OPTS-TIC REPORT FILS
EPA 440/1-74/030
Development Document for
Proposed Effluent Limitations Guidelines
and New Source Performance Standards
for the
FABRICATED AND RECLAIMED
RUBBER
Segment of the
RUBBER PROCESSING
Point Source Category
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
AUGUST 1974
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DEVELOPMENT DOCUMENT
for
PROPOSED EFFLUENT LIMITATIONS GUIDELINES
and
NEW SOURCE PERFORMANCE STANDARDS
for the
FABRICATED AND RECLAIMED RUBBER SEGMENT OF THE
RUBBER PROCESSING POINT SOURCE CATEGORY
Russell E. Train
Administrator
James L. Agee
Assistant Administrator for Water and
Hazardous Materials
f
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Allen Cywin
Director, Effluent Guidelines Division
Richard J. Kinch
Project Officer
August, 1974
Effluent Guidelines Division
Office of Water and Hazardous Materials
U.S. Environmental Protection Agency
Washington, D. C. 20460
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ABSTRACT
This document presents the findings of an extensive study of the rubber
processing industry by Roy F. Weston, Inc., for the Environmental
Protection Agency, for the purpose of developing effuent limitations
guidelines, Federal standards of performance, and pretreatment standards
for the industry, to implement Sections 304, 306, and 307 of the Federal
Water Pollution Control Act, as amended (33 USC 1251, 1314, and 1316; 86
Stat 816) .
Effluent limitations guidelines contained herein set forth in the degree of
effluent reduction attainable through the application of the best
practicable control technology currently available and the degree of
effluent reduction attainable through the application of the best available
technology economically achievable, which must be achieved by existing
point sources by July 1, 1977 and July 1, 1983, respectively. The
Standards of Performance for new sources contained herein set forth the
degree of effluent reduction which is achievable through the application of
the best available demonstrated control technology, processes, operating
methods, or other alternatives.
The development of data and recommendations in the document relate to the
overall rubber processing industry which is divided into four major
segments: general molded, extruded and fabricated rubber products, wet
digester rubber reclaiming, pan (heater), mechanical and dry digestion
rubber reclaiming and latex-based products. The industry has been further
subcategorized into seven subcategories on the basis of the characteristics
of the manufacturing processes involved. Separate effluent limitations
were developed for each category on the basis of the level of raw waste
load as well as on the degree of treatment achievable by suggested model
systems. These systems include both biological and physical/chemical
treatment.
Supportive data and the rationale for development of the proposed effluent
limitations guidelines and standards of performance are contained in this
report.
iii
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CONTENTS
Section Pa£e
ABSTRACT
FIGURES
TABLES
I CONCLUSIONS 1
II RECOMMENDATIONS 3
III INTRODUCTION 7
Purpose and Authority 7
Summary of Methods Used for Development of the
Effluent Limitations Guidelines and Standards
of Performance 8
General Description of the Industry 10
Manufacture of General Molded Products 11
Compression Molding 13
Transfer Molding 16
Injection Molding 17
Manufacture of General Extruded Products 18
Sheeting and Belting 18
Manufacture of General Fabricated Products 23
Hose Production 23
Machine-Wrapped Ply Hose 26
Hand-Built Hose 27
Braided and Spiralled Hose 28
Coated Materials 30
Rubber Footwear 32
Tire Retreading 36
Reclaimed Rubber Production 37
Rubber Separation and Size Reduction 39
Depolymerization 39
Digester Process 39
Pan Process 41
Mechanical Process 42
Final Processing 42
Manufacture of General Latex-Based Products 44
Latex-Based Dipped Goods 44
Cement-Based Dipped Goods 48
Rubber Goods from Porous Molds 51
Tread 53
Latex Foam 53
Foam Backing 55
Polysulfide Rubber Production 55
Summary 55
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CONTENTS
(continued)
Section
IV INDUSTRY CATEGORIZATION
Introduction 57
Molded, Extruded, and Fabricated Rubber Products 57
Manufacturing Process 57
Product 58
Raw Materials 58
Plant Size 59
Plant Age 59
Plant Location 59
Air Pollution Control Equipment 59
Nature of Wastes Generated 60
Treatability of Waste Waters 60
Summary 60
Rubber Reclaiming 60
Manufacturing Process 60
Product 61
Raw Materials 61
Plant Size 61
Plant Age 62
Plant Location 62
Air Pollution Control Equipment 62
Nature of Wastes Generated 62
Treatability of Waste Waters 63
Summary 63
Latex-Based Products 63
Manufacturing Process 63
Product 63
Raw Materails 64
Plant Size 64
Plant Age 64
Plant Location 64
Air Pollution Control Equipment 64
Nature of Wastes Generated 64
Treatability of Waste Water 65
Summary 65
V WASTE CHARACTERIZATION 67
Subcategories E, F, and G — General Molded,
Extruded, and Fabricated Rubber Products 67
VI
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CONTENTS
(Continued)
Section
General 67
Total Effluent 67
Individual Process Streams 69
Summary 70
Subcategory H — Wet Digestion, and Subcategory I
— Pan (Heater), Mechanical, and Dry Digestion
Rubber Reclaiming Industries 72
General 72
Total Effluent 72
Individual Process Streams 75
Summary 75
Subcategories J and K — Latex-Based Products 75
General 76
Total Process Effluent 76
Individual Process Streams 76
Summary 78
VI SELECTION OF POLLUTION PARAMETERS 81
Subcategories E, F, and G — General Molded, Extruded,
and Fabricated Rubber Products 81
BOD 81
COD 82
Suspended Solids 83
Total Dissolved Solids 84
Oil and Grease 85
PH 85
Temperature 86
Lead 88
Chromium 88
Summary of Significant Pollutants 89
Subcategories H and I — Rubber Reclaim Industry 89
BOD 89
COD 90
Suspended Solids 90
Total Dissolved Solids 91
Oil and Grease 92
pH 93
Temperature 94
Zinc 95
Summary of Significant Pollutants 95
vii
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CONTENTS
(continued)
Section
Subcategories J and K — Latex-Based Products 96
BOD 96
COD 97
Suspended Solids 97
Total Dissolved Solids 98
Oil and Grease 99
pH 100
Surfactants 101
Color 101
Temperature 101
Chromium 103
Zinc 103
Summary of Significant Pollutants 104
VII CONTROL AND TREATMENT TECHNOLOGY 107
Survey of Selected Plants 107
Plant A 108
Plant B 111
Plant C 112
Plant D 114
Plant E 116
Plant F 117
Plant G 118
Plant H 119
Plant I 121
Plant J 124
Plant K 125
Plant L 127
Summary of Control and Treatment Technology 128
Subcategories E, F, and F — General Molded,
Extruded and Fabricated Rubber Products 129
In-Plant Control 129
General Spills and Leaks 129
Soapstone and Anti-Tack Dip Solutions 130
Latex Compounds 130
Solvents and Rubber Cements 130
Metal Preparation 131
Air Pollution Control Equipment 131
End-of-Pipe Treatment 131
viii
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CONTENTS
(continued)
Section
Subcategory H — Wet Digestion Rubber Reclaiming
In-Plant Control
General Spills and Leaks
Digestion Liquor and Oil Recycle
Vapor Condensates
Scrap Defibering
Alternative Reclaim Processes
End-of-Pipe Treatment
Subcategory I — Pan (Heater), Mechanical,
and Dry Digestion Rubber Reclaiming
In-Plant Control
General Spills and Leaks
Vapor Condensates
End-of-Pipe Treatment
Subcategories J and K — Latex-Based Products
In-Plant Control
General Latex Spills and Leaks
Foam Rinse Waters
Foam Cleansing Wastes
End-of-Pipe Treatment
132
132
132
132
133
133
134
134
134
134
135
135
135
136
136
136
137
137
138
VIII COST, ENERGY, AND NONWATER QUALITY ASPECTS
Subcategories E, F, and G — General Molded,
Extruded, and Fabricated Rubber Products
Treatment Cost Data
Energy Requirements
Nonwater Quality Aspects
Subcategory H — Wet Digestion Rubber Reclaiming
Treatment Cost Data
Energy Requirements
Nonwater Requirements
Nonwater Quality Aspects
Subcategory I — Pan (Heater), Mechanical,
and Dry Digestion Rubber Reclaiming
Treatment Cost Data
Energy Requirements
Nonwater Quality Aspects
Subcategories J and K — Latex-Based Products
Subcategory J
Treatment Cost Data
Energy Requirements
Nonwater Quality Aspects
141
141
147
150
151
151
153
155
155
155
156
156
158
159
159
159
159
162
162
ix
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CONTENTS
(continued)
Section
Subcategory K
Treatment Cost Data
Energy Requirements
Nonwater Quality Aspects
IX BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY
AVAILABLE - EFFLUENT LIMITATIONS 185
Subcategories E, F, and G — General Molded, Extruded,
and Fabricated Rubber Products
Identification of Best Practicable Control
Technology Currently Available (BPCTCA) 186
Effluent Loadings Attainable with the Proposed
Technology 186
Subcategory E: Small-Sized Production
Facilities 187
Subcategory F: Medium-Sized Production
Facilities 187
Subcategory G: Large-Sized Production
Facilities 188
Subcategory H — Wet Digestion Rubber Relaiming
Identification of Best Practicable Control
Technology Currently Available
Subcategory I — Pan (Heater), Mechanical, and
Dry Digestion Rubber Reclaiming 189
Identification of Best Practicable Control
Technology Currently Available
Effluent Loadings Attainable with the
-I OQ
Proposed Technology ^
Subcategories J and K — Latex-Based Products 190
Type 1 Subcategory J 19°
Type 2 Subcategory K 192
Effluent Loadings Attainable with the Proposed
Technology
Subcategory J
Subcategory K 193
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CONTENTS
(continued)
Section
X BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE -
EFFLUENT LIMITATIONS 195
Subcategories E, F, and G — General Molded,
Extruded, and Fabricated Rubber Products 195
Effluent Loading Attainable with Proposed
Technologies 195
Subcategory E 196
Subcategory F 196
Subcategory G 196
Subcategory H — Wet Digestion Rubber Reclaiming 197
Effluent Loadings Attainable with Proposed
Technologies 197
Subcategory I - Pan (Heater), Mechanical, and
Dry Digestion Rubber Reclaiming 198
Subcategories J and K — Latex-Based Products 198
Subcategory J 198
Subcategory K 199
Effluent Loading Attainable with Proposed
Technologies 200
XI NEW SOURCE PERFORMANCE STANDARDS 201
Effluent Limitations 201
Subcategories E, F, and G -- General Molded,
Extruded, and Fabricated Rubber Products 201
Subcategory H -- Wet Digestion Rubber Reclaiming 201
Subcategory I -- Pan (Heater), Mechanical, and
Dry Digestion Rubber Reclaiming 201
Subcategories J and K — Latex-Based Products 201
Pretreatment Recommendations 201
Subcategories E, F, G — General Molded,
Extruded, and Fabricated Rubber Products 202
Subcategory H — Wet Digestion Rubber Reclaiming 202
Subcategory I — Pan (Heater), Mechanical, and
Dry Digestion Rubber Reclaiming 202
Subcategories J and K — Latex-Based Products 202
XII ACKNOWLEDGEMENTS 203
XIII GENERAL BIBLIOGRAPHY 205
XIV GLOSSARY 207
XV METRIC UNITS AND CONVERSION FACTORS
xi
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FIGURES
Figure No. Title Page No.
1 Flow Diagram for the Production of a
Typical Molded Item 14
2 Flow Diagram for the Production of
Typical Extruded Items Such as Belting
and Sheeting 21
3 Flow Diagram for the Production of
Typical Hose Items (Including Re-
inforced Types) 25
k Flow Diagram for the Production of
Typical Canvas Footwear Items 34
5 Flow Diagram of Typical Mechanical, Pan
(Heater), and Wet Digester Reclaim pro-
cesses 40
6 Flow Diagram for the Production of
Typical Latex-Based Dipped Items 46
7 Flow Diagram for the Production of
Typical Cement Dipped Items 50
8 Flow Diagram for the Production of
Typical Latex Foam Items 54
9 Waste Water Recycle System for the
Wet Digester Reclaim Process 123
10 Hypothetical Waste Water Segregation
and Treatment Facility for Subcategories
E, F, G, and I 148
11 Hypothetical End-of-Pipe Secondary Waste
Water Treatment Facility for Subcategory J
Plants 160
12 Hypothetical End-of-Pipe Primary and
Secondary Waste Water Treatment Facility
for Subcategory K Plants 166
•xii
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TABLES
Table No. Title Page
1 1967 Shipments of General Molded Products
by U.S. Producers 12
2 Process-Associated Waste Water Sources
from the Production of Molded Rubber
Items 19
3 1967 Shipments of General Extruded
Products by U.S. Producers 20
4 Process-Associated Waste Water Sources
from the Production of Extruded Rubber
Products Including Rubber Hose and
Belting (SIC 3041) 22
5 1967 Shipments of General Fabricated
Products by U.S. Producers 23
6 Process-Associated Waste Water Sources
From Rubber Footwear Production 33
7 Consumption of Reclaimed Rubber by
Product 38
8 Process-Associated Waste Water Sources
from Rubber Reclaiming 43
9 1967 Shipments of General Latex-Based
Products by U.S. Producers 45
10 Process-Associated Waste Water Sources
from Latex-Based Dipped Goods Production 49
11 Process-Associated Waste Water Sources
from Cement Dipped Goods Production 52
12 Raw Waste Loads of Total Effluent from
Exemplary Subcategories E, F, and G 68
13 Raw Waste Loads of Process Effluents
from Typical Subcategories E, F, and G 71
14 Raw Waste Loads of Total Effluent from
Exemplary Subcategories H and I Processes 73
xiii
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TABLES
(Continued)
Table No. Title Page
15 Raw Waste Loads of Process Effluents from
Typical Subcategories H and I Processes 74
16 Raw Waste Loads of Process Effluents from
Exemplary Subcategories J and K Facilities 77
17 Raw Waste Loads of Process Effluents from
Typical Subcategories J and K Facilities 79
18 Waste Water Control and Treatment Technologies
at Subcategories E,F, & G Plants with Exemplary
Features 109
19 Waste Water Control and Treatment Technologies
for Subcategories H,I,J, and K plants with
Exemplary Features 110
20 Estimated Waste Water Treatment Costs at
Different Degrees of Treatment for a
Small-Sized Subcategory E Plant 143
21 Estimated Waste Water Treatment Costs at
Different Degrees of Treatment for a
Medium-Sized, Subcategory F Plant 144
22 Estimated Waste Water Treatment Costs at
Different Degrees of Treatment for a
Large-Sized Subcategory G Plant 145
23 Estimated Waste Water Treatment Costs for
Lead Treatment for Subcategories E,F, and G. 146
24 Estimated Waste Water Control Costs for a Wet
Digestion Reclaim Plant (Subcategory H) 154
25 Estimated Waste Water Treatment Costs at
Different Degrees of Treatment for a Pan,
Dry Digester, or Mechanical Reclaim Plant
(Subcategory I) 157
26 Estimated Waste Water Control Costs for a
Latex Dipped Plant (Subcategory J) 163
xiv
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TABLES
(Continued)
Table No. Title Page
27 Estimated Waste Water Treatment Costs at
Different Degrees of Treatment for a
Latex Foam Plant (Subcategory K)
28 BPCTCA and BATEA Treatment Capital
Costs for a Typical Small-Sized Molded,
Extruded or Fabricated Rubber Plant
(Subcategory E) 16S
29 BPCTCA and BATEA Treatment Capital Costs
for a Typical Medium-Sized Molded, Extruded
or Fabricated Rubber Plant (Subcategory F) 169
30 BPCTCA and BATEA Treatment Capital Costs
for a Typical Large-Sized Molded, Extruded
or Fabricated Rubber Plant (Subcategory G) 170
31 BATEA Treatment Capital Costs for a Typical
Wet Digestion Rubber Reclaiming Plant
, (Subcategory H) 171
32 BPCTCA and BATEA Treatment Capital Costs
for a Typical Plan, Dry Digester or Mechan-
ical Reclaim Plant (Subcategory I) 172
33 BPCTCA and BATEA Treatment Capital Costs
for a Typical Latex Dipping Production
Facility (Subcategory J) 173
34 BPCTCA Treatment Capital Costs for a Typical
Latex Foam Plant (Subcategory J) 174
35 BATEA Treatment Incremental Capital Costs
for a Typical Latex Foam Plant
(Subcategory K) 175
36 BPCTCA and BATEA Operating and Maintenance
Costs for a Typical Small-Sized Molded,
Extruded or Fabricated Rubber Plant
(Subcategory E) 176
xv
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TABLES
(Continued)
Table No. Title Page
37 BPCTCA and BATEA Operating and Maintenance
Costs for a Typical Medium-Sized Molded,
Extruded or Fabricated Rubber Plant
(Subcategory F) 177
38 BPCTCA and BATEA Operating and Maintenance
Costs for a Typical Large-Sized Molded,
Extruded or Fabricated Rubber Plant
(Subcategory G) 178
39 BATEA Operating and Maintenance Costs
for a Typical Wet Digestion Rubber
Reclaiming Plant (Subcategory H) 179
40 BPCTCA and BATEA Operating and Maintenance
Costs for a Typical Pan, Dry Digester or
Mechanical Reclaim Plant (Subcategory I) 18°
41 BPCTCA and BATEA Operating and Maintenance
Costs for a Typical Latex Dipping Production
(Subcategory J) 181
42 BPCTCA Operating and Maintenance Cost for
a Typical Latex Foam Production Facility
(Subcategory K) 182
43 BATEA Incremental Operating and Maintenance
Costs for a Typical Latex Foam Production
Facility (Subcategory K) 183
44 Conversion Table 213
xvi
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SECTION I
CONCLUSIONS
There are three major groupings in the fabricated and reclaimed
rubber segment of the rubber processing industry which this report
encompasses. These groupings, determined on the basis of raw
materials used or products produced, include: 1) General Molded,
Extruded, and Fabricated Products; 2) Reclaimed Rubber; and 3)
Latex-based Products.
For the purpose of establishing effluent limitations, the General
Molded, Extruded, and Fabricated Rubber Products sector has been
subcategorized by facility size, as determined by usage of raw
materials. Process waste water flow rates and loadings and costs of
control technologies substantiate this breakdown. Factors such as
manufacturing process, final product, raw materials, plant age,
geographical location, air pollution equipment, and the nature and
treatability of the waste waters are similar within each size
subcategory and further substantiate the subcategorization.
Process waste waters evolved from facilities within Subcategories E,
F, and G (small, medium, and large-sized general molded, extruded,
and fabricated rubber plants) include discharges of processing
solutions, washdown of plant areas, runoff from outdoor storage
areas, spills and leaks of organic solvents and lubricating oils,
and vulcanizer condensate. Primary pollutants (or indicators of
pollution) in these waste waters are oil and grease, suspended
solids, and acidity and/or alkalinity (pH). Lead and COD are other
pollutants of importance encountered in hose fabrication which
employs lead-sheathed or cloth-wrapped cures.
To be controlled and treated, process waste waters must be isolated
from other nonprocess waste waters such as service water discharges
and uncontaminated storm runoff. Treatment of process waste waters
in a combined process/nonprocess system is ineffective because the
relatively large volume of nonprocess waste waters dilute the
contaminated process waste waters. Segregated processing solutions
such as anti-tacking agents can be containerized. Segregated oily
process waste waters can be treated in an API-type separator.
The Reclaimed Rubber sector has been further subdivided in this
study based on the process employed. Subcategory H — Wet Digestion
Rubber Reclaiming employs a wet process; Subcategory I — Pan
(Heater), Mechanical, and Dry Digestion Rubber Reclaiming uses dry
processes. Process waste water flow rates and loadings substantiate
this categorization.
Process waste waters evolved by both Subcategory H and Subcategory I
plants include discharges of processing solutions, washdown and
runoff from all plant areas, spills and leaks of organic solvents
and lubricating oils, and discharges from wet air-pollution devices.
An additional process waste water evolved by the Wet Digestion
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process (Subcategory H) is dewatering liquor. No additional process
waste waters are evolved in the dry processes (Subcategory I).
Primary pollutants (or indicators) are COD, oil and grease,
suspended solids, and acidity and/or alkalinity (pH).
The technologies necessary to control and treat waste waters from
the Pan (heater), Dry Digestion, and Mechanical processes
(Subcategory I) are similar to those employed for the Molded,
Extruded and Fabricated Rubber industry sector. These include
isolation of process waste streams, containment of processing
solution wastes, and treatment of other process waste waters for
suspended solids and oil.
Treatment of processing waste waters from the Wet Digestion process
involves isolation and containment of processing solutions and the
recycle and reuse of oil-contaminated dewatering liquors and
discharges from wet air-pollution equipment.
The Latex-based Products industry sector, has been subcategorized
based on the process, plant size, waste water characteristics, and
treatability of the waste waters. There are two subcategories:
Subcategory J, the latex-dipped, latex-thread, and latex-molded
industry sector; and Subcategory K, the latex foam industry sector.
Process waste waters evolved from both subcategories include product
wash and rinse waters and spills, leakage, washdown, and runoff from
all plant areas. Primary pollutants (or indicators) are COD, BOD,
suspended solids, oil, and acidity and/or alkalinity (pH). In
addition, zinc is present in process waste waters evolved at latex
foam facilities. When chromic acid is used as a form-cleaning
agent, chromium will be present in the process waste waters from
latex-dipped or latex-molded facilities.
The technologies necessary to control and treat waste waters from
the production of latex-based products (Subcategory J and
Subcategory K) include segregation of process waste water streams,
coagulation and clarification of latex-laden waste waters, and
biological treatment. In addition, chemical precipitation of zinc
in rinse waters is necessary at facilities producing latex foam.
Polysulfide Synthetic Rubber (Subcategory L) is not covered in this
document. This industry sector will be examined in a future
document.
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SECTION II
RECOMMENDATIONS
Based on EPA documents, available literature, conversations with
plant personnel, and sampling data obtained at on-site plant
visitation, the following recommended limitations were developed.
Process waste waters evolved from the General Molded, Extruded, and
Fabricated Rubber Plants Subcategories should be treated and
monitored for suspended solids, oil and grease, lead, and pH.
Proposed limitations and standards for the best practicable control
technology currently available are based on raw material usage. For
plants consuming less than 3,720 kg/day (8,200 Ibs/day) of raw
materials these are:
Suspended Solids 0.64 kg/kkg (lb/1,000 Ibs) of raw material
Oil and Grease 0.16 kg/kkg (lb/1,000 Ibs) of raw material
pH 6.0 to 9.0
In addition to the above limitations, discharges attributable to
lead-sheathed hose production are subject to the following
limitation.
Lead 0.007 kg/kkg (lb/1000 Ibs) of raw material
For plants consuming between 3,720 kg/day (8,200 Ibs/day) and 10,430
kg/day (23,000 Ibs/day) of raw materials the limitations and
standards are:
Suspended Solids 0.40 kg/kkg (lb/1,OOC Ibs) of raw material
Oil and Grease 0.10 kg/kkg (lb/1,000 Ibs) of raw material
pH 6.0 to 9.0
In addition to the above limitations, discharges attributable to
lead-sheathed hose production are subject to the following
limitation.
Lead 0.007 kg/kkg (lb/1000 Ibs) of raw material
Finally, for plants using raw material at a rate greater than 10,430 kg/day
(23,000 Ibs/day) the recommended effluent standards are:
Suspended Solids 0.25 kg/kkg (lb/1,000 Ibs) of raw material
Oil and Grease 0.063 kg/kkg (lb/1,000 Ibs) of raw material
pH 6.0 to 9.0
In addition to the above limitations, discharges attributable to
lead-sheathed hose production are subject to the following
limitation.
Lead 0.007 kg/kkg (lb/1000 Ibs) of raw material
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For all three subcategories, no additional reduction is proposed for
the limitation and standards on suspended solids or oil represented
by the best available technology economically achievable (BATEA) or
for new sources coming on-stream after the guidelines are put into
effect. However, for BATEA, limitations and standards are further
restricted for lead in process waste waters. This limitation
applies only to plants producing hose by the lead-sheathed cure
process. For all three size subcategories the lead limitation for
BATEA is 0.0007 kg/kkg (lb/1,000 Ibs) of raw materials.
Process waste waters evolved from the Wet Digestion Rubber
Reclaiming industry (Subcategory H) are contaminated with BOD, COD,
suspended solids, oil and pH. Limitations and standards for BPCTCA
are as follows:
COD 6.11 kg/kkg (lb/1,000 Ibs) of product
Suspended Solids 2.31 kg/kkg (lb/1,000 Ibs) of product
Oil and Grease 0.58 kg/kkg (lb/1,000 Ibs) of product
pH 6.0 to 9.0
For Subcategory H, no additional reduction is proposed for the
limitation and standards on COD, suspended solids, or oil
represented by the best available technology economically achievable
or for new sources coming on stream after the guidelines are put
into effect. It is recognized that no reclaimed rubber sources
using the wet digestion process are likely to come on stream.
Reasonable alternatives to the Wet Digestion process are the pan,
dry digester or mechanical processes. These processes generate a
less contaminated waste water and, according to industry spokesmen,
are economically more favorable.
Process waste waters evolved from the Pan, Dry Digestion or
Mechanical Rubber Reclaiming industry (Subcategory I) should be
treated and monitored for suspended solids, oil and pH. Proposed
limitations and standards for the best practicable control
technology currently available are based on raw material usage and
are as follows:
Suspended Solids 0.192 kg/kkg (lb/1,000 Ibs) of product
Oil and Grease O.OU8 kg/kkg (lb/1,000 Ibs) of product
pH 6.0 to 9.0
No additional reduction is proposed for the limitations represented
by the best available technology economically achievable or for new
sources coming on-stream after the guidelines are put into effect.
Contaminants in the process waste waters evolved from latex-dipped,
latex-thread and latex-molding operations (Subcategory J) should be
controlled and treated for BOD, suspended solids, oil, chromium, and
pH. The proposed limitations and standards for the best practicable
control technology currently available are:
BOD 2.20 kg/kkg (lb/1,000 Ibs) of latex solids
Suspended Solids 2.90 kg/kkg (lb/1,000 Ibs) of latex solids
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Oil 0.73 kg/kkg (lb/1,000 Ibs) of latex solids
pH 6.0 to 9.0
In addition to the above limitations, discharges attributable to
chromic acid form cleaning operations are subject to the following
limitation.
Chromium 0.0036 kg/kkg (lb/1000 Ibs) of latex solids
No additional reduction is recommended for the limitations
represented by the best available technology economically achievable
or for new sources coming on-stream after the guidelines are put
into effect.
Contaminants in process waste waters evolved from latex foam
operations (Subcategory K) include BOD, suspended solids, zinc, and
pH. The proposed limitations for the best practicable control
technology currently available are as follows:
BOD 1.41 kg/kkg (lb/1,000 Ibs) of latex solids
Suspended Solids 0.94 kg/kkg (lb/1,000 Ibs) of latex solids
Zinc 0.024 kg/kkg (lb/1,000 Ibs) of latex solids
pH 6.0 to 9.0
No additional reduction is proposed for the limitations represented
by the best available technology economically achievable or for new
sources coming on-stream after the guidelines are put into effect.
As of the submittal date of this report, no limitations or standards
had been developed for the manufacture of polysulfide synthetic
rubber.
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SECTION III
INTRODUCTION
Purpose and Authority
Section 301(b) of the Act requires the achievement, by not later
than July 1, 1977r of effluent limitations for point sources (other
than publicly owned treatment works) which are based on the
application of the "best practicable control technology currently
available" as defined by the Administrator pursuant to Section
301(b) of the Act.
Section 301(b) also requires the achievement, by not later than July
1, 1983, of effluent limitations for point sources (other than
publicly owned treatment works) which are based on the application
of the "best available technology economically achievable" which
will result in reasonable further progress toward the national goal
of eliminating the discharge of all pollutants, as determined in
accordance with regulations issued by the Administrator pursuant to
Section 30U(b) of the Act.
Section 306 of the Act requires the achievement by new sources of a
Federal standard of performance providing for the control of the
discharge of pollutants that would reflect the" greatest degree of
effluent reduction which the Administrator determines to be
achievable through the application of the "best available
demonstrated control technology, processes, operating methods, or
other alternatives", including, where practicable, a standard
permitting no discharge of pollutants.
Section 304(b) of the Act requires the Administrator to publish,
within one year of enactment of the Act, regulations providing
guidelines for effluent limitations setting forth:
1. The degree of effluent reduction attainable through the ap-
plication of the best, practicable control technology
currently available.
2. The degree of effluent reduction attainable through the ap-
plication of the best control measures and practices
achievable (including treatment techniques, process and
procedure innovations, operation methods, and other
alternatives) .
The regulations proposed herein set forth effluent limitation
guidelines pursuant to Section 30U(b) of the Act for the rubber
footwear, reclaimed rubber, rubber hose and belting, miscellaneous
fabricated rubber products, rubber gaskets, rubber packing and
sealing devices, and tire retreading sector of the Rubber Processing
Industry.
-------
In brief, this document is addressed to all sectors of the Rubber
Processing Industry, with the exception of the tire and inner tube,
and the synthetic rubber subcategories.
Section 306 of the Act requires the Administrator, within one year
after a category of sources is included in a list published pursuant
to Section 306 (b) (1) (A) of the Act, to propose regulations
establishing Federal standards of performances for new sources
within such categories. The Administrator published, in the Federal
Register of January 16, 1973 (38 F.R. 1624), a list of 27 source
categories. Publication of the list constituted announcement of the
Administrator's intention of establishing, under Section 306,
standards of performance applicable to new sources within the rubber
footwear, reclaimed rubber, rubber hose and belting, miscellaneous
fabricated rubber products, rubber gaskets, rubber packing and
sealing devices, tire retreading, and polysulfide synthetic rubber
subcategories of the Rubber Processing Industry, which were included
in the list published on January 16, 1973.
The guidelines in this document identify (in terms of chemical,
physical, and biological characteristics of pollutants) the level of
pollutant reduction attainable through the application of the best
practicable control technology currently available and the best
available technology economically achievable. The guidelines also
specify factors which must be considered in identifying the
technology levels and in determining the control measures and
practices which are to be applicable within given industrial
categories or classes.
In addition to technical factors, the Act requires that a number of
other factors be considered, such as the costs or cost-benefit study
and the environmental impacts not related to water quality
(including energy requirements) resulting from the application of
such technologies.
Summary of Methods Used for Development of the Effluent Limitations
Guidelines and Standards of Performance
The effluent limitation guidelines and standards of performance
proposed herein were developed in a stepwise manner.
The development of appropriate industry categories and subcategories
and the establishment of effluent guidelines and treatment standards
require a sound understanding and knowledge of the rubber industry,
the processes involved, water use, recycle and reuse patterns,
characteristics of waste water, the respective raw waste loadings,
and the capabilities of existing control and treatment methods.
Initial categorizations and subcategorizations were based on raw
materials used, product produced, manufacturing process employed,
and other factors such as plant age. Published literature was
consulted to verify raw waste characteristics and treatabilities in
order to support the initial industry categorizations and
subcategorizations. The raw waste characteristics for each
8
-------
tentative subcategory were then fully identified. Factors con-
sidered in this analysis were: the supply and volume of water used
in the process employed; the sources of waste and waste waters in
the plant; and the constituents, including thermal effects, of all
waste waters together with those contaminants which are toxic or
result in taste, odor, and color in water or aquatic organisms. The
constituents of waste waters which should be subject to effluent
limitations guidelines and standards of performance were identified.
The full range of control and treatment technologies existing within
each subcategory was identified. This involved an identification of
each distinct control and treatment technology (including both in-
plant and end-of-pipe technologies) which are existent or capable of
being designed for each subcategory. It also included an
identification in terms of the amount of constituents (including
thermal effects), the chemical, physical, and biological
characteristics of pollutants, and the effluent level resulting from
the application of each of the treatment and control technologies.
The problems, limitations/reliability of each treatment and control
technology, and the required implementation time were also
identified to the extent possible. In addition, the environmental
impact not pertaining to water quality, such as the effects of the
application of such technologies upon other pollution problems
(including air, solid waste, noise, and radiation) was also
identified to the extent possible. The energy requirements of each
of the control and treatment technologies were identified as well as
the cost of the application of such technologies.
The information, as outlined above, was then evaluated in order to
determine what levels of technology constituted the "best
practicable control technology currently available", the "best
available technology economically achievable", and the "best
available demonstrated control technology, processes, operating
methods, or other alternatives for new sources". In identifying
such technologies, various factors were considered. These included
the total cost of application of technology in relation to the
effluent reduction benefits to be achieved from such application,
the age of equipment and the application of various types of control
technique process changes, the environmental impact aside from water
quality (including energy requirements) , and other factors.
Raw waste water characteristics and treatability data, as well as
information pertinent to treatment reliability and cost evaluations,
were obtained from several sources, including: EPA research
information, published literature, Corps of Engineers Permit to
Discharge Applications, industry historical data, and expert
industry consultation.
On-site visits and interviews were made to selected rubber
processing plants throughout the United States, to confirm and
supplement the foregoing data. All factors potentially influencing
industry subcategorizations were represented in the on-site visits.
Detailed information was obtained on production schedules and
capacities and on product breakdowns, and also on management
-------
practices for water use and for waste water control and treatment.
Flow diagrams showing water uses and process waste water stream
interactions were prepared. Control and treatment design data and
cost information were compiled. Individual, raw and treated
effluent streams were sampled and analyzed to confirm company-
furnished data in order to characterize the raw wastes and determine
the effectiveness of the control and treatment methods. Duplicate
samples were analyzed by participating companies to confirm the
analytical results.
General Description of the Industry
The segment of the Rubber Processing industry covered by this
document are as follows:
Rubber Footwear SIC 3021
Reclaimed Rubber SIC 3031
Rubber Hose and Belting SIC 3041
Miscellaneous Fabricated
Rubber Products SIC 3069
Rubber Caskets, Packing, and
Sealing Devices SIC 3293
Tire Retreading SIC 7534
With the exception of reclaimed rubber, and miscellaneous rubber
products fabricated from latex rubber, the processing operations of
the other industry sectors are based on mechanical and dry
manufacturing processes. Such processes typically are: molding,
extruding, sheeting, foaming, coating, fabrication of sections, and
vulcanization. The initial manufacturing operations involve batch
treatment of the stock to incorporate colorants, extenders,
reinforcers, and special additives such as accelerators and
antioxidants. After the batching step, the production operations
are usually continuous, semi-continuous, or batch-continuous.
Rubber reclaiming utilizes several diverse process technologies
which differ considerably from those processes used by the other
sectors of the rubber industry included in this document. The
reclaimed rubber sector as a whole uses processes which are by
nature mechanical, dry, or wet processes. Since the waste water
impacts of these process types are dissimilar as well as distinct
from those processes used in other sectors of the industry, it is
appropriate to describe and evaluate the process technologies, water
uses, and generated waste waters of the reclaiming industry
separately.
Although rubber items produced from latex rubber are included in SIC
3069, the processes employed and the nature of the waste water are
such that this type of operation warrants separate description and
evaluation. The factor justifying separate discussion is the use of
latex as a raw material. Because of this, the processing operations
are different from those used in other sectors of the industry. As
a result, there is potential to generate latex-laden waste waters
10
-------
which are distinct in their characteristics, properties, and
treatability.
The Polysulfide Synthetic Rubber industry and its manufacturing
processes will be studied in a separate guideline document for that
specific industry.
Based on the foregoing discussion, the industry sectors covered by
this document can be grouped into three (3) broad classifications
based on product and processing type:
1. Regular Rubber Products
a) General Molded Products found under SIC 3069 and
including Gaskets, Packing, and Sealing Devices (SIC 3293).
b) General Extruded Products found under SIC 3069 and
including Rubber Belting as classified under SIC 3041.
c) General Fabricated Products found under SIC 3069
including Rubber Footwear (SIC 3021) , Tire Retreading (SIC
7534), and Rubber Hose as classified under SIC 3041.
2. Reclaimed Rubber (SIC 3031).
3. General Latex-based Products found under SIC 3069.
Manufacture of General Molded Products
Rubber products made by molding processes are diverse in size, shape
and end use. Owing to the product diversity and wide distribution
of manufacturers, it is extremely difficult to determine the
magnitude of the various product types forming the broad molded
product industry in terms of either weight of rubber consumed or
weight of finished products. Table 1 presents, in a relative sense,
the most complete and up-to-date data available on the magnitude of
the various product elements within the general molded product
industry. Table 1 shows the dollar value of the 1967 shipments for
each product type.
During the molding of rubber products, the rubber is cured as it is
shaped. Curing, which is often referred to as vulcanization, is an
irreversible process during which a rubber compound, through a
change in its chemical structure (for example, crosslinking),
becomes less plastic and more resistant to swelling by organic
liquids. In addition, elastic properties are conferred, improved,
or extended over a greater range of temperature. The term
vulcanization was originally employed to denote the process of
heating rubber with sulfur, but has now been extended to include any
process with any combination of materials which will produce this
effect.
Several methods are used to mold rubber products. The selection of
a particular molding technique is dependent on the nature of the
11
-------
Product Type
Battery Parts
Miscellaneous Automotive Parts
Seals, Packing, etc.
Rubber Rolls
Rubber Heels and Soles
Druggist and Medical Supplies '
Stationery Supplies^
Small Molded Items3
Other Miscellaneous Molded Items
Value
Total
(mi 1 1 ion dol lars)
69-9
237. 8
32.8
126.1
36.7
16.3
106.6
]k6.k
917.9
1
For example, water bottles, fountain syringes, nipples, and pacifiers
•
For example, rubber bands, finger cots, and erasers.
example, rubber brushes, combs, and mouth pieces.
SOURCE: "196? Census of Manufacturers — Rubber and Miscellaneous Plastic
Products"; U. S. Department af Commerce (issued 1970).
Table 1 - 196? Shipments of General Molded Products by U.S. Producers
12
-------
product, the type of rubber, and the production economics. The
principal methods used for the manufacture of general molded
products are the compression, transfer, and injection molding
processes. In many cases compression, transfer, and injection
molding techniques are all used at one plant location.
Rubber molding processes typically consist of the following:
1. Compounding of the rubber stock.
2. Preparation of the mold preforms or blanks.
3. Molding.
4. Deflashing.
A flow diagram for a typical molding operation involving
compression, transfer, and injection molding processes is shown in
Figure 1.
Compression Molding
Compression molding is the oldest method of making molded parts.
The uncured rubber is formed to the approximate shape, referred to
as a preform, and placed in the individual cavities of the mold. As
the mold is closed under pressure, the compound conforms to the
shape of the cavity and the excess material is forced out into a
flash groove.
Larger molding facilities, or plants using special rubber compound
recipes, compound their own rubber stock from basic ingredients such
as rubber, carbon black, colorants, extender oils, antioxidants, and
accelerators. Compounding is generally carried out in either a
Banbury mixer or compounding mill. These pieces of equipment
require cooling water. Leakages of lubricating oil and grease are
common. In some plants, airborne particles generated during the
compounding operation are controlled by wet scrubbing devices.
After compounding, the rubber stock is worked on a warm-up mill and
formed to approximately the required shape ready for molding by
either a calender or extruder. The formed rubber is cooled and
generally dipped in an anti-tack agent. In many cases, the formed
rubber is cooled in an open tank which produces a cooling water
overflow. The anti-tack liquid is generally a zinc stearate
solution or its equivalent. Soapstone slurry is not normally used
because its anti-tack properties are persistent and adversely affect
the quality of the subsequent molding operation. The preforms are
prepared from the calendered or extruded stock rubber by cutting,
slicing or stamping out. Cutting can be accomplished by a machine
or by hand. Slicing is generally carried out on a meat slicing
machine or guillotine. In the case of the slicing machine,
lubricant water flows over the cutting surface to facilitate the
operation. The waste lubricant water is noncontaminated. The
preform stamping machine can be equipped with cooling water.
Although the exact shape of preform is not crucial, it is necessary
to ensure that there is sufficient rubber in the preform to fill the
mold.
13
-------
RUBBER STOCK
ORIPPAGE
LEAKAGE
KAG
NASTEWATER
RUBBER,
PIGMENTS
AND MIX
COMPOUNDS
STORAGE
MOLD PRE-FORM
COOLING AND
RINSE WATER
I
COMPOUNDING
MIXING
MILLING
AND STOCK
WEIGHING
COOLING
WATER
RUBBER STOCK
COMPRESSION
MOLDS
MOLDED PRODUCT
LEAKAGE
i
t
WASTEWATER
TRANSFER BLANK
SPILLS
LEAKAGE
WASTEWATER
COOLING AND
RINSE WATER
I
t
WASTEWATER
RUBBER STOCK
TRANSFER
MOLDS
OIL
LEAKAGE
I
I
WASTEWATER
T
EXCESS
BLANK
SOLID
WASTE
M LDED PRODUCT
I
FLASH
SOLID
WASTE
INJECTION
MOLDS
MOLDED PRODUCT
COOLING
WATER
OIL
LEAKAGE
t
WASTEWATER
— COOLING
-*WATER
PERIODIC
SOLVENT
DISPOSAL
-------
The preforms are placed in the open mold, usually by hand. In some
cases release agent powders or liquids are spread on the mold
surfaces. For small molded items, each mold generally has multiple
receptacles which enable several items to be molded simultaneously.
The mold is closed and held together, normally by hydraulic oil
pressure, during the curing cycle. The molds are generally heated
with steam flowing through cl annels in the mold plates. Steam
condensate is recycled to the boiler. Some older mold systems are
electrically heated. Oil leakage frequently occurs from the
hydraulic mold closing systems and the hydraulic pump itself. The
molding cycle can vary considerably depending on the curing prop-
erties of the rubber and the size of the molded item. At the
conclusion of the molding cycle, the items are removed from the mold
and sent to the deflashing operation.
The rubber overflow or flash must be removed from the part before it
is shipped. Deflashing usually is carried out by hand, grinding
wheel, or press-operated dies. In some cases, the rubber parts are
tumbled in dry ice (solid carbon dioxide) using machines that are
similar to cement mixers. The thin rubber flash becomes brittle
while the main body of the part is not cooled sufficiently and
remains flexible. The thinner frozen flash thus breaks off in
tumbling while the heavier main part is not harmed. Blasting frozen
rubber parts with fine shot also removes flash. Rubbers which are
freeze-resistant are not used in this dry-ice process.
Metal-bonded items, which consist of a molded rubber component
bonded to the metal part, are manufactured in a manner similar to
that for all rubber products. In most cases the metal parts enter
the molding plant contaminated by grease. The grease is picked up
during the manufacture of the metal part or is applied for shipping
and storage purposes.
The metal part is first degreased. Usually the degreasing system
consists of a rotating drum in which the part is brought in contact
with a suitable degreasing solvent, frequently trichloroethylene.
The solvent is drummed and hauled from the plant when saturated with
grease. In a few cases the metal part is pickled to prepare the
surface for bonding with rubber. The waste acid pickling liquor
contains metal ions, and frequently heavy metal ions, and requires
containerization or treatment before it is discharged.
In some molding plants, poor quality molded items are recycled to
reclaim the metal component for re-use. This is generally practiced
in cases where the metal part is large or valuable, or where the
molding operation is particularly difficult, producing a high
proportion of rejected molded items. To reclaim the metal, the
reject rubber is ground and buffed from the metal; the metal item is
then sand-blasted clean. The grinding and buffing operations
generally create airborne rubber-buffing particles, which are most
effectively removed from the air with wet scrubbing devices. These
devices produce a wastewater discharge which, if a water recycle
system is used, can be reduced to a low daily volume.
15
-------
The metal surface to which the rubber is to be molded is normally
prepared to provide good adhesion between the metal and the rubber.
The mating surface of the metal part is first sand blasted to
roughen it and then coated with rubber cement to improve the
adhesion of metal to rubber. The metal surface is painted with
cement by hand for small items; larger metal surfaces are often
sprayed with cement.
The prepared metal part and its mating rubber component are placed
in the mold cavity and molded in a similar manner to an all-rubber
product. Deflashing is generally carried out by hand or with a
grinding wheel. One of the disadvantages of compression moldings is
that the flash tends to be largest at the thick side of the molded
item, making removal by tumbling difficult or impossible. The cost
of preparing individual preforms and the placing of each in the mold
cavity is another disadvantage of compression molding.
Transfer Molding
Transfer molding involves the transfer of the uncured rubber stock
from one part of the mold to another. The stock, in the form of
blanks, is placed in a recess called the pot or transfer cavity.
The pot is fitted with a ram or piston which is inserted over the
stock. The force of the press when applied to the ram plus the heat
from the mold causes the stock to be softened and flow through
runners into the previously empty molding cavities, where the stock
is cured in the desired form.
The rubber for transfer molding is compounded in the same way as for
compression molding. The rubber stock blanks, which are fed into
the transfer pot of the mold, are generally cut from extruded or
sheeted-out rubber stock and take the form of slabs. Frequently,
the weight of the rubber blank is brought within a certain weight
tolerance by trimming overweight blanks. Underweight blanks and the
trimmings are recycled to the sheet-out mill. The weight of the
blank is regulated to ensure that sufficient rubber is available in
the transfer pot to fill the mold cavities.
Transfer molds are normally heated by steam and are operated by
hydraulic oil systems similar to compression mold hydraulic systems.
Oil leaks and spillages are frequent. Curing times in the mold are
similar to those of compression molds and likewise are based on
product dimension and rubber stock properties.
When the mold is opened the item is pulled or cut from the runners.
The runners and the residual rubber in the transfer pots are
discarded as waste. The molded item is deflashed by methods similar
to those described above for compression molded products.
Articles containing metal inserts are generally manufactured by
transfer molding and the overall processes are very comparable to
those used in compression molding including the preparation of the
metal component.
16
-------
Transfer molding permits closer dimensional control and generally
reduces flash so that the parts can be easily finished. Complex
shapes can be readily manufactured by this method. Small parts can
be made more economically by this technique because of the labor
cost savings on preforms and finishing. The disadvantages of this
method are that the formulations and control of stocks are much more
critical than with compression molds. Stocks must flow well and
knit properly, and still cure relatively fast. As explained above,
the small amount of compound remaining in the transfer pot, as well
as the material in the runners, is wasted. Therefore, this molding
method requires careful cost calculations for scrap loss when making
items requiring premium priced polymers such as the fluororubbers,
silicones, and polyacrylates.
Transfer molds are more expensive and in general require more
maintenance than compression molds.
Injection Molding
Injection molding is the newest method of molding and requires the
greatest degree of sophistication both from the standpoint of
materials and mold design. Basically, it is the same as transfer
molding with the exception that the stock is injected into the
cavities. There are essentially three different types of injection*
molding machines. One machine uses a ram to force the stock through
runners into the cavities; another uses a screw; the third is a
combination of the first two and is a reciprocating screw. From the
point of view of water use, there is little difference between the
three types of machines. All require cooling water. In some cases
the injection molding machines are equipped with their own closed-
loop cooling systems.
