EPA 440/1-73/
Olo
         DEVELOPMENT  DOCUMENT FOR
   PROPOSED EFFLUENT LIMITATIONS GUIDELINES
   AND NEW SOURCE PERFORMANCE STANDARDS
                   FOR THE
     LEATHER TANNING AND  FINISHING
              POINT SOURCE CATEGORY

           UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                   NOVEMBER 1973

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              DEVELOPMENT DOCUMENT

                      for

    PROPOSED EFFLUENT LIMITATIONS GUIDELINES

                      and

        NEW SOURCE PERFORMANCE STANDARDS

                    for the

         LEATHER TANNING AND FINISHING

             POINT SOURCE CATEGORY
                 Russell Train
                 Administrator

                Robert L. Sansoni
Assistant Administrator for Air & Water Programs

                  Allen Cywin
     Director, Effluent Guidelines Division

                James D. Gallup
                Project Officer
                 November 1973

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

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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                                                        Page
  I    CONCLUSIONS 	   1

 II    RECOMMENDATIONS 	   3

III    INTRODUCTION  	   7

            Scope	7
            Previous Study 	   7
            Industry Trends  	   8

 IV    INDUSTRY CATEGORIZATION 	  11

            Standard Manufacturing Processes 	  11
            Cattlehide Tannery Processes 	  12
            Sheepskin Tannery Processes  	  18
            Pigskin Tannery Processes  	  22
            Classification System  	  26
            Categorization System  	  28

  V    WASTE CHARACTERIZATION  	  31

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

 VI    SELECTION OF POLLUTANT PARAMETERS 	  47

            Waste Water Parameters of Major Significance ....  47
            Rationale for Selection of Major Parameters  ....  47
               Biochemical Oxygen Demand 	  47
                               iii

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                          CONTENTS (Con't)
Section
               Total Chromium	47
               Grease	47
               Sulfide	48
               Suspended Solids  	  48
               Total Kjeldahl Nitrogen 	  48
               Fecal Coliforms	48
               pH	48
            Rationale for Selection of Minor Parameters  ....  48
               Chemical Oxygen Demand  	  48
               Total Solids	  .  .  I	49
               Ammonia Nitrogen	49
               Color	49

VII    CONTROL AND TREATMENT TECHNOLOGY  	  51

            General	51
            Basis of Tannery Waste Treatment 	  52
            In-Process Methods of Reducing Waste 	  54
            Preliminary Treatment  	  58
               Screening	60
               Equalization	61
               Plain Sedimentation	61
               Chemical Treatment - Coagulation and
                 Sedimentation	64
               Chemical Treatment - Carbonation  	  66
               pH Adjustment	67
               Sludge Handling and Disposal  	  67
               Preliminary Treatment - Facility Requirements .  .  69
               Secondary Biological Treatment  	  70
            Major Reduction of BOD5_ and Suspended Solids ....  70
               Combined Municipal - Tannery Treatment Systems  .  70
               On-Site Treatment - Trickling Filter Systems  .  .  74
      :         On-Site Treatment - Aerobic Lagoon Systems  ...  75
               On-Site Treatment - Aerobic - Anaerobic
                 Lagoon Systems  	  79
               On-Site Treatment - Activated Sludge Systems  .  .  84
            Practical Biological Systems 	  90
               Polishing Systems For Biological Treatment  ...  91
            Major Reduction of all Forms of Nitrogen	.94
            Major Removal of All Waste Constituents	97
               Freezing	98
                                 iv

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                          CONTENTS (Con't)

Section
               Evaporation	98
               Electrodialysis 	 98
               Ion Exchange	99
               Reverse Osmosis 	 99

VIII   COST, ENERGY, AND NON-WATER QUALITY ASPECTS 	103

            Cost and Reduction Benefits of Alternative
              Treatment and Control Technologies 	103
            Basis of Economic Analysis	103
            Effluent Reduction Subcategory 1 	112
            Impact of Waste Treatment Alternatives on
              Finished Product Price 	114
            Alternative Treatment Systems  	114
            Related Energy Requirements of Alternative
              Treatment and Control Technology 	117
            Non-Water Quality Aspects of Alternative
              Treatment and Control Technology 	118
               Air Pollution	118
               Solid Waste Disposal	118

IX     BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY
         AVAILABLE GUIDELINES AND LIMITATIONS	121

            General	121
            Effluent Reduction Attainable	122
            Best Practicable Control Technology Currently
              Available	124
            Rationale for Selection of BPCTCA	124
               Total Cost of Achieving Effluent Reduction  .  . .124
               Age and Size of Equipment and Facilities  .  .  . .125
               Engineering Aspects of Control Techniques .  .  . .125
      '•         Processes Employed  	 . 	125
               Process Changes 	125
               Non-water Quality Environmental Impact  	125

 X     BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE -
         GUIDELINES AND LIMITATIONS  	127

            General	127
            Effluent Reduction Attainable  	128
            Best Available Technology Economically Achievable  .130
            Rationale for Selection of BATEA . 	131
               Total Cost of Achieving Effluent Reduction  .  . .131

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                          CONTENTS (Con't)

Section                                                        Page

               Age and Size of Equipment and Facilities  . .  .  .131
               Processes Employed	131
               Engineering Aspects of Control Techniques . .  .  .131
               Process Changes	131
               Non-water Quality Environmental Impact  	132

 XI    NEW SOURCE PERFORMANCE STANDARDS	133

            General	133
            Improved In-plant Process Control	133
            New Source Performance Standards	134
            Pretreatment Requirements	134

 XII   ACKNOWLEDGMENTS 	135

XIII   REFERENCES	137

 XIV   GLOSSARY	143
                                vi

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                             TABLES
Number                       Title
  1     Best Practicable Effluent Limitation Guidelines
             July 1, 1977	4
  2     Best Available Effluent Limitation Guidelines -
             July 1, 1983	5
  3     Classification System 	 27
  4     Principal Processes of Subcategories  	 30
  5     Hide Curing	34
  6     Wastewater Quantities 	 41
  7     Raw Wastewater Characteristics by Category  	 44
  8     Plain Sedimentation 	 62
  9     Chemical Treatment  	 	 65
 10     Combined Municipal - Tannery Treatment Systems  .... 71
 11     Trickling Filter Systems  	 77
 12     Aerobic Lagoon Systems  	 78
 13     Aerobic - Anaerobic Systems 	 81
 14     Activated Sludge Systems  	 85
 15     Estimated Waste Treatment Cost for Subcategory 1  .  .  .106
 16     Estimated Waste Treatment Cost for Subcategory 2  .  .  .107
 17     Estimated Waste Treatment Cost for Subcategory 3  .  .  .108
 18     Estimated Waste Treatment Cost for Subcategory 4  .  .  .109
 19     Estimated Waste Treatment Cost for Subcategory 5  .  .  .110
 20     Estimated Waste Treatment Cost for Subcategory 6  .  .  .111
 21     Estimated Industry Investment to Meet BPCTCA
             Effluent Limitations . . 	115
 22     Estimated Industry Investment to Meet BACTEA
             Effluent Limitations 	116
 23     Best Practicable Effluent Limitation Guidelines -
             July 1, 1977	123
 24     Best Available Effluent Limitation Guidelines -
             July 1, 1983	129
                             vii

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                             FIGURES


Number                       Title                             Page

  1     Flow Diagram - Typical Cattlehide Tannery 	 13

  2     Flow Diagram - Typical Sheepskin Tannery  	 21

  3     Flow Diagram - Typical Pigskin Tannery  	 25

  4     Category System	29

  5     Wastewater Flow vs Tannery Production for Category 1   . 40

  6     Tannery Production vs Relative Cumulative Frequency
         for Category 1	46
                                 viii

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                               SECTION I

                              CONCLUSIONS
For  purposes
standards of
been  divided
been derived
Such  factors
technologies
subcategories
subcategories
    of  establishing  effluent  limitations  guidelines   and
  performance, the leather tanning and finishing industry has
    into  six  major subcategories.  These subcategories have
  principally by similarities in  process  and  waste  loads.
    as  age  and  size  of  plant, climate, and waste control
   favor  segmentation  of  the  industry  into   these   six
      The  following tabulation is a capsule summary of these
   1

   2

   3

   4

   5
   Beamhouse

Pulp hair

Save hair
INDUSTRY SUBCATEGORIES

  	Primary Processes.

            Tanning

             Chrome

             Chrome
                                                          Leather
Save hair

Hair previously removed

Hair previously removed
or retained

Pulp or save hair
             Vegetable

             Previously tanned

             Chrome


             Chrome or no tanning
Yes

Yes

Yes

Yes

Yes


No
Currently, waste from about 60 percent of the  tanneries  (and  approxi-
mately  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  $28  million
(August,   1971,   price   levels).    Total   annual  costs  (including
depreciation,  interest,  operation,  and  maintenance)  for   pollution
control  will  increase  finished  product  costs  from about 1.1 to 3.5

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percent (August, 1971, prices)  depending on industrial subcategory.  For
only one subcategory is the increase in excess of 2.6 percent.

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 about $42.5 million
(August, 1971, prices).  This represents  an  additional  $14.5  million
investment  over  BPCTCA.   Total  annual  costs  for the best available
control  technology  economically  achievable  will  increase   finished
product  prices  from about 0.5 to 2.6 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  1.6  to  6.1 percent for various subcategories and only one
subcategory is in excess of 3.8 percent.

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 removal 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  composite 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.

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
                      (July 1, 1977)
                                    SUBCATEGORY
PARAMETER(l)              kg/1000 kg hide (lb/1000 Ib hide)

BOD5_
TOTAL CHROMIUM
OIL & GREASE
SS

2
0
0
3
1
.7
.05
.53
.0
2
3.
0.
0.
3.

2
06
63
5

2
0
0
2
3
.5
.05
.50
.8

1
0
0
1
4
.0
.02
.24
.1
5
3.
0.
0.
3.

2
06
63
5

1
0
0
1
6
.4
.03
.34
.5
(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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                             TABLE 2

             BEST AVAILABLE EFFLUENT LIMITATIONS
                         (July 1, 1983)
                                       SUBCATEGORY
PARAMETER(l)                 kg/1000 kg hide (lb/1000 Ib hide)
                      123456
BOD5.                 1.35   1.60   1.25   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

SS                   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  ap-
plication 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 fellows:

    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 indus-
         try 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
         ccntrol and treatment, and pretreatment prior to discharge
         to a publicly-owned waste water system.

    U.   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 technol-
         ogy, together with suggested effluent limitations guidelines
         and appropriate cost information.

Preyious^ Study

A  principal  source  of  information  for  this  investigation  is  the
'•Industrial  Viaste  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 some 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 1960, 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  finishinq
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 hido
producing  nations.   This  has  recently  caused  the  price   of   raw
cattlehides  to  increase greatly.  Heavy native steer hides have ranged
in price :frorn 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 pricos
increased to 42.4 cents in August, with an average for the year of  29.7
cents  per  pcund.   These  raw  product prices have now fallen to about
twice those in 1971.   In addition, competition  from  foreign  count rift;
such  as Japan, Italy,  and Spain in the finished leather products market
has reduced the potential revenue from domestic leather firms.

Ccittlehides constitute the bulk of  the  tanning  done  in  the  U.  c;. ,
representing  about  90 percent of the estimated pounds of hides tanned.

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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 agent
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 ccnvert
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 cne 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 cf 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 processes 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)
Cattle hide Tannery Processes

There  are  four  processes  in  a typical cattlehide tannery which con-
tribute waste loads:

    1.   Beamhouse.

    2.   Tanhcuse.

    3.   Petan, color, and fatliquor.

    4.   Finishing.
                                   12

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   FLOW  DIAGRAM
   TYPICAL CATTLEHIDE  TANNERY
                                             LEGFJC



                                             PROCESS HAIERULS	
                                                                 RETAN COLOR FAILIOUOR
JJHMJPE.HEJJS
_il«_lJ—•
           L
                I  | FLESHINGS

                I HAIR

               PliTI EFFLUENT
 I  ! SPLITS

 [_SpL_ID_WASTE_ (SHAV INGS)

WASTE EfHUEMt
                                                                                                    ASH EFFLUENT (CLEAN-UP ONLr)
                                                                                             REIAN-COLOR-FATLIQLfOH
                                                                                                ULTIFNAIE)
                                                                                                         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
         frcm 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 cause 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  en  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 te 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 maintained in

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

3-   Siding_and_Trimminc[ - 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.

