guides to pollution prevention - the paint manufacturing industry

8/9/2019 Guides to Pollution Prevention - The Paint Manufacturing Industry

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EPA/625/7-90/005

June 1990

GUIDES TO POLLUTION PREVENTION:

The Paint Manufacturing Industry

RISK REDUCTION ENGINEERING LABORATORY

AND

CENTER FOR ENVIRONMENTAL RESEARCH INFORMATION

OFFICE OF RESEARCH AND DEVELOPMENT

U.S. ENVIRONMENTAL PROTECTION AGENCY

CINCINNATI, OHIO 45268


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NOTICE

This guide has been subjected to U.S. Environmental Protection Agencyspeer and administrative review and approved for publication. Approval doesnot signify that the contents necessarily reflect the views and policies of theU.S. Environmental Protection Agency, nor does mention of trade names orcommercial products constitute endorsement or recommendation for use.This document is intended as advisory guidance only to paint manufacturersin developing approaches for pollution prevention. Compliance withenvironmental and occupational safety and health laws is the responsibilityof each individual business and is not the focus of this document.

Worksheets arc provided for conducting waste minimization assessments ofpaint manufacturing facilities. Users are encouraged to duplicate portions ofthis publication as needed to implement a waste minimization program.

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FOREWORD

Paint manufacturing facilities generate large quantities of both hazardous andnonhazardous wastes. These wastes are equipment cleaning wastewater andwaste solvent, filter cartridges, off-spec paint spills, leftover containers, andpigment dusts from air pollution control equipment. Reducing the generationof these wastes at the source orrecycling the wastes on- or off-site will benefitpaint manufacturers by reducing raw material needs, reducing disposal costs,and lowering the liabilities associated with hazardous waste disposal.

This guide provides an overview of the paint manufacturing processes and

operations that generate waste and presents options for minimizing wastegenration through source reduction and recycling.

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ACKNOWLEDGMENTS

This guide is based in part on waste minimization assessments conducted byJacobs Engineering Group Inc., Pasadena, California, for the California Departmentof Health Services (DHS). Contributors to these assessments include: David Leu,Benjamin Fries, Kim Wilhelm, and Jan Radimsky of the Alternative TechnologySection of DHS. Much of the information in this guide that provides a nationalperspective on the issues of waste generation and minimization for paintmanufacturers was provided originally to the U.S. Environmental ProtectionAgency by Versar Inc. and Jacobs Engineering Group Inc. in WasteMinimization-Issues and Options, Volume II, Report No. PB87-114369 (1986). JacobsEngineering Group Inc. edited anddeveloped this version of the wasteminimization

assessment guide under subcontract to Radian Corporation (USEPA Contract68-02-4286).

Lisa M. Brown of the U.S. Environmental Protection Agency, Office of Researchand Development, Risk Reduction Engineering Laboratory, was the projectofficer responsible for the preparation and review of this document . HarryFreeman, Risk Reduction Engineering Laboratory, EPA, Benjamin Fries, DHS;Jerry Kohl, Department of Nuclear Engineering, North Carolina State University;Robert Nelson, National Paint and Coatings Association, Washington, D.C.; JoeSeaton, Lilly Industrial Coatings, Montebello, California, and Arnold Hoffman,Major Paint Co., Torrance, California contributed and served as reviewers of thisguide.

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CONTENTS


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SECTION 1INTRODUCTION

This guide is designed to provide paint manufacturerswith waste minimization options appropriate for this in-dustry. It also provides worksheets designed to be used fora waste minimization assessment of a paint manufacturingfacility, to develop an understanding of the facilitys wastegenerating processes and to suggest ways that the wastemay be reduced. Besides paint manufacturing plant opera-tors and environmental engineers, this document may beuseful to our regulatory agency representatives and con-sultants.

The worksheets and the list of waste minimizationoptions were developed through assessments of two LosAngeles area paint manufacturing firms commissioned bythe California Department of Health Services (Calif. DHS1987). The two firms operations, manufacturing proc-esses, and waste generation and management practiceswere surveyed, and their existing and potential wasteminimization options were characterized. Economicanalyses were performed on selected options.

Reducing waste is a high priority for the paint manu-facturing industry. In 1981, U.S. paint, coating, and inkmanufacturers represented 44 percent of the market for

solvents (Pace 1983). Solvents are used in the industry ascarriers for resins and pigments and to clean the variousprocess equipment used for production. Although clean-ing solvents are often distilled and reused, a residual paintsludge remains, which contains solvents and in some cases,toxic metals such as mercury, lead and chromium. De-pending on the constituents, the wastes could be consid-ered RCRA wastes F002 (halogenated solvents), F003(non-halogenated solvents such as acetone and xylene),F004 (non-halogenated solvents such as cresols, cresylicacid, nitrobenzene, and solvent blends), or F005 (non-halogenated solvents such as toluene, methyl ethyl ketone,and benzene). These wastes are currently banned fromland disposal.

The amount of wastes disposed of by paint manufac-turers is high. For example, in 1984 the paint manufactur-ing industry in California disposed of 21,000 tons ofsolvent bearing waste off-site, making this industry thehighest-volume generator of manifested solvent wastes inthat year (ICF 1986).

Waste minimization is a policy specifically mandatedby the U.S. Congress in the 1984 Hazardous and SolidWastes Amendments to the Resource Conservation andRecovery Act (RCRA). As the federal agency responsiblefor writing regulations under RCRA, the U.S. Environ-mental Protection Agency (EPA) has an interest in ensur-ing that new methods and approaches are developed forminimizing hazardous waste and that such information ismade available to the industries concerned. This guide isone of the approaches EPA is using to provide industry-

specific information about hazardous waste minimization.The options and procedures outlined can also be used

in efforts to minimize other wastes generated in a facility.EPA has also developed a general manual for wasteminimization in industry. The Waste Minimization Op-

portunity Assessment Manual (USEPA 1988) tells how toconduct a waste minimization opportunity assessment anddevelop options for reducing hazardous waste generationat a facility. It explains the management strategies neededto incorporate waste minimization into company policiesand structure, how to establish a company-wide wasteminimization program, conduct assessments, implementoptions, and make the program an on-going one. Theelements of waste minimization assessment are explainedin the Overview, next section.

In the following sections of this manual you will find:

l An overview of the paint manufacturing industry

and the processes used by the industry (SectionTwo);

l Waste minimization options for paintmanufacturers (Section Three):

l Waste Minimization Assessment Guidelinesand Worksheets (Section Four)

l An Appendix, containing:

- Case studies of waste generation and wasteminimization practices of two paintmanufacturers;

- Where to get help: additional sources ofinformation.


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Overview of Waste Minimization

Assessment

In the working definition used by EPA, waste minimi-zation consists of source reduction and recycling. Of thetwo approaches, source reduction is usually consideredpreferable torecycling from an environmental perspective.Treatmentof hazardous waste is considered an approachto waste minimization by some states but not by others, andthus is not addressed in this guide.

A Waste Minimization Opportunity Assessment(WMOA), sometimes called a waste minimization audit, isa systematic procedure for identifying ways to reduce oreliminate waste. The steps involved in conducting a wasteminimization assessment are outlined in Figure 1 andpresented in more detail in the next paragraphs. Briefly, theassessment consists of a careful review of a plants opera-tions and waste streams and the selection of specific areasto assess. After a particular waste stream or area is

established as the WMOA focus, a number of options withthepotential to minimize waste are developed and screened.The technical and economic feasibility of the selectedoptions are then evaluated. Finally, the most promisingoptions are selected for implementation.

To determine whether a WMOA would be useful inyour circumstances, you should first read this sectiondescribing the aims and essentials of the WMOA process.For more detailed information on conducting a WMOA,consult the Waste Minimization Opportunity Assessment

Manual.

The four phases of a waste minimization assessmentare:

l Planning and organizationl Assessment phasel Feasibility analysis phasel Implementation

PLANNING AND ORGANIZATION

Essential elements of planning and organization for awaste minimization program are: getting managementcommitment for the program; setting waste minimizationgoals; and organizing an assessment program task force.

ASSESSMENT PHASE

The assessment phase involves a number of steps:

l Collect process and facility datal Prioritize and select assessment targetsl Select assessment teaml Review data and inspect sitel Generate optionsl Screen and select options for feasibility study

Both sourcereduction and recycling options should beconsidered. Source reduction may be accomplishedthrough:

Collect process andfacility data. The waste streams at afacility should be identified and characterized. Informa-tion about waste streams may be available on hazardouswaste manifests, National Pollutant Discharge Elimina-tion System (NPDES) reports, routine sampling programsand other sources.

