United StatesEnvironmental ProtectionAgency

EPA/625/7-90/007Risk Reduction Engineering LaboratoryCenter for Environmental Research Information June 1990Cincinnati, Ohio 45268

Technology Transfer

Guides to PollutionPrevention

The Printed Circuit BoardManufacturing Industry

EPA/625/7-90/007June 1990

GUIDES TO POLLUTION PREVENTION:The Printed Circuit Board Manufacturing Industry

RISK REDUCTION ENGINEERING LABORATORYAND

CENTER FOR ENVIRONMENTAL RESEARCH INFORMATIONOFFICE OF RESEARCH AND DEVELOPMENT

U.S. ENVIRONMENTAL PROTECTION AGENCYCINCINNATI, OHIO 45268

NOTICE

This guide has been subjected to U.S. Environmental Protection Agency’s peerand administrative review and approved for publication. Approval does not signifythat the contents necessarily reflect the views and policies of the U.S. EnvironmentalProtection Agency, nor does mention of trade names or commercial productsconstitute endorsement or recommendation for use. This document is intended asadvisory guidance only to printed circuit board manufacturers in developingapproaches for pollution prevention. Compliance with environmental and occupa-tional safety and health laws is the responsibility of each individual business and isnot the focus of this document.

Worksheets are provided for conducting waste minimization assessments ofcircuit board manufacturing facilities. Users are encouraged to duplicate portionsof this publication as needed to implement a waste minimization program.

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FOREWORD

This guide identifies and analyzes waste minimization methodoligies appropriatefor the printed circuit board manufacturing industry. The wastes resulting fromprinted circuit board manufacturing are associated with five types of processes:cleaning and surface preparation; catalyst application and electroless plating;pattern printing and masking: electroplating; and etching. The wastes includeairborne particulates, spent plating baths, waste rinsewater, and other wastes.

Waste minimization assessment worksheets are contained with in this guideto be of use to shop managers and engineers, or consultants in formulating a wasteminimization strategy for a particular plant, Case histories of waste minimizationassessments performed at three plants are presented.

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ACKNOWLEDGMENTS

This guide is based in part on waste minimization assessments conducted byPlanning Research Corporation, San Jose, 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 circuit boardmanufacturers was provided originally to the U.S. Environmental ProtectionAgency by Versar, Inc. and Jacobs Engineering Group Inc. in Waste Minimization-Issues and Options, VolumeII, ReportNo.PB87-114369 (1986). Jacobs EngineeringGroup Inc. edited and developed this version of the waste minimization assessmentguide, under subcontract to Radian Corporation (USEPA Contract 68-02-4286).

Lisa M. Brown of the U.S. Environmental Protection Agency, Office ofResearch and Development, Risk Reduction Engineering Laboratory, was theproject officer responsible for the preparation and review of this document. Othercontributors and reviewers include: Bonnie Blam, IBM corporation; Bonnie Gariepyand Terrence J. McManus, Intel Corporation; and Arthur H. Purcell, UCLAEngineering Research Center.

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CONTENTS

Appendix A:

Case Studies of Printed Circuit Board Manufacturing Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Appendix B:

V

SECTION 1

I N T R O D U C T I O N

This guide is designed to provide printed circuit boardmanufacturers with waste minimization options appropriatefor this industry. It also provides worksheets designed tobe used for a waste minimization assessment of amanufacturing facility, to develop an understanding of thefacility’s waste generating processes and to suggest waysthat the waste may be reduced.

The worksheets and the list of waste minimizationoptions weredeveloped through assessments of three SantaClara area prototype circuit board manufacturing shops.The assessments were commissioned by the CaliforniaDepartment of Health Services (CDHS 1987). The firms'operations, manufacturing processes, and waste generationand management practices were surveyed, and their existingand potential waste minimization options werecharacterized. Economic analyses were performed onselected options.

Today’s industry is faced with the major technologicalchallenge of identifying ways to effectively managehazardous waste. Technologies designed to treat anddispose of wastes are no longer the optimal strategy forhandling these wastes for two major reasons. First, thepotential liabilities associated with handling and disposingof hazardous wastes have increased significantly. Second,restrictions placed on land disposal of hazardous wasteshave caused considerable increases in waste disposal costs.The economic impact of these changes is causing industryto explore alternatives to treatment and ‘disposaltechnologies.

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.Environmental Protection Agency (EPA) has an interest inensuring that new methods and approaches are developedfor minimizing hazardous waste and that such informationis made available to the industries concerned. This guideis one of the approaches EPA is using to provide industry-specific information about hazardous waste minimization.The options and procedures outlined can also be used inefforts to minimize other wastes generated in a facility.

EPA has also developed a general manual for wasteminimization in industry. The Waste Minimization Oppor-tunity Assessment Manual (USEPA 1988) tells how toconduct a waste minimization assessment and developoptions for reducing hazardous waste generation at afacility. It explains the management strategies needed toincorporate waste minimization into company policies andstructure, 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 next section of this document, the Overview.

In the following sections of this manual you will find:

An overview of the printed circuit board (PCboard) manufacturing industry and the processesused by the industry (Section Two);

Waste minimization options for printed circuitboard manufacturers (Section Three);

Waste Minimization Assessment Guidelinesand Worksheets (Section Four)

An Appendix, containing:

- Case studies of waste generation andwaste minimization practices of threeprinted circuit board manufacturers;

- Where to get help: additional sources ofinformation.

Overview of Waste MinimizationAssessment

In the working definition used by EPA, wasteminimization consists of source reduction (preventing thegeneration of waste at its point of origin) and recycling. Ofthe two approaches. source reduction is usually consideredpreferable to recycling from an environmental perspective.Treatment of hazardous waste is considered an approach towaste minimization by some states but not by others, andis not addressed in this guide.

A Waste Minimization Opportunity Assessment(WMOA), sometimes called a waste minimization audit, is

1

a 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 plant’s operationsand waste streams and the selection of specific areas toassess. After a particular waste stream or area is establishedas the WMOA focus, a number of options with the potentialto minimize waste are developed and screened. Thetechnical and economic feasibility of the selected optionsare then evaluated. Finally, the most promising options areselected for implementation.

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

The four phases of a waste minimization opportunityassessment are:

Planning and organization

Assessment phase

Feasibility analysis phase

Implementation

PLANNING AND ORGANIZATIONEssential elements of planning and organization for a

waste minimization program are: getting managementcommitment for the program; setting waste minimizationgoals; and organizing an assessment program task force.The importance of these initial steps cannot be overestimated.

ASSESSMENT PHASEThe assessment phase involves a number of steps:

Collect process and facility data

Prioritize and select assessment targets

Select assessment team

Review data and inspect site

Generate options

Screen and select options for feasibility study

Collect process andfacility data. The waste streamsat a facility should be identified and characterized.Information about waste streams may be available onhazardous waste manifests, waste profile sheets, routinesampling programs and other sources.

Developing a basic understanding of the processesthat generate 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 beenunaccounted for previously.

Prioritize and select assessment targets. Ideally, allwaste streams in a facility should be evaluated for potentialwaste minimization opportunities. With limited resources,however, a plant manager may need to concentrate wasteminimization efforts in a specific area. Such considerationsas quantity of waste, hazardous properties of the waste,waste disposal restrictions, regulations, safety of employees,economics, cost of disposal, and other characteristics needto be evaluated in selecting a target stream.

Select assessment team. The team should includepeople with direct responsibility and knowledge of theparticular waste stream or area of the plant, includingmachine operators and maintenance personnel.

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 whereproducts and wastes leave. The team should identify thesuspected sources of waste. This may include the productionprocess; maintenance operations; and storage areas for rawmaterials, 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 togenerate a comprehensive set of waste minimization optionsfor further consideration. Since technical and economicconcerns will be considered in the later feasibility step, nooptions 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.

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

l Good operating practices

l Technology changes

l Input material changes

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l Product changes

Recycling includes:

l Use and reuse of waste

l Reclamation

Screen and select options for further study. Thisscreening process is intended to select the most promisingoptions for full technical and economic feasibility study.Through either an informal review or a quantitative decision-making process, options that appear marginal, impracticalor inferior are eliminated from consideration. Some of thecriteria used in screening options include impacts on productquality; employee safety; and environmental impacts ofthe alternatives.

FEASIBILITY ANALYSISAn option must be shown to be technically and

economically feasible in order to merit serious considerationfor adoption at a facility. A technical evaluation determineswhether a proposed option will work in a specificapplication. Both process and equipment changes need tobe assessed for their overall effects on waste quantity,toxicity, and product quality. Also, any new productsdeveloped through process and/or raw material changesneed to be tested for market 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. Savings

and changes in revenue also need to be considered.

IMPLEMENTATIONAn option that passes both technical and economic

feasibility reviews should then be implemented at a facility.It is then up to the WMOA team, with managementsupport, to continue the process of tracking wastes andidentifying opportunities for waste minimization throughouta facility and by way of periodic reassessments. Eithersuch ongoing reassessments or an initial investigation ofwaste minimization opportunities can be conducted usingthis manual.

While it is difficult to quantify the future liabilityreduction that could result from implementing an option,this is an important factor in choosing a particular strategy,and should at least be discussed qualitatively in theevaluation.

ReferencesCDHS. 1987. Waste Audit Study: Printed Circuit Board

Manufacturers. Report prepared by Planning ResearchCorporation, San Jose, California, for the CaliforniaDepartment of Health Services, AlternativeTechnology Section, Toxic Substances ControlDivision, April 1987.

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

SECTION 2PRINTED CIRCUIT BOARD

MANUFACTURING INDUSTRY PROFILE

Manufacturers of printed circuit boards (PC boards)are included as part of the electronic componentmanufacturing industry. As of 1984, the printed circuitboard manufacturing industry consisted of a total of 585plants with an employment of 435,100 (NCO 1984).Industry personnel indicate that the actual number of plantsmay be closer to 1,000 (USEPA 1986).

The industry consists of large facilities totally dedicatedto printed circuit boards, large and small captive facilities,small job shops doing contract work, and specialty shopsdoing low-volume and high-volume precision work.Approximately half of the printed circuit boards producedare by independent producers, while the rest are by captiveproducers. Over 65 percent of all printed circuit boardmanufacturing sites are located in the northeastern statesand in California (NCO 1984).

The printed circuit board manufacturers visited as apart of this study are all considered small. Generally, thesesmall companies can be characterized as those that produceup to 3,000 to 5,000 square feet of processed board eachmonth and require approximately 8,000 to 10,000 squarefeet of building space. Large companies can becharacterizedas those that produce or 30,000 to 50,000 square feet permonth.

Products and Their UsePrinted circuit boards can be classified into three basic

types: single-sided, double-sided, and multi-layered. Thetotal board production in 1983 was 14 million squaremeters (PEI 1983). Double-sided boards accounted forabout 55 percent of the printed circuit boards produced,while multi-layer board production made up 26 percent(PEI 1983). The type of board produced depends on thespatial and density requirement, and on the complexity ofthe circuitry. Printed circuit boards are used mainly in theproduction of business machines, computers,communication equipment, control equipment and homeentertainment equipment.

Raw MaterialsThe following raw materials are used by the industry

(Stintson 1983, PEI 1983, Cox and Mills 1985):

Board materials

Cleaners

Etchants

Catalysts

Electroless copperbath

ScreenScreen ink

Resists

Sensitizers

Resist solvents

Electroplating baths

glass-epoxy, ceramics, plastic,phenolic paper, copper foilsulfuric acid, fluoroacetic acid,hydrofluoric acid, sodiumhydroxide, potassium hydroxide,trichloroethylene, 1,1,1 -trichlorcethane, perchloroethylene,methylene chloridesulfuric and chromic acid,ammonium persulfate, hydrogenperoxide, cupric chloride, ferricchloride, alkaline ammoniastannous chloride, palladiumchloridecopper sulfate, sodium carbonate,sodium gluconate, Rochelle salts,sodium hydroxide, formaldehydesilk, polyester, stainless steelcomposed of oil, cellulose, asphalt,vinyl or other resinspolyvinyl cinnamate, ally ester,resins, isoprenoid resins,methacrylate derivatives, poly-olefin sulfonesthiazoline compounds, azidocompounds, nitro compounds, nitroaniline derivatives, anthones,quinones, diphenyls, azides,xanthone, benzilortho-xylene, meta-xylene, para-xylene, toluene, benzene,chlorobenzene, cellosolve andcellosolve acetate, butyl acetate,1,l ,l trichoroethane, acetone,methyl ethyl ketone, methyl isobutylketonecopper pyrophosphate solution,acid-copper sulfate solution, acid-copper fluoroborate solution, tin-lead, gold, and nickel platingsolutions

5

Resist stripping sulfuric-dichromate, ammoniacalhydrogen peroxide, solutionsmetachloroperbenzoic acid,methylene chloride, methyl alcohol,furfural, phenol, ketones,chlorinated hydrocarbons, non-chlorinated organic solvents,sodium hydroxide

Process DescriptionPrinted circuit (PC) boards, also called printed wiring

boards, consist of patterns of conductive material formedonto a non-conductive base. The conductor is generallycopper, although aluminum, chrome, nickel and othermetals have been used. The metal is fixed to the basethrough use of adhesives, pressure/heat bonding, andsometimes screws. Base materials include pressed epoxypaper, phenolic, epoxy glass resins, teflon-glass, and manyother materials.

There are three common types of PC boards: single-sided, double-sided, and multilayer. Single sided boardsare those with a conductive pattern on one side only.Double-sided boards have conductive patterns on bothfaces. Multilayer boards consist of alternating layers ofconductor and insulating material, bonded together. Theconductors are connected together through plated-throughholes.

Production methods that have been employed by theindustry to produce printed circuit boards includes subtractiveprocesses and additive processes. Detailed descriptions ofthe process sequences are given elsewhere (Yapoujian1982, Coombs 1979, USEPA 1979, PEI 1983). Becauseofthe limitations of the additive processes, the subtractivemethod is currently the one most widely used, although itcan produce more metal wastes than additive methods.The subtractive method is briefly described below fordouble-sided panels. Most of the operations shown arealso common to the production of other types of printedcircuit boards such as single-sidedor multi-layered boards.

The conventional subtractive process employs acopper-clad laminate board composed of anon-conductivematerial such as glass epoxy or plastic. Printed circuitboard manufacturers often purchase panels of board thatare already copper clad from independent laminators. Themanufacturing process consists of the following operations:

Board preparation - The process sequence beginswith a baking step to ensure that the copper laminatedboards are completely cured. Holes for the components arethen drilled through stacks of boards or panels, often fourlayers thick. The drilling operation results in burrs beingformed on one or both sides of the panel. These are

removed mechanically through sanding and deburringsteps to create an even surface.

Electroless copper plating - The smooth copper-cladboard is subsequently electroless- plated with copper toprovide a conducting layer through the drilled holes forcircuit connections between the copper-clad board surfaces.Electroless plating involves the catalytic reduction of ametallic ion in an aqueous solution containing a reducingagent, resulting in deposition without the use of externalelectrical energy. The circuit board must be thoroughlycleaned before it is electroless-plated.

Materials typically used in the operation, that appearin the waste streams, include:

Abrasive and alkaline cleaning compounds

Ammonium persulfate or peroxide-sulfuric acidetchant, for removing the oxidation inhibitor inthe copper foil

Tin and palladium catalyst

Cupric chloride or copper sulfate plating bathcontaining formaldehyde or hypophosphatereducing agents, and amino acid, carboxylicacid, hydroxy acid, or amine chelating agents

Rinsewaters

Pattern printing and masking - Electroless platingwith copper provides a uniform but very thin conductinglayer over the entire surface, that has little mechanicalstrength. It is used initially, to deposit metal on non-conducting surfaces such as inside the holes. Electroplatingis required to build up the thickness and strength of theconducting layers.

Pattern plating is one method of buiding up conductinglayer thickness, and is the most common type of subtractiveprocess used. It consists of electroplating only the insidesof the holes and the circuit patterns. A layer of resist isdeposited, using screen or photolithography techniques, inareas whereelectroplated conducting material is not desired.The layer of resist on these areas is later stripped off, andthe copper foil is etched away.

The area where the resist has not been depositedconstitutes the circuit pattern. These areas receive severalelectrodeposition layers. Tin/lead plating is one of thelayers deposited, and it functions as another resist layer,allowing copper foil in the non-circuit areas to be etchedaway without the circuit pattern being damaged. Thecircuit pattern then receives final electroplated layers ofmetals such as nickel and gold. Chemicals used for theseprocesses include:

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Photo-sensitive inks (for silk screening circuitpatterns onto the board)

l Resists composed of epoxy vinyl polymers,halogenated aromatics, methacrylates, and/orpolyolefin sulfones

l Alkaline cleaners to remove residuals frompattern developing operations

l Acid dips to remove oxides

l Electroplating solutions typically containingcopper, tin/lead, nickel and gold salts, cyanide,sulfate, pyrophosphate, and fluoroboratecompounds

Etchants such as peroxide-sulfuric acid, sodiumpersulfate, ferric or cupric chloride, and chromicacid

Panel plating methods of PC board manufacture differfrom pattern plating in that the entire board is electroplatedwith copper, including the holes, after which the non-circuit areas are etched away. Because of the additionalcopper deposited, panel plating can produce more metalwastes.

The fully additive method differs from the subtractivemethod described above in that it involves deposition ofplating material onto the board only in the pattern dictatedby the circuit, and does not require removal of the metalalready deposited. The process begins with an uncladboard. Plating resist is then applied onto the board in non-circuit areas. Electroless copper is subsequently depositedto build up the circuit to the desired thickness. Since theboard doesn’t initially have any copper in non-circuit areas,a copper etching step is thus eliminated, as well as much ofthe metal wastes.

Waste DescriptionThere are five principal operations common to the

production of all types of printed circuit boards. Theseinclude:

l Cleaning and surface preparation

l Catalyst application and electroless plating

l Pattern printing and masking

l Electroplating

l Etching

Typical waste streams generated from the unitoperations in the printed circuit board manufacturingindustry are listed in Table 1.

Airborne particulates generated from the cutting,sanding, routing, drilling, beveling, and slotting operationsduring board preparations are normally collected andseparated using baghouse and cyclone separators. Theyare then disposed of, along with other solid wastes atlandfills.

Acid fumes from acid cleaning and organic vaporsfrom vapor degreasing are usually not contaminated withother materials, and therefore are often kept separate forsubsequent treatment. The acid fume air stream is collectedvia chemical fume hoods and sent to a scrubber where it isremoved with water. The scrubbed air then passes on to theatmosphere, and the absorbing solution is neutralizedalong with other acidic waste streams. Similarly, organicfumes are often collected and passed through a bed ofactivated carbon. The carbon bed is then regenerated withsteam. In many cases, the regenerative vapor is condensedand the condensate containing water and solvents isdrummed and sent for offsite treatments. In a few cases, theregenerative vapor is combusted in a closed fumes burner.

The spent acid and alkaline solutions from the cleaningsteps are either contract hauled for off-site disposal orneutralized and discharged to the sewer. Spent chlorinatedorganic solvents are often gravity separated, and arerecovered in-house or hauled away for reclaiming.

The remaining majority of the wastes produced areliquid waste streams containing suspended solids, metals,fluoride, phosphorus, cyanide, and chelating agents. LowpH values often characterize the wastes due to acid cleaningoperations. The liquid wastes may be controlled using end-of-pipe treatment systems, or a combination of in-linetreatment and separate treatment of segregated wastestreams. A traditional treatment system for the wastesgenerated is often based on pH adjustment and the additionof chemicals that will react with the soluble pollutants toprecipitate out the dissolved contaminants in a form suchas metal hydroxide or sulfate. The solid particles areremoved as a wet sludge by filtration or flotation, and thewater is discharged to the sewer. The diluted sludge isusually thickened before dumping into landfills. Recentimprovements in in-line treatment technologies such asreverse osmosis, ion exchange, membrane filtration, andadvanced rinsing techniques increase the possibility for therecovery and reuse of water and metallic resources.

Table 1. Waste Streams from Printed Circuit Board ManufacturingWaste Stream Waste Stream

Waste Source Description Composition

Cleaning/Surface preparation 1. Airborne particulates2. Acid fumes/organic vapors3. Spent acid/alkaline solution4. Spent halogenated solvents5. Waste rinse water

Catalyst application/Electroless plating

1. Spent electroless copper bath2. Spent catalyst solution3. Spent acid solution4. Waste rinse water

Pattern printing/masking 1. Spent developing solution2. Spent resist removal solution3. Spent acid solution4. Waste rinse water

Electroplating 1. Spent plating bath2. Waste rinse water

Etching 1. Spent etchant2. Waste rinse water

Board materials,sanding materials,metals, fluoride,acids, halogenatedsolvents, alkali.Acids, stannicoxide, palladium,complexed metals,chelating agents.Vinyl polymers,chlorinatedhydrocarbons, organicsolvents, alkali.Copper, nickel, tin,tin/lead, gold,fluoride, cyanide, sulfate.Ammonia, chromium,copper, iron, acids.

References USEPA. 1979. U.S. Environmental Protection Agency,

Coombs, C.F. 1979. Printed Circuit Handbook. 2nd ed. Office of Water and Hazardous Materials. Development

New York, N.Y.: McGraw-Hill Book Co. Document for Existing Source Pretreatment Standardsfor the Electroplating Point Source Category. EPA-

Cox, D.S., and AR. Mills. 1985. Electronic chemicals: agrowth market for the 80’s. Chem. Eng. Prog. 81(l):11-15.

440-l-79-003. Washington, D.C.: U.S. EnvironmentalProtection Agency.

USEPA 1986. Waste Minimization - Issues and Options,NCO. 1984. National Credit Office. Electronic marketing Volume II. PB87-114369. Prepared by Versar, Inc.

directory. New York: National Credit Office. and Jacobs Engineering Group Inc.

PEI. 1983. Pedco-Environmental, Inc. Industrial Process Yapoujian, F. 1982. Overview of printed circuit boardProfiles for Environmental Use. Chapter 30. The technology. Met. Finish. 80: 21-5.Electronic Component Manufacturing Industry. EPA-600-2-83-033. Cincinnati, Ohio. U.S. EnvironmentalProtection Agency.

Rothschild, B.F., and Schwartz, M. 1988. Printed Circuit/Wiring Board Manufacture. American Electroplatersand Surface Finishers Society.

Stintson, S.C. 1983. Chemicals for electronics: new growthin competitive field. Chem. Eng. News. 61(30): 7-12.

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SECTION 3

WASTE MINIMIZATION OPTIONS FOR PRINTED CIRCUIT BOARDM A N U F A C T U R E R S

This section discusses recommended wasteminimization methods for printed circuit boardmanufacturers. These methods come from accountspublished in the open literature and through industrycontacts. The primary waste streams associated withmanufacturing are listed in Table 2 along with recommendedcontrol methods. Many control measures associated withphotoprocessing and cleaning wastes are not discussed inthis report. The reader is referred to the appropriate referencematerial for information regarding these waste streams(USEPA 1989, USEPA 1990, USEPA 1986, CDHS 1986).

