EPA-440/l-75/040-a
 Group 1, Phase II
   Development Document for Interim
  Final Effuent Limitations Guidelines
                  and
   Proposed New Source Performance
           Standards for the

           METAL FINISHING
            Segment of the

           ELECTROPLATING
         Point Source Category
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

                April 1975

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                             DEVELOPMENT DOCUMENT

                                     for

                      INTERIM FINAL EFFLUENT LIMITATIONS

                                     and

                       NEW SOURCE PERFORMANCE  STANDARDS

»                                   for the

                        METAL FINISHING SEGMENT OF THE
              ELECTROPLATING MANUFACTURING  POINT SOURCE CATEGORY


                               Russell E. Train
                                Administrator
                                 James  L.  Agee
                      Assistant  Administrator for Water
                           and Hazardous  Materials
                                  Allen Cywin
                    Director,  Effluent Guidelines Division
                              Kit R.  Krickenberger
                                Project Officer
                                  April, 1975
                          Effluent Guidelines Division
                    Office of Water and Hazardous Materials
                     U.  S. Environmental Protection Agency
                            Washington, D.C.   20460
                            Environmental Protection
                            Region V, Library
                            230 South Dearborn Street
                            Chi«8fo, IlMnois 60601

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                                                                   1
                                                                   H
W/IRONLSNTAL f^GTLGTIOil AGENCY

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                          ABSTRACT


This document presents the findings of an extensive study of
major segments of the metal finishing industry by Battelle's
Columbus  Laboratories  for  the  Environmental   Protection
Agency  for  the  purpose of developing effluent limitations
guidelines.   Federal   standards   of   performance,    and
pretreatment   standards  for  the  industry,  to  implement
Sections 304, 306, and 307 of the  Federal  Water  Pollution
Control  Act,  as  amended  (33 USC 1251, 1314, and 1316; 86
Stat 816) .

Effluent limitations guidelines contained herein  set  forth
the  degree  of  effluent  reduction  attainable through the
application  of  the  best  practicable  control  technology
currently  available  and  the  degree of effluent reduction
attainable through the application  of  the  best  available
technology economically achievable which must be achieved by
existing  point  sources  by  July  1, 1977 and July 1, 1983
respectively.  The standards of performance for new  sources
contained  herein set forth the degree of effluent reduction
which is achievable through  the  application  of  the  best
available   demonstrated   control   technology,  processes,
operating methods, or other alternatives.

In developing the data and recommendations in this  document
the  metal  finishing  processes  have been divided into two
subcategories that are  distinguished  from  each  other  by
differences  in  water  use  and  the presence or absence of
chelating agents.  Subcategory   (1)  consists  of  processes
anodizing,  immersion  plating,  chemical  milling, chemical
conversion processes and  etching,   chemical  milling,  and
etching.    Subcategory   (2)    consists  of  processes  for
electroless plating on plastics.

Chemical treatment of waste  waters  to  destroy  oxidizable
cyanide,  reduce  hexavalent  chromium,  and  remove all but
small  amounts  of  heavy   metals   represents   the   best
practicable   control  technology  currently  available  for
existing point sources in Subcategories  (1) and  (2) .

Chemical treatment of waste  waters  to  destroy  oxidizable
cyanide,  reduce  hexavalent  chromium,  and  remove all but
small amounts of metals, augmented by in-process  procedures
to  further  reduce  the amount of waste water and the total
pollutional load is the new source performance standard  for
point sources in Subcategories  (1) and  (2) .

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The  Best Available Technology Economically Achievable to be
achieved  by  1983  is  no  discharge  of   pollutants   for
Subcategories (1)  and (2).

Supportive   data  and  rationale  for  development  of  the
proposed effluent limitation  guidelines  and  standards  of
performance are contained in this report.
                                                                        t

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                          CONTENTS


SectiojT.

I        CONCLUSIONS                                    -l

II       RECOMMENDATIONS                                3
           Best Practicable Control Technology          ^
             Currently Available
           Best Available Technology Economically
             Achievable                                 .
           New Source Performance Standards

III      INTRODUCTION                                   ^
           Purpose and Authority
           Summary of Methods Used for Development
             of the Effluent Limitation Guidelines
             and Standards of Performance
           General Description of the Metal
             Finishing Industry                         |
           General Description of Surface Treatment     ™°
           General Description of Metal Removal
           Water Usage in the Metal Finishing
             Industry

IV       INDUSTRY CATEGORIZATION                        j?3
           Introduction                                 *
           Objectives of Categorization                 ~~
           Profile of Production  Processes              ^
           Factors Considered in  Categorization         ^
           Water Use

V       WASTE CHARACTERIZATION                         ^
           Introduction
           Characteristics of Waste for Each
             Subcategory                                41
           Specific Water Uses                           ._
           Sources  of Waste                              f.
           Description  of the Process                    *
           Preparation  for Anodizing
           Anodic  Treatment
           Posttreatment
           Chemical Conversion  Coatings  -
             Chromating
           Chemical Conversion  Coatings  -
                                                         DO
             Phosphating                                 6q
           Posttreatment  Procedures
                           111

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 VI         SELECTION OF POLLUTANT PARAMETERS              73
             Introduction                                 73
             Metal  Finishing  Waste Water
               Constituents                                -73
             Waste  Water Constituents  and  Parameters
               of Pollutional Significance                73
             Rationale  for the Selection of
               Waste Water Constituents  and
               Parameters                                 75
             Rationale  for the Selection of
               Total Metal As a Pollutant
               Parameter                                  QQ

VII       CONTROL  AND  TREATMENT  TECHNOLOGY                83
             Introduction                                 83
             Chemical Treatment Technology                83
             Effectiveness of Chemical Treating
               Techniques                                 gg
             Chemical Treatment of  Effluents From
               Specific  Process Operations                103
             Water  Conservation Through  Control
               Technology
             Methods  of  Achieving No Discharge
               of Pollutants
VIII      COSTS, ENERGY, AND NONWATER QUALITY ASPECTS    143
            Introduction                                 143
            Treatment and Control Costs                  143
            Nonwater Quality Aspects                     165

IX        BEST PRACTICABLE CONTROL TECHNOLOGY
            CURRENTLY AVAILABLE, GUIDELINES,
            AND LIMITATIONS                              171
            Introduction                                 171
            Identification of Best Practicable
              Control Technology Currently
              Available                                  172
            Rationale for Selecting the Best
              Practicable Control Technology
              Currently Available                        175
            Waste Management Techniques Considered
              Normal Practice in the Metal Finishing
              Industry                                   176           i
            Degree of Pollution Reduction Based on                     \
              Existing Performance by Plants of                        *
              Various Sizes,  Ages, and Processes
              Using Various Control and Treat-
              ment Technology                            177
                         IV

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X         BEST AVAILABLE TECHNOLOGY ECONOMICALLY
            ACHIEVABLE, GUIDELINES AND LIMITATIONS           209
            Introduction                                     20'J
            Industry Category and Subcategory
              Covered                                        210
            Identification of Best Available
              Economically Achievable                        210
            Rationale for Selection of Best
              Available Technology Economically
              Achievable                                     211
            Effluent Limitations Based on the
              Application of Best Available
              Technology Economically Achievable             213
            Guidelines for the Application of
              Effluent Limitations                           213

XI        NEW SOURCE PERFORMANCE STANDARDS                   215
            Introduction                                     215
            Industry Category and Subcategory
              Covered
            Identification of Control and Treatment
              Technology Applicable to Performance
              Standards and Pretreatment Standards
              of New Sources                                 216
            Rationale  for Selection of Control  and
              Treatment Technology Applicable to
              New  Source Performance Standards               218
            Standards  of Performance Applicable
              to New Sources                                 219
            Guidelines for the Application of
              New  Source Performance Standards               220

XII       ACKNOWLEDGEMENTS                                   221

XIII      REFERENCES                                         223

XIV       GLOSSARY                                          229
                            v

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                           TABLES


Number

   1     Recommended Effluent Limitations For
           the Metal Finishing Industry to be
           Achieved by July 1, 1977, Based on
           Best Practicable Control Technology
           Currently Available (BPCTCA) 30-Day
           Average                                    5,6,7

   2     Recommended Standards of Performance for
           the Metal Finishing Industry to be
           Achieved by New Sources, 30-Day
           Average                                    8,9,10

   3     Processes for Anodizing                       27

   4     Processes for Chemical Conversion Coatins     29

   5     Processes for Immersion Plating               30

   6     Processes for Chemical Milling and Etching    31

   7     Typical Operating Conditions for Sulfuric-
           Acid Anodizing of Aluminum                  47

   8     Typical Operating Conditions for Chromic-
           Acid Anodizing of Aluminum Alloys           48

   9     Operating Condition for Anodizing
           Magnesium                                   49

  10     Principal Waste Water Constituents in
           Wastes Generated During the Anodizing
           of Metals                                   50

  11     Principal Waste Water Constituents in
           Wastes Generated During Posttreatment
           of Anodic Coatings on Metals                52

  12     Principal Waste Water Constituents in
           Wastes Generated During Preparation
           for Immersion Plating on Various
           Basis Metals                                54

  13     Principal Waste Water Constituents in
           Wastes Generated During Immersion
           Plating of Tin, Copper, Gold, and
           Nickel                                      55
                          VI

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              14      Principal Waste Water  Constituents  in
                       Wastes Generated During Chromating
                       Operations on Various  Metals                      J

              15      Alkaline Cleaners for  Aluminum                      ^8

              16      Representative Deoxidizing and  Desmutting
                       Treatments for Aluminum

",              17      Representative Alkaline  Cleaners
                       for Magnesium

„              18     Chromate Coating of Magnesium by the
                       Chrome Pickle Process

              19     Dichromate Process Cycle for Magnesium             ^
                       Alloys

              20     Principal Waste Water Constituents in
                       Wastes Generated During Phosphating
                       Operations on Various Metals and
                       Alloys

              21     Principal Waste Water Constituents in
                       Effluents Generated During Chemical              71
                       Milling or Etching

              22     Representative Aqueous  Solutions for
                       Chemical  Milling or Etching Various
                       Metals  and Alloys

              23     Comparison  of  Precipitation of Metal
                       Hydroxides  Separately and in Comparison

              24     Concentrations of Heavy Metals  and Cyanide
                       Achievable  by Chemical Treating  of Waste
                       Created by  Copper,  Nickel, Chromium,  and
                       Zinc Plating and Zinc Chromating
                       Operations
*
               25     Comparison  of Soluble Pollutant Parameters
                       after Precipitation by Iron  Sulfide  or
*                      by Hydrolysis

               26     Decomposition Products  of Cyanide  in  Rinse
                       Water from a Cyanide  Zinc Electroplating
                       Operation after Treatment with "Kastone"          1Q5
                       Peroxygen Compound
                                                                         144
               27      Costs for Waste Treatment Facilities

               28      Treatment Equipment Costs, Values in  U.S.           147
                        Dollars,  1974
                                       VII

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29     Annual Operating Costs, Waste Treatment,
         U.S.. Dollars, 1974                                148

30     Investment and Annual Operating Costs
         for Various Types of Waste Treatment
         for Representative Average Plant
         (38 Employees)                                    149

31     Cost Effectiveness of Control Alternatives
         (247 sq m/hr)                                     166

32     Cost of Power Relative to Total Operating
         Cost for Chemical Treatment                       167

33     Concentration of Effluent Constituents            180,181

34     Water Use in Metal Finishing Processes           182,183,184

35     Concentration Values for Waste Water Constituents
         for BPCTCA                                        187

36     Comparison of BCL Analytical Results With
         Typical Analytical Results Reported By
         Plant 33-23 for Treated Effluent                  192

37     Plant 15-1 Monthly Averages                         194

38     Plant 12-6 Monthly Averages                       195,196

39     Plant 33-15 Monthly Averages                        197

40     Plants Meeting BPCTCA Standards                     198

41     Electrochemical Equivalents and Related Data        202

       Conversion Table                                    237

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                          FIGURES

Number                                                 5^2^-

  1       Number of Companies in SIC 3471 According
            to Data in Table 5, Page 9-30, "1967
            Census of Manufacturers" U.S. Bureau
            of Commerce                                   17

  2       Water Use - Anodizing                           35

  3       Water Use - Coatings                            36

  4       Water Use - Etching and Milling                 37

  5       Diagram of a Typical Continuous Treat-
            ment Plant                                    86

  6       Integrated Treatment System                     88

  7       Batch Treatment of Cyanide Rinse Waters
            by  the Kastone  Process
                                                          104
   8        Schematic  of  Cadmium Waste  Water  Treatment
             with  Minimum Solid Disposal                  107

   9        Schematic  for Sulfide Precipitation of
             Cadmium  in  Waste Waters                      109

  10        Schematic  for Chemical Treatment  of Waste-
             waters from Anodizing Operation

  11        Schematic  Presentation of Ion-Exchange
             Application for Plating Effluent
             Treatment                                    -1-2-1-

  12        Representative Closed Loop System for
             Recovery of Chemicals and Water with
             a Single Effect Evaporator                   126

  13        Schematic Diagram of the Reverse Osmosis
             Process for Treating Plating Effluents       131

  14        Schematic Diagram of Freezing Process for
             Recovery of Water and Chemicals from
             Plating Rinses                               -1-33

  15       Schematic Diagram of Ion-Flotation
             Cell for Treatment of Plating
             Effluent                                     137
                            IX

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 16       Investment Costs of Waste Treatment
            Plants with Varying Volume Capacity          145

 17       Operating Costs Related to Plant Size
            and Extent of Waste Treatment                150

 18       Typical Plant Operation - Chemical Treat-
            ment (A);  Coprecipitation Only               152

 19       Typical Plant Operation - Chemical Treat-
            ment (B);  Cyanide Oxidation and
            Coprecipitation                              153

 20       Typical Plant Operation - Chemical Treat-
            ment (C);  Chromium Reduction and
            Coprecipitation                              154

 21       Typical Plant Operation - Chemical Treat-
            ment (D);  Cyanide Oxidation,  Chromium
            Reduction,  and Coprecipitation               155

 22       Phase  I,  IA,  and II Master Flow Pattern         157

 23       Combined  Chemical Treatment and Neutralization
            Precipitation                                 158

 24       Combined  Chemical Treatment and Precipitation
            Followed by End-Of-Line Reverse  Osmosis
            Treatment  for  Zero Liquid Effluent
            Discharge                                     3.59

 25        Batch  Treatment  System  for  Small Plant          160

 26        Distribution  of  Waste Water Volume Treated      179

 27        Schematic Representation  of  Programmed
           Automatic Hoist Rack L|ne  For Anodizing
           Aluminum At  Plant  33-23                       189

 28        Schematic Representation  of  Waste Treatment
           Systems For  Handling Anodizing Effluents
           At Plant 33-23                                190

 29       Schematic Representation of  The Waste Treat-
           ment Facility For Handling Chemical Milling
           And Other Metal Finishing Effluent At Plant
           6—35

30       Example 1                                       207
                           x

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                         SECTION I

                        CONCLUSIONS


For   the   purpose  of  establishing  effluent  limitations
guidelines  and  standards  of  performance  for  the  metal
finishing  segment of the electroplating industry, the metal
finishing process covered by this study  have  been  divided
into  two  subcategories.   The  selection  of processes for
inclusion in each subcategory is based upon a similarity  in
process  configuration,  in the method of treating the waste
waters and a similarity in the amount of water required  for
the metal finishing processes.  The consideration of the age
of  the  plant,  processes employed, geographical locations,
and wastes generated support  this  conclusion.   Guidelines
for   the   application  of  the  effluent  limitations  and
standards of performance take into account the plant size in
that  the  allowable  amount  of  pollutant  that   can   be
discharged is proportional to the size of the plant.

Subcategories  of  the metal finishing point source category
are:

    (1)     Anodizing.

    (2)     Coatings.

    (3)     Chemical etching and milling.

The best practicable control  technology  for  subcategories
 (1)   and   (2) is chemical treatment.  It is estimated that  a
water use of  90  liters  per  sq  m  per  operation  can  be
achieved  for  the anodizing subcategory, 80 liters per sq  m
per operation for the coatings  subcategory  and   120  liters
per   sq  m per operation in the chemical etching  and milling
subcategory.

The average cost for waste treatment reported  by   30  plants
was   $1.06/1000  liters  of waste water  treated.   Investment
costs ranged  from  $1.15  to $43.39/l/hr.  Estimates made from
two modeled waste  treatment  plants  carrying out  cyanide
destruction,      chrornate      reduction,      precipitation,
clarification and filtering were  $1.09  and  $1.41/1000 liters
of  waste  water  treated.    Investment  costs ranged  from
 $22,980   for   a   5-man  plant  plating  75  sq  m/hr and treating
wastes only  by neutralizing  it  to   $378,455   for  a  47-man
plant   plating   815   sq  m/hr  and   treating  for cyanide.

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chromate,  and  heavy  metals  including  clarification  and
filtering.   A minimum cost batch waste treatment system was
designed for $17,700.  This system treats cyanide, chromate,
and heavy metals but  relies  heavily  on  an  operator  for
proper  functioning  and  many manual operations.  Operating
costs  were  estimated  to  be   $10,186/yr   exclusive   of
analytical costs.

The  best  available  technology  economically achievable by
1983 is no discharge of pollutants  for  all  subcategories.
The technology involved consists of both in-process and end-
of-process  methods  of minimizing and eliminating water use
and eliminating effluent.

The new source performance standards are based upon chemical
treatment and a water use estimated to be of the order of 90
1/sq m/operation for subcategory (1),  80  1/sq  m/operation
for subcategory (2)  and 120 1/sq m/operation for subcategory

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                         SECTION II

                      RECOMMENDATIONS


Best Practicable Control Technology Currently Available

Recommended  effluent  limitations  for  the metal finishing
industry  applicable  to  existing  sources  discharging  to
navigable  waters are summarized in Table 1 and the specific
effluent limitation guidelines and rationale  are  discussed
in  greater  detail  in  Section  IX  of  this report.   The
guidelines have been derived from the product  of  pollutant
concentrations   and   water   uses  considered  achievable.
Chemical treatment of waste  waters  to  destroy  oxidizable
cyanide,  reduce  hexavalent  chromium,  and  remove all but
small amounts of the heavy metal pollutants  represents  the
best  practicable  control  technology  currently  available
(BPCTCA) for existing point sources.  A water use of 90 1/sq
m/operation for  subcategory  1,  80  1/sq  m/operation  for
subcategory  2  and  120  1/sq m/operation for subcategory 3
have been estimated to be achievable by the industry.

Additional currently available in-process control technology
designed to recover and reuse process  chemicals  and  water
and/or  reduce water consumption may be required to meet the
effluent limitations depending upon the kind of parts  being
finished or the nature of available process facilities.


Best Available Technology Economically Achievable

The  effluent limitations attainable through the application
of the  best available technology economically achievable  by
existing  point  sources  in  the  subcategories  listed  in
Section I is no discharge of process waste water  pollutants
to  navigable waters by July 1, 1983.  The achievement of no
discharge of pollutants is believed to be possible through a
combination of technologies that are in existence, that  are
being   developed,  and  that  remain  to be developed before
1983.   There is considerable information available on how to
reduce  water use in  the  plant  through  proper  design  of
processing   lines   and   correct   operating   procedures.
Minimizing this water use reduces the  problem  of   treating
the   waste   water  that  is   produced.   Reverse   osmosis,
electrodialysis, and special ion-exchange systems are  under
development  to  recycle  water in  process loops and thereby
reduce  water to be treated and  are   also  being  tested  for
recovery   of   process  water  from  waste  effluent.   New
techniques for water recovery should   come  from  the broad

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scientific  and  engineering  base  in  the  United  States,
although  it  is  difficult  to   pinpoint   what   specific
technologies will emerge before 1983.

New Source Performance standards

Recommended  standards of performance for subcategories (1) ,
(2) and (3)  of the metal finishing  industry  applicable  to
new  sources  discharging to navigable waters are summarized
in Table 2.    The  limitations  are  applicable  to  sources
constructed   after   publication  of  proposed  regulations
prescribing a standard of  performance.   The  standards  of
performance  are  lower  in  value  than  the  corresponding
effluent limitation guidelines in Table 1.  New sources have
the opportunity  to  design  and  economically  install  in-
process  systems that can be operated with a lower water use
than can be achieved in many existing plants.

The single-day maximum is two times the 30-day average given
in Table 2.   The rationale for establishing  the  factor  of
two is given in Section IX.

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Table 1 - BPCTCA Limitations
 for Anodizing Subcategory
Effluent
Characteristic




(Metric


Maximum for
any one day


Effluent
Limitations
Average of daily
values for thirty
consecutive days
shall not exceed
units) milligrams per sq m
per operation
Copper
Nickel
Cr, Total
CrVI
Zinc
CN, Total
CN,A
Fluoride
Cadmium
Lead
Iron
Tin
Phosphorus
TSS
PH
(English

Copper
Nickel
Cr, Total
CrVI
Zinc
CN, Total
CN,A
Fluoride
Cadmium
Lead
Iron
Tin
Phosphorus
TSS
pH
90
90
90
9
90
90
9
3600
54
90
180
180
180
3600
Within
45
45
45
4.5
45
45
4.5
1800
27
45
90
90
90
1800
the range 6.0 to 9.5.
units) pounds per million sq ft

18.4
18.4
18.4
1.8
18.4
18.4
1.8
738
8.8
18.4
36.8
36.8
36.8
738
Within
per operation
9.2
9.2
9.2
.92
9.2
9.2
.92
369
4.4
9.2
18.4
18.4
18.4
369
the range 6.0 to 9.5.

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          Table 1 - BPCTCA Limitations
           for Coatings Subcategory
 Effluent
 Characteristic
                     Maximum for
                     any one day
             Effluent
             Limitations

               Average of daily
               values for thirty
               consecutive days
               shall not exceed
          (Metric units)
       milligrams per sq m
          per operation
 Copper
 Nickel
 Cr,Total
 CrVI
 Zinc
 CN,Total
 CN,A
 Fluoride
 Cadmium
 Lead
 Iron
 Tin
 Phosphorus
 TSS
 PH
  80              40
  80              40
  80              40
   8               4
  80              40
  80              40
   8               4
3600            1800
  48              24
  80              4Q
 160              8Q
 160              80
 160              80
3600            1800
         (English units)
   Within the range 6.0 to 9.5.

       pounds per million sg ft
           per operation
Copper
Nickel
Cr,Total
CrVI
Zinc
CN,Total
CN,A
Fluoride
Cadmium
Lead
Iron
Tin
Phosphorus
TSS
PH
16.4
16.4
16.4
1.6
16.4
16.4
1.6
646
9.8
16.4
32.8
32.8
32.8
646
8.2
8.2
8.2
.82
8.2
8.2
.82
323
4.9
8.2
16.4
16.4
16.4
323
  Within  the range  6.0  to  9.5.

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            Table  I  - EPCTCA Limitations
          for Chemical Milling and Etching
                     Subcategory
Effluent                         Effluent
Characteristic                   Limitations

                    Maximum for     Average of daily
                     any one day     values for thirty
                                    consecutive days
                    	     shall not exceed

          (Metric units)     milligrams per sq m
                               per operation

Copper                120              60
Nickel                120              60
Cr,Total              120              60
CrVT                   12               6
Zinc                  120              60
CN,Total              120              60
CN,A                   18               9
Fluoride             4800            2400
Cadmium                72              36
Lead                  120              60
Iron                  240             120
Tin                   240             120
Phosphorus            240             120
TSS                  4800            2400
pH                      Within the range 6.0 to 9.5.

         (English units)     pounds per million sq ft
                                per operation	

Copper                 24.6            12.3
Nickel                 24.6            12.3
Cr/total               24.6            12.3
CrVT                    2.4             1.2
Zinc                   24.6            12.3
CN,Total               24.6            12.3
CN,A                    3.8             1.9
Fluoride              984             492
Cadmium                14.8             7.4
Lead                   24.6            12.3
Iron                   49.2            24.6
Tin                    49.2            24.6
Phosphorus             49.2            24.6
TSS                   984             492
pH                      Within the range 6.0 to 9.5.

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              Table  2 - NSPS Limitations
              for Anodizing Subcategory
Effluent                         Effluent
Characteristic                   Limitations

                    Maximum for     Average of daily
                    any one day     values for thirty
                                    consecutive days
                    	     shall not exceed

          (JXtetric units)     milligrams per sq m
                               per operation

Copper                 45              23
Nickel                 45              23
Cr,Total               45              23
CrVI                    4.5             2.3
Zinc                   45              23
CN,Total               45              23
CN,A                    4.5             2.3
Fluoride             1800             900
Cadmium                27              14
Lead                   45              23
Iron                   90              45
Tin                    90              45
Phosphorus             90              45
TSS                  1800             900
pH                      Within the range 6.0 to 9.5.

         (English units)     pounds per million sq ft
                                per operation	

Copper                  9.2             4.6
Nickel                  9.2             4.6
Cr,Total                9.2             4.6
CrVT                     .92             .46
Zinc                    9.2             4.6
CN,Total                9.2             4.6
CN,A                     .92             .46
Fluoride              369        .     185
Cadmium                 4.4             2.2
Lead                    9.2             4.6
Iron                   18.4             9.2
Tin                    18.4             9.2
Phosphorus             18.4             9.2
TSS                   369             185
pH                      Within the range 6.0 to 9.5.

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              Table 2 - NSPS Limitations
               for Coatings Subcategory
Effluent
Characteristic
                    Maximum for
                    any one day
         Effluent
         Limitations

            Average of daily
            values for thirty
            consecutive days
            shall not exceed
          (Metric units)
    milligrams per sq m
       per operation
Copper
Nickel
Cr,Total
CrVI
Zinc
CN,Total
CN,A
Fluoride
Cadmium
Lead
Iron
Tin
Phosphorus
TSS
PH
40
40
40
4
40
40
4
1800
24
40
80
80
80
1800
20
20
20
2
20
20
2
900
12
20
40
40
40
900
         (English units)
Within the range 6.0 to 9.5.

    pounds per million sq ft
        per operation
Copper
Nickel
Cr,Total
CrVT
Zinc
CN,Total
CN,A
Fluoride
Cadmium
Lead
Iron
Tin
Phosphorus
TSS
pH
8.2
8.2
8.2
.82
8.2
8.2
.82
323
4.9
8.2
16.4
16.4
16.4
323
4.1
4.1
4.1
.41
4.1
4.1
.41
161
2.5
4.1
8.2
8.2
8.2
161
Within the range 6.0 to 9.5.

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               Table 2 - NSPS Limitations
            for Chemical Milling and Etching
                       Subcategory
 Effluent
 Characteristic
                    Maximum for
                    any one day
            Effluent
            Limitations

               Average of daily
               values for thirty
               consecutive days
               shall not exceed
          (Metric units)
       milligrams per sq m
          per operation
Copper
Nickel
Cr, Total
 Zinc
 CN, Total
 CN,A
 Fluoride
 Cadmium
 Lead
 Iron
 Tin
 Phosphorus
 TSS
 PH
  60              30
  60              30
  60              30
   6               3
  60              30
  60              30
   9               5
2400            1200
  36              18
  60              30
 120              60
 120              60
 120              60
2400            1200
         (English units)
   Within the range 6.0 to 9.5.

       pounds per million sq ft
           per operation
Copper
Nickel
Cr,Total
CrVI
Zinc
CN,Total
CN,A
Fluoride
Cadmium
Lead
Iron
Tin
Phosphorus
TSS
pH
12.3
12.3
12.3
1.2
12.3
12.3
1.9
492
7.4
12.3
24.6
24.6
24.6
492
6.2
6.2
6.2
0.6
6.2
6.2
0.9
246
3.7
6.2
12.3
12.3
12.3
246
   Within the range 6.0 to 9.5.
                             10

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FOOTNOTES FOR TABLES 1 AND 2


(a)  The effluent limitations and  standards  of  performance
are  defined  as  the  weight  of  pollutant  in  milligrams
discharged per sq m per operation (pounds per million sq  ft
per  operation).   The  definition of operation depends upon
the subcategory.  For anodizing, the  term  operation  shall
mean any step followed by a rinse in which a protective film
is  deposited  on  the  object  which  acts as an anode.  In
coatings, the term operation shall mean any step followed by
a rinse in which a protective film is deposited on the basis
material.   In  chemical  etching  and  milling,  the   term
operation  shall  mean any step followed by a rinse  in which
some portion of the basis material is removed.  The  term "sq
m"  ("sq ft") shall mean the area plated expressed in square
meters  (square feet) .

 (b)   Single-Day  Maximum  is  the maximum value for any one
day, and is 2.0 times the 30-Day Average.

 (c)  Thirty-Day Average is  the  maximum  average  of  daily
values  for any consecutive 30 days.

 (d)   Total  metal   (in solution and in suspended solids)  in
sample.

 (e)  Chromium  (total) is the sum of hexavalent  and trivalent
chromium, in solution and in suspended  solids.

 (f)  Oxidizable cyanide is defined as all detectable cyanide
amenable to oxidation  by  chlorine  as  described   in   1972
Annual  Book   of  ASTM  Standards, 1972, Standard D  2036-72,
Method  B, p. 553.

 (g)  Total  suspended  solids retained by a   filter  according
to  standard analytical procedures.
                               11

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                        SECTION III

                        INTRODUCTION
Purpose and Authority

Section  301(b)   of  the Act requires the achievement by not
later than July 1, 1977, of effluent limitations  for  point
sources,  other   than publicly owned treatment works, which
are based on the application of the best practicable control
technology currently available as defined by the Administra-
tor pursuant to Section 30U (b) of the Act.   Section  301 (b)
also  requires  the  achievement  by  not later than July 1,
1983, of effluent limitations for point sources, other  than
publicly  owned  treatment  works,  which  are  based on the
application of the best  available  technology  economically
achievable  which will result in reasonable further progress
toward the national goal of eliminating the discharge of all
pollutants, as determined  in  accordance  with  regulations
issued  by  the  Administrator pursuant to Section 301 (b) to
the Act. Section 306 of the Act requires the achievement  by
new  sources  of a Federal standard of performance providing
for  the  control  of  the  discharge  of  pollutants  which
reflects the greatest degree of effluent reduction which the
Administrator   determines  to  be  achievable  through  the
application  of  the  best  available  demonstrated  control
technology,   processes,   operating   methods,   or   other
alternatives,  including  where  practicable,   a   standard
permitting no discharge of pollutants.

Section  304(b)  of  the  Act  requires the Administrator to
publish within one year of enactment of the Act, regulations
providing guidelines for effluent limitations setting  forth
the  degree  of   effluent   reduction  attainable through the
application of the best practicable control technology cur-
rently  available  and  the   degree  of   effluent  reduction
attainable through  the  application  of   the   best   control
measures   and    practices  achievable  including  treatment
techniques, process  and  procedure  innovations,  operation
methods   and  other  alternatives.   The regulations  proposed
herein  set  forth  effluent  limitations guidelines pursuant to
Section  304 (c) of the Act for the   metal  finishing  source
category.

Section  306  of   the Act requires  the Administrator,  within
one  year  after  a  category of  sources is included in   a  list
published   pursuant  to  Section 306 (b) (1) (A)  of the Act, to
propose   regulations  establishing   Federal    standards   of
                                13

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 performance  for  new  sources  within such categories.  The
 Admxnistrator publxshed in the Federal Register  of  January
 16, 1973  (38 FR 162U) , a list of 27 source categories.
              ?f -the  *ist  constituted  announcement of the
                                               rs.
                                                was
                        _
            Guidelines and
                                         of the
 The   effluent   limitations  guidelines  and  standards   of
 performance  recommended  herein  were  developed   in   the
 following  manner.   Electroplating processes  were considered
 separately  from   metal   finishing   processes    and   the
 development of effluent limitations guidelines  and standards
 of  performance  for electroplating processes are covered in
 two othsr documents.   This  document  covers  the  rollowing
 metal   cznishxng  processes:   anodizing,  coatings (chemical
 ?^rfS-LOn  C?a^in^s  of  Phosphating   and enrooting   and
 immersion   plating),   and  chemical  etching  arid  milling
 Subcatecjonzation of  these  processes   was based  upon   Si
 material   used,  operations employed, and other  factors.   The
 raw-waste characteristics  were identified by  analyses  of  the
 source and volume of  water used  in the process  employed   and
 the sources  of waste and   waste waters in representative
 plants and the constituents of all  waste waters.

 Ranges of control and treatment  technologies  existing  within
 each subcategory were  identified,   including  both   in-plant
 and end-of -process   technologies,  which are  existent  or
 capable of being designed  for waste control.  The   problems
 limitations,   and  reliability  of  treatment  and  control
 technology were  also  identified.                     ^um^roo.

 In  addition, the  nonwater  quality environmental impact, such
 as  the eftects of the  application of such technologies  upon
 other  pollution  problems,  including air, solid waste  and
 noise were also  identified.  The energy requirements of each
 of  the control and treatment technologies were identified as
 well as t.h-2 cost of the application of such technologies.

 The information, as outlined above, was  then  evaluated  in
order to determine what levels of technology constituted the
 best  practicable  control technology currently available''
the "best  available technology economically achievable",  and
the  "best  available   demonstrated   control   technology
                               14

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processes,  operating  methods,  or other alternatives".  In
identifying  such  technologies,  the   fac.torn   considered
included  i he  total  cont  of  application ol technology in
relation ».o the effluent reduction benefit^ to  be  .-ichieved
from  such  application, the age of equipment an
-------
        etc.)
      Chemical milling 
-------
4OOO
Jo 3000
O
CO
c
(0
o>
'c
o
Q.
O
0 2OOO
o
Z
IOOO
19
Est 1974 = 340O-i
324!-^ ^.J^
3170^ \ ^.^^
2968-, \ ^-*°
V O """^
o *~-
2588 -^ ^ — -
2423 -x ^ \-*~ ^
^.^'^
^'
^—1789
i i i i i i i 1 i 1 i til
(47 1954 1958 1963 1966 1970 !974
                              Year
FIGURE 1.  NUMBER  OF  COMPANIES IX SIC 3471 ACCORDING TO  DATA IN TABLE 5,
           PAGE  9-30,  "1967  CENSUS OF MANUFACTURERS" U.S.  BUREAU OF
           COMMERCE

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Some companies have capabilities for finishing ten or twelve
different metals and alloys, but others specialize  in  just
one  or  two.  Because of differences in character, size and
processes, few or no similar plants  exist  at  the  present
time.   Construction of facilities have been custom tailored
to the specific needs of each individual plant.

In the Phase I report the energy consumed by industry in the
electroplating subcategory was estimated to  be  1.7  x  10^
kilowatt  hours.   It also cites that from 90,718 to 108,861
metric  tons   (100,000  to  120,000  short  tons)  of  metal
(principally  copper,  nickel,  zinc, and tin)  are converted
annually to electroplated coatings.  The figures for sheets,
strip, and wire include nonelectroplated  coatings,  applied
by hot dipping.  All the aluminum is applied by hot dipping,
as  is  about 90 percent of the zinc, as are significant but
unidentified percentages of the tin and lead.

These coatings provide corrosion protection,, wear or erosion
resistance,   antifrictional   characteristics,   lubricity,
electrical  conductivity,  heat  and  light  reflectivity or
other special surface characteristics, which enable industry
to conserve several millions of tons of critical metals.  In
the finishing of individual products, electroplated  coating
thickness usually ranges from 0.0006 to 0.004 cm  (0.00025 to
0.0015  inch),  but  thicker  coatings  to  0.025 or 0.04 cm
(0.010 or 0.015 inch) are  sometimes  required  for  special
engineering  purposes  or  for salvaging worn or mismachined
parts.  Tin and chromium coatings from 0.3 to 1 mm (1 x 10-5
to 4 x 10-5 inch)  and 0.003 mm (1  x  10-7  inch)  thickness
respectively  are  applied  to  continuous  steel strip as a
prefinish before coating with an  organic  material  by  the
container industry.

General Description of Surface Treatment

Surface  treatments include anodizing, chemical brightening,
electroless  plating,  and  chromate  or  other   conversion
coating treatment.

Of  158  companies  listed  by  one  source of data on metal
finishing, 94  do  anodizing.   Of  these  94,  43  do  both
anodizing  and  plating,  and  30  do  mechanical treatments
(polishing, buffing, tumbling, etc.) but no  electroplating.
Anodizing  to  customer specification is done manually by 48
percent  of  the  plants,  and  25  percent   do   hard-coat
anodizing.   A  sulfuric  acid  electrolyte is used for most
anodizing  operations,  but  chromic   acid   anodizing   is
generally   specified  for  aircraft  parts,  assemblies  of
intricate design, or parts subject to stress.  Whereas, some
                               18

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companies will treat a variety of lengths and widths,  others
will limit processing of parts to those under 1  to  2  feet
long.   Continuous  coil is anodized in 4.5 percent of these
firms.   Furthermore,  28.5  percent   of   the   firms   do
electroless nickel plating.  Chemical brightening is done by
46  percent  of  the  companies and 60 percent do conversion
coating.

Such a  mixture  of  operations  is  typical  of  the  metal
finishing  industry  and shows the complexity of determining
the best practicable waste  treatment  for  all  facilities.
The  apparent  procedure is to view each operation as a unit
operation that can and should have an associate  best  waste
treatment practice and control.

Anodizing  provides  a  protective  oxide  on  metals.  This
benefit is accomplished by making the metals  anodic  in  an
electrolytically   conducting   solution.    Protection   is
achieved against corrosion, tarnish, and wear.  Aluminum and
its alloys are  the  most  extensively  anodized  materials.
Other   materials   much   less   extensively  anodized  are
magnesium, titanium, and zinc.

Electroless plating of copper, nickel, cobalt, and gold  are
achieved  by  chemical  reduction,  catalyzed  either by the
basis material or by a pretreatment to  activate  the  basis
material surface.

Conversion  coatings of zinc and iron phosphates are applied
to  steel as preparation for subsequent organic coatings  and
for  lubrication in forming dies.  Other types of conversion
coatings impart special color to  metals  as,  for  example:
colors  on  copper,  bronze,  brass,  and  zinc  by chemical
oxidation or  treatment  in  sulfide  solutions;  protective
films   on  zinc, tin, cadmium plate by treatment in chromium
containing or other oxidizing solutions.

Some of the operations as  shown in Phase  I,  chromating  of
zinc  plate  and  coloring of  copper are carried out after
electroplating.  Thus, the waste treatment and control are a
part  of  the  systems  for  handling   the   electroplating
operations.

General Description of Metal Removal

The   only   process   for removal  of  metal  by  chemical
dissolution pertinent  to  the  objectives  of  the  present
report  is  etching.   The printed circuit industry, with a
dollar  volume  of  approximately   $600,000,000,   does   a
considerable .  amount   of etching.   A  single  plant  has
                               19

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facilities to etch 125,000  boards  (printed  circuits)  per
week.   Each board has 206 sq cm  (32 sq in.) with 610 g/sq m
(2 oz/sq ft)  of copper.  On an  annual  basis  of  3,100,000
boards  or  63,358  sq m  (682,000 sq ft), produced 27,522 kg
(60,550 Ib)  of copper are  dissolved  and  reclaimed  in  an
electroplating   operation   and  the  stripped  ©tenant  is
recycled.  Thus, no dumps of concentrated etchant enter  the
waste treatment system.  Only rinse water is treated.

The  yearly  average  production   (by  electrodeposition) of
copper foil  for  the  printed  circuit  industry  is  about
136,363  kg/week (300,000 Ib/week).  Sometimes production is
159,091 kg/week (350,000 Ib/w^eek) .  About 75 percent of  the
foil  is 610 g/m2 (2 oz/sq ft) plus special small quantities
of other weight foil.  Relatively, the amount of nickel foil
is negligible.

There is no single universal figure for the amount of  metal
dissolved  away  in etching printed circuits.  The amount is
estimated to be 75 to 85  percent.   In  order  to  estimate
total  square  feet  processed  and  using  an average of 80
percent removal, the above mentioned 27„523 kg (60,550  Ib.)
of  recovered  copper corresponds to about 31,318 kg  (75,500
Ib.) of 610 g/sq m (2 oz/sq ft)  foil  having  63,357  sq  m
(682,000 sq ft) of surface area.

Chemical  etching  of  aluminum,  brass,  copper,  steel and
stainless steel is used in the production  of  name  plates,
information  plates,  etc.   After  etching, the aluminum is
usually  anodized  and  copper,   brass,   and   steel   are
electroplated for protection.

Water Usage in the Metal Finishipg Industry

In  SIC  3171, the total  intake of water was cited as  3.27 x
1010 liters (8.7 x 109 gallon) in 1968<*».  Of  this   amount
2.78  x  10*°  liters   (7.1  x 109 gallon) was discharged as
follows:

  2,10 x 10»o liters  (5.6 x 10« gal) to public sewers
  6.02 x 109    "     (1.6 x 109 gal) to surface water  bodies
  3.76 x 10"    "     (1.0 x 10" gal) to ground
  7.11 x 108    "     (1.9 x 10» gaij treated before discharge.

This segment of industry, in  1967, had 55,100  employees<7*,
or  an  average  of  about  503,810 liters  (131,000 gal) per
employee.

Of the firms with captive electroplating facilities,  2191 of
them had a few more than  25,709 total  employees.   However,
                               20

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the  number  of employees was not cited where the SIC showed
one or two firms.  At the same water use  rate  these  firms
would  discharge  over 1.182 x 10»° liters (3.14U x 10» gal)
and assuming the same  average  rate  the  remaining  IJ'f00
companies  would discharge over 7.802 x 10»° liters  (2.075 x
1Qio gal).
                               21

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                         SECTION IV

                  INDUSTRY CATEGORIZATION
Introduction

The  rationale  is  developed  for   subcategorizing   metal
finishing   processes  according  to  processes  which  have
essentially the same water use.

Qb-jectives of Categorization

The primary purpose of industry categorization is to develop
quantitative  effluent   limitations   and   standards   for
discharge  of  pollutants that are uniformly applicable to a
specific category or subcategory.  This  does  not  preclude
further  classification within a category for the purpose of
monitoring to insure compliance.

Electroplating is one of several processes  in  the  broader
category  of  metal  finishing.  It is listed under SIC 3471
 (Standard  Industrial  Classification  Manual)  along   with
rtumerous   other   metal  finishing  processes.   The  metal
finishing  industry   was   divided   into   two   segments,
electroplating  and  metal  finishing,  for  the purposes of
developing effluent  limitations guidelines.  Phase I covered
the electroplating of copper, nickel, chromium and  zinc  or
combination  thereof.   Phase  II covers tin, lead, cadmium,
iron, silver, gold,  platinum, palladium,  rhodium,  iridium,
ruthenium,  titanium,  or  any combination thereof.  It also
covers stripping.  This addition is  justified  because  all
electroplating shops have a stripping line to salvage  poorly
plated  or  badly  corroded parts.  This usually exists as a
separate  line.    Also   considered   are   the   pre  and
posttreatment   operations   of   alkaline   cleaning,  acid
pickling,  conversion  coatings,  coloring,  and  descaling.
Although  these  processes  are not strictly electroplating,
they usually  form an integral  part  of an electroplating line
and therefore must   be  considered  under  the  auspices  of
electroplating.   Other metal  finishing operations which are
an end unto  themselves and stand  as  a  separate   line  are
considered  in  separate  documents.   These  are anodizing,
immersion plating, chromating,  phosphating, chemical milling
and etching.

 Profile of  Production  Processes

 The  metal   finishing    industry    utilizes   chemical  and
 electrochemical  operations  to effect an  improvement  in the
                              23

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 surface  and  structural  properties  of  metals  and  other
 materials*    In practice,  the operations are put together in
 sequences  t-.hat  become  the  processes  which  effect   the
 improvement.   Thus,   metal finishing operations may be both
 process and materials oriented.   The processes considered Jn
 Phase II may be briefly described as follows:

 Pretreatment

 Pretreatment steps involve cleaning,  pickling,   degreasing,
 descaling,   desmutting,   vapor blasting,  surface activation,
 etching, abrasion and bright  dipping.    Plating  steps  are
 strikes  and  electroplates,   coatings   and  metal coloring.
 Post  treatment steps  are conversion and drying.    Stripping
 while  performed  separately,  is  an  integral   part  of an
 electroplating shop.   It is employed for the reclamation  of
 badly plated parts.

 Cleaning

 Cleaning involves the  removal  of  oil,  grease and dirt from
 the sur.race of the basis material.   Cleaning  or  degreasing
 may   be  accomplished in ona of  several  ways.  These include
 alkaline electrolytic  (anodic   and   cathodic),    diphase,
 emulsion, soak,  solvent, and ultrasonic  cleaning.

 Alkaline cleaners are the most  widely  used in preparing the
 basis  material.   A good  alkaline or  soak  cleaner  must  be
 soluble in  water,  wet the  surface of the  basis material,  wet
 and   penetrate soil,  saponify  or dissolve oil  and  greases or
 emulsify or suspend insoluble  or nonsaponifiable   oils   and
 greases,  prevent  formation of  calcium and magnesium deposits
 from   hard   water,  prevent tarnish and corrosion of  basis
 material, rinse  freely and minimize foaming.   For  possible
 compositions   of   alkaline cleaners,  see  Chapter V,   Ferrous
 metals  an-3  alloys  can be cleaned using  heavy duty  (pH =  12.1
 - 13.5)  uninhibited alkaline   solutions.    Usually,   though
 weaker   solutions  (pH =  10.5 - 12)  are used  to avoid etching
 and  pitting.   When   cleaning   nonferrous   materials,    an
 inhibitor   must be added to stop the  corrosive action of  the
 cleaner.
Small  volumes  of  work  are  usually  cleaned   by   hand.
Solutions  are  applied  by brushes, swabs, or cloth.  Parts
may also b? immersed in cleaning tanks which may be agitated
or heated <-_o increase efficiency.   The  fastest  method  of
cleaning   is  by  spraying  the  cleaning  solution  in  an
automatic or semi-automatic washing machine.  The mechanical
force of fie spray combined with the chemical  and  physical
action of the cleaning solution increases efficiency.
                                24

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Electrolytic  cleaning  is  best  employed when plating with
brass,  cadmium,  chromium,  copper,  gold,  lead,   nickel,
silver,  tin,  and zinc.  The basis metal acts as either the
cathode or the anode and a  low  voltage  current  for  each
square foot of metal is passed through the alkaline cleaning
solution.  The generation of gases  (H2 at the cathode and O2
at  the  anode) cause increased agitation and the removal of
soil particles.

Diphase cleaning is composed of a two layer system of  water
soluble  and a water insoluble organic solvent.  This set up
is particularly  useful  where  soil  removal  requires  the
action  of  water and organic compounds and when temperature
may not  be  elevated.   Usually,  the  organic  solvent  is
chlorinated.   Because they are non-flammable and are denser
than  water,  trichloroethylene,  rcethylene  chloride,   and
perchloroethylene  are in common use.  This is also known as
solvent cleaning.  Emulsion  cleaning  uses  water,  organic
solvents  and emulsifying  agent.