The molds are often mounted on a revolving turret which takes the
molds through a cyclic process. If required, the mold surfaces are
treated with release agents followed by closing the mold before
injection. Rubber is then injected into the closed mold after which
the mold is opened and the molded item removed.
Deflashing of the molded item can be carried out by either hand or
machine techniques similar to those methods used for the deflashing
of compression and transfer molded products.
In order to make injection molding profitable, very short cycles are
required which are generally in the 45-90 second range. This
requires curing temperatures of approximating UOO°F. Parts must be
readily removed from the molds to keep the heat loss and cycle time
to a minimum.
All the advantages mentioned for transfer molding apply to injection
molding. Efficiency is greatest for a large volume of small items
with relatively thin walls and of complicated shape.
17
-------
Table 2 presents a review of potential process-associated waste
water streams produced in the manufacture of molded items as
described in the foregoing text.
Manufacture of General Extruded Products
As described above, rubber extrusion is used to prepare the preforms
and blanks used in compression and transfer molding processes. The
extrusion operation is a minor element of the overall production
process for molded items. Rubber extrusion, however, plays a more
significant role in the manufacture of such items as rubber belting
and sheeting.
The types of extruded product are varied and the distribution of
manufacturers is wide. Because of this, it is extremely difficult
to compile complete data on the size of the extruded rubber products
industry sector in terms of weight of products or raw material
usage. Table 3 gives an indication of the relative magnitude of the
various types of extruded rubber products in terms of the 1967
dollar value of the shipments of those products.
Extruded rubber products can be grouped into two principal classes
based on the nature of the manufacturing process. The simpler
manufacture, such as sheeting production, involves essentially
compounding, extrusion, and curing. On the other hand, items such
as belting require a more involved manufacture consisting of all the
above processes plus building. However, the building operation, as
used in belting manufacture is a relatively straight forward process
with little waste water impact. Therefore the manufacturing
processes used to produce rubber sheeting and belting will be
described concurrently.
Sheeting and Belting
The majority of the processes used to manufacture sheeting and
belting are very similar and serve as good examples of the
production methods used to manufacture extruded items. A flow
diagram for a typical extrusion production facility is presented in
Figure 2; Table 4 presents the sources of waste water from extrusion
facilities.
The rubber stock is compounded from the basic ingredients on a
compounding mill or Banbury mixer. These pieces of machinery
require cooling water. Leakage of lubricating oil and grease can
occur. Wet scrubbers are sometimes used to control air pollution by
airborne particles produced in the mixing area. In some cases the
rubber is sheeted out on a sheeting mill and dipped in soapstone
slurry. Soapstone leakage can occur in this area.
After compounding, the rubber is worked on a warm-up mill and fed to
the extruder. The extruded rubber is produced as a sheet. In cases
where the dimensions of the extruded rubber sheet is critical, the
extruded rubber is calendered to the desired thickness. The
extruded or calendered rubber is cooled in a cooling tank before
18
-------
Plant Unit or Area
Sou rce
Nature and Origin of Waste Water
Contaminants
Oil Storage
Compounding
Spi1 Is and leaks
Washdown, spills, leaks and
discharges from wet air
pollution control equipment
Oil pick-up by storm run-off
Solids from soapstone dip tank
Oil and water leaks from mixers and mills
Solids from wet air pollution control
equipment discharges
Blank and Pre-form Extrusion
and Preparation
Rinse waters, spills and
leakages
Rubber fines in lubricant and rinse water,
anti-tack agent in cooling tank overflow
oil from machinery
Curing
Spi1 Is and leaks
Oil from hydraulically operated curing
presses
Table 2 - Process-Associated Waste Water Sources from the Production of Molded Rubber Items
-------
Product Type Value
(mi 11 ion dol lars)
Belting — conveyor and elevator 88.2
Belting — flat transmission 13.3
Sheeting — mats, matting, stair treads 17.9
Sheeting — floor and wall covering 16.1
Total 135.5
Does not include V-belt type belting.
SOURCE: " 1967 Census of Manufacturers — Rubber and Miscellaneous
Plastic Products"; U. S. Department of Commerce (issued 1970).
Table 3 - 1967 Shipments of General Extruded Products by U.S. Producers
20
-------
WIRE
STORAGE
•
RUBBER, RUBBER )
CARBON BLACK 0RY COM!
COMPOUNDS
STORAGE
FABRIC FA
STORAGE
WIRE REINFORCEMENT
SOAPSTONE
SOLUTION
DRIPPAGE
LEAKAGE
HASTEWATER
\Hn 1
\
' (Mlrr-r
t
'OUNOS ^ COMPOUNDING RUBBER STOCK FORMATION
* MIXING, " » EXTRUSION
MILLING CALENDERS
T i
COOLING
HATER ~« '
CJ
CD
t—
a:
UJ
aa
CO
0=
i
SPILLS rnniiur
LEAKAGE COOLING
L , WATER
i OVERFLOW
WASTEWATER I
WASTEWATER
(
t
FABRIC
WC _ CALENDERING COATED FABRIC
9 OR
FRICTIONING
1
1
COOLING 1 LEAKAGE
WATER "
WASTEhATER
CURED
* BELT ., -k nnTiri.nr _,.._* ^ BELTING
* FORMATION ^ Lnrco PRODUCT FOR
JG 3
»
EXTRUDED
1 i INSPECTION
f. SHIPMENT
C3
oc
CJ
Of
o
-------
Plant Unit or Area
Oil Storage
Compounding
Source
Extrusion
Calendering
Curing
2
Testing
Spi1 Is and leaks
Washdown, spills, leaks, and discharges
from wet air pollution control equipment
Cooling waters, spoils, and leakages
Spi11s and leaks
Condensate
Spi1 Is and leaks
Nature and Origin of
Waste Water Contaminants
Oil pick-up by storm run-off.
Solids from soapstone dip tank.
Oil and water leaks from mixers
and mills. Solids from wet air
pollution control equipment dis-
charges.
Anti-tack agent in cooling tank
overflows, oil from machinery.
Solids from soapstone dip tank.
Oil and water leaks from mixers
and mills.
Organics and lead leached by
steam vulcanizer condensate.
Oil pick-up hydraulic testing
water.
1
Waste waters generated by curing operations are essentially limited to hose manufacture.
Testing waters are used only in hose manufacture.
Table k: Process-Associated Waste Water Sources from the Production of Extruded Rubber Products
Including Rubber Hose and Belting (SIC 30^1)
-------
storage for further processing. In some cases the extruded or
calendered rubber is dipped in soapstone slurry for storage.
Belting is manufactured by extruding the rubber onto the wire
reinforcement in the extruder, or calendering the rubber sheeting
onto reinforcement fabric that has been frictioned with rubber.
Calenders require cooling water. Oil and grease leakage can be
produced by the calendering machinery.
Belting or extruded and calendered sheeting is cured using a
rotacure or press curing technique. A rotacure is an air heated
drum. The sheeting and belting pass around the rotating drum and
are cured. The press curing technique consists of two heated belts
which hold the rubber belting or sheeting between them under
pressure to facilitate the curing process. The heated belts turn
and drag the sheeting or belting through the press. Cured belting
or sheeting is inspected, cut to length, and stored before shipment.
In some plants a certain amount of the sheeting is shipped in an
uncured state for use in the manufacture of tank linings and other
large rubber items. Such sheeting is supplied from the extrusion or
calendering line before the belting-formation or curing operations.
Manufacture of General Fabricated Products
The types of products and processes covered by this manufacturing
description are varied. It can be said that this industry sector is
a catch-all for manufacturing types not included in the molded or
extruded product groups. Processes employed in this industry sector
are compounding, milling, fabrication, molding, and vulcanization.
Due to the diversity of the product types and the wide distribution
of plants included in this manufacturing group, it is difficult to
estimate the magnitude of this sector of the industry in terms of
rubber usage or product weight. Table 5 does show the relative
magnitude of the various product types which constitute this sector,
in terms of the dollar value of the total 1967 U.S. shipments. Hose
production provides a good example of rubber building or fabricated
manufacturing processes. It can be seen from Table 5 that hose
products constitute a major portion of the shipment value of
extruded rubber products. Figure 3 illustrates the production steps
of typical hose items.
Rubber hose generally consists of three components. They are the
tube (lining), the reinforcement, and the outer cover.
The tube is the innermost rubber element. Some hose, such as a
vacuum cleaner hose, does not have an inner lining or tube inside
the reinforcement (usually a wire spiral). The primary function of
the tube is to retain the transported material. The type and
thickness of rubber used depends upon the intended service of the
hose and the type of hose fitting or connecting device to be used.
23
-------
Product Type Value
(million dollars)
Rubber Hose 398.8
Canvas Footwear 276.1
Waterproof Footwear1 75-3
Other Rubber Footwear 1^.2
Friction Tape 19-0
Fuel Tanks 21.5
Boats, pontoons, and life rafts 15.0
Rubber coated fabrics 15-5
Rubber Clothing 10.7
Total 8U6.1
•"•Includes items manufactured by cement dipping.
Source: "196? Census of Manufacturers — Rubber and Miscellaneous
Plastic Products"; U. S. Department of Commerce
(issued 1970).
Table 5 - 1967 Shipments of General Fabricated Products by U.S.
Producers
24
-------
SOAPSTONE
SOLUTION
DRIPPING
LEAKAGE
WASTEWATER
STRIPPED LEAD FOR RECYCLE
COMPOUNDING
MIXING
MILLING
to
Ui
COOLING
MATER
DRIPPING
LEAKAGE
I
WASTERWATER
WIRE AND
YARN
REINFORCEMENT
STORAGE
FROM
SHEATH AND
WRAP REMOVAL
LU
V)
\
UJ
oe
oe
o
U-
MANDRALS
— •
MANDREL
REMOVAL
TUBE
EXTRUSION
I MANDREL
INSERTION
COOLING
WATER
OVERFLOW
WASTEWATER
HOSE
REINFORCING
COVER
EXTRUDER
CLOTh TAPES FOR RE-USE
LEAD
SHEATHING
OR CLOTH
WRAPPING
COOLING
WATER
OVERFLOW
+
WASTEWATER
I
I
LEAD SHEATH
COOLING WATER
I
WASTEWATER
TO
MANDREL
REMOVAL
STEAM CONOENSATE
I
I
+
WASTEWATER
! J
[ 1
HYDRAULICL
TESTING f
I
TEST
WATER
WAbTERWATER
INSPECTION,
BRANDING,
STORAGE
i, SHIPMENT
FIGURE 3: FLOW DIAGRAM FOR THE PRODUCTION OF TYPICAL HOSE ITEMS (INCLUDING REINFORCED TYPES)
-------
The reinforcement is the fabric, cord, or metal elements built into
the body of the hose to withstand internal pressure or external
forces. The type of reinforcing material depends upon the method of
manufacture and the service conditions. The rubber used to bond
together the individual elements of the reinforcing material is
considered a part of the hose reinforcement.
The cover is the outermost element. It is normally made of rubber
and its prime function is to protect the reinforcement from outside
damage or abuse.
While most hose is used for pressure service, there are many
applications where an essential property of the hose is its
resistance to collapse under suction and vacuum service. The usual
method of preventing hose carcass collapse is to build a metal
reinforcement, generally a steel wire spiralled in the form of a
helix, into the body of the hose.
Hose manufacture can be classified according to the manner in which
the hose is produced. Such factors as service, size, production
volume, and cost usually determine the method by which the hose is
made. The greatest proportion of all hose manufactured today is
produced by highly mechanized equipment specially designed for the
purpose. Three fundamental methods of hose manufacture exist,
producing the following types of hose:
1. Machine-wrapped ply hose.
2. Hand built hose.
3. Braided and spiralled hose.
Machine-Wrapped Ply Hose
Wrapped hose consists of a fabric reinforcement wrapped around a
rubber tube over which is applied a protective rubber cover.
Wrapped hose has been manufactured for approximately 120 years; it
was made at first by hand and later by machine. This type of hose
is most commonly made in lengths approximating 50 meters (150 feet)
and inside diameters (bore) ranging from 5 to 75 millimeters (0.2 to
3 inches).
A seamless rubber tube is formed to the desired diameter and wall
thickness by a continuous extrusion process. The tube is then
mounted on a rod-like form, termed a mandrel, for the hose making
operations using air pressure to enlarge the tube temporarily.
Lubricants are generally injected into the tube as it is being
formed to prevent the inner surface from sticking to itself, and
later in the process to keep the tube from adhering to the mandrel.
The fabric used for reinforcing the hose is received from the
textile mill in large rolls. The roll of fabric is impregnated with
rubber on both sides in a calendering machine. This process is
referred to as frictioning. The frictioned fabric is generally cut
on the bias and is cemented together with overlapped seams to form a
long strip just wide enough to produce the required number of plies
26
-------
plus an overlap when wrapped around the tube. The hose cover is
prepared by working a thin sheet of rubber to the required thickness
on a rubber calender. The calendered cover stock is cut to a width
which will wrap around the hose carcass with a slight overlap.
The actual making of the hose is done on a special purpose machine
known as a "making-machine". The machine consists of three long
steel rolls; two of the rolls are in a fixed parallel position in
the same horizontal plane. The third or top roll is mounted on
lever arms so that it can be raised and lowered. One or more of the
rolls is power driven. The mandrel-supported tube is placed in the
trough formed by the two bottom rolls of the making machine. One
lengthwise edge of the cut fabric is adhered to the tube. The
pressure exerted by the top roll when it is brought down in contact
with the tube forces the tube and mandrel to rotate as the machine
rolls rotate. The fabric is drawn into the machine and wrapped
around the tube as the tube rotates. The pressure from the top roll
helps to form a compact carcass. The machine operation is repeated
for the application of the sheet of cover stock around the hose
carcass.
Wrapped ply hose must be kept .nder pressure during vulcanization to
produce a solid, homogeneous construction. The necessary pressure
is obtained by means of cotton or nylon wraps.
The wrapped hose is loaded into an open steam autoclave and is
vulcanized under controlled conditions of temperature, pressure, and
time. The steam condensate is discharged to the plant drains during
the vulcanization cycle. The condensate can pick up organic
constituents from the hose surface. The autoclave is vented and the
hose removed. The cloth wrap is stripped from the vulcanized hose
after cooling. The final operation is the removal of the hose from
the mandrel, which is accomplished with the aid of compressed air,
or water under pressure, injected at one end between the hose tube
and mandrel. In cases where pressurized water is used, the spent
water is discharged. The water is uncontaminated and could be
recycled.
Hand-Built Hose
The term hand-built hose applies to two general types of hose, non-
wire reinforced and wire reinforced, which are made by hand on a
steel mandrel. The hose is made by hand when it is too large in
diameter, too long to fit in the three-roll making-machine, or when
the hose is made with special ends. The hand method is also used
frequently when the fabric reinforcement must be applied one ply at
a time. The mandrel is mounted on a series of double roller stands,
and one end of the mandrel is held in the jaws of a power-driven
chuck in order to rotate the mandrel during the making operations.
The tube for hose up to 100 millimeters (4 inches) inside diameter
is usually extruded and mounted on a mandrel by methods already
described under machine-made hose. The tube for larger hose is
27
-------
formed by wrapping calendered tube stock around the mandrel with an
overlapping seam running the length of the tube.
Non-wire reinforced hand-built hose is made of the same components
as machine-wrapped ply hose; i.e., a rubber tube, plies of fabric
reinforcement wrapped around the tube, and a rubber cover.
The frictioned and cut fabric is applied to the tube by hand and
rolled down progressively as the mandrel is turned.
A calendered sheet of cover stock is applied to the carcass to
complete the construction of the hose. The hose is cross-wrapped
with one or more layers of nylon or cotton tape using a power chuck
before vulcanization in an open steam autoclave. The wrapping tape
is removed after vulcanization and the mandrel is withdrawn from the
hose.
Wire reinforced hand-built hose, as the name indicates, has wire
added to the reinforcement component of the construction. The wire
may be present to prevent the hose from collapsing in suction
service, to prevent kinking of pressure hose which must be curved in
a small radius loop, or to obtain the strength necessary for high
pressure service.
The wire in suction hose is located underneath the main plies of
fabric reinforcement to provide rib support against the external
pressure. Hose designed for a combination of suction and pressure
is made with the wire placed approximately midway in the plies of
the fabric. In pressure hose, the wire is positioned over the main
plies of fabric to provide hoop strength against high internal
pressure. The wire is present in most wire reinforced hose in the
form of a closely spaced helix or spring which opposes inward or
outward radial stresses but does not add any significant strength to
the hose in the axial direction. When high strength is needed in
both axial and radial directions, the hose is built with two or more
even numbers of layers of wire. Each layer is composed of many
strands of solid round wire or wire cable applied over the fabric
reinforcement. The wire lays on the hose in a spiral forming an
angle greater than 45° with the axis of the hose. The direction of
the wire spiral is reversed with each layer of wire for balanced
strength. The wire is applied to the hose by hand or by a simple
machine using a power-driven chuck to rotate the mandrel and hose.
In all other operations, wire reinforced hand-*built hose is made in
the same manner as non-wire reinforced hand-built hose.
Braided and Spiralled Hose
The term braided hose identifies a type of hose construction and
method of manufacture in which the strands of reinforcement are
interlaced or interwoven in addition to spiralling around the tube.
Braided hose is produced in size ranging from 5 to 200 millimeters
(0.2 to 8 inches) internal diameter. A variety of methods is
available for manufacture. Factors such as internal diameter,
28
-------
length, burst strength, production rate, and cost dictate to a large
extent how the hose is made.
Manufacturing commences with the extrusion of a tube supported on a
flexible mandrel or a non-supported tube in lengths up to 50 meters
(165 feet) or in continuous lengths. Non-supported tube must be
firm enough in the unvulcanized state to resist deformation and
stretching under normal processing conditions. A high percentage of
braided hose is made with a non-supported tube. When the tube is
too thin or too soft to withstand subsequent processing or when the
internal diameter must be kept within a narrow range, it is
supported on a flexible mandrel. The mandrel is at least as long as
the hose to be made, has a round cross-section, and can be coiled in
a small diameter. It is made of rubber or plastic material and may
have a wire core to prevent stretching.
The tube, stored on a circular tray or a reel after extrusion, is
moved to the braider where the reinforcement is applied. The tube
is drawn through the center of the machine while the braid is
forming on the tube surface. The braid formation is brought about
by yarn or wire carriers weaving in and out on a circular track not
unlike the movements and result of the Maypole dance. The speed of
the carriers on the circular track is kept at maximum. The braid
angle can be adjusted by changing the surface speed of the overhead
take-off drum or capstan.
After the hose has been braided, it is normally passed through a
cross-head extruder, where an outer seamless rubber cover is
applied. At this stage, the hose is still in the long length either
coiled on a circular tray or wound on a reel, and consists of an
unconsolidated construction of a tube, braid or braids, and a cover.
The final production operation in hose manufacture is vulcanization.
The lead sheath process is so eminently suited for the vulcanization
of braided hose that only insignificant quantities are vulcanized by
any other method. The lead casing may be formed by means of a lead
press or a lead extruder. (The lead press deforms solid lead into a
continuous sheath whereas the lead extruder forms molten lead into a
continuous casing.) In both techniques, the casing or sheath is
actually formed around the hose as it passes through the press or
extruder. In the case of non-supported hose, the lead-sheathed hose
is filled with water under pressure, wound on reels, and loaded into
an open steam pressure vessel. The internal pressure is maintained
during the vulcanization cycle to force the hose against the lead
casing. The water is drained from the hose after vulcanization and
the lead casing is stripped from the hose. The lead goes back to a
melting pot and is reused.
In the case of supported tube hose, the application of the lead
sheath squeezes the flexible hose down on the mandrel and places the
hose under slight initial pressure. However, most of the internal
pressure comes from the hose's trying to expand as the temperature
is increased during vulcanization yet it is closely confined between
the lead casing and the flexible mandrel. After vulcanization, the
29
-------
lead casing is removed in the same manner as for unsupported hose.
One end of the hose is connected to a high pressure hydraulic system
and the flexible mandrel is forced out of the hose. Braided hose
can also be vulcanized in steel molds which are constructed in two
sections. The unvulcanized hose is laid in the bottom half of the
cavity and the mold closed. The mold is steam heated and the hose
is subjected to internal air pressure causing it to expand, forcing
it against the inside wall of the mold.
A third method of vulcanizing braided hose, which is only used on a
very limited scale, is known as non-mold cure. The hose, coiled one
or two layers deep on a metal pan, is exposed to open steam under
pressure in an autoclave.
The term spiralled hose describes how the reinforcement in the form
of strands of yarn or wire is applied by machine with the strands
drawn from supply spools or packages. This type of hose has all of
the wire or textile strands of each reinforcement layer aligned in
one direction and parallel to each other. In other words, the
clockwise strands are not interwoven with the counter-clockwise
strands. At least two layers of reinforcement are required with the
layers spiralled in alternating directions to form a balanced
construction.
The reaction of spiralled hose constructions to internal pressure is
exactly the same as that of braided hose. The relative simplicity
of both wire and yarn spiralling machines with the carriers fixed on
a rotating plate makes it possible to run at higher speeds with a
corresponding increase in the rate of production compared to braided
hose.
Spiralled hose is not manufactured in as broad a size range as
braided hose. Spiralled hose internal diameters generally range
from 5 to 50 millimeters (0.2 to 2 inches).
The processing equipment used in the operations performed before and
after the application of the reinforcement are the same as those de-
scribed above for braided hose.
The hose is generally vulcanized by the lead sheathing method. In
some cases, the non-mold or the steel-mold vulcanization techniques
are used. In addition, hose on rigid mandrels can also be wrapped
with a curing tape and vulcanized in an open steam pressure vessel.
Coated Materials
Materials coated with rubber compounds are generally an essential
ingredient in the manufacture of fabricated products. Many plants,
starting with a rubber compounding operation, coat the fabric
material and ship the coated fabric to another plant where it is
fabricated into the finished article. Other plants, however, have
an integrated facility where the rubber stock is compounded, the
fabric is coated, and finally the article is built and vulcanized;
all in the one plant.
30
-------
Rubber coated materials generally consist of woven or nonwoven
fabrics to which a rubber compound or composition has been applied
either by impregnation of the fabric or by application to one or
both sides. Synthetic rubber materials such as acrylic rubber,
butadiene-acrylonitrile, butadiene-styrene, chloroprene,
chlorosulphonated polyethylene, fluorinated polymeric compositions,
polyisobutylene, polysulfide and silicone polymers are used where
particular physical properties such as water and solvent resistance,
gas impermeability, flame resistance, surface-release charac-
teristics, abrasion resistance, and good aging properties are
required.
Rubber-coated fabrics are generally used for industrial applications
where their characteristic odor and color limitations are not
objectionable. Such products are frequently specified for usage
requiring low-temperature flexibility. Typical uses for rubber-
coated textiles include service raincoats, ballon bags, diaphragms,
gaskets, inflatable life rafts, pontoons, etc. Rubber coatings are
generally applied by calendering techniques.
Rubber-coated cotton sheeting is used to produce friction tape,
raincoats, gasketing, and diaphragms. Rubberized knit cotton fabric
is used to manufacture rubber overshoes, boots, and diaphragms.
Rubber-coated duck and canvas is fabricated into pontoons,
lifeboats, and tarpaulins. The origin of coated fabrics has been
traced to the application of preservative resins on Egyptian mummy
wrappings. More recent use of coated fabrics during the early
nineteenth century evolved from the linseed oilcoated fabrics
(oilskins) used by seafarers and the rubber-coated protective
garments developed by Charles Macintosh, still known as macintoshes.
These early products were accompanied by objectionable odors and
poor aging properties resulting either in tackiness or in
embrittlement. Improvement in rubber coatings followed Goodyear*s
discovery of the vulcanization technique in 1839.
In early usage of coated fabrics, the base material was required to
give strength and tear resistance to the finished product. In such
constructions heavy cotton sheetings, drill weaves, sateens, broken
twills, and canvas were required to give proper service. The fabric
is often treated before coating. Fabric treatments can include
desizing to produce pliability, surface shearing or brushing to
remove knots and flaws, dyeing to match the coating, matting to
improve softness or coating adhesion, and flame proofing.
Most recent constructions of coated fabrics employ knitted textiles
or non-woven textile webs to achieve maximum softness and tear
resistance. These fabrics depend on the toughness of the coating to
furnish abrasion resistance and long service life. The use of very
lightweight and very strong synthetic fiber fabrics has permitted
design of lightweight air-holding products for inflated structures
and similar uses. Saturated nonwoven cotton textiles have found
extensive applications as garment linings and interfacings.
31
-------
Before the coating process, the rubber stock is compounded from
basic rubber ingredients such as rubber crumb, extenders, pigments,
accelerators, and anti-oxidants. The waste waters arising in a
typical compounding area result from leaks and spillage and the
principal contaminants are oil and grease, and suspended solids.
The fabric to be coated is received from the textile mill either
already dipped in latex or the dipping can be carried out in the
rubber coating plant. If a fabric dipping operation is employed,
latex spillage and washdown are potential waste water sources.
Rubber coating is performed in either three or four-roll calenders.
The compounded rubber stock is generally prepared for the calender
on a warmup mill. The three-roll calender applies the coat to one
side of the fabric and the four-roll calenders coat both sides of
the fabric. The top roll of the three*roll calender or the bottom
and offset rolls of the four-roll calender are run at a different
speed to the center roll, usually two-thirds as fast, to friction
the rubber coating onto the fabric.
Rubber coated fabrics need to be cured at elevated temperatures for
periods of time varying from ten minutes to several hours. The
curing ovens can be 30 feet high and hundreds of feet long, or 6-8
feet in height and 8-20 feet in length for products requiring a
shorter curing cycle. The principal requirement for the ovens is
that of uniform temperature distribution to obtain uniform product
quality. After curing the coated fabric is cooled and rolled.
Fabricated products such as rainwear, rafts and pontoons are built
using dies or jigs to cut the coated material and rubber cements to
join the various sections. In general the building areas are dry
and no waste waters should arise. In the event of a spillage of
rubber cement, the spill or leak would most effectively be wiped
away.
The types and characteristics of waste waters produced by a rubber
coating or fabrication manufacturing facility are similar to those
of a rubber footwear facility and are presented in Table 6.
Rubber Footwear
It can be seen from Table 5 that the rubber footwear industry (SIC
3021) is the second largest subsector of the general fabricated
products group and that within this subsector canvas footwear
constitutes the major product type.
The process description presented below pertains to canvas shoe
production which utilizes all the major processing technologies
commonly found in the manufacture of general fabricated products. A
schematic flow diagram for a typical canvas shoe production facility
is shown in Figure 4.
The various rubber stocks consumed in a canvas shoe plant are
compounded in Banbury mixers or compounding roll mills and then
32
-------
Plant Unit or Area
Source
Nature and Origin of Waste Water
Contaminants
Oil Storage
Latex Storage
Spi11s and leaks
Spills, leakage, washdown,
and cleanout waters
Oil pick-up by storm run-off.
Dissolved organics, suspended and dissolved
sol ids.
U)
Compounding
Pre-form Extrusion
and Preparation
Washdown, spills, leaks and
discharges from wet air
pollution control equipment
Rinse waters, spills and
leaks
Solids from soapstone dip tank. Oil and
water leaks from mixers and mills. Solids
from wet air pollution control equipment
di scharges.
Rubber fines in lubricant and rinse water
anti-tack agents in cooling tank over-
flows, oil from machinery.
Ply Formation
Spills, leaks and washdown
Dissolved organics, suspended and dissolved
soli ds.
Shoe BuiIding
Spills, leaks and washdown
Dissolved organics, suspended and dissolved
sol ids.
Curing
Discharges from ai r
pollution equipment
Ammonia used in curing.
Table 6 - Process-Associated Waste Water Sources from Rubber Footwear Production
-------
RUBBER STOCK
10
COOLING
SATER
MOLDED SOLES
LEAKS
SPILLS
HASTEWATER
RUBBER,
PIGMENTS,
AND MIX
COMPOUND
STORAGE
MOLDED
SOLES
COOLING
WATER
SPILLS
WASHDONN
KASTEWATER
COOLING
I RINSE
NASTEttATER
LEAKS
SPILLS
I
KASTEVIATER
I
LATEX SPILLS
AND LEAKS
I
»AST£»ATER
INSPECTION
PACKAGING
k. STORAGE
COOLING
WATER
FIGURE 4: FLOW DIAGRAM FOR THE PRODUCTION OF TYPICAL CANVAS FOOTWEAR ITEMS
-------
sheeted out. The sheeted rubber is dipped in a anti-tack solution
to prevent sticking during storage.
The canvas shoe is built from four major components: soles, canvas
uppers, boxing, and inner soles. These components are made
separately by varying operations before being brought together in
the fabrication operation.
The soles are generally molded using injection, compression, and
transfer molding techniques. All molding processes can produce oil
spills and leaks; however, compression and transfer molding
equipment generally produce more oil spillage than the injection
molding machines.
The molded soles are deflashed, usually in a buffing machine, before
coating with latex adhesive. The latex coating is dried in an oven.
The canvas components for footwear are made from two or three-ply
fabric. The fabric is received at the plant as single sheets.
Latex is applied to the plies, which are pulled together and passed
over a heated drum. The sheets are stacked and the multilayer
canvas is stamped to shape. The different canvas components making
up the shoe uppers are stitched together on sewing machines. The
boxing, or edging, which protects the join between the sole and the
canvas uppers is extruded as a long strip from rubber stock.
The inner sole is extruded in a flat sheet from a special rubber
stock. The extruded sheet is passed through heated presses.
Blowing agents, such as sodium bicarbonate and azodicarbon amide,
which are mixed into the rubber stock in the compounding area,
decompose and release gases which blow the extruded sheet into
cellular sponge. The inner soles are then stamped out of the
cellular sheet.
The shoe is built from the various components on a last. Firstly
the canvas upper is cemented at its edges, and placed over the last.
The inner sole is attached to bottom of the last. The outer sole,
toe and heel pieces, and boxing are placed on the shoe using latex
as an adhesive. The complete, uncured shoe is usually inspected and
placed in an autoclave to cure.
The autoclave is air heated. Anhydrous ammonia is injected into the
autoclave to complete the cure. Curing with ammonia produces a good
surface texture on the rubber and eliminates the residual tackiness
associated with rubber that is cured conventionally. Some shoes are
cured without ammonia. This is done where the tackiness of the
product is not very important or where the compounding recipe can be
modified to eliminate the tackiness often associated with regular
air curing. Steam is not used for curing because in many cases the
steam would stain the canvas parts of the shoe. The curing cycle
can last about one hour and approximately two to five pounds of
ammonia are used for every thousand pairs of shoes cured. At the
end of the curing cycle the ammonia/air mixture is vented to the
atmosphere. No air pollution problems or requirements appear to be
35
-------
associated with this practice and air pollution control devices are
not envisaged.
As described above, latex is used in several applications as an
adhesive. The latex is received at the footwear plant either in
bulk via tank truck or in 55-gallon drums. Spills, leaks, and
cleanout waste waters, laden in uncoagulated latex solids, are
frequently produced.
The nature of the waste waters produced by a typical footwear
production facility are listed in Table 6.
Tire Retreading
Tire retreading is an industry dominated by independents.
Approximately 5,000 retreading shops or plants are currently
registered with the Federal Department of Transportation and the
number of tires retreaded by the industry as a whole approaches 32
million each year. There are a few large retreading plants which
are operated by the major tire companies; in most aspects these are
very comparable to a plant manufacturing new tires. An average
retreading requires approximately 10 pounds of rubber per passenger
tire and 35 pounds per truck tire. Very few tire retreading
facilities compound their own rubber stock. Those that do mix stock
will have potential waste water contamination problems with oil from
machinery and suspended solids from soapstone dip equipment and wet
scrubbing devices, although well-designed curbing should contain
such spillages. After compounding, the stock is extruded to produce
the camelback tread rubber. The extruded camelback is usually
passed through a water cooling tank which has an overflow. However
this cooling water overflow is uncontaminated and does not require
treatment.
The majority of retreading shops purchase the rubber stock from an
outside supplier in the form of camelback tread or extruded rubber.
The worn tire is first visually inspected to ascertain its
suitability of retreading. Those failing the inspection are removed
from the retreading shop as solid waste. The satisfactory worn tire
is buffed with a grinding wheel to remove the old, worn tread
rubber. Rubber buffings collect in the buffing area are solid waste
and are periodically containerized and removed from the plant. Few
plants have air pollution control devices to remove the fine
buffings from the air.
The buffed casing is coated with rubber cement and the camelback
tread or extruded rubber is applied around the tire and cut to
length. The tire with tread rubber is placed in the curing mold and
the mold is closed. Most of the curing molds are steam heated and
the steam condensate is recycled to the boiler. Some molds, are
heated with electricity; these are generally older than the steam
heated molds.
After curing, the tire is removed from the mold. The rubber flash
is buffed off the tire before it is inspected and shipped.
36
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The process waste water types generated in a typical retreading shop
are minor and arise from spillage and washdowns. These waste water
types are adequately covered by those waste waters listed in Table 2
for general molded products. The contaminants of these waste waters
are oil and suspended solids. However, most plants do not have any
process waste waters at all, and the waste water discharges are
limited to boiler blowdown, cooling water, and sanitary waste
waters.
Reclaimed Rubber Production
The quantity of scrap rubber being reclaimed and re-used and the
number of rubber reclaiming plants operating in the United States
have both steadily declined over the past decade. This decline has
occurred despite increased production and use of rubber products.
As a percent of new rubber produced, reclaimed rubber fell from 19
percent in 1958 to 10 percent in 1968. Some of this reduction is
probably due to development of new rubbers not compatible with
reclaimed rubber, but, undoubtedly, the major decreases were caused
by cost, quality, and environmental reasons. Table 7 indicates the
usage of reclaimed rubber during the 1960's and it can be seen that
substantial reductions have occurred in some applications.
Competitive materials, such as rugs and colored plastics, have
reduced usage in automotive mats and mechanical parts from 105
million pounds in 1960 to approximately 55 million pounds. Similar
reductions are noted for other mechanical goods, hose, shoe heels
and soles, and hard rubber products.
Reclaimed rubber is the product resulting from the treatment of
ground scrap tires, tubes, and miscellaneous waste rubber articles
with heat and chemical agents whereby a substantial devulcanization
or regeneration of the rubber compound to its original plastic state
is effected, thus permitting the product to be reprocessed,
compounded, and revulcanized. The term "devulcanization" which is
frequently associated with reclaiming is a misnomer. Actually all
the commercial reclaiming processes employed are based on
depolymerization of the rubbers. This depolymerization can occur
either by promoting thermal scission or breaking of the polymer
chain or by oxidation at points other than at cross-linking sites.
Some scission of the existing crosslinks may also occur.
There are two fundamental factors which determine the type of
reclaim. The first, and the most important, is the type of scrap
from which the reclaim is made. The second is the process by which
the scrap is reclaimed.
By far the most important source of raw material is tire scrap. The
supply is plentiful and well distributed so that it is relatively
easy to collect. The quality of rubber in tires is high, giving an
unusually high percentage of rubber hydrocarbon at low cost. The
whole tire creates problems due to the tire-cord fiber contained in
the carcass -portion. This fiber has to be removed either by
37
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CO
00
Automotive Products
Tires, Inner Tubes, and Tire Repair Material
Automobile Mats and Mechanical Parts
Hose and Belt
Mechanical Goods
Non-Automotive Products
Cements and Dispersions
Heels and Soles
Hard Rubber
Rubber Surface
Other
Total
Mi
1960
380.6
104.8
36.1
52.6
15.7
17.0
26.2
--
22.9
655.9
1 1 ion Pounds
1967
379.5
55.8
26.2
31.8
16.4
8.7
14.3
4.9
11.0
548.6
of Product
1968
415.3
57.6
24.9
23.5
18.4
11.4
7.4
5.1
12.1
575.7
1969
396.0
55.3
31.8
32.9
19.7
5.6
6.9
3.3
8.3
559.6
Source: "Rubber Reuse and Solid Waste Management" (Part l), R.J. Pettigrew and F.H. Roninger; published by the
U.S. Environmental Protection Agency (1971).
Table 7 - Consumption of Reclaimed Rubber by Product
-------
mechanical means or by chemical methods such as those used in the
digester process.
Three basic techniques are used at existing plants to produce
reclaimed rubber: the digester process, the pan process, or the
mechanical process. A generalized material flow diagram for the
three process is shown in Figure 5. Broadly, the reclaiming process
can be divided into three major parts, two of which are mostly
mechanical and the other predominantly chemical. The rubber scrap
is first separated and ground, then given heat treatment for
depolymerization, and finally processed by intensive friction
milling. All three processes employ similar rubber-scrap separation
and size-reduction methods. They differ in the depolymerization and
the final processing steps.
Rubber Separation and Size Reduction
The rubber scrap is first sorted, and then reduced by mechanical
chopping or cracking on a very heavy cracker mill to a suitable size
for the particular depolymerization step being used. A cracker mill
consists of two horizontal heavy steel rolls revolving at different
speeds. The roll surfaces are corrugated, giving a scissor-cutting
action. In the case of tires, the wire beads are broken in the
cracker mill and removed with magnetic separators along with any
other ferrous material which may have been picked up during their
use. The cracked ground stock is conveyed to a vibrating screen of
a given mesh size. The oversized material is returned to the
crackers for further grinding. The stock which passes through the
screen is conveyed to storage bins to await use in the de-
polymerization process.
Most reclaiming plants require fiber-free scrap in the
depolymerization process. A series of screens, air separators, and
sizing equipment are used to remove fiber from ground rubber scrap.
First the rubber scrap is passed through hammer mills and beaters
which removes fiber from the rubber. This screened mass then goes
to an air-flotation table where the final separation of fiber and
rubber takes place. After passing through magnetic separators, the
rubber crumb which results goes to storage bins.
Rubber scrap separation and size reduction is followed by the
appropriate depolymerization process.
Depolvmerization
Digester Process
The digester process consists of placing the ground scrap, water,
and reclaiming agents into a steam-jacketed agitator-equipped
autoclave (digester). The batch is then cooked for 5 to 2U hours at
370-405°F. During this time the rubber becomes partially
depolymerized, and attains the consistency of soft granules.
Reclaiming agents that are used include petroleum and coal tar-base
oils and resins, as well as various chemical softeners, such as
39
-------
MECHANICAL RECLAIM PROCESS
FINE
GRIN
COOLING— 1
toATER *~~
Q_
1
LEAKS
WASHDOWN
1 HdASTEWATER j
r — _ _ _ _ i
DEPOLYMERIZATION
OILS AND AGENTS
1
SPILLS
LEAKS VA™R
WASTEWATER PROCESS
WATER
FIBER -
COOLING
i
FREE ,, ,- COMPOUNDING: PRODUCT
i. DIIDDCD i»iim»i\tn HULLO VPHAP ULM Diniiiu. spuAP ""^ • •""" UIVCR? sinfiARF
STEEL-BELTED ' All ' ' HBEH
L STUDDED T ^0*0 SCRAP SE
TIRESI COOLINGJ «Acunn *, 1 S
1 LjlTrn ^ 1 nAoMLIUWN • MAI in f^
1 Bflltn ^^ cni i n SOLID
^ ^ SOLID 1(1^5 j£ SI
SOLID WASTE WASTEWATER hASTE £
ce
LU
PROCESS ^
H4TFR
on UCDI TUT inu ' > '
LULJLINbJJ rpjii r
WATER «" {mi* g
WASTEWATER See
>- =» CO
,_ j oS =
PROCESS WATER 4 VAPOR VENT VAPOR VENT4
1 DEWATERED 1
DEVULCANIZED <; 1 OEVULCANIZED DEVULCANIZEQ 1
h^7 RUBBER SLURRY^ BLOWDO*N RUBBER SLURRY ^ ^^AlbMNi,. RUBBER ,1-
AGtNIS ANU OILS ' lnNIV PRESSES u
1 1
SPILLS DIGESTER
WASIIDOWN LIQUOR
WASTEWATER «,cTt.iATrD
WET DIGESTER RECLAIM PROCESS WASTEWATER
.S * AND
MNERS STORAGE
1
LEAKS
WASHDOWN
WASTEWATER
m]
J
NOTE: SOME RECLAIMING FACILITIES OPERATE MORE THAN ONE TYPE OF PROCESS
FIGURE 5: FLOW DIAGRAM OF TYPICAL MECHANICAL, PAN (HEATER), AND WET DIGESTER RECLAIM PROCESSES
-------
phenol alkyl sulfides and disulfides, thiols (mercaptans), and amino
compounds. Reclaiming agents or oils are used to speed the
depolymerization, to impart desirable processing properties.
Natural rubber can be reclaimed in the absence of any reclaiming
agents. SBR types, however, require the assistance of these
reclaiming agents or catalysts to produce a reclaim. The reclaiming
agents generally function by catalyzing the oxidative breakdown of
the polymer chain and oxidatively disrupting sulfur crosslinks.
Rubber scrap which has not been defibered mechanically requires
chemical degradation of the fibers in the digestion process.
Defibering agents, such as caustic soda or the chlorides of zinc and
calcium, and plasticizing oils are added to the digester to complete
the charge. The fiber from tires and other rubber scrap products is
hydrolyzed and goes into solution. The presence of synthetic rubber
such as SBR in the tire scrap necessitates the use of the metallic
chlorides in place of the caustic soda since the caustic solution
produces a heat-hardening effect with SBR instead of softening.
At the end of the digestion period the contents of the digester are
blown down under internal pressure into a blowdown tank. Water is
added to the soupy mass to facilitate the subsequent washing
operations. After thorough agitation, the mixture is discharged
onto continuous vibrating screens where a series of spray nozzle
showers wash the rubber free from the digester liquor.
The washed rubber, which is in the form of a slurry, is then passed
through a dewatering press which forces out much of the occluded
water. The dewatered rubber is dried in a hot-oven or tray dryer
prior to further processing.
In cases where chemical defibering is carried out in the digestion
process, the rubber has to be washed free from the decomposed fiber
as well as the digestion liquor. This washing procedure generates
waste water which can be alkaline or laden with metal chlorides and
fine sludge-like particles of hydrolyzed fiber and rubber. Chemical
defibering and the subsequent washing process create an effluent
problem. At present, mechanical fiber separation is used to reduce
the waste water problem inherent in the digester process.
Pan Process
The finely-cracked scrap, which is usually free from fiber, is
reduced to a finer particle size by grinding on smooth steel rolls.
The finely-ground scrap is blended in an open mixer with the correct
amount of reclaiming oils and is then placed in open pans which are
stacked on a carriage and placed in a large horizontal heater. The
heater is a single-shell pressure vessel into which live steam is
passed. Depolymerization is carried out at about 365°F for 2 to 18
hours. After this treatment the heater is vented, the pans
discharged, and the cakes of rubber sent on for further processing.
Since the condensate from this operation is highly contaminated with
gums, resins, etc., it cannot be returned to the boilers and.
41
-------
therefore, must, be treated as a waste. This waste is similar in
composition to the digester alkali and chloride wastes.
The pan process is relatively inexpensive because the equipment is
simple, and the washing and drying steps are eliminated. The supply
of cheap fiber-free scrap rubber can be a limiting factor in the
operation of the pan reclaiming process.
Mechanical Process
The mechanical reclaiming process, unlike the other two preceding
processes, is continuous. The fine ground, fabric-"free rubber scrap
is fed continuously into a high-temperature, high-shear machine.
The machine is a horizontal cylinder containing a screw for forcing
and working the material along the chamber wall at 350 to UOO°F in
the presence of reclaiming agents and catalysts for
depolymerization. The rate of depolymerization is controlled by the
speed of screw while the compression and temperature is maintained
constant. The discharged reclaimed rubber needs no drying and is
ready for further processing.
Final Processing
The final stage of the reclaiming operation, namely milling, first
involves the mixing and blending of the material from any of the
various depolymerization processes in a Banbury internal mixer with
small amounts of reinforcing materials such as clay, carbon black,
and softeners. This aids in smoothing dried stock and obtaining
uniformity. The reclaim is then given a preliminary refining on a
short two-roll mill having a high-friction ratio between the roll
surfaces. The sheet thickness after the first refiner pass is about
0.01 inch. The reclaim is then strained to remove foreign matter
before going to the final thickness of 0.002 to 0.005 inch. The
strainer is an extruder which contains a wire mesh screen held
between two strong perforated steel plates in the head of the
machine. The strainer not only removes foreign matter, but also
plasticizes and blends the reclaim.
Each reclaimer may complete his reclaiming operations in either of
two ways - by sending his product to the customer in the form of
slabs stacked on pallets or bales. Slabbed reclaim is made on a
mill and the discharged sheet is wrapped on a rotating drum of a
specified diameter, until the proper thickness is obtained. The
wrapped layers or sheet are then cut off the drums, forming a solid
slab of a certain length, width, and weight. The slabs are then
dusted with talc to prevent sticking to each other, tested, and
shipped to the customer. Baled reclaim, is also made on a mill,
except the thin milled sheet is conveyed to a baler, where the
rubber is compacted to form a bale. The bale is then encased in a
bag, stacked on a pallet, tested, and sent to the customer.
The effluent waste waters occuring during the various reclaiming
processes are identified in Table 8.
42
-------
Plant Unit or Area
Source
Nature and Origin of Waste Water Contaminants
•c-
u>
Wet Digester Reclaim Process
Grinding
Oepolymerization, Defibering
and Oi1 Storage
Slowdown Tank
Dewatering
Dryers
Compounding
Pan (Heater) Reclaim Process
Grinding
Depolymerization Agent and
Oil Storage
Devulcanizer
Compounding
Washdown, spills, leaks
Spills, runoff
Air pollution equipment
Digester 1iquor
Air pollution equipment
Washdown, spills, leaks,
air pollution equipment
Washdown, spills, leaks
Spills, runoff
Air pollution equipment
Washdown, spills, leaks,
air pollution equipment
Bearing oil from machine drives. Oil from seals
on milling equipment.
Oil, solids, caustic and organics.
Oi 1s and organics.
Oil, solids, caustic and organics from spent
depolymerization and defibering agents and excess
oil. High concentrations of fibrous material
removed from tires.
Oi1s and organics.
Bearing oil from machine drives. Oils from seals
on milling equipment. Solids from soapstone dip
tanks. Solids from air pollution equipment.
Bearing oil from machine drives. Oil from seals
on milling equipment.
Oil, solids, caustic and organics.
Oi1 and organ i cs.
Bearing oil from machine drives. Oils from seals
on milling equipment. Solids from soapstone dip
tanks. Solids from air pollution equipment.
Table 8: Process-Associated Waste Water Sources from Rubber Reclaiming
-------
Manufacture of General Latex-Based Products
To manufacture sundry rubber goods from latex compounds, it is
necessary to convert the compounds into solids of the desired form.
Latex compounds are generally stabilized by the latex producer
before shipping to the rubber goods manufacturing facility. Here,
the stabilized latex compound is transformed into the final rubber
good.
