»EPA
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Environmental Protection
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Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/M-91/046 Oct. 1991
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a Manufacturer of
Speed Reduction Equipment
F. William Kirsch and J. Clifford Maginn*
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 Manual (EPA/625/7-88/003 July
1988). The WMAC team at Colorado State University per-
formed an assessment at a plant manufacturing speed reduc-
tion equipment - approximately 110,000 speed reduction units/
yr. Plant operations include machining and assembling parts
for worm gear shafts and other shafts, worm gear bodies hubs
and housings, bearings and seals. Keyed and threaded shafts
are case-hardened, ground with athread grinder, and deburred.
Component parts are washed with an aqueous cleaner before
assembly, and finished assemblies are spray painted with
solvent-based paints and lacquer thinner. Spent cutting fluid
and sludge, including turnings, and spent wash water are
shipped offsite for disposal. Spent hydraulic oil and nonaqueous
cutting fluid are shipped to a recycler. Waste paint and spent
lacquer thinner are shipped offsite for incineration. The team's
report, detailing findings and recommendations, indicated that
most waste consists of spent aqueous cutting fluid, and that the
•University City Science Center. Philadelphia, PA 19104.
greatest savings could be obtained by ultrafiltration and recycle
of spent wash water.
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 aseparate report of the same
title available from the authors.
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 Colorado State
University's (FortCollins) WMAC. The assessmentteams 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
{g/y Printed on Recycled Paper
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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 lackinhouse 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.
Methodology of Assessments
The waste minimization assessments require several site visits
to each client served. In general, the WMACs follow the
procedures outlined in the EPA Waste Minimization Opportu-
nity Assessment Manual (EPA/625/7-88/003, July 1988). The
WM AC 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.
Finally, 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 produces speed-reduction equipment. The plant
operates 7,480 hr/yr to produce approximately 110,000 speed
reduction units.
Manufacturing Process
The plant machines and assembles parts for worm gear shafts
and other shafts, worm gear bodies, hubs and housings,
bearings and seals. (The term "worm gear" refers to a compo-
nent part of speed reduction units.) Except for bearings, motors
and cast housings, all speed reduction unit parts are made in
the plant. Raw materials include steel and bronze bar stock,
aluminum and iron castings, cutting fluids, paint and lacquer
thinner.
The following operations are involved in making the speed
reduction units:
• Worm gear shafts are machined from bar stock. Key slots
are cut, and a thread mill cuts worm gear threads in the
shafts. After case-hardening in a gas-fired carburizing
furnace, the shafts are ground with a thread grinder and
deburred in a tumbler with ceramic chips and an aqueous
slurry of aluminum oxide.
• Worm gear bodies, made of a bronze alloy, are machined
on a numerically controlled machine and pressed on the
hubs.
• Spent cutting fluid and sludge containing metal turnings
are shipped for offs'rte disposal. Spent hydraulic oil and
nonaqueous cutting fluid are shipped to a waste oil recy-
cler.
• Most component parts are washed with a water soluble
cleaner before assembly. Spent wash water and mop
water from cleanup around machinery are shipped offs'rte
for disposal.
• Many of the finished assemblies are spray painted using
solvent-based paints and lacquerthinner. Waste paint and
spent lacquerthinner are shipped offs'rte for incineration in
a cement plant. Spent paint-booth air-filter elements are
discarded with conventional trash.
Existing Waste Management Practices
• Metal scraps and chips are segregated and sold to a scrap
metal dealer for recycling.
• For drilling and tapping operations the plant uses a lubri-
cant with reduced emission of volatile organic compounds
(VOCs). Nonhazardous waste oil is processed offs'rte by a
recycler and blended into industrial boiler fuel. Solvent-
based cleaners have been replaced by a nonhazardous
aqueous cleaning solution.
• Spent cutting fluid is occasionally filtered and re-used.
• Dry booths are used for painting, eliminating the aqueous
paint-laden wastes associated with wet paint booths.
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 manage-
ment costs are given in Table 1.
Table 2 shows the opportunities for waste minimization that the
WMACteam recommended forthe plant. The type of waste, the
minimization opportunity, the possible waste reduction and
associated savings, and the implementation cost along with the
payback time are given in the table. The quantities of hazardous
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, in most cases, the economic savings of
the minimization opportunities result from the need for less raw
material and from reduced present and future costs associated
with hazardous 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 should also 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 would result
when the opportunities are implemented in a package.
