United States Off ice of EPA 130/6-80-002
Environmental Protection Environmental Review August 1980
Agency Washington. DC 20460
«>EPA Environmental
Impact Guidelines
NOV?
For New Source
Leather Tanning and
Finishing Industries
I
EJBD
ARCHIVE
EPA
130-
6-
80-
002
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This document Is available to the public through the National
Technical Information Service, Springfield, Virginia 22161.
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EJBD
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ENVIRONMENTAL IMPACT GUIDELINES
For New Source
Leather Tanning and Finishing Industries
Repository Material
Permanent Collection
Prepared by
WAPORA, Inc.
6900 Wisconsin Avenue
Washington, B.C. 20015
r
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ABSTRACT
This guideline document has been prepared to augment the information
previously released by the Office of Environmental Review entitled
Environmental Impact Assessment Guidelines for Selected New Source Industries.
Its purpose is to provide guidance for the preparation and/or review of
environmental documents (Environmental Information Document or Environmental
Impact Statement) which EPA may require under the authority of the National
Environmental Policy Act (NEPA) as part of the new source NPDES permit
application review process.
This document has been prepared in seven sections, organized in a manner
to facilitate analysis of the various facets of the environmental review. The
initial section includes a broad overview of the industry intended to familiar-
ize the audience with the processes, trends, impacts and applicable pollution
regulations commonly encountered in the leather tanning and finishing industry.
Succeeding sections provide a comprehensive identification and analysis of
potential environmental impacts, pollution control technologies available
to meet federal standards, and siting and process alternatives. The document
concludes with three sections: a listing of federal regulations (other
than pollution control) which may apply to the new source applicant, a glossary
tjf terms pertaining to the leather tanning and finishing industry, and a
comprehensive listing of references for further reading.
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Preface
This document is one of a series of industry-specific Environmental
Impact Assessment Guidelines being developed by the Office of Environmental
Review for use in EPA's Environmental Impact Statement preparation program
on New Source NPDES permits. It is to be used in conjunction with
Environmental Impact Assessment Guidelines for Selected New Source Indus-
tries, an OER publication that includes a description of impacts common to
most industrial new sources.
The requirement for federal agencies to assess the environmental
impacts of their proposed actions is included in Section 102 of the
National Environmental Policy Act of 1969 (NEPA), as amended. The
stipulation that EPA's issuance of a New Source NPDES permit as an
action subject to NEPA is in Section 511(c)(l) of the Clean Water Act
of 1977. EPA's regulations for preparation of Environmental Impact
Statements are in Part 6 of Title 40 of the Code of Federal Regulations;
New Source requirements are in Subpart F of that Part.
ii
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TABLE OF CONTENTS
Page
TABLE OF CONTENTS , ill
List of Figures vii
List of Tables viii
INTRODUCTION 1
1.0 OVERVIEW OF THE INDUSTRY 3
1.1 SUBCATEGORIZATION 7
1.1.1 Hair Pulp /Chrome Tan/Retan-Wet Finish 8
(Subcategory 1)
1.1.2 Hair Save/Chrome Tan/Retan-Wet Finish 8
(Subcategory 2)
1.1.3 Hair Save /Non-Chrome Tan/Retan-Wet Finish 8
(Subcategory 3)
1.1.4 Retan-Wet Finish (Subcategory 4) 8
1.1.5 No Beamhouse (Subcategory 5) 8
1.1.6 Through-the-Blue (Subcategory 6) 8
1.1.7 Shearling (Subcategory 7) 8
1.2 PROCESSES . 9
1.2.1 Major Processes of the Leather Tanning and .... 9
Finishing Industry
1.2.1.1 Beamhouse Operations 9
1.2.1.2 Tanhouse Operations 13
1.2.1.3 Retanning, Coloring, and Fatliquoring . . 17
1.2.1.4 Finishing 18
1.2.2 Process Variations for Raw Materials 20
1.2.2.1 Cattle Hide Tannery 20
1.2.2.2 Sheepskin Tannery 22
1.2.2.3 Pigskin Tannery 25
1.2.3 Auxiliary Support Systems,
28
111
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TABLE OF CONTENTS (Continued)
Page
1.3 SIGNIFICANT ENVIRONMENTAL ISSUES 28
1.3.1 Location 28
1.3.2 Raw Materials 29
1.3.3 Processes and Pollutants 29
1.3.4 Pollution Control 31
1.4 INDUSTRY TRENDS 32
1.4.1 Market and Demands 32
1.4.2 Location 33
1.4.3 Raw Materials 34
1.4.4 Processes 36
1.4.5 Pollution Control 37
1.4.5.1 In-Plant Pollution Control, 37
1.4.5.2 End-of-Pipe Pollution Control 40
1.5 POLLUTION CONTROL REGULATIONS 42
1.5.1 Air Pollution 42
1.5.2 Water Pollution 47
1.5.2.1 Best Available Technology (BAT) 51
1.5.2.2 New Source Performance Standards (NSPS) . 52
1.5.2.3 Regulated Pollutants 53
1.5.2.4 Pretreatment Standards for New
Sources (PSNS) 53
1.5.2.5 Best Conventional Pollutant Control
Technology (BCT) 54
1.5.3 Solid Wastes 55
2.0 IMPACT IDENTIFICATION 58
2.1 AIR 58
iv
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TABLE OF CONTENTS (Continued)
Page
2.2 WATER 58
2.2.1 Wastewater Generation and Characteristics 61
2.2.2 Priority Pollutant Generation in Wastewater Streams 65
2.3 SOLID WASTE 68
2.4 OTHER IMPACTS 72
2.4.1 Aesthetics 72
2.4.2 Noise 73
2.4.3 Energy Supply 7^
2.4.3.1 Energy Consumption and Conservation ... 75
2.4.3.2 Cogeneration 76
2.4.4 Socioeconomics 76
2.4.5 Raw Materials Shipment and Handling 79
2.4.6 Site Preparation and Construction 80
2.4.7 Effects on Municipal Treatment Systems . 82
2.5 MODELING OF IMPACTS . 83
3.0 POLLUTION CONTROL 86
3.1 AIR - STANDARDS OF PERFORMANCE TECHNOLOGY 86
3.1.1 Boiler Equipment 86
3.1.2 Buffing Dust Control 86
3.1.3 Hydrogen Sulfide Control , 87
3.1.4 Ammonia ' ' 87
3.1.5 Odor 88
3.2 WATER - STANDARDS OF PERFORMANCE TECHNOLOGY 88
3.2.1 In-Plant Controls 88
3.2.2 End-of-Plant Controls 97
3.2.2.1 Preliminary Treatment .' 98
3.2.2.2 Primary Treatment (Physycal) Operations . 100
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TABLE OF CONTENTS (Continued)
3.2.2.3 Secondary (Biological) Treatment 100
3.2.2.4 Advanced Physical Chemical Processess. . . 103
3.2.3 Toxic Pollutants. 112
3.3 SOLID WASTE - STANDARDS OF PERFORMANCE TECHNOLOGY 113
3.3.1 Reduction of Hazardous Waste Components 114
3.3.2 Solid Waste Utilization 114
3.3.3 Solid Waste Treatment U5
3.3.4 Solid Waste Disposal 116
4.0 EVALUATION OF AVAILABLE ALTERNATIVES 118
4.1 SITE ALTERNATIVES 118
4.2 ALTERNATIVE PROCESSES AND DESIGNS 121
4.2,1 Process Alternatives 122
4.2.2 Design Alternatives 123
4.3 NO-BUILD ALTERNATIVE 123
5.0 REGULATIONS OTHER THAN POLLUTION CONTROL 124
6.0 GLOSSARY 129
7.0 REFERENCES , . . . 146
7.1 REFERENCE LISTING BY TOPIC
7.2 ALPHABETICAL REFERENCE LISTING
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LIST OF FIGURES
Page
Figure
1. Geographical distribution of U.S. tanneries
2. General process flowsheet for leather tanning and finishing
industry 10
3. Flow diagram for a typical cattlehide tannery 21
4. Flow diagram for a typical sheepskin tannery 23
5. Flow diagram for a typical pigskin tannery 26
6. Trends in cost and availability of cattlehides for the U.S. market,
1969-1978 35
7. Technology schematic for in-plant control and preliminary treatment
for the hair pulp/chrome tan/retan-wet finish and hair save/chrome
tan/retan-wet finish subcategories 106
8. Technology schematic for in-plant control and preliminary treatment
for the hair save non-chrome tan/retan-wet finish subcategory . 107
9. Technology schematic for in-plant control for the retan-wet finish
subcategory 108
10. Technology schematic for in-plant control for the no beamhouse and
shearling subcategories 109
11. Technology schematic for in-plant control and preliminary treatment
for the through-the-blue subcategory 110
12. Technology schematic for end-of-pipe wastewater treatment Ill
vii
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LIST OF TABLES
Table Page
1, In-plant process changes indicated on questionaire from total
of 46 leather tanneries 38
2. Applicable Federal ambient air quality standards 43
3. PSD increments: maximum allowable increase by class 45
4. Proposed new source performance standards (NSPS) and' pretreatment
standards for new sources (PSNS) for the seven subcategories of
the leather tanning and finishing industry 49
5. Emissions from the finishing operation of various subcategories
of the leather tanning and finishing industry 59
6. Raw waste loads by subcategory 66
7. Solid waste generation estimates for the leather tanning industry
by effluent guidelines subcategory. . 69
8. "Typical" tannery wastewater treatment plant sludge
characteristics 71
9. Typical permits, licenses, certifications, and approvals required
from Federal, state, regional, and local authorities for construc-
tion and operation of a typical new source tanning facility . . . 126
viii
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INTRODUCTION
The Clean Water Act requires that USEPA establish standards of perform-
ance for categories of new source industrial wastewater dischargers. Before
the discharge of any pollutant to the navigable waters of the United States
from a. new source in an industrial category for which performance standards
have been proposed, a new source National Pollutant Discharge Elimination
System (NPDES) permit must be obtained from either USEPA or the state (which-
ever is the administering authority for the state in which the discharge is
proposed). The Clean Water Act also requires that the issuance of a permit by
USEPA for a new source discharge be subject to the National Environmental
Policy Act (NEPA) . The procedure established by USEPA regulations (40 CFR 6
Subpart F) for applying NEPA to the issuance of new source NPDES permits may
require preparation of an Environmental Impact Document (EID) by the permit
applicant. Each EID is submitted to USEPA and reviewed to determine if there
are potentially significant effects on the quality of the human environment
resulting from construction and operation of the new source. If there are,
USEPA prepares an Environmental Impact Statement (EIS) on the action of issuing
the permit.
The purpose of these guidelines is to provide industry-specific guidance
to USEPA personnel responsible for determining the scope and content of EID's
and for reviewing them after submission to USEPA. It is to serve as supple-
mentary information to USEPA's previously published document, Environmental
Impact Assessment Guidelines for Selected New Source Industries, which in-
cludes the general format for an EID and those impact assessment considera-
tions common to all or most industries. Both that document and these guide-
lines should be used for development of an EID for a new source leather tannery.
These guidelines provide the reader with an indication of the nature of
the potential impacts on the environment and the surrounding region from
construction and operation of leather tanneries. In this capacity, the volume
is intended to assist USEPA personnel in the identification of these impact
areas that should be addressed in an EID. In addition, the guidelines present
(in Chapter I) a description of the industry, its principal processes, environ-
mental problems, and recent trends in location, raw materials, processes,
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pollution control, and the demand for industry output. This "Overview of the
Industry" is included to familiarize USEPA staff with existing conditions in
the industry.
One of the principal sources used in preparing these guidelines is the
Development Document for the Leather Tanning Industry prepared by USEPA (1979).
The Development Document represents an evaluation of the industry with its
purpose to identify appropriate control levels for water-borne pollutants as a
basis for establishing effluent limitations. The Leather Tanning Development
Document was authorized by the Clean Water Act Amendments of 1977 and is
recommended as an additional source of information on the leather tanning
industry.
This guideline document may be transmitted to an applicant for informa-
tional purposes, but is not intended to represent the procedural requirements
for obtaining an NPDES permit or to represent the applicant's total responsi-
bilities relating to the new source EIS program. Because the content of an
EID for a specific new source applicant is determined by USEPA in accordance
with Section 6.908(b) of the Code of Federal Regulations, this document does
not supersede any directive received by the applicant from USEPA's official
responsible for implementing that regulation.
The Guidelines are divided into seven sections. Section 1.0 is the
"Overview of the Industry," described above. Section 2.0, "Impact Identifi-
cation," discusses process-related wastes and the impacts that may occur
during construction and operation of the facility. Section 3.0, "Pollution
Control," describes the technology for controlling environmental impacts.
Section 4.0, "Evaluation of Available Alternatives," discusses the con-
sideration and impact assessment of possible alternatives to the proposed
action. Section 5.0 describes regulations other than pollution control that
apply to the industry. Section 6.0 includes a glossary of terms relating to
the leather tanning industry and the general environmental assessment dis-
ciplines. Section 7.0 presents references available for more in-depth dis-
cussions on the industry, by topic as well as in an alphabetic listing.
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1.0 OVERVIEW OF THE INDUSTRY
Tanning is the process of chemically converting animal skins to leather.
Archaeological evidence indicates that the Egyptians practiced tanning 5,000
years ago and that the Greeks had developed tanning into a well-established
trade by 500 B.C. Tanners' guilds had been established in Europe by the 12th
Century to regulate and improve the art of leather making (New England Tanners
Club 1965).
The American tanning industry originated during colonial times and its
colonial beginnings are evident today in the predominance of tanneries in New
England and the Middle Atlantic States. During the 19th and 20th Centuries,
the source of animal hides shifted westward, leading to the distribution of
some tannery operations west of the Mississippi River (see Figure 1). However,
it is estimated that 85% of all tanneries are still located east of the Missis-
sippi.
The leather tanning and finishing industry is included within the U.S.
Department of Commerce, Bureau of the Census, Standard Industrial Classifi-
cation (SIC) 3100, Leather and Leather Products. The part of the industry
addressed in this report is identified as SIC 3111, Leather Tanning and
Finishing.
"Leather Tanning" is a general term for the numerous processing steps
involved in converting animal skins or hides into leather. The three major
hide and skin types used to manufacture leather are cattlehides, sheepskins,
and pigskins. Cattlehides constitute the bulk of the tanning performed in the
United States, representing about 84% of the total estimated weight of hides
tanned (US Department of Commerce 1979). Smaller quantities of hides and
skins of horses, goats, deer, elk, and other animals also are tanned each year
in the United States. In general, tanneries purchase hides and skins to
manufacture leather for shoes, garments, upholstery, luggage, gloves, handbags,
sporting goods, and a variety of other products.
Three major groups of standard processing steps are required to manufacture
leather: 1) beamhouse operations which wash and soak the hides or skins and
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Figure 1. Georgraphical distribution of U. S. tanneries.
AK: 1
HI: 0
States Containing No Tanneries
SOURCE: SCS Engineers. 1976. Assessment of industrial hazardous waste practices
tanning and finishing industry.
- leather
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remove the attached hair, 2) tanyard processes in which the tanning agent
reacts with and stabilizes the proteinaceous matter in the hides or skins, and
3) retanning and wet finishing processes which accomplish further tanning by
chemical agents such as dyes, lubricants, and various finishes.
The complexity associated with the industry is demonstrated by the pro-
cess combinations. Some plants tan and finish a single species of animal
hide, while others tan and finish various combinations of animal hide types.
Some tanneries have a single, highly specialized end-product such as lace
leather or mechanical cushions for pianos. Other tanneries produce a variety
of leather types for many consumer goods and industrial uses. The variety of
final products produced by the individual tannery influences the hide types
required and processing operations employed by that facility. Many tanneries
produce finished leather from raw, green salted, or brine cured hides; other
tanneries, however, perform only a portion of the total process. Several
facilities purchase previously tanned hides or splits and perform only the
retan, color, fatliquor and finishing processes. A number of tanneries pur-
chase hides and skins which either do not require a complete beamhouse process
(such as pigskins) or which have previously gone through the beamhouse (such
as pickled cattlehides and pickled sheepskins).
Tannery wastes can create or contribute to the following problems for
Publicly Owned Treatment Works (POTW's) and separate industrial wastewater
treatment facilities:
large pieces of scrap hide and leather clogging or fouling operating
equipment;
excessive quantities of hair and other small-scale, screenable solids;
highly acidic or alkaline waste streams;
wastewater flow surges;
excessive loadings of suspended and settleable solids and BOD,., con-
sistently or in surges;
odors, facilities corrosion, very high dissolved oxygen demand in
biological treatment system aeration basins, and hazardous gas genera-
tion from sulfide bearing wastes
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a potential future problem with disposal of sludges containing chrome;
and
pass through of ammonia nitrogen.
Each of the problems outlined, except for pass through of ammonia nitrogen,
can be reduced significantly or eliminated by applying pretreatment technology
in leather tanneries. Fine screening effectively removes hair, fibers, and
scrap material from wastewater and is available in many different configura-
tions, some of which are particularly effective on tannery type wastes.
Screening equipment also must be installed, operated, and maintained properly
to function well.
Waste streams from specific processes in tanneries can be highly acidic
or alkaline. If such streams are discharged without pH adjustment or mixing
with a different neutralizing stream, the waste stream may create problems
within the sewer or at the treatment plant. A pH control mechanism of holding
and mixing various wastes or of directly adjusting the pH of the waste is
easily implemented as a pretreatment technology.
Flow and waste loading surges particularly can disrupt biological treat-
ment systems employed by the POTW's, and they can be minimized by equalizing
the rate of flow or waste loading discharge. If space limitations at a tannery
preclude an equalization tank, discharge scheduling as practiced by at least
one tannery can reduce the magnitude of these surges.
Catch basins, wet wells, and other preliminary treatment facilities that
provide a retention time and space for solids separation from the waste stream
can be very effective if properly designed and maintained. Such a facility
requires regular maintenance in order to operate consistently and effectively.
Municipal problems in disposing of municipal sludge that contains chromium
can be shifted largely back to the tannery. In such cases, a smaller quantity
of sludge containing a higher concentration of chrome is more easily disposed
in a controlled environment. Chrome recovery and reuse technology also is
available and in use by the industry. This substantially reduces the chrome
content of the waste stream and of sludges generated in treatment of these
wastes.
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The leather tanning and finishing industry characteristically is family-
owned, not very progressive or profitable, and dominated by small plants
employing less than 100 people. There are an estimated 188 leather tanning
and finishing plants in the United States today comprised of 170 dischargers
to publicly owned treatment works (indirect dischargers) and 18 direct dis-
chargers. Total industry flow is approximately 52 million gallons daily
(mgd), of which 47 mgd are discharged to POTW's and 5 mgd are discharged
directly to navigable waters (USEPA 1979) .
1.1 SUBCATEGORIZATION
The raw material of the leather tanning industry is the hide or skin
subjected to the processing operations. Manufacturing processes relate to the
type of raw material received by the facility. For example, some tanneries
process previously tanned hides or skins, thus eliminating the need for beam-
house operations. Other significant process considerations include the tanning
process utilized and the presence of finishing operations, including retanning.
Plant size, age, and location (including climate), as well as wastewater
characteristics and treatability, represent the secondary factors of the
subcategorization rationale.
The factors considered for subcategorizing the leather tanning industry
include (USEPA 1979):
Raw material (cattlehide, split, pickled sheepskin, shearling, and
pigskin).
Manufacturing processes [beamhouse operations, tanning process (chrome,
vegetable, alum), and finishing operations (including retanning)].
Plant size.
Plant age.
Plant location and inherent climate.
Wastewater characteristics and treatability.
Raw material and manufacturing processes have been determined to be the
most significant factors in subcategorizing the leather tanning point source
category (USEPA 1979). Seven subcategories have been developed: four of the
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subcategories primarily cover the cattlehide to leather segment of the industry;
two subcategories cover operations which have no beamhouse; and the seventh
subcategory covers shearling tanning (sheepskin with hair intact).
The seven "subcategories are defined as follows (USEPA 1979):
1.1.1 Hair Pulp/Chrome Tan/Retan-Wet Finish - facilities which primarily
process raw or cured cattle or cattle-like hides into finished leather by
chemically dissolving the hair (hair pulp); tanning with chrome; and retanning
and wet finishing.
1.1.2 Hair Save/Chrome Tan/Retan-Wet Finish - facilities which primarily
process raw or cured cattle or cattlelike hides into finished leather by
chemically loosening and mechanically removing the hair; tanning with chrome;
and retanning and wet finishing.
1.1.3 Hair Save/Non-Chrome Tan/Retan-Wet Fj.nish - facilities which process
raw or cured cattle or cattle-like hides into finished leather by chemically
loosening and mechanically removing the hair; tanning with primarily vegetable
tannins, alum, syntans, oils, or other chemicals; and retanning and wet finishing.
1.1.4 Retan-Wet Finish - facilities which process previously unhaired and
tanned hides or splits into finished leather through retanning and wet finish-
ing processes including coloring, fatliquoring, and mechanical conditioning.
1.1.5 No Beamhouse - facilities which process previously unhaired and pickled
cattlehides, sheepskins, or pigskins into finished leather by tanning with
chrome or other agents, followed by retanning and wet finishing.
1.1.6 Through-the-Blue - facilities which process raw or cured cattle or
cattle-like hides into the blue tanned state only, by chemically dissolving or
loosening the hair and tanning with chrome, with no retanning or wet finishing.
1.1.7 Shearling - facilities which process raw or cured sheep or sheeplike
skins into finished leather by retaining the hair on the skin; tanning with
chrome or other agent; and retanning and wet finishing.
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1.2 PROCESSES
1.2.1 Major Processes of the Leather Tanning and Finishing Industry
Animal skin is composed of outer and inner (epidermal and dermal) layers
and it is the inner (dermal) layer which constitutes the leather-making portion
of the skins and hides. This dermal layer consists mainly of the protein
collagen. Tanning is essentially the reaction of collagen fibers with tannin,
chromium, alum, or other tanning agents which help stabilize, or preserve, the
skin and make it useful.
Water is essential to leathermaking and is used in virtually all manu-
facturing processes. Various chemical preservatives, biocides, coloring
pigments, and solvents also are integral to producing leather from animal
hides or skins. The standard manufacturing processes characteristic of the
industry are shown schematically in Figure 2. Each of the four major process
groups (beamhouse, tan, retan, and wet finish) consists of specific subpro-
cesses. For the purpose of 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 subprocesses. In any defined process, sub-
processes remain the same. This concept of manufacturing steps seems best to
allow for the variation of processes used by different plants (USEPA 1979).
The processes required at a specific tannery are dependent on the type of
hide being tanned and the final projected use for the leather product.
Individual tanners will vary process conditions to meet product specifica-
tions, which may result in considerable differences between the way a process
is used from one tannery to another. The use of cattle, pig, or sheep skins
for making leather will also require slightly different processing techniques
(Section 1.2.2).
1.2.1.1 Beamhouse Operations
The beamhouse operations prepare th^ "°w hides received from the meat
packer for tanning.
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Beaahouae
Receive & Score Bides
Figure 2. General process flow-
sheet for leather tanning and
finishing industry.
lanyard
[Bit.]
Pickle
Ran]
I Wring
Split
I Grain Portion
li.
I Shav*
Ratan. Color.
Fatliquor
j Ratan |
| Bleach & Coloring]
1
| Fat liquor ing J
,
| Setting Out {
I
[Hanging J Drying [
j Toggling! |_
Pasting
Vacuum
Finiah
|Conditioning j
I
(Staking & Dry Milling
I Buffing I
"1
Finishing & Plating
Measure I
| Grade |
I Ship |
Source: U.S. Environmental Protec-
tion Agency. 1979. Preliminary
draft development document for
proposed effluent limitations
guidelines and new source perform-
ance standards for the leather
tanning and finishing industry.
10
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Receiving
Most cattlehides are received at the tannery as salt or brine cured hides
unless the packer is close enough to permit shipping of uncured, green hides
directly to the tannery without danger of spoilage. Although the curing
process is generally performed at the meat packer and is therefore more closely
associated with the meat packing industry, the commonly used methods have been
outlined below to indicate more clearly the types of pollutants to be expected
at the tannery.
One process for salt curing involves interlayering hides flesh side up
with granular salt in stacks for 10 to 30 days. The salt is gradually absorbed
by diffusion and osmosis and replaces the moisture of the hides. Excess salt
is removed before the hides are rebundled for shipment.
Currently, the preferred curing procedure for green hides is washing and
soaking in brine. In this process, the hides are agitated in brine until the
desired salt content is reached; then they are drained, given a light coating
of additional salt, and bundled for shipment. The relatively short (2-3 day)
curing time and the associated removal of blood, manure, and other foreign
matter during the washing make this process attractive to both packer and
tanner.
Trimming and Siding
The first process which usually takes place at the tannery after removing
the hides from storage is trimming, to remove ragged edges and loose pieces of
skin. Some cattle hides are cut in half along the backbone (sided) before
further processing. The smaller skins of sheep and pig do not require siding.
Trimmings are collected and sent to by-product manufacturers or rendering
operations.
Washing and Soaking
Although washing may be required several times during the tanning pro-
cess, the first washing is primarily intended to remove the curing salt. In
11
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addition, soaking of the hide helps restore the moisture in the hide lost
during the curing process. Other contaminants such as dirt, blood, manure,
and any preservatives which remain on the hide are also removed during this
process, especially from salt cured or uncured hides. Hides are usually
washed in vats, drums, or in a specially designed concrete mixer device called
a hide processor.
Fleshing
In this operation, hides are drawn through a fleshing machine consisting
of a rubber pressure roller and a set of revolving spiral blades which remove
fat, connective tissue, muscle, and flesh which are left on the hide. Fleshing
is generally done at the packing house or at a separate hide processing facility
but sometimes is also required at the tannery. When this operation is performed
before unhairing, it is referred to as green fleshing. It also may be done
after tanning in the case of sheepskins, or by caustic burning during the
unhairing process, in which case it is called lime fleshing. Because recovery
of fleshings for rendering is common practice throughout the industry, the
waste load from this operation is low. A small volume of cold water is used,
however, to keep the fat congealed during the fleshing operation.
Liming and Unhairing
Hides are soaked in a lime solution and the hair is removed to improve
appearances and open the fiber structure to aid penetration of tanning chemicals.
This process also helps remove unwanted globular proteins from the hide struc-
ture. Due to the use of strong chemicals and the dissolution of hair and
proteins, this process produces the greatest pollution load from the beamhouse.
Unhairing is performed either as a chemical-mechanical process called hair-save,
or by an all chemical process called hair-pulp or hair-burn. In both processes,
hides are loaded into vats, drums, or hide processors with a slurry of lime
and sharpening agents such as sodium sulfide, sodium sulfhydrate, or more
recently, dimethylamine sulfate, which all act to improve the effectiveness of
this process. The highly alkaline unhairing chemicals loosen and dissolve
hair at its roots and cause hide fibers to absorb large amounts of moisture
which makes the hide swell. This alkaline swelling may cause a hide to reach
12
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twice its normal thickness. The concentration of the unhairing slurry and the
length of processing time vary depending on the process. The two major un-
hairing processes involve:
Hair-Pulp. If hair is to be chemically dissolved or pulped, stronger
solutions, higher temperatures, and/or longer processing times are
used. Solubilization of the hair protein in this process produces
high liquid phase pollution loads, particularly with respect to BOD,
COD, sulfides, and nitrogen. The sulfide content of this wastewater
is generally higher than that from the hair-save process due to the
higher concentration of sharpeners. Hides and skins are sometimes
relimed after unhairing to ensure complete hair removal and to ensure
uniform alkaline swelling of the hides prior to beginning the tanning
process.
