40/1-74-016-a
 Development Document for Effluent Limitations Guidelines
 ^'Mttd New Source Performance Standards for the
LEATHER  TANNING
AW FINISHING
        Source Category
                 MARCH 1974
           U.S. ENVIRONMENTAL PROTECTION AGENCY
                 Washington, D.C. 20460

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                   DEVELOPMENT DOCUMENT

                             for

             EFFLUENT LIMITATIONS  GUIDELINES

                             and

            NEW  SOURCE PERFORMANCE STANDARDS

                           for the

              LEATHER TANNING AND  FINISHING

                   POINT SOURCE CATEGORY
                     Russell  E. Train
                       Administrator
                       Roger Strelow
Acting  Assistant  Administrator for  Air & Water Programs
                        Allen Cywin
         Director,  Effluent Guidelines Division

                      James  D.  Gallup
                      Project Officer
                               1974
              Effluent Guidelines Division
            Office  of Air and Water Programs
          U.S. Environmental  Protection Agency
                 Washington,  D.C.  20460
                          U.S. Environmental Protection Agency
                          Region 5 Library (PL-12J)
                          77 West Jackson Blvd., 12th Floor
                          Chicago, IL 60604-3590
    For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.95

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                            ABSTRACT
This document presents the findings of an extensive study of  the
leather  tanning  and  finishing  industry  for  the  purpose  of
developing  effluent   limitations   guidelines,   standards   of
performance,  and  pretreatment  standards  for  the industry, to
implement Sections  304,  306,  and  307  of  the  Federal  Water
Pollution Control Act, as amended.

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

The  proposed  regulations  for  July 1, 1977, and for new source
performance  standards  are  based  on   preliminary   screening,
equalization  and  primary  sedimentation,  secondary  biological
treatment and chrome recycle.

The recommended technology  for  July  1,  1983,  is  preliminary
screening,  equalization  and  primary  sedimentation,  secondary
biological treatment and chrome recycle plus  sulfide  oxidation,
nitrification and denitrification and mixed-media filtration.

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

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                            CONTENTS


Section

  I      CONCLUSIONS                                      1

  II     RECOMMENDATIONS                                  3

  III    INTRODUCTION                                     7

              Scope                                       7
              Previous Study                              7
              Industry Trends                             8

  IV     INDUSTRY CATEGORIZATION                          11

              Standard Manufacturing Processes            n
              Cattlehide Tannery Processes                12
              Sheepskin Tannery Processes                 18
              Pigskin Tannery Processes                   22
              Classification System                       25
              Categorization System                       27

  V      WASTE CHARACTERIZATION                           31

              General                                     31
              Waste Constituents                          32
              Unit Waste Quantities                       32
              Individual Process Contributions            33
                to the Waste
                   Wash and Soak                          34
                   Degreasing                             35
                   Unhairing                              35
                   Bating                                 36
                   Pickling                               36
                   Tanning                                36
                   Retan, Color, Fatliquor                37
                   Finishing                              38
              Total Plant Liquid Waste                    38
              Characteristics of Total Plant              42
                Waste Flows

 VI      SELECTION OF POLLUTANT PARAMETERS                47

              Waste water Parameters of Major             47
                Significance
              Rationale for Selection of Major            47
                Parameters
                   Biochemical Oxygen Demand              47
                             ill

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                        CONTENTS  (Cont«d)
Section

                   Total Chromium                         48
                   Grease                                 48
                   Sulfide                                48
                   Suspended Solids                       49
                   Total Kjeldahl Nitrogen                50
                   Fecal Coliforms                        50
                   PH                                     50
              Rationale for Selection of Minor            52
                Parameters
                   Chemical Oxygen Demand                 52
                   Total solids                           52
                   Ammonia Nitrogen                       52
                   Color                                  52

VII      CONTROL AND TREATMENT TECHNOLOGY                 55

              General                                     55
              Basis of Tannery Waste Treatment            56
              In-Process Methods of Reducing Wastes       58
              Preliminary Treatment                       62
                   Screening                              64
                   Equalization                           64
                   Plain Sedimentation                    64
                   Chemical Treatment - Coagulation       68
                     and Sedimentation
                   Chemical Treatment - Carbonation       70
                   pH Adjustment                          71
                   Sludge Handling and Disposal           71
                   Preliminary Treatment - Facility       73
                     Requirements
                   Secondary Biological Treatment         74
              Major Reduction of BOD5 and suspended  Solids74
                   Combined Municipal - Tannery  Treatment
                     Systems                              74
                   On-Site Treatment - Trickling Filter
                     Systems                              78
                   On-Site Treatment - Aerobic Lagoon
                     Systems                              79
                   Or.-Site Treatment - Aerobic - Anaerobic
                     Lagoon Systems                       82
                   On-Site Treatment - Activated sludge
                     Systems                              87
              Practical Biological Systems                92
                   Polishing Systems for Biological       95
                     Treatment
              Major Reduction of All Forms of Nitrogen   97
              Major Removal of All Waste Constitutents    TOO
                   Freezing                               101
                   Evaporation                             101
                   Electrodialysis                         101
                   Ion Exchange                            102
                   Reverse osmosis                         102

                                    iv

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                        CONTENTS  (Cont•d)


Section

VIII     COST, ENERGY, AND NON-WATER QUALITY ASPECTS       1Q7

              Cost and Reduction  Benefits  of Alternative
                Treatment and control Technologies         107
              Basis of Economic Analysis                   107
              Effluent Reduction  Subcategory 1             116
              Impact of Waste Treatment Alternatives
                on Finished Product Price                  117
              Alternative Treatment Systems                118
              Related Energy Requirements  of Alternative
                Treatment and control Technology          121
              Non-Water Quality Aspects of Alternative
                Treatment and control Technology          122
                   Air Pollution                           122
                   Solid Waste Disposal                    122

IX       BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY
           AVAILABLE GUIDELINES AND LIMITATIONS            125

              General                                      125
              Effluent Reduction  Attainable                126
              Best Practicable Control Technology         128
                Currently Available
              Rationale for Selection of BPCTCA            128
                   Total cost of  Achieving Effluent        128
                     Reduction
                   Age and Size of Equipment and
                     Facilities                            129
                   Engineering Aspects of  Control
                     Techniques                            129
                   Processes Employed                      129
                   Process Changes                         129
                   Non-Water Quality Environmental
                     Impact                                130

X        BEST AVAILABLE TECHNOLOGY ECONOMICALLY
           ACHIEVABLE - GUIDELINES AND LIMITATIONS         131

              General                                      131
              Effluent Reduction  Attainable                132
              Best Available Technology Economically
                Achievable                                 134
              Rationale for Selection of BATEA             135
                   Total Cost of  Achieving Effluent
                     Reduction                             135

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                        CONTENTS  (Cont»d)


     on

              Age and Size of Equipment  and Facilities     136
              Processes Employed                           136
              Engineering Aspects of Control Techniques    136
              Process changes                              136
              Non-water Quality Environmental  Impact       136

XI       NEW SOURCE PERFORMANCE STANDARDS                  137

              General                                      137
              Improved In-plant Process  control            137
              New Source Performance Standards            138
              Pretreatment Requirements                    138

XII      ACKNOWLEDGEMENTS'                                 139

XllI     REFERENCES                                        141

XIV      GLOSSARY                                          147

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                             TABLES
Number                    Titj.e

  1      Best Practicable Effluent Limitation Guide-
           lines July 1, 1977                             4
  2      Best Available Effluent Limitation Guidelines
           July 1, 1983                                   5
  3      Classification System                            26
  H      Principal Processes of Subcategories             29
  5      Hide Curing                                      34
  6      Wastewater Quantities                            41
  7      Raw Wastewater Characteristics by category       44
  8      Plain sedimentation                              66
  9      Chemical Treatment                               69
 10      Combined Municipal - Tannery Treatment Systems   75
 11      Trickling Filter Systems                         80
 12      Aerobic Lagoon Systems                           81
 13      Aerobic - Anaerobic Systems                      84
 14      Activated Sludge Systems                         88
 15      Estimated Waste Treatment Cost for Sub-
           category 1                                     110
 16      Estimated Waste Treatment Cost for Sub-
           category 2                                     111
 17      Estimated Waste Treatment Cost for Sub-
           category 3                                     112
 18      Estimated Waste Treatment Cost for Sub-
           category 4                                     113
 19      Estimated Waste Treatment Cost for Sub-
           category 5                                     114
 20      Estimated Waste Treatment Cost for Sub-
           category 6                                     115
 21      Estimated Industry Investment to Meet BPCTCA
           Effluent Limitations                           119
 22      Estimated Industry Investment to Meet BACTEA
           Effluent Limitations                           120
 23      Best Practicable Effluent Limitation Guide-
           lines - July 1, 1977                           127
 2U      Best Available Effluent Limitation Guide-
           lines - July 1, 1983                           133
                                vii

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                             FIGURES
Number                    Title

  1      Flow Diagram - Typical Cattlehide Tannery
  2      Flow Diagram - Typical Sheepskin Tannery
  3      Flow Diagram - Typical Pigskin Tannery
  14      Category System
  5      Wastewater Flow vs. Tannery Production for
           Category 1
  6      Tannery Production vs. Relative Cumulative
           Frequency for Category 1
gage

 13
 21
 24
 28

 40

 46
                           viii

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                            SECTION I

                           CONCLUSIONS


For  purposes of establishing effluent limitations guidelines and
standards of  performance,  the  leather  tanning  and  finishing
industry  has  been  divided  into  six major subcategories.  The
following tabulation is a capsule summary of these subcategories.

                        INDUSTRY SUBCATEGORIES

           	Primary Processes	
                                                          Leather
SubcateqorY   Beamhouse             Tanning             Finishing

   1       Pulp hair                 Chrome                 Yes

   2       Save hair                 Chrome                 Yes

   3       Save hair                 Vegetable              Yes

   U       Hair previously removed   Previously tanned      Yes

   5       Hair previously removed   Chrome                 Yes
           or retained

   6       Pulp or save hair         Chrome or no tanning   No


These subcategories have been derived principally by similarities
in process and waste  loads.   Such  factors  as  age  of  plant,
climate, and waste control technologies favor segmentation of the
industry  into  these six subcategories.  However, the facility's
size  reguired  an  exception   within   the   subcategorization.
Different  limitations were established for plants within the six
subcategories  due  to  unequal  economic  impacts   created   by
diseconomies of scale.  Currently, waste from about 60 percent of
the tanneries (and approximately 60 percent of the production) is
discharged  to  municipal  sewer  systems, while the remainder is
discharged directly to surface waters.

Compared with other industries, waste  treatment  facilities  for
those  plants  in  the  leather  tanning  and  finishing industry
discharging directly to rivers or streams are  severely  lacking.
There  are  no  exemplary  waste  treatment  plants handling only
tannery waste.

It is concluded  that  the  technology  is  available  to  effect
considerable  improvement  in waste discharges with major removal
of BOD5 and suspended solids by  July  1,  1977.   The  estimated
capital   cost   of  achieving  effluent  limitations  (the  best
practicable control technology currently available)  by  tanneries
discharging  to  receiving waters is $45.8 million (August, 1971,
price  levels).    Total  annual  costs  (including  depreciation.

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interest,  operation, and maintenance)  for pollution control will
increase finished product costs from about  1.7  to  H.U  percent
(August, 1971, prices)  depending on industrial subcategory.

It  is  further concluded that by July 1, 1983, implementation of
treatment facilities to effect further removal of BOD and  SS  as
well as major removal of sulfide and nitrogen  (the best available
control  technology economically achievable)  will be required for
facilities  discharging  directly  to  surface  waters.      Total
capital  investment  for  achieving  1983 effluent limitations is
estimated  at  $61.0  million  (August,  1971,   prices).    This
represents  an  additional  $15.2 million investment over BPCTCA.
Total annual costs for  the  best  available  control  technology
economically  achievable  will  increase  finished product prices
from about 0.6 to 1.4 percent (August 1971, prices)  for differing
subcategories.  The overall cost of  both  best  practicable  and
best  available control technology is estimated to increase final
product  costs  from   2.3   to   5.8.     percent   for   various
subcategories.

Some  economies may be achieved during implementation of the best
available  control  technology  economically   achievable   waste
treatment  facilities  if  the industry can find a substitute for
ammonia compounds used in the  bate  process.    However,  organic
nitrogen  from processing hides will still require some degree of
nitrification-denitrification facilities.

Standards of performance for new sources are  equivalent  to  the
best   practicable   control   technology   currently   available
requirements.

Complete reuse of treated effluent cannot be achieved without re-
moval of dissolved solids.  Methods for removing dissolved solids
and subsequent disposing  of  the  concentrated  brines  are  not
sufficiently   defined  technically  or  economically  to  enable
implementation without a great degree of risk.   In  addition,  a
further  complicating  factor  is  imposed  if  dissolved  solids
removal becomes a requirement for those tanneries providing  only
pretreatment  for  discharge  to  a  municipal  system.   Since an
extremely good quality water  is  necessary  as  an  influent  to
processes  capable  of  dissolved  solids removal, all tanneries,
regardless of discharge  point,  would  require  installation  of
major   biological  treatment  facilities  in  addition  to  that
required for dissolved solids removal.

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                           SECTION II

                         RECOMMENDATIONS
Presented  herein  are  the  recommended   effluent   limitations
guidelines  for  the leather tanning and finishing industry.  The
proposed basic levels of  waste  constituents  in  the  following
tabulations  are  recommended  to  be the average values based on
production  data  and  analyses  of  24-hour  composite   samples
collected during any 30-day period.  However, the pH should never
exceed  values  shown  as  measured by grab or composite samples.
Due to process upsets, emergencies such as a  power  failure  and
other such occurrences, there are times when these average values
may  be exceeded.  The daily maximum allowable level proposed for
all parameters except pH is two times the basic values  presented
here.   Such  a maximum allowable level would be checked by  com-
posite samples collected at any time.

Application of the best practicable control technology  currently
available,   as  shown  in  Table  1,  results  in  the  effluent
limitations guidelines to be met by July 1, 1977,  for  tanneries
discharging  directly  to surface waters.  Additional allocations
of BOD5 and TSS are allowed tanners with a production  less  than
17,000~"kg hide per day.

Application of the best available control technology economically
achievable  results  in the effluent limitations guidelines shown
in Table 2 for tanneries discharging directly to surface  waters.
These limitations are to be achieved by July 1, 1983.

Effluent limitations guidelines for new tanneries yet to be built
(new  source  performance standards)  are the same as for the best
practicable control technology currently available.

The requirement  to  remove  dissolved  solids  by  1983  is  not
recommended.   The technology for widespread removal of dissolved
salts and disposal of concentrated brines is  not  well  defined.
Extensive research efforts should be made by the industry to find
a  substitute  for  salt  used  in  hide curing, which is a major
contributor of the dissolved solids.

The technologies to which the above limitations and standards are
based assume extensive water and chemical conservation within the
industry and  properly  designed  and  operated  waste  treatment
facilities.

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                               TABLE   1

                BEST PRACTICABLE EFFLUENT LIMITATIONS

                      MAXIMUM THIRTY DAY AVERAGE
                             (July 1, 1977)
                                           SUBCATEGORY
PARAMETER (1)
BOD5_
TOTAL CHROMIUM
OIL & GREASE
TSS
kg/1000
1 2
4.0
0.10
0.75
5.0
4.6
0.12
0.90
5.8
kg hide
3
3.8
0.05
0.75
4.8
(lb/1000
4
1.6
0.10
0.25
2.0
Ib hide)
5
4.8
0.06
0.90
6.0
6
2.8
0.10
0.35
3.4
(1)  For all  subcategories pH should range between  6.0 and 9.0 at any time.

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                             TABLE 2

             BEST AVAILABLE EFFLUENT LIMITATIONS
                         (July 1, 1983)
                                       SUBCATEGORY
PARAMETER(l)                 kg/1000 kg hide (lb/1000 Ib hide)
                      123456
BOD_5                 1.40   1.60   1.30   0.50   1.60   0.70

TOTAL CHROMIUM       0.05   0.06   0.05   0.02   0.06   0.03

OIL & GREASE         0.53   0.63   0.50   0.24   0.63   0.34

SULFIDE              0.005  0.006  0.005  0.002  0.006  0.003

TSS                  1.5    1.8    1.4    0.6    1.8    0.8

TKN                  0.27   0.32   0.25   0.10   0.31   0.14
(1) For all subcategories pH should range between 6.0 and
    9.0 at any time

    For all subcategories Most Probable Number  (MPN) of
    Fecal Coliforms should not exceed 400 counts per 100 ml

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                            SECTION III

                           INTRODUCTION
The  1972  Amendments  to the Federal Water Pollution Control Act
require the U. S. Environmental Protection  Agency  to  establish
effluent  limitations  which  may  be achieved by point discharge
sources into navigable waters.  For existing waste  sources,  the
Act   requires   application  of  the  best  practicable  control
technology currently available by July 1,1977, and application of
the best available control technology economically achievable  by
July  1,  1983.   For  new  waste  sources,  the  best  available
demonstrated control technology must be applied.

The broad objectives of this study are to establish  the  control
and  treatment  technology  available  and  to  present suggested
effluent  limitation  guidelines  and  standards  of  performance
applicable  to  the  leather tanning and finishing industry.  The
principal elements of the study are as follows:

    1.   Establish the various subcategories within  the  leather
         tanning  and  finishing  industry  subject  to  effluent
         limitations and standards of performance.

    2.   Characterize wastes from each major subcategory  of  the
         industry  by  assessing  flows  and  constituents in the
         waste water.

    3.   Establish existing and potential control  and  treatment
         technologies  applicable  to  each  subcategory  of  the
         industry.  Such technology includes  in-plant  controls,
         end-of-process  control  and treatment, and pretreatment
         prior to  discharge  to  a  publicly-owned  waste  water
         system.

    4.     Outline   the   best  practicable  control  technology
currently available and the best available  treatment  technology
economically  achievable  for  establishing  effluent  limitation
guidelines.

    5.   Prepare  a  report  summarizing  control  and  treatment
         technology, together with suggested effluent limitations
         guidelines and appropriate cost information.

Previous Study

A  principal  source of information for this investigation is the
"Industrial Waste Study of  the  Leather  Tanning  and  Finishing
Industry"   conducted   for  the  Water  Quality  Office,  U.   S.
Environmental Protection Agency, by Stanley consultants (October,
1971).  Relevant data from that study are included herein.

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Industry Trends

The number of tanneries in the U. S. has steadily decreased  from
around 7,500 operating in 1865 to approximately 1,000 by the year
1900  (1) .   The number has continued to decrease from the turn of
the century to about  200  to  210  tanneries   (wet  process)  in
operation  at  the  present  time.   Another 225 to 260 firms are
engaged in finishing  operations  (essentially  dry  process)  on
leather tanned at seme other location.

Tanneries  are principally clustered in the New England and Mid—
Atlantic  states,  Chicago-Milwaukee  area,   and   Gloversville-
Johnstown  area in New York.  Others are scattered throughout the
U. S.

Since about I960, several  significant  developments  have  taken
place  in  the domestic tanning industry.  Most noteworthy is the
increased export of cattlehides to countries  for  production  of
leather.  In 1972, hides from over 47 percent of the 36.5 million
cattle  slaughtered  in  the  U.  S. went to foreign tanners (2).
Since 1960, export of hides has more than doubled, while domestic
tanning has reduced slightly.  The  increased  number  of  export
cattlehides  has mainly gone to Japan.  Lower labor costs seem to
enable foreign countries to compete in  the  U.  S.  leather  and
leather products industry; hence, the greater demand for hides.

Exporting  hides  for tanning has also had a pronounced effect on
the finished product market.   For  example,  in  1960,  imported
shoes  accounted  for  about  4.3  percent  of  the U. S. market,
contrasted to over 36 percent of the 1972 market  (2).   With  the
increased  import  of  shoes,  domestic  tannage  has  been  used
proportionately more for clothing and other uses.

Other changes in the leather industry include increasing  use  of
leather  substitutes,  such  as  plastic,  which  have absorbed a
larger portion of the total market.  Experimentation  with  other
synthetic products may yield further competitive materials.

From  an  economic  standpoint,  the domestic leather tanning and
finishing industry has recently felt a squeeze from  both  ends--
raw  material  and  finished product.  Greater foreign demand for
cattlehides has resulted in part from a change in  a  restrictive
hide  export  policy  by  other hide producing nations.  This has
recently caused the price of raw cattlehides to increase greatly.
Heavy native steer hides have ranged in price from  8.3  to  20.3
cents per pound in the period 1960-71.  Average price in 1971 was
14.4  cents per pound.  In 1972 prices increased to 42.4 cents in
August, with an average for the year of  29.7  cents  per  pound.
These  raw product prices have now fallen to about twice those in
1971.  In addition, competition from foreign  countries  such  as
Japan,  Italy,  and Spain in the finished leather products market
has reduced the potential revenue from domestic leather firms.

Cattlehides constitute the bulk of the tanning done in the U. S.,
representing about 90 percent of the estimated  pounds  of  hides

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tanned.   Sheep and lamb represent about the next largest volume.
Pigskin  production  is  estimated  to  be  the   third   largest
production  volume  in the U. S.  Since I960, domestic tanning of
cattlehides,  sheepskins,  and  lambskins  has  trended  slightly
downward.

Other  types  of  skins  or  hides processed in the U. S. include
goat, kid, hairsheep, and horse.  All of  these  tanning  volumes
have fallen significantly since 1960.  Various other skins tanned
in  the  U. S.  on a very limited basis include deer, elk, moose,
antelope, and rabbit, as well as rare skins  such  as  alligator,
crocodile, seal, shark, and kangaroo.

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                            SECTION IV

                      INDUSTRY CATEGORIZATION
Standard Manufacturing Processes

Tanning  is  the  process of converting animal skin into leather.
The skin is divided into three layers:  flesh, derma  or  corium,
and  epidermis.   The  epidermal and corium layers constitute the
leather-making portion of the skins or hides, and consist  mainly
of  the  protein collagen after undesirable proteins are removed.
Tanning is essentially  the  reaction  of  collagen  fibers  with
tannin,   chromium,  alum,  or  other  tanning  agents  with  the
resulting formation of leather.

A major factor affecting waste production in the leather  tanning
and  finishing industry is the type of manufacturing process used
to convert the various types of animal skins to  the  tanned  and
finished   leather.    This   variance   is   recognized  in  the
classification system used to describe the industry.

The process of  tanning  originally  developed  as  an  art  many
centuries   ago,  but  has  in  recent  times  been  modified  by
application of scientific principles.  As in  any  industry,  the
approach  to  production  of  a  suitable  leather by the average
tannery relies a great deal on past  experience.   In  a  typical
process,  such  as  unhairing,  the  concentration  of  lime  and
sharpeners (such  as  sodium  sulfide  and  sodium  sulfhydrate),
temperature,   and  processing  time are interrelated.  As in most
chemical reactions, chemical  concentrations  and/or  temperature
may be increased to decrease the processing period.  Tanners vary
process  conditions  to  control  the  quality  of  the  finished
product.  Therefore, there is a significant amount of variance in
processing techniques, even between  two  tanners  producing  the
same finished product, to satisfy individual product needs.

In  this  study,  a  manufacturing process is defined as a single
step in the complete manufacturing  operation  where  alternative
steps    may    result    in    significantly   different   waste
characteristics.  A process can consist of one  or  a  series  of
sub-processes.   In  any  defined  process,   sub-processes  would
remain the same.  The industry can best be described and analyzed
on this manufacturing process concept basis.  This allows for the
variance of processes used among  plants.    with  this  approach,
waste  loads  and  effluent  requirements  can  be  more  readily
described.

For  purposes  of  characterizing  waste  loads,  there  are  the
following  standard  applicable  processes:   beamhouse; tanhouse;
retan, color, and fatliquor; and finishing.    Chemicals  such  as
lime, sodium sulfide, sodium sulfhydrate,  basic chromium sulfate,
vegetable  compounds,  mineral  acids,  and  sodium  chloride are
employed with the various processes.
                               11

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The discussion and description of manufacturing  processes  which
follow are based upon the three major hide or skin types produced
in  the  U. S.:  cattlehides, sheepskins, and pigskins.  The pro-
cesses and sub-processes discussed herein represent an  inventory
of   those   most   typical  of  the  entire  industry.   Process
descriptions which  follow  have  been  kept  brief,  since  more
detailed information is readily available from the literature  (3)
<<*).

Cattlehide Tannery Processes

There  are  four  processes in a typical cattlehide tannery which
contribute waste loads:

    1.   Beamhouse.

    2.   Tanhouse.

    3.   Retan, color, and fatliquor.

    4.   Finishing.
                                12

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FLOW   DIAGRAM
TYPICAL CATTLEHIDE TANNERY
LMEND

HIDES ABO LEATHER   ^^—M—

noaSS MT£JI)*L»   ——	—
                                                                                  LIQUID HASTES
                                                           RETW-COLW-FATLIQUOfi
                                                                                            W1STE EFFLUEIT (CLEtl-UFILV)
                                        I  Lsruia	_
                                        |_S_OU_D_HASTE_[SIUVmOS)	

                                     WASTE EFFLUENT
                                                                                      RETAN- COLOR •FfcTLIQUQR
                                                                                          (ALTERNATE)
                                                                            FROM TiNHOUSE
                                                                                        COLOR

                                                                                        •ATLIQUOR
                                                                                                  FIGURE  1
                                                   13

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These processes are shown schematically on Figure 1.    There  are
alternate  processes  for each of the first three basic processes
which  produce  significantly  different  waste  characteristics.
Sub-processes  and  the  operations  which take place within each
process are described as follows:

    BEAMHOUSE PROCESS:

    1.   Receiving ~ Nearly all cattlehides received at tanneries
         are either cured green  salted  or  brined  hides,  with
         brined  hides   predominating.   In  a few isolated cases
         where transit time is short, green hides  without  prior
         curing  have  been  sent  directly  from  a  packer to a
         tannery and processed.

         Green hides, after trimming and grading,  are  cured  at
         the packing house by spreading the hides, flesh side up,
         and  covering  with  salt.   Another  layer  of hides is
         placed over the salted hides, again flesh side  up,  and
         covered  with salt.  This process continues until a pack
         of hides about 5 to 6 feet high results.  A heavy  layer
         of  salt  is  placed  over  the top layer of hides.  The
         natural liquid of the hides dissolve a  portion  of  the
         salt to form a brine.  In this process, salt is absorbed
         and  by  diffusion and osmosis causes a reduction of the
         moisture content in the hide.  After 10 to 30 days  from
         the  date  the  pack is closed, the hides are considered
         adequately cured.  Each hide then has  the  excess  salt
         shaken  off,  is  folded  individually,  and  shipped in
         packs, either to tanneries or to warehouses for storage.
         The size of the pack depends on a number  of  variables,
         such  as  size  of the packing house, size of shipments,
         and the method of shipment.

         Brined hides are prepared at the packing house or  at  a
         separate  hide  processing  facility  by agitating fresh
         hides in a saturated brine solution until the  salt  has
         replaced the desired amount of moisture within the hide.
         In  this  process,  hides are also cleaned by removal of
         manure and other attached  foreign  matter.    Hides  are
         then  removed,  drained, and bundled in a manner similar
         to that used for  green  salted  hides.   Hides  may  be
         fleshed  before  or  after  brining.   "Safety  salt" is
         usually sprinkled on each  hide  before  shipment.   The
         brining  process takes two to three days, which makes it
         attractive to the packer or hide  curing  establishment,
         since  there  is  no  need  to hold a large inventory of
         hides.  The brining process is preferred by most tanners
         since it tends to produce cleaner hides.  Increased  use
         of  brined  hides  in  recent  years  demonstrates these
         preferences by both packer and tanner.

    2.   Storage - Hides are normally stored at  the  tannery  in
         the pack as received.  No special storage conditions are
                               14

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     maintained in most tanneries other than that required to
     keep hides at the moisture content as received.

3.   Siding and Trimming  -  The  usual  first  step  in  the
     processing  of  hides  from storage at the tannery is to
     open a folded hide and trim it.   The hides then  may  be
     cut  in half along the backbone, which is referred to as
     halving or siding.  Sometimes  hides  are  halved  after
     unhairing or tanning.

     Sides  are  usually  palletized  for transporting to the
     next step in the process.  Trimmings are  collected  for
     shipment to glue or other by-product manufacturers.

4.   Washing and Soaking - Sides  (or  in  some  cases  whole
     hides)  from the siding and trimming operation are placed
     in  vats  (with  or  without  paddles),  drums,   or hide
     processors (concrete mixers with  special  linings)  for
     washing and soaking to restore moisture.  Water usage is
     generally  less  with  hide  processors,  although  some
     tannery  people  have   expressed   the   opinion   that
     equivalent  reduction  in water use can be achieved with
     drums.

     In this process dirt,  salt,  blood,  manure,  and  non-
     fibrous  proteins  are removed from the hides.   There is
     considerable variation in the  quantity  of  such  waste
     material,  depending  on the time of year and the source
     of the hides.

     Depending on the type of  leather  produced,  additional
     washes  (rinses)   may also occur at several other points
     in the  tanning  process,  including  after  liming  and
     dehairing, after bating, after tanning, and prior to and
     following coloring.

5.   Fleshing - Fleshing is the removal of  attached  adipose
     fatty  tissue  and meat which have been left on the hide
     at the packing house.  It is done on a fleshing  machine,
     in which the hide is carried through  rolls  and  across
     rotating  spiral  blades which remove the flesh from the
     hide.   Cold  water  is  necessary  to  keep   the   fat
     congealed,  but  the  fat represents an additional waste
     disposal load.

     Most hides are fleshed at the  packing  house  or  at  a
     separate  hide  processing facility, particularly in the
     case of brined hides.  When flesh is  removed  prior  to
     liming   it  is referred to as green fleshing; when it is
     performed  after  liming  it  is  referred  to  as  lime
     fleshing.   In any case,  fleshings are normally recovered
     and  sold to plants for rendering or conversion  to glue.
     If fleshings are properly handled, there is very  little
     liquid  or solid waste contribution from this operation.
                           15

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6,   Unhairing  -  Hair  is  removed  by  chemical  loosening
     followed   by   either  machine  pulling  or  chemically
     dissolving the hair.  Machine removal is practiced where
     it is desired  to  recover  the  hair.   The  dissolving
     process is referred to as "pulping" or "burning."

     For  either  type  of unhairing, the hides are placed in
     vats  (with  or  without  paddles),   drums,   or   hide
     processors  with  a lime slurry to which sharpeners such
     as sodium sulfide  and  sodium  sulfhydrate  are  added.
     When  the  hair  is  to  be  saved,  the strength of the
     solution and the  time  in  contact  with  the  hide  is
     limited   to   that   necessary   to   loosen  the  hair
     sufficiently for mechanical pulling.  If the hair is  to
     be  pulped, stronger solutions and/or longer time cycles
     are used and the hair may be totally dissolved.

     Sometimes hides are relimed to make the hide  swell  for
     easier  splitting.   In a save hair operation, flesh and
     hair removal is sometimes followed by a "scudding"  step
     to ensure removal of hair roots and fine hairs.

     The liming and unhairing process is one of the principal
     contributors  to  the  waste  effluent.   In a save hair
     operation with good recovery of hair,  the  contribution
     to  the effluent is substantially lower than in the pulp
     hair operation.

TANHOUSE, PROCESS:

1-   Bating - Bating is the first step in preparing the stock
     for the tanning process.  It may be done in either  vats
     (with  or  without  paddles), drums, or hide processors.
     The hides are placed in the processing  equipment  which
     contains  a solution of ammonium salts and enzymes.  The
     purpose of this operation is to:

     a.   De-lime skins.

     b.   Reduce swelling.

     c.   Peptize fibers.

     d.   Remove protein degradation products.

2-   Pickling - The pickling sub-process follows  the  bating
     step  and  is  normally  done  in the same equipment.  A
     brine and acid solution is used to bring the hides to an
     acid condition in  preparation  for  subsequent  tanning
     sub-process.   In  addition to conditioning the hide for
     receiving the tanning agent, it  prevents  precipitation
     of chromium salts.

     Pickling  is  always  done  before  the  chrome  tanning
     process and may be done before vegetable tanning.
                           16

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3-   Terming - Nearly all cattlehides  in  this  country  are
     either chrome or vegetable tanned; very little is tanned
     with alum or other tanning materials.

     Vegetable tanning is the older process, and is performed
     in   a   solution  containing  plant  extracts  such  as
     vegetable tannins.  This method is usually used for  the
     heavy   leathers   such   as  sole  leather,  mechanical
     leathers, and saddle leathers.  Shoe upper leathers  and
     other  lighter  leathers  are  usually  chrome tanned by
     immersion in a bath containing proprietary  mixtures  of
     basic chromium sulfate.

     Vegetable  tanning  is usually done in vats, principally
     due to longer process times, while chrome tanning  takes
     place in drums or hide processors.

     In  some  cases,  depending  on  type  of  leather being
     produced, hides are tanned in  the  tanhouse  and  later
     retanned  as  a  part  of  the  retan,  color, fatliquor
     process.  Where different tanning agents are used in the
     initial  and  retan  steps,  it  is   referred   to   as
     combination tanning.

     Waste   effluents   from   the   tanning   process   are
     substantial.  Recycle  of  vegetable  tan  solutions  is
     becoming  more common in the industry; that which cannot
     be recycled may be used for retanning or evaporated  and
     recovered.   Recycle  and  recovery  of  chrome  tanning
     solutions is also practiced at a few locations.

4.   Splitting - The tanned hide is split to produce a grain-
     side piece of essentially constant thickness and a flesh
     side layer.  The  flesh  side  layer  or  split  can  be
     processed separately or sold to split tanners.

RETAN^_COLOR> FATLIQUOR PROCESS :
            ~  Retanning  is  done  principally   to   impart
     different  characteristics in the finished leather which
     it would lack if tanning were carried out in  one  step.
     Retanning   may  use  chrome,  vegetable,  or  synthetic
     tanning  agents,  and  it  is  usually  done  in   drums
     immediately preceding coloring and fatliquoring.

2.   Bleaching - Bleaching hides with sodium bicarbonate  and
     sulfuric acid after tanning is commonly practiced in the
     sole  leather  industry.   Bleaching  is done in vats or
     drums.

