EPA-440/1-73-003
   Development Document for Proposed
      Effluent Limitations Guidelines
  and New Source Performance Standards
  COPPER, NICKEL, CHROMIUM,
              and ZINC
       Segment  of the Electroplating
          Point Source Category
 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                AUGUST 1973

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                 Publication Notice




     This is a development document for proposed effluent




limitations guidelines and new source performance standards




As such, this report is subject to changes resulting from




comments received during the period of public comments of




the proposed regulations.  This document in its final form




will be published at the time the regulations for this




industry are promulgated.

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              DEVELOPMENT DOCUMENT

                       for

         EFFLUENT LIMITATIONS GUIDELINES

                       and

         NEW SOURCE PERFORMANCE STANDARDS
        COPPER, NICKEL, CHROMIUM, AND ZINC
          SEGMENT OF THE ELECTROPLATING
              POINT SOURCE CATEGORY

                  John Quarles
              Acting Administrator

                Robert L. Sansom
Assistant Administrator for Air & Water Programs
                   Allen Cywin
     Director, Effluent Guidelines Division

               Harry M. Thron, Jr.
                 Project Officer
                   August 1973

          Effluent Guidelines Division
        Office of Air and Water Programs
      U.S. Environmental Protection Agency
            Washington, D.C.  20460

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BHVIRONMETTAL rT^w"HON AGENCY

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                                ABSTRACT
This document presents  the  findings  of  an  extensive  ^tudy  of  the
electroplating  industry  by the Environmental Protection Agency for the
purpose of developing effluent limitations  guidelines, standards of per-
formance,  and pretreatment standards for the industry to implement
Sections 304 (b) and 306 of the "Act."

Effluent  limitations  guidelines  for the copper, nickel, chromium, and
zinc segment 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 souces contained herein  set  forth  the  degree  of
effluent  reduction  which  is achievable through the application of tlr?
best available demonstrated  control  technology,  processes,  operating
methods,  or other alternatives.   The proposed regulations for all thre-
levels of technology set  forth  above  are  presented  in  Section  II,
RECOMMENDATIONS.

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

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                     CONTENTS

Section

I   CONCLUSIONS                                         1

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

III INTRODUCTION                                        8
         Purpose and Authority
         Summary of Methods Used for Development
              of the Effluent Limitations Guidelines
              and Standards of Performance
         Information Sources
         General Description of the
              Electroplating Industry

IV  INDUSTRY CATEGORIZATION                            14
         Introduction
         Objectives of Categorization
         The Relationship of Electroplating
              and Metal Finishing
         Profile of Production Processes
         Materials Receiving Electroplates
         Factors Considered in Categorization

V   WASTE CHARACTERIZATION                             31
         Introduction
         Specific Water Uses
         Quantity of Wastes
         Sources of Waste

VT  SELECTION OF POLLUTANT PARAMETERS                  51
         Introduction
         Metal Finishing Wastewater Constituents
         Electroplating Wastewater Constituents
         Wastewater constituents and Parameters
              of Pollutional Significance
         Rationale for the selection of
              Wastewater Constituents and Parameters
         Rationale for the Selection of Total
              Metal as A Pollutant Parameter
         Rationale for Rejection of Other
              Wastewater Constituents as Pollutants
VTI CONTROL AND TREATMENT TECHNOLOGY                   60
                                    IX

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                                                          Page


         Introduction
         Chemical Treatment Technology
         Process Principles and Equipment
         Practical Operating Systems
         Demonstration Status
         Process Principles and Equipment
         Water Conservation Through Control
              Technology
         Demonstration Status
         Water Conservation
              Extraction
         Methods of Achieving No Discharge of
              Pollutants

VIII     COST, ENERGY, AND NONWATER QUALITY               116
         ASPECTS
         Introduction
         Treatment and Control Costs
         Cost Effectiveness and Treating
              Procedures
         Nonwater Quality Aspects

IX  BEST PRACTICABLE CONTROL TECHNOLOGY                   125
         CURRENTLY AVAILABLE, GUIDELINES,
         AND LIMITATIONS
         Introduction
         Industry Category and Subcategory
              Covered
         Identification of Best Practicable
              Control Technology Currently Available
         Rationale for Selecting the Best
              Practicable Control Technology
              Currently Available
         Waste Management Techniques Considered
              Normal Practice in the Electro-
              plating Industry
         Degree of Pollution Reduction Based
              on Existing Performance by Plants
              of Various, Sizes, Ages, and
              Processes Using Various Control
              and Treatment Technology
         Determination of Effluent Limitations
              Selection of Best Practicable
         Additional Factors Considered in
              Selection of Best Practicable
              Control Technology Currently
              Available

         Effluent Limitations Based on the
              Application of Best Practicable
              Control Technology Currently
              Available
         Guidelines for the Application
                                    111

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              of Effluent Limitations

X   BEST AVAILABLE TECHNOLOGY ECONOMICALLY               180
         ACHIEVABLE, GUIDELINES AND LIMITATIONS
         Introduction
         Industry Category and Subcategory
              Covered
         Identification of Best Available
              Technology Economically Achievable
         Rationale for Selection of Best
              Available Technology Economically
              Achievable
         Effluent Limitations Based on the
              Application of Best Available
              Technology Economically Achievable
         Guidelines for the Application of
              Effluent Limitations

XI  NEW SOURCE PERFORMANCE STANDARDS                     185
         Introduction
         Industry Category and Subcategory
              Covered
         Identification of Control and
              Treatment Technology Applicable to
              Performance Standards and Pre-
              treatment Standards for New Sources
         Rationale for Selection of Control
              and Treatment Technology Applicable
              to New source Performance Standards
         Standards
              New Sources
         Guidelines for the Applications of
              New Sources Performance Standards

XII ACKNOWLEDGEMENTS                                     189

XIII     REFERENCES                                      190

XIV       GLOSSARY                                       194
                                   IV

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                                  TABLES
Number                                                      Page

   1 Recommended Effluent Limitations for                    4
          the Electroplating Industry to be
          Achieved by July 1, 1977, based on
          Best Practicable Control Technology
          Currently Available  (BPCTCA)

   1A     Recommended Standards of Performance               5
          for the Electroplating  Industry to
          be Achieved by New Sources

   2 Process for Plating on Steel                           16

   3 Processes for Plating on Zinc Die                      17
              Castings

   H Processes for Plating on Brass                         18

   5        Processes for Plating on Aluminum               19

   6        Processes for Plating on Plastics               19

   7        Distribution of Electroplate According          22
          to Type of Basis Material

   8 Processing Sequences Decorative Copper-                24
          Chromium Plating

   9 Processing Sequences for Nickel Plating                25

  10        Processing Sequences  for Chromium Plating       25

  11 Processing Sequences for Zinc Plating                  26

  12        Estimated Daily Raw Waste Load of               36
          Principal Salts Used in Copper,
          Nickel, Chromium, Zinc  Plating and
          Related Processes

  13           Principal Wastewater Constituents in         33
          Wastes From Processes for Plating on
          Steel

  14 Principal Wastewater Constituents in
          Waste From Processes for Plating                  39
          on Zinc Die Castings

  15 Principal Wastewater Constituents in                   40
          Waste From Processes for Plating on
          Brass
   16 Principal Wastewater Constituents in                   41
                                   v

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Number
         Waste From Processes for Plating
         on Aluminum

 17 Principal Wastewater Constituents                    42
         in Waste From Processes for Plating
         on Plastics

 18 Approximate Concentrations of Waste-                 53
         Water Constituents Prior to Treatment
         From a Typical Facility Electroplating
         copper, Nickel, Chromium, and Zinc
          (Plant 33-1)

 19 concentrations of Heavy Metals and                   7g
         Cyanide Achievable by Chemical Treating
         of Waste Created by Copper, Nickel,
         Chromium and Zinc Plating and Zinc
         Chromating Operations

 20 Decomposition Products of Cyanide in                 81
         Rinse Water From a cyanide zinc
         Electroplating Operation After
         Treatment with Peroxygen
         Compound

 21 Estimated Costs for Small Electroplating             119
         Facilities With No Waste Treatment
         to Meet Effluent Limitations for
         1977 and 1983

 22 Geographical Distribution of Good                    132
         Electroplating Waste Treatment
         Facilities Based on Initial Referrals,
         Companies Contacted for Information,
         and Representative Facilities Evaluated
         in Detail

 23 Classification by Size, Type of Facility,            134
         and Effluent Discharge for 53 Electro-
         plating facilities selected for
         Evaluation

 24 Classification of 53 Facilities                      136
         Evaluated By Mix of Plating Operations
         and Type of Waste Treatment and
         In-Process Controls

 25 source of Information and Classification             137
         by Size and Waste Treatment Method

 26 Size of Plating Operations                           140

 27 Treated Effluent Data                                147
                                  VI

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Number
 28 Comparison of Treated Effluent Data
         Based on Total Amperage

 29 Summary of Water Use Parameters for
         Four Plants Based on copper. Nickel
         Chromium or Zinc Plating and Ex-
         cluding Nonpertinent Metal Finishing
         Processes

 30 Summary of Treated Effluent from                  2.64
         Copper, Nickel, Chromium or Zinc
         Excluding Nonpertinent Plant
         Metal Finishing Operations

 31 Summary of Treated Effluent Based                 165
         on BCL Sampling and Analysis During
         Second Round Visit for Comparison
         with Table 2

 32 Monthly Average Effluent Concentration            167
         for Plant 33-1 Showing Improved
         Results Obtained Over a 14-Month
         Period

 33 Comparison of Battelle Analytical                 168
         Results with EPA Reference Standards

 34 Typical Current Efficiencies Assumed              17 8
         for Calculation of Plated Area
         Using Equation (2)

 35 Comparison of Effluent Limitations for            179
         BPCTCA (Table 1)  in Terms of
         Concentration for Various Effluent
         With the Prior Interim Guideline
         Concentrations

 36 English/Metric Unit Conversion                    206
                                 VII

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                       FIGURES

Number

  1 Relationship of Total Metal in                    28
         Treated Water Discharge to the
         Production Capacity of Typical
         Electroplating Plants Expressed
         as Metal Deposited Per Hour

  2 Schematic Flow Chart for Water Flow               33
         in Chromium Plating Zinc Die Castings
         Decorative

  3 Alternative Methods of Rinsing after              34
         a Processing Operation

  4 Diagram of a Typical Continuous-Treatment         63
         Plant

  5 Integrated Treatment System                       64

  6 Solubility of Copper, Nickel, Chromium            65
         and Zinc as a Function of Solution pH

  7 Experimental Values - Solubility of               67
         Metal Ions as a Function of pH

  8 Batch Treatment of Cyanide Rinse Waters           80
         by Combined Metal Precipitation and
         Cyanide Destruction
  9 Schematic Presentation of Ion-Exchange            90
         Application for Plating-Effluent
         Treatment  (7,25)

 10 schematic Presentation of Ion-Exchange            91
         Operation at Plant 11-8

11  Representative closed-Loop System for             96
         Recovery of Chemicals and Water with
         a Single-Effect Evaporator

 12 Representative Open-Loop Evaporative              97
         Recovery System

 13 Schematic Diagram of the Reverse-Osmosis          101
         Process for Treating Plating Effluents

 14 Closed-Loop System for Metal Finishing            103
         Process Water at Rock Island Arsenal
  15     Schematic Diagram of Freezing Process        105
                                   Vlll

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         for Recovery of Water and Chemicals
         from Plating Rinses (37,38)
16  Schematic Diagram of Ion-Flotation                '°9
         Cell for Treatment of Plating Effluent

  17     Flow Chart for Treatment of Waste Water      114
         from Cleaner and Acid Dip When Plating
         Operations Have separate stream
         Treatment

  18     Effective of Size of Plating Plant on        117
         Investment Cost of Waste-Treatment
         Facility

  19     Cost Effectiveness of Treatments and         123
         In-Process Water Conservation
         Technigues

  20     Employees Per Shift in Plating Versus        139
         Cumulative Percentage of 53 Plants

  21     Total Installed Current for Plating          142
         Versus Cumulative Percentage of
         53 Plants

  22     Installed Rectifier Capacity in Amperes      143
         for Electroplating Versus Number of
         Employees Per Shift in Electroplating
         for 53 Plant Sample (Ration of Amperes
         Used To Amperes Installed is Typically
         65 Percent)

  23     Effluent Discharge Rate Versus               144
         Cumulative Percentage of 53 Plants

  24     Composite of Pollutant Parameters in         145
         Treated Effluent Versus Cumulative
         Percentage of Plants

  25     Water Use Based on Total Installed           149
         Current Versus Cumulative Percentage
         of 53 Plants

  26     Comparison of the Water Use for Plants       152
         that Use In-Process Chemical Recovery
         Systems on One or More Plating
         Operations with the Water Use of Plants
         that do not Use In-Process Recovery
  27     Copper In Treated Effluent                   153
         From Electroplating

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28     Nickel In Treated Effluent From              154
       Electroplating

29       Hexavalent Chromium In Treated             155
       Effluent From Electroplating

30     Total Chromium In Treated Effluent           156
       From Electroplating

31     Zinc In Treated Effluent From                157
       Electroplating

32     Cyanide In Treated Effluent From             158
       Electroplating

33     Suspended Solids In Treated                  159
       Effluent From Electroplating

34     Typical Variation in Concentration           169
       of Pollutant Parameters From Analysis
       of Daily Composite Over a 4-Month
       Period Reported by Plant 11-8

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                               SECTION I

                              CONCLUSIONS
    The electroplating of copper, nickel, chromium and zinc, on ferrous,
nonferrous, and  plastic  materials  is  a  single  subcategory  of  the
electroplating  point  source  category  for the purpose of establishing
effluent limitations  guidelines  and  standards  of  performance.   The
consideration  of  other factors such as the age of the plant, processes
employed,  geographical  location,  wastes  generated   and   wastewater
treatment  and control techniques employed support this conclusion.  The
similarities of the wastes produced by electroplating operations and the
control and treatment techniques available to reduce  the  discharge  of
pollutants   further  substantiate  the  treatment  of  copper,  nickel,
chromium and zinc  electroplating as  a  single  subcategory.   However,
guidelines for the application of the effluent limitations and standards
of  performance  to specific facilities do take into account the size of
the electroplating facility and  the  mix  of  different  electroplating
processes possible in a single plant.

    Presently, over half of the 53 operating plants for which sufficient
data  were  available  achieve  low  concentrations of pollutants in the
treated effluent using conventional chemical  treatment  systems.   Over
half  of  the plants achieve low water use with such in-process controls
as needed to restrict the  volume  of  treated  effluent  discharged  to
surface  waters.   Therefore,  it was concluded that all 53 plants could
achieve the recommended effluent limitations  by  practicing  both  good
water conservation and good chemical treatment.

    It  is estimated that only a small percentage of the raw waste being
generated by the electroplating industry is being discharged directly to
navigable waters without  any  treatment.   It  is  concluded  that  ~he
remainder  of  the  industry  can  achieve the reguirements as set forth
herein with a minimum investment cost of $50,000 and a minimum opera4-: nq
cost of $13,000/year.  For larger plants plating over 100 sq m/hr  (1076
sq  ft/hr) the operating cost will be less than 5 percent of the pi.Vina
cost exclusive of waste treatment.  The capital investment  will  be  of
the  order  of  $150,000 per 100 sq m/hr ($140,000 per 1000 sq ft/hr)  of
plated area.  It is further estimated that no discharge  of  pollutants,
when  required,  could  be  achieved  with  increased  costs of about 10
percent of the  total  plating  costs  (including  land  and  building).
capital  investment will be of the order of $100,000 to $200,000 per 100
sq m/hr  (93,000 to $186,000 per 1000 sq ft/hr).

    The development of data and recommendations  in  this  document  for
effluent  limitation  guidelines  and  standards  of performance for the
electroplating  industry  (Phase  I)   relate   to   rack   and   barrel
electroplating  of  copper, nickel, chromium, and zinc.  This segment is

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estimated  to  contribute  about  two-thirds   of   the   total   amount  of
chemicals  added  to  wastewater  in  the   electroplating  industry and,
therefore, was selected for study   first.   The   control   and  tr =atmep+-
technology  identified  in  this  report   is  broadly applicsible -^ +*rc>.<*
res-raining areas of study:  (1) electroplating  operations o*hf>r thv  r - ~k
and  barrel;   (2)    electroplating  of metals other than  copper,  'I'.'-"' """ ,
chromium, and zinc; and  (3) other metal finishing processes.   Efflupn-
limitations  guidelines  and  standards of  performance  for the remaining
segments of the electroplating point  source  category   might   require  a
greater or lesser degree of effluent  reduction.

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                               SECTION II

                            RECOMMENDATIONS

Best Practicable^Control Technology
CurrentlY_Available

    Recommended  effluent  limitations  for  the electroplating 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.  Chemical treatment of wastewaters to destroy oxidizable cyanide
and  remove  all  but  small  amounts  of  the  heavy  metal  pollutants
represents the Best Practicable Control Technology  Currently  Available
for existing point sources.

    The  effluent limitations are based on achieving by July 1, 1977, at
least  the  pollution  reduction  attainable  using  this  control   and
treatment  technology  as presently practiced by the average of the best
plants in this  category.   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 on the kind of parts being electroplated
or the nature of available process facilities.

    The technologies on which such limitations are based  emphasize  use
of  end-of-process  chemical  treatment  to  remove  pollutants  to  th°
greatest  practical  degree  with  simultaneous  reduction  of  effluent
discharged  using  currently available in-process control technology and
directed towards eventual elimination  of  discharge  of  pollutants  as
electroplating facility equipment is modified or replaced.

Best Ayailable^Technolpgy Economically
Achievable

For  the  electroplating  industry,  no  discharge of process
waste water  pollutants  to  navigable  waters  is  recommenced  as  the
effluent  limitation to be achieved by existing point sources by July 1,
1983.

This  represents  the  degree  of  effluent  reduction  believed  to  be
attainable by existing point sources through the application of the Best
Available  Technology  Economically Achievable for recovery and reuse of
water.

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  TABLE 1.   RECOMMENDED EFFLUENT LIMITATIONS FOR THE ELECTRO-
            PLATING INDUSTRY TO BE ACHIEVED BY JULY 1, 1977,
            BASED ON BEST PRACTICABLE CONTROL TECHNOLOGY
            CURRENTLY AVAILABLE (BPCTCA)
Effluent Limitations (a)
Single Day Maximum (k)
Parameter mg/sq m lb/10& sq ft
Copper (Cu) (d) 80 16.4
Nickel (Ni) (d) 80 16.4
Chromium
hexavalent
(Cr6+) (d) 8 1.6
Chromium, total
(CrT) ^) (e) 80 16.4
Zinc (Zn) (d) 80 16.4
Cyanide , oxi-
dizable (CN) (f) 8 1.6
Cyanide, total
(CN) w) 80 16.4
Total Suspended
Solids (TSS) (h) 2400 491.0
pH range 6 to
9.5 U)
30-Day Average ^c>
mg/sq m lb/106 sq ft
40 8.2
40 8.2
4 0.8
40 8.2
40 8.2
4 0.8
40 8.2
1200 245.5

See Footnotes on page 6

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   TABLE 1A.   RECOMMENDED STANDARDS OF PERFORMANCE FOR THE
              ELECTROPLATING INDUSTRY TO BE ACHIEVED BY
              NEW SOURCES
Standards of Performance (a)
Single Day Maximum (
D; 30-Day Average (c)
Parameter mg/sq m lb/10b sq ft mg/sq m lb/10
Copper (Cu) (d) 40 8.2
Nickel (Ni) (d) 40 8.2
Chromium,
hexavalent
(Cr6+) (d) (e) 4 0.8
Chromium, total
(CrT) (d) (e) 40 8.2
Zinc (Zn) (d) 40 8.2
Cyanide, oxi-
dizable (CN) (f) 4 0.8
Cyanide, total
(CN) (g) 40 8.2
Total Suspended
Solids (TSS) 00 1200 246
pH range 6 to
9.5 (I)
20 4
20 4
2 0
20 4
20 4
2 0
20 4
600 123

t> sq ft
.1
.1
.4
.1
.1
.4
.1


See Footnotes on page 6

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         FOOTNOTES  FOR TABLES  1 AND  1A
(a)   The  effluent  limitations  and  standards  of  performance
     are  defined as  the  weight of  pollutant  in  milligrams
     discharged per  square meter of total  area  plated.
     The  total  area  plated is  the  sum of the areas  plated
     in each copper, nickel, chromium and  zinc  plating
     solution that requires  a  subsequent rinse.

(b)   Single  Day Maximum  is the maximum value for any one day

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

(d)   Total metal (soluble and  insoluble) in  sample. (4)

(e)   Total chromium  (Cri) is the sum of all  ionic forms
     (Cr3+ + Cr6+).  (5)

(f)   Oxidizable cyanide  is defined as detectable cyanide
     amenable to oxidation by  chlorine according to standard
     analytical procedures.  (6)

(g)   Total cyanide is defined  as all detectable cyanide  in
     the  sample following distillation according to standard
     analytical procedures.  (6)

(h)   Total suspended solids  retained by a  0.45  micron filter
     according  to  standard analytical procedures.  (5)

(i)   A pH in the range of 8  to 9 is the best range for mini-
     mizing  the soluble  metal-concentration  during coprecipi-
     tation, as discussed in Section VII.

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New Source PerfQrmance_Standards

    Table 1A summarizes the recommended  standards  of  performance  for
discharge   to  navigable  waters  applicable  to  new  sources  in  the
electroplating industry, the construction of which  is  commenced  after
publication   of   proposed   regulations   prescribing  a  standard  of
performance.  The standards of performance are based on demonstrated low
water use currently  being  achieved  in  representative  electroplating
process  lines  and the demonstrated low concentration of each pollutant
parameter in the treated effluent currently being achieved by over  half
of  the  plants for which data were available.  The recommended standard
of performance provides for the control of discharge of pollutants which
reflects the greatest degree of effluent  reduction  achievable  through
application  of  the  best  available  demonstrated  control technology,
process, operating methods, or other alternatives.

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                              SECTION III

                              INTRODUCTION


Purgose_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 Administrator pursuant to Section 304(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 304 (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  currently  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 (b) of the Act for the electroplating subcategory
of 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   performances  for  new  sources  within  such
categories.  The Administrator published  in  the  Federal  Register  of
January 16, 1973 (38 FR 1624), a list of 27 source categories.

    Publication   of   the   list   constituted   announcement   of  the
Administrator's intention of establishing, under Section 306,  standards
of  performance  applicable  to  new  sources  within the electroplating

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subcategory of the metal finishing industry which  was  included  within
the list published January 16, 1973.


Summary of: Methods_Used_for Development .of the Effluent
Limitation Guide!ineg_and standards of,Performance

The   effluent   limitation  guidelines  and  standards  of  performance
recommended herein were developed in the following  manner.   The  point
source  subcategory  of  electroplating  was  first  categorized for the
purpose  of  whether  separate  limitations  and  standards   would   be
appropriate  for  different  segments.  Such subcategorization was based
upon  raw  material  used,  product  produced,   manufacturing   process
employed,  and  other  factors.   The raw-waste characteristics for each
subcategory were then identified.  This included an analyses of (1)   the
source  and volume of water used in the process employed and the sources
of waste  and  waste  waters  in  representative  plants;  and  (2)   the
constituents  of all waste waters including toxic constituents and other
constituents which result in taste, odor, and color in water or  aquatic
organisms.  The constitutents of waste waters which should be subject to
effluent   limitation  guidelines  and  standards  of  performance  were
identified.

The full range of control and  treatment  technologies  exisring  within
each  subcategory  was  identified.   This included an identification of
each distinct control and treatment technology, including both  in-plant
and  endof-process  technologies, which are existent or capable of being
designed for each subcategory.  It also included  an  identification  in
terms  of  the  amount  of  constituents and the chemical, physical, and
biological  characteristics  of  pollutants,  of  the   effluent   level
resulting  from  the  application  of  each of the treatment and control
technologies.   The  problems,  limitations  and  reliability  of   each
treatment and control technology were also identified.

In  addition,  the  nonwater  quality  environmental impact, such as the
effects 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  was  identified  as well as the 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,"  "best  available  technology
economically  achievable"  and  the "best available demonstrated control
technology, processes, operating methods, or  other  alternatives."   In
identifying  such  technologies, various factors were considered.   These
included the total cost of application of technology in relation to  the
effluent  reduction  benefits  to be achieved from such application, the

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age of equipment and facilities  involved,   the  process  employed,  the
engineering  aspects  of  the  application  of  various types of control
techniques  process  changes,  nonwater  quality  environmental   impact
(including energy requirements) and other factors.

The  data  for  identification  and  analysis  were derived from several
sources and included EPA  research  information,  published  literature,
information  from  state  water  control  agencies and trade literature.
Supplemental  data  were  obtained  by   making   on-site   visits   and
interviewing   personnel   at   exemplary   electroplating   facilities.
References used during the development of the data in  this  report  are
listed in Section XIII of this document.

    Companies  plating  copper,  nickel, chromium and zinc and reporting
low levels of pollutants  in  their  waste  discharge  to  EPA  regional
offices  or  state  authorities were contacted by telephone or letter to
develop quantitative data on volume of  production  (or  direct  current
use) ,  water  flow  rate and composition of waste water discharge.  This
list  of  companies  was  supplemented  by  others  suggested  by  trade
associations  and  several suppliers of waste treatment equipment.  Prom
the information collected from more than 200 companies, data  on  plants
having  a  volume  of  effluent  flow  or  discharge  of pollutants that
reflected inferior treatment technology were excluded from the  analysis
of  pollutant  reductions  achievable  by  the  application,  of the best
practical control technology.  Data from 53  companies  oract icing  good
waste  treatment  were  expanded  by  23  plant  visits  and analyzed to
identify the control and treatment technologies which became  the  basis
for the effluent limitations and standards of performance recommended in
Section  II.   This  group  of  53 companies included 12 independent job
shops employing as few as 16 to as many as 200 workers.  Size  in  terms
of installed current capacity ranged from 6,000 to 263,000 amperes among
the  independent  shops  and  3,000 to 450,000 amperes among the captive
facilities.  Chemical waste treatment  was  practiced  by  all  but  two
companies,  which  used  evaporators  to recycle plating rinse water; 13
companies  utilized   integrated   chemical   treatment;   13   employed
evaporators to reduce the water flow rate from one, two or three plating
processees.   Four  utilized  ion  exchange  units  and two used reverse
osmosis  for  some  plating  processes.   Two   companies   were   using
counterflow  rinses  for  reclaiming plating solution dragged into rinse
water.  A total of 21 companies employed batch  or  continuous  chemical
treatment exclusively.
    Sources  of  information  utilized  for  developing the data in this
document included the following:

    (1)  Published literature (References appear in Section XIII)
    (2)  Trade literature
                                  10

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    (3)    Technology  Transfer  Program  on  Upgrading  Metal  Finishing
         Facilities to Reduce Pollution, December 12-13, 1972, sponsored
         by Environmental Pollution Agency
    (4)    Pollution  Abatement Seminar, sponsored by the Metal Finishing
         Suppliers Association, January 23,1973, Cleveland, Ohio
    (5)   Ten EPA regional  offices  and  32  state  pollution  abatement
         offices
    (6)   Representatives of the American Electroplaters1 Society,  (AES),
         the  Metal  Finishing  Suppliers'  Association  (MFSA)  and the
         National Association of Metal Finishers (NAMF)
    (7)    Representatives  of  130   companies   with   facilities   for
         electroplating   copper,  nickel,  chromium,  or  zinc,  during
         telephone conferences
    (8)   Representatives of seven companies during office conferences
    (9)   Representatives of  23  companies  who  visited  by  BCL  staff
         members for development of detailed data
    (10)   Analytical  verification  of  effluent  data  for  five plants
         engaged  in  electroplating  copper,   nickel,   zinc,   and/or
         chromium.  These five companies included captive facilities and
         job shops.

General Description of _the Elect ro p. 1 at ing_ Indus try

    The  electroplating  industry,  a subcategory of the metal finishing
activities included in standard industrial classification  (SIC) 3471, is
defined for the purpose of this document as  that  segment  of  industry
applying metallic coatings on surfaces by electrodeposition and includes
both  independent  (job)  platers and captive operations associated with
product fabrication and assembly.  The  annual  dollars-added  value  by
electroplating  exceeds  $2,000,000,000.  Approximately 20,000 companies
are engaged in electroplating; 3500 of these arejob shops supplying only
plating service.  About 25 percent of this segment  is  concentrated  in
the  middle  western states of Illinois, Michigan, and Ohio.  Another 20
percent  is  concentrated  in  Eastern  Pennsylvania  and  the  Atlantic
Coastline  states of Connecticut, Rhose Island, New York and New Jersey.
The location of captive plating  facilities  follows  the  same  general
pattern.

    The energy consumed annually by electroplating is estimated to be in
the  range of 1 to 1.5 x 109 kilowatt hours.  From 9 x 107 to  1 x  108 kg
(100,000 to 120,000 tons)  of metal  (principally  copper,  nickel,  zinc,
and  tin)  is  converted  annually  to  electroplated  coatings.   These
coatings provide  corrosion  protection,  wear  or  erosion  resistance,
antifrictional characteristics, lubricity, electrical conductivity, heat
and  light  reflectivity or other special surface characteristics, which
enables industry to  conserve  several  millions  of  tons  of  critical
metals,    such   as:     cobalt,   chromium,  nickel,  silver  and  gold.
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
                                  11

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 (0.010 to 0.015 in.)  are  sometimes  required  for  special  engineering
purposes or for salvaging worn or mismachined parts.

    An electroplating process includes cleaning,  electroplating,  rinsing
and  drying.   The cleaning operation consists of two or more steps that
are reguired for removing grease, oil, soil,  and  oxide  films  from  the
basic metal surface and insuring good electroplate adhesion.   Sequential
treatments   in   an   alkaline  solution  and an  acid  solution  with
intermediate  rinsing  are  the  minimum  number   customary  for    these
purposes.   In  the  electroplating solution, metal ions in either acid,
alkaline or neutral solutions are reduced on  cathode  surfaces, which are
the work pieces being plated.  The metal ions in   solution  are  usually
replenished  by  the  dissolution of metal from anodes in bar form or in
small pieces contained in inert wire  or  expanded  metal  baskets,  but
replenishment  with  metal  salts is sometimes practiced, especially for
chromium plating.  In this case, an inert material must be selected  for
the  anodes.   Hundreds  of different electroplating  solutions have been
adopted commerically, but only two or three types  are  utilized   widely
for  a single metal or alloy.  Cyanide solutions  are  popular for  copper,
zinc, and cadmium,  for  example,  yet  non-cyanide  alkaline  solutions
containing  pyrophosphate  or  another chelating  agent have been  adopted
recently for zinc and copper.  Acid sulfate solutions also are used  for
zinc,   copper,   and  several  other  metals, especially  for  plating
relatively simple shapes.

    Barrel and rack operations are used  respectively  for  small  parts
that  tumble  freely in rotating barrels and larger parts that cannot be
tumbled without surface impingment.  Perforated plastic barrels range in
diameter from 15 to 75 cm (6 to 30 in.),  depending  on  part  size  and
shape.    Direct  current  loads  up  to  several  hundred  amperes  are
distributed to the parts being  plated  in  horizontal  barrels  through
danglers   suspended   from  a  current  carrying  bar  located  at  the
longitudinal axis.  In oblique  barrels,  a  conductive  button  at  the
bottom transmits the current.

    Rack  plating is required for perhaps 90  percent of the surface area
processed commercially; the parts are attached to plastic-coated   copper
frames designed to carry current equitably to a few hundred small parts,
several medium-sized shapes or just a few large products through  spring-
like rack tips affixed to the rack splines.  Racks fabricated for manual
transfer from cleaning, plating and rinsing tanks usually contain 2 to 7
kg   (5 to 15 pounds)  of parts having a surface area of 0.5 to 1 sq meter
 (5 to 10 sq ft).  Larger racks for holding heavier parts are constructed
for use with mechanical hoist and transfer systems.  Mechanized transfer
systems for both barrels and racks, which range in cost from $50,000  to
more  than  $1,000,000  are  being  utilized   for high-volume production
involving six to thirty sequential operations.  In some instances, dwell
time and transfer periods are programmed on magnetic tape or  cards  for
complete automation.
                                  12

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    Electroplating  facilities  vary  greatly in size and character from
one plant to another.  The  size  of  a  single  facility  expressed  as
plating  solution  volume ranges from less than 400 liters (100 gallons)
to more than 190,000 liters (50,000 gallons).  The area of the  products
being  electroplated  in these facilities varies as much as three orders
of magnitude from less than 10 to more than 1000 sq meters/day  (100  to
10,000  sq ft/day) .  The power consumed by a single facility varies from
a few kilowatt  hours/day  to  as  much  as  20,000  kilowatt-hours/day.
Products being plated vary in size from less than 65 sq cm (1 sq in.)  to
more than 1 sq meter (10 sq ft)  and in weight from less than 30 q (1 oz)
to more than 9000 kg (10 tons).   Continuous strip and wire are plated in
some plants on a 24-hour/day basis.

    Some  companies  have  capabilities for electroplating ten or twelve
different metals and alloys, but other 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
has been tailored to the specific needs of each individual plant.
                                  13

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                               SECTION IV

                        INDUSTRY_CATEGORIZATION
This  section  discusses  in  detail  the  scope  of the metal finishing
industry and  its  subcategories  that  will  be  examined  later.   The
rationale  is then developed for considering the Electroplating Industry
as a separate subcategory for the  development  of  effluent  limitation
guidelines  and  standards of performance.   Further rationale is offered
for the selection of copper, nickel, chromium, and  zinc  electroplating
for  study  in Phase I on which this report is based and all other metal
electroplating in Phase II.  The rationale  is then developed to show why
further subcategorization of the electroplating industry is not required
for  the  purpose  of  developing  effluent  limitation  guidelines  and
standards of performance.


Ob ject ives_of Categori zat ion

A  primary purpose of industry categorization is to develop quantitative
effluent limitations and standards of  performance  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.
The_RelationshiE_gf^Electroplating and Metal^Finishing

Electroplating  is  one  of several processes in the broader category of
metal finishing, which  includes  anodizing,  bright  dipping,  buffing,
coloring,  conversion coating, descaling, electropolishing, galvanizing,
mechanical polishing, tumbling, and  other  finishing  processes.   One,
several,  or  all  of  the  above processes may be performed in a single
facility.  For example, electroplating and its attendent  operations  of
preparation  for  plating  and  post  plating  treatment may be the only
process performed.

As pointed out above, electroplating is one of several processes in  the
broader  category  of metal finishing.  Electroplating is an appropriate
subcategory of metal finishing  because  other  subcategories  of  metal
finishing employ chemical processes exclusively.


