Field Manual--performance Evaluation And Troubleshooting At Metal Finishing Wastewater Treatment Facilities

600284152
                                 FIELD MANUAL
                   PERFORMANCE EVALUATION AND TROUBLESHOOTING
                                      AT
                                METAL-FINISHING
                         WASTEWATER TREATMENT FACILITIES
                                      by
                              T. N. Sargent,  P.E.
                              G. C. Patrick,  P.E.
                            E. H. Snider, Ph.D.,  P.E.
                            Engineering-Science,  Inc.
                             Atlanta, Georgia  30329
                           EPA Contract No. 68-03-3040
                                Project Officer

                               Thomas J. Powers
                      Industrial Pollution Control Division
                  Industrial Environmental Research Laboratory
                             Cincinnati, Ohio  45268
                  Industrial Environmental Research Laboratory
                       Office of Research and Development
                      U.S.  Environmental Protection Agency
                             Cincinnati, Ohio  45268

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                FIELD MANUAL
 PERFORMANCE EVALUATION AND TROUBLESHOOTING
                     AT
               METAL-FINISHING
       WASTEWATER TREATMENT FACILITIES
                     by
             T. N.  Sargent,  P.E.
             G. C.  Patrick,  P.E.
          E. H. Snider, Ph.D.,  P.E.
          Engineering-Science,  Inc.
           Atlanta, Georgia   30329
         EPA Contract No.  68-03-3040
               Project Officer

              Thomas J. Powers
    Industrial Pollution Control Division
Industrial Environmental Research Laboratory
           Cincinnati, Ohio  45268
Industrial Environmental Research Laboratory
     Office of Research and Development
    U.S. Environmental Protection Agency
           Cincinnati, Ohio  45268

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                                 PREFACE
     For  the  first time,  an  operating and  troubleshooting manual  has
been put  together  to  assist plant operators and managers  of  wastewater
treatment plants  for  the  metal  finishing industry.   This  performance
evaluation and troubleshooting guide  has  been reviewed by  true  experts
of plating wastewater  treatment  - the  plant operators.   Without  their
day to day insight into operational  and maintenance problems, the  ini-
tial field manual effort would not have been  possible.

     A more detailed development of this  guide  is destined for  the
future.   Only by widespread use  and  evaluation can  this manual be  re-
vised and upgraded to reflect  the  current and future trends of  complex
treatment and control technology systems required for the metal  finish-
ing industry.   It is   hoped  that this  field manual will guide  plant
operators in  achieving  consistently higher performance  levels.

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                                CONTENTS
Abstract                                                        iv
Figures                                                          v
Tables                                                          vi
Abbreviations and Symbols                                      vii

   1 .  Introduction                                              1
            Purpose and Scope of Manual                          1
            Manual Format                                        1
   2.  Literature Review                                         3
            Analysis of Permit Violations                        3
            Operation and Maintenance Specifics                  4
   3.  Problem Assessment and Recommendations for
       Improving Permit Compliance                               8
            Conventional Wastewater Treatment                    8
            Problem Assessment                                  1 0
            Recommendations for Improving Permit Compliance     14
            Resource Recovery                                   1 6
   4.  Equalization                                             19
            Introduction                                        19
            Theory of Operation                                 19
            Description of Equipment                            21
            Operational Procedures                              25
            Typical Performance Values                          29
            Troubleshooting Guide                               29
   5.  Oil Removal                                     '         29
            Introduction                                        32
            Theory of Operation                                 33
            Description of Equipment                            35
            Operational Procedures                              42
            Typical Performance Values       -                   51
            Troubleshooting Guide                               52
   6.  Cyanide Oxidation                                        57
            Introduction                                        57
            Theory of Operation                                 57
            Description of Equipment                            62
            Operational Procedures                              64
            Typical Performance Values                          70
            Troubleshooting Guide '                              70
   7.  Chromium Reduction                                       74
            Introduction                                        74
            Theory of Operation                                 74
            Description of Equipment                            75
            Operational Procedure                               77
            Typical Performance Values                          85
            Troubleshooting Guide                               85

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Contents (cont.)

   8.  pH Control                                               88
            Introduction                                        88
            Theory of Operation                                 88
            Description of Equipment                            91
            Operational Procedures                              98
            Typical Performance Values                         109
            Troubleshooting Guide                              109
   9.  Metal Precipitation                                     113
            Introduction                                       11 3
            Theory of Operation                                113
            Description of Equipment                           11 5
            Operational Procedures                             118
            Typical Performance Values                         128
            Troubleshooting Guide                              1 32
  10.  Flocculation                                            135
            Introduction                                       135
            Theory of Operation                                135
            Description of Equipment                           136
            Operational Procedures                             137
            Typical Performance Values                         144
            Troubleshooting Guide                              144
  11.  Sedimentation                                           147
            Introduction                                       147
            Theory of Operation                                147
            Description of Equipment                           148
            Operational Procedures                             149
            Typical Performance Values                         159
            Troubleshooting Guide                              159
  12.  Filtration                                              163
            Introduction                                       163
            Theory of Operation                                163
            Description of Equipment                           164
            Operational Procedures                             167
            Typical Performance Values                         171
            Troubleshooting Guide                              171
  13.  Gravity Thickening                                      179
            Introduction                                       179
            Theory of Operation                                1 79
            Description of Equipment                           183
            Operational Procedures                             1 85
            Typical Performance Values                         191
            Troubleshooting Guide                              1 91
  14.  Belt Filter Presses                                     196
            Introduction                                       196
            Theory of Operation                                196
            Description of Equipment                           1 97
            Operational Procedures                             197
            Typical Performance Values                         204
            Troubleshooting Guide                              204
                                  ii

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Contents (cont,)

   15. Vacuum Filtration                                       207
            Introduction                                       207
            Theory of Operation                                207
            Description of Equipment                           208
            Operational Procedures                             214
            Typical Performance Values                         221
            Troubleshooting Guide                              222
  16.  Pressure Filtration for Dewatering                      229
            Introduction                                       229
            Theory of Operation                                229
            Description of Equipment                           231
            Operational Procedures                             235
            Typical Performance Values                         241
            Troubleshooting Guide       •                       241
  17.  Centrifugation                                          245
            Introduction                                       245
            Theory of Operation                                245
            Description of Equipment                           246
            Operational Procedures                             252
            Typical Performance Values                         262
            Troubleshooting Guide                              263

References                                                     271
Appendix A - Computer Literature Search                        273
Appendix B - Regulations Affecting the Metal Finishing         381
             Industry
Appendix C - Metric-English Units Conversion                   410
                                   111

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                                ABSTRACT
     This manual provides  a  technical field guide or reference document
for use in improving  the  performance  of facilities for the treatment of
metal finishing wastes.  The main purpose  of  the manual is to provide a
troubleshooting guide for identifying problems, analyzing problems, and
solving problems.

     The manual describes  general procedures  for evaluating the perfor-
mance of  treatment  processes and equipment commonly  used  in metal fin-
ishing waste  treatment.   The procedures also  cover  other  items related
to the effective operation of treatment facilities.

     The  methodology  used to evaluate  compliance problems  and develop
Operation and Maintenance  (O&M)  specifics are described in a review of
the literature, followed  by  an  assessment of  the  causes of permit vio-
lations and the recommended measures for) improving compliance.

     The unit processes described in this manual are those commonly used
in the  treatment  of metal  finishing  wastes.   They are the following:
equalization, oil  removal,  cyanide oxidation,  chromium  reduction,  pH
control,  metal  precipitation,  flocculation,  sedimentation, filtration,
gravity thickening,  belt  filter  presses,  vacuum filtration,  pressure
filtration for dewatering,  and  centrifugation.  For  each  of these unit
processes, the manual  contains  information on theory of operation,  de-
scription  of equipment,  operational  procedures,  typical  performance
values,  and a troubleshooting guide.
                                   IV

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                                 FIGURES

Number                                                              Page

  1   Electroplating Industry Conventional Wastewater Treatment       9
  2   Methods of Equalization                                        22
  3   API Separator                                                  37
  4   Line Diagrams of Principal DAF Process Variations              39
  5   Destruction Time Required for Cyanate Vs pH                    59
  6   Distribution of HOCL and OCL                                   61
  7   Two-Stage Cyanide Destruction                                  63
  8   Hexavalent Chromium Reduction with Sulfur Dioxide              76
  9   Relationship Between Hexavalent Chromium, pH,  and
      Retention Time for Sulfur Dioxide                              81
 10   Relationship Between ORP, Sodium Bisulfite Required,  and pH    83
 11   A Sample Titration Curve                                       90
 12   Feedback Mode of pH Control                                    93
 13   Feedforward Mode of pH Control                                 94
 14   Feedback-Feedforward Mode of pH Control                        96
 15   Lead Solubility for a Typical Wastewater                      114
 16   Lead Solubility as a Function of Carbonate Concentration      116
 17   Metal Concentration Versus Treatment Process                  117
 18   Metal Concentration After Treatment Process                   119
 19   Metal Concentration Versus Treatment Process                  122
 20   Solubility of Selected Heavy Metal Hydroxides                  124
 21   Theoretical Solubilities of Metal Hydroxides and Sulfides
      as a Function of pH                                           1 26
 22   Wastewater Treatment Processes for Removing Heavy Metals      127
 23   Effect of Gravity Thickening upon Solids Concentration        180
 24   Effect of Time on Sludge Compaction                           182
 25   Liquid Zones in a Continuously Operated Thickener             184
 26   A Simple Belt Filter Press                                    198
 27   Operating Zones of a Vacuum Filter                            210
 28   Typical Equipment Layout of Rotary Vacuum Filter System       213
 29   Cutaway View of a Filter Press                                232
 30   Side View of a Filter Press                                   233
 31   Cross Section of Concurrent Flow Solid-Bowl Centrifuge        247
 32   Schematic Diagram of a Basket Centrifuge                      249
 33   Disc Type Centrifuge                                          251
                                 v

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                                 TABLES
Number                                                             Page

  1    Equalization Troubleshooting Guide                             30
  2   Oil Removal Process Monitoring Requirements                    43
  3   Oil Removal Troubleshooting Guide                              53
  4   Cyanide Oxidation Process Monitoring Requirements              65
  5   Horsepower Requirements for Medium Agitation                   69
  6   Cyanide Oxidation Troubleshooting Guide                        71
  7   Chromium Reduction Process Monitoring Requirements             78
  8   Chromium Reduction Troubleshooting Guide                       86
  9   pH Adjustment Troubleshooting Guide                           110
 10   Metal Precipitation Process Monitoring Requirements           121
 11    Metal Precipitation Troubleshooting Guide                     133
 12   Flocculation Process Monitoring Requirements                  138
 13   Flocculation Troubleshooting Guide                            145
 14   Sedimentation Process Monitoring Requirements                 151
 15   Sedimentation Troubleshooting Guide                           160
 16   Filtration Process Monitoring Requirements                    169
 17   Filtration Troubleshooting Guide                              172
 18   Gravity Thickening Process Monitoring Requirements            187
 19   Gravity Thickening Troubleshooting Guide                      192
 20   Belt Filter Presses Process Monitoring Requirements           200
 21    Belt Filter Press Troubleshooting Guide                       205
 22   Vacuum Filtration Process Monitoring Requirements             216
 23   Typical Performance Values for Vacuum Filtration Dewatering   223
 24   Vacuum Filtration Troubleshooting Guide                       224
 25   Pressure Filtration for Dewatering Process Monitoring
      Requirements                                                  238
 26   Pressure Filtration for Dewatering Troubleshooting Guide      242
 27   Centrifugation Process Monitoring Requirements                254
 28   Summary of Operational Variables Affecting Centrifuge
       Performance                                                  257
 29   Typical Performance Values for Centrifugal Thickening
       and Dewatering                                               264
 30    Centrifugation Troubleshooting Guide                          265

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                    LIST OF ABBREVIATIONS AND SYMBOLS
Abbreviations
           A:S
           API
           DAF
           HRT
           IAF
           ORP
           PI
           PID
           SOR
           SS
           SVR
           TSS
Air to Solids Ratio
American Petroleum Institute
Dissolved Air Flotation
Hydraulic Retention Time
Induced Air Flotation
Oxidation-Reduction Potential
Proportional Plus Integral
Proportional-Integral-Derivative
Surface Overflow Rate
Suspended Solids Concentration
Sludge Volume Ratio
Total Suspended Solids Concentration
Symbols
           C    -   Concentration
           C    -   Effluent TSS Concentration
           C    -   Influent TSS Concentration
           C.    -   Influent TSS Concentration to Clarifier
           C    -   Sludge TSS Concentration
            J\
           MVG  -   Mean Velocity Gradient for Flocculation
           M    -   Dynamic Viscosity
           P    -   Power Input for Flocculation
           PD   -   Polymer Dosage
           q    -   Polymer Flowrate
           Q    -   Flowrate of Wastewater
           Qe   -   Effluent Flowrate
           Q    -   Influent Flowrate
           Q.^   -   Influent Flowrate to Clarifier
           Q_   -   Sludge Removal Flowrate
           SL   -   Solids Loading
           V    -   Volume
                                   vii

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                                SECTION 1
                              INTRODUCTION
PURPOSE AND SCOPE OF MANUAL

     The purpose of this manual is to provide a technical field guide or
reference document  for use in  improving the performance  of facilities
for the  treatment  of  metal finishing wastes.   The main purpose  of the
manual is  to provide  a troubleshooting  guide  for  the following:   1 )
identifying problems,  2) analyzing problems, and 3) solving problems.
     Plant  personnel  responsible for waste  treatment processes and
achieving permit  compliance must  be knowledgeable  about  not  only the
problem areas, but  also with  electroplating and related metal finishing
concepts and  in-plant  process modifications and changes as  they relate
to1 the waste  treatment  processes.   This manual  describes general proce-
dures for evaluating  the  performance of  treatment  processes  and equip-
ment commonly used  in  metal finishing waste treatment.   The procedures
also cover  other  items related to the  effective  operation of treatment
facilities.    Troubleshooting  guides, operating strategies,  and process
monitoring material are discussed in detail for each unit process com-
monly used in metal finishing waste treatment.