3«   Coloring -  Coloring  is  done  in  the  same  drums  as
     retanning,  and  may  be  done  either  before  or after
     fatliquoring.   Natural  dyes  may  be  used,  but  many
     synthetic products are now available for this purpose.
                           17

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    **•   E§£liai32EiIi2 ~ Fatliquoring is the  operation  in  which
         oils  are  added to replace the natural oils lost in the
         beamhouse and tanhouse processes and to make the leather
         pliable.  The amount of oil added depends on the end use
         of the leather.

         Liquid wastes  from  the  retan,  color,  and  fatliquor
         process  may  be  high volume-low strength compared with
         the other processes.

FINISHING PROCESS:

Finishing operations such as drying, wet-in coating,  staking  or
tacking,  and plating which follow the wet processes provide only
minor contributions to the liquid waste primarily from cleanup of
the paster drying plates and from paint spray booth water baths.

Trimmings are disposed as solid waste, and dust collected may  be
disposed in either wet or dry form.

Sheepskin Tannery^Processes

Sheepskin  tanning  processes  are  somewhat  similar  to pigskin
tanning in that generally  there  is  no  beamhouse  process  and
degreasing is required.  The three major processes are:

    1.   Tanhouse.

    2.   Retan, color, and fatliquor.

    3.   Finishing.

These  processes  and  the  sub-processes which take place during
manufacturing are shown on Figure 2 and are described as follows:

    TANHOUSE PROCESS:

    1.   Receiving -  Most  sheepskins  are  received  at  U.  S.
         tanneries  from  both  domestic  and imported sources as
         pickled skins.  These skins, which are salt  cured,  are
         normally  tied  in  bundles  of  one dozen skins.  These
         skins have had the wool removed at the  packer  or  wool
         pullery  and  processed  to  the pickled condition.  The
         wool pulling represents a beamhouse process.

         Skins tanned with the wool intact  are  referred  to  as
         shearlings.   Tanning  of these skins does not involve  a
         beamhouse process.

         Pickled skins  have  been  preserved  for  shipment  and
         storage  by  immersion  in a solution of brine and acid.
         Shearling skins are cured in a salt brine only.   Excess
         solution is drained prior to bundling.
                                18

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2-   Storage - No special provision for storage  is  provided
     at  most  tanneries  other than to keep the skins moist.
     There is some indication that  pickled  skins  held  for
     extended  periods  should  be  kept below 30°C (86°F)  to
     avoid deterioration.

3.   Fleshing - Skins from storage are taken from the bundle,
     inspected, and fleshed.  Hides which have  been  fleshed
     prior   to  receipt  at  the  tannery  will  usually  be
     refleshed after tanning.  Shearling  hides  are  usually
     fleshed  after  a  wash and soak operation.  Fleshing is
     done on the same  type  of  machine  used  for  fleshing
     cattlehides.   The  skin  is  carried  through rolls and
     across rotating spiral blades  which  remove  the  flesh
     from the skins.

     Fleshings  and  trimmings  are  normally  collected  and
     disposed of as a solid waste.

4.   Degreasing - Skins are  placed  in  drums,  washed,  and
     soaked, after which solvent or detergent is added in the
     same drums to remove grease.

     Grease  is  recovered  as  a by-product from those skins
     which  have  had  the  wool   removed.    When   solvent
     degreasing is used, the solvent is recovered and reused.

     Skins    with   the   wool   on   (shearlings)    require
     substantially  more  water  in  the  washing  (scouring)
     operations   and   grease   recovery   is  not  normally
     practiced.

     There is a waste effluent from this process and a  small
     amount  of  vapor,  including  solvent  exhausted to the
     atmosphere.

5-   Tanning - Sheepskins may be either chrome  or  vegetable
     tanned, although the majority are chrome tanned.

     Where the skins have been received at the tannery in the
     pickled   condition,  there  are  no  liming  or  bating
     operations.  Skins from  the  degreasing  operation  are
     placed in drums with salt water and proprietary mixtures
     of   basic   chromium  sulfate  for  chrome  tanning  or
     solutions of the natural tannins for vegetable tanning.

6-   Refleshing -  In  some  cases,  there  is  a  refleshing
     operation  following  tanning,  which  produces  a small
     amount of solid waste.
1.    Coloring - Skins to be colored are  immersed  in  a  dye
     solution  in drums.  Generally, synthetic dyes are used.
                           19

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     Some  bleaching  may  be  done  prior  to  coloring   of
     shearlings.

2-   Fatliquoring - This operation is performed in  the  same
     drum  used  for  coloring.   Skins  are  immersed  in  a
     solution containing various oils to replace the  natural
     oils of the skin lost in the tanning process.

FINISHING PROCESS:

There  are  a  number of operations which follow the coloring
and fatliquor process, including  drying,  skiving,  staking,
carding,   clipping,   sanding,   and   buffing.   These  are
essentially  dry  processes,  and  the  only   liquid   waste
contributed is from cleanup operations.

Solid  wastes  from the finishing operation include trimmings
and skivings.  Dust from the sanding and  buffing  operations
may  be collected dry and disposed of as a solid waste or wet
and carried into the waste water system.
                           20

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    FLOW  DIAGRAM
    TYPICAL  SHEEPSKIN  TANNERY
                                                                     COLOR FATLIQUOR
(l] SHEARLINGS (WOOL LEFT ON) ARE
   RECEIVED AS CURED SKINS  M(f-
   MOIJSE SUB-PROCESSES INCLUDE
   WASH i SOAK FLESHING DEGREiS

   ING  PICKLING iND TANNING
                                             I HASTE EFFLUENT
                                                                                                       FIGURE 2
                                                   21

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Piqskin^TannerY^Processes

The pigskin tanning processes differ from cattlehide  tanning  in
that  there is essentially no beamhouse process, since most skins
have the external hair removed at the packing house.   Degreasing
of  the  skins  is  a  required  tanhouse sub-process.  The waste
characteristics from pigskin tanneries are established from these
three processes:

    1.   Tanhouse.

    2.   Color and fatliquor.

    3.   Finishing.

These processes and the operations which take place  within  each
process are shown on Figure 3 and described as follows:

    TANHOUSE PROCESS :

    !•   BkssiYioS "* Nearly all  pigskins  are  received  at  the
         tannery  either  as  fresh  frozen  skins  or  as brined
         refrigerated skins.  They are usually tied in bundles of
         40 to 50 pounds of skin.  In some cases frozen skins may
         be in paper bags.

    2.   Storage - Refrigerated storage is used at  most  of  the
         tanneries for skins which are to be held before tanning.
    3.   Deceasing - Solvent degreasing has been  used  by  some
         pigskin  tanneries.   In  this  process,  the  skins are
         placed in drums, then washed and soaked in warm water to
         bring them up to a suitable temperature for  degreasing.
         Solvent is added and the skins are tumbled to remove the
         grease.   The  solution of solvent, grease, and water is
         pumped  from  the  drums  to  large  tanks  where   some
         separation is achieved by decanting.  From the tanks the
         solvent  and grease is sent to a stripping column, where
         the solvent is recovered for reuse.  Grease is recovered
         as a by-product.

         There is a waste effluent from this process, as well  as
         a  small  amount  of  vapor,  including solvent which is
         vented to the atmosphere.

         An alternate method, in which the skins are  tumbled  in
         hot  water  and  detergent, has also been used.  In this
         operation, grease is recovered by decanting or  skimming
         it  from  the  top  of  holding  tanks to which waste is
         diverted prior  to  entry  into  the  main  plant  sewer
         system.

    4.   Liming - From the degreasing  operation  the  skins  are
         placed   in   tanning  drums  with  a  lime  slurry  and
                               22

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     sharpeners.  The  purpose  of  this  is  to  remove  the
     embedded portion of the hair from the skins.

5-   Siting ~ Tne bating operation takes place  in  the  same
     drums used for liming.  The purpose of this operation is
     to  delime  the  skins to reduce the swelling and remove
     any protein degradation products.

6-   Pickling - The pickling operation follows the bating  in
     the  same drum.  A solution of brine and acid is used to
     bring  the  skins  to  an  acid  condition  to   prevent
     precipitation   of  chromium  salts  in  the  subsequent
     tanning process.

7.   Tanning  -  Pigskin  may  be  either  chrome  tanned  or
     vegetable  tanned.   However,  the  only major tanner of
     pigskin in this country is using  only  the  chrome  tan
     process.   Chrome  tanning follows in the same drum used
     for  pickling,  using  proprietary  mixtures  of   basic
     chromium  sulfate.  Current practice is to fully tan the
     skins in this operation,  eliminating  any  need  for  a
     retan operation at a later point.

8«   Split and Shave - After tanning, the  skins  are  tumble
     dried  and then split and shaved or skived to obtain the
     desired thickness.  The split part  of  pigskin  has  no
     commercial  value as leather, and it is baled with other
     scrap and sold as a  fertilizer  component.   The  grain
     sides go to the color and fatliguor process.

COLOR AND FATLIO.UOR PROCESS;

1«   £2i°.£iU3 ~ Skins to be colored are  immersed  in  a  dye
     solution in drums.  Generally, synthetic dyes are used.

2.   Fatliquoring - This operation is performed in  the  same
     drum  used  for  coloring.   The skins are immersed in a
     solution containing various oils to replace the  natural
     oils of the skin lost in the tanning process.

FINISHING PROCESS:

There  are  a  number of operations which follow the coloring
and fatliquor process, including  drying,  coating,  staking,
and  sanding.   These  are principally dry processes, and the
only liquid waste contributed  is  from  cleanup  operations.
Where  paster  drying  is used, there is some starch from the
paste which is cleaned from the dryer  plates.   Water  baths
from  spray booths may also represent minor sources of liquid
waste.                                                   ,

Solid waste from the finishing operation includes  trimmings,
which  are  baled with the split and shave wastes for sale as
fertilizer.   Dust collected from  the  sanding  operation  is
disposed of as a solid waste.
                           23

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FLOW  DIAGRAM
TYPICAL PIGSKIN  TANNERY
                                           COLD* FlTLiOUOB
                                                                  FIGURE 3
                                24

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Classification System

As  noted  in  the foregoing discussion on standard manufacturing
processes, there are several variations in process steps.   Under
the  system  prepared  by  the  Technical  Committee  on Standard
Industrial classification, sponsored and supervised by the Bureau
of the Budget, the leather tanning and finishing  industry  bears
SIC Number 3111.

A  supplemental  digit  system  reflecting the many variations in
operations can further classify the industry.    For  purposes  of
this  study,  a  four-digit  system  is  recommended  to  reflect
significant differences in processes.  This  matrix  approach  to
the  classification  system  provides  flexibility and a rigorous
means to  encompass  all  process  variables.    The  supplemental
classification system is shown in Table 3.  Some blank spaces are
available if new processing techniques are developed.

Under  this  system, four digits appear to the right of a decimal
point following the industrial classification.  As shown in Table
1, these relate information by type of skin or  hide,  operations
undertaken  in  the  beamhouse,  tanning method used, and type of
material processed in the retan, color, fatliquor, and  finishing
steps.
                               25

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                              TABLE 3

                       CLASSIFICATION SYSTEM
                            (3111.abed)
Skin or
Hide Type
(a)
1. cattle
2. Pig
3. Sheep
4 . Dee r
5.
6.
7.
8.
9 . Other
0. Various

1.
2.
3.
H.
5.
6.
7.
8.
9.
0.
Beamhouse
Operation
(b)
Pulp Hair
Save Hair
Hair Pre-
viously
Removed
Hair
Retained
Wool
Pullery
Hide Curing
Pulp & Save

Other and
unknown

Retan,
Tanning Color, Fatliquor,
Process Finishina

1.
2.
3.
a.
5.
6.
7.
8.
9.
0.
(c)
Chrome
Vegetable
Alum
Previously
Tanned
Vegetable
and Chrome



Other and
unknown
None

1.
2.
3.
a.
5.
6.
7.
8.
9.
0.
(d)
Sides
Splits
Sides and
Splits
Bends
Skins



Other
None
Several  examples  using  the  classification system for the more
common processing methods are:

    3111.1111 - Cattlehide (including calfskin) , hair is  pulped,
    chrome tanning process used, sides finished.

    3111.1211  -  Same  as  .1111  except  hair is saved as a by-
    product.

    3111.1221 - Same as .1211 except  vegetable  tanning  process
    used.

    3111.1110  - Same as .1111 except no retan, color, fatliquor,
    or finishing is done (tanning to blue stage only).

    3111.1341 - Cattlehide, hair previously removed and hide pre-
    viously tanned prior to  receipt  of  hides  at  a  finishing
    facility (finishing operations only).
                               26

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    3111.2315  -  Pigskin,  most hair removed prior to arrival of
    skin at tannery with small amount of  residual  hair  pulped,
    chrome tanning process used, skins finished.

    3111.3315 - Sheepskin, hair removed prior to receipt of skins
    at tannery, chrome tanning process used, skins finished.

    3111.3415 - Same as .3315 except tanned with hair retained on
    the skin.

Categorization System

The  tanning industry's present standard manufacturing processing
techniques are  covered  with  approximately  35  classifications
which  are  combinations  of the four basic digits that appear in
Table 3.  Based upon available data, these  classifications  were
assessed    for    similarities    in   untreated   waste   water
characteristics and processing techniques.  This analysis results
in grouping the classification into six major  subcategories,  as
shown  on  Figure  U,  for  purposes  of  evaluating  control and
treatment  technology.   Each  subcategory  represents  a  common
manufacturing process, as shown in Table 4.

The  size  of  the  production facilities is a significant factor
which requires an exception within the subcategorization.  Severe
diseconomies of  scale  create  economic  impacts  which  require
different  BOD5_  and  TSS  limitations  for small plants and some
medium sized plants.  The basis for the size exemption allowed to
tanners with a production less than 17,000 kg hide per day  is  a
model  tannery  employing  just  over 100 men and processing just
under 800 hides per day.  Further development is described in the
economic impact study of the leather industry.

These six subcategories only  identify  operations  that  do  not
process  a  combination  of hides or skins.  Tanneries processing
various types of hides  or  skins  should  be  categorized  on  a
prorated  distribution  basis.   For  example,  a tannery that is
pulping,  chrome  tanning,  and  finishing   90,000   pounds   of
cattlehides  per  day  and  chrome  tanning  and finishing 30,000
pounds  of  shearlings  per  day   would   have   a   categorized
distribution  of 75 percent and 25 percent in Subcategories 1 and
5, respectively.   Thus,  the  suggested  control  and  treatment
guidelines  presented later herein may be administered by various
combinations of subcategories where appropriate.
                               27

-------
  STANDARD
  INDUSTRIAL
CLASSIFICATIONS
                                            DRAFT
                                          CATEGORIES
CATTLE 1.I2H
SAVE
CHROME
SIDES

CATTLE 1. 1219
SAVE
CHROME
OTHER OR UNKNOWN

DEER J. 142 IS
SAVE
CHRQ-4E
SKINS










                             ^CATEGOR^^^J
   STANDARD
  INDUSTRIAL
CLASSIFICATIONS
                                                                                 CATTLE     j. 1311
                                                                                 HAIR PREVIOUSLY REMOVE!
                                                                                 CHROME
                                                                                 SIDES
                                                                       CATEGORY  SYSTEM
                                                                                   FIGURE 4
                                                 28

-------
                             TABLE 4

              PRINCIPAL PROCESSES OF SUBCATEGORIES

                               Primary Processes
SubcategorY    Beamhouse            Tanning             Finishing

   1       Pulp Hair                 Chrome                 Yes

   2       Save Hair                 Chrome                 Yes

   3       Save Hair                 Vegetable              Yes

   4       Hair Previously Removed   Previously Tanned      Yes

   5       Hair Previously Removed   Chrome                 Yes
           or Retained

   6       Pulp or Save Hair         Chrome or              No
                                     no Tanning
                               29

-------
                             SECTION V

                      WASTE CHARACTERIZATION
General

The first step in an appraisal of tannery  liquid  wastes  is  to
define  and  quantify  applicable waste constituents.  These data
must then be related to some  unit  of  production.   Information
required  to  meet this need has been obtained from the following
sources:

    1.   Correspondence with individual tanneries.

    2.   Information data sheets for individual tanners  supplied
         through the Tanner's Council of America, Inc.

    3.   Corps of Engineers Permits.

    4.   Regulatory agency data summaries, including  engineering
         reports on individual tanneries.

    5.   Literature review.

    6.   Sampling performed at selected tanneries.

    7.   Tannery visits.

Correspondence and information data  sheets  were  received  from
over  140 wet processing firms,  corps permits for about 40 firms
were submitted and sampling to verify waste  characteristics  was
conducted  at  seven  facilities.   Information was also gathered
from about five regulatory agencies and  from  visits  to  twelve
tanneries  other  than those sampled.  Data has been assembled on
the basis of the various tannery subcategories.
                               31

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haste Constituents

Materials  which  can  appear  in  tannery  wastes  include   the
following:

    Hair                Lime               Sugars and starches

    Hide scraps         Soluble proteins   Oils, fats, and grease

    Pieces of flesh     Sulfides           Surface active agents

    Blood               Amines             Mineral acids

    Manure              Chromium salts     Dyes

    Dirt                Tannin             Solvents

    Salt                Soda ash

The basic parameters used to define waste characteristics are as
follows:

    BOD5  (Five-day Biochemical Oxygen Demand)

    COD  (Chemical Oxygen Demand)

    Suspended Solids

    Total Nitrogen

    Chromium

    Oil and Grease (Hexane Solubles)

    Sulfide

    pH

Additional  data  from  some  sources  permitted  a  check of the
various forms of nitrogen and volatile components  of  total  and
suspended  solids.   No  significant information was available on
color.  Information was also collected on total daily waste flow.

Unit Waste Quantities

Data was obtained for all parameters except water flow and pH  in
terms  of  concentrations  (mg/1).  When* combined with waste flow
records, this permitted computation of waste quantities in  terms
of weight of each waste constituent produced per day.

It  is  also  necessary  to  define  the  quantity  of each waste
constituent generated per unit of production.   Several  measures
of production were considered:

    1.   Weight of raw material processed.


                               32

-------
    2.   Number of hides processed,

    3.   Weight of finished product.

    4.   Square feet of finished product.

Each  of  the  above  has some shortcomings when used as basis of
production, as discussed below.

The weight of raw material  includes  varying  amounts  of  dirt,
manure,  salt,  and flesh.  In some instances raw material may be
green salted hides.  In other cases it may be tanned hides in the
"blue" stage.

Use of the number of hides includes all factors listed  for  hide
weight.   It also introduces a variance in weight.  A tannery may
be using a mixture of heavy and lightweight  hides.   Hides  from
winter reared animals tend to have a heavier hair coat.

Use  of  finished  product  as  a  unit  of  waste  production is
complicated by the industry's use of square feet as a measure  in
some instances and weight in others.

Weight of raw material processed has been selected as the best of
the  possible  production parameters.  The weight of raw material
varies  as  some  firms  process  salted  hides,   some   utilize
previously  tanned  hides  as  raw  material,  and  other similar
variations.  All waste constituent data are related to the weight
of the  raw  material  as  it  enters  a  particular  tannery  or
finishing facility.

Individual Process Contributions to the Waste

Each  process  in  the production of the final product makes some
contribution to the total waste load.

Hide Curing

Hide curing is not performed in the  tannery,  but  rather  in  a
packing  house  or  in a separate hide curing facility.  If it is
performed in a separate facility it is considered to be a part of
the tanning  industry.   The  hide  curing  process  consists  of
washing,   curing,  and  often fleshing of the hides.  Washing and
curing are performed simultaneously in a tank containing a strong
solution of salt.  Subjecting the hides  to  contact  with  brine
permits  penetration of salt into the hide, resulting in moisture
reduction and the inhibition  of  microbiological  decomposition.
The   brine   solution  is  continually  circulated  and  reused.
Blowdown from the system is required to offset water  gains  from
hide   moisture   losses.     This   blowdown  also  prevents  the
accumulation of foreign materials.  Although the  blowdown  which
constitutes   most   of  the  waste  flow  is  quite  small,   the
concentration of waste constituents is  quite  high.   A  typical
characterization of this waste is as follows:
                               33

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                          Table 5
                        Hide Curing
                                Concentration   kg/1,000 kg Hide
Waste Characteristics
BOD5
COD
Total Solids
Suspended Solids
Oil and Grease
Water Use, I/kg
(gal/lb)
(mq/1) (lb/1
15,610
29,610
280,500
10,400
40,200
0.24
(0.03)
,000 Ib Hidel,
3.9
7.4
70.1
2.6
10.0

Tannery Processes

Processes  which  are an integral part of the tannery include the
following:

    Wash and Soak

    Degreasing (sheepskin and pigskin)

    Unhairing (sometimes followed by supplemental liming)

    Bating

    Pickling

    Tanning (including bleaching for some vegetable tanning)

    Retanning, Coloring, and Fatliquoring

    Finishing

The waste contributions are described below:

Wash and Soak - This is the first wet process  performed  on  the
raw  material  as  it begins the tanning process.  The purpose of
this operation is to remove salt, restore the moisture content of
the hides, and remove  any  foreign  material  such  as  dirt  or
manure.  If the raw material are brine cured hides, the hides are
clean  and  the  operation  is  one  of salt removal.  With green
                               34

-------
salted hides, manure and dirt must also be removed.  The quantity
of manure and dirt can vary widely, depending on  the  season  of
the year and the origin of the animal.

Primary waste constituents from the operation are BOD5, COD, sus-
pended  solids,  and  total  solids   (including sodium chloride).
Typical range in quantities for a cattlehide  tannery  with  hair
pulping and chrome tanning are as follows:

        Constituent           kg/1.OOP kg Hide  (lb/l,000_lb Hide}_

    BOD5                                        7-22

    Suspended Solids                            8-43

    Total Solids                              143-267

Following  the  wash and soak operation the hides are fleshed, if
this  has  not  been  done  previously.   Fleshings  are  handled
separately, and should not make a significant contribution to the
liquid  waste if handled properly.  In some instances fleshing is
performed after the unhairing and liming process.

Degreasing - Separate degreasing operations are not normally per-
formed on cattlehide, but only on skins such as those  from  pigs
and sheep.  Two types of degreasing are used:

    1.   Hot water with detergent.

    2.   Solvent.

In  both  cases  the grease is separated and recovered.  However,
some grease is not captured and enters the  plant  waste  system.
In the case of solvent degreasing, the solvent is also recovered.
In  addition to grease, BODJ5, COD, and suspended solids are other
waste constituents.

The grease entering the plant waste system consists of only  that
portion  which escapes the recovery process.  In pigskin tanning,
total grease removed from the skin can approach 100 kg  (Ib)  per
1,000  kg  (lb) of skins.  The quantity entering the waste stream
is only a small part of this.  Unfortunately,  reliable  data  on
grease  content  of the waste stream is not available.  The major
problem  arises  from  the  difficulty  in  obtaining   a   truly
representative sample.

Unhairing - Two processes are used for unhairing:

    1.   Hair save.

    2.   Hair pulp (or hair burn).

In  the  hair save operation, the hair is loosened for subsequent
machine removal.  Lime and sharpeners (sodium sulfhydrate,  etc.)
are used to perform this function.  The waste is characterized by


                               35

-------
a  high  alkalinity,  pH,  sulfide,   and  nitrogen  content.   The
nitrogen content results  from  the   reaction  of  the  unhairing
solution  with  the  protein  matter.   Other constituents of the
waste include COD, BODJ5, suspended solids, and total  solids.   A
part  of the soluble solids is sodium chloride not removed in the
soak and wash.

An additional step in the hair save operation is machine  removal
of  hair  from the hide.  Although the hair is handled as a solid
by-product, it does require washing prior to baling and sale as a
marketable product.  The waste water from  washing  contains  the
same waste constituents as the unhairing solution, only in a more
diluted concentration.

The  hair  pulping  operation  is  similar to that of hair saving
except that higher chemical concentrations are used, particularly
with  respect  to  the   sharpeners.    In   this   process   the
proteinaceous  hair is solubilized sufficiently to disperse it in
the processing liquid.  The waste water, therefore, has a  higher
content  of  waste  constituents,  particularly  with  respect to
sulfides and nitrogen.

For a cattlehide chrome tannery, BOD5 content of the  waste  from
the  hair save process will range from 17 to 58 kg  (Ib)  per 1,000
kg (Ib)  of raw material.  With the hair pulping process this  may
be 53 to 67 kg (Ib) ,  Likewise, the  total nitrogen content of the
hair  save  waste will be substantially less than the 11 to 15 kg
(Ib)  per 1,000 kg  (Ib) experienced with the hair pulp process.

Bating^ - The purposes for  the  bating  process  are  to  delime,
reduce   swelling,   peptize   the  fibers,  and  remove  protein
degradation products.   Major  chemical  additions  are  ammonium
sulfate  to  reduce  pH  to  a  controlled level and an enzyme to
condition the protein matter.  The reaction of lime with ammonium
sulfate produces calcium sulfate.  The total nitrogen content  of
the  waste  is  5  to  8  kg  (Ib)  per 1,000 kg (Ib) of hide with
ammonia nitrogen constituting about two-thirds.


Pickling - The purpose of the pickling operation  is  to  prepare
the  hides  for  the  tanning  process.   In  vegetable  tanning,
pickling may be omitted.  Pickle  solutions  contain  principally
sulfuric  acid  and  salt,  although  a small amount of a wetting
agent and biocide are sometimes used.  Since protein  degradation
products, lime, and other waste constituents have been previously
removed, the quantity of BOD5, suspended solids, and nitrogen are
low.    Principal  waste  constituents are the acid and salt.   The
strong liquor dump after processing is a source  of  waste  since
the hides are normally not rinsed prior to tanning.

Tanning  -  The  purpose  of  the tanning process is to produce a
durable material from the  animal  hide  or  skin  which  is  not
subject  to  degradation  by  physical  or biological mechanisms.
This is accomplished by reaction of  the tanning  agent  with  the
hide   collagen.   Chrome  and  vegetable  tanning  are  the  two


                               36

-------
principal processes, although other materials such as  alum,  and
other metal salts and formaldehyde can be used.

In  the  chrome  process a basic chromic sulfate or a proprietary
chrome  tanning  solution  is  used.   Other   process   solution
constituents  include sodium formate, and soda ash.  The chromium
must be in the trivalent form and in an acid media to  accomplish
desired  results.   Some  tanneries  prepare  chrome  tanning  by
reducing sodium dichromate solution to the trivalent form,  using
glucose  as a reducing agent.  The waste from this process is the
principal source of trivalent chrome in  the  plant  waste.   The
only potential entry of hexavalent chromium into the waste system
comes from spillage.

The spent chromium tanning solution is relatively low in BOD5 and
suspended solids.

Waste  from  a vegetable tanning process is quite different.  The
reaction rate of vegetable tan with the hides is much slower than
that of chrome tanning solution.  Because of the  longer  contact
time,  the process is normally carried out in vats with some type
of gentle agitation.  In some  instances  the  hides  are  passed
through a series of vats with varying solution strength.  Because
of  the  cost of tanning materials, process solution conservation
has  been  practiced.   Therefore,  that  part  of  the  solution
entering  the waste system is due to drag-out or planned blowdown
to maintain tanning solution quality.  Vegetable  tannin  in  the
waste is a source of both BOD5 and color.

Retan,  Color,  Fatliguor - Retanning, coloring, and fatliquoring
are normally performed in drums.  The chrome or vegetable  tanned
hides  are  placed  in the same drums and all three processes are
performed on the hides before they are removed.

The retan process is performed to provide added tanning  solution
penetration  into  hides  after  splitting.   Chemicals  used for
retanning can be chrome, vegetable, or synthetic tanning  agents.
Because  of  the  low  concentrations  of  chemicals in the retan
process, the concentration of the  waste  water  is  not  strong;
usually  this  process does not add a significant quantity to the
total waste flow.

The most varying process in the tannery is coloring.    There  are
hundreds   of   different  kinds  of  dyes,  both  synthetic  and
vegetable.  Synthetic dyes  are  the  most  widely  used  in  the
industry.  When synthetic dyes are used, acid is usually added in
order  to  provide  a  better  uptake  of  dye  into the leather.
Normally, vegetable tanned leathers are not dyed in this  manner.
If  the  vegetable  tanned  leather  is  colored, it is generally
surface dyed by spraying the color on the leather surface.

The fatliquoring operation can  be  performed  either  before  or
after  coloring.  There is a wide range of type and amount of oil
added in this process, depending upon the end use of the leather.
                               37

-------
Liquid waste from the retan, color, and fatliquor operations  may
be  high  volume-low  strength  compared  with  the beamhouse and
tanhouse.

The temperature of the retan, color, and fatliquor waste flows is
generally  high—above  37.7°C  (1QO°F).   The  major   treatment
concern  of  the  retan, color, and fatliquor waste is removal of
color and oil.   These two constituents can be kept to  a  minimum
by  utilizing  chemical  concentrations that provide for the best.
uptake of the chemicals into the hide.  Because of the  color  in
the  waste  water,  recycling  is not normally practiced.   Use of
high temperatures in retanning  will  enable  maximum  uptake  of
chromium and reduce the discharge of this constituent.

Finishing

The  finishing  processes represent the lowest water flows of the
tannery because they are primarily dry processes.  There are some
wet processes such as minor wetting operations to make  the  hide
handle  more  easily  in  the staking or tacking operations.  The
pasting operation also uses small  amounts  of  water.   However,
several  tanneries  report  reusing paste mixtures; therefore, it
does not flow into the waste stream.  This pasting water is water
mixed with starch; thus, it is quite high in  concentration  even
though the volume is very low.

Total Plant Liquid Waste

The  quantity  of  waste  water  is important to the economics of
treatment in that a number of the unit  operations  performed  in
treatment are designed totally or partially on a hydraulic basis.
In  addition, water conservation can often reduce the quantity of
processing  chemicals  used  which  later   become   constituents
requiring removal in treatment processes.  Also, process solution
reuse  practices  such  as that for tanning not only reduce waste
flow but also eliminate the major part  of  a  waste  constituent
from the total plant waste stream.

An  appraisal  was  made  to determine the quantity of waste flow
from "tanneries  in  each  of  the  six   subcategories   defined
previously.   A  typical  plot of waste water flow versus tannery
production is shown in Figure 5 for Subcategory  1.   The  random
nature  of  the  data  is  obvious.   It is apparent that size of
facility is not a factor for low waste water flow.   These  waste
water  quantities  are  characterized  in  Table 6 by the median,
mean, and mode for each subcategory.  Definitions of these  terms
are as follows:

    Median  -  The  number  of tanneries having waste flows lower
    than this value is equal to the number  of  tanneries  having
    waste flows higher than' this value.

    Mean   - This is the average value determined by adding waste
    flow  data  for  all  tanneries and dividing by the number of
    tanneries.
                               38

-------
Mode   - This is the mid-point of the one-gallon interval  in
which  the  most  frequent  occurrence  of  waste  water flow
occurs.  This measure is not too significant since  frequency
of  occurrence in any one interval was not generally too much
greater than adjacent intervals.  Use  of  a  wider  interval
would have reduced significance of this measure.
                           39

-------
19
                           TANNERY PRODUCTION (1000 KG  HIDE/MO)

 0       200      100      600       800      1000      1200      It00      1600     1800
18-                                                                                -0.15
16
                                                                                  - 0.13

15

                                                                                  -JO. 12

                   ©



13   ®                                                                            -I0'1



12                                                                              .   -JO.10

                                                                      ®
                       ©
                                                                                  - 0.09 LJ.


I0h                   ®

                                  ®    0                                         -)0.08


 *                                            .    .@
                  ®                           ® ®®                               HO.07 i
                                                                                  - o.oe a
        ©        „              ©                               ®
                                       ®          ®
                                                                                    0.05
                  ©                               w                               -Jo.oit
                             ©                ®   ®

                                 ®                                                H0.03
                                                          WASTEWATER  FLOW

          ®  ®  ©                                      TANNERY  PRODUCTION   "I"'02
                               ®                         FOR CATEGORY  1
                                                                                    o.oi

           ®                                                     FIGURE 5
          	  lo
           500        1000       1500       2000       2500       3000       3500       TOO
                            TANNERY PRODUCTION (1000 LB HIDE/MO)

-------
TABLE 6
WASTEWATER QUANTITIES
Waste Flow,
cu m/kg of hide
Category
1

2

3

4

5

6

Median
0.040
(4.8)
0.050
(6.0)
0.044
(5.3)
0.017
(2.0)
0.050
(6.0)
	

Mean
0.053
(6.4)
0.063
(7.6)
0.050
(6.0)
0.020
(2.*)
0.063
(7.6)
0.028
(3.4)
(gal/lb
Mode
0.029
(3.5)
0.050
(6.0)
0.021
(2.5)
0.017
(2.0)
0.082
(9.8)
—

of hide)
Range
0.007-0.156
(0.8-18.7)
0.001-0.189
(0.1-22.6)
0.007-0.106
(0.8-12.7)
0.003-0.033
(0.3-3-9)
0.006-0.204
(0.7-24.4)
0.014-0.056
(1.7-6.7)
No. of
Tanneries

46

14

16

10

20

3
Used Later Herein for
Economic Analysts,
cu m/kg of hide (gal/lb of hide)
0.033
(4.0)
0.050
(6.0)
0.042
(5.0)
0.017
(2.0)
0.063
(7.5)
0.017
(2.0)

-------
Although  data  are  quite random for any subcategory, there is a
trend toward distinct levels for each one.   The randomness of the
data is due not only to differences  in  process  operations  but
also  to  the nonscientific methods used to gage and sample waste
streams in the tanning industry.  To determine a waste flow value
for use as the basis of treatment, facility needs, and economics,
it was necessary to take into consideration the  basic  data  for
individual  tanneries  in  addition to that shown in Table 6.  It
was reasoned that the design basis should generally be  equal  to
or  less  than  the median, but in no case greater than the mean.
This approach was used on the basis that if 40 to 50  percent  of
the  tanneries of a similar type could meet processing needs at a
particular level, others  could  also  meet  this  value  through
attainable   conservation   measures.    This   was  prompted  by
observations made on plant visits that many tanneries use  excess
water   by  constantly  running  wash-down  hoses  to  waste,  by
unmetered and poor control of water used for  washing  and  rinse
operations and by other similar practices.

