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STANLEY CONSULTANTS
INTEHNATIOHAL CONSULTANTS IN EMGIHEERINO, ARCHITECTURE, PLANNING. ANU MANAGEMENT
-------
DRAFT
ABSTRACT
This document presents the findings of an extensive study of the
leather tanning and finishing industry for the purpose of developing
effluent limitations guidelines, standards of performance, and 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.
iii
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON INFORMATION
IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED UPON COMMENTS RECEIVED
AND FURTHER INTERNAL REVIEW BY EPA.
-------
Sect! oil
Rat
CONTENTS (Con't)
ionale for Selection of Identified Parameters. . 2
COD .................. ^
Total Chromium ................ ,
Grease
Sulfide
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
General
Basis of Tannery Waste Treatment
In-Process Methods of Reducing Waste
Pretreatment
„
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 ..................
VI
-------
CONTENTS (Con't)
Sect ion
Page
Elect rod ia lys i s .' . 95
Ion Exchange 95
Reverse Osmosis 96
VIII COST, ENERGY, AND NON-WATER Q.UAL ITY ASPECTS 101
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
IX RF<;T PRATT! C^BLE CONTROL TECHNOLOGY CURRENTLY
AVAILABLE - GUIDELINES AND LIMITATIONS 115
General
Effluent Reduction Attainable
Best Practicable Control Technology Currently
Available.
15
16
17
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
X BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE -
GUIDELINES AND LIMITATIONS 121
General 121
Effluent Reduction Attainable 122
Best Available Technology Economically Achievable. 122
vii
-------
CONTENTS (Con't)
Section
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
XI NEW SOURCE PERFORMANCE STANDARDS ........... 127
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
viii
-------
TABLES
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
IX
-------
FIGURES
Number_
1
2
3
5
6
7
8
9
10
Title
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)
12
18
20
25
66
92
97
106
110
-------
DRAFT
SECTION I
CONCLUSIONS
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:
The
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
Chrome
Chrome
Previously tanned
Chrome
C h rome
No tanning
Leather
F in ishing
Yes
Yes
Yes
Yes
No
No
Currently, waste from about 60 percent of the tanneries (and approxi-
mately 60 percent of the production) is discharged to municipal sewer
systems, while the remainder is discharged directly to surface waters.
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.
1
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS EASED UPON INFORMATION
"IN THIS REPORT AND ARE SLBJECT TO CHANGE BASED UPON COMMENTS RECEIVED
AND FURTHER INTERNAL REVIEW BY EPA.
-------
DRAFT
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.
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON INFORMATION
IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED UPON COMMENTS RECEIVED
AND FURTHER INTERNAL REVIEW BY EPA.
-------
DRAFT
SECTION II
RECOMMENDATIONS
Presented herein are the recommended effluent limitations guidelines
for the leather tanning and finishing industry. The proposed basic
levels of waste constituents in the following tabulations are 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.
LfcVtL 1 EhFLUENl
Parareter"'
BODj
COD
Total Chromium
Oi 1 and Grease
Sulfide
Suspended Solids
pH. units
Fecal Coli forms/
100 nl
F LIMITATIONS GUIDELINES - JULY 1, 1977
(Complete Treatment)
Category . .
kg/I, 000 kg hide lib/ 1.000 Ib hide)"'
1
1 3
91
0 03
0.33
0.003
0 67
6.5-8 5
200
Basic values average
these values allowed
exceed 4 tines these
2 tines basic values
tlrci.
Except pH and
2
2 0
<>9
0.05
0 5
O.OOS
1.0
6.5-8 5 6
200
3
1.7
88
0 04
0 d2
0 OOli
083
5-8 5
200
Q
0 7
9 8
0 02
0 20
0.002
0.33
6 5-8 5
200
5
2 5
60
0 06
0 62
0 006
1 3
65-85 6
200
t
0 67
82
0.02
0 20
0 002
0 33
5-8 5
?00
0
0
0
0
0
0
...
0
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*
CE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON INFORMATION
IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED UPON COMMENTS RECEIVED
AND FURTHER INTERNAL REVIEW BY EPA.
-------
DRAFT
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
LEVEL 1 EFFLUENT
Parameter^1*
Total Chromium
Oil
and Grease
Sulfide
PH,
units
0.17
1.7
0.03
5.5-9.5
Basic values average
these values al lowed
exceed H times these
2 times basic value.
(2)
Except pH.
LIMITATIONS GUIDELINES - JULY |, 1977
(Pretreatment)
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 ^ " f°r 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 dissolv«d 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 ab°V6 limitati°ns and standards are
industr!^ extens'vejwater ™<* chemical conservation within the
industry and properly designed and operated waste treatment facilities
T^fc JS ^ TE^T IVE RECOMMENDATIONS BASED UPON INFORMATION
-------
DRAFT
LCVEL II EFFLUENT LIMITATIONS GUIDELINES - JULY 1, 1983
(Complete Treatment)
Parameters
(D
COD
Total Chromium
Oi1 and Grease
Sulfide
Suspended Sol ids
Total Kjeldahl
Nitrogen(3)
Ammon i a
Nitrogenl3)
Nitrate
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 '
0.6?
91
0.03
0.33
0.003
0.67
1.0
^
0.05
0.5
0.005
1.0
0.17 0.25
0 8
88
0.0*1
O.l\2
O.OO't
0.83
0.21
TT
0.33
9.8
0.02
0.2
0.002
0.33
0.08
1.3
60
0.06
0.62
0.006
1.3
0.31
0.33
82
0.02
0.20
0.002
0.33
0.08
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
85
200
85
200
85
200
85
200
85
200
85
200
(1)
0
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
times.
(2)
Except pH, color, and fecal coliforms.
Limitations for nitrogen forms do not apply when the water temperature
is below 10° C (50° F).
CO
No reasonable data is currently available upon which absolute limits
may be established. Treatment can.provide this percent removal,
however.
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON INFORMATION
IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED UPON COMMENTS RECEIVED
AND FURTHER INTERNAL REVIEW BY EPA.
-------
DRAFT
SECTION II I
INTRODUCTION
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.
-------
DRAFT
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.