U.   Waj3hing_and_Soakinc£ - 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.

     Cepending 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-   li§§hiQ3 ~ 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.   UnhajyziDS - 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
     "turning."

     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 sulf hydrate 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, strcnger
     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.

     Ihe  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.

T ANHOU S E_ PRQCES S :

1-   Is!£iQ2 ~ 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-   HisKiiDa " Tiie 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.
                              16

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

3-   Tanning - 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
     Icnger process times, while chrome tanning takes place in drums
     cr 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.

     Viaste  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.

**•   §Eiitting ~ Tne tanned hide is split  to  produce  a  grainside
     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.

BlTANx_COLORi_FATLI2UOR_ PROCESS:

1.   S^tan - 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»   Bitching  ~  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.
                              17

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    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.

    **•    Isltliguoring ~ 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.

    FIN ISH ING_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 tooth water baths.

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

Sheepskin Tanngry__Processes

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

    1.    Tanhouse.

    2.    Retan, color, and fatliquor.

    3.    Finishing.

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

    TANHOU S E PROC ES S :
               ing - 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 shear-
         lings.  Tanning of these skins does not involve a beamhouse
                                  18

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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.

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 deterio-
ration.

lieshing - 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.

£§9£§§sing - Skins are placed in drums, washed, and soaked,
after which solvent or detergent is added in the same drums
tc 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 atmos-
phere.

I§QIiiQ3 ~ Sheepskins may be either chrome or vegetable
tanned, although the majority are chrome tanned.

Vihere 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 sul-
fate for chrome tanning or solutions of the natural tannins
for vegetable tanning.
                         19

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6-   Refreshing - In some cases, there is a refleshing operation
     following tanning, which produces a small amount of solid
     waste.

CQLOJL AND_FATLI2UOR_PROCESS:

!•   Coloring - Skins to fce colored are immersed in a dye solu-
     tion in drums.  Generally, synthetic dyes are used.  Some
     bleaching may be done prior to coloring of shearlings.

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

ONISHI NG_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 pro-
cesses, 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-FftUlQUOR
(I) SHEARLINGS ("ML UFI On) ASE
   HECEIVED AS CURED SKIMS. UN-
   HOUSE SUB-PROCESSES INCLUDE
   WISH t SOA». FLESHING. DECREAS-
   ING. PICKLING MD lANNING.
SKIhS IRON
DECREASING
                                            I HASTE tjfLUEgl
                                                                                                      FIGURE 2
                                                  21

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PiqskinjTannery_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.   Tanhcuse.

    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:

    !•   E§£§iYin-2 ~ 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 tan-
         neries for skins which are to be held before tanning.

    3-   2§3£§§§iD3 - Solvent degreasing has been used by some pig-
         skin 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
         tc a stripping column, where the solvent is recovered for
         reuse.  Grease is recovered as a by-product.

         There is a waste effluent frcm 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 ty decanting or skimming it from the
         top cf holding tanks to which waste is diverted prior to
         entry into the main plant sewer system.

    U.   Liming * From the degreasing operation the skins are placed
         in tanning drums with a lime slurry and sharpeners.  The


                                  22

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

5-   !<*iiD3 - The bating operation takes place in the same drums
     used for liming.  The purpose of this operation is to de-
     lime 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-   Ta_DDiD3 - 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 tan-
     ning 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, elim-
     inating any need for a retan operation at a later point.

8-   §£lit_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 fatliquor process.

CQLOR_AND_FATLI2UOB_PRQCESS:

1-   Co.lP.liD9 ~ Skins to be colored are immersed in a dye solu-
     tion in drums.  Generally, synthetic dyes are used.

2-   I§^ii31i2£ill3 ~ 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 sand-
ing.  These are principally dry processes, and the only liquid
waste contributed is from cleanup operations.  Where paster dry-
ing 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
                              23

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fertilizer.  Dust collected from the sanding operation is dis-
posed of as a solid waste.

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FLOW  DIAGRAM
TYPICAL PIGSKIN TANNERY
                                          COLOR-FAUtQUOF
                                                                 FIGURE 3
                                25

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Classification System

As  noted  in  the  foregoing  discussion on standard manufacturing pro-
cesses, 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 classificaticn.  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.
                                  26

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                              TABLE 3

                       CLASSIFICATION SYSTEM
                            (3111.abed)
                                                      Retan,
Skin or
Hide Type

1.
2.
3.
(a)
Cattle
Pig
Sheep

1.
2.
3.
Beamhouse
Operation
(b)
Pulp Hair
Save Hair
Hair Pre-
viously
Tanning
Process
(c)
1. Chrome
2. Vegetable
3. Alum
Color, Fatliquor,
Finishing
(d)
1. Sides
2. Splits
3. Sides and
Splits
                  Removed
4. Deer

5.

6.
7.
8.
9 . Other

0. Various
4.

5.

6.
7.
8.
9.

0.
Hair
Retained
Wool
Pullery
Hide Curing
Pulp & Save

Other and
unknown

4.

5.

6.
7.
8.
9.

0.
Previously
Tanned
Vegetable
and Chrome



Other and
unknown
None
4

5

6
7
8
9

0
                                                   U.  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-
                                  27

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                 viously tanned prior to receipt of hides at a fin-
                 ishing facility (finishing operations only).

    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.

Categorizatign_Sy_stem

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  4,  for  purposes  of
evaluating   control   and   treatment   technology.   Each  subcategory
represents a common manufacturing process, as shown in Table U.

These subcategories only identify operations that do not process a  com-
bination 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.
                                  28

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  STANDARD
  INDUSTRIAL
CLASSIFICATIONS
                                                       CATEGORIES
                                                                                                             STANDARD
                                                                                                            INDUSTRIAL
                                                                                                         CLASSIFICATIONS
CATTLE       j.1319
HAIR PREVIOUSLY REMOVI
PREVIOUSLY TANNED
OTHER OR UNKNOWN
SHEEP        M3U5
HAIR PREVIOUSLY REMOVED
PREVIOUSLY TANKED
SKINS
CATTLE       .1313
HAIR PREVIOUSLY REMOVI
PREVIOUSLY TANNED
SIDES 1 SPLITS
OEER        I.TO9
HAIR PREVIOUSLY REMOVED
PREVIOUSLY TAHHED
OTHER OR UNKNOWN
                                                                                           CATEGORY  SYSTEM
                                                                                                           FIGURE  4

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                             TABLE H

               PRINCIPAL PROCESSES OF SUBCATEGORIES

        	Primary Processes	
            Searohoy.se            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
                               30

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                             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.

    U.   Regulatory agency data summaries, including engineering re-
         ports on individual tanneries.

    5.   Literature review.

    6.   Sampling performed at selected tanneries.

    7.   Tannery visits.

Correspondence  and  information data sheets were received from over 1UO
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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Waste 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
fellows:

    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.
                                  32

-------
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.

    2.   Number of hides processed.

    3.   Weight of finished product.

    U.   Square feet of finished product.

Each of the above has some shortcomings  when  used  as  basis  of  pro-
duction, 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.

lQdividual_Process_Contributions_to_the_Waste

Each process in the production of the  final  product  makes  some  con-
tribution to the total waste load.

Hide_Curihg

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.


                                  33

-------
The  brine solution is continually circulated and reused.  Slowdown 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:
                          Table 5
                        Hide Curing
                                Concentration
kg/1,000 kg Hide
Waste Characteristics
BOD 5
COD
Total Solids
Suspended Solids
Oil and Grease
Water Use, I/kg
(gal/lb)
Jmg/lj.
15,610
29,610
280,500
10,400
40,200
0.24
(0.03)
_(lb/1xOOO Ib Hide
3.9
7.4
70.1
2.6
10.0

Tanner^_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
                                  34

-------
    Tanning  (including bleaching for some vegetable tanning)

    Retanning, Coloring, and Fatliquoring

    Finishing

The waste contributions are described below:

W§§.h_
-------
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 (Ib) 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.

UQh§i.EiD3 " 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 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, BOD5, suspended solids, and total
sclids.   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
dees  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 con-
trolled level and an  enzyme  to  condition  the  protein  matter.   The
reaction  of  lime  with ammonium sulfate produces calcium sulfate.  The
tctal 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.


                                  36

-------
H.i£]siiJ22 ~ T^e purpose of the pickling operation is to prepare the hides
for the tanning process.  In vegetable tanning, pickling may be omitted.
Fickle  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  degra-
dation  by  physical  or biological mechanisms.  This is accomplished by
reaction cf the tanning  agent  with  the  hide  collagen.   Chrome  and
vegetable  tanning  are  the  two  principal  processes,  although ether
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
scdium  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
ccmes 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.

Retanjt__colorjt	Fatligugr  -  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.

Ihe 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


                                  37

-------
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.

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

The  temperature  of  the  retan,  color,  and  fatliquor waste flows ir
generally high—above 37.7°C  (100°F).  The major  treatment  concern  ot
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 retarming will enable
maximum uptake of chromium and reduce the discharge of this constituent.

Finishing

The tinishing processes represent the lowest water flows of the  tannery
because  they are primarily dry processes.  There are seme wet processes
such eis miner wetting operations to make the hide handle more easily  in
the  staking  or  tacking  operations.   The pasting operation also use:;
small amounts of water.  However, several tanneries report reusing pastt
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.

Tgtal_PlantmLiguid_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.  Tn 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.
                                  38

-------
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
             cf tanneries.

    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 fre-
             quency of occurrence in any one interval was not gen-
             erally too much greater than adjacent intervals.  Use
             of a wider interval would have reduced significance of
             this measure.
                                  39

-------
         ZOO
                    TANNERY PRODUCTION (1000 KG HIDE/MO)
            WO      600 _  800 _   1000      1200     UOO       1600     1800
18-


17


16


15




    H
13


12


II •


10


 9


 8


 7


 6




 4  ©
 ©
©  ©
                ©
               ©
           ©
                          ®
      ©
       _
   ® ®
                                       © 0©
                                       ©
                                                         ©
  WASTEWATER  FLOW
TANNERY  PRODUCTION
  FOR CATEGORY  1

         FIGURE  5
                                                                            0.15
                                                                            0. 13
                                                                            0.12
                                                                            0. II
                                                                            0.10
                                                                            0.09
                                                                            0.08
                                                                            0.07
                                                                            0.06
                                                                            0.05
                                                                            0.04
                                                                            0.03
                                                                                   0.02
                                                                            o.oi
    500
              1000       1500       2000       2500       3000
                     TANNERY PRODUCTION (1000 LB HIDE/MO)
                                                                3500
                                                                          1(5

-------
TABLE 6
WASTEWATER QUANTITIES
Waste Flow,
cu m/kcj
Category Median
1 0.01(0
Ci.8)
2 0.050
(6.0)
3 O.Qltlt
(5.3)
1* 0.017
(2.0)
5 0.050
(6.0)
6

of h
Mean
0.053
(6.1.)
0.063
(7.6)
0.050
(6.0)
0.020
(2.
-------
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  non-
scientific  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 throuqh
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.,

                 f T o t a 1 PI a n t Wa s t e F 1 o ws
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 ot 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 sutcategory is shown  in
Table  7.   The  data  have  been  classified as received and no further
attempt  is  made  toward  explanation  of  inconsistencies  with   seme
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.

