Industry Specific Practices

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An asterisk (*) next to a listed practice indicates that industry reviewers considered it a particularly good suggestion based on effectiveness and effort/expense required to implement.

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Metal Finishing & Printed Circuit Board Manufacturing

Good Housekeeping & Operating Practices

• * Inspect integrity of plating rack coating frequently (pitting in plastic coated racks can cross-contaminate chemistry)
• Clean racks frequently to avoid having to do excessive chemical stripping
• Evenly distribute workpiece load on process lines (allows time for proper dragout, prevents surge of demand on rinse and treatment processes)
• Routinely analyze cleaning bath chemistry and add make-up chemicals to renew bath
• Operate fresh baths at lower concentrations than used baths

Materials Substitution

• Use re-usable bath filters
• Use plastic coated plating racks that do not need stripping
• Use deionized or distilled water for makeup and rinses instead of tap water to reduce water volumes and improve quality

Materials Recovery

• * Reuse compatible process baths (e.g. alkaline cleaners/etches, sulfuric solutions) as feedstock chemicals for pH adjustment and precipitation treatment of wastes
• Purify plating baths for reuse by carbon treatment, electrowinning, electrodialysis, filtration, "dummying" bath, or use of a porous pot
• Regenerate process bath chemicals, rinse water solutions, and dragouts using chemical recovery technologies (e.g. electrowinning, electrodialysis, reverse osmosis, and ion exchange)
• Recover metals from spent plating baths, dragout rinses, or ion exchange acid reagent streams by electrowinning
• Use in-line metal recovery techniques on segregated rinse streams (e.g. using liquid membranes to recover copper from etching solutions, electrowinning, electrodialysis, evaporative recovery, and ion exchange)
• Recycle batch treatment sludges containing metals offsite
• Convert to dry floor (may already be required by local regulatory agency)

Process Modifications

• Do in-house laboratory analysis to determine optimum bath replacement schedule
• Use automated chemical replacement through on-line analyzers and chemical flow meters to optimize bath concentrations
• Use spray nozzles to improve the effectiveness of aqueous cleaners
• * Install bath filters to remove particulates and trace contaminant organics

Rinsewater and Dragout Reduction

Good Housekeeping & Operating Practices

• * Lengthen dragout time to allow more chemical into drip back to process tank
• Reduce pockets on parts to minimize chances of chemical pooling, and/or orient parts for best drainage from pockets
• * Place parts on racks that
  1. have the largest draining surface as near to vertical as possible,
  2. have the longer dimension of the part horizontal, and
  3. have the lower edge slightly tilted so that runoff is from a corner
• * Use drainage boards and/or drip guards to minimize spillage between tanks and capture dragout
• * Install drip bars or hoists above process tanks to hang workpiece racks for hands-free drainage (helps ensure adequate drainage of heavy workpieces)

Materials Recovery

• Use "reactive rinsing" methods (reuse mild acid rinsewater as influent to rinse following alkaline cleaning bath or mild alkaline rinsewater as influent to rinse following acid cleaning bath)
• Use evaporation or reverse osmosis to concentrate dragout for reuse
• * Use multi-stage countercurrent rinses
• * Use static and/or dedicated dragout tanks after process baths to capture dragout for bath replenishment or batch treatment (reduces water volume, discharge, sludge volume)

Process Modifications

• * Agitate rinse bath or parts to promote better and more rapid rinsing (e.g. forced air or water, mechanical or operator agitation)
• Mechanize dragout to ensure proper dragout time
• Minimize plating bath concentration to reduce the degree of subsequent rinsing required
• Reduce prep bath concentrations and increase dwell times
• Increase bath temperature to
  1. reduce dragout due to solution viscosity,
  2. allow for reduced bath concentration, and
  3. provide evaporation to allow for spray rinsing over tanks
• Increase component solubility by heating rinse water, especially through use of "waste" energy (e.g. heat from heated bath, see below)
• Circulate static rinse solutions through plating tank heat exchangers to conserve energy and allow evaporation of rinse solution
• Replace dip and countercurrent rinses with "on-demand" spray systems when part structure allows
• * Use conductivity sensors to control rinsewater cleanliness and reduce wastewater volume and water usage
• * Use spray or fog rinses (especially with heated baths) or air knives above process tanks and/or rinses to reduce rinsewater volume and recover dragout by draining it back into the process tank
• Install flow restrictors and control valves to improve rinsing efficiency and minimize wastewater volume generated by rinsing operations
• Use wetting agents in process baths to reduce surface tension and dragout

