A ^ "P ^\'P T^
                   j=? ^M ^Cs? ^ti .y
                 ? *pr\*p* &PA f'i? ?
s r/w r\ K -.  n  (3 K n l< '-V;^ ,;\ !*& p.ff -^ |,\ n ^  #^g a H r.^, ip- n  f! i\ H if" ,
' s= i,'\:  y     H ;4''!ri   '/t\ v ' IIMV^^  u >--^  :' -  ti h3* n   lt* t ' v
 i= (S J  0   L^ bUllt! L!.V-*iS 2W-'3\^\3I  ^* W! iJ k--*' i^, iU I- L' -d li^
                        , ff  W**.*sa"as-Wa' ff**t'tfr*.\*\ ft
                       of  ^^hru^fe
                                                     STANLEY  CONSULTANTS


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 pre-
treatment standards for the industry, to implement Sections 30**,
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" (Level I)  and
the degree of effluent reduction attainable through the application
of the "best available technology economically achievable" (Level II);
these levels of treatment must be achieved by existing sources by
July 1, 1977, and July 1, 1983, respectively.  The standards of per-
formance 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" (Level III).

Level I proposed effluent limitations for tanneries discharging to
municipal systems  include adjustment of pH, removal of chromium,
oxidation of sulfides, and removal of oil and grease.  Additional
Lr^ukn^ni.  is required foir major removal o" LJ^I/^ sna 5u3p.ric;cO so; ics
by facilities discharging directly to receiving waters.

Level II proposed  regulations  include major reductions of all forms
of nitrcscr., in additicrs to these requirements cstcbl iohcd for
Level !.  Pretreatment for Level  II  is the same as for Level  I.

Proposed regulations for new sources  (Level  III) are the  same as
Levels  I and II, depending on when such new sources are constructed.
Pretreatment for Level  III is  the same as for Level I or  II.

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


Sect! oil
                         CONTENTS (Con't)
               ionale for Selection of  Identified Parameters.  .   2

                 COD   ..................        ^
                 Total Chromium  ................  ,
                  Suspended  Solids  ...............   '
                  Total  Solids  .................   *
                  Ammonia  Nitrogen  ...............   ;?
                  Nitrate  Nitrogen  ...............   *
                  Total  Kjeldahl  Nitrogen  ...........  J*

                  PH ......................  /43
                  Color   ....................  ,k
                  Fecal  Coliforms ................  .,
             Other Constituents of Less  Importance  .......
        rnwTS."! ik.'r> Tr!r.nTwc:K!T TECHNOLOGY
             Basis of Tannery Waste Treatment
             In-Process Methods  of Reducing  Waste
                   Screening ...................  r,
                   Equalization  .................  *L
                   Plain  Sedimentation ..............  >
                   Chemical  Treatment - Coagulation and
                     Sedimentation ................  ,
                   Chemical  Treatment - Carbonation .......  J
                   PH Adjustment .................  ,,
                   Sludge Handling and Disposal .........  
                   Pretreatment - Facility Requirements .....  *>
              Major Reduction of BODc and Suspended Solids   .  .  b/
                   Combined Municipal - Tannery Treatment Systems 67
                   On-Site Treatment  - Trickling Filter Systems . 71
                   On-Site Treatment  - Aerobic Lagoon  Systems  . .  /5
                   On-Site Treatment  - Aerobic - Anerobic
                     Lagoon Systems  ..........        '  '  '
                   On-Site Treatment  - Activated Sludge Systems  .  /y
                    Improvement  of Treatment  Performance  .....  5
                   Facility Requirements .............   '
               Major  Reduction of  all  Forms  of Nitrogen  .....  W
               Major  Removal of  All  Waste  Constituents  ......  j
                    Freezing  ...................  gl|
                    Evaporation ..................

                          CONTENTS (Con't)
Sect ion
                 Elect rod ia lys i s	.' .   95
                 Ion Exchange	95
                 Reverse Osmosis 	   96

            Cost and Reduction Benefits of Alternative
              Treatment and Control Technologies 	 101
            Basis of Economic Analysis	101
            Effluent Reduction - Category 1	105
            Impact of Waste Treatment Alternatives on
              Finished Product Price 	 109
            Alternative Treatment Systems	]09
            Related Energy Requirements of Alternative
              Treatment and Control Technology 	 109
            Non-water Quality Aspects of Alternative
              Treatment and Control Technology 	 112
                 />! !  r L; : : u i. i on	i i /.
                 Solid Waste Disposal	113
            Effluent Reduction Attainable	
            Best Practicable Control Technology Currently

Rationale for Selection of Level  I  Technology. .  .  19
     Total  Cost of Achieving Effleunt Reduction.  .  19
     Age and Size of Equipment and  Facilities. .  . 119
     Processes Employed	120
     Engineering Aspects of Control Techniques .  . 120
     Process Changes 	 120
     Non-water Quality Environmental Impact.  ... 120

            General	121
            Effluent Reduction Attainable	122
            Best Available Technology Economically Achievable. 122

                          CONTENTS (Con't)

            Rationale for Selection of Level  II Technology.  .   12A
                 Total Cost of Achieving Effluent Reduction  .   12*t
                 Age and Size of Equipment and  Facilities  .  .   12*
                 Processes Employed  .............   12"*
                 Engineering Aspects of Control Techniques.  .   12*1
                 Process Changes ...............   125
                 Non-water duality Environmental  Impact  ...   125


            General  .....................   }?'7
             Improved  In-plant Process  Control ........   127
            New Source  Performance  Standards .........   128

  XII   ACKNOWLEDGMENTS ....................   131

 XIII    REFERENCES  ......................   133
  X!V   G! 0*5*5 ARY

Number                         Title

  1     Classification System 	  23
  2     Industry Categories 	  2k
  3     Wastewater Quantities 	  35
  k     Raw Wastewater Characteristics By Category	38
  5     Plain Sedimentation 	  59
  6     Chemical Treatment  	  61
  7     Combined Municipal - Tannery Treatment Systems	68
  8     Trickling Filter Systems	72
  9     Aerobic Lagoon Systems	75
 10     Aerobic - Anaerobic Systems 	  77
 11     Activated Sludge Systems	81
 12     Estimated Waste Treatment Costs For Typical  Size Plants
         (August, 1971 Price Levels) 	 102
 13     Level I  Effluent Limitations Guidelines - July 1, 1977
         (Complete Treatment)	116
 l'     Level I  Effluent Limitations Guidelines - July 1, 1977
         (Pretreatment)	117
 15     Level II Effluent Limitations Guidelines - July 1,  1983
          r^mnlote "'"'"2 f'O'"11)	                '97







Flow Diagram - Typical Cattlehide Tannery 	
Flow Diagram - Typical Sheepskin Tannery	
Flow Diagram - Typical Pigskin Tannery	
Category System 	
Flow Diagram - Pretreatment  	
Flow Diagram - Major Removal of BOD5 and Suspended
  Solids - Activated Sludge  	
Flow Diagram - Major Removal of All Forms of Nitrogen -
  Activated Sludge - Nitrification - Denitrification. .
Flow Diagram - Major Removal of All Waste Constituents
  Activated Sludge - Nitrification - Denitrification -
  Reverse Osmosis  	
Category No. 1 Waste Treatment Cost Sensitivity
   (August,  1971, Price  Levels)	
 Impact  of Waste Treatment  On Finished Product  Price
   (August,  1971, Price  Levels)	





                             SECTION  I

For purposes of establishing effluent  limitat
standards of performance,  the leather  tanning
try has been divided into seven major  cateyor
have been derived principally by similarities
loads, within the accuracy of data available.
and size of plant, climate, and waste  control
justify segmentation of the industry into any
following tabulation is a capsule summary of

                        INDUSTRY CATEGORIES
ions  guidelines  and
 and  finishing  indus-
ies.   These  categories
 in process  and  waste
  Such factors as  age
 technologies  do not
 more categories.
these categories:
                               Primary Processes
Category          Beamhouse

   1       Pulp hair

   2       Save hair

   3       ?3"2 ^2'r

   1       Hair previously removed

   5       Hair previously removed
           or retained

   6       Pu 1 p ha i r

   7       Hide curing
     Tann ing


Previously tanned


C h rome

No tanning
            F in ishing





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.
Pretreatment of waste will be required for tanneries discharging to
municipal  systems so as to remove those waste constituents which
affect  the municipal system treatment processes or pass  through the
system  untreated.   Such pretreatment will also be required to  remove
any  constituent which will cause damage to or  interfere  with opera-
tion of the  sewer system.

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  consider-
able improvement in waste discharges  with  major removal  of  BOD^  and
suspended solids by July 1,  1977.   The  estimated capital  cost  of
achieving effluent  limitations (Level  I)  by all plants within  the
industry is $119 million (August,  1971,  price levels).   Total  annual
costs (including depreciation, interest,  operation, and  maintenance)
for pollution control will  increase finished product costs  from
about 1.8 to 12.^ percent (August, 1971,  prices).

It is further concluded that by July  1,  1983, implementation of
treatment facilities  to effect major  removal of all nitrogen forms
(Level II) will be required for facilities discharging  directly  to
surface waters.  Pretreatment levels  will  remain at those estab-
lished for 1977.  Total capital investment for achieving 1983 efflu-
ent limitations is estimated at about $138 million  (August, 1971,
prices).  Total annual costs for Level  II  pollution control will
increase finished product prices from about 1.8 to  16.0 percent
(August, 1971, prices) .

Some economies may be achieved during implementation of Level II
v/aste 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-denitrificat ion faci1ities.

Standards of performance (Level III)  for new sources are equivalent
to the appropriate Level I and  II  requirements.  New sources con-
structed after  1977  should comply with Level  II limitations.

Complete  reuse  of  treated effluent cannot be achieved without re-
moval of dissolved solids.  Methods for removing dissolved  solids
and  subsequent  disposing of the concentrated brines are not suffi-
ciently 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 neces-
sary  as  an  influent  to processes  capable of  dissolved solids  re-
moval,  all  tanneries,  regardless  of discharge  point, would  require
 installation of major biological  treatment  facilities  in addition
to  that  required  for dissolved  solids  removal.  Provision  of  such
 large,  complicated treatment  facilities within municipalities across
the  U.  S.  is  completely impractical and unreasonable.


                             SECTION II

 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 recom-
 mended  to be the average values based on production data and analyses
 of 2A-hour composite samples collected during any 90-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.  Thus, some exceptions are desirable.
 It  is,  therefore, recommended that any parameter except pH can be
 twice  the basic level  in 5 percent of the composite^ effluent samples
 during  any 90-day period.   The maximum allowable level proposed is
 for  all  parameters except  pH four times the basic values presented
 here.   Such a maximum  allowable level would be checked by both com-
 posite  and grab samples collected at any time.  The exception to
 these  recommended variances is that total chromium should never ex-
 ceed  two  times the basic value indicated.

 Application of the "best practicable control  technology currently
 available" (Level I)  results in the following recommended effluent
 : ! .T : _= _ : _.::, I,;: : UL: i i ill; i> tO  JU mOt Dy Juiy i, I b>77 i I Oi" Ldln'ieiiCb li I s -
 charging  directly to surface waters.
Total Chromium
Oi 1 and Grease
Suspended Solids
pH. units
Fecal Coli forms/
100 nl
(Complete Treatment)
Category . .
kg/I, 000 kg hide lib/ 1.000 Ib hide)"'
1 3
0 03
0 67
6.5-8 5
Basic values average
these values allowed
exceed 4 tines these
2 tines basic values
Except pH and
2 0
0 5
6.5-8 5 6
0 04
0 d2
0 OOli
5-8 5
0 7
9 8
0 02
0 20
6 5-8 5
2 5
0 06
0 62
0 006
1 3
65-85 6
0 67
0 20
0 002
0 33
5-8 5
over a 90-day period are shown, up to 2 lines
In 5 percent of the samples, values nay never
Imitations HaKinun Imit for chro-nlun is
pH rust be within basic limits shown at all
fecal coli forr*

  For ton er.es discharging to municipal sewer systems,  application
  of the  best practicable control technology currently  available"
  (Level  I) results in the following effluent limitations guidelines
  _to be met by July 1, 1977.                                   c-imub

Total Chromium
and Grease

Basic values average
these values al lowed
exceed H times these
2 times basic value.
Except pH.
Category .
kg/1,000 ka hide (lb/1.000 Ib hide)(2)
0.25 0.21 0.08 O.;i 0.08
2'5 2-' 0.83 3.1 0.83 0.01
0.05 O.O'i 0.02 0.06 0.02
5.5-9.5 5.5-9.5 5.5-9.5 5.5-9.5 5.5-9-5 5.5-9.5
over a 90-day period are shown; up to 2 timas
in "> oercunt nf the is-;!--. ...s!.__ . . __ ._
limitations. Maximum value for chromium Is"'
pH must be within basic limits at all times.
aHe' > (fL  ,  M  ^  b?St avaMable technology economically  achieve-
               }  reSU    m ^ 6fflUent  """tations  guidelines  shown
 on the fon                                       ns guenes so
 waters f"Win?.Pa9e for tanneries discharging directly to surface
 waters.  inese limitations are to be achieved by July 1, 1983.

 Pretreatment requirements for Level II  are the same as  for Level  I
 Effluent l.m.tations guidelines for new tanneries yet to be built  '

  Mor'to^vV6^110/^ thS ^  "  fr LeVG'  ' if Constructed
 prior to July 1,  1977,  and the same as  Level  II  if built thereafter
 Pretreatment for  Level  I I I  is the same  as  Level  I.        theredrter'
 ThP  t!?h  ?    *    r^Ve  dissolved  solids  by  1983  is not  recommended.

 of concentred hr-We-Pread  "T^'  f  dissolvd  salts and disposal
 shouM  h2    A   Kbr'CeS.'!  not  wel1 defined.  Extensive  research efforts

 hide  cuMna   h \  *  '     '^ tO  flnd 3  substitute for salt used  in
 h.de  curing, which  ,s a major  contributor of the dissolved solids.

 based^u^lxr tO-Wh'Ch  the  abV6  limitatins and standards are
 industr!^ extens'vejwater <* chemical conservation within the
 industry and properly designed and operated waste treatment facilities


                             (Complete Treatment)

   Total Chromium

   Oi1 and Grease


   Suspended Sol ids

   Total Kjeldahl

   Ammon i a

     Ni trogen'3'

   pH, units

   Color,  %
     Removal W

   Fecal  col i form/
     100 ml
                                               Category           , .
                                 kg/I,OOP kg  hide (lb/1,000  Ib hide)v '










  0.17    0.25
0 8

























  0.10    0.15     0.12     0.05     0.19     0.05

  0.33    0.25     0.17     0.07     0.12     0.33

6.5-8.0   6.5-8.0  6.5-8.0  6.5-8.0  6.5-8.0  6.5-8.0

           Basic values  average over a 90-day period are  shown; up to 2 times
           these values  allowed in 5 percent of the samples, values may never
           exceed *1 times  these limitations.  Maximum limit for chromium is
           2  times basic values.  pH must  be within basic limits shown at all
           Except pH,  color, and fecal  coliforms.

           Limitations for nitrogen  forms do not apply when the water temperature
           is below 10  C  (50 F).
           No reasonable data is currently available  upon which absolute  limits
          may be established.  Treatment can.provide this percent  removal,


                            SECTION II I

The 1972 Amendments to the Federal Water Pollution Control Act re-
quire 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 avail-
able" by July 1, 1977, and application of the "best available tech-
nology economically achievable" by July 1, 1983-   For new waste
sources, the "best available demonstrated control technology" must
be applied.

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

     1.  Establish the various categories wilhin  the leather tanning
         and finishinq industry siihiort fr> e^'F1|jent 1 '""' tst i ~-c. .inrl
         standards of performance.

     2.  Characterize wastes from each major category of the indus-
         try by assessing flows and constituents  in the wastewater.

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

     k.  Outline Level I, II, and III control and treatment technol-
         ogy available for establishing effluent  limitation guide-
         lines and standards of performance.  Level I limitations
         are to be achieved by 1977, Level II by  1983, and Level III
         applies to new sources of waste.

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

Previous Study

A principal source of data for this investigation is the "Industrial
V/aste 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.

                                uiuvr i
 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 arc  engaged  in finish-
 ing  operations  (essentially  dry process)  on leather already  tanned
 at some other  location.

 Tanneries arc principally clustered  in the  New England and mid-
 Atlantic states,  Chicago-Milwaukee area,  and Gloversvi 1 le-Johnstown
 area in New York.  Others are scattered throughout the U. S.

 Since about I960,  several significant developments have taken place
 in the domestic tanning  industry.  Most noteworthy is the increased
 export of cattlehides to countries for production of leather.   In
 1972, hides from  over 47 percent of  the 36.5 million cattle slaugh-
 tered in the U. S. went  to foreign tanners  (2).  Since I960, 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.
finished product market.  For example, in I960, 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 tannaqe has been used proportionately mcre 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 finish-
ing industry has recently felt a squeeze from both ends  raw material
and finished product.   Greater foreign demand for cattlehides has re-
sulted in part from a  change in a restrictive hide export policy by
other hide producing nations.   This has recently caused the price of
raw cattlehides to increase greatly.   Heavy native steer hides have
ranged in price from 8.3 to 20.3 cents per pound in  the period
1960-71.   Average price in 1971  was 14.4 cents per pound.  In 1972
prices increased to 42.4 cents in August, with an  average for the
year of 29-7 cents per pound.   These  raw product prices have now
fallen to about  twice  those in 1971.   In addition, competition from
foreign countries such as Japan,  Italy, and Spain  in the finished
leather products market has reduced the potential  revenue from domes-
tic leather  firms.

CatLlehides constitute the bulk of the tanning done in  the  U.  S.,
representing about 90 percent of thr. estimated pounds of  hides
tanned.  Sheep and lamb represent about the next  largest  volume.
Pigskin production is estimated to be the third largest production
volume in the U. S.  Since I960, domestic tanning of cattlehides,
sheepskins, and lambskins has trended slightly downward.

Other types of skins or hides processed in the U. S. include goat,
kid, hairsheep, and horse.  All of these tanning  volumes  have fallen
significantly since I960.  Various other skins tanned  in  the U.  S.
on a very limited basis include deer, elk, moose, antelope,  and  rab-
bit, as well as rare skins such as alligator,  crocodile,  seal, shark,
and kangaroo.


                            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 epi-
dermis.  The epidermal area and corium constitute the leather-making
portion of the skins or hides, and consist mainly of protein collagen
when 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 con-
vert 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 scien-
tific  principles.  As  in any  industry, the approach to  production of
a suitable  leather by  the average tannery reiies a great aeai on past
experience.   In a typical process, such as unhairing, the concentra-
tion of lime  and sharpeners  (such as  sodium sulfide and sodium sulf-
hydrate) , temperature, and processing time are  interrelated.  As  in
iiiobt cnemicd!  redd ions>, ciiemi i.al ooncenir ai. iun*> CIMU/UI LeiiiiJtsraLure
may be increased to decrease  the  processing period.  Tanners vary
process conditions to  control the quality of the finished  product.
Therefore,  there  is a  significant amount of variance  in processing
techniques, even between two  tanners  producing  the same finished
product,  to satisfy  individual  product needs.

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

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


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

Cattlehide Tannery  Processes

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

     1.  Beamhouse.

     2.  Tanhouse.

     3.  Retan, color,  and  fatliquor.

     A.  Finishing.

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.
H         .:o''ttl
         HOI I (i
         .<:> i to

            [ IU!iHIIK.j 	 	      I  JSCUO tStt

           itit nnurti         [*sn CIHUEM
                                                           FIGURE 1

Sub-processes and the operations which take place within  each  pro-
cess are described as follows:


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

         Green hides, after trimming and grading, are cured  at the
         packing house by spreading the hides flesh side  up  and cover-
         ing 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
         shinopd in npr-k?  "j't^er to t3r>.r>sr i P.F. a~ *"". i.'."i-"u'v"-~T. for
         storage.  The size of the pack depends on a number  of vari-
         ables, such as size of the packing house, size of shipments,
         and the method of shipment.

         Brined hides are prepared at the packing house or at  a
         separate hide processing facility by agitating  fresh  hides
         in a saturated brine solution until the salt has replaced
         the desired amount of moisture within the hide.   In this
         process, hides are also cleaned by removal of manure  and
         other attached foreign matter.  Hides are then  removed,
         drained, and bundled in a manner similar to that used for
         green salted hides.  Hides may be fleshed before or after
         brining.  "Safety salt" is usually sprinkled on  each  hide
         before shipment.  The brining process takes two  to  three
         days, which makes it attractive to the packer of hide cur-
         ing 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.  In-
         creased 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  main-
         tained in most tanneries other than that required to  keep
         hides at the moisture  content  as received.

Siding and Trimming  -  The  usual  first  step  in the process-
ing 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.

Washing and Soaking  -  Sides (or  in some cases whole hides)
from the siding and" trimming  operation are  placed  in vats
(with or without paddles), drums, or hide processors  (con-
crete 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.
Decs^d ;"o o" ths tvoe of leather produced. aHHi i- ional
(rinses) may also occur at several other points in the tan-
ning process,  including after liming and dehairing, after
bating, after  tanning, and prior to and following coloring.

Fleshing - Fleshing is the removal of attached adipose
fatty tissue and meat which have been left on the hide at
the packing house.  It is done on a fleshing machine, in
which the hide is carried through rolls and across rotat-
ing 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  sepa-
rate 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  contri-
bution  from this operation.

Unhai ring - 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  "pulp-
ing" or  "burn ing."

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

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

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


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

    a.  De-1ime  skins.

    b.  Reduce  swel1 ing.

    c.  Peptize  fibers.

    d.  Remove  protein degradation products.

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

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

3-  Tanning -  Nearly all  cattlehide in this country is 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  tan-
    nins.   This method is usually used  for  the heavy  leathers
    such as sole leather, mechanical  leathers, and  saddle  lea-
    thers.   Shoe upper leathers  and other lighter leathers  are
    usually chrome tanned by immersion  in a  bath  containing
    proprietary mixtures of basic chromium  sulfate.

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

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

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

    Spl 1 tt ing - The tanned hide  is split  to  produce a grain-
    side piece of essentially constant  thickness  and  a flesh
    side layer.  The flesh side  layer or  split can  be processed

1.  Retan - 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
    fatl iquoring.

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

3.  Coloring - Coloring is done in the same drums as retanning,
    and may be done either before or after fat 1 iquoring .  Natural
    dyes may be used, but many synthetic products are now avail-
    able for this  purpose.

