United States
Environmental Protection
Agency
Research and Development
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
EPA/600/S-92/030 Sept. 1992
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a
Manufacturer of Finished Metal Components
Harry W. Edwards and Michael F. Kostrzewa*
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 waste but who lack
the expertise to do so. Waste Minimization Assessment Centers
(WMACs) were established at selected universities and proce-
dures were adapted from the EPA Waste Minimization Oppor-
tunity Assessment Manual (EPA/625/7-88/003, July 1988). The
WMAC team at Colorado State University performed an as-
sessment at a plant manufacturing finished metal components
— approximately 260,000 sq ft/yr. Customer-specified coatings
and surface treatments are applied to prefabricated aluminum
and stainless steel parts. Aluminum parts may be finished by
hard-coat or soft-coat anodizing, and chromate conversioq
coating. Stainless steel parts are finished by surface passivation.
Parts are also processed for surface inspection using a fluo-
rescent dye and ultraviolet light. The team's report, detailing
findings and recommendations, indicated that most waste was
generated in the aluminum anodizing process, and that the
greatest savings could be obtained by using hot deionized
water instead of nickel acetate solution to seal pores in the
aluminum oxide coating applied by anodizing.
This Research Brief was developed by the principal investiga-
tors and EPA's Risk Reduction Engineering Laboratory, Cin-
cinnati, OH, to announce key findings of an ongoing research
project that is fully documented in a separate report of the
same title available from University City Science Center.
Introduction
The amount of waste generated by industrial plants has be-
come an increasingly costly problem for manufacturers and an
' Colorado State University, Department of Mechanical Engineering
" University City Science Center, Philadelphia, PA
additional stress on the environment. One solution to the
problem of 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 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 (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 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 $75 million, employ no more than
500 persons, and lack inhouse 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 pro-
cedures outlined in the EPA Waste Minimization Opportunity
Assessment Manual (EPA/625/7-88/003, July 1988). The
Printed on Recycled Paper
-------
WMAC staff locate the sources of waste in the plant and
identify 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 supporting
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 is a metal-finishing job shop that applies coatings
and surface treatments to prefabricated metal parts. The plant
operates 2,448 hr/yr to produce approximately 280,000 sq ft of
finished metal parts.
Manufacturing Process
This plant does hard-coat and soft-coat anodizing, chromate
conversion coating, and surface inspection of aluminum parts.
Processing of stainless steel parts involves surface passivation
surface inspection, or both. The raw materials used include
aluminum cleaner, NaOH aluminum etch, nitric/hydrofluoric (HF)
acid deoxidizer, sulfuric acid, dyes, nickel acetate, sodium
dichromate, chromate conversion coatings, nitric acid, hy-
drofluoric acid, oil-base penetrant, developer, water washable
penetrant, and hydrophilic emulsifier.
The following steps are carried out in the surface finishinq
operations:
• The aluminum anodizing line involves alkaline cleaning
and etching, acidic deoxidizing to remove smut left after
etching, anodizing in an electrolytic solution of sulfuric
acid, dyeing, and sealing the aluminum oxide layer with
aqueous nickel acetate.
• Chromate conversion coating of aluminum involves alka-
line cleaning and etching, acidic deoxidizing, clear or gold-
colored chromate conversion coating, and rinsing in deion-
ized water.
• For stainless steel passivation, parts are degreased, etched,
and immersed in a passivating acid solution.
• For surface inspection, parts are first degreased and etched
A fluorescent dye is then applied and the surface is illumi-
nated with ultraviolet light to reveal surface flaws.
An abbreviated process flow diagram is shown in Figure 1.
Existing Waste Management Practices
• Two-stage and three-stage counterftow rinses in the anod-
izing and chromate conversion lines reduce water con-
sumption and waste generation.
• Process solutions are made up with deionized water to
reduce sludge formation.
• Drain boards are used between solution tanks to reduce
dragout.
• Spent etching solution is used for adjusting the Ph of
spent rinse water.
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 man-
agement 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
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 independently
and do not reflect duplication of savings that would result when
the opportunities are implemented in a package.