Profile of Production Processes

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The   electroplating  industry  utilizes  chemical  and  electrochemical
operations to effect an improvement in the surface properties of  metals
and  other  materials.   In practice, the operations are put together in
sequences that become the processes which effect the improvement.  Thus,
electroplating is both process and materials oriented.

In one segment of the industry, identified as No. 3471 in  the  Standard
Industrial  Classification (SIC)  Manual 1972, published by the Executive
Office of the President (Bureau of the Budget), processes are  performed
on  metals  or  other materials as products owned by someone else, i.e.:
The customer.  Such work is done in job shops,  also  known  as  contract
shops.    The  same  operations  for  electroplating  are  performed  by
manufacturers classified by other SIC  numbers,  on  their  own  metals,
materials,  and  products  in  captive shops under their own management.
Typical processes are the same for both types of  facilities.   Examples
are  shown  for  copper, nickel,  chromium, and zinc plating which is nhe
subject of this report according to basis metal or material  and  opera-
tions  in  Tables  2  to 6.  Not shown in these tables are sequences for
electroplating cadmium,  brass,  gold,  iron,  lead,  silver,  tin,  the
platinum metals, and other metals and alloys which are practiced by only
a  few  companies,  relative  to  the  much  larger  number  engaged  in
electroplating copper, nickel, chromium, and zinc.   These  less  common
electroplating  processes  will  be  examined  and analyzed later durina
Phase II of this program.   Copper, nickel, chromium,  and  zinc  plating
processes  which  is  the  subject  of  this report were selected first,
because a large proportion (about two thirds) of the waste generated  by
electroplating  processes are derived from those associated with copper,
nickel, chromium, and zinc.   Furthermore,  almost  all  facilities  are
equipped for plating at least one of these common metals.
                                  15

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TABLE 3.   PROCESSES FOR PLATING ON  ZINC DIE CASTINGS
Operation
Alkaline clean/
rinse
Acid dip /rinse
Copper strike/
rinse
Acid dip/rinse
Copper/rinse
Nickel/rinse
Nickel/ rinse
Anodic treat/
rinse
Chromium/ rinse
Chromate/ rinse
Decorative
Chromium
Plate
1
X
X
X

X
X
X

X

Decorative
Chromium
Plate
2
X
X
X
X
X
X
X

X

Protective
Finish
3
X
X





X


Protective
Finish
A
X
X







X
                          17

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TABLE 4.  PROCESSES FOR PLATING ON BRASS
Operation
Alkaline clean/
rinse
Acid dip/rinse
Copper strike/
rinse
Acid dip/rinse
Copper/rinse
Nickel/rinse

Nickel/rinse

Anodic treat/
rinse
Chromium/rinse
Chromium
Plate
1
X

X
X



X





X
Decorative
Chromium
Plate
2
X

X
X



X





X
Decorative
Chromium
Plate
3
X

X
X



X

X



X
Protective
Nickel
Plate
A
X

X
X

X

X






                      18

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TABLE 5.   PROCESSES FOR PLATING ON ALUMINUM
Operation
Alkaline
Clean/ rinse
Acid dip/rinse
Activate/rinse
Zinc strike/
rinse
Copper strike/
zinse
Copper/rinse
Nickel/rinse
Nickel/rinse
Chromium/rinse
Zinc/rinse
Chromate/rinse
Decorative
Chromium
Plate
1
X
X
X
X
X
X
X

X


Decorative
Chromium
Plate
2
X
X
X
X
X
X
X
X
X


Decorative
Chromium
Plate
3
X
X
X





X


Protective
Zinc
Plate
A
X
X
X
X





X
X












 TABLE 6.  PROCESSES FOR PLATING ON  PLASTICS
Operation
Alkaline
Clean/rinse
Acid dip rinse
Activate rinse
Catalyze rinse
ElectrolcEs
Deposit/rinse
Copper strike/
rinse
Copper/rinse
Nickel/rinse
Nickel/rinee
Chromium/ rinse
Decorative
Chromium
Plate
1
X

X
X
X

X

X
X
X

X
Decorative
Chromium
Plate
2
X

X
X
X

X


X
X
X
X
Sasis
for
Coating
3
X

X
X
X

X


X
X


Basis for
Magnetic
Coating
4
X

X
.X
X

X



X
















                  19

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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  the  steps of
electroplating, copper, nickel,  chromium,  or  zinc.   These  operating
solutions  are  the  sources  of  pollutants  which appear in the rinses
immediately following the concentrated solutions, in  spills,  and  from
the discard of spent or contaminated solutions.   The intermediate rinses
are  essential  for removing the processing solution from the workpieces
so as to avoid contaminating the next processing  solution.   The  final
rinse assures a clean finished surface.

Some  generalizations  will be encountered as process descriptions.  For
example, decorative chromium plating refers to copper plus  nickel  plus
chromium  plating  and  hard  chromium  plating  refers to only chromium
(usually on steel), as seen in Table 2.

In some facilities, vapor degreasing with tri- or perchloroethylene  may
be used to precede the alkaline cleaner.   The only water associated with
this operation is for cooling.  The cooling water effluent is usable for
rinsing  after  the alkaline cleaning.  Therefore, no further mention is
made of vapor degreasing.  However, it  is  a  source  of  possible  air
pollution.

For each typical electroplating operation, exemplified in Tables 2 to 7,
a  variety of solutions can be selected.   The choice is usually based on
personal knowledge and experience in a specific process for  a  specific
basis  material.   The  selection  of an alkaline cleaner for a specific
basis material could be made from at least five types.   The  number  of
candidate solutions for other operations is as follows:

     (1)  Three to six acid dips each basis material
     (2)  Two to three copper strike solutions
     (3)  Four copper plating solutions
     (U)  Four nickel plating solutions
     (5)  Three chromium solutions
     (6)  Three zinc solutions.

Thus,  the most appropriate solution for a particular operation will not
be the same in all electroplating facilities.  Further evidence  of  the
complex  character  of  the  electroplating industry is seen in the size
range of less than 400 liters  (100 gallons) to more than 190,000  liters
(50,000  gallons)  of  plating solutions in a single facility.  The less
than 400 liter  (100 gallon) installations involve parts either small  in
size or guantity or are specialized as for electrodepositing chromium on
tools  and  custom  parts  in  a  captive shop.   Installations of larger
gallonage process parts large in size  (as bumpers for automobiles, sheet
and strip steel for prefab plating and/or  large  numbers  of  zinc  die
castings and steel and brass stampings or castings).
                                  20

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    At  the  low  and  intermediate  region  of  the  size range are the
contract shops, representing approximately 3500 facilities of  SIC  3471
classification.   Larger facilities are in captive shops where logistics
and process control are more effectively geared  to  a  high  production
volume.   Other  SIC  classification  numbers  cover the captive plating
facilities, estimated to be five to six times the number of contract  or
job shops.  About 90 percent of the volume of electroplating in dollars-
added  value  is supplied by companies doing their own electroplating on
their own products.

    Unlike  most  of  the  captive  plating  operations,  which  process
approximately the same number of the same products each month, job shops
are  required  to handle a greater variety of shapes and different metal
substrates.  Production volume for a specific  type  of  product  varies
appreciably  from  day  to  day.   Thus, an individual job shop might be
generating a large amount of copper,  nickel,  and  chromium  waste  and
little  or no zinc waste during a limited, three- or four-week period at
the beginning of a new model-year season  for  automotive  or  appliance
hardware,  or a much lesser amount of copper, nickel, and chromium waste
and a large amount of zinc waste near the end of a  model-year  run  for
typical  customer products. Day-to-day variations can be expected in the
amount and type of waste generated by a typical independent facility  as
a result of meetina delivery schedules.

Because  of the large variety of products handled by the independent job
shops, in-process controls for minimizing waste are less  effective,  in
comparison with the controls that can be exercised in a captive facility
always  processing the same products and materials.  As a result of this
situation, the advent of rigid waste-discharge enforcement  is  expected
to  encourage  some  degree of specialization among the independent job-
shop establishments.  Such a trend will reverse the tendency established
in the past by companies that have expanded in facilities with a  larger
number  of  electroplating  and  finishing processes in order to provide
improved service to industry in a given geographical area.
Materials Receiying_Electrop-lates

    Regardless of the size of facility  for  copper,  nickel,  chromium,
and/or  zinc electroplating, it will process one or more of the commonly
used basis materials:  steel, zinc die castings,  brass,  aluminum,  and
plastic  such  as  ABS and polypropylene as summarized in Tables 2 to 6.
The distribution of electroplating according to basis material is  shown
in  Table 7.  More than half of all electroplating is done on steel as a
basis material.   Zinc alloys as die castings comprise the  next  largest
category  of  basis  materials.   Reference  to Tables 2 to 5 shows that
basis materials  are first cleaned and acid dipped  prior  to  the  first
electroplating step.
                                  21

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TABLE 7.  DISTRIBUTION OF ELECTROPLATE ACCORDING
          TO TYPE OF BASIS MATERIAL
Plate     Steel  Zinc Die Cast  Brass  Aluminum  Plastics
Copper
Nickel
Chromium
Zinc
50
48
54
100
46
44.9
33.9

2
5
4

2
0.1 2
0.1 2

    When  the  nature  of the industry and the operations performed were
analyzed, consideration was  given  to  the  further  categorization  of
electroplating according to one or more of the following:

    (1)   Type of basis material
    (2)   Product design
    (3)   Raw materials used
    (4)   Size and age of facility
    (5)   Number of employees
    (6)   Geographic location
    (7)   Quantity of work processed
    (8)   Waste characteristics
    (9)   Treatability of wastes
    (10)  Rack plating versus barrel plating.

None of these is a basis for categorization for the reasons given below.


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 wastewater discharge by the treatment
processes adopted for removing copper, nickel, chromium and zinc,  which
are described in section VII.  Furthermore, the basis materials selected
for  most  consumer  products frequently are interchanged from one model
                                  22

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year to another.   Therefore,  the  type  of  basis  material  does  not
constitute a basis for subcategorization.


Product Design

    Although  complex  shapes  tend  to generate more waste than simpler
ones, the premium in costs  for  fabricating  and  plating  the  complex
shapes  far  overshadows any small supplemental waste-treatment cost for
such products.  Product design precepts  for  minimizing  electroplating
costs   also  reduce  wastes  created  by  electroplating  processes.(1)
Furthermore, the in-process controls and rinsing techniques described in
Section VII for minimizing  the  wastes  generated  by  copper,  nickel,
chromium,  and  zinc  electroplating  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
practicable waste-treatment technology  identified  in  Section  VII  is
equally  applicable  to  all  of  the  usual  procedures  and  solutions
described previously for electroplating copper,  nickel,  chromium,  and
zinc.   In  any facility carrying out one or more of the processes shown
in Tables 2 to 10, the same waste-treatment needs  arise.   Such  varia-
tions  as  exist for each operation are not unique and do not affect the
waste-treatment technology and control.
                                  23

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Size and Age of Facility

    The  nature  of  electroplating  is  the  same  in  all   facilities
regardless  of size and age.  For example, copper plating is technically
the same in 190 liters (50 gallons)  as in 19,000 liters (5,000  gallons)
or  larger installations.  Technically, the age of the facility does not
alter this situation.  Electroplating  of  nickel,  chromium,  and  zinc
follows  the  same pattern.  Thus, the characteristics of the waste will
be the same for plants 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 amount of metal
deposited, as shown in Figure 1.   The  amount  of  metal  deposited  in
typical  facilities  is  directly  related  to  the current consumed for
plating, the number of liters of installed  plating  solution,  and  the
volume  of  production.   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  plating  facilities  may have
insufficient space for accommodating effective in-process  controls  for
minimizing  water  use  and/or  conventional  chemical  waste  treatment
equipment.  The capital  investment/burden  for  installing  good  waste
control  may  be greater for such small companies relative to the burden
that can be amortized by larger companies.  In such cases,  heavy  metal
pollutants  can  be  absorbed  on the resins in small ion-exchange units
available at relatively modest investment.  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.  Costs depend on water
volume and the concentration of pollutants.

Number of Employees

    The number of employees engaged in electroplating does not provide a
basis for subcategorization, because electroplating  operations  can  be
carried  out  manually  or  in automatic machines which greatly conserve
labor.   For  example,  an  operation  with  3,785-liter  (1,000-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
in total area.  Other examples could be cited  to  show  that  no  basis
exists  for  relating  the  number  of  employees  to the electroplating
operations carried out and/or to  the  waste  that  results  from  those
operations.
                                  27

-------
                   Production  Capacity,  Lb Metal Deposited/Hour
                  20          40          60           80
                                                  100
                   I
                           I
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                                                        (H-8)
    0.15
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                                                    • (33-1)
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                              (33-6)
         (40-<
             133
          '(36-2)
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                                                                       a>
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                                                                       o
                                                                       in
                                                       in
                                                       i
                                                                   O.I
                   10           20            30            40
                   Production  Capacity,  Kg  Metal Deposited /Hour
         FIGURE 1.   RELATIONSHIP OF TOTAL METAL IN TREATED
                      WATER DISCHARGE TO  THE PRODUCTION
                      CAPACITY  OF TYPICAL ELECTROPLATING
                      PLANTS EXPRESSED AS METAL DEPOSITED
                      PER HOUR

-------
Geographic Location

    Geographic  location  is  not  a  basis  for  subcategorization.  No
condition is known whereby the choice of  electroplating  operations  is
affected  by  the physical location of the facility, except availability
of process water.   If  water  is  not  available,  no  modification  of
electroplating   procedures   can   compensate   for   this   lack.   No
electroplating  facilities  would  be  installed  at  a  water-deficient
location,  because  large  amounts  of  water are required for replacing
water lost by evaporation.  The waste-treatment procedures described  in
Section VII can be 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 rinsewater  conservation
techniques  described  in  Section VII can be adopted for minimizing the
land space required for the endof-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/or   water
consumption.
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  process--1.  The application of the guidelines   provides  for  the
production of a particular facility.
Waste Characteristics

    The physical and chemical characteristics of all wastes generated by
copper, nickel, chromium, and zinc electroplating processes are similar.
Specifically,  all  wastes  are  amenable  to  the  conventional  wasne-
treatment  technology  detailed  in Section VII.  The characteristics of
treated  waste  are  the  same  througout  the  industry.   Thus   waste
characteristics do not constitute a basis for subcategorization.


Treatability of Wastes

    As  no  special  peculiarity  exists between raw materials and waste
characteristics as a basis to separate  facilities  into  subcategories,
none exists for treatability of wastes as a 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.
                                  29

-------
Rack Plating 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 dumping them  in  a  barrel  for  processing  in  bulk.
Technically,  any  plating  operation  can  be done either by rack or by
barrel operations.  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
wastewater  (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  techni-
ques  are  detailed  in Section VTI.  Therefore, rack plating and barrel
plating are not appropriate subcategories.
                                  30

-------
                                SECTION V

                          WASTE CHARACTERIZATION


Introduction

Water flow and the nature and quantity of the wastes  dissolved  in  the
water  during  copper,  nickel, chromium, and zinc plating processes are
described in this section.  Sources of waste are also discussed in  this
section.

    Water  is  a  major  material  in the electroplating industry and is
associated with every operation.  Yet, none  of  the  water  enters  the
product and there is no payment for it as such.


5P.ec if i c _Water_Uses

Water is used in the following ways:

    (1)   Rinsing 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  operations  (3)   Washing the air that passes through
ventilation ducts so as to remove  spray  from  the  air  before  it  is
exhausted
    (4)     Dumps   of   operating  solutions,  mostly  pretreatment  and
posttreatment solutions
    (5)   Rinse water and dumps of solutions  from  auxiliary  operations
such as rack stripping
    (6)   Washing of equipment  (e.g., pumps, filters, tanks)
    (7)    Cooling  water  used  in  heat exchangers to cool solutions in
electroplating processes.

Rinsing

    A large proportion (perhaps 90 percent) of the water usage is in 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
electroplating  process.   The  general  outline  of  operations  in the
processes was given in Tables 2 to 6.
                                  31

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    Figures 2 and 3 schematically illustrate flow charts for work pieces
being processed and show the sites of water usage for rinsing.   Figure 2
shows the minimum number of operations and the water flow  in  the  wide
practice  of  decorative  chromium  plating.  However,  there is 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.

    Charts  for  other  processes  shown in Tables 2 to 6 show analogous
water use for each operation of cleaning,  acid  dipping,  plating,  and
rinsing according to one of the schemes in Figure 3.


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 then 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

    Auxiliary  operations  such  as  rack  stripping  utilize  solutions
containing  acids  or cyanide for removing metal deposited on rack tips.
These solutions  accumulate  large  concentrations  of  metals  and  are
decanted or dumped at regular intervals.  They should be slowly trickled
into  the appropriate rinse water stream that contains similar chemicals
for ultimate treatment.
                                  32

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                 Work flow
                  Alkaline
                   clean
                                           Precipitate
                                        nickel and copper
FIGURE 2. SCHEMATIC FLOW CHART FOR WATER FLOW IN CHROMIUM
          PLATING ZINC DIE CASTINGS, DECORATIVE
                             33

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                                                       Clean water
                                                    one or two rinses
            Work flow
                                                          1
                                                          Sludge
                         a. One or Two (Series) Rinses
                                                                       Effluent
                                                                        water
                                                                    Clean water
            Work flow
                                                                Effluent water
                                                Sludge

                          b.  Two Counter-Flow Rinses
                                                                          Clean water
Work flow1
                          c   Three Counter-Flow Rinses
       FIGURE 3   ALTERNATIVE METHODS OF RINSING AFTER A PROCESSING OPERATION
                                            34

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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  electroplating  solutions  is usually routed to rinse tank's for
water conservation purposes.  If this  practice  is  not  adopted,  exit
water  from  cooling  units  should  be  checked for constituents of the
plating solution to guard against the discharge  of  pollutants  in  the
event of a leak into the cooling unit.


QuantitY_gf_Wastes

    At  least  95  percent  of  the  products  being  electroplated  (or
electroformed)  to provide  resistance  to  corrosion,  wear,  and  other
destructive  forces are processed in medium sized or large plants  (4,000
to 5,000 in number), each deploying at least 11 kg/day  (25  pounds/day)
of raw waste                          into rinse water.  The potentially
toxic  waste  in  -he  ionu  of heavy metal salts and cyanide salts from
these sources is approximately 340,000 kg/day  (750,000 pounds/day  (data
from  a  survey  of  chemicafs  consumed  by electroplating conducted by
Battelle's Columbus Laboratories in 1965, adjusted to reflect trends  in
process  modifications  since  1965)  equivalent to about 110,000 kg/day
(250,000 pounds/day)  of heavy metal and  cyanide  ions.   Of  the  total
salts,  about  two-thirds  or  228,000  kg/day  (505,000  pounds/day)  is
contributed by copper, nickel, chromium, znd zinc plating operations,  as
shown in Table 12.

    Supplementing the chemicals listed in Table  12,  at  least  225,000
kg/day  (500,000  pounds/day)  of alkalies and 450,000 kg/day (1,000,000
pounds/day) of acids are contributed to the total waste by cleaning  and
pickling  operations  that  precede  copper,  nickel, chromium,  and zinc
plating.  The proportion of phosphates in alkaline cleaning chemicals is
unknown, but is believed to be 25 percent of the total alkalies.
                                  35

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  TABLE 12.   ESTIMATED DAILY RAW WASTE LOAD OF PRINCIPAL SALTS
             USED IN COPPER, NICKEL,  CHROMIUM, ZINC PLATING
             AND RELATED PROCESSES(a)
  Operation
                        	Principal Salts
  Identity
kg/day pounds/day
Copper plating



Nickel plating


Chromium plating

Zinc plating
Copper cyanide,       54,000  120,000
 sodium cyanide,  and
 copper sulfate
Nickel chloride and
 nickel sulfate

Chromic acid

Zinc oxide, zinc
 cyanide, sodium
 cyanide, and
 zinc sulfate
54,000  120,000


45,000  100,000

68,000  150,000
Percent of
Total Salts
Consumed by
  Plating
(a)  Data from a survey conducted by Battelle's Columbus
     Laboratories in 1965.
    13



    17


    13

    23
Zinc chromating
Sodium chromate and
sodium dichromate
6,800
227,800
15,000
505,000
2
68
                                36

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Some of the alkaline solution waste and nearly all of the acid  solution
waste  contain  heavy  metals  resulting  from  the dissolution of metal
products  to  be  plated.   Hence,  the  total  amount   of   wastewater
constituents   generated   by   copper,   nickel,   chromium,  and  zinc
electroplating probably exceeds 900,000 kg/day  (2,000,000 pounds/day).

    From the estimated plating salts in Table 12, the  total  metal  and
cyanide load was estimated as follows:

    Copper               11,000   kg/day  (  24,000  pounds/day)  Nickel
    12,000 kg/day ( 27,000 pounds/day) Chromium           25,000  kg/day
    (  55,000  pounds/day)  Zinc                19,000  kg/day   ( 42,000
    pounds/day)  Cyanide           _i*£tOOO  kg/day   (102A000  pounds/day)
    TOTAL             113,000 kg/day  (250,000 pounds/day)"

    The estimated alkali load of 230,000 kg/day  (500,000 pounds/day) and
acid load of 450,000 kg day (1,000,000 pounds/ day)  are usually in about
the  same  ratio  in most plants  (i.e., combined acid/alkali wastewaters
are mostly acid).  Assuming the alkalinity as  sodium  hydroxide  (NaOH)
and  acidity as sulfuric acid (H2SO4), combination/neutralization (about
0.9 kg NaOH/kg H2SO4)  would indicate a total net acid  load  of  350,000
kg/day  (750,000 pounds/day).


Sources_gf_Waste

    In  electroplating  facilities the wastes are derived from the basis
materials receiving electroplates  (discussed  in  Section  IV)  and  the
contents  of operating solutions used for electroplating processes.   The
principal ionic constituents of wastewater from  typical  processes  for
plating  on  five basis materials are listed in Tables 13 to 17.  Wastes
associated with (1)  preparation for plating,  (2) electroplating, and  (3)
postplating  are  combined  in  these  tables.   These  operations   are
discussed below in more detail.


Preparation for Plating

    Wastewater   constituents   derived  from  the  chemicals  generally
utilized  for  maintaining  preplate  preparation  solutions   or   from
reactions  with  the common basis materials processed in these solutions
are as follows:
                                  37

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  TABLE 13.   PRINCIPAL WASTEWATER CONSTITUENTS IN
             WASTES FROM PROCESSES FOR PLATING
             ON STEELS*
Constituent
Iron, ferrous, Fe"*~2
Copper, cuprous, Cu
Copper, cupric, Cu+2
Nickel, Ni+2
Chromium, chr ornate, Cr"1""
Chromium, chromic, Cr"1"-^
Zinc, Zn+2
Cyanide, CN"1
Sulfate, S04"2
Chloride, Cl"1
Car b ona t e , C03 ~ 2
Silicate, Si03~2
Phosphate, P04~3
Fluoborate, BF6*1
Sulfamate, NI^SOs"1
Nitrate, N03*1
.Ammonium , NHA+^
Organics
1
X
2 3
X ' X
i
X X ,
X X
X i X ' X
x ; x x
J
X
X
X

X
X

X


X

X
X
X
X
X

X


X


X
X
X
X
X





4
X

X
X




X
X
X
X
X

X


X
5
X





X
X
X
X
X
X
X





6
X



X
X
X

X
X
X
X
X





7
X
X
X




X
X
X
X
X
X




X
8
X


X




X
X

X
X

X


X
* Process numbers  correspond  to  those  in Table  2.
                    38

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  TABLE 14.   PRINCIPAL WASTEWATER CONSTITUENTS
             IN WASTE FROM PROCESSES FOR PLATING
             ON ZINC DIE CASTINGS*
Constituent
Fe+2
Cu+1
Cu+2
Ni+2
Cr+6
Cr+3
Zn+2
CN"1
SO^2
ri-1
Li
C03~2
Si03~2
PO^'3
BFg'1
NH2S03"1
NOT"-'-
il \S J
NH4+1
Organics
1


X
X
X
X
X
X
X
X
X
X



X
2






X

X
X
X
X



X
3




X
X


X
X
X
X




4
















* Processes correspond to those in Table 3.
                 39

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  TABLE 15.  PRINCIPAL WASTEWATER CONSTITUENTS
             IN WASTE FROM PROCESSES  FOR PLATING
             ON BRASS*
Constituent
Fe+3
Cu+1
Cu+2
Ni+2
Cr+6
Cr+3
Zn+2
CN"1
S04'2
Cl"l
C03"2
Si03~2
P04'3
NH2S03*1
N03"1
Organics
1


X
X
X
X
X
X

X
X
X
X

X
X
2


X
X
X
X
X
X


X
X
X

X
X
3


X
X
X
X
X
X

X
X
X
X

X
X
4


X
X



X

X
X
X
X

X
X
* Processes correspond to those in Table 4.
                40

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     TABLE 16.  PRINCIPAL WASTEWATER CONSTITUENTS IN
                WASTE FROM PROCESSES FOR PLATING ON
                ALUMINUM*
Constituent
Fe+3
Cu+1
Cu+2
Ni+2
Cr+6
Cr~*~3
Zn+2
Aluminum, AP"-^
CN"1
S04'2
Cl"1
C03~2
Si03"2
P04'3
BF6~-*-
NH2S03*1
NH3-1
Organics
1 2



X
X X
X , X
X ; X
y


X
X
X

X


X
y


X
X
X

X



3




X
X

X


X
X
X

X



A


















5


















* Processes correspond to those in Table 5.
                        41

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  TABLE 17.  PRINCIPAL WASTEWATER CONSTITUENTS
             IN WASTE FROM PROCESSES FOR PLATING
             ON PLASTICS*
Constituent







Tin,
Palladium,






Organics


Fe+3
Cu+1
Cu+2
Ni+2
Cr+6
Cr+3
Zn+2
Sn+2
Pd+2
CN"1
804" 1
cr1
0)3 ~2
Si03'2
P04"3
BF6
N03"1
NH3"1
1


X
X
X
X

X
X

X

X
X




2 3



X X
X X
X
X

X X
X

X

X
X




X

X

X
X




4



X



X
X

X

X
X




* Processes correspond to those in Table 6.
                   42

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    Alkyl aryl oxyalcohols     Nitric acid
     Alkyl aryl sulfonates      Phosphoric acid
     Aluminum chloride          Sodium bisulfate
     Aluminum nitrate           Sodium borate
     Aluminum sulfate           Sodium carbonate
     Chromic acid               Sodium hexametaphosphate
    Copper chloride          Sodium hydroxide
    Copper fluoborate        Sodium metosilicate
    Copper nitrate      Sodium orthosilicate
    Copper sulfate      sodium pyrophosphate
    Ferric chloride          Sodium sulfate
    Ferric phosphate         Sodium triphosphate
    Ferric sulfate      stannous chloride
    Ferrous chloride         Sulfamic acid
    Ferrous phosphate        Sulfuric acid
     Ferrous sulfate         Zinc chloride
     Fluoboric acid             Zinc sulfate
    Hydrochloric acid

    Solutions of  all  of  the  above  chemicals  containing  acids  and
alkalies  must  be neutralized prior to discharge into navigable waters.
All of the metals  may be removed to varying degrees by thet    treatment
techniques discussed in Section VII.

    Alkaline	Cleaners.  Regardless of the material to be electroplated,
cleaners are made up with  one  or  more  of  the  following  chemicals:
sodium   hydroxide,   sodium   carbonate,  sodium  metasilicate,  sodium
phosphate  (di- or trisodium), sodium  silicate,  sodium  tetraphosphate,
and  a  wetting  agent.   compositions  for  steel are more alkaline and
active than those for brass,  zinc die castings, and aluminum.  Soils  to
be  removed from basis materials by cleaners are unrelated chemically to
the metal and usually are the same general type.  The need for variation
in cleaner composition is partly based on the nature of the soil and  on
the chemical resistance of the material being prepared for plating.

In  addition  to  the chemicals comprising the alkaline cleaners, rinses
and spills, wastes contain soaps from emulsification of certain  greases
left  on basis material surfaces from polishing and buffing that precede
electroplating.  Also, emulsified oils are likely to  be  present.    The
raw  wastes  from  the  basis  materials  and process solutions prior to
plating show up in the  rinse  waters,  spills,  dumps  of  concentrated
processing  solution,  wash  waters  from  air-exhaust  ducts, and leaky
heating and cooling coils and heat exchangers.

    Acid_Dips.  The nature of the basis  material  requires  selectivity
for  acid  dips.   Acid  solutions  are  made up with one or more of the
following:  hydrochloric acid, sulfuric acid, phosphoric acid, fluoboric
acid, chromic acid, and nitric acid.   The  solution- compositions  vary
according  to  nature of any tarnish or scale, chemically related to the

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metal and to the resistance of the material to  chemical  reaction  with
the   acid  solution.   The  acid-treating  baths  for  preparing  metal
substrates for plating usually have  a  relatively  short  finite  life.
When  used solutions are replaced with fresh solutions,  large amounts of
chemicals must be treated or reclaimed.   Water used  for  rinsing  after
acid  treating  also  collects  heavy metal waste by dragout of solution
from the acid-treating tank.

    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 repeatedly through the cleaning, acid treating,
and elec<- roplating cycle.  In barrel zinc-plating operations, the amount
of zinc dissolved in the acid-treating solution from the  danglers  used
to  make  electrical  contact  to  the  work pieces sometimes equals the
amount of zinc carried over into the water rinse solution following  the
zinc-plating bath.  The copper (and zinc)  accumulated in acid bright dip
solutions  used  to  prepare  electrical  copper  and brass contacts for
plating can exceed in amount the metal contributed to rinse-water  waste
by dragout from the plating bath.

    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  preplate 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, whereas 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.


Electroplating

    Wastewater constituents derived from solutions  generally  used  for
electroplating copper, nickel, chromium, and zinc are as follows:

    Alkylaryl sulfonates        Potassium hydroxide
     Aluminum chloride           Rochelle Salts
     Aluminum sulfate            Saccharin
     Ammonium chloride           Sodium bicarbonate
     Boric acid                  Sodium carbonate
     Chromic acid                Sodium cyanide
     Coumarin                    Sodium ethylene diamine
     Copper cyanide                tetraacetic acid
    Copper sulfate              Sodium fluosilicate
     Fluoboric acid              Sodium hydroxide
                                  44

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     Fluosilicic acid            Sodium pyrophosphate
     Hydrochloric acid           Zinc chloride
     Nickel chloride             Zinc cyanide
     Nickel fluoborate        Zinc fluoborate
     Nickel sulfamate            Zinc oxide
     Nickel sulfate              Zinc sulfate
    Potassium cyanide           Sulfuric acid

    Prior to end-of-process discharge, solutions containing alkalies and
acids  (or  acid  salts)  must be neutralized.  All of the metals must be
removed by the technology detailed in Section VII.

    Copper Plating.  Copper is electroplated from four types  of  baths,
i.e.,  alkaline  cyanide,  acid  sulfate, pyrophosphate, and fluoborate,
which  are  prepared  with  corresponding  copper  salt.   The   cyanide
solutions  also  contain  sodium  carbonate  and may also contain sodium
hydroxide or sodium potassium tartrate.  All four types may also contain
a small amount  of  an  organic  chemical  for  refining  the  grain  or
brightening the plate.  Typical compositions are cited in References (2)
and  (3).   Cyanide solutions are used extensively for copper plating, but
acid  copper  solutions  have  been adopted for plating large numbers of
steel, plastic, and zinc alloy products.  Steel and zinc are customarily
plated first in a  cyanide  strike  bath  to  insure  good  electroplate
adhesion.   Copper plating solutions are rarely dumped, so the principal
source of waste is the rinse water used  to  remove  the  solution  that
remains  on  work  surfaces  (dragout)  after copper-plated articles are
removed from the plating tank.   Rinsing between cyanide copper  striking
and  plating  in  a  concentrated  cyanide  bath  is  not  reguired,  so
facilities equipped with both kinds of solutions create just one  source
of  waste,  in comparison with others eguipped with a cyanide strike and
an acid bath.  Even so, some companies prefer  the  cyanide  strike-acid
copper  sequence  for  minimizing  the amount of cyanide waste requiring
treatment by chemical oxidation (or for improving the quality  of  their
products).

    A  secondary source of waste in a typical copper plating facility is
associated with solution filtration.  Filters, pumps, and pipes commonly
develop leaks, classified as spills.  Not all of the solution is  washed
back  into the plating tank when filter cartridges or bags are exchanged
for new ones  (or washed free of contaminating  solids  that  reduce  the
filtration  rate).   The  high-concentration  cyanide  and  acid  copper
sulfate solutions are usually filtered continuously, in order to prevent
rough deposits.


    A nickel strike  for  steel  has  been  adopted  by  some  companies
choosing  to  eliminate cyanide baths.  The acid copper sulfate bath can
then be used over the nickel strike,  in  a  sequence  similar  to  that
adopted  for  copper  plating  on plastic which is first metallized by a

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thin film of electroless nickel.   A satisfactory nickel shrike  has  not
been  identified  for  zinc  die   castings, which are universally plated
first with a cyanide copper strike.  Copper is extensively electroplated
in combination with nickel and chromium.   About 75 percent of t.he copper
anode consumption (18,000,000  kg/year  or  40,000,000  pounds/year)   i?-,
expended   for   this   purpose,   but  other  applications  aooour^-  fov
significant quantities.  For example, printed circuit boards are  eof •
plated  to  make  through-hole  electrical  contacts between circuits o.
opposite sides of the boards.  Another significant  activity  is  copper
electroforming (including electrotyping) .   Some facilities installed for
electroplating  cabinet  hardware  (principally steel and zinc alloy die
castings)  utilize copper plating  as the only deposition step, to produce
colored finishes.
                       Nickel  is  electroplated  from  Watts  (sulfate-
chloride-boric  acid) ;   sulfamate;   all  chloride;  and fluoborate baths.
Each type of solution is prepared with the corresponding nickel salt,  a
buffer  such as boric acid and a small concentration of a wetting agent.
A small amount of another organic chemical may be added to brighten  the
deposits   or   control   another   property.     Nickel  is  extensively
electroplated in a three-metal composite coating of copper, nickel,  and
chromium.   In  the  best  practice,  nickel plating would follow copper
plating without drying as in Processes 1 and 2, Table 3.  Nickel also is
electrodeposited on steel  for  decorative-protective  finishes  and  on
other  materials  for  electroforming.   In  these   applications, nickel
plating is preceded by cleaning and activating operations in a  sequence
selected  for a specific basis material.  Nickel electroplate is freshly
plated and rinsed without drying and directly chromium plotted  according
to processes shown in Tables 2 through 6.  Typical  solution compositions
are given in References 2 and 3.