Prior to forming the rubber goods, the latex is compounded (mixed)
with various ingredients, such as antioxidants, in accordance with a
specific recipe. The mixing of latex compounds is a simple
operation consisting of weighing out the proper amounts of the
various solutions and emulsions required, and then stirring these
materials into the latex, usually in a large tank equipped with a
mechanical agitator. In some cases, such as the compounding of
latex for foam sponge, some of the ingredients must be added just
prior to or during the foaming operation, and in these cases
complicated automatic proportioning equipment is sometimes used.
Several types of rubber goods are fabricated from latex mixtures.
The basic manufacturing processes and their waste water generations
for these product types are described below. The major classes of
latex-based goods are dipped goods, such as finger cots and surgical
gloves, and foam-backing materials. Table 9 lists the value of 1967
U.S. shipments of the principal rubber products fabricated from
latex mixes. It is believed that many of the foam products listed
in Table 9 are no longer made and have been replaced by chemically
blown sponge or urethane-type foams. As discussed earlier, it is
difficult to obtain more up-to-date production figures for these
items in terms of product or raw material weights.
Latex-Based Dipped Goods
There are two principal techniques used in the manufacture of dipped
rubber goods. One is the straight-dip method employed in the
production of very thin-walled dipped goods from which water can
readily and quickly be removed by evaporation. The second technique
is coagulation-dipping where the rubber goods are produced by
coagulating a film of rubber from a rubber latex onto shaped forms.
Thicker-walled items are made by coagulation-dipping rather than
those manufactured by the straight-dip method. The thicker rubber
deposit cannot be dried as readily and must be assisted by
coagulation in order that it does not disintegrate during subsequent
processing.
Figure 6 is a flow diagram for a typical coagulation dipping
operation. Such a facility might be engaged in the manufacture of
rubber gloves. A close-loop conveyor transports the forms through
various processing units. The forms can be made of glazed procelain
or polished metal.
The forms are first dried and heated to 100-120° in a conditioning
oven prior to dipping in the coagulant solution. The coagulant
44
-------
Product Type Value
(mi 11 ion dollars)
Dipped Goods
Household gloves 11.1
Surgical gloves 20.0
Prophylactics 16.4
Balloons (Toy and Advertising) 10-3
Thread (bare rubber) 25-2
Latex Foam
Automotive Seating 19-3
Upholstery 39.9
Mattresses and Pillows '7.8
Carpet and Rug Cushions 24.2
Other Latex Foam Products- 59-3
Total 243.5
'includes hospital padding and topper pads.
SOURCE: "1967 Census of Manufacturers•-- Rubber and Miscellaneous Plastic
Products"; U. S. Department of Commerce (issued 1970).
Table 9 - 1967 Shipments of General Latex - Based Products by U.S. Producers
45
-------
CLEANING
RINSE WATER
i >
i-^— — i FORM
FORM „ CLEAN _ FORM RETURN VIA
DRYING ' AND *
—•— • RINSE
£ SPENT CLEANING
£ i. RINSE( WATER
z RINSE i
2 WATER HASTEKATER COOL IN
d I HATER
COAGULANT LAIEX PRELIMINARY PRODUCT OVEN 1 1
DIP ....... u RINXF BFAD ROLLING 1
• i ' IRN* "'EN I ™ 1 STAMPING
LEAKS$ SPILLS SPENT
»"« tgBoB !lg|
WASTEWATER ^ +
WASTEKATER WASTEIiiATER
LATEX LATEX XT
STORAGE COMPOUNDING TA
I 1 — COOLING I — COOLING
PILLS **ATER *WATER
EAKS SPILLS
ASHDOWN LEAKS
X WASIIDOKN
CLEANING OPERATION
G RELEASE RINSE
AGENT 1 **!"
^COOLING PRODUCTS ^ FORM ^PRODUCT
* TANK * STRIPPING * RINSE
£ COOLING £ SPENT
o WATER M RINSE
^S OVERFLOW | WATER
Sri * °- 1
= ^ HASTEWATER - WASTEKATER
Q. to j^
1 CO
ERILIZATION 4 STERILIZATION
NK * RINSE
1
SPENT
RINSE
WATER
PRODUCT
DRYING
* OUiTINL
PACKAGING
WASTEKATER
WASTEMATEft
NASTEWATER
SPILLS
LEAKS
ftASIIDOWN
4
MASTENATEft
FIGURE 6: FLOW DIAGRAM FOR THE PRODUCTION OF TYPICAL LATEX-BASED DIPPED ITEMS
-------
solution is usually a mixture of organic solvents and coagulants.
Combinations of ethanol and acetone are generally used as solvents.
Typical coagulants are calcium nitrate, calcium chloride, and zinc
nitrate. A surfactant is sometimes added to the mixture to ensure
good "wetting" of the forms, and release agents are added in cases
where the form has a complicated shape and removal of the dipped
goods from the forms is difficult. After coating with coagulants,
the forms are dipped in the rubber latex. The rubber latex and
ingredients are compounded prior to the dipping operation. In some
cases, the latex storage and compounding tanks are cooled with
cooling coils or jackets to prevent degradation of the latex. The
coagulant film on the surface of the form causes the rubber emulsion
to "break". The latex solids coalesce to produce a film of rubber
that covers and adheres to the form.
The coated forms are passed through a preliminary drying oven to dry
the film sufficiently so that it does not disintegrate and wash away
in the subsequent washing step. In the washing operation the
soluble constituents of the rubber film are leached out and rinsed
away. Important constituents of the leachate are the emulsifiers
used originally in the production of the latex and metal ions from
the coagulant mixture.
The coated forms are sent through a drying oven to dry the goods.
In some applications, such as rubber gloves manufacture, the goods
are not only dried but heated sufficiently so that the rubber
coating can be rolled downward on itself to form a reinforced cuff
bead.
In most applications the rubber goods are stamped with the
proprietary brands and other information such as size in a stamping
unit after the drying process.
The rubber goods are cured in an oven at approximately 200°F. After
curing the items are cooled in a water cooling tank and mechanically
stripped from the forms usually with the aid of a lubricating
detergent. The detergent is subsequently washed from the goods in a
rinse tank.
The final manufacturing operation consists of drying the goods,
dusting them inside and outside with talc to prevent sticking and
packaging.
In cases where sterilized products are required, such as surgical
rubber gloves, the goods can be immersed in a chlorine dip tank
(free chlorine concentration typically 1,000 mg/1) to provide
disinfection and improve the surface finish of the glove. After
disinfection the goods are dipped in a hot water tank (approximately
170°F) to remove the residual chlorine from the rubber product.
These two operations generally occur between the post-curing cooling
tank and the final drying and packaging operation. In many cases
the gloves are sterilized by dipping in a hot water bath
(approximately 200°F).
47
-------
Periodically, it is necessary to clean the form upon which the goods
are deposited. When this is necessary, the forms are passed through
a bath containing a cleaning agent. In the case of porcelain forms
the agent used can be chromic acid (mixture of potassium dichromate,
sulfuric acid, and water). The cleaned forms are rinsed of residual
chromic acid in a subsequent rinse tank. The tank is equipped with
a fresh water makeup and overflow to blow down the accumulation of
cleaning agent. The cleaning frequency is generally in the order of
once a week. Other methods of cleaning involve simply scrubbing the
forms with cleaning agents followed by rinsing.
The waste water sources and characteristics of a typical dipping
operation are presented in Table 10.
The straight-dip method is the simplest of any used in making
articles from latex. The forms are dipped directly into the latex
and slowly removed. After dipping, the form is slowly rotated while
the liquid film is drying to ensure a uniform film thickness. The
films are dried at room temperature or in warm air at 120 to 1UO°F.
Thicker articles can be made by a multiple-dipping process with
drying between dips. Latex deposits vary from 0.005 to 0.10 inch
per dip, depending on the viscosity of the latex compound.
Cement-Based Dipped Goods
It is appropriate to discuss the manufacture of dipped goods from
rubber cement here because the production process has similarities
to the manufacture of latex-based dipped goods as described above.
(see Figure 7.)
Various products are made via cement dipping processes. The
following process description is oriented towards the manufacture of
gloves having a high electrical resistance. Cement dipping results
in a product which has good electrical resistance since no water or
ionic species are trapped in the cement as would be the case with
latex dipped gloves.
The solid rubber required for the cement recipe is compounded in a
small Banbury mixer or compounding mill. The recipe ingredients
include antioxidants, curing agents, and pigments. The compounded
stock is cut in small pieces to facilitate dissolution in the
solvent. These pieces of stock are separated by weight into pre-
determined quantities and placed in a bin. The wastes generated in
the rubber compounding and weighing areas result from spills and
leakages from machinery, powders from compounding, and washdown
waste waters.
The rubber cement is prepared in blend tanks using fixed quantities
of rubber stock and solvent. The solvent used is generally
aliphatic in nature, for example, hexane. The blended cement is
pumped to a storage tank prior to its use in the dipping operation.
Several rubber cements of different colors and properties are stored
simultaneously awaiting the dipping operation. Solvent and rubber
cement leaks can occur in this area. The gloves are formed by
48
-------
Plant Unit or Area
Latex Storage and Compounding
Source
Spills, leaks, and
cleanout rinse waters
Nature and Origin of Waste Water
Contaminants
Dissolved organics, suspended and
di ssolved sol ids.
High quantities of uncoagulated latex.
Coagulant Dip
Spills, leaks, and
cleanout rinse water
Dissolved organics, dissolved solids.
VO
Product Wash, Cooling, and
Rinse Tanks
Steri1ization Process
Spills, leaks and
overflow waters
Spills, leaks, and
rinse overflow waters
Dissolved organics, suspended and
di ssolved sol ids.
Dissolved solids, sterilzation agent.
Form Cleaning
Form wash and rinse
waters
Dissolved organics, suspended and
dissolved sol ids.
Al1 Plant Areas
Area washdown and
storm runoff
Organics, suspended and dissolved solids,
Table 10 - Process-Associated Waste Water Sources from Latex-Based Dipped Goods Production
-------
SOLVENT
STORAGE
m
O
CLEAN FORMS
1
PERIODIC
FORM
CLEANING
FOULED FORMS
T
CLEANING SOLUTION
FOR DISPOSAL
I
WASTEHATER
FORM RETURN TO DIPPING OPERATION
RUBBER
AND MIX
COMPOUNDS
STORAGE
COOL
HATE
ING
COMPOUNDING
MIXING
MILLING
AND STOCK
i ,
R «
1
SPILLS
LEAKS
tvASHDOW
RUBBEF
_^A rriwrm
PREPAI
SP
LEf
N
1
r
UTION
LLS
tKS
I
DIPPING
& DRYING
OPERATION
STEAM
AUTOCLAVE
1
1
STEAM
CONDENSATE
1
~
ANTI-TACK
DIP, DRYING
AND FORM
STRIPPING
1
1
SPILLS
LEAKS
1
^ INSPECTION
* & ItSIINU '
I
1
CONDUCTIVITY
TEST YiATER
1
PACKAGING
— » AND
SHIPMENT
WASTEWATER
KiASTEKATER
i
«ASTE*ATER
*»ASTE»ATER
HASTEViATER
FIGURE 7: FLOW DIAGRAM FOR THE PRODUCTION OF TYPICAL CEMENT DIPPED ITEMS
-------
dipping on glazed procelain forms. In the case of linesmen gloves
the rubber layer is built up with about twenty to thirty dips. The
dipped products are allowed to drip-dry between dips. The
temperature and humidity of the air in the drying room is controlled
to ensure good drying conditions. It is possible that the quality
of the exhaust drying air which is solvent laden, will be subject to
control under air quality legislation in the future.
When the dipping and drying operation is completed, the gloves are
stamped with size and brand information and the cuff bead is formed
by rolling the cuff back on itself.
The gloves are cured in an open steam autoclave vulcanizer. The
temperature and length of curing depends on the type of glove and
properties of the rubber. The steam condensate leaches organics
from the rubber. The condensate is extremely low in volume and is
discharged to the plant drain. At the end of the curing cycle the
gloves are removed from the vulcanizer and left to air cool.
When partly cool the gloves are dipped in a soapstone slurry or
equivalent anti-tack agent prior to final cooling. The soapstone
slurry dries leaving a powder on the gloves which are then stripped
from the forms. The gloves are dusted in a rotating drum with talc
powder and sent to product inspection.
Gloves which pass a visual inspection are tested for electrical re-
sistance. This operation involves filling the gloves with water and
placing the gloves in a tank of water. A high voltage is applied
between two electrodes; one electrode inside the water-filled glove
and the other outside in the water-filled tank. At a given voltage,
a satisfactory glove limits the current flow. Gloves removed from
the tank are dried and packaged prior to shipment.
Periodically the forms require cleaning. This is carried out with a
mild scouring slurry followed by rinsing of the forms. Spent
scouring slurry and the rinse waters are low in volume.
The types of waste water generated by a typical cement dipping
operation are listed in Table 11.
Rubber Goods from Porous Molds
Porous molds prepared from plaster of Paris or unglazed porcelain
with pore sizes smaller than the smallest rubber particles, are used
in the rubber sundry industry. The latex compound is poured through
a funnel-shaped opening into the mold. The latex compound is
allowed to dwell in the mold until a deposit of the desired
thickness has developed on the mold wall. The mold is emptied of
excess compound and placed in an oven to dry at 1UO°F for one hour.
With some articles, to prevent pour lines, the mold is rotated on
all planes for 15 to 30 minutes to give the latex an opportunity to
flow to all extremities of the mold interior before setting. This
technique is used for dolls and squeeze toys. The interior rubber
surfaces are dusted with talc to prevent sticking when being removed
51
-------
Plant Unit or Area
Sou rce
Nature and Source of Waste Water
Contaminants
Oil and Solvent Storage Spills, leaks, and storm runoff Oil and organics pick-up by storm water.
Compounding and Weighing Spills, leaks, and washdown
Rubber ingredient solids, oil and water
leaks from mixers and mills.
l/i
Ni
Cement Preparation
Curing
Spills, leaks and washdown
Condensate
Soluble and insoluble organics from
solvent spills and leaks.
Soluble and insoluble organics leached
from product.
Form Stripping
Form Cleaning
Spills, leaks, and washdown
Spills, leaks, rinse and
cleaning agent discharges
Solids from anti-tack agent.
Solids and surfactants from the cleaning
agent.
Product Inspection
Conductivity Test Water Overflow Water is uncontaminated.
Table 11 - Process-Associated Waste Water Sources from Cement Dipped Goods Production
-------
from the mold. The article, after stripping from the plaster mold,
may be returned to the 140°F oven for 30 minutes or a shorter period
at a higher temperature to facilitate drying.
The types of waste water generated by this sector of the industry
are similar to those produced by a latex-dipping facility. They are
characterized by uncoagulated latex solids, and are evolved by
spills and leaks and tank washing operations. The waste water types
are similar to those produced by the manufacture of latex-dipped
goods (Table 10) .
Thread
The manufacture of thread from latex (referred to as "latex thread")
makes use of some of the general principles and methods described
above. The most widely used method is extrusion of the latex
compound through fine orifices into a coagulant bath which gels the
thread, followed by mechanical handling of the thread during
toughening, washing, drying, and curing operations. The coagulant
bath is usually dilute acetic acid.
Latex Foam
Although the number of plants and rubber companies involved in this
sector of the industry has decreased over the past several years,
foamed-latex sponge rubber still constitutes one of the more
important applications for latex, both natural and synthetic. (See
Figure 8.)
The latex may consist entirely of natural latex or synthetic SBR
latex or it can be a mixture of natural and an SBR latex. The load-
bearing capacity of the foams at a given density falls significantly
as SBR is used in place of natural rubber. Latex rubber foams are
generally prepared in slab or molded forms in the density range of 4
to 8 pounds per cubic foot.
Many different processes are patented for preparing this type of
product, but there are two of prime commercial interest for
manufacturing such articles as molded-foam cushioning stock. These
are the Dunlop -the most widely used — and the Talalay processes.
Some producers have developed variations which in effect are a
combination of the two processes.
The basic aspects of the Dunlop processes are:
1. mechanically whipping the latex to a froth;
2. settling the frothed mass with a coagulant or gelling agent; and
3. vulcanizing the rubber so that the foam is permanent.
The latex is first whipped on a batch or continuous basis to produce
the foam. The Oakes continuous mixer is the standard piece of
equipment used by the industry to prepare the foamed latex. The
gelling agents are added to this foam.
53
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Oi
Ji*
^ CONDENSER
^ COOLING
. WATER
CONDENSER
T
' WATER
COMPOUNDING AND
CURING 1
CONDENSATE VAPOR
WASTEWATER
i
LATEX
STORAGE
CARBON
DIOXIDE
GAS
FREEZE
AGGLOMERATION
t
LATEX
CONCENTRATION
BY
EVAPORATION
INTERMEfllATE
CONCENTRATED 1TC,
LIIEI STORAGE
GENTS
BALL MILL
um GROUND GRINDING OF
COMPOUNDING COMPOUNDING INGREDIENTS
AGENTS
I
SPILLS
WASHDOWN
1 I
WASTEWATER ~"
FOAM
PRODUCT
STORAGE
AND
SHIPMENT
FOAM
DRYING
CLEAN
WATER
fc
SUPPLY "
ec
I L|J
* - i
FOAM
FOAM
RINSING
STEPS
r
Z FOAM
^ RINSING F0*"
J STEPS
UJ
DC
±3
CE
UJ
=
v «^ ,
RINSE
r
WASTEWATER
LU
a
o-
1 ! COOLING
SKILLS * WAIth
WASHDOWN SPILLS
^ LEAKS
WASTEWATER ^
WASNDOWN
t
FOAM
PRODUCT ,.„„„
PREi
SES ^ CARBON
r.»s
SPIL
.S
WASHDOWN
1
WASTEWATER
FIGURE 8: FLOW DIAGRAM FOR THE PRODUCTION OF TYPICAL LATEX FOAM ITEMS
-------
Proper coagulation of the latex to give a stable foam (commonly
referred to as gelation) is the key to the process. The gelling
agent is one that can be mixed into the frothed latex, then remain
dormant long enough to allow the froth to be poured into molds
before producing the gelling effect. The gelling system usually
consists of sodium silicofluoride in conjunction with zinc oxide.
The foam is poured into molds and cured. The molds are usually
steam heated. When the curing cycle is completed, the product is
removed from the mold and washed with water to remove those
ingredients of the latex recipe which are not held permanently in
the foam matrix. The foam is dried in a hot air dryer prior to
inspection, storage, and shipment.
In the Talalay process the froth is produced by chemical rather than
mechanical means. Hydrogen peroxide and enzymatic catalysts are
mixed into latex and the mixture is placed in the mold.
Decomposition of the peroxide by the added enzyme results in the
liberation of oxygen, which causes the latex mix to foam up and fill
the mold. The foam is rapidly chilled and carbon dioxide is then
introduced to gel the latex. The gelled foam is than handled in a
manner similar to that used in the Dunlop process.
The waste water generated by the manufacture of latex foam products
are similar to those produced at a latex-based dipped goods facility
with the exception that there is an additional zinc-laden rinse
water generated by washing the foam product. These waste waters are
identified in Table 10. An important characteristic of this type of
waste water is the presence of uncoagulated latex solids.
Foam Backing
For supported flat-stock foam, that is, foam backing on various
fabrics such as carpets, scatter mats, upholstery fabrics, etc., a
different type of gelatin agent is employed in place of the sodium
silicofluoride gelling agent used in latex foam production. Either
ammonium acetate or ammonium sulfate is employed in combination with
zinc oxide.
The froth is prepared with an Oakes machine, the gelling agent is
added at the machine, and the foam is applied to the fabric by
spreading directly on the fabric or spreading on a belt and
transferring the wet gel to the fabric via the belt. The gelling is
carried out at elevated temperatures, usually with the aid of
infrared lamps. To prevent uneven shrinkage, the fabric is carried
through the high-temperature zone and drying ovens on tenter frames.
For this application the foam is poured in narrow thicknesses, from
1/8 inch up to a maximum of 1/2 inch. The waste waters produced by
the manufacture of foam backing are comparable to those generated by
a typical latex-dipped goods manufacturing facility (Table 10).
Summary
55
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Based on the products and processes comprising the industry as
described above, it is possible to make some general conclusions
about the waste water characteristics of the whole industry and
which sectors should be grouped for further discussion.
Although the types of product manufactured by molding techniques are
diverse, the manufacturing processes are very similar throughout the
industry sector. In addition, it is believed that the
characteristics of the waste waters generated by the three principal
molding technologies (compression, transfer, and injection) are
comparable.
Extrusion is another fundamental rubber processing technology by
which several types of products are made. Rubber extrusion, for
example, is a significant step in the manufacture of rubber hose as
well as belting. The waste water types throughout the industry
appear to be similar and independent of the type of extruded
product.
The final stage in the manufacture of many rubber products involves
fabrication using molded or extruded components. In general,
fabrication operations are "dry" and the necessary waste water
control and treatment requirements appear to be simple.
Based on the apparent nature of the waste waters, it can be
concluded that the molded, extruded, and fabricated rubber industry
sectors are comparable. The processing methods used generate waste
waters limited to spills, leaks, and housekeeping operations. The
waste water is characterized by oil and suspended solids loadings.
The quantity of reclaimed rubber and the number of reclaim plants
have decreased dramatically over the last several years. Associated
with this decline has been a conversion from the wet digestion
process to both pan (heater) and dry digestion processes. Due to
the differences in the waste water generated, the reclaimed rubber
sector shall be separated into two subcategories, the wet digester
process, and the pan, mechanical, and dry digester process.
Two main sectors exist in the latex-based industry. These are the
latex dipped goods and latex foam industry sectors. Two small
rubber industry sectors also utilize latex raw materials: latex
thread and items made in porous molds. The foam industry consists
of one major plant. Other foam plants might exist but their
capacity is insignifcant. Owing to the apparent nature of the
processes and the waste waters produced, the latex-based sector can
be separated into two groups: dipped goods plus latex-thread and
items made in porous molds, and latex foam.
56
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SECTION IV
INDUSTRY CATEGORIZATION
introduction
Industry subcategories were established to define those sectors of
the rubber industry where separate effluent limitations and
standards of control and treatment should apply. The primary
distinctions between the various subcategories have been based on
the waste water generated, its quantity, characteristics, and
applicability to control and treatment. The factors considered in
ascertaining whether the developed subcategories are justified were
the following:
1. Manufacturing Process
2. Product
3. Raw Materials
4. Plant Size
5. Plant Age
6. Plant Location
7. Air Pollution Control Equipment
8. Nature of Wastes Generated
9. Treatability of Waste Waters
As illustrated in Section III, there are obvious and intrinsic
differences between rubber reclaiming, latex-based products
manufacture, and the combined molded, extruded, and fabricated
products sector of the rubber industry. Therefore, rubber
reclaiming, and latex-based products, have been treated separately.
Molded, extruded, and fabricated products will be treated as one
group and the subcategories of the industry to which specific
standards should be applied will be discussed in this section under
one of the following subsections:
1. Molded, Extruded, and Fabricated Rubber Products
2. Reclaimed Rubber
3. Latex-Based Products
Molded, Extruded, and Fabricated Rubber Products
Manufacturing Process
There are two fundamental processes, molding and extrusion, by which
products in this group are made. Although the manufacture of many
products involves fabrication of the final product from several
individual rubber components, the individual components are
themselves manufactured typically by molding or extrusion
techniques. The waste waters created by both molding and extrusion
operations orginate with housecleaning spills, leaks, and washdown.
57
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It can be said, therefore, that in spite of process variations, the
waste waters generated by all products in this group are similar in
volume and constituents and thus further subcategorization is not
warranted.
Product
The basic processes of molding, extrusion, and fabrication are used
to manufacture a wide array of rubber products. The waste waters
associated with the majority of these products are similar and
subcategorization according to product is not justified.
Hose manufacture generally produces a vulcanizer condensate
exhibiting a relatively high concentration of lead (approximating 60
mg/1). The flow rate of this condensate is low (typically less than
1 gpm). As a result the lead-laden waste waters can be segregated
and treated separately, thus separate subcategorization based on
this specific waste stream is not justified.
Raw Materials
The basic raw materials for this industry group are rubber, carbon
black, pigments, and oil. Although some fabrication processes use
latex as an adhesive and the methods for handling such latex vary
within the industry sector, the waste water problems associated with
the use of latex can be overcome readily. In light of these facts,
it is not reasonable to categorize this sector of the industry
further based on raw material usage.
Plant Size
Study of the production facilities included in this group reveals
that the size distribution is broad and ranges from approximately
500 pounds per day to 265,000 pounds per day of raw material. The
small plants in this group are predominantly independent molding
shops manufacturing specialized products for a limited number of
wholesale outlets. At the other end of the spectrum, the larger
plants tend to be integrated plants making several types of
products. The medium sized and large plants are frequently operated
by the large tire and rubber companies. Some products, such as hose
or belting, are produced only by medium or large facilities.
Although the waste water characteristics and treatment methods of
small, medium, and large plants are similar, the impact of waste
water control and treatment costs on the smaller plants is likely to
be more critical than their effect on large plants. This fact tends
to be magnified since most small plants are operated by independent
companies with less financial flexibility or resources.
Based on these observations, it was concluded that this sector of
the rubber industry should be subdivided in order to ascertain the
variability of the cost of waste water control and treatment with
plant size. Accordingly, the molded, extruded, and fabricated
product sector has been split into three production capacity size
58
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ranges. The three size ranges, the percentiles of the whole
industry sector covered by the size ranges, and the corresponding
median, or typical, production capacity for each size range are
shown below.
Range of Plant Percentile of the Typical Size For
Sizes Category Each Range
kg/day (Ibs/day) kg/day (Ibs/day)
less than 3,720 (8,200) 0-30 910 (2,000)
3,720-10,430 (8,200-23,000) 30 - 60 7,710 (17,000)
greater than 10,430 (23,000) 60 - 100 15,420 (34,000)
Plant Age
Rubber molding, extrusion, and fabricated product plants have a
broad age distribution. However, there have been few processing
developments in that period that have had any significant waste
water impact. In general, the waste water control and treatment
costs for an older plant will probably be higher than those of a new
plant, but this is not always the case. In addition, it is
difficult to usefully characterize the cost-to-age relationship
existing within the industry and to define meaningfully the age
demarcation line or lines for this sector. Analysis of waste water
characterization and treatment data reveal that the age of a plant
does not preclude the use of exemplary control and treatment
technologies.
Therefore, it has been concluded that plant age is not a significant
factor for separate subcategorization.
Plant Location
Although a high proportion of the plants in this sector of the
industry are located in one region of the country (Akron, Ohio and
its environs), climate and geographical location are not the reasons
behind this fact. Akron is the traditional center of the rubber
industry where in the past raw materials (rubber and the special mix
ingredients) , rubber processing machinery and equipment, rubber
process technology, and experienced labor have been readily
available. Climate and location do not affect the basic processing
techniques used by the industry and will have little impact on waste
water treatability or effluent quality. Therefore subcategorization
according to plant location is not necessary.
Air Pollution Control Eguipment
The type of air pollution control equipment employed by the facility
can have an effect on the quantity and quality of a plants overall
process waste water flow. The use of dry scrubbing equipment
produces no waste water problem. If wet scrubbing devices are used
solid-laden blowdown can be settled and filtered. By recycling the
water from the settled and filtered discharge, this waste water
59
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problem can be minimized. Thus, air pollution control requirements
do not warrant further subcategorization of this industry sector.
Nature of Wastes Generated
Analysis of available data indicated that the process waste water
types and characteristics generated by the manufacture of those
products included in this sector of the industry are effectively
similar. Some minor variations do occur. Processes utilizing latex
adhesive can produce latex-laden waste waters if inadequate water
management or housekeeping practices are employed. Latex-laden
rinse waters should be low in volume and can be containerized or
replacable liners can be used inside latex containers thereby
eliminating the rinse waters completely. Waste waters created by
wet scrubbing equipment tend to be laden with suspended solids.
This waste water can be recycled with a slipstream to blowdown the
accumulated solids. The slipstream is low in volume and can be
containerized, treated by settling and filtration, or sent to a
municipal system.
Based on these observations, it is not deemed necessary to
subcategorize this industry sector further according to the nature
of the waste waters generated.
Treatabilitv of Waste Waters
The control and treatment practices and technologies employed by
plants throughout the industry sector are similar and are based on
oil and suspended solids separation. In addition, the effluent
qualities of exemplary plants of all processing types and product
mixes are comparable. These facts indicate that subcategorization
of this industry sector is not justified based on waste water
treatability.
Summary
Studies of this industry sector indicate that the only valid basis
for subcategorization is plant size. This is not required owing to
differing waste water types or treatabilities but because the
financial resources of the smaller plants are generally weaker than
those of larger rubber companies. The size-range
subcategorizations, which were selected to reflect fully the
potential economic differences, are as follows:
Small Plants: Less than 3,720 kg/day (8,200 Ib/day) of
raw material.
Medium Plants: 3,720-10,430 kg/day (8,200-23,000 Ib/day) of
raw material.
Large Plants: Greater than 20,430 kg/day (23,000 Ib/day) of
raw material.
Rubber Reclaiming
Manufacturing Process
60
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As described in Section III, there are principally three reclaiming
processes used currently in the United States. Wet digestion, the
oldest of the three, itself has process variations which involve
rubber scrap defibering and the types of digestion medium used. In
some plant, physical defibering is carried out before the digestion
step; in others, chemical defibering is effected in the digestion
process itself. The acidic-medium digester process is virtually
extinct but alkaline- and neutral-medium process variations do
exist. In addition to the wet digester process, there is the dry
digester process which has fundamental process similarities to the
wet process. Some wet digester systems have been or are being
converted to the dry process. The pan, or heater, process is the
most common reclaiming process and has almost replaced the wet
digester process. The least common or least conventional process is
the mechanical process and it is believed that only one plant uses
this technology. Both the pan and mechanical reclaim processes need
defibered scrap rubber produced by the physical defibering process.
It was concluded that there are essentially three distinct process
technologies used by the rubber reclaiming industry sector: 1)
digester (wet and dry) process, 2) pan (or heater) process, and 3)
mechanical process.
Product
There are primarily two types of reclaimed rubber produced by the
industry. One type is general reclaim prepared from general scrap
rubber items but principally scrap tires; the other type of
reclaimed rubber is butyl rubber reclaim produced exclusively from
scrap inner tubes. The scrap inner tube raw material requires no
defibering, whereas general scrap rubber, like tires, requires
either physical or chemical defibering. Although there are distinct
product and process differences inherent in these two types of
reclaim product, there is little waste water impact, since most
reclaim plants produce the two products side by side and, in any
case, the physical defibering which can be used by all reclaim
plants is essentially a dry process.
It was concluded, therefore, that there were no reasonable grounds
for subcategorization of the rubber reclaiming industry based on the
type of product.
Raw Materials
As discussed in the section above, two basic types of raw materials,
general scrap and scrap inner tubes, are used by the reclaiming
industry. Since both of these can be used side by side and because
the quantity of inner tube scrap is normally overshadowed by the
quantity of general scrap rubber being processed in the reclaim
plant, subcategorization according to raw material type is not
deemed necessary.
Plant Size
61
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Most rubber reclaiming plants in business today tend to be large
production facilities. Remaining smaller plants are generally
connected to municipal waste water treatment systems and, as such,
are subject to pretreatment standards. It is anticipated that
future reclaim plants to be constructed or re-opened will have large
production capacities.
Thus, it is concluded that further subcategorization according to
plant size is not warranted for the reclaim industry.
Plant Age
In general, reclaiming plants tend to be old facilities and in the
past, process advances have been incorporated via modification or
refurbishment rather than by the construction of grass-roots
reclaiming plant using the latest process technology. Further, the
age effect of process technology changes and developments are
adequately taken into account by considering subcategorization based
on the reclaim process used as discussed above.
Plant Location
The few surviving reclaim plants are not limited to one particular
region. The location of reclaiming plants is probably linked very
closely to a cheap and available supply of scrap tires. However,
neither the process technology nor the waste water treatment method
is dependent on the geographic location and, therefore, further
subcategorization for reasons of geographic location is not
required.
Air Pollution Control Equipment
Rubber reclaiming plants are infamous for the odor problems they
create in the neighborhood of the plants. Wet air pollution control
devices are common in the industry; however, similar control
measures are required for all plants using the same reclaiming
process. Therefore, subcategorization of the rubber reclaiming
industry according to the extent and type of air pollution control
equipment employed is not necessary.
Nature of Wastes Generated
The types and characteristics of the waste waters produced by the
pan (heater), mechanical, and dry digester processes are similar
although the waste waters generated by the pan and dry digester
processes are probably slightly more contaminated with organics than
the waste waters produced by mechanical process. Therefore, if the
mechanical, dry digester, and pan processes are studied as one
subcategory, the developed guidelines should be based on the
exemplary treatment applicable to the pan and dry digester
processes.
Such a data contraction or simplification is not detrimental to the
objectives of the guidelines study since only one plant is known to
62
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use the mechanical reclaim process. The waste waters produced by
the wet digester process are more contaminated than those generated
by the other reclaim processes and their control and treatment is
more involved. Accordingly, the rubber reclaim subcategorization is
based solely on waste water types. The result is two subcategories:
1) wet digester process, and 2) other reclaim processes to include
the pan, mechanical, and dry digester processes.
Treatabilitv of Waste Waters
The treatabilities of the process waste waters produced by the pan,
dry digestion, and mechanical processes are similar and are based on
suspended solids and oil removal. By contrast, the waste waters
created by the wet digester process, as well as requiring oil and
suspended solids removal, warrant further treatment to reduce
dissolved organic contaminants. In light of these differences, the
reclaiming industry should be separated into two distinct
subcategories: 1) wet digestion reclaimed rubber, and 2) pan, dry
digestion, and mechanical reclaimed rubber.
Summary
In order to establish effluent limitations and standards of control
and treatment, the rubber reclaiming industry sector should be
divided into two subcategories because of differences in the natures
of the generated waste waters and their treatabilities. The two
subcategories are:
1. Wet digestion reclaimed rubber
2. Pan (heater), mechanical, and dry digestion
reclaimed rubber.
Latex-Based Products
Manufacturing Process
Two types of manufacturing process are predominant in the production
of latex-based products. Dipped goods, such as surgical gloves, are
made by single or multiple dipping operations. Latex foam
production, on the other hand, involves the frothing or foaming of
rubber latex followed by curing. It should be noted that although
the two process technologies exhibit distinct differences there are
strong similarities in the two processes from the standpoints of
materials handling and waste water characteristics. It was apparent
that the latex-abased industry should be tentatively subcategorized
into dipped goods and foam subsectors in order to reflect the
differences in the process technologies. Latex-based products such
as latex thread and items formed in porous molds, although minor
product types, must be considered separately until final conclusions
can be made as to which subcategory they should be assigned.
Product
63
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The products made from latex-based raw materials are varied.
However, the manufacturing processes, waste water characteristics,
and treatment efficiencies of many of these product types are
similar. Therefore, only four product segments are required. These
segments are dipped goods and latex foam as well as the minor
products, latex thread and porous mold items.
Raw Materials
The basis for the separation of the latex^based products sector from
the other sectors of the industry covered by these guidelines was
the fact that rubber latex was the common raw material. The various
types of rubber latex used do not have differing waste water impact
and thus there is no need for further subcategorization according to
the type of raw material used.
Plant Size
The size distribution of dipped goods manufacturing facilities is
relatively confined, and it is not necessary to study the waste
water characteristics and treatment techniques of several plant
sizes for this subcategory. The one known latex foam plant has a
raw material usage of 200,000 Ibs/day latex solids and is large in
comparison with latex dipping facilities. It is believed by many
rubber industry experts that no other foam production facilities
exist in the United States. It is certainly true to say that few
significant latex foam plants are currently operating. Therefore,
only one size of foam plant will be studied, namely that of the
plant that is known to exist.
Plant Age
The process technology used by the latex dipping industry has not
changed significantly since the advent of the industry, and
therefore plant age is not considered a necessary factor for further
subcategorization. Since there is only one significant latex foam
production facility, plant age is not a reason for subcategorization
of the latex foam category. This approach is supported by the fact
that the changes in latex foam production methods over the years
have not had a waste water impact.
Geographical location does not have any effect on the process
technologies or waste water treatments used in either the latex
dipping or foam producing industries. Thus plant location is not
justified as a factor for subcategorization.
Air Pollution Control Equipment
Pew air pollution controls and no wet scrubbing devices are used by
either the latex dipped goods or foam industry sectors.
Accordingly, air pollution control equipment needs do not constitute
grounds for further subcategorization of the industry.
Nature of Wastes Generated
64
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Waste waters generated by this sector of the industry are
characterized by latex solids, which result from spills or leaks
around loading/unloading areas, and from operations associated with
tankage, blending, and product wash facilities. Product and
equipment washing operations result in surfactants entering the
waste water. A separate problem for the latex foam industry is the
existance of high zinc concentrations in the foam rinse operations.
Based on the specific characteristics of the zinc-laden foam rinse
waters, the latex-based products industry is divided into two
subcategories: dipped goods (including thread and porous mold
items) and latex foam.
Treatabilitv of Waste Waters
The treatability of latex-laden waste waters from all types of
production facility can be treated similarly with chemical
coagulation and clarification for primary treatment and biological
treatment for the removal of soluble contaminants. The zinc-laden
waste waters generated in foam plants require chemical precipitation
and clarification as primary treatment followed by biological
secondary treatment.
With this in mind, it was deemed necessary to separate this industry
sector into two separate subcategories, dipped goods (as well as
thread and porous mold items) and latex foam, based on the different
treatabilities of the waste waters.
Summary
Investigations of the latex-based products industry point to
subcategorization of this sector based on process, plant size, waste
water characteristics, and treatability. Therefore, the
subcategorization should be:
1. Dipped goods, latex thread, and items made in porous molds.
2. Latex foam.
The arguments presented in this section have produced the following
subcategori zation:
Small-sized general molded, extruded, and fabricated rubber plants
subcategory, medium-sized general molded, extruded, and fabricated
rubber plants subcategory, large-sized general molded, extruded, and
fabricated rubber plants subcategory, wet digestion reclaimed rubber
subcategory, pan, dry digestion, and mechanical reclaimed rubber
subcategory, latex-dipped, latex-thread, and latex-molded
subcategory, and the latex foam subcategory.
65
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SECTION V
WASTE CHARACTERIZATION
General Molded, Extruded, and Fabricated Rubber
Subcategpries
General
Waste water characterization data was obtained from literature, EPA
documents, and company data. Plant visits (refer to Section VII)
were made to confirm this data. Figures 1, 2, 3, 4 and 7 are
generalized process diagrams of typical molded, extruded, hose,
footwear, and cement-dipped production facilities, respectively;
they indicate the location of water supply and waste water
generation streams.
Total Effluent
Table 12 summarizes total effluent quantities and contaminant
loadings. All data is normalized to a unit of raw material
consumption. Indicated flow rate values include both process and
nonprocess waste waters. Nonprocess waste water can include once-
through cooling water, cooling tower blowdown, boiler blowdown,
water treatment wastes, domestic wastes, and steam condensate. The
largest portion of the total effluent flow is cooling water
discharge. Fluctuations in the flow rates generally reflect water
management practices. For instance, plants G and C use recirculated
cooling water, whereas plants A and D have once-through cooling
systems.
Values tabulated for raw waste loads include both process and
nonprocess waste waters. In addition to the values listed, tests
were conducted for other contaminants, such as phenols, chromium,
and zinc. Phenol content in all the plants visited was minimal and
it can be assumed that phenols in Subcategories E, F, and G total
raw effluents will not be significant. Chromium and zinc can be
present in the total plant effluent from nonprocess waste waters
evolved from cooling tower blowdowns, but concentrations are usually
below the measurable level. As with flow rates, COD and BOD load-
ings reflect water management techniques. Typically, the use of
cooling water treatment chemicals in recirculated cooling water
systems will raise the COD and BOD loadings in the final effluent.
Suspended solids and oil loadings are attributable to process waste
water discharges. These loadings in the total effluent appear minor
when compared to COD and BOD loadings. There are two major reasons
for this: first, process flow rates are minor relative to nonprocess
discharges and dilution by nonprocess waste waters reduces their
concentrations in final raw effluents; secondly, the plants listed
are exemplary. Sound housekeeping and maintenance practices
substantially reduce suspended solids and oil loadings in raw
effluents.
67
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Plant
A
B
C
fj\ o
00
E
F
C
H
>S<» 1
Size 2
Size 3
J Included
Table
Product Tvae
Seels, General Molded Items,
Rubber-Mete 1 Bonded Items
Cement Dipped Cloves
Molded Sport Grips,
Rubber-Metal Bonded Items
Hose, Various Sizes
Belting and Sheet Rubber
large Seals and Weather
Stripping
Hose, Various Sizes
Canvas and Cement Dipped
Footwear
Size'
2
2
3
3
3
3
Flow COD
L/kkg (gal/1000 Ib) kg/kkg (lb/1000 Ib)
of raw material of raw material
69.771 (8,362) i.395
II. 3*0 (1,359) 0.028
10,560 (1 ,265) 0.528
120.0142 (114.1405) 2.l40>4
22.122 (2.651) 1.3"«9
29.683 (3,557) 1.703
7.290 (875) 1.903
60,369 (7.235) "1.601
BOD
kg/kkg (lb/1000 Ib)
of raw material
1.6145
0.037
0.21)9
1.211)
0.1914
0.161
0.205
0.385
SS IDS
kg/kkg (lb/1000 Ib) kg/kkg (lb/1000 Ib)
of raw material of raw material
0.0676 1)5.839
0.102 "4.35*
0.137 8.3142
0.120 72.8141
0.221 68.598
1.828 25.189
0.28 2.753
1.731) 12.686
Oil Lead
kg/kkg (lb/1000 Ib) kg/kkg (lb/1000 Ib)
of raw material of raw material
. . 785
0.010
0.07*
0.091) 0.001
0.103
0.138
0.221) 0.059
0.39*
less than 3,720 kg/day (8,200 Ib/day) raw materials consumption.
3,720 - 10.1430 kg/day (8,200 - 23,000 Ib/day) raw materials consumption.
greater than 10,1430 kg/day (23,000 Ib/dey) raw materials consumption.
utility waste waters.
12: Raw Waste Loads of
Subcatesories EL F,
Total
and G
Effluent from Exemplary
Facilities
-------
Dissolved solids loadings in the raw effluents is a function of both
the water management techniques, particularly with utility services,
and the quality of the water supply source. Typically, the use of a
cooling water recirculation system or the use of an underground raw
water source will increase the dissolved solids loadings in the
final effluent.
The raw waste waters from Plant D and Plant G contain lead and, in
general, have a higher COD content. This is attributable to
vulcanization techniques employed in hose manufacturing.
Raw waste water loadings of Plant B are lower than the other plants.
This plant produces cement dipped goods. Their manufacture requires
less heavy machinery and a correspondingly smaller amount of
nonprocess and process waste waters are evolved.
Individual Process Streams
The primary source of process waste waters within the whole
industrial category is related to the use of heavy machinery, and
various anti-tack solutions. Leakage of bearing, gear, and seal oil
can readily pass into nearby drains and be carried into the waste
water effluents. Oil powered hydraulic systems provide additional
potential for oil contamination of waste waters. Anti-tack agents
which are allowed to spill onto the floor can, when not properly
handled, contaminate plant effluents, contributing a potentially
high suspended solid loading. Washdown of the dipping areas where
anti-tack agents are in use will create an additional suspended
solids loading in the effluents. In addition, uncontrolled or
untreated runoff from outdoor oil storage areas will contribute to
additional oil loadings in the effluent. Flow, oil, and suspended
solids contributions from these sources are the major components of
the total process effluent. Smaller plants, with a typically less
efficient operation (smaller throughput per machine) and older
machinery, normally have higher normalized oil and suspended solids
loadings. Larger storage areas in relation to production level are
also typical of smaller plants and potential contamination from
these areas is relatively greater.
The discharge from wet air emission control devices is another
process waste water which, although of less significance, is common
to the entire industry. Particulate air collection equipment is
necessary in the compounding areas and those areas where grinding or
buffing of rubber occurs. This would include such processes as
buffing of products to remove flash and the grinding of rubber from
metal parts. Air pollution control devices in the compounding areas
are typically the dry bag-type collectors. Devices in other areas
can be either wet or dry. If wet, there does exist the potential
for waste waters when discharges are not recycled.
Other process waste waters of minor importance include the discharge
of contact cooling water, product testing waters, and spillage of
mold release solution. Product testing and contact cooling waters
are not contaminated and in some cases are recycled. Mold release
69
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solutions are usually applied manually. Spillage from this area is
minute and easily controlled.
Process waste waters specific to particular products within this
industry include vulcanizer condensate from the curing of both lead-
sheathed and cloth-wrapped hoses, vulcanizer condensate from the
curing of cement dipped items, and latex discharges from fabricated
rubber production facilities.
Discharges of condensate from the curing of lead sheathed hose are
characterized by a high lead concentration (approximately 60 mg/1).
However, a relatively small lead loading results, due to the
extremely low flow rates of the condensate.
Vulcanizer condensate from the curing of cement dipped goods is
characterized by high COD concentrations (approximately 800 mg/1)
caused by solvents evaporated from the product by the steam
condensate. Flow rates, however, are small, resulting in minor COD
loading (O.U kg/kkg of raw material). The vulcanizer condensate
produced during the curing of cloths-wrapped hose has a lower COD
concentration and loading than the cement-dipped condensate.
Latex discharges are characterized by COD, BOD, and suspended solids
loadings, but with proper handling and controls they are relatively
minor.
In summary, the major process streams are:
1. Spills, leakage, washdown, and runoff from processing and
storage areas.
2. Vulcanizer condensate from the curing of lead-sheathed and
cloth-wrapped hoses.
3. Vulcanizer condensate from the cure of cement dipped items.
Flow rates and loadings for these streams are listed in
Table 13.
Summary
Based on the discussion above, several conclusions can be drawn
about the waste waters generated by Subcategories E, F, and G:
1. Process waste waters are of a low flow rate and have little
impact on the total effluent flow rate.
2. The most significant process waste water streams occur by
spillage, leakage, washdowns, and runoff. They contribute
the majority of the suspended solids and oil in the final
effluent. The flow rate of this type of process waste
water is dependent on plant size, and increases relative to
production level as plant size decreases.
