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. In an effort to assist these manufacturers, Waste Minimization Assessment Centers (WMACs) were

established at selected universities, and procedures were

adapted from the EPA Waste Minimization Opportunity Assessment Manual (EPA/625/7-88/003, July 1988). That document has been superseded by the Facility Pollution Prevention

Guide (EPA/600/R-92/088, May 1992). The WMAC team at

Colorado State University performed an assessment at a plant

that applies coatings to metal and plastic components supplied

by its customers. Several different coating operations are performed, but the ones that generate consistent and significant

quantities of waste are anodizing of aluminum parts, chromating

of aluminum parts, and painting of plastic and metal parts. The

team’s report, detailing findings and recommendations, indicated that large quantities of spent rinse water and process

solutions, and spent solvent and still bottoms are generated by

the plant and that the life of the black dye bath could be

extended to yield significant cost savings.

This Research Brief was developed by the principal investigators and EPA’s Risk Reduction Engineering Laboratory, Cincinnati, 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, Philadelphia, PA.

Introduction

The amount of 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 waste generation is to reduce or eliminate the

waste at its source.

University City Science Center has begun a pilot project to

assist small and medium-size manufacturers who want to

minimize their generation of 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 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 in-house expertise in waste minimization.

The potential benefits of the pilot project include minimization

of the amount of waste generated by manufacturers and reduction of waste treatment and disposal costs for participating

plants. In addition, the project provides valuable experience for

graduate and undergraduate students who participate in the

program and a cleaner environment without more regulations

and higher costs for manufacturers.

Waste Minimization Assessment for a Manufacturer

of Finished Metal and Plastic Parts

United States

Environmental Protection

Agency

Risk Reduction

Engineering Laboratory

Cincinnati, OH 45268

ENVIRONMENTAL

RESEARCH BRIEF

Research and Development EPA/600/S-94/005 September 1994

Harry W. Edwards*, Michael F. Kostrzewa*,

and Gwen P. Looby**

* Colorado State University, Department of Mechanical Engineering, Fort Collins,

CO.

** University City Science Center, Philadelphia, PA

E AP
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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 Opportunity

Assessment Manual (EPA/625/7-88/003, July 1988). The 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

This plant is a job shop that applies coatings to metal and

plastic components supplied by its customers. It operates 4,940

hr/yr to produce approximately 234,000 ft2 of product annually.

Manufacturing Process

Prefabricated aluminum, steel, and plastic parts are supplied to

the plant by its customers who specify the coating or paint that

is to be applied. The plant performs several different coating

operations, but the ones that generate consistent and appreciable amounts of waste are anodizing of aluminum parts,

chromating of aluminum parts, and painting of plastic and

metal parts.

Anodizing

Aluminum parts to be anodized are first immersed in a caustic

solution and then an etching solution to remove surface contaminants. Smut that remains on the parts after etching is

removed using an acidic deoxidizing solution. A surface oxide

layer is then formed on the parts in an aqueous electrolytic

bath that contains sulfuric acid. The anodized parts are then

dyed one of five colors or left undyed. Next, an aqueous nickel

fluoride solution is used to seal the oxide layer. The last step is

rinsing of the finished parts. The anodized parts are then

assembled if necessary, packaged, and shipped back to the

customer.

Chromating

Chromate conversion coatings are applied to aluminum parts

by first immersing the parts in a series of aqueous solutions for

cleaning, etching, and acidic deoxidizing. The parts are then

immersed in the chromate conversion solution and rinsed. The

finished parts are then painted if required, inspected, assembled

if necessary, packaged, and shipped back to the customer.

Painting

Parts that require painting are painted in one of three spray

paint booths. Water-based, solvent-based, and powder coatings are used by the plant according to the customer’s specifications. Special tooling supplied by the customer is used to

mount the parts to be painted. After the coating has been

applied, the parts are placed in an oven for curing and drying.

The completed parts are inspected, packaged, and shipped

back to the customer.

An abbreviated process flow diagram for this plant is shown in

Figure 1.

Existing Waste Management Practices

This plant already has implemented the following techniques to

manage and minimize its wastes:

• Flow reducers have been installed on all flowing rinses in the

anodizing and chromating lines.

• A solvent distillation unit is used to recover paint-related

solvents which are then reused by the plant.