MANUAL FORMAT

     It is assumed  that the manual user  has a  general understanding of
treatment facilities and their operation.  The style, language, and for-
mat of the manual  are  directed to  the  level  and  technical knowledge  of  a
technician with some experience with in-plant operation, design, inspec-
tion,  or performance evaluation.

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The manual is organized into the following major sections:

Section 1   INTRODUCTION.   The  purpose,  scope,  and format  of the
           manual are described in this section.

Section 2  LITERATURE  REVIEW.    The  methodology  used  to evaluate
           compliance  problems  and   develop   OSM  specifics  are
           described in this section.

Section 3  PROBLEM  ASSESSMENT  AND  RECOMMENDATIONS  FOR  IMPROVING
           PERMIT COMPLIANCE.  The causes of permit violations and
           the  recommended  measures for  improving  compliance are
           described in this section.

Sections 4 through 17.  UNIT PROCESS EVALUATION AND TROUBLESHOOTING
           INFORMATION.  For each unit process commonly used in the
           treatment of metal  finishing wastes,  this  section con-
           tains the following information:

           o  Introduction
           o  Theory of Operation
           o  Description of Equipment
           o  Operational Procedures
           o  Typical Performance Values
           o  Troubleshooting Guide

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                                 SECTION 2
                             LITERATURE REVIEW
     A literature review was  conducted  utilizing technical publications,
government  reports  and documents, and  a computerized  literature  search
(see Appendix A).   The literature  search also  included  equipment manu-
facturers'   information,  data  provided  by professional   organizations,  and
communications  with personnel who were  familiar with  the  treatment and
disposal  of metal  finishing  wastes.   The  objectives  of  the  literature
review were to collect data  which would aid  in  identifying the  major
causes of permit violation,  and  to collect  information which  could  be
used to  develop OSM  specifics  on the  treatment and  disposal  of  metal
finishing wastes.   Furthermore, by qualifying this  data and information,
methods and techniques for improving compliance of facilities  could  be
developed.

ANALYSIS OF PERMIT  VIOLATIONS

     An analysis  of permit violations  was conducted  to understand the
problems  associated with  treatment  of  metal  finishing wastes.    The
troubleshooting manual was then  prepared to  address  the problems.   An
analysis  of permit violations was  performed utilizing  the Quarterly
Noncompliance  Report  published  by the  Office  of  Water  of the  United
States Environmental  Protection  Agency.   The report  listed  the  major
industries  that were out of compliance  and the parameters  that  were out
of compliance.   The violations in the  Noncompliance Report were  listed
by SIC code.  The SIC  numbers used for identifying  industries  with metal
wastes were 3471  (electroplating),  3631, 3632,  3633,  3639, 3714,  3721,
and 3731 .

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     The report cited thirty-four industries that were out of compliance
from the  third quarter of  1979 to  the  second quarter  1982.    The ten
parameters which were most frequently out of compliance between 1979 and
1982 for metal waste treatment are listed below:

                                                    Number of Permit
                                                       Violation
            Parameter                                 Occurrences
            Nickel                                        17
            Cyanide                                       16
            Chromium                                      15
            pH                                            12
            Copper                                        11
            Phenol                                         8
            TSS                                            7
            Cadmium                                        6
            Zinc                                           6
            Lead                                           4

     This field manual addresses all the parameters listed  above except
phenol.  Treatment for removal of phenol was not included in this manual
because it is  not  specifically  regulated in the effluent guidelines for
the  electroplating industry.   Treatment practices  for  control  of the
other  nine  parameters as  well  as  oil  and grease  are included  in the
manual.

OPERATION AND MAINTENANCE SPECIFICS

     Operation  and Maintenance  (O&M) specifics  for  the  treatment of
metal finishing wastes were obtained from a search of technical publica-
tions,  a  computerized  literature  search,  and contacts  with  equipment
manufacturers  and  operators.    The  information  collected from  these
sources was then  interpreted  and compiled.  This  field  manual was  dev-
eloped from information obtained from these sources.

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Computerized Literature Search

     A computerized literature search was performed using DIALOG™ Infor-
mation Service  of Lockheed  Corporation.   The  computerized  literature
review was conducted in three  steps.   The first step was  to  locate the
abstracts  from  the various  data base  files.   The  second step  was to
search the abstracts  for  the  appropriate  publications  and  documents.
The final step was to review the publications.

     The first step was initiated by selecting, the keywords or series of
keywords used to describe OSM specifics for metal finishing waste treat-
ment.  A series of keywords  coupled by the  words "and"  or "or" is often
used  to  select  the  desired  abstract.   A  question  mark in  a keyword
indicates  that the identity  of  a letter is unknown  and the computer is
to  identify all  references  including  the  letters  which precede  the
question mark.   For  example, the  keyword "chrom?" will  cause the  com-
puter  to  search  records labeled chrome, chromium, chromate,  etc.   The
series of keywords selected  are  listed below:

      1.  NPDES or Permit and (Violation or Exceed) and  Metal
      2.  Wastewater and Operation? and Maintenance
      3.  Operation and Maintenance and Metal?
      4.  Metal? and Precipitate? and Wastewater?
      5.  Cyanide? and  (Oxidation or Removal or Treatment)  and  Wastewater
      6.  Chrom? and  (Reduction  or Removal or Treatment) and Wastewater

      The keywords  were then used  to  search the thirty-seven  data files
in  Lockheed's  DIALINDEX1".    The search  of  the data  files revealed the
number of  abstracts  which contained  the keywords.   The information was
used  to  ensure that  the  keyword series  was  restrictive  enough  without
being overly restrictive.    The two  files which  contained the most ab-
stracts applicable to  this project were  the  Metals  Index (File  32) and
the Pollution Abstracts Index (File  41).  The Metals Index contained 99
abstracts which could be identified by  the six  series of keywords
described  above.  The Pollution Abstracts contained 445 abstracts.

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     The second step in the computerized literature search was  to  review
the  abstracts  identified by  the  keywords.   The  abstracts  reviewed  for
both the metals data  file  and the pollution data file are presented  in
Appendix A.   These  abstracts were  reviewed to  see  which publications
were most applicable to the project.

     The final step in  the  literature search was to review and evaluate
the  articles chosen  from  the abstract  search and  to incorporate  this
information  into  the  O&M manual.  Much  of  the information  was used  to
review current treatment practices and to  develop O&M specifics for  the
troubleshooting manual*   These articles were  only  referenced when  they
contained specific  information such  as surface loading  rates or  mixing
horsepower.

Technical Publications

     The review of literature  included technical  publications which  were
not  included in  the computerized data base  or those publications which
were more  easily obtained  by a manual  literature search.   The  former
category contained  articles  that were published generally  before  1970
and  many reference books.   The search of articles  before 1970 was  per-
formed by reviewing annual indexes from publications such as Proceedings
of  the Purdue  University  Industrial Waste  Conference, Journal  Water
Pollution Control Federation,  and Water and Waste Engineering.

     Sources from which information  and data  on metal  finishing waste
treatment could be  easily  obtained were the U.S. Environmental Protec-
tion Agency  (EPA),  the Water  Pollution  Control  Federation  (WPCF),   the
American Electroplating  Society  (AES), and reference  books.   More  than
40 EPA publications relating to metal finishing wastes were reviewed.  A
series of seven EPA Technology Transfer  documents provided much general
information   about   metal-finishing  waste   treatment.  /2'3'4'5'6'7^
Twelve AES  project reports were also reviewed.  Numerous reference books
on treatment of metal wastes  were also  identified and  reviewed.   This

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review not only  included  books  written for treatment of metal finishing
wastes but also materials which described pH control, sedimentation, and
sludge dewatering.

Equipment Manufacturers

     Several manufacturers of equipment  for  metal  finishing wastes were
contacted.   Information  obtained  from  manufacturers'  representatives
was used  to characterize  and  describe  the  different types of equipment,
to  develop O&M  specifics,  and  to  determine  performance  data.   This
information on  field  operations and  maintenance  was  referenced  when
used.

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                                SECTION 3

                 PROBLEM ASSESSMENT AND RECOMMENDATIONS
                     FOR IMPROVING PERMIT COMPLIANCE
CONVENTIONAL WASTEWATER TREATMENT

     Conventional wastewater  treatment  in  the  electroplating industry
consists of the following unit processes (see Figure 1):

     o  Chromium  reduction (if  needed)  of  segregated chromium  waste
        streams to reduce  the chromium from  its hexavalent  form to the
        trivalent state,  which  then  can  be  precipitated  as  chromium
        hydroxide by alkali neutralization,
     o  Cyanide  oxidation  (if  needed)  of   segregated  cyanide-bearing
        waste streams  to  oxidize the  toxic cyanides  to harmless carbon
        and nitrogen compounds,
     o  Neutralization  of  the  combined   metal-bearing   wastewaters,
        acid/alkali wastewaters, strong chemical dumps, and  the effluent
        from the cyanide and chromium  treatment systems to adjust the pH
        within acceptable  discharge limits  and to  precipitate the dis-
        solved heavy metals as metal hydroxides,
     o  Clarification,  in  which flocculating/coagulating  chemicals are
        added to promote the  initial settling of the precipitated metal
        hydroxides,
     o  Gravity thickening over  extended time to increase  solids content
        of sludge before disposal.

     These unit processes provide effective,  reliable  treatment  for many
electroplating waste  streams.   That  is  not  to  say,  however, that such
treatment  is  suitable for all applications or that the "normal" design

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 Chrom*
                                                    Solid WUM
             CYANIDE
             OXIDATION
S - lulfomtor
C » cflionnarar
P > ondnion rMucnon oounfMl
 Figure 1.       Electroplating industry conventional
                 wastewater treatment.
SOURCE: USEPA ENVIRONMENTAL REGULATIONS AND TECHNOLOGY; THE
        ELECTROPLATING INDUSTRY, EPA 625/10-dO-OOt, AUGUST 1980, P. 13.

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parameters  (retention  time,  reagent dosage, and so  forth)  will provide
effective pollutant  removal from  every individual  plater's  wastewater
discharge.

     Many of  the items  covered in  this  manual have  their basis  in a
conventional wastewater  treatment  system such  as  the one  described in
the preceding.

PROBLEM ASSESSMENT

     A plant assessment  is  the  initial  step in a pollution control  pro-
gram.  A plant assessment involves a thorough analysis of the operations
of a metal  finishing plant  that  relate to pollutant  sources  and water
use.   The information generated  during a  plant assessment is  used in
evaluating  the  application  of  in-plant  changes for  reducing chemical
loss and water use.

     A plant assessment  includes the following  steps:  1)   inspection of
the  plating room  layout,  2) review of  plant  operating  practices, 3)
examination of process water use, 4) performance of  sampling and labora-
tory analysis  to characterize  waste streams  and  to  determine dragout
rates, and  5)  identification of  the frequency, volume,  and character-
istics of batch dumps.

     Laboratory analyses of wastewater  samples are performed using
standard  EPA-approved  techniques.   Throughout this  manual,  various
analytical  parameters  and  their concentrations  are  discussed.   For  all
tests  the analytical methodology presented  in the  EPA document "Methods
                                            (8)
for Chemical  Analysis  of Water and  Wastes"     or  "Standard Methods  for
                                         (9)
the Examination of Water and Wastewater"    should be  followed.