70
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Oil
Lead
Waste Water Types
General Process Wastes
-Spills, Leaks, Washdown
and Runoff
Spills, Leaks, Washdown
and Runoff
Spills, Leaks, Washdown
and Runoff
Specific Process Wastes
Vulcanlzer Conden»ate
Vulcantzer Condensate
1 1 OH t T
1 All Product Types
2 All Product Types
3 All Product Types
All Sizes Hose manufactured by
the lead sheathed
cure process
All Sizes Cement Dipped Goods
Flow
L/kkg(gal/1000 Ib)
of raw materials
16,200 (1.9WO
9,810 (1,177)
6,210 (7<<5)
1*50 (5M
528 (63)
COD
Kg/kkg(lb/1000 Ibi mg/L
of raw materials
2.960 182
1.770 180
1.120 180
-
0.1*35 823
SS
Kg/kkg(lb/1000 Ib) mg/L
of raw materials
3.500 216
1.220 122
0.900 1U5
0.030 63
0.005 10
Kg/kkg (lb/1000 Ib) mg/L Kg/kkg ( Ib/iouo ibl mg/L
of raw materials of raw materials
1.000 62
0.600 60
0.380 61
0.030 63
0.030 63
_
and Hose manufactured
by the cloth wrapped
cure process
Size 1- less than 3,720 kg/day (8,200 Ib/day) raw materials consumption.
Size 2- 3,720 - 10.U30 kg/day (8,200 - 23,000 Ib/day) raw materials consumption.
Size 3: greater than 10,
-------
3. Other process streams worthy of consideration are
vulcanizer condensate from the lead-sheathed and cloth-
wrapped hose production and cement dipped goods
manufacture.
U. Other process streams are of negligible importance, their
impact being minor or undetectable.
Subcategorv H •«•- Wet Digestion, and Subcateaorv I — Pan (Heater) .
Mechanical. and Dry Digestion Reclaimed Rubber Industries
General
Data for characterizing the two reclaim subcategories were obtained
primarily from EPA documents and the companies. A data collection
visit was made at a plant which used both the wet digester and pan
processes in order to obtain further first-hand information. Since
the total number of facilities producing reclaimed rubber is small,
each existing plant was also interviewed to supplement the primary
data on processing techniques, and waste water types and treatment
methods.
Total Effluent
Table 1U summarizes the total process and nonprocess waste water
effluent quantities and contaminant loadings of the plant visited.
All data are normalized to a unit of weight of reclaimed rubber
product. Table 15 presents raw waste loads of process waste water
effluents.
The flow rates presented include both process and nonprocess waste
waters. For this plant, nonprocess waste waters include once-
through cooling water and steam condensate. Nonprocess water
contributes the bulk of the flow rate.
Rubber scrap coining to the plant is segregated. Tires are reclaimed
by the wet digester process; whereas fiber-free scrap, such as inner
tubes, is fed to the pan process. Since tire reclaiming requires
additional grinding and associated cooling water, particularly as
preparation for the mechanical defibering operation, the wet
digester process waste water flow rates are higher than those of the
pan process. Incidentally, if tires were reclaimed by the pan
process, the flow of nonprocess cooling water would be greater.
The nonprocess cooling water is relatively contaminant free,
containing COD, BOD, and suspended solids attributable to the water
source rather than the reclaiming process. Therefore, the
contaminant loadings presented in Table 14 are almost entirely
attributable to process waste water streams.
In the wet digester process (Subcategory H) , the major constituents
include COD, BOD, suspended solids, and oil. Analytical testing was
made for phenols and heavy metals, in particular zinc, but the
levels were negligible. The existing wet digester processes do not
72
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Plant
Product Type
Reclaimed Rubber
SUB CATEGORY
Flow
L/kkg (gal/1000 Ib)
of products
Sg.'tSl (10,720)
COD
kg/kkg (lb/1000 Ib)
of products
1..6862
BOO
kg/kkg (lb/1000 Ib)
of products
0.896
SS
kg/kkg (lb/1000 Ib)
of products
1.890'
TDS
kg/kkg (lb/1000 Ib)
of products
11.832
on
kg/kkg (lb/1000 Ib)
of products
O.U272
Reclaimed Rubber
7<».765 (8.960)
2.813
0.535
7.801
0.210
~^i .
OJ 'Value does not include any flberous material which is removed at this plant prior to digestion.
Includes reductions made through the reuse of digester liquors .
'includes utility waste waters .
Table 14: Rav Waste Loads of Total Effluent from Exemplary
Subcategorles H and I Processes-*
-------
Flow
COD
BOD
SS
Oil
SOBCATEGORY H: Wet Digester Process
Spills, Leaks, Washdown
and Runoff
Vapor Condensate from
Air Pollution Control Devices
Dewaterlng Liquor (Chemical Deflberlng)'
Dewaterlng Liquor (Mechanical Deflbering)
L/kkg(ga 1/1000 Ib)
of products
3130 (37*0
1620 (195)
2391 (286)
2391 (286)
kg/kkg(lb/1000 Ib) mg/L kg/kkg(lb/1000 Ib) mg/L kg/kkg( lb/1000 Ib) mg/L kg/kkg(lb 1000/1b) mg/L
of products of products of products of products
0.3'*5 110 0.085 27 0.190 287 0.760
0.396 2l>0 0.108 70 0.108 70 0.783
9.010 3910 1.800 790 256.000 106,650 25. TtJ
9.010 3910 1.800 790 1 .1*00 585 25.7'»7
2UO
1)80
10,770
10,770
*• SDBCATECORY I: Pan. Dry Dleescer and Mechanical Procesa
Spills, Leaks, Washdown
and Runoff
Vapor Condensate from
3130 (37
-------
produce zinc-laden waste waters as were encountered with the older
or more conventional digester processes.
Values presented in Table 14 for Subcategory H represent raw waste
loads after in-plant control. As mentioned earlier, fiber is
removed from the scrap mechanically, thereby reducing the suspended
solids loading of the effluent. In addition, dewatering liquors and
vapor condensates are reused as makeup to the digester, thus
reducing final oil and COD loadings. The final loadings of
importance are oil, suspended solids, and COD.
In the reclaim processes for Subcategory I (including pan,
mechanical and dry digestion reclaim processes) the process waste
waters have lower flow and contaminant loadings than the wet
digestion process. This is due to the absence of the dewatering
liquor waste water stream and the lower usage of depolymerizing oils
in the dry reclaiming processes.
Individual Process Streams
The primary source of process waste water loadings for Subcategory H
is dewatering liquor. High COD and oil loadings are characteristic
of this discharge. When mechanically defibered scrap is fed to the
wet digester process, suspended solids are contained in the
dewatering liquor owing to the carrying over of depolymerized rubber
fines. If defibering is carried out chemically in the digestion
step, additional suspended solids due to the fiber will be present.
A second major source of contaminant loadings for both Subcategory H
and Subcategory I is spills, leaks, and washdown from processing
areas. The discharge is qualitatively similar to the corresponding
discharge of Subcategories E, F, and G; however, flow rates and
loading on a per-day basis are substantially higher.
A third major source of contaminant loadings is air control
equipment used to collect light organics which are vaporized or
entrained in the vapors leaving the pan devulcanizers or the wet
digester system. Flows and loadings from the wet digester process
are substantially higher than those of the pan process. In the wet
digestion process, the oil contained in these condensates can be
recycled.
Summary
Waste waters generated by the reclaiming industry, Subcategories H
and I contain the following major contaminant constituents: COD,
suspended solids, and oil. Toxic materials like zinc and phenol
were not present in the waste waters from this industry sector. For
Subcategory H, dewatering liquor contributes the majority of the
total COD, oil and suspended solid loadings. In both Subcategories,
spills, leaks, washdown, and runoff from processing areas are a
substantial source of effluent contamination. Additional
contamination is attributable to the control of vapor emissions from
both the pan and wet digester processes.
75
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Loadings for waste waters from Subcategory H are substantially
higher than those of Subcategory I. In-plant controls such as the
use of mechanically defibered scrap and the recycle of dewatenng
liquors does not reduce the waste water loadings associated with the
Subcategory H process to the levels resulting from the Subcategory I
reclaiming process.
Latex-based Products Subcatecrories
General
Waste water characterization data for Subcategories J and K were
obtained from literature, EPA documents, company records, and first-
hand plant data. Plant visits (refer to Section VII) were made at
two latex dipping facilities and one latex foam plant. Generalized
process flow diagrams, indicating both product flow and waste water
generation points, are presented in Figures 6 and 8.
Total Process Effluent
Table 16 summarizes the total process effluent quantities and
contaminant loadings produced by the latex-based - industry sector.
All data is normalized to a unit of latex consumption. Flow rates
are higher for the latex foam due to the larger amounts of
processing and product washing waters required.
Effluent streams were measured for COD, BOD, suspended solids,
dissolved solids, oil, surfactants, zinc, and phenols. Phenols were
not found in any of the waste waters. Zinc was found in process
waste waters from the latex foam facility. No zinc was found in
waste waters generated by latex dipped facilities. COD, BOD,
suspended solids, and dissolved solids are attributable to latex in
the waste water. Loadings for Plant K are substantially higher
because of the contributions of detergent-laden wash waters which
also produce a higher flow. The oil in the waste waters is more an
extractable organic material than bonafide oil and grease. This
characteristic of the oil analysis is based on a carbon
tetrachloride extraction procedure. Surfactants are contributed by
the emulsifying agents used in the latex mix and additionally in
Plant K by the detergent present in the washing waste waters.
Individual Process Streams
The principal source of waste waters within these subcategories is
product wash waters. These wash waters are characterized by a COD,
BOD, dissolved solids and suspended solids loading. The loadings of
these waste waters are highly dependent on the washing techniques
employed by the company. Company K uses detergents in the washing
operations, whereas Company J uses only high temperature water
(approximately 200°F). The use of detergents adds to COD and BOD
loadings in the raw effluent. Flows are also highly dependent on
the technique employed. Higher flow rates are normally envolved
from multiple washings.
76
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Plant Product Type Flow COP BOO SS TOS Oil
J
K
Latex Dipped
Prophylactics,
Balloons,
Finger Cots
Latex Dipped
Gloves
L/kkg (gal/ 1000 Ib)
of raw material
1(3,200 (5,180)
102,920 (12,350)
kg/kkg()b/1000 Ib)
of raw material
7.60
69.73
kg/kkg(lb/1000 Ib)
of raw material
5.75
15.66
kg/kkg(lb/1000 Ib)
of raw material
3.38
310.70
kg/kkg(lb/1000 Ib)
of raw material
'•g.so
39.58
kg/kkg(lb/1000 Ib)
of raw material
0.2l»
13.30
kg/kkg(lb/1000 Ib)
of raw material
0.08
0.66
kg/kkg(lb/1000 Ib)
of raw material
'7'700 (2'12l° 75'85 20-^ 8'71 "•* 10-n 0.09 3.51,
Utility waste waters not included.
Table 16: Raw Waste Loads of Process Effluents from Subcateeoriea J and K
Facilities1
-------
In addition to the other loadings, discharges of product wash water
from latex foam facilities can contain high concentrations of zinc.
Zinc oxide is used as a curing agent during foam manufacture. Zinc
components, which are not held, or fixed, in the foam matrix are
removed by the wash waters.
A second source of contamination results from spills, leaks,
washdown, and runoff from latex storage, compounding, and transfer
areas. This waste water will contain latex and is characterized by
COD, BOD, suspended solids, dissolved solids, oil, and surfactant
loadings. COD, BOD, and suspended solids are present due to the
latex in the waste water. Oil and surfactants are contributed by
coagulation agents, extractable organics, and emulsifier aids.
A third source of waste water, relevant to latex dipping operations,
is form cleaning wastes. Plant J employed a biodegradeable cleaning
compound in hot water. The operation is continuous, the form being
cleaned automatically after each complete dipping operation. Waste
waters from this operation are characterized by loadings of COD, BOD
and suspended solids. Plant K cleans forms manually and only
periodically. Discharges from this area, although characterized by
similar contaminants, will be intermittent in nature and will be of
a substantially lower flow. Literature and EPA documents indicate
that certain latex dip operations use chromic acid solutions to
clean forms. Potentially these waste waters can appear in the
process effluent.
A summary of the individual process stream characteristics is
presented in Table 17.
Summary
Process waste waters from Subcategories J and K operations are
characterized by COD, BOD, suspended solids, oil and surfactant
loadings. In addition, discharges from these operations can contain
substantial quantities of zinc and chromium. The primary waste
water is product wash waters. The characteristics of the wash water
is highly dependent on the techniques employed. In the production
of latex foam, the wash water will contain zinc. Other sources of
process waste waters include spills, leaks, washdown, and runoff
from latex storage, compounding and transfer areas, and discharges
from form cleaning operations.
78
-------
Waste Water Type
-
SPBCATEGORY J
Spills, Leaks, Washdown
and Runoff from Latex
Storage, Compounding and
Dip Tank Areas
Flow
COO
BOD
SS
Surfactants
line
_ _ _
L/kkg (gal/1000 Ib) kg/kkg (lb/1000 Ib) ingTT kg/kkg (lb/1000 Ib) mg/L kg/kkg (lb/1000 Ib) mg/L mg/kkg (lb/1000 Ib) mg/L kg/kkg (lb/1000 Ib) mg/L
of raw material
1*76(57)
of -raw naterial
of raw material
of raw material
1.86
3,900
of raw material
of raw material
Single Product Wash
and Rinse Waters2
Multiple Product Wash
and Rinse Waters
SPBCATEGORY K
Foam Rinse Waters
Sp i 1 1 s , Leaks , Washdown
1*3,200 (5,180)
381,000 (1*5,710)
3,600 (1*32)
600 (72)
7.60
1*1.11*
1*7.63
17.51
176
108
13,230
29,180
5-75
9.2l*
17.62
2.17
133
21*
"*.900
3,620
3.38 78
3-51 9
25.22 7,000
0.72 1,200
0.08 2
0.66 2
0.09 25
0.002 3
-
3.51 975
0.02 33
and Runoff from Latex
Storage, Compounding
and Transfer Areas
Obtained from available U.S. Army, Corps of Engineers - Discharge Permit information; not necessarily typical.
Both single and multiple product wash and rinse water streams do not exist at any one plant.
Table 17: Raw Waste Loads of Process Effluents from Typical
Subcategories J and K Facilities
-------
SECTION VI
SELECTION OF POLLUTION PARAMETERS
subcategories E^ F^ G — General Molded, Extruded, and Fabricated
Rubber Products
From review of the, Corps of Engineers Permit Applications for
molded, extruded, and fabricated rubber production facilities and
from examination of related published data, it appears that the
following pollutants are present in measurable quantities in the
waste water effluents from Subcategories E, Fr and G production
facilities:
BOD
COD
Suspended Solids
Total Dissolved Solids
Oil and Grease
pH
Temperature (Heat)
Lead
Chromium
Examination of in-plant and analytical data obtained during the on-
site inspections of a number of production facilities indicates that
certain parameters: are present only in insignificant amounts; are
present in the raw supply water; or are contributed by discharges
unrelated to the primary production operations. Nonprocess
effluents result mainly from utility and water treatment discharges
and from domestic waste water discharges generated within the plant
boundaries. Such nonprocess discharges are the subject of other
guideline studies and are covered by other EPA documents.
The topics treated in this section include the rationale for
elimination or selection of the aforementioned parameters and
proposed recommendations.
Biochemical Oxygen Demand (BOD)
Biochemical oxygen demand (BOD) refers to the amount of oxygen
required to stabilize biodegradable organic matter under aerobic
conditions. BOD concentrations measured in process waste waters
discharged by Subcategories E, F, and G production facilities were
typically low, i.e., less than 30 mg/1. Their presence is due in
general to the organic content of the anti-tack and latex solutions.
The presence of these solutions in waste waters is better
characterized however by their suspended solids loadings.
Consequently, BOD was considered insignificant in this sector of the
rubber industry.
81
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Biochemical oxygen demand (BOD) is a measure of the oxygen consuming
capabilities of organic matter. The BOD does not in itself cause
direct harm to a water system, but it does exert an indirect effect
by depressing the oxygen content of the water. Sewage and other
organic effluents during their processes of decomposition exert a
BOD, which can have a catastrophic effect on the ecosystem by
depleting the oxygen supply. Conditions are reached frequently
where all of the oxygen is used and the continuing decay process
causes the production of noxious gases such as hydrogen sulfide and
methane. Water with a high BOD indicates the presence of
decomposing organic matter and subsequent high bacterial counts that
degrade its quality and potential uses.
Dissolved oxygen (DO) is a water quality constituent that, in
appropriate concentrations, is essential not only to keep organisms
living but also to sustain species reproduction, vigor, and the
development of populations. Organisms undergo stress at reduced DO
concentrations that make them less competitive and able to sustain
their species within the aquatic environment. For example, reduced
DO concentrations have been shown to interfere with fish population
through delayed hatching of eggs, reduced size and vigor of embryos,
production of deformities in young, interference with food
digestion, acceleration of blood clotting, decreased tolerance to
certain toxicants, reduced food efficiency and growth rate, and
reduced maximum sustained swimming speed. Fish food organisms are
likewise affected adversely in conditions with suppressed DO. Since
all aerobic aquatic organisms need a certain amount of oxygen, the
consequences of total lack of dissolved oxygen due to a high BOD can
kill all inhabitants of the affected area.
If a high BOD is present, the quality of the water is usually
visually degraded by the presence of decomposing materials and algae
blooms due to the uptake of degraded materials that form the
foodstuffs of the algal populations.
COD
Chemical oxygen demand (COD) provides a measure of the equivalent
oxygen required to chemically oxidize the organic/inorganic material
present in the waste water sample. COD in Subcategories E, F, and G
process waste waters is attributable to washdown and runoff from
contaminated oil, to anti-tack dipping, and the latex areas.
Intermittent discharges of spent anti-tack or latex solution
contribute to the COD of process waste water. Discharges of
vulcanizer condensate in cement-dipped goods production and certain
hose production also increase COD loadings. Flow rates from these
COD-contributing waste waters is small, thus resulting in low COD
loadings. Technology is not available for adequate and viable
treatment of such small COD loadings. In addition, other parameters
(such as suspended solids and oil) more readily characterize the COD
loading. Accordingly, it is not deemed necessary to subject
Subcategories E, F, and G production process effluents to COD
limitations.
82
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Total Suspended Solids
Suspended solids (SS) after discharge to a water course can settle
to the bottom, blanket spawning grounds, interfere with fish
propagation, and may exert an appreciable oxygen demand on the body
of water. Suspended solids in Subcategories E, F, and G waste
waters are due to washdown and runoff from compounding areas,
discharges of anti-tack solution and boiler blowdowns, and water
treatment wastes. During normal daily production operations, the
nonprocess blowdowns and the water treatment wastes will contribute
the largest amounts of suspended solids. Suspended solids
concentrations in process waste waters will vary from less than 10
mg/1 (with proper in-plant controls) to over 20,000 mg/1 during
anti"-tack solution dumping and discharge.
Suspended solids include both organic and inorganic materials. The
inorganic components include sand, silt, and clay. The organic
fraction includes such materials as grease, oil, tar, animal and
vegetable fats, various fibers, sawdust, hair, and various materials
from sewers. These solids may settle out rapidly and bottom
deposits are often a mixture of both organic and inorganic solids.
They adversely affect fisheries by covering the bottom of the stream
or lake with a blanket of material that destroys the fish-food
bottom fauna or the spawning ground of fish. Deposits containing
organic materials may deplete bottom oxygen supplies and produce
hydrogen sulfide, carbon dioxide, methane, and other noxious gases.
In raw water sources for domestic use, state and regional agencies
generally specify that suspended solids in streams shall not be
present in sufficient concentration to be objectionable or to
interfere with normal treatment processes. Suspended solids in
water may interfere with many industrial processes, and cause
foaming in boilers, or encrustations on equipment exposed to water,
especially as the temperature rises. Suspended solids are
undesirable in water for textile industries; paper and pulp;
beverages; dairy products; laundries; dyeing; photography; cooling
systems, and power plants. Suspended particles also serve as a
transport mechanism for pesticides and other substances which are
readily sorbed into or onto clay particles.
Solids may be suspended in water for a time, and then settle to the
bed of the stream or lake. These settleable solids discharged with
man's wastes may be inert, slowly biodegradable materials, or
rapidly decomposable substances. While in suspension, they increase
the turbidity of the water, reduce light penetration and impair the
photosynthetic activity of aquatic plants.
Solids in suspension are aesthetically displeasing. When they
settle to form sludge deposits on the stream or lake bed, they are
often much more damaging to the life in water, and they retain the
capacity to displease the senses. Solids, when transformed to
sludge deposits, may do a variety of damaging things, including
blanketing the st-ream or lake bed and thereby destroying the living
spaces for those benthic organisms that would otherwise occupy the
83
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habitat. When of an organic and therefore decomposable nature,
solids use a portion or all of the dissolved oxygen available in the
area. Organic materials also serve as a seemingly inexhaustible
food source for sludgeworms and associated organisms.
Turbidity is principally a measure of the light absorbing properties
of suspended solids. It is frequently used as a substitute method
of quickly estimating the total suspended solids when the
concentration is relatively low.
Total Dissolved Solids
High concentrations of dissolved solids (TDS) originate from the
nonprocess waste water effluents from cooling towers, boiler
blowdowns, and water treatment system backwashes and blowdowns. In
addition, high concentrations of TDS were observed in all effluents
when the raw water supply was from deep wells as opposed to city
water.
In natural waters the dissolved solids consist mainly of carbonates,
chlorides, sulfates, phosphates, and possibly nitrates of calcium,
magnesium, sodium, and potassium, with traces of iron, manganese and
other substances.
Many communities in the United States and in other countries use
water supplies containing 2000 to 4000 mg/1 of dissolved salts, when
no better water is available. Such waters are not palatable, may
not quench thirst, and may have a laxative action on new users.
Waters containing more than 4000 mg/1 of total salts are generally
considered unfit for human use, although in hot climates such higher
salt concentrations can be tolerated whereas they could not be in
temperate climates. Waters containing 5000 mg/1 or more are
reported to be bitter and act as bladder and intestinal irritants.
It is generally agreed that the salt concentration of good,
palatable water should not exceed 500 mg/1.
Limiting concentrations of dissolved solids for fresh-water fish may
range from 5,000 to 10,000 mg/1, according to species and prior
acclimatization. Some fish are adapted to living in more saline
waters, and a few species of fresh-water forms have been found in
natural waters with a salt concentration of 15,000 to 20,000 mg/1.
Fish can slowly become acclimatized to higher salinities, but fish
in waters of low salinity cannot survive sudden exposure to high
salinities, such as those resulting from discharges of oil well
brines. Dissolved solids may influence the toxicity of heavy metals
and organic compounds to fish and other aquatic life, primarily
because of the antagonistic effect of hardness on metals.
Waters with total dissolved solids over 500 mg/1 have decreasing
utility as irrigation water. At 5,000 mg/1 water has little or no
value for irrigation.
Dissolved solids in industrial waters can cause foaming in boilers
and cause interference with cleanness, color, or taste of many
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finished products. High contents of dissolved solids also tend to
accelerate corrosion.
Specific conductance is a measure of the capacity of water to convey
an electric current. This property is related to the total
concentration of ionized substances in water and water temperature.
This property is frequently used as a substitute method of quickly
estimating the dissolved solids concentration.
Oil and Grease
Oil and grease is a measure of the insoluble hydrocarbons and the
free-floating and emulsified oil in a waste water sample. Oil and
grease exist in process waste waters due to washdown, runoff,
spills, and leakage in the process areas which pick up lubricating
oil from machinery, and process and fuel oil from storage areas.
Concentration values in the total effluent range from less than 5
mg/1 to greater than 100 mg/1. Concentrations in the total plant
effluent are not directly indicative of the oil and grease problem
because of dilution by nonprocess waste waters. Loadings in the
plants visited ranged from 0.1 kg/kkg to 1.8 kg/kkg of raw material.
Since oily wastes result from intermittent flows, instantaneous
values could be much higher at times.
Oil and grease exhibit an oxygen demand. Oil emulsions may adhere
to the gills of fish or coat and destroy algae or other plankton.
Deposition of oil in the bottom sediments can serve to exhibit
normal benthic growths, thus interrupting the aquatic food chain.
Soluble and emulsified material ingested by fish may taint the
flavor of the fish flesh. Water soluble components may exert toxic
action on fish. Floating oil may reduce the re-aeration of the
water surface and in conjunction with emulsified oil may interfere
with photosynthesis. Water insoluble components damage the plumage
and costs of water animals and fowls. Oil and grease in a water can
result in the formation of objectionable surface slicks preventing
the full aesthetic enjoyment of the water.
Oil spills can damage the surface of boats and can destroy the
aesthetic characteristics of beaches and shorelines.
PHX Acidity and Alkalinity
Control and adjustment of pH in the process waste waters generated
in the Subcategories E, F, and G sector of the industry should be
practiced. Failure to maintain adequate control can have a
deleterious effect on acquatic life, post-precipitation of soluble
salts, etc.
Acidity and alkalinity are reciprocal terms. Acidity is produced by
substances that yield hydrogen ions upon hydrolysis and alkalinity
is produced by substances that yield hydroxyl ions. The terms
"total acidity" and "total alkalinity" are often used to express the
buffering capacity of a solution. Acidity in natural waters is
caused by carbon dioxide, mineral acids, weakly dissociated acids.
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and the salts of strong acids and weak bases. Alkalinity is caused
by strong bases and the salts of strong alkalies and weak acids.
The term pH is a logarithmic expression of the concentration of
hydrogen ions. At a pH of 7, the hydrogen and hydroxyl ion
concentrations are essentially equal and the water is neutral.
Lower pH values indicate acidity while higher values indicate
alkalinity. The relationship between pH and acidity or alkalinity
is not necessarily linear or direct.
Waters with a pH below 6.0 are corrosive to water works structures,
distribution lines, and household plumbing fixtures and can thus add
such constituents to drinking water as iron, copper, zinc, cadmium
and lead. The hydrogen ion concentration can affect the "taste" of
the water. At a low pH water tastes "sour". The bactericidal
effect of chlorine is weakened as the pH increases, and it is
advantageous to keep the pH close to 7. This is very significant
for providing safe drinking water.
Extremes of pH or rapid pH changes can exert stress conditions or
kill aquatic life outright. Dead fish, associated algal blooms, and
foul stenches are aesthetic liabilities of any waterway. Even
moderate changes from "acceptable" criteria limits of pH are
deleterious to some species. The relative toxicity to aquatic life
of many materials is increased by changes in the water pH,
Metalocyanide complexes can increase a thousand-fold in toxicity
with a drop of 1.5 pH units. The availability of many nutrient
substances varies with the alkalinity and acidity. Ammonia is more
lethal with a higher pH.
The lacrimal fluid of the human eye has a pH of approximately 7.0
and a deviation of 0.1 pH unit from the norm may result in eye
irritation for the swimmer. Appreciable irritation will cause
severe pain.
Temperature
Elevated temperatures in total plant effluents occur when collected
steam condensate (utility waste) is not recycled but is discharged
into the plant effluent. Elevated temperatures are not encountered
in process waste waters. Consequently, a temperature limitation for
process waste waters is not considered necessary.
Temperature is one of the most important and influential water
quality characteristics. Temperature determines those species that
may be present; it activates the hatching of young, regulates their
activity, and stimulates or suppresses their growth and development;
it attracts, and may kill when the water becomes too hot or becomes
chilled too suddenly. Colder water generally suppresses
development, warmer water generally accelerates activity and may be
a primary cause of aquatic plant nuisances when other environmental
factors are suitable.
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Temperature is a prime regulator of natural processes within the
water environment. It governs physiological functions in organisms
and, acting directly or indirectly in combination with other water
quality constituents, it affects aquatic life with each change.
These effects include chemical reaction rates, enzymatic functions,
molecular movements, and molecular exchanges between membranes
within and between the physiological systems and the organs of an
animal.
Chemical reaction rates vary with temperature and generally increase
as the temperature is increased. The solubility of gases in water
varies with temperature. Dissolved oxygen is decreased by the decay
or decomposition of dissolved organic substances and the decay rate
increases as the temperature of the water increases reaching a
maximum at about 30°C (86°F). The temperature of stream water, even
during summer, is below the optimum for pollution-associated
bacteria. Increasing the water temperature increases the bacterial
multiplication rate when the environment is favorable and the food
supply is abundant.
Reproduction cycles may be changed significantly by increased
temperature because this function takes place under restricted
temperature ranges. Spawning may not occur at all because
temperatures are too high. Thus, a fish population may exist in a
heated area only by continued immigration. Disregarding the
decreased reproductive potential, water temperatures need not reach
lethal levels to decimate a species. Temperatures that favor
competitors, predators, parasites, and disease can destroy a species
at levels far below those that are lethal.
Fish food organisms are altered severely when temperatures approach
or exceed 90°F. Predominant algal species change, primary
production is decreased, and bottom associated organisms may be
depleted or altered drastically in numbers and distribution.
Increased water temperatures may cause aquatic plant nuisances when
other environmental factors are favorable.
Synergistic actions of pollutants are more severe at higher water
temperatures. Given amounts of domestic sewage, refinery wastes,
oils, tars, insecticides, detergents, and fertilizers more rapidly
deplete oxygen in water at higher temperatures, and the respective
toxicities are likewise increased.
When water temperatures increase, the predominant algal species may
change from diatoms to green algae, and finally at high temperatures
to blue-green algae, because of species temperature preferentials.
Blue-green algae can cause serious odor problems. The number and
distribution of benthic organisms decreases as water temperatures
increase above 90°F, which is close to the tolerance limit for the
population. This could seriously affect certain fish that depend on
benthic organisms as a food source.
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The cost of fish being attracted to heated water in winter months
may be considerable, due to fish mortalities that may result when
the fish return to the cooler water.
Rising temperatures stimulate the decomposition of sludge, formation
of sludge gas, multiplication of saprophytic bacteria and fungi
(particularly in the presence of organic wastes). and the
consumption of oxygen by putrefactive processes, thus affecting the
esthetic value of a water course.
In general, marine water temperatures do not change as rapidly or
range as widely as those of freshwaters. Marine and estuarine
fishes, therefore, are less tolerant of temperature variation.
Although this limited tolerance is greater in estuarine than in open
water marine species, temperature changes are more important to
those fishes in estuaries and bays than to those in open marine
areas, because of the nursery and replenishment functions of the
estuary that can be adversely affected by extreme temperature
changes.
Heavy metals such as lead are toxic to microorganisms because of
their ability to tie up proteins in the key enzyme systems of the
microorganism. Lead appears in process waste waters from hose
production facilities which use a lead sheath cure. The lead is
picked up by the wasted steam condensate. Loadings in the total
process effluent were less than 0.06 kg/kkg of raw material
consumption.
Chromium
Chromium appears in the nonprocess discharges mainly from the
cooling tower blowdown. Chromium compounds are sometimes used as a
corrosion inhibitor and are added to the tower basin or cooling
tower makeup. Chromimum was not detected in the process waste water
effluent.
Chromium, in its various valence states, is hazardous to man. It
can produce lung tumors when inhaled and induces skin
sensitizations. Large doses of chromates have corrosive effects on
the intestinal tract and can cause inflammation of the kidneys.
Levels of chromate ions that have no effect on man appear to be so
low as to prohibit determination to date.
The toxicity of chromium salts toward aquatic life varies widely
with the species, temperature, pH, valence of the chromium, and
synergistic or antagonistic effects, especially that of hardness.
Fish are relatively tolerant of chromium salts, but fish food
organisms and other lower forms of aquatic life are extremely
sensitive. Chromium also inhibits the growth of algae.
-------
In some agricultural crops, chromium can cause reduced growth or
death of the crop. Adverse effects of low concentrations of
chromium on corn, tobacco and sugar beets have been documented.
summary of Significant Pollutants
Of the pollutants examined, only COD, suspended solids, oil and
grease, lead, and pH are significant characteristics when
considering process waste waters. Of the five, suspended solids,
oil and grease, lead, and pH must be controlled, treated, and
monitored. The recommended list of control parameters for
Subcategories E, F, and G therefore is:
Suspended Solids
Oil and Grease
Lead
pH
Subcategorv H and Subcatecrorv I — Reclaimed Rubber
Review of published literature, EPA documents and industry records,
and the findings of the plant visits indicate that the following
chemical and biological constituents are pollutants found in
measurable quantities from Subcategory H and Subcategory I
effluents:
BOD
COD
Suspended Solids
Total Dissolved Solids
Oil and Grease
pH
Temperature
Zinc
Biochemical Oxygen Demand (BOD)
The presence of BOD in Subcategory H process waste waters is due
primarily to the use of large quantities of process waters in the
digestion of scrap rubber. This waste water is not evolved in
Subcategory I production facilities. A second source of BOD is
organics found in the condensed vapors collected from both
Subcategory H and Subcategory I depolymerization units. Organics
found in anti-tack solution discharges contribute additional BOD.
Normally, the presence of this BOD is more conveniently
characterized by COD and suspended solids since the BOD analytical
test is inherently less consistent and the results are not known
until the sixth day of the test.
Biochemical oxygen demand (BOD) is a measure of the oxygen consuming
capabilities of organic matter. The BOD does not in itself cause
direct harm to a water system, but it does exert an indirect effect
by depressing the oxygen content of the water. Sewage and other
organic effluents during their processes of decomposition exert a
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BOD, which can have a catastrophic effect on the ecosystem by
depleting the oxygen supply. Conditions are reached frequently
where all of the oxygen is used and the continuing decay process
causes the production of noxious gases such as hydrogen sulfide and
methane. Water with a high BOD indicates the presence of
decomposing organic matter and subsequent high bacterial counts that
degrade its quality and potential uses.
Dissolved oxygen (DO) is a water quality constituent that, in
appropriate concentrations, is essential not only to keep organisms
living but also to sustain species reproduction, vigor, and the
development of populations. Organisms undergo stress at reduced Do
concentrations that make them less competitive and able to sustain
their species within the aquatic environment. For example, reduced
DO concentrations have been shown to interfere with fish population
through delayed hatching of eggs, reduced size and vigor of embryos,
production of deformities in young, interference with food
digestion, acceleration of blood clotting, decreased tolerance to
certain toxicants, reduced food efficiency and growth rate, and
reduced maximum sustained swimming speed. Fish food organisms are
likewise affected adversely in conditions with suppressed DO. Since
all aerobic aquatic organisms need a certain amount of oxygen, the
consequences of total lack of dissolved oxygen due to a high BOD can
kill all inhabitants of the affected area.
If a high BOD is present, the quality of the water is usually
visually degraded by the presence of decomposing materials and algae
blooms due to the uptake of degraded materials that form the
foodstuffs of the algal populations.
COD
The presence of organics and inorganics in dewatering waste waters
will contribute to high COD concentrations in Subcategory H process
waste waters. Values for this waste stream are greater than 3,000
mg/1. Other contributors of COD include organics found in condensed
vapor streams for depolymerization units and anti-tack solutions
used in both Subcategory H and Subcategory I production facilities.
Concentrations in these latter sources ranged from approximately 100
mg/1 to 3UO mg/1. A large portion of this COD is directly
attributable to the oil content of these waste streams.
Suspended Solids
Suspended Solids (SS) in Subcategory H and Subcategory I are
attributable to washdown and runoff from compounding areas,
discharges of anti-tack solution, boiler blowdowns, and water
treatment wastes. Additional loadings in Subcategory H discharges
will result when fiberous stock is fed to the digesters. In this
case, the dewatering liquor can contain as much as 10-percent
suspended solids.
Suspended solids include both organic and inorganic materials. The
inorganic components include sand, silt, and clay. The organic
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fraction includes such materials as grease, oil, tar, animal and
vegetable fats, various fibers, sawdust, hair, and various materials
from sewers. These solids may settle out rapidly and bottom
deposits are often a mixture of both organic and inorganic solids.
They adversely affect fisheries by covering the bottom of the stream
or lake with a blanket of material that destroys the fish-food
bottom fauna or the spawning ground of fish. Deposits containing
organic materials may deplete bottom oxygen supplies and produce
hydrogen sulfide, carbon dioxide, methane, and other noxious gases.
In raw water sources for domestic use, state and regional agencies
generally specify that suspended solids in streams shall not be
present in sufficient concentration to be objectionable or to
interfere with normal treatment processes. Suspended solids in
water may interfere with many industrial processes, and cause
foaming in boilers, or encrustations on equipment exposed to water,
especially as the temperature rises. Suspended solids are
undesirable in water for textile industries; paper and pulp;
beverages; dairy products; laundries; dyeing; photography; cooling
systems, and power plants. Suspended particles also serve as a
transport mechanism for pesticides and other substances which are
readily sorbed into or onto clay particles.
Solids may be suspended in water for a time, and then settle to the
bed of the stream or lake. These settleable solids discharged with
man's wastes may be inert, slowly biodegradable materials, or
rapidly decomposable substances. While in suspension, they increase
the turbidity of the water, reduce light penetration and impair the
photosynthetic activity of aquatic plants.
Solids in suspension are aesthetically displeasing. When they
settle to form sludge deposits on the stream or lake bed, they are
often much more damaging to the life in water, and they retain the
capacity to displease the senses. Solids, when transformed to
sludge deposits, may do a variety of damaging things, including
blanketing the stream or lake bed and thereby destroying the living
spaces for those benthic organisms that would otherwise occupy the
habitat. When of an organic and therefore decomposable nature,
solids use a portion or all of the dissolved oxygen available in the
area. Organic materials also serve as a seemingly inexhaustible
food source for sludgeworms and associated organisms.
Turbidity is principally a measure of the light absorbing properties
of suspended solids. It is frequently used as a substitute method
of quickly estimating the total suspended solids when the
concentration is relatively low.
Dissolved Solids
Dissolved Solids (TDS) found in Subcategory H and Subcategory I
effluents are attributable to nonprocess waste water effluents.
These include cooling tower and boiler blowdowns and water treatment
system backwashes and blowdown.
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In natural waters the dissolved solids consist mainly of carbonates,
chlorides, sulfates, phosphates, and possibly nitrates of calcium,
magnesium, sodium, and potassium, with traces of iron, manganese and
other substances.
Many communities in the United States and in other countries use
water supplies containing 2000 to UOOO mg/1 of dissolved salts, when
no better water is available. Such waters are not palatable, may
not quench thirst, and may have a laxative action on new users.
Waters containing more than 4000 mg/1 of total salts are generally
considered unfit for human use, although in hot climates such higher
salt concentrations can be tolerated whereas they could not be in
temperate climates. waters containing 5000 mg/1 or more are
reported to be bitter and act as bladder and intestinal irritants.
It is generally agreed that the salt concentration of good,
palatable water should not exceed 500 mg/1.
Limiting concentrations of dissolved solids for fresh-water fish may
range from 5,000 to 10,000 mg/1, according to species and prior
acclimatization. Some fish are adapted to living in more saline
waters, and a few species of fresh-water forms have been found in
natural waters with a salt concentration of 15,000 to 20,000 mg/1.
Fish can slowly become acclimatized to higher salinities, but fish
in waters of low salinity cannot survive sudden exposure to high
salinities, such as those resulting from discharges of oil well
brines. Dissolved solids may influence the toxicity of heavy metals
and organic compounds to fish and other aquatic life, primarily
because of the antagonistic effect of hardness on metals.
Waters with total dissolved solids over 500 mg/1 have decreasing
utility as irrigation water. At 5,000 mg/1 water has little or no
value for irrigation.
Dissolved solids in industrial waters can cause foaming in boilers
and cause interference with cleaness, color, or taste of many
finished products. High contents of dissolved solids also tend to
accelerate corrosion.
Specific conductance is a measure of the capacity of water to convey
an electric current. This property is related to the total
concentration of ionized substances in water and water temperature.
This property is frequently used as a substitute method of quickly
estimating the dissolved solids concentration.
Oil and Grease
Oil and grease in process waste waters in Subcategory H are
primarily attributable to process oil used in the digester process.
This oil is carried to the effluent with the dewatering liquor.
Sources of oil and grease common to both Subcategory H and
Subcategory I are organics scrubbed from vapor streams and
lubricating oil leakage from heavy machinery. The oil concentration
in the total effluent of the plants visited was less than 10 mg/1.
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However, company data indicated that concentrations in process
streams could be as high as 10,000 mg/1.
Oil and grease exhibit an oxygen demand. Oil emulsions may adhere
to the gills of fish or coat and destroy algae or other plankton.
Deposition of oil in the bottom sediments can serve to exhibit
normal benthic growths, thus interrupting the aquatic food chain.
Soluble and emulsified material ingested by fish may taint the
flavor of the fish flesh. Water soluble components may exert toxic
action on fish. Floating oil may reduce the re-aeration of the
water surface and in conjunction with emulsified oil may interfere
with photosynthesis. Water insoluble components damage the plumage
and costs of water animals and fowls. Oil and grease in a water can
result in the formation of objectionable surface slicks preventing
the full aesthetic enjoyment of the water.
Oil spills can damage the surface of boats and can destroy the
aesthetic characteristics of beaches and shorelines.
Acidity and Alkalinity
Variations in pH of Subcategory H process effluents is highly
dependent on the formula used in digestion. Plant-visit data
indicated a minimum pH of 6.0. Industry data indicate a maximum pH
of approximately 11.0. Fluctuations in Subcategory I process waste
water pH are not expected to be outside the pH range of 6.0 to 9.0.
Acidity and alkalinity are reciprocal terms. Acidity is produced by
substances that yield hydrogen ions upon hydrolysis and alkalinity
is produced by substances that yield hydroxyl ions. The terms
"total acidity" and "total alkalinity" are often used to express the
buffering capacity of a solution. Acidity in natural waters is
caused by carbon dioxide, mineral acids, weakly dissociated acids,
and the salts of strong acids and weak bases. Alkalinity is caused
by strong bases and the salts of strong alkalies and weak acids.
The term pH is a logarithmic expression of the concentration of
hydrogen ions. At a pH of 7, the hydrogen and hydroxyl ion
concentrations are essentially equal and the water is neutral.
Lower pH values indicate acidity while higher values indicate
alkalinity. The relationship between pH and acidity or alkalinity
is not necessarily linear or direct.
Waters with a pH below 6.0 are corrosive to water works structures,
distribution lines, and household plumbing fixtures and can thus add
such constituents to drinking water as iron, copper, zinc, cadmium
and lead. The hydrogen ion concentration can affect the "taste" of
the water. At a low pH water tastes "sour". The bactericidal
effect of chlorine is weakened as the pH increases, and it is
advantageous to keep the pH close to 7. This is very significant
for providing safe drinking water.
Extremes of pH or rapid pH changes can exert stress conditions or
aquatic life outright. Dead fish, associated algal blooms, and
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foul stenches are aesthetic liabilities of any waterway. Even
moderate changes from "acceptable" criteria limits of pH are
deleterious to some species. The relative toxicity to aquatic life
of many materials is increased by changes in the water pH.
Metalocyanide complexes can increase a thousand-fold in toxicity
with a drop of 1.5 pH units. The availability of many nutrient
substances varies with the alkalinity and acidity. Ammonia is more
lethal with a higher pH.
The lacrimal fluid of the human eye has a pH of approximately 7.0
and a deviation of 0.1 pH unit from the norm may result in eye
irritation for the swimmer. Appreciable irritation will cause
severe pain.
Temperature
In reclaim plants, there are individual waste water streams, such as
condenser flows, which have elevated temperatures. However, once
combined with other effluents, elevated temperature in the final
effluent is not a problem.
Temperature is one of the most important and influential water
quality characteristics. Temperature determines those species that
may be present; it activates the hatching of young, regulates their
activity, and stimulates or suppresses their growth and development;
it attracts, and may kill when the water becomes too hot or becomes
chilled too suddenly. Colder water generally suppresses
development. Warmer water generally accelerates activity and may be
a primary cause of aquatic plant nuisances when other environmental
factors are suitable.
Temperature is a prime regulator of natural processes within the
water environment. It governs physiological functions in organisms
and, acting directly or indirectly in combination with other water
quality constituents, it affects aquatic life with each change.
These effects include chemical reaction rates, enzymatic functions,
molecular movements, and molecular exchanges between membranes
within and between the physiological systems and the organs of an
animal.
Chemical reaction rates vary with temperature and generally increase
as the temperature is increased. The solubility of gases in water
varies with temperature. Dissolved oxygen is decreased by the decay
or decomposition of dissolved organic substances and the decay rate
increases as the temperature of the water increases reaching a
maximum at about 30°c (86°F). The temperature of stream water, even
during summer, is below the optimum for pollution-associated
bacteria. Increasing the water temperature increases the bacterial
multiplication rate when the environment is favorable and the food
supply is abundant.
Reproduction cycles may be changed significantly by increased
temperature because this function takes place under restricted
temperature ranges. Spawning may not occur at all because
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temperatures are too high. Thus, a fish population may exist in a
heated area only by continued immigration. Disregarding the
decreased reproductive potential, water temperatures need not reach
lethal levels to decimate a species. Temperatures that favor
competitors, predators, parasites, and disease can destroy a species
at levels far below those that are lethal.
Fish food organisms are altered severely when temperatures approach
or exceed 90°F. Predominant algal species change, primary
production is decreased, and bottom associated organisms may be
depleted or altered drastically in numbers and distribution.
Increased water temperatures may cause aquatic plant nuisances when
other environmental factors are favorable.
Synergistic actions of pollutants are more severe at higher water
temperatures. Given amounts of domestic sewage, refinery wastes,
oils, tars, insecticides, detergents, and fertilizers more rapidly
deplete oxygen in water at higher temperatures, and the respective
toxicities are likewise increased.
When water temperatures increase, the predominant algal species may
change from diatoms to green algae, and finally at high temperatures
to blue-green algae, because of species temperature preferentials.
Blue-green algae can cause serious odor problems. The number and
distribution of benthic organisms decreases as water temperatures
increase above 90°F, which is close to the tolerance limit for the
population. This could seriously affect certain fish that depend on
benthic organisms as a food source.
The cost of fish being attracted to heated water in winter months
may be considerable, due to fish mortalities that may result when
the fish return to the cooler water.
Rising temperatures stimulate the decomposition of sludge, formation
of sludge gas, multiplication of saprophytic bacteria and fungi
(particularly in the presence of organic wastes), and the
consumption of oxygen by putrefactive processes, thus affecting the
esthetic value of a water course.
In general, marine water temperatures do not change as rapidly or
range as widely as those of freshwaters. Marine and estuarine
fishes, therefore, are less tolerant of temperature variation.
Although this limited tolerance is greater in estuarine than in open
water marine species, temperature changes are more important to
those fishes in estuaries and bays than to those in open marine
areas, because of the nursery and replenishment functions of the
estuary that can be adversely affected by extreme temperature
changes.
Subcategory H processes which would result in zinc-laden effluents
are not utilized by industry, therefore zinc is not considered a
signficant parameter. However, historical data from industry
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indicate that, with certain digestion formulations, zinc content
could be as high as 1,700 mg/1. This same data stated that this
zinc was treatable and could be reduced to less than 10 mg/1 in the
digestion dewatering stream.
