EPA 440/1-74/022
DEVELOPMENT DOCUMENT FOR
PROPOSED EFFLUENT LIMITATIONS GUIDELINES
AND NEW SOURCE PERFORMANCE STANDARDS
FOR THE
TEXTILE MILLS
POINT SOURCE CATEGORY
^
& ^m •£
LU
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
JANUARY 1974
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DEVELOPMENT DOCUMENT
for
PROPOSED EFFLUENT LIMITATIONS GUIDELINES
and
NEW SOURCE PERFORMANCE STANDARDS
for the
TEXTILE MILLS
POINT SOURCE CATEGORY
Russell Train
Administrator
Robert L. Sansom
Assistant Administrator for Air & Water Programs
Allen Cywin
Director, Effluent Guidelines Division
James D. Gallup
Project Officer
January 1974
Effluent Guidelines Division
Office of Air and Water Programs
U.S. Environmental Protection Agency
Washington, D.C. 20460
U.S. Environmental r-yfcection
->.-lion 5, Library t^L-^
«."0 S. Dearborn ••
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ABSTRACT
This document presents the findings of a study of the textile
manufacturing industry for the purpose of developing waste water
effluent limitation guidelines and Federal standards of performance for
new sources in order to implement Section 304 (b) and 306 of the Federal
Water Pollution Control Act Amendments of 1972 (the "Act"). This study
covers approximately 7,000 plants in S.I.C. 22.
Effluent limitations guidelines are set forth for the degree of effluent
reduction attainable through the application of the "Best Practicable
Control Technology Currently Available", and the "Best Available
Technology Economically Achievable", which must be achieved by existing
point sources by July 1, 1977, and July 1, 1983, respectively. The
"Standards of Performance for New Sources" set forth the degree of
effluent reduction which is achievable through the application of the
best available demonstrated control technology, processes, or other
alternatives.
The proposed regulations for July 1, 1977, require in-plant waste
management and operating methods, together with the best secondary
biological treatment technology currently available for discharge into
navigable water bodies. This technology is represented by preliminary
screening, primary treatment (wool scouring only), coagulation (carpet
mills only), and secondary biological treatment.
The recommended technology for July 1, 1983, and for new source
performance standards, is in-plant waste management and preliminary
screening, coagulation (carpet mills only), primary sedimentation (wool
scouring only) , biological secondary treatment and advanced treatment
such as multi-media filtration or activated carbon adsorption.
Supportive data and rationale for development of the proposed effluent
limitation guidelines and standards of performance are contained in this
report.
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CONTENTS
Section Pa%
I CONCLUSIONS 1
II RECOMMENDATIONS 3
III INTRODUCTION 7
Purpose and Authority 7
Methodology 8
General Description of the Industry 9
Profile of Manufacturing Processes 17
Wool Fiber and Fabric Finishing Operations 17
Cotton Fiber and Fabric Finishing Operations 19
Synthetic Fiber and Fabric Finishing Operations 21
Process Description by Subcategory 22
IV INDUSTRY CATEGORIZATION 33
Previous Approaches 33
Categorization 35
Economic Considerations 42
V WASTE CHARACTERISTICS 46
Subcategory 1 - Raw Wool Scouring 46
Subcategory 2 - Wool Finishing 48
Subcategory 3 - Greige Mills 51
Subcategory 4 - Woven Fabric Finishing 52
Subcategory 5 - Knit Fabric Finishing 63
Subcategory 6 - Carpet Mills 64
Subcategory 7 - Yarn Dyeing and Finishing 65
VI SELECTION OF POLLUTANT PARAMETERS 66
Waste Water Parameters of Major Significance 66
iii
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CONTENTS (Continued)
Section
VI
VII
VIII
Rationale for Selection of Major Parameters 66
Biochemical Oxygen Demand 66
Suspended Solids 67
pH 67
Chemical Oxygen Demand 67
Fecal Coliforms 67
Grease and Oil 68
Rationale for Selection of Minor Parameters 68
Total Dissolved Solids 68
Alkalinity 68
Ammonia Nitrogen and Other Nitrogen Forms 68
Phosphates 68
Temperature 69
Color 69
Chromium 69
Other Heavy Metals 69
Phenols 70
Sulfides 70
Toxic Organic Chemicals 70
CONTROL AND TREATMENT TECHNOLOGY 72
In-Process Control 72
New Process Technology 75
Specific In-Process Changes 78
Biological Treatment Technology 79
Performance of Biological Treatment Systems 87
Advanced Waste Water Treatment Technology 91
COST, ENERGY, AND NON-WATER QUALITY ASPECTS 112
Cost and Reduction Benefits of Alternative 112
Treatment and Control Technologies
Basis of Economic Analysis 112
Cost Effectiveness of Treatment Alternatives 126
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CONTENTS (Continued)
Section
VIII
IX
Impact of Waste Treatment Alternatives on
Finished Product
Alternative Treatment Systems
Electrical Energy Requirements
Thermal Energy Requirements
Solid Wastes
EFFLUENT REDUCTION ATTAINABLE THROUGH THE
APPLICATION OF THE BEST PRACTICABLE CONTROL
TECHNOLOGY CURRENTLY AVAILABLE EFFLUENT
LIMITATIONS GUIDELINES
Introduction
Effluent Reduction Attainable Through the
Application of Best Practicable Control
Technology Currently Available
Identification of Best Practicable Control
Technology Currently Available
Rationale for the Selection of Best Practicable
Control Technology Currently Available
Age and Size of Equipment and Facility
Total Cost of Application in Relation to
Effluent Reduction Benefits
Engineering Aspects of Control Technique
Applications
Process Changes
Non-Water Quality Environmental Impact
Factors to be Considered in Applying Level I
Guidelines
Page
127
142
142
142
143
144
144
145
149
160
160
160
161
161
161
161
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CONTENTS (Continued)
Section Page
X EFFLUENT REDUCTION ATTAINABLE THROUGH THE 162
APPLICATION OF THE BEST AVAILABLE TECHNOLOGY
ECONOMICALLY ACHIEVABLE EFFLUENT LIMITATIONS
GUIDELINES
Introduction 162
Effluent Reduction Attainable Through 163
Application of the Best Available Technology
Economically Achievable
Identification of the Best Available 163
Technology Economically Achievable
Rationale for the Selection of Best Available 165
Control Technology Economically Achievable
Age and Size of Equipment and Facilities 165
Total Cost of Application in Relation to 165
Effluent Reduction Benefits
Engineering Aspects of Control Technique 165
Application
Process Changes 166
Non-Water Quality Environmental Impact 166
Factors to be Considered in Applying Level 166
II Guidelines
XI NEW SOURCE PERFORMANCE STANDARDS 168
Introduction 168
Effluent Reduction Attainable for New Sources 168
Pretreatment Requirements 169
vi
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CONTENTS (Continued)
Section
Page
XII ACKNOWLEDGEMENTS 170
XIII REFERENCES 172
XIV GLOSSARY 198
XV CONVERSION TABLE 205
vii
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TABLES
Number Page
1 Maximum Thirty Day Average Recommended 4
Effluent Limitation Guidelines for July 1, 1977
2 Maximum Thirty Day Average Recommended 5
Effluent Limitation Guidelines for July 1, 1983
3 Number of Textile Plants by Geographic Areas: 11
1967
4 Water Use by the Textile Industry 15
5 Water Discharged by the Textile Industry 16
6 Industry Categorization 34
7 Basis for Size Exception within Textile 44
Subcategorization
8 Types and Amounts of Dyes Used in the Textile 58
Industry
9 Chemicals Used in Application of Dyes 61
10 Expected Effluent Suspended Solids from Multi- 95
Media Filtration of Biological Effluents
11 Carbon Adsorption Pilot Plant: Average Water 104
Quality Characteristics
12 Accuracy of Standardized Costing Methodology 116
13 Waste Water Treatment Costs for Subcategory 129
l-(Small)
14 Waste Water Treatment Costs for Subcategory 130
1-(Medium)
ix
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Number Page
15 Waste Water Treatment Costs for Subcategory 131
2-(Small)
16 Waste Water Treatment Costs for Subcategory 132
2-(Medium)
17 Waste Water Treatment Costs for Subcategory 133
3-(Average)
18 Waste Water Treatment Costs for Subcategory 134
4-(Small)
19 Waste Water Treatment Costs for Subcategory 135
4-(Medium)
20 Waste Water Treatment Costs for Subcategory 136
5-(Small)
21 Waste Water Treatment Costs for Subcategory 137
5-(Medium)
22 Waste Water Treatment Costs for Subcategory 138
6-(Small)
23 Waste Water Treatment Costs for Subcategory 139
6-(Medium)
24 Waste Water Treatment Costs for Subcategory 140
7-(Small)
25 Waste Water Treatment Costs for Subcategory 141
7-(Medium)
26 Maximum Thirty Day Average Recommended Effluent 146
Limitations Guidelines for July 1, 1977
27 Performance of Biological Treatment Systems 148
28 Performance of Effluent Treatment Systems 150
Subcategory 1: Wool Scouring
29 Performance of Effluent Treatment Systems 155
Subcategory 4: Woven Fabric Finishing
x
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Number Page
30 Performance of Effluent Treatment Systems 156
Subcategory 5: Knit Fabric Finishing
31 Performance of Effluent Treatment Systems 158
Subcategory 6: Carpet Mills
32 Performance of Effluent Treatment Systems 159
Subcategory 7: Stock and Yarn Dyeing
33 Maximum Thirty Day Average Recommended 164
Effluent Limitations Guidelines for July 1, 1983
XI
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FIGURES
Number Title Page
1 Subcategory 1: Wool Scouring 23
2 Subcategory 2: Wool Finishing 24
3 Subcategory 3: Greige Mills 28
4 Subcategory 4: Woven Fabric Finish 29
5 Subcategory 5: Knit Fabric Finishing 30
6 Subcategory 6: Carpet Mills 31
7 Subcategory 7: Stock and Yarn Dyeing and Finishing 32
8 COD Isotherms Using Virgin Carbon and Different 102
Secondary Sewage Effluent
9 Schematic of an Activated Carbon System 103
Including Thermal Regeneration
10 Aerated Stabilization Basin Construction Cost 117
11 Engineering Costs 118
12 Clarifier Capital Cost 119
13 Aerated Stabilization Basin (Aeration Equipment Only) 120
14 Aerated Stabilization Basin Annual Operation and 121
Maintenance Labor
15 Aerated Stabilization Basin (Material and Supply 122
Costs, Annual) (Chemical Costs)
16 Aeration Equipment Annual Power Costs (Aerated 123
Stabilization Basin)
17 Clarifier, Annual Operation and Maintenance Labor 124
xii
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Number Title Page
18 Clarifier (Material and Supply Costs, Annual) 125
(Major Chemical Costs)
19 Typical Seasonal Variation for Biological 147
Treatment
20 Distribution of Water Use for Greige Mills 153
xiii
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SECTION I
CONCLUSIONS
The purpose of this report is to establish waste water effluent
limitation guidelines for the textile manufacturing industry. A
conclusion of this study is that this industry comprises seven
subcateaories:
1. Wool Scouring
2. Wool Finishing
3. Greige Mills
4. Woven Fabric Finishing
5. Knit Fabric Finishing
6. Carpet Mills
7. Stock and Yarn Dyeing and Finishing
The major criteria for the establishment of the subcategories are the
biochemical oxygen demand (BOD5) , chemical oxygen demand (COD) , and
total suspended solids (TSS) in the plant waste water.
Subcategorizaticn is required on the basis of the raw material.used and
the production process employed. Evaluation of such -factors as age of
facilities, location and climate and similarities in available treatment
and control measures substantiate this industry subcategorization.
However, the facility's size required an exception within the
subcategorization. Different limitations were established for plants
within six subcategories due to unequal economic impacts created by
diseconomies of scale.
The wastes from all subcategories are amenable to biological treatment
processes and at least eighteen textile manufacturing plants are able to
achieve high levels of effluent reduction (BODS and total suspended
solids) through secondary biological treatment systems. These systems
treat waste waters from dyeing and finishing broadwoven cotton and
cotton synthetic blends, knits and stock and yarn. It is estimated that
the costs for all plants within the industry to achieve the best
practicable effluent reduction would result in final product price
increases ranging from 0.1 cents per kilogram product (0.2 cents per
pound product) to a high of 0.8 cents per kilogram (1.8 cents per
pound). The average price increase is less than 0.4 cents per kilogram
(0.9 cents per pound).
The cost of achieving the best available effluent limitations is
estimated to result in further final product price increases ranging
from 0.05 to 0.4 cents per kilogram (0.1 to 0.8 cents per pound) product
processed for all greige mills and for all small plants in the other six
subcategories. Cost increases are expected to range from 0.4 to 2.0
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cents per kilogram (0.8 to 4.5 cents per pound) for larger plants in the
industry subcategories (except greige mills) .
The estimated final product costs required to achieve best practicable
and best available effluent reductions range between 0.3 and 1.1 cents
per kilogram (0.6 and 2.5 cents per pound) for small plants and 0.5 to
2.5 cents per kilogram (1.0 and 5.4 cents per pound) for larger plants.
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SECTION II
RECOMMENDATIONS
The waste water effluent reduction limitations attainable through the
application of the best practicable control technology currently
available are based on the performances of exemplary secondary
biological systems treating textile manufacturing waste water. Best
practicable control technology currently available includes the
following treatment components: preliminary screening, primary
sedimentation (wool scouring only) , coagulation (carpet mills only) , and
secondary biological treatment.
The waste water effluent reduction limitations attainable through the
application of the best available control technology economically
achievable are based on the best practicable control technology plus
advanced treatment including multi-media filtration for greige mills and
small textile mills in the remaining six subcategories and activated
carbon adsorption for larger mills in the six subcategories. Both
filtration and carbon absorption may be needed where large quantities of
dispersed dyes or materials with poor adsorptive capacity are
discharged.
Recommended best practicable effluent limitations to be achieved by July
I, 1977, are set forth in Table 1 and recommended best available
limitations to be achieved by July 1, 1983, are set forth in Table 2.
These limitations are the average of daily values for any period of
thirty consecutive days. Maximum limitations for any one day for BOD5,
TSS, COD and oils and grease should not exceed these thirty day
limitations by more than one hundred percent.
The waste water effluent reduction limitations for new sources are the
same as those attainable through the application of the best available
control technology economically achievable. These limitations are
possible because of the present availability of the treatment and
control technology to attain this level of effluent reduction.
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TABLE 1
MAXIMUM THIRTY DAY AVERAGE
RECOMMENDED EFFLUENT LIMITATION
GUIDELINES FOR JULY 1, 1977
Effluent Limitations (1)
BODS TSS ODD
kg/lOOOkg kg/lOOOkg kg/lOOOkg
Plant Subcategory (Ib/lOOOlb) (Ib/lOOOlb) (Ib/lOOOlb)
1. WDOL SCOURING (2)
Plant capacity less than 3.7 3.7 NA
6,500 kg/day (14,300 Ib/day)
Plant capacity greater than 3.7 3.7 24
6,500 kg/day (14,300 Ib/day)
2. WOOL FINISHING
Plant capacity less than 7.5 7.5 NA
900 kg/day (1,980 Ib/day)
Plant capacity greater than 7.5 7.5 56
900 kg/day (1,980 Ib/day)
3. GREIGE MILLS
All plant sizes 0.45 0.45
4. W3VEN FABRIC FINISHING
Plant capacity less than 2.2 6.9 NA
1,000 kg/day (2,200 Ib/day)
Plant capacity greater than 2.2 6.9 33
1,000 kg/day (2,200 Ib/day)
5. KNIT FABRIC FINISHING
Plant capacity less than 1.8 8.0 NA
3,450 kg/day (7,590 Ib/day)
Plant capacity greater than 1.8 8.0 24
3,450 kg/day (7,590 Ib/day)
6. CARPET MILLS
Plant capacity less than 4.3 4.3 NA
3,450 kg/day (7,590 Ib/day)
Plant capacity greater than 4.3 4.3 30
3,450 kg/day (7,590 Ib/day)
7. STOCK AND YARN DYEING AND FINISH-
ING
Plant capacity less than 3.5 9.2 NA
3,100 kg/day (6,820 Ib/day)
Plant capacity greater than 3.5 9.2 47
3,100 kg/day (6,820 Ib/day)
NA MEANS NOT APPLICABLE
(1) Plant capacities and discharge limitations are stated for Subcategories
1 and 2 per weight of raw wool received at the wool scouring or wool
finishing operation and are stated for Subcategories 3, 4, 5, 6 and 7
per weight of final material produced by the facility.
For all Subcategories pH should range between 6.0 to 9.0 at any time.
For all Subcategories Most Probable Number (MPN) of Fecal Coliforms
should not exceed 400 counts per 100 ml.
(2) For all Wool Scouring plants (Subcategory 1) Oils and Grease should
not exceed 1.9 kg (lb)/1000 kg (Ib) grease wool.
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TABLE 2
-MAXIMUM THIRTY DAY AVERAGE
RECOMMENDED EFFLUENT LIMITATION
GUIDELINES FOR JULY 1, 1983
Effluent Limitations (1)
BODS TSS COD
kg/lOOOkg kg/lOOOkg - kg/lOOOkg
Plant Subcategory (Ib/lOOOIb) (Ib/lOOOlb) (Ib/lOOOlb)
1. WOOL SCOURING (2)
Plant capacity less than 2.5 2.5 NA
6,500 kg/day (14,300 Ib/day)
Plant capacity greater than 2.5 2.5 64
6,500 kg/day (14,300 Ib/day)
2. WOOL FINISHING
Plant capacity less than 5.0 5.0 NA
900 kg/day (1,980 Ib/day)
Plant capacity greater than 5.0 5.0 14.9
900 kg/day (1,980 Ib/day)
3. GREIGE MILLS
All plant sizes 0.3 0.3 NA
4. WOVEN FABRIC FINISHING
Plant capacity less than 1.5 4.6 NA
1,000 kg/day (2,200 Ib/day)
Plant capacity greater than 1.5 4.6 8.8
1,000 kg/day (2,200 Ib/day)
5. KNIT FABRIC FINISHING
Plant capacity less than 1.2 5.3 NA
3,450 kg/day (7,590 Ib/day)
Plant capacity greater than 1.2 5.3 6.4
3,450 kg/day (7,590 Ib/day)
6. CARPET MILLS
Plant capacity less than 2.9 2.9 NA
3,450 kg/day (7,590 Ib/day)
Plant capacity greater than 2.9 8.0
3,450 kg/day (7,590 Ib/day)
7. STOCK AND YARN DYEING AND FINISH-
ING
Plant capacity less than 2.3 6.1 NA
3,100 kg/day (6,820 Ib/day)
Plant capacity greater than 2.3 6.1 12.5
3,100 kg/day (6,820 Ib/day)
NA MEANS NOT APPLICABLE
(1) Plant capacities and discharge limitations are stated for Subcategories
1 and 2 per weight of raw wool received at the wool scouring or wool
finishing operation and are stated for Subcategories 3, 4, 5, 6 and 7
per weight of final material produced by the facility.
For all Subcategories pH should range between 6.0 to 9.0 at any tima.
For all Subcategories Most Probable Number (MPN) of Fecal Coliforms
should not exceed 400 counts per 100 ml.
(2) For all Wool Scouring plants (Subcategory 1) Oils and Grease should
not exceed 1.9 kg (lb)/1000 kg (Ib) grease wool.
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SECTION III
INTRODUCTION
Purpose and Authority
Section 301(b) of the Act requires the achievement, by not later than
July 1, 1977, of effluent limitations for point sources, other than
publicly owned treatment works, which are based on the application of
the best practicable control technology currently available as defined
by the Administrator pursuant to Section 304(b) of the Act. section
301(b) also requires the achievement, by not later than July 1, 1983, of
effluent limitations for point sources, other than publicly owned
treatment works, which are based on the application of the best
available technology economically achievable which will result in
reasonable further progress toward the national goal of eliminating the
discharge of all pollutants, as determined in accordance with
regulations issued by the Administrator pursuant to Section 305(b) to
the Act. Section 306 of the Act requires the achievement by new sources
of a Federal standard of performance providing for the control of the
discharge of pollutants which reflects the greatest degree of effluent
reduction which the Administrator determines to be achievable through
the application of the best available demonstrated control technology,
processes, operating methods, or other alternatives, including, where
practicable, a standard permitting no discharge of pollutants.
Section 304(b) of the Act requires the Administrator to publish within
one year of enactment of the Act, regulations providing guidelines for
effluent limitations setting forth the degree of effluent reduction
attainable through the application of the best practicable control
technology currently available and the degree of effluent reduction
attainable through the application of the best control measures and
practices achievable including treatment techniques, process and proce-
dure innovations, operation methods and other alternatives. The regu-
lations proposed herein set forth effluent limitations guidelines
pursuant to Section 304 (b) of the Act for the textile manufacturing
source category.
Section 306 of the Act requires the Administrator, within one year after
a category of sources is included in a list published pursuant to Sec-
tion 306 (b) (1) (A) of the Act, to propose regulations establishing
Federal standards of performances for new sources within such
categories. The Administrator published in the Federal Register of
January 16, 1973 (38 F.R. 1624), a list of 27 source categories.
Publication of the list constituted announcement of the Administrator's
intention of establishing, under Section 306, standards of performance
applicable to new sources within the textile manufacturing source
category, which was included within the list published January 16, 1973.
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The effluent limitations guidelines and standards of performance pro-
posed herein were developed in the following manner. The textile
industry was first categorized for the purpose of determining whether
separate limitations and standards are appropriate for its different
segments. Considerations in the industry categorization process
included raw materials, the products, manufacturing procass, and raw
waste characteristics.
The raw waste characteristics for each subcategory were identified
through analyses of: (1) the sources and volumes of water and waste
waters and (2) the constituents of all waste waters including toxic or
hazardous constituents and other constituents which result in taste,
odor or color. The constituents of waste waters that should be subject
to effluent limitations guidelines and standards of performance were
identified.
The full range of control and treatment technologies existing within
each subcategory were identified. This included an identification of
each distinct control and treatment technology, including both in-plant
and end-of-process technologies, which are existent or capable of being
designed for each subcategory. It also included an identification, in
terms of the amount of constituents and the chemical, physical, and
biological characteristics of pollutants, of the effluent level
resulting from the application of each of the treatment and control
technologies. The problems, limitations, and reliability of each treat-
ment and control technology and the required implementation time were
also identified. The non-water quality environmental impact were also
identified, e.g., ths effects of the application of such technologies
upon other pollution problems, including air, solid waste, noise, and
radiation. The energy requirements of each of the control and treatment
technologies were identified as well as the cost of the application of
such technologies.
The information, as outlined above, was then evaluated to determine what
levels of technology constituted the "best practicable control technolo-
gy currently available," "best available technology economically
achievable" and "best available demonstrated control technology,
processes, operating methods, or other alternatives." In identifying
such technologies, various factors were considered. These included the
total cost of application of technology in relation to the effluent
reduction benefits to be achieved from such application, the age of
equipment and facilities involved, the process employed, the engineering
aspects of the application of various types of control techniques
process changes, non-water quality environmental impact (including
energy requirements), the treatability of the wastes, and water use
practices.
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The data for the identification and analyses were derived from a number
of sources. These sources included EPA research information, published
literature, previous EPA technical guidance for textile manufacture,
various industry associations, qualified technical consultation, and on-
site visits and interviews at exemplary textile manufacturing plants in
the United States. All references used in developing the guidelines for
effluent limitations and standards of performance for new sources
reported herein are listed in Chapter XIV.
§enera1_Description of the^Industry
Since 1638, when the first commercial mill was erected at Raleigh,
Massachusetts, the U.S. textile industry has burgeoned to a point where
there are nearly 7100 plants in 47 states, employing about one million
people, and in 1972 selling goods valued at just under $28 billion.
These plants range from highly integrated manufacturing complexes that
process basic raw materials into finished products, to small non-
integrated contract plants that process goods owned by other producers.
According to the 1967 census of Manufacturers, the textile industry, SIC
Code 22, contains ten major SIC classifications. In recent decades, the
industry has been concentrating in the southeast--notably in the
Carolinas, Georgia and Alabama—and this trend is continuing. Today 38
percent of the textile plants are in the southeast and 92 percent are on
the eastern seaboard. The rest, as shown in Table 3 are scattered
throughout the country. Knitting mills, with almost 2,700 plants
listed, constitute the largest group but there are also about 1,000
weaving mills of various types and over 1,000 plants which process
miscellaneous textile goods. Most of the textile industry is contained
within EPA Regions 1, 2, 3 and 4, with Region 4 accounting for a major
proportion of the industry. As shown below, almost 80 percent of the
industry is located in the southern and mid-atlantic states.
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South 2656 38
Mid-Atlantic 2821 40
New England 978 14
North Central 321 4
West _3.04 _4
7080 100
Source: 1967 Census of Manufacturers
10
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The industry's basic raw materials are wool, cotton, and man-made
fibers. Of the roughly 5.0 billion kilograms (11 billion pounds) of raw
materials consumed by the industry in 1972, wool computed on a clean
basis accounted for about 0.09 billion kilograms (0.2 billion pounds),
cotton for 4.0 billion kilograms (4 billion pounds) and man-made fibers
for 3.2 billion kilograms (7 billion pounds).
Among the man-made fibers, the most important are rayon, acetate, nylon,
acrylic, polyester, polypropylene, and glass fiber.
The natural fibers are supplied in staple form, (staple being short
fibers) . The man-made fibers are supplied as either staple or
continuous filament. In either case the fiber is spun into yarn, which
is simply a number of filaments twisted together. The yarn is woven or
knit into a fabric, and the fabric then dyed and treated to impart such
characteristics as shrink resistance, crease resistance, etc. The
finished fabric is delivered—directly or through converters, jobbers,
and wholesalers-to the manufacturer of textile products.
The many woven fabrics are produced by variations in the weaving
pattern. Plain, or tafeta, weaves give such fabrics as broadcloth,
calico, cheesecloth, muslin, seersucker, flannel and tweed. Twill
weaves are represented by serge, herringbone, jersey, gabardine, and
ticking. Because of their superior strength, twill fabrics are used for
work clothes and men's suits. Satin weaves are smooth but weak; the
best known are crepe satin, sateen, and damask. Dobby and Jacquard
weaves are used to produce patterned fabrics. Dobby weaves are used in
men's shirting and women's dress fabrics. Jacquard weaves are used
extensively for upholstery and drapery materials. Finally, there are
the pile weaves, which include velvets, plushes, corduroys and turkish
toweling.
In transforming a fiber into one of these woven fabrics, two types of
processes are used: wet and dry. The SIC code breakdown is not particu-
larly useful for evaluating the waste effluent problems of the textile
industry. These codes are grouped primarily by the process used--e.g.,
weaving or knitting--whereas the waste effluent problems stem from all
the wet processes which are used to desize, wash, dye and finish the
textile fabric. The wet processes of interest include: scouring, de-
sizing, mercerizing, bleaching, bonding and laminating. Dry processes
include: spinning, weaving and knitting. Although SIC Code 226
identifies textile finishing, Code 221 identifies weaving mills which
may also be integrated mills that have a finishing operation or may be
greige goods mills that have only dry processing. Knitting mills fall
into a similar category; many of the mills identified as knitting mills,
in fact, process dyed yarns and, therefore, essentially carry out dry
operations.
13
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There is no exact figure for the number of wet processing plants or the
total water use by the industry, but the Census of Manufacturers gave
for 1968 under Textile Mill Products a total of 684 wet plants which
consume 412 billion liters (109 billion gallons) of process water per
yaar. (This includes sanitary and cooling water, etc.) A more recent
estimate, by the American Textile Manufacturers' Institute in 1970,
found 346 plants using 394 billion liters (104 billion gallons) per
year, estimated to be 83 percent of the total industry use.
Table 4 gives details of the process water used and discharged divided
as far as possible according to the EPA categories. The largest water
users are undoubtedly the finishing plants, with a total of 269 billion
liters (71 billion gallons) per year, averaging 2800 cubic meters per
day (0.73 million gallons per day) . The next highest category is the
wool finishing operations, with 47.3 billion liters (12.5 billion
gallons) per year averaging 27000 cubic meters per day (0.7 million
gallons per day) but consisting of a much smaller segment of the textile
industry.
A summary of this data is presented in Table 5, which shows that 110
billion liters (29 billion gallons) per year or 26.6 percent of the
water was discharged to municipal sewers and 73.2 percent or 303 billion
liters (80 billion gallons) per year to surface water. The 73.2 percent
also divides into 24.2 percent that received no treatment, 21 percent
that received primary treatment and 28.2 percent that received secondary
treatment before discharge. Since 1968 many more treatment plants have
been built and from a consideration of RAPP data and the recent survey
by the ATMI, we estimate that about 35 percent of the water used is now
discharged to municipal sewers, 15 percent receives no treatment, 5
percent receives primary treatment and 45 percent receives secondary
treatment. Undoubtedly, the smaller mills or those using the least
amounts of water have found it more economical to use municipal
treatment instead of constructing their own facilities.
14
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TOTAL PROCESS WATER 413.
(109.
Sources: Department of Commerce 1967 Census of Manufacturers
Refuse Act Permit Program Data
American Textile Manufacturers Institute
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Profile of Manufacturing Processes
As mentioned above the industry's basic raw materials are wool, cotton
and synthetic fibers. The fiber and fabric finishing operations are
described below for each of these three materials. Finally, these
operations are related to the selected subcategorization through brief
process descriptions of each subcategory. The rationale for
subcategorization along with detailed descriptions of the seven segments
is given in Section IV.
Wool Fiber and Fabric Finishing Operations
Wool fiber consumption is smaller than either cotton or synthetic fiber
consumption and the trend seems to be toward less demand in the future
on a percentage basis. The operations required to produce a piece of
finished woolen fabric are described below; either knitting or weaving
can be done at a given mill. Scouring is the first wet process that
wool fibers receive. This process removes all the natural and acquired
impurities from the wcolen fibers. There are two methods of wool
scouring - detergent scouring and solvent scouring. In the United
States, the detergent scouring process is used almost exclusively.
There are two types of detergent scouring - the soap-^alkali process and
the neutral detergent scouring process. In the soap-alkali process, a
soap or synthetic detergent and a milk alkali such as sodium carbonate
or soda ash is added to a bath at a pH of 9.5 to 10.5 and heated to
temperatures of 130°F. This process consumes a volume of 8,000 to
12,000 gallons of water per 1000 pounds of wool fiber. In the neutral
detergent process, non-ionic detergents fo the ethylene oxide condensate
class are added to water at a pH of 6.5 to 7.5 and a temperature of 135°
to 160°F.
The process is carried out in a series of four open bowls called
"scouring train." The first two bowls contain the detergent or soap
alkali and perform the scour. The last two bowls serve to rinse the
fibers clean. For every pound of scoured woolen fiber one and one-half
pounds of waste impurities are produced; therefore, wool scouring
produces one of the strongest industrial wastes in terms of BOD. This
process contributes 55 to 75 percent of the total BOD load in wool
finishing.
The next processes are the burrpicking and carbonizing step which is
done to remove any vegetable matter remaining in the wool after
scouring. If the wool is to be stock dyed, it is done prior to dyeing;
if the wool is to be piece dyed, the fabric is carbonized prior to
dyeing.
Due to the popularity of multi-colored fabrics, stock dyeing is used
more often today than is piece good dyeing. The two classes of dyes
used on wool fiber are acid dyes and metallized dyes. In the dyeing of
17
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wool fibers it is impossible- to fix definite formulas. The dye, grade
of wool, and the type of dyeing machine will alter the formulation. in
the acid dyeing baths the temperature of the solution will vary from
140° to 212°F. In the metallized dyeing the average final temperature
is 185°F. The pH varies depending on the amount of residual alkali left
in the wool fibers after the scouring process. The volume of waste
water generated by dyeing, either stock or piece goods is large and
highly colored. The BOD load is contributed by the process chemicals
used, and the contribution of wool dyeing to the mill's total BOD load
is 1 to 5 percent.
Although the mixing and oiling step does not contribute directly to the
water waste volume, the oil finds its way into the waste stream through
the washing after fulling operation. The percentage contribution of
total BOD load of this process varies with the type of oil used. The
traditional oiling agent is olive oil, which produces a high BOD that
could contribute 10 percent of the total BOD load; however, there is a
trend toward the use of non-ionic emulsifiers in oiling, that greatly
reduces the BOD contribution in this area.
Fulling is another operation that does not directly contribute to the
waste stream, until the process chemicals are washed out of the fabric
in the wash after fulling operation. There are two common methods of
fulling, alkali fulling and acid fulling. In the former case, soap or
synthetic detergent, soda ash, and sequestering agents are used in the
fulling solution. In acid fulling, the fabric is impregnated with an
aqueous solution of sulfuric acid, hydrogen peroxide, and minor amounts
of metallic catalysts (chromium, copper and cobalt). In either case,
the water is heated to a temperature of 90° to 100°F. Acid fulling is
always followed by alkali fulling.
Following the fulling operation, the goods are washed to remove the
fulling chemicals mentioned above and the carding oil described in the
mixing and oiling disussion. It is estimated that from 10 to 25 percent
of the fulled cloth's weight is composed of process chemicals that will
be washed out in this process and wasted. Due to this large amount of
waste, wool washing after fulling is the second largest source of BOD,
contributing from 20 to 35 percent of the total. The usual procedure in
this process is to subject the fulled cloth to two soapings, two warm
rinses, and one cold rinse. In the first soaping, nothing is added to
the water, the soaping action takes place when agitation of the fabric
causes the soap or synthetic detergent ot produce subs, thus washing the
fabric. In the second soaping, a 2 percent solution of soap or
synthetic detergent is used. The warm water rinsings are done at 100°
to 110°F., while the cold rinse is done below 100°F. This process
consumes from 40,000 to 100,000 gallons of water for each 1000 pounds of
wool fabric. Analyses show that wool, once throughly washed, will
produce little or no BOD of itself on being rewashed.
18
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After the dusting process, which follows carbonizing the fabric or stock
of fibers, the acids used in carbonizing must be removed. In order to
accomplish this, the wool is rinsed to remove the bulk of the acid.
Following the rinse, the wool is neutralized by a low concentration
solution of sodium carbonate. After this neutralization bath the fabric
is rinsed again. Since sulfuric acid and soda ash have little or no
BOD, this process contributes less than 1 percent of the total BOD.
In the processing of woolen fibers, five sources of pollutional load
exist - scouring, dyeing, washing after fulling, neutralizing the
carbonizing, and bleaching with optical brighteners. Figures 1 and 2
outline the operations that take place in woolen fabric manufacturing.
Cotton Fiber and Fabric Finishing Operations
The consumption of cotton fibers by textile mills in the United States
exceeds that of any other single fiber; however, the total synthetic
fiber poundage consumed by the textile industry is greater than that of
cotton. The operations required to produce a piece of finished cotton
fabric are described below; either weaving or knitting can be done at a
given mill.
Slashing is the first process in which liquid treatment is involved. In
this process, the warp yarns are coated with "sizing" in order to give
them tensile strength to withstand the pressures exerted on them during
the weaving operation. Such substances as starch, starch substitutes,
polyvinyl alcohol, carboxy methyl cellulose, gelating glue and gums have
been used as size agents. The source of pollution in this process
results from the cleaning of slasher boxes, rolls, and make up kettles.
The volume is therefore usually low; nowever, the BOD can be quite high,
especially if starch is used.