Developing a basic understanding of the processes thatgenerate waste at a facility is essential to the WMOAprocess. Flow diagrams should be prepared to identify thequantity, types and rates of waste generating processes.Also, preparing material balances for various processescan be useful in tracking various process components andidentifying losses or emissions that may have been unac-counted for previously.

Prioritize and select assessment targets. Ideally, all wastestreams in a facility should be evaluated for potential wasteminimization opportunities. With limited resources,however, a plant manager may need to concentrate waste

minimization efforts in a specific area. Such considera-tions as quantity of waste, hazardous properties of thewaste, regulations, safety of employees, economics, andother characteristics need to be evaluated in selecting atarget stream.

Select assessment team. The team should include peoplewith direct responsibility and knowledge of the particularwaste stream or area of the plant.

Review data and inspect site. The assessment teamevaluates process data in advance of the inspection. Theinspection should follow the target process from the pointwhere raw materials enter the facility to the points where

products and wastes leave. The team should identify thesuspected sources of waste. This may include the produc-tion process; maintenance operations; and storage areas forraw materials, finished product, and work in progress. Theinspection may result in the formation of preliminaryconclusions about waste minimization opportunities. Fullconfirmation of these conclusions may require additionaldata collection, analysis, and/or site visits.

Generate options. The objective of this step is to generatea comprehensive set of waste minimization options forfurther consideration. Since technical and economicconcerns will be considered in the later feasibility step, no

options are ruled out at this time. Information from the siteinspection, as well as trade associations, governmentagencies, technical and trade reports, equipment vendors,consultants, and plant engineers and operators may serveas sources of ideas for waste minimization options.

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Figure 1. The Waste Minimization Assessment ProcedureThe Recognized Need to Minimize Waste

PLANNING AND ORGANIZATION

l Get management commitmentl Set overall assessment program goalsl Organize assessment program task force

Assessment Organization &Commitment to Proceed

l Collect process and facility datal Prioritize and select assessment targets Targets and ReevaluatePrevious Optionsl Select people for assessment teamsl Review data and inspect sitel Generate optionsl Screen and select options for further study

Assessment Report ofSelected Options

FEASIBILITY ANALYSIS PHASE

l Technical evaluationl Economic evaluationl Select options for Implementation

ASSESSMENT PHASESelect New Assessment

Final Report, IncludingRecommended Options

IMPLEMENTATION

l Justify projects and obtain fundingl

Installation (equipment)l Implementation (procedure)Evaluate performance

Repeat the Process

Successfully ImplementedWaste Minimization Projects

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l Good operating practicesl Technology changesl Input material changesl Product changes

Recycling includes:

l Use and reuse of wastel Reclamation

Screen and select options for further study. This screeningprocess is intended to select the most promising options forfull technical and economic feasibility study. Througheither an informal review or a quantitative decision-makingprocess, options that appear marginal, impractical or inferiorare eliminated from consideration.

FEASIBILITY ANALYSIS

An option must be shown to be technically and eco-nomically feasible in order to merit serious considerationfor adoption at a facility. A technical evaluation deter-

mines whether a proposed option will work in a specificapplication. Both process and equipment changes need tobe assessed for their overall effects on waste quantity andproduct quality. Also, any new products developed throughprocess and/or raw material changes need to be tested formarket acceptance.

An economic evaluation is carried out using standardmeasures of profitability, such as payback period, return oninvestment, and net present value. As in any project, thecost elements of a waste minimization project can bebroken down into capital costs and economic costs. Sav-ings and changes in revenue also need to be considered.

IMPLEMENTATION

An option that passes both technical and economicfeasibility reviews should then be implemented at a facil-ity. It is then up to the WMOA team, with managementsupport, to continue the process of tracking wastes andidentifying opportunities for waste minimization, through-

out a facility and by way of periodic reassessments. Eithersuch ongoing reassessments or an initial investigation ofwaste minimization opportunities can be conducted usingthis manual.

References

Calif. DHS. 1987. Waste Audit Study: Paint Manufacturing Industry. Report prepared by JacobsEngineering Group Inc., Pasadena, Calif., for theCalifornia Department of Health Services, AlternativeTechnology Section, Toxic Substances ControlDivision, April 1987.

ICF Consulting Associates, Jacobs Engineering Group,and Versar. 1986. Guide to Solvent Waste Reduction

Alternatives. Prepared for California Department ofHealth Services, Alternative Technology and PolicyDevelopment Section, October 10, 1986.

Pace Company Consultants and Engineers, Inc. 1983.Solvent Recovery in the United States 1980-1990.

Houston, Texas.

USEPA. 1988. Waste Minimization OpportunityAssessment Manual. Hazardous Waste EngineeringResearch Laboratory, Cincinnati, Ohio, EPA/625/7-88//003.

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SECTION 2

PAINT MANUFACTURING INDUSTRY PROFILE

Industry Description

As definedby Standard Industrial Classification (SIC)2851, the paints and allied products industry comprisesestablishments primarily engaged in the manufacture ofpaints (in paste and ready mixed form), varnishes, lac-quers, enamels and shellacs, putties, wood fillers andsealers, paint and varnish removers, paint brush cleaners,and allied paint products. Establishments engaged inthe manufacture ofpigments (organic or inorganic), resins,printing inks, adhesives and sealants, or artist materials are

not included.

The industry is comprised of roughly 1,375 establish-ments nationwide. Approximately 44 percent of all paintmanufacturing plant sites are located in five states (Califor-nia, New Jersey, New York, Illinois, and Ohio), with 67percent being located in ten states. Most of the plants arelocated near major population centers.

Products and Their Uses

Most small plants produce paint in 10 to 500 gallonbatches. Plants with more than 20 employees producepaint in 200 to 3,000 gallon batches. Overall, the paint

industry sold 8.6 billion dollars worth of product in 1983($3.9 billion for architectural coatings, $3.0 billion forproduct coatings, and $1.7 billion for special purposecoatings) (Webber 1984). The amounts and distribution ofproducts manufactured by the paint industry in 1983 areshown in Table 1.

For an average paint plant located in the U.S., 60percent of its total annual production would be solvent-based paint, 35 percent would be water-based paint, and 5percent would be allied products. While a large percentageof paint used for architectural coating is water-based(more than 70 percent), solvent-based paint is still pre-

dominantly used for product and special purpose coatings.

Table 1. 1983 Paint Products and Use

Distribution

Architectural Coatings 463 million gallons

Product Coatings 331 million gallonsMetal containers 19%

Automotive 16%

Machinery 6%

Sheet, strip and coil 6%Metal furniture 5%

Other 48 %Special Purpose Coatings 130 million gallons

High performance maintenance 31%Automotive and machineryrefinishing 29 %

Traffic paint 14%

Other 26%

Source: Chemical and Engineering News (Webber 1984).

Raw Materials

Annual consumption rates of raw materials used bythe paint manufacturing industry are shown for 1982 inTable 2.

The major raw materials used to manufacture paint areresins, solvents, drying oils, pigments, and extenders.Based on the wide variety of paints produced, no one typeof material dominates the market.

Process Description

Detailed process flow diagrams of paint manufactur-ing have been presented in the open literature (Haines1954, Payne 1961). The following description brieflyhighlights the production of the industrys two main prod-ucts: solvent-based paint and water-based paint. At atypical plant, both types of paint are produced. A blockflow diagram of the steps involved in manufacturing paintis presented in Figure 2.


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Table 2. Raw Materials Used by the Paint Manufacturing Industry in 1982

Materials

Resins

Alkyd

Acrylic

Vinyl

OtherSolvents

Aromatic

Aliphatic

Ketones

Alcohols

Other

Pigments

Titanium dioxide

Inorganic(a)

Organic

Extenders

Calcium carbonate

TalcClay

Other

Miscellaneous

Drying oils

Plasticizers

Other

Usage

1844 million Ibs/yr.

33 %

19%

19%

29 %3774 million Ibs/yr.

30 %

27 %

17%

12%

14%


65%

33 %

2%


31 %

25%23%

21%

220 million Ibs/yr.

41%

18%

41 %

Source: Chemical Economics Handbook (SRI 1981) data for 1977 adjusted for 1982 production rates.

(a) Approximately 60 percent of the inorganic pigments used consisted of iron oxide, zinc oxide, zinc dust, andaluminum paste; 27 percent consisted of lead and chrome compounds; and 13 percent consisted of other

compounds.

