United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-92/188
October 1992
Project Summary
An Automated Aqueous Rotary
Washer for the Metal Finishing
Industry
Arun R. Gavaskar, Robert F. Olfenbuttel, Jody A. Jones, and Tad C. Fox
Product quality, waste reduction, and
economic issues involved in the use of an
automated aqueous rotary washer in the
metal finishing industry were evaluated in
this study. The automated washer can be
used for most metal parts that would or-
dinarily be cleaned by vapor degreasing,
hand-aqueous washing, or alkaline tum-
bling. The automated washer had good
potential to reduce waste, was economi-
cally viable, produced good product qual-
ity, and also avoided the vapor degreaser's
use of perch loroethylene. When compared
with hand-aqueous washing and alkaline
tumbling, the automated washer used less
chemicals. The payback period was about
7 years.
This Project Summary was developed
by EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce
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 Pollution Prevention Act of 1990 es-
tablishes pollution prevention as a "national
objective." The Act notes that there are sig-
nificant opportunities for industry to reduce or
prevent pollution at the source through cost-
effective changes in production, operation,
and raw materials use. Source reduction is
fundamentally different from and more desir-
able than waste management and pollution
control. Source reduction is defined in the law
to mean any practice that reduces the amount
of a hazardous substance, pollutant, or con-
taminant entering a wastestream or other-
wise released into the environment before
recycling, treatment, or disposal.
The objective of the U.S. Environmental
Protection Agency's (EPA) Waste Reduction
Innovative Technology Evaluation (WRITE)
Program is to evaluate, in a typical workplace
environment, examples of prototype or com-
mercial technologies that have potential for
pollution prevention. This particular evaluation
was a cooperative effort among EPA's Risk
Reduction Engineering Laboratory, Connecti-
cut Hazardous Waste Management Service,
and Quality Rolling and Deburring (QRD)
Company. The study evaluated an automated
aqueous washer for cleaning small metal parts
in the metal finishing industry. The goal of the
study was to provide information to potential
users of this technology. The objectives were
to evaluate (1) the product quality resulting
from new automated washer versus each of
three older processes, (2) the pollution pre-
vention potential of the new technology, and
(3) the economic attributes of the new tech-
nology.
One of the major steps in metal finishing is
cleaning metal parts to remove oil and grease,
dirt, and metal chips. Cleaning may involve
washing with a detergent or degreasing with
a solvent. Before installing the automated
aqueous washer, QRD (the site for this study)
routed metal cleaning jobs through one of
three cleaning processes: vapor degreasing,
alkaline tumbling, or hand-aqueous washing.
The cleaning process chosen is based on the
type of metal part and the suitability of the
cleaning process.
Product Quality Evaluation
The product quality evaluation was based
on (a) an examination of the cleaned metal
Printed on Recycled Paper
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parts from some of QRD's normally sched-
uled cleaning jobs, (b) an examination of
cleaned test panels inserted along with the
metal parts in the cleaning jobs, and (c) a
water break test conducted on the cleaned
test panels from the alkaline tumbler and
automated washer.
Three cleaning jobs (each containing sev-
eral thousand small metal parts) were selected
from the several that QRD receives every
day. Job A consisted of steel caplets that
were suitable for cleaning on the vapor de-
greaser. Job B consisted of aluminum rivets
that were suitable for cleaning on the hand-
aqueous washer. Job C consisted of steel
cylinders that were suitable for cleaning on
the alkaline tumbler. Job C involved cleaning
as well as electroplating (nickel plating).
Each job was split into halves. Half was
cleaned by the automated washer, and the
other half was cleaned by one of the older
processes. This experimental design provided
a one-to-one comparison between the auto-
mated washer and each of the three older
processes.
After each cleaning run, a predetermined
number (150) of randomly selected, cleaned
parts were examined for product quality. Visual
examination revealed no noticeable contami-
nation on any of the parts for all three jobs
nor on the cleaned test panels. The water-
break test indicated that the parts destined for
electroplating had been cleaned well. The
results of these examinations, therefore, show
that the three old processes and the auto-
mated process resulted in good product
quality, although certain delicate parts still
need vapor degreasing and some parts that
are diffucult to clean need hand-aqueous
washing.
Pollution Prevention Potential
Pollution prevention was measured in terms
of waste volume reduction (Table 1) and
pollutant reduction (Table 2). The total waste
volume generated by the automated washer
is much bwer than either the alkaline tumbler
or hand-aqueous washer. This indicates that
the automated washer needs fewer resources
to process wastes downstream.