The waste minimization methods listed in Table 2 canbe classified generally as source reduction, or recycling.Source reduction can be achieved through material orproduct substitution, process or equipment modification,or better operating practices. Recycling can include recoveryof part of the waste stream or reuse of all of it, and can beperformed on-site or off-site.

Better operating practices are procedural or institutionalpolicies that result in a reduction of waste. They include:

l Waste stream segregation

l 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 todepartments 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.

Product SubstitutionWhile not under the control of most printed circuit

board manufacturers, improvements in the techniques usedin the packaging of microchips can result in a decrease ofwaste associated with printed circuit board manufacturing.Two new techniques include:

Increased use of surface mount technology. Presently,the’ dual-in-line package (DlP) accounts for 80% of allpackaging of integrated circuits (Bowl by 1985). Moreefficient packages, however, are being developed whichutilize a relatively new method of attaching packages toprinted circuit boards. One important method is calledsurface mount technology (SMT). The use of SMT insteadof the conventional through-hole insertion mounting allowsfor closer contact areas of chip leads, and therefore reducesthe size of printed circuit boards required for a givennumber of packages or DIPS. For a fixed number ofpackages, the printed circuit board needs to be only 35percent to 60 percent as large as a printed circuit boarddesigned for the old style package (Bowl by 1985). As themetal area on which cleaning, plating and photoresistoperations are performed is decreased, the wastes associatedwith these operations can also be reduced. At present,however, SMT uses considerably higher quantities ofchlorofluorocarbons for degreasing than through-holemounting. CFC-113 is one of the major degreasing agentsin current use. Because of the danger that somechlorofluorocarbons present to the atmospheric ozone layer,the overall environmental risks of SMT must be carefullyexamined, and alternative degreasing solvents identified,before replacing through-hole technology with SMT.

Use of injection molded substrate and additive plating.The development of high-temperature, high-performancethermoplastics has introduced the use of injection molding

9

Table 2. Waste Minimization Methods for the Printed Circuit Board IndustryOperation Waste Minimization Method

PC Board Manufacture

Cleaning and SurfacePreparation

Product Substitution:Surface mount technologyInjection molded substrate and additive plating

Materials substitution:Use abrasivesUse non-chelated cleaners

Increase efficiency of process:Extend bath life, improve rinse efficiency,countercurrent cleaning

Pattern Printing andMasking

Electroplating andElectroless Plating

Etching

Recycle/reuse:Recycle/reuse cleaners and rinses

Reduce hazardous nature of process:Aqueous processable resistScreen printing versus photolithographyDry photoresist removal

Recycle/reuse:Recycle/reuse photoresist stripper

Eliminate process:Mechanical board production

Materials substitution:Non-cyanide bathsNoncyanide stress relievers

Extend bath life: reduce drag-inProper rack design/maintenance, betterprecleaning/rinsing, use of demineralizedwater as makeup, proper storage methods

Extend bath life: reduce drag-outMinimize bath chemical concentration,increase bathtemperature, use wetting agents,proper positioning on rack, slow withdrawaland ample drainage, computerized/automatedsystems, recover drag-out, drain boards

Extend bath life: maintain bath solution qualityMonitor solution activity. Control temperature.Mechanical agitation. Continuous filtration/carbon treatment.Impurity removal

Improve rinse efficiency:Closed-circuit rinses. Spray rinses. Fognozzles. Increased agitation. Countercurrentrinsing. Proper equipment design/operatnon.Deionized water use.

Recovery/reuse:Segregate streams.Recover metal values

Eliminate process:Differnetial plating

Materials substitution:Non-chelated etchants. Non-chrome etchants

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Table 2. Waste Minimization Methods for the Printed Circuit Board Industry

(continued)Operation Waste Minimization Method

Etching(continued)

Increase efficiency:Use thinner copper cladding. Patternvs. panel plating. Additive vs. subtractivemethod.Reuse/recycle:Reuse/recycle etchants

Wastewater Treatment Reduce hazardous nature:Alternative treatment chemicals that generateless sludge Use of ion exchange and activatedcarbon for recycling wastewater

Reuse/recycle:Waste stream segregation

into the manufacturing of printed circuit boards. In thisprocess, heated liquid polymer is injected under highpressure into precision molds. Since the molded substratesare unclad, semi-additive or fully additive plating is usedto produce metalized conductor patterns (Engelmaier andFrisch 1982). Injection molding, coupled with a fast-rateelectrodeposition (FRED) technique, such as that developedby Battelle (LWVM 1985), can be used to manufacturecomplex three-dimensional printed circuit boards withpossible reduction in hazardous waste generation due tothe elimination of spent toxic etchants.

Cleaning and Surface PreparationAs mentioned in the introduction, the reader should

refer to the appropriate reference material (USEPA 1989,CDHS 1986) for information regarding the reduction ofwaste associated with parts cleaning. Information isprovided below on: abrasive cleaning; use of non-chelatedcleaning chemicals; extending bath life and improvingrinse efficiency; use of countercurrent cleaningarrangements; and reuse/recycle of cleaning agents andrinse water.

USE ABRASIVE INSTEAD OF AQUEOUSCLEANING

Mechanical cleaning methods offer an alternative toaqueous techniques and generate less hazardous, waste;however, these methods can only be employed beforeelectronic components have been added to the boards.Abrasive blast cleaning uses plastic, ceramic, or hardermedia such as aluminum oxide to remove oxidation layers,old plating, paint and burrs from workpieces, and to createa smooth surface. The aim is to select a blast medium thatis harder than the layer to be stripped, but softer than thesubstrate, in order to prevent damage to the part. Abrasives

can also be used in vibratory cleaning (in which parts areimmersed in a vibrating tank containing abrasive materialand water), in tumbling barrels, or applied via a buffingwheel. More information on abrasive cleaning, particularlytumbling barrels and vibratory cleaning, can be found inDurney (1984) and ASM (1987).

USE NON-CHELATED CLEANING CHEMICALSThe use of non-chelate process chemicals instead of

chelated chemical baths can reduce hazardous wastegeneration. Chelators are employed in chemical processbaths to allow metal ions to remain in solution beyond theirnormal solubility limit. This enhances cleaning, metaletching, and selective electroless plating (Couture 1984).Once the chelating compounds enter the waste stream, theyinhibit the precipitation of metals, and additional treatmentchemicals must be used These treatment chemicals end upin the sludge and contribute to the volume of hazardouswaste sludge.

Ferrous sulfate is a common reducing agent used totreat wastewaters that contain chelators. The ferroussulfate breaks down the complex ion structures to allowmetals to precipitate. However, the iron added to thetreatment process also precipitates as a metal hydroxide.Since enough ferrous sulfate is usually added to thewastewater to achieve an iron to metal ratio of 8:1, asignificant additional volume of sludge is generated(Couture 1984). One printed circuit board manufacturervisited during the audit study used ferrous sulfate to breakdown chelators prior to metals precipitation. The ironpresent in the resultant sludge contributed approximately32 percent of the total dry weight of the sludge.

Common chelators used in printed circuit boardmanufacturing chemicals include ferrocyanide,

11

ethylenediaminetetraacetic acid (EDTA), phosphates, andammonia (Foggia 1987). Chelating agents are commonlyfound in cleaning chemicals and etchants. Non-chelatealkaline cleaners are available; however, laboratory testshave shown that some of these products still have theability to chelate metals (Couture 1984).

In addition to using non-chelated chemistries, the useof mild chelators can also reduce the need for additionaltreatment of wastewaters. Mild chelators are less difficultto break down. Therefore, metals can be precipitated outof solution during treatment without using the volume oftreatment chemicals that is often necessary with strongchelators. For example, EDTA is a mild chelator that onlyrequires lowering the pH to below 3.0 to allow metals toprecipitate (Foggia 1987).

One disadvantage of using non-chelated process bathsis that they usually require continuous filtration to removethe solids that form in the bath. The costs of these filtersystems range from approximately $400 to $1,000 for eachtank using anon-chelated process chemistry. Thesesystemsgenerally have a 1 to 5 micron filter with a control pumpthat can filter the tank contents once or twice each hour(Foggia 1987). In addition to the purchase and setupcosts,filter replacement and maintenance costs are incurredwhen this system is used.

EXTEND BATH LIFE AND IMPROVE RINSEEFFICIENCY

This method applies to nearly any tank of processingsolution used in the facility. See the discussion ofelectroplating waste reduction methods for detailedinformation.

USE COUNTERCURRENT CLEANINGARRANGEMENT

A common hazardous waste stream generated byprinted circuit board manufacturers is waste nitric acidfrom the cleaning of electroplating workpiece racks.Typically, racks are placed in a nitric acid bath to clean offthe plated copper. When the copper content in the bath getstoo high to effectively clean the racks, the nitric acid iscontainerized for disposal. Use of a cascade cleaningsystem can significantly reduce nitric acid waste generation.

During the audits, one small printed circuit boardmanufacturer who operated a five tank plating rack cleaningline generated approximately 15 gallons of waste nitricacid in 6 months compared to another small company thatused a single tank for cleaning racks and generatedapproximately 60 gallons each month. Both companiesoperate similar size process lines, and are considered smallprinted circuit board manufacturers (both estimated theirprinted circuit board production to be 3,000 square feet per

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month). Assuming that waste disposal for the spent nitricacid is $50 per 55-gallon drum and the cost of technicalgrade nitric acid is approximately $3.50 per gallon, thedifferential operating costs are $3042 per year (excludingdifferences in labor-increased rack handling versusdecreased waste handling). The total cost of adding fouradditional tanks to the one-cleaning-tank line would be$1620.

REUSE/RECYCLE OF CLEANING AGENTSPeroxide/sulfuric acidsolution is used as a mild etchant

for cleaning copper and removing oxides prior to plating.When the solution is brought off-line and cooled, thecopper crystallizes as copper sulfate. The supernatant canthen be returned to the tank, replenished with oxidizers,and reused. The copper sulfate crystals can be used ascopper electroplating bath makeup (Couture 1984). Thepractice is only advisable, however, if the crystals are firstdissolved into solution and treated with activated carbon toremove the organics. Otherwise, the organics present inthe crystals could ruin the plating bath.

In addition to recovering metals from the spent bath,spent acid can be regenerated by means of ion exchange(Basta 1983). Eco-Tec Ltd., in Ontario, Canada, marketsan acid purification system that employs a proprietary resinthat recovers mineral acids. The metals are recovered in aconcentrated (but still dissolved) form. The concentratedmetals can then be recovered by electrolytic means.

Ion exchange is employed by Modine Manufacturing,in Trenton, MO., to treat copper-contaminated sulfuricacid/hydrogen peroxide solution which is used to brightenbrass (Basta 1983). Sodium phosphate salts, formed innickel/copper electroless plating, can be converted intouseful hypophosphite salts by ion exchangeresins activatedwith hypophosphorous acid. The use of ion exchangeresins for regeneration, however, suffers from thedisadvantage of generating additional wastes, such asspent resins and resin regeneration solutions.

REUSE/RECYCLE OF RINSE WATERAfter rinse solutions become too contaminated for

their original rinse process, they may be useful for otherrinse processes. For example, rinses containing high levelsof process chemicals can be concentrated throughevaporation and returned to the process baths as makeup.Closed-circuit rinsing of this type can dramatically reducethe hazardous chemicals content of the waste stream.

Effluent from a rinse system that follows an acidcleaning bath can be reused as influent water to a rinsesystem following an alkaline cleaning bath. If both rinsesystems require the same flow rate, 50 percent less rinsewater would be used to operate them. In addition, using the

effluent from the rinse solution that follows an acidcleaningprocess as the feed to the rinse system that follows analkaline cleaning process rinse system can actually improverinse efficiency for two reasons. First, the chemical diffusionprocess is acceleratedbecause the concentration of alkalinematerial at the interface between the drag-out film and thesurrounding water is reduced by the neutralization reaction.Second, the neutralization reaction reduces the viscosity ofthe alkalinedrag-out film (USEPA 1982a). One successfulexample of this technique was observed in a nickel platingprocess in which the same rinse water stream was used forthe rinses following the alkaline cleaning, acid dip, andnickel plating tanks. Instead of having three different rinsestreams, only one stream was used, greatly reducing theoverall rinse water requirements (USEPA 1983).

Adding acid rinses to alkaline rinses can result inproblems, however. Unwanted precipitation of metalhydroxides onto the cleaned workpieces can occur in someinstances. Before being implemented, a combined acid andalkaline rinse system must be thoroughly investigated inthe particular environment of the process line.

their process lines and configure rinse systemarrangementsthat take advantage of rinse water reuse opportunities.

Other rinse water recycling opportunities are alsoavailable. Acid cleaning rinse water effluent can be used asrinse water for workpieces that have gone through a mildacid etch process. Effluent from a critical or final rinseoperation, which is usually less contaminated than otherrinse waters, can be used as influent for rinse operationsthat do not require high rinse efficiencies. The water fromfume scrubbers has been shown to be practical for rinsingin certain cases (Cheremisinoff, Peina, and Ciancia 1976).Spent cooling water or steam condensate can also beemployed for rinsing if technically permissible andeconomicallyjustified. Printed circuit board manufacturersshould evaluate the various rinse water requirements for

Use screen-printing instead of photolithography toeliminate the need for developers. Screen-printing hasconventionally been used only to produce printed circuitboards which require very low resolution in the width andspacing of the circuit lines. Some companies have recentlydeveloped screen-printing techniques which can providehigher degrees of resolution. For example, General Electrichas developed a method for screen-printing down to 0.01inch resolution which can be used to manufacture printedcircuit boards for appliances (Greene 1985). The majorityof printed circuit board manufacturers, however, are stillusing the photolithographic technique for printed circuitboards having circuitry finer than 12 mil lines and spaces.

Use Asher dry photo resist removal method to eliminatethe use of organic resist stripping solutions. Although thismethod is increasingly popular in the semiconductorindustry, its use has not been reported by printed circuitboard manufacturers, probably because the printed circuitboard resists are usually much thicker than the correspondingsemiconductor resist layers.

Recycle/reuse photo resist stripper. Photo resist stripperis used to remove photoresist material from the board. Thisphotoresist is a polymer material that remains in the strippertank in small flakes that slowly settle to the bottom. Whenthe sludge formed at the bottom of the stripper tank buildsup, the flakes begin to adhere to circuit boards and thestripper solution is considered spent. Increased use of thesolution can be achieved by decanting and filtering thestripper solution out of the tank into a clean tank. This isfeasible because the stripper usually becomes spent as aresult of the residue buildup long before it becomes spentas a result of a decrease in chemical strength.

Source reduction methods associated withelectroplating and electroless plating center around

Electroplating and Electroless Plating

Pattern Printing and Maskingeliminating the need for the operation, reducing thehazardous nature of the materials used, extending process

Many of the source reduction techniques discussed for bath life, improving rinse efficiency, and recovering/reusingthe photoprocessing industry (USEPA 1988) apply to this spent materials.phase of printed circuit board manufacturing. Listedbeloware several techniques that deal with circuit board ELIMINATE NEED FOR OPERATIONf a b r i c a t i o n .

Use aqueous processable resist instead of solventprocessable resist. Aqueous processable resists (such asthe DuPont Riston photopolymer film resists which allowfor the use of caustic and carbonates as developer andstripper) can be used in place of solvent processable resistswhenever possible to eliminate the generation of toxicspent solvents. Hundred of facilities are now employingthese aqueous processable films for the manufacturing ofprinted circuit boards.

Use mechanical board production methods/systems.For facilities that produce low-volume prototype circuitboards, mechanical board production systems are availablewhich bypass all operations involving chemicals. Circuitboards are designed on a computer and the pattern is thenetched by means of a mechanical stylus on a copper-cladboard. While this system is not viable for producing boardsin large quantities, it is highly suited for use in development/research settings.

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REDUCE HAZARDOUS MATERIALS USEDUse non-cyanide plating baths.Use non-cyanide stress relievers. In the case of

electroless copper plating, water soluble cyanidecompounds of many metals are typically added to eliminateor minimize the internal stress of the deposit. It has beenfound that polysiloxanes are also effective stress relievers(Durney 1984). By substituting polysiloxanes for cyanides,the hazardous nature of the spent bath solution can bereduced.

EXTEND PROCESS BATH LIFEProcess baths may contain high concentrations of

heavy metals, cyanides, solvents and other toxicconstituents. They are not discarded frequently but ratherare used for long periods of time. Nevertheless, they dorequire periodic replacement due to impurity build-upresulting from drag-in or decomposition and the loss ofsolution constituents by drag-out. When a solution iscontaminated or exhausted, the resulting waste solutionmay contain high concentrations of toxic compounds andrequire extensive treatment. The source control methodsavailable for extending process bath life include reducingor removing impurities formed in the bath, reducing theloss of solution (drag-out) from the bath, and maintainingbath solution quality.

Reduce ImpuritiesImpurities come from five sources: racks, anodes,

drag-in, water or chemical make-up, and air. The buildupof impurities can be limited by the following techniques:

Proper rack design and maintenance. Corrosion andsalt buildup deposits on the rack elements contaminatesolutions if they chip away or fall into the solution. Properdesign and regular cleaning will minimize this form ofcontamination. Fluorocarbon coatings applied to the rackshave also been found to be effective (Lane 1985). Such acoating lowers drag-out as well since less bathsolution remains in the corroded crevices on the racks orbarrels.

Use purer anodes and anode bags. During the platingprocess, metal from the anode dissolves in the platingsolution and deposits on the cathode (workpiece). Some ofthe impurities contained in the original anode matrix staybehind in the plating solution, eventually accumulating toprohibitive levels. Thus, the use of purer metal for theanode extends the plating solution life. Anode bags canalso be used to prevent pieces of decomposed anodes fromfalling into the tank.

Drag-in reduction by better rinsing Efficient rinsingof the workpiece between different process baths reducesthe drag-in of plating solution into the next process bath.

Use of deionized or distilled make-up water. Tocompensate for evaporation, water is required for makeupof plating solutions. Using deionized or distilled water ispreferred over tap water, since tap water may have a highmineral or solids content, which can lead to impuritybuildup.

Proper storage of chemicals. Proper storage of theprocess solutions can also reduce wastegeneration. Usually,the process solutions are stored as a two-part solution andare mixed when a batch is needed. Prolonged storage ofmixed solutions may allow some chemical reactions tooccur that could generate contaminants that reduce bathlife. In electroless copper plating, if formaldehyde (areducing agent) is stored with a hydroxide, the hydroxidecan cause the formaldehyde to break down into formic acidand methyl alcohol. Thus, it is better to only store non-reactive mixtures of materials or to store each itemseparately.

Once you have reduced impurity buildup in the bath,you need to concentrate on reducing solution losses throughdrag out.

Reduce Drag-OutSeveral factors contribute to drag-out, These include

workpiece size and shape, viscosity and chemicalconcentration, surface tension, and temperature (USEPA,1982a). By reducing the volume of drag-out that enters therinse water system, valuable process chemicals can besaved and sludge generation can be reduced. Morediscussion of the impact on sludge generation due to drag-out is presented under “alternative treatment methods.”

During the course of this study, it was found that mostprinted circuit board manufacturers have little idea of thevolume of drag-out their various process lines generate.Process chemical suppliers assess drag-out using a standardrate of 10 to 15 ml/ft2 of circuit board (Foggia 1987).However, this standard rate does not take into account thevarious process bath operating parameters that can be usedor the effects of various workpiece rack withdrawal methods.Nevertheless, this standard drag-out rate is a good startingpoint for determining the impact of drag-out on wastegeneration. Factors affecting drag-out are described inTable 3.

Table 3. Factors That Increase the Amountof Drag-Out

High surface tensionHighly viscous plating solutionLarger workpiece sizeFaster workpiece withdrawalShorter drainage timeOrientation of workpiece during removalso that drainage is reduced

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Generally, drag-out minimization techniques include:

Minimize bath chemical concentration. Controllingthe chemical concentration of the process bath can reducedrag-out losses in two ways. Reducing toxic chemicalconcentrations in a process solution reduces the quantity ofchemicals and the toxicity in any dragout that occurs. Also,greater concentrations of some of the chemicals in asolution increase the viscosity (USEPA 1982a). As aresult, the film that adheres to the workpiece as it isremoved from the process bath is thicker and will not drainback into the process bath as quickly. Therefore thevolume of drag-out loss is increased and a higher chemicalconcentration in the drag-out is created. In electrolesscopper plating for printed circuit board manufacture, dilutesolutions have been tried successfully by manymanufacturers (USEPA 1981).

Chemical product manufacturers may recommend anoperating concentration that is higher than necessary toperform the job. A printed circuit board manufacturershould determine the lowest process bath concentrationthat will provide adequate product quality. This can bedone by mixing a new process bath at a slightly lowerconcentration than normal. As fresh process baths aremixed the chemical concentration can continue to bereduced until product quality begins to be affected. At thispoint, the manufacturer can identify the process bath thatprovides adequate product quality at the lowest possiblechemical concentration.Fresh process baths can often be operated at lowerconcentrations than used baths. Makeup chemicals can beadded to the used bath to gradually increase theconcentration. This procedure allows newer baths to beoperated at lower concentrations and older baths to bemaintained for longer periods of time before requiringdisposal.

Increase bath operating temperature in order to lowerviscosity. Increased temperature lowers both the viscosityand surface tension of the solution, thus reducing drag-out.The resulting higher evaporation rate may also inhibit thecarbon dioxide absorption rate, slowing down the carbonateformation in cyanide solutions. Unfortunately, this benefitmay be lost due to the formation of carbonate by thebreakdown of cyanide at elevated temperatures. Additionaldisadvantages of this option would include higher energycosts, higher chance for contamination due to increasedmake up requirement, and increased need for air pollutioncontrol due to the higher evaporation rate.

Use wetting agents. Wetting agents can be added to aprocess bath to reduce the surface tension of a solution and,as a result, reduce the volume of drag-out loss. The use ofwetting agents in the metal finishing industry has been

estimated to reduce drag-out loss by as much as 50 percent(USEPA, 1982a). However, most printed circuit boardmanufacturers prefer using process chemicals that are freeof wetting agents because they can create foaming problemsin the process baths. Although the process bath chemistriesof a printed circuit board manufacturing line may notalways allow the addition of wetting agents, their useshould be evaluated.

Position workpiece properly on the plating rack. Whena workpiece is lifted out of a plating solution on a rack,some of the excess solution on its surface (drag-out) willdrop back into the bath. Proper positioning of the workpieceon a rack will facilitate maximum drainage of drag-outback into the bath. The position of any object which willminimize the carry-over of drag-out is best determinedexperimentally, although the following guidelines werefound to be effective (USEPA 1981):

- Orient the surface as close to vertical aspossible.

- Rack with the longer dimension of theworkpiece horizontal.

- Rack with the lower edge tilted from thehorizontal so that the runoff is from a comerrather than an entire edge.

While positioning of the printed circuit board offerslittle variability -- the boards are generally placed uprightin a rack -- a board that is tilted at an angle, allowing it todrip down onto an adjacent board instead of directly intothe bath, may lead to increased drag-out loss. The operatormust ensure that the workpiece is positioned properly toprevent unnecessary drag-out loss.