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  signifi-
cant  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



Flow: cu m/kg
(gal/lb)
BODj
COD
Total Solids
Suspended Sol ids
Total Chromium
Sul fides
Grease
Total Alkalinity
(as CaCOj)
Total Nitrogen
(as N)
PH
Temperature**: °C
CF)

Category No. 1
No. of
116 0.007-0.156 0.053
(0.8-18.7) (6.M
2* 11.8-270 95
18 10.5-595 260
16 36-890 525
23 6.7-595 HO
18 0.1-19 *i.3
12 O.I-46 8.5
13 0.1-70 19

12 0.5-300 98

7 3.1-H 17
26 1.0-13.0
15 2.8-93.2 21.1
(37-200) (70)

Category No. 2
No. of No. of
H 0.001-0.189 0.063 16^
(0.1-22.6) (7.6)
9 22- HO 69 12
7 88-215 HO 9
7 HO-900 Ii80 9
9 30-350 H5 10
7 0.3-12 li.9 5
k 0.1-2.8 0.8 7
5 0.7-105 li3 7

1 62-85 72 6

6 3.6-22 13 5
8 Ii.0-l2.6 -- 12
6 1.7-27.8 18.3 3
(35-82) (65)
of Hide)'
Category No.
.5 Range
0.007-0.106
(0.8-12.7)
7.ii-130
21.-695
120-800
20-Wi5
0.2-0.6
0. l-ll,2
0. 1-160

1..1-I35

0.9-23
2.0-13.0
l|.4-28.9
HO-811)

3
Average
0.050
(6.0)
67
250
3,5
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 (°F).




"-Average temperature is average summer and winter values; temperature  range is low winter to high

-------
                      TABLE  7  (Continued)


                         RAW  WASTEWATER

                CHARACTERISTICS BY  CATEGORY
        Raw Uastewater Characteristics, kg/1,000 kg of Hide (lb/1,000 Ib of Hide)*

No. of
Tanneries
10
3
3
2
3
3
1
3
Category No.

Range
0.003-0.033
(0.3-3.9)
6.7-67
5.7-63
47-285
7.0-125
0.4-4.8
2.1
2.2-19
4

Average
0.020
(2.4)
37
28
140
47
2.6
2.1
7.9
Category No. 5
No. of
Tanneries
20
8
5
7
8
7
1
7

Range
0.006-0.204
(0.7-24.4)
10-140
11-265
52-980
3.1-865
0.1-2.1
4.5
0.6-46

Average
0.063
(7.6)
67
170
490
88
1.2
4.5
24
Category No. 6
No. of
Tanneries Range
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

Average
0.028
(3.4)
110
230
595
110
4.4
3.7
6.6
I        39       33        3     6.6-180      69        I      37-54      43




2     0.8-6.5     3.7        5     0.6-29      6.0        1      H-18      16


3     3.4-11.2      "        9     1.5-12.5      —        2      9.2-10.4


3    10.0-26.6    20.7       . 3     4.4-36.6     22.8
      (50-80)     (69)              (40-98)     (73)
                                       45

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  MOOD




  3000






  2000
a,  '000

-J   900

g   800


£  700


g   600


o   500

0

I   400
ae.
uJ
    300
    200
    100
                                   1500
                                   1000

                                   900

                                   800


                                   700


                                   600


                                   500



                                   400




                                   300
                                                                             o
                                                                             o
                                                                             o
                                                                         200
                                       o
                                       o
                                       ac.
                                       a.
      TANNERY PRODUCTION

              VS.
RELATIVE CUMULATIVE FREQUENCY
        FOR CATEGORY  I


                   FIGURE 6
                                                                         100
                                                                         50
                     10    20   30  110  50  60  70   80

                         RELATIVE CUMULATIVE FREQUENCY
                   90    95
                                                                        99
                                     46

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                            SECTION VI

                 SELECTION OF POLLUTANT PARAMETERS


WASTE, WATER PARAMETERS OF MAJOR SIGNIFICANCE

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., BOD5)
Total Chromium
Grease Fats and Oils
Sulfide
Suspended Solids (SS)
Total Kjeldahl Nitrogen
Fecal Coliforms
pH

Rationale for Selection of Major Parameters

§i2£h§IDic§l_Qxy3en_pemand __ ( BOD5)  -  This  parameter  is  an  important
measure  of  the  oxygen  utilized  by  microorganisms  in  the  aerobic
decomposition of the wastes at  20°C  over  a  five  day  period.   More
simply, it is an indirect measure of the biodegradability of the organic
pollutants in the waste.  BOD£ can be related to the depletion of oxygen
in a receiving stream or to the requirement for waste treatment.

If  the  EOD5  level  of the final effluent of a processing plant into a
receiving body is too high,  it will reduce the dissolved oxygen level in
that stream to below a level that will  sustain  most  fish  life;  i.e.
below  about  4  mg/1.   Many  states  currently  restrict  the  BODjj of
effluents to below 20 mg/1 if the stream is small in comparison with the
flow of the effluent.  A limitation of 200 to 300 mg/1 of BOD5 is  often
applied  for  discharge  to  municipal  sewer, and surcharge rates often
apply if the EOD£ is above the designated limit.
               - Most of the leather produced in the  U.  S.  is  tanned
with chromium salts.  Chromium, in some forms, can be harmful to aquatic
life  and, therefore, is an important parameter to be identified.  There
is evidence  to  indicate  that  chromium  in  both  the  trivalent  and
hexavalent  state  is  harmful,  and  thus  the total chromium parameter
should be used.

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


                                  47

-------
process.    The  grease  is  usually  all  of nonpetroleum origin.  Large
amounts of cil and grease  can  be  detrimental  to  surface  waters  by
retarding  stream  reaeration.   In  addition,  large amounts of oil and
grease are unsightly and  biological  degradation  may  result  in  odor
problems.

SuljEide  -  A  significant  portion  of  alkaline  sulfides contained in
tannery waste water can be converted to hydrogen sulfide at a  pH  telow
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 can be oxidized to sulfuric
acid, causing "crown" corrosion.  At higher concentrations this gas  can
be  lethal.   This  is  particularly  significant  as  a hazard in sewar
iraintenance.  Sulfide compounds are used extensively  in  the  beamhousp
for the unhairing process, and thus are found in tannery effluents.

Suspended	Solids   (SS)  -  Material  found in suspended form in tannery
wasteuaters consist primarily of proteinaceous substances  (flesh,  hide,
or hair)  and insoluble waste chemicals.   Suspended solids are an iirpor-
tant  measure  of  the pollutional significance of tannery wastes, since
they generally exert a BOD5 and can also result  in  detrimental  sludqr
deposits in streams and lakes.

Total	KjeJ.dahl	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  -  Microbiological  testing  for the presence of t
-------
acid reagent.  COD is a much more rapid measure of  oxygen  demand  than
BOD5 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  BOD5  can  be run.  A given plant or waste treatment system
usually has a relatively narrow range of COD:  BOD.5 ratios, if the waste
characteristics are fairly constant, so experience permits a judgment to
be made concerning plant operation from COD values.   In  the  industry,
COD  ranges from about 1.6 to 10 times the BOD5; 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 frcm 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 froir  an
aesthetic  standpoint.  There is not sufficient information at this time
to establish color limitations.

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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 chetricals and water.

Based upon communication with around 1HO wet  processing  firms  in  the
industry,  approximately  60  percent  of  the  tanneries  discharge  tc
municipal systems.  Analysis of these same data indicates that tanneries
discharging tc 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


                                  51

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facilities are non-existent.   Some pilot studies of reverse osmosis  and
activated  carbon  have  been  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 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  tech-
niques have generally been applied only in those areas where direct cost
savings are demonstrated.  Such practices are tannin and chromium reupp.
Plans  for  reuse  of  some portions of treated waste streams are in thp
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.


                                  52

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     d.   Partial removal of BOD5, COD, suspended solids, and
          total nitrogen.

3.    Major reduction of BOD5 and suspended solids.

     a.   Removal of BOD5 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 bio-
          logical 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.

     t.   Treatment follows biological treatment for BOD5 removal.

     c.   Treatment steps include an aerobic biological process
          followed by an anaerobic biological process.  Each pro-
          cess 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 BOD5, suspended solids, and
          nitrogen.

     b.   Filtered waste enters reverse osmosis process  (or electro-
          dialysis process)  for removal of remaining organic con-
          stituents, as well as major quantities of dissolved salts
          such as sodium chloride.

     c.   Waste stream is directed to evaporators for concentra-
          tion for final disposal.

     d.   Product water is of low solids content suitable for re-
          use.

6.    Waste treatment for hide curing facilities.

     a.   The high strength of this waste requires special con-
          siderations.

     b.   Treatment for all levels except pretreatment requires


                              53

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              direct incineration of total waste or solar evapora-
              tion in arid areas0

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.

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  const! tuents .
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  quantifies.
Tanning  formulas  and  processing  steps  are  developed by experience.
Implementation of many potential waste reduction  steps  are  cont-.inqent-
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  vari-
ations  for  three  subcategories  in which cattlehides are processed is
shown below:
                                                 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


                                  5U

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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.

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 em-
         ployee participation.

    2.   Examine tanning formulas to determine if floats can be re-
         duced.  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 prograir 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


                                  55

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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 delitning will be about 8.35 I/kg of hide (1 gal/  Ib  of  hide) 0
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  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  cperation.  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 #U 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
strec'irn.   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  Wcrld  war  II,  the reuse of chrome tan liquor was
comiron 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


                                  56  '

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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
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  conceiveably  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 net considered substantial.

Tannery  #7 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.

Eased  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 seme 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.
                                  57

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

    1.   Air oxidation.

    2.   Direct chemical oxidation  (8).

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

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

Direct  chemical  oxidation  with  ammonium  persulfate  and  ozone were
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  most  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:


                                  58

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    1.   Sewer safety and maintenance.

    2.   Eiological 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 concentrations as
high as 250 mg/1.  An alkaline sulfide bearing waste from a tannery when
mixed  with  sufficient domestic or acidic 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 concen-
trations (300-14,000 mg/1)  with an expected average of  2,000  to  3,000
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 frcm 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).
                                  59

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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  lew 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 EOD5  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.

    3.   Plain sedimentation.

    4.   Chemical treatment.

         a.   Coagulation and sedimentation.

              1)  Alum.

              2).  Lime.

              3)  Iron salts,

              U)  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
                                  60

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which has a potential for damaging plant equipment and clogging pumps or
sewers.
             ~ 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  fcr  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.

Ei^iD_§^^_il!!®Di§^i2D ~ 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  concen-
trations  cf  both  suspended  solids  and grease.  As shown in Table 8,
suspended solids reductions  can  range  from  approximately  UO  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  syrface   skimmers
installed in clarifiers.
                                  61

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System
lagoon
Sedlmentit Ion tanks,
mechanic*) sludge
fact 11 ties
Sedimentation tanks
Sedimentation tanks
Sedimentation tanks
TABLE 8
PLAIN SEDIMENTATION-
Suspended Solids BOD
Inf. Eff. Removal Inf. £ff. Removal Remarks Reference
«9/l mo/1 t mg/l i»8/l t
80-90 — — 80-90 Fill and draw basins with ()8) (}9)
24-hour capacity.
900 130 83-88 380 146 40-6! Pretreatmenl of vegetable (40)
tan liquors. Detention
time 9-15 hours.
1.200 370 69 — --- — Detention time 2 hours (14)
1,184 680 43 1,046 537 48 Continuous flo» (pilot) (HI)
1.880 461 67 I.28S 873 30 Fi 1 1 and draw (pi lot) (41)
62

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Assumed  to  te  typical for plain sedimentation units is the full-scale
operation cited by Sutherland  (14) .  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.r  (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 #10 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 rerrovals resulted (10).
   Suspended Solids

   BOD 5

   Total Chromium

   Total Alkalinity (as CaCO3)

   Grease
Influent
 mg/1

  3,125

  2,108

     51

    980

    490
Effluent
  mg/1

   945

 1,150

    24

   718

    57
%_Removal


   70

   45

   53

   27

   90
Suspended  solids  and  BOD5  removals  were  70 percent and 45 percent,
respectively.  A  low  chromium  removal  of  approximately  50  percent
occurred.   Higher  reirovals 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.
                                  63

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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 BCD5 (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.

Chem^a^Treatmen^^_Coa3ulation_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
flocculaticn  cf  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  BOD5
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 re-
         sulted in a reduction of about 84 percent in suspended
         solids and 60 percent in BODji.

    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 pro-
         duced average removals of 60 to 65 percent, respectively,
         for suspended solids and BOD5.

    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 per-
         cent and suspended solids from 45 to 57 percent.  Alum con-
         centrations higher than 500 mg/1 created a floe that would
         net settle.

