferred because it delivers a more uniform coating on the part and minimizes the amount of developer used. Dry developer application for either method is carried out in an enclosed booth and excess dust is collected by a filter system. Changing to the silica-based developer would be technically feasible. The same equipment and materials used for pen- etrant and emulsifier application could be used. The current process line would have to be modified so that the dryer preceded the developer station. Some additional space, roughly twice the height of the current developer station, would be re- quired to accommodate the dry developer booth. Switching to the dry developer would not adversely affect the sensitivity of the inspection. The vendor states that the dy- namic cloud yields better sensitivity be- cause a thinner and more uniform coating can be achieved. The dry developer is technically equivalent and meets the same specifications as the current wet devel- oper (including MIL-1-25135 REV.E). The dry developer method is, however, expen- sive in relation to the dollar savings. Palntlng/Palnt Removal/Parts Cleaning The plastic media blasting equipment should be used to eliminate the use of organic solvents in paint stripping. The equipment is onsite and lacks only a few miscellaneous parts before operation can begin. A comprehensive water treatment pro- gram for the wet spray booths should be initiated. By adding a coagulant, the per- cent solids in the sludge could be in- creased thus reducing disposal costs and the frequency of removal. A number of water treatment companies provide prod- ucts to optimize wet booth performance. Converting from a wet operation to a dry painting booth operation would reduce the volume of wastes associated with painting. Filters would collect the overspray solids instead of a water curtain. Dry paint booths do not generate any sludge or waste water, but the filters must be dis- posed of. Scott AFB is implementing the use of high volume, low pressure (HVLP) paint guns. Two such guns (which cost approxi- mately $1,200 each) are on order. The amount of overspray solids can be re- duced to about 10% to 20%, and the amount of VOCs can be substantially re- duced. Since the painting is more effi- cient, less paint is required, less VOCs are emitted, and less solids are collected by the water curtains. Other methods of controlling VOCs include the use of pow- dered coatings and/or the use of electro- static spraying systems. •&-U.S. GOVERNMENT PRINTING OFFICE: 1992 - 648-080/40120 ------- Printed Circuit Board Manufacture The process of manufacturing printed circuit boards is very complex with many steps in which solution compositions, treat- ment times, and temperatures are closely regulated. It may be difficult to modify the process and attain required product qual- ity. One approach to WM that might be considered, however, would be to change the electroless copper plating solution to eliminate materials such as formaldehyde. Other reducing agents such as sodium hypophosph'rte are preferable and produce good quality electroless copper deposits. Copper from the spent electroless plat- ing solution might be recovered with the use of sodium borohydride precipitation. Table 1. Summary of Waste Minimization Feasibility Analysis Phase Waste Minimization Options Capital Net Operating Waste Streams Nature of Investmenet Cost Savings,* Affected WM Option $ $/yr Rank Payback Low to Period, High yr (1-7) Modify eddy-current Penetrant Equipment 70,000 . equipment Emulsifier Developer 4,440 15.8 Modify SOP for changeout of emulsifier and developer Switch to silica- based dry developer Emulsifier Developer Developer Personnel/ 330 Procedure, Equipment Materials, 11,000 Equipment 1,390 0.24 6 400 27.5 1 * Disposal costs associated with wet developer were not Included because of uncertainty about how the developer will ultimately ba handled. Tills Project Summary was prepared by staff of Science Applications International Corporation, Cincinnati, OH 45203 Jamas S. Bridges and Anne ft. Robertson are the EPA Project Officers (see bebw). The complete report, entitled "Waste Minimization Opportunity Assessment- Scott Air Force Base," (Order No. PB92-105 402AS; Cost: $26.00, 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 This generates a metallic precipitate that could be recovered by filtration. Conclusions and Recommendations The results of the study indicate that the fastest payback (0.24 yr) for the NDI inspection of wheel hubs would be from Option 2. Option 2 involves modifying the SOP for changing the emulsifier and de- veloper; the bath life of developer and emulsifier could be extended by skimming off floating contaminants. The capital out- lay needed for this option is estimated to be only $330. Options 1 and 3 had payback periods of 15.8 and 27.5 yr, respectively. Option 1 involved modifying the eddy-current equip- ment so that it could replace the dye pen- etrant method for inspection of the wheel's bead seat area. This method had the high- est cost savings, but with a capital cost of $70,000, it is not economically feasible. Option 3, the switch to silica-based dry developer, has moderate capital invest- ment but low cost savings. If Scott AFB later determines that the wet developer should be treated as a D007 waste, the disposal costs for wet developer will in- crease and Option 3 will have a greater cost savings. The feasabilrty phase was completed for the NDI area only, but the assessment phase was completed for all of the se- lected areas at Scott AFB. Scott AFB is already implementing WM options for its painting operations. Because manufactur- ing printed circuit boards is complex and this operation involved a proprietary pro- cess, only one WM suggestion for the circuit board operation was made—change the makeup of the electroless copper plat- ing solution. The full report was submitted in fulfill- ment of Contract 68-C8-0061, WA 2-05, by Science Applications International Cor- poration under the sponsorship of the U.S. Environmental Protection Agency. 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/S2-91/054 ------- |