The production of solvent-based paint begins by mix-ing some of these: resins, dry pigment, and pigmentextenders, in a high speed mixer. During this operation,solvents and plasticizers are also added. Following themixing operation, the batch frequently is transferred to amill for additional grinding and mixing. The type of millis dependent on the types of pigments being handled, sothat no one style is universal. Next, the paint base orconcentrate is transferred to an agitated tank where tintsand thinner (usually a volatile naphtha or blend of solvents)and the balance of the resin are added. Upon reaching theproper consistency, the paint is filtered to remove any non-dispersed pigment and transferred to a loading hopper.

From the hopper, the paint is poured into cans, labeled,packed, and moved to storage.

The water-based paint process is very similar to thesolvent-based process. The major difference is the substi-tution of water for solvent and the sequencing of materialadditions. Preparation of water-based paint begins bymixing together water, ammonia, and a dispersant in amixer. To this mixture, dry pigment and pigment exten-

ders are added. After mixing, the material is ground in amill and then transferred to an agitated mix tank. Fouradditions of materials occur in this tank. First, resin andplasticizers are added to the mixture; second, a preserva-tive and an antifoaming agent are added; third, a polyvinylacetate emulsion is added; and fourth, water is added as athinner. Following this mixing operation, the handling ofthe paint is similar to that for solvent-based paints. Atmany facilities the grinding and the mixing and grindingoperation may be bypassed with all the dispersion opera-tions occurring in a single high-speed mixer.

Waste Description

Typically, paint facilities segregate and store wasteonly to the degree required by the waste disposal contrac-tor. Since the degree of segregation can affect the amountof material having to be classified as hazardous, and thecost of disposing of hazardous material is increasing, paintfacilities are taking a more active role in waste manage-ment. The major wastes that the paint industry mustmanage are empty raw material packages, dust from airpollution control equipment, off-specification paint, spills,

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Figure 2. Block Flow Diagram for Paint Manufacture

Solvent Based

TintsThinner

ResinsPigments

ExtendersSolventsPlasticizer

Packaging3-5-6

Final Product

Process Waste Categories1 Discarded Raw Material Containers2 Baghouse Pigment Dusts3 Off-Specification Paint4 Filter Cartridges5 Equipment Cleaning Wastes6 Air Emissions of Volatile Organic Compounds

Water Based

WaterAmmonia

DispersantPigmentExtenders

ResinPreservativeAntifoamPVA EmulsionWater

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Table 3. Paint Manufacturing Process Wastes

No Waste Description Process Origin

1. Leftover raw materials Unloading of materials

containers into mixing tanks

2. Pigment dusts from air

3. Volatile organic compounds

4. Off-specification

5. Spills

6. Waste rinsewater

Unloading of pigment

Air emissions from storage

tanks and open processingequipment.

Color matching(small

scale) production

Accidential discharge

Equipment cleaning using

water and/or caustic

solutions

7. Waste solvent Equipment cleaning using

solvent

8.

9.

Paint sludge

Filter cartridges

Equipment cleaning sludges

removed from cleaing

solution

Undispersed pigment

Composition RCRA Codes

Paper bags with a ---

few ounces of left

over pigments

Pigments ___

Resins, solvent ---

Paint

Paint

Paint

Paint, water,

caustic

---

---

---

---

Paint, solvent

Paint, water,

caustic, solvent

F002

F003

---

Paint

and equipment cleaning wastes. Equipmentcleaning wastesare a dominant waste stream.

The primary specific wastes associated with paintmanufacturing are listed in Table 3. Wastes generated bythe industry are usually managed in one of four ways: on-site reuse, on-site recycling, off-site recycling, and off-sitetreatment/disposal. On-site reuse involves the reuse ofwaste (without treatment) as a feed or wash material forproducing other batches of paint. Also included is the saleor in-house use of off-specification paint as utility paint.On-site recycling involves the reclaiming of solvent bydistillation or recovery of heating values by incineration.

Usually, on-site recycling is performed by large companies(those that produce more than 35,000 gallons of solventwaste each year) while small companies (those that pro-

duce 20,000 gallons or less per year) send the waste to anoff-site recycler. The fourth option, off-site treatment/disposal involves incineration or land disposal

References

Haines, H.W. (ed.) 1954. Resin an d Paint Production -1954 Style. Ind. Eng. Chem. 46(10):2010-22.

Payne, H.F. 1961. Organic Coating Technology.2 volumes. John Wiley & Sons, New York, N.Y.

SRI. 1981. Chemical Economics Handbook, 1982.Stanford Research Institute, Menlo Park, Calif.

Webber, D. 1984. Coating industry heading for recordyear. Chem. Eng. News 61(40):51.


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SECTION 3

WASTE MINIMIZATION OPTIONS FOR PAINTMANUFACTURERS

Description of Techniques

This section discusses recommended waste minimi-zation methods for paint manufacturers. These methodscome from accounts published in the open literature andthrough industry contacts. The primary waste streamsassociated with paint manufacturing are listed in Table 4along with recommended control methods. In order ofoccurrence at a facility, the waste streams are: equipmentcleaning wastes; spills and off spec paint; leftover inor-ganic pigment in bags and packages; pigment dust from

baghouses; filter cartridges; and obsolete products/cus-tomer returns.

The waste minimization methods listed in Table 4 canbe classified generally as source reduction, which can beachieved through material substitution, process or equip-ment modification, or better operating practices; or asrecycling. An example of a source reduction method in thetable is the use of countercurrent rinsing to reduce thevolume of cleaning waste, while an example of recyclingis the working of spilled product back into the process.

Table 4. Waste Minimization Methods for the Paint Manufacturing Industry

Waste Stream Waste Minimization Methods

Equipment cleaning wastes(rinsewater, solvent and sludge)

Use mechanical wipers on mix tanks.

Use high pressure wash systems.

install Teflon liners on mix tanks.

Use foam/plastic pigs to clean lines.

Reuse equipment cleaning wastes.Schedule production to minimize need

for cleaning.

Clean equipment immediately.Use countercurrent rinse methods.

Use alternative cleaning agents.

Increase spent rinse settling time.*Use de-emulsifiers on spent rinses.*

Spills and off spec paint Increase use of automation.

Use appropriate clean up methods.Recycle back into process. Implement

better operating practices.

Leftover inorganic pigment Use water soluble bags and liners.

in bags and packages Use recyclable/lined/dedicated

containers.

Air emissions, including pigment Modify bulk storage tanks.

dust Use paste pigments.

Install dedicated baghouse systems.

Filter cartridges Improve pigment dispersion.

Use bag or metal mesh filters.

Obsolete products/customer returns Blend into new products.

*These methods can only be viewed as waste minimization if they allow the continued use of spent cleaning solutions.

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Better operating practices are procedural or institu-tional policies that result in a reduction of waste. Theyinclude:

l Waste stream segregationl Personnel practices

- Management initiatives

- Employee training- Employee incentives

l Procedural measures- Documentation- Material handling and storage- Material tracking and inventory control- Scheduling

l Loss prevention practices- Spill prevention- Preventive maintenance- Emergency preparedness

l Accounting practices- Apportion waste management costs to

departments that generate the waste

Better operating practices apply to all waste streams.In addition, specific better operating practices that apply tocertain waste streams are identified in the appropriatesections that follow.

EQUIPMENT CLEANING WASTES

Equipment cleaning generates most of the waste asso-ciated with paint manufacturing. Following production ofeither solvent or water-based paints, considerable waste orclingage remains affixed to the sides of the preparationtanks. The three methods of tank cleaning used in the paint

industry are solvent washing for solvent-based paint,caustic washing for either solvent or water-based paint,and water washing for water-based paint.

Equipment used for preparation of solvent-based paintis rinsed with solvent, which is then generally reused in thefollowing ways:

Collected and used in the next compatible batchof paint as part of the formulation.Collected and redistilled either on or off-site.Collected and used with or without settling forequipment cleaning, until spent. When thesolvent is finally spent, it is then drummed for

disposal.

In 1985, a survey conducted by the National Paint &Coatings Associations Manufacturing ManagementCommittee showed that over 82% of the respondentsrecycled all of their solvent waste either on-site or off-site.With current costs of disposal, onsite distillation of solvent

can be economically justified for as little as eight gallonsof solvent waste generated per day. Of all the solvent thatis recycled, 75 percent is recovered with the remainingportion disposed of as sludge.

Caustic rinse is used for equipment cleaning of bothsolvent and water-based paints, but more often with wa-

ter-based paints. Water rinsing is usually insufficient inremoving paint that has dried in the mix tanks. Sincesolvent rinsing can usually remove solvent-based paintthat has dried, the need for caustic is less.

There are two major types of caustic systems com-monly used by the paint industry. In one type of system,caustic is maintained in a holding tank (usually heated) andis pumped into the tank to be cleaned. The caustic drainsto a floor drain or sump from which it is returned to theholding tank. In the second type of system, a causticsolution is prepared in the tank to be cleaned, and the tankis soaked until it is clean. Most plants reuse the caustic

solution until it loses most of its cleaning ability. At thattime, the caustic is disposed of either as a solid waste orwastewater with or without neutralization.