The operation of desizing removes the substance applied to the yarns in
the slashing operation, by hydrolyzing the size into a soluble form.
There are two methods of desizing - acid desizing and enzyme desizing.
In acid desizing, the fabric is soaked in a solution of sulphuric acid,
at room temperature, for U to 12 hours, and then washed out. In enzyme
desizing, couplex organic compounds produced from natural products or
malk extracts are used to solubilize the size. The bath is maintained
at a temperature of 130° - 180°F. and a pH of 6-7.7, for a period of 4-8
hours. Due to the unstable nature of these organic compounds, the whole
bath must be discarded after each batch. After the size has been
solubilized, the fabric is rinsed clean. Desizing contributes the
largest BOD of all cotton finishing processes - about 45 percent.
scouring follows desizing. In this process, the cotton was and other
non-cellulosic components of the cotton are removed by hot alkaline
detergents or soap solutions. In most modern plants, scouring is done
in conjunction with desizing rather than as separate operation. Caustic
19
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soda and soda ash along with soaps and synthetic detergents and
inorganic reagents are used to remove the non-cellulois impurities. The
bath is characterized by a pH of 10 to 13 and temperatures of 250°F.
Although the strength of alkali in the beginning of the operation is
between 1 percent and 5 percent, the waste liquor will have a 0.3
percent alkaline concentration, the rest being taken out of solution by
the cotton fibers. As in the desizing operation, the scouring process
is a batch operation requiring the fabric to remain in the kier for a
period of from 2 - 12 hours. Scouring is the second largest BOD
contributing process in the finishing of cotton textiles - about 31
percent. Following the "boil-out," tne goods are rinsed with hot and
cold water to remove residual alkali.
Bleaching, the next process, removes the natural yellowish coloring of
the cotton fiber and renders it white. The three bleaches most commonly
used for cotton are sodium hypochlorite, • hydrogen peroxide, and sodium
chlorite. In hypochlorite bleaching, the fabric is rinsed, saturated
with a weak solution cf sulfuric or hydrochloric acid, rinsed again, and
then passed through the hypochlorite for a period of up to 24 hours.
Then process is done at room temperature with a pH range of 9 to 11.
When bleaching with sodium chlorite, acetic acid is used in place of
sulfuric or hydrochloric acid, the temperature of the bath is hot (180°
185°F), and the pH is 3.5-5.5. Hydrogen peroxide is used for
continuous bleaching. This process calls for a washer, with a 140°
175°F temperature, saturation with caustic soda at 175° - 180°F, passage
through the peroxide at 195°F, and a final rinse. The pH range used in
hydrogen peroxide bleaching is 9 to 10. The final rinse may contain an
antichlor, sodium bisulfite or sulfuric acid, to remove residual
chlorine from the fabric. The bleaching process contributes the lowest
BOD for cotton finishing.
The mercerization process was originally developed to give increased
luster to cotton fabrics. Today it is still used for that purpose, but
more importantly to impart increased dye affinity and tensile strength
to the fabric. It is estimated that only 30 percent of all cotton
fabrics are now mercerized, and with the increasing use of cotton-
polyester blends, less will probably be done in the future. The process
uses a 15 to 30 percent solution of sodium hydroxide at room temperature
for 1/2 to 3 minutes. The fabric is then rinsed in an acid wash to
neutralize the fabric and washed in water and then dried. The effluent
from this process is alkaline and high in dissolved solids, but low in
BOD.
After mercerizing, the goods are sent tc the dye house or color shop.
In the dye house they are dyed either in small volumes of batch process
machines, or on continuous dyeing ranges in large volumes. There are
five important classes of dyes used on cotton fabrics: vat, developed,
sulphur, direct, and aniline black.
20
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The dyeing process is carried out in an aqueous bath with pH variations
In the color shop, the aoods are printed with colored designs or
patterns. The usual method is by roller machines. The color is
imparted to the fabric from the rolls which contain the printing paste.
This paste contains dye, thickener, hygroscopic substances, dyeing
assistants, water, and other chemicals. The pollutional load from the
color shop comes mainly from the wash-down rinses used to clean the
equipment in the shop and the clorh rinsings. The pollutional load is
rather low in both volume and BOD. When a mill does both printing and
dyeing, the BOD contribution of the combined processes is 17 percent,
and the total BOD load comes from -ne process chemicals used.
Synthetic Fiber and Fabric Finishing Operations
In this category of textile fibers there are two broad classifications:
cellulosic and non-cellulosic fibers. The two major cellulosic fibers
are rayon and cellulose acetate. The major non-cellulosic fibers are
nylon, polyester, acrylics and modacrylics. There are other fibers in
both classes, but at present they are not consumed in as large a volume
as the six fibers mentioned above. The largest volume of synthetic
fibers consumed by textile mills comes from the non-cellulosic fibers;
and the trend is toward an even greater demand in the future,
particularly for polyester fibers. Synthetic fibers can be converted
into fabrics in one of two ways. Continuous filament yarns can be used
to manufacture 100 percent synthetic fabrics, or staple yarns can ba
used to produce fabrics that are blends of man-made fibers or man-made
and natural fibers. Blended fabrics are processed according to the
natural fiber component of the yarn. As in cotton and wool processing,
the yarns are either woven or knitted as a given mill.
The first process in which synthetic fibers are subject to an aqueous
treatment is stock dyeing, unless the fabric is to be piece dyed. When
stock dyeing is used, the liquid waste discharge will vary from about 8
to 15 times the weight of the fibers dyed.
Due to the low moisture regain of the synthetics, static electricity is
a problem during processing. To minimize this problem, anti-static oils
are applied to the yarns, which also serve as lubricants and sizing
compounds. These compounds commonly used are: polyvinyl alcohol,
styrene-base resins, polyalkylen glycols, gelatin, polyarylic acid, and
polyvinyl acetate. These compounds become a source of water pollution
when they are removed from the fabrics during scouring. Since the
manufacture of synthetic fibers can be well controlled, chemical
impurities are relatively absent in these fibers; therefore, only light
scouring and little or no bleaching are required prior to dyeing; and if
synthetics are bleached, the process is not normally a source of organic
or suspended solids pollution; however, the process will generate
dissolved solids if chlorine bleaches are used.
21
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Process Description by Subcategory
Y 1 - Wool Scouring^ A generalized flow diagram of the wool
scouring process is shown in Figure 1. Scouring consists of sorting the
fleece and feeding it to a hopper. The wool then is carried through a
series cf scouring bowls where scour liquor flows countercurrent to it.
Detergent is added in the third or fourth bowls to emulsify the greases
and oils. The scoured wool is then dried. In mills where the cleaned
wool is converted into wool top, the wool is combed and gilled. The
products are short fibers (used for wool yarn) and long fibers (used for
worsted yarn) .
Y 2. ~ Wool Finishing: The wool finishing process is depicted
in Figure 2. The three distinct finishing processes are shown as stock,
yarn and fabric finishing. Because the pollution generated by the
fabric finishing operation is similar to that generated by the other
two, fabric finishing is included in this discussion. If the greige
goods are 100 percent wool, they are first cleaned of vegetable matter
by carbonizing and then cleaned of spinning oils and any weaving sizes
by a light scour. The 100 percent woolens are then dimensionally
stabilized, principally by "fulling," or mechanical working of the wet
fabric in the presence of detergents, to produce a controlled shrinkage
or "felting." Worsteds and most wool- synthetic blends are not fulled.
Worsteds are hard, tightly-woven and dimensionally stable as received at
the finishing plant; woclens are loosely-woven, soft and often are
firmed up by fulling.
The fabric is then dyed in batches in vessels called becks, washed in
the same vessels, and taken to dry finishing operations. The only dry
finishing operation of concern to water pollution is mothproofing.
22
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3 - Greicje Mills_:_ weaving textile yarns into a fabric
requires application of size to the warp yarns in order to resist the
abrasive effects of the filling yarns as these are positioned by the
shuttle action of the loom. Greige mills apply the size and complete
the weaving. Many operate as completely independent facilities. Figure
3 shows operations generally performed at this type of greige mill.
weaving is a dry operation, but is normally done in buildings maintained
at high humidity. Under these conditions, the size film is flexible,
and yarn breaks on the loom are minimized. Yarns sized with polyvinyl
alcohol may be woven at a somewhat lower humidity than yarns sized with
starch. Cooling and humidifying water used in a greige mill represents
a substantial portion of the total water usage. Industrial wastes from
knit greige good is nil. If any wastes are generated they are from the
knitting oils, however, these would only enter the waste stream through
spills, wash up or possible washing of the final product.
For carpet backing, a continuous applicator applies a foamed latex layer
to the carpet's underside. In double-backed carpet, a layer of unfoamed
latex is applied in the same manner, and a final fabric backing is
pressed on, being cemented in place by the latex. In either case, a
liquid latex waste is generated. Some of the latex becomes hardened, so
a mixture of solid and liquid latex results. Some of this material is
collected by shovelling it into a barrel for land-fill disposal. The
rest is washed off by hosing and removed by coagulation.
Subcategory ^ ~ Woven Fabric Finishing Wet processes which are used in
finishing woven greige fabric may be divided into two groups: those
used to remove impurities, clean or modify the cloth; and those in which
a chemical is added to the cloth.
The first of these groups includes desizing, scouring, bleaching,
mercerizing, carbonizing and fulling. Only cotton and cotton blends are
mercerized. The last two of these processes are used only on wool and
wool blends.
The second group of processes includes dyeing, printing, resin
treatment, water proofing, flame proofing, soil repellency and a few
special finishes whose use represents a very small proportion of the
total.
Certain fabrics, including denims and some drapery goods, are "loom
finished." In production of these goods, the warp yarns are dyed, woven
to a fabric, and the fabric finished with a permanent size. For these
fabrics, the first group of processes listed above (cleaning and
preparing the cloth) is avoided entirely. For this reason, mills
producing this group of fabrics may be a subcategory, although we have
not treated it as such. The degree of finishing necessary to provide
fabric ready for sale depends significantly on the fiber (s) being
25
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processed. The natural fibers (cotton and wool) contain substantial
impurities, even after they have been woven as greige goods, and require
special treatments to convert them to the completely white, uniformly
absorbent form that is essential for dyeing, resin treatment, etc.
Synthetic fibers contain only those impurities that were necessary for
manufacture of the fiber and spinning to obtain yarn.
The different operations listed above have been described in the
literature. A. flow sheet for woven fabric finishing is given in Figure
4.
Subcategory_ 5 _ Knit Fabric Finishing: The wet processing operations
performed in knit fabric finishing are shown schematically in Figure 5.
This is necessarily a generalized flowsheet; the specific operations
employed in a given plant will vary from plant to plant. In general,
the yarns are purchased in the undyed state, with a knitting oil finish
to provide lubrication for the knitting operation. The amount of finish
on the yarn ranges from 1 to 7 percent depending on the type of yarn and
fiber. This is a significant difference from weaving yarns which are
sized with starch or ether polymeric materials. After the yarn has been
knitted into fabric, the fabric may be processed by one or more of the
alternative routes indicated in Figure 5. The wet process operations
employed in a plant depend on the nature of the goods involved and the
end product requirements.
Subcateqory (5 - Garget Millsi Carpets are yarn dyed, piece dyed, and
printed. When yarn dyed carpets are made, the yarn is often dyed in
another mill and brought to the carpet mill. The relative quantities of
yarn, beck, and continuous dyeing, and printing and latexing may vary
widely.
The yarn is tufted onto a polypropylene or jute woven backing in a dry
operation (Figure 6). Following this, the tufted carpet can be either
printed or dyed. If printed, a semi-continuous screen printing
operation is performed, followed by a wash and rinse step in the same
machine. If dyed, the most common method is beck dyeing, in a manner
quite similar to that described in previous categories for yard goods.
The industry claims a higher liquor-to-fabric ratio, however, because of
the difficulty in making the carpet sink and become thoroughly wetted.
Many small air bubbles become entrapped in the tufts. The continuous
dyeing appears very similar to the continous pad-stream process used for
cotton/synthetic blends broad-woven finishing. After it is dyed the
carpet is dried in a tunnel drier. The carpet is then ready for
application of either a single or a double backing.
Subcategory. 7 - Stock and Yarn Dyeing and Finishing: In this category is
crude yarn obtained from a spinning facility. The yarn may be natural,
synthetic, or blended. Wet processes used by yarn mills include
scouring, bleaching, mercerizing and dyeing (Figure 7).
26
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Several techniques are available for processing raw yarn into the
finished product. The mcst common process is probably package dyeing,
but other processes, such as space dyeing, are widely used. In the
former process, yarn wound on perforated tubes is placed in a large
vessel, which is sealed. The dye solution, at an appropriate
temperature, is circulated through the yarn. The dyed yarn is washed,
rinsed and dried. In space dyeing, yarn is knit and the fabric is piece
dyed, washed, rinsed and dried. The fabric is then unravelled and the
yarn is wound on cones.
27
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SECTION IV
INDUSTRY CATEGORIZATION
PREVIOUS APPROACHES
In deriving this industry categorization system, existing
categorizations and other previous attempts at categorization have been
considered. The principal systems investigated were:
A. SIC codes. These codes do not lend themselves to a
classification of the industry with respect to
characterization of the pollution loads generated. For
example, Subcategory 3, Greige Goods, includes 10 SIC categories.
b. The method advanced by the report, «'A Simplification of Textile
Waste Survey and Treatment" by Masselli, Masselli and Burford.
This approach consists of synthesizing the raw waste load from
a textile mill by additive contributions of the chemicals used.
Tables of BOC values for many chemicals are given in the report.
This method was judged too difficult to be implemented by persons
not versed in Textile chemistry and not knowledgeable about the
chemicals used.
c. A previous categorization scheme prepared for EPA which
employed unit processes to synthesize the raw waste loads.
This method was also judged too difficult to implement.
d. The preliminary system developed by EPA in the "interim
guidance" for the textile industry.
e. The system developed by the Institute of Textile Technology
and Hydrosciences in the study for the American Textile
Manufacturer's Institute, Inc., and Carpet and Rug Institute.
Based on knowledge of the various pollution problems, loads generated by
the different unit operations in the textile industry, actual and
potential waste treatment practices and current manufacturing and
processing practices, these five approaches were combined and
simplified.
The last two methods (d and e) and the present one have in common a
categorization according to the products produced by a mill that in turn
relates to type of wastes.
A comparison of the EPA interim guidance and the ATMI/CRI
categorizations with those used in this study is given in Table 6.
33
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Categorization
The following factors were considered in establishing subcategories in
the textile industry.
a) raw material
b) age and size of facilities
c) products and production processes
d) location and climate
e) waste treatability
The principal basis for subcategorization is the configuration of the
predominant material being processed. Knit and woven fabrics are
different and each is different from carpet, yarn or other fibers.
Special processes such as wool scouring and latex application provide
additional subcategorization. Waste water volume and characteristics
vary widely for the different materials and processes and support the
proposed categorization. Although waste water volume and
characteristics vary significantly, the treatability of textile wastes
by similar biological treatment methods has been demonstrated. Thus,
subcategorization by waste treatability is not required. Location and
climate have a material effect upon pollution control methodology for
any given operation or segment of the industry. However, the impact of
either location or climate is not sufficient for defining or
substantiating subcategories. (Variability in treatment operation has
been taken into account in section IX). Available data indicates that
neither the age nor the size of facilities significantly affects waste
character or water usage. Any technological effect of size or age is
predominately reflected in the type or size of production facility, and
was taken into consideration through this factor.
The subcategorization selected for the purpose of developing waste water
effluent limitations guidelines and standards are as follows:
1. Wool scouring
2. Wool finishing
3. Greige mills
4. Woven fabric finishing
5. Knit fabric finishing
6. Carpet mills
7. Stock and yarn dyeing and finishing
Subcategories 1 and 2 deal with wool processing; subcategories 3,
U, 5 and 7 covers the various types of processing for cotton and
synthetic fibers; and subcategory 6 covers the carpet industry.
These subcategories are described in detail below.
35
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Subcategor_Y 1 - Wool Scouring
Wool scouring and topmaking is conveniently separated as a subcategory
and a significant number of plants perform this function alone. The
initial washing and cleaning of wool generates a wide variety of organic
and inorganic products in the waste effluent. The raw wool contains
suint, dirt, and grease along with oils such as lanolin., In addition,
the preparation and cleaning of wool requires a heavy use of detergents.
Recovery of wool grease has some economic incentive in that it has
market value. However, even with grease recovery, wool scouring wastes
present a highly concentrated waste.
Wool scouring is conveniently separated from other segments of the
textile industry because of its uniqueness. Raw wool (grease wool) must
be wet processed to clean it before the1 fiber may be dry processed to
produce fiber, yarn or fabric for the further wet processing steps found
in a finishing plant. Neither cottcn nor the synthetic fibers require
this initial wet-cleaning. Furthermore, most wool scouring mills are
geographically separate from other textile operations. Exceptions exist
where wool scouring is physically separated from, but shares the waste
treatment plant with, finishing mills.
The grease wool contains 25 to 75 percent non-wool materials, consisting
of wool grease and other excretions and secretions of the sheep such as
urine, feces, sweat and blood, as well as dirt consisting of both soil
and vegetable matter. Additional materials that may be present are
insecticides (sheep dip) , and fugitive dyes used for identification.
This variability in yield and in the composition of impurities and
grease causes a correspondingly variability in raw waste loads.
orY 2 - Wool Finishing
Wool finishing involves the use of specialized dyes peculiar to this
fiber which often result in the presence of chromium in the waste
effluent. In addition, phenols occur from dyeing polyester blends.
Only a small amount of pure wool is now processed. The bulk of the
operations involves wool-polyester blends which give high BOD loads from
the dye carrier which is used. The resulting wastes are similar to
those in Woven Fabric Finishing and Knit Fabric Finishing, but have a
higher raw waste load.
Several major mills have integrated wool scouring and top making with
wool finishing. Such mills can be accommodated by a combination of
Subcategories 1 and 2.
This industry consists of many small mills — most of them in the North
(New England, New York and New Jersey) and most are fully integrated
36
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mills -- and about 25 larger mills, mostly in the South (Virginia, the
Carolinas and Georgia) .
A sample of 29 textile mills participated in a waste treatment survey
prepared by the Wool Manufacturers Council of the Northern Textile
Association. Of the 29 mills, 25 were wool finishers and 4 were cotton
and synthetic mills. Of the 29 mills 7 have completed tie-ins into
municipal treatment facilities: 15 plan to tie into municipal facilities
that are in various stages of construction or planning; 4 have completed
private treatment facilities and 3 have plans to construct private
treatment facilities.
Most small mills do some commission dyeing, and even the larger mills
that are part of the larger corporations commonly perform commission
dyeing. Commission dyeing operations imply a wide range of fabrics and
finishes as well as fiber types.
Probably not more than five mills still do more than 50 percent wool and
wool blends: the rest process primarily other fabrics.
The processes of carding and spinning wool into yarn, and subsequent
weaving or knitting into fabric are included in Subcategory 3, Greige
Mills.
Yarns made from wool are classified into either woolen yarns or worsted
yarns. Woolen yarns are characteristically of loose construction and
composed of relatively short fibers; worsted yarns are of tight
construction with few protruding fiber ends and composed of selected
long fibers (tops). As a result, worsted yarns are stronger.
Wool finishing has been differentiated from other finishing categories
because of (1) the wide variety of chemicals used to process wool
fabrics and (2) high raw waste loading.
In addition to processing all wool fabrics, today's wool finishing mills
process wool blend fabrics and fabrics made of 100% synthetic fibers.
The percentage of wool used by a woolen mill is based on market demand
and availability of wool. The variety of fabrics varies from mill to
mill, season to season and year to year. Shifts back and forth between
fibers cannot be predicted.
Few of today's wool finishing mills process all wool. Many of the
woolen mills by name handle 20 percent or less wool with the balance
being woven and knit synthetics. Also, within the 20 percent or less
portion, woolen/synthetic blends (most often with polyester) usually
constitute the bulk of the fabric.
j
High water usage in the subcategory appears to be a result of washing
after the fulling operation (peculiar to 100 percent wool fabrics).
37
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Size as used on cotton and synthetic wovens is not used by wool mills.
Wax lubricants and emulsified oil are sometimes used in processing wool
yarns. These waxes and oils are difficult to remove and require
thorough washing to be removed properly. Because of the low percentage
of wool actually processed in mills today, and the small amount of
sizing used, this category appears in most ways similar to Subcategory
5, Knit Finishing.
Variations occur in processing, similar to other finishing categories,
in that some fabrics are woven or knit from yarns that are already dyed,
either in the fiber or yarn form. A given mill may dye and finish part
of its production while only finishing the remainder.
SubcategorY 3 - Greige Mills and Garget Backing
Although there are many greige goods mills, they carry out mainly dry
operations (with the exception of slashing) and hence contribute little
to the overall waste problems of the textile industry. In many plants
the sanitary BOD load is comparable to the process BOD load. This
category applies equally well to woven or knitted greige goods, and
because of the similar dry nature of carpet backing operations these
mills are included in this subcategory.
Greige goods manufacturing includes spinning and texturizing of yarns
which require a lubricating oil, similar to mineral oil. This oil is
applied to the fibers or yarns and stays with them, to be removed prior
to dyeing in the dye house. However, some oil finds its way into the
drains because of clean-ups and spills.
Prior to being woven, the yarns are coated with a sizing material to
give the yarn both lubrication and strength that will permit it to
withstand the severe mechanical demands of weaving. Cottons generally
are coated with starch and synthetics with polyvinyl alcohol. Wool and
wool blends are seldom sized, unless the yarns are quite fine. Since
most wool yarns are blends, both starch and PVA may be used. The
slasher, where the sizing is applied, is washed down about once a week
and thus contributes to the liquid wastes. Generally the waste flow
from the slashing operation represents a low percentage of the total
plant flow.
Greige mills generally manufacture yarn and unfinished fabric. In
general greige mills include the production of woven greige goods knit
greige goods and greige yarn production. However, knit greige goods
production is almost always combined with a finishing operation and
therefore may be included in the knit finishing subcate;gory. Carpets
are sometimes backed in a separate plant. The industrial portion of the
waste water consists of equipment washing which may be performed once a
day or once a week. The resulting waste flow is small.
38
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It has been estimated that there are 600 to 700 greige woven mills, 80
percent of which are in North Carolina, South Carolina, Georgia, Alabama
and Virginia. Perhaps 20 percent of the 600 have their own waste
treatment plants, with almost all the rest disposing of wastes at
municipal facilities. Less than 5 percent is believed to dispose of
their wastes in waterways without treatment. No carpet backing mills
were found which did not discharge to a municipal system.
Subcategory ± - Woven Fabric Finishing
This category is one of the most important, because such plants
constitute much of the waste water effluent load in the textile
industry. Integrated woven fabric finishing mills are included in this
subcategory because the greige goods section of these mills contributes
only a small amount to the overall effluent load.
The size removed after weaving is a major contribution to the BOD load
from the plant. Two sizing compounds are commonly employed: starch and
polyvinyl alcohol (PVA) . PVA tends to be less readily biodegradable
than starch and therefore presents a lower BOD5 level but contributes a
high COD level. In addition to high BOD, the wastes generally have high
total dissolved solids, color, and a variety of dispersing agents. They
also may be very alkaline from the use of caustic soda in mercerizing
cottons.
dyes and associated additives used in woven fabric finishing
represent the most complicated problem, since the BOD load and color can
vary considerably with the type of dye fabric being processed and the
color effects to be achieved.
Processing steps in this category generally include cleaning the greige
goods, bleaching, mercerizing of cotton (treating with caustic) , dyeing,
washing and rinsing, followed by application of finishes such as soil
repellents, anti-statics, etc.
This category encompasses mills which finish woven goods (or integrated
greige goods and finishing mills) . It has been estimated that about 600
mills fall into subcategory 4. About 20 percent treat their own waste,
75 percent enters municipal systems, and 5 percent have no waste
treatment.
This category predominates in the Southeast (North and South Carolina,
Georgia, Virginia, Alabama) , but there are some large operations in New
York and New England.
39
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5 - Knit Fabric Finishing
The main difference between woven and knit fabric finishing is that the
sizing/desizing and mercerizing operations are not required for knits;
therefore, raw waste load levels are lower.
The knitting industry is characterized by a large number of plants and a
structure organized along specialized product segments. The major
segments are knit fabric piece goods, hosiery, outerwear, and underwear.
While the industry has shown substantial growth in value of shipments,
it has been estimated that through consolidation and other factors the
current number of plants in this industry is about 2500. Of this
number, it has been estimated that about 1100 plants have only dry
operations. These are plants such as sweater mills in the outerwear
segment, which knit goods from purchased or commission dyed yarns, or
mills which have finished goods dyed on a commission basis and
therefore, have no process water requirements. Most of the sweater
mills are located in the Northeast. In those isolated instances where
sweater or similar mills dye their own yarn, these mills should be
subject to subcategory 7 guidelines.
Of the 1400 plants believed to have wet process operations, it has been
estimated that 85 percent discharge to municipal treatment systems. The
great bulk of these are hosiery plants (700-800) located primarily in
North Carolina, Tennessee, and Pennsylvania.
The knit fabric segment of the industry has about 540 plants. These
plants are the source of finished knit piece or yard goods for the
apparel, industrial, and household goods trades, and also serve to
augment supplies of fabric to underwear and outerwear manufacturers.
These plants are the main subject of subcateogry 5. The large knit
fabric plants are located mainly in North and South Carolina and
Georgia, but substantial numbers are also located in New York, and
Pennsylvania.
£ ~ Carpet Mills
Carpet mills form a distinct part of the industry although their
effluents are similar in many ways to those of Subcategory 5, Knit
Fabric Finishing. Carpets use mostly synthetic fibers (nylon, acrylics
and polyesters) but some wool is still processed. As in Subcategory 2,
Wool Finishing, such wool carpet mills produce synthetics as well. As a
result, no subcategory for wool carpets is proposed.
Carpet sometimes is backed with latex in a separate plant. However,
carpet mills often do latexing in the same plant with the finishing.
Latex is settled in separate basins prior to release of the segregated
40
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stream to the treatment plant and the additional load on these mills is
negligible.
Tufted carpets account for well over 65 percent of the plants and 86
percent of the dollar volume, and constitute 74 percent of the
employment in this industry. Therefore, the guidelines are generated
principally around this segment. About 70 percent of the industry is
located in Dalton, Georgia and these mills are connected into the
municipal treating system. However, the remaining carpet mills are of
sufficient quantity to warrant effluent guidelines.
Tufted carpets consist of face yarn that is looped through a woven mat
backing (mostly polypropylene, some jute), dyed or printed, and then
backed with either latex foam or coated with latex and a burlap-type
woven fabric backing put over the latex.
The dominant face yarn is nylon, followed by acrylic and modacrylic, and
polyester; the latter two groups in total are about equal to nylon.
Since dyeing of these fibers in carpets differs little from dyeing
fabric, the dyeing descriptions for these fibers given in other
categories applies here. Beck, continuous dyeing, and screen printing
are practiced.
The latex operational load on the waste treatment facility of an
integrated mill, after adequate pretreatment by coagulation, is
insignificant.
Subcateqory 7 - Stock and Yarn Dyeing and Finishing
Yarn dyeing and finishing are different from woven fabric finishing
because there is no sizing and desizing operation. They are different
from knit fabric finishing because of their mercerizing operations and
water use. The combined differences are sufficient to justify a
separate category. The waste loads from this type of plant can vary
more than those from other types of integrated textile mills or
finishing mills. Many multiple-operation, commission houses fall under
this category.
Subcategory 7 includes plants which clean, dye and finish fiber stock or
yarn. The plants may or may not have yarn spinning facilities. sewing
thread, textile and carpet yarn are typical products.
It has been estimated that 750 plants fall into this category. Most
(probably 80 percent) dispose of their wastes at municipal facilities.
We believe that 5 to 10 percent treat their own waste and the rest have
no waste treatment facilities.
U1
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About 60 percent of yarn dyeing and finishing is performed in Virginia,
North Carolina, South Carolina, Georgia and Alabama, with the remainder
distributed across the eastern U.S. and the Far West.
Categorization: Economic Considerations
The size of the production facilities is another significant factor
which requires an exception within the subcategorization. Severe
diseconomies of scale create economic impacts which require separate
limitations for small plants. As illustrated in Section VIII, the unit
costs attributable to activated carbon adsorption (best available
technology) for small industry plants as compared to medium sized plants
are reflected in an average price increase for a small plant of 4.2
cents per kilogram product (1.9 cents per pound of product) as compared
with an average price increase for a medium sized plant of 2.3 cents per
kilogram (1.0 cents per pound) . It is estimated that disproportionate
cost increases such as those indicated above would force the closing of
as many as 500 small facilities. Thus, an exemption in the form of less
stringent limitations is required for small textile mills. The basis
for this size exception is based on economic trends developed in Section
VIII and developed in Table 7.
The subcategories including size exemptions selected for the purpose of
developing waste water effluent limitations guidelines and standards are
as follows:
1. WOOL SCOURING
Plant capacity less than 6,500 kg/day (14,300 Ib/day)
Plant capacity greater than 6,500 kg/day (14,300 Ib/day)
2. WOOL FINISHING
Plant capacity less than 900 kg/day (1,980 Ib/day)
Plant capacity greater than 900 kg/day (1,980 Ib/day)
3. GREIGE MILLS
4. WOVEN FABRIC FINISHING
Plant capacity less than 1000 kg/day (2,200 Ib/day)
Plant capacity greater than 1000 kg/day (2,200 Ib/day)
5. KNIT FABRIC FINISHING
Plant capacity less than 3,450 kg/day (7,590 Ib/day)
Plant capacity greater than 3,450 kg/day (7,590 Ib/day)
6. CARPET MILLS
Plant capacity less than 3,450 kg/day (7,590 Ib/day)
Plant capacity greater than 3,450 kg/day (7,590 Ib/day)
42
-------
STOCK AND YARN DYEING AND FINISHING
Plant capacity less than 3,100 kg/day (6,820 Ib/day)
Plant capacity greater than 3,100 kg/day (6,820 Ib/day)
-------
TABLE
BASIS FOR SIZE EXCEPTION WITHIN TEXTILE SUBCATEGORIZATION
Number
of
Employees
1-4
5-9
10-19
20-49
50-99
100-249
250-499
499-2,499
Total
1-19
Percent
Ib product/day
Employee
No. Employees
(Ib/day)
(1000)
kg/day
(1000)
Number of Establishments By
1
14
5
10
21
6
7
4
1
68
29
(43%)
750
19
14.3
6.5
2
54
17
22
64
41
60
35
17
310
93
(30%)
100
19
1.98
0.9
3(1) £
63
27
56
91
76
70
32
51
449
146
(33%)
120
19
2.2
1.0
5 6_(2)
95
59
93
124
63
75
23
9
541
247
(46%)
400 400
19 19
7.59 7.
3.45 3.
Subcategory
1_
38
23
25
40
32
20
10
3
192
86
(45%)
360
19
59 6.82
45 3.10
(1) No size exception for Subcategory 3 because of small waste load.
(2) Size exception calculated from associated data because only
limited economic data available on carpet mills.
-------
SECTION V
WASTE CHARACTERISTICS
INTRODUCTION
Many of the mechanical operations used in the manufacture of textile
fabrics are common to the industry as a whole and the character of the
waste waters are similar. Typically, the textile fibers are combined
into yarns and then the yarns into fabrics. After the fabrics are
manufactured, they are subjec-c to several wet processes collectively
known as finishing and it is in these finishing operations that the
major waste effluents are produced.
In Section III wool, cotton and synthetic fiber and fabric finishing
operations were briefly described. General descriptions of the
manufacturing processes were given in Section IV for the purpose of
industry subcategorization. In this section the waste warers from each
operation within each subcategory are characterized.
The principle parameters used to characterize waste effluents were the
flow, biochemical oxygen demand, chemical oxygen demand, total suspended
solids and oil and grease. As discussed in section VI, these parameters
are considered to be the best available measure of the waste load.
Subcategory 1 - Raw Wool Scouring
The raw waste from raw wool scouring is different from the waste from
all other categories used in this study: it contains significant
quantities of oil and grease, even after in-process recovery. The wool
grease constitutes a special problem in treatment since it does not
appear to be readily biodegradable. Therefore, a grease recovery step
is important to reduce pollution.
Sulfur is brought in with the wool, as well as phenolic and other
organic materials derived from the sheep urine, feces, blood, tars,
branding fluids and sheep-dips used in insecticides. These irems appear
randomly in the effluent.
Wool scouring is generally performed in a series of scouring bowls. In
these scouring bowls, the heavier dirt and grit settles to the cone-
-------
shaped bottoms where it is blown down once an hour or so, and carried to
the treatment plant by scour liquor.
The scour liquor, after picking up the soluble and less heavy dirt and
grit, is piped to a separation tank where further settling of dirt and
grit occurs. This material is also blown down and carried to the
treatment plant once a day, or more often if the dirt content of the
wool is high.
From the separation tank the scouring liquor is processed to break the
emulsion and recovery of the wool grease. Two methods are commonly used
to do this: centrifuging and acid-cracking.
In cantrifuging (as shown in Figure 1) the top low-density stream
contains concentrated grease, which is further dewatered in additional
centrifuges to yield the recovered, unrefined wool grease. The medium-
density stream is combined with the relatively clean bottoms from the
auxiliary centrifuges and recycled to the wool scouring train as fresh
scour liquor. The high-density-bottoms streams consists mainly of dirt
and grit, and is sent to the treatment plant.
An alternative means to break the grease emulsion for wool grease
recovery is the acid-cracking grease recovery system, also shown in
Figure 1. sulfuric acid is added to the scour liquor to break the
grease/water emulsion. Heating the mixture increases the efficiency of
separation. The grease is separated from the liquor in a settling tank
and recovered. The liquor is then treated with lime to neutralize the
acid and subsequently passes through the waste treatment plant.
In the centrifugal method, about 60 percent of the grease is recovered:
the remaining 40 percent is attached to the dirt and grit. In the acid-
cracking method, pilot plant performance indicates a 98 percent recovery
of grease from the degritted liquor.
Grease yield, in total , is 8 to 15 percent by weight of the greasy
wool, and this constitues 50 to 65 percent of the wool grease initially
present. (Ref. 141). Note that 1-3 percent of the wool grease present
in the grease wool is allowed to remain in the wool as a conditioner.
Also, alkaline scouring has been used in which soda ash is added to the
wash water. The soda ash combines with seme of the wool grease to form
a natural soap, thereby requiring less detergent but also lowering
recovered wool grease yield.
Objections to increased recycling of the scour liquor have been voiced
by industry, but with appropriate technological innovation, an even
greater amount of recycling may be possible.
-------
Objections to increased recycling of the scour liquor have been voiced
by industry, but with appropriate technological innovation, an even
greater amount of recycling may be possible.
Some "raw" wools, mostly the Australian and New Zealand wools, are pre-
scoured at the source. However, this fact does not appear to
significantly affect this analysis of U.S. raw wool scouring mills.
Note that scoured wool is often converted into "tops" at the same mill.
In this operation, the short fibers are separated mechanically from the
long ones; the long fiber "tops" are used for worsted yarn and the short
fibers are used to blend into woolen yarns. No added pollution occurs.
Water load is increased by air conditioning and air scrubbing.