Summary of Significant Pollutants
Of the pollutants examined, suspended solids, oil and grease, and pH
are significant characteristics when considering process waste
waters from Subcategory H and Subcategory I reclaim facilities. COD
is an additional contaminant which is significant when considering
waste waters from Subcategory H facilities. The recommended list of
control parameters for each Subcategory is as follows:
Subcategorv H Subcategorv I
COD Suspended Solids
Suspended Solids Oil and Grease
Oil and Grease pH
pH
Subcateaories J and K ~•» Latex-Based Products
Review of published literature, EPA documents, industry records, and
findings of the plant visits indicated that the following chemical,
physical, and biological constituents are found in measurable
quantities in the waste water effluents from facilities
manufacturing latex-based products:
BOD
COD
Suspended Solids
Total Dissolved Solids
Oil and Grease
pH
Surfactants
Color
Temperature (Heat)
Chromium
Zinc
The principal differences between the waste water generated in
Subcategory J (latex dipping, thread, and porous molds) and
Subcategory K (latex foam) plants lie in loadings for BOD, COD,
chromium, and zinc.
Biochemical Oxygen Demand
BOD is attributable to the various organic compounds which contact
process waste waters. For Subcategory J production facilities,
concentrations and loadings are highly dependent on the product
washing technique employed. Concentrations range from 130 to 150
mg/1. The BOD in waste water generated in Subcategory K production
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facilities is again attributable to wash waters, but concentrations
are much higher, ranging as high as 4,900 mg/1.
Biochemical oxygen demand (BOD) is a measure of the oxygen consuming
capabilities of organic matter. The BOD does not in itself cause
direct harm to a water system, but it does exert an indirect effect
by depressing the oxygen content of the water. Sewage and other
organic effluents during their processes of decomposition exert a
BOD, which can have a catastrophic effect on the ecosystem by
depleting the oxygen supply. Conditions are reached frequently
where all of the oxygen is used and the continuing decay process
causes the production of noxious gases such as hydrogen sulfide and
methane. Water with a high BOD indicates the presence of
decomposing organic matter and subsequent high bacterial counts that
degrade its quality and potential uses.
Dissolved oxygen (DO) is a water quality constituent that, in
appropriate concentrations, is essential not only to keep organisms
living but also to sustain species reproduction, vigor, and the
development of populations. Organisms undergo stress at reduced DO
concentrations that make them less competitive and able to sustain
their species within the aquatic environment. For example, reduced
DO concentrations have been shown to interfere with fish population
through delayed hatching of eggs, reduced size and vigor of embryos,
production of deformities in young, interference with food
digestion, acceleration of blood clotting, decreased tolerance to
certain toxicants, reduced food efficiency and growth rate, and
reduced maximum sustained swimming speed. Fish food organisms are
likewise affected adversely in conditions with suppressed DO. Since
all aerobic aquatic organisms need a certain amount of oxygen, the
consequences of total lack of dissolved oxygen due to a high BOD can
kill all inhabitants of the affected area.
If a high BOD is present, the quality of the water is usually
visually degraded by the presence of decomposing materials and algae
blooms due to the uptake of degraded materials that form the
foodstuffs of the algal populations.
COD
Moderate to high COD concentrations are present in Subcategories J
and K process waste waters for the same reasons as those indicated
for the BOD concentration. Concentrations range from 175 to 675
mg/1 for Subcategory J facilities and as high as 29,000 mg/1 for
Subcategory K facilities.
Suspended Solids
Suspended solids in Subcategories J and K waste waters result from
the contamination of process effluents with uncoagulated latex from
washdown and clean out wastes. Loadings in the effluents depend on
washing techniques employed and not on the type of product. Typical
values ranged from 80 to over 3,000 mg/1.
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Suspended solids include both organic and inorganic materials. The
inorganic components include sand, silt, and clay. The organic
fraction includes such materials as grease, oil, tar, animal and
vegetable fats, various fibers, sawdust, hair, and various materials
from sewers. These solids may settle out rapidly and bottom
deposits are often a mixture of both organic and inorganic solids.
They adversely affect fisheries by covering the bottom of the stream
or lake with a blanket of material that destroys the fish-food
bottom fauna or the spawning ground of fish. Deposits containing
organic materials may deplete bottom oxygen supplies and produce
hydrogen sulfide, carbon dioxide, methane, and other noxious gases.
In raw water sources for domestic use, state and regional agencies
generally specify that suspended solids in streams shall not be
present in sufficient concentration to be objectionable or to
interfere with normal treatment processes. Suspended solids in
water may interfere with many industrial processes, and cause
foaming in boilers, or encrustations on equipment exposed to water,
especially as the temperature rises. Suspended solids are
undesirable in water for textile industries; paper and pulp;
beverages; dairy products; laundries; dyeing; photography; cooling
systems, and power plants. Suspended particles also serve as a
transport mechanism for pesticides and other substances which are
readily sorbed into or onto clay particles.
Solids may be suspended in water for a time, and then settle to the
bed of the stream or lake. These settleable solids discharged with
man's wastes may be inert, slowly biodegradable materials, or
rapidly decomposable substances. While in suspension, they increase
the turbidity of the water, reduce light penetration and impair the
photosynthetic activity of aquatic plants.
Solids in suspension are aesthetically displeasing. When they
settle to form sludge deposits on the stream or lake bed, they are
often much more damaging to the life in water, and they retain the
capacity to displease the senses. Solids, when transformed to
sludge deposits, may do a variety of damaging things, including
blanketing the stream or lake bed and thereby destroying the living
spaces for those benthic organisms that would otherwise occupy the
habitat. When of an organic and therefore decomposable nature,
solids use a portion or all of the dissolved oxygen available in the
area. Organic materials also serve as a seemingly inexhaustible
food source for sludgeworms and associated organisms.
Turbidity is principally a measure of the light absorbing properties
of suspended solids. It is frequently used as a substitute method
of quickly estimating the total suspended solids when the
concentration is relatively low.
Dissolved Solids
From in-plant data, it was determined that TDS in process effluents
from Subcategories J and K production facilities were primarily
98
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attributable to the raw intake water and not to process waste water
discharges.
In natural waters the dissolved solids consist mainly of carbonates,
chlorides, sulfates, phosphates, and possibly nitrates of calcium,
magnesium, sodium, and potassium, with traces of iron, manganese and
other substances.
Many communities in the United States and in other countries use
water supplies containing 2000 to 4000 mg/1 of dissolved salts, when
no better water is available. Such waters are not palatable, may
not quench thirst, and may have a laxative action on new users.
Waters containing more than 4000 mg/1 of total salts are generally
considered unfit for human use, although in hot climates such higher
salt concentrations can be tolerated whereas they could not be in
temperate climates. Waters containing 5000 mg/1 or more are
reported to be bitter and act as bladder and intestinal irritants.
It is generally agreed that the salt concentration of good,
palatable water should not exceed 500 mg/1.
Limiting concentrations of dissolved solids for fresh-water fish may
range from 5,000 to 10,000 mg/1, according to species and prior
acclimatization. Some fish are adapted to living in more saline
waters, and a few species of fresh-water forms have been found in
natural waters with a salt concentration of 15,000 to 20,000 mg/1.
Fish can slowly become acclimatized to higher salinities, but fish
in waters of low salinity cannot survive sudden exposure to high
salinities, such as those resulting from discharges of oil well
brines. Dissolved solids may influence the toxicity of heavy metals
and organic compounds to fish and other aquatic life, primarily
because of the antagonistic effect of hardness on metals.
Waters with total dissolved solids over 500 mg/1 have decreasing
utility as irrigation water. At 5,000 mg/1 water has little or no
value for irrigation.
Dissolved solids in industrial waters can cause foaming in boilers
and cause interference with cleaness, color, or taste of many
finished products. High contents of dissolved solids also tend to
accelerate corrosion.
Specific conductance is a measure of the capacity of water to convey
an electric current. This property is related to the total
concentration of ionized substances in water and water temperature.
This property is frequently used as a substitute method of quickly
estimating the dissolved solids concentration.
Oil and Grease
Oil and grease, as carbon tetrachloride extractables, is present at
low concentrations in the process waste waters of all types of
Subcategories J and K plants. It is attributable to organics used
in coagulation agents and wash waters.
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Oil and grease exhibit an oxygen demand. Oil emulsions may adhere
to the gills of fish or coat and destroy algae or other plankton.
Deposition of oil in the bottom sediments can serve to exhibit
normal benthic growths, thus interrupting the aquatic food chain.
Soluble and emulsified material ingested by fish may taint the
flavor of the fish flesh. Water soluble components may exert toxic
action on fish. Floating oil may reduce the re-aeration of the
water surface and in conjunction with emulsified oil may interfere
with photosynthesis. Water insoluble components damage the plumage
and costs of water animals and fowls. Oil and grease in a water can
result in the formation of objectionable surface slicks preventing
the full aesthetic enjoyment of the water.
Oil spills can damage the surface of boats and can destroy the
aesthetic characteristics of beaches and shorelines.
pH. Acidity and Alkalinity
Control and adjustment of pH in process waste waters generated in
Subcategories J and K production facilities is often necessary as a
prerequisite for the chemical coagulation treatment process. In
view of this it is feasible that the uncontrolled effluent pH can
vary appreciably and should be limited to an acceptable range.
Acidity and alkalinity are reciprocal terms. Acidity is produced by
substances that yield hydrogen ions upon hydrolysis and alkalinity
is produced by substances that yield hydroxyl ions. The terms
"total acidity" and "total alkalinity" are often used to express the
buffering capacity of a solution. Acidity in natural waters is
caused by carbon dioxide, mineral acids, weakly dissociated acids,
and the salts of strong acids and weak bases. Alkalinity is caused
by strong bases and the salts of strong alkalies and weak acids.
The term pH is a logarithmic expression of the concentration of
hydrogen ions. At a pH of 7, the hydrogen and hydroxyl ion
concentrations are essentially equal and the water is neutral.
Lower pH values indicate acidity while higher values indicate
alkalinity. The relationship between pH and acidity or alkalinity
is not necessarily linear or direct.
Waters with a pH below 6.0 are corrosive to water works structures,
distribution lines, and household plumbing fixtures and can thus add
such constituents to drinking water as iron, copper, zinc, cadmium
and lead. The hydrogen ion concentration can affect the "taste" of
the water. At a low pH water tastes "sour". The bactericidal
effect of chlorine is weakened as the pH increases, and it is
advantageous to keep the pH close to 7. This is very significant
for providing safe drinking water.
Extremes of pH or rapid pH changes can exert stress conditions or
kill aquatic life outright. Dead fish, associated algal blooms, and
foul stenches are aesthetic liabilities of any waterway. Even
moderate changes from "acceptable" criteria limits of pH are
deleterious to some species. The relative toxicity to aquatic life
100
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of many materials is increased by changes in the water pH.
Metalocyanide complexes can increase a thousand-fold in toxicity
with a drop of 1.5 pH units. The availability of many nutrient
substances varies with the alkalinity and acidity. Ammonia is more
lethal with a higher pH.
The lacrimal fluid of the human eye has a pH of approximately 7.0
and a deviation of 0.1 pH unit from the norm may result in eye
irritation for the swimmer. Appreciable irritation will cause
severe pain.
Surfactants
Surfactants will be present in wash waters evolved in all
Subcategories J and K production facilities. Surfactants are a
primary cause of foamy plant effluents,however, their concentrations
in process waste waters are low. Concentrations range from 2 to 6
mg/1, and can be controlled by COD reduction.
Color
Color is objectionable from an aesthetic standpoint and also because
it interferes with the transmission of sunlight into streams,
thereby lessening photosynthetic activity. Some waste streams which
contain latex can have appreciable color. Generally color is
associated with high COD and suspended solids loadings and can best
be monitored by these two parameters.
Temperature
Temperature is not a significant parameter when considering process
waste streams. Certain wash waters can have a moderately high
temperature, but dilution with other effluent streams significantly
reduces their impact.
Temperature is one of the most important and influential water
quality characteristics. Temperature determines those species that
may be present; it activates the hatching of young, regulates their
activity, and stimulates or suppresses their growth and development;
it attracts, and may kill when the water becomes too hot or becomes
chilled too suddenly. Colder water generally suppresses
development. Warmer water generally accelerates activity and may be
a primary cause of aquatic plant nuisances when other environmental
factors are suitable.
Temperature is a prime regulator of natural processes within the
water environment. It governs physiological functions in organisms
and, acting directly or indirectly in combination with other water
quality constituents, it affects aquatic life with each change.
These effects include chemical reaction rates, enzymatic functions,
molecular movements, and molecular exchanges between membranes
within and between the physiological systems and the organs of an
animal.
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Chemical reaction rates vary with temperature and generally increase
as the temperature is increased. The solubility of gases in water
varies with temperature. Dissolved oxygen is decreased by the decay
or decomposition of dissolved organic substances and the decay rate
increases as the temperature of the water increases reaching a
maximum at about 30°C (86°F). The temperature of stream water, even
during summer, is below the optimum for pollution-associated
bacteria. Increasing the water temperature increases the bacterial
multiplication rate when the environment is favorable and the food
supply is abundant.
Reproduction cycles may be changed significantly by increased
temperature because this function takes place under restricted
temperature ranges. Spawning may not occur at all because
temperatures are too high. Thus, a fish population may exist in a
heated area only by continued immigration. Disregarding the
decreased reproductive potential, water temperatures need not reach
lethal levels to decimate a species. Temperatures that favor
competitors, predators, parasites, and disease can destroy a species
at levels far below those that are lethal.
Fish food organisms are altered severely when temperatures approach
or exceed 90°F. Predominant algal species change, primary
production is decreased, and bottom associated organisms may be
depleted or altered drastically in numbers and distribution.
Increased water temperatures may cause aquatic plant nuisances when
other environmental factors are favorable.
Synergistic actions of pollutants are more severe at higher water
temperatures. Given amounts of domestic sewage, refinery wastes,
oils, tars, insecticides, detergents, and fertilizers more rapidly
deplete oxygen in water at higher temperatures, and the respective
toxicities are likewise increased.
When water temperatures increase, the predominant algal species may
change from diatoms to green algae, and finally at high temperatures
to blue-green algae, because of species temperature preferentials.
Blue-green algae can cause serious odor problems. The number and
distribution of benthic organisms decreases as water temperatures
increase above 90°F, which is close to the tolerance limit for the
population. This could seriously affect certain fish that depend on
benthic organisms as a food source.
The cost of fish being attracted to heated water in winter months
may be considerable, due to fish mortalities that may result when
the fish return to the cooler water.
Rising temperatures stimulate the decomposition of sludge, formation
of sludge gas, multiplication of saprophytic bacteria and fungi
(particularly in the presence of organic wastes), and the
consumption of oxygen by putrefactive processes, thus affecting the
esthetic value of a water course.
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In general, marine water temperatures do not change as rapidly or
range as widely as those of freshwaters. Marine and estuarine
fishes, therefore, are less tolerant of temperature variation.
Although this limited tolerance is greater in estuarine than in open
water marine species, temperature changes are more important to
those fishes in estuaries and bays than to those in open marine
areas, because of the nursery and replenishment functions of the
estuary that can be adversely affected by extreme temperature
changes.
chromium
Chromium was not found in the process waste waters generated by any
of the Subcategories J and K facilities visited. However, available
EPA documents indicate that chromium will be present in process
waste waters when chromic acid is used in the form-cleaning
solution. The chromic acid is rinsed from the form and consequently
enters the plant effluent. For plants utilizing this form-cleaning
technique, it is necessary to limit the discharge of chromium ions.
Chromium, in its various valence states, is hazardous to man. It
can produce lung tumors when inhaled and induces skin
sensitizations. Large doses of chromates have corrosive effects on
the intestinal tract and can cause inflammation of the kidneys.
Levels of chromate ions that have no effect on man appear to be so
low as to prohibit determination to date.
The toxicity of chromium salts toward aquatic life varies widely
with the species, temperature, pH, valence of the chromium, and
synergistic or antagonistic effects, especially that of hardness.
Fish are relatively tolerant of chromium salts, but fish food
organisms and other lower forms of aquatic life are extremely
sensitive. Chromium also inhibits the growth of algae.
In some agricultural crops, chromium can cause reduced growth or
death of the crop. Adverse effects of low concentrations of
chromium on corn, tobacco and sugar beets have been documented.
Zinc
Zinc was not found in the process waste waters generated by
Subcategory J, facilities that were visited. However, available
literature indicates that zinc will be present in Subcategory J
process waste waters when zinc nitrate is used as a coagulant agent.
However both concentrations and loadings will be very low. The
Subcategory J facilities visited either did not use a coagulating
agent or used calcium nitrate. When using natural latex, no
coagulating agent is apparently needed.
Zinc in Subcategory K facility process effluents is attributable to
the zinc oxide used as a rinsing agent. The zinc appears in the
foam wash waters.
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Occurring abundantly in rocks and ores, zinc is readily refined into
a stable pure metal and is used extensively for galvanizing, in
alloys, for electrical purposes, in printing plates, for dye-
manufacture and for dyeing processes, and for many other industrial
purposes. Zinc salts are used in paint pigments, cosmetics,
Pharmaceuticals, dyes, insecticides, and other products too numerous
to list herein. Many of these salts (e.g., zinc chloride and zinc
sulfate) are highly soluble in water; hence it is to be expected
that zinc might occur in many industrial wastes. On the other hand,
some zinc salts (zinc carbonate, zinc oxide, zinc sulfide) are
insoluble in water and consequently it is to be expected that some
zinc will precipitate and be removed readily in most natural waters.
In zinc-mining areas, zinc has been found in waters in
concentrations as high as 50 mg/1 and in effluents from metal-
plating works and small-arms ammunition plants it may occur in
significant concentrations. In most surface and ground waters, it
is present only in trace amounts. There is some evidence that zinc
ions are adsorbed strongly and permanently on silt, resulting in
inactivation of the zinc.
Concentrations of zinc in excess of 5 mg/1 in raw water used for
drinking water supplies cause an undesirable taste which persists
through conventional treatment. Zinc can have an adverse effect on
man and animals at high concentrations.
In soft water, concentrations of zinc ranging from 0.1 to 1.0 mg/1
have been reported to be lethal to fish. Zinc is thought to exert
its toxic action by forming insoluble compounds with the mucous that
covers the gills, by damage to the gill epithelium, or possibly by
acting as an internal poison. The sensitivity of fish to zinc
varies with species, age and condition, as well as with the physical
and chemical characteristics of the water. Some acclimatization to
the presence of zinc is possible. It has also been observed that
the effects of zinc poisoning may not become apparent immediately,
so that fish removed from zinc-contaminated to zinc-free water
(after 4-6 hours of exposure to zinc) may die U8 hours later. The
presence of copper in water may increase the toxicity of zinc to
aquatic organisms, but the presence of calcium or hardness may
decrease the relative toxicity.
Observed values for the distribution of zinc in ocean waters vary
widely. The major concern with zinc compounds in marine waters is
not one of acute toxicity, but rather of the long-term sub-lethal
effects of the metallic compounds and complexes. From an acute
toxicity point of view, invertebrate marine animals seem to be the
most sensitive organisms tested. The growth of the sea urchin, for
example, has been retarded by as little as 30 ug/1 of zinc.
Zinc sulfate has also been found to be lethal to many plants, and it
could impair agricultural uses.
Summary of Significant Pollutants
104
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Of the pollutants examined, only the following are considered
significant characteristics when considering process waste waters
from latex-based production facilities:
BOD
Suspended Solids
pH
Chromium
Zinc
potentially, four of the five must be treated and monitored by
Subcategory J facilities. These are:
BOD
Suspended Solids
PH
Chromium
In many Subcategory J facilities, chromium will not appear in the
process effluents.
Subcategory K facilities will have no chromium present in process
waste waters and therefore only four of the five will be treated and
monitored, namely:
BOD
Suspended Solids
pH
Zinc
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SECTION VII
CONTROL AND TREATMENT TECHNOLOGY
survey of Selected Plants
Several selected rubber processing plants were visited to provide
further accurate data on the performance of the waste water control
and treatment technologies used by the industry. These data
collection visits encompassed analysis of process operations, review
of water and waste water management programs, and evaluation of
waste water treatment facilities. The plants visited were
considered exemplary or advanced in their approach to waste water
control and treatment or the thoroughness of their housekeeping
procedures. The plant selection was made based on effluent and
treatment data obtained from published literature, EPA records.
Corps of Engineers Permit to Discharge Applications, and company
historical data on waste water quality and treatment.
As examples of Subcategories E, F, and G industries, plants
manufacturing molded, extruded, and fabricated products were
sampled. Compression, transfer, and injection molding technologies
were represented as well as small and large-sized molded items. The
major extruded items such as belting and sheeting were inlcuded in
the visits. Diverse fabricated products such as hose and rubber
footwear as well as rare sectors of the industry such as cement
dipped goods were studied during the plant visits. In addition all
three ranges of plant size (as discussed in the final paragraph of
Section IV) were represented by the data-collection plant visits.
As an example of the reclaimed rubber industry, the largest
reclaiming plant in the U.S. was visited. Wet digester and pan
(heater) reclaim processes are employed. Therefore, this plant is
representative of both Subcategories H and I. The wet digester
process is exemplary since physical defibering is carried out and
the highly contaminated digestion-dewatering liquor is recycled. In
addition vapor vents on both the wet digester and pan processes are
condensed and decanted to recover what would otherwise be polluting
reclaiming process oils.
Two plants manufacturing latex dipped goods were visited. The
products made at the two facilities include surgical gloves,
ballons, prophylactics, and finger cots. One plant employed
chemical coagulation and settling before discharge to a municipal
treatment plant. This primary treatment, or pretreatment for a
publicly owned treatment works, produced good effluent. The second
facility utilized a stabilization and settling pond system. This
effluent had good quality for direct discharge.
The only significant latex foam plant in the industry was sampled.
The treatment facilities used by this plant include chamical
coagulation of latex solids and chemical precipitation of the zinc-
laden foam rinse waters.
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A summary of the products, processes, production capacities, and
waste water control and treatment technologies of the exemplary
rubber processing plants visited is presented in Tables 18 and 19.
Plant A
This plant manufactures oil seals, 'O1 rings, rubber-to-metal molded
items, and miscellaneous molded rubber products. The products are
made from specialty-type rubbers using compression and transfer
molding techniques. Approximately 75 percent are nitrile rubbers,
about 20 percent neoprene-type rubber, and 5 percent miscellaneous
rubbers. The plant has approximately 46 employees and operates 3
shifts each day, six days per week. The average daily consumption
of rubber is 750 pounds, and the weight of saleable products
averages U50 pounds per day. The material loss is caused by
production wastage and rejected products.
Approximately 95 percent of the rubber stock used in the plant is
compounded by a supply company. Special recipes and nonstorable
stocks are mixed at the plant in a mixing mill. The stock mixed in
this mill accounts for the other 5 percent. When operating, this
mill uses about UO gpm of cooling water.
The rubber stock is prepared for processing in a warm-up mill. From
the mill the rubber is extruded into a basic shape. This shape can
be a strip, a cylinder, or an annulus. The preforms for compression
molds are made from these basic components by cutting on a
guillotine or fine slicing on a modified meat slicer. The preforms
are then loaded into the molds. The molds are placed between the
heated plates of the mold presses and the mold presses are
hydraulically closed. The hydraulic fluid is oil, at approximately
2,000 psi, and oil leaks are common. The oil leakages are generally
trapped in a small oil pit from which the oil is periodically
removed and reclaimed by decanting, drying and filtering. Large oil
spills overflow this pit and enter the plant drain. Most of molds
are heated with steam at 350°F (125 psi) although a few older molds
are generally slabs of rubber stock which are loaded into the
transfer section of mold. The mold is closed in the hydraulic
press. The rubber wastage on a transfer-molded item is higher than
for compression molding but the labor requirements are less.
The molded items are deflashed in a wheelabrator machine. This
freezes the item with liquid nitrogen, making the rubber brittle,
and then blasts it with small steel shot. The rubber fines and shot
are separated and the fines and dust are collected in a bag
collector and drummed. The steel shot range in size from seven to
twelve thousandths of an inch. In cases where the shot would blind
small crevices of the molded items, manual deflashing is carried
out. Manual deflashing consists of spinning the item on a chuck and
grinding off the flash with a fine sandstone.
The molded products are inspected, packaged and shipped. Rejected
items are removed as solid waste.
108
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o
10
Subcateeorv E - Small Plants
A Seals, General Molded Items
8 Cement Dipped Gloves
Subcatesorv F - Medium Plants
C Molded Sport Grips,
Rubber-Metal Bonded Items
D Hose, Various Sizes
fiuhcategorv G - Larae Plants —
E Belting and Sheet Rubber
F Large Seals and Weather-
Stripping
G Hose, Various Sizes
H Canvas and Cement
Dipped Footwear
Process
Compression and
Transfer Holding
Cement Dipping
Compression, Transfer
and Injection Molding
Extrusion and
Fabrication
Extrusion
Molding and
Extrusion
Extrusion and
Fabricated
Molding, Fabrication
and Cement Dipping
Production
Capacity
kg/day( Ib/day)
3W (75°)
500 (1100)
8,600 (iv, ooo)
9,000 (20,000)
26,000 (58,000)
26,000 (58,000)
Tr.7<» , I6?.SOJ)
120,000 (265,000)
Control Measures
Most drains in milling and curing
areas are blocked.
No floor drains
Most drains in compounding, milling,
and curing areas are blocked.
Dry dust collection devices.
Most drains in compounding and
milling areas are blocked.
In-plam containment of oil leaks
and spi Is.
Most drains in compounding, milling,
and cur.ng areas are blocked.
Block!nc of some floor drains and
use of cry clean-up methods.
In-plani containment of oil leaks
and spi Is.
Primary Effluent Treatment Secondary Effluent Treatment
None
None
None
None
None
Gravity oil separators
and holding pond.
None
Gravity oil separation,
and chemical coagulation
and clarification of
latex-laden wastes.
^The definition of the plant sizes I. based on total raw material usage: Small plants, less than 3,720 kg/day (8 2CX) Ib/day) ;
Medium pi anis? 5.720-:o,l.30 kg/day (8,200-23,000 Ib/day); and Large plants, greater than 10,ky> kg/day (?,.ouu Ib/day).
Hote: Subcategorles E, F, and. G include General Molded, Extruded, and
Fabricated Products, I.e., Hose, Belting, Seals, Packing, Gaskets,
Footwear, Cement Dipped Goods, and Tire Retreading.
None. Direct discharge to stream.
None. Direct discharge to stream.
None. Direct discharge to stream.
None. Direct discharge to stream.
None. Direct discharge to stream.
None Direct discharge to stream.
None. Discharge to municipal
treatment system.
None. Direct discharge to stream.
Table 18: Waste Water Control and Treatment Technologies at Subcategorles E.
F. and G Plants with Exemplary Features
-------
Plant
Product
Process
Production Capacity
kg/day (Ib/day)
Control Measures
Primary Effluent
Treatment
Secondary Effluent
Treatment
Subcategory H
Wet Digestion
Rubber Reclaiming
Subcategory I
Pan (Heater),
Mechanical, and Dry
Subcategory J
Latex-Dipped, Latex Thread,
1 1
Reclaimed Rubber Reclaimed Rubber
Wet Digestion Pan (Heater)
56,000 (123,000) 1*5,000 (100,000)
Physical defibering Return of process
and return of process oils.
oi Is and digester
1 iquor.
J
Ballons, prophylac-
tics, and finger
cots.
Latex Dipping
'OOO (9,500)
Few in-plant drains.
Minimal water usage
for tank cleaning.
K
Surgical gloves, hot
water bottles,
rubber syringes, and
pharmaceutical items
Latex Dipping
Compression Molding
900 (2,000)
Few in-plant drains.
Oi1 separation and
recycle of process
oi Is and digester
Iiquor.
None. Direct dis-
charge to stream.
OiI separation and
recycle of process
oils.
None. Direct dis-
charge to stream.
Sett I ing ponds.
Sett I ing pond efflu-
ent discharged to
stream. Evaporation
pond for latex waste
waters.
Coagulation and
clarification of
latex solids.
None. Discharge to
municipal treatment
system.
Subcategory K
•- Latex Foam
Foam mattresses and
pillows.
Talalay foam process
90,000 (200,000)
Countercurrent foam
rinse system.
Latex waste chemical
coagulation and
clarification. Zinc
precipitation and
clarification.
Proposed: equaliza-
tion, carbonate pre-
cipitation, and fi I-
tration of present
primary effluent.
Table 19: Waste Water Control and Treatment Technologies for
Subcategories H. I. J. and K Plants with Exemplary Features
-------
Metal parts for rubber bonding are first degreased with
perchloroethylene vapor. The waste, grease-laden solvent, is
drummed and removed as solid waste. After degreasing the bonding
surface is sand blasted in a sand blasting drum to impart a rough
surface. The prepared bonding surface is painted with a bonding
agent (rubber cement) and the preform is attached. The metal
preform item is molded in a similar manner to the all-rubber items.
Occasionally the molds require cleaning. This is carried out by a
dry honing process which consists of blasting the molds with fine
glass beads.
Waste waters are generated by: cooling waters from the compounding
mill* the warm-up mill, the extruder and the nitrogen compressor,
blowdown from the boiler (approxiately twice a day, 5 gallons each
time), and regeneration wastes from the boiler feed water deionizer
(approximately 8 Ibs sodium chloride per day) . The steam condensate
recycle rate is high, approximating 100 percent.
Contaminants, oil and grease, and minor quantities of suspended
solids, enter these utility streams at unprotected floor drains.
The raw plant effluent, including utility streams, has oil
concentrations in the order of 40 mg/1 and negligible suspended
solids.
Plant B
This plant manufactures electrical gloves and shoulder-length
sleeves via a dipping process in solvent-based rubber cement. The
principal raw material is natural rubber, although EPDM rubber
gloves are being developed. The solvent is a naphtha type compound.
The material consumptions average 1,100 pounds of rubber and 1,100
gallons of solvent per day. Each pair of gloves requires
approximately one pound of rubber. The sleeves require more rubber.
The plant operates 24 hours per day, 7 days a week.
The rubber, pigments, and vulcanizing agents are compounded on a 2-
roller mill and are sheeted out to approximately one-half of an inch
in thickness. The mill uses once-through cooling water. The
sheeted rubber is fed into a guillotine where it is chopped into
three-inch squares, which are weighed into a container.
The rubber is transported to the cement mixing room where the rubber
is dissolved in solvent in a blend tank. The mixed rubber cement is
transferred from the blend tank to a storage tank where it is stored
before the dipping operation. Cements with different recipes and
colors have their own storage tank systems. The naphtha solvent is
pumped from outside tanks to the blend tank via two solvent pumps.
Solvent spills are very infrequent because of fire protection
requirements. The mixing room is fitted with an automatic fire
system which is designed to shutdown the pumps, close the doors of
mixing room, and fill the room with carbon dioxide gas to extinguish
a fire.
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The gloves are dipped onto glazed porcelain forms in a cement
dipping room. The forms are held on a rack by their bases and
dipped between 20 and 30 times to build up the glove thickness.
Each rubber layer is allowed to drip-dry between dips. The total
dipping-drying operation takes about UB hours. The temperature and
humidity of the air in the drying room is controlled by an air
quality control system. Exhausted air is used to heat incoming air.
No air pollution control devices are believed necessary. The air
quality control system discharges condensation at times when the air
requires dehumidification. This condensation is pure water.
After drying, the base of the glove is trimmed by a cutting wheel
and the cuff bead is formed by rolling up the cuff. Labels
indicating the brand and size are attached to the glove cuffs with
rubber cement.
The gloves still on the forms are loaded into an open steam
autoclave for vulcanization. The forms are allowed to adjust to the
residual temperature of the autoclave before the steam is applied.
The gloves are cured with 35 psig steam (temperature 280°F) for 40
minutes. The forms plus gloves are removed from the autoclave and
allowed to cool. During the curing operation, the steam condensate
that accumulates in the autoclave is discharged for seven seconds
every two minutes under pressure to the plant drain. The condensate
picks up organics from the curing gloves. The COD of this steam is
approximately 800 mg/1. The flow, however, is extremely low, about
3 gph on average.
When partly cooled, the gloves are dipped in a talc slurry and
allowed to dry. The talc slurry is a closed system. Makeup talc
and water are added to the slurry dip tank. The dry gloves are
stripped manually from the molds and placed in a tumbler with a
small amount of talc powder to coat the inside of the gloves.
The procelain molds are cleaned periodically by manual scrubbing.
The scrubbing waste water and rinse waters are containerized and
hauled from the plant by contract haulers.
The gloves are visually inspected for flaws. Gloves which pass the
visual inspection are tested for their electrical resistance in a
water tank. The tank overflow, low in flow and uncontaminated, is
discharged to the plant effluent. Gloves which fail the visual
inspection or the resistance test are sold as industrial gloves.
The green bladders are cured in steam heated stand-presses. These
presses are mechanically closed and the whole bladder building area
is "dry" and oil free. Steam condensate from the presses is
recycled. Metal parts for molding to the bladders are first
degreased using a closed trichloroethylene system, sandblasted, and
sprayed with rubber cement as a bonding agent.
Plant C
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This plant produces molded rubber grips for golf clubs, tennis
rackets, baseball bats and tools. Another major type of product is
bladders for air-activated brakes and clutches. The types of rubber
used are natural rubber (approximately 75 percent) and various
synthetic rubber (about 25 percent) . The daily quantity of
compounded rubber stock used to manufacture the grips is 17,000
pounds, and to build the bladders is 2,240 pounds.
The rubber stock is compounded in a separate building. Stock is
also prepared for a sister plant in another location which does not
have its own compounding facilities. The grips require stock of
various colors, including black. Carbon black is not added at the
plant; instead, black master batch rubber is used. The bladders are
made solely from black rubber. The compounding facilities consist
of a No. 3 Banbury mixer, two intermediary or storage mills, a U
roll, Z-calender mill, a calendered stock sprayer cooling tank, a
zinc stearate dip tank, and a stock drying tower. In addition, a
small calender is used to prepare stock for the pneumatic bladders.
All cooling water, with the exception of the spray cooling tank, is
provided by a closed loop chilled water system (water at 46°F). The
spray cooling water is discharged untreated to the main plant sewer.
The dust collection device for the Banbury mixer is a wet scrubbing
roto-clone. Because of poor performance and maintenance problems,
the roto-clone is not operated and is to be replaced with a bag
collector device.
The rubber grips are molded by compression, transfer, and injection
molding equipment. The injection mold extruder is cooled by its own
closed loop chilled water system. The presses for the compression
and transfer molds are hydraulic oil activated. Oil leaks occur and
are soaked up with absorbent granules. No open floor drains exist
in the molding area.
The molded rubber grips are deflashed by hand using a trimming knife
before painting and final preparation. The grips are dipped in
paint and hung to dry. Paint drippings and spills are contained
since no floor drains exist in this area. The paints are mixed in a
closed room to contain solvent odors. There are no floor drains in
the paint mixing area. There are potential air pollution problems
in this area. A control system has yet to be selected.
After painting, the grips are buffed to impart smoothness and remove
the last traces of the flash. Dry bag collectors are used to trap
the airborne buffing dusts. The molds are periodically cleaned by
blasting with glass beads in a closed hood.
The pneumatic bladders are built on building machines in a manner
similar to tire manufacture. Cord fabric is purchased from an
outside supplier.
The green bladders are cured in steam heated stand-presses. These
presses are mechanically closed and the whole bladder building area
is "dry" and oil . free. Steam condensate from the presses is
recycled. Metal parts for molding to the bladders are first
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degreased using a closed trichloroethylene system, sandblasted, and
sprayed with rubber cement as a bonding agent.
Approximately 80 percent of the steam used in the plant is recycled
to the boiler as condensate. The boiler feed water is not softened
to demineralized. Instead, treatment agents are added to the feed
water to eliminate scale build up. The only process-associated
discharges to the plant sewer are cooling water for the service air
compressors and cooling water for the hydraulic oil pumps, in
addition to the calendered stock spray cooling water. The overflow
from the plant's septic tank systems are routed through the main
plant sewer.
Extruded oil used in the mill room and machinery oil stored in the
compressor area have on occasion entered the effluent via floor
drains. It is the company's belief that these drains can be closed
and the oil involved stored elsewhere.
The plant's effluent has good COD (50 mg/1) , suspended solids (13
mg/1) and oil (7 mg/1) levels. It is believed that the oil can be
further reduced with good housekeeping and the blocking of offending
floor drains.
Plant p
This plant manufactures several types of reinforced hose. The
outside diameters of the hoses range from approximately 3/4 inch to
six inches. Hoses are made on both rigid and flexible mandrels.
Most sizes of hose can be made in lengths up to about 100 meters.
In addition, small bore hose can be produced in continuous lengths.
Hose is reinforced with yarn and wire using braided and spiral
winding methods. Vulcanization is carried out by both cloth wrapped
and lead-sheathed techniques. The plant consumes appoximately
20,000 pounds of raw materials each day. It operates 24 hours per
day for five days each week and employs 530 people. The plant is in
a rural area with a total area of 120 acres, 7.3 acres of which
consist of the roofed plant area.
The plant water is supplied by 3 wells owned by the plant. The
capacities of the wells are 500, 250 and 250 gpm, respectively. The
water from the 500-gpm well is chlorinated for domestic, sanitary
and process usage in order to minimize the activity of ferro-
bacteria.
Rubber stock is prepared in the compounding area. The recipe is
varied to suit the particular service requirements of the hose. The
rubber ingredients are mixed in a Banbury mixer and sheeted out on a
roll mill. The sheet rubber is dipped in soapstone slurry and hung
to drip and dry. An open drain beneath the soapstone drip area
collects soapstone drippings which are discharged to the plant's
final outfall. In addition, the cooling water from the mills is
discharged into an open drain which can readily be fitted with a
collar, or the opening can be completely sealed to prevent the entry
of oil and grease to the drain.
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The tube component of the hose is extruded and cooled in an open
tank by direct contact with cooling water. From the cooling tank,
the tube is passed through a tank of anti-tack agent ("Acrawax").
Soapstone solution is not used for application because its anti-tack
property is more permanent and would adversely affect the future
bonding of the tube to the other components of the hose. The
overflow from the cooling tank and drippings from the anti-tack
system are discharged to the plant1s final outfall. The floor drain
to which the overflow cooling water is discharged could be equipped
with a collar or completely sealed. The extruded and cooled tube is
coiled on a form in a helix.
Hose tube that requires rigid mandrel support is unwound from its
coil and pulled onto the rod-like mandrel in lengths of
approximately 50 meters. Tube to be supported on flexible mandrels
is extruded onto the rubber- or plastic-coated mandrel at the
extruder. A release agent is sprayed between the tube and the
mandrel to facilitate subsequent removal of the mandrel. Some small
bore hose is sufficiently rigid not to require a mandrel.
The hose tube is braided or spirally wound with yarn or wire. The
yarn and wire are manufactured by supply companies and are received
ready for use. The "reinforcing" operations are "dry" and no floor
drains exist in this area. The outer cover is extruded into the
reinforced hose before curing.
Shorter lengths of hose are sheathed with lead in a lead press. The
lead sheath is cooled directly with water. The sheathed hose is
placed in a long autoclave which is heated directly with steam.
After curing, the lead sheath is stripped from the hose and re-cast
into billets to feed the lead press. The cured hose is removed from
the mandrel by water or air pressure, inspected, and coiled for
shipment. Larger sizes of hose are tape-wrapped and charged into a
direct-steam heated autoclave. After curing the tape is removed
from the hose and the mandrel removed by water or air pressure or a
mechanical pulling technique. The condensate from the lead-sheathed
curing autoclaves contains lead (70 mg/1) and is discharged
directly.
Cooling waters from the mills, tube extruders, and lead cooling
processes are discharged via sumps to the final outfall.
Periodically the sumps are cleaned of accumulated oils and solids.
The air compressor condensate passes through a oil trap drum. The
drum is periodically skimmed of oil. The combined waste waters flow
over a V-notch weir into a small creek to the river.
An outside drum storage area contributes to the oil in the plant's
waste water during storms. This area is unroofed and is used to
store new, partly full, and empty drums of various oils and
chemicals. The storm water passes through a sump before its
discharged to the final outfall but the sump is not regularly
cleaned and oil seepage occurs.
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The plant's combined effluent has good quality: COD, 20 mg/1;
suspended solids, approximately 1 mg/1; and oil and grease, less
than 1 mg/1.
Plant E
This plant produces both cured and uncured sheeted rubber, metal-
reinforced heavy service conveyor belting, and fabric reinforced
conveyor belting. The weight of finished products averages
approximately 52,000 pounds per day. Raw materials consumed each
day amount to 52,000 pounds of compounded rubber and 6,000 pounds of
fabric. An additional 2,000 pounds per day of miscellaneous
material, such as reinforcing wire and packaging material is
consumed. The plant is located in a rural community and employs
approximately 183 production and management personnel. The plant
operates three shifts per day, seven days per week.
No compounding is done by this plant. Rubber stock is compounded at
a nearby company owned facility. The fabric consumed by the plant
is dipped in latex and friction-coated with rubber at another
location.
The compounded rubber stock is prepared for processing on four warm*
up mills. Rubber from these mills is formed into sheets in an
extruder-calender machine. The temperatures of the roller mills and
extruder-calender are controlled by recirculated cooling water and
hydro-therm cooling systems. The sheeted rubber is cooled in a water
spray cooling tank. The contact cooling water overflows and is
reused in the plant's main recirculated cooling, water system.
After cooling, the sheeted rubber is dipped in soapstone solution to
prevent it from sticking together during storage. Curbing and a
floor sump have been installed in the soapstone dip area to contain
accidental spills, and overflows. The sump is emptied into a
portable tank and removed by a private hauler.
The dipped sheet rubber is passed over air vents to dry, and is then
rolled up into large rolls. The sheeting operation described above
is performed eight hours each day, five days per week; it uses 60-70
percent of the cooling water circulated through the plant.
Once sheeted, the rubber is sold as uncured or cured sheeted rubber,
or conveyor belting.
Curing of sheeted materials is performed in presses, rotacures, or
hot air curing ovens. The rotacure system employs a combination of
steam, cooling water, and electric heaters to cure sheeted rubber
under prescribed conditions. Both the steam and cooling water are
recycled. Presses employ steam and a hydrotherm cooling system to
cure the sheet. The third system is a gas fired hot air cure. This
technique does not require steam or cooling water.
In addition to the production of sheeted rubber, the plant also
builds the body plies, or carcasses, used to make conventional
fabric-reinforced conveyor belting. Fabric, which has already been
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frictioned with rubber, is shipped to the plant. This material,
which is single ply and has a maximum width of approximately 55
inches, is used to build carcasses of multiple ply thicknesses and
various widths up to approximately 128 inches. Once built, this
belting is rolled in fabric cloth and sent to another plant to have
an upper and lower layer of rubber applied to the fabric. Completed
belts are frequently returned to the plant for curing.
Waste waters are generated by the cooling system overflows, zeolite
softener regeneration wastes, boiler blowdown, plant runoff,
hydrotherm systems, air conditioning systems, and domestic sources.
The principal waste water problems at the plant originate with the
hydraulic oil systems for the curing presses. Oil leaks from the
oil systems are frequent. Curbing and oil sumps have been installed
to contain such leaks. Periodically the collected oil is removed
from the sumps and drummed prior to disposal. The oil leakages from
the hydraulic oil systems have in the past been so severe and
uncontained that the ground beneath the plant contains large amounts
of oil. Since the water table under the plant is very close to the
ground surface, sumps are also used to control the seepage of oil
water into the plant basement. The oil is periodically removed from
these basement sumps and drummed.
It can be said that, by utilizing the oil containment practices
described above, the plant is approaching zero discharge of process
waste waters. It should be noted, however, that this plant has
neither rubber compounding nor process oil storage facilities.
Plant F
This plant manufactures rubber pipe seals, weather stripping, and
rubber-to-metal molded items. The plant employs 377 factory
personnel and operates 24 hours per day, seven days per week. The
daily consumption of rubber is 22,200 Ibs. Other raw materials
incude carbon black (29,400 Ibs/day), chemical compounds (5,100
Ibs/day), and oils and wax (840 Ibs/day).
Rubber stock is compounded in a Banbury mill. Depending on the
amount of stock being processed, both nonreactive and reactive
stocks are compounded. During normal operations, however, the stock
is compounded only once (reactive stock) with all the compounds,
including vulcanizing agents, added at the same time. The material
is batched off in sheets, dipped in soapstone, air dried, and placed
in temporary storage.
Weather stripping, pipe seals, and molding plugs are formed by
extrusion in either short or long barrelled extruders. Short
barrelled extruders require warm-up and strip feed mills, whereas
long barralled extruders do not. All extruders are temperature
controlled; both steam and cooling water are used. The extruded
items are cooled, dipped, cut, and placed in autoclave pans in
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preparation for curing. Extruded items are cured in autoclaves with
100 psi steam.
The final form of the weather stripping product is created by
linking several pieces of weather stripping and using a transfer
molding technique to mold the corners, thereby joining the separate
components. The rubber corners are cured by circulating hot oil or
steam in the cavities of the molding presses. Flash is removed
manually. Before curing, the molds are wiped with a lubricating
liquid to ensure proper release from the mold.
The ends of pipe seal rubber are cemented together to form the large
O-ring type pipe seals. The operation is carried out in an electric
press. When bonding rubber to metal, the metal part must first be
degreased, using trichloroethylene in a closed system, and then
sprayed with an adhesive. The rubber is transfer-molded to the
metal part.
Waste waters generated at this plant include boiler blowdown,
cooling tower and chiller water overflow, once through cooling
water, leakages, from the various hydraulic and curing oil systems,
and spillages and drippings of lubricating solutions.
The greatest problem currently facing the company is storm runoff.
A recent large spillage of oil convinced company officials that
control and treatment of this type problem was a necessity. Sewer
lines are still coated with oil from the spill. To control this
problem, two gravity separators collect all water leaving the plant
including runoff. Oil storage pumping stations are covered. Drip
pans are provided for oil transfer lines.
Steam condensate from the autoclaves flows into a final holding
lagoon and is not discharged. Boiler treatment and blowdown wastes
and one group of roof drains flow into a detention pond to settle
oil and solids. From the detention pond, the water is siphoned from
below the surface and flows to a separator where any residual oil is
removed.
The resultant effluent concentrations are approximately: COD, 100
mg/1; suspended solids, 40 mg/1; and oil, 3 mg/1.
Plant G
This plant manufactures braided and spirally wound, reinforced
rubber hose as well as plastic-based hose. Both metal and fabric
reinforcing components are used. Total raw material consumption for
rubber products is approximately 162,500 pounds per day. The plant
operates 24 hours per day, 5 days per week.
Three different production processes are employed. Industrial hose
is produced by compounding, extruding, and pan curing. Hose, which
requires curing inside a mold, is produced by compounding,
extruding, encasing hose in lead, and curing. Preformed hose is
produced by compounding, extruding, forming, and curing.
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All rubber and compounds are mixed in one of four Banbury mills.
The compounded material is dropped from the Banbury where it is
sheeted out, dipped in a recirculated soapstone solution, air dried,
and piled on skids to await further processing.
TO make the hose, compounded rubber is extruded into a tube. Both
long and short barrelled extruders are employed at this plant.
Short barrelled extrudes require warm up and strip feed mills,
whereas long barrelled extruders do not. The tubing is cooled,
dipped in a zinc stearate lubricating solution and placed in a
temporary storage.