Water wash of equipment used in the production ofwater-based paint is the source of considerable wastewatervolume, which is usually handled as follows:

Collected and used in the next compatible batchof paint as part of the formulation.Collected and used with or without treatmentfor cleaning until spent.

Disposed with or without treatment aswastewater or as a solid waste in drums.

Sludges from settling tanks are drummed and dis-posed of as solid waste. Spent recycle rinsewater isdrummed and disposed of as solid waste after the solublecontent prohibits further use.

The percentage of solvent-base and water-base paintsproduced is the most important factor that affects thevolume of process wastewater generated and discharged atpaint plants. Due to their greater use of water-wash, plantsproducing 90 percent or more water-base paint dischargemore wastewater than plants producing 90 percent or moresolvent-base paint. Additional factors influencing the

amount of wastewater produced include the pressure of therinse water, spray head design, and the existence or ab-sence of floor drains. Where no troughs or floor drainsexist, equipment is often cleaned externally by hand withrags; when wastewater drains are present, there is a greatertendency to use hoses. Several plants have closed theirfloor drains to force the use of dry clean-up methods anddiscourage excessive water use.

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Waste associated with equipment cleaning representsthe largest source of waste in a paint facility. Methods thatreduce the need or frequency of tank cleaning or allow forreuse of the cleaning solutions are the most effective.Waste minimization methods considered include:

Use ofmechanical devices such as rubber wipers. In

order to reduce the amount of paint left clinging to the wallsof a mix tank, rubber wipers are used to scrape the sides ofthe tank. This operation requires manual labor and hencethe percentage of waste reduction is a function of theoperator. Since the benefits will be offset by increasedlabor, mechanization/automation should be considered.Many new mixers are available that are designed withautomatic wall scrapers (Weismantel and Guggilam 1985).These mixers can be used with any cylindrical mix tank(flat or conical bottom).

Us e of high pressure spray heads and limiting wash/

rinse time. After scraping the tank walls, high pressurespray hoses can be used in place of regular hoses to cleanwater-based paint tanks. Based on studies (USEPA 1979),high pressure wash systems can reduce water use by 80 to90 percent. In addition, high pressure sprays can removepartially dried-on paint so that the need for caustic is re-duced. Tanks used for making solvent-based paints nor-mally employ a built-in high pressure cleaning system. AtLilly, in High Point, N.C., a high pressure cleaning systemwas installed in several mix tanks. By continuouslypumping a fixed amount of solvent into a tank until it wasclean, the overall volume of solvent required for cleaningwas reduced (Kohl, Moses, and Triplett 1984).

Use of Teflon* lined tanks to reduce adhesion and

imp rove draina ge. The reduced amount of clingage willmake dry cleaning more attractive. This method is proba-bly applicable only to small batch tanks amenable tomanual cleaning.

Use of a plastic or foam pig to clean pipes. It wasreported that much of the industry is currently using plasticor foam pigs (slugs) to clean paint from pipes. The pigis forced through the pipe from the mixing tank to thefilling machine hopper. The pig pushes ahead paint leftclinging to the walls of the pipe. This, in turn, increasesyield and reduces the subsequent degree of pipe cleaningrequired. Inert gas is used to propel the pig and minimizedrying of paint inside the pipe. The equipment (launcherand catcher) must be carefully designed so as to preventspills, sprays, and potential injuries, and the piping runsmust be free of obstructions so that the pig does notbecome stuck or lost in the system.

Better operating practices. At Desoto, in Greens-boro, N.C., wash solvent from each solvent-based paintbatch is separately collected and stored. When the same

type of paint is going to be produced, waste solvent fromthe previous batch is used in place of virgin solvent. In1981, Desoto produced 25,000 gallons of waste mineralspirits. In 1982, when the system was implemented, wastesolvent production amounted to 400 gallons. This same>technique is currently being applied to their latex paint

production operation (Kohl, Moses and Triplett 1984).In some cases, cleaning sludge can be recycled. One of theaudited facilities discussed in the DHS report (Calif. DHS1987) recycles the sludge from alkaline cleaning of theirwater-based paint mix tanks into a marketable product.

Other waste minimization measures based on good oper-ating practices would be to schedule paint production forlong runs or to cycle from light to dark colors so that theneed for equipment cleaning would be reduced. Forfacilities using small portable mix tanks for water-basedpaints, immediate cleaning after use would reduce theamount of paint drying in the tank and hence reduce theneed for caustic. Many times, dirty equipment is sent to acentral cleaning operation where it waits until a given shift(usually night) to be cleaned. While tanks wait to becleaned, the residual paint dries up, often necessitating theuse of caustic solution for cleaning. By designing andoperating the cleaning operation to handle any peak loadcontinuously, all need for caustic should be eliminated ordrastically reduced.

For plants employing CIP (clean-in-place) and recyclesystems for wash/rinse operations, the inventory replace-ment frequency and waste volume can be minimized byusing these following waste reduction methods:

A countercurrent rinsing sequence. For facilities that

have additional storage space available, countercurrentrinsing can be employed. This technique uses recycleddirty solution to initially clean the tank. Following thisstep, recycled clean solution is used to rinse the dirtysolution from the tank. Since the level of contaminationbuilds up more slowly in the recycled clean solution thanwith a simple reuse system, solution life is greatly increased.Countercurrentrinsing is morecommon with CIP systems,but can be used with all systems.

Alternative cleaning agent. Many facilities usecaustic to clean their mixing equipment. When the build-up of solids and dissolved organics reaches a given con-

centration, the cleaning efficiency decreases and the solutionmust be replaced. As reported by one of the auditedfacilities, substituting a proprietary alkaline cleaning so-lution for their caustic solution cut the solution replacementfrequency in half and thereby reduced the volume ofcleaning solution requiring disposal.

*Registered trademark of E.I. Du Pont de Nemours & Co.

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S ludge d ewatering by filtration or centrifugation.

The above three methods are useful in reducing the amountof waste entering the environment provided they allow thecontinued use of the cleaning solution. Dewatering only toreduce sludge disposal volumes should not be viewed aswaste minimization.

Provision for adequate solid settling time in spent

rinse solution.

Use ofde-emulsifiers in rinse water to promote

emulsion breakdown and organic phase separation.

OFF-SPECIFICATION PAINT

Most off-specification paint is produced by smallshops that deal in specialty paints. Since these paints costmore to produce, and therefore sell at a premium price,most off-spec paint is reworked into a salable product.Since elimination of off-spec paint production has built-in economic incentives, the following techniques are widelyused:

Increased automation.

Better operating practices. Unless the sludge fromwet cleanup can be recycled into a marketable product, theuse of dry cleanup methods should be maximized whereverpossible. By closing floor drains and discouraging em-ployees from routinely (i.e. needlessly) washing downareas, some facilities have been able to achieve a largedecrease in wastewater volume (USEPA 1979). Othereffective ways to reduce water use include employingvolume-limiting hose nozzles, using recycled water forcleanups, and actively involved supervision.

BAGS AND PACKAGES

Inorganic pigments, which may contain heavy metalsand therefore be classified as hazardous, are usuallyshipped in 50 pound bags. After emptying the bag, anounce or two of pigment usually remains inside. Emptycontainers of liquid raw materials that constitute hazardouswaste (e.g. solvents and resins) are typically cleaned orrecycled to the original raw material manufacturer or to alocal drum recycler. Empty liquid containers are excludedfrom the following discussion. The following waste reduc-tion techniques for bags and packages were noted:

Use of water soluble bags for toxic pigments and

compounds used in water-basedpaints. When empty, the

bags could be dissolved or mixed in with the paint. Sucha method is commonly used for handling mercury com-pounds and other paint fungicides. This method could notbe used, however, when producing high quality, smoothfinish paint since the presence of this material could affectthe paints film forming property or could increase the loadon the filters which would increase filter waste.

12

Us e of rinseable/ recyclable drum s with plastic liners

insteadofpaper bags.

Better operating practices. Through industry contacts, itwas established that the most effective way of reducinghazardous waste associated with bags and packages (or anyother waste stream) was to segregate the hazardous materials

from the non-hazardous materials. As an example, emptypackages that contained hazardous materials should beplaced into plastic bags (so as to reduce or eliminatedusting leading to non-hazardous material contamination)and should be stored in a special container to await col-lection.