-------
DRAFT
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.
11
-------
DRAFT
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.
FLOW DIAGRAM
TYPICAL CATTLEHIDE TANNERY
(1OJO
H .:o''ttl
HOI I («i
.<:> i to
-j","r
I"'
[ IU!iHIIK.j I JSCUO «tStt
•itit nnurti [•*sn CIHUEM
FIGURE 1
12
-------
DRAFT
Sub-processes and the operations which take place within each pro-
cess are described as follows:
BEAMHOUSE PROCESS:
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.
13
-------
DRAFT
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."
-------
DRAFT
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.
TANtiOUSE PROCESS:
1. Bating - Bating is the first step in preparing the stock
for the tanning process. It may be done in either vats
(with or without paddles), drums, or hide processors.
The hides are placed in the processing equipment which 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.
15
-------
DRAFT
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
RETAN, COLOR, FATLIQUOR PROCESS:
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.
16
-------
DRAFT
The amount of oil added depends on the end use of the lea-
ther.
Liquid wastes from the retan, color, and fatliquor process
may be high volume-low strength compared with the other
processes.
FINISHING PROCESS:
Finishing operations such as drying, wet-in coating, staking or
tacking, and plating which follow the wet processes provide only
minor contributions to the liquid waste primarily from cleanup
of the paster drying plates and from paint spray booth water
baths.
Trimmings are disposed as solid waste, and dust collected may
be disposed in either wet or dry form.
Sheepskin Tannery Processes
Sheepskin tanning processes are somewhat similar to pigskin 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:
TANHOUSE PROCESS:
1. Receiving - Most sheepskins are received at U. S. tanneries
from both domestic and imported sources as pickled skins.
These skins, which are salt cured, are normally tied in
bundles of one dozen skins. These skins have had the wool
removed at the packer or wool pullery and processed to the
pickled condition. The wool pulling represents a beamhouse
process.
Skins tanned with the wool intact are referred to as shear-
lings. Tanning of these skins does not involve a beamhouse
process.
Pickled skins have been preserved for shipment and storage
by immersion in a solution of brine and acid. Shearling
skins are cured in a salt brine only. Excess solution is
drained prior to bundling.
17
-------
FLOW DIAGRAM
TYPICAL SHEEPSKIN TANNERY
UfihCU'sf
mm mucuc«
(I) l«(*tll»',', (»COl IMi 0») l-F
= E(I liiO 1". CimO Smi. I<»-
r&lAf SUB-^OClSitS IKCIUDI
»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
.ju
\uu
—..- --^
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.
18
-------
DRAFT
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
waste.
COLOR AND FATLIQUOR PROCESS:
. /•_'.__:_.. _ 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.
FINISHING PROCESS:
There are a number of operations which follow the coloring and
fatliquor process, including drying, skiving, staking, carding,
clipping, sanding, and buffing. These are essentially dry 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
19
-------
DRAFT
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:
TANHOUSE PROCESS:
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
FLOW DIAGRAM
TYPICAL PIGSKIN TANNERY
./SEE
! t:
3 °" „
SUM I SHm
| SOllDxtSU SNi.l.U)
i:uini< nn mi
Xsgj*bfe»hSB!te
t Itil'.MIM,
>^^^3^^S
H10ES »"B Lt»m«
PROCESS UlIt^tlLI
FIGURE 3
20
-------
DRAFT
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
degradation
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.
COLOR AND FATLIQUOR PROCESS:
1. Coloring - Skins to be colored are immersed in a dye solu-
tion in drums. Generally, synthetic dyes are used.
21
-------
DRAFT
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.
FINISHING PROCESS:
There are a number of operations which follow the coloring and
fatliquor process, including drying, coating, staking, and sand-
ing. These are principally dry processes, and the only liquid
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.
22
-------
DRAFT
TABLE 1
CLASSIFICATION SYSTEM
(31 11. abed)
Skin or
Hide Type
(a)
1. Cattle
2. Pig
3. Sheep
4. Deer
5.
o .
7.
0
3. Other
0. Various
Beamhouse
Ope rat ion
(b)
1 . Pulp Hair
2 . Save Ha i r
3. Hair Pre-
viously
Removed
A. Hair
Retained
5. Wool
Pullery
o. Hide Curing
7. Pulp & Save
8.
9. Other and
unknown
0.
Tann ing
Process
(c)
1 . Chrome
2. Vegetable
3. Alum
b. Previously
Tanned
5- Vegetable
and Chrome
6.
7.
G .
9- Other and
unknown
0. Hone
Color
F
1.
2.
3.
k.
5.
b.
7.
8.
9.
0.
Retan,
, Fat 1 iquor,
in i sh ing
(d)
Sides
Splits
Sides and
Spl its
Bends
Skins
Other
None
Several examples using the classification system for the more common
processing methods are:
3111.1111 - Cattlehide (including calfskin), hair is pulped,
chrome tanning process used, sides finished.
3111.1211 - Same as .1111 except hair is saved as a by-product.
3111.1221 - Same as .1211 except vegetable tanning process used,
3111.1110 - Same as .1111 except no retan, color, fatliquor, or
finishing is done (tanning to blue stage only).
3111.13*11 ~ Catllehide, hair previously removed and hide pre-
viously tanned prior to receipt of hides at a fin-
ishing facility (finishing operations only).
23
-------
DRAFT
I
1
i
STANDARD
INDUSTRIAL
CLASSIFICATIONS
OttUE I.IIH
PULP
SIDES
CH7LI I.IM9
PULP
CMPO-E
O.ES 0s t'l •*&*!*
||L ^
LL^ 1
t*'7LE J.I7M
P'JL- 1 SIVE
SUES
1_
CHILE !.'7C.I
PULP 1 SAY£
:ivis
PUL? i SAVE
.i^E7t3L£ i CHJCHi
C:-L= 0= UMKO.w
SREtP I.MS
PL1'.0
CATEGORIES
/fM^^fM^i^^^ff.
CATEGORY 1 I ..
PULP !•"!