Ultrasonic  energy is finding increased use in the agitation
of  cleaning  solutions.   Although  it is more expensive to
install, there are substantial savings in  labor  and  time.
It  is  used to remove difficult inorganic and organic soils
from intricate parts.

Descaling

Descaling involves  the  removal  of  oxide  films  and  the
buildup  of  other  contaminants on the surface of the basis
material.   Such  removal  may   be   accomplished   through
mechanical or chemical means.

Pickling

During  the  production  of metals, oxides build up on their
surface during such operations as heat treating and welding.
Also rust may  have  built  up  if  the  part  is  not  used
immediately.   Acid  pickling  is used to remove these oxide
films and involves dissolution of oxide scale in an acid.   A
generalized reaction may be written.

         MO2 +2 HA    MA2 + H2O
          where  M = metal
                 HA = acid

Sulfuric, hydrochloric,  phosphoric  and  chromic  acids  all
find  use  in  this  regard.    Sulfuric  is  most often used
because it is the least expensive.  Rates of  reactions  are
                              25

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increased  hy an increase in acid concentration, temperature
and degree of agitation.

Hydrochloric acid is more  costly  and  there  is  a  fuming
problem.   Nevertheless,  many  small  establishments use it
because it works well without the addition of heat.   It  is
also used for light acid dips before plating,

Phosphoric  acid  is  intermediate  in  cost,  but  it forms
phosphates at the surface of the basis  material.   This  is
desirable  if  rust  resistance  is  needed  but  not  if an
electroplate is to follow.

Mecharical

Removal  of  scale  through  mechanical  means  consists  of
tumbling,   (barrel  finishing),  burnishing,  dry  rolling,
buffing, deburring,  polishing,  desmutting,  and  blasting.
Such   mechanical  treatment  eliminates  or  minimizes  the
pickling to follow.

Activation

Activation involves the elimination of a  condition  on  the
surface  of  the  basis  material  which  would preclude the
adhesioi of an effective electroplate.

Bright Dipping

Bright dipping is used to impart a shiny,  clean  appearance
to  the basis material.  Solutions are comprised of mixtures
of nitric, sulfuric, phosphoric,  chromic  and  hydrochloric
acids.

Anodizing

Anodizinc  involves  the  basis  metals  aluminum, zinc, and
magnasium and  solutions  containing  sulfuric  and  chromic
acids.   Waste  Water  constituents  can be reduced to a low
concentration by chemical treatment, water use is similar to
that for  immersion  plating  processes,  and  anodizing  is
subcategorized with immersion plating processes.  Operations
involved in anodizing are shown in Table 3.

Chemical Conversion Coatings

Chemical   conversion   coatings   are  produced  by  either
chromating or phosphating  aluminum,  zinc,   (die  castings,
hot-dipped  or  electroplated), steel, copper, or magnesium.
Ions in the waste water are reduced to low concentrations by
                                 26

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                     TABLE  3     PROCESSES FOR ANODIZING
Alkaline clean/rinse




Acid dip/rinse



Decorative anodize/rinse




Hard or protective  anodize/rinse




Dye/rinse




 Seal/rinse
                                            27

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  Immersion  Plating
 Milling and Etching
&Etasa ESnslaered  in  Cateaojisati^
          DYP^ °f basis material
          Product design
     (3   Raw materials used

          »»L^-p-y
     (6)   Geographic  location


          £
    <      J
    (' i)   Water use
    H2)   Processing differences
                             28

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                TABLE  4
 PROCESSES FOR CHEMICAL CONVERSION COATINGS
    Operation
                                                    Basis Metal
Steel
                                         Zinc
            Aluminum
                                                                      Steel
                                                     Tin
Alkaline clean/rinse




Acid dip/rinse




Desmut/rinse




Phosphate/rinse




Chromate/rinse
X   X




X   X









X   X




    X
X  X




X  X









X




X  X
X




X




X




X




X
X




X









X
                                         29

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                                    TABLE   5
PROCESSES FOR IMMERSION PLATING
CO
o
Copper Tin Tin Lead Zinc Tin Gold
on on on on on on on
Steel Copper Steel Steel Aluminum Aluminum Copper
Operation Basis Basis Basis Basis Basis Basis Basis
Alkaline clean/rinse
Acid dip
Neutralizer dip/rinse
1- Immersion plate/rinse
2 -limners ion plate/rinse
X
X
X
X
X
X

X
!
X
X

X

X
X

X
X
X
X
X
X

X
X

X

X
X

X

X
X

X


-------
TABLE  6     PROCESSES FOR CHEMICAL MILLING AND ETCHING
Basis Metal
Operation Aluminum Zinc Copper Steels
Alkaline clean/ rinse X
Acid dip/rinse X
Etch/rinse
Chemical mill/rinse X
xx x x
XX X X
XX X
X
X
X
X
                         31

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processes involved,  and upon estimates  of  which  processes
should  use more or less water than others,,   This factor was
primarily responsible for distinguishing between Subcategory
(1)  and Subcategory (2).

Type of Basis Material

The wastes produced by processing all common basis materials
are similar.   A  single  facility  can  process  all  basis
materials  without  significant  change in the raw materials
consumed  or  the  waste-treatment  technique  adopted   for
control  of  end-of-pipe  water  discharge.   Any  materials
dissolved from the surface of  the  customary  basis  metals
during  processing are removed from waste water discharge by
the chemical treatment processes described in  Section  VII.
Furthermore,  the basis materials selected for most consumer
products frequently are interchanged from one model year  to
another.   Therefore,  the  type  of basis material does not
constitute a basis for subcategorization.

Pro du ct  Des ig n

Product  design  concepts for minimizing metal  finishing costs
also reduce wastes created  by  metal  finishing  processes.
Furthermore,  the in-process controls and rinsing techniques
described  in Section  VII for minimizing  the wastes generated
by metal finishing processes have been adopted  for canceling
the effect of the shape factor.  Therefore,   product  design
variance is not a basis for subcategorization.

Raw Materials Used

Raw  materials  do not provide  a basis for subcategorization,
because  practical waste-treatement  technology identified  in
Section  VII  is equally   applicable   to  all   of the  usual
procedures and   solutions   described previously  for  metal
finishing.   In any  facility  carrying out one or more of the
processes  shown, the  same waste  treatment needs arise.   Such
variations as exist  for each  operation  are not  unique and do
not affect the  waste-treatment technology and control.

Size  and Age of Facility

The nature of  metal  finishing is the same in all  facilities
 regardless  of   size  and  age.    For  example, anodizing is
technically the same in  190  liters  (50  gallons),  as  in
 19,000  liters  (5000 gallons), or larger installations.  The
 age of the facility does not alter  this  situation.   Other
 metal  finishing  operations follow the same pattern.  Thus,
 the characteristics of the waste will be the same for plants
                                  32

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of all ages and sizes.  Only the quantity of waste per  unit
time  will  differ.   Yet,  this  factor  is not a basis for
subcategorization, because waste discharge  after  treatment
is  directly  proportional  to  the  size  of  the  facility
expressed as surface area  processed  per  unit  time.   The
guidelines recommended in this document provide for variable
production  volume  with  no  need  to  differentiate  plant
capacity as a subcategory.

It  is  recognized   that   some   small   metal   finishing
installations  may have insufficient space for accommodating
effective inprocess controls for minimizing water use and/or
conventional  chemical  waste  treatment   equipment.    The
capital  investment   for  installing waste control facilities
may  be  greater  for  small  companies  relative  to  their
investment  in  the remaining production facilities than for
larger plants.  In such cases, heavy metal pollutants can be
adsorbed on resins in  small  ion-exchange  units  available.
At  least one vendor of such equipment will replace the resin
beds,  back  wash the used beds in their own facilities and
regenerate the resins  for reuse.  Alternatively, both   local
and  regional  organizations equipped with large tank trucks
supply a hauling  and  treating service in several areas.   It
is  also  possible that a small electrodialysis  system would
provide recycling of  cyanide.  Costs depend on water  volume
and the concentration of  pollutants.

Number of Employees

The  number of employees  engaged  in metal finishing  does not
directly  provide   a   basis  for   subcategorization,   because
metal finishing  operations  can  be  carried out manually  or  in
automatic   machines   which greatly  conserve  labor.   For
example,   an  operation   with   3800   liter    (1000    gallon)
processing    tanks   may   require   six   people  if   operated
 manually,  whereas a  plant of  the  same tank  size and  carrying
out the  same  operations  in an automatic machine  would   need
 only  two  people.    The   same   amount   of   waste would  be
generated in  each case,  if the  products being  plated   were
 equal  to total  area.  Other  examples  could be cited to show
 that no basis exists for relating the number of employees  to
 the metal finishing  processes  carried   out  and/or   to  the
waste  that  results  from  those processes.   However,  it is
 believed that one can relate the number of  employees to  the
 production capacity  of a non-automatic facility.

 Geographic Location

 Geographic  location  is  not a basis for subcategorization.
 No condition is known whereby the choice of metal  finishing
                                33

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processes  is  affected  by  the  physical  location  of the
facility, except availability of process water.   If water is
not available, no modification of metal finishing procedures
can compensate for  this  deficiency.   No  metal  finishing
facilities would be installed at a water deficient location.
The  waste treatment procedures described in Section VII can
he utilized in any geographical area.  In  the  event  of  a
limitation   in   the   availability   of   land  space  for
constructing a  waste  treatment  facility,  the  in-process
controls  and  rinse water conservation techniques described
in lection VTI can be adopted for minimizing the land  space
required   tor  the  end-of-process  treating  facility.   A
compact unit can easily handle end-of-process waste  if  the
best  in-process  techniques  are  utilized  to conserve raw
materials and water.

Quantity of Work Processed

Quantity of work  processed  is  analogous  to  plant  size.
Therefore,  the  discussion  about  plant  size  is  equally
applicable  to  the  quantity  of   work   processed.    The
application  of  the  guidelines provides for the production
volume of a particular facility.

Rack Platinq Versus Barrel Plating

The choice of rack or barrel methods for plating is based on
the size and quantity of the parts to be processed per  unit
of  time.  Neither of these conditions imposes a significant
technical change in the operations for electroplating.   The
selection is always based on economic considerations because
hand  racking  of  small  parts  is usually more costly than
barrel  processing  in   bulk.    Sometimes   plating   bath
compositions  will be modified by altering the concentration
of solution constituents.  However, the same types of salts,
acids, and additives will be  used.   Thus,  the  impact  on
waste  characteristics  is not changed.  The volume of waste
water  (dragout) is  frequently  greater  in  barrel  plating
operations  but the final effluent quality is not a function
of influent  concentration.   Techniques  are  available  to
reduce  the  rinse  water  volumes  in barrel plating to the
levels of rack plating.  These techniques  are  detailed  in
Section VII,  Therefore, rack plating and barrel plating are
not appropriate subcategories.

Treatment Technology

As  no  peculiarity  exists  between raw materials and waste
characteristics as  a  basis  to   separate  facilities  into
suboategories,  none  exists for treatability of wastes as  a
                             34

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                        FIGURE 2
                        ANODIZING
                          l/m2 - op
                    OS X 9BOO
                   «,  Ol
                   o  o
                                                          §
{•)  -ffc  Gl G) ""JOBWO
I  8  g ggggg
1   I  I I I III
        T	T
TTTT
T	1   I   I  I I  Ml	T
"
8 -
  .
  1
§ -
                                                                            01
                                                                            O
                                                     II H
                                                     (O O)
                                                     O O:


-------
                                 9C
                  FIGURES
            w  *  w   «joo«eo
  COATINGS

   l/m  - op
g  S 8    8 8
1   I I I  I I I I
                                                      T	1	1  I  I  I I I 'I
        T   v  I  i i 1111	r
S


s
V
§

-------
                   FIGURE 4
                        ETCH ING & MILLING

                            l/m2 - op
A Ol
o «
                            N>

                            §
§iiii
M III
                                                 T	1  I  I  I I  I
s


§
                                                             s:
                                                              I!  II
                                                              _» (O
                                                              ro o
                                                              o

-------
basis for subcategorization,,  All of the principal treatment
procedures   and   in-process   controls   are   technically
applicable  by choice for any given waste and all operations
generate the same  type  of  raw  waste  regardless  of  the
facility.

Water Use

Water  use  formed  a major basis for differentiation of the
subcategories.   The  median  water  use  for  each  of  the
subcategories is shown in Figures 2, 3 and 4.  It is 60 1/sq
m/operation for anodizing, 12 1/sq m/operation for coatings,
and  90  1/sq  m/operation for chemical etching and milling.
Since it is not known to what extent rinsing  technique  and
product  size  and shape contribute to this factor the water
has been increased to 90 1/sq m/operation for anodizing  and
120  1/sq  m/operation  for  cherrical  milling  and etching.
Coatings represent a special case.  The water use of 12 1/sq
m/operation indicated  on  Figure  3  cannot  be  justified.
Therefore,  the  highest  figure  of  80 1/sq m/operation is
chosen as being more representative.

Processing Differences

Basic differences in  the  type  of  process  performed  was
another factor in subcategorization.  Anodizing involves the
deposition  of a protective layer on the object which itself
acts  as  the   anode.    Coatings   covering   phosphating,
chromating and immersion plating involve the deposition of a
protective  layer.  Chemical etching and milling involve the
dissolution of the basis material.

Categorization Summary

The metal finishing industry consists of three subcategories
for  the  purpose  of  establishing   effluent   limitations
guidelines  and  standards of performance.  The selection of
processes for inclusion in each  subcategory is based upon  a
similarity  in the characteristics of the wastes present and
a similarity  in  the  amount  of  water  required  for  the
processes  and basic processing  differences.  Guidelines for
the application of the effluent  limitations and standards of
performance to specific facilities  take  into  account  the
size  of  the  finishing  facility  and the mix of different
metal finishing processes possible in a single plant.
                              38

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                         SECTION V


                   WASTECHARACTSRIMUQN
water flow  and  the  nature  and  quantity  of  the  wastes
dissolved  in the water during metal finiehing processes are
described in this section for each subcategory.  Sources  of
waste are also discussed in this section.

Water  is  a  major material In the metal finishing  industry

                                                         3S
to the product value.

characteristics of Wjygte fSZ S

waste  water  from  metal   finishing   processes   comes  from
cleaning    pickling,   plating,  etching,  etc.,  operations and
include!' coSEitueSts  SomWfro.  the  basis  mater i-1  being
finished   as  well  as from the components in  the processing
solution.   Predominate ationg the  waste   water  constituents
a?e  the   metal  cations ***
as cooper,  nickel,  chromium, zinc,, lead, tin,  cadmium, gold,
silSSrpiaJinum metals,  and aalons that occur in  cl*anin9'
Scklinq,   or  processing  baths  such  as  phosphates,  and
chlorides,  and various metal cor.rplexing  agents.
 gpeciflc

 Water is used in 'r.oe following ways:

       (1)   Rinsinq to remove films of processing solution
            from the surface of work pieces at the site of
            each operation
       (2)   Washing away spills in the areas of the

       (3>   Skshlng°the air that passes through ventilation
            ducts so as tc remove spray from the air
            before it is exhausted
       (4)   Rinse water  (and dumps^ of solutions from
            auxiliary operations such as  rack stripping
       (5)   washing of equipment  {e.g0, pumps, filters,
            tanks? ion-exchaage -units)
       (6)   Cooling water used in heat exchangers to
            cool solutions in metal  finishing processes.

 supplementing  the  above   uses  for  water  which  acquires
 pollutants,  process  solutions,  especially  for  pre-   and
                                                              (


                                39

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 posttreatment  solutions,   contribute  to  the   waste  water
 requiring  treatment  before   discharge to  navigable waters.
 Such   dumps   are   required   when   contaminants    reach
 concentrations that prevent efficient processing.

 Rinsing

 A  large   proportion (perhaps 90 percent^ of the water usage
 is  Li  the rinsing  operations.  That   used as  cooling  water
 usually  does  second  duty  in  rinsing steps. '  The water is
 used to rinse away the films  of   processing solutions  from
 the  surface  of   the  work  pieces.   In performing this task,
 the  water  acquires  the   constituents  of the  operating
 solutions and is not directly "reusable**.   Thus, the cost of
 water   is an operating expense to which is  added the cost of
 treating  the water to  clean it up for reuse or for  discard.
 Dilute,  water  solutions result  from the raw waste from each
 operation.    Therefore,  the   location  of  rinse  steps  is
 important  relative to the  operations performed  in the metal
 finishing  process*

 There  :.s  no fixed  relation  between water usage and amount of
 work processed.  Some  plants  use  more water than the minimum
 required  to maintain good quality work.

 Spills  and  Air  Scrubbing

 The water from  washing away spills   and  that  from  washing
 down   ventilation   exhaust  air   is   added  to the chemically
 corresponding rinse  water for  treatment.

 Dumps

 Operating solutions  to be dumped  are  slowly  trickled  into
 rinse  water  following the operation and prior to treatment.
 Alternatively, the operating solutions, which are much  more
 concentrated   than   the  rinse  water,  may  be  processed
 batch-wise in  a treating facility.  Subsequent discussion  of
waste  treatment  of rinse water covers  all the water in the
 facility.

Water from Auxiliary Operations

Cyanide solutions are used for stripping deposits  and  rack
tips  to  form  cyanide compounds that are not decomposed by
treatment with chlorine,   i.e.,  nickel  cyanide.   However,
there   are   suitable  alternatives  to  cyanide  stripping
solutions  with  which  the  formation  of  stable   cyanide
compounds can be avoided  in many cases.
                              40

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Washing Equipment

Water  used  for  washing filters, pumps, and tanks picks up
residues of concentrated solutions or salts  and  should  be
routed  to  the  appropriate rinse water stream for chemical
treatment.

Cooling Water

As noted previously, cooling water used in  heat  exchangers
for  cooling  metal  finishing  aolutions should be used for
rinsing purposes in the interest  of  conserving  water.   A
further  advantage  of  this practice is that if the cooling
water is contaminated by the metal  finishing  bath  due  to
leaks  in the heat exchanger, the contaminated water will be
subjected to treatment to remove the contaminants before the
water is discharged.

Sources si Haste

Alkaline Cleaners,  cleaners are made up with one or more of
the following chemicals regardless of  the  material  to  be
electroplated:  sodium  hydroxide9  sodium carbonate, sodium
metasilieate, sodium phosphate  (di-  or  trisodium),  sodium
silicate,   sodium  tetraphosphate,  and  a  wetting  agent.
Compositions for cleaning steel ar® more alkaline and active
than  those  for  cleaning   brass*  sine  die  castings,  and
aluminum.   Therefore,  cleaners vary with the type of  basis
metal being cleaned and also with the  type  of  soil   being
removed.

wastes  contain not only the chemicals found in  the alkaline
cleaners  but also  soaps from the  saponifications of  greases
left  on   the   surface  by  polishing and buffing operations.
some  oils  and greases are not saponified, but  nevertheless,
emulsified.   The  raw  wastes  fro® the basis materials  and
process solutions  for cleaning  the work  show up  in the  rinse
waters, spills,, dumps of concentrated solutions, wash waters
from  air-exhaust ducts, and leaky heating and cooling   coils
and heat  exchangers.

Acid   Dips.   Acid solutions are  made up from one  or more of
the following:  hydrochloric adds, sulfuric acid,  phosphoric
acid,  fluoboric   acid,  chromic  acid, and nitric  acid.  The
solution  compositions vary  according to  the  nature  of  the
basis  metals,   the  type   of   tarnish   or   scale.  The acid
dipping baths  for  treating  metal  substrates  prior  to plating
usually have  a  relatively  short life.  When  these   solutions
are  dumped  and replaced  large amounts  of chemicals must be
 treated and/or  reclaimed.   Water  used  for  rinsing   following
                             41

-------
 acid  dipping   collects  impurities.   Including   heavy metal
 waste from dragout of acid solutions  into the  rinse water.

 Acid  solutions  used  for  pickling,   acid   dipping,   or
 activating  accumulate  appreciable amounts of heavy  metals,
 as  a result of  metal  dissolution from metallic work   pieces
 and/or  uncoated  areas  of  plating  racks that, are recycled
 reoeatedly  through  the  cleaning,    acid  treating,    and
 electroplating   cycle.    The copper (and sine) accumulate in
 acid bright dip solutions used  to prepare electrical   copper
 and brass  contacts for plating.

 The  amount of  waste  contributed  by  preplate  preparation
 steps  varies   appreciably  from  one facility   to   another
 depending   on the substrate material,  the formulation of  the
 solution adopted for  cleaning or  activating   the material,
 the solution temperature,  the cycle time,  and  other factors.
 The  initial condition of  the substrate  material  affects  the
 amount  of  waste  generated  during preplafce   treatment.   A
 dense,  scalefree copper alloy article can be easily prepared
 for  plating by using a mild hydrochloric acid solution that
 dissolves  little or no copper,  where&s products with  a heavy
 scale require   stronger  and hotter   solutions   and   longer
 treating  periods  for   insuring the  complete  removal of  any
 oxide,  prior to plating.

 Anodizing

             pj:  the Pr_gcesg
Anodizlig is an electrolytic oxidation process by which  the
surface  of  the  metal  is  converted to an insoluble oxide
having   desirable   chemical   and   physical   properties.
Considerable   aluminum  is  treated,  some  magnesium,  and
limited amounts of zinc and  titanium.   Anodizing  provides
corrosion   protection,  decorative  surfaces,  a  base  for
painting  and  other   coating   operations,   and   special
electrical and engineering properties.

£L£§J2,aEa£i.2S l2£ Anodes jS,ng

Preparative  operations  for  anodizing can be comparatively
simple or extensive,,  soak cleaning may be carried out in an
inhibited  alkaline  cleaner  such   as   sodium   carbonate
containing   phosphate   or  silicate.   A  phosphoric  acid
solution may also function as a cleaner.  In" most cases  the
cleaner is strong enough to etch the aluminum slightly or is
followed  by  an alkaline etching solution containing sodium
hydroxide:.   The  etching  assures  an  active  surface  for
anodizing,  Alloying elements in the aluminum, particularly
                             42

-------
copper, may not be dissolved by the etchant and give rise to
a  smut  on  the  surface.  A desmutting bath such as nitric
acid may then be used to remove the  amut,   Finally,  if  a
bright  appearance is to be maintained, a bright dip made of
nitric and phosphoric acida wi&y be usad.

Magnesium, zinc, and titanium ara prepared for anoditing  by
cleaning  in  an  inhibited  alkaline  clean«r.  Titanium is
further activated by immersion in & nitric acid" hydrofluoric
acid solution.

&Q2.3J.C Treatment

Aluminum  is  anodized  in  su If uric  acid  to   produce   a
conventional  oxide  coating  for  corrosion protection or a
hard coat for extra wear resistance.  Both  composition  and
operating  conditions are listed in Table 7.  A chromic acid
bath is used where parts  have  recesses  so  that  complete
rinsing of the part may not be achieved™  In such a case the
sulfuric   acid   would  attack  the  aluminum.   Particular
application of the  chromic  acid  process  is  to  aircraft
parts.   The  bath  composition and operating conditions are
shown  in Table 8.

Aluminum may also be anodic-ad ir, oxalic acid or boric  acid.
The  coating  from  the   lat-cer  bath  has  good  dielectric
properties,

The characteristics of anodic coatings on magnesium  can  be
varied from  thin  coatings  to give good  plant adhesion to
heavy  coatings for  abrasion  and  corrosion  resistance  by
adjusting   the   time    and   operating  conditions  during
anodizing.  Both compositions and operating  conditions  for
the two most commonly usec. prccfc&oes are given in Table 9.
Zinc   parts,  i.e.,   for  automatic  clothes  washers,  are
anodized to improve  cor rosier,   resistance.   The  Iridizing
process  uses  alternating current to produce a coating made
up of a fritted structure of oxides, phosphates,  chrotnates,
and  fluorides.  Anodizing is accomplished with a current of
430 amp/sq m  (40 amp/sq ft) for  4.5 to  8 minutes at  155  to
185°F.   The  bath   is replenished  with  ammonia  and  the
Iridizing powder. Sludge  builds  up  in  the  tank  and  is
periodically  removed.

Table   10  lists  the  principal constituents in waste water
generated during the anodizing operation.
                               43

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                     TABLE  7   TYPICAL OPERATING CONDII10NS FOR SULFURIC-ACID
                                ANODIZING OF ALUMINUM
                       Conventional Anodizing
                                                Hard-Coat Anodizing
Electrolyte
15 weight percent sulfuric  acid
Temperature        21 C (70 F)

Current density    130 A/sq M (12 ASF)

Voltage            12 to 22 volts
12 weight percent sulfuric acid ^ Alumelite
 1 weight percent oxalic acid     Process

                     or
15 weight percent sulfuric acid   ^  Martin
  (Saturated with carbon dioxide) r Process

3.9 to 10 C (25 to 50 F)

258 to 387 A/sq M (24 to 36 ASF)

Up to 70 volts and higher

-------
           TABLK  8    TOPICAL OPERATING CONDITIONS
                      FOR CHROMIC-ACID ANODIZING
                      OF ALUMINUM ALLOYS
Electrolyte concentration

Temperature

Voltage

Time


Current density


Film thickness
5-10% Cr03

95F

40 v, programmed

5-7 min for 0.40 v
30 min at 40 v

0.1 - 0.3 amp/dm2
1.8 amp/dm2 at start

0.06 mil in 1/2 hour for
  Al 2024 with:
      10% Cr03
      40 v, pH 0.4, 05F.
                              45

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                                                    TABLE   9      OPERATING  CONDITION  FOR ANODIZING MAGNESIUM
Process
Typical Bath
CO=pO!
iition
type
Coating
Voltage,
volts
Tine,
minutes
Coating
Appearance
Remarks
O--
    Dow So.  17        Solution 8
      (Dow Chemical   Annor.iua acid fluoride
      Company         Sodius dichrocate ;:>a:Cr;07
                     Phosphoric acid (351 =3204)
Solution B
Amoniua acid fluoride (XE4HF2)
Amoniuo acid phosphate (XH4H2PQ4)
Sodiua dichromate
                                      For AC Use       For DC lfse
                                    32 oz/gal       48 oz/gal
                                    13.3 oz/gal      13.3 oz/gal
                                    11.5 fl oz/gal   11.5 £1 oz/gal
27 oz/gal
13.3 oz/gal
10.6 oz/gal
36 oz/gal
13.3 or/g»l
10.6 oz/gal
                               Clear-very thin            40              1-2        Clear
                               Low voltage-thin     60 to 75            2.5-5        Light gray to
                                 (O.2 to 0.3 ail)     (end voltage)                    pale green
                               Regular-full         75-95              15-25         Medina green
                                 <0.9 to 1.2 mils)
Excellent corrosion
  and abrasion re-
  sistance; good paint
  base;  either AC or
  DC nay be used;
  available through
  licensing arrangement
HAE
(Frankford
Arsenal)





Potassium hydroxide (KDH)
Alusinua hydroxide Al (OH)3
Potassiua fluoride (SF)
Trisodiua phosphate (K»3?O4-12H20)
Fotassiua aanganate (K2HoO4) or
Potass iua peroanganate (101004)


22 oz/gal
4.5 oz/gal
4.5 oz/gal
4.5 ox/gal

2.5 oz/gal


Low voltage
(Light coating)

High voltage
(Hard coating,)



9v AC
(40 ASF)

85
(end voltage)
(18-20 ASF)


15-20
(140-150 F)

60-75
(70-80 F)



Tan color, Eieh corrosion and ex-
smooth

Brown color
rougher than
low voltage
coating
cellent abrasion re-
sistance; use only
, AC; the high voltage
coating i» the hardest
of anodized coatings
on Mg; available with
pe mission

-------
                     TABLE 10  PRINCIPAL WASTEWATER CONSTITUENTS IN WASTES GENERATED
                               DURING THE ANODIZING OF METALS
g=
Constituent
Chromate, Cr04"2
Sulfate, S04~2
Oxalate
Borate
Bichromate, Ci^Oy
Fluoride, F"1
_o
Phosphate, PCty
Amnonium, NH4+1
Manganate, MnO^"2
Potassium
Aluminum, Al+3
_i_O
Mafmosium. Me1^
=========_=————=— 	
Basic Metals and Alloys
Aluminum Magnesium
Sulfuric Acid Processes Chromic Dow No. 17 UAJS
Conventional Hard Coat Acid Process Process Process Zinc
XX X
X X
X
X
X
X XX
X XX
x x
X
X
xxx
xx x xx
Titanium
X
X
Zinc, Zn+2
Titanium, Ti*"3
Chromium, Cr+3

-------
 Posttreatment
 The  corrosion resistance of anodic coatings on aluminum  and
 xts  alloys   xs   xmproved  by  sealing  in  hot  water  at a
 temperature, or approximately 99°C {2100?},  using  deionized
 fjaJJ &> *--\ w     O^fc r3 v *•» ^-w3 4 *•*•*• .«• Jt i • __ «.
    v-j. „    wv*^j. win   t-ij.«-nxroma.T;e ozr sodium silicate are sometimes
 added to  the   water.    Unsealed  coatings  on   aluminum  are
 colored   by   immersing  in a solution containing 0.025 to 1 0

 SIiTna °oFan^rgaSiG ?ye at 66°C <1500')'   After  rinsing,
 sealing   OE   the  dye is accomplishad by  immersion in  a hot
 solution  of nickel  or cobalt acetate.   Inorganic  dyes  may
 also  be  used.   colloidal iron oxide in the  anodic film is
 produced  by immersion in ferric ammonium  oxalate followed by
 Anodic coatings on magnesium may be   sealed  wit-h   a   sodium
 silicate solution heated to lOO^C  C2.2<»F).  SeaUng may also
 be  accomplished  with  a  solution containing 100  g/1 (13  3
 Table 11 lists the principal  constituents  in  waste  water
 generated during posttreatment of anodised coatings.

 Immersion Plating

 Description—ol.^Process.   The  term "Immersion Platina" is
 used  to  describe a bhemlcal plating process in which a  thin
 metal deposit  is  obtained by chemical displacement of the
 basis metal.   The thickness of such deposits ia  usually  of
 the   order  of  0.25  urn  (10  nicroinchm),   although a few
 processes produce deposits as thick as 2.5 to 5.0 um (100 to
 200   mioroxnches).    in  immersion  plating  a  metal   will
 Displace  from  solution any other metal that is below it in
 the electromotive  series  of  elements.   The  lower  (more
 noble)   metal will  be deposited from solution while the more
 active metal  higher in the  series  will  be   dissolved    A
 common  example   of  immersion  plating la the deposition of
 copper or, steel  from an acid copper solution.   ThS  thinness
 of    immersion   deposits   limits   their   usefulness   to
 applications   other  than  corrosion  protection,   such   as
 decoration  or as preparation for further processing such as
 painting or rubber  bonding.                         y

 The most widely  used  immersion plating processes are (1)  tin
 on brass, copper, steel,  or  aluminum,  (2)  copper  on  steel
 (j)  gold on copper  or  brass,  and  (H)  nickel on steel.   These
 four processes will be  discussed  below under  "treatment".

P^£§rati.QIi__,|or_PiatIn3.  Preparation for immersion platina
on brass, copper,  steel,  and  aluminum requires   alkaline
cleaning,  which  can   involve electrolysis but  usually does

-------
                    TABLE 11   PRINCIPAL WASTEWATER CONSTITUENTS IN WASTES GENERATED DURING
                               POSTTREATMENT  OF ANODIC COATINGS ON METALS
                                           Basic Metals  and Alloys
                                      Aluminum
                                               Magnesium
     Constituent
 Sulfuric Acid Processes
Conventional   Hard Coat
                                                    Chromic
                                                 Acid Process
                                    Dow No. 17
                                     Process
                                                                                HAE
                                                                              Process
Zinc   Titanium
Posttreatment
  Dichromate,
  Silicate,
  Fluoride, F'1
  Sodium
Organic dyes
Inorganic pigments

Nickel acetate
Cobalt acetate
  Borate
  Iron
  Ammonium
  Oxalate
      X
      X
X
X

X
X

X
X
X
                                 X
                                 X
                                 X

                                 X
                                 X
                                 X
                                                                     X
                                                                     X
                                                                     X
                                                                     X
                                                                      X
                                                    X
                                                    X
                                                    X
                                                         X

-------
 not.   Alkaline  cleaners  contain  silicates,    carbonates,
 phosphates,   singly or in combinations and are  formulated to
 clean the work without  attacking  the  metal  itself.    The
 cleaner becomes contaminated with organic materials from the
 oil and grease on the work.

 Following  alkaline  cleaning  the basis metal  is pickled in
 sulfuric or   hydrochloric  acid,   which  dissolves  a  small
 amount of the base metal.

 The  principal  waste  water  constituents  generated during
 preparation  of the  work  prior  to  immersion   plating  are
 listed in Table 12.
         — Plating Treatment,   Immersion tin  plating  is  used
 to "whiten" pins,  hooks,  eyelets,  screws, buttons, and other
 hardware   items  made  of  copper,   brass,  or  steel.     in
 addition,   aluminum  alloy  pistons   for internal combustion
 engines are coated with an immersion deposit  of  tin.   All
 immersion  tin  plating baths for  copper,  brass, and steel are
 based   on   stannous  chloride  solutions.  Immersion  tin
 solutions  contain,  in addition to  stannous  chloride,  cream
 of  tartar  (potassium  bitartrate) ,  ammonium aluminum sulfate,
 or  sodium  cyanide  and sodium hydroxide.

 Copper i.s  immersion deposited on steel wire prior to drawing
 in  ordex   to  reduce wear on the  dies.  Copper is deposited
 from an acid copper sulfate solution.  Copper-tin  alloy  is
 obtained   on  steel  wire  by adding tin salts to the copper
 sulfate solutions.

 Gold is immersion  deposited on   copper   and  brass  to   gild
 inexpensive    items  of   jewelry.    Typical  immersion   gold
 piating  solutions  contain gold  chloride  and   potassium
 cyanide or pyrophosphate.

 Nickel  is   immersion  deposited  on steel prior to ceramic
 enameling  to improve  the  adhesion of the enamel.    Immersion
 nickel  solutions  contain  nickel sulfate, or nickel chloride
 and boric  acid.

 Table 13 lists the  principal  constituents  in  waste  water
generated  during immersion  plating of tin, copper, gold,  and
 nickel on  various basis metals.   Gold is not listed.

Chemical Conversion Coat ings-Chroma ting

fi§§ciiE£io.?v  of  the  Process.   Chromate conversion coatings
are protective films formed on metal surfaces.  A portion of
the base metal is converted to one of the components  of  the
                            SO

-------

                                                    Bail* Metal
     Pollutant

            '•-—


Alkaline Cleaning


  Iron, ferrous, Fe+2



  Aluminum, Al


  Silicate, Si03~2



  Carbonate,  C03"2


  Phosphate,  P04~3



  Organics



 Acid Dipping


   Iron,  Ferrous,  Fe+2



   Aluminum,
   Copper, Cupric, Cu


           +2
   Zinc, Zn


   Sulfate, S04~


   Chloride, Cl"
                    .+2
t^mg-vmi-mm n i •
ass
•^H- •— »— •— •—

X
X
X
X
Copper


X
X
X
X
Steal Alumiti
X
X
x x
x x
x x
x x
X



X



X


X
X


X
X



X
X



X
                                         51

-------
TABLE  13  PRINCIPAL WASTEWATER CONSTITUENTS IN WASTES
           GENERATED DURING IMMERSION PLATING OF TIN,
           COPPER,  GOLD,  AND NICKEL
Pollutant
Immersion Tin Plating
Tin
Chloride
Tartret.e
Cyanide
Ammonium
Aluminum
Sulfate
Sodium
Immersion Copper Plating
Copper
Sulfate
Immersion Gold Plating
Chloride
Bicarbonate
Pyrophosphate
Cyanide
Potassium
Immersion Nickel Plating
Nickel
Sulfate
Borate
Chloride

Brass
X
X
X
X
X
X
X
X


X
X
X
X
X




Basis
Copper
X
X
X
X
X
X
X
X


X
X
X
X
X




Metal
Steel Aluminum
X X
X X
X
X
X
X
X
X
X
X





X
X
X
Y
                         52

-------
film   by   reaction   with   aqueous  solutions  containing
hexavalent chromium and other active   organic  or  inorganic
compounds.  Chroma te coatings er®  moat frequently applied to
the  following  metals:   sine,  cadmium,  aluminum, magnesium,
copper, brass, bronze, an  a  a-cri!i.c«  with  a   high  luster  or
 polish.   The chrom&t* f \~s,\ f--cv;.d«*s good protection against
 corrosion and auU'iofe -..&. «.'>:- .:r.g  on  unpi&ted  parts.    The
 film also provides a qcccx psiuv Lu^e0

 Chromate  coatings  are  sppiiefi  to silver  electroplates to
 prevent sulfide tarnishing tasing  proprietary   formulations.
 Table  14   lists  the  principal  waste  water  constituents
 generated during  pretxea-coriesvt,  coating  and   postreatments
 steps  in  chromating  zinc,  cadmium,  aluminum  and  other
 metals.

-------
                             TAH.I 14 niNCZPAI. HASTWATE* COMSTITVBm » HASTXS
                                              cwoHAiure oriuixon on MKXOW NRMJ

Ma«n
ChroM-
PiekU
Constituent Al Proeeia

• ilum
Bichromate
Proctn

Zlno or Cadmium
E leC trODle £O a
Bright Yellow, Bronte or
CMtillH 	 OHva Dub Caatin.e

Zinc Die
Yillow, Bronn or
Ollv« Drib Co^ttn.

Copp«n BrMt
Bronco
or
' «"-«•
               ActivatlnB
    Aluminum,  Al*J
    Magneiium.
    Zinc,  Zn«                                             XX
    Cadmium,  Of™                                          X                X
    Copper, Cu*              X                                                                                  x
    Manganeee                X
    Tin,  Sn+2
    Silver, Ag*1                                                                                                 x
    Cyanide,  OT1                                          x                z
    Carbonate,  C03-2          XXX                                                X                x
    Photphate,  PO^-3          XXX                                                T
    Silicate  SlOj-2           XXX                                                X                x
    Kerylbenzene aulflnate    X
    Cllvconatea              X
    Citratea                 X
    Tartratea                X
    Nitrate, N03"1           X                            XX
    Fluoride, F'1            X                X
    Sulfate, SO/(-2           x                                                                 X
    Chromate, CrOi*2         X
    Aluminum, RH^*t                           X
    Sodium                   X      x         X                                                j

toatlnp

  Sodium                     x                            XX                   X                .
  Chromata, CrO^-^           x                            X                X                   X                J
  Iron Cyanide               x
  Fluoride, P'l             x                            XX                   XX
  Bichromate, Cr207'2               j          j
  nitrate, NOj'l             X      X
  Aluminum, Al*3             x
  Kagnailum,  Mg+2                   .          _
  Zinc, Zn+2                                   *
  Cadmium, Cd+2                                           X                x                   «                X
  Copper, Cu*2
  Tin, Sn+2                                                                                                     x
  Silver, Ag+1                                                                                                  x
  Calcium, Ca*2                •                x                                                                X
  Or«anlca                  X       X          x          x                X                   x                X
  Potaieium                 x                             x                X                   X                x
  Phoaphata, PO^*3                                        X                x                   X
  Carbonate C0j~2.                                        X                x                   X
  lodium                    *                             x               I
                                                            54

-------
                                                                                    4,
                                           TABLE  15  ALKALINE  CLEANERS FOR ALUMINUM
        Type
tn Noninhibited
01   Etching

  Inhibited-
    Nonetching
                       Composition
                                                                                             Temp, C
                                                                                     Time
Sodium carbonate (Na2C03): 22.5 g/1 (3.0 oz/gal)
Sodium orthophosphate (Na3P(>4• 12H20: 22.0 g/1  (2.9 oz/gal)

Sodium carbonate (Na2C03): 22.5 g/1 (3.0 oz/gal)
Sodium orthophosphate (Na3P04*12H20: 22.5 g/1  (3.0 oz/gal)
Sodium metasilicate (Na2Si03.9H20: 15.0 g/1  (2.0 oz/gal)
Kerylbenzene  sulfonate (40%): 2.5 g/1  (0.3 oz/gal)
                                                                                             71-? 2
As Required


As Required

-------
 Preparation for Chromatj.ng.    Chromate  conversion  coatings
 are  frequently  applied   to  zinc  or  cadmium-plated parts
 immediately following electrodeposition.   No  preparation   is
 necessary.    in  some  caseo,  a  baking operation to«limlnate
 hydrogen   from  th«   deposit  is   carried   out   following
 electrodeposition.    Alkaline  cleaning  and  an acid dip may
 then  be necessary before  chromating.

 Alkaline cleaning of  zinc die  castings is generally  carried
 out  in a  proprietary solution, or a  solution such as given
 helowf(  under the conditions  shown.

        Sodium carbonate         7.5 a/1  (1 oz/gal)
        Sodium hydroxide         7. 5 g/1  (1 oz/gal)
        Temperature                93°C (^00 F}
        Time                      30-60  seconds.

 This  cleaned work is  rinsed  thoroughly and then dipped in  1
 to  2  percent sulfuric or phosphoric  acid for 15-30 seconds
 at  roon  temperature  to assure   neutralization   of   any
 remaining alkaline films.  Following another  thorough rinse,
 it  is then  chromated.

 Conventlonal  cleaning procedures involving solvent cleaners
 or  vapor degreasing   are  used   routinely on  aluminum  for
 removal  of   grease   and  other  organic  contaminants.  The
 removal of  soil  from  aluminum is most  frequently achieved by
 using alkaline cleaners,  that   function  by  dissolving  or
 dispersing   soils, augmented in  some instances by etching of
 the metal.    TWO representative  cleaner formulations  for
 aluminum  are shown in Table 15.   The  silicate in the second
 formulation   works  as  both  a  detergent   and   corrosion
 Inhibitor;   the   kerylbenzene  sulfonate  is a wetting agent.
 An etching-type  cleaning  treatment  may   be  used  prior  to
 other   treatments  when  a  mat  or  nonapecular  surface is
 desired.  Inhibited nonetching cleaners   are  employed  when
 attack  or   roughening  of  the  aluminum  part  surface are
 undesirable.  Prolonged operations  with aggressive  alkaline
 cleaners  such   as  those containing caustic soda frequently
 cause the precipitation of a  flocculent  hydrated  aluminum
oxide  which  can  interfere  with  effective rinsing of the
work.   Several additional agents, which contain  gluconates,
citrates,   or  tartrates,   have  been  developed to avoid or
minimize sach effects.  These agents  work  by  sequestering
the  hydra ied  aluminum   oxide  to  yield  a  more  granular
precipitate which is less likely  to cake and responds better
to rinsing*

Aluminum alloys containing copper,  manganese,  or silicon are
especially susceptible to smut   on  their  surfaces  during
                              56

-------
alkaline  cleaning  operations.  The smut generally consists
of  loosely  adherent,  finely  divided  particles  of   the
aluminum  alloy metals or their oxides.  Table 16 lists some
typical deoxidizing and desrrratting treatments for  aluminum.
Nitric acid (formulation A) is a general- pur pose reagent for
removal of smut from aluminum and other metals.  Formulation
B,  containing  about  75%  nitric acid and 25* hydrofluoric
acid is especially effective in the removal of  smut  formed
on  high  silicon  (5*  or  more) alloys.  The chromic acid-
phosphoric acid (Formulation D) mixtures are generally  used
for  the  selective  removal  of  oxide  without aignificant
attack of the metal  surface.   Proprietary  deamutting  and
deoxidizing solutions are extensively used.

Alkaline  cleaning is generally the most satisfactory method
for degreasing and cleaning magnesium prior  to  chromating.
Representative  alkaline  cleaner compositions and operating
conditions for processing magnesium are presented  in  Table
17.

Pretreatment of copper, copper alloys, and silver is similar
to the procedures  described for  sslnc, cadmium, and aluminum.

           Treatments*  Zinc and cadmium may be chromated to
provide:


       (1)   bright  chromates  on  zinc  and  cadmium electro-
            deposits,

       (2)   colored coatings  on  zinc  and  cadmium electro-
            deposits,  and

       (3)   colored coatings  on  zinc  die  castings.

The   bright chromate treatments impart a high luster to zinc
or cadmium plates  and also  provide   tarnish  and  corrosion
resistance.     The  chromate  treatment   of  elect rode posits
generally follows  immediately after  the  last  rinse  in  the
plating   cycle.    The  chromate  bath for  coating zinc and
cadmium  parts is  an  acid  solution  containing   hexavalent
chromium,  such as  chromic acids,  plus other inorganic and
organic  compounds  to promote or catalyze the reaction.

The  chromate coating solution for aluminum usually  contains
hexavalent chromium, a fluoride, and an  accelerator, such as
 ferrocyanide  or  ferricyanide.  The pH  range is  usually 1.0
 to 2.5.   Nitric acid frequently is added  as  an   acidifying
agent.    The  fluoride,  in  the  acidified solution, is the
 active reagent;  it dissolves the  existing  oxide  film  and
                             57

-------
                TABLE  16  REPRESENTATIVE DEOXIDIZING AND DESMOTTING
                           TREATMENTS FOR ALUMINUM   .
          Formulation
 (A)  Cone. HN03 (10 to 50% by vol)
 (B)  75% vol cone HNO
     25% vol HF (48 wt%)

(C)  20 g/1  (2.66 oz/gal) Cr03
     35 ml/1 85 wt% H3PO
(D)  100 ml/1 96 wt% H2SO,
     35 g/1  (4.66 oz/gal) Cr03
                                       Temp,  C
Ambient
Ambient

88-93
    Time
    ••MMMMMM
30  to 60 sec
5 to 10 sec


2 to 10 min

1 to 5 min
      Purpose
      •••mMaM^w^
Smut removal
Smut removal,
especially for high
silicon Al alloys
Oxide removal
                              Oxide removal
64-82
                                           58

-------
      Beavy Duty
         Alkaline
                          TABLE  17  REPRESENTATIVE ALKALIHE CLEAHERS FOR MAGNESIUM
                 Sodium hydroxide  (NaOH):  15-60 g/1 (2-8 oz/gal)
                 Trisodium phosphate (Ka3P04 •  12H20)  11 g/1 (1-1/2 oz/gal)
tn
Caustic Soak(a)  Sodium hydroxide (NaOH): 98 g/1 (13 oz/gal)
Immerse parts 3 to 10 minutes
   in bath at 88-100C; clean
   until no water break occurs
   in rinse; rinse thoroughly

Immerse parts in bath  at  88-
   100C; soak for 10-20
   minutes; rinse thoroughly
       (a)  Md 0.1

-------
 reacts   with  the  aluminum.   During  the  coating  process, some
 of  the  hexavalent  chromium  is   reduced   to  the  trivalent
 state,   and a gel-like  film consisting  primarily of aluminum
 and chromium  chromates  is formed.   As   freshly  formed,  the
 gel-like  coating  is   dissolved  readily  in nitric acid.   If
 desired, the  yellow chromate can  be leached with hot  water.
 with   aging,   the  film    becomes insoluble.   For  many
 application,   rinsing   and   drying   complete    the   overall
 chromating operation.