Note that the processing energy require-
ment of the automated washer is higher than
the energy requirement of any of the three
older processes. The moderately higher pro-
cessing energy requirement of the automated
washer should, however, be weighed against
the potentially higher energy requirements of
the older processes in such other areas as
waste treatment. Secondary pollution resulting
from energy consumption was not a part of
this evaluation.
Although the waste volume generated by
the vapor degreaser is bwer than that of the
automated washer, it is much more hazardous.
Table 1. Comparison of Annual Waste Volume from the Cleaning Processes
Wastestrearn
Vapor Degreasing a
Wastewater in separator
Still bottom sludge
Air emissions
Alkaline Tumbling fr
Wastewater
Hand-Aqueous Washingc
Wastewater
Volume Generated
Per Year
Wastestream
Volume Generated
Per Year
(gal)
200
1,440
see Table 2
1,010,880
296,400
Automated Washing'
Wastewater 143,000
Oily Liquid 962
Automated Washing"
Wastewater 85,800
Oily Liquid 577
Automated Washingc
Wastewater 57,200
Oily Liquid 385
3 Based on 5,200 bbl/yr run on automated washer instead of vapor degreaser.
" Based on 3.120 bbl/yr run on automated washer instead of alkaline tumbler.
c Based on 2 080 bbl/yr run on automated washer instead of hand-aqueous washer.
Perchloroethylene, used in vapor degreasing,
is a hazardous chlorinated solvent on the
EPA's Toxics Release Inventory. Perchloro-
ethylene is also one of the 17 prbrity pollutants
targeted in the EPA Administrator's 33/50
Program for 50% reduction in releases by
1995. It is used in degreasing because it has
a high boiling point and is therefore suitable
for removing high melt waxes and for clean-
ing light-gauge metal parts.
Perchloroethylene can be a health prob-
lem, with inhalation and skin as the main
entry routes. Occupational Safety and Health
Administration exposure limits are 100 ppm
(8-hr time weighted analysis), 200 ppm (ac-
ceptable ceiling concentration), and 300 ppm
(acceptable maximum peak). Vapor inhalation
can cause eye irritation (at 400 ppm), respi-
ratory irritation (at 600 ppm), or anesthesia
(200 ppm for 8 hr) according to the Metals
Finishing Guidebook and Directory (1988).
Prolonged or repeated skin exposure can
cause dermatitis.
Spent perchloroethylene is listed under
Resource Conservation and Recovery Act
(RCRA) as a hazardous waste (EPA hazard-
ous waste number F001). Other commonly
used degreasing solvents are methylene
chloride, 1,1,1-trichloroethane, and trichforo-
ethylene, all of which are hazardous. The use
of the automated washer reduces the use of
these solvents.
The automated washer generates a
wastewater containing surfactants, which are
a much lower hazard both in terms of occu-
pational safety and the environment. Surfac-
tants are not RCRA hazardous wastes. They
can, however, cause environmental problems.
Phosphate detergents are the main cause of
increased algal growth (eutrophication) in
Table 2. Pollutants Generated by Cleaning Processes
Pollutant
Vapor Degreasing 3
Perchloroethylene
Perchloroethylene
Perchloroe thylene
Alkaline Tumbling"
Anionic surfactant
Hand-Aqueous Washing
Non-ionic surfactant
Medium
Sludge
Water
Air
Amount
Generated
Per Year
(Ib)
45
negligible
6,145
Pollutant
Automated Washing *
Anionic surfactant
Non-ionic surfactant
Amount
Generated
Per Year
Medium (Ib)
Water 2
Water 22
Water
Water
43
105
Automated Washing"
Anionic surfactant Water 1
Non-ionic surfactant Water 13
Automated Washingc
Anionic surfactant Water 1
Non-ionic surfactant Water 9
3 Based on 5,200 bbl/yr run on automated washer instead of vapor degreaser.
" Based on 3,120 bbl/yr run on automated washer instead of alkaline tumbler.
c Based on 2,080 bbl/yr run on automated washer instead of hand-aqueous washer.
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face waters where they are discharged, cause
waters to have an obnoxious odor and taste,
have a detrimental effect on fish because of
the high biochemical oxygen demand (BOD)
they create, and become a nuisance for rec-
reational activities. Hence, nonphosphate de-
tergents are increasingly being used.
Different surfactants vary widely in terms of
aquatic toxicity and ease of biodegradation.
Surfactants accumulate within aquatic organ-
isms and impair their functions. When com-
pared with alkaline tumbling or hand-aqueous
washing, the automated washer generates
bwer amounts of these surfactant wastes.
The results of the study indicate that mea-
surable pollution prevention accrues from us-
ing the automated washer instead of any of
the three older cleaning processes.