Withdraw boards slowly and allow ample drainage.The faster an item is removed from the process bath, thethicker the film on the workpiece surface and the greaterthe drag-out volume will be. The effect is so significantthat it is believed that most of the time allowed for withdrawaland drainage of a rack should be used for withdrawal only(USEPA, 1982a). However, since workpieces are usuallyremoved from a process bath manually, it is difficult tocontrol the speed at which they are withdrawn. Nevertheless,supervisors and management should emphasize to processline operators that workpieces should be withdrawn slowly.

Workpiece drainage once the part is removed from the bathalso depends on the operator. The timeallowed for drainagecan be inadequate if the operator is rushed to remove theworkpiece rack from the process bath area and place it inthe rinse tank. However, installation of a bar or rail abovethe process tank, and the requirement that all workpiecesbe hung from it for at least 10 seconds, may help ensure that

15

adequate drainage time is provided prior to rinsing. Printedcircuit board manufacturers express concern that increasingworkpiece rack removal and drainage time will allow forchemical oxidation on the board. Although some processsteps may not be amenable to these drag-out reductiontechniques, increased workpiece rack removal anddrainagetime can still be effective for many process steps.

Use computerized/automated control systems.Computerized process-control systems can be used forboard handling and process bath monitoring to preventunexpected decomposition of the plating bath. Since theuse of a computerized control system not only requires alarge capital outlay for initial installation but also increasesthe demand for skilled operations and maintenancepersonnel, only very large companies which manufactureboth printed circuit boards and other electronic componentsare incorporating this change in their manufacturing process.For example, Hewlett-Packard in Sunnyvale, Californiareported its successful use of computers for platingoperations on printed circuit boards (Anonymous 1983).

Recover drag-outfrom baths. In addition to reducingthe volume of drag-out that is lost from the process bath,printed circuit board manufacturers can recover drag-outlosses by using drain boards and close-circuit rinsing.Drain boards are used to capture process chemicals thatdrip from the workpiece rack as it is moved from theprocess bath to the rinse system. The board is mounted atan angle that allows the chemical solution to drain back intothe process bath. Drainage boards should be installed ifthere is space between the process bath tank and the rinsetank where chemical solutions would otherwise drip ontothe floor and enter the wastewater system when the floor iswashed down.

Another method of reducing drag-out loss is to recoverit for reuse in the process tank. The most common way todo this is through use of drag-out tanks (also called still ordeadrinses). Drag-out tanks can be used to capture processchemicals that adhere to the circuit board and return themto the process bath. Drag-out tanks are essentially rinsetanks that operate without a continuous flow of feed water.Chemical concentrations in these tanks increase as moreworkpieces are passed through. Since there is no feedwater flow to cause rinse water turbulence, air agitation isoften used to enhance rinsing. After a period of time, theconcentration of the drag-out tank solution will increase tothe point where it can be used to replenish the process bath.Drag-out tanks are primarily used with process baths thatoperate at an elevated temperature. The high temperaturecauses evaporative water losses that can be compensatedfor by adding the drag-out tank solution back to the processbath. If the evaporation rate of the process tank is not highenough, evaporators can be installed on it. They can also

be installed on the drag-out tank, to further concentrate therinse solution to be used as makeup.

Closed-circuit rinse systems can employ continuouslyflowing rinses as well as static rinses that are periodicallyadded as makeup to the process bath. Often, two or morerinses are used in a counter-current arrangement such as isillustrated in Figure 2. In this arrangement, the work is firstrinsed in the least clean rinse bath, and then in successivelycleaner baths. Spent rinse water from the cleanest bath getsadded to the next cleanest bath, and eventually to theprocess bath itself. The use of closed-circuit rinses can bevery significant in reducing the amount of heavy metalwastes and other hazardous chemicals in the waste streams(Meltzer 1989).

The printed circuit board manufacturing companiesvisited during this study all used drag-out tanks, but noneof them used the drag-out solution to replenish the processbath. Instead, these companies dumped the solutions intotheir treatment systems. They are reluctant to reuse thedrag-out solution because of fear of contamination. Sincea drag-out tank can often be used for more than a weekbetween dumps and because the tank is uncovered, operatorsare concerned that someone could improperly use the tankto rinse a workpiece; the contaminated drag-out solutionwould then contaminate the process bath when used toreplenish the process tank. Also, some process bathchemistries are such that adding drag-out solution backinto the process tank would spoil the bath. For example,electroless copper baths contain chemicals that breakdownin a diluted drag-out solution. If the solution is then addedback to the process tank, these breakdown chemicals couldadversely affect the electroless copper bath (Stone 1987).If the potential for contamination or deterioration of thedrag-out solution can be overcome, however, drag-outtanks can be used on copper and tin/lead electroplatinglines.

Maintain Bath Solution QualityOnce the amount of drag-in and drag-out from the

process bath has been reduced, attention should focus onways to maintain the bath at optimum operating conditions.Many facilities rely on drag-out from the bath as the wayof purging impurities that would otherwise build up andinterfere with operation. From an environmental viewpoint,this is a poor technique since it does not directly address theissue of impurity formation, results in high losses ofvaluable process solutions, and moves the problemdownstream to the treatment unit.

The following methods are noted as ways of increasingbath life and minimizing the impact on existing treatmentsystems:

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Figure 2. Multiple Closed Circuit Counterflow Rinse System

Monitor solution activity. By frequent monitoring ofthe bath activity and regular replenishment of reagents orstabilizers, bath life can be prolonged (Durney 1984).These reagents or stabilizers differ from process to process.Stabilizers such as 2-mercaptobenzothiozole and methanolare found effective in electroless copper plating used formanufacturing printed circuit boards. The addition ofstabilizers can sometimes decrease the deposition rate, butcan still be economical in the long run.

Control bath temperature. Good control of the bathtemperature is important from the viewpoint ofperformancepredictability and is another method of prolonging bathlife. Many surface treatment operations use tanks withimmersed cooling/heating coils. As the salts precipitateand form scales on the coils the heat transfer is impeded andtemperature control becomes increasingly difficult. Heattransfer efficiency can be maintained by periodic cleaningof the coils or by using jacketed tanks instead of coils.

Use mechanical agitation. Many process baths employair agitation to increase and maintain the efficiency of thebath. This practice can introduce contaminants into the

bath. The two principal contaminants are oil from thecompressor or blower and carbon dioxide. The oil will leadto undue organic loading while the carbon dioxide can leadto carbonate buildup in alkaline baths. A viable alternativeis to use mechanical agitation.

Use continuous filtering/carbon treatment. To avoidsurface roughness in the plating resulting in high rejectrates, baths should be continuously filtered to removeimpurities. The flow rate to the filter should be as high aspractical to prevent particles from settling on the parts.Since filters can seldom remove solids at the same rate thatthey are introduced by way of drag-in. filtering should beperformed even when the bath is not in use. Install ascoarse a filter as practical, since coarse filters allow higherloading before requiring replacement, allow for higherflow rates and hence greater tank turnovers, and requireless servicing. When organic buildup is a problem, use ofcarbon filter cartridges is appropriate.

Regenerate solution through impurity removal. Thereare methods that have been successfully used to increasethe longevity ofplating solutions through impurity removal.

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More efficient filtering of a plating solution has kept levelsof impurities low and extended solution life (McRae 1985).Metallic salts can sometimes be removed by temporarilylowering the bath temperature so as to form solid crystals.In the case of electroless nickel plating, the sodium sulfatethat forms can be crystallized by lowering the bathtemperature to 41-500F (Durney 1984). The crystals canthen be removed by filtration.

IMPROVE RINSE EFFICIENCYMost hazardous waste from a printed circuit board

manufacturing plant comes from the treatment ofwastewater generated by the rinsing operations that followcleaning, plating, stripping, and etching processes (Couture1984). Three basic strategies are used to provide adequaterinsing between various process bath operations. These are(1) turbulence between the workpiece and the rinse water,(2) sufficient contact time between the workpiece and therinse water, and (3) sufficient volume of water duringcontact time to reduce the concentration of chemicalsrinsed off the workpiece surface (USEPA 1982a). Thethird strategy is most commonly employed by printedcircuit board manufacturers. Reliance on this strategycauses printed circuit board manufacturers to usesignificantly more rinse water than is actually required(Couture 1984).

Many techniques are available that can improve theefficiency of a rinsing system and reduce the volume ofrinse water used. These techniques include:

Use of closed-circuit rinses. As mentioned above,installing one or more closed-circuit still or counter-flowrinsing tanks immediately after a plating bath allows formetal recovery and lowered rinse water requirements. Thecontents of the rinses are used to replenish the upstreamplating bath. As previously mentioned, a major problemwith the use of still rinses is that while they are commonlyinstalled at many plants, operators typically do not returnthe solution to the bath due to concern over solutioncontamination.

Generally, the use of a drag-out or still rinse tank canreduce both rinse water usage and chemical losses by 50percent or more (USEPA 1982a). Assuming that a chemicalbath processes 3,000 square feet of board each month, thetotal volume of process bath drag-out loss each monthwould be 12 gallons, with a drag-out rate of 15 ml/squarefoot of board. If the rinse system following the process bathoperates at a flow rate of 10 gpm for a total of two hourseach day, water usage would be 24,000 gallons per monthbased on 20 work days per month. A 50 percent reductionin process bath chemical loss and water usage achieved byinstalling a drag-out tank would reduce process bath losses

by six gallons per month and water usage by 12,OOgallons.

Use spray rinsing. Although spray rinsing uses betweenone-eighth and one-fourth the volume of water that a diprinse uses (USEPA 1982a), it is not always applicable toprinted circuit board manufacturing because the sprayrinse may not reach many parts of the circuit board.However, spray rinsing can be performed along withimmersion rinsing. This technique uses a spray rinse as thefirst rinse step after the workpieces are removed from theprocess tank. The spray rinsing typically takes place whilethe parts are draining above the process tank. This permitslower water flows in the rinse tank because spray rinsingremoves much of the drag-out before the workpiece issubmerged into the dip rinse tank.

Use fog nozzles. A variation on the spray nozzle is thefog nozzle. A fog nozzle employs water and air pressureto produce a fine mist. Much less water is needed than witha conventional spray nozzle. It is more often possible to usea fog nozzle rather than a spray nozzle directly over aheated plating bath to rinse the workpiece, because lesswater is added to the process bath using the fog nozzle.

Increase degree of agitation. Agitation between theworkpiece and the rinse water can be performed either bymoving the workpiece rack in the water or by creatingturbulence in the rinse water. Since most printed circuitboard manufacturing plants operate hand rack lines,operators could easily move workpieces manually byagitating the hand rack. However, the effectiveness of thissystem depends on cooperation from the operator.

Agitating the rinse tank by using forced air or water is themost efficient method for creating effective turbulenceduring rinse operations. This is achieved by pumpingeither air or water into the immersion rinse tank rinsingoperations. Air agitation provides the best rinsing becausethe air bubbles create the best turbulence for removing thechemical process solution from the workpiece surface(USEPA 1982a). This type of agitation can be performedby pumping filtered air into the bottom of the tank througha pipe distributor (air sparger). Great care should beexercised, however, to ensure that the air is free of dust oroil so as not to contaminate the boards being cleaned.Assuming the plant has a sufficient quantity of compressedair onsite that is readily available, the cost of installing airspargers is $100 to $125 per tank for a 50 gallon capacitytank.

Use counter current rinse stages. Multiple stage rinsetanks increase contact time between the workpiece and therinse solution and thereby improve rinsing efficiencycompared to a single-stage rinse. If these multiple tanks areset up in series as a counter current rinse system, water

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usage can also be reduced. Manufacturers do not need torely on large volumes of rinse water to prevent chemicalconcentrations in the rinse solution from becomingexcessive. Multiple rinse tanks can be used to providesufficient rinsing while significantly reducing the volumeof rinse water used. A multistage counter current rinsingsystem can use up to 90 percent less rinse water than aconventional single-stage rinse system (Couture 1984).

The effectiveness of a multistage system in reducingrinse water usage is illustrated in the following example. Aplant operates a process line where approximately 1.0gallon of drag-out per hour results from a chemical processbath. This process bath is followed by a single-stage rinsetank. The process requires a dilution rate of 1000 to 1 tomaintain acceptable rinsing in the tank. Therefore, theflow rate through the rinse tank is 1000 gal/hr. If a doublestage counter current rinse system were used, a rinse waterflow rate of only 30 to 35 gal/hr would be needed. If a triplestage counter current rinse system were used, only 8 to 12gal/hr would be requited (Watson 1973).

A multistage counter current rinse system allowsgreater contact time between the workpiece and the rinsewater, greater diffusion of process chemicals into the rinsesolution, and more rinse water to come intocontact with theworkpiece. The disadvantage of multistagecountercurrentrinsing is that more process steps are required and additionalequipment and work space are needed. A counter currenttriple-rinse system requires the installation of two additionalrinse tanks and the associated piping. The cost of such asystem is typically about $1,000 (Terran 1987).

Proper equipment design/operation. Printed circuitboard manufacturers can use excessive amounts of rinsewater if their water pipes are oversized or if the water is lefton even when the rinse tanks are not being used. Rinsewater control devices can be installed to increase theefficiency of a rinse water system. Flow restrictors limitthe volume of rinse water flowing through a rinse system.These are used to maintain a constant flow of fresh waterinto the system once the optimal flow rate has beendetermined. Also, since most small and medium-sizedprinted circuit board manufacturers operate batch processlines in which rinse systems are manually turned on and offthroughout the day, pressure activated flow control devices,such as foot pedal activated valves, can be helpful forassuring that the water is not left on after the rinse operationis completed. If the water lines are over-sized at a plant,pressure-reducing valves can be installed upgradient of therinse water influent lines. This is also helpful forcontrollingwater use in the rinse tanks.

A conductivity probe or pH meter can also be employed tocontrol fresh water flow through a rinse system. A

conductivity/pH cell is used to measure the level of dissolvedsolids or hydrogen ions in the rinse solution. When thislevel reaches a pre-set minimum, the conductivity probeactivates a valve that shuts off the flow of fresh water intothe rinse system. When the concentration builds to the pre-set maximum level, the probe again activates the valve,which then opens to continue the flow of fresh water. Thiscontrol equipment is especially valuable to the printedcircuit board manufacturing industry. A pH meter equippedwith the necessary control valves and solenoids could costapproximately $700 per tank (Ryan 1987).

Use deionized water for rinsing. Natural contaminantsfound in water used for production processes can contributeto the volume of waste generated. During treatment ofwastewater, these natural contaminants precipitate ascarbonates and phosphates and contribute to the volume ofsludge (USEPA 1982b). The extent to which thesecontaminants increase sludge volume depends on thehardness of the rinse water. In addition to the direct effecton sludge volume, the presence of natural contaminants inthe water may reduce rinse water efficiency and the abilityto reuse&cycle rinse water. Therefore, rinse systems mayrequire more water than would be necessary if the waterwere pretreated.

The cost of deionizing process water depends on thecondition of the water supplied to the plant. The cost isdependent on the concentration of total dissolved solids(TDS) in the water (Prothro 1987). For example, in theSanta Clara Valley a plant supplied with surface waterspends approximately 2 cents per gallon to pretreat processwater. A plant supplied with ground water spends close to4 cents per gallon. A typical deionizing system thatincludes two 14-inch mixed bed deionizers costsapproximately $2,000 for equipment and installation andtreats up to 5,000 gallons a day (Prothro 1987).

RECOVERY/REUSE OF SPENT MATERIALSRecycling and resource recovery includes technologies

that use waste as raw material for another process or thatrecover valuable materials from a waste stream before thewaste is disposed of. Opportunities for both the direct useof waste materials and the recovery of materials from awaste stream are available to the printed circuit boardmanufacturing industry. Many of the spent chemicalprocess baths and much of the rinse water can be reused forother plant processes. Also, process chemicals can berecovered from rinse waters, and valuable metals such ascopper can be recovered from waste streams.

A printed circuit board manufacturer must understandthe chemical properties of its waste stream before it canassess the potential for reusing the waste raw material.Although the chemical properties of a process bath or rinse

19

water solution may become unacceptable for their originaluse, these waste materials can still be employed in otherapplications. Printed circuit board manufacturers shouldtherefore evaluate waste streams for properties that makethem useful as well as properties that render them waste.

Segregate Streams to Promote RecyclingIn a typical facility, the mixing of different rinse

streams is not uncommon, and in the recent past, rinsewaters and spent baths were frequently mixed and treatedtogether. By segregating various rinses,, their reuse orrecycling can be promoted. Metal reclamation byelectrolysis from various streams is made easier if they arenot mixed.

Recover Metal Values from Bath RinsesIn the past, copper and other metal recovery from

printed circuit board manufacturing has not proven to beeconomical. However, effluent pretreatment regulationshave made the cost of treatment an economic factor. Also,the cost of management of sludges containing heavy metalshas increased significantly because of the increasedregulatory requirements placed on the handling and disposalof hazardous wastes. As a result, boardmanufacturers maynow find it economical to recover copper and other metalsand metal salts lost due to drag-out from process chemicalbaths.

Recovered metal can be used in two ways: (1) recoveredmetal salts can be recirculated back into process baths, and(2) recovered elemental metal can be sold to a metalsreclaimer. Some of the technologies that are beingsuccessfully used to recover metals and metal salts include:

Evaporation. Waste rinse water is evaporated byheating, leaving behind a concentrated solution. Theequipment used includes single or multiple effectevaporators. Vapor recompression applications have alsobeen reported (Seaburg and Bacchetti 1982). Inevaporativemethods, the solution is concentrated until its metalconcentration is equal to that of the plating bath, and thenthis solution is reused. Using this method, 90-99 percentefficient metal recoveries can be achieved (Clark 1984).Depending on the design, the evaporated water vapor caneither be condensed and re-used as rinse water, or it can bevented off into the atmosphere (Campbell and Glenn1982). Evaporation is the best established of all the metalrecovery techniques used in electroplating. Although it isthe most energy intensive recovery technique, its simplicityand reliability make it an attractive option for metal recovery.In order for evaporation to be economical, multiple countercurrent rinse tanks or spray/fog rinsing should be used tominimize the amount of rinse water being processed(MDEM 1984). Apart from the energy cost, a distinctdisadvantage of evaporative techniques is that the

concentrates may also contain the calcium and magnesiumsalts originally present in the rinse water. Adding them tothe plating solution may result in its more rapid deterioration.This problem is alleviated in situations where rinse wateris de-ionized or softened prior to use.

Reverse osmosis. Reverse osmosis is also used torecover drag-out that can be returned to the process bath.The reverse osmosis process employs a semipermeablemembrane that permits only certain components to passthrough. When pressure is applied, these components passthrough the membrane and concentrate in the recoveredsolution. Although the technology is designed to recoverdrag-out, some materials (such as boric acid) can not befully recovered and are, therefore, returned to the processbath at a lower concentration. Also, reverse osmosis is adelicate process that is limited by the ability of themembranes to withstand pH extremes and long-termpressure. Reverse osmosis systems are commonly used torecover nickel plating solutions and regenerate rinse waters.

Liquid membranes. Liquid membranes are composedof polymeric materials loaded with an ion-carrying solution(Basta 1983). Liquid membranes have been used toremove chromium from rinse waters and spent etchingbaths. Chromium in the form of dichromate is drawnacross the membrane, forming a tertiary amine metalcomplex. This complex is then broken down on the otherside of the membrane with sodium hydroxide solution.

Ion exchange. Ion exchange concentrates metals froma dilute rinse stream onto a resin material. As rinse wateris passed through a bed containing the resin, the resinsubstitutes ions for inorganics in the rinse water. Themetals are then recovered from the resin by cleaning it withan acid or alkaline solution. Ion exchange units can be usedeffectively on dilute waste streams and are less delicatethan reverse osmosis systems. However, the equipment iscomplex and requires careful operating and maintenancepractices.

Electrolytic recovery. This method recovers only themetallic content of rinse water. The process requires acathode and an anode placed in the rinse solution. Ascurrent passes from the anode to the cathode, metallic ionsdeposit on the cathode. This type of system generates asolid metallic slab that can be reclaimed or used as an anodein an electroplating tank. Electrolytic systems can recover90 to 95 percent of the available metals. Electrolyticrecovery has been successfully used to recover gold, silver,tin, copper, zinc, solder alloy, and cadmium (Campbell andGlenn 1982). One great advantage of the electrolyticmethod over other metal recovery techniques is that itrecovers only the plating metal, not the impurities, from thewaste rinse water. Electrolytic metal recovery is most

20

efficient on concentrated solutions. For solutions with lessthan 100 mg/l of the metal ion, low current efficiencieslimit process effectiveness.

Electrodialysis. In electrodialysis, an electric currentand selective membranes are used to separate the positiveand negative ions from a solution into two streams. This isaccomplished by feeding a solution through a series ofalternating cation and anion selective membranes, throughwhich a current is passed. Electrodialysis is used mainly toconcentrate dilute solutions of salts or metal ions.Electrodialysis can remove nickel, copper, cyanide,chromium, iron and zinc from waste rinse water (MDEM1984, Kohl and Triplett 1984). This technology has notbeen used as widely in the electroplating industry as haveother metal recovery techniques (Campbell and Glenn1982, Kohl and Triplett 1984).

High surface area electrowinning/electrorefining. Thismethod operates on the same principle as electrolyticrecovery. The metal-containing solution is pumped through,and plates out on, a carbon fiber cathode (Mitchell 1984).To recover the metals, the carbon fiber cathode assemblyis removed and placed in an electrorefiner, which reversesthe current, removes the metals from the carbon fibers, andallows them to plate onto a stainless steel starter sheet.These systems can be used to recover a wide variety ofmetals and to regenerate many types of solutions.

The cost associated with implementing a chemicalrecovery technology depends on a number of variables: thesize of the unit, the space available, equipmentrearrangement, production down time, and the specificapplication. Table 4 contains cost data for several chemi-calrecovery units from electroplating plants. Although thespecific materials recovered may be different for a printedcircuit board manufacturing plant, the basic technology istransferable between these two industries. While theequipment costs shown can be applied to board manufac-turing, the annual savings depend on the wastewater metalconcentrations and volume of wastewater treated by therecovery systems.

One limiting factor for a small printed circuit boardmanufacturing company is the volume and chemicalconcentration of its various rinse water effluents. Theexamples in Table 4 are all designed to recover a specificmaterial from a single waste generating source (for example,nickel salts from a nickel plating line). To achieve savingsin chemicals and sludge handling that create a justifiablepayback, the waste stream must be fairly concentrated andcontinuous. Eachcompany must evaluate its own conditionsto determine the feasibility of material recovery. Theinformation necessary to determine the feasibility includeswaste stream generation rates and chemical concentrations,and the value of materials to be recovered.

EtchingMost of the source control techniques listed under

plating and electroplating apply as well to waste producedby etching. Special source reduction methods associatedwith etching operations are discussed below.

Use differential plating instead of the conventionalelectroless plating process. If theconcentrations of certainstabilizers in the electroless copper bath are controlled,copper deposits three to five times faster on the through-hole walls than on the copper cladded surface (Poskanzerand Davis 1982). This reduces the amount of copper thatmust be subsequently etched away in the subtractive method.The use of differential electroless plating has not beenreported by printed circuit board manufacturers, and it mayrequire significant developmental work beforecommercialization is possible.