Hair-Save. For the hair-save process, chemical concentrations,
temperatures, and processing time are limited to that necessary to
loosen the hair so that it can be mechanically pulled by a machine
which is similar to the fleshing machine with blunt blades. The
removed hair may be washed, baled, and sold as a by-product, but
markets are limited. Following mechanical removal of the hair, the
hide may be reprocessed to remove fine hairs and roots by reliming the
hide and running it through the unhairing machine a second time.
These unhaired hides are generally considered the product from the beamhouse
and are used immediately at the tanhouse.
1.2.1.2 Tanhouse Operations
The tanhouse operations convert the hide or animal skin (from the beam-
house operations or an outside supplier) to a durable material which is not
subject to physical or biological degradation.
Bating
After unhairing, a hide is swollen from the strong lime solutions. The
bating process is performed to reduce swelling, lower pH, peptize the protein-
aceous collagen fibers, and reopen the hide structure to allow removal of the
protein degradation products. Hides are loaded into vats, drums, or hide
processors with a solution of ammonium salts and enzymes. Ammonium sulfate or
ammonium chloride is added to convert the residual lime to a soluble compound
which can be washed out of the system. Enzymes such as trypsin are also added
13
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during the bating process to separate the collagen fibers and condition the
skin. Ammonia and calcium sulfate (the result of the lime - ammonium sulfate
reaction) are wastes from this process. This is one of the major sources of
nitrogen wastes from tanning. The use of other bating salts, such as magnesium
sulfate or magnesium chloride, is being investigated to replace these ammonium-
based bating solutions (Koopman 1974). After bating, hides are thoroughly
washed to remove any substances that have been loosened or dissolved.
Pickling
When the hide is to be chrome tanned, it must be acidified to prevent
precipitation of insoluble chromium salts on the skin fibers. The pickling
operation is not necessary when vegetable tanning is used. Pickling also is
used to preserve hides if storage is necessary prior to tanning.
Hides are usually pickled for a few hours in the same vat or container
used for bating. Salt is first added to the vat or hide processor to form a
buffer solution and prevent acid swelling which would damage the hide. The
hide is then pickled in a sulfuric acid solution for up to 12 hours. Pollutant
generation from this process is relatively low, but there may be significant
volumes of wastewater unless recycling is practiced.
Degreasing
Skins from sheep, goats, and pigs contain large quantities of fat and
grease that must be removed prior to tanning to eliminate problems with dyeing
and finishing and to allow better penetration of tanning chemicals. There are
several alternative methods of degreasing:
Emulsification. Skins are washed in a hot water and detergent
solution to remove grease and oil. The grease is usually separated
and recovered as a salable by-product.
« Solvent Extraction. Most pigskins are washed and soaked in hot water
to raise their temperature for degreasing. Following washing, sol-
vents are added and the skins are agitated to remove grease. The
grease and solvent are separated from the wash water by decanting.
Grease and solvent recovery are commonly practiced using a solvent
stripping column. Recovery processes make solvent degreasing a rela-
tively low pollution process. However, there is a small volume of
wastewater and some solvent is vented directly to the atmosphere.
14
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Mechanical. Some sheepskins may be degreased by mechanically squeez-
ing the grease, skin oils, and lanolin out of the skin. The grease
and oil are recovered.
Tanning
Hides or skins are tanned to give them the mechanical properties of
leather, such as abrasion resistance and flexibility, and to prevent them from
decaying. The two main tanning agents used commercially are chromium sulfate
solutions and solutions of various vegetable tannins. Alum, other metal
salts, and formaldehyde are tanning agents but are not widely used on a com-
mercial scale. Certain synthetic tanning agents (syntans) have been developed
over the years, but these are used mostly as auxiliary agents to these prin-
cipal tanning agents.
These different tanning agents produce leathers with various working
qualities and end uses. Heavy leathers that require great durability, such as
shoe soles, saddles, or belts, are usually vegetable tanned. Lighter leathers
requiring greater abrasion resistance for use as garments or shoe uppers are
usually chrome tanned. Leather may be tanned by one operation or it may be
tanned and retanned in two different solutions to impart different qualities
to the leather. The major alternatives involve:
Vegetable Tanning. Vegetable tanning, the older of the commercially
used tanning processes, takes several weeks. The hides are gently
agitated in rocker vats containing a solution of vegetable extracts
or they are soaked in vats containing progressively stronger solutions
of tanning liquor. Vegetable tanning solutions are made of quebracho,
wattle, chesnut, eucalyptus, and other vegetable extracts. With the
cost of tanning chemicals and labor escalating, vegetable tanners are
recycling tanning solutions by refortification and using higher con-
centrations of tannins to reduce processing time. Synthetic tanning
agents also may be used to improve dispersion and penetration of the
vegetable tanning solutions into the hide fiber. Following tanning,
the leather is covered, allowed to stand for about 42 hours, and
washed of excess tannins.
Chrome Tanning. Most leathers today are chrome tanned. While they
are light use leathers, they have more resistance to heat and abrasion
than vegetable tanned leathers. Chrome tanning requires less than one
day. Chromium atoms are believed to react with the hide proteins by
bridging the space between carboxyl and amino groups on adjacent
protein molecules. Tanning is generally carried out in a vat or hide
15
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processor using proprietary mixtures of basic chromium sulfate. This
produces a hide at the blue tanned stage, so named due to its color.
Chrome tannery wastes do not contribute high concentrations of con-
ventional wastes such as BOD, but do contain high concentrations of
dissolved solids and potentially toxic trivalent chrome. Tanning
solutions are sometimes made by reducing hexavalent sodium dichroraate
with sulfuric acid and sucrose to produce the trivalent chrome neces-
sary for tanning. Accidental spills are therefore the only source of
the more dangerous hexavalent form of chrome which might be found in a
tannery.
Wringing
Wringing removes excess moisture from the hide before it is split. This
is done by feeding the hides through a machine with two large rollers similar
to a clothes wringer. For plants in the through-the-blue category (Subcategory 6)
this completes the processing of the hides and the wet blue stock generally is
sold to another plant for the retanning and wet finishing operations. For
other tanneries, the tanned hide is processed further to produce the required
leather product.
Splitting
Because hides are usually too thick for most uses, the finer grade grain
leather is often separated from the flesh side leather (called the split)
after the initial tanning operation using a machine resembling a horizontal
bandsaw. Splitting following the unhairing process (referred to as lime
splitting) was once a common practice, but this is not practiced extensively
today. Splits are either processed separately at the tannery or sent to
another tanner who processes splits. In the case of pigskin, the split is
sold to fertilizer manufacturers as a by-product since pig splits are of no
use as leather. The grain portion of a hide may be shaved to remove any
fleshy matter from the hide that was not removed with the splitting knife.
The shaving machine is also used to level the hide to a uniform thickness.
16
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1.2.1.3 Retannlng, Coloring, and Fatliquoring
Following the initial tanning process, which is primarily for preser-
vation of the fibers, operations are carried out to impart the desired look,
feel, and working qualities specified by the customer. Hides at the blue
stage are placed in drums and first treated with retan formulations, followed
by dye formulations, and then by fatliquoring chemicals.
Retanning
Retanning is a second tanning step commonly used to alter the character-
istics of the leather. This may involve vegetable retanning of a chrome
tanned leather to give it some of the plumpness and workability of a vegetable
tanned leather, or chrome or synthetic tanning of a vegetable tanned leather
to give it some of the durable qualities of chrome tanned leather. It is in
the retanning process that most synthetic tanning agents (syntans) are used.
Bleaching
Vegetable tanning of some leathers such as those used for shoe soles may
be followed by bleaching to improve the color characteristics of the tanned
leather. This is usually done immediately following the tanning process.
Coloring
Following the retanning step, leather may be adjusted to the desired
color using natural or synthetic dyes. This is usually done in the same vat
as retanning. These dye wastes are a concern due to the complex organic
composition of some of the dye materials (e.g., analine derivatives and organo-
metallic substances).
Fatliquoring
The final wet process for leather is to add oils and greases to the
tanned hides to replace those lost during processing. This prevents cracking
17
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and makes the leather soft, pliable, strong, and tear-resistant. Fatliquoring
is usually carried out by immersing the hide in an emulsion of oil and fatty
substances at a temperature of 120° - 140°F for a few hours. Aliphatic mineral
oils are sometimes used in small quantities for heavy industrial and shoe
leathers.
1.2.1.4 Finishing
Finishing requires a series of dry operations which give leather its
final attractive surface qualities. Little if any finishing is done to vege-
table tanned hides; however, chrome tanned hides may be put through any of
several finishing processes.
Setting Out
Setting out smooths and stretches the skin, while compressing and squeez-
ing out excess moisture.
Drying
Drying is accomplished by four different methods:
Hanging. The hide is draped over a horizontal shaft which is
usually passed through a large drying oven.
Toggling. The skins are dryed in a stretched position on frames.
The frames are slid into channels in a drying oven.
Pasting. The skins are pasted onto plates which are then transported
into a drying oven.
Vacuum. The hides are smoothed out on a heated steel plate and
covered by a perforated belt or cloth-covered steel plate. A
vacuum is pulled which extracts water from the leather. Unlike the
first three processes riiich take four to seven hours per skin, this
method requires only three to nine minutes. However, this method
has limited application due to shrinkage.
18
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Conditioning
Hides are sprayed with a water mist and then piled on a table, wrapped in
a watertight cover, and kept overnight to permit uniform moisture distribution
in the leather. This improves the handling characteristics of the hides
during subsequent operations.
Staking and Dry Milling
Staking is done on automatic machines which stretch and flex the leather
to make it soft and pliable. Dry milling consists of tumbling the hides in a
large drum.
Buffing
Buffing is a light sanding operation performed on the grain or split side
of leather to smooth or correct irregularities in the grain surface. Dust
from this operation is the industry's most significant air pollutant.
Finishing
A number of finishes may be applied to leather by rolling or spray ap-
plication depending on the end use of the leather and type of hide. Various
coating materials, both water-based and solvent-based, are used to provide
abrasion and stain resistance and to enhance color. Solvent-based coatings
are sometimes used for high luster finishes, but their use is being reduced
due to handling problems and fire hazards.
Plating
The final processing step which influences the appearance and feel of
leather is plating, which is performed by pressing the leather onto a large
smooth surface. This smoothes the surface of coating materials applied to the
leather while bonding them firmly to the grain. The finishing and plating
operations are carried out in conjuction with each other over a period of four
to five days. Hides may also be embossed (stamped with a particular pattern)
in conjunction with this process.
19
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Measuring
The hide area is determined electronically and the area is stamped on the
back side of the hide.
Grading
Grading determines the quality of the finished product. Leather is
graded by experts for temper (the feel and relative solidity), uniformity of
color and thickness, and the extent of any surface defects.
1.2.2 Process Variations for Raw Materials
Significant variations in the basic preparatory and tanning processes
described here are required for the three major types of hides or skins used
by the tanning industry. The major process techniques for these hides are
discussed below.
1.2.2.1 Cattle Hide Tannery
Cattle hides, which make up the vast majority of tannage in the United
States, are typically processed as indicated in Figure 3.
Beamhouse
The hides are first trimmed of ragged perimeter areas and then split down
the backbone (i.e., sided) in order to make manageable-sized hides for pro-
cessing. As outlined in the general process description, these hides are
washed, soaked, fleshed, and unhaired using either the hair save or hair pulp
process. If hair is saved, it may be washed, bundled, and sold as a by-product,
but the hair pulp process is currently favored by tanners due to its lower
handling and labor costs.
20
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Figure 3. Flow diagram for a typical cattlehide tannery.
FUOW DIAGRAM
TYPICAL CATTLEHIDE TANNERY
IMS ut lunn
mccu wnnui
CTM-GKOt-nniQUB
FINIVIM
1 I*1"1 .
|mn tun (IUIMI
«uit imwrt , _
I Ixua -«
j mil urn (UHUMI _
SOURCES U.S. Environmental Protection Agency. 1974. Development document
for effluent limitations guidelines and new source performance
standards for the leather tanning and finishing point source category.
p. 13.
21
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Tanhouse
Most cattle hides are tanned either by chrome or vegetable tanning pro-
cesses as outlined in the general process description. The basic tanning
process used for cattle hides is almost identical regardless of the end use of
the leather. Hides are delimed, bated, and pickled for a few hours in an acid
bath prior to tanning, although the pickling is not necessary for vegetable
tanned hides. The final desired characteristics of the leather are obtained
through retanning and subsequent steps.
Retan. Color, Fatliquor
As outlined in the general process description, retanning may be per-
formed in a drum using a variety of tanning agents (i.e., chrome, vegetable,
alum, syntans, zirconium, and other metal-based tanning agents). Hides may be
colored and fatliquored for short periods in the same drum using analine-based
dyestuffs and animal, vegetable, or mineral-based oils.
Finishing
The finishing of cattlehide leather is dependent on final product re-
quirements, and may involve any of the processes in Section 1.2.1.4.
1.2.2.2 Sheepskin Tannery
Sheepskins are typically processed as shown in Figure 4. Most sheepskins
are received at the tannery with the wool already removed, so there is essen-
tially no beamhouse operation needed. Shearling skins, which are received
with the wool still attached, are tanned to keep the wool intact and require
no beamhouse operation except for fleshing. Most sheepskins are imported so
they are typically received already pickled with brine and acid. Shearlings,
however, are preserved in brine only.
22
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Figure 4. Flow diagram for a typical sheepskin tannery.
FLOW DIAGRAM
TYPICAL SHEEPSKIN TANNERY
COLOft-FATLIQUOR
(>) SHEARLIII&S (WOOL LEFT M) ARE
RECEIVED AS CURED SKINS. TAH-
HOUSE SUB-PiOCESSES INCLUDE
ASH t SOAK, FLESHIW. DEfiHEAS-
!*&. PICKLING AND TAMKITG.
ums
DECREASING
[_>l*STE EFFLUEfT
SOURCE: U.S. Environmental Protection Agency. 1974. Development document
for effluent limitations guidelines and new source performance
standards for the leather tanning and finishing point source category.
p. 21.
23
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Tanhouse
No special provisions for sheepskin storage are made at most tanneries.
The skins are kept moist and biocides (e.g., chlorinated phenolics) are used
to retard bacterial action and increase storage time. Pickled skins held for
extended periods should be kept below 30°C (86°F) to avoid deterioration.
Skins from storage are inspected and fleshed. Skins which have been
fleshed prior to receipt at the tannery will usually be refleshed after tan-
ning. Shearling hides are usually fleshed after a wash and soak operation.
The fleshing machine is similar to that used for cattlehides, with the skin
carried through rollers and across rotating spiral blades. Skins are placed
in drums, washed, and soaked, after which they are degreased as discussed in
Section 1.2.1.2. Grease is recovered as a by-product from those skins which
have had the wool removed. When solvent degreasing is used, the solvent is
recovered and reused. Because shearlings require substantial water in the
soaking and washing (scouring) operations, grease recovery is not normally
practiced.
Sheepskins may be either chrome or vegetable tanned, although the major-
ity 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 mixtures of
basic chromium sulfate for chrome tanning, or solutions of the natural tannins
for vegetable tanning. Shearling skins also require pickling to prepare them
for the chromium tanning process.
In some cases, there is a refleshing operation following tanning, which
produces a small amount of solid waste containing chrome.
Retan, Color, Fatliquor
Retanning is performed in a manner similar to the cattlehide retanning
operation. Skins to be colored are immersed in a dye solution in drums.
Synthetic dyes are generally used, and some bleaching may be done prior to
coloring of shearlings. Fatliquoring is performed in the same drum used for
24
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coloring. Skins are immersed in a solution containing various oils to replace
the natural oils of the skin lost in the tanning process.
Finishing
There are a number of operations which follow the coloring and fat-
liquoring process, including drying, skiving (shaving), staking, carding,
clipping, sanding, and buffing. These are essentially dry processes, and the
only liquid waste contributed is from cleanup operations. Solid wastes from
the finishing operation include trimmings and skivings.
1.2.2.3 Pigskin Tannery
The pigskin tanning processes are similar to those for sheepskins in that
there is essentially no beamhouse process, since most skins have the external
hair removed at the packinghouse. Degreasing of the skins is a required
tanhouse process. A schematic of a typical pigskin tanning operation is shown
in Figure 5.
Tanhouse Process
Nearly all pigskins are received at the tannery either as fresh frozen
skins or as brined refrigerated skins. They are usually tied in bundles that
weigh 40 to 50 pounds. In some cases, frozen skins are received in paper bags
rather than bundles. Refrigerated storage is used at most tanneries when
skins are to be held before tanning. The required degreasing is usually done
by the solvent method described in Section 1.2.1.2. In this process, the
skins are placed in drums, then washed and soaked in warm water to bring them
to a temperature suitable for degreasing. Solvent is then added and the skins
are tumbled to remove the grease. The solution of solvent, grease, and water
is pumped from the drums to large tanks where some separation is achieved by
decanting. From the tanks the solvent and grease are sent to a stripping
column where the solvent is recovered for reuse and the grease is recovered as
a by-product.
25
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Figure 5. Flow diagram for a typical pigskin tannery.
FLOW DIAGRAM
TYPICAL PIGSKIN TANNERY
COlM-FtTllOUOl
SOURCE: U.S. Environmental Protection Agency. 1974. Development
document for effluent limitations guidelines and new source
performance standards for the leather tanning and finishing
point source catagory. p. 24.
26
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An alternate method, In which the skins are tumbled in hot water and
detergent, has also been used. With this operation, grease is recovered by
decanting or skimming from the top of holding tanks to which the waste has
been diverted prior to entry into the main plant sewer system.
From the degreasing operation the skins are placed in tanning drums with
a lime slurry and sharpeners, which remove the embedded portion of the hair
from the skins. This is followed by bating and pickling in the same drum.
While pigskin may be either chrome tanned or vegetable tanned, the only major
tanner of pigskin in this country is using the chrome tanning process. Chrome
tanning is conducted in the same drum used for pickling. Current practice is
to fully tan the skins in this operation, eliminating any need for a retan
operation at a later point.
After tanning, the skins are tumble dried and then split and shaved to
obtain the desired thickness. The split portion of the pigskin has no com-
mercial value as leather, and it is baled with other scraps and sold as a
fertilizer component. The grain sides go to the color and fatliquor process.
Color, Fatliquor
Skins to be colored are immersed in a dye solution in drums, generally
consisting of synthetic dyes. Fatliquoring 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
The operations that follow the coloring and fatliquor process include
drying, coating, staking, and sanding. These are principally dry processes,
and the only liquid waste contributed is from cleanup operations. Solid
wastes from the finishing operations include trimmings, which are baled with
the split and shave wastes and sold as fertilizer.
27
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1.2.3 Auxiliary Support Systems
Relatively few auxiliary support systems are required by the leather
tanning and finishing industry. Boilers are operated for internal heating
systems and steam generation but these are not major demands. Other in-plant
systems, such as solvent recovery systems for the degreasing process and
evaporators for concentrating spent tanning liquor, actually serve as waste
treatment and resource recovery systems.
When hide curing is done at a separate facility rather than at the meat
packing plant, it may be considered a support system for the leather tanning
and finishing industry. In these cases, certain other operations normally
associated with the tannery, such as fleshing and washing, may also be per-
formed. These curing and washing operations can be a significant source of
pollution in the form of dissolved solids, blood, manure, and dirt, and should
be clearly identified if they are to be included at the tannery.
1.3 SIGNIFICANT ENVIRONMENTAL ISSUES
1.3.1 Location
Tanneries traditionally have been relatively small operations which do
not involve large numbers of employees, large volumes of water, or bulk raw
material shipment, and therefore have not been of great significance on a
national or regional level. However, as the trend for new facilities favors
uniform production techniques and mass production, the emphasis on large
facilities can be anticipated. Such facilities may result in the following
local impacts:
A tannery may involve changes in land use and result in direct and
indirect social and ecological impacts.
Significant liquid and solid phase waste loads from a tannery may
overwhelm the publicly owned treatment works (POTW) and land disposal
facilities of a small community if these existing systems are to be
used by the industry.
A new tannery may be a member of an industrial complex involving the
processing of meat and meat by-products which could collectively have
a greater impact on the community than the tannery itself.
28
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Secondary impacts during construction of a new tannery may be signif-
icant in smaller communities.
Long-term trends for larger facilities (Section 1.4.1) and the exis-
tence of tannery towns indicate that income in these areas could be
increased sufficiently to induce spin-off development.
1.3.2 Raw Materials
No raw materials are used in sufficient quantity to constitute a major
environmental problem. Resources required at a tannery include hides; water;
process chemicals such as lime, chromium, sulfides, ammonium salts, and sul-
furic acid; and energy. These requirements usually will not pose a significant
environmental issue if Best Management Practices are required as described by
the Clean Water Act (Section 304e). Special areas of concern include:
Dissolved solids loading in the tannery's liquid waste stream due to
salt or brine cured hides.
Trivalent chrome tanning solution production by reducing the highly
toxic hexavalent sodium dichromate with acid and a carbon source.
1.3.3 Processes and Pollutants
Wastewater characteristics vary among tanneries based on such factors as
type and condition of raw hide, final product, processes and process equipment
used (e.g., hide processors), and tanning agent. The pollutants basically
differ little from those in wastewaters of many other industries and can be
treated by conventional methods for suspended solids reduction, oil and grease
removal, pH control, and BOD reduction. Specific constituents peculiar to
certain tanning processes, such as chromium and sulfide, can be removed with
available treatment methods currently practiced by the industry.
Tannery waste treatment cannot overlook the interrelationship of the
different media (i.e., air, water, and land) for pollutant discharge; for ex-
ample, coagulation-sedimentation and sludge dewatering produce a waste produce
for land disposal. If a chromium tanning process is used, this waste will
contain trivalent chromium and care must be exercised in managing the waste
disposal to prevent leachate contamination of ground or surface waters. The
practice of chromium reuse or recovery within the plant should reduce the
chromium content of the sludge.
29
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The strong chemical solutions required by many of the processes and the
high strength organic wastes can interact to create a wastewater including
toxic substances that may inhibit biological treatment processes. Waste
treatment is difficult because of hydraulic surges from batch process dumps of
waste material. Furthermore, the variability of processes within the industry
can result in treatment problems applicable only to a few tanners, making
these difficult to predict and possibly requiring unique solutions.
The sources and characteristics of process-oriented problems which have
potentially significant environmental effects are highlighted below.
Large quantities of wastewater may be generated containing high con-
centrations of salt and organics in the form of blood, manure, and
dirt from the hide washing operation.
A large volume of high pH wastewater with high alkalinity, sulfide,
nitrogen, and dissolved and suspended proteinaceous matter concentra-
tions is generated by the unhairing process.
A low pH wastewater with high trivalent chromium concentration is
generated by the chrome tanning process.
Toxic hydrogen sulfide gas can be produced if the pH of the unhairing
waste is allowed to fall below 9.0 as a result of mixing with some
other process or waste stream. This is a potentially serious problem
both from the standpoint of worker safety and effects on the sur-
rounding environment.
Process solutions from the dyeing and finishing operations contain
a variety of priority pollutants other than chromium. These include
organic dyes, solvents, heavy metals, chlorinated hydrocarbons, bio-
cides, condensation products of formaldehyde, and others. The National
Institute of Occupational Safety and Health has reported a striking
increase in the incidence of bladder cancer among leather workers
which may be related to dyes (USEPA 1978b).
Large quantities of noxious and in some cases, hazardous, solid wastes
may be generated from screenings, trimmings, and shavings.
Noxious odors may be caused by the sulfides in the unhairing and
bating processes, and from the decay of flesh, or other putrescible
matter that is not quickly and properly disposed.
30
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1.3.4 Pollution Control
Measures taken to control process pollution from the leather tanning
industry constitute an entire set of processes and related environmental
problems within themselves. Because of the nature of tannery wastes, it is
often most effective to eliminate the pollutants at their source by process
substitution or recovery, especially for the toxic or priority pollutants. In
other cases, it is most effective to concentrate wastes by recycle or reuse,
so that process solutions may be more efficiently used and waste products may
be mor6 easily treated and disposed. Still other processes are employed to
physically, chemically, or biologically change the wastes to less hazardous or
objectionable forms. Finally, treated residuals must be properly handled and
disposed, especially in the instance of hazardous solid wastes. The sources
and characteristics of waste treatment related problems which may potentially
have significant environmental effects are highlighted below:
Combined treatment of beamhouse and tanhouse streams require that
pH levels be maintained high before biological treatment so that
hydrogen sulfide will not be generated.
Sludges from screening, coagulation/sedimentation, biological treat-
ment, and dewatering units may contain chromium and other priority
pollutants removed from process waste streams all over the plant.
Care must be taken in disposing these hazardous wastes in accordance
with applicable regulations. For example, chromium may be leached out
of sludge by acetic acid produced by the decay of garbage in landfills
(SCS Engineers 1976).
Odors may be generated by sludge handling processes, if the sludge
has not been properly stabilized prior to dewatering and disposal.
Interstream transfer of wastes occurs in many waste treatment pro-
cesses and this must be considered in the assessment of pollution con-
trol effects. Buffing dust which may contain chromium can be removed
from the air waste stream, enter the liquid waste stream by wet scrub-
bing, and eventually appear in the solid waste stream after wastewater
settling. Conventional and priority pollutants are removed from the
liquid waste stream and enter the solid waste stream in the screening,
sedimentation, and biological treatment steps. Waste may also enter
the air stream from the liquid waste stream, as in the case of hydro-
gen sulfide generation.
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1.4 INDUSTRY TRENDS
1.4.1 Markets and Demands^
Products of the tanning and finishing industry are used to make familiar
consumer goods such as shoes, belts, handbags, and garments as well as saddles,
gaskets, and athletic equipment. The main raw material of the industry is
cattlehides (84% of the industry's production) with much smaller numbers of
sheepskins, pigskins, horsehides, and wild animal skins being used. (U.S.
Department of Commerce 1979). Since hides are a by-product of the livestock/
meatpacking industry, their supply is dictated by the demand for meat rather
than the demand for leather. Worldwide demand for cattlehides exceeds the
supply which has caused a recent escalation in the cost of raw hides and
finished leather products.
Tanners also process significant numbers of tanned sheepskins, calfskins,
lambskins, and pigskins, as well as other types of skins including kip (immature
cattle), cabrettas, and horsehides. Production of these leather types has
declined since 1960, although a trend toward removal of pigskins prior to
butchering may lead to more pigskins and increased production of pigskin
leather.
Beginning in the mid-1960's and continuing until 1974, the domestic
leather tanning and finishing industry experienced a steady decline in the
number of plants, production volume, and profits. This trend was attributed
to: 1) greater foreign demand for cattlehide, which caused an increase in raw
material cost, and 2) competition from foreign countries in the finished
leather products market.
More recent data for 1975 and projections for 1976 production show total
industry production, both in equivalent number of hides and in total dollar
value, to be increasing. Cattlehide exports generally increased from 1965 to
1975. During the same period, a general increase in finished leather import
dollar value was experienced; however, the dollar value of finished leather
exports also increased. Finally, in 1975, leather exports exceeded leather
imports as measured in dollars.
32
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Increase in leather production, increase in dollar value of total industry
production of leather, and increase in dollar value of leather for export are
three indications of a viable U.S. leather tanning and finishing industry.
Management and owners of tanning operations express confidence in the industry
both verbally and by continuing capital investments in tanneries.
The industry's economic situation has continued to decline, despite a
short-term improvement from 1974 to 1976; nevertheless, it may stabilize in
the future as the demand for leather products balances relative to leather
substitutes. Prospects for new plants vary among segments of the industry;
entry of new plants appears likely for tanneries which can take advantage of
strong demand and economies of scale.
1.4.2 Location
The geographical distribution of U.S. tanneries is shown in Figure 1.
The principal areas for tanneries are in New England, the Middle Atlantic
States, the Chicago-Milwaukee area, and the Pacific Coast (USEPA 1979). The
distribution of tanneries has not shifted in recent times as indicated by the
average age of tanneries shown below:
Age of plant Percent of plants
Less than 10 years !
