&EPA
                          United States
                          Environmental Protection
                          Agency
                                  Risk Reduction
                                  Engineering Laboratory
                                  Cincinnati, OH 45268
                          Research and Development
                                  EPA/600/M-91/015  Jul. 1991
ENVIRONMENTAL
RESEARCH   BRIEF
       Waste Minimization Assessment for a Metal Parts Coating 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 manufacturers
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 Minimiza-
tion Opportunity Assessment Manua/(EPA/625/7-88/003, July
1988). The WMAC team at the University of Tennessee per-
formed an assessment at a plant where automotive parts are
coated with epoxy, vinyl, or  polyester powders; with liquid
plastisol; or with  paint. After the WMAC team analyzed five
process lines (for applying coatings) and the reworking opera-
tion (where unacceptably finished parts are stripped), a report
was prepared detailing their findings and recommendations.
They found three ways to reduce the evaporation of methylethyl
ketone (MEK), the largest source of waste on the process lines:
reduce the open surface area of the MEK container, cool the
MEK,  or meter the MEK. They also found ways to reduce
wastes from the rework process by installing controls, repairing
defective drive components, or using alternative methods to
remove defective coatings.

This Research Brief was developed by the principal investiga-
tors and EPA's Risk Reduction Engineering Laboratory, Cin-
cinnati, OH, to announce key findings of an ongoing research
project that is fully documented in a separate report of the same
title available from the authors.
'University City Science Center, Philadelphia, PA 19104.
                     Introduction
                     The amount of hazardous waste generated by industrial plants
                     has become an increasingly costly problem for manufacturers
                     and an additional stress on the environment. One solution 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 manufacturers
                     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 the University of
                     Tennessee's (Knoxville) 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 minimization
                     of the amount of waste generated by manufacturers, reduced
                     waste treatment and disposal costs for participating plants,
                     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 Manua/(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
 The plant coats metal automotive parts with  epoxy, vinyl, or
 polyester powders;  liquid plastisol (a vinyl plastic in a liquid
 carrier); or paint. Each year, the plant produces approximately
 52 million parts ranging in size from 1/4 to 1 Ib.

 Coating Operations
 The following basic steps are employed to coat the  metal parts:

         surface cleaning and/or priming the metal parts,

         heating metal parts for improved coating  in a natural
         gas or electric oven at 350° F to 900° F,

         applying the desired coating,

    •    curing the coated part in a natural gas, electric, or infra-
         red oven, and

         water- or air-cooling the finished parts.

 The following distinct process lines were analyzed by the WMAC
 team, with each line using a different method for applying the
 coating:

         a line for the dipping of parts in a f luidized bed of water
         containing epoxy, nylon, or vinyl powders;

         two lines for dipping parts in plastisol, one of which
         includes a step for applying a priming coat;

         a line in which plastisol is  mechanically applied to
         specific areas of small metal parts;

         two lines for the spraying of parts with a polyester or
         epoxy powder; and

         a line for the electrostatic painting of parts.

 Rework Operations
 Unsatisfactory coating of the parts can result from  inadequate
control of the  level of the coating material in the troughs;
adhesion problems related to improper curing oven tempera-
tures; variations in the speed of the parts conveyors; environ-
mental dust; or inadequate  coating thickness resulting from
mechanical breakdowns. The plant uses three different rework
operations to reclaim unacceptable finished parts.

        Epoxy, nylon, or vinyl coatings applied in the f luidized
        bed line and the coatings apptied to 75% of the parts in
         the electrostatic paint line are removed by incinerating
         the parts in a natural gas oven at 1150° F. (The rework
         operation used for the electrostatically painted parts is
         determined by the type of paint used.)

         Plastisol coatings are removed by overnight immer-
         sion in MEK.

         The coatings of 25% of the parts rejected after the
         electrostatic painting and all of the parts rejected after
         the polyester powder spray lines are removed with a
         commercial acid stripping solution.

 The reclaimed metal parts are sent back to the appropriate
 process line after reworking.

 Water Treatment
 The assessment team also anatyzed the plant's water treatment
 facility. Waste water streams from the process lines are fed into
 three major collection pits; from there, the waste water feeds into
 a large tank. The pH of the water is adjusted as necessary and
 the fluid is pumped to a large sludge tank where solid sludge
 settles out. Plant personnel have  not determined the nature of
 the sludge; however, a substantial amount of sludge has not yet
 accumulated on-site. The water that is separated from the
 sludge goes to a municipal sewer.

 Waste Minimization Opportunities
 The type of waste currently generated by the plant, the source
 of the waste, the quantity of the waste, and the annual treatment
 and disposal costs are given  in Table 1.

 Table 2 shows the various opportunities for waste minimization
 that the  WMAC team identified for the facility. The type and
 source of the waste, the minimization opportunity, the possible
 waste reduction and associated savings, and the implementa-
 tion cost along with the payback time are described in the table.

