EPA-625/7-78-002
ENVIRONMENTAL POLLUTION CONTROL
TEXTILE PROCESSING INDUSTRY
U.S. ENVIRONMENTAL PROTECTION AGENCY
ENVIRONMENTAL RESEARCH INFORMATION CENTER • Technology Transfer
October 1978
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ACKNOWLEDGMENTS
This process design manual was prepared for the Environmental Research Information Center,
U.S. Environmental Protection Agency, by Lockwood Greene Engineers, Inc. Coordination
and technical review were carried out by the Environmental Sciences Technology Committee of
the American Association of Textile Chemists and Colorists. The Industrial Environmental
Research Laboratory's Chemical Processes Branch and the Effluent Guidelines Division in the
Water and Hazardous Materials Branch also reviewed the document.
NOTICE
The mention of trade names of commercial products in this publication is to present examples
of environmental control systems. This does not constitute endorsement or recommendation
for use by the U.S. Environmental Protection Agency; there may be other control devices that
are as capable as the examples presented in this handbook.
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FOREWORD
The formation of the United States Environmental Protection Agency marked a new era of
environmental awareness in America. The Agency's goals are national in scope and encom-
pass broad responsibility in the area of air and water pollution, solid wastes, pesticides, and
radiation. A vital part of EPA's national pollution control effort is the constant development
and dissemination of new technology.
It is now clear that only the most effective design and operation of air, water, and solids waste
control facilities, using the latest available techniques, will be adequate to meet the future air
and water quality objectives and to ensure continued protection of the nation's environment. It
is essential that this new technology be incorporated into the contemporary design of pollution
control facilities to achieve maximum benefit of pollution control expenditures.
The purpose of this manual is to provide the textile industry engineering community with a
new source of information for use in the planning, design, and operation of present and future
control facilities. It is recognized that there are a number of design manuals, manuals of stand-
ard practice, and design guidelines currently available in the field that adequately describe and
interpret current engineering practices as related to traditional environmental control design
concepts. It is the intent of this manual to supplement this existing body of knowledge by de-
scribing new pollution control methods and by discussing the application of new techniques for
more effectively removing a broad spectrum of contaminants from air and water discharges.
Much of the information presented is based on the evaluation and operation of pilot, demon-
stration, and full-scale plants. The design criteria thus generated represent typical values. These
values should be used as a guide and should be tempered with sound engineering judgment
based on a complete analysis of the specific application.
This manual will be updated as warranted by the advancing state-of-the-art to include new data
as they become available and to refine design criteria as additional full-scale operational infor-
mation is generated.
111
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TABLE OF CONTENTS
Chapter Page
1 INTRODUCTION
1.1 The Need for Pollution Control 1-1
1.2 Scope of Manual 1-3
1.3 Sources of Information and References 1-4
2 TREATMENT REQUIREMENTS
2.1 Introduction 2-1
2.2 EPA Industrial Guidelines 2-1
2.3 State, Basin, and Regional Water Quality Standards 2-2
2.4 Pre treatment 2-3
3 CATEGORIZATION OF THE TEXTILE INDUSTRY
3.1 Introduction 3-1
3.2 Categorization by Mill Operation 3-1
3.2.1 Wool Scouring Mill 3-3
3.2.2 Wool Finishing Mill 3-5
3.2.3 Dry Processing Mill 3-7
3.2.4 Woven Fabric Finishing Mill 3-7
3.2.5 Knit Fabric Finishing Mill 3-9
3.2.6 Carpet Mill 3-11
3.2.7 Stock and Yarn Dyeing and Finishing Mill 3-13
3.3 References 3-16
4 SOURCES AND STRENGTHS OF TEXTILE WASTEWATER
4.1 Introduction 4-1
4.1.1 Scouring 4-1
4.1.2 Bleaching 4-2
4.1.3 Dyeing and Printing 4-2
4.1.4 Special Finishes 4-2
4.1.5 Summary 4-3
4.2 Cotton Processing 4-4
4.2.1 Slashing 4-4
4.2.2 Desizing 4-5
4.2.3 Scouring; 4-5
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Chapter Page
4 SOURCES AND STRENGTHS OF TEXTILE WASTEWATER (CONT'D)
4.2.4 Mercerizing 4-6
4.2.5 Bleaching 4-7
4.2.6 Dyeing and Printing 4-8
4.2.7 Finishing 4-11
4.3 Wool Processing 4-20
4.3.1 Scouring 4-20
4.3.2 Washing After Fulling 4-21
4.3.3 Neutralization After Carbonizing 4-21
4.3.4 Bleaching 4-22
4.3.5 Dyeing 4-22
4.4 Synthetics Processing 4-28
4.4.1 Rayon 4-28
4.4.2 Acetate 4-29
4.4.3 Nylon 4-30
4.4.4 Acrylic/Modacrylic 4-30
4.4.5 Polyester 4-31
4.5 Synthetic Blends 4-43
4.6 Individual Mill Operations 4-46
4.6.1 Introduction 4-46
4.6.2 ATMI Study 4-46
4.6.3 National Commission on Water Quality Study 4-49
4.6.4 Established Mill Waste Characteristics 4-51
4.7 References 4-56
5 THE WASTE SURVEY
5.1 Introduction 5-1
5.2 Preliminary Survey 5-1
5.3 Detailed Survey 5-18
5.4 Data Evaluation 5-21
5.5 Continuing Monitoring 5-23
5.6 References 5-25
6 IN-PLANT WASTEWATER CONTROLS
6.1 Waste Volume Reduction 6-1
6.1.1 Previous Studies 6-1
6.1.2 Flow Measurement 6-3
VI
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Chapter Page
6. IN-PLANT WASTEWATER CONTROLS (CONT'D)
6.1.3 Information to Collect 6-3
6.1.4 What Are Others Doing 6-6
6.1.5 Recommended Approach 6-14
6.1.6 Waste Volume Reduction Checklist 6-23
6.2 Waste Strength Reduction 6-25
6.2.1 New Pollution-Free Solvent Wool Scouring Method 6-34
6.2.2 Wool Piece Scouring and pH 6-35
6.2.3 Waste Strength Reduction Checklist 6-37
6.3 Waste and Water Recovery and Reuse 6-39
6.3.1 Beck Cooling Water Savings 6-41
6.3.2 Case Histories 6-42
6.3.3 Waste and Water Recovery and Reuse Checklist 6-51
6.4 Chemical Substitution 6-52
6.4.1 Chemical BOD5 Lists 6-53
6.4.2 Size Substitution 6-53
6.4.3 Size Treatability 6-55
6.4.4 Foam Control 6-56
6.4.5 Wool FuUing 6-59
6.4.6 Carriers 6-59
6.4.7 Substitution for Acetic Acid in Dye Baths 6-60
6.4.8 Dyeing Wool-Replace Acetic Acid 6-60
6.4.9 Reactive Dyes 6-60
6.4.10 Dye Selection 6-60
6.4.11 Resin Selection 6-62
6.4.12 Oil and Lubricant Substitute 6-62
6.4.13 Solvents and Print Pastes 6-62
6.4.14 Phosphates 6-62
6.4.15 Nitrogen 6-63
6.4.16 Phenolics 6-63
6.4.17 Wool Scouring 6-63
6.4.18 Ammonia Mercerization 6-63
6.4.19 Chemical Inventory 6-66
6.4.20 In-Plant Textile Changes in Burlington 6-66
6.4.21 In-Plant Changes at United Piece 6-68
6.4.22 Chemical Substitution Checklist 6-70
6.5 Process Changes 6-71
6.5.1 Existing Process Modifications 6-72
6.5.2 Dyeing Process Modification 6-75
6.5.3 Preparation—Developments 6-94
vii
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Chapter Page
6 IN-PLANT WASTEWATER CONTROLS (CONT'D)
6.5.4 Reduced Processing Sequences 6-99
6.5.5 New Technology 6-105
6.5.6 Process Changes Checklist 6-106
6.6 Good Housekeeping 6-106
6.6.1 Spills 6-107
6.6.2 Organization 6-107
6.6.3 Automatic Shut-Off 6-107
6.6.4 Records 6-107
6.6.5 Degreasing 6-108
6.6.6 Curbing 6-108
6.6.7 Disposal Containers 6-108
6.7 References 6-108
7 WASTEWATER TREATMENT PROCESS SELECTION
7.1 Introduction 7-1
7.2 Wool Scouring Wastewater Treatment 7-1
7.2.1 Screening 7-2
7.2.2 Equalization 7-2
7.2.3 Flotation 7-4
7.2.4 Chemical Treatment 7-4
7.2.5 Biological Treatment 7-4
7.2.6 Sludge Treatment and Disposal 7-4
7.3 Wool Finishing Wastewater Treatment 7-4
7.3.1 Screening 7-5
7.3.2 Equalization 7-5
7.3.3 Biological Treatment 7-5
7.3.4 Chemical Treatment 7-7
7.3.5 Sludge Treatment and Disposal 7-7
7.4 Dry Processing Wastewater Treatment 7-7
7.4.1 Screening 7-8
7.4.2 Equalization 7-8
7.4.3 Chemical Treatment 7-10
7.4.4 Biological Treatment 7-10
7.4.5 Disinfection 7-10
7.4.6 Sludge Treatment and Disposal 7-10
7.5 Woven Fabric Finishing Wastewater Treatment 7-10
7.5.1 Screening 7-11
7.5.2 Biological Treatment: 7-11
viii
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Chapter Page
7 WASTEWATER TREATMENT PROCESS SELECTION (CONT'D)
7.5.3 Chemical Treatment 7-13
7.5.4 Sludge Treatment and Disposal 7-13
7.6 Knit Fabric Finishing Wastewater Treatment 7-13
7.6.1 Chemical Treatment/Air Flotation 7-14
7.6.2 Physical Treatment Using Ultrafiltration Technique 7-17
7.6.3 Biological/Chemical Treatment 7-18
7.7 Carpet Mill Wastewater Treatment 7-19
7.7.1 Latex Segregation 7-21
7.7.2 Screening 7-21
7.7.3 Biological Treatment 7-21
7.7.4 Sludge Treatment and Disposal 7-21
7.8 Stock and Yarn Dyeing and Finishing Wastewater Treatment 7-22
7.8.1 Screening 7-24
7.8.2 Equalization/Neutralization 7-24
7.8.3 Biological Treatment 7-24
7.8.4 Treatment and Disposal 7-24
7.9 Color Removal 7-25
7.9.1 Wool Scouring Wastewater 7-25
7.9.2 Wool Finishing Wastewater 7-25
7.9.3 Dry Processing Wastewater 7-25
7.9.4 Woven and Knit Fabric Finishing Wastewater 7-25
7.9.5 Carpet Mill Wastewater 7-27
7.9.6 Stock and Yarn Dyeing and Finishing Wastewater 7-27
7.10 References 7-28
8 WASTEWATER TREATMENT FACILITIES DESIGN
8.1 Introduction 8-1
8.2 Basic Design Considerations 8-1
8.2.1 In-Plant Changes 8-1
8.2.2 Degree of Treatment Required 8-2
8.2.3 Anticipated Treatment Efficiencies 8-2
8.2.4 Design Period 8-3
8.2.5 Future Expansion 8-3
8.2.6 Seasonal Considerations 8-3
8.2.7 Costs 8-3
8.2.8 Degree of Automation 8-3
8.2.9 Sludge Disposal Methods 8-3
8.2.10 Multiple Units and Emergency Power 8-3
ix
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Chapter
8 WASTEWATER TREATMENT FACILITIES DESIGN (CONT'D)
8.2.11 Design Standards 8-4
8.3 Site Requirements 8-4
8.3.1 Topography 8-4
8.3.2 Buffer Zone 8-5
8.3.3 Flood Plains 8-5
8.3.4 Subsurface Groundwater 8-5
8.3.5 Soil Condition 8-5
8.3.6 Existing Facilities 8-5
8.3.7 Receiving Stream 8-5
8.3.8 Future Expansion 8-5
8.3.9 Miscellaneous 8-6
8.4 Sewers and Pumps 8-6
8.4.1 Gravity Sewers 8-6
8.4.2 Centrifugal Pumps 8-6
8.4.3 Positive Displacement Pumps 8-7
8.4.4 Rotary Screw Pumps 8-7
8.4.5 Air Pumps 8-7
8.4.6 Pumping Stations 8-7
8.5 Suspended Solids Removal 8-7
8.5.1 Screening and Comminution 8-8
8.5.2 Clarification 8-16
8.5.3 Filtration 8-20
8.5.4 Flotation 8-23
8.6 Equalization 8-24
8.7 Neutralization 8-28
8.8 BOD/COD Reduction 8-31
8.8.1 Lagoons 8-32
8.8.2 Activated Sludge 8-35
8.8.3 Nutrient Addition 8-39
8.8.4 Fixed Film Biological Reactors 8-39
8.8.5 Activated Sludge Catalyst 8-44
8.8.6 Chemical Coagulation 8-46
8.8.7 Polishing Ponds 8-47
8.9 Oil and Grease Reduction 8-52
8.10 Chrome Removal 8-52
8.11 Color Removal 8-55
8.11.1 Chemical Precipitation 8-57
8.11.2 Activated Carbon Adsorption 8-58
8.11.3 Synthetic Resin Adsorption 8-62
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Chapter Page
8 WASTEWATER TREATMENT FACILITIES DESIGN (CONT'D)
8.11.4 Ozonation 8-64
8.11.5 Hyperfiltration 8-66
8.12 Other Pollutants Removal 8-67
8.12.1 Phenolics 8-67
8.12.2 Metals 8-69
8.12.3 Sulfide 8-69
8.12.4 Detergents 8-69
8.12.5 Phosphate 8-70
8.12.6 Nitrogen 8-70
8.13 Sludge Treatment 8-70
8.13.1 Aerobic Digestion 8-72
8.13.2 Sludge Thickening 8-73
8.13.3 Dewatering 8-75
8.13.3.1 Drying Beds 8-75
8.13.3.2 Drying Lagoons 8-79
8.13.3.3 Vacuum Filtration 8-80
8.13.3.4 Centrifugation 8-82
8.13.3.5 Pressure Filtration 8-82
8.14 Sludge Disposal 8-85
8.14.1 Spray Irrigation 8-85
8.14.2 Landfill 8-87
8.14.3 Incineration 8-89
8.15 Disinfection 8-89
8.15.1 Chlorination 8-89
8.15.2 Ozonation 8-92
8.16 Emerging Technology 8-92
8.16.1 Pure Oxygen Activated Sludge 8-92
8.16.2 Ultrafiltration 8-94
8.16.3 Hyperfiltration 8-95
8.16.4 Ion Exchange 8-95
8.16.5 Electrodialysis 8-96
8.16.6 Evaporation 8-97
8.16.7 Freezing 8-97
8.16.8 Spray Irrigation 8-98
8.16.9 Algae Harvesting 8-99
8.17 Upgrading Existing Facilities 8-99
8.18 Laboratory Requirements 8-102
8.18.1 Laboratory Facilities 8-104
8.18.2 Reporting Laboratory Results 8-107
8.19 References 8-108
xi
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Chapter Page
9 AIR POLLUTION
9.1 Introduction — Emission Sources 9-1
9.2 Available Abatement Equipment 9-3
9.2.1 Incineration and Chemical Destruction 9-3
9.2.2 Dry Collection Methods 9-10
9.2.2.1 Gravity and Centrifugal Collectors 9-11
9.2.2.2 Filters 9-14
9.2.2.3 Electrostatic Precipitators 9-23
9.2.2.4 Adsorption 9-24
9.2.3 Scrubbers 9-26
9.2.3.1 Gas-Liquid Scrubbing 9-26
9.2.3.2 Scrubbing for Particulate Removal 9-29
9.3 Elimination of Oil and Acid Mists and Associated Pollutants 9-41
9.3.1 Design Considerations 9-41
9.3.2 Emissions Preconditioning 9-44
9.3.3 Process Modifications 9-46
9.3.4 Electrostatic Precipitators 9-46
9.3.5 High Efficiency Fiber Mist Eliminators 9-47
9.3.6 Incineration 9-47
9.3.7 Scrubbing 9-47
9.3.8 High Velocity Air Filters 9-48
9.3.9 Elimination of Acid Mists 9-49
9.4 Heat Recovery Systems 9-49
9.4.1 Economics and Feasibility of Heat Recovery 9-50
9.4.2 General Considerations 9-52
9.4.3 Air-Water Exchangers 9-53
9.4.4 Air-Air Exchangers 9-53
9.4.5 Heat Exchangers Employing Transfer Fluid 9-56
9.5 Solvent Recovery 9-56
9.5.1 Process Description 9-56
9.5.2 Installation and Operation 9-59
9.6 Odor Abatement 9-61
9.6.1 Introduction 9-61
9.6.2 Process Modifications or Chemical Substitution 9-62
9.6.3 Dilution 9-63
9.6.4 Masking and Modification 9-65
9.6.5 Scrubbing 9-66
9.6.6 Dry Adsorption 9-67
xn
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Chapter Page
9 AIR POLLUTION (CONT'D)
9.6.7 Incineration and Chemical Destruction 9-68
9.7 Lint and Dust Removal 9-68
9.8 References 9-72
10 PERSONNEL REQUIREMENTS
10.1 Introduction 10-1
10.2 Adjustment Factors 10-1
10.3 Estimating Annual Manhours 10-2
10.4 References 10-5
11 DESIGN PARAMETER CHECKLIST
11.1 General Process Data 11-1
11.2 Treatment Unit Design 11-6
APPENDIX
A Glossary A-l
B Metric Conversion Chart B-l
C Definitions of Manufacturing Operation C-l
D BOD of Textile Chemicals D-l
E ATMI-CRI Wastewater Survey E-l
F National Commission on Water Quality Survey F-l
G List of Trade Organizations and Journals G-l
xin
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LIST OF FIGURES
Figure No. Page Page
1-1 Textile Industry Distribution 1-1
2-1 EPA Organization Chart 2-3
3-1 Textile Industry Categorization by Fiber Processed 3-2
3-2 Wool Scouring Mill 3-4
3-3 Wool Finishing Mill 3-6
3-4 Dry Processing Mill 3-8
3-5 Woven Fabric Finishing Mill 3-10
3-6 Knit Fabric Finishing Mill 3-12
3-7 Carpet Mill 3-14
3-8 Stock and Yarn Dyeing and Finishing Mill 3-15
5-1 Water Distribution System for a Finishing Plant 5-3
5-2 Formulas for Flow Measurement by Various Devices 5-6 & 5-7
5-3 Sewer System Schematic for Waste Survey 5-8
5-4 Seven Typical Methods for Sampling Wastes 5-9 & 5-10
5-5 Typical Preliminary Results of BOD and Flow as a Function
of Time 5-13
5-6 Dye Range Material Balance 5-15
5-7 Mercerizer and Washer Material Balance 5-16
5-8 Detailed Survey Sampling Points 5-19
5-9 Graphical Results of Detailed Survey 5-22
5-10 Typical Data for Determining Treatability of Process Chemicals 5-24
6-1 Flexible Flow Measurement Device with Leak Detector 6-4
6-2 Weir Box with V-Notch Weir and Hook Gauge 6-5
6-3 Water Usage in Scouring Processes 6-6
6-4 Water Usages: Rope Washing of Cotton Fabrics 6-7
6-5 Rope Washing of Cotton Fabrics: Machine Loading Effects 6-7
6-6 Water Usage for Various Equipment 6-9
6-7 Jig Dyeing — Effect of Cloth Weight and Dyeing Process 6-10
6-8 Scouring Range Material Balance 6-15
6-9 Energy Conservation on the Continuous Range 6-17
6-10 Influence of Design Parameters on Improved Washing 6-20
6-11 Compression of Load Dyeing Using Dye Springs 6-23
6-12 Automatic Control of Chemicals 6-26
6-13 Automatic vs. Manual Chemical Control 6-27
6-14 Points of Application — Automatic Chemical Control 6-27
xiv
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LIST OF FIGURES - Continued
Figure No. Page
6-15 Wet Processing Monitor for Carpets 6-28
6-16 Wet Processing Monitor Chart 6-29
6-17 Schematic of Pad-Batch Unit 6-34
6-18 Continuous Plasma Treatment of Textiles 6-37
6-19 FHR System 6-43
6-20 Variations In Permanganate Value 6-45
6-21 Modified Scouring Dolly for Reuse of Wash-Off Water 6-46
6-22 PVA Recovery System Flow Chart 6-47
6-23 PVA Recovery Operational Cost 6-48
6-24 PVA Recovery of J.P. Stevens Plant 6-48
6-25 Pilot Plant Treatment of Piece Scouring Effluent 6-50
6-26 Acid Cracking Process for Recovery of Wool Grease 6-50
6-27 Centrifugal Separation of Wool Grease 6-51
6-28 PVA/COD Removal - Pilot Activated Sludge Units 6-55
6-29 Measurement of Biodegradation by the River Die-Away Test 6-58
6-30 Approximate Energy Requirements to Dye 100 Pounds of Fabric 6-64
6-31 Bleaching Process Modification 6-72
6-32 Bleach Range Water Lines 6-73
6-33 Mercerizing Range Piping 6-76
6-34 Markal B (Minute Bleach) Range 6-82
6-35 Dow Pilot Solvent Slasher 6-82
6-36 Dow Solvent Desize Process 6-83
6-37 Continuous Solvent Scouring Machine 6-83
6-38 Superheated Perchloroethylene Fixation Unit 6-85
6-39 STX Solvent Dyeing Process 6-87
6-40 STX Exhaustion Graph 6-87
6-41 Duobond Continuous Solvent Scour Range 6-88
6-42 Jeffries Aqueous Scouring of Knits 6-89
643 RAM Dyeing System 6-90
6-44 Duralized Process 6-92
6-45 Farmer Norton Vacuum Impregnator 6-93
6-46 Caustic-Peroxide Saturator & Vaporloc Reaction Unit 6-95
6-47 Chainless Mercerizer 6-96
6-48 Jet Dyeing vs. Beck Dyeing 6-97
6-49 Schematic of Aqualuft Machine 6-98
6-50 Transfer Printing Equipment 6-101
6-51 Taylor 1010 System for Dyehouse Control 6-102
6-52 Layout of Package Dye Operation 6-103
6-53 Triatex MA System 6-105
6-54 Ultrafiltration System 6-105
xv
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LIST OF FIGURES - Continued
Figure No. Page
7-1 Wool Scouring Wastewater Treatment Model Schematic Meeting 7-3
1977 (BPT) Limitations
7-2 Wool Finishing Wastewater Treatment Model Schematic Meeting 7-6
1977 (BPT) Limitations
7-3 Dry Processing Wastewater Treatment Model Schematic Meeting 7-9
1977 (BPT) Limitations
7-4 Woven Fabric Finishing Wastewater Treatment Model 7-12
Schematic Meeting 1977 (BPT) Limitations
7-5 Knit Fabric Finishing Wastewater Treatment Model Schematic 7-15
Meeting 1977 (BPT) Limitations (High Oil Content)
7-6 Knit Fabric Finishing Wastewater Treatment Model Schematic 7-16
Meeting 1977 (BPT) Limitations (Low Oil Content)
7-7 Carpet Mill Wastewater Model Schematic Meeting 1977 7-20
(BPT) Limitations
7-8 Stock and Yarn Dyeing and Finishing Wastewater Treatment 7-23
Model Schematic Meeting 1977 (BPT) Limitations
8-1 Comminutor With Rotating Screen 8-8
8-2 Hand Cleaned Bar Rack 8-9
8-3 Mechanically Cleaned Bar Rack 8-10
8-4 Vibrating Screen 8-11
8-5 Hydrasieve 8-12
8-6 Revolving Drum Screen 8-13
8-7 Settling Basin 8-17
8-8 Clarifier Section 8-19
8-9 Gravity-Type Filter 8-22
8-10 Pressure-Type Filter 8-23
8-11 Dissolved Air Flotation System with Recycle Flow Pressurization 8-25
8-12 Earthen Equalization Basin 8-27
8-13 Control of Variable pH 8-29
8-14 pH Control System 8-31
8-15 Oxygenation and Mixing Devices 8-34
8-16 Activated Sludge Processes 8-36
8-17 Nitrogen Feed System 8-40
8-18 Bio-Oxidation Tower 8-40
8-19 Biological Rotating Disk 8-43
8-20 Powdered Activated Carbon 8-45
8-21 Granular Activated Carbon 8-46
8-22 Chemical Coagulation Flow Diagram and Section 8-48
xvi
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LIST OF FIGURES - Continued
Figure No. Page
8-23 Solids Contact Clarifier 8-49
8-24 Chromium Removal Process 8-54
8-25 Carbon Adsorption System 8-61
8-26 Resin Adsorption System 8-63
8-27 Ozone Treatment System 8-65
8-28 Hyperfiltration (Reverse Osmosis) Treatment System 8-68
8-29 Sludge Handling, Dewatering and Disposal 8-71
8-30 Circular Aerobic Digester 8-72
8-31 Gravity Thickener 8-74
8-32 Sludge Drying Bed 8-77
8-33 Wedgewire Drying Bed 8-79
8-34 Rotary Vacuum Filter System 8-81
8-35 Continuous Countercurrent Solid Bowl Centrifuge 8-83
8-36 Cutaway View of Filter Press 8-84
8-37 Spray Irrigation 8-86
8-38 Sanitary Landfill 8-88
8-39 Chlorination 8-91
8-40 Ozone Injection Methods 8-93
8-41 Pure Oxygen Activated Sludge System 8-94
9-1 Direct Fume Incineration Fuel Costs With No Heat Recovery 9-6
9-2 Total Fuel Costs For Direct Fume Incineration Without Heat 9-6
Recovery
9-3 Catalytic Incinerator 9-9
9-4 Cyclone Scrubber 9-13
9-5 Efficiency of Cyclone With and Without Fabric After Filter 9-14
9-6 Bag House 9-15
9-7 Filtration Efficiency For Oil Mists 9-16
9-8 Brownian Displacement of Small Particles 9-17
9-9 High Efficiency Fiber Mist Eliminator 9-18
9-10 High Efficiency and High Velocity Filter Elements 9-19
9-11 High Velocity Filter System 9-22
9-12 Cyclone Spray Chamber 9-28
9-13 Efficiency of Inertial Impaction 9-31
9-14 Relation of Target Efficiency to Separation Number 9-31
9-15 Efficiency of Various Types of Scrubbers 9-31
9-16 Orifice of an Impingement Scrubber 9-33
9-17 Fluidized - Bed Scrubber 9-33
9-18 Orifice Scrubbers 9-34
xvii
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LIST OF FIGURES - Continued
Figure No. Page
9-19 Yenturi Scrubber 9-35
9-20 Water-Jet Scrubber 9-37
9-21 Two-Phase Flashing Water Jet Scrubber 9-37
9-22 Mechanical Scrubber 9-39
9-23 Flux Force Condensation Scrubber 9-40
9-24 Charged Droplet Scrubber 9-40
9-25 Ionizing Wet Scrubber 9-42
9-26 Electrostatically Enhanced Scrubber System 9-43
9-27 Recoverable BTU/Hr. vs. CFM Exhaust 9-51
9-28 Annual Savings From Heat Recovery 9-51
9-29 Rotary Seal Heat Wheel 9-55
9-30 Heat Pipe 9-55
9-31 Typical Solvent Recovery System for Continuous Drycleaner 9-57
9-32 Spread of Contaminants From A Stack 9-64
xvin
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LIST OF TABLES
Table No. Page
3-1 Textile Industry Categorization by Mill Operation 3-3
4-1 Chemicals Present In Cotton and Wool Dyebaths 4-10
4-2 BOD Contributed By Cotton Fabric Manufacturing Processes 4-12
4-3 TSS Contributed By Cotton Fabric Manufacturing Processes 4-13
4-4 TDS Contributed By Cotton Fabric Manufacturing Processes 4-14
4-5 Characteristics of Wastewater By pH From Cotton 4-15
Manufacturing Processes
4-6 Color Contributed By Cotton Fabric Manufacturing Processes 4-16
4-7 Oil and Grease Contributed By Cotton Fabric Manufacturing 4-17
Processes
4-8 Toxic Material/Detergent Contributed By Cotton Fabric 4-18
Manufacturing Processes
4-9 Comparison of Wastewater Characteristics from Cotton Fabric 4-19
Manufacturing Processes
4-10 BOD Contributed By Wool Wet Processes 4-24
4-11 Total Solids Contributed By Wool Wet Processes 4-25
4-12 Characteristics of Wastewater By pH From Wool Wet Processes 4-26
4-13 An Example of Pollutional Loads Contributed By Wool Wet 4-26
Processes
4-14 Comparison of Wastewater Characteristics From Wool Wet 4-27
Processes
4-15 BOD Loads Contributed By Rayon Fiber Processes 4-33
4-16 Total Solids and Total Suspended Solids Contributed By Rayon 4-33
Fiber Processes
4-17 An Example of Pollutional Loads Contributed By Rayon Fiber 4-34
Processes
4-18 BOD Loads Contributed By Acetate Fibers 4-35
4-19 Total Solids and Total Suspended Solids Contributed By 4-35
Acetate Fiber Processes
4-20 An Example of Pollutional Loads Contributed By Acetate Fiber 4-36
Processes
4-21 BOD Loads Contributed By Nylon Fiber Processes 4-37
4-22 Total Solids and Total Suspended Solids Contributed By Nylon 4-37
Fiber Processes
4-23 An Example of Pollutional Loads Contributed By Nylon Fiber 4-38
Processes
XIX
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LIST OF TABLES - Continued
Table No. Page
4-24 BOD Loads Contributed By Acrylic/Modacrylic Fiber Processes 4-39
4-25 Total Solids and Total Suspended Solids Contributed By 4-39
Acrylic/Modacrylic Fiber Processes
4-26 An Example of Pollutional Loads Contributed by Acrylic/ 4-40
Modacrylic Fiber Processes
4-27 BOD Loads Contributed By Polyester Fiber Processes 4-41
4-28 Total Solids and Total Suspended Solids Contributed By 4-41
Polyester Fiber Processes
4-29 An Example of Pollutional Loads Contributed By Polyester 4-42
Fiber Processes
4-30 Pollutional Loads Contributed By 50/50 Cotton/Polyester 4-44
Blend Fabric Manufacturing Processes
4-31 Pollutional Loads Contributed By 50/50 Cotton/Polyester Blend 4-45
Fabric Manufacturing Processes, Dyeing Including Scouring or
Partial Bleaching
4-32 Established Wastewater Characteristics Wool Scouring Mills 4-52
4-33 Established Wastewater Characteristics Wool Finishing Mills 4-52
4-34 Established Wastewater Characteristics Dry Processing Mills 4-53
4-35 Established Wastewater Characteristics Woven Fabric Finishing 4-53
Mills
4-36 Established Wastewater Characteristics Knit Fabric Finishing Mills 4-54
4-37 Established Wastewater Characteristics Integrated Carpet Mills 4-54
4-38 Established Wastewater Characteristics Stock and Yarn Dyeing 4-55
and Finishing Mills
5-1 Methods of Flow Measurement for Incoming Water and 5-2
Wastewater
5-2 Comparison of Flow-Measurement Techniques 5-4 & 5-5
5-3 Test Methods Recommended By The EPA 5-11
5-4 Sample Preservation Requirements for Various Parameters 5-12
5-5 Preliminary Survey Analytical Requirements on Samples Collected 5-13 & 5-14
5-6 List of Items for Textile In-Plant Surveys 5-16
5-7 Example of Annual Chemical Usage, 1972 5-17
5-8 Detailed Survey Analytical Schedule 5-20
5-9 Listing of Miscellaneous Pollution Sources 5-21
XX
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LIST OF TABLES - Continued
Table No. Page
6-1 Water Usage of Wool Wet Processes 6-1
6-2 Water Usage of Cotton Processing Waste 6-2
6-3 Water Usage of Manmade Wet Fibers Processes 6-2
6-4 Water Usage In Washing Processes 6-8
6-5 Jig Dyeing Water'Usages Compared 6-10
6-6 Water Use Comparison 6-11
6-7 Caustic Removal In Various Washers 6-18
6-8 Flexibility Indicated By Tensitrol Washer 6-19
6-9 Newer Type Washing Machines 6-21
6-10 BOD Loadings of Polyester Dye Carriers 6-30
6-11 Scoured and Dyed Polyester 6-31
6-12 BOD Loads of Vat and Disperse Dyeing of 50/50 Cotton/Polyester 6-32
6-13 FishToxicity 6-33
6-14 Comparison of BOD Loads of Starch and PVA Sizing 6-38 & 6-39
6-15 Water Quality Requirements In Wool Processing 6-44
6-16 Cotton Finishing Process Chemicals Consumption and BOD 6-54
6-17 Size Effluent Comparison - COD 6-56
6-18 Dye Solution 6-57
6-19 Ideal Energy Consumption for Package Exhaust Dyeing 6-61
6-20 Energy Consumption of Commonly Used Continuous Systems 6-62
6-21 Example of Annual Chemical Usage, 1972 6-66
6-22 Environmental Properties of Biphenyl 6-67
6-23 In-Plant Chemical Changes and BOD Effects 6-68
6-24 Foam-Hampered Performance Data 6-69
6-25 Changes in Performance with Foam Control 6-69
6-26 Rapid COD Results on Textile Chemicals 6-70
7-1 Wool Scouring Wastewater Parameters 7-2
7-2 Wool Finishing Wastewater Parameters 7-5
7-3 Dry Processing Wastewater Parameters 7-8
7-4 Woven Fabric Finishing Wastewater Parameters 7-11
7-5 Knit Fabric Finishing Wastewater Parameters 7-14
7-6 Integrated Carpet Mill Wastewater Parameters 7-19
7-7 Stock and Yarn Dyeing and Finishing Wastewater Parameters 7-22
8-1 Anticipated Treatment Removal Efficiencies 8-2
8-2 Design Parameters for Screens 8-14
8-3 Design Parameters for Clarifiers 8-18
8-4 Design Parameters — Multi-Media Filtration 8-21
xxi
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LIST OF TABLES - Continued
Table No. Page
8-5 Flotation Design Parameters 8-24
8-6 Design Parameters for Equalization 8-27
8-7 Neutralization System Design Parameters 8-30
8-8 Suggested Design Parameters for Aerated Lagoons 8-35
8-9 Extended Aeration Design Parameters 8-38
8-10 Trickling Filter Design Parameters 8-42
8-11 Roughing Filter Design Parameters 8-42
8-12 Activated Carbon Catalyst Design Parameters 8-44
8-13 Chemical Coagulation Design Parameters 8-49
8-14 Design Parameters for Polishing Ponds 8-50
8-15 Chromium Removal Design Parameters 8-53
8-16 Coagulation and Adsorption: Best Means of Decolorization by 8-56
Dye Class
8-17 Treatment of Textile Dye Wastes by Chemical Coagulation 8-57
8-18 Textile Industry Wastewater Survey Summary of Adsorption 8-59
Isotherm Results
8-19 Activated Carbon Adsorption Design Parameters 8-62
8-20 Synthetic Resin Adsorption Design Parameters 8-64
8-21 Membrane Characteristics 8-66
8-22 Summary of Performance of Hyperfiltration Modules in 8-67
Demonstration Pilot Plant
8-23 Design Parameters for Aerobic Digesters 8-73
8-24 Gravity Thickening Design Parameters 8-73
8-25 Criteria for the Design of Sandbeds 8-76
8-26 Chlorination Design Parameters 8-91
8-27 Ozonation Design Parameters 8-92
8-28 Upgrading Existing Facilities (Increase BOD, TSS Removal) 8-100
8-29 Upgrading Existing Facilities (Increase Color Removal) 8-101
8-30 Upgrading Existing Facilities (Disinfection Requirement) 8-101
8-31 Upgrading Existing Facilities (Maintain Required D.O. 8-101
Concentration)
8-32 Typical Performance Tests of Effluent Required for Regulatory 8-102
Agencies
8-33 Additional Tests Suggested for Process Control, Cost Control 8-103
and Historical Knowledge
8-34 Laboratory Tests of Aeration Compartments in the Activated 8-104
Sludge System Plants
8-35 Reporting Laboratory Results 8-107
xxn
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LIST OF TABLES - Continued
Table No. Page
9-1 Basic Air Pollution Control Equipment 9-4
9-2 Symbol Table for Chapter 9 9-71
10-1 Personnel Requirements — Category 1 10-3
10-2 Personnel Requirements — Category 2 10-3
10-3 Personnel Requirements — Category 3 10-3
10-4 Personnel Requirements — Category 4 10-4
10-5 Personnel Requirements — Category 5 10-4
10-6 Personnel Requirements — Category 6 10-4
10-7 Personnel Requirements — Category 7 10-4
xxm
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CHAPTER 1
• INTRODUCTION
1.1 The Need for Pollution Control
A recent inventory of the textile industry conducted by Lockwood Greene Engineers, Inc., in-
dicated that there are approximately 5,366 textile operation locations within the United States.
Of this number, 1,588 of the plants contacted did not submit process data. Based upon an
employee count of the no data group, it is estimated these no data mills represent less than 18%
of the industry and less than 12% of wet manufacturing. Of the 3,778 plants which did submit
data, 1,926 plants indicated some type of wet manufacturing process, including slashing opera-
tions, and 1,852 indicated either dry process manufacturing or had no manufacturing at all.
Figure 1-1 illustrates the industry distribution found by this inventory.
5854 Locations
I 1
488 Non Textiles 5366 Textiles
I I
3778 - With Data 1588 - No Data
1852 Dry 1926 Wet
192-No Mfg. 1660 - With Mfg.
FIGURE 1-1
TEXTILE INDUSTRY DISTRIBUTION
Pollution by air emissions and wastewater effluents from many of the 5,366 textile mills pre-
sents an environmental problem in several regions of the United States. Large volumes of waste-
water are generated, and treatment is sometimes difficult because of the character of the waste.
Textile processing plants utilize a wide variety of dyes and other chemicals such as acids, bases,
salts, wetting agents, retardants, accelerators, detergents, oxidizing agents, reducing agents, de-
velopers, stripping agents, and finishes. Many of these are not retained in the final textile prod-
uct but are discarded after they have served their purpose or are driven off into the atmosphere
during heat treatment. The liquid waste effluent and the atmospheric exhaust of a textile plant
1-1
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may, therefore, contain any combination of such materials. Also, since many textile processes
are handled on a batch basis, concentrations of waste materials may fluctuate widely. Specifi-
cally, with regards to textile waste, solids may be present from fibrous substances, process
chemicals, and also as a result of biological wastewater treatment. The solids can affect the
natural aquatic environment by hindering oxygen transfer and reducing light penetration.
Solids that settle on the stream bottom can cover the flora and fauna and result in an anaerobic
sludge layer.
Organic substances in textile waste such as dyes, starches, and detergents are another form of
pollutant which may undergo chemical or biological changes and consume dissolved oxygen
from the receiving water. Such organic substances should be removed to prevent septic or low
dissolved oxygen conditions and obnoxious odors and to avoid rendering the receiving water
unsuitable for municipal, industrial, agricultural, residential and recreational use.
The presence of inorganic salts in high concentrations may make the receiving water unsuitable
for most industrial and municipal uses. Foaming from detergents and colors from dyes are
esthetically objectionable, particularly in drinking and recreational waters. Certain carrier
chemicals used in dyeing, such as phenols, add tastes and odors. Metal toxicity from inorganic
salts of chromium and zinc can be harmful to aquatic life if it does occur. Nitrogen and phos-
phorous from dyes may cause eutrophication problems in receiving waters. In many instances,
even the pH of the textile dyeing and finishing wastes could cause problems in the receiving
streams by upsetting the ecosystem.
Thermal wastes, such as cooling waters, are another source of pollution. Heat may reduce the
amount of oxygen by increasing the consumption of oxygen by biota in the receiving water
and decrease the saturation concentration of dissolved oxygen. Also, thermal waste is detri-
mental to cool water loving species of aquatic life. Perhaps more important to aquatic life is an
upset due to fluctuation of temperature caused by the periodic discharge of cooling water into
the receiving streams. As a result sensitive organisms could be eliminated causing an imbalance
in the biological community.
In the textile industry, some processes require highly acid conditions while others are highly
alkaline. Consequently, wastewater pH can vary greatly over a period of time, and some form of
neutralization and/or equalization is necessary. The degree of neutralization/equalization will
depend upon the extremes of the pH and the alkalinity/acidity of the wastewaters. Biological
wastewater treatment inherently provides an effluent with acceptable pH for discharge to the
receiving stream.
Grease and oil are harmful to biological systems as well as being aesthetically damaging to the
environment; therefore, concentrations in the effluent should be limited. They are especially
prevalent in wool scouring processes. Often sanitary waste is treated with the industrial waste-
waters necessitating the control of bacteria and viruses. Chlorination may be needed with fecal
coliform limits based upon sanitary system guidelines.
1-2
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Operational difficulties in a conventional waste treatment plant may be caused by the pres-
ence of compounds upsetting to treatment plant biota or by fluctuations in the concentration
of components of the waste. Poor results are obtained when materials resistant to biological
attack are passed through biological treatment processes. Such inadequately treated effluents
have very deleterious effects on receiving streams, and the situation is intensified when the
stream flow is small or industry is concentrated in a particular area.
The most significant sources of possible air pollution in the textile industry are the various
heat treatment processes, such as tentering, texturizing, drying, curing, etc., which cause boil-
off of previously applied skimming oils, plasticizers, dye carriers, and finish chemicals. These
condense into opaque, or odorous, and often corrosive mists called blue haze.
Solvent processes, such as solvent scouring and dyeing, can release solvent vapors if the recovery
system is not working properly. Carriers for polyester dyeing, formaldehyde from resin finishes,
and commonly released chemicals may cause odor problems. Dust and lint are released by vir-
tually every operation, especially by those preceding skimming.
The textile industry is dynamic with constantly changing manufacturing processes and result-
ing wastewaters and atmospheric exhausts.
1.2 Scope of Manual
This manual contains information relating to the design of air, water and solids pollution abate-
ment systems for the textile industry. It is intended for use by process design engineers, consul-
tants, and engineering companies active in the design or upgrading of textile waste treatment
facilities.
This manual outlines typical operations used in the manufacture of various types of fabrics as
well as sources and strengths of wastewater, air pollutants and solid waste. Design information
relative to pollution abatement includes in-plant control measures, equipment selection factors
and emerging technology.
The major effort of this manual is directed toward design information of those techniques
most widely used and fully demonstrated for pollution control in the textile industry. Advanced
technology, pilot plant or demonstration data of presumptive operations, although addressed,
will not be covered in detail.
Water pollution control in the textile industry is the major subject covered in this manual.
Portions of the manual include comprehensive descriptions and analyses of the various waste-
water sources and provide the basic data for facility design. Inplant controls are described for
reducing the quantity and/or strength of the wastewater, and waste treatment designs are de-
fined along with information for proper equipment selection.
1-3
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1.3 Sources of Information and References
Much of the basic information and data in this manual was taken from previously published
EPA documents. Chapter 3 entitled "Categorization of the Textile Industry" was written based
on the information contained in: (1) the Federal Register, Friday, July 5, 1974, Volume 39,
Number 130, Part II, Environmental Protection Agency, Textile Industry Point Source Cate-
gory; Effluent Guidelines and Standards and Corrections in Volume 39, Number 163, Wednes-
day, August 21, 1974 and (2) the Development Document for Proposed Effluent Limitations
Guidelines and New Source Performance Standards for the Textile Mills Point Source Category,
U.S. Environmental Protection Agency, June, 1974.
The "Blue Book" developed by the Institute of Textile Technology and Hydroscience, Inc.
entitled Recommendations and Comments for the Establishment of Best Practicable Waste-
water Control Technology Currently Available for the Textile Industry for the American
Textile Manufacturers Institute, Inc. and the Carpet and Rug Institute also provided very in-
formative and useful information.
Chapter 4, entitled "Sources and Strengths of Textile Wastewater," was based on three ex-
cellent publications developed under EPA contract. The majority of the basic data is taken from
work by Arthur D. Little, Inc. and described in their report to the EPA entitled Industrial
Waste Studies Program, Textile Mill Products. Work by Dr. John J. Porter of Clemson Univer-
sity for the EPA entitled State of the Art of Textile Waste Treatment was also invaluable in
providing the data summarized in Chapter 4. The third publication developed for the EPA
which provided much information was prepared by Metcalf & Eddy, Inc., Engineers and entitled
Upgrading Textile Operations to Reduce Pollution. Although other publications were used in
the development of the basic data chapters of this manual, the aforementioned documents
are highly recommended for additional reading.
Chapter 5, entitled "The Waste Survey," was taken from the EPA publication entitled Upgrading
Textile Operations to Reduce Pollution and was prepared by T.L. Rinker of Blue Ridge —
Winkler Textiles, Bangor, Pennsylvania.
Chapter 6, entitled "Inplant Controls," was prepared by the Institute of Textile Technology
located in Charlottesville, Virginia.
Chapters 7 and 8, involving wastewater treatment were based upon Lockwood Green's in-house
expertise, discussions with mill engineers, equipment manufacturers and previous EPA publi-
cations in this subject area.
Special recognition is due to Joseph W. Masselli, Nicholas W. Masselli and M.G. Burford of
Wesleyan University for their continuing work in the textile industry. Much of each document
mentioned above is based on data and information provided by them.
1-4
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Chapter 9, entitled "Air Pollution", was based in part on the references listed at the end of the
chapter. It also relies on information obtained in communications from mill personnel, equip-
ment vendors, state and federal enforcement officers, and on the personal experience of the
chapter author. The author is especially indebted to Mr. John Romans and Mr. Jim Hawkes
of the North Carolina State Board of Water and Air Resources, Mr. Michael R. Beltran of
Beltran Associates, and Mr. Raymond Allen of Deering Milliken, Inc.
1-5
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CHAPTER 2
TREATMENT REQUIREMENTS
2.1 Introduction
The degree of treatment required prior to the discharge of textile waste is dependent upon
several factors. If discharge is into a receiving stream, state, regional, federal, or any combina-
tion of all three agencies may become involved in dictating the effluent characteristics of the
treated waste flow. If, on the other hand, discharge is into a municipal sewer system, the local
municipality may become the governing agency.
At the present time, the federal enforcement agency (EPA) governs waste discharges by re-
stricting the pounds of pollutants discharged based on pounds of product produced. The con-
centration of pollutants allowed in the effluent is therefore dependent upon the amount of
water used in producing the particular product. The EPA approach provides a basic level of
treatment and also promotes the conservation of water during manufacturing. The EPA guide-
lines do not account for receiving stream size and quality. However, by providing stream quality
limitations the Regional or State agencies protect those streams which do not have the ability
to assimilate those pollutants allowed under the EPA guidelines. In cases where stream quality
protection is required, the effluent limitations on pollutants are generally more stringent than
those established by EPA. In addition to closer regulation of effluent concentrations, many
State pollution control agencies may impose additional controls which include limitations of
additional specific pollutants or limitations of the quantity of waste discharged based on the
receiving stream 7 day 10 year (7Q10) low flow.
Local regulatory agencies such as sewer districts, municipalities, etc., often require a greater
degree of treatment than either the Federal or State Authorities. Local ordinances may pro-
hibit the discharge of any metal ions, severely limit the quantity of color, temperature or even
BOD and suspended solids.
2.2 EPA Industrial Guidelines
Discharge of industrial wastewaters is regulated by the Federal Water Pollution Control Act
Amendments of 1972 (PL 92-500) as amended by The Clean Water Act of 1977. The Act pro-
vides for the establishment of nationally applicable effluent limitations on an industry-by-industry
basis.
The Clean Air Act of 1970 specifies standards of performance for new stationary sources
(Section 111) and emission standards for hazardous air pollutants (Section 112). The Clean
Air Act Amendments of 1977 (PL95-95) made extensive changes in the Clean Air Act; however,
specific federal standards for the textile industry have not been promulgated to date.
2-1
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The purpose of this manual is to provide the latest multi-media technology for the textile
industry. It is not intended to provide enforcement or regulatory guidance. The reader should
contact the agency representatives that have responsibility in these areas. The EPA organiza-
tional structure shown in Figure 2-1 will assist the reader when requiring information beyond
the scope of this report.
EPA
Administrator
Enforcement
Water and
Hazardous Materials
Stationary
Source
Enforcement
Division
Wash., D.C.
Effluent
Guidelines
Division
Wash., D.C.
Air and Waste
Management
Research and
Development
Emissions
Standards and
Engineering
Division
Durham, N.C.
Industrial
Processes
Division
(IERL)
RTP, N.C.
FIGURE 2-1
EPA ORGANIZATION CHART
2.3 State, Basin and Regional Water Quality Standards
Most states have passed laws which establish agencies whose responsibility includes protection
of the state's natural water resources. These agencies are empowered to establish standards for
the state's waters and determine the public use or benefits to which the waters may be put. In
determining the quality of the waters, the state is also empowered to determine those causes
which tend to create a condition of pollution. By doing this, the state has the power to deter-
mine if a specific discharge is creating conditions of pollution within the waters or limit the
amount of pollutants discharged based on the established water quality of the stream. It should
be noted that effluent limits for water quality limited discharges may in fact be more stringent
than those limits set forth in the Federal Register guidelines. These situations must be evaluated
on a case-by-case basis.
2-2
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Most states have not developed specific effluent limitations for industrial discharges, but es-
tablish discharge criteria based on existing stream conditions and water quality standards.
Therefore, two similar manufacturing plants may encounter different limitations depending
upon their geographic location.
A summary of the water pollution laws of twelve states wherein the majority of the textile
industry is located has been summarized in a previous EPA publication, entitled "State of the
Art of Textile Waste Treatment," by Dr. John J. Porter, Clemson University. Of common con-
cern is the maintenance of sufficient dissolved oxygen (D.O.) in the receiving stream.
2.4 Pretreatment
Federal regulations regarding pretreatment of textile wastes have to date only been proposed.
Generally, limits are set for discharge of "incompatibles" identified as COD, oil and grease, total
chromium, phenol and sulfide. Depending upon the nature of the particular mill's effluent and
the capabilities of the public facilities to remove these incompatibles, it may require the same
kind of capital investment in control facilities for plants discharging into municipal systems as
will be required for direct dischargers.
In addition, the discharger to publicly owned treatment works (POTW) involved in Federal
construction grant assistance is subject to both a user charge and capital recovery payments
to the municipality.
For situations where the municipality is in the facilities design stage, consideration should be
given to providing the type of treatment compatible with textile waste, thus avoiding possible
duplication of treatment facilities later.
2-3
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CHAPTER 3
CATEGORIZATION OF THE TEXTILE INDUSTRY
3.1 Introduction
The textile industry is a group of related industries which uses natural and/or synthetic fibers
to produce fabric. The industry uses many different raw materials to produce a great variety
of products. Categorization of the textile industry into its various components can utilize one
of several methods.
The classical method of categorizing the textile industry involves grouping the manufacturing
plants according to the fiber being processed, i.e., cotton, wool or synthetics (See Figure 3-1).
This approach may be useful when describing the individual production processes involved in
making different fabrics and the associated waste produced by each unit operation; however,
this method was judged to be too difficult to implement. Other methods such as the use of SIC
codes or synthesizing waste loads by additive contribution from chemicals used were also judged
to be unwieldy and unmanageable. Another approach to textile industry categorization involves
grouping the manufacturing plants according to their particular operation, e.g., dry processing,
knit fabric finishing, carpet, etc. This is the method of categorization recommended by the
Institute of Textile Technology (ITT) and Hydroscience, Inc. in a report prepared for the
American Textile Manufacturers Institute, Inc. (ATMI) and the Carpet and Rug Institute (CRI)
(1). This method of industry categorization has also been adopted by the United States Environ-
mental Protection Agency to describe effluent limitation guidelines and new source perform-
ance standards for the Textile Industry Point Source Category as outlined in Part II Volume 39,
Number 130 of the Federal Register. Although the ITT-Hydroscience report and the EPA docu-
ment are slightly different in categorization approach, for the purpose of this manual, those
categories established by EPA will be used. A listing of the EPA and ATMI/CRI categories is
given in Table 3-1. This chapter will describe each of the EPA categories and the unit opera-
tions that determine their classification.
3.2 Categorization by Mill Operation
The principal basis for categorization by mill operation is the configuration of principal fiber
after processing. Knit and woven fabrics are different and each is different from carpet, yarn or
other processed fiber. Although it is recognized that there may be different ways to produce
knitted fabric, or carpet, or other textile products, there is a distinguishing similarity between
the products in each of the separate categories. It is the similarities of these products that allow
categorization on a mill operation basis.
3-1
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Woven
COTTON
Knit
Worsted
Woven
WOOL
Woolen
SYNTHETICS
Woven
Staple
Knit
Non-Woven
Tufted
Filament
Woven
1
Knit [ Tufted
FIGURE 3-1
TEXTILE INDUSTRY CATEGORIZATION
BY FIBER PROCESSED
3-2
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TABLE 3-1
TEXTILE INDUSTRY CATEGORIZATION
BY MILL OPERATION
EPA ATMI-CRI (ITT-Hydroscience)
1. Wool Scouring 1. Wool Scouring
2. Wool Finishing 2. Wool Finishing
3. Dry Processing 3. Greige
4. Woven Fabric Finishing 4. Woven Fabric Finishing
5. Knit Fabric Finishing 5. Knit Fabric Finishing
6. Greige Mill + Finishing Fabric
6. Carpet 7. Carpet Backing & Foam
8. Integrated Carpet
7. Stock & Yarn, Dyeing & Finishing 9. Stock & Yarn Dyeing & Finishing
10. Greige Mill + Finishing Yarn & Fabrics
11. Combined Materials Finishing, Stock,
Yarn Wovens, Knits
12. Multiple-Operation, Commission House
13. Specialized Finishing
The categories to be used in the development of this manual are as follows:
1. Wool Scouring Mill
2. Wool Finishing Mill
3. Dry Processing Mill
4. Woven Fabric Finishing Mill
5. Knit Fabric Finishing Mill
6. Carpet Mill
7. Stock and Yarn Dyeing and Finishing Mill
Almost all wool processing (except carpet manufacturing) is covered by Categories 1 and 2;
most cotton and synthetic manufacturing is covered by Categories 3, 4, 5 and 7; and the carpet
industry is covered by Categories 3 and 6. These categories are described in detail on the follow-
ing pages.
3.2.1 Wool Scouring Mill
This category of the textile industry includes the following types of mills: wool scouring, top-
making, and general cleaning of raw wool. Wool scouring is conveniently separated from other
segments of the textile industry because of its uniqueness. Raw wool must be cleaned by wet
processes before the fiber can be dry processed to produce fiber, yarn or fabric. Neither cotton
3-3
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nor synthetic fibers require this initial wet cleaning before processing. The number of plants
which perform this function alone and the geographic separation from other textile operations
also conveniently make wool scouring an individual category.
A generalized flow diagram of the wool scouring process is shown in Figure 3-2. Scouring con-
sists of first sorting the fleece and feeding it to a hopper. The wool then is carried through a
series of scouring bowls where scour liquor flows counter-current to it. Detergent is added in
the third and fourth bowls to emulsify the grease 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 wool top).
3.2.2 Wool Finishing Mill
This category of the textile industry includes wool finishing, including carbonizing, fulling, dyeing,
bleaching, rinsing, fire proofing, and other such similar processes. Wool finishing has been dif-
ferentiated from other finishing categories because of: (1) the wide variety of chemicals used to
process wool fabrics; and (2) a high raw wastewater pollutant loading. Wool finishing involves the
use of specialized dyes peculiar to wool fiber, which often results in the presence of chromium
in the waste. In addition, phenols often occur from dyeing wool-polyester blends.
This industry consists of many small mills, most of which are located in New England, New
York and New Jersey, as well as about 25 large mills located primarily in Virginia, the Carolinas,
and Georgia. Few of today's wool finishing mills process wool fabrics exclusively. Many wool
finishing mills handle 20% or less wool with the balance being woven or knit synthetics. Also,
within the 20% or less portion, wool synthetic blends usually constitute the bulk of the
fabric (2).
The wool finishing process is depicted in Figure 3-3. The three distinct finishing processes are
shown as stock, yarn and fabric finishing. Because the pollution generated by the fabric finish-
ing operation is similar to that generated by the other two, only fabric finishing is included in
this discussion. If the greige goods are 100% 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 % 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." Worsted and most wool-synthetic blends are not fulled. Worsted are hard, tightly
woven and dimensionally stable as received at the finishing plant; woolens 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.
3-4
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3-6
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3.2.3 Dry Processing Mill
This category of the textile industry includes the following types of mills; yarn manufacture,
yarn texturizing, unfinished fabric manufacture, fabric coating, fabric laminating, tire cord and
fabric dipping, carpet tufting, and carpet backing. Mills within the dry processing category
typically carry out dry type operations; however, some waste is produced due to spillage and
clean-up.
Since the majority of the dry processing mills listed above are "greige" mills, and due to the sim-
ilar dry nature of carpet backing operations to greige mills, only greige mills will be included in
this discussion. It has been estimated that there are 600 to 700 greige woven mills in the United
States, 80% of which are in North Carolina, South Carolina, Georgia, Alabama and Virginia
(2). Greige mills generally manufacture yarn and unfinished fabric. In general, Greige mills
include the production of yarn, woven greige goods, and knit greige goods. However, knit
greige goods production is almost always combined with a finishing operation and therefore
is included in the knit finishing category.
Although there are many greige goods mills, they carry out mainly dry operation (with the ex-
ception of slashing) and hence contribute little to the overall waste problems of the textile
industry.
Weaving textile yarns into a fabric requires application of size to the warp yarns in order to re-
sist 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 greige mills operate as com-
pletely independent facilities. Figure 3-4 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 generated from knit greige goods is generally
nil. If any wastes are generated through spills, wash up or possible washing of the final product,
the only pollutant would be knitting oils.
3.2.4 Woven Fabric Finishing Mill
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 category because the greige goods section of these mills contributes only a small amount
of the overall effluent load.
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This category is characterized by the following unit operations: desizing, scouring, bleaching,
mercerizing, dyeing, printing, resin treatment, water proofing, flame proofing, soil repellency
application and application of special finishes. This category encompasses mills which finish
woven goods (or integrated greige goods and finishing mills) and it has been estimated that
about 600 mills fall into this category. 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 (2).
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, 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 perma-
nent size. For these fabrics, the first group of processes listed above (cleaning and preparing the
cloth) is avoided entirely. The degree of finishing necessary to provide fabric ready for sale
depends significantly on the fiber(s) being 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. A flow sheet for
woven fabric finishing is given in Figure 3-5.
3.2.5 Knit Fabric Finishing Mill
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. The knit fabric finishing mill category is characterized by the fol-
lowing unit operations: bleaching, dyeing, printing, resin treatment, water proofing, flame
proofing, soil repellency application and application of special finishes.
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 opera-
tions (2). These are plants such as sweater mills in the outerwear segment, knit goods made from
purchased or commission dyed yarns, or mills which have finished goods subsequently dyed on
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a commission basis and, therefore, have no process water requirements. In those isolated in-
stances where sweater or similar mills dye their own yarn, these mills are included under the
Stock and Yarn Dyeing and Finishing Mill category.
The knit fabric segment of the industry has about 540 plants. These plants are the source of
finished knit piece or yarn 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 this category. 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.
The main difference between woven and knit fabric finishing is that the sizing/desizing and mer-
cerizing operations are not required for knits; therefore, raw waste load levels are lower.
The wet processing operations performed in knit fabric finishing are shown schematically in
Figure 3-6. This is necessarily a generalized flow sheet; 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. After the yarn
has been knitted into fabric, the fabric may be processed by one or more of the alternative
routes indicated. The wet process operations employed in a plant depend on the nature of the
goods involved and the end product requirements.
3.2.6 Carpet Mill
Carpet mills form a distinct part of the industry although their effluents are similar in many
ways to those of the Knit Fabric Finishing Mill. Carpet mills use mostly synthetic fibers (nylon,
acrylics and polyesters), but some wool and some cotton are processed. The carpet mill category
is characterized by any or all of the following unit operations: bleaching, scouring, carbonizing,
dyeing, printing, resin treatment, water proofing, flame proofing, soil repellency, backing with
foamed and unfoamed latex and jute. Carpet backing without other carpet manufacturing op-
erations is included in the Dry Processing Mill category. Although some carpet is backed with
latex in a separate plant, some carpet mills do latexing in the same plant with the finishing.
Tufted carpets account for well over 65% of the plants and 85% of the dollar value; they con-
stitute 74% of the employment in this industry (2). Therefore, this section is written princi-
pally around this segment. 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
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from dyeing fabric, the dyeing descriptions for these fibers given in other categories applies
hereto.
Carpets may be yarn dyed, piece dyed, or 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 into a woven or synthetic nonwoven polypropylene or jute primary backing
in a dry operation (Figure 3-7). 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 con-
tinuous dyeing appears very similar to the continuous pad-stream process used for cotton/
synthetic blends broadwoven finishing. After it is dyed the carpet is dried in a tunnel drier. The
carpet is then ready for application of adhesive and a secondary backing.
3.2.7 Stock and Yarn Dyeing and Finishing Mill
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 merceriz-
ing operations and water use. These differences alone are sufficient to justify a separate cate-
gory. Further justifying a separate category is the fact that the waste loads from this type of
plant can vary more than those from other types of integrated textile mills or finishing mills.
This category is typically characterized by any or all of the following unit operations: cleaning,
scouring, bleaching, mercerizing, dyeing and special finishing.
This category includes plants which clean, dye and finish fiber stock or yarn. Sewing thread,
textile and carpet yarn are typical products. In this category crude yarn may be obtained from
a spinning facility or it may be spun in the plant. The yarn may be natural, synthetic or
blended.
Several techniques are available for processing raw yarn into the finished product. The most
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 knitted and the fabric is
dyed or printed, washed, rinsed and dried. The fabric is then unravelled and the yarn is wound
on cones for subsequent use by other mills. Figure 3-8 represents typical operation of a Stock
and Yarn Dyeing and Finishing Mill.
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3.3 References
1. Institute of Textile Technology and Hydroscience, Inc., Recommendations and Comments
For The Establishment of Best Practicable Waste Water Control Technology Currently
Available For The Textile Industry, for American Textile Manufacturers Institute, Inc. and
The Carpet and Rug Institute, 1973.
2. U.S. Environmental Protection Agency, Development Document for Proposed Effluent
Limitations Guidelines and New Source Performance Standards for the Textile Mills Point
Source Category, June 1974.
American Textile Manufacturers Institute, Textile Hi-Lights, June 1974.
USDA, Economic and Statistical Analysis Division, Economic Research Service.
3-16
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CHAPTER 4
SOURCES AND STRENGTHS OF TEXTILE WASTEWATER
4.1 Introduction
Textile mill operations include a number of wet and dry processes, each of which may require
several mechanical manipulations. As a general rule, however, the majority of all aqueous waste
from the textile industry can be described in four separate categories (1):
1. Scouring
2. Bleaching
3. Dyeing or Printing
4. Special Finishing
Special finishing is meant to include all wastes which cannot be included in the first three cate-
gories.
Textile wastes are generally gray in color, or the color of the predominant dye being used, high
in BOD and total dissolved solids, highly alkaline and high in temperature. The wastes usually
exhibit extreme variability in strength and flow and also may at times contain toxic compounds.
The sources of pollution are the natural impurities extracted from the fiber and the chemicals
used in processing the fiber. The basic factors which determine the characteristics of the waste-
water quantity and quality are therefore: 1) the type of fiber being processed; 2) the unit opera-
tions comprising the overall textile process; 3) the chemicals used in the process; and 4) the
degree of "in-house" conservation measures being practiced (2).
Cotton and synthetic fibers are generally woven into cloth before any finishing operations are
applied. Wool is generally washed (scoured) and dyed before being woven into cloth. In either
case, weaving contributes indirectly to the wasteload by the addition of sizes and anti-static
lubricants.
4.1.1 Scouring
Desizing and scouring of natural fibers — cotton and wool — removes natural impurities such as
dirt and grease as well as the chemical additives mentioned above. In the wool industry, scouring
removes impurities approximately equal in weight to the residual fiber weight, creating one of
the strongest liquid wastes, in terms of BOD, of any industry (1). Synthetic fiber scouring
wastes, on the other hand, are relatively low in both pollution and volume due to the lack of
natural impurities and the small amounts of additives used. The cotton finishing industry also
commonly desizes woven cloth for starch removal followed by a thorough scouring, for the
removal of impurities.
4-1
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In both the cotton and wool industries, scouring and washing is the major source of pollution,
contributing over half of the total plant BOD and solids (1). In the synthetic textile industry,
scouring and washing are not major contributors to the wastestreams, generally producing less
than half of the total plant pollution measured as BOD.
4.1.2 Bleaching
Bleaching is generally accomplished by soaking the cloth in a standing bath containing an oxi-
dizing agent in solution, or in a continuous bleaching process. Nearly all of the cotton produced
is bleached, regardless of its final color, using hypochlorite or hydrogen peroxide. Wool is com-
monly bleached with hydrogen peroxide and acid. Synthetics are bleached with hydrogen
peroxide, sodium hypochlorite, peracetic acid, sodium chlorite, or other chemicals.
Only a small percentage of wool and synthetic cloth is bleached white. Natural wool is yellow
in color and bleaching is required only when white of light colors are desired. Synthetic cloth is
bleached for the removal of stains or when a translucent bluish-white color is desired.
Bleach wastes may be toxic and acidic but are not high in organic pollutant concentration and
generally do not contribute more than 5% of the plant's organic wasteload (1).
4.1.3 Dyeing and Printing
The types of dyes commonly employed by the textile industry include direct, disperse, acid and
pre-rnetalized, vat. basic, sulphur, fiber reactive, napthol and azoic. Of these, the first six ac-
count for approximately 85% of the total used. The quantity of dye used depends on the
characteristics of the I'ihei. the color, and the desired finish. Some synthetic textiles require the
use of special currier- to achieve satisfactory penetration of the dye into the fiber. These carriers
are very strong and present a major source of pollution in the finishing of synthetic fibers. It has
been estimated that greater than 90% of the dye processed is exhausted onto the fabric and the
remaining 10% or less is rinsed to waste. In some cases, pressure dyeing at high temperatures is
an alternative method to the use of carriers in dyeing. This method avoids both the cost and pol-
lution of carrier dyeing while allowing satisfactory dye penetration in a shorter period of time.
Printing is most often done by roller application of various dye pastes. Chemical treatment fol-
lows printing to fix the color, and a final wash and rinse is employed to remove any residue.
Printing process waste usually does not contribute significantly to the total waste load. The pol-
lution load from the dyeing and printing sub-processes is approximately 3 to 10% of total plant
BOD and solids in the wool industry. In cotton finishing the range is 15 to 35%, and for synthe-
tics it is 5 to 80% (1).
4.1.4 Special Finishes
Special finishes include waterproofing, moth-proofing, fireproofing, pre-shrinking, brightening,
durable press, etc. In addition, wool is fulled to achieve a felt-like appearance and cotton may
be mercerized or causticized to smooth its surface. Most of these special finishing processes in-
volve chemical treatment and removal of residue by washing and/or rinsing. The pollution con-
tribution of special finishing sub-processes is in the range of 5 to 15% of the plant total (1).
4-2
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4.1.5 Summary
The wasteloads from each individual process may vary over a wide range of values due to the
large number of different fibers produced, each having its own distinctive characteristics. How-
ever, variations also exist between different plants processing the same fiber, due to technologi-
cal differences in production procedures and many other variables which may exist. Addition-
ally, many of the nation's textile mills are involved in the production of cloth composed of a
combination of fibers requiring a variable process methodology dependent on cloth composi-
tion. Although quantities may vary, the wasteload characteristics are generally similar for all
textile mills processing the same fiber.
Wool waste waters are characterized by high BOD, high solids concentration, and high grease
content. Dye waste waters contain color which is extremely difficult to remove by common
waste treatment methods. Wool grease presents an especially difficult problem because pre-
treatment for removal may be necessary before efficient biological treatment of the plant efflu-
ent is feasible. Cotton finishing wastes are not nearly as strong as those produced by the wool
industry, having no grease and a relatively low solids content. Other characteristics are high
BOD (although considerably lower than that found in wool wastes) and possible high color
content. Synthetic finishing wastes are generally lower than cotton finishing wastes in pollut-
ant quantities and characteristics. One significant difference can be the toxicity of synthetic
dye wastes when metallic ion content dyes are used. Pollutant quantities per 1000 pounds of
finished cloth vary over a wide range of values due to the many different types of fibers pro-
cessed (1). Toxicity of synthetic fiber dye wastes can retard or prevent biological waste treat-
ment when concentrations are significant. In such cases chemical pretreatment will be required
prior to biological treatment or discharge to municipal sewers.
Water usage in the textile industries is relatively high due to the large amounts of water required
in washing and rinsing operations. Cotton and wool finishing mills use 30,000 to 70,000 gallons
of water per 1000 pounds of cloth. Synthetic finishing mills use considerably less water, ranging
from 3000 to 29,000 gal/1000 pounds cloth (1). This lower water requirement reflects the lack
of natural impurities on synthetic fibers, allowing less thorough washing as compared to cotton
or wool. Water reuse has not been practiced to a great extent; however, it is expected that
greater recirculation practices will be adopted in the future as water costs and pressures from
regulatory agencies increase.
Wastewater characteristics have been tabulated by fiber processed for each pollutant parameter.
Each table lists unit processes, waste generating sources, wastewater concentrations (in mg/1 and
lb/1000 Ib product) and water use in gallons/1000 Ib product. These tables can be found at the
end of each processed fiber section as follows:
Section 4.2 - Cotton - Table 4-2 thru Table 4-9
Section 4.3 - Wool - Table 4-10 thru Table 4-14
Section 4.4 - Synthetic - Table 4-15 thru Table 4-29
Section 4.5 - Synthetic Blends - Table 4-30 and Table 4-31
4-3
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4.2 Cotton Processing
The basic cotton fabric manufacturing processes which produce aqueous waste are:
• Slashing
• Desizing
• Scouring
• Mercerizing
• Bleaching
• Dyeing and Printing
• Finishing
4.2.1 Slashing
Slashing is the first process during weaving in which liquid treatment is involved. In slashing, the
warp threads are coated with size (either starch or synthetic) to facilitate weaving by giving the
threads tensile strength and smoothness. The compound is then dried on the threads and re-
mains a part of the cloth until it is removed in subsequent processes. Although the slashing
(sizing) compounds used most often are natural starches, other compounds such as poly vinyl
alcohol (PVA), resins, alkali-soluble cellulose derivatives, gelatin glue, locust bean gum and gum
tragacanth have been used. One of these, sodium carboxy-methyl-cellulose, or CMC, is finding
some acceptance, mostly in the sizing of polyester blends. Other chemicals, such as lubricants,
softeners, emulsifiers, humectants, preservatives (ZnCln, phenol, etc.),penetrants, anti-foam
agents, and fillers, are often added to impart additional properties to a fabric. The grey goods
thus prepared usually contain about 10 to 15% add-on, mostly sizing (1).
Liquid waste from slashing operations results from cleaning the slasher boxes, rolls and makeup
kettles. Some spillage also occurs; however, the volume is usually low. Some textile greige mills
produce a wide variety of woven goods, each requiring a specially formulated size. In mills of
this type the size boxes may be dumped and cleaned several times a day depending upon the
production schedule. In unusual cases such as this, slashing operations may produce a great vol-
ume of waste. Although the BOD of slashing waste can be quite high (to 810,000 mg/1 for corn
starch), slashing operations normally contribute only 5% BOD and 4.5% total solids to the
total plant waste load.
Wastewaters from slashing operations are characterized by the following range of pollutants
generated: BOD - 620 to 2500 mg/1, TS - 8500 to 22,600 mg/1, pH - 7 to 9.5 units, and
water use - 60 to 940 gal/1000 Ib. product.
Slashing wastewater is the first heavily contaminated liquid that is discharged during the fabric
production process.
4-4
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4.2.2 Desizing
The operation of desizing removes the sizing compound that was applied to the threads in the
slashing operation, as well as mildewcides and fungicides and other impurities. The most com-
mon desizing operations are acid desizing and enzyme desizing (3).
The acid desizing process utilizes a solution of dilute sulfuric acid to hydrolyze the starch and
render it water soluble, whereas the enzyme desizing process utilizes vegetable or animal
enzymes to decompose starches to a water soluble form. In either case, the desizing mixture is
normally applied to the fabric by means of a padder with a paper roll covering and pressure
to insure that the fabric will be well saturated.
In acid desizing, the fabric soaks in a solution of sulfuric acid, at room temperature, for a period
of 4 to 12 hours and is then washed (4). In enzyme desizing, the fabric and solution are main-
tained at a temperature of 130 to 180° F and a pH of 6 to 7.7 for a period of 4 to 8 hours (5).
After the size has been solubilized, the fabric is rinsed clean. For desizing of polyvinyl alcohol
(PVA) and carboxymethyl cellulose (CMC), materials which are directly soluble in water, no
decomposition is required and the goods are merely washed with water for removal of sizing
agents. This is usually done at 180° F or higher in washers without the use of steamers, J-boxes,
or padders (6).
The waste from desizing operations contributes the largest BOD of all cotton finishing opera-
tions, approximately 45% (5). The waste from starch desizing is very strong with a BOD con-
centration as much as 5,000 ppm (7). This process also contributes the largest total suspended
solids, approximately 86% of the total plant load. The rinse waters following desizing vary in
strength depending on the rinsing method. Desizing of synthetic size (CMC, PVA) results in greatly
reduced BOD load.
Depending upon size material to be removed in the desize operation, the waste characteristics
will have the following range: BOD - 200 to 5200 mg/1, TS - 3800 to 3200 mg/1, pH - 6 to
8 units, and water use - 300 to 2500 gal/1000 Ib. product.
4.2.3 Scouring
Scouring is a process in which the natural impurities (wax, pectins, alcohols, etc.), as well as the
processing impurities (size, dirt, oil and grease, etc.) are removed from the fabric by hot alkaline
detergents 01 soap solutions. Scouring is also used to make the fibers in the cloth whiter and
more absorbent for subsequent bleaching and dyeing.
Scouring is accomplished by one of two methods, kier boiling or open width scouring, depend-
ing on the characteristics of the fabric. Kier boiling is often employed for scouring desized
4-5
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cotton fabrics wherein the fabric (in rope form) is contained in a large vertical pressure vessel.
In this process, the scouring chemicals are recirculated through the goods with heat supplied by
an external heat exchanger. Open width scouring is used on certain heavy weight fabrics not
normally processed in rope form.
Open width goods are processed in an open width boil-out machine, also known as the pro-
gressive jig. The jig is loaded with a scouring solution and the goods are fed continuously
through by the use of eight or ten transfer rolls. The system is heated with steam coils and the
temperature and residence time are maintained for proper scouring of the goods. The goods
are wound onto rolls in the machine 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 roll.
Caustic soda (NaOH) and soda ash (Na2COg) are used in most scouring operations, the former
in concentrations of 1 to 8% of the cloth weight, the latter only 1 to 3% on weight of fibers.
Sodium silicate (Na2SiOg) is generally used in smaller doses (0.25 to \% on weight of fiber)
(1). Pine oil soap to remove wax, and fatty alcohol sulfates to aid in melting, are also some-
times used in scouring. Although the fresh scour solution is clear, after scouring under pres-
sure (5 to 15 psi) and at elevated temperature (200° F) for 2 to 12 hours, the scour liquid is
an opaque brown (1). Methods of scouring and dumping of the scour waste vary from mill to
mill; however, in all mills the cloth is rinsed completely until no brown color is left in the
rinse water.
Scour liquor waste contributes approximately 16% of the total plant BOD. The grease and oil
contribution is approximately 67% of the total. This is due to natural wax, oil and dirt pres-
ent in cotton.
Wastewater characteristics for scour liquor are within the following range: BOD — 100 to
2900 mg/1, TS - 2200 to 17,400 mg/1, pH - 10 to 13 units, temperature - 250° F, and water
use - 300 to 5100 gal/1000 Ib. product.
4.2.4 Mercerizing
The process results in increased tensile strength, increased surface luster, increased abrasion
resistance, reduction in potential shrinkage and increased affinity for dyestuffs.
Mercerization is accomplished by saturating the fabric with cold NaOH (15 to 30%). Physi-
cally, mercerization causes swelling of the cellulose fibers as alkali is absorbed into them,
with higher concentrations, longer residence times, and lower temperatures favoring greater
swelling. Mercerization may be conducted on greige goods (after desizing), on scoured goods
(after kier boiling or caustic treatment) or on bleached goods. More complete mercerization
results from treatment of bleached fabrics (in terms of fiber swelling), but mercerization of
greige goods or scoured goods results in greater tensile strengths.
4-6
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After the desired period of contact, the caustic is thoroughly washed off, sometimes with the
aid of an intermediate acid wash. Generally, the caustic soda dragged out by the cloth is recover-
ed and reused for scouring or mercerization. The mercerizing rinse wastes are alkaline, high in
inorganic solids and caustic alkalinity, and low in BOD. With the increasing trend toward
cotton-polyester blends, much less mercerizing is being done. It is estimated that less than 30%
of cotton is now mercerized or causticized.
Mercerizing wastewater characteristics are dependent upon the degree of caustic recovery
practiced in the mill and generally range as follows: BOD — 50 to 800 mg/1, TS — 320 to
18,000 mg/1, pH - 5.5 to 14 units, and water use - 2,000 to 37,000 gal/1,000 Ib. product.
4.2.5 Bleaching
Bleaching of cotton cloth may be done with oxidizing agents, but sodium hypochlorite, sodium
chlorite and hydrogen peroxide are the most common. Bleaching may be carried out immediate-
ly after scouring or after mercerizing, and may be done in bins, jigs or on a continuous basis.
In sodium hypochlorite bleaching, the cloth is first rinsed, scoured with a weak solution of sul-
furic or hydrochloric acid and rinsed again. The cloth is then passed through a solution of
sodium hypochlorite (about 0.25 to 0.50% available chlorine) and piled into large concrete
bins or fed into a J-box if continuous operation is desired. The time required for hypochlorite
bleaching varies with the type of cloth and may take from a few hours to as long as 24 hours
at room temperature (1). The rinses following sodium hypochlorite bleaching are usually
neutral in pH, vary in BOD depending upon the impurities in the fiber, and contain consider-
able amounts of free chlorine. A final rinse, which may contain an antichlor such as sodium
bisulfite or sulfuric acid, is used to remove residual chlorine from the fabric. When bleaching
with sodium chlorite, acetic acid is used in place of sulfuric or hydrochloric acid, the tempera-
ture of the bath is hot (108 to 185° F), and the pH is 3.5 to 5.5 (3).
Hydrogen peroxide is generally used for bleaching in the continuous process. Continuous
bleaching ranges are employed for processing the majority of the cotton and cotton blended
fabrics today. Fabric is fed in either rope or open width form and, in certain cases, the desizing,
scouring and mercerizing operations are placed in tandem with the continuous bleaching range.
The continuous bleaching process begins with a hot water (140 to 175° F) wash to insure re-
moval of all contaminants. As the goods leave the washer excess water is removed and sodium
hydroxide is added. The saturated material remains at 175 to 180° F for approximately 40
minutes to one hour resulting in the conversion of fats and waxes to soaps. The material is then
rinsed, passed through a peroxide solution and allowed to bleach out at a temperature of 195° F
for approximately 40 minutes to one hour (3).
The bleaching process contributes the lowest BOD to the total plant load. Wastewaters are
characterized by the following ranges: BOD - 100 to 1,700 mg/1, TS - 840 to 14,400 mg/1,
pH - 8.5 to 12 units, and water use - 300 to 14,900 gal/1,000 Ib. product.
4-7
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4.2.6 Dyeing and Printing
Dyeing is the process of applying color to the fiber stock, yarn or fabric. There are various
methods of dyeing and many more types of dyes for each method. There are, however, six main
classes of dyes for cotton fabric: vat, direct, developed, naphthol, sulfur and aniline black.
Vat dyes, known as fast dyes, are insoluble in water. They actually bond-in the colorant and are
the most resistant of any types to light, dry cleaning, sunlight and washing. In the vat dyeing
process, the insoluble dye is first made soluble in water by use of reducing chemicals and is
then applied to the fibers. The absorbed dyestuff is then reoxidized to its insoluble highly color-
ed form. An acid rinse (usually acetic acid) is used to neutralize the alkali present in the dye
bath followed by detergent washing to produce brightness and wash resistance. Vat dyeing may
be accomplished in individual batches or in continuous dye ranges.
Direct dyes are so named because they may be applied to the fibers without pre-application of
chemicals required for retention. The advantages of direct dyes are their ease of application,
low cost and variety of shades while the disadvantages are poor light and wash resistance, and
poor resistance to acids and alkalis. Direct dyeing may be accomplished in dye becks, dyeing
jigs, dye ranges and package dyeing units. Direct dyes may be applied with or without heat
but with higher dye utilization al higher temperatures. Some direct dyes are subjected to post
treatment with copper sulfate and acetic acid to increase light fastness and with potassium
dichromate and acetic acid or formaldehyde to increase wash fastness.
Developed dyeing is a procedure wherein two different chemicals are employed. The first
chemical (Vz to 4% dye) is applied and absorbed into the fibers (1). The second chemical (devel-
oper) is then applied and a reaction with the first takes place directly on the fiber for stable
color development. Dyeing is followed by rinsing to complete this process. The major advan-
tage of developed dyeing is the production of a dyed fabric which possesses greater wash fast-
ness. However, it may not have good light resistance.
Naphthol dyeing is developed dyeing in reverse. The cloth is first impregnated with the develop-
er and then the dye is formed on the fiber by saturation in the dye bath. The advantages of
naphthol dyes are good fastness and economy. Their major disadvantage is a limited range of
colors.
In the actual process, the naphthol dye is dissolved by mixing with either sodium hydroxide
under heat or ethyl alcohol and a cold solution of sodium hydroxide. The dissolved naphthol
dyestuff is then added to the dye bath where the goods are dyed from 20 to 40 minutes at 80
to 100° F(6).
The naphthol is then ready for development in which it is coupled to the other portion of the
final dye molecule. The so-called "fast color bases" are compounds with a free amino acid group
which may be diazotized so that they will react with the naphthol. The base is placed in a solu-
4-8
-------
tion to which sodium nitrite and hydrochloric acid have been added. Temperature is main-
tained at or below 40° F and the chemical reactions are similar to those employed in developed
dyeing. Sodium acetate is employed to neutralize excess chemicals which would hinder the
coupling reaction; acetic acid is used to neutralize excess alkali.
The naphtholated goods are then treated with a diazotized base for 20 to 30 minutes within the
dye bath at room temperature. This coupling reaction can also be done in a dye box or on a
continuous dyeing range (6).
Finally, the goods are detergent washed and rinsed, using a soap solution containing soda ash
for 15 minutes at up to 200° F. The surface dye is removed, the shade is developed and fastness
is improved.
Sulphur dyes are principally used to dye heavy cottons in shades of blacks, dark blues, browns,
and other dark colors. The dyes are generally water insoluble and require dissolving in an alkaline
solution before application. The dye is usually applied at high temperatures (140 to 212° F)
using salt as an exhausting agent (6). Reoxidation is commonly done with sodium dichromate,
acetic acid, sodium perborate or hydrogen peroxide. After dye reoxidation, surplus dyestuffs
are removed by thorough washing with detergents.
Aniline black dye is an insoluble pigment produced by the oxidation of aniline. The cloth is
passed through a dye bath typically consisting of 90 pounds of aniline hydrochloride, 35
pounds of sodium chlorate, and 13 pounds of CuSO^ in 100 gallons of water (1). After impreg-
nation, the cloth is given a steam treatment to develop the black pigment. Alkaline sodium di-
chromate treatment completes the process. Since the dye bath is not exhausted, it is seldom
dumped.
Dyehouse wastewaters may contain quantities of chromium if aniline or sulfur dyeing methods are
used. BOD generated from process chemicals used account for approximately 18% of the total
plant load. Total dissolved solids contributed by dyeing account for approximately 34% of the
total plant load. The high color values of the plant wastes are attributed to this operation.
Table 4-1 presents a list of cotton and wool dyes, and chemicals used in the dyebaths.
Depending upon dye types and dyeing methods the wastewater characteristics are in the follow-
ing ranges: BOD - 60 to 600 mg/1, TDS - 600 to 5,400 mg/1, Cr - 40 to 168 mg/1, pH - 6
to 12 units, and water use - 5,000 to 30,000 gal/1,000 Ib. product.
4-9
-------
TABLE 4-1
CHEMICALS PRESENT IN COTTON AND WOOL DYEBATHS
Cotton
Dye Type Chemicals Present
Aniline Black
Developed
Direct
Naphthol
Sulfur
Vat
Aniline hydrochloride, sodium ferrocyanide, sodium chlorate,
pigment, soap, sodium di-chromate.
Dye, penetrant, sodium chloride, sodium nitrite, hydrochloric acid or
sulfuric acid, developer (beta naphthol), soap or sulfated soap or
fatty alcohol.
Dye, sodium carbonate, sodium chloride, hydrochloric acid, wetting
agent or soluble oil or sodium sulfate.
Dye, caustic soda, soluble oil alcohol, soap, soda ash, sodium
chloride, base, sodium nitrate, sodium nitrite, sodium acetate.
Dye, sodium sulfide, sodium carbonate, sodium chloride,
sodium di-chromate, hydrogen peroxide.
Dye, caustic soda, sodium hydrosulfite, soluble oil, gelatin,
perborate or hydrogen peroxide.
Wool
Acid
Metalized
Mordant
Dye, sulfuric or acetic acid or ammonium sulfate and Glauber Salt.
Dye, acetic or sulfuric acid or ammonium sulfate.
Acetic acid, sodium sulfate, sodium di-chromate.
Source: Reference 3
Colored patterns on cloth are usually printed. In roller printing, the cloth is rolled around a
large central cylinder on top of a "dark" cloth used to absorb any printing paste which may
seep through. Copper rolls with engraved designs on the circumference of the cylinder are pad-
ded with dye paste (from close-by color boxes). These rolls, wiped free of excess paste by a
"doctor" blade, pass tightly against the cloth. Dye paste in the engraved depressions is im-
printed on the cloth. Steaming or aging treatments finally fix the color prior to washing, rinsing,
drying and finishing. Pollution from color shops (where printing is usually done) comes mainly
from the washing tubs, dippers, cloths, drums, and any equipment used to make and carry the
printing pastes. Washing the printed cloth also contributes to pollution.
Printing wastes can contain high concentrations of BOD and dissolved solids. Printing pigments
will also introduce suspended solids into the waste stream.
Wastewater characteristics are defined as the following ranges: BOD — 100 to 650 mg/1, TSS —
10 to 750 mg/1. TDS - 200 to 1000 mg/1, pH - 6 to 11 units, and water use - 1500 to 4000
gal/1000 Ib. product.
4-10
-------
4.2.7 Finishing
Finishing is a general term which covers the treatment of a fabric to give it a desired surface ef-
fect such as calendered, embossed, lacquered, napped, etc. Special finishes can be applied to
make a fabric crease resistant, crease retentive, waterproof, etc. Starch, dextrin, wax, tallow, oil,
clay, talc, and other weighting compounds are typical finishing compounds. In recent years,
resins, cellulosic solutions, lacquers, sulfonated compounds, and quaternary ammonium salts
have been used. Other finishing processes, such as leveling off (hot detergents) to produce a
uniform appearance, softening (hot soap) to produce a soft feel, and rust stain removal (oxalic
acid and sodium acid fluoride) to improve color are also sometimes used.
Finishing wastewaters are low in BOD and wastewater volume produced and can be characteriz-
ed by the following ranges: BOD - 20 to 500 mg/1, TS - 40 to 2340 mg/1, pH - 6 to 8 units,
and water use — 1,500 gal/1,000 Ib. product.
4-11
-------
TABLE 4-2
BOD CONTRIBUTED BY COTTON
FABRIC MANUFACTURING PROCESSES
PROCESS
SLASHING
DESIZING
Enzyme Starch
Acid Starch
Polyvinyl Alcohol
Carboxymethyl
Cellulose
SCOURING-
Unmercenzed
Greige Fabric
Mercerized
Greige Fabric
MERCERIZING.
Greige Fabric
Scoured Fabric
Bleached Fabric
BLEACHING
Hydrogen Peroxide
(Woven Goods)
Hydrogen Peroxide
(Knit Goods)
Sodium Hypochlonte
(Woven Goods)
DYEING.
Direct
(Woven Goods)
Direct
(Knit Goods)
Developed
(Woven Goods)
Developed
(Knit Goods)
Vat
(Woven Goods)
Vat
(Knit Goods)
Sulfur
(Woven Goods)
Sulfur
(Knit Goods)
Naphthol
(Woven Goods)
Naphthol
BOD SOURCES
Natural Starches, resins
Glucose from Starch
Glucose from Starch
Soluble Polyvinyl Alcohol
Soluble Carboxymethyl
Cellulose
Natural Waxes, Pectins,
Alcohol, Etc
Penetrants such as NaOH
Penetrants
Sodium Sulfate, Soluble Oil
Wetting Agent, Etc.
Penetrant, Sodium Nitrate,
Developer, Soap, Etc
Sodium Hydrosulfite, Soluble
Oil, Gelatine, Etc
Sodium Sulfide,
Sodium Carbonate
Sodium Acetate, Soluble Oil,
Soap, Etc
(Knit Goods)
Fiber Reactive
(Woven Goods)
Fiber Reactive
(Knit Goods)
PRINTING
Pigment
(Woven Goods)
Pigment
(Knit Goods)
Vat Dye
(Woven Goods)
Vat Dye
(Knit Goods)
FINISHING
Starch
Resin
Resin Finishing &
Flat Curing
Softener
Sodium Ferrocyamde,
Sodium Chlorite, Pigment
Starch, Glycerol,
Reducing Agent,
Detergents,
Soaps, Etc
Glucose.
Cellulosic Solutions,
Sulfonated compounds,
Detergents, Soaps, Etc
BOD
LB.
1000 LB.
PRODUCT
05-50
456
45 6
25
393
—
21 4
164
129
40
1 66
1 4
235
008
259
21 1
522
268
19 1
42 4
240
424
54
306
58
266
1 3
1 3
21 5
21 5
23
0 7
63
025
mg/l
(620 -
2,500)
(3,645)
(3,645)
(200)
(314)
—
(855)
(655)
(773)
(240)
(100)
(84)
(282)
(5)
(62)
(84)
(125)
(107)
(458)
(169)
(576)
(169)
(129)
(122)
(139)
(106)
(101)
(101)
(644)
(644)
(184)
(56)
(505)
(20)
WATER USE
GALLONS
1000 LB PRODUCT
60-940
1,500
1,500
1,500
1,500
—
3,000
3,000
2,000
2,000
2,000
2,000
10,000
2.000
5,000
30,000
5,000
30,000
5,000
30,000
5,000
30,000
5,000
30,000
5,000
30,000
1,500
1,500
4,000
4,000
1,500
1,500
1,500
1,500
REFERENCE
7
6
6
6
6
—
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
4-12
-------
TABLE 4-3
TOTAL SUSPENDED SOLIDS (TSS) CONTRIBUTED BY COTTON
FABRIC MANUFACTURING PROCESSES
PROCESS
SLASHING
DESIZING
Enzyme Starch
Acid Starch
Polyvinyl Alcohol
Carboxymethyl
Cellulose
SCOURING'
Unmercenzed
Greige Fabric
Mercerized
Greige Fabric
MERCERIZING
Greige Fabric
Scoured Fabric
Bleached Fabric
BLEACHING
Hydrogen Peroxide
(Woven Goods)
Hydrogen Peroxide
(Knit Goods)
Sodium Hypochlonte
(Woven Goods)
DYEING
PRINTING
Pigment
(Woven Goods)
Pigment
(Knit Goods)
Vat Dye
(Woven Goods)
Vat Dye
(Knit Goods)
FINISHING
Starch
Resin
Resin Finishing
& Flat Curing
Softener
BOD SOURCES
-
Substance Removed from
the Yarn Applied in the
Slashing Operation
Cotton, Wax, Non-Cellulosic
Components of the Cotton
Natural Impurities from
Rinsed Water
Residual from Rinsed Water
Impurities in the Fiber
No TSS
Printing Paste, Thickener
Rinsed Water Used for
Cleaning Equipment
Resin, Wax, Talc
TOXIC MATERIAL
LB.
1000 LB
PRODUCT
-
89
895
50
50
50
50
50
50
50
40
—
40
-
013
013
250
250
—
—
12
—
mg/l
(7,114)
(7,154)
(400)
(400)
(200)
(200)
(300)
(300)
(300)
(240)
(240)
(10)
(10)
(749)
(749)
(959)
WATER USE
GALLONS
1000 LB PRODUCT
60 - 940
1,500
1,500
1,500
1,500
3,000
3,000
2,000
2,000
2,000
2,000
10,000
2,000
5,000 - 30,000
1,500
1,500
4,000
4,000
1,500
1,500
1,500
1,500
REFERENCE
7
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
4-13
-------
TABLE 4-4
TOTAL DISSOLVED SOLIDS (TDS) CONTRIBUTED BY
COTTON FABRIC MANUFACTURING PROCESSES
PROCESS
SLASHING-
DESIZ/NG
Enzyme Starch
Acid Starch
Polyvmyl Alcohol
Carboxymethyl
Cellulose
SCOURING
Unmercenzed
Greige Fabric
Mercerized
Greige Fabric
MERCERIZING
Greige Fabric
Scoured Fabric
Bleached Fabric
BLEACHING
Hydrogen Peroxide
(Woven Goods)
Hydrogen Peroxide
(Knit Goods)
Sodium Hypochlonte
(Woven Goods)
DYEING
Direct
(Woven Goods)
Direct
(Knit Goods)
Developed
(Woven Goods)
Developed
(Knit Goods)
Vat
(Woven Goods)
Vat
(Knit Goods)
Sulfur
(Woven Goods)
Sulfur
(Knit Goods)
Naphthol
(Woven Goods)
Naphthol
(Knit Goods)
Fiber Reactive
(Woven Goods)
Fiber Reactive
(Knit Goods)
PRINTING
Pigment
(Woven Goods)
Pigment
(Knit Goods)
Vat Dye
(Woven Goods)
Vat Dye
(Knit Goods)
FINISHING-
Starch
Resin
Resin Finishing
& Flat Curing
Softener
TDS SOURCES
Sizing Liquid
Dissolved Organic Compounds
in Desizmg Liquid
Soluble Impurities Removed
By Hot Alkali and Soap
Detergents
Dissolved Solids in NaOH
and Acid Wash Rinsed
Water
Residual Chlorine from
the Fabric in Rinsed Water
Dye, Sodium Carbonate, Sodium
Chloride, Wetting Agent
Dye, Penetrants, Sodium Chlo-
ride, Soap and Fatty Alcohol
Dye, Caustic Soda, Gelatine,
Sodium Hydrosulfite
Dye, Sodium Sulfide,
Sodium Chloride
Dye, Soda Ash, Caustic
Soda, Soap, Alcohol
Sodium Chloride, Pigment
Soap
Printing Paste, Dyeing
Assistant, Hydroscopic
Substances and Other
Chemicals
Starch, Dextrin, Tallow,
Lacquers, Sulfonated
Compound, Ammonia Salt
Hot Soap
TDS
LB.
1000LB mg/l
PRODUCT
TOTAL SOLIDS
47- (8,500-
67 22,600)
5 1 (408)
7 5 (600)
480 (3,837)
45 0 (3,597)
499 (1,994)
499 (1,994)
148 (8,873)
148 (8,873)
142 (8,513)
21 9 (1,313)
70 7 (838)
55 0 (3,297)
106 (2,542)
260 (1,039)
225 (5,396)
318 (1,271)
117-127 (2,806-3,046)
194 (775)
154 (3,693)
193 (771)
485 (1,163)
143 (572)
180 (4,317)
273 (1,091)
2 5 (200)
2 5 (200)
340 (1,019)
345 (1,034)
4 65 (372)
22 (1,759)
17.3 (1,383)
0 5 (40)
WATER USE
GALLONS
1000 LB. PRODUCT
60 - 940
1,500
1,500
1,500
1,500
3,000
3,000
2,000
2,000
2,000
2,000
10,000
2,000
5,000
30,000
5,000
30,000
5,000
30,000
5,000
30,000
5,000
30,000
5,000
30,000
1,500
1,500
4,000
4,000
1,500
1,500
1,500
1,500
REFERENCE
7
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
4-14
-------
TABLE 4-5
CHARACTERISTICS OF WASTEWATER BY pH FROM
COTTON FABRIC MANUFACTURING PROCESSES
PROCESS
SLASHING:
DESIZING:
SCOURING
MERCERIZING
BLEACHING.