10 to 14.9 years !
15 to 19.9 years 3
20 to 29.9 years 4
30 to 50 years 18
Over 50 years 67
Data not available §.
Total 100
Source: SCS Engineers. 1976. Assessment of industrial hazardous waste
practices, leather tanning and finishing industry.
Beginning in the mid-19601s and continuing until 1974, the domestic leather
tanning and finishing industry experienced a steady decline in the number of
plants (USEPA 1979). Although most tanneries are over 50 years old, the few
built recently have tended to be through-the-blue operations located nearer
the source of hides (SCS Engineers 1976). This reduces the need to transport
33
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unusable portions of hides great distances and also improves the tanner's
control over the curing process. This also will tend to remove the beamhouse
and tanhouse operations, which produce the greatest pollution load, away from
traditional urban locations to areas where industry wastes can be more easily
accommodated. New beamhouse/tanhouse operations of this sort have been opened
in Missouri and Texas in the last few years. These new facilities also will
tend to be larger than the traditional facilities, as uniform production
techniques encourage mass production tanning.
1.4.3 Raw Materials
As a by-product of the meat industry, hides and skins represent only 3 to
6 percent of the value of the live animal (USEPA 1977b). Therefore, the
demand for hides will not effect their supply. During the 1960's and 1970's,
there has been a rapid increase in the supply of cattlehides, which account
for 84% of the hides used by U.S tanners. Due to rapid growth in the demand
for meat, the cowhide supply has been steadily and rapidly increasing from
25.2 million hides in 1960 to more than 42 million in 1976. Even with the
occasional production slumps which follow a cyclical pattern of building up
and reducing herds, the commitment of the livestock industry to long-term
growth assures the tanning industry of a continuously increasing supply of
hides for the future.
Despite this expanded supply of domestically produced hides, the U.S.
tanning industry has not been able to increase its production due to the price
inflating effect of worldwide demand for U.S. produced cattlehides. Because
total hide production has fallen from its 1976 high while exports of raw
cattlehides continue to increase as a percentage of total hide production, the
actual net effect has been a decrease in hides available for domestic leather
production (see Figure 6).
While the supply of cattlehides has grown, the supplies of other types of
animal skins have been decreasing. Calfskin supplies have been shrinking
drastically in the U.S. with the exception of a temporary increase from 1974
to 1977, and are not expected to be a major factor in the market in the future
(U.S. Department of Commerce 1979). Calfskin production declined 20% from 5.5
34
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Figure 6. Trends in cost and availability of cattlehides for
the U.S. market, 1969-1978.
Slaughter Decline, Export Pressure
forcing Cattiehide Prices Up
Million hides Cants par pound
50 ^M^H^^BBHMHHMIM^BBra BO
4O
30
20
10
196970 71 72 73 74 75 76 77 78'
D CATTIEHIOE SHIPMENTS TO U.S. MARKET
D CATTLEHIPE EXPORTS
'Estimated
Source; U.S. D«p«rtm«nl of Agrieu&urt: BufMu of ttw
Industry Mid Trad* AdmmiatrKion IBO8D)
40
30
20
10
SOURCE: U.S. Department of Commerce. 1979. U.S. industrial
outlook.
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million in 1977 to 4.4 million in 1978, with 2.6 million of these hides
(59.1%) exported (U.S. Department of Commerce 1979). Sheep and lambskin
supplies have been declining steadily over the past two decades, and the
long-term prospect for sheepskins from domestic sources indicates this will
continue. Domestic sheep and lambskin production declined 14% from 6.27
million skins in 1977 to 5.5 million in 1978, with 1.2 million of these skins
exported. Pigskin supplies may increase, however, due to the increasing trend
for removing skin before butchering. Other skin sources are not used in the
United States to a great extent.
1.4.4 Processes
Identification of process trends in the leather tanning industry is
complicated because tanning continues to be practiced as an art. The set of
processes and procedures necessary to produce leather of the particular color,
texture, and working qualities desired by customers are the guarded secrets of
the trade, and there is great reluctance on the part of most tanners to make
even minor changes in processes that might affect the quality of the finished
product. The concern with consistent product quality and the uncertainty of
most tanners on how a particular process change may affect their product make
adoption of new processes quite slow and the prediction of trends quite specu-
lative. The toxic nature of many of the industry's wastes (e.g., highly
alkaline unhairing waste, chrome tanning liquor, and priority pollutant-based
dyestuffs) make the most effective treatment method elimination or control at
the source. For this reason, many of the process modifications which are
being adopted by the leather tanning industry have as their sole or primary
purpose pollution control. Those process trends primarily related to pollu-
tion control are discussed in the next section. Highlighted below are other
process trends that are identified for the industry.
Brine hide curing is currently favored over salt curing due to the
reduction in time and labor involved in curing the hides and the
benefits of cleaning the hides of blood, dirt, and manure before they
are delivered to the tanner.
In order to improve the efficiency of the industry, there are expected
to be overall larger tanneries in the future, which will process
greater numbers of hides in larger batches.
36
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Due to competition from synthetics, there is expected to be a con-
tinued decrease in sole leather production which is vegetable tanned.
This follows a long-standing trend toward more chrome tanning and less
vegetable tanning.
Many tanneries (particularly through-the-blue operations) have adopced
the use of hide processors for some or all of their wet processes.
Hide processors offer an advantage in the handling of hides since
washing, beamhouse, and tanhouse operations can be carried out in the
same vessel.
Hair pulp unhairing is increasing because there are few markets
for by-product hair and because this process reduces fine hair carry-
over and requires less handling, which reduces labor costs.
Many tanners have eliminated the solvent-based finishes
used to obtain a high luster surface on leather because of the asso-
ciated hazards from fire and concern for employee safety.
Some tanners have begun to use an extremely accurate hide splitting
method called "splitting to weight." It requires new equipment, but
reduces the need to shave hides to obtain uniform thickness and pro-
duces a more valuable split with a lower volume of shaving waste.
1.4.5 Pollution Control
Because the leather tanning and finishing industry has traditionally been
located in urban areas, many of its pollution problems have been passed on for
the municipality to handle. Consequently, the job of adopting modern pol-
lution control technology to many of the serious environmental problems of the
industry has only begun in the last two decades.
1.4.5.1 In-Plant Pollution Control
As noted in the previous section, the most efficient method for elimina-
ting pollutants from tannery wastes and in reducing the volume of effluent is
through reuse of water and chemical agents and through recovery of materials
which are normally wasted. The acceptance of these la-plant pollution control
measures is slow, as is the case with other process trends. Typical In-plant
pollution control measures currently being investigated by the industry are
shown in Table 1 along with their relative degree of acceptance in a survey of
46 tanneries. The key to industry acceptance of these processes is the ability
to implement them without adverse effects on leather quality. The processes
most favored in this survey are highlighted below (USEPA 1979).
37
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Table 1. In-plant process treatment indicated on questionaire
from total of 46 leather tanneries.
Process Change Methods
Sulfide substitute in unhairing
Ammonium sulfate substitute in
deliming
Eliminate the bating step
Use of hide processors
Wash/soak water reuse
Lime liquor reuse
Unhairing liquor reuse
Protein recovery
Spent chrome liquor reuse
Liritafc vegetable tan process
Recovery of spent vegetable tan
liquor
Process or equipment wash water
reuse
Cooling water reuse
Other
Number of Plants
Which Considered
But Decided Against
Process Changes
17
12
12
14
15
12
8
6
19
5
3
8
4
0
Number of Plants
Which Are or Will
Be Implementing
Process Changes
0
0
13
7
13
10
3
10
5
8
13
14
5
SOURCE: U. S. Environmental Protection Agency. 1979. Preliminary draft
development document for proposed effluent limitations guidelines
and new source performance standards for the leather tanning and
finishing industry.
*At least one plant has abandoned this system since these data were collected
for the USEPA survey.
SOURCE: Kenneth A. Dostal. 1979. Memo, Kenneth Dostal, USEPA Region V, to
Bob Pickett, USESA, Office of Environmental Review, 29 June 1979. 3 p.
38
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In recent years, the hide processor (modified concrete mixer) and
other processing equipment have been found to be effective as a means
of reducing labor, handling, and water use. The amount of new pro-
cessing equipment in use is increasing, most widely for washing the
incoming hides and for beamhouse operations in hair pulp processes. A
few tanners also have used new equipment for the through-the-blue
tanning process.
Lime is used in large quantities in the beamhouse for opening the hide
structure and for unhairing. It has been found that lime solutions
can be recycled many times if solids are removed and the solution is
refortified. By reducing the amount of lime in the effluent, the
alkalinity of the waste and the volumes of insoluble calcium sludges
generated during waste treatment are reduced.
There are a number of vegetable tanneries that are using recycle
systems to reduce the amounts of tan liquor that are discharged into
the waste streams. The Liritan (Leather Industries Research Insti-
tute, South Africa) process employs such a technique by counter-
current flow of tanning solution in relation to the hides. There is
little effluent, but some blowdown is necessary to prevent the build-up
of contaminants in the tanning solution. One tannery recovers this
blowdown tan liquor, concentrates it in a triple effect evaporator,
and sells the concentrated liquor. Other tanneries use this blowdown
liquor in retanning operations. However, the trend for recycle of
these solutions will be limited by the availability of low cost re-
covery energy and a strong market for the recycled solution.
Recycling, reuse, and recovery of chrome tanning solutions are also
being practiced in the industry. During World War II, the reuse of
chrome tan liquor was common practice because of the scarcity of
chromium salts. Chrome tan liquor has been recycled for use as a
pickle/pretan by fortifying it with acid and salt. This has also been
reused for tanning by removing the solids and adding more chromium
salts. Spent chrome tan liquor is also used by some tanners as a
retan solution. Recovery of chrome from the waste stream is not being
widely practiced.
Large volumes of wash water are used in a tannery for equipment and
process washing. Much of the water used to wash incoming hides can be
reused if solids are settled or screened out, but this has been less
well accepted than equipment washwater and process rinse water reuse
from later steps in the tanning process.
Waste stream segregation is being implemented by most tanners for
reuse of process liquors, process solution recovery, and improved
waste treatment efficiency.
The trend toward implementation of in-plant water conservation and pol-
lution control technologies is likely to expand in the future. As chemical
costs rise and regulatory requirements continue to tighten, tanners are likely
to find that control of pollutants at their source, especially toxic and small
39
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volume organics, is easier and less expensive than their removal from the
entire process waste stream.
1.4.5.2 End-o£-Pipe Pollution Control
Pretreatment
The need for pretreatment is based on the following factors:
Pollutants that are not removed by the publicly owned treatment
works (POTW) must be removed by pretreatment.
Pollutants that may cause treatment system upsets or hazards, collec-
tion system obstructions, or may be hazardous (e.g., sulfides) must be
removed by pretreatment.
NPDES permit control requirements imposed upon the POTW may reflect
stringent water quality criteria.
The load to the POTW secondary treatment units may need to be reduced.
Pollutants must be removed that would render the POTW sludge unfit
for reuse or disposal.
It is estimated that 90% of the tanners (who generate 75% of the leather
tanning and finishing industry's wastewater) discharge to municipal sewer
systems (USEPA 1979). Of that number, 12% provide no pretreatment, 20% pro-
vide coarse screening only, and 68% provide some additional pretreatment.
Many of the leather tanning industry's wastes are of such character or
concentration that they require pretreatment as discussed above. As regula-
tions for pretreatment of the industry's wastes become progressively more
stringent, new tanneries discharging to municipal waste treatment systems will
be required to implement progressively more sophisticated pretreatment measures.
Future pretreatment technology includes practically all of the viable treat-
ment methods that have been examined for the leather tanning industry (see
Section 3.2). It is anticipated that the net effect of these stringent pre-
treatment requirements will be that new tanneries will find it increasingly
attractive to construct and operate direct discharge waste treatment systems
rather than pay for both sophisticated pretreatment and a municipal sewer
charge.
40
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Secondary and Advanced Treatment
Only 10% of existing tanneries have a direct discharge of wastewater.
All of these tanneries provide some form of biological treatment as indicated
below, but current and proposed regulatory requirements undoubtedly will
require a substantial upgrading of the industry's waste treatment technology,
since this generally has been found inadequate.
Current level of waste treatment technology among discharging tanneries
No preliminary treatment 0
Preliminary treatment only 0
Secondary treatment 100
Lagoon or other treatment 72
Activated sludge treatment 28
Physical /Chemical Plant Closed
Source: U.S. Environmental Protection Agency. 1979. Preliminary draft
development document for proposed effluent limitations guidelines
and new source performance standards for the leather tanning and
finishing industry.
Because of the increasingly stringent limitations on industrial effluents, the
specific trends will include a move away from lagoons to more reliable biological
treatment in the form of extended aeration or activated sludge. Upgrading
biological treatment (e.g., powdered activated carbon addition) and filtration
of the final effluent also will become more common.
Solid Waste Handling and Disposal
Large volumes of potentially hazardous solid wastes are generated by the
tanning industry. Treatment and disposal of these hazardous materials have
not generally been handled properly by the industry in the past. For example,
it is estimated that only 6% of the chrome waste generated by the industry in
1974 was disposed in certified hazardous waste disposal sites, while the
remainder was disposed in a variety of landfills, lagoons, pits, ponds, and
trenches. With the adoption of strict national hazardous waste regulations,
41
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the industry will be forced either to reduce its hazardous waste load or find
adequate disposal sites (SCS Engineers 1976).
1.5 POLLUTION CONTROL REGULATIONS
1.5.1 Air Pollution
The leather tanning and finishing industry generally is not considered a
major source of air pollutant emissions. Therefore, there are no national air
pollution performance standards which apply to atmospheric emissions from new
source leather tanning and finishing facilities. In the absence of Federal
emission standards for the industry, air quality impacts are assessed based on
ambient air quality standards, and applicable state and local standards.
National Ambient Air Quality Standards (NAAQS) (40 CFR 50) that specify
the ambient air quality that must be maintained in the United States are shown
in Table 2. Standards designated as primary are those necessary to protect
the public health with an adequate margin of safety, and secondary standards
are those necessary to protect the public welfare from any known or anticipated
adverse effects of air pollution.
A combined Federal/state regulatory program is designed to achieve the
objectives of the Clean Air Act and NAAQS. Each state must adopt and submit
to USEPA a State Implementation Plan (SIP) for maintaining and enforcing
primary and secondary air quality standards in Air Quality Control Regions.
USEPA either approves the state's SIP or proposes and implements an alternate
plan. The SIP's contain emission limits which may vary within a state due to
local factors such as concentrations of industry and population. Because
SIP's have been subject to frequent revision, it is best to verify the status
of the SIP requirements before applying them.
There are two alternate programs requiring preconstruction approval of
industrial air pollution abatement systems. These are the Prevention of
Significant Deterioration (PSD) Program which applies to areas in compliance
with NAAQS and the Nonattainment Program for areas which are in violation of
NAAQS. In 1974, USEPA issued regulations for the PSD Program under the 1970
42
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Table 2.
Emission
Sulfur dioxide
Applicable Federal ambient air quality standards.
Secondary Standard*
Particulate matter
Nitrogen dioxide**
Ozone***
Carbon monoxide
Lead
Primary Standard*
80 yg/m annual
arithmetic mean
3
365 yg/m maximum
24-hour concentration
3
75 yg/m annual
geometric mean
260 yg/m maximum
24-hour concentration
100 yg/m annual
arithmetic mean
240 yg/m maximum
1-hour concentration
3
10 mg/m (9 ppm) maximum
8-hour concentration
3
40 mg/m (35 ppm) maximum
1-hour concentration
2
1.5 yg/m (3-month average)
.,300 yg/m maximum
3-hour concentration
150 yg/m maximum
24-hour concentration
60 yg/m annual geometric mean
as guide in assessing
implementation plans
3
100 yg/m annual
arithmetic mean
3
240 yg/m maximum
1-hour concentration
10 mg/m (9 ppm) maximum
8-hour concentration
3
40 mg/m (35 ppm) maximum
1-hour concentration
3
1.5 yg/m (3-month average)
* For any standard other than annual, the maximum allowable concentration may be exceeded
for the prescribed period once each year.
** Within one year after the date of the enactment of the Clean Air Act Amendments of 1977
(PL 95-95), the USEPA Administrator shall promulgate a national primary ambient air quality
standard for NO, concentrations over a period of not more than 3 hours unless, based on the
criteria issued under Section 108(c), he finds that there is no significant evidence that
such a standard for such a period is requisite to protect public health.
*** For ozone the maximum allowable concentration may be exceeded one day each year, but on that
day it may exceed the maximum hourly concentration more than once.
SOURCE: 40 CFR 50.
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version of the Clean Air Act (Public Law 90-604). These regulations estab-
lished a plan for protecting areas that possess air quality which is cleaner
than the National Ambient Air Quality Standards. The PSD Program components
include:
a classification system for areas of the country meeting NAAQS;
limitations on the increase in concentration of pollutants above
baseline conditions;
Best Available Control Technology requirement for large sources; and
preconstruction review and approval by permit of new source air pol-
lution facility abatement programs.
Under USEPA's PSD regulatory plan, all areas of the nation are designated
as one of three classes. The plan permits specified numerical increments of
air pollution increases from major stationary sources for each class, up to a
level considered to be significant for that area (Table 3). Class I provides
extraordinary protection from air quality deterioration and permits only minor
increases in air pollution levels. Under this concept, virtually any increase
in air pollution in these pristine areas is considered significant. Class II
increments permit increases in air pollution levels that would accompany
well-controlled growth. Class III increments permit increases in air pollu-
tion levels up to the NAAQS.
Sections 160 - 169 were added to the Act by the Clean Air Act Amendments
of 1977. These Amendments adopted the basic concept of the above administra-
tively developed procedure of allowing incremental increases in air pollutants
by class. Through these Amendments, Congress also provided a mechanism to
apply a practical adverse impact test which did not exist in the USEPA regula-
tions previously.
The PSD requirements of 1974 apply only to two pollutants: total sus-
pended particulates (TSP) and sulfur dioxide (S02). However, Section 166
requires USEPA to promulgate PSD regulations by 7 August 1980 which address
nitrogen oxides, hydrocarbons, carbon monoxide, and photochemical oxidants,
including use of increments or other effective control strategies. For these
additional pollutants, states may adopt non-increment control strategies
44
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Table 3. PSD increments: maximum
allowable Increase by class.
Class I Class,II Class Til
Pollutant* (yg/m ) (ye/m ) (yg/m3)
Particulate Matter:
Annual geometric mean 5 19 37
24-hour maximum 10 37 75
Sulfur dioxide:
Annual arithmetic mean 2 20 40
24-hour maximum 5** 91 182
3-hour maximum 25** 512 700
* Other pollutants for which PSD regulations will be promulgated are to
include hydrocarbons, carbon monoxide, photochemical oxidants, and
nitrogen oxides.
** A variance may be allowed to exceed each of these increments on 18 days
per year, subject to limiting 24-hour increments of 36 yg/m for low
terrain and 62 yg/m for high terrain and 3-hour increments of 130
yg/m3 for low terrain and 221 yg/m3 for high terrain. To obtain such a
variance both state and Federal approval is required.
SOURCE: Public Law 95-95. 1977. Clean Air Act Amendments of 1977,
Part C, Subpart 1, Section 163.
45
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which, if taken as a whole, accomplish the purposes of PSD policy set forth in
Section 160.
The 1977 Amendments designate certain Federal lands as Class I, including
all international parks, national memorial parks, and national wilderness
areas which exceed 5,000 acres, and national parks which exceed 6,000 acres.
This constitutes 158 areas which may not be redesignated to another class
through state or administrative action. The remaining areas of the country
have been initially designated Class II. Within this Class II category,
certain Federal lands over 10,000 acres (national primitive areas, national
wild and scenic rivers, national wildlife refuges, national seashores and
lakeshores, and new national park and wilderness areas) established after 7
August 1977 will be Class II "floor areas" ineligible for redesignation to
Class III.
The general redesignation responsibility lies with the states. The
Federal land manager has an advisory role for redesignation to the appropriate
state and to Congress. Redesignation by Congress will require the normal
legislative process of committee hearings, floor debate, and action. In order
for a state to redesignate areas, the detailed process (outlined in Section
164(b) of the 1977 Amendments) would include an analysis of the health, environ-
mental, economic, social, and energy effects of the proposed redesignation
which would be discussed at a public hearing.
In theory, all new source tanneries would be subject to complete PSD
review if they obtain their air quality permits after March 1, 1978, commence
construction after March 19, 1978, or have potential (before treatment) emis-
sions in excess of 250 tons/year of certain pollutants. Full PSD review
requires analysis of effect on air quality increments, application of Best
Available Technology, and a comprehensive monitoring program. In practice,
however, small sources of the designated air pollutants (less than 50 tons/
year, 1000 Ibs/day, or 100 Ibs/hour after abatement) are required only to
apply for and obtain a preconstruction permit unless they would impact a Class
I area. Therefore most new source tanneries should not have to go through the
whole PSD review. A similar type of exemption exists for small sources (less
than 50 tons/year after abatement) in non-attainment areas unless the pollutant
46
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emitted is the cause for non-attainment. In that case, a permit would be
issued only after controls (offsets) were obtained by the new source from
existing emission sources sufficient to effect a net reduction of the non-
attainment pollutant.
1.5.2 Water Pollution
The Federal Water Pollution Control Act (FWPCA) Amendments of 1972 estab-
lished two major, interrelated procedures for controlling industrial effluents
from new sources, and specifically included tanneries and related facilities
in the list of affected source categories. The principal mechanism for dis-
charge regulation is the National Pollutant Discharge Elimination System
(NPDES) permit. The other provision is the New Source Performance Standard
(NSPS). The Clean Water Act of 1977 (P.L. 95-217), which amends P.L. 92-500,
made no change in these basic procedures.
The NPDES permit, authorized by Section 402 of FWPCA, prescribes the
conditions under which effluents may be discharged to surface waters. Issuance
of a New Source NPDES permit is considered a significant Federal action and is
subject to the requirements of the National Environmental Policy Act (NEPA).
The conditions applicable to new or expanded tanneries will be in accordance
with NSPS, adopted by USEPA pursuant to Section 306, and pretreatment stan-
dards promulgated to implement Section 307(b). Different standards will be
applicable nationwide depending on the subcategory of tannery under considera-
tion. Stricter effluent limitations may be applied on a site-specific basis
if required to achieve water quality standards.
On 9 April 1974, USEPA published regulations specifying guidelines and
New Source Performance Standards for the Leather Tanning and Finishing Point
Source Category which were to become effective on 4 June 1974 (40 CFR 425: 39
FR 15696). However, these regulations were remanded and USEPA is in the
process of developing new regulations for the industry which have been pro-
posed on 2 July 1979.
The basis for New Source Performance Standards (NSPS) under Section 306
of the Act is the best available demonstrated control technology (BADCT). New
47
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plants have the opportunity to design the best and most efficient leather
tanning processes and wastewater treatment technologies and, therefore,
Congress directed USEPA to consider the best demonstrated process changes,
in-plant controls, and end-of-pipe treatment technologies which reduce
pollution to the maximum extent feasible. The effluent limitations estab-
lished for new sources in each of the seven subcategories of the industry are
shown in Table 4. It might be noted that since removal of toxic pollutants is
of major concern in the leather tanning and finishing industry, the effluent
limitations for BAT (Best Available Technology Economically Achievable), which
must be attained by all existing tanneries by 1 July 1984, are the same as
NSPS.
New sources that discharge wastewater to publicly owned treatment works
(POTW) are required to comply with USEPA's pretreatment regulations, issued in
the 26 June 1978, Federal Register (40 CFR 403). These regulations stipulate
that certain POTW's, categorized by size and influent characteristics, develop
POTW Pretreatment Programs. These programs are intended to prevent the intro-
duction of pollutants by industrial users that would interfere with the opera-
tion of treatment works, would pass through treatment works, or would adversely
affect opportunities to recycle and reclaim wastewaters and sludges.
Regardless of specific limitations required by the Pretreatment Programs,
the regulations (Section 403.5) state that the following may not be introduced
into a POTW:
pollutants which create a fire or explosion hazard in the POTW;
pollutants which will cause corrosive structural damage to the
POTW, but in no case discharges with pH lower than 5.0, unless the
works is specifically designed to accomodate such discharges;
solid or viscous pollutants in amounts which cause obstruction
to the flow in sewers, or other interference with the operation of the
POTW; and
any pollutant, including oxygen-demanding pollutants, released in
a discharge of such volume or strength as to cause interference in the
POTW.
In addition, there is a restriction on thermal discharges that becomes effec-
tive in June 1981.
48
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Table 4. Proposed new source performance standards (NSPS) and pretreatment standards for new
sources (PSNS) for the seven subcategories of the leather tanning and finishing Industry.
Subcategory
Hair Pulp,
Chrome Tan,
Retan - Wet
Finish
2
Hair Save,
Chrome Tan,
Retan - Wet
Finish
Hair Save,
Non- Chrome
Tan, Retan -
Wet Finish
4
Retan - Wet
Finish
No Beamhouse
BOD.
Maximum pollutant discharge for any one day,
kg/1000 Kg (lb/1000 lb-1 of raw material
Oil & Total
COD TSS Grease Chrome TKM Ammonia Phenol Sulfide pH
2.1 9.5 2.5 0.91 0.053 2.3 0.77 0.015 0.0 6-9
BOD
Average for thirty consecutive days not to be exceeded,
ky/1000 kn Clb/1000 Ib) of raw material
Oil & Total
1 COD TSS Grease Chrome TKN Ammonia Phenol Sulfide pH
0.61 5.8 0.70 0.26 0.015 0.66 0.22 0.0043 0.0 6-9
2.3 10.0 2.6 1.0 0.053 2.4 0.81 0.016 0.0 6-9 0.65 6.2 0.74 0.28 0.015 0.69 0.23 0.0046 0.0 6-9
1.6 7.3 1.9 0.70 0.039 1.8 0.60 0.012 0.0 6-9 0.47 4.5 0.54 0.20 0.0110.51 0.17 0.0034 0.0 6-9
0.81 3.5 0.91 0.35 0.018 0.84 0.28 0.0056 0.0 6-9 0.23 2.2 0.26 0.10 0.005 0.24 0.081 0.0016 0.0 6-9
1.4 6.2 1.6 0.60 0.034 1.5 0.49 0.010 0.0 6-9 0.40 3.8 0.46 0.17 0.00960.43 0.14 0.0029 0.0 6-9
6
Through-
the-Blue
Shearling
1.5 6.8 1.8 0.67 0.035 1.6 0.56 0.011 0.0 6-9 0.44 4.2 0.50 0.19 0.0100.47 0.16 0.0031 0.0 6-9
6.7 29.8 7.7 2.9 0.16 7.4 2.4 0.049 0.0 6-9 1.9 18.0 2.2 0.83 0.0462.1 0.69 0.014 0.0 6-9
Source: U. S. Environmental Protection Agency. 1979. Preliminary draft development docun,Cnt for proposed effluent limitations guidelines and new
source performance standards for the leather tanning and finishing industry.
-------
Among the pollutants in the raw waste from tanneries, BOD , TSS, oil and
grease, total chromium, sulfide, ammonia, and other toxic priority pollutants
are present in sufficient concentrations to represent potential problems of
pollutant pass-through or sludge disposal at the POTW. Due to this, Pretreat-
ment Standards for New Sources (PSNS) have been developed in the development
document which will require removal of toxics and will regulate all of the
same pollutants as covered by BAT and NSPS. Since the level of technology
required to achieve PSNS and NSPS will be the same, it is anticipated that new
tanneries will be encouraged to treat their own wastes subject to NSPS and
obtain an NPDES permit for discharge directly to surface waters. The PSNS
concentration limitations for all subcategories are listed below and the pro-
duction-based mass limitations for each subcategory are identical to those
listed in Table 4.