    In  addition  to  the  constituents of new solutions, used solutions
contain small concentrations of other heavy  metals,  depending  on  the
kind  of  material  being  processed.   For  example,  the?  nickel  bath
gradually picks up copper and zinc when copper-plated steel and  copper-
plated  zinc  die  castings  are  being  nickel  plated.   Only periodic
analyses will reveal the amounts present.

    Organic addition agents that refine the grain size  of  the  deposit
and brighten the plate are added to all nickel plating baths adopted for
sequential  nickel-chromium plating.  Proprietary agents are supplied by
metal finishing supply companies that have developed  stable,  effective
chemicals   for   insuring  mirror-like,  corrosion-protective  deposits
requiring  no   buffing.    Aryl   polysulfonates,    sulfonamides,   and
sulfinimides  such as napthylene disulfonic acid, p-toluene sulfonamide,
and saccharin are examples of one class of brightening agents frequently
combined with a sulfonated aryl aldehyde, ethylene   sulfonamide,  amine,
nitrile,  imide,  azo  dye,  or another special compound.  These organic
chemicals  and  the  surface  active  agents   (typically  sodium  lauryl
                                  46

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sulfate) customarily added to reduce surface tension and prevent pitting
contribute  small  concentrations  that  impose a small COD to the water
rinse step following nickel plating.  Because the organic compounds  are
customarily  added  to nickel plating baths in small concentrations (0.5
to 3 g/1), their total concentration in the untreated rinse water seldom
exceeds 4 mg/1.

    Leakage from filters, pumps, and pipes  is  a  secondary  source  of
nickel  waste, although some filters are equipped to recover and recycle
leaks that occur from the pump and filter.  Incomplete washing of filter
cartridges, bags, or plates during filter maintenance is another  source
of  waste.   Continuous  filtration  of  nickel  solution is adopted for
preventing roughness by most of the companies engaged in nickel plating.
Filters sometimes are packed with activated carbon for removing  organic
impurities  that  degrade  the  characteristics  or  properties  of  the
deposit.

    The relatively high value of nickel has encouraged the  adoption  of
in-process   controls  for  minimizing  dragout  into  the  rinse  water
following nickel plating, which is the major source of  waste.   Because
of their relatively high value, nickel plating baths are rarely dumped.

    Chromium  Plating.   All  chromium plating solutions contain chromic
acid and a small amount of either sulfuric acid or a mixture of sulfuric
acid and fluosilicate or fluoride ions.  The  concentration  of  chromic
acid usually is two orders of magnitude higher than the concentration of
the  other materials.  Three basis materials account for the bulk of the
work: steel, nickel-electroplated steel, and nickel-electroplated  zinc.
Solutions containing 150 to 400 g/1 of chromic acid are the common baths
for  electroplating 0.2 to 1.0m  (0.000008 to 0.00040 inch)  of decorative
chromium or hard chromium on steel  and  aluminum  for  resisting  wear.
Unlike  the  copper  and  nickel plating processes which utilize soluble
copper or nickel anodes to replenish in solution the metal deposited  on
the  work  pieces,  chromium plating processes always use insoluble lead
alloy anodes.  Thus, some portion of the chromic  acid  added  regularly
for  maintenance  is  consumed by reduction to chromium metal at cathode
surfaces.   This  proportion  varies  from  only  10  to  20  percent  in
decorative  chromium plating facilities to the range of 25 to 90 percent
in hard chromium installations, depending  on  the  in-process  controls
adopted for reducing the dragout loss to the rinse water.

    Dragout  into  rinse  water is the major source of raw waste.  Spray
carried from the solution by  the  hydrogen  gas  generated  at  cathode
surfaces  and  oxygen  gas  produced  at anode surfaces is a significant
secondary source.  Chromium plating process tanks are customarily vented
to protect workers from this spray, so an appreciable amount of  chromic
acid  is  carried into air ducts in the form of aerosols released to the
atmosphere.  Air scrubbers  are  incorporated  in  the  exhaust  systems
                                  47

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installed  in some plants to recover this source of waste and recycle it
to the chromium plating bath.
                    Zinc  is  electroplated  in  (a)   cyanide  solutions
containing  sodium  cyanide, zinc oxide or cyanide and sodium hydroxide;
(b) noncyanide alkaline solutions prepared with  zinc  pyrophosphate  or
another  chelating  agent  such  as  tetrasodium  pyrophosphate,   sodium
citrate or the sodium salt of ethylene  diamine  tetraacetic  acid:  (c)
acid  or neutral chloride baths prepared with zinc chloride and a buffer
salt such as ammonium chloride; or (d)  acid sulfate solutions containing
zinc sulfate and a buffer salt such as aluminum chloride or sulfate.   A
small concentration of an organic compound such as glucose,, licorice, or
glycerin  may  be added to the chloride or sulfate baths for brightening
purposes.  Formulations for these solutions are given in References  (2)
and  (3) .

    In  addition  to  dragout  of solution into rinse water which is the
major source of waste, zinc waste  is  generated  during  continuous  or
batch  filtration.   Air agitation and hydrogen gas evolution at cathode
surfaces create aerosol particles carried through exhaust  systems  into
the  atmosphere,  unless removed by wash water that is combined with the
rinse water for treatment.


Postplating Treatments

    Postplating  treatment  is  rare  for  nickel   and   chromiumplated
products,  but  a  large  proportion  of zinc-plated steel and a smaller
proportion of copper-plated products are processed to impart a  chromate
film or one of several alternative colored finishes.  Chemicals utilized
for  preparing  postplating  treatment  solutions  for  copper  and zinc
electroplates or derived  by  reactions  with  the  electroplated  metal
include the following:

    Ammonium carbonate         Nickel sulfate
    Ammonium hydroxide         Nitric acid
     Ammonium molybdate         Phosphoric acid
     Ammonium persulfate        Potassium chlorate
    Barium sulfide             Potassium nitrate
    Chromic acid        Potassium permanganate
    Copper acetate      sodium dichromate
     Copper chloride            Sodium hydroxide
     Copper nitrate          Sodium polysulfide
     Copper ssulfate             Sodium sulfide
     Ferric chloride            Sodium thiocyanate
     Ferrous sulfate         Sulfuric acid
    Hydrochloric acid          Zinc nitrate
     Nickel chloride

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    A  dilute solution of nitric acid is an example of a bright dip bath
for zinc plate.  A chromate solution  for  zinc  is  always  acidic  and
contains  hexavalent  chromium  compounds,  such  as  chromic  acid, and
contains inorganic and organic  compounds  as  activators  or  catalysts
known  only  to  the  suppliers.   Both types of posttreatment solutions
accumulate dissolved zinc and require dumping and replacement at regular
intervals,  thereby  creating  waste  that  must  be  treated  prior  to
discharge.    Used   chromate- filming  solution  also  contributes  both
trivalent and hexavalent chromium ions to wastewater.  Of course,  water
rinsing  operations  after bright dipping or chromating also are sources
for waste.  Thus, the rinse water may be mixed with and treated the same
as rinse water from chromium plating.

    Copper (and brass)  plated steel and zinc alloy  products  and  zinc-
plated products are sometimes oxidized or otherwise treated in solutions
that  produce  attractive,  desired  colors  such  as those described in
Reference (3) .  Some of these solutions  are  prepared  with  copper  or
other  heavy metal salts,  others accumulate dissolved copper or zinc as
a result of use, some of which show up in rinse  water  associated  with
the  post  treatment.  Furthermore, all have a finite bath life and must
be replaced at  intervals,  like  the  bright-dip  and  chromate- filming
solutions used for treating zinc.

    Decorative   colors   are   applied   on   copper  and  zinc,  after
electroplating.   Operators  frequently  develop  their   own   solution
compositions.    The following formulation indicate the general nature of
such solutions.

    P? own on copper j _

    Potassium chlorate, KC1O3 - 40 g/1 (5.5 oz/gal)

    Nickel sulfate, Ni2SO4.6H20 - 20 g/1  (2.75 oz/gal)

    Copper sulfate, CUSO4.6H2O - 190 g/1  (24.0 oz/gal)

    Li
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    Ammonium molybdate, NH4MoO4 - 30 g/1  (4 oz/gal)

    Ammonia, NH3 - 47 ml/1  (6 fluid oz/gal) or     copper        sulfate,
CUSO4.6H2O - 45 g/1  (6 oz/gal)

    Potassium chloride, KCl - 45 g/1  (6 oz/gal)

    Brown on zinc:

    Double nickel salts,  (NH4)2SO4.NiSO4  - 4 g/1  (0.5  oz/gal

    Copper sulfate, CuSO4.6H2O - 4 g/1  (0.5 oz/gal)

    Potassium chlorate, KC103 - 4 g/1  (0.5 oz/gal)
                                   50

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                               SECTION VI

                   SELECTIQN_gF_POLLyTANT_PARAMETERS


Introduction

    This  section  of  the  report  reviews  the  waste characterization
detailed in Section V and identifies in terms of chemical, physical, and
biological constituents that which constitutes pollutants as defined  in
the  act.   Rationales  for  the  selection  and, more particularly, the
rejection of wastewater constituents as pollutants is presented.

    First, consideration was given to the broad range of chemicals  used
in  the  metal  finishing  industry.   Constituents  associated with the
subcategory of electroplating and limited to  copper,  nickel,  chromium
and zinc plating were considered next in detail.  Those considered to be
potentially  toxic  pollutants  are identified.  Other constituents were
examined in the light  of  their  probable  concentration  in  untreated
wastewater in relation to water quality criteria for discharge, in order
to form a judgment on pollutants to be monitored.
    Specific  consideration  is  given  in  this section to defining the
physical form of heavy metals to be considered pollutants,  as  well  as
definition  of  analytical technigues for reporting their concentrations
in the wastewater discharge.


Metal_Fini_shing Wastewater_Constituents

    A large variety of chemicals are used in the  metal  finishing  that
become  wastewater  constituents.  The important wastewater constituents
for electroplating copper, nickel, chromium, and zinc were identified in
Section V.   Not  all  of  these  constituents  will  be  found  in  the
wastewaters  from  every facility since the number of metals plated in a
single facility varies as well as the number of basic metals  pretreated
and types of posttreatment operations.  Other metal finishing operations
than  electroplating  and  other  electroplating operations than copper,
nickel, chromium, and zinc would  contribute  other  metal  ions.    When
present,  these other metal ions are usually coprecipitated with copper,
nickel, chromium, and/or zinc unless they are heavy metal pollutants  of
greater  potential  toxicity  requiring  special  control  and treatment
technology.  The nonmetallic  cations  and  anions  from  electroplating
copper,  nickel,  chromium,  and  zinc  can be considered typical  of the
metal finishing industry.


Electroplating_Wastewater Constituents
                                  51

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    The wastewater  constituents  from  electroplating  copper,   nickel,
chromium,  and  zinc  were  identified qualitatively in Section  V.   Each
wastewater  constituent  is  additive  to  the  concentration  of   that
constituent  in  the  raw  water  supply if the latter is not deionized.
Sometimes constituents in the effluent  originate  from  the  raw  water
supply.

    Table  18  shows  approximate  quantitative  values  for  a   typical
facility plating copper,  nickel, chromium,  and zinc (Plant 33-1)  with no
other  metal  plating  or  metal   finishing   operations   other   than
electroplating.   The  values  represent the combined raw waste effluent
assuming no treatment and include  both  chemicals  in  wastewater   from
rinses  and  concentrated solution dumps collected and metered uniformly
into the wastewater.  Good  chemical  treatment  will  oxidize  over  99
percent of the cyanide and normally remove 85 to 99 percent of the  heavy
metals.   The  other  constituents  in  the raw waste having much higher
solubilities  than  metal  hydroxides  are  usually  not  removed,    and
contribute to the total dissolved solids of the treated effluent.

    Some soluble constituents are adsorbed on the insoluble material and
removed  during  clarification.   The  concentration  of total dissolved
solids and the concentration of each soluble constituent depend  on  the
degree  of  water conservation used in the facility.  The concentrations
shown in Table 18 are considered representative  of  water  use  in  the
average electroplating facility.
                                  52

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   TABLE 18.   APPROXIMATE CONCENTRATIONS OF WASTEWATER CONSTITUENTS PRIOR TO
              TREATMENT FROM A TYPICAL FACILITY ELECTROPLATING COPPER,
              NICKEL,  CHROMIUM, AND ZINC (PLANT 33-1)
Estimated Analysis of Water
Untreated Wastewater Treated Effluent Supply
Concentration, Concentration, Analysis,
Wastewater Constituent mg/1 mg/1 mg/1
Copper (Cu+) or Cu2+)
Nickel (Ni+2)
Chromium (Cr3*)
(Cr6+)
(CrT)
Zinc (Zn2+)
Cyanide (CN~)
Sodium (Na~*~)
Potassium (K )
Carbonate (C032~)
Orthophosphate (PO^3 )
Pyrophosphate (P207^~)
Silicate (Si032~)
Metaborate (BO?3")
Perborate (B033~)
Sulfate (S042~)
Bisulfate (HS04)
Fluoride (F~)
Fluosilicate (SiF62~)
Tartrate (C4H4062~)
Chloride (Cl~)
Nitrate (N03~)
Wetting agents (organic)
Sequestrants
Chelates
Additives (organic)
Proprietary acid salts
6.7 0.23
2.4 <0.20
0.05 0.15
17 <0.05
17 <0.20
32 0.1
50 0.21
465 20
2.4
57
47 3.0 <0.01
53
50
36
1.3
19 20
3.7
0.1 0.1
0.5
8.9
228 25
1.4
6.8
6.5
6.5
0.5
32
Total dissolved solids
1150.
                                       53

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water   conservation   while   the  concentration  of  dissolved  solids
containing more innocuous materials increases.


Wastewater Constituents_and^Pararr\eters_of_Pollutional Significance

    The wastewater constituents of  pollutional  significance  for  this
segment of the electroplating industry include copper, nickel, chromium,
zinc, cyanide, suspended solids, and pH.   It is recommended that copper,
nickel,   chromium,  zinc,  and  cyanide  be  the  subject  of  effluent
limitations and standards of performance for the electroplating industry
regardless of the physical form (soluble or  insoluble  metal  *  5)   Or
chemical form (e.g., valence state of metal or type of cyanide complex).
All other heavy metals and chemical compounds in the wastewater that are
not yet specifically the subject of effluent limitations but which would
normally be precipitated during treatment for removal of copper, nickel,
chromium,  and  zinc are considered part of the suspended solids as well
as any chemical or biological material  adsorbed  or  entrapped  by  the
suspended  solids  during clarification and separation.  Thus, suspended
solids are a wastewater constituent of pollutional significance.

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.

    Thus,  the  major  chemical,  physical,  and  biological  wastewater
constituents and parameters of pollutional significance are as follows:

    Copper
    Nickel
    Chromium, hexavalent
    Chromium, total
    Zinc
    Cyanide, amenable to oxidation by chlorine 6
    Cyanide, total *
    Suspended solids
    PH

    Other   wastewater  constituents  of  secondary  importance  in  the
electroplating industry that are not the subject of effluent limitations
or standards of performance are as follows:

    Total dissolved solids
    Chemical oxygen demand
    Biochemical oxygen demand
    Oil and grease
    Turbidity
    Color
    Temperature

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Rationale for the^Selection^gf Wastewater Constituents and^Parameters


Copper

    Copper may be present, in significant amounts in the was tewater  from
this  segment  of the electroplating industry and is amenable to removal
by conventional chemical treatment techniques.


Nickel

    Nickel may be present in significant amounts in the wastewater  from
this  segment  of the electroplating industry and is amenable to removal
by conventional chemical treatment techniques.


Chromium, Hexavalent

    Hexavalent chromium may be present in  significant  amounts  in  the
wastewater  from  this  segment  of  the  electroplating industry and is
amenable to  removal  by  conventional  chemical  treatment  techniques.
Hexavalent  chromium  also  is  an  indicator of the effectiveness of an
important chemical reduction step to insure control of total chromium.


Chromium, Total

    Total  chromium  may  be  present  in  significant  amounts  in  the
wastewater  from  this  segment  of  the  electroplating industry and is
amenable to removal by conventional chemical treatment techniques.


Zinc

    Zinc may be present in significant amounts in  the  wastewater  from
this  segment  of the electroplating industry and is amenable to removal
by conventional chemical treatment techniques.


Cyanide, Amenable to Oxidation by Chlorine

    Oxidizable cyanide may be present  in  significant  amounts  in  the
wastewater  from  this  segment  of  the  electroplating industry and is
amenable to oxidation by chlorine under alkaline conditions.
                                  55

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Cyanide, Total

    Cyanide may be present in various forms and in  significant  amounts
in  the  wastewater  from  this  segment of the electroplating industry.
Cyanide and all cyanide compounds have been proposed as toxic pollutants
pursuant to Section 307 of the Act.   The relative difference in toxicity
between cyanide in various forms such as sodium cyanide,  copper  cyanide
complex,  nickel  cyanide  complex,   ferrocyanide  ion,  and cyanate ion
depends on the kinetics of dissociation under specified conditions which
cannot always be controlled after discharge of the effluent.


Suspended Solids

    Suspended solids was selected as a  parameter  to  insure  that  any
other  metal  or  combination  of  metals than those subject to effluent
limitations that might be present in the wastewater  from  this  segment
and  are  capable  of  being precipitated will be controlled.  Suspended
solids also measures clarification efficiency.

PH

    The pH was selected as a parameter to indirectly control the  amount
of soluble metal relative to total metal in the effluent.


Rationale_for_the_ select ion_of
Total Metal_as_A_Pollutant Parameter

It  is generally accepted that neutralization and precipitation of heavy
metals with no  subseguent  separation  is  insufficient  treatment  for
discharge   to   navigable  waters.    Removal  of  the  insoluble  metal
precipitate  from   the   effluent   is   reguired   by   sedimentation,
clarification, or filtering prior to discharge of the liquid effluent to
streams.   Apart  from  the  adverse visible appearance of effluent with
large amounts of  suspended  metal  hydroxides,  there  is  evidence  of
adverse  effects  on  aquatic life such as clogging of gills of fish and
covering of food supply on the bed of streams.  Also, large  amounts  of
metal  hydroxides in the stream are further sources of metal ions if the
water later becomes acidic  relative  to  the  pH  at  which  the  metal
hydroxides   were   originally   precipitated.   Therefore,  removal  of
precipitated  metal  hydroxides  by  efficient  clarification  prior  to
discharge of the effluent to navigable waters is assumed.

  •  With  removal  of  total  suspended solids to levels of less than 50
mg/lr significant removal of metal  hydroxides  occurs.   However,  some
portion  of  the  total suspended solids contains heavy metals either as
metal hydroxides or adsorbed metal ions.  Regardless of  the  form,  the
                                  56

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heavy  metal  content  of  suspended  solids  represents  a  significant
pollutant in the water.

    Heavy metals are considered  pollutants  regardless  of  form.   The
standard  method  of  analysis for total metal involves acidification of
the sample to analyze for total metal 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  heavy  metals  in  mg/liter  means  total  metal,  as
analytically determined by acid digestion prior to filtering.*
Rationale for Rejection ofBother
Wastewater Constituents_as Pollutants

     Metals

    The  rationale for rejection of any metal other than copper, nickel,
chromium, and zinc as a pollutant  is  based  on  one  or  more  of  the
following reasons:

    (1) They would not be expected to be present in
        electroplating wastes from copper, nickel,
        chromium, and zinc plating processed in
        significant amounts  (e.g., uranium,
        mercury, arsenic), or

    (2) They will be removed simultaneously by
        coprecipitation and clarification along
        with copper, nickel, chromium, and/or zinc
         (e.g., iron) , or

    (3) They will be the subject of effluent
        limitations developed for other segments
        of the electroplating point source category.
         (e.g., electroplating of cadmium, tin,
        lead, silver, gold, platinum, palladium,
        iron, cobalt, and other metals and alloys)
        or

    (4) Insufficient data exists upon which to base
        effluent limitations and standards
        of performance.


Dissolved solids
                                  57

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    Dissolved solids  is  not a  significant  pollution  parameter    in
this   industry.       Although the  concentration  of  total  dissolved
solids  will become higher as efforts are directed to reducing water use
and volume of effluent  discharcred,  the  total  quantity  of  dissolved
solids will remain unchanged.
Chemical Oxygen Demand

    Chemical  oxygen  demand  is  not  an  important  parameter  in  the
electroplating  industry because cyanide is controlled independently and
the quantity of organic compounds or oxidizable inorganic  compounds  in
the wastewater is very low.
Biochemical Oxygen Demand

    Biochemical  oxygen  demand  is  usually  not an important pollution
parameter in the electroplating industry.   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 electroplating wastes
prior to treatment, BOD would be considered a major parameter.


Oil and Grease

    Oil and grease is not normally a significant pollution parameter  in
the  electroplating  industry  because  these materials are removed from
workpieces by nonaqueous solvents.  Added pollution reduction is usually
achieved by the usual practice of installing oil and grease skimmers  on
settling tanks.  Where such control practices are absent,  oil and grease
might be considered a parameter subject to control and treatment.


Turbidity

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


Color

    Color  is  not usually significant in wastewater from electroplating
and is indirectly controlled by the effluent  limitations  on  suspended
                                  58

-------
solids  and  on total metal which controls the amount of colloidal metal
that could color the effluent.


Temperature

    Temperature is not considered a significant pollution  parameter  in
the  electroplating  industry.   However,  cooling  water  used  to cool
plating process tanks and/or evaporative recovery systems that  are  not
subsequently used for rinsing could contain pollutants from leaks in the
system.
                                  59

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                              SECTION VII

                    CNTROLAND_TR EATMENT TECHNOLG Y
    The  control  and -treatment technology for reducing the discharge of
pollutants  from  copper,  nickel,  chromium,  and  zinc  electroplating
processes is discussed in this section.

    The   control   of   electroplating   wastewaters  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  this
industry.

    The  treatment of electroplating wastewaters includes all techniques
for the removal of pollutants and all techniques for  the  concentration
of  pollutants  in  the wastewaters for subsequent removal by treatment.
Although all of the treatment technologies discussed have  been  applied
to  electroplating  wastewaters,  some  may  not  be  considered  normal
practice in this industry.

    Chemical Treatment Technology is discussed  first  in  this  section
because  treatment  of  all  water  waste generated by electroplating is
required, prior to water discharge into navigable streams,  irrespective
of  the  in-plant controls adopted for reducing waste.  Nevertheless, it
is emphasized that the amount  of  pollutants  discharged  to  navigable
waters is directly proportional to the volume of water discharged.

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

Chemical Treatment Technology


Applicability

    Chemical  treatment  processes  for  waste water from electroplating
operations are based on chemical reactions  utilized  for  25  years  or
more.   A  system  has  evolved  that is capable of effectively treating
effluents from plants of any size and reducing metal ion  concentrations
in  the  effluent to 1.0 mg/liter or less.  Control procedures have been
devised to maintain the effectiveness of the process under a variety  of
operating conditions.
                                  60

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Processes

Sep.aration_of_ Streams.  The rinse waters are usually se gated into three
streams  prior to treatment, and consist of 1) those containing chromium
VI, 2)  those containing cyanide,  and  3)  the  remainder,  constituting
water  from  acid  dips,  alkali cleaners, acid copper, nickel, and zinc
baths,  etc.  The cyanide is oxidized by  chlorine  and  chromium  VI  is
reduced  to  chromium  III with sulfur dioxide or other reducing agents.
The three streams  are  then  combined  and  the  metal  hydroxides  are
precipitated  by  adjustment  of  the pH.  The hydroxides are allowed to
settle out, often with the help of coagulating agents, and the sludge is
hauled to a lagoon or filtered and used as  land  fill.   The  treatment
facilities  may  be  engineered  for  batch,  continuous,  or integrated
operation. (7)
2§tch_Treatment •  The batch  method  is  generally  used  for  small  or
medium- sized  plants.   Batch  treatment  is  useful  not only for rinse
waters but for  process  solutions  containing  high  concentrations  of
chemicals  such  as  floor spills.  Holding tanks collect the wastewater
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  bean
obtained.
                        Tne  chemical  treatment  process  may  be  made
continuous  by  (1)   sizing  and  baffling  treatment  tanks  to provide
sufficient hold times to  complete  chemical  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 continuous-overflow settling tank that allows sludge
to be pumped off periodically through the bottom.

    A  diagram  of  a  continuous-treatment  plant  operaing  at maximum
capacity is shown in Figure 4.  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  they  are
transferred to a holding tank and added slowly to the dilute stream.  In
this  manner,  sudden  demands on the reagent additions and upsetting of
the treatment conditions are avoided.   The  dilute  acid-alkali  stream
first  enters a surge tank to neutralize the wastewater and equalize the
composition entering the precipitation tank.  The hexavalent chromium is
reduced at a pH of 3.5,  and  the  addition  of  the  SO2  and  HC1  are
controlled  by suitable monitors immersed in the well-agitated reduction
tank.  Cyanide is destroyed in a large tank with compartments to allow a
two-stage reaction.   Reaction time is about 3 hours.
                                  61

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    The treated chrome, cyanide,  and neutralized acidalkali streams  are
run into a common tank where pH is automatically adjusted to and held at
8.8.   The  stream  then  enters   a  solids  contact  unit where mixing,
coagulation,    flocculation,    recirculation,    solid     separation,
clarification,  solids  concentration,   sludge  collection,  and  sludge
removal are accomplished.  Flocculants are continuously  added  to  this
tank.   Typically,  residence  time  is 2 hours.  The effluent from this
tank constitutes the discharge from the plant.


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      1.0
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FIGURE  6.   SOLUBILITY OF  COPPER, NICKEL, CHROMIUM,
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                             65

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Unit Operations

Precipitation.  The effluent levels of metal ions attainable by chemical
treatment  depend  upon  the  insolubility  of  metal  hydroxides in the
treated  water  and  upon  the  ability  to  mechanically  separate  the
hydroxides  from  the process stream.  Soluble concentrations of copper,
nickel, chromium, and zinc as a function of pH are shown  in  Figure  6,
taken  from  data  published  by  Pourbaix.(8)    At  a  pH  of  9.5, the
solubility of all four metals is of the order  of  0.1  mg/1,  or  less.
Experimental  values  of  Schlegel (9)  have been plotted In Figure 7 and
vary somewhat from the theoretical values of  Figure  6.   Nevertheless,
the   need   for  fairly  close  pH  control  in  order  to  avoid  high
concentrations of dissolved metal in the effluent is evident.  A  pH  of
8.5 to 9.0 is best for minimizing the solubility of copper and zinc, but
a  pH  of 9.5 to 10.0 is optimum for minimizing the solubility of nickel
and chromium.  To limit the solubility of all four  metals  in  a  mixed
solution, a pH of 9.0 appears best.

    The  theoretical  and  experimental results do not always agree well
with results obtained in practice.  Concentrations can be obtained  that
are  lower  than  the above experimental values, often at pH values that
are not optimum on the basis of the above  considerations.    Effects  of
coprecipitation  and  adsorption on the flocculating agents added to aid
in settling the precipitate play a  significant  role  in  reducing  the
concentration  of the metal ions.  Dissolved solids made up of noncommon
ions can increase the solubility of the metal  hydroxides  according  to
the   DebyeHuckel   Theory.   In  a  treated  solution  from  a  typical
electroplating plant, which contained 230 mg/1  of  sodium  sulfate  and
1060 mg/1 of sodium chloride, the concentration of nickel was 1.63 times
its   theoretical   solubility   in   pure   water.    Therefore,   salt
concentrations up to approximately 1000  ppm  should  not  increase  the
solubility  more  than 100 percent as compared to the solubility in pure
water.  However, dissolved solids concentrations of several thousand ppm
could have a marked effect upon the solubility of the hydroxide.

    when solubilizing complexing agents  are  present,  the  equilibrium
constant  of  the  complexing  reaction  has to be taken into account in
determining theoretical solubility with the result that  the  solubility
of the metal is generally increased.  Cyanide ions must be destroyed not
only  because  they  are  toxic  but also because they prevent effective
precipitation of copper and zinc as hydroxides.  If cyanide is  replaced
in a plating bath by a nontoxic complexing agent such as EDTA (ethylene-
diamine-tetraacetic  acid),  the new complexing agent could have serious
consequences upon the removal of metal ions by precipitation.


§2ii
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  O.I
                                                   Zinc
   Legend
O  Nickel
D  Chromium
X  Zinc
A  Copper
                                                      Note : Values plotted as O.I mg/l
                                                           were reported as zero. The
                                                           O.lmg/X value is assumed
                                                           to be the detectable limit.
                                    8       9       10
                                      Solution  , pH
      12
13      14
FIGURE 7.  EXPERIMENTAL VALUES - SOLUBILITY OF METAL IONS AS
              A FUNCTION OF pH
                                         67

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chromium.(10)  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  freguently  added  to  the clarifier of
chemical waste-treatment plants in plating installations.   Flocculat~on
and  settling are further improved by use of polyelectrolytes, which "sr^
high molecular weight polymers containing several ionizable  ions.    DUP
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 clarifiers has been improved through many
years  of  experience, no settling technique or clarifier is 100 percent
effective;  some of the floe is found in the effluent - typically  10  to
20  mg/liter.   This floe could contain 2 to 10 mg/1 of metal.  Polishing
filters  or  sand  filters  can  be  used  on  the  effluent   following
clarification  but this is not commonly done.  The effectiveness of such
filtering has not been ascertained.


Sludge _Disggsal.  Clarifier • underflow or "sludge" contains;  typically  1
to  2  percent  solids  and can be carried to a lagoon.  Run-off through
porous soil to ground-water is objectionable  since  precipitated  metal
hydroxides  tend  to  get  into  adjacent  streams or lakes.  Impervious
lagoons require evaporation into the atmosphere;  however,  the  average
annual   rainfall   just   about   balances   atmospheric   evaporation.
Additionally,   heavy  rainfalls  can  fill  and  overflow  the   lagoon.
Lagooning  can  be  avoided by dewatering the sludge to a semidry or dry
condition.

    Several devices are available for dewatering sludge.  Rotary  vacuum
filters  will  concentrate sludge containing 4 to 8 percent solids to 20
to 25 percent solids.  Since the effluent  concentration  of  solids  is
generally  less  than  4 percent a thickening tank is generally employed
between the clarifier and the filter.  The filtrate  will  contain  more
than  the  allowed  amount  of suspended solids, and must,, therefore, be
sent back to the clarifier.

    Centrifuges  will  also  thicken  sludges  to  the  above  range  of
consistency  and  have  the  advantage  of  using less floor space.  The
effluent contains at least 10 percent solids  and  is  returned  to  the
clarifier.
                                  68

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    Pressure  filters  may  be  used.  In contrast to rotary filters and
centrifuges, pressure filters will produce a filtrate with less  than  3
mq/1  of suspended solids so 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 2.04 to
2.44 liters/min/sq m  (0.05 to 0.06 gpm/sg ft)  of clarifier sludge.

    Solids contents from 25  to  35  percent  in  filter  cakes  can  be
achieved  with  semi-continuous  tank  filters  rated  at 10.19 to 13.44
liters/min/sg m (0.25 to 0.33 gpm/sq ft)  surface.  A solids  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 with 40 to  50  percent
dry  solids and a filtrate with less than 5 mg/1 total suspended solids.
Because automation of these presses is difficult, labor costs tend to be
high.   The  o#erating  costs  are  partially  off-set  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 total suspended
solids.  The filtration rate is approximately 2.04 liters/min/sq m (0.05
gpm/sq ft) filter surface area.   Pressure  filters  can  also  be  used
directly  for  neutralized  wastes  containing  from  300  to  500  mg/1
suspended solids at design rates of 4.88 to 6.52 liters/min/sq  m  (0.12
to  0.16  gpm/sq  ft)  and  still  maintain  a low solids content in the
filtrate.


Filter cakes can easily be  collected  in  solid  waste  containers  and
hauled  away to land fills.  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 material is dumped.


    Several  companies  have  developed  proprietary  chemical  fixation
processes  which  are  being  used  to  solidify  sludges  prior to land
disposal.  In contrast to filtration, the amount of dried sludge  to  be
hauled  away  is  increased.   Claims  are  that  the  process  produces
insoluble metal ions so that in leaching tests only a fraction of a part
per million is found in s61ution.  However, much information is  lacking
on the long term behavior of the "fixed" product, and potential leachate
problems  which  might  arise.   The  leachate  test data and historical
information to date indicate that  the  process  has  been  successfully
applied  in the disposal of polyvalent metal ions and it apparently does
have  advantages  in  producing  easier  to  handle  materials  and   in
eliminating free water.  Utilization of the chemical fixation process is
                                  69

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felt  to be an improvement over nu,ny of the environmentally unacceptable
disposal methods  now  in  common   usage  by  industry.    Nevertheless,
chemically   fixed  wastes  should  be  regarded  as  easier - to - handle
equivalents of the raw wastes and the same precautions and  requirements
required for proper landfilling of raw waste sludges should be applied.
    The  possibility  of recovering metal values from sludges containing
copper, nickel, chrome, and zinc has  been  considered(12)   but  such  a
system  appears to be uneconomic under present circumstances.   It may be
profitable to recover metal values if 900 to 2300  kg  (2,000  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 modifications, 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.


Practical-_Operating_Systems.  Relatively few plating installations  have
installed  filters,  although  the  problems  of disposing of unfiltered
sludge should provide an impetus for use of more filters in the  future.
Plant  12-8  has  a  large  rotary  filter in routine operation, and the
practicality of this unit has been well established.  The Chemfix system
is in use at several plants.


Demonstratign_Status.  Centrifuges are used for  dewatering  sludge  in
the  new  waste  treatment  facility  at  Plant 11-22.
Cy_ani.de	Oxidation.   Cyanide  in  wastewaters  is commonly destroyed by
oxidation with chlorine or hypochlorite prior to  precipitation  of  the
metal  hydroxides.   The  method  is simple, effective, and economically
feasible even for small volume installations.  A comprehensive study  of
the  method  was  made  by Dodge and Zabban(10-13),  the results of which
have been used to work out the practical processes.   The  following  are
proposed reactions for chlorine oxidation:


     (1)  NaCN + C12—>CNC1 + NaCl
                                  70

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    (2)   CNCl «• 2NaOH-»-NaCNO + NaCl +  H2O

    (3)   2NaCNO + 3C12 * 4NaOH-*-N2 + 2CO2 + 6NaCl * 2H2O.


