EPA 440/1-75/032
 Group I, Fhiise II
      r.

   Development Document for Interim
  Final Effluent Limitations. Guidelines
                  and
   Proposed  New Source Performance
           Standards for the
                   INC
             Segment of the
        NONFERROUS METALS
          MANUFACTURING
         Point Source Category
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
               FEBRUARY 1975

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                        EREATA PJ\GE

             Primary Zinc Development Document

1.   pp 3, 4, 129 and 134—change all pH ranges to read
     "pH...Within the range 6.0 to 9.0" and delete Hg
     from tables.

2.   p 67, third paragraph, last line, delete "of the
     discharge" and replace with "during liming and
     settling.,"

3.   p 124, last paragraph, 9th line, change "270 kkg"
     to "222 kkg", change "50 kkg" to "41 kkg".

4.   p 125,-top paragraph, 4th line, change "110 kkg"
     to "91 kkg".

5.   p 65, delete "Mercury" from table.

6.   pp 70 and 71	delete last two paragraphs on p  70 and
     first three on p 71.

7.   p 132—delete first line.

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          DEVELOPMENT DOCUMENT

                  for

PROPOSED EFFLUENT LIMITATIONS GUIDELINES

                  and

    NEW SOURCE PERFORMANCE STANDARDS

                for the

              ZINC SEGMENT
                 of the
    NONFERROUS METALS MANUFACTURING
         POINT SOURCE CATEGORY
            Russell E.  Train
             Administrator

             James  L.  Agee
      Assistant Administrator for
     Water and Hazardous  Materials
                 im
)n Agency

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          DEVELOPMENT DOCUMENT

                   for

PROPOSED EFFLUENT  LIMITATIONS GUIDELINES

                   and

    NEW SOURCE PERFORMANCE STANDARDS

                for the

              ZINC SEGMENT
                 of the
    NONFERROUS METALS MANUFACTURING
         POINT SOURCE CATEGORY
            Russell E. Train
             Administrator

             James L. Agee
      Assistant Administrator for
     Water and Hazardous Materials
                                                    «**»
              Allen Cywin
 Director, Effluent Guidelines Division

        George S. Thompson, Jr.
            Project Officer
            November  1974

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

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t' 3. Environmanta! Protection Agency

-------
                          ABSTRACT
This document presents the findings of an extensive study of
the primary zinc industry by  the  Environmental  Protection
Agency  for  the  purpose of developing effluent limitations
guidelines  and  standards  of  performance,  to   implement
Sections  304,  306,  and 307 of the Federal Water Pollution
Control Act, as amended.

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

The development of data and recommendations in this document
relates the  waste  water  generated  by  the  primary  zinc
subcategory  to  the  production  of  primary  zinc at those
facilities defined by this subcategory.

Supporting  data  and  rationale  for  development  of   the
proposed  effluent  limitations  guidelines and standards of
performance are contained in this report.
                          111

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                           CONTENTS
 Section

 I         CONCLUSIONS

 II        RECOMMENDATIONS
            Best Practicable  Control Technology
              Currently Available
            Best Available Technology Economically
              Achievable                                  4
            New Source  Performance  Standards               5

 III       INTRODUCTION                                     7
            Purpose  and Authority                         7
            Methods  Used for  Development  of
              Effluents Limitations Guidelines
              and Standards of  Performance                 8
            General  Description of  the Primary  Zinc
              Industry                                     9

 IV        INDUSTRY CATEGORIZATION                        19
            Introduction                                 19
            Factors  Considered                            20

 V         WASTE  CHARACTERIZATION                         37
            Introduction                                 37
            Sources  of  Waste  Water                        37
            Waste  Water Characteristics                   42

 VI        SELECTION  OF  POLLUTANT PARAMETERS               65
            Introduction                                 55
            Rationale for  the Selection of Pollutant
              Parameters                                  65
            Rationale for  the Rejection of Other Waste
              Water  Constituents  as Pollutant Parameters  74

VII      CONTROL AND TREATMENT  TECHNOLOGY                81
            Introduction                                  81
           Current  Control and  Treatment Technology      81
           Additional  Treatment  Technology               96

VIII     COSTS, ENERGY, AND NONWATER QUALITY ASPECTS   101
           Introduction                                101
           Basis for Cost Estimation                   101
           Economics of Present Control and
             Treatment Practices                       102
           Economics of Additional Control and
             Treatment Practices                       116
           Nonwater Quality Aspects                    122
                             v

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                    CONTENTS (continued)
Section
IX       BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY
         AVAILABLE—EFFLUENT LIMITATIONS GUIDELINES     127
           Introduction                                 127
           Industry Category and Waste Streams          128
           Recommended Effluent Limitations             128
           Identification of the Best Practicable
             Control Technology Currently Available     129
           Rationale for the Selection of Best
             Practicable Control Technology
             Currently Available                        132

X        BEST AVAILABLE TECHNOLOGY ECONOMICALLY
         ACHIEVABLE--EFFLUENT LIMTATIONS GUIDELINES     133
           Introduction                                 133
           Recommended Effluent Limitations             134
           Identification of Best Available Technology
             Economically Achievable                    135
           Rationale for the Selection of Best Avail-
             able Technology Economically Achievable    136

XI       NEW SOURCE PERFORMANCE STANDARDS               139
           Introduction                                 139
           Recommended Standards                        140

XII      ACKNOWLEDGEMENTS                               141

XIII     REFERENCES                                     143

XIV      GLOSSARY                                       145
                               VI

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                          FIGURES
Number                   Title
Pacje
1.  Primary Production of Zinc in the World
    and in the United States, 1870-1970, and
    Consumption of Zinc, Including Scrap,
    in the United States, 1938-1970.                   12


2.  Generalized Flowsheet of Pyrolytic Zinc
    Plants.                                            21

3.  Diagram of Electrothermic Zinc Furnace.            24

4.  Generalized Diagram of Waste Water Streams
    in Primary Zinc Operations.                        38

5.  Theoretical Solubilities of Metal Ions as a
    Function of pH.                                     86

8.  Experimentally Determined Solubilities of
    Metal Ions as a Function of pH.                     87

7.  Concentration of Metals in the Effluent of a
    Lime and Settle Treatment Operation.                89
                       Vil

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                           TABLES


Number                   Title

1.  Twenty-five Leading Zinc Producing Mines in
    the United States in 1971, in Order of Output         11

2.  Identified and Undiscovered Zinc Resources
    of the United States and the World (Estimated
    in Millions of Metric Tons)                           13

3.  Slab Zinc consumption in the United States by
    Use in 1971                                           15

4.  Primary Zinc Plants in the United States              16

5.  Grades of Commerical Zinc                             17

6.  General Overall Current Process Waste Water
    Discharge Practices in the Primary Zinc Industry      43

7.  Waste Effluents From Plant No. B                      44

8.  Waste Effluents From Plant No. C                      45

9.  Waste Effluents from Plant No. D                      46

10. Waste Effluents From Plant No. F                      47

11. waste Effluents From Plant No. G                      48

12. waste Effluents From Plant No. H                      49

13. Summary of Selected Data on Waste Water From
    Primary Zinc Plants                                   51

14. Waste Effluents From Plant No. B                      53

15. Waste Effluents From Plant No. E                      54

16. Rates of Flow of Acid Plant Slowdown Streams          56

17. Waste Effluents From Plant No. B                      57

18. Characteristics of Gas-Scrubbing Waste Water
     (After Settling)                                      58

19. Characteristics of Gas-Scrubbing Waste Water
     (After Scrubbing)                                     59
                        Vlll

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                     TABLES  (continued)
20. Waste Effluents From Plant No. B                      61

21. Waste Effluents From Plant No. B                      62

22. Waste Effluents From Plant No. B                      63

23. Current and Future Control and Treatment
    Practices in the Primary Zinc Industry                82

24. Analyses of Input and Effluent Streams for a
    Treatment Plant                                       91

25. Calculated Effectiveness of Removal of
    Various' Constituents                                  92

26. Effectiveness of Treatment of Acid Plant
    Slowdown by Lime and Settle                           93

27. Effluent Concentrations From Lime and Settle
    Treatment of Mixed Wastes                             95

28. Solubilities of Metal Sulfides                        97

29. Capital and Operating Costs of Present Waste
    Water Treatment Practices in Primary Zinc
    Industry                                             103

30. Additional Control and Treatment Costs               123

31. Conversion Table                                     155
                         IX

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                         SECTION I
                        CONCLUSIONS
The nonferrous metals manufacturing  point  source  category
has been divided into the following subcategories:

    (1)  Bauxite refining subcategory  *
    (2)  Primary aluminum subcategory
    (3)  Secondary aluminum subcategory
    (4)  Primary copper smelting subcategory
    (5)  Primary copper refining subcategory
    (6)  Secondary copper subcategory
    (7)  Primary lead subcategory
    (8)  Primary zinc subcategory

Each  subcategory  has been found to be distinctly different
from  the  standpoints  of  processes   employed,   products
produced,  and  process  waste  waters generated, as well as
other less significant factors.   Effluent  limitations  and
standards of performance were promulgated on March 26, 1974,
for the first three subcategories listed above.  Development
documents  supporting  the  rationale  for these regulations
have been published.  This development document presents the
rationale for  establishing  proposed  effluent  limitations
guidelines and standards of performance for the primary zinc
subcategory.

The  consideration of such factors as age and size of plant,
processes  employed,   geographic   location,   and   wastes
generated,  substantiates  the treatment of the primary zinc
industry as a single subcategory.  However, the  recommended
effluent  limitations  and  standards of performance do take
the production level of each specific facility into account.

One conclusion derived by this study is that the combination
of lime and settle  treatment  technology  and  a  minimized
process  waste water flow, achieved through best practicable
and best available control, is considered  to  be  the  best
practicable  control  technology currently available and the
best available technology economically achievable.  The best
practicable  and  best  available  flow  usage  values  were
determined  to be 8,350 1/kkg (2000 gal/ton)  and 5,425 1/kkg
(1,300 gal/ton), respectively.   The  best  practicable  and
best  available  effluent  concentrations, derived from lime
and settle treatment  of  zinc  plant  process  waste  water
pollutants,  as  discussed in Section VII, are identical for
each specific significant  process  waste  water  pollutant.

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The  resultant  effluent  limitations,   based  upon the best
practicable control technology currently available  and  the
best   available  technology  economically  achievable,  are
derived as the product of the  respective  flow  values  and
pollutant  concentrations.   The  best   demonstrated control
technology  is  considered  to  be  identical  to  the  best
available technology economically achievable.

It  is estimated that for the existing  plants to achieve the
levels  of  control  of  process  waste   water   pollutants
recommended  for  July  1,  1977, the capital costs required
will  approximate  $1,515,000  and  annual  operating  costs
required will be about  458,000.  Incremental control and/or
treatment  costs  of  approximately  $1,054,000  capital and
$450,000 annual operating will be required of two plants  to
achieve the further reductions in discharge of process waste
water   pollutants   recommended   for   the  best  available
technology effluent limitations  of  1983.   Therefore,  the
total  estimated  capital and annual operating costs to this
industry are $2,569,000 and  $908,000,   respectively.

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                          SECTION  II

                       RECOMMENDATIONS
             Best_Practicable_Control_Technology_
                    Currently._Available

The recommended effluent  limitations  for   the   primary  zinc
subcategory   to  be achieved  by  July  1, 1977,  and  attainable
through the  application   of   the  best  practicable   control
technology currently available,  are as follows:
                           _____ Ef fluent_ limit at ions __  _   __
       Effluent                          ~   Average  of daily
    characteristic          Maximum  for       values  for  30
                              any  1 day       consecutive  days
                                             shall  not  exceed
                                 Metric units  (kilogram  per  1000


    TSS
    As
    Cd
    Hg
    Se
    Zn
    PH

                                 English units  (pounds per 1000
                           ________ lb_of_p.roduct] _______ "_ ________

    TSS                         0.42                 C.21
    As                          1.6x10-3             8.0x10-*
    Cd                          0.008                0.004
    Hg                          8.0x10-5             4.0x10-5
    Se                          0.08                 0.04
    Zn                          0.08                 0.04
0.42
1.6x10-3
0.008
8.0x10-s
C.08
0.08
Within the ram
0.21
8.0x10-*
0.004
4.0x10-5
0.04
0.04
je 7.0 to 10.0
The  best practicable control technology currently available
is considered to include measures to achieve the  reuse  and
recycle  of  process  waste water to minimize discharge, and
treatment  of  the  remaining  waste  water  by  liming  and
settling  before  discharge.   The  effluent limitations and
their rationale are discussed in detail in Section IX.

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The recommended effluent limitations for  the  primary  zinc
subcategory  to  be achieved by July lr 1983, and attainable
through the application of  the  best  available  technology
economically achievable are summarized below:
                           	Effluent_limitations	
       Effluent                              Average of daily
    characteristic          Maximum for       values for 30
                             any 1 day       consecutive days
                                             shall not exceed
                                 Metric units  (kilogram  per  10CO
                           	]£2_of _groduct]	

    TSS                         0.28                  0.14
    As                          1.1x10-3              5.4x10-*
    Cd                          5.4x10-3              2.7x10-3
    Hg                          5.0x10-5              2.5x10-5
    Se                          0.054                 0.027
    Zn                          0.054                 0.027
    pH                     _Within_the_ranc[e_7iO_to_1.0iO	

                                 English units  (Ib  per  1000  Ib
                           	of _2£oductJ	
    TSS                         0.28                  0.14
    As                          1.1x10-3              5.4x10-*
    Cd                          5.4xlO-3              2.7x10-3
    Hg                          5.0x10-5              2.5x10-5
    Se                          0.054                 0.027
    Zn                          0.054                 0.027
    pH                     _Withi£_the_ranc[e_of_7..0_to_10iO	


The  best  available  technology economically  achievable re-
presents an incremental improvement and  refinement   of  the
control  measures  of  decreasing process waste water volume
and the treatment technology  identified as  best   practicable
 (i.e., lime and  settle).  The effluent limitations and their
rationale are discussed in detail in Section X.

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              New Source Performance Standards
The  recommended standards of performance for new sources of
the primary zinc subcategory attainable by  the  application
of the best demonstrated control technology are identical to
the   effluent  limitations  based  on  the  best  available
technology  economically  achievable.   These  standards  of
performance  and  their  rationale  are discussed in greater
detail in Section XI.

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                         SECTION III

                         INTRODUCTION
 Section  301(b)  of  the  Act  requires  the   achievement   by  not
 later  than   July  1,  1977,  of  effluent  limitations for point
 sources,  other  than publicly owned   treatment   works,   which
 are  based on  the application of  the best practicable  control
 technology    currently  available   as   defined   by   the
 Administrator pursuant to  Section 304 (b)  of  the Act.

 Section  301 (b)  also requires the achievement by not   later
 than July  1,  1983,   of   effluent limitations for   point
 sources,  other  than publicly owned   treatment   works,   which
 are   based   on   the   application   of   the  best  available
 technology economically achievable which  will result  in
 reasonable  further  progress  toward the goal of eliminating
 the  discharge of all pollutants, as determined  in accordance
 with regulations issued by  the  Administrator   pursuant  to
 Section  304 (b)  to  the  Act.

 Section   306  of   the   Act  requires  the achievement  by  new
 sources  of a  Federal standard  of performance  providing   for
 the  control  of   the  discharge  of  pollutants which reflects
 the  greatest   degree   of   effluent reduction   which   the
 Administrator   determines  to  be   achievable   through   the
 application  of  the   best  available   demonstrated  control
 technology,   processes,    operating    methods,   or   other
 alternatives,    including,   where  practicable,   a   standard
 permitting no discharge of  pollutants.

 Section   30 4 (b)   of  the  Act  requires  the Administrator to
 publish within  one year of  enactment of  the Act, regulations
 providing guidelines for effluent limitations setting  forth
 the  degree  of  effluent   reduction  attainable through the
 application  of  the  best  practicable  control  technology
 currently  available  and   the  degree of effluent reduction
 attainable through  the  application  of  the  best  control
measures   and  practices   achievable,   including  treatment
techniques,  process  and  procedure  innovations,  operation
methods  and  other  alternatives.   The  proposed regulations
contained herein set forth  effluent  limitations  guidelines
pursuant  to  Section 304 (b) of the Act  for the primary zinc
subcategory of the nonferrous metals category.

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          Methods Used for Development of Effluent
                 Limitations Guidelines and
                  Standards of Performance
The effluent limitations guidelines and  standards  of  per-
formance  proposed herein for the primary zinc industry v/ere
developed in the following manner.  Data  were  gathered  to
create  an  industry  profile.   Data  sources  included the
published literature, telephone survey results, returns from
a  limited  questionnaire  mailing,   Corps   of   Engineers
discharge  permit  applications,  and  state weather control
agency records.   Contact was made with a  representative  of
every United States plant or property engaged in zinc smelt-
ing and refining.

The  information that was gathered provided an industry pro-
file from which  the  need  for  industry  subcategorization
could  be  assessed  and  the  current control and treatment
practices could be identified.  Factors considered for  sub-
categorization  included  water  usage,  process  operation,
products, plant age, plant size,  rainfall  and  evaporation
amount, and geographic location.

Visits  were  made  to  five locations where smelting and/or
refining are being conducted.   These  visits  produced  de-
tailed  information  covering  control  and  treatment tech-
nologies plus associated costs, as well as identification of
waste water streams and their constituents.  Additional data
for four  plant  sites  were  obtained  from  the  Corps  of
Engineers  Permits  to Discharge under the Refuse Act Permit
Program  (RAPP).    These  included  the  varying  degrees  of
detail  composition,  temperature,  and volume of intake and
effluent water plus a general  description  of  waste  water
treatment.   Some  analysis  data  were also provided on the
form completed by several companies.  At one  location,  the
visit  was  followed  by  sampling  and  analysis  of source
streams, selected internal streams, and the  plant  outfall.
Several  production operations are performed at the location
that was sampled; consequently, a variety of  streams  could
be  analyzed,  some segregated and some mixed.  The analyses
identified the chemical and physical characteristics of  the
streams.   On  the  basis  of  the  above  information,  the
constituents of  the waste water, which should be  controlled
by  effluent  limitations and standards of performance, were
chosen.    In    addition,   the    analyses   revealed    the
effectiveness    of  any  control   and  treatment  technology
applied  to the effluent.

Data   gathered   on  control    and   treatment  technologies
currently   in   use  or  under    test  were  supplemented by
information covering other control technologies   that  might

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be  applicable  to  the treatment and control of waste water
from the primary zinc industry.  Consideration was given  to
both   in-plant   and  end-of-process  technologies  and  to
applications for the effluent from  the  various  production
operations.  For each of the control or treatment technology
candidates,  the resultant waste water constituents were de-
termined and the limitations and  problems  associated  with
each technology were identified.  Installation and operation
cost  estimates  for  application  of  the technologies were
calculated.  Possible environmental impacts on air  quality,
solid   waste   disposal,  and  ambient  noise  levels  were
assessed.

All of the information that had been developed was evaluated
in order to determine what levels of  technology  constitute
the best practicable control technology currently available,
the  best  available technology economically achievable, and
the best available demonstrated control technology.


        Gen eral_De script ion^ of _ Primary_Zinc_ Indus try

One  category  of  the  industry  encompassing  the  primary
smelting   and   refining  of  nonferrous  metals  (Standard
Industrial  Classification  Number  333)   is   the   primary
smelting and refining of zinc (SIC Number 3333).   SIC Number
3333  describes  those  establishments  primarily engaged in
smelting zinc from the ore,  or  in  refining  zinc  by  any
process.  Establishments primarily engaged in the mining and
benefication of zinc ore, as well as some lead ores, and the
rolling, drawing, or extruding of zinc are not classified by
this  SIC  and  are  not  the  subject  of  this development
document.   Facilities  for  the   generation   of   on-site
electrical  power,  and  other ancillary operations are also
not the subject of this report.    The  process  waste  water
sources to be covered by the proposed regulations, for which
the  rationale  is derived in this text,  are clearly defined
in later sections.

The U.S. primary zinc industry  includes  both  electrolytic
and  pyrometallurgical  retort  plants.    The  latter, which
produce zinc by volatilization and condensation,  are further
divided by method of operation (i.e.,  into those using small
horizontal retorts and  those  using  much  larger  vertical
retorts  or furnaces).   Because of difficulty in meeting air
pollution   control   standards,    as    well    as    other
considerations,  such  as labor costs,  all of the horizontal
retort plants have closed down or will do so soon.   One  of
the  two  remaining  plants  has a variance to operate until
December 31, 1973; the other until  June  30,  1975.    As  a

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consequence, establishing effluent limitations guidelines is
simplified  to a consideration of four  electrolytic and two
pyrometallurgical plants.  There is a possibility  that  two
new electrolytic plants may be built in the near future.

                      and Rgsourceg

Of  the approximately 500,000 short tons of zinc produced in
the U.S. in 1971, some 51 percent came from  zinc  ores,  30
percent from lead-zinc ores, 10 percent from lead ores and 7
percent   from   copper-base  ores.   Again  based  on  1971
production,  about  24  percent  of  the  zinc   came   from
Tennessee,  13  percent from New York state, 12 percent from
Colorado, 9 percent each from  Missouri  and  Idaho,  and  5
percent each from New Jersey, Pennsylvania, and Utah.  About
60  percent  of the zinc production has come; from mines east
of the Mississippi.  Table 1 shows  the  location,  type  of
ore,  and producers of the 25 leading zinc mines in the U.S.
These account  for  about  83  percent  of  the  total  mine
production,  the first 10 producing 53 percent of the total.
Fifteen mines that produced about 26,000  tons  of  zinc  in
1970  and  20,000  tons in 1971 were shut down by the end of
1971, largely because of the closure of  smelters  that  had
been  treating  their  concentrates   (1).   This  trend  has
continued with more mines and smelters closing in 1972.

As shown in Figure 1, U.S. consumption of primary  zinc  has
exceeded mine production to an increasing extent in the last
20  years.   At present about two-thirds of the primary zinc
used in the U.S. is imported, mostly  from  Canada,  Mexico,
and  Central  and South America.  About half of the imported
zinc has been in the form of concentrates purchased  on  the
world  market  in  competition  with  companies  from  other
countries, but, because of diminishing smelter  capacity,  a
larger  proportion  of imported slab zinc may be expected in
the next few years.

Estimated resources of zinc by the  U.S.  Geological  Survey
(2)  are shown broadly in Table 2.  These estimates indicate
that  the  U.S.  has  about  18  percent  of   the   world's
"recoverable"  zinc  and  7  percent of the subeconomic zinc
resources.  Most of the identified recoverable resources are
in the Mississippi  Valley   (Tri  State,  Upper  Mississippi
Valley,  Missouri lead belts and Middle Tennessee) districts
and the Appalachian  (New  Jersey,  Pennsylvania,  New  York,
East Tennessee, and Virginia) districts.
                         10

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                 T/iBLB 1.  TWENTY-FIVE LEADING ZINC-PRODUCING MINES IN THE
                           UNITED STATES IN 1971 IN ORDER OF OUTPUT  (1)
Rank
1

2
3
4
5


6
7
8
9
10
11

12

13

14

15
16

17

18

19
20

21

22

23
24
25

Balmat

Eagle
Sterling Hill
Friedensville
Bunker Hill


Buick
Young
New Market
Zinc Mine Works
Immel
Austinville and
Ivanhoe
Edwards

Star Unit

Ground Hog

Jefferson City
Burgin

Idarado

U.S. and Lark

Flat Gap
Bruce

Shullsburg

Leadville

Coy
Magmont
Ozark
County and State
St. Lawrence,
N, Y.
Eagle, Colo.
Sussex, N. J.
Lehigh, Pa.
Shoshone, Idaho


Iron, Mo.
Jefferson, Tenn.
it
"
Knox, Tenn.
Wythe, Va.

St. Lawrence,
N. Y.
Shoshone, Idaho

Grant, N. Mex.

Jefferson, Tenn.
Utah, Utah

Our ay and San
Miguel, Colo.
Salt Lake, Utah

Hancock, Tenn.
Yavapai, Ariz.

Lafayette, Wis.

Lake, Colo.

Jefferson, Tenn.
Iron, Mo.
Reynolds, Mo.
Operator
St. Joe Minerals Corp.

The New Jersey Zinc Co.
"
it
The Bunker Hill Co.


Missouri Lead Operating Co.
American Zinc Co.^
New Market Zinc Co. '
United States Steel, Corp.
American Zinc Co.
The New Jersey Zinc Co.

St. Joe Minerals Corp.

Bunker Hill Co. and Hecla
Mining Co.
American Smelting and
Refining Co.
The New Jersey Zinc Co.
Kennecott Copper Corp.

Idarado Mining Co.

United States Smelting,
Refining, Mining Co.
The New Jersey Zinc Co.
Cyprus Mines Corp.

Eagle-Picher Industries,
Inc.
American Smelting and
Refining Co.
American Zinc Co. ^a'
Cominco American, Inc.
Ozark Lead Co.
Source of Zinc
Lead-zinc ore

Zinc ore
ti
1 1
Lead-zinc ore,
lead-zinc
tailings
Lead ore
Zinc ore
1 1
it
"
n

1 1

Lead-zinc ore

n

Zinc ore
Lead, lead-
zinc ores
Copper- lead-
zinc ore
Lead, lead-
zinc ores
Zinc ore
Copper-zinc
ore
Zinc ore

Lead-zinc ore

Zinc ore
Lead ore
n
(a)   Purchased by the American Smelting and Refining Co., November  29,  1971.
                                    11

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                                                          r-5
                               World production
                                      U.S.  consumption
                                                                    en
                                                                    C
                                                                    O
                                                                    • r-l
                                                                    CD
                                                                    C
                                                                    O
                                                                    o
                                                                    •I-t
 1870   1880  1890   1900  1910   1920  1930   1940 1950  1960  1970
Figure 1.  Primary production of zinc in the world and  in  the
           United States, 1870-1970, and consultation of zinc,
           including scrap, in the United States, 1938-1970.
                          12

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        TABLE 2.  IDENTIFIED  AND UNDISCOVERED  ZINC  RESOURCES  OF  THE
                  UNITED  STATES AND  THE WORLD  (ESTIMATED  IN MILLIONS
                  OF METRIC TONS)
                             Identifieda.       Undiscovered
                             Resources            Resources      Total
UNITED STATES
Recoverable
Subeconomic
Total
45
75(c)
120
60
230
290
105
305
410
REST OF THE WORLD
Recoverable
Subeconomic
Total
190 (b)
1,200 (c>
1,390
285
3,000
3,285
475
4,200
4,675
TOTAL WORLD
Recoverable
Subeconomic
Total
235 (b)
1.275(c)
1,510
345
3,230
3,575
580
4,505
5,085
(a)   IDENTIFIED RESOURCES:   Specific, identified mineral deposits that
     may or may not be evaluated as to extent and grade, and whose
     contained minerals may or may not be profitably recoverable with
     existing technology and economic conditions.

(b)   RESERVES:  Identified  deposits from which minerals can be extracted
     profitably with existing technology and under present economic
     conditions.

(c)   CONDITIONAL RESOURCES:   Specific,  identified mineral deposits whose
     contained minerals are  not profitably recoverable with existing
     technology and economic conditions.
                                  13

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Uses and Projected Growth

Zinc  is used largely in die casting,  galvanizing,  and brass
products, as shown in Table 3.   About  half  of  the  total
production  is special high-grade zinc, of which die casting
alloy is the largest application.  Prime Western Zinc,  used
mostly for galvanizing, accounts for about 30 percent of the
total.  This grade, containing up to 2 percent of impurities
(maximum  of 1.6 percent lead, 0.5 percent cadmium, and 0.05
percent iron) is commonly produced in pyrometallurgical zinc
plants  using  a  nonselective  feed  of  zinc  concentrates
containing  appreciable  amounts  of  lead.   A  similar  or
improved quality of zinc, called "Select Grade", is made  in
some  plants  by  using  a  higher  grade of zinc and adding
alloying  constituents  to  give  desired  galvanizing  (hot
dipping) characteristics.

Projected growth is a desirable item of knowledge but a most
difficult  prognostication,  and is mentioned only to show a
possible trend.  An estimate made by the staff of  the  U.S.
Bureau  of  Mines   (3)  indicates  a need for over 3,000,000
short tons of primary zinc for the  year  2000.    (Forecast:
low  2,090,000; high, 4,000,000).  Since production from U.S.
zinc  mines  has  shown  a  downward  trend in recent years,
projections mean little; projecting the mine  production  of
the   last  7 years  shows virtually no zinc production in the
U.S.  in  the  year 2000.   Much  depends  on   the   price
incentives,   availability   of   smelter   capacity  within
practical transportation range,  and changes in technology.

Zinc Plants

Zinc reduction plants  in the U.S. at the  end  of  1973  are
listed   in   Table   4.   The three electrolytic plants may be
supplemented by one or  two additional plants presently under
consideration.  Meanwhile,  over half  of  the  zinc  metal
production   capacity    is    centered   in   the   two  large
pyrometallurgical  plants of New  Jersey  Zinc Company  and  St.
Joe   Minerals   Company.     In   the   interval   1971-1973
 (inclusive),  one   electrolytic   zinc   plant   (Great Falls,
Montana),   two  vertical retort  plants, and  three  horizontal
zinc plants  have  ceased operations.  The   Sauget,   Illinois,
electrolytic plant  of American Zinc  Company was closed  in
June, 1971,  but reactivated by Amax  in May,  1973.

Since commercial  slab zinc of  various  grades   is  produced
directly  at the  zinc reduction  plants, as  shown in  Table  5,
 there are no separate primary zinc  refineries.   What  little
refining  may  be needed is done as  an operating step in  the
 same plant prior  to casting.   However,  in  making  a  higher
                       14

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          TABLL 3.   SLAB ZINC CONSUMPTION IN THE UNITED STATES
                    BY USE IN 1971  (1)
Industry and Product
Galvanizing
Brass products
Zinc-base alloy castings
Rolled-zinc products
Zinc oxide
Other uses lii
Light metal alloys
Other(a)
Total
kkg
430,600
136,491
468,113
35,239
36,319
4,150
26,521
1,137,432
Short Tons
474,752
150,486
516,111
38,852
40,043
4,575
29,240
1,254,059
(a)   Includes  zinc dust,  wet  batteries  desilverizing  of  lead,  bronze
 powder,  alloys,  chemicals,  castings,  and miscellaneous  uses.
                         15

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                                    TABLE 4,   PRIMARY ZINC PLANTS IN THE UNITED STATES
   Company
    Location       TYPe  °f Operation
         Annual
Zinc Producing Capacity   Acid Plant   Products Produced
 kkg/Yr(Short Tons/YrOperation      at Plant Site
American Smelting
and Refining Co.

American Smelting
and Refining Co.
Amax
Bunker Hill
(Gulf Resources
and Chemical Co.)

