US EPA Office of Research and Development
          United States
          Environmental Protection
          Agency
Office of Research and
Development
Washington DC 20460
EPA/625/R-99/008
November 2000
          Technology Transfer
&EPA   Capsule Report
          Approaching Zero
          Discharge in Surface
          Finishing

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                                                  EPA625/R-99/008
                                                     November 2000
         Capsule Report

Approaching Zero Discharge
      In Surface Finishing
     U.S. Environment Protection Agency
     Office of Research and Development
National Risk Management Research Laboratory
  Technology Transfer and Support Division
          Cincinnati, OH 45268
                                            Recycled/Recyclable
                                            Printed with vegetable-based ink on
                                            paper that contains a minimum of
                                            50% post-consumer fiber content
                                            processed chlorine free.

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                               Notice
The U.S. Environmental Protection Agency through its Office of Research and
Development funded and managed the research described here under contract
number 8C-R520-NTSX to Integrated Technologies, Inc. It has been subjected to the
Agency's peer and administrative review and has been approved for publication as an
EPA document. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.

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                              Foreword

       The U.S. Environmental Protection Agency is charged by Congress with
protecting the Nation's land, air, and water resources. Under a mandate of national
environmental laws, the Agency strives to formulate and implement actions leading
to a compatible balance between human activities and the ability of natural systems
to support and nurture life. To meetthis mandate, EPA's research program is providing
data and technical support for solving environmental problems today and building a
science knowledge base necessary to manage our ecological resources wisely,
understand how pollutants affect our health, and prevent or reduce environmental risks
in the future.

       The National  Risk Management Research Laboratory (NRMRL) is the
Agency's center for investigation of technological and management approaches for
preventing and reducing risks from pollution that threaten human health and the
environment. The focus of the Laboratory's research program is on methods and their
cost-effectiveness for  prevention and control of pollution to air, land, water, and
subsurface resources; protection of water quality in public water systems; remediation
of contaminated sites, sediments and ground water; prevention and control of indoor
air pollution; and restoration of ecosystems. NRMRL collaborates with both public and
private sector partners  to foster technologies that reduce the cost of compliance and
to anticipate  emerging  problems.   NRMRL's research  provides  solutions  to
environmental problems by: developing and promoting technologies that protect and
improve the environment; advancing scientific and engineering information to support
regulatory and policy decisions; and providing the technical support and information
transfer to ensure implementation of environmental regulations and strategies at the
national, state, and community levels.

       This publication has been produced as part of the Laboratory's strategic long-
term research plan. It is published and made available by EPA's Office of Research
and Development to assist the user community and to link researchers with their
clients.
                             E. Timothy Oppelt, Director

                             National Risk Management Research Laboratory

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                      Acknowledgments


This guide was prepared by Peter A. Gallerani, Integrated Technologies, Inc., and
Kevin Klink,  CH2M  Hill.  Douglas  Grosse,  U.S.  Environmental  Protection
Agency(USEPA), Office of Research and Development, National Risk Management
Research Laboratory (NRMRL), served as the project officer, co-author, and provided
editorial assistance. Dave Ferguson, U.S. EPA, NRMRL, served as the technical
advisor.

The following people provided technical review, editorial assistance, and graphic
design:

       Dr. David Szlag	USEPA, NRMRL

       Paul Shapiro	 USEPA, Office of Research and Development

       Joseph Leonhardt	Leonhardt Plating Co.

       Dr. John Dietz	University of Central Florida

       Carol Legg	USEPA, NRMRL

       John McCready	USEPA, NRMRL
                                  IV

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                               Contents
Notice	ii
    Foreword	jjj
Acknowledgments	jv

1   Introduction	1

2   Systematic AZD Planning	3

3   Process Solution Purification and Recovery Technologies	5
    3.1  Diffusion  Dialysis	5
        3.1.1   Applications	5
        3.1.2   Limitations	7
        3.1.3   Secondary Stream(s)	7
        3.1.4   Diffusion Dialysis Systems	7
    3.2 Microfiltration	8
        3.2.1   Applications	8
        3.2.2   Limitations	9
        3.2.3   Secondary Stream(s)	9
        3.2.4   Microfiltration Systems	9
    3.3 Membrane Electrolysis	9
        3.3.1   Applications	9
        3.3.2   Limitations	9
        3.3.3   Secondary Stream(s)	9
        3.3.4   Membrane Electrolysis Systems	9
    3.4 Acid (Resin) Sorption	10
        3.4.1   Applications	10
        3.4.2   Limitations	10
        3.4.3   Secondary Stream(s)	10
        3.4.4   Acid (Resin) Sorption Systems	11
    3.5 Electrowinning	 11
        3.5.1   Applications..	,	12
        3.5.2   Limitations	13
        3.5.3   Secondary Stream(s)	13
        3.5.4   Electrowinning Systems	13
    3.6 OtherTechnologies	13

4   Rinse Purification or Concentrate Recovery Technologies	14
    4.1  Ion Exchange	14
        4.1.1   Applications	16
        4.1.2   Limitations	16
        4.1.3   Secondary Stream(s)	16
        4.1.4   Ion  Exchange Systems	16
    4.2  Reverse Osmosis	17
        4.2.1    Applications	17
        4.2.2   Limitations	18
        4.2.3   Secondary Stream(s)	18
        4.2.4   Reverse Osmosis Systems	18

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   4.3 Vacuum Evaporation	18
       4.3.1    Applications	18
       4.3.2   Limitations	•	19
       4.3.3   Secondary Stream(s)	19
       4.3.4   Vacuum Evaporator Systems	19
   4.4 Atmospheric Evaporation	20
       4.4.1    Applications	20
       4.4.2   Limitations	20
       4.4.3   Secondary Stream(s)	20
       4.4.4   Atmospheric Evaporation Systems	20
   4.5 OtherTechnologies	20

5  Alternative Surface Finishing Processes and Coatings	22
   5.1 Process Engineering and Re-engineering	22
   5.2 Surface Finishing Properties	22
   5.3 Surface Engineering	23
   5.4 Surface Finishing Costs	23
   5.5 Alternative Coatings and Processes	23
       5.5.1   Alternative Electroplated and Electroless Coatings	23
       5.5.2   Anodizing	23
       5.5.3   Organic Coatings	24
       5.5.4   Vapor Deposition	24
       5.5.5   Thermal Spray	25
       5.5.6   Hardfacing	25
       5.5.7   Porcelain Enameling...	25
       5.5.8   Metal Cladding and Bonding	25
    5.6 Alternative Substrates	25
       5.6.1   Alternative Substrate Treatments	26
    5.7 Alternative Surf ace Preparation	26
       5.7.1   Alternative Stripping Processes	26
       5.7.2   Alternative Pickling and Descaling	26
       5.7.3   Alternative Etching	26
       5.7.4   Alternative Cleaning	26
       5.7.5   Alternative Cleaning Equipment	27
       5.7.6   Forming and Fabrication	27

6  Existing Processes, Conditions, and Practices	28

7  Conclusions	3°

8  References	31

Appendices

    A.  Systematic Approach for Developing AZD Alternatives	32

    B.  Installed Costs	37
                                      vi

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                                Tables
1-1.  Section/Topic References from Section 8	2
3-1.  Technologies for Concentrated Surface Finishing Process Solution
     Applications	6
4-1.  Typical Ion Exchange Capacities for General Resin Types
     (In milliequivalents per liter, meq/L)	16
4-2.  Technologies for Surface Finishing Rinse Applications	21
6-1.  General Approaches and Specific Techniques for Improving
     Existing Process Conditions and Practices	29
A-1.  Data Requirements for Characterizing Sources and Discharges	33
A-2.  Common AZD Benefits	33
A-3.  Common AZD Constraints	33
A-4.  AZD Alternative Evaluation Criteria	35
A-5.  Costs Savings and Benefits for AZD Actions	35
B-1.  Installed Capital Cost Ranges for Typical AZD Project Approach
     and  Size Ranges	37
                                   VII

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                               Figures
3-1. Diffusion dialysis schematic	
3-2. Microfiltration system schematic	
3-3. Membrane electrolysis schematic	
3-4. Acid sorption system	
3-5. Electrowinning system	
4-1. Ion exchange system	
4-2. Reverse osmosis system	
4-3. Vacuum evaporation system	
4-4. Atmospheric evaporation system	
,..7
,..8
,10
.11
,12
,15
.17
.19
.21
                                   VIII

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                                          1. Introduction
This document provides technical guidance to surface
finishers, environmental managers and decision makers
on control  technologies  and  process-changes  for
approaching zero discharge (AZD). AZD is one of the key
themes underlying the Strategic Goals Program (SGP), a
cooperative  effort  among  the  U.S.  Environmental
Protection Agency (EPA), the American Electroplaters and
Surface Finishers Society, the National Association of
Metal  Finishers,  and the  Metal Finishing  Suppliers
Association to test  and promote innovative ideas  for
improved environmental management  within the metal
finishing industry. For more information on this program,
see http://www.strategicgoals.org/

In its broadest sense, "zero discharge" means no discharge
to any media. More commonly, zero discharge focuses on
zero  wastewater  discharge.  This  report  presents
information and strategies for approaching zero discharge
for  concentrated   process   fluids   and   associated
rinsewaters from surface finishing manufacturing. This
focus is intended to minimize discharges of spent and/or
underused process fluids. Specific SGP goals addressed
in this report are:

    •   Improved use of process chemistry (SGP goal is
       98% metals  utilization on product);

    •   Water use reduction (SGP goal is 50% reduction);
       and

    •   Hazardous waste emissions reduction (SGP goal
       is 50% reduction in metals emissions to air and
       water, and 50%  reduction in hazardous waste
       sludge disposal).

The following list provides a section-by-section overview of
this report:

Section 2: Systematic AZD Planning
This section and  related Appendix  A provide key
considerations for planning through implementation of any
AZD project. Without systematic planning and appropriate
implementation, an AZD  project can fail or  fall short of
overall potential. The  techniques and technologies
presented in Sections 3 through 6 should be pursued within
a systematic framework. Specific approaches within these
general categories may  be used independently or in
combination to meet specific AZD goals.
 Section 3: Process Solution Purification and Recovery
 Technologies
 This section presents technologies for in-plant purification
 and maintenance of surface finishing process solutions
 and rinses. Pursuing this approach results in reduced
 discharges through improved use of process solutions.

 Section 4: Rinse Purification or Concentrate Recovery
 Technologies
 This section presents technologies for purification of rinses
 for recycling to surface finishing processes. Pursuing this
 approach can result in a combination of improved use of
 process solutions and water.

 Section 5: Alternative Surface  Finishing Processes
 and Coatings
 Section  5  advances   alternative  surface finishing
 processes and coatings. Most of the alternative surface
 finishing processes and coatings can result in substantial
 reductions in  discharges  compared  to  traditional
 processes.

 Section 6: Improving Existing Process Conditions and
 Practices
 This section presents techniques for modifying existing
 process  operations  and   plant   practices.  Reduced
 discharges can result in modifications that provide  for
 better process optimization.

 Section?: Conclusions

 Section 8: References

 Appendix A: Systematic Approach for Developing AZD
 Alternatives
This is a supplement  to  Section 2 that presents a
 systematic method to guide the identification, development,
 and implementation of AZD actions.

Appendix B: Installed Costs
This appendix provides installed cost information.

Table 1-1 provides a topical section cross reference.

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Tabls 1-1  Section/Topic References from Section 8
Section         Topic                     References
Section 2  Systematic
           AZD Planning
Section 3  Process Solution Purification
           and Recovery Technologies
              •   Ion Exchange
              •   Reverse  Osmosis
              •   Vacuum Evaporation
              •   Atmospheric
                  Evaporation
              •   Electrodeionization
              •   Electrodialysis
              •   Electrowinning
              •   Nanofiltration
              •   Polymer Filtration
              «   Ultrafiltration
 Section  4   Rinse Purification
            or Concentrate
            Recovery Technologies
 Section  5   Alternative
            Surface Rnishing
            Processes and Coatings
 Section 6   Improving Existing
             Process  Conditions
             and Practices
 Section 7   Conclusions
 Appendix A Systematic
             Engineering Approach
 Appendix B Installed Costs
9, 14, 15
2,3,4,5,6,7,9,10
2, 3, 4, 5, 6, 9
2, 3, 4, 5, 7
3, 4, 6, 7, 9, 17

5
3, 4, 5, 9, 17
3,6,9
5,9
4,5
3, 4, 5, 6, 9
 11,12,18
 1,2,4,5,13,15,16,17,
 19
 1,2,9


 1,6,9
 6, 9, 14, 15

 1,5,7,8,9, 10, 17

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                                2 Systematic AZD  Planning
Systematic AZD solutions can be developed by integrating
holistic source reduction planning, including considerations
for multiple sources, composite solutions, and life cycle
process and facility optimization. Nine key considerations
for systematic AZD planning are:

    1.   Is  the AZD target a fixed endpoint  or  an
        optimization point?

        The type of AZD target frames the overall AZD
        options and  the planning  approach. A fixed
        endpoint could be below or beyond the most cost-
        effective  (optimal)  AZD  target.  For example,
        assume that for a particular wastewater stream,
        the most cost-effective (life cycle) approach would
        be to use single-stage reverse osmosis to recycle
        water and reduce wastewater by 80%. Aless-than-
        optimal AZD target might be to pursue a 50%
        reduction goal, and a beyond-optimal AZD target
        might be to pursue a 90% or 100% wastewater
        reduction  goal. These  endpoint goals may be
        based on specific drivers or  constraints, such as
        cost. As zero discharge is approached, the costs
        for incremental discharge reductions can increase
        significantly in proportion to the benefits achieved.

    2.   What tradeoffs are there between point source and
        more combined reduction strategies?

        Point source AZD strategies involve the use of
        bath or rinse purification systems for individual
        tanks or sources. Alternative strategies  might
        include combining  compatible streams from
        different processes for purification/recovery. This
        could include use of single fixed location recovery
        systems (e.g., centralized reverse  osmosis/ion
        exchange for recycling rinsewaters from several
        process lines). Another combined strategy would
        be to use a mobile system to perform intermittent
        purification/recovery of several point sources. For
        example, a single mobile diffusion dialysis system
        might be used to purify/recycle several different
        acid baths. Combined strategies may be more
        cost-effective, due to economy of scale,  unless
        there are substantially increased plant interface
        requirements. Point source systems may offer
        more flexibility, redundancy, and reliability.
3.  What tradeoffs are there between up-the-p'ipe
    pollution prevention and end-of-pipe pollution
    control?

    Up-the-pipe  systems can reduce end-of-pipe
    system  requirements.   For  example,   bath
    purification and water recycling can combine to
    reduce wastewatertreatment system contaminant
    loading and  hydraulic sizing.  In-plant systems
    may also produce byproducts requiring waste
    treatment or management.

4.  What combination of technology, technique and
    substitution  would provide  the best overall
    solution?

    Sections 3,  4, 5,  and  6 present a  range  of
    technologies, techniques and process substitution
    strategies for AZD. Integrated approaches should
    be considered as potential improvements  over
    single-approach solutions.

5.  What future production  and facility  scenarios
    should be considered?

    AZD solutions should consider overall life cycle
    and future production and facility needs. Potential
    future requirements may lead to modified  AZD
    alternatives,  or  more allowances  for change.
    Defining future scenarios may lead to specific
    phased implementation plans, or decisions  to
    accelerate/delay plans for facility renovation.

6.  Are AZD solutions well defined?

    Whether dealing with a single-point source, multi-
    process or  overall  facility  alternatives,  all
    significant  impacts should  be  identified  and
    implemented  to   define  requirements  for  a
    comprehensive  AZD solution. Those include
    process byproducts, cross-media impacts, plant
    interface and utility requirements, operations and
    maintenance requirements. A particular approach
    may be able to meet the primary AZD performance
    requirement  (e.g., 90% acid  reuse)  but  may
    present implementation problems caused by other
    aspects (air discharge  requiring  ventilation
    system, permitting, etc). Comprehensive definition

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    of AZD alternatives is important to identify barriers
    to implementation.