 Much of  the development   work  on chromate  coatings   on
 magnesium  has been  carried  out by the Dow Chemical  Company.
 Chemical  Treatment No.  1,  also known as  "chrome pickle",  is
 the most commonly  used chemical  treatment  developed  for
 magnesium.    It   can be used on all magnesium alloys.  The
 coatings have good  qualities as a  paint   base  and  protect
 magnesium   parts  during shipment   and   storage.  A typical
 chrome-pickel procedure is  shown  in Table 18.   The  coating
 appearance is usually mat gray   to yellow red, and about
 0.00006  inch  of metal is removed  from the magnesium.

 The dichromate   treatment   (Dow  No.  7)   for  processing
 magnesium   alloys  (except   the   thorium   containing  alloy)
 produces a brassy to dark brown film, which provides a  good
 combination  of   protective   and  paint-base qualities.  The
 dichromate procedure is  described in Table 19.

 Generally,  a  cold rinse   followed by   a  hot  rinse   to
 facilitate  drying complete the overall chromating process on
 magnesium  alloys.

 chromating  treatments  for copper,  copper alloys, and silver
 are  similar to those described for  zinc and cadmium.

 Posttreatment.  Posttreatment of chromated parts, when used,
 can  involve bleaching or  dying  operations  to  produce  or
 Impart   special   characteristics  to the  film.  Clear bright
 finishes for  zinc and cadmium can be obtained  by  bleaching
 or   leaching   the   yellow  coloring  from  the chromate film.
Various mildly acidic  or  alkaline  aqueous  solutions  are
 employed,  such as

      {!)   Sodium hydroxide  23 g/1  (3 oz/gal) ,
            room temperature  5 to 10 seconds,

      (2)   Sodium carbonate  15 to 23 g/1  (2 to 3 oz/gal)
            49 to  5U°C (120 to 130 F) ,

      (3)   Phosphoric acid,   1.0 ml/1 (.13  fl  oz/gal),
           room temperature, 5 to 30 seconds.
                                60

-------
              TABLE 13   CHROMATE COATING OF MAGNESIUM BY
                         THE CHROME PICKLE PROCESS
    Step
          Bath
                                               Procedure or Comments
Cleaning

Rinse


Chrome Pickle
Rinse
Rinse
Alkaline

Cold Water
Sodium dlchromate
  (Na2Cr207 • 2H,0):
  180 g/1 (24 oz/gal)
Concentrated nitric
  acid (to WtX HNO,):
  187 ml/1 (24 fl oz/gal)

Cold Water
Hot Water
Immersion

Rinse thoroughly in
cold running water

Immerse parts 1/2 to
2 minutes in room
temperature solution.
After dip, hold parts
above tank for about
5 seconds.

Rinse thoroughly in
cold running water

Hot water rinse used
to facilitate drying
                                  61

-------
                TABLE  19  DICHROMATE PROCESS CYCLE FOR
                           MAGNESIUM ALLOYS
   Step
               Bath
Procedure or Comments
Cleaning

Rinsing


Acid-fluoride
  pickling



Rinsing
Bichromate
  treating
Rinsing


Rinsing
Alkaline

Cold Water
50 g/1 (6 2/3 oz/gal) sodium acid
  fluoride (NaHFj), potassium acid
  fluoride (KHF2), or ammonium
  acid fluoride (NH4HF2)

Cold Water
120 to 180 g/1 (16-24 oz/gal)
  sodium dlchromate
            • 2H20)
Cold Water
Hot Water
 Immersion

 Rinse thoroughly in
 cold running water

 Immerse parts 5
 minutes at room tem-
 perature.
 Rinse thoroughly in
 cold running water

 Boil parts for 30
 minutes - minimum
 temperature 93C,
 200F

 Rinse thoroughly in
 cold running water

 Hot water rinse used
 to facilitate drying
(a)  The dichromate process is frequently referred to as
     Dow Chemical Treatment No. 7.
                                    62

-------
Dyed coatings can also be applied.


Chemical converiiQ-D Coalings -

Description of the Process

Phosphating  is  the  treatment  of iron, steel, zinc
steel, and other metals by immersion in a aa.j.ufct* solution
phosphoric acid plus other reagents to produce  an  integral
conversion  coating  on the surface.  Phosphate coa^ms are
used to:  (1) provide  a  good  base  for  paints  anc  «"ther
organic  coatings,   (2)  condition  the  surfaces  :. :>i  rold
forming operations by providing & b*84 for drawing com^nds
and lubricants, and  (3) impart corrosion resistance  to  the
metal  surface  by  the  coa-cing  itself  or  by providing a
suitable base for rust-preveatative oils or waxes.

The amorphous aluminum phosphate films are used  extensively
as  a  base  for  organic  coatings.   Crystalline  aluminum
phosphate coatings are used chiefly  for  paint  bonding  to
aluminum  and also to provide  lubrication for cold rooming.

commercial  phosphating solutions are  frequently proprietary
and  usually  consist  of  metal  phosphates  dissolved   in
phosphoric  acid solutions containing  accelerators  and other
special reagents to  improve bath performance.   Commonly used
accelerators  include  nitrites,  nitrates,  chlorates,  and
peroxides.  Phosphating occurs ats follows:
      3Me(H2POi)2  *  Fe   Me3«POi)l * FeHP04 *  3H3.PO§ *  H2

 whe re :

                     Me = Zn, Mn,  or Fe.

 The  metal  is  provided  by  the basis material or from the
 phosphating solution.


 Pretreatment Procedures

 Cleaning of iron or steel parts is generally accomplished by
 alkaline  cleaning  or  solvent  decreasing.   Pickling   in
 phosphoric  acid or other mineral acid solutions is used for
 removal of rust or other corrosion products.  Rinsing in hot
 water,  or  in  special  activating   solutions,   generally
 completes  the pretreatment.  In sojtie instances, cleaning is
 carried out simultaneously ir. the same solution.
                                  63

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The pretreatment procedures  for phosphating aluminum  alloys
include  alkaline  cleaning,  and   sometimes acid or caustic
etching,, desmutting  or   deoxidizing   dips,  along  with  the
attendant  rinses.    These   procedures were described in the
earlier sections of  the  report dealing   with  anodizing  and
chromating of aluminum.

Table  20  lists  the principal  waste  water  constituents
generated during  preparation,  coating,  and  posttreatment
operations in phosphating iron, steel, and aluminum.

PteSBbgtAng	Trjgatjjjents.   Zinc  and  iron phosphate coatings
are applied by spray and immersion  techniques.   Parts  are
immersed  in  a  2-1/2%  by volume zinc phosphate solution at
f90°F) for 30 seconds or sprayed with a  «%  by  volume  zinc
phosphate  solution   at   (1UO  to 180 F) for 3 to 5 minutes.
Sine phosphate may be  applied  to  parts  in  an  automatic
barrel   line   by    immersion  in  a proprietary  solution
containing zinc phosphate, phosphoric acid,  and  nitrates.
Iron  phosphate  is   applied  by immersion in a 5% by volume
solution at (125 F to 160 F)  and pK 3.5 to 4.5 for  3  to  5
minutes or spraying  with a (1/2 to 2  oz/gal)  solution at (90
to  160  F)  and pH 3.5 to 5.0 for 1 to 2 minutes.  Manganese
phosphate is applied by  immersion in  a solution at  (200  F)
for 10 to 20 minutes.

A.   typical   solution   for  producing  amorphous  phosphate
coatingo on aluminum contains 70 g/1  phosphoric acid  and  a
ratio of fluoride ion to chromic acid of 0.25.  The fluoride
removes  the  oxide   film  on  the  surface  and attacks the
aluminum base metal  to   provide  the  ions  needed  to  form
aluminum phosphate*   The treatment times for temperatures of
100  to  130°F  vary  from a few seconds to several minutes.
The coating weights  can be varied from 0.11 to  1.3  g/sq  m
(10 to '400 mg/sq ft).

crystalline  phosphate  coatings  on  aluminum  are produced
using  solutions   containing   zinc   or   manganese   acid
phosphates,   an  oxidizing  agent  such  as  nitrate,   and a
complex fluoride  to  serve  as  the  activating  agent.    A
typical  phosphating  solution contains: Q.7% zinc ion,  1.0%
phosphate  ion  (POU) 3-,   2.0%  nitrate  ion  (NO3J1-,   and
fluoborate ion (BF4)1-.   A satisfactory film can be produced
by  spraying  solution for 1 to 2 minutes at 5«l to 57°C (130
to 135 F) ,  or by immersing for 5 minutes in a solution at 51
to 57°C (130 to 135  F) .
                                 64

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TABLE  20  PRINCIPAL WASTEWATER CONSTITUENTS  IN WASTES
           GENERATED DURING PHOSPHATING OPERATIONS ON
           VARIOUS METALS AND ALLOYS
                Basis Metals  and Alloys
                           Iron, Steel, and
     Constituent            Zinc-Plated  Steel      Aluminum


Preparation-Cleaning
  and Activating

  Sodium,  Na+                      x                  X
  Aluminum  A1+3                                       X
  Zinc, Zn+2+2                     X
  Iron, Fe+2                       x

  Carbonate, C03'2                 X                  X
  Phosphate,    -3                 X                  X
  Silicate, Si02-2                 x                  X
  Gluconate                        X

  Sulfate                          x                  X
  Chloride                         x                  x
  Nitrate                          x                  x
  Chromate                         x

  Titanium, Ti+3                   x
  Antimony, Sb+3                   x

Phosphating

  Sodium, Na+                      X                  v
  Aluminum, A1+3                                      X
  Zinc,  Zn*2                      x                  X
  Iron, Fe+2                       X
  Manganese, Mn+2                  X

  Phosphate, P04'3                 X                  X
  Chromate, CrO^-2                                    X
  Fluoride, F-l                                       x
  Fluoborate, BF^'1                                   x
  Nitrite, N02~J                   x
  Nitrate, NOs"1                   X                  *
  Chlorate, C103"1                 X

Posttreatment
   Chromate,
   Phosphate,  P04"2                 x

   Water  soluble  oils               X
     and  waxes
                             65

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 Posttreatment Procedures

 The final rinse after phosphating of iron, steel,  and  zinc
 is  usually  carried out in a dilute chromic acid-phosphoric
 acid  solution  (0.1%  by  volume).   This   rinse   removes
 unreacted chemicals and improves the corrosion resistance of
 the  phosphated  surface.   The  rinse  8tep  is  frequently
 followed by & dip in a suitable oil, waxr or other lubricant
 before dryirjg in hot air.

 Chemical Milling and Etching

 Introduction..  Chemical milling is the process  of  shaping,
 machining,  fabricating, or blanking metal parts to specific
 design   configurations   and   tolerances   by   controlled
 dissolution with chemical reagents or etchants.   The process
 is  somewhat  similar  to  the  etching  procedures used for
 decades by photoengravers,  except that the rates and  depths
 of metal removal are usually much greater.  Chemical etching
 is the process of  removing relatively small amounts of metal
 from  the  surface  (e.g.,   1-5 mils)  to improve the surface
 condition of the basis metal or to produce a pattern such as
 for  printed  circuit  boards.   Chemical  brightening   and
 chemical polishing are specialized examples of processes for
 improving surfaces by chemical dissolution.

 Much of the early  chemical  milling work was done on aluminum
 and  macmesium  parts  for  the aircraft industry.   Chemical
 milling is especially suited for  removing  metal  from  the
 surface  of  formed or complex-shaped parts (e.g.<,  forgings,
 castings,  extrusions) ,  from thin sections,  and   from  large
 areas  to  shallow  depths.    The  weight saving achieved is
^ especially important in aircraft and space  vehicle  design,
 Ifr^ chemical  milling  or  etching  processes?   metal can be
 ^emjbved from an entire part or restricted to selective areas
 by maskir g.   The amount of  metal removed or depth of etch is
 determined  by  the  time  of  immersion  in  the   etching
 solutions.

 The  overall  chemical milling or machining process consists
 of four main operations

       (1)   Cleaning or surface preparation
       (2)   Masking
       ?3)   Etching
            Mask removal and rinsing,
 Preparat.iLyg^OperatjpOns.   Grease  and  dirt  from  metal  and
 alloy  surfaces   are removed by conventional methods such as
 vapor degreasing  and  alkaline  cleaning.    Scale,   passive
 films,  or   oxidation  products,   or other foreign materials
 that  are  f irmly  attached are removed  by  acid  pickling  or
                                66

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SS
          by
       areas to OK «™e°-   «»               sttlve  resists.
 «ha««*d  parts  of  relatively  *«*» ,r-wj:ch,    parts can be
                   -T -n „_   H ,a oQ  V H ££ if!  Ar AS1  JLI*^**! *   * *»*• *^**
 ...sicknesses  ^sua^/   -ess  jna                sideg   of  the
 blanked by re.-aovsi o-t  ^®taj ™^on  of the overall masking
 sn^ot-  work-piece.    Opon  coi.^ie\-ion  w*.               ...
 operation, the  parts  may be c
 the  surface for  the  etching
 water constii-.u^v.s qer.era-ceo



                ,• — .".  b*._'^fc,  v.j.«ti ^icfci properties of   the
                                        ability to operate  well
  'V    l  foa--ure« of  an  e-
  -ibl*'  ?2 list
  •i f>•»'-' csl r-/  lllr.c;
  <\S 
-------
   fluortds, ?*
   lulf«t«, S04'2
   Chronwt*. CrOi*z
   Chloride, 01*1
  Alufflln«t«,
  Eodtua
         H«t«l
  Sodtua
  Aluninun,
  Cejsp«r,  CuH *nd
  Zinc, Zflta
  Tin, 8*t2
  Chroaiun, cr*"3
Iron, r«   end
Cob«Ze,
          ,  Mp
              +3
 Vatudtum,
Fluoride, F*l
3ulf«t«, S04"2
ClWotMU, CtO*"2
OWostdu, C1"I
            320B"2
           P04*-*
           AlOj"2
X
X
X
X
X
X
X

X
X
X
X
X
X
X
X
*

X
* X

X
X
X
I
X
X
z

V

X
X
X
X
X





X
X
X
X
X
X




X
X
X

X
X



                                             X
                                             X
                                             X
                                                            X
                                                            X
                                                            X
                                                            X
                                                    X

                                                    X
                X
                X

                X
                X
                X
                                                                         X

                                                                         X
                                           X
                                           X
                                           X
X

X
                                                                                     X
                                                                                     X
                                                                                     X
X
X

X
X
                                                 68

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    TABLE 22    REPRESENTATIVE AQUEOUS SOLUTIONS FOR
                CHEMICAL MILLING OR ETCHING VARIOUS
                METALS AND ALLOYS
-------
                         SECTION VI

             SELECTION OF POLLUTANT PARAMETERS

Introduction

This section of the  report  reviews  the  waste  character-
ization  detailed  in  Section  V and identifies in terms of
chemical and physical constituents  that  which  constitutes
pollutants  as  defined  in  the  act.   Rationales  for the
selection and, more particularly g the  rejection  of  waste-
water constituents as pollutants are presented.

First,  consideration  was  given  to  the  broad  range  of
chemicals used  in  the  metal  finishing  industry.   Those
considered to be amenable to treatment are identified.
A  larqe  variety  of  chemicals  that  become  waste  water
constituents are used in the metal finishing.  The important
ones were  identified  in  Section  V.   Not  all  of  these
constituents  will  be  found In the i*&ste waters from every
facility, since the number of processes in a single facility
varies as well as the nurses: of b&sic  materials  pretreated
and  types of posttre&tntent operations.  When present, metal
ions  are  usually  coprecipitated  with   copper,   nickel,
chromium,  and/or  zinc.  The nonmetallic cations and anions
 (hydrogen, ammonium,  sulfate^  phosphate,  chloride,  etc.)
from  electroplating  copper ? nickel, chromium, and zinc can
be considered typical of the metal finishing industry.

waste Water Constituents ami p&raaiatera of Pollutftonal
Significance

The waste water constituents of pollutional significance are
total suspended solids, phosphate^ oxidizable cyanide, total
cyanide, fluoride, aluminum, cadmium^  hexavalent  chromium,
total  chromium,  copper,  iron,  nickel, tin, zinc, and pH.
These constituents are the subject of  effluent  limitations
and standards of performance regardless of the physical form
 (soluble or insoluble metal) or chemical form  (valence state
of a metal and whether or not it is complexed) .

The pH is subject to effluent limitations because it affects
the  solubility of metallic compounds such as zinc hydroxide
and the soluble metal content of the treated effluent.
                               71

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 Thus,  the  major chemical,   physical,  and  biological  waste
 water    constituents    and   parameters   of   pollutional
 significance are as  follows
                Total suspended solids
                Phosphate
                Oxidizable cyanide
                Total cyanide
                Fluoride
                Aluminum
                Cadmium
                Hexavalent chromium
                Total Chromium
                Copper
                Iron
                Nickel
                Tin
                Zinc
               pH.
Other waste water constituents of secondary importance  that
are  not the subject of effluent limitations or standards of
performance are as follows
                Total dissolved solids
                Chemical oxygen demand
                Oil and grease
                Turbidity
                Color
                Temperature
                               72

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                Nitrate

                Ammonia

gaiiorjale £QT the Select log £f HMtS $£&££ G9niSfc4tVtaOtP  ABd
Parameters.,.

       suspended solids .   Suspended  solids was  selected as a
parameter to  further assure  that  efficient clarification  is
practiced.    control   of  total  wsat-al  discharged,  i.e.f  lead,
also assures  that clarification td.il  be  efficient.   However,
control of suspended solids  i.lso  assures that excess  solids
will not be unnecessarily discr* surged.  Furthermore,  in  spite
of  extensive review  of bot:h  compositions and a listing of
waste  water  constituents  there  may    be   waste   water
constituents   In  individual   plants not  covered   by  the
listings and  not selected as polliixarit parameters.   If   such
constituents  are also  precipitated,  by the chemical treatment
methods   employed  to remove  'psllutants  that  have   been
selected as   pollutant pa r& meters,   they  will  be   removed
providing there is a limltstcion en  auipssnded Bolide.  Metals
such  an  arsenic,,  beyllitsmw, co-UKbioif,  g&llium, germanium,
hafnium, manganese, molybdenum, titanium, tungsten,  uranium,
vanadium^, and zirconium would be-  irsmov«d to some  extent  by
neutralization and
Phosphorous.  Phosphate  is prvsse.^v.  ira  significant amounts in
cleaners, acia dips, a ad processing baths  in  Subcategory (1)
processes  and   can ba rencvsii by reaction with  lime to form
insoluble   caxciuEi   phoapLtt'te^    Liuie    is   a   suitable
neutralizing  agenc  and t'na  piioaphate   may therefore  be
coprecipitated ivi-cn the  hesvy aeiiils.

Cyanide, Amenable  to  Qxid£.-cl.:tg|  bv   Chlorine.    Oxidizable
cyanide  may  be present in  significant amounts  in the waste
water from this segment,  of the eLaetroplatiag industry  and
is   amenable   -co  oxidation  by   chlorine  under  alkaline
conditions.

Cyanide.^ Total,  some forms  of cyanide are not   amenable  to
chlorine  oxidation  and can  appear  in  the waste water in
significant amounts which era w.iafc  be   removed.    Cyanide  is
present  in  waste  waters   c.s the  free cyanide  ion (CN-) or
complexed with metals such a.s  copper*  zinc, cadmium,   and
silver.   The  free  cyanide  and   the cyanide  in the metal
complexes mentioned are  destroyed  by chlorine.    However,
more  stable  cyanide  complexes  such as  those  with nickel,
cobalt, and iron are not effectively oxidised by  chlorine,
although  may  be  by  ozone  fsee Section  VII) .   Since iron,
cobalt,, and nickel are not  plated  from   cyanide  solutions
                               73

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their  source, if present, is not from electroplating baths.
However,  some  cleaners  and  stripping  solutions  contain
cyanide  and  the  dumps  and rinses from these are normally
combined with rinses from nickel, cobalt, and iron baths  to
constitute  the  acid-alkali  waste water stream.  There are
alternatives to use of cyanide in stripping solutions and it
is believed that the cyanide in cleaners can be minimized or
eliminated.   Thus, it is practicable to limit the amount  of
cyanide  that  is  not amenable to oxidation and this may be
considered a pollutant parameter.   Total  cyanide  is  more
easily  determined than difficult-to-oxidize cyanide.  Since
it is made up of oxidizable cyanide  which  is  a  pollutant
parameter  and  difficult-to-oxidize cyanide, which could be
regarded as a pollutant parameter, the total cyanide is also
a pollutant parameter.

Fj-uogj-deg

As the most reactive non-metal, fluorine is never found free
In nature but as a constituent  of  fluorite  or  fluorspar,
calcium fluoride, in sedimentary rocks and also of cryolite,
sodium  aluminum fluoride, in igneous rocks.  Owing to their
origin only in certain types of rocks  and  only  in  a  few
regions,  fluorides  in high concentrations are not a common
constituent of natural surface waters, but they may occur in
detrimental concentrations in ground waters.

Fluorides are used as insecticides, for disinfecting brewery
apparatus, as a  flux  in  the  manufacture  of  steel,  for
preserving  wood and mucilages, for the manufacture of glass
and enamels, in chemical industries,  for  water  treatment,
and for other uses.

Fluorides  in  sufficient quantity are toxic to humans, with
doses of 250 to U50 mg giving  severe  symptoms  or  causing
death.

There  are  numerous  articles  describing  the  effects  of
fluoride-bearing waters on dental enamel of children;  these
studies  lead  to  the  generalization that water containing
less than 0.9 to 1.0 mg/1  of  fluoride  will  seldom  cause
mottled  enamel  in children, and for adults, concentrations
less than 3 or 4  mg/1  are  not  likely  to  cause  endemic
cumulative   fluorosis   and   skeletal  effects.   Abundant
literature is also available describing  the  advantages  of
maintaining  0.8  to  1.5  mg/1  of fluoride ion in drinking
water to aid in the reduction of  dental  decay,  especially
among children.
                               74

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Chronic fluoride poisoning of livestock has been observed in
areas   where  water  contained  10  to  15  mg/1  fluoride.
Concentrations of 30 - 50 mg/1  of  fluoride  in  the  total
ration  of  dairy  cows  is considered the upper safe limit.
Fluoride from waters apparently does not accumulate in  soft
tissue  to  a  significant degree and it is transferred to a
very small extent into the milk and to  a  somewhat  greater
degree  into  eggs.   Data  for  freah  water  indicate that
fluorides are toxic to fish at  concentrations  higher  than
1.5 mg/1.
Cadmium in drinking water supplies la extremely hazardous to
humans,  and  conventional  treatment,  as  practiced in the
United states, does not remove ita  Cadmium is cumulative in
the liver, kidney, pancreas, and thyroid of humans and other
animals.  A severe bone and kidney  syndrosne  in  Japan  has
been  associated  with  the  ingsstion  of  as little as 600
ug/day of cadmium.

Cadmium  is  an  extremely  dangerous  cumulative  toxicant,
causing  insidious progressive chronic poisoning in mammals,
fish, and probably other animals because the  metal  is  not
excreted.   Cadmium could form organic compounds which might
lead to mutagertic or teratogenic effects.  Cadmium is  known
to   have  .marked  acute  and  chronic  effects  on  aquatic
organisms also.

Cadmium acts synergisticaily with other metals.  Copper  and
zinc   substantially  increase  its  toxicity.   Cadmium  is
concentrated by  marine  organisms,  particularly  molluscs,
which  accumulate  cadmium  in calc&raous tissues and in the
viscera,  h concentration factor of 1000 for cadmium in fish
muscle has been reported? as have concentration  factors  of
3000  in  marine  plants, and up to 29,600 in certain marine
animals.  The eggs and larvae of fish  are  apparently  more
sensitive  than  adult  fish  to  poisoning  by cadmium, and
crustaceans appear to be more sensitive than fish  eggs  and
larvae.

Chromium

Chromium,  in  its  various  valence states, is hazardous to
man.  It can produce lung tumors when  inhaled  and  induces
skin   sensitizations.     Large   doses  of  chromates  have
corrosive effects on the  intestinal  tract  and  can  cause
inflammation  of  the kidneys.   Levels of chromate ions that
have no effect on man appear to be so  low  as  to  prohibit
determination to date.
                               75

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The  toxicity  of  chromium salts toward aquatic life varies
widely with the species, temperature,  pE,  valence  of  the
chromium,   and   synergistic   or   antagonistic   effects,
especially that of hardness.  Fish are  relatively  tolerant
of  chromium  salts, but fish food organisms and other lower
forms of aquatic life  are  extremely  sensitive.   Chromium
also inhibits the growth of algae.

In  some  agricultural  crops,  chromium  can  cause reduced
qrowth or  death  of  the  crop.   Adverse  effects  of  low
concentrations  of chromium on corn, tobacco and sugar beets
have been documented.

Lead

Lead  is  a  cumulative  poison  to  the  human  system  and
concentrates   itself   primarily  in  bones.   Symptoms  of
advanced lead poisoning  are  anemia,  abdominal  pain,  and
qradual  paralysis.   Immunity  to lead does not develop but
reaction grows more acute.  It is not an elemental essential
to the metabolism of animals.

Lead poisoning has been reported in  humans  drinking  water
with  a  concentration  as  small  as  0.042 mg/1.  However,
concentrations of 0.16 mg/1 seem to have had no effect  over
Long  periods.  It is generally felt that 0.1 mg/1 can cause
poisoning if ingisted regularly.

Chronic Lead poisoning among  animals  h&s  been  caused  by
concentrations less than 0.18 mg/1.  changes have been noted
in  nervous  systems  of  laboratory rats after ingistion of
0.005 mq/ per kg of body weight.

Lead concentrations of approximately of 0.5 mg/1  appear  to
be the maximum safe limit.

studies  on  the effect of lead on fishes indicate that lead
reacts with  an  organic  constituent  causing  a  mucus  to
obstruct  the  gills  and body.  The fish ultimately dies of
suffocation.  Concentrations between 0.1 mg/1 and O.U1  mg/1
have  resulted  in  a TL 50 within 48 hours to sticklebacks,
guppies,, minnous, brown trouts and coho salmon.

Iron

Iron in small amounts is an essential constituent to  animal
diets.  Th<» daily nutritional requirement is 1-2 mg and most
people  intake an average of 16 nig.  However, drinking water
becomes umpalatable at approximately 1.0 mg/1.  Ferrous iron
imparts as taste at 0.1 mg/1 and ferric Iron  at  0.2  mg/1.
                              76

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It   also   tends   to   precipitate   causing   stains  and
discoloration of water.  For these  reasons  drinking  water
limitations have been recommended at 0.1 mg/1.

Very  high  concentrations  of iron have been toxic to fish.
Iron hydroxides have been known to precipitate on the  gills
of  fish  causing obstruction.  Also heavy precipitation may
smother eggs.

Tin

Tin is not a  nutritional  requisite  but  neither  does  it
appear  harmufl  to  human or animal life.  The average diet
contains 17.14 mg/day.  Very  large doses of 30-50  mg/kg  of
body  weight  caused  much  loss  of  weight in cats.  Trace
amounts of tin appear beneficial to some fish.

BMr Acidity ajQg AlkaUnto

Acidity and alkalinity are  reciprocal  terms.   Acidity  is
produced   by  substances  that  yield  hydrogen  ions  upon
hydrolysis and alkalinity is  produced  by  substances  that
yield  hydroxyl  ions.  The terma "total acidity" and "total
alkalinity" are often used to express the buffering capacity
of a solution.  Acidity  in   natur&l  waters  is  caused  by
carbon dioxide, ndner&l &ei
-------
                                33HK -




                                          &£

           aj  £hg  ssissiiaa a« satai mai aa 4


clarification prior  to  discharge  of  the   effluent  t«
naviqable waters is assumed.                einuent  to
than  £nm°^ii °f -t0^}  suspended solids to levels of
than  50  mg/1,  significant  removal of metal  hvdroviri««





suspen

water.

                        78

-------
content (dissolved metal plus any metal in suspended  solids
left  from  clarification) .  For the purpose of establishing
effluent limitations and  standards  of  performance  it  is
herein   specified,   in   the  absence  of  any  qualifying
statement, that the  concentration  of  metals  in  mg/liter
means  total  metal,  aa  analytically  determined  by  acid
digestion prior to filtering,

Rationale for Rejection of other Waste Water Constituents as
Pollutants for Subcategory (1) Processes

Metals.  The rationale for rejection of any metal other than
those described as a pollutant above is based on one or more
of the following reasons:

       (1)  They are not present In the processing
           solutions used  In  the metal finishing
           industry.  It would be redundant to
           make a  long Hat  of materials that
           can be  controlled  but that are not
           present,

       (2)  Insufficient data  exiat upon which
           to base effluent  limitations and
           s-canfiards of performance.  Waste-
           water constituents such as sodium,
           potassium, nitrate and ammonia  are
           present in many prooassing solutions
           and waste waters,  bvit there is  no
           practicable Method s/c prssent of
           removing them  fro.r. solution.

 Dissolved Solids.   Dissolved solids   is  not   a  significant
 pollution   parameter    la   -en is   industry.    Although  the
 concentration  of  total  dissolved solids will   become  higher
 as   efforts  are directed  to  reducing fc*ater use and volume of
 effluent discharged, the  total quantity of dissolved  solids
 will remain  unchanged*
 chemical  Oxygen,.. Sem&Dd.   The chemical oxygen demand can be
 significant in some cases because  of  the  oil  and  grease
 removed  from the work in the cleaning operation, which then
 constitutes a part of the cleaner when it is dumped.  It  is
 possible to minimize chemical oxygen demand in some cases by
 use  of organic vapor degreasers prior to alkaline cleaning.
 However,  if  there  is  a  high  chemical   oxygen   demand
 practicable technology to lower it has not been demonstrated
 in the electroplating industry.
                               79

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Biochemical  oxygen  Demand.   Biochemical  oxygen demand is
usually  not  an  important  pollution  parameter   in   the
Subcategory   (1)  processes.   An  electroplating plant in a
suburban location not discharging to a publicly owned system
must treat its own sanitary sewage in a  separate  treatment
facility.   if the plant chooses to mix the treated sanitary
effluent with process wastes prior to treatment BOD would be
considered a major parameter.

Turbj.di.ty.  Turbidity is indirectly measured and  controlled
independently by the limitation on suspended solids.

Temperaturg.   Temperature  is  not considered a significant
pollution  parameter  in  the  Subcategory  (1)   processes.
However,  cooling  water  used  to cool process tanks and/or
evaporative recovery systems that are not subsequently  used
for  rinsing  could  contain  pollutants  from  leaks in the
system.

Aluminum

Aluminum may be present in significant amounts in the  waste
water  stream.   Limits  are  not placed on aluminum at this
time due to insufficient data.  However,, it is believed that
significant removal will result when  conventional  chemical
treatment techniques are employed.
                                80

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                        SECTION VII

              CQNTRQLAND TREATMENT TECHNQLOQY
Introduction

The  control  and  treatment  technology  for  reducing  the
discharge of pollutants from metal finishing  operations  is
discussed in this section.

The control of metal finishing waste waters includes process
modifications,  material   substitutions,  good housekeeping
practices, and water conservation techniques.  The  in-plant
control  techniques discussed are generally considered to be
normal practice in these industries.

The  treatment  of  metal  finishing  waste  water  includes
techniques  for the removal of pollutants and techniques for
the concentration  of pollutants in  the  waste  waters  for
subsequent  removal  by  treatment or recovery of chemicals.
Although all of the treatment  technologies  discussed  have
been   applied   to   waste   waters  from  metal  finishing
operations, some may not be considered  normal  practice  in
this industry.

Chemical  treatment  technology  is  discussed first in this
section because some treatment of this type is  required  of
many  waste  waters  generated by metal finishing operations
before discharge into  navigable  streams.   After  chemical
treatment  the  amount of pollutants discharged to navigable
waters is  roughly  proportional  to  the  volume  of  water
discharged.

The  proper  design, operation,, and maintenance of all waste
water control and treatment systems are considered essential
to an effective waste management program.  The choice of  an
optimum  waste  water  control  &n& treatment strategy for a
particular metal finishing facility requires an awareness of
numerous factors affecting both the quantity of waste  water
produced and its amenability to treatment.

Chemical Treatment Technology

Applicability

Chemical  treatment  processes  for  waste  water from metal
finishing operations are based upon chemical reactions  many
of  which  go back to the beginning of modern chemistry over
200 years ago.   These reactions have been used as the  basis
                                81

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 for  the  design  and  engineering   of   systems  capable  of
 treating  waste  water  containing   a    large   variety   of
 pollutants  and  reducing the concentration  of metal below  1
 mq/1.   Control procedures have been  devised  to  assure  the
 effectiveness  of the processes,
 Processes
             2f    Stress.    Waste  Waters  from  different
 operations  in  a  metal  finishing  process may be  combined  in
 some  cases and  kept  separate in  other  cases  prior to
 chemical  treatment.  The nature  of the waste waters and  the
 pollutants   present  will determine  where  segregation  is
 desirable  and  where  combination   is   practical.    Some
 pollutants   cannot  be  properly removed in the presence of
 others, while  some are better  removed  when  combined  with
 others.   Combination  of some  streams  will  result  in a
 reaction  to form additional pollutants and ones that can  be
 of  immediate  danger  to personnel  involved  in the metal
 finishing operations,  e.g.,  a  cyanide  containing  stream
 combined  with  an acid  stream may caus® evolution  of gaseous
 hydrogen  cyanide.   In   general,,  waste  waters  containing
 cyanide are segregated aacl treated separately, waste  waters
 containing   hexavalent  chromium are segregated and treated
 separately.  After treatment the cyanide^ chrome, and  metal
 ion   streams    are    combined   for  further  treatment  to
 precipitate metal   hydroxides   which   are   settled   out,
 sometimes   filtered, and  disposed of on land.  The treatment
 facilities  may   be   engineered   for  batch*  continuous,  or
 integrated   operations.   However , the treatment methods for
 several   pollutants  can  deviate  considerably  from   this
 general jlan.  The design of a suitable procedure and system
 to treat  a  specific  pollutant mix requires considerable care
 and experience.
    h.  Treatment.   The  batch  method is generally used for
small or nedium-sized plants.  Batch treatment is useful not
only for rinse waters but for expendable  process  solutions
containing  high  concentrations  ol  chemicals  or  spills,
leaks, or other accidental discharge of  process  solutions.
Holding  tanks  collect the waste water and are large enough
to provide ample time to treat* test, and drain a tank while
another is being filled.  Analytical tests are  made  before
treatment  to  determine  the  amount  of reagent to add and
after treatment  to  establish  that  the  desired  effluent
concentrations have been obtained.

S2fi£«fiiioy_§ Treatment.  ™he chemical treatment process may be
made  continuous  by 
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                        SECTION VII

                      JWP TRMTMSNT TECHNOLOGY
Introduction

The  control  and  treatment  technology  for  reducing  the
discharge of pollutants from metal finishing  operations  is
discussed in this section.

The control of metal finishing waste waters includes process
modifications,  material   substitutions,  good housekeeping
practices, and water conservation techniques.  The  in-plant
control  techniques discussed are generally considered to be
normal practice in these industries.

The  treatment  of  metal  finishing  waste  water  includes
techniques  for the removal of pollutants and techniques for
the concentration  of pollutants in  the  waste  waters  for
subsequent  removal  by  treatment or recovery of chemicals.
Although all of the treatment  technologies  discussed  have
been   applied   to   waste   Tatars  from  metal  finishing
operations, some may not toe considered  normal  practice  in
this industry.

Chemical  treatment  technology  is  discussed first in this
section because some treatment of this type is  required  of
many  waste  waters  generated by metal finishing operations
before discharge into  navigable  streams.   After  chemical
treatment  the  amount of pollutants discharged to navigable
waters is  roughly  proportional  to  the  volume  of  water
discharged.

The  proper   design, operation^ and maintenance of all waste
water control and treatment  systems are considered essential
to an effective waste  management program.  The choice of  an
optimum   waste  water  control  and treatment  strategy  for  a
particular  metal finishing facility requires an awareness of
numerous  factors affecting both the quantity of waste  water
produced  and  its amenability to treatment.

chemfcal  Treatment
 Applicability

 Chemical  treatment  processes   for  waste water  from metal
 finishing operations are based  upon chemical  reactions  many
 of  which  go back to the beginning of modern chemistry over
 200 years ago.  These reactions have been used as  the  basis
                                 81

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 for  the  design  and  engineering  of  systems  capable  of
 treating  waste  water  containing  a   large   variety   of
 pollutants  and  reducing the concentration of  metal  below 1
 mq/l.   Control procedures have been devised  to  assure  the
 effectiveness of the processes.,
 ProceaseR
              of   Streajns.     Waste   Waters   from  different
 operations  in a metal  finishing  process may be  combined  in
 some  cases  and  kept  separate  in   other   cases  prior to
 chemical  treatment.  The nature  of the waste  waters and  the
 pollutants   present  will  determine   where   segregation  is
 desirable  and  where   combination   is   practical.    Some
 pollutants   cannot  be  properly  removed in  the  presence of
 others, while some are better  removed when  combined  with
 others.   Combination   of  some   streams  will  result  in a
 reacticn  to form additional pollutants and ones that can  be
 of   immediate  danger   to  personnal   involved  in  the metal
 finishing operations,   e.g.,   a   cyanide  containing  stream
 combined  with an acid  stream may causa evolution  of gaseous
 hydrogen  cyanide.   in  general ,  vast®  waters  containing
 cyanide are segregated and  treated separately, waste  waters
 containing   hexavalent  chromium  are segregated  and treated
 separately.   After treatment the  cyanide^ chrome, and  metal
 ion    streams   are    combined   for   further  treatment  to
 precipitate  metal   hydroxides  which  are   settled   out,
 sometimes   filtered, and  disposed  of  on land.  The treatment
 facilities  may  foe   engineered  for   batch*  continuous,  or
 integrated   operations.   However^, the treatment methods for
 several  pollutants  can  deviate  considerably  from   this
 general flan.  The design of a suitable procedure and system
 t,o treat a  specific  pollutant  mix  requires considerable care
 and experience.
     .  Treatment.   The  batch  method is generally used for
small or medium-sized plants.  Batch treatment is useful not
only for rinse waters but for expendable  process  solutions
containing  high  concentrations  of  chemicals  or  spills,
leaks, or other accidental discharge of  process  solutions.
Holding  tanks  collect the waste water &n& are large enough
to provide ample tima to treat* test, and drain a tank while
another is being filled,  Analytical tests are  made  before
treatment  to  determine  the  amount  of reagent to add and
after treatment  to  establish  that  the  desired  effluent
concentrations have been obtained.
          . Tgeatmept.  ?he chemical treatment process may be
made  continuous  by 
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reactions;   (2}  providing  continuous  monitoring of pH  and
oxidation/reduction potentials and controls  for  regulating
reagent  additions  by  means  of  these  monitors;  and  (3)
providing a continuousoverflow  settling  tank  that  allows
sludge to be pumped off periodically through the bottom.

A  flow  diagram  for  a large continuous-treatment plant is
shown in Figure 5.  The dilute acid-alkali stream originates
from rinses associated with alkaline  cleaners,  acid   dips,
and   baths   containing  metal  ions*,  but  no  cyanide   or
hexavalent chromium.   When  concentrated  acid  and  alkali
baths  are to be discarded cney ara transferred to a holding
tank and added  slowly  -co  the  dilate  stream.    In  this
manner,   sudden   demands*  ca  the  reagent  additions  and
upsetting of the  treatment:  conditions  are  avoided.    The
dilute  acid-alkali  stre&ir.  i'ire/t  enters  a  surge tank to
neutralize the waste  water  s.r»d  equalize  the  composition
entering the precipitation tank.  Kse hex&valent chromium is
reduced  at.  a pH of £,0 tc 2*5, and the addition of the  SO^
and HC1 are controlled by suitable monitors immersed in  the
well-agitated  reduction  t&ftk*   Cy&nide  is destroyed in a
large tank with coBipartments tc sliow & two-stage reduction.
Reaction time Is about 3 hours™

The treated chrome,,  cyanide,  ar^d  neutralized  acid-alkali
streams are run into a common u^k where pH is automatically
adjusted  to optimise the precipitation of metal hydroxides.
The stream then enters a solide contact  and  settling  unit
where   mixing?  coagulated 4  f Peculation r  re circulation,
solids concentration, sludcjo collection,? and sludge  removal
are  accomplished.   Flocculates  ar^s  usually added to this
tank.  The overflow from the settling unit  constitutes  the
discharge  froifi  trie  plant.  i?h'«s kludge may be dewatered by
filtering and the filtrate x
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       strong
00
*».
                                                                                             1.8 gpm
                                                                                          sludge
                       FIGURE  5  DIAGRAM OF A TYPICAL CONTINUOUS-TREATMENT PLANT

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 Because   metals   are  precipitated separately at a relatively
 high  concentration?   the  metal  hydroxide  settled  in  the
 reservoir  may  be  recovered*  dissolved,  and returned to the
 plating  bath  from which it originated.   In contrast to batch
 and continuous treatments, which are generally  carried  out
 in  a separate   facility,  th«  reservoir in the integrated
 system is in  proximity to  the  plating room  because  of  the
 necessity  for  circulation.    The  layout  of an integrated
 system for treating rinse  water wast® from a cyanide plating
 solution and  & chromium plating bath in  shown in Figure 6«

 Unit  Operations
         ^j.gR.   The  effluent  levels of  metal   attainable  by
chemical  treatment   depend   upon   the  insolubility of  metal
hydrolysis  products  in  the   created  water and  upon  their
settling  and   filtering  characteristics  which   affect the
degree to which  they can  be separated.   The solubilities  of
the  hydrolysis   products are dependent upon  many conditions
during precipitations such as pEs presence of other  cations
and  aniors,  vime allowed oefor* separating  out  the solids,
the precipitation agent used,,,  the degree of agitation,  etc.

Schlegel and Hartinger  have studied precipitation  reactions
extensively  and have bean sblfi to  obtain low concentrations
of metal IOAS in solution iu   a  seasonable  time,   i.e.,   2
hours,

When  metal loris are preeipitamsd separately  the  pH may have
to be adjusted differently for euch ion.    This  immediately
raises the question  of  whet ha;: t^  metals can be  efficiently
precipitated  together  et a  coaiason §>H.   This is  possible as
shown in Table 23
It is apparent tnat It is dif .cic^It to  predict  in detail  the
conditions -chat will give th,e beat precipitation results   in
a  practical situation.  However,, just  as  several parameters
can be adjusted In the labor&tory to obtain optimum results,
suitable eon<5itj.cm8 may be rfouinfi la the field.  Flocculating
agents, o'ddad »co aid in set-cling  th«i   precipitate,  play a
significa-AT  rol<<  i-  r-ediscing  concentration  of suspended
solids.

When  soliabilizimg  cowplftxing  agents  are   present ,    the
equilibrium  constant  of  the completing  reaction has to be
taken into account  in  determining  theoretical  solubility
with  the  result  that  the  solubility   of  the  metal   is
generally increased.  Cyanide iorsa  .-roast   be  destroyed   not
only  because  they  are toscic but alao because they prevent
effective precipitation of copper and   sine  as  hydroxides.
                             85

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                                                                                            Reuse woler
oo
          Sodium
         hypochlorite
                                                                                               L
                                                                                         Chromic
                                                                                        acid wcsfe
                                                                                        treotment
                         Cyonioc
                          woste
                         freotment
                                                                             To pH control
                                                                              clcrifier
                                                                             Water reuse  pump
                                                                             Water slow down
                                                                             to sewer
Feed
pump
Cyonide waste
treatment reservoir



r>



5
U


-d





3-


g
J
Chromium waste
treotment reservoir
g

Feed
pump
Sodium carbonate
Sodium hydro-
      sulfite
                                                                                                    To sludge bed
                                          FIGURE  6 INTEGRATED TREATMENT SYSTEM

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TABLE 23   COMPARISON OF PRECIPITATION OF METAL
           HYDROXIDES  SEPARATELY AND  IN  COMPARISON

Initial
Metal Ions
Cu:Ni


Cu:Cr
Cu:Ni:Cr

Ratio of
in Solution
2:1
1:1
1:2
1:1
1:1:1
Soluble
Metal Two Hour*
after Neutralization,
Cu-H-
0.76
0.6
0.32
<0.2
0.25
Ni-"-
12
15
28
—
0.25
ms/1
Cr*H-
—


0.74
0.19
 Initial PH 8.5
                       87

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 IF  cyanide  is  replaced  in  a  plating bath by a nontoxic
 complexing agent such  as  EDTA  (ethylenedlaminetetraacetic
 acid),    the   new   complexing  agent  could  have  serious
 consequences  as  far  as  the  removal  of  metal  ions  by
 precipitation.     Ammonium   ion*   present  in  many  metal
 finishing baths, will complex copper,  zinc, and other  heavy
 metal   ions  and  interfere  with  their  precipitation  as
 hydroxides.

 Theory  and experimental  results  confirm  that  it  is  not
 possible  to  achieve  complete  removal  of metal ions from
 waste  water  by  precipitation  as   hydroxides   even   if
 separation of  precipitate were 100  percent effective.   Thus,
 a   finite  concentration  of  pollutant  will  remain in the
 etfluent.   The  best indication of what can  be  achieved  in
 reducing   metal  concentration  is the  results  of  daily
 operation  in   exemplary  plants  rather  than   theory   or
 laboratory  experiments.    Clarification  efficiency  is  an
 important factor in determining the total metal  content  of
 tho  effluent.    it  is  safe  to say  that the soluble metal
 content  will be no greater than the total  content  achieved
 in practice and may be  less,

 s2iM§__ Separation.   The  first step  in separating the pre-
 cipitated metals is settling,  which is very slow for gellike
 zinc  hydroxide,  but is  accelerated  by   coprecipitation  with
 the hydroxides  of  copper  and chromium.   Coagulation can  also
 be aided  by   adding   metal  ions  such as ferric iron which
 forms   ferric   hydroxide   and  absorbs  some   of   the   other
 hydroxide,  forming  a floe that  will settle.  Ferric iron has
 been  used   for  this   purpose   in  sewage treatment for  many
 years  as   has   aluminum   sulfate.     Ferric    chloride    is
 frequently  added to the clarifier of chemical wastetreatment
 plants   in  plating  installations.   Plocculation and  settling
 ar*> further  improved by use  of  polyelectrolytee,  which  are
 hlqh  molecular  weight  polymers  containing  several  ionizable
 ions.    Due  to their ionic character   they  are   capable of
 -swelling  in  water  and  adsorbing  the  metal hydroxide which
 they carry  down  during  settling.

