vvEPA
                         United States
                         Environmental Protection
                         Agency	
                                    Risk Reduction
                                    Engineering Laboratory
                                    Cincinnati OH 45268
                         Research and Development
                                    EPA/60Q/S-92/021  May 1992
ENVIRONMENTAL
RESEARCH  BRIEF
              Waste Minimization Assessment for a Manufacturer of
                   Sheet Metal Cabinets and Precision Metal Parts

                                  Gweh P. Looby and F. William Kirsch*
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 Mini-
mization Opportunity Assessment Manual (EPA/625/7-88/003,
July 1988).  The WMAC team at Colorado State, University
performed an assessment for a plant that manufactures sheet
metal cabinets and precision metal parts. To make the cabi-
nets, sheet  metal is cut to size, bent, welded, and polished.
The metal  parts are  then surface treated and painted. The
machined parts are produced from bar stock which is cut,
drilled, milled, and ground as needed. The team's report, de-
tailing findings and recommendations, indicated that the most
waste was generated by the chromate conversion and iron
phosphate coating processes that prepare the parts for paint-
ing. The plant could achieve the greatest cost savings by
replacing solvent-based painting with powder-based painting.

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, which is available from the authors.


Introduction
The amount of hazardous waste generated by industrial plants
has become an  increasingly costly problem for manufacturers
*Universfty City Science Center, Philadelphia, PA 19104.
                         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 Sci-
                         ence 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
                         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
                         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 lack in-house expertise in waste minimiza-
                         tion.

                         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 proce-

                                    '             oĢ6 Printed on Recycled Paper

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durss outlined in the  EPA Waste Minimization Opportunity
Assessment Afam/a/(EPA/825/7-88/003, 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 manufactures sheet metal cabinets and precision
metal parts.  Approximately  1.15  million parts are produced
annually by 140 employees who operate the plant 2,210 hr/yr.


Manufacturing Process

Sheet Metal Parts
Sheets of aluminum and steel are cut to the proper size and
shape. Holes are punched into the metal that is then bent as
needed. Some pieces are welded together. Rough edges and
surfaces are  polished with power sanders and buffers. Metal
scrap is shipped to a scrap metal dealer for recycling. Spent
cutting fluid and waste hydraulic oil are combined and shipped
offsite for recycle or incineration.

Before painting, metal parts are  surface treated to improve
paint bonding and provide corrosion protection. Aluminum parts
receive a chromate conversion coating while steel parts re-
ceive an iron phosphate coating.

Aluminum parts are first dipped in a caustic cleaning solution
that is followed by a continuous-flow tap-water rinse. A third
tank contains a desmut solution  and is followed by another
continuous-flow tap-wafer  rinse tank. A fifth tank contains the
chromic acid-based chromate conversion solution. A sixth tank
is a continuous-flow tap-water rinse and a final tank is a heated
dead rinse of tap water. The caustic cleaner, desmut, and first
rinse tanks  are  dumped  monthly; the  chromic acid tank is
dumped every three to four years; and the remaining solutions
are dumped  every five  months. In addition,  sludge accumu-
lates in the caustic cleaner tank and is disposed of monthly.

In iron phosphate coating of steel parts, the first stage involves
a caustic cleaning tank followed by a continuous-flow tap-water
rinse. A third tank contains the iron phosphating solution and is
followed  by another  continuous-flow tap-water rinse. A final
tank contains a deoxidizing solution. All of these baths  are
dumped and replenished on a monthly basis. Combined waste-
waters from the iron phosphate and chromate conversion lines
drain to an overflow tank and are then drained to the sewer as
Industrial wastewater. Typically, pretreatment before discharge
is not required because the wastewater meets discharge limits
set by the publicly owned treatment works (POTW). Sludge
accumulates in the caustic cleaner and iron phosphate tanks
and is disposed of monthly.

Solvent-based paint  is  applied to metal  parts  in  dry paint
booths. Waste paint that is generated when the paint mixture
becomes too thick to be used is shipped to  a hazardous waste
treatment, storage, and disposal facility  (TSDF). Spent paint
thinner is also shipped offsite. Painted  parts are dried  and
cured in ovens. The plant uses powder-based paint coatings
on a small portion of parts. The type of paint used is dictated
by customer requirements.