Use non-chelated etchants. Non-chelate mild etchantssuch as sodium per-sulfate and hydrogen peroxide/sulfuricacid can be used to replace ammonium persulfate chelateetchant.

Use thinner copper foil to clad the laminated board.This change reduces the amount of copper which must beetched, and thus reduces the amount of waste generatedfrom the etching process. Printed circuit boardmanufacturers are switching to boards cladded with thinnercopper as their starting materials.

Use pattern instead of panel plating. Since panelplating consists of copper plating the entire board area,while pattern plating requires copper electroplating onlythe holes and circuitry, the use of the latter techniquereduces the amount of non-circuit copper which must besubsequently etched away. This practice can thereforereduce the amount of waste generated from the etchingoperation. The switch from panel to pattern plating hasbeen made by a large number of printed circuit boardmanufacturers. Customers demanding applications for auniform cross section of circuitry in computer andmicrowave printed circuit boards, however, may dictatethe use of panel plating to provide highly uniform copperthickness.

Use additive instead of subtractive method. Thischange eliminates the copper etching step, and thereforeeliminates the generation of substantial volumes of spentetchant as well as reducing the amount of metal hydroxidesludges generated. Although the subtractive method is stillthe most widely used in the manufacturing of printedcircuit boards, the additive method is gaining in popularitysince it results in less waste and lower manufacturing costs(Brush 1983). A noted drawback to the additive method,however, is the requirement for solvent processable instead

21

Table 4. Costs of Technology for Material RecoveryMaterials

Technology Recovered

Evaporation Unit: Rinse waterCapacity of’ Chromic acidapproximately20 gph.Reverse Osmosis Nickel saltUnit: Capacity of Plating chemicalsapproximately 100 gph.Ion Exchange Unit: Rinse waterCapacity of Chromic acidapproximately 20 gph.Electrolytic Unit: Rinse waterCapacity of tipperapproximately 15 gph.aEquipment costs include equipment purchase, installation, and materials.Source: USEPA 1987.

of aqueous processable photoresists. Furthermore, the spentadditive plating bath often contains heavily complexedcopper which may result in waste treatment problems.

Use non-chrome etchants. Whenever possible, ferricchloride or ammonium persulfate solution should be usedinstead of chromic-sulfuric acid etchants. Non-chromiumetching solution has reportedly been used by printed circuitboard manufacturers in an effort to reduce the toxicity ofthe waste generated.

Recycle spent etchants. Use of an electrolyticdiaphragm cell for regenerating spent chromic acid frometching operations has been reported (AESI 1981). Theelectrolytic cell oxidizes trivalent chromium to hexavalentchromium and removes contaminants. The quality of theregenerated etchant has been reported to be equal to orbetter than fresh etchant.

In one such application, extensively tested at the U.S.Bureau of Mines in Rolla, MO., copper etching solutionwas regenerated and metallic copper recovered at the sametime. Recovery was accomplished by depositing the copperonto the cathode of the electrolytic diaphragm cell (Basta1983).

Another recycling example involves the regenerationof cupric chloride, used as a strong etchant for producingcircuit patterns on circuit board base material. The etchantbecomes spent as the copper etched from the base materialreduces the cupric chloride (CuC12) to cuprous chloride(CuCl). This spent etchant can be regenerated by oxidizing

EquipmentCostsa

$47,000

$27,000

$38,000

$25,000

to cuprous chloride through direct chlorination (Couture1984).

Wastewater TreatmentProcess chemical loss due to drag-out is the most

significant source of chemicals entering wastewater.Treatment of this wastewater is a major source of hazardouswaste in PC board operation because of the resultingsludge. The volume of sludge generated is proportional tothe level of contamination in the spent rinse water (Couture1984). The major ways of reducing waste associated withtreatment (in addition to those associated with drag-outreduction, reduction in the use of rinse water, and use ofdeionized water) include waste stream segregation, use ofalternative treatment chemicals, and alternative treatmenttechnologies.

WASTE STREAM SEGREGATIONSegregating waste streams can improve the efficiency

of a waste treatment system. An example of waste streamsegregation is the separation of chelating agent wastestreams from nonchelating agent streams. Since mostsmall printed circuit board manufacturing plants usetreatment systems that can be operated as a batch process,they can implement waste stream segregation and selectivetreatment with minimal impact on the production system.The main drawback to this alternative is usually the limitedstorage capacity for the segregated waste streams.

If waste streams containing chelating agents are treatedin a batch process separately from other waste streams, the

22

use of ferrous sulfate to break down the chelators can beminimized. Since the iron in ferrous sulfate will precipitateout in the sludge, reduction in its use will also reduce thevolume of sludge generated.

By isolating cyanide-containing waste streams fromwaste streams containing iron or complexing agents, theformation of cyanide complexes is avoided, and treatmentmade much easier (Dowd 1985). Segregation of wastewaterstreams containing different metals also allows for metalsrecovery or reuse. For example, by treating nickel-platingwastewater separately from other waste streams, a nickelhydroxide sludge is produced which can be reused toproduce fresh nickel plating solutions.

Another waste alternative is to separate noncontactcooling water from industrial wastes. It is likely that thiscooling water can bypass the treatment system and bedischarged directly to the sewer because it does not comein contact with process chemicals. This practice canreduce wastewater volume and, as a result, reduce theamount of treatment chemicals used. Also, acidic oralkaline waste streams that do not contain metals cansimply be neutralized prior to discharge; therefore, if theyare segregated from other wastes that require metal removal,the volume of treatment chemicals can be reduced. This,in turn, will reduce the volume of sludge generated.

USE OF ALTERNATIVE WASTE TREATMENTCHEMICALS

The selection of chemicals used in the waste treatmentprocess can affect the volume of sludge generated. Thisselection should, therefore, consider achemical’s effect onsludge generation rates. For example, lime and causticsoda are two common chemicals used for neutralizationand precipitation. Although lime costs less per unit ofneutralizing capacity, it can produce as much as ten timesmore dry weight of sludge than caustic soda (USEPA1982b).

Alum and ferric chloride are commonly employed ascoagulating agents to improve floc formation. When used,they convert to hydroxides and contribute to the volume ofsludge. Polyelectrolyte conditioners can also be used ascoagulants, but they are more expensive than inorganiccoagulants. However, polyelectrolytes do not add to thequantity of sludge and may actually be less expensiveoverall when considering waste handling costs. Oneprinted circuit board manufacturer visited during this studyrecently switched from alum to a polyelectrolyte coagulantin order to reduce sludge generation. Specific data on thevolume of sludge reduction are not yet available from thecompany.

The selection of alternative treatment chemicalsdepends on specific waste characteristics and removalefficiency needs for a particular treatment facility. Thepotential use of various treatment chemicals should bediscussed with chemical manufacturers’ representativesand experimented with to determine their effectiveness.

ALTERNATIVE WASTEWATER TREATMENT -ION EXCHANGE

Ion exchange systems can be employed to treat theentire wastestream prior to discharge to the publicly-owned treatment works, When used for this purpose, theion exchange units do not recover process chemicals forreuse because all sources of wastewater are mixed prior totreatment. The units can be used to recycle rinse water,however, by utilizing an activated carbon treatment systemfollowing ion exchange treatment. The costs for operatingan ion exchange system depend on the volume and chemicalconcentrations of the wastewater.

One plant visited recently installed an ion exchangesystem to replace its conventional precipitation/clarificationtreatment system. The ion exchange unit is designed for atreatment capacity of 12 to 14 gallons per minute. The unitdoes not generate any sludge but does generateapproximately two 55-gallon drums of spent ion exchangeresin each month. The old treatment system generatedapproximately four to six 55-gallon drums of sludge permonth.

The ion exchange system was purchased and installedfor approximately $16,000 and required one week ofproduction down time to install. The system costs $1,000per month to operate, including material purchases andwaste disposal, compared to $1,500 per month for the oldsystem. The new system also requires less labor to maintainit. The payback on investment for the new system isestimated to be 3.3 years.

ReferencesAESI. 1981. American Electroplater’s Society, Inc.

Conference on Advanced Pollution Control for theMetal Finishing Industry (3rd) held at Orlando HyattHouse, Kissimmee, Florida on April 14-16, 1980.EPA-600-2/81-028. Cincinnati, Ohio: U.S.Environmental Protection Agency.

Anonymous. 1983. California-style circuit manufacturingusing computerization. Plat. Surf. Finish. 70: 26-9.

ASM. 1987. Metals Handbook, Ninth Edition, Volume 5:Surface Cleaning, Finishing, and Coating. AmericanSociety for Metals. Metals Park, Ohio.

23

Basanese. J. 1987. West General Associates, personalcommunication with T. Adkisson. Planning ResearchCorporation (February 1987).

Basta,N. 1983. Total metal recycle is metal finishers’ goal.Chemical Engineering. August 8, 1983. pp. 16-19.

BCL, 1976. Battelle Columbus Lab. Assessment ofIndustrial Hazardous Waste Practices: Electroplatingand Metal Finishing Industries Job Shops. EPA-530-SW-136C. Washington, D.C.: U.S. EnvironmentalProtection Agency.

Bowlby, R. 1985; The DIP may take its final bows! IEEESpectrum. June. 1985. pp. 37-42.

Brush, P.N. 1983. Fast track for printed circuit boards.Prod. Finish. November 1983, pp. 84-5.

Campbell, M.E, and W.M. Glenn, 1982. Proven ProfitFrom Pollution Prevention. Toronto, Canada: ThePollution Probe Foundation.

CDHS. 1986. Guide to Solvent Waste ReductionAlternatives. Final report prepared by ICF ConsultingAssociates, Inc., for Alternative Technology and PolicyDevelopment Section, Toxic Substances ControlDivision, California Department of Health Services.October 1986.

Cheremisinoff, P.N., A.J. Peina, and J. Ciancia. 1976. Ind.Wastes. 22(6):31-4.

Clark, R., ed. 1984. Massachusetts Hazardous WasteSource Reduction. Conference Proceedings, October17, 1984. Boston, Mass.: Massachusetts Departmentof Environmental Management.

Cook, T.M., M.L. Cubbage, and L.J. Fister. 1984. Drainingprocess solutions from sheets, baskets, pipes, threadsand fins. Metal Finishing, (7): 33.

Couture, S.D. 1984. Source Reduction in the PrintedCircuit Industry. Proceedings - the Second AnnualHazardous Materials Management Conference,Philadelphia, Pennsylvania, June 5-7, 1984.

Dowd, P. 1985. Conserving water and segregating wastestreams. Plat. Surf. Finish. 72(5): 104-8.

Durney, L.J., ed. 1984. Electroplating EngineeringHandbook. 4th ed. New York, N.Y.: Van NostrandReinhold Co.

Engelmaier, W., and D.C. Frisch. 1982. Injection moldingshapes new dimensions for boards. Electronics.December 15. pp. 155-158.

Engles, K.O., and J.T. Hamby. 1983. Computerized

controller for electroplating printed wiring boards.Met. Finish. 81: 95-100.

Foggia, M. 1987. Shipley Company, Inc., personalcommunication with T. Adkisson, Planning ResearchCorporation (January 21, 1987).

Greene, R., ed. 1985. CE Alert, New Technology. Chem.Eng. March 4. pp. 85.

Gunderson, R., and H. Holden. 1983. CAM techniquesimprove circuit board production. Control. Eng. 30:141-2.

Kohl, J., and B. Triplett. 1984. Managing and MinimizingHazardous Waste Metal Sludges. North Carolina StateUniversity.

Lane, C. 1985. Fluorocarbon coating eliminates corrosionof acid bath racks. Chem. Process. 48(10): 72.

Lyman, J. 1984. Surface mounting alters the printed circuitboard scene. Electronics. February 9, 1984.

LWVM. 1985. Waste Reduction -- The Untold Story.Proceeding of a seminar at the National Academy ofSciences Conference Center on June 19-21, 1985.Wood Hole, Mass.: The League of Women Voters ofMassachusetts.

Mathews, J.E. 1980. Industrial reuse and recycle ofwastewater.. literature review. Robert S. KerrEnvironmental Research Lab. EPA-600-2-80-183.A&, Okla: U.S. Environmental Protection Agency.

McRae, G.F. 1985. In-process waste reduction: part 1.Plat. Surf. Finish. 72(6): 14.

MDEM. 1984. Massachusetts Hazardous Waste SourceReduction: Metallic Waste Session. Conferenceproceedings May 23, 1984. Boston, Mass.:Massachusetts Department of EnvironmentalManagement.

Meltzer, M.P. 1989. Reducing Environmental Risk:Source Reduction for the Electroplating Industry.Doctoral Dissertation, School of Public Health,University of California, Los Angeles, CA.

Mitchel, G.D. 1984. A Unique Method for the Removaland Recovery of Heavy Metals From the Rinse Watersin the Metal Plating and Electronic InterconnectionIndustries. Proceedings -- Massachusetts HazardousWaste Source Reduction, Clinton, Massachusetts.

Olsen, A.E. 1973. Upgrading Metal Finishing Facilities toReduce Pollution. Oxy Metal Finishing Corp., EPA-625-3-73-002, Washington, D.C.: U.S. EnvironmentalProtection Agency.

24

Poskanzer, A.M. 1983. Plating printed circuit substrates:circuit topics. Plat. Surf Finish. 70: 10.

Poskanzer, A.M., and S.C. Davis. 1982. An efficientelectroless plating system for printed circuitry. Plat.Surf. Finish. 69: 95-7.

Prothro, J. 1987. Culligan Industrial Water Treatment,personal communication with T. Adkisson, PlanningResearch Corporation (March 16, 1987).

Ryan, W.M. 1987. William M. Ryan Company, personalcommunication with T. Adkisson, Planning ResearchCorporation (January 14, 1987).

Seaburg, J.L., and J.A. Bacchetti. 1982. ChemicalProcessing 45( 12): 30-31.

Stone, P. 1987. Shipley Company, Inc., personalcommunication with T. Adkisson, Planning ResearchCorporation (February 24, 1987).

Terran, A. 1987. Advanced Process Machinery, personalcommunication with T. Adkisson, Planning ResearchCorporation (January 14, 1987).

USEPA. 1981. U.S. Environmental Protection Agency,Industrial Environmental Research Lab. ChangesforMetal Finishers. Cincinnati, Ohio.

USEPA. 1982a. Control and Treatment Technology forthe Metal Finishing Industry-In-plant Changes. EPAX8606-0089.

USEPA. 1982b. Environmental Pollution ControlAlternatives: Sludge Handling, Dewatering, andDisposal Alternatives for the Metal Finishing industry.EPA 625/5-82/018.

USEPA. 1983. U.S. Environmental Protection Agency,Office of Water Regulations and Standards.Development Document for Effluent LimitationGuidelines and Standards for the Metal FinishingPoint Source Category. EPA-440-1-83-091.Washington, D.C.

USEPA. 1986. Waste Minimization -Issues and Options,vol II. PB 87-l14369. Prepared by Versar, Inc. andJacobs Engineering Group Inc.

USEPA. 1987. Environmental Pollution ControlAlternatives: Reducing Water Pollution Control Costsin the Electroplating Industry. September 1987. EPA625/5-85/016.

USEPA. 1989. Waste Minimization in Metal PartsCleaning. August 1989. EPA/530-SW-89-049.

USEPA. 1990. Guides to Pollution Prevention: The

Commercial Printing Industry.

Versar, Inc. 1984. Technical Assessment of TreatmentAlternatives for Wastes Containing Metals and/orCyanides. Contract no. 68-03-3149, final draft reportfor U.S. Environmental Protection Agency.Springfield, Va.: Versar, Inc.

Watson, M.R. 1973. Pollution Control in Metal Finishing.Noyes Dam Corporation, Park Ridge, New Jersey.

Wynschenk, J. 1983. Electroless copper plating chemistryand maintenance. Plat Surf. Finish. 70: 28-9.

25

SECTION 4GUIDELINES FOR USING THE WASTE

MINIMIZATION ASSESSMENT WORKSHEETS

Waste minimization assessments were conducted atseveral printed circuit board manufacturing plants inCalifornia. The assessments were used to develop thewaste minimization questionnaire and worksheets that areprovided in the following section.

A comprehensive waste minimization assessmentincludes a planning and organizational step, an assessmentstep that includes gathering background data andinformation, a feasibility study on specific wasteminimization options, and an implementation phase.

Conducting Your Own AssessmentThe worksheets provided in this section are intended

to assist printed circuit board manufacturers insystematically evaluating waste generating processes andin identifying waste minimization opportunities. Theseworksheets include only the assessment phase of theprocedure described in the Waste Minimization OpportunityAssessment Manual. For a full description of wasteminimization assessment procedures, refer to the EPAManual.

Table 5 lists the worksheets that are provided in thissection,

26

Table 5. List of Waste Minimization Assessment WorksheetsNumber

1.

2A.

2B.

2C.

3.

4.

5.

6A.

6B & 6C.

7.

8.

9.

1OA.

1OB.

Title

Waste Sources

Waste Minimization:Material HandlingWaste Minimization:Material HandlingWaste Minimization:Material HandlingOption Generation:Material HandlingWaste Minimization:Material and Process SubstitutionOption Generation:Material and Process SubstitutionWaste Minimization:Process ModificationWaste Minimization:Process Modification

Option Generation:Process ModificationWaste Minimization:Good Operating PracticesOption Generation:Good Operating PracticesWaste Minimization: Segregation,Reuse, Recovery and TreatmentWaste Minimization: Segregation,Reuse, Recovery and Treatment

Description

Typical wastes generated atprinted circuit board manufacturing plants.Questionnaire on general handlingtechniques for raw material handling.Questionnaire on procedures usedfor bulk liquid handling.Questionnaire on procedures usedfor handling drums, containers and packages.Waste minimization options formaterial handling operations.Questionnaire on material andprocess substitutions.Waste minimization options formaterial and process substitution.Questionnaire extending process bathlife by reducing drag-in and drag-out.Questionnaire on: 1) extending bath lifeby avoiding decomposition and impurityremoval; and 2) improving rinse efficiency.Process modification waste minimizationoptions.Questionnaire on use of goodoperating practices.Waste minimization options forgood operating practices.Questionnaire on opportunities forsegregation and reuse of wastes.Questionnaire on opportunitiesfor recovery and treatment of wastes.

27

29

APPENDIX ACASE STUDIES OF PRINTED CIRCUIT BOARD

MANUFACTURING PLANTS

In 1986 the California Department of Health Servicescommissioned a waste minimization study (DHS 1987) ofthree printed circuit (PC) board manufacturing firms, calledplants A, B and C in this guide. The results of the threewaste assessments were used to prepare waste minimizationassessment worksheets to be completed by other printedcircuit board manufacturers in a self-audit process.

The three printed circuit board manufacturing plantswere chosen for their willingness to participate in thestudy, their applicability to the study’s objectives, and thepotential usefulness of the resulting data to the industry asa whole. The waste minimization assessments wereconcerned with waste generated within the plant boundariesand not with waste derived from printed circuit boardapplication or disposal of board parts.

This Appendix section presents the results of theassessments of Plants A, B and C and the waste minimizationoptions either already in use or being considered for use bythe firms.

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 (seealso 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 printed circuit boardmanufacturers themselves to take steps to implement thewaste minimization options that passed the feasibilityanalysis.

PLANT A WASTE MINIMIZATIONASSESSMENTPlanning and Organization

Planning and organization of the assessment was doneby the consulting firm with the assistance of personnelfrom the PC board manufacturing firm. Initial contact wasmade with the PC board manufacturer’s plant operations

manager, a high level manager who could provide thecompany’s commitment to cooperate in the assessment andprovide all the necessary facility and process information.The goal of this joint effort was to conduct acomprehensivewaste minimization assessment for the plant. Underdifferent 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 together withthe plant manager. This task force also functioned as theassessment team.

Assessment Phase: Process and FacilityData

Initial discussions by telephone between the consultantsand the plant manager were used to request process andfacility information prior to a site visit. These discussionsalso served to identify particular waste streams of concernto plant managers.

At the site visit, the plant operations manager andconsultants met to review the facility’s 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 is a prototype circuit board manufacturer that

specializes in jobs involving limited production and fastturnaround. Manufacturing operations include drillingand routing, layering (for multilayer boards), photoresistprinting, plating, etching, and stripping.

PROCESS DESCRIPTIONFigure A-l is a floor plan of the plant’s plating,

etching, and stripping operations. The numbers listed onthe floor plan represent the identification number for eachprocess bath and rinse tank. Tables A-l, A-2, and A-3provide information on the plant’s operations. Table A-ldescribes each process bath used at plant A and Table A-2 describes each rinse system used at the plant.

43

Figure A-l. Plant A’s Plating Etching and Stripping Operations

Table A-l. Process Bath InformationPROCESS BATH/ PROCESSIDENTIFICATION BATHNUMBER VOLUME

(gallons)

Cleaner-Conditioner/lSulfuric-Peroxide Etch/3Catalyst Premix/5Catalyst/6Accelerator/8Electroless Copper/115% Sulfuric Acid/12100% Sulfuric Acid/13NeutralizerEtchback/15Brown Oxide/17Ammonium Biflouride/19Metex Cleaner/2010% Sulfuric Acid/22Copper Gleam/23Copper Gleam/2410% Fluorboric Acid/27Tin Lead/28Resist Stripper/31

Tin ImmersionConditioner/33Ammoniated Etch/34

Reflow Oil/36

303030303030303030

3030204004004002040030disposal30

supplier30

WASTE DESCRIPTION

Production activities that generate hazardous wasteare the plating, etching, and stripping processes. Thesources of waste from these activities are rinsing operations,spent process bath dumping, industrial waste treatment,and equipment cleanout. TableA-3 describesthe hazardouswastes produced at the plant.

Spent Chemical BathWhen a process chemical bath becomes too

contaminated or diluted for use (spent), it is removed fromthe process tank. The spent chemical bath is then eithercontainerized for reclaim by the manufacturer, containerizedfor off-site disposal, used as a neutralization chemical inthe industrial waste treatment system, or dumped into thewastewater collection sump. The chemical baths arechanged periodically according to the plant’s current timeschedule. This schedule was developed by Plant A basedon its experience with various process baths.

Only two of the spent bath handling methods contributeto the amount of hazardous waste generated at the plant.

METHODOFDISPOSALIN TANK

FREQUENCYOF DUMPS

To treatment 2 weeksTo treatment 4 weeksTo treatment 2 weeks--- ---To treatment 2 weeks--- ---To treatment 2 weeksTo treatment 1 weekTo treatment 4 weeks

---To treatmentTo treatmentTo treatment

To treatment

Off-site

Reclaimed bysupplierReclaimed by

Off-site disposal ---

---4 weeks1 week1 week3 years3 years2 weeks3 years2 weeks

---

4 weeks

These methods are containerizing waste for off-site disposaland dumping of spent chemical baths into the wastewatersump. Two process chemical baths are containerized fordisposal: (1) photoresist stripper and (2) reflow oil.Approximately 55 gallons of waste stripper are generatedmonthly. Plant A did not estimate the volume of wastereflow oil generated each month.