 Settling is  accomplished  in the  batch process in  a   stagnant
 tank, and after a time  the sludge may  be emptied  through the
 bottom  and  the  clear effluent drawn off through the side or
top.  The continuous system uses a baffled  tank  such  that
the  stream  flows  first  to  the  bottom  but rises with a
 decreasing vertical velocity until  the  floe can settle in  a
practically stagnant fluid.

Although  the  design  of  the  clarifiera has been improved
through many years of experience, no settling techniques  or
                                88

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clarifier  will  completely  remove solids from the effluent
which contains typically 5 to 20 mg/1 of  suspended  solids.
This floe contains some metal.

3J.pdge  Dj,3po§ajL.   Clarifier underflow or "sludge" contains
typically 1 to 2 percent solids  and  can  be  pumped  to  a
lagoon.

Metal  ions  in  the  liquid  associated with the sludge can
percolate through porous soil and become a. potential  source
of  groundwater  contamination.   Impervious lagoons require
evaporation into the atmosphere. However, in many  parts  of
the  U.S., the average annual rainfall equals or exceeds the
atmospheric evaporation.  Additionally, heavy rainfalls  can
fill  and  overflow lagoons.  Metal ions may be leached from
metal hydroxides and the surface run-off to adjacent streams
or lakes may be in sufficient quantity to be detrimental.

A case in point is contamination of groundwater  by  plating
wastes  held in lagoons in Nassau County, New York.  Plating
wastes have seeped down from the lagoons into  the  aquifier
intermittently  since  19«1«,  This seepage has resulted in a
plume of contaminated water some  
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Centrifuges  will also thicken sludges to the above range of
consistency and have  the  advantage  of  using  less  floor
space.  The effluent contains excessive suspended solids and
is returned to the clarifier.

Pressure filters may be used,  In contrast, to rotary filters
and  centrifuges,  pressure  filters will produce a filtrate
with less <;han 3 ing/1 of suspended solida ao that return  to
the  clarifier  is  not  needed.   The  filter cake contains
approximately 20 to 25 percent solids.  Pressure filters are
usually designed for a  filtration  rate  of  2.01  to  2.W
liters/min/sq  m   (0.05  to  0.06  gprn/aq  ft)   of clarifier
sludge.

Solids contents from 25 to 35 percent in filter cakes can be
achieved with semicontinuous tank filters rated at 10.19  to
13.4«t  liters/min/sq  m (0.25 to 0«33 gpm/sq ft) surface.  A
solide content of less than 3 mg/1 Is normally accepted  for
direct  effluent discharge.  The units require minimum floor
space,,

Plate and frame presses produce filter cakes  of  1*0  to  50
percent  dry  solids  and  a  filtrate with less than 5 mg/1
total smspencled solids.  Because automation of these presses
is difficult, labor costs tend to be  high.   The  operating
costs are partially offset by low capital equipment costs.

Automated  tank  type  pressure filters are just now finding
application.  The solids content of the cake  can  reach  as
high  as 60 percent while the filtrate may have up to 5 mg/1
of  tot.il  suspended  solids.   The   filtration   rate   is
approximately  2.0^1  liters/min/aq m  (0.05 gpm/eq ft) filter
surface area.  Pressure filters containing from 300  to  500
mg/1   tmspended   solids   at   design   of  1.88  to  6.52
liters/min/sq m  {0.12 to 0.16 gpm/aq  fit) and still  maintain
a low scllds content in the filtrate.

Filter   cakes  can  easily  be  collected  in  solid  waste
containers and hauled  away  to  landfills.   There  may  be
situations,  however,  where  the  metal  in the filter cake
could be redissolved if it came  into contact  with  acidic
water.   Careful consideration should be given to where such
a materiel is dumped.

A proprietary process is available for solidifying sludge by
addition of chemical fixing agents.   Relative to filtration,
the amount of dried sludge to be hauled away  is  increased.
The   fixing  process  appears to insolublize the heavy metal
ions  so t.hat in leaching tests only a fraction of a part per
                                90

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 million is found in solution.   A fill is  produced   that   is
 similar to dried clay.

 The   possibility  of  recovering  metal   values from sludges
 containing copper,  nickel,   chromium, and  zinc have been
 considered  but such a  system  appears to be uneconomic under
 present circumstances.  It may  be profitable to recover metal
 values if 900  to 2300 kg ?2POGO to 5,000  pounds)   of  dried
 sludge  solids  can  be  processed per day with a thoroughly
 developed process.   To  attain   this  capacity   would  almost
 certainly  require  that sludge from a large number  of plants
 be brought to  a central processing  station.    The   recovery
 would   be  simpler   if  the  metallic  precipitates were
 segregated,  but   segregation   would   require   extensive
 modification,   investment,   and  increased operating expense
 for  precipitation and clarification.   Laboratory experiments
 showed that  zinc could  be leached from sludge   with  caustic
 after  which  copper,   nickel,  and chromium were effectively
 dissolved with mineral  acids.   Ammonium  carbonate   dissolved
 copper  and  nickel  but  not  trivalent chromium,  thus giving a
 method of separation.    Electrowinning  of the nickel  and
 copper  appeared to be  a  feasible method of recovering these
 metals.

 Cyanide Oxidation.   Cyanide in  waste  waters   is   commonly
 destroyed by   oxidation  with  chlorine or hypochlorite prior
 to precipitation of the metal   hydroxides.   The method  is
 simple,   effective,  and economically feasible for most waste
 waters,  even for small  volume  installations.    A factor  in
 how  rapidly  cyanide is  destroyed,  if  at  all, is  how strongly
 the   cyanide   is complexed  to  metal  iona and how rapidly the
 complex can  be  broken.  Therefore, some  waste waters  present
 special  problems.   A  comprehensive study of the  method  was
 made  by Dodge  and Zabban  the results  of  which have  been used
 to  work   out   the  practical   processes*  The  following are
 proposed  reactions  for  chlorine oxidation.

     (1)   NaCn  +  C12 - CNCi  •» NaCl

     (2)   CNCI  +  2NaOH « NaCNO * NaCi  * H20

     (3)   2NaCNO  + 3C12  +  <4NaOH = N^ * 2CO£ * 6NaCl + 2H2O.
Reaction (2) goes rapidly at pH 11.5, under which conditions
build up of the toxic gas CNCI by Reaction (1)   is  avoided.
Treatment  of dilute rather than concentrated solutions also
minimizes its formulation.  Oxidation to cyanate (NaCNO)   is
completed  in  5  minutes  or  less.   Reaction (3)  goes more
slowlyr requiring an hour in the preferred pH range  of  7.5
to  9.0,  and  a  longer  time  at  higher  pH.    After  the
                              91

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 conversion  to  nitrogen and carbon dioxide,  excess  chlorine
 is Destroyed with sulfite or thiosulfate.

 Sodium  hypochlorlte  may  be  usad  In   place  of chlorine.
 Recent technical innovations in electrochemical hypocblorit*
 generators  for  on-t«ite  use  raise  tha  poesibility   of
 controlling  the  addition  of  hypochiorit®  to tha cyanide
 solution by controlling the current to  the  electrochemical
 generator, using sodium chloride as the feed material.

 Concentrated solutions, such as contaminated or spent baths,
 cyanide  dips,  stripping solutions, and  highly concentrated
 rinses, are normally fed  at  a  slow  rate  into  a  dilute
 cyanide   stream   and   treated  with  chlorine.   However,
 concentrated solutions may also be destroyed by electrolysis
 with conventional equipment available in  the  plating  shop.
 In  normal  industrial  practice  the  process  is  operated
 batchwise, whereas the optimum  system,   from  an  operating
 standpoint,  would  be  a cascaded one in which successively
 larger tanks are  operated  at  successively  lower  current
 densities.   This is the more efficient system.  In addition
 to the oxidat.ion of cyanide at the anodaff valuable metal can
 b® recovered at  the  cathode.   The  process  becomes  very
 inefficient  when  the cyanide concentration reaches 10 ppm,
 but at this point tha solution can bj fed into  the  process
 stream  for  chemical  destruction  of  cyanide 'to bring the
 concentration  to  the  desired  level.   The  addition   of
 chloride  ions  to  the  concentrated solutions, followed by
 electrolysis, produces chlorine or hypochlorite in solution,
which can then destroy Uie cyanide to the sarna low levels as
 obtained by direct chlorination.   With  the  provision  that
 chlorine  or  hypochlorite  be formed at,  a rate equal to the
 concentration of cyanide passing  through the  system,  the
 process can be operated continuously:
  2NaCN -1 2NaOCl •- 2FaCNO * 2NaCl

  2NaCNO_ *_3JJ3QC1_+__.B2Q...* 2C02 * N2 * 2MaOH * 3NaCl

  2NaCN + 5 NaOCl * H2O  2C02 * N2 * 2S&OH * SNaCl.

The Cynox process, based on the above principles,, produces 1
kg  of active chlorine per 5.5 Kwh.  Equipment needs are the
same with the exception that the tanks must  be  lined,  and
graphite or platinized anodes must be used.

Poiysulfide-cyanide  strip  solutions  containing copper and
nickel do not decompose as readily and as completely  as  do
plating  solutions.   Although  the  cyanide  content can be
reduced from  75,000  to  1000  mg/1  during  two  weeks  of
                              92

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 electrolysis   anode   scaling   prevents   further  cyanide
 decomposition unless  anodes  are  replaced  or  freed  from
 scale.  Minimum cyanide concentration attainable is about 10
 mg/1 after which the solution can be treated chemically.

 The electrolysis of dilute cyanide solutions can be improved
 by  increasing the electrode area.  Area can be increased by
 filling the space between flat electrodes with  carbonaceous
 particles.   The carbon particles accelerate the destruction
 process 1000 times, but flow rate through the unit  must  be
 carefully adjusted, if used on a continuous basis to achieve
 complete destruction (Plant 30-1).

 Although  cyanide  can  be  destroyed by oxygen or air under
 suitable conditions, cyanide concentrations in the  effluent
 are  reported  to  be  1.3  to  2.2  mg/1,  which is high for
 discharge to sewers or streams.   A catalytic oxidation  unit
 using  copper  cyanide as a catalyst and activated carbon as
 the  reactive  surface  has  been  described  for  oxidizing
 cyanide  with  air or oxygen and at least two units were put
 in operation.   Performance data  is not available.   Catalytic
 oxidation  units   must   be   custom   designed   for   each
 installation for  maximum effectiveness.

 Ozone  will oxidize cyanide (to  cyanatef  to below detectable
 limits  independent of the starting concentration or  of   the
 complex  form of  the cyanide.  Decomposition can be achieved
 with  cyanides  such as those of nickel and iron that are   not
 readily oxidized  by chlorine.  Systems that will oxidize the
 cyanides  that are  usually treated, i.e.,  copper and  zinc
 compounds   have   been installed   in   production units   and
 demonstrated.  Development work  is  continuing  to enhance the
 efficiency and reliability of modern  ozone  generators and to
 decompose   the   more stable  cyanides   with   the   help of
 ultraviolet radiation and  heat.

 A  method   employing   thermal  decomposition    for   cyanide
 destruction  has been recently announced.   Cyanide  solutions
 are heated to  160  to  200   C  under  pressure   for   5  to  10
 minutes.    Ammonia   and  formate  salts   are   formed.   No
 information is given  on the final cyanide concentration.

 One process destroys cyanides of  sodium,   potassium,  zinc,
 and  cadmium  and  also  precipitates zinc and cadmium.  The
 process xs discussed  later in this section.

 Precipitation of cyanide as ferrocyanide  is  restricted  to
 concentrated   wastes.   Ferrocyanide  is  lees  toxic  than
 cyanide, but Is  converted  back   to  cyanide  in  sunlight.
Treatment  is  accomplished by adding an amount in excess of
                               93

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 amonnf        kg °f PeS°4 *** kg  of  cyanid«| .   Large
 amounts  of  sludge  are produced which add to the pollution
 load.  Complex cyanides do not break down  readily  and  the
 ™SiSn StMPS xhe"*a °°nc«»*»tion °f 10 mg/i of cyanide is
 reached.   No  benefits can be foreseen in terms of reducing
 waste volume and concentration.                       uu^xng

 Cyanide is also destroyed  by  reaction  with  polysulf ides.
  « K "?^6  r?action rates arc obtained only if the solution
 is boiled.   Since the reaction does not destroy all  of  the
 cyanide further treatment is necessary.

 7P^H?£   3*  flMHXalfflp  Chromium.    Hexavalent  chromium
 (crvi)  is usually reduced to trivalent chromium at a pH of 2
 to 3 with sulfur  dioxide  (SO2) ,   sodium  bisulfite,  other
 sulfite-containing   compounds, or  ferrous  sulfate.    The
 reduction makes possible the  removal  of  chromium  as  the
 ooid?M«n   h*dr.oxi?e   wh*ch  Precipitates  under  alkaline
 conditions.   Typical reactions  for  SO£  reduction  are  as
 follows:

              S02 +  H2O =H2_S03

 2H2CrOU  + 3H2SQ3 =Cr2 (SO 4) 3  + SH^O.

 Representative    reactions    for    reduction  of   hexavalent
 chromium under  acid  conditions   using  sulfite   chemicals
 instead  of S0.2.  are  shown below:

      (a)  Using sodium metabisulf ite with  sulfuric acid:

                   *  3Na.|S.205  +  3H2SO4  -
      (b)  Using sodium bisulfite with sulfuric acid:

          4H2Cr04 * 6NaHSO3_ + 3H^SO1 - 3Na^S04

      (c)  using sodium sulfite with sulfuric acid:

          2H2Cr04 + 3Na2S03 + 3H2SOJi = SNa^SOji

                  + 5H20.

Reduction  using  sulfur  dioxide  is  the  most widely used
method, especially with larger installations.   The  overall
reduction  is  readily  controlled  by  automatic pH and ORP
(Oxidation-Reduction Potential)  instruments.  Treatment  can
be carried out on either a continuous or batch basis.
                              94

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 Hexavalent   chromium  can  also  be  reduced  to  trivalent
 chromium in an  alkaline  environment  using  sodium  hydro-
 aulfite as follows:

 2H2CrOf« * 3Na 282.04 + 6N»OH  fiNa^iC^ * 2Cr(OH)£ * 2HJO.

 As   indicated  in  the  above equation,  the chromium is both
 reduced  and  precipitated  in  this   one- step   operation.
 Results  similar  to those obtained with sodium hydrosulfite
 can  be achieved using hydrazine under alkaline conditions.
                     =      4Cr(OH)3  + 3N2 +  i»H2O.


 Sodium  hydrosulfite or hydrazine are frequently employed  in
 the   precipitation   step  of  the integrated system  to  insure
 the complete  reduction of  any hexavalent chromium that might
 have  been  brought over   from  the  prior  reduction  step
 employing sulfur  dioxide or sodium  bisulfite,   where ferrous
 sulfate is   readily  available  (e.g.,   from steel pickling
 operations) ,  it can be  used  for  reduction  of  hexavalent
 chromium; the reaction is  as  follows:
2Cr01 + 6FeSOtJ.7H20  +  6H2S04 = 3Fe^(SO]i)i  * Crg (SO4 ) 3_

         *  48H2.0.

Cr*»  may   be  reduced   at  a  pH  as  high  as  8.5  with a
proprietary compound.  It  is  not  necessary  to  segregate
chroma te- containing   waste   waters  from  the  acid-alkali
stream, and the use  of acid to lower  pH  is  eliminated  in
this   case.   Precipitation  of  chromic  hydroxide  occurs
simultaneously in this case with the reduction.

Cr*« ions may be reduced electrochemically.  A concentration
of 100 mg/1 was reduced to less than 1  mg/1  with  a  power
consumption   of   1.2  kwh/1000  liters.   The  carbon  bed
electrolytic process previously described  for  cyanide  may
also  be  used  for  chromate reduction in acid solution and
Plant 30-1 has achieved a Cr+*  concentration  of  .01  mg/1
using  this  method.   Electrolysis  may  also  be  used  to
regenerate a reducing agent.  A process has  been  described
involving   the   reduction   of   Fe   (III)    to  Fe  (II)
electrochemically and the reduction of Cr (VT)  by  Fe  (II) .
The  method  should  be  capable  of  achieving  low Cr (VI)"
levels.                                                     '
                                  95

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The  siaailataneous   reduction   of   Cr*a   and   oxidative
destruction  of  cyanide  finds limited application in waste
treatment practice.  The reaction requires  mixing  of  Cr+*
and  cit-  in ratios between 2 and 3 using Cu** as a catalyst
in  concentrations  of  50  to  100  mg/1.    The   catalyst
introduces  additional  pollutant  into  the  ^aste  stream.
Reaction rates are generally slow, requiring from  6  to  2U
hours  for cyanide concentrations? ranging from 2,000 to less
than 50 mg/1 at a solution pH of 5.   The  slowness  of  the
reaction  and  the  high Initial concentrations of reactants
required make  the  method  unsuitable  for  treating  rinse
waters.    Its   use   is  limited  to  batch  treatment  of
concentrated solutions,  No benefits are obtained  in  terms
of wa-cer volume and pollution reduction.  Destruction is not
as complete as obtained by the wore common chemical methods.

Practical Operating Systems

Chemical  treatment was used by every plant contacted during
the effluent guidelines study with the  exception  of  those
that  are  allowed to discharge plating waste effluents into
sewers or streams without treatment.

In Plait 33-2 the discharge  of  eyanida  is  eliminated  by
electrochemical decomposition in & t&nk held at uufficiently
high  temperature  to evaporate th® wdBtawator as rapidly as
it is introduced.  Therefore, no liquid  stream  leaves  the
tank.   Fluorides  and fluoborate containing waste waters in
Plant 31-15 are collected separately and treated with lime.

Plant 3')-8 disposes of sludge in a pit  lined  with  special
concrete  blocks  that filter out solids and allow liquid to
permeate into the surroundings.   Relatively  few  finishing
plants  have  installed  filters,,  although  the  problem of
disposing of unflitered sludge in many cases should  provide
an impetus for the use of one or more filters in the future.
Plants   12-8   and    31-16  yuse  large  rotary  filters  to
concentrate sludge fori?: a clarifies:.  Plant 33-30 is able to
filter the solution from the neutralizer directly, without a
preceding clarification step,,  A  settling  tank  centrifuge
combination   is   in   use  in  over  200  waste  treatment
installations, including those in  metal  finishing  plants.
The  Chen.fix  system   for  solidifying  sludge   is in use at
several plants.

Demonstrati90 status.  The us Bureau of Mines has done  some
development  on  a  process  in  which  the  acid wastes and
alkaline cyanide wastas neutralise  each  other.   The  acid
wastes  ere  slowly added to the alkaline wastes in a closed
reactor <;o i7orm easily filtered metal cyanide  precipitates.
                               96

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The  precipitates  are  heated  in  air to form stable metal
oxides.
            'J -ftf _^Jl*!3Jj4ca 1 T^^^rl1^ Techniques

The ef ff;<:l ivoriess of chemiea L treatment  techniques  depend-;
on the nature of the pollutant, the nature and concentration
of interfering ions, the procedure of adding the appropriate
amount of chemicals (or adjusting pH) , the reaction time and
temperature  and  the achievement of effective separation of
precipitated  solids.    Effective  removal  of  heavy  metal
pollutants is inhibited by some types of chelating ions such
as tartrate or ethylene diamine tetracetate ions.

The  concentrations  of metals and cyanide achievable by the
chemical techniques employed for treating waste from copper,
nickel,  chromium,  and   zinc   electroplating   and   zinc
chromating   processes   are   summarized   in   Table   24.
Concentrations lower than those listed as maximum  in  Table
24  were  reported by companies using all three  (continuous,
batch, and integrated) treating systems,

Higher-than-normal  concentrations  of  metals,  when   they
occur,  are usually caused by:  (1) inaccurate pH adjustment
(sometimes  due  to  faulty  instrument  calibration) ;    (2)
insufficient  reaction time; or (3) excessive concentrations
of chelating agents that complex the metal ions and  prevent
their  reaction  with  hydroxyl  ions  to form the insoluble
metal  hydroxides;  (4)   lack  of  suitable  coprecipitating
agents.  The causes for higher-than-normal concentrations of
cyanide  are  similar,  but another important factor must be
added to the list of potential causes for incomplete cyanide
destruction.  In this case, sodium  hydroxide  and  chlorine
must  be  added continuously during the reaction to maintain
the optimum pH and provide sufficient  reagent  to  complete
the  reaction,  which is normally monitored by an Oxidation-
Reduction-Potential     (ORP)    recorder^controller.     The
maintenance  of  this  system is a critical factor affecting
the effectiveness of chemical oxidation.

Suspended Solids.  The  suspended  solids  discharged  after
treatment  and clarification sometimes contribute more heavy
metal than the dissolved metal.  The concentration of  total
suspended  solids  in the end-of-pipe discharge  from typical
chemical treatment  operations  sampled  during  this  study
ranged  from  20  to 21 mg/1.  Lower values are reported for
some facilities.  Maintaining conditions so as not to exceed
these amounts requires   (1)  a  properly  designed  settling
and/or   clarifying   facility,    (2)   effective   use   of
flocculating agents,  (3) rate of removal of settled  solids,

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VO
00
                          TABLE 24    CONCENTRATIONS OF HEAVY METALS AND CYANIDE ACHIEVABLE BY
                                     CHEMICAL TREATING OF WASTE CREATED BY COPPER,  NICKEL,
                                     CHROMIUM AND ZINC PLATING AND ZINC CHROMATING OPERATIONS
Soluble Concentration Contribution From
After Chemical Treating Suspended Solids (2)
Pollutant
Cyanide, oxidizable(^)
Cyanide , total
Phosphorus
Chromium6"1"
Chromium, total
Copper
Nickel
Zinc
Total suspended solids' '
Minimum, mg/£
< 0.01
0.1
0.007
< 0.01
0.05
< 0.01
< 0.01
0.05
20
Maximum, mg/£W Minimum, mg/£ Maximum, mg/ 1
0.03 —
0.2
0.6 — —
0.05
0.25 0.02 0.30
0.2 0.02 0.76
0.5 0.02 0.15
0.5 0.04 0.80
24
        (1)  Values below these limits have been reported by plants utilizing continuous (Plants 40-6, 8-4,
             33-6, and 11-8), batch (Plants 36-1, 21-3, 33-8), and integrated (Plants 36-2 and 20-13) treat-
             ment techniques.  Others (Plants 3-3 and 33-3)  utilize a combination of integrated and batch or
             continuous treatments to achieve these or lower limits.

        (2)  Data for Plants 33-1, 12-8, 36-1 and 11-8.

        (3)  Oxidizable by chlorine.

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and (4)  sufficient retention time for settling,  and (5)  rate
of  overflow  of  clarified  effluent.    Of course, minimum
retention time depends on the facility -size and   design  aiul
the   rate  of  solution  flow  through  the  facility.    In
practice, thi;j time ranges from  about  2  to  H  hours  tot
plants  that are able to reduce suspended solids to about  />•>
mq/1 or less.

Precipitation of Metal Sulfides

Applicability.  The sulfides of metals are much less soluble
than  their  corresponding  hydroxides.    However,   direct
precipitation  of metal ions with hydrogen sulfide or sodium
sulfide involves the problem of excess sulfide ion which can
then become an additional pollutant   parameter.    A  sulfide
precipitation system has recently been developed that avoids
the  possibility  of  excess  sulfide  ion  being present in
treated effluent.  Iron sulfide, which  itself  has  a  very
small  solubility,  is  used  as  the reagent to precipitate
copper, zinc, and nickel sulfides of  even lower  solubility.
Experimental  results  are shown in Table 25 indicating that
low   concentrations   can   be   achieved   with    sulfide
precipitation even when metals are complexed with ammonia.

The  disposal  of  sulfide  solid  wastes  is  a serious and
unsolved  problem.  Unlike the metal oxides, metal  sulfides,
in  the presence  of air, decompose to sulfates and the metal
ions can  thereby  be solublized.  This commonly  happens  to
ferrous   sulfide  as  a result of coal mining operations and
contamination of  streams with acid and  iron  is  a  result.
However,  there   is  insufficient  information  available to
determine whether any significant oxidation will occur  with
mixed   metal   sulfide  sludges  disposed  of  properly  on
landsites.   The  lower solubility of  metal  sulfides  should
reduce    the    amount   leached   directly  into  rainwater.
Therefore,  if significant oxidation  is found to occur, means
will have to  be found to contain the  sulfide precipitates or
insolublize them  by some system  such  as  the Chemfix Process.

Practical Operating Systems.   Plant   9-2   is   precipitating
cadmium  as  the  sulfide.

Demonstration   Status.  The process  described is  still being
developed,  and  it is  anticipated that a  demonstration  plant
will be  built and operating in the near  future.


Combined Metal  Precipitation and Cyanide
Destruction-Proprietary Process  A
                               99

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TABLE 25   COMPARISON OF SOLUBLE POLLUTANT
           PARAMETERS AFTER PRECIPITATION
           BY IRON SULFIDE OR BY HYDROLYSIS
Waste
compo-
sition
in ppm
Unknown

Cu} 100
Ni, 7.7
NH3, 475
NH3, 475
Cr(VI), 4.8
Zn, 3.5
Pollutant residues
Sulfide
precipi-
tation
in ppm
Cu, 0.1
Zn, negligible
Cu, 1.8

Cu, 0.4
Ni, 2.0
Cr(VI), negligible
Zn, 0.03
from--
Hydroxide
precipi-
tation
in ppm
0.8
2.0
95.8
5.9
1.0
2.0
0.05
2.0
                    100

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Applicability.   This  process  is  applicable  to  zinc and
       ^^ide  solutions.    The   metal   hy< iroxlde   is
                                              s
lome  states.   A modified Kastone Process may be App
to copper cyanide.

Process Principles  and  Equipment.   Cyanide  in  zinc  and
fadmiSm -pnti^Tbaths is destroyed by a nuxture of formalin
and hydrogen according to the formula:

3CN-  + 2H202 + HCOH + 2H2O = CNO~  + OR-  * NH3

    + H2C (OH) CONH2)  (glycolic  acid amidej .

The metal hydroxide   is  also   precipitated.   The  hydrogen
peroxide  is  contained   in  the reagent  (41%)  which contains
Stabilizers and  additives to promote  the reactions and  help
in  settling  the  metal hydroxide precipitate.  The  process
may ^carried  out  on a  batch  or continuous  basis,   and  is
particularly convenient  for   the small shop.   However, the
Slycolic  acid generated  is not a desirable   constituent   for
discharge  to   streams  and  the  use of the Kastone  Process
should  be restricted  to  plants discharging  to sewers.

Figure  7  shows  the  apparatus for  batch   treatment.    To  be
economical  the  rinse  water should contain at least 55 ppm of
 cyanide,   and   sufficient  counter-flow  rinses  are  normally
iSSlled to assure a sufficient cyanide concentration.   The
typical treated effluent contains 0.1 mg/1 of cyanide and  1
 to   2  mg/1  of  zinc.   Table  26  shows an analysis of the
 products for decomposing 79U ppm of cyanide.
 is being used in approximately 30 installations.


 chemical Treatinent_gf_Ef fluents From Specific
 Process Operations

 Constituents

 iron.   Iron baths have  relatively   simple  compositions  and
 nasalization  of   waste water constituents "ill  reduce the
 soluble  iron   concentration  well  below  1   JJ'J-   '""^
 chloride   is  a common  constituent  in  such baths and  "used
 as  a  flocculating agent in  clarification systems for  Phase I
                              101

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Air -*-
                                                           Woler from first
                                                           rinse tank
                                                             Air (for mixing)
s-J;(&y$$£tiWv$M
^Fp^p^'.Tp filter v;.1;
                                                                    '.•^'.Measurement
                                                                     '
                                                           To sewer
 FIGURE 7 - BATCH TREATMENT OF CYANIDE RINSE  WATERS BY THE  KASTONE PROCESS
                              102

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  TABLE 26   DECOMPOSITION PRODUCTS OF CYANIDE IN
             RINSE WATER(I) FROM A CYANIDE ZINC
             ELECTROPLATING OPERATION AFTER TREATMENT
             WITH "KASTONE"^2) PEROXYGEN COMPOUND
   Products Formed
    by Treatment
Cyanate                   351

Ammonia  (free-
  Diesolved                57
  Volatilized O)           32

Combined Ammonia
  Calc'd as NH3            95
  Calc'd as glycolic
    acid amide            419
                                 Amount Formed
Actual     Cyanide Equivalent
 ppm         ppm     percent
             265
             164
              91
             274
33
21
11
35
                                      794
                       100
(1)  Analysis of water before treatment:
       Cyanide*    794 ppm
       Cyanate*    336 ppra
       Ammonia *    41 ppm

    * Cyanide calculated as NaCN, cyanate as NaOCN, and
     ammonia as NH~.

(2)  Hu Pont trademark.

(3)  Not determined; estimated by difference.
                          103

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  «f,^ihi f°^low^q  neutralization,  to  give   an   effluent
  suitable  for discharge.  The waste waters  (dilute acid) and
  the concentrated  plating  baths   (cono«ntrat«d  but  weakly
  acidic)  enter  the  waate  treatment ayntftm via the* "diluto
  acid- strong acid" streams of Figure 2.                aumo
           After oxidation of cyanide or in noncyanide  waste
 water,  cadmium  can  be  precipitated  as  the hydroxide by
 adjustment of PH.   The  waste  water  and  strong  solution
 discharge  streams  are  shown as "weak cyanide" and "strong
 oHi^M ^/iqfe l\ Alkalinity has a  significant  effect
 on solubility of cadmium.  The theoretical solubility values
 according to Pourbaix are approximately               values
                                    Solubility
             8                      3000
             9                        30
            1°                         0.03
            11                         0.003  (minimum)

 Therefore,   soluble  cadmium   might  not  be  reduced  to  a  low
 level  by coprecipitation with Cr,  Ni,  Cr, 2n at  pH 8 to   9.
 Should  a   pH  of   11 be used, there  is danger that  the *ini
 concentration  in    the   effluent   will    be   too   hioh
 Consideration  of   the  above theoretical data suggests that
 cadmium  might  not  be  reduced   to   a   low    level   wh*n
 coprecipitated  with  cu.  Mi,  Cr,   Zn  at  pH  8 to 9.  The
 insolubility   of    cadmium    carbonate     suggests   that
 precipitations  with  soda ash may reduce soluble cadmium to
 very low levels in   effluent.   since  many  combined   waste
 waters  contain  some  carbonate   it   is  very possible that
 cadmium  carbonate   rather    than   cadmium   hydroxide   is
 precipitated when  waste waters are neutralized with caustic
 or lime,  some reported values that seem unrealistically low
 for  hydroxide  precipitation may be achieved   by   this
 mechanism.    Cadmium  sulfide is  very insoluble (solubility
 product  K«  10-* •),  yo  that   a  precipitation  system   based
 upon   sulfides, combined with efficient removal of dissolved
 solids,  may  provide  acceptable effluent.   A schematic of the
 treatment scheme is  shown in  Figure 8.  In this figure,  the
 cadmium   sulfide    sludge    is  recovered.    If  segregated
 treatment of  a cadmium  stream is required, the best  way  of
 holding  the  sludge  may  be to ship it to a metal recovery
unit, or convert it to a form suitable  for  return  to  the
 plating bath.

Alternative to recovering sulfide  precipitate,  an evaporator
can be installed to recover plating bath and reusable water.
                              104

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                                   Water

Cadmium
Cyanide
Bath

Cone.
Soln.
I







\


Rinse
1
1


I

Evaporate
to
Concentrate

Evaporate
to
Dryness
I *
2
Water
	 j—


                  Dry Sludge
                  to Recovery
FIGURE  8 SCHEMATIC OF CADMIUM WASTEWATER
          TREATMENT WITH MINIMUM SOLID
          DISPOSAL
                   105

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      omitted,   nuoborate containing  waataa  cane  from
                                                  '
 adjustment.   However,  operating  data sho» that
                                   Solubility
           si
                                      6
8                       500

                          6
                          3


                                                a
 The  chloride  and  aulfate  are  too  soluble  to achieve
 sufficiently   low   lead   concentration,    but    sulfide
 precipitation  should  reduce  the concentration adequately
 Lead carbonates and basic carbonates have  low  solubUitie^
 ™,«-  ^er«fore   carbonate   present  incidentally  in  the
 neutralization process or deliberately added may reduce lead
 to low .levels in effluent.   The problem of suspended  so Ud"s
 remains.   Sludge would most appropriately be sen? to a Seta?
 to^S^  ^ K^ convftrted ^ • form suitable for returi
 to the plating bath.  Waste treatment operations are similar
 to those  shown for cadnium in Figures 8^nd 9° omittina  the
 cyanide  oxidation.    Lead plating wastes contain^ fluSboratJ
 which  13  covered in a subsequent section.          ^Auwoorare
Tin.  The tin concentration can be  reduced to  low  levels

in Utj;i"5?i0? betW?Sn PH  8 and 9 whether the  tS  irpresent
in  the  diyaient  form  from acid  baths or  the quadrivalent
form from alkaline baths.  Therefore, chemical treatment   is
adequate  for  this  constituent,   m principle, thTsulf ide

         S S Sn?*' ^ diSCU88ed  for cedmi«m «- lead,   is
                  °?Pper  all°y  Plati«9 contributes copper,
                   to I*8t  water' a11 of which
*.»» ,*.K.«.».in i M.              , 	r "•-"• ""*• »>«*.v»ii cut« amenaoj
to chemica.1 treatment, as discussed for these metals alone.

Processes
                             106

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                           Water
Cadmium
Cyanide
Bath



Rinso
1

1
1
1
| ^




Rinse
2






Oxidizo
Cyanide







Adjust
pH
Sulfida
Precipitate





                                            #— Liquid of fluent
                                               Metal
                                              Recovery
FIGURE  9  SCHEMATIC FOR SULFIDE PRECIPITATION
           OF CADMIUM IN WASTEWATERS
                   107

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Fluoborate.  Since several of the plating baths  (those  for
lead, tlr>7 and their alloys)  contain the fluoborate ion, the
applicability  of chemical treatment to remove this ion from
liquid  effluent  is  of.  interest.    Upon   dilution   the
fluoborate hydrolyzes:
         BF4™ * EgO - HF + BFJ + OH

The 3F^ is very stable.
Thus,  the  problem  is to reduce the concentration of HF in
the waste water.  The  fluoride  may  be  precipitated  with
lime,   but   the  concentration  can  be  reduced  only  to
approximately  15  mg/1.   This  suggests  that   fluoborate
plating  baths  be  operated  as  closed-loop  systems  with
recovery by  evaporation,  and  that  spills  and  leaks  be
segregated  so that they can be treated separately.  In this
way, the fluoride discharged In liquid effluent can be  held
to a very small amount.

Wire  4pd Strip.  Effluent constituents from cepper, nickel,
chromium, zinc, and  tin  plating  of  wire  and  strip  are
amenable to the same chemical treatment methods as discussed
previously.

Activation  and  catalvzj.tiq»   Chemical precipitation is the
method  generally  used  for  treating  wastes  from   these
operations  for  preparing  pl&stics  and  nonconductors for
plating.  Rinse waters contain tin for activating and palla-
dium  from  catalyzing   operations.    Waste   Waters   are
•segregated  and  treated  separately  by  neutralization and
precipitation,  The tin is precipitated at pH 8 and  removed
by settling or filtration.  The palladium is precipitated at
pH 8 to 9 and recovered by settling or filtration.

           Platipq.   The waste wa'eer constituents in rinses
     .t..
from immersion plating  are  essentially  the  same  as  the
constituents  from electroplating wastes for the same metals
plated.   Waste  Water  treatment  may  be  either  batch  or
continuous, precipitated solids being removed by settling or
filtration.   Acids  are  neutralised  to  pH 6-9 when heavy
metals  e*re  precipitated  as  hydroxides.   The  sludge  is
disposed  of  in the same way as is sludge from treatment of
waste water from electroplating the same metal.  Cyanide  is
destroyed by chlorine oxidation in alkaline  solutions.

Anodising.   Rinse  waters  &re  neutralized  with  lime  to
precipitate aluminum, zinc, copper, chromium as  Cr*3  after
Cr+*  is  reduced,  phosphate? and fluoride^ as shown in the
schematic in Figure 10.  A ferric  iron  salt  is  added  to
                                 108

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  A'l
Anodi.zc
  Mg
Anodize
                Water
                  I
Rinse
Rinse
                  I
                 Water
                                    Lime pp t
                                    pH 7 to 8
                     Sludge
                    Holding
                      Basin
                                        Liquid
                                        Waste
                                                        Stream
     FTGURF 10   SCHEMATIC FOR CHEMICAL TREATMENT OF WASTEWATERS
     FIGURE 10   o    ANODIZING OPERATION
                                 109

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 flocculate   the  precipitated  Hydroxides  of  the  metals
 Klumxnum phosphate precipitates when these two ions  are  in
 the  same  neutral  solution.   Clarification by settling of
 suidge and liquid overflow is  both  batch  and  continuous,
 depending  on effluent water volume.  Aluminum concentration
 is reported to be reduced to 2  mg/1  or  less  by  chemical
 treatment  (Edwards  and Burreli, p 17ft) with 0.5 mg/1 being
 reported.  Reduction of magnesium concentration  to  2  mo/1
 levei   would  probably  require  a  pK  in  excess  of  10.
 orthophosphate ia reported ae a trace ar*d fluoride as 1.5 to
 2«0 mg/1 in effluent.
                       Effluents from  chromating  operations
 are  amenable to chemical treatment to reduce the hexavalent
 chromium and precipitate  triv&lent  hydroxide  as  done  in
 treating waste water from chromium plating-   Phosphates from
 phosphatlng operations can be reduced to the 1 mg/1  level  by
 addition  of  aluminum ions.   Removal of phosphate can occur
 when aluminum  sulfate  ia  added  to  the  elarifier  as   a
 flocculating  agent.    Heavy  metals, auch ad iron and zinc,
 oerived  from the basis metals and solution formulations, are
 removed  by neutralization and precipitation.
                    Both alkaline  and acid waste  waters  are
 involved and  contain  metals  depending on the  basis  materials
 be^ng  processed.   Aluminum is  milled in concentrated caustic
 solution  containir.c?   proprietary  additives  that  are  not
 disclose*,  water  remaining  after neutralization of aluminum
 chemical milling wastes is beneficial to  municipal  sewage
 treatments  plants  that remove phosphates by precipitation.
 Steel  and other alloys (nonaluminuw)  are  milled  in  acidic
 solutions.    The   acidic waste   waters  are  neutralized and
 heavy  metals  are precipitated  by  the  same techniques as  for
 analogoue waste water  in other metal  finishing operations.
          Neutralization and chemical precipitation are used
to  remove  metals  as  for  the  same metals in other metal
finishing operations.  If the waste water contains  chromium
r-rosr.   evening   of  stainless  steel) ,  reduction  is  not
necessary because fche chromium is present in  the  trivalent
form.   Because  the  etching solutions become depleted with
use,, they are regenerated.  Regeneration is  most/ effective
in decreasing copper waste from etching or printed circuits
The  cupric chloride solutions are electrolysed in a closed-
loop  scheme  to  -aiectrodepcsit  the  excess   copper   and
reoxidize   the   solutions.    Copper  ©tenants  containing
chromate, WHftOH to pH 9 to 11,  chloride  and  acetates  are
used  for  etching  printed  circuits.   These are now being
nandled  by  metal  recovery  plants.   Ammonium  persulfate
                            110

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etchants and peroxide-sulfuric acid etchants are also common
and copper can be recovered from them.

   eyr cpngervation TUygugh Control ,
The  volume  of  effluent  is  reduced if water is conserved
during rinsing operations.  The solubility limit of effluent
constituents is essentially constant, so that a reduction in
the effluent volume accomplishes a reduction in  the  amount
of effluent constituents discharged.  Water conservation can
be  accomplished by in-plant process modifications requiring
little capital or new  equipment,  materials  substitutions,
and  good housekeeping practice.  Further water conservation
is obtained by installing counterf low rinse tanks  and  ion-
exchange,  evaporative recovery, or reverse osmosis systems.
Other systems that may  accomplish  water  conservation  are
freezing,  electrodia lysis,  electrolytic  stripping, carbon
adsorption, and liquid-liquid extraction.

Process Modifications

Substitution of low-concentration metal finishing  solutions
for  high-concentration  baths  has  been  adopted in recent
years, principally for reducing the cost of  chemicals  used
for  cyanide destruction.  The dilute solutions require less
water for rinsing when electroplating parts are  transferred
to  rinse  tanks.   Assuming a 50 percent reduction in total
dissolved solids in the plating solution and two rinse tanks
in  series,  a  30  percent   redoc^ion   in   rinse   water
requirements   is   achieved.    U-^ce   Water  constituents
requiring treatment are reduced by the same amount.  Adverse
effects   in   terms   of   lower   efficiency  and  reduced
productivity per  unit  facility  may  be  encountered  when
dilution  is adopted to conserve rinse water and reduce waste
water constituents requiring treatment, unless other factors
affecting  plating  rate  are  modified  to  adjust  for the
effects of dilution.  Thus, dilution should not  be  adopted
before a  complete analysis is made of all pertinent factors.

The  advent of effluent  limitations is expected to encourage
research  and  development  on  other  processes  that  will
eliminate or reduce water waste.  A dry process for applying
chromate  coatings,  which is currently being developed, may
prove useful for such  a  purpose,  for  example.   Chemical
vapor  deposition  processes partially developed a few years
ago may be revived for plating hard chromium.

Material  Substitutions
                               111

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Woncyanide solutions, which have been  developed  for  metal
finishing  operations  in place of cyanide solutions, reduce
the costs of treatment by eliminating  cyanide  destruction,
but  do  not eliminate treatment to precipitate and separate
the metals.  The chelating  agents  employed  in  some  non--
cyanide  baths  to  keep  the  metal  in  soluble  form  are
precipitated when rinse water waste is treated with lime  to
precipitate  the  metals,  but other agents such as ethylene
diamine tetraacetic acid inhibit the precipitation  of  zinc
and  contribute  organic  matter to the treated water waste.
Thus, the  applicability  of  the  noncyanide  solutions  as
replacements  for cyanide baths must be considered carefully
in  the  light  of  the   effluent   limitation   guidelines
recommended in this document.

Trivalent  chromium  baths  have recently been introduced to
the electroplating industry.  They eliminate  the  need  for
sulfur  dioxide  reduction  of  waste  water associated with
chromium plating.  The trivalent chromium  baths  appear  to
have  other advantages for decorative plating such as better
throwing power, current efficiency and  plating  rate.   The
dark  color  of  the  deposits is cited as a disadvantage by
some  purchasers,  however.   Nevertheless 8,   this   process
modification  may  ultimately  prove  to  be significant for
reducinr  waste  treatment  costs.   No  details  have  been
released!  on  the  treatment  required  for  minimising  the
aoiuble chromium concentration in treated effluent, however.

Good Housekeeping Practices

Good housekeeping practices that reduce the waste  generated
in metal finishing facilities include the following:

      (1)   Maintain racks and rack coatings to prevent
           the transfer of chemicals from one operation
           to another. (Loose rack coatings are
           noteworthy as an example of poor practice.)

      (2)   Avoid overcrowding parts on a rack, which
           inhibits drainage when parts are removed
           from a process solutions.

      (3)   Plug all floor exits to the sewer and con-
           tain spills in segregated curbed areas or
           trenches,  which can be drained to direct
           the spills to rinse water effluent with the
           same chemicals.

           Wash all filters, pumps and other auxiliary
           equipment in curbed areas or trenches.
                            .12

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          which  can be  drained  co  direct  the wash
          water  to a  compatible holding tank or
          rinse  water stream,

      (5)  Install anti-syphon devices on  all inlet
          water  lines to process tanks,

      (6)  Inspect and maintain  heating and cooling coils*
          to avoid  leaks.

      (7)   Inspect, and maintain  all piping installed for
          waste  water flow,  including piping  from fume
           scrubbers.

Water Conservation  by reducing Dragout

Draaout.   Dragout   is  defined  as solution on the workplace
carried beyond the edge of the processing tank.  The dragout
of concentrated  solution from the processing tank  can  vary
over a wide range depending on the shape *»<*<» °* th%SfrJl
A  value  of  16-3   liters/1000  sq m  (0.4 gal/1000 sq ft) is
considered a  minimum  for  vertical  parts  that  are  well
drained.   The   practical  range for  parts ot  various shapes
that are well drained is about 40 to  400 liters/1000 sq m  (1
to 10 gal/1000 sq ft).

Reduction of dragout with the above methods is  not  without
problems.   By   returning  chemicals  to the processing t*nk,
impurities tend  to build  up  in  the processing  solution-
Therefore,  purification  systems,  such   as  ion  exchange,
batch-chemical treatments, and/or electrolytic  purification
are   required   to  control  impurities.   The  purification
systems create some effluents which must be treated prior to
end-of-pipe discharge.

Water Conservation During Rinsing

Water conservation procedures that are used after   processed
work is  transferred  fco  a rinse tank include  fl)  adding  a
wetting agent to the  rinse  water,   (2)   installing  air   or
ultrasonic   agitation  and  (3)  installing countarfiow  rinses
whereby water exiting the last  tank in the rinsing operation
becomes  feed water   for the   preceding   rinse.    With  two
counterflow  rinses,  water consumption is  reduced 96 percent
in comparison with a  single  rinse, assuming that  the aragout
 solution  mixes   immediately  with the rinse  water.    *nis
assumption   is   incorrect.   While a  part of   the dragout
 solution  mixes rapidly  with  the rinse water, particularly if
 agitation  is used,  the remaining film on the  work comes off
rather  slowly by a diffusion process.  A  more  typical   value
                              113

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 5?' ,the  W?*?r. reducti<™  might be 85%, cor respon ding to a
 tinsing   efficiency   of   approximately   9055.     Use   of
 conductivity  meters  in  the final rinse provides automatic
 control of water use according to need.   Rinse water flow is
 shut off automatically when  no  work  is  being   processed
 Excessive  use  of  water can also be avoided by  use of flow
 restrictors in the water feed lines.