4.  Fat 1 iquoring - Fat liquor ing 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 lea-

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


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

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

Sheepskin  Tannery  Processes

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

     1 .   Tanhouse.

     2.  Retan, color, and fatliquor.

      3.  Finishing.

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


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

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

          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.

                                      mm mucuc
(I) l(*tll',', (COl IMi 0) l-F
 = E(I liiO 1". CimO Smi. I<-
 1,H I SO'. HF!.MHi|,. OKVU
                                                         FIGURE 2
       Storage - No special  provision  for storage is provided at
       most tanneries other  than  to keep the skins moist.  There
       is some indication that  pickled skins held for extended
                                                    ..-     --^
                                                    avuiu UCLCI i
       rat ion .
       Flesh ing - Skins from  storage are taken from the bundle,
       inspected, and fleshed.   Hides which have been fleshed
       prior to receipt at  the  tannery will usually b.e 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 sol id waste.

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

       Grease is recovered  as a by-product from those skins which
       have had the v/ool  removed.   When solvent degrees ing  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 .

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

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

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


    .    /_'.__:_.. _  S^::;r  ;c be colored .?ri? i^mp.rssd 'P e ^y? oln-
        tTon"  inVumsT^Generally, synthetic dyes are used.  Some
        bleaching may be done prior to coloring of shearlings.

    2.  Fotlignoring - This nnpration is performed in the same drum
        used  for c"oToring.  Skins are immersed in a solution con-
        taining  various oils to replace the natural oils of the
        skin  lost in the  tanning  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
    operat ions.

    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 wastewater  system.

Pigskin Tannery  Processes

The pigskin tanning  processes  differ from cattlehide  tanning in that
there   is  essentially  no beamhouse process, since most skins have the
external  hair removed at  the packing house.  Degreasing of the skins

is a required tanhouse  sub-process.   The waste characteristics  from
pigskin tanneries are established from these three processes:

     1  .  Tanhouse.

     2.  Color and  fatliquor.

     3.  Finish ing.

These  processes and  the operations which take place, within  each pro-
cess are shown on Figure 3 and described as follows:


     1-  Receiving  - Nearly all  pigskins are received  at  the  tannery
         either as  fresh frozen  skins or a.s 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. . Degreas ing -  Solvent  degneasing 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
            !  t:
                               3    "	
                         SUM I SHm
                          | SOllDxtSU SNi.l.U)
                                        i:uini< nn mi
 t Itil'.MIM,
                                            H10ES "B Ltm

                                            PROCESS UlIt^tlLI
                                                           FIGURE 3

    solution  of  solvent,  grease,  and water  is  pumped  from tiie
    drums  to  large  tanks  where  some separation  is achieved  by
    decanting.   From the  lanks  the solvent  and  grease  is sent
    Lo a  stripping  column,  where  the solvent  is  recovered for
    reuse.  Grease  is recovered as a by-product.

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

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

*t .   Liming -  From the degreasing  operation  the skins  are placed
    in tanning drums with a lime  slurry  and sharpeners.  The
    purpose of this is to remove  the embedded  portion  of the
    hair from the skins.

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

7-  Tann ing - 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.  Spl i t 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 fat liquor process.


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

     2.   Fat 1i quori ng - 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.


     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
     v/aste  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
     fertilizer.  Dust collected from the sanding operation is dis-
     posed  of  as a solid waste.
Classification System

A.  *j.l"   I.  r.   --.-'-  .-_   -   -	!..'r..  .*"..   ."-   - i-<" 
. r ; iv.1. .j  . :; L: :^  ** i S'3'' . ; \'^ j . i  -.5 :> . -J( i **: ^ L 01! J^ . * m^i  u  u H . w  i   y  ^ i w
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 tann'PC! 3nd finishinn inHnsfy bears ?'C Wijmber 3111-
A supplemental digit system reflecting the many variations  in opera-
tions can further classify the  industry.  For purposes of this study,
a four-digit system  is recommended to reflect significant differ-
ences in processes.  This matrix approach to the doss i ficat ion sys-
tem provides flexibility and a  rigorous means to encompass  all pro-
cess variables.  The supplemental classification system  is  shown  in
Table 1.  Some blank spaces are available if new processing  techniques
are developed.
Under this system, four digits appear to the right of a decimal point
following the industrial classification.  As shown in Table  1, these
relate information by type of skin or hide, operations undertaken  in
the beamhouse, tanning method used, and type of material processed  in
the retan, color, fatliquor, and finishing steps.

(31 11. abed)
Skin or
Hide Type
1. Cattle
2. Pig
3. Sheep
4. Deer
o .
3. Other
0. Various
Ope rat ion
1 . Pulp Hair
2 . Save Ha i r
3. Hair Pre-
A. Hair
5. Wool
o. Hide Curing
7. Pulp & Save
9. Other and
Tann ing
1 . Chrome
2. Vegetable
3. Alum
b. Previously
5- Vegetable
and Chrome
G .
9- Other and
0. Hone

, Fat 1 iquor,
in i sh ing
Sides and
Spl its

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).

     3111.13*11  ~ Catllehide, hair  previously removed and hide pre-
                 viously tanned prior to receipt of hides at  a fin-
                 ishing  facility (finishing operations only).





O.ES 0s t'l *&*!*

||L ^

LL^ 	 1
t*'7LE J.I7M


.i^E7t3L i CHJCHi
C:-L= 0= UMKO.w


PULP !"!

riNISH .'/

U771- 1.TI9
SEE?. I.S215

Ci77LE LAlJ.1

CHILE [.j??g
emu Lj__ijj 	


C.7TLE Lj.l'i
"E.'iCL'ilr TiitiO
Cl"-,- 1.13-43


SHEEP ).33u.

OIH(R 0iT'"??'?^v^^l31;^E^^v3
! ...^




CHHE [."iVll

CHILE [.1313


PIG 1.J3I*

SHEEP j.aais

SHIIP J.3325

SHEtP |.33

SHEEP [.3390
CIHEft OP Uirpit-h

t'!EC? f.?"1!



CAI7LE |.I?10

NONE ?j)
CATTLE ].i:oo

CHILE 1.1600

                CATEGORY SYSTEM
                        FIGURE 4


                             SECTION  V

                      WASTE CHARACTERIZATION

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 wi th individual tanneries.

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

     3.  Corps of Engineers Permits.

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

     5.  Literature review.

     b.  Sampling performed at  selected  canneries.

     7.  Tannery visits.
 Data  has been assembled on  i.he udsis of  Lhe various tannery categories
 defined hereinbefore.

 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

 Tne basic  parameters  used to define waste  characteristics are  as


     BODr (Five-day Biochemical  Oxygen  Demand)

     COD (Chemical  Oxygen Demand)

     Total  Solids

     Suspended Sol ids

     Total  Nitrogen

     Chromi urn

     Oil and Grease  (Hexane Solubles)


     Total  Alkalinity


Additional  data from some sources permitted a check of the various
forms of nitrogen and volatile component of total and suspended
solids.  No significant  information was available on color.  Infor-
mation 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/l).  When combined with waste flow
records, this permitted  computation of waste quantities in terms of
weight of each waste constituent produced per day.

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

     1.  Weight of raw material processed.

     2.  Number of hides processed.

     3.  Weight of finished product.

     k.  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 win-
 ter 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.

 V/cight 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 con-
 stituent data  are related to the weight  of the raw  material as  it
 enters a particular  tannery  or finishing facility.

 Individual  Process Contributions to  the  Waste

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

 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  in-
 d JS f rv   Thf* h i He  r-'irinn nr-^i.-^r- ,-,-._:_,-c  _.c    _i     __  .	   	,
                   	'  = 	 i___    __	3, ^.uiiny, CIIIU
 cFten fleshing of  the  hides.   Washing and  curing are performed  simul-
 taneously 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  rhp  inhibition of micro-
 biological decomposition.  The brine solution  is continually  circu-
 lated 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:

                                                  kg/1,000 kg Hide
                                Concentration    (lb/1,000  lb Hide)

     BOD5                            15,610               3.3

     COD                            29,610               7.4

     Total Solids                  280,500              70.1

     Suspended  Solids               10,400                2.6

     Oil and Grease                 40,200               10.0
     Water  Use,  cu  m/kg                    O.OOJ3
                (gal/lb)                   (0.03)



Other processes which arc an integral part of the tannery include
the following:

     Wash and Soak

     Dcgreasing  (sheepskin and pigskin)

     Unhairing  (sometimes followed by supplemental liming)

     Bat ing


     Tanning  (including  bleaching  for  some vegetable tanning)

     Retanning,  Coloring, and  Fatliquoring


The waste contributions  are described  below:

Wash and Soak - This is  the first  wet  process  performed  on  the  raw
maTerial as  it  begins the tanning  process.   The purpose  of  this
operation is  to remove salt, restore the moisture content of the

 the*"raw material is brine cured hides, the hides are  clean  and  the
 operation is  one of salt removal.   With green  salted  hides, manure
 and dirt must also be removed.  The quantity of manure and  dirt can
 yar '-''de'y,  depend'"" O" the spason of the year and  the origin of
 the an imal.
 Primary waste constituents from the operation are BOD5, COD,     ^
 pended solids, and total solids (including sodium chloride).  Typi-
 cal range  in quantities for a cattlehide tannery with hair pulping
 and chrome tanning are as follows:

         Constituent              kg/1.000 kg Hide (lb/1.000 lb Hide)

      BOD5                                        7-22

      Suspended Sol ids                            B-^B

      Total Solids                               1^3-267

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

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

     1.  Hot water with detergent.

     2.  Solvent.

In both cases the grease is separated and  recovered.   However,  some
grease is not captured and enters the plant  waste system.   In the
case of solvent degreasing, the solvent  is also  recovered.  In  addi-
tion to grease, BOD^, COD, and suspended solids  are  other  waste  con-
st i tuents .

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.

Unhairing - Two processes are used for unhairing:

      i .  Ha i r save.

     2.  Hair pulp  (or hair burn).

    he hair save operation, the hali" is loosmieu TGI
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, 6005, suspended
solids, and total solids.  A part of the soluble solids is sodium
chloride not removed in the soak and wash.

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

The hair pulping operation is similar to that of hair saving except
that higher chemical concentrations are used, particularly with re-
spect to the sharpeners.   In this process the prote inaceous hair is
solubilized sufficiently to disperse it in the processing liquid.
The wastewater, therefore, has a higher content of waste constitu-
ents, particularly with respect to sulfides and nitrogen.

For a cattlehide chrome tannery,  BOD^ content  of the waste  from the
hair save process v/ill  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
6? 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
swel1 ing, 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
total nitrogen content  of the waste is 5 to 8 kg (ib) per 1,000 kg
(Ib)  of  hide with ammonia nitrogen constituting  about two-thirds of

Pickling - The purpose of the pickling operation is to prepare the
hides for the tanning process.   In vegetable  tanning, pickling may
be omitted.  Pickle solutions contain principally sulfuric acid and
salt, although a small  amount of a wetting agent and biocide are
sometimes used.  Since protein degradation products, lime,  and other
waste constituents have been previously removed, the quantity of 6005,
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 orior to tan-
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 of the tanning agent with the hide collagen.  Chrome
and vegetable tanning are the two principal processes, although
other materials such as alum and other metal   salts as well  as for-
maldehyde can be used.

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

The  chromium  tanning solution  is  relatively low  in  BOD5 and  suspended
sol ids.

Waste from  a  vegetable  tanning process  is quite  different.   The re-
action  rate of  vegetable  tan with the hides  is  much  slower than that

of chrome tanninq solution.   Because of the longer contnct  lime,  the
process is normally carried  out  in vats with somr- type of  gcnlle
agitation.  In some instances the hides are passed through n  scries
of vats v/ith varying solution strength.  Because of the cost  of  tan-
ning 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 8005
and color.

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

The retan process is performed to provide added tanning solution
penetration into hides after splitting.  Chemicals used for retan-
ning can be chrome, vegetable, or synthetic tanning agents.  Because
of the  low concentrations of chemicals in the retan process,  the
concentration of the wastewater 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.
thetic 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
logthor  15 colored   't  's nonoraliv surface dy?d bv spr?y'n(j * he
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 volume-low strength compared v/ith the beamhouse and tanhouse.

The temperature of the  retan, color, and fatliquor waste flows  is
generally highabove 37.7C (100F).  The major treatment concern of
the retan, color, and fatliquor waste  is removal of color and oil.
These two constituents  can be kept to a minimum  by utilizing chemical
concentrations that  provide  for the best uptake  of the chemicals into
the hide.  Because of the color in the wastewater, recycle is not
normally practiced.   Use of  high temperatures  in retanning will en-
able maximum uptake of  chromium and reduce the discharge of this
const i tuent.

Fin!shing - The finishing processes represent the lowest water flows of the
tannery because they are primarily dry processes.  There are  some wet

                               UKAh I
processes such as minor welting operations to make the hide handle
more easily  in the staking or tacking operations.  The pasting opera-
lion also uses small amounts of water.  However, several tanneries
report reusing this; therefore, iL docs not flow into the waste
stream.  This pasting water is v/ater mixed with starch; thus, it is
quite high  in concentration even though the volume is very low.

Total Plant Liquid Waste

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

An appraisal was made to determine the quantity of waste flow from
tanneries in each of the seven categories defined previously.  A
typical plot of wastewater flow versus tannery production is shown
on the following page for Category 1.  The random nature of the data
is obvious.  It is apparent that size of facility is not a factor
for low wastewater flow.  These wastewater quantities are characterized
in Table 3 by the median, mean, and mode for each category.   Defini-
tion of t-i-"sr
     Median - The number of tanneries having waste flows lov/er than
              this value is equal to the number of tanneries having
              waste flows highpr than 1-his yalije.

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

     Mode   - This is the mid-point of the one-gallon interval in
              which the most frequent occurrence of wastewater 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.      \

To determine a v/aste flow value for use as the basis of treatment,
facility needs, and economics, it v/as necessary to take into con-
sideration the basic data for individual tanneries in addition to
that shown in Table 3.  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

Waste flou,
cu rn/kg of hide (gal/lb of hide)
Category Median
1 0 040
i o o:>u
(6 0)
3 0.044
4 0.017
5 0.050
(7 6)
u o|>u
0 082
_ __
o 007-0.156
u ooi-o ioy
(0 1-22 6)
0.007-0 106
0 006-0 204
(0.7-24 4)
0 014-0 056
Used Later Herein for
Economic Analysis ,
cu m/kg of hide (gal/lb of hide)
(2 0)
o 0003


                     TANNERY PRODUCTION (1000 KG HIDC/MO)
                     GOO     800     1000    1200





= II



5 8




	 , 	 , 	 1 	 1 	 1 	 1 	 1 	 1 	 1 i 	 1 	 1 i ' ' ' r


e .




I e 0 

0 500 1000 1500 2000 2500 3000 3500 40

0. 15



0. 1 1

0.09 "-
0.08 =

0.07 ^




                      TANNERY PRODUCTION (1000 LB HIDE/MO)

percent of  the  tanneries of a similar  type could meet processing
needs at a  particular level, others could also meet this value
through attainable conservation measures.  This was prompted by
observations  made on plant visits that many  tanneries use excess
water by constantly running v/ash-down  hoses  to waste, by unmetered
and poor control  of water used for washing and rinse operations and
by other similar  practices.

Characteristics of Total Plant Waste  Flows

An attempt  was  made to rigorously define  flow and the concentration
of waste constituents from each step  in the  tanning process.  This

was not possible due lo lack of reported data and to the difficulty
of isolating all of the individual flows during the plant testing
program made as a part of these studies.  Therefore, a comprehensive
assessment of total plant wastes  is increasingly important.

A summary of raw waste characteristics for each category is  shov/n in
Table k .   Detailed information for individual tanneries is presented
as a part of the documentation submitted as a supplement to  this re-
port.  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 8005 for Category 1,  where
the range in values is ^.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 pro-
cessing techniques among tanneries and partially to lack of  analy-
tical accuracy.  However, it is probable that a major part of the
difference is due to the variations in waste quality associated with
the multiplicity ot 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 in-
crement 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 signifi-

In examination of average values  for various parameters, the sulfide
content of the waste for Category 2 appears low, even though this is
a hair save operation.  Also, the chromium content appears high for
Category k where only some retanning is performed.   The average
chromium content is 60 percent of that for a complete chromium tan-
nery process, as shown in Category 1.  Other such apparent incon-
sistencies occur.  However, the data have been classified as re-
ceived and no further attempt is made toward explanation.

Analyses were made of the size of plants in each industrial  category,
and a typical plot for Category 1 is shown on the following page.
Production capacity coupled with wastewater flows are used later
herein to assess the economics of waste treatment.

                                          TABLE  k
                                     RAW WASTEWATER
                              CHARACTERISTICS BY CATEGORY
                           Raw Uasteiater Characteristics. kg/I.000 kg of Hide (lb/1.000 Ib of Hide)*

C low cu m/l g
Total Solids
Suspended Sol ids
Total Chromiun
Sul fides
Total Alkalinity
(as CaCOj)
Total Nitrogen
(as N)

No Of



Catrgory No 1

0 007-0 156
(0 8-18 7)
4 8-270
10 S-595
o /-Mi
0 1-19
0 1-46
0 1-70

0 5-300

3 1-44
1 0-13 0

0 053
(6 4)
4 3
8 5



No of



Category No I

0 001-0 189
(0 I-2' 6)
0 3-12
0.1-2 8
0 7-105


3 6-22
4 0-12 6

0 063
(7 6)
4 9
0 8



Ko of



Category tio '.

0 007-0 106
(0 8-12 7)
7 4-130
0 2-0 6
0 1-4 2
0 1-160

4 1-135

0 9-23
2 0-1) 0

(6 0)
0 2
1 2


9 2
*C>cept pH. flow in cu m/kg (gal/lb)

                                      TABLE  k   (Continued)

                                        RAW WASTEWATER
                                CHARACTERISTICS  BY  CATEGORY
                                                   s. kg/I,000 Vg of Hide (lb/1.000 Ib of Hide)1
	Category Ho  4	     	Category Ho  5	    	Category tip  6	    	Category Ho  J	
Ho of                         No  of                        Ho  of                         No  of
 Dtita                           Data                          Data                           Data
Point',     Range     Average     Point*     Range     Average    Points      Range     Average     Points     Range      Average

  10    0 003-0 0}3    0 020       20    0.006-0 204    0 063        30 014-0 056   0 028        40 0003-0 002   0 0006
        (0 3-J 9)     (2 "i)              (0 7-24 4)    (76)              (17-67)    (3 "0              (0 03-0 20)   (0 07)

   3      6 7-67       37         8       10-140      67         2       32-160      110         I      3 5-4 5      39

   3      5 7-63       28         5       11-265     170         2       53-155      230         I      66-87      74

   2       47-285      140         7       52-980     4JO         2      210-910      595         1       69-71        70

   3      70-125      47         8      31-865      88         2       H-185      110         1      22-33      26

   3      04-48      26         7      01-21     12         I      38-59      44

   I        21        21         I        45       "> 5         I      20-63      37

   3      2 2-19       79         70 6-46       24         2      I 0-19      66         I         10         10

   I          39       39         36 6-180      69         I       37-54       43

   2      08-65      37         5      0 6-29      6 0         I       14-18       16

   3      3 4-11 2                 91 5-12 5      -         29 2-10 4      --         26 2-67


Raw and treated waste  characteristics were also  assessed for each

category  in  relation  to the size and age of  tanneries.   No signifi-

cant relationship  is  observed.  For example,  some  old,  small tan-

neries produce  effluents of better quality than  those which are new

and large;  the  opposite case  is also noted.
   3000 -
   2000 -
                                                               - 1500
    1000 -

                    10   20   30  40  50  60  70  80   90

                       RELATIVE CUMULATIVE FREQUENCY (%)


                              SECTION VI


 Selected Parameters

 Several sources of data were reviewed to establish the principal
 parameters which indicate the pollutional  significance of tannery
 waste.  These include:  state and local regulatory agency records
 Corps of Engineers' discharge permit application, communication with
 and observations at many tanneries, and literature references.  The
 following constituents are chosen as the major pollutant parameters:

      1.  Five-day biochemical oxygen demand (6005).

      2.  Chemical  oxygen demand (COD).

      3.  Total  chromium.

      *.  Grease.

      5.  Sulfide.

      6.  Suspended  sol ids.

      7. Total  solids.

      8.  Total  kjeldahl  nitrogen.

      9.  Ammonia nitrogen.

     10.  Nitrate nitrogen.

     11.  pH.

     12.  Color.

     13.  Fecal coli forms.

With  the exception of chromium,  nitrate nitrogen, and color, all of
the above constituents are critical parameters for all complete pro-
cessing tanneries (beamhouse  through finishing).  Chromium is pres-
ent only when the firm uses chromium salts for tanning or retanning.
Nitrate nitrogen is not very  prevalent due to lack of nitrogen oxida-
tion  in present waste treatment  systems.  Color is mainly significant
tor firms using vegetable tannins for tanning.

The most significant toxic constituent in tannery waste is chromium
Ammonia nitrogen levels found in tannery wastes can also be toxic to
Ush and lower forms of life.   There have been  a few isolated reports

  of mercury and phenol; these materials have been traced lo preserva-
  t vcs used for some hides being shipped to tanneries.  Sinwsa?  or
  o her bactencides or fungicides are satisfactory for preserving

  u ed i'nmrhCUfy; " T'' ^ "^ SUCh LXiC c?^ should not be
  used m the future due to potential environmental problems.