New Jersey Zinc
(Gulf and Western
Industries)
St. Joe Minerals
Corp.
National Zinc Co.
Amax
Amarillo, Texas    Horizontal Retort
Corpus Christi,     Electrolytic
    Texas
Sauget, Illinois   Electrolytic
Wallace, Idaho     Electrolytic
Palmerton, Pa.      Vertical Retort
Monaca, Pa.
                                        Electrothermic
Bartlesville,      Horizontal Retort
    Okla.
Blackwell,
    Okla.
                                        Horizontal Retort
  42,303(46,641)


  97,956(108,000)



  64,149 (70,727)



 110,312(121,624)



 103,398(114,000)




 226,750(250,000)




  45,350(50,000)


  72,832(80,300)
                                                                                          No
                                                                     Yes
                                                                                          Yes
                                                                                          Yes
                                                                     Yes
                                                                                          Yes
                                                                                          Yes
                                                                                                  Prime Western Zinc
Slab zinc, zinc
alloys, zinc sulfate,
cadmium, sulfuric acid

Slab zinc, cadmium,
zinc sulfate, sulfuric
acid

Slab zinc, zinc alloy-
cadmium, sulfuric ac:
Slab zinc, zinc allo?
zinc dust and pellet;
zinc oxide, ferroalloy,
sulfuric acid

Slab zinc, zinc alloys,
zinc oxide, cadmium,
ferrosilican, mercury,
sulfuric acid
                                                                                                  Zinc

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          TABLE-J 5,  GRADES OF COMMERCIAL ZINC  (4)
                                    Composition, percent
                                                           Zinc
                          Lead,     Iron,     Cadmium,    min. by
                                                        difference
Special High Grade

High Grade

Intermediate

Brass Special

Prime Western
0.003

0.07

0.20

0.6

1.6
0.003

0.02

0.03

0.03

0.05
0.003

0.03

0.40

0.50

0.50
99.990

99.90

99.5

99.0

98.0
                            17

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quality  product  than  that  normally  produced,  a definite
refining step, such as  redistillation,   may  be  necessary.
This  is described in more detail in the discussion on plant
operations.

Some zinc  producing  companies  also  produce  zinc  oxide.
Although  zinc oxide plants are covered in a separate survey
of chemical plants, consideration is included in this  study
where  both  oxide and metal are produced in the same plant.
Zinc  powder   is   commonly   produced,   particularly   in
electrolytic   plants,   for   internal   use   in  solution
purification.  Several other byproducts are listed in  Table
4.
                           18

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                         SECTION  IV

                  INDUSTRY CATEGORIZATION


                        Introduction
In developing recommended  effluent   limitations  guidelines
and  standards  of  performance   for  new sources for  a  given
industry, a judgment must be made as to  whether  effluent
limitations  and  standards  can  be  uniformly and equitably
applied  to  the  entire  industry,   or  whether  there are
sufficient  differences  to  warrant  the  establishment  of
subcategories.   The   purpose    of   effluent   limitations
guidelines can be realized only by categorizing the industry
into  the ^ minimum  number  of  groups  for  which  separate
effluent limitations guidelines and new  source  performance
standards must be developed.

The  objectives  of industry categorization are to allow the
establishment  of  recommended  effluent   limitations   and
standards of performance that are specific, unambiguous, and
uniformly   applicable  to  a  given  industry  subdivision.
Categorization, therefore, involves the  identification and
examination  of  the factors in an industry which might bear
upon such a  classification  in   terms  of  the  recommended
limitations to be developed.

The  factors  considered  in  determining whether additional
subcategories are justified for the   primary  zinc  industry
are:

         (1)   Process,
         (2)   Age,
         (3)   Size,
         (4)   Location,
         (5)   Raw materials,
         (6)   Waste characteristics,
         (7)   Byproducts and ancillary operations.

As  a  result  of  the  following  analysis of each of  these
individual factors, as well as  interrelating  effects  they
may  have upon each other, the primary zinc industry is, for
the  purposes  of  establishing   effluent  limitations   and
standards  of  performance,   considered  as  a  single  sub-
category, the primary zinc subcategory.
                        19

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Process

            £2£_S^li£ii2llj	E2^S^iS3«      T^e    following
discussion of processing is accompanied by the diagram given
in  Figure  2.    Domestic  primary zinc plants treat sulfide
concentrates from various sources.  These are stored,  dried
if  necessary,   and  blended  to  give  a reasonably uniform
charge to the roasters.  The roasting  operation  to  remove
sulfur  is  carried  out  as  completely  as is economically
feasible in the electrolytic  plants,  since  residual  zinc
sulfide  is  insoluble.   In the pyrolytic or retort plants,
where roasting is followed by sintering, complete removal of
sulfur is not as necessary in roasting.   Sulfur  removal  is
usually  rather  complete  to  recover  as  much  sulfur  as
possible in the metallurgical sulfuric acid plant  operating
on  the  roaster  offgases.   One  pyrolytic  plant,  with a
typical feed of 54  percent  zinc  and  31  percent  sulfur,
removes  about  96  percent  of  the sulfur contained in the
feed.

Various types of roasting are used  for  zinc  concentrates.
Multiple-hearth   roasters   are   versatile  and  flexible,
permitting different conditions on different hearths.   They
are used effectively in deleading.  It is not unusual for 90
to 95 percent of the lead in a concentrate containing 0.3 to
0.5  percent  lead to be removed in roasting when this is an
important objective.  Fluid-bed roasters can  be  controlled
to   give   stable   operating   conditions.   An  oxidizing
atmosphere is used to quickly volitilize contained sulfur to
sulfur oxides with the flash roaster.   Both  the  fluid-bed
and  flash roasters give a steady and comparatively high S02
feed  (i.e., about 5.5 to 12 percent SO2, by volume)  to  the
metallurgical  sulfuric  acid  plant.   When  using  a flash
roaster,  the  feed  must  be  carefully  sized,  which  may
necessitate  additional  grinding  for  proper  preparation.
Because of the comparatively high temperatures generated  in
flash   and  fluid-bed  roasters,  waste  heat  boilers  are
commonly used with them.  The roaster offgases, exiting  the
roaster  at  about 1000°C  (1800°F), are cooled down to about
400°C  (750°F) by heat transfer with the waste heat  boilers.
At these lower temperatures, the offgases can be treated for
particulate removal in the dust collection systems.

Roasting  eliminates  some  of  the impurities from the zinc
concentrate, other than sulfur and lead.  Any  mercury  that
may  be  present is volatilized and goes with the gas stream
to scrubbers preceding  the  acid  plant.   As  much  as  20
percent  of  the cadmium present in the zinc concentrate may
be  eliminated.   The  majority  of  the  input  cadmium  is
                            20

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         ZINC  CONCENTRATES
                i
                                          Gases to
                                         atmosphere

Storage, drying, blending
*
Secondary or
oxidic materials

Roasting
1


*
Dust collection '
Scrubbing j Acid
Mercury recovery | Plant
I
,.t .
   Fumes,  dusts,
     residues
          t
          Calcine
                                                                  acid
Moisture
     Preparation
                     Oxides
                                         Coke
                                Pelletizing
                                          Sand

                                             Recycle dust
                     Return
                     sinter
                                 Dust
                              Collection
                                          Gases to
                                         atmosphere

                                         uJ
                                                            f
               Metallics
            Coke
                 T
                                                       Cadmium plant
                                        Briquetting
                      Electrothermic
                         reduction
     Blue  powder
                            \
                Vertical retort
                  reduction
                                      Coal, clay
                                      and binder
                                                                  Stack
                       	1  Carbon monoxide	)
   Products of reduction I
 SLAB ZINC
lower grades

ZINC OXIDE —
                Liquation
                       Oxidation
                         /
                                     Plant use
              Residue treatment
American
process

SLAB ZINC
special
high grade
 ZINC
                         Refining
                     (redistillation)
 French  process
                                 Slag   ,
                                discard
     Ferrosilicon
                                      High zinc
                                      concentrate
                                      recycled

                                  Reclaimed coke
                                  recycled
                                                    Lead-silver cone.
                                                    to lead plant
Figure 2.  Generalized flowsheet of pyrolytic zinc plants.
                        21

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generally recovered in solution purification in electrolytic
plants  or  eliminated  to  a greater extent in sintering in
pyrometallurgical plants.
Sintering __ §nd_Briguetting __ (Pi£2i£tic_ Processes},.   To make a
more  compact  feed,  as  well  as  eliminate  more  of  the
impurities,   the   roasting  product,  calcine,  is  futher
processed pyrometallurgically  by  sintering  (in  pyrolytic
plants) .    However,  since the sulfur has been substantially
removed in roasting, the sinter machine off gases are  vented
to the stack after primary particulate removal.

The  feed for sintering is made up of calcined concentrates,
return portions for resintering, baghouse  or  electrostatic
precipitator  dusts  and  various  residues  and  zinc oxide
materials that may be purchased or  that  originate  in  the
plant.  Fuel, amounting usually to 4 to 5 percent carbon, is
added,  and  in at least one plant, a small amount of silica
sand is also added to give a hard, semifused sinter.   These
constituents  are  mixed, moisture is added,, and the feed is
pelletized to assure a uniform, permeable bed for sintering.
Where  available,  zinc  sulfate  solutions  from   in-plant
leaching  operations  are  used  to  moisten  the  feed  for
pelletizing, since this conserves water  and  enhances  zinc
recovery.

Cadmium  elimination  in sintering is high with as much as a
90 percent removal.  Lead elimination may amount to 70 to 80
percent.    Consequently,  the  dust   collected   from   the
sintering  machine  circuit  is  greatly  enriched  in these
impurities.  By recycling the dust,  the  cadmium  and  lead
content  is built up in the flue dust to a level high enough
to permit economical removal of the cadmium  in  a  separate
division  of  the  plant.   A representative sinter produced
from low impurity concentrates used  in  making  high  grade
metal  may  run  from  58  to 64 percent zinc, 0.005 percent
lead, O.OC5 to 0.01 percent cadmium, and 0.1 to 0.35 percent
sulfur; that for making Prime Western metal may  be  on  the
order of 55 percent zinc, 0.3 percent lead, and 0.01 percent
cadmium.

In   one   pyrolytic   zinc   plant,   an  additional  step,
briquetting, is  undertaken  in  preparing  the  charge  for
reduction.   Sinter  is  ground,  mixed with pulverized coal
(including a coking type) , clay,  moisture,  and  a  binder.
The  mixture  is then pressed into small briquettes weighing
about 1.5 pounds each.  These  are  fed  into  a  step-grade
autogenous   coking  furnace  where  they  attain  a  strong
structure  to  resist   disintegration   in   handling   and
reduction,  as  well as to keep the reductant and zinc oxide
                         22

-------
 in  close  contact.    Heat  for  this  coking  operation  is
 generated by burning the volatile constituents of the charge
 produced inside the  furnace.
 Ey£2lXtic __ Reduction.    Since only two pyrolytic zinc plants
 are involved in this discussion and they  differ  in  retort
 construction  and  operation, a description of the reduction
 step necessarily becomes specific.

 In the vertical retort process, hot briquettes  are  fed  at
 regular intervals into tall  retorts and pass slowly downward
 while undergoing reduction of their zinc oxide content.   The
 residual  or spent briquettes are continuously discharged by
 a  roll extractor into  a quenching  compartment,   from  which
 they are removed for further treatment.   By use of a venturi
 scrubber,   all  gases   are exhausted from the furnace (which
 operates with an internal  pressure  slightly below  ambient) .
 The  gases,   principally  metallic   zinc  vapor  and  carbon
 monoxide,  pass first through a zinc condenser  and  then  to
 the  venturi scrubber.   By means  of a splash system,  whereby
 a _ mechanically driven  device  fills  the  condenser  chamber
 with  a rain of zinc droplets which fall back into a bath of
 molten zinc,  the zinc  vapor  from  the  retorts  is  condensed
 and collected with excellent efficiency.   Over 95 percent of
 the  zinc   vapor  leaving  the retort is condensed to liquid
 zinc.

 The vertical  retort walls  are made  of silicon carbide brick.
 Common dimensions  of the retort are a width of 0.3  meter  (1
 foot),   a   length  of 2.1 meters (7  feet),  and a  height of  10
 meters  (35  feet),  giving a capacity  of   about  7.3   kkg  (8
 short   tons)  of  zinc per retort per day.   Heating the charge
 to  about 1300° C   (2400 ° F)   is  done by   gas  in   chambers
 surrounding    the    retort    side   walls.    Gases  from  the
 combustion chambers  are  used  to  preheat   incoming   air   for
 combustion   by   means  of recuperators.  The  carbon  monoxide
 from the zinc  condensation chamber  is  scrubbed   with water
 sprays   to  remove   entrained  solids,  and  the  gas  is  used  as
 part of  the  fuel for heating the retorts.    Blue   powder,  a
 mixture  of  metallic  zinc   and zinc  oxide,  is  collected  as
 residue  from the scrubbing system and  during  the  periodic
 cleaning of the condenser.  This material  is  recycled.

In  the  process of  electrothermic  reduction of  zinc,  a much-
larger, internally heated retort or  furnace  is used.   Figure
3 shows the general  cross  section.   The  largest  of  such
circular  furnaces   presently in use are 2.4 meters  (5 feet)
inside diameter and  15 meters  (50 feet)  in  height  with  a
zinc  producing  capacity  of about 90.7 kkg  (100 tons/day).
This type of pyrometallurgical retort furnace  is constructed
                        23

-------
les_^
>
f
C
,oke-i
f
/

1
-Br
r

-------
of firebrick; the vapor ring condenser and its cooling  well
are  lined  with  silicon  bricks  for  better conductivity.
Water, for cooling, is used  in  steel  jackets  surrounding
much   of  the  reduction  area  of  the  furnace.   Similar
electrothermic furnaces are used to produce zinc oxide, but,
in place of a vapor  ring  and  condenser  used  to  produce
elemental zinc, multiple outlets permit the vapor to enter a
surrounding combustion chamber where oxidation occurs.

Preheated  coke  and  sinter, along with miscellaneous minor
zinc- bearing products, are fed continuously into the top  of
the  furnace.   This charge passes slowly downward where the
coke serves both as reductant and conductor for the electric
current that enters through graphite  electrodes  positioned
near  the  top  and  base of the furnace.  Zinc vapor passes
from the main furnace to  a  vapor  ring  and  thence  to  a
condenser  where  it is condensed by bubbling through a bath
of molten zinc.  Water cooled hairpin loops at the condenser
cooling well maintain a constant bath temperature of 480  to
500 °C   (900  to  930 °F).  The gas, mostly carbon monoxide,
passing through the condenser is water scrubbed by impingers
and used as fuel elsewhere in the plant.  Some  blue  powder
or  uncondensed zinc-zinc oxide is recovered by settling the
scrubber slurry in ponds.  This is  dried,  briquetted,  and
recycled  with the furnace feed.  Furnace residue after zinc
distillation goes to a reclamation plant where residual coke
and some unreacted zinc are recovered and recycled.  In this
plant, where sand may  be  added  to  make  a  hard  sinter,
sufficient  ferrosilicon  is  present  in  some  residues to
warrant recovery as a byproduct.
              Zinc __ Productioru   Recovery   of   zinc   by
hydrometallurgical-electrolytic  means  has  the  advantages
over pyrometallurgical methods of being able to more readily
treat lower grade concentrates  and  attain  a  high  purity
product.  Recovery of byproducts and the elimination of dust
and   heat   from  furnaces  other  than  roasters  are  two
additional advantages.  However, the high capital cost of an
electrolytic zinc plant has been an adverse factor.

Charge preparation for an electrolytic  zinc  plant  differs
from  that  of a retort plant in that a finely calcined feed
is needed, rather  than  a  compact  hard-sintered  product.
After  completely  roasting  the  concentrates,  sizing  and
regrinding coarse particles may be necessary.  Also, since a
high lime-magnesia feed would introduce  unwanted  magnesium
sulfate  into  the  electrolyte, an acid wash to remove such
solubles is a necessary pretreatment  before  roasting  such
concentrates .
                           25

-------
The substantially sulfide-free calcine from roasting,  along
with  other  zinc  oxide  products,  are  leached with spent
electrolyte,  that  is,  with  a  sulfuric   acid   solution
containing  residual  zinc  sulfate.  This spent electrolyte
may contain around 200 g/1 of sulfuric acid.  The  trend  in
the    United   States   is   to   leach   continuously   or
semicontinuously, rather than  batchwise  as  in  the  past,
since  this  practice  requires  less  equipment, space, and
labor, and is considered to be better adapted  to  automatic
control.   Whether  by  batch  or  continuously,  the  spent
electrolyte and calcine are added to  leaching  tanks  under
conditions  of acidity control to avoid dissolving an excess
of iron, and to  precipitate,  finally,  the  iron  that  is
dissolved.

The  problem  is to selectively dissolve as much of the zinc
as possible, precipitating iron and accompanying  impurities
(such  as  arsenic, antimony, silica, and germanium)  without
precipitating any of the dissolved zinc.   The  presence  of
iron  hydroxide  in  carrying  down  impurities  is  of such
importance that,  if  there  is  insufficient  iron  in  the
concentrates   treated,   scrap  iron  may  be  used  as  an
additional  source.   When   considerable   zinc   is   made
relatively  insoluble  in  roasting by the formation of zinc
ferrites, the practice is to leach with  hot,  comparatively
strong,  spent  electrolyte  to dissolve both zinc and iron,
and then precipitate the iron as jarosite.   This  treatment
may  also be applied to the leached residue.  In double-bath
leaching, calcines are  leached  with  a  deficit  of  spent
electrolyte  to keep the solution slightly basic and free of
dissolved iron.  Residue from this step is  further  leached
with  excess acid and the resultant solution recirculated to
the  first  stage.   Thus,  the  leaching  of  roasted  zinc
concentrates  is mucn more complicated than would be assumed
by the simple exothermic equation ZnO + H2_S04_  	>ZnS04_
+ H20.

After leaching, the neutral or pregnant solution is filtered
and  goes  to  purification.   This is usually done in large
drums  or  filters,  but  when  handling  ve^ry  hot,  highly
concentrated  solutions,  filters  are used..  After washing,
the residue may be processed  further  to  recover  residual
zinc   (as in the jarosite process, or by flotation), and the
final residue containing lead and precious metals is usually
sent to a lead smelter.

Purification is accomplished largely by  additions  of  zinc
dust,  which  precipitates  copper, cadmium, cobalt, nickel,
and other residuals by replacement.  By adding zinc dust  in
multiple  stages,  it is possible to make rough separations,
as a high-copper precipitate and a high-cadmium precipitate,
                          26

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 each carrying down some of the other impurities.   At  times,
 copper  and  arsenic  may  be  purposely  added to give more
 precipitate  in  order  to  bring   down   obnoxious   minor
 impurities.   In  one  plant,  a semicontinuous purification
 step is used.  Purified solution is sent to the electrolytic
 cells.   The high-copper precipitate  is  treated   to  remove
 most  of  the  zinc  and  the final copper cake is sent to a
 copper smelter.   Likewise, the cadmium cake  is  sent  to  a
 cadmium  recovery  plant, where cadmium and other byproducts
 are recovered.

 The electrolytic cell room is  a  large  area  containing  a
 multiplicity  of  tanks  through  which  the zinc-containing
 solution,  or electrolyte, slowly flows.   Each tank  contains
 a number of alternate anodes and cathodes (such as 28 anodes
 and  27  cathodes),   but the number may vary considerably in
 different  plants.   Anodes are rectangular,  commonly made  of
 cast  lead containing 0.75 to 1 percent silver, and are 0.95
 to 0.79 centimeters  (3/8 to 5/16  inch)   thick,   about  0.76
 meters   (2-1/2   feet)   wide,   and  1.2  meters (4  feet)  deep.
 Cathodes are aluminum,   have  slightly   smaller   rectangular
 dimensions  and   are  commonly  only  0.48  centimeters (3/16
 inch) thick.

 Zinc is deposited  from solution onto the  aluminum  cathodes
 at  a  rate governed mostly by the current  density employed.
 Currently  in the United States,  this is  around 750 amp/sq  m
 (70   amp/sq  ft) of  cathode area,  although  in one  plant this
 density may be as  high as 1130  amp/sq m  (105  amp/sq  ft).
 Such    comparatively    high   current   density    develops
 considerable  heat  in the electrolyte and various   means   of
 cooling and recirculation are used,  such as  internal  cooling
 coils  or  external cooling systems.   In  one  plant,  cold well
 water passing through lead coils has been used, but  this  has
 recently been successfully replaced  by a flash cooler   under
 reduced pressure.  Since  current efficiency  is less  than  100
 percent,   some oxygen  is  released  at the anodes and  hydrogen
 at the  cathodes.  The  bursting  of  these  bubbles   causes   an
 acxd  spray   which   can make  the cell room uncomfortable,  as
 well  as  enhance  corrosion   of   equipment.    in  addition   to
 abundant   ventilation,    various    electrolyte  covers   and
 additives  are used with variable success to  curtail misting.
 Strontium  carbonate  (or barium hydroxide) is  added  to   the
 electrolyte  in  some plants to reduce lead contamination of
 the deposited zinc.  Glue  or  gum arabic  are  among the agents
 added to obtain a smoother deposit and less  interference  by
 impurities.

When the deposit attains a desired thickness, for example in
 24  hours,   the  cathodes  are removed and zinc is stripped.
                      27

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This stripping is commonly  done  manually  (a  considerable
cost  item),  although  various  mechanical  means  and  air
blasting  have  been  used  at  least  experimentally.   The
cathode  zinc  is  washed  and  sent  to  the casting plant.
Electrolyte is recirculated after passing through  a  series
of cells, and at least a portion of the spent electrolyte is
sent back to the leaching plant continuously.

Refining^	Melting^	and	Casting.  Cathode zinc sheets from
electrolytic zinc plants are dried, melted,  and  cast  into
various  forms  of  slab zinc.  Alloys of zinc, particularly
for die castings, are also prepared  and  cast.   At  times,
dependent  upon marketing conditions, lead and other  desired
constituents are purposely added to a relatively high grade
of electrolytic zinc to make a Select Grade for galvanizing.
Zinc  dust  is made at the plants for use in purification of
solutions.

Zinc produced in pyrolytic plants is normally less pure than
that produced electrolytically, but this  is  overcome  when
desired  by  (1) careful selection of raw material and taking
special care in preparation  of  the  charge   (roasting  and
sintering)  to  eliminate most of the impurities, and (2) by
refining.   Impure hot metal as produced is given a liquation
treatment.  It is allowed to cool to just above the   melting
point  of  zinc, whereby the lead  and iron present in  amounts
exceeding  their solubility in  zinc separate by precipitation
and can  be  removed mechanically to  a  considerable   extent.
This  dross  can  be  processed in the plant  or treated  in  a
secondary  zinc plant  for recovery of values.  The  partially
purified   zinc  is then cast  as slab zinc  into Prime  Western
grade or higher,  depending on  purity.  By  redistillation  of
impure   zinc,  the  highest purity commerical grades  of  zinc
can be produced,  depending on  the procedure  used.  The   most
common   method  is  to  use   dual fractionating  columns of
silicon  carbide,  heated externally.  Cadmium  and   zinc   are
largely    volatilized  from   the   first   rectifying   column,
leaving    lead,    iron,    and   other    high-boiling    point
constituents,   which  can    be   removed  from  the  base.
Condensate from the   first   column  goes   to  a   second,  or
cadmium   column,   where   by  reflux condensation,  cadmium and
the  low  boiling  impurities  are removed.   These are  sent  to  a
 cadmium  plant  for recovery.

Melting   and  casting  zinc   into commercial  forms   is   a
 relatively  simple  operation as the temperature  required is
 only moderate.   Water is  used in  some  plants  for  rapidly
 cooling   the  molds,  but  commonly does not come into  contact
 with the metal.   Ammonium chloride flux is usually   used  on
 the  molten  zinc in the  melting furnace to retard  oxidation
                        28

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 at the surface and to collect  any  oxides  formed.    Plants
 using  air  pollution control devices on gases from the zinc
 melting operation  will  collect,  in  the  control  device,
 solids  containing  both  zinc oxide and chloride compounds.
 Any processing to recover the  zinc  values  from  this  air
 pollution  control  residue  must  deal  with  the  chloride
 content  of  the  residue.    This  is  especially  true   in
 electrolytic  zinc plants,  because the electrolysis reaction
 is very sensitive to the deleterious effects of chloride  in
 the electrolyte.

 Cadmium	Recovery.    All of the zinc plants produce cadmium.
 Although minor compared with the main  plant  production  of
 zinc,   the U.  S.   zinc plants are producing about 3.6 to 4.9
 million kilograms (8 to 9 million pounds)  of cadmium yearly.

 Electrostatic  precipitator  or baghouse dusts from certain of
 the roasting or sintering operations  in  the  plant,  which
 have   reached   a   desired  concentration  of  cadmium  by
 recycling,   are  treated  hydrometallurgically  for   cadmium
 recovery,   along   with  any  high-cadmium  dusts  from other
 sources.   High-cadmium zinc from zinc  refining  operations,
 and cadmium  precipitated   by  zinc  dust in purifying zinc
 solutions   constitute  important  cadmium   sources,    also.
 Although details  of  operation differ at each zinc plant,  the
 general procedure in treating dusts has been to leach with a
 solvent  for  the cadmium   (and zinc),  filter,  and  send the
 residue (containing   insoluble  lead)   to  a  lead  recovery
 plant.   This solvent usually is  dilute sulfuric acid,  but in
 at  least one plant the dust is first given a sulfating roast
 and is water  leached.   The cadmium zinc sulfate solution is
 treated with zinc dust to precipitate cadmium as a  metallic
 sponge   and  separate it  from most  of the zinc.   This  sponge,
 or  that from electrolytic zinc plant purification  residues,
 may be dissolved and reprecipitated to achieve an  improved
 separation.  Eventually,  the  reasonably  zinc-free   cadmium
 sponge   is   melted   directly  with   a  caustic  flux or  it  is
 distilled in a  graphite  furnace.   If  distilled,   the   metal
 may be further  purified by redistillation.  An alternative
 treatment  used,  particularly  in   the   electrolytic    zinc
 plants,  is  to   dissolve the  sponge  in  dilute  sulfuric  acid
 (return electrolyte)   and  electrolyze   the   sulfate   solution
 much as in electrolytic  zinc  recovery.   The  cadmium metal  is
 melted  and  usually   cast   in   a form convenient  for use  in
 electroplating.

Metallur2ical_Sulfuric_Acid_Plants.  Because of  its usage at
all but one currently operating primary  zinc  smelter,  the
metallurgical  sulfuric  acid  plant  is  considered  as  an
integral part of the primary zinc production  process.   The
                     29

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one  exception  to this practice, a horizontal retort plant,
is not considered  as  an  important  factor,  since  it  is
currently  operating  under  a  variance and is scheduled to
discontinue operation on June 30, 1975.

The offgas from the  multiple-hearth,  fluid-bed,  or  flash
roasters  of  the primary zinc industry contain a sufficient
concentration of SO2 for conventional sulfur oxide  control,
such  as a metallurgical sulfuric acid plant.  After primary
particulate  removal   in   either   a   hot   electrostatic
precipitator  or a baghouse, the strong SO2 offgases must be
preconditioned prior to entrance into the acid  plant.   The
preconditioning  operation  normally consists of humidifying
and  scrubbing  the  effluent  with  a  weak  sulfuric  acid
solution  in  an  open  tower and a packed tower  (or in some
applications, one scrubbing tower  with  a  gas  humidifying
section  and  a scrubbing section); the removing of residual
fume and SO3 particulate in an  electrostatic  precipitator,
called  a mist precipitator; and, finally drying in a drying
tower for removal of entrained moisture.  The preconditioned
gas stream then enters the metallurgical sulfuric acid plant
where conversion of  SO2  to  SO3,  in  the  presence  of   a
vanadium  pentoxide  catalyst,  and absorption of the S03 to
H2SO4 in the acid towers occurs.  The acid  plant  tail  gas
contains  about  2000  to  3000 ppm S02, by volume, and some
entrained acid mist.  Removal of the  acid  mist,  prior  to
atmospheric  release  of  the  tail  gas,  is conventionally
accomplished by  mist  eliminator.   Process  waste  waters,
termed   as   the  acid  plant  blowdown,  result  from  the
preconditioning section and the tail  gas  mist   eliminator.
Large  volumes  of  noncontact  cooling  water   are  used to
maintain   correct   operating    temperatures    within   the
metallurgical sulfuric acid plant.

Summary,, _of	Process.   Two  basically   different  process
approaches~are employed in the primary zinc  industry.  These
are   pyrometallurgical    processing    and     electrolytic
processing.   Except   for  a  preleach operation used by the
electrolytic  processors,  the  first   step  of   roasting   is
practiced  by all, and the offgases  produced  by  the  roasting
step  are  subjected to  convental  SO2  control  by all  (i.e.,  of
consequence   to   the   proposed   effluent   limitations).
Subsequent   processing,  sintering,  reduction,  and  refining
 (if   practiced),   for  the   pyrometallurgical   plants   and
leaching   and  electrolysis   for the electrolytic plants,  do
not  produce  process waste waters  as  defined   later   in   this
document.    Therefore,   for   the  purposes  of   establishing
effluent  limitations  and  standards  of   performance   for  the
primary  zinc  industry, this  industry,  based  upon process,  is
considered  as a  single subcategory.
                         30

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Changes  and improvements made from time to time may largely
nullify the effects of plant age; hence, the  time  a  plant
has  been  operating is not necessarily a good criterion for
additional  subcategorization.   The   oldest   zinc   plant
currently  operating  was  built  originally in 1898, a more
modern addition was built in 1910, and the present  vertical
retort-type  furnaces  were  put  into  operation  in  1929.
Considering the use  of  present  equipment,  the  range  in
starting  time  of  four  of the five plants has been in the
same time frame, 1928 to 1930.  The newest plant started  in
1941.   All the plants, consequently, are 32 to 45 years old
and are considered to be in the same general age category.

Size

Existing electrolytic zinc plants in the United  States  are
roughly  . similar  in  size.   Their  production  rates,  at
present, range only from 63,500 to 109,000  kkg  (70,000  to
120,000  tons)/yr.  The two pyrolytic plants with capacities
of 99,800 and 227,000  kkg  (110,000  and  250,000  tons)/yr
differ  in  size  from  each  other, but are larger than the
electrolytic zinc plants by a factor of  2.   That  is,  the
average  production  rate  of  the  two  pyrolytic plants is
double that of the average of the three electrolytic plants.
On the basis of size, therefore, the zinc  industry  can  be
classified  most  logically  into pyrolytic and electrolytic
groups.

Location

By location, the pyrolytic zinc plants are grouped  together
in  Pennsylvania; the electrolytic plants are scattered from
the Mississippi River to the Northwest and Southwest.   That
is  not a strong factor in determining categories,  but again
the differentiation is between  pyrolytic  and  electrolytic
plants.

By climate,  there is similarity between the locations of all
the  plants,  except  plants  in  the Southwest.   There is a
remarkable similarity in temperature and  solar  evaporation
capacity  at all the other plants.   The plant in the Midwest
has a somewhat higher average temperature and greater  water
evaporation  capacity,  but is not greatly dissimilar in this
respect to the other three.   In the  Southwest,   the  higher
average  temperature  and  slightly lower rainfall  gives the
capacity for considerably greater evaporation.
                       31

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All the plants are located along  rivers  or  streams  where
there   is  no  problem  of  adequate  drainage  and  little
possibility  of  flooding.   The  plant   in   the   Midwest
conceivably  could  be flooded under exceptional conditions,
and the plant in the Southwest could be  inundated  to  some
extent by extreme hurricane conditions.

As   reported   by  one  plant  in  the  geographically-arid
Southwest, land available on the plant site  is  essentially
non-existent   for   impoundment   of  process  waste  water
pollutants   and   subsequent   disposal    through    solar
evaporation.

Therefore, additional subcategorization based upon geography
is unwarranted.