 Although  multitank,   counterflow  rinsing  imposes  capital
 investment  costs  for  tanks,  pumps,  and floor space,  these
 costs  are compensated for by a  savings In water (and  sewer)
 charges.    Further  incentive  is  provided  when regulatory
 agencies require pollutional control.    when  end-of^process
 ch«j»icax   treatment    is  used,   design  of  wastetreatment
 facilities   usually  indicates  the  economic  advantage  of
 r-aucing   rinse-water   flow  by  installing  two  or  more
 counterMow rinses.

 Because  waste  treatment facilities  are usually overdesigned
 to   handle   future  expansion  in  production,  there   is  a
 tendency  to use  the water flow  capacity  of  the  treatment
 facility  whether  or  not it  is  needed for effective  rinsing.
 Furthermore, rinse  water flows  set  by  an  orifice   are  not
 always  -turned off when plating production is  shut down.  It
 is probanly more economical  to  reduce rinse water  usage  bv
 use  of   good  rinsing   practice  than   to  increase  water-
 trodScticn  facilitiea   in  the  event  of   an   increase   in

 Ringing   can foe carried  out beyond the point consistent with
good practice, even though there is an economic incentive to
 save water.  The result  is unnecessary   pollution.   Typical
concentration  levels  permitted  in  the   rinses  followino
various  process  tanks,  should  not  be   decreased  unless
          quality  problems  can be associated with the dis-
                                                           -
       solids concentrations Hated below for representative
rinsing systems;

                                    Max Dissolved Solids
     Alkaline cleaners                     750
     Acid cleaners*  dips                   750
     Cyanide plating                        37
     Copper plating                          37
     Chromi am plating                       15
     Nickel plating                          37
     Chromi am bright dip                    15
     Chromate passivating                350-750
                               114

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 A problem not  considered  in  proposing   a  maximum  dissolved
 solids   in   the  final  rinse,  is  the  dragin of  these rinses
 into a   subsequent   processing   operation.   If  the  dragin
 attained from the  concentration  proposed is deleterious to
 the  following  processing  operation,  the dissolved solids  in
 the   final   rinse would   have   to be  decreased  or means for
 purification provided.

 The   following is    an    example,   using   various   rinse
 combinations,   of the reduction In  water volume that can be
 obtained for rinsing assuming that the dragout and the rinse
 water mix immediately.  A Watts-type plating bath  typically
 contains 270,000 mg/1 of total  dissolved solids.  Obtaining
 37 mg/1  in  the final rinse requires  27,600 (7300 gallons) of
 rinse water if a  single rinse tank   is used,  in"  order  to
 dilute   3.78  liters  (1   gallon)  of   a  Watts-type plating
 solution containing  270 g/1  of dissolved solids.   The  same
 degree   of   dilution in   a  final rinse tank may be obtained
 with less water by use of series and counterflow arrangement
 of two or more rinse tanks.  If  the  tanks  are   arranged  in
 series   and fresh   water is fed in  parallel to  each tank in
 equal volume,  the ratio,  r of rinse  water to dragout is:

                                 i
                                 n
                              Co
                      T * n   CF ,

where Co =  concentration in the process solution
       CF =  concentration in last rinse tank and
       n =  number of rinse tanks.

 If the tanks are  arranged in the same way, but flow proceeds
 from the   last   rinse  tank  to  the   first    rinse   tank
 (counterflow) ,
                              n
                          £2
                    r =   CF

By  feeding water to counterflow tanks instead of in series,
the  reduction  in  water  varies  n-fold.   Values   of   n
calculated  for  several  rinsing combinations, using the Co
and CP values given above for a nickel bath are as follows:


- ,- Rinse Combj.natj.gn __           Rinse Ratio, r

Single rinse                                 7300
                              115

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Two rinses„ parallel  feed                     171

Three rinses, parallel feed                    58.3

Two rinses, counterflow  feed                   85.5

Three rinses,, counter flow  feed                 19.5
There is a significant reduction in water use by addition of
a second rinse tank, and at least two  rinse  tanks  can  be
considered  normal  practice.   These  should best be fed in
countarflow.    Counterflow   rinse   tanks   increase   the
concentration  of  a metal or other constituent in the first
rinse tank following the plating or process bath.  The water
in the first rinse tank can be used to supply makeup   water
for  the  plating  bath.   As the concentration in the first
rinse tank increases„ more of the dragout from  the  plating
bath  can  be  returned to the bath in the makeup water, and
less will require treatment and/or disposal.  Therefore, the
addition of countercurrent rinse tanks can decrease both the
volume of water to be treated and the  amount  of  dissolved
metal  that  must  be  removed,  at  least in some cases.  A
problerr not. considered in using counterflow rinses  is  that
the concentration in the first rinse tank can become so high
that  the  diffusion  of  the  dragout  from the film on the
workpiese can be slowed  considerably  and,  therefore,  the
rinsing  efficiency decreased substantially.  Therefore, the
more cotintercurrent rinse tanks  that  are  used,  the  less
accurate  Is  the  calculation assuming that the dragout and
rinse welter mix immediately*

The rate of evaporation from the plating bath is a factor in
determining how much makeup water must be added.   Operating
a  bath  at  a  higher  temperature  will  allow more of the
dragout  to be returned to the bath because  of  the  higher
rate  of  evaporation.   However, the temperature at which a
bath may foe operated is sometimes  limited  because  of  the
decomposition of bath components.  Progress has been made in
developing   bath   components   that   allow   higher  bath
temperatures to be used.  For example, brighteners for  zinc
cyanide baths have been developed ^hich allow bath operation
at  50  C  (120  F)   as  compared  to  32 C (90 P) .  The new
brightene rs permit the return of more of the dragout to  the
plating  bath  and  a  lessened  load on the waste treatment
system,, in addition to what other processing advantages they
may offer,

Advanced Treatment Technologies
                                116

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Ion Exchange

ADDlicability.  Ion exchange is currently a  practical  com-
Sercially  accepted  method  for the in-procesa treatment of
m raw water, (2) proceatlnq bath*, (3) rlnte wtert.   Raw
water  is treated to provide deioni*«d water for both makeup
and critical  final rinsing operations.   Plating  baths  are
treated  to   remove impurities, i.e., removal of nickel ions
from a chromic acid  bath  with  a  cation  exchange  resin.
Rinse  waters are  treated  to  provide  water  that can be
returned  to  the  process   solution.    The   concentrated
regenerant  can  be  chemically treated more easily than the
original volume  of  rinse  water  and  in  some  cases  the
chemicals  can  be  recovered and returned to the bath.  The
in- process  treatment  of  chromium   and   nickel   plating
effluents  by ion-exchange  techniques are the more econom-
ically  attractive  treatment  operations  currently   being
carried  out.   Ion  exchange  also  is  beginning  to  find
increased use in  combination with  evaporative  and  reverse
osmosis  systems  for the processing of  metal finishing rinse
waters.
 Advantages  an^Ufflitatiaiia.   3om€  ^vantages  of  ion exchange
 for  treatment  of  plating effluents are  as  follows:

       (1)   Ion exchange is an economically attractive
            method for the removal  of  small amounts
            of  metallic impurities  from  rinse  waters
            and/or the concentration for recovery
            of  expensive processing chemicals.

       (2)   Ion exchange permits the recalculation
            of  a high-quality water for  reuse  in  the
            rinsing operations, thus saving on water
            consumption.

       (3)   Ion exchange concentrates  processing  bath
            chemicals for easier handling,  treatment,
            subsequent recovery, or disposal operations.

 Some  limitations  or  disadvantages   of  ion  exchange   for
 treatment of process effluents follow:

       (1)   The limited capacity of parallel bed ion
            exchange systems means that relatively
            large installations are necessary to provide
            the exchange capability needed between
            regeneration cycles.  Continuous ion exchange
            units reduce the size compared to dual-bed
            units.
                                117

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      (2)   Parallel-bed ion exchange systems require
           periodic regeneration with expenditures
           for regenerant chemicals.  Unless regeneration
           is carried out systematically or continuous
           ion exchange units are used, leakage of
           undesirable components through the resin
           bed may occur,:  In addition, the tssual
           treatment methods must be employed to
           dispose of the regenerated materials.

      (3)   Cyanide generally tends to adversely affect
           the resin performance because of tightly
           held metal cyanide co&iplexes on strongly
           basic anion resins r so that processing of
           cyanide effluents fexcept for very dilute
           solutions) does not appear practical at
           the present time.

           Resins, which are not highly cross-linked
           (or macroreticu lar| , slowly deteriorate with
           use under oxidizing conditions.

       -^,           ...„                 on exchange involves a
reversible interchange of ions between a solid phase  and  a
liquid  phase.   There is no permanent or substantial change
in the structure of the solid resin particles.  The capacity
of an ion exchange material is equal to the number of  fixed
ionic  sites  that  can enter into an ion exchange reaction,
and is usually expressed as  milliequivalents  per  gram  of
substance.    Ion   exchange   resins  can  perform  several
different operations  in  the  processing  of  waste  water,
including:

      (1)  Transformation of ionic species
      (2)  Removal of ions
      (3)  Concentration of Ions*

The performance of some of these functions is illustrated in
Figure I'.:.,  which is a generalized schematic presentation of
the application of ion exchange  to  treatment  of  electro-
plating effluents.  In practice, the solutions to be treated
by ion exchange are generally filtered to remove solids such
as   precipitated   metals,   soaps,   etc.,   which   could
mechanically clog the  resin  bed.   Oils,  organic  wetting
agents,  brighteners, etc,, which might foul the resins, are
removed ty passage through carbon filters.

During processing, the granular ion exchange  resin  in  the
column  exchanges  one  of  its ions for one of those in the
                                118

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Waste from
contaminated
rinse overflow
Waste-water
 reservoir
                                                            To clean water
                                                            reservoir and
                                                            process rinse tanks
                                                                        Caustic    -Hydrochloric
                                                                         soda     '   acid
                                                                     rtx
                                                                  _D
n
                                                                 To recovery
                                                                 or waste
                                                                 treatment
            FIGURE 11 SCHEMATIC PRESENTATION OF ION-EXCHANGE APPLICATION    -
                       FOR PLATING-EFFLUENT TREATMENT(7,25)

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 rinse water  or  other  solution being  treated.   This   process
 continues  until   the  solution   being   treated  exhausts the
 resin.   When this  happens,  solution  flow is   transferred  to
 another column with fresh resin.   Meanwhile,, the exhausted
 resin is regenerated  by another  chemical which replaces  the
 ions given up in the  ion exchange operation,  thus converting
 the   resin   back   to  its original composition,   with  a four-
 column installation   consisting   of   two parallel  dual-bed
 units,   as   shown  in  Figure m,  the  ion  exchange process can
 be applied continuously by  utilizing the regenerated units
 while -he exhausted units are being  regenerated.

 Most ion exchange  systems depend upon regenerating with acid
 and   base  t.o  form   the acid   and  base forms of "the resin.
 These ace capable  of  exchanging  with and thereby  removing
 from  solution  both heavy metals and dissolved salts  such as
 sodium chloride.   However,  resins can be regenerated  with
 salts,   i»e.f   sodium  chloride   to  form sodium  and chloride
 forms of the  resin,   These  will  exchange with  heavy  metals
 but   not  the  soluble   salts.    Since   exchange capacity is
 reserved  for  heavy    metals    only,    the   frequency   of
 regeneration  is   decreased  as   is  the  cost  of heavy metal
 removed,

 EEaSti£S]v»afigiaiiaa_SistgiEs.  The Phase  1  report  described
 systems in use to remove nickel ions and trivalent chromium
 ion  from chromium  plating baths.  The more dilute baths  for
 producing  chromium   conversion  coating  are  treated  in a
 similar manner to  remove,, zinc ions.   Aluminum  is   removed
 from  chromic acid anodizing baths,  and  from phosphoric acid
 baths   used   for   bright  dipping.    Cyanides  may  also  be
 removed,  in  a 3-bed system, consisting of strongly  acidic,
weakly  baiiic, and  strongly  basic ion  exchangers.  The system
 provides ease of regeneration and little chance  of   cyanide
 leaking   through.     The   three-bed system  has  been  in
 Commercial operation  in Europe aid only recently  introduced
 in  the  US.   Sevaral of the systems  are being installed one
of which will be supported to a  limited extent under an  EPA
grant to obtain performance and economic information.

Pemonstratj on ^Status.  An ion exchange system using a short
 30-minute cycle, Including a 3  to  H-minute  back  wash  to
recover chromic acid  from rinse waters has been in operation
for   over   a   year,   The  resin  undergoes  very  little
performance deterioration since  the  chromic  acid   is  not
deeply absorbed into the resin during such a short cycle.

Another system under development uses an ion exchange column
to  achieve  separation of components in much the same manner
that chrome tographic  columns  are  used*   For  example,   a
                              120

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solution    for   biio!
phosphoric  acid and a.
basic  ion exchange co
the  ion exchange sit.?-,
retarded  in  comply,
flow unimpeded thrui.g:
considered   a  very
the  ion exchange i. e^I.
much   of  the  alwmiuv
returned  to tbe bricu

Evaporative Recovery-
                       .luauiu
                       'j  a no-.
                       is.;;  c
                       s  -:he
    Th-.-
   t "•<./.
    cr ;.
 ;   aluminumt  containing
   l rv^  through a strongly
.; JA ;*.;-•.-  ions interact with
-,,>..   phosphoric  acid  is
 trie aluminum ions,  which
           which   may  be
         for regenerating
  ii  phosphoric acid   with
  he  phosphoric   acid is
v'J;;".-: ,
distilled   ir-  ;;?<  c
returned to the -•'.ft
res pond i n g  j: i n r f c -;-
on  a  ai.nffl*?   pi«x
distillation,  irou
operating  costs ivfpo
distillation  ev^j! pino-.rc.   ?a:
of 300 gph are m>c~ d .*;-«  pi^ci
tinse water is achieved In, i,,
the   use   of  <^-.  leo^t  vruwe
itself reduces trie waste  c*.t
for   all   of  the  •.-ir.se  eye

tanks  following  j:.-ic.'r.iu9  ?H; .„>;«.
chemicals  and retaoi  tli^sm x.o u.i'.v;
plating costs,  ""n^ >.u;lts "ru-v.5: :
or  acid   dip  II ".e&   Lacuuse  v-
aufficienc i,> saxe  ">_.c,,i
contatninantatf  !««*„    oil  &i-,ci 91
system di f f ic^J t.,

Kvapora-cior? Irs A  fis-^^v oatt;-.,',,'„;:•
recovering pi a tin*? ch^st.icals a;"s-,"-
ef f I ue nt s,.   C online 2 < • .1 A t  « a' t»
nickel, chromium, an?1 ox-nar XL-*.,,
operating   aucceeofH.l,. y  &r,J; e*;.'O
to 10 years  or   io:-.q**,,    ^'^0..^
treatment    of    pl^t .,ug   V^SV.«;A
manufacturers,

At least  100 ev.^pur. ,ts v<-j  :^i•',•;.-. h
means that t.heir a.:•<-. ;; ^
percentage of the shops*
installations and aaviiig
and   evaporative
grow  in use«   fiovve-v^i:';  ..i
         »
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 strictly  on  the basis of savings in chemicals  such  factors
 as value  of  the  chemicals,   their   concentration   in  the
 process   bath,   and  the  dragout rate  are  important  in
 determining whether a savings  is  possible

 Advantages and frj-roitangos.  The  following are some   of  the
 advantages  of  using evaporation for handling plating waste
 effluents:

       (1)   Recovers expensive  plating chemicals, which
            were  either lost by discharge to a sewer or
            effluent which would have  to  be treated or
            destroyed prior to  disposal;  chemicals
            concentrated to plating strength can  be
            returned to the plating tank.

       (2)   Recovers distilled  water for  reuse in the  rinse
            operations,  thus lowering  water and sewer
            disposal.

       (3)   Eliminates or greatly  minimizes the amount of
            sludge  formed during chemical  treatment and
            eliminates or reduces  the  amount requiring
            disposal by hauling or lagooning.

       (<*)   The use  of vacuum allows evaporation to accur
            at relatively low temperatures (e.g., 110°F)
            so that  destruction of  cyanides or other heat-
            sensitive  materials  is  lessened.

       (5)   The technology  of evaporators  (conventional and
            vapor recompression  units)   is  firmly established,
          so their  capabilities are well  known and their
            performance  should  be  readily  predictable  and
            adaptable  to plating effluent  handling.

Some of the  limitations   or   disadvantages  of  evaporative
recovery systems are  given below:

       (1)   The rinse  water saving  (e.g.,  1100 1/hr (300 gph))
            is rather  small, and by  itself  does not signifi-
            cantly lighten  the rinse water  load on the final
            chemical treatment plant.

       (2)   Evaporative  units have relatively high capital
            and operating costs, especially for the vacuum
            units,   steam and coolant water are required.

       (3)  The evaporative units are fairly complex and
            require highly trained personnel to operate
                              122

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           and maintain them.

      W   separate units are  required if or  handling the
           waste effluent from each line,  since various
           solutions,  such as  zinc, nickel, copper,
           chromium, cannot be mixed for chemical
           recovery.

      i*>\   As with all closed- loop systems, evaporation
      ( }   in most cases results in a build-up of impurities
           which must be taken care of by a bleed stream
           or directly in the closed- loop system.

The   advantages   offered  by  evaporative  recovery  o^ten
outweigh  ?he  disadvantages.    Evaporative  recov**y  *%*
nromisinq  and  economical  method  currently  available for
KndlinS plying  waste  effluents  and  limiting  treatment
SlSnt  2i£e    Where   existing  chemical  treatment  cyanide
destruction;  chromate  reduction, and chemical precipitation)
                -
 chemicals  plays the  significant  role  in  judging the  overall
 meri«  of  the evaporative system for  a  specific operation.
 Process Principles_and  Equipment.    A  representative  closed
                              ^himicals   and   water  from  a
       ve   o
 ola?inq  line  with  a  single-effect evaporator is  shown in
 ?iqure 12   A single-effect evaporator concentrates flow from
 the  rinse  wlte?  holding  tank.    The  Concentrated  rinse
 solution  is  returned  to  the  final rinse tank.   With the
 closed^loop system, no external rinse water is added  except
 fo? Sakeup of atmospheric evaporation losses.  The system is
 designed  for  recovering   100  percent  of  the chemicals,
 normally lost in dragout! for reuse in the plating process.

 Sinqle-,  double-,  and  multiple-effect  evaporators,   and
 vapo^recompression  evaporator  units are ^^°*  *a*}dl *ng
 plating effluent.  Open-loop and combined evaporation  (i.e. ,
 evaporation combined with ion exchange, reverse osmosis   or
 other  systems)  are  also  employed  for  Handling  plating
 effluent.

 A  single-effect   evaporator  is  preferred,  if  relatively
 untrained  operating  personnel are  involved, or low initial
 SSpiSl outlSy is  desired.  It's the  simplest in design  and
 ?£ererore  the   easiest  to  operate.   However,  it is less
                                123

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      Concentrotc hold tonk
                           Distillote hold tank
                                                    tasssaaK^i
        Plating work travel	•

Plotingbath.                 Rinse
                                      inse tanks (
-------
economical than a  double-effect. »>r \?a ;.-.-.-* ^compression  unit
with  regard  to   utility  casts,,   « tfou me- effect evaporator
should be considered  when  lower opsrati.^  cost  is  desired
with a modest increase  in  capital
&  vapor-' re compress ion  evaporator should foa considered if no
steam or cooling water  Is  avai'lA&ie.   Where utilities for  a
conventional   steam  evaporator  &rs  available*  the  high
initial  cost  of  the   vapor  r^c OKI press! on  unit  is   not
economically justified.   Its ope/raxing cost is the lowest of
the  three  systems.    I -is  despondence  on  an expensive and
complex mechanical compressor is th<& Kiai/i disadvantage.
Some sources report  considerable Rifii.vi^iiance and  down  time
and  have  dispensed  with   use  of evaporator units.  Other
sources report  little  or no trouble sand are  very  satisfied
with  the  opera.tior?..   It appears; tnai iihe units can perform
very  satisfactorily  If tha   installation   is   properly
engineered,  and   if  preventive  maintenance  and  trouble-
shooting are carried oat by fcnowic-dg^fcible personnel.

In some instances, evaporation procedures snaet  be  used  in
combination  with  chemical  or  other  methods  in order to
handle   small   amounts   of   impurity   build-up   (e.g.,
brighteners,,  carbonates v.   ext.r&neaus  metal  ions, etc. , in
closed loop operation)  or for t nsa tsnerst of  minor  bleed-off
streams (open-loop^ „

Atmospheric evaporation,,  whieii a»es air flow through packing
media  in  an   evaporator,   can concentrate plating solution
such as chromic acid tsp -co  siSQ g/1 {"4 Ib/galJ .

The corning Glass  Company Siss jifstro»5i/:.'e<5 a new  concept  for
evaporative recovery,   h glass shell tiad tv.be heat exchanger
is  motanted  vertically  &n>. -;.r»fese processes.  Small

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 amounts of spxlls,  leaks,  if segregated,  are  evaporated  to
 dryness,  and the solid waste sent to a metal recovery unit.
 Failing film atmospheric evaporators have been installed  in
 a tew plants.
  ,           - Status.     The   "rising   film"   units   are
 undergoing pilot and plant test.

 Reverse Osmosis

 AEElisabjLlity..   Reverse  Osmosis uses a  pressure differential
 across  a membrane to separate  a solution into a  concentrate
 and   a   more  dilute solution that may approach  the purity of
 the  solvent.   It therefore accomplishes  the  same type   of
 fnSJftn1?? a84  di?tlllati°n and  has been applied in plating
 installations in the same  manner.   Small units  under 300  gph
 have been installed to recover plating  baths  chemicals   and
 make closed- loop operation of  a line possible.

 There  are limitations  on the   acidity  and  alkalinity of
 solutions suitable for treatment   by reverse   osmosis  that
 eliminate  some   alkaline   baths and chromic acid baths from
 consideration unless modifications are  made to  the solutions
 prior to treatment.   Another use of  reverse osmosis  is   for
 end~of-process   water recovery following chemical  treatment.
 A recently designed system for Plant 11-22  offers  promise
 that large capacity reverse osmosis  systems are possible and
 therefore  not subject to the size  constraints of evaporative
 systems.    If  so,  they  should play  a key role  in  the design
 of plants that will have no liquid effluent.

 Most  of  the development work and commercial  utilization  of
 the  reverse osmosis  process, especially  for desalination and
 water   treatment   and recovery, has  occurred during the past
 10 years.  There  is  a steadily growing  number of  commercial
 installations  in   plants   for concentration and recovery of
 plating   chemicals   along  with  recovery  of  water   under
 essentially  closed-loop  conditions.   Most of the existing
 commercial installations are for treatment of nickel plating
 solutions,  since reverse osmosis is  especially  suited  for
 handling  nickel solutions and also because of the favorable
 economics associated with recovery and  reuse  of  expensive
 nickel  chemicals.   Commercial  reverse  osmosis  units for
 handling acid zinc and acid copper processes also have  been
installed,  however.   Laboratory pilot plant and full-scale
 in- plant  studies directed at handling cyanide and  chromium-
type effluents are under way.

Reverse  osmosis  is  especially  useful  for treating rinse
water containing costly metals and other  plating   salts  or
                         126

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materials.  Generally, the purified water is recycled to the
rinse,  and  the concentrated salts to the plating bath.  In
instances where the concentrated salts cannot be recycled to
the plating tank,  considerable  savings  will  be  achieved
because  of  the reduced amount of waste-containing water to
be treated.
Advantages jgnj  ]^i!Ei£ja£i£a§.   Some  advantages  of  reverse
osmosis for handling process effluents are as follows:

       (1)   Ability to concentrate dilute solutions
           for recovery of salts and chemicals

       (2)   Ability to recovery purified water for
           reuse

       (3)   Ability to operate under low power require-
           ments  (no latent heat or vaporization or
           fusion is required for effecting separa-
           tions; the main energy requirement is for
           a high- pressure
      (U)  Operation at ambient temperatures  (e.g.,
           about 60 to 90 F)

      (5)  Relatively small floor space requirement
           for compact high-capacity units.

Some  limitations  or  disadvantages  of the  reverse osmosis
process for treatment of process effluents are listed below:

      (1)  Limited temperature range for satisfactory
           operation,,  (For cellulose acetate  systems
           the preferred limits are 65 to 85  F;
           higher temperatures will increase  the rate
           of membrane hydrolysis, while lower temper-
           ature will result in decreased fluxes but
           not damage the membrane) .

      (2)  Inability to handle certain solutions
            (strong oxidizing agents, solvents and
           other organic compounds can cause  dissolu-
           tion of the membrane) .

      (3)  Poor rejection of some compounds  (some
           compounds euch as berates and organics of
           low molecular weight exhibit poor  rejection) .

           Fouling of membranes by slightly soluble
           components in solution.
                          127

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      (5)   Fouling of membranes by feeds high in sus-
           pended solids  (such feeds must be amenable
           to solids separation before treatment by
           reverse osmosis).

      (6)   Inability to treat highly concentrated
           solutions (some concentrated solutions may
           have initial osmotic pressures which are so
           high that they either exceed available
           operating pressures or are uneconomical to
           treat).

Process  Principles  and   Eouip|jfient.   Water  transport  in
reverse osmosis (RO) is opposite to the water transport that
occurs  in  normal  osmosis,  where  water flows from a less
concentrated solution to a more concentrated  solution.   In
reverse osmosis, the more concentrated solution is put under
pressure  considerably  greater than the osmotic pressure to
drive water across the membrane to the dilute  stream  while
leaving  behind  most  of  the  dissolved  salts.   Salts in
plating baths such as nickel sulfate or copper  sulfate  can
be  concentrated to solutions containing up to 15 percent of
the salt,  by weight.

Membrane materials for reverse osmosis  are  fairly  limited
and the bulk of the development work has been with specially
prepared cellulose acetate membranes, which can operate in a
pH  range  of  3 to 8 and are therefore useful for solutions
that are not strongly acid or alkaline,  i.e.,  rinses  from
Watts nickel baths.  More recently, polyamide membranes have
been  developed  that  will  operate  up  to a pH of 12, and
several of these units  are  operating  in  plants  for  the
treatment of cyanide rinse waters.

Figure 13 is a schematic presentation of the reverse osmosis
process  for  treating  plating-line  effluent.   The  rinse
solution from a countercurrent rinse line is pumped  through
a  filter,  where  any suspended solids that could damage or
foul the membrane are removed.  The rinse solution  is  then
raised  to the operating pressure by a highpressure pump and
introduced into the reverse osmosis unit.  The  concentrated
salt  stream  is  returned  to  the  plating tank, while the
dilute permeate stream is returned to the second rinse tank.
Currently,  several  different  configurations  of  membrane
support  systems  are  in  use in commercial reverse osmosis
units.  These  include  plate  and  frame,  tubular,  spiral
wound, and hollow fine fiber designs.
                          128

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to
                                                  Rinse
                                                    1
                                               Low-pressure
                                                 pump
                         Concentrate
R everse-osmosis
    unit
                                                                  Permeate
                                                                                            Parts
                                             Makeup
                                             water
              FIGURE 13 SCHEMATIC DIAGRAM OF THE REVERSEOSMOSIS PROCESS
                         FOR TREATING PLATING EFFLUENTS

-------
                      §y§tejj8.  Reverse osmosis units are in
         ._^         __
operation for recovering  nickel  from  rinse  waters.   The
concentrate is returned to the plating bath.

Demonstration  Status.   The reverse osmosis units installed
at the Rock Island Arsenal  as  part  of  an  en d~of- process
water  recovery system, remains fco be demonstrated as a part
of a total successful system,  A project  sponsored  by  the
American   Electroplating   Society  ha®  demonstrated  that
cellulose acetate  membranes  can  operate  successfully  on
nickel and copper sulfate rinse waters and that spiral wound
and  hollow  fiber  polyamide membranes can be used to treat
copper, zinc, and cadmium cyanide baths.  A second phase  of
this  study  is  a demonstration in a plating shop of a full
scale reverse osmosis system on copper cyanide rinse water.
                The freezing process  would  be  capable  of
recovering  metal  and water values from plating rinae water
to permit essentially closed- loop type  operation  if  fully
developed.   The feasibility of using freezing for treatment
of plating rinse waters was  demonstrated  on  a  laboratory
scale  using a mixed synthetic solution containing about 100
mg/1 each of nickel, cadmium,, chromium,, and sine, along with
30,000 mg/1 of sodium chloride. Greater  than  99.5  percent
removal   of   the   metallic   ions  was  achieved  in  the
experiments, with the purified water product containing less
than 0.5 mg/1 each of the individual  plating  metals.   The
separation tests were carried out using the 9500 1/hr (2500-
gpd)  pilot plant unit at Avco Systems Division, Wilmington,
Massachusetts .

Process Princip_les_and_^guigment.-  The basic  freezing  pro-
cess  for  concentration  ana recovery of water from plating
effluents is similar to that  used  for  recovery  of  fresh
water from the sea.  A schematic diagram of the treatment of
plating  rinses  by  the freezing process is shown in Figure
1U.  The contaminated reuse water is pumped through  a  heat
exchanger  (where  it is cooled by melted product water)  and
into a freezer.  An immiscible refrigerant {e.g., Freon)   is
mixed  with the reuse water.  As the refrigerant evaporates,
a slurry of ice and concentrated solution  is  formed.   The
refrigerant  vapor  is  pumped  out  of  the  freeser with a
compressor.  The slurry is pumped  from  the  freezer  to  a
counterwasher ,  where  the concentrated solution adhering to
the ice crystals is washed off.

The counterwasher is  a  vertical  vessel  with  a  screened
outlet located midway between top and bottom.  Upon entering
                             130

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                                     Pump
                                                 Cooling
                                                  water
To rinse
 Uuuc
              Heat exchanger
                                                         Metter/
                                                        condenser

                                                 Counter
                                                  washer
                                                          1  Concentrate
                                                                      Refrigerant
                                                                       (Freon)
f\  Compressor

     Refrigerant
       vapor
                                                                                   Freezer
                 FIGURE 14 SCHEMATIC DIAGRAM OF FREEZING PROCESS FOR RECOVERY
                 FIGURE    S              CHEMICALS FROM PLATING RINSES (37.38)

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the  bottom,  the  slurry forms a porous plug.  The solution
flows upward through the plug and leaves  the  counterwasher
through  the  screen.   A   small  fraction  of the purified
product water (less than 5 percent)   flows  countercurrently
to  the  ice plug to wash off concentrated solution adhering
to the ice.  The ice is pumped to a condenser and melted  by
the  release  of  heat  from the refrigerant vapor which had
been originally evaporated to produce the ice, and which had
been heated  by  compression  to  a  saturation  temperature
higher then the melting point of the ice«

Because  of  the  pump work, compressor %»ork, and incomplete
heat exchange, a greater amount of refrigerant is  vaporized
than  can  be condensed by the melting ice.  Consequently,, a
heat  removal  system  is   needed   to   maintain   thermal
equilibrium.   This  system  consists  of a compressor which
raises the temperature and pressure of toe excess vapor to a
point where it will condense on contact: with ambient cooling
water.

The freezing process offers  several  advantages  over  some
other  techniques.   Because  concentration  takes  place by
freezing  of  the  water  in   direct   contact   with   the
refrigerant,  there  is  no  heat-transfer  surface   (as  in
evaporation) or membrane  (as  in  reverse  osmosis)  to  be
fouled  by the concentrate or other contaminants.  Suspended
solids do not affect the freezing process  and  are  removed
only  as required by the end use to be made of the recovered
products.

The heat  of  crystallization  is  about  1/7  the  heat  of
vaporization,   so   that   considerably   less   energy  is
transferred for freezing than for a  comparable  evaporation
operation.   Because  freezing is a low-temperature process,
there  will  be  less  of  a  corrosion  problem  than  with
evaporation,  and  less  expensive materials of construction
can  be  employed.   The  freezing  process  requires   only
electrical  power,  as  opposed  to  the evaporation process
which also  requires steam generating equipment.  The cost of
the freezing method may be only  1/3  that  for  evaporative
recovery.

A method of freeze drying metal finishing solutions has been
demonstrated  in  the laboratory.  Droplets of the  solutions
are   injected  into  cold  liquid-hexan*  where   they    are
immediately frozen.  The droplets were  separated out and  the
water removed at subfreezing temperature.  The method leaves
a  dry  chemical residue, and the pure  vaporized water  could
be recycled to process.  The economics  of the process   on a
practical  scale are unknown.
                             132

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Practical  Operating  Systems .  No commercial utilization of
freezing~f or treatment of waste water from  metal  finishing
is known.

Demonstration  Status.  No demonstrations are in progress in
metal finishing plants.  However, a  9500  liters/day   (2500
gpd)  unit  is  in  operation to demonstrate desalination of
water.

Electrodialys is

Applicability.  Electrodialys is  removes  both  cations  and
anions from solution and is most effective with mult i-va lent,
ions.    It is capable of reducing the concentration of heavy
metal ions from solutions whether they are complex  or  not.
Chromate and cyanide ions may also be removed.
Process     Principles    aM    Equipment.    The   simplest
electrodialysis system consists of an insoluble anode and an
insoluble cathode  separated by an anion  permeable  membrane
near  the   anode   and  a   cation permeable membrane near the
cathode.  An  anode  chamber,  cathode  chamber,  and  middle
chamber  are   thereby formed.  Upon  electrolysis anions pass
from  the middle chamber to the anode compartment and cations
pass  from the middle chamber  to  the  cathode  compartment.
The   concentration  of  salt  in  the central compartment is
thereby decreased.  By employing several  anion  and  cation
permeable   membranes between  the electrodes  several chambers
are created.   A stream may then be run  through  several  of
these chambers   in which the concentration is successively
increased.    The   net  effect is  similar   to  that  of    a
continuous   moving  bed   ion  exchange column with electrical
energy  used for regeneration  rather  than chemicals.
          -                       practical operating systems
 have been reported.   However,  development  has  resulted  in
 several demonstrations,  discussed below.

 Deroonstira.fciQIi--J&a&*§«    Several  demonstrations  have shown
 that  electrodialysis  is  a  promising   method.     Further
 development  and  use of the method may be expected.  Copper
 cyanide rinse water may be concentrated sufficiently  to  be
 returned  to  the  bath  by  using  two  units  on  a double
 counterflow rinse system, i.e.,  between the first and second
 rinse tank and  between  the  bath  and  first  rinse  tank.
 Copper  may  be  recovered and chromic acid regenerated in a
 spent etching solution  for  printed  circuits.    The  Metal
 Finishers Foundation has put priority on a future project on
 cyanide removal by electrodialysis^
                              133

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Ion-Flotation Techniques
                  Ion- Flotation  techniques  have  not  been
developed for application to process rinse water  effluents.
If  successfully  developed  into  a  practical  method  for
effluent treatment, ion flotation  offers  possibilities  of
reducing the amount of water discharged by 60-90 percent for
some  operations.   These  savings  are  based on results of
small-scale  laboratory  studies  on  solutions   containing
cyanides or hexavalent chromium.
Process.^ Principles  _and .Bgii^gment,  Separation of ions from
aqueous solutions by a  flotation  principle  is  a  concept
first  recognized  about  25  to  30 years ago.  In the ion-
flotation  operation  a  surface  active  ion  with   charge
opposite  to  that of the ion to be concentrated is added to
the solution and bubbles of air or other gas are  introduced
into  the  solution  to  form  a froth of the surface-active
materials.  The foam is separated and collapses  to  form  a
scum  containing an ion concentrate.  Ion flotation combines
the technologies of mineral flotation and ion  exchange.   A
schematic  diagram  of  an  ion-flotation  cell  is shown in
Figure 15.

Experimental  results  indicate  that  90  percent  of   the
hexavalent  chromium  in  a  10  to  100 ppm solution can be
removed with primary amine surface-active agents.   However,
the amine suffered deterioration when regenerated for reuse,
since the removal efficiency dropped to 60 percent after two
regenerations of the amine.

Grieves,,  et al. , have demonstrated the feasibility of using
ion  flotation  on  dichromatc  solutions  with  a  cationic
surfactant   (ethylhexadecyldimethylaroonium   bromide) .   A
continuous operation with a retention time  of  150  minutes
was   devised.   The   feed  stream  contained  50  mg/1  of
dichromate.  Approximately 10 percent of the feed stream was
foamed off to produce a  solution  containing  150  mg/1  of
dichromate, while the stripped solution contained 15 mg/1.

Cyanides  have been removed from dilute solutions with mixed
results.  The extraction efficiency from a  cadmium  cyanide
solution  containing 10 ppm of cyanide was 57 percent, using
primary,; tertiary,  and  quaternary  ammonium  compounds  as
collectors.   Extraction  efficiencies  for  nickel and iron
cyanide solutions were approximately 90 percent,  but  these
systems are of relatively little interest.

Practical. _ Operating   Systems.   There  are  no  practical
operating systems.
                             134

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Air in

(
lMg
Foam concentrate
lake -off

Purified
solution — « 	
removal

^njcction port .. - 	 	
for collector 	 »*•
ogent




-t-^j-V^J-u-t,

-"-**-"-—
»* »
% 1
0 b
V
•i!
6 0
'U,

i











0







«;
/.
* ft
/ Oi
/
40
'r.«t
poit


FIGURE 15  SCHEMATIC DIAGRAM OF ION-FLOTATION CELL
          FOR TREATMENT OF PLATING EFFLUENT
                    135

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Demonstration fftatus.  The process has not been demonstrated
in an operating plant.

Electrolytic Stripping

Applicability.  Electrolytic stripping is not in general use
for removing heavy metals although some procedures have been
employed for recovering precious metals.

Process Principles and Equipment.  In order to strip a solu-
tion by electrodeposition it is necessary that the  metallic
ions  in  a  dilute  solution reach the cathode surface at a
sufficient rate so that essentially all of the ions  can  be
deposited  in  a  reasonable time.  3isrfleet and Crowle have
discussed several methods of accomplishing this.  One method
called the "integrated" system uses baffles  in  a  tank  to
create  a  very  long  path  through  which the water may be
recirculated at a high velocity.   The  method  is  suitable
only  for  metals  having a relatively high limiting current
density for dilute solutions, such aa gold, silver, and tin.
The fluidized bed electrode is a bed  of  metal  spheres  or
metal-coated  glass spheres that is fluidiaed by pumping the
dilute solution through it and causing aa expansion of 5  to
10 percent,  With spheres of 100 to 300 ailerons in diameter,
a total geometric area of 75 cm'/cm3 Is obtained.  Thus, the
current  density  is  very  low  aad the flow of electrolyte
through the bed provides the forced  convection  to  support
high  currents.   Another  system employs electrodes made of
expanded metal and  the  turbulence  arowxd  this  structure
enhances  the  rate  of deposition of metal when solution is
pumped past it.  Turbulence and an increase in the  rate  of
deposition  at  a  plane  electrode  may also be promoted by
filling the space between electrodes with  a  woven  plastic
screen, glass beads, etc.

In  another system the electrode is introduced into a narrow
gap between two porous carbon electrodes.  The bulk  of  the
solution (99%) is forced through the cathode where copper is
deposited  out.  Predeposited copper on the anodic electrode
is dissolved into the 1  percent  of  the  electrolyte  that
permeates through this electrode and a copper concentrate is
produced.   The  two electrodes are periodically reversed so
that copper deposited from a large  volume  of  solution  is
dissolved  into  a  small  volume of electrolyte.  Copper in
solution has been reduced from 670 mg/1 to 0.55 mg/1 in  the
cathode  stream  and  concentrated  to  4ft  g/1 in the anode
stream.  A similar  system  has  been  used  for  depositing
metallic impurities from strong caustic solutions.
                            136

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Practical  Operating  Systems,   There  are  many systems in
operation for the recovery of precious metals.

Demonstration Status.  The porous electrode system is  still
under  development  at  the University of California and has
been scaled up to handle 250 gpd of copper sulfate solution.
Metal Finishers Foundation has established  priority  for  a
future   project   to   remove   zinc   from   effluent   by
electrodeposition.

Carbon Adsorption

Applicability.  Activated  carbon  has  been  used  for  the
adsorption  of  various  materials  from solution, including
metal ions.  Experimental data show that up to 98 percent ot
the chromium can be removed from waste water.   The  treated
water can be recycled to the rinse tanks.

£rocessi  Pr|.nct6lg§	and gguipment.  The process relies upon
the adsorption of metal ions on specific types of  activated
carbon.   In the case of Chromium VI, a partial regeneration
of the carbon can  be  accomplished  with  caustic  solution
followed  by  an  acid  wash  treatment  to  remove residual
caustic  and  condition  and  carbon  bed   for   subsequent
adsorption  cycles.  The equipment consists of holding tanks
for the raw waste, pumps and piping to circulate  the  waste
through  adsorption  columns  similar  to those used for ion
exchange.

Practical Operating Systems.  Systems  based  on  adsorption
and desorption are still under laboratory development and no
practical operating systems are known.

Demonstration   Status.   Pilot  p?,.ant  equipment  has  been
operated successfully in an  electroplating  plant  treating
chromium  rinses  at a flow rate of 19 liters/min (5 gpm)  at
concentrations from 100 to  820  mg/1  hexavalent  chromium.
Adsorption   was   continued   until  the  effluent  reached
concentrations of 10 ppm of Chromium VI.

Water Conservation by Liquid-Liquid Extraction

Applicability. Liquid-liquid extraction has been used on  an
experimental  basis  only  for  the extraction of hexavalent
chromium from waste waters.  The effect  is  to  concentrate
impurities  in  a smaller volume,, which in turn will have to
be treated by other means  or  suitably  disposed  of.    The
fully  extracted  aqueous phase may be recycled to the rinse
tanks,   water savings from 50 to 73  percent  appear  to  be
possible.
                           137

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        —Principj.es—and Equipment.   The metal-ion pollutant
 is reacted with an organic phase  in  acid  solution,   which
 separates  readily  from the aqueous phase.   Metal is  subse-
 quently stripped from the organic  phase  with  an  alkaline
 solution.    Hexavalent  chromium,   for  example,   has  been
 extracted from  waste  water  at  pH  2  with  tertiary  and
 secondary  amines dissolved in kerosene.   After the reaction
 of the chromium with the amine  and   phase  separation*  the
 chromium is stripped with alkaline  solution  from the organic
 phase  restoring the amine to its original composition.  For
 liquid-liquid  extraction  to  be  feasible   the   following
 conditions would have to be met:

       (1)   The extraction of chromium should be virtually
            complete

       (2)   Reagent recovery by stripping  would be  efficient

       (3)   The stripping operation should produce  a
            greatly concentrated solution

       (4)   The treated effluent solution  should  be
            essentially free from  organic  solvents

       (5)   capital and operating  costs  should  be
            reasonable.

 The  equipment  required   consists basically of  mechanically
 agitated  mixing  and settling  tanks,  in which the phases  are
 intimately dispersed   in   one  vessel by agitation  and then
 permitted  to  flow   by   gravity  to   a  settling  vessel  for
 separation.    Holding   tanks  for  extractant and  stripper and
 circulating pumps   for   these   solutions,  as  well  as  the
 purified   waste water,  are  necessary.  Equipment for liquid-
 liquid extraction would also  include horizontal and vertical
 columns,  pulsed columns and centrifuges.

 Practical	Operating  Systems.    Liquid-liquid   extraction
 systems are not  known to be operating for treatment of metal
 finishing wastes.

 Demonstration  status.   Experimental  evidence exists indi-
 cating that up to  99 percent of chromium can be successfully
 extracted  from rinse waters containing 10 to  1000   mg/1  of
Cr*+.   With   10 ppm of Cr«+ in the rinse water, the treated
effluent contained as little as 0.1 mg/1 of  the  ion;   with
 100  ppm   in  rinse  water  concentration was reduced to 0.4
mg/1.  Stripping was effective as long as  the  amines  were
 not  allowed  in  contact  with the chromium for a  prolonged
period of time which would allow  oxidation  by  Cr*+  ions.
                            138

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The  effluent,  however,  contained  from 200 to 500 mg/1 of
kerosene, which is undersirabie.

NfPthods of Achieving No Dj,sch.arae of gollutants

Although chemical  methods  of  treating  waste  waters  are
achieving  the  low  effluent  discharges  recorded  in this
report, they are not improvable to the  point  of  achieving
zero   discharge   of  pollutants.    Also  the  problem  of
recycling sludges or solid wastes remains.  It  is  easy  to
design systems that will in principle close the process loop
and  prevent discharge.  In practice, however, this can only
be done with considerable forethought and experience,  since
closed  systems  are in general subject to impurity buildup.
Progress in achieving no-discharge systems is likely to take
place in a series of steps in which the amount of  discharge
is consistently reduced until it is negligable.

A  major  problem with a series of metal finishing processes
in a closed cycle is that of dragin.   After a closed  cycle
has  been run  long enough any stagnant tank,, i.e.., a plating
solution that  is normally not discarded,,  will  contain  the
same  concentration  of contaminant as the preceding tank in
the cycle, the assumption being that the  volume  of  dragin
and  dragout   are  equal.   Therefore*  if  the  final rinse
following nickel plating  contains  12  ppm  of  nickel  and
chromium  plating follows, the  chromium bath will ultimately
contain  12 ppm of nickel.  Nickel is frequently removed  from
chromium plating baths  by ion exchange* but  since  the  ion
exchanger  requires  periodic   regeneration^  the regenerant
must somehow  be returned to  the  system  if   it  is  to be
considered a  closed  one.  The nickel in the  regenerant might
be  recovered  and   returned  to  the  nickel  bath, but the
dissolved solids, i.e., sodium  sulfate? and  sodium  chloride
are    really   excess   products  that  cannot   be  completely
returned to the process,  while the main  process loop may be
closed,  the   secondary purification  loops  may   be    more
difficult  to close.   With some process baths, it may not be
possible to find  a  method  for  purification  that  is as
adaptable as  is ion  exchange to the removal  of nickel from  a
chromium  bath.   Alternatives then  are   to   (1)  develop
processing baths that  can tolerate  the impurity  buildup or
 (2)  to  design  rinse systems  in which the  concentration of
impurity in the final  rinse  tank  is reduced  to a   tolerable
 level.

Some   systems, designed  to remove a  specific impurity, are
found  to remove other  components  as well, which may require
further  treatment.   An example  of  such a  system is  that  used
for    removing  carbonates   from  cyanide   baths.   Whether
                              139

-------
freezing  or  precipitation  with  calcium  is   used,   the
carbonates  occlude  and  adsorb  significant  quantities of
cyanide that must then be further treated, with  the  result
that   cyanide   is  not  maintained  in  a  closed  system.
Therefore, with present technology, it is likely that  there
will  be  some discharge from a process loop in spite of the
best efforts that are made to close it.   Some  waste  water
effluent  will be produced and the next consideration is how
well a waste treatment system can be closed.