     The  successful operation and maintenance  (O&M)  of a waste  treatment
plant  requires  consistent  performance that  exceeds   regulatory  compliance
levels.   Failure to meet  these compliance levels can result in  costly
disposal  alternatives,   fines,  damage   to  the  environment,  and adverse
                                   10

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public  reaction.   If  a  treatment  facility  fails  to  meet  compliance
standards, the problem usually falls under one of  the  following  causes:

     1)  Shock loadings (hydraulic or contaminants)  to the  waste
         treatment plant,
     2)  Poor understanding of O&M procedures,
     3)  Poor process control,
     4)  Equipment failure, and
     5)  Treatment plant design inadequacies.

     The potential effect of  good OSM  on each of the  five  categories  of
non-compliance reasons  is  discussed  below.   If  a  plant finds itself  in
non-compliance it should determine which categories  of causes  are  appli-
cable and take appropriate action to see if  improved OSM could be  effec-
tive in improving its performance.

Shock Loadings

     Shock loadings  of  flow or contaminants frequently cause treatment
process upsets  which can  result  in non-compliance.   Sources of  these
shock  loadings  can  be  either  spills  or releases  from production  batch
operations or cleaning  operations.   Their impact  on the treatment pro-
cess  can  be  mitigated  by  installing   sufficient  equalization.    Their
impact can also  often be  controlled by changes  in operating  procedures
in the production facility  or in  the treatment  plant.  Of foremost im-
portance  is  communication  between  production  and waste-treatment  person-
nel.  If waste-treatment personnel are  notified  of potential shock loads
in sufficient time, mitigating action often  can be taken,  such  as
diverting  the shock  load  to  sidestream  equalization to temporarily
bypass  sensitive 'processes,  or  manually  modifying  process  operating
parameters to adjust for the shock loading.

     Modification of production procedures with  respect to  spill control
and operating procedures for batch processes and cleaning operations can
reduce the magnitude of shock  loadings in  several  ways.    Wastes from
batch or cleaning operations  can  be released  slowly or during  times  of
                                   11

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low flow.  Spills can be cleaned up using dry chemicals and not be hosed
down the drain.  Chemical  handling  procedures  can be modified to reduce
the likelihood of spills  and  chemicals can be  stored  in  diked areas  to
contain spills that do occur.

     In all  cases  implementation of the above  procedures requires good
training of  all personnel in  proper  operating  procedures  to  control
shock  loading.   Part  of   this  training  must include  making production
personnel  aware  that  their  procedures  impact  waste  treatment.   This
factor is becoming increasingly important as some facilities have had  to
curtail  production  in  order  to achieve  discharge compliance  levels.
Treatment  plant  personnel also must be  trained in  the proper operating
procedures to mitigate  the impact of a shock load.  This action may  be
diverting  flow to sidestream equalization, bypassing an oil water separ-
ator  while  a  non-oily hydraulic   shock  load  is  occurring,  notifying
production to stop or  slow an excessive  discharge,  or other appropriate
procedures.

Poor Understanding of OSM  Procedures

     A  good  understanding of OSM  procedures  is  essential  to  operate
successfully a facility for the treatment of metal finishing wastes.   An
operator who is  well  versed  in the proper  OSM procedures  can  usually
operate the  treatment facility to meet permit compliance  even though one
or more of the above causes  of permit  violation exists at the treatment
facility.  This manual was developed to assist  operators  in implementing
the proper O&M procedures at  the treatment  facility.   While  no manual
can be  general  enough  for all plants  and yet  specific  enough  for one
plant, the intention  of this manual is  to aid in  the understanding  of
the cause/effect relationship  for several  treatment processes.  Once  an
operator has developed a cause/effect  relationship for the control vari-
ables  at the treatment facility, then specific adjustments  and/or set-
points can be  established.   A successful  OSM  program  will  be attained
when the operator can identify a potential problem, understand the cause
of the problem and what effect it will have  on  compliance, and then ad-
just the control variables so as to mitigate the problem.
                                   12

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Poor Process Control

     One  of  the most  common  causes of  continuous  poor. performance  and
frequent  non-compliance  is poor process control.   Poor process  control
results  in  the treatment  plant not  achieving  its  full  capacity  and
efficiency.   When the full  or  design  efficiency is not achieved,  the
blame is  put frequently  on poor design, but  it must be  remembered  that
the design  is  based upon  the  assumption of  good process control which
may or may not  be  occurring.   Good  process control can only be  achieved
by well  trained operators who know and understand  their equipment  and
the impact  of  all  operating  variables  under their control.   This  in-
cludes understanding the interaction between  operating  variables  and  the
trade-offs often  involved.  As  an  example,  increasing the belt  tension
in a belt filter  press can result in a  drier cake  but  will also result
in more  solids  in the filtrate  and a  shorter belt  life.   However,  the
solids in the  filtrate might  adversely  affect the performance of other
treatment processes such as an oil  coalescer.

     Process control  through   good  operations is particularly important
in the metal finishing industry where  several waste treatment processes
require critical  control  of operating variables  to  achieve good treat-
ment performance.   Examples include pH control for metal precipitation,
and pH and  oxidaton-reduction  potential  (ORP)  control  for  chromium
reduction and  cyanide oxidation.   A relatively  slight change  in these
operating  variables  can  result  in  significant  degradation  in   perfor-
mance, non-compliance, and in  the  case of cyanide reduction, the poten-
tial for  release of toxic gases.

Equipment Failure

     Equipment  failure can readily cause  a treatment  plant  to  fail  to
meet regulatory compliance levels.   The  impact of the equipment  failure
can be minimal when repairs are  implemented quickly or  the impact may  be
major  with parts  and  repairs   taking days  to  obtain and  install. It  is
therefore essential  to minimize equipment  failure  and downtime.   This
                                   13

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minimization of downtime  can be achieved partially by  a  sufficient  parts
inventory  and  overdesign; it  also  requires good operation and  mainte-
nance of existing treatment plant equipment.  Mechanical equipment  has  a
set  of  design operating  conditions and  any time these conditions  are
exceeded,  premature  equipment failure can  occur.   Treatment plant  per-
sonnel  should  be aware  of these  design  conditions and integrate  them
with plant operating procedures to insure  that  mechanical equipment is
not  unduly stressed.   It  should  be  noted that  this  stress  does  not
always  come from  mechanical   forces.   Improper  pH  levels  can  corrode
equipment  and  excessively high  temperatures  can   cause  materials of
construction  to  fail.    Once  equipment  failure  has   occurred,  prompt
repair  of  equipment  by well trained maintenance  personnel is essential
to minimize the impact and prevent recurrence.

     Good  operations  and  maintenance  can  also prevent  equipment  failure
by a regular and orderly  inspection of equipment for wear  or other  early
signs of equipment failure such as vibration.   A good preventive  main-
tenance  program  is   another  essential  facet  of preventing  premature
equipment  failure.

Treatment Plant Design Inadequacies

     No amount of good  operations  and maintenance can make a poorly or
improperly  designed  treatment plant achieve  consistent compliance  with
regulatory  standards;  conversely,  poor  operations  and  maintenance  can
make even  the  best  designed  treatment plant  fall  into noncompliance.
Before any major design modifications are implemented,  the potential for
treatment  plant performance improvement  through improved  OSM  should be
investigated thoroughly.

RECOMMENDATIONS FOR IMPROVING PERMIT COMPLIANCE

     The level of  pollutants   that  may be  discharged  to publicly  owned
treatment  works  (POTW)  is  regulated  by  the  USEPA.    Specifically,  the
                                   14

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level of pollutants  dischargable  by a plant falling within the  electro-
plating and  metal  finishing point source categories is limited by  regu-
lations issued in  the  Federal  Register  on July 15, 1983.      A copy  of
these regulations  is included  as  Appendix B of  this manual.
     Improving  the level  of  permit compliance  for treatment  of  metal
finishing wastes  is  a  two-step process.  The  first step is to  identify
the  problem and  the  second step  is to  take the  necessary corrective
actions.   Permit compliance problems generally  will fall into  the  fol-
lowing four categories:  1) design,  2)  operation, 3) administration,  and
4) maintenance.

     As  mentioned elsewhere  in  this report,  the  importance  of proper
design cannot  be overstated.   Each unit process along  with  the  inte-
grated waste  treatment  system must be  designed with  numerous  factors
accounted for.  A system which is improperly  designed  will seldom be a
system which can  be  operated  well.   Improvement of permit compliance by
improving  design  is  a  long-term process;  near-term  improvements  are
seldom attainable  through  design  changes.

     A well-designed system may not perform  as  expected because of  im-
proper operating  procedures.   A number  of  instances of  improper opera-
tion have existed; improvement of  operation is a direct  function of  the
operators' familiarity with correct OSM procedures.  It is the goal of
this publication  to provide adequate OfiM procedures and  troubleshooting
guides to produce  improved levels of permit compliance  in metal  finish-
ing waste treatment plants.

     Administration also affects permit compliance, although often  in an
indirect manner.   Such items  as  staff  supervision,  motivation,   funding,
and planning affect  the  operation of a  facility, which in turn  affects
all aspects of the treatment plant.

     Finally,  maintenance  affects  permit compliance directly.   In num-
erous instances  throughout the descriptions  which   follow,  routine  in-
spection and maintenance are  cited  as  the chief deterrents to operating
                                   15

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problems,  and hence  to  permit violations.   A  competent,  well-trained
maintenance group  is  indispensable in the smooth  and successful opera-
tion of a  treatment plant.

     Although  the  tendency is to  categorize  permit compliance problems
as belonging strictly to  one  of  the  four areas  discussed above, in fact
most problems have aspects of two  or more areas.  A plant which hopes  to
improve its permit compliance must strive to achieve improvement in all
four areas.

RESOURCE RECOVERY

     Pollution control  legislation has  affected  industry  by increasing
the economic  penalty  associated  with inefficient use  of raw materials.
In  the  plating industry,  for example,  loss  of a  raw material  in the
wastewater can result in  three distinct  cost  items:   replacement of the
material,  removal of  the  material  from the wastewater before discharge,
and disposal  of  the  residue.   Similar  cost items  exist  for  process
water:  replacement of water  (no longer  inexpensive to purchase) used in
processing, processing the water in the wastewater treatment system, and
processing the water by the treatment plant after discharge into a sewer
system.

     In response  to  the  incrased  cost of raw material  losses,  plating
shops are  modifying their processes to  reduce  these losses as  well  as
water  consumption.    Recent  years also have  seen  the  cost-effective
application of various separation  processes  that  reclaim plating chemi-
cals from rinse waters, enabling both  the  raw material and  the water to
be reused.

      The  impact of  resource recovery and  pollutant  load reduction
modifications  on waste treatment and solid waste  disposal  costs must be
measured if these modifications are to be  evaluated.   Cost  of sophisti-
cated  treatment necessary for electroplating wastewater and  of residue
disposal often provides  a significant  economic incentive  for resource
recovery.
                                   16

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     Modifications for reducing the pollutant or wastewater loading on a
treatment facility range from using flow restrictors to eliminate excess
dilution in  rinse tanks to  installing  recovery units, such  as  reverse
osmosis  and  evaporation,  to  separating  plating  chemicals   from  rinse
water for recycle to the plating bath.  Actions that can minimize waste-
water volume include the following:

     o  Implementing  rigorous  housekeeping  practices  to  locate  and
        repair water leaks quickly,
     o  Employing multiple counterflow rinse tanks to reduce rinse water
        use substantially,
     o  Employing spray rinses to minimize rinse water use,
     o  Using conductivity  cells  to avoid excess dilution in the rinse
        tanks,
     o  Installing flow regulators  to minimize water use,
     o  Reusing  contaminated rinse water  and treated  wastewater where
        feasible.

     Steps to minimize pollutant loading include:

     o  Implementing  a  rigorous  housekeeping program  to  locate and
        repair  leaks  around process  baths,  replacing faulty insulation
        on plating racks to  prevent excessive solution drag-out,  instal-
        ling^drip trays where  needed, and so  forth,
     o  Using spray  rinses  or air  knives  to  minimize solution drag-out
        from plating baths,
     o  Recycling rinse water  to  plating bath to compensate for  surface
        evaporation losses,
     o  Using spent  process solutions  as  wastewater treatment reagents
         (acid and alkaline  cleaning baths are obvious  examples),
     o  Using minimum  process  bath  chemical concentrations,
     o  Installing recovery processes to reclaim plating chemicals  from
        rinse waters  for  recycle  to the plating  bath,
     o  Using process  bath  purification to control  the  level of  impur-
       • ities and prolong the  bath's  service  life.
                                    17

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     Closed-loop  chemical  recovery  from  a  rinse stream can  often  provide  the  solution  to
treat.   Applying a  closed-loop recovery  system  to a plating operation
eliminates  the  need to  treat the  rinse  water normally  associated with
that step.