Subcategory 2 - Wool Finishing
As mentioned, the metallized dyes used for wool are very fast (i.e., do
not fade or rub off readily). Hence on 100 percent wool cloth, these
dyes are often used. In the blends, however, the dyes used for
polyester and other synthetic fibers have poorer fastness,, so in these
blends many woolen mills have converted to non-chrome dyes. As a
result, an all-wool mill may be expected to have significant chrome in
its effluent, but in a wool-blend mill, the chrome will be considerably
less or even non-existent.
Since many wool mills investigated are working on blends, principally
polyester, carriers such as orthophenol, phenol, diphenyl, or benzoic
acid derivatives will be present at significant levels in their raw
wastes. Phenolics appear to be losing favor because of their odor, but
current practice includes them and they will be present in most wool-
blend mill wastes.
As a result of the above, the principal component that distinguishes tha
wool mill Subcategory 2 from Subcategory 5, Knit Finishing, is the
chromium used to dye the wool.
The Subcategory 2 mills have a higher water usage rate than any other
finishing category. The heaviest contributor appears to be the rinsing
after fulling. The wet unit processes are described in more detail
below.
Heavy Scour
Heavy scouring is the term applied to The washing of the fabric by the
use of detergents, wetting agents, amulsifiers, alkali, ammonia, or
various other washing agents. The purpose of this heavy scour is to
remove oils, grease, dirt, fulling solutions, emulsified oil, lubricants
or any other substances that are either introduced in prior processing
steps or that is carried to the finished fabric from the raw stock.
-------
This process is one of the most important steps in wool finishing
because if all of the foreign materials are not completely washed out,
the finished fabric is susceptible to rotting, smelling, bleeding and
will not accept dyes uniformly.
Fancy goods, in contrast to piece dyed goods, are only scoured prior to
mechanical finishing. Piece dyed goods on the other hand must be
scoured completely prior ro the dyeing step. The weight, foreign
material content and degree of felting of the fabric all have a direct
bearing on the degree of scouring required.
Heavy weight, closely wcven fabrics with a high percentage of recycled
wool reguire very heavy detergents, long wash times and extensive
rinsing to clean the goods. High organic and hydraulic loadings are
associated with this type of fabric. Light open goods with a low
percentage of wool generally scour more ea'sily with lighter detergents,
shorter wash times and less rinsing resulting in lower organic and
hydraulic discharges.
Some mills produce both types of goods at the same time and relative
proportion of each type will vary greatly causing great fluctuations in
organic hydraulic discharge. Also some mills produce only light open
goods while others produce heavy, close woven fabrics. The majority of
finished product weights range from 12 ounces per yard to 26 ounces per
yard; however, because of the differences in raw stock and felting
requirements the hydraulic and organic discharges may differ greatly.
Carbonizing- Carbonizing consists of soaking the fabric in strong
sulfuric acid, squeezing out the excess, and then heating the wet fabric
in an oven. The hot acid reacts chemically with vegetable matter and
any cotton fiber contaminant and oxidizes these contaminants to gases
and a solid carbon residue. The fabric is then passed between pressure
rolls where the charred material is crushed so that it may be separated
by mechanical agitation and flowing air. A solid waste is produced, and
the acid bath is dumped when it becomes too contaminated for further
use, about once every two days.
Fulling. Fulling is usually used on 100 percent woolen fabrics but not
usually on woolen/polyester blends and not on worsteds. Since this
operation stabilizes the dimensions of the wool by "felting" it, the
blends usually do not need it, nor do the worsted, since they are a very
tight yarn and weave to begin with. Fulling is accomplished by
mechanical work performed on the greige goods while they are in a bath
of detergent and water. Detergent is added as needed but no effluent
occurs until the following washing step. This is true of both "dry" and
"wet" fulling except that in the "wet" fulling, the water bath is dumped
about once every 2 to 3 days. In "dry" fulling, just enough water is
picked up by the fabric to lubricate it so the fabric is not standing in
water between its turn in the fulling device.
-------
The fulling is followed by extensive rinsing to prevent rancidity and
wool spoilage. This step produced over 50 percent of the hydraulic load
in an all- woolen mill investigated.
Crabbing. Crabbing is the name given to the operation used to align the
fabric rectilinear ly. Since the fabric comes in wet and goes out wet,
no effluent of significants occurs.
Pre-Scour. The pre-scour step is a final cleaning of the greige goods
prior to dyeing. Often, if a light scour or fulling is performed before
dyeing, the pre-scour step is not used. On sensitive dyeing, however,
both light scour and pre-scour are sometimes used. Detergents and
wetting agents are added. This and subsequent dyeing and rinsing steps
are performed in becks.
In t*ie dyeing process, the fabric is dyed in atmospheric becks
or pressure becks. Pure wool fabric is dyed only in atmospheric becks,
but blends (mostly with polyester) are dyed in either atmospheric or
pressure becks. Knit wcolen blend fabrics also are dyed in either
atmospheric or pressure becks, but most often they are dyed in jet
becks, a variation of the pressure beck that is supposed to reduce
physical damage to the knits.
In conventional becks the fabric is sewn into a long tube that
alternately soaks in a tube and then is pulled up and over a large
diameter slatted wheel. In a jet beck the fabric is pulled up and put
back in the tub by the action of the dye liquor being pumped through a
venturi and carrying the fabric with it. Pressurizing of becks is
desirable for dyeing the polyester portion of the fabric, since little
or no carrier need be used. At atmospheric pressures large quantitites
of carriers are required to swell the polyester fiber and enable the dye
molecules to penetrate.
In the dyehouse becks, the operation usually consists of filling the
beck with water and a detergent for scouring (pre-scour, described
above) . The scour water is dumped and the beck is refilled with water
and a wetting agent. After the fabric is wet-out, and the temperatures
raised somewhat, the dyestuffs are added and the beck brought up to
temperature ((100°C) 212°F in atmospheric becks, higher in pressure
becks) . After 2 to 4 hours, 90 percent or more of the dye is exhausted,
and the dye bath is discharged to the sewer. This dye step is followed
by a clear water rinse. Since the dyes are very expensive, effort is
made to assure as high an exhaustion level as possible.
Blends are sometimes dyed in a single bath, sometimes in two separate
baths. Therefore, the hydraulic load can from this unit process
increase by 50 percent in the case of two baths (including a rinse step
after all dyeing is completed) .
50
-------
The more commonly used dyes for wool (or the wool in wool blends) are
metallized dyes and top and bottom chrome dyes. Others used include
reactive dyes, mill dyes, and others used for special effects. Use of
chrome dyes is diminishing since their high fastness is superfluous in
wool blends, given the lower fastness of the dyes used for synthetic
fibers, when wocl and synthetic fibers are blended, therefore, non-
chrome wool dyes of fastness equivalent to that of the synthetic fiber
dyes can be used in the interest of economy.
Rework levels appear to be 3 to 4 percent of total production. When
goods are reworked, they are either redyed to a darker shade, or
stripped with reducing chemicals, rinsed and redyed.
After it is dyed, the fabric is cooled with clear water and rinsed until
the dump or overflow water is clear.
Finishing. After it is dyed and rinsed, the fabric is removed from the
beck and, when used, soil repellents and other finishing agents are
padded onto it. Next, the fabric is dried and any subsequent dry
finishing operations -- principally shearing (solid waste) and pressing
(steam condensate) -- are performed.
Mothproofing is accomplished with Mitten-FF for government fabrics or
with Dieldren for certain other specialized fabrics. Spillage appears
to be the only way this material might find its way into the waste
waters.
Any of the finishing chemicals can appear in the waste when the padding
equipment is dumped and washed.
Subcategory 3 - Greige Mills
Waste at greige mills constitute residues in size boxes at the end of a
day or a week, and water used for clean-up. The volumes of textile
wastes in a greige mill are small. Significant amounts of water used in
a greige mill (e.g., cooling water) may not enter the waste treatment
plant.
A typical sizing formulation is composed of a film-forming material, a
fatty or waxy component, and water. In some formulations, a water-
soluble dye may be used to give the grey cloth an identifying color. A
preservative may be used in some sizing mixtures.
The most common film forming materials are starch, polyvinyl alcohol and
carboxymethyl cellulose. Other sizes, such as polyacrylic acid and
styrene-maleic anhydride polymer, are used occasionally in weaving
special cloths.
51
-------
Starch is a traditional sizing material, but in the past several years
the volume of polyvinyl alcohol used in the textile industry has
increased substantially, since starch does not adhere well to the
synthetic hydrophobic fibers. In many cases, mixtures of starch and
polyvinyl alcohol are used.
When formulations based on starch are used, the add-on of size amounts
to 10 to 15 percent by weight or warp yarn. When polyvinyl alcohol is
used, lower add-on, 3 to 8 percent by weight of the fabric, is typical.
The range of add-on depends on cloth construction factors such as warp
yarn diameter, "tightness" of the faoric, etc.
The total waste load at a greige mill is typically greater tan 90
percent sanitary and the remainder is industrial.
Treatability of greige mill wastes is relaxed to the size used. Starch
is very readily degraded biologically, and may be given a preliminary
enzyme treatment to improve biodegradability. On the other hand,
polyvinyl alcohol is consumed by organisms relatively slowly, though
recent studies show that organisms acclimate to polyvinyl alcohol. (See
Subcategory 4 below).
Subcategory 4 - Woven Fabric Finishing
The wastes associated with finishing woven goods result from removal of
foreign material during the cleaning and from the various chemicals used
in finishing the fabric.
Desizing
Enzymatic removal of starch size generates starch solids, fat or wax,
enzyme, sodium, chloride and wetting agent in the effluent, stream. The
waste contains dissolved solids (both organic and inorganic), suspended
solids, and some fat or wax; it has a pH of 6 to 8, is light colored,
and contains no toxic materials.
Sulfuric acid removal of starch size generates waste containing starch
solids, fat or wax and sulfuric acid. It contains organic and inorganic
dissolved solids, suspended solids, and some oil and grease. It has a
pH of 1 to 2 and is relatively light colored.
After the desizing agent has been applied, the goods are placed in a
bind or a steamer to provide the residence time required. Residence
time in storage bins are typically 12 hours or more. If elevated
temperatures are used by employment of J-boxes or steamers the residence
time is reduced to 30 minutes at 180 F or a few minutes at 210 to 212 F.
Finally, the goods are washed with water to remove the decomposed
starches from the fabric. Polyvinyl alcohol and carboxymethyl cellulose
52
-------
are both removable with water alone. The goods are washed with water at
180F or higher on washers without the use of steamers, J-boxes, or
padders. Desizing these materials will thus contribute suspended
solids, dissolved solids and oil and grease. Since these sizes are used
at about one-half the concentration of starch, the total solids
generated in the waste stream are aJocut one-half the level corresponding
to starch use. When mixtures of starch and polyvinyl alcohol are used,
desizing may involve the use of enzyme (to solubilize the starch) and
water; total wastes generated would be intermediate between that
developed by either size used alone.
Desizing may contribute 50 percent or more of the total waste solids in
a woven goods finishing mill.
The contribution of starch to BOD of waste streams has been documented
many times. On the other hand, polyvinyl alcohol has been considered
very slowly biodegradeable, and as such, a major source of COD. Recent
studies performed by producers of polyvinyl alcohol in cooperation with
textile mills, indicate that biological waste systems will develop
organisms acclimated to polyvinyl alcohol, and when this has occured,
biodegradation is relatively rapid and complete.
Scouring
Scouring is dene to remove much of the natural impurities of cotton,
using 2 to 3 percent sodium hydroxide; phosphate, chelating agents and
wetting agents may be used as auxiliary chemicals. The synthetic fibers
require much less vigorous scouring; scdium carbonate and a surfactant
may suffice. In the case of cotton/synthetic blends, Varsol may be used
in conjunction with the aqueous scouring liquor.
The operation known as kier boiling is often employed to scour desized
cotton and cotton/polyester woven fabrics. The kier is a large vertical
cylindrical pressure vessel which can hold up to several tons of
fabrics. The goods (in rope form) are plaited into the kier by the kier
plaiter, the covers are installed, and the scouring chemicals are
recirculated through the goods and an external heat exchanger for
temperature control. An aqueous mixture of sodium hydroxide, soap and
sodium silicate is employed at temperatures of 220 to 250 F and
pressures of 10 to 20 psig. The goods are scoured for 6 to 12 hours.
The kiers are then coded by recirculation of cooling water and the
goods are displacement washed. In certain instances, difficult fabrics
are double-scoured. The scouring step is designed to remove fats, waxes
and pectins from the woven fabric.
Certain heavyweight fabrics normally are not processed in rope as
required for kier boiling since creases result in streaks in subsequent
dyeing steps. These goods are therefore processed in an open-width
boil-out maching, also known as the progressive jig. The jig is loaded
53
-------
with a scouring solution and the goods are fed through continuously by
coils and the temperature and residence time are maintciined for proper
scouring of the goods. The goods are wound onto rolls in the maching
and maintained in contact with scouring liquids for the necessary
period. Then they are unrolled through wash boxes and folded into a
cloth truck or onto a rcll.
The scoured cotton may be used directly for producing dark shades or may
be bleached by padding through hydrogen peroxide solutions, and
subsequently washed, neutralized, and dried before dyeing.
Scouring liquors are strongly alkaline (pH greater than 12), and dark
colored due to cotton impurities. They contain significant levels of
dissolved solids and oil and grease. A modest level of suspended solids
results from the presence of cotton impurities.
The natural cotton impurities removed form greige fabric by scouring
contribute BOD and are fciodegraded rapidly.
Scouring of cotton/polyester greige blends generates the same waste in
proportion to the amount of cotton.
Scouring of synthetic woven goods generates a low level of dissolved
solids from surfactant, soda ash, or sodium phosphate.
Mercerization
Physically, mercerization swells the cellulose fibers as alkali is
asbsorbed into them, with higher concentrations, longer residence times,
and lower temperatures favoring greater swelling. The mercerization
step is conducted with the fabric either under tension or in the slack
condition, with tension mercerizing favoring increases in tensile
strength and slack mercerizing favoring increases in abrasion
resistance.
Mercerization is normally conducted continuously; the operation consists
of the following steps:
(a) A scutcher and water mangle are employed to open the goods
from the rope form, and a mangle is used to deweiter
the goods to a uniform moisture concentration.
(b) A multiple-contact saturating operation is conducted usually
with three saturating bowls. The goods are fed through the
system continuously which provides sufficient residence
time and contact to completely saturate the fabric with
caustic soda solution.
-------
(c) Timing cans are employed to increase the residence time
of the fabric in the sodium hydroxide solution.
(d) A tenter frame is employed to maintain the fabric under
tension as the fabric travels through the system and the
actual mercerization of the cellulose takes place.
(e) At the end of the tenter frame is a washing system that
includes water sprays, vacuum units and wash water heaters
and re-circulators to wash the fabric and reduce the caustic
content while the fabric is still under tension in the
tenter frame.
(f) The fabric is given a final wash in the recuperator, which
removes the remainder of the sodium hydroxide from the
fabric and reduces the residual pH to an acceptable level
(i.e. , 8.5) .
Mercerization wastes are predominantly the alkali used in the process.
The waste stream contains high dissolved solids, and may have a pH of 12
to 13. The BOD level is low due to a penetrant used as an auxiliary
with the caustic. Small amounts of foreign material and wax may be
removed from the fiber, and will appear as suspended solids, and wax in
the wastes; these materials will contribute a small BOD load.
In large mills, caustic soda is recovered and concentrated for re-use,
thus, saving chemical and avoiding a sizeable waste load. Estimates
have indicated that recovery of mercerizing caustic is justified when
the caustic use is more than 5 million pounds per year (dry) , and
concentration of the alkali is not permitted to fall below 2%.
Bleaching
The following process units constitute a typical, continuous peroxide
bleaching range, using J-boxes for storage:
Wa sh ing . The goods are washed, using either open width or rope washers
to ensure removal of converted starches from the desizing step.
Caustic Satura tor. As the goods continuously leave the washer they are
squeezed through rolls to a minimum water content and then saturated
with sodium hydroxide solution in additional squeeze rolls. The goods
may be in either rope or open width form, but must remain in the
saturator long enough to permit them to become completely saturated with
sodium hydroxide solution.
goods are then fed continuously to the caustic J-
boxr whose function is to saturate the cloth for the necessary length of
time at the desired temperature (205-210F). The throughput of the J-box
55
-------
is controlled to provide a residence time ranging from 40 minutes to one
hour, resulting in saponification of natural fats and waxes carried in
the cotton.
Caustic Washers^ The caustic solution is then removed from the fabric
by countercurrent washing, usually with large quantities of hot water to
ensure complete removal.
2®£22£i
-------
Width J-Boxes^ More recent bleaching technology employs more
concentrated solution and more drastic operating conditions and has
resulted in the development of the small open width J-box which permits
effective bleaching with residence times of only 10 to 15 minutes.
Contjnous Pressure Scouring and Bleaching. The newest type of steamer
for bleaching ranges is an enclosed type with pressure locks and seals.
This enables the steamers to be operated as a pressure vessel and the
reaction time for the chemical is reduced from 40 minutes to only one to
two minutes. The treatment of fabrics is a function of time,
temperature and concentration. The increased temperatures made possible
by pressure steamers reduce the time needed for complete chemical
reaction.
The problem associated with equipment designed for operation at 25 psig
and for continuous entry and removal of continuous webs have posed a
substantial design problem. However, several machines are now available
with satisfactory sealing devices, so they may perform well at these
pressures. some of these units utilize rolls as a sealing mechanism and
others have developed a system involving a lip seal. In addition there
are reports of pressure steamers which may be operated at pressures up
to 45 psig and develop temperatures of 292F, resulting in residence
times only of one or two minutes.
Sodium chlorite Bleaching^ Although sodium chlorite bleaching has had
very little economic success in the bleaching of pure cotton goods over
the years, its use in kier steamers and becks is now receiving more
attention since many of the man-made fibers are sensitive to bleaching
and can be bleached successfully with sodium chlorite. It is now used
to a considerable extent either alone or in conjunction with other
bleaching agents for preparation.
Bleaching with hydrogen peroxide contributes very small waste loads,
most of which is dissolved solids. The dissolved solids are both
inorganic (sodium silicate, sodium hydroxide and sodium phosphate) and
organic (a surfactant and chelating agent). The waste stream contains a
low level of suspended solids when goods containing cotton are bleached.
Dyeing
Dyeing is the most complex of all textile finishing processes. Table 8
shows the dyes used in the textile industry, the fibers they are
generally used to color, and the relative amounts of each dye used by
the industry.
57
-------
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When textiles are dyed, an excess of the dyestuff is used, and other
chemicals are used to help deposit the dye, or to develop the color.
Dye loadings vary widely even with a particular dye class, depending on
the weight of fabrics being treated and the depth of color desired. The
range of chemicals employed in dyeing also varies widely from place to
place and operation to operation, and depends substantially upon the
dictates of the marketplace.
Table 9 presents a summary of chemicals used in application of dyes to
textiles. Dyed goods are generally, but not always, washed and rinsed
to remove excess dye and chemicals from the cloth. Washing involves use
of a detergent, and also may involve the use of soda ash or a sodium
phosphate.
The chemical used in dyeing may depend significantly on the dyeing
procedure which the fabric manufacturers finds appropriate. Both batch
and continuous dyeing are practiced, and both may be employed in the
same finishing plant.
Textile goods are dyed continuously when the demand for a single shade
is sufficiently high to justify the necessary equipment. Production of
denims, in which the warp yarns are dyed continuously, is one example;
no special chemicals are required as a result of dyeing continously. In
Thermosol dyeing, which is practiced on woven cotton (or rayon),
polyester blends, a dye blend is padded on the fabric, which is then
dried and heated, washed and dried. Thermosol dyeing requires addition
of a gum to the dye mixture, so that the formulation will deposit
uniformly on the cloth.
Piece dyeing, on runs which are not long enough to justify continuous
processing, are normally performed in an open beck, operated at boiling
temperature, or in a sealed pressure beck, operated at about 250F. in
modern units, the entire dye cycle (including washing and rinsing) is
controlled automatically. Pressure becks have been found advantageous
use of less carrier; wastes are decreased correspondingly.
Dyeing processes contribute substantially to textile wastes. Color is
an obvious waste. A high level of dissolved solids is expected.
Suspended solids should be low. Carriers, which are essential for
dyeing polyester and acetic acid, have high BOD. Sodium hydrosulfite
has a high immediate oxygen demand. Plants using sulfur dyes will
contain sulfides in the raw waste, and dichromates may be a waste when
vat dyeing is practiced.
Some of the wastes from dyeing textile fabrics are related to the
production equipment and to the size of the mill. On long runs, where
continuous Thermosol dyeing of synthetics or synthetic blends can be
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justified, carriers may be avoided; a gum will be used, and will
contribute a low BOD.
Table 9 shows alternative chemicals that may be used as substitutes for
sodium dischromate. Controls are available for the reduction of vat
dyes and their reoxidation; use of the controls will minimize wastes.
Printing
Printing involves application of dyes or pigments in the form of a
pattern on to fabric. Dyes penetrate and color the fiber; pigments are
bonded to the fabric with a resin. In general, the formulated print
paste is applied to one side of the fabric only.
Vat, direct and other dyes may be printed; vats appear to predominate.
The same chemicals used for the regular dyeing process are used in
printing, but in addition, a thickener is used to give the mixture high
viscosity. Many thickeners such as gum arabic, British gum, alginates,
methyl cellulose and others have been used. Urea, diethylene glycol and
glycerol are frequently used in the formulations.
Pigment print formulations are more complex. The pigments are blended
with a resin binder (frequently melamine-formaldehyde), a latex, an
aqueous thickener, Varscl and water.
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Table_9
ChemicalsjUsed_in Application of Dyes
Auxiliary Chemicals ^ece
Vat
Direct
Disperse
Sulfur
Acid
Cationic
Reactive
sodium hydroxide
sodium hydrosulfite
di spe r s i ng a gent
hydrogen peroxide
acetic acid
sodium perborate alternative
sodium dichromate chemicals
acetic acid
sodium chloride
sequestering agent
orthophenyl phenol alternative
butyl benzoate carriers
chlorobenzene
acetic acid
mono sodium phosphate
dispersing agent
sodium sulfide
sodium carbonate
sodium dichronate
acetic acid alternatives
hydrogen peroxide
acetic acid
acetic acid
ammonia sulfate of
ammonia acetate
sodium chloride
acetic acid or
formic acid
sodium sulfate
sodium chloride
urea
sodium carbonate
sodium hydroxide
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Table ,9 (continued)
Chemicals Used in Application, of Dyes1
Dye Type Auxiliary^Chemiqals^NecessarY
Developed developer
sodium chloride
sodium nitrate
sulfuric acid
sodium carbonate
1(In addition to the chemicals listed, all of the dye types will usually
use a small amount of surfactant. After the dyeing has been completed,
the dyed goods are washed and then rinsed. Washing will involve use of
a detergent as well as soda ash and a phosphate.)
Vat dye prints must be oxidized, with sodium dichromate or other
oxidants, to develop the color. Steaming and brief aging aid in the
process. Pigment prints do not require chemical after treatment, but
must be dried and heated to insolubilize the resin-pigment mixture.
Printing a fabric that contains polyester may require a carrier in the
formulation.
Following complete application of the print mixture, the fabric is
washed thoroughly to remove excess color and chemical.
Printing wastes are comparable in many respects to dye wastes. Printing
requires use of gums, which will contribute BOD. Solvents (Varsol) and
glycerine are also common constituents in printing, but pose no special
waste treating problem. Printing pigments will introduce some suspended
solids into the waste. Much of the wastes from printing comes from
cleaning of make-up tanks and process equipment. These relatively
concentrated wastes may justify segregated treatment, perhaps by
incineration.
Other_Treatment Wastes
Special finishes such as resin treatment, water proofing, flame
proofing, and soil release endows the fabric with a particular property
desired by consumers. The property is indicated by the name, except for
resin treatment, which designates finishes that provide wrinkle
resistance. Several of the treatments may be applied from a single
bath.
As would be expected for processes that provide such diverse effects,
the range of chemicals used is very broad. For resin treatment, a urea-
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formaldehyde-glyoxal compound' ("DMDHEU") , a fatty softner, and a
catalyst (zinc nitrate, magnesium chloride) are used together. Water
repellents include silicones, fluorochemicals, and fatty materials, each
generally applied with a catalyst. Soil release treatments include
special acrylic polymers and fluorochemicals.
These finishes are generally applied by impregnation of the fabric
followed by squeezing to the desired add-on. The moist material is
dried and then cured by additional heat. The cured fabric is frequently
packed for shipment without rinsing. Most resin-treated goods are
subsequently cured in a garment factor and must not be rinsed, since the
catalyst would be removed.
Wastes from resin treatment, water-proofing, flame-proofing and soil
release are small, since the chemicals are applied by padding, followed
by drying and curing. The chemicals used are diverse and small amounts
of them will enter the wastes.
Subcategory 5 - Knit fabric Finishing
Typically, knits are processed in piece goods form. The fabric may be
washed on continuous countercurrent washers prior to loading the fabric
in dye machines to remove knitting oils and other contaminents, or
washing may be the first step in the dye machine cycle. Warm water with
a small amount of added detergent is used. In contrast, woven goods
require more extensive treatment to remove starch or polymeric sizes.
The types of dyeing equipment generally employed include: atmospheric
becks, pressure becks, jet (atmospheric or pressure) becks, atmospheric
or pressure beam dyeing machines, and paddle type machines. Some plants
may also package dye a portion of their yarns.
The types of dyestuffs, auxiliaries, and conditions employed for dyeing
knit goods are essentially the same as for woven goods of comparable
fiber composition. See the discussion under subcategory 4 for details
of the dyeing operation.
Some of the fabrics which are beam dyed are first wet batched. In the
wet batching operation, the fabric is passed through a dilute aqueous
surfactant bath at controlled temperatures before being wound on a
perforated beam. Batching helps control shrink and yield, and also
enchances penetration of dye liquors in the dyeing process. There is
some waste generation from the wet batching operation; a small quantity
of the dilute bath is dumped occasionally for cleanup and there is a
continual slow drain of water from the wetted fabric which contains
knitting and yarn lubricants.
In knit plant, finishing cotton fabric — e.g., for underwear and
sleepwear — wet process operations also include scouring and bleaching
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in kiers or comparable equipment. Plants that process either cotton or
synthetic goods may alsc have fabric printing operations.
Most knit fabrics are treated with softners, and resin finished, and in
some cases, with water and oil repellents. These finishes are applied
from a pad bath just prior to final drying and dry finishing operations.
These baths are discharged periodially as required for fabric lot or
formulation changes, but the total daily volume of discharges is very
small.
The main difference between knit and woven fabric wet processing
operations are that knit yarns are treated with lubricants rather than
with the starch or polymeric sizes used for woven goods yarns, and that
mercerizing operations are not employed with knit goods. Otherwise, the
character of the wastes generated frcm comparable unit operations
performed on different fibers—cotton, synthetics, and blends—are
similar to those found in woven fabric finishing.
Lubricating finishes applied to knitting yarns generally are based on
mineral oils, vegetable oils, synthetic ester type oils, or waxes, and
may also contain antistatic agents, antioxidants, bacteriostats, and
corrosion inhibitors. Specific formulations are proprietary with the
yarn suppliers or throwster who applies the finish. The aimount applied
varies with the type of yarn; general levels of add-on by weight percent
on yarn are: untexturized synthetic yarns, 1 and 2 percent; texturized
synthetic yarns, 4 to 7 percent; and cotton yarns 3 percent or less.
These knitting oils are readily emulsified or soluble in water, and are
removed by washing prior to the dyeing operations.
Subcategory 6 - Carpet Mills
The carpet industry wastes are very similar in nature to those from
Subcategory 5, Knit Goods. When polyester is dyed, the carriers present
the same problem as in other categories, but very little polyester is
being used or will be used until a satisfactory answer to fireproofing
is found. Therefore, the nylon, acrylic and modacrylic dyeing
predominate. This means very little phenolics from carriers, and very
little chrome from wool dyeing. Spin cils from the yarns are present.
A special waste, peculiar to this industry, exists because of the use of
foamed and unfoamed latex backing. The latex is not soluble in water
but is used in a highly dispersed form; hence suspended solids and COD
could be a problem unless they are coagulated. This stream (from
equipment washdown once a day to once a week) is usually segregated,
acidified to hasten coagulation, and settled before it joins dyehouse
wastes.
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Municipal treating plants require pretreatment of the carpet mill wastes
to remove fibers and latex. Any latex that enters the sewer lines tends
to form strings and can cause appreciable deposits.
The pH of carpet wastes is usually close to neutral.
With the lack of other wet processing steps in the mill, the hot dye
wastes sometimes present a problem to biological treatment systems.
The color problem is siirilar to that of ether finishing categories.
Where carpets are printed, the thickeners present a high BOD load, as in
fabric printing.
Subcategory 7 - Yarn Eyeing and Finishing
Wastes generated in yarn processing plants will depend substantially on
whether natural fibers, blends, or synthetics alone are processed.
When synthetics alone are handled, only light scouring and bleaching is
required, and wastes would be low levels of detergents, soda ash, sodium
phosphate, and perhaps a low bleach level. Wastes for this step would
have low BOD, and dissolved solids. Dyeing would contribute a stronger
waste, primarily due to the carrier in the case of polyester, and to
some acetic acid; wastes, of course, would contain some color.
Scouring, bleaching, and mercerizing of cotton generate BOD and color
because of the fiber impurities, and high level of dissolved solids
because of the mercerizing. Because of the relatively low amounts
involved, it does not appear reasonable to recover caustic soda.
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SECTION VI
SELECTION OF POLLUTANT PARAMETERS
WASTE WATER,PARAMETERS^.OF MAJOR^SIGNIFICANCE
A thorough analysis of the literature, industry data and sampling data
obtained from this study, and EPA Permit data demonstrates that the
following waste water parameters are of major pollutional significance
for the textile industry:
Biochemical Oxygen Demand (5-day, 20° C., BOD5)
Suspended Solids (SS)
pH
Chemical Oxygen Demand (COD) - (Large plants)
Fecal Coliforms
Grease and Oil (Subcategory 1 - Raw Wool Scouring)
Ratignale_f Qr_Selection.. of MalQr_Parameters
Biochemical Oxygen Demand
This parameter is an important measure of the oxygen utilized by
microorganisms in the aerobic decomposition of the wastes at 20°C over a
five day period. More simply, it is an indirect measure of the
biodegradability of the organic pollutants in the waste. BOD_5 can be
related to the depletion of oxygen in a receiving stream or to the
requirements for waste treatment.
If the BOD5 level of the final effluent of a mill into a receiving body
is too high, it will reduce the dissolved oxygen level in that stream to
below a level that will sustain most fish life; i.e. below about 4
mg/1. Many states currently restrict the BOD5 of effluents to below 20
mg/1 if the stream is small in comparison with the flow of the effluent.
A limitation of 200 to 300 mg/1 of BOD5 is often applied for discharge
to municipal sewers, and surcharge rates often apply if the BOD5_ is
above the designated limit.
Concentrations of BOD_5 in the raw wastes may vary from 50 mg/1 to 3000
mg/1. The values depend on the fibers processed, the chemicals used,
and on processing methods. The oxygen demanding portion of the wastes
are treatable biologically, with only a few exceptions. The use and
degree of removal in a given time are quite variable.
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Suspended Solids
This parameter measures the suspended material that can be removed from
the waste waters by laboratory filtration, but does not include coarse
or floating matter than can be screened or settled out readily.
Suspended solids are present in textile waste waters as a process waste
generated from the fibrous substrate, the chemicals used, and the
biological treatment. Most of the solids may be removed in clarifiers,
in settling basins, by filtration, or by other techniques. Suspended
solids are a visual and easily determined measure of pollution and also
a measure of the material that may settle in tranquil or slow moving
streams. A high level cf suspended solids is an indication of high
organic pollution.
PH
The variations in pH cannot be characterized across the industry since
some processes require highly acid conditions and others highly
alkaline. Neutralization is practical where pH control is necessary to
prevent adverse effects in biological waste treatment systems. These
systems operate effectively at a pH range between 6.0 and 9.0.
Chemical Oxygen Demand (COD)
COD is another measure of oxygen demand. It measures the amount of
organic and some inorganic pollutants under a carefully controlled
direct chemical oxidation by a dichromate-sulfuric acid reagent. COD is
a much more rapid measure of oxygen demand than BOD^ and is potentially
very useful.
COD provides a rapid determination of the waste strength. Its
measurement will indicate a serious plant or treatment malfunction long
before the BOD5 can be run. A given plant or waste treatment system
usually has a relatively narrow range of COD:BODj5 ratios, if the waste
characteristics are fairly constant, so experience permits a judgment to
be made concerning plant operation from COD values. COD limitations are
to be applied only to the large plants.
Fecal Coliforms
Microbiological testing for the presence of fecal coliforms will
indicate the potential for the waste water to contain pathogenic
bacteria. Sanitary sewage is a component of many textile waste
treatment plants, and is often desired for its nutrient value.
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Grease and oil
Wool wax is a substantial pollutant in the wool scouring subcategory; in
other textile subcategories, other materials measured as grease and oil
are much less troublesome.
Rationale for Selectign_of Jginor^Parameters
Total Dissolved Solids (IDS)
The dissolved solids in waste water are mainly inorganic salts. They
are particularly important as they are relatively unaffected by
biological treatment processes and can accumulate in water recirculation
systems. Failure to remove them may lead to an increase in the total
solids level of ground waters and surface water sources. The dissolved
solids in discharge water, if not controlled, may be harmful to
vegetation and may also preclude various irrigation processes. There is
not sufficient data available to establish effluent limitations for TDS,
but at land treatment systems TDS must be managed to insure satisfactory
performance without damage to the physical properties of the soil or to
the quality of the ground waters.
Alkalinity
The measure of alkalinity is an indicator of bicarbonate, carbonate and
hydroxide present in the waste water. The alkalinity of water appears
to have little sanitary significance. Highly alkaline waters are
unpalatable, and may adversely affect the operation of water treatment
systems. However, pH limitations require the control of alkalinity and
thus no alkalinity limitations are needed.
Ammonia Nitrogen and Other Nitrogen Forms
The three most common forms of nitrogen in wastes are organic, ammonia
and nitrate. Organic nitrogen will break down into ammonia, nitrogen
and nitrate, when ammonia nitrogen is present in effluent waste water,
it may be converted to nitrate nitrogen by oxidation. When ammonia and
nitrates are added to ponds and lakes, they contribute to
euthrophication. Additions of ammonia or urea as a nutrient to nitrogen
deficient waste is a common practice in the industry.
Phosphates
Phosphorus like nitrate is linked directly to the eutrophication process
of lakes and streams. When applied to soil, phosphorus does not exhibit
a runoff potential because it is readily absorbed tenaciously on soil
particles. In this case, movement of phosphorus to ground water is
essentially precluded and runoff can only occur if actual erosion of the
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soil takes place. Phosphates may also be added as nutrients to
biological treatment systems.
Temperature
The temperature of effluent waste water is important, since release of
water at elevated temperatures into surface or ground water formations
could result in damage to the micro-ecosystems. The design of treatment
facilities is also dependent upon the plant effluent temperature. Raw
waste from many textile mills is hot, but the temperature reduction
occurs naturally in waste treatment, and the temperature of the final
effluent should be very close to ambient. Therefore, effluent water
temperature does not present a problem.
Color
Color is found throughout the textile industry. Some colors are water
soluble and some are not (dispersed dyes) . Biodegradability is highly
variable. Many hues are used in dyeing, and may appear in wastes; their
combination in waste streams frequently generates a gray or black color.