  Rationale for Selection of Identified Parameters

  BO^ -  Tannery waste contains significant  quantities of matter which
  is  reasonably easy to degrade biologically.   One of the mo   wide-
  spread  Parameters  used for measuring the  strength of waste  s  he

  s.',"o?y,        '  (2? C)"   The BD  P3rame ter  '* Particularly a mea-

  o<'  recVivinYlTr^'n'1  ^  "^  "" ' haVe  n the XV9en -"tent
  o.^ receiving  waters.   Oxygen  ,s  essential  for  fish  and other  aquatic

 ~,~ Tfe 5D  Parameter  's  an  important measure of  waste  strengths
  par  ,cu ar y where a  significant part of the organic matter con' a  ned

  surf?!,    VS-n0t  biode9radab|e-   COD parameters  can  be  used   o  mea

 on the BOD!    " PtenLial f  tannery W8Ste'  "articu'ar'y   a
                -Most of the  leather produced  in  the U.  S.  is  tanned
 tMer.fo-     .                     lX?C t0 a^ati-  life and
 t.ierefore,  is an .mportanr parameter to be  identified.  There  is

 vaienTsta? '   ^ thal fchromi um '" both the trivalent and hexa-
 valent state is toxir:  an.) th._.s +kf i-r>f.-.' ci- Qn :   _______        .
 be used                           " ""        "'" "-" u""JLtl
 Gicase - The grease analysis measures different types of materials
 including oils,  fats,  and other such matPriaU r^L^.. ^..l! If I.1

 ^imarflnn^h5-  h^^ f ^ ^ ^"^ ^^^'^'
                        '  " *" "  ** Ms added tO the hide d"ri
 menta   o  surfu-    ^ amUntS    M  9nd grease can be dt
 Hon   larn            *"   Y retardi"9  ^ream reaeration.   In addi-
 ti on   large  amounts  of  oii  and grease  are unsightly and biological
 degradation  may  result  in  odor problems.                 o.oiog.cai

 |u1fid-e- " A  ^gn^icant portion of  alkaline  sulfides contained in
 tannery wastewater can  be  converted to hydrogen  sulfide at   H b "ow
 0-5 to 9.0,  resulting in the  release of this  gas  to the atmosohere

                                                          " ?
d scooraUonT5' *"  ^ ^  '" Pr'  da-  e  thr    h   ant
furic r?H          MW6rS> hydr9en  sulfide can  be  oxidized  to  sul-

t fs   canCKT?h rW?L'.COrrOSion-  At hi9h- concentrations
inis gas can be lethal.  Th.s  is particularly significant as  a  ha7-

tn the Smh main^anc^  ^f'>* compounds are used extensively
       bf       Unh"Mn Process a"d  thu, are found  in'
       consSI/dS-   Ma5?r'aJ fOUnd '" susPend^d form in tannery waste-
       cons.st primarily of proteinaceous substances (flesh, hide, or


  effec t.ve parameter to assess the impact of dissolved mater
  cite 9su fErt'; H' the dFssolved ^"ds are sodium chlorde'and
  sa t f rrl  h      ^'Um chloride com" Principally from rcmoval  o?
are th^ ''tr^n " TJe Pr!n^Pa> sources of ammonia In tonnery wastes
result frrHUm *   ^ ^ '" the bating proccss and that which
cal U?l ,   ^     POSIt'n f rganic n?tr9e"-  Ammonia is a critl-
" ms of  t?  Parame;er because !t is toxic to fish and other lowe
waters  and T L* a. '^9e1con5umer of dissolved oxygen in receiving
"               Pr'nC'Pal nUtfient "abl
 wters  and             1
 "gal growths!   Pr'nC'Pal nUtfient "Pable f """"'-ting excessive
                         ic and ammonia nitrogen Is progressively
 Hioh C0nc           t:ea!ment P]a"t or stream to nitra'e nitrogen.
                10"    n'
                     K                        tO both huma"= and an i -
                are the orinrinal  ,-=,.,* ~f  _i _____
         , hunans.  Nitro3en in tte^ o^"
 source of nutrients for excessive growth of algae.
 of  the    t       y          'S  Parameter  Is  thus  an  important measure
 of  the  potent, al environmental  impact of tannery wastewater.

          PlVf  tannepy waste  !s dependent  upon  the type of process
conditions may  inhibit growth of st ream% iora' ^Thus '^iis 'an fm
portent parameter to evaluate the  impact of the waste on ^e en^ron-

^frabletan f^l" ta"nerV.resul ts Principally from the chrome or
vegetable tan l.quor and var.ous dyes and paints used during coloring

operations in the production of the leather.   The contribution  by
vegetable tan is by far the greatest.   Excessive color may  inhibit
the activities of some aquatic life, but it is primarily of concern
from an aesthetic standpoint.

Fecal Coliforms - Microbiological testing for the presence  of total
coliforms will  indicate the potential  for the wastewater to contain
pathogenic bacteria.  Since many tanneries have sanitary sewage fa-
cilities connected  into the  industrial waste sewer system,  the fecal
coliform parameter  is an  important one.

Other Constituents  of Less  Importance

As  indicated  above, measurement  of  dissolved solids as a pollutant
parameter  is  not  considered  critical, since this  is a computed value
resulting  from  analyses made  for total  and suspended  solids.  Limits
placed  on  total  and suspended solids  automatically set  limits for
dissolved  sol ids.

Measurement  of  dissolved  oxygen  in  some areas  could be  essential,
particularly where a  large waste flow enters  a very small  stream.
 In  general,  however,  with high levels of treatment to remove oxygen
demanding materials and  reasonable stream dilution, dissolved  oxygen
 should not be a critical  problem.

 Determination of the fixed and volatile portions of both total,  sus-
 pended, and dissolved solids is  not considered particularly signifi-
 cant as a measure of pollution when the previously  identified^para-
 meters are measured,   volatile soiids tests  will ue  .equ.reu ror
 proper in-plant controls and monitoring.  However,  they are not  that
 essential for final effluents when the other tests  identified above
 are performed.  Volatile solids analyses are desirable for plant con-
 trol purposes, however, when suspended solids  in the  effluent rise
 above  normal levels, as this may indicate problems  in an aeration

 Alkalinity and acidity are not  considered key  parameters for assess-
  ing the pollutant  significance  of  tannery wastewaters when  pH and
 other  constituents previously described are monitored.  Although
 high alkalinity  or acidity  can.occur when pH  is  around  7, the likeli-
 hood of this occurring followiAg  proper treatment is somewhat remote.

 The use of  total  organic  carbon (TOC)  is  possibly a  desirable measure
 of the waste strength.   However,  this  analysis requires sophisticated
  equipment and  may not add significantly  to  the information  which  can
  be gained by BOD^ and COD data.

  Temperature is not considered a significant  parameter,  even though
  some  process steps within the tannery can discharge  waste with
  temperatures up to 60C  (l*.0F).   Mixing  of these high temperature
  streams  with other discharges usually results in an  average effluent


temperature much lower.   In  addition,  extensive  aeration  and  deten-
tion time in biological  treatment units will  further reduce the
temperature so that it approaches ambient conditions.   During the
winter months in the northern climates, the warm waste flows  from
the tannery will be beneficial to biological  treatment processes
and are essential for maintenance of treatment efficiency.

Although the tannin used in the vegetable tanning process is  complex
in nature, sometimes difficult to degrade biologically, and is a
major source of color exhibited  in effluents, it is not considered
a key pollutant parameter.  Use of tannin recycle systems generally
are minimizing discharge of these wastes; the impact of tannin  is
indirectly measured through the  BOD5> COD, and color analyses.


                            SECTION VI I


Waste treatment practices in the leather tanning and finishing  in-
dustry 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 munici-
pal sewer have been less stringent than those for a tanner discharging
to a stream, lake, or ocean.  Therefore, those systems providing a
h i n^"r H.Tirr - nf ! - -.-*..= - a-c. =c =n/- !=.<>.-! i ; i-1. --. .:..  .::. . t.   
  \f      ^ '     - -   - - -   -  w w . w fc. C  I.II..I t. U I I I I w I I l~ . t-l*l\*IJWIVJIII^
directly to bodies of water.

Variations in treatment schemes are also due to the differences  in
raw waste characteristic*; assnrI^te^ with processing ^>!des into d:f-
ferent types of leather.  Although the basic unit operations are the
same, variations in sub-unit processes create a variance in both
effluent quantity and quality.  These differences are attributed to
the need to obtain different finished leather characteristics and the
general attitude of tanneries to produce the desired leather quality
without regard to conservation of process chemicals and water.

Based upon communication with around 1^0 wet processing firms  in the
industry, approximately 60 percent of the tanneries discharge  to
municipal systems.  Analysis of these same data indicates that  tan-
neries discharging to municipal sewers also represent about 60  per-
cent 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  (about 21) have
viable on-site secondary waste treatment facilities.  Of those  em-
ploying secondary treatment, only three have activated sludge  plants

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

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

3.   Major reduction of BODr and suspended solids.

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

    b.   Some additional nitrogen removal beyond that provided by

    c.   Normal treatment configuration  includes some type of bio-
        logical  process followed by effective removal of suspended
        sol ids.

I*.   Major reduction of all forms of nitrogen.

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

    b.   Treatment follows biological treatment for BODr 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 BODr,  suspended solids, and
        ni trogen .

    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-

6.  Waste treatment for hide curing facilities.

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

    b.  Treatment for  all  levels except pretreatment  requires
        direct  incineration of  total waste or  solar  evapora-
         tion in ar id  areas.

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

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 con-
stituents.  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 solu-
tions can produce economies which will at  least partially offset

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

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

      i.  w'diei ounber vd i i on.

      2.  Process solution reuse or  recovery.

      3.   !fi-plant  treatment  tO  I'eiiiOvc  a 5p6CifiC waStc CGnS I i Luci'iI .

By reference  to Table  3,  it  is  noted  that  water use per unit weight
of hides processed varies significantly  in all categories.  The vari-
ations  for  three categories  in  which  cattlehides are  processed  is
shown below:

      Category     Unhai ring     Tanning     Range  in  Water  Use
                                              cu m/kg  of hide
                                              (gal/lb  of hide)

         1            Pulp       Chrome         0.007-0.156

         2            Save       Chrome         0.001-0.189

         3            Save       Vegetable       0.007-0.106

 If equivalent leather  quality is  being produced  in each  category
 and  with a reasonable  allowance for process differences,  the vari-
 ation in water use seems unnecessarily large.  It  would  appear logi-
 cal  that tanneries with large water use could implement  some reduc-
 tion measures.

Although reduction wou1d resuH 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 par-
tially on the basis of flow.  Therefore, a reduction in flow would
reduce both treatment plant capital and operation costs.

Realizing the economy of reduced wastewater 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 waier 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

     3.  Limit or  eliminate some washing  and  rinsing operations.

         a.  Change d continuous rinse  to a batch rinse.

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

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

The  Elberle Tanning  Company  in Westfield, Pennsylvania,  has recently
undertaken a comprehensive water conservation program.   Through  im-
plementation 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  hydro-
sieve  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 con-
servation  program can substantially reduce  water use.

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


When hide processors are used in the beamhouse operation, the water
use through deliming will be about 0.00835 cu m/kg of hide  (1 gal/
lb of hide).  Blue Side Company of St. Joseph, Missouri, which uses
hide processors for all operations from the raw product  through
chrome tanning or "blue" stage has indicated  that water  use  is from
0 0125 to 0.0167 cu m/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.  The  Bona Allen Tannery  in Buford,
Georgia, uses the  same  water  for  washing following  their mod.f.ed
pickle"  operation  and  following  their  vegetable  tanning  operation.
The  Elberle Tannery  in  Westfield,  Pennsylvania,  uses  a  similar  pro-
cess  for recycling  the  soak water following  the  vegetable  tanning
operation  back  to  the  color operation  that precedes vegetable tan-
 ning.   There are also  some  indications that  spent  liquors  previously
 used  in vegetable  tanning  are reused in  retan operations.   The
 California  Tanning Company  in St. Louis  indicates  that  they are
 using bate  wastewater  for  alum tanning make-up water.  The  Coey
 Tanning Company in Wartrace, Tennessee,  is planning to recirculate
 approximately 20,000 gallons per day of treatment  plant final efflu-
 ent water for use  in the delime wash water following the pulp hair
 process and for wash water following the batp process.

 Reuse or reduction of process solutions or recovery of process chem-
 icals has  been demonstrated to be a method of waste constituent  re-
 duction.  A detailed summary of methods available  to reduce waste
 constituents by process adjustments is given by Wi11iams-Wynn  (9)

 There are  a number of  vegetable  tanneries that are using recycle sys-
 tems to reduce the amount  of tan  liquor that  is discharged  into  the
 waste stream.  Although these are not total  recycle  systems, they do
 substantially reduce  the amount  of  tannin  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 evapora-
 tor  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  pre-
  sented a  summary  of methods for  recovery  and reuse of  spent chrome
  tanning solutions.   During World War  II,  the reuse of  chrome tan
  liquor was common practice because of the scarcity of  chromium salts.

  Seton Leather  Company has performed a study on the reuse of chrome
  tanning solutions.  These tests showed that the chrome liquors could
  be reused for  periods up  to six weeks without reduction of  leather
  quality.   The spent tan liquor  in this study was settled and sludge
      drawn off the bottom  of the holding tank.  The clarified solution


 was  brought  to the required concentration with chromium salts,  sul-
 furic  acid,  and sodium chloride.   Because of the sludge drawoff,
 this i/as  not  a complete recycle systems,  however,  a substantial'por-
 tion was  recycled and only a small  amount wasted.

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

 The  A. C.  Lawrence Leather Company,  a shearling tannery in Winches-
 ter, New  Hampshire, has been able to reuse  their chrome tan  solu-
 tion 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.

 The  Gunnison  Bros, tannery in Girard, Pennsylvania, reports  reusing
 retan  liquors.   The Howes  Leather Company in  Curwensvi1 le, Pennsyl-
 vania,  reports  reusing  the finishing  oils.   Many tanneries are re-
 porting recycling their pasting frame water  either  wholly or par-

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

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


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

     1.  Air oxidat ion.

     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

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
n.-.-r  .-\\'{.-.! i r.r '-.n 1 .. :mc  at  r.s2r amb'ent 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 effec-
 tive.   Although the relative costs for the tv/o catalysts favor man-
 ganous 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 manganese to sulfide
 weight ratios of 0.15.  Pretreatment facilities employing catalytic
 oxidation should approach 100 percent  removal of sulfides.

 Sulfides are also  removed in the activated sludge.

 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 sul-
 fide bearing wastes.

Pre treatment.

Pretreatment 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
san i tary district.

The need for pretreatment is based on the following factors:

     1.  Sewer safety and maintenance.

     2.  Biological treatment protection.

     3.  Effluent criteria.

     *.  Sludge disposal criteria.

Sewerage systems are particularly susceptible to damage from high
sulfide wastes.  Tannery effluents may contain sulfide concentra-
tions as high as 250 mg/1.  An alkaline sulfide bearing waste from
a tannery when mixed with sufficient domestic or acidic industrial
waste will release hydrogen sulfide gas.  At a pH of 7.5, about 30
percent of th* <;nlfiHp  ion in the 1-.'OStS is nT1".?.^1 ."". 'v.'H-.-!~-'->  s-'J 1 
fide 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  con-
centrations.  Hydrogen  sulfide will also discolor some painted

Tannery effluents exhibit a wide range  in suspended solids concen-
trations (300-1^,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 at a municipal treatment  plant,
grease can coat sewer lines and act as an adhesive for other particu-
late matter.  The suspended material consisting of much lime may  re-
duce sewer capacity through direct sedimentation.  A calcium carbonate
scale will form when sufficient carbon dioxide is present.

Aerobic biological treatment processes can be seriously inhibited by
some tannery waste constituents.  While normal average concentrations
of lime and chromium salts do not appear to damage the system,  short
term high concentrations could be detrimental to biological activity.
The high alkalinity (and corresponding high pH) are caused by lime
discharges from beamhouse operations.  Such discharges are normally
intermittent.  Trivalent chrome is used extensively as a  tanning
agent.  Hexavalent chrome may appear in trace amounts from some
finishing operations, but trivalent chromium is the predominant form


, the waste.   There appears to be some evidence to indicate that
both forms can be toxic (12).  Of prime importance is the solu-
bility.  Trivalent chromium salts are soluble in acid and neutral
solutions.  At a pH greater than 8.5, trivalent chromium will  be
precipitate while hexavalent chromium must be reduced prior to pre-
cipitation.  Total chromium concentrations of 10 mg/1 are indicated
as hardly toxic to biological units  (13), although allowable muni-
cipal treatment plant effluent levels are presently well below this

The batch nature of tannery operations create wide fluctuations  in
waste  flows and waste strength.  Such variance can be difficult  to
handle, particularly at the conventional smaller municipal  treatment
plants'where  tannery wastes are  a  significant part of the total  flow.
The  BOD5  may  be as  low as  150 mg/1  or may exceed 3,000 mg/1 with an
average usually from 1,000  to 2,000 mg/1  (10)  (11).  Significant
reductions  in  BOD5  and equalization of  flow and waste strength may
be  required to avert overloading of municipal bilogical  units not
sized  for the tannery waste.

Effluent  criteria  applied  to municipal  plants  in  regard  to  parameters
such as nitrogen,  color, and dissolved  solids will further  indicate
the need  for  pretreatment  facilities.   Vegetable  tannins, although
not toxic,  combine with  iron derivatives  to  form  oiacK  ifon LanndLtS
which discolor waste  streams and are difficult  to  remove._  Salt
utilized  extensively  in  preserving hides  and  in  the  pickling  pro-
cess cannot be removed  by  normal treatment  processes.   Nitrogen
 levels are high,  since  ammonia  is  utilized  in  Liie  bating process
and considerable protein  comes  off the hides.

 In some  instances, constituents in the waste may affect character-
 istics of and disposal  methods for the sludge produced  by a system
 receiving the waste flow.   For example, the chromium content  of the
 waste may be  low enough to have no effect on biological processes,
 yet be concentrated sufficiently  in the sludge to pose a potential
 leveling problem in a landfill  or  impair the operation of digesters.

 Combinations  of physical and chemical processes have proven effec-
 tive  in  reduction of tannery effluent constituents to levels desir-
 able  for conveyance and treatment  at municipal facilities.   Presently,
 pretreatment  facilities are concerned with reduction of suspended
 solids,  grease, 8005 chromium salts and sulfides, pH adjustment, and
  flow  equalization.

  Pretreatment  operations consist of one or combinations of  the fol-
  1ow i ng:


    1 .   Screen!ng.

    2.   Equali zation.

    3.   Plain sedimentation.

    *4.   Chemical  treatment.

        a.   Coagulation  and  sedimentation.

             1)   Alum.

             2)   Lime.

             3)   Iron salts.

             4)   Polymers.

         b.   Carbonation.

     5.   pH adjustment.

     6.   Sludge handling and disposal.

These same unit operations and unit processes are also 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 wastewater con-
stituents, the screenings themselves create a solid wasre disposal
problem.  The highly putrescible wastes are commonly disposed of
on-site or at remote landfill operations.  Screening equipment in-
cludes coarse screens  (bar screens) and fine screens, either per-
manently mounted or  rotating with self-cleaning mechanisms.  The
exact contribution of  screenings on parameters such as BOD,; and sus-
pended solids is not known,  since large particles are removed prior
to obtaining  samples for testing.  The principal function of screen-
ing  is to  remove objectionable material which has a potential for
damaging plant equipment and clogging pumps or sewers.

Equalization  - Equalization  of waste  streams  is  important  in pre-
treatment  facilities.  The volume and strength of waste  liquors vary
depending  on  process formulations and scheduling of  tannery opera-
tions.  Alkaline wastes  are  associated with  beamhouse operations,
while acid  discharges  occur  from the  tanyard.   In order  to  produce
optimum  results  in  subsequent  treatment operations,  equalization  of
flow, strength,  and  pH of  strong liquors  is  required.  Although some
oxidation  may occur, no  removal  of  waste  constituents  is normally

reported for equalization.  Equalization  basins  provide  storage
capacity for hydraulic balance.  Auxiliary  equipment  must  provide
for mixing and maintaining aerobic conditions.   Detention  times  much
less than one day are usually provided.   Basins  can  be monitored
through pH and flow measurement.

Plain Sedimentation - Plain sedimentation  is  concerned with  the  re-
moval of non-flocculating discrete particles  and floatable low density
materials such as grease and scum.  Tannery wastes  have  high concen-
trations of both suspended solids and  grease.  As  shown  in Table 5,
suspended solids reductions can  range  from  approximately kO  to 90
percent, while reductions  in BOD^ can  range from 30  to 60  percent.
Much of the suspended material  removed  is  in  the form of insoluble
lime which produces a voluminous and heavy  sludge.   Although grease
removals are not indicated, high removals are expected with  surface
skimmers installed  in clarifiers.

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

Laboratory experiments by  Sproul , et al.,  (15) utilizing beamhouse
anH /-hrrtrpo 1 iny^rc  gKr^i.io/H  l-h^f  n ! C ! n S2C! ' r?en t2 tl ! O*"*  ri *" ."?!"! fiVC^^f ^ ril. .'
                     r^i.io/H l-h^f n ! C ! n S2C! ' r?en t2 tl ! O*"*  ri *"  ."?!"! fiVC^
rate of 2k. 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 qave 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 co-
agulant for composite wastes containing 2,000 mg/1  suspended  solids.
Overflow rates of 1A.3 cu m/day/sq m (350 gpd/sq  ft) produced a 2
percent underflow concentration.

Field observations at S. B. Foot Side Leather Tannery  at Red  Wing,
Minnesota, tend to confirm  these removals.  The primary  units con-
sist of two circular clarifiers with overflow rates  of  18.8 cu  m/day/
sq m (A60  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  pump hair beam-
house operations followed by chrome tan and finishing.   The following
average removals resulted  (10):

                                                         TABLE  5
                                              PLAIN  SEDIMENTATION
                                 impended Soil0>                         600
    5,e-                    lif      t'f      Fe-Urfjl         Irf      I't       Fe-o/al                remarks             Fe'ercrje
                             ng/l     ng/l       *            ng/l     /-?/1        t

llgoo,                         ---      ---      BO-90          ---             EO 50          Fill n dr Mnrt w.ih    (It)  (19)   j
                                                                                             ?4-nour CJpjciiy

&edirn[alion tanVs.             900      130      63-88          3SO      1^6       10-63          Prelrclnent of vcscuble       (to)
rvchjnlcal iKSgc                                                                               un llguort   klcnlion
facilln4                                                                                     llw 9-IS >>ours

ScDiPcntllion ltnl,i            1.200      370       M           "-             "           Oelenllon line 2 houn          (ID

Stdin.mil.01 unhi            1.IBI      (CO       M          1.01.6      537        *8           tonl.nuoul flo- (pilo )         HI)

Scdineruiion [an^s            I .tBO      (61       (7          I .ZBS      873        30           Fill ind drw (pilot)          dl)

                                 Influent   Effluent   % Removal
                                   mg/1       mg/1

   Suspended Solids                3,125        945        70

   BOD5                            2,108      1,150        45

   Total Chromium                     51         24        53

   Total Alkalinity (as 3003)       980        718        27

   Grease                            490         57        90

Suspended solids and BODj removals were 70 percent and 45 percent,
respectively.  A low chromium removal of approximately 50 percent
occurred.  Higher removals would result if a pH of 8.5 were main-
tained  (using equal\zat ion or chemical addition) in the primary
clarifiers.  Theoretically, all chrome should precipitate as chromic
hydroxide; however, a very small residual is expected.  Although
chrome  removal from the wastewater is desirable, a sludge problem
is created if proper disposal precautions are not taken.  The total
alkalinity was reduced 27 percent, reflecting sedimentation of sus-
pended  lime.   Grease removal was 90 percent.