Photoresist stripper waste is generated at theconditioning and stripping line. The stripper is used in a30-gallon tank where circuit boards are immersed to stripoff the remaining photoresist material. The chemical bathis changed approximately every 2 weeks. The resultantstripper waste is highly alkaline with a pH over 12. Thewaste stripper contains a polymer residue which, whenagitated, remains suspended in the solution.

Reflow oil is used to enhance the formation of asmooth, uniform film of solder onto printed circuit boards.The reflow oil bath is maintained at an elevated temperatureduring use. When the bath becomes spent, it is containerizedfor off-site disposal. Analytical data for the spent oil werenot available.

45

Table A-2. Rinse System Information

Rinse System/Number

Rinse WaterFlow Rate

NumberOf Tanks

Dip Rinse/12 16 gal/min

Dip Rinse/14 16 gal/min

Dip Rinse/7Dip Rinse/9Dip Rinse/10Dip Rinse/14Dip Rinse/16

16 gal/min16 gal/min16 gal/min16 gal/min16 gal/min

Spray Rinse/21Drag-out/25Spray Rinse/26Drag-out/29Spray Rinse/30

1.5 gal/min---

1.5 gal/min---

1.5 gal/min

one

one

oneonet w o

oneone

oneoneoneoneone

Table A-3. Hazardous Waste DataANNUALQUANTITY

WASTE GENERATED

Industrial Waste 2,400 gal.Treatment Sludge

PhotoresistStripper

Reflow Oil

720 gal.

---

Nitric Acid 120 gal.

Copper SulfateCrystals

---

CounterCurrentSystem

no

no

nonononono

nonononono

DISPOSALMETHOD

off -sitemetal

Process Bath(s)Preceding RinseSystem(Y/N)

Cleaner/conditionerSulfuric/peroxide etchCatalystAcceleratorRinse tank #9Sulfuric acidNeutralizeretchbackMetex cleanerGapper gleamSulfuric acidFluorboric acidDrag-out tank #29

DISPOSALCOST/UNIT

$1.OO/gal

reclamation

off -sitedisposal

off -sitedisposal

off -sitedisposal

off -sitedisposal

-we

---

---

---

EstimatedDaily Water

Use

1500 gallons

1500 gallons

1500 gallons1500 gallons1500 gallons500 gallons500 gallons

ANNUALDISPOSALCOSTS

$2,400

---

---

---

The plant’s standard practice for dumping spentchemical baths into the wastewater sump is to transferwaste chemicals to one of the two metering tanks (tanks Aand B in Figure A-l). These tanks slowly discharge wastechemicals into the waste sump. The purpose for slowlyfeeding the spent bath chemicals into the wastewater sumpis to prevent surges in the waste stream pH or metalscontent. These two metering tanks have not, however,been in operation since July 1986. The present practice isto manually dump the spent baths into the collection sump.

Plant A personnel indicated that this practice causes afluctuation in the pH of the waste stream entering thetreatment system.

Copper sulfate crystals are generated when some ofthe process baths are taken off-line. The crystals form in theprocess bath as the copper content increases. Before theprocess baths are dumped into the wastewater sump, thecrystals are removed and containerized as a solid wastesince they cannot be fed into the treatment system.

46

Rinsing OperationsRinsing operations associated with the chemical

process lines are the major source of wastewater at Plant A.Plant A estimates that approximately 10,000 gallons ofwastewater are generated each day. The rinse operationscontribute to hazardous waste generation because wasterinse water carries away chemicals which are then removedby treatment at the industrial waste treatment plant. Thesludge that is generated from this treatment is handled as ahazardous waste.

Plant A uses nine dip rinse tanks and three spray rinsetanks. All rinse water used at Plant A is deionized onsiteprior to use. All but two of the rinse tanks are plumbeddirectly to the wastewater treatment system through a 500-gallon collection sump. The other two are batch dumptanks which require manual dumping into the sump.

Discussions with facility personnel indicate that waterflows through the dip rinse tanks only when the process lineassociated with the tank is in operation. However, duringboth visits, the assessment team observed water flowingthrough several rinse tanks even when the process line wasnot being operated. The flow rate of water through each diprinse tank was measured to be approximately 16 gallonsper minute. This was measured by closing the drain line,turning on the feed water for 20 seconds, measuring thewater level rise in the rinse tank, and calculating thevolume of water that entered the tank during the timeperiod. The flow rate of water through the spray rinse tankhas been estimated by the assessment team to beapproximately 1.5 gallons per minute.

Industrial Wastewater TreatmentPlant A’s industrial waste treatment facility treats all

wastewater before discharging it to the San Jose/SantaClara Water Pollution Control Plant. Plant A’s treatmentfacility removes metals and adjusts the pH of the wastewaterto meet discharge requirements set by the water poll&oncontrol plant. The maximum allowable concentration ofmetals in the discharged effluent, as set by the San Jose/Santa Clara Water Pollution Control plant, are as follows:

l Chromium 1.0 mg/L

l Copper 2.7 mg/L

l Cyanide 1.0 mg/L

. Lead 0.4 mg/L

l Nickel 2.6 mg/L

l Silver 0.7 mg/L

l Zinc 2.6 mg/L

The treatment process includes metal reduction,neutralization, and flocculation. The treatment plant islocated outside the main building in a fenced and curbedarea The metal hydroxide sludge generated by the treatmentprocess is a hazardous waste.

Chemical treatment is performed in three separatetanks; the wastewater then goes through sludge separationand dewatering. Approximately 10,000 gallons ofwastewater are treated each day. Wastewatercharacterization data were not provided by Plant A. Theincoming wastewater is pumped from the collection sumpto the first tank where ferrous sulfate and sulfuric acid areadded. Ferrous sulfate is used to reduce the copper to itsprecipitable form. The sulfuric acid is used to maintain thepH between 2.0 and 3.0 during the ferrous sulfate reaction.The waste is then neutralized with alum and sodiumhydroxide. The alum causes the suspended solids tocollect, forming larger particles, and the sodium hydroxideraises the pH to approximately 9.0. A polyelectrolytecoagulant is then introduced to aid in the flocculation of thecontaminants. The polyelectrolyte causes the precipitatedcontaminants to congeal into large flakes which can besettled out of the waste stream. Plant A personnel providedinformation on the quantities and costs of treatmentchemicals used each month (Table A-4).

Table A-4. Quantities and Costs ofTreatment Chemicals - Plant AChemical Monthly UsageCost/Unit Cost/Month

Ferrous sulfate 850 Ibs$0.33/lb $280Alum 850 Ibs$0.47/lb $400Sodium hydroxide 200 gallons

(30% solution in$0.55/gal $110 winter

winter)(50% solution in

$0.92/gal $185 summersummer)

Polyelectrolyte 3 Ibs$7.50/lb $22

Total $812/in winter

$887/in summer

The wastewater treatment sludge that is settled out ofthe effluent waste stream is transferred to the sludgedewatering unit, and the effluent is discharged to the San

47

Jose/Santa Clam Water Pollution Control Plant. Sludge isdewatered in a bag filter that increases its solids content to11 percent. The dewatered sludge is transferred into 55-gallon drums and stored for pickup by a metal reclaimer(World Resources Company). Plant A plans to use largestorage bags in the future which will hold the equivalent offour 55-gallon drums. Plant A estimates that four drums ofindustrial waste sludge are generated each month. Thesludge is considered a hazardous waste because of thecopper content.

Analytical data for the sludge were obtained fromWorld Resources Company of Phoenix, Arizona. WorldResources analyzes a sample from each load of sludgetransported to them for metal reclamation. The damprovided by World Resources are as follows:

Percent solids 11%

Metal content in pounds per dry ton

Copper 195

Nickel 6

Tin 46

Iron 399

Zinc 9

Lead 23

Chromium 20

Equipment CleanoutThe primary sources of hazardous waste associated

with equipment cleanout are the cleaning of the copperetching tank, cleaning of tanks used in the electroplatingline, and cleaning of electroplating racks. This equipmentis cleaned by using nitric acid. Plant A estimates that one55-gallon drum of waste nitric acid is generated every 6months. The waste nitric acid has too low a a pH and too higha copper content to be treated at the plant’s wastewatertreatment system. Analytical data on the waste nitric acidwere not available from Plant A.

Other cleaning activities, such as floor washing andchemical bath tank rinsing, generate waste streams thatdischarge into the wastewater collection sump. Accordingto Plant A personnel, these waste streams make up a smallportion of the chemicals that enter the treatment system.

Assessment Phase: Option GenerationThe consultants reviewed the plant operations data

obtained prior to and during the site inspection. Theydeveloped a set of waste minimization options based on

this 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 recommendedoptions.

SOURCE REDUCTIONThe following paragraphs describe the application

and use of source reduction measures to various wastestreams at Plant A.

Material SubstitutionOpportunities for material substitution that apply to

Plant A include (1) using process chemistries that can berecycled or treated prior to discharge to the publicly ownedtreatment works (POTW) and (2) using chemistries thathave less impact on sludge generation. Process chemistriesthat Plant A currently containerizes for off-site disposalinclude spent reflow oil and nitric acid waste. Severalreflow oil products are available that, when spent, eithercan be returned to the supplier for recycling or can betreated by the facility prior to discharge to the POTW.Plant A could eliminate a hazardous waste stream byreplacing its present reflow oil with a recyclable or treatablereflow oil.

Nitric acid waste, which is generated from thecleaningof electroplating racks, can also be eliminated by using analternative cleaning solution. One chemical supplier offersan electroplating rack cleaning solution that can beregenerated. The metal stripped off of racks can be platedout in a tank equipped with a cathode and an anode. Themetallic sludge then settles to the bottom of the cleaningtank where it can be removed and mixed with the waste watertreatment sludge. Once the cleaning solution becomesspent, it can be treated in the plant’s industrial wastetreatment system before being discharged to the POTW.The use of recyclable cleaning solution will eliminate thegeneration of waste nitric acid. The metallic sludge that isgenerated can be sent to a metal reclaimer along with thewastewater treatment sludge.

The use of non-chelated process chemistries can reducethe volume of sludge generated during wastewatertreatment. Plant Auses ferrous sulfate to treat its wastewater.The ferrous sulfate is used to break down chelators so thatmetals can be precipitated. The iron in ferrous sulfate alsoprecipitates as a metal hydroxide and contributes to sludgevolume. The analytical data for Plant A’s industrial wastetreatment sludge indicate that iron contributesapproximately 57 percent of the total metal content of thesludge. If all the iron precipitates as metal hydroxide, theiron hydroxide contributes 34 percent of the total dryweight of the sludge. If plant A used non-chelated process

48

chemistries, ferrous sulfate treatment could be eliminatedand sludge generation could be reduced. Most chemicalsuppliers offer non-chelated process chemistries orchemistries with mild chelators that do not require ferroussulfate treatment, Plant A should consult with chemicalsuppliers to identify alternative process chemistries thatcan be used so that ferrous sulfate treatment can beminimized.

Rinse Water ReductionAlthough rinse water is not a hazardous waste, the

treatment of this waste produces a sludge that is a hazardouswaste. Since the volume of the sludge generated bytreatment is a function of the volume of wastewater treatedas well as the concentration of contaminants in the waste,the plant can reduce the volume of sludge generated byreducing its rinsewater generation. Several rinse reductionoptions are available to Plant A that can reduce the volumeof wastewater requiring treatment. Multiple stage rinsewater systems were not evaluated because not enoughspace is available at Plant A’s facility.

Rinse Tank OperationsPlant A now operates several of its dip rinse tanks as

flow-through tanks. Deionized water is plumbed into thetank during operation and the overflow is plumbed to thecollection sump. Each of the rinse tanks holds approximately30 gallons of rinse water, and the flow of water througheach tank is approximately 16 gallons per minute. PRCbelieves that the plant could modify its operation of theserinse tanks to reduce the volume of wastewater generated.Two options are available for Plant A: (1) the dip rinsetanks can be operated as batch rinse tanks or (2) the flowrate through the tanks can be reduced.

If these seven dip rinse tanks were operated as batchrinse tanks (which means they would operate as stagnantrinse tanks that are emptied between rinse operations andthen refilled with deionized water), Plant A could reduceits rinse water generation significantly. Table A-4 showsthe volume of rinse water generated by Plant A and thevolume that would be generated if the seven dip rinse tankswere operated as batch rinse tanks. The values for the timewater is running and for the number of workpiece racksprocessed daily were provided by Plant A personnel. Thisoption assumes that each rinse tank can provide adequaterinsing of one process rack when filled with fresh deionizedwater. Plant A did not provide the auditors with informationon the required operating parameters of the rinse systems.Therefore, the impact of batch rinsing on the efficiency ofthe rinsing operations could not be assessed. The followingexample, however, illustrates the feasibility of batch rinsing.

The equation for determining the volume of rinsewater needed to rinse a full workpiece rack is as follows:

Q = D(Cp/Cn)

Where Q = rinse tank flow rateD = drag-out rateCp = concentration of salts in process solutionCn = allowable concentration in rinse solution

Several assumptions must be made to use this equationto illustrate the potential for operating the rinse tanks as abatch rinse system. These are as follows:

l The concentration of chemicals in the rinsesolution cannot exceed l/1000 of theconcentration of chemicals in the process bath.This value is a common parameter used in theelectroplating industry for rinse watercontaminant concentration.

l The drag-out rate of chemicals used formanufacturing printed circuit boards isapproximately 15 ml/ft2 of board. This value isa standard approximation used for estimatingdrag-out created by a printed circuit board(Foggia, 1987).

l An average workpiece rack holds approximately2.5 ft3 of boards (example: 30 4-inch by 3-inchboards).

The drag-out rate for each workpiece rack is:

15 ml x 2.5 ft3 = 37.5 ml.

Converted to gallons, drag-out equals 0.01 gallon.

By substituting the values into the equation:

0.01 gallon x 1000 = 10 gallons1

10 gallons of fresh rinse water will provide adequaterinsing under theoperating parameters previously described.Since the rinse tanks hold approximately 30 gallons ofrinse water, theoretically, a full tank of fresh water wouldprovide adequate rinsing without operating the tank as aflow-through tank. Workpiece rack agitation or air spargerscan be used to improve efficiency to assure adequaterinsing in the batch rinse tank.

Although using the dip rinse tanks as a batch processcan provide significant reductions in wastewater generation,there may be several process lines for which this is notfeasible because of the chemistry of the process. However,even if some of the tanks must operate as flow-throughrinse systems, the volume of deionized water used can stillbe reduced for these tanks. The same equation can be usedto demonstrate that the present flow rate used in the rinsetanks may be excessive.

49

The equation can be rearranged to indicate the ratio ofprocess bath concentration to rinse solution concentration,as follows:

The same drag-out volume (0.01 gallon) will be used,and it will be assumed that the process rack remains in therinse tank for 3 minutes. The ratio of the process bathconcentration to rinse solution concentration is as follows:

16 gals/min x 3 min = 4,800

0.01 gal.

Therefore, to justify the present rinse water flow rate,the concentration of chemicals in the rinse solution canonly reach l/4,800 or 2/10,000 of the concentration ofchemicals in the process bath before rinse efficiency isreduced. As previously stated, the electroplating industryusually allows rinse water concentrations to reach l/1000the concentration of chemicals in the process tank. Plant Ashould consult chemical manufacturers’ representativesand perform experiments to determine the proper flow ratefor its rinse tanks if batch operation is not feasible.

By calculating the flow rate necessary to maintain therinse water at an acceptable chemical concentration, PlantA may find that the 16 gallon per minute flow rate presentlyused is too high. In addition, the use of air spargers or workpiece rack agitation should improve rinse efficiency andallow for use of lower rinse water flow rates.

Rinse Water Flow ControlsPlant A presently turns on the rinse water in-flow

valves manually. When the process line is in operation,plant personnel turn on the water for all the rinse tanks andthen turn the water off after the production process iscomplete. However, the consultants observed that rinsetanks were left on even when the process line was not inuse. The use of automated flow controls would be helpfulfor ensuring that rinse water is not left running and forcontrolling the flow rate when the rinse water is turned on.

The plant should consider installing pH meters in eachof the rinse tanks to control the flow of water through therinse systems. The meters should be set to turn the freshwater feed valve on when the chemical concentration in therinse gets too high. If the required pH range for each rinsetank is determined, the meters can be set to turn on the waterautomatically. When the rinse tank solution pH reaches themaximum allowable level to provide efficient rinsing, themeter will send a signal that activates a valve on theinfluent line. When the rinse solution again reaches anacceptable pH, the pH meter will send a signal that turns offthe water feed valve.

Flow restrictors can also be used to reduce flow rates.A limiting orifice or similar flow-restricting device can beinstalled in the water line to each tank to reduce the flowrate to each tank. Plant A uses approximately 2-inchdiameter piping for its rinse inflow lines. This piping maybe oversized for the pressure on the line and the requiredflow rate. The use of flow restrictors, therefore, mayprovide better controls over the rate of rinse water usage.One circuit board manufacturer who installed pH meters,flow restrictors, and other water reduction devices, such asfoot pedal pressure switches, was able to reduce waterusage by two thirds.

Process Bath Drag-OutProcess bath chemicals are carried into the rinse water

when the racks that hold the printed circuit boards areremoved from a process bath tank and placed in a dip rinsetank. This is performed manually at Plant A. The operatorremoves the rack, briefly holds it above the process bathtank, and submerges the rack into the rinse tank. Theconsultants personnel observed plant personnel performingthis operation and found that the racks are quickly removedfrom the process bath and held over the process bath tanksfor less than 10 seconds. This procedure allows excessivechemicals to enter the waste rinse water stream. Actualdrag-out volumes were not available from Plant A, however.

The manner in which racks are removed from processbaths will significantly affect the amount of drag-outcarried into the rinse tanks. Slow removal of workpiecescauses a much thinner film of process chemicals to adhereto the workpiece surface. This effect is so significant thatmost of the workpiece drainage time should be used toremove the workpiece rack from the process bath. Theconsultants observed that Plant A personnel remove racksin one quick movement. We suggest that Plant A train itspersonnel to removeracks in a slow, smooth manner. PlantA could also improve the drag-out recovery efficiency ofthe process lines by installing a bar or rail above the processtank so that the racks can be hung and allowed to drainlonger.

The auditors did not predict the drag-out volume thatcan be recovered by removing racks at a slower rate andallowing racks to drain for a longer period of time. However,the savings realized by reducing drag-out losses includereducing process chemical purchases and reducingwastewater treatment sludge generation. Plant A candetermine the effectiveness of these drag-out reductiontechniques by holding the racks over a collection pan afterremoving them. The volume of drag-out that can berecovered afterremoving racks at various rates and allowingracks to drain for various lengths of time can then bemeasured and the optimal removal rate and drainage timecan be determined.

50

Equipment CleanoutPlant A generates approximately 55 gallons of waste

nitric acid every 6 months from cleaning out theelectroplating tanks and from cleaning the electroplatingracks. Plant A may be able to reduce the volume of nitricacid generated by modifying the existing cleaning methods.

One method for reducing the volume of waste nitricacid produced is to set up a workpiece rack cleaning linewith several small tanks of nitric acid. The cleaning line isthen used like a multi-stage rinse system. The first tankcontains the most contaminated nitric acid solution and thefinal tank in the cleaning line contains the freshest nitricacid. When the first tank no longer performs adequateinitial cleaning, it is containerized for disposal (or used asinitial. cleaning solution for tank cleanout). Then thesecond tank in the cleaning line becomes the first. Theempty tank is then filled with fresh nitric acid and itbecomes the last tank in the cleaning line.

The use of a multi-stage rinse system can providesignificant reductions in waste cleaning solution generation.One printed circuit board manufacturing plant visited bythe consultants uses a five-stage multiple tank cleaning lineand only generates approximately 15 gallons of wastenitric acid each 6 months.

Chemical Process BathsThe chemical load on wastewater can be reduced by

operating the process baths at lower concentrations. Amanufacturer’s recommendations for chemicalconcentrations in process baths are not always appropriate.We recommend that Plant A evaluate the efficiency of theconcentration parameters of its present chemical processbath to determine if these concentrations can be reduced.By reducing the concentration of chemicals in a processbath, the plant will minimize the chemical load in thewastewater when these baths are dumped. This reductionwill also reduce the chemical concentration in the rinsewater by minimizing drag-out chemical loses.

One method of reducing process bath chemicalconcentrations is to operate fresh baths at lowerconcentrations than older baths. Plant A can accomplishthis by gradually increasing the chemical concentration inthe process bath as it gets older. This practice can reducethe chemical concentration of the drag-out from fresh bathsand also extend the life of some process baths.

Waste SegregationThe wastewater generated at Plant A is plumbed or

manually dumped into a 500-gallon collection sump.Therefore, all wastes that can be treated on-site are mixedprior to treatment. This practice may cause excessive useof treatment chemicals and an increase in the volume of

sludge generated. Waste segregation may reduce the useof treatment chemicals and the generation of sludge in twoareas: the non-contact cooling water used for the copperetch machine and the waste streams generated by processesthat contain chelating chemistries.

Plant A personnel indicated that the cooling watersystem used in the copper etcher is a once-through system,with the effluent discharged to the collection sump. If thesystem were operated as a closed loop system, there wouldnot be an effluent waste stream. Also, since this water isused as non-contact cooling water, the effluent that is nowgenerated by the system may not require treatment. Theeffluent, therefore, could possibly be discharged directly tothe sanitary sewer, if permitted by the Publicly-OwnedTreatment Works (POTW).

The use of a closed loop cooling system would lead toreductions in water and sewer fees, treatmentchemical use,and sludge generation. Direct discharge of non-contactcooling water to the sanitary sewer would result in savingsfrom reduced treatment chemical use and sludge handling.The consultant was unable to obtain estimates on thevolume of water used in the etchercooling system; therefore,specific values for savings cannot be presented.

The primary purpose of the treatment system used atPlant A is to remove metals from the waste stream so thatthe discharged effluent can meet San Jose/Santa ClaraWater Pollution Control Plant pretreatment standards. Thehighest metals concentration in the wastewater is copper,and the treatment system is designed to remove the copperthrough a ferrous sulfate reduction process. The ferroussulfate process is designed to break down chelators thatkeep metals in solution past their normal solubility limit.The ferrous sulfate contributes significantly to the volumeof sludge generated in the wastewater treatment process.Analytical data indicate that iron content in the sludge is399 pounds per dry ton of solids. Assuming that all the ironprecipitates as a hydroxide, iron hydroxide contributes 34percent of the total dry weight of solids in the sludge. Ifthere is a direct relationship between solids content andtotal sludge volume, the plant could reduce sludge volumeby 34 percent by eliminating iron from the waste treatmentsystem.

Several options are available to eliminate or reduce theamount of ferrous sulfate used in the treatment process.These include: (1) eliminating the use of chelated processchemistries, (2) using process chemistries that only containmild chelators, (3) segregating waste streams that containchelators from other waste streams, and (4) segregatingwaste streams that contain copper from other waste streams.Plant A was unable to identify which process baths usechelators or what type of chelators are used. Therefore,

51

specific recommendations for waste segregation cannot bedeveloped. However, several waste segregation optionsare described.