DYEING:
PRINTING
FINISHING.
CHARACTERISTIC
Neutral
Neutral
Except Acid Starch Which is
Low pH (1-2) Resulted From
Solution of Sulfunc Acid
High Alkalinity Resulted from
Hot Alkaline Detergents or
Soap Solutions
High Alkalinity Resulted from
15 to 30 Percent Solution of
Sodium Hydroxide Used in Process
Alkaline pH Resulted from
Bleaching Solutions
Neutral to Alkaline pH Resulted from
Dye Used Except Developed
Dyeing Which is Low pH (1-2) Due to
Sulfunc Acid Solution Used in
Dyeing Process
Neutral to High Alkaline
Neutral
pH
UNIT
f
7 0 - 9.5
6- 8
125
120
9- 12
6- 12
6- 11
6- 8
WATER USE
GALLONS
1000 LB PRODUCT
60 - 940
1,500
3,000
2,000
2,000- 10,000
5,000-30,000
1,500- 4,000
1,500
REFERENCE
7
6
6
6
6
6
6
6
4-15
-------
TABLE 4-6
COLOR CONTRIBUTED BY COTTON FABRIC
MANUFACTURING PROCESSES
PROCESS
SLASHING
DESIZING
SCOURING
BLEACHING
DYEING
Direct
(Woven Goods)
Direct
(Knit Goods)
Developed
(Woven Goods)
Developed
(Knit Goods)
Vat
(Woven Goods)
Vat
(Knit Goods)
Sulfur
(Woven Goods)
Sulfur
(Knit Goods)
Naphthol
(Woven Goods)
Naphthol
(Knit Goods)
Fiber Reactive
(Woven Goods)
Fiber Reactive
(Knit Goods)
PRINTING
Pigment
(Woven Goods)
Pigment
(Knit Goods)
Vat Dye
(Woven Goods)
Vat Dye
(Knit Goods)
FINISHING
COLOR SOURCES
—
—
-
—
Dye, Chemicals, Penetrants
Dye, Chemicals, Penetrants
Dye, Chemicals, Penetrants
Dye, Chemicals, Penetrants
Dye, Chemicals, Penetrants
Dye, Chemicals, Penetrants
Dye, Chemicals, Penetrants
Dye, Chemicals, Penetrants
Dye, Chemicals, Penetrants
Dye, Chemicals, Penetrants
Dye, Chemicals, Penetrants
Dye, Chemicals, Penetrants
Printing Paste, Dyeing
Assistant, Chemicals
-
COLOR
LB.
1000 LB
PRODUCT
—
-
-
-
05
075
1 0
1 0
1 6
20
32
35
06
06
06
06
005
—
05
05
—
mg/l
(12)
(3)
(24)
(4)
(38)
(8)
(77)
(14)
(14)
(2)
(14)
(2)
(4)
(15)
(15)
WATER USE
GALLONS
1000 LB PRODUCT
60 - 940
1,500
3,000
2,000 - 10,000
5,000
30,000
5,000
30,000
5,000
30,000
5,000
30,000
5,000
30,000
5,000
30,000
1,500
1,500
4,000
4,000
1,500
REFERENCE
7
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
4-16
-------
TABLE 4-7
OIL AND GREASE CONTRIBUTED BY COTTON FABRIC
MANUFACTURING PROCESSES
PROCESS
SLASHING
DESIZING.
Enzyme Starch
Acid Starch
Polyvinyl Alcohol
Carboxymethyl
Cellulose
SCOURING
Unmercenzed
Greige Fabric
Mercerized
Greige Fabric
MERCERIZING
Greige Fabric
Scoured Fabric
Bleached Fabric
BLEACHING-
DYEING
PRINTING
FINISHING-
OIL AND GREASE SOURCES
Natural Oil, Impurities
from Yarn
Cotton Oil, Wax, Dirt
Cotton Oil, Wax, Dirt
—
—
—
—
OIL AND
LB.
1000 LB
PRODUCT
48
48
24
94
40
30
10
GREASE
mg/l
(384)
(384)
(192)
(751)
(1,599)
(1,199)
(600)
WATER USE
GALLONS
1000 LB. PRODUCT
60 - 940
1,500
1,500
1,500
1,500
3,000
3,000
2,000
2,000
2,000
2,000 - 10,000
5,000 - 30,000
1,500- 4,000
1,500
REFERENCE
7
6
6
6
6
6
6
6
6
6
6
6
6
6
4-17
-------
TABLE 4-8
TOXIC MATERIAL/DETERGENT NUTRIENT CONTRIBUTED BY
COTTON FABRIC MANUFACTURING PROCESSES
PROCESS
SLASHING-
DESIZING.
SCOURING:
Unmercenzed
Greige Fabric
Mercerized
Greige Fabric
MERCERIZING-
BLEACHING-
Hydrogen Peroxide
(Woven Goods)
Hydrogen Peroxide
(Knit Goods)
Sodium Hypochlonte
(Woven Goods)
DYEING.
Direct
(Woven Goods)
Direct
(Knit Goods)
Developed
(Woven Goods)
Developed
(Knit Goods)
Vat
(Woven Goods)
Vat
(Knit Goods)
Sulfur
(Woven Goods)
Sulfur
(Knit Goods)
Naphthol
(Woven Goods)
Naphthol
(Knit Goods)
Fiber Reactive
(Woven Goods)
Fiber Reactive
(Knit Goods)
PRINTING:
FINISHING.
Starch
Resin
Resin Finishing
& Flat Curing
Softener
TOXIC MATERIAL SOURCES
—
—
Detergent, Penetrants
—
Bleached and Rinsed
Solution
—
—
—
—
Chemicals in Dye Bath
—
Dye, Dyeing Assistants
Chemical
—
—
—
—
—
^
Resin, Cellulosic
Solutions, Finishing
Compounds
—
TOXIC MATERIAL
LB.
1000LB. nig/ 1
PRODUCT
—
—
P = 1 04 (42)
P = 1.04 (42)
—
P = 0.76 (46)
P = 2.5 (30)
WATER USE
GALLONS
1000 LB. PRODUCT
60 - 940
1,500
3,000
3,000
2,000
2,000
10,000
— ' 2,000
—
—
—
—
Cr = 3.5 (84)
—
Cr = 7.0 (168)
Cr = 10 (40)
—
—
—
—
—
—
Zn = 0.66 (53)
Zn = 1.3 (104)
—
5,000
30,000
5,000
30,000
5,000
30,000
5,000
30,000
5,000
30,000
5,000
30,000
1,500
1,500
1,500
1,500
1,500
REFERENCE
7
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
P = Phosphorus
Cr = Chromium
Zn - Zinc
4-18
-------
o
cc
m
z
o
I-
o
o
o
cc
Eo
? P£
UJ
CO
xl
u.
o
Z
O
o
o
C)
Z!
Q
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4.3 Wool Processing
The five major sources of pollution which are produced during the processing of woolen fibers
are:
1. Scouring
2. Washing after Fulling
3. Neutralization after Carbonizing
4. Bleaching
5. Dyeing
4.3.1 Scouring
Scouring, the first wet process wool receives, removes the natural and acquired impurities from
the wool fibers. Since raw sheep wool contains from 25 to 75% suint (water soluble excretions
and secretions of the sheep such as urine, feces, sweat, blood, dirt, grease, etc.), the production
of one pound of scoured wool fiber also produces one and one-half pounds of waste impuri-
ties (5). Because of this, the process of wool scouring is known to have one of the strongest
wastes in the textile industry.
Scouring is usually carried out in a series of 2 to 6 bowls (usually 4 bowls of 1,500 to 3,000
gallons capacity each), commonly known as a "scouring train" (1). The first two bowls of the
train are filled with neutral detergents or detergents and a mild alkali such as sodium carbonate
or soda ash. The third bowl is a standing rinse and the last may be either a standing or over-flow-
ing rinse. In many plants, a counterflow arrangement may be used where the relatively cleaner
waters at the end of the train flow backward for reuse in the preceding bowls.
The soap-alkali scouring baths are generally characterized by a temperature of 115 to 130° F
and a pH of 9.5 to 10.5 while the neutral detergent baths normally have a pH of 6.5 to 7.5 and
a temperature of 135 to 160° F (3).
The scouring process emulsifies the dirt and grease and produces a brown, thickly turbid waste
which is often covered with a greasy scum and contains considerable, settleable mineral matter.
It is strongly alkaline and very putrescible. The bowls are generally dumped once at the end of
each 8-hour day at which time BOD concentration may reach 40,000 mg/1 in the first bowl and
the BOD concentration in each succeeding bowl is usually about 10% of that in the previous
bowl. The scouring process contributes 55 to 75% of the total BOD produced during the pro-
cessing of wool fibers (1).
4-20
-------
The grease stream produced by scouring may be passed through a centrifugal separator, permit-
ting recovery of about 1/4 to 1/2 of the grease; the remainder of which would then be dis-
charged with the water to waste (6). The crude, recovered grease is normally refined further to
produce lanolin, a useful byproduct, with the impurities from the refinement step also going
to waste.
i
Scoured wool liquor can be characterized by the following: BOD — 13,000 mg/1, TS — 36,000
mg/1, pH - 9 to 12 units, and water use - 2,000 to 12,000 gal/1,000 Ib. product.
4.3.2 Washing After Fulling
Washing after fulling produces the second largest source of BOD during wool processing, con-
tributing about 20 to 35% of the total (1). Fulling is a process used to shrink, tighten and
smooth the wool fibers for non-woven felts or woven cloth.
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 (5). Acid fulling is always followed
by alkali fulling.
After fulling, the residual materials are washed out of the cloth, generally in a string or rope
washer. The cloth is pulled between the rollers of the washer with the ends of the cloth sewn
together to form a continuous string and circulated through the washer approximately 10 to 20
times. 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 to produce
suds, thus washing the fabric. In the second soaping, a 2% solution of soap or synthetic deter-
gent is used. The warm water rinsings are done at 100 to 110° F, while the cold rinse is done
below 100° F. The rinse rate on most machines is usually 15,000 to 40,000 gal/hr. The total
amount of water used per 1,000 pounds of wool processed averages about 40,000 gallons to
100,000 gallons (1).
Washwaters generally exhibit the following characteristics: BOD — 200 to 9,000 mg/1, TS —
4,000 mg/1, and pH - 9 to 12 units.
4.3.3 Neutralization After Carbonizing
Carbonizing of fabrics is a common finishing process which removes any traces of vegetable
matter remaining on the wool. The actual process involves wetting out the fabric and soaking
in a solution of 4 to 6% sulfuric acid. The fabric is then passed through a series of rollers to re-
move the excess acid and placed in an oven and heated from 212 to 220° F (1). The hot acid
4-21
-------
reacts chemically with vegetable matter, or any cotton fiber contaminant and oxidizes it to
gases and a solid carbon residue. The wool is then passed through another set of rollers crushing
the charred material and is shaken in a duster to remove the particles. A solid waste is produced
during carbonizing but, with the exception of an occasional dump of contaminated acid bath,
no liquid waste results. After the dusting process, the acids used in carbonizing must be remov-
ed. Acid removal is achieved by a preliminary rinse followed by neutralization in a bath of sodi-
um carbonate (2Vz%) and a final rinse. Since the sulfuric acid and soda ash contribute little or
no BOD, and the amount contributed by remaining vegetable matter is relatively small, the over-
all carbonizing process adds less than \% of the total waste load (1).
Wastewater characteristics as a result of this processing step are as follows: BOD — 15 to 100
mg/1, TS - 4,000 mg/1, pH - 2 to 9 units, and water use - 2,000 to 16,000 gal/1,000 Ib.
product.
4.3.4 Bleaching
Wool is bleached if white fabric or very light shades of colored cloth are required; however, the
amount of wool bleached for today's market is rather small. Bleaching of wool fibers may be
accomplished after the scouring process (often the last bowl in the scouring train) or fabric may
be bleached after finishing. There are three methods of bleaching wool: 1) with sulfur dioxide,
2) with hydrogen or sodium peroxide, and 3) with optical brighteners.
Wool may be bleached by reduction of color compounds with sulfur dioxide which is not a
permanent bleach. A true bleach is obtained by the use of hydrogen peroxide mixed with
sodium hydroxide for pH control. Another bleach employs sodium peroxide with acid for pH
control.
Many plants use optical brighteners composed of various organic compounds. Although the
BOD load is generally higher than for other methods, this process still contributes less than 1%
of the total BOD (1).
Bleaching wastewater characteristics are as follows: BOD — 390 mg/1, TS — 900 mg/1, pH —
6.0 units, and water use - 300 to 2,700 gal/1,000 Ib. product.
4.3.5 Dyeing
Wool may be dyed in fiber form (top dyeing) or after spinning (yarn dyeing) or it may be dyed
as a fabric (piece dyeing). Due to the current popularity of multi-colored fabrics, yarn or stock
dyeing is used more often than piece dyeing.
Currently, stock and yarn are usually dyed in pressure vessels with controlled liquid recircula-
tion by pumping. Formerly, stock and yarn dyeing processes used open vats where paddles
moved the wool through the dye bath. Although spool and skein dyeing are both in current use,
most wool is dyed in skeins, placed in packages and then rewound.
4-22
-------
The wool dyeing processes are very difficult to classify or discuss because of the very great
differences in the types of dyes used and the manner in which any one type of dye is applied
to the goods. In acid dyeing the temperature of the solution may vary from 140 to 212° F, and
in metalized dyeing the average final temperature is 185° F (3).
Many of the chemicals used for wool dyeing are toxic, and the pH varies depending on the
amount of residual alkali left in the wool fibers after the scouring process. The BOD load is con-
tributed by the process chemicals used, and the contribution of wool dyeing to the mill's total
BOD is 6 to 9% (5).
Depending upon dye method used, wastewater characteristics will be in the following range:
BOD - 140 to 3,500 mg/1, TS - 2,500 to 9,100 mg/1, pH - 4.8 to 8.0 units, and water use -
2,000 to 3,000 gal/1,000 Ib. product.
4-23
-------
TABLE 4-10
BOD CONTRIBUTED BY WOOL WET PROCESSES
PROCESS
SCOURING
Soap-Alkali Method:
Bowl 1
Bowl 2
Bowl 3
Detergent —
Na2SO4 Method
Bowl 1
Bowl 2
Bowl 3
WASHING AFTER
FULLING
First Soaping
Second Soaping
NEUTRALIZATION
AFTER CARBONIZING:
First Running Rinse
First Soda Ash Bath
BLEACH ING-
DYE ING:
Acetic Acid Used
or
Ammonia Sulfate Used
BOD SOURCES
Natural Impurities,
Sumt, Dirt, Grease
Total Process
Natural Impurities,
Sumt, Dirt, Grease
Total Process
Residual Material,
Soap or Detergent
Penetrants and Carding Oil
Total Process
Residual Vegetable Matter
(Very Little)
Total Process
Organic Compounds,
Chemical used tn process
(Very Little)
Process Chemicals
Average of Process
BOD
LB.
1000 LB PRODUCT
(mg/l)'
(11,900 — 27,000)
(2,340 — 7,350)
(150 — 400)
104.5 — 221.4
(11,000 — 25,000)'
(775— 1,560)'
(115— 260)'
104.5 — 221 42
(3,900 — 24,000)
(4,000 — 4,000)
31 — 942
(20 — 35)
(21 - 36)
1 7 — 2 V
1.4
(390)
(1,440 — 3,450)
(140— 1,020)
9 0 — 34 32
WATER USE
GALLONS
1000 LB PRODUCT
N/l
N/l
N/l
5,500 — 12,000
REFERENCE
5
5
5
5
|
N/l
N/l
N/l
5,500 — 12,000
N/l
N/l
40,000 — 100,000
N/l
N/l
12,500 — 15,700
300 — 2,680
N/l
N/l
1,900 — 2,680
5
5
5
5
5
5
5
5
5
5
5
5
5
5
( )* — Indicates concentration in mg/l
1 — These samples were taken early in the day and give a false impression of low values over the soap — alkali
method Actually, at the end of day results between processes should be similar
2 — No information in (mg/l), only lb/1000 Ib product were given However, the average concentration in mg/l of
the process can be calculated using water use
N/l No Information Available
4-24
-------
TABLE 4-11
TOTAL SOLIDS CONTRIBUTED BY
WOOL WET PROCESSES
PROCESS
SCOURING
Soap-Alkali Method
Bowl 1
Bowl 2
Bowl 3
Detergent — Na2SO4
Method.
Bowl 1
Bowl 2
Bowl 3
WASHING AFTER
FULLING
First Soaping
Second Soaping
NEUTRALIZATION
AFTER CARBONIZING.
First Running Rinse
First Soda Ash Bath
BLEACHING-
DYEING
Acetic Acid Used
or
Ammonia Sulfate Used
TOTAL SOLIDS SOURCES
Dirt, Natural
Impurities, Sumt ('Soluble
Excretions and Secretions)
Total Process
Dirt Sand, Natural
Impurities, Sumt (Soluble
Excretions and Secretions)
Total Process
Residual Matter,
Chemical From Process
Total Process
Very Fine Carbon Particles,
Residual Matter from Treatment
Total Process
Organic Compounds Used in
Process
Process Chemicals
Average of Process
TOTAL SOLIDS
mg/l
42,116 — 76,950
16,650 — 32,532
834— 1,424
N/l
47,108 — 91,456
5,024 — 7,856
1,052 — 2,406
N/l
11,270 — 23,120
4,516— 5,144
N/l
494— 1,988
8,678 — 10,884
N/l
908
2,418— 5,880
7,344 — 9,160
N/l
WATER USE
GALLONS
1000 LB. PRODUCT
N/l
N/l
N/l
5,500 — 12,000
N/l
N/l
N/l
5,500 — 12,000
N/l
N/l
40,000 — 100,000
N/l
N/l
12,500 — 15,700
300 — 2,680
N/l
N/l
1,900 — 2,680
REFERENCE
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
N/l No Information Available
4-25
-------
TABLE 4-12
CHARACTERISTICS OF WASTEWATER BY pH
FROM WOOL WET PROCESSES
PROCESS
SCOURING
Soap-Alkali
Method
Detergent -
N2SO4 Method
WASHING AFTER
FULLING
NEUTRALIZATION
AFTER CARBONIZING:
First Running
Rinse
First Soda
Ash Rinse
BLEACHING:
DYEING
Acetic Acid
Used
Ammonia Sulfate
Used
CHARACTERISTICS
High Alkalinity Resulted
From Hot Alkali Soap
Natural to High Alkaline
High Alkalinity Resulted
From Soap and Detergent
Solution
Acid pH Resulted From
Sulfunc Acid
Alkaline pH Resulted From
Soda Ash
Total Process
Neutral
Acid pH to Neutral
Resulted from Acid Used
Neutral
Average Process
PH
UNIT
95 — 105
64 — 91
90 — 107
1 9 — 24
79—90
N/l
60
48 — 84
50 — 83
N/l
WATER USE
GALLONS
1000 LB PRODUCT
5,500— 12,000
5,500— 12,000
40,000 — 100,000
N/l
N/l
12,500 — 15,700
300 — 2,680
N/l
N/l
1,900— 2,680
REFERENCE
5
5
5
5
5
5
5
5
5
N/l No Information Available
TABLE 4-13
AN EXAMPLE OF POLLUTIONAL LOADS CONTRIBUTED
BY WOOL WET PROCESSES (REFERENCE 5)
PROCESS
SCOURING
Soap-Alkali Method
WASHING AFTER
FULLING:
NEUTRALIZATION
AFTER CARBONIZING
BLEACHING:
DYEING:
Acetic Acid Used
TOTAL
PH
95 — 10.5
90 — 107
1 9 — 9.0
60
4 8 — 8.4
6 — 11
BOD
LB
1000 LB PRODUCT
(mg/l)
1045 — 221 4
31 — 94
1.7— 21
1 4
9 0 — 34 3
1476 — 3532
%
CONTRIBUTION
OF TOTAL
63 — 71
21 — 27
06—1
0.4 — 1
6—9
100
WATER USE
GALLONS
1000 LB PRODUCT
5,500— 12,000
40,000 — 100,000
12,500— 15,700
300— 2,680
1,900— 2,680
60,200 — 133,060
4-26
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4.4 Synthetics Processing
Synthetic fibers fall into two main groups: those produced from cellulose (cellulosic) such as
rayon or cellulose acetate, and those produced synthetically from organic materials (non-
cellulosic) such as nylon, polyester, acrylics or modacrylics.
Synthetic fibers can be converted into fabrics in one of two ways: Continuous filament yarns
can be used to manufacture 100% synthetic fabrics, or staple yarns can be used to produce
fabrics that are blends of man-made fibers or man-made and natural fibers. Since each of the
synthetic fibers is processed in a varying sequence of operation, each fiber will be considered
separately.
4.4.1 Rayon
Rayon is 100% regenerated cellulose and for processing purposes may be considered as clean
cotton. Rayon staple may be sized and desized as cotton, whereas rayon filament is generally
sized with gelatin or anti-static lubricants. The sizes or lubricants are removed during the
scouring process of finishing and thereby contribute a portion of the pollution load. The scour-
ing solution itself will usually contain soluble oils, weak alkalis, and soaps or synthetic deter-
gents which also contribute to the total waste load. The average BOD for this waste is 2,800
mg/1 of which 50 to 60% is contributed by the anti-static compounds, 30 to 40% is due to
the soluble oil and 10 to 20% is due to the synthetic detergents (5).
Dyeing, the second operation which produces aqueous waste, is usually performed concurrently
with rayon scouring. The main reason for scouring and dyeing in the same bath is that very little
rayon is bleached due to its inherent whiteness and possible degradation of the fiber by the
oxidizing agents used in bleaching. Rayon may be dyed by conventional methods using the same
dyes as used for cotton, i.e. acid, vat, or dispersed. However, lower temperatures (180 to
200° F), retarding agents and lower concentrations of electrolytes are used to effect exhaustion
of color.
Scouring and dyeing will generate a waste with the following characteristics: BOD — 2,800 mg/1,
TS - 3,300 mg/1, TSS - 90 mg/1, pH - 8.5 units, and water use - 2,000 to 4,000 gal/1,000
Ib. product.
After the scour and dye bath, rayon is subjected to a salt bath to remove residual scouring
material and to assure fastness of the dyestuff. The bath contains a synthetic detergent and salt
solution which is subsequently rinsed from the fabric.
Practically all the BOD of this discharge is due to residual scour and dye bath solution left in the
fabric. The waste discharge has an average BOD of 58 mg/1, pH of 6.8 units, and a salt content
of 4,000 to 12,000 mg/1 (5). If scouring and dyeing are the only finishing processes given rayon
fabrics, the two baths will produce an equalized effluent of 1,445 mg/1 BOD and 2,000 to 6,000
4-28
-------
mg/1 salt contained in approximately 5,000 gallons of water for each 1,000 pounds of fabric
processed (9).
Special finishing, when used, will result in a BOD of 20 to 30% of total plant load. Suspended
solids from finishing will contribute 60 to 85% of total plant load. Fire retardant finishes for
cellulosics contain high levels of nitrogen and phosphorus.
4.4.2 Acetate
Acetate is the generic name for cellulose acetate fibers and is applied to textile fibers, yarns and
threads made of such fibers. The finishing processes of acetate fibers are similar to those of
rayon fibers and generally consist of the following:
• Chemical Preparation
• Scouring and Dyeing
• Rinsing
• Finishing
The usual procedure for finishing acetate fibers begins with a preliminary desizing action which
removes the starch or anti-static lubricants. The anti-static compounds are solubilized by dia-
static or proteolytic enzymes prior to scouring with a soap or synthetic detergent used in the
actual scouring process (9). Acetate, like rayon, is usually scoured and dyed in the same bath.
The type of dyes used are also similar and include dispersed dyeing, developed dyeing, acid
dyeing and naphthol dyeing.
Because dispersed dyes have very low solubility in water, they are applied as a fine dispersion
of the dye. Sulfonated oil, aliphatic esters, and softeners are applied with each class of dye at a
concentration of 0.02 pounds per pound fiber to facilitate dyeing (4). When the fiber is swelled,
the dye solution penetrates into the fiber. The rinses following dyeing remove the swelling agent;
and as the fiber unswells, the dye solution is encased in the fiber.
Wastes from typical scour and dye baths exhibit a pH of 9.3 units and average 2,000 mg/1 BOD
with 50 pounds of BOD produced for each 1,000 pounds of acetate fabric finished. Total sus-
pended solids generated are approximately 600 mg/1. The combined dye/scour bath will con-
tain anti-static desize waste (40 to 50% of the BOD load), sulfonated oil swelling agents (30 to
40% of the BOD load), aliphatic ester swelling agents (10 to 20% of the BOD load) and the
softener (negligible BOD load) (9). Two rinses follow the scouring/dyeing operation, each of
which contains some amount of the residual chemicals. The three processes — scour/dye/rinse
produce a complete waste of 666 mg/1 BOD for each 1,000 pounds of fabric processed. The
amount of water used to process 1,000 pounds of fabric averages 9,000 gallons (9). If it
is desired that the acetate fabric remain white, a bleaching operation is usually performed after
scouring. Typical bleaching agents are mild oxidizing agents such as hydrogen peroxide or chlo-
rine bleaches. Two rinsing operations usually follow bleaching to remove excess materials.
4-29
-------
If bleaching is substituted for dyeing, the BOD of the discharge of the scouring and bleaching
bath is approximately 750 mg/1. The equalization of this bath with the discharges from the
two rinsings will average 250 mg/1 and 15 to 20 pounds of BOD in 9,000 gallons of wastewater
for the processing of 1,000 pounds of cloth (9).
4.4.3 Nylon
The usual procedure involved in nylon finishing is scouring, two rinses, dyeing, and another
rinse. Nylon differs from other synthetics in that approximately \% of the fiber dissolves
when scoured (3). Nylon fibers can be dyed by every class of dye; however, when nylon is
used in blended fabrics, the choice of dye usually depends on the other fiber component of
the blend (9).
Soap and soda ash are used in the scouring process. When wasted, the bath contains the follow-
ing BOD producing compounds — the anti-static compound, soaps, and fatty esters (from the
dissolving fiber components). The typical nylon scour bath averages 1,360 mg/1 and 34 pounds
of BOD for each 1,000 pounds of cloth processed. The substances present in the bath contrib-
ute the following percentages to the total BOD of the bath: anti-static sizing compound (40 to
50%), soap, (40 to 50%), and fatty esters (10 to 20%) (9). Other characteristics include: pH -
10.4 units, TS - 1,900 mg/1, and water use - 7,000 gal/1,000 Ib. product.
When nylon is dyed, sulfonated oils are used as dye dispersants. These dye dispersants contrib-
ute practically all of the process BOD, which amounts to an average of 600 mg/1 and 15
pounds for each 1,000 pounds of cloth dyed (3). Dye wastewaters exhibit a pH of approxi-
mately 8.4 units.
The two rinses between the scouring and dyeing processes and the rinse following dyeing are
low in BOD, which is caused by scouring and dyeing process chemicals that remained on the
fabric. If the wastes from these five processes are equalized, scouring and dyeing 1,000 pounds
of nylon fabric results in a waste stream which will average 340 mg/1 and 43.2 pounds of BOD
in 15,000 gallons of wastewater. The BOD contribution of the scouring process is roughly 65%,
the remaining BOD being contributed by the dyeing process (5).
4.4.4 Acrylic/Modacrylic
Acrylic/mo dacrylic fibers are defined as those in which the fiber forming substances are any
long chain synthetic polymer composed of at least 85% by weight of acrylonitrile units for
acrylic and less than 85% but at least 35% for modacrylic. The basic finishing processes for
acrylic include:
• Scouring
• Dyeing or Bleaching
4-30
-------
• Scouring
• Special Finishing
Acrylic fabric normally is scoured with a weak alkali solution, an anti-static lubricant and soap
or detergent. This operation may be done by a variety of equipment including the following:
• Beam Dyeing Equipment
• Rope Soaper
• Jig Scour
• Beck Scour
• Drum of Paddle Scour
After scouring, the material is rinsed to remove excess chemicals in preparation for the dye
bath. Acrylic scour and rinse waste have an average BOD of 2,190 mg/1 of which 30 to 40%
is due to anti-static lubricants and 50 to 70% is due to soap (1). The pH ranges from 8.8 to 9.7
units.
Dyeing is the most important part of the acrylic finishing process. Acrylic fibers are hydropho-
bic, resisting water adsorption almost completely and therefore present special problems.
There are several alternate methods of dyeing acrylics. The most prevalent method is basic
dyeing.
High temperature and pressure are sometimes used with dispersed and acid dyes on acrylic
material. A temperature of 212° F may eliminate the need for carriers by softening and swelling
the fibers so dyes can penetrate. This method produces high temperature wastes with no BOD.
Thermosol padding is an alternate means of dyeing which produces only occasional batches of
soap and rinse water. This method involves oven dyeing at 347 to 392° F and is a potential
source of air pollution (1).
Dye wastes are characterized by the following ranges: BOD - 175 to 2,000 mg/I, TS - 800 to
1,900 mg/1, pH - 1.5 to 3.7 units, and water use - 2,000 to 4,000 gal/1,000 Ib. product.
Acrylics normally receive a final scour and rinse with synthetic detergent and pine oil. The scour
waste has an average BOD of 700 mg/1, 90% of which is contributed by the pine oil (1). Other
characteristics include TS - 800 to 1,900 mg/1, pH - 7.1 units, and water use - 8,000 to
10,000 gal/1,000 Ib. product.
4.4.5 Polyester
The American market consumes more polyester than any of the other man-made fibers (10).
Because of the large consumption and character of the fiber, special dyeing and finishing pro-
4-31
-------
cess have been developed. Polyester fabric finishing is usually carried out in the following
order: scour, rinse, dye, and scour again. Because chemical impurities are virtually absent in
polyester fibers, only relatively light scouring is needed to prepare them for dyeing. Scouring
solutions consist of weak alkalis, lubricants and soap. After scouring, the material is rinsed to
remove excess chemicals and to prepare it for dyeing. The polyester scour waste average 500 to
800 mg/1 of BOD. The processing of 1,000 pounds of polyester fabric will produce 15.5 pounds
of BOD, of which 90% is contributed by the anti-static compounds used for lubrication and
sizing (5).
Polyester may be dyed in several different ways. Conventional dyeing temperatures (room tem-
perature to boiling) may be used, but carriers are needed to take the dye into the fiber. A
second method eliminates the carriers, but high temperatures (250° F) and pressures (50 psi)
are required to get desirable results. Carriers used in polyester dyeing include: methyl naphtha-
lene, butyl benzoate, diphenyl oxide, percloroethylene, orthophenylphenol, biphenyl, benzyl-
alcohol and chloro-benzenes. To use these carriers at conventional temperatures, high concen-
trations of from 0.06 to 0.4 pounds of carrier to 1 pound of fiber are required (3).
Thermosol padding is another means of dyeing which produces only occasional batches of soap
and rinse water. This method involves coating the fabric with the dyestuff and oven drying at
347 to 392° F(l).
Because of the high concentrations at which they are used and the inherent high rate of BOD,
the emulsifying and dissolving agents used in polyester dyeing will produce high BOD loads.
At the present time butyl benzoate and percloroethylene are the most widely used dye carriers.
The two rinses of polyester finishing are usually low in BOD as the result of chemicals held in
the cloth after scouring and dyeing. The processing of polyester uses an average of 15,000 gal-
lons of water per 1,000 Ib. of fiber processed (5). Dye take-up and shrinkage of synthetic fibers
can be effected by heat-setting up to 450° F (1). Once this is done, the dimensional stability of
the cloth cannot be changed without repeating the process at a higher temperature. Heat-setting
is widely practiced and may occur at any of several places in the series of finishing processes.
The most usual point of application is before dyeing. This may be a dry process using hot air,
radiant heat, or a hot roll. Steam under pressure and hot water are also used. The two most
prevalent methods in 1963 were hot air and steam (1). Wastes from this process are in the form
of hot air, hot water, or steam. The last part of the overall finishing process may include such
processes as:
• Water proofing
• Water-repellent treatment
• Oil-repellent treatment
• Resin finishing
• Latex backing
• Water retardant treatment
4-32
-------
• Modification of fabric hand
• Drying
Any other minor specialized treatment falls into this category. These processes may contribute
wastes, but the effect is generally not significant.
TABLE 4-15
BOD LOADS CONTRIBUTED BY RAYON FIBER PROCESSES
PROCESS
SCOUR & DYE
SALT BATH
SPECIAL FINISHING
BOD SOURCES
Anti-statics compounds,
soluble oil, synthetic
detergent
Synthetic Detergent
Process Chemicals
BOD
LB
1000 LB PRODUCT
(mg/l)
50 - 70
(2,832)
0- 3
(58)
20
(1,600)
WATER USE
GALLONS
1000 LB PRODUCT
2,000 - 4,000
500- 1,500
500- 1,500
REFERENCE
5, 9
5, 9
5, 9
TABLE 4-16
TOTAL SOLIDS AND TOTAL SUSPENDED SOLIDS CONTRIBUTED
BY RAYON FIBER PROCESSES
PROCESS
SCOUR & DYE
SALT BATH-
SPECIAL FINISHING
TOTAL SOLIDS &
TOTAL SUSPENDED
SOLIDS SOURCES
Anti-static com-
pounds residual
Residual matter
from scour & dye,
chloride sulfate
Process Chemicals
TOTAL SOLIDS
LB
1000 LB PRODUCT
(mg/l)
25 - 39
(3,334)
20 - 200
(4,890)
3 - 100
TSS
LB
1000 LB PRODUCT
(mg/l)
0 - 3
(90)
2 - 6
(160 - 480)
3 - 50
WATER USE
GALLONS
1000 LB PRODUCT
2,000 - 4,000
500- 1,500
500 - 1,500
REFERENCE
5, 9
5, 9
5, 9
4-33
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4-34
-------
TABLE 4-18
BOD LOADS CONTRIBUTED BY ACETATE FIBERS
PROCESS
SCOUR & DYE "1.
or
SCOUR & BLEACHED:
FIRST RINSE
SECOND RINSE
SPECIAL FINISHING
'1 SCOUR & DYE
BOD SOURCES
Anti-static lubricants, oil,
dye
Synthetic detergent,
hydrogen peroxide
negligible
negligible
Process Chemicals
Surfactant & Disperse Dye
BOD
LB
1000 LB PRODUCT
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40- 60
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25- 38
(750)
-
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40
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6
(72)
WATER USE
GALLONS
1000 LB PRODUCT
4,000 - 6,000
4,000 - 6,000
-
-
3,000 - 5,000
1,000
REFERENCES
5, 9
5, 9
5, 9
5, 9
5,9
6
TABLE 4-19
TOTAL SOLIDS AND TOTAL SUSPENDED SOLIDS CONTRIBUTED
BY ACETATE FIBER PROCESSES
PROCESS
SCOUR & DYE '2
or
SCOUR &
BLEACHED.
FIRST RINSE
SECOND RINSE.
SPECIAL FINISHING-
'2 SCOUR & DYE
TOTAL SOLIDS &
TOTAL SUSPENDED
SOLIDS SOURCES
Anti-static com-
pounds residual
Synthetic detergent
residual from
scour
negligible
negligible
Process Chemicals
Residual from scour
TOTAL SOLIDS
LB.
1000 LB PRODUCT
(mg/l)
60
(1,778)
26- 47
(799 - 946)
-
-
3- 300
(120- 2,400)
TDS
10
(120)
TS.S.
LB.
1000 LB PRODUCT
(mg/l)
1 - 20
(600)
N/l
-
-
3- 50
(120- 1,200)
indeterminate
WATER USE
GALLONS
1000 LB PRODUCT
4,000 - 6,000
4,000 - 6,000
-
-
3,000 - 5,000
10,000
REFERENCES
5, 9
5, 9
5, 9
5, 9
5, 9
6
N/l No Information Available
4-35
-------
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4-36
-------
TABLE 4-21
BOD LOADS CONTRIBUTED BY NYLON FIBER PROCESSES
PROCESS
SCOUR T
DYE "1
SPECIAL FINISHING
'1 SCOUR & DYE
Disperse Dye
Acid Dye
Cationic Dye
BOD SOURCES
Anti-static lubricants, fatty
esters
Residual from scour, dye,
sulfonates
Process Chemicals
Anionic surfactant, softener,
disperse dye
Acetic acid, ammonium,
acetate acid, softener
Acetic acid, softener,
nonionic surfactant
BOD
LB
1000 LB PRODUCT
(mg/l)
30- 40
(1,360)
5 - 20
(368)
10
(N/l)
24
(221)
45- 15 5
(42 - 143)
5
(46)
WATER USE
GALLONS
1000 LB PRODUCT
6,000 - 8,000
2,000 - 4,000
4,000 - 6,000
10,000- 16,000
10,000- 16,000
10,000- 16,000
REFERENCES
5, 9
5,9
5, 9
6
6
6
N/l No Information Available.
TABLE 4-22
TOTAL SOLIDS AND TOTAL SUSPENDED SOLIDS CONTRIBUTED BY
NYLON FIBER PROCESSES
PROCESS
SCOUR "2
DYE '2.
SPECIAL FINISHING:
"2 SCOUR & DYE-
Disperse Dye
Acid Dye
Cationic Dye
TOTAL SOLIDS &
TOTAL SUSPENDED
SOLIDS SOURCES
Anti-static com-
pounds residual
Residual
from scour
Process Chemicals
Residual from
scour
Residual from
scour
Residual from
scour
TOTAL SOLIDS
LB
1000 LB PRODUCT
(mg/l)
30- 50
(1,882)
20- 34
(641)
3- 100
(N/l)
T D S
55 - 60
(507 - 553)
T D S
125- 135
(1,150- 1,250)
T D S
105-115
(970- 1,060)
T.SS
LB
1000 LB. PRODUCT
(mg/l)
20- 40
(N/l)
2- 42
(N/l)
3- 50
(N/l)
indeterminate
indeterminate
indeterminate
WATER USE
GALLONS
1000 LB PRODUCT
6,000 - 8,000
2,000 - 4,000
4,000 - 6,000
10,000- 16,000
10,000- 16,000
10,000 - 16,000
REFERENCES
5, 9
5, 9
5, 9
6
6
N/l No Information Available.
4-37
-------
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4-38
-------
TABLE 4-24
BOD LOADS CONTRIBUTED BY
ACRYLIC/MODACRYLIC FIBERS PROCESSES
PROCESS
SCOUR:
DYE
FINAL SCOUR
SPECIAL FINISHING-
BOD SOURCES
Synthetic detergent,
Pine oil
Dye, residual from scour
Anti-static Lubricants,
synthetic detergent
Process Chemicals
BOD
LB
1000 LB PRODUCT
(mg/l)
45- 90
(2,190)
2 - 40
(175 - 2,000)
10- 25
(668)
60
(N/l)
WATER USE
GALLONS
1000 LB PRODUCT
6,000 - 8,000
1,000 - 4,000
8,000- 10,000
5,000 - 7,000
REFERENCES
5, 9
5, 9
5, 9
5, 9
N/l No Information Available
TABLE 4-25
TOTAL SOLIDS AND TOTAL SUSPENDED SOLIDS CONTRIBUTED
BY ACRYLIC/MODACRYLIC FIBERS PROCESSES
PROCESS
SCOUR
DYE
FINAL SCOUR
SPECIAL FINISHING
TOTAL SOLIDS &
TOTAL SUSPENDED
SOLIDS SOURCES
Residual matter
Dye, residual from
scour
Detergent, anti-
static compound
Process Chemicals
TOTAL SOLIDS
LB
1000 LB PRODUCT
(mg/l)
12 - 20
(1,874)
6- 9
(833 - 1,968)
4- 12
(833 - 1.968)
3- 100
(N/l)
TS S
LB
1000 LB PRODUCT
(mg/l)
25 - 50
(N/l)
5 - 20
(N/l)
3 - 7
(N/l)
3 - 50
(N/l)
WATER USE
GALLONS
1000 LB PRODUCT
6,000 - 8,000
2,000 - 4,000
8,000- 10,000
5,000- 7,000
REFERENCES
5, 9
5, 9
5, 9
5, 9
N/l No Information Available
4-39
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4-40
-------
TABLE 4-27
BOD LOADS CONTRIBUTED BY POLYESTER FIBERS PROCESSES
PROCESS
SCOUR "1.
DYE '1-
FINAL SCOUR-
SPECIAL FINISHING:
"1 SCOUR & DYE.
Atmospheric Beck
Pressure Beck
BOD SOURCES
Anti-static compounds
Dye, emulsifying and
disolvmg agents
Synthetic detergents
Process chemicals
Biphenyl phenol,
Anionic surfactant,
Acetic Acid, Sodium
Hydrosulfite
Butyl benzoate, Anionic
Surfactant, Acetic acid,
Sodium Hydrosulfite
BOD
LB
1000 LB. PRODUCT
(mg/l)
15-25
(500 - 800)
15- 800
(480 - 27,000)
15-25
(650)
2 - 80
(N/l)
100- 225
(343 - 770)
33- 70
(113 - 240)
WATER USE
GALLONS
1000 LB. PRODUCT
3,000 - 5,000
2,000 - 4,000
2,000 - 4,000
1,000- 3,000
35,000
35,000
REFERENCE
5, 9
59
5, 9
5, 9
6
6
N/l No Information Available
TABLE 4-28
TOTAL SOLIDS AND TOTAL SUSPENDED SOLID CONTRIBUTED
BY POLYESTER FIBER PROCESSES
PROCESS
SCOUR '2-
DYE '2-
FINAL SCOUR
SPECIAL
FINISHING.
"2 SCOUR & DYE
Atmospheric
Beck
Pressure Beck
TOTAL SOLIDS &
TOTAL SUSPENDED
SOLIDS SOURCES
Residual matter
Dye, residual
from scour
Synthetic
detergents
Process Chemicals
Residual from
scour
Residual from
scour
TOTAL SOLIDS
LB
1000 L B PRODUCT
(mg/l)
25 - 35
(N/l)
30 - 200
(N/l)
10- 50
(N/l)
3 - 100
(N/l)
TDS
80- 90
(275- 310)
TDS
80- 90
(275- 310)
T.SS
LB
1000 LB PRODUCT
(mg/l)
5- 15
(N/l)
—
3- 50
(N/l)
3 - 50
(N/l)
indeterminate
indeterminate
WATER USE
GALLONS
1000 LB PRODUCT
3,000 - 5,000
2,000 - 4,000
2,000 - 4,000
1,000- 3,000
35,000
35,000
REFERENCE
5, 9
5, 9
5, 9
5, 9
6
6
N/l No Information Available
4-41
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4-42
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4.5 Synthetic Blends
Materials of cotton and synthetic fibers or wool and synthetic fibers are usually processed as
would normally be performed on the 100% natural fiber. Tables 4-30 and 4-31 present typical
data for various finishing operations of cotton/synthetic blended fabric.
4-43
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4-45
-------
4.6 Individual Mill Operations
4.6.1 Introduction
The data presented in the preceding part of Chapter 4 dealt with individual operations within
each of the basic types of textile mills (i.e. cotton, wool, synthetic). In order to present a more
realistic view and characterize the types of textile mills now in operation, the results of two
recent nationwide plant investigations will be discussed in this section. The first of these re-
ports was prepared by the Institute of Textile Technology (ITT) and Hydroscience, Inc. for
the American Textile Manufacturers Institute, Inc. (ATMI) and the Carpet and Rug Institute
(CRI) (11). The second study performed by Lockwood Greene Engineers, Inc. for the Nation-
al Commission on Water Quality (NCWQ) was completed in 1975 (12). The data collected for
the latter represents approximately 400 returns from a mailed survey.
4.6.2 ATMI Study
Appendix E is the actual data collected by ATMI and CRI during the development of the "Blue
Book." The data was collected in 1972 and represents actual field investigations and data sub-
missions by a number of textile industries. The values presented are from 309 investigations
considered valid and are probably the most qualitative concerning raw textile waste which
are currently available. The data is presented for 12 of 13 categories defined by ATMI and CRI
Category 7 "Carpet Backing and Foam" has been omitted because of no data input.
The following description of industry categories (presented briefly in Chapter 3) has been
taken verbatim from the ATMI-CRI "Blue Book" and is included to characterize the data
sources.
The principal basis for determining into which of the 13 categories a particular plant
should be placed is the configuration of the predominant material being processed;
i.e., knit fabric, woven fabric, carpet, yarn, etc. Special processes, such as wool scouring
and latex application, provide additional definition. Review of the current structure of
the textile industry also indicates material configuration to be the principal factor for
classification of individual plants. Obviously, clear definition of the categories is essen-
tial in the administration of a viable program, and the following definitions for each
category are suggested:
4.6.2.1 Category 1 — Wool Scouring
Plant operations for the cleaning of raw wool fiber stock. Generally the major wet operation
associated with wool top manufacture and combing. May be a separate commission operation
or integral to a large mill such as a carpet manufacturing plant.
4-46
-------
4.6.2.2 Category 2 - Wool Finishing
Plants processing principally fabrics of wool which may require extremes of pH in finishing,
such as fulling, carbonizing and scouring.
4.6.2.3 Category 3 - Greige Mill
The manufacture of yarn or unfinished fabric which is shipped for subsequent manufacture or
finishing. Essentially a "dry" operation except for the application of lubricants or sizes to the
yarn to facilitate fabric manufacture.
4.6.2.4 Category 4 — Woven Fabric Finishing
The finishing of all woven fabric except wool fabrics. Includes printing, dyeing and other wet
finishing operations.
4.6.2.5 Category 5 — Knit Fabric Finishing
The finishing of all knit fabrics except wool fabrics. Predominant fibers processed tend to be
synthetic.
4.6.2.6 Category 6 — Greige Mill plus Woven Fabric Finishing
Manufacture of unfinished and finished woven fabrics in the same location. A combination of
Groupings 3 and 4.
4.6.2.7 Category 7 — Carpet Backing and Foam Application
Plants which fabricate finished carpets by assembly of previously-processed carpet or rug fabric,
such as tufted, woven or needle punched fabric and secondary backing fabric. May also include
application of foam, vinyl and other component materials.
4.6.2.8 Category 8 - Integrated Carpet Mill
Plants involved in the wet finishing and in most cases also the fabrication of finished carpets
and rugs. Typically includes carpet dyeing and printing operations as well as fabrication pro-
cesses described in Group 7.
4.6.2.9 Category 9 — Stock and Yarn Dyeing and Finishing
Plants which dye or finish textiles in the fiber or yarn form. Includes generally batch processing
operations such as stock dyeing, skein dyeing, thread dyeing and finishing, textile and carpet
yarn package dyeing, space dyeing and beam dyeing.
4-47
-------
4.6.2.10 Category 10 — Greige Mill plus Finishing Yarn and Fabrics
An extension of Group 6 to include also the finishing of yarn and/or knit fabrics.
4.6.2.11 Category 11 — Combined Materials Finishing, Stock, Yarn, Wovens, Knits
Plant dyeing and finishing different material forms. Typically involves various combinations of
Groups 4, 5 and 9.
4.6.2.12 Category 12 — Multiple-Operation, Commission House
Large plants carrying out an extremely varied and variable finishing operation.
4.6.2.13 Category 13 — Specialized Finishing
Plants carrying out processes not within the scope of this study; i.e., coating, tire cord and
fabric manufacture, nonwovens, etc.
Categories 3, 4, 5, 6, 8 and 9 are essentially those as originally proposed in the July 24, 1972,
Effluent Limitation Guidance publication. Categories 1 and 2 have been modified to separate
out wool scouring, and Category 7 has been used to separate out backing operations. Category
10 and 11 are characteristic combinations of other groups, and Category 12 covers the commis-
sion finishing operation. Category 13 covers specialized operations for which little information
is available, and plants in this category are likely outside the scope of the general interest of the
guidelines program.
"Finishing" as used in the preceding categories should be understood to include broadly all
wet-processing operations, such as dyeing, printing, mercerizing, scouring and other operations
used in the finishing of textile materials. As proposed from a preliminary analysis of data and
information, each of the categories accounts for a major identifiable segment of the textile
and carpet industry, having characteristic water use and/or particular effluent characteristics or
problems. With the above definition, 95% of the plants participating in this project could be
identified with a single category, and the remaining plants were identifiable with combinations
of two or possibly three categories.
In most cases the combining of categories may be carried out with a weighted average, prorated
on production, of values for each of the characteristic operations being carried out. In other
cases, however, additive combinations may be necessary, as in the case of a plant which
incorporated wool scouring with other processes. Where combinations are necessary, each case
should be carefully appraised on an invididual basis.
4-48
-------
While further refinement of these categories may reveal better definition of effluent generating
operations of individual plants (for example, fiber type and blend may provide a rationale for
subdividing the major categories), it is believed that the above principal category can provide a
workable basis for identifying characteristic effluent volumes and types.
4.6.3 National Commission on Water Quality Study
This Lockwood Greene study formulated eleven categories. These categories are listed and de-
fined below and correlate with the wastewater characteristics tabulation provided as Appendix F.
4.6.3.1 Category 1 — Wool and Animal Hair Scouring
This category includes all scouring operations for wool and other animal hair fibers. It in-
cludes any plant which receives grease wool or other animal hair fibers and scours to remove
the natural oils and impurities. Generally this is the major wet operation associated with top
manufacturing and combing and may be a separate commission operation or integral to a large
mill such as a carpet manufacturing plant. For the purpose of this report, wool is defined as
fibers taken from the fleece of a sheep. Other animal hair fibers include the hair from the
angora or cashmere goat as well as specialty fibers such as camel, alpaca, llama and vicuna.
4.6.3.2 Category 2 — Wool Raw Stock, Top and Yarn Dyeing
This category covers the dyeing of raw stock, top, or yarn in wool or other animal hair fibers
and is normally separated from either wool scouring or fabric dyeing operations. It should b6
separated from wool scouring (category No. 1) due to the character of the waste since wool
scouring is more normally associated with grease wool and the manufacture of natural wool top.
It is separated from category 11 (Raw Stock and Yarn Dyeing of Cotton and Synthetic
Fibers and Yarns) due to the character of the waste. It is also separated on the basis of process-
ing equipment required and organization in the industry. There is some overlapping of this
category with others, however, this is normally a separate operation.
4.6.3.3 Category 3 — Wool and Other Animal Hair Fabric Finishing
This category includes the dyeing and finishing of fabrics which are made of wool, other
animal hair fibers or blends of wool and synthetics. Both woven and knit fabrics are included,
and processes used could include printing, dyeing and wet or dry finishing. This category has
been differentiated from other finishing categories because of the wide variety of chemicals
used to process the wool fabric such as are used in carbonizing.
4-49
-------
4.6.3.4 Category 4 — Woven Dry Processing Mill
This category covers most greige mill operations which are relatively dry in comparison to
a true wet operation. Generally, the only wet operation is in the slashing of warp yarn. Slashing
is the application of lubricants and sizing (starch, PVA, CMC) where the only waste generated is
in the occasional dumping of starch batches and wash down of the size mixing and slasher area.
4.6.3.5 Category 5 — Adhesive Related Dry Processing Mill
This category covers processes which are basically dry but have some waste and wash down of
the bonding or adhesive chemicals which are normally latex compounds. Operations included
are laminating, coating, nonwoven carpet backing, and flocking. This is separated from cate-
gory 4 due to different waste characteristics and volumes.
4.6.3.6 Category 6 — Woven Fabric Finishing of Cotton and
Cotton/Synthetic Blends
This category is one of the most important since these plants produce most of the wastewater
effluent load in the textile industry. Processes included are desizing, scouring, bleaching, mer-
cerizing, dyeing, printing, resin treatment, and other special finish applications. Included in this
category are 100% cotton and cotton/synthetic blends.
4.6.3.7 Category 7 — Woven Fabric Finishing — Others
This category covers all fibers other than those in category No. 6 and includes 100% synthetics,
bast fibers, glass, silk and metallic fibers. This category comprises a small percentage of the
waste load and is separated for this reason as well as because of the processing methods re-
quired, i.e. no mercerizing, less bleaching and less use of resins.
4.6.3.8 Category 8 — Knit Fabric Finishing of Cotton and
Cotton/Synthetic Blends
This is the largest category of the knit fabric finishing categories and covers 100% cotton
and cotton/synthetic blends. Production processes can include bleaching, dyeing, printing, resin
treatment or other special finishing. This is set aside from hosiery and 100% synthetic knit
goods due to the production processes required and to the character of the effluent.
4-50
-------
4.6.3.9 Category 9 - Knit Fabric Finishing of 100% Synthetics
This category covers all 100% synthetic fabrics including polyesters, cellulosics, nylon and
acrylics and covers both hosiery operations and outerwear fabrics. These fabrics are separ-
ated from category 8 (Knit Fabric Finishing of Cotton and Cotton/Synthetic Blends) due to
characteristics and volume of the waste, i.e., use of different dyes and use of solvent scouring
in category 9.
4.6.3.10 Category 10 —Piece Dyeing and Printing of Carpets of Wool,
Cotton and Synthetics
This category covers the dyeing, printing and finishing of carpets of wool, cotton, or syn-
thetics. Processing operations includes scouring, dyeing, printing and finishing or carpet.
Wool carpets are also included in this category since they now comprise such a small per-
centage of the carpet business and because many carpet manufacturers produce both wool
carpets and synthetic carpets.
4.6.3.11 Category 11 — Raw Stock and Yarn Dyeing of Cotton and Synthetic
Fibers and Yarns
This category covers the scouring and dyeing of 100% cotton, cotton/synthetic blends and
100% synthetic fibers and yarns, and covers any stock or yarn dyeing operation performing
these functions. Mercerizing of cotton yarns is included in this category since this operation
in most cases is a part of the yarn dyeing and finishing operation.
4.6.4 Established Mill Waste Characteristics
In order to establish waste characteristics which represent each of the EPA categories, a com-
parison of results of both the ATMI and NCWQ studies has been made. Tables 4-32 thru 4-38
compare ATMFs average values and standard deviation to NCWQ's arithmetic mean values. It
is noted that ATMI water use figures are generally higher than those reported in the NCWQ
Survey. The values established for this manual are those judged to be reasonably representa-
tive of the specific category. It is these values which will be used in Chapter 7 to determine
the percentage of pollutant removal required to meet effluent requirements and the treatment
process most suitable.
4-51
-------
TABLE 4-32
ESTABLISHED WASTEWATER CHARACTERISTICS
WOOL SCOURING MILLS
(EPA Category 1)
BOD
TSS
COD
Oil & Grease
Total Chrome
Phenol
Sulfide
Color (ADMI)
Fecal Cohform
pH (Units)
Temp
Water Use (gal/lb)
ATMI
Avg.
mg/ 1
3,700
6,600
15,270
3,200
__
087
0 10
—
—
7.23
—
7.45
Std Dev
mg/ I
3,600
2,500
14,700
2,900
—
1 02
—
—
—
046
—
676
NCWQ
Anth Mean
mg/l
5,500
7,500
30,500
5,340
005
1 50
0.20
2,000
—
6-9
82° F
4.3
Use
mg/l
6,000
8,000
30,000
5,500
005
1.50
020
2,000
—
80
82° F
43
TABLE 4-33
ESTABLISHED WASTEWATER CHARACTERISTICS
WOOL FINISHING MILLS
(EPA Category 2)
BOD
TSS
COD
Oil & Grease
Total Chrome
Phenol
Sulfide
Color (ADMI)
Fecal Coliform
pH (Units)
Temp
Water Use (gal/lb)
ATMI
Avg.
mg/l
125
31
—
—
—
—
—
—
—
692
—
1383
Std Dev
mg/l
—
—
—
—
—
—
—
—
—
—
—
459
NCWQ
Anth Mean
mg/l
300
130
1,041
—
4
05
01
500-1700
—
6- 11
144°F
40*
Use
mg/l
300
130
1,040
—
4
05
0.1
1,000
—
7
144°F
40
Based upon data for 6 mills as supplied by the Northern Textile Association
4-52
-------
TABLE 4-34
ESTABLISHED WASTEWATER CHARACTERISTICS
DRY PROCESSING MILLS
(EPA Category 3)
BOD
TSS
COD
Oil & Grease
Total Chrome
Phenol
Sulfide
Color (ADMI)
pH (Units)
Fecal Cohform
Temp
Water Use (gal/lb)
ATMI
Avg
mg/l
274
87
871
—
865*
—
800
—
11 53
—
—
1 51
Std Dev.
mg/l
123
163
230
—
482*
—
—
—
578
—
—
1 52
NCWQ
Arith Mean
mg/l
300
150
950
—
—
—
—
—
6 - 11
—
70° F
1 5
Use
mg/l
350
200
1,000
—
014
—
80
—
10
—
70° F
1 5
*May be due to cooling tower discharges
TABLE 4-35
ESTABLISHED WASTEWATER CHARACTERISTICS
WOVEN FABRIC FINISHING MILLS
(EPA Category 4)
BOD
TSS
COD
Oil & Grease
Total Chrome
Phenol
Sulfide
Color (ADMI)
Fecal Coliform
pH (Units)
Temp
Water Use (gal/lb)
ATMI
Avg
mg/l
592
313
1,093
14
43*
01
2 72
—
—
11 62
—
18 14
Std. Dev.
mg/l
392
533
513
—
423
01
457
—
—
289
—
993
NCWQ
Arith Mean
mg/l
550
185
1,850
—
004
004
2 72
325
—
6-11
99° F
13.5
Use
mg/l
650
300
1,200
14
004
004
30
325
—
10
99° F
135
'High value may be due to sulfur dyeing.
4-53
-------
TABLE 4-36
ESTABLISHED WASTEWATER CHARACTERISTICS
KNIT FABRIC FINISHING MILLS
(EPA Category 5)
BOD
TSS
COD
Oil & Grease
Total Chrome
Phenol
Sulfide
Color (ADMI)
Fecal Cohform
pH (Units)
Temp
Water Use (gal/lb)
ATMI
Avg
mg/l
335
115
1,105
53
—
23.0*
—
1,295
—
690
—
2005
Std Dev
mg/l
303
123
345
—
—
—
—
1,046
—
205
—
9.77
NCWQ
Arith. Mean
mg/l
250
300
850
—
005
024
020
400
—
6-9
102°F
18
Use
mg/t
350
300
1,000
53
005
0 24
020
400
—
8
102°F
18
'One sample mill only
TABLE 4-37
ESTABLISHED WASTEWATER CHARACTERISTICS
INTEGRATED CARPET MILLS
(EPA Category 6)
BOD
TSS
COD
Oil & Grease
Total Chrome
Phenol
Sulfide
Color (ADMI)
Fecal Cohform
pH (Units)
Temp
Water Use (gal/lb)
ATMI
Avg
mg/l
177
75
852
—
042
013
—
—
—
—
—
75
Std Dev
mg/l
73
19
584
—
—
—
—
—
—
—
—
4 7
NCWO
Arith Mean
mg/i
340
120
925
—
—
—
—
600
—
6-9
67°F
8.3
Use
mg/l
300
120
1,000
—
042
0 13
0 14
600
—
8
67° F
83
4-54
-------
TABLE 4-38
ESTABLISHED WASTEWATER CHARACTERISTICS
STOCK & YARN DYEING & FINISHING MILLS
(EPA Category 7)
BOD
TSS
COD
Oil & Grease
Total Chrome
Phenol
Sulfide
Color (ADMI)
Fecal cohform
pH (Units)
Temp
Water Use (gal/lb)
ATMI
Avg
mg/l
240
77
882
—
027
—
—
12
—
8.93
— •
2226
Std. Dev.
mg/l
166
69
733
—
—
—
—
—
—
260
—
17.38
NCWQ
Arith. Mean
mg/l
300
50
52ft
—
0.013
0.12
—
600
—
7-12
100°F
18
Use
mg/l
250
75
800
—
0.27
0.12
0,09
600
—
11
100°F
18
4-55
-------
4.7 References
1. U.S. Department of Interior, Federal Water Pollution Control Administration, The Cost of
Clean Water: Volume III, Industrial Waste Profiles No. 4, Textile Mill Products, June 30,
1967.
2. U.S. Environmental Protection Agency, Technology Transfer, Wastewater Treatment
Systems, Upgrading Textile Operation to Reduce Pollution, Metcalf & Eddy, Inc. En-
gineers, October, 1974.
3. U.S. Environmental Protection Agency, State of the Art of Textile Waste Treatment,
Dr. John J. Porter, Clemson University, February, 1971.
4. Trotman, L., E.R. Dyeing and Chemical Technology of Textile Fibers, London: Charles
Griffin and Company (1964).
5. Masselli, F. and Burford, N.W. and M.G.,_4 Simplification of Textile Waste Survey and
Treatment, Boston New England Interstate Water Pollution Control Commission (1959).
6. U.S. Environmental Protection Agency, Industrial Waste Studies Program — Textile Mill
Products, Arthur D. Little, Inc., May 28, 1971.
7. U.S. Public Health Service, "An Industrial Waste Guide to the Cotton Textile Industry"
USPHS Pub. No. 677, Washington, D.C., U.S. Government Printing Office (1959).
8. U.S. Environmental Protection Agency, Technology Transfer, In Plant Control of Pollu-
tion Upgrading Textile Operations to Reduce Pollution, Institute of Textile Technology,
October, 1974.
9. Masselli, J.R. and M.G. Burford, Pollution Sources from Finishing of Synthetic Fibers,
Boston New England Interstate Water Pollution Control Commission (1956).
10. American Textile Manufacturers Institute, Textile Hi-Lights, June, 1974.
11. Institute of Textile Technology and Hydroscience, Inc., Recommendations and Com-
ments For The Establishment of Best Practicable Waste Water Control Technology Cur-
rently Available For The Textile Industry, for American Textile Manufacturers Institute,
Inc. and The Carpet and Rug Institute, 1973.
12. The National Commission on Water Quality, Textile Industry Technology and Costs
of Wastewater Control, Lockwood Greene Engineers, Inc. (NCWQ Contract No.
WQ54AC021), June, 1975.
Lund, H.F., Industrial Pollution Control Handbook, New York McGraw Hill Book Co.,
1971.
4-56
-------
CHAPTER 5
THE WASTE SURVEY
5.1 Introduction
One of the first major steps in an industrial water pollution control program is to define the
scope of the abatement effort by determining the characteristics of the wastewater. This chapter
deals with the wastewater characteristics, or waste water-survey, segment of the pollution con-
trol program and also with a continuing survey to monitor changing characteristics and to aid
in evaluating production changes.
The waste-survey topic can be broken into the following four essentially chronological seg-
ments:
• Preliminary survey
• Detailed survey
• Data evaluation
• Continuing monitoring
5.2 Preliminary Survey
The initial effort in a water-pollution-control program is typically a feasibility study that at-
tempts to answer the following questions:
• What will be the discharge criteria?
• What are the likely methods of treatment?
• What in-plant alternates are available for waste reduction?
The data base for this feasibility study is the information gathered from a preliminary waste
survey. The goals of this initial survey are to:
• Determine the approximate volume of wastewater
• Determine the approximate wastewater characteristics
• Define the major waste sources and possible methods of in-plant waste reduction and
control
• Define the approximate characteristics of the raw-water source and the receiving stream (1).
The purpose of the survey, therefore, is not to define the problem for the purposes of final
commitments, but only to obtain an accurate overview that will allow selection of the most
likely problem solutions from the many that are available. The duration and complexity of this
work will vary proportionally with the size and complexity of the mill and with the degree to
which experience or the literature can provide direction or answers.
5-1
-------
Any preliminary survey should consist of the following segments:
• Development of an approximate water arid wastewater balance
• Wastewater sampling and analysis
• Review of manufacturing operations and raw material usage
• Flow measurement, sampling and analysis of major waste sources
• Sampling and analysis of the raw water and receiving stream
Incoming-water information for the mill can be developed from any of the methods shown in
Table 5-1. Ideally, there will be water meters installed on the major branches of the mill-distri-
bution system, but this is seldom the case, and an approximate breakdown of the water flow is
usually necessary. These water data should cover several 1-month periods in order to reflect
various production levels and product mixes. This water use should be broken down on a daily
basis, and the production level for each area should be recorded. The final result of this work
will be a drawing such as that shown in Figure 5-1, which indicates the distribution system, the
water usage in gallons per day and the water usage rate in gallons per pound of cloth.
Similarly, a detailed map should be developed showing the location of major sewer lines and
sources of wastewater. Process, sanitary and storm water sources should be indicated, as should
be points of discharge.
Typically, most mills do not have an accurate drawing showing the locations of all sewer lines
and waste sources, but it is important that this map be developed. Dye tracing should be used to
identify what happens to all known sources and to check for cross-connections between separ-
ate sewer systems.
TABLE 5-1
METHODS OF FLOW MEASUREMENT FOR
INCOMING WATER AND WASTEWATER
Water
Method
Incoming
Waste
Daily water-meter readings
Monthly water bills
Records of pump running time
Estimations of capacity of water-use points
Discharge through an orifice
Discharge over a weir
Discharge through a flume
Salt injection
Dye or float timing
Timing of a container
Pump timing
Current meters
Venturi, orifice, or magnetic flow meters
Rotameter
5-2
-------
GALLONS PER DAY/GALLONS PER POUND
Minimum Average Maximum
Evaporation
Finishing room
Bleach range
Continuous range
Dye house
Chemical room
Air-pollution equipment
Sanitary
Utility cooling
Process cooling
FIGURE 5-1
WATER-DISTRIBUTION SYSTEM FOR A FINISHING PLANT
Flow rates for sanitary and storm water sources can be estimated, but flow rates for the process
sewer or sewers should be determined by flow measurement. The method of flow measure-
ment used is dependent on the volume of water, the physical restraints of the measurement
point, and the accuracy required. Tables 5-1 and 5-2 and Figure 5-2 show the various methods
of measuremen normally used and the conditions under which they are appropriate.
For a preliminary study, flows should be measured once per hour over a 24-hour period 1 day
per week for 4 weeks. These data can then be compared with production and water-use data to
extrapolate to vaiious production levels.
The final result of this work will be a drawing such as that shown in Figure 5-3, which indicates
the sewer system, the flow in gallons per day from the major waste sources, and the flow rate
in gallons per pound of cloth from the major waste sources.
Simultaneous with the flow measurement, sampling of the wastewater should be accomplished.
An automatic sampler station that will provide hourly samples is recommended. This equipment
should allow for either continuous or intermittent sampling so that each hour sample will be a
composite. Figure 5-4 shows various sampling equipment arrangements.
5-3
-------
TABLE 5-2
COMPARISON OF FLOW-MEASUREMENT TECHNIQUES
Specific notes
Method
Orifice
Weir
Flume
Salt injection
Dye or float
Container
Pump
Current meters
Flow meters
Rotameter
Open end pipe
Flow range
Small
Small to large
Small to large
Small to medium
Small
Small
Small to large
Small to large
Small to large
Small to medium
Small to medium
Cost
Medium
Medium
High
Low
Low
Low
N/A
Medium
High
Medium
Low
Ease of
installation
Fair
Fair to difficult
Difficult
Fair
N/A
N/A
N/A
Fair
Difficult
Fair
Fair
Accuracy
Excellent
Good to excellent
Excellent
Good
Fair
Good
Fair
Fair
Excellent
Good
Fair
Application
Pipe and open channel
Open channel
Open channel
Pipe and open channel
Open channel
Pipe and open channel
Pipe
Pipe and open channel
Pipe
Pipe
Open channel
General notes
Method
Notes
Orifice
Weir
An orifice can be used to determine the flow from a vessel through a circular outlet by measuring
the height of water in the vessel
A weir is used to determine flow by measuring the difference in elevation between the discharge
edge (crest) and the upstream water level
Weirs are simple, reliable measurement devices when they are installed correctly Accuracy is ±5
percent
• The weir crest must be sharp
• Air must have access to the underside of the falling water
• Leaks must be sealed
• Weir must be exactly level
• Weir approach must be kept clean of sediment
• The head should be measured back of the crest at least five times the height
• The upstream channel should be reasonably free from disturbances
• A weir measurement should consist of the average of several equally timed readings
There is more head generated on a V-notch weir, therefore, these weirs are used for smaller flows
in order to maintain accuracy
Automated level recorders (pressure or mechanical) should be used for permanent installations or
deep sewers
A Parshall flume is a permanent installation that measures the difference in water levels caused by
a constriction m the channel cross section
The advantage of dependable accuracy, low head loss, and large capacity range are offset by the
high installation costs The flume can be purchased as a complete package with flow recording
equipment
An accuracy of ±5 percent is obtained when the equipment is installed properly.
• Standard dimensions must be used
• The downstream head should not exceed the recommended percentage of upstream head
• The upstream head is measured in a stilling well
• The flume is installed in a straight channel, and there is no close upstream turbulence
(Continued)
5-4
-------
TABLE 5-2 (Continued)
COMPARISON OF FLOW-MEASUREMENT TECHNIQUES
General notes
Method
Note
Salt injection
Floats
Container
Pump
Current meters
Flow meters
Rotameters
Open-end pipe
The salt injection method depends on determining the downstream concentration of a readily
detectable chemical (e g lithium chloride) when a known quantity of the material is injected
upstream The method is useful when
• The physical location of the sewer (e g , depth) makes weir measurement impossible
• Waste is flowing under pressure
• Accurate total flow values are required, and mechanical or frequent manual weir height
measurement is not feasible
• A simultaneous sampling is being conducted
This method requires the measurement of water depths and velocity and should only be used for
approximations of flow
This method requires measuring the time for a discharge to fill a vessel of known volume and is
good only for small flows
This method requires timing the amount of time a pump is running and determining the water
volume from the pump characteristics It should only be used for approximations of flow
This method requires determining the cross sectional area of a channel and measuring the water
velocity in several segments The method is used for measumg small stream flows
Flow meters measure water flow in pressure systems by detecting differential pressure across a
contraction (e g , Venturi tube or orifice plate) or by detecting the electrical potential produced by
the flow This equipment is accurate and reliable over a wide range of flows but is an expensive,
permanent installation
These meters measure water flow by the water turning a set of gears to totalize flow or by suspending
a float to indicate instantaneous flow The equipment will vary widely in cost depending on size
and accuracy requirements
This metnod requires the measurement of vertical fall of a free-flowing discharge from a pipe and
should only be used when other methods are not practicable
The test methods recommended by the EPA in the June 29, 1973, Federal Register are sum-
marized in Table 5-3.
At the end of a 4-hour period, the hourly samples should be chemically preserved and refrig-
erated unless analyzed immediately. Table 5-4 shows the preservation procedures recommended
by the EPA. The EPA Methods of Chemical Analysis of Water and Wastes is recommended as
the procedural standard. Figure 5-5 shows the results of a flow and sampling survey.
The analytical schedule for the process sewer samples is dictated by the discharge criteria and
by a knowledge of manufacturing chemicals. EPA and the States require the filing of a permit
application for obtaining a discharge permit under the 1972 amendments. This application re-
quires information on some 60 parameters. In order to limit the extent of the analysis program,
it is recommended that the schedule shown in Table 5-5 be used for the preliminary survey.
The work discussed above is to develop the information necessary for final treatment of the
wastes. Of equal importance is the in-plant analysis to define major sources and possible meth-
ods of waste reduction and/or segregation. This work is started by developing 1) a material bal-
ance for each major production unit and 2) a history of chemical and dyestuff usage.
5-5
-------
c = 0.632
c = 0.966
Q=cA,
A. ORIFICE
2gH
Q = discharge, ftVs
c = constant
A = orifice area, ft2
V = velocity, ft/s
g = acceleration due to gravity,
ft/s2 = 32.2
H = head, ft
« = 671/2° 45° 22'/2°
c - 0.684 0.753 0.882
0.75L
2.5L
&)° V Notch
Q = 2.52H247
Q = discharge, ftVs
H = head, ft
B. WEIRS
H
2.5H
Rectangular Weir
Q = 3.33LH1-5
Q = discharge, ftVs
H = head, ft
L = length of weir, ft
Q = 4WH
n
Q = discharge ftVs
W= throat width, ft
H = head, ft
n = 1.522W0026
1. H<1/3 L
2. 0.5
-------
D. FLOATS
Q=A'.k(D/T)
Q = discharge, ftVs
A = wetted cross sectional area of sewer ft2
D = distance between manholes, ft
T = average time, s
K = 0.8 for floats and 1.0 for dyes
Metering pump
Chemical drum
.. ./" Sampling pump
Sample receivers
Manhole 1
Manhole 2
Q=
Qt(Ct-C)
E. CHEMICAL TRACERS
Q = discharge, ftVs
Q t= discharge of tracer
C = concentration of tracer
in water after injection
Ct = concentration of tracer
being injected
F. END OF PIPE
Q = discharge, gal/min
A = area, ft2
Y = distance from water level
in pipe to water level
in stream at X, ft.
FIGURE 5-2
(Continued)
5-7
-------
Storm water
Cooling
Evaporation
Finishing room
Bleach range
Continuous range
Dye house
Chemical room
Air-pollution
equipment
Sanitary
©
©
©,
GALLONS PER DAY/GALLONS PER POUND
Minimum Average Maximum
2N
O)
c
> E
CD CD
O CD
CD £
DC (o
©
©
©
eatmen
FIGURE 5-3
SEWER-SYSTEM SCHEMATIC FOR WASTE SURVEY
The intent of the material balance is to indicate both the fabric and chemicals going into and
out of a production unit. It is typical that the concentration of the chemicals coming from a
production unit cannot be readily determined. Therefore, at least the wastewater characteristics
should be indicated. The vendors of chemicals used in the mill can be of help in determining ef-
fluent concentrations of their materials. Examples of this work are shown in Figures 5-6 and 5-7
and Table 5-6. The material balance analysis also serves as a check on process efficiency and
may indicate potential cost-saving changes.
The intent of the analysis of chemical and dyestuff usage is to approximate the chemical nature
of the wastewater. As in the case of the water balance, at this stage only one or two representa-
tive months need to be examined. The form of this analysis can be as that shown in Table 5-7
and will indicate the importance of various chemicals to the treatment system. As part of the
in-plant sampling and analysis program, an analysis of the wastewater characteristics of the
major chemicals at various concentrations may be made. The data, when combined with a
knowledge of the concentration in the effluent, will help to evaluate the treatment alternatives.
5-8
-------
Types of Samples
• Grab: A single, manually collected sample
• Continuous: A single sample or a series of samples taken over a period of time by either
— A continuous small volume of flow
—An intermittent small volume of flow
—An intermittent small "Cut" of a larger volume of flow
• Composited: A single sample made up of flow-proportional amounts of several individual
samples. The sample may be either a grab or a continuous composite.
A. Portable, self-contained sampling unit,
variable speed, on/off flow, single composite
B. Same as "A" but with hourly compositor
0
C. Multiple-head, variable-speed pump with on/off flow for semipermanent installation
D. Self-contained sampling unit with
refrigeration unit
FIGURE 5-4
SEVEN TYPICAL METHODS OF SAMPLING WASTES
(Continued)
5-9
-------
n
E. Dipper sampler
F. Mechanical sampler with pump to obtain
a "split" or "cut" sample
G Permanent flow and sample station consisting of a flow recorder,
transmitter, variable-speed pump, and pump timer mounted over a
Parshall Flume
General notes.
• The sample point should be at approximately one-third of the water depth for sewers
and channels.
• Sampling point should not be adjacent to turbulent area, but flow should be mixed to insure
representative sampling, particularly of solids.
• Tube size and sample velocity should be considered to insure proper handling of solids.
• Flow variations can normally be adequately covered with a sampling frequency of 10-15
minutes unless the variations are very large.
• For suction lifts of greater than 12 feet, submersible pumps should be used.
• Sample containers should be glass or inert plastic and adequately washed after being emptied.
• For winter sampling, tubing should be placed in heat-traced pipes and sampler placed in
a box with a heat lamp or heat pad.
FIGURE 5-4
(Continued)
5-10
-------
TABLE 5-3
TEST METHODS RECOMMENDED BY THE EPA
Measurement
Alkalinity
Ammonia nitrogen
Arsenic
Boron
Cadmium
Chloride
Chromium
Conductance specific
Copper
Fluoride
Hardness
Iron
Magnesium
Manganese
Mercury
Nitrate nitrogen
Nitrogen, total Kjeldahl
Organic carbon, total
Organochlorme pesticides
Orthophosphate
Oxygen demand, biochemical
Oxygen demand, chemical
Phosphorus, total
Selenium
Silver
Solids, total
Surfactants
Suspended nonfilterable solids, total
Temperature
Zinc
Reference'
C,
C,
A,
A,
C,
B,
C,
B,
C,
A,
A,
C,
C,
C,
D
A,
A,
C,
D,
C,
A,
A,
C,
A,
C,
A,
A,
A,
A,
C,
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
6
134
65, 4A (digestion) A, p 62, method 104A (measurement
69
83
21,
83
162
83
171
179
83
83
83
458
469
221
method A
, method
method
, method
, method
method
B
121A with p 174, method 121C
122A
213B
216
Appendix A, Part II
P
P
P
P
P
P
P
P
P
P
P
243
489
495
242
296
83
535
559
537
559
83
, method
, method
, method
, method
, method
, method
, method
219
220
150A
224A
229
224C
162
'"A" refers to Standard Methods for the Examination of Water and Wastewater, 13th edition, 1971 This publication is
available from the American Public Health Association, 1015 18th St, NW , Washington, D C 20036
"B" refers to the Annual Book of Standards, Part 23, Water, Atmospheric Analysis, 1972 This publication is avail-
able from the American Society for Testing and Materials, 1916 Race St, Philadelphia, Pa 19103
"C" refers to Methods for Chemical Analysis of Water and Wastes, Environmental Protection Agency, Analytical
Quality Control Laboratory, Cincinnati, Ohio This publication is available from the Superintendent of Documents,
U S Government Printing Office, Washington, D C 20402 (Stock no 5501-0067)
"D" refers to National Pollutant Discharge Elimination, appendix A, Federal Register, 38, No 75, pt II.
5-11
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TABLE 5-4
SAMPLE PRESERVATION REQUIREMENTS FOR VARIOUS PARAMETERS
Parameters
Preservative
Maximum
holding
period
Acidity-alkalinity
Biochemical oxygen demand (BOD)
Calcium
Chemical oxygen demand (COD)
Chloride
Color
Cyanide
Dissolved oxygen
Fluoride
Hardness
Metals, total
Metals, dissolved
Nitrogen, ammonia
Nitrogen, Kjeldahl
Nitrogen, nitrate-nitrite
Oil and grease
Organic carbon
PH
Phenolics
Solids
Specific conductance
Sulfate
Sulfide
Threshold odor
Turbidity
Refrigeration at 4°C
Refrigeration at 4°C
None required
2 ml H2SO4 per'liter
None required
Refrigeration at 4°C
NaOH to pH 10
Determine on site
None required
None required
5 ml HNOs per liter
Filtrate: 3 ml 1:1 HNOa per liter
40 mg HgCl2 per liter—4° C
40 mg HgCl2 per liter—4°C
40 mg HgCl2 per liter—4°C
2 ml H2SO4 per liter—4°C
2 ml H2SO4 per liter (pH 2)
Determine on site
1.0 g CuSO4/1 +HsPO4to pH 4.0—4° C
None available
None required
Refrigeration at 4°C
2 ml Zn acetate per liter
Refrigeration at 4°C
None available
24 hours
6 hours
7 days
7 days
7 days
24 hours
24 hours
No holding
7 days
7 days
6 months
6 months
7 days
Unstable
7 days
24 hours
7 days
No holding
24 hours
7 days
7 days
7 days
7 days
24 hours
7 days
Source Methods for Chemical Analysis of Water and Wastes, EPA, 1971
5-12
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en
E
Q
O
CD
en
Hours
FIGURE 5-5
Hours
TYPICAL PRELIMINARY SURVEY RESULTS OF BOD
AND FLOW MEASUREMENTS AS A FUNCTION OF TIME
TABLE 5-5
PRELIMINARY SURVEY ANALYTICAL REQUIREMENTS
ON SAMPLES COLLECTED
First set of samples
Time of measurement
Item measured
Time-of-flow measurement
Hourly
24-hour composite
Dissolved oxygen
Temperature
BOD
COD
Suspended solids
PH
Color
Alkalinity
Dissolved solids
Various forms of nitrogen
Phosphorus
Turbidity
Various forms of sulfur
Halogens
Cyanide
Phenol
Surfactants
Aluminum
Arsenic
Cadmium
(Continued)
5-13
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TABLE 5-5 (Continued)
PRELIMINARY SURVEY ANALYTICAL REQUIREMENTS
ON SAMPLES COLLECTED
Time of measurement
Item measured
24-hour composite—Continued
Calcium
Chlorinated hydrocarbons
Coliform bacteria
Cobalt
Chromium
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Nickel
Potassium
Zinc
Second, third, and fourth set of samples
Instantaneous and hourly
24-hour composite
Same as first set
Dissolved solids
Forms of nitrogen (p > 0.1)
Phosphorus
Turbidity
Forms of sulfur (p^> 0.1)
Halogens found (p^> 0 1)
Cyanide (p>0.01)
Phenol
Surfactants
Aluminum (p ^>1.0)
Arsenic (p> 0.01)
Cadmium (p^>0.01)
Calcium (p>10)
Cobalt (p>0.01)
Chromium
Copper
Iron
Chlorinated hydrocarbons (p>0.01)
Coliform bacteria (p >1000);
Lead (p >0.01)
Magnesium (p > 10)
Manganese (p > 1)
Mercury (p> 0.001)
Nickel (p> 0.001)
Potassium (p > 10)
Zinc
Mote.—The shorthand (p>0.01) indicates that further analysis is necessary only if the first analysis indicates a value
greater than 001 mg/l
5-14
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Dye mix
Water
Fabric-
p
1
Dye
]
i i
pad
- -j
Washer
Finish pad
Frame
-»- Waste
Equipment
Dye pad Washer Finish pad wash
PH
BOD
COD
Color
Flow
Dye formulas
Finish formulas
Miscellaneous chemicals
Products
Product rate
FIGURE 5-6
DYE-RANGE MATERIAL BALANCE
5-15
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-Fabric
-Caustic soda
_ Water —
Mercenzer
Washer
No. 1
No. 2
No. 3
No. 4
No. 5
No. 6
-»- Waste
Alkalinity
Fabric
Waste
Fabric production rate:
Total water use:
Total caustic use:
Concentration:
FIGURE 5-7
MERCERIZER AND WASHER MATERIAL BALANCE
TABLE 5-6
LIST OF IMPORTANT ITEMS FOR TEXTILE IN-PLANT SURVEYS
Identification of print paste, grease, and solvent wastes for segregation to separate treatment
Identification of sources of chemicals potentially toxic to activated sludge systems (such as
dyes, solvents, carriers, or finishes)
Identification of sources of shock loads (such as finishing bath dumps)
Identification of sources of high concentrations of refractory, nonbiodegradable wastes (such
as carriers and finishes)
Identification of sources of foam-producing chemicals (such as detergents)
Evaluation of size substitutions
Optimization of countercurrent washes
Evaluation of reuse of weak rinse wastes
Evaluation of segregation of high strength (such as BOD, COD, color, or alkalinity) for
separate treatment
Evaluation of processing of caustic wastes for reuse
Evaluation of segregation of dyestuffs (acid, disperse, etc.) for separate treatment
Comparison of hypochlorite and hydrogen peroxide bleaching
5-16
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TABLE 5-7
EXAMPLE OF ANNUAL CHEMICAL USAGE, 1972
Rank
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Chemical (type)1
Carrier NT (B)
Neutrol #9 (C)
Aerotex water repellant 95 (D)
Cap LEV LSP (C)
Soap OFF 60 (A)
Acetic acid (E)
Neoport APO (B)
Solvecrest RB (A)
Monosodium phosphate (E)
Caustic soda (E)
Dispersing agent (C)
Avitone F (C)
Calgon (F)
Fanapon X70 (A)
Neoport DPG (B)
Raycofix NY (H)
Sanopan DTC (A)
Formic acid (E)
Sodium hydrosulfite (A)
Cap Carrier BB (B)
Ammonium chloride (E)
Herriton SWD (C)
Intrawite EBF (G)
Gluconic acid (C)
Tanalube RF (C)
Usage
Pounds
331,457
200,064
136,205
132,685
126,708
124,206
117,609
110,788
92,672
89,673
84,887
72,443
69,130
58,198
51,871
48,428
47,227
46,779
45,983
38,867
38,189
36,698
30,242
27,416
24,654
Percent
12.540
7.569
5.153
5.020
4.794
4.699
4.449
4 191
3.506
3.393
3.212
2.741
2.615
2.202
1.962
1.832
1.787
1.770
1.740
1.470
1.445
1.388
1.144
1.037
0.933
1 A=scour, B=carner, C=dyemg assistant, D=fimsh, E=pH control chemicals, F=softener, G=fluorescent, H=fixmg
For in-plant sampling, the use of appropriately chosen grab samples is usually sufficient. These
samples should be taken during each part of the production cycle, and an estimate or measure-
ment of flow should be made. Important wastewater characteristics should be measured in each
sample, but it is not necessary to perform a full analysis of each sample.
Also, on the day that the process sewers are sampled, a single grab sample should be obtained
from the receiving stream and the raw waste for complete analysis.
It should be apparent at this point in the review of the waste survey requirements that there is
a significant analytical load to any meaningful survey and that there is a strong emphasis on in-
plant production analysis.
5-17
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Considering the degree of treatment being required of the textile industry, an important key to
compliance will be a competent water-quality laboratory to provide both operating and report-
ing data. If a plant does not have sufficient facilities or staff for this work, then serious thought
should be given to acquiring the capability on this early stage to assure maximum familiarity
with the wastewater problem. This decision can usually be economically justified in light of
outside laboratory costs.
Also, the importance of introducing responsible production personnel at the onset of the water-
pollution-control program cannot be understated. This becomes even more important as regula-
tions require consistent removal of virtually all pollutants from the discharge. Soliciting process
information and keeping the production personnel informed of the work under way is the best
way to develop a program of optimum waste reduction and recycling and to determine how the
waste is affected by the operating characteristics of the process and its susceptibility to upset,
misoperation and change.
5.3 Detailed Survey
After completion of the initial feasibility study, a decision will probably be made to evaluate,
over a period of time, the treatment processes and in-plant control measures selected as the
most likely solutions. This additional detailed process evaluation survey is necessary to establish
the process design parameters firmly and should also be utilized to gather additional waste
characterization and in-plant data.
Ideally, this final survey program should last 1 year in order to observe seasonal variations and
production vagaries and to allow time to develop and explore alternatives fully. The elements of
this detailed survey are essentially the same as the initial survey, but the intensity, duration and
precision of the various aspects have increased.
The incoming water balance information should continue to be recorded. Water meters will
allow for daily measurements. These data should be reported both as gallons per day and gallons
per pound of cloth. Similarly, refinement of the sewer balance should be undertaken.
At least one permanent flow measurement station should be built for a continuous record of
total plant effluent volume on a daily basis. This equipment should provide a 24-hour graph of
flow. If the wastewater volume can justify the expense, multiple stations should be installed
to measure flow from each department or division. An example of station locations is shown
in Figure 5-8.
As part of this station, a permanent sampling station should be installed to provide a single
daily-flow composited sample. Periodically, this composite can be removed once every hour to
evaluate variations in waste strength.
5-18
-------
FIGURE 5-8
DETAILED SURVEY SAMPLING POINTS
Storm cooling and water
Sanitary
Process effluent
Finishing room
Frames
Dye house
Chemical room
Continuous range
Becks
Permanent flow and
sampling station
Preparation room
Portable flow and
sampling station
Bleach range
Grab samples
A program of daily analysis of the process sewer waste should be instituted. This program
should attempt to frequently monitor critical wastewater characteristics and to regularly mea-
sure all necessary characteristics. A recommended analytical schedule is presented in Table 5-8.
Both flow and contaminant data should be reviewed frequently to determine trends and to
change the direction of the work as required.
Production data should also be recorded during this period. A history of chemical and dyestuff
usage should be maintained on a monthly basis. A history of production volume by major
product lines should be maintained on a weekly or daily basis. Changes in production chemicals
or processes should be noted.
Sampling and analysis of both raw water and receiving-stream water should continue once every
2-4 weeks. Raw-water samples should be taken on days when complete sewer analyses are
scheduled.
If possible, any planned segregation of sewers should be accomplished during the study to make
sure that valid data are obtained. Frequently, paper "substations" are not duplicated in the field
because complete segregation is not always possible.
5-19
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TABLE 5-8
DETAILED SURVEY ANALYTICAL SCHEDULE
Characteristic
Flow
BOD
COD
Suspended solids
Dissolved solids
pH
Temperature
Dissolved oxygen
Color
Turbidity
Nitrogen
Phosphorus
Detergent
Phenols
Alkalinity
Metals
TOC1 (or other
instrumented method)
Main process
sewer
0
2
2
2
3
2
1
1
2
3
3
3
3
3
2-4
3-4
4
In-plant
sewer
3
4
3
4
4
4
4
4
4
4
4
4
4
4-5
4-5
4-5
4-5
Cooling, sanitary, raw,
and stream water
4
4
4
4
4
4
4
4
4
4
4
4
4
5
4-5
5
5
TOC1 indicates total organic carbon.
Note —0 measured daily, 1 measured in place, 2 measured 3 times per week, 3 measured 1 time per week,
4 measured 2 times per month, 5 measured 1 time per month
The in-plant survey portion of the detailed survey is critically important. At this point, a signifi-
cant amount of time should be spent reviewing the environmental impact of each waste source
and each major chemical used.
It is especially valuable to observe production machinery under various conditions to deter-
mine the validity and variability of the data being collected and to determine the impact of
problems and malfunctions, since these usually result in higher waste loadings.
This is the time to scrutinize each segment of each production process to determine if the mini-
mum amount of water and chemicals are being used. Also, alternate chemicals need to be evalu-
ated to determine if production goals can be met with a lower environmental impact. The pro-
duction machinery itself should be reviewed to determine if the cost of alternate equipment
would offset the cost of treating the pollutants generated. It is helpful at this point to begin to
break down the projected water-pollution-control cost by department to make economic justifi-
cation of charges easier to determine.
This is also the time to police the plant to eliminate unnecessary uses of water and to institute
a program of prevention of accidental pollution. Typical examples are presented in Table 5-9.
As in the case of sewer segregation, any significant process changes should be made during the
course of the study to insure that accurate and updated data are obtained.
5-20
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TABLE 5-9
LISTING OF MISCELLANEOUS POLLUTION SOURCES
Eliminate running hoses.
Replace or repair leaking pumps, compressors, heat exchangers, or other similar equipment.
Install water meters and level controls on process equipment to minimize water use.
Dike chemical storage areas and make sure chemical-handling equipment is designed to
minimize accidental spillage.
Institute dry clean up of dry-chemical spills.
Institute a reporting system for chemical spills and other extraordinary discharges to the
plant sewer system.
Evaluate wet air-pollution equipment for change to dry equipment.
Evaluate maintenance and equipment-cleaning chemicals for pollution potential.
Evaluate boiler and cooling tower chemicals for pollution potential.
At the completion of the detailed survey, a sound foundation exists for establishing the basis for
a treatment system design. The longer the detailed survey, the more variation in wastes will be
seen. This information on variation is critically important. The treatment plants that will be
required to meet new standards will have to achieve very high performance standards. Yet,
unlike other typical chemical processes, there is limited control over the raw material to this
plant.
5.4 Data Evaluation
With an accumulation of data, the evaluation of the data is done statistically. Probability and
daily pollutant load curves, similar to those shown in Figure 5-9, allow for the interpretation of
this large volume of information.
Wastewater data should be evaluated not only by themselves, but also in terms of the produc-
tion. Data should be presented as gallons or pounds per unit of total production. If possible,
production data should be broken down into major categories and a computer correlation should
be made with daily wastewater data broken down to give gallons or pounds per unit of each
product line or production area.
5-21
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co
73
C
D
o
a
"TO
o
^_
CO °-
C CO
o c
= o
ro =
Percent below
Days
.a
ro
T3
C
D
O
a.
^.
0)
Q.
co
c
O
O
Percent below
FIGURE 5-9
GRAPHICAL RESULTS OF DETAILED SURVEY
The data collected should also be interpreted in terms of the production processes and chemi-
cals used, and separate evaluations should be made, when possible, for the various periods.
The final step in the data evaluation segment is to correlate the information on present opera-
tion with the estimated capacity of the present or future manufacturing facility. The more pro-
duction segments that can be used to compile the estimate, the better the validity of the design
basis.
5-22
-------
5.5 Continuing Monitoring
In addition to providing the basis for a rational wastewater-treatment-system design, the infor-
mation collected during the detailed survey will serve as a standard in monitoring the treatment
facility for operational purposes and in comparing alternate production methods and chemicals.
The importance of involvement of production personnel is strongly emphasized. Each super-
visor should be aware of his department's portion of:
• The pollutants in pounds per pound of product
• The flow in pounds per pound of product
• The treatment cost in pounds per pound of product
• The environmental effect of production upsets
• The environmental impact of major production chemicals
Since textile mills are users of a wide variety of chemicals and since product lines regularly
change, there is a continual change in the chemicals found in the sewer. It is imperative that in
addition to production characteristics, the environmental characteristics be considered in evalu-
ating a new chemical. During the detailed survey, the pollution potential should be determined
for important chemicals. In the continuing survey, these characteristics are recorded for all chemi-
cals. Also in the detailed survey, brief treatability studies on the major chemicals may have been
done; this work should be continued. An example of the data that might be collected is given
in Figure 5-10. This information will serve as a standard for comparing alternate chemicals.
Continuing monitoring is incomplete without an analysis of the impact of the discharge on the
receiving stream. First, stream flow records should be obtained from the U.S. Geological Survey
in order to develop critical flow values for various periods during the year. Second, information
on quantity and location should be gathered on users of and dischargers to the receiving stream.
Third, the receiving water should be completely analyzed, with single, representative grab sam-
ples of water above the discharge should be obtained when the process sewers are sampled. Finally,
a single sample of bottom deposit above the discharge should be obtained for examination for
basic indicator organisms and for chemical analysis. This later work will indicate the present
condition of the stream and its tolerance to additional pollutants.
The advent of industrial discharge criteria would seem to obviate the need for consideration of
the effect on the receiving stream, but it should be remembered that many States have or are
developing stream criteria that may be more stringent than the Federal guidelines. This is
especially important when the discharge is to a stream rather than a large river.
In addition to the upstream sampling and analysis of receiving stream water, a profile of the re-
ceiving stream at various stages below the discharge should be examined. This profile should
consist of both chemical and biological analysis of the water and the sediment and will serve
as a baseline of the stream's condition against which the new charge can be compared. A single
5-23
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bioassay and multiple chemical assays will be necessary for accurate results. Also, static toxicity
studies using local species of fish and expected effluent should be performed to determine max-
imum allowable pollutant concentrations and to verify design discharge criteria.
Finally, the continuing survey should monitor individual processes to make sure that unneces-
sary amounts of water and chemicals are not being used. That is, environmental impact should
become a tangible part of the industrial engineering function of process optimization.
COD (TOG) of 1.0% solution:
O
O
LJJ
COD removal by
activated sludge
at MLSS of 3,000 mg/l
Concentration of chemical
COD removal by
coagulation with
400 mg/l alum
O
O
H
Q
O
O
t:
o>
_3
LU
Concentration of chemical
COD removal by
carbon adsorption
with 30 lb/1,000 gal
FIGURE 5-10
TYPICAL DATA FOR DETERMINING TREATABILITY OF
PROCESS CHEMICALS
5-24
-------
5.6 References
1. U.S. Environmental Protection Agency, Technology Transfer, In-Plant Control of Pollu-
tion, Upgrading, Textile Operations to Reduce Pollution: Chapter 1, Waste Survey,
October, 1974.
5-25
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CHAPTER 6
IN PLANT WASTEWATER CONTROLS
6.1 Waste Volume Reduction
It is obvious that the more wastewater volume is reduced in processing, the less water will have
to be treated at the waste treatment plant. Indeed,with all the more pressing production cost
savings, it is sometimes difficult to stop and look at the advantages of reducing water usage.
However, as the price of treated water continues upwards, along with the price of waste treat-
ment, priorities will change and increasingly favor water conservation.
6.1.1 Previous Studies
Numerous studies have been carried out which indicate water usages by industrial subcategory
and process, but no obvious relationships are seen to exist between processes to indicate specific
water uses in gal/lb, and the total quantity of water used. Smaller companies in general show
lower water usage per pound of fabric, but there are also some with usages above the average.
Plants in the same subcategory that carry out many processes will obviously use more water
per pound of product than those performing fewer. Those processing heavier weight fabrics may
use more water than those processing lightweight goods. In other words, the complexity of pro-
cessing and fabric weight are major factors determining water usage.