    6.   Buffing dust resulting from finishing tanned hides was not
         found to be an effective coagulant.
                                  64

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                                                          TABLE   9
                                             CHEMICAL  TREATMENT
                                                 Suspended _Spj_ids_
Coagu1 a t i on-Sed imen ta 11on
   Plain Sedimentation,
   Coagulation, Sedimentation

   Aeration, Coagulation.
   Sedimentation
Coagulation, Sedimentation


Coagulation, Sedimentation


Coagulation, Sedimentation



Coagulation, Sedimentation


Coagulation, Sedimentation
 Lin
             1.550       68

             2,500      850
Iron Salts


Polymer     5,200**    500**
                                 66    3.600    1,030
              918      469       49    1.001       476


             1,980      1(97       75    1.630       623


             3.135      110       95    1,437       619
                                High
 90*    Adjustment of pH water             (42)

        H2S°4
 73     A pilot study with pre-            (16)
        settling of a portion of
        the  raw waste with ad-
        justment of pH to 5-5-
        Mixing aerated raw waste
        with presettled super-
        natant Indicated 93t color
        removal.
 52     Continuous flow with lime          (4|)
        concentrations of I.490
        mg/l.

 49     Fill and draw with lime            (41)
        concentrations of 1,700
        mg/l.
 57     Adjustment of pH with beam-        (37)
        house liquors.  Overflow
        rate, 25.9 cu m/day/sq m
        (635 gal/day/sq ft)
High    Ferric chloride added at           06}
        concentrations of 2,000-
        5.000 mg/l

        Full-scale operation on beam-      (32)
        house wastes with anionlc
        polymer addition of 10 mg/l.
        Overflow rates at 65 cu
        m/day/sq m (1,600 gpd/sq ft)
   Equalization, 2-stage
   Carbonatlon, Coagulatitu
   Sedimentation
Carbonation,  Coagulation,
Sedimentation
                                                                      13,400     I,140
                                 Iron Salts   6,190
                                                                     A pi lot Study wi th
                                                                     equalization of flow,
                                                                     carbonation with flue  yd-.
                                                                     to 6.4-6.7 pH.  Coagulation
                                                                     with  lime followed by  3*
                                                                     hour  sedimentation.
                                                                     Effluent  is then subjected
                                                                     to a  second stage process
                                                                     similar to the first.
                                                                     A 99*  reduction In color
                                                                     resulted.
                                                                     A pilot study with carbona-
                                                                     tion of beamhouse wastes  to
                                                                     a pH of 6.0 followed by coagu-

                                                                     (300-500 mg/l).  Treatment
                                                                     produced a floe which  settled
                                                                     quickly.
                                                                                                                                      (19)
  *  Oxygen demand.
  '  Order-of-magnitude •
                                                             65

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In  general,  polymer  addition  produced a rapid formation of floe min-
imizing the need for flocculating  equipment.   Without  pH  adjustment,
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
ty 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  tcxicity 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 cf 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  che-mical  precipitation  and  coagulation  with  calcium
hydroxide  and  an anionic polymer  (20).  The efficiency is dependent on
pH control arcund 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_-_Carbonati.on  -  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


                                   66

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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.

Stack  gas  containing  8 to 12 percent carbon dioxide obtained frcir, 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 #3 indicate high reductions in suspended solids,
BOD,   and  total  alkalinity.   Estimated  flows  from  the  cattlehide
vegetable tannery were 1,700 cu m/day (O.U5  mg/1).   Primary  clarifier
overflow  rates  were  about  20. U  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.  (Sulf uric acid is also used to assist pH  control) .
The following removals were indicated (21) :

                                 Primary    Primary
                                            Effluent   % Removal
                                   mg/1       mg/1

   Suspended Solids                2,110       100          95

   EOES                            1,660       270          81

   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.

ES_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 ccntrol system.

§iyd^§_fi5I3^1il23_3Ii^_2i§E2§Sl ~ 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.
                                  67

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Seme attempts have been  made  to  dewater  sludges  prior  to  ultimate
disposal  with  varying  success.   The three principal dewateririg tech-
niques include centrifuges, vacuum  filters,  and  pressure  filtration.
The  centrifuges  have  appeared  to  meet with less success than vacuum
filters or pressure filters.

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.

deducing the moisture content of sludge by spreading on drying beds  has
also  been successful in some areas.  This is particularly attractive tc
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 iraterial 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 hexavalerit
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  dev«at.ering  in  mechanical equipment, sludge is normally con-
ditioned by use of ferric salts and lime or polymers or a combination of
these.  The quantity and typ6 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.
                                  68

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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 cf potential toxic or organic materials 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 ^Requirements - Based on an appraisal of
needs and the performance of previously described operating  facilities,
the following processes are included in evaluating preliminary treatment
requirements:
    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.
                                  69

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Secondary _Biglcgical_Treatment

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

    Equalization   Detention:  24 hours at design flow

    Primary Settling    Overflow rates  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 lb/sq ft/hr)

Major __ Reduction __ o£_BO_D5_and_Su^gended_Sglids - Major reduction of BODb
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
rray 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  sclids
removalo    Numerous   biological   treatment  schemes  are,  therefore,
feasible.  Selection of an alternative biolcgical  treatment  system  is
influenced  by waste water constituents, required efficiencies ,? clirratic
conditions,  land   requirements,   operational   characteristics,   and
economics .
Combined __ MujiicjijDal-Tannery. __ S£§SilD^Di __ Sy_s>tems  " Combined treatment of
tannery and municipal vaste waters predominates in  the  industry  since
most  tanneries  are  located  in  urban  communities  (U) =  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.
                                  70

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                  TABLE 10




COMBINED MUNICIPAL-TANNERY TREATMENT SYSTEMS

cu m/day X
(mgd)
Primary
sedimentation, (0.58)
chlorinatlon,
vacuum fl Itratlon


Trickling Filter
Trickling filter IS
sedimentation



sludge digestion (9.5)

sludge digestion, grease re- (6.4)
s 1 udge 1 agoon mova 1

sludge drying ' (3.8)
beds

Activated Sludge
separate sludge ' (!.2>
digestion, land
Irrigation of
liquid sludge
Activated sludge. Screening with 6,056 37
separate sludge potential of (1.6)
digestion, land sedimentation
Irrigation of units
liquid sludge
Activated sludge. Lagoon 14,383 4
separate sludge (3-8)
digestion




Activated sludge, Equal Izatlon, (Variable) 4j
sludge dewatering sedimentation.
by centrlfugatlon, carbonation
land disposal
Other
lo-flltratlon 2- 16,276 6
tage oxidation (4.3)
pond, separate
ludge digestion,
agoon sludge
Isposal
rlmary sedlmen- 1.514
atlon, roughing (0.4)
liter, activated
ludge, secondary
edlmentatlon
BOD. Suspended Solids
mg/l mg/l t mg/l mg/l 1


Pennsylvania result of a chemical
sewage, tannery
waste, and filtrate
from vacuum filters.

90 90 (45)
Engineering loadings of I.J-1.7 kg
ft) . No scale deposi-
tion on media. 1007.
sulf Ide removal.
67 86 Sheboygan. Before Initiating (4?)
problems with hair
and hide scraps in
digester.
Wisconsin tnclner tlon discon-
tinued ue to lack of
efflcle cy.
New York operatl g at double
the des gn capacity
tllng basins.

Ontario. detention times for
Canada each basin are 7 hours.


360 600 ' Barrle, Plant completed in (47)
Ontario. 1965 with capacity
Canada of 13.626 cu m/day
(3.6 mgd).

175 18 90 Columbus. Tannery ovt of oper- (4?)
Indiana atlon since 1962.
Treatment plant experi-
enced operational
problems with con-
mlnutors. dlffusers.
and digesters.
32 90 200 75 South Paris, Pilot operation. (23)
Kaine



242 9 96 325 31 90 Napa, Flow from two tanner- (47)
California les. Chrome reduced
from 6.1 to 0.8 mg/l.
Digester gas 0.585 cu
m/kg (9.5 cu ft/lb)
volatile matter added.
82-99 66-78 GloversvIIle, Prototype operation. (IN)
New Vork visual Indication of
highly effectivn
color removal.
                 71

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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 (#12), 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  cf  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
BOD£ and suspended solids were required to  meet  stream  classification
standards.  The following full-scale unit processes, listed in the crder
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  flews  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 nr,  (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.
                                  72

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Pilot  tests  indicate  that  carbonation  after equalization provides a
rapid absorption of carbon dioxide  (C02) gas.   A  contact  time  of  20
minutes  was sufficient for flue gas carbonation.  The 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 Ih
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 BOD5 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/l,000
cu m  (70 to 200 Ib BOD5/day/1,000 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 BOD5 removals ranged between
80 to 90 percent.


                                  73

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

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 sclids.

On~Site	Treatment_2_Trickling_Filter_Sy_stems - 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 tc
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 (13), 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) :
                                  74

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                            Influent to     Effluent from
                         Trickling_Filter   	Clarifier	
                               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 flew to the filter was approximately 3,785 cu  m/day  (1  mgd),  in-
cluding  a  50 percent recycle of the secondary clarifier effluent.  The
EOC5 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 charac-
teristics of the suspended material and  the  relatively  high  overflew
rate  of  37.6 cu m/day/sq m  (800 gpd/sq ft) in the secondary clarifier.
Eased 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_La2Oon_Sy_stems - 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


                                  75

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efficiencies consistently.  A reassessment of unit  functions  and  more
operative control may te required.
                                  76

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           TABLE  11


TRICKLING FILTER SYSTEMS

             BODj
Carbonation,  primary
  sedimentation,
  trickling filter,
  final sedimentation

Primary coagulation,
  sedimentation,
  trickling fiIter,
  final sedimentation

Dilution,  primary  sedi-
  mentation,  trickling
  filter,  final sedi-
  mentation

Dilution,  primary  sedi-
  mentation,  trickling
  filter,  final sedi-
  mentation
    900
    821
           30-80
56
A8
                    Removal
                    85-95
          80
                                   Remarks              Re fe re nee
                  Indicate 100 per-           (
-------
aoo
Total 5
cu in/day mg/f ng/Y
(«9
Screening. platr, 719 1.800 100
sedimentation (0.19)
Ugoons, aerated
1*90001, final
sedimentation
lagoons
Sedimentation «,5fiO 400 190
lagoons, aerated (1.21)
lagoon, final
sedliwntatlon
lagoon, lagoon
sludge disposal
Scree Ing. plain 2.309 2.250 815
coa ulatlon sedf-
men ation,
«r ted lagoons
sed mentation. {O.Ofc)
fin 1 sedlnn-
TABLE 12
AEROBIC LAGOON SYSTEMS
Suspended Solids Total Nitrogen
* mg/1 mg/1 t mg/1 mg/1 X
95 Hiddlesboro Cattle, Separate screen- (10)
Tanning Co., save-pulp. Ing and tedi-
nidtflesboro, chrome- mentation of tan
Kentucky vegetable and beamhouse
1 iquors prior to
aeration.
5) 5" " 8' =,... js:- J"'^.::2' (!"
Bolivar. chrome sample.
Tennessee .
64 1,500 725 52 Virginia Cattle, Employ the lurl- (10)
Luray, vegetable- effluent vege-
Vlrginia chrome table tanning.
Bros., Inc., save, waste streams
Pennsylvania tlon. Aeration
detention time
20 days.
78

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In  a  prototype  study  at  a  tannery  in  Virginia  (#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 prorated effluent
characteristics, the following removals were observed:
                                                .      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  leading 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
BOD 5/day/ 1,000  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
BOD5 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.
                                                     tems - 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:


                                   79

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methane,  hydrogen  sulfide, and ammonia which are readily available for
utilization or 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 tc prevent escape of anaerobic products which create odors such
as hydrogen sulfide.