Solvent Use-related Practices

Also see:
- General Solvent & Cleaning/Degreasing

• * Cover cleaning tanks when not in use
• Remove sludge bottom buildup from soak tank when contaminants reach 10% of solvent quantity
• Use multiple stage/countercurrent cleaning lines for workpiece racks to minimize waste cleaning solutions (similar to multistage rinse systems, i.e. use dirty solvent for initial cleaning and clean solvent for final cleaning)
• Recycle spent solvent with onsite distillation unit if quantities are sufficient to make it cost-effective
• * Use alkaline substitutes for solvents
• Install ultrasonic units in cleaning tanks
• * Reduce or eliminate solvents for drying parts by
  • Using forced air dryers rather than solvents to evaporate water from parts
  • Using water soluble rinse aids (small percentage in static rinse) to reduce water adhesion and subsequent drying time

Improved Treatment/Minimizing Treatment Wastes

Take a look at the Vendor Directory for companies which sell process bath recovery and wastewater treatment equipment

• * Reduce water use to allow for increased dwell time in treatment unit (reduces chemical consumption and improves effectiveness)
• Use sludge dewatering equipment to reduce sludge volume (e.g. filter press, dryer), making it more economical to recycle
• Segregate chelated waste streams and handle separately to prevent interference with metal precipitation during waste treatment
• Eliminate or reduce chelations to simplify metals precipitation in wastewater treatment system
• Avoid treatment technologies that use standard precipitation/clarification methods which generate heavy metal sludges (do recycle any metal-laden sludges generated)
• Use treatment chemicals which reduce sludge volume (e.g. caustic soda, sodium hydroxide, and/or magnesium hydroxide instead of lime)

Note: Magnesium hydroxide may increase sewage discharge

Metal Finishing-specific Practices

Good Housekeeping & Operating Practices

• * Eliminate the need for protective oils and subsequent solvent degreasing by having suppliers/customers:
  • Provide "just-in-time" delivery of parts
  • Use corrosion inhibiting protective films, provided they can be readily removed (e.g. organic peel coatings like polyethylene shrink-wrapping, dilute oils, organic liquids, alkaline dips)
• Minimize the delay between parts cleaning and plating
• Encourage customer specifications to allow use of technologies which reduce waste generation:
  • Do not specify solvent uses
  • Approve cadmium substitutes
  • Trivalent instead of hexavalent chromium for decorative chromium plating
• Substitute nitric or hydrochloric acids or alkaline activators for cyanide in prep baths
• Substitute non- or low-cyanide zinc plating baths for zinc cyanide (e.g. zinc chloride, alkaline zinc)

Materials Substitution

• Eliminate hexavalent chromium in prep baths
• Replace hexavalent chromium with trivalent chromium for decorative chrome plating baths
• Replace toxic cadmium plating with zinc, zinc alloys, or nickel alloys

Materials Recovery

• Use electrodialysis to recover chromium from hard chromium plating baths and rinsewaters
• Reuse nitric from process solutions for stripping electroless nickel tank or as makeup for nitric rack stripper

Process Modifications

• * Install skimmers in cleaning tanks to remove floating contaminants
• Regularly strip nickel from electroless nickel tank and components to prevent continuous deposition of nickel on the tank walls (or use passivation on stainless components)

Printed Circuit Board Manufacturing-specific Practices

Materials Substitution

• Use a fully aqueous resist instead of a solvent resist (very effective)
• Convert to tin plating and hot air leveling rather than tin/lead plating and conventional reflow
• Use water-soluble binders to minimize abrasive waste
• Use thinner copper foil to clad the laminated board

