&EPA
United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S-92/011 May 1992
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a
Manufacturer Producing Galvanized Steel Parts
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
who lack the expertise to do so. Waste Minimization Assess-
ment Centers (WMACs) were established at selected universi-
ties and procedures were adapted from the EPA Waste Minimi-
zation Opportunity Assessment Manual (EPM625/7-88/QQ3, July
J1988). The WMAC team at Colorado State University per-
formed an assessment at a plant producing galvanized steel
parts-approximately 10,000 tons/yr. The major process opera-
tions are degreasing and rinsing, acid pickling and rinsing,
prefluxing, and galvanizing. All these operations, except galva-
nizing, result in the formation of waste streams requiring off-site
disposal. Bottom dross from the galvanizing kettle and zinc
oxide skimmed from the surface of the molten zinc are sold as
usable products. The team's report, detailing findings and rec-
ommendations, indicated that most waste was generated in
acid pickling and rinsing and that the greatest savings could be
obtained by continuous air agitation to extend the life of the
.pickling acid and rinse by enabling more complete removal of
dissolved iron when those solutions are treated.
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 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
who lack the in-house 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 (Fort Collins) WMAC. The assessment teams have
considerable direct experience with process operations in manu-
facturing 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 an-
nual sales not exceeding $50 million, employ no more than 500
persons, and lack in-house 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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This assessment was done by engineering faculty and students
at Colorado State University's (Fort Collins) WMAC.
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 As-
sassmant Manual (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
This plant produces galvanized steel (reinforcing strips, pipes,
ducts, angle iron, and prefabricated parts). The plant operates
4,420 hr/yrto galvanize about 10,000 tons of steel products.
Manufacturing Process
The plant produces galvanized steel products. The raw materi-
als In addition to the steel include zinc ingots, alkaline phos-
phate cleaner, 10% hydrochloric acid for pickling, and zinc
ammonium chloride for prefluxing the steel.
The following steps are involved in galvanizing the steel:
• The steel parts are carried through an alkaline
phosphate degreasing cleaner solution followed .
by a water rinse.
• Acid pickling is done in 10% to 4% hydrochloric
acid followed by a water rinse.
• The steel is prefluxed by immersion in a 30% zinc
ammonium chloride solution.
• Galvanizing is done by immersion in molten zinc.
Existing Waste Minimization Practices
The plant uses degreasing rinse water as make-up for water
lost 'by evaporation from the degreasing tank. This practice
eliminates the need to dispose of contaminated degreasing
rinse water and reduces the consumption of caustic in the
degreasing tank.
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
WMAC team recommended for the plant. The type of waste, the
minimization opportunity, the possible waste reduction and as-
sociated savings, and the implementation cost along with the
payback time are given in the table. The quantities of hazard-
ous 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 a long payback time as indicated below.
They were brought to the plants's attention for future reference,
however, since these approaches to waste reduction may in-
crease in attractiveness with changing plant conditions.
Use dry descaling by an airless grit blast cleaner
instead of acid pickling to descale reinforcing strips
for galvanizing. A solid waste of scale and spent
grit would be generated instead of spent pickling
acid and rinse. Because the scale would contain a
small amount of hazardous chromium, disposal
would be costly. Pilot tests were suggested to
determine the life of the grit, necessary for eco-
nomic evaluation.
Install an electrodialysis system, a wastewater
treatment system and an ion exchange unit to
reduce the amount of acid pickling wastes gener-
ated. Operating costs, including disposal of large
amounts of chromium-containing sludge, would be
high with a long payback period.
Rinsing efficiency could be improved by dipping
the steel into the rinse tanks twice. However, the
improvement from dipping twice could not be quan-
tified.
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.
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Table 1. Summary of Current Waste Generation
Waste Generated
Sources of Waste
Annual Quantity Generated Annual Waste Management Cost
Degreaser and rinse tank sludge
Spent pickling acid (4% HCL)
and rinse water
Spent preflux solution (zinc
ammonium chloride)
Preflux tank sludge
Sludge from caustic degreasing 20,200 gal
and rinsing of steel to be
galvanized is dried in drums
and disposed of as landfill.
Spent acid solution (from pickling 105,400 gal
the steel for galvanizing) and spent rinse
water each contain about 10% dissolved
iron. They are combined with spent preflux
solution and disposed of as hazardous waste.
Prefluxing of the steel prior to galvanizing 19,300 gal
results in spent preflux-solution containing
about 20% zinc ammodium chloride. It is
combined with spent pickling acid and rinse
water for disposal as hazardous waste.
Iron dissolved in spent preflux solution is 2,400 gal
removed by precipitation as ferric hydroxide.
The resulting non-hazrardous sludge is
separated by decanting, dried and disposed of
as landfill.
$500
66,435
12,165
60
Table 2. Summary of Recommended Waste Minimization Opportunities
Waste Generated
Minimization Opportunity
Annual Waste Reduction Net Annual
Quantity Percent Savings
Implementation Payback
Cost Years
Spent preflux solution
and preflux tank sludge
Spent preflux solution
Spent pickling acid
Spent pickling acid and
spentpreflux solution
Provide continuous air 25,325 gal 62 $24,550
agitation and filtration of ,
the preflux solution for
complete removal of contained
iron as ferric hydroxide on
addition of hydrogen peroxide.
Removal of iron will extend the
life of the preflux solution and - *
the pickling rinse water which
is discarded when the preflux
solution is discarded.
Provide air agitation of the 5,510 gal 29 4,370
acid pickling rinse tank
preceding the preflux tank.
This agitation will reduce
dissolved iron drag-out into j
the preflux solution, extending
its life.
Provide continuous filtration 19,300 gal 22 10,700
of the pickling acid solution
to remove solid contaminants
and extend its life.
Increase drainage time — — . • 990
above the pickling and preflux
tanks from 1 to 15 seconds
to reduce drag-out and
extend reagent life. (A reduction
in the rate of generating spent
solutions is expected but could
not be quantified.)
$16,000
0.7
3,820
0.9
25,040
2.3
•fru.S. GOVERNMENT PRINTING OFFICE: IWZ - «W>80/40Z«6
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Teb)a2. Summary of Recommended Waste Minimization Opportunities (concluded)
Waste Generated
Degreasing rinse sludge
Minimization Opportunity
Parts for re-cleaning after
Annual Waste Reduction
Quantity Percent
7,580 gal 75
Net Annual
Savings
190
Implementation
Cost
0
Payback
Years
0
pickling are rinsed in the
degreasing rinse before
pickling again. Drag-out from
the pickling tank reacts with
alkaline compounds in the
degreasing rinse to form
sludge. Use the pickling rinse,
which is not alkaline,
instead of the degreasing rinse
to avoid forming sludge.
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
Penaity for Private Use $300
EPA/600/S-92/011
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