     In  the  case of rinse  streams requiring pretreatment  (for example,
cyanide  or chromium)  or rinses  containing  pollutants   not  effectively
removed  by  conventional  end-of-pipe technology (for  example,  some types
of  complexed  metals), installing a  closed-loop  system  to recycle  the
rinse  may  reduce  the  investment  needed to  comply  with the  effluent
quality  limitations.
                                   18

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                                SECTION  4
                              EQUALIZATION
INTRODUCTION

     One of  the  most frequently encountered problems in metal  finishing
wastewater  treatment  is  process  upsets  related  to  intermittent  high
flowrates  and highly variable  contaminant levels.   Batch discharge  of
high strength plating solutions and plating wastes  often can  cause large
fluctuations  in  flowrates,  pH,  metals  concentrations,  cyanide  concentra-
tion,  and  other  critical contaminant  levels.   These  fluctuations  are
often  so severe  that process upset and subsequent permit  violations can
occur before the  system is  able to compensate.   For this  reason,  waste-
water  equalization often is implemented  to  control the  extreme  fluc-
tuations in  flow  and contaminant  concentrations.   Likewise,  whenever
treatment process  upsets  occur, especially on  a periodic basis,  proper
equalization  should  be  one  of the  first operating  conditions  to  be
checked.

THEORY OF OPERATION

     Wastewater  equalization can  accomplish  three basic tasks.    The
first  is hydraulic or flow  equalization  which  dampens  hydraulic  surges
to downstream treatment processes.  Flow  equalization can  only  be  accom-
plished by placing some  type of variable liquid volume storage tank  in
the wastewater  flow path upstream of  sensitive process equipment.   The
liquid is  stored in the  variable  volume tank  during  high flow periods
and then is  released during low flow periods.   Therefore, the  hydraulic
equalization power is directly related to  the  utilized variable  volume
of the tank.
                                    19

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     The second equalization task is contaminant or  concentration equal-
ization.   Contaminant  equalization  is accomplished by  mixing  low  and
high contaminant  concentration wastewater, which  results in an  average
concentration  with dampened  fluctuation.   As with flow  equalization,
some type of storage  must  be  provided  which stores  highly  (or slightly)
contaminated  flow  until  such  time  as  the  contaminant  concentration
cycles  to  the other  extreme.   Contaminant equalization  can be  accom-
plished by placing in the  flow path a  storage  tank and mixer  with suffi-
cient volume to mix the low and high concentration wastes  or by  collec-
ting only the  high concentration  wastes  in  a  storage tank and bleeding
them back during  periods  of low  contaminant concentration.  The  latter
system  has  the disadvantage that the  contaminant  concentration must  be
monitored continuously  and rapid action taken based  on  instantaneous
contaminant concentration.

     The third equalization task, an  offshoot of  the earlier discussed
two,  is to allow means to control the  load  that  reaches the  process
within  limits  set by  the operator.   This is accomplished  by  positioning
the outlet  line near  the bottom of  the equalization  basin  and providing
valving that allows the operator  the option of increasing  or decreasing
flows  to his  process  from the equalization basin.   The operator  would
have  the  option  of lowering  flow during period  of  high  concentrations
and raising flows during periods  of  low concentrations and could  control
the load to the process to limits desired.  This  system has the  disad-
vantage that it requires more  analytical  work  than the other  two  systems
and requires a larger  equalization  tank that will allow  the  operator to
vary the tank  level and has the advantage that it will reduce the possi-
bility of organic shock and allows much finer  control of  the  process.

     Mixing is an integral part  of all  equalization techniques.   Flow
equalization requires  mixing  to keep  suspended material in  suspension.
Without it, solids will accumulate  in  the storage tank thereby reducing
the effective  volume  of the   tank.   Contaminant  equalization requires
mixing to blend the low and high strength  wastes  together.  Typically,
the mixers are vertical shafts with turbines  or marine  propellers.   If
                                   20

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tanks  are deep,  draft tubes  are installed  or multiple  impellers  are
placed  on elongated shafts.   Horsepower  requirements  for  equalization
mixing  typically  run between  0.02  and 0.04  horsepower/1000 gallons  if
                                                *
gritty  material is  not present  in the  waste.    If,  however,  gritty
material  is  present,  horsepower requirements for  mixing can exceed  2.5
horsepower/1000 gallons.   In all cases, if mixing is occurring in  cir-
cular tanks, then baffles must be installed on  the  sidewalls.

DESCRIPTION OF EQUIPMENT

     Wastewater  equalization can be  accomplished  by a number  of  dif-
ferent methods.  Some equalization occurs  in  sewer  lines.  Pollution
control equipment also has some surge capacity  available to  dampen out
fluctuations.  However,' due  to the nature  of  the variations  in the metal
finishing  industries,   these methods  provide  little if  any effective
equalization.  Several  typical  equalization  methods other than  inherent
system equalization are described below.

Batch Processing

     Equalization by batch  processing  involves storage  and batch  pro-
cessing of  the  wastewater in the same  tank.   To accommodate continuous
systems,  multiple  reactors are operated in  parallel.  When one reactor
is full,  the flow is switched to another reactor while  the wastewater in
the  first reactor  is being  treated.   Reactor  storage  capacity must  be
sufficient  to  handle  the maximum  volume  of  wastewater  that  could  be
generated during  the time it  takes to  treat  the  wastewater and empty
wastewater from the other reactor (see Figure 2(a)).  Alternatively,  the
*This and the following sections present information in a mix  of English
Engineering  and  metric units.   This mix  of units occurs  because,  al-
though metric  units  are now  preferred  for data  reporting,  many of  the
quantities are  reported still almost exclusively in  English units,  and
"rules of  thumb" have  been cast  in these units.   A  table of metric-
English conversions is provided with this report  as Appendix C.
                                   21

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      (a) Batch Processing
      (b)  Continuous Processing from Batch Storage
             Ws toragri——EXJ-
       (c) Side-Stream Equalization
            •^Storage
       (d) Flow-Through Equalization
Figure 2.        Methods of  equalization.
SOURCE: EPA REPORT NUMBER 600/2-91-148
                         22

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 system  can be operated in batch mode  with one tank when  the system is
 used  to treat wastewater flows from batch  type plating operations.  This
 technique  is  employed often when specialized  treatment  is required for
 intermittent waste flow.

      The  batch processing  procedure   is  a very  effective equalization
 technique  since  wastewater in the  treatment  reactor is  consistent for
 each  treatment cycle.   The system, however,  requires  that  either the
 flow  must  be  intermittent  with  sufficient time for wastewater treatment
 to  occur  between  flows,  or multiple  reactors must  be  provided.   The
 latter  is  usually prohibitively expensive.  Therefore,  this  process is
 found primarily  on small intermittent flows from  batch  metal finishing
 operations  whose  wastewater  requires  specialized  treatment,  such  as
 plating solutions which  contain high concentrations  of cyanide, or
 chromium.

 Continuous Processing from Batch Storage

      Continuous processing from  batch  storage usually involves two
 storage tanks  operating on a  fill-and-draw cycle.   While one  tank is
 being filled,  the  other tank is being discharged to a  waste treatment
 facility (see Figure  2(b)). 'This procedure is unlike batch processing,
 in which the  equalization  and waste treatment steps occur in  the same
 vessel.  Using this  technique the  waste treatment  facility  receives  a
 waste stream with  uniform  characteristics  while  processing the contents
 of an individual tank.   The stream  characteristics,  however,  often vary
 significantly from tank to tank.

     This equalization  technique requires  either  automated influent and
 effluent valves controlled by level indicators in the batch equalization
 tanks, or  intensive  operator  supervision.   The equalization  tanks must
be sized such that the  volume from  at  least one flow cycle  or contami-
nant concentration cycle can be  collected in  one tank.   If contaminant
equalization is desired, the tanks must  also  be mixed.   This  system is
best suited for relatively small flows and/or  rapidly varying (cycling)
flows that will permit  reasonably  sized tanks.  Its  primary  deficiency
                                    23

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is that some  degree of automation or  labor is required  to operate  it.
Also, the  step  change in reactor feed  characteristics that occurs when
the flow is switched from one storage tank to another  can be a disadvan-
tage  unless  the  operator  keeps  his  knowledge  of  tank  concentrations
updated often.

Side-Stream Equalization

     The  side-stream equalization  method  involves  the  collection  and
storage of flow  or contaminant concentration  surges  that result from
scheduled  dumping  operations  in the  production plant.    The  surge  is
diverted  to  a  storage vessel  for subsequent  processing  during  slack
periods.  This procedure is sometimes used  to store  an alkali waste in a
plant for future  combining with  a waste stream that is normally  acidic.
The  collected alkali could be dispensed  into  the normally acidic  waste
stream  to reduce consumption  and cost  of  neutralizing  reagents.    The
reverse is often practiced to acidify  hexavalent chromium wastes  prior
to reduction  (see Figure 2(c)).

     Side-stream  equalization  for contaminant  surges  is  usually  imple-
mented  by manually  opening diversion valves or directly  pumping  to  the
storage tank.  The  major problem with the system  is  that  either advanced
knowledge  of  the  event must  be available or online  monitoring equipment
must  be installed.   With  the  possible exception of monitors for  flow,
conductivity, and pH, on line monitoring  is very  difficult  and expensive
to  implement and maintain.   Probably  the  best  implementation  of  this
type of equalization is as a  spill collection  tank which can be  used to
collect and hold  spills  if and when waste treatment personnel are  noti-
fied of the spill fast enough to implement  the  system.

      If only  flow equalization is required, side-stream equalization  can
be  very  effective.    It  can be implemented  either  using flow  meters
connected to  pumps  and control  valves  or by a  passive system of  weirs
that  diverts  excessive flow  to  a storage  tank.   The stored water  can
then  be pumped  back into the system during low flow.   The major  advan-
tage  of the system is  that it  requires  minimal storage  volume  and is
                                    24

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reliable and relatively simple  to  implement.   The major disadvantage  is
that it provides little contaminant equalization.

Flow-Through Equalization

     The system of flow-through equalization dampens and greatly reduces
flow and concentration  variations, but does not  eliminate them.   Typi-
cally the  system operates on  a continuous basis and  requires  a large
tank, mixers, tank baffles,  and effluent control devices such as weirs,
orifices, control valves, or pumps (see  Figure 2(d)).   For flow equali-
zation,  the tank must be designed  to  fluctuate in volume in response  to
influent flow  rates.   For  contaminant  equalization,  the  tank  must  be
large enough to hold the volume which corresponds to the discharge cycle
of high or low concentration wastes.  The more cycles the  tank can hold,
the better the equalization  achieved.   The mixers for contaminant equa-
lization must be sufficient to keep  the tank completely  mixed  and  all
suspended solids in  suspension.   If the tank  is  round,  baffles must  be
installed  along  the side walls to  assure good  mixing.   The effluent
control devices  selected  will  depend on the objective  of the equaliza-
tion.  For contaminant  equalization,  broad crested weirs are frequently
used.  For simple and reliable flow and contaminant equalization, narrow
weirs, proportional weirs, or  orifices  are used.   Pumps or flow control
valves are used for maximum flow equalization.

The major  advantage of a flow-through  equalization system is  its  sim-
plicity of operation and  the continuous nature of  its  discharge.   Flow
and contaminant concentration changes do occur, but very gradually.  This
gradual change usually  provides  downstream processes  such as pH adjust-
ment  with  adequate  time  to respond.    The major  disadvantage  of   the
system is the large tank size generally required.

OPERATIONAL PROCEDURES

     The objective  of  equalization is  to  limit  fluctuations  in waste-
water flow and/or  contaminant concentration  to  levels  that will   not
adversely affect downstream treatment processes.  Equalization can occur
                                   25

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on a continuous basis such as in a  flow-through  system or can be initi-
ated upon demand as with side stream equalization.

Process Monitoring and Operational Criteria

     Equalization monitoring takes two forms.  First, with the exception
of a continuous flow-through system, the wastewater must be continuously
monitored  for flow  and/or  contaminant  concentration.   Monitoring  is
required to indicate when flow should be diverted to side stream equali-
zation or  to  determine  the fill and draw  cycles  in batch equalization.
Monitoring can be accomplished using  either  automated on-line equipment
or by periodic measurements  by  the  operator.  The  former is  subject to
breakdown and the latter is subject to slow response that may completely
miss flow  or  contaminant surges.   Therefore, it  is necessary to imple-
ment both monitoring techniques whenever possible.