Materials Recovery

• Recycle spent photoresist stripper wastes:
  • Use filters with tank or conveyorized equipment, or
  • Decant off stripper solution to separate it from the polymer residue that forms as the solution is used
• Recover copper sulfate crystals from etching/stripping processes to extend bath life by cooling/crystallization, electrowinning, or precipitation
• Reuse recovered copper sulfate crystals in copper electroplating bath (may be contamination concern) or recycle offsite - (Possible sale as raw material if good purity)
• Recycle photoresist stripper before it enters wastewater treatment stream
• Reuse nitric from stripping electroless copper tank as make-up for rack stripper

Process Modifications

• Use a combined sensitization and activation solution to eliminate an extra rinsing step
• Use pattern instead of panel plating to reduce the amount of non-circuit copper which must be etched away
• Buy efficient etch machine to reduce copper in rinsewater
• Routinely clean/strip electroless copper tank to prevent continuous deposition of copper on tank walls
• Use computerized/automated control systems for board handling and process bath monitoring
• Use additive rather than subtractive etching methods
• Encourage customer specifications to allow use of technologies which reduce waste generation
  • Surface instead of through-hole insertion mounting in printed circuit board packaging
  • Differential plating rather than the conventional electroless plating process

Sources (Appendix A): S4, S5, S6, S11, S13, S22

A metal finisher and graphic anodizer made several modifications which have saved money, eased compliance, improved quality, and increased production capacity. See their Case Study.

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Non-Agricultural Pesticide Application
(Landscape, Structural & Household/Garden)

Good Housekeeping & Operating Practices

• Demand product stewardship from manufacturers (e.g. select those that accept back empty product containers)
• Triple-rinse containers and apply rinsewater on site just treated
• Purchase pesticides in packaging that is reusable, recyclable, or biodegradable (e.g. dissolvable packets)
• Purchases pesticides in "tilt and pour" containers, which eliminate the need for mixing in or transfer to another container
• Carefully evaluate pest control objectives and strategies using integrated pest management (IPM) strategies (see below under Material Substitution)
• Use monitoring devices to determine pest levels and when it is necessary to spray
• Routinely check application equipment for leaks
• Only mix what you can use and spray out that day
• Spot-treat pests whenever possible to reduce chemical usage, exposure, and expense
• Monitor the efficiency of application equipment
• Sequence applications to reduce the need for application equipment cleaning
• When possible, use reusable or semi-disposable protective clothing rather than disposable clothing
• Use measures to reduce rinsewater generated from cleaning application equipment (e.g. wiper blades, high pressure nozzles)
• Clean application equipment and vehicles at site where chemicals are applied
• Dedicate application equipment systems to reduce rinsing (especially with herbicides)

Materials Recovery

• Sweep floor to collect spills of granular products only and apply to appropriate site

Material Substitution/Process Modifications

• Use "cold" or "heat" treatment for structural pest control
• Use aqueous cleaners in place of organic solvents when cleaning application equipment
• Use end-of-hose "proportioners" to meter appropriate amount of pesticide
• Reduce the use of pesticides by using appropriate integrated pest management (IPM) methods:
  • Physical Controls: Barriers, traps, cleanliness, caulking, handpicking, and environmental manipulation (i.e. environmental controls such as climate regulation and limiting availability of pest habitat)
  • Biological Controls: Predatory and parasitoid insects and bacterial insecticides (e.g. green lacewings for aphids, Encarsia partenopea wasps for whitefly, Bacillus thuringiensis israelensis for mosquitoes)
  • Cultural Controls: Planting disease/pest-resistant plant varieties
  • Least-toxic Chemical Controls: Insecticidal soaps, horticultural oils, desiccating dusts (e.g. diatomaceous earth), insect growth regulators (interrupt reproductive cycle; e.g. methoprene for fleas), pyrethrin-based products, etc. (Also, select the most pest-specific chemical available; choose biodegradable rather than persistent organochlorine insecticides; and choose water-based formulations in place of oil/solvent-based products.)