Raw Materials

All  of  the zinc plants use zinc concentrate as their chief
raw material.  These may be company owned  or  purchased  on
the  world  market  in competition not only with each other,
but with zinc plants abroad.  The need for custom processing
results   in   a   variation   in   feed    characteristics.
Consequently,  the effect of the composition of concentrates
used on waste  water  pollution  must  be  regarded  over  a
reasonably   long   time,  rather  than  entirely  from  the
standpoint the material currently used.

In the purchase of some foreign concentrates,  for  example,
mercury  is sometimes encountered.  Mercury is also found in
reasonable trace concentrations  (up to about. 400 ppm) in the
domestically mined and milled zinc concentrates of  up-state
New  York  and  the  Coeur d1 Alene region of the Northwest.
This merely  means  a  quantitative  difference  in  mercury
recovered,  either  intentionally or unintentionally, as all
the  zinc  plants  take  precautions  to   prevent   mercury
contamination of water and air, and all are effected to some
extent  by  its  presence,  at  least  potentially,  in zinc
concentrates.

At one electrolytic plant, deleaded  zinc  oxide  fume  from
lead blast furnace-slag treatment forms an important part of
the   zinc  raw  material.   Similar  oxide,  presently  not
deleaded, is produced at another electrolytic plant and sold
as such, but it may be used as part of the zinc  plant  feed
at  times.   At another plant, considerable crude zinc oxide
is added to the charge.  This is partially  from  Waelz-kiln
treatment of low-grade zinc products.
                          32

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Miscellaneous  secondary  zinc  and  interplant products are
treated from time to time  by  some  of  the  plants.   Such
secondary material may include galvanizing byproducts, which
introduce  substantial  amounts  of  chlorides   (mostly zinc
chloride and ammonium chloride) into the waste water.

One electrolytic plant expects to be treating their  company
owned  concentrates,  presently  processed  at  a horizontal
retort plant.  These  concentrates  are  high  in  magnesium
carbonate.  Leaching the untreated roasted calcine from this
source  would  introduce  a  very  undesirable  quantity  of
magnesium  salts  into  the  electrolytic  plant;  hence,  a
preparatory  acid  leach  of  the concentrates to remove the
magnesium is necessary, and  this  introduces  an  unusually
high  amount  of  magnesium  sulfate  into the process waste
water circuit.

Although  other  raw  materials  are  used,   besides   zinc
concentrates,  oxides,  or secondary zinc materials, they do
not exert significant influence over the quantity or quality
of waste water produced.  Thus, the coal,  clay  and  binder
used  in  briquetting  and  coke  and sand in pelletizing in
electrothermic reduction are minor  contaminants.   However,
some  coke,  such  as  that  currently  used,  does  contain
considerable chlorides, which add to the chloride content of
the  waste  water  stream.   In  the  electrolytic   plants,
additives   used,   such  as  glue,  gum  arabic,  strontium
carbonate or barium hydroxide, recycled  manganese  dioxide,
and zinc dust, have minor effect on the waste water.

Altogether,   no  sharp  distinction  for  the  purposes  of
additional  subcategorization  can  be  drawn  between   the
various plants on the basis of raw materials. Different feed
materials  affect  the  amounts  of  pollutants entering the
waste  water  stream.   In  general,  all  the  plants  have
substantially  the  same  problems,  with  added emphasis on
chlorides introduced in raw materials in one or  two  plants
and on sulfates in another.

Waste_Characteristics

Presented in the next section of this report (Section V)  are
data  on waste characteristics of the primary zinc smelters,
the characteristics, in so far as they are  known,  of  unit
process  waste  water streams, and the current status of the
industry with regard to  present  and  planned  waste  water
treatment  and  control  practices.   On  the  basis  of the
industry's current method of  response  to  water  pollution
control  needs,  the primary zinc industry is considered as a
single category of point sources  in  terms  of  recommended
                          33

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effluent  limitations  guidelines.   That is, the waste water
characteristics  and   quantities   associated   with   unit
operations, as associated with present or planned control or
treatment practices, are a more common feature of the plants
in  this  industry,  than  are  any of the factors described
above.

Byproducts §nd_ Ancillary Operations

Some of the byproducts produced at the domestic primary zinc
facilities, as a result of the primary zinc process, include
commercial grade sulfuric acid, cadmium,  and  metallurgical
fumes,  which  are either shipped out for further processing
or recycled internally.  Zinc oxide, an inorganic  chemical,
is   recovered   at   several  of  the  primary  facilities.
Spiegeleisen, a low content ferromanganese, is produced at a
plant, but is considered as an ancillary  operation.   Other
chemicals  are  produced  on-site,   such as fertilizers, but
again, are considered as ancillary  operations.   A  primary
lead  smelter  and refinery, as well as an integrated mining
and  milling  operation,  are  all   co-located   with   one
electrolytic  zinc  plant.  Facilities for the production of
power are located on-site at several of the  smelters,  both
pyrometallurgical and electrolytic.  Mercury was at one time
recovered  at one facility as a byproduct through the use of
an indirectly-fired rotary kiln and condensor system.   From
the standpoint of effluent limitations for the process waste
waters   of  the  primary  zinc  industry,  the  only  known
byproducts of consequence are  sulfuric  acid  and  cadmium,
both of which are produced on-site at all facilities.

Summary

The  factors of process, age, size, location, raw materials,
waste  characteristics,   and   byproducts   and   ancillary
operations  have  been  discussed  to determine the need for
further subcategorization of the primary zinc industry.   As
illustrated  under  the  discussion  of  size, the two pyro-
metallurgical plants are considerably larger  in  production
capacity  than  the  three  electrolytic  zinc plants.  This
difference  in  size  could  produce  larger  magnitudes  of
process   waste  water  from  such  sources  as  acid  plant
blowdown.   Some  electrolytic  facilities  use  a  preleach
operation  to  limit  the  introduction of magnesium sulfate
into the electrolyte.  The process waste water  volume  from
this  source  should counterbalance any possible waste water
volume effects produced from size differential.
                        34

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Therefore,  for  the  purposes  of   establishing   effluent
limitations  guidelines  and  standards  of performance, the
primary zinc industry is considered as a single subcategory.
                        35

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                         SECTION V

                   WASTE CHARACTERIZATION


                        Introduction
The following discussion first covers the sources  of  waste
water   identifiable  within  plants  in  the  primary  zinc
industry and then presents waste characteristics in terms of
data  showing  quantities  of   flow   and   the   contained
constituents.   Waste  waters  are characterized in terms of
both total discharges and unit  process  operations.   Waste
characteristics  are  further  related  to  past and present
control and treatment practices.
                   Source s_g_f., Wag t e_ Wat er


The sources of waste water identified in primary zinc plants
may be described in terms of two overall classes, noncontact
cooling water and process waste water.

Noncontact cooling waters are considered to be  those  which
are  used  for cooling in heat exchangers and do not contact
any of the raw materials, intermediate or final products, or
byproducts, or any process or waste material characterizable
in terms of thermal load and pollutants associated with  the
cooling circuit (e.g., suspended solids, oil and grease, and
additives  such  as  water-softening  compounds or corrosion
inhibitors).   These  streams  are  not  included   in   the
definition  of  this development document and are dealt with
here only as necessary to define other streams.

Process waste waters are considered  as  those  waste  water
streams which have contacted some material characteristic of
the  process of the industry and, thereby, are considered to
have the opportunity to be potentially polluted in terms  of
constituents  contained  in  those materials.   These process
waste water streams are the subject of this document and are
those  considered   in   terms   of   recommended   effluent
limitations guidelines and standards of performance.

In examining the unit process operations of the primary zinc
industry,  the following associated waste water streams were
identified: (streams are indicated in the diagram  given  as
Figure 4)
                           37

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              Roaster
               Waste
               Heat
              Boilers
oo
oo
             Noncontact
               Cooling
              Slowdown
                 t
                           Cooling Tower(s)
                            for Noncontact
                            Cooling Waters
                               i	L
Sintering
Machines
Reduction
 Furnaces
Gas Cleaning,
Spray Chambers
Scrubbers
Acid-
>lant
                        Acid
                       Plant
                                                                                                   Metal
                                                                                                 Casting
                                                                                                 Cooling
                                                                      Electrolysis  |
                                                            Recycle
                                                           Reservoir
                  1_  	
                                Slowdown
         Cadmium
          Plant
Miscellaneous
  Scrubbers
     and
  Residue
Treatments
Contact
Cooling
 Water
               Figure 4.  Generalized diagram of waste water streams in primary zinc operations.

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      Roasting - noncontact cooling water,
•     Roaster-gas cleaning train - bleed streams from
        gas cooling spray chambers or wet scrubbers
        (i.e., acid plant blowdown),
      Metallurgical sulfuric acid plant - noncontact cooling
        water,
      Reduction furnaces - noncontact cooling water,
•     Reduction furnace gas cleaning operations - bleed
        streams or once-through water streams,
      Electrolysis (of zinc) - noncontact cooling water,
•     Metal casting cooling - direct contact cooling
        waste water streams,
•     Cadmium production - spent process liquor,
      Rectifier cooling - noncontact cooling water,
      Boiler operations - boiler blowdown,
      Miscellaneous cooling waters from pump seals,
        bearing cooling, vacuum pumps, etc.,
•     Auxiliary air pollution control operations -
        including dust control and/or wet processing
        of air pollution control residues to reclaim
        metal values,
•     Electrolytic purification, washwater, and spills,
•     Preleaching of zinc concentrates.

In  the  following discussion, the specific origins of those
waste streams considered as process waste waters   (in  above
listing, preceeded by "•'?)  are identified.

Ac id_ PIant_BIgwdgwn

As  discussed  in  Section IV, zinc sulfide concentrates are
roasted to remove the sulfur by the  oxidation  of  zinc  to
zinc  oxide  and  sulfur  oxide.   The roaster gas generally
passes through a series of facilities which may be  typified
by   the   sequence:    waste   heat  boiler,  cyclones,  hot
electrostatic      precipitators,      gas      conditioning
(humidification)   spray  tower, (or open and packed towers),
electrostatic  precipitator  (mist   precipitator),   dryer,
contact  acid  plant,  and  tail  gas  mist  eliminator.  As
indicated in the diagram,  the  identifiable  process  waste
water streams issuing from this sequence of operations are a
stream  from  the  gas  humidification  chamber  and a bleed
stream from the wet scrubber.  These two streams may be in a
common  circuit  with  recirculation   capacity,   and   are
generally referred to collectively as "acid plant blowdown".
Interviews   with   operating   personnel   established  the
following three  bases  for  the  existence  of  acid  plant
blowdown.

      (1)   Control of temperature of the gases, and.
                       39

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           implicitly,  the  recirculating stream,  involving,
           for example,  the use of  cool makeup water
           as the means  of  temperature control.
      (2)   The prevention of buildup of chloride
           concentration in the recirculating stream
           to a level which would produce significantly
           accelerated  corrosion of the materials of
           construction. For example, a level of
           O.C02 weight percent chloride in the
           recirculating stream was considered tolerable
           in terms of  stainless steel equipment;
           whereas, a chloride level of 0.2 weight
           percent would be considered a level to
           justify an increased bleed rate.
      (3)   The maintenance  of a tolerable level of suspended
           solids in the recirculating system.  The
           tolerable level  would be defined as that at
           which the system functioned continuously,
           and would vary with pipe sizes and pump
           characteristics, but may be characterized
           as having a  maximum in the range of 2  to 3
           weight percent solids.  The origin of  the
           suspended solids is the particulates in the
           gas stream entering the hot electrostatic pre-
           cipitator and subsequently the wet scrubber.  This
           particulate  level is a dependent on the number
           and performance  level of the preceding dust
           control devices   (i.e., waste heat boiler,
           cyclones, and electrostatic precipitator).
           Performance  levels of these devices may vary
           with time, maintenance,  and charge material,
           or even ambient  atmospheric conditions.

Various  aspects  of the acid plant blowdown stream, such as
its   connection   with   air   pollution    control,    its
characteristics,  and  its   treatment  will  be presented in
detail  in  later  discussion.   Acid  plant  blowdown   was
identified as a component of discharge streams in all plants
but  one,  where  it was  routed  to  a  cadmium  byproduct
operation specifically  for reuse.   As  discussed  below,  a
subsequent chloride bleed stream was necessary.

Metaj._C^sting Cooling Water Stream

The other process waste water stream identified as common to
all  zinc  producing plants is a metal casting cooling water
stream.  This stream results from the spraying or  immersion
of   cast  metal  to  cool  the  metal  to  insure  complete
solidification and to produce  a  temperature  suitable  for
handling  of the product (ingots, slabs, pigs, etc.).  Metal
                       40

-------
cooling waste water generally contains suspended solids  and
oil  and  grease  in terms of metal oxides, mold washes, and
lubricants from casting equipment.

Miscellaneous^Sourcgs

Reduction_Furnace_Gas_Scrubber.  In the  case  of  pyrolytic
plants,  the  gases drawn from reduction furnaces are, after
condensation of zinc, washed with water to permit use of the
carbon monoxide as a fuel.  The gas  washing  water  may  be
characterized as generally involving high volumes of use and
as  containing zinc and metal oxides, possibly hydrocarbons,
and various particulates  (as  suspended  solids),  and  the
corresponding products of hydrolysis.

Dust	Control	Operations.  In the same area of waste stream
production,  there  exist  auxiliary dust control operations
using wet scrubbers or  auxiliary  operations  treating  air
pollution   control   residues.   A  stream  which  will  be
considered related will be that  issuing  from  the  aqueous
processing  of  zinc  melting  dross, treated to reclaim the
contained zinc (oxide).  The  dust  control-related  streams
are  from  the  wet  scrubbing  of  dusts  generated  in the
grinding and processing of secondary (scrap)  materials.  The
baghouse  dusts  (from  melting  operations),  drosses,  and
secondary    (scrap)   materials   all   bear   the   common
characteristics of producing, principally, zinc  oxides  and
chlorides   in   the   waste  streams.    One  common  factor
identifiable here is the ammonium chloride or zinc  chloride
flue components associated with each of the materials.

Cadmium	Processing.   All the existing zinc plants produce
byproduct cadmium.   All cadmium processing  circuits  except
one  were  operated  in a closed-loop fashion with regard to
aqueous effluents.   The single open circuit was  that  case,
wherein  acid  plant  blowdown  was  used  for  the  cadmium
leaching operation and the spent  liquor  from  the  cadmium
circuit,  while  subjected to special cadmium control steps,
including liming and  settling,  served  as  an  outlet  for
chlorides from the zinc circuit.

The  closed-loop  operation  characteristic  of most cadmium
producing operations is achieved by virtue of the fact  that
the  circuit  intrinsically  contains chemical precipitation
and filtration steps, termed purifications, which result  in
"bleed"  streams  in  the form of filter cakes, which may be
variously recycled within the plant  operation,  shipped  as
intermediate   product,  or  disposed  of  as  waste.   Some
elements found in these cakes include iron, arsenic, indium,
lead,  mercury,  and copper, as well as zinc and cadmium.
                       41

-------
Electrolytic Processing.  It is noteworthy that no discharge
exists  from  electrolytic  process  streams.    Again,    the
process circuit intrinsically contains purification steps of
chemical  precipitation  and  solids separaition, with filter
cakes  providing  the  outlet  for  impurities,   and   with
recirculation  of  spent  electrolyte  to  the  leach  step.
Careful control of the input of chlorides and  fluorides  to
the  circuit  is  necessary  to maintain control of both the
electrolysis  reaction  and  product  quality   (e.g.,    the
prevention  of  pitting  and  nonuniform  deposition  of the
zinc).  Special make-up water quality is usually provided by
special  wells.   The   electrolyte   composition   may   be
maintained  by special means such as extraction of byproduct
compounds (dependent on concentrate source)   such  as  spray
drying.  Zinc electrolysis is exothermic, and has associated
appropriate  cooling  loops  in  heat  exchangers  or  flash
cooling capability for the electrolyte circuit.  All  spills
and   wash   water  are  considered  valuable  metal-bearing
material and are recycled to the leach-purification circuit.

The  above  are  the  process  waste  water  streams   whose
contributions are of principal significance in the following
discussion  of the qualitative data assembled on waste water
characteristics.
                Waste Water Characteristics
Overall Plant Effluents
As a first measure of waste characterization, the  range  of
characteristics   and   quantities,  of  past  and  existing
discharges from  zinc  plants,  as  available  from  various
sources, are presented in the following discussion.

Some  general  characteristics  of current industry practice
are  listed  in  Table  6.   The  volumetric  flow  rate  of
discharges  vary  from zero at one plant in the southwestern
United States, which is able to practice  complete  disposal
by means of solar evaporation, to 4,060 cu in/day (1.07 mgd) .
Treatment practices at plants discharging waste water varied
from  simple  settling to lime-and-settle treatments applied
to either component streams or to the total plant effluent.

The characteristics of total plant effluents  are  given  in
Tables  7  through  12.  In this series of tables, the basic
concentration, flow, and production rate data are  shown  to
indicate    the    details    of    methodology   of   waste
                        42

-------
    TABLE 6.  GENERAL OVERALL CURRENT PROCESS WASTE WATER DISCHARGE

              PRACTICES IN THE PRIMARY ZINC INDUSTRY^1)
                             Volume of Discharge

Plant   Type of Operation     J&/day     (gal/day)



  A       Pyrolytic             0           (0)



  B      Electrolytic       1,310,000    (346,000)



  C      Electrolytic       1,140,000    (300,000)



  D      Electrolytic       4,060,000  (1,070,000)



  E       Pyrolytic         2,400,000    (633,000)



  F       Pyrolytic         2,460,000    (650,000)



  G       Pyrolytic         1,255,000    (331,000)



  H       Pyrolytic           69,200     (18,300)
                   (2)
Degree of Treatment



Solar Evaporation



Complete lime and settle



Settle



Mix and Settle



Partial Lime and Settle



Partial Lime and Settle



Complete Lime and Settle



(Lime and Settle)
(1)  Sources:   verbal and written information submitted by producers.





(2)  Complete  lime and settle indicates that all waste streams are treated;

     partial lime and settle indicates that one or more component streams

     are so treated.
                           43

-------
                   TABU: 7.  WASTE EFFLUENTS FROM PLANT NO.  B

                Outfall No.:  Total Plant (Treated)  Discharge
                Contributing Operations:  Roasting Acid Plant,  Electrolytic  Zinc,
                                          all associated operations
Total
Plant
Intake,
Parameter mg/1
pH 7.9
Alkalinity no
COD
Total Solids
Dissolved Solids 575
Suspended Solids °
Oil sr\d Grease
Sulfafp (as S) 80
Chloride 106
Cyanide
A I ijTYi-f PUTT]

Cadmi,™
Calcium 64
Chromium
lr™ 3.4
Lead
Magnesium 1'
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silver
Sodium
Tellurium
Zinc
Phenols
Flow,
1/t'flV
gal /day
Prodr:*"1 f "i on ,
kkg/day 272
short, tons/day 300
Total
Plant
Discharge,
mg/1
8.6
17
--
4485
249
4
2221
171
<0.1

<0. 1
<0.02

<0.02
0.06
0.15
0.004
0.13

1.8



50
<0.1

2,763,050
730,000



Change
mg/1

17 (G)
--
+3910 (N)
+ 249 (N)
4 (G)
2141 (N)
65 (N)
<0.01 (G)

<0.01 (G)
<0.02 (G)

<0.02 (G)
-3.3 (N)
0.15 (G)
0.004 (G)
0.13 (G)

1.8 (G)



50 (G)
<0.1 (G)







kg/day
--
46.97
-"*
10,303
688
11.05
5,916
179.6
<0.028

<0.028
<0.056
--
<0.056
NLC
0.414
0.011
0.359
--
4.97
_ —
~~
~~
138.2







Net Loading
kg/kkg
--
0.173
— -
39.72
2.53
0.041
21.76
0.66
<1.0 x 10 4
-A
<1.0 x 10 ^
<2.0 x 10"4
~ ~
<2 x 10~4
NLC
0.0015
4.1 x 10"5
0.0013
~-
0.018
—, _


0.508








Ib/S.Ton
--
0.345
— ~
79.44
5.06
0.081
43.5
1.32
<2.0 x 10 ^
-L
<2.0 x 10 ^
<4 x 10~4
— —
<4 x 10'4
NLC
0.003
8.1 x 10"5
0.0026
~~
0.037
""


1.02







Source:  Plant  Data
                                44

-------
                    TABLL 8. WASTE EFFLUENTS FROM PLANT NO. C

                 Outfall No.:
                 Contributing Operations:  Electrolytic Zinc Production

Parameter
Total Total
Plant Plant
Intake, Discharge,
mg/1 mg/1

Net
Change
mg/1


Net Loading
kg/day kg/kkg
Ib/S.Ton
Alkalinity
COD
Total Solids
Dissolved Solids
Suspended Solids
Oil and Grease
Sulfate (as S)
Chloride
Cyanide
Aluminum
Arsenic
Cadmium
Calcium
Chromium
Copper
Iron
Lead
Magnesium
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silver
Sodium
Tellurium
Zinc
 0.00030
0.00005
                         -0.00025
80
          125
                         45
                                                             81.76
                                                     0.472
                                                                                 0.944
Flow,
  I/day
  gal/day
Production,
  kkg/day
  short tons/day
          18,168,000
           4,800,000

          173.2
          194
Source:   Plant Data
                                 45

-------
                  TABLU 9.   WASTE  EFFLUENTS  FROM PLANT  NO.D
                 Outfall No.:    004
                 Contributing  Operations:
Roasting, leaching, electrolysis,
melting, and casting of Zinc
(Gross Discharge)
Parameter
PH
Alkalinity
COD
Total Solids
Dissolved Solids
Suspended Solids
Oil and Grease
SuUate (as S)
Chloride
Cyr.nide
Aluminum
Arsenic
Cadmium
Calcium
Chromium
Copper
Ir<~>n
Le.-d
Magnesium
MercMry
Molvbdenum
Nickel
Potassium
Selenium
Silver
Sodium
Tellurium
Zinc
Ammonia
Flow,
I/day
gal/day
Production,
kkg/day
short tons/day
Total Total
Plant Plant Net
Intake, Discharge, Change
mg/1 mg/1 mg/1
3.3
NA 416 NA
4
1133
1107
26

750
100


0.68
2.4
32
0.002
0.34
1.93
1.35
208
0.003


8.55


75

243
2

5,450,400
1,440,000

297.3
333

kg/day

2267
268
6175
6033
142
~~
4088
545
--

3.7
13.1
174.4
0.0109
L.85
10.5
7.36
1134
0.016


46.6


408.8

1324
10.9






Net Loading
kg/kkg

7.63
0.07
20.8
20.3
0.48
~~
13.8
1.8
--

0.01
0.044
0.59
0.00004
0.006
0.035
0.02
3.8
0.00005


0.16


1.4

4.45
0.037







Ib/S.Ton

15.3
0.14
41.6
40.6
0.96

27.6
3.6
--

0.02
0.088
0.12
0.00008
0.012
0.07
0.04
7.6
0.0001


0.32


2.8

8.9







Source:    RAPP Data  (1971)
                                 46

-------
                   TABLE 10.  WASTE EFFLUENTS  FROM PLANT NO.  F

                  Outfall No.:   001
                  Contributing Operations:  Pyrolytic Zinc Smelting Operations
Parameter
PH
Alkalinity
COD
Total Solids
Dissolved Solids
Suspended Solids
Oil and Grease
Sulfate (as S)
Chloride
Cyanide
Aluninuni
Arsenic
Cadmium
Calcium
Chromium
Copper
Iron
Lead
Magnesium
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silver
Sodium
Tellurium
Zinc
Ammonia (as N)
F
Flow,
I/day
gal/day
Production,
kkg/day
short tons/day
Total
Plant
Intake,
ma/1
7.7
75
6
260
250
5
5
125
16
<0.001

<0.0001
0.002
58
<0.1
<0.01
0.02
0.01

<0.001
<0.1
<0.1
3.5
0.002
<0.01


0.03
1.05
0.5

44,965,800
11,800,000

611.6
685
Total
Plant
Discharge,
rag/1
7.6
70
12
460
455
10
8
175
60
0.08

0.003
0.2
100
<0.1
<0.01
0.08
0.08

<0.001
<0.1
<0.1
11
0.007
<0.01


5
1.75
2.0






Net
Change
mg/1

-5
6
200
205
5
3
50
44
0.08

0.003
0.2
42
0
0
0.06
0,07




7.5
0.005



5
0.7
1.5






Net Loading
kg/day

NLC
269
8,990
9,217
225
134.9
2,248
1,978
3.6

0.13
9
1,888


2.7
3.1




337
0 0.22



224.8
31.5
67.4






kg/kkg

--
0.44
14.7
15.1
0.37
0.22
3.7
3.2
0.006

0.0002
0.01
3.1


0.004
0.005




0.55
0.0004



0.37
0.05
0.11






Ib/S.Ton

--
0.88
29.4
30.2
0.74
0.44
7.4
6.8
0.012

0.0004
0.02
6.2


0.008
0.01




1.10
0.0008



0.74
0.1
0.22






Source: 1972 RAPP Data
                                     47

-------
 TABLL 11.   WASTE EFFLUENTS FROM PLANT NO. G


Outfall No.:  001
Contributing Operations:  Horizontal Retort Zinc Plant
                          including Sulfuric Acid Plant
Parameter
pH
Alkalinity
COD
Total Solids
Dissolved Solids
Suspended Solids
Oil and Grease
Sulfate (as S)
Chloride
Cyanide
Ali.TnJn.ra
Cadmium
Calcium
Chromium
Copper
Iron
Lead
Magnesium
Mercury
Molybdenum
Nickel
Potassium
SeleTiT u^

Sodium
Tellurium
Zinc
Ammonia
Flow,
I/day
gal/day
Production,
kkg/day
short tons/day
Total Total
Plant Plant Net
Intake, Discharge, Change
mg/1 ms/l mg/1
NA 8.5 NA
48
73
2750
2748
2.5
1.2
360
347

50
0.56
710
0.7
0.044
1.6
1.04
1.9
0.001


40
1.4
0.01
110

11
7.6

1,078,725
285,000

124
137

kg/ day
51.8
51.8
78.8
2967
29.65
2.7
1.3
388
374

54.0
0.60
766
0.8
0.047
1.7
1.12
2.05
0.001


43.16
1.5
0.01
118.7

11.9
8.2






Net Loading
kg/kkg
0.42
0.42
0.64
23.93
0.24
0.02
0.01
3.13
3.02

0.44
0.005
6.18
0.006
0.0004
0.014
0.009
0.017
0.000008


0.35
0.012
0.00008
0.96

0.096
0.66







Ib/S.Ton
0.84
0.84
1.28
47.86
0.48
0.04
0.02
6.26
6.04

0.88
0.010
12.36
0.012
0.0008
0.028
0.018
0.034
0.000016


0.70
0.024
0.00016
1.92

0.192
1.32






                   48

-------
                   TABU; 12.  WASTE  EFFLUENTS  FROM PLANT NO. i;

                  Outfall No.:   001
                  Contributing Operations:   Horizontal Retort Zinc Production
                                            Mixed Wastes
Total
Plant
Intake,
Parameter mg/1
PH
Alkalinity
COD
Total Solids
Dissolved Solids
Suspended Solids
Oil and Grease
Sulfate (as S)
Chloride
Cyanide
Aluminum
Arsenic
Cadmium
Calcium
Chromium
Copper
Iron
Lead
Magnesium
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silver
Sodium
Tellurium
Zinc
Floxj,
I/day
gal/day
Production,
kkg/day
short tons/day
Total
Plant Net
Discharge, Change
mg/1 mg/1
6.7
13 NA
6
1500
1500
13

251
620

0.010
0.010
4.4
44
0.05
0.06
0.02
0.02
12.6
.001


81.5


144

120

69,220
18,288

181.4
220

kg/day

0.9
0.42
103.8
103.8
0.9

17.4
42.9

0.0007
0.0007
0.30
3.0
0.003
0.004
0.0014
0.0014
0.87
0.00007


5.64


9.96

8.3






Net Loading
kg/kkg

0.005
0.002
0.57
0.57
0.005

0.096
0.24

0.000004
0.000004
0.0017
0.017
0.000017
0.00002
0.000008
0.000008
0.0048
4 x 10"6


0.031


0.055

0.046







Ib/S.Ton

0.01
0.004
1.14
1.14
0.01

0.192
0.48
-6
8 x 10
8 x 10"6
0.0034
0.034
3.4 x 10"5
4 x 10"5
1.6 x 10"5
1.6 x 10"5
0.0096
8 x 10"6


0.062


0.11

0.092






Source:   1971 RAPP Data
                                    49

-------
characterization.    Where   both   intake   and   discharge
concentrations  were  available,  intake concentrations were
subtracted  from  discharge  concentrations  to  produce  an
arithmetic   net   concentration,  which  may  be  taken  as
indicating the contribution of the zinc producing  operation
to  the water.  Where the arithmetic net value was negative,
no meaningful loading was  considered  calculable,  and  the
entry NLC, meaning no load calculable, was made.  Where only
discharge  concentrations  were available, a gross discharge
characteristic    was    determined.     Using     discharge
concentrations    (net  or  gross),  unit  waste  loads  were
calculated using the concentration, the flow, and production
rate data as given at the bottom of the  tables.   The  data
given  are  drawn  from  various  sources  covering the time
period 1971 to 1973.  Recent or planned changes in discharge
practices are discussed in various later  portions  of  this
document.

A summary table of selected data is presented in Table 13 to
allow a comparison of unit waste loads expressed in units of
a  constituent per unit of zinc production (i.e., kg/kkg and
lbs/1000 Ibs).  Plant A is not included in these tabulations
because there is no discharge; Plant E is omitted in that no
meaningful overall unit waste load data could  be  developed
for  the  zinc smelting operation, due to the combination of
the multiplicity of  (nonzinc) operations and outfalls.

In general, the data given in Table 7 through 13  exhibit  a
considerable  range  of  practices,  waste water constituent
levels, flows, and other factors.  Plants G  and  H  exhibit
low  production  rates, minimum discharge flows, and minimum
calculated unit waste loads, with low discharge flows  being
considered  the  most  important  factor in making these the
lowest unit waste loads.