The  effluent  will  contain  heavy  metals,  cyanide,   and
chrornate  all  of  which  can  be  treated to relatively low
levels to give (1)  liquid containing small amounts of  heavy
metals,  cyanide  and chromate and larger amounts of soluble
salts  such  as  sulfate  and  chlorides,  and  (2)   sludge
containing heavy metals, phosphate, carbonates, flocculating
agents,  etc.   The  liquid,  if  large  in  volume  may  be
concentrated further by evaporation,  reverse  osmosis,  ion
exchange,  or  some  other  process  followed  by  a further
purification  to  reduce  the  heavy  metal  effluent  to  a
negligable  value.   The  liquid may alternatively be passed
through a salt loaded  ion-exchange  column  to  remove  all
traces  of  heavy  metals  and  yield an effluent containing
essentially soluble salts that  may  be  discharged  to  the
ocean if not to a stream or sewage facility.  Alternatively,
solutions  of soluble salts may be evaporated to dryness and
the solid salt contained or fixed in cement, etc.

Sludge, obtained either directly from waste  water  or  from
ion-exchange regenerants, cleaning and pickling baths, etc.,
would  need  to  be  reclaimed for metal values or the metal
salts separated out for return to process tanks in order  to
provide a closed or recycle system.

Thus,  to attain the ideal of providing a system where input
is energy and materials and  output  is  solely  a  finished
product  will  require  further  research  and  development,
considerable ingenuity, and expert engineering  and  design.
However, the capability for progressing towards this goal is
available.
                              140

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                        SECTION VTII



                           NONWATER QUALITY ASPECTS
                        Introduction

In  this  section,  costs  associated  with  the  degree  of
effluent  reduction  that  can  be  achieved  by   exemplary
treatment  methods  are  discussed.   The  nonwater  qualzty
aspects concerning disposal of solid waste  and  the  energy
impact   of   the  waste  treatment  technologies  also  are
discussed.

Treatment and Control Costs

Chemical Treatment to Achieve Low Levels of Pollutants

BPCTCA LimitatiQns_JTable_ll.  Costs associated with control
technology  consistent  with  the  exemplary   practice   of
chemical  treatment  in 26 plants avera9ed  a1;?^™0 ^"
treated with  a   standard  deviation  of  $1.91/1000  liters
 (Table  27) .  Operating costs  include a cost of capital equal
to   8 percent of  the investment and depreciation equal to 10
percent of  the investment.

The  operating cost of waste  treatment as  a  percent  of   cost
of   metal   finishing  for  13  companies is 7.4  percent with  a
standard  deviation of 5.4  percent.  The figures were arrived
at  from estimates by the plants   themselves  concerning  the
relative  cost of  waste  treatment.

 The    plot  in  Figure   16  shows  the  large  variation in
 investment  costs  for  individual   plants   and  reflects  the
 large deviations  reported  above.   Thus, there are  no typical
 plants.    Rather,  costs   are  highly  dependent   upon  local
 conditions.  Costs  were calculated in  terms  of   volume of
 waste  water   treated   rather  than  surface  area  finished
 because costs  are believed to be  more  closely related to the
 volume treated.   Water  use is highly variable  and  relating
 waste  treatment   costs to area finished would have provided
 even more variable  results.   For  a nominal water  use of  80
 liters/sq  m  (2   g/sq   ft)  the cost of  $1.06/1000 liters  is
 equivalent to $0.085/sq m ($.0079/sq ft).

 In addition to the cost  data  collected  from  plants   with
 waste  treatment  facilities,  costs  were also estimated by
 modeling metal  finishing  facilities  together  with  waste
 treatment  facilities  providing  effluent  that  would meet
                                141

-------
                             TABLE 27   COSTS FOR WASTE TREATMENT FACILITIES
Plant
No.
20-24
33-24
33-25
36-12
33-2
33-4
8-5
6-37
19-11
15-3
9-7
4-9

3J-19
8-8
33-22
33-23
20-22
20-20
33-35
20-23
4-8
5-35
9-2
23-7
30-13
?3-30
19-24
6-35
31-16
46-4
33-29
Investment
Processes (1971)
Plating Cortmon Metals
Plating Cocoon Metals
Plating Coanon Metals
Plating Con. , Prec. Ketals
Placing Free. Metal*
Fiatir.g Free. Metals
Plating Prec. Metals
Plating Prec. Metals
Plating Prec. Xetals
Plating Prec. Metals
Electropainting, Anodizing
Electroless Plating
Electroless Plating
Electroless Plating
Electroless Plating
Anodizing
Anodizing
Anodizing
Anodizing
Anodizing
Ar.ecizing
Chemical Milling
Chemical Milling
Chemical Milling
Chemical : Li 11 ing
Ciienical Milling
Phosp'-iatiny
Etching
Inversion
Printed Circuits
Elect ropolishing
Elect roaachinlng
34,000
172,000
27,932
200,000
25,000
66,000
300,000
400,000
110,000
66,113
100,000
45,325
23,292
217,725
51,679
193,846
167,575
130,902
155,300
125,000
123,414
17,45?
300,000
'',208/100
1^2 /'06
2y',A?>2
9-'t,500
295,615
5b,°s3
1,05 0,0 00
', 1 , 9.1 '->

Operating
Cost/Year
(1971)
14,195
80,430
10,694
72,809
14,968
18,205
115,995
121,905
49,985
25,552
32,249
45,312
9,746
168,312
13,430
51,515
Ay, 658
113,3-0
/ ' '^
2S^2U
41,855
16,675
33,753
685, 847
3'13 .?!•'>
11,'jl?
19,726
1?G,211
ij,7i -1
23V ,611
:4.">6C

Hours
Operated
Per Year
4,800
4,000
7,200
7,520
1,025
1,800
2,400
2,250
2,000
2,000
4,000
4,000
4 , 000
8,400
4,000*
4,000
6,000
6,oeo
7,200
7,200
6,000
4, BOO
2 , 000
6,000
S.OQO
3,'JjO
3,600
2,000
2,250
4,000
4,170
4 , 000
Volume to
Treatment
Plant, 1/hr
26,497
15,897
4,163
6,813
12,615
24,224
34,065
113,562
45,424
57,727
30,851
1,741
3 , 985
104,087
36,794
9,000
13,925
79,485
129,447
3,028
22,712
7,570
7,570
i89,250
159. OCC
6,813
54,509
6,813
11,356
90,849
30,659
22,710
Volume to
Treatment
Plant, 1/yr
1.271 x 108
6.359 x 107
2.997 x 107
•7
5.123 x 107
1.293 x 107
4.366 x 107
8.176 x 107
2.555 x 108
9.08 x 107
1.154 x 108
1.234 x 108
6.964 x 10t>
1.594 x 107
8.743 x 108
1.471 x 108
3.600 x 10'"
Q
1.135 x 10-
4.769 x 108
Q
9.320 x 10a
2.180 x 10'"
1.362 x 108
-7
3.634 x 107
~J
1.514 x 1C'
1.136 x 109
Q
9.540 x 1U8
2.6?!'. x 107
_.^o^ ,-. .,w
1.362 x 107
2.555 x 10 7
3.633 x 10 ^
1.278 x 103
7
9-Ot'4 x 10'
Invest-
ment/
1/hr
$ 1.28
10.82
6.71
29.36
1.98
2.72
8.81
3.52
2.42
1.15
3.24
26.03
5.84
2.09
1.40
21.54
8.85
2.: 8
1.20
41.28
5.43
2.31
3S.63
15.36
3.66
4.^
i. n
43.39
5.19
11.56
L.37

Operating
Cost/
1000 liters
$ 0.30
1.26
0.36
1.42
1.15
0.42
1.42
0.48
0.55
0.22
0.26
6.51
0.61
0.19
0.09
1.43
0.44
0.24
0.09
1.30
0,31
0.46
5.53
0.60
1'. 'ij
0.43
0.30
8.83
O.b2
0.65
0,1.1

Treating
Cost/
Processing
Cost
14


3

0



5
0.65
7

7.5
33
, 7
• A
'•'<
7 .1,
1.0
18


- - "•
•'< •*





hours jer

-------
   I07
                                                                              1   r
   10"
o
•o
o
o

cE
0>


«»
v
>
c
   10=
   10"
                                               i   1   1
                                                         I0a
                                    Capacity Liters.hr
              FIGURE 16
INVESTMENT COSTS OP WASTE  TREATMENT PLANTS

WITH VARYING VOLUME CAPACITY

-------
BPCTCA standards.  By modeling plants  it  was  possible  to
derive selfconsistent costs for various degrees of treatment
and for various plant sizes.  Plants were sized according to
the  number  of employees, which is desirable if data are to
be used for cost impact studies.  Table 28 and 29  summarize
the results of one cost estimate.

The  lowest  investment  cost of $22,980 is for a 5-employee
urban plant that precipitates heavy metals, does  not  treat
cyanide  or hexavalent chromium, and does not clarify.  This
plant also has the lowest operating cost of $12,294/yr.  The
highest investment cost of $378,455 is for a plant  with  HI
employees   carrying  out  complete  waste  water  treatment
including clarification and filtering of sludge.  This plant
also has the highest operating  cost  of  $157,894/yr.   The
operating cost probably could be reduced somewhat by using a
filter  press  directly  on  the  neutralized  waste  water.
However, this technology is not as well established as  that
using a clarifier.

Costs  per  area  are  $1.02/1000 liters for the 5-man plant
neutralizing only and $1.09/1000 liters for the U7~man plant
doing  complete  waste  treatment.   These  figures  compare
favorably  with  the $1.06/1000 liters average value for the
plants listed in Table 28.

The operating costs as a function of plant  size  have  been
plotted in Figure 17 and show that in the size range studied
costs  are roughly linear with the number of employees.  The
makeup of the production  processes  varies  somewhat,  both
with the extent of treatment and with plant size.   Processes
using  cyanide or chromate were not included where treatment
for cyanide and/or chromate was omitted.  The smaller plants
were assumed to be concerned with electroplating only  while
processes  such  as  anodizing  and electroless plating were
confined to the  largest  plant.   Even  among  the  smaller
plants there are some variations in plating processes.  Some
of  the 5-man plants included cadmium plating as a specialty
while the 10-man plant omitted cadmium but concentrated more
on tin plating.  The product mixes listed are  only  one  of
many sets that might have been chosen but reflect in general
the  amount  of  finishing  that  can be accomplished in the
various sized plants with diverse operations.  The amount of
waste water to be treated, and the amount of waste  produced
are thus typical of the various size plants.

The  productivity  of  a  plant, measured in area processed/
hour will vary with the process mix even though  the  number
of  employees  is  not changed.  Thus, in Table 29 the 5-man
plants that require  only  coprecipitation  (A)   or  cyanide
                              144

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                                          TABLE 28
                                                              TtCATMBTT BQUVMENT COSTS. VALUES IN O. S. DOUAM. 1*74

A.












*.







C.


D.
t.


T.


C.


Item
Concrete Holding Pin
Valves. Cootrob. Monitor] * tecotden
Sturert
Pnmpj
Tan to
Clariflen
Lagoons (Soil)
Pointing Fillers
Evaporator
Ion-exchanger
Sulfonatoc
Chlorinaror
Subtotal A
Treatment Building
Land COM. Urban
Rural
LaoJ Cost. Pin & Lagoon). OlbU
•and
Subtotal B
Urban
Rural
Total A&8
Urban
Rural
Equipment InaaUatton
Tout C4D Urban
Rural
C*D. Urn Cluifttt. Urbn
Sludge Filler (Option)
Urban
Rural
Total E4F
Urban
Rural

A
4»
2,600
1.100
3.140
2.945
12.550
100
2.600
—
—
—
—
26.045
1.990
345
SO
40
10

4.215
4.050

so.s*
10.095
5.210
54.51*
M.3D*
•*•*•

3.868
S.»90

19,390
39.195
SEnp
»
420
4. 850
1.10»
4.TW
3.550
12.559
130
2. TOO
--
—
—
1.550
33.629
5.910
365
75
30
10

C,30S
5.995

39.925
19. CIS
C.72S
4«.*S»
4*.M*
M.KO

4.59*
4.CS9

51.24*
50.9SO
BOIpCCS W ElHplOTCd *vB EMpWl'V
c
sso
S.08*
1.100
4.S4S
4.939
14. 900
230
2. "TOO
—
--
1.550
—
11.8*5
8.160
500
100
30
H

•.•98
•,370

4C.S75
4C.15S
7.5*0
54, IS*
M.73*
30. t*»

4.8SO
4. MO

S9.005
St. CIS
D
60S .
7.215
1.100
8,300
5.300
14.900
230
3,300
—
—
3.550
3.550
46.050
9.960
610
125
45
10

a*. CIS
10.095

S4.66S
56. 145
9.310
«.«5
**.*S*
M.91S

4.300
4.330

70.175
89.685
A
950
2.945
1.100
4.940
3,7*0
19,100
100
S.1SO
—
—
—
—
35.065
9.660
595
120
225
45
__
10.480
9.825

45.545
44.898
7.01S
•2.660
51.905
11.460

7,750
7.880

60.310
59.185
»
945
5.080
1.100
6.330
3.700
19.000
130
3.200
—
--
—
3. SSO
43.095
11.160
720
145
185
40

».«8S
11.91$

SS.780
55.040
•.(20
64. HO
83.660
4.538

7.720
7.850

71.100
71.51*
C
1.335
5.310
1.100
6.800
4.605
23.400
230
5.100
--
—
3.550
--
50.430
15.060
925
185
2*5
CO

M.tT*
15.105

•6.700
CS.7*
10.090
76.798
75.815
•4.190

7.745
7. MB

•4.535
«1.7*»
D
1,350
7,445
1.100
1.490
5, MS)
22.490
230
5. WO
—
—
3.550
3.550
51.T3*
16.7M
1.025
3X5
215
55

M.CH
16.970

75.73*
74.C**
11.545
•7.215
M.S3S
M.CT*

7.14»
7.M8

*5.M*
•4.115
A
1.S4S
3.945
1.100
5.650
l.*95
35.400
ICO
5. 600
—
—
—
—
46.295
13,020
795
160
340
45

M.*35
11. 325

«t.32*
M.sn
•.2*0
CS.SM
M.7M
44.1*8

11. 380
11.510

•0.980
•0.290
»
1.S2S
5.310
1.100
1.110
3,440
25.400
160
6.500
--
--
—
3.550
54.095
11.540
1.135
230
310
IS

». 045
W.84S

74". 14*
73.940
10.820
•4.960
•3.760
**.*•*

I1.S40
11.490

98,200
95.250
C
1.725
5.310
1.100
1.880
S.11S
28.000
230
6,500
--
--
3.SSO
—
60,010
19.050
1.110
235
300
60

20.520
19.345

•0.530
19.355
12.005
•3.535
91.360
«4.*3*

11. MO
12.580

104.915
103.940
D
1.740
7.445
1.100
12.340
7.200
28,000
230
6.500
—
—
3.550
3.550
71.665
21.180
1.300
260
310
65

33.791
31.505

•4.455
93.170
14. IK
1*8.7**
KM. SOS
80.180

12.380
. 12.580

121.17*
120. OK
A
2.490
1.185
2.200
9.300
8.355
41,100
410
14.000
146.000
550
--
--
343.200
29.520
1.810
365
475
95

11. MS
39.9*0

MS. 005
373.180
48.640
123. 64S
321,820
31«,S4»

13. MO
13.220

136. SIS
338.040
41CmplorM*
I
2.S3S
10.610
2,200
11.610
13.95S
41.100
410
14,000
146.000
550
--
3. SSO
252. SSO
33.150
2.0 JO
410
520
105

35,100
33.6SS

2M.280
2M.HS
50,520
138,800
MC. 165
tfl.100

12.938
13.220

3S1.130
S49.98*
C
2.890
9.690
2.200
11. U9
12.230
49.630
600
15.600
144.000
--
3.550
--
254.240
44.310
2.720
545
765
155

41.855
45.010

302.095
299.310
SO. SSO
3*2.945
350.160
10. IK

12. SSO
13.050

365.495
36X21*
D
3.9*3
14.485
2.500
12.140
11.130
50.600
110
IS. COO
146.000
—
1,550
3.550
264.130
45.360
2.180
560
805
160

48.9*5
4*. 010

313. r>*
3tt. 31*
52. (5*
IS*. 901
363.040
31*. 30*

11. SM
11. M*

378.4**
31 6. 898
A-Neutrallunon.
• -Cyanide oxidation pan Mntulizatloo,
C-Chramaie reduction pka noilralltatkio.
D- Cyanide oxidation chromate redcctlon.

-------
                                                                TABiuE   29
                                                                                      ANNUAL OPDUTING COSTS, WASTt TMATMENT, U.  S. DOUARS,  1ft4

Proceo
«.'•. of Pate.
t~flr,t*l mTj
» 75
-5
Kt
10 17i
171
zy»
» 2»

•>»
tv» cu
1VS
ITS
riant Size

Vic. Treatment
t/hr Type
«.v/>
t.'/'/O
S.O'/O
11. COT
n.c/ii
18.4W
21.200

10.440
M.feW
SC.400
51.'/.)
«5 200
A
B
r
D
A
t
C
D
A
B

D
A
1

of
Capital'"
2.843
3.1T2
4 111
5.270
4. 2-.S
5.151
6.144
8.8«1
6 137
7 403
8.104
25.832
21. 104
28.236
23.213
Chemical
Depreciation^' Uw
3.553
4. CCS
S.41«
6,588
5.2SG
6.438
1,619
8.728
6.958
8.496
9 254
10.879
32.3C5
33.880
38.295
36.591
481
3.300
2.741
4.589
1.5)2
8,919
4.655
10.789
1.793
11,831
5,592
15,413
4,990
15,829
10,110
24,132
Electric
Labor"1 Maintenance**' Power'5'
4.000
4,000
4.000
4.000
12.000
12,000
12,000
12.000
24,000
24,000
24,000
24,000
32.000
32.000
32.000
32.000
711
933
1,084
1.318
1.052
1,288
1,536
1.146
1,392
1,100
1.851
2.116
(.500
8.776
7.059
7.J19
1,440
1,440
1,826
1.82C
2.217
2.217
2,409
2.409
3,036
3,036
3,198
3.195
11,603
11,803
11.288
13.899
Water
ft
SewcrW
240
240
306
306
380
380
402
402
506
sog
634
634
1.918
1.918
2,258
2,228
evaporator
Stodge Ion
RennvaK1" Exchanged) Treatment?*)
1.536
864
3,012
2,016
2.208
2.592
8,184
8.184
3.456
3,456
5,184
S.184
10,464 ' 650
10,464 880
8.619
18,60*
"*
-•
--
--
—
—
8.080
(.080
8.080
a.o«o
Credit
Save<10' Balance
:: ::
••
„
.. -.
..
« ~.
11,828 3.148
11.828 3,748
11.82* a. 14*
11.S28 3. 748
Urban
14,004
19.040
22,178
•28. 913
C8.95!!
39. 10$
40,009
46.708
59.8.V
87.113
10.185
121.434
136,716
131.114
151.894
Total*1"
Rural
1-I.OS4
19. ICO
M.655
85, 7W
23.709
38. 915
39.608
48.040
46.458
57. 396
70.468
1-V.41S
135. 311
130.048
156.180
Total' 5I1 (Vf.tK filter PicaK
No. Clitltler
16. 7.V
19.198
:;.93J
C5. 139
35.305
33.010
43.7iil
41.613
51.513
65. i:5
IK. 014
126. SSS
121.284
141.174
rrfcan
U.-'oi
I5.JT6
19.706
.3.sr
36.513
34. J-'S
4J.OS7
43. :s:
*- •*-*
65.601
110. »Ti<
IS:. 436
fciral
U. Iti
\?.:a
19.851
•'• **
:*..«*!
34.3:3
J4.c:4
4:. ??»
5r.lU
5...1-
6S..S4
121. m
141. It)
 ID ! ?ercen of H!««ment

 «•» It.V.'bf                           ,
 it, I jtnes of u:\tvrxn

 ri, :. JS - '/. i-5 !/l>•-/ lalloni of »«ef added wlib treatment diemlcab
 Ci r-.l"'i Cvual n UkcnneL! com
 »7) D«u fr>n ?fa«dl« for •>>'> jal/Sr  e»r»ralar
fl':, !**jl on a dra?-»i! rate •sf 2 ?ai/IT<)0 iq ft plated and a w!ulU» con of 2.80/gallon
(llj DLfcreoce between »rban and rural li the eon of aewage charge only
(U, <.KtJ*4 for tic COM of ilutje .etro.al, UK I* conjunction Mlth C<|UlBffleK Con Oau,

-------
• l£l^i*il*'*l \ '<:-l'\

^ti* M-£-|.*\\' \\


^~i\\\\l\  ill  1
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                  £
                 t's H fuj
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                  S  s
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                  tt

                  I
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                  8

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                     8



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                     i
                   ii
                           i, :• £ a ^ a ft
                                   1
                         J*

                         •
                   I   I    i
                         S   §
                                i  i
g  s  s

'§  §  i
*  M  W
*-  S  £

§  §  i

ft  5  3

S  i  §
.*  .3  .3
I  §  S

P  S  »

1  i  i

P  ^  «
5  £  S
                  !  !   i   1  1  1
                                8  S
                             il
                                     i*
ctual
KNtoeiM
nr-/ht
mi
                                     fill
                                     sif
                                     ill
                                      si
***>.
dollan
                                         II
                                     |Sflf
                                     r*Mi

                                     pH|5
                                     I. «i L^ S &
                                     fH«i
                                              f
                                              W

                                              OJ
                                              o
                                              w
                                            ^s
                                            < o
                                            O W
                                            M H
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                                            3*
                                             O
                                            0 C3
                                            DC C/)

                                            M HJ

                                            O J5
                                            *^ Hg
                                            w w
                                            PI Cfl

-------
      160,000
      140,000
      120,000
      100,000
to
Vt
0)
o
•Q
m
o
o

00
a
J-l
a>
a.
o
80,000
       60,000
       40,000
       20,000
                                        Coprecipitatlon only


                                      D Oxidation of cyanide +

                                          coprecipitation


                                        Reduction of chromate +

                                          coprecipitation


                                      X Oxidation of cyanide, reduction

                                          of chromate, coprecipitation
                          10
                               20          30
                                        No. of Employees
40
50
                FIGURE  17  OPERATING COSTS RELATED TO PLANT SIZE AND

                            EXTENT OF WASTE TREATMENT


                                        148

-------
oxidation  plus  coprecipitation for treatment of wastes can
process 75 sq m/hr, while 5-man plants that include chromium
plating and chromating (C,D)  can process 100 sq m/hr.

It was concluded that costs for  a  captive  or  independent
shop would be similar if the waste treatment plant was sized
for  the  metal  finishing  operation  only.   Captive metal
finishing operations may discharge waste waters  into  large
systems  that  handle  other  plant  wastes, but it would be
difficult to estimate what volume  percent  of  waste  water
typically  came from the metal finishing operations and what
portion of total waste treatment costs should  be  allocated
to  them.   Flow  sheets  of the waste treatment plants that
were costed are shown in Figures 18, 19, 20 and 21.

Another  plant  was  modeled  to  ascertain  investment  and
operating  costs  of  a  medium  large  plant  employing (1)
segregated chemical treatment  of  waste  waters  containing
individual  metals,  and   (2)  no  discharge  of pollutants.
Costs for waste treatment employing destruction of  cyanide,
reduction of chromate wastewaters and coprecipitation of all
metals  were also developed as a basis of comparison.  Table
30 summarizes both investment and  operating  costs  of  the
waste  treatment   plants.   Investment  and  operating costs
increase in the order

       (1)  Combined chemical treatment and
             coprecipitation

       (2)  Segregated chemical treatment and
             coprecipitation

       (3)  Combined chemical treatment plus
             end-of-pipe  treatment to eliminate
             discharge of  pollutants.

The operating   cost   for   combined  chemical   treatment  and
coprecipitation is equivalent to  $1.41/1000 liters, which  is
approximately   30  percent  higher than  the $1.09/1000  liter
figure for a  similar  model  in   the   previous   discussion.
While  the  two models are slightly different the difference
is mainly due to the  fact that  the   two  cost  values   were
arrived   at  by two cost  analysts, each  of whom  assumed what
he  considered  were  the  most  realistic costs.    Such   a
discrepancy  is not  surprising  and  indicates the necessity
for making analysis  self-consistent.  Thus, the   results  in
Table  28 and  29 were  made by one  analyst and  are set  of cost
factors   and  the   cases   (1)   through   (3) above by  another
analyst   with   a   different  set   of  cost   factors.    The
                               149

-------
                                              High-ond low-level control
                                             ff
                                     Acid-alkali
                                     holding and
                                       mixing
Sump
                                                       High-and low-level control
                                 Pressure pumpf I  ,. -
                     Stream
FIGURE 18,.TYPICAL PLANT OPERATION
              COPRECIPITATION ONLY
CHEMICAL TREATMENT  (A);
                                         150

-------
                                   Acid-alkali
                                   holding and
                                   mixing
Cyanide
holding and
mixing
                                                             Cyanide
                                                             oxidation
        Optional

        Filter
                     Stream
FIGURE 19 .TYPICAL  PLANT OPERATION - CHEMICAL TREATMEI^ (*}•
            CYANIDE  OXIDATION AND coPRECIPITATION          "
                                  151

-------
                                          HondL
                                  Acid-alkali
                                  holding and
                                  mixing
     Plating
     Non-CN/Non-Cr
M
                           J>H
                                 Neutralization
                                    and
                                 precipitation
                      Hand L
              Chromium
              holding and
              mixing
          ->QSufnp

            D3
                                                         HandL
                                                            •W
*-o^
                                                      HgSO^T
Chromium
reduction
                                                           fro1"*' rv
                                                           ¥^~J   \ ^Circ.
$
                                                              Flocculant
                 To stream
FIGURE 20, TYPICAL PLANT OPERATION - CHEMICAL TREATMENT (C);
           CHROMIUM REDUCTION AND CO PRECIPITATION
                                      152

-------
Cr- cont'q
rinses
r
CN- cont'q
rinses


H and L

H and L |T
Acid-alkali
holding and
mixing
3
} Sump
i
1
CN-holdmg
and .
mixing
-c
j Sump

Ha
rr
Cr-holding
and
mixing
                                                                                 I Sump
                 Neutralization
                     and
                 precipitation
 jin, „„ ^B «M M. A. «•• •— *^
 Filter   Pump
            HandL1
          	Tl '
               I  I I

       i	
Lagoon
                                                                          H and L
                                                                 Cr-reduction
                                                    Pump
                                                               0
                                            M HzS04     Circ.
                                                             OH
                                                             S02
        Pump
                                                     Sump
                   Settling
                                  Pump
                                            Flocculont
 Overflow
H and L
                             Pump
               Filter
       Filter
                                    o
                        Backwosh
   To stream

FIGURE 21 .TYPICAL  PLANT OPERATION - CHEMICAL TREATMENT  (D);
             CYANIDE  OXIDATION,  CHROMIUM REDUCTION, AND
             COPRECIPITATION
                                        153

-------
difference  is  actually  much  smaller  than that of actual
costs reported in Table 27.

The  use  o!:  a  system  to  eliminate  pollutant  discharge
requires  approximately  twice  the investment and operating
cost as a system for combined chemical treatment.  The costs
can be reduced in :~ome  situations  by  in-process  recovery
systems  where the savings in chemicals more than compensate
for the costs of operating the recovery system.  Evaporative
recovery systems were not economical to use  in  the  plants
assumed  since the value,, bath concentration, and dragout of
chemicals were  not  sufficient,  to  make  their  in-process
recovery  worthwhile.,  ihe costs of installing more counter-
current rinse tanks, evaporative equipment, and  steam  more
than offset the savings in
In- process  reverse osmosis systems may have lower operating
costs  than  evaporative  systems,  bat  are  still   in   a
demonstration  stage  for  baths  other than nickel.  Use of
reverse osmosis systems on the nickel  lines  in  the  plant
model  would  not be expected to reduce overall in operating
costs by more than 5 percent „

Figure 22 shows the operations in the plant and a  schematic
iiagram  of  a segregated waste treatment system.  Figure 23
shows  a  coprecinjtation   system   and   Figure   24   the
modifications  made at the end of trie coprecipitation system
with a reverse osmosis unit and. salt evaporator to eliminate
the discharge of pollutants.

Preliminary calculations indicated that use  of  evaporators
in- process  and  a'-,  the  end -of -pipe t.c eliminate pollution
would be more expensive than use of reverse osmosis at  end-
of-pipe for the particular metal finishing lines considered.
With  the  installation,  of  a  reverse  osmosis  system the
neutralizing agent was sodium hydroxide rather than the lime
used with the coprecipitation and  segregated  precipitation
systems.   Lime was used to precipitate phosphate as well as
heavy metalsf  but  precipitatS.on  products  with  lime  are
likely   to  foul  the  reverse  osmosis  membranes.   These
membranes remove phosphate directly and lime is not needed.

The cost of  a  minimum  batch  treatment  system  was  also
estimated.   The layout is shown in the schematic diagram of
Figure 25.  The system was sized  to  handle  tl50Q  1/hr  of
waste  water, which is less than produced by the 5-man plant
discussed above.  For calculating operating costs an  8-hour
day and 5- day week were assumed.,

Small Platers
                               154

-------
U1
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                                     FIGURE  22   PHASE I,  IA,  AND II MASTER FLOW PATTERN

-------
                                                                 MrfM
         C*nM!K4 Cnmiit Sotimi

              C» • Zi » Cd
         CSS • TIO » 115 » UW tpb
                '> » Chroraacc Stfcaa

                  . . 14,1 . 7« . 710  - 113 ' 4^ * -~> gpk
        TotjJ ;»-,l ,3*
               I Ai.v!i^u>c 1 in

          :f.' - C3. • 345 - SSi cpfc
         tUct. Xi   15^ _jfh
         XI rur.n.-i Atul .«r« Sm>m«
         »*>.-:.»» ipk
                             FIGURE  23   COMBINED CHEMICAL TREATMENT  AND  NEUTRALIZATION-PRECIPITATION

-------
                                                  HaC«
Cn
           C. . Z. . O)
            n: ««i . MC « 75 < 710 fph
              110 . 110 . Jtt = "60 jpd
                Tcul 970 gjh
                iiif; tad Zn Phosplutlng Smuu

                • 530 . MS - Si g|*
       £• nvnprjtinc 130 cpb
       W nana; * Caoiblac* Ackl/AH Sliunu
       Ccrabuc4 Acrt Alk  7MO gfk
                         Total 7410 |f*
to Hnd Axaj Dlipnal
               FIGURE   24  COMBINED CHEMICAL TREATMENT AND PRECIPITATION  FOLLOWED  BY END-OF-LINE
                             REVERSE OSMOSIS  TREATMENT FOR  ZERO  LIQUID EFFLUENT DISCHARGE

-------
         L-_^~Ss_|  ?unp
         '  ??h    1	
        Cvanice   ,  „
       TinrgpH—[  Pu:np
00
                                                                    Neutralization
                                                                                             Sludge
                                 FIGURE 25-  BATCH TREATMENT SYSTEM FOR SMALL PLANT

-------
Costs  have  been estimated for the 1-4 man shop and 5-9 man
shop and may be found with accompanying assumptions  in  the
following tables:

Sizing Assumptions

 . 1-4 employee shop (3 employees)
 . 30 sq m plated per hour
 . 80 1/sq m per hour
 . 1/4 of the flow is cyanide bearing  (and can be
     segregated)
 . The cyanide concentration is 20 ppm

   The concentrations in the rest of the flow are equivalent
   to 100 ppm of Fs++*

Engineering Assumptions

 . Complete manual operation utilizing minimal equipment
 . store 1 day of cyanide containing waste and treat overnight
 . Equalize flow in a tanJc corresponding to 1/2 of the
   daily output.  Operate in backmix with adjustment every
   two hours.
. All adjustment from carboys or drums.

                Of Chemicals Verfication
  Cyanide   Total waste flow       2100 1/hr
            Cyanide flow            600 1/hr
            Total cyanide waste    4800 I/day
            Total cyanide in waste   98 gm per day

            Chlorine requirement   approximately 700 gm per
                                     day or 1.5 Ib

            Using hypochlorite  (1 Ib Cl£   1 gal hypochlorite)
                                     1.5 gallons per day.

            Using caustic          1 lb/1 Ib of chlorine - say,
                                     1. 5 Ibs/day

Neutralization   (Assume that the caustic from cyanide treat-
             ~   ment is used in the first 1/2 day)

     Total caustic required   -   about 2 gm per gm of iron  (120/56)
           (120/56) 1/2 day flow      9600 1      960 gm of iron
     Caustic required  -          2800 gm/or 4.5 Ib.
     Additional  -       4.5 -  1,5 * 3 Ibs.
     Rest of day  -      4.5 Ibs.
     Total per day    -           7.5 Ibs
                               159

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     O.K. to add by hand  (drum of caustic - approximately
                            400 Ibs)
     O.K. to use a small bucket (8 gals, approximately or
                                      80 Ibs)

Residence time - 4 hours  (nominal or actual) for equalization
Equipment List
     Equalization tank - 2500 gals.
     Agitator - 5 HP
     Chlorination tanks - 2 x 800 gals.
     2 Agitators - 1 HP
     1 Transfer pump
     High level alarm - 3
     Valves - 5
     Other piping and supplies

     Installation - 25%
              $2500
               1000
               1500
                800
                150
                400
                300
              —HP.
              $6800
               1700
              $8500
     Instrument
          pH meter
          colorimeter
400
1PJ2
                                     Total  $9100

Area required - 400-500 square feet  (assumed available)

Assume that there is room for equipment, e.g. a 2500 gal.
tank of normal configuration is 6.5* in diameter and
101 in height  (without legs).

Sizing Assumptions

   5-9 employee shop  (7 employees)
   70 sq m plated per hour
   80 1/sq m      5600 1/hr of flow
   1/4 flow is cyanide bearing (and can be segregated)
   Cyanide concentration » 20 ppm
   The concentrations in rest of waste flow are equivalent
   to 100 ppm FS++ +

Engineering Assumptions

 . Cyanide flow - 1400 1/hr - say, 350 gals/hr.
 . Assume that a hand operation once a day is used for
   cyanide (Automatic continuous unit would cost about
   $18,000-22,000).
 . Equalize daily flow in a 1/2 day tank.
 . Check for hand addition - or cheapest equivalent.
                                160

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      Cyanide . Cyanide total - 11,200 I/day   2800
                „ .  ,      .„                    gals.  (3000)
              . Total cyanide in wash - 224 am/day
              . Chlorine required - 1500 gm/day say 3 5 ibs
              . Hypochlorite - 1 gal/lb of chlorine  3.5
                gallons (can be added out of a plastic lined
                 55 gallon drum with a hand pump)
              . Caustic -                            3>5 lbg>
                Out of a 55 gallon drum (  500 lb)  with a
                scoop, (a big scoop is about 5 lb)

      pJL.AdJust  2 gm per gm of iron
                 1/2 day flow (total)    22,400 1.  (say 6000 gals)
                    Ir°«                 2,240 gm
                    Caustic              4,500 gm        10 Ibs.
                    2 to 3  scoops.

 Manual  addition from a  drum appears feasible.

      Material  handling  equipment  -  1  chlorine resistant
      hand  pump -  say $200

 Eguipment  List

      1  Equalization tank - carbon steel    6000 gals.     $  4,100
        %S«    ^reat  tankS ~ carbon steel,  epoxy lined*   7,200
        (3000 gal)
                                      (35°0) <2  *  10°°>
     High level alarms                                       ™
     valves  (5)                                              *JJ
     Other piping and supplies                               300

     installation - 25%
     instruments                           T°tal        $22'900
          Hand pump
          PH meter
          Colorimeter                                       200
                                                        $23,700

*Add 20^ for epoxy lining.

     If a 2 hour equalization is required
       use a 3000 gal tank «• 5 HP agitator (3000 + 1000)   4,000
       instead of 4100 + 3500 (7600)
       thus, 18300 - 3600                                1a 700

                                                          3*700
                            161

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                                                         18,400
                                             Save         ft ,500
                                                         19. OO
The total capital investment and operating and maintenance
costs for both size plants are as follows:

  No. of    Capital Investment ($1000)    Annual OSM Costs  ($1000)
employees     80 1/sq m    160 1/sq m       80 1/sq m   160 1/sq m
             tnln    max    min   max       min    max   min   max
  1-4        9.1    13.7   13.7  20.5      3.9    6.5   3.9   6.5
  5-9       23.7    35.6   35.6  53.3      4.3    7.1   4.3   7.1

New  Source  Performance Standards (NSPS1 .  New sources that
are  required  to  meet   the   recommended   standards   of
performance  have  the opportunity of designing and building
plants that reduce water flow.  Such systems as counterflow,
spray, and fog rinses, interlocks to provide water flow only
during  processing  sequences,  drip  tanks,  etc.,  can  be
provided.  The capital investment for installing an extra 31
x  3'  tank  in  each  rinsing sequence of a plating line to
reduce further the water use in counterflow  rinsing  is  of
the  order of $3,000.  The plant modeled in Figure 22 has 27
rinses so adding one more tank for each rinse would increase
capital investment $81,000  for  a  total  of  $300,200  for
combined  chemical  treatment  and precipitation in an urban
plant.  It is probable that water use  can  be  reduced  100
percent  by  installing  only half this number of tanks at a
cost of $40,000 or an increase in capital investment  of  18
percent  over  a  plant meeting BPCTCA standards.  Operating
costs would increase $7200/yr minus a  credit  of  $520  for
water  and  sewer  charges  or  $6680/yr«   The  increase in
operating cost is 6 percent as compared to those for a plant
meeting BPCTCA standards.

No Discharge of Pollutants

The elimination of liquid  discharge  from  metal  finishing
processes has not been demonstrated with present technology.
Anticipating   that   future   development  will  make  this
elimination possible,  it  is  desirable  to  have  a  rough
estimate  of  the  cost  impact of doing this.  Technically,
evaporative recovery, reverse osmosis, and ion exchange  can
concentrate  wastes  after  which  the  concentrate  can  be
evaporated essentially to dryness.  Purified  water  can  be
returned  to  process.   Approximate cost analysis have been
made for a medium large plant 240 sq m (2600 sq ft)  per hour
assuming use of 80 liters/sq m of  water.   The  effects  of
closing  the  liquid  loop without a purge on the buildup of
impurities are not known and the cost  of  solving  problems
                           162

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connected with impurity buildup will depend greatly upon how
much  impurity must be removed, the development of efficient
systems for their removal, and how many  of  the  components
that are recovered can be recycled rather than discarded.

To  determine  the cost effectiveness of various control and
treatment alternatives much of the data developed for  Plant
33-1  in  Phase  I  was  used.  For those examples involving
evaporative recovery, an additional investment  of  $150,000
was  allowed for a unit to evaporate concentrate to dryness.
Results of the  calculations  are  shown  in  Table  31.   A
finishing  cost of $2.70/sq m  ($0.25/sq ft} is equivalent to
$644/hr, and all of the projected costs for waste  treatment
are  less  than  10  percent of this figure.  Of course, the
$2.70/sq m figure  is  too  high  for  soine  processes,  but
provides  a  basis for at least a rough estimate of the cost
impact of waste treatment.

Nonwater Quality Aspects

Energy Requirements

Introduction.  Energy requirements  will  be  discussed  for
chemical  treatment, evaporative recovery, ion-exchange, and
reverse osmosis.

Chemical  Treatment.   Energy  requirements   for   chemical
treatment are low,~"the main item being electrical energy for
pumps,  mixers,  and  control instruments.  Electrical costs
have been tabulated for several plants in  Table  32.   Data
for  Plants 33-1 through 33-6 were obtained from the Phase I
study.  Results indicate that approximately 5 percent of the
waste treatment cost is for electric power.

It is estimated in the Phase I study that electrical  energy
for  treating  2.271  x  10*  liters  per  hour by a reverse
osmosis unit for a000 hours per year would cost $6,400.  The
electrical energy cost  is  therefore  7.0*5  x  10-«.   The
liters  per  year processed by all plants listed in Table 32
add up to 3.964 x 10« liters and the cost of electricity for
processing this water by reverse osmosis is  $279,200.   The
total  electrical cost for chemical treatment for the plants
listed in Table 32 is $75,330.  These figures can be used to
roughly  estimate  the   increases   in   electrical   power
requirements  in  going to a system with no liquid effluent.
For best practical control  technology  currently  available
the  electrical  cost  would  be essentially that of current
estimates or $75,330.  For  the  best  available  technology
economically   achievable   the   combination   of  chemical
treatment  and  reverse  osmosis  plus  evaporation  of  the
                             163

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               TABLE  31  COST EFFECTIVENESS OF
                          CONTROL ALTERNATIVES
                          (247 Sq M/Hr)
Type of Control
Plant 33-1
Rinse System -
Chemical treatment
Three countercurrent
Investment
Cost

$264,274
330,000
Operating
Cost/Year

$112,361
121,387
Water
Treated
1/Hr

25,210
9,766
Operating
Cost per
100 Sq M

$17,30
18.68
rinses - chemical
treatment

Single stage evapor-     890,000
ators (21 units)
Dry evaporator

Five single stage        400,000
evaporative units
and one vapor com-
pression unit - dry
evaporator

Chemical treatment       560,000
plus reverse osmosis
Sludge drier and dry
evaporator for
concentrate
327,895
109,913
161,328
50.47
16.92
24.83
                              16-4

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TABLE
      32
COST OF POWER RELATIVE TO TOTAL  OPERATING
COST FOR CHEMICAL TREATMENT
Plant
No.
33-1
11-8
36-1
20-14
20-17
3-4
33-3
33-6
33-22
20-20
20-22
33-24
36-12
33-2
33-4
8-5
6-35
30-19


Processes
Plating Cu, Ni, Cr, Zn
Plating Cu, Ni, Cr, Zn
Plating Cu, Ni, Cr, Zn
Plating Cu, Ni, Cr, Zn
Plating Cu, Ni, Cr, Zn
Plating Cu, Ni, Cr , Zn
Plating Cu, Ni, Cr, Zn
Plating Cu, Ni, Cr, Zn
Anodizing
Anodizing
Anodizing
Plating Common Metals
Plating Precious Metals
Plating Precious Metals
Plating Precious Metals
Plating Precious Metals
Chemical Milling
Chemical Milling


Electric
Cost/Year
$ 4,100
668
5,220
6,000
8,940
600
240
1,460
1,948
4,763
12,623
1,212
1,894
1,082
120
16,239
3,897
4,330
x = 4,185
o = 4,454
Waste
Treatment
Operating
Cost/Year
$112,361
391,406
221,009
93,240
798,840
4,064
18,019
77,460
51,515
83,481
113,370
80,430
72,809
14,968
18,205
115,995
83,758
168,312
x = 139,957
a = 187,688
Electric
Cost x
100 /Waste
Treatment
Cost
$ 3.65
0.17
2.36
6.44
1.12
14.76
1.33
1.88
3.78
5.71
11.13
1.51
2.60
7.23
0.66
14.00
4.65
2.57
x = 4.75
a = 4.44
                           165

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 concentrate   (that  would  require little electrical energy)
 the electrical  cost  would  be  $75,330  plus  $279,200  or
 $354,530.   The  ratio  of $354,530/75,330 is 4.70.  On this
 basis going to a system without discharge of liquid effluent
 will increase the use and cost of electrical energy 5-fold.
fiYfl PgEfrU YSJS.SSO.YAEY.'  From the Phase I report the  cost  of
steam  for  operating  a  300 gph single-stage evaporator is
approximately  $2100/yr   corresponding   to   approximately
1,900,000   Ib  of  steam.   The  single-effect  evaporators
require  considerable  energy.   This  requirement  can   be
diminished  by  use  of  multiple stage or vapor-compression
evaporators.

Ion Exchange.   The  few  pumps  required  for  ion-exchange
systems should consume very little power.

Reverse osmosis.  The energy requirement for reverse osmosis
systems  is  the electricity for operating the high pressure
across the membrane and for operating low pressure  transfer
pumps.   The  estimate  is  $6400/yr for a 6000 gph facility
operating 4000 hours/yr.

Impact of Power Requirements for Waste

Treatment.  Domestic production of electrical energy in 1971
was  1.717  x  10»«  kwh.   For  the  plating  industry  the
electrical  energy requirement is estimated to be 9.75 x 10»
kwh.   The metal finishing industry as a whole  is  estimated
to  consume  no  more  than twice this value, which would be
1.950 x 10« kwh.  The percentage of  annual  power  that  is
used for metal finishing operations should be no more than:

1.950 x 10it/1.717 x 10»2 = 0.114 percent.

Power  for  pumps,  lights,  fans, etc. , and waste treatment
should not more than double this figure to 0.228 percent.

Cost of Recovery of Metal Values from Sludge

Tribler et. al. is a report on the feasibility of recovering
metal values from sludge b digesting the sludge with acid to
dissolve it  followed  by  electrolysis   and  neutralization
procedures to recover metal values.   The case considered was
a  sludge containing primarily copper, nickel, chromium, and
zinc values.  A cost estimate was included for a small plant
that would treat 45 kg of dry sludge during a 12 hour day to
yield 2.27 kg of copper,  0.09 kg of  nickel* and 4.54  kg  of
chromium.    However,  the  chromium was  obtained as an oxide
mixed with some iron.   The investment for a small plant  was
                            166

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estimated  to  be  $15,130.   Operating  cost  per  day  was
estimated to be $85.30.  This did  not  include  a  cost  of
capital,  which  if  assumed  to  be  eight  percent  of the
investment per year, would raise the daily operating cost to
$91.35.  The total weight of metal recovered per day is 6.90
kg so that the cost is estimated to be $13.23 kg.  The  cost
is obviously very high compared to market prices so that the
small  operation  would  be far from economic.  Undoubtedly,
the  cost  of  processing  would  be  less  with  a   larger
installation,   but   if   more  than  one  metal  finishing
installation were served there would be an  additional  cost
for transporting sludge to the recovery operation.
                              167

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                         SECTION IX

       BffST PRACTICABLE CONTROL TECHNOLOGY Cl
           AVAILABLE. GyIpELlNES* ANQ LIMITA!

Introduction

The  effluent  limitations which must be achieved by July 1,
1977, are  to  specify  the  degree  of  effluent  reduction
attainable  through  the application of the best practicable
control technology currently  available.   Best  practicable
control  technology  currently  available is generally based
upon the average of the best existing performance by  plants
of  various  sizes,  ages,  and  unit  processes  within the
industrial category and/ or subcategory.