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 equal ;zat !OP and sedimentation, eff'uent concentration? r? not-
reported below 130 mg/1 for suspended solids or 146 mg/1 for BOD
(Table  5).  High chromium removals may result while sulfide con-
centrations are relatively unaffected.  As a unit operation, plain
sedimentation has desirable application in tannery wastewater treat-
ment .

Chemical Treatment - Coagulation and Sedimentation - Chemical addi-
tion prior to sedimentation has further increased the removal effi-
ciencies of primary clarifiers.  Chemical coagulation results in
higher  removals of suspended solids, 6005, sulfides, chrome, and
alkalinity through flocculation of colloidal particles.  Alum, lime,
iron salts, and polymers have exhibited satisfactory results.  Data
in Table 6 indicates that suspended solids removals from 50 to
above 95 percent and 8005 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 wastewater analyses indicate concentrations of BODj
at 2,500 mg/1 and suspended solids of about 2,530 mg/1.  The follow-
ing results were drawn  from the laboratory scale investigation (15):


Coif ill* Jon-SeCi^enia.ien
Plun Sedircrtatior
Coagjlat Ion, SrSircntatloi
Aeration, Coagulation.

Coagulation, Segmentation
Coagulation, Sedimentation
Coagulation. Sedirentatlon

Coagulation, Scdirrntatlon
Equalization. 2-sl*ge
Carbonatlon. Coagulation.
Carbonatlon. Coagulation.
 Oxygen demand
* Order-of-nagnitude value*
Sus&erded tol ids B3D
 * 	 ?s7T ng/l  " ^/1 rg/1 ',
Mun 1.5 SO 68 56 -- " 90r djuttnent of 5" water
Alun 2.500 850 66 3.600 1.030 73  Pile. ...<:, .f ore-
j.tcrent of p* to 5 5
lira 918 469 9 1.001 ^76 &2 Continuous flow with line
concentrations of 1,490.
Lire 1.360 197 75 I.6JO El] Ii9 fill ind rw -111 lira
coneeriralions of 1 .700
lier 3. US 110 95 l.<>37 (19 57 Mjuimnt of pi nn b.in-
rioute liquors Dvcr'lo*
KiS g.l/d<)/ Ireatrcnt
produced  floe which settled
qu Icily




     1.  Use of an anionic polymer at a concentration of 1  mg/1 re-
         sulted in a reduction of about 8b percent in suspended
         solids and 60 percent in BODc.

     2.  Adjustment of the waste to pH 9.0 with sulfuric acid and
         subsequent settling gave average removals for suspended
         solids and 8005 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 BOD^.

     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 6005 by 90 per-
         cent and suspended solids from k$ to 57 percent.   Alum con-
         centrations higher than 500 mg/1 created a floe that would
         not settle.

     6.  Buffing dust resulting from finishing tanned hides was not
         foiir.H to -rt " -3"cct'V2 coagi: 1 a~ t.

In general, polymer addition produced a rapid formation of floe min-
imizing the need for flocculating equipment.   Without pH adjustment,
Dolymers produced consistently higher rpmnva 1 <; than ofhpr rnannlflni-<;

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

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

The removal of color is not commonly reported by investigators.  Low
removals are, therefore, expected.  In pilot plant operations des-
cribed by Howalt and Cavett (18) and also by Riffenburg and Allison
(19), 93 and 99 percent removals of color were observed, respec-
tively.  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 v/aste indicate high color
removals  (9^ percent) through a combination of chemical precipita-
tion and coagulation with calcium hydroxide and an anionic polymer
(20).  The efficiency is dependent on pH control around 12.

In general, constituent reductions with coagulants are limited to
suspended solids, chromium, and possibly sulfide and color.  6005
removals are a function of that portion of the 6005 existing in the
colloidal or suspended form.   Soluble 8005  is normally AO  to 50 per
cent of the total BODj (10).  Many  low removal efficiencies may
have resulted from  inefficient control of the phys ical --chemical
operations, which require operator attention to be successful.

Chemical Treatment  - Carbonation - Carbonation  is effective  in the
c r c a n rne n r or c i K i t n c  * ^ 'j L cz j    ;  t  . i  i c  p r j c c s s f  c 2   ~  ; :  *,-:  . ^ -
acts with lime  to  form calcium  carbonate, which  has a solubility of
only 25 to 50 mg/1 .  The  crystalline structure of the carbonate
nucleus provides an effective surface for adsorption of organic
rncsttcr.  Suspended sol ids 2nd BOD*" 2T2  both r^rlnrori ,

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

Table 6  indicates  high removals for  suspended  solids, 8005, and
alkalinity for  carbonation  in conjunction with coagulation.   The
8005  removals  range from  85  to  92  percent, while suspended solids
reductions as  high as 99  percent are  recorded.

Field data from Bona Allen,  Buford,  Georgia,  indicate high reduc-
tions  in  suspended solids,  BOD, and  total  alkalinity.   Estimated
flows  from the cattlehide vegetable  tannery were 1,700  cu m/day
 (O.A5 mg/1).   Primary clarifier overflow  rates were about  20.^
cu m/day/sq  m  (500 gpd/sq ft)  for  a  chemical  system utilizing flue
gas carbonation and a combination  of iron  salts  and polymers.   (Sul
furic  acid  is  also used  to  assist  pH control).   The following re-
movals  were  indicated  (21):

                                 Primary     Primary
                                 Influent    Effluent    %  Removal
                                   mg/1        mg/1

   Suspended  Solids                 2,110        100          95

   BOD5                            1,660        270          M

   Total  Alkalinity  (as CaCO^)        6^0          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 condi-
tions, for suspended solids and BOD-j..

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

Sludge Handling and Disposal - A major part of  tannery waste treatment
is'Tiandling and disposal ot  the  semi-solid  sludges oocainea irum^iiquiu
treatment processes.   The most predominate  methods of  ultimate disposal
of tannery waste  sludges includes  sludge  lagoons,  landfills, dumps, and
spreading on  the  land.

Some  attempts have  been  made to  dewater  sludges  prior  to ultimate
disposal  with varying  success.   The  three  principal  dewatering  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  mat-
 ter  is difficult  to decompose  by biological activity and  probably  is
 the  reason for at least a part of.the difficulties associated  with
 digestion.    In addition, high  chromium levels can inhibit  the  activity
 of some microorganisms which stabilize organic material.

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

 Conditioning and stabilizing a mixed domestic and tannery sludge using
 heat  treatment processes has been employed also at Gloversvi1le-
 Johnstown facility in New York  (about 80 percent of the waste flow
  is tannery waste).  Such heat treatment provides a stable end pro-
 duct  from a  biological  standpoint and can  be  incorporated  in a land-
  fill  or  spread on  the  land.  One  of  the principal difficulties with


tannery waste is the chromium content in sludges and the potential
impact this material has on the environment from a toxic standpoint.
In testing a heat treated sludge, it has been indicated that some
of the trivalent chromium may be oxidized to the hexavalent form.
Apparently, the trivalent chromium is converted through the high
temperature, high pressure, and oxidizing environment of the heat
treatment process.

Prior to dewatering 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 type of chemicals required are dependent
upon characteristics of the sludge being handled.

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

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

Lagoons for dewatering have some limited uses.   In humid areas where
evaoors t i on aocrox i n2 tcs raipfa'l. such applicatio ' s not  como'c te1v
sat isfactory.

Use of lagoons, drying beds,  landfills, and  landspreading all require
key attention to the environmental  impact.   Particularly  important
is the leaching of potential  toxic or organic materials 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 wel1
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.

Pretreatment  - Facility Requirements - Based on  an appraisal of  needs
and  the  performance of previously described  operating facilities, the
following  processes are  included  in evaluating pretreatment require-
ments :

     Waste Flow

     Equali zation
     Primary  settling


     Col lection
     Thicken i ng
     Dewateri ng

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

A flow diagram of  treatment facilities is shown on Figure 5-  Ade-
quate 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
                                                        EFFLUEBT TO KUNICIPIL
                                                       	>	 SEWER SrSTEH


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

     Equalization                Detention:  2'i hours at design flow

     Primary Settling            Overflow rate:  23-5 cu m day/sq m
                                    (500 gpd/sq ft)

     Waste Sludge                2 percent solids

     Vacuum Filter               Loading rate:  15-6 kg/sq m/hr
                                                (3-2 Ib/sq ft/hr)

Major Reduction of BODq and Suspended Solids

Major reduction of BODr and suspended solids requires a higher degree
of treatment than that provided by normal primary or pretreatment
facilities.  This higher  level of treatment  is referred to as secon-
dary treatment.   It generally includes a biological unit process and
may or may not require a  pretreatment step.  Such facilities may be
located at a municipal plant treating a combined municipal-tannery
waste or may be an on-site plant treating only tannery wastes.  Sec-
ondary treatment  can utilize activated sludge, lagoons, or trickling
filters along with required supporting equipment to achieve required
efflupnf quality.  During warm ambient fpmnpratnrp  all ;v;tpiTi<; with
comprehensive design are  capable of equivalent efficiencies in regard
to parameters such as BODr and suspended solids.  However, cold tem-
peratures result  in poorer efficiencies with trickling filters and
lagoons.  Specific treatment system applications arc influenced by
wastewater constituents,  required efficiencies, climatic conditions,
land requirements, operational characteristics, and economics.  Num-
erous treatment schemes are, therefore, feasible.

Combined Municipa 1-Tannery Treatment Systems - Combined treatment of
tannery and municipal wastewaters predominates in the  industry since
most tanneries are located in urban communities (k).  Such systems
normally require  some degree of pretreatment at the tannery.  Typi-
cally, 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 7 are reported
combined municipal-tannery treatment efficiencies.  One example of
primary treatment only has been included to  serve as basis of com-
parison with secondary treatment systems.

All treatment methods have demonstrated capability  in at  least one
installation to  remove 90 percent of BODr 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  (2k)  present  typical appli-
cations of this  approach.

                                                        TABLE  7


                                                                                            I.   lo ft- tl- 'i
Tric.li-s '-I "                            li                  &

Ir.E.II.] '.H..     C>-b9-*..ci               I:    100    15      (S
                 MCi-'f llliol
irllklinf Illlir.    ttrtcning       ii.Hf     II                  (7                   Skbcis.     Ic'o-. .rin.lirt        (Ifl
tlbdfe dipttllci                  <9 5t                                                ^itco^sli     icrcci -s ci^rricrCfd

Ir.c.l.r,, f,li,.    ttronlng.      Jlljl     l|     JW           4!  I OE8           19  torftilit.     Vt.ii  iUr'ici      (17)
K'  S'2     It          -1M     IS         >Wl      90   kugri.        1S<
r.lt ,lunge                    (I 7)                                                0-11'IS        Ir
JKClllO" IM                                                                        '"""         "'
,,,.,jt,o. tf
tiQufa t(u4fc

                                               JEO                 (00  i             S.rrl,.        Mini tm,l, ri In       |k7)
                                                                                    DnlA'la.       1965 >-l|li ctncltv
                                                                                    CtPd*         Q* IJ CH cv r/d*f

                               U JSJ          in     II     >                      
 lotion, rou$nlng                   IB t]                                                *9" *'*      wl*4t InltnitoK of
 *lwdae' mecandarv                                                                                   color tcTOvil

In a pilot study for the A. C. Lawrence Leather Tannery in South
Paris, Maine, appropriate design parameters for combined treatment
of tannery with domestic sewage was investigated.  Approximately
equal portions of tannery and domestic sewage were used.  Test flows
ranged from 0.3-1-3 I/sec  (5-20 gpm).   At the time of the study, the
tannery production was approximately 1,502,7^0 kg (3,310,000 Ib) of
cattlehidcs per month, with an estimated wastewater 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,^63 cu m/day  (2.5 mgd) are proposed for the full-
scale facility.  Removals  in excess of 90 percent BODr and suspended
solids were required to meet stream classification standards.  The
following full-scale unit processes, listed in the order of applica-
tion, were found to be essential to meet requirements (23).

      1 .   Equalization.

      2.   Primary sedimentation.

      3.   Carbonation and sedimentation.

      k.   Addition of municipal sewage.

      5.   Activated sludge  treatment.

      6.   Sludge dewatering by centrifuge.

      7.   Effluent chlorination.

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

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

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

Pilot tests  indicate that  carbonation after equalization provides a
rapid absorption of carbon dioxide  (002) gas.  A contact time of 20
minutes was sufficient  for flue gas carbonation.  The resulting cal-
cium carbonate precipitate is expected to aid in the removal of other
suspended solids by sedimentation prior to secondary treatment.

                               DP. AFT
A volumetric loading of about 973 kg BOD,-/day/l ,000 cu m (60 Ib
BODr/day/1,000 cu ft) foi  the aeration basin with aeration capacity
of 123 kw 0&5 hp) is proposed for combined treatment.  Tests indi-
cate 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 sedi-
mentation.  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, there-
fore, proposed to be dewatered in a solid bowl centrifuge with the
resulting cake containing 20  to 30 percent solids hauled to a sani-
tary landf ill.

Nemerow and Armstrong  (2*0  investigated a two-stage biological sys-
tem.  A prototype plant treated  1,514 cu m/day (0.4 mgd) flow inter-
cepted 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 fi1ter.

     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 BODj. and  2k percent for  suspended solids.  Compar-
able values with polymers were 75  percent and  39 percent, respec-
tively  (24).   The organic  load on  the filter  ranged from  1,135 to
3,242 kg  BOD5/day/1,000 cu  m  (70  to 200  Ib BOD5/day/l,000 cu ft)
with BODr removals of  37 and  30  percent,  respectively  (24).  The
activated sludge unit  produced the highest organic removal effi-
ciency  (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 BODr removals  ranged  between 80  to 90 percent.

 In general, combined treatment  is  viable  if  proper design considera-
tions assessing  the  effects of  tannery  wastewaters are  considered.

High treatment efficiencies are technically possible in all processes.
Combined treatment usually requires that certain restrictions be im-
posed by the municipality on wastewater constituents, including
chrome, sulfides, alkalinity, grease, pH, and in some instances BOD,.
and suspended solids.

On-Site Treatment - Trickling Filter Systems - Trickling filter sys-
tems 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 demon-
strated.  A trickling filter is an aerobic biological unit.  Waste-
water constituents are brought in contact with microorganism mass
developed on the surface of the filter media.  To achieve high re-
movals 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 re-
circulation and improvements in filter media may reduce overall area
needs, the removal efficiency may not be sufficiently consistent
through the warm and cold periods to meet the demands of future efflu-
ent 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 fh<=>. system wit-h carbona-
ceous organic material.  Presented in Table 8 are reported effici-
encies for trickling filter systems.

Data is generally limited on trickling filter applications.  Bona
Allen,  Inc., Buford, Georgia, utilizes a trickling filter as the
first stage in a two-stage biological system.  Operational data re-
ported  in 1972 indicate the plastic media filter was ineffective
with removals of less than 30 percent in BODr 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 Bona Allen indi-
cate the trickling filter (oxidation tower), including secondary
clarification, has the following combined performance characteris-
tics (21):

                                       TABLE  8

                          TRICKLING FILTER SYSTEMS

Carhonation,  primary
  trickling  filter,
  final  sedimentation

Primary  coagulation,
  trickling  fi Her,
Dilution,  primary sedi-
  mentation,  trickling
  Fi Iter,  final sedi-

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

       30-80       80
56        34
821       48
                                                             Remarks             Reference
                  Indicate 100 per-
                  cent removal of
                  sul fides
                 Adjustment of pH           (27)
                 before primary
                 sedi-nerr.at ion
Foreign data (India)       (28)
Influent BODr con-
centration erter
primary sedimentation

Foreign data chrome        (28)
tannery (India).
Influent 8005 con-
centration after
primary sedimenta-

                            Influent to     Effluent from
                         Trickling Fi1ter     Clarificr     Remova1
                               mg/1             mg/1           %

                                270               62          ?8

Suspended Solids                HO               k$          59

COD                             ---              240

Total Kjeldahl Nitrogen
(as N)                                        210

Ammonia Nitrogen (as N)         	               61         	

Color                           	           300 units      	

The flow to the filter was approximately 3,785 cu m/day  (1 mgd),  in-
cluding a 50 percent recycle of the secondary clarifier effluent.
The BOD,, 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 BOD,,  and
suspended solids may not be possible due to the colloidal charac-
teristics of the suspended material and the relatively high overflow
rgtc of 37, A rij sp/Hoy/so, ^ (8f>0 gpc!/:.~. ft) :n thr :.c-n-H.'.ry rl.-ri-
Fier.  Based on estimated influent characteristics, moderate COD  re-
movals are expected, with essentially no reduction  in nitrogen  and

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  incor-
porated  into systems for preliminary treatment prior to a second
stage biological system.

On-Site Treatment - Aerobic Lagoon Systems - Aerated lagoon systems
have been utilized for tannery treatment where land is readily  avail-
able.  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  sedimenta-
tion 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 pro-
duced reasonably consistent effluent characteristics.  Ambient  tem-
peratures are critical because the large surface area permits sizable
and  latent heat loss to the atmosphere.  Low ambient temperature
level controls design.

Presented in Table 9 are removal efficiencies for those tanneries
utilizing aerated lagoons.  Although the design potential  for high
removals is documented, existing operations have not attained high
efficiencies.  A reassessment of unit functions and more operative
control may be required.

In a prototype study at Virginia Oak Tannery, Luray, Virginia,
Parker (29) investigated aerobic treatment of vegetable tanning wastes,
The system included separate equalization for beamhouse and tanning
wastewaters 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 nig)
with 7-5 kw (10 hp) aeration capacity.  Based on average influent
data and prorated effluent characteristics, the following removals
were observed:

                              Influent    Effluent    Removal
                                mg/1        mg/1         %

     BOD5                       1,043          86        92

     Suspended Solids             539         571         0

     COD                        4,4/0       l,6u6        64

     Sulfide                      1.5           0       100

           Kjeiudiil Nitrogen       88          22        75
A relatively high degree of BOD,, removal  (92 percent) resulted at a
volumetric loading of 73 kg BOD^/day/1 ,000 cu m (k.$ Ib BOD^/day/
1,000 cu ft).  Investigators report the loading may range from 16.2
to 130 kg BOD5/day/l ,000 cu m  (1 to 8  Ib  BOD /day/1 ,000 cu ft) for
BOD5 removals exceeding 80 percent (29) (30) (31).
Effluent temperatures varied between 5C  (4lF) to 8C  (46F) 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" K20 ranged from 1.42 day'1 to 1.82 day'1 for
the various operational phases (29).
In general, aerobic lagoons are capable of providing high removals
of BOD,, and sulfides with a potential for some nitrification with

                                                                TABLE  9
                                                  AEROBIC   LAGOON   SYSTEMS
                                                                      1otl Nitro^n
                    r Ibw    Inf    Iff   *f T*xal   llT   ['f   Prnvjl
Screening, plali        7>3   I.800    100      3i
  lrdlEcr.tc.lo->       (0 19)
  l*gw>nt  .rrtt.d
                    I.3.-9   1 l&O   8>S      61   l.SOO   71S
  (Vxf.  laejKii
  1ncge tiltpoial
        Ion. plain      I&I   1,750    IZB
          on       {0 0*)
                                                                                      r-ladl*>>o'e   Cattle
Separate icrccn-     (10)

n.atlon cf ten

liquor* prior to
                                                                                      Arnour       Celtic,
                                                                                      ticther Co .   lave.
                                                                                                                   ti-e Iwrl      (10)
                                                                                                  Chron*      labtc tcnnlnq
                                                                                      Cunnitsn      Cell It,
wailr i f*~i
prior to iera-
tion   I. rtrlon
dvtrnclon d-
20 (!)t


long detention periods.   Existing facilities need upgrading through
proper monitoring and control.   The successful  application of aerobic
systems will  be contingent on the availability of land and proper
assessment of the climatic factors influencing design.

On-Site Treatment - Aerobic-Anaerobic Lagoon Systems - Aerobic-
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 opti-
mum characteristics of both biological functions.  The lower anaero-
bic zone, although requiring an extended contact time, is effective
in treating high strength organic wastes.  The degradation products
produced are:  methane, hydrogen sulfide, and ammonia which are
readily available for utilization or further removal.  Since the
process does not require dissolved oxygen, minimum surface area  to
volume ratios are required.  In general, the anaerobic process pro-
duces a waste which  is more amenable to  subsequent treatment.  A
more complete degradation occurs  in  the  upper or aerobic  zone of  the
lagoon.  The major decomposition products are carbon  dioxide and
water.  Aerobic  surface conditions are  required  to prevent escape
of anaerobic products which create odors such as hydrogen  sulfide.

Stratified lagoons are generally deep,  3-7~/.6 m (12-15  ft), but
shallow depths,  l.z-i.5 m  (*-:>  ft;,  are  SOHICL Imca employee,  f-.ccn-
anical aerators equipped with erosion  shields provide the desired
surface oxygen  requirements without  disturbing  the  lower  anaerobic

Presented  in  Table  10  are  data  for  aerobic-anaerobic  lagoons treat-
 ing  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).

