United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S-94/005 September 1994
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a Manufacturer
of Finished Metal and Plastic Parts
Harry W. Edwards*, Michael F. Kostrzewa*,
and Gwen P. Looby**
Abstract
The U.S. Environmental Protection Agency (EPA) has funded
a pilot project to assist small and medium-size manufacturers
who want to minimize their generation of waste but who lack
the expertise to do so. In an effort to assist these manufactur-
ers, Waste Minimization Assessment Centers (WMACs) were
established at selected universities, and procedures were
adapted from the EPA Waste Minimization Opportunity As-
sessment Manual (EPA/625/7-88/003, July 1988). That docu-
ment has been superseded by the Facility Pollution Prevention
Guide (EPA/600/R-92/088, May 1992). The WMAC team at
Colorado State University performed an assessment at a plant
that applies coatings to metal and plastic components supplied
by its customers. Several different coating operations are per-
formed, but the ones that generate consistent and significant
quantities of waste are anodizing of aluminum parts, chromating
of aluminum parts, and painting of plastic and metal parts. The
team's report, detailing findings and recommendations, indi-
cated that large quantities of spent rinse water and process
solutions, and spent solvent and still bottoms are generated by
the plant and that the life of the black dye bath could be
extended to yield significant cost savings.
This Research Brief was developed by the principal investiga-
tors and EPA's Risk Reduction Engineering Laboratory, Cincin-
nati, OH, to announce key findings of an ongoing research
project that is fully documented in a separate report of the
same title available from University City Science Center, Phila-
delphia, PA.
* Colorado State University, Department of Mechanical Engineering, Fort Collins,
CO.
"University City Science Center, Philadelphia, PA
Introduction
The amount of waste generated by industrial plants has be-
come an increasingly costly problem for manufacturers and an
additional stress on the environment. One solution to the
problem of waste generation is to reduce or eliminate the
waste at its source.
University City Science Center has begun a pilot project to
assist small and medium-size manufacturers who want to
minimize their generation of waste but who lack the in-house
expertise to do so. Under agreement with EPA's Risk Reduc-
tion Engineering Laboratory, the Science Center has estab-
lished 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 ex-
perience with process operations in manufacturing plants and
also have the knowledge and skills needed to minimize 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 $75 million, employ no more than
500 persons, and lack in-house expertise in waste minimiza-
tion.
The potential benefits of the pilot project include minimization
of the amount of waste generated by manufacturers and re-
duction of waste treatment and disposal costs for participating
plants. In addition, the project provides valuable experience for
graduate and undergraduate students who participate in the
program and a cleaner environment without more regulations
and higher costs for manufacturers.
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Methodology of Assessments
The waste minimization assessments require several site visits
to each client served. In general, the WMACs follow the proce-
dures outlined in the EPA Waste Minimization Opportunity
Assessment Manual (EPA/625/7-88/003, July 1988). The WMAC
staff locate the sources of waste in the plant and identify 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 supporting tech-
nological and economic information is developed. Finally, a
confidential report that details the WMAC's findings and recom-
mendations (including cost savings, implementation costs, and
payback times) is prepared for each client.
Plant Background
This plant is a job shop that applies coatings to metal and
plastic components supplied by its customers. It operates 4,940
hr/yrto produce approximately 234,000 ft2 of product annually.
Existing Waste Management Practices
This plant already has implemented the following techniques to
manage and minimize its wastes:
Flow reducers have been installed on all flowing rinses in the
anodizing and chromating lines.
A solvent distillation unit is used to recover paint-related
solvents which are then reused by the plant.
The use of water-based instead of solvent-based paints is
significant and is increasing. Plant personnel encourage
customers to specify water-based and powder-based paints.
Operators use care in raising part racks slowly from the
process solutions and allowing sufficient drainage time to
reduce drag-out in the anodizing and chromating lines.
Water used to cool Freon in the chillers associated with the
anodizing tanks is reused as rinse water.
Manufacturing Process
Prefabricated aluminum, steel, and plastic parts are supplied to
the plant by its customers who specify the coating or paint that
is to be applied. The plant performs several different coating
operations, but the ones that generate consistent and appre-
ciable amounts of waste are anodizing of aluminum parts,
chromating of aluminum parts, and painting of plastic and
metal parts.
Anodizing
Aluminum parts to be anodized are first immersed in a caustic
solution and then an etching solution to remove surface con-
taminants. Smut that remains on the parts after etching is
removed using an acidic deoxidizing solution. A surface oxide
layer is then formed on the parts in an aqueous electrolytic
bath that contains sulfuric acid. The anodized parts are then
dyed one of five colors or left undyed. Next, an aqueous nickel
fluoride solution is used to seal the oxide layer. The last step is
rinsing of the finished parts. The anodized parts are then
assembled if necessary, packaged, and shipped back to the
customer.