In terms of gross concentrations contained in the  discharge
streams,  the  ranges  encountered in the available data for
some  of  the  constituents  given  in  the  tables  may  be
summarized as:

      Dissolved Solids     455-4485 mg/1
      Suspended Solids       25-249 mg/1
      Sulfates             175-2221 mg/1
      Chlorides              60-620 mg/1
      Arsenic                0.1-0.68 mg/1
      Cadmium                0.02-2.4 mg/1
      Copper                 0.01-0.34 mg/1
      Iron                   0.02-1.93 mg/1
      Lead                   0.02-1.35 mg/1
      Mercury                0.00005 - 0.004 mg/1
                            50

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TABLE 13.  SUIMARY OF SULCTLD DATA W 17STL

           PRIfiAMT ZINC PI/OTS (Waste loads
           pound/1000 pounds)
    QIAPACTLPISTICS FRCT

units of Kg/iacg or
              y
Plant
Production Rate, kkg/day
„ (tons/day)
Discharge Rate, A/day
Treatment Practifeeal/da>')


Basis
Source

pH
COD
Dissolved Solids
Suspended Solids
Oil and Grease
Sulfate
Chloride
Arsenic
Cadmium
Copper
Iron
Lead
Mercury
Nickel
Selenium
Zinc
B
272
(300)
2 763,000
^730,000} .
Complete Lime
and Settle

Net &. Gross
Plant Data

8.6
0.173
39.7
2.53
0.04
21.8
0.66
< 1 x 10'4
< 2 x 10"4
< 2 x 10'4
NLC
0.0015
4.1 x 10"J
0.001
0.018
0.508
C
173
(194)
18,168,000
(4,800,000)
Settle


Net
Plant Data

	
-_
--
-_
—
--
__
__
—
--
--
--
NLC
-._
--
0.472
D
297
5,450,400
(1,440,000)
Partial
Lime &
Settle
Gross
1971 RAPP
Data
3.3
0.07
20.3
0.48
__
13.8
1.8
0.01
0.044
0.006
0.035
0.02
5 x 10'5
	
__
4,45
F
611
44,965,800
(11,800,000)
Lime & Settle


Net
1972 RAPP
Data
7.6
0.44
15.1
0.37
0.22
3.7
3.2 ,
2 x 10'4
0.01
__
0.004
0.005
__
__
__
0.37
G
124
1,078,^)
5285,000)
Lime and Settle


Gross
RAPP Data

8.5
0.64
0.24
0.02
0.01
3.13
3.02

0.005
4 x 10"4
0.014
0.009
8 ;< 10"6

0.012
0.096
H
181
(220)
69,220
(18,288)



1971 RAPP
Data
6.7
0.002
0.57
0.005

0.096
n ?A
u. ^M-
4 x 10"6
0.002
1 x 10"5
8 x 10"6
8 x 10"6
4 x 10"6

_ —
0.046

-------
      Selenium               0.007-1.8 mg/1
      Zinc                   5-243 mg/1.

It   must   be   noted   that  these  generalized  discharge
characteristics  include  all  streams   (i.e.,   noncontact
cooling  water,  water  from  auxiliary  operations,  etc.).
Thus, dilution of process waste water with all other  waters
will produce low values of pollutant concentrations.

Thus,  wastes  from primary zinc plants, on the most general
basis, may be characterized as containing,  not unexpectedly,
noteworthy levels  of  zinc  and  sulfates,  accompanied  by
typically  associated  elements  of cadmium, lead, and, less
significantly, arsenic and selenium.

The unit waste loads given in Tables 7 to 13 represent  both
treated  and  untreated  waste waters, and show the range of
waste  characteristics  produced  by  combinations  of  many
factors  of  flow,  treatment effectiveness, different types
and combinations of plant operations, production rates, etc.
More detailed discussion of these individual factors will be
given in the following paragraphs and sections.  It  may  be
noted  here  that  the  waste  loads  of Plant G represent a
combination of relatively  low  flow,  low  production,  and
moderately   high   effectiveness   of  a  lime  and  settle
treatment.  These waste loads may be compared with those  of
Plant  D  where  higher production and flow rates and simple
settling treatment pertain, resulting in higher  unit  waste
loadings  of all constituents.  Plant H is soon to be closed
and little information was available on factors contributing
to the very low waste loads, although the very low  flow  is
considered the major influence.
Unit Process Waste Streams
Both  existing  plant  data  and field verification sampling
provided some basis for the analysis of flows of waste water
streams from unit process operations.

Acid	Plant	Blowdown.  The information developed  on  the
characteristics of acid plant blowdown is given in Tables 14
and  15.  These streams typically contain high sulfates, low
pH, and relatively high levels of lead,  cadmium,  selenium,
zinc, and, depending on the concentrate fed to the roasters,
varying amounts of mercury.
                            52

-------
  T/ABIJ: 14. WASTE EFFLUENTS FROM PLANT NO.   B

Outfall No.:
Contributing Operations:  Scrubber Bleed + ESP Sump (Acid Plant Slowdown)
Total
Plant
Intake,
Paraneter mg/1
pH 7.9
Alkalinity 110
COD
Total Solids
Dissolved Solids 575
Suspended Solids 0
Oil and Grease
Sulfate (as S) 80
Chloride 106
Cyanide
Aluminum
Arsenic
Cadmium
Calcium 64
Chromium
Copper
Iron 3.4
Lead
Magnesium 17
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silver
Sodiuro
Tellurium
Zinc
Flow,
I/day
gal /day
Production,
kkg/dsy 272
short tons/day 300
Slowdown,
mg/1


23.0

135
8
5.0
4572
105


1
0.6


0.2
19
2

0.006

0.26

13



25






Net
Change
mg/1


23.0 (G)

-440 (N)
8 (N)
5.0 (G)
4492 (N)
-1 (N)


1 (G)
0.6 (G)
-64 (G)

0.2 (G)
15.6 (N)
2 (G)
-17 (G)
0.006 (G)

0.26 (G)

13 (G)



25 (G)

47,840
224,000




kg/day


19.50
.
NLC
6.78
4.24
3809
NLC


0.848
0.509
NLC

0.17
13.2
1.7
NLC
0.0051

0.22

11.0



21.2






Net Loading
ks/kkg


0.072

NLC
0.025
0.016
14.004
NLC


0.003
0.0019
NLC

0.0006
0.0485
0.0063
NLC
1.87 x 10"5
/
8 xllO"^

00.0404



0.078







Ib/S.Ton


0.144

NLC
0.05
0.032
28.0
NLC


0.006
0.004
NLC

0.0012
0.097
0.0126
NLC
3.7 x 10"5

16 x 10~4

0.081



0.156






                 53

-------
TALLL 15.   WASTE  EFFLUENTS FROM PLANT NO. E

 Outfall No.:
 Contributing Operations:     Acid Plant Effluent (Untreated)
Discharge,
Parameter ms,/l
pH 2.8
Alkalinity
COD
Total Solids
Dissolved Solids 5400
Suspended Solids 200
Oil and Grease
Sulfate (as S)
Chloride
Cyanide
Aluminum
Arsenic
Cadmium 33
Calcium
Chromium
Copper
Iron
Lead 48
Magnesium
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silver
Sodium
Tellurium
Zinc 1500
CrO, 0.10
Flow,
I/day 1,308,096
gal/day 345,600
Production,
kkg/dsy 321-4
short tons/day 3°°
. Loading
kg/day kg/kkg Ib/S.Ton




7063 21.98 43.95
261.6 0.814 1.628






43.16 0.134 0.268




62.8 0.195 0.391









1962 o.lOS 12.2
0.1308 0.0004 0.0008






                      54

-------
The data given in Tables 14 and 15 are for untreated streams
(i.e., raw waste) and are not, in themselves, representative
of discharge streams.

Of  some  interest  also  are  the flow rates for acid plant
blowdown streams.  Rates  of  flow  for  a  number  of  such
streams are given in Table 16, based on internal stream flow
rate  data  supplied  by  the indicated plants.  In terms of
ranges of flow, the range for the five  plants  varies  from
741,000  I/day (195,000 gal/day)  to 2,400,000 I/day (633,600
gal/day).  On the basis of product (shown for both zinc  and
sulfuric  acid)  the  range  of  flows  varies for zinc, for
example, from 3170 1/kkg (760 gal/ton)  to 7900  1/kkg   (1890
gal/ton).   The  range  for  this  particular  stream, thus,
varies  less  than  the  overall   discharge   rates   given
previously.

The  values given are flows representing mid-range values or
average  values  of  the  flows  reported  by  the   various
producers  and  are  subject  to  variations  due to a large
number  of  factors  such  as  ambient   temperature,   feed
materials, operating conditions, etc.

Metal	Cooling	Water.A waste water stream in zinc producing
operations is from the cooling of the  cast  metal  product,
usually  in  the  forms  of  slabs, ingots, pigs, etc.  Data
obtained on such  a  stream  is  given  in  Table  17.   The
principal  constituents apparently contributed by the use of
water for  direct  contact  cooling  of  the  cast  products
include oil and grease, suspended solids, and zinc, although
the  latter is a contribution appearing at much lower levels
in this stream than in, for example,  acid  plant  blowdown.
The data given were obtained by field sampling and represent
the  average  of samples obtained from sampling two separate
casting operations for  two  days.   This  particular  waste
water  stream  had  an  average  flow  rate of 231,112 I/day
(61,060 gal/day)  or, expressed in terms of flow per unit  of
zinc metal product, 850 1/kkg (203 gal/ton).

Other	P£2£ess	Waste	Waters.  Among other process waste
waters identifiable in the existing  primary  zinc  industry
are  various  internal  streams  associated with either dust
control devices,  gas washing  (i.e., associated with recovery
of retort gas fuel values)  or  streams  resulting  from  the
treatment  of pollution control residues for the recovery of
metal values.

The characteristics of streams from gas scrubbing operations
are given in Tables 18 and 19.  The gases are from reduction
furnaces and the streams referred to  are  internal  process
                          55

-------
                  TABLE 16.  RATES OF FLOW OF ACID PLANT
                             SLOWDOWN STREAMS
Plant

  B

  C

  D

  E

  e
          Acid Plant Slowdown
               Flow Rates
  I/day

  850,300

  741,300

2,180,000

2,400,000

  980,000
(gal/day)

(224,660)

(195,800)

(576,000)

(633,600)

(259,000)
                          Flow Per Unit of
                            Zinc Produced
1/kkg

 3170

 4220

 7220

 7300

 7900
(gal/ton)

   (76C)

  (1010)

  (1720)

  (1760)

  (1890)
                                    Flow Per Unit of
                                  Sulfuric Acid Produced
1/kkg

4900

1960

6850

5300

3920
(gal/ton)

 (1180)

  (470)

 (1640)

 (1270)

  (940)
                                56

-------
 TABLE 17.   WASTE EFFLUENTS FROM PLANT NO.  B


Outfall No.:
Contributing Operations:   Metal Casting  Cooling
Total
Plant
Intake ,
Parameter mg/1
pH 7.9
Alkalinity 110
COD
Total Solids
Dissolved Solids 575
Suspended Solids 0
Oil and Grease
Sulfate (as S) 80
Chloride 106
Cyanide
Aluminum
Arsenic
Ca dmium
Calcium 64
Chromium
Copper
Iron 3 -4
i tUll
Lead
Magnesium 17
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silver
Sodium
Tellurium
Zinc
Flow,
I/day
gal /day
Production,
kkg/day 2T2.1
short tons/day 30°
Discharge,
ms;/l
8.4
14
14
340
5
13
37
95
1
"
<0.02


<0.02
0.05
0.05
<0.002
<0.02

0.03



1.1

231,112
61,060



Net
Change
mg/1

14 (G)
-235 (N)
5 (G)
13 (G)
-43 (N)
-11 (N)
<0.1 (G)
<0.1 (G)

<0.02 (G)
-64 (G)

<0.02 (G)
-3.35 (N)
0.05 (G)
-17 (G)
<0.002 (G)
<0.02 (G)

0.03 (G)



1.1 (G)






Net Loading
kg/day

3.23
-54.3
1.16
3.0
-9.9
-2.54
<0.023
<0.023

<0.046
-14.8

<0.046
-0.77
0.012
3.93
<0.0005
<0.005

'0.007



0.25






kg/kkg

0.012
NLC
0.0043
0.011
NLC
NLC
<0. 00008
<0. 00008

<0. 00017
NLC

<0. 00017
NLC
0.00004
NLC
<1.8 x 10"6
<0. 000018

0.000026



0.00092






Ib/S.Ton

0.024
NLC
0.0086
0.022
NLC
NLC
<0.0002
<0.0002

<0.0003
NLC

<0.0003
NLC
0.00008
NLC
<3.6 x 10'6
<3.6 x 10"5

0.000052



0.00184






                   57

-------
 TABLE 18.  QIARACTERISTICS OF GAS SCRUBBING IZASTE vCVTER  (AFTER SETTLING)
Concentrations ,
Calculated
mg/Ji Raw Waste Load (Combined Streams)
Constituent
pH
Dissolved Solids
Suspended Solids
Sulfate
Chloride
Cadmium
Zinc
Stream 1
--
490
50
150
40
0.05
2
Stream 2
7.8
800
20
100
150
0.3
2
kg/ day
9,788
327
1,417
1,722
3.4
26.16
Ibs/day
21,530
720
3,120
3,790
7, .5
57 .,6
kg/kkg(2) lb/ton(2)
--
16.0
1.17
5.10
6.20
0.012
0.094
(1)   Not a discharge stream, i.e.,  an internal-process stream; total flow of
     combined streams averaged 13,081,000 i/day (3,376,000 gal/day), equiva-
     lent to 21,388 A/kkg (4,930 gal/ton) of zinc produced; data supplied by
     plant operators.

(2)   Metal concentrations reported  on the basis of soluble metals.
                              58

-------
  TABLE  19.  aiARACTERISTICS OF GAS SCRUBBING V?ASTE WATER  (AFTER SCRUBBING)
Concentrations ,
Constituent tng/jj
PH
Dissolved Solids 7.2
Suspended Solids 220
Cadmium 0.15
Lead 58
Cyanide 12
Calculated Raw Waste Load
kg/day
45.5
10.4
0.031
12
2.48
Ibs/day kg/kkg
0.170
0.039
0.00012
0.045
0.009
Ib/ton
0.34
0.077
0.00023
1.5 x 10"4
0.019
(1)   A scrubber-bleed stream;  not a discharge stream; average flow value of
     207,100 A/day (54,720 gal/day), equivalent to 761 4/kkg (182 gal/ton)
     of zinc produced.

(2)   Metals concentrations based on total metals.
                              59

-------
streams  (i.e., they are not discharged as characterized, but
pass  through  other  steps  of  production processes, waste
treatment,  or  mixing  before  becoming  a   component   of
discharge).   The  characteristics  listed  were reported by
producers,  and  the  constituents  for  which   data   were
available  are  those  considered of significant interest by
the producer.  It should be noted that  characteristics  are
reported  after  settling  and  the metal concentrations are
reported in terms of soluble metals in one case  (Table  18)
and  total  metals  in the other case (Table 19).  Water use
levels in the two applications were calculated to be  21,400
1/kkg  (4,900  gal/ton)  of zinc produced, and 461 1/kkg (182
gal/ton)  in the other case, with the difference  being  that
the  first  case  represents  once through water use and the
second case represents a system  involving  recycle  with  a
bleed  amounting  to  approximately 0.1 percent of the total
recirculating  flow.   Efforts  to  completely  close   this
scrubber circuit, have caused problems with spray nozzles to
such   an  extent  as  to  seriously  interfere  with  plant
operation.

Characteristics of waste waters from auxiliary unit  process
operations  are given in Tables 20 through 22.  In the first
two cases,  the  waste  waters  are  produced  by  auxiliary
operations  treating air pollution control or other residues
to  allow  reclamation  of  zinc  values.    The   principal
characteristic  of  these streams are relatively high levels
of dissolved solids (sulfates  and  chlorides).   They  also
contain  varying,  but  significant levels of the previously
discussed constituents arsenic, cadmium, copper,  zinc,  and
lead.  Again, the two streams characterized in Tables 20 and
21  are  internal  process streams and are subject to mixing
and treatment before  discharge.   The  average  flow  rates
associated  with  these  two  streams  were  i?4  1/kkg  (42
gal/ton)  and 353 1/kkg (85 gal/ton)  calculated on the  basis
of zinc production for the plant.

Another  stream  encountered  within the industry was from a
unique chemical conversion  operation  associated  with  the
production   of   an   additive  to  the  electrolyte.   The
characteristics of this waste water are given in Table 22 in
terms  of  grab  samples  from  two   days   of   batch-type
operations.   The principal constituents of those identified
are an alkaline pH  (11)   and  a  high  level  of  dissolved
solids.   The  other  characteristics  reflect  the separate
nature of the chemicals involved and do  not  correspond  to
the previous streams discussed.  The average flow associated
with  this  waste  water stream was calculated as 4150 1/kkg
(900 gal/ton) on the basis of  the  plant  zinc  production.
The stream was subsequently treated before discharge.
                          60

-------
TABLE 20.   WASTE EFFLUENTS FROM PLANT NO. B

Outfall No.:
Contributing Operations:  Auxilary Metal Reclamation Operation
Parameter
PH
Alkalinity
COD
Total Solids
Dissolved Solids
Suspended Solids
Oil and Grease
Sulfate (as S)
Chloride
Cyanide
Aluminum
Arsenic
Ca'dmium
Calcium
Chromium
Copper
Ircr
Lead
Magnesium
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silver
Sodium
Tellurium
Zinc
Phenols
Flow,
I/day
gal/day
Production,
kkg/day
short tons/day
Total Total
Plant Plant
Intake, Discharge,
mg/1 mg/1
6.3
110
4

575 4060
0 9
1
80 33
106 1542
<0.1

0.10
64
<0.02
3.4 0.48
1.8
17
0.003
<0.02
0.01



1300
<0.1






Net
Change
mg/1

4 (G)

3485 (N)
9 (N)
1 (G)
-47 (N)
1436 (N)
<0.1 (G)

0.1 (G)
0.10 (G)
NLC
<0.02 (G)
-2.92 (N)
1.8 (G)
-17 (N)
0.003 (G)
<0.02 (G)
0.01 (G)



1300 (G)
<0.1 (G)

47,464
12,540

272.1
300
Net Loading
kg /day

0.19
,
165.5
10.43
0.048
NLC
68.21
<0.0048

0.0048
0.0048
NLC
<9.5 x 10
NLC
0.086
NLC
kg/kkg Ib/S.Ton

6.99 x

0.61
0.0016
1.7 x
NLC
0.251
<1.7 x

1.7 x
1.7 x
NLC
-4 <3.4
NLC
3.1
NLC
1.4 x
<9.5 x 10-4 0.4
'0.0048



61.75
<0.0048






1.7 x



0.227
<1.7 x







10"4 0.0014

1.2
0.0032
10"4 3.4 x 10-4
NLC
0.502
10-5 <3.4 x 10"5
c . _ c
10 5 3.4 x 10 5
10"5 3.4 x ID'5
NLC
xlO-6 <6.8 x 10"6
NLC
x 10'4 6.2 x 10'4
NLC
10"4 1 x 10-
x ID'6 <6.8 x 10'6
10"5 3.4 x ID'5



0.454
ID'5 <3.4 x 10"5






                  61

-------
 TALLL 21.   WASTE EFFLUENTS FROM PLANT NO.  B

Outfall >'o.:
Contributing Operations:  Auxilary Metal Reclamation Operation
Parameter
p'H
Alkalinity
COD
Total Solids
Dissolved Solids
Suspended Solids
Oil and Grease
Sulfate (as S)
Chloride
Cyanide
Aluminum
Arspn1" c
Cadmium
Calcium
Chromium
Copper
Iron
Lead
Magnesium
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silver
Sodium
Tellurium
Zinc
Phenols
Flow,
1/d.nv
gel/day
Production,
kkg/day
short tons/day
Intake, Discharge,
mg/1 tng/1
7.9 5.2
110
56

575 146,130
0 1,338
10
80 9,259
106 160
<0.1

3.0
<0.02
64

8.0
3.4 33.0
300
17
0.003

1.0


-------
 T/U3LL,  22.  WASTE EFFLUENTS FROM PLANT NO.  B

Outfall No.:
Contributing Operations:  Auxilary Process Ooeration
Total
Plant
Intake ,
Parameter mg/1
pH 7.9
Alkalinity 110
COD
Total Solids
Dissolved Solids 575
Suspended Solids 0
Oil xr,d Grease
Sulfat* (as S) 80
Chloride 106
Cyanide
Aluminum
Arsenic
Cadmium
Calcium ,.
^ • 64
Chromium
Copper
Iron 2 4
Les d
Magnesium ^7
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silver
Sodium
Tellurium
Zinc
Flow,
I/flay
gal/day
Production,
kkg/day 272.1
short tens/day 300
Discharge ,
rng/1
11.0

34

135970
1447
5
10947
295
<0.1

0.1
0.1
<0.02

0.04
1.6
0.05
<0.002
0.02
<0.01


3.5






Net Change
mg/1


34(G)

134595(N)
1447(N)
5(G)
10867(N)
189 (N)
<0.1(G)


O.l(G)
<0.02(G)

0.04(G)
-1.8(N)
0.05(G)
<0.002(G)
0.02(G)
<0.01(G)


3.5(G)

113,020
29,860



ks/day


3.84

15209
163.5
0.565
1228.0
21.357
<0.011


0.011
0.0023

0.0046
NLC
0.0057
NLC
0.0023
0.0011


0.396






kg/M ton


0.0141

55.89
0.601
0.0021
4.513
0.0785
0.00004


0.00004
0.000008

0.000016
NLC
0.0002
NLC
9 x 10"7
0.000008
0.000004


0.0014






Ib/S.Ton


0.0282

111.78
1.202
0.0042
9.026
0.1570
0.00008


0.00008
0.000016

0.000032
NLC
0.0004
NLC
18 x 107
0.000016
0.000008


0.00292






                   63

-------
Summary
The  waste characteristics of the primary zinc industry have
been shown in terms of concentration and  unit  waste  load.
The noteworthy characteristics in the waste waters have been
identified  as  dissolved  solids,  most  commonly sulfates,
metals such as lead, cadmium, zinc,  copper,  selenium,  and
arsenic.   Characteristics  of internal process streams have
been similarly identified in terms of the  common  component
process  waste  water  streams of acid plant blowdown,_metal
casting cooling water, and streams  arising  from  auxiliary
operations  such  as  air  pollution control or treatment of
residues for recovery of zinc values.
                             64

-------
                          SECTION VI

              SELECTION OF POLLUTANT PARAMETERS


                         Introduction

 The  following  waste  water  parameters,   which  have  been
 determined  to be present in the process waste waters of the
 primary zinc industry in sufficient  quantities  to  warrant
 there control and treatment, are as follows:
                    Total suspended solids
                    Arsenic
                    Cadmium
                    Mercury
                    Selenium
                    Zinc
                    PH

The   rationale   for  the designation  of  these  parameters  and
for  the  rejection  of  other parameters are presented   in   the
following  paragraphs.

     Sltiona^_fo^_the_Selection_of_Pollutant_Parameters


The   control and treatment technologies  discussed in  Section
VII  describe the current practices, as well as  those which
are   under  construction,   by the  industry which are  used to
treat and  control  the   selected  pollutants.   From these
discussions,  it  was  concluded that the discharge of total
suspended  solids and heavy (trace) metals can be  controlled
by pH adjustment and suspended solids removal.

Setting  effluent limitations on the prescribed heavy  metals,
which are  the  principal pollutant  metals in the  process
waste waters from the primary zinc industry, and  specifying
a  pH  range will in turn  limit the other trace metals found
in  these  waste  waters.   Such  metals  include  aluminum,
magnesium,   antimony,   chromium,   cobalt,  copper,  iron
manganese, nickel,   silver, and tin.

There is an optimum pH   for  precipitation  of  each  metal,
which  results  in  its  greatest reduction by solids  removal
(settling or filtration).  The pH selected for  the  mixture
of  metals  associated  with  the primary zinc industry is a
compromise between the maximum removal of cadmium and  zinc,
as  hydroxides,   and  that suited for the maximum removal of
                           65

-------
the other metals associated with the process  waste  waters.
Coprecipitation of these heavy metal hydroxides with cadmium
and  zinc  hydroxide  (and  also aluminum, copper, iron, and
magnesium hydroxide,  if  they  are  present  in  the  waste
waters)   at  a pH at which optimum coprecipitation occurs is
used  in  good  water  treatment  practice.   Therefore,  an
appropriate  pH  adjustment,  followed by solids removal will
reduce all the metals to levels  consistent  with  the  best
practicable control technology currently available.
Acidity  and  alkalinity  are  reciprocal terms.  Acidity is
produced  by  substances  that  yield  hydrogen  ions   upon
hydrolysis  and  alkalinity  is  produced by substances that
yield hydroxyl ions.  The terms "total acidity"  and  "total
alkalinity" are often used to express the buffering capacity
of  a  solution.   Acidity  in  natural  waters is caused by
carbon dioxide mineral acids, weakly dissociated acids,  and
the  salts  of  strong  acids and weak bases.  Alkalinity is
caused by strong bases and the salts of strong alkalies  and
weak acids.

The term pH is a logarithmic expression of the concentration
of  hydrogen  ions.  At a pH of 7, the hydrogen and hydroxyl
ion concentrations are essentially equal and  the  water  is
neutral.   Lower  pH  values  indicate  acidity while higher
values indicate alkalinity.  The relationship between pH and
acidity or alkalinity is not necessarily linear or direct.

Waters with a pH below 6.0  are  corrosive  to  water  works
structures,   distribution  lines,  and  household  plumbing
fixtures and can thus  add  such  constituents  to  drinking
water as iron, copper, zinc, cadmium and lead.  The hydrogen
ion concentration can affect the "taste" of the water.  At a
low  pH,  water  tastes  "sour".  The bactericidal effect of
chlorine  is  weakened  as  the  pH  increases,  and  it  is
advantageous  to  keep  the  pH  close  to  7.  This is very
significant for providing safe drinking water.

Extremes  of  pH  or  rapid  pH  changes  can  exert  stress
conditions  or  kill  aquatic  life  outright.   Dead  fish,
associated algal blooms, and  foul  stenches  are  aesthetic
liabilities  of  any  waterway.   Even moderate changes from
"acceptable" criteria limits of pH are deleterious  to  some
species.   The  relative  toxicity  to  aquatic life of many
materials  is  increased  by  changes  in  the   water   pH.
Metalocyanide  complexes  can  increase  a  thousand- fold in
toxicity with a drop of 1.5 pH units.  The  availability  of
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many nutrient substances  varies  with  the  alkalinity  and
acidity.  Ammonia is more lethal with a higher pH.

The    lacrirnal   fluid   of  the  human  eye  has  a  pH  of
approximately 7.0 and a deviation of 0.1 pH  unit  from  the
norm   may   result  in  eye  irritation  for  the  swimmer.
Appreciable irritation will cause severe pain.

The  parameter  of  pH  is   considered   essential   as   a
characteristic  of  waste  water.   Since  it  is  the major
control   parameter   in   neutralization   treatment,   the
pertinency  has  been  indicated  in  terms of current waste
characteristics in Section IV and is  further  discussed  in
subsequent  sections of this document.  When in the range of
pH 7 to ]0, the acid wastes have been neutralized,  but  are
not    excessively   alkaline.    Overall  concentrations  of
dissolved metals can be expected to be at a minimum when the
pH of  the discharge is maintained in this range.

Total  Suspended Solids

Suspended  solids  include  both   organic   and   inorganic
materials.  The inorganic components include sand, silt, and
clay.   The  organic  fraction  includes  such  materials as
grease, oil, tar, animal and vegetable fats, various fibers,
sawdust, hair, and various  materials  from  sewers.   These
solids  may settle out rapidly and bottom deposits are often
a mixture  of  both  organic  and  inorganic  solids.    They
adversely  affect  fisheries  by  covering the bottom of the
stream or lake with a blanket of material that destroys  the
fish-food  bottom  fauna  or  the  spawning  ground of fish.
Deposits containing organic  materials  may  deplete  bottom
oxygen   supplies   and  produce  hydrogen  sulfide,  carbon
dioxide, methane, and other noxious gases.

In raw water sources for domestic use,  state  and  regional
agencies  generally specify that suspended solids in streams
shall  not be  present  in  sufficient  concentration  to  be
objectionable   or   to   interfere  with  normal  treatment
processes.  Suspended solids in  water  may  interfere  with
many   industrial processes, and cause foaming in boilers, or
encrustations on equipment exposed to water,  especially  as
the  temperature rises.  Suspended solids are undesirable in
water  for textile industries,  paper  and  pulp,  beverages,
dairy  products,  laundries,  dyeing,   photography,  cooling
systems, and power plants.   Suspended particles  also   serve
as   a   transport   mechanism   for  pesticides  and   other
substances,  which are  readily  sorbed  into  or  onto  clay
particles.
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Solids may be suspended in water for a time, and then settle
to the bed of the stream or lake.  These  settleable  solids
discharged   with   man's   wastes   may  be  inert,  slowly
biodegradable materials, or rapidly decomposable substances.
While in suspension, they  increase  the  turbidity  of  the
water,    reduce    light   penetration   and   impair   the
photosynthetic activity of aquatic plants.

Solids in suspension are  aesthetically  displeasing.   When
they  settle  to  form sludge deposits on the stream or lake
bed, they are often much more damaging to the life in water,
and they  retain  the  capacity  to  displease  the  senses.
Solids,  when  transformed  to  sludge  deposits,  may  do a
variety of damaging things, including blanketing the  stream
or  lake  bed  and  thereby destroying the living spaces for
those benthic organisms  that  would  otherwise  occupy  the
habitat.   When  of  an  organic  and therefore decomposable
nature, solids use a portion or all of the dissolved  oxygen
available  in  the  area.  Organic materials also serve as a
seemingly inexhaustible  food  source  for  sludgeworms  and
associated organisms.

Turbidity  is  principally  a measure of the light absorbing
properties of suspended solids.  It is frequently used as  a
substitute  method of quickly estimating the total suspended
solids when the concentration is relatively low.

Total suspended solids is a  gross  measure  of  the  solids
remaining  in suspension following treatment of precipitated
dissolved metals.  Compliance with a TSS limitation  insures
that   effective   phase   separation   has  been  achieved.
Relatively unsophisticated methods, the simplest of which is
provision for adequate settling time in a settling pond, are
available for the treatment of waste water to  decrease  the
suspended solids content.

Arsenic

Arsenic  is  found  to  a  small  extent  in  nature  in the
elemental form.  It occurs mostly in the form  of  arsenites
of metals or as pyrites.

Arsenic  is  normally present in sea water at concentrations
of 2 to 3 ug/1 and tends to be accumulated  by  oysters  and
other  shellfish.   Concentrations  of  100  mg/kg have been
reported in certain  shellfish.   Arsenic  is  a  cumulative
poison  with  long-term  chronic  effects  on  both  aquatic
organisms and on mammalian species and a succession of small
doses may add up to a final lethal dose.  It  is  moderately
                         68

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toxic  to  plants  and highly toxic to animals especially as
AsH3.

Arsenic trioxide,  which  also  is  exceedingly  toxic,  was
studied in concentrations of 1.96 to 40 mg/1 and found to be
harmful  in that range to fish and other aquatic life.  Work
by the Washington Department of Fisheries on pink salmon has
shown that at a level of 5.3  mg/1  of  As£O3  for  8  days,
arsenic  trioxide  was extremely harmful to this species; on
mussels, a level of 16 mg/1 was lethal in 3 to 16 days.

Severe   human   poisoning   can   result   from   100    mg
concentrations,  and  130  mg has proved fatal.  Arsenic can
accumulate in the body faster than it is  excreted  and  can
build to toxic levels, from small amounts taken periodically
through  lung  and  intestinal walls from the air, water and
food.

Arsenic  is  a  normal  constituent  of  most  soils,   with
concentrations  ranging  up to 500 mg/kg.  Although very low
concentrations of arsenates  may  actually  stimulate  plant
growth,   the  presence  of  excessive  soluble  arsenic  in
irrigation waters will reduce the yield of crops,  the  main
effect appearing to be the destruction of chlorophyll in the
foliage.   Plants  grown  in  water  containing  one mg/1 of
arsenic  trioxide   showed  a  blackening  of  the  vascular
bundles  in  the  leaves.   Beans  and  cucumbers  are  very
sensitive,  while  turnips,   cereals,   and   grasses   are
relatively  resistant.  Old orchard soils in Washington that
contained 4 to 12 mg/kg of arsenic trioxide in the top  soil
were found to have become unproductive.

