United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S2-91/038 Sep. 1991
Project Summary
Waste Minimization
Opportunity Assessment:
A Truck Assembly Plant
The U.S. Environmental Protection
Agency (EPA) has developed a sys-
tematic approach to identify, evaluate
and implement options to reduce or
eliminate hazardous waste. The ap-
proach is presented in a report entitled
"Waste Minimization Opportunity As-
sessment Manual" (EPA/625/7-88/003).
To encourage use of this manual, EPA
is conducting a series of assessment
projects under the Waste Reduction
Assessments Program (WRAP)—sur-
veys of waste practices and evalua-
tions of waste reduction opportunities
at selected sites.
The report summarized here de-
scribes the application of waste mini-
mization procedures to a truck assem-
bly facility. The focus of the assess-
ment was on painting and related pro-
cedures. A systematic assessment of
the facility identified seven possible
options that would be of interest to
this company and other companies in-
volved in spray painting, solvent
degreasing, zinc phosphating, and
electro-coat painting. This facility vol-
unteered to participate in the project
and provided technical support during
the study.
This Project Summary was developed
by EPA's Risk Reduction Engineering
Laboratory, Cincinnati, Ohio, to an-
nounce 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 purpose of this project was to dem-
onstrate the application of EPA's Waste
Minimization Opportunity Assessment
Manual to a truck assembly facility. The
manual provides a systematic, planned
procedure for identifying ways to reduce
or eliminate waste.
The facility produces trucks and spe-
cializes in custom paint colors and de-
signs. This facility assembles five differ-
ent models. The production processes
are primarily related to assembly and paint-
ing while the majority of the components
of the vehicles are manufactured at other
sites.
Production is done on one main assem-
bly line which begins with the chassis
(frame rails) and ends with a ready-to-
start truck. Associated assembly/finishing
procedures such as cab painting, door
assembly, phosphating of small parts, etc.,
are done on small assembly lines which
incorporate their finished work into the
main assembly line. The assembly line is
continuously moving and tight schedule is
required to produce the specified number
of trucks in one 8-hour period. Production
processes selected for this assessment
include spray painting, degreasing and
phosphating (E-Coat). The following
wastestreams are produced at the facility;
waste paint-liquid, waste paint-solid,
detackified paint, paint booth water,
degreasing solvent, rinse waters, spent
process solutions (cleaner, activator and
sealer), and phosphate bath and tank bot-
toms.
Printed on Recycled Paper
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Procedure
The waste minimization assessment pro-
cedure is a systematic framework that can
be used by a facility's own employees to
identify waste minimization opportunities.
As a structured program, it provides inter-
mediate milestones and a step-by-step pro-
cedure to understand the facility's pro-
cesses and wastes, to identify options for
reducing waste, and to determine if the
options are technically and economically
feasible to justify implementation. These
procedures consist of four major steps: 1)
planning and organization; 2) assessment;
3) feasibility analysis; and 4) implementa-
tion. This project completed the first three
steps of the procedures for various pro-
cesses used. Implementation is at the
discretion of the host facility.
The focus of the waste minimization
assessment was on painting and related
processes. The truck company staff par-
ticipated in the surveys by providing
background information and data about
the facility, equipment, processes, operat-
ing procedures, waste generation, and
waste minimization options. The person-
nel and management at the facility also
provided ideas for waste minimization and
input to the ranking criteria used for evalu-
ating waste minimization options. This
information was used later in the study to
incorporate the facility's preferences in the
evaluation process.
Results and Discussion
Seven options were identified that are
potentially applicable to the facility.
Option 1. Paint Solids
Dewatering and Water Recycle
Detackified paint that has accumulated
in the paint booth reservoirs over a period
of 4 to 6 weeks is pumped directly to a
tank truck and hauled to a disposal site.