    Reaction  (2)  goes rapidly at pH 11.5, under which conditions, build
up of the toxic gas CNCl by  Reaction   (1)  is  avoided.   Treatment  of
dilute  rather than concentrated solutions also minimizes its formation.
Oxidation to  cyanate  (NaCNO)   is  completed  in  5  minutes  or  less.
Reaction  (3)  goes  more  slowly, requiring an hour in the preferred pH
range of 7.5 to 9.0,  and  a  longer  time  at  higher  pH.   After  the
conversion  to nitrogen and carbon dioxide, excess chlorine is destroyed
with sulfite or thiosulfate.

    Sodium hypochlorite may  be  used  in  place  of  chlorine.   Recent
technical innovations in electrochemical hypochlorite generators for on-
site  use (17)  raise  the  possibility  of  controlling  the addition of
hypochlorite to the 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.(18)   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  effecient
system.    In addition to the oxidation of cyanide at the anode, valuable
metal can be  recovered  at  the  cathode.   The  process  becomes  very
inefficient  when  the cyanide concentration reaches 10 ppm, but at this
point the solution can be 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  the  cyanide to the same 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 + 2NaOCl—^. 2NaCNO + 2NaCl
    2NaCN + SNaOCl + H2O—>- 2CO2+ N2 + 2NaOH + SNaCl.
                                  71

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    The Cynox process, based on the above principles, produces 1  kg  of
active  chlorine per 5,5 KwH.(19)   Equipment needs are the same with the
exception that the tanks must be lined and graphite or platimized anodes
must be used.

    Polysulfide-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  nv.i/1
during  two weeks of 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  solution  can  be  improved  by
increasing  the  electrode  area.    Area can be increased by filling the
space between flat  electrodes  with  carbonaceous  particles. (20)    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(21,22),  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 (23) , and at least  two  units  were
put  in  operation.   The most recent information on these units is that
they are not operating and that at present the units are not being sold.

    Ozone will oxidize cyanide (to cyanate)  to below  detectable  limits
independent  of the starting concentration or of the complex form of the
cyanide(24,25,26).  The reaction can be completed  even  with  the  very
stable  iron  complexes if heat or ultraviolet light is used in conjunc-
tion with the ozone.  The potential advantages of  ozone  oxidation  are
enhanced  by  the efficiency and reliability of modern ozone generators,
and development work is continuing.

    A method employing thermal decomposition for cyanide destruction has
been recently announced.(27)  Cyanide solution is 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 is discussed later in this section,,

    Precipitation   of   cyanide   as   ferrocyanide  is  restricted  to
concentrated wastes. Ferrocyanide maybe less toxic than cyanide, but  is
converted back to cyanide in sunlight.    Treatment  is  accomplished by
                                  72

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adding an amount in excess of stoichiometry  (2.3 kg of Feso4 per  kg  of
cyanide).   Large  amounts  of  sludge  are  produced  which  add to the
pollution load.  Complex cyanides do not  break  down  readily  and  the
reaction  stops  when  a concentration of 10 mg/1 of cyanide is reached.
No benefits can be foreseen  in  terms  of  reducing  waste  volume  and
concentration.

    Cyanide is also destroyed by reaction with polysulfides.  Reasonable
reaction  rates  are obtained only if the solution is boiled.  Since the
reaction does not destroy  all  of  the  cyanide  further  treatment  is
necessary.


Reduction^of Hexayalent^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
trivalent  hydroxide  which  precipitates  under  alkaline   conditions.
Typical reactions for SO2 reduction are as follows:


    SO 2 + H2O -*- H2SO3

    2H2CnO4 + 3H2SO3 —9- Cr2 (SO4) 3 + 5H2O.


    Representative  reactions for reduction of hexavalent chromium under
acidic conditions using sulfite  chemicals  instead  of  SO2  are  shown
below:

    (a)  Using sodium metabisulfite with sulfuric acid:

HH2Cr04 + 3Na2S2O5 + 3H2SOi—>-3Na2SO4 + 2Cr2 (S04) 3

+ 7H2O

    (b)  Using sodium bisulfite with sulfuric acid:

    4H2CrOH + 6NaHSO3 + 3H2SO4 —>-3Na2SOt» + 2Cr2 (SO4) 3

+ 10H20

    (c)  Using sodium sulfite with sulfuric acid:

    2H2CrOU + 3Na2S03 + 3H2SO4—»^3Na2SOU + Cr2(SOU)3

+ 5H2O.
                                  73

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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.

    Hexavalent  chromium can also be reduced to trivalent chromium in an
alkaline environment using sodium hydrosulfite as follows:
    2H2Cr04 •*• 3Na  S0  + 6NaOH-* 6NaS0  + 2Cr
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.


    2H2Cr04 + 3N2H2   Na2COj   2Cr (OH) 3 + 3N2 + 2H20.


Sodium   hydrosulfite  or  hydrazine  are  frequently  employed  in  the
precipitation step of the  integrated  system  to  insure  the  complete
reduction  of  any hexavalent chromium tha  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:

    2Cr03 + 6FeSo4 7H2O + 6H2SO4 —»~ 3Fe2 (SO4) 3 + Cr2(804)3

+ 48H20.


    Cr+6may be reduced at a  pH  as  high  as  8.5  with  a  proprietary
compound.(28)    It  is  not  necessary  to segregate chrornate-containing
wastewaters 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+6 ions may be reduced electrochemically.(26) concentration of 100
mg/1  was  reduced  to  less than 1 mg/1 with a power consumption of 1.2
kwh/1,000  liters.   The  carbon  bed  electrolytic  process  previously
described  for  cyanide (24)  may  also be used for chromate reduction in
acid solution and Plant 30-1 has achieved a Cr+6  concentration  of  .01
mg/1  using  this method.  Electrolysis may also be used to regenerate a
reducing  agent.   A  process(27)  has  been  described  involving   the
reduction  of  Fe(III)  to Fe(II) electrochemically and the reduction of
                                  74

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Cr (VI)  by Fe(II).  The method should be capable of achieving low  Cr (VI)
levels.

    The  simultaneous  reduction  of  Cr+6  and oxidative destruction of
cyanide finds limited  application  in  waste-treatment  practice.   The
reaction requires mixing of Cr+6 and CM- in ratios between 2 and 3 using
Cu+2  as  a  catalyst in concentrations of 50 to 100 mg/1.  The catalyst
introduces additional pollutant into the waste stream.   Reaction  rates
are   generally   slow,  requiring  from  6  to  24  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  water  volume  and
pollution  reduction.  Destruction is not as complete as obtained by the
more common chemical methods.


Practical Operating Systems

    Chemical treatment is 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.
    The  effectiveness  of  chemical treatment techniques depends 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.  The concentration of an individual
pollutant in the solution being treated  has  no  effect  on  its  final
concentration  after treatment.  On the other hand, effective removal of
heavy metal pollutants is inhibited by some types of chelating ions such
as tartrate or ethylene diamine tetracetate ions.
                                  75

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    The concentrations of heavy 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  19.   concentrations  lower  than those listed as
maximum  in  Table  19  were  reported  by  companies  using  all  three
(continuous,  batch,  and  integrated)   treating systems.   The data show
that the soluble concentration levels  achieved  in  practice  are  near
those  that  would  be  expected  based  on  solubility  data  discussed
previously.

    Higher-than-normal concentrations of copper, nickel,  chromium,  and
zinc,  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  hydrates.   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 conand 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.
          Solids.  The suspended solids discharged after  treatment  and
clarification  sometimes contribute more copper, chromium,  and zinc than
the soluble metal concentrations, as shown in Table  19.   For  example,
the  copper  contribution from the total suspended solids determined for
four plants engaged in copper, nickel,  chromium, and zinc electroplating
was in the  range  of  0.02  to  0.76  mg/1.   Zinc  contributions  from
suspended  solids  ranged  from  0.03  to  0.80 mg/1.  The total copper,
nickel, chromium, and zinc content in suspended solids was equivalent to
as much as 2.04 mg/1, in comparison with a  maximum  of  L.45  mg/1  for
these metals in the soluble form.

    The  concentration  of  total  suspended  solids  in  the endof-pipe
discharge from typical chemical treatment operations ranged from  20  to
24  mg/1.   Maintaining  conditions  so  as  not to exceed these amounts
requires (1)  a properly designed settling  and/or  clarifying  facility,
                                  76

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(2) effective use of flocculating agents, (3)  careful removal of settled
solids,  and  (U)  sufficient  retention  time for settling.  Of course,
minimum retention time depends on the facility  size  and  In  practice,
this  time  ranges  from  about 2 to 8 hours for plants that are able to
reduce suspended solids to about 25 mg/1.   Even  so,  this  achievement
requires very good control of feeding flocculating agents.


Precipitation of Metal Sulfides
                 The  sul fides of copper, nickel, and zinc are much less
soluble than their corresponding hydroxides.  In  neutral  solution  the
theoretical  concentration  of  metal  ions should be reduced by sulfide
precipitation as follows:

    Copper 10~18 mg/1; Nickel 10"8  mg/1; Zinc   10~7  mg/1


Precipitation using hydrogen sulfide or soluble sulfides (Na2s)  involves
toxicity problems with the excess reagent used.  However, a  system  has
recently  been developed that provides for sulfide precipitation without
the toxicity problems. (31)   It should  be  applicable  to  treatment  of
effluent from electroplating operations.


Process PrinciBles_and_Eguigmerit

    Ferrous  sulfide, which has a higher solubility than the sulfides of
the metals to be precipitated is used as the

precipitating reagent.  However, the solubility of  ferrous  sulfide  is
still  so  small (10-5 mg/1 of sulfide ion) that the toxicity problem is
eliminated.  Freshly precipitated ferrous sulfide is most  reactive  and
is  obtained  by adding an excess of a soluble sulfide for precipitating
the metals to be removed from the effluent and  then  adding  sufficient
soluble  ferrous  salt to precipitate all excess sulfide ion.  The pH is
normally adjusted to the range  of  7  to  8,  prior  to  precipitation.
Hexavalent  chromium  that  may  be present is reduced to Cr(III)  by the
ferrous iron and immediately precipitated as the hydroxide.   Therefore,
no  extra  precipitation steps are necessary to remove the chromium.  If
the extra ferrous ions in solution are considered undesirable  they  may
be  oxidized  to  Fe (III)  which  will  precipitate  as  the  hydroxide.
However, removal of iron would not be possible until after  the  sulfide
precipitates  had  been  separated  from  the  liquid.  In principle, it
should be possible to  precipitate  metallic  sulfides  from  metal  ion
complexes  that  are  not  amenable  to  chemical treatment by hydroxide
precipitation, due to the lower solubilities of the  sulfides.   It  has
been  demonstrated  that copper can be effectively precipitated from the
ammonia complex.

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Practical Operating Systems

    No practical system is in operation.


Demonstration Statug

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


Combined  Metal  Precipitation  and  Cyanide  Destruction


Applicability..        This    process (32)   is  applicable  to  zinc  and
cadmium  cyanide  solutions.   The  metal  hydroxide is precipitated and
cyanide is decomposed.  Applicability depends upon deciding whether  the
products  of  cyanide  decomposition  are suitable for discharge or not.
The effluent is considered suitable for discharge to sewers

in some states and may be acceptable in certain areas for  discharge  to
streams. A modification of this  process  may  be  applicable  to copper
cyanide.


Process_Princip_les_and_Eguip_inent

    Cyanide in zinc and cadmium plating baths is destroyed by a  mixture
of formalin and hydrogen peroxide according to the formula:

    CN- + HCOH + H2O2 + H20    CNO- + NH4

+ H2C(OH)COHN2 glycolic acid amide.

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 be carried out  on  a  batch  or
continuous  basis,  and  is  particularly convenient for the small shop.
Figure 8 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  installed  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 20 shows an analysis  of  the
products for decomposing 794 ppm of cyanide.
                                  79

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FIGURE 8.  BATCH TREATMENT OF CYANIDE RINSE WATERS  BY
           COMBINED METAL PRECIPITATION AND CYANIDE
           DESTRUCTION
                           80

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TABLE 20.  DECOMPOSITION PRODUCTS OF CYANIDE IN RINSE
           WATER(1) FROM A CYANIDE ZINC ELECTROPLATING
           OPERATION AFTER TREATMENT WITH
           PEROXYGEN COMPOUND
   Products Formed
    by Treatment
Cyanate

Ammonia (free)
  Dissolved
  Volatilized

Combined Ammonia
  Calc'd as NH3
  Calti'd as glycolic
    acid amide
                Amount Formed
        Actual
          ppm
          351
           57
           32
           95

          419
Cyanide Equivalent
  ppm     percent
  265
  164
   91
  274
33
21
11
35
                                      794
                              100
* 'Analysis of water before treatment:
     Cyanide      794 ppm
     Cyanate^
     Ammonia^
336 ppm
 41 ppm.
   Cyanide calculated as NaCN, cyanate as NaOCN, and
   ammonia as NH
                3*
                           81

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Practical	Operating	Sy_stems_.    This process is being used in approxi-
mately 30 installations.


Water^cgnservation Through Control Teghnology

    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 counterflow rinse tanks and  ion-
exchange,  evaporative  recovery,  or  reverse  osmosis  systems.  Other
systems that may accomplish water conservation  are  freezing,  electro-
dialysis,  electrolytic  stripping, carbon adsorption, and liquid-liquid
extraction.


Process Modifications

    Wastes from electroplating operations can sometimes  by  reduced  by
the following changes in electroplating processes:

    (1)   Elimination  of  copper  prior to nickel and chromium plating,
especially for plating on steel.

    (2)  Elimination of copper by increasing the thickness of nickel.

    (3)  Substitution of  a  nickel  strike  for  a  copper  strike  and
replacing  the  highrate  copper  cyanide solution with a copper sulfate
bath.

    (4)  Substitution of low-concentration electroplating solutions  for
highconcentration baths.

    Metals  remaining  in  solution  after  chemical  treatment  of  the
effluent from a plant plating decorative copper,  nickel,  and  chromium
can be reduced in amount by eliminating the copper.  Some steel products
can  be  plated  directly  with nickel and chromium, especially when the
quality of the steel surface is improved.  A better grade of steel or  a
change  in  mechanical finishing methods to reduce surface roughness can
sometimes justify the elimination of  copper  without  sacrificing  high
specularity.  To maintain good corrosion resistance  on  steel  products
and  eliminate  copper, it may be necessary to increase the thickness of
the nickel or install duplex nickel in place of bright nickel, which  is
much  better  than a single layer of bright nickel for providing maximum
                                  82

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    corrosion resistance.  To maintain a high degree of specularity  in  the
    absence of a copper plate, leveling nickel is recommended.

        The  substitution  of  a  nickel strike for a copper strike has been
    adopted in several plants plating  nickel  and  chromium  on  steel.   A
    copper  sulfate  solution is then utilized after nickel striking in some
    cases.  This change avoids copper cyanide baths and the  attendant  need
    for  oxidizing cyanide in the treatment system and has been particularly
    successful for steel products.

f        Substitution of low-concentration electroplating 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 electroplated 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  reduction  in  rinse  water  requirements  is  achieved.
    Wastewater  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  wastewater  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.

    Materials Substitutions

        Noncyanide  solutions, which have been developed for copper and zinc
    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 noncyanide 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
                                      83

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reduction of wastewater 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,  this  process  modification   may
ultimately  prove  to be significant for reducing waste treatment costs.
No details have been released on the treatment required  for  minimizing
the soluble chromium concentration in treated effluent, however.


Good Housekeeping Practices

    Good  housekeeping  practices  that  reduce  the  waste generated in
electroplating 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 solution.  (3)  Plug all floor exits  to
the  sewer  and  contain  spills in segregated curbed areas or trenches,
which can be drained to direct  the spills to rinse water  effluent  with
the same chemicals.

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

    (H)  Wash all filters, pumps and other auxiliary equipment in curbed
areas or trenches, which can be drained to 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  wastewater  flow,
    including piping from fume  scrubbers.


Water Conservation by Reducing Dragout


Dragout.  Dragout is defined as solution on the workpiece carried beyond
the edge of the plating tank.  The dragout of concentrated solution from
the  plating  tank  can  vary  over  a wide range depending on the shape

-------
factor of the part.  A value of 16.3 liters/1000 sq m (0.4  gal/1000  sq
ft)(33)   is  considered  a  minimum  for  vertical  parts  that are well
drained.  The practical range for parts of various shapes that are  well
drained is about 40 to 400 liters/sq m  (1 to 10 gal/1000 sq ft).


Dragout	Reduction.   Water  used  for  rinsing  can be conserved by (1)
improving the racking procedure to improve drainage from  surfaces  over
the  process  tank,  prior to transfer to the subsequent rinse tank, (2)
increasing the drainage time over the process  tank,  (3)   reducing  the
viscosity  of  the  process  solution  by  diluting it or increasing its
temperature, (4) adding a wetting  agent  to  the  process  solution  to
reduce  surface  tension,  (5)   installing fog nozzles above the process
tank to return a part of the solution remaining on work surfaces to  the
process  solution, and (6)  installing a drip-save  (reclaim)  tank between
the process and rinse stations to collect dragout that is pumped back to
the process solution.  A mixture of air and water  is  utilized  in  one
version  of a fog nozzle claimed to be especially effective for removing
most of the solution from surfaces lifted above process tanks.  With the
above techniques, the water needed for rinsing can be reduced as much as
50  to  60  percent.   Detailed  comments  on  these  dragout  reduction
techniques appear in Reference 34.

    Reduction of dragout with the above methods is not without problems.
By  returning chemicals to the plating tank, impurities tend to build up
in the plating 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

    When  effective  chemical treatment exists, reduction in pollutional
load can be accomplished by reducing the water use in the facility.  The
principal water use is for rinsing.  Use of only that water  needed  for
effective  rinsing  based  on  dissolved  solids  would  represent  good
practice.

    Water conservation procedures that are used after processed work  is
transferred  to  a  rinse tank include  (1)  adding a wetting agent to the
rinse  water,   (2)  installing  air  or  ultrasonic  agitation  and  (3)
installing counterflow 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, with equivalent rinsing effectiveness.
Use of conductivity meters in the final rinse provides automatic control
of  water  use  according  to  need.   Rinse  water  flow  is  shut  off
                                  85

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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 by
a savings in water (and sewer)  charges.  Further incentive  is  provided
when regulatory agencies reguire pollutional control.  When

end-of-process  chemical  treatment  is  used,  design of wastetreatment
facilities usually indicates the economic advantage of  reducing  rinse-
water flow by installing two or more counterflow 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.
In the case  of  an  overdesigned  installation,  it  is  probably  more
economical  to  reduce rinse water usage by use of good rinsing practice
than to increase water-treatment facilities in the event of an  increase
in production.

    Rinsing  can  be  carried  out beyond the point consistent with good
practice, even though there is an economic incentive to saive water.  The
result is unnecessary pollution.  Typical concentration levels permitted
in the rinses following various process tanks, should not  be  decreased
unless  definite  quality  problems can be associated with the dissolved
solids  concentrations   listed   below   for   representcitive   rinsing
systems:(35)


                                 Max Dissolved Solids
    	Process	            in Final Rinse,, mg/1

    Alkaline cleaners                    750
    Acid cleaners, dips                  750
    Cyanide plating                       37
    Copper plating                        37
    Chromium plating                      15
    Nickel plating                        37
    Chromium bright dip                   15
    Chromate passivating               350-750

    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
liters   (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
                                  86

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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:

                              r   =   (CO/CF)n

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),
                                 1

                    r  =   (CO/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 CF valuesgiven above for a nickel
bath are as follows:


         Rinse_Combination                Rinse^Ratio^ r

Single rinse                                   7300
Two rinses, parallel feed                       171
Three rinses, parallel feed                      58.3
Two rinses, counterflow feed                     85.5
Three rinses, counterflow 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 counterflow.  Counterflow rinse
tanks increase the concentration of a metal or  another  constituent  in
the  first  rinse tank following the plating or process bath.  The water
in the first rinse tank can be used to  supply  make-up  water  for  the
plating  bath.   As the concentration in the first rinse tank increases,
more of the drag-out from the plating bath can be returned to  the  bath
in  the  make-up 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.

    The  rate  of  evaporation  from  the  plating  bath  is a factor in
determining how much make-up water must be added.  Operating a bath at a
                                  87

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higher temperature will allow more of the drag- out to be returned to the
bath  because  of  the  higher  rate  of  evaporation.    However,   the
temperature at which a bath may be 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 (36)  which allow bath operation at 50 C (120 F)  as compared  to
32  C  (90 F)  for baths using older aldehyde-type brighteners.  Thus, the
new brighteners 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.


Water Conservation by Ion Exchange
                Ion  exchange  is  currently  a  practical  commercially
accepted  method  for  the  in-process  treatment  of (1)  raw water, (2)
plating baths, and  (3)  rinse waters.  Raw water is  treated  to  provide
de-ionized  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  economically 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 electroplating rinse waters.


Advantages  and __ Lim itat i oji s .   Some  advantages  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
         plating chemicals.

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

     (3)  Ion exchange concentrates plating  bath  chemicals  for  easier
         handling  or  treatment  or  subsequent  recovery  or  disposal
         operations.
                                  88

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

    (1)    The  limited  capacity  of  ion-exchange  systems  means  that
relatively large installations are necessary  to  provide  the  exchange
capability needed between regeneration cycles.

    (2)     Ion-exchange   systems  require  periodic  regeneration  with
expenditures for regenerant chemicals.  Unless regeneration  is  carried
out  systematically, leakage of undesirable components through the resin
bed may occur.   In  addition,  the  usual  treatment  methods  must  be
employed to dispose of the regenerated materials.

    (3)    Cyanide  generally  tends  to  deteriorate the resins, so that
processing of cyanide effluents  (except for very dilute solutions)   does
not appear practical at the present time.

    (4)    Resins  slowly  deteriorate  with  use  and  the  products  of
deterioration can contaminate the water.


Process_Princi.2les_and_Egui2S3ent.  Ion 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 wastewater, 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
9,  which  is a generalized schematic presentation of the application of
ion  exchange  to  treatment  of  electroplating  effluents.(37,38)    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  by
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 rinse water  or  other
solution being treated.  This process continues until the solution being
                                  89

-------
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9 gpm





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                         Deionized water
FIGURE  10.   SCHEMATIC PRESENTATION OF ION-EXCHANGE OPERATION
             AT PLANT 11-8

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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  9,  the
ion-exchange  process  can  be   applied  continuously   by  utilizing the
regenerated units while the exhausted units are being  regenerated.


Practical Operating Systems.  Figure 10 shows a schematic drawing of the
ion-exchange system used in Plant 11-7 to handle  a flow  ranging   from
2,100  to  4,000 gph of chromium rinse water containing 30 to 250 ppm of
hexavalent chromium.  The unit  saves at least 150,000  liters/day (40,000
gpd)   and  provides a source of deionized water throughout the plant for
preparing plating solutions where good quality water is  required.    The
pure  water  recycled to the chromium rinse tanks is useful for avoiding
spotting of chromium-plated parts.   Regenerated solution from the anion-
exchange  unit  is  treated  by  reducing  the  chromium  to  Cr3+    and
precipitating it.  Regenerated  solution from the cation-exchange unit is
combined with the acid-alkali stream for treatment.

    Cation-exchange  resins  are used widely throughout the industry for
removing nickel, trivalent chromium, and other impurities from  chromium
plating  baths.   Cyanide  may   be  absorbed on ion-exchange resins, but
there is danger of leakage of cyanide through the system.   An  improved
threebed  system consists of strongly acidic, weakly basic, and strongly
basic layers. (39)  In this system the weak base resin   provides  a   high
capacity  for  cyanide  adsorption  and the strong base resin provides a
back up to take care of cyanide leakage.


Demonstratigr^Status^  An  ion-exchange  system  utilizing  a  short  30
minute  cycle,   including  a 3  to 4 minute back wash,  to recover chronic
acid from rinse water has been  in operation over a year. (40)   The  resin
undergoes very little deterioration since the chromic  acid is not deeply
absorbed into the resin during  such a short cycle.


Ion Exchange for Mixed Effluent.  An installation for  handling 6,300 gph
of  wastewater  containing nickel,  chromates, chlorides and sulfates was
installed for recovering 96 percent of the water. (32)   The  cost  saving
in water was more than three times the cost of operation.


Water Conservation by Evaporative Recovery
             .    When  rinse water from one type of bath is distilled in
an evaporative unit, the concentrate may be returned to the plating bath

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and the distillate to the corresponding rinse tank, which is useful  for
closing  the  loop  on  a  single  plating  operation.  The economics of
distillation, from the standpoint  of  either  investment  or  operating
costs  imposes a constraint on the size range of distillation equipment.
Units with a capacity of the order of 300  gph  are  used  in  practice.
Such  a  low  rate  of  flow  of rinse water is achieved in many plating
operations only by the use of  at  least  three  countercurrent  rinses,
which  by itself reduces the wastewater.  Evaporative recovery units for
all of the rinse cycles would reduce the  effluent  to  zero.   So  far,
recovery  units  have  been  installed  on rinse tanks following plating
baths in order to recover plating chemicals and return them to the  bath
and  thereby reduce plating costs.  The units have not been installed on
cleaner or  acid  dip  lines  because  the  cost  of  chemicals  is  not
sufficient to make recovery worthwhile.

    Evaporation   is  a  firmly  established  industrial  procedure  for
recovering plating chemicals and water  from  plating  waste  effluents.
Commercial  units for handling zinc, copper, nickel, chromium, and other
metal plating baths have been operating  successfully  and  economically
for  periods  of one to 10 years or longer.  Packaged units for in-plant
treatment of plating wastes are available from many manufacturers.


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

     (1)  Recovers expensive plating chemicals, which were either lost by
    discharge to a sewer or  stream  or  which  had  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 sewage costs.

     (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 occur at relatively  low
    temperatures  (e.g., 110 F)  so that destruction of cyanides or other
    heatsensitive materials is lessened.

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

    Some  of  the  limitations  or disadvantages of evaporative recovery
systems are given below:
                                  93

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    (1)  The rinse water saving [e.g., 1100 1/hr  (300  gph) ]  is  rather
small,  and by itself does not significantly reduce the rinse water load
on the

    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 and maintain them.
        Separate units are required for handling the waste effluent from
    each  line,  as  various  solutions,  such  as zinc, nickel, copper,
    chromium, cannot be mixed for chemical recovery.

    The  advantages  offered  by  evaporative  recovery   outweigh   the
disadvantages  when  existing  chemical  treatment  facilities  are  not
available.  Evaporative recovery is a promising  and  economical  method
currently  available  for  handling plating waste effluents and limiting
treatmentplant  size.   Where  existing  chemical   treatment   (cyanide
destruction,  chromate reduction, and chemical precipitation)  facilities
are operating at less than capacity, the economics and  practicality  of
installing  new  evaporative  equipment  must be closely evaluated.
small decrease in the rinse water effluent  e.g., 1100 1/hr  (300
by  itself  does  not warrant the installation of an evaporative system.
The savings produced by the recovery  of  plating  chemicals  plays  the
significant role in judging the overall merits of the evaporative system
for a specific operation.


Process __ Principles __ §nd_Eguip_ment .  A representative closed loop system
for recovery of chemicals and water from a plating line with  a  single-
effect  evaporator  is  shown  in Figure 11.  A single-effect 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.   With  the  closedloop  system,  no
external  rinse  water  is  added  except  for  make-up  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.

    Single ,  double „  and  multiple-effect  evaporators,  and   vapor-
recompression  evaporator  units are used for handling 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.

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    A    single-effect    evaporator   is   preferred,   if   relatively
unsophisticated operating personnel are involved, or low initial capital
outlay is desired.  ltfs  the  simplest  in  design  and  therefore  the
easiest to operate.  However, it is less economical than a double effect
or vapor-recompression unit with regard to utility costs.(41)  A double-
effect  evaporator  should  be  considered  when lower operating cost is
desired with a modest increase in capital investment.

    A vapor-recompression evaporator should be considered if no steam or
cooling water is available.  Where utilities for  a  conventional  steam
evaporator   are   available,   the   highinitial   cost  of  the  vapor
recompression unit is not economically justified.  Its operating cost is
the lowest of the three systems.  Its dependence  on  an  expensive  and
complex mechanical compressor is the main disadvantage.

    Some  sources report considerable maintenance and down time and have
dispensed with use of evaporator units.  Other sources report little  or
no  trouble  and are very satisfied with the operation.  It appears that
the units  can  perform  very  satisfactorily  if  the  installation  is
properly  engineered, and if preventive maintenance and trouble-shooting
are carried out by knowledgable personnel.

    In  some  instances,  evaporation  procedures  must   be   used   in
combination  with  chemical  or  other  methods in order to handle small
amounts of impurity build-up (e.g., brighteners, carbonates,  extraneous
metal  ions,  etc.,  in closed-loop operation)  or for treatment of minor
bleed-off streams  (open-loop).

    Atmospheric evaporation, which uses air flow through  packing  media
in  an evaporator, can concentrate plating solution such as chromic acid
up to 480 g/1 (4 Ib/gal)(42).  One manufacturer(43)  has introduced a new
concept for evaporative recovery.  A glass shell and tube heat exchanger
is mounted vertically and the solution is fed through the  bottom.   The
boiling  causes liquid surges that produce a "rising film" effect and an
improvement in heat transfer.  Vapor and liquid overflow the top of  the
tubes  and are separated in a cyclone.  Water with less than 0.05 ppm of
chromic acid has been produced from chromium plating rinse water.


Practical_OEerating_Sv.s_tems.  Extensive use is made  of  evaporators  in
Plant 20-14, where three~units with capacities of 380, 380, and 190 1/hr
(100,  100, and 50 gph) are used to completely close the copper cyanide,
nickel, and chromium rinse lines respectively.   Only  the  cleaning  and
acid  pickling  lines  are  open  and  it  is roughly estimated that the
combined effluent volume from them may be of the order  of  11,300  1/hr
(3000  gph).  The alkali rinse is run directly to the sewer and the acid
line is neutralized and run to the sewer without  clarification.   Small
spills  and washes are treated chemically.  Rearrangement of cleaner and
acid dip rinse tanks to counterflow operation could reduce the volume of

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            co«ecNT*ATE HOI.O TANK (M)
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FIGURE  11.
REPRESENTATIVE CLOSED-LOOP SYSTEM FOR RECOVERY
OF  CHEMICALS AND WATER WITH A SINGLE-EFFECT
EVAPORATOR
                                96

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FIGURE  12.    REPRESENTATIVE OPEN-LOOP EVAPORATIVE  RECOVERY
                 SYSTEM(34)
                                     97

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effluent to a very low level and installation  of  an  evaporator  would
reduce  it  further.  In contrast to the plating tanks, the cleaners and
acids must be discarded periodically so that a completelyclosed loop  on
these  lines  does  not  seem  possible.   However, there is no economic
incentive to change the present arrangement in this plant to reduce  the
present  effluent  volume.   One  manufacturer  has  installed  over 100
evaporative recovery systems in metal finishing shops.

    Figure 12 illustrates an  open-loop,  partial  recovery  evaporation
system,  which  is  suitable for plating installations where there is an
insufficient number  (i.e.,  less  than  three)   rinses.    Although  the
specific  data  shown  in  Figure 12 are for a cyanide plating line, the
general overall A small portion of the cyanide dragout that,  accumulates
in   the   final  rinse  is  not  recirculated  to  the  evaporator  for
concentration.  The circulation loop through the evaporator is opened by
creating another flow path for the cyanide.  With only two rinse  tanks,
the  open-loop system can be operated economically, because only about 4
percent of the dragout is lost; this dragout must  be  treated  by  some
appropriate chemical method before disposal.


Demons tration_status

    Atmospheric   evaporators  have  been  shown  to  be  practical  for
recovering chromic acid from spray mists collected in  chromium  plating
venting  and  scrubbing  units.   A  cation  exchanger is used to purify
concentrated chromic acid before it is recycled  to  the  plating  bath.
Several  units  of  the  glass  "rising film" evaporator are being field
tested in applications involving chromic acid solutions.


Water Conservation by Reverse Osmosis
             .   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 separation as distillation and has been
applied in plating installations in the same manner.   Small units  under
300  gph  have been installed to recover plating bath 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
fromconsideration  unless  modifications are made to  the solutions prior
to 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.

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    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  and  pilot-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   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   rerecycled  to  the  plating  tank,
considerable savings will be achieved because of the reduced  amount  of
waste-containing water to be treated.


Advantages	and	Limitations.   Some  advantages  of reverse osmosis for
handling plating effluents are as follows:

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

     (2) Ability to recover purified water for reuse

     (3)  Ability to operate under low power requirements (no latent heat
of vaporization or fusion is required for effecting separa
    tions; the main energy requirement is for a high-pressure pump).

     (4) Operation at ambient temperatures (e.g., about 60 to 90 F)

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


    Some limitations or disadvantages of the  reversed  osmosis  process
for treatment of plating 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
temperature  will  result  in  decreased  fluxes  but  not  damage   the
membrane) .
                                  99

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

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

     (4) Fouling of membranes by slightly soluble components in solution.

     (5)  Fouling  of  membranes  by feeds high in suspended 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 Equipment.  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. (44,45)

    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 high-
pressure 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.
                                  100

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                    Sy sterns.  Plant 13-2 has installed a reverse osmosis
unit on the rinse line of a 6800 liter (ISOOgal)  bright nickel solution.
Solution from a dragout tank immediately following the plating  bath  is
returned  directly  to  the plating bath.  Water in the succeeding rinse
tanks, containing approximately 25 ppm of nickel,  is pumped through a 50-
micron prefilter and six reverse osmosis modules at the rate of 450 1/hr
(120 gph) .   Concentrate, at the rate of 23 1/hr (6 gph) , is returned  to
the  plating  tank and 445 1/hr (118 gph) of water are returned to rinse
tanks.  The unit is reverse flushed once every two weeks, which produces
23 liters  (6 gallons)  of waste that is sent to a  sludge  holding  tank.
Otherwise  the system operates as a closed loop.   Life of the modules is
estimated to be 2-1/2 years.  This system is typical of the systems that
have been installed until recently.

    A waste-treatment plant designed to produce no liquid  effluent  has
been  recently  installed at                          Plant 11-22.    Key
components in the process are two reverse  osmosis  units  operating  in
parallel  and  capable  of  handling 26,000 1/hr (6800 gph)  of effluent.
This flow rate is typical for a medium-large  plating  installation,  so
that  reverse  osmosis  should  be  capable of treating total wastewater
rather than being used for chemical recovery on individual  lines  where
water  volume  is  much  lower.  Plant 11-22 had no treatment facilities
prior to installation of  the  new  unit.   Dilution  of  plating  plant
effluent  by  other  effluents  at the  site   reduced concentrations of
pollutants  to  very  low  levels.   The  waste-treatment  system  could
therefore  be  designed  from  scratch  rather  than  as an add-on to an
existing system.  The system that was  chosen  uses  chemical  treatment
followed  by  reverse  osmosis.  The flow diagram in Figure 14 describes
Plant 11-22 's zero effluent system.  The  small  amount  of  cyanide  is
pretreated  before  being combined with streams from the chromium, acid,
alkali, acid copper and nickel baths.
                                  102

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    Hexavalent chromium is reduced in the neutralizer tank  at  pH  8.5.
Metal  oxides  are  precipitated  at  the  same time.  Effluent from the
clarifier goes through a reverse osmosis system.  Each of  the  parallel
assemblies  contain  26 units that are operated so that 18 units operate
in parallel, followed by 6 units in parallel, followed  by  2  units  in
parallel.   Thus,  these  three  parallel systems operate in series with
each other.