Reinforcing material is applied to the outside of the tube by
braiding or winding machines. No water is used in this area.
Finally, the outer covering is extruded onto the reinforced rubber
tubing.
Lead sheathing can be extruded onto the hose in a solid or molten
state. The lead covered hose is wrapped onto large spools. The
lead-sheathed hose is filled with water to apply pressure on the
inside of the hose before it is cured in steam heated autoclaves.
After curing, the lead covered hose is cooled and the lead covering
is removed mechanically and recycled to the sheathing process. The
water is released from the inside of the hose. The hose is
hydraulically tested with water before final storage and shipment.
The hydraulic test water is discharged.
Industrial hose which does not require molding is pan cured. The
stock is placed in pans and cured in autoclaves. Preformed hose is
made from uncured or semicured hose which is cut to length, placed
on a form to give it to the proper shape, and cured in autoclaves.
Waste waters from this plant arise from the use of water as a
lubricant, spillages of other lubricating or anti-tack solutions,
condensate from autoclaves, hydraulic testing water, pressure-water
for the curing operation, boiler blowdown, softener backwash, and
cooling system overflows. No steam condensate is recycled.
A municipal system receives all the waste waters from this plant
operation. No pretreatment of waste is practiced.
The effluent quality is comparable to other plants in this industry
group and is acceptable for publicly owned treatment works. The
effluent levels are approximately: COD, 300 mg/1; BOD, 30 mg/1;
suspended solids, 40 mg/1; and oil, 5 mg/1.
This plant produces canvas footwear, cement dipped boots, and foam
rubber for carpet underlay and shoe inner soles. Daily raw material
consumption amounts to approximately 265,000 Ibs per day of rubber
compounds.
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Canvas shoes are the result of many different production operations
including compounding of rubber stocks, molding of the soles,
extrusion of the other various rubber components, cutting and
fabricating of canvas parts, construction of all these items into
the final product, and curing of the final product.
The rubber used in this plant is compounded with other chemicals in
six Banburys and sheeted out in mills. The compounded sheeted stock
is cooled on six cooling conveyers employing three different cooling
techniques: a water spray, a cooling water tank, and water
evaporation. Three cooling conveyers employ a water spray against
the bottom of the conveyer belt carrying the rubber stock. On two
cooling conveyers the rubber is completely immersed in water. The
final system employs a spray directly onto the rubber. Evaporation
of this water supplies the bulk of the cooling. After cooling by
each of the three techniques, the rubber is rolled onto large rolls.
The inner soles of the shoes are cut with dies from sponge rubber
sheets. The sponge rubber sheet is prepared by extruding or
calendering rubber stock, containing blowing agents, into sheets.
The sheets are continuously cured in presses.
The soles are either cut from uncured rubber sheets, or formed in
compression or injection molds. The technique employed depends on
the final product and the technology available.
Compression molding technology is older and requires more manual
labor than the completely automated injection technique. Its
advantage is in the ability to mold many different colors
simultaneously. Oil supplies the hydraulic pressure for both
molding techniques. The curing presses are heated electrically.
After curing the molded soles are buffed to remove the flash. A
coat of latex is applied to the sole after which it is dried in an
electric oven.
Canvas uppers for shoes are made from two or three ply material.
Canvas material arrives at the plant as single ply sheets in various
colors. Latex is applied to the sheets; the sheets are then pulled
together and passed over steam heated drums. The sheets are stacked
and then cut to the proper dimensions using a die and press. The
various pieces composing the canvas portion of the shoe are stitched
together on making lines.
The shoe is fabricated from the various components on a form called
a last. The canvas top is cemented at its edges and placed over the
last. The inner sole is then applied. Before the toe pieces, the
boxing, and the outer sole are applied, the bottom of the inner sole
and canvas is dipped in a latex solution. The latex is used to hold
the entire shoe together. Next the sole, toe and heel pieces, and
boxing are applied. The finished uncured shoes are inspected and
placed on curing racks. The shoes are cured in autoclaves in an
ammonia atmosphere. Approximately 10 Ibs of ammonia is used per
autoclave per cure. At the end of the curing process, the autoclave
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is vented to the atmosphere. The need to collect and control the
ammonia contained in the autoclave ventings is being investigated.
Cement dipped boots involve a slightly different building process.
The pieces of fabric forming the carcass of the boot are applied to
forms which are dipped in a rubber cement solution, dried, cured,
and finally packaged.
process waste waters from this plant consist of latex tank cleaning
waste waters, oil dripping and leakage from heavy processing
machinery, and discharges from wet dust collectors. Waste latex, or
latex remaining in drums that can no longer be used, is removed from
the plant by a private contractor. Latex rinse waters, used to
remove residual quantities from the latex drums, are coagulated with
ammonium alum and settled out in a retaining basin. Clarified water
is allowed to overflow to the river. Coagulated rubber is removed
from the basin whenever necessary. The washing operation is
periodic, occurring approximately 10 to 12 times per 24-hour day.
Discharges from the basin occur for a total of approximately one
hour each day. Plant personnel are considering modifying the system
by adding mixers to the basin. There is currently insufficient
mixing in the basin and large quantities of latex remain
uncoagulated and leave the basin via the overflow. This latex
eventually coagulates in the overflow drains causing them to clog
periodically with solids.
Drippings from open gears and leakages from motor and mill bearings
cause the spillage and leakage of oil and water to accumulate in the
mill and heavy machinery basins. The plant has installed two
systems to cope with these problems. Motor areas are diked and
equipped with a 300-gallon oil collection sump. Mill basin drains
have been intercepted so that leakages that enter these drains flow
via a trough into a holding tank. Oil is removed from the tank by a
stainless steel belt. Plant personnel estimate the retention time
in the tank to be 72 hours. When operating, the unit has a overflow
rate of 1-2 gpm. Oil picked up by the belt passes into a waste oil
storage tank which is periodically emptied and the waste oil
drummed.
Each Banbury line is equipped with a wet dust collector. In
addition, two wet collectors control particulate pollution in the
buffing operation by collecting sole flash. Flow from these
collectors goes untreated to the outfall.
The plant effluent quality is approximately: COD, 76 mg/1; BOD, 6
mg/1; suspended solids, 29 mg/1; and oil, 7 mg/1.
This plant manufactures reclaimed rubber from whole tires and
miscellaneous rubber scrap. Daily raw material consumption includes
175,000 Ibs of whole tires (approximately 8,750 tires) and 127,000
Ibs of miscellaneous scrap, the bulk of which is inner tubes. Total
reclaim production is currently 271,000 Ibs per day. Two reclaim
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processes are employed, one for tires based on the conventional wet
digestion process, and a second process used primarily for scrap
inner tubes, called pan or heater process.
In the digester process, whole tires are brought to the plant and
stored in open areas. Plant personnel manually separate steel
belted and studded snow tires from other conventional tires.
Currently, tires containing steel (other than bead wire) cannot be
processed by this plant and are sent to dumps. Tires to be
processed are passed through a magnetic sensing device which removes
any steel belted or studded tires not previously removed.
Cracker mills grind and break up the whole tire. The ground tires
are screened and oversized particles recycled to the mills. After
the first milling, an operator removes large sections of the bead
wire. A magnetic separator removes the smaller sections of bead
wire which pass through the screens with the ground rubber. The
particles of rubber which still contain fiber from the cords and
belts are further ground in stoners (fine grinding equipment) and
hammer mills. The additional grinding facilitates the removal of
the fibers by air separation techniques. Separated fiber is baled
and sent to landfill sites.
A final grinding operation reduces the rubber particle size to 20
mesh. This grinding is necessary for the removal of the final
traces of fiber from the rubber product. The reduced particle size
also reduces the amount of oil necessary to devulcanize the rubber
in the digestion step.
The fine, fiber-free particles are mixed with oil, water and
chemicals (typically a calcium-based or formaldehyde digestion
solution) and fed to a digester where the rubber is devulcanized.
The digestion liquor is heated with steam injection. From the
digesters, the resultant slurry passes to a blowdown tank. Quench
or cooling water is added to the slurry in the blowdown tank. From
the blowdown tank, the rubber slurry passes to a holding tank, where
additional water is added before dewatering on a screen and finally
in a dewatering press. The dewatered rubber is dried in screw
dryers using recirculated steam. The liquor from the screen and
press pass through a 200-mesh screen where fine rubber particles are
recovered. The dewatering liquor is recycled to the digesters.
Vapors from the blowdown tank are trapped and condensed in a
barometric condenser. Vapors from the dryers are similarly
condensed. Oils are separated from the condensed vapors in a decant
tank and are retured to the digestion stage where they are reused.
The recycle system for the dewatering liquor and the reclaimed
process oils is shown in Figure 9. The waste overflow from the
decanter is approximately one^third of the total of the waste
dewatering liquor plus the vapor condensate without the recycle
system.
The dried devulcanized rubber is mixed with other compounds
including carbon black and oil. The mixing takes place in an
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GROUND DEFIBERED
PROCESS FLOR STREAMS
FOR PROCESS RITHOUT DIGESTER
LIQUOR RECYCLE SYSTEM
HUES SUPPLY
RASTERATER RECYCLE SYSTEM
FOR DIGESTER LIQUOR. COHOENSIBIE
OILS.AND BAROMETRIC COOLING
RATER
ro
CO
DRIED
UHCOMPOUKOEO
RUBBER
EXCESS BAROMETRIC
CONDENSER RATER
DISCHARGED AS
ItSTERATER
FIGURE 9: WASTEWATER RECYCLE SYSTEM FOR THE WET DIGESTER RECLAIM PROCESS
-------
internal mixer-extruder, compound usage follows a specific recipe
related to the endproduct use of the reclaim. Finally the
compounded reclaim is milled into sheets to form the final product.
The pan or heater process, which is used for miscellaneous rubber
scrap but primarily for inner tubes, differs from the wet digestion
process described above in that no fiber separation equipment is
needed and devulcanization of the rubber is carried out via a dry
process.
Operators remove metal, such as inner tube valves, from the scrap
rubber. conveyors carry the metal-free rubber to a cracker mill
where it is ground and screened. The rubber particles are mixed
with oil and other chemicals, placed in bins, and devulcanized in a
large horizontal heater. After devulcanization, the rubber is
milled into sheets to form the final product.
Process waste waters from the wet digester process arise from the
dewatering process and the various vapor condensers in the digester
process area. Discharge of the waste water from the dewatering
press has been eliminated in the past year by recycle of the water
to the digestion stage. Oils condensed from the vapor streams are
separated from the water in a decant tank and fed back to the
digester. Water from the decant tank is recycled to the digestion
makeup stage when possible or discharged as a waste water. Process
waste waters from the pan devulcanizer process are caused by the
condensation of vapor streams. These are combined with digester
vapor streams and decanted together with the digester stream. The
reclaimed oils are recycled to the wet digestion process.
The process waste waters which cannot be recycled are discharged.
The resulting plant effluent quality is approximately: COD, 110
mg/1; suspended solids, 50 mg/1; and oil 10 mg/1. It is believed
that these waste waters would be readily treated in a municipal
sewage treatment system.
Plant J
This plant produces balloons and prophylactics. Finger cots are
also produced, but not on a continuous basis. The plant is located
in a rural area and employs approximately 50 people. Natural latex
is the primary raw material for all dipped items. No other types of
latex are consumed. Approximately 2,650 Ibs latex is used to
produce 3,800 gross of prophylatics per day; 10,170 gross of toy
balloon are likewise produced from 6,810 Ibs of latex. Because of
the proprietary nature of the production equipment and the highly
competitive nature of the operation, inspection of the processing
lines was not permitted.
The natural latex arrives by tank car and is pumped to holding
tanks. The latex recipe is compounded in a water-cooled tank from
which it is pumped into drums together with varying quantities of
dilution, or makeup, water depending on the end-use. This drummed
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latex mixture is used as makeup for the four prophylatic dip tanks
and the twelve balloon dip tanks.
Clean molds are coated with latex in these dip tanks. The tanks are
cooled with recirculated cooling water. The latex-covered molds are
passed through a hot air dryer oven to strenthen the rubber coating.
This process is repeated in a second dip tank and dryer train. The
latex-covered molds are now cured in air-heated curing ovens. Steam
is used to heat both the drying and curing air.
After curing, the dipped goods are sterilized in a 200°F water bath.
Steam injection is used to heat the water bath. The overflow from
the sterilization bath is negligible since the water loss from the
baths by carryover on the molds is approximately equal to the steam
makeup.
The dipped items are coated with a talc and stripped from the mold.
The products are finally inspected, packaged, and shipped.
Stripped of the cured product, the molds are cleaned and rinsed
before being returned to the dip tanks. The cleaner tanks contain a
one-percent solution of Oakite Rustripper in water. There is little
overflow from the cleaning tank. The rinse tank is raw water but it
does pick up talc and cleaning agent from the mold. The rinse
overflow waste water is therefore contaminated with surfactants.
Process waste waters arise from the small overflow from the
sterilizer tanks, minor discharges from the mold cleaning tank, and
from the rinse water overflow. As mentioned earlier, the first two
sources are negligible. All process waste waters and the boiler
blowdown are directed to holding lagoons. The primary constituents
of the process waste waters are the talc and surfactants removed
from the molds in the rinsing process.
The waste water treatment facilities in this plant consist of three
lagoons, one holding lagoon and two detention lagoons. The holding
lagoon is used to contain all washdown and cleaning waters. The
detention lagoons treat the rinse water and blowdown for removal of
solids. In addition, the latex tanks were rinsed with small
quantities of water and wiped clean with rags.
The plant effluent contains: COD, 120 mg/1; BOD, HO mg/1; suspended
solids, 85 mg/1; and oil H mg/1. The effluent surfactants level is
negligible (less than 1 mg/1).
This plant produces compression molded sundries, such as hot water
bottles, hygiene syringes and bulbs, and pharmaceutical items. Also
produced are latex-dipped goods such as gloves. Daily raw material
consumption levels are 28,000 Ibs of compounded solid rubber per day
and 2,000 Ibs of latex per day.
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This company compounds the majority of its solid rubber stock in
Banbury internal mixers and roller mills. The remaining stock is
purchased as a rftasterbatch and is mixed on mills. In either case,
the material is fed to the Banbury or mill and mixed with various
compounding agents. After a prescribed mixing time, the materials
are sheeted off and air cooled. The sheeted compounded stock can be
pelletized or formed into extruded sheets depending on the type of
end product.
To form pelletized stock, the sheeted material is fed to a long-
barreled extruder. The material is extruded into a continuous
cylinder, cooled in a cooling tank, and cut to a prescribed length.
The pellets, referred to as slugs, are fed to a shaker screen where
they are air cooled and dusted with dry talc. The cooled slugs are
stored until needed.
To form extruded sheet stock, the rubber is fed to an extruder-
calender. The extruded sheets are passed over cooling drums, dusted
with talc, cut to length, and finally sent to storage.
All rubber molded items at this plant are compression molded. The
presses are loaded with slugs or sheets depending on the product.
Two hydraulic systems provide pressure for the compression presses.
The first is a deadweight water system. The second is an oil
system. Heat necessary for curing is provided by steam circulated
in the cavities of the molding presses. After molding, an operator
empties the presses, dips the cured molded items in a cooling tank,
and stacks the item on temporary holding skids. The cooling tank
water contains a lubricant. The molded items proceed to a die
cutter which trims the flash. In some cases, an operator applies a
silicone lubricant to aid in the cutting. Finished products, which
are formed from two molded pieces, proceed to a second steam-heated
press where the pieces are joined together with a rubber cement.
Latex used in the manufacture of dipped goods is brought in by tank
cars as a 50 percent emulsion. The stock is blended with other
ingredients in a blend tank before being transferred to a dip tank.
In the formation of a final product, molds are first dipped in a
coagulant. The coagulant is a solution of calcium nitrate dissolved
in alcohol. The molds are next dipped in the latex dip tank and
then into a leach tank. Finally the latex covered molds are cured
in a hot air oven. The leach tank contains mO°F water which is
heated by steam injection. The hot air used in the curing oven is
heated indirectly with steam. Once cured, the dipped goods are
stripped from molds which are recycled to the coagulant tank for the
next dipping operation.
Pharmaceutical items produced by this plant must be washed before
final packaging and shipping. Washing is carried out in a single
100-gallon washing drum using seven sequential steps. The drum is
first rinsed with water to remove contaminants retained from a
previous cycle. Next the items are loaded and washed in a
chlorinated caustic solution. The next two washes are with
detergent. These are followed by a neutralization wash, a hot water
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rinse wash, and a boiling water final rinse. The items are removed
from the drum, dried in a hot air oven, packaged, and eventually
shipped.
Process waste waters from this plant arise primarily from the
washing of molded and dipped goods. These wastes are characterized
by surfactants, BOD, COD, suspended and dissolved solids, and pH
spikes. Other process waste waters arise from leakages and spills
of oil and water from heavy machinery. Washing of dipping molds
also produce a discharge. The molds are cleaned every two to three
weeks. A fourth process waste water comprises overflows and
cleaning liquids from the dip tanks and other latex handling
facilities.
Waste waters are treated with calcium nitrate and "ferro-floc" to
coagulate the latex solids, followed by clarification to settle the
coagulated solids. The clarified effluent is discharged to a
municipal treatment system for further treatment. The principal
characteristics of the primary effluent are: COD, 700 mg/1; BOD,
150 mg/1; suspended solids, 800 mg/1; extractable organics, 130
mg/1; and surfactants, 7 mg/1.
Plant L
This plant manufactures latex foam products. Production lines
include mattresses, pillows, comfort seating, and slab foam. During
normal operating periods the plant is run continuously; however, at
the time of this survey a shortage of raw materials had reduced
production. Production at the plant during the sampling periods was
estimated to consume 200,000 pounds per day of raw materials
including the filler. Approximately 135,000 to 150,000 pounds were
dry latex solids. The plant is located in a minor urban area with
limited plant area available for either production plant expansion
or comprehensive waste water treatment facilities.
Production of the latex goods utilizes the Talalay process.
Following production of latex at another facility, the latex
emulsion is trucked to this plant and pumped into storage tanks.
The latex then passes through a freezing-agglomeration step where
the pH is lowered with carbon dioxide gas. This causes minor
coagulation of the latex to produce larger emulsion solids. The
latex is concentrated in an evaporator which pulls off water vapor
using a steam jet equipped with a barometric condenser to condense
the evaporated water vapor.
After concentrating, additional ingredients (stabilizers, fillers,
surfactants, antioxidants, accelerators) are added in the
compounding step. The latex mix is then transferred to the steam-
heated curing presses using a transfer hose. The high temperature
of the press causes specific latex ingredients to decompose,
liberating gases which produce the foam effect. In addition, carbon
dioxide is injected into the mold to assist the curing process. The
final foam product is cooled, rinsed with water, dried, and
inspected before shipment.
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River water, with a slight chlorine addition, is used in the plant
for washings and cooling. It is the only source of nonpotable water
in the plant.
The principal process waste waters from this plant arise during
process clean up and product washing. Periodic washdowns occur in
the latex storage and freezing-agglomeration areas to clean up latex
spills and leaks. These waste waters are laden with latex solids.
The final foam products are washed countercurrently to the flow of
the wash or rinse water. Progress has been made in reducing the
quantities of washwater needed by using a counterflow washing
recycle system. An additional source of waste water arises during
the evaporation step. Barometric condensers are used to condense
vacuum jet discharges and the combined condensates and cooling
waters are discharged directly.
Cooling water is once-through and is discharged directly to the
river. Boiler blowdown is also discharged without prior treatment.
Waste water facilities are employed primarily for the removal of
latex solids and zinc ions. High concentrations of latex solids are
present in the storage and freezer-agglomeration wash downs. These
waste waters are collected in a pit and transferred batchwise to a
treatment tank where the pH is adjusted and coagulation chemicals
(alum and polyelectrolyte) are added. Latex solids float to the
surface and are removed with the tank overflow.
The clarified underflow waste waters are discharged directly to the
river. The skimmed latex solids in the overflow are screened and
containerized for disposal. The screen filtrate is returned to the
chemical treatment tank for continued treatment.
Waste waters from the product washings are treated in a separate
system. The wash waters are collected in a pit and are then
transferred to a rapid mix tank where lime is added. The resulting
zinc hydroxide precipitate is removed in a primary clarifier. The
settled solids are dewatered in a vacuum filter and trucked to a
landfill. The waste water is discharged directly to the river.
Plans have already been made to upgrade the existing waste treatment
facilities. The proposed plant will collect the effluent from the
batch latex waste water treatment system and the zinc removal
clarifier in an equalization tank. The pH of the waste waters will
be adjusted with carbon dioxide to precipitate zinc carbonates. The
waste water will then be filtered in a diatomaceous earth filter to
remove fine suspended solids and carbonates. The waste waters will
then flow to a municipal treatment plant for additional BOD removal.
At present, with the described zinc removal and latex coagulation
primary treatments, the effluent quality, including the barometric
condenser discharge, is as follows: BOD, UOO mg/1; zinc, H mg/1;
and suspended solids, 50 mg/1.
Summary of Control and Treatment Technology
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General Molded. Extruded, and Fabricated Rubber Subcategories
In-Plant Control
In-plant control measures and practices require proper handling and
isolating general spills and leaks of potential contaminants:
soapstone and other anti-tack agents, latex compounds, solvents and
rubber cements, metal preparation wastes, and wet air-pollution
control equipment discharges.
General Spills and Leaks
Most molding, extruding, and rubber fabrication plants (such as hose
or footwear production facilities) can generate waste water
containing machinery oils and greases as well as suspended solids.
If uncontrolled, these waste waters can enter floor drains, thereby
polluting the plant effluent. In plants, such as cement dipping
facilities where less heavy machinery is used, the oil contamination
problem is noticeably reduced.
The exemplary subcategories E, F, and G plants visited shared the
following common methods to reduce the type of oil contamination
described above: blocking of existing floor drains, removing oil
leaks promptly with dry absorbent granules, and in some cases
curbing the problem area to contain oil or grease leaks. In cases
where a floor drain is required in order to discharge uncontaminated
cooling water, for instance, a collar is installed around the floor
drain opening to prevent floor drainage from passing into the drain
opening.
Plants which have water and oil leakages occurring at the same piece
of equipment often use oily-water sumps inside the oil retention
areas to collect the highly contaminated water in order that it can
be adequately containerized or treated. For cases with relatively
voluminous leakages, these collection sumps are equipped with pumps
which empty the sumps by pumping the oily water to a location where
it can be treated or held or disposal.
Outside storage areas where fuel, maintenance, and process oils are
kept are frequent causes of oil pollution in a plant's effluent.
The situation is aggravated at these facilities by high run-off
rates during storms. The most effective way to prevent
contamination of large quantities of storm water is to retain the
offending oil, preventing its entering the otherwise clean storm
water and, at the same time, roofing the oil contaminated regions to
keep the clean storm water from picking up the oil.
In one case observed, compressor oil was transferred from a 55-
gallon drum to a smaller container in the close vicinity of an open
drain. The floor around the drum and the drain opening was
contaminated with oil. Coincident with this observation, oil
globules appeared in the final plant effluent. In another plant,
discharded drums used to ship process oils were stored in the open.
The ground was coated with oil and the stagnant water in a nearby
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drain had a heavy layer of oil. This oil layer would eventually
enter the plant effluent discharge. These two cases point out that
good housekeeping, as well as installed control equipment, is vital
to the prevention of waste water contamination by oil.
In the plants where good housekeeping and sound control facilities
were used the oil loadings in the plant effluent were satisfactory.
Soapstone and Anti-Tack pip Solutions
The spillage of soapstone and other anti-tack solutions is
controlled in exemplary plants in a manner similar to the
containment methods used for oils and grease. Floor drains have
been blocked or collared to prevent the slurries from entering plant
drains and sewers. Spills and drippage are mopped up or are simply
allowed to evaporate.
In industries such as cement dipping, few floor drains are required.
In the area where the final dipped product is coated with soapstone,
the soapstone slurry system is closed and little spillage occurs. A
similar approach is feasible for all types of industry in this
category.
Latex Compounds
Several types of fabricated product require the use of latex during
the manufacture. Latex spills can occur at the storage loading
areas, facilities where bulk latex is transferred to drums, and at
the processing areas. Where such spills occur, it is common to wash
the latex down with water, producing a latex-laden waste water. In
addition, drums are frequently rinsed clean with water. These latex
waste waters are then chemically coagulated and clarified, usually
in a batchwise treatment system.
A more effective way to handle latex is the use of plastic liners in
latex drums. When the drum is reused, the old liner is discarded.
In this manner, waste waters from drum cleaning are not generated.
Latex spills around storage and transfer facilities are coagulated
with alum in situ and scraped from the ground. In the processing
areas where latex is used, floor drains have been blocked. This
approach is used by a footwear plant which, although it was not
visited, was surveyed on this specific subject.
Solvents and Rubber Cements
Many plants use rubber cements as adhesives. In addition, the
cement dipping industry handles large quantities of cements and
solvents. In most of the cases observed, these organic liquids are
mixed and stored in areas without floor drains. This is by far the
most positive method to control solvent or cement spills and leaks.
Incidentally, solvents should be kept out of plant drains for
reasons of safety as well as effluent quality, since they have high
flammability and explosiveness.
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Metal Preparation
The methods used to prepare and recycle metal components for rubber
bonding were essentially dry. Degreasing liquids were used in
closed systems and discarded when saturated with grease.
It is believed that some plants use acid pickling to prepare metal
components. The pickling and metal rinse waste will exhibit low pH
and high heavy metal concentrations. It is understood that
precipitation of the metals and pH adjustment is carried out to
effectively treat such wastes before combination with other plant
waste waters. Alternatively, the pickling wastes are containerized
and hauled from the plant.
Air Pollution Control Equipment
Wet scrubbing devices are used in the rubber compounding and product
buffing areas. Although wet scrubbing devices are used to trap
rubber-buffing and metal sand-blasting fines, dry air-pollution
control devices are also applicable and are used in many plants
within the industry. In some plants where waste water discharge
requirements are stringent and the use of bag collector devices is
also inappropriate, the waste waters from wet scrubbing devices are
settled and filtered before discharge, or a municipal treatment
system is used to accept the waste waters.
End-gf-Pipe Treatment
In general, only minor end-of-pipe treatment is used by the
industries covered by this industry segment. This is due largely to
the fact that process waste water contamination is limited to
essentially two parameters: oil and grease, and suspended solids.
In addition, good effluent quality can be achieved most economically
by employing good housekeeping practices with well-designed in-piant
control measures.
Of the Subcategories E, F, and G plants visited, only two had
primary treatment systems and none used secondary treatment.
Furthermore, only one of these plants used the local municipal
sewage treatment system to provide the equivalent of secondary
treatment. These facts indicate that the magnitude of waste water
pollution in these industry sectors is not appreciable or the
problem can be effectively controlled by sound prevention and in-
plant control measures.
One plant uses gravity separation to remove oil from the combined
plant effluent. This combined effluent includes utility and storm
waters as well as process waste water. In-plant control measures
are employed as the primary method of oil reduction and the oil
separators are designed as a backup system. In addition the plant1s
boiler blowdown, autoclave condensate, and compressor condensates
pass through a holding pond to separate solids and oils from these
waste water types before discharge. The holding pond also allows
these waste waters to cool before they are discharged.
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The other plant (manufacturing footwear) which does employ primary
treatment uses appreciable quantities of latex adhesives. The
handling of these materials produces latex-laden waste waters which
are chemically coagulated and allowed to separate in a batchwise
manner. It is debatable whether this treatment method for latex
waste waters is the most appropriate or whether the latex waste
water can be eliminated completely in the use of different handling
and dry cleanup techniques. This plant utilizes oil collection-
separation sumps to trap oil leaks produced at the mills and other
heavy machinery.
The quality of the effluent from the one plant which discharges to a
municipal treatment system is satisfactory for the municipal system
without primary treatment or pretreatment. This quality of effluent
can be achieved when correct waste water control and housekeeping
procedures are followed.
Wet Digestion Reclaimed Rubber Subcategorv
In-Plant Control
The wet digestion reclaiming process is declining even more rapidly
than the reclaiming industry as a whole. There are only about five
or six wet digester reclaiming plants remaining, and the incentives
for process modifications, particularly those modifications leading
to lower waste water flows and loadings, are few. However, the
control measures used by the wet digestion industry include
containment of pollutants by the recycle and reuse of waste water
streams.
General Spills and Leaks
Oil and grease spills and leaks occur around the heavy cracking and
grinding machinery used to prepare the scrap rubber for the
digestion process as well as the milling areas for the final reclaim
rubber product. In addition, rubber fines are generated which can
enter into plant drains. Outside storage areas used to store fuel,
machinery, and process oils produce oil-laden waste waters if
spillage and storm water are allowed to contact each other.
The accepted method of controlling these types of contamination is
similar to that employed by general molded, extruded, and fabricated
rubber plants, namely, containment of the leaks and spills with
separate handling and disposal procedures and at the same time
reduction in the volume of water. For example, storm and cooling
waters that are uncontaminated are not allowed to come in contact
with the polluting spills and leaks. Good housekeeping is an
important element in the control of the contamination of cooling
water and storm water.
Digestion Liquor and Oil Recycle
The dewatering liquor is the major waste water stream from wet
digestion reclaim plants. The reclaim plant visited (Plant I) uses
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a recycle system which returns the dewatering liquor and reclaimed
process oils to the digestion step. This system is illustrated in
Figure 9 in the section on Plant I.
The dewatering liquor is collected at the rubber dewatering screen
and sent to a storage tank from where it is returned to the
digester. The liquor storage tank requires constant agitation to
suspend solids, particularly rubber particles, thereby preventing a
dense and tacky buildup in the tank.
Vapor condensates and cooling waters from the blowdown tank and
dryer are sent to a decanting tank where oils and other organics are
decanted.
The decanted oils are sent to an oil storage tank where the residual
water content is drawn off the bottom, and the top layer (oils and
organics) is returned to the digester for reuse. The bottom water
layer is returned to the first decanter.
The bottom water layer from the first decanter is pumped to the
dewatering liquor storage tank where it mixes with the digester
liquor before being returned to the digestion process. Part of the
bottom water layer from the first decanter is slip-streamed to the
sewer to blow down accumulating compounds. It is this stream that
is finally discharged in the plant's effluent. The flow and
loadings of this discharge are lower than the equivalent stream
without the recycle and reclaim system. This comparison is shown in
Table 15.
The oils and dewatering liquor that are returned to the digestion
step of the reclaim process require makeup but the chemical usage is
less than the equivalent process consumption without recycle and
reclaim.
Vapor Condensates
In theory, it should be possible to use vacuum pumps to exhaust the
blowdown tank and dryers. However, the advantages of steam ejectors
over vacuum pumps are their reliability, trouble-free operation and
overall economy. The use of vacuum pumps would reduce the condenser
cooling load and the final volume of condensate.
The above modification has more merit if indirect cooling condensers
are used in place of barometric condensers. The volume of
condensate with a vacuum pump and indirect condenser would be
considerably lower than with a steam ejector and barometric
condenser.
Scrap. Defiberinq
The method by which the scrap rubber is defibered has a considerable
effect on the loading of the digester dewatering liquor. If scrap
containing fiber is' fed to the digester together with the necessary
defibering chemicals, the dewatering liquor will contain the
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solubilized fiber residue. In addition, the defibering chemicals,
which are discharged along with the dewatering liquor, can contain
contaminants, possibly heavy metals. Furthermore, chemical
defibering precludes the use of the recycle and reclaim system as
described above.
As an alternative to chemical defibering, defibering by mechanical
or physical techniques can be used. In brief, the waste water
benefits of this method are: fiber-free dewatering liquor, no
chemical defibering agents in the liquor, and reduced dewatering
liquor discharge due to liquor recycle. In cases where liquor
recycle can be utilized, the usage of process oils and digestion
chemicals is also signficantly reduced.
Alternative Reclaim Process
The conversion of a wet digestion reclaiming plant to any of the
three dry reclaiming processes (pan, mechanical, or dry digestion),
in order to improve the quality of the plant's effluent would
constitute considerably more than an in-plant control measure.
However, it is appropriate to note at this point that the three dry
processes give significantly lower waste water flows and loadings
than the wet digester process. The wet digester process can more
readily be converted to the dry digester process than to either the
pan (heater) or mechanical processes.
End-of»Pip_e Treatment
Plant I employs no end-of-pipe treatment. This is the only wet
digester reclaim process known to discharge directly to a stream or
river. All other wet digester plants discharge to municipalities
which are reportedly able to treat this type of waste water
adequately. In view of the fact that no end-of-pipe treatability
data exist, and since the few wet digester reclaim plants still
operating will most probably continue to use local municipal
treatment systems indefinitely, it is difficult to comment
meaningfully on the merits of potential, but unproven, end-of-pipe
treatments.
However, it can be stated positively that the most common and
apparently most appropriate end-of-pipe treatment for wet digestion
process waste water is afforded by publicly owned treatment works.
No constituents of the wet digester process waste waters are toxic
or refractory in a municipal treatment system.
Pan (Heater) , Mechanical. and Dry Digestion Reclaimed Rubber
Subcategorv
In-Plant Control
In comparison to the wet digester process, the waste waters from the
dry reclaim process (pan, mechanical, and dry digestion) have lower
flow and are less contaminated. This is due primarily to the
absence of the dewatering liquor. The scope for in-plant waste
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water controls is thereby reduced and is limited to the containment
of spills and leaks, and the effective condensation and decanting of
vaporized process oils and organics.
General Spills and Leaks
The flows, characteristics, and applicable control methods of the
spills and leaks in the dry reclaiming industry are similar to those
found in Subcategories E, F, G, and H.
The spills originate at heavy equipment, and material handling and
storage areas. The contaminants are characterized by oil and
suspended solids and are prevalent in the scrap cracking, scrap
grinding, product milling, and oil storage areas.
Successful control techniques include good housekeeping, curbing and
drain blockage to contain the spills, and isolation modifications
which restrict the spread of the polluting material and prevent
contact with uncontaminated waters.
Vapjor Condensates
The exhaust vapors from the devulcanizer ovens require condensing to
minimize air pollution. This exhaustion-condensation is normally
carried out using a steam-ejector barometric-condenser system.
Although this type of system is reliable and economic, the volume of
condensate and cooling water is greater than the volume of
condensate produced by a vacuum pump and noncontact condenser.
Plant I, which operated both wet digester and pan reclaim processes,
decanted the barometric condenser cooling waters plus condensates
from the pan process, recycling both the reclaimed oil and water
layers to the wet digester process. It is believed that the
reclaimed oil cannot be recycled to the devulcanization step of the
pan process because the quality of the feed process oil is more
critical in the pan process. Therefore, for plants with only the
pan process, the oily vapor condensate must be disposed of as a
waste. However, the basic technologies used at Plant I to recycle
the components of the vapor condensates can be applied at plants
operating only the pan process to control the flow and loadings of
vapor condensate waste waters. The barometric-condenser cooling
water and condensibles mixture can be decanted. The top oil layer
can be containerized for disposal and the bottom water layer can be
cooled in a noncontact heat exchanger before it is recycled to the
barometric condenser for cooling water. A portion of the water
layer should be slip-streamed to the plant sewer to blowdown
accumulating organics.
End-of-Pipe Treatment
The dry reclaiming plants throughout the industry do not generally
use end-of-pipe treatment for their waste waters. A large
proportion of the plants in existence discharge their waste waters
to municipal treatment plants. No treatability data exist for the
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biological treatment of pan, mechanical, or dry digester processes.
In fact the BOD is so low (20 mg/1 typically) that biological
treatment is inappropriate.
It is possible that separators or holding ponds are used by some
plants to act as a catch-all for all plant waste waters in order to
trap oils and suspended solids that have bypassed or escaped in in-
plant controls previously described. It is belived that such a
catch-all is not necessary if adequate in-plant control and good
housekeeping are practiced.
Latex-Based Products Subcateggries
In-Plant Control
Since Subcategories J and K represents the latex-based industries,
the in-plant controls employed by this industry are designed
primarily to control, handle, and treat latex-laden waste waters.
In addition, some individual streams such as foam rinse water or dip
form-cleaning water require special control and treatment measures.
General Latex Spills and Leaks
Both the latex-dipped goods (Subcategory J) and the latex foam
(Subcategory K) industries generate latex-laden waste waters. The
quantity of latex consumed by the latex foam plant visited is
considerably higher than the latex usage at the average latex-dipped
goods production facility; generally, the latex shipping, storage,
and handling procedures are different.
In a dipped goods facility the latex is generally shipped in by tank
car or tank truck and transferred to a storage tank. After
compounding, the latex mixture is usually taken into the dipping
areas in 55-gallon drums. The major spillages and washdowns occur
at the storage unloading area and in the latex compounding building.
In addition, the transfer drums require cleaning between latex mixes
and this produces a latex-laden waste water. In the dipped goods
plants that were visited, no treatment of the latex waste waters is
carried out before they mix with the total plant effluent.
In the latex foam plant, the latex-laden waste waters are generated
at the latex concentration, intermediate storage, and curing press
areas. The waste waters from these operations are collected in a
separate drain system and treated by chemical coagulation and
clarification. As part of this overall system, the areas where the
latex spills and leakages occur are designed to restrict the spread
and further contamination by the latex wastes. The coagulation and
clarification system for latex waste water consists of a collection
pit which feeds a batch treatment tank (10,000 gallons). The waste
water pH is adjusted using sulfuric acid and caustic soda and the
solids are coagulated using alum. The coagulated solids float to
the water surface where they are skimmed off and screened in a
strainer. The screened water is returned to the treatment tank and
136
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the solids are landfilled. The clarified waste water overflow is
discharged to the plant drain.
Foam Rinse Waters
After curing, latex foam requires rinsing to remove excess
compounding and curing agents entrained in the foam matrix. The
resulting rinse waters pick up soluble zinc compounds and the zinc
concentration in these wastes is high (typically 700 mg/1). A
significant reduction in the volume of this rinse water was achieved
at Plant L by employing a countercurrent rinsing process. This is
represented schematically in Figure 8 in Section III. The zinc-
laden rinse water is then treated for zinc removal in a continuous
chemical precipitation and clarification system. Precipitation is
accomplished by adjusting the pH to approximately 12 by the addition
of lime, and by the addition of a polyelectrolyte. The operation is
carried out in a rapid mix tank. The mixture then passes to a
flocculation tank where the precipitation and flocculation processes
are completed. The tank has mild agitation sufficient to gently mix
the waste water components but not sufficiently powerful to break or
destroy the desired floe. The flocculation water then enters the
clarifier where the zinc precipitate is settled. The clarified
effluent (zinc concentration about 10 mg/1) is then discharged to
combine with the total plant effluent. The zinc sludge is drawn off
from the bottom of the clarifier and filtered on a vacuum filter.
The filtrate is recycled to the mix tank. The filtered sludge is
sent to landfill. The filtering system at Plant L preheats the
zinc-lime sludge to enhance the filterability of the sludge.
Studies are to be made to reclaim the zinc and recycle it to latex
compounding stage. The feasibility of this approach has yet to be
determined.
Form Cleaning Wastes
In most latex dipping facilities, the dip forms require cleaning.
In some case this is necessary on each dip cycle prior to the first
dip tank; in other plants only periodic cleaning is required.
Frequent cleaning operations can be performed in a tank of water
containing detergent or some other type of cleaning liquid. The
form can be simply dipped into the cleaning water and gently
scrubbed in the tank with mechanized scrubbing equipment. After the
cleaning step, the forms are rinsed before the latex dipping
operation. The rinse water is allowed to overflow from the rinse
tank and contains detergent or cleaning agent and exhibits a BOD
load. Plants limit the volume and loading of the rinse water
overflow more by reliance on mechanical scrubbing than on the
activity of the detergent agent. In addition, countercurrent
rinsing is sometimes employed in which the final rinse water
overflows to the first rinse tank where a higher concentration of
detergent can be tolerated. The volume of rinse water discharged is
thereby reduced.
137
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In some dipping plants, the forms are cleaned only periodically,
usually when they become fouled with rubber. One method to clean
this type of stubborn rubber deposit is to dissolve it in chromic
acid and rinse the acid from the form. The form rinse water
collects the chromic acid and is characterized by low pH and
hexavalent chromium. A satisfactory method of treating this type of
waste water, as employed by the industry, is the batch precipitation
of the chromium. To do this, the chromium has to be reduced to the
trivalent state. The pH of the rinse water is lowered to 2 with
sulfuric acid and the hexavalent chromium reduced to trivalent
chromium using ferrous sulfate. The trivalent chromium is then
precipitated using lime at a pH of approximately 9 and allowed to
settle. The settled lime sludge is then dried on a sludge drying
bed.
End-of-Pipe Treatment
The latex dipping plant visited coagulated the latex solids
chemically and settled them from the total plant effluent. The
clarified primary effluent is then discharged to the local municipal
system. This effluent quality is suitable for treatment in the
municipal treatment works.
The other latex-dipped goods plant passes the bulk of its waste
water through a two-pond settling lagoon system prior to final
discharge to a receiving stream. This treatment system also gives
acceptable effluent quality.
Some latex dipping plants use aerated lagoon and settling pond
treatment systems to treat the waste waters. These systems perform
well. Few plants use activated sludge treatment. It is considered
that the waste water loadings, particularly BOD, are too low to
produce an adequate biomass. Therefore, aerated lagoon and settling
pond systems are more applicable.
Many latex dipping plants use the local municipal treatment plant to
treat the primary effluent after chemical coagulation and
clarification of the latex solids. This type of treatment is very
suitable and is possibly the most attractive economically for most
plants that are adjacent to a municipality.
The latex foam plant that was visited is proposing, based on a pilot
study, to treat the total effluent further before discharging it to
a municipal system. Both the clarified latex wastes and rinse waste
waters after zinc removal will be combined and passed through a
25,000 gallon equalization tank. The equalized flow will be treated
with carbon dioxide to lower the pH to approximately 8 units (the
original pH will be higher than 8 because the clarified rinse water,
after zinc precipitation and removal, has a pH value of 12). At pH
8 some soluble species, particualrly zinc, will be converted to
insoluble carbonates. The waste water will be filtered in a
diatomaceous earth filter before it is discharged. The filter will
generally polish the effluent removing the fine carbonate
precipitate. The carbonate precipitate will include a portion of
138
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the residual zinc that has been carbonated. It is anticipated the
filtered effluent will eventually be discharged to the local
municipal system. This will not occur until the city plant is
expanded, in a few years1 time.
139
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SECTION VIII
COST, ENERGY, AND NONWATER QUALITY ASPECTS
general Molded. Extruded, and Fabricated Rubber Subcateqories
Two fundamental approaches can be applied for the control and
treatment of process waste waters produced by Subcategories E, F,
and G production facilities.
The first approach is to combine process and nonprocess waste waters
and to treat the entire plant effluent. Where land is available,
on-site end-of-pipe treatment is practiced at some of the plants.
At other plants, the total effluent is discharged to the local
municipal treatment facilities. In either case, the reasons for
treating or discharging a combined effluent are as follows:
1. In older plants, in-plant sewers for process and nonprocess
waste waters are usually combined, thus making combined
treatment more attractive.
2. Process flows are usually small relative to nonprocess
flows.
3. The treatment of nonprocess waste waters has received the
bulk of industry's attention. For example, high suspended
solid loadings contained in blowdown and water treatment
wastes are a major pollutant in the combined plant effluent
from rubber processing facilities.
However, end-of-pipe treatment systems also have several
di sadvantages:
1. The combined effluent treatment system usually requires oil
removal equipment and/or a holding pond or lagoon system to
separate the oil. Lagooning of the wastes generally
requires considerable land area.
2. Because of dilution, the effectiveness of treatment for oil
and solids removal from process waste water is reduced. In
several of the systems observed, oil passed through the
system with low removal efficiency, because its
concentration was below the capabilities of the treatment
system employed. This phenomenom occurs even though the
oil loading is significant, because of the dilution
afforded by nonprocess waste waters.
The second approach employed is control and treatment of an isolated
and undiluted process waste water. This approach has been followed
in plants having partially or wholly-segregated process and
nonprocess sewers. The
141
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key to this treatment approach is the reduction, containment, and
isolation of the contaminated process waste waters prior to
treatment. The principal advantages for this treatment approach
over the end-of-pipe treatment of the combined plant effluent are:
1. Higher pollutant (primarily oil and suspended solids)
removal rates.
2. Smaller treatment units and land area requirements.
The primary disadvantage of a segregated system approach is that
separate process and nonprocess sewers are required. This will
necessitate in-plant modifications which, if not carefully planned,
can lead to significant production disruptions.
Evaluation of these alternatives indicated that control and
treatment of segregated process waste waters is the most effective
and generally applicable treatment approach for this industry. End-
of-pipe treatment of combined waste waters is not feasible for
pollution control because of the ineffectiveness of such systems in
removal of diluted process waste water contaminants, and the larger
land requirements.
Incidentally, a viable alternative treatment for waste waters
(process as well as nonprocess) generated by this industry is
discharge to the local publicly owned treatment works. Such
discharge is contingent on adequate pretreatment.
All costs presented are related to the control, followed by
treatment, of segregated process waste water streams. It can be
further stated that this type of treatment approach is considered to
be the best practicable control and treatment technology currently
available to the industry.
With proper in-plant control, the process streams consist of, readily
separable lubricating and extender oils, and settleable solids.
Volumetric flow rates for process waste waters are small.
Therefore, the initial treatment applicable from a proven operation
basis is an API-type gravity separator. The performance and
efficiency of a gravity separator can be improved by addition of an
absorbent filter. The corrugated plate interceptor (CPI) type of
device is also applicable generally to this industry. The choice
between the API or CPI separators will depend on land availability
and the type of waste water control, handling, and treatment equip-
ment already present at the plant. Since the cost and treatment
effectiveness of the API and CPI type separators are comparable, the
effluent limitations treatment and costs presented are based on the
use of API type separators.
Effluent quality data for Subcategories E, F, and G are presented in
Tables 20, 21, and 22. The treatment basis includes isolation of
wastes with curbing, protection of uncontaminated waste streams
(such as cooling water and storm run-off) , blocking unnecessary
floor drains, the covering of oil-handling areas to prevent
142
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o
Investment^
Annual Costs
Capital Costs
Depreciation
Operating and Maintenance Costs
'(excluding energy and power costs)
Energy and Power Costs
Total Annual Costs^
Treatment or Control Technology
A B
$79,000
$ 7,900
15,800
11,400
600
$84,000
$ 8,400
16,800
12,900
600
$35,700
$38,700
CO
Parameters
kg/kkg (lb/1000 Ib) raw materials
Suspended Sol ids
Oi1 and Grease
Raw Waste
Loads
3.500
1.000
Effluent Quality
A
0.640
0.480
IB
0.640
0.160
^Technology A is isolation of process waste waters followed by API gravity separation.
Technology B is Technology A followed by an absorbent filter.
2August 1973 dollars.