CH.ROKE .'{
5*
/S^f-^'3f^MI'l^^-^i
CATEGORY 5 >,|
M*IR PREVIOUSLY RCHGVECI.--3
OR RETAINED ; j
riNISH .'/
St.'-
U771- 1.TI9
SEE?. I.S215
SIVE *
Ci77LE LAlJ.1
SAVE
FINISH
CHILE [.j??g
sm
VEGtliSLE
DIME? OR UHK»0>N
emu Lj__ijj
PULP
VFGEU3LE
FINISH
CHILE Lljjj
PULP
ALUK
FlfilSH
HSI^ PtfEVtOUSLT BEHOVED
PHEVlGUSLf U1XE9
SMNS
C.7TLE Lj.l'i
"E.'iCL'ilr TiitiO
Cl"-,- 1.13-43
;;;;-^iioijsiri^i_
^;;^L;>;;;;;->
SHEEP ).33u«.
«1IB PREVIOUSLT REMOVED
OIH(R 0iT'"??'?^v^^l31;^E^^v3
I CATEGORY 2 H
! ...^
CHROME Kj
FINISH l&y
^^5SS^S§^^^2§
CATEGORY 3 . i
V."
VEGETABLE ^l
FINISH HV
^
x^P^/ss^ss?1)^^*^^^
CATEGORY 6 :$
CHROffi IS
NONE j*
CATEGORY 4 ;?
— • "
PREVIOUSLY TAWED &
STANDARD
INDUSTRIAL
CLASSIFICATIONS
CHHE [."iVll
CHfiOMf.
SICES
CHILE [.1313
hAIS PREVIOUSLi1 KEHOVEO
SPIIIS
]
]
"AIR PREVIOUSLY fEHOVEO
VEGEIiBLE.
SIDES
PIG 1.J3I*
tlAlf PREVIOUS! T KIMOif D
CHPOMt
SI, IKS
SHEEP j.aais
Itilfi PRtVlOUSL' REMOVED
CHSOMt
SHIIP J.3325
HAIR P3EVIOUSU RlKOVtft
VEGETABLE.
SUKS
SHEtP |.33«
tUIS PREVIOUSLY fiE^OVED
VtGEUBLE 1 ChSCMP;
SUMS
SHEEP [.3390
CIHEft OP Uirpit-h
NONE
t'!EC? f.?"1!
CHSOHE .
SKIKS
fi*IS REUINED
•-EG1TABLE i CHBOHL
SMKS
CATItE [.IMP
PULf
CHROME
NOHE
CAI7LE |.I?10
SAVE
CHSOHt
NONE
CATEGORY 7 M
HIDE CURING Sj
NONE ?j)
PULP
NOKE
CATTLE ].i:oo
SAVE
NONE
NONE
CHILE 1.1600
KIDt CURING
^0•.E
hONE
1
CATEGORY SYSTEM
FIGURE 4
-------
DRAFT
SECTION V
WASTE CHARACTERIZATION
General
The first step in an appraisal of tannery liquid wastes is to define
and quantify applicable waste constituents. These data must then be
related to some unit of production. Information required to meet this
need has been obtained from the following sources:
1. Correspondence 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
fo11ows:
27
-------
DRAFT
BODr (Five-day Biochemical Oxygen Demand)
COD (Chemical Oxygen Demand)
Total Solids
Suspended Sol ids
Total Nitrogen
Chromi urn
Oil and Grease (Hexane Solubles)
Sulfide
Total Alkalinity
pH
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.
28
-------
DRAFT
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)
mg/1
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)
29
-------
DRAFT
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
Pickling
Tanning (including bleaching for some vegetable tanning)
Retanning, Coloring, and Fatliquoring
Finishing
The waste contributions are described below:
Wash and Soak - This is the first wet process performed on the raw
maTerial as it begins the tanning process. The purpose of this
operation is to remove salt, restore the moisture content of the
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.
30
-------
DRAFT
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.
31
-------
DRAFT
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
this.
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-
ning.
\
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
32
-------
DRAFT
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 high—above 37.7°C (100°F). The major treatment concern of
the retan, color, and fatliquor waste is removal of color and oil.
These two constituents can be kept to a minimum by utilizing chemical
concentrations that provide for the best uptake of the chemicals into
the hide. Because of the color in the 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
33
-------
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
-------
TABLE 3
WASTEWATER QUANT IT 1
Waste flou,
cu rn/kg of hide (gal/lb of hide)
Category Median
1 0 040
(4.8)
i o o:>u
(6 0)
3 0.044
(5.3)
4 0.017
(2.0)
5 0.050
(6.0)
6
7
Mean
0.053
(6.4)
O.Uoj
(7.6)
0.050
(6.0)
0.020
(2.4)
0.063
(7 6)
0.028
(3-4)
0.0006
(0.07)
Mode
0.029
(3.5)
u o|>u
(6.0)
0.021
(2.5)
0.017
(2.0)
0 082
(9.3)
._.
_ __
Range
o 007-0.156
(0.8-18.7)
u ooi-o ioy
(0 1-22 6)
0.007-0 106
(0.8-12.7)
0.003-0.033
(0.3-3-9)
0 006-0 204
(0.7-24 4)
0 014-0 056
(1.7-6.7)
0.0003-0.002
(0.03-0.20)
Data
Points
46
14
16
10
20
3
4
ES
Used Later Herein for
Economic Analysis ,
cu m/kg of hide (gal/lb of hide)
0.033
(4.0)
0.050
(6.0)
0.042
(5.0)
0.017
(2.0)
0.063
(7.5)
0.017
(2 0)
o 0003
(0.03)
35
-------
200
DRAFT
TANNERY PRODUCTION (1000 KG HIDC/MO)
GOO 800 1000 1200
moo
1600
1600
19
18
17
1C
15
• IM
13
12
o
= II
10
^^
c
5 8
i
6
5
"
3
2
, , 1 1 1 1 1 1 1 i 1 1 i ' ' ' r
3
-
•
-
•
©
©
e® .
©
©
©
© ©
©
© ©a
©
© 0 © ©
©
©
© ®
© ® ©
S © © ® ®
©"
I e 0 ©
©
0 500 1000 1500 2000 2500 3000 3500 40
0. 15
O.IU
0.13
0.12
0. 1 1
0.10'
0
0.09 "-
o
o
•^
0.08 =
ii
0
0.07 ^
UJ
H-
0.06 £
S
0.05
o.ou
0.03
0.02
0.01
0
)0
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
36
-------
DRAFT
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-
cantly.