    A smaller reverse osmosis unit is  used  in  the  plating  plant  to
recover  chromium  dragout.   The  acidity of the rinse water is reduced
somewhat to prevent deterioration of the reverse  osmosis  membrane.   A
deionizer   is   then  used  to  remove  salts  formed  by  the  partial
neutralization, after which the chromium concentrate can be returned  to
the plating tank.
Water Conservation by Freezing
                 Tne  freezing  process  would  be capable of recovering
metal and water values from plating rinse 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 zinc, 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 __ PEinc.ip.les __ and __ Eguip.ro.ej2i-   The  basic  freezing  process for
concentration and 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 15. (46,47)  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  mixesd  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 freezer with a compressor.  The slurry is pumped from the freezer to
a count erwasher, 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
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
                                  10 4

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countercurrervtly 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 than the melting point of the ice.

    Because  of  the  pump  work,  compressor  work, 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 the 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,


Practical_O2erating_SY§tems.  No commercial utilization of freezing  for
treatment  of  waste  water  from metal finishing is known in the United
States.     Practical   systems  may  exist in Japan, however.


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.


Water Conservation by Electrodialysis


Applicability.   Electrodialysis  removes  both  cations and anions from
solution and is most effective with multi-valent  ions.(48)   Therefore,
it is capable of reducing the concentration of copper, chromium, nickel,
                                  106

-------
and zinc ions from solution whether these metallic ions are complexed or
not.  Chromate and cyanide ions may also be removed.


Process	Principles	and 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  such  a pattern that the concentration is reduced in each successive
chamber.   Another  stream  is  run  through  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.  No practical operating systems have been
reported.  However, development has resulted in several  demonstrations,
discussed below.


Demonstration	Status.    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.
Water Conservation by Ion-Flotation Techniques
                 Ion-flotation  techniques  have  not been developed for
application to plating rinse water effluents.  If successfully developed
into a practical method for plating effluent  treatment,  ion  flotation
offers possibilities of reducing the amount of water discharged by 60 to
90  percent  for  some  plating  operations.  These savings are based on
results  of  small-scale  laboratory  studies  on  solutions  containing
cyanides or hexavalent chromium.


Process __ Principles __ and __ Eguip_ment.   Separation  of  ions from aqueous
solutions by a flotation principle is a relatively  new  concept,  first
                                  107

-------
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
material.  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-flotatior,
cell is shown in Figure 16.

    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. (49)   However,  the amine suffered deterioration
when regenerated for re-use,  since the removal efficiency dropped to  60
percent after two regenerations of the amine.

    Grieves,  et al.,(50) have demonstrated the feasibility of using ion
flotation  on  dichromate   solutions   with   a   cationic   surfactant
(ethylhexadecyldimethylammonium 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  450  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.
              ating_Sy.st ems.  There are no practical operating systems.
Demonstration __ Status.   The  process  has  not  been demonstrated in an
operating plant.


Water Conservation by Electrolytic Stripping
                Electrolytic stripping is not in general use for copper,
nickel, chromium or zinc, although some procedures  have • been  employed
for  recovering  precious metals.  Recent technical developments suggest
that they can be used  to  reduce  heavy  metal  concentrations  in  the
effluent  to  very  low  values  as  well as provide for recovery of the
metals.
                                  108

-------
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FIGURE 16.  SCHEMATIC DIAGRAM OF ION-FLOTATION CELL FOR
            TREATMENT OF PLATING EFFLUENT
                               109

-------
Process_Princi2les_and_Egui221§Ilt'   In  order  to  strip  a  solution  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.
Surfleet and Crowle(51)  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  as
gold,  silver,  tin.   The  fluidized  bed  electrode  is a bed of metal
spheres or metal-coated glass spheres that is fluidized by  pumping  the
dilute  solution through it and causing an expansion of 5 to 10 percent.
With spheres of 100 to 300 microns in diameter, a total  geometric  area
of  75  cm2/cm3  is obtained.  Thus, the current density is very low and
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 around  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(52) the electrolyte 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.   Pre-
deposited  copper  on  the  anodic  electrode  is dissolved into the one
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 ing/1 to  0.55  mg/1  in  the  cathode  stream  and
concentrated  to  44 g/1 in the anode stream.  A similar system has been
used  for   depositing   metallic   impurities   from   strong   caustic
solutions. (53)


Practical	Operating	Systems.  There are no practical operating systems
in the electroplating industry, although the caustic purification system
is in use in the chlor-alkali industry.


Demonstration^Status.  The porous electrode system(52)  is  still  under
development  at  The  University of California and has been scaled up to
handle 250 gpd of copper sulfate solution.


Water conservation by Carbon Adsorption
                                  110

-------
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 of chromium can be  removed  from  waste
water. (49)   The treated water can be recycled to the rinse tanks.


Process ___ Principles ___ and __ Equipment.   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  the  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  plant  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 acceptable concentrations of chromium VI.


Water Congeryati.on_bY_Liguid-Liguid Extraction
                 Liquid-liquid  extraction   has   been   used   on   an
experimental   basis   only  for  the  extraction  of  hexavaconcentrate
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.


Process __ Principles __ and __ Eguipjnent.  The metal-ion pollutant is reacted
with an organic phase in acid solution, which separates readily from the
aqueous phase.  Metal is subsequently stripped from  the  organic  phase
with  an  alkaline solution.  Hexavalent chromium, for example, has been
extracted from wastewater 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:
                                  111

-------
     (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.

     (H)  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  y  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_0p.erating_Sy.stems.  Liquid-liquid extraction systems  are  not
known to be operating for treatment of electroplating wastes.


D§!DO!l§tration	Status.   Experimental evidence exists indicating that up
to 99 percent of chromium  can  be  successfully  extracted  from  rinse
waters  containing  10 to 1000 mg/1 of Cr6+.  With 10 ppm of Cr6+ 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 O.U  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 Cr6+ ions.  The effluent, however, contained from 200
to 500 mg/1 of kerosene, which is undesirable.


Methods_of_Achieying_No Discharge of Pollutants

    Although  chemical  methods  of treating electroplating waste waters
are achieving the low effluent discharges suggested in this report, they
are  not  improvable  to  the  point  of  achieving  zero  discharge  of
pollutants.    The  preceding  discussion  of  water  conservation  [ion
exchange, evaporation, and reverse osmosis  (RO) ]  indicates  procedures
for  achieving  no  discharge  of  water.  With closed-loop treatment of
rinse  water  in  separate streams  from   each   electroplating   bath,
evaporation  or  RO  can  be  used to return concentrate directly to the
corresponding plating bath.
                                  112

-------
    Impurities in an electroplating bath are increased in  concentration
when  pollutants  in  rinse  waters are  recycled  and  returned  to the
solution.  High  concentrations  of  impurities  ultimately  affect  the
quality of the electroplates.  Thus, impurity removal becomes necessary.
Methods  for removing impurities usually contribute pollutants that must
be disposed of by chemical  treatment.   For  example,  the  removal  of
carbonates   from   cyanide   solutions by  precipitation  with  calcium
hydroxide or by freezing involves the occlusion  of  cyanide  and  heavy
metals, which must be subjected to chemical treatment.  Activated carbon
for  removing  organic  impurities should be washed before disposal as a
solid and the wash water treated to destroy cyanide  and/or  precipitate
heavy metals.  Spills that cannot be returned to the segregated recovery
cycles  must be treated chemically to avoid pollution.  These sources of
pollutants  can  be  combined  with  waste  water  flows  from  alkaline
cleaners,  acid  dips  and  other preplating and post plating solutions;
from which chemicals cannot be recovered and returned  to  the  process.
These   preplating   and  post  plating  solutions  are  either  changed
irreversibly  during  use  or  become  too  contaminated  for   economic
recovery.   Replacement or makeup is unavoidable if the solutions are to
perform their proper function.  Although rinse water can be recycled,  a
sludge  is inevitable in connection with recovering most of the water by
chemical treatment.  This operation is best performed after  mixing  the
rinse waters from the cleaner and acid dips.

    The  acid  in  acid  dip  solutions gradually becomes neutralized by
reaction with the basis metal being processed, and the concentration  of
the  metal  increases.  Ion exchange can be used in a separate stream of
waste rinse water  to  recycle  the  water  to  rinsing.   However,  the
regenerant  must  be  disposed  because it contains the dissolved metals
that are not recyclable in the acid dipping  operation.   Most  commonly
this will be done by chemical precipitation, after mixing with the rinse
waters.

    A  preferred  procedure   (A)  for eliminating discharge of pollutants
into navigable streams omits the ion exchange step and concentrates  the
rinse  waters  to  recycle  some  of the water and minimize the chemical
treatment load as shown in Figure 17.  Wash water  from  spills  is  fed
into  either  the  alkali  or  acid rinse water holding tank.  Obviously
dumps of concentrated cleaners and acid dips can be  trickled  into  the
respective  rinse  water  holding  tank.   Rinse  water  containing post
plating pollutants also can be treated by directing it to holding  tanks
prior  to treatment by evaporation or RO and ultimate chemical treatment
and precipitation of heavy metal pollutants.

    Another procedure  (B)   for  recycling  water  to  rinse  tanks  and
achieving  no discharge of pollutants includes chemical treatment of the
combined waste from all preplating, plating and post plating  operations
and  separation  of  solids  as  discussed  on  pages 61-79, followed by
further treatment of the effluent by evaporation or reverse  osmosis  to
                                  113

-------
                                        W
                                        &
                                        ID
                                        O
114

-------
recover  high-quality  water  suitable for rinsing.  This water recovery
system is used with an RO unit at  plant 11-22.       (Figure 14).    The
concentrate from the RO unit (or an evaporator) is evaporated to dryness
and  disposed  of  as a granulated salt.  When this method for achieving
zero discharge of pollutants into navigable streams is adopted  with  no
provision  for  recovering  chemicals  reusable in electroplating baths,
costs  will  be  greater  than  the   costs   incurred   for   recycling
electroplating  chemicals in segregated streams and combining preplating
and post plating rinse  water  for  chemical  treatment  and  subseguent
evaporation or RO for water recovery.

    A  possible  future development may be direct treatment of the  waste
water  stream  by  evaporation  or   reverse   osmosis   without   prior
precipitation   of  the  heavy  metals.   The  waste  water  would   need
adjustment to a low enough pH to preclude any precipitation which  could
cause  corrosion  problems  or membrane deterioration.  The method  would
have the obvious merit of reducing the cost of  chemical  treatment  and
limiting  it  to  that  required  for  cyanide  destruction and chromate
reduction.  However, the solid  residue  from  evaporation  may  contain
soluble  heavy  metal  salts that would require further treatment before
being used as land fill.
                                  115

-------
                              SECTION VIII

               CQST^ ENERGYf AND 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.  Costs also are estimated for evaporation and reverse osmosis
technologies that can achieve a further improvement  in  removing  waste
water constituents.  The nonwater quality aspects concerning disposal of
solid  waste  and  the  energy impact of the inprocess control and waste
treatment technologies also are discussed.

Treatment and control Costs

Chemical Treatment to Achieve Low Levels of Pollutants

BPCTCA Limitations .(Table !)_._  Costs associated with control  technology
consistent  with  the  exemplary practice of chemical treatment averaged
$10.24/100 sq m  (9.52/1000 sq  ft)   for  eight  medium-sized  and  large
plants  that  supplied  detailed  cost data.  The standard deviation for
this value was $6.31/100 sq m ($5.86/1000 sq ft)  indicating considerable
spread from the average value.  The operating cost of  waste  treatment,
as  a  percent of cost of plating was 3.80% with a standard deviation of
2.37%.  Plating costs were assumed to be $2.70/sq  m  (0.25/sq  ft)  for
each  deposit  applied.   (Copper,   nickel,  chrome  on  the  same  part
corresponds to three deposits.)    The  minimum  investment  cost  for  a
chemical  treatment  plant  is of the order of $50,000 regardless of the
size of the plating installation.  For plants with a plating capacity of
107 sq m/hr (1000 sq ft/hr), or larger, the investment cost is estimated
at approximately  $150,000/100  sq  m/hr  ($140,000/1000  sq  ft/hr)  of
capacity  (Figure 18) .

    The  control  and  treatment technology on which the above costs are
based will reduce the discharge of waste water constituents to only  0.1
to  1.0 percent of the amount that would be discharged in the absence of
chemical treatment.

    The costs of waste treatment in smaller plants was estimated using a
model that included chemical treatment consisting of cyanide destruction
and hexavalent chromium reduction and precipitation  and  separation  of
heavy metals from the combined waste water from preplating, plating, and
postplating operations.

    A minimum capital investment of $50,000 was assumed for the chemical
treatment  facility  in  any small plant.  Only 2,000 hours of operation
per year  (8 hr/day 5 days/week, 50 weeks/yr) was assumed for  the  small
                                  116

-------
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INVESTMENT COST OF WASTE-TREATMENT

FACILITY
                              117

-------
plants  in  place  of  2,625 hours per year for medium- si zed Plant 33-1,
becuase many small plants confine their operations to only  one,  8-hour
shift.   As  a  result,  of this  assumption, fixed charges and operating
costs, based on area plated,  are higher for the small plants.

    Table 21 shows that estimated costs  for  meeting  the  1977  BPCTCA
effluent limitations by chemical treatment  are greater for small plants
plating less than 33 sq m/hr (360 sq ft/hr)  in comparison with the costs
for  meeting  1977  BPCTCA limitations by larger plants.   The figures in
Table 21 reflect the fixed costs for  capital  investment  depreciation,
interest  on  the  investment and variable costs for chemical treatment.
The variable costs for  chemical  treatment  were  based  on  cost  data
supplied  by  Plant  33-1.   These  variable costs at Plant 33-1 were as
follows:

         Chemicals           $28,439/yr
         Sludge disposal       5,144/yr
         Labor                23,433/yr
         Equipment repair      3,889/yr
         Power                 3,887/yr

         Total               $64,792/yr

Plant 33-1 operates 2,625 hr/yr and has a plating rate of 4,560 sq ft/hr
(12,000,000  sq  f t/yr) .   The  above  cost  is  about  $5.70/100  sq  m
($5.30/1000  sq  ft),  which  is about the average cost calculated for 6
other plants.  The cost is about $2/1000 gal (assuming  2.5  gal/sq  ft)
and is typical of values reported for chemical treatment.

    According  to  the  estimates  in  Table  21, the costs for chemical
treatment in a small plant with 6 to 10 employees  are  approximately  7
percent  of  the  total  plating  costs, assuming that plating -costs are
$2.70/sq m  ($0.25/sq ft).  In comparison, costs for  chemical  treatment
in  a plant with 2 employees are approximately 18 percent of the plating
costs.

    As noted previously, the estimates  in  Table  21  are  based  on  a
capital investment of $150,000/100 sq/hr ($140, OOO/ 1000 sq ft/hr).  Any
plant  capable  of designing and constructing a chemical waste treatment
facility at a lower cost will have a lower waste treatment cost per unit
area plated.  The eight larger plants cited on page 122  obviously  were
able  to  reduce  their capital investment appreciably because operating
costs at these plants averaged only $10.24/100 sq m ($9.52/1000 sq  ft)  ,
which is only about one half of the estimated cost in Table 21 for small
plants with 6 to 20 employees.
     Source Performance Standards INSPSXi  New sources that are required
to meet the standards of performance recommended in Table  IA  have  the
opportunity  of  designing  and  building plants that reduce water flow.
                                  118

-------






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Such a reduction can be accomplished by installing  counterflow  rinsing
for  each  preplating and postplating operation.  The capital investment
cost for installing a supplemental rinse tank for each  operation  in  a
plant  plating  copper,  nickel, chromium and zinc will be approximately
$20,000,  The impact of this supplemental capital  investment  on  waste
treatment costs for small companies is reflected in Table 21.  Estimated
costs for a 6 to 20 employee plant plating 33 to 167 sq m/hr (360 to 800
sq  ft/hr)  amount to approximately 9 percent of the total plating costs,
assuming that plating costs are approximately $2.70/sq m ($0.25/sq ft).
    Large companies plating more tha 167 sq m/hr (1800  sq  ft/hr)   will
incur  costs  of no more than $19.30/100 sq m ($17.9/1000 sq ft)  to meet
new source performance standards.  The level of costs for  meeting  NSPS
might be lower if investment costs for chemical treatment are lower than
$150,000/100 sq m/hr ($140,000/1000 sq ft/hr).


No Discharge of Pollutants

    The   elimination   of  waste  water  discharge  pollutants  can  be
accomplished by water recovery by  evaporation-condensation  or  reverse
osmosis  in  combination  with  chemical  treatment  and  filtration for
acid/alkali waste.  Ion exchange is useful for waste water conservation,
but is not practical for eliminating waste  water  constituents  in  the
end-of-process, point source discharge.  The preferred mode of operation
is to conserve all plating bath chemicals and return them to the plating
bath,  and  concentrate all other chemicals (from preplate and postplate
operations)  for chemical treatment and disposal in a solid state.

    The cost for eliminating waste  water  pollution  using  evaporation
(and no chemical treatment)  in a plant with a plating capaicity of 370 sq
m/hr  ( 4000 sq ft/hr)  is estimated to range from $5.40 to $17.20/100 sq
m  ($5.00 to $16.00/1000 sq ft)  or 2 to 6.5 percent of the plating costs.
The lower figure is associated with  the  use  of  a  vapor  compression
system  for  combined,  preplating  and  postplating waste and individual
single stage evaporators for  recovering  plating  solution  from  rinse
water  following  plating  operations.   The higher figure* is associated
with single effect units employing steam  and  cooling  water  for  each
preplating,  plating, and postplating operation.  The capital investment
estimates for these evaporation systems are $68,659 and $164,000/100  sq
m  ($63,810 and $153,000/1000 sq ft) for the vapor compression and single
effect evaporation system, respectively.

    Costs  incurred  by  a  large  plant  for  eliminating  waste  water
pollutants  by  chemical  treatment  followed  by  reverse  osmosis  are
estimated  to  be  of  the order of $8.60/100 sg m  ($8.00/1000 sq ft) or
less, equivalent to about 3 percent of the plating  cost.   The  capital
investment   estimate   for   this   system   is  $110,000/100  sq  m/hr
($102,100/1000 sq ft/hr).  Waste water pollution will be  eliminated  in
                                  120

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this case but small amounts of both soluble and insoluble solid wastes
will be produced.

    The  incremental  cost for achieving zero discharge of pollutants by
1983 by a large facility plating at least 370 sg m/hr  (4000  sg  ft/hr),
which  is  now  eguipped  for  meeting 1977 new source standards or 1977
existing source limitations via chemical treatment is  estimated  to  be
$3.39/100  sq  m ($3.15/1000 sg ft).  This incremental cost assumes that
effluent osmosis to recover water and that concentrate from the RO  unit
will be evaporated to a granulated salt.

    Estimated  costs  for  eliminating  waste water pollution from small
plants that recover no  plating  solution  via  evaporation  or  reverse
osmosis  are  much higher than the costs for achieving zero discharge of
pollutants in plants that use evaporation or reverse osmosis to  recover
plating solution dragged into rinse water tanks.  The estimates in Table
21  show the higher costs associated with chemical treatment of combined
waste water from all preplating,  plating,  and  postplating  operations
plus  reverse  osmosis  (to  recover  water)   plus  evaporation  of  the
concentrate to granulated salt.  These estimates vary with the  size  of
the  plating  facility.   Costs  increase  appreciably  as plant size is
reduced from 20 to 2 employees.  At the 20  employee  level,  costs  for
achieving  zero  discharge  of  pollutants  with  no recovery of plating
solution amount to approximately 10 percent of the total  plating  costs
(assuming plating costs are approximately $2.70/sg m ($0.25/sq ft)).  In
comparison a plant with only two employees would entail costs eguivalent
to  about  28  percent  of plating costs to achieve the same standard.,


    The incremental cost for achieving zero discharge of  pollutants  by
1983  for  a  small  facility  plating no more than 167 sg m/hr (1800 sg
ft/hr),  which  is  initially  equipped  for  meeting  1977  new  source
standards via chemical treatment can be estimated from data in Table 21.
This increment will vary from $13.40/100 sq m ($12.45/100 sq ft)  for a 2
employee  plant  to  $2.40/100 sq m ($2.34/1000 sq ft)  for a 20 employee
plant.


Cost_Effectiyeness^andjrreating Procedures

    From an analysis of untreated rinse water and effluent in Plant 33-1
which corresponds to a  medium-sized  plant   (50,000  amperes)   with  38
employees,  it was possible to calculate the amount of copper,  chromium,
nickel, zinc, and cyanide removed from the rinse water and determine the
amount discharged with  the  effluent.   The  volume  of  discharge  for
various  rinse-tank  arrangements  and  the  costs associated with these
arrangements were  also  known.   The  costs  of  applying  increasingly
effective  treatment  techniques  to  Plant  33-1 were estimated for the
following systems:
                                  121

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    (1)   A single rinse tank for each rinsing operation;   no  wastewater
         treatment

    (2)   A single  rinse  tank  for  each  rinsing  operation;  chemical
         treatment

    (3)   Two  series  rinses  for  each  rinsing   operation;    chemical
         treatment

    (4)   Three counterflow rinses for each rinsing  operation;  chemical
         treatment

    (5)   Single-stage  evaporation  for  each  process   bath   plus   3
         counterflow  rinses,  cleaners  and  acid  dips  included,  which
         requires a total of 21 evaporators.   All rinse water  would  be
         recycled  and  plating process rinse water would be returned to
         the plating bath.  Thus, no chemical treatment was included

    (6)   A single-stage evaporator for each process bath  and counterflow
         rinse, except for acid and alkaline preplating and  postplating
         rinses.   A  large  vapor  compression unit was  assumed for the
         acid-alkali and postplating stream.   Effluent volume reduced to
         approximately 37.8 1pd  (10 gpd).  No  provision   was  made  for
         evaporating this very small volume to dryness.

    (7)   Process lines as  they  now  exist  in  Plant  33-1.    Chemical
         treatment  is used, followed by reverse osmosis  on the effluent
         from  the  chemical  treatment.   No  provision   was  made  for
         evaporating the small volume of concentrate from the R.O unit.

    From  these data sources, a cost effectiveness curve  was plotted, as
shown in Figure 19.  The volume of water required for rinsing in  single
rinse  tanks  is  so  large that no precipitation occurs  during chemical
treatment and  the  weight  of  discharged  water  constituents  is  not
affected  by  the  treatment.   The lowest cost on the curve is that now
incurred by Plant 33-1 using their present system.  The  options  listed
for eliminating discharge of wastewater constituents are  associated with
costs  ranging  from  $5.40 to $17.20/100 sq m  ($5.00 to  $16.00/1,000 sq
ft).


Nonwater Quality Aspects

Energy Requirements

Chemical_Treatment.  The electric power used for plating  consumes  about
0.06  percent  of  the  nation's  electrical energy (1.7  x 1012 kilowatt
hours).   The power required for chemical treatment is approximately  3.2
                                  122

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percent  of the power needed for plating, based on data developed from a
sample of eight plants with reliable records.

No Pis charge of Pollutants.  Exclusive use of single  or  double  effect
evaporators  for  reducing  rinse  water volume requires steam at a cost
that can be one to four times the cost of power for  plating,  depending
upon  the  degree  of  rinse  water  reduction  achieved.   Use of vapor
compression units in part or in whole will reduce  the  cost  of  energy
requirements  to  about  the  same  as the cost of electrical energy for
electroplating or probably less, and eliminate discharge  of  pollutants
when combined with chemical treatment.  Reverse osmosis will achieve the
same  effluent  limitation (when combined with chemical treatment) using
27 percent of the power required for electroplating.

Solids Disposal

    The cost  of  lagooning  sludge  from  a  clarifier  cifter  chemical
treatment  has  not  been considered, because the method is finding less
and less favor as a means of disposal.   The  volume  generated  by  the
domestic plating industry is estimated to be about 200,000 cu yd/yr.

     It is recommended that metal sludges be disposed of in a  "specially
designated landfill," where "specially designated landfill" means a land-
fill at which protection is provided  for the quality of surface and sub-
surface waters from heavy metal pollutants.  Such sites should be located
an^ engineered to avoir! rlirent hvciraulic continuity with surface  an^ sub-
surface waters, and any leachate or subsurface flow into the disposal  area
should be contained within the site unless treatment is provided.  Pre-
cautions to insure the continued insolubility of the metal sludges should
be taken, such as placing  layers of lime and clay underneath the  landfill.
Additional guidelines for  the proper  disposal are stated in the EPA Guide-
lines for Landfilling of Solid Waste.  The location of the disposal site
should be permanently recorded in appropriate office of legal  jurisdiction
                                  124

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                               SECTION IX

             BEST PgACTICABLE CONTROL TECHNOLOGY CURRENTLY
                 AVAILABLE, GUIDELINES, AND LIMITATIONS
Introduction
The effluent limitations which must be achieved 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.  This average is not  based  upon  a  broad
range  of  plants  within  the  metal finishing industry, but based upon
performance levels achieved by exemplary plants.

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)   non-water 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.
                                  125

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Industry Category^andT subcategory covered

The  pertinent industry category is the electroplating industry which is
part of the metal finishing industry.    This  category  includes  plants
using  electroplating  processes  as  defined  by  SIC  3471  (1972)  and
includes all electroplating processes  and their associated  pretreatment
and post-treatment operations if used  in an electroplating process.   All
other  processes and operations defined by SIC 3U71 that are not part of
processes containing at least one electroplating operation are  excluded
from this category.

The  identification  of  Best  Practicable  Control Technology Currently
Available and recommended effluent limitations presented in this section
cover the  subcategory  of  electroplating  based  on  rack  and  barrel
electroplating  of  copper,  nickel,  chromium,  and  zinc, estimated to
contribute about two-thirds of the amount of waste in the electroplating
industry.  Effluent limitations are not specified as yet for all metals;
all  electroplating  operations,  or  all  metal  finishing   processes.,
However,  the  control  and  treatment  technology identified is broadly
applicable in three other areas:  (1)   electroplating  operations  other
than  rack  and  barrel;  (2)  electroplating of metals other than copper,
nickel, chromium, and zinc; and (3)  other metal finishing processes  than
electroplating yet to be considered.  Recommended  effluent  limitations
applicable  to  these  other  subcategories  might  require a greater or
lesser degree of effluent reduction.

Identification of_Best_Practicable Control
Technology CurrentlY_Available

Best  Practicable  Control  Technology  Currently  Available   for   the
electroplating industry subcategory of rack and barrel electroplating of
copper,  nickel,  chromium,  and  zinc is the use of chemical methods of
treatment of wastewater 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 wastewater 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   discharge   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  in  the heavy metal pollutional load such  that
less than 1 mg of total metal (soluble plus insoluble)  is discharged for
                                  126

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each kilogram of  metal  electroplated  on  products.   This  degree  of
pollution  reduction  is  often  achieved  if  the concentrations of all
metals is high in the raw waste.

No generalization regarding degree of heavy metal pollution reduction is
possible because of the mix of electroplating processes  possible  in  a
single  plant  and  a variety of metals in the raw waste of most plants.
Because of this fact and the high cost of in-plant  segregation  of  all
waste  streams  according  to  metal,  coprecipitation  of metals is the
general practice.  There is an optimum pH for precipitating  each  metal
that  results  in the greatest removal by clarification.  The optimum pH
for removing all metals cannot be utilized for coprecipitation so the pH
selected for a mixture of metals is a compromise.

There are several advanced plating bath recovery methods  available  for
closing  up  the  rinse  water  cycle  on individual plating operations.
These   methods   (evaporation,   ion   exchange,    reverse    osmosis,
countercurrent  rinsing)   have not yet been applied to rinse waters from
pretreatment and  posttreatment  operations.   The  corresponding  rinse
waters plus concentrated solution dumps and floor spills may contain one
or  all  of the pertinent metals (copper, nickel, chromium, and zinc)  in
significant  amounts  reguiring  chemical  treatments.   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
recommended.

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 metal 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 wastewater which is principally that resulting  from  rinsing.
Some  of  these  controls  designed  to minimize dragout of concentrated
plating solution  or  reclaim  as  much  dragout  as  practical  can  be
considered  normal  practice  within  the  industry.   It can be assumed
according to good practice that reclaim tansk 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.

Further reduction in rinse water use can be achieved  by  multiple  tank
countercurrent  rinsing.    Unless the rinse water can be used to make up
evaporation losses of the bath, there is little reduction  in  treatment
                                  127

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chemical  cost  and no economic incentive to add more rinse tanks purely
for  water  conservation.   However,  the  use  of   advanced   recovery
techniques  (evaporation,  ion  exchange,  and  reverse  osmosis)   which
concentrate the  rinse  water  sufficiently  to  allow  reclaim  of  the
valuable  plating  solution  provides the economic incentive to use this
technology and justifies 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.     The
additional  reduction  in  volume  of  wastewater by recovery of all the
rinse water following a plating operation in lieu of chemical  treatment
usually has limited impact on the total water use in the plant.  This is
because  the  volume of rinse waters from pretreatment and posttreatment
operations  (e.g., the acid/alkali wastewater stream)   is  often  several
times larger than the volume of rinses from plating operations.

In the past there has been little economic incentive to reduce water use
for  rinsing  after  pretreatment and posttreatment operations.  For one
reason, the chemicals used in these solutions are not expensive compared
to plating solution chemicals and thus they are not purified for  reuse.
These  concentrated solutions are dumped at frequent intervals and there
is usually little concern for reducing dragout since the dragout reduces
the  rate  of  buildup  of  impurities  and  extends  the  life  of  the
concentrated  solution  and  requires  less frequent dumping.  Thus, for
pretreatment and posttreatment  solutions  that  are  dumped  frequently
(e.g., once a week), dragout does not influence the quantity of material
in  the  wastewater  requiring  treatment.   However, dragout from these
solutions does influence the  amount  of  water  required  for  adequate
rinsing.

While  sufficient  economic  incentive  is  presently lacking 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 discharged provided there is  an  economic  incentive
related to achieving pollution reduction.

Rationale for Selecting^the Best Practicable^Contrgl
T§chnglggy_Currently_jwailable

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
electroplating industry.  Then,  waste-management  techniques  based  on
advanced  technology currently available for in-process control and end-
                                  128

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of-process treatment were evaluated to determine what further  reduction
in  pollution  might  be  achieved considering all the important factors
that would influence the determination of best practicable and currently
available.


Waste_Management Techniques Considered
Normal Practice in the Electroplating Industry

    For that portion of the electroplating industry that  discharges  to
navigable  waters  it is estimated that a large proportion are currently
using chemical treatment for endof-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  electroplating 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
considered as examples of  normal  practice  within  the  electroplating
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 plating solutions such as

          (a)  proper racking of parts for eary drainage
          (b)  slow withdrawal of parts from the solution
          (c)  adequate drip time of dwell time over the plating 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
              plating solutions
          (b)  use of cooling water for noncritical rinses after cleaning
          (c)  use of  treated  wastewater  for  preparing  solutions  of
              waste-treatment chemicals.

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

          (a)  use of reclaim tanks after plating operations  to  recover
              concentrated  solutions  for return to the plating tank to
              make up evaporation losses
                                  129

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          (b)  reduction in wastewater volume by the use of at least  two
              series  flow rinse tanks after each plating operation with
              return of as much rinse water as possible to  the  plating
              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 pollution in the effluent discharged.

Degree of Pollution Reduction Based on
Existing Performance by Plants of Various,
yarious_Cgntrgl_andmTreatment Technology

Identification of Best Waste Treatment Facilities

    There are about  20,000  facilities  for  electroplating  and  metal
finishing  in  the  United  States and identification of the best plants
within the short period of this  study  required  a  rational  screening
approach as follows.  The initial effort was directed toward identifying
those companies which satisfied two criteria:

    1.   Engaged in rack and barrel plating of copper, nickel,  chromium
         and/or zinc

    2.   Achieving good waste treatment.

The 309 companies identified based  on  referrals  by  cognizant  people
associated  with  the  industry   (EPA  regional  representatives,  state
pollution control authorities, trade associations, equipment  suppliers)
and  review  of  permit  applications were distributed geographically as
shown in Table 22.  About 90 percent of the companies were in the  three
principal regions expected to have high concentrations of electroplating
industry:   38  percent  in the Northeast (principally EPA Regions I, II
and III; 28 percent in the Midwest (EPA Region V);  25  percent  in  the
Southeast (Region IV) .

    Of  these  leads,  the 129 companies initially contacted by telephone
were primarily in the principal electroplating regions  (40  percent  in
the  Northeast; 28 percent in the Midwest; 22 percent in the southeast).
The telephone was to verify the existence of  adequate  waste  treatment
facilities  and  the  type  of  plating operations pertinent to Phase I.
Sufficient information was obtained to characterize the facility and  if
pertinent  to  the  scope  of  coverage  desired  operational  data were
obtained.

    These  telephone  contacts  were  continued  until  53  plants  were
identified  that  provided  broad  coverage of the industry pertinent to
Phase I.  Because of the need to achieve variety in  electroplating  and
waste treatment operations, for this study no claim is made that the 53-
                                  130

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TABLE 22.  GEOGRAPHICAL DISTRIBUTION  OF GOOD ELECTROPLATING
           WASTE TREATMENT FACILITIES BASED ON INITIAL
           REFERRALS, COMPANIES  CONTACTED FOR INFORMATION,
           AND REPRESENTATIVE FACILITIES EVALUATED IN
           DETAIL
Area
EPA Region I
Connecticut
Massachusetts
New Hampshire
Rhode Island
Maine
Vermont
EPA Region II
Delaware
New Jersey
New York
EPA Region III
Maryland
Pennsylvania
Virginia
West Virginia
EPA Region IV
Alabama
Florida
Georgia
Kentucky
Mississippi
North Carolina
South Carolina
Tennessee
Referral

32
26
2
1
2
3

3
11
18

7
7
3
2

16
14
5
4
5
15
11
8
Contact

12
2



2

1
2
13


4



4
7
4
2
2
1
1
7
Evaluated

3
2



1


2
4


2



1
2

1



2
                                                (Continued)
                       131

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TABLE 22.GEOGRAPHICAL DISTRIBUTION OF GOOD ELECTROPLATING
         WASTE TREATMENT FACILITIES BASED ON INITIAL
         REFERRALS, COMPANIES CONTACTED FOR INFORMATION,
         AND REPRESENTATIVE FACILITIES EVALUATED  IN
         DETAIL

                            (Continued)
      Area
Referral
Contact
Evaluated
EPA Region V
 Illinois
 Indiana
 Michigan
 Minnesota
 Ohio
 Wisconsin

EPA Region VI
 Arkansas

EPA Region VII
 Iowa
 Kansas
 Missouri
 Nebraska

EPA Region VIII
 Utah

EPA Region IX
 California

EPA Region X
 Washington
   22
   14
   18
    4
   21
    8
   10
    1
    6
    1
    1


    3


    1
  10
   6
  13
  • 1
  19
   2
   2
   1
   4
   1
     3
     6
     7
     1
    11
     1
     1
                         132  .