Stratified lagoons are generally deep, 3.7-U.6 m (12-15 ft), but shallow
depths, 1.2-1.5 m  (U-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  treatiny
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) .
                                   80

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                                                               TABLE   13
                                              AEROBIC-ANAEROBIC   SYSTEMS
    System            Flow    Inf.  Eff.   Removal   Inf.   Ef f.   Removal   Inf.   Ef f.   Removal    Tannery       Process       Remarks        Referenci
    	         cu at/day   SgTT  JSgTT     I     S^TT  roJTT     (     SgTT  SgTT    *	
                    (*gd)

Screening, aerobic-    2,2?)    673    53     92    339    *>&     86                       Pownal        Cattle-      Nitrification-        (10)
  anaerobic I-stage    (0.6)                                                               Tanning Co.,   sheep save,  dsnltrlftcatlon
  lagoons                                                                                North Pownal.  chrome      Is not Indicated.
                                                                                       Vermont


Screening, plain       1,363   2,300   600*     Ik   3,000   165*     95                       Howes         Cattle,      Primary j,«ttl Ing      (10)
  sedimentation,      (0.36)                                                               Leather Co.,   save, vege-  of beamhouse
  aerobic-anaerobic                                                                       Curwensvi1le,  table       flows prior to
  lagoon, final                                                                           Pennsylvania              mixing with
  sedimentation,                                                                                                  spent tans.
  chlorlnation
        ^Arithmetic average.
                                                               81

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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  flews  were  varied to impart various loadings on the system.  In
the initial phase the following removals were experienced:
                               !Qf luent    Effluent        ..
                                 mg/1        mg/1         %

    EOD5                        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~BOB5/day/l,000 cu m  (8.7 Ib BOD5/ day/1, 000 cu ft).  Temperatures
ranged from 5°C (U1°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 202 ku
BOD5/day/l,000 cu m  (17.4 Ib BOD5/day/l ,000 cu ft) did riot significantly
reduce  the  efficiency.   Investigators  report  loadings  of  aerobic-
anaerobic  systems  may range from 130 to 243 kg BOD5/day/ 1,000 cu m  (R
to 15 Ib BOD5/day/l,000 cu ft) for 80 percent organic removals  (29)  (30)
(31)  (35)  (36  (50).  However, loadings above 81 kg BOD5/day/l,000  cu   m
(5  Ib  BCD5/day/l, 000  cu  ft)  are  impractical  because oE 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


                                  82

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percent suspended solids removals.  Later, a  lagoon  with  a  three-day
detention  time  was  found  to  produce  equivalent  removals  and  was
incorporated into the full-scale system.

Subsequent treatment of the clarified teamhouse waste water in  aerobic-
anaerobic  lagoons  created severe odor problems.  The problem was elim-
inated when spent vegetable  tanning  solution  was  combined  with  the
beamhouse  fractions  for  treatment.   Removals  observed  through  the
biological system were as follows  (32) :
                                                 Affluent   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/1, 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  con-
trary  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.  Def earning
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.

Nitrif ication-denitrif ication  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
                                  83

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absence of oxygen, anaerobic  bacteria  reduce  the  nitrate  liberating
nitrogen gas as a respiration product.

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
nitrificaticn-denitrification.    Specific   applications  will  require
extensive pilct  studies  for  evaluation  of  design  parameters,  par-
ticularly 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  (SRT)  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 preceded 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  charac-
teristics,  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.
                                  84

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                                                                 TABLE   ll»
                                               ACTIVATED  SLUDGE   SYSTEMS
                      Total
                                                       Suspended  Solids
                                                                             Total  Nitrogen
 :rcenlng, plain
   sedimentation,
   activated sludge,
   final sedimen-
   tation, sludge
   dewaterlng with
   pressure filters,
   land disposal
                    cu in/day   mg/1
                      («ngd)

                      3,765   1,36*1
                       (0
                              FnT.'TfTT  Removal   IfTfT?fT7   Rerova
                                              76   2,966    325
                                                                                TfTT  Removal
                                                                                SgTT  ~~T^
      S. B. Foot
      Tanning Co.,
      Red Wing,
                               Low removals since
                               biological units
                               not In full opera-
                               tion.
 ireenlng, plain           61
   sedimentation,      (0.016)
   activated sludge,
   final sadlmen-
   Utlon
                                              93   3,135    223
27   Cal dwell
     Lace
                                                                                                             Cattle,
                                                                                                             pulp, ct
                               Primary and sect
                               ary clarifier  ov
                                                                                                                         10.5 cu m/day/sq m
                                                                                                                         (230 and 2$8 gpd/sq
                                                                                                                         ft), respectively.
                                                                                                                         Aeration time 1.6
                                                                                                                         days.
Activated sludge,
   final clari-
                                              80   2,400    190
37   Moench
     Tanning Co.,
     Gowanda,
                                                                                                                         biological unit 3.712
                                                                                                                         kg/day/t,000  cu m (229
                                                                                                                         tb 6005/day/l,000 cu
                                                                                                                         ft).  Final clarlfler
                                                                                                                         overflow rate 20.k-
                                                                                                                         2
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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 (U60 gpd/sq ft) under present conditions.  A potential  of
tcur  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  ot  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 in (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  m
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:
                                  86

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                                      iQf luent   Effluent   Removal
                                        mg/1       mg/1        %

BOD5                                    1,437        96        93

Suspended Solids                        3,135       223        93

COD                                     4,016       481        88

Sulfide  (as S)                            7.9         0       100

Total Kjeldahl Nitrogen (as N)            490       322        34

Organic Nitrogen  (as N)                   328       175        47

Ammonia Nitrogen  (as N)                   162       147         9

Nitrite  (as N)                            0.1        34*      	

Nitrate  (as N)                            0.1       0.4       	

Alkalinity  (as CaC03)                     516       141        73

*Grab Sample

The  BOD5 cf 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
EOD5/day/1,000  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 frcm save hair beamhouse,  chrome  tan,  and
finishing  operations.   Total waste water from these processes is about
1,514 cu  in/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/1,000 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).
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An organic removal of 80 percent produced an effluent BOD5 concentration
of 343 mg/1.  Suspended solids reductions of 92  percent  are  reported.
Effluent suspended solids concentrations 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  whicn  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  (lb)
BOD5  applied,  or  0.55 kg  (lb) dry solids/kg (lb) BOD5 without primary
sedimentation.  The organic lead on the ditch varied from  23.5-48.2  kg
EOD5/day  (51.8 to 106.2 lb BOD5/day).  The oxygen supplied was about 1.5
times  the average BOD5 load, however.  This was not sufficient for peak


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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):

                                Presettled
                                _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         	

Tctal Nitrogen (as N)              250         60-150       40-76

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

*Order-of-magnitude

High removals of BOD5  (98 percent)  and COD (88 percent)   result  at  the
lew  F/M  ratio.  Sulfides were completely oxidized with brush aeration.
Precipitaticn of chrome was highly effective with  concentrations below 1
mg/1 observed in the effluent.  Nitrification was  sporadic,  with  some
denitrificaticn  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 pilct or full-scale facilities is non-existent.
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PracticalBiological Systems

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

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 BCD and
SS discharger are 0.4 and 1.1 kg/kkg  (lb/1000 Ib)  respectively.  The BOD
effluent concentration frcm both sampled data and industry  data  is  16
mg/1.   Tannery 54 in sutcategory 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  kq/kkg
lb/1000 Ib) respectively.  Plant 43 in subcateqory 2 utilizes lagoons to
achieve  a  BOD discharge concentration of 38 mg/1 (industry data) cr 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
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
    Aeraticn
    Secondary Settling

    Sludge

    Collection
    Thickening
    Disposal
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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  cr  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
                   BOD5 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 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.

Pp.lish4.Q3 Systems^for_Biological_Treatment. - Consideration has been given
tc unit operations and process techniques which have been used infre-
quently or not at all in tannery waste treatment.   They are as follows:

    1.   Filtration or microscreening of the effluent.
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    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
seme  instances, this has been well over 100 mg/1.  Undoubtedly, seme 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  sclids
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  sclids.
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 con-
taining granular material resulting in the capture of  suspended  solids
in  the  bed.   Eventually,  the  pressure  drop 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 tack 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  bottcnr,  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 fcr longer periods of time.  Influent solids  should
be  limited  to  about  100  mg/1  to  avoid  too  frequent backwashing.
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


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non-biodegradable.  The granular carbon media  provides  an  effectively
large  surface  area  for  adsorption.   Biodegradation  of the captured
material further increases  the  efficiency  of  the  process.   Theriral
regeneration is used to reactivate spent carbon.

Laboratory  analysis  were  made on carbon treatment of waste water from
Tannery f16 (52).  These laboratory tests were preformed 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
(TOC).  The full-scale design is indicated  as  having  a  potential  of
reducing   the   effluent   tc  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 anticipated 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
pilct 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 #14.  Color  was
effectively removed 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  materially  reduce  the  high  content  of  dissolved
inorganic materials such as sodium chloride (NaCl).

The  problem  cf  color  of  tannery  waste  is most pronounced in those
systems using vegetable tanning.   Color  is  an  optical  effect.   The
measured  magnitude  of  color  is  net  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  stan-
dards.   Therefore,  several arbitrary approaches have been developed tc
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.
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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^Fgrms^gf_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.

    U.   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
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 froir 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
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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 keen used for nitrogen removal:

    1.   Coagulation, flocculation, and settling.

    2.   Ammonia stripping.

    3.   Ammonia ion exchange.

    4.   Chlorination.

    5.   Eiological nitrification-denitrification.

Coagulation, flocculation and settling is effective in  partial  removal
of  soluble  and colloidal protein matter.  To optimize this process, pH
must te reduced to the  isoelectric  point  °f  tne  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  (UOO cu ft/gal) (56).

Difficulties encountered in municipal waste  treatment  include  serious
calcium  carbonate  scaling  and  the reduced efficiency at low air tem-
peratures.  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.

Ammonia vcan  also  be removed from waste water by an ion exchange media
which is a natural zeolite, clinoptilclite.  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.
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Chlcrination  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
2it£2§2fQ2Q§§  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 frcm
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  organises.
Equipment  required is a nitrification basin followed by a clarification
tank.  Optimum pH is 6.5 to 7.5.  Organisms using a  source  of  organic
carbon convert the nitrate to nitrogen gas.  Since the waste is norrrally
lacking  in  organic carbon, methanol is added to provide such a source.
Fate 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 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
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         pH:       8.a

         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 NC3-N/day/l,000 cu ft)

*Mixed Liquor Volitile Suspended Solids

Major Remoyal^of All_Vjaste 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  frpm 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:

    1.   Freezing.

    2.   Evaporation.

    3.   Electrodialysis.

    U.   Ion exchange.
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    5.    Beverse 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 dees 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.
             ~  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 scil
or sealant imposes severe restrictions on the  geographic  location  for
such lagocns.

Multiple  effect  evaporators  have  been  used in industry for many ap-
plications.  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) cf steam used.
                ~ Electrodialysis is a demonstrated process for  reiroval
of  dissolved solids in brackish waters.  Basically, the electrodialysis
cell consists of alternate cationic and anionic permeable membrances  in
a  stack  alternately  charged  by  electrodes 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


                                   98

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concentrated   waste   trine   collects   in   others.   For  waters  of
concentration less than 10,000 mg/lr 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  fcr
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 ex-
changer must te 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 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 meirtrane
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  cf  the  system  is  dependent upon
selection and maintenance of the membrane.   Reverse  osmosis  has  been
effective fcr the treatment of pulp and the paper mill wastes, acid mine
drainage, and municipal supplies with a high mineral content.
                                  99

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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 inq/1.  Th^
permeate contained 55 mg/1  dissolved  solids  producing  a  05  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 siirilar concentration are amenable to reverse
osmosis.   At  these  dissolved  solids  concentrations,   the   osrrotic
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.  Thp
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 cf dissolved solids  (64) .

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
                                  100

-------
methods for handling trines.  A few of the techniques  investigated  are
as follows:

    1.   Various types of solvent extration.

    2.   Electrodialysis.

    3.   Solar evaporation.

    U.   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  fcr
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 trines requires comprehensive geologic study and
field testing of potential disposal  zones  to  assess  the  safety  and
effectiveness  of  underground  strata.  Several potential dangers exist
for such disposal including pollution of fresh  water  supplies  through
encroachment  and  disturbance  to  underground strata.  Injection wells


                                  101

-------
normally require detailed investigations to ensure that liquids  in  the
underground  strata are compatible both physically and chemically tc the
waste trines 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 cosrs 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 fcrine  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 frcm ether 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.
                                  102

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                              SECTION VIII

              COST, ENERGY, AND NON-WATER QUALITY ASPECTS


Cost  and	Induction	Benefits	of	Alternative	Treatment  and ...control
Technologies	

A detailed economic analysis showing the impact of treatment and control
technologies  upon  the six sutcategories within the leather tanning and
finishing industry is given in Supplement  A  of  this  document.   Five
alternative  treatment  methods have been considered for Sufccategories 1
to 6.  For the six sutcategories, 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.
                                  103

-------
     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
     irarked  impact  on the cost cf 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.
2-    E§E£§2i5ti2Q_§D^_Q2§i_2f_Q^£li3.i_llDi§I§st)_ -  It  was  assumed
     that  the  annual  interest  costs (cost of capital)  and depre-
     ciation would be  constant  over  the  life  of  the  treatment
     facilities.   A principal repayment period of 20 years was used.
     Ccsts  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 tc 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.