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.
37
-------
DRAFT
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
(^jl/lb)
BODr
COO
Total Solids
Suspended Sol ids
Total Chromiun
Sul fides
Grease
Total Alkalinity
(as CaCOj)
Total Nitrogen
(as N)
pll
No Of
Data
Points
46
24
18
16
11
18
12
13
12
7
26
Catrgory No 1
Range
0 007-0 156
(0 8-18 7)
4 8-270
10 S-595
36-890
o /-Mi
0 1-19
0 1-46
0 1-70
0 5-300
3 1-44
1 0-13 0
Average
0 053
(6 4)
95
260
525
IUU
4 3
8 5
19
93
17
—
No of
Data
Points
14
9
7
7
S
7
4
5
'
6
8
Category No I
Range
0 001-0 189
(0 I-2' 6)
22-140
68-215
140-900
JU-iiU
0 3-12
0.1-2 8
0 7-105
62-85
3 6-22
4 0-12 6
!
A/erage
0 063
(7 6)
69
1'.0
480
Ili
4 9
0 8
43
72
13
-
Ko of
Data
Points
16
12
9
9
ID
5
7
7
6
5
12
Category tio '.
Range
0 007-0 106
(0 8-12 7)
7 4-130
2I.-69S
120-800
..-.,,»
0 2-0 6
0 1-4 2
0 1-160
4 1-135
0 9-23
2 0-1) 0
1
Average
0 OSO
(6 0)
67
250
345
.»
0 2
1 2
33
66
9 2
--
*C>cept pH. flow in cu m/kg (gal/lb)
38
-------
DKAfT
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
I'
39
-------
DRAFT
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.
MOCC
3000 -
2000 -
- 1500
1000 -
o
o
o
K-
o
o
z:
z:
100
o
o
o
o
O
0£
a.
10 20 30 40 50 60 70 80 90
RELATIVE CUMULATIVE FREQUENCY (%)
-------
DRAFT
SECTION VI
SELECTION OF POLLUTANT PARAMETERS
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 L°XiC 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 B°D 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 5°D 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! " P°tenLial °f tannery W8Ste' "articu'ar'y « a
-Most of the leather produced in the U. S. is tanned
tMer.fo- . l°X?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- ^ am°UntS ° °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> hydr°9en sulfide can be oxidized to sul-
t fs « canCKT?h r°W?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'
consS°I/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?
*'d
.(.
,
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?tr°9e"- 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-
^frable°tan f^l" ta"nerV.resul ts Principally from the chrome or
vegetable tan l.quor and var.ous dyes and paints used during coloring
-------
DRAFT
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
unit.
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 60°C (l*.0°F). Mixing of these high temperature
streams with other discharges usually results in an average effluent
-------
DRAFT
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.
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DRAFT
SECTION VI I
CONTROL AND TREATMENT TECHNOLOGY
General
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
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DRAFT
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
pretreatment.
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-
use.
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.
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DRAFT
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
costs.
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
(0.8-18.7)
2 Save Chrome 0.001-0.189
(0.1-22.6)
3 Save Vegetable 0.007-0.106
(0.8-12.7)
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.
50
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DRAFT
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
floats.
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.
51
-------
DRAFT
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
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DRAFT
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-
tially.
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.
53
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DRAFT
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.
i
Direct chemical oxidation with ammonium persulfate and ozone were
studied by Eye (8). Ammonium persulfate produced low removals.
Ozone was most effective; however, the expense of ozone generating
facilities and developing contact equipment negated further study
(8).
Studies by Chen (22) reveal that many metallic salts are effective
catalysts when compressed air at high temperatures is utilized.
Manganous sulfate proved to be the most effective catalyst in the
•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.
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DRAFT
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
surfaces.
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
55
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in
DRAFT
,„ 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
concentration.
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:
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DRAFT
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
57
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DRAFT
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):
58
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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
&edir«n[alion tanVs. 900 130 63-88 3SO 1^6 10-63 Prelrc«lnent of vcscuble (to)
rvchjnlcal iKSgc un llguort klcnlion
facilln«4 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)
59
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DRAFT
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):
60
-------
S>*te-*
Coif ill* Jon-SeCi^enia.ien
Plun Sedircrtatior
Coagjlat Ion, SrSircntatloi
Aeration, Coagulation.
Coagulation, Segmentation
Coagulation, Sedimentation
Coagulation. Sedirentatlon
Coagulation, Scdirrntatlon
Carbonatlon
Equalization. 2-sl*ge
Carbonatlon. Coagulation.
Sedirvntatlon
Carbonatlon. Coagulation.
Sedinentatlon
• Oxygen demand
•* Order-of-nagnitude value*
TABLE 6
CHEMICAL TREATMENT
Sus&erded tol ids B3D
— * ?s7T ng/l » " ^/1 rg/1 ',
Mun 1.5 SO 68 56 -- " 90r «djuttnent of 5" water
VCi
Alun 2.500 850 66 3.600 1.030 73 » Pile. »...<:, ».f ore-
j.tcrent of p* to 5 5
rero/al
lira 918 469 «9 1.001 ^76 &2 Continuous flow with line
concentrations of 1,490.
r,/l
Lire 1.360 197 75 I.6JO El] Ii9 fill ind «r«w -111 lira
coneeriralions of 1 .700
ng/l
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
(1.1}
(ID
Hi)
(»D
(37)
(32)
(19)
(19)
61
-------
DRAFT
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-<;
tested.
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.
62
-------
DRAFT
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):
63
-------
DRAFT
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
6k
-------
DRAFT
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
Screening
Equali zation
Primary settling
65
-------
DRAFT
Sludge
Col lection
Thicken i ng
Dewateri ng
Landfi11
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
treatment.
EFFLUEBT TO KUNICIPIL
> SEWER SrSTEH
StUDGE
THICKENING
PRETRE4TMENT
FILTER
FIGURE 5
66
-------
DRAFT
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.