-------
plant  sample  includes  all   process  combinations  in  the  electroplating
industry.  However, since the sample selection procedure emphasized good
waste  treatment  practice,  the  sample  illustrates  that  good  waste
treatment can be achieved by a variety of plants, job and captive,  large
and  small,  few  and  many  different  plating  processes,  in  various
geographic locations discharging to municipal systems or directly to  or
navigable waters.

    As  shown  in  Table  23  the  53  plants  consisted  of  39 captive
facilities and 1U job shops;   28  of  these  plants  discharged  treated
effluent  directly  to  streams and the other 25 discharged to municipal
systems.  The relative size of the plants in terms of plating capability
and raw waste load to be treated is  best  indicated  by  the  installed
amperes  for  plating.  Most electroplaters readily knew their installed
rectifier  capacity  in  amperes  which  represented   their   potential
production  capability.   A  lesser number readily knew their production
capacity in area plated per  unit  time  or  production  rate  of  parts
processed through the facility.
                                  133

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TABLE 23. CLASSIFICATION BY SIZE, TYPE OF FACILITY,
         AND EFFLUENT DISCHARGE FOR 53 ELECTRO-
         PLATING FACILITIES SELECTED FOR
         EVALUATION
Captive
Relative
Size
Very large
Large
Medium
Small
Very small
Amperes
Installed
over 200,000
50,000-200,000
10,000-50,000
1,000-10,000
less than 1,000
Munic-
ipal
--
7
4
7
--
Stream
1
2
11
6
1
Job
Munic-
ipal
--
1
5
1
--
Stream
1
2
3
1
--
                     134

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Classification of 53-Plant Sample

    Table  24  shows the scope of coverage for the 53 plants in terms of
the mix of possible  plating  operations  and  variety  of  control  and
treatment  technologies.   Most  plants  (32)  are equipped for decorative
plating of copper-nickel-chromium and of  these  about  half  (14)   also
plate  zinc.   About  75  percent of the plants in the sample that plate
zinc also use a subsequent chromate conversion.  The remaining 21 plants
provide most of the expected process  combinations  of  copper,   nickel,
chromium  and/or  zinc plating that might be found in the industry.  The
53 plants in the industry sample include  the  variety  of  control  and
treatment  combinations to be found.  Most plants (38)  used some type of
chemical treatment such as continous,  (C) batch, (B)   and/or  integrated
to  treat  the metals and cyanide associated with the plating operation.
A few plants use electrolytic treatment  (L)  and one uses  reclaim  tanks
for recovery (R).  The other 15 plants included examples of a variety of
advanced   in-process  controls  combination  of  evaporation  (E) ,  ion
exchange  (D) and reverse osmosis (O).  Most of the plants  used  end-of-
pipe   chemical  treatment   (continuous  or  batch)   for  at  least  the
acid/alkali wastewater stream.

    The classification of the 53 plants  by  size  (based  on  amperes),
number of employees in plating for all shifts and waste-treatment method
is  shown  in  Table  25.   Figure 20 shows that more than half of these
plants had fewer than 20 employees per shift.

    Of the 53  plants,  26  were  visited  for  on-site  inspection  and
verification  of  information.   The  data on rated or installed current
capacity are shown in Table 26.  Figure 21 shows the same data for total
installed current capacity and indicates that 50 percent of  the  plants
had  less  than  18,000  amperes.   The  normal use of installed current
capacity was 67 percent based on the 23-plant average of the fraction of
total rated capacity used shown in Table 26.    Thus,   it  was  estimated
that 50 percent of the plants used less than 12,000 amperes.

    Figure  22  shows  the  relation  of installed rectifier capacity to
number of employees per shift in electroplating for the 53-plant sample.
The average value calculated is about 1000 amperes installed/  employee.
Based  on an estimated typical 65 percent use of installed capacity, the
average value would be 650 amperes used/employee per shift.   The  large
amperage   per  employee  for  automatic  plating  machines  (over  5000
amperes/employee) would be exprected to result in considerable spread in
the data.  Thus,  number of employees per se, is not a definitive indicator
of plant size in terms of pollutional  potential.   Amperes  as  related
to area  plated is a more definitive measure of plant size and raw waste
load.
                                  135

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            TABLE 2 4.CLASSIFICATION OF 53 FACILITIES EVALUATED
                    BY MIX OF PLATING OPERATIONS AND TYPE OF
                    WASTE TREATMENT AND IN-PROCESS CONTROLS

Waste
Treatment (a) Cu Cu
and Control Cu Ni Cr Zn Ni Cr
C
B 1111
CB
CBR
LC
I 1
1C
IB
IR
El 2
EC
EB 11
EDC
EDB
E 2
D
OB
OIC
Metals Electroplated
Cu
Cu Cu Ni Cu Ni
Cu Ni Ni Cr Ni Ni Cr Ni Cr
Zn Cr Zn Zn Cr Zn Zn Zn Zn Totals
2 161 6 16
111 7
3 3
1 1
2 2
12 15
2 2
1 1
1 1
1 3
1 1
2
1 1
1 1
1 3
2 2
1 1
1 1
Totals      01262023    01  18   310  14

(a)  See Footnote  (e) Table  25 for  definition of symbols.


                               136

-------
                  TABLE 25.  SOURCE OF  INFORMATION AND CLASSIFICATION BY
                              SIZE AND WASTE-TREATMENT METHOD
Size of Facility
Company
Code No. ^a'
1-16
3-1
3-3
3-4
6-3
6-12
6-29
8-4
8-5
11-8
11-13
11-22
12-3
12-5
12-6
12-8
12-9
12-12
13-2
15-1
19-2
19-3
20-1
20-6
20-7
20-10
20-13
20-15
20-17
21-3
23-3
25-1
28-9
28-11
30-1
30-5
30-7
30-8
33-1
33-2
33-3F
33-3U
33-6
33-8
33-9
33-11
33-15
33-20
33-21
36-1
36-2
40-4
43-1
Reference^))
S
13
13, L
11
S, 12
S, 13
32
S
S
S, 13, L
S
33, L
15
S
S
S
S
S
L
13
18
1. 21
S
S
S
L, 18
5, 17, L
5
5
S
7, 11
7, S
S
2
14
2
19
19
16, 5, S
S
13
13
17, L
5
S
S
S
S
5
L
32
5
S
Data
Obtained(c>
T
P
P
P
P
P
T
T
T
P
T
P
P
T
T
P
T
T
T
T
T
P
P
T
P
T
P
T
T
T
T
T
T
T
P
T
T
P
P
T
P
P
P
P
P
P
P
P
T
P
P
T
T
Employees
in Plating
10
19
31
40
6
54
20
12
50
165
18
—
90
25
120 ._
100
25
70
20
6
70
30
7
80
25
250
6-10
13
50
16
200
69
15
25
52
30
15
24
38
10
1
5
100
3
16
12
20
12
18
25
13
40
2
Relative
M
M
M
M
S
M
S
S
S
L
M
L
M
M
VL
L
M
L
M
S
M
M
S
L
M
L
M
S
L
S
L
L
M
L
M
M
M
M
L
S
S
S
M
VS
S
M
VL
S
L
M
S
M
S
Classification*-6'
C/S/CCC-CC
C/S/--BEE-
C/S/-IEI-B
C/S/EB--BB
C/S/BII--B
C/M/ENCEEN
J/S/CCICIC
C/M/CCC-CC
C/I./CCC-CC
J/S/CCDECC
J/S/CCC-CC
C/M/000-BC
J/M/NEENNC
J/M/CCCCAC
J/S/DDE-BB
C/M/CCCCCC
C/S/IRI-IC
C/M/---EE-
C/M/COI-CC
C/M/---EE-
J/S/LCLLLC
J/S/--I--C
C/S/C-CCCC
C/S/CCB-BC
C/S/CCBCBC
C/M/-II--C
c/s/icmc
C/M/-BB--B
C/S/CCCCCC
C/S/BBBBBB
J/M/CCC-CC
C/M/CCCCCC
J/L/-B--BB
C/M/CCCCCC
J/M/LCLLLC
C/S/IIIIIC
C/S/III-IC
C/M/--NBBB
J/S/CCCCCC
C/S/BNN-NB
C/M/--IEEC
C/M/--IEEC
J/M/CCC--C
C/S/--B— B
J/M/NDD-NC
C/M/C-CCCC
C/S/CCB-BC
C/M/CCCCCC
C/M/--CCCC
C/S/BBBBBB
C/M/INI-IB
C/S/ODD— C
C/S/RCRBBB
Footnotes appear  on  the following page.
                                     137

-------
              FOOTNOTES FOR TABLE  25


(a)   Company  identification by number  for this  report.

(b)   Source of lead  to company.

(c)   Information  from telephone  call  (T) or  first-round
     visit  (P).

(d)   Relative size based  on total  installed  rectifier
     capacity in  amperes  for plating:

          VL = very large, >200,000 amperes
           L = large, 50,000 to 200,000 amperes
           M = medium, 10,000 to  50,000 amperes
           S = small, 1,000 to  10,000 amperes
          VS = very small, >1,000 amperes.

(e)   Classification  by type of facility  (1st letter):

           J = job  shop  or independent
           C = captive plating  facility,

     where the treated effluent  is discharged,

           S = stream  (or storm sewer to stream)
           M = municipal sanitary treatment system,
           L = liquid effluent  disposed of  on  land

     and  the  following coded waste treatment or in-process
     control  used for each constituent of the final  effluent
     considered in the order; copper,  nickel, chromium,  zinc,
     cyanide,  acid/alkali:

           A - adsorption
           B = batch chemical treatment
           C = continuous chemical treatment
           D = ion  exchange
           E = evaporation
           I = integrated
           L = electrolytic
           N = no treatment beyond pH adjustment
           0 = reverse osmosis
           R = reclaim rinsing  techniques.
                         13&

-------
100
             20
30    40   50    60   70
      Cumulative Percent
80   90
100
  FIGURE 20.  EMPLOYEES PER SHIFT IN PLATING VERSUS
               CUMULATIVE PERCENTAGE OF 53 PLANTS

-------
                             TABLE
                                   26.
SIZE OF PLATING OPERATIONS (RATED AND USED)
Company
Code No.
1-16
3-1
3-3
3-4
6-3 .
6-12
6-29
8-4
8-5
11-8
11-13
11-22
12-3
12-5
12-6
12-8
12-9
12-12
13-2
15-1
19-2
19-3*
20-1
20-6
20-7
20-10
20-13
20-15
20-17
21-3
23-3
25-1
28-9
28-11
30-1
30-5
30-7
30-8
33-1
33-2
33-3F
33-3U
33-6
33-8*
33-9
33-11
33-15
33-20
33-21
36-1
36-2
40-4
43-1
Fraction of Rated
Capacity Used

1




5

1
1
8
3


4
80
6
1

6

2


13
5

1

27

20
2

35
6
3
2

3



7

1
3
63
3

4

8
1
Cu
,500


800

,000
600
,500
,000
,150
,000
500
600
,000
,000
,150
,000

,000

,000

300
,000
,000

,400

,000
750
,000
,650

,100
,750
,300
,000

,000
400


,000

,000
,000
,000
,000

,500
250
,000
,500
Ni
9,000

10,000
12,000
2,500
5,000
1,500
200
2,300
25,150
8,000
1,000
17,000
2,000
120,000
9,250
16,000

5,000

11,000


23,000
20,000
45,000
4,000
8,650
43,500
600
10,000
3,000
6,000
62,000
8,000
4,000
10,000

23,000
350


8,500

4,000

273,000
200

4,500
1,500
8,100
3,000
Cr
6,000

25,000

3,000

3,000
1,500
1,000
23,150
8,000
72,000
8,000
8,000
63,000
15,600
16,000

4,000

2,000
44,250

16,000
7,500
30,000
3,000
250
50,000
750
10,000
20,000

25,000
6,000
1,500
8,000

8,500



10,000
250
4,500

118,000

20,000

1,500
10,000
1,500
Zn

10,000
5,825


20,000
1,000


27,150


10,000


32,500

133,000

6,000
9,000

3,200



2,500

9,000

35,000
48,650

12,500
450
1,200

15,000
15,250

7,000
7,000



12,000

3,000
32,600
6,000


1,500
Total
16,500
10,000
40,825
12,800
5,500
35,000(a>
6,100
3,200
f\. \
8,160(b>
94,600(0
19,000
73,500
35,600
14,000
263,000
63,500
33,000

15,000
6,000
24,000
44,250
3,700
57,000
32,500
75,000
10,900
8,900
129,500
2,100
75,000
74,300
21,700(e>
134,600
21,200
10,000
20,000
15,000
49,750
1,250(0
7,000
7,000
25,500
250
9,500
15,000
454,000
6,200
52,600
16,000
3,650
26,100
7,500
Cu
0.8




0.3
0.04


0.3




1.0
0.3
1.0

1.0

0.8







0.5




0.4




0.2







0.7


0.4
1.0
0.9

Ni
0.8




0.8
0.05


0.6


0.4

0.8
0.4
0.5

1.0

0.9







0.6




0.4




0.2







0.7


0.4
0.3
0.9
0.1
Cr
1.0





0.2


0.5


0.5

0.9
0.3
1.0

1.0

1.0
0.7



0.9


0.7




0.5




0.7







0.8

0.2

0.3
0.9
0.4
2n





0.7
0.5


0.3


1.0


0.5

0.8

1.0
0.8




1.0


0.3




0.7



0.8
0.8









0.6
0.9


0.4
lotal
0.9




0.7
0.1


0.5


0.6

0.9
0.4
0.8
0.8
1.0

0.9
0.7



1.0


0.6




0.5



0.8
0.5







0.7

0.6
0.6
0.3
0.9
0.7
Footnotes  appear on the following
                                               140

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                                             FOOTNOTES FOR TABLE  26






(a)   Includes an additional 5,000 amperes  for Cd.




(b)   Includes an additional 1,000 amperes  for Cd;  2,825 amperes  for Ag;  35  amperes  for Au.




(c)   Includes an additional 11,000 amperes  for Cd.




(d)   Includes an additional 100 amperes  for Cd and 100 amperes  for Sn.




(e)   Includes an additional 5,700 amperes  for Ag and 10,000 amperes for  Sn.




(f)   Includes an additional 300 amperes  for Cd and 200 amperes  for Ag.




(g)   Includes an additional 1000 amperes for anodizing.




(h)   Includes an additional 400 amperes  for Cd.
                                       141

-------
1,000,000



 500,000




 200,000
g  100,000
Q.
E
o

£   50,000
o>
    20,000
2    10,000
      5000
      2000
      1000
               1      I     I     I      T
          1     I
                                I	I
I     I      I  	I
               10    20    30   40   50    60   70    80   90    100
                                Cumulative Percent
       FIGURE 21.  TOTAL INSTALLED CURRENT FOR PLATING
                   VERSUS CUMULATIVE PERCENTAGE OF
                   53 PLANTS
                              142

-------
     500,000
     200,000
      100,000
       50,000
    (A
    0)
    £ 20,000
    Q.
    E
    o
   £•  10,000
   "o
   o
   O
   -o   5000
   •5   2000
         1000
         500
         200
          100
r  |  i  i i i
                     i   i  i  i
                             5      10      20       50
                         Number of Employees per Shift
                                100
FIGURE 22.  INSTALLED RECTIFIER CAPACITY IN AMPERES FOR
             ELECTROPLATING VERSUS NUMBER OF EMPLOYEES
             PER SHIFT IN ELECTROPLATING FOR 53 PLANT
             SAMPLE (RATIO OF AMPERES USED TO AMPERES IN-
             STALLED IS TYPICALLY 65 PERCENT)

-------
200 —
 100
1 1 1 1 1 1 1 1 1 1
0
10 20 30 40 50 60 70 80 90 100
                          Cumulative  Percent

     FIGURE 23.  EFFLUENT DISCHARGE RATE VERSUS
                  CUMULATIVE PERCENTAGE OF 53 PLANTS
                           144

-------
E
Q.
Q.
C
O)
UJ
0)
   0.05 —
   0.02
    0.01
  0.005
  0.002 —
   0.001
             10     20    30   40   50   60    70    80   90    100

                                Cumulative Percent
FIGURE 24.  COMPOSITE OF POLLUTANT PARAMETERS IN TREATED

              EFFLUENT VERSUS CUMULATIVE PERCENTAGE OF

              PLANTS
                                i 45

-------
Waste Treatment Results

    Table  27  shows  the  treated  effluent  data  and  plant  effluent
discharge  rate  (average hourly rate in 1/hr).  Figure 23 shows that 50
percent of the 53 plants evaluated have an effluent of less than  34,000
1/hr.   most  plants  analyze  for  total  metal  and oxidizable cyanide
(rather than total cyanide).  These concentration values reported by the
companies are typical average values (monthly period or longer).  Figure
24 shows  the  range  of  concentration  of  heavy  metals  and  cyanide
(oxidizable)   typically  achieved  by  those  plants  which  report that
pollution  parameter.   The  results  are  representative  of   chemical
treatment.   Figure  24  shows that 50 percent of the plants have values
less than the following:

                        Cu        0.2 mg/1
                        Ni        0.5 mg/1
                        Cr« +      0.055 mg/1
                        CrT       0.3 mg/1
                        Zn        0.3 mg/1
                        CN        0.04 mg/1.

From the limited data on total suspended solids in Table 27  about  half
the plants can achieve less than 15 mg/1.

    Table  28  provides  a comparison of the waste treatment results for
all 53 plants on the basis of total installed amperage.  The total plant
effluent  (1/hr)  in Table 27 was divided by the total  installed  current
capacity  (amperes)  in  Table  26  to obtain the plant water use (kg/AH
which is numerically equivalent to 1/AH)  shown in Table 28..   The  water
use  multiplied  by the concentrations (mg/1)  of each constituent in the
treated effluent shown in Table 27 gave  the  waste  discharged  (mg/AH)
shown  in Table 28.  Table 28 provides an approximate intercomparison of
the waste treatment results for various  plants  for  several  pollutant
parameters  over  a  wide  range  of  plant  sizes.   The data have been
normalized by the use of total current.  However, in order to draw valid
conclusions for direct comparison of two plants in Table  28  additional
information is needed on any unusual differences in thickness of deposit
(e.g., the two extreme cases of thick chromium plating are noted) or the
fraction of the rated current that is normally used  (Table 26).

    Figure 25 shows that 50 percent of the 53 plants can achieve a water
use  of less than  1.35 1/AH  (or kg/AH)  based on total installed current.
The water used would be about 2.0 1/AH based on  the  assumption  of  67
percent  of  the  rated  capacity normally used as indicated previously.
Since the latter water use (1/AH)  is independent  of  the  concentration
values  (mg/1) achieved in chemical treatment,  it is possible to multiply
the  median  water  use  and median concentrations to estimate the waste
discharge (mg/AH) which should be achievable for most plants:
                                  146

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                                        TABLE   2 7. TREATED EFFLUENT DATA
Company
Code
No.
1-16
3-1
3-3
3-4
6-3
6-12
6-29
8-4
8-5
11-8
11-13
11-22
12-3
12-5
]2-6
12-8
12-9
12-12
13-2
15-1
19-2
19-3
20-1
20-6
20-7
20-10
20-13
20-15
20-17
21-3
23-3
25-1
28-9
28-11
30-1
30-5
30-7
30-8
33-1
33-2
33-3F
33-3U
33-6
33-8
33-9
33-11
33-15
33-20
35-21
36-1
3G-2
40-4
43-1
Treated Effluent, m?/l
Classification
C/S/CCC-CC
C/S/--BEE-
C/S/-IEI-B
C/S/EB--BB
C/S/BII--B
C/M/ENCEEN
J/S/CCICIC
C/M/CCC-CC
C/L/CCC-CC
J/S/CCDECC
J/S/CCC-CC
C/M/000-BC
J/M/NEENNC
J/M/CCCCAC
J/S/DDE-BB
C/M/CCCCCC
C/S/IRI-IC
C/M/---EE-
C/M/COI-CC
C/M/---EE-
J/S/LCLLLC
J/S/--I--C
C/S/C-CCCC
C/S/CCB-BC
C/S/CCBCBC
C/M/-II--C
C/S/ICIIIC
C/M/-BB--B
C/S/CCCCCC
C/S/BBBBBB
J/M/CCC-CC
C/M/CCCCCC
J/L/-B--BB
C/M/CCCCCC
J/M/LCLLLC
C/S/II1IIC
C/S/III-IC
C/M/--NBBB
J/S/CCCCCC
C/S/BNN-NB
C/M/--IEEC
C/M/--IEEC
J/M/CCC--C
C/S/--B--B
J/M/NDD-NC
C/M/C-CCCC
C/S/CCB-BC
C/M/CCCCCC
C/M/--CCCC
C/S/BBBBBB
C/M/INI-1B
C/S/DDD--C
C/S/KCRBBB
TSS Cu
0.5

0.018
0.08
3.4 0.08
0.53

0.1

0.03
0.1
0.3
<0.5
2.4
1.0
0.7
<1.0

3


0.15
13 0.18
0.096
25 <0.1

<0.1

21 0.41
0.2
1.75
<0.07
<10.0
15 0.41
0.2
<0.2
<3.5

0.2
9.5 1.47


S.5 <0.1

9.5 0.13
3.1
20 0.2
0.21
106 0.12
<0.01
0.16
<2
0.29
Ni
1.0

0.002
0.48
0.6
19.6
0.6
0.06

0.16

0.00
1.5
2.2
1.0
0.2
<1.0

2.5


<0.20

0.39
<0.7
2
0.3
<1.0
0.48
0.25

0.8

0.5
7.0
<0.2


0.3
1.0


<0.05

1.6

0.42

0.3

39,700
34,000
15,400
1,100
6,800
9,100
18,900
47,300
94,600*
123,000
28,000
401,000
55,300
28,000*
78,700
68,000
39,700
47,300
11,000
3,800
28,400
3,100
42,600
44,700
68,000
39,400
34,000
68,000
250,000
12,000
473,000*
55,300
2,800*
170,000
30,000
91,000
8,700
62,500
32,500
42,600*
11,200
8,100
21,600
32,500
3,800
11,400
295,000
11,500
129,000
36,000
8,700
17,000
620*
(a)   \r.  usterick  after  the  total flow means an assumed 8-hour work day; values could be lower by a factor of 3  if
     liters  per day was based on 24-hour work day.
                                                      147

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                       TABLE   28  COMPARISON OF TREATED EFFLUENT DATA BASED ON TOTAL AMPERAGE
Company
Code No.
1-16
3-1,
3-3
3-4
6-3
6-12
6-29
8-4
8-5
11-8
11-13
11-22
12-3
12-5
12-6
12-8
12-9
12-12
13-2
15-1
19-2
19-3 
33-9
33-11
33-15
33-20
33-21
36-1
36-2
40-4
43-1
Classification
C/S/CCC-CC
C/S/--BEE-
C/S/-IEI-B
C/S/EB--BB
C/S/BII--B
C/M/ENCEEN
J/S/CCICIC
C/M/CCC-CC
C/L/CCC-CC
J/S/CCDECC
J/S/CCC-CC
C/M/000-BC
J/M/NEENNC
J/M/CCCCAC
J/S/DDE-BB
C/M/CCCCCC
C/S/IRI-IC
C/M/---EE-
C/H/COI-CC
C/M/—EE-
J/S/LCLLLC
J/S/--I--C
C/S/C-CCCC
C/S/CCB-BC
C/S/CCBCSC
C/M/-II--C
C/S/ICIIIC
C/M/-B3--B
C/S/CCCCCC
C/S/BBBBBB
J/M/CCC-CC
C/M/CCCCCC
J/L/-B— BB
C/M/CCCCCC
J/M/LCLLLC
C/S/I1IIIC
C/S/III-IC
C/M/--NBBB
J/S/CCCCCC
C/S/BNN-NB
C/M/--IEEC
C/M/--IEEC
J/M/CCC--C
C/S/--B--B
J/M/NDD-NC
C/M/C-CCCC
C/S/CCB-BC
C/M/CCCCCC
C/M/--CCCC
C/S/BBBBBB
C/M/INI-IB
C/S/DDD--C
C/S/RCRBBB
Water
Use,
kg/AH
2.4
3.4
0.38
0.09
1.2
0.27
3.1 ,
15.0
12.0*
1.3
1.5
5.5 -
1.5
2.0*
0.30
1.1
1.2
0.35
0.77
0.64
1.2
0.07
12.0
0.77
2.1
0.55
3.1
7.7
2.0
5.9
6.4*
0.73
0.14*
1.3
1.5
9.1
0.44
4.2
0.65
34*
1.6
1.1
0.86
132
0.40
0.77
0.64
1.9
2.5
2.3
2.4
0.64
0.08
Waste Discharge, tnp; per AH
TSS Cu
1.1

0.007
0.007
4.2 0.098
0.14

1.5

0.026
0.15
1.7
0.75
4.8
0.30
26 0.77
1.2

2.3


0.01
156 2.2
0.074
53 0.21

0.31

42 0.82
1.2
11.0
0.051
1.4
20 0.53
0.30
1.8
1.5

14 0.13
323 50


7.3 0.086

3.8 0.052
2.4
13 0.13
0.40
265 0.30
0.023
0.38
1.3
0.023
Ni
2.4

0.0003
0.043
0.74
5.3
1.9
0.90

0.21

0.05
2.3
4.4
0.30
0.22
1.2
*-
1.9


0.01

0.30
1.5
1.1
0.93
7.7
0.96
1.5

0.58

0.65
11
1.8


0.20
34


0.043

0.64

0.27

0.75
0.023
18
3.2
0.028
Cr+6
0.22


0.022
0.012
0.014
0.93
0.75

0.013
0.015
0.55
1.5

0.015





0.036
0.028
0.36
0.12
0.021



0.10




0.20
0.015
0.41


0.039
0.51


0.43

0.15
0.46
0.026
0.37
0.10

0.072


CrT
3.6
0.17
0.061

0.17
O./A

4.2
12.0
0.026
2.6

2.3
8.2
0.30
0.66
0.06



0.38
0.046

0.77
0.42
1.1
0.31
7.7
0.66
1.2
64.0
O.il

1.6
7.5
6.8

4.2
0.20
4.8
0.08
0.06

6.6
0.21
1.4
0.15
0.52
0.28
0.1.4
0.072
0.64
0.024
Zn

0.51


0.32
5.0



0.16

0.55

0.80

0.66
1.2

0.22
3.2

0.008
15.6

0.53

0.62

0.16
0.18
13.0
0.64

0.50
12
4.1

21
0.52

0.08
0.06



0.39
0.06
0.95
2.1
0.32
0.31


CN
0.22



0.12
0.30
0.22
0.15
0.12
0.013
0.015

9.8
19.8
0.06
0.11
0.03
0.35
0.77
1.9
1.2

0.72
0.008
0.021

0.31

0.003
0.059
1.3
0.022
0.0014
0.065
0.53
0.46

0.17
O.OS5
19
0.21
0.14



0.0077
0.016
0.015
0. 13
0.023
0.043

0.0008
(a)   An asterisk after  the water use means that calculations were based on  an  assumed  8-hour  work day.




(b)   Hard  chromium  only; multiply nuvibers by 50.  No chromium was expected  in  effluent.




(c)   '.lard  chromium  only; multiply numbers by 50.  Large water addition prior  to  treatment.
                                                    48

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  too —
 0.02 —
 0.01
     0    10    20    30    40   50    60    70   80    90    100
                           Cumulative  Percent

FIGURE 25.  WATER USE BASED ON TOTAL INSTALLED  CURRENT
             VERSUS CUMULATIVE PERCENTAGE OF 53 PLANTS

                           349

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                        Cu        0.4 mg/AH
                        Ni        1.0 mg/AH
                        Cr6+      0.11 mg/AH
                        CrT       0.6 mg/AH
                        Zn        0.6 mg/AH
                        CN(oxid)   0.08 mg/AH.

A comparison of the above values with those in Table 28 shows that  many
plants  attain  lower values for a single pollution parameter.  However,
for all pollution parameters (all heavy metals and  cyanide)  the  above
values  are attained by only 11 plants in Table 28  (3-1, 3-3, 3-4, 11-8,
12-6, 19-3, 25-1, 33-1, 33-15,  36-1, and 43-1).
                                  150

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Excepting plant 19-3 which has hard chromium  plating,  the  first  five
plants  listed use some type of in-process control for chemical recovery
whereas, the last five plants listed do not use any such systems.  Thus,
there is no present evidence  that  use  of  chemical  recovery  systems
results  in  less  discharge  of pollutants.  However, there is evidence
that water use can be reduced.

    Figure  26  shows  that  those  plants   (15)  that  are  using  some
combination  of  in-process  control for chemical recovery  (evaporation,
ion exchange, reverse osmosis) in one or more  plating  operations  have
lower  water  use than those plants  (38) that do not use such in-process
controls.  The apparent two to three-fold  reduction  in  water  use  in
probably  indicative  of  the  general  use  of multitank countercurrent
rinsing and other water conservation practices in these plants.

    Figures 27 through 33 show the data of Table 28 on performance being
obtained by various  plants  separately  for  each  parameter:   copper,
nickel, hexavalent chromium, total chromium  (Cr3+ + Cr6+), zinc, cyanide
(amenable to oxidation by chlorine)  and suspended solids.   For a general
estimate,  a  value  of  40  to  80 AH/scr m can be used to convert waste
discharged from mg/AH to mg/sg m and water use from kg/AH (or  1/AH)   to
kg/sa  m  (or  1/sq  m) .  The various waste management technologies were
identified by symbols in Figures 27 through 33.  The appropriar-  symbol
is  used  for  each parameter to show whether a reduction in guantity of
waste discharged was achieved as the  result  of  using  the  particular
technology.
                                  151

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    Continuous   (flow  through)   chemical  treatment  is  the  baseline
technology for  reference  with  inplant  segregation  of  chromium  and
cyanide  streams  for separate treatment prior to recombination with the
remaining waste streams (acid/ alkali and others)  for  final  separation
of  precipitated  metals.    The use of this technology provides the best
overall results for all parameters  because  its  use  insures  complete
treatment of the acid/alkali stream to remove precipitated metal.

    Complete  batch  chemical  treatment of all segregated streams;, is an
alternative to continuous chemical treatment that can provide equivalent
pollution reduction.  Batch chemical treatment of  only  the  hexavalent
chromium and cyanide streams (Figure 18 and 21)  combined with continuous
chemical  treatment  for  metal  removal  does not provide significantly
greater -pollution reduction (Figures 16, 17, 19, and 20) .

    All other technologies currently in  use  for  in-proce>ss  treatment
after one or more plating process such as integrated chemical treatment,
are  combined  with  end-of-process  continuous or batch treatment of at
least the acid/alkali stream for removal of metals.  Where there  is  no
treatment  prior  to  discharge  beyond  pH adjustment, the effluent may
contain a high level of pollutants.  There was no  evidence  from  plant
data  that any in-process treatment achieved greater pollution reduction
than that which can be achieved by end-of-process chemical treatment.

    In-process controls used after plating operations  for  recovery  of
chemicals such as evaporation, ion exchange, reclaim rinses, and reverse
osmosis  and/or  reduction of water use are combined with €>nd-of-process
chemical treatment.  Otherwise, the effluent may contain a high level of
pollutants.  Thus,  there is presently no evidence that greatter pollution
reduction than by chemical treatment can be achieved  by  use  of  these
technologies.   Closing  up one or all plating operations by evaporative
technology does not  presently  succeed  in  eliminating  the  pollution
parameter  from  the final effluent.  In general, the present use of the
above in-process controls does not lead to a  significant  reduction  in
pollution  for  the  total  electroplating facility which includes rinse
water after pretreatment and posttreatment operations.

    The above conclusions based on the  degree  of  pollution  reduction
achieved  by  existing  sources  indicates  that  end-ofprocess chemical
treatment in combination with in-process controls for water conservation
is the Best  Practicable  Control  Technology  Currently  Available  for
existing sources in the electroplating industry.

    In  using the term chemical treatment no distinction is made between
continuous chemical  treatment,  batch  chemical  treatment,  integrated
chemical  treatment  or  other  in-process  treatments  or  combinations
provided that the effluent limitations are achieved.  No distinction  is
made  in  the  specific  chemicals used, specific chemical reactions, or
specific processes employed for destruction  of  cyanide,  reduction  of
                                  160

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hexavalent   chromium,  or  removal  of  metals  provided  -the  effluent
limitations are achieved.  In using the  term  in-process  controls,  no
distinction is made between the various methods of recovery of chemicals
or  water  conservation.  Effluent limitations can be achieved by either
reduction in water use or reduction in concentration of pollutant  after
final  treatment  or both.  It is recognized that the results attainable
with any wastemanagement technology are dependent on  correct  operation
of  the  process,  the  maintenance  of control instrumentation, and the
quality and capability of operating and supervisory personnel.

Detailed Analysis of Plant Data

    From the above analysis of  data  from  53  plants,  5  plants  were
selected  for additional on-site detailed analysis of plating operations
for correlation with in-porcess  controls  for  water  conservation  and
waste  treatment  results  including  sampling  to  verify effluent data
reported.  One of the plants selected  (19-3)   had  only  hard  chromium
plating  operations  which  is  a special situation because of the thick
deposit.  The other four  plants  (11-8,   12-8,  33-1,  and  36-1)   were
selected as representative of the average of the best plants involved in
rack and barrel electroplating of copper, nickel, chromium and zinc.

    The  data  obtained  from each of the four second round plant visits
were analyzed with respect to the various  pertinent  process  lines  of
rack  and barrel plating of copper,  nickel, chromium, and/or zinc.   Non-
pertinent process lines  (e.g., and anodizing,   bright  dipping,  cadmium
plating,  or  other  than  rack and barrel plating) were not included as
well as certain  pertinent  process  lines  not  in  use  or  for  which
insufficient  data were available.  The composite of the pertinent lines
was also analyzed.  The purpose of the analysis was to study water use.