AIR EMISSIONS

The two major types of air emissions that occur in thepaint manufacturing process are volatile organic com-pounds and pigment dusts. Volatile organics may beemitted from the bulk storage of resins and solvents andfrom their use in open processing equipment such as mix

tanks. Since most existing equipment is of open design,reducing or controlling organic emissions from processequipment could require substantial expenditures in retro-fit costs. Additional work on control methods appears to bewarranted in this area, and as a result, the followingmeasures only address bulk storage and pigment handling.

Control bulkstorage air emissions. Many methods areavailable for reducing the amount of emissions resultingfrom fixed roof storage tanks. Some of these methodsinclude use of conservation vents, conversion to floatingroof, use of nitrogen blanketing to suppress emissions andreduce material oxidation, use of refrigerated condensers,use of lean-oil or carbon absorbers, or use of vapor com-pressors. When dealing with volatile materials, employ-ment of one or more of these methods can result in costsavings to the facility by reducing raw material losses.

Some of the dusts generated during the handling,grinding, and mixing of pigments can be hazardous.Therefore, dust collection equipment (hoods, exhaust fans,and baghouses) are provided to minimize a workers expo-sure to localized dusting and to filter ventilation air ex-haust. The waste reduction methods considered consist of:

Use ofpigments in pasteform instead of dry powders.

Pigments in paste form are dry pigments that have beenwetted or mixed with resins. Since these pigments are wet,

less dust or no dust is generated when the package isopened. In addition, most pigments in paste form aresupplied in drums (which can be recycled) and thereforewould eliminate the waste due to empty bags. While thismethod would increase the amount of pigment handlingoccurring at the suppliers facility, it can be argued that theoverall number of handling/transfer points for dry powderwill be greatly reduced along with the probability of spillsand dust generation.


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Dedicated baghouse system for pigment loading area.

At Daly-Herring Co., in Kinston, N.C., (while Daly-Herring is engaged in the formulation of pesticides and notpaints, there are many material handling problems commonto both industries) dust streams from several differentproduction areas were handled by a single baghouse. Sinceall of the streams were mixed, none of the waste could berecycled to the process that generated them. By installingseparate dedicated baghouses for each production line, allof the collected pesticide dust could be recycled (Huisinghand Martin 1985). While this example is not intended toimply that most of the dust generated by the paint industrycould be recycled, it does show the overall importance ofkeeping waste streams segregated.

SPILLS

Spills are due to accidental or inadvertent dischargesusually occurring during transfer operations or equipmentfailures (leaks). Spilled paint and the resulting clean upwastes are usually discharged to the wastewater treatmentsystem or are directly drummed for disposal. If the planthas floor drains, large quantities of water may be used toclean up water-based paint spills. Dry cleaning methodsare employed for cleaning of solvent-containing spills orfor water-based spills where floor drains are not available.Wastereduction methods similar to those for off-spec paintinclude:

Increased automa tion.

Better operating practices. Unless the sludge fromwet cleanup can be recycled into a marketable product, theuse of dry cleanup methods should be maximized whereverpossible. By closing floor drains and discouraging em-ployees from routinely (i.e. needlessly) washing downareas, some facilities have been able to achieve a largedecrease in wastewater volume (USEPA 1979). Othereffective ways to reduce water use include employingvolume-limiting hose nozzles, using recycled water forcleanups, and actively involved supervision.

FILTER CARTRIDGES

Spent filter cartridges are produced during the paint load-ing operation. These cartridges are designed to removeundispersed pigment from the paint during loading and are

saturated with paint when removed. Hence, waste minimi-zation and economy both call for as small a cartridge aspossible so as to reduce the amount of paint lost and thecapital spent for the filters. If frequent filter plugging is aproblem, then it should be first addressed from the stand-point of improving pigment dispersion, and not from thestandpoint of increasing filter area.

Viable alternatives to cartridge filters include bag filtersand metal mesh filters. Metal mesh filters are available invery fine micron sizes and they can be cleaned and reused.Since it is very important to minimize all wastes, the issueof mesh filter cleaning waste reuse or recyling would needto be addressed before switching to these filters.

OBSOLETE PRODUCTS/CUSTOMER RETURNS

Obsolete products and customer returns can be blendedinto new batches of paint. Obsolete products result fromchanges in customer demand, new superior products, andexpired shelf life. Marketing policies, such as discounting

older paints, can reduce the amount of obsolete productsrequiring disposal.

References

Huisingh, D. and L. Martin. 1985. Proven Profit fromPollution Prevention. Conference draft. The Institutefor Local Self-Reliance, Washington, D.C.

Kohl, J., P. Moses, and B. Triplett. 1984. Managing and Recycling Solvents. North Carolina Practices,

Facilities, and Regulations. Raleigh, N.C.; NorthCarolina State University.

USEPA 1979. U. S. Environmental Protection Agency,Office of Water and Waste Management. Developmentdocument for proposed effluent limitation guidelines,new source performance standards, and pretreatmentstandards for the paint formulating point sourcecategory. EPA-440-1-79-049b. Washington, D.C.:U.S. Environmental Protection Agency.

Weismantel, G., and S. Guggilam. 1984. Mixing and sizereduction (A chemical engineering special advertisingsection). Chem. Eng. 92(13): 71-109.

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SECTION 4

GUIDELINES FOR USING THE

WASTE MINIMIZATION ASSESSMENT WORKSHEETS

Waste minimization assessments were conducted atseveral paint manufacturing plants in the Los Angeles area.The assessments were used to develop the waste minimi-zation questionnaire and worksheets that are provided inthe following section.

A comprehensive waste minimization assessmentincludes a planning and organizational step, an assessmentstep that includes gathering background data and informa-tion, a feasibility study on specific waste minimizationoptions, and an implementation phase.

Conducting Your Own Assessment

The worksheets provided in this section are intendedto assist paint manufacturers in systematically evaluatingwaste generating processes and in identifying waste mini-mization opportunities. These worksheets include only theassessment phase of the procedure described in the WasteMinimization Opportunity Assessment Manual. For a fulldescription of waste minimization assessment procedures,refer to the EPA Manual.

Table 5 lists the worksheets that are provided in thissection.

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Table 5. List of Waste Minimization Assessment Worksheets

6.

7.

8.

9.

10.

11.

12.

Number Title Description

1. waste sources Typical wastes generated at

paint manufacturing plants.

2A. Waste Minimization:

Material Handling

Questionnaire on general

handling techniques for raw

material handling.

2B. Waste Minimization:Material Handling

Qnestionnaire on procedures used

for bulk liquid handling.

2c. Waste Minimization:Material Handling

Questionnaire on procedures used

for handling drums, containers

and packages.

Option Generation: Waste minimization options for

Material Handling material handling operations.

Waste Minimization:Material Substitution/

Primary Dispersion

Techniques

Questionnaire on material

substitution and primary dispersion

operations.

Option Generation:

Material Substitution/

Primary Dispersion

Techniques

Waste minimization options for

material substitution and modification

of the primary dispersion opera-

tions.

Waste Minimization:

Process Modification

(Let-Down)

Questionnaire on let-down

procedures.

Option Generation:Let-Down Techniques

Waste minimization opportunitiesfor let-down techniques.

Waste Minimization:

Process Modification

(Filtering and Filling)

Questionnaire on filtering,

filling, and on-site tank

cleaning procedures.

Option Generation:

Filtering and Filling

Filtering and filing waste

minimization options.

Waste Minimization:

Good Operating Practices

Questionnaire on use of good

operating practices.

Option Generation:

Good Operating Practices

Waste minimization options for

good operating practices.

Waste Minimization:

Reuse and RecoveryQuestionnaire on opportunities

for reuse and recovery of wastes.

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What information does the system track?

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Discuss the results of these attempts

Describe method currently used to dispose of this waste:

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OPTION GENERATION:

Material Handling

I Return Obsolete Material To Supplier I I I

! I

! ! ISecondary Containment

Air Emission Control

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WORKSHEET

Do any of the paints or coatings produced contain hazardous materials (i.e., chlorinated

solvents, lead or chrome pigments, mercury, etc.)?

If yes, has material substitution been tried?

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Firm

Site

Date

Is the piping to and from the letdown tanks routinely flushed with water or solvent?

Is the piping pigged before flushing?

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OPTION GENERATION:Good Operating Practices

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if yes, results:

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APPENDIX A

CASE STUDIES OF PAINT MANUFACTURING PLANTS

In 1986 the California Department of Health Servicescommissioned a waste minimization study (DHS 1987) oftwo paint manufacturing firms, called Plants A and B inthis guide. The results of the two waste assessments wereused to prepare waste minimization assessment work-sheets to be completed by other paint manufacturers in aself-audit process. The worksheets were sent to a thirdpaint manufacturer, to test their effectiveness in guiding anassessment.