Additional Recommendations
In addition to the opportunities recommended and analyzed by
the WMAC team, four additional measures were considered.
These measures were not completely analyzed because of
insufficient data or minimal savings as indicated below. They
were brought to the plant's attention for future reference,
however, since these approaches to waste reduction may
increase in attractiveness with changing plant conditions.
• Treat spent wash water and mop water containing sulf uric
acid to separate organic and aqueous phases. The organ-
ics would be shipped for offs'rte disposal, but the water
phase could be sewered to a local industrial wastewater
treatment facility. Because the plant does not have an
industrial sewer connection.at this time, this measure was
not recommended. Ultrafiltration was recommended in-
stead, because it provides an aqueous phase suitable for
discharge to the POTW sewer or re-use as mop water.
• Install a tramp-oil separator and two outside atmospheric
evaporators to reduce the quantity of wastewater shipped
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offsite for disposal. Because expected savings are small,
with a long payback period, this measure was not recom-
mended.
Replace two water-soluble cutting fluids now in use with a
single standardized cutting fluid. Because the resulting
waste reduction and savings resist quantification, this
measure was not recommended. However, if the recom-
mendation to recycle the cutting fluid is implemented, use
of a single cutting fluid will reduce substantially the cost of
equipment and operating costs.
Table 1. Summary of Current Waste Generation
• Install tramp-oil separators on the washers to allow recycle
of the alkaline wash water. The extended life of the wash
water would result in waste reduction, but the expected
cost savings would be small in comparison to operating
costs.
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.
Waste Generated
Spent cutting fluid
Cutting fluid sludge
Cutting fluid and rainwater
Spend hydraulic oil and
nonaqueous cutting oil
Source of Waste
Decanted from metal chips produced in machining operations.
Shipped for offsite disposal.
Metal chips sludge produced in machining operations.
Shipped for offsite disposal.
Runoff to pit drainage from metal chips collection bins.
Drained from machinery when no longer effective. Shipped
to a waste oil recyder.
Annual Quantity
Generated
61. 380 gal
650 gal
12,480 gal
3,000 gal
Annual Waste
Management Cost
$19,640
330
.
300
Waste paint (sludge) and
thinner
Sludge formed as the paint becomes too thick and the
thinner no longer useful for thinning or cleaning. Shipped for
incineration in a cement plant.
2,150 gal
16,250
Spent air filter elements Paint booth ventilation air filtration. Conventional trash disposal.
Spent wash water
Spent mop water
Spent aqueous cleaning solution from cleaning finished metal
parts before assembly. Shipped for offsite disposal.
Soapy mop water from cleanup around plant machinery. Shipped
for offsite disposal.
1,200 gal
9,420 gal
380
3,000
Table 2. Summary of Recommended Waste Minimization Opportunities
Waste Generated
Minimization Opportunity
Annual Waste Reduction Net Implementation Payback
Quantity Percent Annual Savings Cost Years
Paint waste from
cleaning spray guns
Spent aqueous
cutting fluids
Use waste-based paints instead of 2,150 gal
solvent-based paints to eliminate
solvent and thinner and produce only
conventional, nonhazardous waste.
Filter and recycle the aqueous 31,340 gal
cutting fluids.
Spent mop water from Install an ultrafiltration system to 9,420 gal
cleanup around process spent wash water for use as
machinery mop water. Excess treated water can
be discharged to the POTW. Only the
separated oil layer need be shipped
for disposal.
100
51
13
$27,370'
17,430'
33,410'
$13,750
22,400
35,100
0.5
1.3
1.1
Spent cutting fluid
from chip collection
bins
Use a portable sump cleaner to
remove accumulated cutting fluid
from chip collection bins for filtration
and recycle (as proposed above for
recycle of spent cutting fluid).
12,480 gal
100
3,120'
'Includes savings on raw materials.
•ArU.S. GOVERNMENT PRINTING OFFICE: 1991 - 548428/40074
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PAID
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Penalty for Private Use $300
EPA/600/M-91/046
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