Table 20: Estimated Waste Water Treatment Costs at Different Degrees of Treatment for a
Subcategory E Plant"
-------
Investment2
Annual Costs
Capital Costs
Depreciation
Operating and Maintenance Costs
(excluding energy and power costs)
Energy and Power Costs
Total Annual Costs2
Treatment or Control Technology1
A B
$163,000
$ 16,300
32,600
18,200
800
$ 67,900
$171,000
$ 17,100
34,200
23,200
800
$ 75,300
Parameters
kg/kkg (lb/1000 lb) raw materials
Suspended Sol ids
Oi1 and Grease
Raw Waste
Loads
1.220
0.600
Effluent Quality
A
0.400
0.300
B.
0.400
0.100
^Technology A is isolation of process waste waters followed by API gravity separation
Technology B is Technology A followed by an absorbent filter.
2August 1973 dollars.
Table 21: Estimated Waste Water Treatment Costs at Different Degrees of Treatment for a
Subcategofy F Pldnt
-------
o
Investment'1
Annual Costs
Capital Costs
Depreciation
Operating and Maintenance Costs
(excluding energy and power costs)
Energy and Power Costs
Total Annual Costs2
Treatment or Control Technology
A B
$212,000
21,200
42,400
20,800
1,200
$ 85,600
$223,000
22,300
44,600
27,800
1,200
$ 95,900
en
Parameters
kg/kkg (lb/1000 Ib) raw materials
Suspended Sol ids
Oi1 and Grease
Raw Waste
Effluent QualIty
0.250
0.189
B
0.250
0.063
'Technology A is isolation of process waste waters followed by API gravity separation
Technology B is Technology A followed by an absorbent filter
August 1973 dollars.
Table 22: Estimated Waste Water Treatment Costs at Different Degrees of Treatment for a
Subcategory G Plant
-------
Investment2
Annual Costs
Capital Costs
Depredation
Operating and Maintenance Costs
(excluding energy and power costs)
Energy and Power Costs
Total Annual Costs2
Treatment or Control Technology
A B
1
$15,000
$1,500
3,000
2,800
200
$30,000
$3,000
6,000
5,600
400
$15,000
Parameters
kg/kkg (lb/1000 Ib) raw materials
Lead
Raw Waste
Loads
0.030
Effluent Quality
A;
0.0070
0.00070
^Technology A 1s Hme precipitation followed by settling.
Technology B 1s Technology A followed by sand filtration,
2August 1973 dollars.
Table 23: Estimated Waste Water Treatment Costs for Lead Treatment for Subcategories E, F, and G.
-------
contamination of storm run-off, and separation of settleable solids
and oily material from the waste water.
A more detailed description of the recommended facilities is
presented in the Subcategories E, F, and G portion of Section IX,
and a flow diagram of a typical system, used as a basis for costing,
is presented in Figure 10.
Treatment Cost Data
Data collected during the plant operations and waste water analysis
visits plus data from Corps of Engineers permit applications were
utilized to obtain typical plant size and process waste water flows
and raw loadings. The analysis approach and findings are described
in Section V.
As stated previously, Subcategories E, F, and G plant effluents can
be divided into two groups: process and nonprocess waste waters.
The process waste waters consist of mill and curing areas, oily
waters, anti-tack and latex spills and leaks, area washdown waters,
wet scrubber discharges, and contaminated storm waters from material
and fuel oil storage and handling areas. The nonprocess waste
waters, which are not the subject of this document, include
sanitary, noncontaminated storm water, and utility waste waters,
such as once through cooling water, boiler blowdown, cooling tower
blowdown, and water treatment wastes. In addition noncontaminated
process-associated waste waters such as extrusion contact cooling
waters, and hydraulic (hose manufacture) and conductivity (cement
dipped electrical gloves) test waters can be included with
nonprocess waste waters, for the scope of this document, since they
should not require any treatment at all prior to discharge.
The aforementioned data sources indicated that the following flow
adequately described the process waste waters generated by
Subcategories E, F, and G plants:
Process Waste
Typical Plant Size Product Size Range Water Flow
kg/day (Ib/day)raw materials kg/day (Ib/day) raw materials L/day (gpd)
Small: 900 (2,000) less than 3,720 (8,200) 1*4,700 (3,900)
Medium: 7,700 (17,000) 3,720-10,^30 (8,200-23,000) 75,800 (20,000)
Large: 15,*»00 (3^,000) greater than 10,*»30 (23,000) 95,900 (25,300)
From these typical flow values for Subcategories E, F, and G
facilities, treatment cost data were generated and are presented in
Tables 20, 21, 22, and 23, as well as the estimated raw oil and
suspended solids loadings of the process wastes associated with the
three typical plant sizes. The cited costs for all sizes of
Subcategories E, F, and G production facilities are based on the
worst cases where no treatment facilities that could be modified yet
exist, and no reduction or isolation measures for the containment of
contaminated process waste waters have been taken. The worst cases
were chosen since the design considerations (i.e., the influent raw
147
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ROOFED TANK CAR UNLOADING AREAS
ROOFED TANK CAR UNLOADING AERAS
_n—fc»__o0i _—
CURBED
MILL
AREAS
CURBED
PRESS
AREAS
GENERAL
PLANT
AREAS
j-— i n — ,,
—n
BELT SKIMMER AND
OIL COLLECTION/DECANT
SYSTEM
OIL SEPARATOR
ADSORBENT
FILTER
FINAL
PROCESS'
EFFLUENT
PROCESS EFFLUENT
MONITORING STATION
SUMP
FIGURE 10: HYPOTHETICAL WASTE WATER SEGREGATION AND TREATMENT FACILITY
FOR SUBCATEGORIES E, F, G, AND I PLANTS
-------
waste loads) were selected to represent the expected raw waste load
within each subcategory. This results in the generation of cost
data which should be conservative when applied to most of the plants
in this industry. Relatively conservative cost figures are
preferred for this type of general economic analysis.
The total annual costs for the proposed BPCTCA and BATEA control and
treatment technologies can be expressed as incremental costs per
unit of production or raw material consumption. Study of the cost
data for the three typical plant sizes indicates that the BPCTCA and
BATEA treatment costs per unit of raw material consumption are
approximately:
Typical Plant Size Annual Treatment Cost Incremental Treatment Cost
kg/day (Ib/day) raw material August 1973 dollars cents/kg U/lb) raw material
Small: 900 (2,000) 38,700 U.3 (6.5)
Medium: 7,700 (17,000) 75,300 3-3 (1.5)
Large: 15,400 (3*»,000) 95,900 2.1 (0.9)
The above incremental costs are based on a 300 working-day year;
that is, 50 working weeks per year and six (6) operating days each
week.
It can be seen that the incremental treatment costs to the small-
and medium^sized plants are extremely high. Compared to the cost of
rubber raw material (approximately 30 to 50 cents per pound), the
treatment costs appear to be a burden on the small plants in
particular. This analysis underlines clearly the cost benefits to
be derived by complete elimination of process waste waters by good
housekeeping and closed spill and leak containment facilities or by
utilization of the local municipal treatment system. In addition,
the elimination of direct discharge of process waters to navigable
waters will eliminate the need for costly waste water analyses and
permit reporting.
The capital costs were generated on a unit process basis, with the
following "percent add on" figures applied to the total unit process
costs in order to develop the total installed capital cost
requirements:
Percent of Unit Process Capital Costs
Item Small Plants Medium and Large Plants
Electrical 15 12
Piping 20 15
Instrumentation 15 8
Site Work 10 5
Engineering Design and Construction
Supervision Fees 10 10
Construction Contingency 15 15
149
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Some of the "percent add on" costs are higher in the case of the
small, Subcategories E, F, and G plants than the equivalent values
for the medium and large plants since these costs are
disproportionately higher (in terms of a percentage of the unit
process cost) in the case of small plants.
Since land costs vary appreciably between plant locations, it was
decided to exclude land cost from the total capital cost estimates.
Land costs must be added on an individual case basis.
Annual costs were computed using the following cost basis:
Item Cost Allocation
Capitalization 10 percent of investment
Depreciation 5-year straight line with zero
discharge value
Operations and Maintenance Includes labor and supervision,
chemicals, sludge hauling and dis-
posals, insurance and taxes
(computed at 1.6 percent of the
total capital costs), and main-
tenance (3.2 percent of the total
capital cost)
Power Based on $0.015 kw-hr for electri-
cal power
The short-term capitalization and depreciation write-off period is
what is currently acceptable under current Internal Revenue Service
Regulations pertaining to pollution control equipment.
All costs, capital and operating, were computed in terms of August
1973 dollars, which correspond to an Engineering News Record Index
(ENR) value of 1920.
Energy Requirements
Energy input is related solely to the need for electric pumps to
pump process waste waters from the plant areas through the treatment
system. The additional power requirements for control and treatment
systems are small and deemed minor in comparison with the power
usages of rubber processing machinery and equipment common to the
industry. The power requirements for waste water control and
treatment are estimated to be:
Typical Plant Size Treatment Equipment Power Requirements
kg/day (Ib/day) raw material horsepower
Small: 900 (2,000) 6
Medium: 7,700 (17,000) 8
Large: 15,400 (3U,000) 12
150
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Electrical costs, as presented in Tables 20, 21, and 22, are
estimated at $0.015 per kilowatt hour which is equivalent to $98 per
hor sepower-year.
Nonwater Quality Aspects
The primary nonwater quality aspect deriving from use of a separator
is the need for disposal of oil and solids. Additional solid waste
results from the use of a nonregenerative type absorbent filter.
Disposal of process solid waste, such as waste rubber or rejected
products, is a problem confronting the industry as a whole.
Additional solid waste results from the drumming of waste liquid,
such as latex solutions, for off-site disposal. Many manufacturing
plants, particularly in the northern states, are finding it
difficult to locate and arrange for service at satisfactory landfill
sites. Fortunately, the additional solid waste generated by the
proposed treatment technology is very small relative to the normal
solid waste generated by the production facility and is considered
insignificant.
Land requirements for the treatment system are small; nevertheless,
certain facilities located in highly congested urban areas will find
it difficult to allocate space for even this minimal treatment
facility. These plants may be forced to turn to other treatment
methods or to approach zero discharge to navigable waters by
advanced housekeeping and control techniques.
Wet Digestion Reclaimed Rubber Subcateqorv
The rubber reclaiming industry is presently undergoing a decline in
both the number of operating plants and the quantity of reclaimed
rubber produced. The wet digester reclaiming process has borne the
brunt of this decline, and it must be assumed that the financial
resources of wet digester reclaim plants and their ability to
shoulder further operating costs such as waste water treatment costs
are limited. In view of this and since all of the existing wet
digester plants discharge their waste waters directly or are
connected to the local publicly owned sewage treatment works, it is
not possible to propose an end-of-pipe treatment technology which
has been proven to be operable and successful while in service, as
well as economically practicable.
With this in mind, attention as been duly given to in-plant
modifications to the wet digestion process which have been
implemented and proven successful in at least one plant. Such
modifications, while reducing waste water pollution and end-of-pipe
treatment needs, also have the potential to reduce raw material
wastage and consumption. However, based on the preliminary findings
of this guideline study, it cannot be said that the yearly
reductions in process operating costs afforded by the in-plant
modifications will o'ffset the annual operating and maintenance costs
directly attributable to the modifications. Such benefits can be
151
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assessed only by personnel intimately familiar with the wet
digestion process and the economics of is operation.
The principal waste water streams in a wet digestion relaim plant
are the dewatering liquor and the vapor condensates from the
blowdown tank and dryer. The type of . treatment proposed for
Subcategories E, F, G, and I, namely, the isolation of wastes loaded
with oil and suspended solids followed by oil and solids removal, is
not appropriate as BPCTCA control and treatment for Subcategory H
since the costs benefits are not favorable. This argument is
particularly valid when the minimal benefits to be achieved by this
type of alterations are compared to the greater pollution reduction
that can be attained by the application of the recommended recycle.
It should be remembered at this point that the wet digester process
is only marginally profitable and, at present, cannot bear large
waste water treatment costs. In addition, most wet digester plants
discharge to municipal systems and are subject to pretreatment
guidelines.
A fundamental change that can be made to the wet digestion
reclaiming process is the conversion from chemical defibering to
mechanical defibering. With chemical defibering, defibering
chemicals are added to the digestion mix. The fibers are
solubilized in the digestion step and leave the process system in
the dewatering liquor which is discharged. The defibering
chemicals, which can be of a toxic nature, are an additional
constituent of the dewatering liquor. In the mechanical defibering
variation, the scrap rubber is finely ground prior to digestion.
The freed fiber is then elutriated from the rubber scrap on air
separation tables.
With mechanical defibering the dewatering liquor is free of high
levels of solubilized fiber as well as the chemical defibering
agents themselves. Costs incurred by a conversion from chemical to
mechanical defibering have not been fully developed for this
document since the required technology for the conversion is
specific to the reclaiming industry and outside the scope and
technology boundaries of the guideline study. However, the costs
associated with a recent conversion from chemical defibering to
mechanical fiber separation illustrate the order of magnitude of the
capital costs. The conversion of a 130,000-pound per day wet
digestion plant from chemical defibering to mechanical fiber
separation cost $611,000 in 1969-70. This modification included
$31,000 for fiber lint air emission controls.
A major reduction in the volume and loadings of the process waste
waters can be achieved by adding a recovery and recycle system to
the wet digestion process. In essence the dewatered liquor can be
recycled back to the digestion step with a blowdown of accumulating
contaminants and a make-up of the digestion liquor. At the same
time the vapor condensates from the blowdown tank and dryer are
decanted to recover the insoluble oils and organics. The oils and
organics are recycled to the digestion liquor makeup operation, and
the water underflow from the decantation is returned with the
152
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dewatered liquor. As a result of this recycle system, the volume
and loadings of the dewatering liquor are considerably reduced. It
should also be noted that mechanical, opposed to chemical,
defibering is required in order for this system to be feasible. The
dewatering digester liquor must be fiber-free in order that part of
it can be recycled.
The quality of the effluent achieved by this recycle system is
presented in Table 24 together with the associated control and
treatment costs. The costs do not include the costs incurred by the
necessary conversion from chemical to mechanical defibering.
A detailed description of the suggested recycle and reclaim
facilities is presented in the wet digestion subsection of Section
X. A schematic flow diagram of a typical system is given in Figure
9 and is a basis for capital and operating cost estimates.
Treatment Cost Data
A profile of the wet digester reclaiming industry sector was made to
ascertain the typical plant size. The typical, or average, plant is
rated at 54,000 kilograms (110,000 pounds) per day. The process
waste water flow generated by the dewatering liquor and condenser
discharges was estimated to be approximately 392,000 liters per day
(104,000 gpd) from plant visit data.
Designs for the proposed BATEA control technology were costed in
order to fully evaluate the economic impact of the recommended
effluent limitations. The design considerations (i.e., the raw
waste loads) were selected to represent the highest expected raw
waste loads. This results in the generation of cost data which
should be conservative when applied to most of the plants in the wet
digestion reclaimed rubber subcategory. Relatively conservative
cost figures are preferred for this type of general economic
analysis.
The capital costs were generated on a unit process basis, with the
following "percent add on" figures applied to the total unit process
costs in order to develop the total installed capital cost
requirements:
Item
Electrical
Piping
Instrumentation
Site Work
Engineering Design and
Supervision Construction
Construction Contingency
Percent of Unit
Process Capital Cost
15
20
15
10
10
15
153
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Investment
Control Technology
$126,000
1
Annual Costs
Capital Costs
Depreciation
Operating and Maintenance Costs
(excluding energy and power costs)
Energy and Power Costs
Total Annual Costs
12,600
25,200
19,300
$ 61,800
Pa ramete rs
kg/kkg(lb/1000 Ib)
of product
COD
SS
Oil
Raw Waste
Loads
9.75
256.10
27.29
Effluent Quality
6.11
2.31
0.58
The control technology includes recycle of dewatering liquor and decan-
tat ion of vapor condensates followed by recycle of the oils and water
underflow.
Table 24 - Estimated Waste Water Control Costs for a Wet Digestion
Reclaim Plant (Subcategory H)
154
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The total annual costs for the waste water control or recycle system
can be developed in terms of incremental costs per unit weight of
rubber reclaimed. The cost data presented for a typical wet
digestion process of 54,000 kilograms per day indicate that the
BATEA technology will cost $0.004 per kilogram ($0.0019/lb) of
production. These costs are based on six working days each week at
50 operating weeks per year.
Since land costs vary appreciably between plant locations, it was
decided to exclude land cost from the total capital cost estimates.
Land costs must be added on an individual case basis.
Annual costs were computed using the following cost basis:
Item Cost Allocation
Capitalization 10 percent of investment
i
Depreciation 5-year straight line with zero
salvage value.
Operations and Maintenance Includes labor and supervision,
chemicals, sludge hauling and dis-
posals, insurance and taxes
(computed at 1.6 percent of the
total capital costs), and main-
tenance (3.2 percent of the total
capital cost)
Power Based on $0.015/kw-hr
The short-term capitalization and depreciation write-off period is
what is currently acceptable under current Internal Revenue Service
Regulations pertaining to industrial pollution control equipment.
All costs were computed in terms of August 1973 dollars which
correspond to an Engineering News Record Index (ENR) value of 1920.
Energy Requirements
The proposed waste water control and recycle system requires
electrical energy for the operation of pumps and mixers. The power
needs of the equipment are modest and approximate 48 horsepower.
Nonwater Quality Aspects
There are few nonwater quality aspects to be considered with this
control technology. In order to employ the proposed technology,
mechanical defibering is used. As a result the separated fibers are
removed from the system as a solid waste, and dry air pollution
control devices are required to remove fine fibrous emissions from
the air. The costs associated with disposing of the fibrous solid
waste are deemed minor in comparison with the treatment costs
155
-------
required to remove the fibrous material from the dewatering liquor
in cases where chemical defibering is practiced.
Periodically it will be necessary to remove accumulated solids from
the dewatering liquor storage tank. It is estimated that these
solids will amount to less than 15 cubic meters (20 cubic yards)
annually.
Pan (Heater), Mechanical, and Dry Digestion Rubber Reclaiming
The extent of the waste water problems and treatment types for all
dry reclaiming processes can best be represented by those of the
pan, or heater, reclaim process.
The waste water types are essentially similar to those produced by
Subcategories E, Fr and G plants with the additional contribution of
the oven vapor condensates. The majority of the process wastes are
created by spills and leaks in the cracking, grinding, and milling
buildings as well as around material and fuel oil storage areas.
The contaminants are principally oil and suspended solids. The
vapor condensates contain organics vaporized from the rubber mix in
the depolymerization oven.
The control and treatment approach proposed for this subcategory is
isolation of the process waste waters preventing dilution of the
contaminants and a decrease in their treatability. As for
Subcategories E, F, and G wastes, the key to this type of control
and treatment is the reduction and collection of the contaminated
process waste waters prior to treatment for oil and suspended solids
removal in an API-type separator. The separable organics in the
depolymerization oven condensates can also be separated in the
separator.
The anticipated effluent quality achieved by the proposed treatment
is presented in Table 25 together with the associated cost data. In
addition, a detailed description of the recommended technology is
given in Section IX. Figure 10 is a schematic flow diagram of the
required control and treatment facilities and is the basis for the
indicated cost estimates.
Treatment Cost Data
The dry reclaiming industry was reviewed to determine an average or
typical size for a pan process reclaiming plant. The selected size
is 59,000 kilograms (130,000 pounds) per day of reclaimed rubber,
and the corresponding process waste water flow rate is 283,000
liters (75,000 gallons) per day. The design flow rate was supported
by the plant data obtained at the reclaiming plant visited.
The design considerations (i.e., the influent raw waste loads) were
selected to represent the highest expected raw waste load within the
industry sector. This results in the generation of cost data which
should be conservative when applied to most of the plants in this
156
-------
o
Investment
Annual Costs
Capital Costs
Depreciation
Operating and Maintenance Costs
(excluding energy and power costs)
.Energy and Power Costs
Total Annual Costs2
Treatment or Control Technology'
A B
$265,000
26,500
53,000
25,500
1,200
$106,200
$277,000
27,700
55,^00
28,200
1,200
$119,700
en
Parameters
kg/kkg (lb/1000 Ib) product
Suspended Sol ids
Oil and Grease
Raw Waste
Loads
0.192
0.493
Effluent Quality
0.192
0.240
J3
0.192
0.144
iTechnology A is isolation of process waste waters followed by API gravity separation.
Technology B is Technology A followed by an absorbent filter.
2August 1973 dollars.
Table 25: Estimated Waste Water Treatment Costs at Different Degrees of Treatment for a Pan. Dry
Digester, or Mechanical Reclaim plant (Subcategory I)
-------
subcategory. Relatively conservative cost figures are preferred for
this type of general economic analysis.
The capital costs were generated on a unit process basis, with the
following "percent add on" figures applied to the total unit process
costs in order to develop the total installed capital cost
requirements:
Percent of Unit
Item Process Capital Cost
Electrical 12
Piping 15
Instrumentation 8
Site Work 5
Engineering Design and
Construction Supervision Fees 10
Construction Contingency 15
Since land costs vary appreciably between plant locations, it was
decided to exclude land cost from the total capital cost estimates.
Land cost must be added on an individual case basis.
Annual costs were computed using the following cost basis.
Item Cost Allocation
Capitalization 10 percent of investment.
Depreciation 5-year straight line with zero
salvage value.
Operations and Maintenance Includes labor and supervision,
chemicals, sludge hauling and dis-
posals, insurance and taxes
(computed at 1.6 percent of the
total capital costs), and main-
tenance (3.2 percent of the total
capital cost)
Power Based on $0.015 kw-hr for electri-
cal power.
The short-term capitalization and depreciation write-off period is
what is currently acceptable under current Internal Revenue Service
Regulations pertaining to pollution control equipment.
All costs were computed in terms of August 1973 dollars, which
correspond to an Engineering News Record Index (ENR) value of 1920.
Energy Requirements
158
-------
The consumption of power and energy by the proposed control and
treatment system is minor and is limited to electrically operated
pumps to pump process waste waters from the point sources within the
plant through the treatment system. The total power needs of the
facilities are approximately 12 horsepower.
Nonwater Quality Aspects
The primary nonwater quality effect created by the use of the
proposed facilities is the need for disposal of oil and suspended
solids collected in the separator. The total volume of wastes
requiring disposal is estimated to be 172 cubic meters (230 cubic
yards) per year which includes spent absorbent filters.
Subcategorj.es J and K — Latex-Based Products
The latex-based products can be effectively separated into two
subcategories. The first subcategory (Subcategory J) includes latex
dipping, latex thread, and products manufactured in porous molds.
The Subcategory K subcategory consists of latex foam manufacture.
Since the required treatment is different for the two subcategories,
separate discussions of the cost data are presented.
Subcategorv J
Only one level of control and treatment has been considered in the
evaluation of treatment effectiveness versus cost data. This
recommended treatment includes chemical coagulation and primary
clarification of latex-laden wastes followed by biological
oxidation.
The biological treatment cost data have been based on an aerated
lagoon and settling pond system. The reason for this selection is
that the BOD concentration in the process waste waters is typically
too low to support an activated sludge type biomass. Since the
process wastes can be separated from the utility waste waters, the
proposed treatment system is limited to the treatment of the process
wastes.
Treatment Cost Data
A profile was made of the latex dipping industry to determine the
typical size of a production facility. The average, or typical,
plant has a daily consumption of 2,100 kilograms (U,700 pounds) of
latex solids. The associated process waste water flow, derived from
plant visit data, is 153,000 liters (40,000 gallons) per day.
The model treatment plant, consisting of chemical coagulation,
clarification, and bio-oxidation is illustrated in Figure 11. This
plant, equivalent to BPCTCA, is described more fully in Section IX.
The treatment designs upon which the cost data are based correspond
to the highest expected raw waste load within the industry.
159
-------
ACID/ALKALI
CLAY/POLYELECTROLYTE
RAN PROCESS
WASTENATER
PROCESS
WASTEWATER
COLLECTION
SUMP
NUTRIENTS
FLOCCULATOR
CLARIFIER
PRIMARY EFFLUENT
SETTLED SOLIDS
REMOVED PERIODICALLY
BY TANK TRUCK
en
o
FINAL
^
DISCHARGE
EFFLUENT
MONITORING
STATION
SECONDARY
EFFLUENT
SETTLING
POND
*
AERATED LAGOON
* *
SECONDARY SOLIDS
REMOVED PERIODICALLY
BY TANK TRUCK
FIGURE 11:
HYPOTHETICAL END-OF-PIPE SECONDARY WASTE WATER TREATMENT
FACILITY FOR SUBCATEGORY J PLANTS
-------
Relatively conservative cost figures are preferred for this type of
general economic analysis.
The capital costs were generated on a unit process basis, with the
following "percent add on" figures applied to the total unit process
costs in order to develop the total installed capital cost
requirements:
Percent of Unit
Item Process Capital Cost
Electrical 20
Piping 15
Instrumentation 8
Site Work 5
Engineering Design and
Supervision Construction 10
Construction Contingency 15
The treatment costs incurred by the associated technology can be
represented in terms of incremental costs per unit of production.
Treatment cost data for a typical latex dipping plant consuming
2,100 kilograms (4,700 pounds) of latex solids per day indicate that
the BPCTCA and BATEA treatment will cost $0.042 per kilogram
($0.019/lb) of latex solids usage.
Since land costs vary appreciably between plant locations, it was
decided to exclude land cost from the total capital cost estimates.
Land costs must be added on an individual case basis.
Annual costs were computed using the following cost basis:
Item Cost^Allocation
Capitalization 10 percent of investment
Depreciation 5-year straight line with zero
salvage value.
Operations and Maintenance Includes labor and supervision,
chemicals, sludge hauling and dis-
posals, insurance and taxes
(computed at 1.6 percent of the
total capital costs), and main-
tenance (3.2 percent of the total
capital cost)
Power Based on $0.015 kw-hr for electri-
cal power.
The short-term capitalization and depreciation write-off period is
what is currently acceptable under current Internal Revenue Service
Regulations pertaining to industrial pollution control equipment.
161
-------
All costs were computed in terms of August 1973 dollars, which
correspond to an Engineering News Record Index (ENR) value of 1920.
The total capital and annual costs for the model treatment
technologies are presented for a typical latex-dipping plant in
Table 26, together with raw waste load and treated effluent quality.
Energy Reguirements
The primary clarification and biological oxidation treatment
technologies require electrical energy only for operation of
equipment such as pumps and aerators. The power needs are low and
will approximate 16 horsepower.
Nonwater Quality Aspects
The principal nonwater aspect of the proposed technology is the
disposal of the primary coagulated latex solids and the infrequent
removal of the biological solids from the settling pond. Both of
these wastes will be removed most economically by contract disposal
using a vacuum truck. The annual volumes of these wastes will
approximate:
Primary Solids: 910 cubic meters (1,250 cu yds)
Biological Solids: 290 cubic meters (390 cu yds)
Subcateqorv K
Two levels of control and treatment have been studied in the
evaluation of treatment cost and effectiveness. The first level of
the proposed technology is chemical coagulation and clarification of
latex-based wastes, as well as chemical precipitation and
clarification of zinc-laden foam rinse waters. The second
technology level proposed involves biological oxidation of the
combined primary effluents. The biological treatment cost data are
based on an activated sludge treatment system. This type of system
was selected because the BOD loading of the combined effluent is
high (approximately 400 mg/1) and would be able to support an active
mixed liquor. The treatment cost is also based on a combined
process effluent which includes the slightly contaminated barometric
condenser flows. This waste stream has been included in the cost
evaluation because the residual zinc concentration after chemical
precipitation requires dilution by the condenser discharge in order
to avoid biological inhibition.
Treatment Cost Data
The only significant latex foam plant in the United States was used
as a basis for the industry. The plant has a daily consumption of
68,000 kilograms (150,000 pounds) of latex solids; the average
process waste water flow is 1,608,000 liters (425,000 gallons) per
day.
162
-------
Control and Treatment Technology^
Investment $236,700
Annual Costs
Capital Costs 23,700
Depreciation 47,300
Operating and Maintenance Costs 25,100
(excluding energy and power costs)
Energy and Power Costs 1,600
Total Annual Costs $ 96,700
Parameters Raw Waste Effluent Qjjal ity
kg/kkg(lb/100 Ib) Loads
of raw materials
BOD 18.2 2.20
Suspended Solids 10.90 2.90
Oil 0.90 0.73
Chromium 0.0533 0.0036
1
The control and treatment technology includes chemical coagulation,
clarification, biological oxidation, and secondary clarification.
Table 26 - Estimated Waste Water Control Costs for a Latex Dipped Plant
(Subcategory J)
163
-------
The model treatment plant, illustrating both BPCTCA and BATEA,
consists of chemical coagulation of latex solids, chemical
precipitation of zincr and biological oxidations. (See Figure 12.)
This type of plant is described more fully in Sections IX and X.
The influent raw waste loads, upon which the treatment designs are
based, represent the raw effluent conditions at the sole U.S. latex
foam plant. This results in the generation of cost data which are
the most appropriate for the industry as it is known to exist.
The total capital and annual costs for the model treatment
techniques for the sole latex foam plant are presented in Table 27,
together with the raw waste loads and treated effluent qualities.
The treatment costs for a latex foam production facility can be
expressed as an incremental cost per unit of production. The cost
data for a plant consuming 68,000 kilograms (150,000 pounds) of
latex solids daily indicate that the BPCTCA treatment will cost
$0.003 per kilogram ($0.003/lb) of latex consumption and that the
additional costs of the BATEA treatment will approximate $0.003 per
kilogram ($0.003/lb) of latex consumption.
The capital costs were generated on a unit process basis, with the
following "percent add on" figures applied to the total unit process
costs in order to develop the total installed capital cost
requirements:
Percent of Unit
Item Process Capital Cost
Electrical 12
Piping 15
Instrumentation 8
Site Work 3
Engineering Design and
Construction Supervision
Fees 10
Construction
Contingency 15
Since land costs vary appreciably between plant locations, it was
decided to exclude land cost from the total capital cost estimates.
Land costs must be added on an individual case basis.
164
-------
Annual Costs were computed using the following cost basis:
Item Cost Allocation
Capitalization 10 percent of investment
Depreciation 5-year straight line with zero
salvage value
Operations & Maintenance Includes labor and supervision, chemicals,
sludge hauling and disposal, insurance
and taxes (computed at 1.6 percent of
the total capital cost), and maintenance
(3.2 percent of the total capital cost)
Power Based on $0.015 kw-hr for electrical power.
The short-term capitalization and depreciation write-off period is what is
currently acceptable under current Internal Revenue Service Regulations
pertaining to pollution control equipment.
All costs were computed in terms of August 1973 dollars, which correspond to an
Engineering News Record Index (ENR) value of 1920.
Energy Requirements
Energy usage is related to the need for electric pumps to move waste waters
through the treatment system and for several agitator and aerator systems. The
extra power required for treatment and control systems is minor and is estimated
to be 134 HP.
Nonwater Quality Aspects
The main nonwater effect of the proposed technologies is the disposal of the
primary chemical treatment solids wastes and the synthesized biological solids.
The most feasible ultimate disposal of these filtered and stabilized solid
wastes is landfill. The annual volumes of these waters is calculated to be:
Primary Solids: 2,000 cubic meters (1,500 cu yds)
Biological Solids: 800 cubic meters (600 cu yds)
Detailed Cost Information for All Subcategories
Tables 28 through 43 contain detailed cost information used to develop the total
capital and annual costs for best practicable control technology currently
available (BPCTCA) and best available technology economically achievable (BATEA)
treatment systems presented and discussed in Sections VIII, IX and X of this
report.
165
-------
ACID ALKALI.ALUN, POLfELECTROLYTE |
T»IN COAGULATION AND
SETUINGITANKS
I
SETTLED SOLIDS
TO CONTRACT
DISPOSAL
CLARIFIED LATEX IASTE
POLYELECTHOLTTE
CLIRIFIER
EOUALUEO KRINARt ..
EFFLUENT
THICKENER OVEDFLOI
ZINC LINE SLUOCE
FIGURE 12:
HYPOTHETICAL END-OF-PIPE SECONDARY WASTE WATER TREATMENT
FACILITY FOR SUBCATEGORY K
-------
Investment'
Treatment of Control Technology
A B.
$348,000 649,000
Annual Costs
Capital Costs
Depreciation
Operating and Maintenance Costs
(excluding energy and power costs)
Energy and Power Costs
o
Total Annual Costs
34,800
69,600
55,300
3.500
$163,200
65,000
129,800
98,400
13.100
$306,300
Parameters
kg/kkg(lb/1000 Ib)
of raw materials
BOD
Suspended Solids
Zinc
Raw Waste
Loads
20.44
8.71
Effluent Quality
A- B
9.43
1.60
0.083
1.41
0.94
0.083
1
Technology A is chemical coagulation and clarification of latex waste waters and
chemical precipitate and clarification of zinc-laden waste waters. Technology B
is Technology A followed by biological oxidation treatment.
August 1973.
Table.27 - Estimated Waste Water Treatment Costs at Different Degrees of Treatment
for a Latex Foam Plant (Subcateeorv K)
167
-------
Daily Raw Material Consumption = 900 kg (2,000 Ibs.)
Estimated Process Effluent Flow = 14,700 L/day (3,900 gpd)
Description of Treatment Facility Estimated Capital Costs
Sewer Segregation $ 7,200
Process Sumps and Pumps 20,900
Process Waste Water Force Main 1,400
Filter 2,300
Process Effluent Sewer and Monitoring Station 10,100
Sub-Total $41,900
Site Work 4,200
Electrical 6,300
Piping 8,400
Instrumentation 6,300
Sub-Total $67,100
Engineering Fees 6,700
Contingency 10.200
Total Capital Cost (Investment)2 $84.000
Includes sealing existing floor drains, installation of new process
drains, and oily waste water retainment curbing.
2
Land costs are not included.
Table 28 - BPCTCA and BATEA Treatment Capital Costs for a Typical Small
Sized Molded. Extruded or Fabricated Rubber Plant
(Subcategory E)
168
-------
Daily Raw Material Consumption = 7,700 kg (17,000 Ibs.)
Estimated Process Effluent Flow = 75,800 L/day (20,000 gpd)
Description of Treatment Facility
In-plant Sewer Segregation
In-plant Process Sumps and Pumps
Process Waste Water Force Main
Outdoor Waste Water Segregation System^
Outdoor Process Sumps
Oil Separator
Filter
Process Effluent Sewer and Monitoring
Station
Sub-Total
Site Work
Electrical
Piping
Instrumentation
Sub-Total
Engineering Fees
Contingency
Total Capital Cost (Investment)
Estimated Capital Costs
$ 13,900
31,300
10,300
6,300
10,000
11,100
4,600
10,100
$ 97,600
4,900
11,700
14,600
7.800
$136,600
13,700
20.700
$171,000
1
Includes sealing existing floor drains, installation of new process
drains, and oily waste water retainment curbing.
>
"Includes roofing, curbing, and process waste water drains.
Land costs are not included.
Table 29 - BPCTCA and BATEA Treatment Capital Costs for a Typical Medium-
Sized Molded, Extruded or Fabricated Rubber Plant '
(Subcateeorv F)
169
-------
Daily Raw Material Consumption = 15,400 kg (34,000 Ibs.)
Estimated Process Effluent Flow = 95,900 L/day (25,300 gpd)
Description of Treatment Facility
In-plant Sewer Segregation
In-plant Process Sumps and Pumps
Process Waste Water Force Main ~
Outdoor Waste Water Segregation System
Outdoor Process Sumps
Oil Separator
Filter
Process Effluent Sewer and Monitoring Station
Sub-Total
Site Work
Electrical
Piping
Instrumentation
Sub-Total
Engineering Fees
Contingency
7
Total Capital Cost (Investment)
Estimated Capital Costs
$ 22,400
41,700
17,700
11,000
10,000
7,800
6,900
10.100
$127,600
6,400
15,300
19,000
10.100
$178,400
17,800
26.800
$223.000
1
Includes sealing existing floor drains, installation of new process drains
and oily waste water retainment curbing.
>
"Includes roofing, curbing, and process waste water drains and sewers.
Land costs are not included.
Table 3D - BPCTCA and BATEA Treatment Capital Costs for a Typical Large-
Sized Molded, Extruded or Fabricated Rubber Plant
CSubcategory G)
170
-------
Daily Production Capacity = 54,000 kg (110,000 Ibs.)
Estimated Process Effluent Flow = 392,000 L/day (104,000 gpd)
Description of Control/Treatment Unit Estimated Capital Cost
Primary Oil Decant Tank $ 8,800
Waste Oil Pumps 2,800
Waste Oil Storage Tank 5,900
Waste Oil Storage Pump 2,800
Waste Water Storage Tank 12,700
Waste Water Tank Mixer 14,100
Waste Water Tank Discharge Pump 4,100
Waste Water Return Pump 1,400
Monitoring Station 10,400
Sub-Total $ 63,000
Site Work 6,300
Electrical 9,500
Piping 12,600
Instrumentation 9.500
Sub-Total $100,900
Engineering Fees 10,100
Contingency .15.000
Total Capital Cost (Investment) $126.000
Land costs are not included.
Table 31 - BATEA Treatment Capital Costs for a Typical Wet Digestion
Rubber Reclaiming Plant
(Subcategory H)
171
-------
Daily Raw Material Consumption = 59,000 kg (130,000 Ibs.)
Estimated Process Effluent Flow = 283,^00 L/day (7^,900 gpd)
Description of Treatment Facility Estimated Capital Costs
In-plant Sewer Segregation $ Vt,600
In-plant Process Sumps and Pumps 28,400
Process Waste Water Force Main 2 22,500
Outdoor Waste Water Segregation System 19,100
Outdoor Process Sumps 10,000
Oil Separator 16,500
Filter 6,900
Process Effluent Sewer and Monitoring Station 10,100
Sub-Total $158,100
Site Work 7,900
Electrical 19,000
Piping 23,700
Instrumentation 12.600
Sub-Total $221,300
Engineering Fees 22,200
Contingency 33,500
•2
Total Capital Cost (investment) $277.000
Includes sealing existing floor drains, installation of new process
drains, and oily waste water retainment curbing.
2
Includes roofing, curbing, and process waste water drains and sewers.
Land costs are not included.
Table 32 - BPCTCA a.nd BATEA Treatment Capital Costs for a Typical Pan.
Dry Digester or Mechanical Reclaim Plant
(Subcategorv I)
172
-------
Daily Latex Solids Consumption = 2,100 kg (4,700 Ibs.)
Estimated Process Effluent Flow = 153,000 L/day (40,000 gpd)
Description of Treatment Unit Estimated Capital Cost
Collection Sump and Pumps $ 7,300
pH Adjustment and Coagulant Feed 14,800
Mix and Flocculation Tanks 4,700
Clarifier 18,400
Aerated Lagoon 27,300
Aerators 16,600
Settling Pond 36,000
Monitoring Station 10.400
Sub-Total $135,500
Site Work 6,800
Electrical 26,300
Piping 20,000
Instrumentation 10.800
Sub-Total $189,400
Engineering Fees 18,900
Contingency 28.400
Total Capital Cost (Investment) $236.700
Land costs not included.
Table 33 - BPCTCA and BATEA Treatment Capital Costs for a Typical Latex
Dipping Production Facility
(Subcategbry J)
173
-------
Daily Latex Solids Consumption = 68,000 kg (150,000 Ibs)
Estimated Process Effluent Flow = 1,608,000 L/day (425,000 gpd)
Description of Treatment Unit
Latex Collection Sump and Pumps
pH Adjustment and Coagulant Feed
Latex Coagulation Tanks
Zinc Collection Sump and Pumps
Lime Slurry Tank
Zinc Mixer and Flocculator-Clarifier
Thickener
Vacuum Filter and Solids Handling Equipment
Monitoring Station
Sub-Total
Site Work
Electrical
Piping
Instrumentation
Sub-Total
Engineering Fees
Contingency
Estimated Capital Cost
$ 5,800
1,200
37,500
7,600
1,600
40,000
41,200
48,500
15.000
$198,400
9,900
23,900
29,900
15.900
Total Capital Costs (Investment)
1
$278,000
28,000
42.000
$348.000
1
Land costs are not included.
Table 34 - Technology A Capital Costs for a Typical Latex Foam Plant
(Subcategory K)
174
-------
Daily Latex Solids Consumption = 68,000 kg (150,000 Ibs)
Estimated Process Effluent Flow = 1,608,000 L/day (425,000 gpd)
Description of Treatment Unit
Equalization Basins
Aeration Basins
Clarifier
Thickener
Aerobic Digester
Sub-Total
Site Work
Electrical
Piping
Instrumentation
Sub-Total
Engineering Fees
Contingency
Total Capital Costs (Investment)
Estimated Capital Costs
$ 85,700
103,500
100,400
22,400
58,800
$370,800
18,500
44,500
55,600
29.700
1
$519,100
51,900
78,000
$649.000
1
Land costs are not included.
Table 35 - Technology B Capital Costs for a Typical Latex Foam Plant
(Subcategory K)
175
-------
Daily Raw Material Consumption = 900 kg (2,000 Ibs.)
Estimated Process Effluent Flow = 14,700 L/day (3,900 gpd)
Description of Cost Item Annual Cost
Absorbent $ 800
Sludge Disposal 700
Labor 6,300
Power and Energy 600
Maintenance 3>00
Insurance and Taxes 1,700
Total Annual Operating and Maintenance Cost $13.500
Table 3.6 - BPCTCA and BATEA Operating and Maintenance Costs for a Typical
Small-Sized Molded. Extruded or Fabricated Rubber Plant
(Stibcategory E)
176
-------
Daily Raw Material Consumption = 7,700 kg (17,000 Ibs.)
Estimated Process Effluent Flow = 75,800 L/day (20,000 gpd)
Description of Cost Item Annual Cost
Absorbent $ 3,900
Sludge Disposal 2,300
Labor 6,300
Power and Energy 800
Maintenance 7,100
Insurance and Taxes 3,600
Total Annual Operating and Maintenance Costs $2^,000
Table 37 - BPCTCA and BATEA Operating and Maintenance Costs for a Typical
Medium-Sized Molded. Extruded or Fabricated Rubber Plant
(Subcategory F)
177
-------
Daily Raw Material Consumption = 15,^00 kg (3^,000 Ibs.)
Estimated Process Effluent Flow = 95,900 L/day (25,300 gpd)
Description of Cost Item Annual Cost
Absorbent $ 4,900
Sludge Disposal 3,300
Labor 6,300
Power and Energy 1,200
Maintenance 8,800
Insurance and Taxes 4,500
Total Annual Operating and Maintenance Cost $29.000
Table 38 - BPCTCA and BATEA Operating and Maintenance Costs for a Typical
Large-Sized Molded, Extruded or Fabricated Rubber Plant
(Subcategbry G)
178
-------
Daily Production Capacity = 5^,000 kg (110,000 Ibs.)
Estimated Process Effluent Flow = 392,000 L/day (10^,000 gpd)
Description of Cost Item Annual Cost
Sludge Disposal $ ^,500
Labor 8,800
Power and Energy ^,700
Maintenance ^,000
Insurance and Taxes 2,OOP
Total Annual Operating and Maintenance Cost $2^.000
Table 39 - BATEA Operating and Maintenance Costs for a Typical Wet
Digestion Rubber Reclaiming Plant
(Subcategory H)
179
-------
Daily Raw Material Consumption = 59,000 kg (130,000 Ibs.)
Estimated Process Effluent Flow = 283,^00 L/day (7^,900 gpd)
Description of Cost Item Annual Cost
Absorbent $ ^,700
•
Sludge Disposal 3,900
Labor 6,300
Power and Energy 1,200
•
Maintenance 8,900
Insurance and Taxes 4.,400
Total Annual Operating and Maintenance Costs $29,400
Table 40 - BPCTCA and BATEA Operating and Maintenance Costs for a
Typical Pan, Dry Digester or Mechanical Reclaim Plant^
(Subcategory I)
180
-------
Daily Latex Solids Consumption = 2,100 kg (4,700 Ibs.)
Estimated Process Effluent Flow = 153,000 L/day (^0,000 gpd)
Description of Cost I tern Annual Cost
Chemicals $ 1,900
Sludge Disposal 3,000
Labor 8,800
Power and Energy 1,600
Maintenance - 7,600
Insurance and Taxes 3.800
Total Annual Operating and Maintenance Cost $26,700
Table kl - BPCTCA and BATEA Operating and Maintenance Costs for a
Typical Latex Dipping Production Facility
(Subcategory J)
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Daily Latex Solids Consumption = 68,000 kg (150,000 Ibs)
Estimated Process Effluent Flow = 1,608,000 L/day (425,000 gpd)
Description of Cost Item Annual Cost
Chemicals $2^,100
Sludge Disposal 3,300
Labor 11,200
Power and Energy 3,500
Ma i ntenance 11,100
Insurance and Taxes 5,600
Total Annual Operating and Maintenance Cost $58,800
Table k2 Technology A Operating and Maintenance Cost for a Typical
Latex Foam Production Facility (Subcategory K)
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Daily Latex Solids Consumption = 68,000 kg (150,000 Ibs)
Estimated Process Effluent Flow = 1,608,000 L/day (^25,000 gpd)
Description of Cost Item Annual Cost
Sludge Disposal $ 800
Labor 11,100
Power and Energy 9,600
Maintenance 20,800
Insurance and Taxes 10,400
Total Annual Operating and Maintenance Costs $52,700
Table 43 - Technology B Operating and Maintenance Cost for a Typical
Latex Foam Production Facility (SubcateRory K)
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SECTION IX
BEST PRACTICABLE CONTROL TECHNOLOGY
CURRENTLY AVAILABLE - EFFLUENT LIMITATIONS
General Molded. Extruded and Fabricated Rubber Subcategories
The best control and treatment technologies currently in use at
molded, extruded, or fabricated production facilities emphasize in-
plant housekeeping and control measures. End-of-pipe treatment of
combined process and nonprocess waste waters was found at only one
plant.
In-plant techniques varied widely from plant to plant. In general,
they included the isolation of potential waste water sources with
retainment curbing, the elimination of drains in contaminated areas,
and the use of sumps to collect isolated process waste water
streams. The proposed treatment technology for a typical plant is a
combination of the best features of the various plants examined. It
is similar for all three size subcategories.
Basically, the technology employed consists of:
1. Eliminating anti-tack or latex solution discharge.
2. Isolation, control, and treatment of all oily waste
streams.
A flow diagram of the proposed technology is shown in Figure 10.
Previous experience with the tire and inner tube industry indicates
that zero discharge of anti-tack solutions is widely practiced.
Since this waste water problem is common to Subcategories E, F, and
G facilities, it is considered a feasible practice for all
Subcategories E, F, and G facilities to attain zero discharge of
anti-tack solutions by adhering to the following procedures:
1. Recycle of soapstone solution.
2. Installation of curbing around the soapstone dipping
area.
3. Sealing of drains in the dipping area.
4. Reuse of the recirculating system wash water as make-up
for fresh soapstone solution.
