United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/M-91/020 July 1991
$EPA ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a Bumper Refinishing Plant
F. William Kirsch and Gwen P. Looby*
Abstract
The U.S. Environmental Protection Agency (EPA) has
funded a pilot project to assist small- and medium-size manu-
facturers who want to minimize their generation of hazardous
waste but lack the expertise to do so. Waste Minimization
Assessment Centers (WMACs) were established at selected
universities and procedures were adapted from the EPA Waste
Minimization Opportunity Assessment Manual(EP A/625/7-88/
003, July 1988). The WMACteam at Colorado State University
inspected a plant refinishing steel, aluminum, and plastic
bumpers. The plant is new and already incorporates many
hazardous waste management features. After the bumpers are
straightened, the processes to remove old plating and coating,
the rinsing, the caustic cleaning for steel bumpers and de-
smutting for aluminum ones, followed by more rinsing generate
significant quantities of waste. Aluminum bumpers are then
reanodized at another location; the steel bumpers are soaked
in cleaning solutions and rinsed (and soaked and rinsed),
creating still more waste, before being electrolytically replated
with nickel and chromium. The team's report, detailing findings
and recommendations, indicated that the greatest waste re-
duction could occur with the use of additional filtration along
with the existing deionization systems. Their use would reduce
chromium and nickel levels in rinse waters and other liquid
streams to levels acceptable for recycle to the plant. The
collected solids would go to a landfill for disposal. Because
steel and aluminum bumpers generate the most waste, plastic
bumpers were not considered for the purpose of this assess-
ment.
This Research Brief was developed by the principal inves-
tigators and EPA's Risk Reduction Engineering Laboratory,
'University City Science Center, Philadelphia, PA 19104
Cincinnati, OH, to announce key findings of an ongoing re-
search project that is fully documented in a separate report of
the same title available from the authors.
Introduction
The amount of hazardous waste generated by industrial
plants has become an increasingly costly problem for manufac-
turers and an additional stress on the environment. One solu-
tion 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 manufac-
turers who want to minimize their formation of hazardous waste
but lack the inhouse 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
manufacturing 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
annual sales not exceeding $50 million, employ no more than
500 persons, and lack inhouse expertise in waste minimization.
The potential benefits of the pilot project include minimiza-
tion of the amount of waste generated by manufacturers,
reduced waste treatment and disposal costs for participating
plants, valuable experience for graduate and undergraduate
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students who participate in the program, and a cleaner environ-
ment without more regulations and higher costs for manufactur-
ers.
Methodology of Assessments
The waste minimization assessments require several site
visits to each client served. In general, the WMACs follow the
procedures outlined in the EPA Waste Minimization Opportu-
nity Assessment 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
Refinished automobile bumpers - steel, aluminum, and
plastic -- are the chief products of this plant, which operates for
52 wk/yr and spends almost $15,000/yr to treat and dispose of
its wastes. Those costs would be considerably higher if this
plant, which was built only 3 to 4 yr ago, had not incorporated
certain features to aid in hazardous waste management into its
basic design. The WMAC team therefore faced a more difficult
challenge in further reducing hazardous waste emissions.
For example, the design of this plant had eliminated direct
drains from production areas to the sewer, had surrounded
certain chemical tanks with dikes so that any spillage or overflow
would be channeled to a central sump pump, and had taken
other precautions to reduce migration from spillage, such as
locating tanks below ground level.
In general, raw materials (used bumpers) follow one of
three possible paths in this plant:
Steel bumpers are straightened and cleaned before
being plated with nickel and chromium.
Aluminum bumpers are straightened and cleaned
before being reanodized (off-site).
Urethane bumpers (plastic) are treated to remove
paint before being repaired and repainted.
The direct focus of the WMAC team was on the first two
because they account for the bulk of the production and virtually
all of the hazardous waste generated at this plant. For metal
bumpers, the production level averaged almost 16,000/yr, and
about 80% of that was steel.
Steel Bumper Reflnlshlng
After being straightened, the steel bumpers are prepared
for refinishing by soaking in hydrochloric acid to remove old
plating; rinsing; immersing in metal cleaning solution (caustic
and sodium silicate); polishing; and grinding. Then the bumpers
are put through the plating line, where they are successively
soaked in a dilute cleaning solution and a sodium fluoride acid
soap solution with intermediate rinses, before being electrolyti-
cally replated with nickel first and then with chromium. A so-
called drag-out tank reduces liquid carryover from plating, and
deionized water is used for mufti stage countercurrent rinsing.
This sequence of operations includes several steps already
adopted by the plant to reduce the quantity of waste generated,
such as the use of:
Air agitation to ensure good circulation in the rinse
tanks and to lower the volume of rinse needed.
Deionized waterfor making process solutions and
for rinsing, because otherwise the calcium and
magnesium in the water supply would add to the
amount of sludge formed.
Less toxic trivalent chromium in the plating solution
to lessen the concentration (weight of chromium
per unit volume) and reduce treatment costs.
Drag-out tanks to capture most of the solution
carried out of the plating tanks before it reaches
the rinse. When the metal concentration in the
drag-out tank increases over a period of time, the
solution is recycled to the plating tank (for
chromium) or sent to a holding tank (for nickel),
where it is heated to decrease its volume by
evaporation.
Multi-stage countercurrent rinsing (rather than a
continuous flow) so that the bumpers are placed in
the most contaminated stage first and the cleanest
stage last.