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 aera-
 tion capacity of 7.5 kw (10  hp) and volume of the lagoon were held
 constant  while flows were varied to impart various loadings on the
 system.   In  the initial  phase  the following removals were experi-
 enced :                       '

                                Influent    Effluent    Remova1
                                  mg/1        mg/1          %

      BOD5                        1,170         27^        76

      Suspended Solids             	          503

      COD                         ^,730       2,113        55

      Sulfide                        0.7           0        100

      Total Kjeldahl Nitrogen        107          35        67

                                                         TABLE   10
                                          AEROBIC-ANAEROBIC  SYSTEMS
                                             &biprndd lolitfi
                                                             Inf   Iff    Removal    7nncr>      rToct      rcnjrki
Scr.er.lrg. plain      1 IS)  I.)00   603
  tfdlnenttllon       (D 3d

  (goon, f.nal

  eh lor InjtI on
                                          3000   165*     9S
Ttnnlrj CO .  Itwvp Site,  drnitri Mention
frth FoBfMl, chrome     l not Indicated


H(M*t       C(lU.     Prlurr fettling      (10)

Leather Co  .  **. .eQ*  of bM-*ojie
Curwenitfllle. tabtt      flow* prior to
Pcr>niylwanl            rifting with
                     ipcni tani
        Anthnrtlc vcrgr

            on/  W3S aPProxim*tely 76 percent for an organic loading
          g BOD /day/1,000 cu  m (8.7 lb BOD,/day/I,000 cu  ft)    Temp-
  peratures ranged from 5"C (MF)  to 2/i'C ?76F)  for this  operational
  phase.   Suspended solids in  the  effluent were high, indicating the
  need  for more effective  final  clarification.   Sulfides were  completely
  ox,d.zed m the aerob.c  zone.  The kjeldahl  nitrogen removal  of 67
  percent  indicates significant  nitrification  occurring in  the system
  with  hydraulic detention times of  4 to 8 days.
  i   PAH  second  P^se of operation,  doubling  the  organic  load  to  282
  kg  BOD  /day/1,000 cu m  (17.k  lb  BOD./day/l,000  cu  ft) did  not siq-
  mficantly  reduce the efficiency.   ?nvestigators  report  loadings  of
  ae'C~ana<;n0blC systems may  range from  130  to 2^3  kg BODr/day/
  1,000 cu m  (8  to 15 lb BOD  /day/1,000  cu  ft)  for  80  percent  organic

           *     0) (3(3)  (36  (50)"  However>  Ioadin9s  abv* 81
 kg BOD5/day/1,000 cu m  (5  lb BODj/day/l,000 cu  ft) are  impractical
 because of the oxygen requirement  (30).

 Parker indicates the most difficult problem in  treating spent vege-
 table tannings appears to be color removal (29).  Color is not  re-
 duced by biological treatment.  However, reductions were observed
 by blending the influent or effluent with  lime wastewaters or coagu-
 lating with chemicals (29).

 C/e mvesiigawsd 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 beam-
 house fractions were found to be readily clarified by adding an
 cn:cri:c po.yme,- followed by sea imentat ion.   With polymer additions
 of 10 mg/1,  overflow rates of 75.2 cu rn/day/sq m (1,600 gpd/sq ft)
 produced  90 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  beamhouse wastewater in aerobic-
 anaerob.c  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):

                                       Influent   Effluent    RemovaI
                                         mg/1       mg/1         %

 BOD5                                     U46       152         87

 Suspended Solids                          J,o8       ]Q5         ^

 COD                                      2,221       717         68

 Su1fide                                     17        13         24

Total Kjeldahl Nitrogen (approximate)     150       100        33

High removals in BOD^ (87 percent)  ana suspended  solids  (7^  percent)
indicate the wastes are amenable to aerobic-anaerobic  treatment.   The
removals were obtained at volumetric loadings  of  32. *  to 32^ kg  BOD^/
day/1,000 cu m (2 to 20 Ib BOD5/day/l,000 cu ft).   Pilot operations
indicate loading intensities ranging from 32^  to  kQ5 kg  BOD^/day/l,000
cu m (20 to 25 Ib BOD5/day/l,000 cu ft)  are feasible (32).   Total  BOD5
removal throuqh the system averaged 90 percent.   Lower removals  were
experienced in winter operations when  the lagoon  temperature was about
1C (3*0F) .  Sulfide removal was minimal in the  system,  which is con-
trary to other investigations (29).  A kjeldahl  nitrogen removal of
30 to AO percent indicates nitrification in the  aerobic  portion  of the

Foaming periodically creates operation problems.   High pressure  water
sprays are utilized to control foam during summer operations.  De-
foaming 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 eleva-
ting the pH to 11.5 or greater with lime and the addition of an ani-
onic polymer.

Hitrification-denitrification is possible in multi-stage systems (32)
(33).  For this to occur, significant nitrification is  required in a
first stage aerobic operation.  Feeding the nitrified waste  to the
anaerobic zone of the second stage  lagoon denitrifies the waste.  In
the absence of oxygen, anaerobic bacteria reduce the nitrate  libera-
ting 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
nitrification-denitrification.  Specific applications wi11  require
extensive pilot 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  situa-
tions.  With proper operational control, high organic removals are
possible.  Designs  based on solids  retention  time  (SRT)  afford opti-
mum residence  time  for solids with  minimal  hydraulic  detention  period.
However, extensive  pilot  studies are  required to establish  appropri-
ate design parameters  defining  the  relative rate of biological  growth
and decay.  Basically, the  activated  sludge process consists of  (3*0:
mixing of  returned  activated  sludge with the  waste  to be treated;
aeration and agitation of  the mixed liquor  for the  required length
of  time; separation  of the  activated  sludge from the  mixed  liquor;
and disposal of  the  excess  sludge.  Activated sludge  is often pre-
ceded  by some  form  of  pretreatment.   Variations  in  these processes

create numerous operational  phases.   Overall  efficiencies  are highly
dependent upon the monitoring and control  provided by operating per-
sonnel .

Presented in Table 11  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, an exemplary  facility is not in opera-

S. B. Foot Tanning Company,  Red Wing, Minnesota, 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 fin-
ishing operations.  The project is partially  financed through an
Environmental Protection Agency grant.

The combined tannery flows are screened, then pumped to dual plain
sedimentation basins.   The 10.7 m (35 ft)  diameter clarifiers are
equipped with surface skimmers.  Overflow rates are approximately
21.6 cu m/day/sq m (460 gpd/sq ft) under present conditions.  A
potential of four concrete lined lagoons may  be utilized for acti-
vated 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
/ar'ed :~ op-=:- = " "c-.  Ti-s~5te rc-.tro's permit ser'es, ?="=='*', ?
a combination of  lagoon operations.  An aeration capacity of 22.3 kw
(30 hp)  per lagoon was initially indicated; however, a higher capa-
city may be required.   Return sludge design permits recycle to each
lagnnn as well a* ahpad of fhfi primary r.larifiprs.  Aeration  is
followed by final sedimentation in two 12.2 m  0*0 ft) diameter
clarifiers.   The effluent is chlorinated prior to discharge to a
nearby water course.  Primary and v/aste 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 11 repre-
sents only partial operation of the S. B.  Foot facility.  Operating
data to be developed at the plant should be beneficial to the  indus-
try due to the numerous operating ranges and controls provided  in
the system.

A full-scale activated sludge plant at Caldwell Lace Leather, Auburn,
Kentucky, was evaluated in a two-week study by the Environmental
Protection Agency  (37)-  Caldwell 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.* cu m/day/sq m  (290 and 285 gpd/sq  ft) were observed
in primary and secondary units, respectively.  Average hydraulic

                                                             TABLE   11
                                             ACTIVATED   SLUDGE   SYSTEMS
                                                     Suipc-atd Solid*
   dra rrlng with
   prcilbrt filter*
   land ditpotal
                                             76   1 966    3*5
                                                                                           S  B  TMI     Cattle
                                                                                           Tanning Co .   Pulp
                                                                                           ctf Vlng       chrcM
                                                                                                                    Lo rcravali tln
Screening,  plain
   ctI valid iludge
                       6)   I>J7     96
                    (0 Olt)
                                            91   1.135    3
                                                                                      17    Caltf-ell
                                                                                                                    Pnnaiy and letona-
                  PU'P  co^-   ary cl'i'86    160
)7    nonch
     Tanning Co
lolumrlc loatiirg cm     (10)
biological -it ) 711
kg/tfay/l COO tu r (179
Ib bbOj/ea//l OCO cu
ft)  Final Cia'ificr
o^rrlo- rate 19 b-
1* * CL r^dii/iq n
(SCO CtW gpd/i4 'I)
Plain icdlnn-
   final clarlfl-
                                                                                           frlnr         CatUa
                                                                                           Tanning Co
                                                                                                                    Pilot Itudy Of How*
                                                                                                                    fran 0 09 *o 0 19 I/
                                                                                                                    c (1 5 (o 1 gar)
                                                                                                                    ~ K-*.lr le Ictttf mg  f ros

                                                                                                                     OOC CV n (IOS-171 >fa
                                                                                                                    C9j/tfaf/l COO cb ft)
                                                                                                                    rlieafp el*n'lt' O'er
                                                                                                                     IB.* B 1-17 9 c. rj
                                                                                                                     lf\* r (ICO -l>0 Qod/
                                                                                                                    q f.) an final  clarl-
                                                                                                                    tcri II 2-1? 0 cu r/ey

detention time was 1.6 days in the aeration basin.
efficiencies were observed during operations:
            The following
                                      Influent   Effluent    Removal
Suspended Sol ids


Sulfide (as S)

Total Kjeldahl  Nitrogen (ds N)

Organic Nitrogen (as N)

Ammonia Nitrogen (as N)

Nitrite (as N)

Nitrate (as N)

Alkal inity (as C

"Grab Sample
























The BOD5 of the effluent was below 100 mg/1, indicating a removal  of
93 percent at a volumetric loading of 908 kg/day/1,000 cu m (56 Ib
BODj/day/l,000 cu ft).  Although suspended solids reductions were
high  (93 percent), the effluent concentration was slightly above
200 mg/1.  Apparent clarification difficulties exist.  The COD was
reduced 88 percent.  Sulfides were completely oxidized in the aera-
tion 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 at Moench Tanning Company, Inc.,  Gowanda,
New York, is presently treating effluent from save hair beamhouse,
chrome tan, and finishing operations.  Total wastewater from these
processes is about 1,514 cu m/day (0.4 mgd).  Combined flows are
screened prior to equalization and adjustment of pH to 11.0.  In
some  instances addition of lime is required.  The equalization basin
has a 24-hour capacity under present conditions.  The unclarified
discharge from the equalization basin is directed to an aeration
basin with approximately 12 hours detention with a volumetric load

on the basin of about 3,566 kg/day/1,000 cu m (220 Ib BOD5/day/l,000
cu ft).  The final clarifier has an overflov/ rate of 23.5 to 28.2
cu m/day/sq m (500 to 600 gpd/sq ft).

An organic removal of 80 percent produced an effluent BOD^ concentra-
tion of 3^3 m'g/1 .   Suspended solids reductions of 92 percent are  re-
ported.  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 the Moench
treatment operations are the high pH of waste entering the aeration
basin and the high mixed liquor suspended solids concentration main-
tained  in the aeration basin.  Normally, a pH above 11.0 is indicated
as potentially toxic to biological activity.  However, carbon dio-
xide derived from organism respiration is adequate to reduce the  pH
to about 8.0, at which level biological  conversions proceed.  Since
primary clarification is not provided, all suspended solids in the
tannery waste go directly to the aeration basin.  All solids capture
must, therefore, occur in the final clarifier.

Other biological treatment innovations include the oxidation ditch.
The oxidation ditch is essentially a modified form of the activated
sludge system.  Applications of this process on domestic waste treat-
ment 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
lacilities are not required, since the ditch provides excellent
equal izai. ion (13).  An acjustabie speea orusn rotating across the
full width of the  channel imparts oxygen to the wastewater and regu-
lates 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 con-
ventional 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.^75 mgd) of wastewater
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 (0.02A mgd).  The pilot plant feed remained propor-
tional to the fluctuating supply to provide realistic variations  of
flow.  After proportioning, the wastewater was pre-settled for 30 to
*5 minutes, then discharged to the oxidation ditch.  The primary
sludge was thickened for 12 hours prior to dewatering on drying beds.
Hydraulic detention time in the oxidation ditch varied from two to
three days, and the rate of activated sludge return was estimated at


75 percent.  Production of secondary sludge was about 0.3  kg (ib)
dry solids/kg (Ib) BODj applied,  or 0.55 kg (ib) dry solids/kg (Ib)
BODc without primary sedimentation.  The organic load on  the ditch
varied from 23.5-'f8.2 kg BODr/day  (51.8 to 106.2 Ib BOD5/day) .  The
oxygen supplied was about 1.5 times the average 6005 load,  however,
this was not sufficient for peak demands.  Adjustment of  brush ro-
tation and submergence to increase oxygen transfer may be.  required
for peak demands.  The following pilot efficiencies resulted during
summer operation  (13):

                                 Influent-    Effluent-    Removal-
                                   mg/1mg/1          %

BOD5                             500-1,500       >15          98

COD                            1,000-2,300      >300          85

Sulfide                            10-80            0          100

Chrome  (C r+++)                      -"              ]

Total Nitrogen  (as  N)               250          60-150       **0-?6

Ammonia  Nitrogen  (as  N)             100          ^5-125         0-50

*0rder-of-magn i tude

High  removals  of  BOD5 (98 percent) and  COD  (88 percent) result  at the
 low F/M  ratio.   Sulfides were  completely oxidized  with brush  aeration.
Precipitation  of  chrome was  highly effective  with  concentrations  be-
 low 1 mg/1  observed in the effluent.   Nitrification  was sporadic,
with  some denitrification through  the liberation  of  free  ammonia  or
nitrogen gas.   The exact mechanism of removal  was  not  indicated.
 In general,  the oxidation ditch  is an attractive  modification to  the
activated sludge process. Highly  effective removals in  6005, sus-
 pended  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 limit-
 ing 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 8005 removals in
 excess  of 90 percent and effluent concentrations below 100 mg/1.
 Removals of suspended solids appear to be critical with  concentra-
 tions 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 nitrifica-
 tion potential of activated  sludge systems has not been  investigated
 at present facilities.  Although  feasible  in theory, direct applica-
 tion to tannery wastes  in pilot or full-scale  facilities  is non-existent

Improvement of Treatment Performance - Consideration has  been  given
to 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 microsereening of the effluent.

     2.  Carbon adsorption.

     3.  Color removal.

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

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

A microscreen consists of a rotating drum with a fine screen mounted
on  its periphery.  Waste enters the drum through the open end  and
passes through the screen leaving the suspended solids on the   inner
surface of the screen.  At the top of the drum, pressure jets  of
effluent water are directed into the screen to remove the mat  of
deposited solids.  Numerous applications of microscreening of  sec-
ondary wastewater 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 re-
moval  from secondary effluents and  in physical-chemical   systems for
the treatment of  raw wastewater.

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 back-
washed prior  to being placed back into service.   In an ideal  filter,
the size of  the particles should decrease uniformly in the direction
of  flow.  This condition  is partially achieved with the  use of a  multi-
media  deep-bed filter.  This type of filter utilizes materials with
different densities ranging from  the  large size particles at  the  top
of  the filter having  the  lowest density and the smallest particles at
the bottom of the filter having the  highest density.  With this arrange-
ment,  the  filter  has  a  large storage capacity for suspended solids,

and is able to remain in operation for longer periods of time.   In-
fluent solids should be limited to about 100 mg/1 to avoid too fre-
quent 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 non-biodegradable.  The granular carbon media provides an effec-
tively large surface area for adsorption.  Biodegradat ion of  the
cap_tured material further increases the efficiency of the process.
Thermal regeneration is used to reactivate spent carbon.

The Calgon Corporation performed laboratory analysis of carbon treat
ment for wastewater from the Hartland Tannery in Hartland, Maine
(52) .  These laboratory tests were performed on waste that had been
pretreated by pressurized aeration for sulfide removal  and air
flotation/clarification for oil and suspended solids removal.  Re-
sults 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  or-
ganic carbon (TOC) .  The full-scale design is indicated as having a
potential of reducing the effluent to less than  135 mg/1 TOC  repre-
senting approximately 80 percent reduction in oxygen demanding ma-
iei'iciii. \3t-i .  A caiboii eAnau^. L i on idte of \.i.~>  K.y Cdi'ud'i pci" Cu m
(10.5  Ibs) of carbon/1,000 gallons) of preheated wastewater  is anti-
cipated for this removal efficiency.
 A_ - : . . 4. _ J __.!_.*.* ' f ****s4-:f*% ' r* /r*l^\- vnmr\\i a 1   \/
 uiivaicu ia i uw 1 1 t j v- 1 i i-t u i v K iii ^.^iwi t ~in* . * . .  .
and dyeing operations contribute substantially to effluent color.
Color exists as both a soluble constituent and a colloidal suspen-
sion.  The pilot study at Hartland Tannery produces a 95  percent
reduction in color  (52).  Tomlinson, et at. , (53) observed a 90 per-
cent  reduction in color from laboratory studies of spent  dye liquors
at Caldwell  Lace Leather, Auburn, Kentucky.  Color was effectively
removed at 2 to A 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  re-
move suspended solids that  retard the adsorption  of dissolved  ma-
terial.   The process would  not materially reduce  the  high content of
dissolved inorganic materials  such  as sodium chloride (NaCl).

The problem of color of  tannery  waste is  most  pronounced in  those
systems using vegetable  tanning.  Color  is  an  optical effect.   The
measured magnitude  of color  is not  necessarily related  to a  weight
quantity of the hetrogeneous mixture  of materials  which  is its cause.
Because of the nature of  the color, several  investigators (20) (5*0
have found use of APHA cobalt-platinum impractical.   The hue and
tint of vegetable  tanning  solutions are different  from color stan-
dards.  Therefore,  several  arbitrary  approaches  have  been developed

to determine percent of color removed in a particular unit operation.
For this reason, further development of a standard is necessary.
Nevertheless, it is necessary that color removal be incorporated in
any treatment process for vegetable tanning wastes.

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

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

Facility Requirements - No present on-site treatment facility can be
classified as an exemplary facility to be used as a basis for Level  I
performance.  This premise is based on the following facts:

     1 .  The strength of treated tannery waste with respect to most
         parameters  is uigncr ciian inst rcr most rrruniCipsi i L i cs emu
         other  industries.
     2.  Consistent removal of waste constituents by treatment facili-
         ^0^ O'^fiC^^Ot* s* . t^ c i c c ri *. w i   I n i  * L* c r> i cjuCniiiiGS  is  icss uiiOrv
         that of most municipalities and  industries.
     3.  Tanneries now having treatment facilities which produce an
         effluent approaching the quality desired could make neces-
         sary modifications to meet quality standards at a reasonable
         capital investment.

It is recognized that setting forth this need for additional treat-
ment requires some extrapolation of present tannery waste treatment
experience.  Nevertheless, technology transfer and pilot studies can
be utilized to provide basic data required.

The unit operations and unit processes required to achieve the de-
sired effluent quality are as follows:

     Waste Flow

     Equal izat ion
     Primary Settl ing
     Aerat ion
     Secondary Settling
     Fi 1 1 rat ion
     Chlor inat ion


     Col 1ect ion

A schematic arrangement of  treatment facilities is shown on Figure 6.

This particular arrangement  has  been chosen not because it is the
only possible approach to treatment, but  because it is one system
generally applicable  to six  of the  seven  categories.   The system could
be adapted to use  lagoons or an  oxidation ditch if one of these better
fits individual tannery requirements.

The conceptual design shown  will  require  field  verification prefer-
ably by modification of a present full-scale plant.  Nevertheless,
the.design parameters are sufficiently  conservative to permit an
economic analysis as described later herein.
                                  .  .     FLOW DIAGRAM
                                  MAJOR REMOVAL OF BOD5 AND SUSPENDED-SOLIOS
                                           ACTIVATED SLUDGE
                                                          FIGURE 6

Parameters used for design of principal  items of equipment are as
f o 1 1 ows :

     Equalization Basin          Detention:  2k hours at design flow

     Primary Settling            Overflow Rate:  20. k 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
                                      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
                                   sol ids

                                         %>M   1 *J
                                                (2.5 lb/sq ft/hr)

Two factors concerning treatment require special considerations and
;ire included in design r.nns irlprat inn?   Most treatment p'9nts h2Ve
had difficulty with residual  suspended solids in the treated efflu-
ent.  Also, color in the effluent continues to be a problem with
those plants using the vegetable tanning process.

To ensure that the effluent will contain a minimum residual of sus-
pended solids, three 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.

     3.  Filtration of the effluent from the secondary settling tank.

Provision will be made to add lime and polymer to the primary set-
tling tank to remove color.  It is assumed that a substantial part
of the normal lime requirements of 2,000 mg/1  will be used from
beamhouse wastes.

 Major  Reduction of All Forms of Nitrogen

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

      1 .  Organ ic nitrogen.

      2.  Ammonia and ammonium salts.

      3.  Nitrates.

      *.  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 am-
 nunia  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  k.$  mg/1  of oxygen.   Therefore,  a serious  oxygen
 f*f "*i ' f"  f\r  r% * * K *t c *  _-_--,...       -.
 .-,.._ ---- . o. ...ic. SL.CQ,,.  v-udiu 

     3.   Ammonia ion exchange.

     k.   Chlorination.

     5.   Biological  nitrification-denitrification.

Coagulation, flocculation and settling is effective in partial  removal
cf soluble and colloidal  protein matter.   To optimize this process,
pH must  be reduced  to the isoelectric point  of the  protein,  which is
usually in the range of *t.5 to  5.0.  At that point, the protein matter
is least soluble.   Some coagulant addition may be necessary to pro-
vide good settling.

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

Difficulties encountered  in municipal waste treatment include serious
calcium carbonate scaling and the reduced efficiency at low air tem-
peratures.  As the air temperature approaches 0 C  (32 F) the system
becomes essentially ineffective.  Removal efficiency is 90 to 95 per-
cent under ontimum conditions hut organic nitrogpn  is not affected by
ammonia stripping.

Ammonia can also be removed from wastewater by an  ion exchange media
which is a natural  zeolite, clinoptilolUe.   This material  is selec-
tive for the ammonium  ion in the presence of  ions such as calcium,
magnesium, and sodium  found  in wastewater.  For the high ammonia con-
tent of tannery waste, capital   investment for such a system would be
high.  Also, the presence of only a  small concentration of  large or-
ganic molecules can cause serious fouling and degradation with com-
monly used  ion exchange media.   Whether or not this fouling would
pose a problem with the selective  ion exchange media used for tannery
waste has not been established.

Chlorination can be used  to convert  ammonia to nitrate.  However, at
a dosage of 10 mg/1 of chlorine per  mg/1 of ammonia nitrogen, the cost
is excessive except for very small concentrations.
 In a biological system for removal of nitrogen, all organic nitrogen
 must be hydrolyzed to ammonia or be converted to a form from which
 it can be oxidized along with the ammonia present to nitrate.   In
 the activated sludge process, a part of the ammonia and organic ni-
 trogen is converted to nitrate.  A higher conversion is accomplished
 in a system where the F/M ratio is low.  Ammonia is converted to nitrate
 trite by a Nitrosomonas organism; nitrite is converted to nitrate
 by a Nitrobacter organism.  These autotrophic microorganisms have a
 slow growth rate.  One source  (57) indicated that even an extended
 aeration activated sludge plant could not provide complete nitrifi-
 cation on a year-around 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 organtsms utilize an inorganic
source of carbon  (carbon  dioxide  or bicarbonate)  and obtain energy
from the ammonia oxidation reaction.