     It  is also essential  that a  form  of  monitoring be  conducted  by
production personnel.   Whenever production  personnel  anticipate gener-
ating an  abnormal  flow  or  contaminant surge, the  production personnel
must notify waste  treatment prior  to  the  event and  indicate the time,
magnitude, and duration  of the the abnormal waste flow.   Similarly, if a
spill or accidental release of a large quantity of  contaminants or water
is  detected  in  the  production area,  then  production  personnel  must
notify wastewater treatment  personnel  immediately.   This information is
a critical part of wastewater monitoring and  is absolutely essential  for
effective operation of equalization equipment.

     The second part of  wastewater equalization monitoring is a periodic
program to evaluate the  effectiveness of the  equalization process.  As a
minimum,  this evaluation  should  occur  monthly with  batch  systems  or
after any downstream equipment  experiences   operational  problems which
could be attributed to poor equalization.  To be effective, the monitor-
ing must be  set up in  a  rigorous  test program in which  influent  and
effluent flow and  contaminant  concentrations are measured simultaneous-
ly.  The frequency of sample collection during the  test programs  and  the
                                   26

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duration of the program will depend upon the rate of flow and contamina-
tion variability.   Typically,  these variations follow  some  pattern and
exhibit times  of  peak and minimum  flow and  contaminant concentration.
To be  effective,  the  monitoring  program must  collect  sufficient  grab
samples to detect  these  variations, usually sampling every  hour  for 24
to 48 hours.   In some  cases, however,  where  the variations occur rapid-
ly, more samples will be required.   If possible,  the days for equaliza-
tion monitoring  should be selected  such  that the  maximum  variation in
flow and contaminants  that has been experienced  under  normal operating
conditions is occurring.

     Upon  completion  of the test,  the influent  and effluent  flow and
contaminant  concentration  should be  compared  graphically  by  plotting
influent and  effluent parameters versus  time on  the  same  graph.   The
peak effluent values should be  substantially less than the peak influent
values and within  the  design operating values for downstream equipment.
The maximum  rate  of change for effluent  contaminant concentration  must
also be evaluated when the contaminant concentration can affect chemical
feed rates in downstream equipment.   Too rapid a  change  can result in
poor performance of equipment such as pH controllers.

Process Control Strategies

     For the most part,  the operator has  little control over the equal-
ization process.   For  continuous  flow-through equalization,  control can
be exercised  by adjusting the  pumping rate  or orifice  openings.   For
batch  equalization  processes,  little control can be  exercised  over the
equalization  process,  except for the fill-and-draw cycle which is
usually dictated  by flow patterns.   Side-stream  equalization,  however,
is directly  controllable by operators  by  either adjusting set points on
automatic  monitoring  equipment or by  manually  diverting the flow  based
on test  results or information  from production  personnel.   Rigid cri-
teria  for  initiating  side stream  equalization  can  not  be developed;
however, the following facts should be evaluated:
                                   27

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     o  Sensitivity of downstream equipment to the surge.
     o  Potential for violating permit conditions if a treatment process
        upset occurs.
     o  Reserve capacity  in  side stream equalization tank  for  a second
        more severe surge.
     o  Likelihood of  another  event requiring side  stream equalization
        prior to release of current equalization volume.
     o  Compatability  of   liquid currently  in  equalization  tank  with
        current waste stream (i.e., a current  acidic wastestream should
        not be diverted to side stream equalization  if  a  cyanide waste
        is currently stored  there.   Hydrogen cyanide gas  could be pro-
        duced ).

     In addition to the monitoring of process operating variables speci-
fic to side  stream  equalization, several general operating and mainte-
nance  procedures  should  be performed   routinely  on  all  equalization
equipment.  These include  the following:

     o  Equalization tanks should be checked monthly for accumulation of
        solids  on the bottom of  the tank.   When  the  solids accumulation
        significantly reduces tank volume,  the  tank  must be cleaned.
     o  Equalization tanks should be checked weekly  for  accumulation of
        floating material.   If  the floating  material  interferes  with
        weirs,  pump  intakes, level  indicators,  or  mixers it  must  be
        removed.
     o  Tanks,  baffles, mixers,  and pipes  should be  inspected  annually
        for condition  of  materials  of  construction.   Corroded  or  worn
        parts should be repaired or replaced.
     o  Monitoring programs to  evaluate the performance  of equalization
        should  be  conducted approximately  twice per  year or  after  a
        treatment process upset that  could be  linked to inadequate
        equalization.
     o  Flow meters, level  indicators,  and on-line  monitors  should  be
        calibrated annually or  at the  manufacturer's  specified interval,
        whichever is less.
                                   28

-------
     o  All pumps, mixers, and automated  valves  should be included in a
        regular preventive maintenance program.

TYPICAL PERFORMANCE VALUES

     Almost any desired level of equalization can be achieved by varying
the size  and type  of  equalization  equipment.    Therefore,  performance
criteria  must  be  established  for  individual facilities  based  on the
sensitivity of downstream treatment processes.

TROUBLESHOOTING GUIDE

     A troubleshooting guide for  operation  of the equalization tanks or
basin is  presented  in  Table 1 .   Two major operating  problems  are con-
sidered;  these  are inadequate  contaminant equalization  and inadequate
flow equalization.   For each  problem,  several probable  causes,  checks
and monitors, and corrective actions are given.
                                   29

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TABLE 1
EQUALIZATION TROUBLESHOOTING GUIDE
OJ
O
PROBABLE CAUSE
CHECK OR MONITOR
REASON
CORRECTIVE ACTION
OPERATING PROBLEM: 1. Contaminant equalization inadequate.
la. Broken or worn mixer
impeller.
1b. Inadequate basin volume
caused by solids de-
posits on the bottom
of tank.

1c. Missing mixing baf-
fles on circular tank.
Id. Improperly located
mixer.
1e. Inadequate basin
size.
If. Inadequate mixing
horsepoweri
Check condition of mixer
impeller.
Check for solids accumula-
tions by draining tank or
checking tank side wall depth
with a pole or similar device.

Check for condition of
baffles on outer wall of
circular tanks.
Check location of mixers;
stationary mixers may not
have the proper impeller
submergence and mixers in
deep tanks may be missing
draft tubes or multiple
impellers. Submerged mixers
too close to the surface may
vortex and lose efficiency.

Conduct monitoring pro-
gram to determine if basin
is large enough to contain
wastewater flow between
low and high flow and/or
contaminant cycles.
(Note: for good equali-
zation more than one cycle
volume may be required).

Check mixing horsepower;
check for solids deposition
in equalization tank.
Broken or worn impellers
can dramatically reduce
the efficiency of mixing.

Reduced basin volume
limits storage capabil-
ities and hence equali-
zation capacity.

Baffles must be present
to break circular flow
patterns which do not
contribute to mixing.

The efficiency of a mixer
can be dramatically
affected by. improper
placement.
Inadequate basin volume
limits storage capacity
and hence equalization
capacity.
Mixing is directly related
to input horsepower.
Replace if worn.
- Clean tank and remove solids.
Repair or replace damaged or
missing baffles.
Move and adjust as required.
Reference manufacturer's
recommendations and design
speci fications.
Modify or add tank volume as
required.
Add mixing horsepower as
required. Reference
manufacturer's recommen-
dations. Typical values range
between O.02 and 0.04 hp/1000
gallons. If gritty material
is present, much larger mixing
horsepower will be required.

-------
TABLE 1
(Continued)
EQUALIZATION TROUBLESHOOTING GUIDE
PROBABLE CAUSE
CHECK OR MONITOR
REASON
CORRECTIVE ACTION
OPERATING PROBLEM 2: Flow equalization inadequate.
2a. Flow meters or level
indicators that con-
trol tank discharge
are improperly set or
calibrated.

2b. Improper choice of ef-
fluent control device.
2c. Leaks around effluent
control devices.
2d. Inadequate storage
volume.
Check for proper setting
and date of last calibra-
tion.
Check type of effluent con-
trol device.
Check for erosion and wear
around effluent weirs and
orifice plates.
Monitor tank level during
operation.
These devices, when
incorporated into the
system, directly control
the flow to and from the
equalization basin.

Effluent control devices
determine the degree of
control that can be
exercised on effluen flow.
Pumps can provide best
equalization followed by
valves, orifices, propor-
tional weirs, and narrow
rectangular weirs.

The amount of flow equal-
ization is directly
proportional to the
changes in tank volume.
Also, in most equalization
techniques, as the water
level approaches the top of
the tank, the effluent flow
is dramatically increased
to prevent overfilling.
Calibrate and adjust as
required. Reference
manufacturers calibration
procedure and design speci-
fications for proper setting.

Modify discharge device as
required.
Repair or replace as required.
Modify tank design or effluent
control devices as required.

-------
                                SECTION 5
                               OIL REMOVAL
INTRODUCTION

     The  sources of  oil found  in  metal wastewater  are from  cooling
operations,  cleaning operations,  and  lubrication.    Oil is  typically
present in wastewater in  three  forms:  free oils,  emulsified  oils, and
soluble  oils.    Free oils  in  wastewater are  those which  rise  to the
surface of  the  wastewater due  to  buoyant forces  in  a  short  quiescent
period.   Emulsified oil  is  oil dispersed  in  the  wastewater  as small
droplets which can  range  in  size from 0.1  to 100 microns.   Soluble oil
is discussed in the next paragraph.   A  wide  variety of oil removal pro-
cesses is available  for  removing the free and  emulsified forms of oil.
The processes  include skimming, coalescing,  emulsion  breaking, flota-
tion,  centrifugation, ultrafiltration,  reverse osmosis,  carbon  adsorp-
tion,  and  biological oxidation.   The most widely  used and conventional
treatment processes  in the metal finishing  industry are gravity  separa-
tion  and  skimming,  coalescing,   emulsion breaking,  and  flotation.   The
other processes are not widely utilized at this time and, therefore, are
not covered in this manual.

     Soluble  oils  are those organic  oils  which  are  dissolved  in the
wastewater.  Soluble oils are generally the lighter, more polar  fraction
of an  oil mixture.   Soluble oils  are  not  removable  by the techniques
described  in  the preceding  and  in  this  chapter.   Techniques  such as
gravity separation,  flotation,  and  emulsion breaking  result in  removal
of free  and emulsified oil, but soluble oils  remain dissolved in the
wastewater.   Soluble oils are,  in  general,  biodegradable,  so  that the
                                   32

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most  successful  treatment for removal  of soluble oils  is  often biode-
gradation in a biological wastewater treatment system.

     Along with  the topic of  oil removal,  the  subject of  total toxic
organics  (TTO) must be  addressed.   The materials which  make up the TTO
are listed in Appendix B; they are typically degreasing  solvents used in
the cleaning of metal parts.   The waste solvents will contain oils, and
will exist as free, emulsified, and soluble oils in the  wastewater.  The
concentration  of  TTO  in  metal   finishing wastewaters  can  be  greatly
reduced by proper  handling and disposal of solvents and other organics,
•especially  by segregation  of  these  wastes  for  contract  disposal or
reclamation for recycle.

     Control and  management  practices  for waste solvents and  other
components which make  up the  TTO  should  be devised  to  follow resource
recovery  guidelines.   Specifically,  development of  segregation facili-
ties  for  these materials should be implemented, and  disposal should be
by a reputable contractor.   The potential for reclamation of the organ-
ics  should  be explored;  if  reclamation  is  not feasible  then disposal
must  be performed  by  a  reportable disposal  contractor.   The importance
of proper disposal for  materials containing  the  compounds  on  the TTO
list must be emphasized.   Those materials are known to  exhibit signifi-
cant toxicity; severe environmental and human health problems can result
from their improper handling or disposal.

THEORY OF OPERATION

     The  theory of  operation for  the  equipment used  to  remove free and
emulsified oil from wastewater is discussed below.

Gravity Separator

     Separator design  is based on the  specific gravity difference be-
tween the dispersed oil globules  and  the wastewater.   The  lighter oil
globules rise to the wastewater surface and are removed.   The  oil rise
rate is described by Stokes' Law  which  states  the  rise rate is directly
                                   33

-------
proportional  to  the difference  in the weight of the oil globule  and  the
wastewater it displaces.

Emulsion Breaking

     Emulsified  oil is dispersed  in wastewater  as  small droplets.  These
droplets can  range  in size from 0.1  to 100  microns.   With pure  oil  and
pure water, an oil emulsion is  highly  unstable  since both  phases  quickly
separate and  assume  a shape having the minimum interfacial area.  With
oily wastewater, however,  an  oil  emulsion is often formed which  is much
more  stable due  to  emulsifiers which  alter the oil-wastewater interface.
     Three  common  emulsifiers  are  electrical  charge,  chemical  action,
and mechanical  assistance.   Electrical charge  emulsifiers establish  a
repulsive electrical  field at  the oil-wastewater  interface.   This type
of  emulsifier is normally a negligible  cause  of  stability  except  for
those wastewaters that have  a low salt content or dilute  oil concentra-
tions .   Chemical emulsifiers are materials  such as soaps or detergents
which cause  chemical  reactions at the  oil-wastewater  interface.   Mech-
anical  emulsifiers  are finely  divided colloids such  as  silt,  clay,   or
metal fines which attach to the oil or are coated  by the oil.