Characteristics of Total Plant Waste Flows

An   attempt   was   made  to  rigorously  define  flow  and  the
concentration of waste constituents from each step in the tanning
process.  This was not possible due to lack of reported data  and
to the difficulty of isolating all of the individual flows during
the  plant  testing  program  made  as  a  part of these studies.
Therefore, a comprehensive assessment of total  plant  wastes  is
increasingly important.

A  summary  of  raw waste characteristics for each subcategory is
shown in Table 7.  The data have been classified as received  and
no  further attempt is made toward explanation of inconsistencies
with  some  information.   Detailed  information  for  individual
tanneries  is  presented as a part of the documentation submitted
as a supplement to this report.  The sources of this  information
have been described previously.

Examination of the information indicates the following:

    1.   Most data show a wide variance in values.

    2.   Based on average values, some quantities appear
         to be high or low.
         or low.

Typical  variance  is  illustrated by the BOD5 for Subcategory 1,
where the range in values is 4.8 to 270 kg  (Ib) with  an  average
of  95  kg  (Ib) per 1,000 kg (Ib) of hides.  The variance of this
and  other  parameters  is  undoubtedly  due  partially  to  some
difference in processing techniques among tanneries and partially
to  lack  of analytical accuracy.  However, it is probable that a
major part of the difference is due to the  variations  in  waste
quality  associated  with  the  multiplicity  of  waste discharge
patterns which can exist and the sampling methods.  Berthouex and
Brown  (5) utilize a Monte Carlo simulation to  characterize  many

-------
possible  combinations  of  tannery  process solution discharges.
This waste variance, along with the shortcomings  of  the  normal
time spaced proportional flow waste increment method of composite
sample  preparation, are the principal contributions to variance.
If incoming waste were to flow to an  equalization  tank  with  a
relatively  constant  outflow,  it can be reasonably assumed that
variance would have been decreased significantly.

In examination of average  values  for  various  parameters,  the
sulfide  content of the waste for Subcategory 2 appears low, even
though this is a hair save operation.  Also, the chromium content
appears high for Subcategory  4  where  only  some  retanning  is
performed.   The  average  chromium content is 60 percent of that
for a complete chromium tannery process, as shown in  Subcategory
1.  Other such apparent inconsistencies occur and unusual average
values result since information from only one or two tanneries is
available.

Analyses  were  made  of  the  size  of plants in each industrial
Subcategory, and a typical plot for  Subcategory 1  is  shown  in
Figure 6.  Production capacity coupled with waste water flows are
used later herein to assess the economics of waste treatment.

Raw and treated waste characteristics were also assessed for each
Subcategory  in  relation  to  the size and age of tanneries.  No
significant relationship is observed.   For  example,  some  old,
small  tanneries  produce  effluents of better quality than those
which are new and large; the opposite case is also noted.

-------
                                       TABLE  7

                                 RAW WASTEWATER
                        CHARACTERISTICS  BY  CATEGORY
                                R»w Uaitewater Characteristics, kg/1,000 kg of Hide (lb/1,000 Ib of Hide)*

Character 1 st I cs
Flow: cu m/Kg
(gal/ib)
soo5
COD
Total Solids
Suspended Sol I ds
Total ChromI urn
Sul fides
Grease
Total Alkalinity
(as CaC03)
Total Nitrogen
(as N)
pH
Temperature**: °C
CF)

No. of
46

24
18
16
23
18
12
13

12

7
26
15
Category No. '

0.007-0.156
(0.8-18.7)
4.8-270
10.5-595
36-890
6.7-595
0.1-19
0.1-46
0.1-70

0.5-300

3.1-44
1.0-13.0
2.8-93.2
(37-200)
1

0.053
(6.4)
95
260
525
140
4.3
8.5
19

98

17
-
21.1
(70)
Category No. :
No. of
14 0.001-0.189
(0.1-22.6)
9 22-140
7 88-215
7 140-900
9 30-350
7 0.3-12
4 0.1-2.8
5 0.7-105

1 62-85

6 3.6-22
8 4.0-12.6
6 1.7-27.8
(35-82)
I
Average
0.063
(7.6)
69
140
480
145
4.9
0.8
43

72

13
-
18.3
(65)
Category No. :
No. of
Tanneries Range
16 0.007-0.106
(0.8-12.7)
12 7.4-130
9 24-695
9 120-800
10 20-445
5 0.2-0.6
7 0.1-4.2
7 0.1-160

6 4.1-135

5 0.9-23
12 2.0-13.0
3 4.4-28.9
(40-84)
)
Average
0.050
(6.0)
67
250
345
135
0.2
1.2
33

66

9 2
--
17.2
(63)
 •''Except pH, flow in cu m/kg (gal/lb), and temperature in °C (PF) ,
"•>Average temperature is average summer and winter values, temperature  range is  low winter to high summer values.

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    TABLE  7 (Continued)






      RAW  WASTEWATER




CHARACTERISTICS BY CATEGORY

Category No.
No. of
Tanneries Range
10 0.003-0.033
(0.3-3.9)
3 6.7-67
3 5.7-63
2 1.7-285
3 7.0-125
3 0.4-4.8
1 2.1
3 2.2-19

1.

0.020
(2.4)
37
28
140
47
2.6
2.1
7.9
cteristics, kg/1,000 kg
Category No.
No. of
20 0.006-0.201)
(0.7-24. A)
8 10-140
5 11-265
7 52-980
8 3.1-865
7 0.1-2.1
1 4.5
7 0.6-46
of Hide (lb/1
5

0.063
(7.6)
67
170
490
88
1.2
4.5
24
,000 Ib of Hide)*
Category No.
No. of
3 0.014-0.056
(1.7-6.7)
2 32-160
2 53-155
2 210-910
2 44-185
1 3.8-5.9
1 2.0-6.3
2 1.0-19

6

0.028
(3.4)
110
230
595
no
4.4
3.7
6.6
           6.6-180    69      I     37-54    43
2
3
3
0.8-6.5
3.4-11.2
10.0-26 6
(50-80)
3.7
20.7
(69)
5 0.6-29
9 1.5-12.5
3 4.4-36.6
(40-98)
6.0
22.8
(73)
1 14-18
2 9.2-10.4
16
                45

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   woo


   3000
                                                                       1500
   2000
LU
O

   1000
    900
§   800
o
C.  700

    600

    500
o

o
    WO
    300
                                                                       1000

                                                                       900
                                                                       800

                                                                       700

                                                                       600

                                                                       500


                                                                       WO



                                                                       300
                                                                        200
                                                                            o ,
                                                                            a
                                                                            o
    200
                                           TANNERY PRODUCTION
                                                   VS.
                                     RELATIVE  CUMULATIVE FREQUENCY
                                             FOR CATEGORY  1

                                                        FIGURE 6
    100
                                                                        100
                     10    20   30  W 50  60 70   80

                         RELATIVE CUMULATIVE FREQUENCY
                                                        90    95
98
50

9
                                     46

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                            SECTION VI

                 SELECTION OF POLLUTANT PARAMETERS
A thorough analysis of the literature, industry data and sampling
data obtained from this study, and EPA Permit  data  demonstrates
that   the   following   waste  water  parameters  are  of  major
pollutional significance for the leather  tanning  and  finishing
industry:

Biochemical Oxygen Demand (5-day, 20°C. , BODJ5)
Total Chromium
Grease, Fats and Oils
Sulfide
Total Suspended Solids (TSS)
Total Kjeldahl Nitrogen
Fecal Coliforms
PH

Patjonale for Selection of Major Parameters

Biochemical OxiSen Demand (BQPL
Biochemical  oxygen  demand  (BOD)   is  a  measure  of the oxygen
consuming capabilities of organic matter.  The BOD  does  not  in
itself  cause direct harm to a water system, but it does exert an
indirect effect by depressing the oxygen content  of  the  water.
Sewage  and  other  organic  effluents  during their processes of
decomposition exert a BOD, which can have a  catastrophic  effect
on  the ecosystem by depleting the oxygen supply.  Conditions are
reached frequently where all  of  the  oxygen  is  used  and  the
continuing  decay  process causes the production of noxious gases
such as hydrogen sulfide and methane.   Water  with  a  high  BOD
indicates   the   presence  of  decomposing  organic  matter  and
subsequent high bacterial counts that  degrade  its  quality  and
potential uses.

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 D.O. 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
                               47

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consequences  of total lack of dissolved oxygen due to a high BOD
can kill all inhabitants of the affected area.

If a high BOD 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.


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

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

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

Grease  -  The  grease  analysis  measures  different  types   of
materials,   including  oils,  fats,  and  other  such  materials
commonly found in tannery waste waters.  Sources of  grease  from
tanneries  are  from both the animal fat on the hides, as well as
oils added to the hide during the  fatliquor  process.   Oil  and
grease exhibit an oxygen demand.  Oil emulsions may adhere to the
gills  of  fish  or  coat  and  destroy  algae or other plankton.
Deposition of oil in the bottom sediments can  serve  to  exhibit
normal benthic growths, thus interrupting the aquatic food chain.
Soluble  and  emulsified  material ingested by fish may taint the
flavor of the fish flesh.  Water  soluble  components  may  exert
toxic action on fish.  Floating oil may reduce the re-aeration of
the  water  surface  and  in  conjunction with emulsified oil may
interfere with photosynthesis.  Water insoluble components damage
the plumage and costs of water animals and fowls.  Oil and grease
in a water can result in the formation of  objectionable  surface
slicks preventing the full aesthetic enjoyment of the water.
Sulfide - A significant portion of alkaline sulfides contained in
tannery  waste water can be converted to hydrogen sulfide at a pH
below 8.5 to 9.0, resulting in the release of  this  gas  to  the
atmosphere.   This  gas  is  odorous,  and can result in property
damage through paint discoloration.  In sewers, hydrogen  sulfide
                               48

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can  be oxidized to sulfuric acidr causing "crown" corrosion.  At
higher  concentrations  this  gas  can  be   lethal.    This   is
particularly  significant  as  a  hazard  in  sewer  maintenance.
Sulfide compounds are used extensively in the beamhouse  for  the
unhairing process, and thus are found in tannery effluents.

Total  Suspended  Solids (TSS)  - Material found in suspended form
in  tannery  wastewaters  consist  primarily   of   proteinaceous
substances  (flesh, hide, or hair) and insoluble waste chemicals.
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.

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.
                               49

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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	Kjeldahl	Nitrogen  -  Total  kjeldahl  nitrogen  (TKN)  is
ammonia nitrogen plus organic nitrogen content  in  waste  water.
Hence,  TKN  measures  the  major  nitrogen  impact  upon a waste
treatment plant or stream.  This parameter is thus  an  important
measure  of  the  potential environmental impact of tannery waste
water.
Fecal Coliforms

Fecal  coliforms  are  used  as  an  indicator  since  they  have
originated  from  the  intestinal  tract of warm blooded animals.
Their presence in  water  indicates  the  potential  presence  of
pathogenic bacteria and viruses.

The  presence of coliforms, more specifically fecal coliforms, in
water is indicative of fecal pollution.  In general, the presence
of  fecal  coliform  organisms  indicates  recent  and   possibly
dangerous  fecal  contamination.   When  the fecal coliform count
exceeds 2,000 per  100  ml  there  is  a  high  correlation  with
increased numbers of both pathogenic viruses and bacteria.

Many  microorganisms,  pathogenic  to  humans and animals, may be
carried in surface water, particularly that derived from effluent
sources which find their way into surface  water  from  municipal
and  industrial  wastes.   The  diseases associated with bacteria
include   bacillary    and    amoebic    dysentery,    Salmonella
gastroenteritis,  typhoid  and paratyphoid fevers, leptospirosis,
chlorea, vibriosis and infectious hepatitis.  Recent studies have
emphasized the value of fecal coliform density in  assessing  the
occurrence  of Salmonella, a common bacterial pathogen in surface
water.  Field studies involving irrigation water, field crops and
soils indicate that when the fecal  coliform  density  in  stream
waters  exceeded  1,000  per 100 ml, the occurrence of Salmonella
was 53.5 percent.
Elf Acidity and Alkalinity

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.
                                50

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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 many nutrient
substances varies with the alkalinity and  acidity.   Ammonia  is
more lethal with a higher pH.

The lacrimal 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.
                               51

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Rationale for Selection of Minor Parameters

Chemical_ Oxygen Demand	(CQDj -  COD is another measure of oxygen
demand.  It measures the amount of  organic  and  some  inorganic
pollutants under a carefully controlled direct chemical oxidation
by  a dichromate-sulfuric acid reagent.  COD is a much more rapid
measure of oxygen  demand  than  BOD_5  and  is  potentially  very
useful.                             ~~

COD  provides  a  rapid determination of the waste strength.  Its
measurement  will  indicate  a   serious   plant   or   treatment
malfunction  long  before  the BOD!> can be run.  A given plant or
waste treatment system usually has a relatively narrow  range  of
COD:   BOD5>  ratios,  if  the  waste  characteristics  are fairly
constant, permit a judgment to be made concerning plant operation
from COD values.  In the industry, COD ranges from about  1.6  to
10  times  the BOD£; the ratio may be to the low end of the range
for raw  wastes,  and  near  the  high  end  following  secondary
treatment  when the readily degraded material has been reduced to
very low levels.

In summary, BOD and COD measure organic matter  which  exerts  an
oxygen  demand.  Both COD and BOD are useful analytical tools for
the processor.  However, no COD effluent limitations are required
because BOD limitations have been established.
Total Solids - Total solids is a  valuable  parameter,  since  it
measures both suspended and dissolved solids in the waste.  Since
tannery  wastes  are  high  in dissolved solids, the total solids
test is an effective parameter to assess the impact of  dissolved
materials.   The  largest  portion  of  the  dissolved solids are
sodium chloride  and  calcium  sulfate.   Sodium  chloride  comes
principally  from  removal of salt from the raw hides by washing,
and also from salt added  in  the  pickling  operation.   Calcium
sulfate  can  come  from  several  locations  in the tannery, but
principally from the reaction of residual  ammonium  sulfate  and
sulfuric acid with lime used in the unhairing process.  Dissolved
solids  are  particularly  important for consideration of recycle
systems, and also for potential impact on stream life  and  water
treatment   processes.    Total   solids   limitations   are  not
established for tanneries because of insufficient information.

Ammonia Nitrogen - The principal sources of  ammonia  in  tannery
wastes  are  the  ammonium sulfate used in the bating process and
that  which  results  from  decomposition  of  organic  nitrogen.
Ammonia   limitations  are  not  needed  because  total  kjeldahl
nitrogen limits require the control of ammonia.

Color - Color from a tannery results principally from the  chrome
or  vegetable  tan liquor and various dyes and paints used during
coloring operations  in  the  production  of  the  leather.   The
contribution  by vegetable tan is by far the greatest.  Excessive
color may inhibit the activities of some aquatic life, but it  is
primarily  of concern from an aesthetic standpoint.  There is not
                                52

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                           SECTION VII

                CONTROL AND TREATMENT TECHNOLOGY
General

Waste  treatment  practices  in the leather tanning and finishing
industry vary widely.  Some tanneries use no  treatment  or  only
simple   screening.    Others  have  employed  activated  sludge,
trickling  filters,  spray  irrigation,  and  lagoon  systems  to
achieve treatment needs.  The degree of treatment which the waste
receives has been determined by three factors:

    1.   Type of receiving system,

    2.   Quality criteria of the receiving system.

    3.   Tannery processes.

Effluent  quality  requirements  for  a  tanner  discharging to a
municipal sewer have been less stringent than those for a  tanner
discharging  to  a  stream,  lake,  or  ocean.   Therefore, those
systems providing a higher degree  of  treatment  are  associated
with tanneries discharging directly to bodies of water.

Variations  in  treatment schemes are also due to the differences
in raw waste characteristics  associated  with  processing  hides
into  different  types  of  leather.   Although  the  basic  unit
operations are the same, variations in sub-unit processes  create
a   variance  in  both  effluent  quantity  and  quality.   These
differences are  attributed  to  the  need  to  obtain  different
finished  leather  characteristics  and  the  general attitude of
tanneries to produce the desired leather quality  without  regard
to conservation of process chemicals and water.

Based  upon communication with around 140 wet processing firms in
the industry, approximately 60 percent of the tanneries discharge
to municipal systems.  Analysis of these same data indicates that
tanneries discharging to municipal sewers also represent about 60
percent  of  productive  capacity.   This  group  includes  those
discharging  without treatment into municipal systems, as well as
those  providing  pretreatment  prior  to  the  conveyance  to  a
municipal   facility.    With  increasing  effluent  restrictions
imposed by municipal systems, there is a trend  toward  at  least
some pretreatment by all tanneries.

The  survey  of tanners and finishers indicated few (21)  have on-
site biological waste treatment facilities,  of  those  employing
biological  treatment,three  have  activated  sludge plants while
fifteen have lagoons of aerobic and  aerobic-anaerobic  operating
capabilities.   Trickling filters are utilized in three treatment
schemes.  Advanced treatment facilities are  non-existent.    Some
pilot  studies  of reverse osmosis and activated carbon have been
                               55

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made, but without  well  defined  results.   Filtration  and  ion
exchange have not been tested on tannery effluent.

Solids   handling  and  disposal  typically  have  had  secondary
significance at tannery waste treatment  facilities.   Since  on-
site  disposal  in  open  dumps  prevails, sludge and other waste
solids have not in the past had proper disposal; sludge  handling
is   now  receiving  more  emphasis.   Pressure  filters,  vacuum
filters, and centrifuges  are presently utilized  for  dewatering
sludge prior to land disposal.

In-plant  waste  control procedures have included efforts by some
tanneries to conserve water and materials.  A number of tanneries
have intensified housekeeping practices to minimize the entry  of
solid  wastes  into  the  sewer.   Development of hide processors
(concrete  mixers)   has  greatly  influenced   water   usage   in
applicable  wet processing operations.  This equipment requires a
smaller float (processing solution) than vats, paddles, or drums.

The potential for  materials  conservation  has  not  been  fully
realized,  particularly in the beamhouse operations.  Recycle and
recovery techniques have generally been  applied  only  in  those
areas where direct cost savings are demonstrated.  Such practices
are  tannin and chromium reuse.  Plans for reuse of some portions
of treated waste streams are in the conceptual stages at  several
tanneries.

Basis of Tannery Waste^Treatment

The  following  is  a  summary of approaches which can be used to
achieve various levels of tannery waste control and treatment:

    1.   In-process methods of reducing waste.

         a.   Water conservation.

         b.   Process solution reuse or recovery.

         c.   In-plant treatment to remove a waste constituent.

    2.   Preliminary Treatment.

         a.   Disposal to a municipal system or  additional  unit
              operations for further treatment.

         b.   Adjustment of pH,  alkalinity,  and/or  acidity  to
              required levels.

         c.   Removal of chromium, sulfides, hexane solubles, and
              toxic materials  to  levels  which  will  not  pass
              through or harmfully affect subsequent treatment.

         d.   Parrial removal of BODjj, COD, suspended solids, and
              total nitrogen.
                                56

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    3.   Major reduction of BOD5 and suspended solids.

         a.   Removal of BODJ and suspended solids to  levels  of
              less than 50 mg/1.

         b.   Some  additional  nitrogen  removal   beyond   that
              provided by preliminary treatment.

         c.   Normal treatment configuration includes  some  type
              of biological process followed by effective removal
              of suspended solids.

    4.   Major reduction of all forms of nitrogen.

         a.   Reduction of total nitrogen to a level of about  10
              mg/1 or less.

         b.   Treatment follows  biological  treatment  for  BOD5
              removal.

         c.   Treatment  steps  include  an  aerobic   biological
              process   followed   by   an  anaerobic  biological
              process.  Each process is followed by  a  clarifier
              for sludge removal.

    5.   Major removal of all waste constituents.

         a.   Follows   previously   described   biological   and
              settling  processes  for removal of BODJ, suspended
              solids, and nitrogen.

         b.   Filtered waste enters reverse osmosis  process  (or
              electrodialysis  process)  for removal of remaining
              organic constituents, as well as  major  quantities
              of dissolved salts such as sodium chloride.

         c.   Waste  stream  is  directed  to   evaporators   for
              concentration for final disposal.

         d.   Product water is o,f low solids content suitable for
              reuse.

    6.   Waste treatment for hide curing facilities.

         a.   The high strength of this  waste  requires  special
              considerations.

         b.   Treatment  for  all  levels   except   pretreatment
              requires  direct  incineration  of  total  waste or
              solar evaporation in arid areas.

An analysis covering the application for each of these approaches
is described later herein.  Such an analysis also sets  forth  in
more detail the technical and economic considerations involved.
                               57

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In-Process Methods of Reducing Waste

In  an appraisal of any plant waste production, the manufacturing
cycle must first be investigated to determine  any  modifications
which  can  reduce  the waste flow and the concentration of waste
constituents.  Particular emphasis  must  be  given  to  reducing
those factors which would pose problems in treatment of the total
waste.   In  some  instances, reuse or recovery of materials from
process solutions can  produce  economies  which  will  at  least
partially offset costs.

It   is  not  possible  to  identify  every  point  in  the  hide
preparation and tannery  processes  where  a  modification  would
reduce  waste  quantities.  Tanning formulas and processing steps
are developed by experience.  Implementation  of  many  potential
waste  reduction  steps  are  contingent  upon  the effect on the
manufactured product.

The  assessment  of  in-house  conservation  and   treatment   is
considered from the following approaches:

    1.   Water conservation.

    2.   Process solution reuse or recovery.

    3.   In-plant treatment to remove a specific waste constituent.

By  reference  to  Table  6,  it is noted that water use per unit
weight  of  hides   processed   varies   significantly   in   all
subcategories.   The  variations for three subcategories in which
cattlehides are processed is shown below:


    Subcategory     Unhairinq     Tanning     Range in Water Use
                                                 I/kg of hide
                                                  (gal/lb of hide)
       1           Pulp        Chrome            7-156
                                                  (0.8-18.7)
       2           Save        Chrome            1-189
                                                  (0.1-22.6)
       3           Save        Vegetable         7'106
                                                  (0.8-12.7)

If  equivalent  leather  quality  is  being  produced   in   each
subcategory   and   with   a  reasonable  allowance  for  process
differences, the  variation  in  water  use  seems  unnecessarily
large.   It  would appear logical that tanneries with large water
use could implement some reduction measures.

Although reduction would result in some savings  in  water  cost,
the  major  saving would result from lower treatment costs.  Most
unit operations in the treatment process are designed totally  or
partially  on  the basis of flow.  Therefore, a reduction in flow
would reduce both treatment plant capital and operation costs.
                                58

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Realizing  the  economy  of  reduced  waste  water  flows,   many
tanneries  have  attempted  to  decrease  water  use  as  much as
possible.   Some   water   conservation   practices   have   been
implemented  and  have  proven to provide equal or better quality
leather than produced previously.

Some methods of water conservation are listed below:

    1.   Encouraging employees to implement any  potential  water
         saving  practices.   Eliminating  the constantly running
         hoses  observed  in  many  tanneries  is  one   practice
         requiring employee participation.

    2.   Examine tanning formulas to determine if floats  can  be
         reduced.   Use  of  hide processors has permitted use of
         lower floats.

    3.   Limit or eliminate some washing and rinsing operations.

         a.   Change a continuous rinse to a batch rinse.

         b.   Use preset meters or timers to limit total flow.

    4.   Use of wash waters and rinses for process solution make-
         up.

Tannery  #1  has  recently  undertaken  a   comprehensive   water
conservation  program.   Through  implementation of this program,
total  water  use  has  been  reduced  by  nearly   50   percent.
Installation  of  hide  processors for washing the incoming hides
has reduced water use in this process 70 percent.   By  reuse  of
process  water  in the liming operations, a savings of 25 percent
has  been  accomplished.   Installation  of  paddle  vats  and  a
recirculating flume arrangement following the unhairing operation
has  reduced  water  use for washing 80 percent.  Further savings
have resulted from recirculating of hair wash water by installing
a fine screen for solids removal.  Through the installation of  a
vegetable  tannin  recycle  and reclaim system using evaporators,
water use for this process has  been  reduced  65  percent.   The
results of such major water conservation measures indicate that a
comprehensive water conservation program can substantially reduce
water use.

In recent years the hide processor (concrete mixer)  has proven to
be  an  extremely  effective  means  of  reducing water use.  The
number of hide processors in use is increasing.   They  are  most
widely  used  for  washing  the  incoming hides and for beamhouse
operations in pulp hair processes.

When hide processors are used in  the  beamhouse  operation,  the
water  use  through  deliming  will be about 8.35 I/kg of hide (1
gal/ Ib of hide).  Tannery #2, which uses hide processors for all
operations from the raw product through chrome tanning or  "blue"
stage,  has indicated that water use is from 12.5 to 16.7 I/kg of
hide  (1.5 to 2.0 gal/lb of hide).  Some tanneries have  indicated


                               59

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that  hide processors are used in the retan, color, and fatliquor
operations.

There are also reports of water used in one process being  reused
in completely separate processes.  Tannery #3 uses the same water
for washing following their "modified pickle" operation and their
vegetable  tanning  operation.  Tannery #1 uses a similar process
for recycling the soak  water  following  the  vegetable  tanning
operation  back  to  the  color operation that precedes vegetable
tanning.  There are also  some  indications  that  spent  liquors
previously   used  in  vegetable  tanning  are  reused  in  retan
operations.  Tannery fU indicates that they are using bate  waste
water  for alum tanning make-up water.  Tannery #5 is planning to
recirculate approximately 20,000 gallons  per  day  of  treatment
plant  final  effluent  water  for  use  in the delime wash water
following the pulp hair process and for wash water following  the
bate process.

Reuse  or  reduction  of process solutions or recovery of process
chemicals  has  been  demonstrated  to  be  a  method  of   waste
constituent  reduction.   A detailed summary of methods available
to reduce waste constituents by process adjustments is  given  by
Williams-Wynn  (9).

There  are a number of vegetable tanneries that are using recycle
systems to reduce the amount of tan  liquor  that  is  discharged
into  the  waste  stream.   Although  these are not total recycle
systems, they do substantially reduce the amount  of  tanning  in
the  waste  stream.  In most cases, some blowdown is necessary to
prevent the build-up of contaminants  in  the  tanning  solution.
One tannery recovers this blowdown tan liquor and concentrates it
in  a triple effect evaporator and sells the concentrated liquor.
Other tanneries use this blowdown liquor in retanning operations.

Reuse or recovery of chrome tan liquors is being  practiced,  but
not to the same extent as vegetable tanning solutions.  Hauck (6)
has  presented  a  summary  of  methods for recovery and reuse of
spent chrome tanning solutions.  During World War II,  the  reuse
of  chrome tan liquor was common practice because of the scarcity
of chromium salts.  A recent report by the U.S. Geological Survey
states that the country has only "scant reserves" of chromium.

Tannery #6 has performed a study on the reuse of  chrome  tanning
solutions.   These  tests showed that the chrome liquors could be
reused for periods up to six weeks without reduction  of  leather
quality.   The  spent  tan  liquor  in this study was settled and
sludge was drawn  off  the  bottom  of  the  holding  tank.   The
clarified solution was brought to the required concentration with
chromium  salts,  sulfuric acid, and sodium chloride.  Because of
the sludge drawoff, this was  not  a  complete  recycle  systems,
however,  a  substantial  portion  was  recycled and only a small
amount wasted.

Tannery #6 also, in this same study, examined the feasibility  of
recycling  of the unhairing solutions.  Tests on recycling of the


                                60

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unhairing solutions were performed on three  separate  occasions.
The  longest  recycle  time  was  two  weeks.  However, the study
concluded that since the concentration of waste material  in  the
solution  leveled  off  after a few days, the solution could con-
ceiveably be reused indefinitely.  The spent liquor  was  drained
and  settled  much  in  the same manner as the chrome tan liquor.
After removing the sludge from the bottom of the tank, 65 percent
of the  original  volume  remained.   About  50  percent  of  the
sulfhydrate  and  lime  needed  for the next run was available in
that portion retained for reuse.  After two  weeks  of  use,  the
solution  had  no  objectionable  odor  and the amount of ammonia
coming off was not considered substantial.

Tannery f7, a shearling tannery, has been  able  to  reuse  their
chrome  tan  solution  up  to  5  times.   Because  of processing
requirements, spent chrome tan liquors are not at  present  being
reused.

This  same  tannery has been able to reuse their pickle liquor up
to  five  times.   This  is  accomplished  by  adding  additional
chemicals prior to adding another load of hides.

Tannery  #8   reports reusing retan liquors.  Tannery #9, reports
reusing  the  finishing  oils.   Many  tanneries  are   reporting
recycling their pasting frame water either wholly or partially.

Based  on the above, there are numerous possibilities for process
solution reuse.  Of particular importance is reuse of the  chrome
tan  solution.  If this waste stream enters the total plant waste
flow, it will be partially removed in the primary settling  tanks
when  beamhouse  wastes  or  added  alkali increases the pH to at
least 9.0.  This chromic hydroxide precipitate  will  be  removed
with  the  sludge.   An  additional  quantity of chromium will be
removed in secondary treatment with possibly some small  quantity
remaining  in  the  effluent.   In order to minimize the chromium
content of the sludge and subsequent  treatment  process,  it  is
proposed  that  all  chrome tanneries be provided with recycle or
recovery facilities.

Sulfides in the beamhouse waste constitute a potential problem in
subsequent handling.  If mixed with wastes which can  reduce  the
pH of the sulfide bearing wastes, hydrogen sulfide is released.

The complete removal of sulfides is ineffective with either plain
sedimentation or chemical treatment.  Sulfides are more satisfac-
torily  removed through oxidation.  Various methods for oxidizing
sulfides include:

    1.   Air oxidation.

    2.   Direct chemical oxidation (8) .

    3.   Catalytic air oxidation  (7)  (8)  (22) .
                                61

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Air oxidation with diffusers provides some removal, but only with
excessive aeration times.

Direct chemical oxidation with ammonium persulfate and ozone  was
studied  by  Eye (8).  Ammonium persulfate produced low removals.
Ozone  was  most  effective;  however,  the  expense   of   ozone
generating  facilities  and  developing contact equipment negated
further study  (8).

Studies  by  Chen   (22)  reveal  that  many  metallic  salts  are
effective  catalysts  when compressed air at high temperatures is
utilized.  Manganous sulfate proved  to  be  the  most  effective
catalyst   in   the  more  alkaline  solutions  at  near  ambient
temperatures.  Bailey  (7)   and  Eye  (8)   further  describe  the
effectiveness  of  the metallic catalysts.  In a laboratory study
(8), potassium permanganate was the mos^t  effective  agent,  with
manganous  sulfate also proving effective.  Although the relative
costs for the two catalysts favor manganous  sulfate,  the  space
available  and  capital  costs for the two different systems will
determine which catalyst is best for a given situation.   Optimum
results were obtained with a manganese to sulfide weight ratio of
0.15.   Pretreatment  facilities  employing  catalytic  oxidation
should approach 100 percent removal of sulfides.

Sulfides are also removed in the activated sludge process.

In order  to  minimize  dangers  of  potential  hydrogen  sulfide
release and to eliminate the BOD exerted in subsequent biological
processes,  a  catalytic  oxidation  tank  is  proposed  for  all
tanneries with sulfide bearing wastes.

Preliminary Treatment

Preliminary treatment is defined as those operations performed on
the waste stream  to  make  it  suitable  for  introduction  into
another  waste system for further treatment.  Normally, the waste
system  which  receives  the  pretreated  waste  is  that  of   a
municipality or a metropolitan sanitary district; however, it may
be subsequent treatment units on-site.

The  need  for  preliminary  treatment  is based on the following
factors:

    1.   Sewer safety and maintenance.

    2.   Biological treatment protection.

    3.   Effluent criteria.

    4.   Sludge disposal criteria.

Sewerage systems are particularly susceptible to damage from high
sulfide wastes.  Tannery effluents may contain sulfide concentra-
tions as high as 250 mg/1.  An  alkaline  sulfide  bearing  waste
from  a  tannery  when  mixed  with sufficient domestic or acidic
                               62

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industrial waste will release hydrogen sulfide gas.  At a  pH  of
7.5,  about 30 percent of the sulfide ion in the waste is present
as hydrogen  sulfide  gas.   Oxidation  of  hydrogen  sulfide  by
aerobic  bacteria  creates  sulfuric  acid  which is corrosive to
concrete and metal.  This  is  the  major  cause  of  sewer  pipe
"crown"  corrosion.   A  safety problem for maintenance personnel
also develops when hydrogen sulfide gas collects  in  sewers  and
manholes due to extreme toxicity in low concentrations.  Hydrogen
sulfide will also discolor some painted surfaces.

Tannery  effluents  exhibit  a  wide  range  in  suspended solids
concentrations (300-1U,000 mg/1)  with  an  expected  average  of
2,000  to 3,COO mg/1 (10) (11).  Grease concentrations in tannery
waste can be as high as 850 mg/1.

In addition to added removal problems in  a  secondary  treatment
plant,  grease  can  coat  sewer lines and act as an adhesive for
other particulate matter.  The suspended material  consisting  of
much lime may reduce sewer capacity through direct sedimentation.
A  calcium  carbonate  scale  will  form  when  sufficient carbon
dioxide is present.

Aerobic biological treatment processes can be seriously inhibited
by  some  tannery  waste  constituents.   While  normal   average
concentrations of lime and chromium salts do not appear to damage
the  system,  short term high concentrations could be detrimental
to biological activity.  The high alkalinity  (and  corresponding
high pH) are caused by lime discharges from beamhouse operations.
Such  discharges  are normally intermittent.  Trivalent chrome is
used extensively as  a  tanning  agent.   Hexavalent  chrome  may
appear  in  trace  amounts  from  some  finishing operations, but
trivalent chromium is the predominant form in the  waste.   There
appears  to  be  some evidence to indicate that both forms can be
toxic (12).  Of prime importance is  the  solubility.   Trivalent
chromium  salts  are soluble in acid and neutral solutions.  At a
pH greater than 8.5,  trivalent  chromium  will  be  precipitated
while hexavalent chromium must be reduced prior to precipitation.
Total  chromium concentrations of 10 mg/1 are indicated as hardly
toxic to biological units (13).