Consideration must also be given to:

     (a)   the total cost of application of technology
          in relation to the effluent reduction benefits
          to be achieved from such application

     (b)   the size and age of equipment and facilities
          involved

     (c)   the processes employed

     (d)   the engineering aspects of the application of
          various types of control techniques

     (e)   process changes

     (f)   nonwater  quality environmental impact
          (including energy requirements).

The best practicable control technology currently  available
emphasizes   treatment   facilities   at   the   end   of  a
manufacturing process but includes the control  technologies
within  the process itself when the latter are considered to
be normal practice within an industry.

A further  consideration  is  the  degree  of  economic  and
engineering  reliability  which  must be established for the
technology to be "currently  available".   As  a  result  of
demonstration  projects, pilot plants and general use, there
must exist a high degree of confidence  in  the  engineering
and economic practicability of the technology at the time of
commencement  of construction or installation of the control
facilities.
                           169

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 industry Category and Subcategory Covered

 The  effluent   limitations  recommended  herein  cover   the
 following  metal  finishing  processes:  anodizing, chemical
 milling and etching, immersion plating, chemical  conversion
 coating.   These  processes  have  been  divided  into three
 categories:   Subcategory    (1)   consists   of   anodizing,
 Subcategory   (2)  consists  of coatings, and Subcategory  (3)
 consists of chemical etching and milling,


 I<3ejltification  of Best .Practicable, contffsj,
 Technology Currently Ava4J.abj1g

 Best practicable control technology currently available  for
 Subcategories   (1) ,  (2)  and  (3)  is  the  use of chemical
 methods of treatment of  waste  water  at  the  end  of  the
 process  combined with the best practical in-process control
 technology to conserve rinse water and reduce the amount  of
 treated waste water discharged.

 Chemical treatment methods are exemplified by destruction of
 cyanide  by  oxidation,  reduction of hexavalent chromium to
 the trivalent form, neutralization  and  coprecipitation  of
 heavy  metals as hydroxides or hydrated oxides with settling
 and clarification to remove suspended solids prior  to  dis-
 charge  or  prior  to  dilution with other nonelectroplating
 process water before discharge.  The  above  technology  has
 been  widely  practiced  by  many  plants for over 25 years.
 However the above technology cannot achieve  zero  discharge
 of  heavy metals because of finite solubility of the metals.
 In addition, it is not practicable to  achieve  100  percent
 clarification and some small amount of metal is contained in
 the suspended solids.  By optimum choice of pH and efficient
clarification   it  is  possible to achieve a significant re-
 duction in the  heavy metal pcllutional load.

 Zero discharge  of heavy metals in effluent may  be  achieved
only  by  eliminating the effluent itself by such techniques
 as  reverse  osmosis  and  evaporation,  which   offer   the
 possibility  of  p\irifying  all  waste water to a sufficient
 degree to be  recycled  to  process  or  by  evaporating  to
 dryness  so that waste water constituents are disposed of as
 solid waste.

 No generalization regarding the degree  of  metal  pollution
 reduction  is   possible  because  of  the  mij£  of finishing
 processes possible in a single  plant  and  the  variety  of
metals  in  the  raw  waste of most plants.   Because of this
 fact and the high cost of inplant segregation of  all  waste
                              170

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streams according to metal» coprecipitation of metals is the
general  practice.  Thera is an optician pH for precipitating
each  metal  that  results  in  the  greatest   removal   by
clarification.   The  optimum  pH  for  removing  all metals
cannot be utilized for coprecipitaticn so  the  pH  selected
for   a   mixture  of  metals  is  a  compromise.   However,
coprecipitation can result in lower discharge of metals than
if each is precipitated separately at its optimum  pH  value
if  synergistic  effects  of  the type shown in Table 26 are
operating.  For copreeipitatlost to provide  lower  discharge
than  segregated  precipitation  in-process dilution must be
minimal.

There are several advanced recovery  methods  available  for
closing  up  the  rinse  water  cycle  on  individual  metal
finishing  operations.   These  methods  ^evaporation,   ion
exchange,  reverse osmosis, conntarcurrent rinsing)  have not
yet been applied  to  rinse  watars  from  pretreatment  and
posttreatment  operations.   The  corresponding rinse waters
plus  concentrated  solution  draps  and  floor  spills  may
contain  one or all of the pertinent metals (copper, nickel,
chromium,  and  zinc)  in  significant   amounts   requiring
chemical  treatment.   Thus?  chemical treatment of at least
the  typical  acid/  alkali  stream  from  pretreatment  and
posttreatment  operations  represents  the  best practicable
control  technology  currently  Available  to  achieve   the
effluent limitations recomroeadaat

Having   identified   the   technology   for  end-of-process
treatment  and  recognizing  the  technical  and   practical
limitations  on  removal  of heavy metals by this technology
(metal solubility  and  clarification  efficiency),   further
reduction  in  the  quantity  of matal pollutants discharged
must be achieved by reduction in the volume of treated water
discharged.  There are many in-process controls designed  to
reduce  the  volume of waste water which is principally that
resulting from rinsing.  Some of these controls, designed to
minimize dragout of concentrated solutions or to reclaim  as
much  dragout as practical can be considered normal practice
within the industry.  It can be assumed  according  to  good
practice  that  reclaim  tanks and/or still rinses are being
used and that all evaporation losses are made  up  with  the
reclaimed  solution.   Dragout reclaimed does not contribute
to the raw waste load  normally  discharged  from  remaining
rinses.  There is economic incentive to reduce the chemicals
purchased  for  bath makeup and the added economic incentive
to reduce the cost of treatment chemicals required for  end-
of- process   treatment.    Reduction  of  dragout  leads  to
reduction in water requirements for rinsing.
                             171

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 Further reduction  in  rinse water use can be achieved by  use
 of   a  stagnant  rinse   for   recovery  or  by multiple-tank
 countercurrent   rinsing.    Counteracting   the   cost   of
 installing multiple rinse tanks are the savings in treatment
 chemicals, water costs,  and sewer charges.  Further, the use
 of   advanced  recovery techniques  (evaporation, ion exchange,
 and  reverse   osmosis)  which  concentrate  the  rinse  water
 sufficiently   to   allow  reclaim  of  the  valuable  metal
 finishing solution can often provide the economic  incentive
 to   use  this  technology  and  justify the cost of recovery
 equipment   plus   the   cost   of   installing    multitank
 countercurrent  rinsing.   However,  it should be recognized
 that the  major  water  reduction  occurs  because  of  the
 installation  and use  of  multitank countercurrent rinsing.

 In   the  past  there  has  been little economic incentive to
 reduce  water  use  for  rinsing   after   preparatory   and
 posttreatment operations.  The cost of the chemicals has not
 made their   recovery from  rinse  waters worthwhile.  High
 dragout from  preparatory cleaning  solutions  has  not  been
 considered  an  unfavorable  factor  since  the  dragout  of
 impurities along with bath chemicals has prolonged the  life
 of the bath in some cases.  The disadvantage of high dragout
 is   that  more  water must  be  used for rinsing to prevent
 significant concentrations of impurities, i.e., grease, from
 contaminating the processing solutions.

 Best practicable control technology currently available also
 includes water conservation through rinsing.  A water use of
 160  1/sq  m/operatlon   (4  gal/sq  m/operation)  has   been
 estimated  as  that achievable by the industry.  This figure
 precludes  the  use   of  countercurrent  or  series  rinses.
 Exclusive  use  of  single  stage rinsing will not meet this
water use.  It has been calculated  that  for  186  sg  m/hr
 (2000  sq ft/hr)  proudction the rinse water need for various
rinsing techniques are:

     1 - single rinse  1/hr 499,620 (132,000 gal/lir)
     2 - tank countercurrent 2800 1/hr (1HO gal/hr)
     3 - tank countercurrent 477 1/hr (126 gal/hr)
     4 - tank countercurrent 201 1/hr (53 gal/hr)
     5 - tank countercurrent 121 1/hr (32 gal/hr)

This corresponds to a water use of:

     1 - single rinse  2686 1/sq m (66 gal/sq ft)
     2 - tank countercurrent 15 1/sq m (.37 gal/sq ft)
     3 - tank countercurrent 2.56 1/sq m (.06 gal/sq ft)
     4 - tank countercurrent 1.2 1/sq m (.026 ga/sq ft)
     5 - tank countercurrent .65 1/sq m (.016 gal/sq ft)
                               172

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A 3 - stage series rinse  consumes  approximately  the  same
quantity of water as a 2 - stage countercurrent*
The  160  l^q  m  (U  gal/sq  ft)   takes  into  account  the
contributions made by the  pretreatmcnt  steps  of  alkaline
cleaning  and  acid  pickling  and allows some use of single
rinses.

An alternative mode of operation to the  above  is  to  dump
cleaning  baths  frequently so that dr&gout of impurities is
minimized.  Then the amount of rinae water  can  be  reduced
and   can  be  even  further  reduced  by  use  of  multiple
countercurrent rinsing technique®,,  The  increased  cost  of
chemicals  from  more  frequent  dumping  and  the  cost  of
multiple rinse tanks is counteracted by savings in water and
sewer charges.  Water use can therefore be greatly minimized
since preparatory solutions,  i.e*?  alkaline  cleaners  and
acid  dips contain chemicals that can be tolerated in fairly
high  concentrations  in  subsequent  processing  solutions,
i.e.,  plating baths.  In general, the amount of rinse water
required should be substantially less for rinsing  following
alkaline  cleaning  and  pickling than for ringing following
typical metal finishing operations aueh as electroplating.

While sufficient economic incentive may not  be  present  to
achieve reduction in the volume of the rinse water from pre-
and  posttreatment  operations,  there is an opportunity for
significant reduction in pollution.  The above  factors  are
taken into account in recommending the effluent limitations.
Even  in  plants  currently  achieving  good waste treatment
results, there are further opportunities  for  reduction  in
volume of effluent discharge.


Rationale fqr Selecting ^he Best practicable
Control— Technology Currently Available

General Approach

In determining what constitutes the best practicable control
technology   currently   available,   it  was  necessary  to
establish  the  waste  management  techniques  that  can  be
considered   normal  practice  within  the  metal  finishing
industry.   Then,  waste-management  techniques   based   on
advanced   technology  currently  available  for  in-process
control  and  end-of -process  treatment  were  evaluated  to
determine  what  further  reduction  in  pollution  might be
achieved considering all the important  factors  that  would
                            173

-------
influence  the  determination  of  best  practicable control
technology currently available.
      Management Techniques Considered!
Practice jn the Metal Iloighina Industry

For that  portion  of  the  metal  finishing  industry  that
discharges  to  navigable  waters,  many are currently using
chemical treatment for end-of-process  pollution  reduction.
Some  of  these  waste- treatment  facilities  have  been  in
operation for over 25 years with a  continual  upgrading  of
performance to achieve greater pollution abatement.  Because
of the potentially toxic nature of the chemicals used in the
metal  finishing industry, there is a relatively high degree
of  sophistication  in   its   water   pollution   abatement
practices.    For   example,   the   accidental  release  of
concentrated solutions without treatment to navigable waters
is believed to be a rare occurrence today.  This is  because
adequate  safety  features are incorporated in the design of
end-of-process waste  treatment  facilities  in  conjunction
with  good  housekeeping within the electroplating facility.
This example and other waste management techniques were con-
sidered as examples of  normal  practice  within  the  metal
finishing  industry  in  determining  the  best  practicable
control technology currently available.  Other  examples  of
normal practice include:

      (1)   Manufacturing process controls to minimize
           dragout from concentrated solutions such as

           (a)   proper racking of parts for easy
                drainage

           (b)   slow withdrawal of parts from the
                solution

           (c)   adequate drip time or dwell time
                over the tank

           (d)   use of drip collection devices.

      (2)   Effective use of water to reduce the
           volume of effluents such as

           (a)   use of rinse water for makeup of
                evaporation losses from solutions

           (b)   use of cooling water for noncritical
                rinses after cleaning
                           174

-------
           (c)  use  of  treated waste water  for
               preparing  solutions for  waste-
               treatment  chemicals.

      (3)   Recovery  and/or reuse of waste water
           constituents such as

           (a)  use  of  reclaim tanks after  metal
               finishing  operations to  recover
                concentrated solutions for  return
               to the  plating tank to make up
               evaporation losses

           (b)  reduction  in waste water volume by the
                use  of  at  least  two  series  flow rinse
               tanks after each finishing  operation
               with return of  as much rinse water as
                possible to the  finishing tank.


Other  waste-management  techniques   not  considered  normal
practice, but currently in use in one or more  plants,  were
evaluated  on  the  basis  of  reduction  in the quantity of
pollutants in the effluent discharged.

Degree of Pollution Reduction
                     *>v_ pianos
        -               _
       Aaes. and Processes Using
                    Treatment Technology
Identification of Best Waste Treatment Facilities

The initial effort was  directed  toward  identifying  those
companies  that  had  well  engineered  and  operated  metal
finishing  process  and  waste  treatment   methods.    Such
companies   were   identified   on  the  basis  of  personal
knowledge, and referrals by people well acquainted with  the
industry   (EPA  regional  representatives,  state  pollution
control    authorities,   trade    associations,    equipment
suppliers,  consultants) .   Representatives of approximately
75 companies  returned  questionnaires  mailed  to  them  and
these  representatives were further contacted by telephone or
further    correspondence   in  many  cases  to  clarify  the
information in the questionnaires and obtain  further  data.
Furthermore,  visits  were made to 11 plants for development
of detailed data on  several  of  the  processes.   Effluent
samples  were collected  at  five  plants  and  analyzed at
Battelle-Columbus Laboratories.  The above  constitutes  the
data based for the Phase II study.
                             175

-------
Waste Treatment  Results

Volume Capacity  of  Treatment  Plant^sfnigigri-   Figure  26 shows
the  volume  capacity of  the waste  treatment  plants for which
data were received,  as measured  by the  amount, of waste water
treated  per  hour.   The   rang©    of    capacities
approximately  two  orders o£ magnitude.
                                                      covers
The  plot  ie  a  cumtnulative on® indicating how snany  plants
have a water use leas than r.he voitsrwa corresponding  to   the
cummulative  number.   Thu«?,  r.S  plants  have  a  volume of
100,000 liters/hour or less and  4  plants  have  a  greater
volume.

ConsentratJiop ,.o. £.	
-------
   100,000 —
 .c
 ^

 tO
 o>


 a
 to
 o
 a»

 a
     10,000 •-
       1000
                     10         ?-0         30

                    Cumulative Number of Plants
FIGURE  26.  DISTRIBUTION OF WASTEVVIER VOLUME TREATED


                           177

-------
                                                     TABLE 3 3   CGSOSatBATIOa OF BH&DBR COBStlTOSHTS
-J
CO

Plant
So. Processes Ag Al
20-24 1'iating Conon Metals
33-24 Plating Casaaoa Metals
33-26 Plating Coanon Hetals
31-1 Plating CosHBoa Metals
3&-12 Platiag Com, .Free. Metala <0,01
33-2 Plating Precious Metals traces
33-4 Plating Precious Metals
8-5 Plating Precious Hetals
6-37 Plating Precious Metals <5
19- LI Platiag Precious Metals (0)
15-3 Plating Precious Metals
9-7 Electropainting, Amodizing 6.5
9-6 Electropainting
33-34 Electropainting
4-5 Electroless Plating
8-8 Electroless Plating
30-19 Electroless Plating
33-22 Anodizing <0.05
33-23 Anodizing 0.91
20-22 Anodizing 1.0
20-20 Anodizing 3.7
33-35 Anodizing l.OS
20-23 Anodizing 8. IS
47-9 Anodizing
6-35 Chemical Milling <1
9-2 Chemical Milling 0.25
23-7 Chemical Milling 0.5E
33-30 Phosphating
19-24 Etching - 0.5
31-16 Printed Circuits
6-36 Immersion Plating
46-4 Electropolishing
E - estimated
S - soluble
Concentration | mg/1
Total ,
Au Cd CH~ CR Cr Cu F~ Fe RL
0.02 0.54 0,17 11 i.S
<0.025 <1 <0.05 <1 <1
0.05 0.3 7
j __ ]_§
<0, 1
traces 0.1

(0)
<1 <5 <5
(0) (0) <0.5S <1§
0.02 0.04 0.08 0.06 0.03 0.03
'!•


7.7
<0.02
<0.03 0.2 <0.05 20 1.0

0,40 0.37 0.24


0.13 0.05
<0.18

oa (o) i.o 
-------
                                            TABLE 33  COHCEMTRATION OF EFFLUENT COMSTITOEKTS  (Continued}
v»
Plant
Mo,
20-24
33-24
33-26
31-1
36-12
33-2
33-4
8-5
6-37
19-11
15-3
9-7
9-6
33-34
4-5
§-<
30-19
33-22
33-23
20-22
20-20
33-35
2tt~23
4J-f
*-.15
9-2
23-7
33-30
19-24
31-16
6-36
46-4
Concentration, «g/l
Processes Pb
Plating Common Metals 0.6
Plating Common Metals
Plating Coraaon Metals 0.3
Plating Common Metals
Plating Com. ,Prec. Metals
Plating Precious Metals
Plating Precious Metals
Plating Precious Metals
Plating Precious Metals
Plating Precious Metals
Plating Precious Metals
Electropainting
Electropaiating
Elect repainting
Electroless Plating
Electroless Plating
Electroless Plating 0.5
Anodizing
Anodizing
Anodizing
Anodizing
Anodizing
Anodizing
Anodizing
Chemical Milling
Chemical Milling
Chemical Mining
Phosphating
Etching
Printed Circuits <0.2
IsMzcioa Platiaf
ElMtropel 1 ••*•«,
Pt
H>4~3 Metal
<,0
traces



(0)

<0.4

8.1


50
13
180
0.3
0.8

0.17


trace

2
0.15


70-85
Susp.
Sn Zn Solids
<2 0.25 4
<1.0 <25
Mil 78
0.2S
0.5S <10
6
6.9


<20
0.5
10
40
130

<0.02 22.7
100
<10
. 25-60
10
5
16
29
<0.1 <5
(0)


0.1 5
2.2 11

0.1
1-34
Dis.
Solids
676
1400
1250
1642
200

640

2760


250

400

204
500
>10
3600
1500
993



708

300
1690
927
506
220
1200
PH
8.5-9.5
7-9
8.0
7.0-8.0
8.0
5-10
7.5-8.5
7.5-8.0
7-10.5
7-8

7.0
6.2
8.4
7
7
6.5-10
6.5-9.0
6.5-9.0
7.5
6.8-9.2

6.5-9.5
8
8.0


8.6
8.0

S.7
2.6-5.*
Other
BF~ - 75





/COD - 34
ICobalt -
COD = 320
(Barium -
ICOD = 624
Ammonia -
Anemia -


Hitrate -


Hltrate -









mg/1





mg/1
<0.03 •»/:
mg/.i
1.0 mg/1
mg/1
6.8 Bf/1
10 mg/1


50 Bg/1


18 mg/1










-------
TABLE 34 WATER USE IN METAL-FINISH ING PROCESSES
Plant
36-12

30-2
33-30

20-3



33-24
33-5

15-3



9-7
33-34
6-36
31-16

30-19

33-27


33-23
33-22
9-2
20-20
33-35
20-22
20-23
41-2
6-35
47-9
4-8

Line
Sn
Cu-Sn
Rack Cd-Zn
Rack Cd
Barrel Cd
Rack alkaline Sn
Rack acid Sn
Rack Ni, CuPbSn, Sn
Rack zincate dip, Cu,
CuPbSn, Sn
Rack Cu-Sn
Basket Sn
Rack Ni, CuPbSn, PbSn
Rack Cd, manual
Barrel Cd, manual
Barrel Sn, manual
Ditto
Electropaint
Immersion
Electroless Cu
Ditto
"
Electroless Sn
Electroless Ni
Ditto
"
Anodizing Al
Ditto
"
Anodizing Mg
Anodizing Al
Ditto
"
"
"
"
"
Chemical Milling
Ditto
-
Production,
sq m/hr
42.8
122.8
171.5
123.4
45.8
46.5
46.5
9.3
9.3
92.90
21.1
25.1
1.86
11.15
18.58
1.39
139.4
529.5
48.8
23.23
25.08
23.23
13.94
1.39
10.03
11.71
297.4
148.7
83.6
4.65
269.5
55.8
3.253
102.2
16.73
9.29
13.94
37. IT
9.29
9.29
Water Use,
1/hr
454
908
5,995
18,160
11,355
9,463
3.936
6,188
12,737
7,040
3,407
2,725
2,161
220
1,553
2,120
8,395
4,315
1,022
12,491
5,678
5,678
76
1,590
1,590
2,271
18.927
27 , 254
44.895
7,382
79,494
2,082
87 , 064
18 , 927
5,678
2,271
1,930
3,785
1,893
1,893
Number of
Operations
1
2
2
1
1
1
1
3
4
2
1
3
1
1
1
1
1
1
1
5
3
3
1
7
5
10
4
3
4
1
3
6
4
4
4
2
1
2
2
2
Liters/
Sq m/
Operation
10.61
7.39
17.49
147.2
247
203.7
84.7
222
343
37.9
161.5
36.2
1,162
19.7
83.6
1,525
60.22
8.15
20.94
107.5
75.5
81.48
5.45
163
31.7
19.4
15.9
61.09
134.3
1,558.9
98.3
6.2
6.7
46.3
84.9
122.2
138.5
50.9
101.9
101.9
                  180

-------
TABLE 3 4 (Continued)

Plant
30-9


6-36
33-20
23-7
6-37


30-21










31-16

8-5

15-3


33-4
33-2

36-12
30-19

31-16



Line
Chemical Milling
Ditto
„
-
•>
"
Auto rack silver
Ditto
Man rack silver
Ditto
Auto rack silver
Ditto
,i
.,
Man rack silver
ii
Cont strip silver
Auto rack silver
Stripping silver
Man rack gold
Ditto
Auto rack gold
Man rack silver
Man rack gold
Man rack silver
Ditto
Man barrel silver
Auto rack gold
Man rack gold-silver
Man rack silver-rhodium
Cont strip silver
Chemical etching
Ditto
„
„
n
..
Production,
sq m/hr
92.9
9.29
B9.fi
13.4
24.6
27.9
74.33
293
59.5
11.61
35.3
11.61
22.22
4.65
6.50
6.50
4.65
0.84
1.12
1.39
0.74
8.55
0.093
0.093
0.047
1.86
5.57
1.21
2.79
2.79
31.6
92.9
8.36
16.73
18.6
18.6
11.15
Water Use,
1/hr
6,814
2,725
3, 785
3,028
6,613
15, 141
13, 967
20,363
9,084
8,365
8,270
5,602
9,311
8,316
908
908
5,942
(0)
757
8,138
1,817
1,590
3,028
379
460
462
462
4,637
5,678
1,703
454
13,248
2,271
2,725
3,785
6,624
7,570
Liters/
Number of Sq m/
Operations Operation
2
2
2
3
2
2
4
4
3
4
4
4
4
4
3
2
4
1
1
4
3
2
2
1
2
2
2
3
3
3
2
2
2
2
2
2
2
36.7
146.7
31,8
'16.3
134.4
271.3
46.98
17.40
50.92
180.1
58.57
120.6
100.2
447.6
46.54
65.32
319.8
(0)
658
1,460
815
93
16,280
4,080
4,952
124
41.43
1,281
679
204
7.18
71.3
135.7
81.5
101.9
178.3
340.2
         181

-------
TABLE 3 4 (Continued)
Plant
4-9



36-16

33-30
20-25
23-8
46-1
33-29

33-29

4-4

Production,
Line sq m/hr
Chemical etching
Ditto
"
"
Chemical Machining
Ditto
Zn phosphating steel
Ditto
Fe phosphating steel
Electropolishing
Electrochemical machining
(Neutral Salt Electrolyte)
Electrochemical machining
(Acid Electrolyte)
Electrochemical machining
(Neutral Salt Electrolyte)
18.6
13.94
13.94
4.65
6.51
3.12
66.91
464.7
153.4
10.59
0.53

0.37

0.19

Water Use, Number of
1/hr Operations
4,088
1,362
1,362
1,362
5,299
1,514
11,356
11,356
946
1,817
7.6

22,700

7.6

2
2
2
2
2
2
2
2
1
2
1

1

1

Liters/
Sq m/
Operation
110.0
48.9
48.9
146.7
407
203.5
84.9
12.2
6.17
185.8
14.3

61,400
•
40.0

          182

-------
The  flrsst  method of expressing water use requires choosing
what operations in the overall process will be  included  in
calculating  water  use  «nd  what  operations  will  not be
included. "This method was followed in the  Phase  I  guide-
lines,  where all operations involving electrodeposition and
posttreatment were included but cleaning and  pickling  were
omitted.   The  water  use  has  been calculated in terms of
llters/sq in/operation where the square meters refer  to  the
finished  worK  and  the  operations  exclude  cleaning  and
pickling,


This  method  of expressing water use allows one to consider
its  variation  in  terms  of  those  operations  that   are
different from process to process*  on the other hand, those
operations that, are common to moat processes, i.e., cleaning
and   pickling,   and  involve  about,  the  aame  water  use
regardless of'the  process  in  which  they  occur,  can  be
eliminated  from  consideration  as a cause of variations in
water use.  Calculations for Phase II  processes  have  been
made  using the above formula, omitting the initial cleaning
and  pickling  operations^  but  counting   all   subsequent
operations in. a process.

A.S  mentioned previously, lss>8 water is required for rinsing
following alkaline cleaning and pickling  than  for  rinsing
following most other operations.

Data  provided  by the companies on area processed and water
use ia  given  in  Table  3UM   From  this  data,  frequency
distributions for water use  Cl/sq m operation) for processes
in  subeategories  (I) ,  {2} ©nd (3) were derived.  These are
given in Figures 7, 3 and «*.  ?he median water use for  each
subcategory' %*as used as a basis for the guidelines.  It was
felt that the plants identified by the contractor were  well
designed  and  well-operated  and therefore the median value
was a  good  approximation  of  the  ''average  of  the  best
"criteria specified for BPCTC& treatment.

Determination of Effluent Limitationa

Effluent limitations were established from three parameters:
(1)  constituent  concentration  in  the effluent*  (2) water
use, enfi  (3) area  processed  or  plated.   Sosie  dependence
among  these  parameters  is  known*  i»e.,  coagulation  of
precipitates out. of dilute eolation is wore  difficult  than
out  of  more concentrated solutions and area processed in  a
giver, line increases with couples shapes  that  give  higher
dragout  awd require more watar for rinsing*  Th© plant data
obtain.ec show  no  evident  correlation  betw®«n  the  three
                             183

-------
factors  probably  because  variations  in  water  use   and
concentration due to other factors mask out the relationship
between the three factors mentioned.  Within the accuracy of
the   information   available  the  three  factors  will  be
considered   independent,   that   is,   the   concentration
achievable  in  the effluent by exemplary chemical treatment
is not related to the amount of water used  for  processing.
The  best  water  use  is  not  necessarily found in a plant
operating an exemplary waste  treatment  facility  and  vice
versa.   However,  once  exemplary values for both water use
and concentrations have been established the product of  the
two  represents  an  overall figure of merit that takes into
account both parameters.  Therefore, the guidelines  can  be
expressed  in  terms  of  the product of the two parameters:
(mg/1) x (1/sq m) « mg/sq m.  More  water  may  be  used  if
lower concentrations are achieved and vice versa.

Concentrations  of  Effluent  Constituents and pH.  Table 35
lists the concentrationbasisForeachconstituent,  The
values  given  are  for  the  total  amount  of constituent,
dissolved   and    suspended.    Therefore,   both    proper
precipitation  and efficient clarification and/or filtration
are  required  to   meet   the   concentrations   considered
achievable.

Water Use.   The values of water use for each type of process
cover   a   wide   range.    Variations   in   dragout,  the
concentration of dragout, and the degree of rinsing required
vary and are in part responsible for the  range  of  values.
However,  inefficiencies  in  reducing dragout to a minimum,
rinsing beyond requirements,  and  poor  design  of  rinsing
facilities  and  waste  of  water  are  also responsible for
making in making  a  wide  range  of  water  use  .   It  is
necessary,   then, to estimate the minimum water use that can
be achieved by essentially all of the lines of a given  type
of process.

Subcategory (1)

The process covered in this subcategory is anodizing.

Data  on  water use for anodizing operations from ten plants
on  eleven   different  lines  are   given   in   Table   34.
Supplemental information and configuration data was obtained
from two of these plants by plant visits.
                          184

-------
TABLE  35.   CONCENTRATION VALUUS FOR WASTBWATBR
            CONST ITUL7NTS FOR BPCTCA
                              Present Phase  II
Constituent                   Proposal, mg/1
TSS                           20
Cyanide  (oxidizable)             .05
Cyanide  (total)                0.5
Fluoride                      20.0
Cd                             0.3
Cr+0                           0.05
Cr (total)                     0.5
Cu                             0.5
Fc                             1.0
Pb                             0.5
Ni                             0.5
Sn                             1.0
Zn                             0.5
Phosphorus                     I.Q
PH                             6-9
                        185

-------
Plant 33-23 is an aluminum anodissing plant which has a large
automatic  rack  line  for  anodizing  aluminum alloy parts.
Figure 27 is  a  schematic  of  this  facility.   The  waste
treatment  plant for treating the spent processing solutions
and  the rinse water effluents from this operation is  shown
in  Figure  28.   Data  taken  during  the  plant  visit for
treated effluent pollutant concentration are shown in  Table
36.

Plant  6-35  is  a  large  chemical  anodizing  and  milling
facility. Although the  anodizing  line  was  not  operating
during  the  time  of  the  plant visit.  Information on the
sequence of  operating  steps  and  analyses  of  the  waste
treatment plant effluent was obtained and is given in Figure
29.   Addi tonal  data  on  rinse  water flows and production
rates were provided by the plant at  a later date.  The 65th
percentile water use was found to  be  90  i/sq  m-operation
(2.2 gal/sq f t-operation) .

Subcater   2
Subcategory   (2)  covers  coatings - phosphating, chromating
and immersion plating.

One immersion plating  plant  was  visited  in  this  study.
Plant  6-36 has an immersion tin plating facility consisting
of one barrel plating line.  Treatment of  the  wastes  from
this  plant  is  done in an integrated waste treatment plant
which was installed in 1972.  The sludge from the  treatment
reservoirs  is collected in storage tanks and hauled away by
truck to a landfill several times a year.

Three chemical conversion coating  plants  were  covered  in
this  study.   Two  were  zinc  phosphating on steel and the
other was iron phosphating on steel.  The data on water  use
for  these  operations  is  listed  in  Table  34.  The 65th
percentile was found to be 17 1/sq m-operation   (.42  gal/sq
ft-operation) .   since there was no apparent reason for this
much smaller water  compared  to  other  subcategories,  the
largest  value reported of 80 1/sq m-operation (2 gal/sq ft-
operation) was chosen as the water use factor.

Subcateaorv (3)

Subcategory 3 covers chemical milling and etching.

Data on nine chemical milling lines in six plants are  given
in  Tables  33  and  34.   Supplemental data on two of these
plants was obtained on visits to these plants.
                                186

-------
          Water  	•*>-
     Batch Treat
     Then Sent .
     To Tank 1
City and
Used Cooling Water •
  Workplaces go
  into one of the
  threo anodizing
  tanks; after
  anodizing work
  goes to  Station II,
  and then Stations
  15 and  16.
22.
PI Water
Rinse

21.
Dl Water
Rinse


-*r

0.
Diehromata
Sea!
1/10 to 1/2 g/l K2Cr207)
19.
Dl Water
Rinse

«q
KBM
8> Nickel
Acetate Soal
(1/2 g/l Nickel Acetate)

17.
Dl Water
Rinse

-------
         Anodizing
       Waste Effluents
          .Waste
          Effluent
        Collecting and
        Mixing Sump
                               PH-Controlled
                               Automatic
                               Lime Addition
Neutralization
   Vessel
                                                                       Clarified Effluent to Stream
oo
CO
                                                                               Sludge to
                                                                               Storage and
                                                                               Then Hauled
                                                                               Away to Landfffl
                              FIGURE 28,    SCHEMATIC REPRESENTATION OF WASTE TREATMENT SYSTEM
                                             FOR HANDLING ANODIZING EFFLUENTS AT PLANT 33-23

-------










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-------
TABLE 36          COMPARISON OF BCL ANALYTICAL RESULTS  WITH  TYPICAL  ANALYTICAL
                  RESULTS REPORTED BY PLANT 33-23 FOR TREATED  EFFLUENT
Constituent
AT
+ 6
Cr
tot
Cr
PC
4
SS
IDS
pli
Total Concentrat1onB mp/1
Typical Plant 33-23
[ffluent Analysis
0.1
0.30
0.32
9.1
23
3600
7.0
Contractor
Sampled Effluent
0.2
0.10
0.28
10.5
22
3500
8.0
                                     190

-------
 Plant 30-9 is a large aluminum and titanium chemical milling
 installation.  Chemical milling of the two metals is carried
 out in the  same  area  and  some  of  the  tanks  are  used
 interchangably,  since  some  of  the  operating  steps  are
 similar.

 The spent chemcial milling  etchants  a d  other  processing
 solution   frcm  this  plant  are  haule.^  away by a licensed
 scavenger, and  the rinse waters are   it to large  Bettl'.r-j
 ooiids on  company property.

 Data   on   ten  etching  lines  is given in Tables 33 and 34.
 Plant 31-16 was visited during this  study  and  data  t-°cen
 during the  plant  visit  is  covered under subcategory <*)
 processes.

 The 65th  percentile water use for this  eubcategory  is  120
 1/sq  m-operation (3.0 gal/sq ft-operationj.

 Thirty Day Average Vs One D*.y Maximum

 Five   months  of  daily  data were obtained  from plant 15-1.
 This  data appears in Table 35.  ' In this time period the 30-
 day  average  value  of  80  mg/sq  m-operation  for  Zn was
 exceeded  on two occasions,  December *&,  1974  and December 10,
 1974.   The thirty day average of  80  mg/sq  m-operation for
 CNT was never exceeded.   The one-day maximum of 160 mg/sq m-«
 operation was never exceeded by Zn or CN.

 One   month's  effluent  data was  chosen at random from plant
 12-6.   It appears in Table 36.  Ni,  TSS, Cu,  Zn,  CNT are not
 out of  compliance with the thirty  day   average  or  one-day
 maximum.    cr+*   is  not  out  of compliance  with the 30-day
 average but is out on the one-day maximum  three times during
 the month.

 Five  months of twice weekly sampling TSS,  for plant 33-15 is
 shown in  Table 39.   CrT.  Ni,  Cu   never  exceed  the  30-day
 average  or  one-day maximum.   Cr^«  is  not in compliance for
 30-day  average or one-day maximum.

 Plants  Meeting the  Guideline^

 The effluent  concentrations  and water use factors have   been
 collected for  21  plants  in  Table  40.  Except  as indicated on
 the table,  all values  are  in tota*.  solids.  Plants  36-1, 36-
 12,   15-3,   15-1,   12-6,   33-15  and   12-8   meet   the   1977
standards.  Plants   36-1  and   36-12  meet  the  new  source
performance   standards.   Plants   11-8 and 33-:  were out of
compliance  on  only  one or two parameters.
                             191

-------
                                TABLE  37
                                PLANT  1$ - 1
                                                              mgAn2-Operation
DATE
PH
CN    CH-6
CrT
                                                          Cu

6-01-74
6-02-74
6-03-74
6-04-74
6-05-74
6-06-74
6-07-74
6-08-74
6-09-74
6-10-74
6-11-74
6-12-74
6-13-74
6-14-74
6-15-74
6-16-74
6-17-74
6-18-74
6-19-74
6-20-74
6-21-74
6-22-74
6-23-74
6-24-74
6-25-74
6-26-74
6-27-74
6-28-74
6-29-74
6-20-74
HI
9.3
8.6
8.4
8.6
8.1
8.1
8.7
9.5
8.2
9.0
7.9
8.0
8.6
8.9
9.0
8.6
8.1
8.2
8.5
9.1
8.3
9.5
7.9
8.9
8.8
8.9
9.6
9.8
9.5
8.1
Lo
7.5
6.9
6.9
6.3
6.6
6.8
7.8
8.0 •
6.8
7.1
6.6
6.4
7.4
6.4
7.5
7.2
6.9
6.6
7.3
7.3
7.5
8.3
6.6
7.3
7.2
7.6
7.8
8.0
8.3
7.0

5.7
7.4
5.3
6.2
6.6
7.2
10.6
16.6
35.3
22.3
19.2
7.0
6.6
10.1
6.2
7.0
5.7
5.7
6.2
5-7
6.6
8.4
7.4
5.7
6.2
6.2
6.2
5.7
5.7
3^1
•
.52
5.4
.48
2.2
1.8
1.3
4.8
.52
4.2
.62
.60
1.3
.60
.92
.56
1.3
1.0
1.0
2.8
8.3
8.4
40.3
46.2
.52
5.6
2.2
1.7
7.6
78.0
.28

5.2
6.8
4.8
5.6
6.0
6.5
9.6
5.2
6.0
.72
6.0
6.4
6.0
9.2
5.6
6.4
5.2
5.2
5.6
10.4
30.0
15.2
170.
10.4
16.8
5.6
5.6
6.8
130.
22.4

5.2
12.6
19.2
11.2
12.0
19.5
28.8
5.2
12.0
7.2
12.0
19.2
24.0
36.8
16.8
12.8
5.2
10.4
11.2
20.8
12.0
15.0
20.4
10.4
5.6
16.8
11.2
15.6
15.6
11.2

5.2
20.4
48
44.8
48.0
58.5
67.2
31.2
42.0
50.4
^8.0
57.6
60
73.0
39.2
38.0
41.0
36.4
44.8
41.6
42.0
22.8
61.2
52.
50.4
50.4
33.6
52.0
57.2
19.6
•".•II !•!• IJ
15.6
13.6
*^W " "
38.4
56.0
60.0
84.5
96.0
20.8
42.0
21.6
36.0
57.6
66.0
110.4
56,0
25.6
46.8
36.4
67.2
31.2
66.0
30.4
61.2
41.6
56.0
44.8
39.2
31.2
20.8
8.4
                                                                           TSS
                                                                          1508
                                                                           408
                                                                           696
                                                                           476
                                                                           930
                                                                           813
                                                                          3984
                                                                          2392
                                                                           690
                                                                           806
                                                                           360
                                                                           536
                                                                          1560
                                                                          3588
                                                                          1736
                                                                           832
                                                                           416
                                                                           806
                                                                           308
                                                                          3196
                                                                           810
                                                                          2546
                                                                          1156
                                                                          1378
                                                                          1316
                                                                           980
                                                                           644
Average    8.7    7.2
                        8.6
                   8.0
22.4    16.2
                                       46.0
                                1950
                                194

                                1170
                                    192

-------
                        TABLE 38
                        PLANT  12-6
                                         mg/m2-0peratlon

 DATE                     J)H             Zn           CNT
11-13-74                   8             1.3         27-7
11-14-74                   7            11.9'         14.5
11-18-74                   6            15.8         18.5
11-19-74                   7            13.2         22.4
11-20-74                   7            48.8         14.5
11-25-74                   8            15.8         29.0
11-26-74                  10             6.6         31.7

 Average                 7.6            17.4         23-3

12-02-74                   8            10.6         30.4
12-03-74                   7            14.5         46.2
12-04-74                   7            12.1         29.0
12-05-74                   6            55.4         17.2
12-06-74                   6            17.2         21.1
12-09-74    '               9            15.8         31.7
12-10-74                   9            92.4         23.8
12-11-74                   7            29.0         21.1
12-12-74                  10             5.3         23.8
12-13-74                   8            37.0         37.0
12-16-74                   8            ^7.7         22.4
12-18-74                   7             9-2         19.8
12-19-74                   7            25.1         17.2

 Average                 7.6            38.4         26.2

 1-03-75                   6            10.6         23.£
 1-06-75                   9            11.9         15.8
 1-07-75                   7             6.6         19.8
 1-08-75                   7             7-9         13-5
 1-09-75                   7            33.0         15.3
 1-10-75                   8            66.0         18.5
 1-13-75                   8            13.2         29.0
 1-14-75                  10            11.9         52.8
 1-15-75                   8            15.8         27.7
 1-16-75                   7            13.2         111.5
 1-17-75                   7            48.8         13.2
 1-20-75                   6            15.8         18.5
 1-22-75                   8             6.6         15.8
 1-23-75                   7             *.6         15.8
 1-24-75                   8            3^.3         22.4
 1-27-75                   8             9.2         17.2
 1-28-75                   6             7-9         18.5
 1-29-75                   7             1.3         14.5
 1-30-75                   7            26.4         29.0
 1-31-75                   7            21. j.         26.'

                         7.4            18.6         20  9


                                    193

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                                                                                 TABLE 4il
.'U-NT l/m2-op (qal/ft2-or>) Cu Ki • r-i-T ^,+6

2 w — '. **
1--36-1
J. '•36-12
33-5
«5-3
2C-i»
33-2 J.
33-2
S15-1
S12-6
J33-15
*11-8
6-37
43-1
S-7
19-24
2U-17
23-7
30-21
12t (3.0)
...'I (4.4)
29 (.733)
i: (.329)
232 (5.8;
184 (4.6)
232 (5.8)
128 (3-21
4440 (111)
132 (3.3)
60 (1.5)
211 (5.3)
50 (2.0)
52 (1.3)
-
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1-S* -09 .20 .10 .43
•H -08 .06 .36 .34
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-------
The plated area  is the  primary  unit  of  production   on   which
the  effluent  limitations  in Table  1  «re  based.  Plated area
in defined with  reference  to Faraday 2  Law  of   electrolysis
by the  following  equation:

                   JBU
                   100  kt                    ^uation 2

whcve s = arec., sq m  (sq  ft)
v. - cathode current efficiency.,, pcrc
I ~ current used, amperes
T = time,? hours
t = average thickness of  deposit ff  r,ra
k = a constant for each metal  pla-ced baaed on the electro-
    chemical equivalent for metal  deposition, amp-hr/mm-sq  m
    (amp-hr/mil-sci ft) ,

The  numerical product of current  ar»d time  (IT) is the value
that would be measured by an ampere-hour meter.   Values  of
the constant k based on equivalent i/«iffiht ssad the valance of
the metal deposited are shown  in Table 41.

Average thickness can be  approximated by averaging thickness
measurements  at  several points on a single plated part, to
establish  the  ratio  of average  to  minimum   thickness.
Minimum  thickness  is  customarily  monitored  to  meet the
specifications of purchasers of electroplated  parts,  based
on service requirements.

This equation was used in this study to determine the plated
areas  per unit cime in each plating oparation when the only
available information was the  current used and  the  average
thickness  of  deposit.   This  equation  was also used as  a
check on estimates of surface  area plated  provided  by  the
plants contacted.

To  calculate  the  total plated &sr©£ on which the effluent
limitations are based for a specific plsnt? it was necessary
to sum up the area  for   each  electroplating  process  line
using  Equation  (2) .   For  process lines containing two or
more electroplating operations (such  &3  in  copper-nickel-
chromium  decorative  plating^  the plated area is calculated
by Equation (2)  for each  plating oper&ticn in  the  process.
The  results  should  be  the  same, since the same parts are
processed  through  each   operation.    However,   if   the
calculated  plated  area  differed r^..' sach plating operation
in a single process line,   the  average  of  the  calculated
plated  areas  for  the operations was used.  Th? sum of the
plated area for each process line le the total    ated  area
for the plant.
                               197

-------
 Process Chanqor?

 Process changes are not currently available  for  the  metal
 finishing  industry  that  would  lead  -to greater pollution
 reduction than can be achieved by the  recommended  effluent
 limitations.   Some  possible process changes such as use of
 noncyanide  plating  baths  may  eliminate   one   pollution
 parameter,  but  do  not  eiirnineite  all and Bi&y causi. ot-iiar
 problems.   They  may  be  useful  i;i  some  facilities  for
 reducing  the  cost  of  meeting  the  effluent  limitations
 recommended in this document.

 Nonwater Quality Environmental Impact

 As discussed in Section VIII of this report^  the  principal
 nonwater  quality  aspect of metal finishing waste treatment
 is in the area of solid waste disposal.  Disposal of sludges
 resulting from metal removal  by  chemical  treatment  is  a
 current   problem   in   many   states   that  have  a  high
 concentration of facilities.  The problem might be partially
 alleviated by disposal of drier sludge.   Such  added  costs
 for  removal  of  water  from sludge would be imposed by the
 requirements for solid waste disposal and does not  directly
 result from the requirement for water pollution reduction.

 The  use  of  advanced  technology  to recover metal plating
 chemicals from rinse water rather  than  chemical  treatment
which adds to the sludge is being applied in areas where the
 sludge-disposal problem is greatest.  Further impetus in the
 direction of recovery rather than disposal is expected to be
 provided   by   authorities   responsible  for  solid  waste
 disposal.  This will have an overall  beneficial  effect  on
water  pollution  because of the concurrent requirements for
water conservation  for  economic  application  of  recovery
 techniques.

 It  is  estimated  that  many  of  the existing sources dis-
 charging to navigable  waters  are  already  using  chemical
 treatment  methods with a high percentage removal of metals.
 This is particularly true in geographic  areas  where  water
 pollution  reduction  has  been  emphasized  and the sludge-
 disposal problem is most evident.

 There will be no direct effect on air quality as a result of
 the  application  of  recommended   technology   for   water
 pollution  reduction.  Indirect effects related to increased
 energy use are estimated to be modest.