3«    lDsurance_and_Taxes - An annual cost of 1 1/2  percent  of  the
     initial  investment  was  used  for  insurance and taxes on the
     waste treatment plant.
                                 bor  ~  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.
                              104

-------
     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  on  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 ($20.00 per ton)

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

          Ferric Chloride - $8.80 per 100 kilograms ($U.OO  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.   Enejrgy. - 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
     pcwer 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).
                              105

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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 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
$/1000 kg hides/yr
($/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
(1) All Costs Based on August

636
1,400

88
950

- 33
4

$361.5

47.3
21.5

$88.6
0.084
0.008

0.640

1.25
1971 Price

636
1,400

88
950

33
4

$683.8 $1

89.5
40.7

$167.6
0.159
0.015

0.640

2.3
Level s
(2) Raw Material Conversion Factor to Finished Produc




636
1,400

88
950

33
4

,073.1

140.6
63.9

$262.9
0.249
0.023

0.640

3.6

t = 0.68


636
1,400

88
950

33
4

$2,473.1

323.8
147.2

$718.9
0.681
0.063

0.640

9.8

sq Ct
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

                                   106

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                               TABLE 16

                    WASTE WATER TREATMENT COST (1)
                         FOR SUBCATEGORY 2

                                         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
$/1000 kg hides/yr
($/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

$886.7

85.6
38.9

$217.2
0.151
0.014

863
1,900
120
1,290

50
6

$1,342.2

129.6
58.9

$328.8
0.228
0.021

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       2.2        3.3       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

                                   107

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                              TABLE 17

                    WASTE WATER TREATMENT COSTS (1)
                         FOR SUBCATEGORY 3

                                         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)

431
950

51
550

42
5

431
950

51
550

42
5

431
950

51
550

42
5

431
950

51
550

42
5
ESTIMATED INVESTMENT COST(3)
  ($1000)                     $2.84.0      $528.3     $821.1   $2,828.1

ESTIMATED ANNUAL INVESTMENT
   $/1000 kg hides /yr          54.8       101.9      158.4      545.6
  ($/1000 Ib hides /yr)         24.9        46.3       72.0      248.0

ESTIMATED ANNUAL COST
  ($1000)                     $ 69.6      $129.4     $201.2   $  590.2
   $/sq m hide                   0.114       0.211      0.329      0.964
  ($/sq ft hide)        .         0.010       0.020      0.030      0.089

TYPICAL FINISHED PRODUCT
   Price ($/sq ft hide)          0.780       0.780      0.780      0.780

TREATMENT COST AS PERCENT
   OF PRODUCT PRICE              1.3         2.6        3.8        11.4


(1) All Costs Based on August 1971 Price Levels

(2) Raw Material Conversion Factor to Finished Product =  0.58 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

                                    108

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                              TABLE 18

                   WASTE WATER TREATMENT COSTS (1)
                        FOR SUBCATEGORY 4

                                        ALTERNATIVE (4)
PARAMETER/COST                  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)

341
750
84
900

17
2
$177.3

43.3
19.7

$43.5
0.043
0.004

341
750
84
900

17
2
$314.3

76.8
34.9

$76.9
0.076
0.007

341
750
84
900

17
2
$466.6

114.0
51.8

$114.3
0.113
0.010

341
750
84
900

17
2
$986.6

241.2
109.6

$267.3
0.265
0.025
TYPICAL FINISHED PRODUCT
   Price ($/sq ft hide)          0.610      0.610      0.610      0.610

TREATMENT COST AS PERCENT
   OF PRODUCT PRICE              0.7        1.1        1.6        4.1


(1) All Costs Based on August 1971 Price Levels

(2) Raw Material Conversion Factor to Finished Product = 1.2 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

                                    109

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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
($71000 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
$388.7

219.3
99.7

$95.2
0.120
0.011

148
325
66
715

62.5
7.5
$560.4

316.1
143.7

$137.2
0.173
0.016

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       2.3         3.3        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

                                    110

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                               TABLE 20

                    WASTE WATER TREATMENT COSTS (1)
                         FOR SUBCATEGORY 6

                                         ALTERNATIVE (4)
PARAMETER/COST	B	C	D
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 hldes/yr
($71000 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

$408.4

68.0
30.9

$100.0
0.119
0.011
499
1,100

70
750

17
2

$692.4

115.5
52.5

$169.6
0.202
0.019
499
1,100

70
750

17
2

$1,374.4

229.0
104.1

5408.6
0.486
0.045
TYPICAL FINISHED PRODUCT
   Price ($/sq ft hide)           0.31       0.31       0.31       0.31

TREATMENT COST AS PERCENT
   OF PRODUCT PRICE               2.3        3.5        6.1       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


                                  111

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Effluent Rgduction -	Subcategory	1  -  The  following  discussion  for
Sutcategory  1  deals  with  the  sensitivity of effluent reduction with
respect to costs for Subcategory 1.  This subcategory represents a  sub-
stantially  larger  segment  cf the industry than any other subcategory.
Costs are based on an average size  tannery  in  this  subcategory  pro-
cessing 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 BOD5/1,000
kg (95 Ib BOD5/1,000 Ib) of hide.  This  represents  14  times  that  of
normal domestic sewage.

Costs - None.

Reduction Benefits - None.

Alternatiye^B_^Preliminary Treatment and chrome Removal

This   alternative   includes   in-prccess  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  47  kg  BOD5/1,000  kg  (47  Ib
EOD5/1,000  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
tor  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 2.7 kg BOD5/1,000 kg  (2.7 Ib BOD5/1,000 Ib)
cf hide processed  for  the  average  Subcategory  1  tannery  treatment
facility.

Costs  - Alternative C represents a total capital investment of $683,800
and an annual cost of $167,600.  These costs represent  an  increase  of
$322,000  in  capital  costs  and  almost  $80,000  in annual costs over
Alternative B.
                                  112

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Reduction Benefits - Alternative C represents a reduction in BOD5 of  94
percent  over Alternative B.  This represents a total reduction in plant
BOD5 of 97 percent.

Alternative 2 ~ Alternative C Plus Sulfide  Removal^  Nitrification  and
Qenitrificaticn, and Filtration

Alternative  D  includes  the treatment units for Alternative C with the
addition of a sulfide  removal  process,  nitrification  basin,  covered
denitrificaticn  basin,  sulfide  removal  process, aeration flume,and a
graded media filter.   The  effluent  from  the  average  Subcategory  1
tannery  treatment  facility  would  be  1.35  kg EOD5/1,000 kg (1.35 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
$1,073,100 and an annual cost of $262,900.   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 50 percent over Alternative C.  Total reduction  in
BOD5  would  be  about 98.5 percent.  Sulfide and nitrogen removals also
result.

Alternative E - Alternative D Plus Reverse Osmosis^ and Evagoration

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 $1,400,000 more than
Alternative D and annual costs are estimated to be  over  $450,000  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
BOD5  load  of  100 percent.  All other constituents would be completely
removed.
                                  113

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Impact _o f _W as t e_Tr eatnj en t_Al t e rnat i ye s_on_Fi n i shed_Prgd uc t _P r ice

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 1.1 to 3.5 percent for
various subcategories.  For only one  subcategory  is  the  increase  in
excess of 2.6 percent.


For  the  best available control technology economically achievable, the
estimated increase of final product ccst ranges from 0.5 to 2.6  percent
for  various  subcategories and only one subcategory is in excess of 1.3
percent.


The overall ccst of both best practicable  and  best  available  control
technology  is estimated to increase final product costs from 1.6 tc 6.1
percent for various subcategories and only one subcategory is in  excess
of 3.8 percent.

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  $28  million  for  best  practicable
ccntrol  technology  currently available limitations  (see Table 21), and
$42.5 million or an  increment  of  $14.5  million  for  best  available
control technology economically achievable limitations  (see Table 22).

The  1977  investment  consists  of $28.0 million for processors outside
municipal systems.  including about $7 million each for subcategories   1
and  3,  about 6 million each for subcategories 2 and 5 and $1.4 million
for subcategory 4.  Distribution of 1983 costs is similar.

It is estimated that the current in-place treatment system investment is
$11 million.  No credit has been calculated for this in-place  treatment
in Tables 15-20 or Tables 21-22.
                                  114

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                                       TABLE 21

                           ESTIMATED  INDUSTRY INVESTMENT (1)
                          TO MEET BPCTCA EFFLUENT LIMITATIONS
SUBCATEGORY

PRODUCTION
10°kg/yr
(10°lb/yr)
BPCTCA INVESTMENT
$71000 kg/yr($/1000 Ib/yr) PERCENT(2) INVESTMENT
AFFECTED
($1000)(3)
1
2
3
4
5
6
305
149
114
66
69
18.9
(672)
(328)
(252)
(145)
(152)
(41.7)
18
17
21
15
45
14
.5
.7
.0
.8
.3
.0
(40
(38
(46
(34
(99
(30
•7)
.9)
.3)
.9)
.7)
.9)
26
46
62
27
42
0
$7
$5
$7
$1
$6

,100
,900
,200
,400
,400
-
                                                TOTAL INDUSTRY COST
$28,000
(1)  All  costs  based  on August 1971 price levels

(2)  Percent  of subcategory production discharging
    directly to receiving waters

(3)  Assumes  no in-place treatment capital

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                                       TABLE 22

                           ESTIMATED INDUSTRY INVESTMENT  (1)
                          TO MEET BACTEA EFFLUENT LIMITATIONS
SUBCATEGORY
1
2
3
4
5
6
PRODUCTION.
10°kg/yr(10&lb/yr)
305(672)
149(328)
114(252)
66(145)
69(152)
18.9(41.7)
BACTEA INVESTMENT
$71000 kg/yr($1000 Ib/yr)
(29.0(63.9)
26.7(58.9)
32.7(72.0)
23.5(51.8)
65.2(143.7)
23.8(52.5)
TOTAL INDUSTRY
(INCREMENTAL

PERCENT(2)
AFFECTED
26
46
62
27
42
0
COST
COST)

INVESTMENT
($1000) (3)
$11,200
$ 8,900
$11,200
$ 2,000
$ 9,200
—
$42,500
($14,500)
(1)  All costs based on August 1971 price levels

(2)  Percent of subcategory production discharging directly
    to receiving waters

(3)  Assumes no in-place treatment capital

-------
Related Energy^Reguireinents_gf _Alternatiye Treatment and Control
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 7.256 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 7.2% 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


                                   117

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(7,200  Btu/lb)   of  hide  in  the  form  of  steam.  This represents an
increase of approximately 107 percent over the energy requirements of an
average tannery (Sufccategory 1)  without treatment facilities.

Ngnff§tg£-2uglity Aspect of Alternative Treatment_and_Cgntrgl_Technglcgy


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 amironia 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 liguid waste treatment for disposal.

In addition tc process sources, tannery boilers can be a source  of  air
pollution.   With  proper  design  and  maintenance  of gas and oilfired
bcilers, there should be no emission problems.  However, with coal-fired
boilers, tly 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.

Bciler flue gas contains sulfur dioxide when  the  fuel  burned  in  the
bcilers  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.

§2ii^_Waste_Disp_osal - Solid waste from tanneries and tannery wastewater
treatment plants includes the following:

    1.   Fleshings.
                                  118

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    2.   Hair.

    3.   Paw hide trimmings.

    4.   Tanned hide trimmings.

    5.   Sanding and buffing dust.

    6.   Lime sludge.

    7.   Chrome sludge.

    8.   Eiological 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  ty  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  E  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 grcundwater 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  tc  prevent  the  obstruction  of natural drainage channels,


                                  119

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location to avoid flood waters, and the consideration of  possible  fire
hazards.
                                   120

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                               SECTION IX

        BEST PRACTICABLE CONTFOL 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 ccntrol 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 processes, but includes
control technologies within the  process  itself  when  the  latter  are
considered to be normal practice within an industry.