PSNS Concentration Limits Proposed for Leather Tanning (All Subcategories)
BOD
COD
TSS
Oil and Grease
Total Chromium
TKN
Ammonia
Phenol
Sulfide
pH Within
Maximum
any one day
(mg/1)
70
320
90
35
2.0
70
35
1.0
0.0
the range of 6.0 to 9.0 at
Average for
consecutive
(mg/1)
20
195
25
10
0.5
20
10
0.25
all times.
30
days
SOURCE: U.S. Environmental Protection Agency. 1979. Preliminary draft
development document for proposed effluent limitations guidelines
and new source performance standards for the leather tanning and
finishing industry.
Since new sources discharging to POTW's do not require NPDES permits, they are
not subject to NEPA under Section 511(c)(1) of the Federal Water Pollution
Control Act, as amended by the Clean Water Act of 1977.
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NPDES permits also impose special conditions beyond the effluent limi-
tations stipulated, such as schedules of compliance and treatment standards.
Once tanneries are constructed in conformance with all applicable standards of
performance, however, they are relieved by Section 306(d) from meeting any
more stringent standards of performance for 10 years or during the period of
depreciation or amortization, whichever ends first. This guarantee does not
extend, however, to toxic effluent standards adopted under Section 307(a),
which can be added to the NPDES permit when they are promulgated. USEPA
proposes to control the discharge of toxics from the leather tanning and
finishing industry by regulating two toxic pollutants used as indicator pol-
lutants: phenol and chromium. USEPA has found that the treatment technology
required to remove phenol and chromium as well as conventional and non-conven-
tional pollutants also effectively controls the other priority toxic pollutants
found in tannery waste. Therefore, the effectiveness of toxic pollutant
control can be assessed by the monitoring of these indicator pollutants without
the expense and technical difficulties with analysis for many of the complex
organic toxic pollutants.
As encouraged by P.L. 92-500, many states have qualified to administer
their own NPDES permit programs. The major difference in obtaining an NPDES
permit through approved state programs rather than the Federal NPDES permit
program is that the Act does not extend the NEPA environmental impact assess-
ment requirements to state programs. However, over 50 percent of the states
have enacted NEPA-type legislation and it is likely that new tanneries or
major expansions of existing tanneries will come under increased environmental
review. Because the scope of the implementing regulations varies considerably,
current information on prevailing requirements should be obtained early in the
planning process from the permitting authority in the appropriate jurisdiction.
1.5.2.1 Best Available Technology (BAT)
The effluent limitations which must be achieved by July 1, 1984 for
existing facilities are not based on an average of the best performance within
an industrial category. Instead, they are based on the very best control and
treatment technology employed by a specific point source within the industrial
category or subcategory, or by another industry whose technology is readily
51
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transferable. The analysis of control measures and practices to eliminate the
discharge of pollutants also must consider the cost of such measures. BAT
emphasizes in-g>rocess controls as well as end-of-pipe treatment improvements.
Other considerations include: manufacturing processes; age and size of facil-
ities; location of manufacturing facilities; process changes; engineering
aspects of control technologies; cost of technology to achieve control levels;
and non-water quality environmental impacts, including energy.
BAT technology uses BPT technology as a basis for further improvements.
This includes primary coagulation-sedimentation and high solids extended
aeration-activated sludge system with nitrification. Additional technologies
for BAT include:
In-Plant Control and Preliminary Treatment
Water conservation and reuse to reduce flow
Stream segregation for preliminary treatment
Ammonia substitution in deliming
Chrome recovery and reuse
Sulfide liquor reuse followed by catalytic oxidation of
residual sulfide
Fine screening of segregated streams
Flue gas carbonation and sedimentation for beamhouse
wastewaters
End-of-Pipe Treatment
Addition of powdered activated carbon (PAC)
to upgrade extended aeration-activated sludge
Multimedia filtration
Granular activated carbon columns
Physical/chemical treatment (Chappel Process)
The anticipated performance associated with these technologies is in-
cluded in the Development Document for this industry (USEPA 1979).
1.5.2.2 New Source Performance Standards (NSPS)
The basis for NSPS is the best available demonstrated control technology
(BADCT). New plants have the opportunity to design the best and most efficient
leather tanning processes and wastewater treatment technologies. A major
difference between NSPS and BAT is that the evaluation of NSPS does not con-
sider cost. For the Leather Tanning and Finishing Industry, the effluent
limits for NSPS are identical to BAT.
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1.5.2.3 Regulated Pollutants
The BAT and NSPS effluent limitations proposed for the leather tanning
industry focus on three major groups of pollutants (USEPA 1979):
Indicator pollutants. The difficulties of toxic pollutant analyses
have prompted USEPA to propose a new method of regulating selected
toxic pollutants. Historical data and inexpensive analytical methods
are limited for certain toxic pollutants. Therefore, USEPA is pro-
posing numerical limitations on "indicator" pollutants; these include
BOD , COD, TSS, oil and grease, TKN, ammonia, sulfides, total chromium,
and5total phenol. The data available to USEPA revealed that when
these indicator pollutants were controlled, the concentrations of
toxic pollutants were significantly lower than when indicator pol-
lutants were present in high concentrations.
Non-toxic, non-conventional pollutants. The non-toxic non-conventional
pollutants limited by BAT and NSPS include total Kjeldahl nitrogen^
(TKN), ammonia, and sulfide. These pollutants serve as "indicator"
pollutants for the removal of toxic pollutants. These pollutants are
subject to numerical limitations expressed in Ibs per 1000 Ibs of raw
material.
« Toxic pollutants. The toxic pollutants expressly controlled for
direct dischargers in each subcategory are phenol and chromium, which
are subject to numerical limitations expressed in Ibs per 1000 Ibs of
raw material. Since USEPA has adopted the control of "indicator"
pollutants as the basis for controlling toxic pollutants other than
chromium and phenol, no effluent limitations are recommended for any
toxic pollutants other than chromium and phenol. At the same time,
USEPA also is considering the possibility of establishing numerical
limitations (either in concentration or mass units) for the following
toxic pollutants: phenol (by GC/MS methods), 100 yg/1; 2,4,6-trichloro-
phenol, 50 yg/1; pentachlorophenol, 25 yg/1; lead, 250 yg/1; zinc, 250
yg/1; cyanide, 500 yg/1.
1.5.2.4 Pretreatment Standards for New Sources (PSNS)
The effluent limitations that must be achieved by new sources in the
leather tanning and finishing industry that discharge into a POTW are termed
pretreatment standards for new sources (PSNS). Section 307(b) of the Act
requires USEPA to promulgate pretreatment standards to prevent the discharge
of pollutants which pass through, interfere with, or are otherwise incompatible
with the operation of publicly owned treatment works (POTW). The Act also
requires pretreatment for pollutants, such as heavy metals, that limit POTW
sludge management alternatives, including the beneficial use of sludges on
53
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agricultural lands. The pretreatment standards are to be technology-based,
analogous to the best available technology for removal of toxic pollutants.
The considerations in developing PSNS are the same as those enumerated for BAT
(Section 1.5.2.1).
The candidate control technologies for meeting PSNS include (USEPA 1979):
Water conservation and reuse to reduce flow.
Stream segregation for preliminary treatment.
Ammonia substitution in deliming.
Chrome recovery and reuse.
Sulfide liquor reuse followed by catalytic oxidation of residual
sulfide.
Fine screening of segregated streams.
Flue gas carbonation and sedimentation for beamhouse
wastewaters.
Equalization of combined streams followed by primary
coagulation-sedimentation.
Activated sludge (high solids extended aeration with
nitrification).
Powdered activated carbon (PAC) addition to upgrade extended
aeration-activated sludge.
Media filtration.
Physical/chemical treatment (Chappel Process).
These PSNS technologies essentially are identical to BAT because pass
through of toxics in the POTW and presence of toxics in the POTW sludges may
still be of concern. This requirement will encourage new facilities to treat
wastewaters subject to NSPS for direct discharge.
1.5.2.5 Best Conventional Pollutant Control Technology (BCT)
BCT was established for existing industrial point sources that discharge
conventional pollutants. BCT is not an additional limitation but replaced BAT
for the control of conventional pollutants. However, BAT still applies for
all nonconventional and toxic pollutants. The limitations established by BCT
must consider the cost reasonableness of conventional pollutant reduction by
the industry versus reduction by the POTW. Conventional pollutants have been
defined to include BOD, TSS, fecal coliform, and pH, with COD, oil and grease,
and phosphorus also proposed by USEPA as conventional pollutants (USEPA 1979).
For this industry, USEPA is proposing that the conventional "indicator" pollut-
ants (i.e., BOD, COD, TSS, oil and grease) be considered instead as toxic
54
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pollutants and therefore be regulated by BAT so that the cost reasonableness
test would not apply. This definition would be applicable unless the industry
can prove that the toxics, for which these conventional pollutants serve as
indicators, are not present in the wastewater.
The BCT cost test was applied to proposed removal of conventional pollut-
ants associated with BAT technology required for toxic pollutant control
(USEPA 1979). The conclusion from applying this test was that effluent limits
for conventional pollutants using BAT technology also meet the BCT cost test.
Therefore, the BCT effluent limits for conventional pollutants (i.e., BOD,
TSS, pH, COD, oil and grease) and associated control technology are the same
as those determined for the BAT regulation (USEPA 1979).
1.5.3. Solid Wastes
A major part of tannery waste treatment involves the handling and disposal
of the semi-solid sludges obtained from liquid treatment processes. The most
predominant methods of ultimate disposal of tannery waste sludges include
sludge lagoons, landfills, dumps, and spreading on the land (USEPA 1979).
Some attempts have been made to dewater sludges prior to ultimate dis-
posal, with varying success. The three principal dewatering techniques in-
clude centrifugation, vacuum filtration, and pressure filtration. Centrifuges
have appeared to meet with less success than vacuum filters or pressure filters.
Reducing the moisture content of sludge by spreading on drying beds also has
been successful in some areas. This is particularly attractive to smaller
facilities where land area is available (USEPA 1979).
Conditioning and stabilizing a mixed domestic and tannery sludge using
heat treatment processes has been employed where about 80% of the waste flow
is tannery waste. Such heat treatment or similar sludge destruction process
provides a stable end product from a biological standpoint. These stabilized
sludges can then be incorporated into a landfill or spread on the land. One
of the principal difficulties with tannery waste is the chromium content in
sludges and the potential toxic impact of this metal on the environment. In
testing a heat-treated alkaline sludge, it has been indicated that some of the
55
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trivalent chromium may be oxidized to the hexavalent form. Apparently, the
trivalent chromium is converted through the high temperature, high pressure,
high pH, and the oxidizing environment of the heat treatment process (USEPA
1979).
Chromium reuse reduces the levels of chromium in the sludge. Disposal of
sludge containing these lower residual quantities of chromium in a sanitary
landfill will minimize any environmental problems (DSEPA 1979).
Prior to dewatering in mechanical equipment, sludge is normally con-
ditioned by use of ferric salts, lime, 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 such as centrifuges generally can
produce a cake containing 15 to 30% dry solids. Plate and frame filter presses
have been found to produce cakes of 40 to 50% dry solids. The higher capital
cost of filter presses may be quickly offset by lower hauling and disposal
costs where landfills are located great distances from the tannery or the POTW
(USEPA 1979).
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 of chromium or other constituents on
plants, ground water, and surface water supplies. Lagoons for dewatering have
some limited uses. In humid areas where rainfall approximates or exceeds
evaporation, such application is not completely satisfactory. Use of lagoons,
drying beds, landfills, and landspreading all require key attention to the
environmental impacts. Particularly important is the leaching of potential
toxic or organic materials to the groundwater supplies or surface waters.
Proper controls must be taken to ensure that these conditions will not develop
(USEPA 1979).
Under the Resource Conservation and Recovery Act (RCRA) passed by Con-
gress in 1976, solid wastes are divided into two broad categories for the
purpose of regulation, namely hazardous wastes and other solid wastes. Final
56
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regulations for implementation of this statute have not been promulgated, but
they have been proposed (FR 58946-59028, 18 December 1978). Generally this
program will standardize the criteria for construction of landfills for non-
hazardous solid wastes and establish a stringent permit program and manifest
system that will account for hazardous wastes from generation to final dis-
posal.
Under the proposed regulations, wastes may be judged hazardous by four
criteria: ignitability, corrosiveness, reactivity, and toxicity (40 CFR
250.13, proposed). Because the leather tanning and finishing industry gener-
ates large quantities of corrosive, toxic, and reactive wastes, four waste
streams have been defined as hazardous (40 CFR 250.14, proposed):
wastewater treatment sludge from chrome tannery and beamhouse/tanhouse
operations;
wastewater treatment screenings from sheepskin tannery, split tan-
nery, and retan/finish operations;
trimmings and shavings from leather tanning and finishing, chrome
tannery, split tannery, beamhouse/tanhouse, and retan/finish opera-
tions; and
wastewater treatment sludge from unhairing operations.
In their present form the proposed regulations will require that every load of
hazardous waste be tracked at the tannery through the hands of each trans-
porter and then to final disposal at an approved disposal site. The proposed
regulations also require chemical analysis of the wastes, use of appropriate
containers, submission of reports, and monitoring and inspection of disposal
sites. The design as well as the operation of hazardous wastes disposal sites
will be regulated also.
In general, recovery or disposal of non-hazardous tannery wastes in an
approved sanitary landfill will be required under a state regulatory program,
with new open dumps prohibited. Existing state solid and hazardous waste
disposal regulations will be superseded unless they meet or exceed the Federal
standards.
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2.0 IMPACT IDENTIFICATION
The following discussions will identify the major pollutant sources for
the leather tanning industry. The pollutant impact will be discussed for each
of the impact media.
2.1 AIR
Emissions have not been found to be a major environmental impact of the
leather tanning industry, and there are limited data to quantify the genera-
tion of these pollutants. Estimates of the quantity of buffing dust and
finishing solvents generated by some subcategories are available in the
hazardous waste assessment for the industry (SCS Engineers 1976). These are
summarized in Table 5. The established and potential sources for emissions
that should be addressed by a new source tannery would be expected to include:
Beamhouse operation - sulfides from the unhairing process.
Tanning operation - solvents from the degreasing recovery system.
Finishing operation - dust from the buffing operation and solvents
from spray finishes.
Auxiliary support equipment - emissions from boilers and pollution
control equipment.
Odor potential also should be identified in terms of possible sources (e.g.,
sulfides from unhairing) and their impacts on surrounding areas. Due to the
large quantities of putrescible material handled by a tannery, odor problems
also may develop if scraps, screenings, sludge, and similar materials are not:
quickly removed and disposed.
2.2 WATER
The following wastewater parameters are of major pollutional significance
for the leather tanning and finishing industry (USEPA 1979):
58
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Table 5. Emissions from the finishing operation
of various subcategories of the leather
tanning and finishing industry.
Subcategory Buffing Dust(l) Finishing Solvents
1. Hair pulp/chrome 25 450
tan/retan-
wet finish
3. Hair save/non-chrome 90
tan/retan-wet finish
4. Retan-wet finish 25 450
6. Unhair/chrome tan
(through-the-blue)
* Sheepskin Tannery 50
* Split Tannery 180
* Leather Finisher 10 450
* Subcategory used for hazardous waste assessment but not
designated for effluent guidelines.
(1) All estimates appear as dry lbs/1000 equivalent hides where
equivalent hide weighs approximately 50 Ibs.
SOURCE: SCS Engineers. 1976. Assessment of industrial hazardous
waste practices, leather tanning and finishing industry.
59
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Biochemical Oxygen Demand
Chemical Oxygen Demand
Total Chromium
Oil and Grease
Sulfide
Total Suspended Solids (TSS)
Nitrogen Content (Ammonia Nitrogen and
Total Kjeldahl Nitrogen)
Phenols
pH and Alkalinity
Wastewater parameters of minor significance are:
Total Dissolved Solids
Chlorides
Total Volatile Solids
Nitrates and Nitrites
Fecal Coliforms
Priority pollutants of significance are:
Organics
Volatile
Semi-Volatile
Basic/Neutral Fraction
Acidic Fraction
Inorganics
Cyanide
Metals
Pesticides
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2.2.1 Wastewater Generation and Characteristics
Wastewater streams generated by the leather tanning and finishing in-
dustry are highly variable and process dependent. In view of the numerous
modifications that now exist to the basic processes described in Section 1.2,
the specific nature of the wastewater for the New Source tannery must be
carefully documented and specifically related to the processes anticipated
under actual operating conditions.
Process waste stream characterization for the industry should address the
following waste materials and pollutant indicators.
Beamhouse Operation
Hair High pH
Manure Sulfides
Protein Grease
Salt Nitrogen
Flesh
Hide trimmings
Tanhouse Operation
Dyes (complex organics) Low pH
Degraded proteins High chrome
Salt Ammonia
Dissolved organics Color
Retan, color, and fatliquoring operation wastewater would be similar in nature
to tanhouse operation wastewaters, and should be reflected in wastewater
estimates by a New Source tannery applicant. Finishing operations are usually
dry, but liquid wastes could be generated by dust control equipment (e.g., wet
scrubbers).
The industry's wastewaters are characterized by the following major
pollutants:
, Biochemical oxygen demand (BOD). In most leather tannery wastewaters,
the BOD derives principally from organic material, such as dissolved
or "pulped" hair and other extraneous hide substances, and from ammonia
which is derived from residual bating chemicals and from hydrolytic
deamination of proteinaceous hair and hide substance.
61
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The BOD a waste exerts will reduce the dissolved oxygen resources of a
body of water. It is possible to reach conditions which totally
exhaust the dissolved oxygen in the water resulting in anaerobic
conditions and the production of undesirable gases such as hydrogen
sulfide and methane. The reduction of dissolved oxygen can be detri-
mental to fish populations, fish growth rate, and organisms used as
fish food. A total lack of oxygen can result in the death of all
aerobic aquatic inhabitants in the affected area. Water with a high
BOD indicates the presence of decomposing organic matter and asso-
ciated increased bacterial concentrations that degrade its quality and
potential uses. High BOD increases algal concentrations and blooms;
these result from decaying organic matter and form the basis of algal
populations.
Chemical oxygen demand. Tannery wastewaters contribute to high COD
concentrations due to extraneous hide substance, manure, complex
organic and inorganic process chemicals, dyes, and vegetable tannins.
The COD test measures pollutants more resistant to biological oxida-
tion than the BOD test includes. These pollutants are of increasing
interest and concern because of the continuing oxygen demand they
exert and their potential health effects. Some pollutants measured by
the COD test have been found to have carcinogenic, mutagenic, and
similar adverse effects, either singly or in combination. The long
life of these pollutants in the environment, the difficulty in re-
moving them by commonly used systems of water purification, and the
potential for chlorination converting them into even more hazardous
materials magnifies their significance.
Total suspended solids (TSS) . The washing, unhairing, shearing, and
finishing operations are the primary sources.
Suspended solids include both organic and inorganic materials. The
inorganic compounds include sand, silt, and clay. The organic fraction
includes such materials as grease, oil, and animal and vegetable waste
products. These solids may settle out rapidly and bottom deposits are
often a mixture of both organic and inorganic solids. Solids may be
suspended in water for a time and then settle to the bed of the stream
or lake. They may be inert, slowly biodegradable materials, or rapidly
decomposable substances. While in suspension they increase the turbidity
of the water, reduce light penetration, and impair the photosynthetic
activity of aquatic plants.
Aside from any toxic effect attributable to substances leached out by
water, suspended solids may kill fish and shellfish by causing abrasive
injuries, by clogging gills and respiratory passages, screening out
light, and by promoting and maintaining the development of noxious
conditions through oxygen depletion. Suspended solids also reduce the
recreational value of the water.
Some of the solids generated within a tannery, such as hair or scraps,
are removed readily by fine screening; other solids settle readily in
clarifiers. When not removed, these solids can foul or plug pipes,
pumps, and other mechanical equipment.
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Oil and Grease (0 & G) . This is generated most significantly when
pigskins and sheepskins are processed. Other significant sources are
from the soaking, fleshing, and fatliquoring processes.
Even in small quantities, oil and grease cause troublesome taste and
odor problems. They produce scum lines on water treatment basin walls
and other containers and adversely affect fish and waterfowl. Oil
emulsions may adhere to the gills of fish, causing suffocation, and
may taint the flesh of fish microorganisms that were exposed to waste
oil. Oil deposits in the bottom sediments of water can serve to
inhibit normal benthic growth. Oil and grease also exert an oxygen
demand in the natural environment.
Oil and grease levels which are toxic to aquatic organisms vary greatly,
depending on the type of pollutant and the species susceptibility. In
addition, the presence of oil in water can increase the toxicity of
other substances discharged into the receiving bodies of water.
Chrome. Chrome is generated from the chrome tanning process and
subsequent wet processing steps. Trivalent chrome is the only form
normally present, since hexavalent chrome use in tanneries is prac-
tically non-existent.
Chromium can produce lung tumors when inhaled and induces skin sensi-
tizations. Large doses of chromates have corrosive effects on the
intestinal tract and can cause inflammation of the kidneys. A minimum
level for the chromate ion that has no effect on man has not been
determined. The toxicity of chromium salts to fish and other aquatic
life varies widely with the species, temperature, pH, valence of the
chromium, and synergistic or antagonistic effects, especially those of
hard water. Fish appear to be relatively tolerant of chromium, but
some aquatic invertebrates are quite sensitive,
Sulfide. This is introduced in the form of sharpeners in the un-
hairing process.
A significant portion of alkaline sulfides contained in tannery
wastewater converts to hydrogen sulfide at a pH below 8.0, resulting
in the release of this gas to the atmosphere. This gas is odorous,
and can damage property through paint discoloration. In sewers,
hydrogen sulfide can oxidize to sulfuric acid, causing "crown" corro-
sion and corrosion of equipment in POTW. At higher concentrations
this gas can be lethal to operation and maintenance personnel in
sewers, and at POTW headworks, primary treatment, and sludge de-
watering facilities. This is particularly significant as a hazard in
sewer maintenance. Careless mixing of acid and sulfide containing
alkaline streams can also be catastrophic within both tanneries and
sewers. Sulfide compounds are used extensively in the beamhouse for
the unhairing process, and thus are found in tannery effluent.
Nitrogen (total Kjeldahl nitrogen (TKN) and ammonia). Both nitrogen
forms are generated in conjunction with the unhairing and bating
processes.
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Total Kjeldahl nitrogen is ammonia nitrogen plus organic nitrogen in
wastewater. Organic nitrogen is derived primarily from dissolved or
pulped proteinaceous hair removed from hides. Hydrolysis of this
organic nitrogen during biological treatment yields another signif-
icant source of ammonia. Hence, TKN measures the major nitrogen
impact upon a waste treatment plant or stream and is an important
measure of the potential environmental impact of tannery wastewater.
Evidence exists that ammonia exerts a toxic effect on all aquatic life
depending upon the pH, dissolved oxygen level, and the total ammonia
concentration in the water. A significant oxygen demand can result
from the microbial oxidation of ammonia.
Phenol. Phenol and substituted phenolics are generated mainly in
conjunction with coloring of tanned hides. These sources may include
biocides (e.g., pentachlorophenol; 2,4,5 trichlorophenol), synthetic
and natural vegetable tannins, carriers for dyes, and a number of
other adverse sources all of which contribute to significant levels of
phenol in raw wastewaters.
Chlorination of such waters can produce odoriferous and objectionable
tasting chlorophenols which may include o-chlorophenol, p-chlorophenol,
2,6-dichlorophenol, and 2,4-dichlorophenol. Phenolic compounds may
adversely affect fish by a direct toxic action or by imparting a taste
to the fish flesh. The toxicity of phenol towards fish increases as
the dissolved oxygen level is diminished, as the temperature is raised,
and as the hardness is lessened. Phenol appears to act as a nerve
poison, causing too much blood to get to the gills and to the heart
cavity; it appears to have a toxic threshold of 0.1-15 mg/1.
The human ingestion of a concentrated phenol solution results in
severe pain, renal irritation, shock, and possibly death. A total
dose of 1.5 grams may be fatal. Phenols can be metabolized and
oxidized in waste treatment facilities containing organisms acclimated
to the phenol concentration in the wastes.
pH and Alkalinity. Due to the use of strong bases and acids in the
unhairing and tanning processes respectively, wide pH variations and
high alkalinities (from the beamhouse) can be expected in tannery
waste.
Leather tanning and finishing plants which include beamhouse (unhairing)
operations will invariably have excess alkalinity due to the presence
of large quantities of lime. This alkalinity provides buffering
capacity to prevent unacceptably low pH, and enhances precipitation of
many heavy metals, such as trivalent chromium, found in tannery and
other industrial wastewaters.
Knowledge of the pH of water or wastewater aids in determining measures
necessary for corrosion control, pollution control, and disinfection.
To protect POTW from corrosion, pH levels of wastewaters entering the
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sewerage system must remain above 5. Waters with a pH below 6.0
corrode waterworks structures, distribution lines, and household
plumbing fixtures. This corrosion can add such constituents to
drinking water as iron, copper, zinc, cadmium, and lead. Low pH
waters not only tend to dissolve metals from structures and fixtures
but also tend to redissolve or leach metals from sludges and bottom
sediments. The hydrogen ion concentration also can affect the taste
of water; at a low pH, water tastes "sour."
Extremes of pH or rapid pH changes can stress or kill aquatic life.
Even moderate changes from "acceptable" pH limits can harm some
species. Changes in water pH increase the relative toxicity to
aquatic life of materials. Metalocyanide complexes can increase a
thousand-fold in toxicity with a drop of 1.5 pH units. The toxicity
of ammonia similarly is a function of pH. The bactericidal effect of
chlorine in most cases lessens as the pH increases, and it is eco-
nomically advantageous to keep the pH close to 7.
A comprehensive survey of wastewater generation for the entire industry
has been conducted in conjunction with the establishment of effluent limita-
tions for the NPDES permit program (USEPA 1979). A summary of raw water data
for each subcategory of the industry is included in Table 6. Additional data
are available in the Development Document for the industry (USEPA 1979).
2.2.2 Priority Pollutant Generation in Wastewater Streams
Effective control of those pollutants that represent the greatest danger
to aquatic ecosystems and to man is basic to environmental protection. The
most significant pollutants and pollutant parameters detected in the waste-
waters in terms of occurrence and concentration for the industry in general
include: the conventional and proposed conventional pollutants BOD,., TSS, pH,
COD, and oil and grease; and the nonconventional pollutants, ammonia, total
Kjeldahl nitrogen (TKN), and sulfide. The following priority pollutants have
been found at more than two plants and above the nominal limits of detection
(USEPA 1979):
2,4,5-trichlorophenol
chloroform
1,2-dichlorobenzene
1,4-dichlorobenzene
ethylbenzene
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Table 6. Raw waste loads by subcategory.
Sjjbcategory
Pollutants -
Flow - (gal/lb)
BOD5
TSS
COD
Oil and Grease
Total Cr
Sulfide
TKN
Ammonia
Phenol
*c.anme>'t-ric mean o
_ 1
4.6
1620/62.3
2410/92.3
4640/178
401/15.4
76/2.9
64/2.47
328/12.6
104/3.98
1.0/0.038
f collected d
2
5.5
983/45.1
1930/88.3
2610/120
244/11.2
31/1.4
20/0.92
137/6.3
90/4.15
2.2/0.1
ata» reporte*
3
4.0
1180/39.2
1680/56.1
5120/171
339/11.3
11/0.38
68/2.26
202/6.75
90/3.0
1.2/0.04
i as: (mg/1) /
4
1.7
776/11.0
818/11.6
3120/44.2
272/3.85
53/0.75
1.1/0.015
212/3.0
109/1.55
3.9/0.055
(Ib./lOOO Ib.)