The reuse of recirculating system wash water is the key to zero
discharge of this waste. In emptying the system for cleaning, the
soapstone solution should be stored in tanks. The wash water used
should also be collected and stored. Once the system is cleaned,
stored soapstone can then be returned to the system for use in the
new production batch- The collection and stored wash water can then
be reused as make-up water for the soapstone bath' during the normal
production run.
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Elimination of latex discharges from fabricated products facilities
is achieved by:
1. The use of curbing around latex storage and transfer areas.
2. The sealing of all drains in latex use areas.
3. The containment of all latex-contaminated waste streams.
It is normal for latex-using facilities to buy latex in bulk and
then store it in drums as needed, for use within the plant. The
drums normally need to be stripped clean of latex after every use.
When water is used, a waste water is generated. This stream has to
be containerized to eliminate discharge of latex. However, it has
been demonstrated that wash waters emanating from this area are
eliminated when plastic drum liners are used. The liners are
discarded after each drum use.
Control and treatment of oily waste streams involves segregation,
collection, and treatment of these wastes. The wastes to be
segregated include runoff from oil storage and unloading areas and
leakage and spills in the process areas, as shown in Figure 10.
Press and mill basins, when present, are included in the process
area.
To minimize the raw waste load, all process water should be isolated
from the nonprocess waste water used in the plant. This can be
achieved by diverting drippings from heavy machinery in the molding
and curing areas to sumps. These waste flows are intermittent by
nature and, therefore, sizeable flow rates will hardly ever be
obtained without first collecting all wastes in centralized
locations. Waste waters collected in these sumps will be
periodically pumped to an API-type gravity separator, where the
separable oil and solids fraction is removed. The waste water can
be either pumped to the treatment system or collected in batches and
hauled to a treatment or disposal area. The latter method should be
used only when it is shown to be unfeasible to rip out and • install
new sewer lines.
In the medium and large plants, separated oil is removed by a belt
skimmer. A decant drum is provided to allow water removed with the
oil to settle out. Concentrated oil-water mixtures are then removed
from the decant tank, drummed, sealed, and disposed of. Water
removed from the tank is pumped back to the separator. Settled
solids collected in the separator are periodically removed and
disposed of. Additional treatment for oil and suspended solids
removal is obtained by passing the separator effluent through an
absorbent filter. In the small plants, the waste water flow rates
and loadings are low. This allows the waste streams to be pumped
directly from the collection sumps to the filter. Oil and suspended
solids which might be separated in the sump are manually removed.
Effluent Loadings Attainable with the Proposed Technology
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Although the treatment technologies required for each subcategory
are similar, the effectiveness of the system will vary according to
the flow and loadings and, therefore, the size subcategory.
Subcateqory E^ Small-Sized Production Facilities
Based on the control technology data obtained from general molded
extruded, or fabricated rubber manufacturing sources, and treatment
data obtained from industries having similar waste water problems,
it was determined that the proposed control and treatment
technologies are compatible with the following effluent quality for
small-sized molded, extruded and fabricated rubber production
facilities:
Suspended Solids 40 mg/1
Oil and Grease 10 mg/1
Lead 1 mg/1
pH 6.0 to 9.0
Effluent quality is best expressed in terms of the waste load per
unit of raw material consumed and is thereby independent of the flow
and relative size of the plant. Recommended limitations for the
proposed BPCTCA are as follows:
Suspended Solids 0.64 kg/kkg (lb/1000 Ib) of raw material
Oil 0.16 kg/kkg (lb/1000 Ib) of raw material
Lead 0.007 kg/kkg (lb/1000 Ib) of raw material
pH 6.0 to 9.0
Only one of the two small plants visited is currently achieving the
proposed standard for oil. Both small plants are achieving the
proposed standard for suspended solids.
Subcatecrorv F; Medium-Sized Production Facilities
The proposed control and treatment technologies are compatible with
the following effluent quality for medium-sized molded, extruded and
fabricated rubber production facilities:
Suspended Solids 40 mg/1
Oil and Grease 10 mg/1
Lead 1 mg/1
pH 6.0 to 9.0
It is expected that the use of an API separator will result in an
effluent oil concentration of 30 mg/1. The use of an absorbent
filter will further reduce the effluent oil concentration to 10
mg/1. A reduction of suspended solids to 40 mg/1 will result from
the use of an API separator. Additional reduction appears likely
after passage through the absorbent filter.
Effluent quality is best expressed in terms of the waste load per
unit of raw material consumed and is thereby independent of the flow
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and relative size of the plant. Recommended limitation for the
proposed BPCTCA are as follows:
Suspended Solids O.UO kg/kkg (lb/1000 Ib) of raw material
Oil 0.10 kg/kkg (lb/1000 Ib) of raw material
Lead 0.007 kg/kkg (lb/1000 Ib) of raw material
pH 6.0 to 9.0
All the medium-sized plants visited are currently achieving the
proposed standard for both oil and suspended solids.
Subcategory Gj. Large-Sized Production Facilities
The proposed control and treatment technologies are compatible with
the following effluent quality for large-sized molded, extruded and
fabricated rubber production facilities:
Suspended Solids 40 mg/1
Oil and Grease 10 mg/1
Lead 1 mg/1
pH 6.0 to 9.0
Effluent quality is best expressed in terms of the waste load per
unit of raw material consumed and is thereby independent of flow and
size variations within the overall size subcategory. Recommended
limitations for the proposed BPCTCA are as follows:
Suspended Solids 0.25 kg/kkg (lb/1000 Ib) of raw material
Oil 0.063 kg/kkg (lb/1000 Ib) of raw material
Lead 0.007 kg/kkg (lb/1000 Ib) of raw material
pH 6.0 to 9.0
Only one of the four large-sized plants visited is currently
achieving the proposed standards for both oil and suspended solids.
A second plant is achieving the proposed standard for suspended
solids.
Wet Digestion Reclaimed Rubber Subcategory
Identification of Best Practicable Control Technology
Currently Available
Wet digestion rubber reclaiming is a declining industry and
currently only five or six plants remain. The wet digestion process
is essentially phasing out with some of the wet digester reclaimed
rubber production being taken up by the dry reclaiming processes.
Of the existing wet digestion plants, all except one discharge their
contaminated process waste waters to local municipal treatment
systems. The one exception utilizes a waste stream recycle and
reclaim system which appreciably reduces the waste water loadings
prior to direct discharge.
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Only minor waste water quality improvements can be achieved by the
good housekeeping and waste control and treatment techniques that
have been proposed for Subcategories H and I because the greatest
proportion of waste water contamination is generated by the
dewatering-liquor waste stream and not by spills, leaks, and
washdowns.
Pan (Heater), Mechanical and Dry Digestion Reclaimed Rubber
Subcategory
Identification of Best Practicable Control Technology Currently
Available
Currently, the most common method of treating wastes from
Subcategory I reclaim facilities is to discharge to municipally
operated treatment systems. In-house efforts to control the
pollution-producing aspects of the facilities have been directed
mainly toward air emission problems. Water pollution problems have
not been considered a major problem. Therefore, the proposed
treatment technology for a typical Subcategory I reclaim plant is
the same as that used in other industries having similar waste water
problems. It is very similar to the technologies proposed for
Subcategories E, F, and G.
As before, the technology employed consists basically of:
1. Eliminating anti-tack solution discharge.
2. Segregation, control and treatment of all oily waste.
The flow diagram is the same as presented for Subcategories E, F,
and G and is presented in Figure 10. The anti-tack solution
discharges are eliminated by recycling. Wash waters are also
reused. Oily waste streams are segregated, collected and treated.
Segregation involves blocking existing drains in contaminated areas
and installing retainment curbing. Once segregated, the waste
streams are collected in sumps. The waste water is treated in an
API separator and an absorbent filter medium. For a detailed
discussion of the proposed system, refer to the related paragraphs
dealing with Subcategories E, F, and G.
Effluent Loadings Attainable with the Proposed Technology
Based on the control technology obtained from reclaim sources and
data obtained from industries having similar waste water problems,
the proposed control and treatment technologies are deemed
compatible with the following effluent quality for pan (heater), dry
digester or mechanical reclaim facilities.
Suspended Solids 40 mg/1
Oil and Grease 10 mg/1
pH 6.0 to 9.0
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It is expected that the use of an API separator will result in an
effluent oil concentration of 30 mg/1. The addition of an absorbent
filter will reduce the oil concentration to 10 mg/1.
A reduction of suspended solids to UO mg/1 will result from the use
of the API separator. Additional reduction appears likely after
passage through an absorbent filter.
Effluent limitation for the proposed BPCTCA, expressed in terms of
waste load per unit of raw material consumed are as follows:
Suspended Solids 0.192 kg/kkg (lb/1000 Ib) of product
Oil 0.0U8 kg/kkg (lb/1000 Ib) of product
pH 6.0 to 9.0
Subcategories J and K •-- Latex-Based Products
The principal difference in the waste water characteristics found at
latex-based manufacturing facilities and those of the other
subcategories studied in this document, is the presence of
substantial quantities of uncoagulated latex solids in Subcategories
J and K waste waters Subcategory J plants include latex-dipped
goods, latex thread, and products made in porous molds. The one
latex foam plant in existence constitutes Subcategory K
Subcateaorv J
All latex-bearing waste waters should be passed through a chemical
coagulation and clarification primary stage of treatment. In this
process the latex is coagulated to form solid rubber. Treatability
studies will determine whether a "sinker" such as clay is required
to weight down the coagulated solids or whether their buoyancy will
allow them to be skimmed from the clarifier.
The first unit of this treatment is a rapid mix tank where the waste
water pH is adjusted to facilitate coagulation. The coagulating
chemicals, alum and polyelectrolyte are added to the tank. The tank
contents are vigorously mixed to bring together the coagulating
chemicals and the latex solids. Waste water then flows to a
flocculation tank where the coagulation process is completed with
mild mixing in order to create a separate solids floe. The mixture
of flocculated solids and waste water passes to the clarifier where
the coagulated solids separate from the waste water. If a "sinker",
such as clay, is required the solids will settle to the bottom of
the clarifier where they can be drawn off, and the clarifier waste
stream will overflow. If, on the other hand, the latex solids float
and separate readily, the coagulated latex will be skimmed from the
surface of the clarifier and the clarified waste water will under-
flow from clarifier.
The most practicable technique for disposing the small quantities of
coagulated latex solids resulting from this treatment is by
contracting for the transport of the residual wastes to a final
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disposal site. In the case of the sinking solids these can be
pumped from the clarifier to a sludge dewatering bed from where they
can be collected periodically by the disposal contractor. For the
skimmed latex solids, the skimming can be first passed to a screen
where the bulk of the water is removed and returned to the treatment
system. The screened solids can then be containerized.
The clarified waste stream passes from the clarifier into an aerated
lagoon where it is mixed with biological solids. Microorganisms
synthesize new biological solids from organic matter contained in
the waste water. At the same time, some soluble matter is consumed
for energy purposes using oxygen supplied by the aerators in the
lagoon. The net result is that soluble matter is converted into
insoluble biological solids which can be separated from the waste
water thereby reducing the soluble BOD of the waste water.
Treatability studies and waste water analyses will determine if the
nutrient addition, if necessary, can be made in the rapid mix tank.
The mixture of waste water and biological solids in the aerated
lagoon overflows from the lagoon to a settling pond where the
biological solids settle out and additional biological stabilization
of the waste water occurs. The settled solids are removed
periodically, say twice a year, from the pond. The most feasible
and practicable method involves the employment of a contract
hauler's vacuum truck or equivalent apparatus. The clarified waste
water from the settling pond overflows to an effluent monitoring
station, where the waste water flow, temperature, and pH are
recorded and an automatic 24-hour composite sample is collected.
A biological treatment system composed of an aerated lagoon and
settling pond is proposed for Subcategory J facilities since the BOD
levels in this waste water are too low to support a good, settleable
biomass in an activated sludge treatment facility. The proposed
treatment is illustrated schematically in Figure 11.
The above description discusses primarily the treatment of latex-
laden wastes. Non-latex waste waters which require only secondary
biological treatment, such as product rinse waters, should be routed
to the aerated lagoon, bypassing the coagulation and clarification
system. This approach will enhance the treatability of the latex
wastes and reduce the size of coagulation-clarification facilities
by preventing unnecessary dilution.
It should be noted that the latex-laden wastes can be reduced and
potentially eliminated by careful housekeeping and good latex
handling practices. Excessive washdown and cleaning waters should
be avoided when dealing with latex spills. Latex spills can often
be coagulated in situ, with alum or other coagulants, and removal as
a solid mass by shoveling and scraping. Clean out usage can be
prevented in many instances by using disposable plastic drum liners.
The benefits, in treatment costs and effluent quality, created by
these and other techniques are appreciable.
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A few latex-dipping operations generate waste waters which require
additional control and treatment techniques. These techniques are
not included in the cost data presented in Section VIII since they
are not representative of the processes used by the majority of the
latex-based manufacturing facilities. Form-cleaning wastes, such as
chromic-acid-laden rinse waters, should be eliminated by the use of
alternative cleaning techniques believed to be feasible in almost
all cases. If the chromic acid cleaning technique cannot be
replaced, then chromium chemical reduction and precipitation
procedures are required.
Subcategorv K
The proposed BPCTCA treatment for the latex foam industry is based
on the waste water characteristics and treatment approach of the
only existing latex foam plant. Briefly the recommended treatment
consists of chemical coagulation and clarification of latex-bearing
waste waters and chemical precipitation of the zinc-laden rinse
waters and biological treatment.
All latex-laden wastes should be isolated and sent to a chemical
coagulation and clarification system. The proposed system consists
of two dual-purpose coagulation and clarification tanks. The tanks
are filled, treated, and settled alternatively in a batch-^wise
manner. The latex wastes are first adjusted manually for pH using
acid and alkali feed systems and then dosed with coagulating
chemicals such as alum and polyelectrolyte. The coagulated latex
solids are allowed to separate. Treatability studies will ascertain
whether a "sinker", such as clay, is required. Floating latex
solids can be skimmed from the water and screened. The filtrate
water from the screen is returned to the treatment system and the
screened solids are collected and hauled to a final disposal site.
During the entire coagulation, settling, and emptying process the
second identical tank is on-line and being filled.
Zinc-laden rinse waters are treated in another system simultaneously
to the latex-laden wastes. The zinc wastes are pumped to rapid mix
tank where lime and polyelectrolyte are added under virgorous mixing
conditions. The pH of the waste water is raised and the solublized
zinc is precipitated as insoluble zinc hydroxide. The precipitation
process is concluded in a flocculation tank where the zinc hydroxide
and lime solids agglomerate 'under mild agitation. The flocculated
waste water flows to a clarifier where the zinc sludge settles out.
The clarified waste water is discharged with the clarified latex
waste waters to a neutralization tank where the pH of the combined
wastes are adjusted to the acceptable range for biological treatment
(6.0 to 9.0 units).
The zinc-lime sludge is pumped to a holding tank prior to dewatering
on a vacuum drum filter. The filtrate is returned to the mix tank
and the filtered sludge is containerized prior to final disposal.
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The performance of the latex waste water treatment system can be
improved with good housekeeping and handling procedures as described
for Subcategory J industries.
Effluent Loadings Attainable with the Proposed Technology
Subcategorv J
Based on raw waste load and control and treatment data from
Subcategory J plants, it was determined that the proposed control
and treatment technologies can achieve the following effluent
qualities:
BOD 30 mg/1
Suspended Solids UO mg/1
Oil 10 mg/1
Chromium 0.05 mg/1
pH 6.0 to 9.0
The chromium limitation is included to ensure that those plants
using chromic acid form-cleaning techniques do not discharge
chromium containing wastes without adequate treatment. In order to
achieve this effluent quality for chromium it is possible that the
treated chromium waste waters will require gradual bleeding into the
final effluent rather than direct batch dumping or discharging.
The effluent waste loads resulting from the application of treatment
technologies equivalent to chemical coagulation with clarification
and biological treatment, constitute the best practicable control
and treatment standards currently available for the Subcategories J.
Recommendations for effluent limitations are:
BOD 2.20 kg/kkg (lb/1000 Ib) of latex solids
Suspended Solids 2.90 kg/kkg (lb/1000 Ib) of latex solids
Oil 0.73 kg/kkg (lb/1000 Ib) of latex solids
Chromium 0.0036 kg/kkg (lb/1000 Ib) of latex solids
pH 6.0 to 9.0
It is recommended that the monitoring and reporting requirement for
chromium be limited to those Subcategory J plants using chromic acid
form-cleaning techniques. This will minimize analytical and
reporting costs.
Subcateqorv K
The raw waste load and control and treatment data obtained from the
only operating latex foam plant indicates that the recommended
BPCTCA control and treatment technologies for latex foam production
facilities are compatible with the following effluent quality:
BOD 60 mg/1
Suspended Solids UO mg/1
Zinc 3.5 mg/1
pH 6.0 to 9.0
\
\
\
\
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This effluent quality can also be expressed in terms of effluent
waste loads which are independent of waste water flow and dilution.
These effluent waste loads, resulting from the application of
treatment technologies equivalent to chemical treatment and
clarification of both latex and zinc-laden waste waters and
biological treatment, constitute the best practicable control and
treatment technology standards currently available for the latex
foam industry sector. Recommendations for proposed limitations are:
BOD 1.U1 kg/kkg (lb/1000 Ib) of latex solids
Suspended Solids 0.94 kg/kkg (lb/1000 Ib) of latex solids
Zinc 0.083 kg/kkg (lb/1000 Ib) of latex solids
pH 6.0 to 9.0
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SECTION X
BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE -
EFFLUENT LIMITATIONS
General Molded. Extruded. and Fabricated Rubber Subcategories
Effluent limitations on oil and suspended solids applicable to the
best available technology economically achievable (BATEA) and the
best practicable control technology currently available (BPCTCA) are
identical for this sector of the industry. BPCTCA treatment reduces
the prime pollutants, suspended solids, and oil and grease to such a
level that further treatment cannot be justified on a technical,
cost or benefit basis.
However, for plants using a lead-sheathed cure in hose production,
BATEA limitations will further reduce the limitation on lead. Flow
rates of lead-contaminanted vulcanizer condensate are small and in
many cases can be containerized. In cases where this is unfeasible,
precipitation or ion exchange will be necessary. This curing
technique is not universally used and is represented by only a small
segment of the subcategory.
Complete water reuse or elimination of contaminated waste waters,
leading to zero discharge, is not universally feasible. Treatment
of the waste water to approach influent-supply water quality in a
reuse or recycle system requires removal of oils, suspended solids,
total dissolved solids, and trace contaminants that cannot be
substantiated on a technical, benefit, or cost basis. Some small-
capacity manufacturing facilities (where the process waste water
flow is small and slightly contaminated) can eliminate direct
discharge to navigable waters by contract disposal or discharge to
municipal systems. This will most probably be the most economic
approach and will avoid costly discharge monitoring and reporting
procedures.
Effluent Loading Attainable with Proposed Technologies
Proposed limitations and standards for BATEA are identical to those
proposed for BPCTCA with the exception of the limitation on lead.
The proposed control and treatment technologies are compatible with
the following effluent quality for small-sized molded, extruded and
fabricated rubber production facilities:
Suspended Solids UO mg/1
Oil and Grease 10 mg/1
Lead 0.1 mg/1
pH 6.0 to 9.0
Recommended limitations for the proposed BATEA expressed in terms of
loading per unit of production are as follows:
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Suspended Solids 0.64 kg/kkg (lb/1000 Ib) of raw material
Oil and Grease 0.16 kg/kkg (lb/1000 Ib) of raw material
pH 6.0 to 9.0
In addition to the above limitations, discharges attributable to
lead-sheathed hose production are subject to the following
limitation.
Lead 0.0007 kg/kkg (lb/1,000 Ib)
of raw material
Subcateaorv F
The proposed control and treatment technologies are compatible with
the following effluent quality for medium-sized molded, extruded and
fabricated rubber production facilities:
Suspended Solids 40 mg/1
Oil and Grease 10 mg/1
Lead 0.1 mg/1
pH 6.0 to 9.0
Recommended limitations for the proposed BATEA expressed in terms of
loading per unit of production are as follows:
Suspended Solids 0.4 kg/kkg (lb/1000 Ib) raw material
Oil and Grease 0.10 kg/kkg (lb/1000 Ib) raw material
pH 6.0 to 9.0
In addition to the above limitations, discharges attributable to
lead-sheathed hose production are subject to the following
limitation.
Lead 0.0007 kg/kkg (lb/1,000 Ib)
of raw material
Subcategorv G
The proposed control and treatment technologies are compatible with
the following effluent quality for large-sized molded, extruded
fabricated rubber production facilities:
Suspended Solids 40 mg/1
Oil and Grease 10 mg/1
Lead 0.1 mg/1
pH 6.0 to 9.0
Recommended limitations for the proposed BATEA expressed in terms of
loading per unit of raw material comsumption are as follows:
Suspended Solids 0.250 kg/kkg (lb/1000 Ib) raw material
Oil and Grease 0.063 kg/kkg (lb/1000 Ib) raw material
pH 6.0 to 9.0
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In addition to the above limitations, discharges attributable to
lead-sheathed hose production are subject to the following
limitation.
Lead 0.0007 kg/kkg (lb/1,000 Ib)
of raw material
Wet Digestion Reclaimed Rubber Subcatecrorv
The recommended treatment involves recycling of waste water streams
and reclaiming of process oils. The proposed modification is
illustrated schematically in Figure 9 (Section VII).
In a conventional wet digestion reclaiming process, the devulcanized
rubber slurry leaving the digester is screened prior to drying,
milling, and shipment. The dewatering liquor resulting from the
screening operation is one of the principal waste water streams that
can be recycled in part using the recommended BATEA technology.
The dewatering liquor is sent to an agitated storage tank from which
it can be pumped back to the digestion make-up process.
At the same time, the cooling water and condensate from the
barometric condensers on the blowdown tank and dryers are passed to
a decant tank where the oil and separable organics are recovered.
The bottom water layer is pumped to the agitated storage tank and is
mixed with the dewatering liquor. The decant tank is equipped with
an overflow line which controls the level in the decant tank. The
overflow from this decant system discharges to the sewer.
The recovered oils and organics from the decant tanks are sent to a
second oil decant and storage tank where the residual water content
is removed from the oil and returned to the first decant tank. The
reclaimed oils are then returned to the digester to be reused as
digestion ingredients.
The dewatering liquor and water layer from the first decant tank are
mixed in the water storage tank. The level of water in this tank is
maintained and the excess water overflows to the sewer. The water
storage tank is agitated in order to fully mix the various water
streams and to suspend rubber fines and prevent their settling in
the tank.
The net discharge from the wet digestion is reduced to the excess
cooling and condensation waters from the blowdown tank and dryer
vapor streams and the excess dewatering liquor. The flow and
loadings of the combined discharge are lower than the effluent
generated by a digestion process without the recycle system.
Effluent Loadings Attainable with Proposed Technologies
»
Based on the raw waste load and the control and treatment data from
the wet digestion reclaiming plant visited, it has been ascertained
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that the described control and treatment technologies are compatible
with the following effluent quality:
COD
Suspended Solids
Oil
PH
1,750 mg/1
660 mg/1
166 mg/1
6.0 to 9.0
Effluent waste loads, achieved by application of treatment
technologies equivalent to decantation and recycle of oil-laden
wastes and recycle of the dewatering liquor, constitute the best
available technology standards economically achievable for the wet
digestion reclaiming subcategory. Recommendations for proposed
limitations are:
COD
Suspended Solids
Oil
pH
6.11 kg/kkg (lb/1000 Ib) of product
2.31 kg/kkg (lb/1000 Ib) of product
0.58 kg/kkg (lb/1000 Ib) of product
6.0 to 9.0
Pan (Heater) . Mechanical, and Dry. Digestion Reclaimed Rubber
Subcateqorv
For this subcategory, the effluent limitations recommended for the
best available technology economically achievable are identical to
those proposed for the best practicable technology currently
available. No further treatment of the process waste waters after
BPCTCA can be economically achieved.
Although it is not feasible to recycle or reuse entirely the process
waste waters, direct discharge to navigable waters can be eliminated
by employing the local municipal treatment system for the discharge
of those waste waters which would benefit from secondary treatment.
Contract haulage of contaminated waste is not generally feasible
since the volumes involved in this industry are considerable.
Latex-Based Products
Subcateaorv J
Since no further contaminant reduction can be economically achieved
beyond BPCTCA, it is recommended that the effluent limitations
commensurate with the best available technology economically
achievable and the best practicable technology currently available
be identical.
The effluent quality produced by application of BPCTCA cannot be
improved economically by end-of-pipe processes. It is possible in
some cases to reduce the effluent loading by applying good-
housekeeping and materials-handling procedures, such as the
containment and reduction of latex washdown waters; however, the
extent of the effect of these measures cannot be anticipated.
Municipal systems can be used to treat the residual contamination of
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the process wastes, thereby eliminating direct discharge to
navigable waters.
Subcatecrorv K
The proposed BATEA treatment for the latex foam industry is based on
studies made by the only operating latex foam plant in the industry.
In brief, it involves biological treatment using an activated sludge
process. The activated sludge process is selected in this instance
since it is the most feasible and economic biological treatment
approach (based on the high BOD loading of latex foam waste waters
after primary treatment). The treatment system is schematically
represented in Figure 12.
The primary treated latex-based wastes and the zinc-containing rinse
waters (refer to Section IX) are discharged to an equalization basin
where the contaminant levels are equalized prior to secondary
treatment. The equalization basin is agitated to ensure good mixing
and would provide approximately 8-hour detention, which is
equivalent to one shift1s operation. It is anticipated that the pH
control facilities will be used to adjust the equalization influent
pH to approximately 7 to ensure good biological activity and
treatment.
The equalized waste water flows into the aeration basin where it is
well mixed with biological solids. Microorganisms synthesize new
biological solids from ,organic matter contained in the waste water.
At the same time, some soluble waste water constituents are consumed
for energy purposes using oxygen supplied by aerators in the basin.
The result is that soluble material is converted to insoluble
biological solids and the BOD of the waste water is reduced. The
mixed liquor containing biological solids suspended in the waste
water overflows the aeration basins to the secondary clarifier.
The solids in the mixed liquor are settled in the secondary
clarifier, and the clarified waste water overflows and enters an
effluent monitoring station, where the flow, temperature, and pH are
recorded and an automatic 24-hour composite sample is collected.
Part of the settled biological solids is returned to the aeration
basins to maintain the mixed liquor solids concentration in the
basin. The remainder of the bio-solids must be wasted from the
system as a sludge.
The waste sludge is first thickened in a gravity thickener with the
supernatant returning to the head end of the aeration basins. The
thickened sludge underflow enters an aerobic digester, where the
biological sludge is wasted by endogenous respiration to reduce the
bio*solid bulk. This process is referred to as aerobic digestion
and requires oxygen which is supplied by aerators.
This digested biological sludge is then mixed with the zinc-lime
-sludge and further thickened in a secondary thickener. The clear
supernatant from this thickener is recycled to the neutralization
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basin ahead of the equalization basin. The thickened underflow is
then discharged to a vacuum filter for further conditioning,
dewatering, and concentration.
A drum-type vacuum filter separates thickened sludge into:
1. A dewatered cake which is discharged by belt conveyor to a
dumpster bin.
2. A filtrate that is recycled to the neutralization basin.
The dewatered sludge cake is biologically stable and can be disposed
of to a sanitary landfill. Filter aid and precoat tanks, pumps and
metering equipment may be required to assist and maintain the
quality of the filtrate.
Effluent Loading Attainable with Proposed Technologies
Based on the effluent loading data obtained by application of the
proposed BPCTCA treatment and from a knowledge of the typical bio-
kinetics for waste waters from latex-based industries generally, the
recommended control and treatment technologies will result in the
following effluent quality:
BOD 60 mg/1
Suspended Solids 40 mg/1
Zinc 3.5 mg/1
pH 6.0 to 9.0
This effluent quality can be represented as effluent waste loads
which are independent of waste water flow. The effluent loading,
resulting from the application of the treatment technologies
equivalent to biological oxidation treatment as provided by the
activated sludge process, constitutes the best available technology
standards economically achievable for proposed limitations are:
BOD 1.41 kg/kkg (lb/1000 Ib) of latex solids
Suspended Solids 0.94 kg/kkg (lb/1000 Ib) of latex solids
Zinc 0.083 kg/kkg(lb/1000 Ib) of latex solids
pH 6.0 to 9.0
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SECTION XI
NEW-SOURCE PERFORMANCE STANDARDS
Effluent Limitations
General Molded, Extruded, and Fabricated Rubber Subcateqories
Recommended effluent limitations for new sources are identical to
the best available technology economically achievable. These
limitations are presented in Section X of this report.
Wet Digestion Reclaimed Rubber Subcateororv
Technological and economic restraints resulting from air and water
pollution problems point to the eventual phasing out of the wet
digestion process. According to industry spokesman, no new
facilities using the wet digestion process are planned for the
future. In fact, most companies using the process either have
already changed or plan to change to the pan, dry digestion, or
mechanical process. Accordingly, it is recommended that new-source
performance standards be equivalent to best practicable control
technology currently available. New reclaimed rubber facilities
should use the pan, dry digestion, or mechanical process.
Pan (Heater), Mechanical. and Dry Digestion Rubber Reclaiming
Recommended effluent limitations for new sources are identical to
the best practicable control technology currently available. These
standards and limitations are presented in Section IX of this
report.
Latex-^Based Products Subcategorv
Recommended effluent limitations for Subcategory J new sources are
identical to the best practicable control technology currently
available. These standards and limitations are presented in Section
IX of this report.
Recommended effluent limitation for Subcategory K new sources are
identical to those recommended as best practicable treatment
economically achievable. These standards are presented in Section
X.
Pretreatment Recommendations
A minimum level of pretreatment must be given to new production
facilities which will discharge waste water to a publicly owned
treatment works. ' In addition, potential pollutants which will
inhibit or upset the performance of publicly owned treatment works
must be eliminated from such discharge.
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General Molded. Extruded and Fabricated Rubber Products
Subcategories
Pretreatment recommendations for process waste waters from
Subcategories E, F, and G facilities include the separation of oils
and solids in an API gravity separator and the use of an
equalization basin to prevent shock loads of oil, suspended solids
or batch dumps of dipping solutions from entering and upsetting the
performance of a publicly owned treatment works. Oily wastes, after
dilution in a public sewer system, would remain untreated and
therefore must be controlled before discharge from the plant
boundaries. In addition, lead-laden waste waters must be treated
prior to discharge.
Wet Digestion Reclaimed Rubber Subcatecrorv
Pretreatment recommendations for process waste waters from
Subcategory H facilities include the separation of oils and solids
and the use of an equalization basin to prevent shock loads.
Separation of suspended solids and oil can be performed in a API-
type separator if the waste water does not contain any digested
fibrous material (i.e., the fiber is removed mechanically before
digestion) . If the fiber is digested along with the rubber scrap,
the process waste water will contain large quantities of fibrous
material, which are difficult to settle. Industry spokesmen
indicate that a large sedimentation lagoon is adequate if the
material is to be discharged to a municipal system. Such a lagoon
should be designed to contain a 10-year, 24-hour rainfall event, as
defined by the National Weather Service in Technical Paper Number
UO, "Rainfall Frequency Atlas of the United States," May 1961, and
subsequent amendments.
Pan (Heater), Mechanical, and Dry Digestion Reclaimed Rubber
Subcategory
As with Subcategories E, F, and G, pretreatment recommendations for
process waste waters from Subcategory I facilities include
separation of oils and solids. An equalization basin is also
required to prevent shock loads of oil, suspended solids or batch
dumps of processing solutions from entering and upsetting a
municipal system. Process streams must be pretreated prior to
discharge since dilution will render treatment in a public system
ineffective.
Latex-Based Products Subcategorv
Recommended pretreatment of process waste waters from Subcategory J
and Subcategory K facilities include coagulation and clarification
of solids-laden waste water. In addition, precipitation procedures
are required to remove any chromium in Subcategory J waste waters
and zinc in Subcategory K waste waters.
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SECTION XII
AC KNOWLEDGEMENTS
The original draft of this document was prepared by Roy F. Weston,
Inc., West Chester, Pennsylvania, under the direction of Mr. Melvin
J. Sotnick, Manager Chemical Engineering Services. He was assisted
by David C. Day, PhD, Principal Engineer, Mr. Robert A. Morris,
Chemical Engineer and other members of the staff.
The Environmental Protection Agency wishes to acknowledge the
cooperation of the officers and plant personnel in the rubber
industry who provided valuable assistance in the collection of data
relating to process raw waste load and treatment plant performance
at various rubber processing facilities. Special acknowledgement is
made of Mr. Daniel G. Pennington of the Rubber Manufacturers
Association for coordinating the schedule of visits among the
industry members; also the assistance of personnel at the EPA
Regional Centers who were contacted to identify plants in the rubber
processing industry known to be achieving effective waste treatment.
Special mention should be given to Herbert S. Skovonek, PhD, Edison
Water Quality Research Laboratory Division of NERC, Cincinnati; Paul
Ambrose, Enforcement Division, EPA Region III; John Lank,
Enforcement Division, EPA Region IV; and Marshall Dick, Office of
Research and Development, Headquarters.
In addition, special mention and acknowledgement is made of the
following EPA rubber industry working group members who assisted in
field sampling, project evaluation and review of the draft and final
documents: Henry Garrison, Legal Assistant, Effluent Guidelines
Division; Richard Insinger, Planning and Evaluation, Economic
Analysis Branch, Headquarters; Doris Ruopp, Office of Toxic
Materials, Headquarters; Alan W. Eckert, Office of General Counsel;
John E. Riley, Original Project Officer, and Richard J. Kinch,
Project Officer, Rubber Industry. Effluent Guidelines Division.
Acknowledgement is made of the efforts of Jane D. Mitchell and Bobby
Wortman, Effluent Guidelines Division for typing the final
manuscript. Acknowledgement is made of the overall guidance and
direction provided by Mr. Allen Cywin, Director and Mr. Ernst P.
Hall, Deputy Director, Effluent Guidelines Division, and Mr. John E.
Riley, Chief, Technical Analysis and Information Branch, and others
within the Agency who provided many helpful suggestions and
comments.
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SECTION XIII
GENERAL BIBLIOGRAPHY
Shreve, R.N., "Chemical Process Industries, CPI", New York: McGraw-
Hill, Inc., 1967.
Standen, A. ed., "Kirk-Othmer, Encyclopedia of Chemical Technology;
Vol. 17", New York: John Wiley and Sons, 1968.
"Rubber Industry Facts", New York: Rubber Manufacturers
Association, 1972.
"Air Flotation-Biological Oxidation of Synthetic Rubber and Latex
Wastewater". Lake Charles, Louisiana: Firestone Synthetic Rubber
and Latex Company, October 15, 1972.
Rostenback, R.E., "Status Report on Synthetic Rubber Wastes."
Sewage and Industrial Waste, Vol. 24, No. 9, September 1952, 1138-
11U3.
Placek, O.R. and Ruchhoft, C.C., "A Study of Wastes from the
Synthetic Rubber Industry." Sewage and Industrial Waste, Vol. 18,
No. 6, November 1946, 1160-1181.
Martin, A.E. and Rostenback, R.E., "Industrial Waste Treatment and
Disposal." Industrial and Engineering Chemistry. Vol. 45, No. 12,
December 1953, 2680-2685.
Dougan, L.D. and Bell, J.C., "Waste Disposal at a Synthetic Rubber
Plant." Sewage and Industrial Wastes, Vol. 23, No. 2, February 1951,
181-187.
"A Study of Pollution Control Practices in Manufacturing
Industries." Marketing Services Division, Research Services
Department, Dun and Bradstreet, Inc., June 1971.
Hebbard, G.M., Powell, S.T. and Rostenback, R.E., "Rubber Industry"-
Industrial and Engineering Chemistry, Vol. 39, No. 5, May 1947, 589-
595.
Nemerow, N.L., "Theories and Practices of Industrial Waste
Treatment", New York: Addison-Wesley Publishing Co., 1963.
Alliger, G. and Weissert, F.C., "Elastomers." Industrial and
Chemistry. Vol. 59, No. 8, August 1967, 80-90.
Montgomery, D.R., "Integrated System for Plant Wastes Combats Stream
Pollution." Chemical Engineering, Vol. 63, No. 4, February 1967,
108-110.
Ruebensaal, C.F., "The Rubber Industry Statistical Report and
Changing Markets and Manufacturing Patterns in the Synthetic Rubber
205
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Industry." New York: International Institute of Synthetic Rubber
Producers, Inc., 1972.
Hofmann, W., "Vulcanization and Vulcanizing Agents", New York:
Palmerton Publishing Co., Inc., 1967.
Hawley, G.G., "The Condensed Chemical Dictionary", New York:
ReinholdCo., 1971.
Lund, H.F., ed., "Industrial Pollution Control Handbook", New York:
McGraw-Hill, Inc., 1971.
"Methods for Chemical Analysis of Water and Wastes." Environmental
Protection Agency, National Environmental Research Center,
Analytical Quality Control Laboratory, Cincinnati, Ohio, 1971.
Taras, M.J., ed., Standard Methods for the Examination of Water and
Wastewater; American Public Health Association, Washington, D.C.,
1971.
Water; Atmospheric Analysis, Part 23, "Standard Method of Test of
Biochemical Oxygen Demand of Industrial Water and Industrial
Wastewater." 1970 Annual Book of ASTM Standards. American Society of
Testing and Materials, Philadelphia, Pennsylvania, 1970.
Eckenfelder, W.W., "Industrial Water Pollution Control", New York:
McGraw-Hill, Inc., 1963.
"Rubber Products Handbook, Molded, Extruded Lathe Cut, cellular",
3rd ed.r Rubber Manufacturers Association, December 1970.
"Sheet Rubber Handbook, Gasket and Packing Materials", 2nd ed.,
Rubber Manufacturers Association, September 1968.
"Hose Handbook", 3rd ed., Rubber Manufacturers Association, October
1970.
Noble, E.E. and Amendole, G.A., "Zinc Removal from A Rubber
Reclaiming Operation", unpublished internal B.F. Goodrich report to
James Lewis.
Perry, J.H., ed., "Chemical Engineers* Handbook", 4th ed.. New York:
McGraw-Hill, Inc., 1963.
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SECTION XIV
GLOSSARY
Accelerator Agent.
A compound which greatly reduces the time required for vulcanization of
synthetic or natural rubber.
Act
The Federal Water Pollution Control Act, as Amended.
Activator
A metallic oxide that makes possible the crosslinking of sulfur in
rubber vulcanization.
Antioxidant
An organic compound added to rubber to retard oxidation or deterioration.
Anti-tack Agent
A substance used to prevent rubber stocks from sticking together during
periods of storage.
Bag House
An air emission control device used to collect intermediate and large
particles (greater than 29 microns) in a bag filter. (A bag filter
constructed of fabric.) Common usage in the industry is to control and
recover carbon black in a dry state from vapors leaving the compounding
area.
Banburv Mixer
Trade name for a common internal mixer manufactured by Farrel Corporation
used in the compounding and mixing of tire rubber stock.
Best Available Demonstrated Control Technology (BADCT)
Treatment required for new sources as defined by Section 306 of the Act.
Best Available Technology Economically Achievable (BATEA1
Treatment required by July 1, 1983 for industrial discharges to surface
waters as defined by Section 301 (b) (2) (A) of the Act.
Best Practicable Control Technology Currently Available (BPCTCA1
Treatment required by July 1, 1977 for industrial discharges to surface
waters as defined by Section 301 (b) (1) (A) of the Act.
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BQD5
Biochemical Oxygen Demand (5 day) .
Butyl Rubber
A synthetic rubber made by the solution polymerization of isobutylene
and isoprene.
Camelback
Tire tread used in the retreading of tire carcasses.
Capital Costs
Financial charges in August 1971 dollars which are computed as the cost
of capital times the capital expenditures for pollution control. Cost
of capital is assumed to be 10 percent.
Carbon Black
A reinforcing agent used in large quantities in rubber compounds.
Catalyst
A substance that initiates a chemical reaction and enables it to proceed
at a greatly accelerated rate.
Subcateqorv
A division of a particular industry which possess different traits which
affect water quality and treatability.
Cement
A process stream consisting of polymeric rubber solids dissolved in
solvent.
Coagulation
The combination or aggregation of previously emulsified particles into a
clot or mass.
COD
Chemical Oxygen Demand.
Crumb
Small coagulated particles of synthetic rubber.
Curing Agents
Curing or vulcanization agents are substances which bring about the
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rubber crosslinking process. The most important, agent is sulfur. (See
vulcanization.)
Depreciation
Accounting charges reflecting the deterioration of a capital asset over
its useful life. Reported as straight line over five years with zero
salvage value.
Devulcaniz ation
The term is used to describe the softening of a vulcanizate
by heat and chemical additives during reclaiming.
Dry Air-Pollution Control
The technique of air pollution abatement without the use of water.
Emulsion
A stable mixture of two or more immiscible liquids held in suspension by
small percentage of substances called emulsifiers.
Endogenous Respiration
Auto-oxidation of the microorganisms producing a reduction and stabilization
of biological solids.
EPDM
A synthetic rubber based on ethylene-propylene and a controlled amount
of non-conjugated diene. Polymerization is carried out in solution.
Extender
A low specific gravity substance used in rubber formulations chiefly to
reduce costs.
Extrude
To shape by forcing a material through a die. The operation is carried
out in a device known as an extruder.
Filler
A high specific gravity (2.00-1*.50) compound used in rubber mixtures to
provide a certain degree of stiffness and hardness and used to decrease
costs. Fillers have neither reinforcing or coloring properties and are
similar to extenders in their cost-reducing function.
Flash
The overflow of cured' rubber from a mold.
SEE
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Gallons per minute.
IR
Polyisoprene rubber, the major component of natural rubber, made syn-
thetically by the solution polymerization of isoprene.
Investment Costs
The capital expenditures reported in August 1971 dollars required to
bring the treatment or control technology into operation. Included are
expenditures for design, site preparation, purchase of materials, con-
struction and installation. Not included is the purchase of land on
which the system is to be built.
Liter
Latex
A suspension of rubber particles in a water solution. Coagulation of
the rubber is prevented by protective colloids. A protective colloid is
a surface-active substance that prevents a dispersed phase of a suspensio
from coalescing by forming a thin layer on the surface of each particle.
Masterbatch
A compounded rubber stock applicable to a wide variety of uses. Main
ingredients are rubber, carbon black and extender oil.
mg/1
Milligrams per liter.
Modifier
An additive which adjusts the chain length and molecular weight dis-
tribution of the rubber during polymerization.
Monomer
A compound of a relatively low molecular weight which is capable of
conversion to polymers or other compounds.
NBR
Nitrile rubber, a synthetic rubber made by emulsion polymerization of
acrylonitrile with butadiene.
New Source
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Any building, structure, facility, or installation from which there is
or may be a discharge of pollutants and whose construction is commenced
after the publication of the proposed regulations.
Non-Productive Rubber Stock
Rubber stock which has been compounded but which contains no curing
agents. Synonym for non-reactive rubber stock.
Non-Reactive Rubber Stock
Rubber stock which has been compounded but which contains no curing
agents. Synonym for non-productive rubber stock.
Operations and Maintenance
Costs required to operate and maintain pollution abatement equipment.
They include labor, material, insurance, taxes, solid waste disposal,
etc.
PER
Polybutadiene rubber, a synthetic rubber made by solution polymerization
of butadiene.
EH
A measure of the relative acidity or alkalinity of water. A pH of 7.0
indicates a neutral condition. A greater pH indicates alkalinity and a
lower pH indicates acidity.
Pigment
Any substance that imparts color to the rubber. Pigment substances such
as zinc oxide or carbon black also act as reinforcing agents.
Plastic
Capable of being shaped or molded with or without the application of
heat.
Process Water
All waters that come into direct contact with the raw materials and inter-
mediate products.
Productive Rubber Stock
Compounded rubber which contains curing agents and which can be vulcan-
ized. Synonym for reactive rubber stock.
Reactive Rubber Stock
Compounded rubber which contains curing agents and which can be vulcan-
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ized. Synonym for productive rubber stock.
Reclaimed Rubber
Depolymerized (plasticized) scrap rubber, either natural or synthetic.
Reinforcers or Reinforcing Agents
Fine powders used to increase the strength, hardness and abrasion
resistance of rubber. Reinforcing agents used in the rubber processing
include carbon black, zinc oxide, and hydrated silicas.
Rotacure
Trade name for a common curing press.
SBR
Styrene butadiene rubber. A synthetic rubber made either by emulsion or
solution polymerization of styrene and butadiene.
Soapstone
A substance used to prevent rubber stocks from
sticking together during periods of storage. Used in both a dry and
solution form. The major ingredient is usually clay.
Solution
A uniformly dispersed mixture at the molecular level of one or more
substances in one or more other substances.
Stripper
A device in which relatively volatile components are removed from a
mixture by distillation or by passage of steam through the mixture.
Surface Waters
The waters of the United States including the territorial seas.
Vulcanization
Vulcanization is the process by which plastic rubber is converted into
the elastic rubber or hard rubber state. The process is brought about
by linking of macro-molecules at their reactive sites.
Wet Air-Pollution Control
The technique of air pollution abatement utilizing water as an
absorptive media.
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TABLE 44
CONVERSION TABLE
MULTIPLY (ENGLISH UNITS) by TO OBTAIN (METRIC UNITS)
ENGLISH UNIT ABBREVIATION CONVERSION ABBREVIATION METRIC UNIT
acre ac
acre - feet ac ft
British Thermal
Unit BTU
British Thermal
Unit/pound BTU/lb
cubic feet/minute cfm
cubic feet/second cfs
cubic feet cu ft
cubic feet cu ft
cubic inches cu in
degree Fahrenheit °F
feet ft
gallon gal
gallon/minute gpm
horsepower hp
inches in
inches of mercury in Hg
pounds Ib
million gallons/day mgd
mi 1 e mi
pound/square
inch (gauge) psig
square feet sq ft
square inches sq in
ton (short) ton
yard yd
0.405
1233.5
0.252
ha
cu m
kg cal
0.555
0.028
1.7
0.028
28.32
16.39
0.555(°F-32)*
0.3048
3.785
0.0631
0.7457
2.54
0.03342
0.454
,785
1.609
kg cal /kg
cu m/min
cu m/min
cu m
1
cu cm
°C
m
1
I/sec
kw
cm
atm
kg
cu m/day
km
(0.06805 psig +1)* atm
0.0929 sq m
6.452 sq cm
0.907 kkg
0.9144 m
hectares
cubic meters
kilogram - calories
kilogram calories/kilogram
cubic meters/minute
cubic meters/minute
cubic meters
liters
cubic centimeters
degree Centigrade
meters
liters
liters/second
killowatts
centimeters
atmospheres
kilograms
cubic meters/day
kilometer
atmospheres (absolute)
square meters
square centimeters
metric ton (1000 kilograms)
meter
* Actual conversion, not a multiplier
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