    The various factors based on the  composite  of  process  lines  are
shown  in Table 29.  The monthly average concentration of each pollutant
parameter reported by the plant multiplied by  the  specific  water  use
(1/AH)   or  effluent factor (1/sq m)  yields the waste discharge in mg/AH
or mg/sq m respectively as  shown  in  Table  30.   The  values  can  be
compared  to  the  recommended  1977  effluent  limitations for existing
sources for copper, nickel, chromium  (total),  zinc,  and  total  cyanide
(40 mg/sq m)  and for hexavalent chromium and oxidizable cyanide (4 mg/sq
m) and for suspended solids (1200 mg/sq m) .

    For  comparison,  the  corresponding  data  using the results of BCL
sampling and analysis on the day of the plant visit and the  appropriate
water use factors from Table 29 are shown in Table 31.

    For  plants  required to analyze daily composite samples for monthly
reporting to authorities, the monthly averages over a prior period of  6
to  12  months  were used to determine typical average concentrations of
pollutants.  In general, the latter  value  is  more  representative  of
                                  161

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      TABLE 29. SUMMARY OF WATER USE PARAMETERS FOR FOUR
                PLANTS BASED ON COPPER,  NICKEL CHROMIUM
                OR ZINC PLATING AND EXCLUDING NON-
                PERTINENT METAL FINISHING PROCESSES
Company
  No.
 Specific
Water Use,
   I/AH
Effluent
 Factor,
 1/sq m
     Coulombic
Equivalent Factor,
      AH/sq m
  11-8

  12-8

  33-1

  36-1

average
   2.44

   1.77

   1.34

   1.08

   1.66
  170.3

   95.5

   77.3

  114.0

  114.3
        69.7

        53.7

        57.6

       105.6

        71.7
                              162

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waste treatment results than samples obtained over a short period during
a  plant  visit.   However, for Plant 33-1, the average results for 1972
were considerably higher than those obtained after about June  1972,  as
shown  in  Table  32.  A significant reduction in concentration of heavy
metals  occurred  coincident  with   reduction   of   suspended   solids
concentration as a result of improved clarification.  The concentrations
currently  as  achieved  in  1973 are lower than the average values used
previously in Table 30 to determine mg/AH and mg/sq m for each pollutant
parameter.

    One purpose of the sampling during plant visits was  to  verify  the
accuracy  of  the  analytical results for the plant effluent reported by
the plants.  The accuracy of the analytical procedures used at  Battelle
was  verified  by analysis of standard EPA reference samples provided by
the EPA Analytical Quality Control Laboratory,  Cincinnati,  Ohio.   The
subsequent  comparison  of Battelle results with values for the standard
reference samples provided later by EPA are  shown  in  Table  33.   The
agreement  in  results was very good.  In the range of concentrations of
interest  (Samples 2 and 3), the percent deviation  of  Battelle  results
was 2 to  12 percent.

    Daily  variations in concentrations of metals and cyanide in treated
effluent compared to the monthly average are to be expected.  Figure  34
shows  the  typical  variation  in analysis of daily composits over a 4-
month period for Plant 11-8.  Because of the  low  concentrations  being
measured,  daily  concentrations  are at times twice the monthly average
concentration.  One factor is analytical accuracy.  For example, in  the
measurement of copper (1 mg/1) , chromium (0.05 mg/1) and zinc (0.5 mg/1)
by  atomic absorbtion methods the relative standard deviation is 11, 26,
and 8 percent respectively  (4).  Another factor is that daily  composite
samples  are usually analyzed the day following collection.  Thus, there
is a 24-hour time lag in detection of slight changes in waste  treatment
performance  before  corrective  action  is taken.  In view of the above
factors and determination of plated area, effluent limitations should be
based on cumulative 30-day averages with an allowance for daily maximums
exceeding the 30-day average by a factor of 2.
                                  163

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TABLE 30. SUMMARY OF TREATED EFFLUENT FROM COPPER,  NICKEL,
          CHROMIUM OR ZINC EXCLUDING NON-PERTINENT  PLANT
          METAL FINISHING OPERATIONS
Pollutant
Parameter
Cu
mg/1
rag/AH
mg/sq m
Ni
mg/1
mg/AH
mg/sq m
Cr (Hex)
mg/1
mg/AH
mg/sq m
Cr(Tot)
mg/1
mg/AH
mg/sq m
Zn
mg/1
mg/AH
mg/sq m
CN(Ox)
mg/1
mg/AH
mg/sq m
Plant
11-8

.03
.07
5.1

.16
.39
27.2

.01
.02
1.7

.02
.05
3.4

.12
.29
20.4

.01
.02
1.7
Plant
12-8

.70
1.24
66.8

.20
.35
19.1

—
--
— —

.60
1.06
57.3

.60
1.06
57.3

.10
.18
9.6
Plant
33-1

.20
.27
15.5

.30
.40
23.2

.06
.08
4.6

.31
.42
24.0

.80
1.07
61.9

.13
.17
10.0
Plant
36-1

.03
.03
3.4

.02
.02
2.3

.01
.01
1.7

.06
.06
6.8

.14
.15
16.0

.01
.01
1.1
Average

.24
.40
22.7

.17
.29
18.0

.03
.04
2.7

.25
.40
22.9

.41
0.64
38.9

.06
.10
5.6
                     164

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TABLE 33. SUMMARY OF TREATED EFFLUENT BASED ON  BCL
          SAMPLING AND ANALYSIS DURING  SECOND
          ROUND VISIT FOR COMPARISON WITH  TABLE 2
Pollutant
Parameter
Cu
mg/1
mg/AH
mg/sq m
Ni
mg/1
mg/AH
mg/sq m
Cr (Hex)
mg/1
mg/AH
mg/sq m
Cr (Tot)
mg/1
mg/AH
mg/sq m
Zn
mg/i
mg/AH
mg/sq m
CN(Tot)
mg/1
mg/AH
mg/sq m
SS
mg/1
mg/AH
mg/sq m
Plant
11-8

.07
.17
12

.54
1.32
92

.15
.37
25

.33
.80
56

.49
1.20
83

.78
4.64
133

—
—
—
Plant
12-8

.33
.58
31

.17
.30
16

.65
1.15
62

1.33
2.35
127

.42
.74
40

.22
.39
21

24
42
2292
Plant
33-1

.46
.62
36

.22
.29
17
«•
.05
.07
4

.20
.27
15

.90
1.21
70

.21
.28
16

22
29
1701
Plant
36-1

3.16
3.41
360

.44
.47
50

.05
.05
6

.28
.30
32

.66
.71
75

.13
.14
15

20
22
2280
Average

.29
.46
26

.34
.60
44

.22
.41
24

.54
.93
57

.62
.96
67

.33
1.36
46

22
31
2091
                 165

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                 Ef fluentLimitations
    The quantitative effluent  limitations  based  on  Best  Practicable
Control  Technology Currently Available for existing sources discharging
to navigable waters to be achieved by 1977 were listed in Table 1.    The
quantitative  values were based on determination of what can be achieved
by the average of the best plants in the electroplating  category.    The
values  are  based  on technical consideration of what concentrations of
pollutants in the treated effluent can be achieved by chemical treatment
and technical consideration of what reduction in water use  for  rinsing
can   be  achieved  by  normal  practice  by  existing  sources  in  the
electroplating industry.  The basis for the 30- day effluent  limitations
will be reviewed first considering the heavy metal pollutants.

    For  copper,  nickel,  total  chromium,  and  zinc it is possible to
achieve 40 mg/sq m as was shown for the average of four plants  analyzed
in  detail.   In  addition, the average of the median values for copper,
nickel, chromium, and zinc for 53 plants is about 0.3 mg/1.   Thus,  the
effluent  limitations  can be met with an effluent factor as high as 120
1/sq m.  The median water use of 53 plants was shown  to  be  about  1.3
1/AH  based  on  rated  current or about 2 1/AH based on typical current
used.  Thus, a coulombic factor of 60 AH/sq m based on  typical  deposit
thicknesses indicates an effluent factor of 120 1/sq m.

    Water  use  less  than 120 1/sq m can be achieved using good rinsing
practice.

    For example, an automatic  copper,  nickel,  chromium  rack  plating
operation achieved 22 1/sq m and two different zinc platers  (with chromate
conversion) achieved 45 1/sq m.  The above values were attainable by use
of good in-process control without the  use  of  any  advanced  recovery
techniques.

    Allowing  for  the fact that all existing sources may not be able to
use  optimum  water  conservation  because  of  space   limitation   for
additional  rinse  tanks,  a  value  of 80 1/sq m appeared to be broadly
applicable.  Two of the plants studied in  detail  achieve  this  value.
Thus,   the   combination  of  an  effluent  factor  80  1/sq  m  and  a
concentration of 0.5 mg/1 for copper, nickel, total  chromium  and  zinc
appeared  to  be  technically  achievable  by  over 50 percent of the 53
plants studied.  This was the basis for the effluent limitations  to  be
achieved  by  1977.   From the study of plant operations, it was evident
that there are many process lines  on  which  significant  reduction  in
water  use  for  rinsing  could  be  achieved  by  normal electroplating
practice provided there was an incentive.  For  those  existing  sources
that  can  reduce  their water use sufficiently to achieve 40 1/sq m, it
will be sufficient to reduce the total metal concentration below 1  mg/1
to achieve an effluent limitation of UO mg/sq m.
                                  166

-------
    TABLE  32.   MONTHLY  AVERAGE EFFLUENT CONCENTRATION
                FOR PLANT 33-1 SHOWING IMPROVED  RESULTS
                OBTAINED OVER A 14-MONTH PERIOD

Chromium
Year Month
1972 Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
1973 Jan.
Feb.
Mar.
Apr.
Cd
0.31
0.28
0.26
0.54
0.15
0.03
0.07
0.03
0.03
0.01
0.01
0.18
0.05
0.05
0.05
0.09
Cr0^
0.08
0.15
0.12
0.05
0.05
0.04
0.04
0.04
0.05
0.03
0.05
0.03
0.01
0.02
0.01
0.02
Crj+
1.07
1.45
0.08
0.70
0.30
0.16
0.16
0.26
0.15
0.07
0.05
0.05
0.06
0.10
0.02
0.03

1
0
1
1
1
1
0
0
0
0
0
0
0
0
0
0
Cu Fe Ni
.6
.80
.3
. 30
.10
.0
.30 0.30 0.30
.60 0.20 0.60
.80 0.20 0.60
.20 0.10 0.80
.20 0.30 0.70
.15 0.20 0.20
.10 0.20 0.20
.03 0.08 0.10
.09 0.09 0.10
.07 0.20 0.06
Zn
5
16
24
8
2
0
0
0
0
0
0
0
0
0
0
0
.6
.0
.0
.50
.40
.2
.20
.20
.20
.10
.20
.20
.10
.09
.03
.20
CN
0.08
0.08
0.09
0.06
0.06
0.12
0.10
0.11
0.10
0.10
0.02
0.02
0.02
0.01
0.01
0.02
S.
18
32
52
27
12
8
10
10
10
15
11
12
11
8
11
11
S.
.9


.50
.0
.0
.0
.0
.0


.4
.1
.9
.0
.6
pH
7.5
7.6
7.2
8.3
8.4
8.9
8.4
8.1
8.9
8.8
8.5
7.9
7.6
7.8
7.9
7.7

(1)  Averaged concentrations for  each month  are in mg/1 for daily composite
    analysis of waste water.
                           167:

-------
TABLE 33.  COMPARISON OF BATTELLE ANALYTICAL RESULTS
           WITH EPA REFERENCE STANDARDS
Concentration, mg/1

Cadmium
Chromium
Copper
Iron
Lead
Manganese
Zinc
Sample No.
Standard
0.0018
0.0092
0.009
0.018
0.028
0.013
0.010
1
BCL
0.002
0.014
0.012
0.016
0.027
0.015
0.014
Sample
Standard
0.016
0.083
0.067
0.402
0.092
0.096
0.079
No. 1
BCL
0.018
0.089
0.071
0.410
0.094
0.100
0.081
Sample
Standard
0.073
0.406
0.314
0.769
0.350
0.449
0.367
No. 1
BCL
0.064
0.385
0.300
0.740
0.337
0.438
0.384
                     168

-------
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                 5  10 15 20 25     5 10  15 20 25   5 10  15 20 25    5 10 15 20 25
                    January        February         March           April
FIGURE 34.  TYPICAL VARIATION IN CONCENTRATION OF POLLUTANT
              PARAMETERS FROM ANALYSIS OF DAILY COMPOSITE OVER
              A 4-MONTH PERIOD REPORTED BY PLANT  11-8
                                     169

-------
    The  effluent,  limitations  for  hexavalent  chromium and oxidizable
cyanide were determined to be 4  mg/sq  m.    For  example,  an  effluent
factor  of  80  1/sq  m  and a concentration of 0.05 mg/1 in the treated
effluent are both technically achievable.   Several of the  plants  studied
in  detail  could achieve lower than 4 mg/sq m for these peirameters;  the
average for the four plants was close to this value.  The median  values
achieved  by  53  plants  studied  was  about  0.05  mg/1.   Since  both
hexavalent  chromium  and  cyanide  are  normally  chemically treated  in
segregated   streams   there  is  more  latitude  in  achieving  optimum
treatment.  Also, the treated effluent streams are subsequently  diluted
with  other  electroplating  waste  streams  which  further  reduces the
concentration in the final plant effluent.   The concentration  level  of
hexavalent   chromium  and  oxidizable  cyanide  are  not  dependent  on
clarification  efficiency  as  with   metals   that   are   removed   by
precipitation.

    The effluent limitation for total cyanide of 40 mg/sq m was based on
a  concentration of 0.5 mg/1 combined with an effluent factor of 80 1/sq
m.  Some plants may analyze for  total  cyanide  and  report  the  value
simply  as  cyanide meaning maximum oxidizable as well as total cyanide.
However,  some plants report oxidizable cyanide only.  The average value
determined by Battelle analysis of samples from the four  plants studied
in  detail  was  less  than  0.5  mg/1 total cyanide.  Three of the four
plants had 20 mg/m2 or less.

    The effluent limitation for total suspended solids of 1200  mg/sq  m
was  based  on  an  effluent  factor  of  80  1/sq  m  combined  with  a
concentration 15 mg/1 achieved by over half of the plants for which data
was available.  The value for three plants during visits was  22  to  24
mg/1 representative of a single day.

    A  9-month  average  value of about 10 mg/1 achieved by one of these
plants was considered representative.

    The above  values  used  in  determining  effluent  limitations  are
summarized  in  Table  35  in  terms  of  concentration of the pollutant
parameter in mg/1 for selected effluent factors in 1/sq m,  the  product
of  which corresponds to the effluent limitations of Table 1 in mg/sq m.
The concentrations of Schedule A and B in the interim guidelines for the
electroplating industry  as  shown  for  comparison.   In  general,  the
concentration  values  of Schedule A are similar to those for an assumed
effluent factor of 80 1/sq m.   The  latter  values  on  which  effluent
limitations  are  based  represent  what  is technically achievable; the
desired values in Schedule A were derived with  consideration  of  water
quality and stream standards.


    The  effluent  limitations  for BPCTCA in Table  1 are based on total
metal rather than dissolved metal for several reasons,  but  principally
                                 170

-------
because insoluble metal hydroxides can redissolve depending on the pH of
the  receiving  body of water.  The need to limit insoluble metal in the
effluent has been recognized for a long time  (e.g., the limit of  l/i'g/1
for  insoluble metal for ru, Ni, Zn and 1.25 mg/1 for Cr in schedule A).
Good  clarification   and    separation     of    suspended
solids  prior  to  stream  discharge  has been practiced for many years.
Since the plant effluent is usually  discharged  at  the  same  pH  that
clarification  occurs,  the  soluble metal concentration will usually be
significantly less than the total  metal  concentration.   Analysis  for
total metal only reduces the expense of plant monitoring of the effluent
discharge.

Additional^Fgctgrg_Considered_in_Selection
of_Best_Practicable_Control_TechnglogY
Currently Available

Total Cost of Application of Technology in Relation to
Effluent Reduction Benefits

    Based  upon information contained in section VIII of the report, the
average cost of chemical treatment prior to  discharge  of  effluent  to
surface  waters  from medium sized and large plants, is $10.70/100 sq m.
($9.9/1,000 sq ft).  This cost averages 4 percent of the plating cost and
normally will be less than 5  percent  of  the  plating  cost  for  most
plants.   The  application  of  this  technology can achieve an 85 to 99
percent reduction in pollutants in the effluent  discharged  to  surface
waters.

    Cost  of  chemical  treatment  in  small  plants  are  greater  than
$10.70/100 sq m ($9.91/1000 sq ft)  as indicated in Table 21.

    Cost for small plants increase as size decreases because there is  a
minimum  capital  investment  ($50,000)  for  a chemical waste treatment
facility.

Size and Age of Equipment and Facilities

    The size of the electroplating facility in  terms  of  surface  area
plated  or  the  ampere-hours  used  does  not affect the raw waste load
concentration and  the  degree  of  pollution  reduction  attainable  by
application of the waste-treatment technology.  The cost of applying the
technology  is  not significantly different when expressed as percentage
of plating costs for a wide range of plant sizes with the  exception  of
the very small plants discussed above.

    Age  of  waste-treatment facilities is a factor that will affect the
capital cost outlay.   This  will  be  greatest  for  those  plants  not
presently  treating  waste prior to discharge to surface waters.  Modest
investments  will  be  required  to  update  some   existing   treatment
                                  171

-------
facilities  to  meet  the effluent limitations.   Recently constructed or
updated facilities might not require  any  further  capital  investment.
Some  small  increase  in operating costs may be reguired to achieve the
effluent limitations but the total cost of application of the technology
would not exceed that based on the average of the best plants.

    Some existing sources have a large investment in  automatic  plating
machines  which are difficult or expensive to modify for installation of
additional rinse tanks after pretreatment and posttreatment  operations.
For  other  existing  sources  where  space  is  at a premium it might be
expensive and sometimes impractical to redesign  existing  plating  lines
or  redesign the entire plating facility to accommodate additional rinse
tanks for optimum water  conservation  on  all  operations.   For  these
reasons,  extending  in-plant controls for water conservation to closed-
loop operation and/or multitank rinsing following alkaline cleaners  and
acid  dips  was  not  considered  practicable  for all existing sources.
Without such currently available in-process  controls  to  reduce  rinse
water  usage,  other  advanced technology designed to close up the plant
with complete reuse of water  to  achieve  no  discharge  of  pollutants
cannot  be considered for existing sources except in special situations.
It should be noted that limitations of space for sufficient rinse  tanks
would  not  apply  to  design  of  a  new  plating  facility.  Also, the
limitations  of  space  within  existing  automatic  machines  as  older
eqiupment  if retired over the future years.  Thus, age of eqiupment and
facilities is a factor that influences what is practical  to  accomplish
over the years.

    Because  of  the  above factors, Best Practicable Control Technology
Currently  Available  for  existing  electroplating  facilities  in  the
industry would not achieve  the  elimination  of the  discharge  of process
waste water  pollutants.

Processes Employed
    The  possible variations in electroplating processes within a single
existing facility were also considered.  Complete segregation of single-
metal waste streams was not considered  practical,  based  on  available
technology.   Stream integration dilutes one process wastewater with one
or more other and might result in little or no removal of certain metals
in concentrations below the solubility limit.

    In defining the Best  Practicable  Control  Technology,  no  special
allowance was made for variations in product design or shape factor.  If
the  shape  of  the  parts  being  plated  requires the use of inprocess
controls such as countercurrent rinsing, evaporation, or other  advanced
recovery  systems  for  achieving  reduced  water  use to counteract the
effect of unusually high dragout, any supplemental cost  may   be  added
to  the  cost  of plating.  Any such incremental increase in the cost of
plating will direct attention to the design of  parts  that  drain  more
easily to reduce dragout.
                                  172

-------
Engineering Aspects of the  Application  of  Various  Types  of  Control
Technology

    Advanced  in-process  controls for recovery of plating chemicals are
rapidly gaining acceptance and often show a net cost savings compared to
chemical treatment.  However,  the  applicability  of  these  in-process
controls  is  dependent  on  first  achieving  reduction in water use by
multitank countercurrent rinsing.  Such installation is not practical in
all, cases depending on the age of equipment discussed above.

Process Changes

    Process changes are not currently available for  the  electroplating
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 eliminate all.  They may be useful in
some  facilities  for  reducing  the  cost  of  meeting   the   effluent
limitations recommended in this document.

Nonwater Quality Enviromental Impact

    As  discussed in Section VIII of this report, the principal nonwater
quality aspect of electroplating 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  electroplating  facilities.   The  problem  would  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 requriement
for water-pollution reduction.
                                   173

-------
    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  existing  electroplating  sources
discharging 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.  Achieving
the effluent limitations by application of chemicaltreatment  technology
will  have little impact in total quantity  of  sludge where solid waste
disposal  is a problem.

    There will be no direct effect on ai r quality as  a  result  of  the
application  of  recommended  technology  for water-pollution reduction.
Indirect effects related to increased energy use will be minor.   Energy
requirements (mainly electrical)  for chemical treatment are estimated to
be 3.2 percent of the power needed for electroplating.

l-f f luent_Limitations_Bgsed_on_the
Application_of^Best Practicable
Control TechnologY Currently Available

    The   recommended   effluent  limitations  to  be  achieved  by  the
application of Best Practicable Control Technology  Currently  Available
were  shown  previously  in  Table  1  of  Section  II  of  this report.
Expressing effluent limitations in weight per unit of plated area (mg/sq
m) is a new concept that required careful interpretation.  For  example,
one  square metal of surface that is consecutively plated with layers of
copper, nickel, and chromium constitutes three square meteirs  of  plated
area.   The rationals for choice of units is discussed below in relation
to guidelines for application.

Guidelines for_the Application
of_Effluent_Limitations

Selection of Production Unit

    Effluent limitations are intended to specify the maximum quantity of
pollutants which may be contained in  the  discharged  treated  effluent
from  a  point  source.   This  quantity  must  be  related to a unit of
production so that the effluent limitations can be  applied  broadly  to
various  plants  in  the  same  category  regardless of their production
capacity.   For  example,  an  effluent  limitation  for  a   particular
                                  174

-------
wastewater  constituent in mg/unit times the production rate in units/hr
equals the maximum amount of that constituent that can be discharged  in
mg/hr.  Thus, for any production unit:

            	mg    X   Unit      =   mg  X  1__
            Unit          hr           1     hr

    The right-hand side of the  above  equation  represents  the  normal
method  of  monitoring  based on analysis of concentration of individual
pollutants in the effluent in  mg/1  and  measurement  of  the  effluent
discharge  rate  in  1/hr.   Expressing  the  effluent  limitation  as a
function of a production unit compensates for change in production rate,
which changes the effluent discharge rate.  The  effluent  rate  in  the
electroplating industry is closely related to the rinse water rate which
is in turn related to the production rate of electroplated parts.

    The  effluent  discharge rate as volume per day is commonly reported
by electroplating and other industrial sources.  Because many plants  do
not  work on a 24-hour-day basis at all times, it would be preferable to
use the next smaller unit of time, which is an hour.   This  avoids  the
uncertainty  associated with the daily unit which often requires further
defintion as to the number of shifts worked per day and  the  hours  per
shift.

    The  most  appropriate  production unit in some industries is either
the weight of product produced or the weight of raw materials purchased.
Neither a unit quantity of product produced nor a unit quantity  of  raw
material use is appropriate for the electroplating industry, because the
quantity  of product expressed as the weight of products plated does not
bear any relation to raw waste produced.  Electroplating  is  a  surface
process  that  is  not  influenced  by the volume or density of the part
plated.  The raw waste load is related to surface area (not  volume)  of
electroplated  parts which determines the concentrated solution dragout,
rinse water use,  and  ultimately  the  degree  of  pollution  reduction
achievable.   While  it  is  common  in barrel plating of small parts to
weigh the plated parts as a control  measure  for  basket  loading,  the
optimum  weight  of  parts  was originally determined by trial and error
plating or precalculation of the  part  per  unit  weight  in  order  to
achieve  the  correct  total  area  for optimum plating current density.
Regardless of the method  of  controlling  the  plating  operation,  the
dragout is related to the total area of parts plated and not the weight.
Solution  adhering  to  the  surface  of  small  parts  causes  dragout.
Although some cup-shape parts that are difficult to drain or  rinse  may
cause  high  dragout not directly related to area, weight would not be a
good unit quantity applicable to both rack and barrel plating.

    Although the amount of raw material used or chemicals purchased  was
considered  as  a  possible unit quantity related to production, neither
unit appeared suitable as a reliable measure of production.  The  weight
                                  175

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of  material  purchased  and used as soluble anodes ends up on the parts
plated, but this weight must be  divided  by  the  thickness  plated  to
obtain  a  correlation with production rate in area plated per unit time
which is the true determinant  of  raw  waste  load.    In  the.  case  of
chemicals purchased for bath make up and particularly for chromium salts
purchased  for  plating  with  insoluble  anodes,,  there  is  a  further
complication.  A material balance will show that the difference  between
the  chromium  purchased  and  the chromium on the plated parts produced
equals the chromium in the precipitated sludge minus the small amount of
chromium discharged  with  the  treated  effluent.   Thus,  chromium  in
chromium  salts  purchased  in  excess  of that on plated parts reflects
dragout  and  increased  sludge  but  not  necessarily  increased  water
pollution.   The  same  reasoning  applies to all other metal-containing
chemicals  purchased  for  bath  make  up  which  primarily  end  up  as
precipitated  and  separated  sludge.   Although the amount of chemicals
purchased indicates total dissolved salts in the treated effluent, total
dissolved solids is not considered an important pollutant  parameter  in
the electroplating industry.

    Consideration  of  the  above factors led to the conclusion that the
unit of production most applicable to  the  electroplating  industry  is
surface  area.   The surface area withdrawn from a concentrated solution
in a plating operation is the paramount factor  influencing  dragout  of
solution  constituents, some portion of which ends up in the waste water
and treated effluent.  Surface area  influencing  dragout  includes  not
only  the  surface  area  receiving an electroplate but also the surface
area of nonsignificant surfaces receiving little  or  no  electrodeposit
plus the surface area of racks or barrels which hold the parts.

    The total surface area is rarely known and impractical to measure in
some  cases  in  the  electroplating industry.  In this case, the plated
area is the alternative logical unit of  production.    Even  so,  plated
area requires precise definition and is not the type of information that
is  readily  available from all plants.  Alternative units of production
based on amperes and water use, which are  more  easily  measured,  were
developed  and  correlated  with plated area and ultimately to the total
surface area in establishing effluent limitations.

Plated Area Unit of Production

    The plated area is the primary  unit  of  production  on  which  the
effluent  limitations in Table 1 are based.  Plated area is defined with
reference to Faraday's Law of electrolysis by the following equation:

                                 S   =  BIT
                                       100 Kt

where S = area, sq m  (sq ft)
E = cathode current efficiency, percent
                                  176

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I = current used, amperes
T = time, hours
t = average thickness of deposit, mm (mil)
k = a constant for each metal plated based on
the electrochemical equivalent for metal
deposition, amp-hr/mm-sq m (amp-hr/mil-sq ft).

The numerical product of current and time (IT)  is the value  that  would
be  measured by an ampere-hour meter.  Values of the constant k based on
the valence of the metal deposited and the typical current  efficiencies
for various electroplating operations are shown in Table 34.

    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 uni^.  time  in  each  plating  operation  when  the  only  available
information  was  the current used and the average thickness of deposit.
Equation (2) was also used as a  check  on  estimates  of  surface  area
plated provided by the plants contacted.

    To calculate the total plated area on which the effluent limitations
are  based for a specific plant, 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 as in copper-
nickel-chromium decorative plating)  the plated  area  is  calculated  by
the equation   for  each  plating operation 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 for each
plating  operation  in  a  single  process  line,  the  average  of  the
calculated  plated  areas  for  the operations was used.  The sum of the
plated areas for each process line is the  total  plated  area  for  the
plant.

    Small 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 35 which are  to  be
used  for  the  calculation.   However,  experience with data from several
plants indicated that the more likely cause of the  discrepancy  is  the
accuracy of the reported values of average plate thickness.

    The use of ampere-hour on rectifiers might have value for monitoring
or  record  keeping for some plants in lieu of measuring the area of the
parts  plated  provided  the  average  thickness  plated  is  known   or
determined.
                                  177

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            TABLE  34.   TYPICAL  CURRENT EFFICIENCIES ASSUMED
                       FOR  CALCULATION OF PLATED AREA
                       USING  EQUATION (2)
                             Typical
                             Current
            Type  of         Efficiency,   	Constant (k)	
        Plating Operation    percent    amp-hr/mm-sq m  amp-hr/mil-sq ft
Cyanide copper
Noncyanide copper
Nickel
Chromium
Cyanide zinc
Noncyanide zinc
50
100
100
13
60
100
3
7
8
21
5
5
.75
.49
.05
.95
.80
.80
X
X
X
X
X
X
10
10
10
10
10
10
3
3
3
3
3
3
8.
17,
19.
51.
13.
13.
84
68
00
80
70
70
    Records  of  plating  voltage and ampere-hours on each rectifier (or
watt-hours) plus thickness deposited might be correlated with watt-hours
of electricity consumed per  day  or  month  with  allowance  for  other
electricity  uses  (lighting,  pumps, etc)  to estimate total plated area
per day or month.  The total effluent could be approximated by the plant
water purchases if mainly for electroplating.  Thus,  the information  on
electric  power consumption and water consumption from monthly bills for
these services might be used in an approximation of  daily  plated  area
for a cross check against plated area determined by more direct means.

    In  practice,  it  should  be possible for electroplaters to readily
adapt to keeping records of plated area  for  reporting  purposes.   The
fact  that  many  platers do not presently know their production rate in
terms of surface area plated is not a valid  consideration  since  there
has  been no prior requirement to keep such records.   Determining plated
area should not be difficult for  platers  whose  process  operation  is
dependent  on  use  of  the  correct current density for optimum plating
results.
                                  178

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TABLE 3 5  COMPARISON OF EFFLUENT LIMITATIONS FOR BPCTCA (TABLE I) IN TERMS
           OF CONCENTRATION FOR VARIOUS EFFLUENT FACTORS WITH THE PRIOR
           INTERIM GUIDELINE CONCENTRATIONS

Concentration , mg/1
Effluent Factor^,
1/sq m ,
Parameter
Cu
Ni
Cr6+
CrT
Zn
CN, oxid.
CN, total
TSS
40 80
1 0.5
1 0.5
0.1 0.05
1 0.5
1 0.5
0.1 0.05
1 0.5
30 15
160
0.25
0.25
0.025
0.25
0.25
0.025
0.25
7.5
Schedule A^c'
1.2 (0.2)
2.0 (1.0)
0.05
0.25 (0.1)
1.5 (0.5)
0.03
0.5
10
Schedule B
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                               SECTION X

                 BEST AVAILABLE TECHNOLOGY ECONOMICALLY
                 ACHIEVABLEJL_GUIpELINEi_AND_LIMITATigNS
    The effluent limitations which must be achieved July 1, 1983 are  to
specify   the  degree  of  effluent  reduction  attainable  through  the
application of the Best Available  Technology  Economically  Achievable.
This  technology  can  be  based  on the very best control and treatment
technology employed by a  specific  point  source  within  the  industry
category  and/or  subcategory or technology that is readily transferable
from one industry process to another.  A specific finding must  be  made
as  to  the  availability of control measures and practices to eliminate
the discharge of pollutants,  taking  into  account  the  cost  of  such
elimination.

    Consideration must also be given to:

    (a)  the age of the equipment and facilities involved;

    (b)  the process employed;

    (c)   the engineering aspects of the application of various types of
control technologies;

    (d)  process changes;

    (e)  cost of achieving the effluent  reduction  resulting  from  the
technology;

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

    The Best Available Technology Economically Achievable also  assesses
the  availability  in  all  cases  of in-process controls as well as the
control or additional treatment techniques employed  at  the  end  of  a
production process.

    A further consideration is the availability of processes and control
technology  at  the pilot plant, semi-works, or other levels, which have
demonstrated both technological performances and economic viability at a
level sufficient to reasonably justify  investing  in  such  facilities.
Best  Available Technology Economically Achievable is the highest 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
                                  180

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including  no  discharge  of  pollutants.  Although economic factors are
considered, the costs for this level of control are intended to be  top-
of-the-line  of  current  technology  subject  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
development work prior to its application.


Industry Category and Subcategory Covered

    The  pertinent  industry  category is the electroplating industry as
defined previously in Section IX.


Identification of^Best_Ayailable_Technology
EconomicallY_Achievable

    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 inprocess controls to reduce the
volume of  wastewater,  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 to navigable waters.   Solid
constituents in the wastewater are disposed of to landfill or otherwise.
As discussed in sections VTI and VIII one such type of treatment  system
that  has  been  designed  and  is  currently  in  operation supplements
conventional chemical treatment with  the  use  of  reverse  osmosis  to
recover  water  from  the  treated  waste  stream.   Additional water is
recovered for reuse by evaporation and distillation of the  concentrated
waste stream from the reverse osmosis unit.  The concentrated wastewater
solution  from  the  evaporator  is dry salt.  It is expected that other
methods will be developed during the next five years to avoid  discharge
of  effluent  to  navigable  waters  and  thus  achieve  no discharge of
pollutants in an economical manner.


Rationale_for_Selection_of_Best_Available
Technology Economically Achievablg


Time Available for Achieving Effluent Limitations

    As noted previously, the effluent limitations selected for the  Best
Available Technology Economically Achievable for existing sources do not
have  to  be achieved before July 1, 1983.  This longer-range limitation
allows sufficient  time  for  retirement  and  replacement  of  existing
electroplating  and  waste-treatment  facilities  as needed.  Not all of
                                  181

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these necessary changes can be expected by July 1,  1977 without  placing
an  unjustifiable  economic  burden  on those plants which are currently
practicing pollution abatement.


Age of Equipment and Facilities

    Replacement of older electroplating equipment  and  facilities  will
permit  the  installation  of  modern  multitank  countercurrent rinsinq
systems after each operation in each process line with  conservation  of
water  use  for  rinsing.  The use of reclaim and recovery systems after
each plating operation should be possible.  Use of  in-process  controls
to  the  maximum  extent  will  reduce  the volume of effluent such that
recovery and reuse of water is economically attractive.


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  in  the  electroplating
industry.   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 plating is desirable to
improve the quality of the electroplated product.