5
3.3
1000/27.6
632/17.4
1700/46.8
343/9.45
68/1.86
3.2/0.089
168/4.63
36/1.00
1.2/0.034
raw material
6
2.5
2460/51.3
3870/80.7
6400/133
556/11.6
104/2.16
118/2.46
460/9.6
120/2.5
1.5/0.03
7
18.9
349/40.5
388/45
914/106
144/16.7
12.9/1.5
0.2/0.08
53/6.2
13/1.54
0.3/0.03
Subcategory 1 - Hair Pulp/Chrome Tan/Retan-Wet Finish
Subcategory 2 - Hair Save/Chrome Tan/Retan-Wet Finish
Subcategory 3 - Hair Save/Nonchrome Tan/Retan-Wet Finish
Subcategory 4 - Retan-Wet Finish
Subcategory 5 - No Beamhouse
Subcategory 6 - Through-the-Blue
Subcategory 7 - Shearlings
SOURCE: U.S. Environmental Protection Agency. 1979. Preliminary draft development document for proposed
effluent limitations guidelines and new source performance standards for the leather tanning and
finishing point source category.
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methylene chloride (dichloromethane)
naphthalene
pe nt achlo r op henol
phenol
bis (2-ethylhexyl) phthalate
toluene
chromium
copper
cyanide
lead
nickel
zinc
Of the 129 priority pollutants identified by USEPA, 46 have been identi-
fied in the raw wastewaters of the leather tanning and finishing industry.
The number of priority pollutants is higher when beamhouse operations using
the hair pulp process are present.
Several toxic pollutants are major ingredients of chemicals used in
tannery processes; several others are used as solvents and dye carriers. Many
occur as minor or trace components in other chemicals. The most heavily used
toxic pollutant in leather tanning is chromium, but there are several others
used in significant amounts. These include:
syntans based on naphthalene and phenol;
4-nitrophenol (a biocide, as well as a waterproofing agent);
pentachlorophenol (a preservative and biocide);
hexachloroethane, ethylbenzene and toluene solvents;
2,4,6-trichlorophenol (a biocide); and
biocides based on cresol.
The inorganic toxic pollutants (including zinc, lead, nickel, and copper)
typically originate in organometallic dyes. Cyanide also is found in dyes,
and probably in natural tannins as well. The specific ingredients of the
chemical formulations used in the tanning industry often are not known by the
tanner, particularly for compounds used in small quantities. The supplier
also may not have the exact formulation of these products or may be unwilling
to release this information. Many of the tanning chemical solutions are
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special formulations, prepared to serve a specific function rather than de-
veloped with consideration for the specific chemical activity of each ingre-
dient.
2.3 SOLID WASTE
Solid wastes from the leather tanning industry may include both solid
materials (e.g., leather trimmings) and semi-liquid wastes that are most
commonly disposed on land (e.g., wastewater treatment sludges). Reported
significant sources of solid waste include (SCS Engineers 1976):
Leather wastes. Pieces of leather in various stages of processing are
routinely generated as the hide is trimmed for various tannery opera-
tions. Fine leather fibers also are generated in conjunction with
buffing and shaving. Leather wastes comprise about 35% of the industry
solid wastes.
Finishing wastes. Residues from recycled solutions, usually in a
slurry form, typically constitute about 2% of the industry solid
wastes.
Wastewater treatment solids. Essentially all tanneries screen their
wastewater and generate solid waste. Many pretreatment facilities for
tanneries generate sludge solids, as do all direct discharge systems.
Waste treatment sludges constitute 60% of the process solid waste in
the industry.
Floor sweepings. Included in this category are shipping materials
(e.g., twine) and excess salt solids from cured hides. This source
represents about 3% of the process solid wastes from the industry.
Additional solid waste generation estimates for the industry have been
summarized in Table 7. These estimates include total process solid waste and
total hazardous (or potentially hazardous) solid wastes. Information in the
table is also provided for tanneries not included in the effluent guidelines
subcategorization in Section 1.1. Additional breakdowns of these data by
specific process are available in the literature (SCS Engineers 1976) and
could provide guidance for the applicant to use in estimating quantities of
solid wastes to be generated by a new tannery (USEPA 1979).
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Table 7. Solid waste generation estimates for the leather
tanning industry by effluent guidelines subcategory.
lO
Subcategory
1. Hair pulp/chrome
tan/retan-
wet finish
3. Hair save/non-chrome
tan/retan-wet finish
4. Retan-wet finish
6. Unhair/chrome tan
(through-the-blue)
* Sheepskin tannery
* Split tannery
* Leather finishers
1977 Solid Waste Estimate(l)
Total Hazardous(2)
(Dry) (Wet) (Dry) (Wet)
1,800 5,400 1,300 4,900
2,700 12,000 None None
1,200 2,100 920 1,800
2,600 10,200 2,400 10,000
890 2,100 540 1,700
4,300 8,900 4,000 8,600
130 240 55 160
1983 Solid Waste Estimate(l)
Total Hazardous(2)
(Dry) (Wet) (Dry) (Wet)
1,800 5,400 1,300 4,900
2,800 13,000 None None
1,200 2,300 950 2,100
2,600 10,200 2,400 10,000
910 2,300 560 1,800
4,300 8,900 4,100 8,700
130 260 58 170
* Subcategory not designated for effluent guidelines.
(1) All estimate as kg/1000 equivalent hide, where an equivalent hide weighs about 50 pounds.
(2) Defined as hazardous or potentially hazardous.
SOURCE: SCS Engineers. 1976. Assessment of industrial hazardous waste practices leather tanning and
finishing industry.
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Hazardous compounds identified in sludges from tannery wastewater treat-
ment facilities are shown in Table 8 to include (SCS Engineers 1976):
Chromium. The chemistry of chromium is very complex, especially in
untreated raw wastewaters where interferences from complexing mech-
anisms such as chelation by organic matter and dissolution due to
presence of carbonates can cause deviation from predicted behavior in
treatment systems. Disposal of sludges containing very high trivalent
chromium concentrations can potentially cause problems in uncontrol-
lable landfills. Incineration, or similar destructive oxidation
processes can produce hexavalent chromium, which in turn is poten-
tially more toxic than trivalent chromium under certain circumstances.
Studies on the effects of disposal of sludges containing trivalent
chromium on agricultural land have produced conflicting conclusions.
Some studies have not shown adverse effects, and in fact the nitrogen
content of sludges have shown some beneficial effects. In other cases
where high rates of chrome sludge application are used, distinct
growth inhibition and plant tissue uptake have been noted. Therefore,
the use of agricultural land for tannery or POTW sludge disposal
should not be generally adopted in light of potential for long-term
accumulation and toxicity in soils and plant tissue (USEPA 1979).
Copper. This may leach from a landfill into groundwater.
may leach from a landfill into groundwater.
Sulfides. These may leach from a landfill into groundwater. They may
be converted to hydrogen sulfide in a landfill, as the pH is reduced
by biological activity or mixing with other waste streams.
Phenols . These may be leached from a landfill into groundwater.
These compounds may be extremely persistent in the environment and may
be significant in trace amounts.
Disposal of hazardous solid tannery waste has the potential for creating
environmental problems if it is not properly handled. The use of sludge
lagoons, landspreading, and landfilling techniques require attention to proper
controls to assure that the leaching of toxic substances to groundwater or
surface waters does not occur. Spreading tannery sludge on the land may also
be a potential problem depending upon the bacteria present, salt content,
presence of metals, and ultimate use of the crop being grown on the land
receiving the sludge. Guidance on issues to consider in landspreading of
sludge may be found in references such as Application of Sludges and Waste-
waters to Agricultural Land; A Planning and Educational Guide, USEPA, March
1978.
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Table 8* "Typical" tannery wastewater treatment
plant sludge characteristics.*
Chrome leather tannery
Chrome leather Vegetable leather
pretreatment/treatment sludge tannery sewer tannery secondary
before
Constituent dewatering
Solids content 5-10
Chromium (mg/1) 3,000-6,000
Copper (mg/1) 100-150
Lead (mg/1) 10-25
Sulfides (mg/1) 20-50
Phenols (mg/1) <10
after sump sludge treatment sludge
HpwAtfirine (not dewatered) (not dewatered)
20-30 5-15
10,000-15,000 2,000-4,000
150-200 100-200
50-150 10-25
50-150 30-60
<10 <10
3-6
<5
<10
<5
25-50
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If the RCRA regulations are promulgated as presently proposed, most of
the industry's solid waste will have to be disposed of in USEPA approved
landfills in accordance with Subtitle C regulations. These sites will have to
be designed and operated to satisfy all significant environmental concerns
regarding disposal of tannery waste. However, consideration should be given
to the other wastes to be disposed of to assure that waste interaction does
not create or cause leaching of any hazardous substance from the site. (See
Section 3.3 for a discussion of sludge disposal alternative technologies).
2.4 OTHER IMPACTS
The leather tanning industry can have significant impacts on public
health and the ecology of our environment if pollutants from the industry
processes are uncontrolled. The industry can have other impacts that are not
directly generated by the tanning process. In addition, the wastes from the
industry can affect other pollution control systems. These potentials must be
addressed by the applicant.
2.4.1 Aesthetics
New source leather tanneries are usually small, enclosed complexes that
should be designed to blend with the natural surroundings. Although tanneries
do not normally require large tracts of land, waste treatment and disposal
needs for the tannery (e.g., a wastewater treatment plant or a solid waste
landfill) may require sizable tracts of land and may detract considerably from
the surrounding landscape. Also, due to the putrescible matter from the
fleshing and trimming processes, the existence of the wastewater treatment
plant, and the sulfur used in the urihairing process, odor from a leather
tannery may become highly objectionable. Particularly in rural and suburban
areas, leather tanneries along with their waste treatment facilities can
represent a significant intrusion into the environmental landscape. Measures
to minimize the impact on the environment must be developed during site selec-
tion and tannery planning design. The applicant should consider the following
factors to reduce potential aesthetic impacts:
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Existing Nature of the Area. The topography and major land uses
in the area of the candidate sites are important. Topographic condi-
tions and existing trees and vegetation visual barriers can be used to
screen the operation from view. A lack of topographic relief and
vegetation would require other means of minimizing impact, such as
regrading or the planting of vegetation buffers.
Proximity of Parks and Other Areas Where People Congregate for
Recreation and Other Activities. The location of public use areas
should be mapped and presented in the BID. Representative views of
the plant site from observation points should be described. The
visual effects on these recreational areas should be described in the
BID in order to develop the appropriate mitigative measures.
Transportation System. The visual impact of new access roads, rail
lines, haul roads, barge docking, pipelines, and storage facilities on
the landscape or waterfront should be considered. Locations, con-
struction methods and materials, and maintenance should be specified.
2.4.2 Noise
The major sources of noise associated with the leather tanning industry
include:
fans and blowe rs;
pumps and motors;
mechanical unhairing equipment;
splitting and trimming equipment;
mechanical fleshing equipment;
transfer trucks and equipment;
compressors and sprayers;
scrubbers and buffers; and
wastewater treatment equipment (e.g., air compressors).
Various source and operational control methods are available which can
effectively mitigate the undesirable noise impacts. Such measures include:
enclosed process machines;
mufflers on engines;
sound barriers and isolation;
vibration insulation; and
acoustically lined plenums.
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The USEPA has recommended a. maximum 75 dBA, 8-hour exposure level to
protect workers from loss of hearing. A maximum 55 dBA background exposure
level is also recommended to protect from annoyance during outdoor activity
(USEPA 1974d). A suitable methodology to evaluate noise generated from a
proposed new source tannery would require the applicant to:
Identify all noise-sensitive land uses and activities adjoining
the proposed plant site (e.g., schools, parks, hospitals, and busi-
nesses in the urban environment; homes and wildlife sanctuaries in the
rural environment).
Measure the existing ambient noise levels of the areas adjoining
the site.
Identify existing noise sources, such as traffic, aircraft fly-
over, and other industry, in the general area.
Determine whether there are any state or local noise regulations
that apply to the site.
Calculate the noise level of the tannery processes, compare that
value with the existing area noise levels and the applicable noise
regulations.
Assess the impact of the operation's noise and, if required, determine
noise abatement measures to minimize the impact (e.g., quieter equipment,
noise barriers, improved maintenance schedules).
2.4.3 Energy Supply
The impact of a leather tanning facility on local energy supplies will
depend largely on the type of processes proposed and the ancillary facilities.
The applicant should evaluate the energy efficiencies of all processes con-
sidered during project planning and then consider the alternatives. Feasible
design modifications also should be considered in order to reduce energy
consumption.
The design of end-of-pipe wastewater treatment plant units is dependent
on the performance of in-plant and pretreatment technologies for specific
waste streams originating within a tannery. Reuse of process streams, re-
covery and reuse of chemicals, and reduction of wastewater volume are primary
aspects of these technologies. Each of these reuse and reduction processes is
inherently energy conserving in the production of leather and in wastewater
treatment.
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The removal or reduction of pollutants in any wastewater stream requires
an energy expenditure. The higher levels of treatment produce a higher quality
effluent with lower levels of pollutants. This means a greater energy con-
sumption than at lesser levels of performance.
At a minimum, the applicant should provide the following information:
Total external energy demand for operation of tannery.
Total energy available on site.
Energy demands by type.
Proposed measures to reduce energy demand and increase plant
efficiency.
Proposed energy sources and alternatives.
The New Source Tannery EID also should specifically address the topics in the
next sections.
2.4.3.1 Energy Consumption and Conservation
Leather tanning facilities are not large users of energy. The various
leather tanning processes use a small amount of energy, while the facilities'
wastewater treatment plants use the majority of the energy. The focus of
wastewater treatment and control for BAT level of performance is on in-plant
and pretreatment technologies for specific waste streams originating within a
tannery. Reuse of process streams, recovery and reuse of chemicals, and
reduction of wastewater volume are primary aspects of these technologies.
Each of these is inherently energy conserving in the production of leather and
in wastewater treatment.
The removal or reduction of pollutants in any wastewater stream requires
an energy expenditure. The control technologies available to meet NSPS pro-
duce a higher quality effluent with lower levels of pollutants. This means a
greater energy consumption than at lesser levels of performance. The increased
energy requirements to meet the NSPS control requirements are projected to be
small in absolute and relative terms (USEPA 1979).
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2.4.3.2 Cogeneration
The potential for cogeneration (e.g., using steam to generate electricity
on-site and for process requirements) should be evaluated in the BID. However,
it is probable that the economic incentive for this technique will not exist
for most tanneries because of the relatively limited energy consumption for
the industry. The applicant should investigate satisfying all or a portion of
the tannery energy needs using waste energy from nearby industrial facilities.
2.4.4 Socioeconomics
Leather tanning facilities are usually small complexes but are often
associated with large cattle feedlots or meat packing plants. The intro-
duction of a leather tanning facility into a community may cause land use,
economic, and social changes. Therefore, it is necessary for an applicant to
understand the types of impacts or changes that may occur so that they can be
evaluated adequately. The importance of these changes usually depends on the
size of the existing community where the facility is located. The trend now
is for leather tanning facilities to be located in more rural areas instead of
traditional urban areas. The significance of the changes caused by a facility
of a given size normally will be greater near a small rural community than
near a large urban area. This is due to the fact that a small rural community
is more likely to have a nonmanufacturing economic base and a lower per capita
income, fewer social groups, a more limited socioeconomic infrastructure, and
fewer leisure pursuits than a large urban area. There are situations, however,
in which the changes in a small community may not be significant and, con-
versely, in which they may be considerable in an urban area. For example, a
small community may have had a manufacturing (or natural resource) economic
base that has declined. As a result, such a community may have a high Inci-
dence of unemployment in a skilled labor force and a surplus of housing.
Conversely, a rapidly growing urban area may be severely strained to provide
the labor force and services required for a new leather tanning facility.
The rate at which changes occur (regardless of the circumstances) also is
often an important determinant of the significance of the changes. The appli-
cant should distinguish clearly between those changes occasioned by the construc-
76
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tion of the facility, and those resulting from its operation. The former
changes could be substantial but usually are temporary; the latter may or may
not be substantial, but normally are more permanent in nature. The potential
impacts which should be evaluated include:
Increased land consumption and rate of land development.
Land use pattern and compatibility changes.
Economic base multiplier effects.
Population size and composition changes.
Increased labor force participation and lower unemployment rates.
Increased vehicular traffic and congestion.
Loss of prime agricultural land and environmentally sensitive areas.
Increased demand for community facilities and services.
Increased demand for water supply, sewage treatment, and solid
waste disposal facilities.
During the construction phase, the impact will be greater if the project
requires large numbers of construction workers to be brought in from outside
the community than if local unemployed workers are available. The potential
impacts include :
Creation of social tension.
Short-term expansion of the local economy.
Demand for increased police and fire protection, public utilities,
medical facilities, recreation facilities, and other public services.
Increased demand for housing on a short-term basis.
Strained economic budget in the community where existing infra-
structure becomes inadequate.
Increased congestion from construction traffic.
Various methods of reducing the strain on the budget of the local community
during the construction phase should be explored. For example, the company
itself may build the housing and recreation facilities and provide the utility
services and medical facilities for its imported construction force; or the
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tannery may prepay taxes, and the community may agree to a corresponding
reduction in the property taxes paid later. Alternatively, the community may
float a bond issue, taking advantage of its tax-exempt status, and the company
may agree to reimburse the community as payments of principal and interest
become due.
During operation, the more extreme adverse changes of the construction
phase are likely to disappear. Long-term changes may be profound, but less
extreme, because they evolve over a longer period of time and may be both
beneficial and adverse.
The permit applicant should document fully in the EID the range of poten-
tial impacts that are expected and demonstrate how possible adverse changes
will be handled. For example, an increased tax base generally is regarded as
a positive impact. The revenue from it usually is adequate to support the
additional infrastructure required as the operating employees and their families
move into the community. The spending and respending of the earnings of these
employees has a multiplier effect on the local economy, as do the interindustry
linkages created by the leather tanning facilities. The linkages may be
backward (those of the facility's suppliers) or forward (those of the faci-
lity's markets).
Socially, the community may benefit as the increased tax base permits the
provision of more diverse services of a higher quality, and the variety of its
interests increases with growth in population. Conversely, the transformation
of a small community into a larger community may be regarded as an adverse
change by some of the residents who chose to live in the community, as well as
by those who grew up there and stayed, because of its small town amenities.
The applicant also should consider the economic repercussions if, for
example, the quality of the air and water declines as a result of wastes
generated by the leather tanning facility. In some cases, traditional sectors
of economic activity may decline because labor is drawn away from them into
higher paying industrial jobs. Also the tourist sector may decline if air and
water pollution is noticeable or if the landscape is degraded.
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Thus, the applicant's framework for analyzing the socioeconomic impacts
of the location of a leather tanning facility must be comprehensive. Most of
the changes described can and should be measured to assess fully the potential
costs and benefits. The applicant should distinguish clearly between the
short-term (construction) and long-term (operation) changes, although some
changes may be common to both (e.g., the provision of infrastructure). The
significance of the changes depends not only on their absolute magnitude, but
on the rate at which they occur. The applicant should also develop and main-
tain close coordination with state, regional, and local planning and zoning
authorities to ensure full understanding of all existing and/or proposed land
use plans and other related regulations.
USEPA's Office of Environmental Review is developing a methodology to be
used to forecast the socioeconomic impacts of new source industries and the
environmental residuals associated with those impacts. The manual describing
the method and its use is expected to be available in mid-1980.
2.4.5 Raw Materials Shipment and Handling
The leather tanning industry uses raw materials that may have adverse
environmental effects due to improper handling or accidents. The following
materials should be evaluated:
hides and skins, describing their nature upon receipt (e.g., raw,
brine cured, through-the-blue tanned);
tanning agents (e.g., chrome, vegetable, alum, syntans);
finishing materials;
solvents;
bleaching agents;
dyes;
pickling liquors; and
other process chemicals.
The significant factors for these materials include storage, handling,
and contingency methods to avoid adverse impacts in the event of an accident.
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The hide raw materials sources especially should be characterized by the
app1icant:
Sheepskins are mainly imported, so the proximity of the tannery to
port facilities should be indicated.
Reliance on through-the-blue tanned leather as a raw material should
be supported by the probable source (e.g., existing versus new tanneries)
General availability of the tannery agent (e.g., chrome, alum, or
vegetable extract) might have a significant effect on product mix.
Location and operation of brine curing facilities for the hide source
should be addressed because of the putrescible nature of uncured hides
and the associates difficulties with transport (e.g., odor at the new
tannery, spoiled hides requiring disposal).
2.4.6 Site Preparation and Construction
The environmental effects of site preparation and construction of new
leather tanneries are common to land disturbing activities on construction
sites in general. Erosion, dust, noise, vehicular traffic and emissions, and
some loss of wildlife habitats are to be expected and minimized through good
construction practices wherever possible. At present, however, neither the
quantities of the various pollutants resulting from site preparation and
construction nor their effects on the integrity of aquatic and terrestrial
ecosystems have been studied sufficiently to permit broad generalizations.
The major pollutant at a construction site is loosened soil that finds
its way into the adjacent water bodies and becomes sediment. Common remedial
measures include, but are not limited to, proper planning at all stages of
development ..nd application of modern control technology to minimize the
production of huge loads of sediment. Specific control measures include:
the use of paved channels or pipelines to prevent surface erosion;
staging or phasing of clearing, grubbing, and excavation activities to
avoid periods of heavy rainfall;
the use of storage ponds to serve as sediment traps, where the over-
flow may be carefully controlled; and
the use of mulch or seeding immediately following disturbance.
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If the applicant chooses to establish temporary or permanent ground
cover, grasses normally are more valuable than shrubs or trees because of
their extensive root systems that entrap soil. Grasses may be seeded by
sodding, plugging, or sprigging. During early growth, grasses should be
supplemented with mulches of wood chips, straw, and jute mats. Wood fiber
mulch has also been used as an antierosion technique. The mulch, prepared
commercially from waste wood products, is applied with water in a hydroseeder.
The applicant must consider the capacity of the soils and geology to
accommodate production and waste storage. Problems which would require special
consideration include:
unstable soils;
steep topography;
presence of wetlands;
location relative to floodplains;
permeability of soils; and
erosion problems during construction and operation.
In addition to the impact assessment framework provided in the USEPA
document, Environmental Impact Assessment Guidelines for Selected New Source
Industries, the permit applicant should tailor the conservation practices to
the site under consideration in order to account for and to protect site
specific features, including:
critical habitats;
archaeological/historical sites;
high quality streams; and
other sensitive areas on the site.
The evaluation of site limitations should not be limited to the immediate
vicinity of the project but should consider areawide restrictions, such as:
proximity to national refuges, parks, and other pristine areas;
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area water resource compatibility with industrial development;
existing hazardous solid waste disposal facilities for the area;
potential for developing solid waste disposal systems; and
community attitudes and goals relative to industrial development.
These should be addressed with respect to the mitigative techniques available
to the applicant. (See Section 4.0 for a detailed discussion of site selection
criteria).
2.4.7 Effects on Municipal Treatment Systems
The usual alternative to treatment and discharge of treated wastewater
effluents is pretreatment for discharge to a municipal wastewater treatment
facility. For the new source tannery, the effluent limits for both of these
alternatives are identical and equal to BAT limits. When evaluating the
pretreatment alternative, the applicant should consider the following problems:
large pieces of scrap hide and leather clogging or fouling operating
equipment;
excessive quantities of hair and other small-scale, screenable solids;
highly acidic or alkaline waste streams;
wastewater flow surges;
excessive loadings of suspended solids, settleable solids, and BOD ,
consistently or in surges;
odors, facilities corrosion, very high dissolved oxygen demand in
biological treatment system aeration basins, and hazardous gas genera-
tion from sulfide bearing wastes;
a potential future problem with disposal of sludges containing chrome;
and
pass through of ammonia nitrogen.
These factors also are significant for an industry operated waste treatment
facility. The pretreatment standards for new sources (PSNS), if adopted as
proposed, will require pretreatment controls that are adequate to alleviate
these problems.
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2.5 MODELING OF IMPACTS
The ability to forecast environmental impacts accurately often is im-
proved by the use of mathematical modeling of the dispersion and dissipation
of air and water pollutants as well as the effects of storm runoff. Two of
the most widely used and accepted models are:
DOSAG (and its modifications); and
the QUAL series of models developed by the Texas Water Development
Board and modified by Water Resources Engineers, Inc.
These are steady-state, one-dimensional models useful in evaluating stream
impacts. Some of the parameters that these models simulate are:
Dissolved oxygen.
BOD,
Temperature.
pH.
Solids.
The data required for these models include (19761):
DOSAG-I
Flow rates for system inputs and withdrawals.
Information on reaches, junctions, stretches, headwater reaches.
Reaction coefficients.
Concentrations of inflows.
Stream temperature.
QUAL-II
Identification and description of stream reaches.
Initial conditions.
Hydraulic coefficients for de.r-rmining velocity and depth.
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Reaction coefficients.
Headwater data.
Waste loadings and runoff conditions.
If temperature is to be modeled, also requires sky cover, wet bulb/dry
bulb air temperature, atmospheric pressure, wind speed, evaporation
coefficient, and basin elevation.
Other models are available for non-steady state conditions and two dimensions,
as required in modeling estuaries, including:
RECEIV and RECEIV II, developed by Raytheon for the USEPA Water Planning
Division.
These models can evaluate both conservative (e.g., dissolved solids, metals)
and non-conservative materials subject to first order reaction kinetics (e.g.,
BOD, DO). The data required as input to both of these models include:
Tidal variations.
Water surface elevations, area, and depth.
Bottom roughness coefficients.
Meteorological data, including rainfall, evaporation, and wind velocity
and direction.
Downstream boundary conditions.
Junction and channel data.
Water temperature.
Initial pollutant concentrations.
Inflow data.
Oxygen saturation and reaeration coefficients.
In addition, there are many available water quality models that were
developed in association with NPDES activity and the need for optimization of
waste load schemes for an entire river basin.
There are also available mathematical models that have been used for air
pollution studies and solid waste management optimization. A complete dis-
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cussion of available air quality modeling techniques is presented in
"Guideline on Air Quality Models," EPA-450/2-78-027 (USEPA 1978e). Examples
of the application of these models include:
For short-term dispersion modeling of point sources, USEPA's PTMAX,
PTDIS, and PTMTP models may be employed.
For modeling of long-term concentrations over larger areas, the L3EPA
Climatological Dispersion Model may be used for point and area sources.
Input data requirements for air quality modeling include descriptions of the
meteorological setting, the existing air quality, the existing air pollutant
emissions, and the anticipated emissions from the new source. Pollutant
sources may include (USEPA 1978e):
Point sources. Generally considered a major source (e.g., greater
than 50 tons/year) from a stack or group of stacks.
Line sources. Generally confined to roadways and streets with well-
defined motor vehicle movements.
Area sources. Typically treated as a grid network of square areas
with emissions distributed uniformly within each grid square.
In general, the use of mathematical models is indicated when arithmetic
calculations are too repetitious or too complex. Their use also simplifies
analysis of systems with intricate interaction variables. Models thus offer a
convenient way of describing the behavior of environmental systems.
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3.0 POLLUTION CONTROL
New sources must attain discharge levels which are indicated as achiev-
able using technological options which meet the New Source Performance Standards
(NSPS). They may be the technologies identified by USEPA in the development
of these standards or they may be alternatives which meet these standards by
other techniques. For waste streams not specifically addressed by NSPS,
control applications which represent the state of the art should be described
in the BID. The permit applicant must demonstrate that NSPS will be met. The
sections which follow identify and describe typical Standards of Performance
and state of the art technologies with which NSPS can be met.
