United States
Environmental Protection
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
  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
  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-
                                                Printed on Recycled Paper

   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-
  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

 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

 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
  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
   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-

 Option 4. Reduce Paint Mix
   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.

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
  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-

Option 7. E-Coat Line Bath
  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
  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

Table 1. Summary of Waste Minimization Feasibility Analysis Phase
                                          Nature of WM Option
Process & Wastestream
Spray painting:
Waste paint
Detackified paint
Paint booth water
Degreasing of frame rails
 Degreasing solvent

Phosphating of misc. parts
 Rinse waters
 Spent process solutions
 (cleaner, activator and
                           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.

Rank Low
 to High
 * 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
 Center for Environmental
 Research Information
 Cincinnati, OH 45268
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