The nitrate nitrogen content  of tannery  wastes treated by the biolog-
ical nitrification process is  high.  Nitrate nitrogen is essentially
the same level as the ammonia  nitrogen  in the raw waste plus any
organic nitrogen that  is  hydrolyzed prior to treatment.  To remove
this nitrate, a biological denitrification step in the treatment  is
required.  This can be accomplished under anaerobic conditions by
denitrifying organisms.   Equipment  required is a  nitrification basin
followed by a clarification  tank.   The  arrangement is shown on Fig-
ure 7-  Optimum pH is 6.5 to  7-5-   Organisms using a source of or-
ganic carbon convert the  nitrate  to nitrogen gas.  . Since the waste
is normally lacking in organic carbon,  methanol is added to provide
such a source.  Rate.of addition  is about 3 kg of methanol per kg
(3 Ib/lb) of nitrate nitrogen.  Essentially complete denitrification
is accomplished.   If organic  nitrogen  is present,  it will be un-
                                        FLOW DIAGRAM
                                   MAJOR'REKOVAL OF ALL FORMS OF NITROGEN
                                                           FIGURE 7

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.   De-
tails concerning design criteria for  n i tr if icat ion-deni trif icat ion
processes are described in a design seminar paper (58).

Design criteria used are as follows:




    Loading Factor:






    Loading  Factor:
                                 10C (50F)

                                 5,000 mg/1
                                     kg/day/1 ,000 cu m
                                  (27 Ib NH3-N/day/l,000 cu ft)

                                  65 percent of  raw  waste

                                  3,000 mg/1


                                  530 kg/day/1,000 cu m
                                  (33.7 Ib N03-N/day/l,000 cu ft)
 Major Removal of All Waste Constituents

 The major removal of all waste constituents refers to those processes
 which remove dissolved solids.  Tannery wastewaters, after extensive
 chemical and biological treatment, still contain a high concentra-
 tion of inorganic salts.  These salts are principally sodium chloride,
 calcium bicarbonate, calcium sulfate, and calcium hydroxide.  Cal-
 cium hydroxide used  in the unhairing operation reacts with ammonium
 sulfate and  sulfuric acids from the bating and pickling operations
 to form calcium  sulfate.  Residual lime in waste  is removed directly
 by settling  or precipitated by respiration carbon dioxide.  Some
 minor quantities of  salts are present  in the water supply.  The major
 part of dissolved  inorganic solids is  introduced  from the raw hides
 or processing solutions.  Sodium chloride  is present in the incoming
 hides as a preservative.  It  is also present in the pickling opera-
 tion.  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).   Some hide  processing operations  (Category 7)  produce a

waste stream approaching a saturated brine solution.  Physival-chemical-
biological treatment will reduce these concentrations only slightly.

Unit treatment operations for removal of dissolved solids include the

     1 .  Freez ing.

     2.  Evaporation.

     3.  Electrodialysis.

     k.   Ion exchange.

     5.  Reverse osmosis.

Host 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
tne surface of  the  ciys>Ldii> uy wasi'iing.   ; na  ;cc-cr :;;L. JL.^: j.. :-::
has previously  caused operational difficulties.  A  more  effective
wash  is required, and also  one that  does  not create a high volume
of brine  for  ultimate disposal.

The freezing  process  has been proposed  for  treatment of  clarified
tannery discharge at  Drew Tanning of Brockton, Massachusetts  (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

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

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

 Multiple effect evaporators have been used in industry  for many 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 solu-
 tion.   This arrangement is used for a number of stages.   Evaporation
 is carried out in each successive stage.   A triple effect evaporator
 for salt concentration will  evaporate slightly over two  kg (ib)  of
 water  per kg (ib)  of steam used.

 Elect rod!alysis - Electrodialysis is a demonstrated process for
 removal  of dissolved solids  in brackish waters.   Basically, the
 electrodialysis cell consists  of alternate cationic and  anionic per-
 meable 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  concentrated waste brine collects in
 others.   For waters  of concentration less than 10,000 mg/1, the
 energy requirement  in an actual installation is  of the order of
 2.6 to 7.9 kwhr per  cu m (10 to 30 kwhr per 1,000 gallons) of pro-
 duct water (59).   This is  less than the energy required  for the
 distillation process.   The principal disadvantages for tannery
 applications are  membrane  fouling, polarization,  and scaling from
 waste  constituents.   At present,  there is no record of tanneries
 using  the electrodialysis  process.

 Jon  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 applica-
 f ! on hac  Koon i r> i.iaf-or-  c^-P*-^~ !...,U,,..,,  .,  _ 1 4.	.	f.i . -        .
 .  -    __		.,,.,.  ..^ . ..v,,, ,,,.,  niit.it.  a  30 i L  i cycnc i a LCU I.C*LIUII un I L
 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 an ion  ex-
 changer  must  be used.   To  make ion exchange economically  feasible
 for  desalination of  water, special  ion  exchanger  arrangements  have
 been used.   One of these is  the DESAL process  which is a  three  bed
 system (60).  Two of  these beds contain anion  exchange media and
 the  third contains a  cation  exchange media.   The  operation method
 is  such  that  only  stoichiometric  quantities of regenerates are
 used,  thereby providing substantial  economy over  operation of  stan-
 dard demineralization  equipment.

A  suitable  method must  be  used  to dispose of  spent  regenerant  solu-
 tions.   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, appli-
cation for  treatment of  tannery waste which  has a salt content of
well over 3,000 mg/1, waste  is   not considered  feasible.

Peverse Osmosis - Reverse osmosis is a process which is non-selec-
t ive wi th respect lo dissolved solids removal and is reasonably de-
pendable.  In osmosis, when a salt solution and a pure solvent or a
solution of less concentration are separated by a semi -permeable mem-
brane, the pure solvent flows through and dilutes the salt solution.
The process continues until equilibrium is established.  The semi-
permeable membrane allows the pure solvent to pass, but not the solu-
tion.  The driving force is the strong chemical potential of the pure
solvent.  The pressure developed  in the process is the osmotic pres-
sure.   In reverse osmosis, a pressure applied to the salt solution  in
excess of the osmotic pressure forces the pure solvent through the
membrane leaving a concentrated brine.  The success of the system
 is dependent upon selection and maintenance of the membrane.  Re-
verse osmosis has beer, effective  for the treatment of pulp and the
paper mill wastes, acid mine drainage, and municipal supplies with  a
high mineral content.

Pilot treatment of dilute pulp and paper effluents  (61) produced
membrane rejections of 90-99 percent for most feedwater components.
Optimum performance  is indicated  at dissolved solids concentrations
of 5,000 to 15,000 mg/1 .  The resulting brine solution was 8 to  10
percent sol ids .
             i-                                       ^-,     , . v . r  .- 
r ; ; Gi_ SCci i 3 _> t_UCi ; 3 jn uC s is ;;; . nc u rz i nc;y^.  \'^*- / ^i <^^^\-^^ >j  ^i<^^uv.k
water with 10 mg/1 dissolved solids  from an  influent containing 1 ,280
mg/1 dissolved solids.  Product water or permeate was about 75  per-
cent of the total flow.  The permeate did  not meet  drinking water
s 1 2 p. ci 2 r d s

An extensive pilot plant study was performed by  Gulf Environmental
Systems  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 dis-
solved solids concentration of about 1,150 mg/1. The permeate  con-
tained 55 mg/1 dissolved solids producing  a  95 percent removal. Am-
monia nitrogen and nitrate  were reduced 95 percent  and 75 percent
respectively.  The ammonia  nitrogen  in the effluent was about  15  to
20 mg/1.                       I

 There  has been  no  direct  application of  reverse  osmosis  for treaty
 ment  of  tannery  wastewater.  Investigations  in the  pulp  and paper in-
 dustry  indicate  that  wastes of similar concentration are  amenable to
 reverse  osmosis.  At  these dissolved solids  concentrations, the
 osmotic  pressures  encountered are high requiring higher  applied
 pressures.   There  are several  reasons  reverse osmosis  may be more
 appropriate  than other methods discussed for the treatment of  tannery
 wastes.   The equipment is easy to operate.  Energy requirements are

 relatively low.  Also, an elevated operating  temperature is not re-
 quired.  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.   Figure 8 shows
 a schematic of the major operations,  including reverse osmosis, re-
 quired to effect complete removal of all  constituents.
                                          FLOW DIAGRAM
                                   MAJOR REMOVAL OF ALL WASTE CONSTITUENTS
                                                            FIGURE. 8
 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  re-
 covery with brackish water containing 3,000 mg/1 of dissolved solids

 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 wastewater  treatment and  desalination has  pro-
 duced methods  for  handling brines.   A few of the techniques  investi-
 gated are  as  follows:


      1.  Various  types of solvent extration.

      2.  Elect rodialysis.

      3.  Solar evaporation.

      k.  Multiple effect evaporation.

      5.  Submerged combustion.

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

Llectrodialysis has shown the capability of brine concentrations
to 200,000 mg/1 (6^).  However, practical application requires fur-
ther  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
v>aste brines prior to ultimate disposal.  The method is economical
for concentrating solids up to 10 percent.  Higher concentrations
require multi-effect evaporators.

Submerged combustion may be utilized to concentrate brines beyond
saturation yielding crystal formation (65).

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

      1.  Deep-well disposal.

     2.  Ocean d isposal.

     3.  Complete evaporation.

Deep-well  disposal of brines  requires comprehensive geologic study
and field testing of potential disposal  zones to assess the safety
and effectiveness of underground strata.  Several  potential  dangers
exist for such disposal including pollution of freshwater supplies
through encroachment and disturbance to underground strata.   Injection
wells normally require detailed investigations to ensure that liquids

in the underground strata are compatible both physically and chemi-
cally to the waste brines injected.   Usually high pressure pumping
is required for deep-well disposal.

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

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

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

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

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.

Waste Treatment for Hide Curing Facilities

Hide curing  facilities  (Category 7)  constitute a special case with
respect to waste treatment.  The principal processing solution is one
essentially  saturated with salt.  The major waste stream is generated
by dilution of  the brine by moisture released from the raw hides
causing an overflow from the processing vessel.  This overflow
stream permits  removal of other waste materials such as manure and
dirt removed from the raw hide.  There is a minor amount of  liquid
waste generated from the storage of cured hides and the rendering
operation associated with the processing of fleshings.

To characterize this waste concisely,  it should be noted that the
total solids content from a typ'ical  plant  is approximately 280,000
mg/1 while suspended solids, BODg, and COD are 10,^00, 15,610, and
29,600 mg/1, respectively.  Grease  is present at a concentration of
over 1*0,000 mg/1.  Chromium and sulfide are not present and  pH is
normally within an acceptable range of 6.5 to 8.5.

Pretreatment facilities are required when discharging to a municipal
system to reduce the high concentration of suspended solids and
grease.  The waste flow  is low.  It is about 13,2^8 cu m/day (3,500
gpd) for the average facility.  Therefore, a batch-type treatment is
recommended.  This provides for better control of the process.  The

design concept includes two waste receiving and clarification tanks
each sized to hold waste produced in one day.   Provision is included
for waste skimming and the addftFon of chemicals to enhance clari-
fication and settling of suspended solids.   It is anticipated that
suspended solids wi11 thicken to approximately 5 percent.   Sludge
will be pumped from the clarification tank to a sludge storage tank
for hauling to an ultimate disposal pofnt.   Sludge produced v/ill  be
about 1.9 cu m/day (500 gallons/day) based on the 5 percent con-
sistency.  Grease wi11 be skimmed manually fron the clarification
tank and handled as solid waste or by the plant rendering facilities.
Supernatant liquid from the clarification tank will be filtered prior
to being directed to the municipal sewer system.

For all other levels of treatment, the waste will be collected in a
receiving tank and directed to an  incinerator.  The incinerator will
evaporate all liquid and burn all organic constituents.  The ash,
consisting primarily of sodium chloride, will be collected by an
electrostatic precipitator for disposal or reuse.  Although not con-
sidered  in the economic analysis, tanneries in the more arid areas
could use lagooning for this waste disposal at a considerable savings
in both capital and operating costs.  Several are currently  in ex-
istence using solar evaporation.


                            SECTION VIII


 Cost and Reduction Benefits of Alternative Treatment and Control
 Techno log i es                   "        ~                      

 A detailed economic analysis showing the impact of treatment  and  control
 technologies upon the seven categories  within the leather tanning and
 finishing industry is given in Supplement A of this document.   Five
 alternative treatment methods  have been considered for Categories 1
 to 6,  and three alternatives for  Category 7.   For the  six main  cate-
 gories,  the alternatives  include:

      Alternative A -  No v/aste  treatment or control.

      Alternative B -  Pretreatment.

      Alternative C -  Activated  sludge.

      Alternative D -  Activated  sludge,  nitrification,  and denilrifi-
                       cat ion.

      A1, ^crnacive L -  A>_Livdiea  siuage,  nitrification,  deni tri f icat ion,
                       reverse  osmosis, and evaporation.

 For  Category 7,  the alternatives are:

     Alternative A -  No waste treatment or control.

     Alternative B  -  Pretreatment.

     Alternative C -  Evaporation.

Table 12  illustrates  the cost of wastewater treatment for the  average
size plants in each category.  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 Table  12.

     1.   Investment - Investment costs have been derived principally
         from published data on wastewater 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  municipal  wastewater treat-
         ment  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

                                       TABLE 12

                        ESTIMATED WASTE  TREATMENT COSTS

                          FOR TYPICAL SIZE  PLANTS^1'
                          (August, 1971 price  levels)
  Category             Flow      _A_        B          	          	
                     cu m/day

No. 1                965 (0.255)
   Investment Cost               $0   $1,305,000  $1,768,000  $2,320,000   $3,720,000
  Annual  Cost                    0      306,000     518,000     662,000    1,118,000

No. 2                598 (0.158)

   Investment Cost                0    1,336,000   2,165,000   2,720,000    5,075,000
  Annual  Cost                    0      365,000     662,000     812,000    1,557,000

 o. 3                818 (0.216)

   !^.*;: .*.-:_ .:._....                c      63-'-,c:v   i,357,:::   :,soc,c::    3,00-7,000
  Annual  Cost                    0      2A1,000   -  408,000     521,000     910,000

No. 4                257 (0.068)

   Investment Cost                0      405.OOn     703FOr>0     950,000    ! ,''70,000
  Annual  Cost                    0      120,000     205^000     282^000     435^000

 o. 5                420 (0.111)
  Investment Cost                0      473,000     782,000   1,013,000    1,752,000
  Annual  Cost                    0      137,000     226,000     297,000     523,000

No.  6               379  (0.100)

  Investment Cost                0      716,000   1,170,000   1,565,000    2,247,000
  Annual  Cost                    0      219,000     346,000     447,000     686,000

No.  7

  Investment Cost    '5  (0.004)   o       60,000     308.000
  Annual  Cost                    0       15,000     110,000

       Investment costs  include equipment, construction, engineering, overhead,
        and contingencies*   Annual costs include depreciation,  interest, operation
    ...  and maintenance.
       Alternative A = No treatment.
       Alternative 6 = Pretreatment.
       Alternative C = Activated Sludge (except Category 7 " Evaporation).
       Alternative D  Activated Sludge and Nitrification-Denitrification.
       Alternative E = Activated S'ludge and Ni tri f icat ion-Deni tri f icat ion and
                        Reverse Osmosis-Evaporation.

data was 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.

In addition to major facility costs, a broad category of
yard v.-ork has been included.  Yard work includes general
site clearing and grading,  inter-component piping, valves,
electrical wiring and cable, lighting, control structures,
manholes, tunnels and conduits, parking, sidewalk and road
paving, site landscaping, fencing, and other items outside
the structural confines of a particular individual plant
component.  An additional 1 * percent of major facility costs
was allowed for these items.

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

August, 1971, price levels have been chosen  by the Environmental
Protection Agency and are used herein as the base level  for
economic evaluation.   Inflation since August, 1971,  has had
a marked imoar.t on the cost  o'f treatment fgcilit" conr.f^ur;-
tion, 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.

Depreciation and Cost of Capital  (interest)  - It was assumed
that the annualinterest 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.  Costs were depreciated on a straight  line basis and
the depreciation period of 20 years was assumed equal  to the
principal repayment period and the economic  life of  the
faci1i ties.

Cost of money was assumed to be an average of the cost of
debt capital and the cost of equity capital.  Cost of debt
capital  was  assumed to be 8  percent and the  cost of  equity
capital  22 percent.  Data for the last 10  to 12 years in-
dicates 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 invest-
ment was assumed to be debt  capital  and AO 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.


  3.   Insurance 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.

  **'   Operation and Maintenance Labor - Operation and maintenance
      labor manhour requirements  were based mainly on published
      data  (66) (6?) 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
      repai r personnel.

      Based on labor rates in the tanning industry and municipal
     wastewater 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.

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

         Hethanol  -  >O.G6y per  liter ($0.26  per  gallon)

         Lime -  $22.00 per metric ton  ($20.00  per ton)

         Soda A*!.  -  $3.96 per  iOu kilograms  ($1.80  per  100 pounds)

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

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

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

         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 JOO kilograms
         ($3.85 per 100 pounds)

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

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


         For Alternative E, steam is required for evaporation,
         dewatering, and drying of the waste brine.  The cost of
         steam ranged from $1.76 to $2.^2/1,000 kg of steam
         ($0.80 to $1.10/1,000 Ib of steam).

     7-  Other Materials and Supplies - Also included in the total
         annual operating cost for treatment facilities are other
         material  and supply costs.   These  include maintenance and
         repair parts, contract maintenance not normally performed
         by treatment plant personnel, and other routine supplies.

Effluent Reduction - Category 1 - The following discussion for
Category 1  deals with the sensitivity of effluent reduction with
respect to costs for Category 1.   This category represents a sub-
stantially larger segment of the industry than any other category.
Costs are based on an average size tannery  in this category pro-
cessing 29,510 kg (65,000 Ib) of hides per day.  Figure 9 shows
for Category 1, the reduction of pollutant parameters for each
control and treatment alternative.   Similar trends occur for all
other categories,  except that Category 7 can likely achieve zero
discharge with evaporation of the small  waste flows.

     Al ternative A - _No__Waste_ Jt"e_atment_p_r Control

     The estimated organic waste load for Category 1 is 95 kg
     BOD5/1.000 kg (95 Ib BOD5/1,000 Ib) of hide.  This represents
     a BODj concentration of about 2,850 mg/1 or approximately
     IM liineb that of normal domestic sewage.

     Costs  - None.

     Reduction Benefits - None.

     Alternative B - Pretreatment

     This alternative includes pumping,  screening, equalization, and
     primary clarification.   Sludge  handling includes holding tanks,
     thickening units, and dewatering prior to landfill  disposal of
     the dewatered cake.   Effluent waste loads from this alternative
     are estimated to be kj kg BOD5/1,000 kg C7 Ib BODj/l.OOO Ib)
     of hide processed.   Reduction of sulfides, oil and grease, and
     chromium also occur as noted on Figure 9.

     Costs  - Annual  treatment costs  are  $306,000 more than
     Alternative A.

     Reduction Benefits - Alternative B  represents about a 50 percent
     reduction in  800$ compared with Alternative A.  Total  reduction
     in 8005 with  pretreatment would, therefore, be 50 percent.  Other
     constituents  are also removed as noted.



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                                                                                    '-"O      O.OSO      O.OJO
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                                                                               MSTE TBEJTHtllT COSTS (I/IC HIDE)
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N ! IS : M CAT 1 0-[>E 1 IP IM CATION
KUTE ItEintIT COST] (l/ll HIDi)
                                          CATEGORY NO. 1
                                  WASTE TREATMENT COST SENSITIVITY
                                       (August, 1971 Price Levels)
                                                           FIGURE 9

Alternative C - Activated Sludge

This alternative provides the same units as pretreatment v/ith
the addition of an aeration basin, secondary clarifier, graded
media filter, and chlorination.  Combined sludge handling  in-
cludes holding tanks, thickening units, dewatering, and land-
fill disposal.  The effluent waste load is estimated at 1.3  kg
BOD5/1.000 kg (1.3 lb BOD5/1,000 Ib)  of hide processed for
the average Category 1  tannery treatment facility.

Costs - Alternative C represents an annual cost  increase of
$212,000 over Alternative B.  Total annual cost of Alternative  C
is, therefore, $518,000.

Reduction Benefits - Alternative C represents a  reduction  in
6005 of 97 percent over Alternative B..  This  represents a  total
reduction  in plant BODj of  98.5 percent.

Alternative  D - Activated Sludge with  Nitrification and
Deni tr1ficat ion

Alternative  D  includes  nearly  all  treatment  units  for  Alter-
..<:.,,* " i.:*h   '><">  -i/-1.!1 .-"-.-  .-.f  = -:-.-: f :.-=*-:-.- h = =:r.   si***-! :pr.
MClkltfW W Vllkll  kilt*  I* w ~ I h I VI I  w>  ^ ...... ..._*._.   .	   ,  ..-	   I 51
tanks, covered denitrificat ion basin,  and aeration flume.   The
effluent from  the  average Category 1  tannery  treatment facility
would  be 0.67  kg BOD5/1,000 kg  (0.67  lb BOD5/1,000 lb)  of  hide
"recessed.   Sinn' f'cant removal of nifonpn  fnrms  would  also
result  (Figure 9)

Costs  -  Incremental  annual  costs of $1^,000 would be  incurred
over Alternative C.  Total  annual  costs of  treatment with
Alternative  D  is estimated  to  be  $662,000.

Reduction  Benefits - Through Alternative  D,  there  is  an  in-
cremental  reduction  in  6005 of 50  percent over  Alternative C.
Total  reduction  in 8005 would  be  99-3 percent.

Alternative  E  -  Activated  Sludge,  Nitrification,  Denitrification,
Reverse  Osmosis, and Evaporat'jon

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 de-
watering-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 - Estimated annual costs for Alternative E would be
     $^56,000 more than Alternative D.  Thus, the total annual cost
     for Alternative E is estimated to be $1,118,000.

     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 con-
     stitutents would be completely removed.