3.1 AIR - STANDARDS OF PERFORMANCE TECHNOLOGY
Air emissions from tanning and finishing operations are primarily from
the following sources: auxiliary boilers for in-plant heating, dust from the
buffing step of the finishing operations, solvents from the degreasing or
finishing operations, and possibly hydrogen sulfide from the unhairing pro-
cess. Odor may also cause air quality problems, due to either uncontrolled
sulfides or putrescible solid waste materials. In addition, volatile organic
compounds may be released to the atmosphere by aeration systems in biological
treatment.
3.1.1 Boiler Equipment
Boiler flue gas may contain several air contaminants controlled by PSD
and NAAQS (e.g., total suspended particulates, nitrogen oxides, sulfur di-
oxide). However, these are low volume sources, so that oil and gas-fired
units usually require no pollution control measures to comply with guidelines.
If a large coal-fired boiler were proposed for the tannery, then wet scrubbers
or electrostatic precipitators to remove fly ash from the stack gas might be
required. These units are capable of 98+% removal of fly ash.
3.1.2 Buffing Dust Control
The major potential source of particulate emissions from a tannery is
from hide buffing operations. Most tanneries control this by wet scrubbing of
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the buffing area exhaust. Hide buffing particulates also are of concern due
to their chrome content. The wet scrubbing operation transfers this waste
material either to the liquid or solid waste streams. Buffing dust from the
wet scrubber is usually removed as a sludge for disposal with the other chrome
bearing tannery waste.
3.1.3 Hydrogen Sulfide Control
Hydrogen sulfide is the other potential air pollutant of consequence
originating from leather tannery wastes. A significant portion of alkaline
sulfides contained in tannery wastewater can be converted to hydrogen sulfide
at a pH below 9.0, resulting in the release of this gas to the atmosphere.
This gas is odorous, and can result in property damage through paint dis-
coloration. In sewers, hydrogen sulfide can be oxidized to sulfuric acid,
causing "crown" corrosion and corrosion of equipment. At higher concentra-
tions this gas can be lethal to operation and maintenance personnel in sewers,
and at POTW headworks, primary treatment, and sludge dewatering facilities.
This is particularly significant as a hazard in sewer maintenance. Further,
careless mixing of acid and sulfide containing alkaline streams can also be
catastrophic both within tanneries and in sewers.
The sulfide content of tannery wastes must be reduced and maintained at a
low level for other treatment systems to work, to protect the health and lives
of workers exposed to leather tanning waste waters, and to minimize the poten-
tial for air pollution from any waste treatment system. Because of the over-
riding health and safety considerations associated with hydrogen sulfide
control, it should never constitute a significant air pollution problem.
However, a description of the facilities proposed for hydrogen sulfide control
is necessary to assess adequately the potential health and safety impacts of
the tannery.
3.1.4 Ammonia
A potential air pollution source is the ammonia discharged into the air
from specific treatment equipment for ammonia removal. Stripping the wastewater
by any gaseous media would almost certainly produce an ammonia vapor stream
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that would be discharged into the atmosphere. Ammonia may be released as a
free gas from a wastewater stream containing ammonium hydroxide wherever the
pH is in a specific alkaline range. Ammonia would be converted to nitrates
and nitrites in the presence of air and the proper bacteria in an extended air
or activated sludge type of treatment system. Ammonia originates primarily
from the ammonium salts used in the bating step and may be stripped from high
pH wastes even without specially designed ammonia stripping facilities. It is
necessary that all pollution control systems be addressed from the perspective
of pollutant transfer to other media.
3.1.5 Odor
Odor can be associated with sulfide-bearing wastewater streams and with
decay of putrescible waste materials such as trimmings and fleshings. The
control of these materials should be addressed in the EID. The applicant
should specifically identify the control techniques proposed to minimize odor
generation from the tannery:
Closed containers should be available for solid waste materials.
Daily or more frequent removal of wastes should be indicated.
Controls and detection instrumentation for hydrogen sulfide in the
plant atmosphere should be identified.
3.2 WATER - STANDARDS OF PERFORMANCE TECHNOLOGY
3.2.1 In-Plant Controls
Appraisals of plant waste production must first investigate the manufacturing
cycle for any modifications which can reduce the waste flow and the concentration
of waste constituents. Particular emphasis rests on reducing those factors
which pose problems in treatment of the total waste stream. In some instances,
reuse or recovery of materials from process solutions can produce economies
which will at least partially offset costs.
Process changes and waste stream segregation are two methods of pollutant
reduction and/or control essential to achieving the recommended effluent
limitations, wherever appropriate.
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A number of tanneries are considering a variety of process change methods
which could result in reduced waste loads, increased efficiency in use of
chemicals, and reduction of total water use. Tannery justification for these
process change methods depends to some extent on the costs of installation and
operation and the benefits in whatever form for the particular tannery. An
important factor in this decision is the effect of any process change on the
quality of the finished leather product (USEPA 1979).
The following steps can often reduce pollutants and the costs of waste
treatment (USEPA 1979):
Process Changes
Process changes have been difficult to make in this industry because of
the diverse tanning methods employed. While tanning operations traditionally
employed the batch system, it is possible that more of the chemical applica-
tions as well as the washing and rinsing could be handled more efficiently on
a counter-current continuous flow basis. This would achieve maximum utiliza-
tion of all active ingredients, leaving only concentrated wastes of small
volumes for treatment and disposal. Substitution of effluents from one pro-
cess for make-up water in another generally is feasible at some points within
a tannery. Before tanneries can make this change however, they must establish
the quantity of water required for each operation.
Substitution of Process Ingredients
Several options exist for the chemicals used in tanning:
Sulfides used in tanning can be replaced with dimethylamine.
Synthetic tanning agents (syntans) can reduce contamination normally
associated with vegetable tanning.
Unhairing can use enzymes to facilitate mechanical hair removal,
improving the economic attractiveness of unhairing as an alternative
to the high pollutant generating hair pulping process.
The merits of these substitution alternatives as well as similar opportunities
in other processes should be evaluated by the applicant.
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Water Conservation and Reuse
Water recycle and reuse should be maximized in a new tannery as the
initial step in the water pollution control effort. Numerous techniques for
flow reduction have been demonstrated in tanneries throughout the world, but
the application of these techniques to a new tannery is dependent on the
process needs of the particular tanner. The application of the following
water reuse and recycle techniques should be addressed for each new tannery.
Engineering, operation, and process modification aspects of water conservation
measures should be considered.
Rinsing or washing hides in batches rather than using a continuous
rinse system should be examined. This holds potential for the most
significant water savings of any process modification, since hides are
rinsed after every major process step.
Timers, preset meters, and other instrumentation (e.g., conductivity
probes) should be considered for controlling rinse water volumes.
Spent wash water and rinse water should be considered for process
solution makeup.
Non-contact cooling water (e.g., vacuum driers) should be evaluated
for recirculation potential.
Process equipment alternatives (e.g., hide processors, paddle vats,
pumpable drums, float storage tanks) should be considered.
Operation techniques and procedures should be developed to minimize
wastewater (e.g., flow restriction nozzles on washup hoses).
Associated with a water use reduction may be an increase in a pollutant
concentration in pretreated discharges to municipal systems. Most municipal
ordinances regulating discharges to a sewer specify concentration limits. A
joint understanding of the actual municipal requirements at a specific sewer
inlet and of the likely consequences of a water reduction program in a tannery
would be a vital first step controlling wastewater volume, pollutant concen-
tration, and/or pollutant loading.
Recovery and Reuse of Process Chemicals
The most efficient methods for eliminating pollutants from tannery wastes
are the reuse of process solutions and the recovery of materials normally
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wasted. These both have been demonstrated effective for waste constituent
reduction, and the new tannery should consider the possibility of process
solution reuse, recycle, or recovery. Alternatives which bear consideration
include:
Reuse or recycle of unhairing solutions. This requires removal
of solids from spent solutions, refortification with lime and shar-
peners, and addition of make-up water.
Reuse of chrome tanning solutions. This can be performed either
by settling, refortification, and reuse of the solution as the prin-
cipal tanning agent or by reusing spent liquor for retanning.
Reuse of vegetable tanning solutions. The Liritan process employs
such a technique by counter-current flow of tannage in relation to the
hides.
Reuse of retanning liquors or reuse of spent tanning liquors.
Reuse of pickle liquors. Spent pickle liquors can be refortified for
reuse and also can be used as makeup for pickle liquor.
Reduce lime used in unhairing liquors. Excess lime is commonly used
for unhairing because it is easier to control the process in this
manner. Experiments have shown that the lime required for effective
unhairing is less than is required to saturate the protein (USEPA
1979).
Systems for recovery of sulfides from unhairing liquor. A pilot
system has recovered sulfide by acidifying the unhairing waste to
produce hydrogen sulfide (H~S) and then scrubbing the H2S from the air
stream with sodium hydroxide (NaOH) to produce sodium sulfide which
can be reused (USEPA 1977b).
Recovery of chrome from spent tanning liquors. This is becoming more
attractive as the cost of trivalent chromium salts continues to climb.
A chrome recovery system can use lime precipitation of chrome as
chromium hydroxide sludge, sludge dewatering, and acidification of the
chrome hydroxide cake with sulfuric acid to produce an acidic chromium
sulfate solution (USEPA 1977a).
Recovery of system blowdown solutions. System blowdown is required to
prevent buildup of contaminants in tanning, unhairing, washing, and
other process streams where extensive recycling is practiced. Vegetable
tanners should consider concentrating tan solution blowdown for use an
a retanning additive.
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Stream Segregation for Separate Pretreatment
Stream segregation is not an in-plant treatment technology, per se. It
is, in reality, a critical installation or first step to implement most in-plant
technologies available to tanneries. It is the physical separation or segrega-
tion of at least the two major wastewater streams in a tannery. One stream
originates in the beamhouse, is highly alkaline and contains a substantial
organic load of dissolved and suspended hair. The 'other stream originates in
the tanyard, is acidic, and has a chrome content of measurable level.
These two major and substantially different wastewater streams can be
most effectively pretreated as separate streams rather than in a combined
state. Constituent streams of these two major streams are the specific
process waste streams which may also respond better to separate treatment.
Effective segregation techniques that should be considered include the
following physical systems (USEPA 1979):
Processing equipment (e.g., hide processors) can be connected by
in-place piping to holding tanks for reuse or segregated discharge to
treatment.
Below grade sewers can be installed to serve process and rinse
tanks with similar wastewater characteristics.
Above grade sewers can be installed to serve process and rinse
tanks.
Curbs and dikes may be required to ensure wash waters are segregated.
adequately.
Flow diversion gates may be useful to segregate concentrated wastes
in periodic dumps from low-concentration wastewaters.
Control of Specific Waste Constituents
The specific waste constituents associated with the industry may be
targeted for removal in-plant. The waste constituents that could merit such
consideration include (USEPA 1979):
Lime Reduction. Lime used in unhairing liquors is responsible for the
alkalinity of the final effluent. Insoluble calcium compounds simply
add to the sludge quantity. Though the pH of the mixed effluent has
to be sufficiently high to precipitate chromium salts, it is desirable
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to reduce the amount of lime to a minimum. It is reported: "Because
lime has a limited solubility, it is generally regarded as a safe
alkali for use in unhairing. Consequently, tanners are tempted to use
a considerable excess of this materialfar more than is needed to
satisfy the alkali-binding capacity of the skin collagen and to keep
the liquor saturated with lime. Experiments have shown that the
amount of lime needed for effective unhairing is less than is required
to saturate the protein so there is certainly no justification for any
undissolved lime to be present in beamhouse liquors" (USEPA 1979).
Chrome Reduction. lanyard wastewater is generally acidic and, because
of the chrome content, is toxic to some organisms. The acidic nature
of the waste stream can be neutralized by mixing with the beamhouse
wastes that are alkaline or by pH adjustment with chemicals. The
chrome content can be reduced by using one of a number of technologies.
One technique is to increase the uptake of chrome by the leather in
tanning. A second is to reuse chrome liquors, as is, in some part of
the beamhouse, tanyard, or retan process without first recovering the
chrome from the solution. A third way is to precipitate the chrome
with an alkaline chemical, producing a chrome sludge either for dis-
posal or for chrome recovery. The alkaline chemical source can be
beamhouse waters, fresh lime, or bases such as caustic soda or soda
ash.
Aside from their application as methods of reducing the chrome content
in tannery wastewater some of these methods have been used in the past
as chrome conservation methods. During World War II, chrome supplies
were cut off and tanners were able to reduce their chrome use 20%
(USEPA 1979). Under current conditions of increasing chrome prices
and reduced imports, an economic incentive exists for tanneries to
introduce these methods of chrome conservation, which will improve the
wastewater quality as well. In fact, several tanneries have already
started chrome recovery and reuse programs.
Increasing the uptake of chrome is an effective method of reducing
chrome in the wastewater and conserving chrome. Chrome fixation can
be increased by increasing the chrome concentration, increasing the
temperature, adjusting the concentration of neutral salts to the
minimum required to prevent swelling of the hides, increasing the
basicity of the chrome waste slightly, and adjusting the pH of the
tanning liquor during the tanning process. Some of these methods may
affect the quality of the leather (USEPA 1979). After World War II,
tanners went back to the older methods. The efficiency of chrome use
is now about 70% (USEPA 1979).
Sulfide Removal. In situ sulfide oxidation in the drum or paddle with
the hides has been investigated and is in use. TNO Institute investi-
gated this method of oxidizing sulfides in the lime liquors during and
after the liming process (USEPA 1979). It was found that a vigorous
movement of the liquor and a free air supply are very important. In
the alkaline medium, the manganese catalyst converts into insoluble
manganous hydroxide. Flotation of the hydroxide by hair remnants or
foam must be prevented to retain the catalytic activity. When the
oxidation of sulfides is combined with the liming operation the latter
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is started in the usual way, either in a paddle or in a drum. After
complete removal of the hair, a small amount of manganous sulfate,
(e.g., 200 g/cubic meter (m3) ), is added and paddling or drumming is
continued for some additional time. Using hair-burn liming procedures
and the lowest sulfide concentrations necessary for complete unhairing
and the production of good quality leather, over 95 percent of the
residual sulfides could be removed by oxidation within three hours.
This additional drumming had little effect on the appearance and
physical properties of the leather produced in this way.
The TNO technique of in situ sulfide oxidation in combination with a
sulfide liquor reuse system reduced the sulfide content of the waste-
water discharged to POTW from 118 mg/1 to about 2 mg/1 concurrent with
a reduction in wastewater volume.
Ammonia Reduction in the Bating Operation
The major source of ammonia nitrogen and total Kjeldahl nitrogen (TKN) in
the tanning industry is from the bating or deliming operation. Ammonium
sulfate or ammonium chloride are the two most frequently used deliming salts.
They can be used either alone or in combination with acid for deliming. When
combined with acid, they create a buffer solution which is capable of neutral-
izing the residual lime in the hide without drastically reducing pH, which
would cause acid swelling. Significant reductions in the concentration of
ammonia in wastewater effluents can be achieved by substituting other bating
salts or by using weaker deliming acids in place of the commonly used ammonium
salts. Both magnesium sulfate and magnesium chloride have been substituted
successfully and their use should be given consideration as an in-plant pollu-
tion abatement measure (Koopman 1974). Weak acids such as boric acid and
sodium bisulfate can be used to delime hides prior to tanning without the use
of a bating salt buffer solution. These acids are effective and can avoid
swelling the hide, but they are not widely used because they increase pro-
cessing time.
Recycle of Unhairing Liquor
Results of small-scale trials on recycling of lime-sulfide unhairing
liquors have been reported in which the liquors have been recycled up to 27
times without deterioration in leather quality (USEPA 1979). Different soak
methods were compared to determine which did not cause a build-up of salt in
the liquor that would affect the swelling and unhairing. Matched-side trials
were conducted comparing:
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1. conventional unhairing and unhairing with lime recycle after solids
removal;
2. conventional unhairing and unhairing with lime recycle and no solids
removal; and
3. unhairing using lime recycle with solids and unhairing using lime
recycle without solids.
None of the trials produced inferior quality leather. Fats were found to
accumulate in recycled lime liquors when the solids were not removed. Ad-
vantages stated are the improved effluent quality and the savings in water
use. The work has been extended to large-scale tannery trials.
Enzyme Unhairing for Hair-Save Operations.
Prerequisities for any hair-saving method are: it must unhair easily and
mechanically, with removal of fine hair (if possible without reliming); it
must be economical, not time-consuming; it must be suited to mechanized and
automated production processes; and it must give good leather quality. Hair-
saving processes require more labor than hair-burn processes, and tanners will
not incur additional costs unless there is a profit from the proceeds of the
hair and a cost savings in wastewater treatment. Present trends in the in-
dustry are definitely toward the hair-burn process.
Summary of Industry Efforts to Implement In-Plant Controls
Table 1 previously has listed some feasible in-plant process change
methods and indicates the number of tanneries which have considered and de-
cided either positively or negatively to implement these in-plant changes.
Sulfide substitution and elimination of bating were widely considered but the
tanners found no solution which, in their experience, did not interfere with
leather quality. Fourteen tanners considered a substitute for ammonium sulfate
and one tannery is successfully using magnesium sulfate in deliming with no
problem in leather quality and with a considerable reduction in nitrogen waste
load.
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As indicated in the table, opinion is almost equally divided on the use
of hide processors and also almost equally divided on lime and unhair liquor
reuse. Some tanners state that the leather produced in hide processors is of
poorer quality, while others state that the leather is of better quality and
the hide processors improve in-plant control. Some tanners think that hide
processors are more economical because less labor is required and lower water
use results. Others object to the cost of installation and problems of mainte-
nance .
In lime and unhair liquor reuse the question focuses on labor and materials
savings, lower waste load, and questionable leather quality. Several of the
responses recorded on Table 1 in the negative column included comments which
indicated that decisions are still pending and that further studies are being
conducted.
Decisions on protein recovery apparently depend on the economic situation
of each tannery. The important question involves the volume, quality, and the
market for recoverable protein. Reuse or recovery of tan liquors is generally
an economic question with most decisions indicated on that basis. From the
questionnaires it also appears that wash water and cooling water reuse is
usually implemented if convenient and if the tanner perceives some real benefit
from such an investment.
It is quite evident that many of these in-plant technologies are well
established and that a different cost situation (e.g., the cost of ammonia
removal by treatment versus elimination by substituting chemicals) will
motivate tanners to further implement these pollution control methods. As the
cost of processing chemicals and POTW cost recovery and operating charges
increase, the cost-effectiveness for many of these in-plant control tech-
nologies will also become more attractive. Chrome recovery is an excellent
example of the cost of processing chemicals making recovery economically
attractive as well as environmentally sound.
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3.2.2 End-of-Plant-Controls
The Federal Water Pollution Control Act, as amended by the 1977 Clean
Water Act, does not require the use of specific treatment technologies.
Instead, it leaves to the discretion of the individual tannery the selection
of control technologies to meet the New Source Performance Standards (NSPS)
for effluent control. The selected technology may involve end-of-plant controls
only or may involve a combination of in-process and end-of-plant controls.
The technologies described in this section have been identified as appropriate
to achieve NSPS effluent controls, but should not be interpreted as the only
approved technology to meet NSPS (USEPA 1979). These descriptions should be
considered as generally applicable for the entire industry, except as indi-
cated .
The New Source Peformance Standards (NSPS) for each subcategory of the
leather tanning industry were presented in Section 1.5, Table 4. These pro-
posed NSPS include:
Non-toxic, Non-conventional Pollutants. These include total Kjeldahl
nitrogen, ammonia, and sulfide.
Toxic Pollutants. These include phenol and chromium.
Conventional Pollutants. These include the conventional pollutants,
BOD, COD, TSS, oil and grease.
Indicator Pollutants. These include BOD , COD, TSS, oil and grease,
TKN, ammonia, phenol, and chromium.
Control of toxic pollutants by controlling indicator pollutants has been
proposed by USEPA because it has been found that control technologies that
remove these materials also remove toxic compounds (e.g., priority pollutants)
that are present. Because regulation based on specific analysis of all the
various priority pollutants identified in tannery waste would place a severe
financial and administrative burden on the tanneries without a commensurate
benefit to the environment, the alternative of selected indicator pollutant
control was developed (USEPA 1979).
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3.2.2.1 Preliminary Treatment
The need for preliminary treatment or pretreatment is based on the
following factors:
1. Removal of pollutants found to pass through a POTW with inadequate
treatment.
2. Removal of causes of treatment system upset or hazards and of collection
system obstructions or potentially damaging materials.
3. Stringent water quality criteria imposed upon POTW in NPDES permits.
4. Reduction of load to secondary treatment units.
5. Sludge disposal criteria.
Preliminary treatment operations consist of one or combinations of the
following operations and processes:
1. screening;
2. equalization;
3. sulfide oxidation;
4. carbonation of beamhouse wastewaters; and/or
5. ammonia nitrogen removal.
Screening. Fine screening removes hair particles, wool, fleshings,
hide trimmings, and other large-scale particul?tes. While reducing
undesirable wastewater constituents, screening contributes to the
volume of solid waste which must be disposed. The highly putrescible
wastes are commonly disposed of on-site or at remote landfill opera-
tions.
Equalization. Equalization of waste streams is important in pretreat-
ment facilities. The volume and strength of waste liquors vary de-
pending on process formulations and scheduling of tannery operations.
Alkaline wastes are associated with beamhouse operations, while acid
discharges arise from the tanyard. In order to produce optimum results
in subsequent treatment operations, the equalization of flow, strength,
and pH of strong liquors may be necessary. Although some oxidation
may occur, no removal of waste constituents is normally reported for
equalization.
» Sulfide Oxidation. Sulfides in the beamhouse waste constitute a
potential problem because they will release hydrogen sulfide if mixed
with wastes which can reduce the pH of the sulfide-bearing waste.
The removal of sulfides is not accomplished with plain sedimentation.
Sulfides are more satisfactorily removed through oxidation. Various
methods for oxidizing sulfides include: air oxidation; direct chemical
oxidation; and catalytic air oxidation.
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Carbonation of Beamhouse Waste Stream. Carbonation is effective in
the treatment of alkaline wastes. In this process, carbon dioxide
reacts with lime to form calcium carbonate, which has a solubility of
only 25 to 50 mg/1. The crystalline structure of the carbonate nucleus
provides an effective surface for adsorption of organic matter.
Suspended solids and BOD are both reduced. Inorganic suspended
solids in the form of calcium carbonate are significantly reduced and
thus reduce excessive alkalinity, which in turn reduce mixing require-
ments in activated sludge aeration basins and secondary sludge pro-
duction and dewatering requirements.
Carbonation is attractive for tannery pretreatment facilities, where
carbon dioxide is available at the cost of piping from the plant
boilers. Removals are high, under proper operating conditions, for
suspended solids and BOD .
Ammonia Nitrogen Reduction. Ammonia is difficult to remove from
tannery wastewaters. Biological systems which remove BOD have not
been effective in removing ammonia. For this level of treatment, EPA
considered several alternatives for removing ammonia from deliming
wastes by physical-chemical treatment processes. The ammonia intro-
duced into the tannery wastewater stream by the deliming process
ranges from 67 to 90% of all the ammonia in the raw waste. Thus,
substitution for ammonia or treatment of this ammonia containing
stream will greatly reduce the final ammonia content of the total
wastewater effluent.
These processes assure that the primary ammonia containing stream is
segregated and the ammonia removed before it is combined with other
waste streams. The segregated ammonia containing stream has a higher
concentration of ammonia than a combined stream, and it is therefore
easier to treat by physical-chemical methods. The methods considered
were:
1. water evaporation followed by crystallization or pre-
cipitation of ammonium sulfate;
2. distillation of ammonia;
3. precipitation of ammonia as calcium ammonium phosphate;
4. precipitation of ammonium sulfate by addition of ethanol;
5. reverse osmosis; and
6. ion exchange.
No tannery now uses these methods for treating ammonia wastes.
Several of them are technologies used in other industries while others
should work because of known chemical principles.
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3.2.2.2 Primary Treatment (Physical) Operations
These operations are designed to remove suspended pollutants from the
wastewater stream, to reduce solids loadings to subsequent units, and also to
reduce organic loads.
Plain Sedimentation. Plain sedimentation is concerned with the
removal of non-flocculating discrete particles and floatable low-
density materials such as grease and scum. Suspended solids reduc-
tions can range from approximately 40 to 90%, with associated re-
ductions in BOD5 from 30 to 60%. Much of the suspended material
removed is 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. While high
removals of suspended solids (90%) and BOD5 (60%) are reported,
effluent concentrations are not reported below 130 mg/1 for suspended
solids or 146 mg/1 for BOD (USEPA 1979). High chromium removals may
result while sulfide concentrations are relatively unaffected.
Chemical Coagulation and Sedimentation. As an alternative to plain
sedimentation, chemical addition prior to sedimentation has further
increased the removal efficiencies of primary clarifiers. Chemical
coagulation results in higher removals of suspended solids, BOD ,
sulfides, chrome, and alkalinity through flocculation of colloidal
particles. Alum, lime, iron salts, and polymers have exhibited satis-
factory results. Suspended solids removals from 50 to above 98% and
BOD reductions of approximately 50 to 99% may be achieved (USEPA
1979). The following removals have been conservatively established
for coagulation-sedimentation of leather tanning wastewaters: BOD -
60%; TSS - 65%; COD - 60%; Oil and Grease - 70%; Total Chromium - 90%;
TKN - 65%.
3.2.2.3 Secondary (Biological) Treatment
Preliminary treatment and primary treatment do not remove all of the
organic material in a wastewater stream. Most of the BOD,, and suspended
solids can be removed by biological processes which oxidize the organic
materials. Many different systems are known for the biological oxidation of
wastewater. In these systems bacterial respiration is the primary method of
oxidizing organic substances present in the wastewater. This results in a
substantial reduction of the effluent BOD. The higher level of treatment
generally includes one or more biological unit processes following primary
treatment. Secondary biological treatment technology includes activated
sludge, various kinds of lagoons, and trickling filters. Selection of one of
these biological treatment systems is influenced by factors such as wastewater
100
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constituents, effluent requirements, climatic conditions, site constraints,
operating characteristics, and economics. It has been repeatedly observed in
tanneries and other industrial operations that waste treatment systems achieve
the design effluent quality only if: (1) the design is correct for the waste-
water characteristics; (2) the system is not overloaded, (i.e., pollutant and
hydraulic loading not more than 100% of design specifications); and (3) all
components of the system receive regular and necessary maintenance.
Trickling Filter Systems. Trickling filter systems are used to
treat tannery wastewater by very few tanneries (USEPA 1979). Trick-
ling filters have limited application in the treatment of high strength
tannery wastes. System upsets are common due to organic overload and
climatic conditions. Existing filters may be incorporated into systems
for treatment prior to a second stage biological system.
Lagoons. Lagoons, also referred to as oxidation ponds or stabili-
zation ponds, have been used for tannery treatment where land is
available as an economical alternative to activated sludge. Lagoons
provide equalization and a desirable environment for biological ac-
tivity. In lagoons with long retention times, primary and secondary
clarification may be eliminated. However, the efficiency of these
systems is significantly reduced during cold weather and sludge
accumulation will eventually make it necessary to construct a new
lagoon or dredge the old one. The three types of lagoons available
for the stabilization of organic wastes include:
Aerobic Lagoons. Biological stabilization in the presence of oxygen.
These include lagoons that incorporate mechanical methods (i.e.,
stirring, spraying, or bubbling) to increase the dissolved oxygen
content in the lagoon.
Anaerobic Lagoons. Biological stabilization in the absence of free
oxygen.
Aerobic/Anaerobic Lagoons. A stratified lagoon where aerobic activity
predominates near the surface and anaerobic activity takes place near
the bottom of the lagoon.
Activated Sludge Systems. The activated sludge process is one of
the most controllable and flexible of all secondary treatment systems.