7.  How does the surface finishing process chemistry
    change with production?

    One  key   dimension  is  understanding  the
    chemistry for each process step and how the
    chemistry  changes  during  production cycles,
    including:

    •    transfer  or  transformation   of  process
        chemicals rendering them unavailable for
        production and

    •    generation of contaminants that reduce the
        useful life of process chemicals.
Changes in process chemistry can necessitate the need to
purchase  fresh or make-up process bath chemicals.
Similarly, the increased volume of waste process baths
and  rinses requiring treatment  results  in more waste
treatment chemicals and corresponding increases in waste
generated.

    8.  What opportunities are there to  use existing
       systems? New systems?

       Enhancements to existing systems may produce
       significant benefits at low cost and overall effort.
       Additional capital for new systems may result in
       overall   net   beneficial  gains   in  capacity,
       productivity, reduced wastes, automation, and
       space.  Beneficial process  changes  may  also
       result from eliminating or consolidating processes.

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         3.   Process  Solution  Purification  and  Recovery Technologies
Purification of surface finishing process solutions allows
for extended use of bath chemistries while reducing wastes
and  chemical purchases. Without solution purification,
process cycle times often increase over time as the result
of increased contaminant loading and decreased free acid
or alkali concentrations. This is especially true of stripping,
pickling, etching and cleaning process solutions. Process
contaminants are normally controlled  through periodic
solution dumps and drag-out. Continuous, steady-state
bath maintenance can result in more constant production
rates and quality.

This section presents technology descriptions, applications
and limitations, secondary waste stream identification, and
system components and configurations for five process
solution purification  technologies in surface finishing
applications:

    1.  Diffusion dialysis

    2.  Microfiltration

    3.  Membrane electrolysis

    4.  Acid (resin) sorption

    5.  Electrowinning

In addition, Table  3-1  features eight  technologies,
considered to show promise for limited surface finishing
process solution applications:

    1.  Adsorption filtration

    2.  Crystallization

    3.  Electrodialysis

    4.  Ion exchange

    5.  Liquid ion exchange

    6.  Nanofiltration

    7.  Ultrafiltration

    8.  Vacuum evaporation
3.1   Diffusion Dialysis
Diffusion dialysis is a membrane separation process that
typically uses an anionic exchange membrane to transport
acid anions and protons from waste acid solutions into
deionized water streams. This process recovers useable
"free" acid commonly wasted when metals contaminant
buildup levels exceed processing criteria. Consequently,
the resultant acid bath is dumped. Such wasted free acid
consumes significant quantities of neutralization chemicals
and must be replaced in the process.  Free acid readily
diffuses  across the membrane in  proportion  to  a
concentration gradient. Metal cations diffuse at a much
slower rate due to their positive charge and the negative
charge functionality of the anionic exchange membrane.
Typical acid recovery rates are 80-95% and typical metal
rejection rates are 60-95%.

Diffusion dialysis separations use a membrane consisting
of a series of alternating anion exchange membranes and
separators that form countercurrent fluid distribution paths.
Contaminated acid (feed) enters on one side and deionized
(Dl)  water is fed via countercurrent on the other  side.
Concentration gradients exist across the membranes. Free
acid  is transported  from the  waste  acid into the
countercurrent DI water stream via diffusion. Metals in the
feed liquor are rejected by the membrane to a large extent,
and are removed in the waste stream (retentate) for metal
recovery ortreatment. Free acid is collected in the Dl water
(dialysate) for acid recovery.Typically, the feed and exit
stream flow rates are approximately equal.  Figure 3-1
shows the basic function of diffusion dialysis.

The concentration of recovered acid will normally be lower
than that of the feed acid, and make-up acid must be added
to bring the concentration up to the process level. When the
feed has a significant salt concentration, the concentration
of recovered acid can exceed the concentration of the feed
acid.

For diffusion dialysis processing, an increase in membrane
area per unit of acid flow increases the acid recovery rate.
If the flow rate of Dl water increases, the acid recycling rate
increases and the recycled acid concentration decreases.

3.1.1  Applications
Diffusion dialysis is a purification/recycling technology that
can be used to maintain or reclaim spent or contaminated
acids where acid concentrations are greater than 3% by

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Table 3-1. Technologies for Concentrated Surface Finishing Process Solution Applications
   Technology
          Description
                                                                   Status
                         Applications and Limitations
Adsorption Filtration
Crystallization
 Electrodialysis
 Liquid/liquid Ion
 Exchange
 Ion Exchange
 Nanofiltration
 Ultrafiltration
Granulated polypropylene felt or other
lipophilic filter media is placed in filter
housings and used for removal of oils
by adsorption.
Various evaporation and cooling systems
are used to bring solutions to a super-
saturation point where solid crystals
form and can be separated from
solution.
Emerging
Anions and cations are removed from
solutions with an applied electric field in
cells with alternating anion- and
cation-permeable  membranes.


Ionic contaminants are removed from
process solutions  into immiscible
primary liquid extraction solutions.
Secondary liquid extraction solutions
are used to remove the contaminants
and to regenerate the primary extraction
solution.

Ions in solution are selectively removed
by exchanging positions with  resin-
functional  groups.
 Membrane filtration manufactured for
 larger size rejection (rejects molecules
 larger than 0.001  to 0.008 microns)
 than reverse osmosis. Preferentially
 rejects some larger ions and passes
 others.

 Membrane filtration process that
 passes  ions and  rejects macromolecules
 (0.005 to 0.1 micron).
Commercial
technology;
limited surface
finishing
applications
Commercial
technology;
limited surface
finishing
applications

Commercial
technology;
limited surface
finishing
applications
Removes mineral oil derivatives from
aqueous cleaning solutions to less than
10 ppm range. Beneficial cleaner
components are not significantly
removed.

Operates over full pH  range and at
temperatures up to  200 °F (95 °C).

Applicable for some etching or pickling
baths with relatively high metals
concentrations  where controlled metals
removal and  recovery are beneficial
(e.g., removal and recovery of copper
sulfate from peroxide-sulfuric etch
solutions).

Applicable for removal of carbonates to
maintain alkaline and cyanide plating
solutions. Used for acid pickling, aluminum
etchant and cyanide/alkaline plating bath
maintenance.

Used for regeneration  of spent electroless
nickel baths. Sodium, iron and zinc cations
are removed through a cation membrane.
Sulfate and orthophosphite anions are
removed through an anion membrane.

Ammoniacal etch solutions have been
regenerated  by removal of copper, with a
closed-loop extraction solution  system.
 Commercial
 technology;
 commonly
 used in surface
 finishing rinse water
 applications

 Limited concentrated
 solution application.

 Commercial
 technology;
 limited surface
 finishing
 applications


 Commercial
 technology;
 limited surface
 finishing applications
 Used in some applications for tramp metal
 removal from concentrated process
 solutions. A typical application is the removal
 of iron from chromium plating solutions.
 Removal by ion exchange is not viable for
 process solutions more concentrated than
 ion exchange regenerant solutions.
 Concentrated process solutions may  also
 degrade resins.

 Used for separation of metals from spent
 acid solutions, or from reverse osmosis
 concentrates for acid purification/recycling.
 Removes organics from process solutions.
 For aqueous cleaners, removes more
 contaminants compared to microfiltration,
 but may also remove significantly more of
 the beneficial cleaner constituents.
 Vacuum              Reduced pressure and elevated
 Evaporation           temperature combine to separate
                       constituents with relatively high
                       volatility from constituents with lower
                       volatility.
                                             Commercial           Contaminants with lower volatility than
                                             technology;           process solutions can be evaporated (e.g.,
                                             limited use for         removal of water from an acid solution).
                                             surface finishing       Evaporating the process solution.(e.g., acid
                                             concentrates          distillation) from contaminant phases with
                                             (more  commonly      higher volatility can also purify process
                                             used for rinse         solutions. Multiple stages may be used to
                                             applications)          increase separation purity, to reduce energy
                                                                   requirements, or to accomplish multiple
                                                                   phase separations.

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                                   Retentate
                                 (rejected metals)
                                              Metals -
                                          . Dl water -KV,)—

                                              Heat exchanger
                                                      H+ Anions
                         -©(
7            Feed
       (Contaminated acid)
Heat exchanger          Filter
 Anion
membrane
I	   Dialysate
   (recovered acid)
Figure 3-1. Diffusion dialysis schematic.
weight.  Diffusion dialysis is  most typically
used where contaminant metals concentrations
are less than 1 gram per liter. Surface finishing
process solutions  amenable  to  the  use of
diffusion dialysis include:

    •   Hydrochloric acid (HGI)  pickle  and
       strip solutions

    •   Sulfuric acid (H2SO4) anodize solutions

    •   Sulfuric acid pickle and strip solutions

    •   Nitric acid (HNO3) pickle and strip
       solutions

    •   Nitric acid/hydrofluoric acid (HNO3/
       HF) stainless steel pickling solutions

    •   Hydrochloric acid/sulfuric acid (HCI/
       H2SO4) aluminum etch solutions

  .  •   Methane sulfonic acid (MSA) solutions

3.1.2     Limitations
Limitations in  using  diffusion  dialysis to
recover  surface finishing  process  acids
include:

    •   Acids  not  highly dissociated (e.g.,
       phosphoric acid) will  not  diffuse
       across the membrane.

    •   Complexed metal anions (e.g., fluoro-
       titanium  anions) can  readily diffuse
       across the anion exchange membrane
       and are not efficiently separated from
       the acid.
                                    •   Cooling is typically needed if influent waste acid
                                       temperature exceeds 122 °F (50°C).

                                    •   Heating  may be  needed  for low-temperature
                                       influent waste acid. A temperature drop of 3.6 °F
                                       (2°C)  reduces  the  acid  recycling  rate  by
                                       approximately 1.5%.

                                    •   Solvents can cause membrane swelling.

                                    •   Strong oxidizing substances (e.g., chromic acid)
                                       can cause membrane deterioration.

                                3.1.3  Secondary Stream(s)
                                The depleted acid waste stream (after diffusion dialysis
                                processing) is approximately equal in volumetricflowto the
                                waste acid influent. Depending on the application-specific
                                acid removal and metals rejection rates, the depleted acid
                                waste stream (retentate) typically contains 5 to 20% of the
                                acid and 60 to 95% of the metals from the influent waste
                                acid stream. This stream is usually sent to wastewater
                                treatment.

                                3.1.4  Diffusion Dialysis Systems
                                Typical diffusion dialysis system components include:

                                    •   Membrane  stack, including plate  and frame,
                                       membrane spacers, and special anion exchange
                                       membranes

                                    •   Feed and exit stream tanks and pumps

                                    •   Process  I&C and electrical

                                    •   Acid pre-filter (some applications)

                                    •   Dl water system (some applications)

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    •   Heat exchanger (some applications)

Diffusion dialysis systems can be used  for batch or
continuous flow  applications. Small systems are often
configured as mobile units.

3.2  Microfiltration
Microfiltration (MF) is a membrane filtration technology that
uses low applied pressures in the range of 3-50 psi (20 to
350 kPa) with pore sizes in the range of 0.02 to 10 microns
to separate relatively large particles in the macromolecular
to micro  particle size range (approximate  molecular
weights > 100,000).

Microfiltration is typically configured in a crossf low filtration
pattern, rather than in a conventional,  pass through
configuration.  In the crossflow configuration, the  feed
solution flows parallel to the filter media (membrane) and
splits into a permeate (filtrate) stream, which is the cleaned
solution that  passes through  the membrane,  and a
concentrate (retentate or reject) stream that contains the
contaminants  rejected  by the filter membrane. A major
benefit for the crossflow configuration is that relatively
high-solids streams may be filtered without plugging.
Figure 3-2 presents a microfiltration system schematic for
process fluid purification applications.

Four primary operating parameters influence crossflow
filtration performance:

    1.  Trans-membrane pressure difference

    2.  Flow velocity parallel to the membrane

    3.  Temperature

    4.  Bulk stream component concentration

 Increasing trans-membrane pressure will increase flux until
 a constant flux point  is  reached. Increases in trans-
membrane pressure above the constant flux point will
result in  a thicker, more compact particle layer at the
filtration surface.

The flow velocity parallel to the membrane influences the
shearing forces on the particle layer surface. High velocity
results in a constant layer thickness, and a more constant
flux. Generally, the higher the tangential velocity, the
higherthe flux. Higherflux results in a greater pressure drop
in the direction of tangential velocity, and higher energy
consumption. In most cases, temperature increases will
result in a lower viscosity of the liquid to be filtered. Lower
viscosity  influences  flow  through and  parallel  to the
membrane. Temperature changes may cause components
to be precipitated or dissolved, greatly impacting flux.
Increases in bulk stream component concentration cause
a decrease in flux through the membrane. This effect can
vary, depending  on the characteristics  of the filtered
solution.

3.2.1  Applications
Microfiltration applications include:

    •   Cleaner aqueous purification

    •   Removal of oil and grease from process baths

    •   Wastewater treatment  applications  (replaces
        clarification and polishing filters)

Microfiltration  has  become  a  popular process for
continuous or batch maintenance of aqueous cleaning
solutions.  Through  proper  membrane selection, it is
possible  to  remove   both  oily and  solid  solution
contaminants selectively from many proprietary industrial
cleaners. Chemical suppliers can assist in the selection of-
aqueous cleaners and microfiltration  membranes  to
optimize the separation of contaminants from cleaning
agents such as surfactants.
                            Feed
                                    Oil
                                                         Concentrate
                      Oil
                     Solid .
                     phase

^

X"
^»
Sc

^


	
lid
^~







_____ — • — ~~"
___— — -— '
Microfilter

                                                                           Permeate _.
                                                                          [to process)
 Figure 3-2. Microfiltration system schematic.

-------
 3.2.2  Limitations
 Since cleaning agents are typically removed along with oil,
 grease and dirt, the  bath must  be  amenable  to
 replenishment with make-up chemical additives. Cleaners
 with relatively high silicate concentrations are generally
 less  amenable  to   purification  with  microfiltration.
 Aluminum cleaning solutions are typically not recycled with
 microfiltration due to buildup of  dissolved aluminum.
 Recent advances in membrane technology may extend the
 range of microfiltration application to silicated cleaners.

 3.2.3  Secondary Stream(s)
 The separated oil, grease and  dirt  from  one or more
 concentrated stream phases require waste treatment and/
 or disposal. The relatively low-density oil phase is usually
 skimmed off. The relatively dense dirt/grease phase is
 removed in a separate bottom phase for disposal.

 3.2.4  Microfiltration Systems
 Typical microfiltration system components  include:

    •   Membranes and housings

    •   Working tank (containing  process fluid that is
        circulated through the microfilter, and zones for
        light and dense phase separations)

    •   Oil  and dense phase  contaminant removal
       systems (manual or automatic)

    •   Membrane cleaning systems (chemical cleaning
       and/or back pulsing system)

 3.3  Membrane Electrolysis
 Membrane electrolysis uses  one or more ion-selective
 membranes to separate electrolyte solutions within an
 electrolysis cell. The membranes are ion-permeable and
 selective. Cation membranes pass cations such as Cu and
 Al, but reject anions. Anion membranes pass anions, such
 as sulfates and chlorides, but reject cations.

 Membrane electrolysis can regenerate process solutions
 through two primary mechanisms: (1) Selective transfer of
 ions from the process solution, across the membrane, into
 an  electrolyte solution and (2) Regenerating oxidation
 states/ionic forms of key constituents in  the process
 solution through electrode electrochemical reactions.

 A common configuration for removing cation contaminants
 from surface finishing process solutions uses a cation-
 specific membrane coupled with a two-cell compartment
 drawing an  electrical  potential  applied  across  the
 membrane. One cell contains an anode with the anolyte
 solution; the other contains a cathode with the catholyte
 solution. Figure 3-3 presents a flow schematic for a two-cell
 membrane electrolysis system.