The batch nature of tannery operations create  wide  fluctuations
in  waste  flows  and  waste  strength.   Such  variance  can  be
difficult to handle, particularly  on  the  conventional  smaller
treatment  plants.   The  BOD5  may  be as low as 150 mg/1 or may
exceed 3,000 mg/1 with an average usually  from  1,000  to  2,000
mg/1  (10)  (11).   Significant reductions in BOD5 and equalization
of flow and waste strength may be required to  avert  overloading
of biological units.

Preliminary  treatment  operations consist of one or combinations
of the following:

    1.   Screening.

    2.   Equalization.
                               63

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    3.   Plain sedimentation.

    4.   Chemical treatment.

         a.   Coagulation and sedimentation.

              1)   Alum.

              2)   Lime.

              3)   Iron salts.

              4)   Polymers.

         b.   Carbonation.

    5.   pH adjustment.

    6.   Sludge handling and disposal.

These same unit operations and unit processes are   used  in  the
first   stages  of  facilities  providing  a  greater  degree  of
treatment required when the effluent is directly discharged to  a
river or lake.

Screening   -   Fine  screening  removes  hair  particles,  wool,
fleshings, and hide  trimmings.   While  eliminating  undesirable
waste  water  constituents,  the  screenings  themselves create a
solid waste disposal problem.  The highly putrescible wastes  are
commonly  disposed  of  on-site or at remote landfill operations.
Screening equipment includes coarse  screens  (bar  screens)  and
fine  screens,  either permanently mounted or rotating with self-
cleaning mechanisms.  The exact  contribution  of  screenings  on
parameters  such as BOD5 and suspended solids is not known, since
large particles  are  removed  prior  to  obtaining  samples  for
testing.   The  principal  function  of  screening  is  to remove
objectionable material which has a potential for  damaging  plant
equipment and clogging pumps or sewers.

Equalization - Equalization of waste streams is important in pre-
treatment  facilities.   The volume and strength of waste liquors
vary depending on process formulations and scheduling of  tannery
operations.    Alkaline  wastes  are  associated  with  beamhouse
operations, while acid discharges occur  from  the  tanyard.   In
order   to   produce  optimum  results  in  subsequent  treatment
operations, equalization of flow,  strength,  and  pH  of  strong
liquors  is  required.   Although  some  oxidation  may occur, no
removal  of  waste  constituents   is   normally   reported   for
equalization.   Equalization  basins provide storage capacity for
hydraulic balance.  Auxiliary equipment must provide  for  mixing
and  maintaining  aerobic  conditions.  Detention times much less
than one day are  usually  provided.   Basins  can  be  monitored
through pH and flow measurement.
                                64

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Plain^ Sedimentation  - Plain sedimentation is concerned with the
removal of non-flocculating discrete particles and floatable  low
density  materials  such as grease and scum.  Tannery wastes have
high concentrations of both  suspended  solids  and  grease.   As
shown  in  Table  8,  suspended  solids reductions can range from
approximately 40 to 90 percent,  while  reductions  in  BOD5  can
range  from  30  to  60  percent.  Much of the suspended material
removed is in  the  form  of  insoluble  lime  which  produces  a
voluminous  and  heavy  sludge.  Although grease removals are not
indicated, high  removals  are  expected  with  surface  skimmers
installed in clarifiers.
                               65

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                                                          TABLE  8
                                               PLAIN  SEDIMENTATION
                                 Suspended Solids                        BOD
                             Inf^      Eff L     Removal        _[nf_.      Eff.      Removal                Remarks             Reference
                             mg/1      rog/1        %           mg/1      mg/1        %

                              ---      —      80-90          —       —-       80-90          Fill and draw basins with     (J8) (39)
                                                                                             24-hour capaci ty •
Sedimentation tanks,             900      130      83-88          380      146       40-63
mechanical siudge
faci 1ities

Sedimentation tanks            1,200      370        69           -~      ---       -—           Detention time 2 hours          (14)

Sedimentation tanks            1,184      680        43          1,046      537        48           Continuous  flow (pilot)          (41)

Sedimentation tanks            1,880      461        6?          1,285      8?3        30           Fill and draw (ptlot)           (41)
                                                                 66

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Assumed  to be typical for plain sedimentation units is the full-
scale operation cited by Sutherland  (1/4) .  The  suspended  solids
content  of  a  side  leather tannery was reduced 69 percent from
1,200 mg/1 to 370 mg/1 by continuous flow sedimentation  for  two
hours.

Laboratory   experiments   by  Sproul,  et  al.,  (15)  utilizing
beamhouse and chrome liquors showed that plain  sedimentation  at
an  overflow  rate  of  24.5  cu  m/day/sq m (600 gpd/sq ft) gave
average removals of about 22 percent in suspended solids  and  35
percent  in BOD.  Pilot scale experiments by Sproul, et al.,  (51)
show equalization of plant flows followed by plain  sedimentation
gave  suspended  solids and BOD removals up to 99 and 50 percent,
respectively.  Chrome liquors in excess of 1 percent of the total
flow proved to be an effective  coagulant  for  composite  wastes
containing  2,000  mg/1 suspended solids.  Overflow rates of 14.3
cu m/day/sq m (350 gpd/sq ft)   produced  a  2  percent  underflow
concentration.

Field observations at Tannery 110 tend to confirm these removals.
The  primary  units  consist  of  two  circular  clarifiers  with
overflow rates of 18.8 cu m/day/ sq  m  (460  gpd/sq  ft)  at  an
average  flow  of  3,030  cu  m/day  (0.8  mgd).  No equalization
facilities are provided other than mixing in  a  pump  wet  well.
Cattlehide  processing during the sampling period averaged 81,700
kg (180,000 Ib)  green salted hides per day for  pulp  hair  house
operations  followed  by chrome tan and finishing.  The following
average removals resulted (10).

                                 l£^iiJSDi    Effluent   % Removal
                                  mg/1         mg/1

   Suspended Solids                3,125        945        70

   BOD5                            2,108      1,150        45

   Total Chromium                     51         24        53

   Total Alkalinity (as CaCO3)        980        718        27

   Grease                            490         57        90

Suspended solids  and  BOD5  removals  were  70  percent  and  45
percent,  respectively.   A low chromium removal of approximately
50 percent occurred.  Higher removals would result if a pH of 8.5
or  greater  were  maintained  (using  equalization  or  chemical
addition)   in  the  primary  clarifiers.   If  sodium  alkali  is
contributing to the high pH, a pH of 10-10.5 may  be  needed  for
best  removal.   Theoretically,  all chrome should precipitate as
chromic hydroxide; however,  a very small  residual  is  expected.
Although  chrome  removal  from  the  waste water is desirable, a
sludge problem is created if proper disposal precautions are  not
taken.   The  total alkalinity was reduced 27 percent, reflecting
sedimentation of suspended lime.   Grease removal was 90 percent.
                               67

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In general, plain sedimentation is a physical separation of  some
suspended   particles  from  the  waste  stream.   Although  high
removals of suspended solids (90 percent)  and  BOD  (60  percent)
are  indicated  with  equalization  and  sedimentation,  effluent
concentrations are not reported  below  130  mg/1  for  suspended
solids  or  146  mg/1 for BOD^ (Table 8).   High chromium removals
may  result   while   sulfide   concentrations   are   relatively
unaffected.    As  a  unit  operation,  plain  sedimentation  has
desirable application in tannery waste water treatment.

Chemical Treatment - Coagulation	and  Sedimentation  -  Chemical
addition prior to sedimentation has further increased the removal
efficiencies of primary clarifiers.  Chemical coagulation results
in  higher  removals  of suspended solids, BOD, sulfides, chrome,
and  alkalinity  through  flocculation  of  colloidal  particles.
Alum,  lime, iron salts, and polymers have exhibited satisfactory
results.   Data  in  Table  9  indicates  that  suspended  solids
removals  from  50  to above 95 percent and BOD^ reductions range
from approximately 50 to 90 percent are achieved.

Chemical  coagulation  followed   by   sedimentation   has   been
investigated by Sproul, et al. (15) at a cattlehide tannery using
the   chrome   process.    Raw   waste  water  analyses  indicate
concentrations of BOD5_ at 2,500  mg/1  and  suspended  solids  of
about  2,530  mg/1.   The results drawn from the laboratory scale
investigation are shown in Table 9  (15).

    1.   Use of an anionic polymer at a concentration of  1  mg/1
         resulted in a reduction of about 84 percent in suspended
         solids and 60 percent in BODJ3.

    2.   Adjustment of the waste to pH 9.0 with sulfuric acid and
         subsequent settling gave average removals for  suspended
         solids and BODJ5 of 90 and 67 percent, respectively.

    3.   Use of ferric chloride at a concentration  of  600  mg/1
         produced   average   removals   of  60  to  65  percent,
         respectively, for suspended solids and BODEi.

    4.   Ferric  chloride  coagulation  was  less  effective   in
         removal  of  suspended solids than was adjustment to the
         same pH with sulfuric acid.

    5.   Coagulation with alum at concentrations  less  than  500
         mg/1  after adjusting to a pH of 6.5 reduced the BOD5 by
         90 percent and suspended solids from 45 to  57  percent.
         Alum  concentrations higher than 500 mg/1 created a floe
         that would not settle.

    6.   Buffing dust resulting from finishing tanned  hides  was
         not found to be an effective coagulant.

In  general,  polymer addition produced a rapid formation of floe
minimizing the  need  for  flocculating  equipment.   Without  pH
adjustment,


                               68

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                                                         TABLE  9
                                             CHEMICAL  TREATMENT
                                                Suspended Sol Ids
Coagulation-Sedimentation
   Plain  Sedimentation,
   Coagulation, Sedimentation

   Aeration, Coagulation,
   Sedimentation
Coagulation, Sedimentation       Lime


Coagulation, Sedimentation       Ltme


Coagulation, Sedimentation       Lime
1,550


2,500
                                                     Iff.    Removal     Inf.,
                                                     iSgTT       I       SgTT
 68


850
  $18     469


1,980     497


3,135     HO
          66    3,800    1,030






          49    1,001      476


          75    1,630      823


          95    1,437      619
Coagulation, Sedimentation       Iron Salts                       High


Coagulation, Sedimentation       Polymer      5,200**    500**      90
                                                        Adjustment  of pH water
the raw waste with ad-
justment of  pH  to 5-5.
Nixing aerated  raw waste
with presettled super-
natant indicated 93% color
removal.
Continuous flow with lime
concentrations of 1,4go
mg/1.

Fill and draw with 11 me
concentrations of 1,700
mg/1.
Adjustment of pH with  beam-
house  1fquors.  Overflow
rate,  25.9 cu m/day/sq m
(635 gal/day/sq ft)

Ferric chloride added  at
concentrations of 2,000-
5,000  mg/1

Full-scale operation on beam-

polymer addition of 10 mg/1.
Overflow rates at 65 cu
m/day/sq m (1,600 gpd/sq ft)
(42)


(18)
(41)


(37)



(16)


(32)
   Equalisation, 2-stage
   Carbonation, Coagulation,
   Sedimentation
CarbonatIon,  Coagulat io
Sedimentation
  *  Oxygen demand.
  *  Order-of-magnitude
                                                                      13,400
                                 Iron Salts   6,190
                                                        A pilot study with                 (19)
                                                        equalfzatfon of flow,
                                                        carbonation with flue gas
                                                        to 6.4-6.7 pH.   Coagulation
                                                        wftn lime followed by 3-
                                                        hour sedimentation
                                                        Effluent is then subjected
                                                        to a second stage process
                                                        similar to the  fi rst.
                                                        A 99* reduction in color
                                                        resulted.

                                                        A pilot study with carbona-        (19)
                                                        tion of beamhouse wastes to
                                                        a pH of 6.0 followed by coagu-
                                                        lation with ferric chloride
                                                        (300-500 mg/1).   Treatment
                                                        produced a floe which settled
                                                        quickly.
                                                             69

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polymers   produced   consistently  higher  removals  than  other
coagulants tested.

Sulfides appearing in the primary  influent  are  not  completely
removed  in  chemical units.  Inconsistent removals are indicated
in  the  literature  by  researchers  (8)  (16)   (17).   With  pH
adjustment  to  8.0,  an upper limit on sulfide removal may be 90
percent (15).  Sulfide removal reduces BOD5 and  averts  hydrogen
sulfide problems.                         "~

Chromium  will  precipitate  as  a hydroxide at a pH greater than
8.5.  A 90 percent removal in a laboratory study  by  Sproul,  et
al.  (15)   occurred  at  a pH of 8.0.  Precipitation in a primary
sedimentation unit is desirable to prevent any potential toxicity
in subsequent biological treatment units.

The removal of color is not commonly reported  by  investigators.
Low removals are, therefore, expected.  In pilot plant operations
described  by Howalt and Cavett (18) and, also, by Riffenburg and
Allison (19), 93 and 99 percent removals of color were  observed,
respectively.   The  exact  mechanism of removal in each of these
studies is not indicated.  However, since  color  exists  in  the
colloidal region, a physical-chemical process is implied.

In  a thesis by Hagan (20), color removal through coagulation and
precipitation was investigated.  In  coagulation,  inter-particle
attraction  created  by  suitable  polymers develops a large floe
that tends to settle at an optimum  pH.   Hagan,  also,  reported
that  common  ion  effect assisted in precipitation removal.  The
basis  of  this  contention  is  that  the  high   hydroxyl   ion
concentration  at high pH reduces the solubility of color vectors
such as digallic acid which contains hydroxyl functional  groups.
Addition  of  coagulants and pH control at this point may further
increase  the  relative  efficiency.   Laboratory  results  on  a
vegetable tannery waste indicate high color removals  (94 percent)
through  a  combination of chemical precipitation and coagulation
with  calcium  hydroxide  and  an  anionic  polymer   (20).    The
efficiency is dependent on pH control around 12.

In general, constituent reductions with coagulants are limited to
suspended  solids,  chromium,  and  possibly,  sulfide and color.
BOD5 removals are a function of that portion of the BOD5, existing
in the colloidal or suspended form.  Soluble BOD5 is normally  40
to   50  percent  of  the  total  BOD   (10) .   Many  low  removal
efficiencies may have resulted from inefficient  control  of  the
physical-chemical operations, which require operator attention to
be successful.

Chemical  Treatment	-	carbonatj.pn - carbonation is effective in
the"treatment  of  alkaline  wastes.   In  this  process,  carbon
dioxide  reacts  with lime to form calcium carbonate, which has a
solubility of only 25 to 50 mg/1.  The crystalline  structure  of
the   carbonate   nucleus   provides  an  effective  surface  for
adsorption of organic matter.  Suspended solids and BOD are  both
reduced.
                               70

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Stack  gas  containing  8  to 12 percent carbon dioxide, obtained
from any fuel combustion process, can be used.   Introduction  of
gas into the waste stream requires a suitable diffuser system and
reaction vessel.

Table  9  indicates high removals for suspended solids, BOD5, and
alkalinity for carbonation in conjunction with coagulation.   The
BOD5 removals range from 85 to 92 percent, while suspended solids
reductions as high as 99 percent are recorded.

Field  data from Tannery t3 indicate high reductions in suspended
solids, BOD, and total  alkalinity.   Estimated  flows  from  the
cattlehide  vegetable  tannery  were  1,700 cu m/day  (0.45 mg/1).
Primary clarifier overflow rates were about 20.4  cu  m/day/sq  m
(500  gpd/sq  ft)  for  a  chemical  system  utilizing  flue  gas
carbonation and a combination of iron salts and polymers.    (Sul-
furic acid is also used to assist pH control).  The following re-
movals were indicated (21):

                                 Primary    Primary
                                 Influent   Effluent   %_Rempyal
                                   mg/1       mg/1

   Suspended Solids                2,110       100          95

   BOD5                            1,660       270          84

   Total Alkalinity (as CacO3)       640         0         100

Carbonation  is  attractive  for tannery pretreatment facilities,
since in most cases carbon dioxide is available at  the  cost  of
piping  from  the plant boilers.  Removals are high, under proper
operating conditions, for suspended solids and BOD.

pH Adjustment - In some instances, pH  correction  of  the  waste
effluent  from  other pretreatment processes has been required to
meet restrictions of a receiving system.  Normally, this has been
accomplished by feeding sulfuric  acid  or  sodium  hydroxide  to
lower  or  increase  pH  as required.  This requires a relatively
simple chemical feeding equipment with  pH  sensing  and  control
system.

Sludge  Handling	and  Disposal  -  A major part of tannery waste
treatment is handling and  disposal  of  the  semi-solid  sludges
obtained  from  liquid treatment processes.  The most predominate
methods of ultimate disposal of tannery  waste  sludges  includes
sludge lagoons, landfills,  dumps, and spreading on the land.

Some attempts have been made to dewater sludges prior to ultimate
disposal  with  varying  success.  The three principal dewatering
techniques include  centrifuges,  vacuum  filters,  and  pressure
filtration.    The  centrifuges  have  appeared  to meet with less
success than vacuum filters or pressure filters.
                               71

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Stabilization of sludges prior  to  disposal  using  aerobic  and
anaerobic  digestion  has  not been used extensively and where it
has been tried, it has not, always,  been  extremely  successful.
Some   of  the  organic  matter  is  difficult  to  decompose  by
biological activity and probably is the reason  for  at  least  a
part of the difficulties associated with digestion.  In addition,
high   chromium   levels   can   inhibit  the  activity  of  some
microorganisms which stabilize organic material.

Reducing the moisture content of sludge by  spreading  on  drying
beds   has   also   been  successful  in  some  areas.   This  is
particularly attractive to smaller facilities where land area  is
available.

Conditioning  and stabilizing a mixed domestic and tannery sludge
using heat treatment processes has been employed also at  Tannery
#11  (about 80 percent of the waste flow is tannery waste).  Such
heat treatment provides a stable end product  from  a  biological
standpoint and can be incorporated in a landfill or spread on the
land.   One  of  the principal difficulties with tannery waste is
the chromium content in sludges and  the  potential  impact  this
material  has  on  the  environment  from a toxic standpoint.  In
testing a heat treated sludge, it has been indicated that some of
the trivalent chromium may be oxidized to  the  hexavalent  form.
Apparently,  the trivalent chromium is converted through the high
temperature, high pressure, and oxidizing environment of the heat
treatment process.

When chromium is reused in the tannery, levels in the sludge  are
reduced.  Disposal of sludge containing these residual quantities
of   chromium   in   a   sanitary   landfill  will  minimize  any
environmental problems.

Prior to dewatering in mechanical equipment, sludge  is  normally
conditioned  by  use  of  ferric  salts and lime or polymers or a
combination  of  these.   The  quantity  and  type  of  chemicals
required  are  dependent upon characteristics of the sludge being
handled.

Dewatering with mechanical  equipment  generally  can  produce  a
solid cake containing 15 to 30 percent solids.

Some  sludge  is  disposed of on the land taking advantage of its
lime content for agricultural purposes.  One disadvantage of this
type of disposal practice is the potential  toxic  effects  which
chromium  or  other  constituents might have on plants or through
leaching to ground or surface water supplies.

Lagoons for dewatering have some limited uses.   In  humid  areas
where  evaporation approximates rainfall, such application is not
completely satisfactory.

Use of lagoons, drying beds,  landfills,  and  landspreading  all
require  key attention to the environmental impact.  Particularly
important is the leaching of potential toxic or organic materials
                                72

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on the ground water supplies or surface waters.  Proper  controls
must be taken to ensure that these conditions will not develop.

Spreading  tannery  sludge  on the land may, also, be a potential
problem from the standpoint of bacteria present.   However,  with
the  high  amount  of  lime  waste commonly found in most tannery
sludges,  as  well  as  the  lime  dosages  required   prior   to
dewatering,  there  is  usually  sufficient  contact  time of the
sludge at a high pH to afford some degree  of  disinfection.   In
most  cases,  it is desirable to have the sludge elevated to a pH
of about 11.5 or greater for about two hours or  more  to  effect
proper control.

Preliminary  Treatment   	Facility JRecruirements  -  Based on an
appraisal of needs and the performance  of  previously  described
operating  facilities,  the  following  processes are included in
evaluating preliminary treatment requirements:

    Waste Flow

    Screening
    Equalization
    Primary settling

    Sludge

    Collection
    Thickening

Provision is also included for chemical addition to  the  primary
settling tank to aid in clarification and sludge settling.

Adequate   experience   has   been  accumulated  to  ensure  that
facilities  will  perform  satisfactorily.   However,   in   some
installations,  attempts  have  been made to combine equalization
and settling in one unit.  In some instances,  a  large  settling
tank  has been utilized to perform this function.  The success of
such an approach depends on a waste  dump  program.   In  theory,
continual  vigorous mixing required for rapid equalization is not
compatible with the essential quiescent condition  desirable  for
efficient  settling.  Initial screening of the waste is desirable
to remove large particles prior to further treatment.
                               73

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Secondary^BiolQCfical Treatment

Parameters used for sizing principal items of  equipment  are  as
follows:

    Equalization   Detention:  2H hours at design flow

    Primary Settling    Overflow rate:  23.5 cu m day/sq m
                     (500 gpd/sq ft)

    Waste sludge   2 percent solids

    Vacuum Filter  Loading rate:  15.6 kg/sq m/hr
                                  (3.2 Ib/sq ft/hr)

Major Reduction of BQD5 and Suspended Solids - Major reduction of
EOD5  and  suspended solids requires a higher degree of treatment
than that provided by normal  primary  or  preliminary  treatment
facilities.   This  higher  level  of treatment is referred to as
secondary  biological  treatment.   It   generally   includes   a
biological unit process and may or may not require a pretreatment
step.   Such  facilities  may  be  located  at  a municipal plant
treating a combined municipal-tannery waste or may be an  on-site
plant   treating   only  tannery  wastes.   Secondary  biological
treatment can utilize activated  sludge,  lagoons,  or  trickling
filters  along  with  required  supporting  equipment  to achieve
required effluent quality.  All systems  with  sufficient  design
capabilities   and   adequate  operation  can  attain  equivalent
efficiency  of  BOD5  and  suspended  solids  removal.   Numerous
biological treatment schemes are, therefore, feasible.  Selection
of  an  alternative  biological treatment system is influenced by
waste  water  constituents,   required   efficiencies,   climatic
conditions,  land  requirements, operational characteristics, and
economics.

Combined Municipal-Tannery Treatment Systems - Combined treatment
of  tannery  and  municipal  waste  waters  predominates  in  the
industry  since  most  tanneries are located in urban communities
(4).  Such systems normally require some degree  of  pretreatment
at  the  tannery.   Typically,  tannery effluents are combined in
various  proportions  with  domestic  flows  and   subjected   to
treatment by activated sludge or trickling filter systems.  Other
combined  treatment  facilities  such as lagoons are not commonly
reported.  Shown in Table 10  are  reported  combined  municipal-
tannery treatment efficiencies.  One example of primary treatment
only  has  been  included  to  serve  as basis of comparison with
secondary biological treatment systems.
                                74

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                                                            TABLE   10

                      COMBINED  MUNICIPAL-TANNERY   TREATMENT  SYSTEMS
                                                         iODc
                      Tannery       Total   Tannery   	
                     -e treatment     Flow    Flow    Inf   Eff
                                 cu m/day    f     rng/1   mgT
                                  (mgd)
                                                                         Suspended Sol Ids
                                                                      nf    Ejf    Removal   Locatu
                  Holding tank     2,195      35     326    156
                                 (0 58)
                                                                  52    883   760
Trickling  Filter

  Trickl ing fill.
  Trickling filter,   Screening       35,958
  sludge digestion                    (9-5)
  sludge digest I
  sludge lagoon
  Tnckl ing filte
  sludge  drying
                                            1*0     600     65
                                                                                      15   W!1 1 lamsport,
                                                                                          Pennsylvania
                                                                                          Engine
                                                                                          Experi
                                                                                                      Removal obtained with
                                                                                                      loadings of 1.3-1.7 kg
                                                                                                      BODj/day/cu m (3,500-
                                                                                                      4,500  )b BODs/day/ac
                                                                                                      ft)    Mo scale deposi-
                                                                                                               media,   100?
                                                                                                        .ulfide renx
                                                                                                        pr fa 1 ems with hair
                                                                                                           hide scraps  in
                                                                                                        the design capacity
                                                                                                        wfth obsolete set-
                                                                                                        tling basins
Activated sludge,
separate sludge
digest ion,  land
,rr,g,t,on  of
I iquid si udge

Activated sludge,
separate sludge
  Act
          sludge
         sludge
      a ted sludge,
                                    .
                                   0 2)
                                   6,056
                                   (1.6)
                                 1^,383
                                 (3 8)
                                            H          >100      95
                                                                             200      75   South Pa
                                                                                                         ich bas in are 7 hoi
Plant completed  in
1965 with capac.ty
of  13,626 cu m/day
(3 6 mgd)
                                                                                                        jtion since 1962

                                                                                                        ;nced operat ional
  stage oxi dat 101
  pond, separate
  sludge digest"
  lagoon sludge
  disposal
 sludge, secondary
                                                                 96    325    31
                                   I.5H
                                   (0 4)
                                                                                    90   Napa,          Flow from two tanner-
                                                                                         California     ,es   Chrome reduced
                                                                                                      from 61 to 0 8 mg/1
                                                                                                      Digester gas 0  585 cu
                                                                                                      m/kg (9  5 cu ft/lb)
                                                                                                      volatile matter  added

                                                                                  66-78   Gloversville,   Prototype operation,
                                                                                         New York       visual  indication  of
                                                                                                      highly effective
                                                            75

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All treatment methods have demonstrated capability  in  at  least
one  installation  to  remove  90  percent  of BOD5 and suspended
solids.  However, other installations using  the  same  treatment
methods have not achieved this degree of treatment.  Tannery flow
combined with domestic sewage has ranged from less than 5 percent
to  more  than  80  percent  of  the  total,  studies of combined
treatment by Camp,  Dresser,  and  McKee  (23)   and  Nemerow  and
Armstrong (24)  present typical applications of this approach.

In   a  pilot  study  for  a  tannery  in  the  Northeast   (t12),
appropriate design parameters for combined treatment  of  tannery
with  domestic  sewage  was  investigated.   Approximately, equal
portions of tannery and domestic sewage were  used.   Test  flows
ranged  from 0.3-1.3 I/sec  (5-20 gpm) .  At the time of the study,
the tannery production was approximately 1,502,740 kg  (3,310,000
Ib)  of cattle hides per month with an estimated waste water flow
of 3,785 cu  m/day  (1  mgd)  from  beamhouse,  chrome  tan,  and
finishing processes.  Combined flows consisting of equal portions
of  tannery  and  municipal effluent totaling 9,463 cu m/day  (2.5
mgd)  are proposed for the  full-  scale  facility.   Removals  in
excess  of  90 percent BOD5_ and suspended solids were required to
meet stream classification standards.  The  following  full-scale
unit processes, listed in the order of application, were found to
be essential to meet requirements (23) .

    1.   Equalization.

    2.   Primary sedimentation.

    3.   Carbonation and sedimentation.

    4.   Addition of municipal sewage.

    5.   Activated sludge treatment.

    6.   Sludge dewatering by centrifuge.

    7.   Effluent chlorination.

Equalization, carbonation with flue gasses, and sedimentation are
proposed as a pretreatment for tannery wastes.

Equalization   is   an  important  unit  process  for  minimizing
variations in discharge flows and waste strength.  Based  on  the
quantity  and  quality  of  the tannery discharge, a minimum of 4
hours was found to provide sufficient equalization capacity.

Primary sedimentation basins designed with an  overflow  rate  of
32.9 cu m/day/sq m  (700 gpd/sq ft) should produce a sludge with 8
percent  solids.   Heavy  duty  sludge  removal equipment will be
required due to the volume and density of the sludge produced.

Pilot tests indicate that carbonation after equalization provides
a  rapid absorption of carbon dioxide  (CO2) gas.  A  contact  time
of  20  minutes  was  sufficient  for  flue gas carbonation.  The
                                76

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resulting calcium carbonate precipitate is expected to aid in the
removal of other  suspended  solids  by  sedimentation  prior  to
secondary treatment.

A  volumetric  loading of about 973 kg BOD5/day/l,000 cu m  (60 Ib
BOD5_/day/l,000 cu  ft)  for  the  aeration  basin  with  aeration
capacity  of  123 kw  (165 hp) is proposed for combined treatment.
Tests indicate foaming may be an operational problem.  The  full-
scale  design  should  include  provisions for surface sprays and
chemical addition.

The biological floe produced in the pilot aeration basin was very
light and settled with  difficulty.   An  overflow  rate  not  to
exceed  23.5  cu  m/day/sq  m   (500  gpd/sq  ft)  is proposed for
secondary sedimentation.  Upon resettling of the waste  secondary
sludge  in  the  primary  clarifier,  a  mixture  resulted  which
dewatered readily on drying beds.  Since large volumes of  sludge
are  produced,  excessive  amounts  of land would be required for
drying beds.  Sludge is, therefore, proposed to be dewatered in a
solid bowl centrifuge with the resulting cake containing 20 to 30
percent solids hauled to a sanitary landfill.

Nemerow and Armstrong (24) investigated  a  two-stage  biological
system.   A prototype plant treated 1,514 cu m/day  (0.4 mgd) flow
intercepted  from  a  combined  municipal  and  tannery  sewerage
system.   The  exact proportions of each were not indicated.  The
treatment system consisted of the following processes:

    1.   Primary sedimentation.

    2.   Roughing filter.

    3.   Activated sludge.

    4.   secondary sedimentation.

The primary sedimentation unit with overflows  between  15.5  and
23.0  cu  m/day/sq  m   (330  and  490 gpd/sq ft) produced removal
efficiencies of 48 percent for BOD_5 and 24 percent for  suspended
solids.   Comparable  values with polymers were 75 percent and 39
percent, respectively (24).   The  organic  load  on  the  filter
ranged  from  1,135 to 3,242 kg BOD5/day/1,000 cu m  (70 to 200 Ib
BOD5/day/l,000 cu ft)  with BOD5 removals of 37  and  30  percent,
respectively  (24).   The  activated  sludge  unit  produced  the
highest organic removal efficiency  (85 percent) at food to active
mass  (F/M)  ratio of  0.2.   The  mixed  liquor  suspended  solids
(MLSS)  concentrations  in the parallel basins were maintained at
2,000-3,500 mg/1.  Flotation  thickeners  without  polymers  were
loaded  at  5.9  to  17.1 kg/sq m/hr (1.2 to 3.5 Ib/sq ft/hr) and
consistently produced sludge concentrations of 5 percent.   Total
system BOD5i removals ranged between 80 to 90 percent.

In  general,  combined  treatment  is  viable  if  proper  design
considerations assessing the effects of tannery waste waters  are
considered.
                               77

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High  treatment  efficiencies  are  technically  possible  in all
processes.  Combined  treatment  usually  requires  that  certain
restrictions  be  imposed  by  the  municipality  on  waste water
constituents, including chrome, sulfides, alkalinity, grease, pH,
and in some instances BOD5 and suspended solids.

On-Site Treatment - TricJcling^Filter Systems -  Trickling  Filter
Systems  are  not  extensively  utilized  for  tannery treatment.
Reasonably high efficiencies are technically  possible,  yet  the
positive control needed for high strength waste treatment has not
been generally demonstrated.

A  trickling  filter  is  an aerobic biological unit.  Wastewater
constituents are  brought  in  contact  with  microorganism  mass
developed  on  the  surface of the filter media.  To achieve high
removals from tannery effluents, toxicity and  excessive  organic
loads must be prevented.  Lime deposition on filters has, in some
instances, retarded biological activity.  Also, the high strength
of  tannery wastes require that a large surface area be provided.
Although, recirculation and  improvements  in  filter  media  may
reduce  overall  area  needs,  the  removal efficiency may not be
sufficiently consistent through the warm and cold periods to meet
the demands of  future  effluent  requirements.   Temperature  is
critical  in  operation.   High  heat  losses can result from the
spray  distribution  system   and   bed   media,   yielding   low
efficiencies.  Populations of nitrifying organisms are suppressed
due  to  the  continual  dosing  of  the system with carbonaceous
organic material.

Data is  generally  limited  on  trickling  filter  applications.
Presented  in  Table  11  are reported efficiencies for trickling
filter systems.  A tannery in  the  Southeast   (#3),  utilizes  a
trickling  filter  as  the  first stage in a two-stage biological
system.  Operational data reported in 1972 indicate  the  plastic
media  filter  was  ineffective  with  removals  of  less than 30
percent in BOD5 and suspended solids  (25).   After  cleaning  the
media  and  increasing  the air supply to the filter, Kinman (26)
reported improvements to the  overall  system.   Confirming  data
obtained  in  a  recent  field  survey at Tannery  #3 indicate the
trickling   filter    (oxidation   tower),   including   secondary
clarification,    has    the   following   combined   performance
characteristics  (21):
                                78

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                            Influent to     Effluent from
                                              £i§rif ier__ Removal
                               mg/1             mg/1         %

BOD5                            270               62        78

Suspended Solids                110               45        59

COD                             ---              240       ---

Total Kjeldahl Nitrogen
(as N)                          ---              210       ---

Ammonia Nitrogen  (as N)         ---               61       ---

Color                           ---           300 units    ---

The flow to the filter was approximately 3,785 cu m/day (1  mgd) ,
including  a  50  percent  recycle  of  the  secondary  clarifier
effluent.  The BOD5 and suspended solids were reduced 78  percent
and  59  percent,  respectively.   considering  the  low influent
concentrations,  these  removals  appear  to   be   satisfactory.
Further  reduction  in  BOD5  and  suspended  solids  may  not be
possible due to the colloidal characteristics  of  the  suspended
material  and  the  relatively  high  overflow  rate  of  37.6 cu
m/day/sq m (800 gpd/sq ft) in the secondary clarifier.  Based  on
estimated  influent  characteristics,  moderate  COD removals are
expected, with essentially no reduction in nitrogen and color.

Trickling filters have limited application in  the  treatment  of
high  strength  tannery  wastes.  System upsets are common due to
organic overload and climatic conditions.  Existing  filters  may
be incorporated into systems for preliminary treatment prior to a
second stage biological system.