The following Tables 6-1, 6-2, and 6-3, indicate water usages in wool, cotton and man-made
fiber processing. These tables should be regarded as estimates of water use, due to lack of
accurate flow measurement and small samplings.
Refer to Chapter 4 for an understanding of the processes listed.
TABLE 6-1
WATER USAGE OF WOOL WET PROCESSES
Process Volume in
gal/1000 Ib product
Scouring
Dyeing
Washing
Neutralization
Bleaching
5,500- 12,000
1,900- 2,680
40,000- 100,000
12,500- 15,700
300 - 2,680
6-1
-------
TABLE 6-2
WATER USAGE OF COTTON WET PROCESSING WASTE
Process
Volume in
gal/1000 Ib
product
Slashing, sizing yarn1
Desizing
Kiermg
Scouring
Bleaching (range)
Mercerizing
Dyeing:
Aniline black
Basic
Developed colors
Direct
Naphthol
Sulfur
Vats
60 - 940
300 - 1,100
310 - 1,700
2,300-5,100
300- 14,900
27,900 - 36,950
15,000- 23,000
18,000-36,000
8,900 - 25,000
1,700 - 6,400
2,300- 16,800
2,900 - 25,600
1,000 - 20,000
'Cloth-weavmg-mill waste (composite of all waste connected with each process)
TABLE 6-3
WATER USAGE OF MANMADE WET FIBER PROCESSES
Process
Scour
Scour and dye
Dye
Salt bath
Final scour
Special finishing
Fiber
Nylon
Acrylic/modacrylic
Polyester
Rayon
Acetate
Nylon
Acrylic/modacrylic
Polyester
Rayon
Acrylic/modacrylic
Polyester
Rayon
Acetate
Nylon
Acrylic/modacrylic
Polyester
Volume in
gal/1,000 Ib
product
6,000 - 8,000
6,000 - 8,000
3,000 - 5,000
2,000 - 4,000
4,000 - 6,000
2,000 - 4,000
2,000 - 4,000
2,000 - 4,000
500- 1,500
8,000- 10,000
2,000 - 4,000
500 - 1,500
3,000 - 5,000
4,000 - 6,000
5,000 - 7,000
1,000- 3,000
Source John J Porter et al , "State of the Art of Textile-Waste Treatment " EPA Pub No. 12090 ECS, Clemson University
Clemson, S.C., 1971 (1).
6-2
-------
6.1.2 Flow Measurement
It is difficult from available information to account for high or low water usages in both small
and large plants. Some studies have been performed which have estimated the manner in which
water is employed in textile work (Tables 6-1, 6-2, and 6-3) (2), (3). In general there is little
to be gained in discussing processes where the use of water is small, or the processes not of wide-
spread application, in the trade. It also must be noted that measuring the quantity of water used
in a machine for a certain process is not always simple with so many types of machines in use,
and with great variations in size. Even with a number of machines of the same type it may not
be feasible to employ the same method owing to inaccessibility of pipes or variations in piping
sizes or types of joints.
The obvious method of measuring with a meter the amount of water going to or from a ma-
chine is an easy way of determining the volumes used by taking readings at each step of the pro-
cess. Indicated in Figure 6-1 is a meter which features flexibility of installation and a "leak
detector." But there are a number of difficulties that may prevent use of meters, such as high
costs, temperature, corrosive liquids, and accessibility.
Rotometer devices are commonly found on textile ranges. Unfortunately many are neglected.
Total water to a plant may be known, but rates of flow to continuous processes are generally
not closely controlled.
Two excellent reference sources which simply and practically discuss flow measuring options
available are the Handbook for Monitoring Industrial Wastewater (EPA), and information pro-
vided at the EPA Technology Transfer Seminar, Boston, January 1975 (4), (5). These methods
include details from the simple "bucket timing" procedure, pump timing, a portable weir dis-
charge system (can be used in trenches), to the more difficult salt injection procedure. Other
procedures may include calculating the volume of a simple machine from its dimensions. An-
other method is collecting outflow from a machine by means of a portable pump with a suction
leg, and pumping through a meter or vessel where it can be measured. Figure 6-2 shows a hook
and gauge portable weir system used by one consultant (5).
6.1.3 Information to Collect
Recording loading, depth of water used, spray rates (bucket and stop watch), number of fills,
etc., will help enable working figures to be obtained for process water usage per pound of
material processed. Measurements should be taken for at least 3 months, but, ideally, for 12
months to give the most reliable information (3).
In individual reports, it is necessary to obtain figures related to specific fiber type, speed, and
weight showing water usage for that particular production period. This is because when a low
production rate occurs it is often found that low loading of many machines occur, rather than
6-3
-------
FIGURE 6-1
FLEXIBLE FLOW MEASUREMENT DEVICE
WITH LEAK DETECTOR
6-4
-------
in
i^
o>
UJ 2
< UJ
O w
OE
O (/)
iz
Q<
CNJ ± O
«o Sgi 2
LU -r O
? o?
D »- M
O O[jj
u. i i-
UJ <
UJ Q.
> LU
tl
^°
O m
m -
Eg
UJ U.
6-5
-------
the correct loading. This, of course, gives high values for water usages per pound of material.
Therefore, it is felt that long term figures will give a better indication of water usage because of
the great variations in production rates that can occur over a period of time. It is also important
to have information related to vessel temperatures recorded.
6.1.4 What Are Others Doing
6.1.4.1 CDTRA Study Results
It is useful to have an idea of how much water is used by others in various textile processes. The
following sequence of tables is admittedly limited in scope, but attempts to provide insight into
how much water has been used by process, equipment type, and dyestuff (3). It should be men-
tioned that little has been studied industry-wide in the U.S., and the generalities which are made
are based on limited results; therefore, they should be tempered with engineering judgement.
In Figure 6-3 scouring water usages by equipment are compared.
Desize
I VTA I \/Wl I V/%*
kier boilJKier boill Beck
' open I rope ' scour
open ' rope
width
scour scour I soaper
FIGURE 6-3
WATER USAGE IN SCOURING PROCESSES
(Fabrics)
It should be noted that kier boiling of cotton allows batch treatment of up to 2 tons or more
at a time. Man-made fibers are less amenable to bulk handling and loads of 500 Ibs. are uncom-
mon. Scouring in kiers gives very low water usage in the process itself; subsequent washing is
discussed later. Desizing water usage varies due to the variety of methods employed for desiz-
ing. A range of usage is included in the table from 0.03 to 0.16 gal/lb., with usage in washing
from 0.4 to 2.9 gal/lb. A usage rate for several man-made fiber fabrics used from 8.3 to 17.4
gal/lb. in desizing. Scouring in a beck is usually followed by bleaching or dyeing. Beck scouring
alone required water usage from 1.2 to 3.6 gal/lb. The table reflects the overall total. All the
6-6
-------
values for washing above 5 gal/lb. were produced by running rinses. Values for jigs depended on
the fabric batch size. Values of 0.06 to 0.5 gal/lb. were obtained for scouring. Washing figures
ranged from 0.2 to 0.3 gal/lb. Overall jig figures are indicated in Figure 6-3.
Comparing continuous scouring figures is difficult because of range configurations and inter-
mediate treatments. Therefore overall scour and wash figures are given. The point to be made
here is that many machines run at the same cloth speed and water input. Therefore, lightweight
fabrics show high water usage values.
Focusing on strictly washing, Figure 6-4 shows considerable difference in water usage between
firms.
15
10
CO
O)
Mean values S
Range of results in survey^
2 I 11 13
FIRM No,
FIGURE 6-4
WATER USAGES: ROPE WASHING OF COTTON FABRICS,
DIFFERENCES BETWEEN FIRMS
The major differences between water usage seen in Figure 6-4 appears in the manner in which
machines are loaded as shown in Figure 6-5.
20
16
12
8
4
Single
Double
Treble
0 40 80 120
LOADING, Ib/min
FIGURE 6-5
ROPE WASHING OF COTTON FABRICS:
EFFECT OF MACHINE LOADING
6-7
-------
Although it may not be feasible to alter cloth speed because of mechanical difficulties, judicious
reduction in water feed rate for light fabrics may give rise to substantial economies. However,
it is true that this can be detrimental for certain heavier fabrics. In general, usage figures were
below 4 gal/lb. The same should hold true for open-width fabrics. A good figure to focus on,
derived from this study, is approximately 0.7 gal/lb. goods.
Table 6-4 compares water usage for cotton fabric washing. Rope figures were higher than open
width. However, in any specific case, it is a combination of fabric weight, temperatures, equip-
ment type, speed, and water feed rate which primarily dictate water usage.
TABLE 6-4
WATER USAGE IN WASHING PROCESSES
Method
Rope
Open width
Jig
Winch
Beam
Pit
Water Usage — gal/lb
Average
3.5
1 3
7.0
8.3
4.6
3.4
Range
0.65- 15.4
0.23 - 5.8
006-35.6
2.0 -32.5
3.8 - 5.4*
0.93- 80
"Without cooling water
In the jig, static washes showed the highest usage figure to be 3.3 gal/lb. Running washes pro-
duced figures from 0.06 to 35.6 gal/lb. In some cases longer rinses were used to remove loose
color in reactive or azoic dyeings. In other cases running water was used to oxidize vat and
sulfur dyes. Batch weights of from 2.4 to 100 pounds were also observed. To further indicate
reasons for.the wide discrepancies, cloth speeds were seen to vary from 53 to 140 yds/min
among the jigs surveyed.
Becks are used to wash after scouring, bleaching, and dyeing. The water usage figures reflect the
degree of residue removal difficulty. The figures are also somewhat cloudy because processes
interspersed with washing may be included. A single wash was seen to run between 1 and 14
gal/lb. Table 6-4 shows the overall range.
Beam washing figures may double when cooling water is figured in. Efforts should be made to
reclaim this cooling water.
6-8
-------
6.1.4.2 Dyeing Process
Accurate data on dyeing are difficult to obtain. One reason is because of the variations in pre-
treatment and aftertreatment which can take place. Therefore, strict comparisons should not
be attempted.
A general trend which occurs on the same equipment (jig or beck) is that particular dyes or
certain fabrics can use far more water than when other dyes or fabrics are processed.
Figure 6-6 indicates the wide range of water used for fabric dyeing on various types of equip-
ment.
In an attempt to focus more closely on the reasons for wide swings of water usage, water usage
by dyestuff was examined for jig dyeing. Table 6-5 shows the water usage of various dyes using
the jig.
Again it is seen that wide variations in water usage occur. However, when the effect of cloth
weight is considered, trends become apparent as is shown in Figure 6-7.
40
35 -
30
25
£
15 20
O)
15
10
Dyeing processes (fabrics)
Mean values
Range of results I
in survey
Jig IWinchl Cont I Pad I Beam
FIGURE 6-6
WATER USAGE FOR VARIOUS EQUIPMENT
6-9
-------
TABLE 6-5
JIG DYEING WATER USAGES COMPARED
Type of Dyestuff
Direct
Azoic
Vat
Reactive
Sulphur
Water Usage gal/lb
Mean
4.5
158
6.4
12.0
97
Range
0.7- 17.4
-
27-126
65 - 21.1
22 - 35.8
.Q
O)
24
20
16
12
8
4
0
1 Reactive
2 Sulphur
3 Vat
4 Direct
10 20 30 40 50 60 70 80 90
lb/100 yd
FIGURE 6-7
JIG DYEING — EFFECT OF CLOTH WEIGHT AND DYEING PROCESS
For a given size beck and a given dyestuff, the effect of batch size is seen to be marked.
Batch size — Ib.
Water usage — galAb.
380 450 505 600 750
16 13.5 12 9.8 8.4
On the other hand, the effect of fabric weight was seen to be small, as was the effect of the
type of dyeing. The following table shows that, if the batch size remains the same, water usage
was seen to increase linearly with machine volume.
6-10
-------
Machine volume (gal)
Batch Size - 250 Ib. Crimplene
600 800 1000
Water Usage
12.2 15.8 20
Continuous dyeing data was scarce in the CDTRA study (3), but water usages appeared to be in
the range of 2 to 3 gal/lb. (pad, develop, wash). Usage decreased with increase in speed (Ib/min)
as with other continuous processes.
Beam dyeing using disperse dyes ranged from 3 to 24 gal/lb. High water usages could be related
to the amount of cooling water used.
Table 6-6 gives information comparing various average usages with equipment. Insufficient data
increases the unreliability of the information, but trends are indicated.
TABLE 6-6
WATER USE COMPARISON
Jig
Beck
Beam
Continuous
Water Usage gal/lb
Vat
5.7
-
2.3
Direct
4.0
10.4
-
-
Disperse
12.5
11.0
-
Reactive
9.7
21.4
-
-
All dyes
7.7
20.3
11.0
2.3
Package dyeing was studied at four plants using a variety of machines and sizes, a variety of fibers,
and a variety of dyes (3). Water usage figures varied from 2 to 23 gal/lb. with the bulk of the
figures in the 5 to 10 gal/lb. range. Focusing on machines loaded to the maximum enabled pat-
terns to become clearer. Cotton yarn dyed with direct dyes, and polyester and nylon dyed with
disperse dyes, used comparatively less water than reactives and vats, reflecting the complexity
with dyeing procedure of these dyes. In direct dyeing, cotton running washes accounted for
two-thirds of the water used. Whereas, in dyeing polyester yarn, running washes accounted for
one-quarter of the total usage. Cooling water was 14 to 60% of the total. For the dispersed
dyed polyester, overall consumptions ranged from 3.6 gal/lb. for the large units to 16 gal/lb.
for the small units. Larger machines used proportionally less cooling water than smaller ma-
chines to account for some results.
Four plants were studied to determine water use in nylon hose dyeing in paddle machines.
Water usage varied on the average from 9 to 24 gal/lb. (3). Measurements indicated that 15 to
55% of the water could be saved. Practical changes likely to affect water savings included
the use of larger bags, fewer baths, heavier loads, and a comparison of running vs. static rinses.
6-11
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Four plants were also studied to determine water usage for acrylic garment dyeing in paddle ma-
chines (3). Average water use for the plants varies from 10 to 23 gal/lb. Measurements indicated
that 33 to 65% of the water used could be saved. Practical changes likely to affect water savings
included achieving greater consistency, reduction in time and volume for running rinses, heavier
loads, and also where feasible, machine conversion to closed coil cooling and heating systems.
Again, four plants were studied to determine water usage in paddle machines for wool garment
dyeing (3). Average water usages ranged from 26 to 46 galAb. Practical changes likely to
affect water savings included a reduction in time and volume of running rinses, more careful
loading of machines, and greater consistency. The measurements suggested that 18 to 48% of
the water used could be saved.
Water used in blanket washing for roller printing in three plants varied from 0.1 to 5.6 gal/yd.
Three plants reported water usage for print screen washing. About 15 gal/screen or 0.3 to 0.5
gal/yd printed fabric was used (3).
6.1.4.3 J. P. Stevens
Samuel Griggs of J.P. Stevens made the following general observations for water conservation
efforts (4):
1. Turn off water to equipment that is not being used. Use of automatic shut-offs on
hoses, etc.
2. Supply only the needed amount of water to a machine. (Don't use 30 or 40 gallons
when 20 gallons will accomplish the same job.)
3. Modulate water use depending upon throughput of material. Use less water for nar-
rower width fabric than for wider fabric.
4. Reuse non-chemical treated cooling water. Reclaim by running through a cooling
tower or reuse in processes not requiring tap water quality.
5. Chemically treat waters for reuse. Print waste water can be clarified and returned
to wash the blankets and screens of the print machine.
6. Steam condensate return.
Four Stevens plants in which the above methods were utilized are described briefly on the
next page:
6-12
-------
Plant 1
A plant with 13 300-pound kiers on stream with no water recovery was using approxi-
mately 700,000 GPD. Water supply was limited by pressure drop, etc.
Added 5 more 1000-pound kiers and activated a recovery system into a new hot water
system under pressure. Also restricted water usages by placing flow reducers into large
lines. Current wastewater is approximately 400,000 GPD.
Plant 2
Where 30 to 35 gallons of water was being used per pound of fabric dyed, conservation
reduced the use to 18 gallons per pound of fabric dyed. This was accomplished by exam-
ining the process and restricting the water use.
Plant 3
Reduction of approximately 800,000 GPD going to waste treatment by the addition of a
cooling tower on non-chemical treated cooling waters.
Plant 4
Savings of 288,000 GPD by adding a cooling tower to reclaim air compressor cooling
water. Savings of approximately $18,000 per year resulted.
6.1.4.4 American Thread
Fred Eslick, American Thread, reported in 1975 on the results of his dyehouse Wastewater
Management program at two plants (6).
Plant 1 — 18% reduction in water usage per pound of yarn dyed and finished.
Plant 2 — Dyehouse effluent and water used per pound of yarn was reduced 15%.
6.1.4.5 Corlin Processing, Landis S.C.
Lane Drye, President, says his company cut yarn dyeing water requirements from 75 to 35
gal/lb. by discovering and eliminating waste areas (7). This good water management was accom-
plished in 1971 and both cut costs and reduced the load on the municipal treatment plant.
6.1.4.6 Springs Mills
J.D. Lesslie, Director, Utilities Service, stated that in April of 1974, Grace Finishing Plant re-
duced its water usage in ony year by 25% (8). This is more dramatic when observing that the
reduction was from 16 million gal/day to 12 million gal/day.
6-13
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These previous case histories were offered as various examples of what can be accomplished.
The potential at this time is obviously considerable, even without extensive study or elaborate
equipment redesign.
The next area of discussion considers what specific steps may be taken, and what equipment
manufacturers are doing, to help the situation for the future. It may also be taken to indicate
where vendors might be actively encouraged to intensify efforts for the future.
6.1.5 Recommended Approach
Perhaps the most important approach for the textile engineer of the future is to devise material
balances for each major production area. An example is given in Figure 6-8 of a cotton scour-
ing material balance for a particular style. A complete and concise idea of chemical formulation,
estimated waste output, moisture lost, water used per pound of product and a waste parameter
analytical checklist are readily apparent at a glance. Any changes can be gauged against this ma-
terial balance and cost/benefit decisions can be made. Other material balances including compar-
ing starch sizing with PVA sizing, a vat dyeing material balance indicating the various alterna-
tives available for oxidizing the dyestuff, etc., should also be drawn up to stimulate thought.
Note particularly where BOD sources occur.
A more detailed material balance, perhaps best conducted by a consultant, is shown in Chapter
5, Figure 5-7. Here the fabric and wash box water alkalinity are measured to determine whether
excessive washing might allow elimination of a wash box. Another reason for such a study
would be to determine whether counterflow washing at reduced rates and temperature is
feasible (4). Chapter 5, Figure 5-7, it should be said, is a somewhat simplified worksheet.
Chapter 5, Figure 5-6 shows, in simplified form, how a dye range material balance might be
approached (4). Changes in formulations, flow rates, etc., can be gauged against this basic
evaluation for cost benefit purposes.
These are but some of the approaches which can be used, not only to reduce water volume, but
also to provide cost saving benefits in general.
6-14
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25,000 Ibs water
fabric
^-
i
'
Scour
1
Washers
1
1.
Water c
2
Dry
ut
24,200 Ibs
.water
evaporated
. fabric
out
Chemical Throughput
NaOH
Detergent
Tri-Sodium Phosphate
Chelate
Tri-Ethanol Amine
Cotton Wax
Suspended Solids (SS)
Input
(Ibs)
46
1.3
1.5
0.4
0.7
30
5
Output
(Ibs)
46
1.3
1.5
0.4
0.7
30
5
Ib BOD per
100 Ibs output (%)
0
50
0
50
50
50
2
BOD output
(Ibs)
0
0.65
0
0.2
0.4
15.0
0.1
Flow rate = 70 GPM
1. percent moisture on fabric = 80% pick-up
2. avg. 80% pick-up = 800 Ib water lost (evaporated)
water used 25,000 Ibs 4- 8.33 Ib/gal = 3000 gal
wastewater out 24,200 Ibs
4. /iu t u •
water/lb fabric =
o ,/,u
= 3 gal/lb
Analytical Checks
BOD
Total SS
Total Dissolved Solids
PH
Oil and Grease
Toxic Materials and Other
16.4 total
Production rate = 80 yds/min
16.4 Ib
5 Ib
49.9 Ib
12.5
30 Ib
1.04 Ib (as phosphate)
FIGURE 6-8
SCOURING RANGE MATERIAL BALANCE
Scour — 100% cotton woven, 3.5 yds/lb, 80 x 80 construction (light weight) Lot X, Total
Production Basis — 1000 Ibs.
6-15
-------
Elaboration on a specific study may be helpful here (9). The scenario includes a single stage
bleach range processing 65/35 polyester/cotton knit goods in rope form, a saturator, J-box with
wet-heel, and six box-washers with acetic acid scour form the equipment units. Specifications
require 30-40 GPM flow between 170-190° F. Fabric caustic concentrations ranged from 0.21
to 0.33%. Washed fabric concentration of caustic averaged about 0.025% at 40 GPM.
Reducing the flow to 15 GPM only increased the washed fabric average concentration of caustic
to 0.033%. Measurements were taken at the fourth wash box before the acid scour. Temperature
increase of the wash water from 145 to 205° F showed only a 0.01% decrease in caustic resid-
ual. By lowering the flow rate to a conservative 20-25 GPM and lowering the water temperature
to 140 to 160° F an energy savings of approximately 50% is possible, as shown in Figure 6-9.
After considerable experience gained on washing caustic scoured cotton yarn packages in the
laboratory, mill trials were conducted (9). Gaston County equipment holding 100 packages of
1.25 Ibs/ package was used. The packages were impregnated with approximately 1.2-2% caustic
on the weight of the yarn. The trial indicated that yarn washed with a 3-minute hot running
rinse and 3-minute cold rinse at 2 gal/min/lb. was essentially equivalent in residual caustic con-
tent to a 10-minute hot running rinse and a 10-minute cold rinse, the latter being the routine
plant procedure.
6-16
-------
2800.
2400-
2000-
O
c.
E
en
.Q
1600-
1200-
800-
400-
f I I I F I '
130° 120° 110° 100° 90° 80° 70°
60°
Degrees Cold Water Is Raised
190° 180° 170° 160° 150° 140° 130° 120°
Actual Hot Water Temperature
FIGURE 6-9
ENERGY CONSERVATION ON THE CONTINUOUS RANGE
6-17
-------
Other conclusions included:
1. Due to caustic's high affinity for cotton, running rinses, rather than recirculating
rinses, were recommended.
2. Flow of 2 to 3 gal/lb/min at 140 to 150° F for approximately 3 minutes running
rinse (inside-out) are suggested starting points for 40's 2-ply to 90's 2-ply yarn.
3. It is indicated that approximately 0.05% residual caustic on the weight of the yarn
is generally a good degree of removal.
4. Significant differences in efficiency of removal were seen to occur between very
coarse and fine yarn counts, yarn twist, and packages winding densities.
Other studies compared high energy open-width washers with the conventional box washer in
terms of caustic removal efficiency (9). It was found that the important variables involved
ranked differently for the various washers. The variables are ranked in order of importance for
caustic removal by washer in Table 6-7.
TABLE 6-7
PREDOMINANCE OF VARIABLES IN CAUSTIC REMOVAL
BY THREE WASHERS
Box
High energy
cascade principle
Gaston County Alternator
High energy
vibration principle
Daiwa Vibro
Fabric caustic concentration
Water temperature
Fabric speed
Liquor/fabric ratio
Fabric caustic concentration
Fabric speed
Liquor/fabric ratio
Water temperature
Water temperature
Fabric caustic concentration
Rotor speed
Fabric speed
Temperature was seen to be the second most important aspect of caustic removal efficiency in
the box washer. The high energy imparted by the Cascade concept displaces the dominant rank
of temperature in the scale of importance to last. Restricted by the limitations of temperature
effects in caustic removal, the box cannot compete in potential caustic removal effectiveness
with the Cascade. Studies with the vibrating washer indicate that not all the principles of high
energy washers will provide greater efficiencies at economical prices (9). For example, in this
study it was observed that the vibrator was similar to the box washer in caustic removal effi-
ciency without the rotor operating. In order to reach the Cascade efficiency, uneconomically
high rotor speed power was required.
6-18
-------
In a mill trial, the Cascade equipment was compared to a vibrating washer after a recuperator in
a chainless mercerizing range using 65/35 polyester/cotton fabric (9). The alternator was found
to be substantially more efficient.
Tables 6-1 and 6-2 serve especially to indicate that the washing of wool and the washing of
cotton after dyeing are two areas suggesting great potential for improved water economy (10).
Washing operations are obviously then high priority areas for water economy improvements. It
is not difficult to envision washing machines that can achieve considerable savings in water
usage. This is particularly true in view of the fact that water economy has not been a high prior-
ity design consideration in the past.
The need for less water usage and increased efficiency of washing is accompanied by the need
for other important design considerations. These considerations include:
no excessive tension or abrasion
reasonable cost
easy thread up
capability of accommodating a range of fabric weights, width and types
durability to high speed operation
low energy consumption
The Tensitrol washer for rope goods can perhaps be called a forerunner of sophisticated devel-
opment in washer design. The test results shown in Table 6-8 for the Tensitrol are good ex-
amples of the information which should be demanded by mill personnel (11).
TABLE 6-8
FLEXIBILITY INDICATED BY TENSITROL WASHER
MATERIAL
WATER USED
STEAM USED
(Ibs. of water
evaporated/hr.)
SPEED
(yds./min.)
WATER
TEMPERATURE
WASH RESULTS
Before wash
After wash
Test A
Caustic treated dress
goods, 4.73 yds./lb.,
singed, mercerized but
not scoured
40 gal./min.
1050
208
160°F
0.193%
0.015%
Test B
Caustic treated poplin
3.04 yds./lb., remer-
cerized but not scoured
47 gal./min.
1120
215
160°F
1.661%
0.165%
Test C
Acid treated fabric
hbSCU singed, mer-
cerized and scoured
with excess of acid
48 gal./min.
1120
215
160°F
4.36%
0.21%
6-19
-------
The information provided in Table 6-8 suggests versatility and therein makes available a con-
crete basis for reliable comparisons with other machines.
An open-width washer manufacturer attempts in Figure 6-10 to illustrate the influence of
different design parameters in their washer on improved washing (12).
It is reasonable to encourage vendors to continue to improve their advertising by providing in-
formation on the effects of new design additions as indicated by the literature represented in
Table 6-8 and Figure 6-10.
Table 6-9 is provided to indicate some of the varieties of new equipment types currently on the
market and some of their important differences.
ixxxi L_ I
Water Steam Efficiency
consumption consumption
Water
consumption
Steam
consumption
Conventional
unit
Addition of
wave rollers
Addition of
pressing
rollers and
division
plates
Addition of
serpentine
counter-
current
flow
High
temperature
FIGURE 6-10
INFLUENCE OF DESIGN PARAMETERS ON IMPROVED WASHING
6-20
-------
TABLE 6-9
SOME NEWER WASHING MACHINES
Type
Open-width
Open-width
Open-width
Open-width
Open-width
Open-width
Open-width
Open-width
Open-width
Open-width
Open-width
Manufacturer
Rodney Hunt
Greenville Steel
Farmer Norton
Prelaval, Jawetex
Aqua-Blast,
Amer. Laundry Mach.
Lite-o-matic Omez
100 plus unit,
Kleinwefers, B-K
Greenville Steel
Gaston County
Alternator
Mather-Pratt
Aquatex
American Artos
Features Claimed
Enclosed, requires less steam, can contain
vapors and toxic fumes
Counterflow arrangement, double-lacing allows
6 boxes to do work of 10 single laced boxes
Suction washing
For printed goods, special jet spray nozzles,
woven or knits, 1:10 liquor-to-fabric ratio,
22 yds/min, 500 Ibs/hr steam consumption
Four high velocity jet manifolds, 20 gal/min with
55 yds/min, knits and woven, printed goods
Water sucked through perforated drums,
tensionless for knits and prints, sprays both
surfaces
Fabric fed horizontally from bottom to top, water
cascades from top to bottom, enclosed, under
pressure (7 psig, 232° F), steam reduces fabric
tension to promote flow through
Horizontal carpet washer, 3 immersions-
3 nips, agitators in each box
Carpet, Cascade principle, adjustable gap
setting
Wave rollers, compartmentalization, high
temperature, countercurrent flow
Horizontal fabric flow, no pressure, replaces
three conventional washers
No matter whether water is forced through fabric by squeezing, suction, cascading, beaters,
spraying, pulsing, or by other ways of creating turbulence, one is faced with a physical law
which seems best overcome by time. It is in this respect that the means to improve the exchange
between water and chemicals through fabric may be most limited.
For this reason the two most fundamental principles of washing which go into producing a good
wash without excessive use of water warrant discussion. Generally, the effectiveness of a wash-
ing can be seen to increase directly with the volume of the wash water used, but it increases
with the power of the number of washings used. Thus, fundamentally, four washings with 2.5
gal/lb. goods each can be a great deal more effective than a single 10 gal/lb. washing. Further-
more, it would be ideal to remove as much of the liquid as possible by squeezing and collecting
before adding the next portion of wash water.
For example, Russell (ICI) argues in package dyeing operations that: The washing or soaping
of dyed goods following the dyeing operation is an area where energy conservation is possible.
6-21
-------
The use of running rinses should be avoided, as they are great wasters of energy. Ini-
tially a running rinse should be used to remove the excess dye liquor. Thereafter, a
drop and fill method is preferred to a running wash for two reasons. The governing
rate in washing or soaping is the diffusion rate of the dye. This rate is best increased by
increasing the temperature of the wash liquor. This will speed cleanup by increasing the
diffusion rate of the dye. If hot water is pumped through the goods and allowed to go
to drain, vast amounts of water and energy are wasted. This excess water also increases
the cost of effluent treatment which is generally based on treated volume. Two fills
and drops heated to 200° F will often accomplish as much as an hour of running wash
at 160° F and will consume much less energy (13).
Eslick suggests that a careful look should be given to dye machinery that will be purchased in the
future for replacement or expansion (6). Those machines with excessive or long runs of piping
below the beck, kier or vat are less desirable than the same machines with short, compact pip-
ing. The liquor-to-pound of material ratio will be lower with the compactly piped unit, hence
the water consumption will be lower. As a side benefit, the electrical cost to circulate the liquor
will likely be lower.
Gelders (Lockwood Greene) reported that water usage can be reduced by one-third through
utilization of dye cycle control (14). The controllers referred to are punch-card, program-
med-type dye cycle controllers. Full automation also offers desirable side benefits of better
product repeatability, low chemical utilization per pound of material, and lower maintenance
cost to the dye machine itself. Eslick reported ontwo plants producing essentially the same
goods, one was automated and computerized more fully than the other (6). The more automated
plant showed significantly less water usage. More will be said on automation in subsection 6.5.
Solvent processing offers considerable potential for water conservation. This topic is treated
under Process Changes, subsection 6.5.
There are trends which indicate a new generation of rapid package dyeing machines using short
liquor ratios may be developing. Such equipment is said to offer rapid dyeing, reduced dye cycle
time, and have reduced steam, energy and water usage (15). One manufacturer uses a tube ar-
rangement with perforated tubes inside to hold packages. The outside tubes act as heat ex-
changers. This step eliminates the need for external heat exchangers and reduces the liquor
ratio. The primary feature of this equipment is the pulsation principle which directs flow
through only a certain number of packages while the remaining packages are shut off from
liquor circulation for short intervals. If such equipment gains wide commercial acceptance the
package dyer can be expected to use considerably less water.
There is a possibility where some package dyers may improve on water usage utilizing existing
equipment. Those dyers who are using relatively non-compressible fibers might consider switch-
ing from rigid dye tubes to dye springs. Consider that the water and steam used to dye an over-
6-22
-------
load is the same as a normal load. The results might be viewed as a 30% increase in production
capacity for the same amount of fuel. Figure 6-11 indicates the compression obtainable using
dye springs (16).
FIGURE 6-11
COMPRESSION OF LOAD USING DYE SPRINGS SEEN ON LEFT
For example, a package dyehouse dyeing 150,000 pounds of yarn in 120 hours uses 7,143 gallons
of fuel oil to produce one million pounds of stream at 125 psig (0.0476 gallons of fuel oil per
pound of yarn). Using dye springs and a 50% kier overload in lieu of any rigid tube method of
dyeing reduces the fuel requirement to 0.0317 gallons of fuel oil per pound of yarn — for a pos-
sible savings of over 30%. For a 100,000-pound-per-week dyehouse, the savings are approximately
1,600 gallons of fuel oil per week, which is the equivalent of enough raw crude saved to produce
12,000 pounds of polyester.
6.1.6 Waste Volume Reduction Checklist
This section emphasizes the advantage of keeping waste volume as low as possible in order to
get greater treatment efficiency on a "per pound of product" basis. Points touched upon in-
cluded:
• Improved washer designs.
• Overflow vs. recirculating rinses in package dyeing.
• "Tailored rinses" — to fit the particular shade, style or severity of treatment.
6-23
-------
• More careful control and testing to ensure that "over-rinsing" of fabric does not take
place.
• Closed steam heating coils in dye becks, etc., rather than open steam, to allow return
of condensate.
• Use of closed cooling coils rather than overflow cold water input.
• Return of suction slot liquors to wash-box make-up.
• Use of the counterflow principle, on continuous ranges.
• Vacuum extract on package dye machines.
• In-plant re-use of lightly contaminated rinse waters for other, more "concentrated"
chemical processes.
• Return of water from water-cooled rolls (e.g., on coaters).
• Using automatic water cut-offs on ranges, for when range stops.
• Liquor ratio consideration in batch processes.
• Elimination of reworks by more careful control of processes and greater automation.
• Consider compressible springs in package dyeing for greater loads, less water and
energy.
• Replace leaking pumps, heat exchangers, compressors, etc.
• Meter each range, keep shift or daily records on water use per unit of goods.
• Automatic cut-off on water hoses.
• Spring controlled faucets.
• In-line flow restrictions for certain machines.
6-24
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6.2 Waste Strength Reduction
This subsection attempts to suggest some of those in-plant practices and equipment which
might be considered in reducing plant waste strength. Two obvious purposes towards this end
are to:
• Reduce treatment requirements and costs.
• Prevent troublesome or toxic chemicals from interfering with the waste system.
Perhaps, less obvious in this context, is that reducing waste can also reduce general wastefulness
and lead to more efficient processing and cost savings.
The first step in such an undertaking is to have an idea of what materials and ingredients, such
as, chemicals, dyes, oils, solvents, etc., are used in the plant and exactly how they are disposed of.
Before discussing more sophisticated approaches, the matter which should first be discussed is
that of avoiding spillage. The production staff should periodically be made aware of the general
wastefulness and potential harm to the treatment system that spills can contribute. Once the
easy things are done, old habits reappear as the routine day-to-day continues. Monthly meet-
ings are suggested which should partly concern themselves with how to motivate workers, keep
their interest, and make them aware of the fact that top management is concerned. You can tell
a man to watch that he doesn't spill, but the problem is that the tendency is to continue spill-
ing. Today numerous companies create humorous, low-pressure, positive attitude posters. These
posters can plant the seed of a positive attitude towards a man's job and the company he works
for. They can also subtly remind workers to stay alert without confrontation or finger pointing.
A general waste reduction suggestion is to see that chemical mix amounts are carefully calcu-
lated, and periodically reviewed, to accommodate a specific fabric lot size, thereby preventing
excessive dumps. Probably more overall care could also be taken to adjust process chemicals to
more nearly correspond to the particular fabric weight being run. For example, a number of
continuous bleach ranges have been observed running on formulations which are designed to
take care of the most intractible fabric style being run. This means that there is "overkill," or
chemical wastage on lighter, more easily treated fabrics (9). Thoughtful segregation of various
styles into groups, with different formulations for each group, is suggested.
In a similar vein, the use of control equipment designed to feed in chemicals should be con-
sidered. Experience has indicated that poor results have occurred from low concentrations, and
fabric damage has resulted from high concentrations (9). There is available proven equipment
which can maintain bath concentrations of predetermined levels. This can reduce waste strength
and save chemical costs for the mill. One piece of equipment on the market, Figure 6-12, has
suggested potential application for all chemical concentrations which can be analyzed by
6-25
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Redox Potential Meter
Limit Indicators
Low High
Controller Set Point
Alarm Lights Thumbwheel Ad|ustment
Limit Setting Knobs
Low High
\ \
ontroller Set
Point Indicator
Recording
Controller
Control Valve
Position
Indicator
Zero Adjustment Calibration (Span) Pushbutton Power Manual Loading
Adjustment On-Off Switches Thumbwheel Adjustment
FIGURE 6-12
AUTOMATIC CONTROL OF CHEMICALS
redox titration, such as peroxide, caustic, silicate, sodium hydrosulfite bichromate, bromite
and so on (17). Savings at Dan River, for example, have been claimed to be up to 30% using
such equipment (18).
The following curves, Figure 6-13, indicate the difference between automatic control of perox-
ide and alkali over manual control. Such units would sell for approximately $23,000. Applica-
tion examples for this equipment are shown in Figure 6-14.
In bleaching an automatic system can replace constant feed pumps which would otherwise
pump caustic and peroxide into the saturators of the bleach range. In the manual mode, an
operator usually withdraws a sample from a saturator and titrates to an indicated end-point, and
thereby determines the chemical concentration. Then he either increases or decreases the pump-
ing rate to compensate for any deviations from desired levels. After calibration and a short
stabilization period in the morning, automatic controls constantly monitor bath concentrations
and adjust control valves that meter in chemicals. For example, a manual system running 30%
over a desired 1.0% caustic concentration for polyester/cotton blends can run 6,000 yards of
goods by, if the titration period is 30 minutes and the speed 200 yds/min. This means wasted
chemical, possible dye problems ahead, and more alkali for the waste treatment system to
handle.
6-26
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13
11
24
_ 22
-13
24 ?
7;
>
22 E
•20
8 10 12 14 16 18 20
30-MINUTE TITRATIOM.INTERVALS
22 24
FIGURE 6-13
COMPARES AUTOMATIC CHEMICAL CONTROL WITH MANUAL CONTROL.
DOTTED LINES ARE MANUAL CONTROL.
PREPARATION
I ir
DYEING
Scour
if
I/
Bleaching
range
/
II
II
Color
pad
f\
i,
| Heat
set
£
/
i Chem
pad
/
;>
/
Dryer
7*
\
Washer
k
^Oxidizing
bath
/
k
\
Washer
/
1
u.
/ finishing
._IL
ACC Controls
Bleaching
1 Peroxide
2 Caustic and
Sodium Silicate
ACC Controls
Dye Reduction
1 Hydrosulfite
2 Caustic
ACC Controls
Dye Oxidation
1 Dichromate,
Peroxide
Bromite,
lodates
2 Acetic Acid
FIGURE 6-14
POSSIBLE POINTS OF APPLICATION FOR
AUTOMATIC CHEMICAL CONTROL
Computer interface
(Optional)
6-27
-------
The best point of application of automatic control equipment in general would be in prepara-
tion. It is here where the potential for error and problems is greatest, i.e., it is difficult to see
when an error has been made. Perhaps the operation of such delicate equipment, i.e., the set-
up and calibration, should be left to the research or engineering departments (18).
A recent wet process monitor, Figure 6-15, for carpets is said to have saved $120,000/year in
carpet latex overages. A fabric model would cost approximately $8,000, while a carpet model
should be expected to cost approximately $15,000. Wet process monitors designed to prevent
chemical overages in open-width processing suggest themselves, also. Such equipment is applied
at the pad nip to determine wet pick-up. Proper use and stable humidity are two critical factors
in successful usage. In suitable applications such equipment can aid uniform wet process appli-
cation, Figure 6-16.
A great degree of waste strength reduction can be obtained by removing fibers and lint. Fibers
and lint can contribute "latent" or hidden BOD, add to COD, and cause SS carryovers from
FIGURE 6-15
WET PROCESS MONITOR FOR CARPETS HELPS PREVENT
LATEX OVERAGES
6-28
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6-29
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clarifiers. Lint has also been known to clog flow meters, pipes, pumps and tangle aerators. Fine
screens applied in drainage ditches is one way of collecting undesirable fibers.
If an analysis indicates that a plant has high concentrations of BOD, COD, heavy metals, oil/
grease, etc., compared to its ATMI Category average, then it is suggested that a shift of chemi-
cals may reduce the concentrations in the wastewater. Eslick suggests that much of the clean-
up work must be done by the plant dyer and dye chemist (6). Sodium chloride, sodium sulfate
and sodium hydrosulfite are cheap, commonly used chemicals in the dyehouse. Since they are
cheap, it is not unusual to see them over used. These chemicals cannot be removed by biologi-
cal methods and management should therefore insist on minimal use of these chemicals. Further-
more, sodium hydrosulfite has been seen to contain residual zinc catalyst.
Many solvents contain phenols and many lubricating oils and greases contains substantial
amounts of zinc and lithium. Some departments have been observed simply to pour these items
down the plant drains after use.
Eslick goes on to suggest that production planning done strictly on the basis of customer ser-
vice may require consideration in the near future. For example, short dye cycling for dye days
can lead to inordinately high daily flows and pollutant concentrations. It would be better for
the dyer and dye chemist to inspect orders on a weekly basis in an effort to plan production and
avoid shock loading of the treatment system and still provide good customer service.
Carriers are known to contribute heavily to waste strength. Table 6-10 indicates the BOD5 of
various polyester dye carriers. Dye formulations for atmospheric dyeing will be using the great-
est amount of carrier annually. Many of these carriers today will likely contain phenols also.
Higher temperature dye machines can help reduce the use of carriers and should be considered
for use when replacement is necessary. Table 6-11 compares the discharge characteristics when
various carriers are used. Table 6-12 shows the priority potential for waste strength reduction
in vat/disperse dyeing is greatest for carrier reduction.
TABLE 6-10
BOD LOADINGS OF POLYESTER DYE CARRIERS
Carrier
Orthophenylphenol (most used)
Benzoic acid
Salicylic acid
Phenyl methyl carbinol
Monochlorobenzene (toxic)
ROD
ppm
6,000
27,000
24,000
19,000
480
lb/1,000 Ib cloth
180
810
720
570
14
Source. John J Porter et al , Sfate of the Art of Textile-Waste Treatment, EPA Pub No 12090 ECS.
Clemson University, Clemson, S.C., 1971 (1)
6-30
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TABLE 6-11
SCOURED AND DYED POLYESTER
Chemical throughputs
Item:
Nonionic surfactant
Anionic surfactant
Carrier-o-phenyl phenol
or trichlorobenzene
or biphenyl (atmospheric beck)
or butyl benzoate (pressure beck)
Disperse dye
Sequestrant (EDTA)
Acetic acid, 56 percent
or monosodium phosphate
or monosodium phosphate acetic
acid, 56 percent (preferred)
Soda ash
Sodium hydrosulfite
Water
Input,
pounds
30-35
10
60-150
60-150
60-150
15-40
5-40
2.5-5
20
20-30
5
50
10
Output,
pounds
30-35
10
60-150
60-150
60-150
15-40
0.2-1.5
2.5-5
11
20-30
3
50
10
290,000
Unit
BOD, lb/100
Ib output
3
80
140
3
140
140
5
2
35
0
35
0
22
BOD output,
pounds
0.1
8
84-210
2-5
84-210
21-56
0.05
0.1-0.2
4
0
1.5
0
2.2
Effluent-calculated:
BOD
Total suspended solids
Total dissolved solids
PH
Color
Toxic materials
Net effluent water
100-225 pounds (atmospheric beck), 33-70(pressure beck)
Indeterminate
80-90 pounds
6-8
Indeterminate
Orthophenyl phenol, trichlorobenzene
35 gal/lb goods (average)
NOTES Data given above refer to disperse dyeable fiber, but are essentially the same for cationic-dyed fiber
Data refer to polyester knits, piece dyed, using regular or textured yarn Package dyeing will use the same chemicals,
but less water For woven goods, size must be added—30 Ibs sodium polyacrylate, output, 30 Ibs, BOD, 03 Ib
Allow additional chemical and BOD output for goods to be reworked, assume 3-5 percent of fabric is reprocessed
BOD outputs calculated from data given in American Dyestuff Reporter, pp 39-42, August 29, 1966 A biodegradable
anionic surfactant was assumed
Source Industrial Waste Studies Program, Textile Mill Products, May 1971, for EPA by A D Little, Inc ,
Cambridge, Mass , unpublished
Haas, et al of Sun Oil Co., developed some basic data on biodegradation, fish toxicity, vapor
pressure and other environmental aspects of certain dye carriers (19). Work such as this can
help industry determine which carriers would be acceptable or harmful under given circum-
stances. Table 6-13 indicates fish toxicity found in their study (Sure Sol — 160 = alkylben-
zene biphenyl; Sure Sol — 170 = polymethyl biphenyl; Sure Sol — 190 = alkyl-naphthalene).
Eslick reported that experiments were made with a series of formulations to ascertain whether
carriers known to contain phenols could be eliminated (6). The tests showed such carriers
could be removed, but about 30% more dyestuff and chemicals were required. This markedly
6-31
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TABLE 6-12
VAT AND DISPERSE DYEING OF 50/50 COTTON/POLYESTER KNIT FABRICS
INCLUDING SCOURING OR PARTIAL BLEACHING
(Production basis: 1,000 pounds goods)
Chemical throughputs
Item:
Vat dye
Disperse dye
Carrier
Monosodium phosphate
Dispersing agent
Sequestrant
Sodium hydrosulfite
Sodium perborate
Detergent
Natural impurities
Rework
Total
Input,
pounds
20.0
7.5
40.0
25.0
10.0
5.0
25.0
5.0
12.5
25.0
Output,
pounds
1.0
0.375
40.0
25.0
10.0
5.0
25.0
5.0
12.5
25.0
Unit
BOD,lb/100
Ib output
—
5
85
—
50
50
22
—
50
50
BOD output,
pounds
—
0.02
34.00
—
5.00
2.50
5.50
—
6.25
12.50
2.6
68.4
Effluent:
BOD
Total suspended solids
Total dissolved solids
PH
Color
Oil and grease
Net effluent water
68.4 pounds
189
12
1.4 pounds
30 gal/lb goods
Source Industrial Waste Studies Program, Textile Mill Products, May 1971, for EPA by A D Little, Inc ,
Cambridge, Mass , unpublished
increased the BOD, COD and costs of the formulation. The final solution was to locate a non-
phenolic carrier to substitute in the original formulation.
Routine cleaning might be viewed by an environmental team. For example, a thermosol range
steamer was degreased in one plant observed, and the grease and oils were discharged to the treat-
ment system (9). Needless to say the treatment plant grease levels increased dramatically. Further-
more, grease slick could be seen in the clarifier weir overflow for months afterwards. Spreading
of canvas during such cleaning is suggested. Isolation of the grease and separate disposal by
incineration or landfill is indicated. Another plant experienced a similar grease discharge and
found straw thrown into the equalization basin that absorbed the grease. The grease laden straw
was raked out and burned (9).
6-32
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TABLE 6-13
FISH TOXICITY
Substance tested
95% Biphenyl
Sure Sol-160
SureSol-170
Sure Sol-190
A. Coal-tar derived
methyl-naphthalenes
B. Coar-tar derived
methyl-naphthalenes
C. Petroleum derived
methyl-naphthalenes
Butyl benzoate
Ortho'phenylphenol
3-Methyl methylsalicylate
1 ,2,4-Trichlorobenzene
Perchlorcethylene
X
Water
solubility
total*
(mg/l)
1.8
2.4
17
30
110
24
242
59
200
50,000
16
92
Y
Concentration
fatal to
50% of fish
in 96 hr
(mg/l)
1.5
8
1.5
4
30
4
35
6
20
2
2.5
7
Hazard
factor
X/Y
1.2
3
11.3
7.5
3.6
6
6.9
9.8
10
25,000
6.4
13
Biode-
gradable
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
Sinks or
floats
Floats
Floats
Floats
Floats
Most sinks
50-50
Sinks
Sinks
Sinks
Sinks
Sinks
Sinks
*Parts per million parts of water (mg/l) These values were obtained from the analysis of the aqueous phase from which the
serial dilutions were made
American Thread routinely boils out seven high speed yarn dryers about once a quarter (6).
The boil out bath is dropped into the waste treatment plant. Samples of the boil out baths were
sent to a lab for analysis. The results showed 1200 ppm copper, 800 ppm zinc and 600 ppm
chrome. This bath is now pumped into a tank and then transported to a chemical soak-away
on company land.
Metal salts have generally not been seen to be troublesome in treatment systems. There are
reports of those who have been able to segregate and hold wastes containing copper and chro-
mium and use them again, with strengthening when required. On the other hand, scrap iron has
been used to render copper salts innocuous, and bisulfite is commonly used to reduce chro-
mium (3).
Stetson (ICI) gave a cogent argument for the use of pad-batch (cold) dyeing of cellulosics (20).
In Stetson's experience, mills using the cold pad-batch system with high reactivity dyes have
experienced flexibility advantages, low energy requirements, high color yield (less waste), high
production speeds, substantial overall cost savings, etc. In view of the arguments made, a mill
should consider the possible advantages of such methods when possible. The pad-batch system,
Figure 6-17, utilizes a dyestuff and alkali tank, mixing tank and proportioning pump. The mix
6-33
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is then pumped to a pad unit which usually employs a hollow spacer to achieve a narrow pass-
age for the fabric. Thus the volume of liquor is kept low: about 5 gallons. This ensures rapid
turnover of liquor so that decomposition is kept to a minimum.
FIGURE 6-17
SCHEMATIC OF PAD-BATCH UNIT
The dyer and dye chemist might also critically examine methods used for dyeing blends where a
two-bath process is now used; ways should be examined for converting to a one-bath or even a
one-step process.
Perhaps the most radical proposal for reducing waste strength is to suggest that instead of ac-
cepting size "adulterant" and pollutant from greige mills, the size should be removed by the
greige mill in the future. Transporation costs and cost for unnecessarily heavier fabric (and 5%
weight of fabric) support the argument for this change. The idea will become even more ra-
tional in conjunction with advances in the development of solvent sizing and desizing. This
would allow reuse of solvent soluble polymer size. In 1974 Dow and ICI were primary devel-
opers of this concept.
Focus is now given to the area of raw wool scouring. Soaps, synthetic detergents and soda
ash have been used in scouring wool. It has been observed in alkaline scouring that soda ash
combines with part of the wool grease to form natural soap thereby requiring less detergent.
This has the advantage of lowering the waste strength, but is also said to lower recovered wool
grease yields (3).
6.2.1 New Pollution-Free Solvent Wool Scouring Method
Two Belgian companies have developed a new method of scouring wool by solvent, which they
claim is faster than classical wool washing, creates no pollution, and extracts large quantities of
lanolin and fertilizer by-product.
The two companies — Le Solvent Beige (Verviers) and Extraction de Smet (Antwerp) — have
formed a new company, Sover S.A., to promote the process. So far, it has sold one plant each in
6-34
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Russia and Japan, for a total of $9.3 million. The first sale was made in December. Sover is
also negotiating with firms in Poland, Austria, Yugoslavia, Uruguay, Brazil, Italy and the United
Kingdom. The plants will be built by co-parent Extraction de Smet, an engineering consultant
firm specializing in refining and extraction of fats and oils.
How It Works: Basically, the process removes from the wool all grease and suint (organic and
mineral potassium salts accumulated from sheep sweat) by dissolving the compounds in water,
isopropyl alcohol and hexane. Dirt on the wool is removed by spray jet pressure. The entire
process is carried out in a hermetically sealed system that recycles the solvent mixture. At the
same time, it collects lanolin and fertilizer. The lanolin is extracted in the hexane, and the fer-
tilizer comes from the alcohol residual sludge.
Raw wool is spread out on a perforated steel belt. It is sprayed once with hexane, then five
times with an aqueous alcohol solution at low spraying pressure, to avoid felting or matting
down the wool. After each spraying, the wool is squeezed under rollers. The amount of alcohol
used depends on the quality of the wool, but varies from 1 to 2 quarts per pound of wool.
Following the aqueous alcohol washing, the wool passes to two high-pressure hexane sprays for
degreasing, each time being squeezed under rollers.
The wool then enters the dryer, where air, deoxygenated by oil burners and continually moni-
tored for oxygen content, passes through it. Solvents left in the wool are recovered by the air-
induced evaporation (thus the need for deoxygenated air and a hermetically sealed unit to pre-
vent explosions).
The solvent mixtures are recirculated through a separator, where three phases form: the top
layer of hexane enriched with the dissolved grease; an intermediate layer of insoluble impurities;
and a bottom layer of alcohol, water, soaps and suint. The three layers are continuously drawn
off for treatment.
6.2.2 Wool Piece Scouring and pH
In wool piece scouring plants, studies have indicated pH spreads of 2.5 to 10 (3). The variance
was explained as intermittent discharges from sulfuric acid carbonizing. In such instances, it is
suggested that equalization or neutralization tanks be used to blend periodic discharges from
acid and alkali processing operations. In scouring woolen piece goods, whether in yarn or piece
form, the main contents of discharges are soaps or detergents, lubricants, and dirt; this applies
whether solvent or aqueous scouring techniques are used. Soaps can be "cracked" by strong
mineral acids while soft detergents are now usually relatively completely biodegradable although
there have been difficulties in obtaining biodegradable non-ionic detergents. Self scouring oils,
i.e., usually mineral oils or saponifiable scouring lubricants, create large amounts of effluent
with high solids content. Careful regulation of soda ash quantitites for scouring and neutraliza-
6-35
-------
tion of acid from carbonizing can lower the sulfate content. Avoidance of greasy carbonizing,
acid milling and acid bleaching can also help. The sometimes excessive amounts of soda ash used
in scouring or alkaline bleaching may cause the pH to rise to unacceptable levels and formula-
tions should be reviewed (3), (21).
It has been noted that relatively recently new fiber lubricants have come onto the market
claiming full biodegradability. These are mainly water-soluble. Since they are often applied at
very low levels, they do not interfere with the milling processes. The use of such products
could reduce water consumption, while at the same time lowering the sulfate and solids content
of discharges from scouring and milling (21).
In wool dyeing with acid dyestuffs, the level of sulfates discharged can depend on control of
the amount of Glauber's salt used. It has been observed that as much as 20% o.w.f. has been
widely used. The use of 10% o.w.f. is recommended and should be examined (21).
Raising, softening and certain shrink-resist processes should produce little if any effluent if they
are applied by padding without any rinsing process.
Polyvinyl alcohol has become the most commonly used sizing agent for fibers such as cotton
and polyester. Proper selection of the grade of PVOH can greatly facilitate its removal in desize
operations. Furthermore, "rapid desizing" using a peroxide-caustic soda combination at ele-
vated temperature may provide better and faster size removal using less equipment and en-
ergy (22). This procedure reduces waste strength and provides a more easily biodegradable waste.
Fully hydrolyzed grades of PVOH produce fibers that are stronger and tougher than partially
hydrolyzed grades, but require large amounts of hot water close to the boil to remove the size.
Although more expensive partially-hydrolyzed grades have lower tensile strength and produce
more foam, they are more easily soluble in warm water. Obviously then, proper selection of the
grade of PVOH is important. Next, the traditional method of removal requires use of large
quantities of hot water in the early removal stages. This is due to the high viscosity of the
PVOH tending to gel during early removal stages. Furthermore, accumulation in the washers,
which can cause redeposition on the fabric, is occasionally overcome by continuous over-
flowing. A more practical method which overcomes these problems is to use hydrogen
peroxide to decompose the PVOH. However, peroxide by itself requires steaming for effective
removals. The use of caustic in a two bath system with peroxide has been shown to produce a
thorough rapid continuous desizing. The conditions in the first bath include 0.8% ^02, pH
6.5, and 194° F. The second bath includes 0.5% NaOH at 194° F. Wash water at 159° F is
recommended. One bath system, using caustic and peroxide at 160° F followed by steaming,
recuperator and countercurrent washing at 160° F, has also proven successful on certain
blend materials. Another successful desize may be accomplished using 1% caustic at 160° F
followed by a steamer, recuperator and wash boxes.
A novel approach to PVOH desizing involves "plasma" treatment (23). Low energy excited
oxygen gas (plasma) was reported in 1973 to convert up to 60% of PVOH size on 50/50 poly-
6-36
-------
ester/cotton to harmless gases. When washed with water at ambient temperature, 95% of the
PVOH was removed. The proposed process is shown in Figure 6-18.
To
vacuum
pump
Electrodes
Exhaust
&-
Vacuum lock f Vacuum lock Wash box
Gas
FIGURE 6-18
PROPOSED PROCESS FOR CONTINUOUS PLASMA
TREATMENT OF TEXTILES
This system has not gained commercial acceptance, but it offers the potential, with further
research and development, of being a desizing method which could contribute considerably to
"zero discharge" requirements.
Table 6-14 compares starch waste degradability with PVA waste. Early work with unaccli-
mated organisms suggested PVA was hardly degraded and could replace high BOD starch. Re-
cent work indicates PVA can indeed be broken down to exhibit a high BOD. PVA is also
high in COD (4).
Before leaving the area of size, starch overuse as a size should be mentioned. A study of cotton
mills showed from 2 to 24% starch used on the weight of yarn (9). While most of the con-
centrations were justified, the major reasons for overuse were the lack of control of the rela-
tionship between relative humidity and the amount of size required. For example, 85% RH can
require considerably more starch than at 65% RH.
In summary, the importance of waste strength reduction is obvious in that not only are the
costs of treating wastes minimized, but also there will be savings in the costs of supplies. It is
easy to see that any savings from such remedial measures can go a long way toward paying for
the cost of waste treatment.
6.2.3 Waste Strength Reduction Checklist
Institute dry clean up of dry chemical spills
Display positive attitude posters to remind workers to stay alert.
Consider segregating styles into groups with different formulations for each group;
prevent "overkill."
6-37
-------
— Carefully calculate mix sizes to accommodate only the fabric lot sizes to be run.
— Consider automatic feed-in of chemicals on continuous ranges.
— Consider segregating print pastes, greases and solvent wastes to separate treatment.
— Study reducing overusage of surfactants and cheap salts.
— Consider wet process monitors to check coating depths to prevent wastage and ensure
a uniform product.
— Consider fiber and lint removal by screening.
— Consider requiring purchasing to request certificates of content on all chemicals
bought.
— Consider minimizing use of carriers by equipment substitution.
— Consider reducing processing sequences by combining processes.
— Consider holding wastes which can provide neutralization.
TABLE 6-14
COMPARISON OF BOD LOADS OF STARCH AND PVA SIZING
Enzyme starch desizing of 100-percent cotton-woven goods (60 percent warp)
[Production basis: 1000 pounds greige goods (containing 5 percent water), starch loading 14
percent based on warp]
Chemical throughputs
Item:
Starch
Fats and wax
Oil
Enzyme
Salt
Wetting agent
Suspended solids
Water
Total
Input,
pounds
84.0
4.4
0.4
1.6
2.5
1.0
Output,
pounds
84.0
4.4
0.4
1.6
2.5
1.0
5
12,500
Unit
BOD, lb/100
Ib output %
50
80
80
2
—
—
2
—
BOD output,
pounds
42.0
3.2
0.3
—
—
—
0.1
—
45.6
Effluent:
BOD
Total suspended solids
Total dissolved solids
PH
Color
Oil and grease
Toxic materials
Net effluent water
45.6 pounds
89.0 pounds
5.1 pounds
6-8
4.8 pounds
1.5 gal/lb goods
(Continued)
6-38
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TABLE 6-14 (con't)
Poly vinyl alcohol desizing of 100-percent cotton-woven goods (60 percent warp)
[Production basis: 1,000 pounds greige goods]
Chemical throughputs
Item:
Polyvinyl alcohol
Wax
Oil
Suspended solids
Water
Total
Input,
pounds
48.0
2.4
—
—
—
Output,
pounds
48.0
2.4
—
5.0
12,500
Unit
BOD, lb/100
Ib output%
1
80
—
2.0
—
BOD output,
pounds
0.48
1.92
—
0.10
—
2.50
Effluent:
BOD
Total suspended solids
Total dissolved solids
PH
Color
Oil and grease
Toxic materials
Net effluent water
2.50 pounds
5.0 pounds
48.0 pounds
6-8
2.4 pounds
1.5 gal/lb goods
Source- Industrial Waste Studies Program, Textile Mill Products, May 1971, for EPA by A D Little, Inc.,
Cambridge, Mass , unpublished
6.3 Waste and Water Recovery and Reuse
There is no doubt that future prospects for water supplies in certain areas of the U.S. will
depend heavily on the creation of a situation in which water can be reused and where chemicals
can be reused. To those who might argue that the reuse of water means a reduction in quality,
the following consideration is offered. The total flow of the River Thames is already being used
one and a half times before it reaches London Bridge, and some of its waters are being used
several times, having been extracted, treated, used, discharged to sewage works, and thence to
the river repeatedly (3). In terms of chemical recovery, many chemicals in textile operations
remain as relatively "pure" (unreacted) wastes, which indicates good potential for recovery and
reuse.
6-39
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In order to accomplish waste recovery and water reuse we need to enlarge our perspectives and
reassess our thinking. There are no simple answers, and the real contributions will be made by
textile engineers and chemists. It is from within that the real expertise for the future must
come. Management's motivation is also very critical. Otherwise, the options are clear — continue
to add-on more cost technology and pay more operational costs. At this time, the major task is
seen to be in making better use of available personnel. The predominant attitude, or philosophy,
is to let the treatment plant handle waste problems. However, there are some individuals in each
organization who believe that a discharge of 10,000 lb COD/day represents excessive waste, and
that opportunities for by-product recovery can and do exist. The first task of reassessment is to
identify interested, knowledgeable people and let them identify interfaces where opportunities
for reclamation, substitution or less usage might take place. However, before they can suitably
perform their task, they need more exposure to information describing what is available and what
it takes to get the job done. Only then can the resourcefulness and ingenuity of those interested
people be fully utilized.
In conjunction with encouraging those who are interested and who presumably are the readers
of this manual, the end-of-the-pipe philosophy should be supplanted by involving all key person-
nel through individualistic responsibility. This might easily be accomplished by the devising of
material balances for each major production area discharge point. In this way, production
people can readily see what is wasted, what causes problems downstream, what needs substitu-
ting, and what might profitably be considered for recovery.
To indicate just how great the potential for reuse may be, the summary of a recent study in the
U.K. between a West Riding Local Authority (Wira), and the Department of the Environment,
to study the possibility of using the outfall from a domestic sewage plant for all the process
water of a local woolen mill is reproduced below (3):
The textile chemist may think this is a foolish dream because of the very stringent
requirements that he traditionally places on the quality of his process water. But the
results of analyses of 1,000 samples of water used in the U.K. wool textile industry,
and the assessments of the industry's water chemists as to whether suitable 'as is' or
unsuitable without further treatment, show no agreement in many properties and there
are obvious and very wide tolerances in the quality of water that can be used success-
fully.
The outfall from the sewage works meets the average of this analysis except for tur-
bidity, colour and suspended solids. We believed that the turbidity and colour might
be acceptable. We reduced the solids content by installing a re-circulating sand filter
at the sewage works, and we treated the outfall with gaseous chlorine to achieve an
acceptable standard of sterility.
6-40
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Initial trials on a laboratory scale were very promising, and piping was installed to use
this treated effluent as an alternative to mains water at each of the normal mill pro-
cesses. Throughout the period of 18 months the use of this treated effluent has been
gradually extended, with detailed chemical monitoring and subjective judgment of
coloration to all the processes of piece scouring, milling, dyeing, washing off.
This mill produces a substantial proportion of the blazer cloth made in the UK cov-
ering a complete range of weights and qualities; in particular it produces a wide range
of colours from very light pastel shades for ladies' wear to dark meltons for industrial
clothing, and it uses a wide range of dyestuffs representative of all those used by this
sector of the industry. The mill staff, including the very particular cloth inspector,
have found it impossible to tell which cloths have been processed with which source
of water.
Following this technological success the local authority has now made arrangements
to install a full-scale tertiary treatment plant at the sewage works output; the water
will then be chlorinated, stored and piped to the mill to meet all its process require-
ments.
The mill uses some 200,000 gallons per day at a charge of approximately 25p per
1,000 gallons. This will be reduced to less than 5p per 1,000 by the new supply, a
saving of £40 per day.
Water of a relatively "pure" nature can be collected and reused directly. Much of it may be hot
water. Such sources include condensate water from high pressure lines, drying units, sizing ma-
chines, calenders, caustic recovery, etc. It is a reasonable estimate that between 40 and 70%
condensate water can be easily reclaimed from the steam generated from boilers. Also, various
cooling waters from compressors, hydraulic drives, evaporators, dye becks, etc., can be re-
claimed. Water from suction slots or hydroextractors can also be returned to wash boxes. Two
carpet mills reuse acid dye water decolorized by chlorine (Hollytex, California; Salem, Georgia).
6.3.1 Beck Cooling Water Savings
A simplified example based on an actual plant study of dye becks (10 becks) cooling water re-
clamation and savings is outlined below (9):
Flow Average 60 gal/min
Normal Cool Down Time (average) 45 minutes
Add Cool Down Time-(average) 30 minutes
Boil Out Cool Down Time (average) 25 minutes
6-41
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Water Savings — normal cool down:
45 min/day x 60 gal/min x 20 cycles/day = 54,000 gal/day
Water Savings — add cool down:
30 min/day x 60 gal/min x 20 cycles/day = 42,000 gal/day
Water Savings — boil out cool down:
25 min/day x 60 gal/min x 0.2 cycles/day = 300 gal/day
Water Savings — total:
54,000 + 42,000 + 300 = 96,300 gal/day
Steam Savings
Recover 96,300 gal @ 180° F - 60° F = AT 120° F.
96,300 x 8.33 x 120°
or
856 BTU/lb.
• Dollar Savings
1) oil - 112,000 Ibs. steam/day x $3.00/1,000 = $336/day (72 days)
2) natural gas - 112,000 x $1.00/1,000 = $112/day (240 days)
3) water saving - 112,000 x $0.20/1,000 gal = $22/day (350 days)
4) waste treatment saving - 112,000 x $0.25/1,000 gal - $28/day (350 days)
In this plant it was seen that a savings of approximately $68,500/year might be realized. Note
water costs are given as $0.20/1000 gal and wastewater treatment costs are given as $0.25/1000
gal.
6.3.2 Case Histories
One vendor offers what is relatively expensive fiber and suspended particle filter/heat exchanger
(24). The unit does not remove dissolved solids, i.e., salts, ionic dyes, surfactants, etc. Capacity
is around 100 GPM with automatic self cleaning. It is designed to feed clean, hot water back
into a washer. Effluent discharge temperature may be reduced from 180 to 100° F, water usage
down to 70% and heat usage down to 85%. The system is shown in Figure 6-19-
Burlington Engineering is one company that offers a hot water recovery system designed to re-
cover the cooling water from pressure becks, jets, package and beam dyeing machines, and
store it at a pre-set controlled temperature. The water may then be reused as make-up water or
rinse water in wet finishing or dyeing equipment. The recovered water, heated by means of
exchangers or coils, is collected in an accumulator tank and pumped automatically into a
10,500 gallon stainless steel holding tank. Here, the water is constantly circulated by pumps
through heat exchangers to maintain a pre-set temperature.
6-42
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6.3.2.1 Stafford
After printing at Stafford the knit goods go to a rinsing/finishing range (25). The rinsing section
is comprised of a Daiwa "Vibro" washer and an American Laundry "Jet" washer. After rinsing
in a relaxed state the water is collected in a tank beneath the washers and recycled before going
to treatment.
FIGURE 6-19
FHR SYSTEM
6-43
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6.3.2.2 Cone Mills
Cooling water that does not come in contact with cloth or have excess chemicals added is used
as a final rinse in dyeing (4). Cooling water in a hydrosulfite operation is reused as indigo wash
water. In printing, cooling water is reused to wash blankets or back greiges.
Alspaugh pointed out, during an EPA Technology Transfer Seminar (Atlanta, 1973) that a fer-
tile area for research exists in water reuse. He cautioned, however, that without top manage-
ment's backing, operating personnel regard suggestions as outside interference, and nothing con-
structive is accomplished. One of the important questions that requires an answer before gener-
ally effective water reuse can be accomplished deals with water quality. Alspaugh writes, "Unless
the minimum level of water quality necessary for processing is known, no effective program of
reuse is practical (4)." Also a collection of tables in this same seminar indicated diverse opinion
regarding tolerable limits of various substances before water can be reused. Table 6-15 is a com-
prehensive study of the quality of water used (a) for wet processing in the wool industry, and
(b) that considered unsuitable by industry (26). It is of interest to note that, for some of the
factors tested, rejected waters (b) were better than those accepted (a).
TABLE 6-15
WATER QUALITY REQUIREMENTS IN WOOL WET PROCESSING
Quality of water (a) used and (b) rejected in the processing of wool textiles
Number of samples a
b
Turbidity a
(Formazin units)* b
Colour (Hazen units)*a
b
Iron (mg/litre) a
b
Manganese (mg/litre) a
b
Suspended solids a
(mg/litre) b
Total hardness a
(mg CaCQs/litre) b
Alkalinity a
(mg CaCQs /litre) b
Raw
wool
scouring
33
13
18
67
0.70
0.75
0.77
0.18
40
150
68
90
Loose
wool
dyeing
25
8 ,
92
357
33
98
0.26
1.50
0.10
0.26
40
150
46
56
Top
dyeing
15
6
0.50
1.20
0.10
0.05
56
88
Hank
scouring
15
7
26
162
12
52
0.18
0.34
0.12
0.15
2
14
55
69
Package
dyeing
13
6
95
89
43
33
0.65
0.44
0.12
0.15
2
2
58
223
Piece
scouring
64
40
27
46
0.09
0.19
3
10
60
160
108
107
Piece
dyeing
46
20
73
255
26
81
0.30
0.65
0.10
0.28
4
19
60
160
78
82
*The higher the vajue, the poorer the quality of the water
6-44
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It has been stated that it would be ill-advised to state unequivocally what the optimum quality
for wet processing plant water should be (4). The experience and judgment of the water
chemist, the plant chemist, the dye chemist, and the dyer, are suggested to be best suited in
each individual case to determine at what level a contaminant may be troublesome. Tolerances
can only be set with a good knowledge of current operations and processes.
The following rough guide suggests the quality of water required for textile operations:
BLEACHING — no color, no metals to catalyze the decomposition of bleach or interfere
with dyeing, no high concentrations of organic (oxidizable) material to
cause dye resists, moderate levels of salts tolerable.
DYEING — pastels — no color or metal ions to affect shade, moderate quantities of
salt tolerated generally.
— dark — some color allowed, salts probably plateau with make-up water.
FINISHING — requires little water, use fresh.
6.3.2.3 Textile Research Associations
A wool piece scouring operation was closely studied in the U.K. (3). The results indicated that a
large proportion of water used during a single washing was still of reasonable quality for reuse.
Figure 6-20 indicates, in the graph on the right, that after 1000 gallons of wash-off water is
used, the remainder contains very little oxidizable material, as shown by the permanganate
number, and might be reused successfully.
E
CL
CL
LLJ
LLJ
O
z
<
2
DC
LLJ
CL
5000
4000
3000
2000
1000
0
(a)
0 200 400 600
WATER USED IN SCOUR,
gals
0 1000 2000
WATER USED IN
WASH OFF, gals
FIGURE 6-20
VARIATION IN PERMANGANATE VALUE WITH VOLUME OF
WATER USED DURING (a) SCOUR AND (b) WASH OFF
6-45
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Piping modifications were then made to the scouring machine, and a storage tank, valves, and a
pump were added. Figure 6-21 shows the final arrangement. The reclaimed water is then used
for the first part of the subsequent processing. Mains water is switched on for the final rinse and
acts as make-up. No complaints were received from the dyeing department and the system is
considered successful.
Mams water
supply
Scouring machine
Two way
valve
Diverting
valve
Dram
FIGURE 6-21
MODIFIED SCOURING DOLLY FOR REUSE OF
WASH-OFF WATER
6.3.2.4 C.E. Bryan
Size recovery has received considerable attention over the past few years. Originally in the early
1950's CMC was substituted for starch as a means of reducing the high BOD5 contribution of
starch. Since then Carl E. Bryan (N.C. State) has performed elaborate investigations of processes
for precipitating synthetic warp sizes (27). Aluminum sulfate was found to be most suitable
for CMC recovery. Four cycles of CMC reuse were reported to give results equivalent to yarns
sized with new CMC. Brown color observed in the recovered CMC indicated that natural im-
purities from cotton, and/or spinning oils from polyester may be retained on the yarn and in
solution. However, performance was said not to be affected by these materials, and none was
found retained by the yarns after desizing. Work was also conducted on PVA and starch precipi-
tation, but no substantive recommendations resulted. During exploratory attempts to find a
procedure for removing starch, modification of the molecule was attempted. Study of starch
desizing wastes from two plants did, interestingly, indicate that enzymatically desized starch
may not consist mostly of dextrose and other sugars of low molecular weight, as popularly
thought. The starch although degraded was still found to consist of relatively high molecular
weight polymers.
6.3.2.5 Gaston County
Perhaps one of the most sophisticated innovations to be introduced recently into the textile
industry is the Gaston County PVA Reclamation System. During this seminar speakers from
Gaston County, Clemson and J. P. Stevens described the system and its operational perform-
ance at J.P. Stevens Utica Mohawk plant. Approximately 1% million yards of sheeting were
6-46
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said to have been run at that time (28). Loom efficiency studies showed 10% virgin PVA added
to 90% reclaimed could be selected, as mix ratios were not found to be critical. The flow chart
in Figure 6-22 indicates the overall scheme. PVA must be kept as \% concentration (1), for opti-
mum efficiency, in the desize washer. Next, a vibrating screen (2) removes lint. After equaliza-
tion (3) the ultrafiltration system (4) rejects concentrated PVA and returns hot water (5) back
to the washer for reuse. Reclaimed PVA is stored (6) at 170° F and is reconstituted with 10%
virgin PVA before reuseThe filtration system involves four "stages." The first stage concentrates
to 3%, second to 6%, third to 8% and fourth to 10%. The reclaimed PVA was shown to have a
brown color. Fabric samples, however, were shown to have barely noticeable color compared
to virgin-sized fabric. This color was said to be no problem. However, colored or tinted yarn
bleeding could be a distinct problem in this system. Capital costs for a 20 GPM system were
said to be $300,000. A cost breakdown is given in Figure 6-23. The bactericide was found
necessary because of biological growth occurring in the reclaimed size. Figure 6-24 shows the
equipment in place at Utica Mohawk. In general, this equipment must still be given more time
to demonstrate its capabilities clearly.
REUSE PROCESS CYCLE
Warp
Virgin PVA
PVA Recovery System Flow Chart
4
Ultra-
filtration
system
Reusable
hot water
(permeate)
210°F
Waste
Slowdown
Reusable
PVA
(concentrate)
FIGURE 6-22
PVA RECOVERY SYSTEM FLOW CHART
6-47
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Conventional Recovery
Operation Operation
533,333 Ib of PVA per year at $ 36/1 b
5% of PVA wax add-on at $ 25/lb
1% PVA in wash water
Water at $ 207/1000 gal
Steam at $1 25/1000 Ib
Electrical power at $ 01/kwhr
Bactencide at $1 25/lb
PVA Cost
Wax Cost
Water Cost
Steam Cost
Electrical
Power Cost
Bactericide
Total
$200,000 $150,000 $100,000 $50,000
$50,000
FIGURE 6-23
FIGURE 6-24
PVA RECLAMATION SYSTEM AT J. P. STEVENS UTICA MOHAWK PLANT
6-48
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6.3.2.6 McCormick Mills
Hyperfiltration appears to be a practical approach to rejecting certain soluble and insoluble
chemicals for reuse or disposal and providing good quality water for reuse in certain situations.
A federally funded (EPA) project with Clemson and the South Carolina Textile Manufacturers
Association has demonstrated this technology by mobile facilities transported to various mills in
South Carolina (29). Such a system has special appeal in single shade dyehouses where dyes,
heat and water can be reused. Hollow nylon fiber membranes were found to require excessive
filtration procedures. Cellulose acetate membranes appear to perform better from a prefiltra-
tion standpoint but are temperature and pH sensitive. High-pressure (1000 psi) coated ceramic
membranes and low-pressure (400 psi) cellulose acetate membranes are being studied cur-
rently for application (30). Hyperfiltration membranes produce water of lesser quality than
produced by reverse osmosis. It must be said the cost may be high.
All reverse osmosis membranes used in desalting today, excluding developmental models, suffer
from gradual compaction under pressure. This causes gradual deterioration in flux levels and
often in salt rejection efficiency. In recognition of this most plants do not operate over
400 psi.
The recovery of spent mercerizing caustic is a practice with many-fold benefits. Reduction in
use of raw materials due to product recovery from the waste stream is the major cost benefit.
Lower waste treatment cost is another major benefit. In one plant 5% spent caustic averaging
100° F is stored before treatment in double effect evaporators. After the second stage, caustic
is concentrated to approximately 30% at a temperature of 260° F. Settling in conical columns
is the final step before reuse. Heat and water are reclaimed in the system. Adequate measures
(screening, presettling, etc.) should be taken to prevent fibers or gelatinuous PYA from clog-
ging such equipment (9). It has been suggested that if there is as much as 400 tons of sodium
hydroxide available annually, at a minimum strength of 2%, recovery by evaporation for reuse
may be economically feasible (31). However, other sources suggest that for economical con-
centration in a double or three state evaporation unit, feed should not drop below 4% (w/w
NaOH) (32).
The treatment of textile effluents containing large quantities of grease presents special
problems because wool grease and many of the traditional processing lubricants are not
readily biodegraded. Even where recovery of wool grease is practiced, by centrifuging or acid
cracking, residual grease present in treated liquor may be as high as 10,000 mg/1 and is un-
likely to be less than 1000 mg/1. Additional treatment is, therefore, still required before the
effluent can be discharged to a river.
Methods examined in detail at Wira for the treatment of effluent have resulted in the develop-
ment of the Traflo-W process (Figure 6-25). The process essentially entails chemical coagulation
of impurities followed by vacuum filtration, and, at its optimum, is capable of removing 100%
of the suspended solids and grease and of reducing the BOD by at least 80%. Manufacture of this
treatment plant is covered by a license agreement between Wira and Petrie & McNaught Ltd. (3).
6-49
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Holding tank
Filter cloth
Rotary vacuum
filter
-•-Filtrate
FIGURE 6-25
OUTLINE OF MILL-BASED PILOT-SCALE PLANT FOR TREATMENT OF
PIECE-SCOURING EFFLUENT
In considering the recovery of wool grease, acid cracking is still widely used in the U.K. Figure
6-26 shows one process configuration in outline. This method is reasonably effective in pro-
ducing a greasy sludge for separation from the mother-liquor. Grease from acid-cracking is usual-
ly dark brown and high in free fatty acid content. Efficiency varies in general from 50 to 70%.
The cake usually contains 15 to 25% grease and up to 1.5% can still remain in the mother-
liquor. The economics of such a process depend mainly on overall efficiency, labor costs, and
the current price for the relatively low-quality grease. BOD5 values are said lowered about one-
third using this process (3).
Wash
liquors
Acid
Mixing
Grease
Presses
Press cake
Acid
liquor
vSludge (Magma)
Acid liquor
FIGURE 6-26
OUTLINE OF ACID CRACKING PROCESS FOR
RECOVERY OF WOOL GREASE
6-50
-------
Centrifuged grease, on the other hand, commands a higher market price than acid-cracked
grease, but generally costs more to produce. Practically, efficiencies may run about 40% but can
vary widely. The grease concentration is approximately 1 to 2% when it is taken from the scour-
ing bowls. The concentration of grease is reduced to approximately 0.7% and is returned to the
scouring bowl. The effluent can still contain about 7000 mg/1 grease and the bulk of the or-
ganic matter. An example of a general arrangement for centrifugal separation is shown in Figure
6-27 (3).
Self-cleaning centrifuge
or
Cyclone
or
settlement
Liquor
Flock
catcher
3andl Rec.rculate s
' or ^
to sewer |iquo
or
acid-crack
Heat
*" excnanger
*
Primary centrifuge
"~ (concentration)
(Concentrate
Heat
exchanger
t
Secondary centrifuge
(purifier)
Aqueous
phase
I Grease
FIGURE 6-27
OUTLINE OF GENERAL ARRANGEMENT FOR CENTRIFUGAL SEPARATION
Chances of woolen piece or yarn scouring mills gaining profitable return from recovered grease
are considerably less than where raw wool is scoured. Costs of segregation of waste streams with
separate treatment, and poor quality grease containing varying amounts of free fatty acids, are
some of the reasons.
6.3.3 Waste and Water Recovery and Reuse Checklist
— Consider total treatment for water reuse
— Reuse cooling waters directly
— Reuse condensate waters directly
— Consider filtration before reuse
— Organize in-plant team and establish water quality criteria
6-51
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— Determine piping changes, storage costs, and pumping costs
— Determine where economy exists if on contract with municipality
— Determine whether increase in load to waste treatment will accompany flow reduction
— Can reclaimed water be used for preliminary equipment cleaning?
— Can bleach rinses be reused in scouring?
— Consider investigating solvent sizing and desizing
— Consider PVA size recovery and reuse
— Consider recovery of carpet-backing latices
— Consider application of hyperfiltration equipment
— Consider recovery of mercerizing liquors
— Consider recovery of wool grease
— Consider using air washer overflow in flushing or washing of toilets
— Consider suction slot extraction after last wash box with return of water to washer
— Consider returning vacuum water seal, or packing gland water to wash box
6.4 Chemical Substitution
In 1956 Masselli saw that the textile industry could quickly reduce its pollution load by 40 to 70%
using substituion practices (2). However, pollution at that time was mainly a matter of
BOD5- Since the 1950's additional pollution parameters have continually been added to a list
which makes a clearly defined goal difficult at this time. It should be more accurate then to
assume that chemical substitutions will also take place for continually changing reasons. Since
what is important now may have changing importance in the future, the suggestions in this sub-
section appear in a more or less randomized listing.
At this time one may substitute chemicals in processing for the following reasons:
1. To provide a more easily treated chemical by the treatment system in use. Consider
the consequences of flow reductions occurring while waste strength remains high.
6-52
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2. To provide a more easily recoverable chemical by reclamation equipment.
3. To provide for shortages in supply of chemicals (ex., disperse dyes based on anthra-
quinone reported in short supply).
4. To reduce the possibility or effects, of toxic chemicals harming the treatment
system or environment (including ultimate disposal techniques or discharge of
treated effluent).
5. To reduce a high pollution parameter to within permit requirements.
6. To replace materials in the waste which leave residues after treatment that may be
undesirable in the receiving stream.
7. To provide a less costly chemical, one which increases processing efficiency or one
that consumes less energy during processing.
6.4.1 Chemical BODs Lists
In terms of BOD 5 characteristics of textile chemicals, the classical document useful in a sub-
stitution program would be the AATCC Committee RA58's listing which appeared in the
American Dyestuff Report, August 29,1966. A more detailed version of cotton finishing
chemical BOD's was provided by Masselli and Burford (Table 6-16).
Other tables are provided in the EPA Transfer Technology Manual, In-Plant Control of Pollu-
tion, Upgrading Textile Operations to Reduce Pollution, EPA-625/3-74-004 (33).
6.4.2 Size Substitution
In view of the high BOD 5 load imposed on a treatment system by starch desizing, the substitu-
tion of this material by others with lesser pollution load may be considered. It should first be
stated that prehydrolyzed, low viscosity modified starches possess better penetration and film
formation than other types of starches available, and thereby reduce the quantity required for
sizing. Substitution of water soluble cellulose ethers such as the low BOD 5 CMC for starch can
still be rewarding under the proper circumstances. Refer to Subsection 6-3 for Dr. Carl Bryan's
(N.C. State University) work on CMC reclamation and reuse (27). On the other hand PVA is
used mainly for sizing cotton blends at this time. PVA reclamation has been discussed in the
previous subsection also. One study indicates that one PVA brand has a COD of Approxi-
mately 160% of its weight, while starch has a COD per unit weight of 100% (one pound starch
exerts one pound of COD) (9). From Appendix 5-1-2 it can be seen that the COD of starch
would amount to about 84 Ibs., while that for PVA (at 160%) would be 77 Ibs. of COD. This is
a difference of 7 Ibs COD/1000 Ibs. goods in PVA's favor (note that the add-on basis compared
is 8% PVA vs. 14% starch based on the warp).
6-53
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TABLE 6-16
COTTON FINISHING PROCESS CHEMICALS, CONSUMPTION AND BOD1
Chemical
B-2 Gum
Wheat Starch
Pearl Cornstarch
Brytex Gum No. 745
KD Gum
Slashing Starch
Total
Carboxymethyl Cellulose
Hydroxyethyl Cellulose
Tallow Soap
Nacconal NR
Ultrawet 35 KX
Acetic Acid, 80%
Mixture of 18 Dyes
Cream Softener, 25%
Formaldehyde-bisulfite Condensate
Glycerin
Sodium Hydrosulfite
Urea
Finish T.S.
Kierpine Extra
Merpol B
Glucose
Gelatin
Caustic, 76%
Soda Ash
Ammonia
Potassium Carbonate
Trisodium Phosphate
Sodium Perborate
Sodium Silicate
Liquid Soda Bleach
Hydrogen Peroxide
Sodium Chloride
Sodium Dichromate
Sulfuric Acid
Hydrochloric Acid
Amount used,
Ib.
1000 Ib. goods
22
16
14
4
4
96*
150
—
—
20-100
1
—
27
37
20
14
3
11
13
8
5
4
—
—
118
42
7
3
2
3
6
4
5
7
6
10
6
BOD, %2
61
55
50
61
57
—
—
3
3
55**
4
0
52
7
39
27
64
22
9
39
61
44
71
91
* * *
* * *
* * *
***
* * *
* * *
* * *
* * *
** *
* * *
** *
* * *
* * *
BOD
Ib.
1000 Ib. goods
13.4
8.8
7.0
2.4
2.3
53.0
86.9
—
—
11-55
0.04
0
14.0
2.6
7.8
3.8
1.9
2.4
1.2
3.1
3.1
1.8
—
—
* * *
* * *
* * *
** *
***
** *
* * *
** *
** *
* * *
***
* * *
** *
1 From Masselli, Masselli, and Burford, A Simplification of Textile Waste Survey and Treatment, New England
Interstate Water Pollution Control Commission, (1959) (2)
2 Based on weight of chemical; for example, 1 Ib. of B-2 gum (61% BOD) would require 0.61 Ib. of oxygen
for stabilization.
* Calculated from analytical survey
** Apparently contained high water content, dry soaps averaged 130 to 150% BOD
*** Negligible BOD assumed
6-54
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At this point it should be mentioned that individual chemical COD values are conspicuous for
their absence in the literature. This is because until fairly recently this parameter was of rela-
tively little concern. It now ranks as a major concern, and a study similar to the previously
mentioned AATCC BOD5 listing is awaited. Table 6-26 on page 6-70 provides a listing of textile
chemical COD's using the Rapid COD method (34) (35).
6.4.3 Size Treatability
Since ease of treatability has been mentioned as a possible reason for substitution, the studies
of Blair Mills, Belton, S.C., and Cone Mills are discussed (4). "Acclimated" organisms formed in
Blair's treatment system were found capable of reducing PVA from 420 mg/1 to nearly zero.
When a 10% "seed" was added to Cone Mills pilot system, the PVA removal rate increased
significantly within days. The following Figure 6-28 indicates PVA and COD removals by
"acclimated" activated sludge treatment at Cone Mills.
1UU
90
on
oU
— 70
-------
microorganism which degrades PVA was thought to grow at approximately l/10th the rate of
"normal" heterotrophic bacteria. In an aerated lagoon where the sludge age is the detention
time of the system, the sludge may never reach the required detention time. In an activated
sludge system, where l/10th the sludge is wasted, most newly acclimated microorganisms may
be wasted from the system. Another important aspect is that because the molecular weight of
PVA is so large, (approximately 80,000-100,000) degradation becomes a long, time dependent
process, and the degradation becomes an enzymatic function first rather than a biological assim-
ilation function.
TABLE 6-17
SIZE EFFLUENT COMPARISON — COD
STARCH SIZE
PVA SIZE AND FINISHING OILS
Inlet (Pounds) 75
Effluent (Pounds) 10
Possible further reduction in
Biotreatment — minimal
Inlet (Pounds)
Effluent (Pounds)
100
60
Possible further reduction in Biological
treatment 45 to 50 pounds.
Minimum effluent value = 10 Ibs.
6.4.4 Foam Control
Before departing the area of treatment, the topic of foam needs to be touched on. Everyone is
aware of the foaming problem, especially on prolonged cloudy winter days. Residual wetting
agents are a large contributor towards this problem. Furthermore, studies of textile chemicals
indicated that a commonly used anionic surfactant could exert as much as 140% of its weight
in COD (1.4 Ib. COD exerted per pound surfactant), and a commonly used non-ionic surfactant
exerted over 200% of its weight in COD (34).
Barnhart showed (Table 6-18) a simplified dye solution analysis in 1975, which demonstrated
that the amount of wetting agent used in processing would exit to a waste treatment plant in
identical concentrations (37).
It becomes obvious that surfactants can constitute a large part of the COD, and ways to reduce
usage and substitute surfactants should be explored. The BOD5 problem of surfactants in re-
spect to foaming was approached in the early 1960's. Since then so-called "hard" detergents
have been replaced by so-called "soft" detergents. The facts are that even though the literature
indicates that surfactants are more easily biodegradable than ever, they are still very difficult to
degrade.
6-56
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TABLE 6-18
DYE SOLUTION
(% as weight of cloth)
In
Out
Carrier
Wetting Agents
Dye
Salt
Acid and Miscellaneous (non-organic acids)
3.0
0.5
0.5
5.0
1.0
3.0
0.5
-0.05
5.0*
1.0*
*No Impact on COD.
Adams (C.H. Patrick Co.) reported that linear alkyl derivatives tend to foam more than branch-
ed derivatives (38). However, they are also more readily and completely biodegradable than
branched aliphatic or alkyl aryl types. Generally, 8 to 12 carbon hydrophobes give optimum
wetting efficiency, while 16 to 18 is best for cotton detergency. Understanding how structure
relates to properties, such as wetting, detergency and emulsification can help a mill select an
optimum surfactant for a given job. For example, selection of a surfactant for a denim pad box
would involve one that has maximum wetting ability and minimum detergency. Non-ionic sur-
factants with branching hydrophobes give superior wetting results over linear hydrophobe sur-
factants. (See also Tables 6-22 and 6-23 on pages 6-67 and 6-68).
Many surfactants, such as the alkylphenol ethoxylate and ethoxysulfate types, are resistant to
attack by bacteria found in treatment systems and streams. Consequently such surfactants con-
tinue to foam and pollute natural waters and retard the efficiency of treatment systems. The
River Die-Away test shown in Figure 6-29 (by Union Carbide) indicates what happens using
low bacterial populations found in natural rivers under laboratory conditions. The Tergitol S
series (linear alcohol ethoxylates and derivatives) of non-ionics degrade more rapdily than the
other surfactants compared. Such a test coupled with foaming tests and performance applica-
tion tests (wetting ability, leveling, scouring assistance, bleaching assistance, etc.) will indicate
the optimal product for a specific application.
The River Die-Away test is conducted in an aerobic environment employing the low bacterial
populations found in natural rivers. Consequently, fairly long periods are required for degrada-
tion. To conduct the test, 20 mg. of active surfactant were added to a one-liter sample of river
water contained in a suitable bottle. The contents were mixed using a magnetic stirrer prior to
sampling for methylene blue and cobalt thiocyanate activity. In between sampling, the flasks
remained quiescent on a laboratory shelf at ambient temperature and light conditions. A loosely
fitting rubber stopper was used to prevent excessive evaporation.
6-57
-------
100
90
80
70 -
60 -
O
z
< 50 -
LU
QC
40
30 -
20 -
10 -
p,t-Octylphenol Nonionic
(a)
Linear Alkylphenol Nonionic
/ (b)
Linear Alkylphenol Ethoxysuifate
/ (c)
Tergitol
15-S-3A
Tergitol
15-S-9
DAYS
(a) Such as, "Igepal" CA-630 (General Aniline & Film):
"Polytergent" G-3000 (Olm) "Triton" X-100 (Rohm & Haas):
(b) Such as, "Igepal" LO-630 (General Aniline & Film)-
"Sterox" MJB (Monsanto)
(c) Such as, "Alipal" LO-436 (General Aniline & Film)
NOTE' Nonylphenol derivitives' such as "Polytergent" B-300 (Olm)1
"Igepal" CO-630 (General Aniline & Film)- "Triton" N-100
(Hohm &Haas). and TERGITOL Nonionic NPX, aresimilarto
the actylphenols m biodegradability
FIGURE 6-29
MEASUREMENT OF BIODEGRADATION BY THE RIVER DIE-AWAY TEST
(Anionics by Methylene Blue; Nonionics by Cobalt Thiocyanate; 20 mg. per Liter
Initial Concentration)
6-58
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The results presented in Figure 6-29 indicate that the linear alcohol-derived ethoxylates degrad-
ed more rapidly and more completely than do the alkylphenol derived materials. Comparable
foamability losses and surface tension recoveries were measured in the case of the linear alcohol
ethoxylates; this loss-of-surfactancy was not found,with the alkylphenol-based materials. (See
Case History at end of subsection 6-4).
An interesting finding appeared in the February 1972 American Dyestuff Report.EPA investi-
gators from Athens, Ga., found an 80-fold increase in p-nonylphenol between a carpet yarn
mill's treatment influent and effluent. Their explanation was that the phenol increase was
likely due to biological degradation of the surfactant.
6.4.5 Wool Fulling
Soap used in fulling can contribute high BOD levels (2). If detergents or sulfuric acid are used,
the table below shows the BOD equivalent of a "hard" detergent (Lissapol N) and that of a
"soft" detergent (Empilan KL10).
BOD equiv.
Chemical (Ib./lb.)
Soap (textile flakes) 1.06
Lissapol N 0.06
Empilan KL10 0.72
Sulfuric acid 0
6.4.6 Carriers
The topic of carriers has been approached in subsections 6-1 and 6-3 (see Table 6-3, page 6-2 and
Table 6-10, page 6-30 for a comparison of some carrier BOD's). These substances can be highly
polluting and toxic. The use of high-pressure equipment, when possible, to reduce the concen-
tration of these materials discharged, is strongly suggested. Table 6-18 indicates that the amount
of carrier in a dye bath formulation exits in identical concentration to a waste treatment plant.
Vendors at this time, the literature indicates, are developing carriers which are more susceptible
to biodegradation and less toxic. These efforts should be vigorously encouraged. The user
should know a great deal about the degradability and toxicity of any new chemicals. If the ma-
terial is said to be susceptible to biodegradation, evidence should be produced showing how a
typical waste treatment system removes it, before it reaches the receiving body of water.
Furthermore, information on concentrations in wasted sludge should also be provided. If de-
gradation is not complete, discussion on the chemicals' chances of building up in the food chain
should be provided. Preliminary studies of toxic materials should indicate low, acute, and chronic
toxicity values in animals, suggesting no hazard with normal usage. The chemical should be com-
pared in reactivity to a standard. In use concentrations, it should be compared to regulations,
such as California's Rule 66. Lastly, but not least, in terms of a carrier it should certainly pro-
duce a high color yield, no harmful effects on thermofixed goods, good effect on dye migration,
6-59
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and no harmful effects on lightfastness. It should also be readily emulsifiable, have good wash-
fastness, give level dying, and have good abrasion resistance.
Another area of toxicity concerns chrome. Many vat and sulfur dye shades can be very satis-
factorily oxidized by using peroxide over dichromate (9). Optimum fastness is achieved by
maintaing the proper pH using peroxide oxidation. Study showed actual chemical cost
was approximately half that for dichromate, using a peroxide concentration of 0.35%. Indica-
tions were that this concentration could be reduced considerably for many sulfur dyes. While
automatic control of peroxide concentration (see Figure 6-13) is not a necessity, there can be
advantages to the use of such equipment. In cases where dichromate or peroxide may not be
suitable, sodium iodate or laking agents may be substituted. One mill experience indicated
that substituting iodate for dichromate, in some instances, actually produced better absorbency
and luster in their dyeing than dichromate.
6.4.7 Substitute for Acetic Acid in Dye Bath
Substitution of formic acid for acetic acid in dyeing gives a substantial reduction in BOD and,
because of its lower equivalent weight, can give a cut in costs (2).
BOD equiv.
Chemical (Ib./lb.)