The anolyte solution is typically the spent process solution
 requiring regeneration. Contaminant cations are removed
 from the anolyte solution and transferred into the catholyte
 solution. Anode and cathode reactions occur based on the
 relative electronegativity and concentration of specific ions
 in each solution, as water decomposes.

 3.3.1  Applications
 Membrane electrolysis has been used with chromic acid-
 based solutions, including chromium plating, chromic acid
 anodizing, etchants and chromating solutions. Trivalent
 chromium can be beneficially reoxidized at anodes to
 hexavalent chrome. Contaminant metals are transported
 into the catholyte. Membrane electrolysis has also been
 applied to various acid-based etchants,  stripping and
 pickling solutions to remove contaminant metals. Multi-cell
 systems with special anolyte and/or catholyte solutions
 have been used with highly corrosive acids, such as nitric
 and hydrofluoric, to isolate the electrodes.  Membrane
 electrolysis can be used on a batch or continuous basis,
 and is often configured as a mobile unit for smaller point-
 source applications.

 3.3.2  Limitations
 Limitations of membrane electrolysis:

    •   Special  materials  of construction  and  cell
        configurations may be required for processing
        highly corrosive fluids.

    •   Fume collection and treatment may be required if
        hazardous gases are generated in  electrode
        reactions.

    •   Anionic metal complexes require pretreatment
        prior  to removal  across a  cation  exchange
        membrane.

    •   Operating temperatures are typically limited from
        60°Fto140°F.

    •   Oil, grease and solvents can  adversely affect
        membranes.

    •   Suspended  solids  and precipitates  can clog
        membranes.

3.3.3   Secondary Stream(s)
Contaminant metals are typically transferred from process
solutions into catholyte solutions. The catholyte solution is
periodically replaced.  The spent catholyte solution  is
usually a small percentage of the treated process solution
volume, and  contains concentrated removed metals.
Spent catholyte solutions can be processed  for metals
recovery or handled as waste.

3.3.4   Membrane Electrolysis Systems
Typical membrane  electrolysis  system  components
include:

    •   Cell with anolyte and catholyte compartment(s)

-------
                  Feed
                        ~  To  '
                        process
                          tank
                            I
                           From
                          process
                           tank
                           Anolyte
                            tank
                            (pro-
                            cess
                           solution
                                           0       0
Filter
          Anions
                Cation:
             Membrane
             electrolysis
                                                   pell
                                                     Cation
                                                     membrane
                                                                    Periodic waste
Figure 3-3. Membrane electrolysis schematic.
    •    Ion exchange membrane(s)

    •    Rectifier, buss bars, and bussing

    •    Anolyte and catholyte process tanks, pumps, and
        piping systems

    •    Process instrumentation and controls (if needed)

    •    Ventilation systems (if needed)

Membrane electrolysis systems can  be  configured as
multi-cell   systems   to   enhance   capacity.   Three
compartment cells are used for special applications where
the electrodes must be isolated from the feed stream. A
range of  selective and  custom-made  electrodes  are
available for removal of special and noble metals.

3.4  Acid (Resin) Sorption
Acid  (resin) sorption is a technology  used primarily for
recovering acids  from surface finishing etch and pickle
solutions. Configured similarly to ion exchange, resins are
designed to  selectively  adsorb mineral  acids while
excluding metal salts (adsorption phase). Purified acid is
recovered for reuse when the resin is regenerated with
water (desorption phase).  Figure 3-4 shows a general
process flow diagram for acid sorption.

3.4.1  Applications
Acid  sorption is used to  separate dissolved ionic metal
contaminants from acid baths. Applications include:

    •   Sulfuric acid anodizing baths for aluminum

    •  Sulfuric or hydrochloric acid pickling baths for
        steel and galvanized steel
                      •   Sulfuric or  nitric  acid  pickling,  etching,  or
                          brightening baths for copper or brass

                      •   Nitric/hydrofluoric acid pickling  baths used for
                          processing stainless steel

                      •   Phosphoric and/or sulfuric acid baths for stainless
                          steel or aluminum electropolishing

                      •   Cation ion exchange acid regenerant solutions

                   3.4.2  Limitations
                   Acid sorption limitations include:

                      •   Not  applicable for some highly concentrated
                          acids.

                      •   Should not be used on  acids with anionic
                          complexes that sorb to the resin, thus reducing
                          acid recovery.

                      •   Application-specific temperature limitations should
                          not be exceeded  (e.g., approximately 90°F for
                          nitric acid,  and  up  to  160°F  for sulfuric or
                          hydrochloric acid).

                   3.4.3  Secondary Stream(s)
                   The acid  sorption process recovers only a portion of the
                   free or unused acid. It does not recover any of the combined
                   acid (salt). As a result, approximately 35 to 70% of the total
                   acid used is incorporated  into a waste  stream from the
                   process and will require treatment. Depending on the metal
                   involved,  treatment  will  range  from  conventional
                   neutralization  (pH adjustment with caustic) to metals
                   removal (e.g., precipitation).
                                                    10

-------
                     01 Water
                                                                          Residual Acid
                                                                            Waste
                                                   Resin
                                                  Columns
Feed
!
(Spent Acid) !
,1




j
.
Reclaimed
Acid
i
|
i
i
Feed
(Spent Acid)
J
Reclaimed
Acid
s
i
Figure 3-4. Acid sorption system.


3.4.4 Acid (Resin) Sorption Systems
Typical acid sorption system components include:

    •   Resin columns with resin

    •   Feed and discharge pumps, piping, and tanks

    •   Process automation for adsorption and desorption
       cycling

    •   Prefiltration

    •   Feed stream cooling

3.5   Electrowinning
Electrowinning (also called electrolytic metal recovery) is
an electroplating process used for recovery or removal of
metals from process solutions. Electrodes are placed in
electrolyte solutions with direct current power applied to the
cell. Electrochemical reactions occur  at the electrode/
electrolyte interfaces. Cations migrate to and electrons are
consumed at the cathode (reduction). Anions migrate to
and electrons are supplied at the anode (oxidation). Metal
deposition rate is a function of the electrode area, current,
solution agitation rate, solution chemistry and temperature.
Metals deposited  at the  cathode are removed  by
mechanical or chemical means and are reused or recycled.
Figure 3-5 presents a flow schematic for electrowinning.
Three  basic  approaches  are  used for the  electrolytic
recovery of metals: conventional  electrowinning, high
surface area and extractive methods.

Conventional electrowinning uses  solid cathodes. The
recovered metal is removed in strips or slabs  and can be
sold to a refiner or used in-house as an anode material.
Several variations  of the conventional electrowinning
process are available to overcome electrode polarization
and low ion diffusion rates, which reduce recovery rates in
low concentration solutions. This is typically achieved by
reducing the thickness of the diffusion layer  through
agitation of the solution or through movement of the
cathode. Conventional  electrolytic recovery units are
usually operated on a batch basis.

High surface area electrowinning is most often used in
continuous rinsing operations, where low concentrations
are present. High surface area units  extract the metal onto
cathodes  made of fibrous  material such as  carbon.
Passage of a strip solution through the unit and reversal of
the current regenerate the fiber cathode.

Extractive electrowinning methods are  used to remove
dissolved metals from solution, without regard to recovery.
Extractive  methods may include using  disposable
cathodes. Dummy  plating, an important form of the
extractive method for surface finishing,  is an  electrolytic
treatment process in which metallic contaminants in a
surface finishing solution are either plated out (low-current
density electrolysis, LCD)  or oxidized  (high-current
                                                  . 11

-------
                                                 Recirculatiorr
                                            ACACACACACA
                        C - cathode
                        A - anode
                                               Scrap metal      Recycle or
                                            (periodically scrape   wastestream
                                              from cathode)  (end ofi batch cycle)
Figure 3-5. Electrowinning system.
density/high anode: cathode ratio electrolysis, HCD). LCD
dummy plating uses an average current density of 5 amps
per square foot (ASF). Copper and  lead are removed
preferentially at 2-4 ASF and zinc and iron at 6-8 ASF.
Increasing the overall cathode surface area and current
while maintaining the average current density can increase
the rate of removal. Solution agitation will improve the
overall efficiency of the process.

High-current density (HCD) dummy plating typically refers
to the  practice  of oxidizing  trivalent  chromium  to
hexavalent chromium in chromium plating and chromic
acid anodizing solutions. It has also been used to gas-off
chloride as chlorine. This process requires the  use of
anode:cathode ratios of between 10:1 and 30:1. Lead or
lead alloy anodes are typically used in the process. Current
densities ranging between 100-300 ASF are used. The
overall cathode and anode areas and current control the
rate of conversion.

Electrowinning uses insoluble anodes in all cases except
the  specialized dummy  plating previously described.
Anode materials include graphite,  lead,  lead  alloys,
stainless steel, and coated (platinum, iridium, ruthenium
oxide) titanium, tantalum,  tungsten,  niobium,  and
conductive ceramics. Anode material selection is based on
anode corrosion, overvoltage characteristics, available
forms and life cycle cost factors. Typical cathode materials
include stainless steel, steel, porous carbon,  graphite,
metallized  glass and  plastic beads,  and substrates
equivalent to the metal being deposited.

 3.5.1  Applications
Electrowinning is applied to  a wide variety of surface
finishing solutions.  Electrolytic recovery  works best in
concentrated solutions. In the electroplating industry,
metals most commonly recovered by electrowinning are
precious metals, copper, cadmium, zinc, tin and tin /lead.
The more noble the metal in solution, the more amenable
it is to electrowinning from solution. For example, with
adequate agitation, solution conductivity and temperature,
gold can be removed from solution down to 10 mg/L using
flat-plate cathodes.

Applications include:

    •    Acid purification  (e.g., sulfuric acid used  for
        copper wire pickling)

    •    Recovery   of  metals  from   ion  exchange
        regenerants and reverse osmosis concentrates

    •    Controlling metal concentrations in electroplating .
        solution applications where the metal concentration
        increases over time

    •    Recovery of metals from spent surface finishing
        solutions

    •    Use of low-current density (LCD) dummy plating in
        the purification of nickel plating, nickel strikes,
        copper plating, cadmium plating, and trivalent
        chromium plating

    •    Use of electrolysis to oxidize  concentrated
        cyanide solutions

LCD dummy plating can be used in both a continuous and
batch mode. Continuous dummy plating is often practiced
in high-build sulfamate nickel plating applications such as
aerospace  overhaul  and   repair  operations  and
electroforming. Batch treatment is usually performed in the
process tank and requires periodic down time. Continuous
treatment is usually performed in a side tank, which should
be sized to allow approximately 0.05 ampere-hours per
                                                    12

-------
 gallon of plating solution. The side tank can normally be
 connected into the process filtration loop.

 3.5.2  Limitations
 Chromium is the only commonly  plated  metal  not
 recoverable  using electrowinning. Nickel recovery is
 feasible, yet requires  close  control of pH.  Minimum
 practical concentration requirements vary for the specific
 metal to be recovered and for cathode type. Systems with
 flat-plate  cathodes  operate  efficiently  with   metal
 concentrations greater than 1 to 5 g/L. For copper and tin,
 a concentration in the range of 2 to 10 g/L is required for
 homogeneous metal deposits.

 Metals recovery can be difficult to perform for solutions that
 contain chelated orcomplexed metals, reducing agents, or
 stabilizers.

 3.5.3  Secondary Stream(s)
 Solutions depleted by electrolytic recovery can often be
treated using ion  exchange to reconcentrate the ions.
 Piated-out metals  can often be reused or sold as scrap
 metal.

 3.5.4  Electrowinning Systems
Typical system components include:
    •   Electrowinning tanks

    •   Electrodes

    •   Feed pump

    •   Ventilation system

    •   Rectifier, buss bars, and bussing

A variety of cell designs is available to provide a range of
voltage drop, mass transfer, and specific electrode area
properties. Electrolytic cells that use metal fiber cathodes
can  recover metals at significantly lower concentration
than can flat plate cathodes. Many techniques can be used
to improve the hydrodynamic conditions of the cell and
force convection. These include electrolyte agitation,
pumped recirculation, rotating electrodes, and fluidized
beds. As the complexity of the system increases, so do
capital cost and operation and maintenance costs.

3.6   Other Technologies
Table  3-1  (page 6) presents a description of eight
technologies  with  relatively  limited existing surface
finishing concentrated process solution applications. Note
that some of these technologies, like ion exchange, are
used extensively for rinse water applications.
                                                  13

-------
        4.    Rinse  Purification or Concentrate Recovery  Technologies
Purifying and recycling process rinse water reduces water
use, wastewater generation and contaminant load from
influent  water.  Influent water  contaminants  must be
removed in water pretreatment systems, to prevent entry
into the processes. Purifying and recycling rinse water can
improve  process  rinsing  quality,  thereby  improving
production. In some cases,  it is  possible to recover
concentrated solutions during rinse water purification.

This section presentstechnology descriptions, applications
and limitations, secondary stream  identification, and
system  components and  configurations for four  key
technologies for surface finishing rinse water purification
and process solution recovery:

    •   Ion Exchange

    •   Reverse Osmosis

    •   Vacuum Evaporation

    •   Atmospheric Evaporation

 Brief summaries follow for another six technologies that are
 either commercial, with relatively limited existing surface
 finishing concentrated process solution applications, or are
 emerging:

     •   Electrodeionizaton

     •   Electrodialysis

     •   Electrowinning

     •   Nanofiltration

     •   Polymer Filtration

     •    Ultrafiltration

  4.1  Ion  Exchange
  Ion exchange is a chemical  reaction where ions from
  solutions are exchanged for ions attached to chemically
  active functional groups, on  ion  exchange  resins.  Ion
  exchange  resins  are typically  classified  as  cation
  exchange resins oranion exchange resins. Cation resins
  usually exchange sodium or hydrogen ions for positively
  charged cations such as nickel, copper and sodium. Anion
resins typically exchange hydroxyl  ions for  negatively
charged ions such as chromates, sulfates and chlorides.
Cation and anion exchange resins are both produced from
three-dimensional, organic polymer networks. However,
they have different ionizable functional group attachments
that provide  different  ion  exchange  properties.  Ion
exchange resins have varying ion-specific selectivities
(preferences for removal).

The following chemical equilibrium equation describes a
cation exchange process:

    zR - A + zB+ -> zR - B + zA+

    R - = Resin functional group

    A+ = R'esin-bound cation

    B+ = Water phase cation

    z = Number of equivalents

 Ion exchange systems typically consist of columns loaded
 with ion exchange  resin beads. Process solutions are
 pumped through the columns for treatment. Figure 4-1
 presents  a general flow schematic for ion exchange
 purification of rinse water.

 Key features of ion  exchange column systems:

     •  Ions are removed in a continuous flow system.

     •  The ion exchange resins load in the direction of
        flow until the entire column is loaded.

     •   Resins  can be regenerated,  whereby acidic
         solutions are typically used to remove metals from
         cation exchange resins, and caustic solutions are
         typically used to remove resin-bound salts. Rinse
         solutions are used to remove excess regeneration
         fluids from the columns.

     •   The linear flow velocity through the resin bed
         impacts the ion exchange rate.

  The major types of ion exchange resins include:

      •   Strong acid resins.  A typical strong acid resin
         functional group is the sulfonic acid group (SO3H).
                                                    14,

-------
                                               Acid water
                                                  Cation
                                                  exchange
                                                Feed
                                              (rinsewater)
Figure 4-1. Ion exchange system.
                                                                  Base water
                 Anion
               exchange
                                                Regeneration solution
                                                to reuse o treatment
              Regenera Ion solution
              to reuse or treatment
       Strong  acid  resins  are highly ionized  cation
       exchangers.  The exchange capacity of  strong
       acid resins is relatively constant over specific
       functional pH ranges.