67
-------
DRAFT
TABLE 7
COMBINED MUNICIPAL-TANNERY TREATMENT SYSTEMS
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 « Sk«bcis«». 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. V«t.ii iUr«'ici »»» (17)
»K«' S'2 It -1M IS >Wl 90 kugri. 1S<
»»r.lt ,lunge (I 7) 0-11'IS Ir
JKClllO" I«M '""" "'
,,,.,jt,o. tf
tiQufa t(u4fc
JEO (00 i S.rrl,. Mini tm,l, ri In |k7)
DnlA'la. 1965 >-l|li ctncltv
CtP«d* Q* IJ CH cv r/d*f
U JSJ • in II >»
lotion, rou$nlng IB t] *9" *•'* wl*4«t InltnitoK of
*lwdae' mecandarv color tcTOvil
68
-------
DRAFT
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.
70
-------
DRAFT
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):
71
-------
TABLE 8
TRICKLING FILTER SYSTEMS
BOD;
Carhonation, primary
sedimentation,
trickling filter,
final sedimentation
Primary coagulation,
sedimentation,
trickling fi Her,
Dilution, primary sedi-
mentation, trickling
Fi Iter, final sedi-
mentation
ililution, primary sedi-
mentation, trickling
filter, final sedi-
mentation
900
Eff.Removal
mg/i
85-95
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-
tion
72
-------
DRAFT
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
color.
Trickling filters have limited application in the treatment of high
strength tannery wastes. System upsets are common due to organic
overload and climatic conditions. Existing filters may be 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.
73
-------
DRAFT
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 5°C (4l°F) to 8°C (46°F) during
winter operation. Sulfides were completely oxidized. The kjeldahl
nitrogen removal (75 percent) indicates some nitrification occurred
in the lagoon with hydraulic detention times of 16 to 35 days. The
"BOD removal factor" 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
1ot«l Nitro^n
r Ibw Inf Iff *f T*xal llT ['f Prn»vjl
Screening, plali 7>3 I.800 100 3i
lrdlEcr.tc.lo-> (0 19)
l*gw>nt .rrtt.d
lagoon*
I.3.-9 1 l&O 8>S 61 l.SOO 71S
Kdlneniatlon
(•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)
Luri,
VlrgmU
Chron* labtc tcnnlnq
Cunnitsn Cell It,
Clr.rd.
•cnns/Ivanl*
wailr i f*~i
prior to iera-
tion I. rtrlon
dvtrnclon d-«
20 (!«)t
75
-------
DRAFT
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
zone.
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
76
-------
TABLE 10
AEROBIC-ANAEROBIC SYSTEMS
&biprnd«d lolitfi
Inf Iff Removal 7«nncr> rToct»» rcnjrki
Scr.er.lrg. plain 1 IS) I.)00 603•
tfdlnenttllon (D 3d
terabit-anaerobic
(•goon, f.nal
eh lor InjtI on
3000 165* 9S
Ttnnlrj CO . Itwvp Site, drnitri Mention
f«rth FoBfMl, chrome l» not Indicated
Venom
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 «vcr«gr
77
-------
DRAFT
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 (M°F) to 2/i'C ?76°F) for this operational
phase. Suspended solids in the effluent were high, indicating the
need for more effective final clarification. Sulfides were completely
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 ab°v* 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
78
-------
DRAFT
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
1°C (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
lagoon.
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
79
-------
DRAFT
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-
tion.
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
80
-------
TABLE 11
ACTIVATED SLUDGE SYSTEMS
Suipc-atd Solid*
*»«••
<«gd)
nnTT F^
!i"^J
Scittnlng pUIr. J.7BJ I.J&t 315
iidlifirntatlon. (1)
activated iludje
[*rlo*> iludv
dr«a rrlng with
prcilbrt filter*
land ditpotal
76 1 966 3*5
S B TMI Cattle
Tanning Co . Pulp
•ctf Vlng chrcM
Mrnetota
Lo« rcravali tln»
Screening, plain
waimentatton
•ctI valid iludge
6) I>J7 96
(0 Olt)
91 1.135 »3
17 Caltf-ell
Pnnaiy and letona-
Cattle.
PU'P co^- ary cl«'i'86 160
)7 no»nch
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-
cat'on
frlnr CatUa
Tanning Co
Berwick.
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/e«y
81
-------
DRAFT
detention time was 1.6 days in the aeration basin.
efficiencies were observed during operations:
The following
Influent Effluent Removal
Suspended Sol ids
COD
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
mg/1
1,437
3,135
4,016
7.9
490
328
162
0.1
0.1
516
mg/l
96
223
0
322
175
147
34*
0.4
141
93
93
88
100
34
47
9
73
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
82
-------
DRAFT
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
83
-------
DRAFT
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):
Presettled
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
-------
DRAFT
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,
85
-------
DRAFT
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 **££**s»4-:«f*% '• r* /»r*l^\»- vnmr\\i a 1 \/
uiivaicu i»a 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
86
-------
DRAFT
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
Screening
Equal izat ion
Primary Settl ing
Aerat ion
Secondary Settling
Fi 1 1 rat ion
Chlor inat ion
87
-------
DRAFT
Sludge
Col 1ect ion
Thickening
Dewatering
Landfill
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
88
-------
DRAFT
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.
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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
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DRAFT
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.
i
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).
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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-
affected.
FLOW DIAGRAM
MAJOR'REKOVAL OF ALL FORMS OF NITROGEN
ACTIVATED SLUDGE-NITRIFICATION-DENITRIFICATION
FIGURE 7
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DRAFT
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:
Nitrification
Temperature:
MLVSS:
pH:
Loading Factor:
Loading:
Denitrification
Temperature:
MLVSS:
pH:
Loading Factor:
10°C (50°F)
5,000 mg/1
kg/day/1 ,000 cu m
(27 Ib NH3-N/day/l,000 cu ft)
65 percent of raw waste
10°C
3,000 mg/1
7-5
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
93
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DRAFT
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
following:
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
reliable.
Evaporation - This process is perhaps the oldest method for removal
of dissolved solids. In principal, a saline solution is evaporated
with heat energy. The vapor produced is mineral free and condensed
for disposal or reuse. A strong brine solution alone or with some
salt crystallization remains for disposal.