Impact of Waste Treatment Alternatives on Finished Product Price

Figure 10 illustrates the probable increase in finished product prices
for various categories to pay for wastewater treatment.  The increas-
ing product costs resulting from waste treatment are evident.

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 may provide the same degree of biological
treatment.  These lagoons require substantial areas and can only be
utilized xvhere land is readily available near the tannery.  Lagoons
will usually resul't in some cost savings from those presented herein.

In Alternatives D and E where nitrification and denitrification
facilities are provided, the lagoons probably cannot be utilized.
The nitrification and denitrification steps are both quite temper-
at'_ire sens' ti"e snd requ're str'ct control o^ rec' rc'j'at ipcj so'Ids.
Lagoons generally allow maximum temperature loss from the waste.
They also are of a configuration which is difficult to maintain
solids and provide year-around results.

Alternatives B through E include the cost of vacuum filtration for
sludge dewatering.  For tanneries with relatively small sludge
volumes and access to open land, sludge drying beds may be employed
in lieu of vacuum filters to effect cost savings.  Dried sludge cake
from the drying beds would also be hauled to a sanitary landfill.

Related Energy Requirements of Alternative 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


        >?SQ H HIDE
       4.00     6.00
	1	1	
                        e.oo       10.00
                         - 7.1S
            0.50          0.75
         J/SQ FT HIDE
    CATEGORY  NO.  2
                                                                PRESENT PRODUCT
            /S? H HIDE
          ".00      6.00
                   "ICE -I   HCilS
                                                                                       6.00	10.00
    0-25         0.50         0.75          I.CO

                S/ SO H HIDE
     2.00	1.00	6.BO      8.00
	1	r^	1	1
            0.60         0.75
           Q FT HIDE
                                                PRESENT PRODUCT PR I
                                                                     J/S9 H HIDE
                                                                    1.00       6.00
            J.'SQ FT HIDE
                           0.75         1.00

             CATEGORY  NO.   3
                      T P803UCT PHlCt  .1  . IHCtUS
                   tin, mot

                      J/LB HIDE
                CATEGORY  NO.   7

       t/KG HIDE
                        I/IS HIDE
                                                                     CATEGORY  NO.
                                                                         PRCSENT PBCDUC
                                                                     JCT PRlCE-4'CEiSE
                                                                  J/SQ H BIDE
                                                                 U.OO       6-00
                                                                                                 8.00     10.00
                                                                     s.'sg FT HID:

                                                                           ALTERNATIVE A - NO TREATMENT

                                                                           ALTERNATIVE B - PRETREATMENT

                                                                           ALTERNATIVE C - ACTIVATED SLUDGE

                                                                           ALTERNATIVE 0 - ACTIVATED SLUDGE AND

                                                                           ALTERNATIVE E - ACTIVATED SLUDGE AND
                                                                                       AND REVERSE OSMOSIS-EVAPORATION

                                                                           ALTERNATIVE C - EVAPORATION
                                                                             IMPACT OF WASTE TREATMENT
                                                                               FINISHED PRODUCT PRICE

                                                                               (August,1971 Price Levels)
                                                                                                   FIGURE 10


     3.  Degree of mechanization within the tannery.

     k.  Climate of  the tannery  location.

Energy  requirements  for a typical Category  1 tannery processing hide
from raw material to finished product are approximately 0.^6 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

Alternative  B treatment energy requirements are approximately 0.0^9
kwhr/kg (0.022 kwhr/lb) of hide.  This represents about 10 percent
of the  tannery electrical energy demand.  The major units requiring
this energy  are the pumps, equalization tank mixers, and the vacuum

The treatment units  in Alternative C require nearly 0.17*f kwhr/kg
(0.079  kv/hr/lb) of hide processed.  This represents a power use
approximately 36 percent above that needed for Alternative B.  The
nidjor power  demanding units in Alternative C are pumps, equalization
tank mixers, aeration equipment, and sludge dewatering equipment.

The energy required for Alternative D treatment is 0.3'46 kwhr/kg
(0.157 kwhr/lb) of hide.   This is twice tne energy required in
Alternative  C.  Major energy use is similar to that in Alter-
native C with the addition of recycle pumping and the aeration
equipment for the nitrification basin and aeration flume.

The electric energy requirements for Alternative E total 0.37^ kwhr/
kg (0.170 kwhr/lb) of hide.   This amounts to an increase of approxi-
mately 8 percent over Alternative D and is due principally to re-
quirements of the feed pumps for the reverse osmosis unit.

In addition  to electrical  requirements, steam is needed for evapor-
ation and drying the salt.  Steam requirements are about 3,820 kg
cal/kg (7,200 Btu/lb) of hide in the form of steam.  This  represents
an increase of approximately 107 percent over the energy require-
ments of an  average tannery (Category 1) without treatment facilities

Non-water Quality Aspects of Alternative Treatment and Control

Ai r Pollution - Particulate  matter and hydrogen sulfide are the two
potential  causes of air pollution from the leather tanning and fin-
ishing 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 unhair-
inq process.

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

In addition to process sources, tannery boilers can be a  source of
air pollution.  With proper design and maintenance of gas and oil-
fired boilers, there should be no emission problems.  However, with
coal-fired boilers, fly ash emissions are a problem.  Fly ash emis-
sions can be kept to a minimum with proper design and operation.
Dust collection equipment may be used to further control  air pol-
lution.  Wet scrubbers or electrostatic precipitators are capable
or 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 wastewater treatment system.   Fly ash from the electrostatic
precipitators can be combined with the dewatered sludge for disposal.

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

Sol id Waste Disposal - Solid waste from tanneries and tannery waste-
water treatment plants includes the following:

     1.  Fleshings.

     2.  Hair.

     3-  Raw hide trimmings.

     I*.  Tanned hide trimmings.

     5.  Sanding and buffing dust.

     6.  Lime sludge.

     7.  Chrome sludge.

     8.  Biological sludge.

     9.  Office and general plant waste.

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

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

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

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

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

The selection of a proper site for landfill  operations is of prime
consideration.  Requirements in the selection include:  sufficient
area; reasonable haul distance; remote location relative to  resi-
dential, commercial, and recreational developments; soil  conditions
and rock formations; accessibi1itv to existing trsnsonrtatinn
networks; and proximity to existing groundwater supplies. The
soil cover should be sloped such that precipitation will  run off
rather than percolate and pollute groundwater sources.  Other
factors to be considered include provisions  to prevent the obstruction
of natural  drainage channels,  location to avoid flood waters,  and  the
consideration of possible fire hazards.


                            SECTION IX



The effluent limitations which must be achieved by July 1,  1S77,  are
to specify the degree of effluent reduction attainable through the
application of the "Best Practicable Control  Technology Currently
Available" (designated as Level I).  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 finish-
ing industry, but upon performance levels achieved by exemplary
plants.  In industrial categories where present control and treat-
ment 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,

In establishing Level I  effluent limitations guidelines, consider-
ation must also be given to:

      i.  Tne total cost of application of technology in relation
         to the effluent reduction benefits to be achieved  from
         such applicat ion.

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

     3.  The processes employed.

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

     5.  Process changes.        i

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

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



A further consideration is the degree of economic and engineering
reliability which must be established for the technology to be
"currently available."  As a result of demonstration projects,
pilot plants, and general use, there must exist a high degree of
confidence in the engineering and economic practicability of the
technology at the time of commencement of construction or install-
ation 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 practic-
able control technology currently available.  The effluent limita-
tions guidelines resulting from implementation of this technology
are presented in Table 13.  These are the recommended guidelines
for each industrial category for plants discharging directly to
surface waters.   The limitations require major removal of 6005 and
suspended soli ds.
Category ...
/n kg/1,000 kg hide (lb/1,000 Ib hide)v '
Parameter*' 1
BOD 1.3
COD 91
Total Chromium 0.03
Oil and Grease 0.33
Sulfide 0.003
Suspended Solids 0.67
pH, units 6.5-8.5
Fecal Coliforms/ 200
100 ml
Basic values average
these values allowed
exceed k times these
2 times basic values
Except pH and fecal
2 3 fr
2.0 1.7 0.7

Based upon  previously presented  information, an assessment  has  been
made of  the degree of effluent reduction attainable for facilities
discharging to a municipal sewer  system.   The constituents  which
will interfere with, pass through,  or otherv/ise be imcompatible
with a well  designed and operated publicly-owned waste treatment
facility  are identified in Table  1A.   The effluent limitations
indicated in Table B are the recommended guidelines for pretreatment
of  tanning  wastes entering a municipal  system.
                              TABLE 1A


                                        Category          , .
                           kg/1,000 kg hide  Mb/1.000 Ib hide)* *
 Total Chromium

 G i i diiu ui


 pH, units
            0.17     0.25    0.21     0.08    0.31    0.08

            !./'     2-5     Z.i      G.b3    3-1     0.65    O.Oi

            0.03     0.05    O.Ol)     0.02    0.06    0.02

           5.5-9.5  5.5-9.5  5.5-9.5  5-5-9.5 5.5-9.5  5-5-9-5  5.5-9.5
Basic values average over a 90-day period are shown; up to 2 times
these values allowed in 5 percent of the samples; values may never
exceed * times these limitations.  Maximum value for chromium is
2 times basic value.  pH must be within basic limits at all times.

Except pH.
Best Practicable Control Technology Currently Available

The best practicable control technology currently available  for
the leather  tanning and finishing  industry has previously  been
identified  in  Section VII (for  Categories 1  through 6) under the
headings "In-Process Methods of Reducing Waste," "Pretreatment,"
and "Major  Reduction of BODj and Suspended Solids."  Typical  sche-
matic  treatment flow diagrams are  presented.  Principal control and
treatment operations needed to  meet these limitations are  generally
summarized  below for wastes discharging to a municipal system (pre-
treatment)  and for wastes directly entering surface waters (complete

     Pre treatment - Categories  1  to 6

          1.  Water conservation  to reduce the size of treatment

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

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

          k.  Fine screening.

          5-  Equalization to dampen quality and quantity fluctua-
             tions which will  impair subsequent settling.

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

          7.  Adjustment of pH prior to discharge to the municipal

          8.  Sludge handling and disposal using thickening, chemical
             conditioning, dewatering, and landfill for final dis-
             posal .

     Complete Treatment - Categories 1 to 6

          1.  Water conservation  to reduce the size of treatment units.

          2.  Recycle of chrome and vegetable tan solutions (where

          3.  Collection of beamhouse wastes containing sulfide;
             oxidation of sulfides using a catalyst such as manganous

          k.  Fine screening.

          5.  Equalization to dampen quality and quantity fluctua-
             tions which wi11  impair subsequent processes, parti-
             cularly biological units.

          6.  Primary settling to provide oil  and grease separation,
             precipitate chromium from rinse v/aters,  and partially
             remove 6005,  COD, and suspended solids.



      7.   Aeration and secondary settling to further reduce  BODc,
          COD,  and suspended solids.

      8.   Filtration  of the final  effluent using deep-bed, mixed-
          media filters or  similar devices to improve  6005,  COD, and
          suspended solids  removals.

      9.   Chlorination to disinfect the  final  effluent.

     10.   Sludge  handling and disposal using thickening,  chemical
          conditioning,  dewatering,  and  landfill  for final disposal.

 The  above summary of treatment  steps generally  applies  to most of
 Categories  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).  Anocher modifi-
 cation  includes  elimination of  in-plant  sulfide oxidation when a
 facility  does  not have a beamhouse  operation.

 Category  7  (hide  curing) usually  results  in  very  low  flow with high
 concentrations of dissolved solids.  In arid areas, solar evaporation
 ponds are being  used to  treat these wastes,  hence zero discharge re-
 sults.   In  the more  humid  areas of  the U.  S., other evaporation tech-
 n;qwiC5 piu5  i nC. i nci'dL iun wiii be  required  to eliminate the discharge.
 In humid  areas,  Category 7 will generally  require primary settling
 prior to  an evaporation  process or prior  to  discharge to a municipal
 sewer system.

 Rationale for  Selection  of Level  I Technology

 Total Cost of Achieving  Effluent  Reduction - Based  upon  information
 contained in Section  VIM  of this  report,  the entire  leather tanning
 and  finishing  industry would have  to invest an estimated $119 million
 (August,  1971, price  levels)  to achieve the effluent  limitations
 recommended herein.  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 1.8  to 12.*  percent.

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

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 establish-
ing seven major industry categories for effluent limitations.

Engineering Aspects of Control Techniques - There are no current
waste treatment facilities in the industry achieving the control
technology proposed for Level I.  One or two existing activated
sludge plants may be capable of meeting these limitations with some
modifications in operation and with improved solids removal  in the
final effluent.  Deep-bed, mixed-media filters or other such filtra-
tion units are proven unit operations in many other suspended solids
removal applications although they have not been specifically applied
to the tanning  industry.  The concepts of control and treatment pre-
sented herein for Level I are proven.  However, some testing may be
required to substantiate performance.

Process Changes - The control and technology required for  implementing
LevelI does require some in-process changes for some tanneries.  These
modifications are principally water conservation practices and chrome
and vegetable tan solution reuse which are currently practiced by
several industries.  Technical feasibility of sulfide oxidation has
Non-water Qual ity Environmental  Impact - There is one essential impact
of waste treatment upon non-water elements of the environment and this
 s disnosa' on t^e land o^ nersral tanner" sc! Id v/cctcc ond v/cstc
sludge from treatment facilities.  Most of the waste trimmings and
hair from hides are being recovered as by-products.  Reuse of chrome
in the tannery wi11 substantially reduce chrome levels in waste
sludge from the treatment facility.  This will also reduce the
potential release of toxic chrome to the environment when the de-
watered 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 dis-
posal of waste solids from the tannery on the land.


                         SECTION  X




 technology which  is  readily transferable to the -ndustry.  S.nce
 there are no exemplary faci 1 i ties which may be cons ^red  for
 assessment of Level  II control and treatment technology, transfer
 of  concepts applied  elsewhere are utilized.

 Consideration must be given to the following in determining  Level  II

      1   The total cost  of achieving the effluent  reduction
          resulting from application of Level  II technology.

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

      3.   The processes  employed.

      k.   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 Level  I  technology, Level  II assesses  the  avail-
  ably of in-process  controls as well as additional  treatment
  techniques employed at  the end of a product.on process.

  Level II  is the highest degree of control technology that has been
  acMeved  or has been demonstrated ^.be  capable of  e.ngdes.ged
  for plant scale operation up to  and .nclud.ng no Discharge  of
  pollutants.  This level of control is intended to be the top-of
  Pthe-line of current technology  subject to 1 1m tat '"S imposed by
economic  and engineering feasibility.  Level  II may
ized by some technical  risks with respect to  performance and



   certainty  of  costs.  Some  further  industrially sponsored develop-
   ment work  pnor  to  its  application may  be  necessitated.

   Effluent Reduction  Attainable

   Based upon the informat ion contained in Sections III through VIM
   an  assessment has been made of  the  degree of effluent reduction  '
   technoZv   ?CM6V?cd thrU9h thC  ^""tion of best available
   Level  M9yff,e,5.SU"iarlZeS freach  indu^rial category the
   Level   I effluent   imitations guidelines for facilities discharging
   anexlns onrofe,IVin? V3terS:  Th'S limitation evel is principally
       *        f                      to provide for
  munTclialP  \      ' reqmrements for tanneries  discharging  to
  T^h   ff   Yc   S are recom^^'ed the same as  for Level  I   See
  Table 14 ,n Section !X for these limitations guidelines.

  Best Available Technology Economically Achievable

  The best available  technology  economically achievable for the leather
  r"1?   f   f;ni?hln9  industry (Categories 1 through 6)  is major
  renoval  of  all  ni trogen^ form?  (as  discussed  in Sect^i V i i} in
 r.ow cnagram is shon on Figure 7 in Section VII ."'

 inlLuon !x?  " 6re ^ "^ 3S fr Uvel ' and
      Complete Treatment - Categories 1  to 6

          1.  Water conservation to reduce the size of treatment

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

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

          4.   Fine  screening.

          5.   Equalization  to dampen variations  in  quality and
              quant.ty which will impair subsequent  processes,
              particularly  biological  units.




                                  TABLE  15


                           (COMPLETE TREATMENT)

 Total Chromium

 Oi I and Grease


 Suspended Sol ids

 Total Kjcldahl

   Ni trogen*3)

   Ni trogen'3)

 pH, un i ts

 Color, %

 Fecal col i form/
   100 ml
                                             Category            , 
                               kg/1.000 kg hide  (1b/l,000 Ib hide)v '




































  0.10    0.15     0.12     0.05     0.19     0.05

  0.33    0.25     0.17     0.07     0.12     0.33

6.5-8.0   6.5-8.0  6.5-8.0  6.5-8.0  6.5-8.0  6.5-8.0





        Basic values average over a 90-day period ere shown; up to 2  times
        these values allowed in 5 percent of the samples; values may  never
        exceed A times these limitations.  Maximum limit for chromium is
        2 times basic values.  pH must be within basic  limits shown at all

        Except pH, color, and fecal coliforms.

        Limitations for nitrogen  forms do not apply when the water  temperature
        is below 10 C (50 F).
        No reasonable data is currently available  upon which absolute limits
        may be established.  Treatment can provide this percent removal,


          6.   Aeration  and clarification  of solids  to  remove
              carbonaceous 6005,  COD,  and suspended solids.

          7.   Aeration  to nitrify organic and  ammonia  nitrogen
              followed  by settling.

          8.   Mixing  with a carbon source to cause  deni tri f icat ion ;
              an  aeration flume  to assist nitrogen  gas  removal;
              and a  final  settling tank.

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

         10.   Chlorination to disinfect the final effluent.

         11.   Sludge  handling and disposal  using  thickening, chemical
              conditioning,  dewatering, and landfill for  final dis-
              posal .

     Complete Treatment  - Category 7

          This will be  the same as  defined  previously  for  Level  I
          witn zero discharge.

Rationale for Selection  of  Level  II Technology

Tt'Ld'i Cubt of Achieving  Effluent  Reduction  -  As  presented in Section
VIM, to  meet Level  II effluent  limitations,  the industries all would
hsve to  invest an estimated $138  million  (August,  1971, price levels).
Total annual costs (inc'uding depreciation, interest, operation and
maintenance)  to  achieve  these limitations  are estimated to increase
the cost  of the  finished  product  from 1.8  to  16.0  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.

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

Engineering Aspects  of Control  Techniques  - Level  II technology
appears achievable considering  the developmental  work  being  done
on ni tri f ication-deni trif ication of municipal  wastes.   There are
several technical questions which need to be  resolved prior to
initiation of full-scale  ni tri f icat ion-deni tri f 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 nitrification-denitrifIcation of tannery waste,
hence studies will be required to confirm design parameters  required
to implement an efficiently designed and operated  facility.

Process Changes - Process changes required for Level II  are  the
same as for Level I  (see Section IX).  The industry should  initiate
research  to find potential substitutes for ammonium salts  used  in
the bate operation and salt used for hide curing.   These process
changes would reduce treatment costs for Level  II  and also  effect
considerable  reduction  in dissolved solids which are economically
very unattractive for removal in a waste treatment  facility.

Non-water Quality Environmental  Impact - The  impact upon the land as
a  result of  liquid waste treatment  is the same  as outlined for Level
 in Section  IX.



                             SECTION XI


 The  standards of  performance  for new  sources are to reflect the
 greatest  degree of effluent reduction achievable through the appli-
 cation of the "best available demonstrated control technology, pro-
 cesses, operating methods, or other alternatives"  (Level II!).  A
 new  source is defined as any  construction which  is commenced after
 publication  of the regulations prescribing the standards of perfor-
 mance.   In addition to considering the best  in-planl and end-of-
 process control technology  identified for Level  II, Level  III  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
 pract icable.

 For  establishing  Level III effluent limitations guidelines, consid-
 eration must also be given to:

     1.   The type of p.-oc-E^  e^cy^J ^;.d procc-^ chenges.

     2.   Operating methods.

     3-   Bfltch ai onnn^pH fr  cOnt'n'JCUS O^sra t Icr.S .

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

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

     6.   Recovery of pollutants as by-products.

 According  to the Federal  Water Pollution Control Act, as amended (Act),
 once the  plant is constructed so as to meet all applicable standards
 of performance, it shall  not  be subject to any more stringent stan-
 dards during the ten-year period\following completion of construction
 of the facility, or during the period of depreciation or amortization
 of such facility, whichever period ends first.

 Improved  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 Level I  and Level II effluent limitations guidelines.


A new facility, due to more efficient layout and more automation,
can effect better process control, thus minimizing water use and
optimizing chemical use.  In addition, general  housekeeping pro-
cedures should improve.

The net effect of  improved process layout, control and monitoring
in a new tannery will mainly be to decrease water use and discharge
of some chemicals.  Organic loads resulting from hide processing
are not expected to change, however.   Hence, the waste discharge
in kg (lb)/l,000 kg  (ib) hide may not change significantly.  Im-
proved equipment and controls in a new plant merely reduce some of
the tank sizes at the treatment facility utilized to meet the
variable waste characteristics from a tannery not equipped with
new equipment.  For example, better scheduling and control of
different types of waste may reduce the size of equalization faci-
lities 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 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.

Ne;/ 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 faci-
lities should be set consistent with those required for Level  I
and Level II.  Although standards of performance for Level III
should generally comply with the higher levels established for
Le/el II, it does not seem conceivable that nitrification-denitri-
fication processes wi 11 be demonstrated on tannery wastes much
before 1977 without  intensive efforts by the tanning industry and/or
the Environmental Protection Agency.   Thus, it appears that in the
next three or four years, the best demonstrated control technology
would be that represented by Level I, and subsequently that as
proposed for Level II.  However,  it appears from the Act that
Level II effluent  limitations are the minimum standards for new
sources; therefore, a new source would have to  implement nitri-
fication-den i tr if ication facilities.   Once  in operation, though,


the new source would have a period of ten years before more
stringent criteria could be applied,  unlike existing sources.

As regards pretreatment of waste from new tanneries, it is recom-
mended that standards of performance  comply with that previously
established for Level I.  No further  reduction of constituent
levels in pretreatment are warranted  for newly constructed faci-



                            SECTION XI I

A number of individuals and organizations have contributed to the
investigation reported herein.  The response, cooperation, and
assistance from tanneries too numerous to mention is greatly appre-
ciated.  Without this assistance and provision of available data,
the project could not have been effectively completed.   The willing
cooperation given by tannery personnel to Stanley Consultants' sam-
pling teams in their assignment of gathering wastewater and in-house
process samples is especially appreciated.  Personnel at other tan-
neries visited were also quite helpful.