Sources (Appendix A): S6, S18

Integrated Pest Management (IPM) - IPM is a pest control approach which utilizes monitoring to determine if and when treatments are needed. IPM then employs a variety of non-chemical (physical, biological, and cultural) tactics to keep pest nnumbers low enough to prevent intolerable damage or annoyance. Lease-toxic chemical controls are used as a last resort.

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Painting, Coating, & Stripping

Also see:
- General Solvent & Cleaning/Degreasing

Painting & Coating Practices

Good Housekeeping & Operating Practices

• Ensure adequate training of personnel
• * Store paints and thinners in tightly-closed containers
• Separate paint brushes, rollers, and cans from waste paint to ease waste paint collection by vacuum truck
• Post mixing instructions for coatings to stay at or below allowable VOC (volatile organic compound) content – do not add additional solvents and use measuring sticks or scales for accuracy
• * Make sure parts are clean, dry, and rust-free before painting
• Avoid adding excess thinner
• Purchase bulk quantities of commonly used coating formulations
• Reduce the need for cleaning by scheduling similar operations back-to-back and producing large batches of similarly-produced items instead of small batches of custom items
• Keep the curtain head clean at all times on curtain (flow) coating machines
• Segregate water- from solvent-based paint spray units
• * Clean paint application equipment properly:
  • Clean equipment immediately after each use before paint can harden.
  • For hand-held spray units, use a solvent rinse with occasional blow-back (cover the fluid tip and operate the trigger)
  • Direct clean-up solvents under minimal air pressure into containers to prevent evaporation
  • Soak air spray guns in closed containers and avoid the use of volatile organic compounds for clean-up
  • Rollers on roller coating machines should be cleaned regularly to remove dried paint and inspected for swelling material
• * Use the following good manual spraying technique:
  • Overlap the spray pattern by 50 percent
  • Maintain a 6 to 8 inch distance between the gun and the workpiece
  • Maintain a constant and moderate gun speed (about 250 feet/minute)
  • Trigger the gun at the beginning and end of each pass
• When using air spray guns:
  • Reduce cross drafts when applying paint
  • Reduce overspray by adjusting nozzle and avoiding excessive air pressures
  • Reduce air pressure at the spray gun nozzle on non High Volume Low Pressure (HVLP) guns
  • Use HVLP spray guns with adequate air supply and proper nozzle tips
• When using spray booths:
  • Make sure filters are installed properly and cover all openings
  • Replace filters regularly
• When using washwater booths:
  • Make sure the water curtain is continuous
  • Remove the booth and repair water lines if dry spots appear
  • Routinely check water for the proper chemical and additive mixture

Material Substitution

• Substitute high-solids formulations for solvent-based formulations
• Use paints with the lowest possible volatile organic compound (VOC) content
• * Avoid using paints with heavy metal pigments
• Where practicable, use powder coatings
• * Substitute water- for solvent-based paints whenever possible

Materials Recovery

• Use an industrial laundry service for rags (Keep rags in a covered container and do not saturate. Try to find a service that recycles its wastewater.)
• Encourage use of leftover paint to avoid disposal:
  • Offer customers discounts on leftover paints to encourage their use
  • Give unused paint to community groups (e.g. drama groups, studio arts, schools, churches, graffiti abatement programs)
  • Use a waste exchange program (see Appendix D)
• * Allow paint solids to settle in used solvent and decant liquid solvent for reuse (e.g. reuse as pre-soak for brushes and equipment, reuse spent stripper as rough prestrip on next item)

Process Modification

• Use a high transfer efficiency application methods to reduce the quantity of paint used:
  • High Volume Low Pressure (HVLP) or electrostatic spray units in place of conventional units
  • Use flowcoat, dipcoat, rollercoat, brushcoat, or powder coating methods
• Reduce overspray by using pressurized airless atomized spray guns
• * Install onsite paint mixers to control materials usage
• Install carbon adsorption or spray absorption systems to capture and recover solvents from air after passing through spray booth and oven (expensive)
• Used closed-loop washwater booths (expensive)