It is applicable to almost all treatment situations. With proper
design and operational control and use, high organic removals are
possible. Designs based on solids retention time (SRT) afford optimum
residence time for solids with minimal hydraulic retention. However,
pilot studies are recommended to establish appropriate design para-
meters defining the relative rate of biological growth and decay with
a given wastewater. Basically, the activated sludge process consists
of: mixing of returned activated sludge with the waste to be treated;
aeration and separation of the activated sludge from the mixed liquor;
and disposal of the excess sludge. Activated sludge is typically
101
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preceded by some form of primary treatment especially in tannery
applications. Activated sludge systems, including various modifica-
tions, such as extended aeration, carousel, and oxidation ditch (Barber
1978) have been and can be effective in organic reductions to low BOD
concentrations. Removals of suspended solids appear to be dependent
on the design and operation of the final clarifier. During the program
for preparation of the Development Document, BOD removal from 89 to
98% and suspended solids removal from 90 to 98% were observed (USEPA
1979).
Rotating Biological Contactor. The rotating biological contactor
(SBC) consists of a series of closely spaced flat parallel disks which
are rotated while partially immersed in wastewaters being treated. A
biological growth covering the surface of the disk adsorbs dissolved
organic matter present in the wastewater. As the biomass on the disk
builds up, excess slime is sloughed off periodically and is settled
out in sedimentation tanks. The rotation of the disk carries a thin
film of wastewater into the air where it adsorbs the oxygen necessary
for the aerobic biological activity of the biomass. The disk rotation
also promotes thorough mixing and contact between the biomass and the
wastewaters. Rotating biological contactors could be used as a sub-
stitute for an entire aerobic system. The number of stages required
depends on the desired degree of treatment and the influent strength.
More typical applications of the rotating biological contactors,
however, may be for polishing the effluent from biological processes,
nitrification of effluents, and as pretreatment prior to discharging
wastes to a municipal system. A BOD reduction of 98% is reportedly
achievable with a four-stage RBC.
Nitrogen Control-Nitrification. Nitrification is the biological
conversion of nitrogen in organic or inorganic compounds from a more
reduced to a more oxidized state. In the field of water pollution
control, nitrification usually is referred to as the process in which
ammonia as ammonium ion is oxidized to nitrite and nitrate sequen-
tially. Process controls are critical for nitrification to be suc-
cessful. Dissolved oxygen should be maintained above 1 to 2 mg/1 to
assure consistent nitrification. System pH for domestic wastewater
has been shown critical, with pH 7.5 to 8.5 the optimum range. Since
nitrification generates acidity (excess of hydrogen ions), a buffered
wastewater, either naturally or by addition of alkaline chemicals, is
required to maintain the optimum pH range. Nitrification is extremely
temperature sensitive, with a minimum of 12 to 15° C required for
effective treatment. Sulfides should be reduced to less than 1 mg/1
and chrome reduced to 2 to 10 mg/1 to avoid inhibitory effects on
nitrification. Nutrients are critical as for all biological systems,
with phosphorus normally required for a tannery wastewater.
Nitrogen Control-Denitrif ication. Denitrification, the conversion
of nitrites and nitrates (primarily nitrates) to nitrogen is accom-
plished under much less stringent conditions and with a larger range
of organisms than nitrification. The process consists of biologically
reacting a carbon source (essentially fuel), such as residual organic
pollutants or methanol, glucose, methane, or low nitrogen organic
waste, with the nitrite-nitrate, oxidizing the carbon source to C02 by
102
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using the oxygen from the nitrite-nitrate, and liberating nitrogen
gas. Many denitrification processes are designed to use methanol as
the carbon source because of ease of process control, cost, and water
and bacteriological compatibility.
Nitrogen Control-Summary. Nitrification-denitrification has not
been applied to tannery wastes on a full scale, but the technology has
been applied to a variety of wastes. Total nitrogen reduction can
range from 30 to 90% with removal efficiencies extremely dependent on
system operation.
3.2.2.4 Advanced Physical^Chemical Processes
There are several technologies available for the new source tannery that
the applicant might consider. These are not used by the industry at this
time, but they could be effective in meeting NSPS.
Combined Primary and Secondary Treatment. Physical-chemical processes
have been proposed for treating wastewater streams where all pollutant
components can be flocculated and removed by sedimentation. Such a
system for the leather tanning industry has been patented by Chappel
(USEPA 1979) using an acidic solution (mineral acid, aluminum sulfate,
and oxidizing chemicals) and an alkaline solution (sodium hydroxide,
dissolved aluminum, and oxidizing chemicals). Separate treatment with
these solutions is given to two segregated wastewater streams from the
tannery, after which these are combined. Flocculation and pollutant
removal is reported for both separate treatment and after combining
the streams. Sludge is recirculated to aid in flocculation. When
this system was used on a retan facility wastewater, removal effi-
ciencies were reported at 99+% for BOD, 95+% for TKN and ammonia, and
99+% for chrome. When the process was tested on other tanneries, it
was found similarly effective for BOD, chrome, and sulfides.
Powdered Carbon Addition to Activated Sludge. This process involves
metering activated carbon into the activated sludge facility influent.
The process effectiveness relies on the processes complementing each
other and thereby improving overall treatment effectiveness. Improve-
ments reported include:
- improved organic pollutant removals, including BOD, COD, and TOC;
- more uniform operation and effluent quality, particularly during
periods of widely varying organic and hydraulic loads;
- decreased effluent solids and thicker sludges resulting in reduced
sludge handling costs;
- adsorption of organics, such as detergents, oils, and dyes, that
are refractory to the biological system;
103
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- protection of the biological system from toxic waste components;
- more effective removal of phosphorus and nitrogen; and
- increased effective plant capacity at little or no additional
capital investment.
A major inhibition to the widespread use of granular activated carbon
has been the high capital cost of installing thermal regeneration
facilities in small installations. A possible solution to this problem
has been developed by a major chemical company whereby customers can
lease carbon adsorption systems at a guaranteed monthly charge. The
company assumes the responsiblity for regeneration at central facilities.
Multi-media Filtration. 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 phosphorus
removal from secondary effluents, and in physical-chemical systems for
the treatment of raw wastewater. Waste containing suspended solids is
passed through the filter containing granular material resulting in
the capture of suspended solids in the bed. Eventually, the pressure
drop through the bed becomes excessive or the ability of the bed to
remove suspended solids is impaired. The filtration cycle is terminated
and the bed is backwashed prior to being placed back into service. In
an ideal filter, the size of the particles should decrease uniformly
in the direction of flow. This condition is partially achieved with
the use of a multimedia deep bed filter. This type of filter utilizes
materials with different densities ranging from the large size par-
ticles at the top of the filter having the lowest density and the
smallest particles at the bottom of the filter having the highest
density. With this arrangement, the filter has a large storage capa-
city for suspended solids, and is able to remain in operation for
longer periods of time. Influent solids should be limited to about
100 mg/1 to avoid too frequent backwashing. Effluent suspended solids
are normally less than 10 mg/1. The following conservative long-term
performance is reasonable after application to PAC upgraded activated
sludge effluent: BOD - 14 mg/1; TSS - 16 mg/1; Oil and Grease - 6
mg/1; COD - 40 mg/1; Total Chromium - 0.25 mg/1; TKN - 15 mg/1.
Electrodialysis. Various membrane processes that are finding interest
in pollution control applications as end-of-pipe treatment and for in-
plant recovery systems are ultrafiltration, reverse osmosis, and
electrodialysis. Although these processes are available for producing
a concentrated solution from a relatively dilute feed, each process
tends to occupy a specific region of application due to economic as
well as technological considerations.
Whenever an effluent stream contains an organic or inorganic ionic
material, electrodialysis offers a possible method for recovery,
separation, segregation, or concentration of that material, provided
adequate pretreatment requirements are consistently achieved. Of
paramount importance, of course, is the avoidance of membrane fouling,
either by scaling or suspended solids, when considered for tannery
applications. Other conditions such as pH fluctuations and dissolved
104
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organic solids concentrations also must be carefully controlled if
electrodialysis is used in the tannery. Yet, with water recovery
rates of 80-90%, greatly reduced disposal volumes, the independence of
chemical additives and low energy requirements, electrodialysis
streams may be an economically feasible means of meeting the parallel
challenge of wastewater treatment and recovery through brine concentra-
tions .
Nitrogen Removal. While biological removal methods are effective
for control of ammonia in wastewater effluents, various physical-chemical
methods are also available. In general, the following systems might
be effective for treatment of a segregated, ammonia-bearing wastewater
from the deliming process:
- Use of alternative deliming agents, such as epsom salts.
- Evaporation of water followed by crystallization or precipitation of
ammonium sulfate.
- Distillation of ammonia.
- Precipitation of ammonia as calcium ammonium phosphate.
- Precipitation of ammonium sulfate by addition of ethanol.
- Reverse osmosis.
- Ion exchange.
The use of alternative deliming agents is now being investigated in
the industry. None of the other technologies are now used in a tannery
for treating ammonia wastes, but these technologies are used in other
industries or should work because of known chemical principals.
, Protein Precipitation. The beamhouse waste stream can be successfully
treated to reduce COD, BOD, nitrogen, dissolved solids, and suspended
solids contributed by the unhairing process. Proposed technologies
include plain and chemical coagulation, sedimentation, flue gas car-
bonation, screening, filtration, and centrifugation. The effective-
ness of this technique on the total waste stream varies. The removed
materials are largely proteinaceous matter, and can be used as feed
for chickens when supplemented with key amino acids.
Summary of Waste Control and Treatment Technology
The preceding discussion addresses numerous technologies which can
be employed in-plant or end-of-pipe to minimize the quantity of pollutants
discharged by tanneries to POTW's or surface waters. These technologies are
pertinent to the leather tanning industry because they (1) reflect current
105
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Fismre 7. Technology schematic for in-plant control and preliminary treatment for the hair pulp/
chrome tan/retan-wet finish and hair save/chrome tan/retan-wet finish subcategories.
BEAM HOUSE
CARBON AT ION/
SEDIMENTATION
AMMONIA
SUBSTITUTION
CHROME
TANNING
STREAM
COMBINED
WASTE
STREAMS
TOEND-OF-PIPE
TREATMENT
Source:
1979 Preliminary draft development document for proposed
new source performance standards for the leather tanning and
finishing industry.
-------
Figure 8. Technology schematic for in-plant control and preliminary treatment
for the hair save/non-chrome tan/retan-wet finish subcategory.
BEAM HOUSE
ALKALINE
UNHAIRING
STREAM
SULFIOE
RECOVERY/
REUSE
FLUE GAS
CARBONATION/
SEDIMENTATION
TAN YARD
OELIME
STREAM
COMBINED
WASTE
STREAMS
TOEND-OF-PIPE
TREATMENT
LEVEL I
LEVEL
Source: U.S. Environmental Protection Agency. 1979. Preliminary draft development document for proposed
effluent limitations guidelines and new source performance standards for the leather tanning and
finishing industry.
-------
Figure 9. Technology schematic for In-plant control for the retan-wet finish subcategory.
BEAM HOUSE
NO BEAM HOUSE WASTE STREAM
TAN YARD
o
oo
RETAN-
WET FINISH
STREAM
SCREENS-
ftOIT
REMOVAL
TO ENO-OF-PIPE
TREATMENT
LEVEL 2
Source: U.S. Environmental Protection Agency. 1979. Preliminary draft development document for proposed
effluent limitations guidelines and new source performance standards for the leather tanning and
finishing industry.
-------
Figure 10. Technology schematic for in-plant control for the no beamhouse and shearling subcategories.
BEAM HOUSE
NO BEAM MOUSE WASTE STREAM
TAN YARD
CHROME
TANNING
STREAM
CHROME
REUSE
>
SCREENS-
GRIT
REMOVAL
TO END-OF-PIPE
TREATMENT
LEVEL I
LtVEL Z
Source:
U.S. Environmental Protection Agency. 1979- Preliminary draft development document for
effluent limitations guidelines and new source performance standards for the leather tanning and
finishing industry.
-------
Figure 11. Technology schematic for in-plant control and preliminary treatment for the through-the-blue subcategory.
BEAM HOUSE
FLUE GAS
CAftBONATION/
SEDIMENTATION
TAN YARD
COMBINED
WASTE
STREAMS
TO ENO-OF-PIPE
TREATMENT
LEVEL I
LEVEL 2
Source; U.S. Environmental Protection Agency. 1979. Preliminary draft development document for proposed
effluent limitations guidelines and new source performance standards for the leather tanning and
finishing industry.
-------
Figure 12. Technology schematic for end-of-p±pe wastewater treatment.
^
J
LEVELS \&Z
COMBINED
WASTE
STREAMS
EQUALIZATION
AND
COAGULATION-
SEDIMENTATION
f'MYSICAL-
CHEMICAL
1 KLAI MtNT
/OMPPELt
VPROCESS;
1
LEVEL 4A 1
f
1 1 Tu
RECEIVING
WAI
i
EXTENDED
AERATION
ACTIVATED
SLUDGE
V
ACTIVATED
SLUDGE
WITH
PAC
ADDITION
>-
MULTI-
MEDIA
FILTRATION
GRANULAR
ACTIVATED
CARBON
COLUMNS
ERS
LEVEL
LEVEL 4
LEVEL 5
LEVEL 6
LEVEL 7
Source: U.S. Environmental Protection Agency. 1979. Preliminary draft development document for proposed
effluent limitations guidelines and new source performance standards for the leather tanning and
finishing industry.
-------
practices of the industry, (2) were evaluated during demonstration studies
conducted by the industry, or (3) will control or remove selected pollutants.
In instances where the control of specific constituents is a primary concern,
technology transfer was necessary. An example of this approach is the up-
grading of secondary biological treatment with PAG addition. To control toxic
organic compounds and heavy metals, EPA assessed this technology from infor-
mation developed by the organic chemicals and petroleum refining industries
and then applied to leather tanning effluents.
Applicable technologies for the leather tanning industry and their per-
formance were determined upon the best available information. As can be seen
from Figures 7 through 11, segregation of the waste streams from the beamhouse
and tanyard operations is an integral part of comprehensive waste management
for the industry. For subcategories with beamhouse operations, the segregated
waste stream will be subjected to sulfide oxidation and flue gas carbonation.
Ammonia substitution in the bating process and chrome recovery and reuse are
applicable to the tanyard processes. The effluents resulting from these
measures, which are defined as Levels 1 and 2, are then combined for equaliza-
tion followed by coagulation-sedimentation (Level 3). A schematic of the
appropriate end-of-pipe treatment technologies, including Level 3, is pro-
vided in Figure 12.
3.2.3 Toxic Pollutants
The effectiveness of the treatment processes described previously has
been investigated for toxic pollutants (USEPA 1979). The conclusions relating
to the removal of these materials are (USEPA 1979):
Volatile organics are largely removed in any type treatment system
that is in use in the leather tanning industry, except for some degree
of persistence of chloroform. It also appears that this occurs regard-
less of treatment effectiveness on any other pollutant parameters
whether standard or priority.
Semivolatile organics also receive a significant degree of removal
by all waste treatment systems in use. Those systems that are most
effective in removing the standard pollutants (COD, BOD5, TSS, Oil and
Grease) also seem to be most effective on semivolatiles.
112
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Metals comprise the inorganic groups of toxic pollutants and
include chromium. All of the treatment systems remove the metals to
some extent, and performance on the metals seems to correlate with
removal of standard pollutants. The most effective treatment system
on metals is the physical-chemical system.
The fate of the toxic pollutants is not certain. It is highly
probable that a substantial percentage of the pollutants are removed
with the solids separated from the wastewater.
Toxic pollutant removal effectiveness in general correlates with
standard pollutant removal.
The Pretreatment Standards for New Sources (PSNS) have been proposed as
equivalent to NSPS due to the control requirements for priority pollutants
(USEPA 1979). Therefore, the technologies previously described would also be
considered as appropriate for new leather tannery and finishing facilities
that propose discharge to a publicly owned treatment works.
3.3 SOLID WASTE - STANDARDS OF PERFORMANCE TECHNOLOGY
As described in Section 2.3, solid waste from a tannery with a wastewater
pre treatment/treatment system may include any or all of the following:
Fleshings.
Hair.
Hide trimmings.
Tanned hide trim and shavings.
Leather trimmings.
Buffing dust.
Leather finishing residues.
Wastewater treatment sludges.
General plant waste.
The specific types of solid waste generated by a tannery depend upon the type
of processing operations conducted, and the quantity of each type of waste
generated depends upon the volume of production at the tannery.
In view of the hazardous nature of much of the tanning industry's wastes,
there is reason for concern over concentrating priority pollutants removed
from the other plant waste streams in the plant's solid waste. The fate of
the priority pollutants as they are removed from tannery waste is unknown at
this time. Currently, the predominant assumption is that a significant pro-
113
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portion of these pollutants remains intact in the solids that are removed from
the wastewater. These solids are subsequently disposed in landfills and dumps
with varying levels of control (SCS Engineers 1976). Identification of four
tannery processes as hazardous waste sources under the proposed RCRA regula-
tions (Section 1.5) may help reduce the uncertainty concerning the fate of
some priority pollutants, but the entire solid waste stream for a new tannery
should be thoroughly evaluated.
3.3.1 Reduction of Hazardous Waste Components
The primary contaminants of solid tannery wastes are chromium, zinc,
lead, and copper, with smaller but unknown quantities of organic and inorganic
priority pollutants also present. In-plant process modifications to eliminate
the use of as many of the priority pollutants as possible at their source
would obviously reduce their concentration in solid tannery residuals. Reuse
and/or recovery of waste streams containing chrome, dyes, or other toxic
pollutants not only reduces the contamination of solid waste residuals but
makes more efficient use of materials which, as in the case of chrome, are
becoming increasingly more expensive. Some metals are introduced into the
waste stream as corrosion products from tannery equipment. Alternative con-
struction materials should be considered as a possible means of reducing the
introduction of metals from this source.
When the treatment of segregated waste streams produces a solid waste,
the specific contaminants in the solids are generally known and these con-
taminants are in their most concentrated form. Solid wastes in this form are
most manageable in terms of control and appropriate disposal. Taken in general
perspective, numerous small quantities of solid waste of more concentrated
composition are generally more economical to handle and transport, and are
much more environmentally manageable than a single, large, dilute, and multi-
contaminated solid waste from a POTW.
3.3.2 Solid Waste Utilization
Tanneries which generate fleshings and hide trimmings may be able to sell
these waste materials to rendering plants, or occasionally to glue manufac-
114
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turers. Since these waste materials are highly putrescible, daily collection
is required. Most vegetable leather tanneries and a few chrome leather tan-
neries remove hair from hides using a hair save operation. If a market is
available, the hair can be washed, dried, and baled, and subsequently sold as
a by-product. Since few markets exist, however, most hair is simply disposed
of in a landfill.
Some chrome leather tanneries which generate large quantities of tanned
hide trimmings and shavings, particularly split leather tanners located in the
northeastern United States, are able to sell this waste material as a by-product.
By-product uses include manufacture of fertilizer, chrome glue, hog feed
supplement, or leather board. The majority of this type of waste, however, is
disposed as solid waste.
Four alternative uses for scrap leather examined in a report for the
Tanners Council of America (1977) and summarized in the effluent guidelines
development document (USEPA 1979) were:
i Incineration of blue split and finished leather waste.
Fiberized leather for loose building insulation.
Pyrolyzed leather waste to make activated carbon and by-product
chemicals.
Hydrolyzed leather and cattle hair to make leather and hair meals
for use in animal and pet foods.
Possible economic incentives exist for each of these alternative uses. However,
their actual application has been limited to date. Such alternatives could be
economically viable for new plants. More information on these alternative
uses may be found in USEPA's Development Document (USEPA 1979).
3.3.3 Solid Waste Treatment
Approximately 60% of the solid waste generated by the leather tanning and
finishing industry is wastewater treatment residue (SCS Engineers 1976).
Therefore, a major part of tannery waste treatment involves the handling and
disposal of the semi-solid sludges obtained from liquid treatment processes.
115
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Primary and/or secondary treatment sludge from chrome tanneries normally is
dewatered prior to disposal. Sludge dewatering may be accomplished by:
Gravity dewatering (sequential settling). This is relatively un-
common, but sludge drying beds on the tannery plant site may be
successful where rainfall is less than evaporation.
Mechanical sludge dewatering. Normally this is accomplished using
vacuum filters, centrifuges, or filter presses, which have all been
found to be effective in producing sludge cakes ranging from 10 to 40%
solids.
Evaporative lagoons. Secondary wastewater treatment sludges from
vegetable tanneries are normally dewatered in this manner, after which
the sludge is used as a soil conditioner or disposed of in a dump or
landfill.
Conditioning or stabilization of waste treatment plant sludge using heat
treatment provides a stable end product, but may have adverse effects on the
chemical quality of the sludge. In testing a heat-treated alkaline sludge, it
has been indicated that some of the trivalent chromium may be oxidized to the
more soluble and toxic hexavalent form. Apparently, the trivalent chromium is
converted through the high temperature, high pressure, high pH, and the oxi-
dizing environment of the heat treatment process (USEPA 1979).
3.3.4 Solid Waste Disposal
The predominant methods of ultimate disposal of tannery waste include
sludge lagoons, landfills, dumps, trenches, and land spreading. Some of these
facilities are not entirely adequate as disposal sites for hazardous wastes
since they do not provide adequate isolation of the hazardous substances from
the human environment. Their use will no doubt be eliminated once RCRA regu-
lations regarding hazardous tannery wastes are promulgated. The factors that
should be considered during solid waste disposal evaluations include:
Sludge lagoons, dumps, landfills, and land spreading areas present the
potential for leaching of toxic materials into the groundwater table.
Incineration, pyrolysis, wet oxidation, or similar high temperature
and pressure sludge destruction processes can generate hexavalent
chromium, which is more soluble than trivalent chromium in the acid
range of pH generally found in landfills.
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Acetic acid produced by the anaerobic decay of garbage in landfills
can solubilize trivalent chrome, increasing its susceptibility for
leaching, and can contribute to oxidation of trivalent chrome to
hexavalent chrome.
Leather finishing residues may contain significant quantities of
flammable organic solvents, indicating that disposal sites which
receive this type of waste need to take precautions to minimize the
potential fire hazard from this material. The quantities of this type
of waste which are generated are small enough that land disposal is
thought to be an environmentally adequate disposal alternative.
A hazardous waste disposal site must be carefully selected to minimize surface
water flow across the site, and the predominant soil types should be able to
contribute to leachate attenuation. Operational procedures should be employed
which will minimize percolation of precipitation through the refuse. Leachate
collection systems at landfills used for hazardous solid waste disposal are
recommended to include impermeable barriers as a minimum to provide adequate
assurance that ground and surface waters will be protected from contamination.
Monitoring wells around the site also are recommended to detect any break-
through or leachate before it spreads to other areas.
Tannery wastes such as vegetable tannery sludge, general plant waste
(strings, paper, boxes), and uncontaminated scraps or hair may be nonhazardous
and therefore amenable to disposal in a regular landfill. This would require
segregation from the potentially hazardous wastes. Since these potentially
nonhazardous wastes make up a relatively small portion of the industry's total
solid waste production, it may not be economical to dispose of them separately.
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4.0 EVALUATION OF AVAILABLE ALTERNATIVES
The alternatives section of the BID should address each reasonable alter-
native available for the new source leather tanning and finishing facility.
The purpose of this analysis is to identify and evaluate alternate plans and
actions that may accomplish the desired goals of the project. These alterna-
tives can include process modifications, site relocations, project phasing, or
project cancellation.
For the alternatives to a. proposed project to be identified and evaluated
properly, the impact assessment process should commence early in the planning
phase. In this manner, social, economic, and environmental factors against
which each alternative is to be judged can be established. Cost/benefit
analysis should not be the only means whereby alternatives are compared. The
environmental and social benefits of each alternative also must be considered.
In general, the complexity of the alternative analyses should be a function of
the magnitude and significance of the expected impacts of the proposed pro-
cessing operations. A small tannery that uses purchased raw materials or
existing by-products may have a relatively minimal impact on a region and
generally would require fewer alternatives to be presented in the EID.
The public's attitude toward the proposed operation and its alternatives
also should be evaluated carefully. In this way key factors such as aes-
thetics, community values, and land use can be assessed properly.
4.1 SITE ALTERNATIVES
New leather tanning facilities are usually located on the basis of the
following:
convenience to hide sources;
an adequate labor force and water supply;
proximity to energy supplies and transportation; and
minimization of environmental problems.
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Preliminary site selection activities normally take place before the EID
document is prepared. The potential impacts that a new leather tanning
facility may have on the alternative site areas should be evaluated as to
their significance; magnitude; frequency of occurrence; cumulative effects;
reversibility; secondary or induced effects; and duration. The identification
and analysis of the alternative site areas should be described in the EID and
the reasons for eliminating a site(s) should be specified. The EID discussion
should particularly emphasize the environmental considerations given during
the site selection process. This should particularly identify the existence
of sensitive areas, environmental constraints at each considered site (e.g.,
effluent receiving stream conditions, air quality, water and groundwater con-
ditions), and the significance of these constraints with respect to the specific
facility. Consultation with the appropriate resource agencies during the
early stages of site selection is recommended. Key agencies that can provide
valuable technical assistance include:
State, Regional, County, or Local Zoning or Planning Commissions.
These sources can describe land use programs and determine if vari-
ances would be required. Federal lands are under the authority of the
appropriate Federal land management agency (Bureau of Reclamation,
U.S. Forest Service, National Park Service, etc.).
State or Regional Water Resource Agencies. These sources can pro-
vide information relative to water appropriations and water rights.
Air Pollution Control Agencies. These sources can provide assistance
relative to air quality allotments and other air-related standards and
regulations.
« The Soil Conservation Service and State Geological Surveys. These
sources can provide data and consultation on soil conditions and
geologic characteristics.
Further consideration should be given to any state siting laws. The appli-
cable regulations should be cited and any applicable constraints described.
The EID should include the potential site locations on maps, charts, or
diagrams that show the relevant site information. (A consistent identifica-
tion system for the alternative sites should be established and retained on
all graphic and text material.) They should display pertinent information
that includes, but is not limited to:
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areas and sites considered by the applicant;
major centers of population density (urban, high, medium, low density,
or similar scale);
water bodies suitable for cooling water or effluent disposal;
railways, highways (existing and planned), and waterways suitable
for the transportation of materials;
important topographic features (such as mountains and marshes);
dedicated land use areas (parks, historic sites, wilderness areas,
testing grounds, airports, etc.); and
other sensitive environmental areas.
Using the foregoing graphic materials, the applicant should provide a con-
densed description of the major considerations that led to the selection of
the final candidate areas, including:
proximity to markets and raw materials;
economic analyses with trade-offs;
adequacy of transportation systems;
environmental aspects, including the likelihood of floods;
license or permit problems;
compatibility with existing land use planning programs; and
current attitudes of interested citizens.
The BID should indicate the steps, factors, and criteria used to select
the proposed site. Quantification, although desirable, may not be possible
for all factors because of lack of adequate data. Under such circumstances,
qualitative and general comparative statements, supported by documentation,
may be used. Where possible, experience derived from operation of other
plants at the same site, or at an environmentally similar site, may be helpful
in appraising the nature of expected environmental impacts.
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Economic estimates should be based at least on a preliminary conceptual
design that considers how construction costs are affected by such site related
factors as:
topography;
geology;
tectonics; and
meteorology.
A. specific site for location of the leather tanning facility may be
unacceptable and require abandonment for a number of reasons. This could
include:
Impact on a unique, recreational, archaeological, or other important
natural resource area. Reviews are mandated in the permitting process
by several public agencies relative to these factors, including the
Soil Conservation Service, Fish and Wildlife Department, State Historic
Preservation Officer, and others.
Destruction of the rural or pristine character of an area.