Acetic acid 0.64
Formic acid 0.12
6.4.8 Dyeing Wool-Replace Acetic Acid
Masselli (2) demonstrated that in dyeing procedures using acetic acid, the acid may contribute
85% of the BOD5- If ammonium sulfate is used in place of acetic acid, the BOD can be reduced
the full 85%. Furthermore, the ammonium content will serve as a nutrient in the activated
sludge process. Of course, the salt content of the waste will be increased.
6.4.9 Reactive Dyes
A relatively recent development in the area of dyeing is the improved range of reactive dyestuffs
with shorter fixation time and higher yields, which may also result in less wastage to the drain.
6.4.10 Dye Selection
ICI addressed the topic of dye selection for the times in Textile Industries, July 1974. A related
paper appeared later in the Textile Chemist and Colorist, January 1975, which emphasized
energy conservation. The rationale suggested that enough potential existed for dyehouses to
consider dyeing processes that can minimize energy consumption. The latter paper acknowl-
6-60
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edged that a dyer may not always be able to select a class of dyes which minimizes energy con-
sumption, but once the choice is made, dictated by the customer's idea of end-use fastness,
the dyer can select the method of application that minimizes the energy consumed in applying
a given class of dye.
In considering package exhaust dyeing, Table 6-19 shows an idealized ranking of dyes by ICI.
The table includes the energy required for dye application and subsequent clean up, but not the
energy used in drying. Drying was assumed equal for all dye classes. The figures in the table re-
quire balancing against dye costs, level of redyes, and cost of application.
In discussing continuous dyeing methods, the pad-bath semi-continuous method is seen in
Table 6-20 to have the lowest energy use of any method of dyeing cellulosic material. When
washing is added the energy required is additive. Continuous methods of washing are suggested
best.
Assuming 150,000 BTU/gallon fuel oil, costing can be estimated using Table 6-20. For exam-
ple, the pad-dry chemical pad-steam method uses about 610,000 BTU/100 Ib. goods dyed. The
pad-dry method uses 90,000 BTU less. At 24 million pounds per year this could save approxi-
mately 160,000 gallons of fuel/year. At 20e
-------
TABLE 6-20
APPROXIMATE ENERGY CONSUMPTION OF
COMMONLY USED CONTINUOUS SYSTEMS3
Method
Pad-Batch13
Pad-Dry
Pad-Dry-"Bake"
Pad-Dry-Chemical Pad-Steam
Pad-Dry-Thermofix-Chemical
Pad-Steam
Energy
Consumption
(BTU/100 Ib)
3.6 x 105
5.2 x 105
5.9 x 105
6.1 x 105
7.0 x 105
a Drying is not included and is assumed equal for all methods
^Semicontmuous method
6.4.11 Resin Selection
Vendors of resin/catalyst systems are currently advertising modified conventional resins and
catalysts which will cure quickly at relatively low temperatures. Although no wide-spread appli-
cation appears indicated at this time, there may be certain applications where these systems can
provide advantageous substitutions and should be examined. In response to reported carcino-
ogenic effects of chloride catalysts, one firm reports switching to sulfate catalysts. This firm
also reports favorable results with a glyoxal resin bath using hot catalysts such as metal salts
of i^-hydroxy carboxylic acid to cure at lower temperatures and to save energy (39).
6.4.12 Oil and Lubricant Substitute
Carding oils and antistatic-lubricants might be replaced by mineral oils with non-ionic emulsi-
fiers and other low-BOD substitutes according to Masselli (2).
6.4.13 Solvents and Print Pastes
Masselli reported that elimination of hydrocarbon solvent usage in print-paste makeup reduced
the BOD load from 6,000 to 2,000 pounds per day in one mill (4). One or two barrels per
day of hydrocarbon solvent may contribute as much as 1,000 to 2,000 pounds of BOD, and sub-
stitution of aqueous print pastes should be considered where possible.
6.4.14 Phosphates
If a reduction in phosphate is required, substitution of non-phosphate chemicals such as, ethy-
lene-diaminetetra-acetic acid, and others, might be considered (4). Phosphate removal by chemi-
cal coagulants is readily accomplished and has been applied successfully before, during or after
6-62
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activated sludge treatment. Unless usage of high-phosphate containing flame retardants occurs,
phosphates are generally not a problem.
6.4.15 Nitrogen
Although not anticipated to be a major problem in textile wastes (nitrogen is often added for
nutrient benefit in textile waste treatment systems), nitrogen compounds are worthy of men-
tion here in terms of future considerations. Nitrogen can occur in wastes as ammonia, nitrate,
nitrite, and organic nitrogen. Flame retardants may be a major N source. Ammonia has a very
high oxygen demand (423%) and can deplete oxygen resources in a stream given time (4). On
the other hand, ammonia has a very high chlorine demand and may produce possibly toxic
chlorinated amines (40). The well-known increase in algae blooms caused by nitrites and nitrates
is also a problem. Dr. A.W. Lawrence (Cornell) discussed the elaborate biological treatment re-
quirements necessary to reduce wastewater nitrogen (36). In some cases treatment might need
to be doubled. It is apparent that if increases in nitrogen use occur in the industry, the process
should be designed to utilize the compounds very efficiently.
6.4.16 Phenolics
The common test for phenolics indicates compounds containing the phenol structure. Many
textile chemicals can contain this structure. Some of the following have been identified: certain
detergents, phenol-formaldehyde resins, carriers, solvents, lubricating oils, certain toilet bowl
cleaners, etc. Substitution, if necessary, should be examined cautiously. For example, pheno-
lics used in synthetic dyeing may be reduced in a formulation, but too great a reduction may
require use of more dye and other auxiliaries. Solvents and used lubricating oils containing
phenolics are occasionally disposed of down floor drains. This should be prevented, and is often
easy to see by oil stains in the vicinity of a drain. Such chemicals, and also unused phenolic-
formaldehyde resins (pad), may be collected, and, perhaps, sprayed on plant waste rags, etc.,
and incinerated (4), (6).
6.4.17 Wool Scouring
The use of alkaline scouring instead of neutral scouring of wool top has been said to convert
some greases to soap and thereby reduce the amount of detergent needed. However, Wira
chromatographic studies have confirmed that the composition of the residual wool grease after
a neutral scour is different than that after a soap-soda ash scour. Possible effects in later process-
ing must also be considered (3).
6.4.18 Ammonia Mercerization
J.P. Stevens' Technical Center investigators suggest that liquid ammonia treatment prior to
durable press and flame-retarding finishes may be a viable approach to attain improved overall
6-63
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1,100
1,000
900
800
700
600
^ 500
D
t-
CO 400
CO
o
T-
•2- 300
200
100
BATCH
(in Beck at 15:1 Liquor Ratio)
Semi-
Continuous
Pad-batch
CONTINUOUS
1,100
1,000
900
800
700
600
500
400
300
200
100
B
BECK DYEING
A = Direct Dyes
B = Naphthols
C = After-treated Directs
D = High reactivity (low energy) fiber
reactives; e.g. Procion MX,
Levafix E, Remazol, Drimarene K
E = Lower reactivity fiber reactives;
Reactone, Cibacron, Procion H,
Drimaren X
G
H
I
PAD-BATCH, (Semi-continuous) PROCESS
F= Pad-Batch, applicable with low
energy reactives: e.g. Procion MX
CONTINUOUS PROCESSES
G = Pad/Dry, for use with
Procion MX (low energy reactives)
H = Pad/Dry/Bake, for most classes
of reactive dyes
I = Pad/Dry/Chemical Pad/Steam,
for vats, sulfurs or reactives
FIGURE 6-30
APPROXIMATE ENERGY REQUIREMENTS TO DYE 100 POUNDS OF FABRIC
6-64
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fabric performance (41). Significant efforts have been made in the past several years to utilize
the rapid swelling and plasticizing effects of liquid ammonia on cotton. These efforts have led
to the Prograde process for treating sewing threads (42). Norwegian research workers explored
the effects of liquid ammonia on cotton fabric (43). Improved luster, dye affinity, strength, and
dimensional stability were in the range obtained by caustic mercerization. Furthermore, am-
monia produced a softer hand improved resistance to wear and crease shedding compared to
caustic. USDA workers disclosed a patent in 1973 for mercerization with liquid ammonia in a
chainless mercerizer (44). In general, the better the easy-care performance of a garment, the
worse its strength and durability.
The mechanical performance of DP fabrics are mainly governed by the fiber structure, the pre-
treatment, and the cross-linking treatment. On the other hand caustic mercerization performed
today often imparts a superficial treatment as concerns are with good luster and color yield.
Caustic mercerization in these cases may not give good fiber strength due to non-uniform treat-
ment as a result of too short immersion time (high speeds), inadequate shrinkage of the fabric,
and the poor wetting and penetrating power of strong caustic liquors. Under the conditions
above, the potential application of ammonia treatment suggests itself as a future alternative to
caustic mercerization. At this time, it should be said, work is still continuing to improve the
technology. Furthermore, economical recovery of the ammonia must be demonstrated. It
should also be mentioned that work is being conducted to ascertain whether conventional
caustic mercerization can be improved. Steam, for example, is felt capable of reducing the sur-
face tension of fabric, by replacing air in the fabric, before mercerizing. Trials using cotton
print cloth indicate significant increases in strength may result compared to conventionally
mercerized fabric (45). Another possible application of liquid ammonia, as a low pollution
substitution for conventional caustic mercerization is being explored by a Norwegian firm.
Heavy cotton treated with liquid ammonia gave better form and dimensional stability, gave
less shrinkage during laundering, required less dye for a given depth of shade, and could be
made shrinkfast on a Sanforizing machine. The hand was said to be better, and progressive
shrinkage was virtually nil. However, the process is meant to be supplementary to and not a
replacement for resin finishing.
Current development includes modifying machinery to reduce liquid ammonia uptake. Still
as for its promise, the first commercial application of liquid ammonia processing will be in-
stalled by Burlington Industries' Erwin Mill. After four years of intensive research and develop-
ment by the Sanforized Co., the process, trademarked Sanfor-Set, will process about 20 million
pounds per year of 14 oz. cotton jean fabric. Fabrics will be trademarked "Duralized." The
process schematic and operating factors are given in subsection 5.5, "Process Changes." Whether
liquid ammonia will replace caustic mercerization cannot yet be foreseen as the process still
awaits exploitation and development. Mr. C.C. Ware (Sanforized Co.) suggest that the luster
from liquid ammonia may not be as great as with caustic soda (46). However, shrinkage stabil-
ity, crease recovery, and smooth drying are said better. It is reasonable to assume that programs
will be undertaken to assess the advantages in specific cases, where the features of ammonia-
treated fabrics may be more desirable than caustic-mercerized fabrics.
6-65
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6.4.19 Chemical Inventory
An inventory of chemical usage is the first step in substitution considerations for various rea-
sons. A summary of annual chemical usage by one firm is given in Table 6-21, in which chemi-
cals are ranked in terms of pounds used. Here the priority of carrier NT is established by usage.
Inquiry may be made into the disposition of the chemical as it is discharged. What amount es-
capes to the air versus that discharged in the waste water? Table 6-22 provides additional in-
formation for substitution considerations. The information here, provided by Dow Chemical,
should be encouraged by all vendors.
Two case histories may be helpful to indicate the potential of a program including chemical
substitution. The first case is significant in that it took place before 1960.
6.4.20 In-Plant Textile Changes at Burlington
In-plant studies to reduce volume and pollution load of wastes at Burlington are summarized (47).
TABLE 6-21
EXAMPLE OF ANNUAL CHEMICAL USAGE, 1972
Rank
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Chemical (type)1
Carrier NT (B)
Neutrol #9 (C)
Aerotex water repellant 95 (D)
Cap LEV LSP (C)
Soap OFF 60 (A)
Acetic acid (E)
Neoport APO (B)
Solvecrest RB (A)
Monosodmm phosphate (E)
Caustic soda (E)
Dispersing agent (C)
Avitone F (C)
Calgon (F)
Fanapon X70 (A)
Neoport DPG (B)
Raycofix NY (H)
Sanopan DTC (A)
Formic acid (E)
Sodium hydrosulfite (A)
Cap Carrier BB (B)
Ammonium chloride (E)
Herriton SWD (C)
Intrawite EBF (G)
Gluconic acid (C)
Tanalube RF (C)
Usage
Pounds
331,457
200,064
136,205
132,685
126,708
124,206
117,609
110,788
92,672
89,673
84,887
72,443
69,130
58,198
51,871
48,428
47,227
46,779
45,983
38,867
38,189
36,698
30,242
27,416
24,654
Percent
12.540
7.569
5.153
5.020
4.794
4.699
4.449
4.191
3.506
3.393
3.212
2.741
2615
2.202
1.962
1.832
1,787
1,770
1.740
1.470
1.445
1.388
1.144
1.037
0.933
1A = scour, B = carrier, C = dyeing assistant, D = finish, E = pH control chemicals, F = softener, G = fluorescent,
H = fixing
6-66
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TABLE 6-22
ENVIRONMENTAL PROPERTIES OF BIPHENYL
Stability
Flash Point °F
Chemical Reactivity
Water
Oxygen
B.O.D. % Theoretical
5 day
10 day
20 day
Movement
Vapor Pressure, mm Hg at 25°C
Water Solubility,mg/l
Aeration Stripping, % C.O.D. removed after
4 hours
Bioconcentration
Log P (Calculated)
Toxicity
Acute
Oral, LDso, mg/kg for rats
Skin Irritation
Skin Absorption
Eye Irritation
Vapor Inhalation, TLV, ppm
Fish, LCso for fathead minnows mg/l
260
stable
stable
3
71
79
0.008
7.5
89
4.1
1600-3000
very slight
may be absorbed slowly
moderate
0.2
5
Water usage was reduced by returning pump cooling water to the reservoir and by better con-
trol of the pressure water filter backwash. A program was put in effect to reduce the volume
of water used in the various processes. This program evolved slowly because of the reluctance to
change or to reduce any component of the operation, such as the elimination or reduction of
various washing operations or the reuse of these wash waters in other processes. Reuse of certain
wash waters in dyeing showed promise, but these methods of re-use were not studied further.
The pH of the waste was reduced by the installation of a caustic recovery unit. This unit has
resulted in a significant reduction in the pH and hydroxyl alkalinity, making the waste more
susceptible to biological action. The caustic recovery not only reduced the pollutants dis-
charged into the stream, but also was a good investment by returning re-usable caustic soda to
the process.
One of the major sources of BOD load was starch used in the warp sizing operation. Because of
this, CMC (Carboxymethyl Cellulose) was evaluated as a replacement for the starch, and after
nearly 15 months of studies and trials, methods were developed which permitted the sub-
stitution in the mill operation. While substitution of CMC for starch sizes resulted in an over-
all BOD reduction of about 50% for the entire mill operation, it was found somewhat
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more expensive than starch, and additional studies were made with combinations of CMC and
low BOD starches in order to achieve the same BOD reduction at a lesser cost of sizing materials.
This was successful.
Further studies of chemicals in the plant brought about the substitution of detergents for soaps,
reducing the BOD of many individual samples by 70 to 80%. Some finishes were found to have
less BOD than others, and, although the overall waste volume of finishes was relatively low, '
substitutions of finishes were made wherever practicable. Certain dyestuffs were given consid-
eration because of low pollutional load, but studies were not carried to completion, Table 6-23.
TABLE 6-23
DATA REFLECTING IN-PLANT CHEMICAL SUBSTITUTION CHANGES
Item
Five-Day BOD
pH
Total Alkalinity
Hydroxyl Alkalinity
Carbonate Alkalinity
Before
Changes
410 ppm
11.5-12.0
1600 ppm
After
Changes
210 ppm
10.0-10.5
560 ppm
180 ppm
380 ppm
Reduction
190 ppm
2.0
1040 ppm
6.4.21 In-Plant Changes at United Piece Dyeworks
This case, described by Randall (VP1) involves excessive foaming which washed solids onto the
sides of the lagoon, retarding efficient treatment (4). Initially, the system discharged 1 MGD into
a 3.25 MG aeration basin. The system began with 44 hp/MG applied which was inadequate to
maintain MLSS above 350 ppm. BOD reduction at this level was only 55 to 65%. When 135
hp/MG was installed to reach the 1,500 to 2,000 ppm MLSS desired, excessive foaming pre-
vented the MLSS from rising above 600 ppm. Sprays and defoamers were found inadequate.
Investigations were carried out and chemical substitution was decided on.
The chemical changes made were as follows: 1) Tar Remover SW, an 85% xylene compound,
and its carrier, Tanavol, a non-ionic detergent that is a linear ethylene oxide condensate, were
replaced with Tanaclean HFP, a high-flash naptha solvent that contains no toluene, and its
carrier, Carolid AL, a biphenyl and ester mix; and 2) TSPP, a tetrahexaphosphate chemical,
was removed from the scour bath and replaced with a much smaller quantity of soda ash.
The latter change was possible because a dry-cleaning unit had been added.
Tables 6-24 and 6-25 show the differences before and after chemical substitution. Table 6-26
shows some COD results on various textile materials. Additional COD information on textile
chemicals is needed along with information concerning toxicity.
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TABLE 6-24
FOAM-HAMPERED PERFORMANCE DATA
Date
11/2/72
11/9/72
11/16/72
11/22/72
11/29/72
12/4/72
12/14/72
12/22/72
12/29/72
1/4/73
1/11/73
1/18/73
Average
Influent
BOD's
mg/l
400
390
340
390
400
369
360
390
380
400
370
380
381
Effluent
BOD's
mg/l
120
130
120
120
130
141
130
130
120
130
110
120
125
Removal
efficiency,
percent
70
67
65
69
68
62
64
67
68
68
70
67
67
MLSS,
mg/l
620
420
520
540
440
420
420
420
400
400
410
410
TABLE 6-25
CHANGE IN PERFORMANCE WITH FOAM CONTROL
Date
2/22/73
3/1/73
3/8/73
3/9/73
3/14/73
3/22/73
3/29/73
4/5/73
5/10/73
6/7/73
6/13/73
6/18/73
6/26/73
Average
Influent
BOD's
mg/l
370
370
360
357
300
329
330
360
340
317
359
362
339
Effluent
BOD's,
mg/l
120
130
130
70
50
70
75
75
60
52
65
65
65
Removal
efficiency,
percent
68
65
64
80
83
79
77
79
82
84
82
82
81
MLSS,
mg/l
440
370
890
1,200
1,280
1,400
1,500
1,670
1,760
2,180
2,299
2,340
2,370
Source In-Plant Control of Pollution, Manual 1, EPA 625/3-74-004, Oct 1974 (4)
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TABLE 6-26
RAPID COD RESULTS ON TEXTILE CHEMICALS (39)
Compound
Globe Dextrin (glucose)
Dextrose (Baker-glucose)
Fibraloid L-136 (mod cornstarch)
Covol (PVA)
Sandopan DTC (anionic)
Triton X-100 (nonionic)
Aerotex Resin 52
Cotton (bleached)
Vat Green 1
Disperse Blue 79
Direct Red 81
add 1000 mg/t NaC I
add 5000 mg/l NaC I
Mixture
40% disperse dye
40% Covol PVA
20% Triton X-100
Concentration
(mg/l)
1200
1200
1100
1000
1000
400
1000
1000
500
1000
500
250
150
75
1000
500
250
500
500
(1560 mg/l anicipated COD)
COD
Rapid Method
(mg/l)
1167
1130
1147
1585
1390
980
435
1062
644
1094
580
330
160
66
990
520
215
592
707
1460
6.4.22 Chemical Substitution Checklist
— Obtain inventory of process chemicals used and BOD5, COD, and toxicity information
on individual chemicals
— Consider substitution of sizes
— Consider substitution of wetting agents
— Consider substitution of carriers
— Consider substituting formic for acetic acid
— Consider use of reactive dyes
— Consider evaluating new resin/catalyst systems
6-70
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• Consider changing to aqueous print pastes
• Consider alkaline scouring of wool
• Consider use of peroxide or iodate for dichromate oxidation
6.5 Process Changes
This subsection incorporates some of the objectives of the previous subsections. Priority is given
to unit operations and process concepts which may reduce waste volume and strength and
which possibly could make use of recovered by-products or chemical substitutions. Thought is
also given to the majority of readers here who want to learn specifically what changes can be
made in the many textile unit processes which can result in savings by increased production,
increased efficiency, reduced time, reduced energy requirements, and reduced costs. Considera-
tion is also given to radical thinking in terms of entirely new or emerging technology, since some
of this technology will be tomorrow's conservative processing.
The following areas are covered in this subsection:
• Existing process modification
• Comparing similar conventional operations
• New technology
• Emerging technology
There is much fertile area to consider concerning upgrading the unit operations which are cur-
rently used to convert raw products to finished materials. This is because in the past little regard
has been given to concepts and equipment design dealing with relatively inexpensive resources
such as water, certain chemicals, and energy. For example, a very recent ITT mill project indi-
cated that drying the same style 100% polyester on a Marshall-Williams tenter frame consumed
around 50% more gas per pound of goods than by use of a Krantz tenter frame (3.4 cu ft/lb. vs.
2.26 cu ft/lb.). This example is used to indicate that the improvements to be made in the years
ahead will rely heavily on equipment manufacturers supplied with accurate feedback from tex-
tile engineers and chemists. Emphasis is placed on the need for providing feed-back from
common problems experienced in production to equipment manufacturers. Also, well-designed
projects should be conducted on the mill level and this information quickly channeled to the
equipment manufacturer. Participation by trade organization and involvement through con-
ferences is also important. Increased resourcefulness at the individual level and better commun-
ication with vendors will be indispensible to accomplishing more efficient production at less
cost and with less environmental impact in the near future.
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6.5.1 Existing Process Modifications
Several examples of how process modifications have accomplished water and chemical savings
are provided next.
Process modification for woven goods preparation in rope form is discussed in the first example
(9). The goods in this case could be whites or dyed, and are a polyester/cellulosic blend. Fabric
enters from the left at a rate of 225 yds/min. (88 Ibs/min.). Initially this range was arranged
and counterflowed as seen in Figure 6-31.
40 GPM
Fabric
225 yds/min
Washer 2 Washer 3 Satura-
Washer 4 Washer 5
Drain
30 GPM
FIGURE 6-31
BLEACHING PROCESS MODIFICATION
After process modification, the major changes were as follows. Washer 1 was eliminated. Flow
from Washers 5-3 drain was found to provide adequate washing by reducing from 30 to
20 GPM. Hot water from Washer 4-2 drain was reduced from 40 to 20 GPM. A chemical
control monitor was added to meter in constant concentrations of peroxide and silicate. Steam
was added to only the middle of three steam chests. Thought is also being given to reducing
temperatures from 180 to 170° F, or even to 160° F. There are unquestionably difficult
decisions to make when considering process changes in preparation. There may be no better
way than to make small incremental changes based on logical thought, then wait for repercus-
sions from dyeing and finishing. If trouble-free production occurs, then further incremental
changes, based on logical thought, may be indicated. Surely no one wishes to be responsible for
damaged goods, and this is primarily why the present examples are offered. Again, recall that no
sophisticated study has been performed in the past dictating the process criteria needed for
optimum trouble-free production. Therefore, the necessity created by the energy "crisis," and
environmental concerns, may be the motivation required to improve and optimize textile pro-
cessing as any technology is meant to be.
The second example deals with continuous open-width bleaching of woven polyester/cellulosic
goods (9). These goods are run from 55 to 75 yds/min. or 34 to 60 Ibs/min. At 1% bleach,
such goods can range from 1.3 to 2.2 gal/lb. wash water usage. After process modification,
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this range was successfully controlled by automatic monitoring of peroxide and silicate. It
should be mentioned here that for uniformity to be ensured, chemical should be applied
across the width of the saturator. Wash boxes were counterflowed, and temperatures did not
exceed 160° F. Consideration was given, after wash box liquor and fabric analysis of residual
chemicals, to eliminate possibly one or more wash boxes. The use of vacuum-slot extrac-
tion, with water returned to the washer, was found helpful before the dry cans. Staggered slot
(off-set) boxes were found preferable over conventional slot boxes, as they allowed the use of
greater pressures without pulling of fabric into the slots. This is especially true in cases of light-
weight goods running at slower speeds. Figure 6-32 shows a water-line diagram for a rope bleach
range.
In the third example, a study involving batch-piece dyeing preparation resulted in better quality
goods, more efficient production, and cost savings (48). Unheat-set polyester/ray on containing
4.75% PVA size was prepared continuously by saturation, steaming, high-energy wash, slack
loop boil-off, and rinse tank. This resulted in 0.63% residual size which decreased dyeing quality.
The initial arrangement used counterflow, but there were no squeeze rolls between stages caus-
ing carryover of water and chemicals. Changes included adding nips after the washer and the
boil-off, addition of another high-energy washer with nip after the boil-off, and reuse of PVA
recovered from the system. Savings totaled $677/day.
A fourth study involving polyester/cotton sateen containing 8.56% PVA starch size con-
sisted of heat setting, enzyme/detergent saturator, steamer, 2 high-energy washers, 2 conven- -
tional washers, peroxide saturator, batching dwell, 9 progressive jig boil-offs with rinsing,
mercerizing with recuperator, steam washers, conventional washers, and final drying before
batch-up (48). Size residual was 0.072%. Changes recommended were nips between high-energy
washers, replacement of progressive jigs by a steamer followed by washers with squeeze rolls,
the use of counterflow at all units, adjustment of flows in certain washers to concentrate wash
liquors, counterflow water in steam washers, and installation of heat reclamation units for the
entire range.
The fifth example concerning open-width preparation deals with mercerization (9). This range
is run at 80 to 125 yds/min. depending mainly on the finish to be applied. It was found that
cloth entering the recuperator contained approximately 4.5% alkalinity on the weight of the
fabric. After the recuperator, the concentration of alkalinity was reduced to approximately
0.25%. The value of the recuperator is obvious. Previously, this range contained six wash boxes
following the recuperator. After further consideration, other modest process modifications were
undertaken, such as elimination of the sixth wash box. Acid for neutralization was added to the
third wash box instead of to the fourth, as previously applied. Counterflow of water went from
washer 5 to 4 to 3 to 2 to drain. Previously, washer 5 was not included in the counterflow ar-
rangement, and fresh water went directly to the drain. Spray stations before the recuperator
were reduced from 7 to 4. Analysis of residual fabric alkalinity after the first washer indicated
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residual alkalinity was reduced to 0.05% (owf). Such findings strongly suggest reassessment of
the practice of acid neutralization and what might be excessive washing at too high tempera-
tures. Current practice indicates temperatures over 180° F (approaching 200° F) in three of the
remaining five wash boxes. Study has indicated temperatures closer to 160° F may be all that is
actually necessary under these production conditions. Water usage in this mercerizing range
generally averages about 1 gal/lb. In summary, possibilities for water reduction and heat savings
have been indicated in the mercerizing range by simple process modification.
The final example of good preparation practices shows specifically how a mercerizing range
might be piped for counterflow and reuse in Figure 6-33 (9).
6.5.2 Dyeing Process Modification
Preparation has been given exceptional attention in this discussion. This is because most plants
feel that good preparation may be more critical than what follows. However, there are those
who would advocate that thinking back from the finished product is the better approach. Be
that as it may, at this stage in the assessment of plant operations, the potential for process
modification appears great enough to allow both schools of thought to prevail profitably.
This example describes suggested procedures which could be profitably incorporated into dis-
perse dyeing on a thermosol range (9). Various styles should be grouped by weight. The lighter
weight goods would run at a faster speed through the equipment, requiring less energy (less
predrying), and may, or may not, profit from the use of vacuum slot extraction before final
drying cans. It has been discussed that off-set vacuum slots may best be applied to light weight
goods. Suction water should also be re-entered into the wash boxes for reuse. Total hot water
flow in a disperse dye system would be greater than most other dyeings, such as disperse/
reactives, disperse/sulfur, disperse/vat, reactives only, sulfur only, or vat only. Vats and disperse/
vats would probably require half the total hot wash water flow than disperse dyeing alone. It
seems doubtful that thermosol dye washing would require water higher than 170° F. Exceptions
might be side/center/side shading, poor appearance, and when a particularly good after wash is
required. A hand meter should set cloth final moisture after drying to process conditions to
prevent overdrying when possible. It can also be repeated that iodate, peroxide, or laking agent
oxidation may be used to replace dichromate.
Considerable attention has been given to continuous operation, and at this point comment is
made on beck dyeing. It has been suggested in earlier subsections that although long holds may
be necessary for heavy shades to exhaust, light shades will exhaust much more rapidly. Holds
possibly no longer than 20 minutes should be investigated (9). Temperatures should be consid-
ered carefully. Perhaps, temperatures of 250° F could be cut back to 240° F. Temperatures
running at 240° F may be cut back to 230° F.
It has also been suggested that running rinses may be profitably replaced by fill and drop wash-
ing. Russell (ICI) has suggested two fill and drops heated to 200° F will often accomplish as much
6-75
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as an hour of running wash at 160° F (13). The virtues of this suggestion should be considered
where appropriate. The reuse of cooling and steam condensate water has been discussed in
subsection 6.2.
For the optimal utilization of water and chemicals during processing of textured polyester
wovens, the following factors should be taken into consideration (49). If pre-heat setting can
be avoided, it is desirable since pre-heat setting can decrease dye yield, reduce stretch, and make
scouring more difficult. A key-step in producing optimal results with minimal water usage and
reworks may be warp and filling tensionless open-width boil-off. Equipment such as washers
from Brich Bros., Fleissner Suction, Jawetex rotating jet, Mezzera, and the Nizzen Sofcer are
proven toward this end. The latter machine utilizes a net conveyor to induce relaxation and
spray jets for scouring. Non-ionic detergents and mild alkali around 208° F might best be used.
Scouring and dyeing in one bath, although seemingly more economical in resources and total
cost, can lead to problems of nonuniform dyeings due to insufficiently clean fabric. Carriers
often preferred in dyeing are o-phenyl phenol or biphenyl for atmospheric dyeing, butyl ben-
zoate or modified aromatic solvent types in pressure becks, and special low-foaming carriers for
jet dyeing. At this time, it is still controversial whether pre-heat setting improves barre' or filling
bands. Optimal finishing steps to consider include moisture extraction to 25 to 30% moisture,
relaxed loop drying at 250 to 275° F to minimize puckering, and heat setting to maximize
overfeed on a pin tenter at 340 to 370° F for 20 to 30 seconds.
6.5.2.1 Resin Finishing
In resin finishing, Newport Finishing Corp., Fall River, Mass., reported very favorable experience
with hot catalyst mixtures using glyoxal resins, i.e., magnesium chlorine/aluminum salts or
metal salts/ip-hydroxycarboxylic acid (39). These systems were said to cure at lower tempera-
tures and save energy. It is essential to precheck additive compatibility with the hot catalyst,
particularly softeners, brighteners, and hand builders.
Clean-up wastage was improved in a resin usage scheme reported by Towne (Fiber Ind.) (37).
Clean-up went to the drain after each use of the make-up tank, the supply tank, and the use
tank. Pumping, piping, and automatic closing valves were installed providing return lines from
the use tank to the supply tank, and from the supply tank to the make-up tank. This procedure
reduced wastage during clean-up and prevented wastage during shut-down periods.
6.5.2.2 Compatible Process Sequencing
Mill experiences indicate that considerable potential often is seen to exist for better flow of pro-
cessing (9). For example, in wool processing, sequence of acid fulling-alkaline bleach-acid dye-
ing was observed to be poor from a water-use standpoint because lengthy rinses were required
between processes. This is because residual acidity from fulling would tend to neutralize (waste)
the alkaline bleach if not rinsed adequately. Furthermore, alkaline fabric after bleaching could
interfere with acid dyeing if not properly rinsed. Thought should be given to the possibility of
6-77
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slightly acid bleaching which can provide perfectly adequate bleaching and considerably less
water and perhaps less chemical usage.
6.5.2.3 Improved Sizing, Slashing and Weaving
Various aspects of sizing have been considered in other subsections. This includes size reclama-
tion; use of prehydrolyzed sizes which provide better penetration, better film forming proper-
ties, and better biodegradability; and solvent size application and recovery. This discussion now
considers the topic in somewhat wider perspective, i.e., size formulation, slashing, weaving, de-
sizing, and finishing plant performance.
In opening, comment should first be made about claims of new, improved warp sizes which
occur so frequently and without sufficient evidence, that most mills are loath to consider
change. Olson (National Starch) has given a concise state-of-the-art summary at this point (50).
Trends indicate that PVA will be increasingly used in the future, cost being a major deterent in
its more wide-spread use currently.
Some theoretical discussion of the ideal is warranted here. If a yarn requires 7% PVA sizing,
Olson suggests 4% provides the weight and bulk needed to absorb the strains and blows of
the loom. This he calls the threshold size percentage. The other 3% provides the required
adhesion and abrasion resistance. Starch, which has functionality of its own, could provide the
4% "filler," and lower costs, while PVA provides the film-strength it is best suited for. Unfor-
tunately, compatibility has not yet been accomplished, although substantial progress towards
this goal has been indicated. From cost/performance and pollution standpoints, it must be said
that this route could appear most beneficial for some in the future. The reasoning behind this
suggested approach begins with formulation benefits. A proper mixture of compatible modified
starch/PVA should possess the proper viscosity for minimum application and penetration. The
film forming properties should then be adequate for good weaving performance. Then relatively
easy removability (minimal desizing requirements) should also be accomplished. Obviously,
with this accomplished, the PVA/starch desize could optimize the task of degradability by con-
ventional biological treatment. There is neither too great a BOD5 load as with starch alone, nor
too great a COD problem as with PVA alone.
The potential benefits of such an approach include:
* Use of less size
• Satisfactory weaving
• Less chemical, heat, and water used
• Better treatability
• Less overall cost
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6.5.2.4 Solvent Processing
After approximately 15 years of serious study involving solvent processing, the AATCC gathered
a symposium in Atlanta during January 1973 to discuss the state of the art. This landmark meet-
ing focused attention on the capabilities and problems of solvent processing. It was an invigor-
ating forum where mill men spoke freely of their likes and dislikes, and chemical and equipment
manufacturers went back to the drawing boards for more work. After the meeting was com-
pleted, it became clear that the idea of solvent processing gaining acceptance merely to provide
relief from environmental problems was untenable. Solvent processing will be introduced and
accepted in general only when superior results in processing and product are demonstrated at
economical costs.
Some of the major lessons learned as a result of the Atlanta symposium were:
• Suitable machines can be manufactured and operated so as to control air pollution in the
work space.
• Solvent loss can be expected to be an economic problem, and tight control is needed to
keep solvent loss per operation below 5% of fabric weight.
• There is no immediate widespread commercial use of solvent finishing expected for woven
goods.
• A firm position has been established for solvent scouring and finishing of synthetic knit
fabrics. The primary reasons are that it is beneficial to fabric quality to avoid wetting with
water and some finishes (silicones) can only be used in solvents.
Solvent scouring of woven fabrics has not indicated that the properties of solvent scoured
fabrics are generally superior to aqueous methods. This is despite intense efforts towards this
goal. Many functional finishes have been demonstrated to be applied from solvents. It has been
suggested that the advantages of the properties shown so far have been insufficient to justify a
change-over from the more familiar aqueous systems. In speciality cases, the applications of stain
and soil resistant finishes to upholstery fabrics and drapery materials have become fairly stand-
ard procedures.
Synthetics' Finishing (Hickory, N.C.) pioneered the application of stain repellents via solvents
in 1960 (51). After engineering modifications, the system was capable of reclaiming 95% of
the solvent for reuse in 1969. Approximately 3000 Ibs. of activated carbon adsorbed 400-500
Ibs. of trichloroethylene in this plant. Two adsorption columns were used, one adsorbing vapor
while the other discharged. Control was automatic. Steam was used to discharge the adsorbed
solvent. After saturation and a build-up of 3 psi, the stearn picked up the solvent as a vapor.
The steam-solvent mixture proceeded to a condenser that cooled the mix, which then dropped
into a decanter. Separation was quick, and the bottom solvent layer was drawn off for reuse.
Water was discharged to the drain.
6-79
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Synthetics' Finishing also applied Scotchgard or Zepel stain repellents and a stabilizer to high-
grade woolen apparel fabric. Both chemicals were sprayed in one bath by staggered spray
nozzles. The spray cabinet was also saturated with solvent-chemical vapor. Runoff was collected
and recirculated. From the spray cabinet, goods moved into the steam-heated drying chamber
where the plant circulated about 3,500 CFM of air at 200° F. It then was led to the solvent
recovery system.
Synthetics also applied latex backing to automobile and furniture upholstery. Knitted and
woven fabrics were treated on a plant-designed range which could back fabrics by spray, roller
coating, knife coating, or transfer-kiss methods. In addition to the various methods of applying
latex backings, electric heating units (Calrod) were used in the drying section. Drying essentially
only removed moisture from the coating applied. The heated air was applied from top, bottom
and halfway from each end. Four sections with damper control of each section added to the
equipment flexibility. A moisture indicator was used to adjust speed by varying motor speed.
Certainly, this example indicates that on technical grounds solvent processing can offer an at-
tractive solution to some problems. However, it should be pointed out that new problems associ-
ated with air pollution may arise in the future. It has been mentioned that tight control over
solvent systems is required to keep solvent losses below 5% of the fabric weight. Porter reported
in 1972 that nearly one ton of solvent per day per range might reach the atmosphere (52).
Raymond Allen reported that processing of fancy or yarn-dyed goods was attractive for solvent
processing and recovery (4). This is because aqueous methods generally appear better suited
for oil-based lubricant removal before dyeing. The use of solvent versus aqueous methods has
demonstrated a total plant water requirement reduction from 20 to 5 gallons per pound. It
was pointed out that such comparisons were made between different plants rather than actual
reductions in one plant.
Allen suggests that the most reasonable approach for a plant deciding to employ solvent process-
ing is to buy both solvent processing and solvent recovery systems from one supplier. Such an
approach is usually most economical from a capital cost and installation standpoint, and it also
would tend to help ensure successful operation while providing easier maintenance and repair.
Also, consideration should be given to fixed detection units located at the entry and exit ends
of the production equipment and near the recovery unit. A portable unit should be on hand and
any area indicated to be susceptible to leaks should also be considered for a fixed detector.
OSHA regulations provide for concentration limits of solvent in the operating area, and equip-
ment should be thoroughly examined before purchase.
There have been examples of problems strongly felt associated with solvent vapors in the plant.
Drawing of solvent-laden air to dryers or tenter frames may result in the conversion to
hydrochloric acid gas (9). Fabric weakening, browning of cellulose, or dye degradation are
6-80
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some of the possible difficulties which should be anticipated. Allen estimates the critical concen-
tration of perchloroethylene to cause such problems to be in the range of 200 to 500 ppm (4).
Actual problems experienced by a plant reported by Allen in the installation, startup and opera-
tion of a solvent dry-cleaning process with solvent recovery are summarized as follows:
• Solvent consumption during start-up ranged from 20 to 30%. After fine-tuning consump-
tion decreased to 5 to 8%. It was felt that manufacturer's claims of 3% solvent consump-
tion would be extremely difficult to attain.
• Factors contributing to solvent consumption were mainly machinery vibration causing leak-
age, poor fitting couplings and hose problems, poor door seals, recovery unit malfunctions,
and squeeze-roll deterioration. Tweksbury suggested that if the 950 million pounds of knit
polyester and nylon finished in 1972 were solvent scoured, with a recovery rate of 99%,
nearly 10 million pounds of solvent could be released to atmosphere (4).
On the other hand, John Steward (Northern Textile Assoc.), acting as mill liaison, reported that
a solvent system used on wool-nylon-cotton fabrics cut water consumption in a mill from 150,000
to 10,000 GPD (53). It was added that reductions in chemical consumption, labor costs and
time spent were also achieved. A 92% BOD5 reduction was reported in terms of Ibs./l ,000
Ibs. goods. But in concentration units (mg/1), higher values were said to occur. In this completely
sealed system, solvent was said not to be lost to the atmosphere. However, 10 gallons per day of
1,1, 1-trichloroethane solvent were lost from the 1,200 gallon capacity unit.
Solvent preparation has been vigorously investigated by the Shirley Institute and ICI Scientists
since the late 1950's. The basic steps in the process development by ICI proceeded essentially
as follows. Hydrocarbon solvents were found to wet out fabric rapidly. A fabric's oils, fats and
waxes were dissolved in a very short time. Solvent soluble surfactants were found to simplify
removal of the oils, fats and waxes. Enzymes were found that were suitable for suspension in
solvent. Adequate desizing was demonstrated. Partial bleaching was demonstrated in the Markal
III process. It should be stated that in at least one U.S. plant, the early generation ICI desize
equipment was shown to be inefficient and was not used in production (9).
The newest Markal "B" pilot process (scour/desize/bleach) eliminates the wash-off between steam-
ing and bleach pad. Furthermore, the water seal after steaming is modified to serve as seal and
pad applicator also. Eliminating the separate pad application and wash-off saves floor space and
capital expenditure. Figure 6-34 shows an example of an envisaged Markal B minute range (34).
A pressure bleach can replace the "steam" unit if desired.
As it stands now the Markal ranges have no significant economic advantage over conventional
aqueous methods in range cost, total processing costs per pound, labor, steam, water or elec-
tricity. The Markal B range may cut costs in range costs, total processing, steam, water and elec-
tricity.
6-81
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Markal
application
Steam Pad
bleach
Steam
Wash off
Dry
FIGURE 6-34
MARKAL B ('Minute Bleach') RANGE
Confirmation must await the installation and operation of a successful commercial Markal
machine. Dow has reported development work on a process to recover and recycle size mate-
rial in a solvent system (34). Increased equipment costs associated with size recovery can be
off-set by reuse of the size chemical, it is said. The primary problem appears to be development
of a new size which can be recovered and reused. Another problem would be the logistics of
such an operation. Conventionally, desizing is performed at the finishing plant, and greige mills
would face, in general, a radical departure from traditional procedures of processing. Another
problem is related to the rapid wetting out of fabric by solvents. This has tended to allow too
much penetration of size into the yarn bundle and too little peripheral coating. Higher viscosity
sizes would produce problems later in solvent and size recovery. However, the potential advan-
tages of solvent sizing and desizing are also impressive. These include: better weaving perform-
ance, size recycle, possible improved dyeability, decreased floor space, decreased utility and
manpower requirements, and humidity insensitivity. This has not mentioned that less water
usage would also occur, and no size would need treating. Certainly, the promise of solvent
sizing and desizing is great. However, since the 1973 Atlanta Solvent Symposium, no successful
commercial application has been reported. Reluctance on the part of textile management to
encourage or accept the innovation has been mentioned as a deterrent to vigorous developmen-
tal efforts. It can be said that the technical difficulties with this concept have off-set strong
motivational textile interests at this time. Figures 6-35 and 6-36 indicate the Dow Solvent
slasher and desize concepts.
Section
beam
creel
Dryer-solvent
recovery
FIGURE 6-35
DOW PILOT SOLVENT SLASHER
6-82
D
Head
end
-------
Recovered
solvent
Woven fabric
with size
Wash and
scour
chamber
Dirty
solvent
Drying and
solvent
recovery
chamber
Desized and
scoured fabric
To normal
finishing
steps
Solvent
recov.
still
Recovered
solvent
Size
clean-up
Recovered
size to
slasher
Size residue
to solid waste
disposal
FIGURE 6-36
DOW SOLVENT DESIZE PROCESS
Commerical solvent scouring equipment vendors today claim that 10 to 12 oz. polyester can be
scoured from 4 to 6% oil to around 0.2 to 0.4% residual at speeds between 25 to 35 yds/min.
Perchloroethylene losses are said to be around 2.5 Ibs. per 100 Ibs. of goods. Furthermore,
vendors are continually modifying current equipment. For example, one vendor has replaced
nips with suction slots to eliminate roll break down problems. It is also emphasized that to
maintain high efficiency, maintenance and seal replacement need to be carried out on a regu-
lar basis (whether or not the seal has failed). An equipment schematic by Bruckner is shown
in Figure 6-37.
Oil residues resulting from the cleaning operation may be preferably burned. Some companies
specialize in this field and collect the residues.
FIGURE 6-37
BRUCKNER CONTINUOUS SOLVENT SCOURING MACHINE
FOR KNIT GOODS - TYPE: SOLVENT
6-83
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6.5.2.5 Solvent Dyeing
Solvent dyeing has received most of its criticism regarding the lack of adequate dyestuff (54).
However, in proper order, the solvent should first be commented on. Briefly, a solvent to be
suitable for dyeing must be a solvent for the dye, must be a swelling agent for the fiber, must be
safely containable at dyeing conditions, and it must be easily recoverable. In fact, there is not
such material available. Therefore, compromise has been necessary. The most significant suc-
cesses in the development of solvent dyeing systems have been in the conversion of existing
dyes into forms compatible with selected solvents. Ciba-Geigy and Allied Chemical in conjunc-
tion with Dow Chemical have been the most vigorous advocates of solvent dyeing systems.
Allied reports formulations and procedures for use in the Burlington Engineering laboratory
beam dyeing unit (55) (56). In the same reference, and in the Atlanta Symposium, a continuous
procedure using superheated vapor fixation was described (54). It can be said that limited
solvent dyeing systems have been shown to be technically feasible on a pilot scale basis. How-
ever, of the hundreds of European and American patents issued, most have been assigned to
dye manufacturers. Since the features of most patents will be practiced by the dyer, rather
than the dye manufacturer, most probably the successful commercial venture, should it appear,
will be a combination of several contributors (57). Judging from the lack of enthusiam on in-
dustry's part, this innovation is difficult to envision soon. At this point it appears that someone
will have to demonstrate clearly the economic advantage of solvent dyeing over existing pro-
cedures, before commercial acceptability on any size scale becomes a general reality. Once the
economic feasibility is established, then perhaps some of the promises of solvent dyeing may be
realized. These advantages may include:
• ,Elimination of a pre-scour
• Smaller, less costly equipment
• Flexibility of making short, continuous runs
• Low utility requirements
• Considerable water usage reductions
• Better-leveling and uniformity
• Better reproducibility between runs
• Possibility of integrated dyeing and finishing
The schematic in Figure 6-38 shows the dye padder and superheated perchloroethylene fixa-
tion unit for continuous processing as used by Ciba-Geigy and Allied Chemical (54).
6-84
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Condenser
coils
Boiling sump
FIGURE 6-38
SCHEMATIC DIAGRAM
SUPERHEATED PERCHLOROETHYLENE FIXATION UNIT
During the 1973 AATCC Solvent Symposium in Atlanta, Gaston County defined its responsi-
bility as equipment manufacturers to industry. "Most textile mills expect practical assessments
of processes from their suppliers. We, as equipment suppliers, cannot take the responsibility of
solving the water and air pollution problems of the mills, but we have a duty to help them in the
attainment of set standards such that, overall, reasonable profits can still be assured."
Gaston County contended also that economy is the only criterion of importance if the quality
of processing is not affected. Assuming that the quality of goods is the same when solvent pro-
cedures are compared to conventional procedures, the following list gives some key factors
which should be considered in an economic evaluation:
• Look at your total operation from receiving to shipping, including costs to assure
compliance with air and water pollution standards.
• The type of people in your plant.
• Do you need new equipment or can the existing equipment be converted?
• Can you afford to have adequate waste treatment facilities and still have solvent
6-85
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reclamation systems or would the installation of solvent equipment lighten the load
on your wastewater treatment plant significantly?
* Your water and utility costs.
* Your location.
• Solvent costs and availability.
• Dyestuffs and chemical costs.
• Can you maintain the necessary flexibility?
• In what time frame do you have to work? You may not have a choice, except to
update your water treatment plant.
• Examine your present operation carefully. It is quite possible that you do not
utilize your water and utilities in the most efficient manner.
• Labor market, automation, material handling, etc., are still often points of con-
sideration.
6.5.2.6 Remaflam Machine — Artos
In the 1973 Atlanta Solvent Technology Up-Date, Farbwerke Hoechst AG described a venture
with Artos for a rather spectacular piece of equipment. In this process, polyester dyestuffs are
dissolved in methyl alcohol and the fabric is padded in the solution. The fabric is then ignited
and the methyl alcohol burns off as the fabric passes along at 130 to 140 ft/min. Dyeing takes
place at this point and the equipment is intended to replace the Thermosol process. Balmforth
reported 10 months later (ATME-1-1973, Greenville) that the Artos machine (Remaflam) was
not on display but is apparently soon to be available for dyeing polyester (9). This process is
cited as middle of the road between aqueous and solvent dyeing.
6.5.2.7 SIX Solvent Dyeing
STX (Paris, France) offers a solvent dyeing process which uses methanol and perchloroethylene
(1:10 ratio). During dyeing, the methanol is slowly distilled off (and recovered) causing the dis-
solved dye to become less soluble. This state causes the dye to exhaust into beamed fabric.
STX says polyester, silk, wool and nylon have been dyed by this process with 100% dye exhaus-
tion. This is said to eliminate pollution from dyebath's dumps. STX claims dyeing is faster and
at lower cost because nearly pure methanol and perchloroethylene can be recycled as is. Very
little information is available on commercial application of this equipment. Contrary to STX
claims, it is reasonable to assume that fiber extractables and conventional dyestuff ingredients
(salts, oils, diluents, dispersants, etc.) will eventually build up.
Operational sequences are shown in Figure 6-39.
6-86
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Dyeing autoclave iv'S
41-
£
to
CL
Pump Reheater
FIGURE 6-39
STX SOLVENT DYEING PROCESS
(Dyeing until total exhaustion by progressive separation of the dye solubilizer.)
beginning of the separation
ot the dye solubilizer
end of the separation
of the dye solubilizer
100%
75% - -
Exhaustion graph
with the STX process
50% - -
25%
0 15' 30' 45'
FIGURE 6-40
STX EXHAUSTION GRAPH
6-87
Temperature
of the dye-bath
Exhaustion graph
without separation
of the dye solubilizer
-------
The dye-bath exhaustion graph shown in Figure 6-40 provides an illustration of the STX pro-
cess. Exhaustion without separation of the dye solubilizer (methanol) may reach 20 to 70%.
This would depend on the dyes and operational conditions. Progressive separation of the dye
solubilizer makes a controlled and complete exhaustion of the bath possible at the end of the
operation with dyes insoluble in the diluant (perchlorethylene).
6.5.2.8 Duobond Corporation
An August 1974 report told of an invested $200,000 for a continuous solvent scour range
manufactured by Rimar (Italy) and sold in the U.S. by ITM Ltd. (58). The range replaces three
batch machines and the company expects pay back within two years. Called the Vibro scour, it
operates at 25 yds/min. (manufacturer claims 35 yds/min.). Polyester doubleknit and polyester/
acrylic blends are processed in weight from 5 to 16 oz/yd. Oil content reaches 7% in, and
residuals range from 0.2 to 0.5% out. The distillation unit recovers solvent around 600 GPH.
A schematic and technical data follows in Figure 6-41.
TECHNICAL DATA
Skeleton drum width
Width of material, up to
Speed of work
Absorbed power
Voltage
Frequency
Saturated vapor
Consumption of vapor
Water not more than 20° C
Water consumption not polluted and
totally recoverable at a temperature of
40-45° C.
Compressed air
Consumption of air
Consumption of solvent (on weight of
material)
Residual grease (within 5%)
Output (average per hour)
23m
22m
5-25 m /mm
20 KW
to be stated
50 Hz
4-6 Atm
300-600 kg
1 5-6 Atm
5-10 Cu m
5-6 Atm
700 l/hr
5%
05%
LEGEND
A = Scourer
B = Dryer
1 = Inlet of deodorizer
2 = Pre-scour spray tube
3 = Vibro Scour patented scouring device
4 = First aspiration tube
5 = Spray head for rinse
6 = Second aspiration tube
7 = Drying drum
8 = Outlet, deodorizing cylinder and material
500 kg
FIGURE 6-41
DUOBOND CONTINUOUS SOLVENT SCOUR RANGE
6-88
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6.5.2.9 Aqueous Scouring of Knits
Early in 1970, Jeffries Southern Processors, Albemarle, N.C., used conventional open-width
washers to scour circular doubleknits and tricots (59). Oil contents from 6% were reduced to
residuals of around lVz%. In addition to the poor scouring performance, the open-width
washers stretched the fabric about 3%. With modifications to a conventional aqueous washer,
Jeffries reduced residual oil down to 0.01% with a 10% bulking efficiency while operating at
22 to 35 yds/min. The bulked fabric capability, it is said, is nearly able to eliminate redyes, saving
water consumption, chemicals and overall cost. The first stage of the system is a dwell in a J-scray,
fed with 140° F scouring liquor. Fabric leaving the J-scray goes over scroll rolls directly onto a
tensionless stainless steel conveyor screen. At this point, jet scouring sprays spray water circu-
lated at a rate of 500 GPM at about 40 psi. The fabric then enters the bulking tank where it
receives mechanical agitation between 160 to 200° F, depending on the fabric type and the bulk
required. Tighter constructions usually require higher temperatures. After bulking, a series of
spray pipes alternates with air knives to rinse the fabric, and a vacuum extractor at the exit end
helps to recirculate and counterflow water (Figure 6-42).
FIGURE 6-42
JEFFRIES AQUEOUS SCOURING OF KNITS
6.5.2.10 Aqueous Knit Washer — Birch
Balmforth (I.T.T.) reported in 1973 on a Birch Bro. aqueous knit washer exhibited in Green-
ville (ATME-1-73). This equipment consisted of three box washers through which the goods are
conveyed on a mesh screen at around 30 yds/min. Vacuum extraction was used after the last
two boxes. Other manufacturers were seen exhibiting very similar equipment. Birch feels
aqueous scouring is cheaper than solvent processing, gives better bulking and better hand to the
fabric. Running costs were said to be approximately half that of a continuous solvent range.
Capital cost of this range was quoted at $75,000.
6-89
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6.5.2.11 Liquid Ammonia Technology
In 1973 liquid ammonia processing was hailed as the biggest scoop of recent years (60). How-
ever, due to the scarcities in natural gas feedstock, used in liquid ammonia production, costs
have more than tripled.
Before costs skyrocketed, liquid ammonia had potential reuse, or could be removed by a roof
burner breaking the ammonia down to nitrogen and hydrogen, it held the edge on solvent dye-
ing (because it could handle water soluble dyes), and appeared utilizable in conventional equip-
ment. Economic and pollution advantages were obvious. Liquid ammonia dyeing was loosely
said to fall into the category of dry dyeing.
Briefly, on cellulose, liquid ammonia rapidly penetrates native cellulose forming a complex and
resulting in the cleavage of hydrogen bonds (61). This is accomplished by swelling and plasticizing
effects. If the ammonia is removed by evaporation, cellulose III is found to predominate. If the
ammonia is displaced by water or alcohol, cellulose I predominates.
6.5.2.12 Mercerization
See subsection 6-4 for discussion.
6.5.2.13 Dyeing
Exceptionally rapid dyeing has been claimed using direct, disperse, reactive, naphthol and sulfur
dyes from liquid ammonia dye baths. Arthur D. Little patented the idea of continuous dyeing
with liquid ammonia. Seth Kane (Kane Inds., Gastonia, N.C.) produced commerical equipment
reported in 1973 called the Rapid Anhydrous Method (RAM) shown in Figure 6-43 (62).
Exhaust
Pad
Steamer
FIGURE 6-43
Wash
Wash
FLOW DIAGRAM OF THE RAM DYEING SYSTEM SHOWING
THE EQUIPMENT NEEDED
6-90
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In this system all fibers but acetate and wool are said to work. About 95% of available dyestuffs
are said to be compatible. Speeds up to 120 yds/min. have been obtained because ammonia
"wet-out" is nearly instantaneous. Speed was limited by steaming times of 3 to 30 seconds de-
pending on fiber and construction. Here the fabric is padded with dye dissolved in anhydrous
ammonia at—40° F. Steam then flashes off ammonia and sets the color. An afterwash rinses off
excess dyestuff. Exhausted ammonia is usually scrubbed with acid and sent to the atmosphere.
Advantages include less water used and less chemicals (no carriers, surfactants, penetrants, salt
or sequestrants).
6.5.2.14 DP Finishing
J. P. Stevens' investigators indicated that liquid ammonia pretreatment and the removal of
ammonia by air drying prior to the application of resin from aqueous solution or emulsion re-
sulted in permanent press cotton with improved over-all performance, especially when the cur-
ing consists of short steaming and subsequent dry heating (see subsection 6.4 for discussion) (41).
6.5.2.15 Flame Retardant Finishing
The use of anhydrous ammonia after applying flame retardant to cotton with the THPOH/NH3
procedure has been reported mainly by the British, SRRL and Hooker Chemical Corporation.
Both liquid and gaseous ammonia have been used in such procedures, J.P. Stevens reported in
1974 that where aftertreating has little effect on the physical properties of fabric, pretreatment
followed by exchange of ammonia with water improved fabric performance (41). Specifically,
the workers reported that when treatment before the FR finish is applied, it modifies the
cellulose so that no significant fabric stiffening occurs. Flame resistance is still adequate. The
effectiveness of PE/cotton blends was less pronounced.
It is difficult at this point to envision exactly what processes will be created around liquid
ammonia. Indications are that new fabric properties are created which will take time to explore
and evaluate. If new feedstocks are found and/or costs again become economical, it is reason-
able to assume the same interests as shown in 1973 may be rekindled.
At this time the Sanforized Co. has acquired the original Norwegian patent and with Burlington's
Erwin Mills has a full-scale operation (46). Termed the Sanfor-Set process by the Sanforized Co.,
liquid ammonia will treat jean materials, such as denim, and follow it by compressive shrinkage
to yield a wrinkle-free soft fabric. The process is said to be continuous, non-polluting and af-
fords a 90 to 95% recovery of the ammonia. Briefly the process, as shown in Figure 6-44 con-
sists of pre-drying to remove moisture, followed by entry into a sealed chamber which is kept
at a negative pressure to prevent ammonia fumes from escaping. The fabric then passes through
a bath of liquid ammonia (bp-28° F). After squeezing, it is given sufficient reaction time before
passing over two Palmer blanketed drying cylinders where the fabric width is controlled to the
desired dimension. At this time the ammonia is driven off and collected in a recovery unit.
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Fabric
NH3gasout
air.
NH3 Liquid
storage
^N. Waste air
)NH3 liquid
Recovery
unit
FIGURE 6-44
FABRIC FLOW IN THE DURALIZED PROCESS, SHOWING THE
MAIN COMPONENTS OF THE LIQUID AMMONIA RECOVERY SYSTEM
About 5% still remains attached to the fabric and is removed next by light steaming. This am-
monia-laden steam is collected and sold as ammonium hydroxide for fertilizer manufacture.
This commerical application is the major process use of liquid ammonia today. It is indicated
that liquid ammonia may also be marketed as a replacement for caustic mercerization. Al-
though luster is said not to be as great as by caustic mercerization, the shrinkage stability, crease
recovery, and smooth drying may be better (46). Dyeing applications appear to have cooled
considerably as this point. No commercial dyeing equipment has yet been demonstrated.
6.5.2.16 Vacuum Impregnation
It was reported in 1971 by ICI investigators that when fabrics, particularly heavy weight goods,
are exposed to high vacuum and then immersed in liquor, they become completely saturated
with the liquor (63). Under normal pad procedures, short dwell time often makes it diffi-
cult to impregnate heavy weight fabrics. Trapped air in the goods is said primarily responsible
in preventing quick and complete fabric wet out. Therefore, the efficiency of liquor flow can
be reduced along with chemical penetration and levelness. Vacuum impregnation overcomes
these problems.
A commerical application of a vacuum impregnation unit used in dyeing corduroy fabrics was
reported in 1972 (64). Fabric in the system comes into contact with a perforated stainless steel
cylinder from which a vacuum pump draws air. The fabric hugs the surface of this cylinder
closely via an endless rubber belt which acts as a seal for the applied vacuum. The perforated
6-92
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LIQUOR CIRCUIT FOR
VACUUM IMPREGNATION
MACHINE
(for liquors which are
suitable for re-circulation)
1 Cloth passing through
machine.
2. Rubber belt
3. Cylindrical screen.
4. Vacuum box-
impregnation unit.
5. High vacuum pump
6. High vacuum receiver.
7. Pumping traps.
8 Liquor box-impregnation
unit.
9. Liquor level trough —same
level as (8)
Liquor supply from mixing
tanks.
Suction box-liquor extrac-
tion unit
Suction receiver
Suction pump
Drip trough
Wash water.
Squeezer
FIGURE 6-45
SCHEMATIC OF FARMER NORTON VACUUM IMPREGNATOR
cylinder acts as a combination vacuum-liquor tube, and the fabric and dye liquor come into
contact prior to the fabrics return to normal pressure. Operating speed is up to 100 yds/min. A
schematic of the equipment valued at approximately $20,000 is shown in Figure 6-45.
Vats, sulfur and reactive dyestuffs were successfully used in this process. The economy and
advantage of this system is felt to be in that much of the goods preparation can be bypassed.
Furthermore, reworks may be minimized.
The process may also be applicable to durable-press resins, i.e., goods not getting uniform pen-
etration of the resins due to rapid production speeds and short baths. The problem is that resins
buildup on the fabric surface and crosslinking occurs at the fiber surface. This can lead to low
DP performance and low abrasion resistance. This equipment was reported in 1973 as having
considerable potential in supplementing conventional operation (65). Balance must be struck in
considering the migration effects caused by drying also.
The promise, although not yet demonstrated full-scale, is that polyester doubleknits, textured
polyester, acrylic-based fabrics, and fiberglass fabrics have been satisfactorily vacuum impreg-
nated in production dyeing trials. Furthermore, unsecured knits containing knitting lubricants
have also been evenly dyed with pilot-scale equipment. Bleaching was also said to give the same
degree of whiteness, more uniformly with less chemical used, and in less time than by conven-
tional means. The environmental advantages strongly indicated are that reduced production
sequences (less water) may occur, and if less chemical is used more efficiently, then less dis-
charge of chemical will occur. General application does not appear indicated, but specific
situations may warrant consideration.
6-93
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6.5.3 Preparation — Developments
Kiers for the scouring of cotton are tending to disappear because of their incompatibility with
some of the more modern concepts of finishing. Furthermore, kier-boiling operations are more
prone to suffer from human frailty and to produce more undesirable problems than semi-continu-
ous and continuous bleaching ranges. The use of open-width scouring and bleaching is tending to
increase for processing medium-to-heavy weight fabrics at the expense of rope processing for
two reasons. One reason is that creasing tends to be eliminated, which can show up in later
processes. The other reason is that less weft distortion occurs.
It has been said a number of years ago that cloth continuously prepared in the open-width
while under light warp tension is considered by many dyers and finishers to be the prime condi-
tion to obtain highest quality dyeing and finishing (66). Scouring and bleaching under pressure
offered early promise for operating under these conditions. By 1968 at least six manufacturers
offered pressure equipment (67). The major problem in each case was the pressure-retaining
seals. In 1966, Riegel reported success with pressure scouring of 8'/2 oz. of cotton goods (68).
Riegel reported caustic scouring in the open-width in one minute at 27 psig (about 2 atm.,
270° F). Problems encountered at that time included misalignment causing wrinkling and turned
selvages, a slow heating up and cooling down time (5 hrs) when seams break, lint buildup be-
hind entry seal rolls, frequent replacement of seals, and rapid wearing out of the saturator rolls.
Major advantages were said to be less chemicals used, rapid treatment and correction of errors
before too much fabric was improperly treated.
Since 1966 Riegel's pressure scour has fallen into disuse, just as did certain other one-stage
scouring and bleaching processes. Neither produced the desired results for wide-spread com-
mercial application.
By 1975 the concept of pressure scouring and bleaching experienced a revival in the U.S. (69).
Improvement in seals and separation into two-stage operation were seen to be the major modifi-
cations (70). In 1973 two-stage pressure scour and bleach were to be employed to handle
125,000 yds/day with substantial reduction in costs of chemicals, water, steam and labor (70).
A possible sequence for single-stage scouring is shown in Figure 6-46.
Another manufacturer offers a variation (Kleinwefers 100+ unit) of the concept of pressure
scouring. In this equipment, cloth is horizontally led upwards in a saturated steam environment
of 230° F. Meanwhile, liquor proceeds downward. Heated liquor is pressed by deflection rolls
through the fabric and then is channelled to a collection vat and led on to the following cloth
width below. It is said the best working pressure appears to be 7 psig (232° F), with caustic at
5%. No U.S. reports are available at this time discussing use of this equipment.
6-94
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Caustic Peroxide Solution
FIGURE 6-46
SINGLE STAGE SCOURING SYSTEM
Vaporloc Reaction Unit
6.5.3.1 Mercerizing — Development
The 100-plus-system discussed previously is also said to offer several advantages in comparison
with conventional washing machines after mercerization. The washing effect of three 100-plus
units is said comparable to that of six conventional machines. The main advantage of the equip-
ment is said to be that the total volume of water may be fed into the mercerizing compartment
without loss. Although no machines are known to be operating in the U.S. at this writing, sev-
eral are operating in Europe (71). The fact that the system is said to offer no environmental
pollution by waste caustic, reduced water and steam consumption, and reduced space require-
ments makes it worthy of investigation. The system is shown in Figure 6-47 as it follows a
chainless mercerizer.
Before leaving the area of mercerization, it was reported in 1973 that a mill mercerizing cordu-
roy modified conventional processing by steam spraying the bottom of the goods on the tenter
frame (69). This reduced acid requirements in later stages. Furthermore, three "S-laced" wash-
ers, operating at 208° F, neutralized fabric without acetic acid. This procedure saved the firm
more than $400/day in chemical costs alone.
It is also suggested that the more reproducible mercerizing liquor is kept, the better and more
uniform results will be. Research suggests that optimum mercerizing effects (swelling) are ob-
tained with a liquor of 52.2° Tw (72). This is achieved quickest in production around 63° F.
Some say it is essential to keep the temperature constant, and cooling units are available which
pump Freon through the system. Control thermostats can keep temperatures between 50 and
68° F. The wetting agent is also important and cotton should be wet out in 3 to 5 sec. The fiber
needs to be penetrated to the core before the peripheral zone is fully-swelled. Wetting agent con-
centration and wetting time, in certain instances, can alter the color of the cotton. Chemically
6-95
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FIGURE 6-47
CHAINLESS MERCERIZER AND THE 100-PLUS-SYSTEM.
BETTER ECONOMY OF PRODUCTION BY SIGNIFICANTLY REDUCED
WATER AND STEAM CONSUMPTION.
speaking, mercerization will be uniform when caustic and wetting agent concentrations are con-
stant and liquor temperature is kept constant. This research indicates the potential for the
greatest economy in chemical and water usage.
On the other hand, advocates of hot mercerizing say rapid penetration to the fiber core pro-
duces a more easily stretched fiber-fabric, with better subsequent chemical processing, and
better finished fabric properties (73). These results are said to be accomplished at lower cost,
energy, water, and chemicals than b) conventional mercerization.
6.5.3.2 Knit Dyeing
The availability of even proven new technology does not necessarily mean universal acceptance
will occur. This is also true in cases where the technology may have minimal water and energy
requirements. Knit dyeing is such an unsettled area currently, and a short overview may provide
insight and perspective to some of the forces opposing acceptance of new technology and
processes.
6-96
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In the recent past, paddle, skein, and package dyeing of knitting yarns predominated. The intro-
duction of fabric dyeing was accompanied by the use of atmospheric becks. Relatively large vol-
umes of water are used in these processes which also often result in high strength wastes. Diffi-
culties in dyeing newer textured polyester doubleknits next promoted an increase in the use of
pressure becks. Since increased pressures allowed use of less carriers, this was an advantage in
decreasing waste strength. Efforts to improve beam equipment and overcome flattening prob-
lems saw innovations such as the jet air principle. Introduction of the jet dyeing machine saw
widespread acceptance gained because jet machines promised to overcome problems of crease
marking, rope marks, tension, and distortion. Jet machines compromised in principle between
the technically more favorable procedure of circulating liquor through fabric and the less-
efficierit procedure of circulating goods through a bath. Although problems such as foaming
were still of considerable trouble, jet equipment generally used less water and energy and
reduced waste strength. The next step appeared to be towards overall more efficient processing,
less water use, and minimally polluting waste waters by continuous open-width methods. As
early as 1971, continuous knit open-width dyeing and washing machines were operating in the
U.S. The equipment was said to be versatile enough for use in desizing, scouring, and bleaching
also. Cost was $150,000 in 1971. Major criticism concerns lack of control over curling fabric
and tension effects (stretching).
Below, a schematic indicates the major advantages of a jet dye machine over the winch or
beck, Figure 6-48.
Liquor Ratio
Water „
Steam
Chemicals
Dyeing Time
,,R Soft-Stream
The Winch
,R" SOFT-STREAM THE WINCH
FIGURE 6-48
ENVIRONMENTAL COMPARISONS OF JET DYEING vs. BECK DYEING
6-97
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6.5.3.3 Immersible Dyeing Systems
McNally (William Heller Co.) discussed the virtues of the immersible dyeing jet (fully-flooded)
(74). The main advantage of such a system was said to be its potential for removing dye
stain defects. A side-tank feature allows removal of agglomerated dyestuffs which cause such
problems. Other advantages of this equipment included the absence of foam and associated
problems, absence of scum lines, leveling of streaky and blotchy goods, high degree of shade
reproducibility, and a high production rate. The main pollution advantages are that this equip-
ment allows reduced cleaning prior to following batches and reduced temperatures (dropped
from 275 to 265° F for polyester dyeing). McNally finds brighter shades are produced in the
pure, no carrier method. Besides polyester, Qiana and some acrylics appear to run well.
6.5.3.4 Sancowad Dyeing Process
Gaston County offers the Aqualuft Jet Dyeing Machine and the Sandoz Sancowad Process
(invented by G.H. Lister, Sandoz). The principle in essence is that fabric is impregnated with
dyes suspended in a micro-foam. The process is started cold to minimize dye substantivity.
After uniform distribution through the fabric, temperature is raised to provide dye fixation to
the fabric. The major advantage is low liquor, material ratios of about 1:1, and consequent
lowering of the effluent volume (see Figure 6-49).
Dye add line
Nozzle
Heat exchanger
to remove "energy"
from air stream
Front
view of
circular
kier
FIGURE 6-49
SCHEMATIC OF AQUALUFT MACHINE
6-98
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Resource comparisons were given between Gaston's H-Jet Machine (represents conventional
jet dyeing machine) and the Aqualuft for one cycle.
H-Jet Aqualuft
Total Water 10,800 (75:1) 1,140 (10:1) (13% of H-jet)
Total Steam 2,530 Ibs. 630 IBs. (25% of H-Jet)
Total Electricity 240 kilowatt hours 330 kilowatt hours (140%) of H-Jet)
Claim was made that fabrics (woven and knit) may need no prescouring, and that textured
polyester was dyed with PVA size on, and that the system lends itself to high energy dyes which
normally give barre'. These features were mentioned to offset the high equipment cost because
if there were no water pollution problems and energy considerations, it might otherwise be
difficult to justify the Aqualuft over conventional jet dyeing equipment. Balmforth reported
favorably on the feasibility of the system and cited the plus values concerning energy and pollu-
tion (9). He cautioned that the equipment was high cost and was emerging technology with
little substantive data on its use beyond the manufacturer's claims. The first commercial installa-
tion of the Sancowad dyeing process is using 20 to 25% less dye than the standard paddle meth-
od. Cormier Hosiery, Laconia, N.H., who purchased the system from Bentley-Pegg, also are
saving 80% of the usual water used, with savings also noted in steam and electricity (75).
6.5.4 Reduced Processing Sequences
6.5.4.1 Concurrent Slashing and Dyeing
Reducing processing sequences can provide an economy in water and chemical use and dis-
charge. In 1972 Atlantic Chemical Corporation reported three U.S. firms were using the Pada-
zoic slasher-dyeing system to process denim (76). About 50,000 yards of fabric were said dyed
by the system without dyes or water being discharged to local waters. In March 1975 about
300,000 million yards were reported processed (77). Another benefit asserted was that a strong-
er yarn is produced, since it is processed with all its impurities. This is said to aid weaving
performance, and reduce cotton waste. Recently, equipment developers have improved on the
system and have marketed newer versions. This form of modification should be considered
where feasible as a replacement for indigo dyeing.
6.5.4.2 Concurrent Dyeing and Finishing
A number of years ago several classes of water soluble dyes were applied concurrently with resin
precondensates with the intent of simplifying the finishing process. The environmental savings
in energy, chemical and water usage are potentially great enough to suggest that consideration be
given to such systems. In this work selected acid and direct dyes were applied to cotton by plac-
ing them in a resin finishing bath, padding on, and curing (78). Several resin systems were studied.
6-99
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The results showed that covalent bonding of the dye structure to the resin system was not
absolutely necessary. By choosing suitable disperse colors, a polyester/cotton blend was also
dyed with a simple pad-dry-cure procedure. If the resin is fully cured at the plant, a dyer has
the advantage of seeing the final shade without having to coordinate two separate procedures.
6.5.4.3 Transfer Printing
In its present form, transfer printing is only suitable for some synthetic fibers. It has been par-
ticularly successful with polyester, and some transfer printing has been done on acrylic, nylon
66, and triacetate. Some wool has been successfully printed by means of the so-called Fastran
process after a pretreatment. A further breakthrough in transfer printing on natural fibers is
not clearly foreseeable at the present time in the same simple way.
Due to the nature of the present transfer process as well as to the low quantity of dyestuff deliv-
eredjto the paper, the penetration of the dye into the fiber is limited. This is a particular problem
with knit goods as the base color of the substrate becomes visible when the cloth is stretched.
Many other advantages and disadvantages, such as high paper costs, exist, but within the limi-
tations of this discussion, only a few more pertinent points will be made. Rapid developments
can be anticipated in vacuum transfer printing systems and new dye formulation technologies;
good results are already discussed using existing rotary screen printing equipment. Stork sug-
gests production speeds up to 90 yds/min. with a two section dryer are practical with paper.
Important advantages from the viewpoint of this discussion are:
• Dyestuff consumption is considerably lower than with direct printing on textiles. A dye
yield of 80% can be realized with printed paper, and penetration can be better controlled.
• Hardly any water is consumed leading to less environmental pollution because there is
no need of aftertreatment.
• Considerably less energy is consumed during drying. Approximately one-half ounce of
water per square yard is used in transfer printing compared with approximately y/2 to 7
ounces of water per square yard used in direct printing.
• No aftertreatment such as steaming, washing, or drying is required and results in lower
cost, less production space, less skilled personnel requirements, and less pollution.
A piece of equipment offered by one vendor performs in the following manner. At the front
of the unit, transfer paper, fabric, and backing paper (when necessary) are fed into the nip.
Figure 6-50 shows the schematic cut away of one piece of equipment and the actual equipment
of another vendor (79), (80).
6-100
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Discarded print paper
Pnntmg paper / Discardmg ro,,er
Fabric supply
18"(455mm}
max dia
Air cooler
Printed fabric
Motor & Gearbox
Discarded backing
paper
FIGURE 6-50
TRANSFER PRINTING EQUIPMENT
Heat is applied and is controlled within 212 to 414° F. In this particular unit the paper and
fabric are taken around the heated cylinder by a Nomex endless blanket, and then each one is
rolled up again at the rear with controlled tension. The fabric is cooled before the roll up.
6.5.4.4 Process Controls
In February 1974, R.J. LeBrun (Foxboro Co.) stated textile industry lags far behind other
industries in adopting new control concepts (81). A major reason suggested was early failures
of computerized systems. LeBrun feels that major improvements resulting in the past 5 years
warrant attention. He stated about 10 companies are now using computers to direct sequential
machine functions with a few companies computer operating continuous operations. Foxboro is
currently automating a continuous finishing plant in Europe, composed of a bleach range,
thermosol dye range, tenter frame and print steamers. LeBrun said the Foxboro Textile Dye
Control System is feasible for 8-plus atmospheric, pressure, jet, beam and package machines.
The system is said able to provide the necessary sequential controls to handle up to 30 machines
of any combination at the same time.
Freeman (Foxboro) discussed the whys and hows of computer control of textile operations in
detail (82). Neish (Taylor) described the use of a digital computer to improve the effectiveness
of dyehouse management in a two-series article (83). The schematic of the Taylor 1010 system
for dyehouse control is shown below (see Figure 6-51).
6-101
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r"
Spectrophoto meter
Te
r1
etypewriter
^^
0
Ta
CPU
disc
0
/lor
equip
display
!. . 1 Teletypewnte
1 1 ,i i
I
r
r~
Scale
Crop
I
.J
Dye
machines
Mop j
o
Dye house
1
i
Drop
Teletypewriter
Dye mixing plant
FIGURE 6-51
TAYLOR 1010 SYSTEM FOR DYEHOUSE CONTROL
Burlington Engineering Sales, Dye Control Systems, Inc., Gaston County and Steel Heddle
representatives presented their equipment line features and discussed advantages of automatic
controllers (84). Essentially, within the scope of this manual the main advantages include:
• Reduction in utilities used
• Less waste of chemicals and dyestuffs
• Reduction in redyes
• Reduced cycle times
Morris Gelders suggested a layout for a package dyeing operation in 1971 (85). Gelders felt
steam and water usage could be reduced by one-third, less chemicals and dyes could be used, and
heat could be reclaimed (see Figure 6-52).
Avondale Mills plans to install an advanced energy-saving dyehouse control system.
The system, designed by Process Systems, will control Morton beam-dyeing machines in the
company's Bevelle Plant in Alexander City, Alabama.
6-102
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Built-up roofing
' insulation
metal roof deck
From
11 air washer
Bar joists &
steel framing
Brick wall
Air intake
for dryer
vv
AAAAAAAAAAAA/I
Material handling crane
Cheeses of yarn
PROPOSED LAYOUT of package dyeing operation is depicted in this schematic drawing by
Lockwood Greene Engineers of Spartanburg, S. C. This dyehouse, intended for processing
sewing thread and knitting yarn of synthetics and cottons, has bays 40 by 50 feet with
channel slab roof deck. Winding and warehouse space have bays 40 by 40 feet with metal
deck. The structure consists of an all steel frame with brick and block walls. In the dye-
house are keirs, vacuum extractor, and Avesta dryers.
FIGURE 6-52
In addition to providing the advantages of computer-controlled dyeing, the PSI 1210 system has
two new features previously unavailable to textile companies:
1. The system will monitor and report consumption of electricity, steam, hot and
cold water, and untreated water for each machine. The dyes will receive a report
on all utilities and amounts of energy and utilities used per pound of fabric dyed.
Machine malfunction, inefficient dye cycles, and excessive use of utilities can be
easily spotted and corrected with this report.
2- Labor and production reports on each shift, each maning, and each worker are
available with the PSI 1210 system. Machine production, down time, and opera-
tor delays are logged by the system and are available to the supervisor on a dis-
play tube or to management in printed form. Reports can be generated each
shift, for daily production, or as a weekly summary of machine and labor per-
formance.
6-103
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An Avondale spokesman said the savings in energy and the increased efficiency of the new dye-
house control system will be a considerable improvement over conventionally controlled dyeing
machines.
Where should one start in an automation program? Waiting to build a new dyehouse or "going
all the way when we start" have been voiced as primary reasons why some have not begun. This
does not have to be the case. There are immediate areas which one might consider. First, list
problem areas, and categorize the priorities for solutions. Following is an example of the appli-
cation of simple control equipment where money should not be wasted if a more complex sys-
tem were to be installed later (86). A basic atmospheric dye beck for polyester/cotton might
have 7 filling operations, 8 rinses and 22 separate temperature and time control settings. There are
thousands of gallons of water used, and an operator in charge of several becks can waste con-
siderable amounts due to overfilling and extended rinses. Better manual control of water usage
would result in longer labor time. A time/temperature programmer could reduce errors,
and save time, labor, energy and chemicals. A little more sophisticated might be equipment,
such as the Celcon 3002, which allows automatic programming of time/temperature control
and automatic operation of filling, draining, rinsing and addition valves.
Eslick reported a comparison between two plants within American Thread using essentially the
same formulations (6). One plant was automatied while the other was not. Substantial improve-
ments in various areas resulted in the automated plant. Plans are to automate further and to com-
puterize raw water treatment, boiler operation, dyehouse operation and waste treatment opera-
tion in both plants.
6.5.4.5 Minimum Application Machinery
Burkitt (11C) suggested in 1974 that after conventional easy-care finishing, most of the resin
lies on the fabric surface and that this contributes to poor fabric wear life (87). Study indicated
that the uneven distribution of chemical was, in large, due to migration during drying. It was
felt that reducing the amount of water applied with the resin could improve on migration ef-
fects. It was suggested that water be removed from the usual 60 to 70% wet pick-up to 30%.
About the time the principle was being demonstrated on a laboratory scale, i.e., improved easy-
care performance with less chemical, Triatex AG of Zurich marketed a commercial machine.
Both methods of application required lick roller application of the resin solution. The Triatex
equipment is shown in Figure 6-53.
The results of using this equipment suggested that improvements in losses of durability might
occur in 100% cotton goods, less chemical might be required, less energy might be needed in
drying, and processing might be shortened.
The increase in efficiency implied by this system, and its resultant environmental benefits,
must be balanced by the fact the technique may not be suitable for continuous, high-speed,
6-104
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Diagram of Triatex MA machine showing how liquid add-on
is controlled by roller speed and monitored by Beta gauge.
FIGURE 6-53
TRIATEX MA SYSTEM
full-scale operations. Lack of immersion time to provide adequate diffusion of material into the
fiber under usual processing conditions is cited as the primary disadvantage.
6.5.5 New Technology
It is also within the textile engineers domain to gauge the application of chemical engineering
technology to textile processing. The reality of PVA size reclamation and reuse by Gaston
County has already been mentioned. Union Carbide markets membranes similar to those used in
the Gaston County equipment under the trade name of Ucarsep. This system is shown, Figure
6-54, removing and concentrating oil and dirt from a metal phosphating line. Also a photo of
a pilot scale module is included.
Filtration layers
Ultrafiltrate
Concentrate
Oil — dirt
concentrate discharge_
oUUU orU
^
Typical operating conditions in metal washer cleanup
FIGURE 6-54
PROCESS IMPROVEMENT PLUS POLLUTION CONTROL
6-105
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This equipment is said to be capable of withstanding temperatures up to 200° F, pH's in the
range of 1 to 14, and pressures up to 100 psi (88). The equipment suggests itself for starch and
CMC size removal, dye reclamation, mercerizing liquor clean up, latex removal, wool grease re-
covery, with reuse of hot cleaned water directly. With the development of tighter membranes,
separation of smaller molecules, such as carriers, may be possible.
6.5.6 Process Changes Checklist
• Determine proper quality, quantity and temperature of water needed.
• Consider reclamation of heat from all wash water effluents.
• Counterflow as much as possible.
• Minimize quantity of water used in early rinse stages to suit operation requirements.
• Optimize cloth speed vs. water throughput as a function of fabric weight.
• Control steam quality and uniformity.
• Control to prevent excess use of steam.
• Use moisture meters to prevent over-drying.
• Determine absolute need for drying stages and evaluate addition of extraction before
drying.
• Meter all chemicals into make-up tanks and processing equipment. Recycle overflows
by proper piping.
* Establish minimum preparation standards, i.e., size removal, tensile strength, absorb-
ency, and whiteness related to following process problems.
• Consider automation and computerization of plant processes.
• Consider proper sequencing of unit operations for minimum equipment usage.
6.6 Good Housekeeping
Good housekeeping practices must be a cooperative effort between management, plant person-
nel, and the maintenance crews. This cooperation must include continuing education, especial-
ly for the operating personnel, because a lot depends on them. It has been discussed (53) that,
"The normal workday routine does not lend itself to an individual making extended efforts
6-106
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at correcting sloppy habits which have usually developed over a period of years." Once the easy
things have been done the task should be concerned with how to motivate workers, keep their
interest, and make them aware of the fact that top management also is concerned. A routine
monthly meeting of supervisors might include this matter in the agenda. The success had by
American Thread of appointing one man responsible for environmental and energy programs,
should be noted as an excellent approach worthy of consideration.
Although good housekeeping practices do not bring about spectacular reductions in pollution
loads or energy savings, they are indispensible to the goals of both concepts. Over the long term,
significant savings can be realized and certainly benefit can be gained in the thought that safer
working conditions should also be an advantage.
6.6.1 Spills
Focus can now be made on specific suggestions for good housekeeping.
Obviously, accidental spills, breakage, making of excessive mixes, and simply spilling excess
chemicals down drains are some of the elements of bad housekeeping. Evidence of such spillage
can often be detected by staining seen around drains. Oil or kerosene spills can be sopped up
with Dow polymer imbiber beads. Toktuft, a Phillips 66 non-woven fabric, marketed by Gedcor
Corporation, Westland, Michigan, is used to bag the beads. The bags are non-organic and can be
safely disposed of by incineration. Other similar products are also marketed.
The humorous, positive-attitude posters, mentioned previously, can go a long way in keeping
employees aware and alert that management's position is also an enduring one.
6.6.2 Organization
Better process organization may often be possible and should be considered. For example,
installing a central drug room in the dyehouse where mixing of chemicals can be closely super-
vised is one possibility.
6.6.3 Automatic Shut-Off
A large reduction in overall water wastage can be simply achieved by fitting every water tap or
hose with an automatic shut-off valve.
6.6.4 Records
Keeping records of production sizes and matching batch sizes can prevent making up too large
batches.
6-107
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6.6.5 Degreasing
If machinery requires degreasing, careful spreading of canvas and disposal by incineration are
recommended.
6.6.6 Curbing
Curbs around equipment with adequate slope to drains can prevent dangerous spills and contain
leaks.
6.6.7 Disposal Containers
Providing containers clearly labeled "trash" or "waste for incineration" is recommended.
6.7 References
1. Shift of the Art of Textile Waste Treatment, Clemson University for the EPA, Feb. 1971,
Pub. No. 12090ECS.
2. Masselli, J.W., A simplification of Textile Waste Survey and Treatment, New England
Interstate Water Pollution Commission.
3. Effluent Treatment and Water Conservation, Committee of Directors of Textile Research
Associations; T.R.C., 2 First Avenue, Sherwood Rise, Nottingham NG7 6HL, England.
4. In-Plant Control of Pollution, Manual 1, EPA-625/3-74-004, Oct. 1974.
5. Steffen, A.J., "Basics of Pollution Control," EPA Technology Transfer Seminar, Boston,
Mass., Jan. 15-16, 1975.
6. EPA Technology Transfer Seminar, Boston, Mass., Jan. 15-16, 1975.
7. Water Pollution: Soul-Searching Time, Textile World, pg. 69, Jan. 1971.
8. Private conversations with J.D. Lesslie, Springs Mills, November 13, 1974.
9. Institute of Textile Technology, Charlottesville, Virginia, pilot and mill projects and audits.
10. Porter, J.J., et al., "Water Uses and Wastes in the Textile Industry," Envir. Sci. Techn. 6(1):
36-41, 1972.
11. Rodney-Hunt advertising.
6-108
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12. Mather-Platt advertising.
13. Textile Chemist and Colorist, pg. 15-31, January 1975.
14. Automated Waste Treatment Seen as Feature of Modern Dyehouse, Am. Textile Rep.:
9, 29, June 10, 1971.
15. Sources and Resources, pg. 30, 1974/75.
16. American Dyestuff Reporter, July 1974.
17. Uster Corporation advertising.
18. Textile World, B.L. Rutledge, pg. 80, March 1974.
19. Environmental Guide to Dye Carrier Selection, J.M. Haas, Amer. Dyestuff Rep. pg. 34-
36-44, March 1975.
20. American Dyestuff Reporter, pg. 26-27, March 1975.
21. Practical Steps to Reduce Pollution from the Textile Industry, Textile Institute and In-
dustry, August 1974.
22. Textile Chemist and Colorist, pg. 33-35, June 1974.
23. Textile Chemist and Colorist, pg. 27, November 1973.
24. Gaston County advertising.
25. Textile Industries, pg. 122, November 1972.
26. Wool Industries Research Association, pg. E43, Year Book 1973.
27. Water Pollution Reduction through Recovery of Desizing Wastes, C.E. Bryan, EPA 12090,
EOE 01/72.
28. Polyvinyl Alcohol Reclamation, Seminar Sponsored by Gaston County, J.P. Stevens,
Clemson University and Union Carbide, Clemson, July 1974.
29. On-Site Visit, McCormick Mills, McCormick, South Carolina, March 12, 1975.
30. Recovery of Plant Waste Water and Chemicals for Reuse by Hyperfiltration: J.J. Porter,
Amer. Chem. Society Nat'l. Meeting, April 8, 1975.
6-109
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31. Industrial Waste Guide to the Cotton Textile Industry, USPHS Pub. 677, Washington,
D.C. 1959.
32. S.A. Textile, pg. 54, October 1971.
3:5. The Wasle Survey, T. Rinker (BRW), In-Plant Control of Pollution, EPA-625/3-74-004.
34. The Rapid COD Test, M.S. Bahorsky and C.E. Tate, I.T.T. publication, November 1974.
34. Water and Wastes Eng., J. Jeris, May 1967.
36. Textile Wastewater Treatment, Clemson Midwinter Conference, Hilton Head, South
Carolina, January 1975.
37 American Chemical Society National Meeting, Philadelphia, Penn., April 9, 1975.
38. Sources arid Resources, pg. 13, 1975/3.
39. Sources and Resources, pg. 31, 1975/2.
40. Chemical and Engineering News, pg. 36, April 23, 1973.
41. The Role of Liquid Ammonia in Functional Textile Finishes, Textile Research Journal,
pg. 680, September 1974.
42. British Patent, 1,136,417 (1968).
43. British Patent 1,084,612 (1967).
44. U.S. Patent 3,724,243 (1973).
45. Knitting Times, pg. 27, December 30, 1974.
46. Textile Industries, pg. 77, September 1974.
47. Treatment of Textile Mill Wastes in Aerated Lagoons, S. Williams, Industrial Waste Con-
ference, Purdue University 16: 518-528, 1961.
48. Sources and Resources, J.G. Camp, pg. 24, 1975/2.
4<). Sources and Resources, M. Davis (DuPont), pg. 26, 1975/2.
50. Textile Industries, Olson (Nat. Starch), pg. 79, March 1975.
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51. Textile World, pg. 131, May 1969.
52. Environmental Science and Technology 6: 36-41, January 1972.
53. Recommendations and Comments for the Establishment of Best Practicable Waste Water
Control Technology Currently Available for the Textile Industry, American Textile Manu-
facturers Institute, Inc. and The Carpet and Rug Institute, January 15, 1973.
54. Textile Solvent Technology-Update 1973, AATCC, Atlanta, Georgia, January 10-11, 1973.
55. On-Site Visit, F. Sievenpiper, Allied Chemical Company, Buffalo, New York, January, 1973.
56. American Dyestuff Reporter, pg. 50, May 1972.
57. What's New About Solvent Dyeing, F. Sivenpiper Textile Chemist and Colorist, pg. 49,
March 1971.
58. Solvent Finishing Range Cuts Costs, The Knitter, pg. 41, August 1974.
59. Cutting Polyester Piece Goods Redyes, Textile World, pg. 117. August 1974.
60. American Textile Reporter, February 1973.
61. Textile Research Institute, pg. 680, September 1970.
62. American Dyestuff Reporter 62 (5): pg. 27, 1973.
63. Journal Soc. Dyes and Colorists, December 1971.
64. Textile World, pg. 107, December 1972.
65. American Textile Reporter and Bulletin, pg. 43, February 1973.
66. Textile Industries, September 1966.
67. American Dyestuff Reporter, pg. 46, August 26, 1968.
68. Textile Industries, September 1966.
69. America's Textile Reporter/Bulletin, pg. 45, February 1973.
70. On-Site Visit, Dan River Mills, Danville, Virginia, to observe operation of the Mather and
Platt Vaporloc Pressure Scour and Bleach System, August 20, 1975.
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71. America's Textile Reporter/Bulletin, pg. 75, January 1975.
72. International Textile Bulletin, pg. 245, 1973/3.
73. Canadian Textile Journal, page 149-152, September 1975.
74. Sources and Resources, pg. 3, February 1974.
75. American Dyestuff Reporter, pg. 13, November 1974.
76. Daily News Record 2: 12, February 1, 1972.
77. Sources and Resources, pg. 16, 1975/3.
78. American Dyestuff Reporter, pg. 48, November 18, 1968.
79. Bates Textile Transfer Printing Machine, Brian Lyttle Inc., U.S. Representative, Spartan-
burg, South Carolina.
80. Herbert Kannegiesser Corp., Vacumat 200, Riverside, Conn.
81. Sources and Resources, pg. 4, February 1974.
82. American Dyestuff Reporter, 57: 24-31, September 9, 1968.
83. International Dyer and Textile Printer, pg. 248, September 6, 1974.
84. American Dyestuff Reporter, November 1974.
85. American Textile Reporter, pg. 9, June 10, 1971.
86. American Dyestuff Reporter, A.F. Withey, Steel Heddle, pg. 30, November 1970.
87. Canadian Textile, J.F. Burkett (11C), pg. 77, May 1974.
88. Chemical Progress (Union Carbide publication), May 1974 and Metal Progress, June 1974.
Chemical Week, pg. 39, February 20, 1974
Draft, Development Document for Effluent Limitations Guidelines and Standards of
Performance, Arthur D. Little for the EPA.
On-Site visit, Salem Carpet Mills, Chickamanga, Georgia, March 28, 1977.
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Sweco Inc. and Bauer Bros. Company advertising.
Textile Industries, pg. 122, July 1974.
The Cost of Clean Water, FWPCA, Dept. Interior, Industrial Waste Profile No. 4
Water and Waste Engineering, pg. 35, April 1975.
6-113
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CHAPTER 7
WASTEWATER TREATMENT PROCESS SELECTION
7.1 Introduction
This chapter presents suggested wastewater treatment techniques for each of the EPA textile
categories. Using average effluent wastewater characteristics and point-source limitations set
for 1977, a suggested treatment model is developed and discussed for each category.
Upgrading treatment facilities to meet future limits (1983) will generally require the addition of
one or more of mixed-media filtration, activated carbon adsorption, and chemical coagulation.
Specific needs, however will be determined at the completion of reconsideration studies for
1983 (BAT) limitations.
7.2 Wool Scouring Wastewater Treatment
Wool scouring wastes are highly concentrated, and their treatment is bolh difficult and cosily to
the manufacturer or to the municipality which must cope with the material. Wool scouring
mills, for the most part, are quite decentralized and in small units, so that the installation of
waste treatment facilities represents a substantial capital investment.
The use of neutral detergent scouring to process wool has evolved through an effort to produce
a waste effluent more amendable to subsequent treatment. Consequently, most of the wool
scoured in the United States over the past 10 years has been by the neutral detergent scouring
method. Also, along this same line of reasoning, if a new approach is used, either along the lines
of solvent extraction or other modifications, it can have a pronounced effect on the waste
treatment process anu its associated cost.
In-plant recovery of wool grease is practiced by a number of mills with varying degrees of effi-
ciency (usually less than 50%). Wool grease can be used in inks, paints, lubricants, and can be
refined to produce lanolin. Methods of recovery include centrifuging and hot acid cracking. Re-
covery will substantially reduce the pollutant load to the treatment facility.
Characteristics of wool scouring effluent wastewater have been established in Chapter 4, and
effluent requirements for point-source discharge are described in Chapter 2. These parameters
and required removal efficiencies are summarized in Table 7-1 on the following page.
7-1
-------
TABLE 7-1
WOOL SCOURING WASTEWATER PARAMETERS
(Point Source Discharge)
Parameter
BOD
COD
TSS
Oil & Grease
Total Chrome
Phenol
Sulfide
pH (units)
Mill Effluent*
mg/l
6,000
30,000
8,000
5,500
0.05
1.50
0.20
8.0
1977 Limit**
mg/l
296
3848
898
201
2.8
2.8
5.6
6.0 to 9.0
Percent
Removal Required
95.1
87.2
88.8
96.3
0
0
0
—
'Mill Effluent values established as representative of processing subcategory, see Chapter 4
"Effluent guideline limits based upon raw, not finished product (Finished product is approximately 50% by weight
of raw ) Values are 30-day average - Maximum for any one day is twice the 30 day average
A treatment facility capable of achieving these removal efficiencies may be constructed utilizing
a number of different processes. One such arrangement is presented in Figure 7-1.
In wool scouring there are two main wastewater sources; the scour water and the rinse water.
The scour water is by far stronger and when segregated from the rinse waters provides the
advantage of reduced treatment unit size. The initial effort in treatment of wool scouring
waste is usually to remove the heavy solids such as grit, suint and the grease. Biological treat-
ment may then be used to remove the remaining organic material. (Consideration may also be
given to evaporation followed by incineration for concentrated waste streams.) The treatment
process shown in Figure 7-1 is presented for meeting the BPT standards. Discussions of each
unit process are presented in the following paragraphs.