     Emulsion stability  is affected  by droplet  size,  emulsion  age,  and
wastewater  viscosity.   Smaller  droplets  are   typically  more   stable.
Emulsions generally  become more stable with age because  the emulsifier
is  transported  to  the  oil  through  the wastewater  by diffusion.    A
higher wastewater viscosity  generally results in a more stable emulsion
since there  is  more resistance to  the movement of  small droplets thus
reducing the possibility of coalescence.

Coalescing Separator

     Coalescing  separators work in a  similar manner  to  gravity separ-
ators with skimmers  except that coalescing separators remove smaller  and
less bouyant  particles.  The  basic principle of coalescing involves  the
preferential wetting of a  coalescing  medium  by  oil droplets which accu-
mulate on the medium, and then rise to the surface of the  solution.   The
                                   34

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most  important  requirements  for  coalescing  media are  wettability  for
oil,  large surface  area,  and contact Between  the  oil particles and  the
coalescing medium.

Air Flotation

      In  a  flotation process, fine  gas  bubbles  are  introduced into  the
wastewater.   These  gas bubbles attach  to oil globules  resulting in  an
aggregate with a specific gravity much less than that of  the  surrounding
wastewater.  The attachment  of  the  fine,  micron size air bubbles  to  the
oil globules  occurs  by several mechanisms.   The first mechanism  is  the
adhesion of an air bubble to the  oil globule by precipitation or  by  the
collision of the air bubble  with  the oil globule.   The second mechanism
is  the trapping  of the  rising air  bubble under  an oil  globule floe
structure.  The  third  mechanism is  the adsorption of the air babble  by
an  oil globule  floe.   The  rise rate of  the aggregate  is  described  by
Stokes1 Law which states  that the rate  of rise  is directly proportional
to  the difference  in  weight  of  the  aggregate and  the wastewater   it
displaces.  The quantity of  gas which can be dissolved in the wastewater
is described by Henry's Law, which states that for gases  of low solubil-
ity the  gas mass  dissolved  in  water is  directly proportional  to  its
partial pressure.

DESCRIPTION OP EQUIPMENT

Gravity Separators and Skimmers

     Gravity separators normally remove  free  oil and little  or no emul-
sified or  soluble oil.   The separators  are  used as primary treatment
processes  and  are particularly applicable  for  the  separation of large
quantities of free oil.

     Gravity separators range from  lagoons  with oil  retention booms  and
oil removal devices  to  tanks with automatic oil skimmers.  The American
Petroleum Institute  (API) has developed  design criteria for  gravity  oil
                                   35

-------
separators.   Separators  based on  these  design principles  are  the most
common type of oil separator and are referred to as API separators.

     A line diagram of an API  separator  is presented in Figure  3.  The
separator includes a trash rack, a  forebay with oil skimmer and baffle,
an  inlet diffusion  device,   and  oil  separation  channels  each  with a
scraper and oil  skimmer.   The trash rack  removes  sticks,  rags, stones,
and other debris.  The forebay  distributes the influent.   The oil which
rises to  the  surface  in the forebay is  retained by the baffle and re-
moved by  the  skimmer.   The  inlet  diffusion baffle  reduces flow  turbu-
lence and distributes the flow  equally over the channel cross sectional
area.   The free oil rises in  the channels,  is collected with the
scraper, and is removed with the skimmer.

     A  variation of  the  gravity  separator called  the parallel plate
separator  is  also commonly  used.   It  consists of  a  gravity separator
with parallel plates installed in the tank  to  assure laminar flow  condi-
tions.  The small distance  between the plates  also reduces the distance
the oil  globule  must rise,  which  in turn results in a  decrease in the
required actual surface overflow rate and  detention  time.

Emulsion Breaking

     Chemical  emulsion  breaking can be  accomplished as either a batch
process  or  a  continuous  process.    The  emulsion  breaking  process
resembles  gravity  separation except that  concurrent chemical  treatment
occurs  to  break  up  the  emulsified oil.   The mixture of emulsified oils
and  water is  initially treated  by the  addition  of  chemicals  to  the
wastewater.   A means of  agitation (either mechanical  or  by increasing
the turbulence of the wastewater  stream)  is provided to ensure that  the
chemical added and the emulsified oils are  adequately mixed to break  the
oil/water  emulsion  bond.    Finally, the  oily   residue  (commonly  called
scum) that results  rises  to the surface  and  is separated  from the re-
maining  wastewater  by a  skimming  or  decanting process.   The skimming
process  can  be  accomplished by  any  of  the   many types  of  mechanical
surface  skimmers  that  are presently in use.   Decanting methods include
                                   36

-------
Adjustable
 weir
                                                                         Influent
                     Figure  3.
        S Judge pipe-
              Sludge hopper -

API separator.
                                       37

-------
removal of the oily  surface  residue via a technique  such as controlled
tank overflow  or by   removal  of  the  demulsified  wastewater  from the
bottom of  the  tank.   Decanting can  be accomplished  with a  series  of
tap-off lines at  various  levels which  allows  the separated  oils  to be
drawn off  the  top or allows the wastewater  to be drawn  off  the bottom
until oil  appears  in the  wastewater line.   With any  of  these arrange-
ments,  the oil is usually diverted  to  storage  tanks for further proces-
sing or hauling by a licensed contractor.

Coalescing

     Coalescing also resembles  gravity  separation,  except that the tank
is filled  with various  configurations  of coalescing media.  The coales-
cing media can be plates,  fibrous media, reticulated polyurethane foams,
or loose media  so long as they  provide a tortuous path  for the waste-
water.  Most media are installed in  the form of  relatively small dia-
meter  cartridges of a  standard size,  stacked in  a  parallel position.
Orientation  may  be  vertical or  horizontal;  however,  horizontal designs
can be more  difficult  to  service since the entire separator vessel must
first be drained.

Air Flotation

     A variety of flotation methods are commonly used  for oil-wastewater
separation.   The  fundamental  difference between  these  methods  is the
mechanism  by which  the  air  is introduced into the  wastewater.  The two
most common  methods are  the  dissolved air  flotation  (DAF)  process and
the induced  air  flotation (IAF)  process.

     Many  variations  of the  DAF process  are used.   Three  principal
variations are  full, partial,  and  recycle operation.   Simplified  line
diagrams of  the  three  principal DAF process variations are presented  in
Figure 4.   These variations  differ in the  portion  of the wastestream
which  is  pressurized and saturated  with gas.    The full  pressurization
operation  treats  the entire influent wastestream.  The  partial operation
treats a  portion of the  influent  wastestream.   The  recycle operation
                                   38

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                      COMPRESSED
                         AIR
            INFLUENT
                     PRESSURIZATION
                        SYSTEM
           A-TOTAL PRESSURIZATION
            INFLUENT
                     PRESSURIZATION    *
                        SYSTEM        I
                       COMPRESSED
                          AIR

          B- PARTIAL PRESSURIZATTON


             INFLUENT
            COMPRESSED
                     PRESSURIZATION
                         SYSTEM
                                                  FLOTATION
                                                    TANK
                                                  FLOTATBN
                                                    TANK
                                                   FLOTATION
                                                    TANK
                                                               EFFLUENT
OIL DISCHARGE
                                                               SLUDGE DISCHARGE
                                                               EFFLUENT
OIL DISCHARGE
                                                               SLUDGE  DISCHARGE
EFRUENT
OIL DISCHARGE
                                                                SLUDGE DISCHARGE
           C- RECYCLE PRESSURIZATION  -

Figure  4.        Line diagrams of principal OAF process variations.
                                             39

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treats a portion of  the  effluent wastestream.   A typical recycle  system
includes a compressed  air  source,  an aeration tank,  a  feed pump, and  a
flotation tank.  The compressed  air  is  dissolved into the  return  waste-
water  at  an elevated  pressure and  stored in the  aeration tank.   The
pressurized wastewater is  subsequently  mixed with  the  main wastestream
and  released  to atmospheric  pressure in  the  flotation  tank  where  the
dissolved air  is  released  from  solution as fine  air bubbles,  approxi-
mately 30 to 120 microns in diameter.  The gas bubbles attach  to the  oil
globules and the aggregate  rises to surface and is  collected.

     The induced air flotation process  consists of a multicelled tank,
froth  launders, a  recycle  pump,  and  static air inductors or aspirators.
The  flow  through  the  cells is  in series.   The wastewater  enters  the
first  cell where air is  introduced through the  action  of  an  aspirator.
The aspirator utilizes recycle process effluent.  The air is released in
the cell in the form of  air bubbles  approximately  1000  microns in dia-
meter, somewhat coarser  than those in a DAF  process.   The air bubbles
attach to the oil globules  and the aggregate rises  to the surface  and is
collected.   The remaining  wastewater flows  through a  baffle into  the
subsequent cells and ultimately  out  of  the system.  Alternate  IAF sep-
arators use different  methods to  induce air  into  the  wastewater.   One
system forces air under pressure into the  liquid-.   Another  common  system
induces air into the wastewater  through  high speed  mixers.

     DAF separators commonly include a chemical feed  system to introduce
coagulant aids such  as polymers  and  metal salts, including ferric chlo-
ride,  alum, and lime.  IAF  separators almost without  exception include  a
chemical feed  system.    The chemicals  are introduced  at  a  variety of
points in  the  system.   Some systems include  a  separate  rapid mix  and
flocculation chamber.

Skimming Devices

     Skimming devices to remove floating oil are an integral part  of  API
gravity,   parallel  plate,   and  coalescing  separators.    Four   common
                                   40

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skimming devices  are  the rotary drum,  the  rotatable slotted  pipe,  the
floating weir, and the belt (or rope)  type.

     With the rotary drum device, a horizontal drum approximately 0.3 to
0.6  meters  (1  to 2  feet)  in  diameter  is  partially  submerged  in  the
wastestream.   Skimming  is  accomplished  as  the  drum  rotates  with  the
flow, picking up a thin oil film which is later scraped off the drum and
removed.  The depth of  submergence is not critical as  long  as the drum
is in contact with the  oil  layer.   A  submergence depth of approximately
3  cm (1  inch)  is  typical.   The rotational  speed is typically 0.15 to
0.45 m/sec  (0.5 to 1.5  ft/sec), but the optimum  speed  depends upon the
amount of  oil to be  removed  and oil viscosity.   The  device typically
results in a recovered oil that is low in water content.

     With the rotatable slot  device,  a horizontal slotted pipe is sub-
merged  in  the  wastestream  with the  slots  normally above  the surface.
Skimming is  accomplished by rotating the pipe such that the slots are
submerged,  allowing  the oil to flow  into the  pipe  and to  be removed.
This device  can result in  a  recovered  oil that  may be low  or high in
water  content depending on the amount  of care  exercised  in  submerging
the  slot and adjusting it during the skimming operation.
                                    t-
     With a  floating  weir  device,  a floating device suspends a horizon-
tal  weir  in the wastewater channel.  The device is weighted such that
the  weir crest is just above the water  surface  but below  the  oil
surface.  This  positioning  results in the oil flowing continuously into
the  weir  channel.  The recovered  oil  exits  the  channel  to  a  discharge
point via a  flexible  hose.  The device  typically results in a  recovered
oil  high in water content.

     With the belt (or rope)   device  an endless  belt  is  pulled  through
the  wastewater.   Skimming is accomplished as floating oils adhere  to the
belt.   After passing  through  the  wastewater,  the  belt continues on  a
device located above  the liquid level where  the recovered  oil is
squeezed or  scraped from the belt  and removed.  The oil viscosity
                                    41

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and attraction to the belt material  affects  the  belt speed and perform-
ance.  Baffles are commonly used to direct the floating oil to the belt.
Belts are  typically 0.3  to  0.6 meters  (1  to 2 feet)  in width.   The
device typically results in a recovered oil with low water content.

OPERATIONAL PROCEDURES

     The objective  of oil removal is to  reduce free,  emulsified,  and
soluble oil  to a level  that is acceptable  for  discharge.   This often
requires multiple steps  that first remove free  oil  and then emulsified
oil by emulsion breaking or air flotation.

Process Monitoring

     The performance  criterion  for evaluating oil removal equipment is
effluent  total oil concentration.,  While  this  parameter  provides  the
overall performance of  the  system,  several other  parameters  must be
measured and  incorporated  into  a  regular monitoring  program to success-
fully and  consistently operate  an  oil removal system.  These parameters
are listed in Table 2.