Arsenic  is  also  identifiable  as a characteristic process
waste water pollutant contributed by primary zinc operations
and is also not proven to be reliably controlled  by  common
practicable  control  or  treatment methods such as lime and
settle.  In order to achieve the desired  goal  of  improved
control  and reduction of the discharge of pollutants, it is
deemed necessary to select arsenic as a specific parameter.

Cadmium

Cadmium in drinking water supplies is extremely hazardous to
humans, and conventional  treatment,   as  practiced  in  the
United States, does not remove it.  Cadmium is cumulative in
the liver, kidney, pancreas, and thyroid of humans and other
animals.   A  severe  bone  and kidney syndrome in Japan has
been associated with the  ingestion  of  as  little  as  600
ug/day of cadmium.
                        69

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

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

Cadmium is identifiable as  a  characteristic  component  of
process  waste  water  in the primary zinc industry and is a
characteristic byproduct of zinc production.   The  chemical
behavior   in  lime-and-settle  treatment  processes  varies
considerably from that  of  zinc  and  its  selection  as  a
pollutant  parameter  for  purposes of establishing effluent
limitations provides another parameter indicating the  level
of   performance  achieved  in  any  control  and  treatment
technology.

Mercury

Although elemental mercury occurs as a free  metal  in  some
parts  of  the  world,  it  is  rather  inert chemically and
insoluble in water; hence, it is not likely to  occur  as  a
water  pollutant.   It  is used in scientific and electrical
instruments, in dentistry, in power generation, in  solders,
and  in  the  manufacture of lamps.  Mercuric salts occur in
nature chiefly as  the sulfide HgS, known as  cinnabar,  but
numerous  synthetic  organic  and inorganic salts of mercury
are  used  commercially  and  industrially.   Many  of   the
mercuric and mercurous salts are highly soluble in water.

Mercury and mercuric salts are considered to be highly toxic
to  humans.   They  are  readily  absorbed  by  way  of  the
gastrointestinal tract, and fatal doses for man vary from  3
to 30 grams.  Adults may safely drink water containing about
4  to   12  mg  of  Hg per day and a fatal does of such water
would be about 75 to 300 mg per day.
                         70

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Mercuric ions are considered to be highly toxic  to  aquatic
life.   For freshwater fish, concentrations of 0.004 to 0.02
mg/1 of Hg have been reported harmful.

Mercury salts,  such  as  the  unstable  compounds  mercuric
sulfate  and nitrate, have killed minnows at a concentration
of  0.01  mg/1   as   mercury,   after   80-92   days.    At
concentrations  of  0.05  and 0.1 mg/1 as mercury, fish were
killed in 6 to 12  days.   For  phytoplankton,  the  minimum
lethal  concentration  of mercury salts has been reported to
range from 0.9 to 60 mg/1  of  Hg.   The  toxic  effects  of
mercuric  salts  are  accentuated  by  the presence of trace
amounts of copper.

The available information serves to identify  mercury  as  a
process  waste  water  pollutant  characteristic of the zinc
industry.  Further, mercury  is  currently  the  subject  of
control  and  treatment efforts including methods other than
lime-and-settle treatment.  The chemical behavior of mercury
in a lime-and-settle  treatment  process  is  not  currently
demonstrated  conclusively.   Thus, the selection of mercury
as a process  waste  water  pollutant  parameter  is  deemed
appropriate in that it is characteristic of zinc operations,
but  not automatically or concurrently controlled by control
and treatment technology applicable to other constituents.

Selenium

Analogous to sulfur in many of  its  chemical  combinations,
selenium  is used in its elemental form and as several salts
in  a  variety   of   industrial   applications,   such   as
pigmentation  in  paints,  dyes,  and glass production; as a
component  of  rectifiers,  semiconductors,   photo-electric
cells,  and  other  electrical apparatus; as a supplement to
sulfur in the rubber industry; as a component of alloys; and
for insecticide sprays.  Selenium occurs in  some  soils  as
basic  ferric  selenite,  as  calcium selenate, as elemental
selenium, and in  organic  compounds  derived  from  decayed
plant  tissue.   In  some areas of South Dakota and Wyoming,
soils may contain up to 30 mg/kg of selenium.  Selenium  may
be expected in trace quantities in the municipal sewage from
industrial communities.

Proof  of  human  injury  by selenium is scanty and definite
symptoms of selenium poisoning have not been identified; but
it is widely believed that selenium is highly toxic to  man.
It  has  been stated that the symptoms of selenium poisoning
are similar to those of  arsenic  poisoning.   Mild  chronic
selenium  poisoning  has  been  observed in humans living in
areas where the soil and produce are rich in  selenium.   In
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addition,  there  have been cases of selenosis at industrial
establishments  that  use  or  produce  selenium  compounds.
Selenium  in  trace  amounts appears to be essential for the
nutrition of animals, including man, although very little is
known about  the  mechanism  of  its  action.   Arsenic  and
selenium  are  apparently  antagonistic  in  their toxicity,
tending  to  counteract  each  other.   Selenium  salts  are
rapidly  and efficiently absorbed from the gastro-intestinal
tract and excreted largely through the urine.  Retention  is
highest  in  the  liver and kidney.  Surveys have shown that
dental caries rates of permanent  teeth  were  significantly
higher in seleniferous areas than in non-seleniferous areas.
There  is  also  a  tendency  for increased malocclusion and
gingivitis in seleniferous areas.  The USPHS Drinking  Water
Standards  have  restricted  selenium  to  0.05  mg/1  on  a
mandatory basis for many years.  In 1962, however,  the  new
standards lowered the mandatory limit to 0.01 mg/1.  The WHO
International   and   European   Drinking   Water  Standards
prescribe a mandatory limit  of  0.05  mg/1.   These  strict
standards  were  undoubtedly  set  because of the similarity
between arsenic and selenium poisoning, the  dental  effect,
and the known toxicity to livestock, as described below.

In  general,  the  soil in parts of the world where selenium
poisoning occurs naturally contains 1 to 6 mg/kg of selenium
in the top eight inches.   However,  plants  vary  in  their
ability    to    absorb   selenium;   the   final   selenium
concentrations in the  plant  will  be  determined  by  many
factors,  including the species and age of the plant, season
of the year,  and  the  concentration  of  soluble  selenium
compounds in the root zone.

Selenium  poisoning  ("alkali  disease" or "blind staggers")
occurs  frequently  among  livestock  in  the  Great  Plains
regions of the United States and Canada, and also in Mexico.
It can be produced in laboratory rats, as well as livestock,
by  feeding abnormal amounts or inorganic selenium compounds
of seleniferous feed.  Selenium poisoning  occurs  naturally
among cattle, sheep, horses, pigs, and even poultry, in both
chronic  and  acute  forms.   It is characterized by loss of
hair from mane and tail and soreness of the feet, as well as
by deformity, loss  of  condition,  and  emaciation.   Among
poultry,  the  eggs  give  rise  to abnormal or weak chicks.
Impairment of vision, weakness  of  limbs,  and  respiratory
death   have  resulted  from  livestock  feeding  on  plants
containing ICO to 1000 mg/kg of selenium.

Added as a sodium selenite, 2.0 mg/1 of  selenium  has  been
toxic  to  goldfish  in  eight  days, and lethal in 18 to 46
days.  Minute concentrations of selenium appear  not  to  be
                           72

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harmful  to  fish during an exposure period of several days;
however, constant exposure to traces of selenium has  caused
disturbances   of  appetite  and  equilibrium,  pathological
changes, and  even  deaths  of  fish  after  several  weeks.
Concentrations  considered  safe  for  human  beings  over a
period of weeks have been toxic to fish.

The rationale for the selection of  selenium  as  a  process
waste  water  pollutant  parameter  is  based  on  the  same
considerations as for  mercury  and  arsenic  (i.e.,  it  is
identifiable   as  a  characteristic  contribution  of  zinc
producing operations, but exhibits  chemical  behavior  such
that it is not automatically removed concurrently with other
constituents by current treatment practices.

Zinc

Occurring  abundantly  in  rocks  and  ores, zinc is readily
refined into a stable pure metal and is used extensively for
galvanizing, in alloys, for electrical purposes, in printing
plates, for dye-manufacture and for  dyeing  processes,  and
for  many other industrial purposes.  Zinc salts are used in
paint   pigments,    cosmetics,    pharmaceuticals,    dyes,
insecticides,  and  other  products  too  numerous  to  list
herein.  Many of these salts  (e.g., zinc chloride  and  zinc
sulfate)  are  highly  soluble  in  water; hence it is to be
expected that zinc might occur in  many  industrial  wastes.
On  the  other  hand,  some zinc salts  (zinc carbonate, zinc
oxide, zinc sulfide) are insoluble in water and consequently
it is to be expected that some zinc will precipitate and  be
removed readily in most natural waters.

In  zinc  mining  areas,  zinc  has  been found in waters in
concentrations as high as 50  mg/1.   In  most  surface  and
ground  waters,  it is present only in trace amounts.  There
is some evidence that zinc ions are  adsorbed  strongly  and
permanently on silt, resulting in inactivation of the zinc.

Concentrations of zinc in excess of 5 mg/1 in raw water used
for drinking water supplies cause an undesirable taste which
persists  through  conventional treatment.  Zinc can have an
adverse effect on man and animals at high concentrations.

In soft water, concentrations of zinc ranging  from  0.1  to
1.0  mg/1  have been reported to be lethal to fish.  Zinc is
thought to exert  its  toxic  action  by  forming  insoluble
compounds  with  the mucous that covers the gills, by damage
to the gill epithelium, or possibly by acting as an internal
poison.   The  sensitivity  of  fish  to  zinc  varies  with
species, age and condition, as well as with the physical and
                          73

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 chemical  characteristics  of  the  water.   Some  acclimatization
 to  the   presence   of  zinc   is   possible.   It has  also been
 observed  that  the  effects of zinc poisoning may  not  become
 apparent   immediately,  so  that  fish   removed  from  zinc-
 contaminated to  zinc-free water  (after  4-6  hours  of exposure
 to zinc)  may die 48 hours later.   The presence of copper  in
 water   may    increase  the   toxicity   of   zinc  to  aquatic
 organisms, but the  presence  of  calcium   or  hardness  may
 decrease  the relative toxicity.

 Observed  values  for the distribution of zinc  in ocean waters
 vary widely.    The  major  concern  with   zinc compounds in
 marine waters  is not one  of  acute toxicity,   but  rather  of
 the long-term  sub-lethal effects of the metallic  compounds
 and complexes.   From an acute  toxicity  point  of  view,
 invertebrate   marine animals seem to  be the most  sensitive
 organisms tested.    The   growth  of  the   sea urchin,   for
 example,  has been  retarded by as little as  30 ug/1  of zinc.

 Zinc sulfate  has  also   been  found   to   be lethal  to many
 plants, and it could impair  agricultural uses.

 Zinc has, not  unexpectedly,  been  identified   as  a  process
 waste  water pollutant characteristically contributed t>y the
 zinc industry.   As will be developed in more   detail   later,
 the chemical  behavior   of   zinc makes  it   a component of
 special   nature    in  current   lime-and-settle    treatment
 technology  and  is,  thus, a  critical indicator of  the level
 of  performance achieved in treatment operations.


        Siii2nale_for_Rejection_of_Other_Waste_Water
            £onstituents_as_PoJLlutant_Parameters
Dissolved Solids

In natural waters the dissolved  solids  consist  mainly  of
carbonates,  chlorides,  sulfates,  phosphates, and possibly
nitrates of calcium, magnesium, sodium, and potassium,  with
traces of iron, manganese and other substances.

Many communities in the United States and in other countries
use water supplies containing 2000 to 4000 mg/1 of dissolved
salts,  when  no better water is available.   Such waters are
not palatable,  may  not  quench  thirst,  and  may  have  a
laxative  action  on new users.  Waters containing more than
4000 mg/1 of total salts are generally considered unfit  for
human  use,  although  in  hot  climates  such  higher  salt
                         74

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concentrations can be tolerated; whereas, they could not  be
in  temperate climates.  Waters containing 5COO mg/1 or more
are reported to be bitter and act as bladder and  intestinal
irritants.    It   is   generally   agreed   that  the  salt
concentration of good, palatable water should not exceed 500
mg/1.

Limiting concentrations of dissolved solids for  fresh-water
fish  may  range  from  5,000  to  10,000 mg/1, according to
species and prior acclimatization.  Some fish are adapted to
living in more saline waters, and a few  species  of  fresh-
water  forms  have  been found in natural waters with a salt
concentration of 15,000 to 20,000  mg/1.   Fish  can  slowly
become acclimatized to higher salinities, but fish in waters
of  low  salinity  cannot  survive  sudden  exposure to high
salinities, such as those resulting from discharges of  oil-
well brines.  Dissolved solids may influence the toxicity of
heavy metals and organic compounds to fish and other aquatic
life,  primarily  because  of  the  antagonistic  effect  of
hardness on metals.

Waters with  total  dissolved  solids  over  500  mg/1  have
decreasing  utility  as  irrigation  water.   At 5,000 mg/1,
water has little or no value for irrigation.

Dissolved solids in industrial waters can cause  foaming  in
boilers  and  interference with cleanliness, color, or taste
of many  finished  products.   High  contents  of  dissolved
solids also tend to accelerate corrosion.

Specific  conductance  is a measure of the capacity of water
to convey an electric  current.  This property is related  to
the  total  concentration of ionized substances in water and
water temperature.  This property is frequently  used  as  a
substitute method of quickly estimating  the dissolved solids
concentration.

From the standpoint of quantity discharged, dissolved solids
could  have been considered a pollutant  parameter.  However,
there is no readily available  treatment for  significantly
decreasing  dissolved  solids  beyond the levels achieved by
the  limitations  on   metals   content   and   pH.    Energy
requirements,  especially  for  evaporation,  are such as to
preclude  limiting dissolved solids at this time.   Operators
should,  however,  be  encouraged  to  minimize discharge of
excessive dissolved   solids  by   intelligent  management  of
those  plant  operations  resulting  in  the contribution of
additional dissolved  solids to  the waste effluents.
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 Lead,  Nickel,  and Copper

 Lead has  been  identified  as  a  constituent  in   process  waste
 waters,   but   is   considered to be  responsive  to  the control
 technologies   applicable   to  the    control   of  cadmium
 Specifically,   a   lime-and-settle  treatment operated   to
 produce optimum values  of zinc and  cadmium   (both  selected
 above)  will   necessarily result   in associated degrees  of
 reduction of lead,  copper, nickel,  and some other metals.

 Chemical  Oxygen Demand

 The  chemical oxygen demand is  a measure of the quantity   of
 the  oxidizable  materials   present in water and  varies with
 water  composition,  temperature,   and   other   functions.
 Dissolved oxygen  (DO) is a water  quality constituent that,
 in appropriate  concentrations, is essential not only to keep
 organisms living  but also to sustain  species  reproduction,
 vigor,    and   the  development of  populations.   Organisms
 undergo stress  at reduced DO concentrations that  make  them
 less   competitive  and  able to sustain their  species within
 the  aquatic    environment.    For    example,   reduced    DO
 concentrations  have  been   shown   to  interfere  with  fish
 population through  delayed hatching of  eggs,  reduced  size
 and  vigor  of  embryos,  production of deformities in young,
 interference with  food   digestion,   acceleration  of  blood
 clotting,  decreased tolerance to certain toxicants, reduced
 food   efficiency   and  growth  rate,  and  reduced   maximum
 sustained swimming  speed.  Fish food organisms are likewise
 affected  adversely  in conditions with suppressed DO.   Since
 all  aerobic  aquatic  organisms  need  a  certain amount  of
 oxygen, the consequences  of total lack of  dissolved  oxyaen
 due  to   a high COD can kill all inhabitants of the affected
 area.

 If a high COD is  present,  the  quality  of  the  water   is
 usually  visually  degraded  by  the presence of decomposing
materials and algae blooms due  to  the  uptake  of  degraded
materials that form the foodstuffs of the algal populations.

The low concentration of oil and grease found in the process
waste  waters  of  this  industry  will minimize the organic
 sources of COD.  Limitations on pli will control ferrous-iron
content of effluents.

Cyanide

Cyanides  in  water  derive  their  toxicity  primarily   from
undissolved  hydrogen  cyanide   (HCN)   rather  than from the
cyanide ion (CN~).  HCN dissociates  in water into  H+ and CN~
in a pH dependent  reaction.   At a pH of  7   or  below,  less
than 1 percent  of  the cyanide is  present  as CN~;  at a ph of 8,
                           76

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6.7 percent; at a pH of 9, 42 percent; and at a pH of 10, 87
percent  of  the  cyanide  is  dissociated.  The toxicity of
cyanides is also increased by increases in  temperature  and
reductions  in  oxygen tensions.  A temperature rise of 10°C
produced a two- to threefold increase in  the  rate  of  the
lethal action of cyanide.

Cyanide  has  been  shown to be poisonous to humans; amounts
over 18 ppm can have adverse  effects.   A  single  dose  of
about 50-60 mg is reported to be fatal.

Trout and other aquatic organisms are extremely sensitive to
cyanide.   Amounts as small as  0.1 part per million can kill
them.  Certain metals, such  as  nickel,  may  complex  with
cyanide  to reduce lethality especially at higher pH values,
but zinc  and  cadmium  cyanide  complexes  are  exceedingly
toxic.

When   fish  are  poisoned  by  cyanide,  the  gills  become
considerably brighter in  color  than those  of  normal   fish,
owing   to   the   inhibition   by  cyanide  of  the  oxidase
responsible for  oxygen   transfer  from  the  blood  to  the
tissues.

While cyanides are used  in the  concentrating of zinc ores by
floatation,  they are not used  in zinc smelting or  refining,
nor are they formed by any of the processing operations, and
no need exists for cyanide limitations.

Temperature

Temperature is one of the most important  and   influential
v/ater quality  characteristics.  Temperature  determines  those
species   that  may  be present; it activates the  hatching of
young,  regulates  their  activity,   and  stimulates  or
suppresses  their  growth and  development;  it  attracts,  and
may  kill  when  the water  becomes too  hot  or  becomes chilled
too     suddenly.      Colder   water    generally   suppresses
development.   Warmer  water   generally accelerates   activity
and   may   be  a primary cause of aquatic  plant  nuisances when
other  environmental  factors  are suitable.

Temperature is a prime regulator  of  natural  processes  within
the  water environment.   It governs   physiological  functions
in   organisms   and,    acting   directly  or  indirectly  in
combination  with  other  water  quality  constituents,   it
affects  aquatic  life  with  each   change.    These  effects
 include  chemical  reaction   rates,    enzymatic   functions,
molecular   movements,    and   molecular  exchanges  between
                            77

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 membranes  within  and  between  the  physiological   systems   and
 the organs of  an  animal.

 Chemical   reaction  rates  vary with temperature  and  generally
 increase as the temperature is increased.   The  solubility of
 gases  in water varies with temperature.  Dissolved  oxygen is
 decreased  by the  decay or decomposition of  dissolved  organic
 substances and the  decay  rate increases as  the temperature
 of   the  water increases reaching  a maximum  at about  30°C
 (86°F).    The  temperature  of stream  water,   even   during
 summer,    is   below  the  optimum for  pollution-associated
 bacteria.   Increasing the water   temperature  increases   the
 bacterial   multiplication  rate  when  the environment  is
 favorable  and  the food supply is  abundant.

 Reproduction   cycles   may be  changed   significantly    by
 increased   temperature because   this  function takes place
 under  restricted temperature  ranges.  Spawning  may  not occur
 at  all because temperatures are   too  high.   Thus,   a   fish
 population may  exist in  a heated area  only by  continued
 immigration.   Disregarding    the   decreased    reproductive
 potential,  water   temperatures need not reach  lethal levels
 to  decimate a  species.  Temperatures that favor competitors,
 predators,  parasites,  and disease can destroy a species  at
 levels far  below those that are lethal.

 Fish   food  organisms  are altered severely  when temperatures
 approach or exceed  90°F.  Predominant algal species  change,
 primary  production   is   decreased,  and  bottom associated
 organisms  may  be depleted or  altered drastically in  numbers
 and  distribution.    Increased  water temperatures  may cause
 aquatic plant  nuisances when  other environmental factors  are
 favorable.

 Synergistic actions of pollutants are more  severe at  higher
water  temperatures.   Given  amounts  of   domestic  sewage,
 refinery wastes,  oils, tars,   insecticides,   detergents,   and
 fertilizers  more  rapidly deplete oxygen in water  at higher
 temperatures,   and the  respective  toxicities   are  likewise
 increased.

When  water  temperatures  increase,   the  predominant algal
 species may change from diatoms to green algae,  and  finally
at high temperatures to blue-green algae,  because of species
temperature   preferentials.    Blue-green  algae  can  cause
serious odor  problems.   The   number  and  distribution  of
benthic  organisms  decreases  as water temperatures increase
above 90°F, which is close to  the tolerance  limit  for  the
population.   This  could seriously affect certain fish that
depend on benthic organisms as a food source.
                         78

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The cost of fish being attracted to heated water  in  winter
months may be considerable, due to fish mortalities that may
result when the fish return to the cooler water.

Rising  temperatures  stimulate the decomposition of sludge,
formation  of  sludge  gas,  multiplication  of  saprophytic
bacteria  and fungi  (particularly in the presence of organic
wastes), and  the  consumption  of  oxygen  by  putrefactive
processes,  thus  affecting  the  esthetic  value of a water
course.

In general, marine  water  temperatures  do  not  change  as
rapidly  or range as widely as those of freshwaters.  Marine
and  estuarine  fishes,  therefore,  are  less  tolerant  of
temperature  variation.   Although this limited tolerance is
greater in estuarine than  in  open  water  marine  species,
temperature  changes  are  more important to those fishes in
estuaries and bays than  to  those  in  open  marine  areas,
because  of  the  nursery and replenishment functions of the
estuary  that  can  be   adversely   affected   by   extreme
temperature changes.

Temperature  is  an indicator of unusual thermal loads where
waste heat is  rejected  from  a  process.    Excess  thermal
loads,  even in noncontact cooling operations, have not been
and are not expected to be  a  significant  problem  in  the
primary  zinc industry.  In most fresh water operations, the
cooling water is used in closed circuit with a cooling  pond
or  cooling  tower;   in seawater applications, where a once-
through scheme is used, flows are so large that  temperature
rise is insignificant.
                           79

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                        SECTION VII

              CONTROL AND TREATMENT TECHNOLOGY

                        Introduction

The  current  treatment  practices  applied to process waste
water streams in the  primary  zinc  industry  include  both
settling  and  lime-and-settle  of  either  segregated  unit
process streams or total plant effluents.  control  measures
currently used include recycle with bleed and reuse of waste
water.

In  the context of this report the term "control technology"
refers to any practice applied in order to reduce the volume
of waste water discharged.  "Treatment technolgoy" refers to
any practice applied to a waste water stream to  reduce  the
concentration of pollutants in the stream before discharge.

Information   on   planned   treatment  serves  to  identify
increased  applications  of  the  same  measures,   or   the
application   of   refined   lime-and-settle  treatments  of
considerably  increased  performance.   The  application  of
sulfide-precipitation   treatment   is   a  possible  future
development.  Other alternatives, such as  reverse  osmosis,
are not currently considered applicable.

          Current Contrgl_and_rTreatment_Technolggy

Of the eight plants discussed in Section IV, one exhibits no
discharge  by  virtue of location  (i.e., solar evaporation),
and one is so near to closure that no meaningful information
was obtained on treatment or control practices.  The current
practices of the  remainder  of  the  industry  are  briefly
summarized in Table 23.

The  specific  streams to which various control or treatment
measures are applied consist of the following cases:

   Acid plant blowdown  (i.e., wet scrubber bleed streams and
     gas-humidification chamber) effluents are treated in the
     following ways:

       Individually treated
         by liming and settling                1 plant

       Reuse                                   1 plant

       Mixed with other streams
         liming and settling                   2 plants
                        81

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    TABLE 23.   CURRENT A11D FUTURE CONTROL AMD TP£ATMENT
               PRACTICES  Hi TIiE PRIMARY  ZINC IIOJSTRY
                  Current Practices
                                                    Future Practices
Plant
Internal
Streams
Total Plant
 Effluent
Internal
Streams
Total Plant
 Effluent
             Some recycle    Lime and
                              settle
                                       No change announced
             Settle, lime
              and settle
                             Settle
                Mix and
                 settle

                pH adjustment
                  Recycle        Lime and
                                  settle (and
                                  other)

                                 Lime and
                                  settle

                  Various changes considered
             Reuse, settle
              lime and
              settle
                Settle
                  Increased
                   recycle
                             Lime and
                              settle
                             82

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       Mixed and settled                       2 plants

   Metal casting cooling waste water is currently only settled,
     with various degrees of recycle practiced in the industry.

   In two pyrolytic zinc plants using major amounts of water
     for the cleaning of CO-bearing retort exhaust gases, one
     plant practices recycle using associated pH control and
     settling, and the other plant uses settling and mixing
     of wastes to achieve control over final plant effluents.

No other significant control, recycle, or treatment measures
may  be  identified in terms of internal, unit process waste
water streams; it  may  be  noted  that  mixed  plant  waste
treatments  are  eventually  applied  to  some streams, with
usually some reduction of pollutant  loads  occurring  as  a
result of mixing and settling.

Lime and Settle Treatment

As  a  requisite  part  of  developing  information on waste
characteristics and control and  treatment  technology,  the
technical and practical aspects of lime and settle treatment
technology assume considerable importance.

The  choice  of  lime  as a reagent for treating plant waste
water is generally based on economics.  Caustic soda,  (NaOH)
and soda ash, (Na2C03_) are possible  substitutes,  but  both
are  more  costly  alkalies, and both are currently in short
supply.   Also,  neither  forms  an  insoluble  sulfate,  so
neutralization  with these alkalies does nothing for sulfate
concentrations.  Ammonia, NH3_, an alkali easy to handle  and
convenient  to use in automatic neutralization systems, does
not reliably precipitate  all  metals.   Also,  addition  of
nitrates  to  receiving  bodies  of  water  is not currently
recommended, in view of the deleterious  effects  associated
with them; they are, themselves, pollutants.

There  is no "typical" waste stream; characteristically, the
important waste streams  from  a  plant  will  contain  some
sulfuric  acid and may have a pH of less than two, and there
will be trace-level concentrations of a number of pollutants
associated with ores  (e.g., arsenic, selenium, lead, nickel,
or zinc).

Addition of a  lime  slurry   ("milk  of  lime")   to  such  a
solution  will  precipitate the hydroxides of several of the
metals and  will  reduce  dissolved  sulfate  concentrations
                          83

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through the formation of gypsum, CaSOU.2H2O.  (Formation  of
gypsum  is,  in  some respects, a disadvantage.   The treated
effluent from such a system can well exist in a condition of
supersaturation with  respect  to  gypsum  and  can  readily
precipitate   when   conditions   are  favorable,  sometimes
plugging large pipes with surprising rapidity.)

Iron hydroxide is a  good  flocculant  and  "collector"  for
scavenging  other  ions  from solution, and the formation of
iron hydroxide by the addition of a soluble iron salt  to  a
solution  already  basic or to be made basic by the addition
of an alkali is widely practiced, both in the laboratory and
in practice.  The addition of ferric chloride, for  example,
is a standard procedure in the treatment of sanitary wastes.
The  natural  presence  of  iron  in  effluents  results  in
percentage removals  of  some  ions  by  neutralization  and
precipitation better than would be expected in pure chemical
systems.   Iron  may  have  other  beneficial  effects  too,
although these are difficult to document in the very complex
ionic solutions involved.

In treating an effluent  stream,  sufficient  lime  will  be
added to raise the pH to between 10 and 11.5, and the closed
stream  will  normally  be  conveyed  to  a settling pond to
settle out suspended solids.   Upon  exposure  to  the  air,
carbon  dioxide  is absorbed, gradually reducing the pH.  If
the  retention  time  in  the  pond  is  long  enough,  this
carbonation will reduce the pH to 9.5 or below.   During this
time the precipitated solids will be settling out, so that a
final  effluent  containing  less  than  10 ppm (10 mg/1) of
total suspended solids (TSS) can be achieved.

Some  of  the  solids  are  colloidal  in  nature.   If  the
retention  time  is  not  long  enough,  or if wind and wave
action in the pond stir up the sediments,  the  desired  low
total  suspended solids levels may not be aichieved.  In such
situations, another treatment  technology  can  be  applied.
There are now available a number of organic polyelectrolytes
which,  though  costly per pound, are very effective at very
low concentrations in providing additional flocculation  and
clarification.

Achieving  a  low  total  suspended  solids  content  is not
generally a major problem in treating effluents from primary
zinc   facilities.    Neutralization,   precipitation,   and
settling   should   reduce   total   suspended   solids   to
satisfactory levels in almost all situations.  The principal
problems with effluents from zinc smelters  are  related  to
dissolved   metals,   most  of  which  are  precipitated  as
hydroxides  and  anions,  especially  sulfate.   Removal  of
                       84

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suspended  solids  is  a  problem  only  with respect to the
removal of these precipitates after neutralization.

It has long been known that the solubilities of  many  metal
hydroxides and hydrated oxides is markedly influenced by pH.
Pourbaix  (7)    has  calculated and compiled "Potential - pH
Diagrams" and solubility curves for many elements, based  on
theoretical  considerations.   Curves  based  on  Pourbaix1s
results are shown in Figure 5 for Ag, As, Cd,  Cu,  Fe,  Hg,
Ni,   Pbr   Te,  and  Zn.   These  curves  are,  of  course,
equilibrium curves for pure compounds in simple systems, and
cannot be extrapolated to the complex multi-ion  systems  of
zinc plant waste waters.

While  they  cannot  be  extrapolated  directly to practical
solutions, they do show that there is no single pH at  which
minimum  concentrations  will  be achieved for all elements,
and also that in the pH range  of  interest,  pH  6  to  12,
nearly  all  of the elements pass through a minimum, most of
them in the pH range 9 to 11.

Arsenic has a high solubility plateau, 17 g/1, up through pH
9, and increases rapidly beyond this point.  The  solubility
of  mercury  is also constant, over an even wider range, (pH
3.04 to 14.88), and is also so high, 47  g/1,  that  it  too
does not appear in the graph.

Experimental  values  of metal solubilities as a function of
pH  have  been  presented  by  Hartinger   (8).   Data   from
Hartinger  for  several  metals  are  plotted  in  Figure 6.
Although they differ somewhat from the theoretical values in
Figure 5, including generally having a higher solubility  at
a given pH, the general shapes of the curve are similar, and
again  suggest  that  optimum pH's are in the 9 to 11 range.
These data are for simple  pure  systems.   Solubilities  of
mixed systems as a function of pH are not given.

Information   in   the  literature  indicates  that  cadmium
concentrations can be greatly reduced by precipitation  with
lime.   Jenkins  et al.  (9)  report that freshly precipitated
cadium hydroxide leaves approximately 1 mg/1 of  cadmium  in
solution at pH 8, but this then is reduced to 0.1 mg/1 at pH
10.  Hartinger shows even lower values, 0.002 mg/1, at pH 11
(Figure  6).   High levels of iron appear beneficial for the
removal of cadmium when liming; evidence for the  beneficial
effects of iron has been presented by Marayama, et al.  (10).