Machined Parts
Bar stock is cut, drilled, milled, and ground as needed. Fin-
ished parts are assembled  (if required) and shipped to custom-
ers. Metal scrap is shipped to a scrap metal dealer for recycle.
Spent cutting fluid and waste hydraulic oil are combined with
similar waste from the manufacture of sheet metal parts and
shipped offsite for recycle or  incineration.


Existing Waste  Management Practices
This plant has taken the following steps to manage and mini-
mize its wastes:

  • Scrap metal is segregated onsite and sold to a recycler.

  • All reagent tanks in the phosphating and chromating lines
    are located in a large pit with a central drain to contain
    spills.

  • Drain boards are used between surface treatment tanks to
    reduce drag-out.

  • Reagent solutions in the surface treatment lines are agi-
    tated with air to  increase the effectiveness of the reagents.

  • Dry paint booths are used for painting to avoid generating
    aqueous paint-laden wastes that  are generated in wet
    paint booths.

  • A small powder coating unit is used for painting some
    products in order to avoid using solvent-based paints.

  • Tank  dumps are coordinated to achieve neutralization so
    that the sewered effluent meets POTW requirements.


Waste Minimization Opportunities
The type of waste currently generated by the plant, the waste
management method used, the quantity of the waste, and the
annual management costs  are given in  Table 1.

Table 2 shows the opportunities for waste minimization that the
WMAC team recommended for the plant. The present practice,
the recommended action, and the waste reduction and associ-
ated savings are also given in Table 2.  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.

ft 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.

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Additional Recommendations
In addition to the opportunities recommended and analyzed by
the WMAC team, several additional  measures were consid-
ered. These measures were not analyzed completely because
of insufficient data, implementation  difficulty, or a projected
lengthy payback. Since  one or more of  these  approaches to
waste reduction may,  however, increase  in attractiveness with
changing conditions  in  the  plant, they  were brought to the
plant's attention for future consideration.

  • Install filtration units for the iron phosphating and caustic
    cleaner solutions to  increase solution lifetime.

  • Use deionized water to make-up and maintain the caustic
    cleaner and iron phosphating solutions, thereby reducing
    sludge formation.

  • Substitute nonchromate conversion  coating for the chro-
    mate conversion coating currently used on aluminum parts.
                            •  Increase  drainage times over  the tanks  in  the  iron
                              phosphating and chromate conversion lines  in order to
                              reduce drag-out.

                            •  Segregate waste oil from the spent cutting fluid and re-
                              cycle ft.

                            •  Improve segregation of scrap metal before recycling.

                            •  Implement a preventive  maintenance program for the ma-
                              chine shop to reduce the quantities of spent cutting fluid
                              and waste oil.

                         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.
Table 1. Summary of Current Waste Generation
Waste Generated
                                      Waste Management Method
                                         Annual Quantity
                                         Generated (gal)
                       Annual Waste
                   Management Cost ($)
Machining '
   Scrap metal
   Cutting fluid/hydraulic oil
Chromate Conversion Coating
   Spent caustic cleaner
   Caustic cleaner sludge
   Caustic cleaner rinse water
   Spent desmut solution
   Desmut rinse water
   Spent chromating solution
   Chromating rinse water
   Heated dead rinse
Iron Phosphate Coating
   Spent caustic cleaner
   Caustic cleaner sludge
   Caustic cleaner rinse water
   Spent iron phosphate solution
   Iron phosphate sludge
   Phosphating rinse water
   Spent deoxidizer solution
Painting
   Waste paint and paint sludge
   Spent paint thinner
Shipped to scrap dealer for recycle
Off site recycle or incineration

Sewered as industrial wastewater
Conventional disposal in landfill
Sewered as industrial wastewater
Sewered as industrial wastewater
Sewered as industrial wastewater
Sewered as industrial wastewater
Sewered as industrial wastewater
Sewered as industrial wastewater

Sewered as industrial wastewater
Conventional disposal in landfill
Sewered as industrial wastewater
Sewered as industrial wastewater
Conventional disposal in landfill
Sewered as industrial wastewater
Sewered as industrial wastewater