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


                                   121

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the engineering and economic practicability of  the  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 sutcategory (see Table 7).  BOD5 and SS calculations
are  based  on  an effluent concentration of 50 mg/1; total chromium and
oil and grease are based on 1 mg/1  and  10  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
EOD5 and suspended solids.
                                  122

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                         TABLE 23

          BEST PRACTICABLE EFFLUENT LIMITATIONS
                      (July 1, 1977)
                                    SUBCATEGORY
PARAMETER(l)              kg/1000 kg hide (lb/1000 Ib hide)

BOD.5
TOTAL CHROMIUM
OIL & GREASE
SS

2
0
0
3
1
.7
.05
.53
.0

3
0
0
3
2
.2
.06
.63
.5

2
0
0
2
3
.5
.05
.50
.8
4
1.
0.
0.
1.

0
02
24
1

3
0
0
3
5
.2
.06
.63
.5
6
1.4
0.03
0.34
1.5
(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
                                 123

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Best__Practicable Control Technology Currently^Av ail able

The best practicable control  technology  currently  available  for  the
leather 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 BOD^ 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 treatment: operations.
Other  industries such as the meat packing industry currently treat high
strength wastes 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 EPCTCA is not
achieved  consistently,  technology and performance information has been
transferred from other industry treatment operations.

    Complgte 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 tc 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) .

Eationale  for  Selection  of  the  Best  Practicable  control Technology
          Available
Total_Cost  of .Achieving JEf fluent .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


                                  124

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an  estimated  $28  million   (August, 1971, price levels) 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 1.1 to 3.5 percent
for the various subcategories.  For only one subcategory is the increase
in excess of 2.6 percent.

Aqe^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 seme  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 50 mg/1, the following
plants achieve 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  50  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
cooperaticn frcm 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.

Nojiw^ter^uality__Enyironmental_Imp_act - 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


                                   125

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from  treatment  facilities.   Most of 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 sludqe 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.
                                  126

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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.

    4.   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
                                   127

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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 character-
ized by some 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.  BOD5
and SS 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 24 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.
                                   128

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                           TABLE 24

             BEST AVAILABLE EFFLUENT LIMITATIONS
                         (July 1, 1983)
                                       SUBCATEGORY
PARAMETER(l)                 kg/1000 kg hide (lb/1000 Ib hide)
                      1      2      3      A      5      6
BOD5.                 1.35   1.60   1.25   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

SS                   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
                              129

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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 tc
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 ether
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 r_SubcategQries__l_tQ_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).

         3.  Fine screening.

         <4.  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 denitrification;
             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.
                                   130

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Rationale for Selection of the gest Available^ Technology
Economical l_Y_Achievable


Total Cgst^gf Achieying_Eff luent_Reduction -  As  presented  in  Section
VIII,  to  meet  the  best  available  control  technology  economically
achievable effluent  limitations,  tanneries  discharging  to  receiving
waters  wculd  have  to invest an estimated $42.5 million  (August, 1971,
price levels).  This $M2.5 million includes the $28  million  investment
required  to  meet  the  best  practicable  control technology currently
available guidelines and assumes no  in-place  treatment  systems.   The
incremental  cost  is  $14.5 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  0.5  and
2.6   percent   for   various   industrial  classifications.   Only  one
subcategory is in excess of 1.3 percent.

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 __ lniEi2y.§^  ~ Differences in processes within the industry have
been accounted for in establishing the effluent limitations.

En3ineering_Asgects_of_Contrgl_Technigues - The best  available  control
technology  economically  achievable  appears achievable considering the
developmental work being done on sulfide  oxidation  and  nitrif ication-
denitrif icaticn.  There are several technical questions which need to be
resolved prior to initiation of full-scale nitrif ication-denitrif icat ion
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  nitrif ication-denitrif ication  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 tc 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.
                                  131

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Nonwater_QualitY_Envirgnmental_Irngact - The impact upon the  land  as  a
result  of  liquid  waste treatment is the same as outlined for the best
practicable control technology currently available in Section IX.
                                   132

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

    6.   Recovery of pollutants as by-products.


Im]groyed_ In-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  procedures should


                                  133

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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  ot  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.

N6w_Source_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.


Pretreatment_Reguiremgnts


Three  constituents  of  the  waste water from plants within the leather
tanning and finishing industry have been  found  which  would  interfere
with,  pass  through,  cr 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.
                                  134

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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.
                                   135

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                              SECTION XIII

                               REFERENCES

 1. "Industrial Waste - Profile No. 7, Leather Tanning and  Finish-
    ing, " The_Cost_of_Clean_Water_-_Volume_IiJ[,  Federal  Water  Quality
    Administration Report, 1967.

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

 3. 0'Flaherty, F., Roddy, w. T., and Lollar, R. M. , Chem_istry__and
    J§£llI10l23Z_21_i£at£££» Volumes I-IV, Reinhold  Publishing Cor-
    poration.

 U. Masselli, Joseph W., Masseli, Nicholas w. , and  Burt'ord, 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^Diyisionx_Procgedings_of the^American^Sgciety^gf
    Civil_Engineers, Volume 95, No. SA5, October,  1969.

 6. Hauck, Raymond A., "Report on Methods of  Chromium Recovery and
    Reuse from Spent Chrome Tan Liquor," Journal_of_the_American
    Leather_Chemists^_Assoc.iation, Volume LXVII, No. 10,
    1972.

 7. Bailey, D. A., and Humphreys, F. E., "The Removal of Sulphide
    from Limeyard Wastes by Aeration," British^Leather Manufac-
    tl}]L§£lji_B§§lM;£h_A§3Ocj.ationx_LJlbj2ra^             xv» No-  1»
    196fi7~

 8. Eye, J. David, and Clement, David P., "Oxidation of  Sulfides
    in  Tannery Waste waters," Journal^pf the_American Leather
    Chemistsl_Association, Volume LXCII, No.  6,  June, 1972.

 9. Williams-Wynn, D. A., "No-Effluent Tannery Processes,"  Journal
    of  the American^Leathgr^Chemists^_A5SOciatign,  Volume LXVIII,
    No. 1, 1973.

10. Data obtained through communication with  tannery firms.

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

12. McKee, Jack Edward, and Wolf, Harold W.,  eds..  Water Quality
    Criteria.  2nd ed., The Resources Agency  of  California, State
    Water Quality Control Board, Publication  No. 3-A 1963.
                               137

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13.  Bailey,  D.  A., Dorrell, J. J., and Robinson, K. S., Journal
    of_the_SgcietY_of_Leather_Tradesl_Chemists, 5J4, 91, 1970.
    Cited in Journal_of_the_American_Leather_Chegiists^_Associa-
    tion, Volume LXVIlT Mo7~9, September, 1972.

14.  Sutherland, R.,  Indu3trill_and_Erigineerincj_ChemistrY, J9,  628,
    19U7.  cited in Reference 11)".

15.  Sproul,  Otis J., Atkins, Peter F., and Woodward, Franklin  E.,
    "Investigations on Physical and Chemical Treatment Methods
    for Cattleskin Tannery Wastes," Journal_Wat'jr_Pollution
    Control.,Federation, Volume 38, No. U, April, 1966.

16.  Kunzel-Mehner, A., Geaundhi_Inar, 66, 300,  19U3.  Cited  in
    Reference 11) .

17.  "Report of the Symposium on Industrial Waste of the Tnnninq
    Industry," Journal_of_the_American_Leather_chemistsl Associ-
    ation, Supplement No. 15, 1970.

18.  Howalt,  W., and Cavett, E. S., Transactions of American  Society
    Ql_Civil_Engineers, 92, 1351,  19287clted~in Reference  11).

19.  Riffenburq, H. B., and Allison, W. W., Industrial_and_En(3Jr
    £!§ er in g_Che m is t r_ y, .33, 801, 19U1.  Cited in Reference 11).

20.  Haqan, Jamas R., and Eye, J. David, and Gunnison, G. C.,
    "Investiqations into the Removal of Color  from Dioloqically
    Treated. Vegetable 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
    Qiyil_Engineers, Volume 98, No. SA1, February, 1972.

23.  The A. C. Lawrence Leather company, Acti^vated_Slud2e_Treat2
    ment_of_Chrome_TjnnerY_Wastes, Federal Water Pollution Control
    Administration, Department of  the Interior, Grant No. WPHD
    133-01-68, Proqram No. 12120,  September, 1969.

2U.  Nemerow, N. L., and Armstronq, R., "Prototype Studies of Com-
    bined Treatment of Wastes from 22 Tanneries and Two Munici-
    palities," Purdue Industrial_Waste^cgnferjgnce_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.
                                138

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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 jthg America n_Leather_Cherni5ts^
    Association, 36, 463, "1941.  Cited~in Reference  U) .
28. "Tannery Effluent. Report to the Members of  the  Effluent Com-
    mission of the International Union of Leather Chemists'
    Societies, " Journal of the_Amer ican_ Leather _Chemists*_ Associ-
    ation. Volume LXVII, No. 10, October, 1972.  Reprinted from
    1972?

29. Parker, Clinton E. , Anae robic- Aerobic Lagoon_Treatment for
    Vegeta ble_Tann in_2_Wa s tes , Federal Water Quality Administra-
    tion, Environmental Protection Aqency, Grant No. WPD-199-01-67,
    Program No. 12120 DIK, December, 1970.

30. Sawyer, C. N. , "New Concepts in Aerated Laqoon  Design and
    by Gloyna, E. F. and Eckenf elder, 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," Adyances_in_Water_2uality_Imgrovement, edited by
    Gloyna, E. F. and Eckenf elder, W, W. , Jr.), U. of Texas Press,
    Austin, 1968.  Cited in Reference 29).

32. Eye, J. David, Treatment of _Sgle_Leather_yegetable 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.

34. Clark, John W. , and Viessman, Warren, Jr.,  "Biological-
    Treatment processes, Activated Sludge," Water_Supply._and
    Po 1 lut i on_cont rol , 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,"
    Proceed! ngg oflthe_16th _Indugtrial_Waste_CQnference , Purdue
    University, U23, 1961.  Cited in~Reference  29).

36. Gates, W. E. , Smith, J. H. , Lin, S., and Ris, C. H., Ill,
    "A Rational Model for the Anaerobic Contact Process,"
    Journal^Water Polluticp Control_FederatiQn , 39, 1951.
    1967.  Cited i~Reference 29).
                                139

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37. "Industrial Waste Survey at Caldwell Lace Leather company,"
    EPA, Office of Operations, Radioloqical and  Industrial  Waste
    Evaluation Section, Cincinnati, Ohio.

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

39. Reuninq, H. T., Sewage Jrfcrks_Journal,  2Q, 525,  1948.  Cited
    in Reference 11).

40. Harnley, John W., Waqner, Frank R.,  and Swope,  H. Gladys,
    "Treatment of Tannery Wastes at the  Griess-Pfleqer Tannery,
    Waukeqan, Illinois," Sewage_Works_Journal, Volume XII,  No. 4,
    July, 1940.

41. Eldridqe, E. F., Michigan_Rngineering_Exgeriment_Station
    Bulletin, &1* 32» November," 19397  Cited  In~Reference'Il) .

42. Fales, A.L., Industrial_and_£ngineerin3_Chemistry_, _2J»  216
    1929.  Cited by Reference 11).

43. Sproul, Otis J., and Hunter, Robert  E., "Appendix A,  Indus-
    trial Waste Treatment Investiqations,  Prime  Tanninq Company
    and Berwick Sewer District Activated Sludqe  Pilot Plant,
    Berwick, Maine," Berwick^Sfewer_DistrictA_Preliminary^Design
    Re£grtA_Pol_luticn_Control_SYStem, Edward  C.  Jordan Co.,  Inc.,
    Portland - Presque Isle, Maine, 1967.

44. Haseltine, T. R., "Tannery wastes Treatment  with Sewage-at
    Williamsport, Pennsylvania," Sewaqe_and^Indijstrial.Wastes,
    Volume 30, No.  1, January, 1958.

45. Hartman, B. J., Sewage_and_Industrial_Wastes, ^5, 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-Johnstown,  New York,"
    Purdue_IndustriaJ._Waste_Conf eren^e_Proceedj.ngs,  1966.