       Weak acid resins.  A typical  weak  acid resin
       functional group is  a  carboxylic acid  group
       (COOH). Weak acid resins exhibit a much higher
       affinity for hydrogen ions than do strong acid
       resins, and can be regenerated using significantly
       lower  quantities of  regeneration  reagents.
       Dissociation  of  weak acid  resins  is strongly
       influenced by solution  pH. Weak acid  resin
       capacity is influenced by pH  and has  limited
       capacity below a pH of approximately 6.0.
                           /
       Strong base resins.  A typical strong base resin
       functional group is the quaternary ammonia group.
       Strong base  resins  are highly ionized  anion
       exchangers.  The exchange  capacity of strong
       base resins is relatively constant over specific
       functional pH ranges.

       Weak base resins. Weak base resins exhibit a
       much  higher affinity  for hydroxide ions than do
       strong base resins and can be regenerated using
       significantly lower quantities  of  regeneration
       reagents. Dissociation of weak base resins is
       strongly influenced by solution pH; resin capacity
       is influenced by pH and has limited capacity above
       a pH of approximately 7.0.
     •   Chelating  resins.  Chelating  resins  behave
         similarly to weak acid cation resins but exhibit a
         high degree of selectivity for heavy metal cations.
         One  common  type   of  chelating  resin  is
         iminodiacetate chelant resin. This resin has two
         carboxylic acid functional groups attached to a
         nitrogen atom that is attached  to  the  resin
         polymeric structure. The carboxylic acid groups
         exchange with different cations, similar to a weak
         acid resin. However, the nitrogen  atom can also
         form a ligand bond with metal cations, thereby
         adding  another  cation capture  mechanism.
         Chelating  resins are  particularly  selective  for
        'heavier divalent  cations  over monovalent or
        trivalent cations due  to the presence  of two
        desirably spaced functional groups.

The following lists illustrate relative ion-specific selectivity
preferences for common commercial ion exchange resin
types. The ions on each list are ordered from highest to
lowest selectivity.

Strong acid (cation) resin selectivity:
Barium> Lead> Strontium> Calcium> Nickel> Cadmium>
Copper> Zino lron> Magnesium> Manganese> Alkali
metals> Hydrogen

Strong base (anion) resin selectivity:
lodide>   Nitrate>  Bisulfite>   Chloride>  Cyanide>
Bicarbonate> Hydroxide> Fluoride> Sulfate

Weak acid (cation) resin selectivity:
                                                   15

-------
Copper>Lead> lron>Zinc> Nickel> Cadmium> Calcium>
Magnesium> Strontium> Barium> Alkalis

Chelating resin selectivity (iminodiacetate):
Copper> Mercury> Lead> Nickel> Zino Cadmium  >
Cobalt>  lron>  Manganese> Calcium> Magnesium>
Strontium> Barium> Alkalis

Chelating resin selectivity (aminophosphonic):
Lead> Copper> Zino Nickel>  Cadmium>  Cobalt  >
Calcium> Magnesium> Strontium> Barium> Alkalis

The exchange capacity of typical ion exchange resins can
be expressed in milliequivalent per liter (meq/L = ppm of
ions/equivalent weight per liter). Table 4-1 presents typical
exchange  capacities  for  common   commercial  ion
exchange resins.

4.1.1  Applications
Ion exchange has been used commercially for many years
in water deionization, water softening applications, and
wastewatertreatment applications. There are widespread
applications for rinse water recovery and metals recovery
in the surface finishing  industry.  The most common
applications include recovery of copper (from acid copper
solutions), nickel and precious metals from plating rinse
water.

 Ion exchange is an excellent technology for recovering
 plating chemicals from dilute rinse waters. In the typical
 configuration, rinse watercontaining a dilute concentration
 of plating chemicals  is passed through an ion exchange
 column where metals are removed from the rinse water and
 held by the ion  exchange resin. When the capacity of the
 unit is reached, the resin is regenerated and the metals are
 concentrated into a manageable volume of solution.

 For conventional chemical recovery processes, systems
 are designed with either cation oranion beds, depending on
 the charge of  the ionic species being recovered. After
 passing through the column, the treated rinse water is
 discharged  to the  sewer  or  undergoes  subsequent
 treatment. In most cases, rinse water is recycled to  the
 process. Such systems  include both cation and anion
 columns to completely deionize the rinse water.

 Drag-out recovery  tanks  can be combined  with  ion
 exchange to reduce the required capacity of the  ion
  Table 4-1.    Typical Ion Exchange Capacities for General Resin
             Types (in milliequivalents per liter, meq/L)

  Resin Type               Exchange Capacity (meq/L)
  Strong Acid (Cation)
  Weak Acid (Cation)
  Strong Base (Anion)
  Weak Base (Anion)
  Chelating (Sodium form)
1800

4000

1400
1600
1000
exchange columns. Using this configuration, the drag-out
tank(s) are followed by an overflow rinse that feeds an ion
exchange column. In operation, the drag-out tanks return
the bulk of the plating chemicals to the plating bath and an
ion exchange column captures only the residual chemical
load.  This reduces  the ion exchange system  size
requirement.

4.1.2  Limitations
Common limitations for ion exchange:

    •   Ion exchange may become impractical for use
        with total dissolved solids concentrations above
        500  ppm,  due to  the   need for  frequent
        regeneration.

    •   Resins have different effective pH  ranges. For
        example, iminodiacetate Chelating  resin works
        best in a slightly acidic range; selectivity is lower
        at higher pH and below a pH of approximately 2.0.

    •   Oxidants, solvents, organics, oil and grease can
        degrade resins.

    •   Suspended solids can clog resin columns.

 4.1.3   Secondary Stream(s)
 Regenerant chemicals can be selected to optimize the
 products derived from the regeneration of ion exchange
 resins. Chemicals are selected to produce salts that can be
 directly  recovered in the treatment process. Metals are
 recovered via electrowinning and salts are recovered off-
 site.

 Depending on the chemical product specification of the
 recovery process, the regenerant solution can be returned,.
 directly to the plating tank for reuse, further processed, or
 -the metals recovered  by another technology, such as
 electrowinning.  The most common applications of this
 technology are in the  recovery of copper, nickel and
 precious metals.

 Countercurrent regeneration mechanisms can result in
 significantly lower chemical use for regeneration^ the
 regenerated  zone is  always maintained  in a "clean"
 condition.  Co-current   regeneration  requires  higher
 chemical use and/or results in lower initial water quality as
 the "regenerated zone" is left in a semi-contaminated state
 following regeneration.

  4.1.4  Ion  Exchange Systems
 Typical system components include:

      •   Ion exchange columns with resin

      •   Process pumps, piping and valves

      •   Regeneration tanks, pumps and piping
                                                    16

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        Regeneration  chemicals and  chemical  mix
        systems

        Prefliters (to remove solids and organics)
        Process  controls  (for  automated
        automated regeneration cycles)
or  semi-
 Depending on the application, various combinations of
 anion, cation, and mixed-bed (anion/cation) resins may be
 used.

 4.2  Reverse Osmosis
 Reverse osmosis (RO) is a membrane separation process
 that separates  dissolved salts  from water  using a
 hydrostatic pressure gradient across a membrane. An
 applied hydrostatic pressure  exceeding the  osmotic
 pressure of the feed solution causes water to flow through
 the membrane from the more concentrated feed solution
 into the relatively low-concentration  permeate solution.
 This flow is the reverse of natural osmotic diffusion where
 water  would  flow  from  the  dilute .phase  into  the
 concentrated phase. Dissolved solids are  rejected by the
 membrane surface. Many multi-charged ions can be
 rejected at rates exceeding  99%. Single-charged ions
 typically have rejection rates in the range of 90-96%.

 Three important parameters impact the performance of the
 RO process:

    •    Recovery, defined as the percentage of the feed
       that is converted to permeate

    •   Permeate flux, or the rate at which the permeate
       passes through the membrane per  unit of
       membrane surface area

    •   Rejection,  which  describes  the  ability of the
       membrane to restrict the passage  of  specific
       dissolved salts into the permeate
The flux is determined by the hydrodynamic permeability
and the net pressure differential (hydrostatic pressure
difference between feed and permeate minus the osmotic
pressure  difference)  across the  membrane.  Higher
pressure differentials generally result in higher flux rates.
The applied pressure is generally between 400 and 800
PSI. In some specialized applications, pressures greater
than 1000 PSI are used. Permeate flux decreases over
time as an  RO system is operated and the membranes
become fouled. Periodic  cleaning  of  the  membrane
restores flux. Cleaning should be initiated when a decrease
of  10-15%  permeate  flow,  an increase of 10-15%
normalized differential pressure or a decrease of 1-2%
rejection is observed.

Rejection efficiency is specific to each component, and is
a function of concentration gradient across the membrane.
As  the  concentration gradient increases, the rejection
efficiency decreases. The  leakage of various salts is a
function of the molecule size, ion radius, ion charge and the
interacting forces between the solute and the solvent. The
rejection of organic molecules is mainly a function of the
molecular weight and size of the molecules.

4.2.1  Applications
Reverse osmosis is used in the surface finishing industry
for purifying rinse water and for recovery of chemicals from
rinse waters. It has also been used to purify raw water for
the generation of high-quality deionized water in rinsing and
plating solutions. Figure 4-2 presents a reverse osmosis
flow schematic for rinse water applications.

Reverse osmosis applications involving the separation of
plating chemical drag-out  from rinse  water have been
applied  mainly to nickel plating  operations (sulfamate,
fluoborate,  Watts and  bright nickel). Other  common
applications include copper (acid and cyanide) and acid
zinc.  Recently,  RO has been applied  successfully to

	 	 n- 	 £*;•»»»
*• — ° « 	
High pressure
pump
Periodic
cleaning* 	

/ t (y\ ~~
/ * /--<
Pre-filter High pressure
pump
/^ Cone.
" " ^y recycle
(optional)
Reverse osmosis
	
Permeate
(to process^
i Periodic' cleaning
Concentrate waste
* *
Reverse osmosis
^^^
1
Concentrate per;c
(to reuse or treatment)
periodic cleaning waste
	 1
Permeate
recycle
(optional)
i Permeate
| (to process)
>dic cleaning waste
+
Figure 4-2. Reverse osmosis system.
                                                  17

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chromate rinse water. In the typical configuration, the RO
unit is operated in a loop with the first rinse following plating.
The concentrate stream is recycled to the plating bath and
the permeate stream is recycled to the final rinse.

Reverse osmosis is commonly used for water treatment
(with and  without ion  exchange) applications requiring
production of high-quality water from high total dissolved
solids (TDS) sources. Large-scale wastewater recycling is
evolving as an important application for RO in the surface
finishing industry. Microfiltration, ultrafiltration, nanofiltration
and reverse osmosis are often used in series to provide
pretreatmentfora range of filtration size separation needs
and to maximize performance of the total system.

Specialty membranes are available that offer an extended
pH range (1-13) and  greater resistance to oxidizing
chemicals.

4.2.2  Limitations
Membrane performance of all polymer-based membranes
decreases overtime. Permeate flow (flux) and membrane
rejection performance are reduced. RO membranes are
susceptible to fouling by organics, water hardness, and
suspended solids  in the feed stream or materials that
precipitate during processing. Installing prefilters can
control solids  in the.feed stream. Changing operational
parameters, such as pH, inhibits precipitation. Oxidizing
chemicals like peroxide, chlorine and chromic acid can
also  damage polymer membranes. Acid and alkaline
solutions with concentrations greater than .025 molar can
also deteriorate membranes.

 In most applications, the feed solution will have significant
 osmotic  pressure  that  must  be  overcome  by the
 hydrostatic pressure. This pressure requirement limits the
 practical  application of this technology to solutions with
 total dissolved solids concentrations below approximately
 5000 ppm (with the exception of disc tube applications).

 Specific ionic levels in the concentrate must be kept below
 the solubility product points to prevent precipitation and
 fouling. Ionic species differ with  respect to  rejection
 percentage. Some ions such as borates exhibit relatively
 poor rejection rates for conventional membranes.

 4.2.3 Secondary Stream(s)
 Reverse osmosis concentrate streams can be recycled to
 the process, sent to reclamation, or  managed as a
 concentrated waste. Acid, EDTA and alkaline cleaning
 solutions are used to clean RO membranes, depending on
 the nature of the foulant. These cleaning solutions  are
 residual wastes that need to be managed.

 4.2.4 Reverse Osmosis Systems
 Typical system components include:

     •   Pressure  vessel(s)  with application-specific
         membrane modules
   •   Applicable feed, pressure, and recycle pumps,
       valves, and piping

   •   Application-specific  flow,  level,  temperature,
       conductivity, and pressure instrumentation and
       controls

   •   Feed and discharge tanks and systems

   •   Application-specific pretreatment systems (e.g.,
       cartridge  filtration,   carbon,  pH   adjustment,
       microfiltration, ultrafiltration, nanofiltration)

Selection of the RO membrane type depends on both the
application and the plating bath chemistry. RO membranes
are most common  in spiral-wound  or  hollow fiber
configurations. More advanced systems use a disc tube
modular configuration.

Many systems are designed with two or more RO stages.
This design feature will allowthe concentrate stream from
the first stage to be passed through a second stage to
further concentrate the chemicals. The practical limit for
plating chemical concentration is up to 15 to 20 g/L (or lower
if compounds are neartheirlimitforprecipitation). In some
cases, insufficient surface evaporation in the plating tank
limits  direct reuse of the RO concentrate stream.  An
evaporator can be used to further concentrate the solution
or to supplement bath evaporation.

4.3   Vacuum Evaporation
Vacuum evaporators distill waterfrom process solutions at
reduced  temperatures  compared  with   atmospheric
evaporation. Vacuum evaporators work without the need
for an air stream feed or discharge. Vacuum evaporators
produce a distillate and a concentrate. The distilled water
is typically condensed and recovered as high-quality rinse
water. The  concentrate contains process  chemistry to
return to the appropriate process bath. Figure 4-3 provides
a process flow schematic for vacuum evaporation.

4.3.7   Applications
Vacuum evaporators are used for concentrating and
recovering  process solutions  and  rinses,  and  are
particularly well-suited for specific applications where:

    •   Air  pollution control is a potential  problem  (Air
        discharge is typically not an issue for vacuum
        evaporation).

    •   Relatively low evaporation  temperatures  are
        needed to avoid problems with temperature-
        sensitive products.

    •   Alkaline   cyanide   solutions   that  build   up
        carbonates are present (atmospheric evaporators
        would  aerate the solution and  accelerate the
        buildup of carbonates).

    •  Process solutions are sensitive to air oxidation.
                                                    18

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                                    Liquid/
                                     vapor^
                                   separatorN
                                                      Condenser
                                      Feed—••

                                     Heat
                                     exchanger
                                                                  Vacuum^
                                                                  source
                                     Condensate
                                      (distillate)
                                               Concentrate
                                             (return.to process)
 Figure 4-3. Vacuum evaporation system.
        Energy  costs
        evaporation.
are  high  for  atmospheric
 4.3.2  Limitations
 Limitations associated with vacuum evaporation systems
 include relatively high capital cost, and application-specific
 potential for fouling and separation limitations.

 4,3.3  Secondary Stream(s)
 Vacuum evaporators produce a high-quality condensate
 that can be reused as a process rinse and a concentrate
 that contains  the process  chemistry  to  be  reused,
 recycled, or managed as a waste. Potential secondary
 waste streams could be  generated if there are periodic
 system cleanout  requirements  to  remove  fouling
 compounds.

 4.3.4  Vacuum Evaporator Systems
 Several types of vacuum evaporators are used in the
 surface finishing  industry: rising film, flash-type,  and
 submerged tube. Generally,  each consists of a boiling
 chamber under a vacuum, a liquid/vapor separator and a
 condensing system. Site-specific conditions and the mode
 of operation influence the system selection.

 Energy for evaporation can be supplied either thermally
 or mechanically. Two techniques have been applied
 successfully to reduce the steam or electricity demand
for  evaporation,  multiple-effect  evaporation  and
 mechanical vapor recompression. Both involve reusing
 the heat value contained in the vapor from the separator.