Use of non-chelated process chemistries or mildchelators may allow Plant A to eliminate the use of ferroussulfate. Since the primary purpose of ferrous sulfate is tobreak down chelators so that copper can be precipitatedfrom the wastewater, non-chelated process chemistrieswould allow the use of an alternative precipitant such ascaustic soda. Mild chelators, such as ethylene diaminetetraacetic acid (EDTA), can be broken down through pHreduction. Therefore, if EDTA is used where chelators areneeded, such as in an electroless copper bath, ferroussulfate may not be required for wastewater treatment.

Mixing waste streams that contain chelating agentswith waste streams that are non-chelated appears to causea significant increase in the amount of treatment chemicalsused, and should be avoided when possible. Ferroussulfate use can also be reduced by segregating wastestreams. According to Plant A personnel, the sources ofcopper that enter the wastewater are (1) the copper drag-outtank, (2) spray rinse tank 29, and (3) dip rinse tanks 9 and10. If these waste streams were segregated from the rest ofthe wastewater, ferrous sulfate treatment would only benecessary for apercentage of the waste. This could be doneon a batch treatment basis if a holding tank is used to storethe waste until treatment. The remaining wastewater couldhave metals removed by neutralization and precipitationwith caustic soda. This would reduce the amount oftreatment chemicals used at the facility. If other wastestreams contain chelators, these could also be segregatedfrom the rest of the waste stream.

RECYCLE AND RESOURCE RECOVERYALTERNATIVES

Recycling and resource recovery includes the directuse of a waste stream or the recovery of materials from awaste stream. Plant A appears to handle many of its wastestreams in this manner. Spent sulfuric acid is used in thewastewater treatment system, and several chemical processbaths are returned to the manufacturer when they becomespent. This chapter describes several additional recyclingand resource recovery techniques that may be implementedby Plant A.

Shipper WastePlant A personnel indicated that the plants stripper

waste is an alkaline solution that could be reused or used inthe treatment system if the polymer residue could beremoved. The plant could use a filter or decantation systemto separate the residue from the waste solution. Also, the

volume of stripper waste generated can be reducedsignificantly by using a multiple tank stripper system. Thistype of system allows the first stripper tank (the one withthe most contaminated stripper solution) to be used for alonger period of time because the second stripper tank willbe used for additional photoresist stripping. Therefore, thephotoresist stripper does not have to be replaced every 2weeks. When the first tank is dumped, the second tankbecomes the first. Fresh resist stripper is then added to thesecond tank.

Rinse Water RecyclingCurrently, Plant A plumbs all its rinse water effluent

directly into the collection sump. However, the plant maybe able to recycle some of the rinse water solutions. Forexample, rinse systems that follow an acid process chemicalbath, such as a peroxide/sulfuric acid etch, can sometimesbe used for feed water to a rinse system that follows analkaline cleaning bath. Implementation of such a system,however, should be done only after careful testing to makesure that addition of acid rinse water to the alkaline rinsebath does not cause problems with metal hydroxideprecipitation on clean parts.

The configuration of Plant A’s process lines may allowsome of these rinse systems to be plumbed together inseries. For example, rinse tank 14, which follows a sulfuricacid bath, could be plumbed into rinse tank 16, whichappears to follow an alkaline cleaning bath. Based on damof the existing water used, rinse tanks 14 and 16 both useapproximately 500 gallons each day. If 100 percent of thewater used in rinse tank 14 could be used for rinsingoperations in tank 16,500 gallons of water could be savedeach day. The plant would also reduce the volume ofwastewater treated each day by 500 gallons and could,therefore, reduce treatment chemical usage and sludgegeneration. Rinse water could also be recycled if the rinsetanks were operated on a batch process.

Copper Sulfate CrystalsPlant A personnel indicated that they were unsure of

how to handle the copper sulfate crystals generated at theplant. Currently, these crystals are disposed of offsite as ahazardous waste. One option available to the facility is tomix the crystals with the industrial waste treatment sludge.Since this sludge is sent to a reclaimer, the copper contentin the crystals may bring Plant A a larger payment onreclaimed copper. This practice will also prevent Plant Afrom accumulating containers of crystals.

TREATMENT ALTERNATIVESWaste reduction through alternative treatment can be

achieved by modifying a treatment system to reduce the

52

volume of hazardous waste generated. One of the treatmentalternatives available to Plant A is segregation of wastestreams, which is described earlier in this report. Anothertreatment alternative available to Plant A is sludgedewatering.

Sludge DewateringWastewater treatment sludge generated at Plant A is

dewatered by a gravity filter system. Although this type ofdewatering can remove some of the free water in thesludge, it is not as effective as mechanical dewatering.Analytical data for the waste treatment sludge show thatthe gravity filter system can increase solids content to 11percent. Mechanical dewatering equipment can achieve asolids content up to 35 percent for most industrial wastesludge. Figure A-2 shows the decrease in sludge volumethat can be achieved by increasing solids content. Thefigure shows that increasing the solids content from 10percent to 35 percent reduces sludge volume from 80gallons to 20 gallons.

Plant A now removes the sludge from the filter systemand allows it to air dry in open drums. This has significantlyreduced the sludge volume, according to Plant A personnel.However, this method of dewatering will not work duringthe rain season, and it also presents problems for complyingwith the 90-day accumulation limits placed on hazardouswaste generators. Therefore, the use of a mechanicaldewatering system may be beneficial for reducing sludgevolume and also for complying with hazardous wasteregulations.

Assuming a direct correlation between wastewatervolume and sludge volume, Plant A could also reduce itssludge generation by 80 percent. This would equal threedrums less each month at a savings at $50 per drum, or$150. Total savings for operating each rinse tank as a batchrinse system could be as great as $1020 each month.

Savings from reducing the flow rate of water througheach rinse tank depends on the minimum flow rate that canbe used to maintain adequate rinsing. In the Rinse WaterReduction section, it was shown that the present flow rateof 16 gallons per minute creates a ratio of process bathconcentration to rinse solution concentration of 5,000 to 1.For illustration purposes, assume the flow rate could bereduced to 12 gallons per minute; ratio would be reducedto 3750 to 1. The rinsing requirements for Plant A rinsesystems were not available to the consultants. However,since the standard ratio of process chemical concentrationto rinse solution concentration used in the electroplatingindustry is approximately 1000 to 1, a 25 percent reductionin flow rate, which produces a 3750 to 1 ratio, appearsachievable. If the flow ratecould be reduced by 25 percent:(1) water and sewer fee savings would be $46 per month

(based on a reduction in water usage of 34,600 gallons andwater and sewer fees of $0.50 per 750 gallons each); (2)treatment chemical savings would be $210 per month(based on a 25 percent reduction in existing treatmentchemical costs); and (3) sludge disposal cost savingswould be $50 per month (based on a 25 percent reductionin sludge volume generated each month). Total savingswould be approximately $310 per month.

The use of automated rinse water flow controls willrequire significant capital investment. A pH/conductivitymeter used to automatically turn rinse water on and off willcost approximately $700 to purchase and install. If thesecontrols were purchased for all nine rinse tanks, the totalcost would be $6,300. Savings would depend on thereduction in water usage that could be achieved. Sincedrag-out rates for process baths and operating parametersfor the rinse systems were not available, estimates onsaving that can be achieved by installing automated flowcontrols cannot be calculated. However, one printedcircuit board manufacturer estimated that water use wasreduced by 67 percent by installing flow control meters.For illustrative purposes, a more conservative estimate of25 percent reduction in water use will be used. Therefore,the use of automated flow control meters could also saveSun Circuits $310 per month. At that savings rate, paybackon investment would take 21 months.

Feasibility Analysis PhaseThe recommended options were evaluated for their

technical andeconomic feasibility by the consultants, whoobtained cost and performance data from vendors wherenew equipment was recommended. The result of thetechnical and economic feasibility analyses was a list offeasible options, which became part of the assessment’sfinal report. The next waste minimization assessmentphase, Implementation, was left to the discretion of theprinted circuit board manufacturer, Plant A.

The specific economic aspects of implementing eachof the source reduction/resource recovery options were notseparately documented by Plant A. Most of the sourcereduction options employed are essentially good operatingpractices, and hence did not require a large capitalinvestment. However, the rework strategies and theirevolution did require a large R&D expenditure. Theimplementation of these measures seemed to be guidedmore by the intuition and foresight of the plant personnelthan by the calculated benefits that may have been indicatedby a specific detailed economic evaluation.

RINSE WATER REDUCTIONOperating the rinse tanks as batch rinse systems or

reducing the rate of water flow through the rinse tanks can

53

54

be implemented for minimal costs. To operate the rinsetanks as batch rinse systems, the plant would need additionallabor to manually dump the rinse tanks. Plow restrictors forreducing the flow of water through rinse tanks wouldrequire only mirror capital investments. The resultingsavings in water usage, sewer fees, and treatment chemicalcosts woulddepend on the reduction in water use achieved.

Table A-5 indicates that water usage can be reduced by6,920 gallons per day, or approximately 80 percent, if allthe rinse tanks were operated as batch rinse systems.Assuming 20 work days per month, water usage could bereduced by 138,400 gallons each month. Since both waterusage and sewer discharge fees are approximately $0.50per 750 gallons, Plant A would save approximately $190each month on water and sewer fees by reducing waterusage by 138,400 gallons. As stated in Section 2.3, PlantA spends approximately $850 each month on treatmentchemicals. Therefore, an 80 percent reduction in wastewatergeneration could reduce treatment chemical costs by asmuch as 80 percent. This would amount to a savings of$680 each month. Actual treatment chemical savings maybe less because the wastewater will have a highercontaminant concentration and thus may require greatertreatment chemical feed rates per volume of wastewater.Reductions in sludge volume will depend on the efficiencyof the treatment system and the actual reductions in treatmentchemical usage.

The use of various drag-out reduction techniques willincrease the potential for reducing rinsewater usage becauseless process chemicals will enter the rinse system. Byinstalling a bar rail above each process tank for hangingworkpiece racks, the plant could allow for greater drainagetime before rinsing. This bar could be installed by Plant Apersonnel for a few hundred dollars if constructed out of 1inch PVC piping. Other drag-out reduction techniquessuch as slowing workpiece rack removal rates and operatingprocess baths at the lowest possible concentration can beimplemented for little cost. Savings associated with drag-out minimization cannot be quantified until the techniquesare implemented.

EQUIPMENT CLEANOUTPlant A can reduce waste nitric acid generation by

using a multiple tank cleaning line. The costs associatedwith setting up such a system include the cost of additionaltanks and the installation labor costs. The costs for settingup a cascade cleaning line would be approximately $350per tank. Labor costs of $55 an hour for 4 hours would be$220.

The savings associated with a multiple tankplating rack cleaning line include reduced costs for nitricacid purchases and waste acid handling. The consultants

visited one plant that used five 15-gallon tanks as a multiplestage cleaning line. The plant generates 15 gallons of wastenitric acid every 6 months. If Plant A could reduce its wastenitric acid generation from 60 gallons to 15 gallons per 6months, it would achieve a savings of $140 in nitric acidpurchases and $90 in waste disposal costs each 6 months.This is based on nitric acid costing approximately $3.10per gallon and waste disposal costs being approximately$2.00 per gallon.

MATERIAL RECYCLINGThe auditors identified three waste materials for

recycling: (1) photoresist stripper waste, (2) acidic rinsewater effluent, and (3) copper sulfate crystals. Decantingor filtering spent stripper waste so it can be reused willrequire minor purchases to set up a decantation system ora filter system. Savings would include fewer fresh stripperpurchases and lower stripper waste disposal costs. Ifdecantation or filtration could be used to extend the processbath life from 2 weeks to 4 weeks, Plant A could reducestripper purchases by 30 gallons each month. Once thestripper becomes too dilute for continued use, it can befiltered once more and used in the treatment system for pHadjustment. This could save Plant A $50 each month fordisposal of stripper waste. A polymer sludge residuewould still be generated, however.

To implement a system to reuse rinse water effluentfrom rinse tank 16 for feed water into rinse tank 14, PlantA would need to spend approximately $1,000. This includes$500 for contractor labor for 1 day and $500 for materialsthat include piping materials and a three-quarter horsepowerpump, which would be adequate for a typical rinse system.Assuming that both rinse systems operate at the same flowrate, no storage tank capacity would be necessary.

Savings associated with recycling rinse water havebeen estimated based on Plant A’s current water usage.Water and sewer fee savings would be approximately $13each month based on a reduction in water usage of 500gallons each day. Since wastewater generation would bereduced by 5 percent, treatment chemical usage could alsobe reduced by approximately 5 percent. A 5 percentreduction in the company’s existing treatment chemicalcosts, which are $850 per month, would save Plant A $42each month in treatment chemical purchases.

Copper sulfate crystals generated by Plant A could berecycled by adding them to the industrial waste sludge.There is no additional cost associated with mixing thecrystals and the sludge since the crystals are also handledas hazardous waste if kept separate. Since the sludge is sentto a metal reclaimer, Plant A may receive a larger paymentfor reclaimed metals due to increased copper content in thesludge.

55

Table A-5. Rinse Water-Waste GenerationOperating as Flow-Through Tanks at a Rate of 16 gpm

Tank Time WaterNumber is Running

2 96 minutes4 96 minutes7 96 minutes9 96 minutes

10 96 minutes14 30 minutes16 30 minutes

Daily Flow Rate

1536 gallons1536 gallons1536 gallons1536 gallons1536 gallons480 gallons480 gallons

8640 gallons8640 gallons wastewater generated each day.

Operating as Batch Tanks Holding 30 Gallons ofRinse Water

Tank Number ofNumber Batches Daily

2 124 126 128 12

10 1214 216 2

Volume ofWastewaterGenerated Daily

360360360360360

6060

1720 gallons1720 gallons generated each day.

WASTE SEGREGATIONThe costs and savings associated with segregating

chelated and nonchelated waste streams will depend on thedesign requirements of the segregation and the modificationsto the treatment system that can be made once the materialsare segregated. Assuming segregation will only entailinstalling a 500-gallon storage tank, pumps, gauges, andnecessary piping, equipment costs would range between$2,000 and $4,000. Double containment would be moreexpensive. In addition, installation costs may be as high as100 percent of equipment costs.

As discussed in Section 5.1, the ferrous sulfate used totreat the wastewater contributes approximately 34 percentof the total sludge volume. The ferrous sulfate also costsPlant A approximately $250 each month to purchase.Savings associated with segregating chelated waste streamsand batch treating them will depend on the percentage offerrous sulfate usage that can be eliminated through batch

treatment of chelated waste streams. Since information onwhich process chemicals contain chelators was not availableto the audit team, development of segregation alternativesand estimates for material and waste disposal cost savingscould not be developed.

SLUDGE DEWATERINGSmall filter press units designed to handle from 0.75 to

3.75 gallons of sludge per load cost between $2,800 and$4.900. Assuming that Plant A already has a source ofcompressed air, the company can install the unit itself. Theunit can handle 7.5 to 37.5 gallons of sludge per 5 day workweek. These units can increase solids content from 1percent to approximately 35 percent. Plant A’s current bagfilter dewatering unit can achieve a sludge solidsconcentration of 11 percent. An increase in solidsconcentration from 11 percent to 35 percent will reducesludge volume by approximately 75 percent. This couldreduce the plant’s sludge generation from approximately200 gallons to about 50 gallons per month. Since Plant Aestimates that sludge disposal costs approximately $1.00per gallon, this sludge dewatering could save the companyapproximately $150 each month in disposal costs.

S U M M A R YThe audit of Plant A was performed to identify

opportunities for waste reduction. The following hazardouswastes are generated by Plant A each month:

Industrial waste sludge- Approximately 200gallons

Photoresist stripper waste- Approximately 60gallons

Copper sulfate crystals- Undetermined

Nitric acid waste- Approximately 10 gallons

Reflow oil - Undetermined

The audit provided information that is useful to identifyseveral waste reduction techniques that may be feasible forPlant A to implement. The following waste reductionopportunities were identified:

l Use process chemistries that can be recycled ortreated when they are spent instead ofchemistries that currently are containerized foroff-site disposal.

l Use non-chelated process chemistries to replacechelated chemistries.

l Operate the rinse tanks as batch rinse systems.

56

Reduce the flow rate used in the flow-throughrinse tanks.

Use flow restrictors and automated flow controlsto reduce rinse water usage.

Aggressively pursue drag-out reduction bydeveloping operational procedures and trainingpersonnel to slowly remove workpiece racksand increase drainage time prior to rinsing.

Install a multiple-stage electroplating rackcleaning line to reduce nitric acid wastegeneration.

Reuse rinse water effluent from rinse systemsfollowing acidic baths as rinse water influent torinse systems that follow alkaline cleaning baths.

Mix copper sulfate crystals with industrial waste

sludge for off-site metals reclamation.

Segregate chelated waste streams from non-chelated waste streams and batch treat them.

Dewater sludge using a mechanical filter press.

ReferencesDHS. 1987. Waste Audit Study - Printed Circuit Board

Manufacturers. June 1987. Prepared for CaliforniaDepartment of Health Services, AlternativeTechnology Section (Sacramento, California) byPlanning Research Corporation.

57

PLANT B WASTE MINIMIZATIONASSESSMENT

The waste minimization assessment of Plant B followedthe same protocol used for Plant A, and included:

l Planning and organization

l Assessment phase

l Feasibility analysis phase

Implementation of selected waste minimization optionswas left to the discretion of Plant B.

Planning and OrganizationPlanning and organization of the assessment were a

joint effort of the consulting firm and the PC boardmanufacturing plant’s operations manager. As summarizedin Figure 1, this phase of the assessment involved gettingcompany management commitment to the project, settinggoals for the assessment, and establishing a task force (theconsultants working in cooperation with the plant operationsmanager) to conduct the assessment.

Assessment Phase: Process and FacilityData

The consultants worked with the plant operationsmanager to establish a data base of the facility’s rawmaterial needs, materials handling procedures, andoperations processes. Block flow diagrams were drawn upto identify where materials are used and where waste isgenerated. Initial study of this information and discussionsof waste stream concerns at the plant served as preliminarysteps to the site inspection, during which additional processand waste handling information was obtained.

FACILITY DESCRIPTIONPlant B is a prototype circuit board manufacturer

specializing in jobs involving limited production and fastturnaround. Manufacturing operations include drillingand routing, layering (for multilayer boards), photoresistprinting, plating, etching, and stripping.

PROCESS DESCRIPTIONFigure B-l is a floor plan of the plant’s plating and

etching process area. The numbers listed in the floor planrepresent the identification number for each process bathand rinse tank. Tables B-l and B-2 describe Plant B’srinsing operations and chemical process baths, respectively.

The plant presently uses seven dip tanks and two sprayrinse tanks. All the dip rinse tanks are equipped with pH/conductivity meters that control the flow of water throughthe rinse tanks. The spray rinse tanks are all operated withfoot pedals for turning on the water.

WASTE DESCRIPTIONProduction activities that generate hazardous waste

are the plating, etching, and stripping processes. Thesources of waste from theseactivities are rinsing operations,spentprocess bath dumping, and industrial wastetreatment,and equipment cleanout. This chapter describes thehazardous waste generating and handling activitiesperformed at Plant B and describes the volume andcharacteristics of the hazardous wastes generated. TableB-3 lists Plant B’s hazardous waste managementcharacteristics.

Rinsing OperationsRinsing operations associated with the chemical

process lines are the major source of wastewater at Plant B.Wastewater generation fluctuates between 7,000 to 11,000gallons per day. The rinse operations contribute to hazardouswaste generation because waste rinse water carries awaychemicals which are then removed by treatment at theindustrial waste treatment plant. The sludge that is generatedfrom this treatment is handled as a hazardous waste.

Spent Chemical Bath DumpingWhen process chemical baths become too contaminated

or diluted for use (spent), it is removed from the processtank. The spent chemical bath is then either containerizedfor reclamation by the manufacturer, containerized for off-site disposal, used as a neutralization chemical in theindustrial waste treatment system, or dumped into thewastewater collection sump. A schedule for dumping eachspent process bath was not available from Plant B, but plantpersonnel indicated that the frequency varies. A bath ischanged when personnel recognize that the effectivenessof the bath is no longer adequate.

Only two of the spentbath handling methods contributeto the amount of hazardous waste generated at the plant.These methods include containerizing spent baths for off-site disposal and dumping of spent chemical baths into thewastewater sump. The only process chemical bathscontainerized for disposal are the photoresist strippers andthe reflow oil. Approximately 25 gallons of waste reflowoil is generated every 2 months. The volume of stripperwaste generated was not estimated by Plant B. Chemicalbaths treated at the industrial waste treatment facility aretransferred to one of the two wastewater sumps where thechemicals are neutralized. The waste is then fed into theindustrial waste treatment system.

Copper sulfate crystals are also generated when someof the process baths are taken off-line. The crystals formin the process bath as the copper concentration increases.Before the process baths are dumped into the wastewatersump, the crystals are containerized as a solid waste since

58

Figure B-l Plant B’s Etching and Plating Facility

59

Table B-l. Rinse System InformationRINSE TANK/ RINSE WATER NUMBERNUMBER FLOW CONTROLS OF TAN KS

IN SYSTEM

Dip Rinse/l pH/ConductivityMeters

Dip Rinse/3 pH/ConductivityMeters

Dip Rinse/5 pH/ConductivityMeters

Dip Rinse/12 pH/ConductivityMeters

Drag-out/14 Manual DumpingSpray Rinse/15 FootpedalsDrag-out/18 Manual DumpingSpray Rinse/19 FootpedalsDip Rinse/26 pH/Conductivity

MetersDip Rinse/27 pH/Conductivity

MetersDip Rinse/30 pH/Conductivity

MetersDip Rinse/32 pH/ConductivityConditioner Meters

one

one

one

one

oneoneoneonetwo

two

one

one

COUNTER PROCESS BATHCURRENT PRECEDINGSYSTEM RINSE

no AmmoniumBifluoride/2MBL Cleaner/4no

no

no

NANANANAno

no

no

no

98% SulfuricAcid/6Black Oxide/11 andTin Immerse/13---Drag-out Tank/14---Drag-out Tank/18Rinse Tank/27

Catalyst

Sulfuric-PeroxideEtch/31Cleaner-33

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Table B-2. Process Bath InformationPROCESS BATH/ PROCESS BATHNUMBER VOLUME (gallons)

Ammonium Bifluoride/2 50 gal.MBL Cleaner/4 50 gal.98% Sulfuric Acid/6 20 gal.Tin-Lead Bath/7 400 gal.Fluorboric Acid/8 50 gal.Copper Sulfate/9 400 gal.Copper Sulfate/10 400 gal.Black Oxide/11 50 gal.Tin Immerse/13 50 gal.10% Sulfuric Acid/16 50 gal.Sulfuric/Peroxide Etch/17 50 gal.Soap Cleaner/20 50 gal.Reflow Flux/21 2 gal.Reflow Oil/22 15 gal.Reflow Oil/23 15 gal.Electroless Copper/24 50 gal.Accelerator/25 50 gal.Catalyst/28 50 gal.Catalyst Prep/29 50 gal.Sulfuric-Peroxide Etch/31 50 gal.Cleaner-Conditioner/33 50 gal.

