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
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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.
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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
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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
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