 Multiple-effect evaporators are vacuum evaporators in
 series with different boiling points, operated at different
 vacuum levels. The solution to be concentrated is fed into
 the boiling chamber of the first effect and external heat is
 introduced to volatilize the water. The water vapor is then
 condensed at a different vacuum level and the energy is
 used to heat the subsequent vacuum chamber. Energy is
 used several times in multiple stages. Multiple-effect
 evaporators are practical for larger scale applications and
 those in which high-boiling point elevations make vapor
 compression  ineffective.   These  systems can  be
 configured so that a final effect can create crystal solids.
 Increasing  the number of  effects increases  energy
 efficiency, but also increases the capital cost  of the
 system. Optimization involves balancing capital versus
 operating costs.

 The second technique is  the  use of a mechanical
 compressor. These evaporators are similar to single effect
 units, except that the vapor released  from the boiling
 solution is compressed in  a mechanical  or thermal
 compressor. This compressed water vapor condenses,
yielding latent heat of  vaporization, which  is  used to
evaporate more waterf rom the Concentrated liquid. These
types of evaporators  can concentrate to about 50%
dissolved solids, and evaporative capacities  range from
200-2400  liters  (50-600  gallons) per hour.   Vapor
                                                  19

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recompression evaporators are the highest-capital-cost
evaporators, but are the most energy efficient.

4.4  Atmospheric Evaporation
Atmospheric evaporators use an air stream to strip water
from a process solution. The process solution is pumped
through the evaporator where it contacts the air stream
blown through the evaporator. The humidified air stream is
discharged to the atmosphere. The evaporation chamber is
usually filled with a packing material to increase the air-to-
water evaporation surface.  Depending on the process
solution and air conditions, heating the process solution
and/or the air stream may be necessary to achieve
sufficient evaporation.

4.4.1   Applications
Atmospheric evaporators are relatively basic, uncomplicated
low-capital-cost systems. Atmospheric evaporators are
used in conjunction with plating bath rinses to recover
process chemistry  removed  by drag-out. Two basic
approaches where atmospheric evaporators are used to
help achieve chemical recovery:

    •   The solution from a heated plating tank is fed to
        and concentrated by an atmospheric evaporator
        and returned to the plating tank. This increases the
        quantity of recovery  rinse water that can be
        transferred to the plating tank.

    •   The recovery rinse water is fed to the evaporator,
        concentrated, and returned to the plating tank.

 Figure  4-4 illustrates  a process  flow  schematic for
 atmospheric evaporation. One application particularly well-
 suited for atmospheric evaporation is drag-out recovery for
 hard chrome baths,  where  heat  is suppljed  to  the
 evaporator by the hard chrome bath. This achieves drag-
 out recovery  and removes excess heat from a high-
. amperage plating bath.

 4.4.2   Limitations
 Atmospheric evaporation systems have several limitations:

     •    When the feed process stream and/or air stream
         needs to  be  heated,  atmospheric evaporators
         typically have a high energy use.

     •    The discharge air stream may require treatment to
         avoid discharge of hazardous substances.
   •   In  some  applications,  there  is  a  risk  of
       overconcentration and fouling the evaporatordue
       to salting-out.

   •   Surfactants or wetters used in plating baths can
       cause foaming problems in the evaporator.

   •   Some bath constituents may be susceptible to
       heat degradation or may be oxidized by exposure
       to air.

   •   Aeration of the process solutions can  cause
       carbonates to build up.

   •   Recovery  results vary depending on changing
       process conditions and air stream conditions.

4.4.3  Secondary Stream(s)
Humidified  air streams are vented from atmospheric
evaporators. These streams may present air emission
problems.

4.4.4  Atmospheric Evaporation Systems
Common atmospheric evaporator system components
include:

    •   Process solution feed pump

    •   Blower to draw air into and move through the
       evaporator with sufficient exit velocity

    •   Heat source

    •   Evaporation chamber in which the water and air
       can be mixed

    •   Mist eliminatorto remove any entrained liquid from
       the exit air stream

Typical commercial units have evaporation rates of 10 to
30 gph, depending on the size of the unit and.operating
conditions   (e.g., solution  temperature).  For  larger
applications, multiple atmospheric evaporators are used in
parallel.

4.5  Other Technologies
Table 4-2 presents comments for six technologies that are
commercial technologies with relatively limited  surface
finishing  rinse  applications,  or  that are  emerging
technologies:
                                                   20

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                                                                 Liquid/
                                                                 vapor
                                                             to atmosphere
                                                    Feed	•

                                                     Heat
                                                  exchanger
                                         Inlet
                                        ' Air '
                                          T > ambient
                                          P< ambie it
                                                              Liquid/
                                                               vapor
                                                            Separator
 Figure 4-4. Atmospheric evaporation system.
                                                                Concentrate
                                                            (return.to process)
 Table 4-2. Technologies for Surface Finishing Rinse Applications

    Technology                     Description
                                               Status
                                                                                            Applications and Limitations
 Electrodeionization
 Electrodialysis
Electrowinning
Nanofiltration
Polymer Filtration
Ultrafiltration
 Ions are removed using conventional ion
 exchange resins. An electric current is
 used to continuously regenerate the
 resin (instead of regeneration chemicals).


 Anions and cations are removed from
 solutions with an applied electric field in
 cells with alternating anion- and cation-
 permeable membranes.

 Electrodes are placed in solutions,
 and direct current power is applied.
 Electrochemical reactions occur at
 the electrode/electrolyte interfaces.
 Cations migrate to, and. electrons
 are consumed  at the cathode (reduction).
 Anions migrate to, and electrons are
 supplied at the anode (oxidation).
Membrane filtration that operates at
larger pore sizes (rejects molecules
larger than 0.001 to 0.08 microns),
and lower typical pressure (50 to 400 psi)
than reverse osmosis.  Preferentially rejects
some ions and passes others.

Chelating, water soluble polymers
selectively bind target metals in aqueous
streams.

Membrane filtration process  that passes
ions and rejects macromolecules
(0.005 to 0.1 micron).
Commercial
technology;
limited surface
finishing applications.


Commercial
technology;
limited surface
finishing applications.

Commercial
technology;
widely used for
removal of metals
from surface finishing
concentrated solution;
limited applications
for rinses.
                                                                 Commercial
                                                                 technology;
                                                                 limited surface
                                                                 finishing applications.
 Effective for relatively high-purity water
 purification/recovery applications, including
 polishing treatment of reverse osmosis
 permeate to meet process
 rinse purity requirements.

 Electrodialysis has been used in the surface
 finishing industry to recover nickel salts from
 rinse water.
Electrolytic cells that use a metal fiber
cathode have demonstrated the ability to
remove less-noble metals, such as copper
and cadmium, from recirculated rinses to
concentrations in the range of 10 to 50 mg/L.

High-surface-area units are used to recover
metals from cyanide-based plating process
rinses (e.g., cadmium, copper, zinc, and
brass). These units remove metal ions to
low concentrations and also oxidize the
cyanide in the rinse water.

Recovery of metals and water recycle for
rinse waters.
                                                                 Emerging
                                                                 Commercial
                                                                 technology;
                                                                 limited surface
                                                                 finishing applications.
                     Selective metals removal from rinse waters.
                     Removal of oils, colloidal silica, particles, and
                     proteins from rinse waters for reclamation.
                                                              21

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           5.   Alternative  Surface Finishing  Processes and Coatings
Process substitution is a form of process optimization,
where environmentally  cleaner process  alternatives
replace existing processes in part or in whole. Process
substitution, however, will not  automatically  result  in
cleaner manufacturing. In assessing alternative processes,
the  first step  is  to  review existing  processes  for
opportunities to optimize those processes. Adaptation of
new processes is generally desirable when implemented
on a progressive  basis,  but  can  often fail when
implemented without  careful  planning basis. Process
change can  be  complicated  and deserves careful
evaluation.  New processes  may present unexpected
problems that are relatively difficult to manage compared
to known problems with existing processes.

Successful  process  substitution requires  well-defined
goals. This involves identifying the drivers which impact
the   manufacturing   process.  Too   often,   process
substitution is begun  prematurely  without  a  clear
understanding of the drivers and constraints.

 One common misconception is that toxic use reduction
(TUR) and toxic waste reduction (TWR) are synonymous.
TUB may require process change; whereas, TWR often
favors process optimization. Toxic  use reduction has a
primary goal of reducing the amount of hazardous raw
materials used. This goal can be accomplished by a variety
of methods that follow substitution,  reuse and  recycling.
Toxic waste reduction seeks to reduce hazardous waste
generation by optimizing the existing process, rather than
a wholesale process  substitution. Both techniques can
 result in  more efficient  processes by  incorporating
 recovery and/or recycling options.

 Another common misconception in process substitution is
 that substitute technologies must embody all of the
 finished surface properties of the existing finished surface.
 Alternatives should possess the properties critical to that
 application. The  application should  be  assessed  to
 determine critical and non-critical properties. The result will
 be a wider range of possible alternatives.

 Athird common misconception is that alternatives must be
 universal. There are rarely any universal substitutes.
 Instead, several alternatives may be required to satisfy a
 range of applications.
5.1  Process Engineering and
     Re-engineering
Process  engineering  and  re-engineering costs and
success can be impacted by a variety of factors, including
chronology.  Mature processes  are often  significantly
constrained by product specifications and the expected life
of the process. A process that will be phased out within a
few years will undoubtedly receive little new investment for
engineering or capital. Many mature processes are also
constrained by risk factors. A failure of a new coating in a
jet engine can result in human tragedy. Process changes
can require significant testing and associated costs.

How changes impact overall product and process flow is
also an important consideration. Manufacturing flow  is
becoming more cellular and this  results in the addition of
multiple smaller-scale  wet processes to  support the
manufacturing cells. Key questions to consider for overall
impacts:

    •   How will new process(es) affect manufacturing
        flow?

    •   How will the new process(es) fit into the overall
        facility?

5.2  Surface Finishing Properties
Finished surface properties and variability with different
process factors are  important to evaluate to consider
substitute processes. Decorative and functional properties
are affected by key process parameters such as solution
concentration,  bath  additives,  bath  temperature, and
current density. Careful consideration of these parameters
in the context of process substitution or optimization is key
to successful process change. Coating  adhesion, pre-
 processing requirements, and plating characteristics over
 a range of operating parameters all can vary for a process
 substitution.

 Questions to consider for potential substitutions include:

     •   How will processing times be affected?

     •   Are different pre-processing steps required?

     •   How will the pre-processing treatment steps affect
        the substrate?
                                                    22

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    •   Will additional procedures, such as grinding or
        coating, be required to achieve the final surface
        requirements?

5.3  Surface Engineering
Surface  finishing  is  an  integrated  system.  Surface
engineering that considers the entire product manufacturing
cycle will result in much greater choices and efficiency.
Successful process change is the product of a logical
evaluation of not only the immediate process, but also how
this process  fits into  the   scheme  of  the  entire
manufacturing picture.

5.4  Surface Finishing Costs
Overall costs to produce a finished surface determine the
efficacy of a process substitution. Coatings are generally
applied to reduce net product cost and/or enhance product
properties. Copper-plated aluminum may be used instead
of  solid  copper to reduce  cost or  weight.  In  many
applications, both the substrate and the coating are critical
to the application. The substrate provides material strength
or other properties, while the coating provides corrosion
resistance or cosmetic appeal. Polished stainless steel is
often used in place of chromium-plated trim. Chromium-
plated plastic may be a viable lower-cost alternative to
stainless steel.

5.5  Alternative Coatings and  Processes
There is a wide range of alternative processes and coatings
available. Some are common surface finishing techniques
in which the range of application is being expanded by
subtle  change.  Others are newer  solutions  that have
applicability in specific situations, such as vacuum and
thermal spray  techniques.  Alternative  coatings and
processes include:

   1)  Alternative Electroplated and Electroless Coatings

   2)  Anodizing

   3)  Organic Coatings

   4)  Vapor Deposition

   5)  Thermal Spray

   6)  Hardfacing

   7)  Porcelain Enameling

   8)  Metal Cladding and Bonding

   9)  Alternative Substrates

  10)  Alternative Substrate Treatments

  11)  Alternative Surface Preparation

  12)  Alternative Stripping Processes
  13)  Alternative Pickling and Descaling

  14)  Alternative Etching

  15)  Alternative Cleaning

  16)  Forming and Fabrication

 5.5.1  Alternative Electroplated and
        Electroless Coatings
 Much  process  change  is  focused  on  alloy  plating
 techniques. For some applications, alloy  plating  can
 replace chromium, cadmium and other metals. These
 solutions require more attentive control and are typically
 more difficult to recover from rinse streams, primarily due
 to the selectivity of recovery processes for specific atomic
 species. The control and recovery factors, if not properly
 handled, can lead to increases in labor, processing times
 and product defects.

 Alloy plating processes include nickel/tungsten/boron, tin/
 nickel, tin/zinc,  zinc/nickel,  copper/tin/zinc, and zinc/
 cobalt alloys. Nickel composite processes are important in
 applications requiring lubricity and/or wear resistance.
 Aluminum electroplating has replaced cadmium in some
 applications. Zinc and cadmium (cyanide and non-cyanide)
 are the most important  sacrificial .coatings available.
 Copper (cyanide and non-cyanide) plating is ubiquitous.
 Trivalent chromium has replaced hexavalent chromium in
 many decorative plating  applications and is becoming
 more important in functional applications.  Nonchromate
 conversion coatings are  evolving rapidly, and in some
 cases offer better  performance than chromates.  Silver
 (cyanide and  non-cyanide), tin and  lead-free tin-alloy
 plating alternatives have  also been developed and  are
 gaining  acceptance in some applications.  Electroless
 alternatives include nickel, copper, gold,  silver, cobalt,
 platinum, palladium, ruthenium, and palladium, ruthenium,
 rhodium, and iridium alloys. Hot dipping processes include
 zinc,  aluminum,,  tin  and lead. Mechanical  plating
 processes  include zinc,  cadmium,  zinc/cadmium,  tin/
 cadmium, tin, copper, and lead.

 5.5.2 Anodizing
 For many years, sulfuric acid anodizing and chromic acid
 anodizing have been used widely in industry. One of the
 main benefits of chromic acid anodizing is that residue in
 lap joints  or blind  holes  is not  corrosive to the part.
 However, in this age of strict specifications, the staining
these residues cause leads to rejection on  a cosmetic
 basis. In addition,  the residue represents lost material
valuable to the process. Coupled with risk from its health
 hazards, chromic acid anodizing is declining. In many
applications it can be replaced  by sulfuric/boric acid
anodizing.

Other alternative anodizing processes include sulfuric,
sulfuric/oxalic, sulfuric/boric, phosphoric, oxalic, sulfamic
(NH2SO2OH),  malonic   (CH2(COOH)2),  and  mellitic
                                                  23

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(C6(COOH)6) chemistries and numerous variations thereof
with special additives.

5.5.3  Organic Coatings
Organic coatings have always  been an alternative to
electroplating, and recent formulations  and application
methods have increased the substitution of  organic
coatings fortraditional electroplating applications. Higher-
efficiency coating techniques, such as powder coating and
electrocoating,  have  made  organic  coatings  very
attractive.  In addition,  many  solvent systems  that
eliminate the traditional  VOCs  are  appearing. Some
drawbacks occur with two-part epoxy finishes, due to their
limited application times, ("pot life") after mixing. Another
difficulty that can  arise,  particularly with thermal  cure
coatings, is a loss of viscosity priorto final cure. This effect
can result in non-uniform coatings. Sometimes, partial cure
can reduce this effect. Many of the more efficient coating
techniques are capital-intensive for  equipment. Since
newer coatings are quite expensive, it is easier to justify
equipment on the basis of savings these improvements
yield.  Organic  finishing  can  produce  bright,  metallic-
looking coatings, as well as a variety of colors and textures.