Nickel  is also precipitated by neutralizing with lime.  The
nickel hydroxide has a  minimum  theoretical  solubility  of
0.01  mg/1  at  pH  10,  according  to  Jenkins  et al. (9).
                        85

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 1
 E
 o
 C/)
     0.01
    0.001
  0.0001
Figure 5.  Theoretical solubilities of netal ions as a  function of
                                86

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0.01
                     7       8        9       10
                       pH(After 2-hr Standing)
         Figure  6.  Experimentally determined solubilities
                    of metal ions as a function of pH.
                           87

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Kantawala and  Tomlinson  have  reported  the  reduction  of
nickel  concentration  from 100 mg/1 to 1.5 mg/1  (pH 9.9) by
the addition of 250 mg/1 of lime. (11)

Upon neutralization, coprecipitation and adsorption  may  or
may  not  bring  the  concentration  of  a  metal  below its
equilibrium value for the adjusted pH.   Little research  has
been  published  on  the  role  of such parameters as pH, Eh
(oxidation potential), noncommon ions,  and complexing agents
upon the solubilities of the metals  found  in  plant  waste
streams.    For   this  reason,  waste  water  treatment  by
neutralization and precipitation (liming  and  settling)  is
largely  empirical  at  the  present  time,  although  it is
generally  known  that  many  metals  can  be   reduced   in
concentration  to low values by neutralization, while others
are not dependably reduced.

Data on concentrations of metals in treated waste water  are
plotted  in  Figure  7.   These data were supplied by a zinc
producer operating a lime and settle treatment facility  for
mixed plant wastes.  The data represent daily averages of pH
and  soluble  metal  analyses  in 24-hour composite samples.
The treatment facility operates with effluent  ranging  from
pH  6.5 to 10.5 and a level of suspended solids ranging from
nil to a  daily  maximum  of  64  mg/1.   The  data  plotted
represented  29  daily  determinations  over a period of two
months of  continuous  operation  with  an  average  treated
volume  of  2,650  cu  m/day   (0.7 mgd).  The data fell into
various bands  as  indicated  in  the  figure.   The  lowest
concentration  band  developed was that for copper, with the
concentration band descending to the  maximum  pH  included,
giving  levels of 0.05 to 0.15 mg/1 of copper at pH 10.5.  A
band of data for lead showed a similar behavior, covering  a
range  of maximum values of about 0.6 mg/1 at pH 6.5 to 0.05
to 0.2 mg/1 at pH 10.5.  Zinc and  cadmium  showed  somewhat
different  behavior  with  a  band  of  data descending from
concentrations including single values on the order of 30 to
100 mg/1 at pH 6.5 to 7.0 to  the  minimum  values  recorded
(i.e.,  0.1  to 0.3 at pH 10.5).  The plant data for complex
waste water show a general trend in  agreement  with  theory
and  experiment  in that concentration limits appear changed
in complex coprecipitation compared with theoretical values,
and the increase in concentrations of lead and zinc above  a
pH of about 9.2 is not evident in the scatter bands based on
the  plant  data.   Both  of  these  differences may well be
attributable to the differences between static  (equilibrium)
and dynamic systems.  In the latter,  precipitation  may  be
accompanied by instantaneous variations in pH and continuing
separation  of  precipitate  and  supernatant so that solid-
liquid equilibrium is not possible.   The  role  of  complex-
                          88

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                                                                _1.2
   20
o
c
•H
tSI
C
O
 C
 
-------
compound formation and the solubility effects thereof remain
unknown in practical operations.

An  indication  of the effectiveness and performance of this
treatment plant is given in Tables  24  and  25.   The  data
given  are based on composited grab samples taken over a two
day period.  The concentrations of constituents of two input
streams to the treatment,  and  the  concentrations  in  the
effluent  are  given  in Table 24.  The effectiveness of the
treatment in removing various constituents is given in Table
25, which also shows the mass  balance  type  data  used  to
derive the effectiveness level.  All data are based on a two
day sample period, an average operating pH level of 8.2, and
a  suspended  solids  level  of  about  25 mg/1 in the final
effluent.

The positive values given for a few of the constituents  are
subject  to  some  interpretation.   The  positive change in
suspended solids is atypical of plant opercition according to
prior operational data, and  represents  only  the  sampling
period.   The  increase  in  oil and grease is considered an
artifact of sampling  and  calculation,  as  all  input  and
output  concentrations are near the practical minimums.   The
calculated positive change in  dissolved  solids  may  be  a
result of grab sampling or may well be realistic.

Both sulfates and chlorides, components of dissolved solids,
showed  net  decreases  due  to the treatment.   Insufficient
data are available on all cations or anions to  provide  any
confirmation  of  the  observed  dissolved solids data.   All
other constituents were removed to some degree by  the  lime
and  settle treatment.   Over 90 percent removal was observed
for iron, zinc, and cadmium.

Data on the removal of selected constituents from acid plant
blowdown by a lime and settle treatment are given  in  Table
26.   It may be noted that a pH of 11.8 is maintained in the
effluent from this plant.  While no net change in  suspended
solids  is indicated by the data, considerable reductions in
cadmium, lead, and zinc concentrations are achieved.   It may
be noted that the concentrations of lead and zinc associated
with the pH of 11.8 are above those shown in  the  data  for
the  treatment  plant  operating  up to a pH of 10.5.   These
data would seem compatible with the  trends  in  theoretical
data,    although  practical  differences  among  plants  may
overshadow equilibrium considerations.   The high pH of  11.8
is maintained to achieve improved settling of fine suspended
solids  associated with the presence of zinc (i.e., the high
pH represents an optimum balance, for this effluent,  between
metals concentrations and suspended solids)„
                          90

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TAbLE 24.  ANALYSES OF INPUT AND EFFLUENT STREAMS  FOR A
           TREATMENT PLANT
Inputs to Treatment Plant

Parameter
PH
Alkalinity
COD
Total Solids
Dissolved Solids
Suspended Solids
Oil and Grease
Sulfate (as S)
Chloride
Cyanide
Aluminum
Arsenic
Cadmium
Calcium
Chromium
Copper
Iron
Lead
Magnesium
Mercury
Molybdenum
Nickel
Potassium
Selenium
S i Ive r
Sodium
Tellurium
Zinc
Flow,
I/day
(gal/day)
Stream 1,
mg/1
2.5

23.0

135
8
5.0
4,572
105


1
0.6


0.2
19
2

0.00&

0.26

13



25

847,840
( 224,000)
Stream 2,
mg/1
0.5

15

5,o50
13

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TABLE 25. CALCULATED EFFECTIVENESS OF REMOVAL OF VARIOUS CONSTITUENTS^


Parameter
pH
Alkalinity
CCD
Total Solids
Dissolved Solids
Suspended Solids
Oil and Grease
Sulfate (as S)
Chloride
Cyanide
Aluminum
Arsenic
Cadmium
Calcium
Chromium
Copper
Iron
Lead
Magnesium
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silver
Sodium
Tellurium
Zinr
Flow,
I/day
(gal/day)
Input
Stream 1,
kg/day
2.5
--
19.50
--
114.46
6.78
4.24
3,876.
89.02
--
—
0.85
0.51
~
—
0.17
16.11
1.70
—
0.005
-—
0.22
--
11.02
--
—
—
21.20

847,840
(224,000)
Input
Stream 2,
kg /day
6.7
--
28.73
—
10,820.94
24.90
1.92-5.75
4,290.07
463.48
0.19
--
0.19
0.31
--
--
0.06
0.33
3.44
--
0.008
— *•
0.59
--
1.03
—
—
—
2,035.87

1,915,210 2
(506,000)
Total
Input ,
kg /day
„.
--
48.23
--
10,935.40
31.68
6.16-9.99
8,166.07
552.50
0.19
--
1.04
0.82
--
--
0.23
16.44
2.14
--
0.013
--
0.81
—
12.05
—
--
—
2,056.89

,763,050
(730,000)
Total
Output ,
kg/day

—
46.97
--
12,392.28
688.00
11.05
6,136.73
472.48
0.28
--
0.28
0.06
--
—
0.06
0.17
0.41
—
0.010
_-
0.36
—
4.97
--
--
—
138.15

2,763,050
(730,000)
Net
Change (-b-)
kg /day

--
-1.26
--
+1,456.88
+657.00
1.06-+4.89
-2,029.34
-80.02
—
--
-0.76
-0.76
—
--
-0.17
-16.27
-1.73
—
-0.003
--
-0.45
—
-7.08
—
--
--
-1,918.74

—
— —
Net
, Change (b)
percent

--
-2.6
—
+13.3
+2,070.
+49-+17
-24.8
-14.5
--
—
-73.1
-92.7
_.
—
-73.9
-98.97
-80.8
--
-23.1
~ ~
-55.6
—
-58.8
—
--
--
-93.3

--
™" ™
(-a'  Calculations for each entry = -Sp x -^— x 1 x 10





'  '  Negative numbers indicate removal  by treatment.
                                     "6
                                          =  kg/day;  see  Table  24    for mg/1 values.
                             92

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               TABLE 26.  EFFECTIVENESS OF TKLJffiMtNT OF ACID PLAOT
                                    BY LIME >\ND SETTLE
                                                                t ct Lo£.diir.
                                                        fret
Parameter
                  I nt ake,     D i s ch ax vs.,    Ch ar<;,»
                    o/I
    ^c-,   kg/Metric    Ib/Short
per cert	   ton          ton
pH 2.8
Alkalinity
COD
Total Solids
Dissolved Solids 5,400
Suspended Solids 2CO
Oil and Grease
Sulfate (as S)
Chloride
Cyanide
Aluminum
Arsenic
Cadmium 33
Calcium
Chromium
Copper
Iron
Lead 48
Magnesium
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silver
Sodium
Tellurium
Zinc 1,500
Flow,
I/day 1,308,096
(gal/day) (345,600)
_1LJ' i- -_r . - _ -^.- 	 	 . - 	 	 -—,-... . -..„.— ....i. — ... : «... 	 — — — .. -
11.3



2,500 -2,900 -53.7
100 0 C






0.03 -32.97 -99.9




6.9 -41.1 -35.6









2.6 -1,497.4 -99.3



                                     93

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The concentrations of various constituents from a  lime  and
settle treatment plant treating mixed plant wastes are given
in  Table  27.  Here the average value of pH is 9.6, and the
average values for zinc and cadmium fall  within  the  range
previously  indicated  by the plot of data in Figure 7.  The
values for lead fall somewhat above the prior data.

A new  treatment  facility  at  one  domestic  primary  zinc
smelter  is  currently  being  lined-out.  This new facility
will use a lime and settle method on the total  plant  waste
water,  which  includes the primary zinc plant process waste
waters (745 gpm),  the  waste  water  of  its  primary  lead
smelter,  and  the  waste  water  from integrated mining and
milling  operations.   The  anticipated  concentrations   of
selected  process  waste water pollutants from this facility
are as follows:

              Process waste water          Concentration
              	pollutant	           	(212/1)	

                    TSS                         60
                    Cd                           0.5
                    Hg                           0.006
                    Pb                           1.0
                    Zn                           1.7

Except for the higher value indicated  for  total  suspended
solids,  the  anticipated  concentrations  for the remaining
pollutant characteristics fall within  the  range  shown  in
Table 27.

Mercury and Selenium Removal

Some   domestic   and  imported  zinc  concentrates  contain
appreciable  trace   quantities   of   mercury.     Operating
experience  at  several  currently  operating  primary  zinc
smelters, which either  routinely  or  occasionally  process
these high mercury-content concentrates, has shown that most
of   the   mercury   is   volitilized   during   the   first
pyrometallurgical step.  This step is roasting,  the offgases
from  which  conventionally  proceed  to   a   metallurgical
sulfuric  acid  plant.   Two smelters have found that much of
this   mercury   accumulates   in   the    acid    plant-gas
preconditioning  equipment  of the open and packed weak acid
scrubber and the mist precipitators  (coke  boxes  at  older
acid plants).

One smelter developed a mercury recovery facility,  comprised
essentially  of  an indirectly-fired,  continuous-feed rotary
kiln with a condenser system.   The charge  material  to  the
                          94

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  TABLE 27.   EFFLUENT CONCENTRATIONS FROM LIME AND SETTLE
             TREATMENT  OF MIXED WASTES
Concentrations^ mg/l^a)
Constituent
PH
Total Solids
Sulfur
Chloride
Cadmium
Lead
Selenium
Zinc
Minimum
9.3
1430
250
140
0.03
0.5
0.8
1.0
Maximum
10.8
4050
730
490
0.7
1.8
5.0
8.8
Average
9.6
-
650
480
0.3
0.7
-
2.0
(a)   Except  for  pH .
                         95

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kiln  was spent coke, taken from the coke boxes of the older
metallurgical  sufluric  acid  plants.   Another   currently
operating  smelter  removes  a "high-mercury" purge from its
acid plant scrubber  (i.e., a scrubber having  two  sections,
one  for gas humidification and the other for scrubbing)  and
washdown from its mist precipitators, holds this effluent in
a tank, and adds zinc  dust  to  precipitate  out  the  vast
majority  of  both mercury and selenium.  A similar practice
is used by an European company.
              Additional Treatment Technology

Additional treatment methods, which could  be  employed  for
further  reduction  of  pollutants  from process waste water
discharges include:  (1)  hydrogen  sulfide  treatment,  (2)
reverse osmosis,  (3) evaporation, and (4) chemical fixation.

Hydrogen Sulfide Treatment

Hydrogen-sulfide  treatment would be an effective method for
the removal of heavy metals as sulfide  precipitates,  which
are known to have extremely low solubility.  Solubilities of
the  sulfides  of  typical  heavy  metals found in the waste
water discharges from the primary zinc industry are shown in
Table 28.  Since the solubilities of the sulfides are higher
at low pH, the precipitation reaction should be carried  out
at a neutral or alkaline pH.

Some  investigative  studies involving the basic application
of the hydrogen sulfide (H2S) precipitation process to  zinc
smelter  process  waste  waters  are  being performed by one
domestic primary zinc company.  Even though no  pilot  plant
studies  have,  as  yet,  been  conducted,  the  bench scale
experimental data to date have indicated that the  following
treated   pollutant   parameter   concentrations   could  be
achievable:
Process waste water
       TSS
       As
       Cd
       Hg
       Se
       Zn
       pH
                                        Treated concentration
                                              0.01
                                              0.01
                                              0.0005
                                              0.10
                                              1 . 0
                                              6.0 - 6.4
                               96

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TABLE 28.  SOLUBILITIES OF METAL SULFIDES
                    Solubility,
  Metal       Neutral Solution       Low pH





   Ni               < 1              100,000




   Cd               < 1                5,000




   Pb               < 1                   70




   Cu               < 1                < 1




   Hg               < 1                < 1
                  97

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The company  considers  this  potential  application  to  be
specific  to  its  own  zinc concentrates, which have a high
magnesium content.  Problems associated with this  treatment
process  are  stated  by  the  company  to be based upon the
complexity of the process, as well  as  the  resultant  high
economics.

Reverse Osmosis

Reverse  osmosis   (RO)  is  a process, whereby a waste water
stream is passed at pressures from 34 to  136  atm   (500  to
2000  psia)  over  a  membrane.  The membrane is cast from a
solution of  cellulose  acetate  and  has  the  property  of
allowing  passage  of  water through the film, but rejecting
ions.  The permeate is almost completely of ionic  material,
while  the concentrate having almost all of the ions must be
further treated.  The advantage of RO is that recoveries  of
75  to  90 percent of the inlet water can be obtained, which
results in only a small fraction of the stream needing to be
treated further by chemical means or by evaporation.

Unfortunately, the application of RO can be done only  under
fairly  stringent  waste  water  conditions.   The suspended
solids content of the inlet water should  be  low  (probably
less  than  200  ppm), otherwise/  a coating will develop on
the membrane surface, slowing down the process.  The  pH  of
the  inlet  water is fairly critical and should be from 6 to
7.5 for optimum results.  Waste water outside of this  range
will tend to cause rapid hydrolysis of the acetate groups in
the  membrane  and  subsequent  failure  of  the  film.    In
addition, quantities of slightly soluble materials  must  be
kept  low to prevent fouling of the film by precipitation of
these materials on the film.

In the case of the waste water from the zinc  smelters,   the
concentration  of ions,  with the possible exception of zinc,
is  low  enough  for  reverse  osmosis   treatment   to   be
considered.

A  test  program to determine the applicability of RO to the
waste stream would be required prior to the  application  of
this  technique.   At  present,  RO  must  be  considered as
unproven technology.

Evaporation

Evaporation is comparable with reverse osmosis in  cost  and
effectiveness  for waste water treatment.   The technology is
more advanced for  evaporation  than  for  reverse  osmosis.
                           98

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Evaporation  is  currently  used  on  a commercial scale for
desalination of brackish water or  seawater  and  for  waste
water  treatment.   The  process  used most commonly for the
above  applications  is  the  multiple-effect   evaporation/
distillation   process.   With appropriate control of pH and
suspended solids to minimize the fouling  of  heat  transfer
surfaces,  this  type of evaporation process can be employed
for waste water treatment with an economic  usage  of  fuel.
Evaporative  treatment  usually  produces concentrated waste
liquor, which must be disposed of  by  complete  evaporation
using  a separate evaporator or by some other means, such as
chemical fixation, which is discussed below.

Chemical^Fixation

Chemical fixation is a  process  for  detoxifying  hazardous
liquid wastes by means of the reaction of chemical additions
with   the   waste   material   to  form  a  chemically  and
mechanically stable solid.  The process can be used for  the
chemical  fixation  of  polyvalent  metal ions in stable and
insoluble inorganic compounds.  Monovalent cations and  many
anions  are  physically  entrapped  in  the matrix structure
resulting from the reaction process.  Chemical  fixation  is
costly  when  compared  with the treatment methods discussed
thus far and probably would  rarely  be  used  for  directly
treating  the  large volume of process waste water effluents
from the primary zinc  operations.   The  process,  however,
might prove useful and economic for the ultimate disposal of
concentrated liquor wastes generated from reverse osmosis or
evaporative treatment.
                             99

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                        SECTION VIII

        COSTS, ENERGY, AND NONWATER QUALITY ASPECTS

                        Introduction
This  section  deals  with  the  costs  associated  with the
various treatment methods  available  to  the  primary  zinc
industry  for  the  reduction  of  the pollutant load in the
process waste water effluents.  In addition, other  nonwater
quality aspects of waste water treatment are discussed.

The  treatment  cost study was performed on a plant-by-plant
basis on six (Plants B, C, D, E, F, and G)  of  the  existing
primary zinc plants.  One plant (Plant A),  excluded from the
cost  study,  is a plant located in the Southwest, where the
arid climate permits this plant to operate with no discharge
of process waste water through solar evaporation.

The  costs  for  the  present  treatment  practices  in  the
industry  were  obtained  directly from the six plants.  The
costs  for  additional  waste  water  treatment  beyond  the
current  practices  were  estimated  by using published cost
data, rather than the cost  data  supplied  by  the  plants.
This  approach  was  considered  necessary  in  view  of the
findings from the plant survey  that  either  the  pertinent
cost  data  were  not  available from the plants or the cost
data supplied by the plants show substantial variation owing
to the differences among the plants with  respect  to  water
usage, treatment, and cost reporting procedure.
                 Basis for Cost Estimation
Data  on  capital costs and annual costs for present control
practices were obtained from selected  zinc  plants.   These
data  were  modified,  as needed, in the following manner to
put all costs on a common basis.

          (1)  The capital costs reported were converted
               to 1971 dollars by using the Marshall &
               Swift Index (quarterly values of this
               index appear in the publication Chemical
               Engineering, McGraw Hill).

          (2)  The annual costs were recalculated to
               reflect common capitalized charges.
               To do this, the annual costs were
                          101

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               calculated by using a factor method
               as described below:

                 Operating and maintenance - as
                   reported by plants,
                 Administrative overhead - 4 percent
                   of operating and maintenance,
                 Depreciation - 5 percent of the 1971
                   capital.
                 Property tax and insurance - 0.8
                   percent of 1971 capital.
                 Interest - 8 percent of the 1971
                   capital.
                 Other - as reported by plants.

In the following discussion, capital costs are expressed  in
$/annual  kkg  ($/annual  ton)   and  annual  costs  in $/kkg
($/ton)  based on annual production capacity of zinc metal or
its equivalent.
              Economics of Pgesent_Control and
                    Treatment Practices
The cost data supplied by the plants on current control  and
treatment   practices  in  the  primary  zinc  industry  are
summarized in Table 29.  Data reflects the difference  among
the  plants  with  respect  to  processes,  water  usage and
conservation, waste water treatment, extent of  plant  water
circuit  revisions,  and cost reporting procedures employed.
A description of present treatment practices and  associated
costs are given below for each plant.
Plant B
Discharges  of  process  waste  water  from  this plant were
reported as follows:
                                      Di sc ha r ge_ Rates
                        E_ff luent       u
   1.  Acid plant blowdown              850       (156)
   2.  Celestite conversion
        a.  sulfide circuit              33         (6)
        b.  oxide circuit                82       (15)
   3.  Metal cooling                     76       (14)
   4.  Dust washing                      49         (9)
                         102

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TABLE  29.  CAPITAL AND  ANNUAL  COSTS OF  PRESENT  WASTE  WATER
            TREATMENT PRACTICES  IN PRIMARY ZINC  INDUSTRY
Annual Zinc
Production, Capital
Plant kkg Total, $
Designation (tons)
M
S B 97
(108
C 64
(70
D 110
(121
E 104
(115
F 226
(250
G 45
(50
,956 3,176,000
,000)
,149 3,580,000
,727)
,313 306,900
,624)
,300 492,000
,000)
,750 3,113,600
,000)
,350 328,000
,000)
Cos t s
$ / annual kkg
($/annual ton)
32 .42
(29.40)
55. 81
(50.61)
2.78
(2.53)
4. 72
(4.28)
13.73
(12.45)
7.23
(6.56)
Annual Costs
Total, $/year $/kkg
($/ton)
828,000 8.45
(7.66)
567,000 8.83
(8.01)
112,500 1.02
(0.12)
233,000 2.23
(2.02)
677,900 2.99
(2.72)
98,600 2.17
(1.97)

-------
   5.  Dross leaching
   6.  Baghouse dust leaching

                          TOTAL
   98
  J.20.

1,308
 (18)
_I221

(240)
Waste  water  treatment  processes  include  settling  in  a
central  lagoon  and  heavy metal removal by lime treatment.
The acid plant blowdown is discharged directly to  the  lime
treatment  plant.   All  other process waste water effluents
are discharged first to the  central  lagoon.   The  central
lagoon   also   receives   indirect  cooling  water,  boiler
blowdown, and treated sanitary waste water, with a  combined
discharge  rate  reported  at 1,466 cu m/day  (269 gpm).  The
overflow from the central lagoon, with a combined output  at
1,924  cu  m/day  (353  gpm),  is  discharged  to  the  lime
treatment plant.  The total inflow  to  the  lime  treatment
plant is 2,774 cu m/day (509 gpm).

Cost  data  were  supplied  by  the  plant on capital costs,
operating, and maintenance costs.  Cost data are  summarized
below.

Basis:  Zinc Production = 97,956 kkg/yr  (108,000 tons/yr)

         £a£ital_Costs                     1971 $

         Lime treatment plant               496,000

         Central settling lagoon            595,000

         Plant water circuit revisions    1,496,000

         Miscellaneous                    	589,000

           Total Capital Costs            3,176,000

           Jf/Annual kkg                     32.42

           ($/Annual ton)                   (29.40)
         Annual_Costs

         Operating  and maintenance

         Overhead

         Depreciaiton
      374,800

       15,000

      157,000
                           104

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         Interest                           251,000

         Tax and insurance                	2^xl££

           Total Annual Costs              $828,000

           $/kkg                             8.45

           ($/ton)                           (7.66)
Plant C
This   plant   indicated   that  it  was  planning  a  major
modification of plant water usage and  process  waste  water
treatment.   A  mercury-selenium removal system is currently
in operation.  Conservation of process waste water  measures
include  the  conversion of vacuum evaporators, operating on
electrolyte cooling, to a cooling tower; a cooling tower  to
minimize  the blowdown from casting; and the minimization of
acid plant blowdown by efficient  cooling  tower  operation.
The  status  of this company's progress toward a new process
waste water treatment facility does not allow the listing of
the possible economics as  "present  control  and  treatment
practices."   The   two   alternatives,   which   have  been
investigated include a  lime  and  settle  treatment  and  a
hydrogen  sulfide  precipitation  treatment.  Currently, the
company is investigating the possibility of  lime  treatment
with a sodium silicate flocculent.

The  waste  water  conservation modifications, scheduled for
implementation in 1974, will reduce  current  plant  process
waste water sources to the following:

                                      Discharge Rates
    Process, WasteTTWaterr Effluent      cujoQ/day   _(ggm)

   1.  Acid plant blowdown              741       136
   2.  Preleaching liquor bleed       	392     	H!l_
                   TOTAL              1,133       (208)

The  current  "control and treatment practice" economics for
both the mercury-selenium collection system and the  process
waste water flow volume reduction are presented below:

    Basis:  Zinc Production = 64,149 kkg/yr  (70,727 ton/yr)
                            105

-------
    Capital Costs                            1971 $

      Mercury-selenium removal               65,000

      Electrolyte cooling (conversion
        to cooling tower)                 2,460,000

      Other water conservation
      Total capital costs                $2,935,000

      $/Annual kkg                           45.90

      ($/Annual ton)                          (41.40)


    Annual Cost s

      Water conservation                     41,000

      Mercury- selenium removal               16,000

      Overhead                                3,000

      Depreciation                           148,000

      Interest                               235,000

      Tax and insurance                   ____ S^CKM)

      Total Annual Costs                   $467,000

      $/kkg                                  $7.29

      ($/ton)                                 ($6.58)
Plant D
This  zinc  plant  is  a  part  of a complex operation.  The
entire  plant  complex  is  currently  in  the  process   of
extensive  modificiation  of  water usage and treatment with
the installation of a  new  central  waste  water  treatment
facility,  which  will  serve the entire plant complex.  The
modification is scheduled to be completed in 1974.

Under the modified plan for waste water treatment, the  zinc
plant  will  discharge  4,060  cu m/day (745 gpm)  of process
                          106

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waste water to the central treatment facility, consisting of
the following effluents:

                                      Discharge_Rate
    Process Waste Water Effluents     SU—JS/d^i  JL2S21L
    1.  Acid plant blowdown             2,180     (400)
    2.  Miscellaneous wet scrubbers     1,090     (200)
    3.  Preleaching liquor bleed          545     (100)
    4.  Miscellaneous drainages         __ 245   ___ [IJil
         TOTAL                          4,060     (745)
In addition to the above plant discharges destined  for  the
central  treatment  facilities,  the  zinc  plant  will also
discharge 1,362 cu m/day  (250 gpm) of indirect cooling water
to a nearby operation and an additional 4,115 cu m/day   (755
gpm)  of indirect cooling water to a creek without treatment.

The  central  treatment  facility  consists  of  a  117 acre
central impoundment area  and  a  central  treatment  plant.
Waste water discharges from the plant complex, including the
zinc  plant,  are collected in the central impoundment area.
The combined waste water is  withdrawn  from  the  pond  and
treated  in  the  central  treatment  plant.   The treatment
process  employed  is   lime   addition   and   liquid/solid
separation by settling in a thickener.  The underflow sludge
from  the  thickener  is returned to the central impoundment
area for permanent disposal.  The  clarified  overflow  from
the thickener is both discharged to a creek and recirculated
to the plant's concentrator.

The costs for the central treatment facility assigned to the
zinc  plant  include:   (1)   the retrofit cost for the water
circuit revisions in the zinc plant,  (2) the  cost  for  the
central  impoundment area apportioned to the zinc plant, and
(3)  the cost for the central treatment plant apportioned  to
the zinc plant.  Since only the total costs are known or can
be  calculated  for  the  central  impoundment  area and the
central treatment plant, the  costs  assigned  to  the  zinc
plant  were  estimated by multiplying the total costs by the
ratio of the waste water discharge from the zinc  plant  and
the  total  waste  water discharge from the plant complex to
the central impoundment area.  The total waste  water  input
to  the  central  impoundment area is estimated at 31,174 cu
m/day (5,720 gpm), which consists of:   (1)   4,060  cu  m/day
(745  gpm)   from  the zinc plant, (2) 572 cu m/day (105 gpm)
from a lead smelter, (3)  6,595 cu m/day (1,210 gpm)   from  a
mill  concentrator, and (4)  16,568 cu m/day (3,040 gpm)  from
a mine.
                           107

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Under the above assumption, the capital and annual costs for
the zinc plant portion of  the  central  treatment  facility
were  estimated  as  follows  from  the data supplied by the
plant.
       Basis:  Zinc Production = 110,313 kkg/yr
               (121,624 tons/yr)
       Capital Costs

         Central treatment plant

           Total
           Zinc plant portion

         Central Impoundment Area

           Total
           Zinc plant portion

         Zinc plant retrofit costs

           Total Zinc Plant Portion

           $/Annual kkg

           ($/Annual ton)

       &Qnual_Costs

         Central treatment plant and
           impoundment area

           Total Operating and
             Maintenance
           Zinc plant portion

           Overhead
           Depreciation
           Interest
           Tax and insurance

           Total Operating Costs

           $/kkg

           ($/ton)
  1971 $
$518,000
  75,600
$644,000
  94,000

_ 112x3 00.,

f306,900

 2.78

(2.53)

$/Year
$656,000

  95,500

   3,800
   4,800
   7,600
  	800

$112,500

   1.02

   (0.92)
                            108

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This plant comprises two production  facilities  located  at
two  separate  sites  with separate water circuits.  The two
facilities are designated as Plant E-l and Plant  E-2.   The
two plants are discussed separately.
fiant^EXL .  Discharges of process water from Plant E-l were
reported as follows.

                                      Discharge_Rate
   P£2£§ss_Waste_Water_Ef fluent    £U_m/daY      _IH£J2}L_

   1. Acid plant blowdown           1,090-3270    (200-600)
   2. Sinter plant humidifier       _ 16 3-27 2_   _J3_0;-50l_
            TOTAL                   1,253-3,542   (23C-650)
The above process waste water  effluents  are  combined  and
treated  by  lime precipitation.  Indirect cooling water and
plant runoff water are discharged  without  treatment  to   a
creek.

Lime  treatment  of  the process water effluents consists of
precipitation of metal hydroxides by lime addition   followed
by  clarification  in a thickener and settling lagoons.  The
underflow  sludge  from  the  thickener,  containing  metal
hydroxide  precipitate,  is  either  returned to the process
(roaster or sinter plant) or discarded on  land  within  the
plant.

The costs for the lime treatment process were estimated from
the cost data supplied by the plant.

     Basis:  Total Zinc Production = 104,300 kkg/yr
              (115,000 tons/yr)

     Ca£ital_Costs                      1221-Jl


     Total Capital Costs               $220,000
     Annual_costs

       Operating and maintenance          117,000
                           109

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       Overhead

       Depreciation

       Interest

       Tax and insurance

         Total Annual Costs


Plant ___ E-2.  The only source of process water discharge from
Plant E-2 is a bleed  from  scrubbers  used  in  the  retort
operation.   The scrubber water is recycled.  The bleed from
the recycle circuit reported at 136 to 272 cu m/day   (25  to
50  gpm)   is  treated by settling in a pair of concrete bins
and discharging to a  creek.   Indirect  cooling  water  and
plant runoff water are discharged without treatment.