On-Site _ Treatment  -Aerobic  Lacroon  Systems  - Aerated lagoon
systems have been utilized for tannery treatment  where  land  is
readily  available.   Lagoons serve a two-fold purpose, providing
equalization and a desirable environment for biological activity.
In a large lagoon with proper inlet and outlet  control,  primary
and   final   sedimentation   may   be  eliminated.   An  aerobic
environment is maintained by mechanical  aerators  designed  with
capacities  to  introduce  sufficient  oxygen  to  meet metabolic
requirements and to  provide  adequate  mixing.   Under  variable
loadings,   the   usually  long  detention  times  have  produced
reasonably consistent effluent characteristics.   Temperature  is
important  because  the  large  surface  area permits sizable and
latent heat loss to the atmosphere.

Presented  in  Table  12  are  removal  efficiencies  for   those
tanneries   utilizing   aerated  lagoons.   Although  the  design
potential for high removals is  documented,  existing  operations
have not attained high efficiencies consistently.  A reassessment
of unit functions and more operative control may be required.
                               79

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Carbonation, primary
sedimentation,
trickling filter,
final sedimentation
Primary coagulation,
sedimentation,
trickl ing fi Iter,
final sedimentation
Dilution, primary sedi-
mentation, trickling
f i Iter, f i nal sedi-
mentation
Dilution, primary sedi-
mentation, trickling
filter, final sedi-
mentat ion
TABLE 11
TRICKLING FILTER SYSTEMS
BODj
Inf. Eff. Removal Remarks
mg/1 mg/1 %,
85-95 Indicate 100 per-
cent removal of
sulfides
30-80 80 Adjustment of pH
before primary
sedimentation
900 56 91! Foreign data (India).
Influent BOD<- con-
centration after
primary sedimentation
821 48 84 Foreign data chrome
tannery (India) .
Influent 8005 con-
centration after
primary sedimenta-
tion


Reference

CO
(27)
(28)
(28)
80

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                                                                   TABLE   12
                                                    AEROBIC   LAGOON   SYSTEMS
                                                   Suspended Solid
                    (mgd)
                            mg/t   mgTT
                                                 I nfT  EfTTRemoval   TnfTEffRamovi
                                                mg/l   mgT)      I     mg/1   mg/T     %
Screening, plain

  lagoons, aerated
  lagoons, final
  sedimentation
                                                                                         Mlddlesboro,   chrome-     mentation of tan
                                                                                         Kentucky      vegetable    and beamhouse
                                                                                                                 1Iquors prior to
Sedimentation
  lagoons, aeratei
  lagoon, final

  lagoon, lagoon
  sludge  disposal
                                   190      53    564
Leather Co.,

Tennessee
                                                                                                                 Represents  l
                                                                                                                 hr" «mp« 11
                                                                                                                 sample
                    2,309   2,250    615
                   (0 61)
                                           6
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In  a prototype study at a tannery in Virginia (f 13) , Parker  (29)
investigated aerobic treatment of vegetable tanning wastes.   The
system  included  separate equalization for beamhouse and tanning
waste waters prior to mixing with bating flows.  Beamhouse wastes
were  eventually  diverted  to  another  facility  when   pumping
problems  developed.   Mixed  tannin  and bating wastes were then
aerated in a lagoon.  The lagoon volume was  approximately  2,984
cu  m  (0.77 mg) with 7.5 kw (10 hp) aeration capacity.  Based on
average influent data and probated effluent characteristics,  the
following removals were observed:

                              Influent    Eff luent    Removal
                                mg/1        mg/1         %

    BOD5                       1,043          86        92

    Suspended Solids             539         571         0

    COD                        4,470       1,608        64

    Sulfide                      1.5           0       100

    Total Kjeldahl Nitrogen       88          22        75

A relatively high degree of BOD5_ removal  (92 percent) resulted at
a  volumetric  loading  of  73  kg  BOD5_/day/l,000  cu  m  (4.5 Ib
BOD5/day/ 1,000 cu ft) .  Investigators  report  the  loading  may
range  from  16.2  to  130  kg  BOD5/day/l,000  cu  m   (1 to  8 Ib
BOD5/day/l,000 cu ft) for BOD5 removals exceeding 80 percent  (29)
(30)  (31).

Effluent temperatures varied between 5°C  (41°F)   to  8°C   (46°F)
during winter operation.  Sulfides were completely oxidized.  The
kjeldahl   nitrogen   removal    (75   percent)   indicates    some
nitrification occurred in the  lagoon  with  hydraulic  detention
times  of  16  to  35 days.  The "BOD removal factor" ranged  from
1.42 day-* to 1.82 day-* for the various operational phases  (29).

In  general,  aerobic  lagoons  are  capable  of  providing   high
removals   of  BODJ5  and  sulfides  with  a  potential  for   some
nitrification with long detention periods.   Existing  facilities
need  upgrading  through  proper  monitoring  and  control.   The
successful application of aerobic systems will be  contingent  on
the  availability  of  land and proper assessment of the climatic
factors influencing design.
On - S ite Treatment _-_ Aerobic _ P 1 vos _ Ana e r ob_i c __ t-agoon  Systems
Aerobic plus anaerobic lagoons are finding increasing application
in tannery waste treatment.  Existing lagoons are easily modified
to  operate  simultaneously  in these modes.  A stratified lagoon
offers the optimum characteristics of both biological  functions.
The  lower anaerobic zone, although requiring an extended contact
time, is effective in treating high strength organic wastes.  The
degradation products produced are:   methane,  hydrogen  sulfide,
and  ammonia  which  are  readily  available  for  utilization or
                                82

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further removal.  Since the process does  not  require  dissolved
oxygen,  minimum  surface area to volume ratios are required.  In
general, the anaerobic process produces a  waste  which  is  more
amenable  to  subsequent  treatment.  A more complete degradation
occurs in the upper or aerobic zone of  the  lagoon.   The  major
decomposition  products  are  carbon  dioxide and water.  Aerobic
surface conditions are required to prevent  escape  of  anaerobic
products which create odors such as hydrogen sulfide.

Stratified  lagoons are generally deep, 3.7-4.6 m (12-15 ft), but
shallow depths, 1.2-1.5  m  (4-5  ft),  are  sometimes  employed.
Mechanical  aerators  equipped  with  erosion shields provide the
desired surface oxygen requirements without disturbing the  lower
anaerobic zone.

Presented  in  Table  13  are  data for aerobic-anaerobic lagoons
treating tannery effluents.  The limited data available indicates
some inconsistency in results.  A better analysis of  the  system
merits are covered in the studies of Parker (29)  and Eye (32).
                               83

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                                                       TABLE  13
                                        AEROBIC-ANAEROBIC   SYSTEMS
  5ystem           Flo*"    lnf-  Eff -  Removal   Inf   Eff   Removal   Inf   tf f.   Removal    Tannery       Pr
               ci7 m/day   rag/1  mg/t     i     ragTT  mg/1     ?     Hig/T  mgTT     5
                2,271     673    53     92    339    ^8     86                     Pownal       Cattle-     Nitrification-       (10)
                                                     84
•eenmg, plain      I.3&3  2,300   600^    V*  3,000   IcS*    95                     Howes        Cattle,     Primary settling     (10)
.edimeritation,     (0.3&)                                                         Leather Co ,   save, wege-  of beamhouse


                                                                             Pennsylvania             mixing with
                                                                                                  spent tans.
      ^Arithmetic average

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An  aerobic-anaerobic prototype system was investigated by Parker
(29) for treatment of a vegetable  tannery  waste  consisting  of
bating  and vegetable tanning waste flows in a proportion of 8:1.
The aeration capacity of 7.5 kw  (10 hp) and volume of the  lagoon
were  held  constant  while  flows  were varied to impart various
loadings on the system.   In  the  initial  phase  the  following
removals were experienced:

                               Influent    Effluent    Removal
                               ~ mg/1        mg/1         %

    BOD5                        1,170         274        76

    Suspended Solids             ---          503       	

    COD                         4,730       2,113        55

    Sulfide                       0.7           0       100

    Total Kjeldahl Nitrogen       107          35        67

The  BOD5  removal  was  approximately  76 percent for an organic
loading of 141 kg BOD5/day/l,000 cu m  (8.7 Ib  BOD5/day/l,000  cu
ft).  Temperatures ranged from 5°C (41°F)  to 24°C  (76°F) for this
operational  phase.   Suspended solids in the effluent were high,
indicating the  need  for  more  effective  final  clarification.
Sulfides  were  completely  oxidized  in  the  aerobic zone.  The
kjeldahl nitrogen removal of  67  percent  indicates  significant
nitrification  occurring  in  the system with hydraulic detention
times of 4 to 8 days.

In the second phase of operation, doubling the  organic  load  to
282 kg BOD5/day/l,000 cu m (17.4 Ib BOD5/day/1,000 cu ft) did not
significantly   reduce   the  efficiency.    Investigators  report
loadings of aerobic-anaerobic systems may range from 130  to  243
kg  BOD5/day/ 1,000 cu m  (8 to 15 Ib BOD5/day/1,000 cu ft)  for 80
percent~organic removals  (29) (30) (31) (35)  (36  (50).   However,
loadings  above 81 kg BOD5/day/I,000 cu m (5 Ib BOD^/day/1,000 cu
ft) are impractical because of the oxygen requirement (30).

Parker indicates the most difficult  problem  in  treating  spent
vegetable  tannings  appears  to be color removal  (29).  Color is
not reduced by biological treatment.    However,  reductions  were
observed  by  blending  the  influent or effluent with lime waste
waters or coagulating with chemicals (29).

Eye investigated aerobic-anaerobic treatment of waste from a sole
leather  tannery   (32).   Laboratory  and  pilot   studies   were
conducted  prior  to  the initiation of full-scale systems.  Lime
bearing beamhouse fractions were found to be readily clarified by
adding  an  anionic  polymer  followed  by  sedimentation.    With
polymer  additions of 10 mg/1, overflow rates of 75.2 cu m/day/sq
m   (1,600  gpd/sq  ft)   produced  90  percent  suspended   solids
removals.   Later,  a  lagoon with a three-day detention time was
                                85

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found to produce equivalent removals and  was  incorporated  into
the full-scale system.

Subsequent  treatment  of  the clarified beamhouse waste water in
aerobicanaerobic  lagoons  created  severe  odor  problems.   The
problem  was eliminated when spent vegetable tanning solution was
combined with the beamhouse fractions  for  treatment.   Removals
observed through the biological system were as follows  (32):

                                      Influent   Effluent Removal
                                        mg/1       mg/1      %

BOD5                                    1,146       152      87

Suspended Solids                          408       105      74

COD                                     2,221       717      68

Sulfide                                    17        13      24

Total Kjeldahl Nitrogen (approximate)      150       100      33

High  removals  in  BOD5  (87  percent)   and suspended solids  (74
percent)  indicate the wastes are  amenable  to  aerobic-anaerobic
treatment.   The removals were obtained at volumetric loadings of
32.4 to 324 kg BOD5/ day/1,000 cu m (2 to 20 Ib BOD5/day/l,000 cu
ft).  Pilot operations indicate loading intensities ranging  from
324  to 405 kg BOD5/day/l,000 cu m (20 to 25 Ib BOD5/day/l,000 cu
ft) are feasible (32).  Total BOD5  removal  through  the  system
averaged  90  percent.  Lower removals were experienced in winter
operations when the lagoon  temperature  was  about  1°C   (34°F).
Sulfide  removal  was minimal in the system, which is contrary to
other investigations  (29).  A kjeldahl nitrogen removal of 30  to
40  percent indicates nitrification in the aerobic portion of the
lagoon.

Foaming periodically creates operation problems.   High  pressure
water   sprays   are  utilized  to  control  foam  during  summer
operations.  Defearning  chemicals  may  be  required  during  low
temperature operation.

In  Eye's  tests  (32), biological activity did not remove color.
Color could be precipitated before or after biological  treatment
by elevating the pH to 11.5 or greater with lime and the addition
of an anionic polymer.

Nitrification-denitrification  is possible in multi-stage  systems
(32) (33).  For  this  to  occur,  significant  nitrification  is
required  in  a  first  stage  aerobic  operation.   Feeding  the
nitrified waste to the anaerobic zone of the second stage  lagoon
denitrifies  the  waste.   In  the  absence  of oxygen, anaerobic
bacteria  reduce  the  nitrate  liberating  nitrogen  gas  as   a
respiration product.
                                86

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Aerobic-anaerobic  lagoons  offer  several  advantages, including
(32): relatively small land  requirements,  low  sludge  volumes,
reduced  air  requirements  since  organics are decomposed in the
anaerobic zone, heat conservation during winter operation, and  a
potential   for   some  nitrification-denitrification.   Specific
applications will require extensive pilot studies for  evaluation
of  design  parameters,  particularly in regard to nitrification-
denitrification.

On-Site Treatment - Activated	Sludge _Systems  -  The  activated
sludge process is perhaps the most innovative and flexible of all
secondary  treatment  systems.   It  is  applicable to almost all
treatment situations.   With  proper  operational  control,  high
organic removals are possible.  Designs based on solids retention
time  (SPT)  afford optimum residence time for solids with minimal
hydraulic detention period.  However, extensive pilot studies are
required to establish appropriate design parameters defining  the
relative  rate  of  biological  growth and decay.  Basically, the
activated sludge process consists of  (34):  mixing  of  returned
activated  sludge  with  the  waste  to  be treated; aeration and
agitation of the mixed liquor for the required  length  of  time;
separation  of  the  activated  sludge from the mixed liquor; and
disposal of the excess sludge.  Activated sludge  is  often  pre-
ceded   by  some  form  of  pretreatment.   Variations  in  these
processes   create   numerous   operational   phases.     Overall
efficiencies are highly dependent upon the monitoring and control
provided by operating personnel.

Presented  in  Table  14  are  results  of  full-scale  and pilot
activated sludge systems treating tannery wastes.  Based  on  the
effluent  characteristics,  operating  difficulties  are plaguing
full-scale activated sludge facilities.   At present, no  facility
is  in  operation  that  attains  high  removal efficiencies on a
consistent basis.  An exemplary facility does not exist.
                                87

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                                         TABLE   1**
                         ACTIVATED   SLUDGE  SYSTEMS
                                Suspended  Sol ids
  Flow    Inf    Eff    Removal   Tnf    Eff   Ren*
;u in/day   mgTT   rogTT     ?     mgTT   mg/1     '
  (mgd)


 3,WS   1,36*    !25      It   2.9«   3J5
                                                                     S  B.  Foot
                                                                     Tanning Co
                                                                     Red Wing,
                        93   3,135   223
                                                                                            U30 and 256 gpd/sq
Variable  2,500*-
                      7M7   2,500"
                                                                     Moench
                                                                     Tanning Co
                                                                     Gowanda,
                                                                     New York
Volumetric loading on
biolog.cal unit 3,7\2
kg/day/1,000 cu m (229
Ib BODj/day/l,000 cu
ft)   F.nal clanf,er
overflow rate 20.4-
2k !( cu m/day/sq m
(500-600 gpd/sq ft)
                                                                                            Pi lot study of flows
                                                                                            from 0 09 to 0 19 I/
                                                                                            sec (1.5 to 3 gp"0 .

                                                                                            1,751-4,409 kg/day/
                                                                                            1,000 cu m (108-272  Ib
                                                                                            BOD5/day/l,000 cu ft) .

                                                                                            flows 8.M7 9 cu m/
                                                                                            day/sq m (200-^0 gpd/
                                                                                            sq  ft) and final clarl-
                                                                                            fiers 12 2-22.0 cu in/day
                                                                                            sq m (SOO-S^O gpd/sq  ft).
                                             88

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Tannery #10  is  in  the  process  of  initiating  full  facility
operations  for  an estimated 3,785 cu m/ day  (1 mgd) flow  from a
chrome tanning, hair pulp facility and finishing operations.  The
project is partially financed through an Environmental Protection
Agency grant.

The combined tannery flows are  screened,  then  pumped  to  dual
plain   sedimentation  basins.   The  10.7  m   (35  ft)  diameter
clarifiers are equipped with surface  skimmers.   Overflow  rates
are  approximately  21.6  cu  m/day/sq  m   (460  gpd/sq ft) under
present conditions.  A potential of four concrete  lined  lagoons
may  be  utilized  for  activated  sludge  aeration basins.  Each
lagoon has a capacity of about 3,785 cu m (1 mg) at 1.8 m  (6  ft)
operating depth.  The depth may be varied in operation.  Separate
controls  permit  series,  parallel,  or  a combination of  lagoon
operations.  An aeration capacity of 22.3 kw (30 hp)  per   lagoon
was  initially  indicated;  however,  a  higher  capacity  may be
required.  Return sludge design permits recycle to each lagoon as
well as ahead of the primary clarifiers.  Aeration is followed by
final sedimentation in two 12.2 m  (40  ft)   diameter  clarifiers.
The  effluent is chlorinated prior to discharge to a nearby water
course.  Primary and waste activated sludge will be dewatered  in
a  pressure  filter  and  landfilled on-site.  Automatic samplers
permit monitoring of individual treatment units to ensure  better
operational  control.   The data presented in Table 14 represents
only partial operation of this facility.  Operating  data  to  be
developed  should  be  beneficial  to  the  industry  due  to the
numerous operating ranges and controls provided in the system.

A full-scale activated sludge plant in Kentucky, Tannery #14, was
evaluated in a two-week study  by  the  Environmental  Protection
Agency (37).  This tannery is a cattlehide tannery with pulp hair
beamhouse  operations  and  a  combination  of  alum, chrome, and
vegetable tanning.  At the time of the study, flow was only 61 cu
m/ day (0.016 mgd) of an anticipated 136  cu  m/day  (0.036  mgd)
operation.   The  treatment system consists of screening, primary
sedimentation, activated  sludge,  and  secondary  sedimentation.
Overflow rates of 13.6 and 13.4 cu m/day/sq m  (290 and 285 gpd/sq
ft)   were  observed in primary and secondary units, respectively.
Average hydraulic detention time was 1.6  days  in  the  aeration
basin.     The   following   efficiencies   were  observed  during
operations:
                               89

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BOD5

Suspended Solids

COD

Sulfide  (as S)

Total Kj^ldahl Nitrogen (as N)

Organic Nitrogen (as N)

Ammonia Nitrogen (as N)

Nitrite  (as N)

Nitrate  (as N)

Alkalinity (as CaCO3)

*Grab Sample
                 mg/1

                 1,437

                 3,135

                 4,016

                   7.9

                   490

                   328

                   162

                   0.1

                   0.1

                   516
                                                Mfluent Removal
                                                  ~mg/l    ~" %
   96

  223

  481

  0

322

  175

  1U7

   34*

  0.4

  141
 93

 93

 88

100

 34

 47

  9
 73
The EOD5 of the effluent was below 100 mg/1, indicating a removal
of 93 percent at a volumetric loading of 908  kg/day/1,000  cu  m
(56   Ib   BOD5/day/l,000  cu  ft).   Although  suspended  solids
reductions were high  (93 percent), the effluent concentration was
slightly above 200  mg/1.   Apparent  clarification  difficulties
exist.  The COD was reduced 88 percent.  Sulfides were completely
oxidized  in  the  aeration  basin.   The low removal of kjeldahl
nitrogen  (34 percent)  shows minimal nitrification  occurred  even
at  the  extended  aeration time of 1.6 days.  The possible toxic
effects of high ammonia concentrations on nitrifying bacteria  is
indicated as a cause for the low removal  (37).  The alkalinity of
the effluent was 114 mg/1 with a pH of 7.3

An activated sludge facility in New York State  (Tannery #15), is,
presently,  treating  effluent  from  save hair beamhouse, chrome
tan, and finishing operations.   Total  waste  water  from  these
processes  is about 1,514 cu m/day  (0.4 mgd).  Combined flows are
screened prior to equalization and adjustment of pH to 11.0.   In
some  instances  addition  of lime is required.  The equalization
basin has a  24-hour  capacity  under  present  conditions.   The
unclarified  discharge from the equalization basin is directed to
an aeration basin with approximately 12 hours  detention  with  a
volumetric  load  on  the  basin of about 3,566 kg/day/1,000 cu m
(220 Ib BOD5/day/l,000  cu  ft).   The  final  clarifier  has  an
overflow  rate  of  23.5 to 28.2 cu m/day/sq m  (500 to 600 gpd/sq
ft).
An organic removal  of
concentration  of  343
percent are reported.
 80  percent  produced  an  effluent  BOD5
 mg/1.    Suspended solids reductions of 92
Effluent suspended  solids  concentrations
                                90

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of  190  mg/1  reflect  ineffective  solids  capture in the final
clarifier.   The  pH  of  the  effluent  is  8.0-8.5.   The  most
interesting aspects of these treatment operations are the high pH
of  waste  entering  the aeration basin and the high mixed liquor
suspended solids concentration maintained in the aeration  basin.
Normally,  a  pH  above 11.0 is indicated as potentially toxic to
biological  activity.   However,  carbon  dioxide  derived   from
organism  respiration  is adequate to reduce the pH to about 8.0,
at which level biological  conversions  proceed.   Since  primary
clarification  is  not  provided,  all  suspended  solids  in the
tannery waste go directly to  the  aeration  basin.   All  solids
capture must, therefore, occur in the final clarifier.

Another  biological  treatment innovation is the oxidation ditch.
The oxidation  ditch  is  essentially  a  modified  form  of  the
activated   sludge  system.   Applications  of  this  process  on
domestic waste treatment are numerous in Europe.   Pilot  studies
indicate a potential for high strength tannery waste treatment.

As  proposed for tannery treatment, clarified wastes are directed
to  an  oval  ditch  or  "race  track"  for  aeration.   Separate
equalization   facilities  are  not  required,  since  the  ditch
provides excellent equalization (13).  An adjustable speed  brush
rotating  across  the full width of the channel imparts oxygen to
the waste water  and  regulates  the  velocity  of  flow  in  the
channel.   The  effluent is clarified prior to discharge with the
sludge returned  to  the  aeration  zone.   The  oxidation  ditch
provides   a   much  larger  aeration  volume  than  conventional
activated sludge.  The resulting F/M ratio  is  very  small.   At
these  low  F/M ratios (0.05) and long detention time, endogenous
respiration minimizes the amount of waste sludge.

A pilot operation treated  portions  of  the  flow  from  a  side
leather  tannery  utilizing  25,060  kg/day of green salted hides
(55,200 Ib/day).  The tanning process  produced  1,800  cu  m/day
(0.475  mgd)   of  waste  water  from  pulp  hair, chrome tan, and
finishing operations.  The average flow to the pilot facility was
5 percent of the tannery discharge, or 90 cu m/day  (0.024  mgd).
The  pilot  plant  feed  remained proportional to the fluctuating
supply  to  provide  realistic   variations   of   flow.    After
proportioning,  the  waste  water  was  pre-settled  for 30 to 45
minutes, then discharged to the  oxidation  ditch.   The  primary
sludge  was  thickened for 12 hours prior to dewatering on drying
beds.  Hydraulic detention time in  the  oxidation  ditch  varied
from  two  to three days, and the rate of activated sludge return
was estimated at 75 percent.  Production of secondary sludge  was
about  0.3  kg  (Ib)   dry solids/kg (Ib)  BOD5_ applied, or 0.55 kg
(Ib)  dry solids/kg (Ib)  BOD5 without primary sedimentation.   The
organic load on the ditch varied from 23.5-48.2 kg BOD5/day (51.8
to  106.2  Ib BOD5_/day) .   The oxygen supplied was about 1.5 times
the average BOD5 load., however.  This was not sufficient for peak
demands.   Adjustment  of  brush  rotation  and  submergence   to
increase  oxygen  transfer may be required for peak demands.  The
following pilot efficiencies  resulted  during  summer  operation
(13):
                                91

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                                Preset, tied
                                 Influent*    Effluent*   Removal*
                                   mg/1         mg/1         %

BOD5                             500-1,500       15         98

COD                            1,000-2,300      7300        85

Sulfide                           10-80           0        100

Chrome (Cr+++)                     	             1        	

Total Nitrogen (as N)               250         60-150      UO-76

Ammonia Nitrogen (as N)            100         45-125       0-50

*0rder-of-magnitude

High removals of BOD5  (98 percent)  and COD (88 percent) result at
the  low F/M ratio.  Sulfides were completely oxidized with brush
aeration.  Precipitation of  chrome  was  highly  effective  with
concentrations   below   1   mg/1   observed   in  the  effluent.
Nitrification was sporadic, with some denitrification through the
liberation of free ammonia or nitrogen gas.  The exact  mechanism
of removal was not indicated.  In general, the oxidation ditch is
an  attractive  modification  to  the  activated  sludge process.
Highly effective removals in BOD5,  suspended  solids,  sulfides,
and  chrome are demonstrated under desirable summer temperatures.
With the extremely  low  F/M  ratio  and  adjustment  for  winter
operations,  large  system  volumes  are  required.  The limiting
factor on application appears to be the availability of land.

Activated sludge systems, including various  modifications,  have
been  and  can  be  effective  in  organic  reductions  with BOD5_
removals in excess of  90  percent  and  effluent  concentrations
below  100  mg/1.   Removals  of  suspended  solids  appear to be
critical with concentrations  observed  to  be  above  200  mg/1.
Proper  design  and  operation  of  final  clarifiers may improve
results;   however,   further   treatment   is   indicated    for
significantly  higher  efficiencies.  The nitrification potential
of activated sludge systems has not been investigated at  present
facilities.   Although  feasible in theory, direct application to
tannery wastes in pilot or full-scale facilities is non-existent.

Practical Biological Systems

Several tanneries do have biological treatment systems  that  are
partially  effective.   However,  the  treatment systems have not
maintained high levels of effluent reduction.

Reliability, operability and  consistency  of  operation  of  the
waste  water treatment processes found to be most frequently used
in the leather tanning and finishing  industry  can  be  high  if
appropriate designs and operational techniques are employed.  The
                               92

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end-of-pipe  treatment  utilizing  biological  systems  is a well
established technology  that  requires  attention  to  a  limited
number of variables to insure a high degree of reliability.

The  most  important  operational  aspects  of  these  biological
systems are equipment  reliability  and  attention  to  operating
detail   and  maintenance.   Spare  aeration  equipment   (usually
floating surface aerators) improves the possibility of consistent
operation; however,  many  treatment  systems  have  an  adequate
overcapacity  already  installed as insurance against the results
of equipment failure.  It is desirable to install spare equipment
at critical points, for example, sludge return pumps.  Perhaps of
equal  importance  is  a  design  that  permits  rapid  and  easy
maintenance of malfunctioning equipment.

Therefore,  control  of  the  biological  treatment plant and the
consistency of the results  obtained  are  largely  a  matter  of
conscientious adherence to well-known operational and maintenance
procedures.   Automatic control of biological treatment plants is
far from a practical point.  Although in-line instrumentation for
measurement of pH, dissolved oxygen, temperature,  turbidity  and
so  on,  can  improve  the effectiveness of operation, its use is
minimal in the industry's existing waste water treatment  plants.
Neveretheless,  no  practical in-line instrumentation can replace
the judicious attention to operational details of a conscientious
crew of operators.

Plant 383 in subcategory 1 employs aerated lagoons  to  attain  a
BOD   discharge   of  1.9  kg/kkg  (lb/1000  Ib).   Plant  24  in
subcategory 3 utilizes a trickling filter plus aerated lagoons to
achieve a BOD discharge of 1.0 kg/kkg (lb/1000 Ib).  The  average
effluent  BOD  concentration of sampled data and industry data is
32 mg/1.  Plant 47 in  subcategory  3  has  an  activated  sludge
system  with  lagoons.  The BOD and SS discharger are 0.4 and 1.1
kg/kkg (lb/1000 Ib) respectively.  The BOD effluent concentration
from both sampled data and industry data is 16 mg/1.  Tannery  54
in  subcategory  5 utilizes an anaerobic/aerobic lagoon system to
achieve a BOD and  SS  discharge  of  1.7  kg/kkg   (lb/1000  Ib).
Industry  data  indicated  a BOD concentration of 20 mg/1.  Plant
179 employs lagoons to attain a BOD and SS discharge of  2.7  and
1.5  kg/kkg  lb/1000 Ib)  respectively.  Plant 43 in subcategory 2
utilizes lagoons to achieve a BOD discharge concentration  of  38
mg/1  (industry  data)  or  30  mg/1  (sampled data).  Three other
tanneries (185,400 and 447)  report a BOD concentration of 50 mg/1
or less.

Although these systems  are  partially  effective,  there  is  no
present  on-site  tannery  treatment facility which can achieve a
high level of effluent reduction of all  major  pollutants  on  a
consistent  basis.   Thus,  an exemplary tannery treatment system
does not  exist  and  the  best  practicable  control  technology
currently  available is not the average of the discharge from the
best tannery  waste  treatment  systems.   The  best  practicable
control  technology  currently  available  is  an  integration of
present tannery waste treatment experience with performance  data


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transferred  from  other industrial treatment operations, such as
from the meat packing industry.   The  unit  operation  and  unit
processes  combined  to  achieve  the  best  practicable effluent
reduction are as follows:

    Waste Flow

    Screening
    Equalization
    Primary Settling
    Aeration
    Secondary settling

    Sludge

    Collection
    Thickening
    Disposal


This particular arrangement has been chosen not only  because  it
is  a  practical  approach  to  treatment,  but because it is one
system applicable to each of the six subcategories.   The  system
could  utilize activated sludge or trickling filters or anaerobic
or aerobic  lagoons  or  an  oxidation  ditch  depending  on  the
individual tannery requirements.

Parameters  used  for  design  of  principal  items  of equipment
employing activated sludge are as follows:

    Equalization Basin  Detention:  24 hours at design flow

    Primary settling    Overflow Rate:  20.4 cu m/day/sq m
                                   (500 gpd/sq ft)

    Secondary Settling  Overflow Rate:  12.2 cu m/day/sq m
                                   (300 gpd/sq ft)

    Aeration Basin F/M Ratio:  0.5
                   MLVSS:  4,000 mg/1
                   BOD.5 Reaction Rate constant:  0.0015

    Deep Bed Filtration Unit Flow Rate:  0.16 cu m/min/sq m
                                    (4 gpm/sq ft)

    Waste Sludge   Primary:  2 percent solids
                   Secondary;  1 percent solids
                   Mixture thickened to 2.5 percent
                     solids

    Vacuum Filter  Loading Rate:  12.2 kg/sq m/hr
                    (2.5 Ib/sq ft/hr)

One factor concerning treatment  requires  special  consideration
and  is included in design considerations:  most treatment plants
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have had difficulty with residual suspended solids in the treated
effluent.  To ensure that the effluent  will  contain  a  minimum
residual  of  suspended  solids,  two factors are included in the
proposed design:

    1.   A low overflow rate of 12.2 cu m/day/sq  m  (300  gpd/sq
         ft)  in the secondary settling tank.

    2.   Provision for the addition of polymers to the  secondary
         settling tank as an aid to clarification.

Polishing  Systems  for	Biological Treatment - Consideration has
been given to unit operations and process techniques  which  have
been  used infrequently or not at all in tannery waste treatment.
They are as follows:

    1.   Filtration or microscreening of the effluent.

    2.   Carbon adsorption.

    3.   Color removal.

One problem experienced consistently with secondary treatment  of
tannery  wastes is the high suspended solids content of the plant
effluent.  In some instances, this has been well over  100  mg/1.
Undoubtedly,  some  of  this  may  be  due to poor design or poor
operation.  Nevertheless, there appears to be some evidence  that
filtration  or microscreening may be effective in correcting this
problem.

There  are,  at  the  present  time,  numerous  applications   of
suspended  solids  removal  by filtration or microscreening being
used as  a  tertiary  treatment  process  following  conventional
secondary  biological  treatment.   However,  there  is  no known
application of this waste water treatment process existing in the
tannery industry.

A microscreen consists of a rotating  drum  with  a  fine  screen
mounted on its periphery.  Waste enters the drum through the open
end and passes through the screen leaving the suspended solids on
the  inner  surface  of  the  screen.   At  the  top of the drum,
pressure jets of effluent water are directed into the  screen  to
remove  the  mat  of  deposited solids.  Numerous applications of
microscreening of secondary waste water effluent illustrates from
55 to 99 percent removal of suspended solids.

With the exception of gravity sedimentation, deep-bed  filtration
is   the   most   widely  used  unit  process  for  liquid-solids
separation.  Deep-bed filters have been employed in  systems  for
phosphorous  removal  from  secondary effluents and in physical -
chemical systems for the treatment of raw waste water.

Waste containing suspended solids is passed  through  the  filter
containing   granular   material  resulting  in  the  capture  of
suspended solids in  the  bed.   Eventually,  the  pressure  drop
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through  the  bed  becomes excessive or the ability of the bed to
remove suspended solids is impaired.   The  filtration  cycle  is
terminated  and  the bed is backwashed prior to being placed back
into service.  In an ideal filter,  the  size  of  the  particles
should  decrease  uniformly  in  the  direction  of  flow.   This
condition is partially achieved with the use of a multimedia deep
bed  filter.   This  type  of  filter  utilizes  materials   with
different  densities ranging from the large size particles at the
top of the filter having the  lowest  density  and  the  smallest
particles at the bottom of the filter having the highest density.
With  this  arrangement,  the filter has a large storage capacity
for suspended solids, and is able  to  remain  in  operation  for
longer  periods  of  time.   Influent solids should be limited to
about 100 mg/1  to  avoid  too  frequent  backwasiiing.   Effluent
suspended solids are normally less than 10 mg/1.

Carbon  adsorption using activated carbon in fixed beds is highly
effective in the removal of organic  dissolved  solids,  many  of
which  are  non-biodegradable.  The granular carbon media provide
an effectively large surface area for adsorption.  Biodegradation
of the captured material further increases the efficiency of  the
process.   Thermal  regeneration  is  used  to  reactivate  spent
carbon.

Laboratory 'analyses were made on carbon treatment of waste  water
from  Tannery #16  (52).  These laboratory tests were performed on
waste that  had  been  pretreated  by  pressurized  aeration  for
sulfide  removal  and  air  flotation/clarification  for  oil and
suspended solids removal.  Results of these tests  indicate  that
carbon  adsorption  can  provide  an effluent essentially free of
suspended  solids  and  colloidal  material.   The  pilot   plant
effluent  contained  approximately  300 mg/1 total organic carbon
(TOG).  The full-scale design is indicated as having a  potential
of  reducing the effluent to less than 135 mg/1 TOC representing,
approximately, 80 percent reduction in oxygen demanding materials
(52).  A carbon exhaustion rate of 1.25 kg carbon per cu m   (10.5
Ib  of  carbon/1,000  gallons) of pretreated waste water is anti-
cipated for this removal efficiency.

