United States
                Environmental Protection
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-
                  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).

                  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.

  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
  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-
  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-
  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
  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-
  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
  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-
   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
   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

 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
   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
   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
   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
  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
                          Capital     Net Operating
Waste Streams  Nature of  Investmenet   Cost Savings,*
   Affected    WM Option      $           $/yr
Payback Low to
 Period,   High
   yr     (1-7)
Modify eddy-current   Penetrant    Equipment    70,000 .
  equipment         Emulsifier
Modify SOP for
changeout of
emulsifier and
Switch to silica-
based dry
Personnel/ 330
Materials, 11,000
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
  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
                        Center for Environmental Research
                        Cincinnati, OH 45268
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