Conflict with the planned development for the area.
Opposition by citizens groups.
Meteorological and climatological aspects.
Periodic flooding, hurricanes, earthquakes, or
other natural disasters.
4.2 ALTERNATIVE PROCESSES AND DESIGNS
The following presents a methodological approach to the analysis of
process and design alternatives. The discussion of specific system alter-
natives is presented in Section 3.0.
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4.2.1 Process Alternatives
Process alternatives are usually selected on the basis of the following:
product demand;
reliability of the process;
economics;
availability of required raw materials; and
environmental considerations.
Those alternatives that appear practical should be considered further on the
basis of criteria such as:
land requirements of the tanning facility, fuel storage facilities,
waste storage facilities, and exclusion areas;
release to air of dust, sulfur dioxide, nitrogen oxides, and
other potential pollutants, subject to Federal, state, or local
limitations;
releases to water of heat, chemicals, and trace metals subject to
Federal, state, and local regulations;
water consumption rate;
fuel consumption;
social impacts of increased traffic as materials are transported to
the site and wastes are transported from the site;
social effects resulting from the influx of construction, operation,
and maintenance crews;
economics;
aesthetic considerations for each alternative process; and
reliability and energy efficiency.
A tabular or matrix form of display often is helpful in comparing the
feasible alternatives. The EID should present clearly and systematically the
methodology used to identify, evaluate, and select the preferred process
alternative. Alternative processes which are not feasible should be dismissed
with an objective explanation of the reasons for rejection.
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4.2.2. Design Alternatives
In order to properly present alternative facility designs available for
the project in the EID, the combination of component systems available for
selection should be analyzed and described for the following factors:
Economic. This should include capital and operating costs.
Environmental. These should be documented and quantified where-
ever possible.
Engineering. System reliability and safety should be discussed
in conjunction with product requirements.
4.3 NO-BUILD ALTERNATIVE
In all proposals for industrial development, the alternative of not
constructing the proposed new source facility must be considered. This
analysis is not unique to the development of leather tanning facilities (see
Chapter IV, Alternatives to the Proposed New Source, in the USEPA document,
Environmental Impact Assessment Guidelines for Selected New Sources Industries,
October 1975). The key aspects of the no-build alternative should be identi-
fied to include:
Market Effect. Not constructing the facility may result in pro-
duct shortages.
Industry Effect. Not constructing the facility may cause dated
facilities to be renovated.
Technology Effect. Not constructing the facility may only delay
the need for expanded capacity, which may allow time for improved
technology to be incorporated into the facility.
, Environmental Effect. Not building the facility might avoid ad-
verse environmental effects at the proposed site, but may therefore
cause similar effects at a more sensitive site.
Other factors should be considered (e.g., specific environmental issues)
as appropriate for the situation leading to the proposed action.
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5.0 REGULATIONS OTHER THAN POLLUTION CONTROL
There are various regulations other than pollution control that may apply
to the siting and operation of leather tanning facilities. Some Federal
regulations that may be pertinent to a proposed facility include, but are not
limited to, the following:
Coastal Zone Management Act of 1972 (16 USC 1451 et seq.)
Fish and Wildlife Coordination Act of 1974 (16 USC 661-666)
National Environmental Policy Act of 1969 (42 USC 4321 et seq.)
USDA Agriculture Conservation Service Watershed Memorandum 108 (1971)
Wild and Scenic Rivers Act of 1969 (16 USC 1274 et seq.)
Flood Control Act of 1944
Federal-Aid Highway Act, as amended (1970)
Wilderness Act of 1964
Endangered Species Preservation Act, as amended (1973)
(16 USC 1531 et seq.)
National Historical Preservation Act of 1966 (16 USC 470 et seq.)
Executive Order 11593 (Protection and Enhancement of Cultural
Environment, 16 USC 470) (Sup. 13, May 1971)
Archaeological and Historic Preservation Act of 1974 (16 USC 469
et seq.)
Procedures of the Council on Historic Preservation (1973)
(39 FR 3367)
Occupational Safety and Health Act of 1970
Executive Order 11988 (Floodplain Management - replaced Executive
Order 11296 on 10 August 1966)
Executive Order 11990 (Wetlands)
Energy Policy and Conservation Act of 1975
Energy Conservation and Production Act of 1976
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Particular emphasis should be placed on obtaining the services of a qualified
archaeologist to determine the potential for disturbance of an archaeological
site, such as an early Indian settlement or a prehistoric site. The National
Register of Historic Places also should be consulted for historic sites such
as battlefields. The appropriate wildlife agency (state and Federal) should
be contacted to ascertain that the natural habitat of a threatened or endan-
gered species will not be affected adversely; other resource agencies also
should be consulted to avoid or minimize impacts to areas that previously have
been determined to be sensitive or uniquely important (wetlands, floodplains,
prime farmlands, etc.).
From a health and safety standpoint, most industrial operations involve a
variety of potential hazards and to the extent that these hazards could affect
the health of plant employees, they may be characterized as potential environ-
mental impacts. Company policy should provide and maintain safe and healthful
conditions for employees and establish operating practices that will result in
safe working conditions and efficient operations. All proposed plans to
maximize health and safety should be described in the EID.
The plant must be designed and operated in compliance with the standards
of the U.S. Department of Labor, the Occupational Safety and Health Administra-
tion, and the appropriate state statutes relative to industrial safety. Close
coordination with local and/or regional planning and zoning commissions is
recommended to determine possible building or land use restrictions. State
and local regulations may exist that affect the facility, and the EID should
indicate that these have been considered.
Table 9 presents a range of typical permits, licenses, certifications,
and approvals that could be required from local, regional, state, and Federal
officials for construction and operation of a major new source leather tanning
facility. Although this list doubtless will vary between jurisdictions, it is
intended primarily to be illustrative. The new source NPDES permit review
process normally will be expedited by documenting in the EID all known permits,
licenses, and approvals that are needed to construct and operate the proposed
plant, and the status of each.
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Table 9. Typical permits, licenses, certifications, and
approvals required from Federal, state, regional, and
local authorities for construction and operation of a
typical new source leather tanning facility.
Agency
Local Planning Organization
(regional, county, city)
Local Department of Public Works
Local Beautification Board
Local Department of Development
and Licensing
State Planning Department
State Fire Marshall
State Department of Environ-
mental Protection
Requirement
Rezoning of plant site
Approval of access road rights-
of-way
Permit for filling or construction
operations in flood plains
Construction on public property if
required
Building permit for each structural
component of facility
Use and occupancy permits
Coastal zone permit, if required
Permit to store flammable liquids
Approval of facility for fire
protection
Water use and discharge permits
Test well permit
Commercial well permit
Permit for dewatering excavation
Permit for fuel oil storage tanks
Permit for solid waste disposal
Dredging and construction of intake
structure
Sedimentation control approval
Noise control approval
State water quality certification
Construction permit for combustion
equipment
Registration of gaseous emissions
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Table 9. Typical permits, licenses, certifications, and approvals (continued).
Agency
State Air Pollution Control
Department
State Board of Health
State Department of Highways
and Transportation
US Environmental Protection
Agency (Regional Office)
US Army Corps of Engineers,
(District Office)
(COE, Washington Office)
Requirement
Permit for construction of stationary
source of air pollutants
Open burning of construction refuse
Review of indirect (mobile) emission
sources
Permit to construct and operate
approved sewage disposal and potable
water facilities
Permit for highway entrance of plant
access road
Approval of public road improvements
Permits for oversize or overweight
vehicles
National Pollutant Discharge Elimina-
tion System Permit (NPDES) for waste-
water discharge
Prevention of Significant Deteriora-
tion of air quality (PSD) permit prior
to commencement of construction
activities
Spill Prevention, Control, and
Countermeasure (SPCC) plan
Hazardous/toxic waste disposal plan
Permit to construct structures or
works* in navigable waters (Section
10, Rivers and Harbors Act of 1899)
Permit to dispose of dredged or fill
materials in waters of the US (in-
cluding wetlands) (Section 404,
FWPCA)
Permit to construct any dam or dike
in a navigable water of the US
(Section 9, Rivers and Harbors Act of
1899)
* Structures may include piers, breakwaters, bulkheads, revements, and aids
to navigation; works may include dredging, stream channelization, excava-
tion and filling. 127
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Table 9. Typical permits, licenses, certifications and approvals (concluded),
Agency
Occupational Safety and Health
Administration
Requirement
Permit to ocean dump dredged
materials (Section 103, Ocean Dump-
ing Act)
Permit to discharge refuse matter
into navigable waters of the US or
their tributaries (Section 13, The
Refuse Act 1899)
Test boring on Federal land
Certification of safety and health
criteria for plan operation (noise
in the work place, etc.)
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6.0 GLOSSARY
Aerobic
A biological process in which oxygen is used for microorganism respiration
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 micro-
organism respiration needs; relating to biological degradation of waste
matter in the absence of dissolved oxygen.
Back
That portion of the animal hide, especially cattlehide, consisting of the
center portion of the hide along the backbone and covering the ribs, shoulders,
and butt (excluding the belly).
Bating
The manufacturing step following liming and preceding pickling. The purpose
of this operation is to delime the hides, reduce swelling, peptize fibers, and
remove protein degradation products from the hide.
Beamhouse
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.
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Bend
That portion of the hide representing the entire hide cut down the backbone
with the belly and shoulder removed.
Biochemical Oxygen Demand (BOD,.)
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
in mg/1.
Slowdown
The amount of concentrated liquor wasted in a recycle system in order to
maintain an acceptable equilibrium of contaminants in any process liquor.
Blue
The state or condition of hides subsequent to chrome tanning and prior to
retanning. Hides in this stage of processing are characteristically blue in
color.
Buffing
A light sanding operation applied to the grain or underside of leather and
also to splits. Buffing smooths the grain surface and improves the nap of the
underside of the leather.
Buffing Dust
Small pieces of leather removed in the buffing operation. Buffing dust also
includes small particles of abrasive used in the operation and is of a coarse
powder consistency.
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Carding
Method using a wire brush to disentangle wool. One of the shearling finishing
processes.
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 in 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 in mg/1 as Cr.
Clarification
A physical means for the removal of suspended particles in a liquid by gravity
sedimentation (settling).
Coagulant
A substance which forms a precipitate or floe when added to water. Suspended
solids adhere to the large surface area of the floe, thus increasing their
weight and expediting sedimentation.
Collagen
The fibrous protein material within the hide which provides the bulk of the
volume of the finished leather and its rigidity.
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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 turbidity has
been removed. One unit of color is that produced by one mg/1 of platinum as
K2 PtCl6.
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.
Combination Tanned
Leathers tanned with more than one tanning agent. For example, initially
chrome-tanned followed by a second tannage (called a retan) with vegetable
materials.
Composite Sample
A series of small wastewater samples taken over a given time period and com-
bined 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.
Conditioning
The introduction of controlled amounts of moisture to the dryed leather in
order to give it varying degrees of softness.
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Corlum
The layer of hide between the epidermis and the flesh. Also called the dermis.
Currying
Oil incorporation into leather in a low water system, classically used to
lubricate vegetable tanned leather.
Degreasing
In pigskin and sheepskin tanneries a solvent or detergent is added to the drum
containing washed hides. Grease is removed from the hides and recovered as a
by-product.
Deliming
The manufacturing step in the tanyard that is intended to remove the lime from
hides coming from the beamhouse.
Demineralization
The process of removing dissolved minerals from water by ion exchange, reverse
osmosis, electrodialysis, or other processes.
Dermis
That part of the hide which is between the flesh and the epidermis.
Desalinization
The process of removing dissolved salts from water.
Detention (Retention)
The dwelling time of wastewater in a treatment unit.
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Dewatering
The process of removing a large part of the water content of sludges.
DO
Dissolved oxygen, measured in mg/1.
Drag-out
Loss of process chemicals and solution onto products during processing which
is made up by periodic fresh addition of chemicals and solution.
Drum
A large cyclinder, usually made of wood, in which hides are placed for wet
processing. The drum is rotated around its axis, which is oriented hori-
zontally. This also may be called a wheel.
Dry Milling
The rotating of leather in a large wooden drum with no added chemicals or
water. Dry milling softens the leather.
Electrodialys is
A form of advanced waste treatment in which the dissolved ionic material is
removed by means of a series of semipermeable membranes and electric current.
Embossed
A mechanical process of permanently imprinting a great variety of unique grain
effects into the leather surface. Done under considerable heat and pressure.
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Enzymes
Complex protein materials added to the hide in the bating step in order to
remove protein degradation products that would otherwise mar hide quality.
Epidermis
The top layer of skin; animal hair is an epidermal outgrowth.
Equalization
The holding or storing of wastes having differing qualities and rates of
discharge for finite periods to facilitate blending and achievement of
relatively uniform characteristics.
Equivalent Hides
A statistical term used to relate the production of tanneries using various
types of raw materials. An equivalent hide is represented by 3.7 sq m of
surface area and is the average size for a cattlehide.
Eutrophication
The excess fertilization of receiving waters with nutrients, principally
phosphates and nitrates, found in wastewater which results in excessive growth
of aquatic plants.
Fatliquoring
A process by which oils and related fatty substances replace natural oils lost
in the beamhouse and chrome tanning processes. Regulates the softness and
pliability of the leather.
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Finishing
The final processing steps performed on a tanned hide. These operations
follow the retan-color-fatliquor processes, and include the many dry processes
involved in converting the hide into the final tannery product.
Fleshing
The mechanical removal of flesh and fatty substances from the underside of a
hide prior to tanning. In the case of sheepskin tanning, fleshing is often
accomplished after the tanning process.
Float
The proper level or volume of skins or hides, chemicals, and water that is
maintained in any wet process unit (vats, drums, or processors) within the
tannery.
Floe
Gelatinous masses formed in liquids by the addition of coagulants, by micro-
biological processes, or by particle agglomeration.
Flocculation
The process of floe formation normally achieved by direct or induced slow
mixing.
Flume
An open, inclined channel or conduit for conveying water or water and hides.
Grab Sample
A single sample of wastewater which will indicate only the constituent levels
at the instant of collection; contrasted to a composite sample.
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Grain
The epidermal side of the tanned hide. The grain side is the smooth side of
the hide where the hair is located prior to removal.
Grease
A group of substances including fats, waxes, free fatty acids, calcium and
magnesium soaps, mineral oils, and certain other non-fatty materials. The
grease analysis will measure both free and emulsified oils and greases.
Generally expressed in mg/1.
Green Hides
Hides which may be cured but have not been tanned.
Head
That part of the hide which is cut off at the flare into the shoulder; i.e.,
the hide formerly covering the head of the animal.
Hide
The skin of a relatively large animal, at least the size of mature cattle.
Ion Exchange
The reciprocal transfer of ions between a solid and a solution surrounding the
solid. A process used to demineralize waters.
lonization
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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Liming
The operations in the beamhouse where a lime solution comes in contact with
the hide. Liming in conjunction with the use of sharpeners such as sodium
sulfhydrate is used either to chemically burn hair from the hide or ^o loosen
it for easier mechanical removal. Hair burning normally utilizes higher
chemical concentrations.
Multi-Media Filter
A filtration device designed to remove suspended solids from wastewater by
trapping the solids in a porous medium. The multi-media filter is charac-
terized by fill material ranging from large particles with low specific
gravities to small particles with a higher specific gravity. Gradation from
large to small media size is in the direction of normal flow.
Nitrogen, Ammonia
A measure of the amount of nitrogen which is combined as ammonia in waste-
water. Expressed in mg/1 as N.
Nitrogen, Kjeldahl (Total Kjeldahl Nitrogen or TKN)
A measure of nitrogen combined in organic and ammonia form in wastewater.
Expressed in mg/1 as N.
Nitrogen. Nitrate
A measure of nitrogen combined as nitrate in wastewater. Expressed in mg/1 as
N.
Nutrient
Any materials used by a living organism which serve to sustain its existence,
promote growth, replace losses, and provide energy. Compounds of nitrogen,
phosphorus, and other trace materials are particularly essential to sustain a
healthy growth of microorganisms in biological treatment.
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Outfall
The final outlet conduit or channel where wastewater or other drainage is
discharged into an ocean, lake, or river.
Pack
Layers of salted hides formed at the slaughterhouse or hide curing firm
(usually approximately 20 to AO 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.
Pasting
The process step generally following the retan-color-fatliquor operations
whereby the hide is attached to a smooth plate with a starch and water paste
and dried in a controlled heated vessel.
pH
The reciprocal logarithm of the hydrogen ion concentration in wastewater
expressed as a standard unit.
Pickling
The process that follows bating whereby the hide is immersed in a brine and
acid solution to bring the skin or hide to an acid condition; prevents pre-
cipitation of chromium salts on the hide.
Plating
The finishing operation in which the skin or hide is "pressed" in order to make
it smoother. Plating may be done with an embossing plate which imprints
textured effects into the leather surface.
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Polymer
An organic compound characterized by a large molecular weight. Certain polymers
act as coagulants or coagulant aids. Added to the wastewater, they enhance
settlement of small suspended particles. The large molecules attract the
suspended matter to form a large floe.
POTW
Publicly owned treatment works (i.e., municipal waste treatment system).
Parts per million. The expression of concentration of constituents in waste-
water, determined by the ratio of the weight of constituent per million parts
(by weight) of total solution. For dilute solutions, ppm is essentially equal
to mg/1 as a unit of concentration.
Pul lery
A plant where sheepskin is processed by removing the wool and then pickling
before shipment to a tannery.
Pulp
Method of unhairing in which depilatory agents are used to dissolve hair
entirely in a few hours.
Re tanning
A second tanning process utilizing either the natural tanning material (chromium
or vegetable extracts) or synthetic tanning agents. Retanning imparts special-
ized properties to the leather.
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Reverse Osmosis
A process whereby water is forced to pass through semipermeable membranes
under high pressures. Water passing through the membrane is relatively free
of dissolved solids; solids are retained in concentrated form on the feed side
of the membrane and are wasted.
Sanding
A dry operation performed on the tanned and fatliquored hide in order to
achieve the desired surface texture of the leather. Sanding operations
include the use of abrasive or buffing wheels.
Sedimentation
Clarification (settling)
Setting Out
A multi-purpose operation which smoothes and stretches the skin while com-
pressing and squeezing out excess moisture. Puts hides into proper condition
for drying.
Sharpeners
Chemicals (such as sodium sulfide and sodium sulfhydrate) used in addition to
lime to assist in the unhairing process.
Shaving
An abrasive, mechanical action used to correct errors in splitting and thus
yielding a uniformly thick grain side or split.
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Shavings
The waste products generated during the shaving operations. These are
essentially small pieces of the tanned hide, which are approximately the size
of wood shavings.
Shearling
A lamb or sheepskin tanned with the hair retained.
Shoulder
That part of the hide between the neck and the main body of the hide.
Side
One-half of a hide, produced by cutting the hide down the backbone. Normally
done to facilitate processing using smaller equipment than would be required
if full hides were processed.
Skin
The pelt or skin of animals smaller than mature cattle (e.g., pigskin, sheep-
skin, calfskin).
Skiver
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 industrial wastes.
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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
Mechanically softens the leather by stretching and flexing it in every
direction. Usually done on automatic machines which move leather between
rapidly oscillating, overlapping fingers.
Sulfide
Ionized sulfur. Expressed in mg/1 as S.
Suspended Solids (SS)
Constituents suspended in wastewater which can usually be removed by sedi-
mentation (clarification) or filtration.
Syntan
Synthetic tanning materials, generally used in combination with vegetable,
mineral, or formaldehyde tannages. Syntans are almost exclusively used in
retanning rather than tanning operations.
Tannin
The chemicals derived from the leaching of bark, nuts, or other vegetable
materials used in the vegetable tanning process.
Tanyard (Tanhouse)
That portion of the tannery in which the bating, pickling, and tanning are
performed on the hides or skins.
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Toggling
Method of drying in which skins are kept in a stretched position by means of
clips called toggles. The skin is attached to a perforated frame which is
slid into a drying oven.
Total Dissolved Solids (TDS)
The total amount of dissolved materials (organic and inorganic) in wastewater.
Expressed in mg/1.
Total Solids (TS)
The total amount of both suspended (TSS) and dissolved (TDS)materials in waste-
water. Expressed.in mg/1.
Trimming
The removal of the ragged edges and inferior portions of hides and skins
either before or after tanning. Trimming is normally accomplished by workers
using knives.
Trimmings
The hide and leather scraps produced during the trimming operation.
Unhairing
The process whereby the hair is removed from the hide.
Volatile Solids
Solids, dissolved or suspended, which are primarily organic and during
stabilization exert the significant portion of the BOD5.
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Weir
A control device placed in a channel or tank which facilitates measurement or
control of the water flow.
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7.0 REFERENCES
The literature references in this section include cited references and
additional bibliographic references. The listings immediately below are
short form citations arranged according to topics. A complete listing of
full references, arranged alphabetically, follows the short form citations.
7 .1 REFERENCE LISTING BY TOPIC
General
Anonymous 1965
0'Flaherty 1956
O'Flaherty 1958
0'Flaherty 1962
O'Flaherty 1965
Perry 1973
Quarles 1979
Reed 1972
Schaklette
Stcckdale 1941
TCA 1978
Thorstensen 1969
Wiley 1977
Markets & Demands
Steadman 1977
TCA 1978
USBC 1978a
USBC 1978b
USDC 1976
USDC 1978
USDC 1979
USEPA 1977b
USEPA 1978d
Trends
TCA 1978
USBC 1978a
USBC 1978b
USDC 1976
USDC 1978
USDC 1979
USEPA 1976b
USEPA 1977b
USEPA 1978d
Processes
Anonymous 1965
Anonymous 1970
Davis 1973
Eye 1966
Eye 1970
France 1975
Freudrup 1970
Happich 1974
Hauck 1972
Koopman 1974
Larsen 1971
Money 1974
O'Flaherty 1956
O'Flaherty 1958
O'Flaherty 1962
O'Flaherty 1965
Perry 1973
Perkowski 1970
Pierce 1976
Robinson 1976
Steadman 1977
Steffman 1973
Stockdale 1941
Theis 1942
Thorstensen 1969
USEPA I977a
USEPA 1977d
van Vlimmeren 1972b
van Vlimmeren 1976
Ward 1976
Williams-Wynn 1973
Wilson 1941
Wilson 1931
Emissions
Cheremisinoff 1976
USEPA 1978b
USEPA 1978c
USEPA 1978e
Solid Wastes
Barber 1978
Bradford 1975
Cheremisinoff 1979
Dawson 1978
Giordano 1976
Keeney 1975
Loehr 1974
Lue-Hing 1974
Schaklette
SCS Engineers 1976
Touchton 1976
USEPA 1976a
USEPA 1976h
USEPA 1978d
USEPA 1979
Ward 1976
Waste Treatment
Adams 1977
Anonymous 1970
Anonymo us 19 7 7
Anthonisen 1974
Bailey 1966
Barber 1978
Barry 1976
Bell 1973
Black 1977
Brown 1976
Chen 1972
Cheremisinoff 1974
Cheremisinoff 1976
Davis 1973
Downing 1964
Eckenfelder 1970
Eichelberger 1976
Eldridge 1939
Envirogenics 1974
Eye 1966
Eye 1970
146
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Waste Treatment (cont.)
Eye 1972
Ferguson 1975
Ferguson 1976
France 1975
Freudrup 1970
Giusti
Hagan 1972
Hager 1976
Hager 1974
Happich 1974
Harnly 1940
Hauck 1972
Kennedy 1973
Kessick 1974
Koopman 1974
Larsen 1971
Leitz 1976
Lue-Hing 1974
Marks 1974
Minor 1974
Money 1974
Mulligan 1976
Numerow 1956
Parker 1970
Perkowski 1970
Perry 1973
Pierce 1976
Poats 1973
Prakasan 1974
Robinson 1976
Siebert 1940
Sproul 1966
Steffan 1973
Sweeny 1970
Sweeny I973a
Sweeny I973b
Sweeny I973c
Tomlinson 1975
USDI 1967
USEPA 1973a
USEPA 1973b
USEPA 1974a
USEPA I974b
USEPA 1974c
USEPA 1975a
USEPA I975b
USEPA 1976b
USEPA 1976d
USEPA I976e
USEPA 1976f
USEPA 1977a
USEPA 1977d
Waste Treatment (cont.)
USEPA 1978a
USEPA 1979
Ueno 1974
Ueno 1976
van Meer 1973
van Vlimmeren I972a
van Vlimmeren I972b
van Vlimmeren 1976
Ward 1976
Whitehouse 1967
Williams-Wynn 1973
Hazardous Waste
Anonymous 1970
Barber 1978
Barry 1976
Baumhardt 1972
Bradford 1975
Cheremisinoff 1979
Dawson 1978
Envirogenics 1974
Eye 1966
Ferguson 1975
Fields 1975
Giordano 1976
Giusti
Hager 1974
Happich 1974
Keeny 1975
Kennedy 1973
Marks 1974
Minor 1974
Robeck 1965
Robinson 1976
Sanders 1973
Sax
SCS Engineers 1976
Sweeny 1970
Sweeny 1973a
Sweeny 1973b
Sweeny I973c
USEPA 1975a
USEPA 1975b
USEPA 1976a
USEPA 1976c
USEPA 1976g
USEPA 1976h
USEPA 1977b
USEPA 1977c
USEPA 1978d
USEPA 1978f
USEPA 1979
Whitehouse 1967
147
-------
Regulations Human Health
McKee 1963 USEPA 1974c
Quarles 1979 USEPA 1976g
USEPA 1974e USEPA 1977c
USEPA 1975c USEPA 1978f
USEPA 1976c USEPA 1979
USEPA 1976d
USEPA 1976f
USEPA 1976g
USEPA 1979
Ecological Impacts
Baunhardt 1972
Bradford 1975
Cheremisinoff 1979
Envirogenics 1974
Fields 1975
Giordano 1976
Jain 1977
Keeney 1975
McKee 1963
Sanders 1973
Touchton 1976
USEPA 1976a
USEPA 1976c
USEPA 1976i
USEPA 1977c
USEPA 1978f
USEPA 1979
Wiley 1977
Modeling
USEPA 1978e
Socioeconomics/Land Use
Jain 1977
USEPA 1975c
USEPA 1976i
Wiley 1977
Aesthetics/Cultural Resources
Jain 1977
USEPA 1974c
USEPA 1975c
USEPA 1976i
Wiley 1977
Noise
TT3ETA" 1974c
USEPA I974d
148
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7.2 ALPHABETICAL REFERENCE LISTING
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aew
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155
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156
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158
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
1. REPORT NO.
EPA-130/6-80-002
3. RECIPIENT'S ACCESSION NO.
4. TITLE ANO SUBTITLE
Environmental Impact Guidelines for
Leather Tanning and Finishing Industries
5. REPORT DATE
August 1980
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Robert P. Stevens, Don McCombs
8. PERFORMING ORGANIZATION REPORT NO.
625-050
9. PERFORMING ORGANIZATION NAME AND ADDRESS
WAPORA, Inc..
3301 Buckeye Rd., N.E.
Suite 301
Atlantic, Georgia 30341
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-01-4157 Task 015
12. SPONSORING AGENCY NAME AND ADDRESS
EPA
Office of Environmental Review
401 M Street, S.W.
Washington, D.C. 20460
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA/100/102
15. SUPPLEMENTARY NOTES
EPA Task Officer: Robert Pickett (202) 755-9394
16. ABSTRACT
(See Attached)
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OP£N ENDED TERMS
c. COSATl Field/Group
Industrial Wastes/Waste Treatment
Water Pollution
Environmental Requirements
Assessment
Pollutant Control
Environmental
Impact
Document
Assessment Methodologies
Stationary Source
43F
680
910
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
OU.S. GOVERNMENT PRINTING OFFICE: 1980 311-132/98 1-3
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