7.2.1 Screening
A troublesome factor in the treatment of wool scouring waste is wool fiber within the waste.
The fibers may come from improperly operated scouring equipment, washdown or other
sources. The problems are encountered as the fibers degrade and cause odors and may also cause
mechanical problems in pumps and other treatment equipment. It is usually necessary to pro-
vide coarse and fine mesh screening for removal of the fiber. Devices such as fine mesh vibrating
screens have proven excellent for the removal of wool fiber.
7.2.2 Equalization
An equalization tank or basin is provided to receive the treatment scouring waste, the rinse
waters after scouring, and supernatant from subsequent treatment processes. Equalization is
required because of the batch dumps of waste, the surges and other flow variations which would
upset downstream processes.
7-2
-------
Scour
liquor
Screening
Rinse water
Equalization
Solids to
landfill
Grease
recovery
Flotation
Q)
+-•
CO
i_
c:
0)
O
Clarifier
Chem-sludge
Aeration basin
Supernatant
Centrifuge
To landfill
Flocculation
Rapid
mix
Clarifier
Bio-sludge
Aerobic digester
To receiving
stream
FIGURE 7-1
WOOL SCOURING WASTEWATER TREATMENT MODEL SCHEMATIC
MEETING 1977 (BPT) LIMITATIONS
7-3
-------
7.2.3 Flotation
Flotation is provided to remove the substantial quantity of grease remaining after in-plant
attempts at grease recovery. Floated grease may be returned to the grease recovery system and
settled sludge can be dewatered with treatment-plant sludge.
7.2.4 Chemical Treatment
Chemical treatment is used to remove the high concentration of suspended solids composed of
proteins, soaps and fibers. It can also reduce remaining oil and grease. These materials exhibit a
high COD and turbidity which may be removed prior to biological treatment. Chemical coagu-
lants suggested for use in this system are lime and calcium chloride. Ferric sulfate has also been
used successfully.
The system consists of rapid mixing, flocculation and clarification. Upflow clarifiers with sludge
blankets are sometimes used.
7.2.5 Biological Treatment
With most of the grease removed, biological treatment is used to remove BOD in the waste-
water. Activated sludge has been successful in this, however, experience indicates extended de-
tention periods of 10 to 20 days may be required. Food to microorganism ratios should be
maintained at a low level (.03 to .05). Effective suspended solids removal is achieved with a low
clarifier overflow rate of approximately 200 GPD/sq. ft.
7.2.6 Sludge Treatment and Disposal
Waste sludge from biological treatment is stabilized using aerobic digestion. The digested sludge
is then dewatered by centrifuging. Supernatant is returned to the aeration basin influent. De-
watering using the centrifuge appears to have had some success with wool scouring wastewater
sludges. Both the biological and chemical sludges are dewatered in a horizontal solid bowl type
centrifuge. The centrate produced is returned to the rapid mix tank of the chemical coagulation
process. Sludge from the centrifuge may best be disposed of in a sanitary landfill either on the
site or off.
7.3 Wool Finishing Wastewater Treatment
Wool finishing mills are characterized as having the highest water usage per pound of product of
finishing operations. Specialized dyes that are used may contribute chromium to the wastes.
Dyeing of polyester blends involves the use of phenols. Most of the BOD is generated by wash-
ing after fulling and from dyeing operations. Chemical substitution such as the use of sulfuric
acid in place of soap will substantially reduce pollutant loads requiring treatment.
7-4
-------
With the exception of the chrome and phenol content, wool finishing wastewaters are similar
in nature to those of woven and knit fabric finishing.
Wool finishing parameters for average mill effluent, limitations for point source discharge, and
required removal efficiencies are summarized in Table 7-2 below:
TABLE 7-2
WOOL FINISHING WASTEWATER PARAMETERS
(Point Source Discharge)
Parameter
BOD
TSS
COD
Oil & Grease
Total Chrome
Phenol
Sulfide
pH (Units)
Mill Effluent
mg/l
300
130
1,040
—
4
0.5
0.1
7
1977 Limit*
mg/l
33.6
52.8
244
—
021
0.21
0.42
6 to 9
Percent
Removal Required
88.8
59.4
76.5
—
94.8
58
0
—
"Values are 30 day average - Maximum for any one day is twice the 30 day average
Figure 7-2 represents the flow diagram of a treatment plant capable of achieving the 1977 efflu-
ent limitations guidelines. The facility would consist of screening, equalization, biological treat-
ment and chemical treatment.
7.3.1 Screening
Wool fibers are removed using fine mesh type screens. Vibrating machines have been successful
with these fibers. Suspended solids removals of up to 20% are possible with these screens.
7.3.2 Equalization
Equalization may be required if segregated chrome wastes are reduced and introduced into mill
effluent, or if conventional activated sludge is selected as a treatment method. The equalization
basin should be provided with adequate aeration and mixing to prevent solids deposition and
septicity.
7.3.3 Biological Treatment
Activated sludge treatment may be best accomplished using extended aeration with a retention
time of 3 to 4 days. If the conventional activated sludge system is used, equalization is suggested
since the conventional method provides a retention time of approximately 6 to 8 hours.
7-5
-------
Segregated
chrome
waste
Chrome reduction
unit
Mill
effluent
Screening
Equalization
Solids to
landfill
Clarifier
Aeration basin
Bio-sludge
•Ferrous sulfate
-Lime
Rapid
Mix
Flocculation
Clarifier
Centrifuge
To
Receiving stream
To landfill
FIGURE 7-2
WOOL FINISHING WASTEWATER TREATMENT MODEL SCHEMATIC
MEETING 1977 (BPT) LIMITATIONS
7-6
-------
Nitrogen and phosphorus deficiencies have not been reported for wool finishing wastewaters.
Excess ammonia nitrogen may be a problem in the effluent. If nitrogen is needed, ammonium
sulfate used in place of acetic acid in processing will serve as a nutrient in the treatment system.
Chrome, if present from the dyeing process, may not upset the biological process even when
present at concentrations of 50 to 150 mg/1 (as reported by Masselli). In addition, reductions
of approximately 73% chrome have been reported for the biological process. If, however,
chrome must be removed to meet stringent limits or to protect biological treatment, then it is
suggested that, if feasible, chrome-bearing waste streams be segregated for separate treatment.
At low flows, chrome reduction may be best accomplished using one of a number of package
treatment units on the market.
7.3.4 Chemical Treatment
The chemical coagulation process is used as a tertiary treatment step to remove additional
chromium and COD. Chemicals used for chromium reduction are ferrous sulfate (copperas)
and lime. pH adjustment to 8.5 prior to entering the chemical coagulation process is necessary.
The system would consist of rapid mix, flocculation, and clarifier tanks; however, solids contact
clarifiers may be suitable.
7.3.5 Sludge Treatment and Disposal
A horizontal, solid-bowl centrifuge can be used for dewatering biological and chemical sludges.
Biological and chemical sludge are to be fed to the unit separately at 1.5 to 2.5% solids. A
cationic polymer is used as a conditioner at the rate of 10 to 20 pounds per ton of solids to
yield a sludge cake of 12 to 15% solids. The centrate is returned to the rapid mix tank in the
chemical coagulation process. Other sludge dewatering methods are available, as discussed in
Chapter 8, and should be investigated. Sludge cake from the centrifuge may be disposed of to
a landfill.
7.4 Dry Processing Wastewater Treatment
Dry processing wastes are generated at both greige mills and adhesive-related operations such as
carpet backing, laminating, or non-woven mills.
Wastes at greige mills are composed of residues washed out of size boxes. Volume is small when
compared to sanitary wastes at typical mills. The sanitary portion is generally 70 to 90% of total
mill effluent. Treatability of greige mill wastes is related to the type of size used. Starch exhibits
a high BOD and is readily biodegraded, while synthetic sizes such as polyvinyl alcohol or car-
boxymethyl cellulose exhibit much lower BOD and degrade more slowly as organisms take
longer to acclimate to the synthetics.
7-7
-------
Wastes from adhesive related operations are composed of bonding chemicals, mainly latex com-
pounds. Latex generally enters the waste stream as washdown from equipment. The latex is
not soluble in water but is used in a highly dispersed form and is therefore high in suspended
solids and COD. Since the volume of process wastewaters is low, segregation and separate treat-
ment may prove to be economical.
Representative mill wastewater parameters, effluent limitations for point source discharge and
required removal efficiencies are summarized in Table 7-3 below:
TABLE 7-3
DRY PROCESSING WASTEWATER PARAMETERS
(Point Source Discharge)
Parameters
BOD
TSS
COD
Oil & Grease
Total Chrome
Phenol
Sulfide
pH (Unit)
Fecal Coliform**(MPN)
Mill Effluent
mg/l
350
200
1000
—
—
—
—
10
—
1977 Limit*
mg/l
56
56
112
—
.014
—
—
6-9
4007100ml
Percent
Removal Required
84
72
88.8
—
—
—
—
—
—
'Values are 30 day average - Maximum for any one day is twice the30 day average
"Max Value
Figure 7-3 represents the flow diagram of a treatment facility capable of achieving the required
removal efficiencies. The facility consists of screening, equalization, chemical treatment (ad-
hesive waste only), biological treatment and disinfection.
7.4.1 Screening
Screens are provided for removal of sanitary debris and processing yarn and fiber. A commi-
nutor may be required upstream on the sanitary line. Screens with mesh sizes in the 40 to 80
range are suitable.
7.4.2 Equalization
Equalization is used to combine process and sanitary wastes prior to subsequent treatment.
Adequate mixing is recommended to prevent solids deposition and septicity.
7-8
-------
Segregated
latex
waste
effluent
To
receiving
stream
Rapid
mix
Flocculation
Clarifier
Chem-sludge
Screening
Solids to
landfill
Clarifier
Bio-sludge
Centrate
Centrifuge
Chlorination
if sanitary
included
Equalization
Aeration basin
To landfill
FIGURE 7-3
DRY PROCESSING WASTEWATER TREATMENT MODEL SCHEMATIC
MEETING 1977 (BPT) LIMITATIONS
7-9
-------
7.4.3 Chemical Treatment
The chemical coagulation process is used as a primary treatment for reduction of suspended
solids and COD exerted by the adhesive compounds. (Greige mill wastewaters will not require
this step.) This treatment is necessary because insoluble latex compounds are difficult to treat
biologically. Coagulation may be accomplished using alum and a polyeletrolyte. Optimum pH
and dosages will have to be determined in the laboratory. It should be noted that the physical
characteristics of the coagulated sludge are important in terms of further dewatering and dis-
posal, i.e., rubbery balls are sometimes formed in chemical treatment.
7.4.4 Biological Treatment
The conventional activated sludge process may be used because of the high percentage of sani-
tary wastes. Nutrients are generally adequate also due to the large portion of sanitary waste in
the total effluent. If, however, sanitary and process wastes are segregated, a nitrogen source
such as ammonia must be added to the process.
7.4.5 Disinfection
Dry processing mills are limited by guidelines in fecal coliform discharged in the effluent. Dis-
infection of process wastes will not be necessary if the sanitary portion is treated separately or
discharged to a municipal system.
Chlorination may be selected as the method of disinfection. The system consists of chlorine
feed equipment, 150 Lb. liquid cylinders or calcium or sodium hypochlorite, and a chlorine
contact tank.
7.4.6 Sludge Treatment and Disposal
The horizontal solid-bowl centrifuge has been effective in dewatering the dry processing waste
sludge. Biological and chemical sludge enters the centrifuge at approximately 1.5 to 2.5%
solids. A cationic polymer is used as a conditioner at the rate of 10 to 20 pounds per ton of dry
solids to yield a sludge of 12 to 15% solids. The centrate is returned to the rapid mix basin of
the chemical coagulation process. Sludge concentrated from the centrifuge may be disposed of
in a sanitary landfill.
7.5 Woven Fabric Finishing Wastewater Treatment
In terms of number of mills and total pounds of production, woven fabric finishing is the largest
single wet processing subcategory in the textile industry. Wastes are generated as a result of re-
moval of foreign matter during cleaning and various chemicals used in finishing.
7-10
-------
Composite plant wastes vary depending upon fibers processed; however, the effluent is generally
high in BOD and COD with a modest suspended solids content. Small amounts of oil and grease
appear from cotton impurities, and the pH may be alkaline from caustic soda scouring. Sulfide
and chrome appear in the effluent from sulfur and vat dyes respectively.
In-plant controls such as caustic recovery, use of synthetic size, PVA reclamation and water use
conservation will reduce pollutants and affect treatment plant sizing.
In Table 7-4, representative mill wastewater parameters, effluent limitations for point source
discharge and required removal efficiencies are summarized.
TABLE 7-4
WOVEN FABRIC FINISHING WASTEWATER PARAMETERS
(Point Source Discharge)
Parameter
BOD
TSS
COD
Oil & Grease
Total Chrome
Phenol
Sulfide
pH (Unit)
Mill Effluent
mg/l
650
300
1200
14
0.04
0.04
3.0
10
1977 Limit*
mg/l
29.3
79
266
—
0.44
0.44
0.42
6 to 9
Percent
Removal Required
95.5
73.7
77.8
—
0
0
86
—
'Values are 30 day average - Maximum for any one day is twice the 30 day average.
Figure 7-4 represents the flow diagram for a treatment facility capable of achieving the removal
efficiencies necessary to meet the 1977 effluent limitations guidelines. The facility consists of
screening, biological treatment and chemical treatment.
7.5.1 Screening
Cotton impurities, fiber and other solids are removed by fine mesh screening. A screen with a
mesh size of 80 has been effective for this application.
7.5.2 Biological Treatment
The activated sludge system is most effective for woven fabric wastes when designed as extend-
ed aeration with a retention time of 3 to 4 days.
Nitrogen deficiencies may be frequently found in woven finishing wastes. Aqueous ammonia or
anhydrous ammonia may be added prior to entering the aeration basin. Sanitary sewage may
7-11
-------
Nutrient feed
(if required)
Mill
effluent
Screening
Alum-
Polymer-
Flocculation
Clarifier
Chem-
sludge
Solids to
I landfill
Rapid
mix
£
"c
03
o
Activated carbon
catalyst
Aeration basin
Bio-sludge
Centrifuge
pH adjust
(if required)
Clarifier
pH adjust
(if required)
To
receiving stream
To landfill
FIGURE 7-4
WOVEN FABRIC FINISHING WASTEWATER TREATMENT
MODEL SCHEMATIC MEETING 1977 (BPT) LIMITATIONS
7-12
-------
also provide a nitrogen source. Phosphorus content is generally adequate for the activated sludge
system.
Foaming problems are common in the aeration basin and cannot always be controlled by con-
ventional water sprays. Powdered activated carbon or a defoaming agent can be introduced to
reduce or eliminate the foaming. Though not as effective as a defoamer, activated carbon will
also act as a catalyst improving BOD, COD and color removal efficiencies of the biological
system.
7.5.3 Chemical Treatment
The levels of BOD and COD removal required in Table 7-4 are difficult to maintain consistently
with the biological system alone. Chemical treatment will serve to remove additional BOD, COD
and TSS. Common coagulants used are alum and polymer. Optimum treatment may require
lowering the pH. If so, pH adjustment before discharging the effluent may also be necessary.
7.5.4 Sludge Treatment and Disposal
Biological and chemical sludges may be dewatered using a horizontal solid bowl centrifuge.
Vacuum filters have been tried but blinding problems have been experienced. Sludge is fed at
approximately 1.5 to 2.5% solids and is pre-conditioned with a cationic polymer. The cen-
trate is returned to the rapid mix tank. Sludge from the centrifuge may be suitable for dis-
posal in a landfill. Other methods are available as detailed in Chapter 8.
7.6 Knit Fabric Finishing Wastewater Treatment
Knit fabric finishing mills are characterized by a large number of plants and a structure organiz-
ed along specialized product segments. Knit fabric finishing operations are also similar to woven
fabric finishing except that sizing/desizing and mercerizing operations are not required for knit
fabric finishing. Instead, knit yarn is treated with lubricants rather than with the starch or poly-
meric sizes used for woven goods. Lubricants (knitting oils) are applied to knitting yarns and
generally contain mineral oil, vegetable oil, synthetic ester type oil or waxes and may also con-
tain anti-static agents, anti-oxidants, bacteriostats and corrosion inhibitors. The amount of oil
applied varies with the type of yarns. Knitting oils are also injected into the needles of knitting
machines in order to lubricate and lower the temperature of the needles. The knitting oil pres-
ent in knit greige goods is readily emulsified or soluble in water and easily scoured or washed
out before dyeing. Generally the mineral oil and scour detergents in the effluent are not readily
biodegradable.
Table 7-5 represents the average mill raw waste load characteristics, effluent limitations for
point source discharge, and required removal efficiencies of knit fabric finishing mills.
7-13
-------
TABLE 7-5
KNIT FABRIC FINISHING WASTEWATER PARAMETERS
(Point Source Category)
Parameter
BOD
TSS
COD
Oil & Grease
Total Chrome
Phenol
Sulfide
pH (Units)
Mill Effluent
mg/l
350
300
1000
53
0.05
0.24
0.20
8
1977 Limit*
mg/l
16.7
72.6
200
—
0.33
0.33
0.67
6 to 9
Percent
Removal Required
95.2
75.8
80
—
0
0
0
—
"Values are 30 day average - Maximum for any one day is twice {he 30 day average
Although oil and grease are not considered as a separate pollutant parameter required for 1977
limitations, it has been required by individual authorities for wastewater discharged to natural
waters at limits of 10 to 30 mg/l. Emulsified oil in knit fabric finishing plants at high concen-
trations will interfere with the biological process and COD removals.
The model for treating wastewater containing high concentrations of emulsified oil capable of
meeting 1977 effluent limitations is shown in Figure 7-5, which is the flow diagram for chemical
treatment and air flotation followed by biological treatment. Physical treatment using the ultra-
filtration technique to concentrate oil from its emulsified form may be another potential treat-
ment method. It may be possible to produce a permeate which will contain less than 5 mg/l oil
and be reusable as process water. The concentrate (less than 10% by volume) may be dewatered
further by the addition of a de-emulsifier and separation by air flotation. The concentrated oil
has a potential use as a fuel for plant boilers. Long term problems with filtration membrane
failure may be a major drawback in using this process.
Where emulsified oil concentration is lower than approximately 100 mg/l and is not expected
to present problems in a biological system, treatment using biological/chemical methods is sug-
gested as shown in Figure 7-6.
7.6.1 Chemical Treatment/Air Flotation
Chemical coagulation using alum as a coagulant may be used to break the oil-in water emul-
sion. This method allows treatment of process and sanitary waste simultaneously.
7.6.1.1 Screening
An 80-mesh screen may be used to remove fiber, lint and solids before entering subsequent
processes.
7-14
-------
Mill
effluent
(high oil content)
Screening
Solids to
landfill
Caustic-
pH adjust
•Polyelectrolyte
Flocculation
To
receiving
stream
Clarifier
Bio-sludge
To landfill
Equalization
Alum-
Sulfunc acid-
Reaction tank
Rapid
mix
Air flotation
Chem-sludge
Nutrient
(if required)
Aeration basin
.. 1 r-
Centrifuge
Polymer
Centrate
FIGURE 7-5
KNIT FABRIC FINISHING WASTEWATER TREATMENT MODEL SCHEMATIC
MEETING 1977 (BPT) LIMITATIONS
(High Oil Content)
7-15
-------
Nutrient feed
(if required)
Mill
effluent
(low oil content)
Screening
Alum-
Polymer-
Flocculation
Clarifier
Chem-
sludge
Solids to
landfill
Rapid
mix
Q)
"«
c
o>
O
Activated carbon
catalyst
Aeration basin
Bio-sludge
Centrifuge
pH adjust
(if required)
Clarifier
pH adjust
(if required)
To landfill
To
receiving
stream
FIGURE 7-6
KNIT FABRIC FINISHING WASTEWATER TREATMENT MODEL SCHEMATIC
MEETING 1977 (BPT) LIMITATIONS
(Low Oil Content)
7-16
-------
7.6.1.2 Equalization
Equalization of mill effluent is desirable since chemical addition and pH adjustment are sensitive
to waste characteristics. Adequate mixing should be provided in equalization to prevent septic
conditions and solids deposition.
7.6.1.3 Chemical Treatment
Coagulation is accomplished by using alum and a polyelectrolyte. pH adjustment may be neces-
sary to provide proper reaction between alum and emulsified oil. After forming the floe, the pH
may have to be readjusted to meet effluent limits.
7.6.1.4 Flotation
Air flotation is used to separate the chemically coagulated floe. Flotation skimmings and settled
sludge are further dewatered. Clarified effluent is introduced to the biological system.
7.6.1.5 Biological Treatment
Activated sludge extended aeration is used with 3 to 5 days retention time. Aqueous or anhy-
drous ammonia is added to serve as a nitrogen source. Sanitary sewage may also be used. Foam-
ing problems are not anticipated unless a large percentage of fiber processed is cotton.
7.6.1.6 Sludge Treatment and Disposal
Centrifugation may be used for sludge dewatering of both chemical sludge and biological sludge.
The sludges are fed separately to the centrifuge unit and are conditioned with a cationic polymer.
The centrate is returned to the flocculation basin. Final disposal of sludge from the centrifuge
is to a landfill. Other methods are available as illustrated in Chapter 8.
7.6.2 Physical Treatment Using Ultrafiltration Technique
Segregation of process effluent and sanitary wastewater is necessary to eliminate large solids to
the system. Sanitary waste may be discharged to a package type plant or to a municipal sewer
if available.
7.6.2.1 Screening
An 80-mesh screen is suitable to remove large particulates and fiber from the process effluent.
7-17
-------
7.6.2.2 Equalization and pH Adjustment
Equalization is used to smooth the flow from batch dumps and to cool the effluent before
pumping through the filter membrane. Adjustment of pH to a range of 5.5 to 7.5 is necessary
to maintain proper operation of the ultrafiltration unit. Wastewaters from knit synthetic goods
generally exhibit a pH within this range since only light scouring is needed. Knit cotton waste-
waters usually have a high pH due to heavier scouring than is needed for knit snythetic goods and
may require pH adjustment.
7.6.2.3 Ultrafiltration
Ultrafiltration may be used to separate the oil from the liquid waste. The system relies on the
permeation of water through a semipermeable membrane under a hydraulic driving pressure
(100 to 200 psi). Before entering the ultrafiltration modules, a 25 micron cartridge filter is used
as a prefilter.
7.6.2.4 Flotation
Concentrate from the ultrafiltration unit is chemically de-emulsified. The mixture of oil and
water is then separated by an air flotation unit. Underflow is recycled to the equilization basin.
7.6.3 Biological/Chemical Treatment
In the absence of excessive oil in the waste stream, biological treatment will operate effectively.
However, in order to consistently meet the stringent removal efficiencies, chemical coagulation
may be necessary for removal of remaining BOD, COD, and TSS.
7.6.3.1 Screening
Solids from knit fabric finishing such as natural fiber, lint, and short synthetic fiber are removed
by fine screening. An 80-mesh screen is suitable for removing these solids.
7.6.3.2 Biological Treatment
An activated sludge system with 3-to-5 day retention time may be used to treat knit fabric
finishing waste. Anhydrous or aqueous ammonia is added to serve as a nitrogen source in the
aeration basin. In knit fabric finishing, the MLSS level may be found to be inadequate in the
aeration basin. Powdered activated carbon is effective in bringing the MLSS level up. In addi-
tion, the carbon will increase efficiency in the aeration basin. Potential foaming from heavily
scoured cotton knits would also be reduced by the carbon addition.
7-18
-------
7.6.3.3 Chemical Treatment
Chemical coagulation and clarification will serve to reduce pollutants passing through the bio-
logical stage. Alum is used along with a polymer. Optimum treatment may require lowering the
pH. If so, pH adjustment before discharging the effluent may also be necessary.
7.6.3.4 Sludge Dewatering
Biological and chemical sludges are dewatered separately by a horizontal solid bowl centrifuge.
The centrate is returned to the rapid mixing basin.
7.6.3.5 Sludge Disposal
Centrifuged sludge is generally suitable for landfill.
7.7 Carpet Mill Wastewater Treatment
Carpet yarns in general use today include nylon, polyester, acrylic, modacrylic and wool. The
dyeing of polyester and wool may generate phenols and chromium respectively. Process dye
wastewaters are generally hot due to the lack of other wet processing steps in the mill. The high
temperatures may present problems in biological treatment systems. Though knitting oils are
not present in carpet yarn there may be traces of spinning oils.
TABLE 7-6
INTEGRATED CARPET MILL WASTEWATER PARAMETERS
(Point Source Category)
Parameters
BOD
TSS
COD
Oil & Grease
Total Chrome
Phenol
Sulfide
pH (Units)
Mill Effluent
mg/l
300
120
1000
—
0.42
0.13
0.14
6 to 9
1977 Limit*
mg/ I
56.3
79.3
507
—
0.29
0.29
0.58
6 to 9
Percent
Removal Required
81.2
338
49.3
—
31
0
0
—
*Values are 30 day average - Maximum for any one day is twice 30 day average
Figure 7-7 represents the flow diagram of a treatment facility capable of achieving the removal
efficiencies necessary to meet 1977 regulations. This facility consists of latex segregation and
settling, screening and biological treatment.
7-19
-------
Segregated latex waste
Mill effluent
To
receiving
stream
Clarifier
Latex recovery or
dewater & disposal
to landfill
Settling or
chemical
coagulation
Screening
Nutrients
(if required)
Solids to
landfill
Anti-foam
(if required)
Aeration basin
Bio-sludge
Aerobic
digester
Gravity
thickener
Supernatant
Drying bed
Supernatant
To landfill
Filtrate
FIGURE 7-7
CARPET MILL WASTEWATER TREATMENT MODEL SCHEMATIC
MEETING 1977 (BPT) LIMITATIONS
7-20
-------
7.7.1 Latex Segregation
Latex wastewaters from backing operations are segregated and collected separately. The latex
solids are settled in lagoons or are chemically coagulated and precipated. Sludge may be disposed
of in a landfill; however, recent regulations governing such disposal must be complied with. The
State of Georgia requires that latex sludge be "bladable" prior to landfill disposal. To meet this,
a cake of approximately 55% solids may have to be produced using more extensive sludge de-
watering methods.
7.7.2 Screening
Carpet mills discharge short fibers, strings, lint, fluffy yarns and small solids. If not removed,
these materials impair subsequent biological treatment, particularly in low flow plants. These
solids have been effectively separated using a hydraulically-cleaned sieve.
7.7.3 Biological Treatment
The activated sludge-extended aeration process may be selected for treating carpet mill waste-
waters. Nutrient deficiency occurs in carpet wastes as it does in most textile wastes. Nitrogen as
aqueous ammonia or anhydrous ammonia may be added to the waste as it enters the aeration
basin.
Foaming problems are common due to latex foam in the backing process. Some mills experience
foaming throughout the entire treatment facility. Conventional water sprays are not capable of
effectively reducing the foaming. Anti-foam agents may be used to alleviate this problem.
Though activated carbon may also be used to control foaming, its catalyst effects on biological
treatment are not necessary to meet effluent limits.
7.7.4 Sludge Treatment and Disposal
Biological sludge is stabilized using aerobic digestion. This process has consistently demonstrat-
ed its value in the digestion of biological textile sludge. Supernatant from the digester is re-
turned to the aeration basin. Digested sludge is thickened using a gravity thickener. Supernatant
is also returned to the aeration basin.
Sludge disposal on open sand drying beds is common practice for many textile mills. A well di-
gested sludge will result in optimum drying. Filtrate from drying beds is returned to the aera-
tion basin, and dried sludge is hauled to a landfill. An alternative method of sludge disposal may
be land application. Sludge at concentrations of 1.5 to 4% solids have been successfully sprayed
onto the land. The system consists of pumps, distribution pipes and sprinkler heads.
7-21
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7.8 Stock and Yarn Dyeing and Finishing Wastewater Treatment
Stock and yarn dyeing and finishing wastes are different from those of woven fabric finishing
because there are no desizing operations performed. They are different from knit fabric finish-
ing because there are no knitting oils to be scoured out before dyeing.
Wastewater characteristics in stock and yarn dyeing and finishing plants vary from plant to
plant. Wastes generated depend substantially on whether natural fibers, blends or synthetics
alone are processed.
When cotton thread is processed, mercerizing and heavy bleaching are required because of fiber
impurities. Wastewaters generated are relatively high in BOD, detergent level, fiber impurities,
dissolved solids, color, and pH. Because of the small amount involved, caustic soda recovery from
mercerizing is generally not practiced. When synthetic yarn or raw stock is processed, merceriz-
ing is not required, and only a light bleaching is performed. These wastewaters reflect lower BOD
and dissolved solids.
Table 7-7 below represents average mill waste load characteristics, effluent limitations for point-
source discharge, and required removal efficiencies for stock and yarn dyeing and finishing
operations.
TABLE 7-7
STOCK AND YARN DYEING AND FINISHING WASTEWATER PARAMETERS
(Point Source Discharge)
Parameters
BOD
TSS
COD
Oil & Grease
Total Chrome
Phenol
Sulfide
pH (Units)
Mill Effluent
mg/l
250
75
800
—
0.27
0 12
0.09
11
1977 Limit*
mg/l
22.6
58
282
—
0.4
0.4
0.8
6 to 9
Percent
Removal Required
91
22.7
64.8
—
0
0
0
—
*Values are 30 day average - Maximum for any one day is twice the 30 day average
The flow diagram presented in Figure 7-8 represents a treatment facility capable of achieving
removal efficiencies necessary to meet 1977 effluent limitations.
The treatment facility consists of screening, neutralization, and biological treatment. Sludge
treatment involves aerobic digestion, gravity thickening, and disposal via drying beds and landfill
or spray irrigation.
7-22
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•Acid
Mill effluent
Screening
(if required)
Neutralization
(if required)
To
receiving
stream
Clarifier
Bio-sludge
Sludge
lagoon
Aerobic
digester
Gravity
thickener
Supernatant
Nutrient
(if required)
Aeration basin
Drying bed
Supernatant
To landfill
Filtrate
FIGURE 7-8
STOCK AND YARN DYEING AND FINISHING WASTEWATER
TREATMENT MODEL SCHEMATIC
MEETING 1977 (BPT) LIMITATIONS
7-23
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7.8.1 Screening
Stock and yarn dyeing and finishing mills generate very small amounts of suspended solids.
These suspended solids are natural fiber impurities from bottom yarn and short fiber resulting
from mercerizing, bleaching, and dyeing. Fibers cause clogging in the system and impair the
biological process and, therefore, if present, should be removed. A fine mesh screen is suitable
for this task.
7.8.2 Equalization/Neutralization
Equalization, with or without neutralization, may be necessary when wastewaters exhibit a
widely fluctuating pH due to changing of yarn types. When cotton yarns are processed, sodium
hydroxide used in mercerizing may result in a mill effluent with a pH in the range of 11 to 14.
While raw stock or synthetic yarns do not require mercerizing, mill effluent pH is about 8.0.
Although activated sludge systems can be operated with textile wastes at a high influent pH up
to 10.5, the system is easily upset when changes of one or two pH units occur. Specialized
bacteria are developed which acclimate to the high pH mill wastewaters. However, when changes
occur in processed materials and when pH is affected, bacterial kills lower the efficiency of the
biological process.
As discussed above, neutralization may be practiced ahead of biological activated sludge where
dyeing and finishing of more than one yarn type are involved. Neutralization to a pH range of 7
to 8 should be adequate.
7.8.3 Biological Treatment
The extended aeration activated-sludge system is effective in treating stock and yarn dyeing and
finishing wastewaters. Nitrogen deficiency is experienced in stock and yarn dyeing wastes as it is
in other textile subcategories. Aqueous ammonia or anhydrous ammonia is added to serve as a
nitrogen source. Color, though relatively high, will not interfere with biological treatment. The
activated sludge process may be capable of removing better than 50% of the incoming color.
Chromium content is generally low and, therefore, is not expected to present problems in bio-
logical treatment.
7.8.4 Treatment and Disposal
Sludge treatment may not be necessary since solids content is very low. Wasted sludge of small
amounts from the activated sludge system can be treated in sludge lagoons. In cases where
wasted sludge is a substantial amount, aerobic digestion is found suitable. Digested sludge may
be thickened by a gravity thickener. Supernatant is returned to the aeration basin, and thicken-
ed sludge is dewatered before final disposal. Thickened sludge may be further dewatered by open
drying beds. Sludge cake is then suitable for disposal to a landfill. Filtrate from the drying beds
is returned to the aeration basin. An alternative disposal method is to pump thickened sludge to
a spray irrigation site.
7-24
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7.9 Color Removal
7.9.1 Wool Scouring Wastewater
Color from wool scouring is generated from impurities (dirt, blood, suint, etc.) in raw wool
fiber and is likely to be reduced as a result of reduction in oil and grease and suspended solids.
7.9.2 Wool Finishing Wastewater
At the present time, most wool that is dyed is wool/polyester blends with very little 100% wool
being dyed. The most common dyes used for wool and wool/polyester blends are acid and metal-
lized dyes. Others used are mordant (chrome) dyes. Generally 100% wool cloth is dyed using
metallized dyes which have a high affinity for wool and are considered fast.
Acid dyes are water soluble while disperse dyes are water insoluble. Acid dyes are responsive to
activated carbon adsorption and lime coagulation. Disperse dyes are responsive to alum coagula-
tion and respond reasonably well to lime coagulation; however, they are not responsive to acti-
vated carbon adsorption.
Chrome removal using copperas and lime will result in some color removal as well. The color
removal is not significant since optimum pH for chrome reduction is 8.5 while that for color
removal is 5.0. Additional color removal, if required, can be achieved by alum coagulation and
activated carbon adsorption.
7.9.3 Dry Processing Wastewater
Color is not likely to be a problem for this category.
7.9.4 Woven and Knit Fabric Finishing Wastewater
The three most common dyes used in the dyeing process of 100% cotton woven or 100%
cotton knit fabrics are direct, vat, and sulfur dyes. For cotton/synthetic blends, disperse dyes
are commonly used in combination with direct, vat, or sulfur dyes. In processing 100% synthet-
ic fibers, the most common dyes used are disperse, acid, and basic (also known as cationic) dyes.
Additional dye types include developed, naphthol, and fiber reactive dyeing. It should be noted
that most finishing plants use more than one class of dye thus complicating color removal.
Color removal for both woven and knit fabric finishing using direct dyeing would require physi-
cal treatment using activated carbon adsorption. Chemical coagulation cannot achieve satisfac-
tory removal of soluble dyes, and biological treatment may not provide adequate color removal.
Some of the direct dyes would have sufficient affinity for the sludge in a biological waste treat-
ment plant to be absorbed and removed from the wastewater. Color removal by biological
7-25
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treatment could be improved by adding activated powdered carbon (as a catalyst) to the aera-
tion basins of activated sludge systems. Of course, this treatment will not remove color as effi-
ciently as adsorption in activated carbon columns; however, an additional color reduction of
about 20 to 55% could be realized from this process. Experiments by Rodman of the Fram
Corporation on color removal for direct dyes showed that in a catalyzed reactor when am-
monia sulfate is used as a nutrient instead of ammonium chloride, better color removal will
result. Biological treatment with powdered activated carbon appears feasible for treating woven
finishing wastes where effluent limitations require approximately 80% color removal. Additional
benefits of the use of powdered carbon would be the increase in efficiencies of BOD and COD
removal and reduction in foaming problems.
In both woven and knit fabric finishing mills using vat dyes, color removal using alum coagula-
tion may be accomplished following the biological process. The chemical process is capable of
removing approximately 80% of the color. Optimum removals are achieved when the pH is ad-
justed to about 5.0 in the chemical coagulation process. If biodegradable dispersing agents
are used in the commercially prepared vat dyes, the dispersion may be destroyed in biological
treatment and the dye may be reduced by adsorption on the sludge. However, the pigment is
fairly inert and therefore chemical coagulation by alum addition appears to be the best method
for color removal.
In some cases where color removal requirements are more stringent than chemical coagulation
can achieve, ozonation may provide the additional color removal necessary.
Color removal for woven and knit fabric using sulfur dyes may also be provided by chemical
coagulation using alum as a coagulant and a polymer as a flocculant. Alum coagulation can re-
move up to 80% of the color. If color limits require additional removals, ozonation may pro-
vide the remaining reduction. Excess sulfide used in the dyeing process will be readily oxi-
dized in the activated sludge system, and odor is not expected to be a problem if the pH is
above 7.5.
Chemical coagulation using alum is excellent for color removal of disperse dye wastes while
chemical coagulation using lime also produces good color removal. Disperse dye wastewaters
are not responsive to color removal by activated carbon adsorption because their rate of adsorp-
tion onto carbon, like their rate of adsorption on textile fibers, is prohibitively long at room
temperature. The rate of adsorption can be increased with heat, but heating is not usually
feasible with most waste streams. Although disperse dye wastewater is not responsive to acti-
vated carbon adsorption, color removal is good in the activated sludge extended aeration system
when activated carbon is used as a catalyst. Color removal of approximately 70% has been
achieved in the catalyzed extended aeration process.
In woven and knit fabric finishing of 100% synthetic fibers using acid dyeing, the treatment
process used to meet 1977 limitations will also result in some color removal. Acid dyes have
good water solubility and are difficult to remove by the activated sludge process. Activated
7-26
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sludge may remove 30 to 40% of the color. In an activated sludge process with activated car-
bon as a catalyst, color removals of approximately 90% can be achieved. Activated carbon
adsorption is an excellent method for color removal of acid dye waste. Experiments by
Rodman (Textile Chemist and Colorist Nov. 11, 1971) showed that although acid dyes have
good water solubility, chemical coagulation by lime produces excellent color removals for acid
dyes wastes and that chemical coagulation by alum also produces good color removal.
Color removal for 100% synthetic woven and knit fabric finishing using basic dyes is accom-
plished to a great extent in activated sludge treatment. Activated carbon added as a catalyst
will increase color removal. Additional color removal if required would necessitate activated
carbon adsorption.
In knit fabric finishing mills where knitting oils are present in high levels and cause problems in
biological treatment, both color removal and oil removal may be effectively accomplished using
ultrafiltration. This process, though not considered established technology, has the potential
for recycle of both the permeate (water) and concentrate (dyes).
7.9.5 Carpet Mill Wastewater
Acid dyes are the most common dyes used in carpet dyeing since nylon fiber is widely used as
well as other synthetic fibers. Most wool used in carpets is dyed in yarn form with the use of
acid dyes predominating. Other dyes used for carpets are disperse and small amounts of cationic.
Acid dyes are water soluble and may or may not be removed by the activated sludge process.
Activated carbon adsorption is considered the best method for color removal. Ozonation has
also been successful in reducing color from carpet mill wastewater effluents. See Chapter 8,
Section 8.11.4 for details.
7.9.6 Stock and Yarn Dyeing and Finishing Wastewater
Dyes used for stock and yarn dyeing are similar to those used for woven and knit fabric finish-
ing. Dye types will depend substantially on whether natural fibers, blends or synthetics are
processed. Most common dyes used for stock and yarn dyeing are vat, direct, sulfur, disperse,
acid and basic dyes. Some of this color may be removed by the activated sludge process. A re-
duction of approximately 30 to 44% is possible at a retention time of 3 to 4 days.
Direct, acid and basic dyes are water soluble. They are responsive to activated carbon adsorp-
tion. Adding activated carbon into the aeration basin as a catalyst will improve color removal
in the activated sludge process. Acid dyes are also responsive to lime coagulation while direct
dyes are not.
7-27
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Vat, sulfur, and disperse dyes are insoluble dyes. They are responsive to alum coagulation. Dis-
perse dyes are not responsive to activated carbon adsorption; however, adding activated carbon
into an aeration basin as a catalyst will improve color removal in the activated sludge process.
Additional color removal may be achieved by ozonation.
7.10 References
Rhame, G.A., "Aeration Treatment of Textile Finishing Wastes in South Carolina", American
Dyestuff Reporter, November, 1971.
McCarthy, J.A., "A Method for Treatment of Wool Scouring Wastes", Sewage Works Journal,
Volume 21, No. 1, January, 1949.
U.S. Environmental Protection Agency, Technology Transfer, "Anaerobic-Aerobic Treatment
of Textile Wastes with Activated Carbon", Calvin P.C- Poon and P.P. Virgadamo. Project 12090
EQO, May, 1973.
U.S. Environmental Protection Agency, Technology Series, "Chemical/Physical and Biological
Treatment of Wool Processing Wastes", L.T. Hatch, et. al. Project 12130 HFX-660/2-73-036,
January, 1974.
U.S. Environmental Protection Agency, Development Document for Effluent Limitations
Guidelines and New Source Performance Standards for the "Textile Mills", June, 1974.
American Dye Manufacturers Institute, "Dyes and the Environment", Volume I, September,
1974.
American Dye Manufacturers Institute, "Dyes and the Environment", Volume II, September,
1974.
Federal Register, Chapter 40, Environmental Protection Agency, Effluent Guidelines and
Limitations for Textile Mills as found in July 5, 1974.
Ameen, J.S., "How the Effluent Guidelines Affect You", Textile Industries, October, 1974.
Lund, H.F., Industrial Pollution Control Handbook, Chapter 15, McGraw Hill Book Company,
1971.
U.S. Environmental Protection Agency, Technology Transfer, "In-Plant Control of Pollution,
Upgrading Textile Operations to Reduce Pollution", Institute of Textile Technology, October,
1974.
7-28
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U.S. Environmental Protection Agency, Technology Transfer Seminar, "Pretreatment of Textile
Wastes," Lockwood Greene Engineers, Inc., January, 1975.
Rodman, C.A., "Removal of Color from Textile Dye Wastes," Textile Chemists and Colorists
(3), No. 11,239-247, 1971.
U.S. Environmental Protection Agency, Industrial Waste Studies Program, "Rough Draft Report
on Textile Mill Products," Arthur D. Little, Inc., May, 1971. (Unpublished).
U.S. Environmental Protection Agency, State of the Art of Textile Waste Treatment, Clem-
son University (FWPCA Project 12090 ECS), August, 1971.
"Symposium on the Textile Industry and the Environment," American Association of Textile
Chemists and Colorists, March 31, 1971.
"Symposium on Textile Technology/Ecology Interface 1975," American Association of Textile
Chemists and Colorists, May 28, 1975.
The National Commission on Water Quality, Textile Industry Technology and Costs of Waste-
water Control, Lockwood Greene Engineers, Inc., (NCWQ Contract No. WQ5AC-021), June,
1975.
Masselli, J.W., et al., "Textile Waste Treatment — Past, Present and Future," American Asso-
ciation of Textile Chemists and Colorists, Symposium, May, 1973.
Souther, R.H. and T.A. Alspaugh, "Textile Wastes Recovery and Treatment," Sewage and Indus-
trial Wastes, Volume 29, No. 8, August, 1957.
U.S. Department of the Interior, Federal Water Pollution Control Administration, The Cost of
Clean Water: Volume III, Industrial Waste Profiles No. 4, Textile Mill Products, (FWCA Con-
tract Number 14-12-101), June 30, 1967.
Porter, J.J., "Treatment of Textile Waste With Activated Carbon," American Dyestuff Reporter,
24-27, August, 1972.
Leatherland, L.C., "Treatment of Textile Wastes," Proceeding 24th Purdue Industrial Wastes
Conference, Purdue University, Lafayette, Indiana, May, 1969.
Rodman, C.A. and P. Virgadamo, "Upgrading Treated Textile Wastewater," American Dye-
stuff Reporter, August, 1972.
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U.S. Environmental Protection Agency, Technology Transfer, "Wastewater Treatment System,
Upgrading Textile Operations to Reduce Pollution", Metcalf and Eddy, Inc. Engineers, October,
1974.
Hill, B.V., "Water Pollution Control in the Textile Industry", Industrial Water Engineering,
April, 1969.
Federal Register, Chapter 40, Environmental Protection Agency, Water Program, Pretreatment
Standard, November 8, 1973.
Porter, J.J., "What You Should Know About Waste Treatment Processes", American Dyestuff
Reporter, August, 1971.
Anderson, C.A., "Wool Grease Recovery and Effluent Treatment", Textile Journal of Australia,
A'pril, 1965.
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CHAPTER 8
WASTEWATER TREATMENT FACILITIES DESIGN
8.1 Introduction
This Chapter is intended to be a practical guide, or aid, to be used with engineering judgment
and experience in the design of textile wastewater treatment facilities.
The reader is reminded that the design parameters contained herein are intended only as a guide
based upon past experiences. It is suggested that where possible laboratory treatability studies
be conducted to determine most effective treatment methods and optimum parameters for
full scale design. For detailed design techniques and calculations of industrial waste treatment
units, the reader is referred to the following sources: References 1, 2, 3, and 4.
In meeting the objectives of the water pollution abatement program, it will be necessary for the
textile industry to achieve very high percentage removals of pollutants; capital investments will
naturally be substantial. It is for these reasons that the designer must utilize optimum design
capabilities for all equipment used as part of the complete waste treatment system.
A qualified engineer can usually select a preferred treatment method from the available alterna-
tives based upon accumulated data, past experience, and logic. Occasionally, two systems or pro-
cess units will appear so nearly comparable that it is difficult to make a decision. Cost estimates
can usually resolve this problem. Capital, operating, and maintenance cost estimates are evalu-
ated as part of the decision making process. The subject of unit cost, both capital and O&M,
has been detailed by a number of publications to which the reader is referred as follows: Refer-
ence 5, 6, 7, 8, and 9. These publications generally provide graphical relationships between cost
(capital, annual) and size (flow, production).
In addition, consideration for future expansion or upgrading of facilities cannot be overempha-
sized. Much can be gained by preplanning and incorporation of adequate space, capacity, and
durability for the future into today's designs.
8.2 Basic Design Considerations
8.2.1 In-Plant Changes
Changes in plant processes or chemicals used will affect waste effluent quantity and quality.
Consideration should be given to planned changes and their potential effect.
8-1
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8.2.2 Degree of Treatment Required
Initial design is based upon meeting EPA point source limits using best practicable control
technology (BPT). However, special consideration must be given for the more stringent water
quality limited situation and, of course, for pretreatment before discharge to municipal systems.
8.2.3 Anticipated Treatment Efficiencies
The ability of a particular unit process to remove pollutants is dependent upon specific effluent
wastewater characteristics. Table 8-1 illustrates a range of treatment removal efficiencies gener-
ally attainable with textile wastewaters.
TABLE 8-1
ANTICIPATED TREATMENT REMOVAL EFFICIENCIES
Treatment Unit
Process
Primary Treatment
Screening
Equalization
Neutralization
Chemical Coagulation
(removals vary with chemicals
and dosage used)
Flotation
Secondary Treatment
Conventional Activated
Sludge and Clarification
Extended Aeration and
Clarification
Aerated Lagoon and
Clarification
Aerobic Lagoon
Packed Tower
Roughing Filter
Tertiary Treatment
Chemical Coagulation
Mixed Media Filtration
Carbon Adsorption
Chlorination
Ozonation
Advanced Treatment
Spray Irrigation
Evaporation
Reverse Osmosis
Range of Removal Efficiency in Percent
BOD5
0-5
0-20
40-70
30-50
70-95+
70-94+
60-90
50-80
40-70
40-60
40-70
25-40
25-40
0-5
—
90-95
98-99
95-99
COD
—
40-70
20-40
50-70
50-70
45-60
35-60
20-40
20-30
40-70
25-40
25-60
0-5
30-40
80-90
95-98
90-95
TSS
5-20
30-90
50-60
85-95
85-95
85-95
50-80
—
30-90
80
25-40
50-70
95-98
99
95-98
Grease
=
90-97
90-98
0-15
0-15
0-10
0-10
—
90-97
0-5
—
—
Color
=
0-70
Color
removals for
biological
treatment
units not
documented
0-70
80-90
0-5
70-80
—
Source National Commission on Water Quality. Textile Industry Technology and Costs of Wastewater Control,
Lockwood Greene Engineers, Inc , June 1975
8-2
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8.2.4 Design Period
It is usual practice to design treatment facilities for a 15- to 25-year life span.
8.2.5 Future Expansion
Anticipated manufacturing plant expansion should be considered in terms of sizing wastewater
conduits, structures and equipment for the most economical accommodation of future waste
loads.
8.2.6 Seasonal Considerations
It is possible that manufactured goods will change, depending upon the season of the year. Of
course, in the textile industry, this change is more directly related to market demands (fashions)
and is almost impossible to predict, e.g., the surge in the use of denim.
Another seasonal consideration is that of climate. Ambient temperatures have a definite effect
on biological treatment processes as well as on the operation of mechanical equipment.
8.2.7 Costs
In our cost-conscious society, it behooves the design engineer to investigate the most economi-
cal construction methods and materials available to accomplish the abatement project; e.g., the
use of earthen lagoons and, where possible, locally available materials.
8.2.8 Degree of Automation
It is important at the onset of the project that the design engineer determine from the client
the extent of automation he wishes built into the treatment facility. Automation has the po-
tential for reducing otherwise necessary labor costs as well as reducing chemical wastage.
8.2.9 Sludge Disposal Methods
The decision making for sludge disposal will depend heavily upon economics. There are, how-
ever, other considerations such as ultimate disposal regulations, availability of landfill, and po-
tential markets such as agricultural uses or energy sources.
8.2.10 Multiple Units and Emergency Power
It is the practice of most regulatory agencies to require continuous operation of the treatment
facilities with the largest unit out of service with essentially no change in the degree of treat-
ment. Emergency storage alone may be adequate for industrial facilities.
8-3
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Standby power is required by most agencies for municipal facilities. It is not expected that
standby power is required for industrial facilities, unless the manufacturing plant is so equipped
to maintain operation during periods of primary power failure.
It should be recognized, however, that a biological treatment facility without power for feeding
raw waste or providing oxygen, for an extended period of time, may result in a kill of micro-
organisms.
8.2.11 Design Standards
A recent survey of most state environmental agencies in the U.S. revealed that none have formal
design standards which relate to textile manufacturing. In fact, with regard to industrial facili-
ties most states review design requirements on a case-by-case basis. As a guide, many states uti-
lize established criteria such as those created by the Ten States and New England Interstate
Water Pollution Control Commission (10), (11). These works are based upon municipal facilities
treating domestic wastes. Some states have written their own set of design standards for sew-
agei works; however, many of these are also based upon the most popular Ten States.
Though commonly known as the Ten States Standards, these standards were created by a com-
mittee of the Great Lakes — Upper Mississippi River Board of State Sanitary Engineers. Member
states include the following: Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, New York,
Ohio, Pennsylvania and Wisconsin. The intent of these standards is contained in the foreword of
the 1971 revised edition and reads as follows:
These standards are intended for use as a guide in the design and preparation of plans and
specifications for sewage works; to list and suggest limiting values for items upon which an
evaluation of such plans and specifications will be made by the reviewing authority; and
to establish, as far as practicable, uniformity of practice among the several states. Statu-
tory requirements among the states are not uniform and use of the standard must adjust
itself to these variations.
The design section of this chapter will present excerpts of design considerations from the Ten
States or New England standards considered applicable to textile wastewater treatment.
8.3 Site Requirements
8.3.1 Topography
Site selections will depend very heavily upon topography of the area under consideration. The
terrain will determine the ability to utilize gravity flow or the need for pumping facilities. Costs
will be affected by power for pumping facilities and during construction by the amounts of cut
and fill required.
8-4
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8.3.2 Buffer Zone
Affecting site selection will be local zoning restrictions and the requirements for buffer areas.
Distances to nearest habitable and adjoining property owners are set by some states while other
states review on a case-by-case basis. Following are examples of minimum distances set:
Treatment Units — 150 ft. from habitable property lines
— 300 ft. from residences
Spray Irrigation Sites — 200 ft., preferably wooded
8.3.3 Flood Plains
Most regulations require that if any portion of the facilities will be subject to upland or tidal
flooding, the engineer must discuss the extent and effects of such flooding with the agency.
Precautions against flooding will usually be required to be incorporated into the design.
8.3.4 Subsurface Groundwater
The existence of a high groundwater table on the plant site can cause difficulties. There is the
problem of below ground construction as well as the potential for groundwater contamination
from spills and leaks.
8.3.5 Soil Conditions
Subsurface soil bearing loads and the existence of rock will seriously affect foundation require-
ments and construction methods to be employed. Soil boring tests should be performed.
8.3.6 Existing Facilities
The location of existing facilities and the capacity to deliver necessary power, chemicals, water,
etc. is an item of concern related to construction cost as well as operating cost.
8.3.7 Receiving Stream
It is important to know the capacity and quality of receiving waters as water quality effluent
limitations may be more stringent than EPA guidelines.
8.3.8 Future Expansion
Associated with site selection is the consideration for expanding the proposed facilities, either
by enlarging existing units or providing additional units. The site should be flexible and allow
for future expansion without disrupting present operations.
8-5
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8.3.9 Miscellaneous
Good design practices also suggest the need for providing the following at selected sites:
• Access Roads
• Walkways
• Area Lighting
• Fencing
• Warning Signs
8.4 Sewers and Pumps
8.4.1 Gravity Sewers
A sewer has two main functions: 1) To carry the maximum discharge for which it is designed;
and, 2) to transport suspended solids without their deposition into the pipe. The first function
requires that an estimate be made of the peak flow which the sewer must carry; and the second
requires that the designer have information as to the fluctuation of discharge during periods of
low flow and as to the character of the suspended matter to be transported.
In terms of pipe materials, sewers may be vitrified clay, cast iron, or concrete to name a few.
Cast iron is generally the preferred choice because though more expensive it can be used under-
ground without fear of leaks or breakage. Vitrified clay may also be considered a good choice
because of its resistance to varying pH of textile waste and because of its lower costs. Trench
load will also have a bearing on pipe selection.
In the design of sewers, the following considerations are given by the Ten States Standards:
• Design for mean velocities, when flowing full, of not less than 2.0 feet per second, based
on Kutter's formula using an "n" value of 0.013.
• Sewers to be laid with uniform slope between manholes.
• Avoid velocities greater than 15 feet per second.
• Manhole required every 400 feet for sewer 15 inches diameter or less and 500 feet for
sewers 18 to 30 inches diameter.
• Drop type manhole required for sewer entering manhole 24 inches or more above manhole
invert.
8.4.2 Centrifugal Pumps
In general, most textile mill effluents can be pumped by centrifugal pumps. This classification
includes radial flow, axial flow and mixed flow types. Pump impellers may be closed, semiopen
or open. Radial flow pumps are manufactured as horizontal or vertical while axial or mixed flow
are constructed vertically.
8-6
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Centrifugal pumps should be avoided for applications with very viscous liquids, high solids con-
tent or low flows with high heads.
8.4.3 Positive Displacement Pumps
Included in this classification are piston, plunger and diaphragm type pumps. These pumps are
used to feed metered quantities of chemicals and also to pump waste sludge. Suction and dis-
charge valves used are commonly ball-type.
8.4.4 Rotary Screw Pumps
This type of pump is commonly used to transfer sludge. The progressing cavity rotary pump is
suitable for handling heavy concentrated sludge.
8.4.5 Air Pumps
These are specialized pumps such as the pneumatic ejector or air-lift pump. The pneumatic
ejector is used when quantities of waste are small and future increase in flow is limited. An
advantage of this type of pump is its lack of moving parts in contact with the waste, therefore,
less tendency to clog. Air-lift pumps are suited to the transfer of mixed liquors or slurries. Flow
rates can be high for short distances.
8.4.6 Pumping Stations
Pumping stations are generally either of the dry well type or the wet well type. Prefabricated
package type stations are available to meet the needs of the largest textile treatment uses. The
Ten State Standards, though written for domestic wastes, presents some important considera-
tions in the design of pumping stations:
• Protect pumps from clogging by use of bar racks or screens.
• Make provisions for removing pumps and motors.
• Provide duplicate pumps of equal capacity.
• Provide automatic controls and automaticaDy alternate pumps in use.
• Activate an alarm in case of pump failure.
• Adequate ventilation should be provided.
8.5 Suspended Solids Removal
Suspended solids include both organic and inorganic materials. The inorganic components
include sand, silt, and clay. The organic portion may include grease, oil, tar, animal fats, fibers,
hair and various other materials.
8-7
-------
Methods most frequently employed for liquid-solids separation include: Screening, sedimenta-
tion (clarification), filtration and flotation. The following sections will present design parameters
for methods most often associated with the removal of suspended solids in textile wastewaters.
8.5.1 . Screening and Comminution
The primary purpose of screening is to prevent clogging of pipes and equipment and to avoid
entrance of fibers and debris into successive treatment units. Clogging is generally caused by
rags, strings or individual fibers of 1 to 2 inches which gather together to form balls or mats.
Fibers which pass through an aeration basin may rise to the surface of settling basins to form
mats or scum and may pass through into the final effluent resulting in an increased suspended
solids concentration. Comminutors are generally required only for shredding the larger solids
and rags associated with the sanitary portion of the plant wastewaters. See Figure 8-1. Textile
waste solids are best handled using one of a number of screening devices available. The type of
screening equipment used will depend upon the fiber size, concentration, subsequent treatment
processes, allowable suspended solids concentration and relative operation and maintenance
costs. If careful in-plant control is used, only a simple bar screen or rack may be required;
however, if a large amount of fibrous material is present, a fine screen will be necessary. A bar
screen or rack may be either hand or mechanically cleaned, (see Figure 8-2 and 8-3).
Rotating screen
with cutters
FIGURE 8-1
COMMINUTOR WITH ROTATING SCREEN
Source: Environmental Engineer's Handbook
8-8
-------
21/4" x %" bar
welded to
rack bars
Grout bar
rack
in place
1— — r-6" — *-J
I I
1" diam. drainage
hoes
> o'<
t
ooooooo-gl^
0000000-grE
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DRAINAGE PLATE PLAN
4'/z" button head
SS bolts
3/8" drainage plate
1" square bar welded'
to each rack bar
Variable-
s'' channel at
4 25 Ibs/ft
RACK DETAILS
FIGURE 8-2
HAND CLEANED BAR RACK
Source: Metcalf & Eddy, Wastewater Engineering: Collection, Treatment, Disposal
8-9
-------
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Fine screens utilize varied methods for solids removal. A description of a number of those
used at textile mills follows:
8.5.1.1 Vibrating Screens
Removal of materials with the vibrating screen is accomplished by an eccentric rotating weight
which causes the screen to vibrate in an orbital pattern forcing solids to roll to the perimeter
where they are collected (see Figure 8-4). Vibration reduces the blinding and clogging of the
fine screens. To further reduce clogging, the screen may be equipped with spray washers or
steam jets.
8.5.1.2 Hydrasieve
Hydraulically-cleaned screens use a jet of water to propel the waste against a series of tiny bars
that allow the water to pass over while the solids are retained and washed to the bottom of the
screen for collection.
Wastewater is fed by gravity to the screen from a headbox. There are no moving parts and the
screen is self-cleaning (see Figure 8-5).
FIGURE 8-4
VIBRATING SCREEN
8-11
-------
Gravity feed of
liquids and solids
Self-cleaning
non-clogging
stainless steel
screen for
continuous
dewatering
Removed or
recovered
solids
Stainless steel
or fiber glass
construction
Headbox
Alternate
feed inlet
Solids
Liquid
ENLARGED SECTION OF THE SCREEN
FIGURE 8-5
HYDRASIEVE
Source: Environmental Engineer's Handbook
8-12
-------
8.5.1.3 Rotating Drum Screen
Removal of materials is accomplished by a screen applied to a cylindrical frame which rotates
while being 1/2 to 2/3 submerged. Solids are retained on the inside or outside of the screen
(depending upon inward or outward flow) and are removed by water sprays, scrapers or brushes
when rotated above the liquid level (see Figure 8-6).
Effluent
Drive sprocket
with shear pin hub
Drive chain
and sprocket
Drumshaft in
grease lubricated bearings
Influent Seal
Wash water spray pipes
Screening
and
wash water
discharge
flume
Refuse trough
Screen frame
and cloths
Link-belt
Splash housing sPraV nozzles motorized
\ / Splash worm gear
lnS^'°n>riX/Plates
reducer
SECTION AA
B
SECTION BB
c
Weir
adjustable
6" vertically
to control
water depth
through
screen
FIGURE 8-6
REVOLVING DRUM SCREEN
Source: Environmental Engineer's Handbook
8-13
-------
Following is a tabulation of screen types and factors used in design and installation of each:
TABLE 8-2
DESIGN PARAMETERS FOR SCREENS
Screen Type
Trash Rack
Manually Cleaned
Mechanically Cleaned
Hydrasieve
Fine Mesh
Comminutor
Spacing
2" to 6"
1" to 2"
5/8" to 1"
.02" to .03"
40 to 80 mesh*
>1/4" slots
Slope
30° to 45°
30° to 45°
—
25°, 35° , & 45°
None
90°
Velocity
—
2.0 fps. Max.
—
Gravity Flow
—
—
*Mesh size can be obtained in the field
Whenever possible, thorough field or pilot testing of equipment is recommended. Most larger
equipment manufacturers have pilot facilities available for such purposes. It should be noted
that "highly efficient" screening might mean removal of only 10% of the total filterable solids.
One might argue logically that lagooning would probably be cheaper and more effective, but
this method also removes some organic material that can lead to objectionable odors. Also,
extended cloudy periods tend to increase the possibility of carry-overs which could upset sub-
sequent treatment. Other possibilities for fiber removal include simple sand beds or automated
sand filters.
Design flow rates are best determined by field testing. One such test revealed that 900 gpm is
the optimum for a 60-inch vibrating screen. Lower flows increase blinding while higher flows
reduce removal efficiency. Mesh sizes of 40 to 80 may be suitable for removal of lint, but actual
practice has shown 40-mesh screens, in particular, to be inadequate in some cases for this task.
A carpet mill, for example, will discharge longer fibrous waste than would a package dye plant
processing short staple spun yarns. A 40-mesh screen would be appropriate for the carpet; 80-
mesh for the package dyer (12). One manufacturer of a high-speed vibrating screen makes the
following mesh size recommendations (13):
Wool wash water — 40
Mercerizing wash water — 80
Cotton towelling wash water — 60
To aid in the detailed design and installation of screening facilities, the following are considered
widely adopted standards:
• Deep pits containing screens shall be provided with stairway access, adequate lighting and
ventilation, and convenient and adequate means for removing screenings.
8-14
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* Screening devices installed in a building where other equipment or offices are located
should be separated from the rest of the building, provided with separate outside entrances,
and provided with adequate means of ventilation.
* Manually Cleaned Screens: Clear openings between bars should be 1% to 2 inches. Design
and installation of bar screens shall be such that they can be conveniently cleaned. Hand-
cleaned screens should be placed on a slope of 30 to 45 degrees with the horizontal.
* Comminuting devices shall have slots not less than 1/4 inch wide and be designed to shred
material below the surface of the wastewater. Comminutor capacitor shall be adequate to
handle peak flows.
* A by-pass screen shall be provided except where there are multiple units. Where a by-pass
screen is utilized, the overflow to the by-pass channel should occur when the influent
channel is flowing at a depth which corresponds to the design flow through the comminu-
tor. The overflow to the by-pass screen should be automatic so as to prevent flooding
caused by clogging of the comminutor.
• Velocities: Screen chambers should be designed to provide a good velocity distribution
across and through the screen of approximately two feet per second at average rate of
flow. The velocity shall be calculated from a vertical projection of the screen openings on
the cross-sectional area between the invert of the channel and the flow line.
• Channels: The channel preceding and following the screens shall be shaped to eliminate
standing and settling of solids. Fillets may be necessary.
• All mechanical units which are operated by timing devices should be provided with auxili-
ary controls which will set the cleaning mechanism in operation at predetermined high
water marks.
• Screenings: Adequate facilities must be provided for removal, handling, storage, and dis-
posal of screenings.
• Auxiliary Screens: Where mechanically operated screening or comminuting devices are
used, axuiliary hand-cleaned screens shall be provided. Design shall include provision
for automatic diversion of the entire wastewater flow through the auxiliary screens
should the mechanical units fail.
• Fine Screens: The use of fine screens may be required in special cases where the fea-
tures peculiar to this equipment may be used to advantage.
8-15
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8.5.2 Clarification
Clarification, also termed sedimentation, uses the force of gravity to remove settleable solids
from wastewaters. Sedimentation is one of the simplest and most widely employed waste treat-
ment processes. Sedimentation is usually used for BOD and settleable-solids removal. Primary
sedimentation is usually omitted in most textile waste treatment plants due to low settleable
solids levels. However, the settling basin may be a useful site for other pretreatment, when it is
available, and may be part of the pretreatment system. It may be used for partial equalization,
fiber removal, scum removal, pH regulations, chromium removal, chemical coagulation, sulfide
treatment, and phenolic treatment. Usually, the tank is sized to provide a 3-hour detention, and
scum and settleable-solids removal are mechanically accomplished. Chemical coagulation at this
point may aid in reducing the insoluble BOD loads to the treatment plant. An idealized sedi-
mentation basin is shown in Figure 8-7 (14). The basin is divided into four zones; inlet, outlet,
settling, and sludge. The inlet zone must dissipate the kinetic energy of the feed stream and pro-
vide a uniform distribution of the flow entering the settling zone without creating excessive
turbulence. The relative importance of proper inlet conditions as compared to outlet conditions
has been shown. The outlet zone is less critical to basin performance, but low approach veloci-
ties to effluent weirs must be maintained for maximum sedimentation efficiency. The difficul-
ties in obtaining optimum inlet and outlet conditions vary with basin shape and flow patterns.
The idealized rectangular basin shown in Figure 8-7 illustrates the situation which occurs when
a perfect inlet distribution of discrete particles occurs with no particle interaction and no resus-
pension of particles from the sludge zone. The resultant vector on the discrete particle is then
made up of its theoretical settling velocity, usually described by Stokes' Law, and the superficial
uniform velocity of the liquid.
In reality, uniform flow has been unattainable in the large tanks normally designed. Short-cir-
cuited turbulence and density currents have been cited as causing the major deviations from the
ideal situation.
The sludge zone serves the two-fold function of retaining the solids so that a minimum of re-
suspension occurs and providing sufficient time for compaction, thereby minimizing sludge
pumping requirements. In most cases, mechanical scrapers are utilized to move the sludge
slowly to the pump draw-off area. An alternative device uses suction to remove the sludge at
its deposition point, thereby eliminating the need for displacement prior to removal.
8.5.2.1 Primary Sedimentation
Primary clarifiers are designed to remove the settleable solids and their associated organic load
from the wastewater. Textile wastewaters are generally low in settleable solids and often do not
need primary clarification. The basis of design is the overflow rate, usually expressed in gallons/
day/square foot (gpd/sq. ft.), which is equal to the flow in gallons/day divided by the surface
8-16
-------
area of the clarifier in square feet. It is obvious that overflow rate in itself does not totally deter-
mine the efficiency of a tank. In addition to the previously noted influent and effluent zone
effects, the basin shape and size as well as the settling characteristics of each individual waste-
water will influence the solids removal efficiency of a given sedimentation tank. Seasonal tem-
peratures can also exert a significant influence on basin performance. The efficiency of primary
sedimentation facilities varies widely.
Inlet
zone
Outlet
zone
\
^ Effective ^
settling
— »- zone — »~
"~ t t t t t * * ~~
Solids removal zone
/
FUNCTIONAL ZONES IN AN IDEALIZED
SEDIMENTATION'BASIN
Surface area A
IDEALIZED SETTLING PATHS OF DISCRETE
PARTICLE IN A HORIZONTAL FLOW TANK
FIGURE 8-7
SETTLING BASIN
Source: Environmental Protection Agency, Process Design Manual for
Suspended Solids Removal
8-17
-------
8.5.2.2 Secondary Sedimentation
The principles governing design of secondary sedimentation tanks are significantly different
from those used for primary clarifiers. The major reason for the difference lies in the amount
and nature of the solids to be removed. While primary settlers are designed on the basis of
overflow rate alone, secondary clarifiers must be designed on the basis of overflow rate and
solids loading. The greater concentration and lighter nature of the mixed-liquor suspended
solids requires that the underflow concentration be considered in design. Settling rates are
slower, as hindered settling prevails instead of free settling which occurs in primary basins. The
information needed for an accurate determination can be obtained from laboratory settling
tests. After the limiting solids loading has been determined on the basis of desired underflow
concentration, the required area of basin can be computed using design flow and mixed-liquor
suspended solids (MLSS)Concentrations. The area required by this calculation and the area re-
quired by the overflow rate must then be compared, with the larger being the design size. A
factor which strongly affects the limiting solids loading is the sludge volume index (SVI). As
this value increases, sludge settling and concentration become more difficult.
TABLE 8-3
DESIGN PARAMETERS FOR CLARIFIERS
Overflow Rate (gpd/ft2)
Detention Time (Hours)
Depth (ft )
Weir Rate (gpd/ft)
Primary
600-800
1-2
7-12
10,000 to 15,000
Final
200-400*
2-4
8-12
5,000 to 10,000
'For extended aeration process lower end of range is suggested
The performance of secondary clarifiers is not generally cited, as they are considered integral to
activated sludge systems; however, they can be rated on the basis of effluent quality to some
extent. Usually, a large portion of the effluent organic content is associated with the suspended
solids. Although no clarifier will completely remove all suspended solids, a properly designed
facility should yield a good product if the biological process is working properly. Figure 8-8
illustrates a section through a typical circular clarifier.
Design considerations for secondary settling tanks should include the following:
• Inlets should be designed to dissipate the inlet velocity, to distribute the flow equally and
to prevent short-circuiting. Channels should be designed to maintain a velocity of at least
one foot per second at one-half design flow and to distribute the flow proportionately be-
tween parallel units. Corner pockets and dead ends should be eliminated.
8-18
-------
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8-19
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• The minimum lengths of flow from inlet to outlet should be 10 feet unless special provi-
sions are made to prevent short-circuiting.
• Scum baffles shall be provided ahead of outlet weirs.
• Overflow weirs shall be adjustable. Multiple weir troughs shall be placed sufficiently far
apart to avoid excessive upward velocity between the troughs.
• All settling basins shall be designed to provide easy access for maintenance and protection
to operators. Such features should include stairways, walkways and handrails.
• Provisions shall be made for convenient manual scum removal or for automatic equipment
for scum removal.
• Removal of sludge from primary settling tanks shall be by direct pump suction.
• The liquid depth of mechanically cleaned settling tanks shall be as shallow as practical but
not less than seven feet. Where activated sludge is returned to the settling tanks, the liquid
depth of the tank shall not be less than eight feet.
• The minimum slope of the side walls of sludge hoppers shall be 1.7 vertical to 1.0 hori-
zontal.
• Inlets, sludge collection, and sludge withdrawal facilities shall be so designed as to minimize
density currents and to assure rapid return of sludge to the aeration tanks.
• Multiple units capable of independent operation are desirable and shall be provided in all
plants where design flows exceed 40,000 gallons per day, unless other provisions are made
to assure adequate treatment.
• Effective baffling and scum removal equipment shall be provided for all final settling tanks.
8.5.3 Filtration
Filtration of suspended or colloidal material is accomplished by passing the wastewater through
a bed of granular material resulting in deposition of suspended solids in the bed.
Filtration is the most common form of advanced wastewater treatment practiced. It is used to
treat effluent from secondary biological systems. Of the filter bed types, multi-media filters
exhibit a 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.
8-20
-------
Multi-media beds are composed of various combinations of anthracite, sand, activated carbon,
and resins. Conventional single-medium filters have a fine-to-coarse gradation in the direction of
flow while multi-media is placed coarse to fine providing greater utilization of bed depth. The
filtration units may be either gravity or pressure types as illustrated in Figures 8-9 and 8-10.
Filter performance is directly related to the characteristics of the liquid to be filtered. There-
fore, it is recommended that pilot plant studies be conducted to determine the optimum com-
bination of filter materials. As a guide, the following tabulation of design parameters is pre-
sented:
TABLE 8-4
DESIGN PARAMETERS — MULTI-MEDIA FILTRATION
Hydraulic Load
Solids Load
Depth
Filter Run Time
6 to 12 gpm/ft2
15 Ib/day/ft2
18 to 42 inches
8 hours
Design considerations for granular filters are summarized in EPA's Process Design Manual for
Suspended Solids Removal and include the following:
• Variable hydraulic and suspended solids load must be considered to avoid short filter
runs and excessive backwash. Equalization prior to filtration would be ideal.
• Coarse-to-fine filtration will allow reasonable filter runs.
• Auxiliary agitation of the media is essential to proper backwashing.
• The filtration rate and terminal head loss should be selected to achieve a minimum filter
run length of 6 to 8 hours during peak conditions.
• High filtration rates and/or high influent suspended solids to the filters will cause high
terminal head losses and may favor the use of pressure filters over gravity filters.
• At least two filters should be provided; each should be capable of handling peak design
flows.
8-21
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Graded
gravel
supporting
layers
Transition layer
Fine gravel
Medium gravel
Coarse gravel
M-blocks
Air laterals
Steel plates
Concrete piers
FIGURE 8-10
PRESSURE-TYPE FILTER
Source: Environmental Engineer's Handbook
8.5.4 Flotation
The flotation process most commonly employed in textile waste treatment is that of dissolved
air flotation. Fine air bubbles, less than 100 microns in diameter, are introduced into the ef-
fluent, where due to surface interactions they become attached to the solid particles. As the
bubbles decrease the density of the solids, the separation takes place at the surface of the efflu-
ent rather than at the bottom of the settling basin. Wastewater flotation generally involves pre-
surization of recycled effluent to avoid solids destruction. The raw waste is blended with this
stream following pressure release. Wastewater constituents less dense than water (dye pigments,
solvents, and grease and oil) float to the top of the unit and are removed by a surface skimmer.
Particles heavier than water settle to the bottom of the unit and are removed by a sludge scraper
mechanism and periodic blowoff.
8-23
-------
The principal components of a flotation system include a pressurizing pump, air injection facili-
ties, a retention tank, a back pressure regulating device, and a flotation tank unit (see Figure
8-11). If chemical addition appears warranted, as can be determined by laboratory jar tests,
then a rapid mix tank and flocculation chamber are added to the system.
Advantages of flotation over the use of sedimentation include: less space required, thicker
sludge produced, and an increase in dissolved oxygen content of wastewater.
The following tabulation provides a range of parameters used in the design of a dissolved air
flotation system:
TABLE 8-5
FLOTATION DESIGN PARAMETERS
Hydraulic Loading
Operating Pressure
Gas-to-sohds
Pressurization System Types
Chemical Aids
Contaminant Removals (%)
Grease & Oil
BOD
S.S.
1 to 3 (gpm/ft2)
30 to 75 (psig)
0.01 to 0.06 (Weight Ratio)
Recycle Flow (30 to 50%)
Partial Flow
Total Flow
Alum
Lime
Polyelectrolyte
90+
30 to 50
50 to 60
8.6 Equalization
Equalization is the process whereby the volume or analytical content of the waste may be dis-
charged evenly to the treatment facility throughout the day. It may be necessary when batch
discharges, intermittent rinsing, or intermittent operation produce wide variations in flow or
analytical content. All treatment plants will operate more efficiently if the hydraulic, BOD,
and other loads are more constant throughout the week.
The primary objective of flow equalization is to provide uniform conditions before entering
physical, chemical, and biological treatment systems. Experience has shown that up to 24 hours
detention or a volume equal to the mill's daily flow of equalization is recommended ahead of
most biological systems. If there are wide flow variations, a flow equalizing method must be
8-24
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devised to prorate the discharge rate. This may be done by means of pumps, siphons, valves, or
combinations of these. In some mills, tanks providing only 3 to 8 hour detention times will
provide sufficient equalization. In many mills, continuous processing methods are being used
and equalization will not be necessary.
The major reason for equalization is usually to level the BOD loads. Variations in loading are
eliminated by mixing highly concentrated waste with very diluted waste. The differences in
production such as batch processing and the possibility of variation in the work week require
equalization of waste streams to insure that the secondary treatment system will not be
damaged.
If the major part of the BOD is being contributed by only one or two washes, only these need
to be segregated at the source of discharge and stored in much smaller equalization tanks for
controlled discharge. This is practicable for the desi/e and scour waste in cotton mills, scour
and wash after fulling waste in woolen mills, and the knitting oil scour in polyester knit mills.
Usually, segregating a volume equal to only 1 to 3% of the total mill flow will provide equali-
zation for 50 to 90% of the total BOD.
Equalizing lagoons with detention times greater than one day are likely to develop odor prob-
lems through anaerobic decomposition and the resultant evolution of hydrogen sulfide. This
has been known to occur even when the effluent pH is in the 11 to 12 range. Deep pockets,
which collect sludge, will usually intensify the problem.
Some additional methods giving a degree of odor control include oxidation by hydrogen perox-
ide, oxygen, ozone and chlorine; odor neutralizing chemicals; lime addition to raise the alkalin-
ity; and activated charcoal addition. Perhaps the best method is simply to add an aerator. Al-
though the retention time in an equalization basin is usually too short to permit much oxida-
tion, preaeration, in addition to keeping waste from becoming septic, has been found to aid in
subsequent settling and may provide from 10 to 20% reduction in BOD.
Equalization also provides a significant degree of cooling which is usually sufficient to reduce
hot textile wastewaters to temperatures suitable for a municipal sewer. Equalization basins may
be constructed of earth, concrete or steel. Earthen basins are generally the least expensive. A
cross section of a typical basin is illustrated in Figure 8-12.
8-26
-------
•153'-
Floating aerator
r-n^ El 150'
3 0' freeboard
Maximum surface level
Minimum required —
operating level
Minimum allowable
operating level to
protect floating aerator*
Concrete scour pad*
Volumes
El 0 0'to El 7 0'approximately 260,000 gallons
El 7 0'to El 15 0'approximately 740,000 gallons
Total volume = 1,000,000 gallons
"These dimensions will vary with aerator design and horsepower
FIGURE 8-12
EARTHEN EQUALIZATION BASIN
Source: Environmental Protection Agency, Technology Transfer Seminar Publication —
Flow Equalization
Following is a suggested tabulation of basic design parameters for an earthen equalization basin:
TABLE 8-6
DESIGN PARAMETERS FOR EQUALIZATION
Detention Time
Volume
Mixing Requirement
Maintain Aerobic Conditions
Side Slopes
Depth
Freeboard
Minimum Operating Level
24 Hours
Daily Mill Flow
0.02 to 0.04 HP/1000 Gal.
1.15 to 2 ft3 Air/Min.71000 Gal.
3:1 to 2:1
Approximately 15 ft
3ft
5ft
General design considerations for equalization basins should include the following (15):
• Gravity discharge from equalization basin will require an automatically controlled flow-
regulating device.
• A flow measuring device downstream of the basin will monitor equalized flow.
8-27
-------
• Surface aerators should be fitted with legs or lift-out hooks to protect units when tank is
dewatered.
• Facilities should be provided to flush solids and grease accumulations from basin walls.
• An emergency overflow should be provided.
8.7 Neutralization
Generally speaking, textile wastes are within a pH range of 5 to 12 units. Meeting the required
effluent range of 6 to 9 units will require pH adjustment for some mills. Equalization will serve
to reduce fluctuations in pH produced from batch dump processing and thus reduce or elimi-
nate chemicals needed for neutralization.
Studies performed at Cone Mills during the period of 1950 to 1960 indicated that biological
activated sludge processes develop specialized bacteria which will work efficiently within a
range of 4 to 11 pH units. However, once these specialized bacteria and their optimum pH are
developed, it is believed that changes of one or two pH units may cause upsets.
Additional studies by Masselli revealed that textile wastewaters with influent pH above 10 have
been successfully treated in activated sludge systems since the biocarbonate alkalinity buffer
in the aeration tank reduces pH to 10 or below on first contact. Bacterial oxidation subse-
quently produces acidic carbon dioxide from the organic carbon in the waste, and the remain-
ing carbonate alkalinity will be reduced so that effluent pH's of 6.8 to 8.0 are developed.
Acidic effluents were rarely encountered in textile finishing until the advent of polyester knits.
When large portions of knits are being dyed, the acetic acid used in dyeing may produce final
effluents in the pH 5.0 to 6.0 range. Mills with acidic pH's may consider doing some cotton
finishing since the use of sodium hydroxide in scouring and mercerizing will supply the neces-
sary alkalinity.
Acid wastes may be neutralized using lime which is the least expensive alkali source available.
Handling and feeding of lime, however, may be difficult as it must be slaked and fed as a slurry.
Lime also reacts slowly and has the tendency to settle out in piping and equipment. Easiest to
handle and control is 50% sodium hydroxide (caustic soda).
Alkaline wastes may also be neutralized using strong acids having reaction rates which are
practically instantaneous or by the addition of boiler flue gases which contain sufficient carbon
dioxide and sulphur dioxide to reduce the pH of most caustic liquors.
8-28
-------
Batch neutralization may be suitable for waste flows under 100,000 gpd. When wastewaters
exhibit a highly variable pH, it is usually more effective to stage neutralize (see Figure 8-13).
Reagents are added in a step-wise fashion to dampen fluctuations.
A/C
A/O
Increasing air signal
pressure closes valve
Increasing air signal
pressure opens valve
Full
closed 1 ~
1
0
1
1
25
1
50
1
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i
75
1
F
1
100
I
Full open
Acid
reagent
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Full
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A/O
pH
Nonlinear recorder
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r
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Neutralized
effluent
Reaction tank
Attenuation tank
FIGURE 8-13
CONTROL OF VARIABLE pH
Source: Environmental Engineer's Handbook
Regulation of pH by chemical means is usually accomplished by a system consisting of a chemi-
cal storage tank, metering pump or control valve, reaction tank or compartment with agitator,
and control instruments (see Figure 8-14). Control methods used include: feed forward, propor-
tional and feedback systems. Following is a tabulation of design considerations for each of the
above.
8-29
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TABLE 8-7
NEUTRALIZATION SYSTEM DESIGN PARAMETERS
Chemical Storage
Tank
Reaction Tank'
Size
Retention Time
Influent
Effluent
Agitator:
Propeller Type
Axial Flow Type
Peripheral Speeds
pH Sensor
Metering Pump or Control Valve
Liquid - use stored supply vessel
Dry - dilute in a mix or day tank
Cubic or cylindrical with liquid depth equal to diameter
5 min. to 30 min. (lime - 30)
Locate at tank top
Locate at tank bottom
Under 1000 gallon tanks
Over 1000 gallon tanks
12 fps for large tanks
25 fps for tanks less than 1000 gal
Submersible are preferred to flow through type
Pump delivery range limited to 10 to 1; valves have
greater ranges.
The selection of neutralizing agents will depend upon availability, chemical cost and feeding
methods. Following is a tabulation of generally acceptable reagents:
COMMON NE UTRA LIZA TION RE A GENTS
Alkalinity Source
Dry Lime
Caustic Soda (50%)
Ammonia (57.6%)
Sodium Carbonate
Trisodium Phosphate
Limestone
Waste Alkali
Form
Powder
Liquid
Liquid
Solid
Chips
Remarks
280 Ibs/MG Yields 60 mg/1 Alkalinity
63 gal/MG Yields 60 mg/1 Alkalinity
81 gal/MG Yields 60 mg/1 Alkalinity
Acid Source
Sulfuric Acid (66 Be0)
Nitric Acid (100%)
Hydrochloric Acid
(22 Be0)
Carbon Dioxide
Sulfur Dioxide
Flue Gas
Waste Acid
Liquid
Liquid
Liquid
Gas
Liquid
Gas
Liquid
8-30
-------
Chemical storage
Lime, caustic, acid
Control
valve
or
control
pump
Recorder
pH analyzer
Controller
Influent
Mixer
CT
Baffle k
I
u u b
i
J
n u
Effluent
Sensing
electrode
FIGURE 8-14
pH CONTROL SYSTEM
Source: Lockwood Greene Engineers, Inc.
8.8 BOD/COD Reduction
It should be noted that COD, total oxygen demand and TOG are rapid analytical measures of
organic matter and are used in conjunction with the slower BOD determination. Consequently,
the same procedures indicated for BOD removal are used for COD removal.
In some instances, there may be adequate BOD removal but inadequate COD removal, indicat-
ing that soluble or colloidal nonbiodegradable organic matter is present in the waste. If further
COD removal is required, all efforts to identify the nature of the compounds contributing the
COD should be made, and biodegradable process chemicals should be substituted for the non-
biodegradable compounds. If this is not possible, treatment by chemical coagulation or acti-
vated carbon will have to be used, and costs may be doubled or tripled.
8-31
-------
Measurement of BOD is usually necessary for determining the size of treatment units and aera-
tion devices. The ultimate BOD (BODjj, BODL, or BOD2Q) *s sometimes required by regulatory
authorities. Excessive BOD loads will produce zero dissolved oxygen in the aeration tank, and
bulking sludge, anaerobic odors and high effluent BOD's will result. These "shock" BOD loads
may come from dump discharges of high BOD baths at the end of a run, a shift, a week or
before vacation. Occasionally, processing changes, such as the use of Xylene or Varsol in scour-
ing, may cause excessive increases. Many chemical compounds are apparently nonbiodegradable
or slightly biodegradable in BOD tests, but are readily biodegraded by the acclimated bacteria
that develop in the activated sludge after continuous contact with these compounds. In many
instances the actual oxygen demand exerted in the aeration tank will be 10 to 100 times greater
than the demand estimated from the BOD test. If appreciable amounts of such chemicals with
"hidden" BOD's are present, the oxygen demand may exceed the aeration capacity of the sys-
tem. Some of the compounds with hidden BOD's are cellulose, poly acrylic acids, poly vinyl
alcohol, naphthalene, and alkyl benzene sulfonate (ABS) detergents.
The temperature of wastewaters is an important consideration in selection of biological treat-
ment systems. High temperature wastes in excess of 100° F are not amenable to short deten-
tion systems such as conventional activated sludge or even trickling filters. Low temperature
wastes are not amenable to treatment in aerated lagoon systems in cold climates where tem-
peratures drop below freezing. High temperatures above 95° F are reported to produce dis-
persed growths and lower BOD efficiencies. The likelihood of such temperatures will be increased
when water use is reduced, therefore, heat reclamation by heat exchangers may be required.
8.8.1 Lagoons
Lagoons can be divided into five general classes. They are high-rate aerobic ponds, facultative
ponds, anaerobic ponds, tertiary ponds (maturation or polishing ponds) and aerated lagoons.
High-rate ponds and facultative ponds are also called oxidation ponds.
In high-rate aerobic ponds, algae production is maximized by allowing maximum light pene-
tration in a shallow pond. These ponds are generally only 12 to 18 inches in depth and are inter-
mittently mixed. The main biological processes are aerobic bacterial oxidation and algae photo-
synthesis. Organic loadings range from 60 to 200 pounds BODg per acre per day. Usually 80
to 95% of the waste organic matter is converted to algae.
8-32
-------
These ponds cover a large area and have waste detention times as great as several months. BOD
loading must be light to avoid anaerobic conditions and the generation of odors. While some
means of controlling the water level is usually necessary (variable weirs, etc.), the equipment
cost for such is minimum. The major portion of this system's cost is for acquiring land.
Facultative ponds are perhaps the most numerous of the pond systems, having a depth of 3 to
8 feet. The greater depth allows two zones to develop: an aerobic surface zone and an anaerobic
bottom layer. Oxygen for aerobic stabilization in the surface layer is provided by photosynthe-
sis and surface reaeration, while sludge in the bottom layer is anaerobically digested. Loadings
generally range from 15 to 80 pounds BOD per acre per day, and BODg removal from 70 to
95%, depending on the concentration of algae in the effluent.
Tertiary ponds are generally used for polishing effluents from conventional secondary processes,
such as trickling filter or activated sludge. Settleable solids, BOD5 fecal organisms, and ammonia
are reduced. Algae and surface aeration provide the oxygen for stabilization. BOD5 loadings are
generally less than 15 pounds BOD5 per acre per day.
Aerated lagoons have been used successfully for many years in textile waste treatment. They re-
quire only 3 to 5% of the land needed for high-rate ponds. They are 8 to 15 feet deep and have
waste detention times of 2 to 10 days, although 5 days is usually appropriate if the heat loss
is great. Oxygen is introduced into the lagoon either by fixed mechanical turbine-type or float-
ing propeller-type low speed aerators, or a diffused air system (see Figure 8-15). If the turbu-
lence level is insufficient to maintain solids in suspension, then insert solids and nonoxidized
biological solids settle to the bottom of the basin where they undergo anaerobic decomposition.
This is sometimes referred to as a facultative lagoon. If the turbulence level in the basin is in-
creased to maintain solids in suspension, the system becomes analogous to the activated sludge
process without solids recycle. In order to obtain a good quality effluent from the aerated
lagoon system, the biological solids should be separated, generally by a settling basin.
BOD and suspended solids reductions vary widely from 50 to 90+% depending upon detention
time and temperature as well as the degree of mixing. Aerated lagoon design is based upon the
following factors: BOD removal rate, oxygen requirements, temperature effects, and energy
required for mixing. BOD removal rate with or without nutrient addition can be determined in
the laboratory by batch aeration of waste seeded with an acclimatized effluent. Oxygen require-
ments are computed knowing the BOD of the waste and the amount of organisms wasted from
the system per day. Temperature affects treatment by reducing biological activity and treatment
efficiency. Design calculations include temperature effects. The BOD removal rate is lower in
winter than in summer and, therefore, optimum design for detention time is controlled by winter
temperatures; however, oxygen requirements will usually be controlled by summer conditions
in the basin. Mixing requirements vary with the type of aerator and lagoon geometry. It is im-
portant to check mixing because in many cases the energy required for mixing is greater than
that for oxygen transfer.
8-33
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8-34
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Following is a tabulation of suggested design parameters for aerated lagoons:
TABLE 8-8
SUGGESTED DESIGN PARAMETERS FOR AERATED LAGOONS
Detention Time
Depth
Side Slopes
Oxygen Utilization
BOD Removal
2 to 10 days
6 to 15 feet
3:1 to 2:1
36 Ib BOD/day/HP
50 to 90+%
It is generally desirable to divide the required lagoon volume into at least two basins for opera-
tional flexibility. Another possibility is to arrange lagoons in a series of up to four units.
For details of lagoon inlets, outlets and dike construction see section 8.8.7 entitled "Polishing
Ponds".
8.8.2 Activated Sludge
The activated sludge process was developed by Ardern and Lockett in England during 1912 —
1914, and was named for the activated sludge produced. The activated sludge process basically
involves two unit operations; contacting and liquid-solids separation. The contacting portion
involves the mixing of wastewater and microorganisms. The second unit operation involves the
liquid-solids separation step. Since the presence of microorganisms is the key to biological
oxidation, it is necessary to return them to the contactor. Therefore, a liquid-solids separation
unit removes the microorganisms from the treated wastewater. This separation not only allows
for the collection and recycling of the valuable microorganisms, but also results in clarification
of the wastewater. The recycling of microorganisms is the unique aspect of the activated sludge
process. If sludge is not returned quickly enough, denitrification and rising sludge can occur.
Denitrification can result in the formation of a layer of biological solids over the clarifier surface.
It is necessary in this case to agitate the scum layer to release nitrogen gas and to permit it to re-
settle. Generally, spraying the surface with water will break up the scum without excessive loss
of solids. By definition, activated sludge involves the concept of the return of microorganisms
to the contactor to achieve maximum treatment efficiency in the shortest time possible.
Many modifications of the conventional (original) activated sludge process have become stand-
ardized since its inception. They are complete-mix, step-aeration, tapered-aeration, modified
aeration, contact-stabilization, extended-aeration, high-rate aeration, oxidation-ditch, Kraus-
process and pure-oxygen systems. Figure 8-16 illustrates schematically the conventional, com-
plete mix and extended aeration methods. For textile wastewaters, extended-aeration activated
sludge process is usually preferred. This section will discuss the design basis of conventional and
extended-aeration activated systems.
8-35
-------
Influent
Recycled sludge
Aeration
basin
Conventional
Waste sludge
Effluent
Influent
Recycled sludge
Complete - Mix
Recycled sludge
Aeration
basin
Extended aeration
FIGURE 8-16
ACTIVATED SLUDGE PROCESSES
Source: Lockwood Greene Engineers, Inc.
Waste sludge
Effluent
Effluent
8-36
-------
The conventional process is normally designed for an F/M ratio (F/M ratio is defined as the
amount of biodegradable organic material available to a given amount of microorganisms per
unit of time = Food/Microorganisms) of 0.2 to 0.5 Ib. BODr per Ib. MLSS/day. For municipal
wastewaters containing approximately 250 mg/1 BODp, the MLSS concentration is maintained
at approximately 2,000 mg/1, and the contactor retention time ranges between 3 and 5 hours.
The degree of treatment normally achieved with the conventional activated sludge treatment is
90% suspended solids removal. For textile wastewater, an F/M ratio of 0.25 Ib. BOD5 per Ib.
MLSS/day is normally preferred. The MLSS concentration is maintained at 2,500 mg/1, and
the retention time ranges between 12 and 24 hours.
Having a small volume to dissipate a surge, shock loads do have an adverse effect on a conven-
tional activated sludge system. Therefore, the application of the conventional activated sludge
process to textile wastewater results in the need for pretreatment facilities such as equalization
basins and neutralization equipment. Color removal by conventional activated sludge is usually
less than 50%. High sludge production in the conventional activated sludge system may be a
costly factor.
8.8.2.1 Extended Aeration
The extended aeration modification of the activated sludge process is similar to the convention-
al activated sludge process, except that the mixture of activated sludge and raw materials is
maintained in the aeration chamber for longer periods of time. With domestic wastewater,
the F/M ratio is usually satisfied with 24-hour detention period. For textile wastewaters, aera-
tion periods of 36, 48, 60, 72, 96 or over 120 hours may be required. During this prolonged
contact between the sludge and raw waste, there is ample time for organic matter to be
absorbed by the sludge and also for the organisms to metabolize the organic matter which has
been built up into the protoplasm of the organism. Hence, in addition to high organic removals
from the wastewaters, up to 75% of the organic matter of the microorganisms is decomposed
into stable products and consequently less sludge will have to be handled.
A highly purified effluent is possible with BODp removals greater than 90%. Also, due to the
longer detention time and consequently larger volumes, the process is more resistant to upsets
from shock loads.
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 finely divided
and therefore settle slowly, requiring a longer period of settling. Clarifiers should be equipped
with mechanical sludge removal equipment and in some cases an oil removal device. See section
8.5.2 for the design of final clarifiers.
Oxygen is introduced into the aeration tank by means of mechanical aerators or diffused air
systems. Most newer treatment plants use mechanical aerators, either fixed or floating. If ef-
fluent BOD is above 500 mg/1 and soluble, both diffused and mechanical aeration may be used
8-37
-------
TABLE 8-9
EXTENDED AERATION DESIGN PARAMETERS
Retention Time
Depth
Recirculation of Activated Sludge
Excess Sludge Produced
Organic Loading (F/M)
Sludge Volume Index
Mixed Liquor Volatile Suspended Solid
(MLVSS) Concentration in Reactor
Aerator Type'
Low-speed Surface Aerator
(Power Level)
Diffused Air System
(Air Requirement)
D.O in Mixed Liquor
Overflow Rate for Clarifiers
3 to 5 days
10ft. minimum; 15ft maximum
100 percent
01 to 02 Ib/lb BOD removed
0 04 to 0 1 Ib BOD/day/lb MLVSS
150 ml per gram of settled MLSS
2500 to 3500 mg/l
1.75 HP/1000 cu. ft. volume of tank
(1 HP/36 Ib BOD loading/day) or
(70 HP/1 MGD Flow)
1,500 cu. ft. of tank
Ib/BOD Loading/Day
/ 56 cu. ft. air \
^ cu. ft volume of tank or
/ 3.5 x 10 cu. ft. air \
V 1 MGD Flow '
2 mg/l
300 gpd/ft2
together. This method releases compressed air below the mechanical aerator. The oxygenation
capacity of an aeration device is a function of the standard efficiency of the aerator, temperature,
the oxygen deficit, and dissolved impurities which may affect molecular oxygen transfer.
Standard transfer efficiencies for surface aerators may vary from 2.5 to 3.5 Ib. oxygen/HP.-hr.
Oxygen deficit is the difference between saturated dissolved oxygen concentration and the
operating dissolved oxygen level in the basin. When calculating aeration requirements, it is
recommended that oxygen requirements be based on the 90 percentile (statistical distribution)
BOD loading. See Table 8-9 for suggested design parameters for extended aeration.