As a pollutant parameter, color is an aesthetic rather than a toxicity
problem, and there is no universally accepted monitoring method,
although several techniques are being tried.
Chromium
selection of chromium as a pollutant parameter is based on its wide use
as an oxidant in the form of sodium dichromate for vat and sulfur dyes
and as a component of wcol dyes. Substitutes are available, and several
mills are abandoning its use, but it is still widely used. Chromium is
the most significant heavy metal in the textile industry, although
others are employed selectively.
Other Heavy Metals
Copper salts are still used in some dyeing operations of the textile
industry. Since it is harmful in biological systems, it should be
considered as a pollutant. Zinc nitrate is widely used as a catalyst
for durable press goods, and small amounts will enter waste systems.
Magnesium chloride may be used in the same process. Mercury was
considered because of its known occurrence in raw materials such as
sodium hydroxide which is used in large amounts by the textile industry.
In normal operation, we would not expect the concentration of these
materials in the waste water to exceed harmful limits.
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Phenols
Phenols are widely used as carriers in dyeing polyester and blends.
Some dye compositions (naphthols) will probably analyze as phenols also.
In addition, some natural materials, such as lignin residues removed in
scouring cotton, probably analyze as phenols.
Sulfides
Since sodium sulfide is used in one type of dyeing, and other sulfur
containing chemicals are used, it was presumed that sulfides should be
considered among the parameters. Small amounts of sulfides may be
generated in processing wool.
Toxic Organic Chemicals
Dieldrin, a moth proofing agent used for carpers would fall into this
grouping, but this chemical is no longer used. Some carriers,
particularly chlorinated benzenes, are toxic and should not be used.
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SECTION VII
CONTROL AND TREATMENT TECHNOLOGY
The technology for control and treatment of waterborne pollutants in the
textile industry can be divided into two broad categories: in-process
and end-of-pipe. In-process control of waterborne pollutants in turn
depends upon two major conditions: (1) altering the process requirements
that generate water pollutants, and (2) controlling water usage in non-
process as well as process areas. For example, pollutants can often be
kept from entering waste water streams through the institution of better
housekeeping procedures, containment of leaks and spills, good mainten-
ance practices, and the segregation and treatment of selected
concentrated waste water streams.
At present, the textile industry is concerned principally with end-of-
pipe treatment of its waste waters. However, the application of waste
water treatment technology has often been instituted without detailed
investigation of the alternatives to water and waste water management
within the process operations. This approach, of course, is a natural
one to follow since institution of in-process changes for an operating
plant is frequently time consuming and expensive. Furthermore, the
incorporation of in-process control of waterborne pollutants demands
attention to specific operations which are often proprietary whereas
end-of-pipe waste water treatment technology is based on generally
similar principles which are available from consultants, equipment
manufacturers and the company's own competitors.
The textile industry relies principally upon biological treatment of its
waste waters at the end-of-pipe. A large number of plants, especially
small ones, send waste waters into municipal sewage systems where they
may be a minor portion of the total flow; however, in some instances the
waste water flow to a municipal plant is predominantly waste water from
textile plants.
In Process Control
Ancillary Process __ Control Technology. A big portion of the textile
waste loads is inherent in the methods of textile processing and
independent of the efficiency of the processing plants. For example,
size is applied to warp yarns to give them mechanical strength in the
weaving operations; all of this size must be taken off before subsequent
bleaching and dyeing. A finishing plant can use variable amounts of
water in removing this size, but the raw waste load due to size is
unchanged. The same applies to spinning finishes on synthetic fibers,
which are put on the yarn as a lubricant and to reduce static in the
high-speed spinning and textile operations. All of these "temporary"
72
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finishes must be removed before dyeing of the yarn, so again the raw
waste load is almost independent of scouring efficiency.
On the other hand there are many unit operations which are dependent on
chemical concentrations to provide desired effects. The raw waste loads
of pollutants produced by these processes can be substantially reduced
through water reduction. A plant can also reduce the other raw waste
loads—such as spills, reworks, etc.—in many ways. These are
considered below.
The principal axiom in reducing the waterborne pollutant loads through
control external to the process is to prevent pollutants from entering
the water streams. Although this seems obvious, its successful applica-
tion requires continual attention by operating personnel. In fact, it
is synonomous with creation of an effective work safety program. In the
textile industry, with its large number of batch operations, one of the
most important aspects of reducing waterborne pollutants is to institute
an effective water management program--including expanded use of liquid-
level-controls, flow indicators and flow meters, adequate capacity for
generating hot water for wash operations, etc.--in conjunction with a
good maintenance program which will insure that leaks from valves,
pipes, pumps, etc., are promptly repaired so as to prevent process
fluids from entering floor drains, etc. Except for subcategory 1 the
concentration levels of pollutants at the inlet to the waste water
treatment plants are not excessively high for industrial waste waters.
Consequently, a significant reduction in hydraulic capacity should
normally effectively lower the total emitted pollutants from a given
waste water treatment plant even if the concentration level in the
effluent rose moderately. Obviously, if process operations can be
changed to reduce the pollutant load to the waste water treatment plant
simultaneously with a reduction in hydraulic flow the emitted pollutants
will be reduced even more.
Procedures and methods for preventing spills and leaks should be the
paramount consideration, but passive systems for containment or pre-
venting their entry into water courses should be part of any control
plan. Only through assessment of the potential for pollutants to enter
water streams from accidential occurences and the development of action
plans is it possible to develop a high degree of assurance that spilled
liquids will be prevented from polluting water courses.
In summary, strict attention to housekeeping procedures and process
operation, can minimize abnormal waste loads.
conventional Processing_With_Better_Viater Economy The greatest potential
for improved water economy in the textile industry stems from the use of
better washing methods. About 80 percent of all the water used in
textile wet processing is used for removing foreign material—either
that carried on the raw fiber, or materials resulting from treating
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operations such as sizing, scouring, dyeing and finishing. Furthermore,
most applications of treating materials are already carried out at low
liquor ratio for the sake of material and time economy. It follows that
important water economies in conventional processing can be made by
reducing the amount of wash water.
Water usage can be improved substantially as design engineers take water
economy into more active consideration. For example, so-called "double
laced" box washers have recently been introduced, with claimed savings
of up to 40 percent in a number of machines. Significant water savings
are claimed, but detailed quantitative data are not available. More
complex open-width washing machines designed to induce greater
turbulence, have been offered without great success. Since the physical
aim to be accomplished is clear, i.e., breaking down an effective thick
diffusion film in the fabric interstices, it is likely that more
efficient open-width machines can be developed.
Rope washers generally are more effective than open-width washers, but
may be susceptible to further improvement if back-mixing can be
controlled in a practical manner.
In addition to better washer design, there are opportunities for water
economy in more counter-current flows. A finishing plant operator
prefers to use fresh water at every machine, for ease of control anc?
adjustment, and for freedom from danger of cross-contamination.
However, some opportunities for counter-flow are neither unduly
difficult nor hazardous to quality. For example, it is almost always
acceptable to counter-flow water from machine to machine where several
machines are used in series at the same point in the process. For
example, it is common to use 5 or 6 or more open-width box washers in
series after scouring or mercerizing operations, or two Tensitrol-type
rope washers after scouring operations. It is best for water economy to
counter-flow the water through the series. This is frequently but not
universally practiced today. Furthermore, it is practical to counter-
flow water from some later stages to seme earlier stages. For example,
white washer effluent can almost certainly be used as feed water for
caustic washers. Additional opportunities for backflow of water also
exist. However, there are limitations; wash wat€?r from dyeing
operations, for example, always contains color, and is generally
unsuitable for re-use without cleanup. Caustic scour and desizing wash
waters are heavily laden with dissolved and suspended solids and
unsuitable for re-use.
In principle, water cleanup could be used around particular machines or
groups of machines, thus extending water economy still further. Pre-
liminary consideration of investment and operating costs indicates that
rhis is generally less economical than pooling effluents and operations
of one large treating plant. Closing of water cycles around individual
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operations or groups of operations will probably be limited to very
special circumstances.
In summary, further water economies can be achieved by machine
improvements and by wider use of countercurrent flow.
New Process Technology
Solvent Processing : Serious study of textile processing in organic
solvents dates back at least 15 years, although batch applications of
special finishing, such as water repellents has been practiced for more
than a generation. In the late 1950's, Imperial Chemical Industries
pioneered a solvent system for continuous scouring of cotton piece
goods. Several large machines of this type have been operated in the
United States at various times since 1960. During the 1960's, a number
of continuous solvent scouring and finishing ranges were devised and
tested in Europe. In most of these cases the development work has been
carried out by solvent suppliers or equipment manufacturers.
In the course of this wcrk it has become clear that chlorinated solvents
such as perchloroethylene and trichloroethylene are the most
advantageous materials now available. It has also become clear that
suitable machines can be manufactured and operated so as to control air
pollutions ir. the work space. Solvent less remains an economic problem.
Extremely tight control is needed to keep solvent loss per operation
below 5 percent of fabric weight. To date, there has been no
appreciable commercial use of solvent finishing for woven goods.
However, solvent processing has established a firm if specialized
position in knit fabric finishing, especially in the finishing of
synthetic knits.
Solvent processing has found commercial use only where superior fabric
properties have been achieved. For example, solvent applications of
stain repellent finish to upholstery and drapery materials are widely
practiced. In this case, aqueous treatment is not always possible,
because the fabric is sensitive to water. Similarly, solvent scouring
and finishing of synthetic knit fabrics is widely practiced because it
is, in these cases, advantageous to quality to avoid wetting with water.
Some finishes, furthermore, are not available in water soluble or dis-
persible form and can be used only in solvents.
On the other hand, very substantial research and development efforts in
the last decade or so have not led to replacement of aqueous processing
to any appreciable extent.
Adoption of a complete solvent processing scheme avoids the problem of
dealing with both aqueous and solvent wastes. As noted above, however,
a complete line of textile processing and finishing compounds would
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first be required. Some thousands of different dyestuffs and chemicals
are now used in commercial textile processing. Only a limited number
can be directly transferred to solvent use.
On the grounds noted above, it is becoming clear that solvent processing
generally will be introduced only as superior results are demonstrated.
In general, this implies better properties in the finished fabric,
although processing advantages may lead the way in a few cases. The
prospects for solvent processing are outlined below for each of several
important finishing steps.
Solvent Scouring of Woven Fabric. Despite intense effort solvent
scouring of woven fabrics has not established a firm place. The
properties of solvent scoured fabrics are not generally superior. The
wastes generated are the same with respect to organic content, but, of
course, free from the alkali generally used for aqueous scouring.
Solvent Scouring of Knit Fabric. Solvent scouring of some synthetic
knit fabrics is well established and growing. Commercial use is based
on superior results, fast drying and easy extension to specialized sol-
vent finishing. Contribution to water pollution abatement is modest
because scouring of knits does not contribute very heavily to rextile
pollution loads.
Bleaching. It is possible to bleach from solvent sytems and large scale
demonstrations have been carried out. However, the process used
generates both aqueous and solvent wastes. No advantages have been
demonstrated with respect to fabric properties.
Dyeing. A very large effort has been devoted to solvent dyeing. Some
fibers are commercially dyed from solvent systems, notably nylon sports-
wear and carpets by the STX beam dyeing process. The advantages and
limitations of solvent dyeing, both practical and theoretical, were
discussed at length in a January 1973 AATCC Symposium. Collected
papers, available from the American Association of Textile Chemists and
colorists Research Triangle Park, North Carolina, 27709, should be
consulted for details. Although many important textile' fibers can be
dyed from solvent systems, practical applications will apparently be
limited to special cases. There are not grounds for broad reliance on
solvent processing to solve current liquid effluent problems arising
from dyeing operations.
Solvent Finishing Woven Goods. It has been shown that many functional
finishes can be applied~from solvents. Some advantageous properties
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have been demonstrated, but no practical use has been achieved. It is
believed that advantages shown so far have been insufficient to justify
a cnangeover from the familiar aqueous systems. In any event, chemical
finishing is but a modest contributor to textile effluents, since the
aim is to capture a very high fraction of the active agent on the cloth.
In special cases, i.e., water-sensitive fabrics, solvent finishing has
become fairly standard practice. Application of stain and soil resist
finishes to upholstery fabrics is a typical example.
solvent __ Finishing ___ of ____Knit __ Fabric. Synthetic knit fabrics lend
themselves admirably to combination scouring and finishing from
solvents. Some modern finishes such as silicone polymers for single-
knits, can be applied only from solvent. In other cases, solvent
processing recommends itself because of ease and speed of drying, or
because of superior properties developed by solvent finishing. Although
much of this development started with batch operations in dry cleaning
machinery, high developed continuous processing machines are now
available from several manufacturers, both domestic and foreign. It is
clear that solvent processing of knit fabrics is established and
growing.
In summary, solvent processing is clearly finding a place in modern
textile processing. There are, however, no grounds for supposing that
aqueous processing will be totally displaced by solvent processing.
Most woven goods require the use of
warp size during manufacture. The sizing, traditionally starch, coats
the warp yarns and binds the individual fibers together. This acrion is
necessary to preserve the warps from excessive abrasion damage during
weaving. The sizing is generally removed as the first operation in the
fabric finishing sequence. Warp size constitutes, on the average, about
5 percent of the weight of the fabric, and it all ends up in the
effluent waters. Accordingly, it is a very substantial contributor to
the total BOD and COD in textile mill effluents. Sizing waste accounts
for about half the total BOD and COD load from textile operations.
Since the advent of synthetic fibers, newer sizing agents have been
developed. A solubilized cellulose derivative, and polyvinyl alcohol
have been widely used. At this time, PVA, alone or in blends with
starch, is the most popular size for the important cotton/polyester
blend fabrics.
Solvent methods offer one possible route to allocation of the heavy
pollution load from warp sizes. The concept is to apply a solvent-
soluble polymer, then remove it by solvent washing following weaving
and, finally, to recover the polymer for re-use. There is every reason
to suppose that suitable polymers can be found. At least two companies
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are actively working in this direction. Early indications are that
solvent- applied warp size can be effective. The future potential of the
process depends upon successful recovery and re-use of the size.
Since the size is to be used repeatedly, some means to purge impurities
is mandatory. While this is a difficult problem, the potential advan-
tages of solvent size and desize are substantial. Solvent size/desize
will eventually find practical application. It is likely that adoption
of new sizing technology will be based on demonstrated advantages over
conventional methods rather than on pollution control considerations
alone.
Specific I n^ Pr oce s s Changes
Wool Scourimj. ORe °f "^fr6 problems in defining wool scour wastes and in
controlling the process for optimum performance is that detergent is
added on a fixed flow basis, and the demand for it varies widely with
the natural variations in the fleece as received. Future effort may
profitably be spent in developing a method to measure the detergent
demand and control its addition accordingly; less detergent will be
used, BOD load reduced and perhaps a more easily separated emulsion will
yield higher grease recoveries.
In addition, in the centrifuge recovery system described, rewashing of
the grit for recovery of up to 40 percent more grease than is presently
being recovered, appears possible with developmental efforts.
Furthermore, the value of centrifuge-recovered wool grease is higher
than that of acid-cracked grease (20£ per pound in 1973).
Re-use of the waste treatment plant effluent as make-up water to the
scouring train may be feasible. One of the obvious problems is that
dissolved salts will build up.
solvent scouring has been used to remove the wool grease from the wool.
Jet fuel, benzene, carbon tetrachloride, ethyl alcohol, methyl alcohol
and isopropyl alcohol have been tried. The problems of f laimmability and
explosive hazards, and of efficiency of solvent recovery have prevented
its use in the United States.
Solvent scouring requires subsequent detergent washing to remove the
dirt. More efficient methods of grease recovery using the water
scouring process appear capable of achieving grease recovery levels
comparable to that with solvent methods, and hence would probably offer
the better choice for further reducing pollution load in the future.
wool Finishing. Further effort should be extended to segregating waste
streams within the mill. In particular, many of the rinse waters appear
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satisfactory for reuse both for subsequent initial rinses and for pre-
scouring steps and perhaps for fulling rinses.
Solvent scouring is practiced in several mills in place of initial
detergent scouring, to remove spin oils, sizes, and fugitive tints. The
savings in detergent costs appear to justify these systems resulting in
a lower BOD load and somewhat lower water use.
Woven and Knit Fabric Finishing and _Stock and Yarn Dyeing^ The
possibilities for reducing water consumption in finishing woven fabric
were discussed earlier. In this section we will emphasize pollutants
other than water.
Scouring, mercerizing and bleaching generate substantial wastes, parti-
cularly in textiles containing cotton. Large textile users already
recover spent caustic soda and this should be extended to other users.
Better control and automation of dyeing processes could bring about:
reductions in dye and chemical usage as well as in water.
There is no simple way to reduce the amounts of auxiliary chemicals
essential for dyeing, e.g., salts, sodium hydrosulfite and a few others.
some mills are abandoning the use of chromates, and substitutes are
generally as effective. The use of pressure becks for dyeing polyester
is increasing, and reducing carrier usage significantly. Printing pro-
cesses frequently use solvents (Varsol) which can be recovered by flo-
tation and distillation.
Carpets. Continuous dyeing has been stated to use 20 to 25 percent of
the amount of water used in beck dyeing. Stock dyeing and printing
rinse also are similar lower level uses. However, a mill can use a
continuous process only if the volume of a given shade is sufficiently
high.
If polyester regains as a major face-yarn material, there will be an
increase in raw waste load. This can be abated to some extent by the
use of pressure dye becks, as in subcategories 4 and 5, that permit a
reduction in the use of carriers and their attendant heavy BOD load.
Biological Treatment Technology
The treatment of waste effluents by biological methods is an attractive
alternative when a high proportion of the biodegradable material is in
the soluble form, as is the case in the textile industry. These methods
are applicable in this industry irrespective of plant size, age or
location.
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Many types of microoganisms remove organic materials from liquid wastes.
Those most commonly used in Treatment systems are heterotrophs, which
utilize organic carbon for their energy and growth. Some are aerobic
and require molecular oxygen for converting wastes to carbon dioxide and
water. Others are anaerobic and grow without molecular oxygen.
Anaerobic microorganisms grow more slowly than aerobes and produce less
sludge per unit of waste treated than do aerobic microorganisms.
Anaerobes also release acids and methane, and their action on sulfur-
containing wastes may create odor problems. Some microorganisms are
facultative; that is, they can grow in either an aerobic or anaerobic
environment.
The biological treatment of industrial wastes often lacks necessary
nutrients in the waste to sustain desirable biological growth. Added
nutrients, most often nitrogen and sometimes phosphorus, may be required
for efficient biological treatment cf processing wastes. Processing
wastes generally requires the addition of nitrogen before successful
biological treatment. Often this can be economically accomplished by
the addition of nutrient-rich wastes from another source for combined
treatment.
A discussion of the various methods of biological treatment is presented
in the following sections.
ln this case the active biota is maintained as a
suspension in the waste liquid. Air, supplied to the system by
mechanical means, mixes the reaction medium and supplies the
microorganisms with the oxygen required for their metabolism. The
microorganisms grow and feed on the nutrients in the inflowing waste
waters. There are fundamental relationships between the growth of these
microorganisms and the efficiency of the system to remove BOD5.
A number of activated sludge systems have been designed, all of which
have their own individual configurations. Basically, these designs
consist of some type of pretreatment, usually primary sedimentation, and
aeration, followed by sedimentation which will allow the sludge produced
to separate, leaving a clear effluent. Portions of the settled sludge
are recirculated and mixed with the influent to the aeration section,
usually at a proportion ranging between 10 to 100 percent, depending
upon the specific modification ot the basic activated sludge process.
The goal of these plants is to produce an actively oxidizing microbial
population which will also produce a dense "biofloc" with excellent
settling characteristics. Usually, optimization of floe growth and
overall removal is necessary since very active microbial populations do
not always form the best floes.
Activated sludge treatment plants are capable of removing 95 percent or
better of the influent BOD5 from textile manufacturing plants.
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The extended aeration modification of the activated sludge process is
similar to the conventional activated sludge process, except that tha
mixture of activated sludge and raw materials is maintained in the
aeration chamber for longer periods of time. The common detention time
in extended aeration is one to three days, rather than six hours.
During this prolonged contact between the sludge and raw waste, there is
ample time for organic matter to be adsorbed by the sludge and also for
the organisms to metabolize the removal of organic matter which has been
built up into the protoplasm of the organism. Hence, in addition to
high organic removals from the waste waters, up to 75 percent of the
organic matter of the microorganisms is decomposed into stable products
and consequently less sludge will have to be handled.
In extended aeration, as in the conventional activated sludge process,
it is necessary to have a final sedimentation tank. some of the solids
resulting from extended aeration are rather finely divided and therefore
settle slowly, requiring a longer period of settling.
The long detention time in the extended aeration tank makes it possible
for nitrification to occur. If it is desirable for this to occur, it is
necessary to have sludge detention times in excess of three days. This
can be accomplished by regulating the amounts of sludge recycled and
wasted each day. Oxygen enriched gas could be used in place of air in
the aeration tanks to improve overall performance. This would require
that the aeration tank be partitioned and covered, and that the air
compressor and dispersion system be replaced by a rotating sparger
system, which costs less to buy and operate. When co-current, staged
flow and recirculation of gas back through the liquor is employed,
between 90 and 95 percent oxygen utilization is claimed.
Activated sludge in its varied forms is an attractive alternative in
textile waste treatment. Conventional design criteria is not directly
transferrable from municipal applications. However, high levels of
efficiency are possible at the design loadings normally employed in
treating other types of high strength organic wastes. The general
experience has been that biological solids separation problems can be
avoided if the dissolved oxygen concentration remains above zero
throughout the aeration basin, if management minimizes very strong,
concentrated waste releases, and if sufficient amounts of nitrogen are
available to maintain a critical nitrogen: BOD5 ratio. This ratio has
been recommended to be 3 to 4 kg(Ib) N per 100 kg(Ib) of BOD5 removed.
Numerous cases have been reported of successful combined treatment of
textile and domestic wastes by activated sludge and its modifications.
Activated sludge systems require less room than other high reduction
biological systems, but have higher equipment and operating costs.
Properly designed and operated systems can treat textile wastes to
achieve high BOD reductions.
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°2i£iLi FjItgation _fTrickling gilter): The trickling filter process
has found application in treatment of many industrial wastes. Very tall
filters employing synthetic media, high recirculation, and forced air
circulation have been used to treat strong wastes in the 300-4000 mg/1
BOD5 range.
The purpose of the biofilter system is to change soluble organic wastes
into insoluble organic matter primarily in the form of bacteria and
other higher organisms. As the filter operates, portions of the
biological growth slough off and are discharged as humus with the filter
effluent. Usually, some physical removal system is required to separate
this insoluble organic material which can be treated by other suitable
methods, usually anaerobic fermentation in a sludge digester.
Trickling filters are usually constructed as circular beds of varying
depths containing crushed stone, slag, or similar hard insoluble
materials. Liquid wastes are distributed over this bed cit a constant
rate and allowed to "trickle" over the filter stones. Heavy biological
growths develop on the surface of the filter "media" throughout the
depth of the filter and also within the interstitial spaces.
The biological film contains bacteria, (Zooglea, Sphaerotilus, and
Beggiatoa); fungi (Fusarium, Geotrichum, sepedonium); algae, both green
and blue-green (Phormidium, Ulothrix, Mononostrona); and a very rich
fauna of protozoa. A grazing fauna is also present on these beds
consisting of both larval and adult forms of worms (Oligochaeta),
insects (Diptera and Coleoptera among others), and spiders and mites
(Arachnida) .
A common problem with this type of filter is the presence of flies which
can become a severe nuisance. Insect prevention can usually be
prevented by chlorinating the influent cr by periodically flooding the
filter.
Recirculation of waste water flows through biological treatment units
are often used to distribute the load of impurities imposed on the unit
and smooth out the applied flow rates. Trickling filtejr BOD5 removal
efficiency is affected by temperature and the recirculation rate.
Trickling filters perform better in warmer weather than in colder
weather. Recirculation of effluent increases BOD5 removal efficiency as
well as keeping reaction type rotary distributers moving, the filter
media moist, organic loadings relatively constant, and increases contact
time with the biologic mass growing on the filter media.
Furthermore, recirculation improves distribution, equalizes unloading,
obstructs entry and egress of filter flies, freshens incoming and
applied waste waters, reduces the chilling of filters, and reduces the
variation in time of passage through the secondary settling tank.
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Trickling filter BOD5 removal efficiency is inversely proportional to
the BOD5 surface loading rate; that is, the lower the BOD5_ applied per
surface area, the higher the removal efficient. Approximately 10-90
percent BOD reduction can be attained with trickling filters.
Anaerobic Processes: Elevated temperatures (29° to 35°C or 85° to 95°F)
and the high concentrations typically found in industrial wastes make
these wastes well suited to anaerobic treatment. Anaerobic or
faculative microorganisms, which function in the absence of dissolved
oxygen, break down the organic wastes to intermediates such as organic
acids and alcohols. Methane bacteria then convert the intermediates
primarily to carbon dioxide and methane. Also, if sulfur compounds are
present hydrogen sulfide may be generated. Anaerobic processes are
economical because they provide high overall removal of BOD5 and
suspended solids with no power cost (other than pumping) and with low
land requirements. Two types of anaerobic processes are possible:
anaerobic lagoons and anaerobic contact systems.
Anaerobic lagoons are used as the first step in secondary treatment or
as pretreatment prior to discharge to a municipal system. Reductions of
85 percent in BOD5 and 85 percent in suspended solids can be achieved
with these lagoons. A usual arrangement is two anaerobic lagoons
relatively deep (3 to 5 meters, or about 10 to 17 feet), low surface-
area systems with typical waste loadings of 240 to 320 kg BOD5/1000
cubic meters (15 to 20 Ib BOD5/1000 cubic feet) and a detention time of
several days.
Plastic covers of nylon-reinforced Hypalon, polyvinyl chloride, and
styrofoam can be used on occasion to retard heat loss, to ensure
anaerobic conditions, and hopefully to retain obnoxious odors. Properly
installed covers provide a convenient method for collection of methane
gas.
Influent waste water flow should be near, but not on, the bottom of the
lagoon. In some installations, sludge is recycled to ensure adequate
anaerobic seed for the influent. The effluent from the lagoon should be
located to prevent short-circuiting the flow and carry-over of the scum
layer.
Advantages of an anaerobic lagoon system are initial low cost, ease of
operation, and the ability to handle shock waste loads, and yet continue
to provide a consistent quality effluent. Disadvantages of an anaerobic
lagoon are odors although odors are not usually a serious problem at
well managed lagoons.
Anaerobic lagoons used as the first stage in secondary treatment are
usually followed by aerobic lagoons. Placing a small, mechanically
aerated lagoon between the anaerobic and aerobic lagoons is becoming
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popular. It is currently popular to install extended aeration units
following the anaerobic lagoons to obtain nitrification.
The anaerobic contact system requires far more equipment for operation
than do anaerobic lagoons, and consequently is not as commonly used.
The equipment, consists of equalization tanks, digesters with mixing
equipment, air or vacuum gas stripping units, and sedimentation tanks
(clarifiers). Overall reduction of 90 to 97 percent in BOD and
suspended solids is achievable.
Equalized waste water flow is introduced into a mixed digester where
anaerobic decomposition takes place at a temperature of about 33° to
35°C (90° to 95°F). BOD5 loadings into the digester are between 2.4 and
3.2 kg/cubic meter (0.15 and 0.20 Ib/cubic foot), and the detention time
is between three and twelve hours. After gas stripping, the digester
effluent is clarified and sludge is recycled at a rate of about one-
third the raw waste influent rate. Sludge at the rate of about 2
percent of the raw waste volume is removed from the system.
Advantages of the anaerobic contact system are high organic waste load
reduction in a relatively short time; production and collection of
methane gas that can be used to maintain a high temperature in the
digester and also to provide auxilary heat and power; good effluent
stability to waste load shocks; and application in areas where anaerobic
lagoons cannot be used because of odor or soil conditions.
Disadvantages of anaerobic contractors are high initial and maintenance
costs and some odors omitted from the clarifiers.
Anaerobic contact systems are usually used as the first stage of
secondary treatment and can be followed by the same systems that follow
anaerobic lagoons or trickling filter roughing systems.
Other^Aerobic^Procegses^ Aerated lagoons have been used successfully for
many years in a number of installations for treating industrial wastes.
However, with recent tightening of effluent limitations and because of
the additional treatment aerated lagoons can provide, the number of
installations is increasing.
Aerated lagoons use either fixed mechanical turbine-type aerators,
floating propeller-type aerators, or a diffused air system for supplying
oxygen to the waste water. The lagoons usually are 2.4 to 4.6 m (8 to
15 feet) deep, and have a detention time of two to ten days. BOD5
reductions range from 40 to 60 percent with little or no reduction in
suspended solids. Because of this, aerated lagoons approach conditions
similar to extended aeration without sludge recycle.
Advantages of this system are that it can rapidly add dissolved oxygen
(DO) to convert anaerobic waste waters to an aerobic state; provide
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additional BOD5 reduction; and require a relatively small amount of
land. Disadvantages are the power requirements and that the aerated
lagoon, in itself, usually does not reduce BOD5 and suspended solids
adequately to be used as the final stage in a high performance secondary
system. Aerated lagoons are usually a single stage of secondary
treatment and should be followed by an aerobic (shallow) lagoon to
capture suspended solids and to provide additional treatment.
Aerobic lagoons (or stabilization lagoons or oxidation ponds), are large
surface area, shallow lagoons, usually 1 to 2.3 m deep (3 to 8 feet),
loaded at a BOD5 rate of 22-56 kilograms per hectare (20 to 50 pounds
per acre). Detention times will vary from several days to six or seven
months; thus aerobic lagoons require large areas of land.
Aerobic lagoons serve three main functions in waste reduction:
1. Allow solids to settle out.
2. Equalize and control flow.
3. Permit stabilization of organic matter by aerobic and facultative
microorganisms and also by algae.
Actually, if the pond is quite deep, 1.8 to 2.4 m (6 to 8 feet), so that
the waste water near the bottom is void of dissolved oxygen, anaerobic
organisms may be present. Therefore, settled solids can be decomposed
into inert and soluble organic matter by aerobic, anaerobic or
facultative organisms, depending upon the lagoon conditions. The
soluble organic matter is also decomposed by microorganisms causing the
most complete oxidation. Wind action assists in carrying the upper
layer of liquid (aerated by air-water interface and photosynthesis) down
into the deeper portions. The anaerobic decomposition generally
occurring in the bottom converts solids to liquid organics which can
become nutrients for the aerobic organisms in the upper zone.
Algae growth is common in aerobic lagoons; this currently is a drawback
when aerobic lagoons are used for final treatment. Algae may escape
into the receiving waters, and algae added to receiving waters are
considered a pollutant. Algae in the lagoon, however, play an important
role in stabilization. They use CO2, sulfates, nitrates, phosphates,
water and sunlight to synthesize their own organic cellular matter and
give off free oxygen. The oxygen may then be used by other
microorganisms for their metabolic processes. However, when algae die
they release their organic matter in the lagoon, causing a secondary
loading. Ammonia disappears without the appearance of an equivalent
amount of nitrite and nitrate in aerobic lagoons. From this, and the
fact that aerobic lagoons tend to become anaerobic near the bottom, it
appears that some denitrification is occurring.
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High winds can develop a strong wave action that can damage dikes;
Riprap, segmented lagcons, and finger dikes are used to prevent wave
damage. Finger dikes, when arranged appropriately, also prevent short
circuiting of the waste water through the lagoon. Rodent and weed
control, and dike maintenance are all essential for good operation of
the lagoons.
Advantages of aerobic lagoons are that they reduce suspended solids,
oxidize organic matter, permit flow control and waste water storage.
Disadvantages are the large land required, the algae growth problem, and
odor problems.
Aerobic lagoons usually are the last stage in secondary treatment and
frequently follow anaerobic or aerated lagoons. Large cierobic lagoons
allow plants to store waste water discharges during periods of high flow
in the receiving body of water or to store . for irrigation during the
summer. These lagocns are particularly popular in rural areas where
land is available and relatively inexpensive.
Rotatin3_Biolx>gi£al_Contcictor:The rotating biological contactor (RBC)
consists of a series of closely spaced flat parallel disks which are
rotated while partially immersed in the waste waters being treated. A
biological growth covering the surface of the disk adsorbs dissolved
organic matter present in the waste water. As the biomass on the disk
builds up, excess slime is sloughed off periodically and is removed in
sedimentation tanks. The rotation of the disk carries a thin film of
waste water into the air where it absorbs 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 waste
waters. In many ways the RBC system is a compact version of a trickling
filter. In the trickling filter the waste waters flow over the media
and thus over the microbial flora; in the RBC system, the flora is
passed through the waste water.
The system can be staged to enhance overall waste water reduction.
Organisms on the disks selectively develop in each stage and are thus
particularly adapted to the composition of the waste in that stage. The
first couple of stages might be used for removal of dissolved organic
matter, while the latter stages might be adapted to other constituents,
such as nutrient removal.
The major advantages of the RBC system are its relatively low installed
cost, the effect of staging to obtain dissolved organic matter
reductions, and its good resistance to hydraulic shock loads.
Disadvantages are that the system should be housed to maintain high
removal efficiencies and to control odors. Although this system has
demonstrated its durability and reliability when used on domestic
wastes, it has not yet been fully tested to treat textile processing
wastes.
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Rotating biological contactors could be used for the entire aerobic
secondary system. The number of stages required depend on the desired
degree of treatment and the influent strength. Typical applications of
the rotating biological contactor, however, may be for polishing the
effluent from anaerobic processes and from roughing trickling filters
and as pretreatment pricr to discharging wastes to a municipal system.
A BODS reduction of over 90 percent is achievable with a multi-stage
RBC.
£§£f o^E^nce of Biological Treatment Systems
Evaluation of data obtained from the textile waste water treatment
plants surveyed indicate that the operational mode for exemplary
biological systems is extended aeration. No exemplary plant has an
average residence time in the aeration basin of less than 17 hours.
Eighteen exemplary biological systems with an average BOD removal
efficiency of greater than 95 percent are listed in Table 27. The
complete treatment scheme for most exemplary waste treatment plants
includes screening and extended aeration followed by clarification and
polishing lagoons.
Removal of fibers from the waste water prior to their entering the
aeration basin is often necessary to prevent floating scum from building
on the surface of the basin or to prevent the aeration equipment from
malfunctioning and reducing oxidation efficiency. Usually, these fibers
are removed satisfactorily through the use of bars or screens.
Removal of BODS and suspended solids from textile waste water is
accomplished most satisfactorily through the employment of extended
aeration including clarification and sludge return. Textile waste water
usually contains ample phosphates which are available as nutrients for
the microorganism of the biological system. Nitrogen in the form of
ammonia or nitrate may be required in some cases in which this nutrient
deficiency has been identified.
Suspended solids are removed from biologically-treated waste water by
gravity sedimentation. The concentrated slurries are recycled to
aeration basins while the overflow from the clarifier goes to lagoons
for further polishing or discharge to the receiving stream. Because of
colloidal particulates from certain operations, chemical coagulation may
be required prior to biological treatment. This operation is usually
carried out by the addition of coagulating chemicals and/ or the use of
coagulant aids to improve sedimentation. In general, the clarifiers
used in the textile industry are designed for overflow rates
considerably less than those usually found in municipal systems.
