United States
                         Environmental Protection
                                    Risk Reduction
                                    Engineering Laboratory
                                    Cincinnati OH 45268
                         Research and Development
                                    EPA/600/S-92/011 May 1992
                         Waste Minimization Assessment for a
                   Manufacturer Producing Galvanized Steel Parts

                               F. William Kirsch and J. Clifford Maginn*
 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.
                        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.

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-

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

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.
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.)
                                                                             •fru.S. GOVERNMENT PRINTING OFFICE: IWZ - «W>80/40Z«6

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
                        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
Center for Environmental
Research Information
Cincinnati, OH 45268
Official Business
Penaity for Private Use $300