Flotation is sometimes used instead of a clarifier to handle the waste activated sludge when
bulking problems occur with settling type clarifications. Conventional recycle pressurization is
used with a solids loading rate of approximately 1.5 Ibs./hr./sq. ft.
The advantages of flotation include:
• Sludge concentration of 3 to 4% can be expected as compared to less than 1% for conven-
tional clarifiers.
• Clarified effluent contains about 5 mg/l of BOD, and this may eliminate the need for
possible reaeration.
8-38
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8.8.3 Nutrient Addition
Supplemental nutrients, if required to maintain a BOD: N:P ratio of 100:5:1 for high-rate syn-
thesis, 100:3:0.5 for medium-rate synthesis and 100:2:0.3 for low-rate synthesis should be
added to the waste stream as it enters the aeration basin. Indications are that a minimum nitro-
gen content of 1% and minimum phosphorus content of 1.2% of the volatile suspended solids are
necessary to avoid a reduced BOD removal efficiency. In textile wastes, sufficient phosphate
is usually present (concentration of inorganic phosphorus is approximately 9 mg/1), but occa-
sionally a nitrogen source may have to be added. Quantities of N & P are calculated by sub-
tracting the Ibs./day of each in the waste from the Ibs./day required to obtain the above ratio.
Feeding excess nitrogen is not desirable as ammonia has a high potential oxygen demand
(423%) as well as a high chlorine demand.
Following is a suggested list of nutrients sources:
Nutrient Form Remarks
Nitrogen Anhydrous Ammonia Provides Alkalinity, 82.3% N
Domestic Sewage Provides Acidity
Ammonium Nitrate 35% N
Ammonium Sulfate 21.2% N
Phosphorus Trisodium Phosphate Provides Alkalinity
Domestic Sewage Provides Acidity
Ammonium Phosphate Provides Nitrogen
Di-Ammonium Phosphate Provides Nitrogen
Nutrients, preferably in a gas or liquid form, are added to the waste stream under pressure by
metering pumps or by gravity (see Figure 8-17).
8.8.4 Fixed Film Biological Reactors
8.8.4.1 Trickling Filters
Trickling filters usually contain media composed of rock, redwood or synthetic material. The
hydraulic loading of rock filters is usually 10 to 40 million gallons per acre per day; the BOD
loadings are from 0.015 to 3.0 Ibs. BOD per cubic yard of material per day. Rock filters are
usually 10 to 50 feet deep, and may require large land areas for settling and recirculation,
which is usually on a ratio of 1:1 to 10:1 raw waste to treated effluent.
The relatively new synthetic filter media have several advantages over the rock filter types. They
are lighter than rock and can be stacked 30 feet high (see Figure 8-18). The surface area per unit
volume is controlled when the media is manufactured so that more space for bacterial attach-
ment is provided. The hydraulic loadings can be as high as 20 to 40 million gallons/acre/
8-39
-------
Pressure
regulator
Flow meter
Anhydrous ammonia
FIGURE 8-17
NITROGEN FEED SYSTEM
Source: Lockwood Greene Engineers, Inc.
Corrugated siding
Dickey blocks
Flocor filter modules
(2' x 2' x 4')
Source: Ethyl Corporation
FIGURE 8-18
BIO-OXIDATION TOWER
8-40
-------
day and BOD loading of 5 to 10 Ibs. per cubic yard per day can be obtained. Above ground
units may be adversely affected by cold weather.
The rate of waste addition to the filter media may be classified as standard or high rate loading.
The difference is that standard rate addition is intermittent for loading periods of 5 minutes or
less, whereas high rate types are continuously fed by means of a variable recirculation system. The
standard rate filter has a hydraulic loading of 4 million gallons per day per acre, organic loadings
of 15 Ibs. of BOD per acre-foot per day, and intermittent releasing of dead bacteria. The sludge
from the process is a black, highly oxidized product containing light, fine particles and a highly
nitrified effluent with less than 20 milligrams of BOD per liter. The effluent is usually dis-
charged after one pass through the filter. The corresponding hydraulic load, organic load, and
sludge discharge rate of the high rate type are respectively: 10 to 30 million gals./day/acre, 30 Ibs.
of BOD/acre-foot/day, and continuous. The sludge produced in the secondary settling tank is
brown in color and not fully oxidized; the effluent is not fully nitrified and has a BOD of 30
or more milligrams per liter. Recirculating the effluent makes the final discharge as good as it is
with the standard rate; however, the efficiency is lowered appreciably.
The term single stage trickling filter refers to the process of passing the waste through one trick-
ling filter and then to a secondary settling tank. Two stage treatment refers to the passing of the
effluent from primary settling through two trickling filters in series before the secondary
settling stage. With single stage treatment, BOD removal is about 50 to 75%. Although the
two-stage method has a higher rate of BOD reduction than the single stage method, it is more
costly than the activated sludge method. Trickling filters may also be used as roughing filters
ahead of an activated sludge basin. This works best at soluble BOD levels above 200 mg/1.
Trickling filters exhibit variable behavior, and this is their greatest shortcoming. They are sen-
sitive to changing characteristics expected in textile wastes, and they allow little modification of
operation to optimize treatment.
8.8.4.2 Rotating Disks
The rotating-biological-disk system consists of large-diameter, lightweight plastic disks, which
are closely packed and mounted on a horizontal shaft located in a semicircular tank. A series
of these units treats the waste, which flows from one tank to another. The microorganisms
present in the wastewater adhere to the plastic surfaces as they rotate through the tank. The
wastewater is picked up on the surface of the disk and the portion that is not submerged
absorbs oxygen from the atmosphere. The microorganisms then aerobically degrade organic
matter present in the waste. As they multiply, excess microorganisms are sloughed off the
disks into the wastewater. Mixing action provided by the disks keeps solids suspended. After
treatment through a series of rotating biological disks, a final clarifier removes suspended
solids. A BODr reduction of over 90% may be achievable with a multi-stage rotating biologi-
cal contactor.
8-41
-------
Biological rotating disks have been found to be flexible with respect to varying organic and
hydraulic loads, but the short detention times of each unit make them vulnerable to toxic
shock loads. Reduction in waste temperature would be slight, and high influent temperature
would adversely affect treatment. This treatment method offers the advantage of low space
requirements and, in some instances, may be economically competitive with other methods.
Four-stage treatment by biological rotating disks has demonstrated BOD removals from 60
to 95% for domestic wastewaters (see Figure 8-19). The final effluent is well oxygenated.
Oxidation of ammonia, sulfides and phenols would likely take place. Pilot installations are
presently treating textile wastes in North Carolina. In one instance, biological disks are used
to reduce further the BOD of activated-sludge effluent from an existing plant. The disks are
also useful as a nitrogen removal stage.
Table 8-10 and 8-11 present suggested design parameters for trickling filters.
TABLE 8-10
TRICKLING FILTER DESIGN PARAMETERS
Rock Media
Hydraulic Loading
BOD Loading
Recirculation Rate
Media Size
Filter Bed Depth
Synthetic Media
BOD Loading
Recirculation Rate
BOD Removal
Filter Bed Depth
3.5 mgd/acre
36 Ib. BOD/1000 cu. ft./day
5:1 to 10:1
2" to 4" Granite
14 feet
51 to 93 Ib. BOD/1000 cu. ft./day
2:1
75 to 78%
21+ feet
TABLE 8-11
ROUGHING FILTER DESIGN PARAMETERS
Rock Media
Hydraulic Loading
BOD Loading
Recirculation Rate
Filter Bed Depth
6.9 mgd/acre
60 lb/1000cu. ft./day
1.7:1
6 feet
8-42
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8-43
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8.8.5 Activated Carbon Catalyst
BOD/COD and color have been shown to be reduced markedly when activated carbon (granular
or powdered) has been placed in the aerobic reactor of an activated sludge system. In addition
activated carbon will reduce the foaming tendency of the aeration system, and the sludge will
act as a sink to trap heavy metals.
Though most testing has been with granular activated carbon, powdered carbon is now being
considered because it can be produced considerably cheaper, and because of the smaller particle
size, the adsorption rate is much more rapid.
Recent testing at a textile finishing plant (16) indicated that the carbon feeding position does
not appear to be critical. Carbon can be simply fed using an open top 55-gallon drum with a
water spray pipe in the center. The carbon is washed out of the tank through a drain in the bot-
tom to feed points along the aeration basin (see Figure 8-20). Granular activated carbon was
pilot tested at approximately 5 grams per liter (one time addition). It was found during the test
period of nine months that sludge wasting was required on a regular schedule to produce con-
stant good color removals and to reduce the heavy metal concentration adsorbed in the sludge
(see Figure 8-21).
When starting a system, carbon is fed daily until the mixed liquor suspended solids activated
carbon level is maintained at approximately 25% of the MLSS with a relatively low level of
sludge wasting. The level of carbon in the MLSS is important since the continuous build-up of
inert material (possibly metals) can reduce the biologically viable component of the mixed
liquor suspended solids.
Carbon carryover to the clarifier may be difficult to settle. Chemical treatment may be required
to provide effective removal of these solids. To insure effective clarification and to remove the
dark, hazy appearance of the treated water, it may be necessary to provide granular media
filtration.
Spent carbon can be effectively concentrated by gravity thickening and vacuum filtration or
by dewatering through centrifugation. Regeneration of the carbon is best accomplished by
thermal regeneration, although for small plants it is more economical to use the carbon on a
throwaway basis.
TABLE 8-12
ACTIVATED CARBON CATALYST DESIGN PARAMETERS
Range of Carbon Dosages
Range of Carbon Resident Time
Powdered Activated Carbon.
Effective Size
Adsorption Surface Area
Apparent Density
50 to 3000 mg/l
48 to 120 hours
2JU.
750m2/gram
15.2 Ib/cu ft
8-44
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CARBON CONCENTRATION, g/l
Project 12090 HLO
Catalyzed Bio-Oxidation and Tertiary Treatment
of Integrated Textile Wastewaters.
EPA-660/2-74-039 June, 1974
Equilibrium Isotherms
20
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MAY
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Project 12090 HLO
Catalyzed Bio-Oxidation and Tertiary Treatment
of Integrated Textile Wastewaters
EPA-660/2-74-039 June, 1974
Comparison of Catalyzed and Non-Catalyzed
Biological Reactors
FIGURE 8-21
GRANULAR ACTIVATED CARBON
Source: Textile Technology/Ecology Interface, 1975, Advanced Waste Treatment,
Hodges and Alspaugh
8.8.6 Chemical Coagulation
Chemical coagulation as a major treatment method for removal of BOD/COD is not well suited
to textile wastes with the possible exception of wool processing wastewaters or when the waste
stream is only partially biodegradable. The chemical process when applied as supplemental
treatment before or after biological treatment will improve BOD/COD removals associated with
the removal of suspended solids, a source of organic pollution.
Chemical coagulation before biological treatment may cause erratic pH levels, biomass growth,
and erratic BOD removal. When applied after biological treatment, a satisfactory effluent may
be produced with less expenditure of chemicals.
Coagulation is generally accomplished by adding coagulants that contain multivalent cations.
These include lime, aluminum sulfate, ferric chloride, ammonia alum, potash, alum, ferrous
sulfate, ferric sulfate and sodium aluminate. Addition of coagulants to the suspended solids
and colloidal substances produces a floe which is allowed to settle in a clarifier. To dissipate the
coagulant throughout the wastewater as fast as possible, flash mixing at point of entry to the
8-46
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clarifier is normally used. The correct coagulant dose for a specific wastewater and particularly
the precise pH for maximum effectiveness must be determined experimentally. Polyelectrolytes
are sometimes added to colloidal dispersions which are difficult to destabilize.
Chemical treatment facilities traditionally include a rapid mix basin wherein chemicals are
introduced, followed by a flocculation basin, then a sedimentation tank (see Figure 8-22). In
recent years the solids-contact or sludge blanket type clarifiers have become popular due to
their inherent size reduction (see Figure 8-23). These units provide coagulation, settling and up-
ward filtration in one unit. Influent wastewater is mixed with coagulants as it is fed to the
center chamber where floe is formed. The floe moves to the outer chamber and rises up through
a bed of previously formed floe which retains the new floe. Clear effluent flows up and out
through a weir at the top of the unit. Collected sludge is periodically blown off from the
bottom.
When the wastewaters contain oil and grease, the floe may be removed more effectively by the
use of dissolved air flotation.
Design considerations for solids contact clarifiers are discussed in EPA's suspended solids
removal manual and include:
• Provide rapid and complete mixing of chemicals, feedwater and slurry solids.
• Maximum peripheral speed of mixer blades should not exceed 5 ft./sec.
• Provide means for measuring and varying slurry concentration in contacting zone.
• Maintain sludge blanket levels a minimum of 5 feet below water surface.
• Space effluent launders to minimize horizontal movement of clarified water.
Table 8-13 presents suggested parameters for the design of a chemical coagulation system.
8.8.7 Polishing Ponds
Polishing ponds, often referred to as stabilization ponds, are used for tertiary treatment of ef-
fluents from conventional secondary biological processes, such as fixed film reactors or acti-
vated sludge. Advantages of polishing ponds are that they reduce suspended solids, oxidize
organic matter, permit flow control, and wastewater storage.
Generally, polishing ponds are shallow with large surface areas. If the pond is deep (5 to 8 feet),
the wastewater near the bottom is void of dissolved oxygen and anaerobic organisms may be
present. Settled solids can be decomposed into inert and soluble organic matter by aerobic,
8-47
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Effluent collector flume
Agitator
/ . Chemical feed inlet
sample
indicator
O oooooogoooott
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SOLIDS-CONTACT CLARIFIER
Source: Environmental Engineer's Handbook
Precipitator
dram
TABLE 8-13
CHEMICAL COAGULATION DESIGN PARAMETERS
Rapid Mixing.
Detention Time
Depth
Mixing Power (Turbine Mixers)
Mixing Speed
Chemical Addition:
Liquid Alum
(Commercial Grade, 17% Al2 63)
or Alum (as Al2 (804)3 18 H2°)
Anionic Polymer
(Feed to Flocculation Zone)
Flocculation:
Detention Time
Depth
Mixing Power (Turbine Mixers)
Mixing Speed
Clarification:
Overflow rate
Depth
30 sec. to 5 minutes
5 feet
50 HP/1000 cu ft vol
84 to 168 rpm
300 mg/l
300-500 mg/l
5 mg/ I
10 to 30 minutes
7 feet
1.5 HP/1000 cu ft vol
12 to 37 rpm
300 gpd/ft2
14ft
8-49
-------
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 photosyn-
thesis) 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 ponds; this currently is a drawback when aerobic ponds 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 stabil-
ization. Sulfates, CC>2, nitrates, phosphates, water and sunlight are used to synthesize their own
cellular matter and give off free oxygen. The oxygen may 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 equi-
valent 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.
The following tabulation illustrates suggested design parameters for polishing ponds:
TABLE 8-14
DESIGN PARAMETERS FOR POLISHING PONDS
Depth
Loading Rate
Detention Time
BOD Removal
2 to 6 (ft.)
20 to 50 (Ib BOD/acre/day)
7 to 30 (days)
70 to 85 (%)
In the design of earthen ponds or lagoons there are a number of important considerations. The
following were taken from State Standards and EPA publications:
8.8.7.1 Compartments
• At least two compartments of approximately equal size shall be provided.
• The compartments shall be shaped so as to preclude stagnant areas.
• Wastewater shall be fed to the cells with adequate velocities to assume self-cleansing of the
distribution piping.
8-50
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8.8.7.2 Distribution
• The piping and control arrangement shall be such that the individual cells may be operated
in series or in parallel so as to allow complete flexibility of operation.
• The control arrangement shall be such that it is possible to maintain a different water level
in each cell when operated in series.
8.8.7.3 Inlet and Outlet Structures
• Inlet structures may be designed on the basis of using weirs for distributing and measuring
flows to the cells.
• Steel, concrete or other durable material should be used in all portions of the control
devices.
8.8.7.4 Inlets
• Inlets to the cells must be so designed as to eliminate erosion of the cell bottom.
• Inlets shall be located so as to prevent short-circuiting.
8.8.7.5 Outlet Structures
• Outlet structures should generally utilize weirs for liquid level control.
• A portion of the outlet structure must act as a scum baffle, unless separate scum baffles
are provided.
• Weirs and control devices should be aluminum or fiberglass.
• Outlet structures shall provide means for complete drainage of the cells.
8.8.7.6 Transfer Pipes
• Provide seepage collars near midpoint.
• Provide fiberglass plugs to close transfer pipes.
8.8.7.7 Operating Level
• Stabilization ponds shall be designed to normally operate within overall depths of three
feet minimum to five feet maximum.
8.8.7.8 Construction
• Dikes shall either be constructed of relatively impermeable material or be lined with suit-
able liners.
• The top of the dikes shall be a minimum of 12 feet wide to provide access for maintenance
equipment.
8-51
-------
• Dike corners shall have radii such that maintenance equipment will have complete freedom
of movement over all portions of the dikes.
• In general interior slopes should be a minimum of 3:1 and exterior slopes should be a
minimum of 2:1.
• All slopes on dikes shall be protected from erosion. Protection against erosion shall extend
one foot below minimum water surface and one foot above maximum water surface.
• Stabilization ponds shall have a minimum freeboard of two feet.
• Stabilization ponds shall be so constructed as to minimize percolation through the bottom.
• The stabilization pond area shall be enclosed with a suitable fence to exclude livestock and
discourage trespassing. A vehicle access gate of sufficient width to accommodate mainten-
ance equipment shall be provided.
8.9 Oil and Grease Reduction
Oil and grease reduction methods are dependent upon the form in which the oil is present in
the waste stream. That is, free oils or grease are removed by flotation, centrifugation or gravity
separators. Where free floating oil is encountered, it can be removed by directing the flow into a
basin having a retention period of 30 minutes to 1 hour and a velocity not greater than 2 fpm. Oil
collected at the surface is skimmed off using a rotating half pipe, top scraper mechanism, rotary
blade mechanism, etc. Information on the design of gravity separators is provided by the Amer-
ican Petroleum Institute. When oil and grease are introduced into the waste stream by scouring
with non-biodegradable detergents, an oil-in-water emulsion is formed. This emulsion cannot be
effectively treated in a biological system. Reduction of these oils will require emulsion breaking
using acid cracking, chemical coagulation or de-emulsifying agents. One knit fabric finishing mill
pilot tested the use of ultrafiltration for separating and concentrating waste knitting oils. The
pilot system operated at a flux rate of 60 gpd per square foot at 200 psig and temperatures of
77° F. Initial results were not encouraging due to fouling of the membrane. Other membranes
are being investigated.
8.10 Chrome Removal
Chromium is used for oxidation in some cotton and rayon dyeing and for chemical fixation in
wool dyeing. Usually, sodium dichromate, the hexavalent or oxidized form of chromium, is
used, and a small percentage of chromic (trivalent) chromium is produced on reduction. The
hexavalent form is yellow and soluble at all pH's, while the trivalent form is greenish and
insoluble at pH's above 6.5.
In cotton and synthetic dyeing, other oxidants (air, hydrogen peroxide, peroxy acids and their
salts) may be used in place of the chromate, and complete chromium removal may be obtained.
In wool dyeing, excessive chrome add-ons are often used. A considerable reduction in effluent
chromium concentrations may be obtained by reducing the add-ons.
8-52
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Concentrations of chromates used in dyeing are not expected to significantly reduce the effi-
ciency of the activated sludge process, but may affect anaerobic sludge digestion.
When in-plant removal is not possible, removal of chromium is best accomplished on segregated
waste streams by chemical treatment. Chromium as hexavalent chrome (Cr ") is toxic. It is
removed by reduction to its trivalent form (Cr+^) which is less toxic by a factor of about 100.
After reduction, the trivalent chrome may be precipitated as the hydroxide and removed as a
sludge. The effluent is introduced into the mill wastewater treatment plant.
The reduction of chrome is pH dependent, at lower pH (less than 4) requires less retention
time. Sulfur dioxide (S02) is generally used as a reducing agent though other chemicals such as
ferrous sulfate (FeS04) and sodium metabisulfite (^28205) have also been used.
Precipitation reactions are also pH dependent with pH 9 as the optimum. Hydroxide sources
used for precipitation are generally sodium hydroxide (NaOH) or lime.
The treatment process may be best suited to a batch type system when the daily volume is less
than approximately 50,000 gallons. Two tanks each with one day's flow are used. Continuous
treatment will require a reaction tank, pH adjustment tank, and a settling tank (see Figure 8-24).
Suggested design parameters are given in the following Table:
TABLE 8-15
CHROMIUM REMOVAL DESIGN PARAMETERS
Reduction pH — <3
Precipitation pH — 8.0 to 9.9
Flocculation Time — 20 minutes
Clarifier Overflow Rate — <500 gal/day/sq. ft.
Clarifier Depth — 10 to 12 feet
Sludge concentration — 1-2% by weight
The continuous chrome reduction process requires instrumentation and control. The reduction
tank should be controlled using pH and ORP (oxidation reduction potential); the adjustment
tank requires pH control.
8-53
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Chromium waste
Reducing
agent
(sulfur dioxide)
Mixing
tank
Mixing
tank
Acid (sulfuric)
Alkaline (caustic)
Flotation
or
sedimentation
Sludge
Treated effluent
FIGURE 8-24
CHROMIUM REMOVAL PROCESS
Source: Lockwood Greene Engineers, Inc.
8-54
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8.11 Color Removal
Color is found in wastewater throughout the textile industry. Some colors are water soluble and
some are not (dispersed and vat 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. Since color chemicals are specifically formulated for resistance to degrada-
tion under the oxidizing conditions of the world, it is not surprising that removal of color in an
aerobic biological system is erratic. Activated sludge systems can generally remove about 50 to
90% of the color.
When color removal is required, all in-plant means of reducing the color in the waste must be
used. This may involve the following:
• Segregate all waste print pastes, if any, and dispose of separately in landfill, ocean or incin-
erator.
• Reduce losses in the color shop by careful hand cleaning of all brushes, troughs, doctor
blades, cans, tanks, and screens.
• Attempt to get weaving mills to reduce the use of fugitive tints in weaving.
• Try to exhaust the dyes more thoroughly in the dye process.
• Use dye processes that cause less color loss; for example, solvent, pad-and-stream, micro-
foam, methanol, and ammonia dyeing.
Following this, only the concentrated color wastes should be segregated and treated, as this may
possibly produce enough color removal to satisfy the requirements. This will usually involve the
exhausted-dye baths and the color-shop wastes (cleanup, wash after printing and blanket wash).
Color removal technology at present includes the use of chemical coagulation and/or carbon
adsorption. See following sections 8.11.1 and 8.11.2. Generally water insoluble dyes can be
handled by chemical coagulation while soluble dyes require carbon adsorption. Some waste-
waters may require both processes. A recent study conducted at North Carolina Wastewater
Research Center, (co-sponsored by ADMI and EPA) investigated the best methods of decolori-
zation by dye class using coagulation and adsorption. The results of this study is described in
Table 8-16.
Additional color removal methods under investigation are the use of ozone and hyperfiltration.
A few years ago pholodegradation was investigated but was found to require many weeks of
exposure.
8-55
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8.11.1 Chenrri cal Precipation
Color removal of dispersed, vat, and sulfur dyes is well suited to chemical treatment. Coagulants
such as alum and ferric sulfate applied at approximately 300 to 600 mg/1 or lime at approxi-
mately 300 to 600 mg/1 will remove 75 to 90% of the color. In addition to the quantity of
chemical required, significant consideration in the selection of coagulant to be used are the
characteristics,of sludge produced. Alum sludge is generally most voluminous; ferric sulfate
produces a sludge with less volume than alum but larger than lime. Lime sludge settles fast and
can be thickened to the highest concentration. In addition, lime sludge dewaters easily on a
vacuum filter.
The results of laboratory scale pilot plant studies on chemical coagulation of dye wastes were
reported by Souther and Alspaugh of Cone Mills Corporation (17). The pilot plant consisted of
waste storage, rapid mixing, flocculation, and 2-hour sedimentation. Chemicals were fed on a
continuous basis. The findings of this study are illustrated in Table 8-17.
TABLE 8-17
TREATMENT OF TEXTILE DYE WASTES BY CHEMICAL COAGULATION
Waste
A
A
A
B
B
B
B
Coagulant
Chemicals
FeSO4
Lime*
Alum
H2SO4
CaCl2
FeSO4
FeSO4
Lime*
Alum
H2SO4
CaCl2
Dosage
ppm
700
700
2510
780
2950
700
490
490
2000
800
900
PH
Initial
10.2
10.2
102
11 0
11 0
11 0
11.0
Final
102
60
8.4
102
11 0
5.7
10.8
BOD
Initial
1028
1028
1028
—
—
—
—
Color
Initial
40000
40000
40000
—
—
—
—
Removals %
BOD
41 5
42.7
425
425
52 5
56.9
49.0
Color
91 0
975
85
80
80
90
84
Waste A — Waste water from sulfur and indigo dye mill
Note: 14 days storage in lagoon effected no observable reduction in color
Waste B — Waste water from vat, sulfur, and indigo dyeing and finishing mill
* High calcium hydrate Ca(OH>2
Representative value
8-57
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8.11.2 Activated Carbon Adsorption
8.11.2.1 Carbon Characteristics
Granular activated carbon can be manufactured using a number of source materials, including
bituminous coal, coconut shells, and pulp mill black ash. The surface area of a pound of granular
carbon is equal to 125 acres, thus illustrating the magnitude of the porosity involved.
When a wastewater containing organic chemicals passes through a bed of carbon, the chemical
molecules come in contact with the surface of the carbon and are held there by weak physical
forces called Van de Waals forces. The water continues through the bed, with a reduced concen-
tration of organic contaminants.
It is important to note when there is a mixture of organic molecules present, adsorption selec-
tivity becomes a prime factor in the efficiency of the unit process. That is, carbon will pre-
ferentially adsorb some organic molecules over others. This selectivity is governed by three
properties of the molecules: molecular structure, molecular weight, and molecular polarity.
For example, if a wastewater contains a combination of an organic dye and a solvent, the
dye, being a larger compound with a higher molecular weight than the solvent, would be
more readily adsorbed by the carbon; therefore, there is a lack of correlation between the initial
color value and the required carbon dosage. Activated carbon adsorption is generally effective
in decolorizing reactive, basic, acid, azoic, and 1:2 metal complex dyeing wastewaters.
8.11.2.2 Adsorption Feasibility
An adsorption isotherm is usually run on representative samples of wastewater to determine the
feasibility of using granular carbon to remove the organics. This test is a very useful tool in
determining the feasibility of carbon treatment. (See Table 8-18 for isotherm results from tests
on textile wastewater.) The dosages from an isotherm may be very conservative, since they do
not include the effects of biological degradation of organics during treatment.
An adsorption isotherm will provide the following useful information:
• Adsorb ability
• Weight pickup
• Degree of removal
• Sensitivity to containment
• Effect of variables such as pH, temperature, etc.
8-58
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TABLE 8-18
TEXTILE INDUSTRY WASTEWATER SURVEY
SUMMARY OF ADSORPTION ISOTHERM RESULTS
TOC
Color
Untreated
Wastewater
Range
9-4670
(OD) 002-540
(APHA)
50-7000
Median
290
056
450
Following
Filtration
Range
9-3335
0 02-1 64
0 3-3500
Median
183
029
410
Following
Adsorption
Range
1-440
0 005-0 09
0-15
Median
16
001
0
Organic
Reduction (%)
Range
75-99
78-100
98-100
Median
94
98
100
*OD — Optical Density
"APHA — American Public Health Association
Source Calgon Corporation From Experience with Granular Activated Carbon In Treatment of Textile Industry
Wastewaters, EPA Seminar, Atlanta Ga , September 1973
8.11.2.3 Pilot Carbon-Column Tests
The purpose of pilot tests is to obtain operating and design information. The test which should
be carried out in conjunction with pretreatment studies involves passing a side stream to four
columns filled with granular carbon and connected in series. The data obtained from the pilot
column study tests indicate:
• The effect of biological activity
• Performance under dynamic conditions
• Filtration characteristics
• Contact time necessary to accomplish objectives
8.11.2.4 Pretreatment Requirements
It sometimes becomes necessary to treat wastewater prior to adsorption. Suspended solids con-
tent above 50 mg/1, for instance, would collect in the carbon bed and create excessive head
loss across the bed. Lint can also cause premature pressure drop and problems by clogging
pumps and valves. General practices employed for suspended solids or lint removal are screen-
ing devices, sand filters, diatomaceous earth filters, or conventional clarifiers. Adjustments in pH
might also be necessary to destabilize colloidal materials or to optimize the adsorption process.
8.11.2.5 Adsorbers
Either pressure vessels or common wall concrete containers may be employed to house the car-
bon. The choice of adsorber types will be based on economics, land availability, and the amount
of suspended solids present in the influent to the adsorption system.
8-59
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These adsorbers are similar in design to rapid sand filters found in potable water plants. Water
may be percolated through these adsorbers either upflow or downflow at surface loading rates
anywhere up to 10 to 12 gpm/ft2.
Adsorption systems configurations fall into four basic categories:
• Moving beds
• Fixed beds in series
• Fixed beds in parallel
• Expanded beds
8.11.2.6 Carbon Usage and Thermal Reactivation
When activated carbon has become exhausted, three available alternatives may be considered:
• Throw the exhausted carbon away
• Thermally reactivate the carbon to its virgin quality and reuse it
• Have another company pick up the exhausted carbon and reactivate it for you (custom
reactivation)
The method chosen is usually a matter of economics. Naturally, the most expensive method
would be to employ the carbon on a throwaway basis. This method is usually reserved for the
very small adsorption systems in which the carbon exhaustion rate is extremely low. When
carbon usage rate reaches 400 Ibs/day thermal regeneration may be economical.
If the choice is made to reactivate the carbon, then thermal regeneration equipment must be
designed and installed based on the carbon exhaustion rate. Normally, 30 to 50% extra capa-
city is designed into the thermal-reactivation unit, since the increase in costs is not signifi-
cantly greater than a unit sized to handle the specific exhaustion rate that was determined
through testing. Figure 8-25 illustrates a typical reactivation system.
Both multiple-hearth furnaces and rotary kilns have been employed for thermal regeneration
of the carbon. Since thermal reactivation equipment is a significant portion of the capital in-
vestment, individuals may consider having someone else thermally reactivate their carbon.
This approach to reactivation is usually chosen by those persons who do not want to reactivate
the carbon themselves or to expend the capital required to purchase a thermal-reactivation unit.
8.11.2.7 Biological Reactivation
Spent carbon granules can be subjected to a virile aerobic biological culture that desorbs and
bio-oxidizes the desorbed matter, thereby reactivating the carbon.
8-60
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TABLE 8-19
ACTIVATED CARBON ADSORPTION DESIGN PARAMETERS
System Types.
Mesh Carbon
Flow Rate
Contact Time
Column Bed Dimensions:
pH of Regenerant Liquor
DO of Regenerant Liquor
Bed Backwash Rate
Reactivation:
Temperature
Furnace Loading
Carbon Loss
Fixed Beds (Series or Parallel)
Moving Beds
Expanded Beds
8 x 30, 12 x 30 to 12 x 40
5 to 15 gpm/sq. ft.
45 to 75 min.
Depth — 10 to 30 ft.
Diameter — 4 to 20 ft.
Maintain 6.5 to 8 0
Maintain 2 mg/l
20 to 30 gpm/sq. ft.
1600° to 1800° F.
50 to 100 Ib/sq. ft./day
2 to 10%
8.11.3 Synthetic Resin Adsorption
Synthetic resins are used to remove refractory organic matter (soluble color, phenols, surfact-
ants and dissolved metals) from wastewaters. The resins can be regenerated for reuse with
dilute alkali (2% NaOH) or solvents (methanol). Adsorbent resins and granular carbon are used
in a similar way. Resins exhibit a higher adsorption rate than carbon, thus permitting smaller
equipment sizes. Columns of different types of resins can be arranged in series for the removal
of different specific classes of dyes and the system can be automated.
Regeneration may be keyed to effluent color or a timer. Tests at one textile finishing mill
required regeneration after 7 to 10 days. The spent caustic soda is neutralized with a sulfuric
acid rinse.
When methanol is used for regeneration, the spent dyes can be distilled, condensed and re-
covered and disposed of by thermal oxidation. Indications are that synthetic resins can remove
approximately 90% color, 60% COD and 40% BOD. The life expectancy of caustic-regenerable
resins is about 3 to 5 years, and methanol-regenerable resins could last indefinitely (18).
Figure 8-26 represents a typical resin adsorption system.
8-62
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8-63
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TABLE 8-20
SYNTHETIC RESIN ADSORPTION DESIGN PARAMETERS
Hydraulic Loading
Regeneration Time
Backwash Rate
Regenerant Dosage
1-2 GMP/cu. ft. resin
7 to 10 days
10 x Flow
2% NaOH @ 130° to 140° F.
8.11.4 Ozonation
Research work at a finishing mill revealed successful color removal using ozone. It was found
necessary to use a multiple contact (2-stage) process. Substantially less ozone is required at a
pH of 5.0 rather than at 6.5. Little COD decrease or BOD increase was found to occur with
low ozone dose and contact time (16).
Based upon the previously mentioned work at the Wastewater Research Center, ozone treat-
ment is effective with reactive dyes but not with disperse dyes.
Additional work on samples from a carpet mill revealed an 80% color reduction using an
ozone dosage of 15 mg/1 (19).
Because ozone is unstable, it must be produced on site; it cannot be shipped. Ozone is produced
by passing dry air or oxygen between two plates connected to an alternating current source. The
process produces ozone as a mixture with either air or oxygen, and the exit gas from the ozon-
ator typically contains 1% ozone from air feed or 1.7% ozone using oxygen feed. The ozonized
gas can then be dispersed into the water to be treated either by various injection methods or by
forcing the pressurized gas through a porous diffuser at the bottom of a contact tank or column
(see Figure 8-27).
In one method, ozone containing gas and water mixes in a specially designed positive pressure
injector and flows concurrently through the system before the gas and liquid are separated.
Ozonation of dispersed, metallic dyes and their aromatic dye carriers and additives appears
practical with and without the conjunctive use of exchange resins or lime addition. Laboratory
studies were successful in deodorization of sulfur dye waste and reduction of copper and color
in metallic dye wastewaters (20).
8-64
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Off
gas
Ozonated
wastewater
Wastewater
Contact
column
Oxygen
cylinder
FIGURE 8-27
OZONE TREATMENT SYSTEM
Source: Lockwood Greene Engineers, Inc.
8-65
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8.11.5 Hyperfiltration
Hyperfiltration (reverse osmosis) involves the filtering of aqueous solutions by membranes or
hollow fibers with fluxrates of 5 to 50 gpd per square foot at 350 to 1000 psig. The system is
capable of removing substantial fractions of dissolved impurities, including organic and in-
organic material.
There are four basic configurations of hyperfiltration available: spiral, tubular, hollow-fine
fiber and dynamic. See Table 8-21 for characteristics of each.
TABLE 8-21
MEMBRANE CHARACTERISTICS
Membrane
Material
Production Rate
gal/ft3 - day
Method of Mem-
brane Replacement
High Pressure
Limitation
Particles in Feed
Permissible Feed
Range, pH
Maximum
Temperature, F°
Spiral
Cellulose acetate
500-7500
Module (on-site)
Membrane
compaction
Filtration required
5.5-7.5
100
Tubular
Cellulose acetate
100-1500
Tubes (on-site)
Membrane
compaction
No problem
5.5-7.5
100
Hollow-Fine Fiber
Polyamide
200-15000
Module (on-site)
Fiber collapse
Filtration required
2-10
100
Dynamic
Hydrous Zr (IV)
oxide-polyacrylate
1500-15000
In-situ
No problem
No problem
4-11
200
Source Textile Technology/Ecology Interface, 1975, Recycle of Textile Wastewaters, Brandon and Porter
A recent on-site pilot plant investigation (under EPA Grant # S-800929) (16) at a 2 mgd dyeing
and finishing plant indicates color removal of approximately 99% and water recovery of up to
90%. It was found that batch dyehouse discharges need only be filtered through 25 micron and
1 micron cartridge filters in series before passage through hyperfiltration membranes. Tempera-
ture and pH were controlled per the manufacturers recommendations. For a summary of the
study's performance see Table 8-22.
The results of this study indicated that hyperfiltration is capable of renovating composite
dyeing and finishing plant wastewater such that the purified water and concentrated waste dyes
may be reused in production dyeing. Though the results of this work have been encouraging,
additional work will be necessary to establish the process fully. Figure 8-28 illustrates a typical
hyperfiltration and recovery system.
8-66
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TABLE 8-22
SUMMARY OF PERFORMANCE OF HYPERFILTRATION MODULES IN
DEMONSTRATION PILOT PLANT1
Manufacturers:
Membrane:
Configuration:
Test Date:
Hours of Test:
Test Conditions:
Pre-filtration
PH
Temperature, °F
Pressure, psi
Average Rejection,
% Total Solids
Color
Conductivity
COD
Westinghouse
Cellulose
internal tubular
12/73 - 1/74
1059
25-micron
cartridges
5.6- 7.0
55 - 90
300 - 450
95
99+
92
96
Dupont
Polyamide
hollow-fine fiber
2/74 - 3/74
187
D.E.3
6.2-83
52 - 90
350
95
99+
94
92
Gulf2
Cellulose Acetate
spiral wound
4/74
804
25-micron
cartridges
5.8 - 7.0
59 - 78
400
96
99+
95
94
Selas Flotronics
Zr (IV) - PAA
externally coated
tube bundle
6/74 - 7/74
944
250-micron
screen
6.6- 8.5
68-195
350- 1050
90
98+
85
95
1 Total plant composite and dyehouse (only) wastewaters used in this study
2 Now ROGA, a Division or U O P , Inc
3 Diatomaceous earth - swimming pool filter - preceded 25-micron and 1-micron cartridge filter
Source Textile Technology/Ecology Interface, 1975, Recycle of Textile Wastewaters, Brandon and Porter
8.12 Other Pollutants Removal
8.12.1 Phenolics
Phenolics in the wastewater indicate the use of chemical compounds containing the phenol
structure. Low concentrations in the parts-per-billion range may cause off-tastes in drinking
water after chlorination or in fish. Many process chemicals, including some detergents, have this
structure as part of the molecule, but the major sources are probably the orthophenylphenol
used as a dye carrier and the phenol-formaldehyde resin used for final finishing. The only dis-
charge from the final finishing process is the excess solution left in the pad or impregnating
trough. This should never be dumped to waste. It may be sprayed on the wastepaper or wood
collected in the mill and incinerated.
Activated sludge will oxidize most of the phenolics if the associated chemical structure is not
too complicated, but the rigorous treated-effluent guideline concentrations may still be exceed-
ed. When this happens, a process-chemical survey may reveal the probable source, and treatment
8-67
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8-68
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or process-chemical substitution should involve the point of origin. Chemical coagulation, oxida-
tion with potassium permanganate or physical adsorption may be useful in removing these
compounds.
8.12.2 Metals
Metals enter the waste stream from mordants, metallized dyes, dye oxidants, catalysts for resin
treatment, acid fulling, sizing preservatives and impurities found in common chemicals. Copper,
zinc and chromium are normally used at low levels in textile processing. These are concentrated
in the activated sludge at 20 to 100 times the influent concentrations. AcidL pH's may cause
some bacterial kills, since dissolved metallic ions are more toxic than the insoluble metallic
hydroxides and carbonates normally present. Of particular concern are the so called toxic
metals, whose discharge to the receiving waters may be limited. In general, most metals do not
have serious effects in biological waste treatment systems, provided the pH is maintained in the
range of 8 or above. Under such conditions the metals are precipitated as the hydroxides be-
come incorporated in the sludge, and the amount of metal that can exist in ionic form is negli-
gible. The presence of the precipitated hydroxides, however, constitutes a serious threat. If the
pH should fall, large amounts of metals in the ionic form could be released and cause great harm
to the treatment plant and stream biota. Mercury is an exception and should be recognized. It
should be removed at the source by isolation and separate treatment.
8.12.3 Sulfide
Sulfide usage in textile processing is very low, and sulfide is occasionally present in mill wastes.
If present, the pH should be kept in the alkaline region of 9 to 10 to prevent the volatilization of
the very odorous hydrogen sulfide. The activated-sludge process will readily oxidize sulfide to
sulfate. Generally, the presence of sulfide will be no problem. The major source of trouble will
be production of sulfide odors in the lateral lines to the sewage plant if acidic pH's are produced
by other wastes in the system. If desired, sulfide may be oxidized by hydrogen peroxide, chlor-
ine, hypochlorite or potassium permanganate.
8.12.4 Detergents (MBAS, ABS, LAS)
Detergents are usually measured by the methylene-blue active substances (MBAS) and may be
composed of alkyl benzene sulfonates (ABS), normally considered as nonbiodegradable, and
linear alkyl sulfonates (LAS), normally considered as biodegradable. The nondegradable ABS
compounds are no longer manufactured for general detergent use, but they may be used in some
textile operations in which a considerable portion may pass through the activated-sludge treat-
ment process. When reductions are required, the most practical way is to trace the source (e.g.,
through a process-chemical inventory survey) and to eliminate its use by substituting a biode-
gradable LAS detergent or even soap.
8-69
-------
8.12.5 Phosphate
In some instances, phosphate removal may be required. If so, it may be more readily done by
substituting nonphosphate chemicals such as ethylene-diaminete-triacetic acid (EDTA) and
others for the phosphates normally used. When using EDTA or other chelating agents, care must
be taken to determine if a reaction takes place with metals to form soluble forms which escape
into the effluent. If treatment is necessary, phosphate may be readily reduced to below 1 mg/1
by chemical coagulation with ferris, ferrous and aluminum salts or with lime (9). The coagula-
tion may be done before, after or even in the aeration tank of the activated-sludge process.
8.12.6 Nitrogen
Nitrogen in wastes may occur as ammonia, nitrite, nitrate or organic nitrogen. In biological-
oxidation, ammonia may be converted to organic nitrogen in the bacterial bodies and to nitrites
and nitrates. The organic nitrogen may be removed as sludge, but the unconverted ammonia,
nitrite arid nitrate are soluble and will be present in the effluent. In some cases, oxidation of
the ammonia in the stream may deplete the oxygen resources in the stream, since ammonia has
a very high potential oxygen demand of 423%. In addition, ammonia has a very high chlorine
demand and may raise chlorine use for disinfection to high levels. This may also tend to make
the effluent toxic to fish because of the chlorinated amines produced.
Ammonia removal may be accomplished in two ways. Carbonaceous BOD such as methanol
may be added to aeration tank to convert the excess ammonia to organic nitrogen as bacterial
bodies and may be removed as sludge. It also may be removed by raising the pH to 9 to 11 with
lime or sodium hydroxide and by aerating the mixture to gasify the ammonia.
Nitrites and nitrates though usually low in textile effluents can cause problems since they may
be denitrified by certain bacteria to produce nitrogen gas, which causes sludge rising in second-
ary settling basins. In addition, they may cause excessive algae growths in the receiving stream.
They may be removed by creating favorable conditions for the denitrification process, described
above to occur, but this also presents many difficulties.
The best way to solve the nitrogen problem is to limit ammonia, nitrite and nitrate use in proces-
sing. If such use is fixed to produce a BOD :N ratio of 100:5, practically all of the nitrogen will
be converted to organic nitrogen and may be removed as sludge.
8.13 Sludge Treatment
Sludge treatment generally consists of all or part of digestion, dewatering and ultimate disposal.
A number of alternative techniques are available as illustrated in Figure 8-29.
8-70
-------
Filtrate
return
Vacuum m Filter \ I Centri
filters / \ press / \ fuge
FIGURE 8-29
SLUDGE HANDLING, DEWATERING AND DISPOSAL
Source: National Commission on Water Quality, Textile Industry Technology and Costs of
Wastewater Control, Lockwood Greene Engineers, Inc., June, 1975
8-71
-------
8.13.1 Aerobic Digestion
The major objective of aerobic digestion is to produce a biologically stable end product suitable
for disposal or subsequent treatment in a variety of processes. Aerobic digestion is generally de-
fined as a process in which microorganisms obtain energy by endogenous or auto-oxidation of
their cellular protoplasm. The biologically degradable constituents of the cellular material are
slowly oxidized to carbon dioxide, water and ammonia, with the ammonia being further con-
verted to nitrates during the process. The aerobic digestion of secondary excess activated
sludge may be considered to be a continuation of the activated sludge process.
The suggested minimum detention time for excess activated sludge is approximately 15 days. If
the actual temperature in the digestion basin is anticipated to be much less than 60° F., addi-
tional capacity should be provided.
In general, aerobic digesters are similar to conventional activated sludge tanks in that they are
not covered or insulated. Thus they are generally more economical to construct than are cover-
ed, insulated, and heated anaerobic digesters (see Figure 8-30). Most digesters are operated on a
flow-through basis where raw excess sludge enters the digester directly from the clarifier. Simi-
lar to conventional aeration tanks, if diffused aeration is employed, the aerobic digesters may be
designed for spiral roll or cross roll aeration. Recently, surface mechanical aeration is finding
popularity in the design of aerobic digesters. The mixing qualities and oxygen transfer capa-
bility of the surface aerators are generally superior to the diffused aeration systems per unit
horsepower input.
Air plug valve
Supernatant
draw off.
Baffle" t
plate
Decant
chamber
4" return sludge
air lift pump
Waste
sludge-*
draw-off
FIGURE 8-30
CIRCULAR AEROBIC DIGESTER
Source: Environmental Protection Agency, Process Design Manual for
Sludge Treatment and Disposal
8-72
-------
Design parameters for aerobic digesters are suggested as follows:
TABLE 8-23
DESIGN PARAMETERS FOR AEROBIC DIGESTERS
Detention Time
VSS Loading
Air Requirements:
Diffusers
Mechanical
Temperature
Tank Depth
Volatile Solids Reduction
15 (days)
0.024 to 0.14 (Ib/ftVday)
15to20(cfm/1000ft3)
100 to 125 (HP/MG)
15 (°C)
15 (ft)
60 (% Eff.)
8.13.2 Sludge Thickening
Thickeners are used to decrease the hydraulic loading in sludge digestion and dewatering units
and, thus, increase their efficiency in terms of the weight of solids processed per unit area or
volume per unit time. The sludge may be thickened either by gravity or dissolved air flotation
(see Section 8.5.4).
Gravity thickeners are continuously fed by waste sludge, and thickened sludge is continuously
withdrawn from the thickener. Design is on the basis of unit area, square feed per pounds/solids
per day, in which the required surface area is related to solids entering and leaving the unit.
Required design data are derived from batch settling tests and analysis of the settling curve.
Gravity thickeners resemble conventional circular clarifiers with the exception of having a great-
er tank bottom slope and pickets on the mechanical scraping mechanism (see Figure 8-31). The
pickets stir the sludge gently, release water, air and gas and push the concentrated sludge to a
central collection well. In some cases, flotation thickening will produce a sludge (float) which
will dewater more readily.
Following is a tabulation of typical design parameters for gravity thickening:
TABLE 8-24
GRAVITY THICKENING DESIGN PARAMETERS
Influent Solids Concentration
Solids Flux Rate
Underflow SS Concentrations
Overflow Rate
1.0 (%)
4-13 (Ib SS/sq. ft-day)
2 (%)
200 (gal/day/sq. ft.)
8-73
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8.13.3 Dewatering
In the past, sludge dewatering of textile wastes has been via the simplest and least cost options
such as lagoons or drying beds. These methods appeared most attractive to the large number of
mills located in the southeast where climatic conditions and land values were most suitable.
With today's considerations for groundwater protection, elimination of odors and increasing
land values, these methods may no longer be the best suited. Though considerably more costly,
dewatering using vacuum filtration, centrifugation and filter presses are gaining in use in order
to eliminate these problems. Other dewatering units include the horizontal belt/press filter, dual
cell gravity filter and multi-roll press. Design experience, however, is quite limited for textile
sludges, and difficulties have been encountered with each dewatering method. Chemical floes,
especially alum, are particularly difficult to dewater due to their more delicate, finely divided
character.
8.13.3.1 Drying Beds
8.13.3.la Factors Affecting Design
A most widely used dewatering method in the United States is drying of sludge on open or un-
covered sandbeds. Sandbeds possess the advantage of needing little operator attention and skill.
Air drying is normally restricted to well digested sludge, because raw sludge is odorous, attracts
insects, and does not dry satisfactorily when applied at reasonable depths. Oil and grease dis-
charged with raw sludge clog sandbed pores and thereby seriously retard drainage. The design
and use of drying beds are affected by many parameters. They include weather conditions,
sludge characteristics, land values and proximity of residences, and use of sludge conditioning
aids. Climatic conditions are most important. Factors such as the amount and rate of precipi-
tation, percentage of sunshine, air temperature, relative humidity, and wind velocity determine
the effectiveness of air drying.
The nature and moisture content of the sludge discharged to drying beds influences the drying
process. Sludges containing grit dry rapidly; those containing grease more slowly; aged sludge
dries slower than new sludge; primary sludge dries faster than secondary sludge; and digested
sludge dries faster than fresh sludge and cracks earlier. It is important that wastewater sludge
be well digested for optimum drying. In well digested sludge, entrained gases tend to float the
sludge solids and leave a layer of relatively clear liquid, which can readily drain through the
sand. The use of dewatering polymer when pumping to a drying bed may greatly reduce drying
time and increase bed efficiency.
8.13.3.1b Design Criteria for Sandbeds
Design standards vary from region to region in the United States. This variance is partly due to
climatic differences. However, Table 8-25 presents typical criteria for the design of open sand
drying beds.
8-75
-------
TABLE 8-25
CRITERIA FOR THE DESIGN OF SANDBEDS
Type of Digested Sludge
Sludge Loading
Dry Solids
(Ib/sq. ft./yr.)
Standard Trickling Filter
Activated
Chemically precipitated
22.0
15.0
22.0
Sandbeds can be enclosed by glass. Glass enclosures protect the drying sludge from rain, control
odors and insects, reduce the drying periods during cold weather, and can improve the appear-
ance of a waste treatment plant. Experience has shown that only 67 to 75% of area required
for an open bed is needed for an enclosed bed. Good ventilation is important to control humid-
ity and to optimize the evaporation rate. As expected, evaporation occurs rapidly in warm, dry
weather. Adaptation of mechanical sludge removal equipment to enclosed beds is more diffi-
cult than to open drying beds.
Drying beds usually consist of 4 to 9 inches of sand which is placed over 8 to 18 inches of
graded gravel or stone. The sand typically has an effective size of 0.3 to 1.2 mm and a uniform-
ity coefficient of less than 5.0. Gravel is normally graded from 1/8 to 1.0 inch. Drying beds
have underdrains that are spaced from 8 to 20 feet apart. Underdrain piping is often vitrified
clay laid with open joints, has a minimum diameter of 4 inches, and has a minimum slope of
about \%. Collected filtrate is usually returned to the treatment plant (see Figure 8-32).
The Ten State Standards make the following design recommendations:
• The top 3 inches of gravel consist of 1/8 to 1/4-inch gravel
• The gravel extends at least 6 inches above the top of the underdrains
• The gravel layer should be 12 inches deep
• The sand layer should be at least 6 to 9 inches deep
• Underdrains should be no more than 20 feet apart
• Bed walls should be watertight and extend 15 to 18 inches above and at least 6 inches
below the surface
• Outer walls should be curved to prevent soil from washing onto the beds
• At least 2 beds should be provided
• Pairs of concrete truck tracks at 20-foot centers should be provided for all beds
• The influent pipe should terminate at least 12 inches above the surface with concrete
splash plates provided at discharge points.
Mechanical lifting of sludge has been practiced for many years at some large treatment plants,
but now it is receiving more attention as labor costs continue to rise. Mechanical devices can
remove sludges of 20 to 30% solids while cakes of 30 to 40% are generally required for hand
removal.
8-76
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walk
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6-m. underdrain laid
with open joints
FIGURE 8-32
SLUDGE DRYING BED
Source: Metcalf & Eddy, Wastewater Engineering: Collection, Treatment, Disposal
8-77
-------
8.13.3.1c Results of Sandbed Drying
Typical performance data show rapid dewatering during the first one to two days while water
removal by drainage predominates. This is followed by two to five weeks of slow dewatering
principally by evaporation. In good weather, a cake of 45% solids may be achieved in six weeks
with a well digested sludge. As with any dewatering technique, the performance of a sandbed
may be improved by proper chemical conditioning, and the dewatering time may be reduced
by 50% or more. Liftable sludges have been achieved in less than one day with proper chemi-
cal conditioning. Solids contents at 85 to 90% have been achieved on sandbeds.
8.13.3.1d Other Types of Drying Beds
In recent years, there has been increased interest in the use of paved drying beds with limited
drainage systems for dewatering wastewater sludges. The original reasons for proposing paved
bed design were to permit the use of mechanical equipment for cleaning the beds and thereby
to reduce the cost of labor and sand replacement. Modification of drying beds to provide only
limited drainage facilities does not necessarily impair bed performance. In fact, the use of paved
drying beds with limited drainage resulted in shorter drying time as well as more economical
operation when compared with conventional sandbeds. The shorter time occurred because the
use of mechanical equipment for cleaning permits the removal of sludge with a higher moisture
content than in the case of hand cleaning. The use of paved beds of center drain design for de-
watering aerobically digested activated sludge is not as desirable as conventional sandbeds.
Lateral drainage of activated sludge on paved bed is very poor and does not contribute signifi-
cantly to the dewatering process. The supernatant overlying the sludge cake may drain but the
reduced drainage area of the paved bed compared to the sandbed greatly hampers the rate of
drainage for aerobic sludges.
Wedge wire drying beds have been used successfully in England, a cross-sectional view of one
is shown in Figure 8-33. This approach prevents the rising of water by capillary action through
the media, and the construction lends itself well to mechanical cleaning. The first United States
installations have been made at Rollinsford, New Hampshire, and in Florida. The procedure
used for dewatering sludge begins with the placement of water or effluent to a depth of up to 1
inch over the wedge wire. This water serves as a cushion permitting the added sludge to float
without causing upward or downward pressure across the wedge wire surface and prevents
compression or other disturbance of colloidal particles. The water is then run off by opening
the control valve and controlling the rate so as to prevent a turbid effluent from the bed. After
the free water has been drained, the bed is allowed to dry by drainage and evaporation until the
sludge can be removed. It is possible, in small plants, to place the entire dewatering bed in a tilt-
able unit from which sludge may be removed merely by tilting the entire unit mechanically.
The Rollingford, New Hampshire, plant reports that it dewaters excess activated sludge condi-
tioned with polymers from two percent solids to a liftable condition in four hours.
8-78
-------
Controlled differential head in vent
by restricting rate of drainage
_v
ent
"1
Partition to
Outlet valve to control
rate of drainage
FIGURE 8-33
WEOGEWIRE DRYING BED
(Cross Section)
Source: Environmental Protection Agency, Process Design Manual for Sludge Treatment and
Disposal
8.13.3.2 Drying Lagoons
8.13.3.2a Factors Affecting Design
Lagoon drying is a low cost, simple system for sludge dewatering that has been commonly used
in the United States. Drying lagoons are similar to sandbeds in that the sludge is periodically
removed and the lagoon is refilled. Lagoons have seldom been used where the sludge is never re-
moved, because such systems are limited in application to areas where large quantities of cheap
land are available. Sludge is stabilized to reduce odor problems prior to dewatering in a drying
lagoon. Odor problems with lagoons can be greater than with sandbeds, because sludge in a
lagoon retains water for a longer period than does sludge on a conventional sand drying bed.
Other factors affecting design include consideration of groundwater protection and access con-
trol. Major design factors include climate, subsoil permeability, lagoon depth, loading rates, and
sludge characteristics. The design should provide for uniform distribution of the sludge and for
decanting of supernatant to speed the drying process.
8-79
-------
8.13.3.2b Design Criteria for Drying Lagoons
Criteria cited in the Ten States Standards are given below:
• The soil must be reasonably porous, and the bottom of the lagoon must be at least 18
inches above the maximum groundwater table.
• Surrounding areas must be graded to prevent surface water from entering the lagoon.
• The lagoon depth should not be more than 24 inches.
• At least two lagoons should be provided.
Underdrains have often been proposed where permeable soils are unavailable; however, evapora-
tion is the main mechanism for water removal from a lagoon.
Solids loading rates suggested for drying lagoons are 2.2 to 2.4 Ib./yr./cu. ft. of lagoon capacity.
A dike height of about 2 feet with the depth of sludge after decanting of 15 inches has been
used. Sludge depths of 2.5 to 4 feet may be used in warmer climates where longer drying per-
iods are possible. Dikes should be of a shape and size to permit maintenance, mowing and en-
trance of trucks and front-end loaders for sludge removal.
8.13.3.2c Results of Lagoon Drying
Sludge will generally not dewater in any reasonable period of time to the point that it can be
lifted by a fork except in an extremely hot, arid climate. If sludge is placed in depths of 15
inches or less, it may be removed with a front-end loader in 3 to 5 months. When sludge is to be
used for soil conditioning, it may be desirable to stockpile it for added drying before use. One
proposed approach utilizes a 3-year cycle in which the lagoon is loaded for 1 year, dries for 18
months, is cleaned, and is allowed to rest for 6 months. Definitive data on lagoon drying are
scarce. Sludge may be dewatered from 5% solids to 40 to 45% solids in 2 to 3 years using
sludge depths of 2 to 4 feet.
8.13.3.3 Vacuum Filtration
The function of the vacuum filtration unit is to dewater sludge under applied vacuum by means
of a porous medium which retains the solid but allows the liquid to pass. Vacuum filtration is a
continuous process generally accomplished on a cylindrical drum which passes through the
slurry tank and retains solids on its surface due to an internal vacuum. Drum media may be of
cloth, steel mesh or tightly wound coil springs (see Figure 8-34).
Textile sludges tend to blind the filter medium rapidly. It is possible to reduce this tendency by
using chemical coagulants which reduce specific resistance and increase filtration rate. Common
coagulants used for this purpose include ferric chloride, lime and organic polyelectrolytes.
8-80
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A vacuum filter loading of approximately 3 Ib/sq.ft./hr. may be suitable for textile sludges;
however, due to the differences in drying characteristics of sludges from plant to plant it is
essential to develop design parameters from leaf tests or pilot-plant tests.
The New England Standards provide a number of design considerations:
• Chemical conditioning should precede vacuum filtration
« Filler operation usually does not exceed 30 hrs/wk to allow time for conditioning and
cleaning
• Provide a variable speed drive on filter drum
• Provide vacuum pumps with a capacity of 1.5 cfm/sq. ft. for fabric coated type and
3 cfm/sq. ft. for metal-covered
• Provide filtrate pump and return filtrate lo raw waste stream
8.13.3.4 Centrifugation
Centrifuges have been widely used by industry for separating liquids of different densities or
removing solids. The unit operates basically by feeding a sludge through a stationary feed pipe
and by settling solids out against the bowl wall by centrifugal force. A screw continuously
conveys the solids to the end of the machine for discharge.
There are a number of different types of centrifuges on the market today. The type most often
used for dewatering sludge is the horizontal solid bowl as shown in Figure 8-35.
As in the case of vacuum filtration, chemical conditioning will improve the dewatering process.
One textile finishing mill dewatering a combination biological/chemical sludge uses a cationic
polymer at 10 to 20 Ibs/ton of dry solids for conditioning. A sludge cake with a solids concen-
tration of 12 to 15% is produced with a 95 to 99% solids recovery (10).
Design considerations given by the New England Standards are for the most part very similar to
those for vacuum filtration. In addition, special considerations should be made for foundations
and soundproofing because of the vibration and noise associated with the operation of the cen-
trifuge.
8.13.3.5 Pressure Filtration
The plate and frame filter press is a batch device, which has been used in industry and in Euro-
pean wastewater plants for many years to process sludges difficult to dewater. The press consists
of vertical plates which are held rigidly in a frame and which are pressed together between a
fixed and moving end as illustrated in Figure 8-36. On the face of each individual plate is
mounted a filter cloth. The sludge is fed into the press and passes through feed holes in the trays
along the length of the press. The water passes through the cloth while the solids are retained
8-82
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Cover
Differential speed
gear box
Main drive sheave
Feed pipes
(sludge and
chemical)
Base not shown
Centrate
discharge
Sludge cake
discharge
FIGURE 8-35
CONTINUOUS COUNTERCURRENT SOLID BOWL CENTRIFUGE
Source: Environmental Protection Agency, Process Design Manual for
Sludge Treatment and Disposal
forming a cake on the surface of the cloth. Sludge feeding is stopped when the cavities or cham-
bers between the trays are completely filled. Drainage ports are provided at the bottom of each
press chamber. The filtrate is collected in these, taken to the end of the press, and discharged to
a common drain. At the commencement of a processing cycle, the drainage from a large press
can be in the order of 2,000 to 3,000 gallons per hour. This rate falls rapidly to about 500 gal-
lons per hour as the cake begins formation and to virtually nothing when the cake completely
fills the chamber. The dewatering step is completed when the filtrate is near zero. At this
point the pump feeding sludge to the press is stopped and any back pressure in the piping is re-
leased through a bypass valve. The electrical closing gear is then operated to open the press. The
individual plates are next moved in turn over the gap between the plates and the moving end.
This allows the filter cakes to fall out. The plate moving step can be either manual or automatic.
When all the plates have been moved and the cakes released, the complete pack of plates is then
pushed back by the moving end and is closed by the electrical closing gear. The valve to the press
is then opened, the sludge feed pump is started, and the next dewatering cycle is begun.
8-83
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Filter cloths
Fixed end
Sludge in
Filtrate drain holes
FIGURE 8-36
CUTAWAY VIEW OF FILTER PRESS
Source: Environmental Protection Agency, Process Design Manual for
Sludge Treatment and Disposal
8-84
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One manufacturer has pilot tested pressure filtration of activated sludge from treatment of
dyehouse wastewater. Depending upon sludge thickening methods used (alum or polymers) and
the concentration of sludge entering (1 to 3%) the filter system, results were as follows (21):
Sludge Conditioning Chemical Hydrated Lime
Filtration Cycle Time 75 to 120 min.
Filter Pressure 225 psig
Filter Cake Solids 33 to 39% dry
Filter Cake Density 70 to 75 Ib/cu. ft.
8.14 Sludge Disposal
8.14.1 Spray Irrigation
Design criteria for sludge disposal by spray irrigation is not well suited to standardized para-
meters as the acceptability and success are related to many variables. Of special consideration in
the design of a land application system are the following:
• Sludge Characteristics (heavy metals, etc.)
• Climate
• Geology
• Soil Type
• Plant Cover
• Topography
• Spray Method Used
• Potential Production of Viable Aerosols
A large finishing mill has successfully spray irrigated aerobically digested sludge for more than 8
years (22). Figure 8-37 illustrates a typical spray irrigation system.
The following general requirements were established by the State of South Carolina for the
physical characteristics of a spray site. Additional requirements are found in Addendum No. 2
(April, 1971) of the Ten States Standards:
• Water table depth must be greater than five feet
• Spray rate equal to or less than 2 in/wk or 1/4 in/day depending upon soil type, slopes, etc.
• Soil types - silty or sandy loams (GM-d, SM-d, ML, OL, MH and PT classification).
• Spray schedule — spray 8 hours and rest 160 hours or spray 4 hours and rest 80 hours
• Holding pond — 4 to 7 day holding pond
• Two-foot berm around entire spray area
• Percolation rate — 4 to 15 min/in
8-85
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• Buffer zone — 100 feet beyond spray influence
• Slopes — less than 10%
• Maintain natural vegetation and natural topsoil, as much as possible, adding mulch to bare
or disturbed areas
• Groundwater monitoring well to test subsurface aquifier located in direction of ground-
water flow
• Fencing and appropriate signs around spray site and buffer zone
8.14.2 Landfill
The disposal of industrial and potentially hazardous wastes is generally regulated by State
environmental agencies. Regulations are established for the following types of disposal sites:
• Sanitary
• Milled or Shredded Refuse
• Industrial
Though there is a potential for disposal of industrial wastes at sanitary and shredded refuse
sites, each request is considered on a case-by-case basis. Solid waste generated at industrial
sources is generally divided into five categories:
• Putrescible
• Non-burnable
• Cellulosic
• Inert
• Hazardous
The State of South Carolina includes as hazardous wastes: solvents, solvent residues, oils and
grease, heavy metals, dyes, chemical precipitates, sludges, and slurries.
Landfill sites may be privately owned, owned by a municipality, or constructed by the textile
mill. State permits are generally required for disposal on company owned land. If wastes are not
found acceptable for disposal into an existing landfill it will be necessary to consider disposal to
an area used exclusively for the particular waste, chemical fixation and burial, encapsulation and
burial, or possible incineration. Figure 8-38 illustrates both the area method and trench method
of landfilling.
The important considerations in locating and designing a landfill are as follows:
• The site should be easily accessible and safeguarded against uncontrolled gas movement
• The site should provide for adequate protection of groundwater
• An adequate quantity of earth cover should be available at the site
8-87
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Final earth cover (2 ft.)
Portable fence to
catch blowing paper
Original
ground
Compacted
solid waste
Daily earth
cover (6-in )
AREA METHOD
Earth cover obtained by
excavation in trench
Original
ground
Compacted
solid waste
TRENCH METHOD
FIGURE 8-38
SANITARY LANDFILL
Source: Environmental Engineer's Handbook
8-88
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• Wastes are to be spread in uniform layers not to exceed 2 feet thick
• Compacted wastes should have a minimum cover of 2 feet of compacted earth
• Monitoring of the system should include groundwater observation wells, surface water, and
soils.
8.14.3 Incineration
Sludge disposal via on-site incineration is generally not practiced at textile facilities due to high
costs and potential air pollution problems. Textile wastes are generally low in Btu value. For
mills with limited land available for sludge drying beds or lagoons it may be possible to reduce
sludge volume by thickening and dewatering and to haul sludge cake to a central incineration fa-
cility. Two types of incinerators in common use for sludge are the multiple hearth and fluidized
bed. The multiple-hearth incinerator consists of four or more refractory lined trays and is oper-
ated at about 1350° F. A fluidized bed consists of sand suspended in air and heated to a temper-
ature of 1400 to 1500° F.
8.15 Disinfection
Disinfection for the reduction of fecal coliforms is generally not limited to point source dis-
charges until the deadline for BAT. (Dry processing mills are limited to 400/100 ml for 1977).
Water quality limited discharges, however, may require disinfection by 1977.
Fecal coliform may be present in most textile wastes from domestic facilities. Experience has
shown that due to the chemical concentration of textile wastewater, some effluents exhibit a
very low or non-existent fecal coliform count. Segregation of sanitary streams has the advantage
of reducing required disinfecting facilities to handle less than 5% of the total plant flow. Disinfec-
tion is most often accomplished with the use of chlorine; however, ozone has recently gained
partial acceptance.
8.15.1 Chlorination
When chlorine is added to water, two reactions, hydrolysis and ionization, take place as shown
in the following:
8-89
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Hydrolysis
C]2 + H20 *- HOC1 + H+ + Cl
(Chlorine (Hypochlorous + (Hydrogen + (Chloride
Gas) Acid) ion) ion)
lonization
HOC1 "-OC1- + H+
(Hypochlorite
ion)
lonization is dependent upon the pH and temperature of the wastewater. The quality of HOCl
and OC1" that is present in water is called the free available chlorine. Free chlorine can also be
added to water in the form of hypochlorite salts such as calcium hypochlorite. The free chlorine
in solution will react with ammonia or organic amines to form chloramines which also serve as
disinfectants, although they are slower reacting.
The quantity of chlorine required for disinfection will depend upon chlorine demand; that is,
the amount of chlorine which will combine with various chemicals before it begins to appear as
a free chlorine residual. The actual dosage required will vary depending upon the characteristics
of the wastewater (organics present, pH, etc.) and therefore is best determined by laboratory
studies.
Chlorine is fed into wastewater either directly as a gas or is mixed with a small flow of water to
produce a precisely controlled, concentrated solution which is then injected into the waste
stream (see Figure 8-39). When hypochlorite is used, it is mixed in a drum to form a concen-
trated solution and is fed by a diaphragm or metering pump. The design goal of the chlorine
mixing process is to provide rapid, intimate mixing of the chlorine solution stream with the
wastewater stream in the shortest possible period. Mixing methods include turbulent flow in a
pipe, mechanical in-line mixing, or the use of a hydraulic pump.
Chlorine is contacted with the wastewater for a period of time (usually 15 to 30 minutes) in a
contact chamber or equivalent volume effluent pipe. Currently there are no commonly accepted
design criteria for contact tanks. They may be circular, rectangular with transverse baffling, or
rectangular with longitudinal baffling. Of importance is the avoidance of short circuiting and
solids deposition.
8-90
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Vent
Wall mounted ejector
Booster pump with
built in strainer
Chlorine solution
diffuser
• Chlorine contact
chamber
FIGURE 8-39
CHLORINATION
Source: Capital Controls Company
Control of the chlorination system will depend upon wastewater flow. If the flow rate is con-
stant, a manual feed system may be adequate. If the flow is variable, the system may be con-
trolled by flow rate alone or in combination with a residual chlorine analyzer.
The following tabulation lists a range of design parameters used in chlorination:
TABLE 8-26
CHLORINATION DESIGN PARAMETERS
Chlorine Dosage
Contact Time
Effluent Residual
Chlorine Forms:
5 to 15 mg/l
15 to 30 min. (@ max. hourly flow)
0.2 to 1 mg/l
Liquid (gas at room temp.)
Powder (Calcium Hypochlorite)
Solution (Sodium Hypochlorite)
8-91
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8.15.2 Ozonation
Ozone is a powerful oxidizing agent; in fact, its oxidation potential is higher than all commonly
used oxidizing agents. It effectively destroys bacteria and viruses when used as a disinfectant.
Ozone may be generated on site from dry air or from oxygen. There are two types of generators
used, the tube type and the plate type. The generators convert only 1 to 4% of the feed oxygen
gas into ozone. Because of its low solubility, ozone is fed into the wastewater by diffusing or
injecting it into a mixing chamber (see Figure 8-40).
The advantages of using ozone for disinfection include its rapid action; no danger of overtreat-
ment; unaffected by temperature and pH; reduces color (see Section 8.11), phenol and BOD;
and its oxidation products are not poisonous. The following tabulation lists some considera-
tions in the design of an ozonation system:
TABLE 8-27
OZONATION DESIGN PARAMETERS
Ozone Dosage
Contact Time
Ozone Concentration
in Generated Air or Oxygen
Power Consumption:
From Air
From Oxygen
5 to 25 mg/l
1 to 5 minutes
1 to 2% by weight
10 to 13 kwh/lb. ozone
5 to 6 kwh/lb. ozone
8.16 Emerging Technology
8.16.1 Pure Oxygen Activated Sludge
Pure oxygen activated sludge is a relatively new modification of the conventional activated
sludge process. Recent advances in oxygen production technology have improved the economics
of this system. There are two proprietary systems currently being marketed in the United States.
Generally, the oxygen gas is generated on site using either the cryogenic process or the absorp-
tion process.
Atmospheric oxygen (21% by volume) has a relatively low solubility in water (9 mg/l at 20° C.).
In the pure oxygen system (90 to 100% volume) the solubility is increased to almost 45 mg/l.
This allows a more rapid reduction of BOD and may result in less horsepower consumed per
pound of oxygen dissolved.
8-92
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Ozonated air
or oxygen
under
pressure
'Injector air to
water ratio 0 1
Minimum contact time ' Point of injection
in line - 2 minutes Double baffled (see detail below)
in line mixer
Stainless steel diffusion
tube. Length = 0 75 * dia.
of pipe
1" corporation cock'
1" N P T \.SX
or Mueller ^-J
pipe thread
Screen
Vent-*
Water pump
Ozonated air or
oxygen under
pressure
Water influent
•«— Injector
n
Mixer drive system
Sealed opening
Ozone gas
N)
zonated water out
Stainless steel tank or
concrete basin
Alternate design with sparge
ring gas diffusor used instead
of partial injection
FIGURE 8-40
OZONE INJECTION METHODS
Source: Water and Wastes Engineering, Nov., 1974, Ozone for Water! What's the Story?,
Harris, W. C.
8-93
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Additional advantages claimed for this approach include: 1) improved settling characteristics;
2) elimination of odors; and 3) reduced land requirements.
The typical pure oxygen system uses three closed tanks in series with oxygen entering the first
tank and flowing concurrently with the wastewater through the third tank which is vented.
Slow speed aerators are used to bring oxygen into contact with the wastewater. The aerator
motors are placed above the tanks for safety reasons (see Figure 8-41).
At the present time there are no pure oxygen activated sludge systems treating textile waste
exclusively. There are, however, several plants in operation and under construction which ef-
fectively treat domestic waste with contributions from textile mills of up to 80% of the total
volume. There have also been a number of treatability tests performed on 100% textile wastes,
including waste containing PVA, with effective treatment results being reported in most cases.
wastewater
feed
Waste activated sludge
FIGURE 8-41
PURE OXYGEN ACTIVATED SLUDGE SYSTEM
Source: Lockwood Greene Engineers, Inc.
8.16.2 Ultrafiltration
Ultrafiltration is a separation process involving the filtering of an aqueous solution by a mem-
brane capable of removing macromolecules and suspended solids. Thus, salts, solvents and low
molecular weight organic solutes pass through the filter membrane into the permeate.
A 25 micron cartridge filter is used to pre-filter the wastewater before entering the ultrafiltra-
tion unit. Pressure required for operating the Ultrafiltration unit is approximately 100 to 200
psi. Ultrafiltration membranes are cleaned periodically depending upon waste characteristics.
Replacement of filter membrane depends upon membrane tolerance to wastewaters.
8-94
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The ultrafiltration technique has been demonstrated in treating wastewaters from metal fin-
ishing operations and food processing plants.
A pilot testing program recently completed at a knit fabric finishing mill indicates substantial
removals of oils (knitting oils) and dyes with the potential of recovery and reuse of greater than
90% of the treated dyehouse wastewaters. Maintaining flow rates through the system has been
a problem, and long-term testing will be necessary to determine applicability to textile waste-
waters containing knitting oils (23).
8.16.3 Hyperfiltration (RO)
Reverse osmosis (RO) is a process whereby dissolved salts are separated from solution by fil-
tering through a semi-permeable membrane at a pressure greater than the naturally occurring
osmotic pressure. Colloidal and organic matter that foul the membrane surfaces can cause high
losses in the quantity of water than can be produced. Salts with low solubility will precipitate
on the membrane and will reduce the quality of product water. Treatment of the wastewater
prior to application of RO, such as activated carbon adsorption or chemical precipitation
followed by filtration, should be added to prevent these losses. Concentrated liquors from
the membrane exchange can be incinerated, in which case scrubbers may be required to protect
air quality.
Two basic membrane materials are in use today; cellulose acetate and aromatic polyamide.
There are three basic membrane configurations; the tabular, the spirally wound, and the hollow
fiber. Of these, the hollow fiber has the most compact equipment.
Though unaware of the use of RO at any textile treatment facility, this process looks promising.
The RO process results in excellent color removal and substantial removal of residual BOD and
COD (using carbon adsorption, chemical coagulation, or filtration as a pretreatment). A form of
RO known as hyperfiltration has been recently studied at a pilot plant level using a dyeing and
finishing plant wastewater. Results indicate recovery of 75 to 90% of the water with successful
reuse in production dyeing (16).
Another potential application of reverse osmosis is recovery of sizing materials. CMC and PVA
will both be retained at great efficiency, allowing these sizing materials to be concentrated for
reuse.
8.16.4 Ion Exchange
Ion exchange is a process in which ions of given species are displaced from an insoluble ex-
change material by ions of a different species in solution. Upon exhaustion of the exchange
medium (resin), the system can be regenerated by flushing with a concentrated solution of the
8-95
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original ion. The exchanged ions in the waste stream are usually concentrated and disposed of
by other means such as evaporation.
This method might not be practical for textile waste since organic material can cause ion ex-
change material to foul. Treatment of secondary effluents for suspended solids and organic
removal is necessary.
A British textile finishing plant uses ion exchange and adsorption to treat dyehouse waste-
waters and reclaim process water. Chemical coagulation and clarification are used as a pre-
treatment (24). The system works as follows:
1. Flocculating chemical and coagulants are vigorously mixed with effluent in the rapid
mixing tank.
2. Low-speed mixing follows to facilitate formation of floe in flocculating basin.
3. Floe settles in settling basin, clarified water is withdrawn at the top, and sludge is
collected in separate tank.
4. Clarification tank.
5. Ion exchange and adsorption tank which consists of three sections: The first contains
a special patented resin. The resin was developed to remove high molecular weight
compounds through ion exchange and adsorption. The second and third sections con-
tain special cationic and macroporous anionic resins for the exchange of metals and
salts, and for the adsorption of low molecular weight compounds. After leaving the
ion exchange component, the water is piped to the reservoir. It is reusable for the
various processes.
6. Caustic soda is employed to regenerate the ion exchanger.
In textile wastewater treatment, one advantage of using this process is that ion exchange is ap-
plicable to highly alkaline waste streams. If the effluent is sodium hydroxide, the anion ex-
changer alone may be used.
It appears that projected costs of ion exchanges for textile waste clean up are sufficiently low
to justify a study to determine long-term applicability.
8.16.5 Electrodialysis
Electrodialysis is a type of ion separation using applied electrical potentials rather than ion
"exchange".
8-96
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Problems associated with the electrodialysis process for wastewater renovation include chemi-
cal precipitation of salts with low solubility on the membrane surface and clogging of the mem-
brane by the residual colloidal organic matter. To reduce membrane fouling, activated carbon,
chemical precipitation, and mixed media filtration may be necessary for pretreatment.
Electrodialysis has not been used for treatment of textile wastewater 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 electro-
dialysis to remove dissolved salts from dye solutions but this has not yet been demonstrated.
8.16.6 Evaporation (Distillation)
Evaporation is the oldest demineralization process. It separates wastes from water through a
liquid vapor conversion. The water is converted to steam, leaving non-volatile waste behind.
When it is condensed back to liquid form, it may be very pure.
To carry out evaporation at reasonable cost, it is necessary to devise special equipment that will
allow for multiple reuse of the heat needed to vaporize the water. Three general types of equip-
ment employed are multi-stage flash evaporation, vertical tube evaporation, and thermal recom-
pression evaporation.
Textile wastewater has a moderately high concentration of organic chemicals in comparison
with the concentrations in brackish or saline waters; therefore, it may be necessary to remove
organic matter first by activated carbon before going to evaporation. Organic chemicals may
have appreciable vapor pressure at the temperature of evaporation. Vapor-liquid equilibrium
relationships will determine whether these organic pollutants can be removed successfully by
evaporation.
Consequently, the application of evaporation to wastewater demands a thorough consideration
and knowledge of the physical chemistry of these wastewaters, especially vapor-liquid equili-
brium, and the subsequent determination of the quality of the condensate acceptable for reuse.
If the wastewater contains very low concentrations of organics and high concentrations of
dissolved inorganic salts, the applicability of evaporation is more readily predicted, being essen-
tially an evaluation of economics.
8.16.7 Freezing
Freezing is a process where pure water collects in crystals on the surface of the wastewater
while the impure compounds remain in solution. When ice crystals are removed and thawed, the
water is very pure. Although the process is usually considered demineralization, it also is capable
of removing organic materials from water. Sand and diatomaceous earth filtration and air for
foam removal are considered necessary preliminary steps before freezing. There are two types
of systems in use; vacuum freeze vapor compression and refrigerant vaporizing.
8-97
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A few small vacuum freeze vapor compression plants have been erected in the U.S.A. and
abroad for desalinization of seawater, but have not had enough service to develop any useful
histories.
Although none of the freezing plants has been used in textile wastewater treatment, its use
appears attractive to the textile industry because of its tolerance of high levels of salts, organics,
suspended solids, and other materials in the feed water. There is insufficient information concern-
ing capital cost, maintenance cost and reliability.
8.16.8 Spray Irrigation
The use of spray irrigation as a method of treating liquid wastes is not a new one. It was used
in this country as far back as 1928. Most spray irrigation systems use domestic sewage effluents
to irrigate agricultural lands. In the past decade, irrigation with industrial wastewaters has grown
more popular. To date, most of the installations have used food processing wastes and organic
chemical wastes. The first few inches of soil will biologically degrade the wastes. Effective
treatment with wastes having extremely high BOD and TSS values has been proven. Operations
at 0° F have been reported. Though no data has been found as to treatability by land applica-
tion of textile wastes, it would appear that this method is certainly a viable option. In fact, it
may prove to be the most economical method of complete treatment available.
Industrial wastewaters having little or no pretreatment have been successfully sprayed. (When
sanitary waste is present, chlorination is required). Application can be made into open fields
where grasses are planted and periodically harvested or into wooded areas where evapotran-
spiration effects are high. Pretreatment would consist of screening, flotation for removal of
grease, chemical coagulation of solids, and aeration in a holding pond. Another possibility is
overland flow using terraced plots.
Regardless of which application methods are investigated, a comprehensive site investigation
study including climatology, geology, hydrology, topography, and agronomy will have to be
made with subsequent pilot plot studies. Of major concern will be potential ground water
contamination, toxic effects from build up of metals, and offensive odors. Nitrogen levels will
also be an important consideration because insufficient nitrogen for plant growth will necessitate
chemical fertilization; conversely, excess nitrogen beyond ability of plants to utilize and store it
will be detrimental. A pH of 5.5 to 7.5 should be maintained which would mean neutralization
may have to be practiced by a number of mills. Grease and oil removal is essential for satisfac-
tory operation of the sprinkling equipment, thus questioning the suitability of this method for
category 1 (wool scouring).
8-98
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8.16.9 Algae Harvesting
Harvesting of algae removes nitrogen from wastewater. Waste effluent is usually deposited in
ponds where the algae are then removed from the wastestream by microstraining or other fil-
tration techniques.
Although this process is theoretically feasible where large quantities of nitrate are to be remov-
ed, it may be necessary to supplement the untreated waste with carbon dioxide to achieve com-
plete nitrogen removal.
The major disadvantages of this process are the large land area requirement and the problems
and costs associated with the harvesting and disposal of the algae. The harvested algae, after
drying, has some value as an animal feed supplement due to its very high protein content. Re-
search on this subject is presently underway in Japan.
8.17 Upgrading Existing Facilities
This section is intended as a guide to possible alternative methods of upgrading existing treat-
ment facilities in an attempt to meet more stringent effluent requirements. Upgrading to in-
crease hydraulic and/or organic loadings due to increased plant production will not be discussed.
Upgrading textile mill effluents will generally involve the following regulatory stipulations:
• Increased BOD, TSS and COD removal
• Reduction of Chromium, Phenol and Sulfide
• Color Removal
For those mills classified as water quality limited, the regulations are generally more stringent
and may include any or all of the following limits:
• Disinfection
• Maintain minimum D.O.
• Remove ammonia — nitrogen
• Remove phosphorus
• Reduce heavy metals including zinc, copper, antimony, lead, etc.
Existing facilities will require modifications and/or new additions to meet specific limits.
Tables 8-28 through 8-31 are presented to illustrate some possible methods of upgrading com-
monly employed present day facilities.
8-99
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TABLE 8-28
UPGRADING EXISTING FACILITIES
(Increase BOD, TSS Removal)
Existing Facilities
Modification or Addition
1. Aerated lagoon
2. Trickling filters
3. Secondary treatment
(activated sludge)
4. Stabilization pond
a Add one or two lagoons and operate in series providing
sufficient aeration of 0.2 to 0.4 HP/1000 cu. ft. volume.
b. Modify existing parallel lagoons to series system.
c. Modify to activated sludge extended aeration by recycle of
sludge from clarifier to aeration basin.
d. Modify to activated sludge system and polish effluent by
mixed media filtration
a. Use of fine mesh screening to eliminate lint and short fiber
to increase filter efficieny.
b. Modify trickling filter for use as a roughing filter and add
activated sludge system
c. Increase recirculation rate from clarifier to trickling filter
d. Modify existing single-stage trickling filter to two-stage
trickling filter.
e. Change stone to synthetic filter media.
a. Add equalization basin (with mixing) in front of
aeration basin.
b. Increase recirculation from clarifier to aeration basin.
c. Add clarifier to decrease overflow rate of existing clarifier
and increase capability of BOD, TSS removal.
d. Add mixed-media filtration following final clarifiers
e. Polish effluent by adding polishing pond following
final clarifiers.
f. Add powdered carbon as a catalyst in aeration basin to
increase efficiency
g. Add nutrient prior to entering aeration basin if the system
is nutrient deficient.
a. Modify stabilization pond to aerated lagoon system.
b. Add aerated lagoons, operate in series and use existing
stabilization pond as polishing pond.
8-100
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TABLE 8-29
UPGRADING EXISTING FACILITIES
(Increase Color Removal)
Existing Facilities
Modification or Addition
1. Aerated lagoon
2. Trickling filter
3. Secondary treatment
(activated sludge)
4. Stabilization pond
a. Add equalization basin followed by flocculation and settling
basins ahead of modified series aerated lagoon system.
b. Add activated carbon as a catalyst.
a. Add chemical coagulation system consisting of rapid mix,
flocculation and clarifier following modified trickling
filter system.
a. Add chemical system following modified activated
sludge system.
b. Add activated carbon as a catalyst.
a. Add equalization basin followed by chemical coagulation
system ahead of modified stabilization pond.
TABLE 8-30
UPGRADING EXISTING FACILITIES
(Disinfection Requirement)
Existing Facilities
1. Aerated lagoon
2. Trickling filters
3 Secondary treatment
(activated sludge)
4. Stabilization pond
Modification or Addition
a. Segregate sanitary wastes and treat separately.
b. Add chlorine contact chamber and chlorine feed facilities.
c. Add ozonation.
TABLE 8-31
UPGRADING EXISTING FACILITIES
(Maintain Required D. O. Concentration)
Existing Facilities
Modification or Addition
1. Aerated lagoon
2. Trickling filters
3. Secondary treatment
(activated sludge)
4. Stabilization pond
a. Add gravity reaeration channel prior to entering the
receiving stream.
b. Add mechanically mixed reaeration basin.
8-101
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8.18 Laboratory Requirements
An integral part of any wastewater treatment and monitoring program is an adequately equip-
ped and operated laboratory. Many textile mills have quality control laboratories located in the
manufacturing plant and, in some cases, with modifications and additions, this laboratory may
also function for wastewater analysis.
The following sections will present recommended laboratory tests and associated equipment
required for presentation of effluent analysis to regulatory authorities as well as tests suggested
as part of the treatment process control program. Federal or State authorities may require dif-
ferent test frequencies as listed in individual NPDES permits. Also discussed are design consid-
erations for the construction and equipping of a laboratory and information regarding report-
ing of laboratory test results. Typical required effluent performance tests are shown in Table
8-32 below. Additional tests used for control of the treatment facility are suggested in Tables
8-33 and 8-34.
TABLE 8-32
TYPICAL PERFORMANCE OF EFFLUENT REQUIRED
FOR REGULATORY AGENCIES
Item
BOD
Total Suspended Solids
COD
Oil & Grease
Total Chromium
Phenol
Sulfide
Color
Fecal Coliform
PH
Flow
Temperature
Test
Frequency
2/week
3/week
2/week
1/week
1/week
1/week
1/week
2/week
Daily
Continuous
Continuous
Continuous
Method of
Sample
24 Hr. Composite
24 Hr. Composite
24 Hr. Composite
24 Hr. Composite
24 Hr. Composite
24 Hr. Composite
24 Hr. Composite
24 Hr. Composite
Grab
Sense
Continuously
Sense
Continuously
Sense
Continuously
Major Equipment*
BOD Incubator, Distillation
Apparatus
103°C Oven, Desiccator,
Analytical Balance
Heating Mantle,
Triple Beam Balance
103°C Oven, Desiccator
Analytical Balance,
Spectrophotometer, Water Bath
Analytical Balance,
Spectrophotometer, pH Meter
Spectrophotometer (if use
methyl blue photometric)
Spectrophotometer
Analytical Balance, Water
Bath, Filtration Apparatus
Monitoring
Instrumentation
Including Sensors,
Transmitters and
Recorders
"Major equipment suggested has been selected based upon needs of regulatory agencies and control necessary to
achieve reasonable plant efficiency Miscellaneous equipment, expendables, glass and plasticwares and test kits
have not been listed since they are usually for general laboratory uses and not dependent on the type of tests.
Guidelines for these items are available in EPA Publication "Estimating Laboratory Needs For Municipal Wastewater
Treatment Facilities", June, 1973
8-102
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TABLE 8-33
ADDITIONAL TESTS SUGGESTED FOR PROCESS CONTROL,
COST CONTROL, AND HISTORICAL KNOWLEDGE
Item
D. 0.
NHs-N
Organic-N
NOa-N
Total Phosphorus
Turbidity
Total Solids
Total Volatile Solids
Dissolved Solids
Alkalinity
Test
Frequency
Daily
1/week
1/week
1/week
1/week
Continuous
2/week
2/week
2/week
2/week
Method of
Sample
24 Hr. Composite
24 Hr. Composite
24 Hr. Composite
24 Hr. Composite
24 Hr. Composite
Sense
Continuously
24 Hr. Composite
24 Hr. Composite
24 Hr. Composite
24 Hr. Composite
Major Equipment*
Oxygen Meter, Oxygen Probe
and Accessory Kits
Analytical Balance,
Spectrophotometer
Analytical Balance,
Kjeldahl App.
Spectrophotometer
Filtration, Water Bath
Hotplate, Spectrophotometer
Turbidimeter
103° C Oven, Desiccator,
Steam Bath
Muffler Furnace, Desiccator,
Analytical Balance
(Total Solids)
(Total S. S.)
Stirrer Hotplate
(Magnetic), pH Meter
'Major equipment suggested has been selected based upon needs of regulatory agencies and control necessary to
achieve reasonable plant efficiency Miscellaneous equipment, expendables, glass and plasticwares and test kits
have not been listed since they are usually for general laboratory uses and not dependent on the type of tests.
Guidelines for these items are available in EPA Publication "Estimating Laboratory Needs For Municipal Wastewater
Treatment Facilities", June, 1973
8-103
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TABLE 8-34
LABORATORY TESTS OF AERATION COMPARTMENTS IN
THE ACTIVATED SLUDGE SYSTEM PLANTS
Item
Mixed Liquor D. O.
Mixed Liquor
Suspended Solids
Settleability of
Activity Sludge
Sludge Volume Index
Plant Loading
lb/BOD/1000cu. ft.
Return Sludge MLSS
Test
Frequency
Daily
2/week
5/week
2/week
2/week
Daily
Method of Sample
Grab
24 Hr, Composite
Grab
Grab
24 Hr. Composite
Grab
8.18.1 Laboratory Facilities
When planning wastewater laboratories it is suggested the following items be considered:
8.18.1.1 Location
• Ground level
• Accessible to all sample points
• Northerly exposure to light
• Away from vibrating machinery
8.18.1.2 Space
• Floor space — 180 sq. ft. minimum (EPA) and non-glare
(Ten states 400 sq. ft. minimum)
• Bench area — must be 40% of floor area. If 2 persons work add 100 sq. ft. or more
• Aisle width between work benches must be at least 4 feet
• Ceiling height — 8.5 feet minimum
8.18.1.3 Materials of Construction
• Floor, bench top, shelving, cabinets must be highly acid, alkali, solvent and salt resistant,
vinyl or rubber
• Walls — ceramic tile or empty coated concrete block
• Ceiling — acoustic tile
8-104
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• Windows — non-glare type
• Doors — strong, permit a straight egress from the lab and must not be swing doors
8.18.1.4 Cabinet & Bench Top
• Wall-hung cabinets must be 30-inch from bench top
• Bench-top height should be 36-inch. Sit-down bench top should be 30-inches high
8.18.1.5 Hoods
8.18.1.5a Fume Hoods
• Location — should be located where air disturbance at the face of the hood is minimal
• Materials should be plastic or equally resistant material. Sash should be provided. Sliding
horizontal or vertical door may be used in sash
• One cup sink should be provided inside the hood. All switches, electrical outlet, utility and
baffle adjustment handles should be explosion proof
• Exhaust — 24-hour capability should be provided with buzzer indicating exhaust fan failure
failure
8.18.1.5b Canopy Hoods
Should be installed over the bench top area where hot plate, steam bath and other equipment
is used.
8.18.1.6 Sinks
• Minimum 3 sinks, 2 of them should be double well with drainboards and 1 cup sink
• Sinks should be constructed of material highly resistant to acids, alkalies, solvents and
salts. In addition, they should be abrasion and heat resistant, non-absorbent and light in
weight
8.18.1.7 Ventilation and Lighting
• Laboratories should be separately air conditioned
• Separate exhaust ventilation should be provided
• Good lighting, free from shadows for reading dials, meniscuses, etc.
8-105
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8.18.1.8 Power
• All electrical lines coming into the laboratory should be controlled with CVS harmonic
neutralized type transformer to eliminate line fluctuation
• The 220 volt line should be regulated for higher voltage requirements
8.18.1.9 Gas and Vacuum
• Natural gas should be supplied to the laboratory
• Provide adequate vacuum pumps
8.18.1.10 Safety
Safety equipment must be provided and easy to reach when needed.
• Eye wash — irrigator type, face wash type or hand held spray
• Safety shower
• First aid kit — industrial type
• Fire extinguisher
• Fire blanket w/wall case
• Safety cabinet — proper storage of hazardous chemicals for fire prevention
• Safety ladder
8-106
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8.18.2 Reporting Laboratory Results
When reporting laboratory analytical results, the following tabulation is suggested as a guide to
recording values:
TABLE 8-35
REPORTING LABORATORY RESULTS
Parameter
BOD
Solids
COD
Oil and Grease
Total Chromium
Phenol
Sulfide
NH3
Organic-N
NOs-N
Total Phosphorus
Alkalinity
D. 0.
PH
Color
Fecal Coliform
Range
0-9.9 mg/l
1 0-499 mg/l
500-1000 mg/l
0-99.9 mg/l
100-1000 mg/l
0-9.9 mg/l
10-1000 mg/l
0-99 mg/l
10-100 mg/l
0-9.9 mg/l
0-9.9 mg/l
0-9.9 mg/l
0-2 mg/l
2-10 mg/l
0-2 mg/l
2-10 mg/l
0-10 mg/l
0-10 mg/l
—
—
0-14 mg/l
—
MPN Technique
Report to Nearest
mg/l
0.1
1
10
0.1
1
0.1
1
1
10
0.01
0.01
0.01
0.01
0.1
0.01
0.1
0.01
0.01
1
0.1
0.1 unit
10 ADMI
10/100 ml
lb/1000 Ib product
0.01
0.1
1
0.1
1
0.1
1
0 1
1
0.01
0.01
0.01
0.01
0.1
0.01
0.1
0.01
0.01
1
0.1 unit
10 ADMI
10/100 ml
8-107
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8.19 References
1. Liptak, E.G., Environmental Engineers' Handbook, Volume I, "Water Pollution", Chilton
Book Company, 1974.
2. Metcalf and Eddy, Inc., Wastewater Engineering: Collection, Treatment, Disposal, McGraw
Hill Book Company, 1972.
3. Adams, C.E. and Eckenfelder, W.W., Process Design Techniques for Industrial Waste Treat-
ment, Enviro Press, 1974.
4. Gulp, L. Russell, Gulp, Gordon L., Advanced Wastewater Treatment, Van Nostrand Rein-
hold Company, 1971.
5. The National Commission on Water Quality, "Textile Industry Technology and Costs of
Wastewater Control" Lockwood Greene Engineers, Inc.,(NCWQ Contract No. WQ5AC021)
June, 1975.
6. U.S. Environmental Protection Agency, Development Document, Economic Analysis of
Proposed Effluent Guidelines - Textiles Industry EPA-230/I-73-028, March, 1974.
7. U.S. Environmental Protection Agency, Estimating Costs and Manpower Requirements
for Conventional Wastewater Treatment Facilities, Black and Veatch Engineers, October,
1971, (EPA No. 17090DAN).
8. U.S. Environmental Protection Agency, Socioeconomic Environmental Studies Series,
Capital and Operating Costs of Pollution Control Equipment Modules, EPA-R5-73-023a,
H. Blecker, T. Cadman, July, 1973.
9. U.S. Environmental Protection Agency, Technical Report, A Guide to the Selection of
Cost-Effective Wastewater Treatment Systems, R. Note, P. Albert, et. al., EPA-430/9-
75-002, July, 1975.
10. Recommended Standards for Sewage Works, A Report of Committee of the Great Lakes —
Upper Mississippi River, Board of State Sanitary Engineers, 1971 Revised Edition.