Solar energy may provide the required heat of evaporation when wastes
are retained in large lagoons. However, climatic conditions coupled
with relatively high continuous flows and the need for impervious soil
or sealant imposes severe restrictions on the geographic location
for such lagoons.
Multiple effect evaporators have been used in industry for many ap-
plications. A saline solution is heated to the boiling point, normally
at an elevated pressure. The steam produced is directed to cooling in
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DRAFT
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.
95
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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
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DRAFT
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
" ACTIVATED SLUDGE-NITRIFICATION-DENITRinCATION-REVERSE OSMOSIS
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
(6*0.
• 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:
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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
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DRAFT
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
brines.
In the tanning industry, a substitute for salt in the hide curing
process and increased reuse of process chemicals would be a major
step in eliminating this problem.
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
99
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DRAFT
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.
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SECTION VIII
COST, ENERGY, AND NON-WATER QUALITY ASPECTS
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
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TABLE 12
ESTIMATED WASTE TREATMENT COSTS
FOR TYPICAL SIZE PLANTS^1'
(August, 1971 price levels)
Alternatives
Category Flow _A_ B
cu m/day
(mgd)
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.
102
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DRAFT
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.
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DRAFT
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
pounds)
Sulfuric Acid - $36.40 per metric ton ($33.00 per ton)
Ferric Sulfate - $46.30 per metric ton ($42.00 per ton)
Sodium Hydroxide (50%) - $8.50 per 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.
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DRAFT
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 C«7 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.
105
-------
DRAFT
• *$•£
tt
Jc
S
* 0
" t
8 6
o
3 *
£
t 2
0
o O.I-
- ....
1 «•••
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~ 0.06-
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0.02-
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0 o. c-:
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"ISIE THEIIMEUT COSTS (1/1.8
irrLUHT OH „»
IG/IOOO KG H
00 •
10 -
EO •
« -
I !°-
m
| 10-
2. ' •
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£ c-i -
O.OB -
0.06-
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HIDE)
K
0.02-f?
•sf
'•' \4
%A
'•/.*
'f/h
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• ' \ F^T
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f 2-
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u. i^u u. )6U 0.200
V
uxf
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P:
O.OW 0.060 O.OtO
USTE TIElTMEtT COSTS (I/LI HIDE)
™ '-"O O.OSO O.OJO
«SIE T««niE«T COSIS (I/I. HIDE)
MSTE TBEJTHtllT COSTS (I/IC HIDE)
o o.ow o.oeo 0.120 « «"
;
5
z 1 .0-
_ 0.8-
c O.H-
S 0.2-
3
§0.1-
oil-
's 0.06-
§ O.Oi)
1
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_, 0.02-
S o.oi.
S o.ooj-
t 0. 006-
0.00«-
0.001-
0.001-
v. i /u o. 1 60 0.200
I
I
'% V
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1
;
-
r
V
B
0 0.020 0.040 O.HO 0.0*10 0.
MSTE 1IE1THEIT COSTS (t/LI HIDE)
106
-------
DRAFT
?n» ° "•?"
IK
H
10
20
3 .0 -
2 ,.
1
S 2-
^ 1.0 -
: o.i •
2 o.e.
0.2 -
0 I
_V
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•'
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0 0.020
rt rgEi-
o.cac
i
•-
•'*•:
'a-
/
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#.
o.;;o
i/
^V
o.o»o o.oeo
WASTE TREATMENT COSTS (l/LB
1 '(0 O.«0 0 O.OlO
r
i ywy -
100.
IOC-
^ »00-
1 JM
— '00-
s "-
* «0-
5
i i-
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'"" 4'
3
2-
r~y
\
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6 MO 0 10 C -iC 0.200
rf-T
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1 1
0.0*0 0.060 O.OSO 0.
00
•ASTE TDEATHUT COSTS (l/ll «IOE)
• ~-T
O.CfO 0. 00
NiDE)
«AST£ T»EATKE«T COSTS (1/IG KIDfl
WASTE TRfiTMEKT COSTS (I/KG H
,0 "•; ?
1
1 _
"•
2-
5 1.0-
i 0.1-
j o.e -
o.»-
£ °-!"
e "•''
g o.ct-
5 0.06-
wl O.OH-
5
*" 0.02-
jj
S <>.<"•
0.001-
O.OD6-
0.0/
_/ /
-'i
'j
%
y
^;
// '^;
'1 1
•X'
1 I_
O.C«> O.OiO 0.080 0.100
•ASTf THEATHEUT COSTS (1/11 Bid!)
LEGF«D
ALTERKATlVE A •
AL1ESMA1 It | .
ALTERNATIVE D -
ALTERNATIVE E •
O.CSO 0.100
NO TREATMENT
PBET5EATVENT
ACTIVATED SUJOG=
ACTIVATED SLliOOE AND
N ! IS : M CAT 1 0»-[>E« 1 IP IM CATION
ACTIVATED SLU3GE AND
KITKIFICATION-DENITIMFICATION
ADD REVERSE OSMOSIS-EVAPORATION
KUTE ItEintIT COST] (l/ll HIDi)
CATEGORY NO. 1
WASTE TREATMENT COST SENSITIVITY
(August, 1971 Price Levels)
FIGURE 9
107
-------
DRAFT
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.
108
-------
DRAFT
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
Technology
The energy requirements (electric power and fuel) for tanneries
vary considerably based upon reported data. This variation is due
to the following factors:
1. Type of hide tanned.
2. Type and extent of beamhouse, tan yard, and finishing
operations.
109
-------
DRAFT
CATEGORY NO.
PRESENT PRODUCT PRICE
>?SQ H HIDE
4.00 6.00
1 1
NC5E1SE
•r/TRL»rMENT
e.oo 10.00
0.25
- 7.1S
-1.21
0.50 0.75
J/SQ FT HIDE
CATEGORY NO. 2
PRESENT PRODUCT
»/S? H HIDE
".00 6.00
"ICE -I • HC»ilS
K/TREAT
E
KENT
6.00 10.00
15.7'
-8.2'
-d.T.
-3.71.