Economic Evaluation
The economic evaluation of automated
washing was based on (a) major operating
costs of the automated washer compared
with each of the three older cleaning pro-
cesses and (b) an estimation of the return on
investment (ROI) and payback period for the
automated washer. The number of barrels of
metal parts that were used in this estimate
was based on the annual number of barrels
processed through the automated washer.
This total was divided into three parts based
on the percentages of the parts run on the
automated washer that could have gone to
each of the three older processes. Of the
10,400 barrels run on the automated washer
per year, 5,200 would have gone to vapor
degreasing, 3,120 to alkaline tumbling, and
2,080 to hand-aqueous washing.
Tables 3, 4, and 5 compare the operating
costs of the older cleaning processes and
those of the automated washer. The results
of the economic calculations showed that,
based on a capital requirement of $207,260,
the payback period for QRD (where the ROI
exceeds 15%) was about 7 yr. Reducing the
amount of solvent used can also reduce pos-
sible liability resulting from health claims or
pollution fines, but these savings were not
quantified by this study and were not in the
economic calculations.
Discussion and Conclusions
The automated aqueous washer evaluated
in this study is an example of a pollution
prevention technology for the metal finishing
industry. Source reduction is achieved by
substituting an aqueous cleaning process for
a solvent cleaning process (vapor degreasing).
Source reduction is also achieved by reducing
the amount of raw materials (cleaners or
detergents) and process water used (alkaline
tumbling and hand-aqueous washing). Auto-
mated washing reduces the volume of
wastewater that has to be treated (either on-
srte or at the publicly owned treatment works)
Table 3. Operating Costs of Vapor Degreasing and Automated Washing
Cost Element
Vapor Degreasing Cost •
($/Yr)
Automated Washing Cost'
($/Yr)
Labor(base rate)
Energy
Chemicals
Water
Onsite Waste Treatment
Offsite Waste Disposal
Total
13,866
2,943
1,795
0
Negligible
1,440
20,044
17,300
10,712
2,711
665
1,032
2,624
35,044
* Based on 2,080 bbl/yr.
and discharged downstream. This is done
without compromising the cleaned product
quality, and no additional skill (above that
required to operate the old processes) is re-
quired to operate the automated washer. Parts
cleaned in the automated washer can be
either electroplated or sent out as finished
products.
One current limitation is that the automated
washer cannot yet totally substitute for the
three older processes. Certain delicate parts
have to be sent through the vapor degreaser
and some difficutt-to-clean parts have to be
processed through the hand-aqueous washer.
Most jobs that can be run on the older pro-
cesses can, however, be routed through the
automated washer. Thus the automated
washer is a good technology for metal finish-
ers who are considering an expansion in
capacity.
In summary, use of the automated washer
results in good product quality, increased
pollution prevention, and economic savings.
An added incentive for using the automated
aqueous process is its potential to reduce
liability as a result of reducing solvent use.
The full report was submitted in fulfillment
of Contract No. 68-CO-0003 by Battelle un-
der the sponsorship of the U.S. Environmen-
tal Protection Agency.
Table 4. Operating Costs of Alkaline Tumbling and Automated Washing
Cost Element
Alkaline Tumbling Costa
($/Yr)
Labor 18,720
Energy 2,847
Chemicals 2,434
Water 4,700
Onsite Waste Treatment 7,299
Offsite Waste Disposal 0_
Total 36,000
3 Based on 3,120 bbl/yr.
Automated Washing Cost3
($/Yr)
10,380
6,427
1,626
399
619
1+57A
21,025
Table 5. Operating Costs of Hand-Aqueous Washing and Automated Washing
Cost Element
Labor
Energy
Chemicals
Water
Onsite Waste Treatment
Offsite Waste Disposal
Total
Hand-Aqueous Washing Cost'
($/Yr)
16,640
3,256
33,134
1,213
2,140
Q
56,383
Automated Washing Cost'
($/Yr)
6,920
4,285
1,084
266
413
LQ50_
14,018
' Based on 2,080 bbl/yr.
'U.S. Government Printing Office: 1992— 64B-080/60134
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A.R. Gavaskar, R.F. Olfenbuttel, J.A. Jones, and T.C. Fox are with Batelle,
Columbus, OH 43201
Lisa Brown is the EPA Project Officer (see below).
The complete report, entitled "An Automated Aqueous Rotary Washer for the
Metal Finishing Industry," (Order No. PB92-228469/AS; Cost: $19.00,
subject to change) will be available only from:
National Technical Information Service
5285 Port 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, NC 27711
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/SR-92/188
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