Engineering Aspects of the  Application  of  Various  Types  of  Control
Techniques

    Many  plants  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, chromium and zinc plating operations„  some plants  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  reuse of water are sufficiently well esta-
blished.  Sufficient operational use has been accumulated to reduce  the
technical  risk  with  regard  to  performance  and any uncertainty with
respect to costs.

    The technical feasibility of end-of-process water  recovery  systems
has  been  established  by extensive development of the recovery of pure
water in many related industrial processes.  Although  some  uncertainty
may  remain  concerning the overall costs when applied to electroplating
wastewaters, such uncertainty primarily relates to the volume  of  water
that  must  be  processed  for  recycling  and reuse.  The fact that the
technology as applied to  the  electroplating  industry  has  progressed
beyond  the  pilot  plant stage and has been designed and is being built
                                  182

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for  full-scale  operational  use  indicates  that  the  technology   is
available and probably economical.


Process Changes

    Application  of  the  technology  is  not  dependent  on any process
changes.  However, process changes and improvements are  anticipated  to
be a natural consequence of meeting the effluent limitations in the most
economic manner.


Cost of Achieving the Effluent Reduction

    The  costs  of  achieving  no  discharge  of  pollutants  from large
facilities  electroplating  copper,  nickel,  chromium,  and  zinc   are
expected  to  be no greater than $17.20/100 sq m ($16.00/1,000 sq ft)  as
discussed in section VIII.  With lower cost  techniques,  the  cost  for
achieving  no  discharge of pollutants may be about the same as the cost
for conventional chemical treatment, which averages about $10.70/100  sq
m  ($9.91/1,000  sq  ft).   The cost range for achieving no discharge of
pollutants is expected to be only U to 6.5 percent of the plating costs.
It may be possible to recover and reuse sufficient chemicals  and  water
to  offset  the  costs  of  achieving no discharge of pollutants in some
plants.

    Cost for small plants of achieving zero discharge of  pollutants  to
navigable  waters  are greater than $17.20/sq ft ($16.00/1,000 sq ft)  as
indicated in  Table  21.   Costs  for  small  plants  increase  as  size
decreases  because  there  is a minimum capital investment for equipment
required to achieve reuse of water.

Nonwater Quality Environmental Impact

    Application of technology to achieve no discharge 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  beyond
that  envisioned  to  meet  effluent limitations recommended for July 1,
1977.

    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,  all  of  the dissolved solids in the effluent which are primarily
innocuous salts would be disposed of on land with suitable precaution to
avoid any ground water contamination.  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.
                                  183

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    No impact on air pollution is expected as the result of. achieving no
discharge of pollutanzs to  surface  water.   The  available  technology
creates no air pollutants.

    Energy  requirements  will  increase  with  the  achievement  of  no
discharge of pollutants to surface water.   The  amount  will  vary  from
about  27 percent of the energy consumed by electroplating sources to as
much as four times the energy  needed  for  plating,   depending  on  the
specific  process controls adopted in individual plants for achieving no
discharge of pollutants.


Effluent ^imitationg Bgsed^on the Application
of_Best_Available_TechnologY Economically Achievable

    The recommended effluent limitations to be achieved by July 1,  1983
for  existing  sources  based  on  the  application  of  B€JSt  Available
Technology Economically Achievable is  no  discharge   of  process  waste
water pollutants to navigable waters.

Gu i del i n es for_the Applic at i on of
Effluent Limitations

    Achieving  the effluent limitations of no discharge of pollutants by
achieving no discharge of effluent to surface waters  is the most  direct
method  that eliminates the need for sampling and analysis.  If there is
other effluent discharge to surface waters from the plant riot associated
with electroplating, a determination is  required  that  no  wastewaters
originating  from  electroplating  processes are admixed with this other
plant effluent.
                                  184

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                               SECTION XI

                    NEW SOURCE PERFORMANCE STANDARDS
Introduction
    The standards of performance which must be achieved by  new  sources
are  to  specify the degree of effluent reduction attainable through the
application of the best available demonstrated control technology, pro-
cesses, operating methods, or other alternatives.
          The added consideration for  new  sources  is  the  degree  of
effluent  reduction  attainable  through  the use of improved production
processes and/or treatment techniques.  The term "new source" is defined
by the Act to mean "any source, the construction of which  is  commenced
after  publication  of  proposed  regulations  prescribing a standard of
performance".

    New Source Performance Standards are based on the best in-nlan^  and
end-of-process   technology  identified.
                                               Additional 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   well   as   control
technology),  rather  than  prescribing  a particular 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 to:

    (a) the type of process employed and process changes
    (b) operating methods
    (c) batch as opposed to continuous operations
    (d) use of alternative raw materials and mixes of raw
    materials
    (e) use of dry rather than wet processes (including
    substitution of recoverable solvents for water)
    (f) recovery of pollutants as by-products.

    Standards  of  Performance  for  New Sources are based on applicable
technology and related effluent limitations covering discharges directly
into waterways.
                                  185

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    Consideration must also be given  to  the  fact  that  Standards  of
Performance  for  New Sources could require compliance about three years
sooner than the effluent limitations to be achieved by existing  sources
by  July 1, 1977.  However, new sources should achieve the same effluent
limitations as existing sources by July 1, 1983.


Industry category and Subcategorv Covered


    The  recommended  new  source  performance   standards  apply  to the
electroplating industry category as previously defined in Section IX.


Identification of Control and Treatment
TectoQlo^Y-Applic^ble to Performance
Standards and Pretreatment Standards for_New_sources

    The   technology   previously  identified  in  Section  IX  as  Best
Practicable Control Technology Currently Available is also applicable to
New Sources,                       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  rinsewater
conservation after each operation by multitank rinsing, there are  fewer
restrictions  on  the use of advanced techniques  for recovery of plating
bath chemicals and reduction  of  wastewater  from  rinsing  after  pre-
treatment   and   posttreatment.    Maximum   use   of  combinations  of
evaporative, reverse osmosis, and ion  exchange  systems  for  inprocess
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.
Rationale for Selection of Control and
Treatment Technology Applicable to
New Source s

    The  rationale  for  the  selection  of  the  above  technology   as
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 advan-
                                  186

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        tageous electroplating 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 at
        present a large capital investment in waste treat-
        ment facilities to meet effluent limitations by
        July 1, 1977, a new source has complete freedom in
        the selection of the Best Available Technology
        Economically Achievable in the design of new waste
        treatment facilities.

    (3)  In contrast to an existing source, a new source has
        freedom of choice with regard to geographic location
        in seeking any economic advantage relative to power
        cost or land cost.
Standardsof_Perfornianc
    The recommended Standards of  Performance  to  be  achieved  by  new
sources discharging to navigable waters was shown previously in Table 1A
of section II.

    The  quantitative  values  for  the 30-day average standard for each
parameter in mg/sq m (lb/106 sq ft)   is  based  on  a           effluent
factor  of  40   1/sq  m  (1  gal/sq ft) combined with the concentrations
achievable by chemical treatment as previously  shown  in  Table  33  of
                                  187

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Section  IX  for existing sources based on an effluent factor of 80 1/sq
m.  For example, 0.5 mg/1 for copper,  nickel, total chromium, zinc,  and
total cyanide, 0.05 mg/1 for hexavalent chromium and oxidizable cyanide,
15  mg/1  for suspended solids,  when combined with an effluent factor of
40 1/sq m are the basis for the  30-day average standards of  performance
in Table 1A.

    In effect, Standards of Performance for New Sources Table 1A are 1/2
the  values  of the Effluent Limitations for existing sources to achieve
by July 1, 1977, as shown in Table 1.   The rationale  for  selection  of
Standards  of  Performance  is  based  on  the  technical feasibility of
achieving greater reduction in water use by  multitank  rinsing  at  the
time  of  construction  of  new   facilities  in  contrast to the present
limitations for some existing sources.   For  example,  if  an  existing
source  can achieve an effluent  factor of 80 1/sq m, a new source should
be able to design a new facility to achieve an  effluent  factor  of  40
1/sq  m.   As  discussed  previously  in  Section  IX,  the  Standard of
Performance in mg/sq m is the product of the plant  effluent  factor  in
1/sq m and the concentration of  the parameter in the treated effluent in
mg/1.   The  choice  of  whether  to reduce concentration by emphasis on
optimum chemical  treatment  and  clarification  or  whether  to  reduce
effluent   volume  by  water  conservation  or  a  combination  of  both
approaches is left to the discretion of the new source.

    The rationale for establishing the daily maximum value of  Standards
of  Performance  at twice the 30-day average is based on the limitations
in accuracy of analytical methods for  measuring  small  concentrations,
the usual 24-time lag after analysis for corrective action, the accuracy
of   measurement  of  effluent  flow,   and  plated  areas  as  discussed
previously in Section IX.
Guidelines_f.or^the Application of
New Source 3Perfgrmance_Standards

    The  recommended  guidelines  for  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.
                                  188

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                              SECTION XII


                            ACKNOWLEDGEMENTS
    The  following  organizations  associated  with  the  electroplating
industry provided information on waste treatment technology:

    American Electroplaters1 society. East Orange, New Jersey E.  I.  du
Pont  de  Nemours & Company, Wilmington, Delaware Heil Process Equipment
Corporation, Cleveland, Ohio
    Industrial Filter 5 Pump Manufacturing Co., Cicero,  Illinois  Ionic
International,   Incorporated,  Detroit,  Michigan  Lancy  Laboratories,
Zelienople, Pennsylvania M & T  Chemicals,  Incorporated,  Matawan,  New
Jersey
    Metal  Finishing  Suppliers'  Association, Incorporated, Birmingham,
    Michigan National Association of Metal Finishers,  Upper  Montclair,
    New  Jersey Osmonics, Incorporated, Minneapolis, Minnesota Oxy Metal
    Finishing  Corporation,  Warren,  Michigan  The  Permutit   Company,
    Paramus, New Jersey Pfaudler Sybron Corporation, Rochester, New York

    The  assistance of personnel of all the EPA Regional Centers and the
many  State  agencies  that  were  contacted  to  obtain  assi stance  in
identifying  those  plants  in  the  electroplating  industry  achieving
effective waste treatment.

    Acknowledgement is made of the  cooperation  of  personnel  in  many
plants  in  the  electroplating  industry  that  were  contacted and who
voluntarily provided plating operations data  in  addition  to  effluent
data.   Special  acknowledgement  is  made  of those plant personnel and
company officers that cooperated in providing detailed  plant  operating
data and cost data to support this study of waste-treatment technology.

    Acknowledgement  also  is  made of the assistance provided by Walter
Hunt, Edward Dulaney, Murray Strier,  John  Ciancia,  Hugh  Durham,  Lew
Felleison,  Tom Gross, Tim Field, Alan Eckert, and Swep Davis and others
who provided helpful suggestions and comments.

    Finally, the assistance of Linda Rose was invaluable in the timely
preparation of this report.
                                  189

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                              SECTION XIII

                               REFERENCES


(1)   Safranek, W. H., "The Role of  Design  in  Better  Plating",   Metal
    Progress, pp 67-70 (June 1968) .

(2)    Modern	Electrop.lating, Edited by F. A. Lowenheim, Second  Edition,
    John Wiley~and~Sons (1963), Chapter 7, pp 154-205.

(3)   Metal	Finishing	Guidebook	§_nd__pirectory,  Metals  and   Plastics
    Publications, Inc. (1973).

(4)    "Methods for Chemical Analysis of Water and Wastes", Environmental
    Protection Agency, Water  Quality  Office,  Cincinnati,,  Ohio   (July
    1971).

(5)    Standard	Methods	for	the	Examination	of Water_and Wastewater/
    Thirteenth Edition (1971).

(6)   ASTM Designation 2036-72.

(7)   Ceresa, M., and Lancy, L.   E.,  "Metal  Finishing  Waste  Disposal.
    Part One", Metal Finishing, 66  (4), 56-62  (April 1968).

(8)    Pourbaix,  Marcel,   Atlas_of_Electrochemical_Eguilibria in Aqueous
	Solutions	, Pergamon Press, New York  (1966) .

(9)     Marquardt,   Kurt,   "Erfahrungen   mit   lonensautauschern   als
Endreinungsstufe nach Entgiftung- und Neutralisationsanlagen aller  Art",
Metalloberflache Angew. Elektrochemie 26  (11),  434  (1972).

(10)   Personal communication from Dr. Coleman,  Western Electric  Company,
Indianapolis, Indiana.

(11)    Environmental Sciences,  Inc., "Ultimate  Disposal of Liquid Wastes
by Chemical Fixation".

(12)   Tripler, A. B., Cherry, R. H., Smithson,  G. Ray, Summary Repbrt  on
    the Reclamation of Metal Values from Metal  Finishing Waste Treatment
    Sludges", Battelle Columbus Laboratories report to Metal  Finisher's
    Foundation, July 6, 1973.


(13)    Dodge,  B.  F., and Zabban, W., "Disposal of Plating Room Wastes.
III.   Cyanide Wastes:   Treatment  with  Hypochlorites  and  Removal   of
Cyanates", Plating, 38 (6), 561-586  (June 1951).
                                  190

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(14)    Dodge,  B.  F., and Zabban, W., "Disposal of Plating Room  Wastes.
III.   Cyanide Wastes:   Treatment  with  Hypochlorites   and   Removal   of
Cyanates.  Addendum", Plating, 39  (4), 385  (April 1952).

(15)    Dodge,  B.  F., and Zabban, W., "Disposal of Plating Room  Wastes.
IV.  Batch Volatilization of Hydrogen Cyanide
    From Aqueous Solutions of Cyanides",  Plating,  39   (10),   1133-1139
    (October 1952) .

(16)    Dodge,  B.  .F., and Zabban, W., "Disposal of Plating Room  Wastes.
    IV.  Batch #olatilization of Hydrogen Cyanide From Aqueous  Solutions
    of Cyanides.  Continuation", Plating, 39  (11),  1235-1244   (November
    1952).

(17 Overflow", Chemical Week, 111  (24),  47  (December  13,  1972) .

(18)    Oyler,  R.  W.,  "Disposal  of  Waste  Cyanides   by  Electrolytic
    Oxidation", Plating, 36  (4), 341-342  (April  1949).

(19)   Kurz, H., and Weber, W., "Electrolytic Cyanide  Detoxication by  the
    CYNOX  Process",  Galvanotechnik  and   Oberflaechenschutz,  3,  92-97
    (1962) .

(20)       "Electrolysis  Speeds  Up  Waste   Treatment",   Environmental
    Science and Technology", 4  (3) , 201  (March 1970) .

(21)    Thiele,  H., "Detoxification of Cyanide-Containing Waste Water by
    Catalytic   Oxidation   and    Adsorption   Process",    Fortschritte
    Wasserchemie  Ihrer  Grenzgebiete,   9,  109120  (1968):  CA, 70, 4054
    (1969) .

(22)   Bucksteeg, W., "Decomposition of   Cyanide  Wastes   by   Methods   of
    Catalytic  Oxidation Absorption", Proceedings of  the  21st  Industrial
    Waste Conference, Purdue University  Engineering  Extension  Series,
    688-695  (1966) .

(23)    "Destroy  Free  Cyanide  in  Compact,  continuous  Unit",   Calgon
    Corporation  advertisement,  Finishers'  Management,  18    (2) ,    14
    (February 1973) .

(24)   Sondak, N. E., and Dodge, B. F., "The Oxidation of  Cyanide  Bearing
    Plating  Wastes  by  Ozone.    Part   I", Plating,  48  (2),   173-180
    (February 1961).

(25)   Sonday, N. E., and Dodge, B. F., "The Oxidation of  Cyanide  Bearing
    Plating Wastes by Ozone.  Part II",  Plating, 48  (3),  280-284   (March
    1961).
                                   191

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(26)    Rice,  Rip G.,  letter from Effluent Discharge Effects committee to
    Mr.  Allen Cywin,  Effluent Guidelines Division, July 9, 1973.

(27)   "Cyanide Wastes Might Be Destroyed at One-Tenth  the  Conventional
    Cost",  Chemical  Engineering,  79 (29), 20 (December 25, 1972).

(28)    Manufacturers'  Literature,   DMP  Corporation,  Charlotte,  North
    Carolina  (1973) .

(29)   Ible, N.,  and  Frei,  A.  M.,  "Electrolytic Reduction  of  Chrome  in
    Waste   Water", Galvanotechnik und Oberflaechenschutz, 5 (6), 117-122
    (1964) .

(30)   Schulze,  G., "Electrochemical Reduction of Chromic Acid-Containing
    Waste  Water", Galvanotechnik,   58  (7) ,  475-480  (1967) :    CA,  68,
    15876t  (1968).

(31)    Anderson,  J.  R.,  and Weiss,  Charles O., "Method for Precipitation
    of Heavy  Metal Sulfides", u.  S. Patent No. 3,740,331, June  19, 1973.

(32)   Lancy,   L.  E.,  and  Rice,   R.   L.,   "Upgrading  Metal   Finishing
    Facilities   to   Reduce  Pollution",   paper  presented  at  the  EPA
    Technology Transfer Seminar,  New York,  N.Y.   (December 1972) .

(33)   ElectroBllting_Erigineering_Handbook,   Edited  by  A.  K.   Graham,
    Third  Edition, Van Nostrand Reinhold Company, New York (1971).

(34)    Olsen,  A.  E.,  "Upgrading  Metal Finishing Facilities to Reduce
    Pollution;   In-Process   Pollution   Abatement   Practices",   paper
    presented  at the  EPA Technology Transfer Seminar, New York, N. Y.
    (December,  1972).

(35)   Novotny,  C. J. , "Water  Use and Recovery",  Finishers'  Management,
    18 (2) ,  43-46 +  50 (February 1973) .


(36)    Rushmere,  J.   D.,   "Process  for  Brightening  Zinc  and Cadmium
    Electroplates Using  an   Inner  Salt  of  a   Quaternary   Pyridine
    Carboxylic  Acid  and  Composition Containing the Same", U.  S. Patent
    3,411,996,  November 19, 1968.

(37)   Ceresa, M. , and Lancy,  L. E. ,  "Metal  Finishing  Waste   Disposal.
    Part Two",  Metal Finishing, 66 (5), 60-65  (May 1968).

(38)    Ceresa,   M. ,   and  Lancy,  L. E., "Metal Finishing Waste  Disposal.
    Part Three",  Metal Finishing,  66 (6), 112118  (June 1968).
                                  192

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(40)   Brown,  C.  J.,  et al.,  "Plating Waste  Recovery  by  Reciprocating-
    Flow   Ion   Exchange",    Technical   conference   of  The  American
    Electroplaters1  Society,  Minneapolis, Minnesota, June 18, 1973.

(41)   Oh,  C.  B.,  and Hartley, H.  S., "Recycling Plating Wastes by  Vapor
    Recompression",  Products  Finishing, 36 (8), 90-96 (May 1972).

(42)    Kolesat,   T.  J.,  "Employment of Atmospheric Evaporative ##wers in
    the Electroplating  Industry  as  a  Means  of  Recycle  and  Waste
    Elimination", Technical   Conference of The American Electroplaters'
    Society,  Minneapolis, Minnesota, June 18, 1973.

(43)   McLay,  W.  J.,  Corning Glass Company, Personal Communication.

(44)   Spatz,  D.  D.,  "Industrial Waste Processing With Reverse  Osmosis",
    Osmonics, Inc.,  Hopkins,  Minnesota (August 1, 1971).

(45)    Spatz, D.  D., "Electroplating Waste water Processing Wirh Revers^
    Osmosis", Products Finishing, 36 (11), 79-89 (August 1972).

(46)   Campbell,  R. J., and Emmerman, D. K.,  "Recycling  of  Water  From
    Metal   Finishing  Wastes  by Freezing Processes", ASME Paper 72-PID-7
    (March 1972) .

(47)   Campbell,  R. J., and Emmerman, D. K., "Freezing and  Recycling  of
    Plating  Rinsewater",  Industrial  Water  Engineering,  9  (4), 38-39
    (June/July 1972) .

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                              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.

Acidity.

The concentration of acid ions expressed as pH for a solution.

Act

The Federal Water Pollution Control Act Amendments of 1972.

Activator

Chemical   substance,  usually  stannous  chloride,  that  triggers  the
electroless deposition process on a nonconducting surface.

Addition^Agent

Substance, usually an  organic  material,  added  to  an  electroplating
solution to improve the properties of the electroplate.

Alkalinity

The concentration of base ions expressed as pH for a solution.

Allowable ..Water Use

The  sum of water used for each plating process or the sum of water used
for each necessary rinsing operation.

Ampere

Unit of electricity, amount of which is the current  that  will  deposit
silver at the rate of 0.0011180 gram per second.

Ampere-hours

Product of amperes of electricity being used and time of that use.


Anions
                                  194

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The negative charge ions in the solution, i.e., hydroxyl.

Anode

The  electrode  that  takes  electrons  from  the anions in solution  (is
connected to the positive terminal of the direct current source).

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.

Ba rr el _Plating

Electroplating of workpieces in barrels  (bulk) .

S§§i§_Metal_or_Material

That substance of which the workpieces are made and  that  receives  the
electroplate and the treatments in preparation for plating.

Best Available Technology Economically Achievable

Level of technology applicable to effluent limitations to be achieved by
July  1, 1983, for industrial discharges to surface waters as defined by
Section 301  (b)  (2) (A) of the Act.

Best Practicable^Contrgl Technology Currently Available

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.

BOD

Biochemical oxygen demand.

BrjLght_pip_

A solution used to produce a bright surface on a metal.

Cagital_Cgsts

Financial  charges  which  are computed as the cost of capital times the
capital expenditures for pollution control.  The
                                  195

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cost of capital is based upon a weighed average of the separa## costs of
debt and equity.

Ca]3tive_O]3eratiQn

Electroplating facility owned and operated by the same organization that
manufactures the workpieces.

Cagtivexpiating Shops

Companies engaged in product fabrication and/or  assembly  and  normally
process  approximately  the  same number of the same products per month.
The volume of toxic wastes created by captive operations is expected  to
be more or less constant.

Carbon_Bed_Catalytic^Destruction

A  nonelectrolytic process for the catalytic oxidation of cyanide wastes
using trickling filters filled with low-temperature coke.
Chemical substance, usually palladium chloride, in  a  dip  solution  to
cause electroless deposition of a metal on a nonconducting surface.

Category,and^Subcategory

Divisions  of a particular industry which possess different traits which
affect  waste  treatability  and  would   require   different   effluent
limitations.

Cathode

The   electrode    (the  workpieces  in  electroplating)   that  transfers
electrons to the cations in the solution.

Cations

The positive-charge  ions  in  the  solution,  i.e.,  the  metal  to  be
electrodeposited, hydrogen, copper, nickel, etc.

Chelate Compound

A compound in which the metal is contained as an integral part of a ring
structure and is not readily ionized.

Chelating Agent

A compound capable of forming a chelate compound with a metal ion.
                                  196

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Chemical^RecQvery Systems

Chemical treatment of electroplating wastes utilizing (1) batch methods,
(2)  continuous methods, or (3)  integrated procedures.

Chromium^CatalYSt

Plating  bath  constituent  that  in  small  amounts  makes possible the
continuing capability to  electrodeposit  chromium.   Usually  fluoride,
fluorosilicate and/or sulfate.

Cleaner

Usually an alkaline solution pretreatment to remove surface soil such as
oils,   greases,  and  substrates  chemically  unrelated  to  the  basis
material.

Closed-Loop Evaporation System

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
dragout, for reuse in the plating process.

COD

Chemical oxygen demand.

Comgatible^Pgllutgnts

Those  pollutants  which  can  be  adeguately  treated in publicly owned
treatment works without harm to such works.

Continuous_Treatment

Chemical waste treatment operating uninterruptedly as opposed  to  batch
treatment; sometimes referred to as flow through treatment.

Conyersion_Coating

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.

Coulomb
                                  197

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Product of current in amperes and time in seconds.   Thus, one coulomb is
1 ampere-second.

Coulombic

A   term   used   to   denote  a  relationship  based  in.  coulombs  and
electrochemical equivalents according to Faraday's  Law.

Count erf 1 ow_Ri n s i n g

Series of rinses; usually three, in which water flow  is  from  last  to
first  rinse,  thus counterflow to direction work loads move through the
rinses.

d-c Power source

Direct Current power source.
Refers to the multilayer electroplate of copper + nickel +  chromium  in
that  order,  on  the  basis  material  to provide the bright decorative
appearance.

Deposit

The material formed on the electrode or workpiece surface, i.e., a metal
in electroplating.
Accounting charges reflecting the deterioration of a capital asset  over
its useful life.

Dracfout

The  solution  that  adheres  to  the objects removed from a bath.  More
precisely defined as that solution which is carried past the edge of the
tank.

Dual Nickel Plate

Two layers of nickel electroplate with different properties  to  enhance
corrosion   resistance   and  appearance  under  chromium  electroplate.
Requires two different nickel plating baths.

Effluent

The waste water discharged from a point source to navigable waters.
                                  198

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Ef fluent^Lirnitation

A maximum amount, per unit of production of each specific constituent  of
the effluent that is subject to limitation in the discharge from a point
source.

Electrochemical_Eguivalent

The  weight  of  metal  electrodeposited  (or  other  substance  changed
chemically by reduction or oxidation) per  unit  of  time  and  unit  of
current; i.e., pound per ampere-hour, grams per ampere-second.

Electrode

Conducting  material  for passing the electric current out of a solution
by taking up or into it by giving up electrons from or to  ions  in  the
solution.

Electrodeposition

The  transfer of electrons from the cathode to metal ions at its surface
to produce the metal on the cathode surface.

El ectr g forming

The production or reproduction of articles by electrodeposition  upon  a
mandrel or mold that is subsequently separated from the deposit.

Electroless Plating

Deposition of a metallic coating by a controlled chemical reduction that
is catalyzed by the metal or alloy being deposited.

Electrolysis

The  passage  of  current through an electrolyte bringing about chemical
reactions.
A unit apparatus in which  electrochemical  reactions  are  produced  by
applying  electrical  energy,  or  which supplies electrical energy as a
result of chemical reactions and which includes two or  more  electrodes
and one or more electrolytes contained in a suitable vessel.

Electrolytic Decomposition

An  electrochemical  treatment  used for the oxidation of cyanides.  The
method  is  practical  and  economical  when  applied  to   concentrated
                                  199

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solutions such as contaminated baths, cyanide dips,  stripping solutions,
and  concentrated  rinses.   Electrolysis  is  carried  out at a current
density of 35 amp/sq ft at the anode and 70 amp/sq ft  at  the  cathode.
Metal is deposited at the cathode and can be reclaimed.
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  workpieces,  and
drying.

Exhaust Wash

Water  used  to  trap  droplets  and  solubles from air passed to remove
spray, vapor, and gasses from electroplating and process tanks.
The number of coulombs (96,490)  required for an electrochemical reaction
involving one chemical equivalent.

Free Cyanide

(1)  true - the actual concentration of cyanide radical,  or  equivalent
alkali cyanide, not combined in complex ions with metals in solutions.

(2)   calculated  -  the  concentration  of  cyanide, or alkali cyanide,
present in solution in excess of that calculated as necessary to form  a
specified complex ion with a metal  or metals present in solution.

(3)   analytical  - the free cyanide content of a solution as determined
by a specified analytical method.

Hard_Chrome

Chromium  electroplate  applied  for  nondecorative  use  such  as  wear
resistance in engineering applications.

Immersion Plate
                                  200

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A  metallic  deposit  produced  by  a displacement reaction in which one
metal displaces another from solution, for example:

Fe + Cu-n- T Cu + Fe+ +

Incomp_atible_Pollutants

Those pollutants  which  would  cause  harm  to,  adversely  affect  the
performance  of,  or be inadequately treated in publicly owned treatment
works.
Independent Operation

Job shop or contract shop in which electroplating is done on
owned by the customer.

Integrated Chemical Treatment
                                                              workpieces
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.

Jnvestment_ Costs

The  capital  expenditures  required  to  bring the treatment or control
technology into operation.  These include the  traditional  expenditures
such  as  design;  purchase  of  land  and  materials;  etc.;  plus  any
additional expenses required to  bring  the  technology  into  operation
including  expenditures  to  establish  related  necessary  solid  waste
disposal.
Treatment in  publicly  owned  treatment  works  of  combined  municipal
wastewaters of domestic origin and wastewaters from other sources.

Mandrel

A form used as a cathode in electro forming; a mold or matrix.

N§w_Source

Any  building,  structure, facility, or installation from which there is
or may be a discharge of pollutants and whose construction is  commenced
after the publication of the proposed regulations.

New Source Performance Standards
                                  201

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Performance  standards  for  the  industry and applicable new sources as
defined by Section 306 of the Act.

ohm

The unit of electrical resistance.   The resistance at OC of a column  of
mercury  of  uniform  cross section, having a length of 106.300 cm and a
mass of 14. 4521 gm.

Ogen-Logp Evaporation System

A system used for the partial recovery of chemicals  and  water  from  a
plating line using less than 3 rinses.  The circulation loop through the
evaporator  is  opened  by  creating  another  flow  path  resulting  in
wastewater.  A small  percentage  (4-5  percent)   of  the  dragout  that
accumulates in the final rinse is not recirculated to the evaporator and
must be treated by a chemical method before disposal.

ORP_Recprderg

Oxidation- reduction potential recorders.

Oxidizable_Cy_anide

Cyanide   amenable  to  oxidation  by  chlorine  according  to  standard
analytical methods.
A unit for measuring acidity or alkalinity of water, based  on  hydrogen
ion  concentrations.  A pH of 7 indicates a "neutral" water or solution.
At pH lower than 7, a solution is  acidic.   At  pH  higher  than  1,  a
solution is alkaline.

Pickle

An acid solution used to remove oxides or other compounds related to the
basis  metal  from its surface of a 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.

Plated_Area

The area of the workpiece receiving an elect rodeposit.  The thickness of
deposit usually varies over the plated area.
                                  202

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Plating_Barrel

Container in which parts are placed loosely, so they can tumble  as  the
barrel rotates in the plating or processing solution.
Fixture  that  permits  moving  one  or  more workpieces in and out of a
treating or plating  tank  and  transferring  electric  current  to  the
workpieces when in .the tank.

Point Source

A single source of water discharge such as an individual plant.

Preplating Treatment Waste

Waste  contributed  by  preplating  treatments  is affected by the basis
materials, any surface soil on the workpieces, formulation of  solutions
used  for  cleaning  or activating the materials, solution temperatures,
and cycling times.
Treatment performed in wastewaters from any source prior to introduction
for joint treatment in publicly owned treatment works.
Electroplating of workpieces on racks.

Re cla j m^Ri ns es

Reclaim rinses are used as the first step following a plating process to
retain as much of the chemicals as possible and to allow return  of  the
dragout solution to the plating tank.

Rectifier

A  device  which  converts  ac  into  dc  by  virtue of a characteristic
permitting appreciable flow of current in only one direction.

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.

Rinse
                                  203

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Water for removal of dragout by dipping, spraying, fogging, etc.

Rochelle_Salt

Sodium potassium tartrate:  KNaC4Ht»06.4H20.

Running Rinse

A rinse tank in which water continually flows in and out.

Saye_Rinse

Same as reclaim rinse.

Still_Rinse

Does not have water flowing in and out as a running rinsej and may  be  a
reclaim rinse or dumped periodically to wastewater.

Standard of Performance

A  maximum weight discharged per unit of production for each constituent
that is subject to limitation and applicable to new sources  as  opposed
to existing sources which are subject to effluent limitations.

Strike

(1)   noun  -  a thin coating 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 - to plate for a short time, usually at a high initial current
density.

Tank

Term for vessel that contains the solution and auxiliary  equipment  for
carrying out the electroplating or other operational step.

T.ank_Current

Total  amperage  required  to  electroplate all the workpieces of a tank
load.

Tank_Load

Total number of workpieces being processed simultaneously in the tank.
                                  204

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Total_Chromijrri

Total chromium (CrT) is the sum of chromium in all valences

      Cyanide
The total content of cyanide expressed as the  radical  CN-,  or  alkali
cyanide  whether present as simple or complex ions.  The sum of both the
combined and free cyanide content of a plating solution.  In  analytical
terminology,  total  cyanide is the sum of cyanide amenable to oxidation
by chlorine and that which  is  not  according  to  standard  analytical
methods.

Total_Metal

Total  metal  is  the  sum  of  the  metal  content  in both soluble and
insoluble form.

ynit_OE§ ration

A single, discrete  process  as  part  of  an  overall  sequence,  e.g.,
precipitation, settling, filtration.

y§ed_current

Current that is used in electroplating operations and related to (1)  the
area  being  pla##d  for  a  particular  deposit  thickness  and (2)  the
processing time  (area per unit time) .

Volt

The voltage which will  produce  a  current  of  one  ampere  through  a
resistance of one ohm.

Watt

An  energy  rate  of  one  joule per second, or the power of an electric
current of one ampere with an intensity of one volt.

Workpiece

The item to be electroplated.
                                  205

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                                    TABLE  36

                                 CONVERSION TABLE -. .

MULTIPLY (ENGLISH UNITS)                   by                TO OBTAIN (METRIC UNITS)

    ENGLISH UNIT      ABBREVIATION    CONVERSION   ABBREVIATION   METRIC UNIT
acre                    ac
acre - feet             ac ft
British Thermal
  Unit                  BTU
British Thermal
  Unit/pound            BTU/lb
cubic feet/minute       cfm
cubic feet/second       cfs
cubic feet              cu ft
cubic feet              cu ft
cubic inches            cu in
degree Fahrenheit       F°
feet                    ft
gallon                  gal
gallon/minute           gpm
horsepower              hp
inches                  in
inches of mercury       in Hg
pounds                  lb
million gallons/day     mgd
mile                    mi
pound/square
  inch (gauge)          psig
square feet             sq ft
square inches           sq in
tons (short)            t on
yard                    y d
       0.405
    1233.5

       0.252

       0.555
       0.028
       1.7
       0.028
      28.32
      16.39
     0.555(°F-32)1
       0.3048
       3.785
       0.0631
       0.7457
       2.54
       0.03342
       0.454
         3,785
       1.609

(0.06805  psig +1)1
       0.0929
       6.452
       0.907
       0.9144
ha           hectares
cu m         cubic meters

kg cal       kilogram - calories

kg cal/kg    kilogram calories/kilogra
cu m/min     cubic meters/minute
cu m/min     cubic meters/minute
cu m         cubic meters
1            liters
cu cm        cubic centimeters
°C           degree Centigrade
m            meters
1            liters
I/sec        liters/second
kw           killowatts
cm           centimeters
atm          atmospheres
kg           kilograms
cu m/day     cubic meters/day
km           kilometer

atm          atmospheres (absolute)
sq m         square meters
sq cm        square centimeters
kkg          metric tons (1000 kilogr;
m            meters
1 Actual conversion, not a multiplier
                                            206

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