0-25 0.50 0.75 I.CO
CATEGORY NO. 5
PRESENT PRODUCT PRICE—4—INCREASE
N/TREATMEKT
S/ SO H HIDE
2.00 1.00 6.BO 8.00
1 r^ 1 1—
-12.7*
-7.21
-6.5?,
-3.35
0.60 0.75
Q FT HIDE
1.00
CATEGORY NO. 6
PRESENT PRODUCT PR I
CE-4— INCREASE
K/TRE»TMtNT
J/S9 H HIDE
1.00 6.00
• 24.6t
16.OS
0.25
0.50
J.'SQ FT HIDE
10.00
—-)
0.75 1.00
110
-------
DRAFT
CATEGORY NO. 3
• T P803UCT PHlCt .1 . IHCtUS
• /I8E»
O.iO
tin, mot
l.OO
2.7"
O.iO
J/LB HIDE
CATEGORY NO. 7
PBES'.HT
PSCPUCT
PRICE
INCREASE W/TREA1HENT
t/KG HIDE
l.OO
-I"
O.JO
I/IS HIDE
2.00
CATEGORY NO.
PRCSENT PBCDUC
JCT PRlCE-4—'«C»EiSE
•/TREATMENT
J/SQ H BIDE
U.OO 6-00
8.00 10.00
-3.1'
0.25
0.50
s.'sg FT HID:
1.00
LEGEND
ALTERNATIVE A - NO TREATMENT
ALTERNATIVE B - PRETREATMENT
ALTERNATIVE C - ACTIVATED SLUDGE
ALTERNATIVE 0 - ACTIVATED SLUDGE AND
NITRIFICATION-OENITRIFICATION
ALTERNATIVE E - ACTIVATED SLUDGE AND
NITRIFICATION-DENAZIFICATION
AND REVERSE OSMOSIS-EVAPORATION
•ALTERNATIVE C - EVAPORATION
IMPACT OF WASTE TREATMENT
ON
FINISHED PRODUCT PRICE
(August,1971 Price Levels)
FIGURE 10
111
-------
DRAFT
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
zero.
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
filters.
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
Technology
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.
112
-------
DRAFT
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.
113
-------
DRAFT
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.
-------
DRAFT
SECTION IX
BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY AVAILABLE - '
GUIDELINES AND LIMITATIONS
General
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,
1977.
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.
H5
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON INFORMATION
IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED UPON COMMENTS RECEIVED
AND FURTHER INTERNAL REVIEW BY EPA.
-------
DRAFT
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.
TABLE 13
LEVEL 1 EFFLUENT LIMITATIONS GUIDELINES - JULY 1, 1977
(COMPLETE TREATMENT)
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
times.
Except pH and fecal
2 3 fr
2.0 1.7 0.7
-------
DRAFT
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
LEVEL I EFFLUENT LIMITATIONS GUIDELINES - JULY 1, 1977
(PRETREATMENT)
Parameter
(1)
Category , .
kg/1,000 kg hide Mb/1.000 Ib hide)* *
I
Total Chromium
G i i diiu ui
Sulfide
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
(1)
(2)
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
treatment).
NOTICE:
IN THIS
AND FURTHER
THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON INFORMATION
REPORT AND ARE SUBJECT TO CHANGE BASED UPON COMMENTS RECEIVED
INTERNAL REVIEW BY EPA.
117
-------
DRAFT
Pre treatment - Categories 1 to 6
1. Water conservation to reduce the size of treatment
units.
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
system.
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
applicable).
3. Collection of beamhouse wastes containing sulfide;
oxidation of sulfides using a catalyst such as manganous
sulfate.
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.
118
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON INFORMATION
IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED UPON COMMENTS RECEIVED
AND FURTHER INTERNAL REVIEW BY EPA.
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DRAFT
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
faci1ities.
19
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON INFORMATION
IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED UPON COMMENTS RECEIVED
AND FURTHER INTERNAL REVIEW BY EPA.
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DRAFT
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.
120
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON INFORMATION
IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED UPON COMMENTS RECEIVED
AND FURTHER INTERNAL REVIEW BY EPA.
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DRAFT
SECTION X
BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE
GUIDELINES AND LIMITATIONS
General
SSrsSS
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
technology:
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
r
-
economic and engineering feasibility. Level II may
ized by some technical risks with respect to performance and
121
NOTICE- THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON INFORMATION
TTTHTS REPORT MD ARE SUBJECT TO CHANGE BASED UPON COMMENTS RECE.VED
AND FURTHER INTERNAL REVIEW BY EPA.
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DRAFT
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 thr°U9h thC ^""tion of best available
Level M9yff,e,5.SU™"iarlZeS f°reach 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 sho«n on Figure 7 in Section VII ."'
inlLuon !x? " 6re ^ "^ 3S f°r Uvel ' and
Complete Treatment - Categories 1 to 6
1. Water conservation to reduce the size of treatment
units.
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.
122
TFTr^ P™P' ± InE^IvL!^0OHcMENDATIONS BASED UPON .NFORMATION
EPA.
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TABLE 15
LEVEL II EFFLUENT LIMITATIONS GUIDELINES - JULY 1, 1983
(COMPLETE TREATMENT)
Parameters
(1)
BOD,.
COD
Total Chromium
Oi I and Grease
Sulfide
Suspended Sol ids
Total Kjcldahl
Nitrogen(3)
Ammonia
Ni trogen*3)
Nitrate
Ni trogen'3)
pH, un i ts
Color, %
RemovalW
Fecal col i form/
100 ml
1
Category , »
kg/1.000 kg hide (1b/l,000 Ib hide)v '
3
0.67
91
0.03
0.33
0.003
0.67
0.17
1.0
49
0.05
0.5
0.005
1.0
0.25
0.8
88
0.04
0.42
O.OO'i
0.83
0.21
0.33
9.8
0.02
0.2
0.002
0.33
0.08
1.3
60
0.06
0.62
0.006
1.3
0.31
0.33
82
0.02
0.20
0.002
0.33
0.08
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
85
200
85
200
85
200
85
200
85
200
85
200
(I)
0
0
0
0
0
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
times.