The high water content of the detackified
paint increases disposal costs, which are
based solely on volume. Dewatering this
detackified paint can significantly reduce
disposal costs by reducing the volume of
waste sent to disposal. Further, recycling
the paint booth water will reduce water
use and extend the period between re-
quired draining and cleaning of the booths;
thus both the production downtime and
the chemicals needed to maintain the qual-
ity of the paint booth water can be re-
duced.
The detackified paint can be dewatered
with the use of a belt filter. The belt filter
is an automatic gravity filtration system
that typically uses a disposable fabric as
the filter media. The detackified paint will
be pumped from the paint booth to the
belt filter. The fabric media filters out the
paint solids and other debris while the
water passing through is recycled to the
paint booth reservoir. The detackified paint
is rolled off of the fitter into a drum for
disposal.
Option 2. Improve Painting
Transfer Efficiency
Transfer efficiency refers to the per-
centage of paint that leaves the paint gun
and is actually deposited on the part's
surface. Two types of spray painting
equipment having high transfer efficien-
cies are high volume-low pressure (HVLP)
and electrostatic. The facility currently
uses HVLP in their chassis paint booth
and achieves a transfer efficiency of ap-
proximately 50%. Electrostatic spray paint-
ing may further increase chassis painting
efficiency; some preliminary tests at the
plant have achieved positive results.
The cab painting equipment has been
modified and the operating pressure was
reduced from 60 to 40 psi. Although trans-
fer efficiency is approximately 35%, it is
unclear whether further increases in effi-
ciency are technically feasible for cab
painting.
Option 3. Procedural and
Small-Equipment Changes
The facility is currently investigating a
variety of procedural and small-equipment
changes to improve their waste minimiza-
tion efforts for the spray painting opera-
tions. The following is a discussion of
each change.
Shipping Unused Paint With the
Finished Truck—
Small volumes (<1 gal) of unused paint
are left over from the cab painting opera-
tion. Many of the cabs are custom painted,
and the unused paint that is not immedi-
ately reusable is discarded. The proposed
change involves packaging the unused
paint in a suitable container and shipping
it with the truck for later use by the cus-
tomer for needed touch-ups. Before imple-
mentation, regulatory constraints govern-
ing this option will be evaluated.
Adjusting the Production
Schedules to Reduce Color
Changes—
After painting each truck cab, the paint-
ing system must be cleaned out unless
the same color is used to paint the next
truck. Although the painting sequence is
presently considered when the overall pro-
duction schedule is developed, improve-
ment is still possible. The painting se-
quence should receive still greater con-
sideration because the waste generated
from painting is so closely tied to the num-
ber of clean-outs.
Installation of Control and
Monitoring Devices and Alarms on
Painting Systems—
The transfer efficiencies of the spray
painting operations are operator depen-
dent and are partly related to the air pres-
sures used. High pressures generally re-
duce the transfer efficiency and therefore
increase waste generation. Operators of-
ten use higher-than-necessary air pres-
sures because the higher pressures re-
duce painting time. Reducing air pres-
sure levels involves the use of air pres-
sure controls on the painting system, digi-
tal displays of the air pressure that are
visible by the foremen, and high pressure
alarms. Another device that could be
used is a microprocessor control for paint
flow; these devices closely control the flow
rate of paint and can be expected to in-
crease transfer efficiency.
Painting Details Over Background
Colors—
Many of the trucks produced at the fa-
cility are custom painted. The painting
designs often include details such as
stripes. Currently, when stripes are or-
dered, the cab is entirely painted with the
color of the stripe. The stripe is then
masked, and the cab is repainted with the
general or "background" color. This pro-
cedure is used because it requires less
masking, which is labor intensive.
Changing this procedure by reversing
the sequence would significantly reduce
the volume of paint sprayed and therefore
the waste produced by overspray. The
higher masking costs may be justified
when both the costs for paint and the
disposal costs for related wastes are con-
sidered.
Option 4. Reduce Paint Mix
Volume
Paints for cab painting are custom mixed
with the use of an automated device in
the paint mix room. The volume of paint
mixed is recorded in a computer data base,
with the volume depending on the truck
model and the type of paint. After paint-
ing, the painters return the unused paint
to the mix room where it is discharged
into drums. The unused volume is re-
corded in the data base. By reviewing
this data base, the facility is able to mini-
mize waste.