Paint Stripping - Alternatives to Solvents

• * Use racks which can be cleaned using caustic soda or hot stripping (thermal oxidation) rather than solvent stripping
• Use aqueous stripping agents such as caustic soda rather than methylene chloride to remove alkyl resins, oil paints, cellulosics, and phenolic/gum varnishes
• Use "cryogenic stripping" and bead blasting on parts with very hard paint
• Use molten salts such as sodium metasilicate, sodium phosphate, sodium bicarbonate, or sodium hydroxide to remove heavy films of epoxy and silicon coatings (expensive)
• Use hot stripping (thermal methods) for objects that cannot be immersed

Sources (Appendix A): S7, S23

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Photoprocessing

Good Housekeeping & Operating Practices

• Use lids or floating covers on all bulk solutions to prevent oxidation and contamination
• * Prolong the potency of oxidizable process baths by reducing exposure to air
• Follow manufacturer’s specifications when mixing chemistries (or use an automatic blender) to ensure proper chemical make-up in process baths
• Use squeegees, air blades, and other devices between process tanks to prevent solution carryover
  • If using squeegees, make sure it is in good condition and is wiping the film or print material tightly across full width
  • If using air blades, make sure the air jet is not obstructed and is continuous in intensity across full width
• Segregate spent processing baths from wastewater stream (i.e. silver-bearing chemistry, rinse water, and other residue)
• Conduct laboratory analysis of silver content in wastewater discharge to ensure recovery equipment is working properly
• Monitor temperature and specific gravity to maintain proper water to chemistry ratio
• Replace chemistry on an as-need basis rather than a set schedule to optimize bath life and image color and reduce wastewater generation:
  • Continuous processing - adjust chemical replenishment rates and wash-water flow rate one at a time, using test strips to check product quality
  • Batch processing - use test strips frequently during processing to check on product quality. Make up only enough chemical solution to complete a reasonable production batch
• Make sure electrolytic silver recovery units operate within the range specified by the manufacturer
• Test the discharge water from a metal replacement canister daily using a silver test strip

Material Substitution

• Substitute paper that uses less water and/or chemistry

Materials Recovery

• Reuse and/or recycle plastic slide boxes, waste film and negatives, 35mm film canisters, cardboard cores, metal 35mm film cassettes, 35mm and 120mm film spools, skids, office paper, and cardboard,
• * Install an ion exchange water recycling unit
• Regenerate chemistry whenever feasible (e.g. bleach fix, developers)
• Recover silver by:
  • Installing an electrolytic silver recovery unit (stand alone or in-line) and/or metallic replacement cartridges
  • Contracting with a silver recovery/hauler service

Process Modification

• * For black and white processing, use a stop bath and hypo-cleaning agents to control processing better, increase fix life, and reduce washwater use
• Purchase new or retrofit equipment to use less rinsewater (e.g. countercurrent rinsing, rinse saver, shorter processing time)
• Purchase equipment with effective squeegee action and timers that turn equipment off automatically when not in use
• Install flow meters
• Install a solenoid valve (on/off toggle switch that senses electrical current) to automatically stop wash flow when not required
• Install a stand-by mode for idle periods to turn off dryer, drive motor, and washwater, and save energy
• Install an automatic blender to eliminate worker exposure to chemistry, reduce labor costs, minimize amount of replenisher needed, and achieve better image quality
• If using silver recovery units, consider plumbing changes that would combine washwater with fixer solutions before entering the units

Sources (Appendix A): S6, S13, S22

A Palo Alto, CA photo lab tested a "regenerative" bleach fix and made several other changes to reduce wastewater discharges and chemistry use. See their Case Study.

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Printing & Allied Industries