Continuous filtration of the chromium and nickel
plating solutions to remove solid contaminants
and to allow the filtrate to be returned to the plating
tanks.
Periodically the cleaning solutions and the rinse tanks are
dumped into a sump and transferred to a storage and evapora-
tion tank. The metals are removed by adding sodium bicarbon-
ate, and the resulting sludge settles to the bottom. The remain-
ing liquid, after pH adjustment, has been hauled to a sanitary
landfill. The sludge has been sent to a hazardous waste landfill
even though not all the metals are hazardous.
Aluminum Bumper Reflnlshlng
The potential for hazardous waste to be derived from
aluminum bumper refinishing at this plant is considerably less
than it is for steel. First, the number of aluminum bumpers
among the plant's raw materials is only about one-fourth that of
the steel ones. Second, only part of the overall refinishing occurs
at this plant, and the operations that are carried out have
generated less hazardous waste than do those for refinishinq
steel. y
To remove the anodized coating on the bumpers brought
into the plant, they are first soaked in a tank of heated alkaline
de-ruster. After rinsing with tap water, the aluminum bumpers
are immersed in a de-smut tank and then rinsed again with tap
water. Aluminum bumpers are then reanodized at another
location.
Spent solutions and rinse water containing suspended
solids are accumulated in a sump, from which they are pumped
periodically to a storage and evaporation tank.
Summary of Hazardous Waste Generation and
Minimization
Table 1 integrates the information on hazardous waste
generation, listing the origins of hazardous liquid and solid
wastes, their quantities, and the magnitudes of their treatment
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and disposal costs before the WMAC team came to the plant.
Three waste minimization opportunities (WMOs) recom-
mended to the manufacturer will, if implemented, save about
half the current hazardous waste management costs at this
plant. They are summarized in Table 2, together with the
reductions in emissions and the associated savings and costs.
The quantities of hazardous waste emitted before and after
the WMOs are implemented will depend on the production level
of the plant. All values stated should be considered in that
context.
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. Environ-
mental Protection Agency. The EPA Project Off icer was Brian A.
Westfall.
The EPA contact, Emma L. George, can be reached at:
Pollution Prevention Research Branch
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
Table 1. Summary of Current Waste Generation
Waste Stream
Hazardous Liquid Waste
Stripping Line:
Rinse tank
Hot soak
Rinse hose
Plating Line:
Metal cleaner rinse
Acid soap rinse
Nickel rinse
Hazardous Solid Waste
Storage Tank:
Combination of stripping
and plating lines
Filters:
Nickel plating
Chromium plating
Hazardous Waste Generated
Hydrochloric acid drag-out
Spent metal cleaner
Alkaline de-ruster and de-smut
Annual Quantity
Generated
11,100 gal
9,700 gal
16,500 gal
Metal cleaner drag-out 21,900 gal
Sodium fluoride acid soap drag-out 14,500 gal
Nickel plating drag-out 10,900 gal
Total 84,600 gal
Metal hydroxide sludge
Filter cake and filters2
Filter cake
Total
4,500 Ib
500 Ib
500 Ib
5,500 Ib
Annual Waste Management Costs
Treatment Disposal
$6,8001
$3,910
4.2003
All liquids, after transfer to storage tank, are treated before disposal.
Note that although the filter cakes and filters from the nickel plating tank are presently classified as nonhazardous, management has chosen to
treat this waste as hazardous in the event that nickel is reclassified in the near future.
Cost of solids testing, hauling, and disposal.
•&U.S. GOVERNMENT PRINTING OFFICE: 1991 - 548-028/40024
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Table 2. Summary of Recommended Waste Minimization Opportunities
Present Practice Proposed Action
Rinse water and other liquid
streams are collected and treated
with sodium bicarbonate to
precipitate most of the metals as
sludge.
Sludge from precipitation of metals
is combined with residue from
filtration of plating solutions and
sent to hazardous waste landfill.
Weight = 5500 Ib/yr.
Tap water is used freely to rinse
aluminum bumpers after they are
stripped of anodized coating. This
rinse is combined with other liquids
and the total is sent for landfill disposal.
Use additional filtration
and existing deionization
systems to reduce chromium
and nickel levels to
acceptable limits and to
ensure quality of water for
recycle to plant. Add
small additional solid
collected to hazardous waste
going to landfill for disposal.
This WMO is a volumetric
reduction only.
Dewater the sludge by
heating it. Continuous
dewatering is possible by
loading the sludge into a
hopper and feeding it by an
auger to a burner tube fueled
by natural gas or LPG. The
weight of hazardous waste sent to
the landfill will be reduced.
Constrict the flow of tap water
from 6 to 3 gal/rnin. If a higher
pressure water, stream is needed,
substitute a wand spray gun. Then a
booster pump will be needed, but
the flow can be reduced to
about 06 gal/min.
Waste Reduction and Associated Savings
Waste reduction = 84,600 gal/yr
Net cost saving = $ 3,625/yr
Implementation cost = $ 4,500
Simple payback = 1.3 yr
Waste reduction = 3,874 Ib/yr
Net cost saving = $ 2,914/yr
Implementation cost = $ 10,000
Simple payback = 3.4 yr
Estimated waste reduction = 8,246 gal/yr
Estimated cost reduction = $ 1,039/yr
(based on the cost to haul liquids to landfill)
Estimated implementation cost = less than $10
Simple payback = less than 1 mo
United States
Environmental Protection
Agency
Official Business
Penalty for Private Use $300
Center for Environmental
Research Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/M-91/020
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