 Plated Area Unit of Production
                              198

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Sma.ll discrepencies in the above calculation for  two  or  more
plating operations in the same process  line might be  related
to  a  difference  in  the  actual current efficiencies  from
those in Table 37 which are to be us«d  for the  calculation.
However,  experience with data from  several plants indicated
that the  more  lively  cause  of  the   diicrepancy  is   the
accuracy of the reported values of &va^fe,g  plate  thickness.
ThM  use  of  ampere-hour on rectifiers - ..ght have value  fo:
monitoring or record keeping for  scsva  plants  In   lieu   of
measu
-------
                                TABtK 4 1 jLECTOtiCKEMICAI. EQUIVALENTS AHO tiE'-ATES
                            (All n»ur«>  In this t»'»;« «<• b*«« hf M »-,- !>? ll
dijWUil 9.891 ^.ifedl it to. . ,! *
ld./M| tk iietocnt Htf'-» * iff
It. 05 *J
17.4 ft
10,*
24,1 An
14.3
14.S 11
S.93
9.73 C4 «,.«• , ,fr.lC«
Si.8 Cr 21 » 13
23.1
1».0 Co t,®S li»
17.7 Cu 7.30 100
8.W 3.5* 39-108
14.0 Oa
• is. 6 e«
U.6 Au
12.4
t.t ?,£3 100
U.I Xc. S.1J 56 :«»
29.4 IK
12.1
17. » I* 7.38 tvi
*.91 n I.J3 100
16.3 Ha
8.55 K«
4.27
19.0 »1 8.05 180
28.6 N 12.12
- 21.4 ».07
14.2 6.02
27.6 ?S 11. »? *0
13.85 *•*!» *0
.„».» »0
30. g KB li.OS
23.1 ».?•» *0
15,3? *.:.
»a S K.
13.4 1*
6.14 *t *•«*• i"9
12.4 T*
(.19
3.12 n ,
13,63 IB 6.62 «
7.12 3.31 I''*
13.7 lu 3.80 1UO (ACID)
••* i'J 
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                 be defined as any  step  followed  by
                 a rinse in the electroplating  process
                 in which a metal is  «electrodeposited
                 on a basis material.  Electroless
                 plating on non-metallic materials
                 for the purpose of providing a
                 conductive surface on tha basis
                 material and preceding  tJ 3 actual
                 electroplating stepp and the past
                 treatment steps of chroirating,
                 phosphating and coloring uhere an
                 integral part of tr,3 plating line
                 and stripping whers  DQ^chicted  in
                 conjunction with el a .strop I at, ing  for
                 the purpose of stlvagirscf improperly
                 plated parts na^ "o
-------
            in the effluent  da*; to
            processes before dilution by
            from other processes favarag® fv?,,  ?C
            sequential daysj .

Determination of Finished Area/Hr/Qperation
         •*•"'"• ..... "" m*'**"-*™"-™*-*-****"*** immi IB«^»^»»— •» J»«KII'I IM;I i na^n»»K*^«» 1,1 1. ili*limB.HTH^i»-»iift nslr. i ~- ja» JflBm»B«j j»

The  area  for each line  will be determined  ttom
on the  (1)  average amperes  used,,  (2)  th^ sequence  of  plating
operations,   and  (3)    the   average tMcicn^s in mil  o'~  ,-*< h
type of plate.  If complete datd  on  thickness  is?  la.-kii-g,
the  following value will be usedi

          Copper             0,,3 ,'RlI
          Nickel             0.3 mil
          Zinc               Q»3 mil
          Chromium           0.015  ri'i 1

Where  chroma ting follows plating,  the area will be the same
an that of  tho primary  plating operation.  The equation:

          S  = El T/ 100 kt

is then used to calculate plated   area.'\ir/cper«<-io»«    In  a
line with   several sequential operations, it is likely that
the  calculated plated areas i',v  e^ch :\I ;-.ting operation  will
vary from  each other although the act u '. snea plated should
be the same.   The difference  in calculatec- areas may  vary by
a factor  of  two or three.   When applying t.'bs qt^idelines,  the
figure used  for area plated should be th ,: at3 bhmetic  average
of the calculated pi'\'  -^ areas.
Where actual  amperes **.& not  knowny  ,.,' ,-,  ., c- equal to  2/3
the  installed  capacity for  the line s-*  .-'Jd be u&ed,   »-'
information on amperes is completely lackincf for a  li>e
water use  is  available,, i.be sq  m/hr  may be ileteiisstned by
    Sq m/hr  --  t£..hr.,jised__?u
               (?00 1 /?<--. rn) (no.  of

    Sq ft/ht  -  S^lifli, .,!«§S3_2D_£iJS
                (5 gal/or) (no.  of  opera "icr'«^

Once the  plated area h--^  ' •:•,.•;*  measured tiie t^f'.cJ'- lines  can be
used  to   det^ttfurva  tr*e  total -v. lowable disr.hara-*:  of waste
water constituents fzor? i.he  plant   Every time   the  surface
is  rinsed,  following SOTO ^v>aratLot! in the process;  line, it
is assumed that more waste water  ia produced, and a  greater
quantity  of  -,'aste wait..-: constit.ueuto may be disefa
-------
therefore incorporated into the rinse  following  the  first
plating  operation for purposes of calculating the allowable
amount of waste water constituents  discharged.   The  total
allowable discharge in g/day will b«:

  (lO*) (sq m plated/hr) (effluent ilmitatior in mg/sq m)
      (No. of oper.) (hr/day)

The total allowable discharge in ib/dey  It s

         (sq ft plated/hr)(effluent limitation
      in Ib/million sq ft  (No. of oper.J fhr/day)

These relations hold for each effluent limitations guideline
value  listed  in  Table   1.   The  relations  apply to  each
process line or part of a  process line if  the area plated/hr
changes in the line.

The actual discharge from  the plant is the product  of   the
volume  of  effluent/hr and the concentration of waste water
constituent in the effluent.

Thus,

     q/day »  (liters/hr) (mg/1) (10-«J Chr/dayJ
    Ib/day =  (8.33 x 10-*) (gal/hr) (ng/1) (hr/day)
Figure 30 represents  such a  situation   The   line  processes
15  sq  m/hr.   The   volume  of  effluent is  3,000 1/hr.   The
plant operates  10 hr/day.  There are  three  operations  in
this line, chromium electroplating*  etching, and anodizing.

The discharger  is allowed:   (10-*) (sq m/hr) Jeffluent
limitation in mg/sq m-operation)(number of operation)
 (hr/day) = kg/day pollutant

The actual discharge  is  the  product  of  the volume of efflu-
ent/hr and the  concentration of  waste water  constituent.

    Kg/day =  (liters/hr) (mg/1) (10-»J ^hr/dayj

Thus, in this example the dischargai  .s allowed to discharge
the following amount  of  chromium fox chromium electroplate

 (10-*) (15 sq m/hr) (80 mg/sq  m-operation) {1 operatl ,n)
 (10 hr/day) = 1.2 x  10-* kg/day
                                203

-------
for anodizing

(10-6) (15) (t»5) (1) (10) = 6.75 x  10-'  kg/day

for etching

(10-») (15) (60) (1) (10) = 9.0 x 10-3 kg/day

In total he may discharge  the sum of the three:
2.78 x 10~z kg/day of chromium  total.

He may discharge  one-tenth of that or
    2.78  x  10~1 kg/day of  Cr+6

If the final  effluent concentration  is equal to 0.56 rn.g/1
for CrT and 0.06  mg/1 for  Cr+6, the  actual discharge will be
     (3000  l/hr)(.56  mg/1)(10~6)
     (10 hr/day) = 1.68 x  10~2)  kg/day of CrT
                and
     (3000  l/hr)(.06  mg/1)(10-6)
     (10 hr/day) = 1.8 x  10-1  kg/day  of Cr+6

Thus,  the  plant  is meeting the  guidelines.
                                  204

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  Alkaline
  Clean
   Rin&e
  Acid
Pickling
    I
   Rinse
     f
Chromium.
  Plate
 Rinse
   Etch
  Rinse
  Anodi ze
  Rinse
   Dry
       205

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BEST AVAILABLE TECHNOLOGY BCCaOMICALLY
 ACHIEVABLE.... Q^lpB^Sf *~_AJfo._.LXMI5?ATIOHS
                limitations
    „ are   o   specify  r,i;e
attainable  through
  ch       ecoomic
j&troductloja

The  effluent
1983 „ are  to
attainable  through  the  applies .^
technology economic-"" *   i r:hlav&lJ
based  on  the  very  !.:-ast  convr^s"..
employed by a specific   point  ^ , r.
category  and/or   suhrav sgcry  cr !".
transferable  from  one  lr,5r:<5-ir"  •;
specific  finding   must  be  r.ad
control measures and prec-dces t%, ^
pollutants, taking into acr.ou:"   w,~
tion.

Consideration must also tj-s given to

      (a)  the age  of the
          involved
                                 :•*,< achieved July  1,
                                 'f fluent  reduction
                              of -cLe
                                     best available
                             *is technology can  be
                             d treatment technology
                              uilthin  the  industry
                             :iology that is readily
                             ,; &£3  tc  another.   A
                             r.o the availability of
                                   the discharge of
                                 of  such  elimina-
                              facilities
      (b)

      (c)


      (d)

      (e)
the process
          the  ens  neevring aep«£Ct & cC  ria application
          of var* ous types of

          process  changes
                       .';v.
                          Oi
cost of achieving -che
resulting from  -the  t
                                reduction
      (f)  non water  qua lit./ etWirc.'^
           (including enerc,y requi.'.'.e-

The  best  available tecL^olog:/ ^.,o:.;
assesses  the   availaoilicy  .In  .^ll
controls  as  well   as  tirae  concrol
techniques employed ar the enfi cf e

A further consideration is the dv&iLl.
control technoloqy  at tha pilot plar
levels,   which  have   fieKori^trtt*
performances and economic viability ,•-
reasonably  justify
           lnve&tir.g
                                Impact
                              ^wlly achievable also
                             cases  of   in-process
                             .r aa
-------
available  technology economically achievable is the hiyLast
degree of control technology that has been achieved  or  has
been  demonstrated to be capable of being designed for plant
scale  operation  up  to  and  including  no  discharge   of
pollutants.   Although  economic factors are considered, 1.he
co.ts for this level of control are intended to  be  top-of-
the-lirsc   of  current  technology  siibject  to  limitations
imposed by economic and engineering  feasibility.   However,
best  available  technology  economically  achievable may be
characterized  by  some  technical  risk  with  respect   to
performance  and with respect to certainty of costs and thus
may necessitate some industrially sponsored  work  prior  to
its application.

Industry category and Subcat^orx Cgve^ejl

The  pertinent  industry  category  is  the  metal finishing
segment  of  the  electroplating   industry   divided   into
Subcategories (1) and (2)  as previously discussed in Section
IV,

Identification,of Best Available Economically Achievable

Subcategory  (1)

The best available technology economically achievable is the
use  of  in-process and end-of-process control and treatment
to achieve no discharge of pollutants.  By the  use  of  in-
process  controls  to  reduce  the volume of waste water, it
becomes economical to use end-of-process treatment  designed
to  recover  water and reuse the water within the plant thus
avoiding any discharge  of  effluent  :-.o  navigable  w#Aers.
Solid  constituents  in  the  wastewa*. Jt,  are disposed of to
landfill or otherwise.  A line in Plant J.u-21 plating Oliver
has eliminated liquid effluent discharge for several mcmtha,
and continued demonstration of this operation  will  support
the  fact  that  technology  is  available  to achieve this.
Plant 11-22, a chromium electroplater studied in £hase I, Is
using a system designed  to  eliminate  liquid  effluent  by
subjecting  effluent  from  the  clarjfier  of  the chemical
treatment plant to reverse osmosis and  recycJ ing  water  to
process.    The  concentrate from the reverse osmosis unxt i&
evaporated to dryness.  It is expected  that  other  methods
will  be  developed  dux ,.ag  the  next  five  years to avoid
discharge of effluent to navigable waters and  thus  achieve
no  discharge  of pollutants in an economical manner.   While
the above examples of zero discharge are being  achieved  in
conjunction  with  electroplating operations, the similarity
of operations in processes in Subcategory (I)  to  those  in
the  electroplating  processes,  and  the  similarity of the
                              208

-------
was.-e waters, suggests that  techniques  of  obtaining  zero
discharge   for   electroplatiaq   processes   are   equally
applicable to the other processes in Suboategory  (1) .
Subcategory (2) and

The best available technology economically achievable is the
use of in-process and end- of -process contr©   and  treatment
to   achieve  no  discharge  of  pollutants   Processes  in
Subc<.teqory (2) are distinguished from fchoae in  Subcategory
 (1)   only   by  water  use.   The  operations  in  the  two
subcategorlos are very similar, the types  of  waste  waters
obtained  are  essentially  the same, and the types of waste
treatments that are applicable are the same.   The  evidence
that  zero  discharge  is  being  and  will  be attained for
processes  in  Subcategory   (1)  is  equally  applicable  to
processes in Sutcategory  (2) .
Rationale for  Selegt^op of  Best Aval lab. 1 8
Technology Economically Achievable

Age  of  Equipment  and  Facilities

Replacement  of   older  equipment and  facilities will  permit
i-he  installation  of modern  multitank countercurrent  rinsing
systems after each  operation  in each   process line with
conservation of water use for rinaing.  The use  of  reclaim
and   recovery  systems after  each finishing operation  should
be possible.   Use  of inprocess  controls  to  the  maximum
extent   will reduc< the volume of effluent -co the point that
recovery and reuse of water is economically feasible.

Process Employed

The   application   of   the  technology    for   end-of -process
recovery  and  reuse  of water to the maximum extent  possible
is not  dependent  on any  significant change in the   processes
 now  used.   Most  water   recovery   technology can  produce a
 higher  quality of water than normally  available from  public
 or  private water supplies.  High  purity water for  the final
 rinse after  metal  finishing  operations  is  desirable  to
 improve the quality of the product.

 Engineering  Aspects   of  the Application of Various Types of
 Control ^echniques

 Many slants  are  successfully  using  evaporative  recovery
 systems  after  one  or  more  plating operations with a net
 savings compared to chemical treatment.   Evaporative systems
 are in current use after  copper,   nickel,  chromi*  n,   zinc,
                               209

-------
brass,  tin, lead, and gold plating operations.  Some pie fits
have succeeded in using recovery systems after  all  plating
operations  in  their facility.  The engineering feasibility
of in-process controls for recovery of chemicals  and  reusfe
of  water  are  sufficiently  well  established.  Sufficient
operational use has been accumulated to reduce the technical
risk w*th regard to performance  arid  any  uncertainty  with
respect to costs.

The  technical  feasibility of end-of-process water recovery
systems has been established by extensive development of tint
recovery of pure water in many related Industrial processes.
Although some uncertainty may remain concerning the  overall
costs  when  applied  to  metal finishing wast* waters, such
uncertainty primarily relates to the volume  of  water  that
must  be  processed  for recycling and reuse.  Th© fact th&t
the technology as applied to the electroplating industry has
progressed  beyond  the  pilot  plant  stage  and  has  been
designed  and  is  being built for fullscale operational use
indicates that the  technology  is  available  and  probably
economical.    These   systems  are  equally  applicable  to
processes other than electroplating due to the similarity in
the waste water produced.

Process Changes

Application of  the  technology  is  net  dependent  on  any
process  changes.  However, process changes and improvements
are anticipated to be a natural conscience of  meeting  the
effluent limitations in the most economic mannei1*

Nonwater Quality Environmental Impact

Application   of  technology  to  achle^ j  no  diacterg-e  of
pollutants to navigable waters by July 1,  1983,  will  have
little  impact  on  the  solid  waste  disposal problem with
regard to metal removal as sludge beyoad that envisioned  to
meet effluent limitations recommended for July 1;, 1977.  The
volume of soluble salts will be substantially increased.

In  general,  it  is anticipated that the technology will be
applied in a manner such that no discharge  of  effluent  to
surface  waters  occurs.  Thus, metal oxide sludges would be
disposed of on land with suitable precautions.  The  soluble
salts  which  are  largely  innocuous should be suitable for
disposal in salt water.  Because these salts are  not  large
in   amount   and   can  be  dewatered  to  dry  solids   (by
incineration if necessary) very little additional impact,  on
the solid waste disposal problem is anticipated.
                            210

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No  impact  on  air  pollution  is expected as the result of
achieving no discharge of pollutants to surface water.    The
available technology creates no air pollutants.
                       B *6 fflLdMLABSiSffcffl  of
The  recommended effluent limitations to I a achieved by July
1, ,983, for existing sources based on  -c '•*«  application  of
Best  Available  Technology  Economically  Achievable  is no
dis^harq*.'   of   pollutants   to   navigable   waters    for
Subca -egories  (1) r  (2) and  (3).
Achieving  the  effluent  limitations  of  no  discharge  of
pollutants by achieving no discharge of effluent to  surfaje
waters  is  the  most direct method that eliminates the need
for sampling and  analysis.   If  th@re  is  other  effluent
discharge  to  surface  waters from the plant not associated
with metal finishing, a determination is  required  that  no
waste  waters originating from met&I finishing processes are
admixed with this other plant effluent.
                             211

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                         SECTION XI

                  SOURCE PERFORMANCE STANDARDS

Introduction

The standards of performance which nmat be achieved  by  new
sources   are  to  correspond  to  the  degree  of  effluent
reduction  attainable  through  the  application  of  higher
levels  of  pollution  control than those identified as best
avc,:.A.able -sctoG.,ogy economically  achievable  for  existing
sources..   .'he  added  consideration  for new sources is the
degree c/; ' •-:fl;eat redaction attainable through the  use  of
improver  production  processes and/or treatment techniques.
The term "new sources" Is defined by the Act  to  mean  "any
source,   the  construction  of  ^hich  is  commenced  after
publication of proposed regulations prescribing  a  standard
of performance."

New  source  performance stane^rda ar« based on the best in-
plant  and  end—of-process  technology  identified  as  best
available  technology  economically  achievable for existing
sources.  Additionel considerations applicable to new source
performance  standards  take  into  account  techniques  for
reducing  the  level  of effluent by changing the production
process itself or adopting alternative processes,  operating
methods,  or other alternatives.  The end result will be the
identification of effluent standards which reflect levels of
control achievable through the use  of  improved  production
processes   (as  w.-ll  as  control  technology),  rather than
prescribing a pa~-.icular type of process or technology which
must be employed,,  A further determination must be  made  as
to  whether a standard permitting no discharge of pollutants
is practicable.

Consideration must also be given tos

      (a)  The type of process employed and process
          changes

      fb)  operating methods

      (c)  batch as opposed to continuous operations

      "-•u  uge of  alternative raw materials and mixes
          of  raw  materials

      (e)  use of  dry rather than wet  processes
           (including substitution of recoverable
          solvents  for
                           213

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      (f)  r covery of pollutants as by-products.

Standards of  performance  for  new  sources  are  based  on
applicable   technology  and  related  effluent  limitations
coveri'.q discharges directly into waterways.

consideration  iust also be given to the fact that  Standards
of  Performer  -  for  Net--  Sources  could require compliance
about three  ?^ra sooner than the effluent limitations to be
achieved by eAi.itinq sources by July 1, 1977.  However,  new
sources  should  achieve  the  same  effluent limitations as
existir-a sources by July 1, 1983 .

Industry Category and Subcategory Covered

The pertinent  industry  category  is  the  metal  finishing
industry   divided   into  Subcategories  (1)  and   (2) ,  as
previously discussed in Section IV.

Identification Qf control and Treatment
Ifichnology Applisablg to,
                                 .
Standards and Pretreatment 3tan.da.rde of
New Soytrcei-t

Subcategory  (1)

The technology previously identified  in  Section  IX  under
Subcategory  (1)   as  best  practicable  control  technology
currently  available  is  al 30  applicable  to  new   source
performance  standards.   IN  addition,  a  new  source  can
utilize the best practice in multitank  rinsing  after  each
operation  in  the  process as required to meet the effluent
limitations at the time  of  construction.   Thus,  with  no
practical  restrictions  on  rinse  water conservation after
each  operation  by  multitask  rinsing,  there  are   fewer
restrictions  on the use of advanced techniques for recovery
of bath chemicals and reduction of wastewater  from  rinsing
after   pretreatment  and  post treatment.   Maximum  use  of
combinations  of  evaporative,  reverse  osmosis,  and   ion
exchange  systems for in-process control currently available
should  be  investigated.   A  small  end~of-pipe   chemical
treatment  system  can be used to treat spills, concentrated
solution dumps,,  and any other water flows  not  economically
amenable to in-process water and chemical recovery.

The  net  res a    of  the  improvements  cited  should  be a
reduction in  Baiter  use  as  compared  to  that  considered
achievable for best practicable control technology currently
available.    This   reduction  should  result  in  a  lowe^
                            214

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discharge of waste water constituents.  Although methods are
beinq developed that may make possible a  further  reduction
in  the concentration of constituents and a reduction in the
discharge of waste water constituents in chemically  treated
effluents,  present  technology Is capaiale only of achieving
the concentrations listed in Table 39 by exemplary  chemical
treatment.   It  would  be  anticipated that some plants now
operating, due to having been designed recently to  minimize
water  use  or because of other favorable circumstances such
as adequate space to make  modifications«.  are  attaining  a
water  use  well below 120 1/sq la/operation.  Table 37 shows
12 lines involving processes in Subca^agory fl) that achieve
a water use of less than H5  1/sq  m/op©ration.   These  are
found in Plants 33-23, 33-35, 20-22, 20-23.  It is estimated
that  a  new  source  can  achieve  a  water  use of U5 1/sq
m/operation for processes in Subcategory (1)  by use  of  the
technology described above for reducing water use,

Subcategory (2)

The  technology  previously identified in Section IX as best
practicable  control  technology  currently  available   for
processes  in  Subcategory   (2)   Is  also  applicable to new
sources.  In addition, a new source  can  «aa  best  rinsing
practice  and  advanced  techniques  for  recovery  of  bath
chemicals and reduction of rinse water  a*3  described  under
Subcategory  (1)   above.   The  similarity  of operations in
processes of Subcategory (2)  to the operations of  processes
in  Subcategory  (1) ,  and  the  similarity  in  waste water
compositions and treatment methods can be cited to  indicate
that  the  same methods of reducing water use are applicable
to Subcategory (2)  as are  applicable  to  Subcategory  (1) .
The   application   of   the  same  techniques  to  the  two
Subcategories  should reduce  the  waiter  proportionately  so
that  if  a  reduction  of  90  1/sq  m/optration to U5 1/sq
m/operation  can  be  achieved  by  a  new  source  with   a
Subcategory    (1)    process,    a   reduction  from  80  1/sq
m/operation for a  Subcategory  C2J   process  in  a  present
source  to 40  1/sq m/operation for the aam© process in a new
source should be achievable.    Th«r^fosr«s  it  is  estimated
that  new  sources  can  achieve  a  w&fcer  use  of  HO 1/sq
m/operation for Subcategory  {2}   processes.   Two  lines  in
Table  34  involving  Subcategory (2f  processes have a water
use of less than MO 1/sq m/operatioru   These  lines  are  in
Plants 6-3&, 20-25, 23-8.

Subcategory (3)

The  technology  previously identified in Section IX as best
practicable  control  technology  currently  avaf .able   for
                         215

-------
 processes   in   Subcategory   $2)  ia   also  applicable  to  new
 sources.   In addition,  a  new  source   can   use  best  rinsing
 practice   and   advanced  techniques   for   recoverv   of bath
 chemicals  and reduction of rinse water  as described  under
 Subcategory  (1)  above.   The  similarity of operations in
 processes  of Subcategory  (2)  to the  operations of  processes
 in  Subcategory  (1),   and  the  similarity in  waste water
 compositions ai-d treatment methods can be cited to   indicate
 that  the   same methods of reducing  water uss are : [-r »,icafole
 to Subcategorv  (2) as are  applicable to  St^ntegorv  (1).
 The   application    of   the  same   technique-*-  to   t!  a   two
 Subcategories should reduce   the  water   proportionately   so
 that  if   a  reduction  of  90  1/sq m/operation to 45 1/sq
 m/operation  can  be achieved  by   a new source   with   a
 Subcategory   (1)     process,   a  reduction from  120 1/sq
 m/operation for a  Subcategory  (2)   process  in  a  present
 source  to  60 1/sq m/operation for the same process  in a  new
 source should be achievable.   Therefore,   it  is  estimated
 that  new   sources   can achieve  a   water ue@  of  60 1/sq
 m/operation for Subcategory (2)  procaaees.   Two  lines   in
 Table  34   involving Subcategory  (2) processes have a water
 use of less than 60  1/sq m/operation.  These  lines  are   in
 Plants 4-8, 30-9,  9-2,  4-9.


 Rationale for Selection of Control and
Treatment Technology Applicable to New
 Source Performance Standards

The  rationale  for  the selection of  the  above technology  is
applicable to new sources discharging to  navigable waters is
 as follows:

     (1)   In contrast to an existing  source, a new
          source has complete freedom to  choose the
          most  advantageous equipment and  facility
          design to maximize water conservation by
          use of as  many multitank rinsing operations
          as necessary.   This, in turn,  allows for
          economic use of in-process controls for
          chemical and water recovery and reuse.

     (2)   in contrast to an existing source which may
          have 2c  present a large capital investment
          in was'-e treatment facilities to meet
          effluent limitations by July 1,  1977,  * new
          source has complete freedom in the selection
          the design of new waste treatment facilities.

     (3)   In contrast to an existing source, a new
                           216

-------
          source has freedom of choice with  regard  to
          geographic location*

Standards of Performance Apg^JLca|?l^ .to
The recommended St s.ndards of Perfosrffl&nc®  t-  b®   achieved  by
new  sources  discharging  to  navig*bl«   .atera  waa  shown
previously in Tc.ble 2 of Section  II,

The quantitative values for the SO-da^  .average  standard  for
eaeli  p^'-weter  in  mg/sq  K   -J'.b*-.. 5o  0*3 ft)  is based on a
nomin- 1 water use  one-half as l&/gc  &&  tlrioae used to develop
1977 guidelines combined with tits concestrrations  achievable
by  chemir.al  tre&w.-inc  as  previously shown in Table 39 of
Section IX.  For examp^, G.5 asg/* for  copper,,  nickel, total
chromium, zinc, and total cyanide? 0,05 Rig /I for  hexavalent
chromium  and  .,075 mg/l for oscidlsable cyant'ie,  20  mg/1 fjr
suspended solids,  when combined with &$i effluent  factor  of
45  1/sq m are the basis for the  30*»d&y 8V
-------
Guidelines for the Application of
New Source Performance Standards

The  recommended guidelines tor the application of standards
of performance for  new  sources  discharging  to  navigable
waters  are  the  same  as  those  in Section IX relating to
existing sources  based  on  use  of  the  best  practicable
control  technology currently available and those in Section
X based on use of  best  available  technology  economically
achievable.
                             218

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                        SECTION XII
                      ACKNOWLEDGEMENTS
The   Environmental  Protection  Agency  was  aided  in  the
preparation  of  this  Development  Document   by   Battelle
Columbus  Laboratories  under  the  direction  of William H.
Safranek, Luther Vaaler, John  Gurklis  and  Carl  Layer  on
Battelle*s staff made significant eontributions.

Kit  R.  Krickenberger  served  as  project  officer on this
study.  Allen Cywin^ Director, Effluent Guidelines Division,
Ernst P. Hall, Deputy Director, Effluent Guidelines Division
and Walter J. Hunt, Chief, Effluent  Guidelines  Development
Branch,   offered   guidance  and  suggestions  during  this
program.

The members of  the  working  group/steering  committee  who
coordinated the internal EPA review are:

    Walter J. Hunt, Effluent Guidelines Division
    Kit R. Krickenberger, Effluent Guidelines Division
    Devereaux Barnes, Effluent Guidelines Division
    Murray Strier, Office of Permit Programs
    John Ciancia, NERC, Cincinnati, (Edison)
    Alan Eckert, office of General Counsel
    James Kamihachi, Office of Planning and Evaluation

Acknowledgement  and  appreciation  is  also  given to Nancy
Zrubek, Kaye Starr,  and  Alice  Thompson  of  the  Effluent
Guidelines Division for their effort in the typing of drafts
and  necessary  revisions, and the final preparation of this
document.

Appreciation is  extended  to  the  following  organizations
associated with the electroplating industry:

      American Electroplaters0 Society, East Orange,
        New Jersey
      Aqua-Chem, Milwaukee, Wisconsin
      Artisan Industries, Inc., Waltham, Massachusetts
      E.I. duPont de Nemours and Co.g Wilmington,
        Delaware
      Heil Process Equipment Corporation, Cleveland,
        Ohio
      Haviland Products company, Grand Rapids, Michigan
      Industrial Filter and Pump Manufacturing Co ,
        Cicero, Illinois
                             219

-------
Institute of Printed Circuits, Chicago, Illinois
Ionic International, Incorporated, Detroit,
  Michigan
Lancy Laboratories, Zelienople, Pennsylvania
M & T Chemicals, Incorporated, Matawan, New Jersey
Electroplating Suppliers* Association, Incorporated,
  Birmingham, Michigan
National Association of Metal Finishers, Upper
  Montclair, New Jersey
Osmonics, Incorporated, Minneapolis, Minnesota
Oxy Electroplating Corporation, Warren, Michigan
The Permutit Company, Paramus, New Jersey
Pfaudler Sybron Corporation, Rochester, New York
                      220

-------
                        SECTION XIII


                         References

(1)   Table 3,  pg 36,  "1967 Census of Manufacturers",
     U.S.  Bureau of Commerce.

m   "Where to Buy Metal Finishing Services", Modern
     Metals, 28 (6),  p. 71 (July, 1972).

(3)   Institute of Printed Circuits* Chicago, Illinois.

(4)   jjgfrfl Finishing, p. 42, March 1972.

(5)   Sidney B. Levinson, J. Paint Technology, 44  (569)  49.

(6)   J. Schrantz, industrial Finishing, 20-29, October,  1972.

(7)   Table 3, p. 7-45,  "1967 Census of Manufacturers",
     U.S. Bureau of commerce.

(8)   Modern Electroplating,  Edited  by P. A.  Lowenheim,
     2nd Ed., John Wiley  ind Sons  (1963), Chap.  7,
     pp 154-205.
(9)   M»+*l FMpfghincr Guidebook and Directory, Metals
         Pstics Publications, Inc., 1973.

(10)
     and Plastics Publications,  Inc
                                               Metals
          i   i.
     and Plastics Publications,  Xnc.  1972.

 (11) Modern  fi jflcfrr opiating— *  P  69
 (12) Mo^£D_£l££^rQplflUngy  P 708.
                    ^^            Q
      Ed. ,  Van Nostrand Rheinhold, 3rd Ed., 1971, p

 (1«»)  schrantz, J.  Industrial Finishing, April, 1973,
      pp 37-40.

 (15)  Stiller, Frank P.., Metals Finishing guidebook and
      Directory, Metals and Plastics Publications, Inc.,
      pp 548-553, 1972.

 (16)  George, D.J., Walton, C.J., and Zelly, W.G.,
      pahr|c3tion and Finishing. Vol 3, Am Soc for Metals,
      1967, pp 387-622.
                                221

-------
(17J  Innesf  W.P. , Metal Finisaing Gu4debook and Directory,
     1972,  p 554.                       ~~~

(^8)  Pocock, Walter, E. Metal Finishing Guidebook and
     A£
-------
(33)  Environmental  Sciences.  Inc.,  "Ultimate Disposal
     of  Liquid Wastes by Chemical Fixation".
(34)  Dodge,  B.F.,  and Zabban. W. , "Disposal of *ljtinj
*  '  Room wastes.  III.   cyanide Wastes"  Treatment with
     Hypochlorites and Removal of Cyanates", Plating
     18 (6), 561-586 (June, 1951).
(35)  Dodge, B.F., and Zabban, W. , "Disposal of
(  }  Room wastes. III.  Cyanide wastes: Treatment
     Hvoochlorites and Removal of Cyanates.  Addendum ,
     Plating, 39  (4) , 385 (April, 1952) .

(36)  Dodge, B.F., and Zabban. W. . "Disposal of Plating
C  '  Room wastes. IV.  Batch Volatilization of Hydrogen
     Cyanide From Aqueous Solutions of Cyanides",
     Plating, 12  (10), 1133-1139  (October, 1952).

 (37)  Dodge, B.F., and Zabban, W. , "Disposal of Plating
 (  '  Room Wastes. IV.  Batch Volatilization of Hydrogen
     Cvanide From Aqueous Solutions of Cyanides.
     continuation", Plating, 32  (11).  1235-1244  (November,
     1952).

 (38)  "Overflow",  Chemical Week, HI  (24),  47  (December,
     1972),

 (391 ovler,  R.W. , Disposal  of Waste Cyanides  by  Electro-
 (  * ?yt!c Oxidation"? Plating, 16  (4),  341-342  (April,
     1949) .

 (UO) Kurz, H. ,  and  Weber, W. ,  "Electrolytic Cyanide
     Dedication by the CYNOX  Process" , Galvanotechnik
     and Oberflaechenschutz,  3,  92-97 (1962).

 (41) "Electrolysis  speeds Up Waste  Treatment",  Environmental
     Science and Technology",  4 (3),  201 (March, 1970).

 (42) Thiele, H., "Detoxification of cyanide-Containing
     waste Water by Catalytic oxidation and Adsorption
     Process",  Fortschritte wasserchemie Ihrer
     Grenzgebiete,  9, 109-120 (1968): CA, 70, 4054
      (1969) .

 rim Bucksteeq, W. , "Decomposition of Cyanide Wastes by
 (  } Se?hods of Catalytic 6xidation Absorption", Proceedings
     of the 21st Industrial Waste Conference, P«rdue
      University Engineering Extension series, 688-59b
      (1966) .
                              223

-------
(44)  "Destroy Free Cyanide in Compact, Continuous Unit",
     Calgon Corporation Advertisemente Finisher's
     Management, 19 (2), 14 (February,, 1973),

(45)  sondak, N. E., and Dodge, 3. F., W1h« QKidation
     of Cyanide Bearing Plating Pastes by Ozone.
     Part I", Plating, US (2)  173-180 (February,
     1961).

(46)  Sondak, N.E., and Dodge, B.F., "The Oxidation
     of Cyanide Bearing Plating Wastes by Ozone.
     Part II", Plating, J8 (3), 280-284 (March,
     1961) .

(47)  Rice,  Rip G., letter from Effluent Discharge
     Effects Committae to Mr. Alien Cvwin? Effluent
     Guidelines civiaion, July 9, 1973.

(48)  "Cyanide Wastes Might Be Destroyed at One-Tenth
     the Conventional Cost",  Chemical Engineering,
     79 (29), 20 (December 25, 1972).

(49)  Manufacturers' Literature, DMP Corporation,
     Charlotte, North Carolina (1973*.

(50)  Ible,  N., and Frei, A.M., "Electrolytic Reduction
     of Chrome in Waste water", Galvanotechnik and
     Oberflaechenschutz, 5 (6), 117-122 (1964).

(51)  schulze, G., "Electrochemical Reduction of
     Chromic Acid-Containing Wast® Water*1, Galvanotechnik,
     58 (7), 475-480 (1967):  CA, 6jfr 15876t C1968).

(52)  Anderson, J.P., and Weiss, Charles c%, "Methods
     for Precipitation of Heavy Metal 3«lfid
-------OCR error (C:\Conversion\JobRoot\000005YR\tiff\2000LWNZ.tif): Saving image to "C:\Conversion\JobRoot\000005YR\tiff\2000LWNZ.T$F.T$F" failed.

-------
(68) Campbell,  R.J.,  and Eimnerman,  O.K. r "Freezing and
    Recycling  of  Plating Rinse Water",  Industrial water
    Engineering,  9  (4),  38-39  (June/July,  1972).

(69) A.J.  Avila, H.A.,  Sauer, T.J.  Miller,  and R.E.
    Jaeger,  Plating,  60 239 (1973).

(70) Dvorin,  R., "Dialysis for  Solution Treatment in
    the Metal  Finishing Industry", Metal Finishing,
    57 (4),  52-54 4  62 (April, 1959).

(71) Ciancia, John,  Plating 60, 1037 (1973).

(72) communication with P. Peter Kovatia, Executive
    Director,  National Association of  Metal Finishers.

(73) "An Investigation of Techniques for Removal of
    Chromium From Electroplating Wastes",  Battelle,
    Columbus Laboratories Report on Program No.
    12010 EIE  to  the Environmental Protection Agency
    and Metal  Finishers1  Foundation (March,  1971) .

(74) Grieves, R.,  et  al.,  "Dissolved-Air Ion Flotation
    of Industrial Wastes.  Hexavalent  Chromium",
    Proc. 23rd Industrial Waste Conference,  Purdue,
    University, 1968,  p 154.

(75) Surfleet,  B., and crowle,  V.A., "Quantitative
    Recovery of Metals from Dilure Solutions",
    Transactions  of  the Institute of Metal Finishing,
    50, 227  (1972).

(76) Bennion, Douglas N.,  and Newman, John, "Electro-
    chemical Removal of Copper Ions from Very Dilute
    Solutions", Journal of Applied Electrochemistry,
    2, 113-122 (1972).

(77) Carlson, G.A.,  and Estep,  E.E., "Porous Cathode
    Cell for Metals  Removal from Aqueous Solutions",
    from Electrochemical Contributions to Environmental
    Protection, a symposium volume published by the
    Electrochemical  Society, Princeton, New Jersey,
    p 159.

(78)  "Water Quality  Criteria 1972," National Academy of
    Sciences and  National Academy of Engineering for the
     Environmental Protection Agency, Washington,  D.C.
     1972 (U.S.  Govt. Printing  Office  Stock No. 5501-00520)
                               226

-------
                        SECTION XIV


                          GLOSSARY
Acid Dip

An  acidic  solution  for  activating  the workpiece surface
prior to electroplating in an  acidic  solution,  especially
after  the  workpiece  has  been  processed  in  an alkaline
solution.
Alkaline Cleaning

Removal of grease or other foreign material from  a  surface
by means of alkaline solutions.
Anodizing

The  production  of  a  protective oxide film on aluminum or
other light  metals  by  passing  a  high  voltage  electric
current through a bath in which the metal is suspended.  The
metal  serves  as  the  anode.   The  bath  usually contains
sulfuric, chromic, or oxalic acid.
Automatic Plating

(1)   full - plating in which the cathodes are  automatically
conveyed through successive cleaning and plating tanks.  (2)
semi   -   plating   in  which  the  cathodes  are  conveyed
automatically through only one plating tank.
garrel Plating

Electroplating of workpieces in barrels (bulk).


Basis Metal or Material

That substance of which the workpieces  are  made  and  that
receives  the electroplate and the treatments in preparation
for plating.

Batch Treatment
                               227

-------
 Treatment  of  electroplating  rinse  waters  collected    in
 adjacent tanks.   Water is not allowed to leave the tank  till
 treatment is completed.


 Best  Available TechnQloqY_gconomicallv Achievable

 Level of technology applicable to  effluent  limitations to  be
 achieved  by  July  I,   1983,   for  industrial discharges  to
 surface  waters as defined by  Section 301 (b)  (2)  (A)  of  the
 Act.

 Level of technology applicable to  effluent  limitations to  be
 achieved  by  July  1,   1977,   for  industrial discharges  to
 surface  waters as defined by  Section 301 (b)  (1)  (A)  of  the
 Act.


 Bright Qj.g

 A solution used to produce a bright  surface  on a metal.


 Captive  Operation

 Electroplating facility   owned  and  operated by  the  same
 organization  that manufacturers the  workplaces.
Process utilizing  an  addition  agent  that  leads  to  the
formation of a bright plate, or that improves the brightness
of the deposit.


Chemical Etch ^ng

To  dissolve  a part of the surface of a metal or all of the
metal laminated to a base.


Chemical Metal Coloring

The production  of  desired  colors  on  metal  surfaces  by
appropriate chemical or electrochemical action.
                                 228

-------
The  improvement  in surface smoothness of a metal by simple
immersion in a suitable solution.
Chromati^jng

To  treat  or  impregnate  with  a  chromate  or  dichromate
especially with potassium dichromate.
Chrome-Pickle Process

Forming  a  corrosion^resistant oxide film on the surface of
magnesium-base metals by immersion in a bath  of  an  alkali
bichromate.
cosed-Loop Evaporation
A system used for the recovery of chemicals and water from a
plating  line.   An  evaporator  concentrates  flow from the
rinse water holding tank.  The concentrated  rinse  solution
is  returned  to  the  plating  bath, and distilled water is
returned to the final rinse tank.  The  system  is  designed
for  recovering  100 percent of the chemicals, normally lost
in d ragout, for reuse in the plating process.
Continuous Treatment

Chemical  waste  treatment  operating   uninterruptedly   as
opposed  to  bath  treatment;  sometimes referred to as flow
through treatment.
Conversion Coatipq

A coating produced by chemical or electrochemical  treatment
of  a  metallic  surface  that  gives  a  superficial  layer
containing a compound of the metal,  for  example,  chromate
coatings on zinc and cadmium, oxide coatings on steel.
Deoxidizing

The  removal of an oxide film from an alloy such as aluminum
oxide.
Descaling
                                229

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The  process  of  removing  scale  or  metallic  oxide  from
metallic surfaces.
De s mutt ing

The removal of smut, generally by chemical action,


Draqin

The  water  or  solution that adheres to the objects removed
from a bath,


Draqout

The solution that adheres to  the  objects  removed  from  a
bath,  more  preciously  defined  as  that solution which is
carried past the edge of the tank,
Abbreviation for ethylfnediamine-tetr$*cetic acid,,


Effluent

The waste water discharged from a point source to  navigable
waters.
Electrobrighten^ng

Electrolytic  brightening  (electropolishing) produces smooth
and bright surfaces by  electrochemical  action  similar  to
those that result from chemical brightening.


Electrochemical Mach|,nin^  (ff9M|

A  machining process whereby the part to be machined is made
the anode and  a  shaped  cathode  is  maintained  in  elope
proximity  to  the  work.  Electrolyte is pumped between the
electrodes and a potential  applied  with  the  result  that
metal  is  rapidly  dissolved  from  the work in a selective
manner and the shape produced on the work  complements  that
of the cathode,
                                230

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Electrodialvsis

Membrane  dialysis  under  the  influence  of direct current
electricity.
Electroless Plating

Deposition of a metallic coating by  a  controlled  chemical
reduction  that  is  catalyzed  by  the metal or alloy being
deposited.
fflectropainting

A coating process in which the  coating  is  formed  on  the
workpiece  by making it anodic or cathodic in a bath that is
generally an aqueous emulsion of the coating material.
The electrodeposition of an adherent metallic  coating  upon
the  basis  metal  or material for the purpose of securing a
surface with properties or dimensions different  from  those
of the basis metal or material.

Electroplating Process

An   electroplating   process   includes   a  succession  of
operations starting with  cleaning  in  alkaline  solutions,
acid dipping to neutralize or acidify the wet surface of the
parts,  followed  by  electroplating,  rinsing to remove the
processing solution from the workpiece, and drying.
Electrolytic corrosion process that increases the percentage
of specular reflectance from a metallic surface.
Electrostatic Precipitation

Use of an electrostatic field for precipitating  or  rapidly
removing  solid  or liquid particles from a gas in which the
particles are carried in suspension.
Heavy Metals
                               231

-------
Metals which can be precipitated by hydrogen sulfide in acid
solution,  e.g.,   lead,   silver,  gold,  mercury,   bismuth,
copper, nickel, iron, chromium, sine, cadmium, and tin.


Hot Dipping

A  method  of  coating  one  metal with another to provide a
protective film.


Hydrogen, Embr|,ttleme nt

Embrittlement of a metal  or alloy caused  by  absorption  of
hydrogen during a pickling, cleaning, or plating process.


Immersion Plate

A  metallic  deposit  produced by a displacement reaction in
which  one  metal  displaces  another  from  solution,   for
example:

             Fe + Cu++    Cu * Fe++


Independent
Job shop or contract shop in which electroplating is done on
workpieces owned by the customer.
Integrated chemiqal Treatment

A  waste  treatment method in which a chemical rinse tank is
inserted in the plating line between the  process  tank  and
the  water  rinse  tank.   The  chemical  rinse  solution is
continuously circulated through the  tank  and  removes  the
dragout while reacting chemicals with it.


Ion-Flotation Technique

Treatment   for   electroplating  rinse  waters  (containing
chromium and cyanide)   in  which  ions  are  separated  from
solutions by flotation.
Iridite Dip Process
                                 232

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Dipping  process  for  zinc  or  zinc  coated  objects  that
deposits an adherent protective film that is a  chrome  gel,
chrome oxide or hydrated chrome oxide compound.
Phosphatizing

Process  of  forming rust- resistant coating on iron or steel
by immersing in a hot solution of acid manganese,  iron,  or
zinc phosphate.
An  acid  solution  us«d to r«mov« oxides or other compounds
related to the basis metal from its surface of  •  metal  by
chemical or electrochemical action.
Pickling

The  removal  of  oxides  or  other compounds related to the
basis metal from its surface by immersion in a pickle.
Point Source

A single source of water discharge  such  as  an  individual
plant.
precious petals

Gold, Silver, Platinum, etc.
Electroplating of workpieces on racks.
Reverse osmosis

A  recovery  process in which the more concentrated solution
is put under a pressure greater than the osmotic pressure to
drive water across the membrane to the dilute  stream  while
leaving behind the dissolved salts.
Rochell salt
                                 233

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 Sodium potassium tartrate:   KNaCUH4O6  .  4H20.



 Shot  Peening


 Dry   abrasive  cleaning   of  metal  surfaces  by  impacting  the
 surfaces with  high velocity  steel shot.



 Sludgy


 Residue in the  clarifier of  a  chemical   waste   treatment
 process.
Strike
nnAAi      7  a  thin  coafcing  of metal  (usually  less than
0.0001 inch in thickness) to be followed by other   coatings.
 (2)   noun - a solution used to deposit a  strike.   (3)  verb
- a plate for a  short  time,  usually  at  a  high initial
current density.



Stripping


Removal of an electrodeposit by a chemical agent or reversed
electrodeposition.



Workpiece


The item to be electroplated.
                                234

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to
en
               MULTIPLY (ENGLISH UNITS)


                      English Unit
Abbreviation
Conversion Table


        by


    Conversion
             TO OBTAIN  (METRIC  UNITS)


Abbreviation          Metric  Unit
acre
acre - feet
British Thermal Unit
British Thermal Unit/pound
cubic feet/minute
cubic feet/second
cubic feet
cubic feet
cubic inches
degree Fahrenheit
feet
gallon
ga 1 Ion/minute
horsepower
inches
inches of mercury
pounds
million gallons/day
mile
pound/square inch (gauge)
square feet
square inches
tons (short)
yard
ac
ac ft
BTU
BTU/lb
cfm
cfs
cu ft
cu ft
cu in
op
ft
gal
gpm
hp
in
in Hg
Ib
mgd
mi
psig
sq ft
sq in
ton
yd
0.405
1233.5
0.252
0.555
0.028
1.7
0.028
28.32
16.39
0.555(°F-32)*
0.3048
3.785
0.0631
0.7457
2.54
0.03342
0.454
3785
1.609
(0.06805 psig+1)*
0.0929
6.452
0.907
0.9144
ha
cu m
kg cal
kg cal/kg
cu m/rein
cu m/min
CU Bt
1
CU On
°c
m
1
I/sec
kv
cm
atir.
kg
cu m/day
kra
atm
sq n>
sq cm
kkg
n>
hectares
cubic meters
kilogram - calories
kilogram calories/kilogram
cubic meters/minute
cubic meters/minute
cubic meters
liters
cubic centimeters
degree Centigrade
meters
liters
liters/second
kilowatts
centimeters
atmospheres
kilograms
cubic meters/day
kilometer
atmospheres (absolute)
square meters
square centimeters
metric tons (1000 kilograms)
meters
                 Actual conversion, not a multiplier

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