Except pH, color, and fecal coliforms.
Limitations for nitrogen forms do not apply when the water temperature
is below 10° C (50° F).
(4)
No reasonable data is currently available upon which absolute limits
may be established. Treatment can provide this percent removal,
however.
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON INFORMATION
IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED UPON COMMENTS RECEIVE!-
AND FURTHER INTERNAL REVIEW BY EPA.
123
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DRAFT
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
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON INFORMATION
IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED UPON COMMENTS RECEIVED
AND FURTHER INTERNAL REVIEW BY EPA.
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DRAFT
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.
125
NOTICE- THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON INFORMATION
IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED UPON COMMENTS RECEIVED
AND FURTHER INTERNAL REVIEW BY EPA.
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DRAFT
SECTION XI
NEW SOURCE PERFORMANCE STANDARDS
General
The standards of performance for new sources are to reflect the
greatest degree of effluent reduction achievable through the 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.
127
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON INFORMATION
IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED UPON COMMENTS RECEIVED
AND FURTHER INTERNAL REVIEW BY EPA.
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DRAFT
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,
128
NOTICE: THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON INFORMATION
IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED UPON COMMENTS RECEIVED
AND FURTHER INTERNAL REVIEW BY EPA.
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DRAFT
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-
1ities.
129
NOTICE; THESE ARE TENTATIVE RECOMMENDATIONS BASED UPON INFORMATION
IN THIS REPORT AND ARE SUBJECT TO CHANGE BASED UPON COMMENTS RECEIVED
AND FURTHER INTERNAL REVIEW BY EPA.
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DRAFT
SECTION XI I
ACKNOWLEDGMENTS
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
131
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DRAFT
SECTION XI I I
REFERENCES
(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
1973-
(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.
133
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DRAFT
(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.
1967-
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DRAFT
(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,
1972.
(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
finality
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).
135
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DRAFT
(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.
136
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DRAFT
(i»8) Wims, F. J., "Treatment of Chrome-Tanning Wastes for Accept-
ancc'by an Activated Sludge Plant," Purdue Industrial Waste
Conference Proceedings. 19&3-
(1»9) 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.
137
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DRAFT
(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.
138
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SECTION XIV
GLOSSARY
Acidity
A measure of the ability of the waste to provide hydrogen ions when
treated with alkaline materials. Generally expressed in mg/I as
CaC03.
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.
Aerobic
A biological process in which oxygen is used for microorganism respi-
ration needs. Especially relating to the degradation process of
waste matter in the presence of dissolved oxygen.
Anaerobic
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.
Alkalinity
A measure of the ability of the waste to provide hydroxyl ion to
react with acidic materials. Generally expressed in mg/1 as CaCO-j.
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Back
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
hide.
Beamhoiise
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.
Bend
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
Act.*
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
1972.
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DRAFT
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 ir«n
A physical means for the removal of suspended particles in a liquid
by gravity sedimentation (settling).
Coagulant
A substance which forms a precipitate or floe when added to water.
Suspended solids adhere to the large surface area of the floe, thus
increasing their weight and expediting sedimentation.
Collagen
The fibrous protein material within the hide which provides the bulk
of the volume of the finished leather and its rigidity.
Colloids
Microscopic suspended particles which do not settle in a standing
liquid and can only be removed by coagulation or biological action.
Color
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
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DRAFT
Coloring
A process step in the tannery whereby the color of the tanned hide
is changed to that of the desired marketable product by dyeing or
painting.
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.
Deliming
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.
Derma
That part of the hide which is between the flesh and the epidermis.
Desalinization
The process of removing dissolved salts from water.
Detent ion (Retention)
The dwell time of wastewater in a treatment unit.
Dewatering
The process of removing of a large" part of the v/ater content of
siudges.
PJL
Dissolved oxygen. Measured in mg/1.
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DRAFT
Drum
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.
Enzyme
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 .
Epidermis
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 .
Float
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.
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DRAFT
Floe
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
sample.
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.
Grain
The epidermal side of the tanned hide. The grain side is the smooth
side of the hide where the hair was located prior to removal.
Grease
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.
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DRAFT
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.
Membrane
A semi-permeable barrier used in reverse osmosis and electrodialysis
which allows water molecules and certain dissolved molecules^to pass
through it while impeding the passage of other dissolved solids.
Nitrogen, Ammonia
A measure of the amount of nitrogen which is combined as ammonia in
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
Nutrient
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.
Outfall
The final outlet conduit or channel where wastewater or other drain-
age is discharged into an ocean, lake, or river.
Pack
Layers of salted hides formed at the slaughter house or hide curing
firm (usually approximately 20 to ^0 feet in area and 5 to 6 feet
high).
Paddle Vat (Paddle)
A vat with a semi-submerged rotating paddle arrangement used for the
mixing of water and chemicals with the hide.
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DRAFT
EH.
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.
Pasting
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.
Pickle
The process that follows bating whereby the hide is immersed In a
brine and acid solution to bring the skin or hides to an acid con-
dition; prevents precipitation of chromium salts on the hide.
Plating
The finishing operation where the skin or hide is "pressed" in order
to make it smoother.
Polymer
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.
Processor
A mixing apparatus resembling a concrete mixer which is used in some
tanneries.
Pullery
A plant where sheepskin is processed by removing the wool and then
pickling before shipment to a tannery.
Retan
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.
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DRAFT
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.
Scouring
A process where shearlings are washed.
Scudding
An operation following the major unhairing step where the last of
the hair is removed from the hide.
Sedimentation
Clarification (settling).
Side
A side represents halt a hide which has been cut along the spine.
Sharpeners
Chemicals used in addition to lime to assist in the unhairing pro-
cess (such as sodium sulfide and sodium sulfhydrate).
Shearling
A lamb or sheepskin tanned with the hair retained.
Shoulder
That part of the hide which represents the shoulder of the animal.
Sk i v i ng
The thin layer shaved or cut off the surface of finished leather,
principally sheepskin.
Sludge
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.
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DRAFT
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.
Staking
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.
Sulfide
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.
Tacking
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.
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DRAFT
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.
Wheel
Drum.
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