48. Wims, F. J., "Treatment of Chrome-Tanning Wastes for  Accept-
    ance by an Activated Sludqe Plant,"  Purdua  Industrial^Waste
    Conf e rence_Proc§edi.ng §, 1963.

49. Maskey, D. F.,  Journaljjof_the_American_Leather_Cherriists^
    Association,  36, 121 1941.  Cited by Reference  11) .
                                 140

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50. Mccarty, P. L., "Anaerobic Treatment of Soluble Wastes,"
    Advances in Water_puality^jmjjrgyement 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
    Waste_Conf_erence_Proceedirigs, 1966.

52. Zanitsch, Roger H. , Laboratory Column Studies for
    Coffin & Richardson Engineers, Hartland Tannery, Hartland,
    Maine, Environmental Engineering Department, Water Management
    Division, Calgon corporation, A Subsidiary of Merch 6 Co., inc.,
    Pittsburgh, Pennsylvania, Report No. C-781, June 16, 1972.

53. Tomlinson, H. D. , Thackston, Edward L., Krenkel, Peter A., and
    McCoy, V. Wayne, Cgm2lete_Treatment_of_TannerY_Wastes, Technical
    Report No. 15, Department of Sanitary and Waste Resources
    Engineering, Vanderbilt University, Nashville, Tennessee,  1968.

54. Tomlinson, H. D., Thackston, E. L., Krenkel, P. A., and
    McCoy, V. W., "Laboratory Studies of Tannery Waste Treatment,"
    Journal of Watgr Ppllutjon Control Federation, Volume 41,
    No. 47 April, 1969.

55. Thackston, Edward L., Secondary, Waste Treatment for
    a Small DiversiJied_TannerY, Office of Research and Monitoring,
    U.S. Environmental Protection Agency, Grant No. WPRD 25-01,
    Project 12120 EFM, April, 1973.

56. Gulp, R. L. and Gulp, G. L., Advanced_Wa^tewater_Treatment.

57. Wild, Harry E., Jr., Sawyer, Clair N., and McMahon,
    Thomas C., "Factors Affecting Nitrification Kinetics,"
    Journal of Water Pollution_Contrgl Federation, Volume 43,
    No, 9, September, 1971.

58. Wild, Harry E., Jr., sawyer, Clair N., and McMahon,
    Thomas C., Nitrification and Denitrifjcation Facilities,
    Environmental Protection Agency Technology Transfer
    Program - Design Seminar for Waste Water Treatment
    Facilities, Kansas City, Missouri, September 8-9, 1971.

59. Dodge, Barnet F,, "Fresh Waters from Saline Waters," Amer-
    ican Scientist , Volume 48, No. 4, December, 1960.  Cited in
    Reference 347.
                                 141

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60. Downing, D. G. , Kunin, R.f and Pollio, F. X. , "Desal Process-
    Economic Ion Exchange System for Treating Brackish and Acid
    Mine Drainage Waters and Sewage Waste Effluents," Chemical
    En2ineering_Prggress_S^m2gs^ium_Seri9S, Volume 64, No. 90,  1968.

61. Wiley, Averill, J., Duhey, George A., and Bansal, I.K.,
    Rgverse^QgmosrigCQnccntration_of Pi lutgr Pulp and Paper
    Effluents, 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, Kycte, Japan.

63. "Rex Chainbelt Inc., The Ecology Division,  Reverse
    gsmosis_Deminerali^atign_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 FQR, March,  1972.

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

65. Burns and Roe, Inc., Dig po sal of Brines Produced in Renovation  of
    MunJ.cij3al_Wastewat er , Federal Water Quality  Administration,
    Department of the Interior, contract No. 1U- 12-492, Program
    No. 17070 DLY, May, 1970.

66. "Patterson, W. L. , and Banker, R.F. , Estimating
    Trej*tment_ Facilities, office of Research and Monitoring,
    Environmental Protection Agency, Contract No.  14-13-462,
    Project No. 17090 DAN, October, 1971.

67. Smith, Robert, and McMichaol, Walter F.,
    Perf or ma nce_ Estimate s^for_Te rt jar y_Wastewat er_ Treat mgnt
    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," Jou^nal_of_Wa^r_Polj.utign_contrgl._Federation, Volume  45,
    No. 2, February, 1973.
70. OiljL_Painti_and_Drug_Rjej20rter, August  2, 1971.
                                  142

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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 £aCO3
The Act is the Federal Water Pollution Control Act Amendments of 1972.

Ac tiyatecL. Sludge

A waste water treatment process using a mixed microbiological culture
and molecular oxyqen 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
population in the process.

Adipose

Of, or related to, animal fat; fatty.

Adsorption

J.he adhesion of a gas, liquid, 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.
A biological process in which oxygen is used for microorganism respi-
ration needs.  Especially relating to the degradation process of waste
matter in the presence of dissolved oxygen.

Alkalinity

A measure of the ability of the waste to provide hydroxyl ion to react
with acidic materials.  Generally expressed in mg/1 as CaCO_3.
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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 oxyqen.

Back

Jhat portion of the animal hide, especially cattlehide, consisting of
the center portion of the hide alonq the backbone and covering the ribs,
shoulders, and butt  (excluding the belly).

Bating

The manufacturing step following liminq and precedinq pickling.  Tho
purpose of this operation is to delime the hides, reduce swelling,
geptize fibers, and remove protein degradation products from the hide.

Beamhouse

That portion of the tannery where the hides are washed, limed, fleshed,
and unhaired when necessary prior to the tanning process.

Bell*

That portion of the hide on the underside of the animal usually
representing the thinnest part of the tannable hide.

Bend

That portion of the hide representing the entire hide cut down the
backbone with the bellies and shoulders removed.

gest Available_Demonstrated Centrol Technology

Treatment and control required for new sources of industrial discharge
to surface waters as defined by Section 306 of the Act.

Best Ayailabig nTfechnology_iEcpnomicallyAchj.eyable

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 Pragticable Control TechnologyCurrently Available

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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                en Demand  (BOD 5)
The amount of oxyqen 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

T.he amount of concentrated liguor wasted in a recycle system in order to
maintain an acceptable eguilibrium of contaminants in any process
3.iquor.
A hide after tanning with chromium salts.  Hide usually has a slight
blue color.

Chemical Oxyqen^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 (Tota1)

Total chromium is the sum of chromium occurring in the trivalent and
Ijexavalent state.  Expressed as mg/1 as Cr.
A. physical means for the removal of suspended particles in a liquid by
gravity sedimentation  (settling) .
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.

Col lag en

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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Colloids

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

Color

A measure of the liqht absorbinq capacity of a waste water after tur-
bidity has been removed,  one unit of color is that produced by one mq/1
Of platinum as K2PtClo.

Coloring

A process step in the tannery whereby the color of the tanned hide is
chanqed to that of the desired marketable product by dyeinq or painting.

          Sa mj3 j. e
A series of small waste water samples taken over a qiven time period and
combined as one sample in order to provide a representative analysis of
the averaqe waste water constituent levels durinq the sampling period.

Concrete Mixer

A term often applied to hide processors.

Cerium

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

De liming

The manufacturinq step in the tanhouse that is intended to remove lime
from hides cominq from the beamhouse.

Demine ralizatign

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

Derma

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

Desalinization

The process of removinq dissolved salts from water.

Detention  (Retention)

The dwell time of waste water in a treatment unit.
                               146

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Dewatering

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

DO

Dissolved oxygen.  Measured in mg/1.

Drum

A large cylinder, usxially 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.

Electro-dialysis

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.

Epidermis

The top layer of skin; animal hair is an epidermal regrowth.

Equalization

T.he holding or storing of wastes having differing gualities and rates of
discharge for finite periods to facilitate blending and achievement of
relatively uniform characteristics.

Eutrophication

The excess fertilization of receiving waters with nutrients, principally
phosphates and nitrates, found in waste water which results in excessive
growth of aguatic plants.

Fatliquorin 3

The process of adding oils, fats, and greases (fatliquor) to tanned
hides to improve and prevent cracking.
                               147

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Finishing

The final processing steps performed on a tanned hide.  These operations
follow the retan-color-f atliguor processes, and include the many dry
processes involved in converting the hide into the final tannery
product.
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.

Flgcculation

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.

Grain

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.
                               148

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Grease

A qroup of substances including fats, waxes, free fatty acids, calcium
and maqnesium soaps, mineral oils, and certain other non-fatty
materials.  The grease analysis will measure both free and emulsified
oils and greases.  Generally expressed as mg/1.

Green Hides

Hides which may be cured but have not been tanned.

Ion Exchange

The reciprocal transfer of ions between a solid and a solution sur-
rounding the solid.  A process used to demineralize waters.
jhe 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.
The operations in the beamhouse where a lime solution comes in contact
with the hide.  Liming in conjunction with use cf 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.

Membrane

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.

tjitrogen. Kjeldahl (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 orqanism which serves to sustain its
existence, promote growth, replace losses, and provide energy.  Com-
pounds of nitrogen, phosphorus, and other trace materials are par-
ticularly essential to sustain a healthy qrowth of microorganisms in
biological treatment.

Outfall

Jhe final outlet conduit cr channel where waste water or other drainage
is discharged into an ocean, lake, or river.
Layers of salted hides formed at the slaughter house or hide curing firn
(usually approximately 20 to 40 feet in area and 5 to 6 feet high) .

Padd.le_yat (Paddle)

A vat with a semi-submerged rotating paddle arrangement used for the
mixing of water and chemicals with the hide.

J2i!

The reciprocal logarithum of the hydrogen ion concentration in waste-
water expressed as a standard unit.
Parts per million.  The expression of concentration of constituent.^; in
waste water; determined by the ratio of the weight of constituent B5r
million parts  (by weight)  of total solution.  For dilute solutions, ppm
is essentially equal to mg/1 as a unit of concentration.

Pasting

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

j.he 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 the 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
joolymers 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.

Processor

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
         before shipment to a tannery.
Re tan

The process step following tanning and any intermediate drying whereby
hides 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.

v3andinc[

A dry operation performed on the tanned and fatliguored 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) .
                              151

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Chemicals used in addition to lime to assist in the unhairinq grocers
(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.

Side

A side represents half a hide which has been cut alonq the spina.

Skiving

The thin layer shaved or cut off the surface of finished leather,
jorincipally sheepskin.

Sludcje

A concentrate in the form of a semi-liquid mass resulting from settling
of suspended solids in the treatment of sewage and industrial wastes.

   it-
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_Classifi cation

The numerical designation given to various industries by the Bureau  of
the Budget.  The leather tanning and finishing industry bears SIC No.
3111.

Submerge/.! Combustion

A flash evaporation type procedure used in the separation of dissolved
solids from water.
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Suifide

^onized sulfur.  Expressed as mg/1 as S.

       ed Solids (SS)
Constituents suspended in waste water which can usually he removed by
sedimentation  (clarification) or filtration.

Tacking

Staking using tacks to fasten skins or hides to a large frame.

Tannin

The chemicals derived from the leaching 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 Dissolved_Solids (TCS)

The total amount of dissolved materials {organic and inorganic) in waste
water.  Expressed as mg/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.

Volatile_Solids

Solids, dissolved or suspended, which are primarily organic and during
stabilization exert the significant portion of the BOD5.

weir

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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                                   METRIC UNITS
                                 CONVERSION TABLE
MULTIPLY (ENGLISH UNITS)

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

     CONVERSION   ABBREVIATION   METRIC UNIT
       0.405
    1233.5

       0.252
ha
cu m

kg cal
0.555
0.028
1.7
0.028
28.32
16.39
0.555(°F-32)*
0.3048
3.785
0.0631
0.7457
2.54
0.03342
0.454
3,785
1.609
kg cal/kg
cu m/min
cu m/min
cu m
1
cu cm
°C
m
1
I/sec
kw
cm
atm
kg
cu m/day
km
(0.06805 psig +1)*
       0.0929
       6.452
       0.907
       0.9144
atm
sq m
sq cm
kkg
m
* Actual conversion, not a multiplier
                     Environmental Protection Agency.
                     Library,  Region V
                     1  North Wacker Drive
                     Chicago,  Illinois   60606
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
                                       154

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