 As shown in Table 2, two sources of waste are the focus of the
 waste minimization opportunities analyzed and recommended
 by the WMAC. The first is the evaporation of MEK used as a
 primer thinner in the plastisol dipping and mechanical applica-
 tion lines. Three possible methods for reducing the amount of
 evaporation are described in the table. The other source of the
 waste  is the rework operation. The generation of waste by the
 rework processes can be reduced either by reducing the number
 of parts that require reworking (through installation of controls or
 repair of defective drive components) or by using an alternative
 method to remove the defective coatings.

 The quantities of hazardous waste currently generated by the
 plant and possible waste reduction depend upon the production
 level of the plant. All values stated should be considered in that
 context.

 Issues for Further Consideration
 In addition to the recommended waste minimization opportuni-
ties, the  WMAC team indicated that plant personnel should
continue to investigate the possible availability of a new, less
 hazardous stripper/thinner to replace MEK and that each waste
water stream should be analyzed to determine its composition.
The current method for handling the waste water in the plant is
inefficient and imprecise.

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Table 1. Summary of Current Waste Generation.
Waste Generated
MEK (used as a primer thinner)
MEK
Plastisol sludge (contains
plastisol & MEK)
Spet acid stripping solution
Stripped paint residue & residual
spent stripper
Paint residue in paint tank
Spent, contaminated primer
Ash
Source of Waste
Evaporation from plastisol dipping and
mechanical application lines
Evaporation from plastisol rework line
Plastisol rework line
Acid stripping rework line
Acid stripping rework line
Electrostatic painting line
Plastisol lines
Incineration oven in rework line
Annual Quantity
Generated
8,400 gal
3,900 gal
600 gal
2, 100 gal
250 to
4,800 gal
680 gal
1,200 to4
Annual Waste
Management Cost
$0'
O1
O2
10,410
O3
20,020
3,560
1,260
 1 Currently there are no costs for monitoring or controlling MEK emissions from evaporation; however, the MEK that evaporates must be
  replaced.
 2 Plastisol sludge is disposed of in municipal waste.
 3 The material is accumulating on-site. There are no current costs for waste management.
 4 Of the total 1,200 Ib/yr of ash produced, 700 Ib/yr resulting from the electorstatic painting rework is considered hazardous. The remaining
  ash is disposed of in municipal waste.


 Table 2.  Summary of Recommended Waste Minimization Opportunities.
Annual Waste Reduction
Waste Generated
Evaporation of MEK from
plastisol dipping and
mechanical application
lines

Minimization Opportunity
Reduce open surface area
of primer/MEK container.
Cool MEK to reduce its
partial pressure.
Meter MEK concentration
Quantity
3, 160 gal
840 gal
1 ,400 gal
Percent
37.6
10.0
16.7
Net Annual
Savings
$11,240'
3.0001
4,980'
Implementation Payback
Cost Years
$3,000
2.900
12,400
0.3
1.0
2.5
Spent acid stripper from
the rework line

Stripped paint residue
and residual stripper
from rework line

Ash from the incineration
oven
MEK used in rework
line

Plastisol sludge

Spent acid stripper from
rework line
automatically to reduce
peak evaporation rate.

Install interlocking controls    1,510 gal
on the conveyor's speed and
paint volume flows in the
electrostatic painting and      180lb
powder spray lines
Replace defective drive
system components in
electrostatic paint line.
469 Ib
Install a cryogenic-           3,900 gal
mechanical stripping system
to remove coatings of rework
parts.                        600 gal

                            2,100 gal
 72.1


 72.1



 67.0



100.0


100.0

100.0
 22.4302


134.0403



  2.5304



 13.8801


     O4

 42.780s
                                                  24,600
0.2
                                                   3,400         1.3
                                                 150.000         2.6
1  Cost savings because less MEK needed.
2  Includes $14,810/yr because less stripper is needed.
3  The material is accumulating on-site. There are no current costs for waste management. The cost savings are because less coating material
  needed.
4  Includes $1,900/yr because less paint needed.
5  Includes $32,370/yr attributed to purchase of stripper.
                                                                               6 U.S. GOVERNMENT PRINTING OFFICE: 1991 - S4»-0«t/40036

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This Research Brief summarizes a part of the work done under      The EPA contact, Emma L. George, can be reached at:
Cooperative Agreement No. CR-814903 by the University City
Science Center under the sponsorship of the U.S. Environmen-          Pollution Prevention Research Branch
tal Protection Agency. The EPA Project Officer was Brian A.          Risk Reduction Engineering Laboratory
Westfall.                                                        U.S. Environmental Protection Agency
                                                               Cincinnati, OH 45268
United States                           Center for Environmental Research           BULK RATE
Environmental Protection                 Information                                POSTAGE & FEES PAID
Agency                                 Cincinnati OH 45268                       EPA PERMIT NO. G-35
Official Business
Penalty for Private Use $300

EPA/600/M-91/015

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