Chromating
Chromate conversion coatings are applied to aluminum parts
by first immersing the parts in a series of aqueous solutions for
cleaning, etching, and acidic deoxidizing. The parts are then
immersed in the chromate conversion solution and rinsed. The
finished parts are then painted if required, inspected, assembled
if necessary, packaged, and shipped back to the customer.
Painting
Parts that require painting are painted in one of three spray
paint booths. Water-based, solvent-based, and powder coat-
ings are used by the plant according to the customer's specifi-
cations. Special tooling supplied by the customer is used to
mount the parts to be painted. After the coating has been
applied, the parts are placed in an oven for curing and drying.
The completed parts are inspected, packaged, and shipped
back to the customer.
An abbreviated process flow diagram for this plant is shown in
Figure 1.
Waste Minimization Opportunities
The type of waste currently generated by the plant, the source
of the waste, the waste management method, the quantity of
the waste, and the annual waste management cost are given
in Table 1.
Table 2 shows the opportunities for waste minimization that the
WMAC team recommended for the plant. The minimization
opportunity, the type of waste, the possible waste reduction
and associated savings, and the implementation cost along
with the payback time are given in the table. The quantities of
waste currently generated by the plant and possible waste
reduction depend on the production level of the plant. All
values should be considered in that context.
It should be noted that the economic savings of the minimiza-
tion opportunity, in most cases, results from the need for less
raw material and from reduced present and future costs asso-
ciated with waste treatment and disposal. Other savings not
quantifiable by this study include a wide variety of possible
future costs related to changing emissions standards, liability,
and employee health. It also should be noted that the savings
given for each opportunity reflect the savings achievable when
implementing each waste minimization opportunity indepen-
dently and do not reflect duplication of savings that may result
when the opportunities are implemented in a package.
Additional Recommendations
In addition to the opportunities recommended and analyzed by
the WMAC team, one additional measure was considered. This
measure was not completely analyzed because it was beyond
the scope of this analysis. Since this approach to waste reduc-
tion may, however, yield significant savings, it was brought to
the plant's attention for future consideration.
Modify the on-site solvent distillation unitinorderto raise the
temperature and the recovery factor.
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. Environmen-
tal Protection Agency. The EPA Project Officer was Emma
Lou George.
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Steel parts,
plastic parts
Aluminum parts
Aluminum parts
1
Chromate conversion
alkaline cleaner
alkaline etch
acidic deoxidizer
chromating
rinse
Spenf solutions,
rinse water
treated on-site
1
Anodizing
alkaline cleaner
alkaline etch
acidic deoxidizer
anodizing
dye
seal
rinse
/ Solvent
\ evaporation
Painting
masking
coating
Inspection
Curing & drying
I
Spent solvent
recycled on-site
Packaging
T
Inspection
Coated parts
returned to
customers
Packaging
Coated parts
returned to
customers
Figure 1. Abbreviated process flow diagram.
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Table 1. Summary of Current Waste Generation
Waste Generated
Spent process solutions
Spent black dye solution
Spent rinse water
Caustic sludge
Spent solvent and still bottoms
Paint sludge
Evaporated solvent
Aluminum oxide sludge
* Includes waste treatment, disposal,
Table 2. Summary of Recommended
Minimization Opportunity
Source of Waste
Anodizing and chromating
Anodizing
Anodizing and chromating
Wastewater treatment
Painting and on-site solvent
recovery unit
Washer in painting line
Painting
Stripping of anodizing racks
and reject parts
Waste Management Method
pH adjusted; sewered
pH adjusted; sewered
pH adjusted; sewered
Stored on-site pending disposal
(Plant personnel are evaluating
possible reuse of this material for
neutralizing rinse water and spent
acidic solutions.)
Shipped to a treatment, storage,
disposal facility
Stored on-site pending disposal
(Sludge will be shipped off-site when
a larger quantity has accumulated.)
Evaporates to plant air
Stored on-site pending disposal
(Sludge will be shipped off-site when
a larger quantity has accumulated.)
Annual Quantity
Generated (Ib)
3,140,810
21,660
17,840,700
7,330
13,580
1,440
2,940
N/A
Annual Waste
Management Cost*
$37,920
13,640
5,600
2,100
11,970
1,640
870
N/A
and handling costs and applicable raw material costs.
Waste Minimization Opportunities
Waste Stream
Annual Waste Reduction
Reduced Quantity (Ib) Per cent
Net Annual
Savings
Implementation
Cost
Simple
Payback
(yr)
Extend the life of the black dye bath by
installing a cation exchange column to
remove dissolved aluminum, and a filtration
unit to remove particulate contaminants suspend-
ed in solution and sulfate in the form of insoluble
barium sulfate precipitate. A small amount of
barium sulfate sludge will be generated.
Operate the on-site solvent recovery unit more
frequently to reduce the amount of spent
solvent that is shipped off-site without being
reprocessed.
Black dye solution
17,330
80
$10,240
$4,930
Spent solvent and still bottoms
3,920
29
2,770
0.5
Immediate
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United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/S-94/005
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