The   water  treatment  system  includes  recycling  of  the
scrubber water and settling of the scrubber bleed,  as  well
as  recycling  of  water used for quenching of spent furnace
charge.  Data were supplied by  the  plant  on  the  capital
costs  for  the treatment system, excluding the two concrete
settling bins, and annual operating and  maintenance  costs.
Treatment costs are summarized below:

      Basis:  Zinc Production = 104,300 kkg/yr
              (115,000 tons/yr)
      Ca£ital_Costs

        Treatment system                   216,000

        Concrete bins                       56,000

          Total Capital Costs              272,000


      Annual^Cgjjts

        Operating and maintenance           41,700

        Overhead                             1,700

        Depreciation                        13,600

        Interest                            21,800

        Tax and insurance                 _____ 2X20_0_

          Total Annual Costs              $  81,000
                            110

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Total E-1 and E-2.
         Capital Costs  (E-l+E-2)

         $/annual kkg

         ($/Annual ton)

         Annual Costs  (E-l+E-2)

         $/kkg

         ($/ton)
492,000

 4.72

(4.28)

233,000

 2.23

(2.02)
Plant F
Discharges  of  process  waste  water  from  this  plant were
reported as follows:
                                             Discharge^Rate
                        Effluents
1.  Scrubbers  (2 streams)
    a. first scrubber  (High grade)
    b. second scrubber  (P.W.-*-
           Intermediate)
2.  Dust Control Scrubber
3.  Gas cooling and scrubbing
4.  A bleed of spent liquor from
      cadmium leaching

                             TOTAL
                                            2,180

                                           10,900
                                             708
                                            2,180

                                           	218

                                           16,186
              (400)

            (2,000)
              (130)
              (400)

            	140).

            (2,970)
Process water effluents are  currently  treated  by   various
chemical  and  physical methods, which include pH  adjustment
with lime or sodium hydroxide and settling  in  a   series   of
concrete  basins,  ponds,  and  lagoons.  All of the  process
water effluents after treatment are  impounded  in a  final
settling  lagoon.  The latter also receives  indirect  cooling
water and plant runoff water, neither of which  is treated.
An overflow from the lagoon is discharged to a river.
                         Ill

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There  are two furnace offgas scrubbers, designated as first
and second, producing separate effluents on  a  once-through
basis.   The  effluent  from  the  first furnace scrubber is
combined with the effluent from the dust  control  scrubber,
and  the  combined  stream is treated by a combination of pH
adjustment  with  sodium  hydroxide  and   settling   before
discharge to the final settling lagoon.

The  spent  leach  liquor  bleed  from  the cadmium leaching
operation  is   first   treated   for   cadmium   and   zinc
precipitation  by  lime  addition and seguently for residual
cadmium by cementation.  The spent leach liquor is  combined
with  the effluent from the second furnace scrubber, and the
combined stream undergoes settling before discharge  to  the
final  settling  lagoon.   (The effluent used as the cadmium
leach liquor was originally the acid plant blowdown).

The effluent from the gas scrubber (3 above)   is  discharged
directly  on  a  once-through basis without treatment to the
final settling lagoon.

Data were supplied by the plant on  the  capital  costs  and
operating  and  maintenance  costs for various components of
the present treatment  system.   Cost  data  are  summarized
below:

      Basis:  Zinc Production = 226,750 kkg/yr (250,000 tons/yr)

      SsMtaijCpjsts                             .JL22I-IL

        Settling ponds                          440,000

        Slag plant water recirculation           33,800

        Cadmium control treatment               131,2CO

        Final settling lagoon                   328,000

        Cooling facilities                      662,600

        Effluent monitoring                     103,100

        Miscellaneous system                 	22j.HQ.Q.

          Total Capital Costs                 1,778,100

          $/Annual kkg                          7.84

           ($/Annual ton)                       (7.11)
                          112

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      £nnual_Costs

        Operating and maintenance              184,600

        Overhead                                 7,400

        Depreciation                            88,900

        Interest                               142,200


        Tax and insurance                    ___ .Iii.c20p_

          Total Annual Costs                   437,300

          $/kkg                                  1.93

           ($/ton)                              (1-75)

Plant  F is currently in the process of reducing its process
waste water usage from 26,000 1/kkg  (6,250  gal/ton) ,  based
on  16,200  cu  m/day  (2,970  gpm)  and  620  kkg/day   (685
tons/day)  zinc, to 3,945 1/kkg (945 gal/ton) , based on 2,450
cu m/day (450 gpm) and the same zinc production rate.   This
reduction   will   be   achieved   through   a   90  percent
recirculation of the prime western and intermediate  furnace
washer  water,  the high-grade furnace washer water, and the
carbon monoxide scrubber water.  The  costs  for  this  flow
reduction scheme follow:
     Piping and pumping of 90 percent
     recycle of:

       High-grade furnace scrubbers                75,500

       P-W and Intermediate furnace scrubbers      135,000

       CO scrubber                                 75, COO

       Clarification of recirculated flow        1,000,000

       Oil and Grease removal from CO water    ____ 50^000

         Total Capital Costs                     1,335,500

         ^/Annual kkg                                5.89

          ($/Annual  ton)                             (5.34)
                           113

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     Annual Costs

     Operating and maintenance:

       Recycle, pumping and piping                  14,000

       Recycle, clarification                       40,000

     Overhead                                       2,200

     Depreciation                                   66,700

     Interest                                     107,000

     Tax and insurance                           __ .HLt.2CK)

        Total Annual Costs                        240,600

        $/kkg                                       1.06

        ($/ton)                                     (0.97)

Total CurrentContrglandTreatment Costs .
Plant_G
       Grand Total                               3,113,600

       $/Annual kkg                                  13.73

       (I/Annual ton)                               (12.45)

     Operating Costs                                1971$

        Grand Total                                 677,900

        $/kkg                                         2.99

        ($/ton)                                      (2.72)
This  plant  is  currently  converting its horizontal  retort
plant to an electrolytic zinc plant.  Its existing   roasters
                          114

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and  acid  plant  will remain in use.  Discharges of process
water from this plant were reported as follows:
   Process_Wagte Water Effluents

1.  Roaster gas sprays
2.  Storage pond overflow

                          TOTAL
	Discharge_Rate
cu_m/day
817 - 1,226
	0_-	545

817 - 1,771
(150 - 225)
	IO_Z_1CO)_

(150 - 325)
The process water effluent is treated by  lime  addition  to
remove  heavy metals as a hydroxide precipitate.  The sludge
produced from  lime  treatment  is  currently  dewatered  by
filtration and returned to the sinter plant.

Cost  data  were  supplied by the plant on the capital costs
and  the  operating  and  maintenence  costs  for  the  lime
treatment plant.  Treatment costs are summarized below:
      Basis:  Zinc Production = 45,350 kkg/yr
              (50,000 tons/yr)
      Cagital^Costs

      Total Capital Costs

        $/annual kkg

        (^/annual ton)
     .1971	$_

     $328,000

        7.23

        (6.56)
      Annuaj._Cgsts

        Operating and maintenance

        Overhead

        Depreciation

        Interest

        Tax and insurance

          Total Annual Costs

          $/kkg

           ($/ton)
       51,300

        2,100

       16,400

       26,200

       -2x600

       98,60C

        2.17

        (1.97)
                           115

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            Economics of Additional_Control_and
                    Treatment^Practiceg

Of the six primary zinc facilities which should be operating
in  1977,  one  plant,  by  virtue  of  current  control and
treatment practices, meets the proposed effluent limitations
guidelines derived in this development document.   This  one
plant,  therefore,  is  not  economically  impacted  by  the
proposed limitations.  One other plant currently  meets  the
1977  recommendations, but must resort to additional control
and/or treatment practices to comply to  the  proposed  1983
limitations.

The  economics  of  the  necessary  additional  control  and
treatment  practices  for  the  remaining   facilities   are
discussed in the ensuing paragraphs.

Plant B

This  electrolytic  zinc plant generates 1,308 cu m/day (240
gpm)  of process waste water.  Liming  and  settling  is  the
treatment  practice  employed  on this effluent.  Based on a
production rate  of  268  kkg  (296  tons)/day,  this  plant
currently  has a process waste water discharge rate of 4,880
1/kkg (1,170 gal/ton), which is  below  the  1977  and  1983
recommendations  of  8,350  1/kkg   (2,000 gal/ton)  and 5,425
1/kkg (1,300  gal/ton),  respectively.   As  shown  in  this
document,  zinc  concentrations  after  treatment  have been
reported to be high.  Plant personnel indicate that low zinc
concentrations are difficult to maintain  primarily  because
of low pH (acidic) surges entering the treatment facility as
acid  plant blowdown.  One possible solution to this problem
is the addition of a surge tank  to  the  plant's  lime  and
settle  treatment  facility.   Costs for this tank, which is
lined and has a one-week capacity, are:

     Ca2ital_Costs                             _12Zi_JL

     Surge tank   (241,000 cu ft cap.)            33,000

     $/Annual kkg                                0.34

     ($/Annual ton)                             (0.30)

     Operating Costs

     Total  (25% of capital)                       8,300
                        116

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     $/kkg                                       0.08

     ($/ton)                                     (0.08)

Plant C

Plant  C  is  an  electrolytic zinc plant which is currently
reducing the volumetric  flow  rate  of  its  process  waste
water.     After   the   new   control  practices  have  been
implemented,  the anticipated  production  of  process  waste
water  will  be  about  6,440  1/kkg (1,550 gal/ton).  These
control practices, the economics  of  which  were  discussed
previously  in  this  section,  are  considered  as  current
practice for this  plant  and  are  also  considered  to  be
specific  to  this  one  plant,  due  to the usage of vacuum
evaporators.    The  plant  is  anticipating   the   possible
application  of  either  a  lime and settle treatment with a
sodium  silicate  flocculent,  or  a  sulfide  precipitation
treatment.   Resulting  effluent  data  from these potential
applications are not yet to pilot plant stage, but  economic
investigations   have  been  conducted  for  each  treatment
system.  The results are tabulated below:

Lime and Settle Treatment.

    Capital Costs                             1971  $

      Lime facility                          1,230,000

      $/Annual kkg                             $19.20

       ($/Annual ton)                          ($17.30)

    Annual Costs

      Lime treatment                           503,000

      $/kkg                                     $7.85

       ($/ton)                                  ($7.10)


Sulfide Precipitation Treatment.

    Capital Costs                             1971  $

      H2_S treatment                          2,620,000

      $/Annual kkg                             $41.00
                            117

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       ($/Annual ton)                          ($37.00)

    Annual Costs

      H2_S treatment                            777,000

      $/kkg                                    $12.20

       ($/ton)                                 ($11.00)

The above cost estimates  have  been  made  by  the  smelter
operators  and  are  considered  to  be highly conservative.
Utilizing the costs  of  other  lime  and  settle  treatment
facilities,  such  as those for Plant F, the following costs
for Plant C, which are used  in  this  analysis,  have  been
estimated:

    Capital Costs      "                         1971 $

    Lime and settle facility                   500,000

    $/Annual kkg                                $7.80

    ($/Annual ton)                              ($7.04)

    Annual Costs

    Lime and settle facility                   152,000

    $Akg                                       $2.37

    ($/ton)                                     ($2.16)

Plant D

Current  data  indicate  that  Plant D's new lime and settle
treatment plant receives 4,060 cu m/day (745 gpm)  of process
waste water from its  electrolytic  zinc  operation.   After
passage   through  the  treatment  plant,   approximately  35
percent  of  the  total  input  flow  is  recycled  to   the
integrated  flotation  operation.   Based  upon a production
rate of 302 kkg (333  tons)/day,  the  process  waste  water
discharge  rate is about 8,350 1/kkg (2,000 gal/ton), which,
along   with   lime   and   settle    pollutant    parameter
concentrations,  indicates  compliance to the 1977 criteria.
A flow value reduction to 5,425 1/kkg (1,300 gal/ton) and/or
pollutant concentration values less than  those  recommended
for  lime  and  settle  by  this  document  would have to be
achieved in order to comply to the recommended 1983 effluent
                           118

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limitations.  From a  control  technology  standpoint,  this
reduction  could  be  achieved through increased recycle and
reuse  in  other  on-site  operations,  such  as  the   mill
concentrator  and  the fertilizer plant.  Replacement of wet
scrubbing devices with dry  collection  devices  would  also
ensure  compliance.   Since  cost  data  are  not  currently
available  for  these  control  measures,   the   costs   of
artificially  evaporating  the necessary flow value decrease
(i.e.,   (2,000   minus   700   equals   1,300)gal/ton,   as
recommended)  are used to typify the highest compliance cost
which this plant should have:

     Cap,ital_Costs                                   _19jU_!_

     Incremental control and/or treatment           $909,000

     $/Annual kkg                                     $8.25

      ($/Annual ton)                                   ($7.45)

     Annual Costs

     Incremental control and/or treatment           $414,000

     $/kkg                                             3.76

      ($/ton)                                           (3.40)
Portion E-1 of Plant E produces  calcine  and  sinter.   Two
process waste water streams, the acid plant blowdown and the
sinter  plant  humidifier,  account  for a range of 1,253 to
3,542 cu in/day (230 to 650 gpm) .  After  lime  precipitation
of  this  effluent,  data  indicate  a  high total suspended
solids concentration.  Therefore, further  clarification  to
reduce  the TSS concentration to the recommended value of 25
mg/1 may be in order.  Portion E-2 of  Plant  E  contains  a
small  process  waste  water  source,  the  vertical  retort
scrubber purge.  This effluent, ranging from 136 to  272  cu
m/day  (25  to  50  gpm)   has high metal values.  Therefore,
liming and settling of this small stream may  be  in  order.
The  treatment  technologies  recommended  above for Plant E
should aid in complying to the  1977  effluent  limitations.
Costs for such actions are given below:
                          119

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     Ca£ital_Costs                                ___

     Clarifiers, two each, 38 ft drain,
       for Plant E-1 effluent                     96,000

     Lime and settle treatment plant
       for Plant E-2 effluent                    _86^000^

     Total                                       182,000

     S/Annual kkg                                  1.75

     (S/Annual ton)                                (1.58)

     Annual Costs

     Clarifier operating costs                    24,000

     Lime and settle operating costs

       Operating and maintenance                  50,600

       Depreciation, taxes and insurance,
         and interest                           	J.lxj600_

     Total                                        89,200

     $/kkg                                         0.86

     ($/ton)                                        (0.78)

Various  methods  exist  for  Plant  E's  achievement of the
recommended 1983 effluent limitations.  The one method  used
in  this  analysis  is by means of flow reduction of process
waste waters.  By 1983, the flow rates for each of the three
process waste water sources should approach the lower end of
the  indicated  flow  ranges.   The  largest  of  the  three
sources,  acid plant blowdown, can be greatly reduced by the
addition of a cooling tower, so that temperature will not be
the major reason for a large blowdown.  The costs for such a
cooling tower follow:

     Cagjtal Costs                                _J.9_21 JL

     Cooling tower                                145,000

     $/Annual kkg                                    1.39

     ($/Annual ton)                                (1.26)
                            120

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Annual Costs

Total

$/kkg

($/ton)
                                                   36,000

                                                    0.35

                                                    (0.32)
The total costs attributable  to  the  recommended  effluent
limitations for Plant E are:
^/Annual kkg

($/Annual ton)

To tal_ Ajinual_Cos t s

$/kkg

($/ton)
                                                  327,000

                                                    3. 14

                                                    (2.84)

                                                  125,200

                                                    1.21

                                                    (1-10)
Plant F

Current  control  technology  for  Plant  F  has permitted a
volumetric flow reduction so that the discharge,  considered
as  current, is about 2,450 cu m/day  (450 gpm) .  In order to
assure compliance to both the 1977 and the 1983  recommended
effluent  limitations,  this flow, equivalent  to 3,945 1/kkg
(945 gal/ton) ,  should  be  subjected  to  lime  and  settle
treatment.   Plant  personnel  indicate that some noncontact
cooling water must also be segregated from the process waste
water prior to treatment.  The costs for these measures  are
as follows:
Capital Costs

Segregation of noncontact
  cooling water

Lime and settle treatment
  of 2,450 cu m/day  (450 gpm)

Total

$/ Annual kkg
                                                   _12!1_J


                                                   250,000


                                                   55.0X000

                                                   800,000

                                                     3.52
                             121

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     (S/Annual ton)                                  (3.20)

     Annual^Cpgts

     Lime treatment                                  57,000

     Overhead, depreciation, taxes and
       insurance, interest

     Total

     $/kkg

     ($/ton)
Plant G

Data  used  for  this plant indicate a current flow value of
9,940 1/kkg (2,360 gal/ton) and an  anticipated  flow  value
for  1983  of  6,900 1/kkg (1,570 gal/ton).  Plant personnel
indicate that minor reductions in the usage of  roaster  gas
spray  blowdown  will  allow the achievement of the selected
flow values.  Current effluent data from the lime and settle
treatment  facility  indicate  good  significant   pollutant
concentrations.   Therefore,  no  additional costs should be
incurred by this  plant  for  achieving  compliance  to  the
recommended effluent limitations guidelines.

Tota.j._Costs

The  total  estimated costs to Plants B, C, E, and F, on the
basis of 1971 dollars, for achievement  of  the  recommended
1977   effluent  limitations,  are  $1,515,000  capital  and
$458,000 annual.  The  costs  for  compliance  to  the  1983
recommendations  for  Plants  D and E are $1,054,000 capital
and $450,000 annual.  Therefore, the total estimated capital
and  annual  costs  to  this  industry  are  $2,569,000  and
$908,000,    respectively.   A  summary  of  these costs are
shown in Table 30.
                  Nonwater,Quality Aspects
Energy Requirements

Specific data on energy requirements were not available from
most of the plants surveyed.  The current waste water treat-
                         122

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                                 TABLE 30.   ADDITIONAL CONTROL Aid TREATMENT COSTS (1971 $)
00
Plant
Designation
B
C
D
E
F
G
1977
Capital
$ 33,000
500,000
0
182,000
800,000
0
Costs
Annual
$ 8,000
152,000
0
89,000
209,000
0
1983
Capital
0
0
$909,000
145,000
0
0
Costs
Annual
0
0
$414,000
36,000
0
0
Total
Capital
$ 33,000
500,000
909,000
327,000
800,000
0
Costs
Annual
$ 8,000
152,000
414,000
125,000
209,000
0
        TOTAL
$1,515,000    $458,000
$1,054,000     $450,000
$2,569,000    $  908,000

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ment  practices  are  confined  to  cooling towers, settling
ponds, and lime treatment, which  require  an  insignificant
amount  of  electrical and thermal energy.  Data supplied by
Plant E-l on lime treatment  indicate  a  power  consumption
estimated  at  about  4.3  kwhr/kkg  (3.9  kwhr/ton) of zinc
production.

Two zinc plants reported that the  zinc  production  process
consumed  approximately 99 percent of all plant power needs.
The remaining one percent is the energy value necessary  for
all other plant needs, including water pollution control.  A
new  waste  water treatment facility which limes and settles
the combined effluents from a lead-zinc mining, milling, and
smelting complex employs about lOO horsepower-worth of power
equipment.  This power  need  is  considered  negligible  in
comparison to total plant needs.
Solid Waste Generation

When  the  process waste waters of the primary zinc industry
are neutralized with lime, a sludge will be  produced.   The
volume  of  this sludge will primarily be dependent upon the
desired pH adjustment (i.e., the higher the value of pH, the
larger the volume of generated sludge).

Plant C, while investigating the potential application of  a
lime treatment facility to its process waste water effluent,
characterized  both  the  probable volume of generated waste
and its constituents.  The approach taken  was  a  two  step
neutralization  of  approximately  800  1/min  (210  gpm)  of
process waste water with 10 percent milk of lime.  The first
stage of pH was assumed to reach 9.5, while the second stage
reached  10.7.   The  resulting  sludge  calculated  out  to
approximately   270  kkg  (245  tons)/day  or  (50  kkg  (45
tons)/day dry weight).   The  primary  constituent  of  this
sludge  was  gypsum,  CaS04_ 2H2_0.   Other major constituents
were the hydroxides of magnesium, zinc, iron, and manganese.
Since the large  volume  of  this  sludge  would  present  a
disposal  problem  at  this  facility,  plant  personnel are
conducting waste water treatment studies by the  application
of  sulfide  precipitation, as well as lime treatment with a
sodium silicate flocculent.   With  the  possible  usage  of
sulfide  precipitation,  a  smaller  volume of gypsum sludge
would be produced and a sulfide cake, containing  the  major
heavy  metal  values,  would  also be generated.   The latter
material would  be  recirculated  in  the  smelting  system,
either  as  feed  to  the  roasters  or  through  a separate
leaching step.  Recent studies using sodium  silicate  as  a
flocculent  have  shown a much smaller generation of sludge.
                          124

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Because of the addition of the flocculent, a lower pH (about
9.5) can be used to acheive similar effluent results as with
the   higher   pH   achieved    through    simple    liming.
Approximately,  one-third  (about ]]0 kkg (100 tons)/day)  of
sludge would be generated by this application of liming with
flocculent addition.

A new treatment facility, employing  milk  of  lime,  ferric
chloride,  and  a  polyelectrolyte  to neutralize and settle
68,400 cu m/day (18 mgd) of commingled process  waste  water
from  an  integrated  domestic  primary  copper  smelter,  is
currently preceding through start-up.  Approximately 36  kkg
(40 tons)/day of sludge, by dry weight, will be generated.

One  currently operating primary electrolytic zinc facility,
(Plant B) neutralizes 2,774 cu  m/day  (509  gpm)  of  total
plant  effluent  with  lime.   A  large  volume of sludge is
generated.   Approximately  half  of  the  influent  to  the
treatment facility is comprised of noncontact cooling water,
boiler  blowdown,  and  treated  sanitary  waste water.  The
reported volumetric flow rate of  process  waste  water,  as
defined  by  this document, is 1,300 cu m/day (240 gpm).  If
the  two  flows  (i.e.,  process  waste  water   from   zinc
production  and  other  plant  water)  were segregrated, the
generation of sludge due to  the  treatment  recommended  by
this document would be much smaller.  The operators at Plant
B  are currently reducing the water content of the "lime and
settle" sludge generated  by  their  treatment  practice  by
solar  evaporation.   Nearly  7,000  wet  tons   (64  percent
moisture) of this solid waste have been shipped  to  one  of
the  company's  primary  lead  smelters, where the sludge is
charged to a zinc  (lead slag) fuming furnace.   As  reported
by this company, the zinc content of the sludge, as shipped,
is averaging about 25 percent (range of 15 to 30 percent).

Thus,  sludge  generation  volume can be reduced by one or a
combination of the following:

     (1)  Usage of lower neutralization pH,  by  addition  of
         flocculents;

     (2)  Segregation of non-process  waste  water  effluents
         from treatment plant influent;

     (3)  Minimize process waste water volume by maximization
         of internal reuse and recycle;

     (4)  Application  of  dewatering  techniques,  such   as
         centrifuging.
                          125

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                         SECTION IX
       BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY
         AVAILABLE—EFFLUENT LIMITATIONS GUIDELINES
                        Introduction
The  effluent  limitations  that must be achieved by July 1,
1977  are  to  specify  the  degree  of  effluent  reduction
attainable  through  the application of the best practicable
control  technology  currently  available.    Such   control
technology  is  based on the average of the best performance
by plants of various sizes and ages, as  well  as  the  unit
processes  within  the industrial category.  This average is
not based upon a broad range of plants  within  the  primary
zinc  industry,  but upon the performance levels achieved by
the exemplary plants.   Additional  consideration  was  also
given to:

          (1)  The total cost of application of
               technology in relation to the effluent
               reduction benefits to be achieved
               from such application.
          (2)  The size and age of the equipment and
               plant facilities involved.
          (3)  The process employed.
          (U)  The engineering aspects of the
               application of various types of
               control techniques.
          (5)  Process changes.
          (6)  Nonwater quality environmental
               impact (including energy requirements).

The  best  practical  control technology currently available
emphasizes effluent treatment at the end of a  manufacturing
process.   It  includes  the  control  technology within the
process itself when the latter is considered  to  be  normal
practice within the industry.

A  further  consideration  is  the  degree  of  economic and
engineering reliability, which must be established  for  the
technology  to  be  currently  available.   As  a  result of
demonstration projects, pilot plants, and general use, there
must exist a high degree of confidence  in  the  engineering
and economic practicability of the technology at the time of
commencement  of construction or installation of the control
or treatment facilities.
                        127

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         Industry Category and Waste Water Streams
One  category  of  the  industry  encompassing  the  primary
smelting   and   refining  of  nonferrous  metals  (Standard
Industrial  Classification  Number  333)   is   the   primary
smelting and refining of zinc (SIC Number 3333).   SIC Number
3333  describes  those  establishments  primarily engaged in
smelting zinc from the ore,  or  in  refining  zinc  by  any
process.  Establishments primarily engaged in the mining and
benefication of zinc ore, as well as some lead ores,  and the
rolling, drawing, or extruding of zinc are not classified by
this  SIC  and  are  not  the  subject  of  this  development
document.   Facilities  for  the   generation   of   on-site
electrical  power,  and other ancilliary operations are also
not the subject of this report.   The  process waste  water
sources  to  be  covered  by  the  proposed regulations, the
rationale for which is derived in this  section,   have  been
clearly defined in past sections.

As  developed  in  previous  sections  of this document, the
primary zinc industry is  considered,  for  the  purpose  of
establishing recommended effluent limitations guidelines, as
a   single   subcategory.   The  principal  basis  for  this
consideration is the similarities  in  process waste  water
characteristics   and   applicable   control,  and  treatment
technologies.

The process  waste  water  sources  from  the  primary  zinc
industry  include  acid  plant  blowdown,  reduction furnace
offgas scrubbing, metal casting cooling,   cadmium  leaching,
dust   control   scrubbers,   offgas   humidification,   and
preleaching operations.

              Recommended Effluent Limitations

The  recommended   effluent   limitations   based   on   the
application  of  the  best  practicable  control   technology
currently available for the primary zinc subcategory are:
                                Effluent limitations
       Effluent                              Average of daily
    characteristic          Maximum for       values for 30
                             any 1 day       consecutive days
                                             shall not exceed
                                 Metric units (kilograms per 1000
                                    kg of product)	
                           128

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    TSS                         0.42                 0.21
    As                          1.6x10-3             8.0x10-*
    Cd                          0.008                0.004
    Hg                          8.0x10-5             4.0x1C-5
    Se                          C.08                 0.04
    Zn                          0.08                 0.04
    pH
                                 English units (pounds per 1COO
                           ______ lb_of_eroduct]

    TSS                         0.42                 0.21
    As                          1.6x10-3             8.0x10-*
    Cd                          0.008                0.004
    Hg                          8.0x10-5             4.0x10-5
    Se                          0.08                 0.04
    Zn                          0.08                 0.04
    pH                     _Within_the_range_7iO_to_^£iO

           Identification^of_the_Best_ Practicable
           Control^ TechnglogY_Currently Available
The best practicable control technology currently  available
is  identified  as  the minimization of discharge or process
waste water by the practices of recycle, reuse, segregation,
and,  finally,  chemical  treatment  to  achieve  controlled
precipitation followed by sedimentation (lime and settle).

The  review  of water use practices in various plant systems
has shown that in specific cases, some process waste  waters
are  currently  being used on a once-through basis; whereas,
in other  existing  plants,  the  discharge  from  the  same
process  operation  is  considerably lower on a unit-product
basis by virtue of recycle.  Further,  various  examples  of
reuse of process waste water  (e.g., acid plant blowdown used
for   cadmium   leaching)   were  also  identified.   Further
evidence of potential  reductions  in  process  waste  water
volume  is  given  in  various  proposed plans for decreased
discharge  of  process  waste  waters.   However,   internal
streams  in zinc smelters vary considerably with differences
in  plant  operations,  and  no  specific  list  of  control
measures  may  be  presented for all plants.  Those measures
that have been identified include:

         The  minimization  of  acid   plant   blowdown   by
         appropriate  proper  operation  of  prescrubber gas
         cleaning   facilities   to   minimize   particulate
         loadings  into  the wet scrubbers, cooling capacity
                        129

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         and provisions for settling in the scrubber  liquor
         recycle circuit, and possibly reuse of the scrubber
         bleed stream in other plant operations.
    •    The minimization of  metal  casting  cooling  water
         discharge by recycle, possibly including provisions
         in the circuit for removal of suspended solids, oil
         and grease, and thermal load.
    •    The exploitation of the evaporative capacity of hot
         gases or hot metal for inplant  disposal  of  waste
         water.

The  end-of-pipe  treatment  identified  as part of the best
practicable control technology currently  available  is  the
lime-and-settle  treatment.   Currently,  some  form of this
treatment is applied to some portion of process waste  water
at  five  of  the  eight   (soon  to  be  six)  plants in this
industry.  The principles of the  lime-and-settle  treatment
technology  are thus known to most of the industry; however,
the current application of the technology  is  extended,  in
some  cases  to  considerably  less  than all of the process
waste water streams, and, as reflected in Section V of  this
document,  the technology is applied with varying degrees of
effectiveness.   The  lime-and-settle  treatment  identified
herein  implicitly  includes  a  "best practicable" level of
performance,  described   below   in   terms   of   effluent
concentrations.

The  combination  of  neutralization  and  clarification  is
required to achieve the best practicable control  technology
currently  available.   Clarification alone will reduce only
total suspended solids; neutralization without clarification
will reduce dissolved metals, but not  suspended  ones,   and
will  not  provide  an  effluent  of  satisfactory  quality.
Neutralization with lime to a pH in the 8 to 11  range  will
reduce  the  concentrations  of those metals precipitable as
hydroxides, and with properly designed retention  facilities
will  also  reduce  total  suspended  solids  to  below  the
recommended effluent limitations guidelines.   Use  of  lime
has  the  further  advantage  that  it,  unlike sodium-based
alkalies, forms a relatively insoluble sulfate, CaSO4, which
will tend to also reduce  the  concentrations  of  dissolved
sulfate   in   the   effluent.    Neutralization   will  not
significantly reduce concentrations of those parameters that
are soluble at an alkaline pH.

In order to achieve the desired concentrations,  indications
are  that  the pH of the solution should be raised to the 10
to 11 range.  As  discussed  in  Section  VII,   arsenic  and
selenium  are  not  effectively removed at pH's above 7, and
their removal depends upon absorption  and  coprecipitation.
                          130

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In  spite  of  this deficiency, neutralization with lime and
settling of the reaction mixture seems to represent the best
practicable control technology currently  available.   There
is  not  the  requisite  high  degree  of  confidence in the
engineering and economic practicability of  the  alternative
control   and   treatment   technologies  to  warrant  their
recommendation at this time.

The selection of  recommended  effluent  concentrations  and
flows  was made on the basis of the information presented  in
Sections V, VII, and VIII of this  document.   Specifically,
the  flow  rates  of  discharges  of  process  waste  waters
presented in Section VIII of this document were inspected  to
determine the range of current effluent rates.  As discussed
in Section VIII,  these  rates  do  not  include  those  for
noncontact  cooling water, and reflect the assumption of the
institution of recycle practices in one plant  (Plant F) with
an exceptionally high rate of process waste  water,  because
of  present  once-through  practice.   Hence,  this range  of
flows as detailed in Section VIII,  (1) is based  on  process
waste  water  only  and   (2) includes projected decreases  in
flows as reported by industry; that is,  the  flows  reflect
"best  practicable control" measures.  Average flow rates  of
process waste water effluents were  converted  to  discharge
rates per unit of product to obtain the following values:

            Flow            Production       Discharge Rate
£iili£   cu_m/day	iSSffll   kJS2/day.	(£°.S/<2£Y.L   1/kkg  (gal/ton)
  B       1,308   (240)     268      (296)       4,880   (1,170)
  C       1,134   (208)     176      (194)       6,440   (1,550)
  D       4,060   (745)     302      (333)      13,440   (3,220)
  E       2,400   (440)     285      (315)       8,415   (2,01C)
  F       2,450   (450)     621      (685)       3,945     (945)
  G       1,250   (230)     124      (137)       9,940   (2,360)

Taking  the  average of the above six  flow values  produces  a
selected value of 8,350 1/kkg  (2,000 gal/ton).   This   value
is slightly rounded-up, primarily because Plant  F  reuses  its
acid plant blowdown for cadmium leaching.