     Of the  parameters  listed in Table  2,  flow should be monitored
continuously.  Total  influent and  effluent oil along with pH, suspended
solids,  and   temperature  should  be  measured at  regular  intervals as
specified  or  after  any  oil violation or process upset caused by  exces-
sive oil.  Sampling may  be either composite  or  grab with grab sampling
normally preferred  for oil measurements.   Samples always should be  col-
lected  in  areas  of sufficiently  high  turbulence to  entrain free  oil.
Influent and  effluent oils also should be analyzed for  free,  emulsified,
and  soluble  oil  fractions on a monthly  basis or after poor  performance
of oil  removal equipment is  noted  or suspected.   More  frequent analyses
will be required  if a plant upset  or  permit violation  is suspected.

     Determination  of oil  content of  water is a  critical procedure.
Procedures for  sample collection,  storage, and  analysis  should  be  per-
formed  in  strict  accordance  with  established  standards.    Quality
                                   42

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                                 TABLE 2

                               OIL REMOVAL
                     PROCESS MONITORING REQUIREMENTS
           Parameter
     Frequency
      Comment
 1 . Plow
 2. Influent total oil
 3. Influent free,  soluble,
    or emulsified oil
 4. Effluent total oil
 5. Effluent free,  soluble,
    or emulsified oil

 6. Suspended solids

 7. Waste oil volume


 8. Waste sludge volume



 9. Temperature



10. pH


11 . Oil volume collected
   Continuously
   Weekly
   Monthly
   Weekly
   Monthly


   Weekly

   Weekly


   Daily
Continuously
or per shift
Continuously
or per shift

   Daily
To determine overflow
rate and hydraulic
retention time (HRT).

To determine mass
loading of oil.

To determine mass
loading for a partic-
ular form of oil.

To determine perfor-
mance and determine
loading to downstream
processes.

To determine perfor-
mance of the system.
To determine quantity
of oil to be disposed.

To determine quantity
of sludge to be
disposed.

Temperature will affect
oil removal perfor-
mance .

pH will affect oil
removal performance.

To determine mass
balance for oil.
                                   43

-------
assurance including duplicate analyses and blanks is indispensable.   If
a violation of permit  conditions  is  detected,  sample collection,  stor-
age,  and analysis  procedures  should be  investigated  as part  of an
assessment of the plant program.

     The analysis of samples  for  total oil content should be conducted
according  to  one of  the procedures  given in  the current  edition of
                                                                    (9)
"Standard  Methods  for  the  Examination  of  Water  and  Wastewater".
While other techniques are  commonly  used,  they may  not  be accepted by
local regulatory agencies.   "Standard  Methods",  however,  does  not pro-
vide  a  technique  for  differentiating between free,  emusified,  and
soluble oil.  This differentiation is  particularly  important when evalu-
ating equipment  that is  effective in  removing  one oil classification,
but not  another.   As  an example,  a gravity separator may  appear  to be
malfunctioning because  it is removing only  a  small  fraction of the total
oil.   If the  majority  of the oil  is  free oil,  this will  be the case.
If, however, the majority of  the  oil  is  soluble or emulsified oil,  the
gravity  separator may  be  doing  an excellent job  removing  the  free  oil
that it was designed to  remove.   A procedure for determining the free,
soluble, and emulsified fractions  of  oils  is provided below.

Free Oil—
     Place  a  measured  amount of  the raw wastewater  in a  separatory
funnel.   Shake  the sample  vigorously and  let stand  quiescently  for
approximately two hours.   Draw  off a portion of  the subnatant  and de-
termine  its oil  concentration.  The  oil  measured is the emulsified and
soluble  fraction.   The difference between the  total oil  concentration
and  that measured  is  the  free  oil  concentration  of  the  wastewater
sample.

Soluble Oil-
     Place  a  measured  amount of  the  raw wastewater  in a  separatory
funnel  and  acidify with  10  ml/1 of  concentrated  hydrochloric  acid.
Next, add 200 g/1 sodium chloride  and  5  g/1  diatomaceous  earth.   Shake
vigorously  and  let stand  quiescently for a minimum  of  eight  hours.
Filter .the mixture through  a wet filter paper  and measure the  oil
                                  44

-------
concentration  of  the filtrate.   The oil concentration  measured is  the
soluble fraction of  the wastewater sample.

Emulsified Oil—
     The difference  between  the  oil  concentration of the emulsified  and
soluble  fraction  measured  in the Free Oil  determination and  the  oil
concentration of the soluble fraction measured in the Soluble Oil deter-
mination is the emulsified oil concentration of the wastewater sample.

Example Calculations

     Several  example calculations are provided  below  for calculating
operating parameters  essential to operation  of  an oil  removal system.

Hydraulic Retention Time (HRT)—
     HRT is the average length of time wastewater spends  in  a process
tank.   Since  the  removal of oil  does  not occur  instantaneously,  it is
essential that the wastewater spend a minimum time in the oil separator.
The HRT calculation is:
                       VOL
where VOL is the liquid capacity of the tank and FLOW is the flow to the
separator.   Note that  the VOL  and  FLOW must  be  expressed  in similar
units such as cubic meters  or  gallons.   As an example,  if  an oil water
separator had a volume of 10,000 m3 and the flow to the tank was 2500 m3
per hour the calculation would be:
                     2500 m
                          hr
Surface Overflow Rate —
     Surface  overflow rate is the  process  flow rate  divided  by the
active surface of the  area  of  a clarifier or oil water  separator.   The
                                   45

-------
 result  is  usually expressed  as  gallons per  square  foot per minute  and
 represents  the  loading  on  the  treatment  process with  respect to  its
 surface  area.   The loading can also be  expressed as a velocity  by con-
 verting  gallons  to cubic meters.   This  parameter is  usually expressed as
 meters/minute  and is  used  primarily  for  circular  clarifiers  and  air
 flotation  devices where it  represents  the  average vertical velocity of
 the  water  from the submerged center feed  well  to the surface  overflow
 weirs.

     The surface  overflow  rate is  calculated  as  follows:

         SURFACE OVERFLOW RATE =      FL°W
                                SURFACE  AREA
where surface  area  is the quiesant area of the oil separator  excluding
influent  and  effluent weirs and baffles,  and flow includes any  recycle
flow.  As an  example,  if a 10-foot diameter dissolved air  flotation oil
water separator with  a  3-foot  diameter center feed well had a  flow rate
of 80 GPM and  a recycle  flow rate  of  40%,  the  calculation would be:
                                  80 +  (0.4 X  80)
                                                              2
        SURFACE OVERFLOW RATE =          2    2     =1.6  Gal/ft /min
Air to Solids Ratios  (A:S)—
     The air  to  solids  ratio is used in  conjuction with the air  flota-
tion process  and represents  the  ratio  of  the mass of applied air  to  the
mass of oil.  This ratio is  calculated as follows:
           A-S ratio  -     8,990 SCFM
           A.s ratio  -   OIL CONC x FLOW

where OIL CONC is oil concentration in milligrams per liter  (mg/L), FLOW
is wastewater flow in gallons per minute  (gpm),  and SCFM is air flow in
standard cubic feet per minute (scfm).

     As an  example the  air  requirement  for a dissolved  air flotation
tank with an  influent oil concentration of  60  mg/L, a  flow rate  of  50
GPM, and an A:S ratio of 0.03 would be calculated as follows:
                                   46

-------
                      o,
Process Control Strategies

Gravity Separation & Skimmers—
     Gravity separators typically offer minimal opportunity for operator
control.  Periodically, the  tank  must be  checked for solids deposits  on
the bottom of the tank or on the parallel plates if a plate separator  is
used.  Similarly, if any  influent and effluent weirs are used they must
be periodically  checked  for  trash and debris  accumulations  which might
impede even flow distribution.  The weirs must also be checked to assure
they  are  level  and to  maintain  proper  liquid depth.   The  latter  is
extremely important when  slotted  pipes are used to remove the collected
oil.

     The hydraulic  retention time and surface overflow rate should also
be calculated and compared to equipment design values.   Flow to an oil
water  separator  is  usually  not  controllable, but  the  calculations can
indicate  if  the  system  is  overloaded or  requires  more equalization.
Similarly  the  temperature  and  suspended solids  should  be  monitored.
Cold  temperatures  can reduce  the rise velocity  of oil  globules  by  as
much  as  50%  and high  suspended  solids can  lead to  rapid solids accu-
mulation in the  tank.

     The oil removing  or  skimming equipment should be checked daily for
proper operation and  depth of floating oil  blanket.  Excessive blanket
depth, i.e., more than a  few inches for most  equipment,  can rapidly  lead
to a  system  failure.   Rotary  drum and belt  skimming devices should  be
checked  at least weekly for  drum or  belt  surface  integrity,  scraper
blade  integrity, and  tension against  drums.   Rotating  slot skimming
devices  should   be  checked  as  often  as  required  to keep  oil blanket
depths within  safe  operating  ranges.   Care must be taken in operating
the slots  to prevent  excessive water  entrainment.   The slots must  also
be  checked periodically  for  levelness  and   accumulation  of  trash  or
debris.  Floating weirs must be  checked daily to make sure trash is not
                                    47

-------
collecting on the weirs and to make sure the weirs  are  free  floating and
properly balanced.   Periodically,  the flexible hose must be checked for
integrity.

Coalescers—
     The  operation  of coalescers  is  essentially  the same  as  that  for
gravity separators.  The frequency of inspection for  solids  accumulation
and plugging of  the  coalescers  must,  however, be  on  at least a  monthly
basis.

Emulsion Breaking—
     Chemical  addition is  not  a  separate unit  process  for oil-water
separation.  Rather,  it is used prior  to  or  in  conjunction with  other
separation  processes.    Chemical  addition is  first used   to  break or
demulsify emulsified oils  in  the wastewater.   The treatment is  usually
directed  toward  destabilizing the  dispersed oil  droplets  or chemically
binding or destroying any emulsifying agents present.

     As  previously  stated,  chemical  demulsifying  processes   include
acidification,  coagulation,  salting  out,  and demulgation  with  organic
cleaving agents.  Acids generally cleave emulsions  more effectively than
do coagulant salts, but are more expensive.   In addition,  the resultant
wastewater  must be  neutralized  after  separation.    Coagulation   with
aluminum or iron salts may be effective and  is commonly used.  However,
the resultant hydroxide  sludges  may be voluminous  and  are difficult to
dewater.   Coagulation with polymer may be  effective  and  is sometimes
used.  The resultant sludge quantities  are smaller than those for  metal
salts but are sometimes more  difficult to dewater.   The  salting out of
an emulsifier may be  achieved with the addition  of large  quantities of
an inorganic  salt,  thereby increasing  the dissolved solids content of
the wastewater.  Organic  demulgators  may  be  extremely  effective demul-
sifying agents but are generally very expensive and specialized.  Demul-
gators  are normally considered only if they are found to be  effective in
extremely low concentration due to  cost and,  in many  cases,  their  toxi-
city at higher concentrations.
                                   48

-------
     The effectiveness of  chemical pretreatment is  normally  determined
with bench  scale jar  testing.   A  representative  wastewater sample  is
split into several aliquots.   Each aliquot is reacted with  a different
quantity of the  chemical under consideration.  After each addition,  the
aliquots may  be  flash mixed,  flocculated,  and quiescently  settled  and
then examined  to note any reaction  and  emulsion breaking and  the rate
and effectiveness of separation.

     One  typical procedure  for jar  tests is  that suggested by  the
Tretolite Division of  Petrolite  Corporation,  in their  Industrial  Bench
Testing Procedures Manual.      The procedure is as follows.

     1.  Secure  appropriate sample for testing.
     2.  Fill  one  liter  beakers to  either 500 or  1000  ml mark.   Test
         volume  is  dependent on volume  of sample  available  and volume
         required for water quality analysis.
     3.  Place beakers  on paddle  mixer and  begin mixing  at  maximum
         speed.
     4.  Dose  beakers  with  appropriate  chemical(s)  and  appropriate
         volumes.
     5.  Mix on  high speed for 1 minute.
     6.  When  chemical additions and  1  minute rapid mix intervals  are
         complete, reduce  stirrer  speed to slow mix for  1  minute mini-
         mum.   (Note:  Mix times can be varied to more closely duplicate
         full  scale system).
     7.  Turn  mixer off  and  remove beakers for settling.   Settling time
         is  dependent on system and rate  of  contaminant  removal  (10-30
         minutes should prove adequate).
     8.  Wipe  paddles  clean with a paper towel or rag in  preparation for
         the next test.
     9.  Repeat  steps  2-8  until the desired  treatment  program has been
         thoroughly investigated.
     10.  After the  chosen  settling time has elapsed, sample beakers for
         appropriate water quality  analysis.
                                    49

-------
     The j ar test procedure is useful for determining  the  optimum pH for
separation, the  most  effective coagulant and coagulant aid,  the  optimum
chemical dosage  and order of  chemical  addition,  the required rapid and
slow  mix times,  the  required  settling, and the  estimated  separation
effectiveness.