Also see:
- Photoprocessing

Good Housekeeping & Operating Practices

• * Train press workers to minimize solvent use
• Minimize cleaning between jobs:
  • Schedule "gang-up" jobs to minimize the number of color changes required
  • If practical, schedule jobs so that they progress from lighter- to darker-colored
• Squeegee excess ink off press to minimize clean up wastes
• Instead of disposable wipes, use shop towels and contract with an industrial laundry service. (Do not saturate towels . Keep them in a covered container. Try to find a laundry service that recycles its wastewater and/or can otherwise properly manage its wastewater.)
• If disposable wipes are used, reduce usage by using dirty ones for the first pass and clean ones for the second pass
• * If possible, keep presses that use soybean, vegetable, or nut oil and are alcohol-free separate from presses using petroleum-based distillates
• Dedicate a press to toxic ink pigments and solvents
• * Fill ink fountains only when necessary to prevent contamination and possible emulsification
• Where appropriate, keep roller blade in good condition and check its angle for most effective cleaning
• Segregate aqueous wastes derived during equipment clean-up from solvent wastes
• Segregate different grades and types of paper in accordance with recycler’s specifications
• * Investigate the use of aqueous cleaners – ask distributors for samples
• * Integrate amount of waste generated per process into a formula which indicates press performance
• Encourage ink distributors to take back unused and spent ink products

Material Substitution

• * When available, substitute citric acid- and aqueous-based cleaners for petroleum-based solvents or those containing aromatics, such as phenol, benzene, toluene, and xylene
• If practicable, convert to UV (ultra violet) -curable inks
• Switch to soy or other vegetable-based inks for multicolor process inks and PMS colors (at least 30 percent of the vehicle should be soy oil)
• Switch from hydrocarbon-based varnish to aqueous-based varnishes
• Convert to alcohol substitutes for press fountain solutions, or reduce amount of alcohol to lowest possible level
• Avoid using chlorinated solvents and toxic pigments or inks containing heavy metals

Materials Recovery

• Recycle or donate waste ink, paper, film, printing plates, negatives, containers, skids (pallets), cardboard, and oil
• Save all unused portions of ink for house colors (offer customer discounts on leftover inks or use on donated jobs)
• * Recycle spent solvent:
  • Use an onsite distillation unit if quantities make it cost-effective
  • Use a solvent sink/parts washer and contract with a service which replaces dirty solvent with fresh on a regular or as-need basis

Process Modification

• Use automated features where cost effective and appropriate:
  • Non-contact electronic systems which detect web breaks
  • Web splicer
  • Blanket cleaner
  • Ink leveler
  • Plate scanner
  • Ink key setting system
• Install a waterless press (cost approximately 18 % '>' a water press)
• Install electronic imaging or laser platemaking to eliminate the need for photoprocessing

Printers can obtain valuable waste reduction compliance assistance from their trade association, Printing Industries of Northern California (PINC). See the Printing Case Study and a Profile of PINC.

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Plate Processing-specific Practices

• * Prolong the potency of oxidizable process baths by reducing exposure to air
• Use floating lids/covers on all bulk solutions to prevent oxidation and contamination
• Store metal plates at recommended conditions
• Monitor plate processor conditions frequently
• Use presensitized plates
• Use nonchromate etchants
• Use a plate processor that has an automatic replenishment system for developer/fixer
• Recover metals from solution bath dumps and waste streams
• Recycle spent plates
• Investigate the use of water-based plate development systems

Sources (Appendix A): S4, S6, S12, S13, S22

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Process Equipment Cleaning

Also see:
- General Solvent & Cleaning/Degreasing

Good Housekeeping & Operating Practices

• Use "procedural scheduling" strategies (see Optimizing Operations and Processes)
• Clean mix tanks immediately after use
• Increase spent rinse settling time
• Maximize dedication of equipment to reduce the need for cleaning
• Keep different cleaning schedules for dedicated and undedicated equipment

Material Substitution

• Re-examine the need for chemical cleaning and substitute:
  • Mechanical methods (see below)
  • Process fluids rather than chemicals or water (filter to remove solids)
  • Water rather than chemicals (e.g. hydroblasting with high velocity water jets)