Coating techniques include spray coating, powder coating,
electrocoating, autodeposition and dip processes. Organic
coatings are made up of polymers or binders, solvents,
pigments and  additives. Polymers or  binders include
natural oils,  alkyds,  polyesters, aminoplast resins,
phenolic resins, polyurethane resins, epoxy resins, silicon
resins, acrylic  resins, vinyl  resins,  cellulosics  and
fluorocarbons. Pigments are classified as colored, white,
metallic and functional. Solvents are classified as active
solvents,  dilutants  and  thinners.  Additives  include
surfactants,  colloids, thickeners, biocides, fungicides,
freeze/thaw stabilizers, coalescing agents, defoamers,
plasticizers, flattening agents, flow modifiers, stabilizers,
catalysts  and  anti-skinning agents. Organic  coatings
 require careful screening to optimize life cycle cost factors.

 5.5.4 Vapor Deposition
Vapor deposition  offers  finishing alternatives  in some
specific and ever- expanding applications. The equipment
 used  is relatively expensive,   can  require  high-level
 operators  and  is  sensitive  to contamination.  Vapor
 deposition is, generally, a high-vacuum process. The
 systems are sensitive to humidity, often require controlled
 environments  and  are  vented with  dry  nitrogen  or
 compressed air. Some cycle times are quite short, while
 others can take several hours.

 In a typical vapor deposition system, two or more stages
 of vacuum pumping are required (rough and high vacuum).
 Mechanical roughing pumps can achieve pressures of 10-
 100 to millitorr (760 torr = atmospheric pressure). High
 vacuum pumps can achieve pressures in the range of
 10-s-10'a torr. These systems  operate by isolating the
 vacuum chamberf ram the pumps, enabling the parts to be
 handled without complete  system shutdown.  A typical
 operating cycle involves set-up, rough pumping, high-
vacuum pumping, coating, venting and part removal. Cycle
times can be as short as a few minutes or may require
several hours. Internal systems to coat  the parts vary
depending on the coating material and performance
requirements. There  are  three basic types of vapor
deposition systems: chemical vapor deposition, physical
vapor deposition, and ion vapor deposition.

Chemical vapor deposition (CVD) is  a  heat-activated
process that relies on the reaction of gaseous chemical
compounds with heated and suitably prepared substrates.
The CVD process can produce a variety of high-density,
high-strength, and high-purity coatings. The process has
exceptional throwing power, and complex components can
be  coated  successfully.  Most  materials   readily
electroplated are not suitable  for CVD because these
metals are  not normally available as CVD-compatible
halide salts.

In CVD, an inert gas is bled into the system after pump-
down, to a few torr of pressure. A high voltage is applied to
the gas to create a reactive plasma. Depending on the
material used forcoating, it may be evaporated directly and
then ionized in the plasma, or  ions may combine with a
second  gas (oxygen or  nitrogen, for  example) and
molecules will cool and crystallize upon striking the part
surface. The compound formation reaction usually occurs
in the plasma. Plasmas are very energetic, and care must
be exercised to prevent overheating the parts.  Typical
coatings  include refractory compounds and refractory
metals.

Physical vapor deposition  (PVD) uses similar equipment
and operating procedures. PVD describes a broad class of
vacuum coating processes, wherein material is physically
emitted  from a source by evaporation or  sputtering,
transmitted through a vacuum or partial vacuum by the
energy of the vapor particles, and condensed as a film on
a substrate. Chemical compounds are deposited  by
 selecting an equivalent source or by reacting the vapor
 particles  with  an  appropriate  gas.  Three   primary
 characteristics  of  all  PVD   processes are:   source-
 generated coating emissions, vapor transport through a
 vacuum, and condensation on  a substrate.

 The PVD process is generally limited to thinner coatings of
 1-200 microns. Fixturing is critical because the process is
 "line-of-sight." Stationary, rotary and rotary with planetary
 motion fixtures are used to produce uniform coatings on
 complex parts. The  process  is  capable of producing
. coatings with  extraordinary decorative and functional
 properties.

 Ion vapor deposition (IVD) was originally developed as an
 ion plating process for aluminum. The properties of IVD
 aluminum coatings are nearly identical to aluminum. The
 IVD process takes place in an evacuated chamber where
 an inert gas is added to raise the pressure of the chamber.
 The gas (typically argon)  becomes ionized when a high
 negative potential is applied to the parts to be coated. The
                                                    24

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 positively charged ions bombard the negatively charged
 parts and provide final cleaning. Aluminum or other metals
 are melted and vaporized in the chamber, and some metal
 vapor is ionized, coating the parts. The  IVD process
 produces dense, highly adherent and uniform coatings over
 complex parts. Hydrogen embrittlement is notafactor. IVD
 eliminates solid-metal embrittlement of titanium and does
 not reduce the fatigue strength of aluminum.

 Other more specialized vapor deposition processes are
 vacuum metallizing and sputtering. Vacuum metallizing
 consists of evaporating a metal or metal compound at high
 temperature in  an  evacuated chamber.  The vapor
 condenses on a substrate in the chamber, at a relatively
 low temperature. Vacuum metallized coatings are typically
 very thin, 0.2-20 microinches. Decorative products are
 typically coated with protective organic  topcoats. In
 principle, virtually all metal and metal compounds can be
 deposited as coatings. In practice, the process has been
 generally limited to aluminum, selenium, cadmium, silicon
 monoxide,  silver,  copper,   gold,   chromium,  nickel-
 chromium, palladium, titanium and magnesium fluoride.

 Sputtering is a specialized PVD process. Virtually all
 metals  and compounds can be  sputter-coated. This
 technique generates an  energetic particle that strikes a
 target of the coating material, ejecting a molecule that
 strikes and cools on the part.  Sputtering is very much a
 "line-of-sight" process and has difficulty coating surfaces
 perpendicular to the target plane. Coatings are generally
 thin (angstroms to microns), although thicknesses greater
 than 25 microns are possible. A variety of PVD processes
 exist, including:

    •    Diode  and triode sputtering

    •    Planarand cylindrical magnetron sputtering

    •    Direct  current (DC) and radio frequency (RF)
        sputtering

    •    Electron beam evaporation

    •    Arc evaporation

 5.5.5  Thermal Spray
Thermal spray is a process that deposits a molten and
semi-molten matrix, including  metals, metal alloys and
ceramics on substrate materials. The process does  not
normally change the  mechanical  properties of  the
substrate. Spray materials can be in the form of rod, wire,
cord or powders. Materials are heated to a molten or semi-
molten state and then atomized or projected onto the target
substrate. Heating is accomplished by a variety of means.
As sprayed particles strike the substrate, they flatten and
form thin platelets.

Coating techniques include flame spray, high-velocity oxy/
fuel (HVOF), electric arc, plasma spray, and detonation
gun. A wide range of coating compositions is possible with
 thermal spray. Substrate heating  is normally minimal.
 Surface preparation is  usually limited to cleaning and
 roughening.  Masking  and fixturing  are important for
 effective coating.  Fixtures become coated  during the
 process and will require frequent stripping, using strong
 acids to maintain the fixtures. Thermal spray is a line-of-
 sight process and coating of complex components can be
 difficult. Automation  of the  process with  robots or
 specialized machinery is almost always required  for a
 quality coating. Post-coating finishing, such as grinding, is
 usually required to obtain desired surface finish because
 the as-sprayed surface finish is often rough.

 5.5.5   Hardfacing
 Hardfacing produces a buildup of material in specific areas
 to  improve wear resistance or to reclaim worn parts.
 Mechanical  finishing  techniques  such as  grinding,
 polishing and lapping may be required to achieve the
 desired work surface. Hardfacing materials are generally
 applied by a variety of welding methods. Very thick layers
 can be built  up with manual or automated equipment.
 Thermal spray and hardfacing coatings include tungsten
 carbide, high chromium irons, martensitic alloy irons,
 austenitic alloy irons, martensitic,  semi-austenitic and
 pearlitic steels, chromium-tungsten alloys, chromium-
 molybdenum alloys, nickel-chromium alloys, chromium-
 cobalt-tungsten   alloys,  nickel-based  alloys,  and
 copper-based alloys.

 5.5.7  Porcelain Enameling
 Porcelain enamels are highly durable, alkaliborosilicate
 glass coatings bonded  by fusion to a variety of metal
 substrates at temperatures  above  800°F.  Porcelain
 enamels differ from other ceramics by their predominantly
 vitreous nature. Porcelain enamels  have good chemical
 resistance,  good  corrosion  protection,  good  heat
 resistance, reasonably good abrasion resistance and good
 decorative properties. Porcelain enameling is commonly
 applied to food processing equipment, cooking and serving
 utensils, jet engine components, induction heating coils,
 transformer cases, mufflers,  home  appliances,  and
 architectural materials.

 5.5.5  Metal Cladding and Bonding
 Metal cladding and bonding applications include stainless
 steel (SS) to copper and aluminum cookware, titanium and
 SS to copper and aluminum buss bars, electroplated
 plastic to aluminum and steel automotive components.

 5.6  Alternative Substrates
 Alternative substrates  can replace  many  coatings.
 Stainless steel is  commonly substituted for chromium-
 plated steel. Copper replaces copper-plated aluminum.
 Anodized aluminum replaces chromium-plated steel in
 some  applications. As the  environmental  costs of
.manufacturing processes are considered in overall product
 cost, more-expensive materials can often be justified.

Alternative substrates include stainless steel, copper and
copper  alloys,  aluminum and magnesium,   titanium,
                                                  25

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tungsten  and   molybdenum,  superalloys,  plastics,
composites, and powdered metals.

5.6.1   Alternative Substrate Treatments
Alternative substrate treatments can be used to extend the
application range of coated and  uncoated  substrates.
Many substrate treatments are available including vacuum
impregnation,  heat treatment,  ion  implantation, laser
hardening, carburizing, electron-beam hardening, nitriding,
flame hardening, carbonitriding, boronizing,  chromizing,
induction hardening  and high-frequency resistance
hardening. With the exception of  vacuum impregnation
these treatments usually convert the surface structure of
the metal substrate by the addition of small amounts of
various elements at elevated temperatures. The crystal
structure of the surface is altered and the new surface
provides additional  hardness,  wear  resistance  or
toughness,  depending on the specific  treatment used.
These treatments often allow the substrate to function with
 little additional surface treatment, thereby reducing  the
 plating or surface finishing steps required.

 5.7  Alternative Surface  Preparation
 Many alternative surface preparations can be used to
 extend  the application  range  of  substrates  or to
 complement treatment and coating processes. Surface
 preparation, prior to plating and finishing, is also an
 important surface finishing stepfrom a pollution prevention
 standpoint. First, these techniques remove loose metal
 chips and also deburr parts. If left on the part, burrs  can
 dissolve preferentially  in many  of the  pretreatment
 solutions, adding to metal loading. They also alter the local
 current density and can lead to additional rejects. Finally,
 these  surface  preparations can'impact compressive
 stresses on the part, which improve fatigue strength. This
 can improve plating adhesion and  lengthen the service life
 of the  part.  Alternative  surface preparations include
 chemical polishing and bright  dipping, electropolishing,
 mass finishing, abrasive flow machining, abrasive blasting
 (dry and wet blasting), shot peening, mass finishing, and
 thermal deburring and deflashing.

 5.7.1  Alternative Stripping Processes
 Stripping process alternatives are usually focused around
 the substitution of non-maintainable strips for maintainable
 strips. Many of the non-maintainable strippers are heavily
 chelated to improve their  useful processing capacity.
 Chelating chemicals bind metals to prevent immersion
 deposition and smut formation, and separation of these
  metals to extend bath life can be difficult. In addition, these
  materials aredifficulttotreatforwaste. Maintainable strips
  are often more predictable, because some metal loading is
  maintained in the solution. This constant loading removes
  the highs and lows of processing rates related to low or high
  dissolved metal concentrations.

  Abrasive stripping alternatives are normally applied to soft
  organic coatings and are  not  generally  applicable to
  inorganic coatings. Chemical  strippers used on organic
  coatings  create  considerable  waste  volumes.  The
strippers cause swelling of the coating to destroy the
surface bond. The strippers are often hazardous, while the
cured coating is not necessarily. Abrasive blasting or water
jet blasting can efficiently remove these coatings, generate
less waste (often non-hazardous), and can be configured
with materials that do not abrade the part surface.

5.7.2   Alternative Pickling and Descaling
There  is a variety of alternative pickling and descaling
processes,  most of which are  acid-based. Alkaline
processes are normally electrolytic and have historically
contained cyanide. Non-cyanide alkaline descalers are
heavily chelated and can cause wastewater treatment
problems. Chromic acid is normally used for nonferrous
alloys. Nonchromic alternatives almost always contain
nitric acid, and NOJs  becoming  an  increasing difficult
environmental control problem. Acid salts are commonly
substituted for mineral acids, and ammonium bifluoride is
substituted for HF to minimize safety concerns. Ammonia,
however, can cause wastewater treatment problems.
Potassium permanganate is used for descaling wire and
other steel products, and molten salt descaling is used for
a variety of applications.

 5.7.3  Alternative Etching
Aluminum finishers  often used etching as  a cleaning
 process, which generated  a considerable  amount of
 unnecessary  waste. Caustic etching is  a source of
 considerable waste. Substrates are often over-etched,
 generating excessive  dissolved  aluminum. Aluminum
 preparation for  anodizing, chromating or electroplating
 does not always require etching. Acid etching is commonly
 substituted for alkaline  etchants in aluminum finishing and
 yields a lighter etch. Non-etch cleaners are available. The
 printed  wiring board (PWB) industry uses a variety of
 etchants. Considerable effort has been focused on fully-
 additive processing as  an alternative  to  subtractive
 processes. PWB etchants include peroxide, ammoniacal,
 cupric chloride, ferric chloride, and chromic acid.

 5.7.4  Alternative Cleaning
 Proper cleaning and preparation forfinishing is critical. With
 the environmental controls required for vapor decreasing,
 a variety of technologies have re-emerged. Typically, the
 lower vapor pressure cleaners (aqueous, semi-aqueous,
 etc.) were not used because of the additional rinsing and
 drying  steps required compared to  vapor decreasing.
 Generally, these  cleaners  have  higher  soil-bearing
 capacities than vapor-phase solvents. Efficient rinsing is
  important, because residues can interfere with subsequent
  processes or can corrode the part surface.  Selection of
  alternative cleaning equipment, however, is often more
  important  than the chemistry. Many of the alternative
  cleaning  technologies  can  be operated  at elevated
  temperatures to improve evaporative drying. Hot rinses
  and air knives are often used to assist drying. With some
  metals, rust-inhibiting additives  are used to prevent
  corrosion  from occurring before  final  processing is
  completed. A variety  of cleaning equipment is available.
                                                     26

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Alternative cleaning processes include aqueous, semi-
aqueous, solvent, abrasive blasting and vacuum de-oiling.

5.7.5  Alternative Cleaning Equipment
Various equipment features are added to improve the
activity of the cleaner on soils. These features include
mechanical agitation, sprays, eductors (fluid jets)  and
ultrasonics. All  act to mechanically remove soils  and
particles, as well as carry fresh solution to the part surface.
Vapor degreasers are still used in strategic applications,
particularly in ultra-precision cleaning. The new solvents
are expensive (some approaching $100/gal) and are used
in  totally enclosed machines. Many shops that used
traditional  vapor  degreasing  have  switched  back to
trichloroethylene while other alternatives are investigated.
Alternative cleaning equipment includes immersion, spray,
spray-under-immersion, ultrasonic, vapor degreasing and
hermetically sealed vapor degreasers.
5.7.6  Forming and Fabrication
Improving forming and fabrication processes can often
reduce surface finishing requirements. Improved casting
methods can reduce surface porosity, improve surface
finish, and reduce surface contamination and inclusions.
Improved rolling, forging, drawing and stamping can reduce
burrs, and  likewise  reduce surface contamination and
inclusions.  Improved substrates  can  also dramatically
reduce  surface  finishing  costs  by reducing  surface
preparation. Furthermore, standardizing and maintaining
coolants and  lubricants  can substantially  reduce in-
process and final cleaning requirements. Depending upon
the cleaning process used, petroleum-based lubricants
may be easier to clean and/or separate from cleaners.
Coordination between forming and fabrication operations
and  surface finishing operations can pay enormous
dividends.
                                                 27

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                6.    Existing Processes, Conditions, and  Practices
A  range  of process conditions  and practices can be
changed  to reduce the generation of waste. General
approaches are described below, with specific examples
listed in Table 6-1:

    (1) Improve facility conditions and housekeeping.
       General facility conditions  and housekeeping
       practices can be improved to help reduce process
       bath  contamination and  overall facility waste
       generation.