• The use of water-based instead of solvent-based paints is

significant and is increasing. Plant personnel encourage

customers to specify water-based and powder-based paints.

• Operators use care in raising part racks slowly from the

process solutions and allowing sufficient drainage time to

reduce drag-out in the anodizing and chromating lines.

• Water used to cool FreonTM in the chillers associated with the

anodizing tanks is reused as rinse water.

Waste Minimization Opportunities

The type of waste currently generated by the plant, the source

of the waste, the waste management method, the quantity of

the waste, and the annual waste management cost are given

in Table 1.

Table 2 shows the opportunities for waste minimization that the

WMAC team recommended for the plant. The minimization

opportunity, the type of waste, the possible waste reduction

and associated savings, and the implementation cost along

with the payback time are given in the table. The quantities of

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 the economic savings of the minimization opportunity, in most cases, results from the need for less

raw material and from reduced present and future costs associated with 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 also should 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 may result

when the opportunities are implemented in a package.

Additional Recommendations

In addition to the opportunities recommended and analyzed by

the WMAC team, one additional measure was considered. This

measure was not completely analyzed because it was beyond

the scope of this analysis. Since this approach to waste reduction may, however, yield significant savings, it was brought to

the plant’s attention for future consideration.

• Modify the on-site solvent distillation unit in order to raise the

temperature and the recovery factor.

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.
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Aluminum parts

Chromate conversion

• alkaline cleaner

• alkaline etch

• acidic deoxidizer

• chromating

• rinse

Anodizing

• alkaline cleaner

• alkaline etch

• acidic deoxidizer

• anodizing

• dye

• seal

• rinse

Aluminum parts

Painting

• masking

• coating

Steel parts,

plastic parts

Spent solutions,

rinse water

treated on-site

Solvent

evaporation

Spent solvent

recycled on-site

Curing & drying

Inspection

Packaging

Coated parts

returned to

customers

Inspection

Packaging

Coated parts

returned to

customers

Figure 1. Abbreviated process flow diagram.
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Table 1. Summary of Current Waste Generation

Annual Quantity Annual Waste

Waste Generated Source of Waste Waste Management Method Generated (lb) Management Cost*

Spent process solutions Anodizing and chromating pH adjusted; sewered 3,140,810 $37,920

Spent black dye solution Anodizing pH adjusted; sewered 21,660 13,640

Spent rinse water Anodizing and chromating pH adjusted; sewered 17,840,700 5,600

Caustic sludge Wastewater treatment Stored on-site pending disposal 7,330 2,100

 (Plant personnel are evaluating

 possible reuse of this material for

 neutralizing rinse water and spent

 acidic solutions.)

Spent solvent and still bottoms Painting and on-site solvent Shipped to a treatment, storage,

 recovery unit disposal facility 13,580 11,970

Paint sludge Washer in painting line Stored on-site pending disposal

 (Sludge will be shipped off-site when

 a larger quantity has accumulated.) 1,440 1,640

Evaporated solvent Painting Evaporates to plant air 2,940 870

Aluminum oxide sludge Stripping of anodizing racks Stored on-site pending disposal N/A N/A

 and reject parts (Sludge will be shipped off-site when

 a larger quantity has accumulated.)

* Includes waste treatment, disposal, and handling costs and applicable raw material costs.

Table 2. Summary of Recommended Waste Minimization Opportunities

Annual Waste Reduction

Simple

Net Annual Implementation Payback

Minimization Opportunity Waste Stream Reduced Quantity (lb) Per cent Savings Cost (yr)

Extend the life of the black dye bath by Black dye solution 17,330 80 $10,240 $4,930 0.5

 installing a cation exchange column to

 remove dissolved aluminum, and a filtration

 unit to remove particulate contaminants suspend-

 ed in solution and sulfate in the form of insoluble

 barium sulfate precipitate. A small amount of

 barium sulfate sludge will be generated.

Operate the on-site solvent recovery unit more Spent solvent and still bottoms 3,920 29 2,770 0 Immediate

 frequently to reduce the amount of spent

 solvent that is shipped off-site without being

 reprocessed.
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BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35

United States

Environmental Protection Agency

Center for Environmental Research Information

Cincinnati, OH 45268

Official Business

Penalty for Private Use

$300

EPA/600/S-94/005