Table B-3. Hazardous Waste Data

METHOD OFDISPOSAL

To wastewater treatment facilityTo wastewater treatment facilityTo wastewater treatment facility

To wastewater treatment facility

---

To wastewater treatment facilityTo wastewater treatment facilityTo wastewater treatment facilityTo wastewater treatment facilityTo wastewater treatment facilityOff-site disposalOff-site disposalOff-site disposalTo wastewater treatment facilityTo wastewater treatment facilityTo wastewater treatment facilityTo wastewater treatment facilityTo wastewater treatment facilityTo wastewater treatment facility

61

they cannot be fed into the treatment system. The crystalsare mixed with the plant’s industrial waste sludge, which istransported offsite for metal reclamation.

Industrial Wastewater TreatmentPlant B’s industrial waste treatment facility treats all

wastewater prior to discharge to the San Jose/Santa ClaraWater Pollution Control Plant. Plant B’s treatment facilityremoves metals and adjusts the pH of the wastewater tomeet the maximum allowable concentration of metals inthe discharged effluent, as set by the San Jose/Santa ClaraWater Pollution Control Plant. These maximumconcentrations are as follows:

Chromium 1.0 mg/L

Copper 2.7 mg/L

Cyanide 1.0 mg/L

Lead 0.4 mg/L

Nickel 2.6 mg/L

Silver 0.7 mg/L

Zinc 2.6 mg/L

The treatment process includes neutralization, metalsprecipitation, filtration, and sludge dewatering. Thetreatment plant is located outside the main building in acurbed area. The metal hydroxide sludge generated by thistreatment process is a hazardous waste. The treatmentsystem generates approximately 25 gallons of sludge everymonth. The sludge dewatering unit produces a sludge thathas a solids concentration of 35 percent. The sludge istransported offsite to World Resources of Phoenix, Arizonafor metal reclamation. World Resources analyzes a samplefrom each load of sludge it receives. The analytical dataprovided by World Resources for the sludge generated byPlant B are as follows:

Percent solids 35%

Metal content in pounds per dry ton

Copper 250

Nickel 11

Tin 59

Iron 12

Lead 22

Zinc 8

Equipment CleanoutThe primary source of hazardous waste associated

with equipment cleanout is the cleaning of electroplatingracks. Plant B uses nitric acid in a five tank cleaning lineto clean electroplating racks. Each tank holds approximately15 gallons of nitric acid. The acid in the first tank requireschanging approximately every 6 months. When the nitricacid in the first tank is dumped, the remaining four tanks allmove up one step in the cleaning line. The empty tank isfilled with fresh nitric acid and is used as the last tank in thecleaning line. The waste nitric acid has too low a pH andtoo high a copper content to be treated in the industrialwaste treatment system.

Other cleaning activities, such as floor washing andchemical bath tank rinsing, generate waste streams thatdischarge into the wastewater collection sump. Accordingto Plant B personnel, these waste streams make up a smallportion of the chemicals that enter the treatment system.

Assessment Phase: Option GenerationAfter the site inspection, the plant operations manager

and the consultant team reviewed the raw material, process,and waste stream information and developed a number ofwaste minimization options for consideration. Theseoptions fall into the categories of source reductiontechniques and recycling and resource recovery techniques.

SOURCE REDUCTION MEASURESPlant B appears to have effectively implemented several

technologies to reduce the volume of hazardous waste itgenerates. Water conservation techniques, such as rinsewater flow control meters and pressure activated sprayrinse tanks, are presently used at the plant. The industrialwaste treatment system appears to effectively treatwastewater without producing excessive volumes of sludge.Plant B personnel stated that their effluent consistentlymeets the discharge requirements set by the San Jose/SantaClara Water Pollution Control Plant. Also, the volume ofsludge generated by the wastewater treatment system islower than the volume generated at other manufacturingplants of comparable size and wastewater generation rates.For example, Plant B generates approximately 50 gallonsof sludge every 2 months compared to another plant witha comparable wastewater generation rate that generatesapproximately 200 gallons of sludge every month.Nevertheless, several additional opportunities for wastereduction may be available to Plant B that can furtherreduce its hazardous waste generation. This sectiondescribes these opportunities.

MATERIAL SUBSTITUTIONPlant B may be able to reduce the volume of spent

process chemicals and cleaning solutions containerized foroff-site disposal by substituting materials. Two materialsthat Plant B handles as hazardous waste are spent reflow oil

62

and spent nitric acid. Several reflow oil products areavailable that, when spent, either can be returned to thesupplier for recycling or can be treated by the facility priorto discharge to the Publicly Owned Treatment Works.Plant B could eliminate a hazardous waste stream byreplacing its presentreflow oil with a recyclable or treatablereflow oil.

Nitric acid waste, which is generated from the cleaningof electroplating racks, can also be eliminated by using analternative cleaning solution. One chemical supplier offersan electroplating rack cleaning solution that can beregenerated. The metal stripped off of racks during thecleaning process can be plated out in a tank equipped witha cathode and an anode. The metal stripped from the racksis plated onto the cathode and forms a metallic sludge thatsettles to the bottom of the cleaning tank. Once the solutionbecomes spent, it can be treated in the plant’s industrialtreatment system instead of being containerized for off-sitedisposal. Plant B should consult with chemical suppliersto identify alternative materials that can be recycled ortreated and that will meet its specific operating requirement.

DRAG-OUT LOSS REDUCTIONDiscussions with Plant B personnel indicated that

little attention is placed on drag-out reduction. Althoughthe plant does not generate excessive amounts of sludge,further reductions in sludge volume may be obtained byusing drag-out reduction technologies. Reductions in drag-out loss should also have a direct impact on water usage.Since water flow through the rinse systems are controlfedby pH/conductivity controls, drag-out reduction willdecrease the frequency of rinse water flow through therinse tanks. Plant B may be able to reduce drag-out byinstituting operational modifications and training personnelin drag-out reduction techniques. Drag-out reductiontechniques include slowing the workpiece rack withdrawalrates and increasing drainage time prior to rinsing. Otherdrag-out reduction methods include operating processbathsat the lowest allowable concentration and using heatedprocess baths when possible.

The faster an item is removed from the process bath,,the thicker the film on the workpiece surface and thegreater the drag-out volume will be. The effect is sosignificant that most of the time allowed for withdrawaland drainage of a rack should be used for withdrawal only.Plant B management should emphasize to process lineoperatorsthat workpieces should be withdrawnslowly. Anoptimal removal rate can be determined by removingloaded workpiece racks from process baths at differentrates and allowing the rack to drain into a catch basin.Drag-out volume can then be measured volumetrically.

Workpiece drainage also depends on the operator.

The time allowed for drainage can be inadequate if theoperator is rushed to remove the workpiece rack from theprocess bath and place it in the rinse tank. However,installation of a bar or rail above the process tank may helpensure that adequate drainage time is provided prior torinsing. Plant B has expressed concern that increasingworkpiece rack removal and drainage time will allow forchemical oxidation on the board Plant B should identifythe processes that are not highly susceptible to oxidationand emphasize drag-out minimization techniques topersonnel operating those processes.

RINSE WATER RECYCLINGPlant B may be able to recycle its rinse water by further

treating effluent from the industrial waste treatment plant.This additional treatment may only require activated carbontreatment to remove trace organics from the water. PlantB should assess the need for other levels of treatment, suchas ion-exchange or other technologies, based on the qualityof the treated effluent. This recycled water would containless natural contaminants, such as phosphates andcarbonates, than tap water, which is presently used. Sincethese natural contaminants contribute to sludge volumebecause they precipitate during treatment, the use of recycledrinse water can reduce hazardous waste sludge generationand significantly reduce water usage and sewer dischargefees.

Feasibility Analysis PhaseAfter discussions with Plant B personnel, some of the

options discussed in the previous section were selected forinvestigation of their technical and economic feasibility.The economic analysis was based on the raw material andwaste disposal costs provided by the facility personnel andon economic and technical information provided byequipment manufacturers. The measures evaluated in thissection include: material substitution, drag-out lossreduction and rinse water recycling.

MATERIAL SUBSTITUTIONThe benefits associated with using recyclable and/or

treatable process chemistries will depend on the costs ofsubstitute materials compared with the costs of materialspresently used. Also, additional process bath maintenancerequirements and treatment costs need to be identified.These costs will depend on the type of substitute materialchosen by Plant B .

Savings will include reduced waste disposal costs andmaterial usage costs if the substitute material can berecycled. Plant B generates 150 gallons of waste reflow oiland 30 gallons of waste nitric acid annually. Since wastedisposal costs for the waste reflow oil and waste nitric acidare both $1OO per 55-gallon drum, which is the average cost

63

for disposing of various liquid hazardous wastes accordingto PC board manufacturers, waste disposal cost savingswould be approximately $300 per year for spent reflow oiland $50 per year for nitric acid waste. Actual savingsassociated with using recyclable reflow oil and nitric acidwill depend on the difference in the cost of the substitutematerials.

DRAG-OUT LOSS REDUCTIONSeveral drag-out minimization techniques can be

implemented at Plant B for minimal costs. The use of a barrail above each process tank for hanging workpiece rackswill allow for greater drainage time before rinsing. Thiscould be installed by Plant B’s personnel for a few hundreddollars if constructed of 1 inch PVC piping. Other drag-outreduction techniques, such as slowing workpiece rackremoval rates and operating process baths at the lowestpossible concentration, can also be implemented for littlecost. Developing a training program and emphasizingdrag-out minimization will require time from managementand operations personnel. Since information on drag-outrates and workpiece rack removal and drainage times werenot available from Plant B, savings associated with drag-out minimization cannot be quantified prior toimplementation.

RINSE WATER RECYCLINGConsiderable capital investment may be needed to

recycle wastewater for reuse in production. The costsassociated with recycling treated wastewater effluent willdepend on the level of additional treatment necessary toreturn the effluent back into the production processes.Other plants that are considering rinse water recyclinghave indicated that their primary concern is to removeorganics from the treated effluent before reusing the water.An activated carbon system to treat the effluent can be usedto remove organics from the water. If various anions and/or cations in the effluent must also be removed, treatmenttechnologies such as reverse osmosis or ion-exchange maybe required.

Information describing the rinse system operatingparameters and the water quality or Plant B’s treatedeffluent were not obtained during the audit. Therefore,treatment requirements for returning treated effluent to therinse systems could not be developed. Plant B should

investigate the potential for recycling rinse water bycharacterizing its rinse water effluent, determining thewater quality needs for reusing treated effluent, andidentifying potential technologies that can be used to treatthe effluent for reuse.

The primary savings associated with recycling rinsewater is lower water purchase and sewer discharge fees.Plant B generates approximately 7,000 to 11,000 gallons ofwastewater each day. For an average daily water usage of9,000 gallons, and assuming that 90 percent of the watercan be recycled, Plant B could reuse approximately 8,000gallons of water each day. Since water and sewer fees areboth approximately $0.50 per 750 gallons, Plant B couldsave approximately $10 each day in water and sewer costs.

S U M M A R YThe audit of the Plant B was performed to identify

opportunities for waste reduction. The following hazardouswastes are generated by Plant B annually:

Industrial waste sludge- Approximately 300gallons

Photoresist stripper waste- Undetermined

Copper sulfate crystals- Undetermined

Nitric acid waste- Approximately 30 gallons

Reflow oil- Approximately 150 gallons

The audit was used to identify several waste reductiontechniques that may be feasible for Plant B to implement.The following waste reduction opportunities wereidentified:

l Use alternative reflow oil and electroplatingrack stripper materials that can be recycled ortreated when they are spent instead ofchemistries that currently are containerized foroff-site disposal.

l Aggressively pursue drag-out reduction bydeveloping operational procedures and trainingpersonnel to slowly remove workpiece racksand increase drainage time prior to rinsing.

l Recycle treated effluent for reuse in theproduction process.

64

PLANT C WASTE MINIMIZATIONASSESSMENT

The waste minimization assessment of Plant C followedthe same protocol used for Plant A, and included:

l Planning and organization

l Assessment phase

l Feasibility analysis phase

Implementation of selected waste minimization optionswas left to the discretion of Plant C.

Planning and OrganizationPlanning and organization of the assessment were a

joint effort of the consulting firm and the paintmanufacturing plant’s operations manager. As summarizedin Figure 1, this phase of the assessment involved gettingcompany management commitment to the project, settinggoals for the assessment, and establishing a task force (theconsultants working in cooperation with the plant operationsmanager) to conduct the assessment.

Assessment Phase: Process and FacilityData

The consultants worked with the plant operationsmanager to establish a data base of the facility’s rawmaterial needs, materials handling procedures, andoperations processes. Block flow diagrams were drawn upto identify where materials are used and were waste isgenerated. Initial study of this information and discussionsof waste stream concerns at the plant served as preliminarysteps to the site inspection, during which additional processand waste handling information was obtained.

FACILITY DESCRIPTIONPlant C is a prototype circuit board manufacturer

specializing in jobs involving limited production and fastturnaround. Manufacturing operations include drillingand routing, layering (for multilayer boards), plating, andetching.

PROCESS DESCRIPTIONFigure C-l is a floor plan of the plant’s plating and

etching process area. The numbers listed on the floor planrepresent the identification number for each process bathand rinse tank. Tables C-l and C-2 describe Plant C’srinsing operations and chemical process baths, respectively.

WASTE DESCRIPTIONProduction activities that generate hazardous waste

are the plating and etching processes. The sources of wastefrom these activities are rinsing operations, spent processbath dumping, industrial waste treatment, and equipment

cleanout. This chapter of the report describes the hazardouswaste generating and handling activities performed atPlant C and describes the volume and characteristics of thehazardous wastes generated. Table C-3 lists Plant C’shazardous waste management characteristics.

Rinsing OperationsRinsing operations associated with the chemical

process lines are the major source of wastewater at Plant C.Facility personnel estimate that approximately 3,000 gallonsof wastewater are generated each day. The rinse operationscontribute to hazardous waste generation because wasterinse water carries away chemicals which are then removedby treatment at the industrial waste treatment plant. Thesludge waste that is generated from this treatment is thenhandled as a hazardous waste.

The plant uses 11 dip rinse tanks that discharge to theindustrial waste treatment plant and twodrag-out tanks thatare periodically dumped manually into the wastewatersump. All of the rinse tanks are plumbed directly to thewastewater treatment system via a collection sump.Discussions with facility personnel indicate that waterflows through the dip rinse tanks only when the process lineassociated with the tank is in operation. Water flow foreach rinse tank is turned on and off manually by productionpersonnel. Plant C installed flow restrictors in each rinsesystem’s water inflow line to control water usage.

Four of the rinsing operations are double rinse tanksystem (tanks 5 and 6, tanks 15 and 16, tanks 21 and 22, andtanks 30 and 31). These four rinse systems, however, arenot plumbed in series as counter-current rinse systems.Instead, each tank has a separate rinse water influent andeffluent water line.

Spent Chemical Bath DumpingWhen process chemical baths become too contaminated

or diluted for use (spent), they are removed from theprocess tank. The spent chemical bath is then eithercontainerized for reclamation by the manufacturer,containerized for off-site disposal, or dumped into thewastewater collection sump. A schedule for dumping eachspent process bath was not available from Plant C, but plantpersonnel indicated that the frequency varies. A bath ischanged when personnel recognize that the effectivenessof the bath is no longer adequate.

Only two of the spent bath handling methods contributeto the amount of hazardous waste generated at the plant.These methods are containerizing waste for off-site disposaland dumping of spent chemical bath into the wastewatersump. The process chemical bath containerized for disposalis the reflow oil. The plant generates approximately 20gallons of waste reflow oil each month.

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Figure C-1. Plant C’s Etching And Plating Facility

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Table C-l. Rinse System InformationRINSE SYSTEM NUMBERNUMBER OF TANKS

Dip Rinse/3Dip Rinse/5Dip Rinse/6Dip Rinse/9Dip Rinse/12Dip Rinse/l5Dip Rinse/l6Dip Rinse/20Dip Rinse/21Drag-out/27Drag-out/29Dip Rinse/30Dip Rinse/31

OneTwoTwoOneOneTwoTwoTwoTwoOneOneTwoTwo

Table C-2. Process Bath Information

COUNTERCURRENTSYSTEM

NoNoNoNoNoNoNoNoNoNoNoNoNo

PROCESS BATH/IDENTIFICATION NUMBER

Nickel Sulfate/lSoap Cleaner/2Peroxide Etchback/410% Hydrochloric Acid/7Catalyst/8Accelerator/l0Electroless Copper/1110% Hydrochloric Acid/l3Tin/Lead Stripper/l4Reflow Oil/l7Ammonium Etchant/18Micro Etch Cleaner/l9Sulfuric Acid/22Fluorboric Acid/23Solder Bright/24Nitric Acid/25Copper Sulfate/26Tin-Lead/28

PROCESS BATHVOLUME IN TANK

30 gal.30 gal.30 gal.30 gal.30 gal.30 gal.30 gal.30 gal.30 gal.20 gal.

50 gal.50 gal.50 gal.50 gal.50 gal.

400 gal.400 gal.

PROCESS BATHPRECEDING RINSESYSTEM

Soap Cleaner/2Peroxide Etchback/4Dip Rinse Tank/5

Catalyst/8Electroless Copper/11Tin/Lead Stripper/l4Dip Rinse Tank/5Micro Etch Cleaner/l9Dip Rinse Tank/20Copper Sulfate/26Tin-Lead/28Reflow Oil/17Reflow Oil/17

METHOD OFDISPOSAL

Discharge to treatment facilityDischarge to treatment facilityDischarge to treatment facilityDischarge to treatment facilityReplenished, not disposedDischarge to treatment facilityReplenished, not disposedDischarged to treatment facilityDischarged to treatment facilityOff-site disposalRecycled by manufacturerDischarged to treatment facilityDischarged to treatment facilityDischarged to treatment facilityDischarged to treatment facilityOff-site disposalReplenished, not disposedReplenished, not disposed

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Table C-3. Hazardous Waste Data

WASTE

Spent Ion 1200 gal.Exchange Resin

Nitric Acid

Reflow Oil

Copper SulfateCrystals

480 gal.

240 gal

Undetermined

DISPOSAL DISPOSALMETHOD COST/UNIT

Transported $2.OO/gal.off-site fordisposalTransported $2.OO/gal.off-site fordisposalTransported $2.OO/gal.off-site fordisposalTransported $2.OO/gal.off-site fordisposal

ANNUALDISPOSALCOSTS

$2,400

$ 960

$ 480

___

Other process baths are discharged to the treatment The treatment process includes filtration, ion-exchange,plant when they are spent (except for the etchant, which is and neutralization. The ion-exchange (IE) system wassent back to the supplier for reclaim). Copper sulfate recently installed to replace Plant C’s conventionalcrystals are also generated when some of the process baths, precipitation/clarifier treatment system. The Ion Exchangesuch as the peroxide/sulfuric etch, are taken off-line. The unit has a treatment capacity of 12 to 14 gallons per minute.crystals form in the process bath as the copper content The Ion Exchange unit produces less hazardous waste thanincreases. Before the process baths are dumped into the the old treatment system. The hazardous waste generatedwastewater sump, the crystals are removed and by the Ion Exchange treatment process is spent ion-exchangecontainerized as a solid hazardous waste since they cannot resin. Approximately 100 gallons of waste resin arebe fed into the treatment system. Plant C did not estimate generated each month, compared to approximately 300the volume of copper sulfate crystals generatedeach month. gallons of sludge generated by the old treatment system.

Industrial Wastewater Treatment Equipment CleanoutPlant C’s industrial waste treatment facility treats all

wastewater prior to discharge to the San Jose/Santa ClaraWater Pollution Control Plant. Plant C’s treatment facilityremoves metals and adjusts the pH of the wastewater tomeet the maximum allowable concentration of metals inthe discharged effluent, as set by the San Jose/Santa ClaraWater Pollution Control Plant. These maximum

The primary source of hazardous waste associatedwith equipment cleanout is the cleaning of the copperetching tank, the tanks used in the electroplating line, andthe electroplating racks. This equipment is cleaned byusing nitric acid. Plant C estimates that approximately 40gallons of waste nitric acid are generated each month. Thewaste nitric acid has too low of a pH and too high of acopper content to be discharged to the treatment facility.concentrations are as follows:

Chromium

Copper

Cyanide

Lead

Nickel

Silver

Zinc

1.0 mg/L

2.7 mg/L

1.0 mg/L

0.4 mg/L

2.6 mg/L

0.7 mg/L

2.6 mg/L

The nitric acid solution is stored in a single 50-gallontank where electroplating racks can be immersed in thesolution for cleaning. The nitric acid is used to strip thecopper, tin, and lead from the equipment. When the acidloses its ability to effectively oxidize the metal, it iscontainerized for disposal. Electroplating rack cleaning isthe greatest source of waste nitric acid.

Assessment Phase: Option GenerationAfter the site inspection, the plant operations manager

and the consultant team reviewed the raw material, process,and waste stream information and developed a number ofwaste minimization options for consideration. These

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options fall into the categories of source reductiontechniques andrecycling and resource recovery techniques.

RINSE WATER REDUCTION

SOURCE REDUCTION MEASURESPlant C appears to have effectively implemented several

technologies to reduce the volume of hazardous waste itgenerates. Water conservation techniques such as rinsewater flow restrictors are presently used at Plant C, theplant’s water use appears to be significantly lower than thatof other plants of comparable size and production. Forexample, two other plants visited by the consultant generateapproximately 10,000 gallons of wastewater each daycompared to 3,000 gallons generated by Plant C each day.The ion exchange treatment system effectively treatswastewater without producing a hazardous waste sludge.This new treatment system produces approximately 100gallons of spent ion exchange resin each month, with nosludge generated; the old treatment facility producedapproximately 300 gallons of sludge each month.Nevertheless, several additional opportunities for wastereduction may be available to Plant C to further reduce itshazardous waste generation. This section describes theseopportunities.

Plant C can reduce rinse water usage, as well as reducethe quantity of hazardous chemicals entering the wastestream, by converting several of its double tank rinsesystems into two-stage, closed circuit counter-current rinsesystems. By reducing water usage and quantity of chemicalwastes, the load on the treatment system will be reducedand the longevity of the ion exchange resin can be increased.The plant currently uses four double tank rinse systems(tanks 5 and 6, tanks 15 and 16, tanks 20 and 2l, and tanks30 and 31; see Figure Cl). Each tank, however, is plumbedseparately. If the two tanks associated with each of the fourrinse systems were plumbed in series as counter-currentrinse systems, the plant could significantly reduce its rinsewater use. Figure C2 illustrates the set-up for a two stagecounter-current rinse system.

Material SubstitutionPlant C may be able to reduce the volume of spent

process chemicals and cleaning solutions containerized foroff-site disposal by substituting materials. Two materialsthat Plant C handles as hazardous waste are spent reflow oiland spent nitric acid. Several reflow oil products areavailable that, when spent, either can be returned to thesupplier for recycling or can be treated by the facility priorto discharge to the Publicly Owned Treatment Works.Plant C could eliminate a hazardous waste stream byreplacing its presentreflow oil with a recyclable or treatablereflow oil.