11. Guides for the Design of Wastewater Treatment Works, Technical Advisory Board of New
England Interstate Water Pollution Control Commission, June, 1971.
12. Institute of Textile Technology and Hydrosciences, Inc., "Recommendations and Com-
ments For The Establishment of Best Practicable Wastewater Control Technology Cur-
rently Available For The Textile Industry", for American Textile Manufacturers Institute,
Inc. and The Carpet and Rug Institute, 1973.
8-108
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13. The Textile Manufacturer, "Process Water and Textile Effluent Problems", Part 2 F.H.
Slade, Page 89 - 99, March, 1968.
14. U.S. Environmental Protection Agency, Technology Transfer, "Process Design Manual for
Suspended Solids Removal", Burns and Roe, Inc., January, 1975.
15. U.S. Environmental Protection Agency, Technology Transfer, "Flow Equalization",
Metcalf and Eddy, Inc., May, 1974.
16. "Symposium on Textile Technology/Ecology Interface 1975", American Association of
Textile Chemists and Colorists, May 28, 1975.
17. Souther, R.H. and Alspaugh, T.A., Proceedings 13th Industrial Waste Conference, Purdue
University, Page 662 - 713, 1958.
18. Fram Corporation, Pawtucket, Rhode Island.
19. Stuber, L.M., "Tertiary Treatment of Carpet Dye Wastewater Using Ozone Gas and its
Comparison to Activated Carbon". Special Research Problem, School of Civil Engineering,
Georgia Institute of Technology, Atlanta, Georgia, August, 1973.
20. Textile Technology/Ecology Interface — 1977, The Present and Future of Ozone in Treat-
ment of Textile Wastes, A. Maggiolo, et. al., Bennett College, N.C.
21. Correspondence Between Passavant and Lockwood Greene Engineers, Inc., December 4,
1975.
22. Case History, Lyman Printing and Finishing, Lockwood Greene Engineers, Inc., 1975.
23. Pilot Study, "Stehli, Knit Finishing Plant Fork Union, Va., April, 1976.
24. Anonymous, "Treating Dyehouse Effluent and Recycling Water", Textile Industries.
May, 1974.
U.S. Environmental Protection Agency, Development Document for Effluent Limitations
Guidelines and New Source Performance Standards for the "Textile Mills", June, 1974.
U.S. Environmental Protection Agency, Operation and Maintenance Program. "Estimating
Laboratory Needs for Municipal Wastewater Treatment Facilities", CH2M/HILL, June, 1973.
8-109
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U.S. Environmental Protection Agency, Technology Transfer, "In-Plant Control of Pollution,
Upgrading Textile Operation to Reduce Pollution", Institute of Textile Technology, October,
1974.
U.S. Environmental Protection Agency, Construction Grants, Operation and Maintenance,
"Laboratory Procedures, Analysis for Wastewater Treatment Plant Operators, "David Vietti,
June, 1971.
Manual of Instruction for Sewage Treatment Plant Operators, New York State Department of
Health Office of Professional Education, Division of Environmental Health Services, Office of
Public Health Education, Water Pollution Control Board.
U.S. Environment Protection Agency, Technology Transfer, "Process Design Manual for Carbon
Adsorption", Swindell-Dresser Company, Cornell, Howland, Hayes and Merryfield. Clari A.
Hill and Associates, October, 1973.
U.S. Environmental Protection Agency, Technology Transfer, "Process Design Manual for
Sludge Treatment and Disposal", Black, Crow and Eidsness, October, 1974.
U.S. Environmental Protection Agency, Technology Transfer "Upgrading Lagoons", Brown
and Caldwell, August, 1973.
ASCE, Manuals of Engineering Practice, No. 36, (WPCP Manual of Practice No. 8). "Sewage
Treatment Plant Design", a Joint Committee of the American Society of Civil Engineers and
the Water Pollution Control Federation, 1959.
U.S. Environmental Protection Agency, Technology Transfer, "Wastewater Treatment Systems,
Upgrading Textile Operations to Reduce Pollution", Metcalf and Effy, Inc., Engineers, October,
1974.
Fiar, G.N., Geyer, J.C. and Okum, D.A., Water and Wastewater Engineering, Volume II, "Water
Purification and Wastewater Treatment Disposal", John Wiley and Sons, Inc., 1968.
Clark, J.W., Viessman, W. Jr. and Hammer, M.J., "Water Supply and Pollution Control", Inter-
national Textbook Company, 1971.
8-110
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CHAPTER 9
AIR POLLUTION
9.1 Introduction — Emission Sources
The textile industry has not, by the nature of its operations, been one of the major sources of
pollution in the United States, and its air pollution problems have been considerably less severe
than its water pollution problems. Consequently, this area is only beginning to receive serious
and widespread attention within the industry and from the State and Federal enforcement agen-
cies. Most of the air pollution abatement equipment in operation in textile mills today has only
recently been installed, and its long-term performance has yet to be evaluated. In addition, the
technology has not yet matured, and many of the shortcomings associated with particular
generic types of air pollution abatement equipment have been or are now being overcome by
specific equipment manufacturers. This chapter can, therefore, only give indications of areas
where problems may be anticipated and cannot specify exactly which type of equipment is best
for abatement of each type of pollutant under all circumstances.
Relevant regulations and enforcement procedures vary widely from state to state and from re-
gion to region in the same state, and many states have not yet developed guidelines for the tex-
tile industry. Therefore, users of this manual should consult the appropriate state authorities to
find out what is required at their specific locations and what will be required in the future. Fed-
eral regulations presently affecting the textile industry are chiefly concerned with stack emis-
sions from incinerators and steam generating plant (1) which are not a problem specific to the
textile industry and are, therefore, not the subject of this report.
Emissions from textile processes excluding steam generation fall into four general categories:
• Oil and acid mists
• Solvent vapors
• Odors
• Dust and lint
Oil mists are produced when textile materials containing oils, plasticizers, and other materials
that can volatilize or be thermally degraded into volatile substances are subjected to heat.
Volatile material is driven off and is condensed on cooling into a blue haze of droplets, most of
which are in the range of 0.1 to 1 micron diameter.
Since this is about the wavelength range of visible light, a maximum plume opacity is obtained
from very low contaminant concentrations. Typical particulate emission codes require particu-
late stack emission concentrations to be less than 0.02 grain/SCF. This can be exceeded by a
boil-off rate of 1 pint/hr in 5000 CFM of exhaust giving 0.023 grain/ACF. A tenter frame with a
stack exhaust particulate concentration of 0.03 to 0.11 grain/ACF will have a plume of 40 to 60%
9-1
-------
opacity before abatement (2). The threshold of opacity is about 0.003 to 0.006 grain/ACF.
Fibers and lint are usually present in the mist also.
Texturizers produce the cleanest oil mists, consisting mainly of spinning oils, which are relatively
undegraded because of the low temperatures at which texturizing takes place. Exhaust air, which
is usually cool, (200 to 250° F) has oil droplet concentrations ranging from 0.008 to 0.09 grain/
ACF. In general, texturizing of fine yarns produces a lower volume of evaporated oil than tex-
turizing of heavy yarns. Oil can be recovered and used for heating, since it has a higher BTU
value than number 2 fuel oil. In one instance, an electrostatic precipitator operating at 95%
efficiency recovered 350 gal/wk of oil from a 25,000 CFM texturizing plant exhaust (3).
The most common source of oil mists in the textile industry is the tenter frame, which produces
oil mists with droplet concentrations of 0.03 to 0.45 grain/ACF. Because of the higher operat-
ing temperatures, which range from 300 to 400° F, compounds in tenter exhausts are partially
oxidized and, therefore, more odorous and corrosive than otherwise. Exhaust composition
is a function of the fabric pre-history, and can contain oils, subliming dyes, carrier residues
such as o-phenylphenol and its esters, brighteners, emulsifiers, gylcerides, waxes, fatty acids and
fatty acid phosphatides, plasticizers, resins, ethylene oxide, and lower molecular weight frac-
tions of the polymer itself (4). These substances can sometimes solidify in the collection equip-
ment. A typical tenter frame produces 25 to 200 Ibs/day of effluent (5), (6). In one instance
a tenter frame with a 29,000 CFM exhaust produced 1000 to 1800 gallons of oil per week (7).
Similar processes producing oil mists include heat setting and drying.
Plasticizers are driven off from all high temperature processes involving vinyl, such as extrusion,
coating, tentering and calendaring. Flame bonding, laminating, coating, drying and curing of
carpets and upholstery fabrics volatilizes plasticizers, adhesives, jute oils, etc., producing gummy
odorous mists. Particularly troublesome are mists consisting of mixtures of plasticizer and
stearic acid produced during heat treatment of latex foam backed carpets and upholstery fab-
rics. At 400° F, most of the plasticizer, and a considerable proportion of the stearic acid, is
driven off.
Oil mist elimination techniques are discussed in Section 9.3.
Acid mists are produced during the carbonizing of wool and during some types of spray dyeing
and acetic acid mist dyeing. Because of their corrosive nature, some techniques for oil mist
elimination are not applicable to this type of dyeing. They are therefore discussed separately
at the end of Section 9.3.
Organic solvent vapors are released during and after all solvent processing operations. The most
common use of solvent processing in the textile industry is the use of chlorinated hydrocarbons
for dry cleaning. These cannot generally be treated by scrubbing because of their limited solu-
bility in the water. On incineration, they release hydrogen chloride gas. Particulate removal
9-2
-------
techniques are also inapplicable since the solvents are present entirely in the vapor phase. Sol-
vent dyeing and printing and the application of finishes from solvent solution present similar
problems. Complete solvent recovery systems are available, often as an integral part of the sol-
vent processing equipment itself. Solvent recovery by adsorption onto activated carbon is
discussed in Section 9.4.
Odors are often associated with oil mists or solvent vapors and are removed by removal of the
mist or by recovery of the vapor. In other cases, the odorant is present mainly in the vapor phase
and in such small concentrations as to make recovery in a solvent recovery system inapplicable.
The most common odor problems of this type are the carrier odors from aqueous polyester
dyeing and processes subsequent to it. Resin finishing also produces odors, chiefly of formalde-
hyde. Other sources of odor are sulfur dyeing on cotton and cotton blends; reducing or strip-
ping dyes with hydrosulfite, bonding, laminating, backcoating; and bleaching with chlorine diox-
ide. Odor abatement techniques are discussed in Section 9.6.
Dust and fly are produced in the greatest quantity by the processing of natural fibers and syn-
thetic staple prior to and during spinning, and by napping and carpet shearing. To a lesser ex-
lent, most other textile processes produce lint, which, while it is not a major pollutant in it-
self, complicates abatement processes for other pollutants. Its removal as a secondary con-
taminant will be discussed in Sections 9.2 through 9.6. Removal of dust from otherwise clean
air is discussed in Section 9.7.
9.2 Available Abatement Equipment
A wide variety of equipment is available for abatement of the various types of air pollution
produced by textile processes. The abatement techniques may be divided into three categories:
1) those that destroy the pollutant; 2) those that collect it in a relatively concentrated "dry"
form; and 3) those that wash it from the exhaust into water or some other collecting liquid (see
Table 9-1). This section attempts to provide a detailed description of each type of available
equipment, to which subsequent sections of this chapter will refer when discussing specific pol-
lution problems. Where coverage is adequate, the reader is referred to the EPA Air Pollution
Handbook, 2nd Edition (8), and to Perry's Chemical Engineers' Handbook, 5th Edition (9), stand-
ard references which this discussion does not attempt to duplicate.
9.2.1 Incineration and Chemical Destruction
Where applicable, incineration of pollutants has the advantage that it results in their total des-
truction if carried to completion, the products being H2O, CO2, and N02- It is also the simplest
and most reliable method of pollution abatement, but the high and rising costs of energy makes
it the most costly method as well, especially if heat recovery is not employed subsequently. For
this reason, it is generally not preferred for exhaust flow rates above 5,000 CFM. It is often used
for destruction of previously concentrated exhausts, such as steam stripped solvent from carbon
solvent recovery beds and lint laden air from blow-down of lint filters (see Sections 9.5, 9.6
and 9.7).
9-3
-------
TABLE 9-1
BASIC AIR POLLUTION CONTROL EQUIPMENT
Incineration.
Open Flame
Direct Fume
Catalytic Oxidation
Dry Collectors:
Cyclone Separator
Filters:
Bag House
Mist Eliminator
High Velocity Fiber Mat
Electrostatic Precipitator
Absorption
Scrubbers'
Packed Tower
Plate Column
Spray Tower
Inertial Impaction
Fluidized Bed
Orifice
Venturi
Water Jet
Mechanical
Fiber Bed
Reinstate
Ionizing Wet
Compounds containing only C, H, and 0 can be oxidized completely to C02 and H20. Nitro-
gen will form NC>2 to a significant extent at high temperatures, but this can be disregarded
below 3,000° F. Other elements will form solid or gaseous substances that must subsequently
be removed by scrubbing; chlorine, bromine, and flourine form HC1, HBr, and HF, respectively,
while sulfur, phosphorous, silicon, and metals form their oxides.
Since all substances that can be destroyed by incineration are flammable, care must be taken to
prevent their condensation and buildup in the ducts leading to the incinerator. Oil vapors must
be kept above their condensation temperature. To maintain the flammable vapor concentration
below 25% of the lower explosion limit, the National Fire Protection Association recommends
that 10,000 CFM of air (measured at 70° F) be vented with each liquid gallon of evaporated oil
or solvent (10). If insufficient air is vented from the particular piece of textile processing ma-
chinery to effect this, additional dilution air should be added prior to incineration.
Hydrocarbon oxidation is generally a complex, stepwise process, with aldehydes, ketones, and
organic acids as intermediates. Since these are generally more odorous and corrosive than the
original emissions, care must be taken to see that incineration is carried to completion.
9-4
-------
Three methods of incineration are available: open flame incineration, direct fume incineration
and catalytic oxidation. In addition, pollutants can be destroyed chemically by reaction with
dry solids. Of the various methods, open flame burning is the least reliable, since the contact
time between the flame and the pollutants is usually too short to insure complete destruction.
This method can be used only with readily combustible products (2). It can produce soot, car-
bon monoxide and partially oxidized hydrocarbons that are often more objectionable than the
original substance.
Open flame combustion is discussed in detail in the EPA Air Pollution Engineering Manual (8),
pages 171-9, to which the reader is referred for design criteria. An energy saving variation of this
method of incineration is to use the pollutant laden exhaust as a source of combustion air for
a boiler or furnace. This allows a considerable savings in incinerator capital costs and fuel costs,
but it limits plant flexibility by requiring operation of the boiler at all times when the exhaust is
being produced. Care must also be taken to avoid flashback or condensation in the ducts leading
to the boiler and to avoid fouling of the boiler heat exchange surfaces with the products of pol-
lutant combustion. Adequate oxygen for boiler fuel combustion must also be assured, both
when the exhaust is being fed to the boiler and when it is not. This option is discussed in detail
in the EPA Air Pollution Manual, pages 183-9.
Direct fume incineration requires heating of the pollutant-air mixture to 1,400 to 1,500° F
for 0.3 to 0.5 seconds, generally in an externally heated combustion chamber. Since liquid,
solids and vaporized hydrocarbons are all oxidized completely to water and carbon dioxide, no
pre-filter is required for lint removal. Installed costs for direct fume incinerators without heat
recovery were approximately $4.00 per CFM in 1975. Heat recovery generally doubles the ini-
tial investment and halves the operating cost (see Section 9-4). Direct fume incinerators re-
quire very little maintenance (11). However, care must be taken to ensure and maintain prop-
er operating conditions, as discussed above.
Figures 9-1 and 9-2 show the relationships between fuel cost, incinerator inlet temperature, and
exhaust volume for a direct fume incinerator operating 8000 hours per year at 1,500° F
without heat recovery at 80% efficiency on number 2 fuel oil at $0.30 per gallon. This fuel was
selected as the example because of the high sulfur content of most other liquid and solid fuels
and the increasing scarcity of natural gas. Figure 9-2 assumes a typical inlet temperature to the
incinerator of 300° F.
No credit has been taken for the heating value of the pollutant, since this is dependent on the
nature of the process producing the emissions, the material being processed and the operating
conditions. Emissions produced by boil-off tend to increase as the process operating tempera-
ture is increased, as the boiling point of the volatiles is decreased (by process or product
changes), and as the amount of volatile material in the textile is increased. In any event, the
total heat value of the pollutants must be kept low to avoid fire and explosion hazards, as dis-
cussed previously. Where process improvement is possible, it is wisest to reduce the pollutant'
9-5
-------
$64
$60
$56
O
CO
~ $52
tn
O
O
3
<
$48
$44
$40
0° 100° 200° 300° 400°
Exhaust Temperature (Degrees F.) to Incinerator
FIGURE 9-1
DIRECT FUME INCINERATION FUEL COSTS WITH NO HEAT RECOVERY,
NO. 2 FUEL OIL AT $.30/GAL.
Source: Lockwood Greene Engineers, Inc.
$400
CO
b
o
o
C $300
CO
o
O
15
D
LL
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3
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c
$200
$100
0 123456789 10
SCFM: Thousands
FIGURE 9-2
TOTAL FUEL COSTS FOR DIRECT FUME INCINERATION WITHOUT
HEAT RECOVERY, EXHAUST AT 300° F, NO. 2 FUEL AT $.30/GAL.
Source: Lockwood Greene Engineers, Inc.
9-6
-------
concentration in the incinerator rather than to take a heating credit for it, since most volatile sol-
vents and plasticizers are considerably more expensive than fuel oil.
Catalytic incinerators cost about $3.50 to $5.00 per CFM installed (1975 prices) and can be
used only for destruction of pollutants that are gaseous at the incinerator operating tempera-
tures. Therefore lint, dust, etc. must be removed from the exhaust with a pre-filter. Impuri-
ties in the vapor phase are first adsorbed onto the catalytically active surface where reaction
takes place.
The principal advantage of catalytic destruction over other techniques for oxidation of air pol-
lutants is due to the reduced operating temperature. Without heat recovery, the fuel costs for
any process involving the heating of process air are given by the expression:
Annual cost/SCFM^2900 ^ ~TI> (9.1)
114,000- 27 TH v '
Here, TJJ and Tja are the air outlet and inlet temperatures (° F), and the assumptions used are
those used in deriving the relations graphed in Figures 9-1 and 9-2.
Catalytic oxidation of organic pollutants takes place at temperatures at or below 850° F,
depending on the catalyst and the pollutant. Since operating temperatures are lower than for
other forms of incineration, fire and explosion hazards are also reduced, though this should not
be relied upon in system design because of the possibility of ignition by hot spots in the catalyst
bed. Oxides of nitrogen can also be destroyed catalytically at these low temperatures (12).
Catalytic oxidation causes an increase in the temperature of the exhaust gas that is given in
steady state by the relationship :
XAH
AT=-
C
P (9-2)
where: A T = temperature rise (° F)
X = pollutant weight fraction in the inlet gas
A H = pollutant heat of combustion, BTU/lb
Cp = Specific heat of exhaust stream after combustion, BTU/lb ° F.
If the exhaust stream is virtually pure air, the heat capacity is 0.25 BTU/lb ° F, and equation
9.2 simplifies to:
AT = 4XAH (9.3)
aAll symbols are defined in Table 9-2 located at the end of this Chapter (page 9-71).
9-7
-------
If the incinerator inlet and outlet temperatures are known, the inlet pollutant concentration can
be determined, assuming complete combustion. The response time of the outlet temperature is
sufficiently rapid that it can be used to regulate the flow of additional dilution air to the incin-
erator (13). The 1973 edition of the National Fire Protection Association handbook states that
for each gallon of organic solvent evaporated, 10,000 cfm of air at 70° F should be exhausted
(14). At a typical A H of 120,000 BTU/gal, this gives a temperature rise of about 660° F across
the catalyst.
Oxidation catalysts are generally platinum group metals (since these give the lowest ignition
temperature), or copper or silver. The required surface area for platinum group metals as oxida-
f\
tion catalysts is approximately 0.2 ft. /CFM, but in difficult situations, surface areas as high as
0.5 ft2/CFM may be required (12). To maximize the surface area obtainable per pound of the
expensive catalyst, the active metal is generally deposited on a cheap, more or less inert support,
such as silica, alumina, activated carbon or a ribbon of inexpensive metal. The support is often
made porous to increase its surface area per cubic foot. Figure 9-3 shows a typical catalytic
incinerator.
Catalysts employed in destruction of emissions should have the following featues: (13).
• Mechanical strength and rigidity: one of the chief causes of catalyst attrition is abrasion
to irretrievable fines.
• Thermal stability, both in the range from room temperature to the operating temperature
and above that to the temperatures encountered in catalyst regeneration.
• Thermal conductivity to dissipate heat from areas of high reaction rate to prevent hot
spotting.
• Resistance to damage by water. Most exhausts contain water vapor that can condense on
the catalyst surface.
• Slow rate of deactivation. Catalyst reactivation or replacement costs are substantial, run-
ning as high as $1.00/CFM (12).
• Modular element configuration for ease of replacement.
• Easy cleanability, preferably by washing.
Decomposition catalysts, which have limited use for decomposition of relatively unstable sub-
stances, include manganese dioxide or cupric oxide on activated carbon. Oxides of chromium,
molybdenum and tungsten supported on carbon perform intermittently. The pollutant is ad-
sorbed onto the carbon at low temperature (below 120° F), and then the temperature is raised
to cause catalytic surface oxidation (11).
The most serious problem with catalytic emission destruction is loss and deactivation of the
catalyst. Catalyst losses are due primarily to abrasion, which is expecially severe with heavy
particulate loading. Deactivation occurs because of clogging with particulates, carbonization on
the catalyst surface or in the pores, and poisoning. Metallic and organometallic vapors of arsenic,
9-8
-------
FIGURE 9-3
CATALYTIC INCINERATOR
Source: Catalytic Products International Inc.
9-9
-------
lead, zinc, and mercury are the most common catalyst poisons, though most textile process
emissions do not contain these.
Poisons can often be eliminated before contact with the catalyst. They are sometimes removed
by essentially irreversible adsorption in a small sacrificial bed of catalyst or decomposed to more
easily treatable substances. Metal-organic compounds, for example, can be broken down into
hydrocarbons and solid metal oxides which can be removed by subsequent scrubbing or electro-
static precipitation (13.). Other substances requiring subsequent treatment include fly ash, sih-
cones and inorganic salts.
For these reasons, it is necessary to know the composition of the emission before installation of
a catalytic system. Regeneration and/or catalyst replacement will always be necessary from time
to time, and the frequency of this should be determined in advance. In one application involv-
ing the destruction of oil mist from a tenter by catalytic incineration, the catalyst required
washing every 6 months and replacement every 3 years (15).
Chemical destruction of some pollutants can be accomplished by reaction with activated
alumina impregnated with potassium permanganate, or by activated carbon impregnated with
bromine, iodine, lead acetate or sodium silicate. Reaction is stoichiometric and requires a
relatively large catalyst surface area. Adsorbents may therefore have to be replaced frequently.
Costs are about equivalent to those of a chemical scrubber system, with the scrubber having
the advantages of ease of control and replacement of the chemical liquor (11).
9.2.2 Dry CoDection Methods
Pollutant destruction, discussed in the previous section, has the advantage that it eliminates the
need for subsequent disposal, albeit at the cost of high consumption of energy and/or chemicals.
Dry collection methods concentrate arid collect the waste for subsequent reuse, combustion or
disposal, but they generally require far less energy than incineration or chemical destruction.
In this category fall such methods as filtration, adsorption (generally onto activated carbon),
and electrostatic precipitation.
There are four basic methods of particle collection (8):
1. Collision of the particle with a filter surface and subsequent adhesion. This can be due
to impingement, whereby the particle collides with the filter because it cannot follow
the flow line of the exhaust gas at an abrupt bend because of inertial or gravitational
forces, or flow line interception, whereby the particle's flow path itself brings it into
contact with the collection surface. This collection mechanism tends to become more
efficient as the exhaust velocity and particle size are increased. Particle sizes below
about 2 microns have little inertia, and are collected by flow interception, if at all;
larger particles can be collected by impaction (defined here as forcible impingement,
due to inertial forces).
9-10
-------
2. Straining, whereby the particle cannot fit through the pores of the filter medium.
This effect increases with particle size and loading of the filter; however, the pres-
sure drop required to obtain a specific volume of exhaust flow also increases as the
loading of the filter increases and as its mesh size decreases.
3. Brownian motion: The particles collide with the collection medium because of their
random motion caused by the uneven bombardment of air molecules on them. This
effect becomes more pronounced as particle size decreases and as exhaust velocity de-
creases.
4. Electrostatic attraction of the particles to oppositely charged collection plates. This
is the mechanism responsible for collection by electrostatic precipitation.
The collection efficiency, 77, is defined as the weight fraction of entering particles collected.
Since efficiencies generally decrease with decreasing particle size, the overall efficiency of col-
lection cannot be used to predict reduction of plume opacity. The smaller particles (0.1 to 1
micron diameter) which contribute most to the opacity often are a small proportion of the
total weight of pollutant. Overall efficiency is related to the efficiency of removal of particles
of any given diameter by the expression:
(Dp) dDp (9.4) (Reference 16)
o u
(See Table 9-2 (page 9-71) for an explanation of the symbols.) It is also useful to express per-
formances as efficiency obtained per unit of pressure drop according to the expression:
Y =—— (9.5) (Reference 9, p 20-78)
A Pi
9.2.2.1 Gravity and Centrifugal Collectors
Gravity collectors consist generally of long empty rectangular chambers through which the
exhaust flows slowly enough to allow the particles to settle out. In the Howard fume arrester,
many horizontal plates are arranged as shelves in the chamber to minimize the distance through
which the particles must drop. The minimum size of particles that can be completely removed
is determined by balancing the required settling time, calculated from the Stokes' law velocity,
against the exhaust gas residence time:
18/igq
NLB
sss P - p
(9.6) (Reference 9, p 20-80)
9-11
-------
In practice, particles as small as 10 microns can be removed. The pressure drop across these de-
vices is generally a fraction of an inch of water, consisting mainly of entrance and exit losses.
Gravity settlers are gradually being replaced by other, more compact, lower cost separators (17),
but these settlers still find use as precleaners for coarse dust and fiber removal.
Cyclone separators operate on essentially the same principle as gravity settlers, employing cen-
trifugal force rather than gravitation as the impetus for separation. Figure 9-4 shows a cutaway
view of a typical commercially available cyclone. They are generally preferred to gravity settlers
for removal of coarse particles and mists because of their smaller size and lower cost. The mini-
mum particle size removable ranges down to 15 to 40 microns for most models, though at least
one new model is claimed to remove particles as small as 5 microns (18). Figure 9-5 shows the
estimated efficiency of a cyclone of the type shown in the previous figure. As can be seen,
greater dry particle removal efficiencies are obtained if the cyclone is used as a pre-filter prior to
a cloth bag.
Detailed design and application criteria for cyclones are given in the EPA Air Pollution Manual
(8), pp. 91-99, and also Perry's Chemical Engineer's Handbook (9), 5th ed., pp. 21-81 to 21-87.
9-12
-------
Dust laden air
Clean air
FIGURE 9-4
CYCLONE SCRUBBER
Dust, lint,
and fibre
caught in base
Source: The Torit Corporation
9-13
-------
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Cyclone — cloth X
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FIGURE 9-5
EFFICIENCY OF CYCLONE
WITH AND WITHOUT FABRIC AFTER FILTERS
Source: The Torit Corporation
9.2.2.2 Filters
Filters may be used for particulate removal in cases where the particles are either dry solids that
can be easily removed from the filter, freely flowing oils that will drain from the filter, or pre-
sent in sufficiently small concentration that the collection device can be cleaned or replaced
infrequently. For collection of dry dusts down to the submicron range, with 99+% efficiency,
bag filters are most commonly used, generally arranged into bag houses. Filtration efficiency
and pressure drop through a bag filter are initially low, until a mat of collected material builds
up. This mat then performs most of the filtration. Cleaning is performed by mechanical vibra-
tion or reverse air flow, usually on an automatic cycle. Cloth bag filters usually operate with a
pressure drop of 2 to 6 inches of water and an air-to-cloth ratio of 1 to 8 CFM per ft.'' of fabric,
though with fine dusts, 3 CFM/ft.^ is about the maximum air-to-cloth ratio, since higher air
velocities tend to destroy the particulate mat that performs the filtration. Felted fabric bags
can be operated at up to 30 CFM/ft^, since the particulate mat plays a less important part in the
filtration, but they are generally operated at 5 to 10 CFM/ft^. Figure 9-6 shows a typical simple
bag house. Detailed design and application criteria for bag houses may be found in the EPA Air
Pollution Manual (8), pp. 106-135, and in Perry's Chemical Engineer's Handbook (9), 5th ed.,
pp. 20-89 to 20-95.
9-14
-------
FIGURE 9-6
BAG HOUSE
Source: Sly Manufacturing Company
9-15
-------
In the collection of solids, high efficiencies may be achieved due to solids buildup on the filter
surface; this mechanism does not apply to aerosols. Figure 9-7 shows a plot of filtration effi-
ciency for oil mists, the most common aerosol produced by textile operations, versus air velo-
city through one commercial filter. High collection efficiencies are achieved at low air velocities,
because the droplets collide with the filter medium due to Brownian motion. Figure 9-8 shows
the rate of Brownian displacement of small particles as a function of droplet size. As can be
seen, smaller particles migrate further in a given amount of time, making their probability of
collision with the fibers and capture greater than with large particles. At high velocities, impac-
tion is the principal collection mechanism, and efficiencies again rise until the air velocity be-
comes so high that re-entrainment is a problem.
100
o
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CD
LU
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50
0
100
400
500
200 300
Air Velocity (Ft./Min.)
FIGURE 9-7
FILTRATION EFFICIENCY FOR OIL MISTS
Source: Reference 19
9.2.2.2a High Efficiency Fiber Mist Eliminators
Operating at the lower end of the velocity range are the high efficiency fiber mist eliminators.
Figure 9-9 shows a typical set-up. Mist laden gas flows radially through a fiber bed, which re-
moves the droplets by impaction, interception and, in the case of the small particles, Brownian
motion. The droplets condense in the fiber matrix into a liquid film that flows downward and
inward to a collection point.
Vapor velocities are typically 15 to 40 ft/min., for a pressure drop of 5 to 15 inches of water, and a
collection efficiency of 95 to 99+% on all particles smaller than 3 microns. Collection efficiency
for fine droplets increases slightly with decreasing droplet size and decreasing air flow rate, so
9-16
-------
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Clean gas to
atmosphere
Mist-laden
gas in
Collected
liquid
FIGURE 9-9
HIGH EFFICIENCY FIBER MIST ELIMINATOR
Source: Monsanto Enviro-Chem Systems, Inc.
9-18
-------
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In 1975, installed costs were $2.00 to $4.00 per CFM for total systems using high efficiency
fiber mist eliminators to clean up texturizer exhausts, where no cooling is necessary, and $3.25
to $8.00 per CFM to clean up tenter frame exhausts. A 10,000 CFM system operating at a
14 in. to 15 in. pressure drop requires a 40 HP fan, with a power consumption of 15 KW, or
$0.30 per hour at $0.02 per KWH. For proper system specification, the particle size distribu-
tion, loading, and condensation temperatures should be known.
High efficiency fiber mist eliminators require prefiltration for lint removal and pre-cooling of
the exhaust air, generally to 110° F. Because of their weight, they are generally mounted
on the ground rather than on the roof. This also facilitates replacement of the elements. Clean-
ing is performed, if necessary, by steam, hot air or water. When they become completely fouled,
the elements must be replaced. However, frequent replacement has generally not been necessary.
One installation on a dryer has been operating for 2 years without element replacement (7).
Another mill has used mist eliminators on tenter frames, operating at exhaust velocities of 5 to
10 CFM/ft2, with element changes every 2 to 3 years (21).
With gummy or waxy condensates, operating temperatures should be adjusted to avoid solids
deposition. Phenolic resins may cause problems. One installation, operating on a vinyl plastici-
zer mist, has reported gradual loss in collection efficiency, possibly due to channeling and by-
passing caused by settling of the fiber bed.
Although they cannot start fires, mist eliminators will be ruined by fires started elsewhere in
the exhaust system. For this reason, they should be equipped with spark arresters, quick acting
bypass dampers or washers that will activate in case of fire.
9.2.2.2b High Velocity Fiber Mist Eliminators
High velocity fiber mist eliminators generally consist of a fiber mat held between two screens.
They operate in the upper region of high efficiency aerosol collection, where the primary me-
chanisms are interception and impingement. Efficiency of collection increases both with pres-
sure drop and with droplet diameter. Collection is generally 100% for particles over 3 microns.
For particles under 3 microns diameter, collection efficiency depends on the design of the filter.
One company (22) advertises two types: A high velocity (H-V) filter and a spray cleaner. Both
are designed to operate at 400 to 500 ft/min linear velocity, but the H-V filter operates at 6 to 8
inches of water pressure, with a collection efficiency of 85 to 97% for 1 to 3 micron particles,
50 to 85% for 0.5 to 1 micron particles, while the spray cleaner has a pressure drop of 1 to 2
inches of water and a collection efficiency of 15 to 30% for particles of less than 3 microns
diameter. The two filter packings are interchangeable, allowing for experimentation at rela-
tively low cost. Filters of this type are often used after scrubbers, cyclones and other devices
that produce sprays of relatively large droplet size. Some varieties are irrigated with water or
another liquid, allowing them to serve as filters for coarse droplet removal and as packed towers
for removal of gases and soluble dusts.
9-20
-------
For removal of oil mists, with particle sizes in the range of 0.1 to 1 Micron, pressure drops of
25 to 35 inches of water are required. Installed costs (in 1974) ranged from $0.50 to $3.50 per
CFM (11). Filter replacement costs (1975) for one such unit were reported to be $600 to $1200
per 10,000 CFM per year (19). In this unit, which is especially suited to removal of sticky
aerosols of low droplet concentration, the filter medium is supported on a drum that indexes
as the filter becomes clogged. The filter is fed across the drum from roll to roll and thrown
away after use. Figure 9-11 shows a drawing of this setup.
Pre-filtration for removal of lint is recommended and pre-cooling of the exhaust is necessary.
Post-filtration may also be necessary for re-entrained particles, though their size will be larger
than those in the original mist.
9.2.2.2c Other Types of Filters
A large number of self-cleaning filters are available, mostly for the removal of dry dusts and fly.
Bag houses are often equipped with automatic blowers on the clean air side that sweep each bag,
continuously cleaning it one small area at a time. Rotating drum filters are also used, whereby
lint-laden air is fed to the inside of the drum and removed from one area of the outside, or vice-
versa. As the filtering position becomes clogged, the drum indexes, exposing a fresh section to
the air stream, and the collected material is removed for disposal by pressure or suction.
Another type of self-cleaning filter consists of a flat surface that is continually cleaned by a
vacuum nozzle that sweeps its entire surface. This is usually used for removal of finer particles
than a rotating drum. One system has a swept filter following a rotating drum. Exhaust from the
cleaning system of the swept filter is recycled to the input of the rotating drum, where it is
caught and removed in the fiber mat that collects on the rotating drum.
Other types of self-cleaning filters are available. In many systems, filter fabric is reeled from roll
to roll across the exhaust stream. This setup is similar to a rotating drum, but the clogged filter
medium is collected on the output roll for off-line cleaning or disposal. In another type, a steel
mesh wheel is slowly rotated with the bottom passing through a cleaning oil bath. Such a setup
would be useful for removal of oily lint which would clog other types of self-cleaning systems.
Replaceable filters or filters with elements that must either be replaced or manually washed,
have a low installation cost, but a high operating cost in situations where large quantities of par-
ticulates must be removed. They are used chiefly for removal of small amounts of lint from an
air stream, often as pre-filters prior to oil mist abatement systems, heat exchangers or solvent
recovery systems (see Section 9.3 through 9.6) Their advantage is low initial cost, durability and
simplicity. Fiberglass or fiber elements are used for low temperature applications, while for tem-
peratures above 250° F, as with tenter frame exhausts, steel mesh filters are preferred. When
loaded, these filters are manually cleaned and an adhesive is reapplied to improve collection
efficiency.
9-21
-------
FIGURE 9-11
HIGH VELOCITY FILTER SYSTEM
Source: Johns-Manville Corporation
9-22
-------
9.2.2.3 Electrostatic Precipitators
Electrostatic precipitators can be used for collection of participates down to 0.1 microns with
95 to 99+% efficiency (3), (23), (24). Exhaust air is first passed through an ionizing grid, where
the dust and droplets receive a positive change, which subsequently causes them to be attracted to
negatively charged collection plates. Freely flowing oils will coalesce on these plates and run off
into a collection device., while dust, tars, etc. will remain on the plates, from which they must
be removed by periodic washing or rapping. Since excessive buildup on the collection plates in-
sulates them, causing loss in collection efficiency, it is generally best to remove large easily re-
moved particles prior to electrostatic precipitation. Water droplets should also be removed, as
they can cause excessive arcing between the charged plates and damage. However, specially de-
signed electrostatic precipitators are presently being used to collect acid mists (9), (25).
Electrostatic precipitators cannot collect vapors, and they will not therefore remove odorants
from the exhaust, unless these odorants are carried by other liquid or solid contaminants. They
are not recommended for use with explosive vapors or highly flammable liquids, as they are
subject to occasional arcing even when operated properly. For collection of oil mists, arcing
has not been found to be a problem. Some systems provide automatic power cutoff in event
of arcing, with power restored when the arcing ceases.
However, precipitators can be damaged by stack fires that start in other places. Spark arrestors
and quick acting bypass dampers are available. Some systems can also be made to begin their
wash cycles or to flood themselves with steam or carbon dioxide gas in event of fire. Breakage of
ionizing wires due to excessive arcing and power pack failures are the most common electronic
problems that can occur.
Most maintenance problems are associated with dust and sludge buildup. Automatic cleaning
is generally provided, either with steam or with a detergent wash. Generally the systems are
shut down once a week for a 2 to 4 hour cleaning cycle, which can be either automatic or manu-
ally initiated. Manually initiated cleaning is recommended, since it forces regular observation of
the equipment, which may otherwise be overlooked, because it is generally located on the plant
roof and is not directly associated with production.
Installed costs of systems that include electrostatic precipitation vary widely with the complex-
ity of the abatement problem. For cleanup of exhausts containing oil mists from texturizers,
where no pre-cooling is necessary, installed costs of the entire electrostatic precipitation system
range from $2.00 to $3.25 per CFM (1974 prices). For cleanup of tenter frame exhausts, where
cooling of the air is necessary to condense the oil prior to precipitation, installed costs of the
total system range from $2.22 to $4.00 and up per CFM (1974 prices). Systems which incorpor-
ate heat recovery devices or which require complex cleaning can cost as much as $12.00 per
CFM capacity. If additional capacity or efficiency may be needed in the future, space can be
provided for addition of future precipitation cells in series or parallel with the first.
9-23
-------
Operating costs are extremely low because of the low pressure drops required (1/4 to 1/2 inches
of water) and the small consumption of electric power. A 1000 CFM system typically requires a
5 HP blower and one kilowatt of electric power to energize the precipitator. At $0.02 per KWH,
the electricity cost would be about $0.10 per hour.
Detailed design and application criteria for electrostatic precipitators are given in the EPA Air
Pollution Manual (8), pp. 136 to 166, and in Perry's Chemical Engineers' Handbook (9), 5th ed.,
pp. 20-103 to 20-115.
9.2.2.4 Adsorption
Gaseous pollutants can be removed from exhaust air by selective adsorption onto solids. Ad-
sorption of gases onto solids and desorption from them are complex physical and chemical
phenomena that are not entirely understood. In general, substances adsorb more readily (and
are consequently more difficult to desorb) the higher their boiling points. Adsorption also takes
place more readily in small diameter pores than on open surfaces. In addition, the solids them-
selves will preferentially adsorb certain compounds. Activated carbon adsorbs all organics in
preference to water, while other common adsorbents such as silica gels, synthetic zeolites, and
metallic oxides are more selective in the substances they will adsorb and, generally, will adsorb
water in preference to organics (11), (26).
The present discussion is related to the general case, which is primarily physical adsorption.
Chemical adsorption is a special case, where chemical bonding is added to the physical mechan-
ism, creating complex relationships in adsorption, desorption and deactivation, which do not
lend themselves readily to general treatment.
Adsorption is a competitive dynamic phenomenon, so that more strongly adsorbed substances,
such as oil vapors, will gradually displace less strongly adsorbed substances such as low molecu-
lar weight organic solvents. At any temperature, there is an equilibrium between the molecules
on the solid surface and those in the gas phase. Adsorbed substances can, therefore, be evaporat-
ed from the surface into a vacuum or into an inert carrier gas, or they can be boiled from the
surface by heat. Common drycleaning solvents, for example, can be flushed from activated
carbon with low pressure steam, but spinning oils, plasticiers, etc., that generally comprise oil
mists can only be driven off with steam superheated to 650° F (8).
Activated charcoal is best employed for removal of organic substances with a molecular weight
above 45 or a boiling point above 32° F (11); however, it is not feasible to use it for removal
of high boiling oils, as these deactivate the charcoal by almost irreversible adsorption as men-
tioned above. For compounds containing chlorine, fluorine or sulfur, carbon adsorption is
often the only economically feasible means of removal, since incineration produces HC1, HF
or S02 respectively. If the system is sized and operating properly, it is possible to remove vir-
tually all of the pollutants, reducing exhaust concentration to less than 1 ppm. Typical solvents
recovered by carbon adsorption include hexane, heptane, alcohol, carbon tetrachloride, freon,
9-24
-------
ethylene dichloride, chloroform, toluene, acetone, methylene chloride, perchloroethylene,
trichloroethylene and 1, 1, 1, trichloroethane (11).
All catalysts lose activity with time, and activated carbon is no exception. Deactivation of the
carbon beds has several causes:
1. Loss of surface area due to mechanical abrasions, sintering and plugging of the pores.
Since the adsorption of hydrocarbons on activated charcoal is primarily a physical
process, it takes place according to the classical Brunauer Emmett & Teller isotherm,
whereby a disproportionate amount is adsorbed in the small diameter pores, which
are most easily plugged or sintered shut.
2. Adsorption of high boiling oils, which are not removed by low pressure steam strip-
ping. Physical adsorption is most easy and desorption most difficult for substances
with higher boiling points such as oils. These can gradually render the carbon surface
unavailable for solvent adsorption.
3. Poisoning of the catalyst. Substances like tri-isotoluene, which is used in urethane
manufacture, and probably also cyclohexenone, can irreversibly deactivate activated
charcoal catalysts.
4. Channelling and bypassing in the bed, due to settling.
The deactivation process can be substantially slowed if proper precautions are taken to avoid
deactivation conditions. A pre-filter, regularly changed, can eliminate most entrained oils and
lint. Catalyst poisons can be largely removed by inclusion of a small sacrificial charcoal bed
before the main bed. One manufacturer claims that properly maintained carbon beds will last
5 to 15 years (probably an optimistic figure), but recommends laboratory checks of the
carbon activity every 3 months. The simplest check on activity is with the stack analyzer, since
a properly sized working system will reduce hydrocarbon concentrations in the exhaust air to 1
to 3 ppm.
When chlorinated solvents such as perchloroethylene, trichloroethylene, methylene chloride,
and especially 1, 1, 1, trichloroethane are steam stripped, hydrochloric acid is present in the
bed. Since the activated carbon has catalytic properties, corrosion problems can be severe, and
304 and 316 stainless steel is not acceptable for carbon beds to recover chlorinated solvents.
Most carbon adsorption systems are therefore lined with baked phenolic. A carbon bed for
methylene chloride recovery with a baked phenolic coating can last 20 years under these condi-
tions, while a bed of 304 stainless steel would last only 3 months.
Typically, activated carbon beds are arranged in parallel for continuous operation. While one
bed is being stripped of adsorption substances, the other beds are adsorbing impurities from the
9-25
-------
exhaust. In some non-continuous operations a single bed can be used if it has sufficient capa-
city to adsorb all the gaseous pollutants emitted from the process, and if it can be regenerated
in time to be used the next time the process is performed. Detailed design and application
criteria for carbon adsorption systems are given in the EPA Air Pollution Manual (8), pp. 189-
199.
9.2.3 Scrubbers
Scrubbers are gas-liquid contacting devices, in which liquid, solid, or gaseous components car-
ried in the gas stream are removed by adsorption into and by adhesion to the liquid. The liquid
employed may be water, a water solution, or slurry of chemicals that will react with the substan-
ces to be collected, or it may be an organic liquid. Non-aqueous scrubbing is used principally for
collection of organic vapors that are only slightly soluble in water. Scrubbers have the disadvan-
tage that the pollutants are collected in a liquid, so that an air pollution problem may be solved
by creation of a water pollution problem. However, if existing water effluent treatment facili-
ties have the capacity to handle the additional load produced by the scrubbers, or if the pollu-
tants can be easily removed from the water by filtration, oil skimming, etc., scrubbing is a
feasible method of pollution abatement that has the advantage that its technology is relatively
well developed.
9.2.3.1 Gas-Liquid Scrubbing
Removal of vapors from an exhaust stream can be accomplished most effectively by packed
towers or tray towers. Packed towers are hollow cylindrical vertical towers, where the liquid is
introduced as a spray at the top and flows downward through the packing, which may consist
of marbles, ceramic saddles, raschig rings, crushed glass, etc. The packing serves to disperse the
liquid into a high surface area film to facilitate contact with the gas, which travels upward
through the tower. Wetted fiber or wire mesh filters can also serve as packed towers to a certain
extent. In plate towers, the packing is replaced by perforated, horizontal plates. The liquid
flows across each plate as it descends the column, while the gas bubbles up through the holes in
the plate.
Packed columns have the advantage of low liquid holdup in the column. Corrosive materials,
such as acids, can be easily handled, because the packing can be made of inert material. Degree
of liquid agitation is low, allowing liquids that tend to foam to be more easily handled. Unless
packed columns are greater than 2 ft. in diameter, packings must be of expensive alloys, packed
columns are generally cheaper than plate columns (9).
Plate columns exhibit broader operating ranges than packed columns, and they can handle high-
er liquid rates more efficiently than packed columns. They are easier to clean if there are solids
present in the system. Cooling coils can be incorporated into them more easily than into packed
columns. They are not subject to damage by thermal shock or packing breakage during installa-
tion as are packed columns and they are completely wetted at low flow rates, whereas packed
columns can develop dry spots, resulting in reduced efficiency (9).
9-26
-------
Both packed and plate columns can be plugged by solids buildup and therefore require pre-
filters if lint or high concentrations of dust are present in the exhaust. They can both pre-cool
the exhaust and remove vapors, though care must be exercised in the case of packed columns, as
they can develop hot dry spots at the bottom at low water flow rates. They are not effective
in removing sub-micron particulates, such as oil mists, which require higher energy scrubbing.
When properly operated, liquid entrainment is not a serious problem.
Detailed design and application criteria for plate and packed columns are given in the EPA Air
Pollution Engineering Manual (8) 2nd ed., pp. 207-229, and in Perry's Chemical Engineers'
Handbook, 5th ed., (9) Section 14 and 18.
Spray towers consist of open chambers in which the scrubbing liquid is sprayed downward
from the top, while the gas rises countercurrently. Liquid droplets should be 500 to 1000
microns in diameter for optimum results (8). Smaller droplets require a higher pressure drop in
the nozzles and can be entrained by the gas. In cyclone spray chambers, of the type shown in
Figure 9-12, liquid entrainment is less of a problem, since the liquid is thrown to the walls by
centrifugal force, exactly as in a cyclone dust collector (see Section 9.2.1). However for both
types of spray chambers, mass transfer is limited to one, or at the most two theoretical stages.
Therefore spray chambers can be used as gas absorbers only in cases where the gas is readily
soluble in the liquid. They are generally used to pre-cool and humidify an exhaust stream prior
to cleanup. Lint, fly, and other particles down to 10 microns can also be removed by spray
towers. Cyclone spray scrubbers are capable of removing particles as small as 2 microns in
diameter (9).
Another method of scrubbing a gas is to bubble it through a tank of absorbing liquid, or
through several tanks in series. The gas is dispersed into fine bubbles, either with a sparger
or with a mechanical agitator, to obtain the maximum possible surface area for mass transfer.
Because of the agitation of the gas bubbles, the liquid can be assumed well mixed. Mass trans-
fer is therefore limited to one theoretical stage, but if the liquid contains a chemical that can
destroy the absorbed pollutant, higher levels of efficiency can be achieved.
Design criteria for bubble type absorbers have been well developed only for the oxygen-water
system, which finds extensive application in aeration lagoons. Other gas-liquid systems are
generally correlated with reference to it. The principal parameters are gas phase mass transfer
resistance, interfacial area (interfacial resistance) liquid phase mass transfer resistance and hold-
up of the gas phase. Of these, gas phase mass transfer resistance is generally low and can be
disregarded.
Interfacial area depends on the fractional gas holdup, the liquid volume, and the Sauter bubble
diameter, which is defined as that bubble diameter that will give the observed average bubble
surface to volume ratio. The relationship for spherical bubbles is:
6 e V i
a = -—- (9.7) (Reference 2, p 18-78 Adapted)
9-27
-------
Antispm vanes
Core buster disk
Tangential
gas inlet
Swinging
inlet damper
Damper
position
indicator
Spray
manifold
Water Water
outlet inlet
FIGURE 9-12
CYCLONE SPRAY CHAMBER
9-28
-------
Except at gas velocities below 0.2 ft/sec, where sparge design has an influence, bubble size and
fractional gas holdup depend chiefly on the degree of agitation and the properties of the gas and
liquid.
The interfacial area increases with increased mixing horsepower and gas velocity and decreases
as the surface tension increases.
Interfacial effects are complex and difficult to predict in advance. Impurities concentrating at
the interface can cause variations in surface tension which can increase or decrease interfacial
turbulence, depending on the system. Smaller bubbles can be produced by reduction in surface
tension, by surfactant imparted electrical charges that hinder bubble coalescence, or by large
concentration gradients and heat effects that cause bubble break-up. In addition, impurities
can concentrate at the interface, adding an interfacial resistance to mass transfer.
Liquid phase resistance to mass transfer is dependent principally on liquid phase viscosity,
density, and diffusivity, which are difficult to alter at will. However, the driving force for
transfer into the liquid phase can be increased by addition of a chemical to the liquid that will
complex or destroy the dissolved vapor. Liquids in which the vapor is readily soluble should
also be selected in preference to those in which it is sparingly soluble.
Gas holdup time should be maximized to provide adequate time for mass transfer to take place.
The relationships are complex and empirical but, generally, increased agitation increases, and
increased gas throughout decreases gas holdup time.
Greater detail is presented in Perry's Chemical Engineers' Handbook, (9), 5th edition, pp.
18-70 to 18-81, from which this discussion has been abridged. Bubble tank absorbers are useful
chiefly as intermittent duty devices to remove vapors from the air being vented from a liquid
storage tank during filling. They have the advantage that they are cheap, and easy to design,
install, operate and upgrade if necessary.
9.2.3.2 Scrubbing for Particulate Removal
9.2.3.2a Inertial Impaction Scrubbers
The primary mechanism for removal of particulates from a gas by scrubbing is inertial impac-
tion of the droplet and the pollutant particle. Figure 9-13 shows how this is accomplished.
Particles following the gas streamlines approach a collecting surface with relative velocity Vo. As
the gas streamlines bend around the collecting surface, the particles are unable to follow them
because of their inertia. Those within the flow cross section of width X, will be intercepted by
the collector. The collection target efficiency NT, is defined as the ratio of the interception
9-29
-------
area of a collector to its cross sectional area. In the case of a spherical droplet of diameter D
NT = x2/Dd2 (9-8)
The target efficiency is related to a dimensionless separation number Ngf according to the graph
in Figure 9-14. The separation number is given by:
o (99)
18MgDd
Therefore, particulate collection efficiency of a conventional scrubber is increased by increas-
ing the particle-droplet relative velocity and by decreasing the droplet diameter. Since either of
these methods requires an increase in applied power, collection efficiency of all scrubbers in-
creases as the energy input to them is increased. As a rough approximation, all scrubbers operat-
ing at the same horsepower have the same efficiency for collection of particles of a given size.
However in practice, particulate losses have been observed to vary by more than a factor of
three from one scrubber to another at the same pressure drop.
Figure 9-15 shows the minimum particle size at which various types of conventional scrubbers
have an 80% collection efficiency. As can be seen, scrubbers capable of operating at higher pres-
sure drops can collect particles of smaller diameter. Knowledge of pollutant particle size distri-
bution is therefore essential to proper scrubber specification. If the actual particle size distri-
bution is not known, or if it may be subject to change, a scrubber of variable efficiency should
be considered, such as Venturi scrubber with throat of variable cross section.
If gas absorption is to be carried out concurrently with particulate removal, a scrubber with long
countercurrent gas-liquid contact time, such as a packed tower, should be considered. Packed
towers as vapor absorbers are discussed in section 9.2.3.1.
If the solids loading in the exhaust exceeds about 20 grains per cubic foot, plugging can be a
problem. Open scrubbers, such as spray towers or baffle towers, are least susceptible to plugging
and are often used as pre-cleaners in preference to easily plugged scrubbers.
Other common problems associated with inappropriate design include re-entrainment of scrub-
ber droplets, stack condensate blow-out, and freezing. Re-entrainment is generally prevented by
use of a mist eliminator (see section 9.2.2.2) after the scrubber. Stack condensate fallout occurs
when vapors condensing downstream of the scrubber adhere to the walls of the stack and collect
some of the particles that escaped the scrubber. This buildup can blow out of the stack as a
slurry if the stack velocity exceeds 20 ft/sec. Freezing in cold weather can be avoided by making
provisions for complete drainage of water from all parts of the scrubber system.
A detailed schematic of an impingement scrubber illustrating the gas flow through the orifice is
9-30
-------
Inertial
impaction
FIGURE 9-13
EFFICIENCY OF INERTIAL IMPACTION
Source: Re
1 0
0 9
08
•*— •
. 07
O
c 06
0)
O „ r-
— 05
"CD
*- 04
O>
cn
CO °3
H
02
0 1
0
OC
ference 9
Intercepts
Ribbon or
Sp
hers
i
24
c
\
/h
i
nd
er
I/I
1
j. /
"/<
?/
"">».
c
/I
V
'
/.
V
^
- a-5
/
/
/
?
*x
•
1 J
i%
0^
^
0
/
/^
^
^ff
,
'/
**•
/
•*•
s
ff
s*
— -
**"
^"
**•
^-
^
^
pi
V
•
Mi
•1
11 0110 10 1
Source: Reference 9
Separation Number, utVo/g|_ Db
FIGURE 9-14
RELATION OF TARGET EFFICIENCY
TO SEPARATION NUMBER
Spray towers
Cyclone spray scrubbers
Impingement scrubbers
Packed- and fluidized-bed scrubbers
Orifice scrubbers
Venturi scrubbers
Fibrous-bed scrubbers
Pressure
drop,
in. water
0.5-1.5
2-10
2-50
2-50
5-100
5-100
5-110
Min.
particle size, M
10
2-10
1-5
1-10
1
0.8
0.5
FIGURE 9-15
MINIMUM PARTICLE SIZE FOR
VARIOUS TYPES OF SCRUBBERS
Source: Reference 9
9-31
-------
shown in Figure 9-17. Gas at 75 to 100 ft/sec, is blown through modified sieve plates, where it
contacts the liquid, forming droplets which are atomized by collision with the baffles located
above each orifice. The droplets thus formed have a target efficiency of 80% for one micron
particles of 2.7 specific gravity with a gas velocity of 75 ft/sec. Pressure drops are about 1.5
inches of water per plate. The gas is generally pre-wetted, and the coarse particles are removed
with a spray tower scrubber.
Fluidized bed scrubbers, of the type shown in Figure 9-18, consist of sections containing low
density spheres held between perforated plates. Scrubbing liquor flows downward, counter-
current to the gas. The violent motion of the spheres minimizes fouling. Pressure drop is 4 to 6
inches of water per stage.
With orifice scrubbers, high gas velocities are created by a restricting orifice prior to gas-liquid
contact. Droplets are formed when the gas is blown over the surface of the scrubbing liquid.
Equation 9.10 gives the droplet size produced by orifice scrubber as a function of liquid-to-gas
ratio (gallons/1000 ACF) and superficial gas velocity:
Dd = 16,050+ 1.41 (L/G)1-5 (9 10) (Reference 9, p 20-100)
Vg
Collectible particle size decreases with increasing gas velocity, with velocities exceeding 400 ft/
sec being required for collection of submicron particles. Figure 9-18 shows three models of ori-
fice type scrubber.
Venturi scrubbers operate by injection of a water spray into a gas stream as it is accelerated
through a Venturi nozzle. Equations 9.9 and 9.10 can be used to estimate their performance.
Generally a pressure drop of 40 to 70 inches of water is required to remove the submicron drop-
lets of a textile oil mist (23). Figure 9-19 shows a typical Venturi scrubber, with a cyclone fol-
lowing to collect the water mist created by the Venturi.
Water jet scrubbers of the type shown in Figure 9-20 function as aspirators, with the high velo-
city water stream pumping the gas. Pressure increases of up to 8 inches of water can be achieved
in the gas, with 50 to 100 gallons per 1000 cubic feet of air required to create a one inch pres-
sure increase. Relative liquid gas velocity is low, resulting in low collection efficiencies for par-
ticles of less than 5 microns diameter. Water jet scrubbers require a collection device following
the scrubber for air-water separation.
One patented system, shown in Figure 9-21, employs the waste heat of the exhaust gases to
power the water jet. Exhaust gases at 800 to 4000° F are heat exchanged with 0.8 to 1.0 Ib/lb
of scrubbing water. Water (3 gallons/1000 ACF) at 400° is sprayed from the nozzle with 15%
vaporization, to give 10 micron droplets travelling at 1000 ft/sec, in a gas of 100 ft/sec, velocity.
Removal efficiency is reported at 99.6% for particles of which 85% are smaller than 0.1 micron
"diameter (27), (28).
9-32
-------
FIGURE 9-16
ORIFICE OF AN IMPINGEMENT SCRUBBER
Source: Sly Manufacturing Company
Cleaned gas
Mist eliminator
Scrubbing liquor
Retaining grid
Floating bed of
low-density spheres
Retaining grid
Dust-laden gas
FIGURE 9-17
FLUIDIZED-BED SCRUBBER
Source: UOP, Air Correction Division
9-33
-------
to
O)
oo
CO
DC
111
s
D W
— ' IN
O o
u. ^
cc
o
c
TO
CL
E
si-i
if 2 E
TO "5 C
•- CO *
CD 0> g
E Si
< tr CD
"nT-Q U
en
cri
o
o
U)
9-34
-------
Gas out
Gas in
Quench
spray
Slurry
inlet
Venturi
Effluent
drain
FIGURE 9-19
VENTURI SCRUBBER
9-35
-------
FIGURE 9-20
WATER-JET SCRUBBER
Source: Schutte and Koertmg Company
9-36
-------
Clean gas
Two-phase
jet nozzle
Make-up
water
Dirty gas
Sludge
FIGURE 9-21
TWO-PHASE FLASHING WATER JET SCRUBBER
Source: ADTEC, Inc.
9-37
-------
In mechanical scrubbers, jets of water are sprayed at rotating blades which atomize the water
droplets and accelerate them. A cyclone is usually provided to remove the dirty liquid. Dust
loading is usually limited to 0.5 grains per cubic foot to minimize build-up of deposit on the
rotor. Figure 9-22 shows a typical mechanical scrubber. Collection efficiency varies with con-
figuration and blade speed. The Theisen Disintegrator, a common mechanical scrubber, can col-
lect particles down to one micron with a power consumption of 10 HP/1000 CFM.
Fiber bed scrubbers are combination filters/scrubbers in which the pollutant particles are col-
lected by impaction on a wetted fiber matrix. The matrix is generally kept continuously clean,
either by a liquid wash or by deliberate re-entrainment of the liquid droplets and subsequent
collection. Fiber bed scrubbers function essentially as high velocity air filters, which are dis-
cussed in Section 9.2.2.2c.
Additional information on inertial impaction scrubbers is given in Perry's Chemical Engineers'
Handbook, 5th ed., pp. 20-94 to 20-104 (9).
9.2.3.2b Other Particle Scrubbers
Two other collection mechanisms can be employed to obtain greater collection efficiency at a
lower expenditure of energy than can be obtained with a scrubber operating purely on the prin-
ciple of inertial impaction. These are condensation and electrostatic attraction.
Figure 9-23 shows a scrubber operating on the flux force condensation principle, which is cur-
rently being demonstrated by Air Pollution Technology, Inc., of San Diego, California (28).
Steam is injected into the exhaust stream and then cooled. Pollutant particles serve as conden-
sation nuclei, thereby increasing in size and becoming more easily collectable by impaction.
An additional phenomenon known as Stegan flow (9), causes particles to be attracted to the
condensing droplets, facilitating agglomeration. A 1000 CFM unit has successfully been oper-
ated, and a 5000 to 10,000 CFM unit is being started up on a secondary metals recovery furnace.
Electrostatic attraction is combined with wet scrubbing for fine particulate removal at low pres-
sure drop in three recently developed systems (29), (30), (31). The first, called a charged droplet
scrubber, is shown in Figure 9-24. It collects pollutant particles with a spray of electrostatically
atomized charged water droplets that are accelerated toward a collection plate. The pollutants
are collected by the droplets by a combination of impingement and the electrostatic attraction
of the dipoles induced in them in the presence of the charged droplets, called image force at-
traction. The scrubber has been used successfully in the Japanese steel and pulp and paper
industries, collecting one micron particles with 99% efficiency, and submicron particles with
90 to 96% efficiency at a water consumption of one gallon/1000 ACF. It is offered by TRW
Environmental Products Division, Redondo Beach, California.
9-38
-------
FIGURE 9-22
MECHANICAL SCRUBBER
Source: American Air Filter
9-39
-------
Particle accelerator
\
Mixing tube V
Injection water
Steam nozzle inlet
Atomizer water
Inlet duct —.
Flue gas from waste-heat boiler
^Cyclones
Cyclone slurry
-_ .Atomizer chamber (optional)
Atomizer slurry
FIGURE 9-23
FLUX FORCE CONDENSATION SCRUBBER
Source: Air Pollution Technology, Inc.
Estimated Performances
Power
watts (ft 'mm)
Residence time^
mm
Collecting area/flowrate.
fty(ftVmin)
Pressure drop.
in H20
Venturi
Scrubber4
40-120
001
not
applicable
20 0-60 0
Bag
House?
1 0-1 3
009-0 14
02-05
40-60
Electrostatic
Precipitator"'
03-08
0 12-020
02-0 6
02-05
CDS'
03-05
0 03-0 04
0 06-0 20
05-07
1 —For 3 to 4-m collector spacing
2—At air-to-cloth ratios or 3 and 6, pulse air cleaned
3—For 2-3 and 3-5 field sectionalization
4—For 20-60 in H2O pressure drop
5—Includes process gas fan, power supplies and auxiliaries
6—Includes demisters, hoppers, gas distribution, and
collecting sections
CDS Scrubber Wet Electrostatic Precipitator
Clean air Clean air
Electrostatic ^
atomization x-
Fed tube r \j— ,^
+50kV x 1 \
\ JL \
P™ V
Water ^-m
Positive- or
negative-charged
water droplets
4-
Collector --*.
Air and droplets -
contacting at
terminal velocity /
a 1
ri
„ — n^ tnt\/
>^ ^.
> -*^
) ,^:
#§J»»'*;
n
^Corona wire
— Collector
Corona-charged
"water droplets
^_ Sludge
"Hi1" F
ee tube
~ /)\ Watpr
I- _t faT^ 3
Mechanical / t x Neutral-charged
atomization droplets
Dirty air
FIGURE 9-24
CHARGED DROPLET SCRUBBER
Source: TRW, Environmental Products Division
9-40
-------
The second is an ionizing wet scrubber (shown in Figure 9-25) offered by Ceilcote Company,
Berea, Ohio. Contaminated gases are passed through an ionizing section into a crosscurrent
packed bed scrubber, where the charged particles are collected on Tellerettes by a combina-
tion of impingement and image force attraction. Collection efficiencies are 70 to 95% for
particles down to 0.05 micron, and greater efficiency can be achieved by putting multiple
units in series. Power consumption is 0.2 to 0.4 KVA/1000 ACF, with a pressure drop of 1.5
to 2 inches of water.
The third device, shown in Figure 9-26, is offered by Air Pollution Systems, Inc. of Tukwila,
Washington. Particles are ionized prior to collection in a conventional scrubber, which in this
case was a low energy Venturi scrubber. An electrical energy input equivalent to one to two
inches of water resulted in improvement of collection efficiency to the same extent obtainable
by an increased pressure of 20 to 25 inches of water in a conventional scrubber. With water
usage of 9 gal/1000 ACF and a pressure drop of 11 inches of water, 97% removal of 0.8 micron
particles was obtained.The ionizing system could be installed prior to any conventional scrub-
bing system to increase efficiency.
9.3 Elimination of Oil and Acid Mists and Associated Pollutants
9.3.1 Design Considerations
When textile materials are subject to heat treatment above 200° F, some volatilization of oils,
waxes, plasticizers, etc., that are present on or in the material occurs, as was described in Sec-
tion 9.1. The mist is formed when the vapor laden air is cooled to 110 to 160° F, causing re-
condensation of these low vapor pressure organic compounds into droplets of a diameter
range of 0.1 to 1 micron, with 75% of the droplets being less than 0.5 micron in diameter.
Because of the small size of the droplets, techniques applicable primarily to lint removal or gas
adsorption, such as bag filters and low energy scrubbers of the spray or packed tower type are
not effective.
Feasible abatement techniques include process modification, incineration, high energy scrub-
bing, or the use of electrostatic precipitators, high efficiency fiber mist eliminators, or high
velocity air filters. Three things must be known for proper specification of a mist eliminator
system. These are:
• Air volume to be processed
• Temperature of air to inlet to abatement system
• Approximate exhaust composition
Exhaust air volume, in CFM, can generally be obtained from the manufacturer of the process
equipment for which emission control is necessary. Figures supplied by equipment manufactur-
ers are generally conservative, resulting in some overdesign of the emission control system.
9-41
-------
Electrode
wires
Spray header
$&&;^;?$£%£
&&&tig&&#«::*
Grounded plates
Packing
Out
FIGURE 9-25
IONIZING WET SCRUBBER
Source: Ceilcote Company
9-42
-------
High-voltage
power supply
100'
2 90
85-
I
Particle size distribution
Microns
< 022
0 22-0 5
05-1 5
1 5-33
>33
Percent
2
8
40
30
20
Insulator
Electrode
Charged
particles
05 10 15 20
System pressure drop, in w.g
25
30
35
Particles and
water contacting
Clean gas
FIGURE 9-26
ELECTROSTATICALLY ENHANCED
SCRUBBER SYSTEM
Source: Air Pollution Systems, Inc.
However, this overdesign constitutes a margin of safety which may subsequently allow for pro-
cess changes that would tend to increase pollution problems, such as operating at higher tem-
peratures or processing of fabrics containing larger quantities of volatilizable material.
In cases where the recommended CFM is not available from the process equipment manufac-
turer, or where abatement equipment is being added to existing processes, the minimum recom-
mended CFM is limited by three factors: (2)
1. It must be sufficient to carry off all evaporated water in drying applications.
2. If the exhaust contains combustible material, the National Fire Protection Associa-
tion recommends that exhaust air volume be high enough to assure that the flam-
mable vapor concentration remains below 25% of the lower explosive limit in the
worst case. 10,000 CFM of air (measured at 70° F) should be vented with each liquid
gallon of evaporated oil or solvent (14).
9-43
-------
3. Air velocities must be high enough to prevent recondensation of the oils and their
dripping back onto the fabric and to prevent escape of the contaminants into the
in-plant air.
Sometimes with multiple stack processes, abatement is not necessary on all stacks. In the case
of tenters which also dry the fabric, for example, water is driven off first and can be exhausted
without removal, while oils are driven off subsequently. On the other hand, volatile organics
may be driven off the fabric at the start of a tentering operation, so that the first stack might
need abatement, but the second might not. Knowledge of oven zoning may also allow the adop-
tion of different emission control systems on different stacks, resulting in cost savings and/or
greater efficiencies of removal (2). One disadvantage of this approach, however, is that it restricts
the flexibility of the process equipment. When different materials are processed in the same
equipment under a different operating condition, one cannot always anticipate which pollu-
tant will be driven off at which stack.
Inlet air temperature to the pollution abatement equipment will determine whether further
cooling is necessary, and whether it is economical to recover the exhaust heat. Composition of
the pollutant is often the deciding factor in choice of a system. Mists that condense into rela-
tively freely flowing liquids can easily be removed by electrostatic precipitators or by most high
efficiency fiber eliminators, but mists that leave gummy or tarry deposits may require scrub-
bing, incineration or the use of renewable high velocity air filters. Quantity and condensation
temperature of the pollutant determine the extent to which it would condense in a precooling
system. Safety precautions required are determined by the flammability of the condensate,
especially with electrostatic precipitators, mist eliminators and some heat recovery systems
which are damaged by fire. Fires are especially common with tenter frame exhausts, since heat-
ing is often done with open flames. The exhaust gases are hot, and flammable liquids condense
throughout the exhaust system. Stainless steel ductwork is recommended in places where fires
can be a problem. Especially corrosive mists may require the treatment system to be construct-
ed from special corrosive resistant materials.
An estimate of the chemical composition of the mist can be obtained from knowledge of the
pre-history of the processed material, including the nature and amount of oils, plasticizers,
solvents, dyes, carriers, resins, etc., applied to it, both previously in the mill and by its original
manufacturers. Stack testing and knowledge of the emission character of other similar process-
es are also helpful. Stack testing is greatly simplified by foreknowledge of the pollutant chem-
icals likely to be present (2).
9.3.2 Emissions Preconditioning
Oil mist abatement consists of four steps, some of which may not be necessary, depending on
the nature of the mist and on the abatement techniques chosen:
• Pre-removal of lint and dust
• Cooling of the contaminated air to condense the vapors to mist
9-44
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• Removal of the mist from the air
• Collection and disposal of the contaminant
Removal of lint and dust is necessary with systems that would tend to become clogged with it.
These include electrostatic precipitators, high efficiency fiber mist eliminators, and packed
tower scrubbers. Some types of heat recovery equipment also require pre-filters (see Section
9.4). Lint and dust removal is not necessary prior to an incinerator, a venturi scrubber, or a
high velocity air filter (though it would prolong its life). It is generally accomplished with a
screen filter or a fabric filter placed in the exhaust line prior to cooling of the exhaust for oil
condensation. For temperatures above 250° F, steel mesh filters are often used.
Cooling of the vapor laden exhaust air, generally down to 110 to 160° F, is necessary to effect
recondensation of the organics prior to collection, unless removal is to be performed by an
incinerator without recovery of the organics. With texturizer fumes, this is not necessary, as
the air is already cool, but most other exhausts require some temperature reduction. This may
be accomplished either by direct contact cooling or by heat recovery via a heat exchanger. Use
of water scrubbing for pre-cooling reduces the problem of stack fires. Heat recovery equipment
is generally more expensive than simple direct or indirect contact cooling equipment, but if
some use can be found for the recovered heat, the additional expense can often be justified by
reduced energy costs. Heat recovery from exhaust air is discussed in Section 9.4.
Precooling by direct contact water evaporation is accomplished by low-energy scrubbers. One
manufacturer of electrostatic precipitators includes an optional pre-cooler consisting of a series
of wetted filters through which the exhaust passes for lint removal and cooling prior to droplet
precipitation.
Spray towers may serve as evaporative coolers as well as removing lint from the exhaust. These
have a disadvantage, however, in that they can add water droplets to the mist, causing emulsions
to coalesce in the mist-removing equipment. The effluent, therefore, can have a greater tendency
to gum and solidify, and oil-water separation equipment is required after collection.
Packed towers combine the function of a pre-cooler and an absorber for odorous water soluble
vapors. They can be plugged by lint and, therefore, require a pre-filter if the exhaust contains
large amounts of lint. Chemicals can be added to the scrubbing liquid to facilitate pollutant
vapor removal. Section 9.6 describes the use of packed tower scrubbers for odor removal.
Both as pre-coolers and as mist removers, scrubbers have the disadvantage that they are poten-
tial sources of water pollution. If water purification facilities already exist that can handle this
additional source, then scrubbers are a relatively inexpensive form of emission pretreatment.
Installation costs of various types of scrubbers are listed in Section 9.6.5. If space has been al-
lowed at installation, the efficiency of a low-energy scrubber can be increased by addition of a
venturi throat inlet (32).
9-45
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9.3.3 Process Modifications
Since oil mists are caused by evaporation of oils from textile materials, their formation can be
prevented by reduction of the oil content of the materials prior to heat treatment. Careful con-
trol of the application of spinning oils and fabric finishes to prevent excessive buildup on the
fabric can reduce mist problems and simultaneously result in material savings. Scouring before
tentering rather than after is possible in some cases, though in others tentering is required before
scouring to impart dimensional stability to the fabric. To eliminate oil mist problems from
tenter frames, input oil content must be reduced to below 0.5 weight percent (2).
Careful control of the heat input to the fabric can also prevent excessive oil evaporation as well
as save energy. Dielectric drying and curing are feasible in some instances, either as total replace-
ments for other forms of energy input or as supplementary energy inputs to effect precise
energy control. Dielectric energy as an input source is inherently self-regulating since the rate at
which any material absorbs dielectric energy is proportional to its dielectric constant. Water,
with a high dielectric constant, absorbs energy rapidly and is dried from the fabric. When the
fabric is dry, overheating does not occur, because the dielectric constant of the fibers is much
lower. Dielectric heating can also be employed as a means of precise energy input in the curing
of plastisols. While economics have previously not favored dielectric heating, the rising cost of
energy and the increasing stringency of antipollution laws are making it increasingly attractive.
9.3.4 Electrostatic Precipitators
For mists that can be condensed into relatively freely flowing oils, electrostatic precipitators
are the preferred abatement device because of their low operating and energy cost and their
effective elimination of small diameter particles. The liquid effluent produced is relatively pure,
presenting minimal disposal problems. For texturizing applications, no pre-cooling is neces-
sary, but oil mists from tenter frames require pre-cooling and are also apt to be more gummy,
waxy, and corrosive, because the higher temperatures involved in tentering cause evaporation
of higher boiling point substances and partial oxidation of them to acids and gummy polymers.
Most maintenance problems are associated with dust and sludge buildup. A pre-filter is neces-
sary to remove dust and lint. Dust can insulate the ionizing wires, causing loss of efficiency and
arcing. Automatic cleaning is generally provided, either with steam or with a detergent wash.
Water washes contaminate the effluent oil and may require a water separator for oil recovery.
Generally the systems are shut down once a week for a 2 to 4 hour cleaning cycle. More trouble
is experienced with condensates that can gum and solidify than with free flowing liquids, but
ease of manual cleaning is always an important factor.
Gumming and solidification of the condensate can sometimes be avoided by raising the col-
lection temperature above the gummy region. Since effluent mists of this type would be ex-
pected to have lower vapor pressures, they can often be collected at higher temperatures than
can more freely flowing oils.
9-46
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Arcing can also cause fires, but this has not generally been found to be a problem. However,
stack fires can start in other places and can spread to the precipitator, which can be damaged by
them. Spark arresters and quick bypass dampers are available. Some systems can also be made
to begin their wash cycles or to flood themselves with carbon dioxide gas in event of fire.
Unless designed for the application, electrostatic precipitators are not recommended where
water droplets or condensation of water mists are expected, since water can cause arcing and
short circuiting. In some applications, such as drying, where the exhaust air contains large
amounts of water vapor, operating temperatures should be kept above 160° F to allow conden-
sation of most of the oil without water condensation. Electrostatic precipitators designed for
wet operation have found application in collecting sticky particulate.
Operation of electrostatic precipitators is discussed in greater detail in Section 9.2.2.3.
9.3.5 High Efficient Fiber Mist Eliminators
For removal of oil mists containing water, mist eliminators are preferred to electrostatic pre-
cipitators for reasons mentioned above. Such mists are produced during the drying, curing or
tentering of fabrics containing significant amounts of moisture. High efficiency fiber mist elimi-
nators can easily be installed after low energy scrubbers, which would be used for lint removal,
pre-cooling, and abatement of odors due to gaseous contaminats. If a water spray can feasibly
be incorporated in a mist eliminator, it will function as a packed tower scrubber, removing both
mists and odors at once. Operating costs are higher than with an electrostatic precipitator be-
cause of the higher pressure drop required, which ranges from 5 to 15 inches of water. Mist
eliminators are discussed in detail in Section 9.2.2.2.
9.3.6 Incineration
Incineration is the most proven and reliable method of emission destruction, since virtually
everything in the exhaust is destroyed. Therefore it is worthy of consideration for destruction
of oil mists, especially if they contain fibers, gums, and odorous vapors that would require addi-
tional treatment. Because of the high and rising cost of energy, incineration is generally also the
most costly method of oil mist elimination. Care must be taken to prevent condensation of oil
in the exhaust ducts leading to the incinerator, since this can create a fire hazard. Incineration
is discussed in detail in Section 9.2.1. Heat recovery, which can reduce the operating c^sts of an
incinerator, is discussed in Section 9.4.
9.3.7 Scrubbing
Because of the small diameters of oil mist droplets, they cannot be removed by low energy
scrubbers, such as packed towers, spray towers or cyclone scrubbers, but removal efficiencies
of up to 99% by weight can be obtained with Venturi scrubbers operating at pressure drops of
40 to 70 inches of water (23). Since the energy costs for operating scrubbers, even at this high
9-47
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pressure drop, are still lower than the energy costs of incineration, high energy scrubbers are
generally preferred to incinerators for removal of extremely gummy mists, where electrostatic
precipitators and high efficiency mist eliminators are generally inapplicable. They are also pre-
ferred to incinerators for removal of materials containing chlorine, fluorine, sulfur, phosphorous,
etc., which would be incinerated to gaseous compounds that would still have to be removed
from the exhaust by adsorption. In 1974, installed costs varied from $0.50 to $4.00 per CFM
(11), with operating costs approaching those of fume incinerators.
Pre-filters and pre-coolers are not required, since Venturi scrubbers can also cool the exhaust
and remove lint. If additional scrubbing is desired for odor removal (see Section 9.6), Venturi
scrubbers can be followed by packed tower scrubbers.
If greater efficiency is required, the operating pressure drop of a Venturi can be increased if
provisions have been made for this. Removal efficiency can also be increased by addition of
surfactants to the water to promote emulsification, though this complicates the problems of
liquid effluent disposal. Another type of Venturi consists of a tray of closely spaced cylindrical
bars, which serve as slot orifices. Capacity can be decreased or pressure drop can be increased by
blanking off sections of the tray. Additional trays can also be added, or the tray can be replaced
by others with different bar spacings, permitting considerable flexibility of operations.
Because they require several hundred horsepower per 10,000 CFM (2), Venturi scrubbers are
usually noisy. If they are not followed by mist eliminators, they produce water plumes which,
while not illegal, can focus attention on effluent odors and become a source of complaint. They
are subject to abrasion, especially at high lint loadings, and in the presence of corrosive sub-
stances (17).
The recovered pollutants are mixed with water, making reuse less feasible and disposal more
cumbersome, and creating potential water pollution problems unless the effluent can be handled
by existing water treatment facilities. In some cases, if the spray nozzles are properly designed,
the contaminated water can be re-cycled. Solids must be removed, and if the scrubber is also to
be used for absorption of odorous vapors, their buildup in the recycled water will limit the re-
cycle ratio.
Additional information on the use of scrubbers for odor abatement is given in Section 9.6.
Further details on the principles of scrubber operation and design criteria for scrubbers are
given in Section 9.2.3.
9.3.8 High Velocity Air Filters
High velocity air filters are in-line fiber or mesh filters that remove fine mists from air streams
by high velocity impaction of the droplets on the filter medium. They are best suited for re-
moval of low droplet concentration aerosols of sticky particles, where re-entrainment of the
droplet is less of a problem. Pre-filtration for lint removal is recommended to extend filter life,
9-48
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and pre-cooling is necessary to condense the mist. Post-filtration may also be necessary for re-
entrainment particles, though their size will be larger than those in the original mist. High velo-
city air filters are discussed in greater detail in Section 9.2.2.2.
9.3.9 Elimination of Acid Mists
The techniques applicable to oil mist elimination apply for the most part to elimination of acid
mists as well, though special consideration must be given to the corrosive nature of the mists.
Incineration is practical only if the mists contain no inorganic acids, such as t^SOzj,, HC1, HF,
etc., or halogenated organic acids, such as trichloracetic acid. Mineral acids are unaffected by
incineration, and halogenated organic acids are merely oxidized to the corresponding mineral
acids. Specially designed electrostatic precipitators, generally lead lined, have long been used
successfully in the chemical industry for acid mist elimination (9), (10), (25). High efficiency
mist eliminators can also be used effectively if constructed of acid resistant material. Systems
that employ high velocities, such as Venturi scrubbers and high velocity mist eliminators, are
less suitable, especially in the presence of abrasive solid particles, since the acid corrosion re-
sistance of many substances is due to the maintenance of a protective surface film, which is
continually destroyed by abrasion. A detailed discussion of scrubber design for corrosion
resistance is given in Section 9.2.3.
9.4 Heat Recovery Systems
Although the waste heat discharged to the atmosphere by textile processes is not yet considered
to be itself a pollutant, heating and/or cooling of effluent air streams is often a necessary step in
the pollution abatement process, especially in the removal of oil mists and in the recovery of
solvents. With the exception of the texturizing processes, most processes that produce mists by
thermal evaporation of oils, waxes, resins, etc. from textiles require pre-heated air and generate
effluent air containing large amounts of recoverable heat. Pre-cooling of the exhaust air for con-
densation of the organics is necessary with mist eliminators, electrostatic precipitators, and high
efficiency air filters, and it can be used with Venturi scrubbers if the economics of heat recovery
warrant it. With incineration, on the other hand, the contaminated air must be heated, and heat
can be recovered from the incinerator exhaust gases. In solvent recovery systems (see Section 9.5),
precooling of the effluent air below 100° F is necessary prior to its introduction to the activated
carbon beds.
Shortages and increased prices of fossil fuels have made the possibility of heat recovery from ex-
haust air an increasingly important consideration in specification of a treatment system. In
choices between treatment systems of approximately equivalent performance, energy costs and
savings can be the deciding factor.
9-49
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9.4.1 Economics and Feasibility of Heat Recovery
The first consideration in the design of a heat recovery system should be the use to which the
recovered heat can be put. Where possible, the most effective use of recovered heat is to recycle
it to the process. Incinerator off gases can be used to preheat the contaminant laden input air.
Exhausts from tenter frames, drying ovens, curing ovens, etc., can also be used to preheat the
input air to these processes. However, it is not generally wise to use heat recovered from one
process for a second unrelated process, since this greatly restricts mill operating flexibility.
Moreover, even where recovered heat is reused in the same process, consideration must be given
to the problems of startup, shutdown and unsteady state operation. For example, in the case of
a tenter frame that recycles its heat, more input heat will be required at startup than at steady
state to prime the system, while at shutdown, or when it is necessary to decrease the operating
temperature, the recovered heat must be wasted or directed elsewhere.
If recovered heat cannot be recycled directly, heat recovery savings will be largest where the re-
covered heat can be used most continuously and over the longest possible period of time, as in
the production of hot water or steam for which there is a continuous demand. If the recovered
energy is used only for heating during the winter months, savings will be more limited, and al-
ternative provisions will have to be made for disposal of this heat at other times.
The amount of heat recovery possible from oven exhausts can be calculated if the temperature
and flow rate of the exhaust stream are known. Figure 9-27 shows the possible heat recovery in
BTU/hr. which can be recovered from oven exhausts as a function of the exhaust air flow rate
(CFM) for exhaust temperatures of 250. 300 and 350° F. It was assumed that the exhaust air
was cooled to 150° F, since this temperature is easily achievable with ambient air or water as
a coolant, even in the summer months. Figure 9-28 shows the annual dollar value of the re-
covered heat as a function of exhaust CFM for fuel costs of $1.00 to $4.00 per million BTU.
It is assumed that the exhaust air is cooled from 300 to 150° F and that the heat recovery
equipment operates 6,000 hrs./yr. In each case, it is necessary to correct these numbers for
heat losses, both in the system for heat recovery and reuse and in the heat generation system,
so that the number of BTU's the heat recovery system will actually deliver at the desired loca-
tion can be compared to the cost of delivering the same number of BTU's to the same loca-
tion by means of fuel consumption.
For example, if heat is recovered from one process for use at a distant location, heat losses in
transmission and storage of the heated transfer fluid will reduce the number of BTU's actually
delivered per BTU recovered from the exhaust. If a second heat exchanger is needed to recover
heat from the transmission fluid, additional losses will be encountered there.
9-50
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3.C
2.5
BTU
£ 1.5
o
o
0>
DC
ro 1-0
0>
I
O.i
X
Based on
Cooling -
to 150°F.
5000
10000
Exhaust CFM
15000
20000
FIGURE 9-27
RECOVERABLE BTU/HR. VS. CFM EXHAUST
Based on Cooling
From 300° F. to
150°F. for 6000
Hr./Yr.
10000
Exhaust CFM
FIGURE 9-28
ANNUAL SAVINGS FROM HEAT RECOVERY
Source: Lockwood Greene Engineers, Inc.
20000
9-51
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On the other hand, the inefficiencies of the heat generation system must also be considered.
With direct gas fired ovens, assuming complete combustion, every BTU of heat value in the gas
will produce one BTU of heated air in a tenter, but if the heat is produced by steam coils heated
with an oil fired boiler, the number of BTU's required in the process must be divided by the ef-
ficiencies of the boiler and the steam transmission system to obtain the true number of BTU's
of oil required.
From the estimates of net annual savings, the maintenance cost of the heat recovery equipment
must be subtracted. In cases where an oil laden exhaust is cooled below the condensation point
of the oils, gums and waxy solids, these costs can be significant. However, in cases where the
exhaust must be cooled anyway for mist condensation, the installation and operating costs of
a heat recovery system must be compared to the alternative cost of a system simply designed to
cool the exhaust and waste the heat.
9.4.2 General Considerations
The generalized equation for heat recovery in a heat exchanger is:
Q (BTU/hr) = hA (Tx - T2) (9.11)
where Tj and T2 are the temperatures of the hot and cold streams at the point of heat transfer,
A is the effective heat transfer area, and h is a heat transfer coefficient to account for the var-
ious resistances to heat flow. It can be seen that the amount of heat recovered can be increased
by increasing A or h, while (Tj — T2) is the driving force for heat flow and is a measure of the
amount of heat that has not been recovered from the hot stream. Effective heat transfer area
can be increased by increasing the size of the heat exchanger or increasing the complexity of
the heat transfer surface. The heat transfer coefficient will be increased by increasing the de-
gree of contact of the hot exhaust air with the heat exchanger surface, preventing the formation
of an insulating layer of stagnant air along the surface. Use of a heat recovery fluid such as water
instead of air results in decreased resistance to heat flow. Condensation of oils and waxes on the
heat exchanger surface reduces the heat transfer coefficient by formation of an insulating layer.
This reduction must be considered in estimation of the size of heat exchanger required.
The preferred heat exchanger type varies with the characteristics of the exhaust air stream and
the use for which the recovered energy is intended. For most exchangers recovering heat from
exhaust air, maintenance of the equipment in clean condition for efficient operation will be an
important consideration. Since cooling lowers the temperature of the exhaust air in the vicinity
of the heat exchanger surface, oils, waxes and gums can deposit on the surface, resulting in grad-
ual and often unnoticed losses in heat exchanger performance and in extreme cases in plugging.
A lint screen or filter should be placed before the heat exchanger inlet. If large amounts of lint
are expected, this should be of the self cleaning variety (see Section 9.7). Provisions for drainage
and collection of condensed oils must be provided. Internal cleaning equipment for cleaning
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with steam, hot water or detergents is necessary with exhausts that can gum or solidify. In addi-
tion, provisions should be made for easy manual cleaning from time to time for removal of ac-
cumulated solid deposits (33).
Three basic types of heat recovery systems exist: air-water exchangers, where heat is trans-
ferred between air and water; air-air exchangers, where heat is transferred directly to another air
stream; and heat exchangers, which transfer heat to an intermediate working fluid for subse-
quent utilization.
9.4.3 Air-Water Exchangers
Air-water exchangers are useful for preparing heated process water for dyeing, washing, etc. The
heated water can be stored in a reservoir, and supplemental heat can be provided there so that
the operation of processes requiring hot water is not dependent on simultaneous operation of
the process producing hot exhaust air.
Air-water heat exchangers have the advantage of small size and ease of control. A hot water
finned tube exchanger that can cool a 6,000 CFM air flow from 300 to 150° F, producing
17 gpm of water heated from 60 to 80° F measures 4*/2 by 3J/4 by 3 inches (33). Water flow
rates can be controlled relatively inexpensively, and ambient water is subject to less seasonal
temperature variation than ambient air. Initial costs for air-water heat exchangers are generally
lower than for air-air heat exchangers.
Hot water produced must be used immediately, disposed of or stored. It is generally not possi-
ble to expect that all hot water produced can be used immediately. Storage facilities, if not al-
ready present, may add more to the cost of the system than can be justified by the expected
savings. Disposal can present thermal pollution problems in some areas and can result in excessive
cost for plant input water.
Coils consisting of bare tubes or finned tubes can be used for the exchanger. Bare tubes are
easier to clean but require a larger sized exchanger because of their smaller surface area. For
most textile applications with relatively clean exhausts, finned tubes with fin spacings of 6 to 10
fins per inch can be employed. Countercurrent heat exchangers are slightly more expensive than
the concurrent type, but they are more efficient and can produce outlet water temperatures
higher than the outlet air temperature. The water system must be provided with a drain which
is either insulated or located inside the building to prevent freezing (33).
9.4.4 Air-Air Exchangers
Air-air exchangers can be used to recover heat for reuse by the process, or for plant heating in
the winter months. If more heat is recovered than can be used, the rest can simply be wasted.
If the heat exchanger is used to recover heat for return to an oven, some of the returning hot
air may have to be directed elsewhere. Most ovens require a negative pressure to prevent the
9-53
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escape of smoke and odors into the room. Preheated air may also be too hot to pass through a
burner where the fan is mounted directly (33). During the summer months, higher outside air
temperatures (up to 100° F) require that a larger volume of cooling air be used per CFM of
exhaust than is true in the winter, and some additional cooling with water may be required
to reduce the exhaust to the required temperature for oil mist elimination. The three types of
commonly used air-air heat exchangers are tube type exchangers, heat wheels, and heat pipes.
Tube type heat exchangers are the simplest in design and lowest in cost, with hot and cold air
alternating either inside or outside the tubes. With oil and dust laden emissions, where buildup
is likely to occur, contaminated air should be kept on the side that is easiest to clean. For those
with slide out racks that can be cleaned, or those with integral wash systems, this would be the
outside of the tubes, while for finned tubes, the tube insides might be easier to clean. Due to
the relatively large surface area required, size and weight considerations limit heat exchange
efficiencies to 35 to 50% (33).
Heat wheels or rotary heat exchangers are fairly light weight and have high efficiencies. As
co-current heat exchangers, close mesh heat wheels approach 80% efficiency for clean exhausts.
Experience to date with heat wheels has not been favorable in the textile industry. This type
operates by rotating a closely packed metal mesh wheel through adjacent hot and cold ducts.
The metal mesh picks up heat as it rotates through the hot duct and then gives up its heat as
it rotates back through the cold duct. Air exchange between the two ducts is claimed to be as
Since close packed metal mesh heat wheels are constructed like filters, they cannot be used on
exhaust streams where fouling is likely to be a problem. This would include any mist laden ex-
haust from which gummy or waxy contaminants would condense in large quantity. Some de-
signs provide built in cleaning facilities which will allow operation on exhausts from which
relatively freely flowing oils condense. However, even in this case, efficiency is reduced by
condensation of the oil on the mesh. Metal mesh heat wheels also permit mixing of the two
streams, which allows mist and oil buildup in the clean air intake ducts. This is a maintenance
problem at best and a potential fire hazard. It is undesirable if the air is to be used for in-plant
heating.
Figure 9-29 shows another type of heat wheel, consisting of preshaped channels separated by
rotary seals. A purge from the clean air intake sweeps the first chamber on the clean side,
sending the dirty air back into the exhaust to reduce mixing to below 1% (34). Because of the
relatively low surface area of this design, heat transfer efficiencies are lower than with the metal
mesh type.
Heat pipes (see Figure 9-30) are probably the most expensive heat transfer system, costing
about $2.00 per CFM in 1974, although installation costs are not high. Typically, heat pipes are
constructed from aluminum or copper, with plate or spiral fins on the outside in contact with
the air streams. Inside is a heat transfer fluid selected for the temperature range to be encount-
ered. (Water is used in the 150 to 400° F range.) The fluid condenses on the cold side,
9-54
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Supply
Purge
Exhaust
Purge
FIGURE 9-29
ROTARY SEAL HEAT WHEEL
Source: Lockwood Greene Engineers, Inc.
1
/
i.
-
<
\
Heat 1 in
II II
II II
f 1
y 1
Heat i out
1 1
Vapor
\
/ /.
1 1
1 1
FIGURE 9-30
HEAT PIPE
Source: Lockwood Greene Engineers, Inc.
9-55
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sticks to the hot side, and evaporates. Very high transfer rates and an extremely uniform inter-
nal temperature result; however, like other tube and finned tube heat exchangers, their heat
transfer efficiencies are limited by the film coefficient on the outside of the tube. Condensation
of oils, gums and waxes on the exhaust air side of the finned tubes causes loss of efficiency and
difficult cleaning problems. Because of this, heat pipes would not be preferred for heat transfer
involving dirty exhaust air. Maintenance costs for the heat pipes themselves are no higher than
for other types of finned tube heat exchangers.
9.4.5 Heat Exchangers Employing Transfer Fluid
Additional flexibility in heat recovery is provided by the use of heat transfer fluids. Heat is re-
covered from the exhaust gases in a finned tube exchanger similar to an air-water exchanger. It
heats a transfer fluid which circulates in a closed system, being pumped through one or more
additional heat exchangers where it gives up its heat to air or water as required. Process water
can be heated on demand, or make-up air can be heated for the oven. Plant air can be heated with
the thermo-fluid, or the heat can simply be wasted. Use of ambient water for cooling in the sum-
mer allows more effective cooling of the exhaust than would use of hotter ambient air. Heat
can be pumped for long distances through properly insulated piping with relatively little loss.
Operation below the freezing point or above the boiling point of water is also possible.
Systems using transfer fluids are inherently more costly and less efficient than single exchanger
systems, since there are at least two heat exchangers and an entire recirculating system involved.
They are most effective for recovering large quantities of high temperature heat for use at multi-
ple points.
9.5 Solvent Recovery
Following each process in which textile materials are treated with organic solvents, the solvents
are driven off, generally by hot air drying, and then are recovered by condensation followed by
adsorption on activated charcoal. Solvent recovery systems are more complex and expensive than
other pollution abatement systems, costing for installation $5.00 to $20.00 per CFM of treated
air (1974 prices), but they can usually be justified by process cost savings (11).
9.5.1 Process Description
Figure 9-31 details the complete solvent recovery system for a typical continuous dry cleaning
system using a chlorinated solvent. The system removes the solvent from the dry cleaned fabric
by countercurrent hot air evaporation. Effluent air is cooled to 100° F, during which time
most of the solvent is recovered by condensation. Since temperatures below 100° F are re-
quired for adsorption of organics onto charcoal, it is necessary to perform the final precooling
with refrigerated water during the summer months.
9-56
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9-57
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Prior to the charcoal beds, a pre-filter must be employed to remove lint and entrained oils from
the effluent air. This pre-filter can also include a small sacrificial bed of charcoal to remove
catalyst poisons.
The charcoal beds operate in parallel; one adsorbs solvent from the effluent stream while the
other is being steam stripped. For each pound of solvent adsorbed, about 10 pounds of charcoal
are required per bed, and from 3 to 6 Ibs. of steam are required for stripping. Following strip-
ping, air is blown through the bed for at least 1 minute to exhaust the steam.
The steam is condensed and sent to a water separator, from which the recovered solvent is
decanted. If the solvent is significantly soluble in water, as is the case with methylene chloride, a
stripper can be used to remove it from the wastewater, which can itself be recycled to the boil-
er. For completely miscible solvents, the stripper would be used in place of the water separator.