    (2) Reduce process  solution drag-out. Reducing
       process  solution  drag-out  directly  reduces
       process solution contaminant loading to  rinse
       baths and subsequent  wastewater treatment
       systems. Since drag-out removes process bath
       contaminants as well as beneficial chemicals, the
       impacts  on bath  contamination  buildup  and
       potential bath purification requirements should be
       considered  when  evaluating  any  drag-out
       reduction alternative.

    (3) Improve rinsing (reduce drag-in). Improving rinsing
       performance reduces the carry-over of process
       bath constituents into subsequent process steps.
    Improving rinsing efficiency and reducing wasteful
    rinsing reduces wastewater and conserves water.

(4)  Improve process  solution  control.  Improving
    process solution control helps maintain production
    consistency  and  reduces  wastes  from  less
    efficient processing, shorter process bath life, or
    longer processing times. Methods for process
    solution  control  range from  simple  process
    operations and maintenance procedures to more
    sophisticated  systematic or  even  automated
    chemistry monitoring and controls.

(5)  Select  and   maintain  process  materials  to
    minimize contamination. Process equipment can
    contribute to  waste  generation if not properly
    selected  and maintained for the application.
    Corrosion-resistant equipment should be selected
    for new or replacement applications. Maintenance
    procedures should be developed and followed to
    maximize equipment life and minimize corrosion,
    and to avoid spills or upsets.

(6)  Enhance process  procedures.  A  number of
    process  modifications  can   reduce  waste
    generation.  Each  process  step  should  be
    considered for potential beneficial changes.
                                                   28

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 Table 6-1.
                  General Approaches and Specific Techniques for Improving Existing Process Conditions and Practices
               General Approach

 Improve Facility Conditions and Housekeeping
                 Specific Technique
 Reduce Drag-Out
Improve Rinsing
Improve Process Solution Control
Enhance Process Procedures
 Control material purchases to maximize material use and
 minimize waste
 Control air contaminants
 Plan and implement programs to avoid spills and minimize
 wastes from cleanup  operations

 Use proper rack and barrel design and
 maintenance
 Reduce plating bath viscosity (reduce temperature,
 concentration, surface tension)
 Capture drag-out before rinsing
 Install fog or spray rinses
 Use drag-out tanks to return chemicals to process tanks
 Use multiple drag-out tanks to increase the chemical
 recovery rate
 Adjust part withdrawal and drip times to minimize drag-out

 Control the rate and time of water flow to match process
 needs
 Turn off rinse water when not in use
 Use spray rinsing to mechanically remove  chemicals and
 contaminants
 Use countercurrent rinsing
 Use cascade or reactive rinsing
 Track water use

 Promptly remove materials that fall into the tanks
 Filter baths to remove suspended solids
 Use carbon filtration on baths, where effective, to remove
 contaminant  organics
 Use conductivity and pH monitoring to detect chemical losses
 Implement statistical process monitoring and control
 Implement real-time system monitoring and control

 Use good cleaning and surface preparation techniques and
 part inspections to minimize bath contamination and part
 rework
 Define water quality standards and use feed water of
 appropriate purity
 Document and follow good operating procedures
 Mask areas not to be  processed
 Eliminate obsolete processes
 Use both soluble and insoluble anodes in the same bath to
 balance cathode and anode efficiencies
 Remove anodes from idle baths where this  will reduce metals
buildup (e.g.,  cadmium and zinc anodes)
Nickel plate copper buss bars to reduce the rate of corrosion
and bath contamination
                                                             29

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                                             Conclusions
A variety of management practices and technologies are
available to  enable surface finishing  manufacturers to
approach  or achieve  zero discharge. Individual  or
combined actions consisting of source reduction, process
water recycling,  and process substitution  need to  be
considered to determine the best approach for specific
applications. Understanding  process  chemistry and
production impacts  are essential to  the identification,
evaluation,  and  implementation  of  successful  AZD
actions.  Systematic  methods can  be used to help
managers move effectively through the planning, decision-
making,   and  implementation  phases.  Systematic
considerations can be included in AZD planning to optimize
integrated process, environmental, and facility benefits.

Benefits from implementing AZD projects  can include:
reduced costs,  waste generation, and chemical usage,
increased regulatory performance, and enhanced facility
operations. However, as zero discharge is approached, the
costs for incremental discharge reductions can increase
significantly in relation to the benefits achieved.

Suggested  areas for  additional  development to help
advance AZD initiatives include:

    •   Water and rinse water quality standards

    •   Process solution contaminant standards

    •   Process  pollution  prevention  and  control
        technology  verification data linked  to specific
        applications

    •   Installed cost  and operations and maintenance
        (O&M)  cost survey data  corresponding to AZD
        implementation
                                                    30

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                                     8.   References
1)  Benchmarking Metal Finishing, National Center
    for Manufacturing Sciences, June 2000.

2)  Metal Finishing 2000 Guidebook and Directory
    Issue, Elsevier Science, Vol. 98, No. 1, Jan. 2000.

3)  21 st AESF/EPA Pollution Prevention and Control
    Conference, Jan. 2000.

4)  Products Finishing2000 Directory and Technology
    Guide, Gardner Publications.

5)  Proceedings:   AESF/EPA  Conference  for
    Environmental Excellence, Jan. 1999.

6)  Gallerani, Peter A., P2 Concepts and Practices for
    Metal Plating and Finishing, AESF/EPA Training
    Course, 1998.

7)  "19th AESF/EPA Pollution Prevention and Control
    Conference," Jan. 1998.

8)  "18th AESF/EPA Pollution Prevention and Control
    Conference," Jan. 1997.

9)  Reinhard, Fred P. and Kevin L. Klink, Innovative
    Recycling and  Maintenance Technologies for
    Surface Finishing Operations,  18th AESF/EPA
    Conference on Pollution Prevention and Control,
    Jan. 1997.

10)  "17th AESF/EPA Pollution Prevention and Control
    Conference," Feb. 1996.
11) Wick, Charles and Raymond F. Veilleux, Tool and
    Manufacturing Engineer's Handbook, "Materials,
    Finishing and Coating," Volume 3,4th Edition.

12) "Surface Cleaning, Finishing and Coating," Metals
    Handbook, Volume 5, 9th Edition.

13) Altmayer, Frank, Pollution Prevention and Control
    -An Overview, AESF Press, 1995.

14) Higgins,  Thomas  E.,   Pollution  Prevention
    Handbook, Lewis Publishers, 1995.

15) Byers, William, et al., Howto Implement Industrial
    Water Reuse: A Systematic Approach, Centerfor
    Waste  Reduction Technologies - American
    Institute of Chemical Engineers, 1995.

16) Lowenheim, FrederickA., Electroplating,Technical
    Publications, Ltd., Arrowsmith, 1995.

17) Cushnie,  George,  Pollution Prevention and
    Control  Technology for  Plating  Operations,
    National Center  for Manufacturing Sciences,
    National Association of Metal Finishers, 1994.

18) US Department of Commerce, Advanced Surface
    Engineering, NISTGCR 94-640-1.

19) Gallerani, Peter A., Summary Report: Minimization
    of Metal Finishing Wastes at Pratt and Whitney,
    Jan. 1993.
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                                           Appendix  A
             Systematic Approach for Developing AZD Alternatives
Systematic AZD planning can be achieved by integrating  process facilities. Opportunities should be identified where
holistic  and  specific  source  reduction assessment,  discharge  reductions  can  solve  discharge-related
including considerations for multiple sources, composite  problems, or can otherwise benefit production operations
solutions, life cycle design and facility optimization.       and overall costs.
Systematic AZD solutions  can be  relatively  easy to
develop, or may require extensive data collection, scenario
development and failure analysis. Accurate data collected
from technologies and process changes are needed to
evaluate case-specific application potential. Evaluation
tools  such as  process  modeling and demonstration
projects help to determine future needs. A combination of
in-plant and  outside  expertise  helps  to  focus AZD
implementation encompassing a range of applicable
solutions. The level of effort needed to pursue systematic
solutions  enables  the decision  makers to weigh the
potential value gain toward implementing a systematic
AZD solution.

Step 1.       Establish Goals
Establishing goals provides a foundation  for an AZD
project. As the project progresses, goals and priorities can
be revisited and adjusted as deemed appropriate. Although
the objective is to proceed with minimal changes, the
process  can lead to new information that results  in
decisions towards  beneficial  changes  in  goals and
priorities. For goals to be implemented effectively, they
should be specific, appropriate and measurable.

Goals directly or indirectly related to AZD are to:

    _  Achieve discharge reduction targets.

        Stay  within  budgets  and  meet  payback
        timeframes.

    _  Achieve  regulatory compliance  and beyond-
        compliance targets.

    _  Improve process consistency and quality.

    _  Improve plant space use.

    _  Meet schedule targets.

 Step 2.   Identify Opportunities
 AZD opportunities can be identified for individual process
 solutions, process lines,  multi-process  lines, or entire
General steps to identify viable AZD opportunities:

    •    List discharges  and  sources  for  potential
        reduction.  Wastewater  treatment  and waste
        disposal  data  need to be reviewed to provide
        information on discharges from process baths and
        rinses.  Discharges  can  be associated  with
        specific upstream, in-plant sources. Depending on
        the available data and the level of complexity of
        the facility processes, it  may be necessary to
        perform a plant-wide process survey to identify
        specific waste sources.

    •    Characterize sources and discharges. The type
        and magnitude of each identified discharge should
        be estimated,  including constituents, mass and
        volumetric rate, and variation with  time  (for
        projected production type and level). Table A-1
        presents   data  objectives  for characterizing
        sources  and  discharges. This can include  a
        combination of  measurements and analyses,
        calculations, and modeling.

    •   Identify drivers and benefits. Identifying drivers
        and benefits for source-specific zero discharge
        opportunities helps provide a basis for setting AZD
        goals. Benefits associated with source-specific
        reductions include a range of net cost and no-cost
        gains or improvements that would result directly or
        indirectly from actions implemented to reduce
        waste discharges. Table A-2 lists common AZD
        benefits. Drivers are major benefits that represent
        primary reasons for implementing source-specific
        AZD alternatives.

    •   Identify  impediments.   Constraints  represent
        limitations that apply to source-specific AZD
        considerations. Table A-3 lists some common
        constraints.  After constraints are  identified,
        assess whether measures could be implemented
        to remove the constraints.  For example, if  a
        capital-cost ceiling is identified for a project,  it
        might be possible to finance the capital project
        with no increase, or even a reduction in net short-
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  Table A-1.  Data Requirements for Characterizing Sources and Discharges
 Waste quantity
 and characterization data
 Production information
 Wastewater treatment
 chemical additions

 Water supply characteristics

 Chemical use and wastes
 from water pretreatment
 processing
  Bath dumps, wastewater discharge flow and analyses, waste chemicals and raw materials
  information on spills or process upsets, and residuals and byproducts from process purification
  and treatment systems (including routine operations and wastes from periodic cleaninq and
  maintenance)                                                                 a

  Process sequences and bath chemistries, process specifications, component data (type,  size
  throughput, and output), bath chemistry additions, rectifier amp-hours totals (specific to production
  periods), part rejects and reprocessing

  Chemical quantity and frequency of addition


  Total dissolved solids, conductivity/resistivity, hardness, temperature, pH, specific ions

  Chemical quantity and frequency of addition
 Table A-2.  Common AZD Benefits

    Overall Benefits
                                                                     Specifications
 Reduced costs
 Reduced waste generation
 Production improvements
 Reduced chemical use
 Increased regulatory performance
 Enhanced facility operations

 Enhanced environmental
 and production performance
 Capital costs (e.g., overall capital costs for new projects that include new or expanded wastewater
 treatment systems may have reduced capital costs due to more focus on in-piant discharge
 reductions), operating costs, and life-cycle costs

 Wastewater,  wastewater treatment residuals, bath dumps, process bath and rinse treatment
 wastes


 Reduced rejects, reduced processing variability, improved product consistency and quality
 updated/increased capacity


 Surface finishing bath chemicals, wastewater treatment chemicals, process maintenance treatment
 chemicals


 Compliance or beyond-compliance performance,  wastewater discharges, air emissions, hazardous
 wastes, and toxic chemical use

 Space availability, energy consumption, safety, and reduction of water use

 Corporate goals, customer requirements, environmental metrics
Table A-3. Common AZD Constraints

Constraints                         Specifications
Financial

Process

Facility

Equipment

Operational

Regulatory

Schedule

Data
Capital spending limits, payback timeframe requirements

Limitations on changing processes

Space or location limitations that could impact plant modifications or the addition of new systems

Existing equipment that must be used or must stay at a fixed location

Limited operator availability and capabilities

Multimedia permit requirements or triggers

Difficult requirements for project milestones and completion

Limited process data and ability to gather project data
                                                              33

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       term cash flow due to operational cost savings.
       Removing a short-term capital ceiling constraint
       could lead to significant net cost savings over the
       long term.

Step 3.       Identify and Screen
               Alternatives
 A preliminary range of plausible alternatives for AZD
should be identified to address specific AZD opportunities.
To gain afull perspective on potential costs and benefits of
AZD, it  is often beneficial to consider alternatives that
range  from  simple process modifications  to   more
comprehensive process enhancements. General types of
AZD alternatives include:

        Process solution purification systems (Section 3)

    _   Process rinse water recycle systems (Section 4)

    _   Alternative processes (Section 5)

    _   Improving existing  processes and operations
        (Section 6)

 Priorto more detailed evaluations, preliminary alternatives
 should  be screened to  eliminate those that have serious
 flaws. This will result in  a range of specific alternatives for
 detailed evaluation. Another important level of consideration
 for AZD alternatives are systematic approaches, which
 provide enhanced solutions for multiple AZD opportunities,
 and integrate overall facility and life cycle considerations.
 Section 2 discusses systematic AZD approaches.

 Target alternatives need to be defined to provide scenarios
 that can be evaluated in accordance with application-
 specific requirements.  The information needed to build a
 scenario for an AZD alternative varies substantially with
 the type of  alternative. It is important to  consider the
 complete implementation requirements, including plant
 and process interfaces, and construction and  operations
 requirements.

 Step  4.      Evaluate Alternatives
 Alternatives that have passed initial screening should be
 thoroughly  evaluated  using a  consistent,  systematic
 evaluation method encompassing evaluation categories
 and evaluation metrics. Typical evaluation categories are
 described below. Table A-4 lists specific evaluation criteria
 for each category.

     •    Technical  Feasibility.   Technical   feasibility
          evaluations  typically involve  identification of
          essential   implementation  and  operational
          performance  criteria for an alternative. Relevant
          information is collected and  evaluations  are
          performed to determine how  each alternative
          corresponds with the technical criteria. For some
          applications, it may be necessary to perform more
          extensive evaluations,  including  bench and/or
          pilot testing to determine technical feasibility. The
      technical criteria vary depending on the type of
      alternative and specific impacts on the facility and
      its processes and operations.

  •   Cost. Cost evaluations include developing capital
      and operations and maintenance (O&M) estimates
      for AZD alternatives and  comparing costs for
      existing  operations.   Projections  for  futur§
      production requirements need to be included as a
      basis for cost estimating.