Excluding the high BODS values for wool scouring-subcategory 1, the
average BODS concentration of the exemplary treatment is about 20 mg/1,
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running from a low of 2 'to a high of 83 mg/1. Of this group
approximately 20 percent exceeded 30 mg/1.
In effect, many of the waste water treatment plants are being operated
as a two-stage biological system since polishing lagoons of various
residence times may follow the aerated basin.
Chemical oxygen demand (COD) is measured less frequently than BODS. As
in the case of BODS, the COD of wool scouring waste is greater than that
of waste waters from other categories, both on a concentration basis.
Exclusive of the wool scouring waste, the industry's average COD for the
plants surveyed is 222 mg/1 with a low value of 68 mg/1 and a high of
427 mg/1. The ratio of COD to BODS increases significantly across the
waste water treatment plants, which indicates the refractory nature of
some of the components of the waste waters. Although COD is probably a
better measure of the pollutant level of waste waters, other parameters
such as total organic carbon (TOG) or total oxygen demand (TOD) might be
even more indicative.
Although the ratio of CCD to BOD is generally recognized as an indicator
of the biologically refractory nature of waste water pollutants, the
variability in this ratio is affected by many factors. One is the
capabilities of a specific biological system to degrade carbonaceous
substances. For example, PVA, one of the biggest sizes used in the
textile industry, has been considered to be essentially refractory in
terms of its loading on an activated sludge plant, 1 percent BOD,
whereas the theoretical oxygen demand is 36 percent. This would
indicate that only 3 percent of the PVA is normally attacked in a five-
day BOD test, or loosely speaking, 97 percent of it would pass
unaffected through an activated sludge plant. However, recent data
shows that this is not the case; in some activated sludge plants where
the organisms have become acclimated to the PVA, substantial PVA
reduction is achieved.
Textile process operations often require high-temperature water,
however, heat reclamation is also widely practiced as a matter of
economics so the waste waters sent to the treatment plcints usually do
not present any significant thermal shock problems. Furthermore, the
long residence time generally found in the waste water treatment systems
serves effectively to prevent rapid changes in temperature. The most
important temperature effect is not expected to be high temperatures,
but low temperatures. In northern areas, the low wintertime
temperatures in biological treatment systems will reduce the biological
activity and thus the efficiency of BODS removal.
Color in the waste waters of the textile industry is inherent in the
nature of the operations. Since color chemicals are specifically
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formulated for resistance to degradation under the oxidizing conditions
of the world, it is not surprising that removal of color in aerobic
biological systems is erratic. Although color concentration normally is
reduced somewhat in the biological systems surveyed, data obtained were
in arbitrary units, most often APHA(Y) standard. Color removal
efficiency is known to be highly specific to the individual plant and
the particular processes being operated at a given time. Although a
number of research and development projects have been carried out, there
is no one generally accepted method for color removal. Use of
adsorptive technology—such as flocculation and activated carbons—and
anaerobic treatment appear to offer the best possibility for removing
color.
Chromium is the most significant heavy metal of concern in the textile
industry although others are employed selectively. There is good
evidence that at low levels of chromium in the raw waste an activated
sludge treatment plant removes a substantial portion.
Pollution experts within the textile industry have noted that chrome
removal across a waste treatment plant is proportional to the amount of
BOD removed (more specifically the excess sludge removed) and is
inversely proportional to the amount of suspended solids carried over in
the final effluent from the secondary clarifier. Proper removal of
chrome is dependent on proper removal of suspended solids.
Other constituents; Wastewaters from ancillary operations such as
cooling towers, steam generating facilities and water treatment plants
may be significant factors in the waste water volumes emitted from the
textile industry. In those instances where one must handle cooling
tower and boiler blowdowns that contain corrosion inhibiting chemicals,
algacides and biocides, the technology for selective removal is usually
available. Of course, the best practicable control technology currently
available for process waste waters will not remove soluble inorganic
salts which predominate in these blcwdowns. Toxic and hazardous
substances in these systems can be controlled either by eliminating
them, replacing them with less toxic and hazardous substances or
treating isolated streams to remove them. Selection of a course of
action to cope with toxic and hazardous materials in these blowdowns is
more a question of economics than a question of technology.
Reliability, operability and consistency of operation of the waste water
treatment processes found to be most frequently used in the textile
industry can be high if appropriate designs and operational techniques
are employed. The end-of-pipe treatment utilizing extended aeration
biological systems is a well established technology that requires
attention to a limited number of variables to insure a high degree of
reliability. Although many variables can affect the operability of a
89
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biological system, in general the best overall performance is achieved
when the highest consistency of flow and waste water composition occurs.
Since the textile industry is predominantly a batch type process
operation rather than continuous, it follows that both flow rates and
waste water composition will vary significantly. That the industry
recognizes this variability is apparent from the nature of the waste
water treatment systems, i.e., long residence time systems which hold
sufficient volumes so that high instantaneous flow rates or high
concentrations can be rapidly equalized to prevent shock loading of the
biological system.
The most important operational aspects of these extended aeration
systems are equipment reliability and attention to operating detail and
maintenance. Spare aeration equipment (usually floating surface
aerators) improves the possibility of consistent operation; however,
many treatment systems have an adequate overcapacity already installed
as insurance against the results of equipment failure. It is desirable
to install spare equipment at critical points, for example, sludge
return pumps. Perhaps cf equal importance is a design that permits
rapid and easy maintenance of malfunctioning equipment.
Therefore, control of the biological treatment plant and the consistency
of the results obtained are largely a matter of conscientious adherence
to well-known operational and maintenance procedures. Automatic control
of biological treatment plants is far from a practical point. Although
in-line instrumentation for measurement of pH, dissolved oxygen,
temperature, turbidity and so on, can improve the effectiveness of
operation, its use is minimal in the textile industry's existing waste
water treatment plants. Nevertheless, no practical in-line
instrumentation can replace the judicious attention to operational
details of a conscientious crew of operators.
An activated sludge system which is permitted to operate at a constant
F:M ratio all year round and with minimum operational changes would have
a natural variation as shown in section IX by the solid line in Figure
19. A similar system with careful operational control would have a
controlled monthly average variation as shown by the points. Although
the mean value is the same, the amount of natural variation is
controlled by the operator through aeration rate control, sludge
recycling and F:M ratio adjustments. These adjustments can be made
daily so that monthly averages can be held within the desired limits.
Although a well-operated and properly designed facility can be
controlled within +25 percent of the average on a monthly operating
basis. A system with minimal operational control or an allowance of +50
percent of the averages on a monthly basis has been used to calculate
the maximum monthly effluent limitation.
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ADVANCED WASTE WATER TREATMENT TECHNOLOGY
In all categories of textile plants, it is assumed that good secondary
treatment will have a high quality effluent as demonstrated by the
exemplary plants. The definition of advanced treatment systems is
therefore confined to tertiary treatment of the secondary effluents,
dewatering and incineration of sludges, and possibly to preconditioning
of some specialized waste streams to render them compatible with the
advanced waste treatment process.
In some cases, advanced treatment systems have been tried out on textile
wastes and their effectiveness in dealing with these various pollutant
parameters has been assessed. In other cases it is necessary to predict
their usefulness to the textile industry from experience with other
similar waste streams or by an understanding of the physico-chemical
principles involved.
The processes under consideration have been grouped according to the
overall chemical or physical mechanism of their operation:
1. phase change
2. physical separation
3. sorpt ion
4. chemical clarification
Phase_Chanqe
Distillation; The multistage flash MSF process consists essentially of
pumping hot salt, brackish, or contaminated water through suitable
nozzles into a chamber in which the temperature and pressure are lower
than that of the water itself. Part of the water flashes off instantly
as steam which passes through demisters to remove entrained droplets of
impurities and condenses on tubing cooled by entering feed water. The
distilled water drops off the tubes into a trough and is collected as
the product water.
In order to improve the efficiency of the process and recover most of
the heat energy a multi-stage system is preferred in which the latent
heat from the condensation of the steam produced in the evaporation
chamber is used to preheat the cooler feed water flowing in the conden-
ser tubes counter current to the brine in the flash chambers. Thus, the
chief thermal energy requirement is that needed to raise the feed water
from ambient temperatures to the temperature of the outgoing brine.
Recirculation of the brine improves thermal efficiency considerably and
all modern MSF plants are of this design.
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Two types of feed water treatment are generally employed to reduce scale
formation, Frequently a proprietary material is used, containing a
polyphosphate or polyelectrolyte as the active ingredient. These com-
pounds do not prevent scale from forming but rather modify its character
so that it may be easily washed out or dissolved by weak acids periodi-
cally. Often acid treatment is used, with sulfuric acid generally pre-
ferred. The acid is added continuously to the feed water in small a-
mounts to reduce the pH below 7 and decompose the carbonate compounds
that cause hard scaling in the tubes and flash chambers. In many of the
units using acid, the carbon dioxide released by the acid, is removed in
a separate decarbonatcr placed in the feed water circuit after the
reject stages. Otherwise the carbon dioxide is removed with the other
dissolved gases by the steam jet deaerator. In modern units steam jet
deaerators are used to deaerate the flash chambers and to produce a
vacuum.
The vertical tube evaporator (VTE) is a long-tube vertical distillation
type of desalting plant, (146.3 mgd) .
In the climbing-film vertical evaporator, the most common design, the
brine is maintained at a predetermined level inside the vertical tubes.
These tubes are heated externally by the incoming steam in the first
effect or by the hot product vapors in subsequent effects. This is in
direct contrast to a submerged tube type of unit which has the steam
inside and the boiling brine outside the tubes. The vapors from the
boiling brine rise in the vertical tubes into a vapor chamber and are
led from there into the vertical tube heat exchanger in the next effect
where the heat is given up to the brine circulating in these tubes.
The resulting fresh water condensed on the outside of the tubes is re-
moved and combined with product from the subsequent effects. The com-
bined product is cooled in a final condenser with feed water. The in-
coming feed water is fed into the first effect and the concentrated
brine flows in the same direction as the vapors. The brine in each
effect circulates either by natural temperature differences or by forced
circulation.
In another modification, known as the thermal recompression evaporator,
part of the vapors from the last effect are entrained and compressed by
expanded live steam from the boiler. The resulting mixture becomes the
heating medium for the first effect. This scheme is particularly
advantageous where high-pressure steam is available as a source of heat
and it can be used in conjunction with a single or multiple effect
vertical-tube evaporator.
Relevance to Textile Waste Treatment.The waste waters from the textile
industry may have a moderately high concentration of organic chemicals
in comparison with the concentrations in brackish or saline waters.
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In some instances, it might be necessary to treat waste water by
activated carbon adsorption to insure adequate removal of organic
species. Therefore, a thorough consideration of the entire process
chemistry will be required before one can determine whether evaporation
can be successfully applied to waste waters containing carbonaceous
substances. If the waste water streams contain very low concentrations
of organics and high concentrations of dissolved inorganic salts, the
applicability of evaporation is more readily predicted, being
essentially an evaluation of economics.
Freezing Techniques :
It has long been recognized that individual ice crystals formed in
chilled impure water are composed of pure water. Much effort has
therefore gone toward the development of practical processes to take
advantage of this phenomenon for the desalination or purification of
water. Attention is presently centered on two types of equipment.
The vacuum freeze vapcr compression (VFVC) system has the longest his-
tory. In this type of device, feed water is chilled and exposed to a
slight vacuum. Some of the water vaporizes and the resulting loss of
heat of vaporization causes ice crystals tc form in the system.
The ice crystals are separated mechanically from the brine by means of
sieves and scrapers and transferred to melting chambers. At the same
time the water vapor formed during the boiling-freezing stage is com-
pressed and introduced also to the melting chamber, where it condenses
on the ice crystals. In practice the system is more complicated, with
particular care being required to wash the ice crystals free from feed
water and to maintain the correct temperatures and pressures throughout.
The second type of design employs as the vaporizing constituent a secon-
dary refrigerant which is insoluble in water. Usually, liquid butane
under pressure is bubbled through the feed water, vaporizing, expanding
and causing ice crystals to form. As in the vacuum freeze system, the
crystals are then separated mechanically and washed by liquid butane.
The secondary refrigerant system has the advantage that the equipment
operates at higher pressures and smaller volumes of gas (butane) , re-
sulting in less expensive and more reliable pumps and compressors.
£o Textile Waste Treatment. A few small VFVC plants have been
erected in this country and abroad for desalination of seawater, but
have not had enough service to develop useful histories.
Their principal advantage appears to be that they are relatively
insensitive to the nature of the chemicals in the feed water and,
because they operate at low temperatures, resist the scaling and
corrosion problems which plague most other types of plants. None has
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been used for waste water treatment. The secondary refrigerant system
is still in the pilot plant stage of development.
Although neither type of freezing plant has been used in the textile
industry for waste water treatment. it might be attractive because of
its tolerance of high levels of salts, organics, suspended solids and
other materials in the feed water. It can be operated at brine-to-
product ratios as low as about 0.02, and brine concentrations as high as
60,000 mg/1 TDS. This, of course, considerably reduces the cost of
ultimate brine evaporation or disposal.
Physical Separation
Filtration:
The removal of suspended solids or colloidal material from water by
filtration is accomplished by one of a number of mechanisms which may be
generally classified as straining or transport attachment. Straining is
the elimination of particulate matter by size discrimination; that is, a
particle of greater diameter than a pore opening will be physically
restrained from passage.
Transport - Attachment refers to a two step principle and is applied to
particulate matter which may be much smaller than the pore size. The
particles are transported across the stream lines to the proximity of
the filter medium where attachment forces predominate.
Filtration is the most common form of advanced waste water treatment
practiced today. This is due to its relatively inexpensive nature and
its effectiveness in removing suspended solids and the organics
associated with those solids. It provides excellent preparation of
waste for application of other advanced waste treatment techniques and
is an integral part in many designs of these systems.
Relevance to Textile Waste Treatment. Rapid sand type filters have had
considerable use in waste treatment systems for direct filtration of
secondary effluent.
Early work on filtration of secondary effluent took place in Europe.
Truesdale and Birkbeck reported on tests run between October, 1949, and
May 1950, at the Luton Sewage works. Beds of sand 2 feet deep, ranging
in size from 0.9 mm to 1.7 mm, exhibited 72 to 91 percent removal of
suspended solids and 52 to 70 percent removal of BOD. Flow rates ranged
from 1.33 to 3.3 IMP.gal/min/ft2.
Naylor, Evans and Dunscome later reviewed 15 years of studies of
tertiary treatment at Luton. A 3-foot deep bed of 10 to 18 mesh sand
consistently provided an effluent of 4 to 6 mg/1 suspended solids at
flow rates of 3.3 Imp.gal/min/ft2.
-------
In the U. S., most direct filtration work has been with activated sludge
effluent. At the Hyperion Plant in Los Angeles, sand of 0.95 mm
effective size was used in a shallow bed (11 inches deep) traveling
backwash filter. This study lasted for six months during which time U6
percent suspended solids removal and 57 percent BOD removal were
obtained. Filtration rate was 2 gal/min/ft2. Difficulty was
encountered in cleaning the filters and performance gradually
deteriorated during the study. Use of a finer sand (0.45 mm effective
size) in an attempt to yield a better effluent was a failure due to very
rapid clogging of the filter.
Much greater success utilizing the traveling backwash filter for
activated sludge effluent treatment was obtained by Lynam in Chicago.
The effective size of sand used in this study was 0.58 mm. Suspended
solids removal of 70 percent and BOD removal of 80 percent were obtained
at flow rates of 2 to 6 gal/min/ft2. Terminal headloss was quite low
(11 inches of water.) The range of flows studied exhibited no
significant difference in terms of suspended solids removal.
Gulp and Gulp reviewed the work on plain filtration of secondary
effluent with both single medium and multimedia filters. They concluded
that, with either type of filter, better results would be obtained as
the degree of self flocculation of the sludge increased. Thus, a high-
rate activated sludge effluent which contains much colloidal material
should filter poorly, while an extended aeration effluent should filter
well. Multi-media filters exhibit a marked superiority for filtration
of activated sludge effluent because of the high volume of floe storage
available in the upper bed and the polishing effect of the small media.
They indicated the expected performance of multi-media filters for plain
filtration of secondary effluents as shown in Table 10.
Table 10
EXPECTED EFFLUENT SUSPENDED SOLIDS FROM MULTI-MEDIA
FILTRATION OF BIOLOGICAL EFFLUENTS
Biological System Effluent TSS
(mg/1)
High Rate Trickling 10-20
2 - Stage Trickling Filter 6-15
Contact Stabilization 6-15
Conventional Activated Sludge 3-10
Extended Aeration 1-5
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The application of filtration to biologically treated effluent is
dependent on the nature of the biological system and the biological
solids produced by that system rather than the nature or characteristics
of the raw waste. That is, application of filtration to secondary
effluent from textile wastes will remove the biological solids the same
as it would remove the biological solids generated from other wastes.
. Osmosis ._ Reverse osmosis for desalinization of sea water and
brackish water has been under extensive investigation since the
discovery in the early 1960' s of high flux membranes capable of re-
jecting salts. Much of the research and development work was made ,
with a view toward recovering potable water from sea water. Although
this aim still has not been fully attained at prices competitive with
other processes such as flash distillation, improved technology arising
from these programs and increased commercial interest has resulted in
some successful utilization of reverse osmosis for removal of dissolved
salts from industrial waste streams.
The process of reverse osmosis relies upon the ability of certain
specialized polymeric membranes, usually cellulose acetate or nylon to
pass pure water at fairly high rates and to reject salts. And to do
this saline feed streams are passed at high pressures over the surfaces
of the membranes. The applied hydraulic pressures must be high enough
to overcome the osmotic pressure of the saline feed stream, and to
provide a pressure driving force for water to flow from the saline
compartment through the membrane into the fresh water compartment.
In a typical reverse osmosis system. Feedwater is pumped through a
pretreatment section which removes suspended solids and, if necessary,
ions such as iron and magnesium which may foul the system. The
feedwater is then pressurized and sent through the reverse osmosis mo-
dules. Fresh water permeates through the membrane under the pressure
driving force, emerging at atmospheric pressure. The pressure of the
concentrated brine discharge stream is reduced by a power recovery tur-
bine, which helps drive the high pressure pump, and then is discharged.
Three types of reverse osmosis configurations are currently popular.
The first, known as the "spiral wound" configuration, uses flat sheet
cellulose acetate membranes wound in a spiral to produce a multitude of
thin channels through which the feed water flows under high laminar
shear. This configuration is inexpensive, produces high water fluxes,
and consequently efficient use of membrane area. Its major difficulty
is that the resulting thin channels become easily fouled and plugged, so
a process stream must have a very low level of suspended solids.
The second configuration uses tubular cellulose acetate membranes to
bring about turbulent flow and overcome concentration polarization. The
96
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membrane is formed into a tube—with an inside diameter of about 1 inch,
and the "active" (salt rejecting) face of the membrane on the inside of
the tube—through which the feed stream is recirculated at high
turbulent speeds. Membrane utilization is not as efficient as in the
spiral wound configuration, but there is less trouble with flow
distribution, fouling and plugging. This system can handle highly
contaminated wastes with high concentrations of suspended solids.
Finally, a reverse osmosis system using a multitude of hollow nylon
fibers has shown considerable utility on commercial waste streams. A
bundle of fibers, with the "active" side of the nylon membranes on the
exterior of the fibers, is encased in a module. Feed water is passed at
high velocities between the fibers, and fresh product water permeates
into the interior lumens of the fibers from where it is collected. This
configuration results in rather low utilization of membrane area, but
since the cost per unit area of the membranes is considerably lower than
the cost of the cellulose acetate membranes, the ultimate cost of water
recovery is competitive for low salinity feed streams. This
configuration, like the spiral wound one, is highly susceptible to
fouling by suspended solids, and requires thorough pre-treatment of the
feed stream.
Relevance to Textile Wastes Treatment^ The major application of reverse
osmosis to textile wastes would appear to be in removal of salt from
secondary sewage plant effluent. The technology appears adequate to
reduce the effluent salts to potable levels (less than 200 mg/1). The
process should also result in excellent color removal, and substantial
removal of residual BCD and COD. The major limitation appears to be
cost: for large plants, 19,000 cu m/day (5 mgd) or greater, costs are
13 to 192/1000 liters (50 to 750/1000 gallons). However, the costs
increase greatly for smaller plants, because of greater labor costs.
The major technical limitation of the process for treatment of secondary
effluent is the requirement of feed stream quality. High levels of
suspended solids greatly reduce water flux rates through the membranes,
and increase costs substantially. It will therefore be necessary to
remove the suspended solids from the feed. Grease and oil in the feed
may also retard fluxes to some degree, although this effect reportedly
is not as great in the tubular configurations.
In addition to treatment of secondary sewage effluent, reverse osmosis
has been considered for a number of other applications in textile
wastes. An experimental hollow-fiber reverse-osmosis pilot plant
operates on the total waste stream from a textile plant. This system,
which has allowed 80% recovery of the product water, with good color
removal. Data on flux rates, cost, or longevity is inadequate to
extrapolate to the ultimate utility of the process. It is expected that
flux decline, because of suspended solids, may be a problem, and COD may
not be removed adequately.
97
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Another potential application of reverse osmosis is recovery of sizing
materials. Carboxymethylcellulose (CMC) and polyvinylalcohol (PVA) will
both be retained at great efficiency by reverse osmosis, allowing these
sizing materials to be concentrated for reuse. The savings from reuse
of these sizing streams may offset the costs of the smaller plants re-
quired to process just the sizing waste streams.
Ultrafiltratjoni Ultrafiltration is similar to reverse osmosis in that
it relies on the permeation of water through a semipermeable membrane
under a hydraulic driving pressure. The distinction between reverse
osmosis and Ultrafiltration lies primarily in the retention properties
of the membranes: reverse osmosis membranes retain all solutes,
including salts, while Ultrafiltration membranes retain only
macromolecules and suspended solids. Thus salts, solvents, and low
molecular weight organic solutes pass through Ultrafiltration membranes
with the permeant water. Since salts are not retained by the membrane,
the osmotic pressure differences across Ultrafiltration membranes are
negligible. Flux rates through the membranes usually are fairly high,
and hence lower pressures can be used than are practical in reverse
osmosis. Typical pressure driving forces for Ultrafiltration are 20 to
100 psi.
Membranes may be made from cellulose acetate, polyelectrolyte complexes,
nylon, or a variety of inert polymers. Hence, highly acidic or caustic
streams may be processed, and the process is not usually limited by
chemical attack of the membranes.
Relevance to Textile Waste Treatment^ Since Ultrafiltration does not
remove salts and low molecular weight organic compounds such as
dissolved dyes, its utility in textile waste treatment would appear to
be limited to macromolecules and suspended solids.
Concentration and recovery of disperse dyes by Ultrafiltration may be
feasible, where a single color is in the waste stream. concentration
of polymeric cotton sizing materials (PVA and CMC) is technically
feasible since the UF membranes will retain the polymers and pass the
polymer-free water at reasonable fluxes. An experimental system is
being used to test the feasibility of PVA concentration by
Ultrafiltration, with the ultimate aim of re-using the sizing polymer.
The membrane in this system is a new experimental "dynamically formed"
membrane based on deposition of organic surfactants on porous carbon,
but the process should be feasible on more conventional UF membranes at
a cost of 132 to 260 per 1000 liters (502 to $1.00 per thousand gallons)
of water removed.
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Electrodialysis: The production of potable water from brackish waters
by electrodialysis is a mature desalting process. Economically, the
process is usually limited to feed waters having total dissolved solids
up to 10,000 mg/1 and more commonly it treats waters with 1000 to 2000
mg/1 solids. It is not practical to reduce the total solids in the
produce water to a few rrg/1 as is done in distillation plants; about 200
mg/1 is the highest purity attainable in a practical plant.
The general principles of electrodialysis are as follows. The process
involves the separation of a given flow cf water containing dissolved
and ionized solutes into two streams, one more concentrated and one more
dilute than the original, by specially synthesized semi-permeable mem-
branes. Some ion exchange membranes are permeable only to cations;
thus, only positive ions will migrate through them under the influence
of an electric field. Other ion exchange membranes, permeable only to
anions, will permit migration of negative ions only.
In electrodialysis, water is fed, usually in parallel, into the compart-
ments formed by the spaces between alternating cation permeable and
anion permeable membranes held in a stack. At each end of the stack is
an electrode having the same area as the membranes. A d-c potential
applied across the stack causes the positive and negative ions to
migrate in opposite directions. Because of the properties of the
membranes, a given ion will either migrate to the adjacent compartment
or be confined to its original compartment, depending on whether or not
the first membrane it encounters is permeable to it. As a result, salts
are concentrated or diluted in alternate compartments.
To achieve high throughput, the electrodialysis cells in practice are
made very thin and assembled in stacks of cells in series. Each stack
consists of more than 100 cells. Feed water is first filtered to remove
suspended particulate matter which could clog the system or foul the
membrane and, if required, is given an ion exchange treatment to remove
oxidizing materials such as ferrous or manganous ions which would damage
the membranes. Very high organic levels may also lead to membrane
fouling. The catholyte stream is commonly acidified to offset the in-
crease in pH which would normally occur within the cell, and an anti-
scaling additive may be required as well. An operating plant usually
contains many recirculation, feedback and control loops and pumps to
optimize the concentrations and pH's at different points and thus
maximize the overall efficiency.
Relevance to Te xti lg Wa^te Treatment The mechanism of the
electrodialysis process limits it to the removal of relatively small,
mobile, ionized constituents from the waste stream. Sodium, potassium,
chlorides and sulfates readily pass through the membranes. Larger ions,
and those doubly charged, such as phosphate, calcium or barium, have
limited mobility in the membranes and tend to remain in the feed stream.
There may be some incidental transport of small dissolved organic
99
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species through the membranes but it is not significant.
Electrodialysis has been used successfully for more than a decade to
convert brackish (2000-5000 mg/1 TDS) water to potable water ( 500 mg/1
TDS). While this does not represent a waste water treatment application
per se, it can provide useful reliability and cost data from the 150
plants which have been built.
Unfortunately, electrodialysis has not been used to treat textile plant
wastes although some efforts have been made to investigate its use in
dye removal. Because of their large molecular size, dye materials do
not traverse the membranes readily. There may be some possibility of
using electrodialysis to remove dissolved salts from dye solutions, but
this has not yet been demonstrated.
Suspended solids in the feed stream are undesirable. High levels of
organic materials must be avoided as they may attack the membranes.
Thus feed water to the plant should have a low BOD and COD and these
will not be substantially changed by the process.
Sorption Systems
This group of advanced waste treatment processes is concerned with
methods in which the waste water is contacted with a material which
sorbs components of the water. The material is usually regenerated and
the sorbed material ejected into a gaseous or more concentrated liquid
waste stream. The concentrated liquid waste stream is normally
converted to a solid waste by evaporation. Such processes include
adsorption on activated carbon and ion exchange.
Activated Carbonj. Activated carbon is a commercially available and
particularly versatile absorbent primarily because of its relatively low
cost (22 to 1102/kg or 10 to 500/lb) and large surface area (about 112
hectares per kilogram or 126 acres per pound) which relates directly to
its capacity for adsorbed material (0.7 to 0.9 kilograms of adsorbed
material per kilogram of carbon) .
The most popular form of activated carbon is the granular, which is
easily handled, deposits the minimum of fines into the water stream, and
may be regenerated by heat with less than 10% loss per cycle. However,
attempts are being made to develop techniques for the use of powdered
carbon, which is considerably less expensive (about 220/kg or 100/lb)
than granular carbon (662/kg or 300/lb) but which is difficult to
separate efficiently from the waste water and regenerate.
Activated carbon, while acting largely as a general adsorbent, shows
some selectivity:
100
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Strongly Adsorbed Weakly adsorbed
weak electrolytes strong electrolytes
sparingly soluble materials very soluble materials
high molecular wt. compounds low molecular wt. compounds
The amount of a given material absorbed is a function of its chemical
nature, the amount in solution, the pH and the temperature.
Typical adsorption capacities of activated carbon at different residual
COD levels are illustrated in Figure 8.
Several types of water carbon contactors have been proposed and
utilized. Usually one cr more fixed bed columns are linked in parallel.
Carbon capacity is utilized more efficiently by placing several fixed
bed columns in series, the spent upstream column being replaced with a
regenerated column at the downstream side as appropriate. A recent,
more efficient development is the use of moving bed systems.
The carbon is usually regenerated in multiple hearth furnaces; in some
cases, such as in the adsorption of phenol, partial regeneration may be
achieved by chemical treatment. A schematic of a treatment process
including thermal regeneration is illustrated in Figure 9.
Relevance to Textile Waste Treatment. The Environmental Protection
Agency has undertaken detailed studies of the use of activated carbon
for the tertiary treatment of municipal wastes - primarily at Pomona,
California and Lebanon, Ohio. The Pomcna plant has been run for over
four years and deserves detailed description.
The plant has a capacity of 1100 cu m/day (0.3 mgd) and is a four-stage,
fixed-bed, gianular activated carbon plant.
The carbon is periodically backwashed to remove entrapped suspended
solids and regenerated when necessary after a steady state adsorption
capacity of about O.U to 0.5 kilograms of COD per kilogram of carbon has
been reached. Carbon losses averaged 8 1/2 percent per cycle. One
complete cycle of the 12,200 kilograms (26,800 pounds) of carbon in the
plant is achieved each year of operation. The effectiveness of the
plant in improving water quality is illustrated in Table 11.
101
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1-0
il
o
JU
El
0-1
001
.--•*
**tf
^ >
_L
Co C0
0-1
LO 10-0
(C) Residual COD cone, (ppm)
1OO-0
Figure 8
COD Isotherms Using Virgin Carbon and
Different Secondary Sewage Effluents
(after Masse, 1967)
102
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Influent
i
i
Regenerated t
Carbon
"\
j
i
1 1
V.
\
\
J
1
) * W
Carbon
t . t
1 '
Spent
Carbon
Tank
}
r
Regeneration
Furnace
I
•
Quench
Tank
Make-up
Carbon
1 1
i
Regenerated
Carbon Storage
fc, ' '
^ ,
Regenerated Carbon
Figure 9
Schematic of an Activated Carbon System
Including Thermal Regeneration
103
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Table 11
Carbon Adsorption Pilot Plant:
Average Water Quality Characteristics
(June 1965 to July 1969)
Parameter
Suspended solids mg/1
COD mg/1
Dissolved COD mg/1
TOC mg/1
Nitrate as N mg/1
Turbidity (JTU)
Color (Platinum-Cobalt)
Odor
CCE mg/1
BOD mg/1
Influent
9
43
30
12
8.1
8.2
28
12
__
3
Effluent
0.
10
8
3
6.
1.
3
1
0.
1
6
6
2
026
104
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About 75% of the influent COD is removed, and the values of most other
parameters such as suspended solids, turbidity, color, odor, and BOD are
reduced to insignificant levels. The effluent water had an average dis-
solved COD of 8 mg/1.
Another activated carbon plant studied by the EPA is part of the
advanced waste treatment facility at the District of Columbia's advanced
waste treatment facility. Following lime precipitation, filtration and
water stabilization, the secondary effluent is passed through five
pressurized activated carbon columns in series at a rate of 190 cu m/day
(50,000 gallons per day). When the preceding clarification was
operating efficiently, up to 75 percent of the TOC was removed by the
carbon adsorption system. Because of operating difficulties the carbon
had to be replaced before saturation, at a loading of only 0.133
kilograms TOC/kilogram carbon.
Activated carbon treatment was also used successfully at Lake Tahoe to
produce drinkable water from secondary effluent. A 28,000 cu m/day (7.5
million gpd) unit operated at a cost of 60/1000 liters (230 per 1000
gallons) .
Experience with the Use of Activated Carbon on Textile Wastes. The use
of activated carbon to treat textile wastes was pioneered at a carpet
mill, in Pennsylvania. Of the raw waste from the dyeing and rinsing
plant, 80 percent was treated and reused. Capacity of the system was
1900 cu m/day (500,000 gallons per day) and it utilized 22,700 kilograms
(50,000 pounds) of granular activated carbon. The carbon was
regenerated by heating it in a furnace.
EPA has supported work in a unique activated carbon system in which
regeneration is accomplished by backwashing the absorbed organic
material into an aerobic biological treatment unit.
After encouraging results in a laboratory unit operating on synthetic
textile waste water, a pilot system was installed at a carpet yarn fiber
dyeing plant. The flow of the pilot system has a capacity of 190 cu
m/day (50,000 gpd).
A range of studies on the treatment of dye waste waters were made by a
textile company in North Carolina. The company encountered only partial
success in the use of carbon for effluent polishing following biological
treatment. In this study anthracite-based media proved unreliable in
removing color contamination; bone char proved successful but cost
about $2.20 per kilogram ($1.00 per pound) compared to 660 per kilogram
(300 per pound) for the former materials.
105
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There are several further instances of the use of activated carbon
adsorption for the treatment of textile wastes, particularly in regard
to color removal. A mill in Pennsylvania, operates a closed dye cycle
using alum, diatomaceous earth, and carbon to yield a color of less than
50 units. The consensus appears to be that while color can be removed
by activated carbon, some elements (particularly the dispersed dyes) are
not adsorbed. cherrical coagulation supplemented by cictivated carbon
adsorption remains the best method for the dispersed dyes, while carbon
adsorption alone may be adequate for dissolved dyes.
To summarize, activated carbon treatment is a common technique in indus-
trial processes, has been evaluated in some detail and has been success-
ful in treating secondary effluent following biological treatment of
municipal waste water. Some successful experience also has been accu-
mulated in the treatment of textile wastes. The advanced process is
suitable for reducing low-level organic contamination, but it affects
the levels of dissolved ionic solids very little.
Ion Exchange. Ion exchangers are solid materials, insoluble in
electrolyte solution, which are capable of exchanging soluble anions or
cations with electrolyte solutions. For example, a cation exchanger in
the sodium form, when contacted with a solution of calcium chloride,
will scavenge the calcium ions from the solution and replace them with
sodium ions. This provides a convenient method for removing the
"hardness" from waters.
Ion exchange can also be used for total salt removal from waste streams,
by employing a series of beds of anion and cation exchangers. The
cation exchanger is used in its "acid" form, exchanging hydrogen ions
for the cations in the stream. The anion exchanger is used in its
"base" form, exchanging hydroxyl ions for the waste strecim anions. The
hydroxyl and hydrogen ions thus liberated from the ion exchanger re-
combine to form water, and thus replace the salts in the stream by pure
water.
The exchange of ions on ion exchangers is stoichiometric and usually re-
versible. Thus, after the ion exchanger becomes saturated with the con-
taminant ion, it can usually be "regenerated" by flushing with a concen-
trated solution of its original ion. The waste regenerate streams are
usually quite concentrated and can be disposed of economically by simple
evaporation.
The most important class of ion exchangers, is the organic ion-exchange
resins made from cross-linked polyelectrolytes. The exchanger exchanges
the counter ions to the fixed charges on the polyelectrolyte. These
resins are insoluble but swell to a limited degree, allowing ions from
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solution to penetrate into the gel matrix formed by the swollen
polyelectrolyte.
They are conventionally used in particulate form in packed beds. The
ion exchange behavior of the resins depends on the nature of the fixed
ionic groups, with the exchanger preferring those ions which strongly
associate with the fixed ions.