Plant C did not provide data on the flow rate used foreach rinse tank. Therefore, calculations on actual water usesavings cannot be presented. However, the followingexample illustrates how acounter-current rinse system canreduce water use compared with the present rinse systemused at the plant. A facility operates a two stage rinsesystem with: (1) each tank having a separate water inflowline; (2) a water flow rate of 10 gallons per minute; and (3)the rinse water for the system turned on a total of 120minutes per day. The total water usage for this systemwould be 2,400 gallons per day. The following equationcan be used to illustrate how a two stage counter-currentsystem could reduce rinse water usage at the facility:

Q= [(Cp/Cr)l/n + l/n]D

Q= rinse tank flow rate

Nitric acid waste, which is generated from equipmentcleanout, can also be eliminated by using an alternativecleaning solution. One chemical supplier offers anelectroplating rack cleaning solution that can be regenerated.The metal stripped off of racks during the cleaning processcan be plated out in a tank equipped with a cathode and ananode. In this method, metal stripped from the racks isplated onto the cathode and forms a metallic sludge thatsettles to the bottom of the cleaning tank. Once the solutionbecomes spent, it can be treated in the plant’s industrialtreatment system instead of being containerized for off-sitedisposal. Plant C should consult with chemical suppliersto identify alternative materials that can be recycled ortreated and that will meet its specific operating requirement.

D= drag-out rate

Cp = chemical concentration on processsolution

Cr = allowable chemical concentration inrinse solution

n = number of rinse tanks in series

Several assumptions must be made to use this equation.These are as follows:

l The concentration of chemicals in the rinsesolution cannot exceed l/l000 of theconcentration of chemicals in the process bath.This value is a common parameter used in theelectroplating industry for rinse watercontaminant concentration.

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The drag-out rate of chemicals used formanufacturing printed circuit boards isapproximately 15 ml/ft2 of board. This value isa standard approximation used for estimatingdrag-out created by a printed circuit board.

An average workpiece rack holds approximately2.5 ft3 of boards (example: 30 4-inch by 3-inchboards).

The drag-out rate for each workpiece rack is:

15 ml x 2.5 ft3 = 37.5 ml.

Converted to gallons, drag-out equals 0.01 gallon.

By substituting the values into the equation:

[(1000)1/2 + l/2] 0.01 gallons/minute = 0.32 gallon/minute.

Therefore, if the facility converted its existing rinsesystem into a two-stage closed circuit counter-current rinsesystem, it could reduce the flow rate from 10 gallons perminute through each tank to 0.32 gallon per minute throughboth tanks. This would in theory reduce the daily waterusage from 2,400 gallons to 38 gallons and wouldsignificantly reduce the quantity of hazardous chemicalsentering the shop’s treatment system. The actual volume ofrinse water reduction that can be achieved by Plant Cdepends on the drag-out rate from the plant’s process bathsand the rinse system parameters for the four double rinsetank systems.

DRAG-OUT LOSS REDUCTIONDiscussions with Plant C personnel indicated that

little attention is placed on drag-out reduction. The plantmay be able to generate less spent ion-exchange resin byusing drag-out reduction technologies. Reductions indrag-out loss should also have a direct impact on waterusage. Since water flow through the rinse systems arecontrolled by pH/conductivity controls, drag-out reductionwill decrease the frequency of rinse water flow through therinse tanks. Plant C may be able to reduce drag-out byinstituting operational modifications and training personnelin drag-out reduction techniques. Drag-out reductiontechniques include slowing workpiece rack withdrawalrates and increasing drainage time prior to rinsing. Otherdrag-out reduction methods include operating process bathsat the lowest allowable concentration and using heatedprocess baths when possible.

The faster an item is removed from the process bath,the thicker the film on the workpiece surface and thegreater the drag-out volume will be. The effect is sosignificant that most of the time allowed for withdrawaland drainage of a rack should be used for withdrawal only.

Plant C management should emphasize to process lineoperators that workpieces should be withdrawn slowly. Anoptimal removal rate can be determined by removingloaded workpiece racks, from process baths at differentrates and allowing the racks to drain into a catch basin.Drag-out volume can then be measured volumetrically.

Workpiece drainage also depends on the operator.The time allowed for drainage can be inadequate if theoperator is rushed to remove the workpiece rack from theprocess bath and place it in the rinse tank. However,installation of a bar or rail above the process tank may helpensure that adequate drainage time is provided prior torinsing. Other printed circuit board manufacturers haveexpressed concern that increasing workpiece rack removaland drainage time will allow for chemical oxidation on theboard. Plant C should identify the processes that are nothighly susceptible to oxidation and emphasize drag-outminimization techniques to personnel operating thoseprocesses.

EQUIPMENT CLEANOUTPlant C generates approximately 40 gallons of waste

nitric acid every month from equipment cleanout. Plant Cmay be able to reduce the volume of nitric acid generatedby modifying the existing cleaning methods.

One method for reducing the volume of waste nitricacid produced is to setup a workpiece rack cleaning linewith several small tanks of nitric acid. The cleaning line isthen used like a multi-stage rinse system. The first tankcontains the most contaminated nitric acid solution, and thefinal tank in the cleaning line contains the freshest nitricacid. When the first tank no longer performs adequateinitial cleaning, it is containerized for disposal (or used asinitial cleaning solution for tank cleanout). Then thesecond tank in the cleaning line becomes the first. Theempty tank is then filled with fresh nitric acid and itbecomes the last tank in the cleaning line.

The use of a multi-stage rinse system can providesignificant reductions in waste cleaning solutiongeneration.One printed circuit board manufacturing plant uses a five-stage multiple tank cleaning line and only generatesapproximately 15 gallons of waste nitric acid each 6months.

RINSE WATER RECYCLINGPlant C may be able torecycle its rinse water by further

treating effluent from the industrial waste treatment plant.This additional treatment may only require activated carbontreatment to remove trace organics from the water. Thisrecycled water would contain less natural contaminants,such as phosphates and carbonates, than the tap water thatis presently used. Since these natural contaminants

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Path of Makeup Water

Figure C-2. Multiple Closed Circuit Counterflow Rinse System

contribute to ion-exchange resin use because they areremoved during treatment, recycling of rinse waters canreduce spent resin generation and significantly reducedwater usage and sewer discharge fees.

Feasibility Analysis PhaseAfter discussions with Plant C personnel, some of the

options discussed in the previous section were selected forinvestigation of their technical and economic feasibility.The economic analysis was based on the raw material andwaste disposal costs provided by the facility personnel andon economic and technical information provided byequipment manufacturers. The measures evaluated in thissection include: material substitution, rinse water reduction,drag-out loss reduction, equipment cleanout reduction andrinse water recycling.

MATERIAL SUBSTITUTIONThe benefits associated with using recyclable and/or

treatable process chemistries will depend on the costs ofsubstitute materials compared with the costs of materialspresently used. Also, additional process bath maintenancerequirements and treatment costs need to be identified.These costs will depend on the type of substitute materialchosen by Plant C.

Savings will include reduced waste disposal costs andmaterial usage costs if the substitute material can berecycled onsite. Plant C generates approximately 250gallons of waste reflow oil and 500 gallons of waste nitricacid annually. Since waste disposal costs for the wastereflow oil and waste nitric acid are both $100 per 55-gallondrum, which is the average cost for disposing of variousliquid hazardous wastes according to circuit boardmanufacturers, waste disposal cost savings would beapproximately $500 per year for spent reflow oil disposaland $1,000 per year for nitric acid waste. Actual savingsassociated with using recyclable reflow oil and nitric acidwill depend on the difference in cost of the substitutematerials.

RINSE WATER REDUCTIONThe costs associated with converting the plant’s four

double tank rinse systems into two stage counter-currentrinse systems would be minimal. Since the pairs of tanksare already next to each other, the only modificationsnecessary would be to re-plumb each rinse system. Thiscould be done by Plant C personnel for less than a fewhundred dollars. Savings would include reduced water useand sewer fees and reduced ion exchange resin purchases.Since rinse water flow rates, drag-out rates, and rinse

71

system operating parameters were not available, we couldnot calculate estimates on savings in water use, sewer fees,and ion exchange resin purchases.

DRAG-OUT LOSS REDUCTIONThe use of a bar rail above each process tank for

hanging workpiece racks will allow for greater drainagetime before rinsing. This could be installed by Plant C’spersonnel for a few hundred dollars if constructed of 1 inchPVC piping. Other drag-out reduction techniques, such asslowing workpiece rack removal rates and operating processbaths at the lowest possible concentration, can also beimplemented for little cost. Developing a training programand emphasizing drag-out minimization will require timefrom management and operations personnel. Sinceinformation on drag-out rates and workpiece rack removaland drainage times were not available from Plant C, savingsassociated with drag-out minimization cannot be quantifiedprior to implementation.

EQUIPMENT CLEANOUT REDUCTIONPlant C can reduce waste nitric acid generation by

using a multiple tank cleaning line. The costs associatedwith setting up such a system include the cost of additionaltanks and the installation labor costs. The costs for settingup a cascade cleaning line would be approximately $350per tank. Labor costs of $55 an hour for 4 hours would be$220.

The savings associated with a multiple tank platingrack cleaning line include reduced costs for nitric acidpurchases and waste acid handling. Plant C now generatesapproximately 480 gallons of waste nitric acid annually.The consultants visited one plant that used five 30-gallontanks as a multiple stagecleaning line. That plant generates30-gallons of waste nitric acid each year. If Plant C couldreduce its waste nitric acid generation down to 30 gallonsper year, it would achieve an annual savings ofapproximately $1,400 in nitric acid purchases and $800 inwaste disposal costs. This assumes that nitric acid costs$3.10 per gallon and waste disposal costs are $100 per 55-gallon drum.

RINSE WATER RECYCLINGConsiderable capital investment may be needed to

recycle wastewater for reuse in production. The costsassociated with recycling treated wastewater effluent willdepend on the level of additional treatment necessary toreturn the effluent back into the production processes.Other plants that are considering rinse water recyclinghave indicated that their primary concern is to removeorganics from the treated effluent before reusing the water.An activated carbon system to treat the effluent can be usedto remove organics from the water. Waste treatment

effluent data for the plant were not available from Plant C.Therefore, specific treatment requirements for recyclingtreated effluent could not be identified. Plant C shouldinvestigate the potential for recycling rinse water bycharacterizing its rinse water effluent, determining thewater quality needs for reusing treated effluent, andidentifying potential technologies that can be used to treatthe effluent for reuse.

The primary savings associated with recycling rinsewater are lower water purchase and sewer discharge fees.Plant C generates approximately 3,000 gallons ofwastewater each day. Assuming that 90 percent of thewater can be recycled, Plant C could reuse approximately2,700 gallons of water each day. If water and sewer fees areboth $0.5 per 750 gallons, Plant C could save approximately$75 each month in water and sewer costs, assuming a 20-day work month.

SUMMARYThe audit of Plant C was performed to identify

opportunities for waste reduction. The following hazardouswastes are generated by Plant C each month:

Spent Ion Exchange Resin - Approximately100 gallons

Copper Sulfate Crystals- Undetermined

Nitric Acid Waste - Approximately 40 gallons

Reflow Oil- Approximately 20 gallons

The audit provided information that was used to identifyseveral waste reduction techniques that may be feasible forPlant C to implement. The following waste reductionopportunities were identified:

Use alternative reflow oil and electroplatingrack stripper materials that can be recycled ortreated when they are spent instead ofchemistries that currently are containerized foroff-site disposal.

Aggressively pursue drag-out reduction bydeveloping operational procedures and trainingpersonnel to slowly remove workpiece racksand increase drainage time prior to rinsing.

Convert the four double tank rinse systems intotwo-stage counter-current rinse systems.

Install a multiple stage electroplating rackcleaning line to reduce nitric acid wastegeneration.

Recycle treated effluent for reuse in theproduction process.

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APPENDIX BWHERE TO GET HELP

FURTHER INFORMATION ON POLLUTION PREVENTION

Additional information on source reduction, reuse andrecycling approaches to pollution prevention is availablein EPA reports listed in this section, and through state pro-grams (listed below) that offer technical and/or financialassistance in the areas of pollution prevention and treat-ment.

In addition, waste exchanges have been established insome areas of the US. to put waste generators in contactwith potential users of the waste. Four waste exchanges arelisted below. Finally, EPA’s regional offices are listed.

EPA REPORTS ON WASTEMINIMIZATIONU.S. Environmental Protection Agency. “Waste

Minimization Audit Report: Case Studies of Corrosiveand Heavy Metal Waste Minimization Audit at aSpecialty Steel Manufacturing Complex.” ExecutiveSummary.*

U.S. Environmental Protection Agency. “WasteMinimization Audit Report: Case Studies ofMinimization of Solvent Waste for Parts Cleaning andfrom Electronic Capacitor Manufacturing Operation.”Executive Summary.*

U.S. Environmental Protection Agency. “WasteMinimization Audit Report: Case Studies ofMinimization of Cyanide Wastes from ElectroplatingOperations.” Executive Summary.*

U.S. Environmental Protection Agency. Report toCongress: Waste Minimization, Vols. I and II. EPA/530-SW-86-033 and -034 (Washington, D.C.: U.S.EPA, 1986).**

U.S. Environmental Protection Agency. WasteMinimization - Issues and Options, Vols. I-III EPA/530-SW-86-041 through -043. (Washington, D.C.:U.S. EPA, 1986).*** Executive Summary available from EPA,

WMDDRD, RREL, 26 West Martin Luther Ring Drive,Cincinnati, OH, 45268; full report available from theNational Technical Information Service (NTIS), U.S.Department of Commerce, Springfield, VA 22161.

** Available from the National Technical InformationService as a five-volume set, NTIS No. PB-87-114-328.

WASTE REDUCTION TECHNICAL/FINANCIAL ASSISTANCE PROGRAMS

The EPA’s Office of Solid Waste and Emergency Re-sponse has set up a telephone call-in service to answerquestions regarding RCRA and Superfund (CERCLA):

(800) 242-9346 (outside the District of Columbia)

(202) 382-3000 (in the District of Columbia)The following states have programs that offer technicaland/or financial assistance in the areas of waste minimiza-tion and treatment.AlabamaHazardous Material Management and Resources Recov-ery ProgramUniversity of AlabamaP.O. Box 6373Tuscaloosa, AL 35487-6373(205) 348-8401AlaskaAlaska Health ProjectWaste Reduction Assistance Program431 West Seventh Avenue, Suite 101Anchorage, AK 99501(907) 276-2864ArkansasArkansas Industrial Development CommissionOne State Capitol MallLittle Rock, AR 72201(501) 371-1370CaliforniaAlternative Technology SectionToxic Substances Control DivisionCalifornia State Department of Health Service714/744 P streetSacramento, CA 94234-7320(916) 324-1807ConnecticutConnecticut Hazardous Waste Management ServiceSuite 360900 Asylum AvenueHartford, CT 06105(203) 244-2007

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Connecticut Department of Economic Development210 Washington StreetHartford, CT 06106(203) 566-7196GeorgiaHazardous Waste Technical Assistance ProgramGeorgia Institute of TechnologyGeorgia Technical Research InstituteEnvironmental Health and Safety DivisionO’Keefe Building, Room 027Atlanta, GA 30332(404) 894-3806Environmental Protection DivisionGeorgia Department of Natural ResourcesFloyd Towers East, Suite 1154205 Butler StreetAtlanta, GA 30334(404) 656-2833IllinoisHazardous Waste Research and Information CenterIllinois Department of Energy of Energy and NaturalResources1808 Woodfield DriveSavoy, IL 61874(217) 333-8940Illinois Waste Elimination Research CenterPritzker Department of Environmental EngineeringAlumni Building, Room 102Illinois Institute of Technology3200 South Federal StreetChicago, IL 60616(313) 567-3535IndianaEnvironmental Management and Education ProgramYoung Graduate House, Room 120Purdue UniversityWest Lafayette, IN 47907(317) 494-5036Indiana Department of Environmental ManagementOffice of Technical AssistanceP.O. Box 6015105 South Meridian StreetIndianapolis, IN 46206-6015(317) 232-8172IowaCenter for Industrial Research and Service205 Engineering AnnexIowa State UniversityAmes, IA 50011(515) 294-3420

Iowa Department of Natural ResourcesAir Quality and Solid Waste Protection BureauWallace State Office Building900 East Grand AvenueDes Moines, IA 50319-0034(515) 281-8690KansasBureau of Waste ManagementDepartment of Health and EnvironmentForbes Field, Building 730Topeka, KS 66620(913) 269-1607KentuckyDivision of Waste ManagementNatural Resources and EnvironmentalProtection Cabinet18 Reilly RoadFrankfort, KY 40601(502) 564-6716LouisianaDepartment of Environmental QualityOffice of Solid and Hazardous WasteP.O. Box 44307Baton Rouge, LA 70804(504) 342-1354MarylandMaryland Hazardous Waste Facilities Siting Board60 West Street, Suite 200 AAnnapolis, MD 21401(301) 974-3432Maryland Environmental Service2020 Industrial DriveAnnapolis, MD 21401(301) 269-3291(800) 492-9188 (in Maryland)MassachusettsOffice of Safe Waste ManagementDepartment of Environmental Management100 Cambridge Street, Room 1094Boston, MA 02202(617) 727-3260Source Reduction ProgramMassachusetts Department of Environmental Quality En-gineering1 Winter StreetBoston, MA 02108(617) 292-5982

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MichiganResource Recovery SectionDepartment of Natural ResourcesP.O. Box 30028Lansing, MI 48909(517) 373-0540MinnesotaMinnesota Pollution Control AgencySolid and Hazardous Waste Division520 Lafayette RoadSt. Paul, MN 55155(612) 296-6300Minnesota Technical Assistance ProgramW-140 Boynton Health ServiceUniversity of MinnesotaMinneapolis, MN 55455(612) 625-9677(800) 247-0015 (in Minnesota)Minnesota Waste Management Board123 Thorson Center7323 Fifty-Eighth Avenue NorthCrystal, MN 55428(612) 536-0816MissouriState Environmental Improvement and EnergyResources AgencyP.O. Box 744Jefferson City, MO 65102(314) 751-4919New JerseyNew Jersey Hazardous Waste Facilities Siting

CommissionRoom 61428 West State StreetTrenton, NJ 08608(609) 292-1459(609) 292- 1026Hazardous Waste Advisement ProgramBureau of Regulation and ClassificationNew Jersey Department of Environmental

Protection401 East State StreetTrenton, NJ 08625Risk Reduction UnitOffice of Science and ResearchNew Jersey Department of Environmental Protection401 East State StreetTrenton, NJ 08625

New YorkNew York State Environmental Facilities

Corporation50 Wolf RoadAlbany, NY 12205(518) 457-3273North CarolinaPollution Prevention Pays ProgramDepartment of Natural Resources andCommunity DevelopmentP.O. Box 27687512 North Salisbury StreetRaleigh, NC 27611(919) 733-7015Governor’s Waste Management Board325 North Salisbury StreetRaleigh, NC 27611(919) 733-9020Technical Assistance UnitSolid and Hazardous Waste Management BranchNorth Carolina Department of Human ResourcesP.O. Box 2091306 North Wilmington StreetRaleigh, NC 27602(919) 733-2178OhioDivision of Solid and Hazardous Waste ManagementOhio Environmental Protection AgencyP.O. Box 10491800 WaterMark DriveColumbus, OH 43266-1049(614) 481-7200Ohio Technology Transfer OrganizationSuite 20065 East State StreetColumbus, OH 43266-0330(614) 466-4286OklahomaIndustrial Waste Elimination ProgramOklahoma State Department of HealthP.O. Box 53551Oklahoma City, OK 73152(405) 271-7353OregonOregon Hazardous Waste Reduction ProgramDepartment of Environmental Quality811 Southwest Sixth AvenuePortland, OR 97204(503) 229-5913

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PennsylvaniaPennsylvania Technical Assistance Program501 F. Orvis Keller BuildingUniversity Park, PA 16802(8 14) 865-0427Center of Hazardous Material Research320 William Pitt WayPittsburgh, PA 15238(4 12) 826-5320Bureau of Waste ManagementPennsylvania Department ofEnvironmental ResourcesP.O. Box 2063Fulton Building3rd and Locust StreetsHarrisburg, PA 17120(717) 787-6239Rhode IslandOcean State Cleanup and Recycling ProgramRhode Island Department of Environmental Management9 Hayes StreetProvidence, RI 02908-5003(401) 277-3434(800) 253-2674 (in Rhode Island)Center for Environmental StudiesBrown UniversityP.O. Box 1943135 Angell StreetProvidence, RI 02912(401) 863-3449TennesseeCenter for Industrial Services102 Alumni HallUniversity of TennesseeKnoxville, TN 37996(615) 974-2456VirginiaOffice of Policy and PlanningVirginia Department of Waste Management11th Floor, Monroe Building101 North 14th StreetRichmond, VA 23219(804) 225-2667WashingtonHazardous Waste SectionMail stop PV-11Washington Department of EcologyOlympia, WA 98504-8711(206) 459-6322

WisconsinBureau of Solid Waste ManagementWisconsin Department of Natural ResourcesP.O. Box 7921101 South Webster StreetMadison, WI 53707(608)267-3763WyomingSolid Waste Management ProgramWyoming Department of Environmental QualityHerchler Building, 4th Floor, West Wing122 West 25th StreetCheyenne, WY 82002(307) 777-7752

WASTE EXCHANGESNortheast Industrial Exchange90 Presidential Plaza, Syracuse, NY 13202(3 15) 422-6572Southern Waste Information ExchangeP.O. Box 6487, Tallahassee, FL, 32313(904) 644-5516California Waste ExchangeDepartment of Health ServicesToxic Substances Control DivisionAlternative Technology & Policy Development Section714 P streetSacramento, CA 95814(916) 324-1807

U.S. EPA REGIONAL OFFICES

Region 1 (VT, NH, ME, MA, CT, RI)John F. Kennedy Federal BuildingBoston, MA 02203(617) 565-3715Region 2 (NY, NJ)26 Federal PlazaNew York, NY 10278(212) 264-2525Region 3 (PA, DE, MD, WV, VA)841 Chestnut StreetPhiladelphia, PA 19107(215) 597-9800Region 4 (KY, TN, NC, SC, GA, FL, AL, MS)345 Courtland Street, NEAtlanta, GA 30365(404) 347-4727

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Region 5 (WI, MN, MI, IL, IN, OH)230 South Dearborn StreetChicago, IL 60604(312) 353-2000Region 6 (NM, OK, AR, LA, TX)1445 Ross AvenueDallas, TX 75202(214) 655-6444Region 7 (NE, KS, MO, IA)756 Minnesota AvenueKansas City, KS 66101(9 13) 236-2800Region 8 (MT, ND, SD, WY, UT, CO)999 18th StreetDenver, CO 80202-2405(303) 293-1603

Region 9 (CA, NV, AZ, HI)215 Fremont StreetSan Francisco, CA 94105(415) 974-8071Region 10 (AK, WA, OR, ID)1200 Sixth AvenueSeattle, WA 98101(206) 442-5810

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*U.S. GOVERNMENT PRINTING OFFICE: 1995 650-006/22001