Option 4 involves more extensive use
of the painting data base to reduce the
volumes of paint mixed and paint wasted.
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The computer software can generate sta-
tistical analyses of paint mixed and wasted
for different truck models and paint types.
Implementing this option is expected to
reduce raw material costs (paint) and
waste disposal costs (unused paint).
Options. Minimize
Contamination of Degreaslng
Solvent
During the wiping process used to
degrease the chassis, operators currently
use solvent-soaked rags, which are rinsed
and stored in a bucket. When the solvent
in the bucket becomes overly contami-
nated with oil, grease, and dirt, it is dis-
carded into a drum to await disposal. This
option involves a minor equipment and a
procedural change to prevent the con-
tamination of solvent.
To reduce the volume of discarded sol-
vent, the solvent bucket should be elimi-
nated. Instead, a container that delivers
fresh solvent by hand pumping should be
used to soak the wiping rags. This con-
tainer should have a secure lid to prevent
the operators from rinsing rags in the fresh
solvent. Dirty rags should be wrung-out
over a waste solvent container.
This option may require that the rags
be changed more frequently because the
rinsing step currently used would no longer
be available. Because these rags are
currently recycled through an industrial
laundry, additional wastes are not expected
from this practice.
Option 6. Ion Exchange With
Recycle of Rinse Waters
On the zinc phosphate/E-Coat line,
which consists of several processing and
rinsing steps, there are three rinse tanks:
hot rinse, ambient temperature rinse, and
distilled water rinse. The rinse tanks are
fed on a continuous basis and discharged
to a sewer line that conveys the wastewa-
ter to the pretrealment system where it is
combined with paint booth waters and then
chemically treated. The resultant sludge
is considered a listed hazardous waste.
This option involves the use of an ion
exchange recycle system to treat the rinse
waters, after which they would be recycled
to the phosphating line on a continuous
basis. The system would reduce water
usage and may also reduce the volume of
sludge generated by the pretreatment sys-
tem. Currently, the pretreatment process
includes the use of ferric chloride in the
flocculation/precipitation system; this re-
sults in high sludge volumes. The ion
exchange system may reduce the use of
ferric chloride by breaking the phosphate
complex and by reducing the hydraulic
loading of the pretreatment system. The
heavy metals, such as zinc, would be
retained on the cation column, and the
anions, such as phosphate, would be re-
tained on the anion column. The
regenerant from the cation column would
contain regulated metals and would re-
quire pretreatment before discharge. The
regenerant from the anion column may
not contain any regulated pollutants, and
it may be possible to discharge it following
simple neutralization, thus eliminating it
from the treatment process.
Before implementing this option, the fa-
cility should conduct tests to select the
optimal ion exchange resins and to deter-
mine its effect on the ferric chloride re-
quirements.
Option 7. E-Coat Line Bath
Maintenance
The spent process solutions (cleaner,
activator and sealer) are discarded ap-
proximately every 2 weeks and reformu-
lated with fresh chemicals. The discarded
solutions are drained to the treatment sys-
tem. Concentrated wastewaters such as
these require a significant volume of chemi-
cal reagents for treatment and result in
high sludge volumes. This option involves
the use of filtration devices to remove
undissolved contaminants and to maintain
the solution in working condition for an
extended time period.
Conclusions and
Recommendations
The assessment phase of the waste
minimization procedure included collect-
ing the data, selecting the target areas,
reviewing the data, and generating and
screening options Based on the results
of the assessment phase, six waste mini-
mization options were selected for further
evaluation in the feasibility analysis phase.
The waste minimization feasibility analy-
sis phase is summarized in Table 1.