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.  Through their efforts with
the Tanners' Council, much of the data were gathered.  Thanks are
also due Dr. J. David Eye, Professor of Envi ro.imental Health Engi-
neering, University of Cincinnati, who served as a Special Consult-
ant on the study.

The cooperation of other consultants, state and  local regulatory
agencies, analytical  laboratories, and chemical and equipment manu-
facturers is appreciated, particularly for their assistance in pro-
 .  j  . _ j_ ,. _, _  .1 i	i	 _ j  _ _ _i._ j.   ir^i-u  _ j-i .-___:__ -_ J . .__4- __
viuiiiy uata aim ua^.t\y i UUMU i n i wi ma L lui i uuin  in LUG Lauuiii^ auu xuaic
water treatment fields.

The advice, support, and guidance of Dr. William R. Hancuff, of  the
Effluent Guidelines Division, Office of Air and Water Programs,
Environmental  Protection Agency, who served as Project Officer,  is
sincerely appreciated.  Assistance  provided by many other personnel
of the Environmental  Protection Agency is also acknowledged.

The principal  Stanley Consultants personnel on the project team  for
this study are:

     Kenneth M.  Bright, P.E., Project Manager and Vice  President
     John L. Thomas,  P.E., Associate Chief Sanitary  Engineer
     Robert L. Thoem, P.E., Project Engineer
     Terry G.  Lorber, P.E., Staff Engineer
     David R.  Thomas, E.I.T., Staff Engineer
     Angel C.  Campos, Associate Engineering Technician


                         SECTION XI I I

(1)   "Industrial  Waste - Profile No.  7, Leather Tanning and Finish-
     ing," JjTeJCosJ^_p_fJ^jiajTj.^^                FWQA Report, 1967-

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

(3)   O'Flaherty, F., Roddy, W.  T., and Lollar, R. M. , Chemistry and
     Technology of Leather, Volumes I-IV, Reinhold Publishing Cor-
     porat ion .

(k)   Masselli,  Joseph W. , Massel i , Nicholas W., and Burford, M. G. ,
     Tannery Wastes - Pollution  Sources and Methods of Treatment,
     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 Division, Proceedings of the American Society of
     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'  Association, Volume LXV I I , No.  10,
 (7)  Bailey, D. A., and Humphreys,  F.  E., "The Removal of  Sulphide
     from  Limeyard Wastes by Aeration,"  British Leather Manufac-
     turer's Research Association,  Laboratory Reports, XV,  No.  1,
 (8)   Eye,  J.  David, and  Clement,  David  P.,  "Oxidation  of  Sulfides
      in  Tannery Waste Waters,"  Journal  of  the American Leather
      Chemists' Association,  Volume  LXCII,  No. 6,  June, 1972.

 (9)   Wi 1 1 iams-Wynn, D. A.,  "No-Effluent Tannery Processes," Journal
      of  the  American Leather Chemists'  Association, Volume LXVI I I ,
      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 Qual i ty
      Cr I ter ia.  2nd ed., The Resources  Agency of  California,  State
      Water Quality  Control  Board, Publication No.  3-A  19&3.

(13)   Bailey,  D.  A.,  Dorrell,  J.  J..  and Rob nson  K.  S. .,  J""Sl
      of the Society  of Leather Trades'  Chemists. 5*,  9  (1970).
      Tired in Journal  of the American Leather Chemists'  Assoc.a-
      tion, Volume LXVII, No.  9, September, 1972.

(HO  Sutherland, R. , Industrial and Engineering Chemistry. 39, 628
      (19*7).   Cited by Reference (1 U 

MO  Soroul  Otis J., Atkins, Peter F., and Woodward, Franklin E. ,
      "Investigations on Physical and Chemical Treatment Methods
      for  Cattleskin Tannery Wastes," Journal of Water Pol lut ron
      Control Federation. Volume 38, No. A, Apr.l,  1966.

(16)  Kunzel-Mehner, A., Gesundh.  Ing..  66, 300. 19*3.  Cited  by
      Reference  (11).

 (17)  "Report of the Symposium on  Industrial  Waste of the Tanning
       Industry!" Journal of the American Leather Chemists' Associ-
      ation,  Supplement No. 15,  1970.

 (18)  Hounlt. M .   ' f  "  F  S--  Transactions of  American Society
 (    of Civil  Engineers.  92., 1351,  1928.   Cited by Reference UU-

 (19)   Riffenburg, H. b., and Aiiibuu, w. w., Ir.s^l.-.^- and E-.g  -
       neering Chemistry. 33_, 801, 19*1.  Cited by Reference (11).

 (20)   Hagan. James R.,.and Eye.J. David , and J-nison.^C. , ^ ^
       "I nvest i aat ions  ITILU LMC ucmwvai  ** /<   -   -  
       Treated Vegetable Tannery Wastes," Masters  Thesis,  Un.vers.ty
       of  Cincinnati ,  1972.

  (21)   Data obtained by  Stanley  Consultants  field  investigations.

  (22)   Chen   Kenneth Y. , and  Morri s ,  J .  Carrel 1 , "Oxidation of Sulf.de
  (  }   by  Si-  Catalyst and  Inhibition,"  ..n..rnal  of  the San, tary
        FnniSeerlna Division.  Proceedings of the American Soc.ety of
        cTvTT  Engineers,  Volume 9.  No.  SA1 . February, 1972.

  (23)   The A. C. Lawrence  Leather Company, Activated  Sludge Tr^at-
        n, of  Chrome Tannery Wastes. Federal Water Pol ^. on Control
        Administration, Department ot the Interior  Grant  No. WPRD
        133-01-68, Program No. 12120, September, 19&9-

  (2k)  Nemerow, N. L., and Armstrong, R. , "Prototype Studies  of  Com-
        bined Treatment of Wastes from 22 Tanneries and Two Munic,
        palities," Purdue Industrial Waste Conference  Proceed. ngs.

(25)   Kinrnan,  Riley N.,  "Evaluation  of  WasLc  Treatment  Process  for
      Treating Waste from Bona  Allen,  Inc.,  Buford,  Georgia."   Un-
      published article.   January  30,  1972.

(26)   Kinman,  Riley N.,  "Evaluation  of  Bona  Allen  Wastewater Treat-
      ment for Period February  I,  1972,  to January 25,  I973-"   Un-
      published article.   March 5,  1973.

(27)   Sarber,  R.  W. , Journal  of the  American  Leather Chemists'
      Association,  36,  ^63 (19^1) .   Ci ted by  Reference  (*) .

(28)   "Tannery Effluent  Report  to  the Members of  the Effluent  Com-
      mission  of the International  Union of  Leather  Chemists'
      Societies," Journal  of  the American Leather  Chemists' Associ-
      ation, Volume LXVII, No.  10,  October,  1972.   Reprinted from
      Journal  of the Society  of Leather  Trades'  Chemists,  56,  AO,

(29)   Parker,  Clinton E.,  Anaerobic-Aerobic  Lagoon Treatment for
      Vegetable Tanning  Wastes. Federal  Water Quality Administra-
      tion,  Environmental  Protection Agency,  Grant No.  WPD-199-01 -67 ,
      Program  No.  12120  D IK,  December,  1970.

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

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

(32)   Eye,  J.  David,  Treatment of  Sole  Leather  Vegetable Tannery
      Wastes ,  Federal  Water Pollution Control Administration,
      Department  of  Interior, Program Number 12120,  Grant Number
      WPD-185,  September,  1970.

(33)   Conversation with J.  David Eye.

(3*0   Clark,  John  W. ,  and Viessman, Warren,  Jr.,  "Biological-
      Treatment Processes,  Activated  Sludge," Water  Supply  and
      Pol lut ion Control ,  International  Textbook Company, Scranton,
      Pennsylvania,  March,  1966.

(35)   Steffen,  A.  J.,  and Bedker,  M. , "Operation  of  Full-Scale
      Anaerobic Contact Treatment  Plant  for  Meat  Packing Wastes,"
      Proceedings  of  the 16th Industrial Waste  Conference,  Purdue
      University,  423,  1961.   Cited  in  Reference  (29).

(36)   Gates, W. E., Smith,  J.  H., Lin, S., and Ris, C.  H.,  III,
      "A Rational Model  for the Anaerobic Contact Process,"
      Journal of Water Pollution Control Federation, 39,  1951,
      1967.   Cited in  Reference  (29).

(37)   "Industrial Waste  Survey at Caldwell Lace Leather Company,"
      EPA, Office of Operations, Radiological and Industrial  V/aste
      Evaluation Section,  Cincinnati,  Ohio.

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

(39)   Reuning, H. T..  Sewage Works Journal , 2, 5?5, 1948.  Cited
      by Reference (llT^

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

(41)   Eldridge, E. F., Michigan Engineering Experiment  Station
      Bulletin, 87., 32-41,  November, 1939.  Cited by Reference (11).

(1*2)   Fales, A. L. , Industrial  and Engineering Chemistry,  21 , 216
      1929.   Cited by  Reference  (11).~

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

(44)   Haseltinc, T. R. ,  "Tannery Wastes Treatment with  Sewage at
      Wi11iamsport, Pennsylvania," Sewage and Industrial  Wastes,
      Volume 30, No.  1,  January, 1958.

(45)   Hartman, B. J.,  Sewage and Industrial Wastes. 25_, 1419  (1953).
      Cited  by Reference (4).7~

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

(47)   Nemerow, N. L.,  and Armstrong, R. , "Combined Tannery and
      Municipal Waste  Treatment, Gloversvi1le-Johnstown,  New  York,"
      Purdue Industrial  Waste Conference Proceedings,  1966.


(i8)   Wims,  F.  J.,  "Treatment  of Chrome-Tanning Wastes  for Accept-
      ancc'by an Activated Sludge Plant," Purdue Industrial Waste
      Conference Proceedings.  19&3-

(19)   Maskey, D. F., Journal  of the American Leather Chemists'
      Association,  36., 121 19^1.  Cited by Reference (11).

(50)   McCarty, P. L., "Anaerobic Treatment of Soluble Wastes,"
      Advances  in Water Quality  Improvement  (edited by Gloyna,
      E. F.  and Eckenfelder,  W. W., Jr.), U. of Texas Press, Austin,
      1968.   Cited  in Reference  (29).

(51)   Sproul, 0. 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  Conference Proceedings,  1966.

(52)   Calgon Corporation, Laboratory Column  Studies for Hartland
      Tannery,  Report No. C-8?l ,  June, 1972.

(53)  Tomlinson, H.  D., Thackston, E. L., Krenkel,  P. A.,  and
      McCoy, V.  M.  "Complete Treatment of Tannery Waste,"  Technical
      Report No. 15,  Department of Sanitary  and V/aste Resource
      Fnginppring.  V^nderbilt  Universitv.

      Tomlinson, H.  D., Thackston, E. L., Krenkel,  P. A.,  and
      McCoy, V.  M.,  "Laboratory Studies  of  Tannery  V/aste  Treatment,"
      Journal of Water Pollution Control  Federation. Volume  Al,
      No~.~V ApVil",  1969.  '

 (55)  Secondary Waste Treatment for  a  Small  Diversified  Tannery,
      U.  S.  Environmental  Protection Agency, EPA-R2-73-200,
      April,  1973.

 (56)  Culp,  R.  L.  and Culp,  G.  L., Advanced Wastewater Treatment.

 (57)  Wild,  H.  E.,  Sawyer, C.  N., and  McMohon, T.  C.,  "Factors
      Affecting Nitrification  Kinetics," Journal  of Water Pollution
      Control  Federation. Volume A3, No. 9, September,  1971.

 (58)   Nitrification and  Denitrification  Facilities, EPA  Technology
      Transfer Program -  Design Seminar  for Waste  Water  Treatment
       Facilities,  September,  1971.

 (59)   Dodge, Burnett, F., "Fresh Waters  from Saline Waters," Amer-
       ican  Scientist, Volume A8, No. A,  December,   I960.   Cited by
       Reference (3*0 

 (60)   Downing, D.  G., Kunin, R., and Pollio, F. X., "Desal Process-
       Economic  Ion Exchange System for Treating Brackish and Acid
       Mine Drainage Waters and  Sewage Waste Effluents," Chemical
       Engineering Progress,  Volume 6k, No.  90, 1968.

(61)   "Reverse  Osmosis  Concentration of Dilute Pulp and  Paper
      Effluents,"  EPA Water Pollution Control  Research  Series
      120^0 EEL,  February,  1372.

(62)   Kremen,  S.  S. ,  "The  Application and Performance of Spiral
      Membrane  Module Systems  in  Reverse Osmosis  Processing of
      Water and Waste Streams," presented to Japanese Sea Water
      Science  Group  Meeting,  November, 1971.

(63)   "Reverse  Osmosis  Demi nera 1 izat ion of Acid Mine Drainage,"
      EPA Water Pollution  Control  Research Series,  I'iOlO FQR
      March, 1972.

(6*0   Saline Water Conversion  Summary Report (1972-1973) Office
      of Saline Water/U.  S. Department of Interior.

(65)   "Disposal of Brines  Produced in Renovation of Municipal
      Wastewater"  FWQA  Water Pollution Control Research  Series
      ORD 17070 DLY,  May,  1970.

(66)   "Estimating  Costs and Manpower Requirements for Conventional
      Wastewater Treatment Facilities," Black and Veatch for EPA
      Office of Research and Monitoring, Project 17090  DAN,
(67)   Smith,  R.,  and McMichael, W.  F.,  "Cost Performance Estimates
      for Tertiary Wastewater Treatment Processes," FWPCA Advanced
      Waste Treatment Research Laboratory.  June.
(68)  Correspondence with Mr. Irving Glass of the Tanners'  Council
      of America,  Inc.

(69)  Voegtle, J.  A., and Vilen, F. I., "A New Concept for Operators
      Wages," Journal of Water Pollution Control  Federation, Volume
      No. 2, 1973.

(70)  Oil, Paint,  and Drug Reporter, August 2, 1971.


                            SECTION XIV


A measure of the ability of the waste to provide hydrogen ions when
treated with alkaline materials.  Generally expressed in mg/I as

Activated Sludge

A wastewater treatment process using a mixed microbiological culture
and molecular oxygen to satisfy waste stabilization requirements.
Provision is made to return some solids settled from the effluent
flow  to the  influent, and thereby maintain the desired microorganism
population  in the process.

Ad i pose

Of, or related to, animal fat;  fatly.

Adsorpt ion

The adhesion of a gas,  liquid,  or dissolved substance to the surface
of a  sol id  or  1iquid.

Aerat ion
 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.


 A  biological  process  in which chemically  combined oxygen is used  for
 microorganism respiration needs.  Relating to  biological degradation
 of waste matter in the absence of dissolved oxygen.


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


 That portion of the animal hide, especially catllehide, consisting
 of the center portion of the hide along the backbone and covering
 the ribs, shoulders, and butt (excluding the belly).

 Bat ing

 The manufacturing step following liming and preceding pickling.   The
 purpose of this operation is to delime the hides, reduce swelling,
 peptize fibers, and remove protein degradation products from the


 That  portion of the tannery where the hides are washed, limed,
 fleshed,  and unhaired when necessary prior to the tanning process.
 That portion of the hide on  the underside of the animal  usually
 representing the thinnest part  of the tannable hide.


 That portion of the hide representing the entire hide  cut  down the
 backbone  with the bellies and shoulders  removed.
      A >-. I
                        .. *.  i  ^ _ . .   * i-   i   i
                        a ecu  v^QiiLiui  imnnoiugy
 Treatment  and  control  required  for new  sources of  industrial dis-
 charge  to  surface waters  as defined  by  Section 306 of  the Act.*

 Best Available Technology Economically  Achievable

 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

 Best Practicable Control  Technology Currently Available

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

 B 1 owdown

 The amount of concentrated liquor wasted in a recycle system in order
 to maintain an acceptable equilibrium of contaminants  in any process
 1 iquor.

* The Act   is the Federal Water Pollution Control  Act  Amendments of

 Biochemical Oxygen Demand  (BODc)

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

 Chemical  Oxygen Demand  (COD)

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

 Chlorine  Contact Tank

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

 Chromium  (Total)

 Total chromium is the sum of chromium occurring in the trivalent and
 hexavalent state.  Expressed as mg/1 as Cr.
       i rat irn
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.


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

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


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


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

Composite Sample

A series of small wastewater samples taken over a given time period
and combined as one sample in order to provide a representative
analysis of the average wastewater constituent levels during the
sampling period.

Concrete Mixer
A term often applied to hide processors.

Cori urn

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


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

Deminerali za t i on

The process of  removing dissolved minerals  from water by  ion ex-
change,  reverse osmosis, electrodialysis, or other process.


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


The process of  removing dissolved salts from water.

Detent ion  (Retention)

The dwell  time  of wastewater  in  a treatment unit.


The process of  removing of  a  large"  part of  the v/ater  content  of

 Dissolved oxygen.  Measured in  mg/1.


A large cylinder, usually made of wood, in which hides are placed
for wet processing.  The drum is rotated around its axis, which  is
oriented horizontally.  Also called wheel.

Electrodialys is

A form of advanced waste treatment in which the dissolved  ionic  mate
rial is removed by means of a series of semi -permeable membranes and
electric current.


Complex protein materials added to ihe hide in the bating  step  in
order to remove protein degradation products that would otherwise
mar hide qual i ty .


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

Equal izat ion

 i ue no Iding or storing sr G'j tc^ ricv ! rig c ; i"! cr ; ny  cjuj : 1 1. : co  Cii;u :u>.c,
of discharge for finite  periods to facilitate blending  and achieve-
ment of relatively uniform  characteristics.
The  excess  fertilization  of  receiving waters  with  nutrients,  princi
pally  phosphates  and  nitrates,  found  in  wastewaler which results in
excessive growth  of aquatic  plants.

Fat ] iquor

The  process of  adding oils,  fats,  and greases to tanned hides to im
prove  and prevent cracking.

Fin ish ing

The  final processing  steps performed  on  a tanned hide.   These opera
 tions  follow the  retan-color-fat 1 iquor  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 v/ater
 that is maintained in any wet process unit (vats,  drums, or pro-
 cessors) within the tannery.


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

Flocculat ion
The process of floe formation normally achieved by direct  or induced
slow mixing.

Fl ume

An open, inclined channel or conduit for conveying water or water
and hides.

Grab Sample

A single sample of wastewater which will indicate only the constitu-
ent levels at the instant of collection; contrasted to a composite

Graded Media FiIter
A filtration device designed to remove suspended solids from waste-
water by trapping the solids in a porous medium.  'I he graded media
filter is characterized by fill material ranging from large particles
with low specific gravities to small particles with a higher speci-
fic gravity.  Gradation from large to small media size in the direc-
tion of normal flow.


The epidermal side of the tanned hide.  The grain side is the smooth
side of the hide where the hair was located prior to removal.

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

Ion Exchange

The reciprocal transfer of ions between a solid and a solution sur-
rounding the solid.  A process used to demineralize waters.

Ion izat ion

The process by which, at the molecular level, atoms or groups of
atoms acquire a charge by the loss or gain of one or more electrons.

L iming

The operations in the beamhouse where a lime solution comes  in  con-
tact with the hide.  Liming in conjunction with use of sharpeners
such as sodium sulfhydrate is used to either chemically burn hair
from the hide or to loosen it for easier mechanical removal.  Hair
burning normally utilizes higher chemical concentrations.


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
wastewater.   Expressed  in mg/1 as N.

 Nitrogen, Kjeldahl  (Total Kjeldahl Nitrogen or TKM)

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 wastewater.  Expressed
 -c  rr/i /I  ac  M

 Any material used by a living organism 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 growth of microorganisms
 in biological treatment.


 The final outlet conduit or channel where wastewater or other drain-
 age is discharged  into an ocean, lake, or river.


 Layers of salted hides formed at the slaughter house or hide curing
 firm  (usually approximately 20 to ^0 feet  in area and 5 to 6 feet

 Paddle Vat  (Paddle)

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


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


The process step generally following the retan-color-fat 1 iquor opera-
tions whereby the hide is attached to smooth plates with a starch and
water paste and dried in a controlled heated vessel.


The process that follows bating whereby the hide is immersed In a
brine and acid solution to bring the skin or hides to an acid con-
dition; prevents precipitation of chromium salts on the hide.


The finishing operation where the skin or hide is "pressed"  in order
to make it smoother.


An organic compound characterized by a large molecular weight.  Certain
polymers act as coagulants or coagulant aids.  Added to the waste-
water, they enhance settlement of small suspended particles.  The
large molecules attract the suspended matter to form a large floe.

A mixing apparatus resembling a concrete mixer which is used in some


A plant where sheepskin is processed by removing the wool and then
pickling before shipment to a tannery.


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 fat 1iquoring.

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  con-
centrated form on the feed side  of the membrane and are wasted.

Sand ing

A dry operation performed on the tanned and falliquored hide in order
to achieve the desired surface texture of the leather.   Sanding opera-
tions include the use of abrasive or buffing wheels.


A process where shearlings are washed.


An operation following the major unhairing step where the last  of
the hair is removed from the hide.

Clarification (settling).


A side represents halt a hide which has been cut along the spine.


Chemicals used in addition to lime to assist in the unhairing pro-
cess (such as sodium sulfide and sodium sulfhydrate).


A lamb or sheepskin tanned with the hair retained.


That part of the hide which represents the shoulder of the animal.

Sk i v i ng

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


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

Spl 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 non-uniform thickness called a split.


The finishing process wherein the hide or skin is stretched to make
it more pliable and to avoid shrinkage.   Tacking.

SIC (Standard Industrial Classification)

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

Submerged Combustion

A flash evaporation type procedure used in the separation of dis-
solved solids from water.


ionised sulfur.  Expressed as mg/l as b.

Suspended Sol ids (SS)
             bubperideu in wastewarer which can usually De removed
by sedimentation (clarification) or filtration.


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

Tann in

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 tan-
ning is performed on the hides or skins.

Total Dissolved Sol ids (TDS)

The total amount of dissolved materials (organic and  inorganic)  in
wastewater.  Expressed as mg/l.

Total Solids (TS)

The total amount of both suspended and dissolved materials in waste-
water.  Expressed as mg/l.

Unhal ring
The process where the hair is removed from the hide.

Volatile Sol ids
 Wei r
 A control  device placed  in  a  channel  or  tank which  facilitates  mea
 surement or control  of the  water flow.