One of the major advantages of the synthetic resins is the wide ranges
of ion exchange properties which can be built into them, allowing con-
siderable latitude in the designing of processes. These exchangers have
the additional advantage of being capable of absorbing non-ionic organic
solutes from solution.
In general, ion exchange processes are limited by the selectivity of the
exchanger for the contaminant ion over its own counter ion. Divalent
ions such as calcium and magnesium in general have high affinities for
the ion exchange resins, and can therefore be removed with extremely
high efficiencies. In general, also, ion exchange is less efficient
than electrodialysis or reverse osmosis for high concentration streams.
An upper limit frequently given for efficient removal of ions by ion
exchange is 200-500 mg/1, but others quote efficient cleansing of 2500
mg/1 streams at costs less than that for electrodialysis or reverse
osmosis.
Relevance to Textile Waste Water Treatment.Direct data on the applica-
bility of ion exchange to textile wastes is scarce. Extrapolation of
data from other waste streams is therefore necessary. It would appear
that the major application of ion exchange to textile waste treatment
would be to reduce the dissolved solids level of the effluent from the
secondary treatment plants or the effluent from other operations such as
electrodialysis or reverse osmosis. The dissolved solids levels of the
secondary sewage effluents would appear to be in the proper range for
effective use of ion exchange. Costs for a 50 percent reduction of this
salinity, assuming no other complications, would be expected to be about
120/1000 liters (450/1000 gallons) of product water, not including the
cost of evaporating the concentrated regenerate waste stream. This
latter is estimated to be of the order of 3 to 5 liters of concentrated
waste saline per 1000 liters of feed water. Recently, a new form of
organic ion exchange resin has been developed which may allow economical
de-ionization of waste streams at dissolved salt levels of 1000 to 3000
mg/1. This "Desal" process is based upon the discovery that certain
weakly basic anion exchange structures can form the bicarbonate salt
with solutions of carbon dioxide, and also have a favorable chloride-
bicarbonate selectivity coefficient. The process relies on a series of
three ion exchange beds.
This process has been operated successfully at the pilot plant scale on
brackish water; the concentration was reduced to a final effluent of 20
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to 30 mg/1, at an operating cost estimated to be equivalent to 5.30/1000
liters (20 0/ 1000 gallon) (1970) and a total capital investment for a
3785 cu m/day (1-mgd) plant of about $250,000 ( 1970). A commercial
plant achieving similar results was operating in the United States for
several years.
More conventional icn exchange resins have been used for the
desalination of brackish water. A pilot plant operation at Pomona,
California has reduced the salinity of tertiary sewage from 1500 to 250
mg/1 with an estimated cost (based on a 37850 cu m/day or 10-mgd plant)
reported to be 2.6 to 6.10/1000 liters (10-230/1000 gallons).
Recently, countercurrent ion exchange has begun to make an impact on
American ion exchange technology. This process allows more efficient
use of regeneration chemicals, and therefore significantly reduces cost
and pollution by regeneration waste streams. Apparently, European
manufacturers of ion exchange equipment have recognized the savings for
some years and have incorporated the new technology into their systems.
It has been predicted that this technology whose success relies upon
novel methods of preventing fluidization of the ion exchange resin
particles during back flow, will soon become dominant in U.S. markets
also, and will lower the cost of ion exchange use. It is predicted that
the cost of reducing the salinity of waste water containing 1000 mg/1
NaCl to 250 mg/1 will be 10 to 120/1000 liters (40-450/1000 gallons),
including amortization of equipment, labor costs, chemicals, etc.
One additional advantage of ion exchange is applicable to highly
alkaline textile waste streams. For example, if the effluent is sodium
hydroxide the cation exchanger alone may be used.
Thus it may be advantageous, where possible, to leave the alkalinity in
the hydroxide form and removing it by ion exchange.
The quality of the waste stream necessary to make ion exchange feasible
is a major factor in its usefulness. The level of suspended solids in
the waste stream can have a considerable deleterious effect on the long-
term operation of the ion exchange columns. It will therefore be
necessary to filter suspended solids to a low level before allowing the
water to enter the ion exchange columns. Any oxidizing agents in the
waste stream will have an adverse effect on the life of the cation
exchangers, while organic constituents may shorten the life of the anion
exchange resins.
108
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It appears, however, that the projected costs of ion exchange for tex-
tile waste clean-up are sufficiently low to justify a study to determine
long-term applicability.
Chemical Clarification
Suspended solids are a significant element of raw textile mill waste
water. The larger components such as lint are readily removed by
screens prior to entering a waste water treatment process. Residence in
a clarifier permits other smaller yet macroscopic particles to settle as
a sludge. Following activated sludge treatment and clarification the
waste water still contains a variety of suspended solids. These may be
removed by chemical clarification methods, which, in addition, have been
found to be effective for color removal.
Textile wastes typically contain a complex mixture of suspended solids/
mostly of organic composition. They include color bodies, proteins,
soaps, fibers, mineral fines, oil and grease. Carpet mill wastes can
contain considerable guantities of latex. These suspended solids have
deleterious effects on the other advanced waste treatment processes used
in tertiary treatment of waste streams; they load secondary treatment
plants, blind sorbent beds and deposit on membrane surfaces. In
themselves, they contribute undesirable properties to the waste water --
suspended COD, turbidity, color, etc.
In addition to the obvious difficulty of removing small particles, the
suspensions are stabilized by two effects: hydration and electrostatic
charge. Most such particles adopt a negative charge and are prevented
from coalescing to the larger, more easily removed particles by elec-
trostatic repulsion. Neutralization of these charges destabilizes the
system and leads to coagulation and precipitation or easier filtration.
This process is the basis for chemical clarification.
Coagulation is generally accomplished by adding coagulants that contain
multivalent cations. These include:
lime, aluminum sulfate, ferric chloride, copperas, ferrous
sulfate, ferric sulfate and scdium aluminate.
The multivalent cations A1+++, Fe+++ and Fe-n- are strongly hydrated and
hydrolyzed, forming acidic solutions. Sodium aluminate, on the other
hand, forms a strongly alkaline solution and is sometimes used in
combination with aluminum sulfate to improve the resulting floe.
Addition of coagulants to the suspended solids and colloidal substances
produces a floe which is allowed to settle in a clarifier using gentle
agitation. It is important to dissipate the coagulant throughout the
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waste water as fast as possible; flash mixing at point of entry to the
clarifier is normally used.
The correct coagulant dose for a specific waste water and particularly
the precise pH for maximum effectiveness must be determined
experimentally. Unfortunately, the optimum values of these parameters
may not be the same fcr different components of the waste water; thus
turbidity removal may demand an operating pH different from that needed
for color removal.
Coagulant aids may also be used to create larger, tougher floes that are
more amenable to sedimentation or filtration. Activated silica has been
used for many years; more recently, water soluble polymers, usually
polyelectrolytes, have been used successfully for this purpose. They
are available in anionic, cationic, or neutral form to treat floes of
differing electrostatic characteristics.
Relevance to Textile Waste Water Treatment^ Coagulation and
flocculation is a widely used technique in waste water treatment and in
the preparation of potable water. Costs typically range from 1-5£/ 1000
liters (5 to 200/1000 gallons) .
Chemical clarification has frequently been used in the treatment of
textile waste. Apart from its use to remove suspended solids, it has
found particular promise in the removal of troublesome disperse dye
particles which are generally not adsorbed by activated carbon. A
description of some typical experience in the textile industry will
illustrate the usefulness of the process.
A two-stage flocculaticn process using ferric sulfate as a coagulant was
used to treat the combined wastes of a wool scouring and dyeing plant in
Virginia. BOD of the combined wastes was reduced by 60 percent and
suspended solids by over 90 percent.
In Israel, experimental results showed that flocculation with alum and
filtration would reduce color by 95% and turbidity by 97% in a highly
colored simulated waste water. Performance was shown to be a strong
function of pH and alum dosage; maximum reduction of color levels and
turbidity did not necessarily occur at the same pH value. The Cationic
polyelectrolytes were found to be affective coagulant aids, but only at
very high doses (about 30 mg/1) .
The treatment of wool processing effluent using coagulants has been dis-
cussed by Stewart. Calcium chloride coagulation was used in a plant
England. Addition of 2,000 mg/1 of calcium chloride followed by
filtration reduced a BOD of 15,000 to 30,000 mg/1 to 2,700 to 3,800
110
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mg/1, suspended solids cf 20,000 to 32/000 mg/1 to 1,000 mg/1 and grease
levels of 17,000 to 20,000 mg/1 to 50 mg/1. But the cost was over $1.30
per 1000 liters ($5 per 1,000 gallons) in 1964.
In a review of treatment methods for dye waste waters, it was reported
that the most successful coagulation technique for color removal
consisted of the use of alum or a combination of alum and a cationic
polyelectrolyte. Treatment of wastes before and after activated sludge
treatment was studied; in general, less chemical requirement was found
prior to biological treatment. Mixed liquor treated with 150 to 250
mg/1 alum, 10 mg/1 lime and 20 mg/1 cationic polymer produced an
effluent color with zero suspended solids, but the chemical cost alone
was 2.1 to 2.60/1000 liters (8 to 100/1000 gallons). If chemical
clarification must follow biological treatment, 200 to 400 mg/1 alum and
no coagulant aid may be used. Color removals of about 95 percent can be
expected.
The use of a polyelectrolyte has been found to be a useful aid to alum
dewatering in other work.
A company in Pennsylvania reports successful color removal of a closed
dye cycle water using a combination of alum treatment, diatomaceous
earth filtration and carbon adsorption.
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SECTION VIII
COST, ENERGY, AND NON-WATER QUALITY ASPECTS
Reduction Benefits of Alternative Treatment and Control
Technologies ~
A detailed economic analysis showing the cost effectiveness of various
treatment and control technologies upon the seven subcategories within
the Textile industry is given in this document. Five alternative
treatment methods have been considered for Subcategories 1 to 7. For
the seven subcategories, the alternatives include:
Alternative A - No waste treatment or control.
Alternative B - Preliminary and biological treatment.
Alternative C - Multi-media Filtration
Alternative D - Activated Carbon Adsorption
Alternative E - Multiple Effect Evaporation and Incineration.
Basis of__Economic Analysis - Following is a summary of the basis for
cost estimates:
1- Investment - Investment costs have been derived principally
from published data on waste water treatment plant construction
costs, consultants1 cost data, and information from equipment
manufacturers and suppliers.
Published cost data for treatment facilities is derived
primarily from experience with waste water treatment
installations. Cost information has been reported by some
textile manufacturers, but the data are not extensive enough to
serve as a basis for the estimates presented herein. Basic
data were developed by preparation of graphical relationships
between cost and size for each unit operation. Based on
treatment plant configuration, design criteria, and size, costs
for individual unit operations were added together to determine
major facility costs.
An allowance of 15 percent of the total investment has been
included as yardwork which includes general site clearing and
grading inter-component piping, lighting, control structures,
road paving, and other items outside the structural confines on
an individual plant component. An additional allowance of up
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to 25 percent of the total investment has been included to
cover land, contingencies, engineering and overhead.
2. Depreciation, and_CQst_Qf_Capital_(Integest) - It was assumed
that the annual interest costs (cost of capital) and
depreciation would be constant over the life of the treatment
facilities. A principal repayment period of 10 years was used.
Costs were depreciated on a straight line basis and the
depreciation period of 10 years was assumed equal to the
principal repayment period and the economic life of the
facilities.
Cost of money was assumed to be an average of the cost of debt
capital and the cost of equity capital. Cost of debt capital
was assumed to be 8 percent and the cost of equity capital 22
percent. Data for the last 10 to 12 years indicated that the
average net return on equity capital for the chemical industry
and other manufacturing has been 10 to 12 percent. Assuming
corporate income tax is equal to net return (50% of gross
return)/ gross return is estimated to be debt capital and 40
percent equity capital. From this analysis, an average rate
for the cost of money equal to 13.6 percent was determined. An
average annual value for cost of money was derived by
subtracting the straight line depreciation cost from the
investment cost, times the capiral recovery factor. The costs
were about 8 percent of the capital investment.
3. Insurance_and Taxes - An annual cost of 1 1/2 percent of the
initial investment was used for insurance and taxes on the
waste treatment plant.
4- Operation _and^Maintenance_Labor - Operation and maintenance
labor manhour requirements were based mainly on published data
and independent estimates. The operational requirements
include general management and supervisory personnel, equipment
operators and laborers, and clerical and custodial personnel.
Maintenance labor includes mechanical electrical, laborers, and
other appropriate repair personnel.
Based on labor rates in the Textile industry and municipal
waste water treatment plants an August, 1971 average labor rate
of $5.00 per hour (including fringe maintenance labor costs).
5. Chemicals - Chemical costs used in the economic analysis are
based on published literature typical in the U.S. The costs
used are:
Lime - $22.00 per metric ton ($20.00 per ton)
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Soda Ash - $3.96 per 100 kilograms ($1.80 per 100 pounds)
Ferric Chloride - $8.80 per 100 kilograms ($4.00 per 100
pounds)
Polymer - $0.44 per kilogram ($0.20 per pound)
Chlorine - $13.20 per 100 kilograms ($6.00 per 100 pounds)
Sulfuric Acid - $36.40 per metric ton ($33.00 per ton)
Ammonia - $35.90 per metric ton ($32.50 per ton)
~ ^n byroad context, energy includes electric power and
fuel. Electric power consumption for major units such as
aeration, pumping, and mixing was estimated from available
data. An allowance of ten percent was made for small power
users such as clarifiers, chemical feed equipment, ventilation
equipment, and so forth. The cost of electric power was
assumed to be $0.015/kwhr. Motor efficiency was assumed to be
70 percent.
For alternative E, steam is required for evaporation. The cost
of steam ranged from $1.76 to $2.42/1,000 kg of steam ($0.80 to
$1.10/1,000 Ib of steam).
Information on actual treatment cost experience in the textile industry
was available in varying degrees of completeness from the exemplary
plants visted. To verify the quality of the data received and to
provide a broader basis for estimation, a costing model was developed
based on standard waste water treatment practice. This model covers
both capital and operating costs for the equivalent of what appears to
be the best technology currently practiced by the industry: essentially
primary and secondary treatment as extended aeration with stabilization
ponds. Over a plant size range of 400-12,000 cubic meters per day (0.1
to 3.0 MGD) , the cost experience data from the plants visited came
within 30 percent of that predicted by the cost model, as shown by the
examples in Table 12. The costs calculated from the model, therefore,
are believed to be realistic bases for estimating the (replacement)
value of existing facilities and the economic impact of further
secondary-type treatment requirements.
Cost curves developed from the cost model are presented in Figures 10 to
18. (For very small plants (about 110 cu m/day or 30,000 gpd) , an
overall cost figure of $264 for 1 cu m/day or $1.00 for 1 gpd was
assumed.) Figures 14 to 18 present the operating and maintenance costs
over the ranges of production found. The initial capital cost of
biological treatment systems depends mainly upon (and here is related
to) the hydraulic load, the other factors making only minor variations
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in the total cost. Operating costs, on the other hand, have been viewed
as dependent on pollutant as well as hydraulic loads.
Costs for representative large plants in industry categories were
developed using these curves and assuming an aerated stabilization
basin, which is widely used by the industry when land is readily
available. The following items were determined for the individual
treatment steps:
(1) Construction costs as function of hydraulic land at a given
pollutant level;
(2) Operating and maintenance labor as a function of hydraulic
load;
(3) Chemical requirements as a function of hydraulic and pollutant load;
(4) Power requirements as a function of hydraulic and pollutant
load;
(5) Additional material and supply cost as a function of hydraulic
load.
Costs have been adjusted to a national average cost level of January
1973 using the ENR Construction Cost Index. The estimated cost curves
have been adjusted to exclude unusual construction or site-specific
requirements. The curves have been adjusted to exclude unusual
construction or site-specific requirements. The curves include all
elements of construction cost which a contract bidder would normally
encounter in completing the waste water treatment. Included are
building materials, labor, equipment, electrical, heating and
ventilation, normal excavation and other similar items. Also included
are the engineering costs. The annual operating costs include operation
and maintenance labor, chemicals, power, material and supplies, and
depreciation.
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TABLE 12
Accuracy Of Standardized Costing Methodology
Example Plant
EPA
cost estimate
company reported
cost for actual plant
Ratio
EPA
reported
Plant A (0.394 MGD)
Subcategory 1
Aeration basin
Aeration equipment
Clarifier
3 day lagoon
yard work (15% const)
engineering
Plant Q (2.5 MGD)
Subcategory 4
Aeration
Aeration equipment
Clarifier
3 day lagoon
yard work (15% const)
engineering
Plant X (1.7 MGD)
Subcategory 5
Aeration basin
Aeration equipment
Clarifier
3 day lagoon
yard work (15% const)
engineering
$ 27,000
136,900
35,600
12.500
$212,000
31,800
42,400
$286,200
$ 59,000
123,400
116,400
3,200
$330,800b
49,600
60,000
$440,400
$ 57,000
23,600
98,800
27,000
$206,400
31,000
47.000
$284,400
$210,000
1.36
$554,000
0.79
$335,400
.85
(Land cost left off these estimates in order to compare with plant reported
cost—maximum land cost, plant Q, is $6,000)
116
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1,000,000
o
0
100,000
o
o
10,000
10.0
Figure 10
Aerated Stabilization Basin Construction Cost
117
-------
10,000
_ 1,000
o
O
O)
c
100
10
100
1,000 10,000
Total Construction Cost, ($000)
100,000
Figure 11
Engineering Costs
118
-------
o
Q
10 x 105
1 x 105
ENR Index = 1811.93,
Jan. 1973
1.0
10.0 100.0
Flow, mgd
Figure 12
Clarifier Capital Cost
119
-------
10x103
1.0x10
o
o
1,000
i i i i
ENR Index = 1811.93, Jan. 1973
10,000
BOD removal, Ib/day
ii i i
100,000
Figure 13
Aerated Stabilization Basin
(Aeration Equipment Only)
120
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10,000
o
.c
c
ra
i 1,000
100
1.0
Operation
Maintenance
i i i i I i I
10.0
Flow, mgd
100.0
Figure 14
Aerated Stabilization Basin
Annual Operation and Maintenance Labor
121
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10,000
o
Q
o 1,000
Chemicals for "Typical" Plants
ENR = 1811.93, Jan. 1973
100
i i i i
Material &
Supply Costs
1.0 10.0
Flow, mgd
Figure 15
Aerated Stabilization Basin
(Material and Supply Costs, Annual)
(Chemical Costs)
100.0
12?
-------
100,000
o
Q
Q 10,000
3
C
C
1,000
1,000
10,000
BOD removal, Ib/day
Figure 16
Aeration Equipment
Annual Power Costs
(Aerated Stabilization Basin)
100,000
123
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10,000
D
o
c
0!
1,000
c
c
Operation
100
1.0
Maintenance
10.0
Flow, mgd
100.0
Figure 17
Clarifier, Annual Operation
and Maintenance Labor
12 ^
-------
100,000
o
Q
10,000
c
1,000
Material and Supply Costs
1.0 10.0
Flow, mgd
Figure 18
Clarifier
(Material and Supply Costs, Annual)
(Major Chemical Costs)
100.0
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of Treatment Alternatiyeg
Alternative A - No Waste Treatment or Control
Costs - None
Reduction Benefits - None
Alternative B - Preliminary and Biological Treatment
This alternative includes preliminary screening, primary clarification
(wool scouring only) and biological treatment.
Costs - The total capital investment cost is estimated to range from
$10,200 to $336,000 for the model plants. • The annual treatment cost is
estimated to range from $3,900 to $88,000.
Reduction Benefits - Alternative B represents about a 95 percent
reduction in BOD5 compared with Alternative A. There are also
significant reductions in TSS and some reduction of COD. Oils and
grease are reduced from wool scouring operations.
Alternative C - Multi-media Filtration
This alternative consists of a filtration process that is compatible
with biological treatment (Alternative B).
Costs - Alternative C represents a total capital investment of from
$10,000 to $140,000 over Alternative B costs and an increased annual
cost estimated to range from $3,000 to $41,300.
Reduction Benefits - Alternative C represents a further reduction in
BOD5 and TSS due to solids removal and optimum control over the
biological treatment system.
Alternative D - Activated Carbon Adsorption
Alternative D includes an activated carbon adsorption system including
carbon regeneration facilities. This system is compatible with
biological treatment (Alternative B) and may reguire filtration
(Alternative C) . It may also be used for total eff luent treatment.
Costs - Alternative D represents a total capital investment which ranges
from $385,000 to $1,050,000 over Alternatives B or C and an increased
annual cost from $113,100 to $404,800.
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Reduction Benefits - Through Alternative D, there are some reductions in
BOD5 and TSS. There are significant reductions in COD, TOG, and color.
Alternative E - Multiple Effect Evaporation and Incineration
Alternative E includes a multiple effect (three stage) evaporator and a
fluid bed incinerator. Residual solids are disposed of by landfill.
Costs - The capital investment is estimated to range from $196,000 to
$3,148,00 and annual costs are estimated to range from $95,000 to
$2,210,000.
Reduction Benefits - There would be complete removal of all waste water
constituents. There would be no waste water discharge.
Impact of Waste Treatment Alternatives on Finished_Product
Tables 13-25 illustrate the probable increases in finished product
prices for small and medium size plants in the seven textile
subcategories required to pay for waste water treatment. Each Table
lists the increased cost attributable to biological treatment
(Alternative B) and the additional cost increases in finished product
prices for multi -media filtration (Alternative C) , activated carbon
adsorption (Alternative D) and multiple effect evaporation and
incineration (Alternative E) . Several conclusions are apparent from
this economic analysis.
(1) The estimated increase in final product costs for the bes
practicable control technology currently available (Alternative
B) are economically feasible for small and large plants in all
seven subcategories. The estimated final product cost
increases range from 0.1 to 0.8 cents per kilogram of product
(0.2 to 1.8 cents per pound of product) for various
subcategories. The average increase is less than 0.4 cents per
kilogram (0.9 cents per pound).
(2) The estimated increase in final product costs for multi-media
filtration (Alternative C) are significantly less than costs
for Alternative B. These costs are not excessive and should be
economically achievable for all plant sizes in each
subcategory. The maximum cost for any industry model plant is
less than 0.4 cents per kilogram of product (0.8 cents per
pound of product) .
(3) The price increases attributable to activated carbon adsorption
appear to create an unequal economic impact. Variations in
unit costs for small industry plants as compared with medium
sized plants are reflected in an average price increase for a
127
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small plant of 4.2 cents per Kilogram of product (1.9 cents per
pound of product) as compared with an average price increase
for a medium sized plant of 2.3 cents per kilogram (1.0 cents
per pound). The diseconomy of scale with the associated
unequal economic impact resulted (as discussed in Section IV
and later in sections IX and X) in further segmentation.
Different effluent limitations have been established for small
plants than for medium or large sized plants in six
subcategories.
(4) The estimated price increase in final product costs for
evaporation and incineration (Alternative E) appear to be
excessive for all industry subcategories except wool scouring
(subcategory 1) . The average price increase; for all model
plants is 7.5 cents per kilogram product (16.5 cents per pound
of product). However, the average price increase for wool
scouring plants is 1.8 cents per kilogram(4.C cents per pound).
Thus, no discharge of pollutants via evaporation and
incineration is a feasible alternative treatment for wool
scouring plants.
Tables 13-25 indicated the additional price increases for the best
available technology economically achievable range from 0.05 to 0.4
cents per kilogram (0.1 ro 0.8 cents per pound) product processed by all
plants in subcategory 3 and by small plants in subcategories 1,2,4,5,6
and 7 with capacities less than 6,500 kg/day (14,300 Ib/day), 900 kg/day
(1,980 Ib/day), 1,000 kg/day (2,200 Ib/day), 3,450 kg/day (7,590
Ib/day), 3,450 kg/day (7,590 Ib/day), and 3,100 kg/day (6,280 Ib/day)
respectively. For larger plants in the industry, the price increases
ranged from 0.4 cents per kilogram (0.8 cents per pound) to a high of
2.0 cents per kilogram (4.5 cents per pound). The overall costs of best
practicable and best available technology is estimated to range between
0.3 and 1.1 cents per kilogram (0.6 and 2.5 cents per pound) produced
from small plants and between 0.5 and 2.5 cents per kilogram (1.0 and
5.4 cents per pound) for products from larger plants.
128
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TABLE 13
WASTE WATER TREATMENT COSTS
FOR SUBCATEGORY 1-(SMALL)
ALTERNATIVE (2)
Parameter/Cost B C D E
Plant Finished Material Production
1000 kg product/day 6.1 6.1 6.1 6.1
(1000 Ib product/day) 13.3 13.3 13.3 13.3
Average Water Usage
I/kg product 12.5 12.5 12.5 12.5
(gal/lb product) 1.5 1.5 1.5 1.5
Estimated Investment Cost (1) 41.0 15.0 385.0 392.0
($1000)
Estimated Annual Cost 16.0 4.4 113.1 190.0
($1000)
Estimated Product Cost
$/kg product 0.002 0.0005 0.015 0.026
($/lb product) 0.005 0.001 0.034 0.057
(1) Assumes treatment facilities sized to meet production with no
allowance for growth.
(2) Alternative B = Preliminary and Biological Treatment
Alternative C = Multi-Media Filtration
Alternative D = Activated Carbon Adsorption
Alternative E = Multiple Effect Evaporation and Incineration
129
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TABLE 14
WASTE WATER TREATMENT COSTS
FOR SUBCATEGORY 1-(MEDIUM)
ALTERNATIVE (2)
Parameter/Cost B C D E
Plant Finished Material Production
1000 kg product/day 30.3 30.3 30.3 30.3
(1000 Ib product/day) 66.7 66.7 66.7 66.7
Average Water Usage
I/kg product 12.5 12.5 12.5 12.5
(gal/lb product) 1.5 1.5 1.5 1.5
Estimated Investment Cost (1) 103.0 38.0 480.0 768.0
($1000)
Estimated Annual Cost 30.0 11.2 135.6 398.0
($1000)
Estimated Product Cost
$/kg product 0.001 0.0002 0.004 0.011
($/lb product) 0.002 0.001 0.008 0.024
(1) Assumes treatment facilities sized to meet production with no
allowance for growth.
(2) Alternative B = Preliminary and Biological Treatment
Alternative C = Multi-Media Filtration
Alternative D = Activated Carbon Adsorption
Alternative E = Multiple Effect Evaporation and Incineration
130
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TABLE 15
WASTE WATER TREATMENT COSTS
FOR SUBCATEGORY 2-(SMALL)
ALTERNATIVE (2 )
Parameter/Cost B C D E
Plant Finished Material Production
1000 kg product/day 8.2 8.2 8.2 8.2
, (1000 Ib product/day) 18.1 18.1 18.1 18.1
Average Water Usage
I/kg product 115.1 115.1 115.1 115.1
(gal/lb product) 13.8 13.8 13.8 13.8
Estimated Investment Cost (1) 164.0 60.0 450.0 1,316.0
($1000)
Estimated Annual Cost 46.0 17.7 132.8 759.0
($1000)
Estimated Product Cost
$/kg product 0.005 0.002 0.013 0.076
($/lb product) 0.010 0.004 0.029 0.168
(1) Assumes treatment facilities sized to meet production with no
allowance for growth.
(2) Alternative B = Preliminary and Biological Treatment
Alternative C = Multi-Media Filtration
Alternative D = Activated Carbon Adsorption
Alternative E = Multiple Effect Evaporation and Incineration
131
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TABLE 16
WASTE WATER TREATMENT COSTS
FOR SUBCATEGORY 2-(MEDIUM)
ALTERNATIVE (2)
Parameter/Cost B C p E
Plant Finished Material Production
1000 kg product/day 24.7 24.7 24.7 24.7
(1000 Ib product/day) 54.3 54.3 54.3 54.3
Average Water Usage
1/kg product 115.1 115.1 115.1 115.1
(gal/lb product) 13.8 13.8 13.8 13.8
Estimated Investment Cost (1) 336.0 135.0 910.0 2,991.0
($1000)
Estimated Annual Cost 84.0 39.8 292.5 2,087.0
($1000)
Estimated Product Cost
$/kg product 0.003 0.001 0.010 0.070
($/lb product) 0.006 0.003 0.022 0.154
(1) Assumes treatment facilities sized to meet production with no
allowance for growth.
(2) Alternative B = Preliminary and Biological Treatment
Alternative C = Multi-Media Filtration
Alternative D = Activated Carbon Adsorption
Alternative E = Multiple Effect Evaporation and Incineration
132
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TABLE 17
WASTE WATER TREATMENT COSTS
FOR SUBCATEGORY 3-(AVERAGE)
ALTERNATIVE (2)
Parameter/Cost B C D
Plant Finished Material Production
1000 kg product/day 1.5 1.5 1.5 1.5
, (1000 Ib product/day) 3.3 3.3 3.3 3.3
Average Water Usage
I/kg product 12.5 12.5 12.5 12.5
(gal/lb product) 1.5 1.5 1.5 1.5
Estimated Investment Cost (1) 10.2 10.0 — 196.0
($1000)
Estimated Annual Cost 3.9 3.0 — 95.0
($1000)
Estimated Product Cost
$/kg product 0.002 0.001 — 0.044
(S/lb product) 0.004 0.003 — 0.100
(1) Assumes treatment facilities sized to meet production with no
allowance for growth.
(2) Alternative B = Preliminary and Biological Treatment
Alternative C = Multi-Media Filtration
Alternative D = Activated Carbon Adsorption
Alternative E = Multiple Effect Evaporation and Incineration
133
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TABLE 18
WASTE WATER TREATMENT COSTS
FOR SUBCATEGORY 4-(SMALL)
ALTERNATIVE (2)
Parameter/Cost B C D E
Plant Finished Material Production
1000 kg product/day 2.5 2.5 2.5 2.5
(1000 Ib product/day) 5.6 5.6 5.6 5.6
Average Water Usage
I/kg product 150.1 150.1 150.1 150.1
(gal/lb product) 18.0 18.0 18.0 18.0
Estimated Investment Cost (1) 103.0 38.0 450.0 768.0
($1000)
Estimated Annual Cost 30.0 11.2 145.8 398.0
($1000)
Estimated Product Cost
$/kg product 0.008 0.003 0.039 0.107
(S/lb product) 0.018 0.007 0.087 0.237
(1) Assumes treatment facilities sized to meet production with no
allowance for growth.
(2) Alternative B = Preliminary and Biological Treatment
Alternative C = Multi-Media Filtration
Alternative D = Activated Carbon Adsorption
Alternative E = Multiple Effect Evaporation and Incineration
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TABLE 19
WASTE WATER TREATMENT COSTS
FOR SUBCATEGORY 4-(MEDIUM)
ALTERNATIVE (2)
Parameter/Cost B C D E
Plant Finished Material Production
1000 kg product/day 12.6 12.6 12.6 12.6
(1000 Ib product/day) 27.8 27.8 27.8 27.8
Average Water Usage
I/kg product 150.1 150.1 150.1 150.1
(gal/lb product) 18.0 18.0 18.0 18.0
Estimated Investment Cost (1) 254.0 102.0 860.0 2,197.0
($1000)
Estimated Annual Cost 74.0 30.1 372.7 1,472.0
($1000)
Estimated Product Cost
$/kg product 0.004 0.002 0.020 0.080
($/lb product) 0.009 0.003 0.045 0.177
(1) Assumes treatment facilities sized to meet production with no
allowance for growth.
(2) Alternative B = Preliminary and Biological Treatment
Alternative C = Multi-Media Filtration
Alternative D = Activated Carbon Adsorption
Alternative E = Multiple Effect Evaporation and Incineration
135
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TABLE 20
WASTE WATER TREATMENT COSTS
FOR SUBCATEGORY 5-(SMALL)
Parameter/Cost
Plant Finished Material Production
1000 kg product/day
(1000 lb product/day)
Average Water Usage
I/kg product
(gal/lb product)
Estimated Investment Cost (1)
($1000)
Estimated Annual Cost
($1000)
Estimated Product Cost
$Ag product
($/lb product)
ALTERNATIVE (2)
B C D E
6.8
15.0
166.8
20.0
160.0
44.0
6.8
15.0
166.8
20.0
74.0
21.8
6.8
15.0
166.8
20.0
135.6
6.8
15.0
166.8
20.0
480.0 1,496.0
960.0
0;004 0.002 0.014 0.097
0.010 0.005 0.030 0.213
(1) Assumes treatment facilities sized to meet production with no
allowance for growth.
(2) Alternative B = Preliminary and Biological Treatment
Alternative C = Multi-Media Filtration
Alternative D = Activated Carbon Adsorption
Alternative E = Multiple Effect Evaporation and Incineration
136
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TABLE 21
WASTE WATER TREATMENT COSTS
FOR SUBCATEGORY 5-(MEDIUM)
ALTERNATIVE (2)
Parameter/Cost J3 C D ..E. _.
Plant Finished Material Production
1000 kg product/day 18.2 18.2 18.2 18.2
, (1000 Ib product/day) 40.0 40.0 40.0 40.0
Average Water Usage
I/kg product 166.8 166.8 166.8 166.8
(gal/lb product) 20.0 20.0 20.0 20.0
Estimated Investment Cost (1) 327.0 140.0 910.0 3,148.0
($1000)
Sstimated Annual Cost 88.0 41.3 267.5 2,210.0
($1000)
Sstimated Product Cost
$/ kg product 0.003 0.002 0.010 0.084
($/ Ib product) 0.007 0.003 0.022 0.184
!l) Assumes treatment facilities sized to meet production with no
allowance for growth.
[2) Alternative B = Preliminary and Biological Treatment
Alternative C = Multi-Media Filtration
Alternative D = Activated Carbon Adsorption
Alternative E = Multiple Effect Evaporation and Incineration
137
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TABLE 22
WASTE WATER TREATMENT COSTS
FOR SUBCATEGORY 6-(SMALL)
ALTERNATIVE (2)
Parameter/Cost B C D E
Plant Finished Material Production
1000 kg product/day 5.4 5.4 5.4 5.4
(1000 Ib product/day) 11.9 11.9 11.9 11.9
Average Water Usage
I/kg product 70.1 70.1 70.1 70.1
(gal/lb product) 8.4 8.4 8.4 8.4
Estimated Investment Cost (1) 103.0 38.0 400.0 768.0
($1000)
Estimated Annual Cost 30.0 11.2 116.0 398.0
($1000)
Estimated Product Cost
$/ kg product 0.004 0.001 0.015 0.051
($/ Ib product) 0.008 0.003 0.032 0.111
(1) Assumes treatment facilities sized to meet production with no
allowance for growth.
(2) Alternative B = Preliminary and Biological Treatment
Alternative C = Multi-Media Filtration
Alternative D = Activated Carbon Adsorption
Alternative E = Multiple Effect Evaporation and Incineration
138
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TABLE 23
WASTE WATER TREATMENT COSTS
FOR SUBCATEGORY 6-(MEDIUM)
ALTERNATIVE (2)
t Parameter/Cost B C D
Plant Finished Material Production
1000 kg product/day 43.2 43.2 43.2 43.2
(1000 Ib product/day) 95.2 95.2 95.2 95.2
Average Water Usage
I/kg product 70.1 70.1 70.1 70.1
(gal/lb product) 8.4 8.4 8.4 8.4
Estimated Investment Cost (1) 327.0 140.0 1,050.0 3,148.0
($1000)
Estimated Annual Cost 88.0 41.3 404.8 2,210.0
($1000)
Estimated Product Cost
$/ kg product ' 0.001 0.0006 0.006 0.035
($/ Ib product) 0.003 0.001 0.014 0.077
(1) Assumes treatment facilities sized to meet production with no
allowance for growth.