   •   Regulatory.  Regulatory  evaluations  identify
      applicable  regulations   and  performance
      requirements that determine how specific AZD
      alternatives fall short of, achieve, or exceed the
      requirements and guidelines.

   •   Company/staff acceptability. Company and staff
      acceptability evaluations assess how AZD fits a
      specific application from the operator to corporate
      management.  Evaluations of  AZD alternatives
      can be based on a range of qualitative (e.g., high,
       medium, or low) or quantitative (e.g.,  1  to 10)
       metrics specific to  each evaluation category.  A
       matrix format  is  often  useful  to  summarize
       alternative evaluations. In some cases, evaluation
       results are combined from different categories into
       a single overall score for each alternative. This
       involves  development of a consistent scoring
       basis and category-specific weightings to allow for
       calculation of an overall score.

Decision analysis methods may assist in evaluating large,
complex AZD applications when alternatives depend on
highly variable production scenarios and when  expected
costs and benefits vary greatly. Powerful decision analysis
software tools are available that generate ranges  of
probabilistic outcomes and delineate key variable impacts.

Step 5.   Select Action(s)
Specific actions need  to be selected based  on the best
individual or combination of alternatives to satisfy short
and long-term needs. Actions can be implemented in one
or more  phases  to  satisfy project-specific  resource
limitations,  sequencing to  maintain  operations, and
priorities for achieving maximum results. Lastly, project
funding and implementation support should be secured to
allow for implementation within desired projecttimeframes.

StepG.   Implement Action(s)
Successful AZD solutions require good implementation to
gain the desired reductions and cost benefits. Technical,
strategic,  and management experience  is  important
throughout each general implementation phase to achieve
 overall success with AZD projects. General implementation
 phases include:

     1.   Develop a design basis. Fixed and variable facility
         data, site factors, production requirements, and
         process parameters are essential in the design
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 Table A-4. AZD Alternative Evaluation Criteria
 Evaluation Category

 Technical Feasibility
                  Specific Criteria or Parameter
Ability to maintain process chemistry, recovery percentages for water recycle or
chemical recovery, reliability, operability, facility space and interface requirements^ level of
technology and applications development, byproducts and waste generation

Engineering, process modifications or new process systems, pollution prevention and control
systems, facility costs, utility connections and plant interfaces,  training, start-up and commission-
ing, general construction and implementation, permitting and regulatory, plant space cost of money
internal coordination and administration costs


Operations labor for new or modified process systems, utility costs, chemicals and consumable
materials, analytical  requirements, and management of byproducts from new process
maintenance systems


Permitting, data collection, record keeping and reporting, and compliance requirements and
guidelines, voluntary and  beyond-compliance programs

Company policies, standards, and goals relevant to AZD including preferences and dislikes of AZD
decision makers, owners,  and implementers for specific AZD alternatives
 Cost: Capital
 Cost: Operation
 & Maintenance (O&M)
 Regulatory
 Company and Staff Acceptability
 S™SiVe T f eV^?rS ln? Ude- Capital and 0&M cost savi"9s with ^D alternatives compared to existing operations. Table A-5
 lists common capital and O&M cost savings and benefits that may result from implementing AZD actions.'
Table A-5. Cost Savings and Benefits for AZD Actions
Major Capital Cost Savings and Benefits                                  "                           ~	
    •   Downsized wastewatertreatment requirements

    •   Salvage value or reuse of existing  equipment

    •   Gain in plant space (e.g., with downsized wastewater treatment systems)

    •   Gain in tax credits

    •   Additional project funding resources

Major O&M Cost Savings and Benefits
    •   Reduced rework and rejects

    •   Increased revenue and/or cost to produce -product quality improvements, increased throughput or yield and
        decreased effort to produce

    •   Reduced waste management costs — bath dumps, wastewater treatment and discharge

    •   Reduced process bath chemistry costs

    •   Reduced water supply and pretreatment costs

    •   Reduced insurance and liability costs

    •   Gained revenues from byproducts
                                                        35

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    factors. Pilot testing may be necessary to verify
    technical assumptions.

2.  Prepare the design. The type and level of design
    (ranging from  performance-based  design to
    detailed design) should be appropriate for the
    application.

3.  Procure systems and services. Implementation
    needs to be appropriate for the application.

4.  Perform installation and startup. Careful planning
    and coordination in implementing new systems
    minimizes disruptions to existing operations.

5.  Perform ongoing implementation. New systems or
    procedures need to operate in accordance with
       well-defined  plans (O&M  plan or procedure
       protocol).

   6.  Monitor operations and identify improvements.
       Pre-defined monitoring identifies potential problems
       or possible enhancements that might require
       additional process changes.

Step 7.   Follow-up Monitoring and Actions
Scheduled monitoring of  AZD systems will determine
whether the actions taken are being executed properly and
that the desired results have been achieved. Changes
needed to optimize or enhance the system may be
identified through ongoing monitoring of  actions and
results.
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                                  Appendix B   Installed  Costs
 This Appendix provides a  limited overview of  typical
 installed capital costs forcontrol technologies and process
 changes for approaching zero discharge  (AZD) in the
 surface finishing industry. Many approaches are presented
 in  this document for  process solution purification and
 recovery, rinse purification/concentrate recovery, alternative
 surface  finishing  processes and 'coatings,  and  for
 improving existing process conditions and practices. Table
 B-1 presents representative ranges of installed  capital
 costs that are size- and approach-specific.  Described
 below are representative projects that would be expected
 to fall within the Table B-1 cost ranges for project sizes
 defined as small, medium, large, and very large.

 B.1 Process  Solution  Purification  and  Recovery
     (Section 3)
 Examples corresponding to the process purification and
 recovery cost ranges in Table B-1:
 Small
         A 100-gallon per day throughput microfiltration
        system to maintain an alkaline cleaner bath at a
        target contaminant concentration at less than 250
        ppm soil, with 100 g/day contaminant loading.

        A diffusion dialysis or resin sorption system to
        purify 20 gallons per day of Type 2 sulfuric acid
        anodize bath with an aluminum concentration of 10
        g/L, recovering more than 80% of free acid.
Medium
    •   A 500-gallon per day throughput microfiltration
        system to maintain three alkaline cleaner process
        baths at less than 250-ppm soil with overall 500-g/
        day contaminant loading.

    •   A diffusion dialysis or resin sorption system to
        purify 100 gallons per day of Type 2 sulfuric acid
        anodize bath with an aluminum concentration of 10
        g/L, recovering more than 80% of free acid.

Moderately large
    •   A 500-gallon per day throughput microfiltration
        systemto maintain three alkaline cleaner process
        baths at less than 250-ppm soil with overall 500 g/
        day contaminant loading.

    •   A diffusion dialysis or resin sorption system to
        purify 250 gallons per day of Type 2 sulfuric acid
        anodize bath with an aluminum concentration of 10
        g/L, recovering more than 80% of free acid.
Large
        Diffusion dialysis system to reclaim 5,000 gallon
        per day of  hydrochloric  acid  7 wt  % waste
        hydrochloric acid steel pickle stream with 4 wt %
        iron. Reclaimed acid to have less than 1 wt % iron.

        Membrane electrolysis system for maintaining a
        full production, 50,000 gallon chromate conversion
        coat  bath,  to  remove  and   maintain  total
Table B-1:  Installed Capital Cost Ranges for Typical AZD Project Approach and Size Ranges
                                            Installed Capital Cost (in thousands of dollars)
                                                         Project Size
AZD Approach
Process Technique
Water Purification/Recycle
Bath Purification
Process Replacement
Small'
<5
<20
<20
20 to 100
Medium2
5 to 20
20 to 100
20 to 100
100 to 500
Moderately Large3
20 to 100
100 to 500
10010500
500 to 2500
Large"
100 to 500
500 to 2500
500 to 2500
2500to 10000
 A point-source-purification system for a single small to medium-sized surface finishing bath with low to moderate contaminant loading
 A point-source-purification system for multiple small to moderate-sized baths with low to moderate contaminant loading.
3 A bath maintenance system for a relatively large process bath or process baths with low to moderate contamination or several bath
 maintenance systems for a medium-sized shop.
"Several multi-tank bath maintenance systems for a moderate to large shop or single bath maintenance systems for very large process
 tcin ks.
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                                                   Small
       contaminant  (iron,  aluminum,  and  copper)   Medium
       concentration below 1 g/L and to reoxidize trivalent
       chromium to hexavalent chromium.

B.2 Rinse Purification/Concentrate Recovery
    (Section 4)
Examples corresponding to the rinse purification cost
ranges in Table B-1:

•   Small
       Single rinse point source ion exchange system,
       equipped with a manual regeneration system, for
       water purification/recycle of a 1 to 3 gpm nickel
       plating rinse system with 300 ppm TDS influent
       and 10 ppmTDS rinse water purification required.

•   Medium project:
       A 5 to 20 gpm ion exchange system or reverse
       osmosis system for purification/recycle of several
       nickel plating rinses with 300 ppm TDS influent
       and 10 ppm TDS rinse water purification required.
       The ion exchange system would be equipped with
       an automatic, PLC-controlled regeneration system.
       The reverse osmosis  system would be PLC-
        controlled.

 •   Moderately Large
        A 50 to 100 gpm ion exchange system or reverse
        osmosis system for  centralized  purification/
        recycle of  several  compatible  metal  finishing
        process rinses with 100 ppm TDS influent and 10
        ppmTDS rinse water purification required. The ion
        exchange  system would  be equipped with an
        automatic, PLC-controlled regeneration system.
        The  reverse osmosis system would be PLC-
        controlled.

 •   Large
        A 100  to 1000 gpm combined reverse osmosis
        system followed by ion exchange system for
         centralized   purification/recycle  of   several
         compatible metal finishing process rinses with 100
         ppm TDS influent and 2  ppm TDS rinse water
         purification required. The overall system includes
         complete  redundant reverse osmosis modules
         and ion exchange resin 'beds to maintain highly
         reliable continuous operations. The ion exchange
         system would be equipped with an automatic,
         PLC-controlled regeneration system. The reverse
         osmosis system would be PLC-controlled.

  B.3 Alternative Surface Finishing Processes and
     Coatings (Section 5)
  Examples corresponding to the alternative  surface
  finishing processes and coatings cost ranges in Table
  B-1:
                                                         Change anodizing chemistry on large line from
                                                         chromic acid to sulfuric/boric acid.

                                                  Moderately Large
                                                     •   Small electrocoat line for 10,000-sq ft per day
                                                         production.

                                                     •   Limited production single chamber scale batch
                                                         vapor deposition system.

                                                  Large
                                                     •   Electrocoat  line  for 100,000-sq  ft  per  day
                                                         production.

                                                     •   Fully automated production scale continuous
                                                         vapor deposition system.

                                                  B.4 Improving Existing Process Conditions and
                                                      Practices (Section 6)
                                                  Examples corresponding to the Table B-1 cost ranges for
                                                  improving existing process conditions and practices:
                                                          Implement  more  frequent  bath  chemistry
                                                          monitoring and maintenance for single process
                                                          bath.

                                                          Install fog or spray rinses on several small tanks.

                                                          Add water conductivity controller for single rinse
                                                          water make-up.
Small
       Change anodizing chemistry on small or medium-
       sized line from chromic acid to sulfuric/boric acid.
Medium
    •   Add  automated  chemistry  monitoring  and
       maintenance for a single electroless nickel bath

       —  Add water purification system for 5-gpm city
           water supply with 100-ppm TDS to provide
           <10-ppm TDS influent process water.

       —  Add   water  conductivity  controller  for
           automatic rinse water make-up for several
           tanks.

Moderately large
    •  Add  automated   chemistry  monitoring  and
       maintenance for several electroless nickel baths

       —  Install 50-gpm water purification system for
           city water supply with 100-ppm TDS to provide
           <10-ppm TDS influent process water.

       —  Install three  triple  countercurrent  rinse
           systems with 200-gallon tanks.

       — Add automated feed and  bleed systems for
           maintaining more uniform  process chemistry
           for four, 500-gallon metal finishing process
           tanks with a combined total of seven different
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           process  make-up chemistries  and  three
           segregated bleed waste streams.

Large
    •   Install six triple countercurrent rinse systems with
       500-gallon tanks.

    •   Install 500-gpm water purification system for city
       water supply with 100-ppm TDS to provide <10-
       ppm TDS influent process water.

    •   Add automated feed  and bleed systems  for
       maintaining more uniform process chemistry for
       ten 500-gallon metal finishing process tanks with
       a combined total of 12 different process make-up
       chemistries  and  four  wastewater treatment
       streams.

Factors Influencing Installed Costs
Installed  costs for process systems can vary significantly
depending on many site-specific and other project-specific
factors that can affect system, installation, and operational
requirements. These factors should be considered when
extrapolating costs  from other  installations  or when
estimating installed costs from equipment only. Project
budgets  are often set prior to consideration of these
factors, frequently leading to insufficient funding and
corresponding delays and cost increases for overall project
implementation.   Some  common  factors  that  can
significantly impact implementation costs for process or
production systems for AZD projects include:

    •   Relative inlet and required outlet concentrations
        for  process  systems.  Differences in overall
        percent  removal  and final concentrations may
        require  supplemental  pretreament  or  post-
        treatment unit processes.  It  is important to
        adequately characterize process streams and
        their inherent variability, and define the outlet
        process fluid purity requirements for estimating
        specific process system requirements and costs.

    •   Materials of construction. Equipment material
        requirements may vary significantly based on the
        chemicals and concentrations handled, along with
        required effluent process fluid purity requirements.
        If premium materials of construction are required,
        costs can increase greatly compared to typical
        systems  costs  with standard materials  of
        construction. If the need for specialty materials is
        not recognized until  after installation, this can
        result  in  significant  costs   for   equipment
        maintenance and early replacement.
Site  installation. Installation requirements and
costs may vary significantly, even for identical
process systems,  installed at different project
locations. Site installation costs can range from a
fraction to a total multiplier of equipment costs.
Some  modular, skid-mounted  systems can be
easily  set in place and quickly connected  to
utilities and fluid inlet and outlets. Other process
systems or locations can require a combination of
facilities  modifications  or expansions,  utility
upgrades, seismic  restraints, or other significant
site work to complete installation.

Start-up   and  commissioning  requirements.
Process system or client-specific requirements
can   vary  substantially  for  start-up  and
commissioning, ranging from a few  hours  to
weeks. The extent of these requirements and the
degree of  proper installation  and  systems
application  implementability  can  significantly
impact the duration and effort required to meet
these  requirements. Unanticipated installation
and operation difficulties can result in significant
schedule and cost impacts for systems start-up
and commissioning.

Process  system  redundancy/reliability.
Application-specific redundancy and  reliability
requirements can impact the number of parallel
and/or series process trains, with corresponding
multiple or additive system costs.

Level  of automation.  Local  and  centralized
instrumentation  and  control   requirements for'
process automation can vary significantly. Where
automation  can   significantly  increase  initial
capital costs, overall  life  cycle costs can  be
reduced due to improved production efficiencies.

Equipment quality. Process systems  may vary
significantly in quality and corresponding capital
costs. In  evaluating comparative systems it is
important to consider the comparative life cycle
costs  for systems. Higher-priced, better-quality
systems may provide longer and more trouble-free
service life, thereby reducing overall life cycle
costs.

 Location  specific  configuration  requirements.
 Facility-specific footprint  space  and   height
 requirements  may  require  custom  system
 configurations and corresponding custom system
 design and fabrication, increasing costs compared
to standard off-the-shelf systems.
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Allowances  for  production  expansion  and
flexibility.   When  considering  AZD-related
replacement  process  systems  or  process
systems that interface with primary production
systems (e.g., water recycle  or process  bath
maintenance systems) it is important to consider
and plan for production expansion and potential
production  changes.  Proper  allowances  for
production expansion and/or changes may result
in significant increases in short-term AZD-related
capital costs but may reduce future costs related
to systems modification, expansion, or replacement
in  response  to  production  increases  and/or
changes.
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