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. Environmental
Protection Agency. The EPA Project Officer was Emma Lou
George.
Aluminum Parts
from Customers'
Surface Inspection
- Cleaning
- Etching
• Inspection
Anodizing
- Cleaning
- Etching
- Anodizing
- Dyeing
- Sealing
Chromate
Conversion Coating
- Cleaning
- Chromate Conversion
Stainless Steel
Parts from
Customers
Surface Inspection
- Cleaning
- Etching
- Inspection
Passivation
- Cleaning
- Passivation
Finished
Parts
Shipped
to Customers
Figure 1. Abbreviated process flow diagram.
-------
Table 1. Summary of Current Waste Generation
Waste Generated
Source of Waste
Spent rinse water
Spent anodizing solutions
Spent chromate conversion
coating solutions
Spent passivation solutions
Spent acidic etchant solution
Spent penetrants
Batch treatment sludge
Annual Quantity
Generated (gal)
Annual Waste
Management Cost
Rinse waters from anodizing, chromate conversion 1,547,734
coating, and surface inspection are Ph adjusted
and discarded as industrial wastewater.
Aluminum cleaner, alkaline etch bath, acidic 5,000
deoxidizer solution, anodizing reagent solution,
and dyeing and nickel acetate seal solutions are
batch treated (Ph adjusted) and discarded with
rinse water as industrial wastewater.
Hexa valent chromate solutions are reduced with 641
sodium metabisulfite; then, with aluminum cleaner,
alkaline etch bath, and acidic deoxidizer solution,
are batch treated (Ph adjusted) and discarded
with rinse water as industrial wastewater.
Hexavalent chromium solutions are reduced with 125
sodium metabisulfite and, with nitric acid solutions,
are batch treated (Ph adjusted) and discarded with
rinse water as industrial wastewater.
Spent acidic etchant from surface inspection is 40
batch treated to adjust Ph and precipitate dissolved
metals then discarded as industrial wastewater.
Spent dyes, developer, and emulsifier from surface 20
inspection are shipped as hazardous waste for use
as cement kiln fuel.
Sludge (metal hydroxides and trivalent chromium 150
compounds) from treatment of spent process
solutions and rinse waters is disposed of as
hazardous waste.
$19,963
8,589
759
306
123
985
5,191
•fru.g. GOVERNMENT PUNTING OFFICE: MM - 55»4C7/M)Ma
-------
Table 2. Summary of Recommended Waste Minimization Opportunities
Waste Generated
Minimization Opportunity
Annual Waste Reduction
Net
Quantity (gal)
Implementation
Percent Annual Savings Costs
Payback
Years
Spent nickel acetate
seal solution
Nickel hydroxide
sludge from treatment
of spent nickel acetate
solution
Spent anodizing
solutions
Spent reagent solutions
from chromate
conversion coating
Anodizing and chromate
conversion coating
water rinses
Alkaline etch
water rinses
Anodizing and chromate
conversion coating
water rinses
Use hot deionized water instead
of nickel acetate as a seal after
anodizing.
Use hot deionized water instead
of nickel acetate as a seal after
anodizing.
Neutralize the spent solutions with
50% aqueous caustic instead of
sodium hydroxide pellets. Use
automated metering equipment to
reduce raw material and labor costs.
Allow increased drainage time above
the chromate conversion coating
line reagent baths. Increased solution
life will result in waste reduction and
cost savings.
Eliminate the soft-coat anodizing
rinse (use the hard-coat rinses for
both treatments), and install timer
switches to shut off all flowing rinses
when not in use.
Use spent acidic deoxidizer rinse
water instead of tap water for the
anodizing and chromate conversion
coating alkaline etch rinses.
Install flow reducers and flow
meters on flowing water rinses in
the anodizing and chromate
conversion coating lines to avoid
excessive use of rinse water.
2,275
104
100
100
1,292
651,346
259,820
144,015
20
42
17
10
$3,094
1,109
2,933
2,498
2,351
756
419
$ 1,020
0
1,140
2,081
260
1,210
0.3
0
0.4
0.9
0.3
2.9
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/S-92/030
------- |