The technical feasibility evaluation ini-
tially determines the nature of the waste
minimization options, either equipment-re-
lated, personnel/procedure-related or ma-
terials-related. For each of the three types
of options, specific information and data
are required. For equipment-related op-
tions, the information requirements relate
to the state of the technology, availability
of equipment, performance specifications,
testing, space and utilities, production ef-
fects, and training. For personnel/proce-
dure-related options the required informa-
tion relates to training and operating in-
struction changes. For materials-related
options, the required information relates
to production impacts, storage and han-
dling, training, and testing.
The relative comparison used in this
study indicates that the three best options
are: Option 4—reducing paint mix vol-
umes through closer control, Option 5—
minimizing solvent contamination by using
a different working container and proce-
dures, and Option 2—improving transfer
efficiency by installing electrostatic paint-
ing in the chassis booth. Two options
ranked with moderately good scores: Op-
tion 1—dewatering paint solids and recy-
cling the booth waters and chemicals and
Option 6—using ion exchange to recycle
the phosphate/E-coat rinse water. Option
7—bath maintenance on the phosphate/
E-coat line ranked last, although still within
a reasonable range. Option 3—proce-
dural and small-equipment changes for
painting—was not evaluated during the
feasibility analysis phase because the
costs and savings could not be projected
at this time. The Option 3 waste minimi-
zation techniques, however, appear to be
technically and economically viable.
Some testing is needed before imple-
menting several of the options. For Op-
tion 1, testing should focus on determin-
ing if recycle can significantly reduce booth
chemical use. A conservative assumption
was made during the analysis that a 10%
reduction is possible. For Option 2, the
facility should contact electrostatic paint
equipment suppliers and request an onsite
demonstration. For Option 6, bench-scale
testing and possibly pilot-scale testing is
needed to determine the most suitable ion
exchange resins. Testing is also needed
to evaluate the effect of recycle on the
current pretreatment process since a sig-
nificant portion of the savings projected
for this option relate to reducing both the
use of treatment reagent and the amount
of sludge generated. Bath maintenance
(Option 7) can be evaluated with the use
of simple cartridge filtration devices to re-
move solids from one of the process tanks.
The full report was submitted in fulfill-
ment of Contract No. 68-C8-0061, WA2-
05 by Science Applications International
Corporation under the sponsorship of the
U.S. Environmental Protection Agency.
&U.S. GOVERNMENT PRINTING OFFICE: 1991 - 548-028/40083
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Table 1. Summary of Waste Minimization Feasibility Analysis Phase
Nature of WM Option
Process & Wastestream
Spray painting:
Waste paint
Detackified paint
Paint booth water
Waste
Minimization
Option
2
3
4
1
2
1
2
Degreasing of frame rails
(Chassis):
Degreasing solvent
Phosphating of misc. parts
(E-Coat)
Rinse waters
Spent process solutions
(cleaner, activator and
sealer)
Capital
Invest-
ment ($)
Improve transfer efficiency 27,456
Procedural/small-equip. Link.*
Fleduce paint mix volumes 2,725
Paint solids dewatering 11,151
Improve transfer efficiency
Paint solids dewatering
Improve transfer efficiency —
Minimize solvent
contamination 466
Ion exchange recycle 45,500
Eiath maintenance 13,200
Net Op.
Cost
Savings
($/yr)
152,698
Unk.*
26,315
14,998
17,219
19,311
3,332
Payback
Period
(yr)
0.2
Unk.*
0.1
0.7
2.4
4.0
Rank Low
to High
(1-6)
2
NA
1
4
* The investment and projected savings for the procedural/small-equipment changes (Option 3) were not determined during the feasibility analysis
phase. However, the majority of minimization techniques which make up this option are expected to be implemented by the facility.
This Project Summary was prepared by the staff of Science Applications International
Corporation, McLean, VA 22101.
Mary Ann Curran is the EPA Project Officer (see below).
The complete report, entitled "Waste Minimization Opportunity Assessment: A Truck
Assembly Plant, "(Order No. PB91-220392/AS;Cost: $23.00, subject to change) will
be available only from:
National Technical Information Service
5285 Pon 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
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/S2-91/038
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