(2) Alternative B = Preliminary and Biological Treatment
Alternative C = Multi-Media Filtration '
Alternative D = Activated Carbon Adsorption
Alternative E = Multiple Effect Evaporation and Incineration
139
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TABLE 24
WASTE WATER TREATMENT COSTS
FOR SUBCATEGORY 1- (SMALL)
ALTERNATIVE (2)
Parameter/Cost B C D E
Plant Finished Material Production
1000 kg product/day 4.1 4.1 4.1 4.1
(1000 Ib product/day) 9.1 9.1 9.1 9.1
Average Water Usage
I/kg product 183.5 183.5 183.5 183.5
(gal/lb product) 22.0 22.0 22.0 22.0
Estimated Investment Cost (1) 125.0 59.0 400.0 1,132.0
($1000)
Estimated Annual Cost 35.0 17.4 11.6.0 638.0
($1000)
Estimated Product Cost
$1 kg product 0.006 0.003 0.019 0.106
($1 Ib product) 0.013 0.006 0.042 0.234
(1) Assumes treatment facilities sized to meet production with no
allowance for growth.
(2) Alternative B = Preliminary and Biological Treatment
Alternative C = Multi-Media Filtration
Alternative D = Activated Carbon Adsorption
Alternative E = Multiple Effect Evaporation and Incineration
-------
TABLE 25
WASTE WATER TREATMENT COSTS
FOR SUBCATEGORY 7-(MEDIUM)
ALTERNATIVE (2)
Parameter/Cost B C D E
Plant Finished Material Production
1000 kg product/day 12.4 12.4 12.4 12.4
(1000 lb product/day) 27.3 27.3 27.3 27.3
Average Water Usage
I/kg product 183.5 183.5 183.5 183.5
(gal/lb product) 22.0 22.0 22.0 22.0
Estimated Investment Cost (1) 277.0 120.0 730.0 2,521.0
($1000)
Estimated Annual Cost 73.0 35.4 221.4 1,721.0
($1000)
Estimated Product Cost
$/ kg product 0.004 0.002 0.012 0.095
($/ lb product) 0.009 0.004 0.027 0.210
(1) Assumes treatment facilities sized to meet production with no
allowance for growth.
(2) Alternative B = Preliminary and Biological Treatment
Alternative C = Multi-Media Filtration
Alternative D = Activated Carbon Adsorption
Alternative E = Multiple Effect Evaporation and Incineration
-------
Alternativejifreatment Systems
It has been assumed in the economic analysis that an extended biological
stabilization process will be utilized for the biological treatment.
However, aerobic-anaerobic lagoons or trickling filters or activated
sludge can be designed to provide the same degree of biological
treatment. These systems require less area and can only be utilized
where land is not readily available near the textile facility.
Activated sludge may result in additional annual costs of as much as
$200,000 over those costs presented for Alternative B.
It is also assumed that wool scouring plants (Subcategory 1) with
capacities greater than 6,500 kg/day (14,300 Ib/day) will utilize
activated carbon adsorption. Table 13 indicates that
evaporation/incineration is a feasible alternative for large wool
scouring plants. Costs could be as much as 0.6 cents per kilogram of
product (1.4 cents per pound product) higher.
Electrical Energy Requirements
The energy requirements (electric power and fuel) for textile facilities
vary considerably based upon reported data. This varieition is due to
the following factors:
1. Type of fiber processed.
2. Type of extent of cleaning and finishing operations.
3. Degree of mechanization within the textile facility.
4. Climate of the textile location.
It is estimated that the contribution of waste treatment is considerably
less than 10 percent of the total industry energy consumption at present
and is not likely to exceed 10 percent in the future.
Thermgl_EnergY_Reguirgmentg
Thermal energy costs are considerably less than electrical energy costs
for operations within the industry. Waste treatment syistems impose no
•significant addition to the thermal energy requirements of plants.
Wastewater can be reused in cooling and condensing service if it is
separated from the process waters in non-barometric type condensers.
These heated waste waters improve the effectiveness of ponds which are
best maintained at 90°F cr more. Improved thermal efficiencies are
coincidentally achieved within a plant with this technique.
142
-------
Wastewater treatment costs and effectiveness can be improved by the use
of energy and power conservation practices and techniques in each plant.
The waste load increases with increased water use. Reduced water use
therefore reduced the waste load, pumping costs, and heating costs, the
last of which can be further reduced by water reuse as suggested
previously.
Solid Wastes
The disposal of solid wastes from the textile industry are generally
disposed of by landfill. The solid materials, separated during waste
water treatment, containing organic and inorganic materials, including
those added to promote solids separation, is called sludge. Typically,
it contains 95 to 98 percent water prior to dewatering or drying. Some
quantities of sludge are generated by both primary and secondary
treatment systems with the type of system influencing the quantity. The
following table illustrates this:
Treatment System
Dissolved air flotation
Anaerobic lagoon
Extended Aeration
Aerobic £ Aerated Lagoons
Activated sludge
Extended aeration
Anaerobic contact process
Sludge Volume as Percent of
n flaw Wastewater Volume
Up to 10%
(Sludge accumulation in these
(lagoons is usually not sufficien
(to require removal at any time)
10
5
- 15%
10%
approximately 2%
The raw sludge can be concentrated, digested, dewatered, dried,
incinerated, land-filled, or spread in sludge holding ponds. Sludge
from secondary treatment systems is normally dewatered or digested
sufficiently for hauling to a land fill. The final dried sludge
materials can be safely used as an effective soil builder. Prevention
of runoff is a critical factor in plant-site sludge holding ponds.
Costs of typical sludge handling techniques for each secondary treatment
system generating enough sludge to require handling equipment are
already incorporated in the costs for these systems. All other non-
water quality environmental impacts of the alternative treatment and
control technologies described appear minor.
143
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SECTION IX
EFFLUENT REDUCTION ATTAINABLE THROUGH THE
APPLICATION OF THE BEST PRACTICABLE CONTROL
TECHNOLOGY CURRENTLY AVAILABLE
EFFLUENT LIMITATIONS GUIDELINES
INTRODUCTION
The effluent limitations which must be achieved July 1, 1977, are to
specify the degree of effluent reduction attainable through the appli-
cation of the Best Practicable Control Technology Currently Available.
Best Practicable control Technology Currently Available is generally
based upon the average of the best existing performance: by plants of
various sizes, ages, and unit processes within the industrial category
and/or subcategory. This average is not based upon a broad range of
plants within the textile industry, but based upon performance levels
achieved by exemplary plants.
Consideration must also be given to:
The total cost of application of technology in relattion to
the effluent reduction benefits to be achieved from such
application;
The size and age of equipment and facilities involved;
The processes employed;
The engineering aspects of the application of various types
of control techniques;
Process changes;
Non-water quality environmental impact (including energy
requirements) .
Also, Best Practicable Control Technology Currently Available emphasizes
treatment facilities at the end of a manufacturing process, but includes
the control technologies within the process itself when the latter are
considered to be normal practice within an industry.
A further consideration is the degree of economic and engineering
reliability which must be established for the technology to be
"currently available". As a result of demonstration projects, pilot
plants and general use, there must exist a high degree of confidence in
the engineering and economic practicability of the technology at the
time of start of construction of installation of the control facilities.
144
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EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF
BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY AVAILABLE
Based on the information contained in Section III through VIII of this
report, a determination has been made that the quality of effluent
attainable through the application of the Best Pollution Control
Technology Currently Available is as listed in Table 26. A number of
plants in the industry which have biological treatment systems for which
effluent quality data were available are meeting these standards.
A biological treatment system which is permitted to operate at a
constant food to microorganism ratio throughout the year and with
minimum operational changes would have a natural variation of 50 percent
as explained in Section VII and as shown by the solid line in Figure 19.
A similar system with careful operational control and proper design can
be operated within 25 percent of the average on a monthly operating
basis, A system without optimum operational control has been used to
account for normal treatment variation. Thus, a factor of 50 percent
has been used to calculate the maximum 30 day effluent limitation. A
further allowance of 100 percent has been applied to a maximum 30 day
effluent limitation in order to develop the maximum daily effluent
limitation.
-------
TABLE 26
MAXIMUM THIRTY DAY AVERAGE
RECOMMENDED EFFLUENT LIMITATION
GUIDELINES FOR JULY 1, 1977
Effluent Limitations (1)
BODS TSS COD
kg/lOOOkg kg/lOOOkg kg/lOOOkg
Plant Subcategory (Ib/lOOOlb) (Ib/lOOOlh) (Ib/lOOQlb)
1. WOOL SCOURING (2)
Plant capacity less than 3.7 3.7 NA
6,500 kg/day (14,300 Ib/day)
Plant capacity greater than 3.7 3.7 24
6,500 kg/day (14,300 Ib/day)
2. WOOL FINISHING
Plant capacity less than 7.5 7.5 NA
900 kg/day (1,980 Ib/day)
Plant capacity greater than 7.5 7.5 56
900 kg/day (1,980 Ib/day)
3. GREIGE MILLS
All plant sizes 0.45 0.45
4. WOVEN FABRIC FINISHING
Plant capacity less than 2.2 6.9 NA
1,000 kg/day (2,200 Ib/day)
Plant capacity greater than 2.2 6.9 33
1,000 kg/day (2,200 Ib/day)
5. KNIT FABRIC FINISHING
Plant capacity less than 1.8 8.0 NA
3,450 kg/day (7,590 Ib/day)
Plant capacity greater than 1.8 8.0 24
3,450 kg/day (7,590 Ib/day)
6. CARPET MILLS
Plant capacity less than 4.3 4.3 NA
3,450 kg/day (7,590 Ib/day)
Plant capacity greater than 4.3 4.3 30
3,450 kg/day (7,590 Ib/day)
7. STOCK AND YARN DYEING AND FINISH-
ING
Plant capacity less than 3.5 9.2 NA
3,100 kg/day (6,820 Ib/day)
Plant capacity greater than 3.5 9.2 47
3,100 kg/day (6,820 Ib/day)
NA MEANS NOT APPLICABLE
(1) Plant capacities and discharge limitations are stated for Subcategories
1 and 2 per weight of raw wool received at the wool scouring or wool
finishing operation and are stated for Subcategories 3, 4, 5, 6 and 7
per weight of final material produced by the facility.
For all Subcategories pH should range between 6.0 to 9.0 at any time.
For all Subcategories Most Probable Number (MPN) of Fecal Coliforms
should not exceed 400 counts per 100 ml.
(2) For all Wool Scouring plants (Subcategory 1) Oils and Grease should
not exceed 1.9 kg (lb)/1000 kg (Ib) grease wool.
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IDENTIFICATION OF BEST PRACTICABLE CONTROL
TECHNOLOGY CURRENTLY AVAILABLE
Best Practicable control Technology Currently Available for the textile
manufacturing industry includes preliminary screening, primary settling
(wool scouring only), coagulation (carpet mills only), secondary
biological treatment and chlorination. Strict management control over
housekeeping and water use practices result in raw wastes loads which
can be treated biologically to the effluent levels listed in Table 26.
No special in-plant modification is required. The performances of
eighteen different biological treatment systems that achieve these
effluent limits are given in Table 27.
Wool Scouring and Wool Finishing
The stated guidelines for subcategory 1(wool scouring) and subcategory 2
(wool finishing) can be achieved by applying the best practicable
control technology to the appropriate subcategory raw waste load. The
best practicable control technology for wool scouring includes
screening, settling, biological treatment and chlorination; best
practicable control technology for wool finishing includes screening
biological treatment and chlorination. The average raw waste BOD5 load
resulting from wool scouring is almost 50 kg (Ib) of BOD5 per 1000 kg
(Ib) of grease wool as received and weighed at the plant. The average
raw waste BOD5 load resulting from wool finishing is estimated at 100
kg(Ib) of BOD5 per 1000 kg (Ib) of dry wool received at the plant. The
basis of this number is a single facility which is a 100 percent wool
finishing operation. It is further substantiated by estimates of
knowledgeable textile consultants. The recommended effluent limitation
guidelines for July 1, 1977, for the wool scouring and wool finishing
subcategories are based on results from eighteen exemplary biological
treatment systems (see Table 27) . These systems treat textile waste
waters from dyeing and finishing of broadwoven cotton and cotton-
synthetic blends, knits and stock and yarn.
149
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The average BOD5 removal efficiency of these eighteen systems is greater
than 95 percent. The BOD5 effluent limitation is calculated by applying
this average BOD.5 removal efficiency (95 percent) to the appropriate
subcategory raw waste load, and allowing 50 percent to account for
normal operational variation. Thus, the BOD5 effluent limitation for
subcategory 1 (wool scouring) is 3.7 kg/kkg (lb/10001b) of grease wool
and the BOD5 effluent limitation for subcategory 2 (wool finishing) is
7.5 kg/kkg (lb/10001b) of dry wool.
The subcategory 1 effluent limitations are substantiated by data given
in Table 28 for a full-scale biological treatment system at Mill A and a
pilot project at Mill B. The treatment system at Mill A can achieve
sufficient effluent reduction to meet the effluent limitations. This is
based on normal water usage and production at Mill A and average 30 day
effluent BOD5 concentration of 150 mg/1. These results are confirmed by
several months of effluent data. Results from Mill B indicate this
biological treatment system can also meet the effluent limitations.
This is confirmed by several months of effluent data during both warm
and cold weather operation. The subcategory 2 effluent limitation is
substantiated by water usage and waste water treatment data from a study
supported by the American Textile Manufacturers Institute, Inc., and the
Carpet and Rug Institute.
The total suspended solids (TSS) effluent limitations are identical to
the BOD5 effluent limitations. Results from the exemplary biological
treatment systems as well as from Mills A and B indicate that the
suspended solids can be consistently reduced to at least this level.
Thus the TSS effluent limitation for subcategory 1 (wool scouring) is
3.7 kg/kkg (lb/10001b) of grease wool and the TSS effluent limitation
for subcategory 2 (wool finishing) is 7.5 kg/kkg (lb/10001b) of dry
wool.
Much of the chemical oxygen demand (COD) in the effluent from the
exemplary biological treatment systems and Mills A and B is associated
with the suspended solids in the effluent. The COD effluent limitations
are based on an average COD effluent concentrations of 1250 mg/1 for
subcategory 1 and 325 mg/1 for subcategory 2. Using the mean water
usages of 12.5 I/kg (1.5 gal/lb) for subcategory 1 and 12.5 I/kg (1.5
gal/lb) for subcategory 1 and 115 1/kg (13.8 gal/lb) for subcategory 2,
the COD effluent limitations are 24 kg/kkg (lb/10001b) of grease wool
for subcategory 1 (wool scour) and 56 kg/kkg (lb/10001b) of dry wool for
subcategory 2 (wool finishing). Effluent data from biological treatment
systems at Mills A and E confirm that these systems can meet the COD
limitation.
COD limitations for subcategories 1 and 2 are applicable only to plants
with capacities greater than 6,500 kg/day (14,300 Ib/day) and 900 kg/day
(1,980 Ib/day) respectively. As discussed in Sections IV and VIII
151
-------
severe diseconomies of scale create economic impacts which require
different limitations for small plants.
Grease is a serious problem in the wool scouring subcategory. Effluent
levels observed especially at Mill B indicate the grease is recoverable
and treatable to levels less than 100 mg/1 in the final effluent.
Applying this concentration to the mean water usage the grease effluent
limitation is 1.9 kg/kkg (lb/10001b) of grease wool.
Effluent limitations for subcategories 1 and 2 include pH and fecal
coliforms. Control cf pH in the range of 6.0-9.0 is commonly
encountered in treated effluents and control of fecal coliforms to less
than 400 per 100 ml is readily accomplished by chlorination.
Greige Goods
The stated guidelines for subcategory 3 (greige goods Mills) can be
achieved by applying the best practicable control technology to the
greige goods raw waste load. The best practicable control technology
include screening, biological treatment and chlorination.
As described in Section IV, greige Mills are essentially a dry
operation. Most greige goods Mills discharge their waste to sanitary
systems. Of the Mills that treat their own waste most combine their
sanitary and industrial waste loads; the respondees to an industry
questionnaire indicated that 70 to 90 percent of the load, was sanitary.
The only current compilation of water use figures for various textile
subcategories is that presented to EPA by the American Textile
Manufacturers Institute and the Carpet and Rug Institute. Although it
has not as yet been completely verified, it appears to present the full
range of water uses to be expected for each subcategory. Water use
distribution for greige Mills as shown in Figure 20 illustrate an
extremely wide variation. This can be explained by the overriding
influences of nonprocess water such as boiler water, cooling water and
sanitary wastes which are very significant in some cases and less
significant in others.
152
-------
10
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X X
X X
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MEDIAN
xx WATER USAGE ~ °-9 GAL/LB
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Figure 20
DISTRIBUTION OF WATER USE
FOR GREIGE MILLS
10-2
1 II I I I I I I I I
5 10 20 30 40 50 60 70
(PERCENT)
80
95 98
-------
From the water usage distribution presented, it can be seen that the
median water use value is 7.5 I/kg (0.9 gal/lb). It has been
demonstrated that BOD5 from a greige mill can be reduced to a low level.
Because of this high treatability and the influence of sanitary waste,
the best practicable control technology should consistently attain 40
mg/1 BODf>. The BOD5 effluent limitation can be computed by applying
this concentration factor to the median water usage and allowing a 50
percent increase to account for normal operations variation. Thus, the
BOD5 effluent limitation for greige Mills (subcategory 3) is 0.45
kg/kkg(lb/10001b) of product.
The total suspended solids (TSS) effluent limitations are identical to
the BOD5 effluent limitations. Results from the exemplary biological
treatment systems indicated that TSS can be consistently reduced to at
least this level. Thus, the TSS effluent limitation for greige Mills is
0.45 kg/kkg (lb/1000 Ib) of product.
These BOD5_ and TSS effluent limitations are substantiated by plant I.
Two years of data indicate a BOD5 and TSS effluent discharge of less
than 0.1 kg/kkg (lb/10001b).
Effluent limitations for subcategory 3 (greige Mills) also include
control of pH within the range of 6.0-9.0 and chlorination to control
fecal coliforms to a level of 400 per 100 ml or less.
Woven Fabric Finishing
The effluent guidelines for July 1, 1977, subcategory 4 (woven fabric
finishing) are the average of data from exemplary biological systems
treating wastes from the dyeing and finishing of broadwo>ven cotton and
cotton-synthetic blends. The BOD5 effluent limitation is calculated
from data tabulated in Table 29 from the average of the BOD5_ discharge
from the biological treatment systems at Mills J, K, M, O, Q, R, S and
U; the TSS effluent limitation is based on the average of treatment
systems at Mills K, Q, and S; and the COD effluent limitation is based
on the average of treatment systems at Mills M, O, S, and U. The
effluent guidelines for subcategory 4 (woven fabric finishing) are as
follows: BOD5 limitation is 2.2 kg/kkg (lb/10001b); TSS limitation is
6.9 kg/kkg (lb/10001b).
Effluent limitations also include control of pH within the range of 6.0
to 9.0 and chlorination to control fecal coliforms below 400 per 100 ml.
154
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The effluent guidelines for July 1, 1977 for subcategory 5 (knit fabric
finishing) are the average of data from exemplary biological treatment
systems. The BOD5_ and TSS effluent limitations are calculated from the
average of the BOD5 and TSS discharges from the biological treatment
systems at Mills X, Y, and Z (see Table 30). The BOD5 and TSS effluent
limitations are based on these plants allowing a 50 percent increase to
account for treatment plant variation: BOD5 is 1.8 kg/kkg (lb/10001b)
and TSS is 8.0 kg/kkg (lb/10001b). The COD effluent discharge is
developed from data at Mills W and Y. Approximately 70 percent of the
COD is removed by treatment plants at these Mills. The following
correlation was developed between monthly average COD and BOD5_ in the
effluent: BOD5 limitation is 3.5 kg/kkg (lb/1000 Ib) and TSS limitation
is 9.2 kg/kkg (lb/1000 Ib). The COD effluent limitation is based on
three months effluent data in which COD averaged 13 times the BOD. The
COD effluent guidelines is 47 kg/kkg(lb/1000lb).
Effluent limitations also include control of pH within the range of 6.0-
9.0 and control of fecal coliforms to allow no more than 400 per 100 ml
of discharge.
Carpet Mills
The effluent guidelines for July 1, 1977 for subcategory 6 (carpets) are
the average of data from exemplary biological systems treating carpet
mill wastes. The BOD5, TSS and COD effluent limitations are based on
the average BOD5, TSS and COD discharges listed in Table 31 for systems
treating waste water from Mills, MC, BS, CC and BB. The effluent
limitations for carpet Mills (subcategory 6) are as follows: BOD5 is 4.3
kg/kkg (lb/1000 Ib); TSS is 4.3 kg/kkg (lb/1000 Ib); and COD is 30
kg/kkg (lb/1000 Ib).
Effluent limitations also include control of pH within the range of 6.0-
9.0 and control of fecal coliforms to allow no more than 400 per 100 ml
of waste water discharge.
157
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Stock and Yarn Dyeing and Finishing
The effluent guidelines for July 1, 1977, for subcategory 7 (stock and
yarn) are the average of data from exemplary biological systems treating
wastes from dyeing and finishing stock and yarn. The BOD5 and TSS
effluent limitations are based on the average BOD5 and TSS discharges
listed in Table 32 for biological treatment systems at Mills EE, GG and
NS. The effluent guidelines for subcategory 7 are as follows: BOD5_
limitations is 3.5 kg/kkg (lb/1000 Ib) and TSS limitation is 9.2 kg/kkg
effluent data in wich COD averaged 13 times the BOD5;. The COD effluent
guidelines is 47 kg/kkg (lb/1000 Ib).
Effluent limitations also include control of pH within the range of 6.0-
9.0 and control of fecal coliforms to allow no more than 400 per 100 ml
of discharge.
COD limitations for subcategories 4,5,6, and 7 are applicable only to
plants with capacities greater than 1000 kg/day (2,200 Ib/day), 3,450
kg/day (7,590 Ib/day), 3,450 kg/day (7,590 Ib/day) and 3,100 kg/day
(6,820 Ib/day) respectively. As discussed in Sections V and VIII severe
diseconomies of scale create economic impacts which require different
limitations for small plants.
RATIONALE FOR THE SELECTION OF
BEST PRACTICABLE CONTROL TECHNOLOGY
CURRENTLY AVAILABLE
Age and Size of Equipment and Facility
The industry has generally modernized its plants as new methods that are
economically attractive have been introduced. No relationship between
age of production plant and effectiveness of its pollution control was
found. Size was shown in Section IV to require separate limitations for
small facilities because of severe diseconomies of scale. Differences
in effluent limitations have resulted.
Total Cost of Application in Relation to Effluent Reduction Benefits
Based on information contained in Section VIII of this report, the
estimated increase in final product costs required to achieve the best
practicable effluent reductions range from small and large plants in the
seven subcategories from 0.1 cents per kilogram product (0.2 cents per
pound product) to a high of 0.8 cents per kilogram (1.8 cents per
pound). The average price increase is less than 0.4 cents per kilogram
(0.9 cents per pound) .
160
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Engineering Aspects of Control Technique Applications
The specified level of technology is practicable because it is being
practiced by plants representing a wide range of plant sizes and types.
Eighteen exemplary biological treatment systems have been utilized to
develop the effluent limitations (see Table 27). These systems treat
textile waste waters from knit fabric finishing, dyeing and finishing of
broadwoven cotton and cotton-synthetic blends, carpet manufacturing, and
stock and yarn dyeing and finishing. The average BOD_5 removal
efficiency of these systems is greater than 95 percent, this efficiency
has been utilized to develop limitations in subcategories without
exemplary treatment operations. In the subcategories there are
treatment systems that should be capable of meeting those limitations
with some modification in operation, perhaps the presence of a
knowledgeable operator. In general, some minor plant design changes
along with cooperation from management and plant personnel will be
required.
Process Changes
Significant in-plant changes will not be needed by textile plants to
meet the specified effluent limitations. Some plants may need to
improve their water conservation practices and housekeeping, both
responsive to good plant mangement control.
Non-Water Quality Environmental Impact
The major impact when the option of a biological treatment process is
used to achieve the limits will be the problem of sludge disposal.
Nearby land for sludge disposal may be necessary. Properly operated
biological systems would permit well conditioned sludge to be placed in
small nearby soil plots for drying without great difficulty.
It is concluded that no new kinds of impacts will be introduced by
application of the best current technology.
Factors to be Considered in Applying Level I Guidelines
1. Limitations are based on 30 day averages. Based on
performances of biological waste treatment systems, the maximum
daily limitations for BOD5,TSS,COD and oils and grease should
not exceed the 30 day average limitations by more than 100
percent. The maximum 30 day and daily limitations for pH and
fecal coliforms are identical.
2. If a plant produced materials in more than one subcategory, for
instance wool and synthetics, the effluent limitations should
be set by proration on the basis of the percentage of fiber
being processed to a product.
161
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SECTION X
EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF
THE BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE
EFFLUENT LIMITATIONS GUIDELINES
INTRODUCTION
The effluent limitations which must be achieved no later than July 1,
1983, are not based on an average of the best performance within an
industrial category, but are determined by identifying the very best
control and treatment technology employed by a specific point source
within the industrial category and subcategory, or by one industry where
it is readily transferable to another. A specific finding must be made
as to the availability of control measures and practices to eliminate
the discharge of pollutants, taking into account the cost of such
elimination.
Consideration must also be given to:
The age of the equipment and facilities involved;
The process employed;
The engineering aspects of the application of various types
of control techniques;
Process changes;
The cost of achieving the effluent reduction resulting
from application of the technology;
Non-water quality environmental impact (including energy
requirements).
Also, Best Available Technology Economically Achievable emphasizes in-
process controls as well as control or additional treatment techniques
employed at the end of the production process.
This level of technology considers those plant processes and control
technologies which, at the pilot plant, semi-works, and other levels,
have demonstrated both technological performances and economic viability
at a level sufficient to reasonably justify investing in such
facilities. It is the highest degree of control technology that has
been achieved or has been demonstrated to be capable of being designed
for plant scale operation up to and including "no discharge" of
pollutants. Although economic factors are considered in this
development, of current technology, subject to limitations imposed by
economic and engineering feasibility.
162
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EFFLUENT REDUCTION ATTAINABLE THROUGH APPLICATION OF
THE BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE
Based on the information contained in Section III through VIII of this
report, a determination has been made that the quality of effluent
attainable through the application of the Best Available Technology
Economically Achievable is as listed in Table 33. The technology to
achieve these goals is generally available, although the advanced
treatment techniques may not have yet been applied at full scale to
plants within each subcategory.
IDENTIFICATION OF THE BEST
AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE
Best available control technology economically achievable for the
textile manufacturing industry includes the preliminary screening,
primary settling (wool scouring only) , coagulation (carpet mills only) ,
secondary biological treatment and chlorination listed under the Best
Practicable Control Technology Currently Available. In addition, it
includes advanced treatment techniques such as multi-media filtration
and/or activated carbon adsorption following biological treatment.
Management controls over housekeeping and water use practices will be
stricter than required for 1977. However, no additional in-plant
controls will be required to achieve the specified levels of effluent
reduction. There are several in-plant controls and modifications that
provide alternatives and trade-offs to additional effluent treatment.
For example, a scouring bowl train designed for complete counter-current
operation can significantly reduce water usage at wool scouring
facilities.
The stated guidelines for July 1, 1983, for small plants in six
subcategories (wool scouring, wool finishing, woven fabric finishing,
knit fabric finishing carpet Mills and stock and yarn dyeing and
finishing) and both small and large plants in subcategory 3 (greige
goods) can be achieved by adding a multi-media filtration system to the
best practicable control technology. This advanced technology can
insure that operational variability is minimized. The recommended
effluent limitations are based on the effluent reduction attainable with
the best practicable control technology without an allowance for
operational variability.
163
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TABLE 33
MAXIMUM THIRTY DAY AVERAGE
RECOMMENDED EFFLUENT LIMITATION
GUIDELINES FOR JULY 1, 1983
Effluent Limitations (1)
BODS
kg/lOOOkg
Plant Subcategory (Ib/lOOOlb)
1. TOOL SCOURING (2)
Plant capacity less than 2.5
6,500 kg/day (14,300 Ih/day)
Plant capacity greater than 2.5
6,500 kg/day (14,300 Ib/day)
2. WOOL FINISHING
Plant capacity less than 5.0
900 kg/day (1,980 Ib/day)
Plant capacity greater than 5.0
900 kg/day (1,980 Ib/day)
3. GREIGE MILLS
All plant sizes 0.3
4. WOVEN FABRIC FINISHING
Plant capacity less than 1.5
1,000 kg/day (2,200 Ib/day)
Plant capacity greater than 1.5
1,000 kg/day (2,200 Ib/day)
5. KNIT FABRIC FINISHING
Plant capacity less than 1.2
3,450 kg/day (7,590 Ib/day)
Plant capacity greater than 1.2
3,450 kg/day (7,590 Ib/day)
6. CARPET MILLS
Plant capacity less than 2.9
3,450 kg/day (7,590 Ib/day)
Plant capacity greater than 2.9
3,450 kg/day (7,590 Ib/day)
7. STOCK AND YARN DYEING AND FINISH-
ING
Plant capacity less than 2.3
3,100 kg/day (6,820 Ib/day)
Plant capacity greater than 2.3
3,100 kg/day (6,820 Ib/day)
TSS
kg/lOOOkg
(Ib/lOOOlb)
2.5
2.5
5.0
5.0
0.3
4.6
4.6
5.3
5.3
2.9
2.9
6.1
6.1
COD
kg/lOOOkg
(Ib/lOOOlb)
NA
64
NA
14.9
NA
NA
8.8
MA
6.4
:MA
8.0
NA
12.5
NA MEANS NOT APPLICABLE
(1) Plant capacities and discharge limitations are stated for Subcategories
1 and 2 per weight of raw wool received at the wool scouring or wool
finishing operation and are stated for Subcategories 3, 4, 5, 6 and 7
per weight of final material produced by the facility.
For all Subcategories pH should range between 6.0 to 9.0 at any time.
For all Subcategories Most Probable Number (MPN) of Fecal Coliforms
should not exceed 400 counts per 100 ml.
(2) For all Wool Scouring plants (Subcategory 1) Oils and Grease should
not exceed 1.9 kg (lb)/1000 kg (Ib) grease wool.
161*
-------
The guidelines for large plants in six subcategories (wool scouring,
wool finishing, woven fabric finishing, knit fabric finishing, carpet
Mills and stock and yarn dyeing and finishing) can be achieved by adding
an activated carbon adsorption system to the best practicable control
technology. This advanced technology has been shown to effectively
(greater than 90 percent) remove COD from textile wastes. In some
plants where large quantities of dispersed dyes or materials with poor
adsorptive capacity are discharged, a multi-media filtration system may
also be needed. The recommended effluent limitations are based on the
best effluent reduction attainable with the best practicable control
technology and include an additional reduction on the order of 60
percent of the remaining COD.
*
RATIONALE FOR THE SELECTION OF BEST
AVAILABLE CONTROL TECHNOLOGY ECONOMICALLY ACHIEVABLE
Age and Size of Equipment and Facilities
The industry has generally modernized its plants as new methods that are
economically attractive had been introduced. No relationship between
age of production plant and effectiveness of its pollution control was
found, size was shown in section IV to require separate limitations for
small plants because of severe diseconomies of scale. significant
differences in effluent limitations have resulted.
Total Cost of Application in Relation to Effluent Reduction Benefits
Based on information contained in Section VIII of this report, the
estimated increase in final product costs required to achieve the best
available effluent reductions range from 0.05 to 0.4 cents per kilogram
(0.1 to 0.8 cents per pound) product processed by all plants in
subcategory 3 and by small plants in subcategories 1, 2, 4, 5, 6, and 7
with capacities less than 6,500 kg/day (14,300 Ib/day), 900 kg/day
(1,980 Ib/day), 1,000 kg/day (2,250 Ib/day), 3,450 kg/day (7,590
Ib/day), 3,450 kg/day (7,590 Ib/day), and 3,100 kg/day (6,820 Ib/day)
respectively. For larger plants in the industry, the price increases
ranged from 0.4 cents per kilogram (0.8 cents per pound) to a high of
2.0 cents per kilogram (4.5 cents per pound). The estimated costs
required to achieve best practicable and best available effluent
reductions range between 0.3 and 1.1 cents per kilogram (0.6 and 2.5
cents per pound) product from small plants and 0.5 to 2.5 cents per
kilogram (1.0 and 5.4 cents per pound) product from larger plants.
Engineering Aspects of Control Technique Application
The specified level of technology is achievable. Biological treatment
is practiced throughout the textile industry and activated carbon
adsorbtion is practiced at four textile plants. The use of activated
carbon to treat textile wastes was pioneered at a Pennsylvania carpet
165
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mill and at least one synthetic knit goods plant (mill HH) is installing
activated carbon.
Multi-media filtration has been used effectively in various EPA
applications including Lebanon, Ohio, and Washington, B.C. Filtration
is also used as pretreatment before carbon adsorption at a Virginia
textile mill.
Process Changes
No in-plant changes will be needed by most plants to meet the limits
specified. Some in-plant techniques are available as alternatives to
effluent treatment techniques.
Non-Water Quality Environmental Impact
The non-water quality environmental impact will essentially be those
described in Section IX. It is concluded that no new serious impacts
will be introduced.
Factors to be Considered in Applying Level II Guidelines
1. Limitations are based on 30 day averages. Based on
performances of biological waste treatment systems, the maximum
daily limitations for BOD5, TSS, COD and oils and grease should
not exceed the 30 day average limitations by more than 100
percent. The maximum 30 day and daily limitations for pH and
fecal coliforms are identical.
2. If a plant produced materials in more than one subcategory for
instance wool and synthetics, the effluent limitations should
be set by proration on the basis of the percentage of fiber
being processed to a product.
166
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SECTION XI
NEW SOURCE PERFORMANCE STANDARDS
INTRODUCTION
The effluent limitations that must be achieved by new sources are termed
performance standards. The New Source Performance Standards apply to
any source for which construction starts after the publication of the
proposed regulations for the Standards. The Standards are determined by
adding to the consideration underlying the identification of the Best
Practicable control Technology Currently Available, a determination of
what higher levels of pollution control are available through the use of
improved production processes and/or treatment techniques. Thus, in
addition to considering the best in-plant and end-of-process control
technology, New source Performance Standards are based on an analysis of
the process itself. Alternative processes, operating methods or other
alternatives are considered. However, the end result of the analysis is
to identify effluent standards which reflect levels of control
achievable through the use of improved production processes (as well as
control technology), rather than prescribing a particular type of
process or technology which must be employed. A further determination
made is whether a standard permitting no discharge of pollutants is
practicable.
Consideration must also be given to:
Operating methods;
Batch, as opposed to continuous, operations;
Use of alternative raw materials and mixes of raw materials;
Use of dry rather than wet processes (including substitution
of recoverable solvents for water) ;
Recovery of pollutants as by-products.
EFFLUENT REDUCTION ATTAINABLE FOR NEW SOURCES
The effluent limitation guidelines for new sources are identical to
those for the Best Available Control Technology Economically Achievable
(See Section X). This limitation is achievable in newly constructed
plants. In-plant controls and waste treatment technology identified in
Section X are available now and applicable to new plants.