The paint manufacturing plants were chosen for their

willingness to participate in the study, their applicability tothe studys objectives, and the potential usefulness of theresulting data to the industry as a whole. Plant A produceswater-based architectural coatings and Plant B producessolvent-based industrial coatings. The waste minimizationassessments were concerned with waste generated withinthe plant boundaries and not with waste derived from paintapplication or disposal of painted parts or stripped paint.

This Appendix section presents the results of theassessments of Plants A and B and potentially usefulwaste minimization options identified through the assess-ments. Also included are the practices already in use at theplant that have successfully reduced waste generation frompast levels.

The waste minimization assessments were conductedaccording to the description of such assessments found inthe Introduction: Overview of Waste Minimization, inthis guide. The steps involved in the assessments were (see

also Figure 1):

l Planning and organizationl Assessment phasel Feasibility analysis phase

The fourth phase, Implementation, was not a part ofthese assessments since they were conducted by an outsideconsulting firm. It was left to the paint manufacturersthemselves to take steps to implement the waste minimiza-tion opyions that passed the feasibility analysis.

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PLANT A WASTE MINIMIZATION ASSESSMENT

Planning and Organization

Planning and organization of the assessment was doneby the consulting firm with the assistance of personnelfrom the paint manufacturing firm. Initial contact wasmade with the paint manufacturers plant operations man-ager, a high level manager who could provide the com-panys commitment to cooperate in the assessment andprovide all the necessary facility and process information.The goal of this joint effort was to conduct a comprehen-sive waste minimization assessment for the plant. Under

different circumstances, in a company with its own on-going waste minimization program, goals could be set totarget a specific amount or type of waste to be reduced; orto conduct a waste minimization assessment each year; orother goal. The waste assessment task force in the case ofPlant A consisted of the consultants working togetherwith the plant manager. This task force also functioned asthe assessment team.

Assessment Phase: Process and Facility

Data

Initial discussions by telephone between the consult-

ants and the plant manager were used to request processand facility information prior to a site visit. These discus-sions also served to identify particular waste streams ofconcern to plant managers -- in particular, the disposal ofcartridge filters.

At the site visit, the plant operations manager andconsultants met to review the facilitys operations and itspotential target waste streams. The manager conducted afacility tour and introduced the consultants to processmanagers and workers involved in materials and wastehandling. Some of these people wereinterviewed to obtaininformation about specific procedures used at the plant.

FACILITY DESCRIPTIONPlant A produces a wide variety of architectural coat-

ings: 76 lines of paint products and eight lines of aerosolspray paints for distribution through retail outlets, and 55lines of aerosol and specialty paints for sale through

distributors. About 80 percent of the paints produced at thisfacility are water-based and the remainder are solvent-based. The water-based coatings are latexes and thesolvent-based coatings are mostly alkyd resins dissolved insolvents. Figure A-l presents the annual production ratesof paints since 1982. Most of the paints produced are foruse by the general public.

RAW MATERIALS MANAGEMENT

The raw materials used at Plant A include resin solu-tions, emulsions, solvents, pigments, bactericides, fungi-cides, and extenders. Some defoamers and surfactants arealso added to the water-based batches. Table A-l lists the

principal raw materials used by the plant in 1985.The solvents used at this facility include aliphatics,

aromatics, ketones, or glycol ethers. Glycols such asdiethylene glycol, propylene glycol, or Texanol are addedto the water-based formulations to increase the paintdrying time and to act as an anti-freeze. The solvents are


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either delivered and stored in drums or delivered in bulkand held in the above-ground diked storage tanks.

The pigments are delivered in bags when used inpowder form, and in drums or in bulk when used in slurriedform. The use of slurried pigments is predominant inwater-based formulations. Some solvent-based formula-

tions use pigments in paste form, which are purchased infive gallon containers.

A complete inventory check is done four times a year,though limited inventory checks are done on a daily basis.Plant A is planning to convert from a manual to a compu-terized inventory system.

Table A-l. Raw Materials Used at Plant A

Description

Solvents

Material

AliphaticsAromaticsKetones

AlcoholsDiethylene glycol

Propylene glycol

Resins Acrylics

Vinyl-acrylics

Alkyds

Pigments Titanium dioxide

Organic pigments

Red oxide

Extenders

Yellow oxide

Other inorganic pigments

Calcium carbonateClay

Talc

Silicates

Miscellaneous Additives Bactericides and fungicides

Surfactants and defoamers

Viscosity modifiers

Ammonia

Others

PROCESS DESCRIPTION

The production of paints at Plant A is shown in blockflow diagrams in Figures A-2 through A-7. The descrip-tion is general enough to apply to the production of bothsolvent- and water-based paints in most cases.

The first step in paint production is the dispersion ofthe pigments (see Figure A-2). The pigments in emulsion

or slurry form, along with the solvents, resins, and addi-tives are added directly to a mill in the primary dispersionstep. The dispersed material from the mill is then pumpeddirectly to the let-down tanks. In less than five percent ofthe cases, the pigments (in emulsion, slurry, or dry form)are added to other raw materials in a portable tank or a smallcontainer. The contents of the tank or container are then

dispersed in a sand mill, ball mill, or high-speed mill andeither collected in another portable tank or directly addedto the let-down tank. In all cases, the portable tanks orcontainers are reused several times without any cleaningbut are ultimately sent for cleaning.

The dispersion mills are dedicated to a particular typeThe dispersion mills are dedicated to a particular type ofproduct to the fullest extent possible. The dedicated millsare not cleaned. The non-dedicated mills are purged withsolvent or water at the end of the dispersion process and thewash material is mixed with the dispersed product in thelet-down step.

In the let-down step (see Figures A-4 and A-5), thedispersed pigments from milling operation are mixed inportable or stationary tanks with additional diluents, res-ins, and additives. The tanks have capacity varying from50 to 10,000 gallons. The additives constitute bactericides,fungicides, surfactants, defoamers, or extenders. Thebactericides and fungicides used for water-based batchesare mercury-based whereas non-mercurials are used forsolvent-based batches. Solvents such as diethylene glycolor propylene glycol are added to water-based paints toextend the drying time and act as an anti-freeze in coldclimates.

The stationary tanks have a capacity greater than 400gallons while the portable tanks have a 50- to 400-galloncapacity. About 25 percent of the total number of batchesare let down using portable tanks, which accounts for lessthan 10 percent of the total paint volume produced at PlantA. The mixing in the tanks is performed using turbinemixers. When the properties of the batch reach therequiredstandards, the mixing is stopped. The tank contents arethen pumped through bag filters to the filling unit, whichcan fill five gallon, one gallon, l/4 gallon, or l/2 pint cans.

WASTE DESCRIPTION

The principal waste streams generated by Plant A include

the following:

l Equipment cleaning wastes

l Obsolete stock

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Rinse

See Figs. A-4, A-5

water or solvent

Figure A-2. Dispersion and Let-Down Steps - Prevalent Route

Note: The process shown in this diagram is used in less than5% of the cases. The most commonly used procedure forprimary dispersion is shown in Figure A-2.

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Figure A-4. Let Down Operation for Portable Tanks at Plant A.


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Blending

Figure A-6. Management of Solvent Cleaning Waste at Plant A.


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Machine

Filling Blending

Rinse water fromcleaning ofstationary tanks

Note

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l Returns from customers

l Off-specification products

l Spills

l Spent filter bags

l Empty bags and packages

Table A-2 shows thevarious waste streams along withtheir origin and treatment/disposal methods used in thepast and present. The waste generation rates for individualstreams could not be established. Figure A-8 shows theamount of waste landfilled by Plant A since 1982. As seenfrom this figure, landfill disposal is no longer employed.From Table A-2, it is seen that the waste managementmethods have evolved into the present state, where most ofthe wastes are recycled, reused, or reworked. The follow-ing sections discuss each of these waste streams.

Equipment Cleaning WastesThe process equipment is routinely cleaned to prevent

product contamination and/or to restore operational effi-ciency. The resulting cleanup residuals constitute a majorwaste stream generated by the facility. Most of the cleanupwastes generated at Plant A are reprocessed into market-able products.

Mill cleaning. The mills are dedicated to a single typeof product whenever possible. In such cases, post-batchcleaning of the mills is not necessary. If dedication of a millto a single product is not possible, e.g. due to demandfluctuation, then cleaning is necessary. Cleaning is ac-

complished by flushing the mill either with water or asolvent, depending on the batch. The flush is then mixedwith the batch in the let-down step. Thus, mill cleaningdoes not produce a disposable waste at Plant A.