     The pretreatment chemicals  may be  added directly to  a  process  line
or may require separate rapid mix and flocculation  chambers.  The opera-
tion  of  these chambers  is discussed  elsewhere in  this  document  under
"Chemical Addition  Equipment"  and "pH Control".

Air Flotation

     Air flotation, as  compared to  gravity separation, has  several  con-
trol  mechanisms  that are directly  under  the control  of the operator.
These  include  the  system pressure, recycle  rate,  air to solids  ratio,
and  chemical addition  rate.    The   operator  also  has some control  of
surface  overflow rate and hydraulic residence time.   Typically  increas-
ing the  system  operating pressure  and  air  to solids ratio  will  improve
performance.  However,  care should  be  taken  in increasing these  because
past  a certain  air to solids  ratio very little improvement is  obtained
and a considerable amount of energy is  expended.   As the air to solids
ratio  is increased it may also be necessary to  increase the recycle rate
in  order to  provide sufficient water  for  air  to initially dissolve.
However,  the  increase in  recycle rates will increase the  surface over-
flow  rate,  a  situation  which can lead  to performance  degradation if the
overflow rate exceeds the system design specifications.

     The DAF pocess is  typically operated with  a  40 to 60 psig pressure,
20 to  50 percent recycle, 1  to 4 gpm/sq ft  surface  overflow rate, 1  to 2
minute aeration  tank detention  time,  0.01  to 0.06 air to  solids ratio
and 20 to  40  minute flotation  tank detention time.  Typically with the
DAF process, compressed air  is used as  the feed gas because it  is rela-
tively inexpensive.  However,  inert gases are  sometimes used  instead.
.For example, nitrogen gas is  used   to minimize corrosion  by  keeping iron
in solution.  The choice of gas can depend  also  upon the nature  of the
                                    50

-------
wastewater and  any  regulations concerning off-gas  removal.   The volume
of froth layer produced in the DAF process is approximately equal to 0.2
to 2.5 per cent of the influent waste flow.

     IAF separators  typically use  a recycle  flow rate  of 100  to 400
percent with  5  to 10 minute  detention  time  and result in  a froth pro-
duction rate equal to 1 to 15 percent of the influent  flow  rate.

     When operating  air flotation units,  pressure gauges and flowmeters
should be checked daily for proper readings and calibrated  on at least  a
yearly  basis.   In  addition,  any  weirs should  be checked  monthly for
trash or debris accumulation and  levelness.  If scraper arms are used to
skim the float,  they should be checked monthly for proper submergence,
usually around 1 /2 to 3/4 inches  when water  level is  at the base of the
weirs.  They must also be checked for scraper blade integrity and proper
seal when crossing the sludge hopper.

TYPICAL PERFORMANCE VALUES

     The performance of  oil  removal'equipment  is  extremely dependent
upon the distribution  of  oil between the  free,  emulsified, and soluble
forms.  Gravity oil  separators typically have produced an effluent with
a  total  oil concentration between  50  and  100  mg/L.   However,  gravity
separators  with  an  emulsion  breaking  pretreatment  step  give  typical
performance ranges from less than detectable to 40  mg/L of  effluent oil.
Coalescers  should  provide slightly better  performance   than  gravity
separators.   Limited information regarding  their performance indicates
that an effluent of 1 to  50 mg/L  of  oil can be achieved (includes units
with and without emulsion breaking).

     DAF and  IAF  separators  typically produce effluents  of equal qual-
ity.   A flotation separator,  preceded  by a  gravity  or  parallel plate
separator,  typically produces an effluent with an oil  concentration less
than 20 mg/L.   When used without pretreatment,  the flotation separator
can produce an effluent with an oil concentration of 25 to  100 mg/L.
                                   51

-------
TROUBLESHOOTING GUIDE

     A guide for troubleshooting the oil removal process is presented  in
Table 3.   Six  problem areas  are noted; all  the  problem areas deal with
either excessive oil  in the  aqueous effluent  or  excessive water in the
collected  oil  phase.   In many cases  a  detailed  analysis of  the oil
emulsion  breaking  treatment will  be required,  to correct  the problem.
Careful sampling, jar test evaluations, and oil analyses are required  to
define the problem and  investigate corrective actions.
                                    52

-------
TABLE 3
OIL REMOVAL TROUBLESHOOTING GUIDE
Ln
OJ
PROBABLE CAUSE
CHECK OR MONITOR
REASON
CORRECTIVE ACTION
OPERATING PROBLEM 1: Gravity separator has high effluent oil concentration.
1a. Flowrate too high.
Ib. Emulsified and/or
soluble oil present.
1c. Short circuiting of
tank occurring.
Id. Separator tank
filled with solids.
le. Excessive floating
oil blanket in
separator tank.
If. Change in influent
characterization.
Check peak and average flow
rate, hydraulic retention
time (HRT), and surface over-
flow rate and compare manu-
facturer's recommendation and
design criteria.

Monitor/ the free, emulsified,
and soluble oil concentration
entering and leaving the
separator.
Check influent and effluent
weirs and baffles for
plugged, broken, or missing
units. Check weirs for
for levelness.

Drain tank and inspect or
rod with a pole to detect
the presence of solids or
sludges on the bottom of
the tank.

Monitor effluent for free
oil and visually
inspect for floating oil
in effluent.

Check viscosity, temperature,
and density of oil-water
solution and collected oil.
Compare to original design
conditions and manufacturer's
recommendations.
Separators are designed
to achieve quiescent
conditions in the oil-
water separation zone.
Excessive flow promotes
turbulence.

Gravity separator is
effective for free
oil only.
When short circuiting
occurs the oil does not
have time to separate
from the water.
As the solids collect in
the tank the HRT is
decreased and the oil does
not have sufficient time to
separate from the water.

If floating oil layer
becomes too deep it can
extend down to treated
water effluent port.

If process changes result
in changes in the density
and viscosity of the oil
and water, the design
requirement for gravity
separators can change.
Decrease flow rate; add
more oil-water separator
capacity) increase equaliz-
ation if peak flow is
excessive.
Trouble shoot Step 6;
install emulsion breaking
equipment if not present;
control sources of soluble
oil.

Clean, repair, replace, or
adjust as needed.
Clean and remove all solids
and sludges.
Adjust oil skimming devices
as required.
Modify separator design as
required.

-------
TABLE 3
(Continued)
OIL REMOVAL TROUBLESHOOTING GUIDE
PROBABLE CAUSE
CHECK OR MONITOR
REASON
CORRECTIVE ACTION
OPERATING PROBLEM 2: Gravity separator has a very high water content in collected oil.
2a. Holes or cracks in
collection slots.
2b. Poor operation of oil
collection slot or
tilted floating weir
which allows water
to enter.

2c. Floating weir has
improper ballast result-
ing in weir floating
too low in water.
2d. Slot oil collectors are
located too near the oil
water interface.
Inspect and monitor for water
flow when oil is not being
removed.

Monitor operation of collec-
tion slot, inspect floating
weir for levelness and presence
of trash in weirs.
Check distance between
bottom of weir and oil-water
interface.
Check distance between slot
and oil water interface during
nonskiroming operation.
Treated water can contam-
inate collected oil.
Treated water can contam-
inate collected oil.
If water too close to the
bottom of the weir, wave
action caused by wind or
hydraulic surges can cause
water to enter the weir.

If water too close to the
bottom of the slot, wave
action caused by wind or
hydraulic surges can
cause water to enter the
slot.
- Repair as required.
Adjust equipment or instruct
operators as required.
Clear weir to remove heavy
deposits! adjust weir as
specified by manufacturer.
Adjust as required (may
require adjusting of an
effluent weir opposed to
adjusting slot).
OPERATING PROBLEM 3: Coalescer has high effluent oil concentration.
3a. Coalescers clogged or
broken.
3b. pH of oil-water solu-
tion different from
design or normal
operating condition.

3c. See Step 2.
Drain tank and inspect.
Monitor pH.
See "Troubleshooting
Gravity Separators"
For proper performance
oil must come in contact
with coalescing plates
and proper velocities
must be maintained.

pH can affect surface
properties of oil
droplets and their
ability to coalesce.

See "Troubleshooting
Gravity Separators"
Clean and repair as required.
Adjust pH to design or normal
operating conditions.
- See Step 2.

-------
TABLF 3
(Continued)
OIL REMOVAL TROUBLESHOOTING GUIDE
PROBABLE CAUSE
CHFCK OR MONITOR
REASON
CORRECTIVE ACTION
OPERATING PROBLEM 4: Air flotation unit has high effluent oil concentration.
4a. Inadequate dissolved
air being supplied.
4b. Inadequate recycle
flow.
4c. Inadequate delivery
pressure.
4d. Inadequate hydraulic
retention time (HRT).
4e. Excessive surface
overflow rate.
4f. Short circuiting of
DAF occurring.
4g. Skimmer not removing
solids fast enough.
4h. Improper chemical
addition (where
applicable).
- Monitor oil concentration!
monitor air flow; determine
air:solids (oil) ratio.

Check recycle flow rate.
Check delivery pressure and
check calibration of pressure
gauge.
Monitor flow ratei check tank
for accumulation of solids;
calculate HRT.
Monitor flow rate and
calculate surface overflow
rate.

Check effluent weirs for
plugging and levelness.
Check influent baffles.

Inspect skimmers for
broken scapers, proper
submergence in the water,
poor seal along the edges
or sludge hopper,- check
speed.

Check chemical feed pumps
for proper operation,
setting, and calibration.
Insufficient air being
supplied to float the
mass of oil present.

Recycle flow is often
essential to provide
enough water to dissolve
the required air.

Insufficient pressure
can result in the air not
dissolving in the water.
Short HFT's do not allow
sufficient time for solids
to separate.
Large overflow rates can
carry solids out of the
tank and break foam..

Short circuiting can
result in inadequate
detention times.

Air flotation foam breaks
with time and can cause
reentrainment of oil
particles.
Inadequate chemical
conditioning can result
in significantly reduced
performance of air
flotation equipment.
Adjust as required; typical
range is 0.01 to O.06 pounds
of air per pound of oil.

Adjust as required; see design
and manufacturer's recommen-
dations. Typical values range
from 20 to 50% recycle.

Adjust as required; see design
and manufacturer's recommen-
dations. Typical values range
from 40 to 60 psig.

Decrease flow rate; trouble-
shoot "Equalization"; clean
tank. Typical values are 20
to 40 minutes.

Decrease flow rate; trouble-
shoot "Equalization". Typical
values are 1 to 4 gpm/sq ft.

Clean and adjust weirs as
required.
Repair and replace damaged
scapers as required.
Adjust submergence and rota-
tional speed as required.
Clean, repair, and adjust as
required.

-------
TABLF 3
{Continued)
OIL REMOVAL TROUELFSHOOTIHG GUIDE
PROBABLE CAUSE
CHECK OR MONITOR
REASON
CORRECTIVE ACTION
Perform jar test to
optimize type dosage and
pH of chemical conditioning
agent. The nature of the
waste may have changed.

If polymer is being used
check initial dilution and
placement of polymer addition.
Inadequate chemical
conditioning can result
in significantly reduced
performance of air
flotation equipment.

Proper mixing of polymer
and waste essential.
Polymers must be initially
diluted to 0.1 to 0.5% for
proper mixing to occur.
Polymer can be sheared by
injecting it upstream of
a centrifugal pump.
Adjust chmical addition
equipment as required.
Adjust initial polymer
dilution procedures as
required. Change polymer
addition point to assure
adequate mixing prior to
downstream release in air
flotation tank. Move addi-
tion point of centrifugal
pump.
Ul
cr>
OPERATING PROBLEM 5: Float from air flotation unit contains excessive water.
5a. Leak in float
collection hopper.
Check hopper with skimmer
arm turned off. If water
enters hopper, leak is pres-
ent in hopper or top of
hopper located below
water surface.
Water contaminating
concentrated oil.
- Repair or adjust as required.
OPERATING PROBLEM 6: Emulsion breaking is not converting all emulsified oil to free oil.
6a. Poor mixing between
oil and chemicals.
Check mixing equipment for
worn mixers, missing
baffles, and adequate horse-
power (See Table 1).
Proper mixing of condi-
tioning agent and waste
water is essential for
conditioning agents to be
effective.
Repair and replace as
necessary.
6b. Improper conditioning
agent or dosage.
6c. Fluctuating or
improper pH.
Perform jar test to determine
optimum conditioning agent,
dosage, and pH.
See "pH Troubleshooting
Guide."
Waste characteristics
determine optimum
conditioning agent,
dosage, and pH.