Activated  carbon  is  effective  in  color  removal.   Vegetable
tanning   and   dyeing  operations  contribute  substantially  to
effluent color.  Color exists as both a soluble  constituent  and
colloidal  suspension.  The pilot study at Tannery #16 produced a
95 percent reduction in color  (52).   Tomlinson,  et  al.,   (53)
observed  a 90 percent reduction in color from laboratory studies
of spent dye liquors at Tannery #1U,  Color was  effectively  re-
moved at 2 to 4 grams of carbon/liter of spent dye liquors  (53).

Activated   carbon   may  have  limited  application  in  tannery
treatment since removals are confined to dissolved organic solids
such as spent dyes and tannin  liquors.   As  an  alternative  to
secondary   treatment,   carbon   adsorption  requires  extensive
pretreatment to effectively remove suspended solids  that  retard
the  adsorption  of  dissolved  material.  The process would not.
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materially,  reduce  the  high  content  of  dissolved  inorganic
materials such as sodium chloride  (NaCl).
                                               I
The problem of color of tannery waste is most pronounced in those
systems  using  vegetable  tanning.   Color is an optical effect.
The measured magnitude of color is not, necessarily,  related  to
a weight quantity of the heterogeneous mixture of materials which
is  its  cause.   Because  of  the  nature  of the color, several
investigators  (20)  (54) have suggested the use  of  APHA  cobalt-
platinum  to  be  impractical.   The  hue  and  tint of vegetable
tanning solutions are different from color standards.  Therefore,
several arbitrary approaches have  been  developed  to  determine
percent  of  color  removed  in a particular unit operation.  For
this reason, further development  of  a  standard  is  necessary.
Nevertheless,  it is necessary that color removal be incorporated
in any treatment process for vegetable tanning wastes.

In no case observed or reported in the literature is a completely
effective system for color removal in operation.  This  does  not
mean that such a system does not exist, but only that data is not
readily available.  Data on activated carbon presented previously
indicates  the  anticipated  performance of a full-size plant for
carbon removal.  Eye (32)  and Hagan  (20)  have  both  determined
that addition of 2,000 mg/1 of lime and 2 mg/1 of anionic polymer
to  plant  waste  would  produce  90  percent color removal.  The
resulting pH of the waste was 11.5.

In many tanneries, the beamhouse  waste  can  provide  the  major
portion of the lime requirements.

Major Reduction of All Forms of Nitrogen

The  need  for  limiting  the  amount  of  the nitrogen compounds
entering rivers and lakes has been receiving increased attention.
The concern is for the fixed nitrogen and not elemental nitrogen.
Forms of fixed nitrogen include the following:

    1.   Organic nitrogen.

    2.   Ammonia and ammonium salts.

    3.   Nitrates.

    4.   Nitrites.

Normally, nitrites are  not  of  major  concern  since  they  are
readily  oxidized  to  nitrate  or reduced to nitrogen gas by the
environment.  All nitrogen forms can be considered as a  nutrient
source  for plant life including the simpler forms such as algae.
Ammonia can be toxic to fish and lower animals.  Organic nitrogen
can be converted to ammonia in the stream and  produce  the  same
results.   Ammonia entering a stream will exert an oxygen demand.
Organisms  will  convert  ammonia  to  nitrate  utilizing  stream
dissolved  oxygen.   One mg/1 of ammonia nitrogen reacts with 4.5
mg/1 of oxygen.  Therefore, a serious  oxygen  depletion  of  the
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stream could occur with only a small ammonia concentration in the
waste.  All of these factors emphasize the need for consideration
of nitrogen control.

Waste  from the tannery contains nitrogen in both the organic and
ammonia forms.  Organic and  ammonia  are  reported  together  as
total  kjeldahl  nitrogen (TKN).  Organic nitrogen in waste comes
principally from the unhairing operation resulting  from  removal
of  protein  degradation products.  Where an amine is used in the
unhairing operation it contributes to the total organic nitrogen.
Some ammonia is formed in  the  unhairing  operation  by  further
breakdown  of  protein  material.   However,  the major source of
ammonia is ammonium sulfate in the waste stream from  the  bating
process.  TKN content of the total plant waste stream can be over
900  mg/1 in some tanneries.  The organic nitrogen portion of the
TKN can vary.  One tannery  (55)  reports organic nitrogen  content
equal  to  about 60 percent of the TKN.  During detention periods
hydrolysis  or  other  mechanisms  convert  organic  nitrogen  to
ammonia.   A  large portion of the organic nitrogen is present in
colloidal materials.

The following processes have been used for nitrogen removal:

    1.   Coagulation, flocculation, and settling.

    2.   Ammonia stripping.

    3.   Ammonia ion exchange.

    4.   Chlorination.

    5.   Biological nitrification^denitrification.

Coagulation, flocculation and settling is  effective  in  partial
removal  of  soluble  and  colloidal protein matter.  To optimize
this process, pH must be reduced to the isoelectric point of  the
protein,  which  is  usually in the range of 4.5 to 5.0.  At that
point, the protein  matter  is  least  soluble.   Some  coagulant
addition may be necessary to provide good settling.

Ammonia  stripping has been applied to municipal waters where the
ammonia nitrogen content is normally in the range  of  15  to  30
mg/1.  The pH of the waste must be increased to 11.0.  No data is
available   for   tannery  waste.   Even  at  the  lower  ammonia
concentrations 3.0 cu m of air is required  per  liter  of  waste
(400 cu ft/gal)  (56) .

Difficulties  encountered  in  municipal  waste treatment include
serious calcium carbonate scaling and the reduced  efficiency  at
low  air  temperatures.   As  the air temperature approaches 0° C
(32° F) the  system  becomes  essentially  ineffective.   Removal
efficiency  is  90  to  95  percent  under optimum conditions but
organic nitrogen is not affected by ammonia stripping.
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Ammonia can also be removed from waste water by an  ion  exchange
media  which is a natural zeolite, clinoptilolite.  This material
is selective for the ammonium ion in the presence of ions such as
calcium, magnesium, and sodium found in  waste  water.   For  the
high  ammonia  content  of  tannery waste, capital investment for
such a system would be high.  Also, the presence of only a  small
concentration  of  large  organic  molecules  can  cause  serious
fouling and degradation with commonly used  ion  exchange  media.
Whether  or  not  this  fouling  would  pose  a  problem with the
selective ion exchange media used for tannery waste has not  been
established.

Chlorination can be used to convert ammonia to nitrate.  However,
at  a dosage of 10 mg/1 of chlorine per mg/1 of ammonia nitrogen,
the cost is excessive except for very small concentrations.

In a biological system  for  removal  of  nitrogen,  all  organic
nitrogen  must be hydrolyzed to ammonia or be converted to a form
from which it can be oxidized along with the ammonia  present  to
nitrate.   In the activated sludge process, a part of the ammonia
and  organic  nitrogen  is  converted  to  nitrate.    A   higher
conversion  is  accomplished  in  a system where the F/M ratio is
low.  Ammonia is converted to nitrite by a Nitrosomonas organism;
nitrite is converted to nitrate by a Nitrobacter organism.  These
autotrophic microorganisms have a slow growth rate.   One  source
(57)  indicated  that  even an extended aeration activated sludge
plant could not provide complete nitrification  on  a  year-round
basis.   In  activated sludge plants treating tannery wastes, TKN
is reduced about 35 percent.  Data for one plant is cited (55).

To be  effective,  the  nitrification  must  be  performed  in  a
separate biological system with a nitrification basin followed by
a  settling  tank.   Optimum  pH  is  8.3  to 8.5.  The organisms
utilize  an  inorganic  source  of  carbon  (carbon  dioxide   or
bicarbonate)   and  obtain  energy  from  the  ammonia  oxidation
reaction.

The nitrate nitrogen content of tannery  wastes  treated  by  the
biological  nitrification  process  is high.  Nitrate nitrogen is
essentially the same level as the ammonia  nitrogen  in  the  raw
waste  plus  any  organic  nitrogen  that  is hydrolyzed prior to
treatment.  To remove this nitrate, a biological  denitrification
step  in  the  treatment  is  required.  This can be accomplished
under anaerobic conditions by denitrifying organisms.   Equipment
required  is  a  nitrification  basin followed by a clarification
tank.  Optimum pH is 6.5 to 7.5.  Organisms using a source of or-
ganic carbon convert the nitrate  to  nitrogen  gas.   Since  the
waste is normally lacking in organic carbon, methanol is added to
provide  such  a  source.   Rate  of  addition  is  about 3 kg of
methanol per kg   (3  Ib/lb)   of  nitrate  nitrogen.   Essentially
complete denitrification is accomplished.  If organic nitrogen is
present, it will be unaffected.

Since  there  has  been  no  experience with major removal of all
forms of nitrogen  in  the  tanning  industry,  these  biological
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processes  are  used  for the design and economic studies covered
later   herein.    Details   concerning   design   criteria   for
nitrification-denitrification processes are described in a design
seminar paper  (58) .

Design criteria used are as follows:

    Nitrification

         Temperature    10°C (50°F)

         MLVSS*:   5,000 mg/1

         pH:       8,4

         Loading Factor:     438 kg/day/1,000 cu m
                   (27 Ib NH3-N/day/l,000 cu ft)

         Loading:  65 percent of raw waste NH3-N

    Denitrification

         Temperature:   10°C (50°F)

         MLVSS*:   3,000 mg/1

         pH:       7.5

         Loading Factor:     530 kg/day/1,000 cu m
                   (33.7 Ib N03-N/day/l,000 cu ft)

*Mixed Liquor Volitile Suspended Solids

Major Removal of All Waste constituents

The  major  removal  of  all  waste  constituents refers to those
processes which remove dissolved solids.  Tannery  waste  waters,
after  extensive chemical and biological treatment, still contain
a  high  concentration  of  inorganic  salts.   These  salts  are
principally   sodium   chloride,   calcium  bicarbonate,  calcium
sulfate, and calcium hydroxide.  Calcium hydroxide  used  in  the
unhairing  operation  reacts  with  ammonium sulfate and sulfuric
acids from the bating and pickling  operations  to  form  calcium
sulfate.   Residual lime in waste is removed directly by settling
or  precipitated  by  respiration  carbon  dioxide.   Some  minor
quantities  of  salts are present in the water supply.  The major
part of dissolved inorganic solids is  introduced  from  the  raw
hides or processing solutions.   Sodium chloride is present in the
incoming  hides  as  a  preservative.   It is also present in the
pickling operation.  Dissolved  solids  concentrations  prior  to
treatment  may  range  from  6,000  mg/1  -  38,000 mg/1, with an
expected average of 10,000 mg/1 (10).

Unit treatment operations for removal of dissolved solids include
the following:
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    1.   Freezing.

    2.   Evaporation.

    3.   Electrodialysis.

    4.   Ion exchange.

    5.   Reverse osmosis.

Most of these processes produce a brine solution  which  requires
further concentration and special disposal.

Freezing - Freezing is a non-selective method of dissolved solids
removal.  During freezing, ice crystals of pure water are formed.
The  dissolved  constituents  are  forced to the periphery of the
crystal platelets and adhere to the surface.  The brine  film  is
removed  from  the  surface of the crystals by washing.  The ice-
brine separation has previously caused operational  difficulties.
A  more  effective wash is required, and, also, one that does not
create a high volume of brine for ultimate disposal.

The freezing process has been proposed for treatment of clarified
tannery discharge at a tannery (10).  However, to date  no  full-
scale  operations  have  been implemented.  Extensive pilot scale
studies  are  required  prior  to  expenditures  for   full-scale
facilities.   Freezing  will  have limited application in tannery
treatment until all phases of the process are proven reliable.

Evaporation - This process  is  perhaps  the  oldest  method  for
removal  of dissolved solids.  In principal, a saline solution is
evaporated with heat energy.  The vapor produced is mineral  free
and  condensed  for  disposal  or reuse.  A strong brine solution
alone or with some salt crystallization remains for disposal.

Solar energy may provide the required heat  of  evaporation  when
wastes   are   retained  in  large  lagoons.   However,  climatic
conditions coupled with relatively high continuous flows and  the
need  for  impervious soil or sealant imposes severe restrictions
on the geographic location for such lagoons.

Multiple effect evaporators have been used in industry  for  many
applications.   A saline solution is heated to the boiling point,
normally at an elevated pressure.  The steam produced is directed
to cooling in a second stage where the latent  heat  is  used  to
evaporate  more  solution.  This arrangement is used for a number
of stages.  Evaporation is carried out in each successive  stage.
A  triple effect evaporator for salt concentration will evaporate
slightly over two kg  (Ib) of water per kg  (Ib) of steam used.

Electrodialysis - Electrodialysis is a demonstrated  process  for
removalofdissolved solids in brackish waters.  Basically, the
electrodialysis cell consists of alternate cationic  and  anionic
permeable membrances in a stack alternately charged by electrodes


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at.  each  end.   An external power source maintains the potential
across the electrodes.  Based on the charge, an ion will  migrate
towards the oppositely charged electrode, but will be selectively
captured  between  the  membrane  stacks.   Relatively pure water
remains between alternate membranes while the concentrated  waste
brine  collects 'in others.  For waters of concentration less than
10,000 mg/1, the energy requirement in an actual installation  is
of the order of 2.6 to 7.9 kwhr per cu m (10 to 30 kwhr per 1,000
gallons)   of  product  water  (59).  This is less than the energy
required   for   the   distillation   process.    The   principal
disadvantages  for  tannery  applications  are  membrane fouling,
polarization, and scaling from waste constituents.   At  present,
there  is  no  record  of  tanneries  using  the  electrodialysis
process.

Ion Exchange  -  This  process  is  one  in  which  there  is  an
interchange  of ions between the liquid being treated and a solid
particulate media.  The media is normally a zeolite or  synthetic
resin.   Major  application  has  been in water softening where a
salt regenerated cation unit removes calcium and  magnesium  ions
from the water and replaces them with sodium ions.

For  salt  removal from tannery wastes both a cation and an anion
exchanger must  be  used.   To  make  ion  exchange  economically
feasible   for  desalination  of  water,  special  ion  exchanger
arrangements have been used.  One of these is the  DESAL  process
which  is  a  three  bed  system  (60).  Two of these beds contain
anion exchange media and the third  contains  a  cation  exchange
media.   The  operation  method  is such that only stoichiometric
quantities of regenerates are used, thereby providing substantial
economy over operation of standard demineralization equipment.

A suitable method must be used to  dispose  of  spent  regenerant
solutions.   According to one manufacturer of ion exchange media,
this process is generally applicable to solutions containing less
than 3,000 mg/1 of ionizable solids.  Based on this fact and that
resin fouling  occurs  from  even  small  quantities  of  organic
matter,  application  for  treatment of tannery waste which has a
salt content of well over 3,000 mg/1,   waste  is  not  considered
feasible.

Reverse  Osmosis  -  Reverse  osmosis  is a process which is non-
selective  with  respect  to  dissolved  solids  removal  and  is
reasonably  dependable.   In  osmosis, when a salt solution and a
pure solvent or a solution of less concentration are separated by
a semi-permeable membrane, the pure  solvent  flows  through  and
dilutes   the   salt   solution.   The  process  continues  until
equilibrium is established.  The  semipermeable  membrane  allows
the  pure  solvent  to  pass,  but not the solution.  The driving
force is the strong chemical potential of the pure solvent.   The
pressure  developed  in  the process is the osmotic pressure.  In
reverse osmosis, a pressure  applied  to  the  salt  solution  in
excess  of  the  osmotic pressure forces the pure solvent through
the membrane leaving a concentrated brine.  The  success  of  the
system  is  dependent  upon  selection  and  maintenance  of  the
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membrane.  Reverse osmosis has been effective for  the  treatment
of  pulp  and  the  paper  mill  wastes,  acid mine drainage, and
municipal supplies with a high mineral content.

Pilot treatment of dilute pulp and paper effluents  (61)  produced
membrane   rejections   of   90-99  percent  for  most  feedwater
components.  Optimum performance is indicated at dissolved solids
concentrations of 5,000 to  15,000  mg/1.   The  resulting  brine
solution was 8 to 10 percent solids.

Pilot scale studies on acid mine drainage (62) produced a product
water  with  10 mg/1 dissolved solids from an influent containing
1,280 mg/1 dissolved solids.  Product water or permeate was about
75 percent of the total flow.  The permeate did not meet drinking
water standards.

An extensive pilot plant study was performed in California at the
Pamona Water Rennovation Plant   (63).   This  study  demonstrated
reverse  osmosis obtained excellent rejection of dissolved solids
from the effluent of a  waste  treatment  plant  using  activated
sludge  and  from  a  parallel  plant  using a granular activated
carbon bed.  Effluent from both  systems  contained  a  dissolved
solids concentration of about 1,150 mg/1.  The permeate contained
55 mg/1 dissolved solids producing a 95 percent removal.  Ammonia
nitrogen  and  nitrate  were  reduced  95  percent and 75 percent
respectively.  The ammonia nitrogen in the effluent was about  15
to 20 mg/1.

There  has  been  no  direct  application  of reverse osmosis for
treatment of tannery waste water.  Investigations in the pulp and
paper industry indicate that wastes of similar concentration  are
amenable   to   reverse   osmosis.   At  these  dissolved  solids
concentrations,  the  osmotic  pressures  encountered  are   high
requiring  higher  applied  pressures.  There are several reasons
reverse osmosis  may  be  more  appropriate  than  other  methods
discussed  for the treatment of tannery wastes.  The equipment is
easy to operate.  Energy requirements are relatively low.   Also,
an  elevated  operating temperature is not required.  The process
is non-selective in dissolved solids  capture  producing  a  high
purity  product  water.   The  principal  disadvantage is a large
volume of low concentrated  brine.   Membrane  fouling  has  been
cited  as  a potential operational problem.   Although, not proven
specifically for treating tannery wastes, it has been selected as
the most applicable for this study based on data  available.   It
will  be  necessary to prove by a demonstration project that this
is a viable process for this application.

Design is based on a projected  75  percent  recovery  of  usable
water  with  a  dissolved  solids  content of less than 500 mg/1.
This is an interpolation based on  present  experience  of  a  25
percent  recovery  with  sea  water   (3.5  percent  salt)  and an
approximate 90 percent recovery with  brackish  water  containing
3,000 mg/1 of dissolved solids (64) .
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Disposal  of  waste  brine  from  the reverse osmosis process can
create a major problem.  The waste brine constitutes  25  percent
of  the  waste  treated..   Further  treatment  prior to ultimate
disposal is required.  Research in advanced waste water treatment
and desalination has produced methods for handling brines.  A few
of the techniques investigated are as follows:

    1.   Various types of solvent extraction.

    2.   Electrodialysis.

    3.   Solar evaporation.

    4.   Multiple effect evaporation.

    5.   Submerged combustion.

The   various   solvent   extraction   techniques    for    brine
concentrations  are not fully developed for practical application
at this time.

Electrodialysis has shown the capability of brine  concentrations
to  200,000  mg/1  (64).  However, practical application requires
further development.

Solar evaporation ponds are, normally, the most economical  means
for  disposal  of  waste  brines,  however,  their application is
restricted to areas where evaporation exceeds annual rainfall  by
over  20  inches.   These  areas  are  principally in the west to
southwest.  Unfortunately, most  tanneries  are  located  in  the
northeast, southeast, and midwest, where humid climates make such
operations unpractical.

Multi-stage  flash  evaporators  are applicable for concentrating
waste  brines  prior  to  ultimate  disposal.   The   method   is
economical  for  concentrating  solids  up to 10 percent.  Higher
concentrations  require  multi-effect  evaporators.     Submerged
combustion   may   be   utilized  to  concentrate  brines  beyond
saturation yielding crystal formation  (65) .

None of these processes have  been  demonstrated  on  brine  from
tannery  waste.   However,  no  special problems are anticipated.
The principal problem is ultimate disposal of the concentrate  if
a  salt  is  not crystallized and removed.  Several possibilities
exist for ultimate disposal of concentrated brine;

    1.   Deep-well disposal.

    2.   Ocean disposal.

    3.   Complete evaporation.

Deep-well disposal  of  brines  requires  comprehensive   geologic
study and field testing of potential disposal zones to assess the
safety   and   effectiveness   of  underground  strata.   Several


                               104

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potential dangers exist for such disposal including pollution  of
fresh  water  supplies  through  encroachment  and disturbance to
underground strata.  Injection wells  normally  require  detailed
investigations  to  ensure that liquids in the underground strata
are compatible both  physically  and  chemically,  to  the  waste
brines  injected.  Usually, high pressure pumping is required for
deep-well disposal.

Ultimate  disposal  in  such  reservoirs  as  the  ocean  may  be
feasible,  Normally, tanneries are not located in close proximity
to the ocean so that direct  discharge  is  possible.   Transport
costs  make  ocean  disposal  from  most  tanneries  economically
unattractive.

For study purposes, a triple-effect evaporator is used  for  salt
crystallization followed by filtration and drying.  The recovered
salt can be marketed for reuse.

Complete  evaporation  of  the  brine  appears  to  be  the  most
generally applicable approach to the problem.

The impact of disposal of waste brines from the tannery  industry
as  well  as  those from other industries is likely to be a major
problem in future  years  as  higher  degrees  of  treatment  are
implicated.   Further  study  is required to determine methods of
disposal of brines.

In the tanning industry, a substitute for salt in the hide curing
process and increased reuse of process chemicals would be a major
step in eliminating this problem.
                              105

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                          SECTION VIII

           COST, ENERGY, AND NON-WATER QUALITY ASPECTS


Cost_an^Reduction Benefits^of Alternative Treatment arid _Control
Technologies

A  detailed economic analysis showing the impact of treatment and
control  technologies  upon  the  six  subcategories  within  the
leather  tanning  and finishing industry is given in the document
"Economic  Analysis  of  Proposed  Effluent  Guidelines,  Leather
Tanning  and  Finishing  Industry."  Five  alternative  treatment
methods have been considered for Subcategories 1 to 6.   For  the
six subcategories, the alternatives include:

    Alternative A - No waste treatment or control.

    Alternative B - Preliminary treatment and chrome removal

    Alternative C - Alternative B plus activated sludge.

    Alternative   D   -   Alternative  C  plus  sulfide  removal,
              nitrification, and denitrification and filtration.

    Alternative E -  Alternative  D  plus  reverse  osmosis,  and
              evaporation.
Tables 15-20 illustrate the cost of waste water treatment for the
average  size  plants  in  each subcategory.  Both investment and
total annual costs are shown for the various alternatives.

Basis of Economic Analysis - Following is a summary of the  basis
for cost estimates presented in Tables 15-20.

    1.   Investment  -  Investment  costs   have   been   derived
         principally from published data on waste water treatment
         plant construction costs (66) (67), Stanley consultants'
         cost  data, and information from equipment manufacturers
         and suppliers.

         Published cost data for treatment facilities is derived,
         primarily, from experience with  waste  water  treatment
         installations.   Cost  information  has been reported by
         some tanneries, but the data are not extensive enough to
         serve as a basis for  the  estimates  presented  herein.
         Basic  data  were  developed by preparation of graphical
         relationships  between  cost  and  size  for  each  unit
         operation.   Based  on  treatment  plant  configuration,
         design criteria, and size,   costs  for  individual  unit
         operations   were  added  together  to  determine  major
         facility costs.
                              107

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An allowance of 15 percent of the total  investment  has
been included to cover land, contingencies, engineering,
and overhead.

August,  1971  price  levels  have  been  chosen  by the
Environmental Protection Agency and are used  herein  as
the base level for economic evaluation.  Inflation since
August,  1971,  has  had  a marked impact on the cost of
treatment facility construction, labor, and other  costs
involved  in  this  analysis as well as raw and finished
product prices.  Inflationary  trends  should  be  taken
into  consideration  when evaluating the costs presented
herein in comparison with current costs.

Deprecjation_and Cost of^Capital  jlnterest)  -  It  was
assumed that the annual interest costs  j(cost of capital)
and  depreciation would be constant over the life of the
treatment facilities.  A principal repayment  period  of
20 years was used.  Costs were depreciated on a straight
line  basis  and the depreciation period of 20 years was
assumed equal to the principal repayment period and  the
economic life of the facilities.

Cost  of  money was assumed to be an average of the cost
of debt capital and the cost of equity capital.  Cost of
debt capital was assumed to be 8 percent and the cost of
equity capital 22 percent.  Data for the last 10  to  12
years  indicates  that  the average net return on equity
capital   for   the   chemical   industry   and    other
manufacturing  has  been  10  to  12  percent.  Assuming
corporate income tax is equal to net return (50  percent
of  gross  return),  gross  return is estimated to be 22
percent.  Sixty percent of the investment was assumed to
be debt capital and 40  percent  equity  capital.   From
this  analysis,  an  average  rate for the cost of money
equal to 13.6 percent was determined.  An average annual
value for cost of money was derived by  subtracting  the
straight  line  depreciation  cost  from  the investment
cost, times the capital recovery factor.  The costs were
about 8 percent of the capital investment.

Insurance andJTaxes - An annual cost of 1 1/2 percent of
the initial investment was used for insurance and  taxes
on the waste treatment plant.

Operation  and	Maintenance	Labor   -   Operation   and
maintenance labor manhour requirements were based mainly
on published data,  (66) (67), and independent estimates.
The  operational requirements include general management
and  supervisory  personnel,  equipment  operators   and
laborers,   and   clerical   and   custodial  personnel.
Maintenance  labor  includes   mechanical,   electrical,
laborers, and other appropriate repair  personnel.
                      108

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pounds)
         Based  on  labor  rates  in  the  tanning  industry  and
         municipal waste water treatment plants,   (68)   (69),  an
         August,  1971,  average  labor  rate  of  $4.90 per hour
         (including fringe benefits) was used  to  compute  total
         annual operation and maintenance labor costs.  The costs
         were approximately 10 percent of the capital investment.

         Chemicals - Chemical costs used in the economic analysis
         are based or. published literature typical in the  U.  S.
         (70).  The costs used are:

              Methanol - $0.069 per liter ($0.26 per gallon)

              Lime - $22.00 per metric ton ($2C.OO per ton)

              Soda  Ash  - $3.96 per 100 kilograms ($1.80 per 100


              Ferric Chloride - $8.80 per  100  kilograms   ($4.00
              per 100 pounds)

              Polymer - $0.44 per kilogram ($0.20 per pound)

              Chlorine  - $13.20 per 100 kilograms ($6.00 per 100
              pounds)

              Sulfuric Acid - $36.40 per metric ton   ($33.00  per
ton)

              Ferric  Sulfate - $46.30 per metric ton ($42.00 per
ton)

              Sodium Hydroxide (50%) - $8.50  per  100  kilograms
              ($3.85 per 100 pounds)

              Manganous  Sulfate  - $90.50 per metric ton  ($82.00
              per ton)

    6.   Energy - In  broad  context,  energy  includes  electric
         power  and  fuel.   Electric power consumption for major
         units  such  as  aeration,  pumping,  and   mixing   was
         estimated  from available data, (66) (67).  An allowance
         of ten percent was made for small power  users  such  as
         clarifiers,   chemical   feed   equipment,   ventilation
         equipment, and so forth.  The cost of electric power was
         assumed to be $0.015/kwhr.

         For Alternative E, steam is  required  for  evaporation,
         dewatering,  and drying of the waste brine.   The cost of
         steam ranged from  $1.76  to  $2.42/1,000  kg  of  steam
         ($0.80 to $1.10/1,000 Ib of steam).
                               109

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                           TABLE 15

                WASTE WATER TREATMENT COSTS (1)
                     FOR SUBCATEGORY 1
                                         ALTERNATIVE (4)
PARAMETER/COST	B	C	D
PLANT RAW MATERIAL PRODUCTION
1000 kg hides/mo
(1000 Ib hldes/mo)
EQUIVALENT FINISHED PRODUCT (2)
1000 sq m hldes/mo
(1000 sq ft hides/mo)
AVERAGE FLOW
I/kg hide
(gal/lb hide)
ESTIMATED INVESTMENT COST(3)
($1000)
ESTIMATED ANNUAL INVESTMENT
$/1000 kg hides/yr
($/1000 Ib hides/yr)
ESTIMATED ANNUAL COST
($1000)
$/sq m hide
($/sq ft hide)

636
1,400

88
950

33
4

$361.5

47.3
21.5

88 ,6
0.084
0.008

636
1,400

88
950

33
4

$1,209.3

158.5
71.9

$296.3
0.281
0.026

636
1,400

88
950

33
4

$1,598.7

209.5
95.1

391.7
0.371
0.034

636
1,400

88
950

33
4

$2,473.1

323.8
147.2

$718.9
0.681
0.063
TYPICAL FINISHED PRODUCT
  Price ($/sq ft hide)            0.640       0.640     0.640      0.640

TREATMENT COST AS PERCENT
  OF PRODUCT PRICE                1.25        4.1        5.4        9.8


(1) All Costs Based on August 1971 Price Levels

(2) Raw Material Conversion Factor to Finished Product * 0.68 sq  ft
                                                               Ib

(3) Assumes Treatment Facilities Sized to Meet Plant Production
    with No Allowance for Growth

(4) ALTERNATIVE B - Preliminary Treatment (Chrome Removal)
    ALTERNATIVE C - Alternative B plus Activated Sludge
    ALTERNATIVE D - Alternative C plus Sulfide Removal,
                    Nitrification and Denitrificatlon, and Filtration
    ALTERNATIVE E - Alternative D plus Reverse Osmosis and Evaporation

                                   110

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                               TABLE 16

                    WASTE WATER TREATMENT COST (1)
                         FOR SUBCATEGORY 2

                                         ALTERNATIVE (A)
PARAMETER/COST	B	C	D
PLANT RAW MATERIAL PRODUCTION
1000 kg hides/mo
(1000 Ib hides/mo)
EQUIVALENT FINISHED PRODUCT(2)
1000 sq m hides/mo
(1000 sq ft hides/mo)
AVERAGE FLOW
I/kg hide
(gal/lb hide)
ESTIMATED INVESTMENT COST(3)
($1000)
ESTIMATED ANNUAL INVESTMENT
$71000 kg hides/yr
($/1000 Ib hides/yr)
ESTIMATED ANNUAL COST
($1000)
$/sq m hide
($/sq ft hide)

863
1,900

120
1,290

50
6

$517.2

49.7
22.6

$126.8
0.088
0.008

863
1,900

120
1,290

50
6

$1,459.0

140.9
64.0

$357.5
0.248
0.023

863
1,900

120
1,290

50
6

$1,914.6

184.9
83.9

$469.1
0.326
0.030

863
1,900

120
1,290

50
6

$3,697.2

356.8
162.2

$1,073.8
0.746
0.069
TYPICAL FINISHED PRODUCT
  Price ($/sq ft hide)            0.640      0.640      0.640      0.640

TREATMENT COST AS PERCENT
  OF PRODUCT PRICE                1.25        3.6        4.7       10.8


(1) All Costs Based on August 1971 Price Levels

(2) Raw Material Conversion Factor to Finished Product - 0.68 sq ft
                                                              " Ib

(3) Assumes Treatment Facilities Sized to Meet Plant Production
    with No Allowance for Growth

(4) ALTERNATIVE B - Preliminary Treatment (Chrome Removal)
    ALTERNATIVE C - Alternative B plus Activated Sludge
    ALTERNATIVE D - Alternative C plus Sulfide Removal,
                    Nitrification and Denitrification, and Filtration
    ALTERNATIVE E - Alternative D plus Reverse Osmosis and Evaporation


                                   111

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                              TABLE 17
PARAMETER/COST
WASTE WATER TREATMENT COSTS (1)
     FOR SUBCATEGORY 3

                     ALTERNATIVE (4)
            BCD
PLANT RAW MATERIAL PRODUCTION
1000 kg hides/mo
(1000 Ib hides/mo)
EQUIVALENT FINISHED PRODUCT (2)
1000 sq m hides/mo
(1000 sq ft hides/mo)
AVERAGE FLOW
I/kg hide
(gal/lb hide)
ESTIMATED INVESTMENT COST(3)
($1000)
ESTIMATED ANNUAL INVESTMENT
$/1000 kg hides /yr
($71000 Ib hides /yr)
ESTIMATED ANNUAL COST
($1000)
$/sq m hide
($/sq ft hide)

431
950

51
550

42
5

$284.0

54.8
24.9

$ 69.6
0.114
0.010

431
950

51
550

42
5

$925.4

178.9
81.2

$226.7
0.370
0.034

431
950

51
550

42
5

$1,218.3

235.6
106.9

$298.5
0.488
0.045

431
950

51
550

42
5

$2,828.1

545.6
248.0

$ 590.2
0.964
0.089
TYPICAL FINISHED PRODUCT
   Price ($/sq ft hide)

TREATMENT COST AS PERCENT
   OF PRODUCT PRICE
             0.780
             1.3
0.780


4.4
0.780
5.8
 0.780


11.4
(1) All Costs Based on August 1971 Price Levels

(2) Raw Material Conversion Factor to Finished Product
(3) Assumes Treatment Facilities Sized to Meet Plant  Production
    with No Allowance for Growth

(4) ALTERNATIVE B = Preliminary Treatment  (Chrome  Removal)
    ALTERNATIVE C = Alternative B plus Activated Sludge
    ALTERNATIVE D = Alternative C plus Sulfide Removal,
                    Nitrification and Denitrification and  Filtration
    ALTERNATIVE E   Alternative D plus Reverse Osmosis and  Evaporation
                                     112

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                              TABLE 18

                   WASTE WATER TREATMENT COSTS (1)
                        FOR SUBCATEGORY 4

                                        ALTERNATIVE  (4)
PARAMETER/COST	B	C	D
PLANT RAW MATERIAL PRODUCTION
1000 kg hides/mo
(1000 Ib hides/mo)
EQUIVALENT FINISHED PRODUCT(2)
1000 sq m hides/mo
(1000 sq ft hides/mo)
AVERAGE FLOW
I/kg hide
(gal/lb hide)

341
750

84
900

17
2

341
750

84
900

17
2

341
750

84
900

17
2

341
750

84
900

17
2
ESTIMATED INVESTMENT COST(3)
  ($1000)                     $177.3      $466.2      $618.5     $986.6
ESTIMATED ANNUAL INVESTMENT
$/1000 kg hides/yr
($/1000 Ib hides/yr)
ESTIMATED ANNUAL COST
($1000)
$/sq m hide
($/sq ft hide)
TYPICAL FINISHED PRODUCT
Price ($/sq ft hide)
TREATMENT COST AS PERCENT
OF PRODUCT PRICE