If the recovered solvent cannot practicably be recycled and if it does not contain chlorine,
fluorine or sulfur, the steam-hydrocarbon mixture can be sent directly to an incinerator. Calcu-
lations have shown that in this case, the necessary heat for incineration can be obtained almost
entirely from combustion of the solvent vapors. Exhaust heat from this process can be used to
generate the steam necessary for stripping (35).
With stabilized chlorinated hydrocarbons, some stabilizer loss is encountered on recovery. Ex-
cept in the case of 1, 1, 1, trichloroethane, stabilizer losses are not appreciable at recycle ratios
below 75%, but above that level, restabilization must be performed, or an especially heavily
stabilized solvent must be employed.
With 1, 1, 1, trichloroethane, the stabilizer is almost completely lost during steam stripping,
resulting in a highly corrosive liquid that must be dried, neutralized and restabilized before
reuse. Special materials are equipped for such systems. Pre-packaged systems that can handle
1, 1, 1, trichloroethane are available at a slightly higher cost than is available in standard systems.
Despite this extra cost, economics may still favor recovery of 1, 1, 1, trichloroethane.
Process requirements for a 1000 CFM system are quoted by one manufacturer as follows:
Carbon 300-500 Ib.
Steam 400 Ib./hr
Water 670 gph
Electricity 14 amps at 220 volts
The pressure drop necessary is about equivalent to that for a low energy scrubber (11).
In addition to recovering solvent from the drying air, many commercially available solvent re-
covery systems clean and recycle the dirty wash liquid. Wastes are concentrated in an evapora-
tor fed from the dry cleaner overflow and then are steam stripped. The remaining sludge contains
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dirt and spinning oils that can be recovered for use as heating oils if all chlorinated solvents
have been stripped out.
With solvent recovery systems, sludge disposal requires consideration. Commercial reprocessors,
where available, can alleviate the problem by further solvent reclaiming and diminishing sludge
volume.
9.5.2 Installation and Operation
Pre-packaged solvent recovery systems are commercially available at capacities of up to 4,000
Ibs/hr of solvent or 200,000 CFM of air for most commonly used solvents, and are often includ-
ed with the solvent processing machinery itself. Purchase of one of these is generally cheaper
than engineering and construction of a tailor-made system. However, before purchase it is wise
to consult with other users of the systems under consideration, as some commercial solvent
recovery systems do not perform according to the manufacturer's promises under mill condi-
tions. Because of the complexity of the recovery system, it is also recommended that the mill
have at least one person in house who is experienced in its operation and understands the
principles by which it operates.
Solvent detection devices should be installed permanently at the fabric inlet and outlet slots
and at the stack and at any other point where leaks are likely to occur. Automatic analyzers
vary in price from $800 to $3,000 each (1974 prices) and can be powered to drive recorders,
ring bells, etc. A portable analyzer, such as propane halo-torch, is also recommended for spot
checks of the entire system. Leaks can be caused by machinery vibrations, poorly or improperly
fitted couplings and flexible hoses, kinks in hoses, failure of door seals on machines, or mal-
functions in the recovery system.
OSHA has set the following 8-hour average exposure limits for some of the commonly used sol-
vents: (36).
Benzene 10 ppm
Carbon tetrachloride 10 ppm
Xylene 100 ppm
Trichloroethylene 300 ppm
Perchloroethylene 100 ppm
Methyl Alcohol 200 ppm
Toluene 200 ppm
1, 1, 1, trichloroethane 350 ppm
Ethyl Acetate 400 ppm
Acetone 1000 ppm
Maximum exposures of 300 ppm for 5 minutes of each 3-hour period are allowed for perchloro-
ethylene (37).
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Ethylene, xylene, trichloroethylene and toluene are considered photochemically active. Perch-
loroethylene or 1, 1, 1, trichloroethane are recommended as substitutes for trichloroethylene.
(36).
Contact of chlorinated hydrocarbon vapors with open flames should be avoided, as hydrogen
chloride and small amounts of phosgene are generated. If solvent contaminated air is drawn into
gas fired tenters, etc., the hydrogen chloride thus generated could cause browning of cotton and
dye degradation resulting in off-shade goods. The initial concentration of perchloroethylene for
this is estimated to be 200 to 500 ppm (37).
When chlorinated solvents such as perchloroethylene, trichloroethylene, methylene chloride,
and especially 1, 1, 1, trichloroethane are steam stripped, hydrochloric acid is present in the
bed. Since the activated carbon has catalytic properties, corrosion problems can be severe, and
304 or 316 stainless steel is not acceptable for carbon beds to recover chlorinated solvents.
Most carbon adsorption systems are therefore lined with baked phenolic. A carbon bed for
methylene chloride recovery with a baked phenolic coating can last 20 years under these condi-
tions, while a bed of 304 stainless steel would last only 3 months.
Solvent losses are claimed by manufacturers to be 1 to 3%, but 5 to 8% may be a more realistic
figure. Larger losses, of up to 20%, may be expected during startup (37). Some commonly ex-
perienced problems with solvent recovery systems are listed below:
• Overloading of the charcoal beds because of insufficient cooling of the inlet air. In-
let temperatures of 100° F or lower are necessary, since the amount of solvent
in solvent saturated air increases with temperature and the capacity of the charcoal to
adsorb it decreases. The refrigeration system must be designed for conditions during
the warmest summer months.
• Inadequate stripping of the waste oil-sludge mixture due to poor contact between the
stripping steam and the sludge and failure to optimize the stripping cycle. Since the
stripping rate is controlled by the rate of diffusion of the solvent from the sludge to
the steam bubbles, the steam must be evenly and finely dispersed.
• Pressure-flow instabilities due to inadequate provisions for venting, siphoning, un-
stable control loops, etc. If these are not corrected, they can cause inefficiency and
operational failure.
• Emulsions in the water separators due to introduction of surfactants, dirty water and
solvent, etc.
• Squeeze roll deterioration (37).
The use of activated carbon and other adsorbents for selective adsorption of vapors from an ex-
haust is discussed in greater detail in Section 9.2.2.4, and in the EPA Air Pollution Manual (8),
pp. 189-199.
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9.6 Odor Abatement
9.6.1 Introduction
Odor pollution may be defined simply as "the development of any substance that affects our
olfactory organs in a disagreeable manner" (38). As such, it is a highly subjective problem, since
an odor that is disagreeable to one person may not be so to another. Further, the concentration
at which a substance must be present in the atmosphere to create disagreeable odors varies
widely from compound to compound. The odor recognition threshold for some tests is defined
as that concentration at which 100% (or as low as 50% in other tests) of those present in an
odor panel can smell and identify a particular odor (39). Listed below are the odor recognition
thresholds of a few common odor causing substances (38).
Methyl methacrylate 0.2 ppm
Monochlorobenzene 0.21 ppm
Aniline 1.0 ppm
Formaldehyde 1.0 ppm
Hydrogen sulfide 0.00047 ppm
Odors may consist of vapors, of liquid mists, or of particulates with adsorbed odorous sub-
stances. If the odorous substance is not present in significant quantities in the vapor phase,
odor abatement can be carried out by the techniques for mist and particulate removal detailed
in Section 9.3. In some cases, techniques for visible emission reduction and odor abatement
must be combined. The presence of visible mists or particulate emissions, either carrying an
odor or accompanying it, can increase the nuisance factor of the odor by drawing public atten-
tion to it.
Common textile processes and substances that cause odor problems include aqueous polyester
dyeing, where most of the carriers have extremely annoying odors at low concentrations. These
cause problems not only at dyeing, but at subsequent drying steps. Commonly used odorous
carriers are ortho phenyl phenol, methyl salicylate, trichlorobenzene, ortho dichlorobenzene,
biphenyl, butyl benzoate and the menthyl naphthalene sulfonates (39). Of these, the most im-
portant and possibly the most disagreeable is biphenyl. Finishing operations to impart flame
proofing, rot proofing, water repellency, crease resistance, etc. often employ odorous (and pro-
prietary) compounds (26). Gradual release of formaldehyde from the finish resins can cause
odor problems.
Other sources of odor are solvents used in solvent processing, which is discussed in detail in
Section 9.5, defoamers used in some dyeing and printing processes, sulfur dyeing of cotton and
cotton blends, reducing or stripping dyes using hydrosulfites, bonding, laminating and back-
coating operations, and bleaching with chlorine dioxide.
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Most enforcement agencies today handle odor problems on a complaint basis. It is therefore
best to apply odor abatement techniques before the public is aroused. Once the odor source
has been identified, dilution, reodorization, or partial abatement may not be acceptable to
neighbors who have become accustomed to being offended by it.
Abatement techniques vary with the nature of the odor causing substances and other accom-
panying pollutants. For selection of the best technique for each particular process, it is neces-
sary to know the CFM, temperature and approximate contaminant concentration and composi-
tion of the air to be processed. Mist and particulate concentrations in the effluent air should be
known, as well as water vapor concentration, since some odor abatement techniques will not
function under certain conditions or when subjected to some pollutants (11). The options
include:
• Process or chemical substitution and housekeeping improvement
• Dilution
• Masking or modification
• Scrubbing
• Dry adsorption
• Incineration
Odor-laden air is drawn off the process and is ducted to the odor abatement system. Since odor
abatement costs are directly proportional to the volume of air to be processed, hooding and
venting should be designed to remove odors with a minimum of dilution air (11).
9.6.2 Process Modification or Chemical Substitution
Odor problems can often be eliminated or reduced if the processes involved are modified so that
the odor causing chemicals are eliminated or emitted in smaller amounts, or so that other vapors
are emitted which are either less odorous or easier to remove from the atmosphere.
In the case of polyester dyeing, pressure dyeing will produce fewer odor problems than atmos-
pheric dyeing, since the required carrier concentration is lower. Substitution of solvent dyeing
for aqueous dyeing can eliminate carrier odors, since no carrier is necessary with solvent sys-
tems. With existing processes, where major changes in equipment would not be feasible, it is
often possible to substitute less odorous carriers, or carriers that are easier to mask or to treat
with inexpensive techniques. Optimization of carrier concentration and of the time-temperature
cycle for dyeing can sometimes result in decreased carrier consumption.
In cases where the odorous compound is generated in the process or is present in excess concen-
tration, it can sometimes be removed by addition of chemicals that will react with it. One ex-
ample is the use of formaldehyde acceptors to react with the excess of free formaldehyde pres-
ent in resin finishing. This example also illustrates the limitations of such a solution because in
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some cases the formaldehyde acceptors will also react with formaldehyde in the resin itself, cLs-
troying fabric properties such as wash-wear and smoothness. If this reaction continues during
storage of the fabric, amine odors are produced. Formaldehyde acceptors have been used success-
fully for many years, but they require extreme care in application (39).
Good housekeeping and proper maintenance of existing antipollution equipment can alleviate
some odor problems. Proper adjustment of air flow rates to the odor abatement system can
sometimes result in reduced volumes of air to be processed and, therefore, in greater efficiency
of odor removal at lower operating cost.
With solvent recovery systems using activated charcoal, there are generally no odor problems if
they are properly sized, operated and maintained. See Section 9.5 for details.
In some cases, an odorous compound is applied to the fabric that comes off gradually in later
processes. Immediate and thorough drying can result in this compound's removal at a single
location, simplifying odor collection problems. There exist non-odorous deformers that per-
form as well as the odorous ones. Other oxidizing agents can sometimes be substituted for
chlorine dioxide in the bleaching process.
9.6.3 Dilution
Dilution of the effluent air can alleviate odor problems in cases where the odorant concentra-
tion is already relatively close to the odor recognition threshold and where emissions do not
exceed overall limits for hydrocarbon emissions in general or for emission of the specific com-
pounds in the exhaust. Since the purpose of dilution is to reduce the concentrations of odor caus-
ing emissions to acceptable levels at all points outside the plant boundary at ground level, it is
most effective if the stack is located at the furthest possible distance from potential sources of
complaint. In most cases, this will be the center of the plant property.
Under normal atmospheric conditions, pollutants spread from a point source, such as the outlet
of a stack, in a roughly parabolic pattern for the first two miles (40) (see Figure 9-32). This
means that the radius of the plume increases as the square root of the distance from the stack,
and the pollutant concentration, which varies inversely as the cross-sectional area of the plume
(or as the square of the cross-sectional radius), decreases linearly with distance.
C = K!/X (9.12)
In the event of an inversion, where a warm air layer overlies a layer of colder ground air prevent-
ing upward dispersion of the plume, pollution is trapped below the inversion level, and pollutant
concentration at the ground decreases only as the square root of distance.
(9.13)
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Property line
FIGURE 9-32
SPREAD OF CONTAMINANTS FROM A STACK
Source: Lockwood Greene Engineers, Inc.
The effective height of a stack is defined as the true height, plus a correction factor for exhaust
exit velocity and the buoyancy due to its higher than ambient temperature. Increasing the ef-
fective stack height increases the dispersion distance of the pollutants before they reach the
ground. Correlations for maximum pollutant concentration at the ground as a function of stack
height differ for various weather conditions, but in general, maximum pollutant concentra-
tion at ground level decreases more slowly than would be expected if it were inversely propor-
tional to stack height (40). Increasing the effective stack height also increases the probability
that the emission will break through any inversion layer and be carried away by the warmer
upper air.
Addition of diluent air to the exhaust air will have a slight effect, as it will reduce the pollutant
concentration at the stack outlet and will increase the effective stack height slightly by increasing
the stack velocity. However, the total amount of odorant release will not be decreased, and the
additional volume of dilution air will be small in proportion to the volume of outside air with
which the odorant will mix naturally downwind of the stack. It is generally not economical to
try to increase the effective stack height by increasing either the exhaust velocity or tempera-
ture. However, combining two exhausts into one higher stack will increase both the true stack
height and the velocity correction, and is worth considering (40).
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9.6.4 Masking and Modification
Odor masking and modification are accomplished by adding small amounts of a reodorant,
either to the process bath itself or to the exhaust air. The purpose is to render the final exhaust
odor more acceptable, either by overpowering the initial odor with the reodorant, or by "marry-
ing" the two odors to form a third odor of lower odor profile for greater acceptability. If the
odor modifier is added to the process itself, care must be taken that it does not alter the process
chemistry unfavorably. Since the original substance is not destroyed or modified, this technique
cannot be used for toxic or physiologically irritating fumes or odors whose presence is neces-
sary to detect leaks and malfunctions, such as hydrogen sulfide in natural gas. Furthermore, the
reodorant may have different properties from those of the original odorant and can sometimes
become separated from it during atmospheric dispersion (11).
Where applicable, odor neutralization has the advantage that initial equipment costs are low,
negligible space is required, and the odorous air need not be contained or collected. Operating
costs are also low. Generally 0.25 to 1% reodorant is employed, based on the weight of the
initial odorant (11), (39).
Odor masking is accomplished with a chemical that has a distinctive or overriding odor such that
it hides the original malodor. In some cases, this can be done successfully, but in many cases a
sweet or perfumed odor results that can become as objectionable as the original malodor. This
has become known as the "Persian Bordello" effect (38).
Odor modification, on the other hand, seeks to blend the original odor with a second specific
odor to produce an odor that is either reduced or at least more acceptable. Commonly used
reodorants include mixtures of aldehydes, ketones, essential oils, etc., such as citronellin, vani-
lin, oil of sandlewood, oil of cedarwood, or piperonal (38). For each specific odor, a uniquely
tailored combination of reodorants is employed.
Reodorants have been successfully used to alleviate odors from polyester dye carriers, such as
biphenyl. Typically 0.75 Ib of reodorant is used per 100 Ibs of carrier, half being added to the
dyebath at the start of the dye cycle, and the rest 1 hour later. The reodorant reduces carrier
odor by simultaneous evaporation, both during dyeing and subsequently during drying. To
eliminated odors during heat setting, 0.25 Ib of reodorant per 100 Ibs of carrier can be added
during the final rinse (38), (39).
Reodorants are also available for the synthetic latexes and emulsions used in the carpet industry,
for elimination of sulfide odors from sulfur dyeing, for bonding and laminating, for fluoro-
carbon oil and water repellent finishing, for fire retardant finishing, and for control of formal-
dehyde odors from resin finishes, both during resin application and during subsequent storage
of the finished fabric (39).
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9.6.5 Scrubbing
Virtually all odors can be eliminated from exhaust air by scrubbing, either with water or with a
chemical solution to dissolve and then destroy the odorant. In cases where the effluent contains
both oil mists and odors in the gaseous phase, pre-cooling prior to mist elimination (see Section
9.3.5) can be accomplished in a packed tower, by a cooling coil or in a low energy wetted filter
scrubber, which doubles as a means of odor elimination. Addition of a water spray to a mist
eliminator can cause it to function as a packed tower for gas adsorption, thereby removing
odors and oil mists at once (30). Several firms sell prepackaged units consisting of a pre-filter, a
scrubber, and an electrostatic precipitator. The principal disadvantage of scrubbers for odor
removal is that they present a potential liquid disposal problem, especially if organic solvents
or aqueous chemical solutions are used for the scrubbing.
In odor abatement applications, scrubbers function by adsorption of the contaminant by the
scrubbing liquid, followed in some cases by chemical reaction of the contaminant, either with
dissolved solutes or with the scrubbing liquid itself. Therefore diffusion, especially through the
gas phase, and absorption tend to be rate limiting, and maximization of gas-liquid contact is
essential. Spray towers, which are used primarily to cool gases, and impingement type scrubbers,
which are useful for removal of large particles by impaction on wetted surfaces, give little gas-
liquid contact. Venturi scrubbers and other types of high energy scrubbers are used primarily
for removal of mists and fine particulates (see Section 9.3.7). Packed towers are preferred for
odor absorption because of their large wetted surface areas.
Packed towers are available with various shaped packings to obtain intimate air-liquid contact.
They can be plugged with high particulate loadings and may require a pre-filter for removal of
lint. In some applications, a Venturi scrubber is used for elimination of particulates prior to a
packed tower scrubber. If chemical scrubbing is used, removal of the particulates prior to scrub-
bing minimizes the chemical costs by removing a substantial fraction of the reactive material
beforehand. The marble bed scrubber scrubs vapors with a bed of rotating, self cleaning marbles,
combining to some extent the absorption properties of the packed bed and the particulate re-
moving properties of the Venturi (11). Operating costs of packed towers and other low energy
scrubbers are low because of the low pressure drop required. If chemicals or organic solvents
are used for the scrubbing, these costs are additional.
Installed costs of the various types of scrubbers in 1974 were: (11)
Packed towers: $0.25 - $1.00/CFM
Spray chambers: $0.25 - $0.50/CFM
Other low energy scrubbers: $0.50 - $3.25/CFM
Venturi scrubbers: $0.50 — $4.00/CFM (and operating costs approach
those of fume incineration)
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Chemicals are often added, either in solutions or as slurries, to destroy the absorbed pollutant
after absorption. This eliminates the necessity of subsequent disposal of the pollutant itself
(though the reacted solution must be disposed of or recycled) and increases scrubbing efficiency,
since liquid phase resistance to absorption is eliminated and the solution never approaches sat-
uration with respect to the pollutant. Lime slurries neutralize acidic effluents such as HC1 or
S02, and dilute sulfuric acid is used to react with nitrogen bases (26). Oxidizing agents used
include sodium hypochlorite, chlorine, chlorine dioxide, ozone, potassium permanganate, and
dichromates. Chlorine, chlorine dioxide, and ozone are pollutants in themselves, but they have
been used successfully in some instances. Hypochlorite and dichromate solutions are not strong
enough oxidizing agents for some odors (11).
Potassium permanganate has been used to abate odors from a wide variety of organic com-
pounds. It is a readily soluble purple crystalline solid costing about 50 cents per pound (1975
prices). As it is reduced in solution, it loses its purple color, becoming pink and then brown and
finally precipitating as an insoluble black-brown sludge of manganese dioxide, which must be
cleaned periodically from the system. Potassium permanganate solutions are non-corrosive to
most metals and plastics in their optimum operating pH range of 8.9 to 9.5. Buffers such as sodi-
um bicarbonate or borax can be used to maintain this pH, especially in cases where adsorption of
atmospheric carbon dioxide causes a drop in pH. Optimum permanganate concentration for
scrubbing is usually 1 to 2% wt. Typical operating costs for a potassium permanganate wet
scrubbing system range from $5.00 to $100.00 per day for 20,000 CFM (1974 prices) (11).
In cases where odorants have very little solubility in water, scrubbing can be performed at
greater expense with an organic liquid. Stripping oils with vapor pressures of below 0.1 mm of
mercury are recommended. These can be steam stripped and recycled, and the odorant can be
either recovered from the exhaust steam after condensation or fed directly to a fume
incinerator (41).
9.6.6 Dry Adsorption
Adsorption of pollutants from an effluent stream can be used either to concentrate the pollu-
tants for subsequent recovery or disposal, or for direct chemical catalytic destruction of the
pollutants. Of the various available adsorbents, activated carbon is the most widely used, as it is
non-selective but adsorbs organics in preference to water. Other common adsorbents such as
silica gels, synthetic zeolites, and metallic oxides are more selective in the type of odorants they
will absorb, and will generally adsorb water in preference to organics (11), (26).
Activated carbon systems are discussed in detail in Section 9.2.2.4. They are expensive for high
flow rates and in cases where recovery of the adsorbent is not practical.
Initial installed costs run from $5.00 to $20.00 per CFM, but due to the low pressure drop,
operating costs are not high, unless the carbon must be sent back for regeneration (11). Pollu-
tants are collected, but must be subsequently steam stripped and disposed of. When used
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solely for the removal of low concentrations of odorants generated intermittently, such as car-
rier odors from polyester dyeing, an activated carbon system consisting of a single bed would
be feasible. Steam stripping of the pollutant would be performed during times when the odor-
ant was not being released by the process.
9.6.7 Incineration and Chemical Destruction
Direct fume incineration is the most proven and accepted method of odor control and can be
used in all situations except for those where the exhaust contains high concentrations of com-
pounds containing chlorine, fluorine or sulfur, which would be converted to the extremely
odorous and corrosive compounds HC1, HF, and 862, respectively. In this case, scrubbing
would have to follow incineration. Incineration has not always been economical for flow
rates above 5000 CFM, since operating costs are high: $1.00 to $2.00 in 1974 per hour per 1000
CFM for direct fume incineration without heat recovery (11). Incineration is often used for
destruction of an effluent that has been concentrated by some preprocess, such as charcoal
adsorption.
Catalytic incineration requires less energy than direct fume incineration, because it takes place
at a lower temperature, but equipment costs are higher, and the catalyst requires periodic re-
placement or reactivation. The nature of the odor causing impurities must also be known
before specification of a catalytic system, as some catalysts are deactivated by some impurities.
Chemical destruction of odorants can be used if the odorants are present in very low concen-
tration. The odorant is first adsorbed onto granules of the reactive chemical or onto an inert
support that has been impregnated with the reactive chemical, and then it is destroyed, being
used up in direct proportion of the odorant destruction.
Incineration and chemical destruction are discussed in detail in Section 9.2.1.
9.7 Lint and Dust Removal
Lint and dust are processed in greatest quantity by spinning and the processes preceding it, and
by shearing, napping, and singeing. With the exception of singeing, these processes produce very
little atmospheric pollution and other than dust and fly, and they do not drastically change the
temperature and humidity of the air exhausted from them. Since each of these processes has an
optimum temperature and humidity, it is generally more economical to remove the particulates
from the exhaust air and to recycle it to the same area than to send the exhaust to the outside
and to bring in fresh air which must be brought to the optimum conditions (42).
Of all iypes of particuktes, the most undesirable is cotton dust, because of its potential for
causing byssinosis. OSHA regulations presently limit the quantity of cotton dust to 1.0 mg/m^
A Q
per cubic meteri(4.37 x 10 grain/AFC). Dust levels above 3 mg/m are considered a serious vio-
lation. Permanent standards have not yet been set, and they may be reduced to 0.5 mg/m^ or
even lower. It is, therefore, wise to purchase dust removal systems that can be increased in effi-
ciency as regulations become more stringent.
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The cotton industry is currently attempting to develop strains of cotton with a lower trash
content, and it is investigating methods of trash removal during ginning and ways of rendering
the remaining trash less objectionable (43). However, it is unlikely that these efforts will entire-
ly solve the problem. It also has not been shown conclusively that hand picked cotton has less
dust than machine picked cotton (44).
Pre-cleaning of the incoming cotton has been shown to remove the dust. Burlington has develop-
ed a continuous steam cleaning apparatus for removal and deactivation of the dust prior to card-
ing. Cotton is steamed for 5 minutes with low pressure steam, a time sufficient to remove the
dust, but not so long that it has an adverse effect on further processing. Dust remaining in the
cotton is rendered less harmful, probably because steaming has destroyed the bacteria and
enzymes suspected of causing byssinosis (43).
Dust and fly are most efficiently removed at the process where they are produced, or in the case
of cotton processing at the first process step. Otherwise the dust will continue to drop out at
each succeeding process through spinning, until it is finally stuck into the yarn by the applica-
tion of spinning oils.
Plenums are used on cards, stretch breakers, Pacific converters, etc., to remove dust and fly as
they are created. Succeeding processes generally also require vacuum cleaning, especially at
points where the sliver or roving goes through orifices or around turns. Exhaust air is then fed
to the dust removal system. This generally consists of two or three stages, each removing succes-
sively finer particles.
With all lint and dust removal systems other than scrubbers, fire prevention is of critical import-
ance. Filters with a UL class 1 rating do not contain combustible material, while filters with a
UL class 2 rating contain combustible material in small amounts, but generally do not support
combustion. Both types, however, can collect enough flammable dust to become highly flam-
mable themselves. Lint and dust removal systems should be equipped with fire detection devices,
spark arrestors, and emergency shutdown and fire extinguishing equipment.
Low energy scrubbers can be used effectively for removal of lint and coarser dust (45). Most
commonly used are cyclone scrubbers and spray towers. Where the exhaust air contains entrain-
ed droplets of water or oil, scrubbers are preferred to self-cleaning filters, which would become
plugged. Low energy scrubbers cannot remove fine dust of 5 microns and below, but if space
has been allowed for this, a Venturi throat can be added at the inlet to remove finer particles
(32). They produce humid air and must be operated with care if succeeding removal steps can-
not tolerate water droplets. The use of scrubbers as devices for particulate removal is discussed
in detail in Section 9.2.3.
Filters may also be used to remove lint and coarser dust. A large number of types are available,
and the correct choice depends on the nature and quantity of particulate matter to be remov-
ed. Replaceable filters or filters with elements that must either be replaced or manually washed
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have a low installation cost, but a high operating cost in situations where large quantities of par-
ticulates must be removed. They are used chiefly for removal of small amounts of lint from an
air stream, often as pre-filters prior to oil mist abatement systems, heat exchangers, or solvent
recovery systems (see Sections 9.3 through 9.6). Their advantages are low initial cost, durability,
and simplicity. Fiberglass or fiber elements are used for low temperature applications, while for
temperatures above 250° F, as with tenter frame exhausts, steel mesh filters are preferred.
When loaded, these filters are manually cleaned, and an adhesive is reapplied to improve collec-
tion efficiency.
With filters of this type, operating pressure and efficiency change during the filter life. Initially
when the filter is clean, both the pressure drop across it and the operating efficiency are low. As
it collects fibers and dust, the air passages become partially plugged, so that both pressure and
efficiency increase toward final replacement values. When designing a system, it is safest to use
the initial efficiency of a filter, but the final pressure drop. If constant airflow is required, a
variable pressure across the filter can be compensated by a variable damper after the filter.
Automatic self-cleaning filters are generally used for fly removal in high fly areas, such as with
exhausts from cards, breakers, etc. These are discussed in Section 9.2.2.2d.
Collected lint can be compacted for disposal or salvage as a byproduct, or it can be disposed of
by incineration. In one plant (46), shearing waste is being collected using a rotary pre-filter.
Slowdown from this pre-filter sends the waste to a gas fired incinerator, with only 10% of the
initial exhaust air volume required for blowdown. The system was reported to have functioned
with one 30 minute shutdown in one year, producing no solid waste. Installation costs were
below $2.20 per initial CFM, and 1972 operating costs were below $0.70 per hour per 10,000
CFM. No solid waste was produced. Incineration is also effective in destruction of lint mixed
with other liquid or gaseous pollutants. Since cost is directly proportional to the CFM of treated
air, it can be prohibitively expensive if the exhaust air is not first reduced in volume by pre-
filtration. Incineration is discussed in greater detail in Section 9.2.1.
Fine dust that passes through a coarse filtration system can be removed by electrostatic precipi-
tators, high efficiency air filters, Venturi scrubbers, or direct fume incinerators. These are all
discussed in detail in Section 9.2. In the case of dust removal, the quantity of pollutant per
CFM is generally lower than when they are used to remove oil mists. With Venturi scrubbers,
potential water pollution problems are less serious than in oil mist removal. High efficiency air
filters used for this purpose must be impregnated with adhesive to catch the dust. Electrostatic
precipitators are the preferred method for fine dust removal because of their low operating
costs and ease of maintenance. However, as explained in Section 9.2.2.3, they must be protect-
ed from entrained water droplets if a low energy scrubber is used as a pre-filter. For greater
efficiency, a second stage can be added in series with the first.
9-70
-------
TABLE 9-2
SYMBOL TABLE FOR CHAPTER 9
Symbol
Meaning
A Heat transfer area - ft.2
a Gas-liquid interfacial area - ft.2
(j (Dp) Proportion of partiples with diameter Dp - dimensionlesb
Bs Width of gravity settling chamber - ft.
Cp Specific heat of exhaust stream after combustion - BTU/lb °F
Db Bubble diameter - ft.
Dd Droplet diameter - ft.
Dp Pollutant particle diameter - ft.
g Gravity conversion factor - 32.17 Ib. mass - ft/lb force sec2
h Heat transfer coefficient - BTU/hr ft2 °F
AH Pollutant heat of combustion - BTU/lb
Km Stokes - Cunningham correction factor - dimensionless
Ls Gravity settling chamber length in gas flow direction - ft
Ns Number of compartments - gravity settling chamber
(L/G) Liquid to gas ratio - gallons/1000 ACF
NSF Separation number - dimensionless
AP, Pressure drop - Ib/ft2
Q Heat transfer - BTU/hr
q Gas volumetric flow rate - ft3/sec
AT Temperature rise across a catalytic converter - °F
TH Heater outlet temperature - °F
t|-| Gas holdup time - sec
T| Heater inlet temperature - °F
Vg Linear gas velocity ft/sec
v\ Liquid volume - ft3
X Pollutant weight fraction in inlet gas - Ib/lb
Vo Pollutant - droplet relative velocity ft/sec
XT Droplet target width - ft
Y Collection efficiency factor - dimensionless
e Fractional gas holdup in liquid - ft3/ft3
Mg Gas viscosity - Ib ft/sec
rj Weight fraction of pollutant particles collected Ib/lb
T? (Dp) Collection efficiency for particles of diameter Dp
Pg Gas density - Ib/ft3
Pi Liquid density Ib/ft3
Pp Pollutant particle density Ib/ft3
a Surface tension - Ib/ft
ACF Actual Cubic Feet
CFM Cubic Feet per Minute
CFS Cubic Feet per Second
SCF Standard Cubic Feet (at 32°F, 1 atm)
SCFM Standard Cubic Feet per Minute
HP Horsepower
Ugt Superficial gas velocity - ft/sec
Ur Terminal bubble rise velocity ft/sec (.87 ft/sec for all practical purposes)
9-71
-------
9.8 References
1. Walters, Donald F.: "The Textile Industry and the Environment 1973". American Assoc.
Text. Chemists and Colorists, May 22-24, 1973, Washington, B.C., pp. 28-36.
2. Beltran, Michael R.: Amer. Dyestuff Kept. 62, 26-31, 62 (8/73).
3. Anon: Textile World 123, 107-111 (8/73).
4. Text.-Prax. 9, 508-9 (1973).
5. Noel, Thomas M.: "The Textile Industry and the Environment — 1973" Amer. Assoc. Text.
Chemists and Colorists, May 22-24, 1973, Washington, B.C., pp. 37-39.
6. Anon: Textile Industries 8/73, 89-90.
7. Miller, Peter and Wilki, John L.: Modern Textiles 55 (2), 21-2 (2/74).
8. Banielson, John A., ed: Air Pollution Engineering Manual, Environmental Protection
Agency, Research Triangle Park, N.C., May 1973, U.S. Govt. P. 0. #055-003-00059-9,
Cat. EP 4.9:40.
9. Perry, Robert H. and Chilton, Cecil H., ed: Chemical Engineer's Handbook, 5th ed.;
McGraw Hill, New Uork, 1973.
10. Pfoutz, B.B. and Stewart, L.L.: "Electrostatic Precipitators — Materials of Construction"
Chem. Eng. Prog. 71 (3) 53-57 (1975).
11. Beltran, Michael R.: Chem. Eng. Prog. 70 (5), 57-64 (5/74).
12. "Pollution Control Technology": Staff of the Research and Education Foundation, 324
Madison Ave., New York, N.Y. 10017, 1973.
13. Betz, E.G.: "Energy Economics-Environment: A Convergency of Interests", Catalytic
Products International, Inc., 3750 Industrial Ave., Rooling Meadows, 111. 60008; Bulletin
G-ll/74, Becember, 1974.
14. National Fire Protection Association, Section 86-A, Articles 310-34, 410-1, and 410-2;
470 Atlantic Ave., Boston, Mass. 02210 (1975).
15. Coyne, A.E.: International Byer and Textile Printer 3/16/73, 316-22 (Robertson, James E.)
16. Kline, Richard, Personal Communications, 2/12/75.
9-72
-------
17. Pond, Robert W.: Paper Delivered at the llth Annual Clemson Seminar on Air and Water
Pollution, Clemson Univ., October 23, 1975.
18. Cyclotech of Burbank, Calif., Described in Chemical Engineering, 10/27/75, p. 79.
19. Johns-Manville, Denver, Colo.: HEAP Unit Brochure.
20. Brink, Can J.: Chem. Eng., 41, 134 (1975).
21. Stevens, Charles H.: Modern Textiles 54, 24-5, 35 (2/73).
22 Brink Fact Guide: Monsanto Enviro-Chem Systems, Inc., 800 N. Lindberg Blvd., St. Louis,
Mo. 63166.
23. "The Textile Industry and Pollution Control". Sub-Council Report to the National Indus-
trial Pollution Control Council (2/73).
24. Anon: Textile World 124, 207 (9/74).
25. Schneider, Gilbert G; Horzella, Theodore I.; Cooper, Jack and Stiegl, Philip J.: Chemical
Engineering, May 26, 1975, pp. 94-108, and August 18, 1975, pp. 97-100.
26. Turk, Amos; Haring, Robert C.; Okey, Robert W.: Environmental Sci. and Tech 6 (7),
602-7 (7/72).
27. Chemical Engineering 9/20/71, pp. 96-98.
28. Immartino, Nicholas R.. ed: Chemical Engineering, 6/23/75, pp. 86-90.
29. Chemical Engineering, 4/28/75, p. 66.
30. Chemical Engineering, 7/21/75, p. 74.
31. Chemical Engineering, 12/8/75, p. 101.
32. Robertson, James E.: Textile Industries 4/71, 105-111.
33. Beltran, Michael R.: American Dyestuff Reports 4/74.
34. Heat Recovery Corp., Kearny, N.J.: Rotary-X-Changer literature.
35. Cannon, Thomas: "Energy Recovery from Solvent Vapors" Pollution Engineering, 11/74.
9-73
-------
36. Farber, Hugh A.: Knitting Industry 9/73, 48-60.
37. Allen, Raymond: "In Plant Control of Pollution: Upgrading Textile Operations to Reduce
Pollution": EPA Technology Transfer 10/74, pp. 95-6.
38. Singer, Robert E.: American Dyestuff Reporter 6/72, 55-6.
39. Singer, Robert E.: American Dyestuff Reporter 2/74, 57-8, 67.
40. Bibbero, Robert J. and Young, Irving G.: "Systems Approach to Air Pollution Control"
John Wiley & Sons, New York, 1974, pp. 290-295, 316-327.
41. Ostojie, Ned: Pollution Control Systems, Coon Rapids, Minn.: Personal Communication to
R.W. Kline (2/6/75).
42. Ratteree, C.H.: Lockwood Greene Engineers, Inc., Spartanburg, S.C.: Personal Communi-
cation to R.W. Kline (1/17/75).
43. Davis, Ronald C.: Textile World 122, 38-66 (10/72).
44. Lyons, Donald W. and Hatcher, John D.: Textile World 124, 56-62 (3/74).
45. Page, Gordon C. and Bethea, Robert M.: J. Air Poll. Cont. Assoc. 22 (5), 372-3 (5/72).
46. Anon; Modern Textiles 54, 72-3 (1973).
Beltran, Michael R.: Fibre and Fabric, pp. 8-10.
North Carolina Dept. of Natural and Economic Resources; Board of Water and Air
Resources, Raleigh, N.C. "Rules and Regulations Governing the Control of Air Pollu-
tion" January, 1972.
Rumy, S.: "Textile Process Application Bulletin", Monsanto Enviro-Chem Systems, Inc.,
St. Louis, Mo. (1974).
9-74
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CHAPTER 10
PERSONNEL REQUIREMENTS
10.1 Introduction
This chapter contains information relating to the staffing requirements associated with textile
wastewater treatment facilities. Manhour estimates have been prepared for each EPA subcate-
gory according to plant wastewater flows assumed for small, medium, and large textile produc-
tion facilities. Plant production and water use are taken from the National Commission on
Water Quality Report (1). Personnel requirements are based upon "average" plant conditions
assuming the following:
• Standard plant layout
• Commonly used equipment in relatively new and well cared for condition
• Moderate climate
• Certified plant operator with average productivity
• Plant wastewater flow not in excess of design flow
10.2 Adjustment Factors
A number of local conditions tend to affect average situations presented in the tabulations in
this chapter. Values given to these adjustment factors are presented in the EPA publication en-
titled: Estimating Staffing for Municipal Wastewater Facilities (2). Local conditions are de-
scribed as follows:
10.2.1 Plant Layout
Unusual layout conditions will affect operating and maintenance staffing because of the time
required to walk from one piece of equipment to another.
10.2.2 Unit Processes
A plant with multiple process equipment units of the same type which come from different
manufacturers is less efficient to maintain than a plant where all or most of the equipment of
the same type is from the same manufacturer. A plant with non-standard process equipment will
also be less efficient to maintain and operate than a plant with standard equipment.
10.2.3 Level of Treatment
Where a level of treatment is more stringent than BPT and requires more than the treatment
models shown in Chapter 7, adjustment of manhours is necessary.
10-1
-------
10.2.4 Productivity of Labor
The productivity for labor assumes 6.5 hours of productive work per man per day which
amounts to 1,500 hours per year as the normal level of labor productivity.
10.2.5 Climate
Where winters are severe, maintenance manhours should increase.
10.2.6 Training
The manhours required are based on plant personnel which have the uniformly high level of
training indicated by certification, but do not have the benefit of a continuing education pro-
gram. The importance of competent plant operators cannot be overemphasized.
10.2.7 Off Plant Laboratory Work
Where laboratory work is done by outside contractors, laboratory staffing needs would be re-
duced. In the small plant, laboratory work may be done by the lab technician or chemist serving
in textile operation plant.
10.2.9 Off Plant Maintenance
Ground and building maintenance for small plants may be done by the manufacturing plant
personnel. Instrument and control system maintenance which requires special skill may be
contracted by outside contractors. Some maintenance that cannot be scheduled, such as electric
rewinding or mechanism repair, may be done by outside personnel on a job-by-job basis.
10.2.10 Age and Conditions of Equipment
Maintenance workload should be increased if plant equipment is old or improperly cared for.
10.2.11 Safety
From a safety standpoint it may be advisable to have a minimum of 2 men working at the plant
facility during any shift.
10.3 Estimating Annual Manhours
Manhour estimates have been made for operation, maintenance and laboratory functions re-
quired for an effective treatment program. Tables 10-1 through 10-7 illustrate annual manhours
required for each function associated with meeting BPT.
10-2
-------
It should be noted that supervisory manhours are included in annual operation and that yard-
work is included in maintenance manhours. Clerical manhours are not included as it is assumed
manufacturing plant personnel will perform this function. The 1500 manhours per year per man
assumes 5-day work week and an average of 29 days for holidays and vacation. The tables also
present the total number of men required. It is, of course, possible for one man to perform
more than one function.
TABLE 10-1
CATEGORY 1
WOOL SCOURING
MILL SIZE
(Ib./day)
30,000
80,000
150,000
FLOW
MGD
0.13
0.344
0.645
MANHOURS FOR BPT
Operation
1,400
1,776
2,560
Maintenance
1,300
1,672
2,079
Lab
300
350
550
TOTAL MAN REQUIREMENTS
BPT
2.0
2.5
3.5
TABLE 10-2
CATEGORY 2
WOOL FINISHING
MILL SIZE
(Ib./day)
5,000
20,000
135,000
FLOW
MGD
0.2
0.8
5.4
MANHOURS FOR BPT
Operation
900
2,150
6,450
Maintenance
950
1,815
3,840
Lab
240
500
1,600
TOTAL MAN REQUIREMENT
BPT
1.5
3.0
8.0
TABLE 10-3
CATEGORY 3
DRY PROCESSING
MILL SIZE
(Ib./day)
20,000
60,000
140,000
FLOW
MGD
0.03
0.16
0.66
MANHOURS FOR BPT
Operation
700
970
1,860
Maintenance
800
1,035
1,752
Lab
180
200
480
TOTAL MAN REQUIREMENT
BPT
1.0
1.5
3.0
10-3
-------
TABLE 10-4
CATEGORY 4
WOVEN FABRIC FINISHING
MILL SIZE
(Ib./day)
40,000
180,000
500,000
FLOW
MGD
0.54
2.43
6.75
MANHOURS FOR BPT
Operation
1,775
3,840
7,890
Maintenance
1,345
2,860
4,990
Lab
420
1,000
1,800
TOTAL MAN REQUIREMENT
BPT
2.0
5.0
10.0
TABLE 10-5
CATEGORY 5
KNIT FABRIC FINISHING
MILL SIZE
(Ib./day)
20,000
60,000
110,000
FLOW
MGD
0.36
1.08
1.98
MANHOURS FOR BPT
Operation
1,240
2,400
3,270
Maintenance
1,190
2,040
2,600
Lab
350
650
900
TOTAL MAN REQUIREMENT
BPT
2.0
3.5
4.5
TABLE 10-6
CATEGORY 6
INTEGRATED CARPET MILL
MILL SIZE
(Ib./day)
20,000
60,000
100,000
FLOW
MGD
0.166
0.498
0.83
MANHOURS FOR BPT
Operation
740
1,190
1,730
Maintenance
800
1,190
1,640
Lab
230
400
540
TOTAL MAN REQUIREMENT
BPT
1.0
2.0
2.5
TABLE 10-7
CATEGORY 7
STOCK AND YARN DYEING AND FINISHING
MILL SIZE
(Ib./day)
20,000
65,000
130,000
FLOW
MGD
0.4
1.2
2.4
MANHOURS FOR BPT
Operation
1,130
2,200
3,390
Maintenance
1,090
1,790
2,525
Lab
380
650
1,000
TOTAL MAN REQUIREMENT
BPT
2.0
3.0
5.0
10-4
-------
10.4 References
1. The National Commission on Water Quality, "Textile Industry Technology and Costs of
Wastewater Control". Lockwood Greene Engineers, Inc., (NCWQ Contract No. WQ5AC-
021), June, 1975.
2. U.S. Environmental Protection Agency, Operation and Maintenance Program, "Estimating
Staffing for Municipal Wastewater Treatment Facilities" Office of Water Program Opera-
tions, March, 1973.
U.S. Environmental Protection Agency, Water Pollution Control Research Series, Office
of Research and Monitoring, "Estimating Costs and Manpower Requirements for Con-
ventional Wastewater Treatment Facilities*1, Black and Veatch, October, 1971.
U.S. Environmental Protection Agency, Office of Water Programs, "Procedures for
Evaluating Performance of Wastewater Treatment Plants", URS Research Company,
San Mateo, California.
10-5
-------
CHAPTER 11
11.1 General Process Data
Company Name:
Plant Name:
Address:
DESIGN DATA CHECKLIST
Telephone No:.
Contacts:
.Plant Engr.
.Plant Mgr.
.Other
A. MANUFACTURING
1. Fibers Used:
.Wool
.Cotton
.Acetate
. Acrylic
.Modacrylic
.Nylon
.Polyester
.Rayon
.Other
Production Processes:
Slashing.
Weaving:
Broad
Narrow
Non Woven:
Chem. Bond
Mech. Bond
Therm. Bond
Tufting
Knitting:
Circular
Warp
Flocking
Preparation:
Bleaching
Washing
Scouring
Carbonizing
Mercerizing
Printing
Finishing:
Softening
Waterproof
Fireproof
Tentering
. Mildew Proof
. Wash & Wear
. Perm. Press
. Other
11-1
-------
Dyeing:
Yarn (space or skein)
Piece
Package
3. End Products:
Greige Goods.
Knitted
Tufted Carpets
Woven
Dyed Yarns
Finished Fabrics:
Knitted
Tufted Carpets
Woven
Other
4. Volume Produced:
. Ib/week avg.
. Ib/week max.
5. Operation:
. hrs/wk
shifts/day
6. Number of Employees:.
7. Process Water Use:
. gal/day (avg.)
8. All Other Water Use:
. gal/day (avg.)
9. Intake Water Source:
. Municipal
. Surface
. Subsurface
. Other
B. CHEMICAL AND DYES USED
1. Size:
. %Starch
.%PVA
,%CMC
11-2
-------
2. Desizing:
Sulfuric Acid
Enzymes
. Other
3. Scouring or Washing:
Soap
Detergent
. Caustic Soda
.Soda Ash
.Other
4. Bleaching:
Sulfur Dioxide
. Sodium Chlorite
. Sodium Hypochlorite Hydrogen Peroxide
.Other
5. Fulling:
.Acid
Alkali
. Other
6. Neutralizing:
Sulfuric Acid
Other
7. Dyeing:
Vat
. Direct
Disperse
. Sulfur
.Acid
. Cationic
.Developed
. Reactive
.Other
8. Finishing:
Starch
Dextrin
Wax
Tallow
Oil
. Clay
. Talc
. Lacquers
. Sulfonated Compounds.
. Ammonium Salts
.Cellulosic Compounds
.Special Finishes
.Detergents
.Soaps
.Other
11-3
-------
C. WASTEWATER CHARACTERISTICS
1.
Flow:
Average .
Maximum.
.gal./day
.gal. /day
2. Waste Components:
% Industrial
% Sanitary
3. Effluent Quality
BOD
COD
TSS
Chromium
Phenol
Sulfide
Color
pH
mg/1
mg/1
mg/1
mg/1
mg/1
ADMI
Units
. % Other
4. Available Discharge Points:
Receiving Stream
Municipal Sewer
Other
D. EXISTING TREATMENT FACILITIES
Temperature
Oil & Grease
Nitrogen
Phosphorus
Alkalinity
Other Metals
Fecal Coliform
.mg/1
.mg/1
.mg/1
.mg/1
.mg/1
.MPN
1. Physical Pretreatment:
Equalization
Screening
Pre-aeration
Sedimentation
. Flotation
. Temperature Control
. Other (describe)
11-4
-------
2. Chemical Pretreatment:
Neutralization
Primary Chemical Coagulation
Chemical Treatment
3. Biological Treatment:
Stabilization Basins
Activated Sludge
Trickling Filter
Aerated Lagoon
Anaerobic Contact (6 to 12 hours)
. Odor Control
. Nutrient Addition
.Other (describe)
. Anerobic Pond (3 to 30 day)
. Denitrification
. Aerobic or Anaerobic-Digestion
of Solids
. Other (describe)
4. Sludge Handling:
Thickening
Lagooning or Drying Bed
Centrifugation
Vacuum Filtration
Filter Pressurization
5. Terminal Secondary Treatment:
Biological Sedimentation
Final Chemical Coagulation
Sedimentation
Sand Filtration
. Dry Combustion
. Wet Combustion
. Land Disposal
. Sea Disposal
. Other (describe)
. Diatomite Filtration
. Chlorination
. Other (describe)
6. Temperature Change Processes:
Evaporation
Freezing
. Distillation
. Eutectic Freezing
.Wet Oxidation
. Process Residue, Handling &
Disposal
. Other (describe)
11-5
-------
7. Miscellaneous:
Absorption Reverse Osmosis
Electrodialysis Foaming
Ion Exchange Electrochemical Treatment
Solvent Extraction _ Other (describe)
8. Treated Wastewater Disposal:
Controlled Discharge Ocean Disposal
Surface Storage and Evaporation , Surface Discharge
Deepwell Disposal Other (describe)
Surface (spray) irrigation
DESIGN PARAMETER
CHECKLIST
11.2 Treatment Unit Design
1. Influent Design Conditions:
Wastewater Flow
Average mgd
Maximum mgd
Minimum -mgd
BOD Loading
Average Ib/day
90 Percentile Ib/day
Wastewater Temp. _°F
2. Effluent Design Conditions:
Wastewater Flow
Average mgd
Maximum mgd
BOD Loading
Average Total Ib/day
Maximum Total Ib/day
VSS Concentration mg/l
11-6
-------
3. Screening:
Flow Rate
Spacing
Slope
Velocity
.gpm
.in. & mesh
.degrees
.fps
4. Clarification:
Overflow Rate
Detention Time
Depth
Weir Rate
-gpd/ft2
.Hours
.ft.
-gal/day/ft.
5. Multi-Media Filtration:
Hydraulic Load
Solids Load
Depth
Filter Run Time
.lb/day/ft2
.inches
.hours
6. Flotation:
Hydraulic Loading
Operating Pressure
Gas to Solids
Pressurization Type
.gpm/ft2
.psig
.weight ratio
. recycle/partial/total
7. Equalization:
Detention Time
Volume
Mixing Required
Depth
.hours
.gallons
.HP/1000 gal
.ft.
8. Neutralization:
Detention Time
Agitator Speed
Chemicals Used
Feed Range
.minutes
.fps
11-7
-------
9. Aerated Lagoons:
Detention Time
Depth
Oxygen Utilization
10. Extended Aeration:
Detention Time
Depth
Recirculation
Organic Loading (F/M)
MLVSS Concentration
Air Requirements
Sludge Volume Index
.days
.feet
_lb. BOD/day/HP
. days
.ft.
.%
Ib BOD/day
Ib MLVSS
mg/1
HP of ft3/lb BOD/day
ml/g settled MLSS
II. Trickling Filter:
(Synthetic Media)
BOD Loading
Recirculation Rate
Filter Bed Depth
12. Activated Carbon Catalyst:
Carbon Dosage
Resident Time
Regenerate/Throwaway
. Ib BOD/1000 ft3/day
. ratio
.ft.
mg/1
hours
13. Chemical Coagulation:
Rapid Mixing
Detention Time
Depth
Mixing Power
Mixing Speed
Chemical Requirements
Coagulant
Polymer
. minutes
ft.
HP/1000 ft3
. rpm
.mg/1
.mg/1
11-8
-------
Flocculation
Detention Time
Depth
Mixing Power
Mixing Speed
Clarification
Overflow Rate
Depth
minutes
.feet
. HP/1000 ft3
. rpm
. gpd/ft2
.ft.
14. Polishing Ponds:
Depth
Loading Rate
Detention Time
.ft.
Ib BOD/acre/day
days
15. Chrome Removal:
Reduction pH
Precipitation pH
Flocculation Time
Clarifier Overflow Rate
Clarifier Depth
Sludge Concentration
units
units
minutes
. gpd/ft2
.ft.
. % weight
16, Activated Carbon Adsorption:
Flow Rate _
Carbon Size _
Backwash Rate _
Reactivation
Temperature _
Furnace Loading _
Carbon Loss _
. gpm/ft2
. mesh
gpm/ft 2
°F
Ib/ft2/day
Jf 7, Synthetic Resin Adsorption:
Hydraulic Loading
Regeneration Time
Backwash Rate
. gpm/ft2
. days
.gpm
11-9
-------
18. Hyperfiltration:
Membrane Type
Pre-Filter Size
pH
Temperature
Pressure
. microns
. units
.°F
. psi
19. Aerobic Digester:
Detention Time
VSS Loading
Air Requirements
Temperature
Tank Depth
days
Ib/ft3/day
hp or cfm vol.
.°F
.ft.
Volatile Solids Reduction.
20. Gravity Thickener:
Influent Solids
Concentration
Solids Flux Rate
Underflow SS
Concentration
Overflow Rate
Ib. ss/ft2-day
gal/day/ft2
21. Sludge Drying Beds:
Solids Loading
Media Size
Bed Depth
. Ib/sq. ft./yr.
mm
, inches
22. Spray Irrigation:
Application Rate
Spray Schedule
in/wk.
spray-rest
23. Chlorination:
Chlorine Dosage
Contact Time
Form of Chlorine
mg/1
min.
11-10
-------
24. Ozonation:
Ozone Dosage mg/1
Contact Time min.
Form of Ozone
11-11
-------
Accelerators
Acetate
Acetic Acid
ACFM
Acrylic
Acid Dye
ADMI Color
Adsorption
Aerobic
Ageing
Agglomeration
Alkaline
APPENDIX A
GLOSSARY
Chemical used to increase color development in tex-
tile dyeing operation or to promote cross-linking be-
tween two chemicals on a fiber or a chemical and a
fiber.
A manufactured fiber made from cellulose acetate.
A weak acid used in wool, nylon, polyester, etc., dye-
ing. Normally can be replaced by ammonium sulfate.
Actual cubic feet per minute. Air flow at the actual
operating condition of temperature and pressure.
A manufactured fiber in which the fiberforming sub-
stance is any long chain synthetic polymer composed
of at least 85% by weight of acrylonitrile units. Made
in both filament and staple form.
A type of dye commonly used to color wool and
nylon but may be used on other fibers.
Analytical method of evaluating color, developed by
the American Dye Manufacturer's Institute.
The adhesion of an extremely thin layer of molecules
to the surfaces of solids or liquids with which they are
in contact.
Living or active only in the presence of oxygen.
Fabrics are aged by heat, acid or some other means.
A phenomenon where particles mass together.
Presence of the hydroxides, carbonates, and bicarbon-
ate of elements, such as calcium, magnesium, sodium,
potassium; or of ammonia. Alkaline pH ranges from 7.1
to 14.
A-l
-------
Ammonium Sulfate
Anaerobic
Ash
Azoic
Basic Dye
Beam
Beck
Bleaching
Blend
Slowdown
BOD
Acid forming salt used in wool stock dyeing.
Living or active only in the absence of free oxygen.
The combustible solid matter in fuel or refuse.
A type of dye used to color cotton, rayon, polyester
and cotton/polyester blends, but not commonly used.
Also known as cationic dye. It is used to color synthe-
tic fiber or cotton/polyester blends.
Any of various machines for dyeing which use a per-
forated beam through which the dye bath is circulated.
Any of various machines for scouring (cleaning), dye-
ing, etc., goods while in the form of rope or endless
belt. A roller gradually moves the cloth through the
bath in a slack condition.
The treatment of textile fibers, yarns or cloth to des-
troy the natural coloring matter and leave the material
white. Hydrogen peroxide is a widely used bleaching
agent.
The combination of two or more types of fibers and/
or colors in one yarn.
Periodic or continuous draw-off of a mixture from a
system to prevent buildup of contaminants.
Biochemical oxygen demand. A method of measuring
rate of oxygen usage due to biological oxidation. A
BODg of 1000 mg/liter means that a sample (1 liter)
used 1000 mg of oxygen in 5 days.
Calender
Carbonizing
A machine using heavy rollers to impart a variety of
effects in the finishing of cloths, particularly cotton
and rayon.
An acid treatment of wool to remove vegetable matter
(burrs, straw, etc.) followed by heat.
A-2
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Carbonizing
Carding
A phenomenon where a carbonaceous material is de-
composed leaving a residue of essentially black carbon,
e.g. soot.
Fibers are separated and aligned in a thin web, then
condensed into a continuous, untwisted strand called
a "sliver".
Carrier
Catalytic Incinerators
Cellulose
A water-insoluble organic compound which accelerates
the absorption of dyes by a fiber. Disperse dyes used
with polyester most commonly utilize carriers.
Incinerators for gaseous materials which utilize a
catalyst to reduce the operation temperature.
Major component of cotton and rayon. Also used as
the base for acetate fiber.
CMC
COD
Combing
Compacting
Decating
Carboxmethyl cellulose. Synthetic size used in sizing
process of cotton fabric manufacturing.
Chemical oxygen demand. The amount of oxygen
required for the chemical oxidation of organics in a
liquid.
A method removing short fibers and foreign matter
from cotton or wool stock by processing it through a
series of needles (or combs).
A mechanical compressive shrinkage operation.
Using a combination of steam and pressure to give a
soft hand and feel to the fabric.
Denitrification
Desize
Desuinting
The reduction of nitrate to nitrogen gas by denitri-
fying organisms.
A process for removing size material from greige (gray)
goods in preparation for bleaching, dyeing, etc.
Removing of natural impurities and dirt in wool fiber.
A-3
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Developers
Direct Dye
Disperse Dye
Dissolved Oxygen
Drawing
Dry Cleaning
Dyeing Jigs
Electrostatic Precipitation
Emission
Eutrophication
Extracting
Chemicals used in dyeing process, whose color is de-
veloped by reaction on cotton.
Anionic, water soluble dye used primarily for dyeing
full shade ranges on cotton and rayon.
Water insoluble dye used to color several synthetic
fibers. Applied as a fine dispersion using a carrier.
On cloth, padded dye may be baked on or "thermo-
fixed".
Oxygen in water required for the respiration of aerobic
microorganisms.
Straightening and paralleling the fibers after combing
or carding.
Cleaning of dyed yarn or fabric with a solvent rather
than scouring in a water solution.
Open width on the dyeing machine. Cloth moves from
one roll to another through the dye liquor until the
desired shade is obtained.
A process in which particles are collected by means of
electric charge.
In environmental work, a reference to gaseous dis-
charges to the atmosphere as opposed to effluent
which refers to liquid and solid discharges.
Process whereby lakes or streams become enriched
with biological nutrients, usually nitrogen and phos-
phorus.
Water is removed by centrifuge prior to slitting.
F/M
Fecal Coliform
Food to microorganism ratio.
An indicator organism for evaluating the micro-bio-
logical suitability of the water.
A-4
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Felt
Fiber Reactive
Filament
Fleece
Floe
Fly Ash
Framing
Fulling
Gilling
Grain
Greige
Hank
Heat Pipe
Impaction
A fabric made with no systems of threads but con-
structed by interlocking of fibers in the fabric. Wool
and cotton are the most common fibers used.
A type of dye used to color cotton, nylon and poly-
ester/cotton blend. This dye gives bright shades, good
all around fastness and easy application.
A man-made continuous strand of yarn of near infinite
length.
Quantity of wool cut from individual sheep at shearing
time.
An agglomeration of finely divided or colloidal parti-
cles.
Fine particles of ash carried by the products of com-
bustion.
Drying or impregnating of fabric with a resin or
starch and drying at the correct width.
A shrinking process for wool utilizing moisture, heat,
friction and pressure. Also, known as felting or milling.
The operation in wool yarn manufacturing to straight-
en and parallel the fibers.
A unit of weight measure (gr): 7,000 gr = 1 Ib.
Fabrics in unbleached, undyed state before finishing.
In U.S. "gray goods" or "grey goods".
A definite length of material which varies for different
fibers, basically the number of yards equivalent to one
pound.
A long cylindrical sealed heat transfer element that
operates by means of an internal flowing medium.
A phenomenon wherein particles are stopped or col-
lected by collision with a material or medium.
A-5
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Incineration
J-Box
Jet Dyeing
Jig
With reference to gaseous materials, an abatement
technique where the stream is heated to a specified
temperature for a specified length of time to enable
combustion of the pollutants. It is commonly
1,400° F for one half second.
A J-shaped device often used in bleaching continuous-
ly. Cloth is stored in the J-shape arrangement for a re-
quired dwell time at a designated temperature.
A tubular machine utilizing water jets to circulate
fabric in a dye bath.
An open vat which passes full width cloth from a roller
through dye liquor and then onto another roller. The
operation is repeated until the desired shade is ob-
tained.
Jute
Kier
Knitting
Loading
Coarse, brown fiber from the stalk of a bast plant
grown in India. Used mainly for burlap, cordage,
and as a backing for rugs and carpets.
A piece of equipment in which cotton is boiled with
dilute caustic soda to remove impurities. Also, desig-
nates a pressure vessel used for the dyeing of yarn and
fabric.
Process of making fabric by interlocking series of loops
of one or more yarns. Types are: jersey (circular knits),
tricots (warp knits), double knits.
In air and water pollution, a term generally referring
to the weight rate of an emission as opposed to
concentration.
Lower Explosive Limit (LEL)
Mercerizing
The lowest concentration of a dust, gas or vapor in
which flame propagation can occur.
A process given to cotton yarns and fabrics to in-
crease luster, improve strength and dyeability. Treat-
ment consists of impregnating fabrics with cold con-
centrated sodium hydroxide solution.
A-6
-------
Metalized Dye
Milling
Mist Eliminator
MLSS
MPN
Modacrylics
Napthol
Nip
Nitrified Effluent
Nutrient
Nylon
Oxidizing Agents
Two acid dyes (anionic, water soluble) joined to-
gether to make a larger molecule which has greater
light and wet fastness. Used primarily for dyeing
nylon and wool where high fastness is required.
See Fulling.
A device for removing mist from a gas stream.
Mixed Liquor Suspended Solids. The concentration of
suspended solids carried in the aeration basin of an
activated sludge process.
Most probable number. Expressed as density of
organisms per 100 ml.
Generic name established by the Federal Trade Com-
mission for a "manufactured fiber in which the fiber-
forming substance is any longchain synthetic polymer
composed of less than 85% but at least 35% by weight
of acrylonitrile units".
An azo dye whose color is formed by coupling with a
naphthol. Used chiefly on cotton.
A squeeze performed by two rolls under pressure.
Effluent in which ammonia is converted to nitrate or
nitrite.
Any substance assimilated by an organism which pro-
motes growth and replacement of cellular constituents.
Generic name for "a manufactured fiber in which the
fiber forming substance is any long-chain synthetic
polyamide in which less than 85% of the amide in
linkages are attached to two aromatic rings".
Any substance which can receive electrons and thereby
cause some other chemical to increase in positive
charge.
A-7
-------
Package Dyeing
Pad
Paddle Machine
Participate Matter
pH
Phenols
Picking
Pierce Dyeing
Plume Opacity
Polyester
Printing
PVA
The dyeing of yarns in the form of a package of vari-
ous kinds and sizes. Packages wound onto perforated
tubes or springs are placed on perforated spindles in a
closed vat and the dye bath is circulated in and out of
the package.
A machine for impregnating fabrics with chemicals.
It consists essentially of a trough followed by two or
more pairs of squeeze rolls.
A dye vat that uses paddle to convey the goods through
the dye bath.
Any material except uncombined water which exists
in a finely divided form as a liquid or solid.
Unit used to describe acidity or alkalinity. pH 7 is
neutral; above 7 is alkaline and below 7 is acidic.
Organic compounds which cause taste problems in
water particularly when the water is chlorinated.
The process of yarn manufacturing in which cotton is
opened, cleaned and rolled into a lap.
A method used to dye fabrics a solid color. May be
done continuously, jig, pad, beck, etc.
The resistance of air emission material to passage of
visible light.
A manufactured fiber in which the fiberforming sub-
stance is any long-chain synthetic polymer composed
of at least 85% by weight of an ester of dihydric alco-
hol and terephthalic acid.
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.
Polyvinyl Alcohol. Synthetic size used in sizing process
in cotton fabric manufacturing.
A-8
-------
Quilling
Raising
Rayon
Receiving Water
Recuperator
Reducing Agent
Resin
Retard ants
Rope Soaper
Sanforizing
Saturator
SCFM
Scouring
Yarn which is to go on the loom as filling is wound
onto a quill which is placed in the shuttle at the loom.
A woolen finishing process designed to create a nap on
the surface of the cloth.
A generic name for man-made fibers, mono-filaments
and continuous filaments, made from regenerated
cellulose. Fibers produced by both viscose and cup-
rammonium process are classified as rayon.
Surface waters which assimilate effluent discharge.
An enclosed wash box utilizing low pressure steam.
Most often found on a mercerizing range.
Any substance that can give electrons.
A chemical finish used to impart a property desired
in a fabric, such as water repellency or hand, etc.
Chemicals applied topically to fabrics or in-situ to
fibers to retard burning, etc.
A piece of equipment used for scouring fabrics to
remove impurities, processing oils, excess dye etc.
A mechanical shrinkage of the fabric.
A box used to impregnate fabric with chemicals in a
continuous range.
Standard cubic feet per minute. Air flow corrected to
predefined standard conditions of temperature and
pressure, generally 32° F and one atmosphere in
air pollution work.
Removal of foreign components from textiles. Normal
scouring materials are alkalies (e.g. soda ash) or trisodi-
um phosphate, frequently used in the presence of a
surfactant. Textile materials are sometimes scoured by
use of a solvent.
A-9
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Scray
Scrubber
Septic
Singeing
Sizing
Slashing
Souring
Spinning
SS
Starch
Stiochiometric
A device used primarily to provide some flexibility or
dwell time in continuous range.
In air pollution, a device in which a contaminated
stream is contacted with a liquid to reduce contami-
nant emission.
Causing anaerobic biological activities due to insuffi-
cient oxygen present in wastewaters.
Cloth passes across an open gas flame at a high rate
of speed to burn off the loose surface fibers.
Applying starch, PVA or CMC to warp yarns to mini-
mize abrasion during weaving.
A number of beams from the warper are placed into a
creel, run through a size solution and dried on a series
of drying cans.
Usually a cotton treatment using a weak acid solu-
tion to neutralize excess amounts of alkali.
A process by which a large strand of fibers is drawn
out to a small strand and converted into a yarn. After
drawing out (or drafting), twist is inserted, and the re-
sulting yarn is wound into a bobbin.
Suspended Solids. Solids that either float on the sur-
face of or are in suspension in water.
Organic polymer material used as a size; highly bio-
degradable.
A reference to the combining weights of the elements
in a chemical reaction.
Stripping Agents
Suint
Chemical used in textile processing to take off impuri-
ties covering the fabric.
Dried sheep perspiration.
A-10
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Sulfur Dyes
Tentering
Textured
Thermosol (DuPont)
Top
Tufted Yarn
TSS
Unrolling
Vat Dye
Venturi Scrubber
vss
A class of dyes which dissolve in an aqueous sodium
sulfide forming product with a marked affinity for
cotton; the dyes are regenerated by air oxidation.
Open width fabric is run through a tenter frame which
holds it at the desired width, fabric is dried and wound
onto a roll.
Bulked yarns that have greater volume and surface in-
terest than conventional yarn of same fiber.
A continuous dyeing process where the fabric is
padded with dye, dried and the dye is fixed at tem-
peratures between 180-220° C in an oven.
A continuous untwisted strand or sliver of wool
fibers wound into a large ball.
These are very coarse yarns, usually plied, designed
for the tufting trade. Most tufting yarns are made
from nylon, acrylic or polyester fiber.
Total suspended solids. Amount of solids separated
by filtration of a sample of wastewater.
Knitted fabric is unrolled into a box or basket in
preparation for scouring.
A type of insoluble dye applied from a liquor con-
taining alkali and a powerful reducing agent, generally
hydrosulfite. The dye then becomes soluble and com-
pletely permeates the cotton fiber. It is then oxidized
and again becomes insoluble.
A scrubber in which gas velocity is increased in the
presence of a liquid due to a decrease in cross section
area of the duct causing particulate matter to be cap-
tured by impaction into the liquid.
Volatile suspended solids.
A-ll
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Warp
Weaving
Winch
Winding
Worsted
Yarn
Set of lengthwise yarns in a loom through which the
crosswise filling yarns (weft) are interlaced. Some-
times called "ends".
The process of manufacturing fabric by interlacing a
series of warp yarns with filling yarns at right angles.
See (Beck).
Yarn is wound onto one of several different types of
large packages and most of the slubs or thick places
are taken out.
A wool fabric which uses finer grades of wool with
finer yarns and higher weaving constructions than a
woolen fabric.
An assemblage of fibers or filaments, either manu-
factured or natural, twisted or laid together so as to
form a continuous strand which can be used in weav-
ing, knitting or otherwise made into a textile material.
A-12
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APPENDIX B
Multiply
Inches
Feet
Square Feet
Cubic Feet
Pounds
Gallons
Gallons/Minute
Feet/Second
Fahrenheit
Acre
BTU
Horsepower
METRIC CONVERSION CHART
By
2.54
0.3048
0.0929
0.0283
0.454
3.79
5.458
0.305
0.555 (°F-32)
0.405
0.252
0.7457
To Get
Centimeters
Meters
Square Meters
Cubic Meters
Kilograms
Liters
Cubic Meters/Day
Meters/Second
Centrigrade
Hectares
Kilogram — Calories
Kilowatts
B-l
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APPENDIX C
DEFINITIONS OF MANUFACTURING OPERATION
1. Commission Scouring shall mean the scouring of wool, 50% or more of which is owned
by others, in mills that are 51% or more independent (i.e. only a minority ownership by
company (ies) with greige or integrated operations); the mills must process 20% or more of
their commissioned production through batch, noncontinuous processing operations.
2. Commission finishing shall mean the finishing of textile materials 50% or more which are
owned by others, in mills that are 51% or more independent (i.e. only a minority owner-
ship by company (ies) with greige or integrated operations); the mills must process 20%
or more of their commissioned productions through batch, noncontinuous processing
operation with 50% or more of their commissioned orders processed in 5,000 yards or
smaller lots.
3. Simple manufacturing shall mean all the following processes: Desizing, fiber preparation
and dyeing.
4. Complex manufacturing shall mean simple manufacturing processes plus any additional
manufacturing operations such as printing, water proofing, or applying stain resistance
or other functional fabric finishes.
5. Complex manufacturing shall mean fiber preparation, dyeing, carpet backing plus addi-
tional operations such as printing or dyeing and printing.
C-l
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APPENDIX D
BOD OF TEXTILE CHEMICALS
An abbreviated list of the 5-day BOD of Textile Chemicals. These values are based on the weight
of chemicals as received, i.e., if a chemical shows a BOD of 140%, then 1 pound will yield 1.4
pounds of BOD. The exception to this is reference 5 where the BOD is based on the dry weight
of chemicals.
Name Ref.
Acetic Acid, 56% (2)
Acetone (2)
Aerotex Resin M-3 (2)
Aerotex Syrup 250 Cone (2)
Ahcovel G (2)
Alkamine C (5)
AvcosoI20 (1)
Avitex R (2)
B-2 Gum (2)
Brytex Gum No. 745 (2)
Carbonwax 200 (5)
Cetosol SF (2)
C-Prosan (6)
Duponol C (2)
Duponol RA (7)
Dyes
Alizarine Cyanine Green GHN
Cone. CF (2)
Calcogene Black GXCF Cone ... (2)
Celliton Fast Blue AF 100% (2)
Erie Brilliant Black S 150% (2)
Fast Red Salt 3GL (2)
Khaki carbanthrene 2G (2)
Naphthol AS-BR (2)
Nyaform Blue 2B (2)
Mixture of 18 dyes (2)
DypensolSED (1)
Elvacet (4)
Elvanol 72-60 (2)
Ethanol (2)(4)
Ethyl Acetate (2)
Experimental 377 (6)
Formaldehyde, 37% (2)
Formic Acid, 85% (2)
Foryl R 333 (6)
Globe Easy Flow Starch (6)
Gelatin (1)
Glue (1)
BOD
Composition: use percent
; dyeing, scouring 33,36
CH3COCH3; solvent 122*
Melamine-formaldehyde; finishing 23.
Urea-formaldehyde condensate; durable finishes 5.
Fatty carbamide; cation-active sustantive softening agent. 2.
Fatty amide condensate 45.
Waxy sorvital ester; sizes, spinning and carding oil 42.
High alkylamine; special finishing agent 5.
Starch dextrins; printing ink, size 61.
Starch: printing ink, sizes 61.
Polyethylene glycol 2.
Synthetic resin; finishing 24.
Synthetic wax 129.
Lauryl sulfate: detergent and wetting agent 125.
Surface active agent 13.
Acid dye Near 0**.
Sulfur dye 10.
Acetate color 3.
Direct dye 8.
Insoluble azo compound 2.
Vat dye 0.
Prepare 10.
Direct dye (formaldehyde after treatment) Near 0**
Dyes 7.
Polyhydric alcohol and cresylates; mercerizing assistant . 39.
Poly vinyl acetate water emulsions 1.
Poly vinyl alcohol; finishing agent, sizing compound .... 1.
C2H50H; solvent 93*, 125.
C2H5C02CH3; solvent 66*.
Detergent 12.
HCHO: shrinkproofing, creaseproofing, modifying dye-
ing characteristics 37.
HCOOH; scouring 2.
Scouring 66t-
Size 65.
Gelatin; sizes 100.
Glue, sizes 66.
D-l
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70% Hydroxyacetic acid (6)
Hydroxy Ammonium sulfate (4)
Igepal (2)
Ivory Snow (1)(4)
Kyro EO (1)
Lanalbine (6)
Monochlorobenzene (2)
Morningstar Starch (2)
Morpholine (2)
Nacconol NR (2)
Neutronyx 600 (2)
Nopco 1111 (1)
Nopcolube 55 (6)
Norane W-l (1)
Orvus EC Paste (3)
Oxalic Acid (2)
Oxytrol (5)
Paralube 20 (Tween 20) (6)
Parval (2)
Penetrant GW (6)
Peter Copper Size (1)
Phenol (1)
Picking Oil (1)
Product BCO (7)
Rapidase M (2)
Red Oil (2)
Resloom NP Special (2)
Rhonite313 (2)
RhoniteR-1 (2)
Salicylic Acid (1)
Soap, Nonpareil (2)
Sodium Alginate (2)
Sodium Hydrosulfite (2)
Softener Cream 25% (2)
Special Textile Flakes (2)
Surfactant DN-40 (6)
SulfanoleKB (3)
Sulfonated Castor Oil (1)
Sulfuric Acid (1)
Stymer S (1)
Tall Oil Soap (6)
Tallow (2)
Tergitol 4 (3)
Triethanolamine (2)
Triton X-100 (1)(5)
UconH-6 (1)
Ultrawet60L (1)
HOCH2COOH 7.
(NH2OH2S04 4.
Polymerized ethylene oxide alkyl phenol condensation
product; detergent, wetting agent, emulsifying, dispersing4.
Sodium salt of fatty acid 122,141.
Polyethylene oxide condensate; synthetic detergent.... 0.
Protein hydrolyzate; wool protective agent 13.
Cgl^Cl; swelling agent in dyeing of Dacron, dyeing
assistant 3.
Starch; sizes, spinning and carding oils 47.
0: (CH2CH2): NH; dye solvent, emulsifying agent,
corrosion inhibitor 2*.
Sodium alkylarylsulfonate; detergent 0,4.
Aromatic polyglycol ether; scouring agent for all fibers . 0.
Sulfonated coconut oil; emulsifying agent 96.
Synthetic wax for warp sizing 80.
Wax emulsion; water repellent with Norane W—2 70.
Mod. Sodium alkyl sulfate type 23.
H2C204 2H20; rust removal 14.
Highly substituted starch 15.
Anti-static 33.
Fatty amine condensate plus amine soap; scouring,fulling. 5.
Leveling agent 14.
Glue; sizes, spinning and carding oils 118.
C6H5OH; dyeing 200.
Sizes, spinning and carding oils 13.
Surface active agent 3.
Amylolytic and proteolytic enzymes, desizing agent.... 4.
Sulfonated castor oil, soapmaking, carding 68+.
Melamine-formaldehyde condensate; finishing 11,14.
Urea-formaldehyde resin; finishing 11.
Modified urea-formaldehyde resin; finishing 7.
C0H4(OH) COOH; dyeing 141.
Fatty acid soap; scouring, fulling washing 140.
Size, thickening agent 36.
Na2S2O4; reducing, stripping 22.
Sulfonated tallow oil; finishing 39.
Sodium salt of fatty acid; detergent 112.
Scouring 15.
Sodium alkylarylsulfonate 0.
Castor oil, sulfonated 52.
H2S04; dyeing 0.
Styrene maleic anhydrous salt; size, spinning and
carding oils 1.
Soap 147.
Tallow; soap making 152.
C4H9CH (C2H5) C2H4CH (S04Na) CH2CH (CH3>2 ... 0.
(HOCH2CH2)3N; emulsifier, dispersing agent 1;0.
Alkylarylpolyether alcohol 0.15,0.2.
Polyalkalene glycols; size, spinning and carding oils .... 4.
Sodium alkylarylsulfonate; wetting, detergent 0.24
D-2
-------
Wheat Starch (2) Starch; printing inks, size 55.
Wool Oil (mineral oil + base) (6) Spinning 3.
Zelan AP Paste (2) High molecular nitrogen compounds; durable water
repellent 19.
Zelec NK (7) Nondurable antistatic agent 54.
*Calculated from the theoretical BOD and the published percent of theoretical.
**The dye color interfered with the determination.
fNew biodegradable type.
+Believed to be low since sample was very old.
References:
1. Masselli, Joseph W., and Burford, Gilbert. "Pollution Reduction Program for the Textile
Industry," Sewage and Industrial Wastes, October 1956; Vol. 28, No. 10, table VII, Process
Chemical BOD, pp. 1273-1289.
2. Stafford, William, Chm; and Northup, Harold J., Secty. "The BOD of Textile Chemicals,"
American Dyestuff Reporter, May 23, 1955, Vol. 44, No. 11, table I, pp. 355-359.
3. Souther, R.H. and Alspaugh, T.A. "Current Research on Textile Waste Treatment,"
Sewage and Industrial Wastes, August 1958, Vol. 30, No. 8, table III, pp. 992-1011.
4. Masselli, Joseph W., and others of the Wesleyan University. "A Simplification of Textile
Wastes Survey and Treatment," for the New England Interstate Water Pollution Control
Commission.
5. Patton, James P. Jr. Cone Mills Research and Development Laboratory, Cone Mills Corp.
6. Smith, A.L. and Grey, J.C. Chatham Manufacturing Co.
7. Bacon, Osborne C. E.I. du Pont de Nemours & Co., Inc., Waynesboro Works, Waynesboro,
Va.
NOTE:
An expanded list of chemicals and BOD appeared in the August 29, 1966 Proceeding of
the American Association of Textile Chemists and Colorists on pages 685 to 688.
D-3
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APPENDIX E
ATMI - CRI WASTEWATER SURVEY
The following tabulations represent the results of a comprehensive survey of the industry per-
formed in 1972. The survey was conducted using questionnaires distributed to members of
ATMI and CRI, and by collection and analysis of mill effluent samples taken from selected
plants. The field testing program was performed in an effort to validate questionnaire data
and to help better characterize textile process discharges. (Note: Subcategory 7 has been
omitted because no data input was available.)
To aid in this Appendix, the terms denoted are described. "Number" refers to the number
of textile mills responding. The number of observations from each plant were averaged to
obtain the single plant input. "Maximum" denotes the largest value of plant inputs. Like-
wise, "Minimum" denotes the smallest value for the plant inputs. "Average" is the mathe-
matical mean of all the single plant values while "standard deviation" is the population
deviation. A discussion of the methodology used by ATMI and CRI is included in the
"Blue Book".
E-l
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ATMI-CRIWASTEWATER SURVEY
BOD
Number = 3
COD
Number = 3
TOC
Number = 1
OIL
PH
Number - 3
Number
CATEGORY 1 - WOOL SCOURING
mg/1
Maximum = 7,900
Minimum = 1,630
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
31,600
3,105
2,816
2,816
6,500
1,106
7.50
6.70
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
mg/1
3,739
3,604
15,268
14,698
2,816
3,195
2,896
7.23
0.46
ALKALINITY
Number = 3
Maximum
Minimum
1,900
42
Average
Std. Dev.
993
930
SUSPENDED SOLIDS
Number = 3
DISSOL VED SOLIDS
Number = 3
VOLATILE SOLIDS
Number = 3
PHENOL
Number = 3
SULFIDES
Number = 1
WATER USE (Gal/lb.)
Number = 5
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
9,500
4,880
12,800
7,405
10,285
5,904
2.00
0.00
0.10
0.10
20.00
2.10
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
6,595
2,529
9,987
2,705
7,863
2,227
0.87
1.02
0.10
7.45
6.76
E-2
-------
ATMI-CRI WASTEWATER SURVEY
BOD
Number = 1
CATEGORY 2 - WOOL FINISHING
mg/1
Maximum = 125
Minimum = 125
Average
Std. Dev.
mg/1
125
DO
Number = 1
Maximum
Minimum
5.92
5.92
Average
Std. Dev.
5.92
pH
Number - 1
SUSPENDED SOLIDS
Number = 1
VOLATILE SOLIDS
Number = 1
WATER USE(Gal/lb.)
Number = 3
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
6.92
6.92
31
31
27
27
20.00
9.00
Average
Std. Dev.
Average
Std. Dev.
Average
Average
Std. Dev.
6.92
31
27
13.83
4.59
ATMI-CRI WASTEWATER SURVEY
BOD
Number = 7
CATEGORY 3 - GREIGE MILL
mg/1
Maximum = 362
Minimum = 78
Average
Std. Dev.
mg/1
274
123
COD
Number = 6
Maximum = 996
Minimum - 425
Average
Std. Dev.
871
230
TOC
Number = 2
Maximum
Minimum
129
108
Average
Std. Dev.
119
15
DO
Number - 4
Maximum
Minimum
3.72
3.72
Average
Std. Dev.
3.72
pH
Number - 7
Maximum
Minimum
23.23
6.23
Average
Std. Dev.
11.53
5.78
E-3
-------
ALKALINITY
Number = 7
SUSPENDED SOLIDS
Number = 6
DISSOLVED SOLIDS
Number = 2
VOLATILE SOLIDS
Number = 1
TOTAL CHROME
Number = 5
SULFIDES
Number - 4
WATER USE (Gal/lb.)
Number = 30
BOD
Number - 21
COD
DO
Number = 13
Number = 10
COLOR
Number
OIL
Number
pH Number
= 6
= 1
= 21
Maximum -
Minimum ~
Maximum =
Minimum -
Maximum =
Minimum =
Maximum =
Minimum -
Maximum =
Minimum =
Maximum -
Minimum =
Maximum =
Minimum -
ATMI-CRI
CATEGORY 4 -
Maximum =
Minimum =
Maximum =
Minimum =
Maximum =
Minimum =
Maximum =
Minimum =
Maximum =
Minimum =
Maximum =
Minimum =
1928
41
408
2
234
216
242
242
10.81
0.03
8.00
8.00
4.70
0.08
Average =
Std. Dev. =
Average =
Std. Dev. =
Average =
Std. Dev. =
Average =
Std. Dev. =
Average =
Std. Dev. =
Average =
Std. Dev. =
Average -
Std. Dev. =
1131
994
87
163
225
13
242
8.65
4.82
8.00
1.51
1.52
WASTEWATER SURVEY
WOVEN
mg/1
1800
134
2288
378
9.43
0.00
692
115
14
14
23.22
7.50
FABRIC FINISHING
Average =
Std. Dev.
Average =
Std. Dev.
Average =
Std. Dev. =
Average =
Std. Dev. =
Average =
Std. Dev. =
Average =
Std. Dev. -
mg/1
592
392
1093
513
3.04
3.17
389
207
14
11.62
2.89
E-4
-------
ALKALINITY
Number = 14
SUSPENDED SOLIDS
Number = 16
DISSOL VED SOLIDS
Number =11
VOLATILE SOLIDS
Number = 11
TOTAL CHROME
Number = 8
PHENOL
Number = 3
SULFIDES
Number - 3
WATER USE (Gal/lb.)
Number = 29
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
= 1928
26
= 2180
— 0
= 4296
228
= 3228
83
= 10.81
= 0.31
- 0.02
= 0.00
= 8.00
0
= 40.73
= 3.87
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
706
597
313
533
= 1975
= 1195
960
977
= 4.30
= 4.23
= 0.01
= 0.01
= 2.72
= 4.57
= 18.14
= 9.93
BOD
ATMI-CRI WASTEWATER SURVEY
CATEGORY 5 - KNIT FABRIC FINISHING
mg/1
mg/1
Number =
COD
Number =
TOC
Number =
DO
Number =
COLOR
Number =
6
3
1
2
3
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
= 800
= 80
= 1501
= 869
= 250
250
= 4.00
= 3.93
= 2500
= 625
Average =
Std. Dev.
Average =
Std. Dev.
Average =
Std. Dev.
Average =
Std. Dev. =
Average =
Std. Dev. =
355
303
1105
345
250
3.96
0.05
1295
1046
E-5
-------
OIL
Number = 1
PH
Number = 5
ALKALINITY
Number = 3
SUSPENDED SOLIDS
Number = 5
DISSOLVED SOLIDS
Number = 3
VOLATILE SOLIDS
Number = 3
PHENOL
Number = 1
WATER USE(Gal/lb.)
Number =
CATEGORY
BOD
Number =10
COD
Number = 5
ALKALINITY
Number = 6
SUSPENDED SOLIDS
Number = 6
Maximum =
Minimum =
Maximum =
Minimum =
Maximum =
Minimum =
Maximum =
Minimum =
Maximum =
Minimum =
Maximum =
Minimum =
Maximum =
Minimum =
Maximum =
Minimum =
ATMI-CRI
53
53
9.19
3.95
149
0
332
40
2275
684
464
306
23.00
23.00
40.20
6.00
Average =
Std. Dev. =
Average =
Std. Dev.
Average —
Std. Dev. =
Average =
Std. Dev. =
Average =
Std. Dev. =
Average =
Std. Dev. =
Average =
Std. Dev. =
Average =
Std. Dev. =
53
6.90
2.05
68
75
115
123
1225
909
373
82
23.00
20.25
9.77
WASTEWATER SURVEY
6 - GREIGE MILL PLUS
Maximum =
Minimum =
Maximum =
Minimum =
Maximum =
Minimum =
Maximum =
Minimum =
mg/1
2200
28
1822
295
782
342
390
46
WOVEN FABRIC
Average =
Std. Dev. =
Average =
Std. Dev. =
Average -
Std. Dev. =
Average —
Std. Dev.
FINISHING
mg/1
636
618
1266
620
519
205
232
136
E-6
-------
DISSOLVED SOLIDS
Number = 3
VOLATILE SOLIDS
Number = 3
TOTAL CHROME
Number = 4
PHENOL
Number - 1
SULFIDES
Number = 1
WATER USE (Galllb.)
Number = 15
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
= 2542
= 1513
= 749
= 700
= 8.70
= 0.02
= 0.06
- 0.06
= 0.10
= 0.10
= 76.00
= 2.50
ATMI-CRI WASTEWATER
CATEGORY 8
BOD
Number = 9
COD
Number = 9
ALKALINITY
Number = 5
SUSPENDED SOLIDS
Number = 4
DISSOLVED SOLIDS
Number = 4
VOLATILE SOLIDS
Number = 4
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
- INTEGRATED
mg/1
= 309
= 47
= 2264
= 531
= 204
= 91
= 88
= 48
= 1788
= 360
= 1099
= 176
Average -
Std. Dev. =
Average =
Std. Dev. =
Average -
Std. Dev. =
Average =
Std. Dev. =
Average -
Std. Dev. =
Average =
Std. Dev. =
SURVEY
CARPET MILL
Average -
Std. Dev.
Average -
Std. Dev. =
Average =
Std. Dev.
Average =
Std. Dev.
Average =
Std. Dev. =
Average =
Std. Dev. =
2062
518
727
25
4.54
4.81
0.06
0.10
15.74
18.60
mg/1
177
73
852
584
134
55
75
19
754
690
460
429
E-7
-------
TOTAL CHROME
Number
PHENOL
Number
WATER USE
Number
= 2
= 2
(Gal/lb.)
= 38
Maximum -
Minimum =
Maximum =
Minimum =
Maximum =
Minimum =
ATMI-CRI
CATEGORY 9 - STOCK
BOD
Number
COD
Number
DO
Number
COLOR
Number
pH
Number
= 9
= 2
= 4
= 4
= 9
Maximum —
Minimum =
Maximum =
Minimum =
Maximum =
Minimum =
Maximum =
Minimum =
Maximum =
Minimum =
0.42
0.42
0.13
0.13
17.00
1.81
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
= 0.42
= 0.13
= 7.49
= 4.67
WASTEWATER SURVEY
AND YARN
mg/1
600
73
1400
363
5.53
0
12
12
11.80
4.52
DYEING AND
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
FINISHING
mg/1
240
166
882
733
= 2.68
= 3.10
12
= 8.93
= 2.60
ALKALINITY
Number
S[/SPEJVI>EZ)
Number
DISSOL VED
Number
Q
SOLIDS
= 5
SOLIDS
= 2
Maximum =
Minimum =
Maximum -
Minimum =
Maximum =
Minimum =
2730
187
160
22
2100
1639
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
1037
= 1466
77
69
= 1869
326
FOL^T/L£SOL/DS
Number
= 2
Maximum =
Minimum =
1140
32
Average
Std. Dev.
586
783
E-8
-------
TOTAL CHROME
Number = 1
Maximum
Minimum
0.27
0.27
Average
Std. Dev.
0.27
WATER USE (Gal/lb.)
Number = 33
Maximum
Minimum
81.89
1.68
Average
Std. Dev.
22.26
17.38
ATMI-CRIWASTEWATER SURVEY
CATEGORY 10 - GREIGE MILL PLUS FINISHING YARN AND FABRICS
BOD
m
g/1
Number = 6 Maximum = 566
Minimum = 123
Average
Std. Dev.
mg/1
355
179
COD
Number = 2 Maximum - 500 Average
Minimum = 344 Std. Dev.
422
110
COLOR
Number = 2 Maximum = 692 Average
Minimum = 650 Std. Dev.
671
30
OIL
Number = 1
Maximum = 216
Minimum = 216
Average =
Std. Dev. =
216
pH
Number = 6
Maximum = 11.20 Average
Minimum = 6.50 Std. Dev.
9.69
1.76
ALKALINITY
Number - 3
SUSPENDED SOLIDS
Number = 5
Maximum = 304 Average
Minimum = 67 Std. Dev.
Maximum = 261 Average
Minimum - 20 Std. Dev.
219
132
114
98
DISSOL VED SOLIDS
Number = 2 Maximum = 1700 Average = 1489
Minimum = 1277 Std. Dev. = 299
VOLATILE SOLIDS
Number = 2 Maximum = 188
Minimum = 143
Average = 166
Std. Dev. = 32
TOTAL CHROME
Number = 2 Maximum = 1.53 Average
Minimum = 0 Std. Dev.
0.77
1.08
E-9
-------
PHENOL
Number - 1
Maximum = 0.07
Minimum = 0.07
Average =
Std. Dev. =
0.07
WATER USEfGal/lb.)
Number = 8 Maximum - 28.91
Minimum = 4.56
Average = 15.06
Std. Dev. = 7.71
ATMI-CRIWASTEWATER SURVEY
CATEGORY 11 - COMBINED MATERIALS FINISHED,
STOCK, YARN, WO YENS, KNITS
BOD
mg/1
Number = 10 Maximum = 807
Minimum = 73
Average
Std. Dev.
mg/1
381
286
COD
Number - 6 Maximum - 2149
Minimum = 310
Average = 986
Std. Dev. = 672
COLOR
Number = 4 Maximum - 7500
Minimum = 12
Average = 3013
Std. Dev. = 3175
OIL
PH
Number = 2 Maximum = 15
Minimum - 1
Number = 10 Maximum = 12.00
Minimum = 5.30
Average =
Std. Dev. =
Average =
Std. Dev. =
8
11
8.64
2.37
ALKALINITY
Number = 6 Maximum = 1315
Minimum = 11
Average - 492
Std. Dev. = 476
SUSPENDED SOLIDS
Number = 8 Maximum = 350
Minimum = 22
Average = 101
Std. Dev. = 105
DISSOLVED SOLIDS
Number = 7 Maximum = 4302
Minimum = 504
Average - 1916
Std. Dev. = 1509
VOLATILE SOLIDS
Number = 4 Maximum = 1656
Minimum = 39
Average = 552
Std. Dev. = 747
TOTAL CHROME
Number = 4 Maximum = 5.00
Minimum = 0.00
Average = 1.32
Std. Dev. = 2.45
E-10
-------
PHENOL
Number
SULFIDES
Number
WATER USE
Number
= 2
= 1
(Gal/lb.)
= 16
Maximum =
Minimum =
Maximum =
Minimum -
Maximum =
Minimum =
ATMI-CRI
0.51
0.05
0.60
0.60
69.58
12.00
Average =
Std. Dev.
Average =
Std. Dev.
Average =
Std. Dev.
0.28
0.33
0.60
—
32.32
16.61
WASTEWATER SURVEY
CATEGORY 12 - MULTIPLE OPERATION COMMISSION
BOD
Number
COD
Number
DO Number
COLOR
Number
PH
Number
= 4
= 2
— O
= 1
= 4
Maximum -
Minimum =
Maximum —
Minimum -
Maximum =
Minimum =
Maximum =
Minimum =
Maximum -
Minimum =
mg/1
277
44
904
504
10.4
5.8
115
115
11.70
6.19
Average -
Std. Dev. =
Average =
Std. Dev.
Average =
Std. Dev.
Average =
Std. Dev. =
Average =
Std. Dev.
HOUSE
mg/1
190
102
704
283
7.39
2.61
115
—
9.25
2.82
ALKALINITY
Number
= 3
Maximum =
Minimum =
873
96
Average =
Std. Dev.
476
388
SUSPENDED SOLIDS
Number
DISSOLVED
Number
= 2
SOLIDS
= 2
Maximum =
Minimum =
Maximum -
Minimum =
42
12
232
722
Average -
Std. Dev.
Average =
Std. Dev. =
27
21
1523
1133
VOLATILE SOLIDS
Number
— j
Maximum =
Minimum =
1052
1052
Average =
Std. Dev. =
1052
—
E-ll
-------
TOTAL CHROME
Number = 1
Maximum
Minimum
WATER USE (Gal/lb.)
Number = 3 Maximum
Minimum
2.13
2.13
75.00
18.00
Average
Std. Dev.
Average
Std. Dev.
2.13
42.60
19.92
ATMI-CRI WASTEWATER SURVEY
BOD
CATEGORY 13 - SPECIALIZED FINISHING
mg/1 mg/1
Number = 2
COD
Number = 1
ALKALINITY
Number = 1
SUSPENDED SOLIDS
Number = 2
DISSOLVED SOLIDS
Number = 1
VOLATILE SOLIDS
Number = 1
TOTAL CHROME
Number = 1
SUL FIDES
Number = 1
WATER USE (Gal/lb.)
Number = 2
Maximum = 362
Minimum = 182
Average - 272
Std. Dev. = 127
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
Maximum
Minimum
= 996
= 996
= 1928
= 1928
= 719
2
= 551
= 551
= 352
= 352
= 10.81
= 10.81
= 8.00
= 8.00
= 1.30
= 0.23
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
Average
Std. Dev.
= 996
= 1928
= 360
= 507
= 551
- 352
10.81
= 8.00
= 0.76
= 0.53
E-12
-------
APPENDIX F
NATIONAL COMMISSION ON WATER QUALITY SURVEY
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APPENDIX G
LIST OF TRADE ORGANIZATIONS & JOURNALS
American Association of Textile
Chemists & Colorists
P. 0. Box 12215
Research Institute Park
North Carolina 27709
(919) 549-8141
American Dye Manufacturers Institute, Inc.
74 Trinity Place
New York, New York 10006
(212) 421-9390
American Textile Manufacturers Institute, Inc.
1501 Johnston Building
Charlotte, North Carolina 28201
(704) 334-4734
Carpet & Rug Institute
P. 0. Box 2048
Dalton, Georgia 30720
(404) 278-3176
Institute of Textile Technology
P. 0. Box 391
Charlottesville, Virginia 22902
(804) 296-5511
Textile Research Institute
P. 0. Box 625
Princeton, New Jersey 08540
(609) 924-3150
Northern Textile Association
211 Congress Street
Boston, Massachusetts 02110
(617) 542-8220
TRADE JOURNALS
American Dye Stuff Reporter
America's Textiles
American Textile Reporter
Daily News Record
Modern Textiles
Textile Chemist & Colorist
Textile Industry
Textile World
G-l
*US GOVERNMENTPRINTINGOFFICE 1978—658-160
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