Portable tank cleaning. Portable tanks are first scrapedmanually to remove residual clingage. Next, the tanks arewashed with high pressure jets of acommercially availablealkaline cleaning solution. The cleaning solution isrecirculated and the blowdown or purge is sent to wastewa-

ter treatment. This process consists of flocculation and pHadjustment. The clear water effluent is drained to thesewer, and the settled solids containing 70 to 7.5 percentwater are sent to a blending tank (see Figure A-7).Blending with new material produces a beige-coloredcoating which is sold as a general purpose coating.

Stationary tank cleaning. The stationary tanks are toa large extent dedicated to the making of a single product.In such cases, the residue on the tank walls (clingage) isallowed to build up to a certain thickness, before beingscraped off manually. Following the manual cleaning, nofurther rinsing is necessary. The scraped paint residueswere drummed and disposed of in a landfill until Septem-ber 1986. Since that time, Plant A has developed a processto rework these residues into a useful product.

Non-dedicated tanks are rinsed with high pressure jetsof water or hosed with solvent depending on whether thetank is used for water- or solvent-based product prepara-

tion. The rinse water is sent to a holding tank where it isblended with other aqueous wash streams to produce ageneral purpose paint following flocculation and pHadjustment. The rinse solvent is reused several times andthen sent to an on-site still, where the solvent is recoveredfor reuse. The distillation bottoms are converted into aprimer product by blending with solvents and other addi-tives.

Filling unit cleanup. Separate filling units are used forwater- and solvent-based paints. Filling units for water-based products are rinsed with water. The rinse water issent for treatment as described previously. The filling lines

used for solvent-based paints are back-flushed with acompatible solvent into the tank from which the productwas drawn. The spent solvent is then reused or sent to thesolvent recovery still, as described previously.

Container cleaning. The small containers (cans, pails,etc.) containing residual paint are sent for metal reclama-tion without any on-site cleaning. Containers in whichmercury-based bactericides are delivered are returned tothe supplier without any cleaning.

Obsolete Stock

Obsolete stock is the paint that is no longer marketed

or raw material that can no longer be used. The obsoletepaints that are made by Plant A are reworked into othermarketable products. The obsolete raw material is returnedto the suppliers.

Returns From Customers

As with the obsolete stock, the returns from customersare reworked at Plant A into other products and the emptycontainers are sent off-site for metal reclamation.

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Mechanical cleaning ofprocess equipment

Paint that is no longermarketed or outdatedraw materials

Unused or spoiled paints

returned by customers

Spoiled batches

I I

I I

B B B

C C C

B

B

B

B B B

I I I

I I I

A-Reused to the extent possible, distill on-site to recover solvent, rework still bottomsB-Blend to make a marketable productC-Landfill disposal (Discontinued in September 1986)

D-Off-site recycling

E-Same as A except that the still bottoms are land disposedF-Overflow discharge to the sewer and landfill disposal of the solids settled in weirsG-Flocculation followed by discharge of decanted water to the sewer and landfill disposal of the settled solidsH-Vacuum filtrationI-Sanitary landfill after washing

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Off-Specification Products

Off-specification products are theresult of bad batchesthat are caused by errors in batch formulation or the failureof quality control to detect off-specification raw materials.At Plant A, the off-specification products are reworkedinto other usable products.

Spills

Spills are inadvertent discharges that occur at variousplaces in the plant. At Plant A, the spills are scooped up tothe fullest extent possible. If the scooped up materials arewater-based then they are sent to the water treatment unit.If they are solvent-based then they are sent to the solventrecovery still. The spills that cannot be scooped up arecleaned with commercially available adsorbents. The useof dry cleaning methods over manual scooping is dis-couraged, since it is difficult to rework the adsorbentscontaining the spilled material.

Filter BagsPlant A uses bag filters for all filtering applications.

Cartridge filters are not used due to the associated disposalproblems. The spent bag filters (used for both water- andsolvent-based products) are washed and dried and dis-posed of as non-hazardous waste.

Empty Bags and Packages

Plant A has eliminated the use of all hazardous leadand chromate pigments, as most of the paints produced byPlant A are for use by the general public. Therefore, thepresence of residual pigments does not make the bags/packages hazardous and thus they are disposed of as non-

hazardous waste. In addition, since the pigments used atPlant A are mostly in slurried form, the use of pigments inbags and packages is limited.

Assessment Phase: Option Generation

The consultants reviewed the plant operations dataobtained prior to and during the site inspection. Theydeveloped a set of waste minimization options based onthis information and on information in the literature. Theseoptions were screened for their effectiveness in reducingwaste and for their future implementation potential Theplant manager participated in this screening, with the resultthat there was general consensus on the list of recom-

mended options.

SOURCE REDUCTION MEASURES

The following paragraphs describe the applicationand use of source reduction measures to various wastestreams at Plant A.

Equipment Cleaning Wastes

This stream constitutes a large portion of the totalwaste generated. The following source reduction meas-ures are in current use:

Replacement of caustic cleaning solution

In the past, the portable tanks and small containerswere cleaned with caustic solution. Three years ago, thecaustic cleaning solution was replaced by a proprietaryalkaline solution. As the replacement frequency of thiscleaning solution is half that of the regular caustic solution,the cleanup residuals volume was cut nearly in half.

Use of high-pressure spraying systems

In the past, the water-based process equipment wasrinsed clean with water from low-pressure hoses. Sincethis procedure generated a large quantity of wastewater, aportable high pressure spraying system was purchased.This modification contributed to a reported 25 percent

reduction in cleanup waste volume.

Dedication of let-down tanks

The let-down tanks that make white paints are dedi-cated to making whites alone which minimizes the inter-mediate washing of these tanks. The deposits in the station-ary tanks are allowed to build up for a period of time andthen are scraped off manually. Dedication of the stationarytanks contributed to a reported 5 to 10 percent reduction inassociated cleanup waste volume, when compared to aprevious situation where the tanks were not dedicated andhence required cleaning after each batch.

Proper batch scheduling

At Plant A, certain batches are sequenced in the orderof light to dark paint manufacture. This scheduling ofteneliminates the need for intermediate cleanup steps.

Pigment substitution

Plant A has already eliminated the use of lead andchromium pigments, since these pigments are prohibitedfrom use in consumer products.

The only place where a future raw material substitu-tion will reduce the degree of hazard is for mercury-basedbactericides. Non-mercury-based bactericides have re-placed mercury-based counterparts in all solvent-basedpaints but not in water-based formulations. Plant A contin-ues to use mercury-based bactericides for water-basedpaints since their search for effective non-mercury substi-tutes was unsuccessful. It is suggested that the search forthe substitutes should continue in spite of continual set-backs.

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Obsolete Stock

Prevent obsolescence of raw material.

Prevention of raw material obsolescence is accom-plished by careful control and monitoring of the inventory.The raw material is used up as quickly as possible to avoidexpiration or degradation. The raw materials are accepted

from the suppliers only when they meet stringent qualitycontrol standards. When a raw material becomes obsolete,it is returned to the supplier.

Prevent obsolescence offinished stock

Obsolete finished material can be virtually eliminatedby proper production planning and inventory control. Thecurrent manual inventory control system is very efficient inlimiting the obsolete stock. The company is planning topurchase a computerized raw material inventory controlsystem. The computerized system is expected merely toprovide more detailed information about the inventory ina shorter time period.

Off-specification Products

The off-specification products are reworked on-site toproduce marketable products. To achieve additional sav-ings in reprocessing cost, however, reduction of off-speci-fication product generation can be further promoted byproper quality control of the raw material, increased proc-ess automation, and by ensuring effective cleanup ofequipment. Tight control measures have been extremelyeffective at Plant A.

Spills

As mentioned previously, the spills are first recoveredby manual scooping, then reworked into useful products.Only the residuals remaining after the recovery are subjectto dry cleaning using adsorbents. Direct use of adsorb-ents (i.e. without prior recovery) is discouraged as theresulting waste is difficult or impossible to reprocess.

Filter Bags

The use of cartridge filters was eliminated since theirdisposal proved problematic. Plant A, at present, uses bagfilters for all purposes. These filters are reused to theextentpossible. The spent bag filters when rinsed and dried arenot considered hazardous waste.

Empty Bags and PackagesUse of non-hazardous pigments.

As none of the pigments used at Plant A are hazardous,the empty bags and packages containing residual amountsare not considered hazardous.

Use of pigments in slurry form.

Most of the pigments used by Plant A are in slurry or

paste form, and therefore, the use of bags and packages forpigments is minimal.

Use of water-soluble bags.

Some of the mercury-based bactericides are deliveredto Plant A in water-soluble bags. These bags are added to

the batch along with the bactericides, thus avoiding thegeneration of waste in the form of empty bags and pack-ages.