As  developed in Sections V and VII, current  lime-and-settle
treatment operations  (Figure 7 and  Tables  24  and  27)   for
which  reasonable  amounts  of  data   are available  show  the
following concentrations of constituents to be achievable in
effluents.

         Total Suspended Solids     25 mg/1
         Zinc                        5 mg/1
         Cadmium                     0.5 mg/1
                            131

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         Mercury                     0.005 mg/1
         Selenium                    5 mg/1
         Arsenic                     0.1 mg/1

These demonstrated levels of  concentrations  were  applied,
together  with  the  selected  flow  value,,  to  derive  the
recommended effluent limitations.
      Rationale for the_Selectj,ori_of_Best_Practicable
           £gntrol_Technology CurrentlY_AvajJ.able
    (1)   The selected lime-and-settle technology is  capable
         of achieving significant reductions in discharge of
         pollutants,  as indicated by industry-supplied data
         and  as  verified  by  the  analysis   of   samples
         collected  on-site  at  plants where the technology
         was applied.
    (2)   The  technology   is   compatible   with   industry
         variations,   including  age  and  size  of  plant,
         processes employed, raw material variations,  plant
         location,   and   nonwater   quality  environmental
         impact.
    (3)   The technology, as an end-of-pipe treatment, can be
         an add-on to existing plants, and need  not  affect
         existing    internal    process    and    equipment
         arrangements.
    (4)   The ratios of recommended maximum daily  values  to
         30-day  averages  are  based  on an analysis of the
         RAPP data reported by the producers, from which  an
         average  ratio of maximum concentrations to average
         concentrations was derived.   This  analysis  showed
         that some parameters, suspended solids for example,
         exhibited  a  fairly narrow and consistent maximum:
         average ratio of between 1 and  2;  whereas,  trace
         elements   covered  a  much  wider  span,  and  the
         differences  between  plants   were   greater.    A
         maximum: average ratio of 2:1 appeared to represent
         a   fair   central  value  for  the  pollutants  of
         interest.
    (5)   It  is  concluded   that   the   effluent-reduction
         benefits  balance  the costs of the technology.  On
         the basis of the information contained  in  Section
         VIII,  those  plants  not  presently  achieving the
         recommended 1977 effluent limitations would require
         an estimated capital investment of  $1,515,000  and
         an  increase  in  annual  operating  cost  of about
         $458,000 to achieve the recommended limitations.
                            132

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                         SECTION X

           BEST AVAILABLE TECHNOLOGY ECONOMICALLY
        ACHIEVABLE—EFFLUENT LIMITATIONS GUIDELINES

                        Introduction

The effluent limitations that must be achieved  by  July  1,
1983,  are  to  specify  the  degree  of  effluent reduction
attainable through the application  of  the  best  available
technology  economically  achievable.   The  best  available
technology economically achievable  is  not  based  upon  an
average   of  the  best  performance  within  an  industrial
category, but is to be determined by  identifying  the  very
best control and treatment technology employed by a specific
point  source within the industrial category or subcategory,
or where it is  readily  transferable  from  one  industrial
process  to  another.  A specific finding must be made as to
the  availability  of  control  measures  and  practices  to
eliminate  the  discharge of pollutants, taking into account
the cost of such elimination.

Consideration must also be given to:

          (a)  The age of equipment and facilities
               involved,
          (b)  The process employed,
          (c)  The engineering aspects of the applica-
               tion of various types of control
               techniques,
          (d)  Process changes
          (e)  Cost of achieving the effluent reduction
               resulting from application of the best
               economically achievable technology,
          (f)  Nonwater quality environmental impact
               (including energy requirements).

In contrast  to  the  best  practicable  control  technology
currently   available,   the   best   available   technology
economically achievable assesses  the  availability  in  all
cases   of   inprocess  controls,  as  well  as  control  or
additional treatment techniques employed at  the  end  of  a
production process.

The best available technology economically achievable is the
highest  degree of control technology that has been achieved
or has been demonstrated to be capable of being designed for
plant-scale operation up to and including "no discharge"  of
process  waste  water pollutants.  Although economic factors
are considered in this development, the costs for this level
                            133

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of control are intended to be the top-of-the-line of current
technology subject to limitations imposed  by  economic  and
engineering   feasibility.    However,  the  best  available
technology economically achievable may be  characterized  by
some  technical  risk  with  respect to performance and with
respect  to  certainty  of  costs.   Therefore,   the   best
available technology economically achievable may necessitate
some  industrially  sponsored  development work prior to its
application.
              Recommended_Effluent_Limitations

The  recommended   effluent   limitations   based   on   the
application  of  the  best available technology economically
achievable for the primary zinc subcategory are:
   Effluent
characteristic
TSS
As
Cd
Hg
Se
Zn
pH
TSS
As
Cd
Hg
Se
Zn
pH
                                Ef f 1 u en t 1 im j. t a t ions _________
                                             Average of~daily"
                            Maximum for       values for 30
                             any 1 day       consecutive days
                                             shall not exceed
                                 Metric units (kilogram per 1,000
                                                 0.14
                                                 5.4x10-*
                                                 2.7x10-3
                                                 2.5x10-5
                                                 0.027
                                                 0.027
                                0.28
                                1.1x10-3
                                5.4x10-3
                                5.0x10-5
                                0.054
                                0.054
                            Within_the_ranae_7_iO_to_JJ)iO _______

                                 English units (Ib per 1000 Ib
                                                of_2roduct] ______
                            0.28
                            1.1x10-3
                            5.4x10-3
                            5.0x10-5
                            0.054
                            0.054
                                                     0.14
                                                     5.4x10-*
                                                     2.7x10-3
                                                     2.5x10-5
                                                     0.027
                                                     0.027
                             134

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        Identification of Best Available Technology
                  Economically Achjeyable
The  identification  of  the   best   available   technology
economically  achievable  is  analogous  to  the  technology
defined in Section IX,  and  includes  control  measures  to
further  minimize  the volume of process waste water streams
by  additional  recycle,   reuse,   segregation,   and   the
application  of  chemical  treatment  to  achieve controlled
precipitation followed by sedimentation.


The control measures identified as part  of  the  applicable
technology include the following:


          o  Minimization of acid plant blowdown
             streams by appropriate measures of
             cooling  (i.e., by cooling towers or ponds),
             control of particulate loadings entering
             gas scrubbers, recycle, and/or reuse of
             the stream within the plant;
          o  Minimization of metal casting cooling
             waste water discharge by recycle, reuse,
             or treatment allowing reuse or recycle
             within the operation or the plant;
          o  Exploitation of evaporative capacity
             wirhin the plant in terms of hot gas,
             hot metal, or evaporative equipment
             operations to maximize inplant disposal of
             waste waters;
          o  Process modifications to maximize the
             reuse of water within the processes
             at each specific plant.

The  selection  of  recommended  effluent concentrations and
flows was made on the  basis  of  information  presented  in
Section V, VII, and VIII of the document.  Specifically, the
flow  rates  of  current and potential discharges of process
waste waters, as discussed in Section VIII,  were  inspected
to  determine the best available technology flow value.  The
data used to develop this value follows:

          Flow                Production         Discharge Rate
Plant   cu_m/day. __ (2J22J1
  B     1,3C8     (240)      268     (296)          4,880  (1,170)
  C     1,134     (208)      176     (194)          6,470  (1,550)
                         135

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  D     4,060     (745)      302     (333)         13,400  (3,210)
  E     1,390     (255)      285     (315)          4,880  (1,170)
  F     2,450     (450)      621     (685)          3,945    (945)
  G       818     (150)      124     (137)          6,900  (1,570)

The  selected  value  of  5425  1/kkg   (1300  gal/ton)   was
developed by averaging the best discharge rates shown in the
above  tabulation,  namely those from Plants B, C, E, F, and
G.  Plant B is currently operating at its  indicated  value;
Plant C will shortly reduce its flow value to its  indicated
value;  Plants  E  and  G  indicated  flow  ranges,  so  the
indicated values for these two  plants  were  taken  at  the
bottom  of  each  range;  Plant  F has indicated a method of
process waste water effluent  minimization  through  recycle
and  reuse;  and,  finally, the current value for Plant D is
not used.

The same treatment technology pollutant  concentrations,  as
were  used'  in  the  calculations  of  the  best practicable
effluent limitations, were considered  as  those  achievable
through  the  application  of the best available technology.
These concentrations are achievable by  means  of  lime-and-
settle technology.  Values for pollutant concentrations from
such  possible  technologies  as  sulfide  precipitation  or
others, as described in Section VII, cannot, as yet, be used
for  the  derivation  of   the   best   available   effluent
limitations.
       £ationale_fgr^the_SelectiQn_of_Best_Available
Numerous methods of control and treatment technology are, or
should  shortly  be available, which would enable compliance
to the proposed  effluent  limitations  based  on  the  best
available  technology  economically  achievable.   The  best
available limitations are principally based upon the control
technology of maximum reuse and  recycle  of  process  waste
water  and the treatment technology of lime and settle.  The
Idential treatment technology was used in Section IX as part
of the best practicable effluent limitations rationale.

Compliance to the proposed best  available  limitations  can
also  be  achieved  by  either  employing  better  treatment
technology (lower  pollutant  concentrations  than  used  in
calculations)  and  a  lesser  degree  of control technology
(less recycle and  reuse,  producing  a  higher  flow  usage
value,  as  used  in  the  calculations)  or  better control
technology and a  lesser  degree  of  treatment  technology.
                           136

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Current  industrial  research  on the application of sulfide
precipitation,   flocculent    additions,    polyelectrolyte
additions, and other treatment methods will undoubtedly lead
to  both  lower pollutant discharge concentrations and lower
sludge volume generation.

Incremental capital and annual operating costs for  the  two
primary  zinc  plants,  which would need incremental control
and treatment practices to comply to  the  recommended  1983
effluent   limitations,  are  approximately  $1,054,000  and
$450,000, respectively.
                           137

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                         SECTION XI

              NEW SOURCE PERFORMANCE STANDARDS

                        Introduction

In addition to guidelines reflecting  the  best  practicable
control  technology  currently available and the best avail-
able  technology  economically  achievable,  applicable   to
existing  point  source discharges by July 1, 1977, and July
1, 1983, respectively, the  Act  requires  that  performance
standards  be  established  for  new sources.  The term "new
source" is defined in the  Act  to  mean  "any  source,  the
construction  of which is commenced after the publication of
proposed regulations prescribing a standard of performance".
New source technology shall be evaluated by  adding  to  the
consideration   underlying   the   identification   of  best
available technology economically achievable a determination
of what higher levels of pollution control and treatment are
available through the use of improved  production  processes
and/or   treatment   techniques.    Thus,   in  addition  to
considering the  best  inplant  and  end-of-process  control
technology,   identified   in   best   available  technology
economically achievable, new  source  technology  is  to  be
based  upon  an analysis of how the level of effluent may be
reduced by changing  the  production  process  itself.   Al-
ternative    processes,    operating   methods,   or   other
alternatives must be considered.  However, the end result of
the analysis will be to identify effluent  standards,  which
reflect  levels  of  control  achievable  through the use of
improved  production   processes    (as   well   as   control
technology),  rather  than  the prescription of a particular
type of process or technology which  must  be  employed.   A
further  determination  that  must  be  made  for new source
technology is whether a standard calling for no discharge of
process  waste  water  pollutants  to  navigable  waters  is
applicable.

The  following  factors should be considered with respect to
production processes which are to be analyzed  in  assessing
new source technology:

           (a)  The type of process employed and process
               changes
           (b)  Operating methods
           (c)  Batch as opposed to continuous operations
           (d)  Use of alternative raw materials and mixes
               of raw materials
           (e)  Use of dry rather than wet processes  (in-
               cluding substitution of recoverable solvents
                            139

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               for water)
          (f)   Recovery of pollutants as byproducts.

Consideration must also be given to the fact that new source
performance  standards  could  require  compliance at a much
earlier time than the effluent limitations to be achieved by
existing sources by July 1, 1977.


                   Recommended Standards

The  best   available   demonstrated   control   technology,
processes,   operating  methods,  or  other  alternatives are
identical to  the  best  available  technology  economically
achievable.    The  corresponding  standard of performance is
identical to the effluent  limitations guidelines established
from usage of the  best  available  technology  economically
achievable.
                          140

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                        SECTION XII

                      ACKNOWLEDGMENTS

This  document was developed by the Environmental Protection
Agency.   The  original  contractor's  draft  report,  dated
December   1973 was prepared by Eattelle Memorial Institute,
Columbus, Ohio, under contract no. 68-01-1518.  Mr. John  B.
Hallowell   prepared   this  original  (contractor's)  draft
report.

This study was conducted under the supervision and  guidance
of   Mr.   George   S.   Thompson,   Jr.,  Project  Officer.
Preparation, organizing, editing,  and  final  rewriting  of
this report was accomplished by Mr. Thompson.

The  following  members  of  the  EPA working group/steering
committee provided detailed review, advice and assistance:
W.J. Hunt, Chairman
G.S. Thompson, Jr.,
  Project Officer
S. Davis
D. Fink
J. Ciancia

T. Powers
Effluent Guidelines Division
Effluent Guidelines Division

Office of Planning and Evaluation
Office of Planning and Evaluation
National Environmental Research
   Center, Edison
National Field Investigation Center,
   Cincinnati
Excellent  guidance  and  assistance were  provided  to  the
Project Officer by his associates in the Effluent Guidelines
Division,   particularly   Messrs.  Allen  Cywin,  Director,
Effluent  Guidelines  Division,  Ernst   P.   Hall,   Deputy
Director, and Walter J. Hunt, Branch Chief.

The  cooperation  of  individual primary zinc companies, who
offered their plants for survey  and  contributed  pertinent
data, is greatly appreciated.  These include:

    American Smelting and Refining Company
    St. Joe Minerals Corporation
    New Jersey Zinc company
    Amax Zinc Company, Inc.
    Bunker Hill Company

The  cooperation of the Water Pollution Control Subcommittee
of the American Mining Congress is also appreciated.
                            141

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Acknowledgmenr and appreciation is also  given  to  Ms.  Kay
Starr,  Ms.  Nancy  Zrubek,  and  Ms.  Brenda Holmone of the
Effluent Guidelines Division secretarial staff.
                          142

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                        SECTION XIII

                         REFERENCES

1.  Brobst, Donald A., and Pratt, Walden P., editors,
    United States Mineral Resources, Geological Survey
    Professional Paper, United States Government Printing
    Office, Washington, D. C., 1973.

2.  Bureau of Mines, Minerals Yearbook, 1971, "Volume I,
    Metals, Minerals, and Fuels", United States Depart-
    ment of the Interior, Bureau of Mines, U. S. Govern-
    ment Printing Office, Washington, D. C.  (1973).

3.  Bureau of Mines, "mineral Facts and Problems, 1970
    Edition", Bureau of Mines Bulletin 650, U. S. Depart-
    ment of the Interior, Bureau of Mines, U. S. Govern-
    ment Printing Office, Washington, D. C.  (1970).

4.  cotterill, C. H., and Cigan, J. M. .(editors), AIME
    World Symposium of Mining and Metallurgy of Lead and
    Zinc, "Volume II, Extractive Metallurgy of Lead and
    Zinc", The American Institute of Mining, Metallurgical,
    and Petroleum Engineers Inc., Port City Press,
    Baltimore, Maryland  (1970).

5.  1970 E/MJ International Directory of Mining and
    Mineral Processing Operations, Published by Mining
    Informational Services, Engineering and Mining
    Journal, McGraw-Hill, New York  (1970).

6.  1973 Annual Book of ASTM Standards, Part 7, Nonferrous
    Metals and Alloys, "Standard Specification for Lead",
    B29-55  (Reapproved 1971), pp 30-32.

7.  Pourbaix, Marcel, "Atlas_gf_Electrochemical_Eguilibria
    in Aqueous Solutions", Pergamon Press, New York
    (1966)".~

8.  Hartinger, Ludwig; "Waste Water Purification in the
    Metalworking Industries, Precipitation of Heavy
    Metals:, Part 1, Problems, Bander Bleche Rohre
    Dusseldorf, October,  1963, pp 535-540.

9.  Jenkins, S. N. Knight, D. G., and Humphreys, R. E.,
    "The Solubility of Heavy Metal Hydroxides in Water,
    Sewage, and Sewage Sludge, I. The Solubility of
    Some Metal Hydroxides:, Int. Jour. Air & Water
    Pollutionn 8, 537-556  (1964).
                          143

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10. Maruyama, T., S. A. Hannah, and J. M. Cohen,
    "Removal of Heavy Metals by Physical and Chemical
    Treatment Processes", presented at 45th Annual
    Water Pollution Control Federation Meeting  (1972).

11. Kantawala, D., and H. D. Tomlinson, "Comparative
    Study of Recovery of Zinc and Nickel by Ion Exchange
    Media and Chemical Precipitation", Water, Sew Works,
    111 R-281 - R 286  (1964).

12. Kolthoff, I. M., and Sandell, E. B., Textbook of
    Quantitative Inorganic Analysis, 3rd Ed., The
    McMillan Company, New York (1952).

13. "Ultimate Disposal of Liquid Wastes by Chemical
    Fixation", Chemfix Division,  Environmental Sciences,
    Inc., Pittsburgh, Pa.  (1973).
                          144

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                        SECTION XIV

                          GLOSSARY

Acid Plant

In  primary  zinc   reduction   operations,   an   adjoining
metallurgical plant which utilizes the sulfur oxide offgases
from the roasters to produce sulfuric acid.


Act

The Federal Water Pollution Control Act Amendments of 1972.
A  term  representing  the  presence of salts of weak acids.
The hydroxides, carbonates,  and  bicarbonates  of  calcium,
sodium,  and  magnesium are the common impurities that cause
alkalinity.  An alkaline solution has a pH greater than 7.
Anc ilia ry Oper ation s

Operations which are  often  carried  out  at  primary  zinc
plants  but are not an essential part of the processing, for
example, power generation.
Anode

The positive electrode in  electrolysis;  electrode  through
which a current enters an electrolytic cell from an external
electro-motive  furnace.   In  zinc  electrolytic  practice,
insoluble rectangular lead anodes are used.
Large chamber for holding bags used  in  the  filtration  of
gases  from  a  furnace,  for  the recovery of metal oxides,
dust, and similar solids suspended in the gases.
Best Available Technology, Eggnomically Achievable

Level of technology applicable to effluent limitations to be
achieved by  July  1,  1983  for  industrial  discharges  to
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 surface  waters   as  defined  by  Section  3Cl(b)  (2)(A)  of the
 a «—+•
Act.
Level of technology applicable to  effluent  limitations  to  be
achieved by July  1,  1977,   for   industrial  discharges   to
surface  water  as  defined   by Section  301(b)  (1) (A) of the
Act.
Slowdown

A discharge from a system, designed to prevent a buildup   of
some material, as in a boiler to control dissolved  solids.
Brass

An  alloy  consisting mainly of copper  (over 50 percent) and
zinc, to which smaller amounts of other metals may be  added.


Calcination

Heating of a solid to a temperature below its melting   point
to  bring  about  a  state of thermal decomposition or phase
transition other than melting.


Calcine

The impure zinc oxide product of the roasting operations.


Capital Costs

Financial charges which are computed as the cost of  capital
times  the  capital expenditures for pollution control.  The
cost of capital is based upon  a  weighted  average  of  the
separate costs of debt and equity.


CategorY^and^Subcategory

Divisions  of  a particular industry which possess different
traits affecting waste treatability and requiring  different
effluent limitations.
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Cathode

The   negative  electrode  in  electrolysis;  the  electrode
through which a  current  leaves  an  electrolytic  cell  to
return  an  external source of electromotive force.  In zinc
electrolytic practice,  rectangular  aluminum  cathodes  are
used.
Cathode Deposit

Metal  formed  on  a  cathode  during electrolysis.  In zinc
electrolysis, zinc is deposited  onto  aluminum  rectangular
cathodes from which it is stripped at regular intervals.
Clarifi cation

Process  of  removing  turbidity  and  suspended  solids  by
settling.  Chemicals can be added to improve  and  speed  up
the settling process through coagulation.
Cooling Tower

A  device in which hot water is pumped to the top of a rower
and cooled by allowing it to flow downward in  thin  streams
from one container to another.
Concentrates

The  product  of milling operations in which the ore values,
usually after grinding, are separated and concentrated.
Custom Smelt_er

A smelter processing zinc concentrates purchased from  other
sources.   These  different  concentrates  are  specifically
blended to produce a specific quality "custom" product.
Depreciation

Accounting charges reflecting the deterioration of a capital
asset over its useful life.
Dewat.ering_Classif igr

(Sometimes referred to as a  dewatering  bin  or  tank).   A
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settling tank for clarifying process  water;  the  tank  may
have a continuously operating rake at the bottom which moves
the  settled  solids or sludge towards an outlet pipe in the
bottom.
Die Casting

A casting process where a  molten  metal  such  as  zinc  is
forced under high pressure into the cavity of a metal mold.


Dust Collector

An  air  pollution control device for removing dust from air
streams.   Filtration,   electrostatic   precipitation,   or
cyclonic  principles  may  be utilized, but the term usually
infers a dry system, not involving a water stream.


Effluent

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

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

The quantity or concentration of specified materials in  the
water stream from a unit or plant.
Electrolyte Purification

Removal  of impurities, copper, cadmium, cobalt, nickel, and
other residuals from the electrolyte by means of replacement
through additions of zinc dust.
Electrolytic Refining

Recovery of metal from concentrates in an  aqueous  solution
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by   electrolysis,   and   the   concomitant  separation  of
impurities from solution as sludge.


Electrolytic Zinc

Zinc produced from its ores by roasting (to convert  sulfide
to   oxide),   solution  of  the  oxide  in  sulfuric  acid,
precipitation of impurities by adding zinc dust,  and  final
electrolytic  deposition  of zinc on aluminum cathodes.  The
product has a purity of 99.9 +• percent.


Electrostatic Precipitator

A gas cleaning device using  the  principle  of  placing  an
electrical  charge on a particle, which is then attracted to
oppositely charged plates or wires.  The device uses  a  d-c
potential approaching 40,000 volts to ionize and collect the
particulate matter.  The collector plates are intermittently
rapped  to discharge the collected dust into a hopper below.
The system may operate dry or the plates may be continuously
cleaned by a falling film of water.
Electrothermic Reduction

A continuous reduction-volatilization process in  which  the
internal  heating  of a large vertical cylindrical retort is
supplied  by  electrical   energy;   the   feed   materials,
consisting  of  sinter  and  coke,  set up resistance to the
electrical current and serve as a heating element.  The zinc
vapor and carbon  monoxide  produced  are  collected  in  an
annular  ring  encircling  the  furnace  at mid-height, from
which they pass into a u-shaped condenser,  where  the  zinc
vapor is condensed to zinc metal, and the carbon monoxide is
caught, cleaned, and compressed for use as fuel.
Flash Roasting

Rapid removal of  sulfur  from sulfide mineral concentrates by
allowing   the  concentrates to  fall through a heated oxiding
atmosphere.   Alternatively,    dried   and   finely   ground
concentrates  may be  blown  into  a combustion chamber and
burned  to  calcine and  sulfur dioxide.
Flotation

A method of  mineral  separation  in which  a  froth,  created   in
water   by  air  bubbles  and  a  variety  of reagents,  selectively
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 float some  minerals  (in  a  finely  divided  condition)  by  means
 of adherence  to film bubbles, while  other minerals   are  not
 so wetted and sink.


 Fluidized-Bed Roasting

 A  roasting  process in  which   concentrates are fed into  a
 cylindrical combustion chamber when  they  become  suspended in
 a bed supported on an air  column.  After  oxidation  of  the
 finely   ground  sulfide  concentrate  occurs,   the  calcine
 overflows a retaining wall inside the  roaster.   Separation
 of  the   calcine and sulfur dioxide is  accomplished in  hot
 cycles.
Flux

A  substance  added  to  a  retort  or  furnace  charge  that
promotes  fusing  of  minerals  or  metals,  or prevents the
formation of oxides.
Galvanizing

Tne coating of steel with zinc, which may be done by  either
not dip or electrolytic methods.


Horizontal Retort Process

A  batch  reduction-volatilization  process  in  which  clay
retorts filled with sinter, zinc oxide, coal  or  coke,  and
small  amounts  of  dross  are placed in banks in a furnace,
where  the  zinc  oxide  constituent  is  reduced  to  zinc,
volatilized,  and  the  evolved  zinc  vapor is subsequently
condensed to metallic zinc in refractory condensers.


Indirect Cooling

Water cooling in which water is  not  in  contact  with  any
material in process; jacket cooling of pyrothermic equipment
is an example.


Jarosite

A  hydrated  sulfate  of iron and potassium crystallizing in
the rhombohedral system.
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Jarosite Process

A process of treating concentrates of  leached  residues  in
which the iron impurity present is precipitated as jarosite.
Leaching

The  extraction of a soluble metal  (or metals) by dissolving
in  a  solvent.   In   electrolytic   zinc   recovery,   the
concentrates  are  leached  with spent electrolyte until all
the zinc is dissolved  in  a  still  slightly  acid   (H2S04_)
medium.
Lime Sump

A  pit  or  tank  to  which lime is added to precipitate out
dissolved metallic impurities from plant waste water.
Multiple-Hearth Roas ting

A roasting process in which the concentrates  enter  at  the
top  of  a  multiple  hearth roaster and drop from hearth to
hearth in succession until discharged at  the  bottom.   The
concentrates  are  raked  over  each  hearth by rubble arms.
Concentrates are first  dried  on  the  upper  hearth,  then
roasted in heated air, as they progress downward through the
roaster.   In  addition to removing sulfur as S02_, multiple-
hearth roasters are effective in removing lead.
New Source

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

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

A natural mineral from which materials such as metals can be
economically extracted.
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A measure of  the  alkalinity  or  acidity  of  a  solution,
numerically  equal  to  7  for neutral solutions, increasing
with increasing alkalinity and  decreasing  with  increasing
acidity.  A one unit change in pH indicates a tenfold change
in acidity or alkalinity.


Point Source

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

Those  constituents  of  waste  water   determined   to   be
detrimental and therefore requiring control.


Prime Western Zinc

A  commercial  grade  of zinc containing at least 98 percent
zinc.  Maximum limits of impurities are  lead,  1.6  percent
iron  0.05  percent;  and cadmium, 0.50 percent.  It is used
mostly for galvanizing.


Prolongs

In a  horizontal  retort  plant,  metal  extensions  to  the
refractory condensers used to collect zinc vapor that escape
the condensers.
Pyrolytic Reduction of Zinc

Recovery  of  zinc by either the horizontal retort, vertical
retort, or electrothermic processes.


Roasting

In zinc plants, the operation of heating sulfide ores in air
to convert them to oxides;  lead may or may not be removed in
this operation depending on specifications of  the  finished
product.
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Select Grade

A  grade of zinc for use in galvanizing made from high-grade
zinc and added  constituents  to  give  desired  hot-dipping
(galvanizing)  characteristics.
Settling Pond

A  pond, natural or artificial, used for settling out solids
by gravity from waste water effluents.,
Sinter

The product of the sintering process; agglomerated masses of
relatively sulfur free concentrates  of  suitable  size  for
subsequent  pyrothermic  plant  processing, in which some of
the  impurities  such  as  arsenic  and  cadmium  have  been
removed, at least partially, by volatilization.
Sintering

A process for agglomerating calcine into masses suitable for
subsequent processing in pyrothermic plants, and at the same
time  removing  volatile  impurities  such  as  cadmium  and
arsenic.
Sintering Machine

A  horizontal   sintering   furnace   containing   traveling
articulated grates, which move the feed continuously in belt
conveyor  fashion  under controlled conditions of combustion
to produce  sulfur  free  sinter  of  a  size  suitable  for
subsequent, pyrothermic plant processing.
Special High-Grade Zinc

High  purity,  99.990  percent zinc, with a maximum limit of
lead, iron, and cadmium of  0.003  percent  each.   Tin,  if
present,  should  not  exceed 0.001 percent.  Die casting is
the largest application for this grade.
Spent Electrolyte

In the electrolytic recovery of zinc, the electrolyte  after
recovery  of  zinc by electrolysis; a sulfuric acid solution
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of  about  200  grams  per liter of sulfuric acid containing
some residual zinc sulfate.


Sphalerite

Zn S, the principal ore mineral of zinc.  A  maximum  weight
discharged  per unit of production for each, constituent that
is subject to limitation and applicable to new  sources,  as
opposed  to  existing sources, which are subject to effluent
limitations.
Suspension Roasting

(See Flash Roasting)


Thickener

A vessel or apparatus for separating waste solids from waste
water.


Vertical Retort Process

A  continuous  reduction-volatilization  process  in   which
briquettes  of  a  zinc calcine-anthracite coal mixture pass
downward through  vertical  silicon-carbide  retorts,  while
undergoing  a  reduction of their zinc oxide contents.  Zinc
vapor formed during the downward passage flows  upward  with
the  carbon  monoxide gas formed in the redxiction to a water
cooled condenser.
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                                    TABLE  31
                                 CONVERSION TABLE
MULTIPLY (ENGLISH UNITS)

    ENGLISH UNIT      ABBREVIATION
acre                    ac
acre - feet             ac ft
British Thermal
  Unit                  BTU
British Thermal
  Unit/pound            BTU/lb
cubic feet/tninute       cfm
cubic feet/second       cfs
cubic feet              cu ft
cubic feet              cu ft
cubic inches            cu in
degree Fahrenheit       %F
feet                    ft
gallon                  gal
gallon/minute           gpm
horsepower              hp
inches                  in
inches of mercury       in Hg
pounds                  Ib
million gallons/day     mgd
mile                    mi
pound/square
  inch (gauge)          psig
square feet             sq ft
square inches           sq in
ton (short)             ton
yard                    yd
         by               TO OBTAIN (METRIC UNITS)

    CONVERSION  ABBREVIATION  METRIC UNIT
       0.405
    1233.5

       0.252
ha
cu m

kg cal
0.555
0.028
1.7
0.028
28.32
16.39
0.555&F-32)*
0.3048
3.785
0.0631
0.7457
2.54
0.03342
0.454
3,785
1.609
kg cal/kg
cu m/min
cu m/min
cu m
1
cu cm
%e
m
1
I/sec
kw
cm
atm
kg
cu m/day
km
(0.06805 psig  +1)*   atm
       0.0929        sq m
       6.452         sq cm
       0.907         kkg
       0.9144        m
hectares
cubic meters

kilogram - calories

kilogram calories/kilogram
cubic meters/minute
cubic meters/minute
cubic meters
liters
cubic centimeters
degree Centigrade
meters
liters
liters/second
killowatts
centimeters
atmospheres
kilograms
cubic meters/day
kilometer

atmospheres (absolute)
square meters
square centimeters
metric ton (1000 kilograms)
meter
* Actual conversion, not a multiplier
                                       155

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