43.3
19.7
$43.5
0.043
0.004
0.610
0.7

113.9
51.7
$114.2
0.113
0.010
0.610
1.7

151.1
68.6
$151.1
0.150
0.014
0.610
2.3

241.2
109.6
$267.3
0.265
0.025
0.610
4.1
(1)  All Costs Based on August 1971 Price Levels

(2)  Raw Material Conversion Factor to Finished Product =


(3)  Assumes Treatment Facilities Sized to Meet Plant Production
    with No Allowance for Growth

(4)  ALTERNATIVE B = Preliminary Treatment (Chrome Removal)
    ALTERNATIVE C = Alternative B plus Activated Sludge
    ALTERNATIVE D = Alternative C plus Sulfide Removal,
                    Nitrification and Denitrification and Filtration
    ALTERNATIVE E = Alternative D plus Reverse Osmosis and Evaporation

                                    113

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                               TABLE 19

                    WASTE WATER TREATMENT COSTS (1)
                         FOR SUBCATEGORY 5

                                         ALTERNATIVE  (4)
PARAMETER/COST	B	C	D
PLANT RAW MATERIAL PRODUCTION
1000 kg hides/mo
(1000 Ib hides/mo)
EQUIVALENT FINISHED PRODUCT (2)
1000 sq m hides/mo
(1000 sq ft hides/mo)
AVERAGE FLOW
I/kg hide
(gal/lb hide)
ESTIMATED INVESTMENT COST (3)
($1000)
ESTIMATED ANNUAL INVESTMENT
$71000 kg hides/yr
($/1000 Ib hides/yr)
ESTIMATED ANNUAL COST
($1000)
$/sq m hide
($/sq ft hide)

148
325
66
715

62.5
7.5
$249.5

140.8
64.0

$61.2
0.077
0.007

148
325
66
715

62.5
7.5
$540.5

304.3
138.2

$132.4
0.167
0.015

148
325
66
715

62.5
7.5
$756.3

425.8
193.3

$185.3
0.234
0.022

148
325
66
715

62.5
7.5
$1,299.4

733.0
333.2

$363.2
0.459
0.042
TYPICAL FINISHED PRODUCT
  Price ($/sq ft hide)            0.48      0.48         0.48        0.48

TREATMENT COST AS PERCENT
  OF PRODUCT PRICE                1.5       3.2          4.5         8.8


(1) All Costs Based on August 1971 Price Levels

(2) Raw Material Conversion Factor to Finished Product  = 2.2  sq  ft
                                                               Ib

(3) Assumes Treatment Facilities Sized to Meet Plant  Production
    with No Allowance for Growth

(4) ALTERNATIVE B = Preliminary Treatment  (Chrome Removal)
    ALTERNATIVE C = Alternative B plus Activated Sludge
    ALTERNATIVE D = Alternative C plus Sulfide Removal,
                    Nitrification and Denitrification and Filtration
    ALTERNATIVE E = Alternative D plus Reverse Osmosis  and  Evaporation

                                    114

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                               TABLE 20
PARAMETER/COST
WASTE WATER TREATMENT COSTS (1)
     FOR SUBCATEGORY 6

                     ALTERNATIVE  (4)
             BCD
PLANT RAW MATERIAL PRODUCTION
1000 kg hides/mo
(1000 Ib hides/mo)
EQUIVALENT FINISHED PRODUCT
1000 sq m hides/mo
(1000 sq ft hides/mo)
AVERAGE FLOW
I/kg hide
(gal/lb hide)
ESTIMATED INVESTMENT COST(3)
($1000)
ESTIMATED ANNUAL INVESTMENT
$/1000 kg hides/yr
($/1000 Ib hides/yr)
ESTIMATED ANNUAL COST
($1000)
$/sq hide
($/ sq ft hide)
499
1,100
(2)
70
750

17
2

$254.4

42.5
19.3

$62.3
0.074
0.007
499
1,100

70
750

17
2

$747.2

124.8
56.7

$183.1
0.218
0.020
499
1,100

70
750

17
2

$1,031.2

172.2
78.2

$252.6
0.301
0.028
499
1,100

70
750

17
2

$1,374.4

229.0
104.1

$408.6
0.486
0.045
TYPICAL FINISHED PRODUCT
   Price ($/sq ft hide)

TREATMENT COST AS PERCENT
   OF PRODUCT PRICE
              0.31


              2.3
0.31
6.5
0. 31
9.0
0.31
                     14.5
(1) All Costs Based on August 1971 Price Levels

(2) Raw Material Conversion Factor to Finished Product
                                     0.68 sq  ft
                                           Ib
(3) Assumes Treatment Facilities Sized to Meet Plant Production
    with No Allowance For Growth

(4) ALTERNATIVE B = Preliminary Treatment (Chrome Removal)
    ALTERNATIVE C = Alternative B plus Activated Sludge
    ALTERNATIVE D = Alternative C plus Sulfide Removal,
                    Nitrification and Denitrification and Filtration
    ALTERNATIVE E = Alternative D plus Reverse Osmosis and  Evaporation
                                 115

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Effluent Reduction - Subcateqory^l - The following discussion for
Subcategory  1  deals  with the sensitivity of effluent reduction
with respect  to  costs  for  Subcategory  1.   This  subcategory
represents  a  substantially  larger segment of the industry than
any other subcategory.   Costs  are  based  on  an  average  size
tannery  in  this subcategory processing 29,510 kg (65,000 Ib) of
hides per day.

Alternative A - No Waste,Treatment or Control

The estimated organic waste load  for  Subcategory  1  is  95  kg
BODj/1,000  kg (95 Ib BOD5/1,000 Ib) of hide.  This represents 14
times that of normal domestic sewage.

Costs - None.

Reduction Benefits •<• None.

Alternative B - Preliminary Treatment and Chrome^Removal

This alternative includes in-process chromium  removal,  pumping,
screening,   equalization,  and  primary  clarification.   Sludge
handling includes holding tanks and  thickening  units,  Effluent
waste  loads  from  this  alternative  are  estimated to be HI kg
BOD5/1,000 kg (47 Ib BODjj/1,000 Ib) of hide processed.  Reduction
of oil and grease, and chromium also occur.

Costs - The total capital investment  cost  is  estimated  to  be
$361,500  for  the  model  plant.   The  annual treatment cost is
estimated to be less than $90,000.

Reduction Benefits - Alternative B represents about a 50  percent
reduction  in  BOD5 compared with Alternative A.  Total reduction
in BOD5  with  preliminary  treatment  would,  therefore,  be  50
percent.  Other constituents are, also, removed as noted.

Alternative C Alternative B Plus Activated Sludge

This alternative provides the same units as pretreatment with the
addition  of  an  aeration  basin  and  secondary clarifier.  The
effluent waste load is estimated at 4.0 kg BOD5/1,000 kg  (4.0  Ib
BODJ/1,000  Ib)   of  hide processed for the average Subcategory  1
tannery treatment facility.

Costs - Alternative C represents a total  capital  investment  of
$1,209,300 and an annual cost of $296,300.  These costs represent
an increase of $850,000  in capital costs and almost over  $200,000
in annual costs over Alternative B.

Reduction Benefits - Alternative C represents a reduction in  BOD5
of  91  percent  over  Alternative  B.   This  represents a total
reduction in plant BOD5  of 95.8 percent.

Alternative D - Alternative C Plus  Sulfide Re.2i2y.alx. Nitrification
and Denitrification, and Filtration
                               116

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Alternative D includes the treatment units for Alternative C with
the  addition  of  a  sulfide  removal   process,   chlorination,
nitrification   basin,  covered  denitrification  basin,  sulfide
removal process, aeration flume,and a graded media  filter.   The
effluent   from  the  average  Subcategory  1  tannery  treatment
facility would be 1.4 kg BOD5/1,000 kg  (1.4 Ib BOD5/1,000 Ib)  of
hide  processed.   Significant  removal  of  sulfide and nitrogen
would, also, result.

Costs - Alternative D represents a total  capital  investment  of
$1,598,700  and  an annual cost of $391,700 These costs represent
an increase of almost $390,000 in capital costs and about $95,000
in annual costs over Alternative C.

Reduction  Benefits  -  Through  Alternative  D,  there   is   an
incremental  reduction  in BOD5_ of 65 percent over Alternative C.
Total reduction in BODJ would be about 98.5 percent.  Sulfide and
nitrogen removals, also, result.

Alternative  E  -  Alternative  D  Plus  Reverse   QsmosiSj,   and
Evaporation

Alternative  E includes the same operations as Alternative D with
the addition of  a  reverse  osmosis  unit  for  the  removal  of
dissolved solids, evaporation facilities for concentration of the
rejection    water   from   the   reverse   osmosis   unit,   and
dewatering-drying facilities for the waste brine.  In addition to
these, the final clarifier in Alternative D would be replaced  by
a  reactor  clarifier  with  provisions  for soda ash addition to
soften prior to reverse osmosis and evaporation.  Reverse osmosis
product water and condensed evaporator water would be recycled to
the tannery wet processes.  Alternative E would  result  in  zero
discharge and no liquid wastes to the receiving streams,

Costs - The capital investment is estimated to be almost $900,000
more than Alternative D and annual costs are estimated to be over
$325,000 more than Alternative D.

Reduction  Benefits  - There would be an incremental reduction in
BOD5 of 100 percent over  that  of  Alternative  D,  or  a  total
reduction   in  plant  BODI5  load  of  100  percent.   All  other
constituents would be completely removed.


Impact of Waste Treatment Alternatives, on Finished Product Price

Tables  15-20  illustrate  the  probable  increases  in  finished
product  prices  for the six subcategories to pay for waste water
treatment.  For the best practicable control technology currently
available, estimated increases in final product costs range  from
1.7 to 4.4 percent for various subcategories.
                              117

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For   the   best   available   control   technology  economically
achievable, the estimated increase of final product  cost  ranges
from 0.6 to 1.4 percent for various subcategories.


The  overall  cost  of  both  best practicable and best available
control technology is estimated to increase final  product  costs
from 2.3 to 5.8 percent for various subcategories.

Alternative Treatment Systems

It  has  been  assumed in the economic analysis that an activated
sludge process will be utilized  for  the  biological  treatment.
However,  aerobic or aerobic-anaerobic lagoons can be designed to
provide the same degree of biological treatment.   These  lagoons
require  substantial areas and can only be utilized where land is
readily available near the tannery.  Lagoons may result  in  cost
savings  of  almost  $150,000  over  those  costs  presented  for
Alternative c.

The estimated waste treatment  costs  for  each  subcategory  are
given  in  Tables 15-20.  The total investment cost estimated for
the leather tanning and finishing industry is $45.8  million  for
best   practicable   control   technology   currently   available
limitations (see Table 21), and $61.0 million or an increment  of
$15.2   for   best   available  control  technology  economically
achievable limitations  (see Table 22).

The 1977 investment consists  of  $45.8  million  for  processors
outside  municipal  systems.   including about $12.5 million each
for subcategories 1 and 3, about 9 million each for subcategories
2 and 5 and $2 million for subcategory 4.  Distribution  of  1983
costs is similar.

It  is  estimated  that  the  current  in-place  treatment system
investment is in excess of  $11  million.   No  credit  has  been
calculated  for this in-place treatment in Tables 15-20 or Tables
21-22.
                               118

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                                120

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Related Energy Requirements of Alternative Treatment and control
Technology

The energy requirements  (electric power and fuel)  for  tanneries
vary  considerably  based  upon reported data.  This variation is
due to the following factors:

    1.   Type of hide tanned.

    2.   Type and extent of beamhouse, tan yard, and finishing
         operations.

    3.   Degree of mechanization within the tannery.

    4.   Climate of the tannery location.

Energy  requirements  for  a  typical   Subcategory   1   tannery
processing  hide  from  raw  material  to  finished  product  are
approximately 0.46 kwhr/kg of hide  (0.21 kwhr/lb)  of  electrical
energy  and  3,560  kg  cal/kg  of hide  (6,700 Btu/lb) for steam.
Following is a discussion of the  additional  power  requirements
for waste treatment Alternatives A through E.

There  is  no  treatment provided by Alternative A, hence, energy
use is zero.

Alternative B treatment  energy  requirements  are  approximately
0.049  kwhr/kg (0.022 kwhr/lb) of hide.  This represents about 10
percent of the tannery electrical energy demand, and about 1%  of
total energy required.  The major units requiring this energy are
the pumps and equalization tank mixers.

The treatment units in Alternative C require nearly 0.174 kwhr/kg
(0.079  kwhr/lb)   of hide processed.  This represents a power use
approximately 36 percent above that needed for Alternative B, and
about 7.2% of total energy required.  The major  power  demanding
units  in  Alternative  C are pumps, equalization tank mixers and
aeration equipment.

The energy required for Alternative D treatment is 0.346  kwhr/kg
(0.157  kwhr/lb)   of  hide.  This is twice the energy required in
Alternative C, and about 1,2% of total  energy  required.   Major
energy  use is similar to that in Alternative c with the addition
of  recycle  pumping  and  the   aeration   equipment   for   the
nitrification basin and aeration flume.

The  electric  energy  requirments  for Alternative E total 0.374
kwhr/ kg (0.170 kwhr/lb)  of hide.  This amounts to an increase of
approximately  8  percent  over  Alternative  D   and   is   due,
principally,  to  requirements  of the feed pumps for the reverse
osmosis unit.

In addition to  electrical  requirements,  steam  is  needed  for
evaporation  and  drying  the salt.   Steam requirements are about
3,820 kg cal/kg (7,200 Btu/lb) of hide  in  the  form  of  steam.
                              121

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This represents an increase of approximately 107 percent over the
energy requirements of an average tannery (Subcategory 1)  without
treatment facilities.

Nonwater  Quality  Aspect^ of	Alternative  Treatment and Control
Technology	_-,-^	_


Air Pollution - Particulate matter and hydrogen sulfide  are  the
two  potential  causes  of air pollution from the leather tanning
and finishing process.  Hydrogen sulfide is  toxic  even  in  low
concentrations  and  is the main cause of process odor.  Hydrogen
sulfide is formed  principally  by  reactions  involving  sulfide
wastes  from  the unhairing process.  Proposed in-process control
includes oxidation of sulfides with a catalyst prior to discharge
to the main plant sewers and  treatment.   This  avoids  any  air
pollution  problems  that could result from sulfides and improves
the safety of workers in and around the treatment system.   Use of
biological  systems  to  remove  nitrogen  instead   of   ammonia
stripping  also  avoids potential air problems which could result
from venting ammonia from the highly concentrated waste.

The major potential source  of  air  particulate  matter  from  a
tannery is from hide buffing operations.  However, most tanneries
control  this  by  wet  scrubbing.   Scrubber  water is generally
combined with the total  waste  stream.   Several  tanneries  are
adding buffing dust to sludge derived from liquid waste treatment
for disposal.

In  addition  to process sources, tannery boilers can be a source
of air pollution.  With proper design and maintenance of gas  and
oilfired boilers, there should be no emission problems.  However,
with  coal-fired  boilers,  fly ash emissions are a problem.  Fly
ash emissions can be kept to a minimum  with  proper  design  and
operation.   Dust  collection  equipment  may  be used to further
control  air   pollution.    Wet   scrubbers   or   electrostatic
precipitators  are  capable  of providing in excess of 98 percent
removal of the fly ash.  If a wet scrubber  is  used,  the  waste
dust  slurry  can  be  discharged  to  the  waste water treatment
system.  Fly ash from  the  electrostatic  precipitators  can  be
combined with the dewatered sludge for disposal.

Boiler  flue  gas contains sulfur dioxide when the fuel burned in
the boilers contains sulfur.   Some  coal  and  heavy  fuel  oils
contain  sulfur and emit sulfur dioxide when burned.  Burning low
sulfur fuel is  one  method  of  minimizing  sulfur  dioxide  air
pollution  problems.  Gas scrubbing devices for removal of sulfur
dioxide are now in the development stages.

Solid Waste Disposal - Solid waste  from  tanneries  and  tannery
wastewater treatment plants includes the following:

    1.   Fleshings.

    2.   Hair.
                               122

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    3.   Raw hide trimmings.

    4.   Tanned hide trimmings.

    5.   Sanding and buffing dust.

    6.   Lime sludge.

    7.   chrome sludge.

    8.   Biological sludge.

    9.   Grease

    10.  General plant waste.

Most  tanneries recover fleshings and raw hide trimmings for sale
to rendering plants or conversion into glue at the tannery  site.
Tanned  hide trimmings are often sold as by-products.  Office and
general plant waste is either  hauled  away  by  a  local  refuse
disposal service or disposed of on-site.

In  save-hair operations, the tannery has facilities for washing,
drying, and baling of the hair.  The baled hair is sold as a by—
product.

Sanitary landfills are best suited for disposal of tannery waste.
Incineration and high temperature treatment are  not  recommended
for  sludges  containing chrome, since chrome may be reduced from
the trivalent to the hexavalent state.

Tannery sludges containing chrome should not  be  spread  on  the
land until further efforts are made to define the impact of these
waste materials upon the environment.

Alternatives  B through E assume sludge disposal costs.  Disposal
includes hauling the dewatered sludge to a landfill  as  well  as
landfill  operating costs.  Anticipated for disposal in landfills
are chemical, lime, chrome, and biological sludges.

The selection of a proper site  for  landfill  operations  is  of
prime  consideration.   Requirements  in  the  selection include:
sufficient  area;  reasonable  haul  distance;  remote   location
relative    to    residential,   commercial,   and   recreational
developments; soil conditions and rock formations;  accessibility
to  existing  transportation  networks; and proximity to existing
groundwater supplies.  The soil cover should be sloped such  that
precipitation  will  run  off  rather  than percolate and pollute
groundwater sources.  Other  factors  to  be  considered  include
provisions   to  prevent  the  obstruction  of  natural  drainage
channels, location to avoid flood waters, and  the  consideration
of possible fire hazards.
                               123

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                           SECTION IX

     BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY AVAILABLE

                   GUIDELINES AND LIMITATIONS

General

The  effluent limitations which must be achieved by July 1, 1977,
are to  specify  the  degree  of  effluent  reduction  attainable
through   the   application   of  the  Best  Practicable  Control
Technology Currently Available.   The  best  practicable  control
technology  currently  available  is  generally  based  upon  the
average of the best existing performance  by  plants  of  various
sizes, ages and unit processes within the industry.  This average
is  not  based  upon  a  broad range of plants within the leather
tanning and  finishing  industry,  but  upon  performance  levels
achieved  by  exemplary  plants.   In industrial categories where
present control and treatment practices are uniformly inadequate,
a higher level of control than any  currently  in  place  may  be
required  if  the  technology to achieve such higher level can be
practicably applied by July 1, 1977.

In establishing the best practicable control technology currently
available effluent  limitations  guidelines,  consideration  must
also be 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 age and size of equipment and facilities involved.

    3.   The processes employed.

    4.   The engineering aspects of application of various types
         of control techniques.

    5.   Process changes.

    6.   Non-water quality environmental impact (including
         energy requirements).

Also,  best  practicable  control  technology currently available
emphasizes treatment facilities at the end of manufacturing  pro-
cesses,  but includes control technologies within the process it-
self when the latter are considered to be normal practice  within
an industry.

A further consideration is the degree of economic and engineering
reliability  which  must  be established for the technology to be
"currently available."  As a result  of  demonstration  projects,
pilot  plants, and general use, there must exist a high degree of
confidence in the engineering and economic practicability of  the
                              125

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technology  at  the  time  of  commencement  of  construction  of
installation of the control facilities.

Effluent Reduction Attainable

Based upon information contained in Sections III through VIII  of
this  report,  a  determination  has  been  made of the degree of
effluent reduction attainable through the application of the best
practicable control technology currently available.  The effluent
concentrations which could be achieved were estimated and applied
to the respective water uses for each subcategory  (see Table  7).
BOD5  and TSS calculations are based on an effluent concentration
of about  75  mg/1;  most  total  chromium  and  oil  and  grease
limitations  are based on 2 mg/1 and 15 mg/1 respectively.  These
values then determine the weight  of  pollutants  per  weight  of
product.    Effluent   limitation   guidelines   resulting   from
implementation of this technology  are  presented  in  Table  23.
These   are   the  recommended  guidelines  for  each  industrial
subcategory for plants discharging directly  to  surface  waters.
The  limitations  require  major  removal  of  BODJ and suspended
solids.
As described in  Section  IV,  severe  economic  impacts  require
different  BOD5  and  TSS  limitations  for small plants and some
medium sized plants.  Accordingly, additional  allocations  equal
to  one half the effluent limitations guidelines for BOD5 and TSS
are allowed tanners with a production less than  17,000  kg  hide
per day.
                               126

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                                    TABLE  23

                     BEST PRACTICABLE EFFLUENT LIMITATIONS

                          MAXIMUM THIRTY DAY AVERAGE
                                (July 1,  1977)



                                                SUBCATEGORY
PARAMETER (1)
BOD5_
TOTAL CHROMIUM
OIL & GREASE
TSS
kg/1000
1 2
4.0
0.10
0.75
5.0
4.6
0.12
0.90
5.8
kg hide
3
3.8
0.05
0.75
4.8
(lb/1000
4
1.6
0.10
0.25
2.0
Ib hide)
5
4.8
0.06
0.90
6.0
6
2.8
0.10
0.35
3.4
(1)   For all subcategories pH should range between 6.0  and 9.0 at any time.
                                    127

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Best. Practicable Control^TechnologY^gB££gS^j-Y,
The  best  practicable control technology currently available for
the feather tanning and finishing industry  has  previously  been
identified  in  Section VII (for Subcategories 1 through 6)  under
the headings "In-Process Methods of Reducing Waste," "Preliminary
Treatment," and "Major Reduction of BOD5, and  Suspended  Solids."
Principal  control  and treatment operations needed to meet these
limitations  are  generally  summarized  in  Section  VII.    The
effluent  reduction  attainable  is  based  upon  the transfer of
performance data from other industrial operations whose treatment
technologies are generally believed  to  be  transferred  to  the
leather  industry.   Other  industries  such  as the meat packing
industry currently treat high strength wastes containing  organic
matter   and  suspended  solids  and  achieve  the  high  removal
efficiencies required by BPCTCA.  The required  effluent  quality
is  being  achieved  by  the  tanning  industry,  but  not  on  a
consistent basis.  Because the effluent quality representing that
attainable through the implementation of BPCTCA is  not  achieved
consistently,  technology  and  performance  information has been
transferred from other industry treatment operations.

    Complete Treatment - Subcategories 1 to 6

         1 .   Recycle of chrome and vegetable tan solutions
              (where applicable) .

         2.   Fine screening.

         3.   Equalization to dampen quality and quantity fluc-
              tuations which will impair subsequent processes,
              particularly biological units.

         U.   Primary settling to provide oil and grease
              separation, precipitate chromium from rinse
              waters, and partially remove BOD5, COD, and
              suspended solids.

         5.   Aeration and secondary settling to further reduce
              BOD5, COD, and suspended solids.

         6.   Sludge handling and disposal.

The above summary  of  treatment  steps,  generally,  applies  to
Subcategories 1 through 6.  A few minor alterations are required.
One  change  in the steps includes addition of lime after primary
settling for tanneries which have acid waste  (sheepskin) .

Rationale  for  Selection  of  the   Bejst   Practicable   Control
Technology Currently Available

To^§l^gost_of Achieving Effluent Reduction Based upon information
contained  in  Section  VIII of this report, the  leather tanning
and finishing industry discharging to receiving waters would have
to invest an estimated $45.8 million  (August, 1971, price levels)
                               128

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to achieve the effluent limitations recommended herein.   No  in-
place  treatment  capital is assumed.  The total annual costs for
pollution control including depreciation, interest, and operation
and maintenance will likely result in  an  increase  in  finished
product  price  ranging  from 1.7 to 4.4 percent  for the various
subcategories.

Age  and__Size	of  Equipment	and  Facilities  -  As   indicated
previously  in  this  report,  there appears to be no significant
data to substantiate that either the age or size of  the  tannery
justify  special consideration of different effluent limitations.
Data indicates some of the  oldest  and  smallest  tanneries  are
currently  achieving  levels  of  treatment  equivalent  to those
achieved by large new facilities.

Engineering Aspects of Control Technique Application

The specific level of technology is  practicable  because  it  is
being  practiced  by  plants  in  the tannery industry as well as
other industries with high strength wastes.  The tannery industry
does not achieve this level of effluent reduction.  One plant  in
subcategory  1 (383) and one plant in subcategory 3 (24) meet the
BOD limitations in kg/1000 kg (16/1000 Ib) but  not  TSS  limits.
Two plants in subcategory 3  (47 and 179)  meet the TSS limitations
and almost achieve the BOD limitation.

In  terms  of  achieving a BOD effluent discharge of 75 mg/1, the
following plants achieve less than this level of reduction: plant
43 in subcategory 2; plants 24 and 47 in subcategory 3; and plant
54 in subcategory 5.  Tanneries 185, 400 and 447 also achieve  an
effluent  discharge  with less than 75 mg/1 BOD.  Thus, there are
tannery plants that are capable of achieving the stated  effluent
limitations  on a consistent basis.  In a few cases, the presence
of a knowledgable operator is the only requirement.  In  general,
some  minor  plant  design  changes  along  with cooperation from
management and plant personnel will be required.

Processes Employed - As indicated in earlier sections, there  are
differences  in  tanning  processes  which  result in varying raw
waste characteristics.  These variations have been recognized  by
establishing   six  major  industry  subcategories  for  effluent
limitations.
Process  Changes  -  The  control  and  technology  required  for
implementing  the  best  practicable control technology currently
available  does  require  some  in-process   changes   for   some
tanneries.    These  modifications  are  principally  chrome  and
vegetable tan solution reuse which  are  currently  practiced  by
several industries.

Nonwater  Quality ^Environmental	Impact - There is one essential
impact  of  waste  treatment  upon  nonwater  elements   of   the
environment  and  this is disposal on the land of general tannery
solid wastes and waste sludge from treatment facilities.   Most of
                               129

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the waste trimmings and hair from hides are  being  recovered  as
by-products.   Reuse  of chrome in the tannery will substantially
reduce chrome levels in waste sludge from the treatment facility.
This will, also, reduce the potential release of toxic chrome  to
the  environment when the dewatered sludge cake is disposed of in
a landfill.  In all cases, however, dewatered sludges from chrome
tanneries should be handled separately at a landfill to avoid any
potential  difficulties.   Proper  siting  and  operation  of   a
landfill  will  minimize  the  impact of disposal of waste solids
from the tannery on the land.
£^£i2£§ i2 be Considered in Applying Level I Guidelines

1.  Limitations are based  on  thirty  day  averages.   Based  on
performances  of  exemplary  biological  waste treatment systems,
daily limitations  should  not  exceed  the  thirty  day  average
limitations by more than one hundred percent.

2.  If a tanner processes hides in more than one subcategory, for
instance cattlehides and  shearlings,  the  effluent  limitations
should  be set by proration on the basis of the percentage of the
total hide weight being processed in each subcategory.

3.  If a tanner is required to provide nitrification in order  to
meet water quality standards, that portion of the BOD5 exerted by
nitrogenous matter (measured in the total kjeldahl nitrogen test)
should  not  be included in the total effluent BOD5 reading.  The
nutrient requirement  for  the  oxidation  of  organic  materials
should be included in the BOD.5.

U.  The production basis which is recommended for applying  these
limitations is the daily average production of the maximum thirty
consecutive days.
                               130

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                            SECTION X

       BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE -

                   GUIDELINES AND LIMITATIONS
General

The  effluent limitations which must be achieved by July 1, 1983,
are to  specify  the  degree  of  effluent  reduction  attainable
through the application of the "best available control technology
economically   achievable".    The   best   available  technology
economically achievable is to be based on the very  best  control
and   treatment  employed  within  the  industry  or  based  upon
technology which is readily transferable to the industry.   Since
there  are  no  exemplary  facilities which may be considered for
assessment of the best available  control  technology  achievable
control  and  treatment  technology, transfer of concepts applied
elsewhere are utilized.
Consideration must be given to the following in  determining  the
best available control technology economically achievable:

    1.   The total cost of achieving the effluent reduction
         resulting from application of the best available control
         technology economically achievable.

    2.   The age and size of equipment and facilities involved.

    3.   The processes employed.

    U.   The engineering aspects of the application of various
         types of control techniques.

    5.   Process changes.

    6.   Non-water quality environmental impact (including
         energy requirements).

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

The  best available control 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
pollutants.  This level of control is intended to be the top-of—
the-line  of current technology subject to limitations imposed by
economic and engineering feasibility.  The best available control
technology economically achievable may be characterized  by  some
                              131

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technical  risks  with  respect  to  performance and certainty of
costs.  Some  further  industrially  sponsored  development  work
prior to its application may be necessitated.

Effluent Reduction Attainable

Based  upon  the  information  contained  in Sections III through
VIII, an assessment has been  made  of  the  degree  of  effluent
reduction  which  may be achieved through the application of best
available technology.  BODjj and TSS calculations are based on  an
effluent  concentration  of  25  mg/1; total chromium and oil and
grease are based on 1 mg/1 and 10 mg/1 respectively; and  sulfide
and  total  kjeldahl  nitrogen  are  based on 0,1 mg/1 and 5 mg/1
respectively.   Table   2U   summarizes   for   each   industrial
subcategory  the  best  available control technology economically
achievable  effluent  limitations   guidelines   for   facilities
discharging  directly to receiving waters.  This limitation level
is principally an  extension  of  the  best  practicable  control
technology   currently  available  requirements  to  provide  for
additional removals of BOD and SS as well as sulfide and nitrogen
removal.
                               132

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PARAMETER (1)
                                 TABLE  24

                    BEST AVAILABLE  EFFLUENT LIMITATIONS

                         MAXIMUM THIRTY DAY AVERAGE
                               (July 1, 1983)
              SUBCATEGORY
kg/1000   kg hide   (lb/1000   Ib hide)

BODJ5
TOTAL CHROMIUM
OIL & GREASE
SULFIDE
TSS
TKN
I
1.40
0.05
0.53
0.005
1.5
0.27
2
1.60
0.06
0.63
0.006
1.8
0.32
3
1.30
0.05
0.50
0.005
1.4
0.25
4
0.50
0.02
0.24
0.002
0.6
0.10
5
1.60
0.06
0.63
0.006
1.8
0.31
6
0.70
0.03
0.34
0.003
0.8
0.14
 (1)  For all subcategories pH should range between 6.0 and
     9.0 at any time.

     For all subcategories Most Probable Number  (MPN) of
     Fecal Coliforms should not exceed 400 counts per 100 ml.
                                     133

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Best Available Technology Economically Achievable

The best available technology  economically  achievable  for  the
leather  tanning  and finishing industry (Subcategories 1 through
6)  is removal of BOD and SS and sulfide and  nitrogen  reductions
(as  discussed  in  section VII)  in addition to those constituent
removals established for the best practicable control  technology
currently available.  Following is a general summary of the major
steps  required  for achieving this level for a tannery providing
complete treatment before discharge directly to  surface  waters.
As   with  the  best  practicable  control  technology  currently
available, guidelines for the best available  control  technology
economically  achievable  are  based  on  control  and  treatment
efficiencies achieved by some tanneries some of the time  and  by
other  industrial  treatment  operations  on  a consistent basis.
With proper operation and adequate design, tanneries in  each  of
the   six   subcategories   can  achieve  the  required  effluent
reduction.

    Complete Treatment_- Subcategories 1 to 6

         1.  Recycle of chrome and vegetable tanning solutions
             (where applicable).

         2.  Collection of beamhouse wastes containing sulfide;
             oxidation of sulfide using a catalyst such as
             manganous sulfate (where applicable).
             sulfate (where applicable).

         3.  Fine screening.

         U.  Equalization to dampen variations in quality and
             quantity which will impair subsequent processes,
             particularly biological units.


         5.  Aeration and clarification of solids to remove
             carbonaceous BOD5, COD, and suspended solids.

         6.  Aeration to nitrify organic and ammonia nitrogen;
             mixing with a carbon source to cause denitri-
             fication; an aeration flume to assist nitrogen
             gas removal; and a final settling tank.

         7.  Filtration of the final effluent using deep-bed,
             mixed-media filters or similar devices for final
             suspended solids removal.

         8.  Sludge handling and disposal.
                               134

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Rationale for Selection of the Best Available Technology
Economically Achievable            ~"
Total Cost of Achieving Effluent	Reduction  -  As  presented  in
Section" VIII,  to  meet  the~"""best  available control technology
economically   achievable   effluent    limitations,    tanneries
discharging to receiving waters would have to invest an estimated
$61.0  million  (August, 1971, price levels).  This $61.0 million
includes the $45.8 million investment required to meet  the  best
practicable control technology currently available guidelines and
assumes  no  in-place treatment systems.  The incremental cost is
$15.2  million  for  treatment  plants  for  processors   outside
municipal  systems.   Total annual costs (including depreciation,
interest, operation and maintenance) to achieve these limitations
are estimated to  increase  the  cost  of  the  finished  product
between    0.6   and   1.3   percent   for   various   industrial
classifications.

Age and Size of  Equipment	and  Facilities  -  As  indicated  in
section  IX,  no" differentiation  of  the  effluent  limitations
guidelines can be made on the basis of age or size.

Processes Employed - Differences in processes within the industry
have been accounted for in establishing the effluent limitations.

Engineering Aspects of Control^Technigues -  The  best  available
control  technology  economically  achievable  appears achievable
considering  the  developmental  work  being  done   on   sulfide
oxidation  and  nitrificationdenitrification.   There are several
technical questions which need to be resolved prior to initiation
of  full-scale  nitrification-denitrification  facilities  on   a
tannery  waste.  However, it is deemed that such questions can be
answered  by  on-going   research   in   other   areas   and   by
investigations  initiated  prior to 1983.  To date, no pilot work
has been reported for  nitrification-denitrification  of  tannery
waste,   hence,  studies  will  be  required  to  confirm  design
parameters required to  implement  an  efficiently  designed  and
operated facility.