RECYCLING AND RESOURCE RECOVERYMEASURES

Waste segregation, on-site recycling, and off-site re-cycling were evaluated for their effectiveness in reducingwaste generation at Plant A. These are discussed in thefollowing paragraphs.

Waste Segregation

Segregate water- and solvent-based wastes.

The solvent-based equipment cleanup wastes aresegregated from the water-based wastes. This facilitatesthe rework of both these streams into marketable products.The solvent- and water-based wastes are reworked asshown in Figures A-6 and A-7, respectively. The reworkstrategies shown in these figures would not be effective ifthe waste streams are allowed to mix.

S egregate alkaline cleanu p w astes from rinse water

wastes.

The alkaline cleanup wastes are segregated from rinsewater wastes. Both these waste streams are separatelyreworked (see Figure A-7) into useful products.

On-site Recycling

Reuse of water-based equipment cleanup wastes.

In the past, partially dewatered cleanup wastes werelandfilled. Ten years ago a flocculation step was intro-duced to remove the solids prior to discharging the streamto the sewer. The flocculated solids containing 70 to 75percent water were disposed of in landfills. Six years agothis procedure was again modified by adding a vacuumfilter to reduce the water content in the disposed solids to30-35 percent.

Since all these process modifications still involved

disposal of solids in a landfill, Plant A decided to pursueother process changes that would eliminate such disposal.This decision was based, in part, on anticipated landfillban. Currently, the water-based equipment cleaning wastesare blended with additives after flocculation to generate abeige-colored product (see Figure A-7) which is sold as ageneral purpose paint. Thus, by rework, the landfilling ofwater-based equipment cleanup wastes is avoided alto-gether.

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Reuse of alkaline cleaning wastes.

The alkaline cleaning of portable tanks generates awaste stream. This stream is segregated from the aqueouswastes described in the previous paragraph, but processedin the exact samemanner (flocculation, pH adjustment andblending) to produce a marketable product (see Figure A-

7).Reuse of solvent-bearing cleanup wastes.

The cleanup solvents are reused several times forrinsing tanks. This procedure ensures that the total solventusage for cleaning is minimized. When the rinse solvent isconsidered too dirty for direct reuse, it is distilled on-site.The solvent reclaimed by distillation is recycled to thecleaning operation. The distillation bottoms are sent to aholding tank, where they are blended with solvents andother raw materials to produce a primer product (see FigureA-6).

Rework wastes.

All of the wastes due to customer returns, scrapedpaint residues, obsolete finished products, off-specifica-tion products, and scooped up spills are reworked intomarketable products. Proper identification of thecustomerreturns is central to determining the rework strategy forthis waste. For the scraped paint residues (generated dueto the mechanical cleaning of stationary and portabletanks), Plant A has developed a process to rework theseresidues into a useful product. This process is currentlybeing refined.

Off-site Recycling

In the past, the solvent-based cleanup wastes were sentto an off-site recycler for reclamation. The reclaimedsolvent was purchased from the recycler and reused. Asthis process proved expensive, Plant A discontinued off-site recycling four years ago in favor of on-site recycling.At present, off-site recycling is practiced only on an oc-casional basis.

Feasibility Analysis Phase

The recommended options were evaluated for theirtechnical and economic feasibility by the consultants, whoobtained cost and performance data from vendors wherenew equipment was recommended. The result of the

technical and economic feasibility analyses was a list offeasible options, which became part of the assessmentsfinal report. The next waste minimization assessmentphase, Implementation, was left to the discretion of thepaint manufacturer, Plant A.

The specific economic aspects of implementing eachof thesource reduction/resource recovery options were notseparately documented by Plant A. Most of the source

reduction options employed are essentially good operatingpractices, and hence did not require a large capital invest-ment. However, the rework strategies and their evolutiondid require a large R&D expenditure. The implementationof these measures seemed to be guided more by theintuition and foresight of the plant personnel than by thecalculated benefits that may have been indicated by aspecific detailed economic evaluation.

The plant personnel indicate that the increase in oper-ating expense for rework has been matched by the in-creased revenues due to the sale of reworked products. Theavoided disposal costs, however, are expected to be quitesignificant. In 1984, 181 tons of waste (equivalent to about660 fifty-five gallon drums) was landfilled (see Figure A-8). In 1985, due to a comprehensive rework strategy, nowaste was landfilled. Using landfill disposal costs of $155/drum, Plant A saved $102,000 in avoided disposal costs ascompared to 1984. By reducing its waste from the 1982level of 1226 tons landfilled, over the years 1983-1985

Plant A avoided paying a total of $1.78 million in landfilldisposal costs. This assumes that waste generation wouldhave remained constant without waste minimization -- aconservative assumption since production rates actuallyincreased somewhat.

RATING OF WASTE MINIMIZATIONMEASURES

Table A-3 lists the various source reduction measuresnoted above for each waste stream. Table A4 lists therecycling and resource recovery options. Each measure isqualitatively rated on a scale of 0 (low) to 10 (high) for itswaste reduction effectiveness, extent of current use, and

future application potential. The waste reduction effec-tiveness indicates the amount of waste reduction that ispossible by implementing a particular source reduction/recycle measure. The extent of current use, as the nameimplies, is a measure of current usage of a particular wastereduction option. The future application potential is aqualitative measure of the probability that the measurewould be implemented in the future. This probability is afunction of the cost, degree of technical risk, and the extentof current use.

Because most of the waste minimization methodspresented in this report are already in use to a large extent

at Plant A, the future reduction index is low in most cases.The following source reduction measures are currentlyused by Plant A to a large extent: pigment substitution,proper batch scheduling, dedication of process equipment,preventing obsolescence of raw material, ensuring properbatch formulation, and washing and drying filter bags priorto disposal.

The extensive rework of wastes is responsible for zero

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waste generation at present and therefore given a zerofuture reduction index in Table A-4. The use of non-mercury bactericides and the use of pigments in slurry orpaste form are rated high for future application potential.These two measures, however, have a very low impact onreducing waste volume because these processes generateonly a small volume of waste.

SUMMARY

The data on production and waste generation rates forPlant A for 1982 to 1985 can be used to determine specificwaste generation rates (lb waste/gal product). These ratesare plotted in Figure A-9. The waste reduction programused by Plant A is clearIy effective; the specific wastegeneration rate was reduced from 0.34 lb/gal in 1982 tozero in 1985. The following factors contributed to thissuccessful waste reduction effort at Plant A:

l Proper planning and foresight. Theproblemsassociated with off-site waste disposal were

anticipated well in advance and measureswere implemented ahead of time. Totalelimination of landfill disposal was a goal setby management. Waste minimization andother environmental issues are given highpriority.

l Proper perspective of the wasteminimizationissue. Good operating practices contributedto successful source reduction, recycling,and reworking of all the wastes generated.The research and development effort resultedin the formulation of new products from the

waste and at the same time reduced the needfor disposal.

l Experienced employees. The averageseniority is well over 10 years for theemployees at Plant A. Because the employeesunderstand the process very well, mistakesthat result in waste generation are few andinfrequent.

l Product usage. Most of the paints producedby Plant A are for use by the general public.For this reason, extreme care is taken in thechoice of raw material and product

formulation. This is seen in the rapidreplacement of solvent-based formulationsby water-based formulations in thearchitecturalpaints category in the last decade.

l Product variety. Most of the paints producedat Plant A are water-based latexes andblending of waste latexes to produce amarketable product is easier than for non-latexpaints. Hence, waste reuse, by blending,to produce a marketable product may not be

a viable option for industrial paintmanufacturers who produce solvent-basedacrylics, epoxies, urethanes and otherproducts.

l Marketing outlets. Plant A markets itsproducts through retail outlets andcommercial service centers. Any new productresulting from reworking processes can beeasily sold from these outlets using pricediscount programs. Also, because homeinterior paint is purchased for aesthetic ratherthan functional attributes, consumers are moreliberal in experimenting with new products.

The same advantage may not pertain toindustrial paint manufacturers, where thefunctions of the products limit their usageand marketability.

FigureA Specific Waste Generation Rates for Plant A Since 1982,

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Reference

DHS. 1987. Hazardous Waste Minimization AuditStudy of the Paint Manufacturing Industry. April 24, 1987.Prepared for California Department of Health Services,Alternative Technology Section (Sacramento, California)by Jacobs Engineering Group Inc.

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The waste minimization assessment of Plant B fol-lowed the same protocol used for Plant A, and included:

l Planning and organization

l Assessment phase

. Feasibility analysis phase

Implementation of selected waste minimization op-tions was l

guides to pollution prevention - the paint manufacturing industry

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