Materials Recovery

• Recycle spent rinsewater

Process Modification

• Convert from batch to continuous processes where applicable (less labor, material transfer, cleaning)
• Use closed process equipment with an inert atmosphere (prevents drying of materials such as paint, requiring less cleaning)
• Use mechanical cleaning methods rather than solvents or other chemicals
  • Manual wiping or squeegeeing of process vessels (e.g. wire brush, rubber wipers, etc.)
  • "Pigging" process pipelines with plastic or foam pigs (slugs)
• Inhibit fouling deposit formation to reduce the need for frequent cleaning
  • Remove deposit precursors from materials prior to use (filter, use deionized water, etc.)
  • Install corrosion-resistant pipes, vats, and materials
  • Use smooth heat transfer surfaces
  • Increase turbulence and/or reduce film temperature
  • Apply less corrosive and more thermally stable heat transfer fluids
  • Use better design and control of fired heaters
• In closed cooling water systems, inhibit fouling through proper water treatment by using a lower number of concentration cycles in the cooling tower or using make-up water with low total solids content (e.g. deionized water)
• Minimize the amount of cleaning solution or water needed:
  • Use high pressure spray nozzles
  • Use on-stream mechanical cleaning or clean-in-place (CIP) system with staged rinses
  • Filter process fluids used for cleaning and return to make-up solution
  • Control time, temperature, concentration, and turbulence of cleaning solution (less is needed as these conditions increase)
  • Use "flow-over" methods (solution is sprayed and allowed to flow off) rather than "fill-and-empty" methods
  • Use additives (e.g. defoamers, suspending agents, emulsifiers, wetting agents)
  • Use countercurrent rinse sequence
• Minimize the equipment surface exposed to process fluids by
  • Eliminating or reducing undrainable pockets
  • Using cylindrical tanks with height-to-diameter ratios close to one
  • Designing the plant accordingly if new, renovating, or relocating
• Minimize the residue left after a process by:
  • Using non-stick surfaces (e.g. Teflon coated tanks) and/or mechanical or manual wall wipers
  • Providing adequate batch drainage time
  • Rotating agitator after batch dump
  • Maximizing batch size
• De-water spent rinse sludge

Sources (Appendix A): S7, S13, S19

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Semiconductor Manufacturing

Good Housekeeping & Operating Practices

• Minimize the number of different types of solvents used
• Place covers on chemical baths when not in use to reduce vapor emissions
• * Charge short- and long-term waste management costs to the fabrication laboratories and departments responsible for waste generation
• If using a solvent-based cleaner, top off solvent baths rather than using the "fill and empty" method
• Use repeated small volume rinsing rather than single large volume rinsing
• Segregate hydrofluoric acid wastestreams from other acid wastes

Material Substitution

• If using positive photoresist, substitute non-phenolic for phenolic- based stripper
• Substitute aqueous cleaning solutions (e.g. dilute sodium hydroxide) for organic solvents
• Substitute deionized water for isopropyl alcohol and solvents in assembly area, where applicable
• Substitute magnesium hydroxide (noncorrosive and nontoxic) for sodium hydroxide in acid neutralization (in some applications may increase wastewater discharge/sewage rate)
• Where applicable, use reclaimed water in cooling towers and scrubbers

Materials Recovery

• Have solvent contaminated clothing, rags, etc. cleaned on- or offsite using industrial laundering equipment which recovers the solvents
• Separately collect and store waste cleaning solvent for reuse in the next batch formulation or for lower grade uses
• Recycle spent solvent with onsite distillation unit if quantities are sufficient to make it cost-effective
• Reclaim vacuum pump and other hydrocarbon-based oil through onsite filtration system
• Install chemical sinks that can reuse acids
• Install onsite system to recycle hydrofluoric acid and arsenic wastes

Process Modification

• When purchasing new equipment:
  • Consider dry pumps (saves on oil changes)
  • Install computerized in-line process/production equipment to reduce acid consumption
• Reduce waste volume by using an air aspirator for room temperature acids, or water aspirator for hot acids
• Instead of aspiration, modify baths for gravity drain and direct discharge of acids to neutralization or treatment
• Install separate solvent drain systems to segregate chlorinated from non-chlorinated solvents, aliphatic from aromatic solvent wastes
• * Circulate chemical baths using in-line filters to maintain purity and pro-long bath life

Sources (Appendix A): S9

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Acknowledgements for this Section

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| Introduction |
| Good Housekeeping Practices |
| Industry Specific Practices I |
| Industry Specific Practices II: A-M |
| Industry Specific Practices III: M-Z |