Process Changes - Process changes required for the best available
control  technology economically achievable include those for the
best practicable  control  technology  currently  available  (see
Section  IX).   In addition sulfide oxidation is recommended; its
technical feasibility has been  demonstrated  on  a  pilot  plant
scale.   The  industry should initiate research to find potential
substitutes for ammonium salts used in  the  bate  operation  and
salt  used  for  hide curing.  These process changes would reduce
treatment  costs  for  the  best  available  control   technology
economically achievable and also effect considerable reduction in
dissolved  solids  which  are  economically very unattractive for
removal in a waste treatment facility.

Nonwater Quality Environmental Impact - The impact upon the  land
as a result of liquid waste treatment is the same as outlined for
                              135

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the  best  practicable  control technology currently available in
Section IX.

Factors to be considered in AjDEi^isH Level II Guidelines

1.  Limitations are based  on  thirty  day  averages.   Based  on
performances  of  exemplary  biological  waste treatment systems,
daily limitations  should  not  exceed  the  thirty  day  average
limitations by more than one hundred percent.

2.  If a tanner processes hides in more than one subcategory, for
instance cattlehides and  shearlings,  the  effluent  limitations
should  be set by proration on the basis of the percentage of the
total hide weight being processes in each subjcategory.

3.  The production basis which is recommended for applying  these
limitations is the daily average production of the maximum thirty
consecutive days.
                           SECTION XI

                NEW SOURCE PERFORMANCE STANDARDS
General

The  standards  of performance for new sources are to reflect the
greatest degree of  effluent  reduction  achievable  through  the
application   of   the   "best   available  demonstrated  control
technology, processes, operating methods, or other alternatives".
New source is defined as any construction  which  is  recommended
after publication of the regulations prescribing the standards of
performance.   In  addition  to considering the best in-plant and
end- of - process control  technology  identified  for  the  best
available  control technology economically achievable, new source
performance standards is to establish effluent  reductions  which
may  be  achieved by changing or improving the production process
itself.  A determination must  be  made  of  whether  a  standard
permitting no discharge of pollutants is practicable.

For   establishing  new  source  performance  standards  effluent
limitations guidelines, consideration must, also, be given to:

    1.   The type of process employed and process changes.

    2.   Operating methods.

    3.   Batch as opposed to continuous operations.

    4.   Use of alternative raw materials and mixes of raw
         materials.

    5.   Use of dry rather than wet processes (including sub-
         stitution of recoverable solvents for water).

    6.   Recovery of pollutants as by-products.


                               136

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ImprovedrIn-plant Process Control

For  new  sources  of  tanning  wastes,  several  items  may   be
considered  to either reduce water use or discharge of waste to a
treatment facility.  Most of  the  possible  changes  are  merely
improvements  on  those  which  are  already  assumed  capable of
implementation  for  meeting   the   best   practicable   control
technology  currently  available  and  the best available control
technology   economically   achievable    effluent    limitations
guidelines.

A new facility, due to more efficient layout and more automation,
can  effect better process control, thus minimizing water use and
optimizing chemical use.  In addition, general housekeeping  pro-
cedures  should  improve.   The  net  effect  of improved process
layout, control and monitoring in a new tannery will mainly be to
decrease water use and  discharge  of  some  chemicals.   organic
loads  resulting from hide processing are not expected to change,
however.  Hence, the waste discharge in  kg  (lb)/l,000  kg  (Ib)
hide  may  not  change  significantly.   Improved  equipment  and
controls in a new plant merely reduce some of the tank  sizes  at
the  treatment  facility  utilized  to  meet  the  variable waste
characteristics from a tannery not equipped with  new  equipment.
For  example, better scheduling and control of different types of
waste may reduce the size of equalization facilities required  to
level out the quality and quantity of waste reaching a biological
aeration tank.  In addition, reduction of waste process chemicals
may  lower  addition  of  neutralizing  chemicals  at  the  waste
treatment facility.

Two chemicals employed in the production process that could  sub-
stantially  reduce the treatment needs if a substitute were found
are ammonium salts used in bating and sodium salt from the hides.
There is no indication that a significant change  could  be  made
for   these,   but   it  is  recommended  the  industry  research
possibilities.

Use of dry processes or other drastic  process  modifications  do
not appear feasible for the tanning industry.

New gource Performance Standards

Although,  better  process  control  and  more  efficient tannery
operations may result for new facilities, the  actual  raw  waste
load  in  terms  of  kilograms  (pounds)   per  thousand kilograms
(pounds)   of  hide  is  not  expected  to  change  substantially.
Treatability  of  the  waste  is,  also,   not  likely  to  differ
significantly from that existing for present facilities.    Hence,
standards  of  performance  for  new  facilities  should  be  set
consistent with those required for the best  practicable  control
technology currently available.
                              137

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Pretreatment Requirements
Large  quantities  of  three constituents of the waste water from
plants within the leather tanning  and  finishing  industry  have
been   found  which  could  interfere  with,  pass  through,  or,
otherwise, be incompatible with  a  well  designed  and  operated
publicly  owned  activated sludge or trickling filter waste water
treatment plant.  Waste water constituents include chromium  from
the  tanning  or  retanning operation, sulfide from the unhairing
process, and oil and grease from the fatliquour process  or  from
animal  fat.   Adequate control methods can and should be used to
keep significant quantities of these materials out of  the  waste
water.
                               138

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                             SECTION  XII

                           ACKNOWLEDGMENTS
The  Environmental  Protection  Agency  wishes  to   acknowledge   the
contributions  of  the  Stanley  Consultants who prepared the original
draft of this document.  The efforts of Mr.  Kenneth  M.  Bright,  Mr.
John L. Thomas and Mr. Robert L. Thoem are appreciated.

Special thanks and appreciation are due Mr. Irving R. Glass, President
of  the  Tanners'  Council  of  America;  Professor  William T. Roddy,
Director of the Tanners' Council Research  Laboratory,  University  of
Cincinnati;  and  Mr.  Robert M. Lollar, Coordinator for Environmental
Affairs, Tanners' Council of America.

Appreciation is expressed for  the  interest  of  several  individuals
within  the  Environmental Protection  Agency:  W. L. Banks, Region VII;
William Hancuff, George Webster, Ernst Hall, Allen Cywin, EGO.

Special thanks are due Richard Sternberg for his advice,  support  and
guidance.   Thanks  are  also  due  the many secretaries who typed and
retyped this document: Aqua McNeal, Pearl Smith, Chris Miller, Vanessa
Datcher, Karen Thompson, and Fran Hansborough.

Special acknowledgment  is  made  of  the  contributions  of  industry
personnel  who  provided  information   to  the  study.   Their  active
response, cooperation and assistance is greatly appreciated.
                                   139

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                              SECTION XIII

                               REFERENCES

 1. "Industrial Waste - Profile No. 7, Leather  Tanning  and  Finish-
    inq," The_Cost_of_Clean_Water_-_Volume_I^I,  Federal Water  Quality
    Administration Report, 1967.

 2. "Membership Bulletin Leather Industry Statistics,"  Trade Survey
    Bureau - Tanners' council of America, Inc.,  1971, 1972, arid
    1973,

 3. O'Flaherty, F., Roddy, w. T., and Lollar, R. M., CheinistrY_and
    TechnojLogv._of_Leather, Volumes I-IV, Reinhold  Publishing cor-
    poration.

 U. Masselli, Joseph w., Masseli, Nicholas W, ,  and  Burford, M.  G.,
    wesleyan University, June, 1958.

 5. Berthouex, Paul M., and Brown, Linfield,  C. , "Monte Carlo  Simu-
    lation of Industrial Waste Discharges," Journal_of_the_Sanitary
    Engineering_Diyisignf _Proceedings_of the  American^Society  of
    Civil_Eno[ineers, Volume 95, No. SA5, October,  1969.

 6. Hauck, Raymond A., "Report on Methods of  Chromium Recovery and
    Reuse from Spent Chrome Tan Liquor," Journal_ofmthe_American
    L§§^h§£_Cj2§m^stsJ. Association, Volume LXVII, No. 10,
    1972.

 7. Bailey, D. A., and Humphreys, F. E,, "The Removal of Sulphide
    from Limeyard wastes by Aeration," BritishmLeather_Manufac-
    turerj.^_Research_A§sociationA_LaboratorY_Re£orts, XV, No.  1,
    19667

 8. Eye, J. David, and Clement, David P., "Oxidation of sulfides
    in  Tannery Waste Waters," Journal^of_the_American. Leather
    £k§H!i§.£.§.L_Association, Volume LXCII, No.  6,  June, 1972.

 9. Williams-Wynn, D. A., "No-Effluent Tannery  Processes,"  Journal
    of __the American_Leather_.Chemists« Assgciation,  Volume LXVIII,
    No. 1, 1973.

10. Data obtained through communication with  tannery firms.

11. Moore, Edward W., "Wastes from the Tanninq,  Fat Processing,
    and Laundry Soap Industries."  Source unknown.

12. McKee, Jack Edward, and Wolf, Harold W.,  eds.,  Water_2uality.
    Criteria.  2nd ed., The Resources Agency  of  California, State
    Water Quality Control Board, Publication  No. 3-A 1963.
                               141

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13. Bailey, D. A., Dorrell, J. J., and Robinson, K. S. , Journal
    o|_£ha_Societi_of_Leat.her_Tradesi_Chemists, 54, 91, "1970."
    Cited in Journal^gfLthe^ American Leather^Chemists1 Associa-
    tion, Volume~LXVII, No." 9, "sept ember 7 19727

14. Sutherland, R. ,  Industrial and^Engineering^ChemigtrY, J9, 628,
    1947.  cited in Reference 11).

15. sproul, Otis j. , Atkins, Peter F. , and woodward, Franklin E. ,
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    for Cattleskin Tannery Wastes," Journal Water_Pgllutign
    ControlFe deration . Volume 38, No. 4, April, 1966.

16. Kunzel-Mehner, A., Gesundh. Ing. , 66, 300,  1943.  cited in
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17. "Report of the Symposium on Industrial Waste of the Tanning
    Industry, " Journal_of_the_American_Leathgr^Chemi.3tsl Associ-
    ation, Supplement No. 15, 1970.

18. Howalt, W. , and Cavett, E. S., Transactions_of_A!Tierican^SocietY
    of_CiYil_En3ineers, 92, 1351,  1928." Cited" in Reference"! if.

19. Riffenburq, H. B., and Allison, w. w., In^us^rial
                     , 33, 801, 1941.  cited in Reference 11)
20. Haqan, James R. , and Eye, J. David, and Gunnison, G. C. ,
    '•Investiqations into the Removal of Color from Bioloqically
    Treated Veqetable Tannery Wastes," Masters Thesis, University
    of Cincinnati, 1972.

21. Data obtained by Stanley consultants field investiqations.

22. Chen, Kenneth Y. , and Morris, J. Carrell, "Oxidation of Sulfide
    by O2:  Catalysis and Inhibition," Journal._of_the_SanitarY
    Civil_Engineers, Volume 98, No. SAl7 February, 1972.

23. The A. C. Lawrence Leather company, ActiyatedLSludqe ^Treat-
    ment _of Chrome Tannery Wastes, Federal Water Pollution Control
    Administration, Department of the Interior, Grant No. WPRD
    133-01-68, Proqram No. 12120, September, 1969.

24. Nemerow, N. L. , and Armstronq, R. , "Prototype Studies of Com-
    bined Treatment of Wastes from 22 Tanneries and Two Munici-
    palities , " Purdue 'Industrial Waste Conference, Proceedings,
    1967.

25. Kinman, Riley N. , "Evaluation of Waste Treatment Process for
    Treatinq Waste from Bona Allen, Inc., Buford, Georqia."  Un-
    published article.  January 30, 1972.
                                142

-------
26. Kinman, Riley N. , "Evaluation of Bona Allen wastewater  Treat
    ment for Period February 1, 1972, to January  25,  1973,"  Un-
    published article.  March 5, 1973.

27. Sarber, R.W. , Journal _of^thg^ American^ Leather^Chernists^
         i§£ion , 36, ?63, 7941.  cited~in Reference  4)".
28. "Tannery Effluent Report to the Members of  the  Effluent  Com-
    mission of the International Union of Leather chemists'
    Societies, " Journal_of^the_American_Leather_Chemistsl_ Associ-
    ation. Volume LXVllT No7 10, OctoberT 1972.  Reprinted from
    1972.

29. Parker, Clinton E. , Anaerobic- Aerobic_Lagoon_Treatment_f or
    Ye3etable_Tarming_Wastes , Federal Water Quality Administra-
    tion, Environmental Protection Aqency, Grant No. WPD-199-01-67,
    Proqram No. 12120 DIK, December, 1970.

30, Sawyer, C. N. , "New concepts in Aerated Laqoon  Design and
    by Gloyna, E. F. and Eckenfelder, W. W., Jr.),  U. of Texas
    Press, Austin, 1968.  Cited in Reference 29) .

31. Steffen, A. J. , "Waste Treatment in the Meat Processing  In-
    dustry," Advajices_in_W^ter_2uality_Imgr_ovement,  edited by
    Gloyna, E. F. and Eckenfelder, W. W. , Jr.), U.  of Texas  Press,
    Austin, 1968.  Cited in Reference 29) .

32, Eye, J. David, Treatment of Sole Lea ther^yggetable^Tannery
    Wastes, Federal Water Pollution Control Administration,
    Department of Interior, Grant Number WPD-185, Program
    Number 12120, September, 1970.

33. Conversation with J. David Eye.

3U. Clark, John W. , and Viessman, warren. Jr.,  "Biological-
    Treatment Processes, Activated Sludge," Water_Suppl2_and
    Po 1 lut i on_ cont r gl , International Textbook Company, Scranton,
    Pennsylvania, March, 1966.

35. Steffen, A. J. , and Bedker, M. ,  "Operation of  Full-scale
    Anaerobic Contact Treatment Plant for Meat  Packing Wastes,"
    Proceedings^ of^thg_16th_Industrial_Wa3te^Conference , Purdue
    University, «4237 1961." Cited in Reference~29) .

36, Gates, W. E. , Smith, J. H. , Lin, S. , and Ris, C. H., Ill,
    MA Rational Model for the Anaerobic contact Process,"
    J2S£Ml_ W§.te£_£2liU^i£Q_£2St rol _Federa ti on , 39,  1951.
    1967.  Cited~in~Reference 29) .
                                143

-------
37. "Industrial Waste Survey at caldwell Lace Leather company,"
    EPA, office of Operations, Radiological and Industrial Waste
    Evaluation section, Cincinnati, Ohio.

38. Siebert, C. L. , "A Digest of Industrial Waste Treatment,"
    Pennsylvania State Department of Health, 1940.  Cited in
    Reference 11) .

39. Reuning, H. T. , Sewage Works Journal , 20, 525, 1948.  Cited
    in Reference 11) .

40. Harnley, John W. t Wagner, Frank R. , and Swope, H. Gladys,
    "Treatment of Tannery Wastes at the Griess-Pfleger Tannery,
    Waukegan, Illinois," sewage Works Journal, Volume XII, No. 4,
    July, 1940.

41. Eldridge, E. F. , Michigan, Engineering^ Ex periment^Station
              JLZ* 32/ November, 1939.  Cited in Reference ll) .
42. Fales, A. L. , Industrial and Engineering chemistry,  2J[,  216
    1929.  Cited by Reference 11).

43. Sproul, Otis J, , and Hunter, Robert E. , "Appendix A, Indus-
    trial Waste Treatment Investigations,  Prime Tanning Company
    and Berwick Sewer District Activated Sludge Pilot Plant,
    Berwick, Maine," Berwick Sewer District, Preliminary Design
    Report, pollution Control System, Edward C. Jordan  Co.,  Inc.,
    Portland - Presque Isle, Maine, 1967.

44. Haseltine, T. R. , "Tannery wastes Treatment with Sewage at
    Williams port, Pennsylvania," Sewage and industrial ^Wastes,
    Volume 30, No. 1, January, 1958.

45. Hartman, B. J., Sewage and Industrial^Wastes,  25, 1419,  1953.
    Cited in Reference 4) .

46. Rosenthal, B. L. , Sanitalk, 5, No. 4,  21,  1956,  Cited  in
    Reference  4) .

47. Nemerow, Nelson L. , and Armstrong, Richard, "Combined Tannery  and
    Municipal  Waste Treatment - Gloversville- Johns town. New York,"
    Purdue Industrial Waste Conference Proceedings ,  1966.

48. Wims, F. J, , "Treatment of Chrome-Tanning  Wastes for Accept-
    ance by an Activated Sludge Plant," Purdue Indus tr ia lm Waste
    Conference Proceedings, 1963.

49. Maskey, D. F. , Journal of the American Leather Chemists*
    Association, 3.6, 121 1941.  Cited by Reference 11)7
                                 144

-------
50. Mccarty, P. L., "Anaerobic Treatment of soluble Wastes,"
    Adyances^in Water^gualitY^Imgroyement edited by Gloyna,
    E.  F. and Eckenfelder, W. W., Jr.), U- of Texas Press, Austin
    1968.  Cited in Reference 29).

51. Sproul, O. J., Keshaven, K., and Hunter, R. E., "The  Extreme
    Removals of Suspended Solids and BOD in Tannery Wastes by
    Coagulation with Chrome Tan Dump Liquors," Purdue_Industrial
    H§§^§_£2Sf §££S£i--J?£o.c.§e.
-------
60. Downing, D.  G., Kunin, R., and Pollio, F. X., "Desal Process-
    Economic Ion Exchange System for Treating Brackish and Acid
    Mine Drainage waters and Sewage Waste Effluents," Chemical
    Engineering Progress Symposium Series, Volume 64, No. 90, 1968.

61. Wiley, Averill, J., Dubey, George A., and Bansal, I.K.,
    Reverse Osmosis concentration of Dilute Pulp and Paper
    M£iiJ§Bis, Office of Research and Monitoring, Environmental
    Protection Agency, Contract No. WPRD 02-01-68, Program
    No. 12040 EEL, February, 1972.

62. Kremen, Seymour S., "The Application and Preformance of Spiral
    Membrane Module Systems in Reverse Osmosis Processing of
    Water and Waste Streams," preprint of a paper to be
    presented at the Japanese Sea Water Science Group Meeting,
    November 12, 1971, Kyote, Japan.

63. "Rex Chainbelt Inc., The Ecology Division, Reverse
    Osmosis DemineralizatiQn of _Acid Mine... Drainage, for the
    Commonwealth of Pennsylvania, Department of Environmental
    Resources, Harrisburg, Pennsylvania, and the Office of
    Research and Monitoring, Environmental Protection Agency,
    Contract No. CR-86-A, Program No. 14010 FOR, March, 1972.

64. 1972-1973 Saline Water Conversion Summary Report,
    United States Department of Interior, office of Saline Water.

65. Burns and Roe, Inc., Disposal of Brines Produced in Renovation of
    Municipal Wastewater, Federal Water Quality Administration,
    Department of the Interior, Contract No. 14-12-492, Program
    No. 17070 DLY, May, 1970.

66. "Patterson, W. L., and Banker, R.F., Estimati.ng
    Costs and Manpower Requirements for Conventional_Wastewater
    Treatment Facilities, Office of Research and Monitoring,
    Environmental Protection Agency, Contract No. 14-13-462,
    Project No. 17090 DAN, October, 1971.

67. Smith, Robert, and McMichael, Walter F.,
    Performance Estimates_for_Tertiarv Wastewater_Treatment
    Processes, U.S. Department of"the Interior, Federal Water
    Pollution Control Administration, Advanced Waste
    Treatment Research Laboratory, June, 1969.

68. Correspondence with Mr. Irving Glass of the Tanners' Council
    of America, Inc.

69. voegtle, John A., and Vilen, Frank I., "A New Concept for Operator
    Wages," Journal^gf^Water Pgllution^Control Federation, Volume  45,
    No. 2, February, 1973.
70. Oil^ Paint^ and^Drug Reporter, August 2, 1971.
                                  146

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                              SECTION XIV

                                GLOSSARY


Acidity

A measure of the ability of the waste to provide hydroqen ions when
treated with alkaline materials.  Generally expressed in mq/1 as caCO3

ACT

The Act is the Federal Water Pollution Control Act Amendments of 1972.
A waste water treatment process using a mixed microbiological culture
and molecular oxygen to satisfy waste stabilization requirements.
Provision is made to return some solids settled from the effluent flow
to the influent, and thereby maintain the desired microorganism
copulation in the process.

Adipose

of, or related to, animal fat; fatty.

Adsorption

The adhesion of a gas, liguid, or dissolved substance to the surface of
a solid or liquid.

Aeration

A process for mixing and contacting air with water or liquid waste by
natural or mechanical means.

Aerobic

A biological process in which oxygen is used for microorganism respi-
ration needs.  Especially relating to the degradation process of waste
matter in the oresence of dissolved oxygen.
A measure of the ability of the waste to provide hydroxyl ion to react
with acidic materials.  Generally expressed in mq/1 as CaCO3.
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Anaerobic

A bioloqical process in which chemically combined oxygen is used for
microorganism respiration needs.  Relating to bioloqical degradation of
waste matter in the absence of dissolved oxygen.
That portion of the animal hide, especially cattlehide, consisting of
the center portion of the hide along the backbone and covering the ribs,
shoulders, and butt (excluding the belly).

Bating

The manufacturing step following liming and preceding pickling.  The
purpose of this operation is to delime the hides, reduce swelling,
peptize fibers, and remove protein degradation products from the hide.
That portion of the tannery where the hides are washed, limed, fleshed,
and unhaired when necessary prior to the tanning process,
That portion of the hide on the underside of the animal usually
representing the thinnest part of the tannable hide.
That portion of the hide representing the entire hide cut down the
backbone with the bellies and shoulders removed.

gest Available Demonstrated Control Technology

Treatment and control required for new sources of industrial discharge
to surface waters as defined by Section 306 of the Act.
gest _Ayailable^TfechnoloqY Economical lY-Achie

Treatment and control required by July 1, 1983, for industrial dis-
charges to surface waters as defined by Section 301 (b) (2) (A) of the Act.

Best Practicable, Control .Technology CurrentlY_Ayai.lable

Treatment and control required by July 1, 1977, for industrial dis-
charges to surface waters as defined by Section 301{b) (1) (A) of the Act.
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Biochemical Oxygen Demand  (BODS)

The amount of oxygen required by microorganisms while stabilizing
decomposable organic matter under aerobic conditions.  The level of BOD
is usually measured as the demand for oxygen over a standard five-day
period.  Generally expressed as mg/1.

.Slowdown

The amount of concentrated liquor wasted in a recycle system in order to
maintain an acceptable equilibrium of contaminants in any process
liquor.
A hide after tanning with chromium salts.  Hide usually has a slight
blue color.

Chemical Oxygen, Demand  (COD)

A measure of the amount of organic matter which can be oxidized to
carbon dioxide and water by a strong oxidizing agent under acidic
conditions.  Generally expressed as mg/1.

Chlorine Contact Tank

A detention basin designed to allow sufficient time for the diffusion
and reaction of chlorine in a liquid for disinfection purposes.

Chromium  (Total)

Total chromium is the sum of chromium occurring in the trivalent and
nexavalent state.  Expressed as mg/1 as Cr.

Clarification

A physical means for the removal of suspended particles in a liquid by
gravity sedimentation (settling).

Coagulant

A substance which forms a precipitate or floe when added to water.
Suspended solids adhere to the large surface area of the floe, thus
increasing their weight and expediting sedimentation.

Collagen

The fibrous protein material within the hide which provides the bulk .of
the volume of the finished leather and its rigidity.
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golloids

Microscopic suspended particles which do not settle in a standing liquid
and can only be removed by coagulation or bioloqical action.

Color

A measure of the light absorbing capacity of a waste water after tur-
bidity has been removed,  one unit of color is that produced by one mg/1
of platinum as K2PtCl6.

Coloring

A process step in the tannery whereby the color of the tanned hide is
changed to that of the desired marketable product by dyeing or oainting.

gompgsite Sample

A series of small waste water samples taken over a given time period and
combined as one sample in order to provide a representative analysis of
the average waste water constituent levels during the sampling period.
A term often applied to hide processors.

Corium

The layer of hide between the epidermis and the flesh.  Also called the
derma.

De liming

The manufacturing step in the tanhouse that is intended to remove lime
from hides coming from the beamhouse.

pemineralizatlon

The process of removing dissolved minerals from water by ion exchange,
reverse osmosis, electrodialysis, or ether process.

Derma

That part of the hide which is between the flesh and the epidermis.

Desalinizatign

The process of removing dissolved salts from water.

S§tention  (Retention)

The dwell time of waste water in a treatment unit.
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Dewatering

The process of removing of a large part of the water content of sludges.



Dissolved oxygen.  Measured in mg/1.

Dr. urn

A large cylinder, usually made of wood, in which hides are placed for
wet processing.  The drum is rotated around its axis, which is oriented
horizontally.  Also called wheel.
A form of advanced waste treatment in which the dissolved ionic material
is removed by means of a series of semi- permeable membranes and electric
current.

Enzyme

Complex protein materials added to the hide in the bating step in order
to remove protein degradation products that would otherwise mar hide
quality.
The top layer of skin; animal hair is an epidermal regrowth.
The holding or storing of wastes having differing qualities and rates of
discharge for finite periods to facilitate blending and achievement of
relatively uniform characteristics.

jSutrophication

The excess fertilization of receiving waters with nutrients, principally
phosphates and nitrates, found in waste water which results in excessive
growth of aquatic plants.
The process of adding oils, fats, and greases (fatliquor) to tanned
hides to improve and prevent cracking.
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The final processing steps performed on a tanned hide.  These operations
follow the retan-color-f atliquor processes, and include the many dry
processes involved in converting the hide into the final tannery
product.

Flpa.1

The proper level or volume of skins or hides, chemicals, and water that
is maintained in any wet process unit  (vats, drums, or processors)
within the tannery.

Floe

Gelatinous masses formed in liquids by the addition of coagulants, by
microbiological processes, or by particle agglomeration.

Flocculation

The process of floe formation normally achieved by direct or induced
slow mixing.

Flume

An open, inclined channel or conduit for conveying water or water and
hides.

Grab Sample

A single sample of waste water which will indicate only the constituent
levels at the instant of collection; contrasted to a composite sample.

Graded Media Filter

A filtration device designed to remove suspended solids from wastewater
by trapping the solids in a porous medium.  The graded media filter is
characterized by fill material ranging from large particles with  low
specific gravities to small particles with a higher specific gravity.
Gradation from large to small media size in the direction of normal
flow.
The epidermal side of the tanned hide.  The grain side is the smooth
side of the hide where the hair was located prior to removal.
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grease

A group of substances including fats, waxes, free fatty acids, calcium
and magnesium soaps, mineral oils, and certain other non-fatty
materials.  The grease analysis will measure both free and emulsified
oils and greases.  Generally expressed as rag/1.

£reen_Hides

Hides which may be cured but have not been tanned.
The reciprocal transfer of ions between a solid and a solution sur-
rounding the solid.  A process used to demineralize waters.

Jonizatjon

The process by which, at the molecular level, atoms or groups of atoms
acquire a charge by the less or gain of one or more electrons.

Liming

The operations in the beamhouse where a lime solution comes in contact
with the hide.  Liming in conjunction with use of sharpeners such as
sodium sulfhydrate is used to either chemically burn hair from the hide
or to loosen it for easier mechanical removal.  Hair burning normally
utilizes higher chemical concentrations.

Sgembrane

A semi-permeable barrier used in reverse osmosis and electrodialysis
which allows water molecules and certain dissolved molecules to pass
through it while impeding the passage of other dissolved solids.

Nitrogen, Ammonia

A measure of the amount of nitrogen which is combined as ammonia in
waste water.  Expressed in mg/1 as N.

flitrogen,._Kieldahl (Total Kjeldahl Nitrogen or TKN)

A measure of nitrogen combined in organic and ammonia form in waste-
water.   Expressed in mg/1 as N.

Nitrogen, Nitrate

A measure of nitrogen combined as nitrate in waste water.  Expressed as
mg/1 as N.
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Nutrient

Any material used by a livinq organism which serves to sustain its
existence, promote growth, replace lossas, and provide energy.  Com-
oounds of nitrogen, phosphorus, and other trace materials are par-
ticularly essential to sustain a healthy growth of microorganisms in
biological treatment.
The final outlet conduit cr channel where waste water or other drainage
is discharged into an ocean, lake, or river.

Pack

Layers of salted hides formed at the slaughter house or hide curing firm
(usually approximately 20 to ^0 feet in area and 5 to 6 feet high) .

Paddle_Vat (Paddle)

A vat with a semi-submerged rotating paddle arrangement used for the
mixing of water and chemicals with the hide.
The reciprocal logarithum of the hydrogen ion concentration in waste-
water expressed as a standard unit.

J2ES3

Parts per million.  The expression of concentration of constituents in
waste water; determined by the ratio of the weight of constituent per
million parts (by weight)  of total solution.  For dilute solutions, ppm
is essentially equal to mg/1 as a unit of concentration.
The process step generally following the retan-color-fatliquor opera-
tions whereby the hide is attached to smooth plates with a starch and
water paste and dried in a controlled heated vessel.

Pickle

The process that follows bating whereby the hide is immersed in a brine
and acid solution to bring the skin or hides to an acid condition;
prevents precipitation of chromium salts on the hide.

Plating

The finishing operation where tha skin or hide is "pressed" in order to
make it smoother.
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An organic compound characterized by a large molecular weight,  certain
polymers act as coagulants or coagulant aids.  Added to the wastewater,
they enhance settlement of small suspended particles.  The large
molecules attract the suspended matter to form a large floe,

Proces sor

A mixing apparatus resembling a concrete mixer which is used in some
tanneries.

Pullgry

A plant where sheepskin is processed by removing the wool and then
oickling before shipment to a tannery.

Retan

The process step following tanning and any intermediate drying whereby
hidas which have not been fully tanned in the chrome tanning process may
be retanned either with chrome, vegetable, or synthetic tanning agents.
This operation generally precedes coloring and fatliguoring.

Reverse Osmosis

A process whereby water is forced to pass through semi-permeable
membranes under high pressures.  Water passing through the membrane is
relatively free of dissolved solids; solids are retained in concentrated
form on the feed side of the membrane and are wasted.

Sandj.ng

A dry operation performed on the tanned and fatliquored hide in order to
achieve the desired surface texture of the leather.  Sanding operations
include the use of abrasive or buffing wheels.

Scouring

A process where shearlings are washed.

Scudding

An operation following the major unhairing step where the last of the
hair is removed from the hide.

Sedimentation

Clarification (settling),
                              155

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Chemicals used in addition to lime to assist in the unhairinq nrocess
{such as sodium sulfide and sodium sulfhydrate) .

Shearling

A lamb or sheepskin tanned with the hair retained.

Shoulder

That part of the hide which represents the shoulder of the animal.
A side represents half a hide which has been cut alonq the spine.

Skiving

The thin layer shaved or cut off the surface of finished leather,
principally sheepskin.
A concentrate in the form of a semi-liquid mass resultinq from settling
of suspended solids in the treatment of sewage and industrial wastes.
   i ti
A side which has been cut parallel to its surface to provide one large
piece of leather of approximately uniform thickness and a thin, smaller
piece of nonuniform thickness called a split.

Staking

The finishing process wherein the hide or skin is stretched to make it
more pliable and to avoid shrinkage.  Tacking.

Standard_Industrial_Cl assrfication	(SIC)

The numerical designation given to various industries by the Bureau of
the Budget.  The leather tanning and finishing industry bears SIC No.
3111.

Submerged combustion

A flash evaporation type procedure used in the separation of dissolved
solids from wat«=r.
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Ionized sulfur.  Expressed as mq/1 as S.

Suspended... go lids { s S )

Constituents suspended in waste water which can usually be removed by
sedimentation  (clarification) or filtration,

Tacking

Stakinq using tacks to fasten skins or hides to a larqe frame.

Tannin

The chemicals derived from the leachinq of bark, nuts, or other
vegetable materials used in the vegetable tanning process.

Tan. Yard (Tan House)

That portion of the tannery in which the bating, pickling, and tanning
is performed on the hides or skins.

Total Dissolve d Solids (TBS)

The total amount of dissolved materials (organic and inorganic) in waste
water.  Expressed as mq/1.

Total Solids (TS)

The total amount of both suspended and dissolved materials in waste
water.  Expressed as mg/1.

Unhairing

The process where the hair is removed from the hide.

Vo la tile Sol ids

solids, dissolved or suspended, which are primarily organic and during
stabilization exert the significant portion of the BOD5.
A control device placed in a channel or tank which facilitates mea
surement or control of the water flow.

Wheel

Drum.
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                                   TABLE

                                METRIC UNITS

                              CONVERSION TABLE
MULTIPLY (ENGLISH UNITS)
  by.
TO OBTAIN (METRIC UNITS)
   ENGLISH UNIT

acre
acre - feet
British Thermal
  Unit
British Thermal
  Unit/pound
cubic feet/minute
cubic feet/second
cubic feet
cubic feet
cubic inches
degree Fahrenheit
feet
gallon
gallon/minute
horsepower
inches
inches of mercury
pounds
million gallons/day
mile
pound/square inch
  (gauge)
square feet
square inches
tons  (short)

yard
                     ABBREVIATION   CONVERSION •, ABBREVIATION  METRIC UNIT
                        ac
                        ac ft

                        BTU
                        BTU/lb

                        cfm
                        cfs
                        cu ft
                        cu ft
                        cu in
                        °F
                        ft
                        gal
                        gpm
                        hp
                        in
                        in H?
                        Ib
                        mgd
                        mi
                        psig

                        sq ft
                        sq in
                        ton

                        yd
0.405
1233.5
0.252
0.555
0.028
1.7
0.028
28.32
16.39
0.555(°F-32)*
0.3048
3.785
0.0631
0.7457
2.54
0.03342
0.454
3,785
1.609
ha
cu m
kg cal
kg cal/kg
cu m/min
cu m/min
cu m
1
cu cm
°C
m
1
I/sec
kw
cm
atm
kg
cu m/day
km
(0.06805 psig +l)*atm
   0.0929
   6.452
   0.907

   0.9144
 sq m
 sq cm
 kkg

 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 tons
 (1000 kilograms)
meters
* Actual conversion, not  a multiplier
                                                    MJ.S. GOVERNMENT PRINTING OFFICE: 1974 546-318/348 1-3

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