Offsite recycle or incineration
Offsite recycle or incineration
    N/A
   1,320

 14,400
     60
359,160
 14,400
345,260
    300
345,260
  2,880

 33,600
     60
378,360
 33,600
     60
378,360
 33,600

  1,430
  1,320
   N/A
 5,780

    20
     0
   660
    20
   640
     0
   640
     0

    60
     0
   700
    60
     0
 1,160
    60

61,370
11,330
                                                                         A U.S. GOVERNMENT PRINTING OFFICE: 199Z - 648-080/40265

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         Summary of Waste Minimization Opportunities Recommended

Present Practice                      Proposed Action
                                       Savings
Solvent-based paints are used to
coat tho majority of this plant's
products. Wasta paint, paint
sktdgo, and spent thinner are
disposed of off site.
A solvent recovery unit In tfte plant
currently Is not operational because
of o/7 and water leaks.
 Cutting fluid currently is used
 until It becomes malodorous or until
 Us viscosity and lubricity are
 unacceptable. Average fluid
 Sfoiimo is about three months.
 Rinso water rates set by operators
 exceed flow rates required by the
 rinses in the chromate conversion
 and phosphating lines.
Replace solvent-based painting
with powder-based painting for a
portion of the plant's products.
Cost savings will result from reduced
disposal costs and reduced raw
material costs. Installation of a
batch spray booth for powder
coating will be required.

Replace solvent-based painting
with water-based painting fora
portion of the plant's products (a
separate portion from previous WMO).
Cost savings will result from
reduced disposal costs and reduced
raw material costs. Requires the
purchase of new paint application
equipment and may require  increased
curing times.

Overhaul the solvent recovery unit to
permit reuse of spent paint thinner.
Cost savings will result from reduced
disposal costs and reduced purchases
of thinner.
 Institute a program to recycle the
 cutting fluid onsite. Fluid should be
 filtered periodically to remove metal
 chips and particulate matter, thereby
 extending the life of the cutting fluid.
 In addition,  the spent cutting fluid can
 be treated with acid to reduce the
 volume of wastes that must be shipped
 offsite. The  addition of acid will cause
 a phase separation; the aqueous
 phase can be neutralized and sewered
 and the organic phase should be
 disposed of offsite.

 Install a flow reducer and flow meter
 in the water supply line upstream of
 the rinses in the chromate conversion
' andiron phosphating lines, thus reduc-
 ing the quantity of water purchased
 and sewered.
Waste reduction = 72 gal/yr
  (waste paint and paint sludge) + 66 gal/yr (spent thinner)
Waste management cost savings = $740/yr
Net raw material cost savings = $14,230/yr
Total cost savings = $14,970/yr
Implementation cost = $20,600
Simple payback = 1.4 yr
                                                                            Waste reduction = 72 gal/yr
                                                                              (waste paint and paint sludge) + 66 gal/yr (spent thinner)
                                                                            Waste management cost savings = $740/yr
                                                                            New raw material cost savings = $10,930/yr
                                                                            Total cost savings = $11,670/yr
                                                                            Implementation cost = $2,500
                                                                            Simple payback = 0.2 yr
Waste reduction = 660 gal/yr
Waste management cost savings = $3,890/yr
Raw material cost savings = $1,780/yr
Operating cost of recovery unit = $430/yr
Net cost savings = $5,240/yr
Implementation cost = $2,500
Simple payback = 2.1 yr

Waste reduction = 425 gal/yr
Waste management cost savings = $2,920/yr
Raw material cost savings = $570/yr
Operating cost of filtration unit = $370/yr
Total cost savings = $3,120/yr
Implementation cost = $7,050
Simple payback = 2.3 yr
 Waste reduction = 331,500 gal/yr
 Waste management cost savings = $100/yr
 Raw material cost savings = $510/yr
 Total cost savings - $610/yr
 Implementation cost = $100
 Simple payback = 0.2 yr
 United States
 Environmental Protection
 Agency
                 Center for Environmental Research
                 Information
                 Cincinnati, OH 45268
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