The new source technology is the same as that identified in section X:
preliminary screening, primary settling (wool scouring only),
coagulation (carpet mills only), biological treatment and multi-media
168
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filtration and/or activated carbon adsorption. The conclusion reached
in section X with respect to Total Cost of Application in Relation to
Effluent Reduction Benefits, the Engineering Aspects of Control
Technique Application, Process Changes, Non-Water Quality Environmental
Impact and Factors to be Considered in Applying Level II Guidelines,
aPPly with equal force to those New Performance Standards.
FRETREATMENT REQUIREMENTS
Three constituents of the waste water from plants within the textile
industry have been found which would interfere with, pass through, or
otherwise be incompatible with a well designed and operated publicly
ownad activated sludge or trickling filter waste water treatment plant.
Waste water constituents include grease from wool scouring operations,
latex from carpet mills and heavy metals such as chromium used in dyes.
Adequate control methods can and should be used to keep significant
quantities of these materials out of the waste water. Dye substitutes
are available for many dyes containing heavy metals.
169
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SECTION XII
ACKNOWLEDGMENTS
Special thanks and appreciation are due the following manufacturing
organizations: The American Textile Manufacturers Institute; The
Northern Textile Association; The Carpet and Rug Institute; and
The American Association of Textile Chemists and Colorists.
Appreciation is expressed for the interest of several individuals
within the Environmental Protection Agency: W. H. Cloward, Region IV;
Thomas Sargent, SERL, Athens, Georgia; Edmund Struzeski, NFIC, Denver,
Colorado; Charles Ris, 0 R & D; William Hancuff, George Webster,
Ernst Hall, Allen Cywin, EGD.
Special thanks are due to Richard Sternberg for his advice, support
and guidance. Thanks are also due the many secretaries who typed
and retyped this document: Aqua McNeal, Pearl Smith, Chris Miller,
Vanessa Datcher, Karen Thompson, and Fran Hansborough.
Special acknowledgment is made of the contributions of industry
personnel who provided information to the study. Their active response,
cooperation and assistance is greatly appreciated.
170
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SECTION XIII
REFERENCES
A review of the recent literature for references on Textile wastes and
waste treatment has produced over 200 references. Brief abstracts of
50 of these references are included as well as the full list of references,
(2) "The BOD of Textile Chemicals, Updated List - 1966"
American Dyestuff Reporter, (55) No. 18, 39-42, 1966.
(s elf-explanat ory)
(15) "What the Mills are Doing to Control Water Pollution"
Textile Chemist and colorist, (1) No. 6, 25-36, 1969.
This article gives a brief rundown of waste control activities at:
1. American Enka, N.C. facility, where rayon, nylon, and
polyester are produced
2. Burlington Industries (general)
3. Cannon Mills (discussed new design in detail)
4. Cone Mills (general)
5. Dan River Mills (Danville plant)
6. M. Lowenstein & sons (Lyman Printing and Finishing Co.)
(18) Molvar, A., C. Rodman, and E. Shunney
"Treating Textile Wastes with Activated Carbon"
Discusses activated carbon treatment in general, pilot plant
work, and actual operating data for a full size waste treatment
system. The mill's identity is nor given (dyeing and finishing).
(21) Souther, R.H.
"Waste Treatment Studies at duett, Peabody 6 Company Finishing Plant"
American Dyestuff Reporter, (58) No. 15, 13-16, 1969.
Detailed operating data on the Arrow Co., Division at Waterford, New
York. The treatment system consists of an "extended-contact,
activated sludge step, bio-aeration process." Also includes caustic
recovery.
172
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(22) "Wastewater Treatment Recycles 80 Percent of Industrial Flow"
American Textile Reporter, (83) No. 51, 14-15, 1969.
Very brief description and general flow diagram of the waste treat-
ment system using activated carbon at Hollytex Carpet Mills (near
Philadelphia). No real operating data is given.
(25) Jones, E.L., T.A. Alspaugh, and H.B. Stokes
"Aerobic Treatment of Textile Mill Waste"
JWPCF (34) No. 5, 495-512, 1962.
Cone Mills, joint treatment of mill and municipal sewage by
contact stabilization process. (Pilot plant operating data.)
(47) Poon, C.P.C.
"Biodegradability and Treatability of Combined Nylon and
Municipal Wastes"
JWPCF (42) No. 1, 100-105, 1970.
Treatability study of wastes taken from the Belding Chemical Co.
in Thomaston, Connecticut. Strictly a laboratory study.
(49) Kwie, W.W.
"Ozone Treats Wastestreams from Polymer Plant"
Water and sewage Works, 116, 74-78, 1969.
Laboratory study on ozone treatment of wastes from polymer plant
(including SANS). The study did not produce very satisfying results.
(52) Wheatland, A.B.
"Activated Sludge Treatment of some Organic Wastes"
Proc. 22nd Ind. Waste Conf. Purdue Univ. 983-1008, 1967.
Treatability study on a simulated synthetic fiber production and
dyeing waste using a bench scale activated sludge unit.
(53) Carrigue, C.S., and L.U. Jauregui
"Sodium Hydroxide Recovery in the Textile industry"
Proc. 22nd Ind. Waste Conf. Purdue Univ., 1966.
Castelar Textile Mill, Argentina (cotton goods)
Description of NaOH recovery from the mercerizing process. NaOH
is filtered and then concentrated by evaporating. Design criteria,
operating data and capital and operating costs are given.
(56) Taylor, E.F., G.C. Gross, and R.F. Rocheleau
"Biochemical Oxidation of Wastes from the New Plant for Manufacturing
Orion at Waynesboro, Va."
173
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Proc. 15th Ind. Waste Conf. Purdue Univ., 1961.
Detailed description of Dupont's Waynesboro works. Wciste facilities
consist of a catalytic oxidation unit which completely oxidizes the
organics associated with the recovery of dimethylformamide and an
activated sludge unit for treatment of dilute organic materials such
as acrylonitrile, dimethylformamide and formic acid.
(57) Sadow, R.D.
"The Treatment of Zefran Fiber Wastes" (acrylic fiber)
Dow Chemical Company's Williamsburg, Va., plant. Description of
waste treatment process which includes primary settling, chemical
coagulation, a Dowpac oxidation tower, and secondary settling.
Operating data and design criteria are given.
(61) Jones, L.L.
"Textile Waste Treatment at Canton Cotton Mills"
JWPCF (37) No. 12, 1693-1695, 1965.
Gives a rather brief description of their activated sludge unit with
design criteria, operating data (sketchy) and cost information.
(62) Smith, A.L.
"Waste Disposal by Textile Plants"
JWPCF (37) No. 11, 1607-13, 1965.
Very general article, gives some synthetic textile waste characteris-
tics and very brief descriptions of waste characteristics and treat-
ment methods at:
1. Chatham Manufacturing Co., Elkin, N.C. (multi-fiber woolen mill)
2. J.P. Stevens Co., Wallace Plant
(63) Dean, B.T.
"Nylon Waste Treatment"
JWPCF (33) No. 8, 864-70, 1961.
Operating experience of the Chemstrand Corp. Pensacola plant which
utilizes an activated sluge unit followed by a post-treatment lagoon,
(76) Suchecki, S.M.
"A Dyer's "Operation Cleanup"
Textile Industries (130) No. 6, 113, 1966.
Description of Northern Dyeing Co., Washington, N.J. treatment
facilities. Very little operating data given.
(86) Souther, G.P.
174
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"Textile Water Pollution woes Can be Resolved by Solvents"
American Textile Reporter (54) No. 9, 11, 13, 1970.
Describes solvent sizing and dyeing processes. This is an infor-
mative but not very detailed article.
(95) Porter, J.J.
"Concepts for Carbon Adsorption in Waste Treatment"
Textile Chemists and Colorists (4) No. 2, 29-35, 1972.
The history of carbon's entry into the waste treatment field is
presented. Interpretations of teh fundamental kinetics and
thermodynamics of carbon adsoption are also given with several
specific examples cited.
(99) Rodman, C.A.
"Removal of Color from Textile Dye Wastes"
Textile Chemists and Colorists (3) No. 11, 239-47, 1971.
Solutions of four types of dyestuffs were treated by several methods
that have been used practically or experimentally for color removal.
Among these were coagulation by lime and by alum; extended aeration,
activated carbon adsorption, reverse osmosis, and treatment with high
pressure oxygen and cobalt-60 radiation.
(100) Rhame, G.A.
"Aeration Treatment of Textile Finishing Wastes in South Carolina"
American Dyestuff Reporter (60) No. 11, 46, 1971.
Operating data of several unidentified plants is presented along
with general design criteria.
(103) Porter, J.J.
"Treatment of Textile Waste with Activated Carbon"
American Dyestuff Reporter (61) No. 8, 24-7, 1972.
Considerations in evaluating the potential application of carbon
adsorption to a waste stream are discussed along with procedures
for conducting laboratory studies.
(106) Stone, R.
"Carpet Mill Industrial Waste System"
JWPCF (44) No. 3, 470-478, 1972.
A description of the waste treatment system of the Walter Carpet
Mill, City of Industry, California is presented.
(108) Little, A.H.
"Use and Conservation of Water in Textile Processing"
175
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Journal of the Society of Dyers and Colorists (87) No. 5, 137-45, 1971.
Investigation of water usages in unit processes under normal pro-
duction conditions. The effects of different dyeing and bleaching
processes have been studied. Possible methods of conservation of
water are discussed, including Contra-flow washing. In addition,
the effects of changes in processing, the size, type and speed of
machines and the effects of cloth weight and batch size are discussed.
(110) Masseli, J.W., N.W. Massell, and M.C. Burford
"Factors Affecting Textile Waste Treatability"
Textile industries for October 1971, p. 84-117
General design parameters of activated sludge waste treatment are
discussed along with startup and operational considerations. Waste
contributions (in terms of % total BOD), are given for the individual
process chemicals used in a typical cotton mill, cotton/synthetic
mill, and woolen mill.
(Ill) Shunney, E.L., Perratti, A.E., and Rodman, C.A.
"Decolorization of Carpet Yarn Dye Wastewater"
American Dyestuff Reporter (60) No. 6, 32-40, 1971.
Laboratory and full-scale operation of bio-regenerated activated
carbon treatment of carpet yarn fiber dyeing are discussed. The
facility described is the C. H. Masland & Sons plant in Wakefield,
Rhode Island.
(113) Rodman, C.A., and E. L. Shunney
"A New concept for the Biological Treatment of Textile Finishing
Wastes"
Chem. Eng. Progr. Symp. ser. 67, 107, 451-457, 1971.
(Same subject as ref. Ill)
(115) Rodman, C.A. and E. L. Shunney
"Novel Approach Removes color from Textile Dyeing Wastes"
Water and Waste Eng. (8) No. 9, #18-23, 1971.
(Same subject as ref. Ill)
(118) "Bio-regenerated Activated Carbon Treatment of Textile Dye Wastewate
Water Pollution Control Research Series 1209 OD WW 01/71.
(Same subject as ref. Ill)
(122) Powell, S.D.
"Biodegradation of Authraquinone Disperse Dyes"
Thesis, Georgia Inst. Tech., 9, 238, 1971,'
176
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Three authraquincne disperse dyes, Disperse Violet 1 (C.I. 61100),
Disperse Blue 3 (C.I. 61505), and Disperse Blue 7 (C.I. 62500),
were partially metabolized by bacteria normally present in domestic
activated sludge. Disperse Red 15 (C.I. 60710), was left unchanged
by the sludge. The nature of the metabolites produced showed that
the dyes had not actually been degraded, but merely converted to
derivatives of the original dyes.
(123) Hood, W.S.
"Color Evaluation in Effluents from Textile Dyeing and Finishing
Processes"
Initial concentration and rates of degradation of dyes and chemicals
in textile effluents were studied. Field studies were made to
observe conditions and to collect samples of water from streams in
the Coosa River Basin. The samples were analyzed for content of
specific dye auxiliaries and color. Color degradation was achieved
under simulated stream conditions, both in textile effluents and in
river samples.
(124) Soria, J.R.R.
"Biodegradability of Some Dye Carriers"
Thesis, Georgia Inst. Tech., 9, 238, 1971.
Carriers covered in this study were resistant to degradation in
conventional activated sludge waste disposal plants. Where bacteria
were acclimated to the chemicals and treatment times were extended,
degradation did occur.
(125) Arnold, L.G.
"Forecasting Quantity of Dyestuffs and Auxiliary Chemicals Dis-
charged into Georgia Streams by the Textile Industry"
Thesis, Georgia Inst. Tech., 9, 238, 1971.
The quantity and concentration of the major textile wet-processing
chemicals in effluents are reported.
(126) Pratt, H.D., Jr.
"A Study of the Degradation of Some Azo Disperse Dyes in Waste
Disposal Systems"
Thesis, Georgia Inst. Tech., 9, 238, 1971.
Two azo disperse dyes, Disperse Orange 5 (C.I. 11100) and Disperse
Red 5 (C.I. 11215), were degraded by the bacteria in conventional
waste treatment facilities into aromatic amines. Biological de-
gradation produced identical metabolites as those formed by chemi-
cal reduction.
177
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(127) Anderson, J.H.
11 Biodegraelation of Vinyl Sulfone Reactive Dyes"
Thesis, Georgia Inst. Tech., 9 238, 1971.
Biodegradation of three vinyl sulfone reactive dyes, Reactive
Blue 19, Reactive Violet 5, and Reactive Black 5, were investigated
under laboratory conditions simulating those employed in conventional
activated sludge plants. The study failed to show any evidence of
degradation. Reactive Blue 19, and Reactive Violet 5 showed evidence
of degradation under anaerobic conditions.
(141) "The Centrifugal Recovery of Wool Grease"
Wool Science Review #37, p. 23-36, 1969.
This very detailed article discussed the composition of wool scour
liquor, general principles of recovery, detailed operating charac-
teristics of centrifuges, and the economics of wool grease recovery.
(143) Harker, R.P., and E.M. Rock
"Water conservation and Effluent Disposal in the Wool Textile Industry
J. Soc. Dyers and Colourists (87), No. 12, 481-3, 1971.
Discusses the wool textile industry in the U.K. Givess water con-
sumption for various unit processes in terms of gal/lb product.
This article also gives typical wool processing effluents and a
description of the Traflo-W process which entails ch€;mical coagu-
lation followed by vacuum filtration. BOD is reduced by 80%.
(149) Rea, J.E.
"Treatment of Carpet Wastes for Disposal"
Proc. industrial Waste and Pollution conference and Advanced
Water conference, 22nd and 3rd. Oklahoma State University,
Stillwater, Oklahoma, March 24-30, 1971.
This paper identifies design criteria and operating data for the
waste treatment facilities at Sequoyah Mills in Anadarko, Okla.
The waste treatment facilities consist of an aerated lagoon and
stabilization pond. Pilot work is included which shows the re-
lationship of BOD removal to aeration time.
(150) Paulson, Per
"Water Purification - An Alternative to Solvent Dyeing"
International Dyer & Textile Printer - June 4, 1971.
A brief description of a new waste treatment process employing
sedimentation followed by ion exchange. Pilot plant work on
dyeing liquor showed COD removals greater than 90%.
(161) Kulkarni, H.R., S.U. Khan, and Deshpande
178
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"Characterization of Textile Wastes and Recovery of Caustic Soda
from Kier Wastes"
Environmental Health (13) No. 2, 120-127, 1971.
A case study of "A Typical cotton Textile Industry" is presented
in the paper with reference to economical method of treatment of
the waste waters and recovery of caustic soda during the process
of treatment. Ninety-eight percent caustic recovery has been
accomplished using dialysis.
(162) "Biodegradation of "Elvanol" - A Report from Du Pont"
The report concludes that domestic and textile mill activated
sludge microorganisms can acclimate to "Elvanol" T-25 under con-
ditions attainable in conventional waste treatment systems and
that removals of over 90% can be achieved if the organisms are
properly acclimated.
(164) Ryder, L.W.
"The Design and construction of the Treatment Plant for Wool
Scouring and Dyeing Wastes at Manufacturing Plant, Glasgow, Va."
J. Boston Soc. Civil Engrs., 37, 183-203, April 1950.
This article gives a very detailed description and design basis
for the waste treatment system consisting of equalization, acid-
flocculation, and neutralization. The plant achieves a BOD re-
moval of 60%, SS removal of 96% and a grease removal of 97%.
(168) Rodman, C.A. , and E.L. Shunney
"Clean Clear Effluent"
Tex. Manufacturer (99) No. 49, 53-56, 1972.
A description of the Fram Corporation bio-regenerated carbon
adsorption process is given along with laboratory and pilot plant
operating data. The pilot plant treated waste water from the
carpet yarn fibre dyeing plant of C.H. Masland & Sons, Wakefield,
Rhode Island. A COD reduction of 81% and a color reduction of
99.436 is reported.
(175) Wilroy, R.D.
"Industrial Wastes from Scouring Rug Wools and the Removal of
Dieldrin"
Proc. 18th Ind. Waste conf., Purdue Univ., April 30, May 1-2, 1963,
The article describes design considerations and operating exper-
ience of a waste treatment system consisting of fine screens,
sedimentation basin, and an anaerobic lagoon. A BOD reduction
of between 80 and 9038 and a Dieldrin reduction of 99% is claimed
for the system.
179
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(181) Stewart, R.G.
"Pollution and the Wool Industry"
Wool Research Organization of New Zealand, Report No. 10, 1971.
This article is a rather general outline of the sources of wool
processing wastes and the present waste treatment technology
available.
(190) Rebhu.n, M., A. Weinberg, and N. Narkis
"Treatment of Wastewater from Cotton Dyeing and Finishing Works
for Reuse"
Eng. Bull. Purdue Univ., Eng. Ext. 137 (pt. 2), 1970.
This article describes the results of pilot plant work on the
waste from a cotton dyeing and finishing mill in Israel. Alum
flocculation followed by filtration was shown to produce a 95%
color reduction and a 61% COD reduction. Activated carbon was
shown to be a poor sorbent, and greater success was achieved
using a weak base ion exchange resins.
(202) Alspaugh, T.A.
"Treating Dye Wastewaters"
45th Annual Conference of tne Water Pollution Control Federation
Atlanta, Georgia, Oct. 8-13, 1972.
Alspaugh gives a very thorough evaluation of presently employed
and promising future waste treatment unit operations. Experienced
removal efficiencies and general treatment costs are also given.
A summary of current waste treatment research is given.
(213) Corning, V.
"Pollution Control in Jantzen Dyehouse"
Knitting Times (39) No. 35, 44-45, 1970.
Brief description of Portland, Oregon plant, little detail.
(214) "Textile Water Pollution cleanup Picks Up Speed"
Textile World, 54-66, November 1967.
Fairly general arcicle but does give some operating data and waste
treatment descriptions for several plants:
1. J.P. Stevens & Co., Wallace, N.C. plant
2. UPD's Bluefield, Va., plant
3. Burlington's Cooleemee, N.C.
180
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4. Lyman Printing and Finishing Co., Lyman, N.C.
5. J. P. Stevens 6 Co., Utica-Mohawk plant
(215) Sahlie, R.S., and C.E. Steinmetz
"Pilot Wastewater Study Gives Encouraging Indications"
Modern Textiles, (50) No. 11, 20-28, 1969.
Description of pilot plant work at fiber Industries, Shelby, N.C.
plant. Article is not very detailed.
(216) "Trade Effluent Control in the Carpet Industry"
Textile Institute and Industry, (3) No. 9, 237-40, 1965.
General discussion, gives values for typical effluents.
181
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41 Ibid—Contract C 12090 ESG, American Enka "Hydroxide Precipitation
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42. Ibid—Contract C 12090 GOX, Fiber Industries, "Reuse of Chemical Fibe
Plant Wastewater and Cooling Water Slowdown."
43. Ibid—contract 12090 EGW, Holliston Mills, "Treatment of Cotton Texti."
Wastes by Enzymes and Unique High Rate Trickling Filter System."
184
-------
44. Ibid—Contract 12090 EQO, "Palisades Industries," Demonstration of a
New Process for the Treatment of High Concentration Textile Dyeing
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45. Ibid—contract 12090 FWD, American Association of Textile Chemists
and Colorists, "The use of oxygen and ionizing radiation to decolorize
dye wastes."
46. Ibid—Contract 12090 EOE, North Carolina State University, "The
Feasibility of Precipitation Removal of Synthetic Sizing Materials
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204. "Color, Heavy Metal Removed by Adsorption," Chemical Processing, (
No. 9, 13, 1972.
205. "Water Usage in the Wet Processing of Wool Textiles," wira Report
206. Cosgrove, W.J., "water Pollution and the Textile Industry," Canadian
Textile J., 63-6, January 1970.
207. Eguchi, Y., and Y. Uda, "Wastewater Treatment by Granular Activate
Carbon," J. Textile Machinery Soc. Japan, (24) No. 8~, 555-61, 1971.
208. Jones, T.R., "Textile Industry Wastes; Effluent Treatment: Waste
Reclamation: Man-made Fibers," Effluent & Water Treatment Journal,
London, (12) No. 1, 352-355, July 1972.
209. Simon-Hartley, "Treatment of Dyeing and Finishing Effluents from ;
Textile Works," Intern. Dyer, (143) No. 51, 53-4, January 2, 1970.
210. Button, D.G., "Improved biological wastewater treatment," Du Pont
Innovation, (3) No. 1, 6-8, 1972. (Eng.)
211. Rhame, G.A., "Review of South Carolina Practices in Textile Finis
Wastes," industrial Waste, 18 IW/U9-53, September-October 1972.
212. "Textile Industry Wastes: Effluent Treatment: Water Reclamation:
Great Britain," Textile Res. Conference, Final Report, 73 pages.
213. Corning, V. , "Pollution Control in Jantzen Dyehouse," Knitting Ti
(39) No. 35, 44-45, 1970.
196
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214. "Textile Water Pollution Cleanup Picks Up Speed," Textile World,
54-66, November 1967.
215. Sahlie, R.S., and C.E. Steinmetz, "Pilot Wastewater Study Gives
Encouraging Indications," Modern Textiles, (50) No. 11, 20-28, 1969.
216. "Trade Effluent control in the Carpet Industry," Textile Institute
and Industry, (3) No. 9, 237-40, 1965.
197
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'SECTION XIV
GLOSSARY
acetate - A manufactured fiber made from cellulose acetate;.
acid dye - A type of dye commonly used to color wool and nylon but may
be used on other fibers.
Acrilan - Trademark of Monsanto for acrylic fiber.
acrylic - A manufactured fiber in which the fiber-forming substance is
any long chain synthetic polymer composed of at least 85% by weight of
acrylonitrile units. Made in both filament and staple form. (See
Acrilan, Orion, Creslan.)
Arnel - Trademark (Celanese Corp.) for cellulose triacetate fiber.
Avicron - Trademark (FMC Corp.) for rayon filament yarn.
Avril - Trademark (FMC Corp.) for staple and filament rayon.
beck - A chamber in which goods may be scoured and dyed. May be operated
at atmospheric pressure or at elevated temperature and pressure.
biphenyl (or diphenyl) - A carrier used in dyeing polyester.
biochemical oxygen demand (BOD) - A method of measuring rate of oxygen
usage due to biological oxidation. A BODS of 1000 mg/liter means that
a sample (1 liter) used 1000 mg of oxygen in 5 days.
bleaching - Removal of colored components from a textile. Common bleaches
are hydrogen peroxide, sodium hypochlorite, and sodium chlorite.
blend - the combination of two or more types of fibers and/or colors in
one yarn.
bottom chrome - Term used in application of certain dyes to wool.
Involves use of chromium compounds.
butyl benzoate - A carrier used in dyeing polyester.
carded - Yarn in which fibers are separated and aligned in a thin web,
then condensed into a continuous, untwisted strand called a "sliver."
carrier - An organic material used in dyeing polyester. (See biphenyl,
orthophenyl phenol, trichlorobenzene, butyl benzoate.)
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cationic dye - The colored component of this type of dye bears a
positive charge.
caustic soda - A strong alkali used, for example, in mercerizing.
cellulose - Major component of cotton and rayon. Also used as the base
for acetate fiber.
chemical oxygen deman (COD) - The amount of oxygen required to oxidize
materials in a sample by means of a dichromate solution.
combed cotton - Cotton yarn that is cleaned after carding by wire
brushes (combs) and roller cards to remove all short fibers and
impurities.
crease-resistant - Fabrics that have been treated to make them resistant
to wrinkling. One of the most common methods is to incorporate a resin.
Creslan - Trademark owned by American Cyanamid Co. for acrylic fibers.
cross-dyed - Multicolored effects produced in one dye bath from fabrics
containing fibers with different affinities to the same dye.
Dacron - Trademark owned by Du Pont for polyester filaments and staple
fibers.
denier - Unit of weight indicating size of a fiber filament based on
weight in grams of a standard strand of 9000 meters.
desize - Removal of size. Several methods may be used. (See enzyme.)
developed dye - An azo dye whose color is developed by reaction on
cotton.
dichromate - A chemical used widely in applying some dyes. Also used
in boiler water. A toxic material.
fieldrin - Chemical applied to wool to eliminate damage due to moths.
Toxic.
diphenyl - (see biphenyl).
direct dyes - Class of dyestuffs that colors cellulosic fibers in full
shades.
disperse dye - A type of dye used to color several synthetic fibers.
Applied as a fine dispersion using a carrier. On cloth, padded dye
may be baked on or "thermofixed."
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dissolved solids - Total solids - suspended solids in a sample of
waste water.
dope-dyed - Trade slang for "solution dyed" or "spun dyed" meaning that
color is put into the chemical liquid from which synthetic fibers are
drawn. Filaments emerge colored.
double knit - Knitted fabric made on a special knitting machine that
combines a double set of needles to produce a fabric.
Durable Press - Goods that require no ironing during the normal use-
life of a garment. The term applies to apparel and other textile
products such as sheets, draperies, etc. As a rule, DP is achieved
in two ways: 1. Pre-curing fabrics with a special resin finish then
pressing made-up garment. 2. Post-curing fabric with a resin finish
then cooking made-up garments in an oven. As a rule, polyester-cotton
blends are used, but there are 100% cottons, and other blends also.
enzyme - An agent used to remove starch size.
felt - A mat of fiber of wool often mixed with cotton or rayon.
flock - Short fibrous particles of fibers or short hairs applied by
various processes to the surface of a fabric.
fly - Waste fibers or particles which fly out into the air during
carding, drawing, spinning, or other fiber processing.
Fortrel - Trademark owned by Fiber Industries, Inc., for polyester
fiber.
greige - Fabrics in unbleached, undyed state before finishing. In
U.S., "gray goods" or "grey goods."
Herculon - Trademark owned by Hercules, Inc., for polypropylene fibers.
jig-dyed - Dyed in open width on a machine called a "jig." Cloth moves
from one roll to another through the dye liquor until the desired
shade is obtained.
jute - Coarse, brown fiber from the stalk of a bast plant grown in
India. Used mainly fcr burlap, cordage, and as a backing for rugs
and carpets.
kier - A piece of equipment in which cotton is boiled with dilute
caustic soda to remove impurities. Also used as a verb to describe
the process.
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knitting - Process of making fabric by interlocking series cf loops
of one or more yarns. Types are: jersey (circular knits), tricots
(warp knits), double knits.
Kodel - Trademark owned by Eastman Chemical Products Inc. for polyester
yarn and fiber.
Lycra - Trademark (Du Pont) for polyurethane multifilament elastic
yarn. The fused multifilaments in a bundle form a monofilament yarn
that stretches and snaps back.
mercerizing - Finish used on cotton yarns and fabrics to increase
luster, improve stretch and dyeability. Treatment consists of im-
pregnating fabrics with cold concentrated sodium hydroxide solution.
Mitin - Trademark owned by Geigy Co., Inc. for a moth-repellent finish
for woolens.
modacrylic - Generic name established by the Federal Trade Commission
for a "manufactured fiber in which the fiber-forming substance is any
long-chain synthetic polymer composed of less than 85% but at least
35% by weight of acrylonitrile units."
mordant - A metallic salt used for fixing dyes on fibers.
naphthol dye - A azo dye whose color is formed by coupling with a
naphthol. Used chiefly en cotton.
non-woven •* A material made of fibers in a web or mat generally held
together by a bonding agent.
nylon - Generic name for "a manufactured fiber in which the fiber-
forming substance is any long-chain synthetic polyamide having recurring
amide groups as an integral part of the polymer chain."
Orion - Trademark (Du Pont) for acrylic fiber.
ortho phenyl phenol - A carrier used in dyeing polyester.
package dye - A method for dyeing many cones of yarn at once by
pumping a dye solution through the yarn.
permanent finish - Fabric treatments of various kinds to improve
glaze, hand, or performance of fabrics. These finishes are durable
to laundering.
pH scale - A method used to describe acidity or alkalinity. pH 7
is neutral; above 7 - alkaline; below 7 - acid. The scale extends
from 0 to 14 and a change of 1 unit represents a tenfold change in
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acidity or alkalinity.
pigment prints - Made with insoluble pigment mixed with a binder and
thickener to form the printing paste.
pile fabric - Fabric with cut or uncut loops which stand up densely on
the surface.
polyamide - (See nylon.)
polyester - A manufactured fiber in which the fiber-forming substance
is any long-chain synthetic polymer composed of at least 85* by weight
of an ester of dihydric alcohol and terephthalic acid. (See Dacron,
Fortrel, Kodel.)
polypropylene - Basic fiber-forming substance for an olefin fiber.
precured fabric - Technique for imparting durable press by impregnating
fabrics with special resins then curing same. Does not require oven
after-treatment of apparel. (See durable press.)
Post-cured - Technique for imparting durable press that requires baking
apparel in ovens to cure fabrics that have been impregnated with special
resins. Most common technique used with polyester and cotton blends.
(See durable press.)
printing - Process of producing designs of one or more colors on a
fabric. There are several methods, such as roller, block, screen, etc.,
and several color techniques, such as direct, discharge, and resist.
print paste - A mixture containing a dye or pigment used in printing.
Generally contain gums (thickener) and a solvent. (See also pigment
prints.)
raschel - Warp-knit, similar to tricot, but coarser. Made in a wide
variety of patterns.
rayon - A generic name for man-made fibers, monofilaments, and con-
tinuous filaments, made from regenerated cellulose. Fibers produced
by both viscose and cuprammonium process are classified as rayon.
reactive dyes - Dyes that react chemically with the fiber.
resin - A chemical finish used to impart a property desired in a fabric,
such as water repellency or hand, etc. (See durable press.)
resist dye - Method of treating yarn or cloth so that in dyeing the
treated parts do not absorb the dyestuff.
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roller prints - Machine made, using engraved copper rollers, one for
each color in the pattern.
scouring - Removal of foreign components from textiles. Normal
scouring materials are alkalies (e.g., soda ash) or trisodium phos-
phate, frequently used in the presence of a surfactant. Textile
materials are sometimes scoured by use of a solvent.
screen prints - A screen of fine silk, nylon, polyester, or metal mesh
is employed. Certain areas of the screen are treated to take dye,
others to resist dye. A paste color is forced through the screen onto
the fabric by a "squeegee" to form the pattern.
sequestrant - A chemical used to bind foreign metal ions. Frequently
used in dyeing. A common sequestrant is EDTA.
size - A material applied to warp yarns to minimize abrasion during
weaving. Common sizes are starch, polyvinyl alcohol (PVOH), and
carbonxymethyl cellulcse. Sizes are applied continuously in a slasher.
softener - A chemical used to apply a soft, pleasant hand. Fat
derivatives and polyethylene are common softeners.
solution-dyed - Synthetic fibers sometimes are dyed by adding color
to the chemical polymer before fibers are formed. Also called dope
dyed.
standard raw waste load (SRWL) - A description of the properties of
waste water before treatment.
starch - Organic polymer material used as a size; highly biodegradeable.
sulfur dye - A class of dyes which dissolve in aqueous sodium sulfide
forming products with a marked affinity for cotton; the dyes are
regenerated by air oxidation.
suspended solids - Amount of solids separated by filtration of a
sample of waste water.
textured - Bulked yarns that have greater volume and surface interest
than conventional yarn of same fiber.
top chrome - Term used in application of certain dyes to wool. Involves
use of chromium compounds.
top-dyed - wool which is dyed in the form of a loose rope of parallel
fibers prior to spinning fibers into yarn.
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total organic content (TOC) - The total organic materials present in
a sample of waste water.
total oxygen demand (TOE) - The amounr. of oxygen necessary to completely
oxidize materials present in a sample of waste water.
total solids - Amount of residue obtained on evaporation of a sampla
of waste water.
triacetate - Differs from regular cellulose acetate, which is a di-
acetate. The description implies the extent of acetylaticn and
degree of solubility in acetone.
tricot - Warp-knitted fabric. Tricots are flat knitted with fine ribs
on the face (lengthwise) and ribs on the back (widthwise).
tufted fabric - Fabric decorated with tufts of multiple ply yarns.
Usually hooked by needle into fabric structure. Used widely for carpets.
vat dye - A type of dye applied from a liquor containing ailkali and a
powerful reducing agent, generally hydrosulfite. The dye is subsequently
oxidized to the colored form. Widely used on cellulosic fibers.
warp - Set of lenthwise yarns in a loom through which the crosswise
filling yarns (weft) are interlaced. Sometimes called "ends."
weaving - The process of manufacturing fabric by interlacing a series
of warp yarns with filling yarns at right angles.
yarn - An assemblage of fibers or filaments, either manufactured or
natural, twisted or laid together so as to form a continuous strand
which can be used in weaving, knitting, or otherwise made into a
textile material.
yarn-dyed - Fabrics in which the yarn is dyed before weaving or
knitting.
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METRIC UNITS
CONVERSION TABLE
MULTIPLY (ENGLISH UNITS) by TO OBTAIN (METRIC UNITS)
ENGLISH UNIT ABBREVIATION CONVERSION ABBREVIATION METRIC UNIT
acre ac
acre - feet ac ft
British Thermal
Unit BTU
British Thermal
Unit/pound BTU/lb
cubic feet/minute cfm
cubic feet/second cfs
cubic feet cu ft
cubic feet cu ft
cubic inches cu in
degree Fahrenheit F°
feet ft
gallon gal
gallon/minute gpm
horsepower hp
inches in
inches of mercury in Hg
pounds Ib
million gallons/day mgd
mile mi
pound/square
inch (gauge) psig
square feet sq ft
square inches sq in
tons (short) t
yard y
0.405
1233.5
0.252
ha
cu m
kg cal
0.555
0.028
1.7
0.028
28.32
16.39
0.555(°F-32)*
0.3048
3.785
0.0631
0.7457
2.54
0.03342
0.454
3,785
1.609
kg cal/kg
cu m/min
cu m/min
cu m
1
cu cm
°C
m
1
I/sec
kw
cm
atm
kg
cu m/day
km
(0.06805 psig +1)* atm
0.0929 sq m
6.452 sq cm
0.907 kkg
0,9144 m
hectares
cubic meters
kilogram - calories
kilogram calories/kilogram
cubic meters/minute
cubic meters/minute
cubic meters
liters
cubic centimeters
degree Centigrade
meters
liters
liters/second
killowatts
centimeters
atmospheres
kilograms
cubic meters/day
kilometer
atmospheres (absolute)
square meters
square centimeters
metric tons (1000 kilograms)
meters
* Actual conversion, not a multiplier
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